JP2024063150A - Polyolefin-based adhesive composition - Google Patents

Abstract

[Problem] To provide an adhesive composition containing an acid-modified polyolefin and a polyfunctional polyisocyanate curing agent, which has a good pot life, and good adhesion between metal substrates and polyolefin resin substrates, chemical resistance, and moldability. [Solution] An adhesive composition containing an acid-modified polyolefin (A), a polyfunctional polyisocyanate curing agent (B), and an organic solvent (C), wherein the acid-modified polyolefin (A) is a propylene-α-olefin copolymer to which at least one of an α,β-unsaturated carboxylic acid and an acid anhydride thereof has been grafted, and the organic solvent (C) is a mixture of solvent (C1) which is one or more solvents selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, and solvent (C2) which is one or more solvents selected from the group consisting of alcohol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents. [Selected Figure] None

Description

The present invention relates to an adhesive composition that exhibits good adhesion between a polyolefin resin substrate and a metal substrate, chemical resistance, and moldability. More specifically, the present invention relates to an adhesive composition that contains an acid-modified polyolefin, a multifunctional polyisocyanate curing agent, and an organic solvent. In particular, the present invention relates to an adhesive composition for lithium ion batteries (hereinafter abbreviated as LiB), and a packaging material that is a laminate containing the adhesive composition.

In recent years, LiBs that can be made ultra-thin and compact have been actively developed for use in personal computers, mobile terminal devices such as mobile phones, video cameras, satellites, etc. Unlike the metal cans that have been used traditionally, the packaging material for these LiBs has come to be a laminate with a structure such as a base layer/barrier layer/sealant layer, due to its advantages of being lightweight and allowing the shape of the battery to be freely selected.

LiB contains propylene carbonate, ethylene carbonate,
The electrolyte layer is made of an electrolyte solution in which a lithium salt is dissolved in an aprotic solvent such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate, or a polymer gel impregnated with the electrolyte solution. If such a highly penetrating solvent passes through the sealant layer, it reduces the laminate strength between the barrier layer and the sealant layer, causing delamination, and ultimately causing the electrolyte to leak. The lithium salt that is the electrolyte of the battery is LiPF6,
However, these salts generate hydrofluoric acid through hydrolysis with moisture, which corrodes the barrier layer and reduces the laminate strength. Thus, battery packaging materials need to be resistant to electrolytes.

LiBs also need to be more resistant to harsh environments, assuming they will be used in a variety of environments. For example, when used in mobile devices, they must be leak-resistant in high-temperature environments of 60 to 70 degrees Celsius, such as inside a car. They also need to be water-resistant to prevent moisture from seeping in, assuming they are used in mobile phones and accidentally dropped in water.

Under these circumstances, various packaging materials for lithium batteries with improved electrolyte resistance have been proposed (see, for example, Patent Documents 1 to 3).

Furthermore, when battery packaging materials are used to encapsulate battery elements, they are molded in a mold to form a space to accommodate the battery elements. During this molding process, the battery packaging material is stretched, which can easily cause cracks or pinholes to form in the barrier layer at the flange of the mold. In particular, with the recent demand for smaller and thinner batteries, there is a demand for even thinner battery packaging materials, making such problems more likely to occur.

Under these circumstances, battery packaging materials with improved moldability have been proposed (see, for example, Patent Documents 4 and 5).

JP 2001-243928 A JP 2004-42477 A JP 2009-238475 A JP 2002-216714 A JP 2003-31188 A

However, the above-mentioned proposed packaging materials for lithium batteries are still insufficient in terms of electrolyte resistance and moldability, and even if the electrolyte resistance and moldability are greatly improved, problems remain.
Specifically, it is difficult to ensure both the pot life of the adhesive after the hardener is mixed and the electrolyte resistance (Patent Document 1), the lamination machine is restricted because the bonding is performed by extrusion lamination, and the polyolefin substrate is affected by heat shrinkage due to lamination at high temperatures (Patent Document 2), and the drying time is long because the polyolefin base material is water-based, which limits the production conditions (Patent Document 3). In addition, a process of coating an amide-based slip agent on the surface of the outer layer film is required, which reduces productivity, and the laminate strength between the outer layer film and the aluminum foil is not sufficient due to the coated amide-based slip agent (Patent Document 4). Since only an unstretched polypropylene resin film is arranged on the inner layer side of the aluminum foil, or only a film of a blended resin of polypropylene and polyethylene is arranged on the inner layer side of the aluminum foil, pinholes are generated in the aluminum foil when it is molded into a rectangular parallelepiped shape, or breaks (cracks) are easily generated in the aluminum foil, and sufficient moldability is not obtained (Patent Document 5).

The object of the present invention is to provide an adhesive composition that is excellent in adhesion, chemical resistance (electrolyte resistance) and moldability without problems such as pot life and restrictions on production conditions. It is also an object of the present invention to provide a battery packaging material that includes an adhesive layer made of the adhesive composition, and a battery that uses the packaging material.

In order to achieve the above object, the inventors conducted extensive research and discovered that it is effective to provide layers on both the outer and inner layers of the aluminum foil that can adequately accommodate the elongation that occurs during molding, leading to the proposal of the following invention.

An adhesive composition containing an acid-modified polyolefin (A), a multifunctional polyisocyanate curing agent (B) and an organic solvent (C), in which the acid-modified polyolefin (A) has an acid value of 2 to 50 mg KOH/g-resin and an acetone extractable component ratio of 0.01 to 2 mass%.

It is preferable that the polyfunctional polyisocyanate curing agent (B) is contained in an amount of 0.5 to 40 parts by mass, and the organic solvent (C) is contained in an amount of 80 to 2000 parts by mass, per 100 parts by mass of the acid-modified polyolefin (A). In addition, it is preferable that the organic solvent (C) is a mixture of solvent (C1) and solvent (C2), in which solvent (C1) is one or more solvents selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, solvent (C2) is one or more solvents selected from the group consisting of alcohol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents, and the ratio of solvent (C1)/solvent (C2) is 50 to 97/50 to 3 (mass ratio).

The adhesive composition is preferably used to bond a polyolefin resin substrate to a metal substrate.

A laminate of a polyolefin resin substrate and a metal substrate bonded with the adhesive composition, and a packaging material for lithium ion batteries having the laminate as a constituent member.

The adhesive composition of the present invention contains an acid-modified polyolefin, a multifunctional polyisocyanate curing agent, and an organic solvent, and can maintain a good pot life without thickening or gelling even when stored for a long period of time. Furthermore, even when the composition is bonded at a low temperature of 120°C or less, where the thermal shrinkage effect of the polyolefin substrate is small, and aged at a low temperature of 40°C or less, it is possible to achieve good adhesion between the polyolefin resin substrate and the metal substrate, as well as good chemical resistance and moldability.

According to the present invention, the adhesive can be sufficiently cured by the aging process after lamination while maintaining a good pot life, and excellent adhesion and chemical resistance can be achieved. Furthermore, it is possible to obtain an adhesive layer that satisfies the storage modulus and breaking elongation required to achieve excellent moldability.

The following describes in detail the embodiments of the present invention.

<Acid-modified polyolefin (A)>
The acid-modified polyolefin (A) used in the present invention is an acid-modified polyolefin having an acid value of 2 to 50 mg KOH/g-resin and an acetone extractable component ratio of 0.01 to 2 mass %.

The acid-modified polyolefin (A) used in the present invention is not limited, but is preferably one obtained by grafting at least one of polyethylene, polypropylene, and propylene-α-olefin copolymer with at least one of α,β-unsaturated carboxylic acid and its acid anhydride.

Propylene-α-olefin copolymers are copolymers of propylene with an α-olefin as the main component. As the α-olefin, for example, one or more of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used. Among these α-olefins, ethylene and 1-butene are preferred. There are no limitations on the ratio of the propylene component to the α-olefin component in the propylene-α-olefin copolymer, but the propylene component is preferably 50 mol% or more, and more preferably 70 mol% or more.

Examples of at least one of the α,β-unsaturated carboxylic acids and their acid anhydrides include maleic acid, itaconic acid, citraconic acid, and their acid anhydrides. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred. Specific examples include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc., and these acid-modified polyolefins can be used alone or in combination of two or more kinds.

From the viewpoint of adhesion between the polyolefin resin substrate and the metal substrate and resistance to electrolyte, the acid value of the acid-modified polyolefin (A) must be in the range of 2 to 50 mgKOH/g-resin. It is preferably in the range of 3 to 45 mgKOH/g-resin, more preferably 5 to 40 mgKOH/g-resin, and particularly preferably 7 to 35 mgKOH/g-resin. If it is less than the above value, compatibility with the curing agent may be poor. As a result, the crosslinking density may be low, and the adhesive strength and chemical resistance (resistance to electrolyte) may decrease. If it exceeds the above value, the molecular weight is low and the cohesive force is weak, so the adhesive strength and chemical resistance (resistance to electrolyte) may decrease. Furthermore, production efficiency also decreases, which is not preferable.

The acid value of the acid-modified polyolefin (A) can be adjusted by the amount of α,β-unsaturated carboxylic acid, α,β-unsaturated carboxylic acid anhydride, and radical generator used.

The acetone extractable component ratio of the acid-modified polyolefin (A) must be in the range of 0.01% to 2% by mass from the viewpoint of adhesion between the polyolefin resin substrate and the metal substrate and resistance to electrolyte. It is preferably 0.03% to 1.7% by mass, more preferably 0.05% to 1.4% by mass, even more preferably 0.07% to 1.2% by mass, and particularly preferably in the range of 0.1% to 1% by mass. If it is less than the above value, the production efficiency decreases, which is not preferable. If it exceeds the above value, the cohesive force may be weakened, resulting in poor adhesion, chemical resistance, and moldability.

The storage modulus (E') of the acid-modified polyolefin (A) at 25°C is preferably in the range of 10 to 2000 MPa from the viewpoint of adhesion and chemical resistance (electrolyte resistance) between the polyolefin resin substrate and the metal substrate. More preferably, it is 15 to 1700 MPa, even more preferably 20 to 1400 MPa, particularly preferably 25 to 1100 MPa, and most preferably 30 to 800 MPa. If it is less than the above value, the adhesive layer made of the adhesive composition may have insufficient cohesive force, and the adhesiveness and chemical resistance (electrolyte resistance) may be poor. If it exceeds the above value, the conformability of the adhesive layer made of the adhesive composition may decrease, and the adhesiveness may be poor. In addition, if it is within the above range, the adhesiveness and substrate conformability are improved, and the moldability of the laminate is also improved, making it more preferable as a packaging material for lithium-ion batteries.

The tensile elongation at break (Eb) of the acid-modified polyolefin (A) at 25°C is 50% to 100%.
0%. More preferably, it is 80% to 900%, even more preferably, it is 120% to 800%, particularly preferably, it is 160% to 700%, and most preferably, it is 200% to 600%. If it is less than the above value, the conformability of the adhesive layer made of the adhesive composition decreases, which may lead to pinholes during molding and poor moldability. In addition, the tensile breaking elongation (Eb) and the storage modulus (E') are generally contradictory properties, and if it exceeds the above value, the storage modulus (E') decreases, and the adhesiveness and electrolyte resistance may be poor. In addition, if it is within the above range, the adhesiveness and substrate conformability are improved, and the moldability of the laminate is also improved, making it more preferable as a packaging material for lithium ion batteries.

The weight average molecular weight (Mw) of the acid-modified polyolefin (A) is preferably in the range of 10,000 to 200,000. More preferably, it is in the range of 20,000 to 180,000, even more preferably in the range of 30,000 to 160,000, particularly preferably in the range of 40,000 to 140,000, and most preferably in the range of 50,000 to 110,000. If it is less than the above value, the cohesive force may be weak and the adhesiveness may be poor. On the other hand, if it exceeds the above value, the fluidity may be low and problems may occur in operability during adhesion. If it is within the above range, the curing reaction with the curing agent is utilized, which is preferable.

The crystallinity of the acid-modified polyolefin (A) refers to the fact that a clear melting peak is shown during the temperature rise from -100°C to 250°C at a rate of 20°C/min using a differential scanning calorimeter (DSC).

By making acid-modified polyolefin crystalline, it has the advantage of having stronger cohesive strength and better adhesiveness and chemical resistance than amorphous polyolefins.

The melting point (Tm) of the acid-modified polyolefin (A) is preferably in the range of 50°C to 120°C. More preferably, it is in the range of 60°C to 100°C, and most preferably, it is in the range of 70°C to 90°C. If it is less than the above value, the cohesive force derived from the crystals may be weak, and the adhesiveness and chemical resistance may be poor. On the other hand, if it exceeds the above value, the solution stability and fluidity may be low, and problems may occur in operability during adhesion.

The heat of fusion (ΔH) of the acid-modified polyolefin (A) is preferably in the range of 1 J/g to 60 J/g. More preferably, it is in the range of 3 J/g to 50 J/g, and most preferably in the range of 5 J/g to 40 J/g. If it is less than the above value, the cohesive force derived from the crystals may be weak, and the adhesiveness and chemical resistance may be poor. On the other hand, if it exceeds the above value, the solution stability and fluidity may be low, and problems may occur in operability during adhesion.

The method for producing the acid-modified polyolefin (A) is not particularly limited, and examples thereof include a radical graft reaction (i.e., a reaction in which radical species are generated in the main chain polymer and the radical species is used as the polymerization initiation point to graft polymerize an unsaturated carboxylic acid and an acid anhydride).

As the radical generator, although there is no particular limitation, it is preferable to use an organic peroxide. As the organic peroxide, although there is no particular limitation, peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, lauroyl peroxide, etc.; azonitriles such as azobisisobutyronitrile, azobisisopropionitrile, etc. can be mentioned.

<Multifunctional polyisocyanate curing agent (B)>
The polyfunctional polyisocyanate curing agent (B) used in the present invention is not particularly limited as long as it is a polyisocyanate having two or more isocyanate groups in one molecule, and well-known diisocyanates and compounds derived therefrom can be preferably used.
Examples of the diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, bis(4-isocyanatocyclohexyl)methane, and hydrogenated diphenylmethane diisocyanate. Further examples include compounds derived from the diisocyanates, that is, isocyanurates, adducts, biuret types, uretdione types, allophanate types, prepolymers having an isocyanate residue (low polymers obtained from diisocyanates and polyols), and complexes thereof. These may be used alone or in any combination of two or more.

In addition, a compound in which some of the isocyanate groups of the above isocyanate compounds are reacted with a compound having reactivity with the isocyanate groups may be used as a polyfunctional isocyanate curing agent. Examples of compounds reactive with isocyanate groups include compounds containing amino groups such as butylamine, hexylamine, octylamine, 2-ethylhexylamine, dibutylamine, ethylenediamine, benzylamine, and aniline; compounds containing hydroxyl groups such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, octanol, 2-ethylhexyl alcohol, dodecyl alcohol, ethylene glycol, propylene glycol, benzyl alcohol, and phenol; compounds containing epoxy groups such as allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and cyclohexanedimethanol diglycidyl ether; and compounds containing carboxylic acids such as acetic acid, butanoic acid, hexanoic acid, octanoic acid, succinic acid, adipic acid, sebacic acid, and phthalic acid.

As the multifunctional polyisocyanate curing agent (B) used in the present invention, one having an isocyanurate of the above diisocyanate is preferred because it has excellent electrolyte resistance.

The amount of the polyfunctional polyisocyanate curing agent (B) used in the present invention is preferably in the range of 0.5 to 40 parts by mass, more preferably 1 to 35 parts by mass, even more preferably 2 to 30 parts by mass, and particularly preferably 3 to 25 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin (A). If it is less than the above value, sufficient curing effect may not be obtained, and adhesion and chemical resistance may be low. If it exceeds the above range, pot life and adhesion may decrease, and pinholes may occur during molding due to decreased followability. Furthermore, it is not preferable from the viewpoint of cost.

<Organic Solvent (C)>
The organic solvent (C) used in the present invention is not particularly limited as long as it dissolves the acid-modified polyolefin (A) and the polyfunctional polyisocyanate curing agent (B).Specific examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as hexane, heptane, octane, and decane, alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane, halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform, alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol, and ketones such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone. Cellosolves such as methyl cellosolve and ethyl cellosolve; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate and butyl formate; glycol ether solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether, and the like can be used alone or in combination of two or more of these.

The organic solvent (C) is preferably in the range of 80 to 2000 parts by mass relative to 100 parts by mass of the acid-modified polyolefin (A). More preferably, it is 90 to 1600 parts by mass, even more preferably 100 to 1200 parts by mass, and particularly preferably 110 to 800 parts by mass. If it is less than the above range, the solution state and pot life may be deteriorated, and if it exceeds the above range, it may be disadvantageous in terms of productivity, production cost, and transportation cost of the laminate and the LiB packaging material containing the laminate.

From the viewpoint of the solution state and pot life of the adhesive composition, the organic solvent (C) is preferably a mixture of one or more solvents (C1) selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, and one or more solvents (C2) selected from the group consisting of alcohol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents. The mixing ratio is preferably in the range of solvent (C1)/solvent (C2) = 50-97/50-3 (mass ratio), more preferably 55-95/45-5 (mass ratio), even more preferably 60-90/40-10 (mass ratio), and particularly preferably 70-80/30-20 (mass ratio). Outside the above range, the solution state and pot life of the adhesive composition may be reduced. It is also particularly preferable that the solvent (C1) is an aromatic hydrocarbon or an alicyclic hydrocarbon, and the solvent (C2) is a ketone-based solvent.

<Adhesive Composition>
The adhesive composition according to the present invention is a mixture of the acid-modified polyolefin (A), the polyfunctional polyisocyanate curing agent (B) and the organic solvent (C), and the acid-modified polyolefin (A) and the curing agent (B) may be dissolved or dispersed in the organic solvent (C). From the viewpoint of pot life, it is preferable that they are dissolved.

In the adhesive composition of the present invention, various tackifiers, thermoplastic elastomers, and plasticizers can be blended in addition to the acid-modified polyolefin (A), the polyfunctional polyisocyanate curing agent (B), and the organic solvent (C) as long as the performance of the present invention is not impaired. Examples of tackifiers include, but are not limited to, polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, and hydrogenated petroleum resins. Examples of thermoplastic elastomers include styrene-ethylene-butylene-styrene copolymer resins, styrene-ethylene-propylene-styrene and other styrene-based elastomers, ethylene-propylene copolymer resins, ethylene-butene copolymer resins, ethylene-vinyl acetate copolymer resins, and ethylene-ethyl acrylate copolymer resins, and other olefin-based elastomers. Examples of plasticizers include liquid rubbers such as polyisoprene and polybutene, and process oils. These tackifiers, thermoplastic elastomers, and plasticizers may be used alone or in combination of two or more.

In the adhesive composition of the present invention, various curing agents can be used in combination with the acid-modified polyolefin (A), the polyfunctional polyisocyanate curing agent (B), and the organic solvent (C) as long as the performance of the present invention is not impaired. Examples of the curing agent include, but are not limited to, epoxy resins, carbodiimide compounds, oxazoline compounds, coupling agents, and the like. Examples of the epoxy resin include glycidyl ester types such as hexahydrophthalic acid glycidyl ester and dimer acid glycidyl ester, triglycidyl isocyanurate, 3,4-epoxycyclohexylmethylcarboxylate, epoxidized polybutadiene, alicyclic or aliphatic epoxides such as epoxidized soybean oil, glycidyl ether type epoxy resins, and glycidyl amine type epoxy resins. Examples of the carbodiimide compound include monocarbodiimide compounds such as dimethylcarbodiimide, diisopropylcarbodiimide, dicyclohexylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, and di-β-naphthylcarbodiimide, and polycarbodiimide compounds which can be produced by carrying out a decarboxylation condensation reaction of an organic diisocyanate such as an aliphatic diisocyanate, an aromatic diisocyanate, or an alicyclic diisocyanate in the presence of a condensation catalyst in the absence of a solvent or in an inert solvent. Examples of oxazoline compounds include monooxazoline compounds such as 2-oxazoline, 2-methyl-2-oxazoline, 2-phenyl-2-oxazoline, 2,5-dimethyl-2-oxazoline, and 2,4-diphenyl-2-oxazoline, and dioxazoline compounds such as 2,2'-(1,3-phenylene)-bis(2-oxazoline), 2,2'-(1,2-ethylene)-bis(2-oxazoline), 2,2'-(1,4-butylene)-bis(2-oxazoline), and 2,2'-(1,4-phenylene)-bis(2-oxazoline). Examples of coupling agents include silane coupling agents and titanate coupling agents.

The adhesive composition according to the present invention may contain a curing accelerator in addition to the acid-modified polyolefin (A), the polyfunctional polyisocyanate curing agent (B), and the organic solvent (C) within a range that does not impair the performance of the present invention. The curing accelerator is not particularly limited, but examples thereof include metal carboxylates, tertiary amines, quaternary ammonium salts, organic peroxides, hydrazine compounds, metal chelate compounds, phosphorus-containing compounds, and basic vulcanizing agents. Examples of the metal carboxylates include metal salts of carboxylic acids having 1 to 30 carbon atoms. Examples of the carboxylic acid constituting the carboxylate metal salt include aliphatic carboxylic acids such as acetic acid, butyric acid, octanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid, octenoic acid, erucic acid, elaidic acid, adipic acid, malonic acid, succinic acid, glutaric acid, citric acid, tartaric acid, malic acid, and diglycolic acid; aromatic carboxylic acids such as benzoic acid, chlorobenzoic acid, anisic acid, aminobenzoic acid, phthalic acid, terephthalic acid, naphthoic acid, naphthalenedicarboxylic acid, and benzenetricarboxylic acid; naphthenic acid; acetone acid, etc. Examples of the metal constituting the carboxylate metal salt include Li, Na, K, Mg, Ca, Zn, Al, Cu, Pb, Co, Fe, Mn, Sn, and Ti. Specific examples of the metal carboxylate include lithium acetate, sodium acetate, magnesium acetate, aluminum acetate, potassium butyrate, calcium butyrate, zinc butyrate, sodium octanoate, calcium octanoate, potassium decanoate, magnesium decanoate, zinc decanoate, lithium laurate, sodium laurate, calcium laurate, aluminum laurate, potassium myristate, sodium myristate, aluminum myristate, sodium palmitate, zinc palmitate, magnesium palmitate, sodium stearate, potassium stearate, calcium stearate, and stearic acid. Examples of the suitable oleic acid salts include zinc, sodium oleate, sodium behenate, sodium benzoate, zinc benzoate, sodium phthalate, aluminum phthalate, magnesium terephthalate, calcium naphthalenedicarboxylate, dibutyltin laurate, tributyltin laurate, dioctyltin laurate, tributyltin acetate, dibutyltin diacetate, dioctyltin diacetate, dibutyltin 2-ethylhexoate, tetrabutyl titanate, tetraisobutyl titanate, tetra 2-ethylhexyl titanate, cobalt naphthenate, copper naphthenate, magnesium naphthenate, cobalt acetoacetate, etc. Among these, preferred are lithium laurate, sodium laurate, calcium laurate, aluminum laurate, potassium myristate, sodium myristate, aluminum myristate, sodium palmitate, zinc palmitate, magnesium palmitate, sodium stearate, potassium stearate, calcium stearate, zinc stearate, and sodium oleate. As the metal salt of carboxylic acid, a polymer having a metal salt structure of carboxylic acid can be used. Examples of such polymers include those having a structure obtained by copolymerizing ethylene with a radical polymerizable carboxylic acid salt of a metal of Group IA, Group IIA, Group IIB, or Group IIIB (e.g., Li, Na, K, Mg, Ca, Zn, Al, etc.); and those having a structure obtained by multi-component copolymerization of ethylene with a metal salt of a radical polymerizable carboxylic acid and another radical polymerizable carboxylic acid and/or its derivative. Examples of the tertiary amines include dimethylaniline, triethanolamine, and dimethyl-p-toluidine. Examples of the hydrazine compounds include 1-acetyl-2-phenylhydrazine. Examples of the metal chelate compounds include vanadium acetylacetonate. Examples of the phosphorus-containing compounds include dimethylphosphine and triphenylphosphine. Examples of the basic vulcanizing agents include hexamethylenetetramine, n-butylaldehyde-aniline condensate, etc.

In addition to the acid-modified polyolefin (A), the polyfunctional polyisocyanate curing agent (B) and the organic solvent (C), various additives may be added to the adhesive composition of the present invention, provided that the performance of the present invention is not impaired. The additives are not particularly limited, but it is preferable to use a flame retardant, a pigment, an antiblocking agent, etc.

<Laminate>
The laminate of the present invention is obtained by laminating a polyolefin resin substrate and a metal substrate with the adhesive composition of the present invention.

The lamination method can utilize a conventionally known laminate manufacturing technique. For example, although not particularly limited, the adhesive composition is applied to the surface of the metal substrate using a suitable application means such as a roll coater or a bar coater, and then dried. After drying, while the layer of the adhesive composition (adhesive layer) formed on the surface of the metal substrate is in a molten state, a polyolefin resin substrate is laminated and bonded (laminated) to the applied surface to obtain a laminate.
The thickness of the adhesive layer formed from the adhesive composition is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 0.8 to 9.5 μm, and even more preferably 1 to 9 μm.

<Polyolefin resin substrate>
The polyolefin resin substrate may be appropriately selected from conventionally known polyolefin resins. For example, polyethylene, polypropylene, ethylene-propylene copolymer, etc. may be used, but are not particularly limited thereto. Among them, the use of a non-oriented polypropylene film (hereinafter also referred to as CPP) is preferred. The thickness is not particularly limited, but is preferably 20 to 100 μm, more preferably 25 to 95 μm, and even more preferably 30 to 90 μm. The polyolefin resin substrate may be blended with pigments or various additives as necessary, or may be subjected to a surface treatment.

<Metal substrate>
The metal substrate is not particularly limited, and may be, for example, various metals and alloys thereof, such as aluminum, copper, steel, chromium, zinc, duralumin, and die-casting. The substrate may be in any shape, such as metal foil, rolled steel plate, panel, pipe, can, or cap. In general, aluminum foil is preferred from the viewpoint of workability. Although it may vary depending on the purpose of use, it is generally used in the form of a sheet having a thickness of 0.01 to 10 mm, preferably 0.02 to 5 mm.
The surfaces of these metal substrates may be either previously treated or left untreated, with the same effects being achieved in either case.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples. In the examples and comparative examples, parts simply indicate parts by mass.

<Production Example of Acid-Modified Polyolefin (A)>
Production Example 1
Into a 1 L autoclave, 100 parts by mass of a propylene-ethylene copolymer (storage modulus at 25°C: 320 MPa, tensile elongation at break at 25°C: 760%), 233 parts by mass of toluene, 1 part by mass of maleic anhydride, and 0.5 parts by mass of di-tert-butyl peroxide were added, and the mixture was heated to 140°C and further stirred for 1 hour (here, it is said to have been "reacted" for 1 hour).
The resulting reaction solution was then cooled to 100°C, and poured into a container containing 717 parts by mass of toluene and 950 parts by mass of methyl ethyl ketone, which had been preheated to 40°C, while stirring, cooled to 40°C, stirred for another 30 minutes, and further cooled to 25°C to precipitate a resin (here, the operation of pouring the reaction solution into a solvent such as methyl ethyl ketone while stirring and cooling to precipitate a resin is referred to as "reprecipitation"). The slurry containing the resin was then centrifuged to separate the acid-modified propylene-ethylene copolymer in which maleic anhydride had been graft-polymerized, (poly)maleic anhydride, and low-molecular-weight substances.
Furthermore, the acid-modified propylene-ethylene copolymer extracted by centrifugation was poured into a container containing 2000 parts by mass of new methyl ethyl ketone previously kept at 25° C. while stirring, and stirring was continued for 1 hour. Thereafter, the slurry liquid was centrifuged to further separate the acid-modified propylene-ethylene copolymer from the (poly)maleic anhydride and low molecular weight substances. This operation was repeated twice for purification (here, the operation of strengthening purification by pouring the acid-modified propylene-ethylene copolymer extracted by centrifugation into methyl ethyl ketone while stirring and centrifuging again is referred to as "reslurry").
After purification, the mixture was dried at 70°C under reduced pressure for 5 hours to obtain an acid-modified polyolefin, maleic anhydride-modified propylene-ethylene copolymer (PO-1, acid value 2 mg KOH/g-resin, acetone extractable component ratio 0.1 mass%, storage modulus at 25°C 300 MPa, storage elasticity at 25°C 300 MPa, storage elasticity at 25°C 300 MPa).
The polymer had a tensile elongation at break of 600%, a weight average molecular weight of 190,000, a Tm of 88° C., and a ΔH of 37 J/g.

Production Example 2
The same procedures as in Production Example 1 were carried out except that the amount of maleic anhydride charged was changed to 3 parts by mass, the number of reslurries was changed to 1, and the amount of methyl ethyl ketone charged during the reslurry was changed to 1,000 parts by mass, thereby obtaining an acid-modified polyolefin, a maleic anhydride-modified propylene-ethylene copolymer (PO-2, acid value 5 mg KOH/g-resin, acetone extractable component ratio 1.8 mass%, storage modulus at 25° C. 280 MPa, tensile break elongation at 25° C. 650%, weight average molecular weight 180,000, Tm 88° C., ΔH 36 J/g).

Production Example 3
A maleic anhydride-modified propylene-ethylene copolymer (PO-3, acid value 48 mg KOH/g-resin, acetone extractable component ratio 0.1 mass%, storage modulus at 25° C. 180 MPa, tensile elongation at 25° C. 35%) was obtained as an acid-modified polyolefin by the same procedure as in Production Example 1, except that the amount of toluene charged was 150 parts by mass, the amount of maleic anhydride charged was 40 parts by mass, the amount of di-tert-butyl peroxide charged was 8 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 700 parts by mass of methyl ethyl ketone, and the number of reslurries was 5.
0%, weight average molecular weight 31,000, Tm 85°C, ΔH 31 J/g).

Production Example 4
The same procedure as in Production Example 1 was repeated except that the amount of toluene charged was 150 parts by mass, the amount of maleic anhydride charged was 40 parts by mass, the amount of di-tert-butyl peroxide charged was 8 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 700 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1000 parts by mass of methyl ethyl ketone, and the number of reslurries was 3. An acid-modified polyolefin, maleic anhydride-modified propylene-ethylene copolymer (PO-4, acid value 48 mg KOH/g-resin, acetone extractable component ratio 1.8% by mass, storage modulus at 25° C. 150 MPa, tensile elongation at break 300% at 25° C., weight average molecular weight 2
7,000, Tm 85°C, ΔH 30 J/g).

Production Example 5
A maleic anhydride-modified propylene-ethylene copolymer (PO-5, acid value 25 mg KOH/g-resin, acetone extractable component ratio 0.9 mass%, storage modulus at 25° C. 400 MPa, tensile elongation at break 500% at 25° C., weight average molecular weight 600 nm, weight average molecular weight 1 ...
0,000, Tm 87°C, ΔH 35 J/g).

Production Example 6
A maleic anhydride-modified propylene-ethylene copolymer (PO-6, acid value 25 mg KOH/g-resin, acetone extractable component ratio 1.0% by mass, storage modulus at 25 ° C. 52 MPa, tensile elongation at break 1050% at 25 ° C.) was used as 100 parts by mass, toluene was charged at 150 parts by mass, maleic anhydride was charged at 30 parts by mass, di-tert-butyl peroxide was charged at 6 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 700 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1000 parts by mass of methyl ethyl ketone, and the number of reslurries was changed to 2 times. The same procedures as in Production Example 1 were carried out to obtain an acid-modified polyolefin, a maleic anhydride-modified propylene-ethylene copolymer (PO-6, acid value 25 mg KOH/g-resin, acetone extractable component ratio 1.0% by mass, storage modulus at 25 ° C. 12 MPa, tensile elongation at break 900% at 25 ° C., weight average molecular weight 60,000, Tm 58 ° C., ΔH 7 J/g).

Production Example 7
A maleic anhydride-modified propylene homopolymer (PO-7, acid value 25 mg KOH / g-resin, acetone extractable component ratio 0.9 mass%, storage modulus at 25 ° C. 2100 MPa, tensile elongation at break 900% at 25 ° C.) was used as 100 parts by mass, toluene was charged as 150 parts by mass, maleic anhydride was charged as 30 parts by mass, di-tert-butyl peroxide was charged as 6 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 700 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1000 parts by mass of methyl ethyl ketone, and the number of reslurries was changed to 2 times. The same procedures as in Production Example 1 were carried out to obtain an acid-modified polyolefin, a maleic anhydride-modified propylene homopolymer (PO-7, acid value 25 mg KOH / g-resin, acetone extractable component ratio 0.9 mass%, storage modulus at 25 ° C. 1800 MPa, tensile elongation at break 60% at 25 ° C., weight average molecular weight 60,000, Tm 85 ° C., ΔH5J / g).

Production Example 8
A maleic anhydride-modified propylene-ethylene copolymer (storage modulus at 25 ° C.: 2720 MPa, tensile elongation at break at 25 ° C.: 400%) was used in an amount of 100 parts by mass, toluene was charged in an amount of 186 parts by mass, maleic anhydride was charged in an amount of 20 parts by mass, di-tert-butyl peroxide was charged in an amount of 6 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 700 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1000 parts by mass of methyl ethyl ketone, and the number of reslurries was changed to 2 times. The same procedures as in Production Example 1 were carried out to obtain an acid-modified polyolefin, a maleic anhydride-modified propylene-ethylene copolymer (PO-8, acid value 25 mg KOH / g-resin, acetone extractable component ratio 1.0 mass%, storage modulus at 25 ° C.: 2350 MPa, tensile elongation at break at 25 ° C.: 38%, weight average molecular weight 60,000, Tm 125 ° C., ΔH 63 J / g).

Production Example 9
A maleic anhydride-modified propylene-ethylene copolymer (PO-9, acid value 25 mg KOH/g-resin, acetone extractable component ratio 1.2 mass%, storage modulus at 25° C. 7 MPa, tensile elongation at 25° C. 1200%, weight average molecular weight 60.0 mm2) was obtained as an acid-modified polyolefin by the same procedure as in Production Example 1, except that the amount of toluene charged was 186 parts by mass, the amount of maleic anhydride charged was 20 parts by mass, the amount of di-tert-butyl peroxide charged was 6 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 1200 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1200 parts by mass of methyl ethyl ketone, and the number of reslurries was changed to two.
0,000, no Tm peak, ΔH0 J/g).

Production Example 10
A maleic anhydride-modified propylene-ethylene copolymer (PO-10, acid value 1 mg KOH/g-resin, acetone extractable component ratio 0.1 mass%, storage modulus at 25 ° C. 400 MPa, tensile elongation at break at 25 ° C. 680%) was used as 100 parts by mass, toluene was charged at 150 parts by mass, maleic anhydride was charged at 0.5 parts by mass, di-tert-butyl peroxide was charged at 0.2 parts by mass, the reaction time was changed to 1 hour, the solvent used for reprecipitation was 1000 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1000 parts by mass of methyl ethyl ketone, and the number of reslurries was changed to two.
The polymer had a tensile elongation at break of 600%, a weight average molecular weight of 65,000, a Tm of 71° C., and a ΔH of 35 J/g.

Production Example 11
The amount of toluene charged was 150 parts by mass, the amount of maleic anhydride charged was 50 parts by mass, the amount of di-tert-butyl peroxide charged was 10 parts by mass, the reaction time was 3 hours, the solvent used for reprecipitation was 700 parts by mass of methyl ethyl ketone, the solvent used for reslurry was 1000 parts by mass of methyl ethyl ketone, and the number of reslurries was changed to 3 times. By carrying out the same procedures as in Production Example 1, a maleic anhydride-modified propylene-ethylene copolymer (PO-11, acid value 55 mg KOH/g-resin, acetone extractable component ratio 1.0 mass%, storage modulus at 25 ° C. 150 MPa, tensile elongation at break 320% at 25 ° C., weight average molecular weight 30,000, Tm 83 ° C., ΔH 25 J/g) was obtained as an acid-modified polyolefin.

Production Example 12
The same procedures as in Production Example 1 were carried out except that the amount of toluene charged was 150 parts by mass, the amount of maleic anhydride charged was 40 parts by mass, the amount of di-tert-butyl peroxide charged was 8 parts by mass, the reaction time was 3 hours, and the number of reslurries was 3 times. In the same manner as in Production Example 1, a maleic anhydride-modified propylene-ethylene copolymer (PO-12, acid value 46 mg KOH/g-resin, acetone extractable component ratio 4.5 mass%, storage modulus at 25° C. 110 MPa,
The tensile elongation at break at 25°C was 90%, the weight average molecular weight was 35,000, Tm was 86°C, and ΔH was 30 J/g.

(Preparation of main agent 1)
In a 500 ml four-neck flask equipped with a water-cooled reflux condenser and a stirrer, 100 parts by mass of the maleic anhydride modified propylene-ethylene copolymer (PO-1) obtained in Production Example 1, 280 parts by mass of methylcyclohexane, and 120 parts by mass of methyl ethyl ketone were charged, and the mixture was heated to 80° C. with stirring, and after stirring was continued for 1 hour, it was cooled to obtain main agent 1. The solution state is shown in Table 1.

(Preparation of base materials 2 to 19)
Main agents 2 to 19 were prepared in the same manner as main agent 1, except that the acid-modified polyolefin and organic solvent were changed as shown in Table 1. The blend amounts and solution states are shown in Table 1.

Example 1
500 parts by mass of the base agent 1 and Sumidur (
The results of evaluation of pot life, adhesion, chemical resistance and moldability are shown in Table 2.

Examples 2 to 21, Comparative Examples 1 to 3
The base resins 1 to 19 and the curing agents were changed as shown in Tables 2 and 3, and Examples 2 to 21 and Comparative Examples 1 to 3 were carried out in the same manner as in Example 1. The results of the blending amounts, pot life, adhesion, chemical resistance and moldability are shown in Tables 2 and 3.

The curing agents used in Tables 2 and 3 are as follows.
<Multifunctional polyisocyanate curing agent (B)>
Isocyanurate of hexamethylene diisocyanate: Sumidur (registered trademark) N
-3300 (manufactured by Bayer)
Biuret form of hexamethylene diisocyanate: Duranate (registered trademark) 24A-100 (manufactured by Asahi Kasei Chemicals Corporation)

The acid-modified polyolefins, base resins and adhesive compositions obtained as described above were subjected to analysis and evaluation according to the following methods.
Acid Number Measurement
The acid value (mg KOH/g-resin) in the present invention refers to the amount of KOH required to neutralize 1 g of acid-modified polyolefin (A), and was measured in accordance with the test method of JIS K0070 (1992). Specifically, 1 g of acid-modified polyolefin was dissolved in 100 g of xylene adjusted to a temperature of 100 ° C., and then titrated with 0.1 mol/L potassium hydroxide ethanol solution [product name "0.1 mol/L ethanolic potassium hydroxide solution", manufactured by Wako Pure Chemical Industries, Ltd.] at the same temperature using phenolphthalein as an indicator. At this time, the amount of potassium hydroxide required for titration was converted to mg to calculate the acid value (mg KOH/g).

Measurement of acetone extract component ratio The acetone extract component ratio in the present invention was measured by refluxing with acetone for 2 hours using a Soxhlet extractor. Specifically, 50 g of acid-modified polyolefin (A) was weighed out on a cylindrical filter paper and placed in a Soxhlet extraction tube, and then a flat-bottom flask containing 1100 mL of acetone and a cooling tube were attached and assembled, and acetone extraction was performed by refluxing in a water bath for 2 hours. Thereafter, the cylindrical filter paper was removed, the acetone extract in the flat-bottom flask was distilled off, and the weight of the residue after further drying under reduced pressure at 100°C for 1 hour was measured, and the value was calculated according to the following formula.
Acetone extract component ratio (mass%) = (extraction residue weight / sample amount) x 100

Measurement of storage modulus (E') at 25°C The storage modulus (E') in the present invention was measured in accordance with the test method of JIS K7244-4 (1999). Specifically, it is a value measured using a dynamic viscoelasticity measuring device DVA-200 manufactured by IT Measurement & Control Co., Ltd., at a frequency of 10 Hz while increasing the temperature from -50°C at a rate of 5°C/min.

Measurement of tensile elongation at break (Eb) at 25°C The tensile elongation at break (Eb) in the present invention was measured in accordance with the test method of JIS K7161 (2014). Specifically, it is the value measured as the elongation (%) at break when tensile at a speed of 50 mm/min in an environment of 25°C using a Tensilon RTM-100 manufactured by Orientec Corporation.

Measurement of Weight Average Molecular Weight (Mw) The weight average molecular weight in the present invention is a value measured using a gel permeation chromatograph Alliance e2695 manufactured by Nippon Waters (hereinafter referred to as GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-806 + KF-803, column temperature: 40° C., flow rate: 1.0 ml/min, detector: photodiode array detector (wavelength 254 nm = ultraviolet light)).

Measurement of Melting Point and Heat of Fusion The melting point and heat of fusion in the present invention are values measured using a differential scanning calorimeter (hereinafter, abbreviated as DSC, manufactured by TA Instruments Japan, Q-2000) from the top temperature and area of the melting peak when the material is heated and melted at a rate of 20° C./min, cooled to form a resin, and then heated and melted again.

Evaluation of the Solution State of the Main Agent The solution state of the main agents 1 to 19 was evaluated by measuring the solution viscosity at 25° C. using a Brookfield viscometer TVB-10M (hereinafter also referred to as a B-type viscometer) manufactured by Toki Sangyo Co., Ltd.
<Evaluation criteria>
◎ (Excellent for practical use): Less than 500 mPa·s ○ (Practical): 500 mPa·s or more and less than 1000 mPa·s × (Not practical): 1000 mPa·s or more or viscosity measurement impossible due to gelation

Pot life evaluation Pot life refers to the stability of a solution immediately after or after a certain time has elapsed since blending a crosslinking agent or a curing agent into an acid-modified polyolefin. When the pot life is good, the viscosity of the solution increases little and it can be stored for a long time, whereas when the pot life is poor, the viscosity of the solution increases (thickening) and, in severe cases, gelation occurs, making it difficult to apply to a substrate and making it impossible to store for a long time.
The pot life of the adhesive compositions obtained in Examples 1 to 21 and Comparative Examples 1 to 3 was evaluated by storing them in an atmosphere of 25° C. and 40° C. for 24 hours and then measuring the solution viscosity at 25° C. using a B-type viscometer. The evaluation results are shown in Tables 2 and 3.
<Evaluation criteria>
◎ (Excellent for practical use): Less than 500 mPa·s ○ (Practical): 500 mPa·s or more and less than 1000 mPa·s × (Not practical): 1000 mPa·s or more or viscosity measurement impossible due to gelation

Preparation of a laminate of a metal substrate and a polyolefin resin substrate An aluminum foil (manufactured by Sumikei Aluminum Foil Co., Ltd., 8079-0, thickness 40 μm) was used as the metal substrate , and a non-oriented polypropylene film (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) film CT, thickness 40 μm) (hereinafter also referred to as CPP) was used as the polyolefin resin substrate.
The adhesive compositions obtained in Examples 1 to 19 and Comparative Examples 1 to 15 were applied to a metal substrate using a bar coater, with the thickness of the adhesive layer adjusted to 3 μm after drying. The coated surface was dried for 1 minute in a 100° C. atmosphere using a hot air dryer, to obtain a metal substrate laminated with an adhesive layer having a thickness of 3 μm. A polyolefin resin substrate was placed on the surface of the adhesive layer, and the laminate was laminated at a lamination temperature of 80° C. or 120° C., 0.3 MPa, 1 m/min using a small tabletop test laminator (SA-1010-S) manufactured by Tester Sangyo Co., Ltd., at 25° C. or 120° C., and aged for 36 hours at 25° C. and 50% RH to obtain a laminate.

The laminate obtained as described above was evaluated using the following methods.

The laminate was cut into a size of 100 mm×15 mm, and the adhesion was evaluated by a T-peel test according to the following criteria. The evaluation results are shown in Tables 2 and 3.

<T-type peel test>
In accordance with the test method of ASTM-D1876-61, the peel strength was measured at a tensile speed of 50 mm/min in an environment of 25° C. using a Tensilon RTM-100 manufactured by Orientec Corporation. The peel strength (N/cm) between the metal substrate and the polyolefin resin substrate was taken as the average value of five test values.

<Evaluation criteria>
☆ (particularly excellent in practical use): 8.0 N/cm or more or CPP breaks (hereinafter, also simply referred to as "breakage"). Breakage refers to the destruction of the metal substrate or CPP without the occurrence of peeling at the interface between the metal substrate and CPP.
◎ (Excellent for practical use): 7.5 N/cm or more and less than 8.0 N/cm ○ (Practical): 7.0 N/cm or more and less than 7.5 N/cm × (Not practical): Less than 7.0 N/cm

Chemical resistance evaluation
In order to examine the usability as a packaging material for LiB, chemical resistance (hereinafter, also referred to as electrolyte resistance) was evaluated by an electrolyte test. The laminate was cut into a size of 100 mm x 15 mm and immersed in an electrolyte [ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (volume ratio) to which lithium hexafluorophosphate was added] at 85 ° C. for one day. Thereafter, the laminate was taken out, washed with ion-exchanged water, wiped off with a paper wiper, thoroughly dried, and the chemical resistance was evaluated by a T-peel test according to the following criteria. The evaluation results are shown in Tables 2 to 3.

<Evaluation criteria>
☆ (particularly excellent for practical use): 8.0 N/cm or more or material breakage ◎ (excellent for practical use): 7.5 N/cm or more and less than 8.0 N/cm ○ (practical): 7.0 N/cm or more and less than 7.5 N/cm × (not practical): less than 7.0 N/cm

Evaluation of formability Similarly, in order to examine the usability as a packaging material for LiB, the formability was evaluated using a deep drawing tester.
The laminate was cut into a size of 80 x 120 mm and cold-formed. Specifically, using a stretch forming machine (product number: TP-25C-X2) manufactured by Amada Co., Ltd., a forming die (female die) having a diameter of 55 mm x 35 mm, and a corresponding forming die (male die), cold forming was performed on 10 samples (laminates) at a 25 ° C. atmosphere with a pressing pressure of 0.4 MPa, changing the forming depth in 0.5 mm increments from a forming depth of 0.5 mm. For the samples after cold forming, the deepest forming depth at which wrinkles, pinholes in the aluminum foil, and cracks did not occur in all 10 samples was taken as the limit forming depth of the sample. From this limit forming depth, the formability of the battery packaging material was evaluated according to the following criteria. The evaluation results are shown in Tables 3 to 4.
<Criteria>
☆ (particularly excellent for practical use): limit forming depth 6.0 mm or more ◎ (excellent for practical use): limit forming depth 4.0 mm or more and less than 6.0 mm ○ (practical): limit forming depth 2.0 mm or more and less than 4.0 mm ×: limit forming depth less than 2.0 mm

The adhesive composition of the present invention contains an acid-modified polyolefin, a polyfunctional polyisocyanate curing agent, and an organic solvent, and maintains a good pot life without thickening or gelling even when stored for a long period of time, and can achieve good adhesion between a metal substrate and a polyolefin resin substrate, electrolyte resistance, and moldability. Therefore, a laminate of a polyolefin resin substrate and a metal substrate formed from the adhesive composition of the present invention can be widely used not only in fields such as outer panels of home appliances, furniture materials, and building interior components, but also as a packaging material (pouch form) for lithium batteries used in personal computers, mobile phones, video cameras, etc.

Claims (6)

An adhesive composition comprising an acid-modified polyolefin (A), a multifunctional polyisocyanate curing agent (B), and an organic solvent (C),
The acid-modified polyolefin (A) is a propylene-α-olefin copolymer grafted with at least one of an α,β-unsaturated carboxylic acid and an acid anhydride thereof,
The acid-modified polyolefin (A) has an acid value of 2 to 50 mg KOH/g-resin and an acetone extractable component ratio of 0.01 to 2 mass%,
The storage modulus (E') of the acid-modified polyolefin (A) at 25°C is 400 to 1800 MPa;
The tensile elongation at break (Eb) of the acid-modified polyolefin (A) at 25° C. is 60 to 500%,
The organic solvent (C) is a mixed liquid of a solvent (C1) and a solvent (C2), the solvent (C1) being one or more solvents selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, and the solvent (C2) being one or more solvents selected from the group consisting of alcohol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents.
Adhesive composition. The adhesive composition according to claim 1, which contains 0.5 to 40 parts by mass of a multifunctional polyisocyanate curing agent (B) and 80 to 2000 parts by mass of an organic solvent (C) per 100 parts by mass of the acid-modified polyolefin (A). The adhesive composition according to claim 1 or 2, wherein the ratio of solvent (C1)/solvent (C2) is 50-97/50-3 (mass ratio). The adhesive composition according to any one of claims 1 to 3, which is used for bonding a polyolefin resin substrate to a metal substrate. A laminate of a polyolefin resin substrate and a metal substrate bonded with the adhesive composition according to any one of claims 1 to 4. A packaging material for lithium ion batteries comprising the laminate according to claim 5 as a constituent member.