Polyolefin adhesive composition

Abstract

[Problem] The present invention provides an adhesive composition which achieves good adhesion between a polyolefin resin base material and a metal base material, while exhibiting electrolyte solution resistance and excellent heat resistance. The present invention also provides: a multilayer body which comprises an adhesive layer that is formed of the above-described adhesive composition; a packaging material which is required to have heat resistance and electrolyte solution resistance, and uses the above-described multilayer body; and a packaging material for lithium ion batteries, said packaging material comprising the above-described multilayer body as a constituent member. [Solution] An adhesive composition which contains (A) an acid-modified polyolefin, (B) an isocyanate curing agent and (C) an acid anhydride-containing compound, wherein from 0.1 part by mass to 20 parts by mass of the acid anhydride monomer (C) is contained relative to 100 parts by mass of the acid-modified polyolefin (A).

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition, a laminate, and a packaging material for lithium-ion batteries. [Background technology]

[0002] In recent years, lithium-ion batteries (hereinafter referred to as LiBs), which can be made ultra-thin and compact, have been actively developed for use in personal computers, mobile phones and other portable terminal devices, video cameras, satellites, etc. Unlike the metal cans that have been used conventionally, the packaging materials for these LiBs have the advantages of being lightweight and allowing for flexible selection of the battery shape, and so laminates with a structure such as a base layer / barrier layer / sealant layer have come to be used.

[0003] LiBs contain cathode and anode materials as the battery contents, as well as an electrolyte layer made of an electrolyte solution containing a lithium salt dissolved in an aprotic solvent such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate, or a polymer gel impregnated with such an electrolyte. If such highly permeable solvents penetrate the sealant layer, they can reduce the laminate strength between the barrier layer and the sealant layer, causing delamination and ultimately electrolyte leakage. Furthermore, while lithium salts used as battery electrolytes, such as LiPF6 and LiBF4, generate hydrofluoric acid upon hydrolysis with water, which corrodes the barrier layer and reduces laminate strength. Battery packaging materials must be resistant to these electrolytes.

[0004] 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 60-70°C, such as inside a car. They also need to be water-resistant to prevent water from seeping in, assuming they are used in mobile phones and accidentally dropped into water.

[0005] Under these circumstances, various packaging materials for lithium batteries with improved electrolyte resistance have been proposed (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 123183 Brochure [Patent Document 2] International Publication No. 2017 / 187904 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] However, the proposed adhesive composition was still insufficient in terms of heat resistance. Specifically, in-vehicle applications are expected to be used in even harsher environments than those used in general small LiB applications. Therefore, the proposed adhesive composition was still insufficient in terms of heat resistance and durability, as the adhesive strength of the adhesive after curing in a high-temperature environment was poor and the adhesive strength decreased after long-term immersion in an electrolyte solution.

[0008] The present invention provides an adhesive composition that exhibits good adhesion between a polyolefin resin substrate and a metal substrate, good electrolyte resistance, and excellent heat resistance, as well as a laminate including an adhesive layer made of the adhesive composition, a packaging material using the laminate that is required to have heat resistance and electrolyte resistance, and a packaging material for lithium-ion batteries that includes the laminate as a constituent member. [Means for solving the problem]

[0009] In order to achieve the above object, the present inventors have conducted extensive research and found that by blending predetermined amounts of an acid-modified polyolefin, an isocyanate curing agent, and an acid anhydride compound, it is possible to achieve excellent heat resistance and electrolyte resistance, as well as good adhesion, and have come to propose the following invention. That is, the present invention comprises the following configurations.

[0010] [1] An adhesive composition containing an acid-modified polyolefin (A), an isocyanate curing agent (B), and an acid anhydride-containing compound (C), wherein the amount of the acid anhydride monomer (C) is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the acid-modified polyolefin (A). [2] The acid anhydride group-containing compound (C) preferably contains a hydrocarbon group having 3 to 20 carbon atoms. [3] The acid-modified polyolefin (A) preferably has an acid value of 2 to 50 mgKOH / g. [4] It is preferable to contain 0.5 to 70 parts by mass of an isocyanate curing agent (B) and 80 to 2000 parts by mass of an organic solvent (D) per 100 parts by mass of the acid-modified polyolefin (A). [5] It is preferred that the organic solvent (D) is a mixed liquid of solvent (D1) and solvent (D2), in which solvent (D1) is one or more solvents selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, solvent (D2) is one or more solvents selected from oxygen-containing organic solvents, and the ratio of solvent (D1) / solvent (D2) is 50 to 97 / 50 to 3 (mass ratio). [6] The acid anhydride group-containing compound (C) preferably has a molecular weight of 100 g / mol or more and 500 g / mol or less, and an acid value of 150 mg KOH / g or more and 800 mg KOH / g or less. [7] An adhesive composition used for bonding a polyolefin resin substrate and a metal substrate. A laminate of a polyolefin resin substrate and a metal substrate bonded with the adhesive composition. A battery packaging material comprising the laminate described above as a constituent member. A lithium-ion battery packaging material comprising the laminate described above as a constituent member. [8] An adhesive composition for lithium-ion battery packaging materials, comprising an acid-modified polyolefin (A), an isocyanate curing agent (B), and an acid anhydride group-containing compound (C). [Effects of the Invention]

[0011] The adhesive composition of the present invention contains an acid-modified polyolefin, an isocyanate curing agent, and an acid anhydride, and therefore is able to exhibit good adhesion between a polyolefin resin substrate and a metal substrate, as well as long-term electrolyte resistance, and also exhibits excellent heat resistance after curing. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail.

[0013] <Acid-modified polyolefin (A)> The acid-modified polyolefin (A) used in the present invention is not limited, but an acid-modified α-olefin polymer or copolymer can be preferably used, and more preferably one obtained by grafting at least one of α,β-unsaturated carboxylic acid and its acid anhydride onto at least one of polyethylene, polypropylene, and propylene-α-olefin copolymer.

[0014] α-olefins having two or more carbon atoms include ethylene, propylene, 1-butene, 2-methyl-1-propene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, and ethyl-1-pentene. Examples of the α-olefins include 1-octene, methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. One or more of the above α-olefins can be polymerized to produce an α-olefin polymer or copolymer.

[0015] Propylene-α-olefin copolymers are copolymers of propylene with an α-olefin. Examples of α-olefins that can be used include ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, and vinyl acetate. Among these α-olefins, ethylene and 1-butene are preferred, with 1-butene being the most preferred.

[0016] The acid-modified polyolefin preferably has an acid functional group polymerized therein. The acid functional group can be at least one of α,β-unsaturated carboxylic acids and their derivatives, with acid anhydrides being preferred as the derivatives of α,β-unsaturated carboxylic acids. Examples of at least one of 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, with maleic anhydride being more preferred. Specific examples include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-1-butene copolymer, and maleic anhydride-modified propylene-ethylene-1-butene copolymer. These acid-modified polyolefins can be used alone or in combination of two or more. Among these, maleic anhydride-modified propylene-1-butene copolymer is preferred.

[0017] The acid value of the acid-modified polyolefin (A) is preferably in the range of 2 to 50 mgKOH / g from the viewpoints of adhesion to polyolefin resin substrates and crosslink density with the isocyanate curing agent (B). It is more preferably in the range of 3 to 40 mgKOH / g, even more preferably 4 to 30 mgKOH / g, and particularly preferably 5 to 20 mgKOH / g. When it is 2 mgKOH / g or more, the crosslink density increases, and therefore adhesion tends to be excellent. On the other hand, when it is 50 mgKOH / g or less, the pot life becomes good.

[0018] The melting point (Tm) of the acid-modified polyolefin (A) is preferably in the range of 50°C to 95°C, more preferably in the range of 60°C to 93°C, particularly preferably in the range of 65°C to 92°C, even more preferably in the range of 75°C to 90°C, and most preferably in the range of 78°C to 85°C. If the temperature is 50°C or higher, the cohesive force derived from crystals becomes strong, and adhesiveness and chemical resistance tend to be excellent. On the other hand, if the temperature is 95°C or lower, the pot life and fluidity become good, and operability during bonding improves.

[0019] The acid-modified polyolefin (A) preferably contains 40% by mass or more of propylene as an olefin component, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more. The higher the propylene content, the more improved the adhesion to polyolefin substrates.

[0020] The acid-modified polyolefin (A) preferably contains propylene and 1-butene as olefin components. The preferred range of the molar ratio of propylene to 1-butene is propylene / 1-butene = 98-60 / 2-40, more preferably 90-70 / 10-30. A propylene molar ratio of 60% or more can exhibit excellent adhesion to polyolefin substrates. A 1-butene molar ratio of 2% or more increases solubility in organic solvents, improving application properties as an adhesive.

[0021] As the olefin component, the total amount of propylene and 1-butene components is preferably 62 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may even be 100 mol%. When it is 62 mol% or more, adhesiveness and chemical resistance are good.

[0022] 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 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. When it is 10,000 or more, the cohesive force tends to be strong and the adhesiveness tends to be excellent. On the other hand, when it is 200,000 or less, the fluidity is good and the operability during adhesion is improved.

[0023] 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 a polymer that becomes the main chain, and an unsaturated carboxylic acid and an acid anhydride are graft polymerized using the radical species as a polymerization initiation point).

[0024] The radical generator is not particularly limited, and examples thereof include organic peroxides and azonitriles. Among these, it is preferable to use organic peroxides. Examples of organic peroxides include 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, and lauroyl peroxide. Examples of azonitriles include azobisisobutyronitrile and azobisisopropionitrile.

[0025] These acid-modified polyolefins (A) may be used alone or in combination of two or more.

[0026] <Isocyanate curing agent (B)> The adhesive composition of the present invention contains an isocyanate curing agent (B). By using an isocyanate as a curing agent, excellent adhesive strength and heat resistance can be exhibited from the initial stage of adhesion. The isocyanate curing agent used in the present invention is not particularly limited, and diisocyanates, triisocyanates, and compounds derived therefrom can be preferably used. Examples of isocyanate curing agents include aromatic curing agents, aliphatic curing agents, and alicyclic curing agents. Examples of aromatic curing agents include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and 1,5-naphthalene diisocyanate. Examples of aliphatic curing agents include hexamethylene diisocyanate (HDI). Examples of alicyclic curing agents include diisocyanates such as isophorone diisocyanate, bis(4-isocyanatocyclohexyl)methane, and hydrogenated diphenylmethane diisocyanate. Further examples include compounds derived from the diisocyanates, i.e., isocyanurates, adducts, biuret-type compounds, uretdione compounds, allophanate compounds, prepolymers having an isocyanate residue (low polymers obtained from diisocyanates and polyols), triglycidyl isocyanurate, and complexes thereof. These may be used alone or in any combination of two or more. Aliphatic curing agents are preferred as the isocyanate curing agent used in the present invention.

[0027] As the isocyanate curing agent (B) used in the present invention, those having an isocyanurate of the above diisocyanate compound are preferred because they have excellent electrolyte resistance.

[0028] The amount of isocyanate curing agent (B) in the adhesive composition of the present invention is preferably in the range of 0.5 to 70 parts by mass, more preferably 5 to 50 parts by mass, even more preferably 15 to 40 parts by mass, and particularly preferably 28 to 35 parts by mass, per 100 parts by mass of the acid-modified polyolefin (A). In particular, by using 15 parts by mass or more of the isocyanate curing agent (B), an adhesive composition with high heat resistance can be obtained. If the amount is less than 0.5 parts by mass, a sufficient curing effect may not be obtained, resulting in poor adhesion and chemical resistance. If the amount is in the range of 0.5 to 70 parts by mass, the pot life and adhesion are good, and the occurrence of pinholes during molding due to poor conformability is suppressed. This is also preferred from the perspective of cost.

[0029] <Acid anhydride group-containing compound (C)> The adhesive composition of the present invention contains an acid anhydride group-containing compound (C). The acid anhydride group-containing compound (C) is a compound other than the acid-modified polyolefin (A). By containing the acid anhydride group-containing compound (C), the electrolyte resistance can be maintained without deterioration even when the amount of isocyanate curing agent (B) blended in the laminate after isocyanate curing is 10 parts by mass or more per 100 parts by mass of the acid-modified polyolefin (A). The reason why the electrolyte resistance can be maintained is unclear, but it is presumed that this is because the isocyanate terminals are lost by reaction with unreacted isocyanate groups, resulting in a high molecular weight.

[0030] The molecular weight of the acid anhydride group-containing compound (C) that can be used in the present invention is preferably 100 g / mol or more and 500 g / mol or less. It is more preferably 150 g / mol or more, and even more preferably 200 g / mol or more. It is also preferably 450 g / mol or less, and even more preferably 400 g / mol or less. A molecular weight of 500 g / mol or less improves compatibility with the acid-modified polyolefin (A) or the isocyanate curing agent (B), resulting in improved adhesiveness. A molecular weight of 100 g / mol or more tends to prevent bleed-out of the acid anhydride group-containing compound (C) before curing, resulting in improved adhesiveness.

[0031] The acid value of the acid anhydride group-containing compound (C) is preferably 150 mgKOH / g or more and 800 mgKOH / g or less. It is more preferably 250 mgKOH / g or more, and even more preferably 300 mgKOH / g or more. It is more preferably 600 mgKOH / g or less, and even more preferably 500 mgKOH / g or less. When the acid value is 800 mgKOH / g or less, the acid anhydride group-containing compound (C) does not bleed out before curing, and adhesion tends to be good. Furthermore, when the acid value is 150 mgKOH / g or more, the effect of maintaining electrolyte resistance tends to be good.

[0032] The acid anhydride group-containing compound (C) has one or more acid anhydride groups in one molecule. The acid anhydride group is preferably cyclic, and the acid anhydride group-containing compound (C) more preferably has a structure represented by chemical formula (1). *1 and / or *2 represent bonds to carbon atoms or hydrogen atoms in the acid anhydride group-containing compound (C). Examples of the acid anhydride group-containing compound (C) include succinic anhydride, maleic anhydride, glutaric anhydride, butylsuccinic anhydride, hexylsuccinic anhydride, octylsuccinic anhydride, dodecylsuccinic anhydride, 3-dodecenylsuccinic anhydride, tetrapropenylsuccinic anhydride, butylmaleic anhydride, pentylmaleic anhydride, hexylmaleic anhydride, octylmaleic anhydride, decylmaleic anhydride, dodecylmaleic anhydride, butylglutamic anhydride, hexylglutamic anhydride, heptylglutamic anhydride, octylglutamic anhydride, decyl Examples of suitable compounds include acid anhydride group-containing compounds having an alkyl chain and an acid anhydride group, such as glutamic anhydride and dodecyl glutamic anhydride; and acid anhydride group-containing compounds having an alicyclic structure or an aromatic ring structure and an acid anhydride group, such as pyromellitic anhydride, trimellitic anhydride, benzophenone tetracarboxylic dianhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylpentahydrophthalic anhydride, methyltrihydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexene dicarboxylic anhydride, HET anhydride, and tetrabromophthalic anhydride. One compound may be used alone, or multiple compounds may be used in combination. Among these, 3-dodecenyl succinic anhydride, which is liquid at room temperature, is preferred from the viewpoint of ease of handling. [ka]

[0033] The acid anhydride group-containing compound (C) preferably has a hydrocarbon group, and more preferably has a hydrocarbon group bonded to an acid anhydride group. The hydrocarbon group is more preferably linear. The inclusion of a hydrocarbon group improves solvent solubility and compatibility with the acid-modified polyolefin (A) or the isocyanate curing agent (B), enhancing the effect of maintaining electrolyte resistance. Furthermore, linearity is preferred because it provides particularly good compatibility with the acid-modified polyolefin (A) and improves pot life.

[0034] The hydrocarbon group preferably has 3 or more and 20 or less carbon atoms, more preferably 5 or more, and even more preferably 8 or more. It is more preferably 18 or less, and even more preferably 15 or less. When the hydrocarbon group has 3 or more carbon atoms, compatibility with the acid-modified polyolefin (A) and the isocyanate curing agent (B) is improved, resulting in good electrolyte resistance and adhesion. In particular, when the hydrocarbon group has 11 or more and 15 or less carbon atoms, compatibility is further improved, resulting in a better pot life.

[0035] The content of the acid anhydride group-containing compound (C) in the adhesive composition of the present invention is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the acid-modified polyolefin (A). It is more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and particularly preferably 1 part by mass or more. It is more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and particularly preferably 5 parts by mass or less. A content of more than 20 parts by mass may significantly reduce electrolyte resistance. Furthermore, when the content is 0.1 parts by mass or more, the effect of adding the acid anhydride group-containing compound (C) is exhibited, and when an excess of the isocyanate curing agent (B) is blended, electrolyte resistance is improved. Furthermore, when the content is 20 parts by mass or less, not only good heat resistance and adhesion but also excellent electrolyte resistance over a long period of time tends to be exhibited.

[0036] <Organic solvent (D)> The adhesive composition of the present invention may further contain an organic solvent (D). The organic solvent (D) used in the present invention is not particularly limited as long as it can dissolve the acid-modified polyolefin (A), the isocyanate curing agent (B), and the acid anhydride group-containing compound (C).

[0037] The amount of the organic solvent (D) is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 110 parts by mass or more, relative to 100 parts by mass of the acid-modified polyolefin (A). It is also preferably 2000 parts by mass or less, more preferably 1800 parts by mass or less, even more preferably 1500 parts by mass or less, even more preferably 1200 parts by mass or less, particularly preferably 1000 parts by mass or less, and most preferably 900 parts by mass or less. If the amount is less than the above range, the solution state and pot life may be reduced, and if the amount is greater than the above range, it may be disadvantageous in terms of production costs and transportation costs.

[0038] From the viewpoint of the solution state and pot life of the adhesive composition, the organic solvent (D) is preferably one or more solvents (D1) selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, and alicyclic hydrocarbons. A mixture of (D1) and one or more solvents (D2) selected from oxygen-containing organic solvents is more preferred. Oxygen-containing organic solvents are organic solvents containing oxygen atoms in their structure, and preferred examples include alcohol-based solvents, ketone-based solvents, ester-based solvents, and glycol-based solvents. Specific examples of organic solvent (D1) include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; and alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane. One or more of these can be used in combination. Using (D1) as the organic solvent improves the solubility of the acid-modified polyolefin (A), which is advantageous in terms of solution stability and wettability to the substrate. Methylcyclohexane and toluene are particularly preferred from the viewpoints of work environment and drying properties. Specific examples of the solvent (D2) include alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone-based solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, amyl acetate, methyl propionate, and butyl formate; and glycol ether-based solvents such as methyl cellosolve, ethyl cellosolve, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, triethylene glycol mono-n-butyl ether, and tetraethylene glycol mono-n-butyl ether. These may be used alone or in combination of two or more.

[0039] The mixing ratio of solvent (D1) and solvent (D2) is preferably solvent (D1) / solvent (D2) = 40 to 97 / 60 to 3 (mass ratio), more preferably 45 to 95 / 45 to 5 (mass ratio), even more preferably 50 to 80 / 50 to 20 (mass ratio), and particularly preferably 55 to 70 / 45 to 30 (mass ratio). By keeping the ratio within the above range, the solution state and pot life of the adhesive composition are improved. Furthermore, it is particularly preferred that solvent (D1) is an aromatic hydrocarbon or an alicyclic hydrocarbon, and solvent (D2) is a ketone-based solvent or an ester-based solvent. More preferably, solvent (D1) is cyclohexane and methylcyclohexane, and solvent (D2) is methyl ethyl ketone and ethyl acetate.

[0040] In addition to the acid-modified polyolefin (A), the isocyanate curing agent (B), and the acid anhydride group-containing compound (C), the adhesive composition of the present invention may contain various additives such as tackifiers, plasticizers, stress relaxation agents, curing accelerators, flame retardants, pigments, and antiblocking agents, as long as the performance of the present invention is not impaired.

[0041] <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.

[0042] As a lamination method, a conventionally known laminate manufacturing technique can be used. For example, although not particularly limited, an adhesive composition is applied to the surface of a metal substrate using an appropriate 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 can be laminated (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.

[0043] <Polyolefin resin substrate> The polyolefin resin substrate may be appropriately selected from conventionally known polyolefin resins. For example, polyethylene, polypropylene, ethylene-propylene copolymer, etc. can be used, but are not particularly limited thereto. Among these, the use of a non-oriented polypropylene film (hereinafter also referred to as CPP) is preferred. Its 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, or may be surface-treated, as necessary.

[0044] <Metal base material> The metal substrate is not particularly limited, and various metals and alloys thereof, such as aluminum, copper, steel, chromium, zinc, duralumin, and die-cast metals, can be used. The substrate can take any shape, such as metal foil, rolled steel plate, panel, pipe, can, or cap. Generally, aluminum foil is preferred from the viewpoint of workability. Although the thickness varies depending on the intended 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 surface-treated or left untreated, with the same effect being achieved in either case. [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] The acid-modified polyolefin (A) and the adhesive composition were subjected to analytical measurements and evaluations according to the following methods. <Acid value measurement> The acid value (mg KOH / g) 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 at the same temperature with a 0.1 mol / L potassium hydroxide ethanol solution (trade name "0.1 mol / L ethanolic potassium hydroxide solution", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) using phenolphthalein as an indicator. The amount of potassium hydroxide required for the titration was converted to mg to calculate the acid value (mg KOH / g).

[0047] <Measurement of number average molecular weight (Mn) and weight average molecular weight (Mw)> The number average molecular weight and weight average molecular weight in the present invention are values ​​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 and KF-803, column temperature: 40°C, flow rate: 1.0 ml / min, detector: photodiode array detector (wavelength 254 nm = ultraviolet light)).

[0048] <Melt point measurement> The melting point in the present invention is a value measured using a differential scanning calorimeter (hereinafter referred to as DSC, manufactured by TA Instruments Japan, Q-2000) from the top temperature of the melting peak when the material is heated to melt at a rate of 10°C / min, cooled to form a resin, and then heated to melt again.

[0049] <Pot life evaluation> Pot life refers to the stability of a solution obtained by blending an acid-modified polyolefin with a curing agent, either immediately after blending or after a certain period of time has passed since blending. A good pot life means that the viscosity of the solution increases little and it can be stored for a long period of time, while a bad pot life means that the viscosity of the solution increases (thickens), and in severe cases, it gels, making it difficult to apply to a substrate and making it impossible to store for a long period of time. The pot life of the adhesive composition was evaluated by storing it in an agitated state in air at 25°C for 8 hours and then measuring the solution viscosity at 25°C using a Brookfield viscometer. The Brookfield viscometer used was a TVB-10M manufactured by Toyo Sangyo Co., Ltd., and measurements were taken at a liquid temperature of 25°C and a rotation speed of 60 rpm. When the viscosity of the adhesive composition was less than 100 mPa·s, SPINDLE No. M1 was used as the rotor, and when the viscosity was 100 mPa·s or higher, SPINDLE No. M2 was used as the rotor. (Evaluation criteria) ☆ (particularly excellent for practical use): Less than 30 mPa·s ◎ (Excellent for practical use): 30 mPa·s or more and less than 50 mPa·s ○ (practical): 50 mPa·s or more and less than 100 mPa·s × (Not practical): Viscosity measurement is impossible due to 100 mPa·s or more or gelation

[0050] <Preparation of Laminate of Metal Substrate and Polyolefin Resin Substrate> The metal substrate used was aluminum foil (manufactured by Sumikei Aluminum Foil Co., Ltd., 8079-0, thickness 40 μm), and the polyolefin resin substrate used was unstretched polypropylene film (manufactured by Toyobo Co., Ltd., Pylen (registered trademark) Film CT, thickness 80 μm) (hereinafter also referred to as CPP). The resulting adhesive composition was applied to a metal substrate using a bar coater, adjusting the thickness of the adhesive layer after drying to 3 μm. The coated surface was dried for 1 minute in a 100°C atmosphere using a hot air dryer, yielding a metal substrate laminated with a 3 μm-thick adhesive layer. A polyolefin resin substrate was placed on the surface of the adhesive layer, and the two were bonded using a small desktop test laminator (SA-1010-S) manufactured by Tester Sangyo Co., Ltd. at a lamination temperature of 80°C, a roll load of 0.3 MPa, and a pressing speed of 1 m / min. The laminate was then aged for 5 days at 40°C and 50% RH to obtain a laminate.

[0051] The laminate obtained as described above was evaluated by the following methods. <Evaluation of initial adhesion> The laminate was cut into a size of 100 mm x 15 mm, and the adhesiveness was evaluated by a T-peel test according to the following criteria. The T-peel test was performed in accordance with the test method of ASTM-D1876-61, and 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 for practical use): 12.0N / cm or more ◎ (Excellent for practical use): 10.0N / cm or more and less than 12.0N / cm ○ (practical): 7.0N / cm or more and less than 10.0N / cm × (not practical): Less than 7.0N / cm

[0052] <Evaluation of 85°C electrolyte resistance> To investigate its applicability as a packaging material for lithium-ion batteries, the electrolyte resistance was evaluated. The laminate was cut into a size of 100 mm x 15 mm and immersed in an electrolyte solution [100 g of ethylene carbonate / diethyl carbonate = 1 / 1 (volume ratio) to which 13.6 g of lithium hexafluorophosphate was added] at 85°C for 7 days. The laminate was then removed, washed with ion-exchanged water, wiped with paper wipes, thoroughly dried, and evaluated for electrolyte resistance using a T-peel test according to the following criteria. ☆ (particularly excellent for practical use): 8.0N / cm or more ◎ (Excellent for practical use): 6.5N / cm or more and less than 8.0N / cm ○ (practical): 5.0N / cm or more and less than 6.5N / cm × (Not practical): Less than 5.0N / cm

[0053] <Evaluation of heat resistance at 80°C> The laminate was cut into a size of 100 mm x 15 mm, and the heat resistance was evaluated by a T-peel test in a thermostatic chamber at 80°C according to the following criteria. Using an AG-IS manufactured by Shimadzu Corporation equipped with a thermostatic bath, the cut laminate was placed in the thermostatic bath heated to 80°C, and after preheating for 1 minute, the peel strength was measured at a tensile speed of 50 mm / min in an 80°C environment. 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 for practical use): 6.0N / cm or more ◎ (Excellent for practical use): 4.5N / cm or more and less than 6.0N / cm ○ (practical): 3.0N / cm or more and less than 4.5N / cm × (not practical): Less than 3.0N / cm

[0054] <Production Example of Acid-Modified Polyolefin (A)> (Production Example 1) A 1-L autoclave was charged with 100 parts by mass of a propylene-butene copolymer (Tm: 80°C, propylene / butene molar ratio = 80 / 20), 233 parts by mass of toluene, 10 parts by mass of maleic anhydride, and 5 parts by mass of di-tert-butyl peroxide. The mixture was heated to 140°C and stirred for an additional hour (referred to as a "reaction" period of 1 hour). After completion of the reaction, the reaction solution was poured into a large amount of methyl ethyl ketone to precipitate a resin. This resin was further washed several times with methyl ethyl ketone to separate the acid-modified propylene-butene copolymer graft-polymerized with maleic anhydride, (poly)maleic anhydride, and low-molecular-weight substances. After purification, the obtained resin was dried under reduced pressure at 70°C for 5 hours to obtain an acid-modified polyolefin, maleic anhydride-modified propylene-butene copolymer (A-1, acid value 15 mg KOH / g, weight-average molecular weight 80,000, Tm 80°C).

[0055] (Production Example 2) A maleic anhydride-modified propylene-butene copolymer (A-2, acid value 5 mg KOH / g, weight average molecular weight 90,000, Tm 80°C), which is an acid-modified polyolefin, was obtained by the same procedure as in Production Example 1, except that the amount of maleic anhydride charged was changed to 3 parts by mass and the amount of di-tert-butyl peroxide charged was changed to 1 part by mass.

[0056] (Production Example 3) A maleic anhydride-modified propylene-butene copolymer (A-3, acid value 5 mgKOH / g, weight average molecular weight 90,000, Tm 90°C), which is an acid-modified polyolefin, was obtained by the same procedure as in Production Example 1, except that the propylene-butene copolymer (Tm: 80°C) used in Production Example 1 was changed to a propylene-butene copolymer (Tm: 90°C, propylene / butene molar ratio = 85 / 15), and the amount of maleic anhydride charged was changed to 3 parts by mass and the amount of di-tert-butyl peroxide charged was changed to 1 part by mass.

[0057] (Production Example 4) A maleic anhydride-modified propylene-butene copolymer (A-4, acid value 5 mgKOH / g, weight average molecular weight 90,000, Tm 70°C), which is an acid-modified polyolefin, was obtained by the same procedure as in Production Example 1, except that the propylene-butene copolymer (Tm: 80°C) used in Production Example 1 was changed to a propylene-butene copolymer (Tm: 70°C, propylene / butene = 75 / 25 molar ratio), and the amount of maleic anhydride charged was changed to 3 parts by mass and the amount of di-tert-butyl peroxide charged was changed to 1 part by mass.

[0058] <Preparation of the base agent> (Preparation of main agent 1) A 500 ml four-neck flask equipped with a water-cooled reflux condenser and a stirrer was charged with 100 parts by mass of the maleic anhydride-modified propylene-butene copolymer (A-1) obtained in Production Example 1, 320 parts by mass of methylcyclohexane, and 80 parts by mass of methyl ethyl ketone, and the mixture was heated to 80°C with stirring. Stirring was continued for 1 hour, and the mixture was cooled to below 40°C. After that, 3 parts by mass of the acid anhydride group-containing compound (C-1) was added, and the mixture was stirred for a further 10 minutes to obtain main component 1.

[0059] (Preparation of main agents 2 to 14) Main agents 2 to 14 were prepared in the same manner as main agent 1, except that the acid-modified polyolefin, acid anhydride group-containing compound, and organic solvent were changed as shown in Table 1. The blending amounts are shown in Table 1.

[0060] [Table 1]

[0061] Example 1 An adhesive composition was obtained by blending 503 parts by mass of the base agent 1 and 20.0 parts by mass of the curing agent (B-1). Using this adhesive composition, a laminate of a metal substrate and a polyolefin resin substrate was produced by the method described above, and various evaluations were performed.

[0062] Examples 2 to 10 and Comparative Examples 1 to 4 Adhesive compositions were prepared by changing the base agent and curing agent as shown in Table 1, and laminates were prepared in the same manner as in Example 1, and various evaluations were carried out.

[0063] The curing agent (B) used in Table 1 is as follows. B-1: Sumidur (registered trademark) N3300 (manufactured by Covestro) (HDI type isocyanurate) B-2: Duranate 24A-100 (Asahi Kasei Corporation) (HDI type biuret) B-3: Epiclon (registered trademark) HP-7200 (manufactured by DIC Corporation) (dicyclopentadiene skeleton-containing epoxy resin)

[0064] The acid anhydride group-containing compounds (C) used in Table 1 are as follows. C-1: Rikacid DDSA (manufactured by New Japan Chemical Co., Ltd.) (acid value 394-432 mg KOH / g resin, molecular weight 266, hydrocarbon group C12) C-2: PDSA-DA (Sanyo Chemical Industries, Ltd.) (acid value 350 mg KOH / g resin, molecular weight 320, hydrocarbon group C15) C-3: Benzophenonetetracarboxylic dianhydride (manufactured by Daicel Corporation) (acid value 620-680 mg KOH / g resin, molecular weight 322, no hydrocarbon group) [Industrial Applicability]

[0065] The adhesive composition of the present invention contains an acid-modified polyolefin, an isocyanate curing agent, and an acid anhydride group-containing compound, and therefore exhibits good adhesion between a polyolefin resin substrate and a metal substrate, long-term electrolyte resistance, and excellent heat resistance after curing. Therefore, laminates of a polyolefin resin substrate and a metal substrate formed from the adhesive composition of the present invention can be widely used not only for home appliance exterior panels, furniture materials, and building interior components, but also for personal computers, mobile phones, and video cameras, as well as for packaging materials (in the form of pouches) for lithium-ion batteries, which require high heat resistance for in-vehicle applications.

Claims

1. An adhesive composition comprising an acid-modified polyolefin (A), an isocyanate curing agent (B), and an acid anhydride group-containing compound (C), the content of the acid anhydride group-containing compound (C) is 0.1 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acid-modified polyolefin (A), The adhesive composition for battery packaging materials, wherein the acid anhydride group-containing compound (C) contains a hydrocarbon group having from 11 to 20 carbon atoms.

2. 2. The adhesive composition for battery packaging according to claim 1, wherein the acid-modified polyolefin (A) has an acid value of 2 to 50 mgKOH / g.

3. 3. The adhesive composition for battery packaging materials according to claim 1, wherein the isocyanate curing agent (B) is contained in an amount of 0.5 to 70 parts by mass per 100 parts by mass of the acid-modified polyolefin (A).

4. The adhesive composition for battery packaging materials according to any one of claims 1 to 3, comprising 80 to 2000 parts by mass of an organic solvent (D) per 100 parts by mass of the acid-modified polyolefin (A).

5. the organic solvent (D) is a mixed liquid of a solvent (D1) and a solvent (D2), the solvent (D1) is one or more solvents selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, the solvent (D2) is one or more solvents selected from oxygen-containing organic solvents, The adhesive composition for battery packaging materials according to claim 4, wherein the solvent (D1) / the solvent (D2) is 50 to 97 / 50 to 3 (mass ratio).

6. The adhesive composition for battery packaging materials according to any one of claims 1 to 5, wherein the molecular weight of the acid anhydride group-containing compound (C) is 100 g / mol or more and 500 g / mol or less.

7. 7. The adhesive composition for battery packaging materials according to claim 1, wherein the acid anhydride group-containing compound (C) has an acid value of 150 mg KOH / g or more and 800 mg KOH / g or less.

8. The adhesive composition for battery packaging materials according to any one of claims 1 to 7, which is used for bonding a polyolefin resin substrate to a metal substrate.

9. A laminate of a polyolefin resin substrate and a metal substrate bonded with the adhesive composition for battery packaging according to any one of claims 1 to 8.

10. A packaging material for batteries, comprising the laminate according to claim 9 as a constituent member.

11. A packaging material for lithium ion batteries, comprising the laminate according to claim 9 as a constituent member.

12. The composition contains an acid-modified polyolefin (A), an isocyanate curing agent (B), and an acid anhydride group-containing compound (C), the content of the acid anhydride group-containing compound (C) is 0.1 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the acid-modified polyolefin (A), an adhesive composition for lithium-ion battery packaging materials, wherein the acid anhydride group-containing compound (C) contains a hydrocarbon group having from 11 to 20 carbon atoms;

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