Adhesive composition, heat-fusible member, and packaging material for power storage device

Abstract

This adhesive composition comprises: a polyolefin resin including an acid-modified polyolefin modified with a compound that has at least one of a carboxylic acid group and a carboxylic anhydride group; a polyfunctional isocyanate compound; and an epoxy resin. In the adhesive composition, the total amount of the polyolefin resin, the polyfunctional isocyanate compound, and the epoxy resin is 90 mass% or more in the total solid content. The adhesive composition satisfies the formula: 0.5 ≤ ([EPOXY] + [NCO]) / [COOH] ≤ 50. Provided that [EPOXY] represents the total amount by mole of epoxy groups in the epoxy resin, [NCO] represents the total amount by mole of isocyanate groups in the polyfunctional isocyanate compound, and [COOH] represents the total amount by mole of carboxy groups in the polyolefin resin.

Description

Adhesive Composition, Heat-Fusible Member, and Packaging Material for Power Storage Device Cross-Reference to Related Applications

[0001] This application is based on Japanese Patent Application No. 2024-196157 filed in Japan on November 8, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to an adhesive composition, a heat-fusible member, and a packaging material for a power storage device.

[0003] Hot-melt type adhesive compositions are processed into film or sheet form for use, and are used as adhesive films or sheets in which the adhesive composition is laminated on the surface of a member in various industrial product fields such as the electrical, automotive, and other industrial fields. Further, as an adhesive composition, a mode of preparing it as a solution containing an organic solvent or the like, directly applying it to an adherend and drying it, and then adhering it to the other adherend is also known.

[0004] In addition, various adhesive compositions have been proposed for adhering metal materials such as iron, aluminum, titanium, and other metals, as well as alloys thereof, and molded bodies or film laminates made of polyolefin having poor adhesiveness, which are used in the above fields. Further, a heat-fusible member in which a metal layer is joined to one side of an adhesive layer formed by curing an adhesive composition and a heat-fusible resin layer is joined to the other side of the adhesive layer is also known.

[0005] As a technology of this kind, for example, Patent Document 1 and Patent Document 2 disclose a battery case packaging material including a heat-resistant resin stretched film layer as an outer layer, an unstretched thermoplastic resin film layer as an inner layer, and an aluminum foil layer disposed between these two film layers, wherein the unstretched thermoplastic resin film layer and the aluminum foil layer are adhered via an adhesive layer, and the adhesive layer is configured to contain a polyolefin resin having a carboxyl group and a polyfunctional isocyanate compound, and the equivalent ratio [NCO] / [OH] of the isocyanate group of the polyfunctional isocyanate compound to the hydroxyl group constituting the carboxyl group of the polyolefin resin is set to 1.0 to 10.0.

[0006] Japanese Patent Publication No. 2010-92703 Japanese Patent Publication No. 2014-89985

[0007] The adhesive layer formed by curing the adhesive composition containing the aforementioned polyolefin resin having a carboxyl group and a polyfunctional isocyanate compound may be exposed to temperatures of around 40°C, and it is necessary that it maintains sufficient adhesion even under such conditions.

[0008] Furthermore, adhesive layers are sometimes used in contact with organic solvents that dissolve polyolefins. In particular, adhesive layers may need to maintain sufficient adhesion even when exposed to high-temperature vapor organic solvents at around 80°C. For example, in packaging materials for energy storage devices such as lithium-ion batteries, the electrolyte may contain organic solvents, and these organic solvents dissolve polyolefins. Therefore, adhesive layers used in such applications are required to maintain sufficient adhesion even when exposed to electrolytes containing high-temperature organic solvents at around 80°C, as a precaution against abnormalities.

[0009] However, conventional adhesive compositions have the problem that the adhesive layer formed by curing cannot exhibit sufficient adhesion after being exposed to a temperature of about 40°C, and also cannot exhibit sufficient adhesion after being exposed to an organic solvent that dissolves polyolefins at a temperature of about 80°C.

[0010] This disclosure has been made in view of the above problems, and aims to provide an adhesive composition in which the adhesive layer maintains sufficient adhesion even after exposure to a temperature of about 40°C (hereinafter sometimes referred to as heat-resistant adhesion), and also maintains sufficient adhesion even after exposure to an organic solvent that dissolves polyolefins at a temperature of about 80°C (hereinafter sometimes referred to as high-temperature chemical resistance), as well as a heat-sealable member using the same, and a packaging material for energy storage devices using the same.

[0011] The adhesive composition, heat-sealable member, and packaging material for energy storage devices relating to this disclosure are as follows: [1] An adhesive composition comprising a polyolefin resin, a polyfunctional isocyanate compound, and an epoxy resin, wherein the polyolefin resin comprises an acid-modified polyolefin modified with a compound having at least one of a carboxylic acid group and a carboxylic anhydride group, the total amount of the polyolefin resin, the polyfunctional isocyanate compound, and the epoxy resin is 90% by mass or more of the total solids, and satisfies the following formula (1). 0.5 ≤ ([EPOXY] + [NCO]) / [COOH] ≤ 50 ... Formula (1) (In Formula (1), [EPOXY] represents the total number of moles of epoxy groups in the epoxy resin, [NCO] represents the total number of moles of isocyanate groups in the polyfunctional isocyanate compound, and [COOH] represents the total number of moles of carboxyl groups in the polyolefin resin. However, the carboxylic anhydride structure (-CO-O-CO-) contained in the polyolefin resin is included in the total number of moles of carboxyl groups as 2 moles of carboxyl groups per mole.) [2] The adhesive composition according to [1], satisfying the following formulas (2) and (3). 0.25 ≤ [EPOXY] / [COOH] ≤ 25 ... Formula (2) 0.25 ≤ [NCO] / [COOH] ≤ 25 ... Formula (3) (In formulas (2) and (3), [EPOXY], [NCO], and [COOH] are the same as those described in [1].) [3] The adhesive composition according to [1] or [2], wherein the acid value of the polyolefin resin is 1 mg KOH / g or more and 50 mg KOH / g or less. [4] The adhesive composition according to any one of [1] to [3], further comprising at least one of a first curing catalyst that promotes the reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin, and a second curing catalyst that promotes the reaction between the epoxy resin and the acid-modified polyolefin. [5] The adhesive composition according to any one of [1] to [4], wherein the hydroxyl value of the polyolefin resin is 1 mg KOH / g or less.[6] The adhesive composition according to any one of [1] to [5], wherein the polyolefin resin, the polyfunctional isocyanate compound, and the epoxy resin are in separate containers, and the composition is multi-component. [7] A heat-sealable member comprising an adhesive layer formed by curing the adhesive composition according to any one of [1] to [6], a metal layer bonded to one side of the adhesive layer, and a heat-sealable resin layer bonded to the other side of the adhesive layer. [8] A packaging material for an energy storage device having the heat-sealable member according to [7].

[0012] The above adhesive composition has the above configuration. Therefore, when the adhesive composition hardens to form an adhesive layer, the adhesive layer will have sufficient adhesion (heat-resistant adhesion) even after being exposed to a temperature of about 40°C, and the adhesive layer will have sufficient adhesion (high-temperature chemical resistance) even after being exposed to an organic solvent that dissolves polyolefins at a temperature of about 80°C.

[0013] Furthermore, since the heat-fusible member includes an adhesive layer formed by the curing of the adhesive composition, the adhesive layer can achieve both heat resistance and high-temperature chemical resistance.

[0014] Furthermore, since the above-mentioned packaging material for energy storage devices has the above-mentioned heat-sealable member, the adhesive layer provided by this heat-sealable member can achieve both heat resistance and high-temperature chemical resistance.

[0015] Figure 1 is a schematic perspective view showing an example of a heat-fusible member according to the embodiment. Figure 2 is a schematic perspective view showing another example of a heat-fusible member according to the embodiment.

[0016] An embodiment of this disclosure will be described below, but this disclosure is not limited to the examples given below. Furthermore, the lower and upper limits of the numerical ranges shown below can be arbitrarily combined, including the values ​​described in the examples (details omitted below).

[0017] 1. Adhesive Composition The adhesive composition of this embodiment will now be described. The adhesive composition of this embodiment contains a polyolefin resin, a polyfunctional isocyanate compound, and an epoxy resin. The composition of the adhesive composition will be described in detail below.

[0018] 1.1 Polyolefin Resin In the adhesive composition of this embodiment, the polyolefin resin is a component containing acid-modified polyolefin and is an important adhesive component as the base of the adhesive composition.

[0019] Acid-modified polyolefins are obtained by modifying unmodified polyolefins with a compound having at least one of a carboxylic acid group and a carboxylic anhydride group (carboxylic acid anhydride group). Polyolefin resins containing acid-modified polyolefins may consist solely of acid-modified polyolefins, or they may also contain unmodified polyolefins that have not been acid-modified. Furthermore, polyolefin resins containing acid-modified polyolefins may also contain polyolefins modified with acidic groups other than carboxylic acid groups and carboxylic anhydride groups. Examples of acidic groups other than carboxylic acid groups and carboxylic anhydride groups include sulfonic acid groups, sulfonic acid anhydride groups, phosphoric acid groups, and phosphoric acid anhydride groups.

[0020] The acid-modified polyolefin contained in the polyolefin resin is preferably a polyolefin that has been graft-modified with a compound having at least one of a carboxylic acid group and a carboxylic anhydride group, and more preferably a polyolefin that has been graft-modified with a compound having a carboxylic anhydride group.

[0021] Unmodified polyolefins for constituting acid-modified polyolefins, unmodified polyolefins that can be included in polyolefin resins separately from acid-modified polyolefins, and unmodified polyolefins for constituting polyolefins modified by acidic groups other than carboxylic acid groups and carboxylic anhydride groups are collectively referred to as unmodified polyolefins below.

[0022] Examples of monomers that form monomer units constituting unmodified polyolefins include ethylene, propylene, and α-olefins such as 1-butene, isobutylene, 1-pentene, 1-hexene, and 1-octene. In this disclosure, "α-olefin" refers to α-olefins having 4 or more carbon atoms unless otherwise specified.

[0023] As the above monomer, at least one monomer selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, and 1-hexene is preferred. Among these, when the adherend is a poorly bonded nonpolar polyolefin resin such as crystalline polyethylene or polypropylene, at least one monomer selected from the group consisting of ethylene, propylene, and 1-butene is more preferred from the viewpoint of improving high-temperature peel strength and chemical resistance such as electrolyte resistance.

[0024] Examples of unmodified polyolefins include polyethylene, polypropylene, random copolymers of propylene and ethylene, block copolymers of propylene and ethylene, random copolymers of ethylene and α-olefins, block copolymers of ethylene and α-olefins, random copolymers of propylene and α-olefins, and block copolymers of propylene and α-olefins. These can be used individually or in combination of two or more. Examples of α-olefins include 1-butene, isobutylene, 1-hexene, and 1-octene.

[0025] Among these, when the substrate is a non-polar polyolefin resin that is difficult to adhere, such as crystalline polyethylene or polypropylene, polypropylene polymers such as propylene-ethylene copolymer, propylene-1-butene copolymer, and propylene-ethylene-1-butene copolymer are even more preferred, and propylene-1-butene copolymer is particularly preferred, from the viewpoint of improving high-temperature peel strength and chemical resistance such as electrolyte resistance. Furthermore, it is particularly preferable that the propylene units in the unmodified polyolefin be 50% by mass or more.

[0026] Furthermore, in the adhesive composition of this embodiment, the content of monomer units consisting of 1-butene in the acid-modified polyolefin is preferably 5 mol% to 40 mol%, and more preferably 10 mol% to 30 mol%, relative to the total monomer units constituting the acid-modified polyolefin, from the viewpoint of peel strength, high-temperature peel strength, etc.

[0027] Known methods can be used for acid modification to obtain acid-modified polyolefins. Examples of acid modification methods include graft modification, in which a carboxylic acid anhydride-containing monomer, or a carboxylic acid anhydride-containing monomer and a carboxylic acid anhydride-containing monomer are added to a polyolefin in the presence of a known radical polymerization initiator such as an organic peroxide or an aliphatic azo compound in a melt kneading or organic solvent. Other acid modification methods include copolymerization of a carboxylic acid anhydride-containing monomer, or a carboxylic acid anhydride-containing monomer and olefins.

[0028] Examples of monomers containing carboxylic acid groups include compounds that have an ethylenic double bond and a carboxylic acid group within the same molecule, and specifically include various unsaturated monocarboxylic acid compounds, unsaturated dicarboxylic acid compounds, and unsaturated tricarboxylic acid compounds.

[0029] Examples of unsaturated monocarboxylic acid compounds include acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid. Examples of unsaturated dicarboxylic acid compounds include maleic acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, nadic acid, and endic acid. Examples of unsaturated tricarboxylic acid compounds include aconitic acid.

[0030] As carboxylic acid group-containing monomers, unsaturated dicarboxylic acid compounds and unsaturated tricarboxylic acid compounds are preferred from the viewpoint of being easily acid-modified and having excellent adhesion, with maleic acid, itaconic acid, and aconitic acid being more preferred, and maleic acid being particularly preferred. These carboxylic acid group-containing monomers can be used individually or in combination of two or more. If some of the carboxylic acid group-containing monomers used for acid modification remain unreacted, it is preferable to remove the unreacted carboxylic acid group-containing monomers by known methods such as heat distillation or reprecipitation purification in order to suppress adverse effects on adhesion, and then use the resulting acid-modified polyolefin.

[0031] Furthermore, examples of monomers containing carboxylic anhydride groups include compounds that have an ethylenic double bond and a carboxylic anhydride group within the same molecule. Specifically, examples include acid anhydrides of the above-mentioned unsaturated monocarboxylic acid compounds, acid anhydrides of the above-mentioned unsaturated dicarboxylic acid compounds, and acid anhydrides of the above-mentioned unsaturated tricarboxylic acid compounds.

[0032] Examples of acid anhydrides of unsaturated monocarboxylic acid compounds include acrylic anhydride, methacrylic anhydride, crotonic anhydride, and isocrotonic anhydride. Examples of acid anhydrides of unsaturated dicarboxylic acid compounds include maleic anhydride (maleic anhydride), itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, nadic anhydride, and endicic anhydride. Examples of acid anhydrides of unsaturated tricarboxylic acid compounds include aconitic anhydride.

[0033] As monomers containing carboxylic anhydride groups, acid anhydrides of unsaturated dicarboxylic acid compounds and acid anhydrides of unsaturated tricarboxylic acid compounds are preferred, acid anhydrides of unsaturated dicarboxylic acid compounds are more preferred, maleic anhydride and itaconic anhydride are even more preferred, and maleic anhydride is particularly preferred, from the viewpoint of being easily acid-modified and having excellent adhesive properties. The above embodiment is preferred because it can reduce the amount of free carboxylic acid in the acid-modified polyolefin, and the pot life of the prepared adhesive composition is extended. These monomers containing carboxylic anhydride groups can be used individually or in combination of two or more. If some of the monomers containing carboxylic anhydride groups used for acid modification remain unreacted, it is preferable to remove the unreacted monomers containing carboxylic anhydride groups by known methods such as heat distillation and reprecipitation purification in order to suppress adverse effects on adhesive strength, and then use the resulting material as the acid-modified polyolefin.

[0034] The acid value of polyolefin resins containing acid-modified polyolefins is preferably 1 mg KOH / g or more, more preferably 5 mg KOH / g or more, and even more preferably 10 mg KOH / g or more, from the viewpoint of heat resistance, adhesion, and resistance to high temperatures and chemicals. Furthermore, the acid value of polyolefin resins containing acid-modified polyolefins is preferably 50 mg KOH / g or less, more preferably 40 mg KOH / g or less, and even more preferably 30 mg KOH / g or less, from the viewpoint of heat resistance, adhesion, and resistance to high temperatures and chemicals. The above acid value can be measured by infrared absorption spectroscopy, as will be described later.

[0035] The hydroxyl value of polyolefin resins containing acid-modified polyolefins is preferably 1 mg KOH / g or less, more preferably 0.5 mg KOH / g or more, and even more preferably 0.3 mg KOH / g or more, from the viewpoint of heat-resistant adhesion and high-temperature chemical resistance. The above hydroxyl value can be measured by neutralization titration in accordance with JIS K 0070:1992, as described later.

[0036] The melting point of the acid-modified polyolefin is preferably 50°C to 110°C. From the viewpoint of easily obtaining sufficient peel strength, the melting point of the acid-modified polyolefin is preferably 50°C or higher, and more preferably 60°C or higher. Furthermore, from the viewpoint of solubility in solvents and suppressing the decrease in fluidity of the adhesive composition due to polymer crystallization during low-temperature storage, the melting point of the acid-modified polyolefin is preferably 110°C or lower, and more preferably 100°C or lower.

[0037] The weight-average molecular weight of the acid-modified polyolefin is preferably 15,000 or more and 200,000 or less. From the viewpoint of heat-resistant adhesion and high-temperature chemical resistance, the weight-average molecular weight of the acid-modified polyolefin is preferably 15,000 or more, more preferably 30,000 or more, and even more preferably 40,000 or more. Furthermore, from the viewpoint of improving solubility in organic solvents in the adhesive composition, the weight-average molecular weight of the acid-modified polyolefin is preferably 200,000 or less, more preferably 150,000 or less, and even more preferably 100,000 or less. Note that the above weight-average molecular weight is the value obtained by converting the molecular weight measured by gel permeation chromatography (GPC) to polystyrene equivalent.

[0038] 1.2 Polyfunctional Isocyanate Compounds In the adhesive composition of this embodiment, the polyfunctional isocyanate compound is an important component as a crosslinking agent for forming crosslinks by reacting with at least the acid-modified sites in the acid-modified polyolefin contained in the polyolefin resin.

[0039] As the polyfunctional isocyanate compound, isocyanate compounds having an alicyclic structure and / or derivatives thereof, and aliphatic isocyanate compounds without an alicyclic structure and / or derivatives thereof can be preferably used. From the viewpoint of curability and adhesive strength in a high-temperature atmosphere, it is preferable that the polyfunctional isocyanate compound contains isocyanate compounds having an alicyclic structure and / or derivatives thereof, and aliphatic isocyanate compounds without an alicyclic structure and / or derivatives thereof. Examples of polyfunctional isocyanate compounds other than these components include diphenylmethane diisocyanate, xylylene diisocyanate, and their biuret, isocyanurate, or adduct forms. These can be used individually or in combination of two or more.

[0040] Isocyanate compounds and / or derivatives having an alicyclic structure have good compatibility with acid-modified polyolefins, which increases the crosslinking density of the cured adhesive composition, improves high-temperature peel strength, and reduces swelling of the adhesive composition due to electrolytes, etc. Aliphatic isocyanate compounds and / or derivatives without an alicyclic structure have the effect of improving adhesion to the adherend.

[0041] Examples of isocyanate compounds having an alicyclic structure include hydrogenated xylylene diisocyanate (including its structural isomers 1,2-bis(isocyanate methyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane, and 1,4-bis(isocyanate methyl)cyclohexane, as well as their stereoisomers), 4,4'-methylenebis(cyclohexyl isocyanate) and its structural isomers (2,2'-methylenebis(cyclohexyl isocyanate) and 2,4'-methylenebis(cyclohexyl isocyanate)), as well as their stereoisomers, norbornane dimethyl isocyanate, and isophorone diisocyanate (including its isomers).

[0042] As the isocyanate compound having an alicyclic structure, from the viewpoint such as having a high effect of improving the high-temperature peel strength, a diisocyanate compound having at least one or more alicyclic structures is preferable. Among these, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and 4,4'-methylenebis(cyclohexyl isocyanate) and its isomers are particularly preferable.

[0043] As the derivative of the isocyanate compound having an alicyclic structure, a compound containing an isocyanurate bond, a burette bond, a urethane bond and / or an allophanate bond is preferable, and a compound containing an isocyanurate bond is particularly preferable.

[0044] The derivative of the isocyanate compound having an alicyclic structure may have a urea bond and / or a uretdione bond.

[0045] As the isocyanate compound having an alicyclic structure, commercially available products can be used. Examples of the isocyanate compound having an alicyclic structure include HMDI (manufactured by Wanhua Chemical Japan Co., Ltd.), Desmodur W (manufactured by Sumika Covestro Urethane Co., Ltd.), Fortimo (manufactured by Mitsui Chemicals, Inc.), Takenate 600 (manufactured by Mitsui Chemicals, Inc.), Cosmonate NBDI (manufactured by Mitsui Chemicals, Inc.), IPDI (manufactured by Beyond Industries Limited), etc.

[0046] Examples of commercially available products of the compound having an isocyanurate bond include Desmodur Z4470BA (manufactured by Sumika Covestro Urethane Co., Ltd.), Takenate D127N (manufactured by Mitsui Chemicals, Inc.), Duranate T4900-70B (manufactured by Asahi Kasei Corporation), etc.

[0047] Examples of commercially available products of the compound having an allophanate bond include Desmodur XP2565 (manufactured by Sumika Covestro Urethane Co., Ltd.), etc.

[0048] Commercially available compounds containing urethane bonds include Takenate D-140N (manufactured by Mitsui Chemicals), which is an adduct of isophorone diisocyanate with trimethylolpropane, and Vestanat EP-DC1241 (manufactured by Evonik Japan), which is a monoadduct of isophorone diisocyanate with hydroxyethyl acrylate.

[0049] As for aliphatic isocyanate compounds that do not have an alicyclic structure, those having a linear alkyl group with 4 to 18 carbon atoms are preferred from the viewpoint of being highly effective in improving the peel strength of the adhesive composition at room temperature.

[0050] Examples of aliphatic isocyanate compounds that do not have an alicyclic structure include hexamethylene diisocyanate, pentamethylene diisocyanate, and tetramethylene diisocyanate. Among aliphatic isocyanate compounds that do not have an alicyclic structure, hexamethylene diisocyanate is preferred from the viewpoint of its high effect in improving adhesion to the adherend.

[0051] As derivatives of aliphatic isocyanate compounds that do not have an alicyclic structure, compounds containing isocyanurate bonds, biuret bonds, urethane bonds and / or allophanate bonds are preferred. Compounds containing isocyanurate bonds are particularly preferred from the viewpoint of improving adhesion to the adherend, room temperature peel strength and electrolyte resistance.

[0052] Derivatives of aliphatic isocyanate compounds that do not have an alicyclic structure may have urea bonds and / or uretdione bonds.

[0053] Commercially available derivatives of aliphatic isocyanate compounds that do not have an alicyclic structure can be used. Examples of commercially available compounds having an isocyanurate bond include Duranate TPA-100 (manufactured by Asahi Kasei Corporation), Duranate MFA-75B (manufactured by Asahi Kasei Corporation), Duranate TUL-100 (manufactured by Asahi Kasei Corporation), Duranate TSA-100 (manufactured by Asahi Kasei Corporation), Coronate HX (manufactured by Tosoh Corporation), and Takenate D-170N (manufactured by Mitsui Chemicals Corporation).

[0054] Examples of commercially available compounds containing a biuret bond include Duranate 24A-100 (manufactured by Asahi Kasei Corporation), Duranate 21S-75E (manufactured by Asahi Kasei Corporation), Takenate D-165NN (manufactured by Mitsui Chemicals Corporation), and Desmodule N3200 (manufactured by Sumika Covestro Urethane Co., Ltd.).

[0055] Commercially available compounds containing urethane bonds include Duranate P301-75E (manufactured by Asahi Kasei Corporation), which is an adduct between hexamethylene diisocyanate and trimethylolpropane, and Sumijool HT (manufactured by Sumika Covestro Urethane Co., Ltd.).

[0056] Examples of commercially available compounds containing allophanate bonds include Desmodule XP2580 (manufactured by Sumika Covestro Urethane Co., Ltd.).

[0057] 1.3 Epoxy Resin In the adhesive composition of this embodiment, the epoxy resin, when used in combination with a polyfunctional isocyanate compound, is an important component mainly for improving the high-temperature chemical resistance of the adhesive layer formed when the adhesive composition is cured.

[0058] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, or hydrogenated versions thereof; glycidyl ester epoxy resins such as diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, glycidyl p-hydroxybenzoate, diglycidyl tetrahydrophthalate, diglycidyl succinate, diglycidyl adipic acid, diglycidyl sebacate, and triglycidyl trimellitic acid; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and 1,4-butanediol. Examples of glycidyl ether epoxy resins include glycidyl ether diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether; glycidylamine epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil, but are not limited to these. In addition, novolac-type epoxy resins such as phenol novolac epoxy resin, o-cresol novolac epoxy resin, and bisphenol A novolac epoxy resin can also be used.

[0059] Furthermore, examples of epoxy resins include brominated bisphenol A type epoxy resin, phosphorus-containing epoxy resin, epoxy resin having a dicyclopentadiene skeleton, epoxy resin having a naphthalene skeleton, anthracene type epoxy resin, tert-butylcatechol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, biphenyl type epoxy resin, bisphenol S type epoxy resin, and the like. These epoxy resins may be used individually or in combination of two or more.

[0060] As for the epoxy resin, one having two or more epoxy groups in a single molecule is preferred. This is because it can form a crosslinked structure through reaction with a polyolefin resin containing acid-modified polyolefin, thereby exhibiting high heat resistance.

[0061] As for the epoxy resin, polyfunctional epoxy resins having an alicyclic skeleton and epoxy resins having a polycyclic aromatic hydrocarbon skeleton are preferred from the viewpoint of easily ensuring sufficient adhesive strength. These can be used individually or in combination of two or more.

[0062] 1.4 Component Content 1.4.1 Total Amount of Polyolefin Resin, Polyfunctional Isocyanate Compound, and Epoxy Resin The adhesive composition of this embodiment has a total amount of polyolefin resin, polyfunctional isocyanate compound, and epoxy resin of 90% by mass or more of the total solids. By having a total amount of polyolefin resin, polyfunctional isocyanate compound, and epoxy resin of 90% by mass or more of the total solids, the adhesive layer can have high adhesion.

[0063] The total amount of polyolefin resin, polyfunctional isocyanate compound, and epoxy resin is preferably 92% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, from the viewpoint of heat resistance, adhesion, and high-temperature chemical resistance. In this disclosure, "total solids" of the adhesive composition means the sum of each component excluding the organic solvent.

[0064] 1.4.2 Content of Acid-Modified Polyolefin in Polyolefin Resin In the adhesive composition of this embodiment, from the viewpoint of adhesion, it is preferable to incorporate acid-modified polyolefin in a high content. Specifically, the content of acid-modified polyolefin in the polyolefin resin is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by weight or more, and all of the polyolefin resin may be acid-modified polyolefin.

[0065] 1.4.3 [EPOXY] + [NCO]) / [COOH] The adhesive composition of this embodiment satisfies the following formula (1): 0.5 ≤ ([EPOXY] + [NCO]) / [COOH] ≤ 50 ... Formula (1)

[0066] In formula (1), [EPOXY] represents the total number of moles of epoxy groups in the epoxy resin. Also, [NCO] represents the total number of moles of isocyanate groups in the polyfunctional isocyanate compound. [COOH] represents the total number of moles of carboxyl groups in the polyolefin resin containing acid-modified polyolefin. However, the carboxylic anhydride structure (-CO-O-CO-) contained in the polyolefin resin containing acid-modified polyolefin is included in the total number of moles of carboxyl groups as 2 moles per mole.

[0067] Specifically, [EPOXY] can be calculated from the content of epoxy resin contained in the adhesive composition and the epoxy group content of the epoxy resin contained in the adhesive composition. Furthermore, [NCO] can be calculated from the content of polyfunctional isocyanate compound contained in the adhesive composition and the isocyanate group content of the polyfunctional isocyanate compound contained in the adhesive composition. Furthermore, [COOH] can be calculated from the content of polyolefin resin containing acid-modified polyolefin contained in the adhesive composition and the acid value of polyolefin resin containing acid-modified polyolefin contained in the adhesive composition.

[0068] The lower limit of ([EPOXY] + [NCO]) / [COOH] is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2 or more, from the viewpoint of heat-resistant adhesion and high-temperature chemical resistance. On the other hand, the upper limit of ([EPOXY] + [NCO]) / [COOH] is preferably 30 or less, more preferably 10 or less, and even more preferably 6 or less, from the viewpoint of improving electrolyte resistance.

[0069] 1.4.4 [EPOXY] / [COOH] The adhesive composition of this embodiment can satisfy the following formula (2): 0.25 ≤ [EPOXY] / [COOH] ≤ 25 ... Formula (2) In formula (2), [EPOXY] and [COOH] are the same as those described above.

[0070] In this case, the heat resistance and high-temperature chemical resistance of the formed adhesive layer can be ensured.

[0071] The lower limit of [EPOXY] / [COOH] is preferably 0.5 or higher, more preferably 0.8 or higher, and even more preferably 1 or higher, from the viewpoint of heat-resistant adhesion and high-temperature chemical resistance. On the other hand, the upper limit of [EPOXY] / [COOH] is preferably 15 or lower, more preferably 5 or lower, and even more preferably 3 or lower, from the viewpoint of heat-resistant adhesion and high-temperature chemical resistance.

[0072] 1.4.5 [NCO] / [COOH] The adhesive composition of this embodiment can satisfy the following formula (3): 0.25 ≤ [NCO] / [COOH] ≤ 25 ... Formula (3) In formula (3), [NCO] and [COOH] are the same as those described above.

[0073] In this case, the heat resistance and high-temperature chemical resistance of the formed adhesive layer can be ensured.

[0074] The lower limit of [NCO] / [COOH] is preferably 0.5 or higher, more preferably 0.8 or higher, and even more preferably 1 or higher, from the viewpoint of adhesion to the substrate. On the other hand, the upper limit of [NCO] / [COOH] is preferably 15 or lower, more preferably 5 or lower, and even more preferably 3 or lower, from the viewpoint of high-temperature chemical resistance.

[0075] When the adhesive composition of this embodiment satisfies both formulas (2) and (3) described above, the heat resistance and high-temperature chemical resistance of the adhesive layer can be made more reliable compared to when only one of formulas (2) or (3) is satisfied.

[0076] 1.5 Other Components In addition to the polyolefin resin, polyfunctional isocyanate compound, and epoxy resin described above, the adhesive composition of this embodiment may also contain, for example, a curing catalyst, an organic solvent, and the like.

[0077] (Curing Catalyst) Examples of curing catalysts include a first curing catalyst that promotes the reaction between a polyfunctional isocyanate compound and an acid-modified polyolefin, and a second curing catalyst that promotes the reaction between epoxy resin and an acid-modified polyolefin. These can be used individually or in combination of two or more. The curing catalyst can also be called a curing accelerator. In improving adhesive strength, it is preferable to include only one of the first curing catalyst or the second curing catalyst.

[0078] When the adhesive composition contains a first curing catalyst, the crosslinking reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin is promoted, thereby ensuring both heat-resistant adhesion and high-temperature chemical resistance. Furthermore, when the adhesive composition contains a second curing catalyst, the crosslinking reaction between the epoxy resin and the acid-modified polyolefin is promoted, thereby ensuring both heat-resistant adhesion and high-temperature chemical resistance. Furthermore, when the adhesive composition contains both the first and second curing catalysts, both the crosslinking reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin, and the crosslinking reaction between the epoxy resin and the acid-modified polyolefin are promoted, thus ensuring an even greater balance of heat-resistant adhesion and high-temperature chemical resistance. Note that the first curing catalyst may be one that can promote the reaction between the epoxy resin and the acid-modified polyolefin, as long as it can promote the reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin. Similarly, the second curing catalyst may be capable of promoting the reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin, as long as it can promote the reaction between the epoxy resin and the acid-modified polyolefin.

[0079] The first curing catalyst is preferably a tertiary amine, a metal carboxylate or complex salt, or an organometallic compound. These can be used individually or in combination of two or more.

[0080] Examples of tertiary amines as the first curing catalyst include tetraalkylethylenediamines such as tetramethylethylenediamine; N,N'-dialkylbenzylamines such as dimethylbenzylamine; triethylenediamine, pentamethyldiethylenetriamine, N-ethylmorphilin, N-methylmorphilin, 1-methyl-4-dimethylamineethylpiperazine, and 1,8-diazabicyclo[5.4.0]undecene-7.

[0081] Examples of metal carboxylates and complex salts include metal acetates, metal hexanoates, metal octanates such as metal 2-ethylhexanoate, metal neodecanoates, metal laurates, metal stearates, metal oleates, and metal complex salts such as metal acetylacetonates.

[0082] The organometallic compound is not particularly limited as long as it is a metal compound having a bond between a metal atom and a carbon atom, but examples include organometallic oxides. Preferably, the metal is one or more metals selected from the group consisting of metals from Groups 7, 12, and 14 of the periodic table.

[0083] Of these, the first curing catalyst is more preferably a carboxylate salt, acetylacetonate, or organometallic compound of any of tin, zinc, or manganese, from the viewpoint of adhesion when the adhesive layer comes into contact with the electrolyte. Specifically, the first curing catalysts include zinc neodecanoate, dibutyltin dilaurate, dioctyltin dilaurate, dioctyltin diacetate, dibutyltin maleate, dibutyltin oxide, dioctyltin oxide, bis(neodecanoate)zinc, bis(2-ethylhexanoate)zinc, zinc distearate, zinc(II) acetylacetonate, bis(2-ethylhexanoate)manganese, etc. Of these, the first curing catalyst is more preferably dibutyltin dilaurate, dioctyltin dilaurate, and / or dioctyltin oxide from the viewpoint of balancing adhesion, electrolyte resistance, and heat resistance of the adhesive layer.

[0084] As the second curing catalyst, tertiary amines, tertiary amine salts, imidazole compounds, etc., are preferred. These can be used individually or in combination of two or more.

[0085] Examples of tertiary amines used as a second curing catalyst include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, and 1,8-diazabicyclo[5.4.0]undecene.

[0086] Examples of tertiary amine salts include formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene, and formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

[0087] Examples of imidazole compounds include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, and 2,4-diamino-6-[2 Examples include '-undecylimidazolyl-(1')']ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

[0088] The curing catalyst content (total content of the first and second curing catalysts) is preferably 0.001 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of polyolefin resin, polyfunctional isocyanate compound, and epoxy resin. A total curing catalyst content of 0.001 parts by mass or more makes it easier to obtain a sufficient catalytic effect, while a total curing catalyst content of 5 parts by mass or less makes it easier to ensure the storage stability of the adhesive composition and the pot life after curing agent addition.

[0089] (Organic Solvents) Organic solvents can be added, for example, to dissolve or disperse components such as polyolefin resins containing acid-modified polyolefins, or to make the adhesive composition liquid to facilitate the formation of an adhesive layer of a desired thickness.

[0090] Examples of organic solvents include aromatic organic solvents such as toluene and xylene; aliphatic organic solvents such as n-hexane; alicyclic organic solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane; ketone organic solvents such as acetone and methyl ethyl ketone; alcohol organic solvents such as methanol and ethanol; ester organic solvents such as ethyl acetate and butyl acetate; and propylene glycol ether organic solvents such as propylene glycol methyl ether, propylene glycol ethyl ether, and propylene glycol-t-butyl ether. These can be used individually or in combination of two or more.

[0091] The organic solvent is preferably one that can be easily removed by volatilization through heating of the adhesive composition, and is particularly preferable to use a mixed solvent of an aromatic or alicyclic organic solvent and an ester or ketone organic solvent.

[0092] The content of the organic solvent can be determined, for example, by the type of polyolefin resin containing the organic solvent and acid-modified polyolefin. Furthermore, the content of the organic solvent can also be determined for purposes such as adjusting viscosity and solid content concentration, taking into consideration the suitability of the coating device for applying the adhesive composition.

[0093] The content of the organic solvent is preferably 50% to 95% by mass, and more preferably 70% to 90% by mass, when the total amount of the polyolefin resin containing the organic solvent and acid-modified polyolefin is taken as 100% by mass. In this case, the adhesive composition is easy to apply to the adherend and has excellent workability.

[0094] The adhesive composition of this embodiment may also contain styrene-based thermoplastic elastomers, tackifiers, antioxidants, hindered amine-based light stabilizers, ultraviolet absorbers, antistatic agents, flame retardants, colorants, dispersants, adhesion promoters, defoamers, leveling agents, plasticizers, lubricants, fillers, etc. These can be used individually or in combination of two or more.

[0095] The adhesive composition of this embodiment can be manufactured using known methods. Specifically, examples include a method in which a solution obtained by dissolving an acid-modified polyolefin resin in an organic solvent is mixed with other components except for a polyfunctional isocyanate compound and epoxy resin, and then the resulting mixture is mixed with the isocyanate compound and epoxy resin. Alternatively, for example, the composition can be prepared by mixing an isocyanate compound with a first curing catalyst, mixing an epoxy resin with a second curing catalyst, and then mixing the resulting mixture with an acid-modified polyolefin resin, an organic solvent, and other components. The mixing temperature is preferably 40°C or lower, more preferably 10°C to 30°C.

[0096] The adhesive composition of this embodiment is preferably a multi-component type, in which at least one of an acid-modified polyolefin, a polyfunctional isocyanate compound, and an epoxy resin is stored in separate containers and mixed before use. Specifically, it can be a two-component or three-component adhesive composition. By storing it in this manner, the storage stability of the adhesive composition can be improved.

[0097] Furthermore, the descriptions in "2. Heat-fusible components" and "3. Packaging materials for energy storage devices," which will be described later, can be applied to "1. Adhesive compositions" individually or in any combination as needed.

[0098] 2. Heat-Fusable Member The heat-fusible member of this embodiment will be described with reference to Figures 1 and 2.

[0099] As illustrated in Figure 1, the heat-fusible member 1 of this embodiment comprises at least an adhesive layer 12 formed by curing the adhesive composition of this embodiment described above, a metal layer 13 joined to one side of the adhesive layer 12, and a heat-fusible resin layer 11 joined to the other side of the adhesive layer 12. The other side of the adhesive layer 12 means the side opposite to the one side of the adhesive layer 12.

[0100] As illustrated in Figure 2, the heat-fusible member 1 may further include another layer 14 joined to one side of the metal layer 13. Note that "one side of the metal layer 13" refers to the side opposite to the adhesive layer 12.

[0101] In other words, the heat-fusible member 1 illustrated in Figure 1 comprises, in order, a heat-fusible resin layer 11, an adhesive layer 12, and a metal layer 13. Similarly, the heat-fusible member 1 illustrated in Figure 2 comprises, in order, a heat-fusible resin layer 11, an adhesive layer 12, a metal layer 13, and another layer 14. The shape of the heat-fusible member 1 in this embodiment can be selected as appropriate.

[0102] The heat-fusible resin layer 11 is a layer containing a resin that melts when heated and can fuse the material constituting one side of the layer with the material constituting the other side of the layer. Preferably, this heat-fusible resin layer contains a resin that melts at a temperature of 50°C to 200°C. Examples of resins having such properties include polyolefin resins, polyamide resins, polyester resins, etc. These can be used individually or in combination of two or more. Among these, polyolefin resins are preferred from the viewpoint of being able to heat-fuse with sufficient strength. Furthermore, polypropylene is preferred as the polyolefin resin. In particular, when the heat-fusible member 1 is used to integrate with other members, unstretched polypropylene is more preferred from the viewpoint of having less dimensional change (shrinkage).

[0103] The heat-sealable resin layer 11 may, if necessary, contain additives such as lubricants, fillers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, colorants, dispersants, and adhesion promoters.

[0104] The thickness of the heat-sealable resin layer 11 is not particularly limited, depending on the material of the resin, etc., but can usually be 10 μm or more and 200 μm or less. For example, if the heat-sealable resin layer 11 is a layer containing unoriented polypropylene, the thickness of the heat-sealable resin layer 11 can preferably be 10 μm or more and 200 μm or less, more preferably 20 μm or more and 100 μm or less, and even more preferably 60 μm or more and 100 μm or less. When the thickness of the layer containing unoriented polypropylene is 10 μm or more and 200 μm or less, a heat-sealable composite product such as a sealed container can be obtained that is not easily damaged and has high durability.

[0105] The adhesive layer 12 is a layer formed by curing the adhesive composition of Embodiment 1 described above. That is, the adhesive layer 12 is a layer consisting of a cured product containing a reaction product of a polyolefin resin including an acid-modified polyolefin, a polyfunctional isocyanate compound, and an epoxy resin. The thickness of the adhesive layer 12 is not particularly limited, but is preferably 1 μm or more and 20 μm or less, and more preferably 2 μm or more and 10 μm or less. When the thickness of the adhesive layer is 1 μm or more and 20 μm or less, the heat-sealable member 1 can be easily processed, for example, by bending when it is in the form of a sheet.

[0106] The metal layer 13 is a layer containing a metal (including alloys, hereafter omitted). The metal is not particularly limited, but aluminum (including aluminum alloys, hereafter omitted) is usually used because of its excellent workability. The thickness of the metal layer 13 is not particularly limited, depending on its material and so on. For example, if the metal layer 13 is made of aluminum, the thickness of the metal layer 13 can be preferably 20 μm or more and 100 μm or less, more preferably 20 μm or more and 80 μm or less, and even more preferably 30 μm or more and 60 μm or less.

[0107] As described above, the heat-sealable member 1 of this embodiment may have another layer 14 on the surface of the metal layer 13. The material constituting the other layer 14 preferably includes a resin, from the viewpoint of protecting the metal layer 13. That is, the other layer 14 is preferably a resin layer. This resin is not particularly limited and can be, for example, a polyamide resin, a polyester resin, etc. One or more of these can be used in combination. The transparency of the resin layer is not particularly limited, but when this resin layer is transparent or translucent, an excellent appearance can be obtained when the heat-sealable composite product is used as a sealed container, etc. The thickness of the other layer 14 is not particularly limited and can be preferably 30 μm or more and 60 μm or less, more preferably 30 μm or more and 50 μm or less.

[0108] The method for manufacturing the heat-fusible member 1 illustrated in Figure 1 can be as follows, for example.

[0109] (1) A method of applying an adhesive composition to the surface of a metal foil, metal film, etc. for forming a metal layer 13, then removing any organic solvents that may be optionally contained in the adhesive composition to form an adhesive layer 12 before curing, and then bringing a resin film for forming a heat-fusible resin layer 11 (heat-fusible resin film) into contact with the surface on which the adhesive layer 12 is formed, and pressing it down while heating. (2) A method of applying an adhesive composition to the surface of a resin film for forming a heat-fusible resin layer 11 (heat-fusible resin film), then removing any organic solvents that may be optionally contained in the adhesive composition to form an adhesive layer 12 before curing, and then bringing a metal foil, etc. for forming a metal layer 13 into contact with the surface on which the adhesive layer 12 is formed, and pressing it down while heating.

[0110] Furthermore, the manufacturing method of the heat-fusible member 1 illustrated in Figure 2 can be as follows, for example: (3) Applying an adhesive composition to the surface of the metal layer 13 in a composite film having a resin layer constituting another layer 14 and a metal layer 13 formed by vapor deposition or the like on one side of the resin layer, then removing any organic solvent that may be optionally contained in the adhesive composition to form an adhesive layer 12 before curing, and then bringing the surface on which this adhesive layer 12 is formed into contact with a resin film for forming a heat-fusible resin layer 11 (heat-fusible resin film) and pressing them together while heating. (4) Applying an adhesive composition to the surface of a resin film for forming a heat-fusible resin layer 11 (heat-fusible resin film), then removing any organic solvent that may be optionally contained in the adhesive composition to form an adhesive layer 12 before curing, and then bringing the surface on which the metal layer 13 is formed in a composite film having a resin layer constituting another layer 14 and a metal layer 13 formed by vapor deposition or the like on one side of the resin layer into contact with the surface on which this adhesive layer 12 is formed, and pressing them together while heating. (5) A method of extruding a film for forming another layer 14 onto the surface of the metal layer 13 in the laminate obtained by the method of (1) or (2) above.

[0111] The adhesive composition is often applied to a material for forming a metal layer, such as metal foil, or to the surface of the metal layer 13 in a composite film comprising a metal layer 13 and other layers 14 (resin layers), but is not particularly limited. When metal foil is used as the metal layer 13, it is preferable to use aluminum foil with a thickness of 20 μm or more and 100 μm or less. This makes it possible to easily form a heat-sealable member 1 with suppressed damage. When a composite film is used, it is preferable that the metal layer 13 contains aluminum and the other layers 14 (resin layers) contain polyamide resin, polyester resin, etc. Furthermore, when manufacturing the heat-sealable member 1 shown in Figure 2 without using a composite film, that is, when employing the method of (5) above, it is preferable to use a film containing polyamide resin, polyester resin, etc. as the film for forming the other layers 14.

[0112] Furthermore, polyolefin resin films, polyamide resin films, polyester resin films, etc., can be used as the heat-sealable resin film. These resin films can be obtained by film-forming methods such as extrusion, casting, T-die, and inflation. The thickness of the heat-sealable resin film can usually be 10 μm or more and 200 μm or less. From the viewpoint of facilitating heat fusion to complete the heat-sealable member 1 and heat fusion when manufacturing heat-sealable composite products, polyolefin resin films are preferred, and unoriented polypropylene films are more preferred. When using this unoriented polypropylene film, the preferred thickness can be 10 μm or more and 200 μm or less, more preferably 20 μm or more and 100 μm or less, and even more preferably 60 μm or more and 100 μm or less.

[0113] The adhesive composition can be applied by conventionally known methods, such as using a bar coater or gravure coater. The thickness of the coating film and its drying temperature are not particularly limited. The drying temperature of the coating film can preferably be 30°C to 100°C.

[0114] As described above, the dried coating generally has adhesive and bonding properties, allowing two members to be bonded together without heating. However, when manufacturing the heat-fusible member 1, it can be subjected to pressing or other processes while being heated to a temperature that takes into account the melting point and melt viscosity of the resin component based on the polyolefin resin containing acid-modified polyolefin.

[0115] The heating and pressing conditions for completing the heat-sealable member 1 are not particularly limited, and are preferably set appropriately depending on the material of the metal layer 13 such as metal foil, the material of the heat-sealable resin film, the melting temperature, the composition of the adhesive layer 12, etc.

[0116] In the heat-sealable member 1, if the heat-sealable resin layer 11 includes unstretched polypropylene, a heat-sealable composite product such as a sealed container that is less prone to breakage and has excellent durability can be obtained.

[0117] The heat-sealable member 1 can be used in various industrial product fields, including the electrical, automotive, industrial, and other fields.

[0118] Examples of applications in the electrical field include packaging materials for energy storage devices such as secondary batteries (lithium-ion batteries, lithium-ion polymer batteries, etc.), decorative application of decorative sheets to mobile devices, television casings, and white goods casings, bonding of metal components to resin, and sealing of electronic components.

[0119] Examples of applications in the automotive sector include bonding metal / resin exterior materials to interior and exterior components such as pillars, moldings, door trims, spoilers, and roofs, as well as bonding genuine leather, fabric, instrument panel foam sheets, and decorative sheets to base materials.

[0120] Examples of industrial applications include industrial packaging materials and the bonding of films between layers of multilayer films such as barrier films.

[0121] Other applications include, for example, adhesives for logistics materials, building materials, daily necessities, and sporting goods.

[0122] Among these, the heat-sealable member 1 is preferred as a packaging material for energy storage devices because it has excellent adhesive properties and high electrolyte resistance.

[0123] Furthermore, the descriptions in "1. Adhesive Compositions" above and "3. Packaging Materials for Energy Storage Devices" below can be applied to "2. Heat-Fusable Members" individually or in any combination as needed.

[0124] 3. Packaging material for energy storage devices The packaging material for energy storage devices of this embodiment will now be described. The packaging material for energy storage devices of this embodiment has the heat-sealable member of this embodiment described above.

[0125] Examples of energy storage devices include secondary batteries such as lithium-ion batteries and lithium-ion polymer batteries. In these secondary batteries, an organic solvent that dissolves polyolefin is used in the electrolyte, so the effects of an adhesive composition that can achieve both heat resistance and high-temperature chemical resistance, and a heat-fusible member having an adhesive layer, can be fully demonstrated.

[0126] Examples of secondary batteries used as energy storage devices include laminate-type secondary batteries. Packaging materials for laminate-type secondary batteries can have a laminated structure. Specifically, a laminated structure may include a base layer that becomes the outside of the battery after the laminate-type secondary battery is formed, a barrier layer formed from metal foil such as aluminum foil or stainless steel foil to prevent the penetration of moisture and air, and a sealant layer intended to insulate the barrier layer from contacting the electrodes and electrolyte and to bond the outer periphery by heat fusion, in this order, with the barrier layer and sealant layer joined together by an adhesive layer. In this laminated structure, each layer may be formed from two or more layers. Furthermore, the barrier layer and base layer may be joined together by an adhesive layer.

[0127] In this laminate-type secondary battery packaging material, the sealant layer corresponds to the heat-fusible resin layer of the heat-fusible component, the barrier layer corresponds to the metal layer of the heat-fusible component, the adhesive layer between the sealant layer and the barrier layer corresponds to the adhesive layer of the heat-fusible component, and the base layer corresponds to the other layers of the heat-fusible component.

[0128] In packaging materials for laminate-type secondary batteries, a polyolefin film such as a polypropylene film can be suitably used as the sealant layer that comes into contact with the electrolyte.

[0129] In this case, the adhesive composition described above is mainly used as an adhesive solution dissolved in an organic solvent, and after being applied to a metal foil or a film for a sealant layer and dried, a laminate film can be formed by a method called dry lamination, which involves bonding the metal foil and the polyolefin film together, thereby creating a packaging material for laminate-type secondary batteries.

[0130] Furthermore, the descriptions of "1. Adhesive Composition" and "2. Heat-Fusable Member" mentioned above can be applied to "3. Packaging Material for Energy Storage Devices" individually or in any combination as needed.

[0131] This disclosure will be described more specifically with reference to examples, but is not limited thereto.

[0132] 1. Raw materials for the adhesive composition The following raw materials were prepared as raw materials for the adhesive composition.

[0133] (Polyolefin resin containing acid-modified polyolefin) ・Acid-modified polyolefin a1 100 parts by mass of propylene-butene copolymer (Mitsui Chemicals, "Tafmer® XM7070"), 150 parts by mass of toluene, 11 parts by mass of maleic anhydride, and 2 parts by mass of di-tert-butyl peroxide were added to a 1 L autoclave, and the temperature was raised to 140°C and stirred for 3 hours. After the resulting reaction solution was cooled, it was poured into a container with a large amount of methyl ethyl ketone while stirring, and stirred for a further 30 minutes to precipitate the resin. Subsequently, the slurry liquid containing the resin was separated from the acid-modified propylene-butene copolymer, maleic anhydride, and low molecular weight substances by centrifugation. Furthermore, the acid-modified propylene-butene copolymer separated by centrifugation was added while stirring to a new container with 2,000 parts by mass of methyl ethyl ketone that had been kept warm at 25°C, and stirring was continued for 1 hour. Subsequently, the slurry was centrifuged to further separate the acid-modified propylene-butene copolymer from maleic anhydride and low molecular weight substances. This procedure was repeated twice for purification. After purification, the mixture was dried under reduced pressure at 40°C for 5 hours to obtain acid-modified polyolefin a1. The obtained acid-modified polyolefin a1 had an acid value of 18 mg KOH / g, a hydroxyl value of 0 mg KOH / g, a melting point of 70°C, and a weight-average molecular weight of 79,000.

[0134] Acid-modified polyolefin a2 Acid-modified polyolefin a2 was obtained in the same manner as in the preparation of acid-modified polyolefin a1, except that the amount of maleic anhydride used as a raw material was changed to 6 parts by mass and the amount of di-tert-butyl peroxide was changed to 1 part by mass. The obtained acid-modified polyolefin a2 had an acid value of 10 mg KOH / g, a hydroxyl value of 0 mg KOH / g, a melting point of 73°C, and a weight-average molecular weight of 91,000.

[0135] Acid-modified polyolefin a3 was prepared by adding 1,000 parts by mass of propylene-butene copolymer (Mitsui Chemicals, "Tafmer® XM7080"), 15 parts by mass of maleic anhydride, 40 parts by mass of lauryl methacrylate, and 15 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane to a twin-screw extruder with L / D = 42 and φ = 58 mm. The reaction was carried out for a residence time of 10 minutes at a barrel temperature of 180°C (barrels 1 to 7). Degassing was performed in barrel 7 to remove any remaining unreacted material, thereby obtaining acid-modified polyolefin a3. The obtained acid-modified polyolefin a3 had an acid value of 27 mg KOH / g, a hydroxyl value of 0 mg KOH / g, a melting point of 84°C, and a weight-average molecular weight of 150,000.

[0136] Acid-modified polyolefin a4 was prepared by adding 1,000 parts by mass of ethylene-propylene copolymer (ExxonMobil Corporation's "Vistamax 3980FL"), 10 parts by mass of maleic anhydride, and 10 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane to a twin-screw extruder with L / D = 42 and φ = 58 mm. The reaction was carried out for a residence time of 10 minutes at a barrel temperature of 180°C (barrels 1 to 7). Degassing was performed in barrel 7 to remove any remaining unreacted material, thereby obtaining acid-modified polyolefin a4. The obtained acid-modified polyolefin a4 had an acid value of 10 mg KOH / g, a hydroxyl value of 0 mg KOH / g, a melting point of 77°C, and a weight-average molecular weight of 110,000.

[0137] Acid-modified polyolefin a5 Acid-modified polyolefin a5 was obtained in the same manner as in the preparation of acid-modified polyolefin a1, except that the raw material polyolefin was changed to a propylene-butene copolymer (Mitsui Chemicals, Ltd., "Tafmer® XM7090"), the amount of maleic anhydride was changed to 10 parts by mass, and the amount of di-tert-butyl peroxide was changed to 3 parts by mass. The obtained acid-modified polyolefin a5 had an acid value of 18 mg KOH / g, a hydroxyl value of 0 mg KOH / g, a melting point of 95°C, and a weight-average molecular weight of 59,000.

[0138] Acid-modified polyolefin a6 Acid-modified polyolefin a6 was obtained in the same manner as in the preparation of acid-modified polyolefin a3, except that the propylene-butene copolymer was replaced with "Tafmer (registered trademark) XM7080" manufactured by Mitsui Chemicals, Inc., 60 parts by mass of maleic anhydride, and 60 parts by mass of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane. The obtained acid-modified polyolefin a6 had an acid value of 40 mg KOH / g, a hydroxyl value of 0 mg KOH / g, a melting point of 86, and a weight-average molecular weight of 150,000.

[0139] Table 1 summarizes the acid value, hydroxyl value, melting point, and weight-average molecular weight of acid-modified polyolefins a1 to a6.

[0140]

[0141] The acid value, hydroxyl value, melting point, and weight-average molecular weight of the acid-modified polyolefins a1 to a6 described above were measured according to the following method.

[0142] -Measurement of Acid Value- (1) 35 g of unmodified polyolefin (in this experiment, propylene-butene copolymer or ethylene-propylene copolymer) and octadecyl succinic anhydride (no additive, 1 g, 2 g, 4 g) were weighed out before acid modification. These were placed in a laboplast mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) heated to 170°C, and heated and stirred to prepare samples with different octadecyl succinic anhydride content. (2) Small amounts of each sample were cut out, sandwiched between two 1 mm thick fluororesin sheets, and molded into a film by hot pressing at 110°C. This film was vacuum dried at 130°C for 5 hours to completely close the acid anhydride ring, cooled to room temperature, sealed in a moisture-proof bag with a desiccant, left at room temperature for more than one day, and then the infrared absorption spectrum was measured by transmission method. (3) From the transmission IR spectra of each sample, the absorption peak derived from the resin (in this experimental example, propylene-butene copolymer: approximately 1165 cm⁻¹) －１ Absorption of ethylene-propylene copolymer: approximately 1170 cm －１ Absorption of (in this experimental example, the absorption peak originating from acid anhydride was approximately 1799 cm⁻¹) －１ A calibration curve was created by plotting the absorbance ratio of the absorption peaks with the octadecyl succinic anhydride content. (4) Acid-modified polyolefins a1 to a6 were each vacuum-dried at 130°C for 5 hours to completely close the acid anhydride rings, cooled to room temperature, left in a dry state for more than one day, and then the infrared absorption spectra were measured by transmission. (5) The absorbance ratio of the absorption peaks derived from acid anhydride to the absorption peaks derived from resin was determined from the infrared absorption spectra measured in (4), and the acid value of each acid-modified polyolefin was measured by comparing it with the calibration curve created in (3).

[0143] - Measurement of Hydroxyl Value - The hydroxyl value of acid-modified polyolefins was measured in accordance with JIS K0070-1992. Specifically, an acetylating reagent was added to the sample and heated in a 92°C bath for 1 hour. After cooling, a small amount of water was added and heated in a 92°C bath for 10 minutes. After cooling, the hydroxyl value was determined by titrating the acid with potassium hydroxide ethanol solution using phenolphthalein solution as an indicator. In the above measurement, five times the amount of pyridine used in the method described in JIS K0070-1992 was used.

[0144] -Measuring the Melting Point- The melting point of the acid-modified polyolefin was measured in accordance with JIS K7121 (2012). Specifically, the melting point was determined from the temperature at which the secondary heating of the heat flux curve obtained using a differential scanning calorimeter was minimized. The heat flux curve was obtained by cooling approximately 10 mg of the sample to -50°C and holding for 5 minutes, heating to 150°C at a rate of 10°C / min and holding for 5 minutes, cooling to -50°C at a rate of 10°C / min and holding for 5 minutes, heating to 150°C at a rate of 10°C / min and holding for 5 minutes, and then cooling to -50°C at a rate of 10°C / min. The apparatus and atmosphere used for the measurement were as follows: Apparatus: DSC6220, manufactured by SII Nanotechnology Inc. Measurement atmosphere: Nitrogen atmosphere

[0145] - Measurement of Weight-Average Molecular Weight - The weight-average molecular weight of acid-modified polyolefins was determined by gel permeation chromatography (GPC) and converted to polystyrene equivalent. The apparatus and measurement conditions used were as follows: Apparatus: Tosoh Corporation, model "HLC-8320" Column: Tosoh Corporation, TSKgel-SuperMultipore HZ-M (4.6 mm ID × 15 cm) × 3 Solvent: Tetrahydrofuran column Temperature: 40°C Detector: RI (Differential Refractive Index Detector) Flow Rate: 350 μL / min

[0146] (Polyfunctional isocyanate compounds) ・Polyfunctional isocyanate compound b1 (polyisocyanate of hexamethylene diisocyanate) (manufactured by Asahi Kasei Corporation, "Duranate TPA-100", isocyanate group content: 5.50 mmol / g, NCO equivalent: 181.82 g / eq.) ・Polyfunctional isocyanate compound b2 (dicyclohexylmethane-4,4'-diisocyanate) (manufactured by Sumika Covestro Urethane Co., Ltd., "Desmodule W", isocyanate group content: 7.62 mmol / g, NCO equivalent: 131.25 g / eq.)

[0147] (Epoxy Resins) ・Epoxy resin c1 (Bisphenol A type epoxy resin) (Mitsubishi Chemical Corporation, "jER-828", epoxy group content: 5.26 mmol / g, epoxy equivalent: 190.11 g / eq.) ・Epoxy resin c2 (Dicyclopentadiene type epoxy resin) (DIC Corporation, "EPICLON HP-7200", epoxy group content: 3.85 mmol / g, epoxy equivalent: 259.74 g / eq.) ・Epoxy resin c3 (Bisphenol A type epoxy resin) (Mitsubishi Chemical Corporation, "jER-1001", epoxy group content: 2.11 mmol / g, epoxy equivalent: 475.00 g / eq.) ・Epoxy resin c4 (Cresol novolac type epoxy resin) (Chang Chun Plastics Co., Ltd. manufactured by ``CNE-195XL'', epoxy group content: 5.13 mmol / g, epoxy equivalent: 195.00 g / eq.)

[0148] (Curing catalysts) ・Curing catalyst d1 (dioctyltin dilaurate) (manufactured by Nitto Chemical Co., Ltd., "U-810") ・Curing catalyst d2 (2-ethyl-4 methylimidazole) (manufactured by Shikoku Chemicals Co., Ltd., "Curesol 2E4MZ") ・Curing catalyst d3 (2,4,6-tris(dimethylaminomethyl)phenol) (manufactured by Mitsubishi Chemical Corporation, "jER Cure 3010") Curing catalyst d1 corresponds to a first curing catalyst that promotes the reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin, and curing catalysts d2 and d3 correspond to second curing catalysts that promote the reaction between the epoxy resin and the acid-modified polyolefin.

[0149] (Organic solvents) Methylcyclohexane, methyl ethyl ketone, toluene

[0150] 2. Preparation of the adhesive composition A predetermined amount by mass shown in Tables 2 to 5 was measured out of a four-necked flask equipped with a condenser and a stirring motor, and a mixed organic solvent prepared by mixing a predetermined acid-modified polyolefin with methylcyclohexane, methyl ethyl ketone, and toluene. The mixture was heated to 70°C while stirring under a stream of dry nitrogen gas, and the acid-modified polyolefin was completely dissolved. The mixture was then cooled to room temperature. Next, the entire volume of a solution prepared by stirring and mixing a predetermined amount by mass shown in Tables 2 to 5, consisting of a predetermined epoxy resin, a polyfunctional isocyanate compound, and a curing catalyst, was added to this mixture and stirred to obtain a liquid adhesive composition (hereinafter sometimes referred to as adhesive solution).

[0151] 3. Total amount of polyolefin resin, polyfunctional isocyanate compound, and epoxy resin in the adhesive composition For each adhesive composition, the total amount (mass%) of polyolefin resin, polyfunctional isocyanate compound, and epoxy resin in the total solid content of each adhesive composition was calculated.

[0152] 4. ([EPOXY] + [NCO]) / [COOH], [EPOXY] / [COOH], and [NCO] / [COOH] in adhesive compositions For each adhesive composition, as described above, the values ​​of [EPOXY], which is the total number of moles of epoxy groups in the epoxy resin used in each adhesive composition, and [NCO], which is the total number of moles of isocyanate groups in the polyfunctional isocyanate compound, were calculated. In addition, the measured acid value results were converted to moles, and the value of [COOH], which is the total number of moles of carboxyl groups in the polyolefin resin containing acid-modified polyolefin (here, corresponding to acid-modified polyolefin), was calculated. In this case, the carboxylic acid anhydride structure (-CO-O-CO-) contained in the polyolefin resin containing acid-modified polyolefin was included in the total number of moles of carboxyl groups as 2 moles per mole. Furthermore, using the obtained values ​​of [EPOXY], [NCO], and [COOH], the values ​​of ([EPOXY] + [NCO]) / [COOH], [EPOXY] / [COOH], and [NCO] / [COOH] were calculated.

[0153] 5. Evaluation of the Adhesive Composition (Preparation of Test Specimens for Peel Adhesion Strength Evaluation) The adhesive solution was applied to 40 μm thick aluminum foil, which had been chemically treated on the surface to which the adhesive solution was applied, using a bar coater. At this time, the pitch of the bar coater was selected so that the average thickness of the adhesive layer after drying was 2 to 4 μm. In addition, the portion that would be clamped in the grips of the tensile testing machine during the subsequent measurement of peel adhesion strength was not coated with the adhesive solution. This aluminum foil was dried in an oven heated to 80°C for 1 minute, and an 80 μm thick CPP (cast polypropylene) film, which had been corona discharge treated on the surface to be in contact with the adhesive layer, was placed on top and bonded together by clamping in a roll laminator at a roll temperature of 80°C. This was then cured in an oven at 40°C for 7 days to allow the curing reaction to proceed, and then cut into 15 mm wide strips to be used as test specimens. For the test specimen of sample 28, it was cured in an oven at 80°C for 7 days.

[0154] -Measurement of T-peel adhesion strength- Using a tensile testing machine with a constant temperature chamber (Shimadzu Corporation, "Autograph AGS-X"), a T-peel test was performed at a tensile speed of 100 mm / min until the grips of the test specimen moved 100 mm. The average peel strength from 40 mm to 100 mm of movement was taken as the T-peel adhesion strength (N / 15 mm). The T-peel test was performed at room temperature (23°C).

[0155] We determined that heat-resistant adhesion was ensured if the peel adhesion strength (after 7 days at 40°C or 80°C, and at room temperature) was 8 N / 15 mm or higher.

[0156] -Measurement of chemical resistance- The test specimen was placed in a pressure vessel with a fluororesin wetted part, and the solvent was added and the container was sealed tightly until the specimen was completely submerged. The solvent used for immersion was a mixed solvent of ethylene carbonate (EC), diethylene carbonate (DEC), and dimethyl carbonate (DMC) (volume ratio 1 / 1 / 1) with LiPF ６An electrolyte solution containing 1 mol / L of [substance name] was used. This heat-resistant container was placed in an oven set to 85°C and left for 7 days. After that, the test specimens were removed, washed with water, and the surface water was wiped off. After being left for 20 minutes, the T peel adhesion strength (N / 15mm) was measured at room temperature (23°C) in the same manner as above.

[0157] We determined that high-temperature chemical resistance was ensured if the T-peel adhesion strength (after immersion at 85°C for 7 days, T-peel adhesion strength at room temperature) was 8 N / 15 mm or higher.

[0158] 6. Evaluation Results and Discussion The detailed composition and evaluation results of each adhesive composition are shown in Tables 2 to 5. Note that blank spaces in each table indicate that the specified component shown on the left side of each table is not included.

[0159]

[0160]

[0161]

[0162]

[0163] Tables 2 to 5 show the following: Samples 1C to 4C do not contain polyfunctional isocyanate compounds in their adhesive compositions. Therefore, Samples 1C to 4C could not ensure both heat resistance and high-temperature chemical resistance.

[0164] Samples 5C to 6C do not contain epoxy resin in their adhesive compositions. Therefore, while samples 5C to 6C were able to ensure heat resistance, they could not ensure high-temperature chemical resistance.

[0165] Although sample 7C contains the essential components of the adhesive composition, the value of ([EPOXY] + [NCO]) / [COOH] of the adhesive composition is below the lower limit specified in this disclosure and does not satisfy formula (1). Therefore, sample 7C could not ensure both heat-resistant adhesion and high-temperature chemical resistance.

[0166] Although sample 8C contains the essential components of the adhesive composition, the value of ([EPOXY] + [NCO]) / [COOH] of the adhesive composition exceeds the upper limit specified in this disclosure and does not satisfy formula (1). Therefore, sample 8C could not ensure both heat-resistant adhesion and high-temperature chemical resistance.

[0167] In contrast, Samples 1 to 28 satisfy the requirements specified in this disclosure for their adhesive compositions. Therefore, Samples 1 to 28 were able to ensure both heat-resistant adhesion and high-temperature chemical resistance.

[0168] This disclosure is not limited to the embodiments and examples described above, and various modifications are possible without departing from its essence. Furthermore, each configuration shown in the embodiments and examples can be combined in any way.

Claims

1. An adhesive composition comprising a polyolefin resin, a polyfunctional isocyanate compound, and an epoxy resin, wherein the polyolefin resin comprises an acid-modified polyolefin modified with a compound having at least one of a carboxylic acid group and a carboxylic anhydride group, the total amount of the polyolefin resin, the polyfunctional isocyanate compound, and the epoxy resin is 90% by mass or more of the total solids content, and satisfies the following formula (1). 0.5 ≤ ([EPOXY] + [NCO]) / [COOH] ≤ 50 ... Formula (1) (In Formula (1), [EPOXY] represents the total number of moles of epoxy groups in the epoxy resin, [NCO] represents the total number of moles of isocyanate groups in the polyfunctional isocyanate compound, and [COOH] represents the total number of moles of carboxyl groups in the polyolefin resin. However, the carboxylic anhydride structure (-CO-O-CO-) contained in the polyolefin resin is included in the total number of moles of carboxyl groups as 2 moles per mole.) 2. The adhesive composition according to claim 1, satisfying the following formulas (2) and (3): 0.25 ≤ [EPOXY] / [COOH] ≤ 25 ... Formula (2) 0.25 ≤ [NCO] / [COOH] ≤ 25 ... Formula (3) (In formulas (2) and (3), [EPOXY], [NCO], and [COOH] are the same as those described in claim 1.) 3. The adhesive composition according to claim 1, wherein the acid value of the polyolefin resin is 1 mg KOH / g or more and 50 mg KOH / g or less.

4. The adhesive composition according to claim 1, further comprising at least one of a first curing catalyst that promotes the reaction between the polyfunctional isocyanate compound and the acid-modified polyolefin, and a second curing catalyst that promotes the reaction between the epoxy resin and the acid-modified polyolefin.

5. The adhesive composition according to claim 1, wherein the hydroxyl value of the polyolefin resin is 1 mg KOH / g or less.

6. The adhesive composition according to claim 1, wherein at least one of the polyolefin resin, the polyfunctional isocyanate compound, and the epoxy resin is contained in separate containers.

7. A heat-sealable member comprising an adhesive layer formed by curing an adhesive composition according to any one of claims 1 to 6, a metal layer bonded to one side of the adhesive layer, and a heat-sealable resin layer bonded to the other side of the adhesive layer.

8. Packaging material for energy storage devices having the heat-sealable member described in claim 7.

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