JP2018161896A - Adhesive composition, packaging material for cell, and container for cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition allowing formation of a laminate that develops stable and sufficient adhesive strength in adhesion between a thermal bonding film and a metal foil and maintains the adhesion strength in a high level even when immersed in electrolyte solution at a higher temperature, the adhesive composition giving no influences on insulating properties even when thermal bonding film layers are thermally bonded to each other under conditions that sufficient bond strength can be developed.SOLUTION: A adhesive composition comprises a polyolefin resin (A) having a carboxyl group or an acid anhydride group, a polyfunctional isocyanate curing agent (B), and solvent (C). The polyolefin resin (A) has a glass transition temperature of -30 to 10°C, a melting point of 60 to 110°C, and melting energy of 15 to 50 mJ/mg.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive composition that can be suitably used for a laminate for forming a battery container of a non-aqueous electrolyte secondary battery such as a lithium ion battery. Moreover, this invention relates to the packaging material for batteries which laminated | stacked the metal foil layer and the heat-fusible film using the said adhesive composition. Furthermore, the present invention relates to a battery container obtained by processing the battery packaging material so that the heat-fusible film becomes an inner surface, and a battery using the battery container.

  In recent years, with the rapid growth of electronic devices such as mobile phones and portable personal computers, the demand for lightweight and small non-aqueous electrolyte secondary batteries is increasing. Among these, a bag-shaped or tray-shaped battery container using a laminate film including a metal foil represented by aluminum foil, which can be made lighter and more compact, has attracted attention.

A battery using a bag-like or tray-like battery container can be obtained as follows.
Examples of the simplest packaging material include a laminate composed of an outer resin film layer, an outer adhesive layer, a metal foil layer, an inner adhesive layer, and a heat-fusible film in this order from the outer layer side. The laminate is heat-sealed so that the heat-fusible film is on the inside, thereby creating a bag-shaped battery container, or the heat-fusible film is on the upper side and heat-sealed to the laminate. A tray-shaped battery container can be formed by pressing a punch from the adhesive film side to form a recess. A battery can be produced by sealing the battery contents inside the bag-shaped or tray-shaped battery container. The battery contents referred to here include a positive electrode, a separator, a negative electrode, an electrolyte, a tab composed of leads and a tab sealant, and the like.

Therefore, the following performance is mainly required for the adhesive for bonding the metal foil and the heat-fusible film among battery packaging materials.
(1) The adhesive strength between the metal foil and the heat-fusible film is large.
(2) The adhesive layer has an electrolyte solution resistance. That is, the adhesive strength between the metal foil and the heat-fusible film can be maintained even if the electrolyte is sealed in the battery container.
For example, the electrolyte solution of a lithium battery includes a lithium salt such as lithium hexafluorophosphate and a solvent such as propylene carbonate, ethylene carbonate, diethyl carbonate, and dimethyl carbonate.
When the electrolyte solution is put into the battery container, the electrolyte solution passes through the heat-fusible film, reaches the adhesive layer, and causes a decrease in the adhesive strength between the heat-fusible film and the metal foil. Further, when moisture enters the electrolyte solution from the outside of the battery container, a lithium salt such as lithium hexafluorophosphate reacts with water to generate hydrofluoric acid. The generated hydrofluoric acid passes through the heat-fusible film and the adhesive layer, reaches the metal foil, and corrodes the metal foil. This corrosion significantly lowers the adhesive strength between the heat-fusible film and the metal foil.
Therefore, the adhesive layer for bonding the heat-fusible film and the metal foil is required to have resistance to the electrolyte solution.
Among them, the electrolyte solution resistance differs depending on whether the battery is used for consumer use or for in-vehicle use, and the in-vehicle use requires better electrolyte solution resistance.
(3) When the heat-fusible film is heat-sealed, the adhesive layer that has bonded the heat-fusible film and the metal foil is not melted or deformed.
If the adhesive layer is melted or deformed by heat at the time of heat-sealing, the electrode terminal and the metal foil may be electrically connected. If it becomes conductive, it will not function as a battery. Therefore, it is required that the adhesive layer is not melted or deformed by heat at the time of heat fusion so that the insulation between the electrode terminal and the metal foil is ensured after heat fusion.

  Patent Document 1 (Japanese Patent Laid-Open No. 2001-236932) discloses a battery package in which a modified olefin resin layer containing hydrotalcite, which is an acid receiving layer, is provided between a metal foil and an olefin resin layer. A material is disclosed. As the modified olefin resin, maleic anhydride polypropylene is disclosed.

  Patent Document 2 (Japanese Patent Laid-Open No. 2003-123708) uses an adhesive composition containing an acid-modified thermoplastic elastomer (A) and a coupling agent (B), and is one of heat-fusible plastic sheets. A laminate of a structure of unstretched polypropylene film / adhesive layer / aluminum foil / nylon film bonded together with an unstretched polypropylene film and a laminated aluminum foil in which an aluminum foil as a metal foil is laminated on a nylon film. It is disclosed that a secondary battery is obtained using the laminate as a packaging material. It is further disclosed that a tackifier can be included in the adhesive composition. As the acid-modified thermoplastic elastomer (A), a maleic acid-modified styrene elastomer is disclosed.

Further, Patent Document 3 (WO 2004/041954) discloses an adhesive composition containing a carboxyl group-containing thermoplastic elastomer (A), a polyolefin polyol (B), a tackifier (C) and a polyfunctional isocyanate (D). It is disclosed. And it is described that an aluminum foil, a polyethylene terephthalate film, and an unstretched polypropylene film are bonded together using the adhesive.
Also, Patent Document 4 (Japanese Patent Application Laid-Open No. 2005-063685) discloses an adhesive similar to that of Patent Document 3, and an aluminum foil and a thermoplastic resin film are bonded to each other using the adhesive. It describes that it can be used as a packaging material for battery cases having a plastic resin film as an inner layer.
As the carboxyl group-containing thermoplastic elastomer (A), a maleic acid-modified styrene elastomer is disclosed.

Patent Document 5 (WO2009 / 087776) discloses an adhesive composition having a polyolefin resin having a carboxyl group dissolved or dispersed in an organic solvent and a polyfunctional isocyanate.
Also, Patent Document 6 (Japanese Patent Laid-Open No. 2010-092703) discloses an adhesive similar to that of Patent Document 2, and an aluminum foil and a thermoplastic resin film are bonded together using the adhesive, and the heat It describes that it can be used as a packaging material for battery cases having a plastic resin film as an inner layer.

JP 2001-236932 A JP 2003-123708 A WO2004 / 041954 pamphlet Japanese Patent Laying-Open No. 2005-063685 WO2009 / 087776 pamphlet JP 2010-092703 A

Patent Document 1 describes that even when immersed in a mixed solvent at 60 ° C. or sealed with a solution of hydrofluoric acid at 60 ° C. in a pouch, the adhesive strength can be maintained to some extent.
However, it has been desired to develop an adhesive that can maintain the adhesive strength even when exposed to a higher temperature environment.

  The adhesives described in Patent Documents 2 to 4 use maleic acid-modified styrene elastomers. According to Patent Document 5, an adhesive using a maleic acid-modified styrene elastomer has not only low initial adhesive strength and adhesive strength after immersion in hot water, but also high moisture permeability. Therefore, it is not preferable as an adhesive for forming a battery packaging material that dislikes the entry of moisture into the electrolyte solution.

Patent Documents 5 and 6 disclose the use of an adhesive composition containing a polyolefin resin having a carboxyl group and a polyfunctional isocyanate as described above.
However, in Examples of Patent Document 5, it is described that the melting energy must be about 5 to 10 (mJ / mg) in order to develop excellent adhesive strength (initial and after immersion in warm water). .
Certainly, as a polyolefin resin having a carboxyl group, a resin having a low melting energy can be used to exhibit an excellent adhesive force.
However, since the melting energy is small, the heat resistance of the adhesive layer obtained by reacting with the polyfunctional isocyanate is insufficient, and the adhesive layer is heated by heat when the heat-fusible film layers are heat-sealed. However, there is a problem that the insulating property which is important as a battery container is impaired.
By lowering the temperature at the time of heat-sealing or lowering the pressure, it is possible to suppress deformation and flow of the adhesive layer during heat-sealing of heat-fusible films. However, there is a problem that sufficient heat seal strength cannot be secured.
Or it can suppress that an adhesive bond layer deform | transforms and flows at the time of heat-sealing of heat-fusible films also by raising a crosslinking density. However, since the adhesive layer becomes hard, there is a problem that the adhesive strength between the metal foil and the heat-fusible film cannot be secured.

  The present invention forms a laminate that exhibits stable and sufficient adhesive strength in the adhesion between a heat-fusible film and a metal foil, and can maintain the adhesive strength at a high level even when immersed in a higher-temperature electrolyte solution. PROBLEM TO BE SOLVED: To provide an adhesive composition that does not affect insulation even if heat-fusible film layers are heat-sealed with each other under a condition capable of exhibiting sufficient fusing strength. And

This invention solved the said subject by using specific polyolefin resin (A).
That is, the present invention is an adhesive composition containing a polyolefin resin (A) having a carboxyl group or an acid anhydride group, a polyfunctional isocyanate curing agent (B), and a solvent (C),
The polyolefin resin (A) has a glass transition temperature of −30 to 10 ° C., a melting point of 60 to 110 ° C., and a melting energy of 15 to 50 (mJ / mg). About.

  The present invention is a laminate in which a metal foil and a heat-fusible film are laminated via an adhesive layer, and the adhesive layer is formed from the adhesive composition of the present invention. It is related with the laminated body characterized by being an adhesive layer.

  Furthermore, the present invention provides an inner layer in the battery packaging material, in which the outer layer side resin film layer, the outer layer side adhesive layer, the metal foil layer, the inner layer side adhesive layer, and the heat-fusible film layer are essential in order from the outer layer. The present invention relates to a battery packaging material characterized in that a side adhesive layer is formed of the adhesive composition of the present invention.

  Furthermore, this invention relates to the battery container formed from the battery packaging material of the said invention, Comprising: The heat-fusible film layer comprises the inner surface.

  With the adhesive composition of the present invention, it is possible to stably form sufficient adhesive strength, and to form a laminate that can maintain the adhesive strength at a high level even when immersed in a high-temperature electrolyte solution. Even if the heat-fusible film layers are heat-sealed together under the condition that the fusion strength can be expressed, the battery container can be formed without impairing the insulating properties.

The polyolefin resin (A) having a carboxyl group or an acid anhydride group used in the present invention (hereinafter sometimes abbreviated as polyolefin resin (A)) will be described.
The polyolefin resin (A) used in the present invention forms a strong crosslinked structure by reacting a carboxyl group or an acid anhydride group with an isocyanate group in a polyfunctional isocyanate curing agent (B) described later, An adhesive having excellent adhesion strength to a metal substrate and durability to an electrolytic solution can be obtained.
The polyolefin resin (A) is preferably non-crystalline because it has solubility in a solvent used for the adhesive and can be stably stored without precipitating the dissolved solution (having storage stability). Moreover, in order to have electrolyte solution resistance, it is preferable to also have a crystalline part, and the balance becomes important.
Non-crystallinity can be represented by the glass transition temperature (Tg), and crystallinity can be represented by the melting point and melting energy (ΔE) of the polyolefin resin (A).
The polyolefin resin (A) used in the present invention has a Tg of −30 to 10 ° C., a melting point of 60 to 110 ° C., and ΔE of 15 to 50 (mJ / mg).

Since the polyolefin resin (A) has a Tg of −30 to 10 ° C., the storage stability as a polyolefin resin (A) solution constituting the adhesive and the resistance to electrolyte (electrolyte) as a battery packaging material Adhesive strength after immersion) and heat-fusibility can be achieved.
That is, when the Tg of the polyolefin resin (A) is less than −30 ° C., the electrolytic solution resistance and heat-fusibility as a battery packaging material are lowered. Storage stability at ℃ decreases. More preferably, Tg of polyolefin resin (A) is -30-0 degreeC.

The polyolefin resin (A) has a melting point of 60 to 110 ° C. and ΔE of 15 to 50 (mJ / mg). The wearability can be satisfied in a well-balanced manner.
That is, when the melting point of the polyolefin resin (A) is less than 60 ° C., the adhesive strength and heat-fusibility after immersion in the electrolyte are reduced, and when it is higher than 110 ° C., the adhesive strength (initial, after immersion in the electrolyte) is reduced. To do. More preferably, the melting point of the polyolefin resin (A) is 60 to 90 ° C.
Also, if the ΔE of the polyolefin resin (A) is less than 15 (mJ / mg), the adhesive strength and heat-fusibility after immersion in the electrolyte will decrease, and if it exceeds 50 (mJ / mg), the crystallinity will be high. Storage stability as a polyolefin resin (A) solution is lowered. More preferably, ΔE of the polyolefin resin (A) is 20 to 50 (mJ / mg), more preferably 20 to
40 (mJ / mg).

In addition, Tg, melting | fusing point, and (DELTA) E of polyolefin resin (A) in this invention can be calculated | required by DSC measurement according to JISK7121. Specifically, it is obtained as follows.
When the diameter or each side of the polyolefin resin (A) of about 10 mg is 0.5 mm or less, it is used as it is, and if it exceeds 0.5 mm, it is cut into 0.5 mm or less and put into a container.
Heat to about 30 ° C above the melting point at 10 ° C per minute and then cool to about 50 ° C below Tg at 10 ° C per minute. If no clear Tg is observed, cool to about 50 ° C. below the melting point. Then, it calculated | required from the chart corresponding to the glass transition and melting which appear when it heats to about 30 degreeC higher than melting | fusing point at 10 degreeC per minute. Tg was determined from the peak top using the onset method and the melting point. Further, ΔE was obtained from the area of the part from the time when the peak corresponding to melting was separated from the baseline until it returned to the baseline again.

  In the present invention, “preserving stability” means that 10 g of resin is added to 90 g of toluene, the resin is heated and dissolved to obtain a transparent solution, and then cooled to 25 ° C. for one week at the same temperature. A thing that does not cause precipitation upon standing.

The polyolefin resin (A) in the present invention only needs to have a carboxyl group or an acid anhydride group. For example, the polyolefin resin (A1) having no carboxyl group or acid anhydride group has an ethylenically unsaturated carboxyl group. Alternatively, a modified polyolefin resin obtained by graft polymerization of an acid anhydride thereof, a copolymer of an olefin monomer and an ethylenically unsaturated carboxylic acid or an acid anhydride thereof, and the like can be given. Moreover, the polyolefin which has a carboxyl group can also be obtained by making it react with the acid anhydride group of polyolefin which has an acid anhydride group, and water or alcohol.
The amount of the carboxyl group or acid anhydride group in the polyolefin resin (A) will be described later.

The method for graft polymerization of polyolefin is not particularly limited. For example, the method disclosed in JP-A-11-293216 can be used.
The polyolefin (A1) is not particularly limited. For example, a homopolymer of olefin monomers such as ethylene, propylene, butene, butadiene, isoprene, hexene, octene, a copolymer of olefin monomers, or It refers to a polymer mainly composed of a hydrocarbon skeleton, such as a copolymer with other monomers and a hydride or halide of the obtained polymer. A copolymer of olefin monomers is preferred.

  As a copolymer of olefin monomers, a copolymer of ethylene, propylene and 1-butene is preferable, a binary copolymer of ethylene and propylene, a binary copolymer of ethylene and 1-butene, and propylene. A binary copolymer of 1-butene and a ternary copolymer of ethylene, propylene, and 1-butene are exemplified, and a binary copolymer of propylene and 1-butene is more preferable. The copolymerization ratio is preferably propylene: butene = 10: 90 to 80:20 (molar ratio), and more preferably 30:70 to 60:40 (molar ratio). In the copolymer of propylene and 1-butene, when propylene is less than 10 mol%, Tg may be lower than −30, and when it is higher than 80 mol%, the melting point may be higher than 110 ° C.

Other monomers that may be copolymerized with the olefin monomer are not particularly limited, for example,
Aromatic vinyl compounds such as styrene, α-methylstyrene, and indene;
Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, Alkyl (meth) acrylate compounds such as behenyl (meth) acrylate;
(Meth) acrylate compounds having an alicyclic structure such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate;
(Meth) acrylate compounds having an aromatic ring such as benzyl (meth) acrylate;
Hydroxyl group-containing (meth) acrylate compounds such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate;
(Meth) acrylate compounds having an amino group such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate;
Acrylamides such as (meth) acrylamide, dimethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, isopropyl (meth) acrylamide, diethyl (meth) acrylamide, hydroxyethyl (meth) acrylamide;
(Meth) acrylonitrile, acryloylmorpholine, etc. are mentioned.
Styrene, dodecyl (meth) acrylate, and stearyl (meth) acrylate are preferable from the viewpoint of graft polymerization and compatibility with polyolefin.
The ethylenically unsaturated carboxylic acid is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, and itaconic acid. These ethylenically unsaturated carboxylic acids or acid anhydrides thereof may be used alone or in combination of two or more.

  The polymerization method of the olefin monomer is not particularly limited. For example, a metal catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst such as the method disclosed in Japanese Patent Publication No. 07-080948, or (methyl) aluminoxane as necessary. A cocatalyst can be added to polymerize.

The polyolefin resin (A) used in the present invention preferably has a number average molecular weight in the range of 10,000 to 200,000, more preferably 30,000 to 150,000, from the viewpoint of excellent adhesion. Range.
When the number average molecular weight of the polyolefin resin (A) is in the above range, both coating suitability as an adhesive and resistance to electrolytic solution as a battery packaging material can be satisfied.
Specifically, when the number average molecular weight of the polyolefin resin (A) is smaller than 10,000, the entanglement of the polymer chain of the polyolefin resin (A) is insufficient, so that the film strength of the adhesive layer is lowered and the electrolytic solution resistance is reduced. There is a risk of shortage. Moreover, when the number average molecular weight of polyolefin resin (A) is larger than 200,000, there exists a possibility that the viscosity of an adhesive solution may be too high and coating property may deteriorate.
In addition, the number average molecular weight of polyolefin resin (A) is calculated | required as follows.
The measurement was carried out under the conditions of tetrahydrofuran as an eluent and a flow rate of 0.35 ml per minute using an HLC-8220GPC system manufactured by Tosoh Corporation with two TSKgel superHZM-N columns connected. A sample was prepared by dissolving 2 mg of polyolefin resin (A) in 5 ml of tetrahydrofuran. The number average molecular weight was calculated in terms of standard polystyrene.

  In the present invention, in addition to the polyolefin resin (A) having a carboxyl group or an acid anhydride group, a polyolefin resin not having a carboxyl group or an acid anhydride group may be used in combination as long as the effects of the invention are not impaired. .

Examples of the polyolefin resin having no carboxyl group or acid anhydride group used in the present invention include Kuraray LIR-30 (isoprene polymer), LIR-200 (hydrogenated isoprene polymer) manufactured by Kuraray Co., Ltd. LBR-300 (butadiene polymer), Kuraray Co., Ltd. Septon 2002, 2004 (above, hydrogenated styrene-isoprene-styrene copolymer), 2104, 4033, HG252 (above, hydrogenated styrene-isoprene / butadiene-styrene) Copolymer), Asaprene T-432 and T-437 manufactured by Asahi Kasei Chemicals Corporation, Clayton D1155 manufactured by Kraton Polymer Japan Co., Ltd. (above, styrene-butadiene-styrene copolymer), Tuftec P1500 manufactured by Asahi Kasei Chemicals Corporation , P2000, M 10 (partially hydrogenated styrene-butadiene-styrene copolymer), H1052, H1043 (above, hydrogenated styrene-butadiene-styrene copolymer), Super Clon C (chlorinated product of propylene polymer) manufactured by Nippon Paper Chemicals Co., Ltd. )
, Lexpearl EMA (ethylene-methyl acrylate copolymer) manufactured by Nippon Polyethylene Co., Ltd., Lexpearl EEA (ethylene-ethyl acrylate copolymer), Everflex (ethylene-vinyl acetate) manufactured by Mitsui DuPont Polychemical Co., Ltd. Copolymer), Bond First (ethylene-glycidyl methacrylate copolymer) manufactured by Sumitomo Chemical Co., Ltd., and the like. These may be used alone or in any combination of two or more.

Next, the polyfunctional isocyanate curing agent (B) used in the present invention will be described.
The adhesive composition of the present invention creates a crosslinked structure by reacting with a carboxyl group or an acid anhydride group of a polyolefin resin (A) having a carboxyl group or an acid anhydride group, and has high adhesive strength, electrolyte resistance, A polyfunctional isocyanate curing agent (B) is included for the purpose of imparting adhesive strength in a high temperature environment.

The polyfunctional isocyanate curing agent (B) used in the present invention is not limited to the following, but well-known diisocyanates and compounds derived therefrom can be preferably used.
For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, bis (4-isocyanatocyclohexyl) methane, or water Diisocyanates such as diphenylmethane diisocyanate and compounds derived therefrom, that is, isocyanurates, adducts, biurets, uretdiones, allophanates, and prepolymers having isocyanate residues (obtained from diisocyanates and polyols) Low polymer), or a composite of these, and these may be used alone, or two or more may be arbitrarily selected. Also together look may be used.

Moreover, you may use the compound obtained by making a part of isocyanate group of the said isocyanate compound react with the compound which has reactivity with an isocyanate group as a polyfunctional isocyanate hardening | curing agent (B).
Compounds having reactivity with isocyanate groups include compounds containing amino groups such as butylamine, hexylamine, octylamine, 2-ethylhexylamine, dibutylamine, ethylenediamine, benzylamine, 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, phenol;
Compounds having an epoxy group such as allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether;
Examples thereof include 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 polyfunctional isocyanate curing agent (B) used in the present invention, a polyfunctional isocyanate curing agent (B) having an isocyanurate of the above-mentioned diisocyanate is preferable because of its excellent resistance to electrolytic solution.

The number of isocyanate groups in the polyfunctional isocyanate curing agent (B) used in the present invention is preferably 2 to 7 on average per molecule, and more preferably 3 to 5. When the number of isocyanate groups in one molecule of the polyfunctional isocyanate curing agent (B) is less than 2, a sufficient amount of crosslinking cannot be obtained, and the electrolytic solution resistance may be deteriorated. Further, when the number of isocyanate groups in one molecule of the polyfunctional isocyanate curing agent (B) is more than 7, a carboxyl group or an acid with respect to one molecule of the polyfunctional isocyanate curing agent (B) in the adhesive solution at the time of coating. Since there is a high possibility that a plurality of polyolefin resins (A) having an anhydride group will react, there is a risk of significant increase in viscosity during coating, resulting in poor coating properties.

From the viewpoint that the polyolefin resin (A) having a carboxyl group or an acid anhydride group used in the present invention is excellent in adhesion and solubility, the content of carboxyl groups per 1 g of the polyolefin resin (A) is X ( mmol), when the content of the acid anhydride group is Y (mmol), X + 2Y is preferably 0.05 to 0.6.
When X + 2Y is less than 0.05, there are few acidic groups that serve as crosslinking points, crosslinking is not sufficient, and sufficient adhesion and electrolyte resistance may not be obtained. If it is larger than 0.6, the crosslinking shrinkage of the coating film is large, so that the adhesive force may be insufficient, or the solubility in a solvent may be reduced.

When the polyolefin resin (A) having a carboxyl group or an acid anhydride group contained in the adhesive composition is P (g) and the isocyanate group derived from the polyfunctional isocyanate curing agent (B) is Z (mmol), The polyfunctional isocyanate curing agent (B) is contained in the range where Z / [(X + 2Y) P] is 0.5 to 10, and more preferably in the range of 0.5 to 7.
When Z / [(X + 2Y) P] is smaller than 0.5, the amount of isocyanate group is small relative to the active hydrogen derived from the carboxyl group of the polyolefin resin (A) having a carboxyl group or an acid anhydride group. A sufficient cross-linked structure may not be formed, resulting in insufficient cohesive strength and insufficient adhesive strength and electrolyte resistance. When it is larger than 10, the unreacted polyfunctional isocyanate curing agent (B) may be present in an excessive amount, thereby deteriorating the electrolytic solution resistance.

Next, the solvent (C) used in the present invention will be described.
The solvent (C) that can be used in the adhesive composition of the present invention can dissolve the material used in the present adhesive alone or as a mixed solvent, and the reactivity with the polyfunctional isocyanate curing agent (B) is inactive, It will not specifically limit if it can be volatilized and removed by the overheating in the drying process at the time of adhesive coating. Specific examples of these solvents include aromatic organic solvents such as toluene and xylene;
aliphatic organic solvents such as n-hexane and n-heptane;
Cycloaliphatic organic solvents such as cyclohexane and methylcyclohexane;
Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone;
Ester solvents such as ethyl acetate and butyl acetate;
Alcohol solvents such as ethanol, methanol, n-propanol, 2-propanol, butanol, hexanol;
Ether solvents such as diisopropyl ether, butyl cellosolve, tetrahydrofuran, dioxane, butyl carbitol;
Glycol ether solvents such as diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether;
Examples include glycol ester solvents such as ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and diethylene glycol monoethyl ether acetate. These may be used alone or in combination of two or more.

In the adhesive composition of the present invention, known additives such as a tackifier and a plasticizer may be blended as necessary within a range not impairing the effects of the invention.
Examples of tackifiers that can be used in the present invention include polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymer petroleum resins, styrene resins, and hydrogenated petroleum resins. Used for the purpose of improving strength. These may be used alone or in any combination of two or more.
Examples of the plasticizer used in the present invention include liquid rubbers such as polyisoprene and polybutene, and process oil.

The adhesive composition of the present invention is suitably used for laminating a metal foil and a heat-fusible film.
Examples of the metal of the metal foil include aluminum, copper, and nickel. These metal foils may be subjected to various surface treatments. Examples of the surface treatment include chemical treatment such as physical treatment such as sand blast treatment and polishing treatment, degreasing treatment by vapor deposition, etching treatment, and primer treatment applying a coupling agent or coating agent.
Examples of the heat-fusible film include polyolefin films such as polyethylene and polypropylene, and an unstretched film is particularly preferably used.

A laminate using the adhesive composition of the present invention can be obtained, for example, as follows.
The adhesive composition of the present invention is applied to one surface of a metal foil (or heat-fusible film), the solvent is stripped (dried), and an uncured adhesive layer is formed. After stacking a heat-fusible film (or metal foil) on the surface of the uncured adhesive layer under pressure at 0 ° C., leave it at 40-80 ° C. for about 3-10 days to make the adhesive layer sufficiently A laminate can be obtained by curing (also referred to as aging) and bonding the metal foil and the heat-fusible film together.
For coating of the adhesive composition, a general coating machine such as a comma coater can be used. Moreover, it is preferable that the thickness (amount) of the cured adhesive layer at the time of dry curing is about 1 to 30 g / m ² .

In addition, metal foil can comprise another sheet-like member on the other surface (the surface where the adhesive layer formed from the adhesive composition of the present invention is not in contact).
Other sheet-like members may be laminated on a metal foil in advance using an adhesive composition (may be the same as or different from the adhesive composition of the present invention), After obtaining the laminated body of metal foil and a heat-fusible film using the adhesive composition of this invention, another sheet-like member can also be laminated | stacked on metal foil.
Other sheet-like members used include stretched films such as polyester resin and polyamide resin (nylon), and other sheet-like members use a laminate as a battery packaging material to form a battery container. At this time, the outer layer side resin film is located on the outside not in contact with the electrolytic solution.

The battery container using the laminated body which bonds together metal foil and a heat-fusible film using the adhesive composition of this invention is demonstrated. The laminated body using the adhesive composition of the present invention is suitably used for forming a battery container of a secondary battery, particularly a nonaqueous electrolyte secondary battery.
The secondary battery includes a battery body, a plurality of terminals respectively joined to the positive electrode and the negative electrode of the battery body, a battery container, and an electrolyte. The battery container is obtained from a laminate in which a metal foil and a heat-fusible film are laminated via an adhesive layer formed from the adhesive composition of the present invention, and the heat-sealing The conductive film is in contact with the electrolyte.

Battery containers include a bag-shaped container (pouch type) and a tray-shaped container type formed by molding a flat laminate using a mold. One form of the bag-like container is illustrated in FIG. 8 of JP-A-2007-2949481. Further, one form of the tray-like container is shown in FIG. 9 of the publication, and the other form is shown in FIG. The laminate using the adhesive composition of the present invention can be used to form both types of containers, bags and trays. In either case, a part of the heat-fusible film is heat-sealed in a state where the heat-fusible film faces inward and the tips of the plurality of terminals protrude to the outside. Seal the electrolyte solution.

  The electrolyte solution starts to penetrate from the heat-fusible film toward the metal foil, but the adhesive layer formed from the adhesive composition of the present invention is excellent in resistance to the electrolyte solution, so that the heat-fusible property The adhesive strength between the film and the metal foil does not decrease, and problems such as liquid leakage do not occur.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, a following example does not restrict | limit the right range of this invention at all. In addition, each evaluation in an Example followed the following method. In Examples, “%” represents “% by weight” and “parts” represents “parts by weight”.
<Quantification of carboxyl group>
The weighed sample x1 (g) was dissolved in refluxed xylene, cooled to room temperature, and then titrated with 0.1M ethanolic potassium hydroxide using phenolphthalein as an indicator. The end point of the titration was when the color of the indicator remained for 10 seconds. If the titer is x2 (ml), X can be obtained from the following equation.
X = 0.1 × x2 / x1
<Quantification of acid anhydride group>
The weighed sample y1 (g) was dissolved in refluxed xylene, cooled to room temperature, and then octylamine y2 (mmol) equal to or greater than the acid anhydride group of the sample was added. The remaining octylamine was quantified by titrating with 0.1M ethanolic perchloric acid. If the titer is y3 (ml), Y can be obtained from the following equation.
Y = (0.1 * y3-y2) / y1

<Number average molecular weight>
The measurement was carried out under the conditions of tetrahydrofuran as an eluent and a flow rate of 0.35 ml per minute using an HLC-8220GPC system manufactured by Tosoh Corporation with two TSKgel superHZM-N columns connected. A sample was prepared by dissolving 2 mg of polyolefin resin (A) in 5 ml of tetrahydrofuran. The number average molecular weight was calculated in terms of standard polystyrene.

<Glass transition temperature (Tg), melting point, melting temperature energy (ΔE)>
The melting energy was measured by using a DSC (SSC-5200) manufactured by Seiko Denshi Kogyo Co., Ltd. according to JIS-K-7121.
When the diameter or each side of the polyolefin resin (A) of about 10 mg is 0.5 mm or less, it is used as it is, and if it exceeds 0.5 mm, it is cut into 0.5 mm or less and put into a container.
Heat to about 30 ° C above the melting point at 10 ° C per minute and then cool to about 50 ° C below Tg at 10 ° C per minute. If no clear Tg is observed, cool to about 50 ° C. below the melting point. Then, it calculated | required from the chart corresponding to the glass transition and melting which appear when it heats to about 30 degreeC higher than melting | fusing point at 10 degreeC per minute. Tg was determined from the peak top using the onset method and the melting point. Further, ΔE was obtained from the area of the part from the time when the peak corresponding to melting was separated from the baseline until it returned to the baseline again.
<Copolymerization composition ratio>
The copolymer composition ratio of polyolefin was determined by ¹³ C measurement using NMR (JNM-LA400) manufactured by JEOL Ltd.
A 20 mg sample was dissolved in 1 ml deuterated chloroform and measured. The copolymer composition ratio was calculated from the integration ratio of the peak, assuming that methylene groups derived from ethylene were contained in 40-50 ppm, methine groups derived from propylene were contained in 25-30 ppm, and methine groups derived from 1-butene were contained in 30-35 ppm. .

<Synthesis Example 1>
Purified toluene 250mL, methylaluminoxane 0.5mg in terms of Al atom, dimethylsilyl-bis- (4,5,6,7,8-pentahydroazulen-2-yl) in a 500mL glass autoclave purged with nitrogen Zirconium dichloride was charged with 1.25 μg atoms in terms of Zr atoms and heated to 40 ° C. Subsequently, while supplying ethylene and propylene at a constant rate of 50 L / hr and 40 L / hr, respectively, 1-butene monomer was continuously supplied to maintain a constant pressure of 1.32 MPa at 40 ° C., and polymerization was started. . After polymerization at 40 ° C. for 8 hours, isopropanol was added to terminate the polymerization. The obtained polymer solution was added to a large amount of methanol to precipitate a polymer. The precipitated polymer was filtered and dried to obtain a polyolefin copolymerized with ethylene / propylene / 1-butene = 46/33/15 (molar ratio).
20 g of the obtained polyolefin and 20 g of cellosolve acetate were charged and dissolved by heating in a nitrogen stream to a solution temperature of 110 ° C. A solution prepared by dissolving 4 g of maleic anhydride, 2 g of lauryl methacrylate and 0.6 g of benzoyl peroxide in 239.4 g of cellosolve acetate was added dropwise over 2 hours. The reaction was continued at that temperature for an additional hour after the addition. The obtained polymer solution was added to a large amount of methanol to precipitate a polymer. The precipitated polymer was filtered and dried to obtain a polyolefin resin (A1) having an acid anhydride group.
The Tg, melting point, and ΔE of the polyolefin resin (A1) were 5 ° C., 103 ° C., and 45 mJ / mg, respectively.

<Synthesis Examples 2-4, 6-12>
The polyolefin resins (A2) to (A4) and (A6) to (A12) having an acid anhydride group in the same manner as in Synthesis Example 1 except for the flow rate ratio of the mixed gas shown in Table 1 and the monomer addition amount during graft polymerization. Got.

<Synthesis Example 5>
A polyolefin resin having an acid anhydride group was obtained in the same manner as in Synthesis Example 1 except for the flow rate ratio of the mixed gas shown in Table 1 and the monomer addition amount during graft polymerization. The obtained polyolefin resin was stored in an environment of 85 ° C. and 85% RH for 3 days to obtain a polyolefin resin (A5) having a carboxyl group.

ＬＭＡ：ラウリルメタクリレート
Ｓｔ：スチレン

LMA: Lauryl methacrylate St: Styrene

<Example 1>
15 parts of polyolefin (A1) was dissolved by heating in 113.3 parts of xylene. By adding 5 parts of Duranate 24A-100 (Asahi Kasei Chemicals Corporation, hexamethylene diisocyanate (HDI) biuret) and stirring, an adhesive solution having a solid content of 15% was obtained.

The adhesive solution was applied to one side of an aluminum foil having a thickness of 50 μm with a bar coater and dried at 100 ° C. for 1 minute to obtain an adhesive layer of about 2 g / m ² . Next, an unstretched polypropylene film (hereinafter referred to as CPP) having a thickness of 30 μm was superposed on the adhesive layer and passed between two rolls set at 60 ° C. to obtain a laminate. Thereafter, the obtained laminate was cured (aging) at 40 ° C. for 5 days. The aluminum foil / CPP laminate film thus obtained is hereinafter referred to as “Al / CPP laminate film”.

[Storage stability]
Each of the polyolefins (A1) to (A12) was dissolved in the solvent used in each example to obtain a resin solution having a solid content of 15%, and the resin solution was allowed to stand for 24 hours in an environment of 25 ° C. The appearance was observed and evaluated according to the following criteria.
○ Excellent in practical use: colorless and transparent × Not practical: no fluidity or cloudiness

[Adhesive strength-After immersion in electrolytic solution and before peel test (initial adhesive strength)]
The Al / CPP laminated film was allowed to stand for 6 hours in an environment of 25 ° C. and a humidity of 65%, then cut to a size of 200 mm × 15 mm, and a tensile tester was used according to the test method of ASTM-D1876-61. Then, a T-type peel test was performed at a load speed of 100 mm / min in an environment of 25 ° C. and a humidity of 65%. The peel strength (N) of 15 mm width between the aluminum foil / CPP is shown as an average value of five test pieces. Judgment was made according to the following criteria.
◎ Excellent in practical use: 7N or more ○ Practical range: 5N or more to less than 7N × Not practical: Less than 5N

[Adhesive strength-After electrolytic solution immersion and after peel test (electrolytic solution resistance)]
A test piece similar to that used in the initial adhesion strength test was dissolved in an electrolytic solution [lithium hexafluorophosphate dissolved in ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1/1/1 (volume ratio). In a lithium hexafluorophosphate solution] at 85 ° C. for 7 days. Thereafter, the test piece was taken out and washed with running water for about 10 minutes. After sufficiently wiping off the water with a paper wiper, the adhesive strength of the test piece was measured in the same manner as the adhesive strength measurement before the immersion test. Judgment was made according to the following criteria.
◎ Excellent in practical use: Less than ± 10% change rate with respect to initial bond strength ○ Practical range: Less than ± 30% change rate with respect to initial bond strength × Impractical use: Change rate with respect to initial bond strength Is more than ± 30%

[Heat fusion]
A 100 mm × 150 mm Al / CPP laminated film was folded in half with a 150 mm side so that the CPP was on the inside, so that it was 100 mm × 75 mm (hereinafter referred to as “bi-fold film”).
The 50 mm side of a 10 × 50 mm aluminum piece (thickness: 40 μm) is located approximately 50 mm from one side of 75 mm of the bi-fold film and is approximately parallel to the 75 mm side. About 25 mm was inserted from the open end, and a part (10 × 25 mm) of the aluminum piece was set so as to come out of the folded film.
The two-fold film is heated and pressed (180 ° C., 1 kgf, 2 seconds, or 180 ° C., 2 kgf, 2 seconds) with the aluminum piece sandwiched between them, and the CPPs are heat-sealed to each other on both sides of the 10 mm wide aluminum piece. CPP was heat-sealed.
After heat sealing, a portion where an aluminum piece having a width of 10 mm was sandwiched and another portion were separated.

<Heat fusion strength>
Five test pieces for peel strength measurement having a width of 15 mm were cut out from the other portions, and the peel strength between CPPs (heat fusion strength) was measured under the same conditions as those for measuring the adhesive strength between the aluminum foil / CPP described above.
◎ Excellent in practical use: 40N or more ○ Practical range: 30N or more and less than 40N × Not practical: Less than 30N

<Resistance value>
The portion between which an aluminum piece having a width of 10 mm was sandwiched was used as a test piece, and the resistance value between the aluminum foil derived from the Al / CPP laminated film and the aluminum piece was measured. Judgment was made according to the following criteria.
○ Excellent in practical use: heat-sealing and resistance value of 100Ω or more.
× Not practical: No heat fusion or resistance value of less than 100Ω.

<Examples 2 to 12><Comparative Examples 1 to 7>
An Al / CPP laminated film was produced and evaluated in the same manner as in Example 1 except that the composition of the adhesive was changed to the composition shown in Table 2. The results are shown in Table 2.

The symbols in Table 2 are as follows.
Duranate 24A-100 (Asahi Kasei Chemicals Corporation, hexamethylene diisocyanate (HDI) biuret, NCO content: 23.5%
Duranate TPA-100: Asahi Kasei Chemicals Corporation, HDI isocyanurate, NCO content: 23.1%
Death module XP2580: manufactured by Sumika Bayer Urethane Co., Ltd., HDI allophanate, NCO content: 20%
Duranate TSE-100: Asahi Kasei Chemicals Corporation, weak solvent soluble HDI isocyanurate, NCO content: 12%
Duranate D101: Asahi Kasei Chemicals Corporation, HDI-based isocyanurate bifunctional prepolymer, NCO content: 19.7%
Death Module N3400: manufactured by Sumika Bayer Urethane Co., Ltd., HDI uretdione, NCO content: 21.8%
Desmodule Z4470 MPA / X: manufactured by Sumika Bayer Urethane Co., Ltd., isophorone diisocyanate-based isocyanurate (propylene glycol monomethyl ether acetate / xylene = 1/1 solution, solid content 70%, NCO content: 11.9%

As shown in Examples 1 to 14 in Table 2, it is possible to provide an adhesive having good storage stability, adhesive strength (initially and after immersion in an electrolytic solution), and heat-fusibility.
Since the adhesives of Comparative Examples 1 to 3 have a high melting point and ΔE of the polyolefin resin (A9) or (A10), they do not impair the insulation even when thermally fused at a high pressure. The initial adhesive strength is weak. In addition, it is estimated that the adhesive strength after immersion in the electrolyte was improved because the adhesive layer was softened by the heat during immersion.
In Comparative Examples 4 and 5, since the Tg of the polyolefin resins (A11) and (A12) is low, the adhesive layer is excessively deformed at the time of heat-sealing, and insulation cannot be ensured.
Comparative Example 6 is a case where a polyolefin resin (A12) having a low Tg is used, and insulation cannot be ensured even if the pressure during heat fusion is reduced.
Comparative Example 7 uses a polyolefin resin (A12) having a low Tg, and increases the Z / [(X + 2Y) P] to make it difficult to deform the adhesive layer at the time of heat fusion. Insulating properties could be ensured, but the crosslink density was high and the initial adhesive strength was weak.

The adhesive of the present invention is excellent in storage stability. If the adhesive of the present invention is used, the adhesive of the heat-fusible film and the metal foil stably exhibits sufficient adhesive strength, and the electrolyte solution has a higher temperature. Even if it is immersed in the laminate, it is possible to form a laminate that can maintain the adhesive strength at a high level. Further, even if the heat-fusible film layers are heat-sealed with each other under the condition that sufficient fusion strength can be expressed, the adhesive layer does not significantly deform. Then, the laminated body using the adhesive agent of this invention is used suitably for a battery packaging material, and is suitable for formation of battery containers, such as a battery soft pack and a battery tray.
In particular, the soft pack for a nonaqueous electrolyte secondary battery using the adhesive of the present invention can contribute to the safety and life extension of the nonaqueous electrolyte secondary battery. Such a high quality non-aqueous electrolyte secondary battery leads to the spread of non-aqueous electrolyte secondary batteries, and contributes to environmental conservation from the viewpoint of high-efficiency use of energy as a new energy material.

  In addition, the adhesive composition according to the present invention is a polyolefin-based resin that requires high adhesive strength and chemical resistance in various industrial fields such as architecture, medical care, and automobiles, in addition to soft packs for non-aqueous electrolyte secondary batteries. Suitable as an adhesive for the materials used.

Claims (1)

After applying the following adhesive composition on one surface of the metal foil or the heat-fusible film, volatilizing the solvent, and forming an uncured adhesive layer, 60 to 150, the uncured under pressure After laminating a heat-fusible film or metal foil on the surface of the adhesive layer, the laminate is allowed to stand at 40 to 80 for about 3 to 10 days, and the adhesive layer is aged. Method.
<Adhesive composition>
Containing a polyolefin resin (A) having a carboxyl group or an acid anhydride group, a polyfunctional isocyanate curing agent (B), and a solvent (C);
The polyolefin resin (A) has a glass transition temperature of −30 to 10 ° C., a melting point of 60 to 110 ° C., and a melting energy of 15 to 50 (mJ / mg),
An adhesive composition in which the polyolefin resin (A) is any of the following (A) or (A).
(A) A binary copolymer of propylene and 1-butene or a terpolymer of ethylene, propylene and 1-butene is mixed with an ethylenically unsaturated carboxylic acid or acid anhydride thereof, styrene, dodecyl (meta ) A modified polyolefin resin obtained by graft polymerization of a monomer selected from the group consisting of acrylate and stearyl (meth) acrylate.
(A) Modification by graft polymerization of an ethylenically unsaturated carboxylic acid or its acid anhydride to a binary copolymer of propylene and 1-butene (except when 1-butene is 60 mol% or less). Polyolefin resin.