CN115537170A

CN115537170A - Polyurethane adhesive for electricity storage element packaging material, electricity storage element container, and electricity storage element

Info

Publication number: CN115537170A
Application number: CN202210732467.XA
Authority: CN
Inventors: 花木寛; 白石功贵; 广嶋努; 秋山崇文
Original assignee: Toyo Morton Ltd; Toyo Ink SC Holdings Co Ltd; Toyochem Co Ltd
Current assignee: Toyo Morton Ltd; Toyochem Co Ltd; Artience Co Ltd
Priority date: 2021-06-30
Filing date: 2022-06-24
Publication date: 2022-12-30
Also published as: KR20230004285A; JP7099593B1; JP2023006643A

Abstract

The invention provides a polyurethane adhesive for an electricity storage element packaging material, an electricity storage element container and an electricity storage element, wherein the polyurethane adhesive has excellent adhesiveness and formability, has strict heat-resistant sealing performance of a formed product, has excellent formability after a long-term durability test of heat resistance and humidity resistance, and does not generate appearance defects such as floating between layers. The problem can be solved by a polyurethane adhesive for an electricity storage element packaging material, which contains a polyol main agent (A) and a polyisocyanate curing agent (B), wherein the polyol main agent (A) contains a polyurethane resin having a hydroxyl group as a reaction product of a polyester polyol and a polyisocyanate, and contains a phenol antioxidant (C) in an amount of 0.03 to 3 mass% based on the mass of the polyol main agent (A).

Description

Polyurethane adhesive for electricity storage element packaging material, electricity storage element container, and electricity storage element

Technical Field

The present disclosure relates to a polyurethane adhesive for an electric storage element packaging material having good appearance and excellent adhesion strength, moldability, and durability of a molded product, and an electric storage element packaging material, an electric storage element container, and an electric storage element using the same.

Background

With the rapid development of electronic devices such as mobile phones and portable personal computers, there is an increasing demand for power storage elements such as secondary batteries such as lithium ion batteries and nickel hydrogen batteries, and electrochemical capacitors such as electric double layer capacitors. Among these, small lithium ion batteries have attracted attention in terms of high energy density and light weight. As an outer package of a lithium ion battery, a metal can has been used, but from the viewpoint of weight reduction and productivity, a packaging material obtained by laminating a plastic film, a metal foil, or the like has become the mainstream.

For example, patent document 1 discloses a laminate adhesive and a packaging material having unevenness and formed of the adhesive, wherein a polyol component includes a polyurethane polyol modified with an aromatic polyisocyanate, an epoxy component and a polyisocyanate component in which the content ratio of an epoxy unit is defined.

Patent document 2 discloses an adhesive composition in which a polyester polyol having a defined molecular weight and a defined aromatic carboxylic acid ratio and a polyester urethane having a trifunctional or higher hydroxyl group and a defined molecular weight and a defined aromatic carboxylic acid ratio are mixed at a certain ratio, and a polyfunctional isocyanate curing agent are blended at a certain ratio.

Patent document 3 discloses a 2-pack adhesive comprising a polyol composition containing a polyester polyol containing a polyol having a specific number of methylene chains between two hydroxyl groups, and a polyisocyanate composition.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open publication No. 2019-156925

[ patent document 2] Japanese patent laid-open publication No. 2017-25287

[ patent document 3] International publication No. 2021/039338

Disclosure of Invention

[ problems to be solved by the invention ]

In recent years, as the use of electric storage devices in vehicles or homes has expanded, secondary batteries have been required to have a large capacity, and packaging materials for electric storage devices have been required to have good moldability. In addition, in the vehicle-mounted applications, excellent outdoor long-term durability is required for heat resistance and moist heat resistance, and in terms of safety, polymer-type lithium ion batteries and all-solid batteries are being developed, and the heat-resistant durability temperature required is also increased by removing the carbonate solvent having a low boiling point contained in the electrolyte solution. Therefore, the packaging material is required to have good initial adhesion strength and formability between the film and the metal foil and good heat-resistant sealing properties of the formed product, and the formed product is required to maintain a shape free from delamination even after a long-term durability test, and further required to have no appearance abnormality. However, the adhesives described in patent documents 1 to 3 use a polyurethane resin having a hydroxyl group as a reaction product of a polyester polyol and a polyisocyanate, but have a problem in long-term durability against heat and moist heat required for in-vehicle applications and the like. Accordingly, an object of the present disclosure is to provide a polyurethane adhesive for an electric storage element packaging material, which has excellent adhesiveness, moldability, and heat-resistant sealability of a deformed molded product, and further has excellent moldability even after a long-term durability test of heat resistance and moist heat resistance, and which does not cause appearance defects such as floating between layers, and an electric storage element packaging material, an electric storage element container, and an electric storage element using the adhesive.

[ means for solving problems ]

As a result of repeated research to solve the above problems, the following embodiments have found that the above problems can be solved, and the present disclosure has been completed.

An embodiment of the present disclosure relates to a polyurethane adhesive for an electricity storage element packaging material, which contains a polyol main agent (a) and a polyisocyanate curing agent (B), wherein the polyol main agent (a) contains a polyurethane resin having a hydroxyl group as a reaction product of a polyester polyol and a polyisocyanate, and contains a phenol antioxidant (C) in an amount of 0.03 to 3 mass% based on the mass of the polyol main agent (a).

Another embodiment of the present disclosure relates to the polyurethane adhesive for an electricity storage element packaging material, wherein the polyol main agent (a) further contains an epoxy resin.

Another embodiment of the present disclosure relates to the polyurethane adhesive for an electricity storage device packaging material, wherein the polyol base material (a) further contains an amino group-containing silane coupling agent.

Another embodiment of the present disclosure relates to the polyurethane adhesive for electricity storage device packaging material, wherein the content of the amino group-containing silane coupling agent is 0.05 to 5% by mass based on the mass of the polyol base agent (a).

Another embodiment of the present disclosure relates to the polyurethane adhesive for a power storage element packaging material, wherein the polyurethane resin having a hydroxyl group has a structure in which at least a part of the phenolic antioxidant (C) is bonded via a covalent bond.

Another embodiment of the present disclosure relates to the polyurethane adhesive for an electricity storage element packaging material, wherein the polyurethane resin having a hydroxyl group has a urethane bond concentration of 0.10mmol/g or more and 0.90mmol/g or less.

Another embodiment of the present disclosure relates to the polyurethane adhesive for an electricity storage element packaging material, wherein the weight average molecular weight of the polyurethane resin having a hydroxyl group is 30,000 or more and 100,000 or less.

Another embodiment of the present disclosure relates to the polyurethane adhesive for a power storage element packaging material, wherein the polyester polyol constituting the polyurethane resin having a hydroxyl group is a reaction product of a polybasic acid and a polyhydric alcohol, and the polybasic acid component contains 55 to 80mol% of an aromatic polybasic acid component in 100mol% of the polybasic acid component.

Still another embodiment of the present disclosure relates to a packaging material for an electricity storage element, which has a structure in which at least an outer layer side resin film layer (1), an outer layer side adhesive layer (2), a metal foil layer (3), an inner layer side adhesive layer (4), and a heat seal layer (5) are laminated in this order from the outside, and in the packaging material for an electricity storage element, the outer layer side adhesive layer (2) is a cured product of the polyurethane adhesive for an electricity storage element packaging material.

In another embodiment of the present disclosure, the container for an electric storage element is formed from the electric storage element packaging material, and in the container for an electric storage element, the outer layer side resin film layer (1) forms a convex surface, and the heat seal layer (5) forms a concave surface.

Still another embodiment of the present disclosure relates to an electric storage element including the container for an electric storage element.

[ Effect of the invention ]

The present disclosure provides a polyurethane adhesive for an electric storage element packaging material, which has excellent adhesiveness or moldability, heat-resistant sealability of a deformed molded product, and further has excellent moldability even after a long-term durability test of heat resistance and moist heat resistance, and does not cause appearance defects such as floating between layers, and an electric storage element packaging material, an electric storage element container, and an electric storage element using the adhesive.

Drawings

Fig. 1 is a schematic cross-sectional view of the power storage element packaging material of the present disclosure.

Fig. 2 is a schematic perspective view of one form (tray-like) of the energy storage element container according to the present disclosure.

[ description of symbols ]

(1): outer layer side resin film layer

(2): outer layer side adhesive layer

(3): metal foil layer

(4): inner layer side adhesive layer

(5): heat sealing layer

Detailed Description

< polyurethane adhesive for electric storage device packaging Material >

The disclosed polyurethane adhesive for electricity storage element packaging materials contains a polyol main agent (A) and a polyisocyanate curing agent (B), wherein the polyol main agent (A) contains a polyurethane resin having a hydroxyl group as a reaction product of a polyester polyol and a polyisocyanate, and contains 0.03 to 3 mass% of a phenol antioxidant (C) based on the mass of the polyol main agent (A). Hereinafter, the present disclosure will be described in detail.

< polyol base (A) >

The polyol main agent (A) contains a polyurethane resin having a hydroxyl group as a reaction product of a polyester polyol and a polyisocyanate, and 0.03 to 3 mass% of a phenol-based antioxidant (C) based on the mass of the polyol main agent (A). The polyurethane resin having a hydroxyl group can be obtained by subjecting a hydroxyl group in a polyester polyol described later and an isocyanate group in a polyisocyanate to a urethanation reaction under a condition that the hydroxyl group is excessive. In the present disclosure, it is important that the polyol main agent (a) contains a polyurethane resin having a hydroxyl group, and the content of the phenolic antioxidant (C) is controlled within a predetermined range. This stabilizes the thermal oxidation degradation and improves the high-temperature durability of the molded article, and an adhesive layer having excellent adhesiveness and moldability before and after the high-temperature durability can be formed.

< polyurethane resin having hydroxyl group >

The polyurethane resin having a hydroxyl group in the present disclosure is a reaction product of a polyol including a polyester polyol and a polyisocyanate, and is a polyester polyurethane polyol.

(polyester polyol)

As the polyester polyol, for example, a reaction product of a polybasic acid and a polyhydric alcohol; polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, polypentanolide, and poly (. Beta. -methyl-. Gamma. -valerolactone). The polybasic acids are not limited to the following, and examples thereof include: terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, itaconic anhydride, or other dibasic acids, or their dialkyl esters, or mixtures thereof. The polyhydric alcohol is not limited to the following, and examples thereof include: glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, butanediol, neopentyl glycol, butylethylpropylene glycol, 2-methyl-1,3-propanediol, trimethylolpropane, glycerol, 1,6-hexanediol, 1,4-butanediol, 1, 4-cyclohexanedimethanol, 3-methyl-1, 5-pentanediol, 3' -dimethylolheptane, 1, 9-nonanediol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol, and polyurethane polyol, or a mixture thereof. The polybasic acid component and the polyhydric alcohol component may be used alone or in combination of two or more.

The weight average molecular weight of the polyester polyol is preferably 10,000 to 30,000. When the weight average molecular weight is 10,000 or more, the rigidity of the ester bond remains after the reaction with polyisocyanate to obtain a polyurethane resin having a hydroxyl group, and the moldability is also excellent. When the weight average molecular weight is 30,000 or less, the concentration of the hydroxyl group at the end of the polyester polyol is not excessively low, and the reaction does not take too much time when the polyurethane resin having a hydroxyl group is obtained by reacting with a polyisocyanate.

The polyester polyol is preferably a reaction product of a polybasic acid and a polyhydric alcohol, and the polybasic acid preferably contains 55 to 80mol% of an aromatic polybasic acid component in 100mol% of the polybasic acid component. When the aromatic polybasic acid component is 55mol% or more, the cohesive force derived from the aromatic ring is improved, and the moldability is improved, and when it is 80mol% or less, the decrease in the adhesiveness can be suppressed, so that it is preferable.

(other polyols)

As the polyol constituting the polyurethane resin having a hydroxyl group, a polyol other than the polyester polyol or a short-chain diol may be used in combination. Examples of the usable polyol include: polyether polyol, polycarbonate polyol, acrylic polyol and polybutadiene polyol. The short-chain diol includes the above-mentioned polyols, and is preferably a linear diol such as 1,4-butanediol in view of reactivity with an isocyanate.

(polyisocyanate)

Examples of the polyisocyanate constituting the polyurethane resin having a hydroxyl group include: aliphatic diisocyanate, alicyclic diisocyanate, aromatic aliphatic diisocyanate, a monomer of a trifunctional or higher polyisocyanate, and various derivatives derived from diisocyanate.

Examples of the aliphatic diisocyanate include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1, 2-propylene diisocyanate, 1, 2-butylene diisocyanate, 2, 3-butylene diisocyanate, 1, 3-butylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate or 2, 4-trimethylhexamethylene diisocyanate, 2, 6-diisocyanate methylhexanoate.

Examples of the alicyclic diisocyanate include: 1, 4-cyclohexane diisocyanate, 1, 3-cyclohexane diisocyanate, 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate, 4' -methylenebis (cyclohexyl isocyanate), methyl-2, 4-cyclohexane diisocyanate, methyl-2, 6-cyclohexane diisocyanate, 1, 4-bis (isocyanatomethyl) cyclohexane, 1, 3-bis (isocyanatomethyl) cyclohexane.

Examples of the aromatic diisocyanate include: m-phenylene diisocyanate, p-phenylene diisocyanate, 4'-diphenyl diisocyanate, 1, 5-naphthalene diisocyanate, 4' -diphenylmethane diisocyanate, 2, 4-toluene diisocyanate or 2, 6-toluene diisocyanate or a mixture thereof, 4 '-toluidine diisocyanate, dianisidine diisocyanate, 4' -diphenyl ether diisocyanate.

Examples of the araliphatic diisocyanates include: 1, 3-xylylene diisocyanate or 1, 4-xylylene diisocyanate or a mixture thereof, omega' -diisocyanate-1, 4-diethylbenzene, 1, 3-bis (1-isocyanate-1-methylethyl) benzene or 1, 4-bis (1-isocyanate-1-methylethyl) benzene or a mixture thereof.

Examples of the trifunctional or higher polyisocyanate monomer include: triisocyanates such as triphenylmethane-4, 4',4 "-triisocyanate, 1,3, 5-triisocyanate benzene, 2,4, 6-triisocyanate toluene and the like; and tetraisocyanates such as 4,4' -diphenyldimethylmethane-2, 2' -5,5' -tetraisocyanate, and the like.

As various derivatives derived from diisocyanates, there may be used: adducts (adducts) of diisocyanates with low-molecular-weight polyols having a molecular weight of less than 200, such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1, 5-pentanediol, 3' -dimethylolpropane, cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, or castor oil, etc.; trimers (also known as trimers, nurate (nurate) entities) of diisocyanates; a biuret body; an allophanate body; further, polyisocyanates having a 2,4,6-oxadiazinetrione ring obtained from carbon dioxide and diisocyanate, and the like can also be used.

As the polyisocyanate constituting the polyurethane resin having a hydroxyl group, tolylene diisocyanate, 4' -diphenyl diisocyanate, or 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate is more preferable, particularly from the viewpoint of moldability into a packaging material or heat-resistant sealing properties of a deformed molded article.

The reaction temperature of the polyol and the polyisocyanate in obtaining the polyurethane resin having hydroxyl groups is preferably in the range of 50 to 200 ℃, more preferably 80 to 150 ℃. In the urethanization reaction, the molar ratio of the isocyanate group of the polyisocyanate to the hydroxyl group in the polyol (the number of moles of the isocyanate group/the number of moles of the hydroxyl group) is preferably 0.1 to 0.9, more preferably 0.3 to 0.8.

The weight average molecular weight of the polyurethane resin having a hydroxyl group is preferably 30,000 to 100,000, more preferably 50,000 to 100,000. When the weight average molecular weight is 30,000 or more, the elongation of the resin is improved and the processability is improved. If the weight average molecular weight is 100,000 or less, the viscosity of the adhesive solution is not excessively high, and appearance defects are not generated.

The hydroxyl value of the polyurethane resin having a hydroxyl group is preferably 0.5mgKOH/g to 20mgKOH/g, and more preferably 1mgKOH/g to 10mgKOH/g. The hydroxyl group is used in a crosslinking reaction with the polyisocyanate curing agent (B) described later, and the crosslinking reaction increases the molecular weight of the adhesive, thereby improving the heat resistance as a packaging material. The hydroxyl value can be determined, for example, by a method in accordance with Japanese Industrial Standards (JIS) K1557-1.

The urethane bond concentration of the polyurethane resin having a hydroxyl group is preferably 0.10 to 0.90mmol/g, more preferably 0.10 to 0.50mmol/g. When the content is 0.10mmol/g or more, excellent drawability is exhibited and moldability is further improved. When the concentration is 0.90mmol/g or less, the urethane bond concentration is not too high and the viscosity becomes appropriate, and thus the coating property and the appearance are more excellent. The urethane bond or urea bond has a hydrogen bond and a high polarity, and therefore has poor compatibility with a resin, and may cause deterioration in appearance or defects at the time of molding processing.

The urethane bond concentration can be calculated by using the following formula 1.

Formula 1: urethane bond concentration (mmol/g) = (NCO mass of polyisocyanate) × (mass of polyisocyanate%) + 42 × 1000+ (number of urethane bonds inside polyisocyanate ÷ polyisocyanate molecular weight) × (mass of polyisocyanate) × 1000 ×

For example, since the NCO mass% of toluene diisocyanate was 48.2%, the added amount was 2.5 mass%, and the number of internal urethane bonds was zero, the urethane bond concentration of the polyurethane resin having a hydroxyl group shown in synthesis example (a) -1 was set to be urethane bond concentration =0.482 × 0.025/42 × 1000=0.29mmol/g.

< phenol antioxidant (C) >

The polyol base (a) of the present disclosure contains 0.03 to 3 mass% of a phenolic antioxidant (C) based on the mass of the polyol base (a). It is important that the content of the phenolic antioxidant (C) is in the range of 0.03 to 3 mass%, and 0.03 mass% or more can provide an excellent stabilizing effect against thermal oxidation deterioration and improve the high-temperature durability of the molded product. By setting the content to 3% by mass or less, brittleness of the adhesive layer can be suppressed, appropriate toughness can be obtained, and both initial adhesion and high-temperature durability of the molded article can be achieved. The content of the phenolic antioxidant (C) is more preferably 0.05 to 1% by mass. In the present invention, "comprising the phenol antioxidant (C)" means that the phenol antioxidant (C) is contained and/or that the partial structure derived from the phenol antioxidant (C) is contained. The phrase "comprising a partial structure derived from the phenolic antioxidant (C)" means, for example, a case where the reaction product of the phenolic antioxidant (C) and the polyurethane resin having a hydroxyl group is contained, and also includes a case where a part of the phenolic antioxidant (C) is reacted. The hydroxyl group-containing polyurethane resin preferably has a structure in which at least a part of the phenolic antioxidant (C) is bonded via a covalent bond. More preferably, the polyester polyol has a structure in which at least a part of the phenolic antioxidant (C) is bonded to the polyester polyol through a covalent bond.

Examples of the phenolic antioxidant include: monophenol antioxidants such as 2, 6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2, 6-di-t-butyl-4-ethylphenol, and stearyl β - (3, 5-di-t-butyl-4-hydroxyphenyl) propionate; bisphenol antioxidants such as 2,2 '-methylenebis (4-methyl-6-tert-butylphenol), 2' -methylenebis (4-ethyl-6-tert-butylphenol), 4 '-thiobis (3-methyl-6-tert-butylphenol), 4' -butylidenebis (3-methyl-6-tert-butylphenol), and 3, 9-bis [1, 1-dimethyl-2- [ beta- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] ethyl ]2,4,8, 10-tetraoxaspiro [5,5] undecane; examples of the antioxidant include high-molecular-weight phenol antioxidants such as 1, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [ methylene-3- (3 ',5' -di-t-butyl-4 ' -hydroxyphenyl) propionate ] methane, bis [3, ' -bis- (4 ' -hydroxy-3 ' -t-butylphenyl) butyrate ] diol ester, 1,3, 5-tris (3 ',5' -di-t-butyl-4 ' -hydroxybenzyl) -S-triazine-2, 4,6- (1h, 3h, 5h) trione, and trisphenol. Particularly preferred is a high molecular weight hindered phenol antioxidant of a tetraphenol or a trisphenol type.

The high molecular weight type having a plurality of phenol skeletons has low volatility and high retention even at high temperature. Further, the phenolic antioxidant is preferably contained in a polyester polyol contained in a hydroxyl group-containing polyurethane resin, and a part of the phenolic groups are incorporated into the resin through an ester bond as a covalent bond under reduced pressure at 230 to 250 ℃. Further, it is particularly preferable that the pressure is reduced at 260 to 280 ℃ to increase the incorporation amount of the phenolic antioxidant, and the phenolic antioxidant is integrated by multi-dimensional branching. As an effect of incorporating the phenolic antioxidant into the polyester polyol, even if entanglement of the polyester polyol main chain is disentangled in a high-temperature environment, the polymer radical and the phenolic antioxidant are located in the vicinity, whereby radical exchange can be efficiently performed, and thermal oxidative degradation can be suppressed. Further, incorporation of a phenolic antioxidant into a polyester polyol at high temperature can form multi-dimensional branches and also suppress thermal decomposition and deterioration.

The phenolic antioxidant (C) may be used alone or in combination of two or more. Further, a sulfur-based antioxidant or a phosphorus-based antioxidant may be used in combination.

Examples of the sulfur-based antioxidant include: dilauryl 3,3' -thiodipropionate, dimyristyl 3,3' -thiodipropionate, distearyl 3,3' -thiodipropionate, and the like. Examples of the phosphorus-containing antioxidant include: triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite, and the like.

< polyisocyanate hardener (B) >

The polyisocyanate curing agent (B) performs a crosslinking reaction with the hydroxyl groups in the polyurethane resin having hydroxyl groups, and thus acts to increase the molecular weight of the adhesive layer and increase the internal cohesive force that exhibits energy elasticity. In addition, since the isocyanate group can react with water to form a urea bond having a high cohesive force, the cohesive force of the adhesive layer can be increased by performing a self-crosslinking reaction during curing.

The polyisocyanate curing agent (B) has an action of enhancing an interaction with a surface of a substrate described later, and particularly when a substrate subjected to physical treatment such as corona discharge treatment or chemical treatment such as organic primer is used, a strong interaction can be exhibited between the outer layer side adhesive layer and the substrate by a chemical reaction between an isocyanate group in the polyisocyanate curing agent (B) and an active hydrogen group on the surface of the substrate. As described above, by using the polyisocyanate curing agent (B), a strong outer layer-side adhesive layer can be formed, and the adhesive layer can suppress the expansion and contraction movement of the base material accompanying a rapid environmental change, and can maintain the adhesive strength at a high level.

As the polyisocyanate curing agent (B), the compounds listed in the above-mentioned item [ polyisocyanate ] constituting the polyurethane resin having a hydroxyl group can be used, and one kind may be used alone, or two or more kinds may be used in combination. In particular, as the polyisocyanate curing agent (B), an uretate of diisocyanate, an adduct of trimethylolpropane to diisocyanate, a biuret type, a prepolymer having an isocyanate residue (an oligomer obtained from diisocyanate and polyol), a uretdione (uretdione) having an isocyanate residue, an allophanate, or a composite thereof is preferable. In the case of the use for a vehicle-mounted electric storage device, an adduct of tolylene diisocyanate and trimethylolpropane, or a urethane of 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate or hexamethylene diisocyanate is preferable from the viewpoint of achieving excellent high-temperature durability, high cohesive force and high processability. From the viewpoint of adhesiveness, a urethane product of 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate or hexamethylene diisocyanate is more preferable.

The content of the polyisocyanate curing agent (B) is preferably 25 to 60 mass% based on the mass of the solid content of the polyol base (a). When the polyisocyanate curing agent (B) is 25 mass% or more, the molecular weight of the adhesive layer can be efficiently increased. This improves the increase in internal cohesive force, and enables to obtain high adhesiveness and moldability. When the content is 60% by mass or less, the amount of a highly polar urethane bond or urea bond formed by the crosslinking reaction can be appropriately controlled, and the adhesiveness and the durability of the molded product can be simultaneously achieved.

< epoxy resin >

The polyol base (a) may further contain an epoxy resin in order to improve the adhesive strength to a metal material such as a metal foil. The polyurethane resin having a hydroxyl group in the present disclosure has a polyester skeleton, and thus there is a case where an acid is generated by hydrolysis in resistance to moist heat, but by including an epoxy resin, the generated acid reacts with the epoxy resin, and the moist heat resistance can be further improved.

The epoxy resin is not limited to the following, and examples thereof include: bisphenol a-type epoxy resin, bisphenol F-type epoxy resin, phenol novolac-type epoxy resin, cresol novolac-type epoxy resin, polyglycerol polyglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol a diglycidyl ether, propylene oxide-modified bisphenol a diglycidyl ether, bisphenol F diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. From the viewpoint of adhesiveness and durability of the molded product, a semisolid bisphenol a type epoxy resin is preferable. These epoxy resins may be used singly or in combination of two or more.

From the viewpoint of adhesiveness and durability of the molded product, the weight average molecular weight of the epoxy resin is preferably 400 to 3,000. From the viewpoint of adhesiveness and durability of a molded product, the amount of the epoxy resin blended is preferably 10 to 50% by mass based on the mass of the solid content of the polyol base (a). If the content is 10% by mass or more, the durability of the molded product is effectively improved, and if the content is 50% by mass or less, the heat-resistant sealing property of the deformed molded product can be suppressed from being lowered.

< silane coupling agent having amino group >

The polyol base (a) may further contain a silane coupling agent having an amino group in order to improve the adhesive strength to a metal material such as a metal foil. Examples of the silane coupling agent having an amino group include: 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, bis (3-triethoxysilylpropyl) amine, bis (3-trimethoxysilylpropyl) amine, N- (N-butyl) -3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldimethoxysilane, aminosilane oligomers containing aminosilane, silane oligomers containing diaminosilane. The content of the amino group-containing silane coupling agent is preferably 0.05 to 5% by mass, more preferably 0.5 to 3% by mass, based on the mass of the solid content of the polyol base (a). When the content is 0.05% by mass or more, the adhesiveness to the metal foil is improved, and when the content is 5% by mass or less, the heat-resistant sealing property of the deformed product can be suppressed from being lowered.

The silane coupling agent having an amino group may be used in combination with an epoxy resin. By using these compounds in combination, a part of glycidyl groups of the epoxy resin are opened by amino groups to form secondary hydroxyl groups, and a plurality of secondary hydroxyl groups are formed until the amino groups become tertiary. By incorporating a tertiary amino group into the epoxy resin by the reaction, a catalyst effect is produced, and the crosslinkability of the epoxy resin having a branched skeleton and the polyisocyanate hardener (B) is improved. Thus, in the adhesive layer containing a large excess of the polyisocyanate curing agent (B), the urethane resin containing a polyester polyol and the epoxy resin having a branched skeleton contain multi-dimensional branches, and when composite urethane crosslinking is performed, different resins form a uniform highly crosslinked film, and the glycidyl group and the polyester portion are integrated in the vicinity, and the moisture and heat resistance and durability of the molded product are improved.

< solvent >

In order to adjust the viscosity of the coating liquid to an appropriate level when the polyurethane adhesive is applied to a substrate, the polyurethane adhesive of the present disclosure may contain a solvent in a range that does not affect the substrate in the drying step. Examples of the solvent include: ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester compounds such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and methoxyethyl acetate; ether compounds such as diethyl ether and ethylene glycol dimethyl ether; aromatic compounds such as toluene and xylene; aliphatic compounds such as pentane and hexane; halogenated hydrocarbon compounds such as dichloromethane, chlorobenzene, and chloroform; alcohols such as ethanol, isopropanol, and n-butanol; water, and the like. These solvents may be used alone or in combination of two or more.

< optional Components >

The polyurethane adhesive of the present disclosure may further contain other components within a range not to impair the effects of the present disclosure. Other components may be added to either the base or the curing agent, or may be added during the preparation of the base and the curing agent. These optional components may be used alone or in combination of two or more, and may be appropriately selected depending on the required properties.

(reaction Accelerator)

In order to promote the urethanization reaction, the polyurethane adhesive may further contain a reaction promoter. Examples of the reaction accelerator include: metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate and dibutyltin dimaleate; tertiary amines such as 1, 8-diaza-bicyclo (5, 4, 0) undecene-7, 1, 5-diazabicyclo (4, 3, 0) nonene-5, 6-dibutylamino-1, 8-diazabicyclo (5, 4, 0) undecene-7; reactive tertiary amines such as triethanolamine.

(phosphoric acid or a derivative thereof)

The polyurethane adhesive may contain phosphoric acid or a phosphoric acid derivative in order to improve the adhesive strength to a metal material such as a metal foil. The phosphoric acid may be any phosphoric acid having at least one free oxoacid, and examples thereof include: hypophosphorous acid (hypophosphorous acid), phosphorous acid, orthophosphoric acid (orthophosphoric acid), and hypophosphoric acid (hypophosphoric acid); condensed phosphoric acids such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, and ultraphosphoric acid (ultraphosphoric acid). Examples of the derivative of phosphoric acid include a derivative obtained by partially esterifying the phosphoric acid with an alcohol while leaving at least one free oxoacid. Examples of the alcohols include: aliphatic alcohols such as methanol, ethanol, ethylene glycol and glycerin; aromatic alcohols such as phenol, xylenol, hydroquinone, catechol, and phloroglucinol (phloroglucinol).

(leveling agent or defoaming agent)

In order to improve the laminated appearance of the packaging material, the polyurethane binder may contain a leveling agent or an antifoaming agent. Examples of the leveling agent include: polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyether ester-modified hydroxyl-containing polydimethylsiloxane, acrylic copolymer, methacrylic copolymer, polyether-modified polymethylalkylsiloxane, alkyl acrylate copolymer, alkyl methacrylate copolymer, and lecithin (lecithin). Examples of the defoaming agent include silicone resins, silicone solutions, and copolymers of alkyl vinyl ethers with alkyl acrylates and alkyl methacrylates.

(additives)

The polyurethane adhesive may also contain additives within a range that does not impair the effects of the present disclosure. Examples of the additives include: inorganic fillers such as silica, alumina, mica, talc, aluminum flakes and glass flakes, lamellar inorganic compounds, stabilizers (ultraviolet absorbers, hydrolysis inhibitors, etc.), rust inhibitors, thickeners, plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, crystal nucleating agents, catalysts for adjusting the hardening reaction, and the like.

< packaging Material for Power storage device >

The polyurethane adhesive of the present disclosure can be preferably used as an outer layer side adhesive for forming an outer layer side adhesive layer of a packaging material for an electricity storage element. The disclosed packaging material for an electricity storage element has a structure in which at least an outer layer side resin film layer (1), an outer layer side adhesive layer (2), a metal foil layer (3), and a heat seal layer (5) are laminated in this order from the outside, and the outer layer side adhesive layer (2) is a cured product of the polyurethane adhesive. The method for producing the power storage element packaging material is not particularly limited. For example, the production can be carried out by laminating the outer layer side resin film layer (1) and the metal foil layer (3) with a polyurethane adhesive for forming the outer layer side adhesive layer (2) to obtain an intermediate laminate having a structure of the outer layer side resin film layer (1)/the outer layer side adhesive layer (2)/the metal foil layer (3), and then laminating the heat seal layer (5) on the surface of the metal foil layer (3) of the intermediate laminate with the inner layer side adhesive (hereinafter, production method 1). Alternatively, the metal foil layer (3) and the heat seal layer (5) may be laminated using an inner layer side adhesive to obtain an intermediate laminate having a structure of the metal foil layer (3)/the inner layer side adhesive layer (4)/the heat seal layer (5), and then the metal foil layer (3) and the outer layer side resin film layer (1) of the intermediate laminate may be laminated using the polyurethane adhesive to produce the laminate (hereinafter, production method 2).

In the case of the production method 1, it is preferable that a polyurethane adhesive is applied to one surface of either the outer layer side resin film layer (1) or the metal foil layer (3), the solvent is evaporated, then the other substrate is laminated to the uncured outer layer side adhesive layer under heat and pressure, and then aging is performed at room temperature to less than 100 ℃ to cure the outer layer side adhesive layer. When the aging temperature is less than 100 ℃, thermal shrinkage of the outer layer side resin film layer (1) does not occur, and therefore, a reduction in elongation at break or stress at break, which affects molding, and a reduction in molding productivity due to film curl are not caused. The coating weight of the adhesive on the outer layer side after drying is preferably 1g/m ² ～15g/m ² Left and right.

In the case of the production method 2, the polyurethane adhesive may be applied to either the outer layer side resin film layer (1) or the metal foil layer (3) surface of the intermediate laminate.

Examples of the method for forming the outer layer side adhesive layer include a method using a notch roll coater, a dry laminator, a knife roll coater, a die coater, a roll coater, a bar coater, a gravure roll coater, a reverse roll coater, a blade coater, a gravure coater, a micro gravure coater, and the like.

[ outer layer side resin film layer (1) ]

The outer layer side resin film layer (1) is not particularly limited, and an extended film containing polyamide or polyester is preferably used. Further, the coloring may be carried out by using a pigment such as carbon black or titanium oxide. The non-lamination surface of the outer resin film layer (1) may be coated with a coating agent or a slip agent for the purpose of preventing damage or electrolyte resistance, or may be coated with a printing ink for the purpose of design. In addition, the outer layer side resin film layer (1) may be formed by laminating two or more films in advance. The thickness of the outer resin film layer (1) is not particularly limited, but is preferably 12 to 100. Mu.m.

[ Metal foil layer (3) ]

The metal foil layer (3) is not particularly limited, and is preferably an aluminum foil layer. The thickness of the metal foil layer (3) is not particularly limited, but is preferably 20 to 80 μm. Further, the surface of the metal foil layer (3) is preferably subjected to an anticorrosive treatment by a phosphate chromate treatment, a chromate treatment, a chromium oxide treatment, a zinc phosphate treatment, a zirconium oxide treatment, a titanium phosphate treatment, a hydrofluoric acid treatment, a cerium (cerium) treatment, a hydrotalcite (hydrotalcite) treatment, or the like. By performing the anticorrosion treatment, corrosion deterioration of the surface of the metal foil due to the electrolyte of the battery can be suppressed. Further, it is preferable that the surface to be treated for corrosion prevention is treated by baking an organic primer such as a phenol resin, an amide resin, an acrylic resin, polyvinyl alcohol, or a coupling agent to a metal at a high temperature of about 200 ℃. By applying the organic primer treatment, the metal foil and the adhesive can be more firmly bonded, and the floating between the metal foil and the adhesive can be further suppressed.

[ Heat-seal layer (5) ]

The heat-sealing layer (5) is not particularly limited, and is preferably an unstretched film comprising at least one thermoplastic resin selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers. The thickness of the heat-seal layer is not particularly limited, but is preferably 20 μm to 150 μm.

[ inner layer-side adhesive layer (4) ]

The adhesive for forming the inner layer-side adhesive layer (4) is not particularly limited, and an adhesive in which the adhesive strength between the metal foil layer (3) and the heat-seal layer (5) is not reduced by the electrolyte of the power storage element can be used. The inner-layer-side adhesive layer (4) can be formed, for example, by applying an adhesive comprising a combination of a polyolefin resin and a polyisocyanate, or an adhesive comprising a combination of a polyol and a polyisocyanate to the metal foil layer (3) using a gravure coater or the like, drying the solvent, laminating the heat-seal layer (5) on the adhesive layer under heat and pressure, and then aging the laminate at normal temperature or under heat. Alternatively, an adhesive such as acid-modified polypropylene may be melt-extruded onto the metal foil layer (3) by a T-die extruder to form an adhesive layer, the heat-seal layer (5) may be superimposed on the adhesive layer, and the metal foil layer (3) and the heat-seal layer (5) may be bonded to each other to form the inner-layer-side adhesive layer (4). When both the outer layer side adhesive layer (2) and the inner layer side adhesive layer (4) need to be aged, a laminate having a structure in which an outer layer side resin film layer (1), an uncured outer layer side adhesive layer, a metal foil layer (3), an uncured inner layer side adhesive layer, and a heat seal layer (5) are laminated in this order from the outside may be collectively aged.

< Container for electric storage device >

The container for an electric storage element of the present disclosure can be obtained by molding the outer layer side resin film layer (1) to form a convex surface and the heat-seal layer (5) to form a concave surface, using the packaging material for an electric storage element of the present disclosure. In the present disclosure, the "concave surface" means a surface having a depression capable of accommodating an electrolyte solution therein when a flat packaging material for an electric storage element is molded into a tray shape as shown in fig. 2, and the "convex surface" means a self-back surface of the surface having the depression.

< storage element >

The electric storage element of the present disclosure is formed using a capacitor for an electric storage element, and examples thereof include secondary batteries such as lithium ion batteries, nickel hydrogen batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors. A general electric storage element includes: the electric storage device of the present disclosure includes a battery member including an electrode, a lead extending from the electrode, and a container for housing the battery member. The container for storage is formed from the electric storage element packaging material such that the heat seal layers (5) are on the inner side, and can be obtained by overlapping the heat seal layers (5) of the two packaging materials so as to face each other and heat-welding the peripheral edge portions of the overlapping packaging materials, or by folding back and overlapping one packaging material and heat-welding the peripheral edge portions of the packaging material in the same manner.

[ examples ]

Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples. In examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass", unless otherwise specified.

< measurement of Acid Value (AV) >

About 1g of a sample (a polyester polyol solution) was precisely measured in a stopcock flask, and 100m1 of a toluene/ethanol (volume ratio: toluene/ethanol = 2/1) mixture was added and dissolved. Phenolphthalein test solution was added thereto as an indicator and held for 30 seconds. Then, the solution was titrated with a 0.1N alcoholic potassium hydroxide solution until the solution became pale red, and the acid value (mgKOH/g) was determined by the following equation.

Acid value (mgKOH/g) = (5.611 × a × F)/S

Wherein, S: sample collection amount (g)

a:0.1 consumption (ml) of the alcoholic potassium hydroxide solution

F: titre of 0.1N alcoholic potassium hydroxide solution

< measurement of hydroxyl value (OHV) >

About 1g of a sample (polyester polyol, hydroxyl group-containing urethane resin, or the like) was precisely measured in a stopcock flask, and 100ml of a toluene/ethanol (volume ratio: toluene/ethanol = 2/1) mixture was added and dissolved. Further, 5m1 of an acetylating agent (a solution prepared by dissolving 25g of acetic anhydride with pyridine and having a capacity of 100 ml) was accurately added thereto, and the mixture was stirred for about 1 hour. Phenolphthalein test solution was added thereto as an indicator for 30 seconds. Then, the resulting solution was titrated with a 0.1N alcoholic potassium hydroxide solution until the solution became pale red, and the hydroxyl value (mgKOH/g) was determined by the following equation.

Hydroxyl value (mgKOH/g) = { (b-a) × F × 28.05}/S ] + D

Wherein, S: sample Collection volume (g)

a:0.1 consumption (ml) of the alcoholic potassium hydroxide solution

b: consumption (ml) of 0.1N alcoholic potassium hydroxide solution for blank experiment

F: titre of 0.1N alcoholic potassium hydroxide solution

D: acid value (mgKOH/g)

< measurement of weight-average molecular weight (Mw), number-average molecular weight (Mn), molecular weight distribution (Mw/Mn) >

The average molecular weight and the molecular weight distribution were values in terms of standard polystyrene measured in such a manner that Socker (Shodex) (registered trademark) (manufactured by Showa Denko K.K.), column: KF-805L, KF-803L, and KF-802 (all trade names, manufactured by showa electrician, showa), the column temperature was set to 40 ℃, the flow rate was set to 0.2 ml/min using Tetrahydrofuran (THF) as an eluent, the detection was set to infrared (RI) detection, and the sample concentration was set to 0.02 mass%.

< glass transition temperature (Tg) >

The glass transition temperature is measured by a Differential Scanning Calorimeter (DSC). Specifically, about 2mg of the compound to be measured was weighed on an aluminum pan, the aluminum pan was placed on a DSC measurement holder, the endothermic peak of the graph obtained under a temperature rise condition of 5 ℃/min was read, and the peak temperature at that time was taken as the glass transition temperature.

< Synthesis of polyester polyol >

(polyester 1)

166.4 parts of isophthalic acid, 138.6 parts of terephthalic acid, 219.5 parts of adipic acid, 83.4 parts of ethylene glycol, 199.8 parts of neopentyl glycol, 92.4 parts of butyl ethyl propylene glycol and 10102.7 parts of phenol antioxidant Irganox, and the mixture was subjected to esterification reaction at 170 ℃ to 230 ℃ for 6 hours. After a predetermined amount of water was distilled off, 0.36 part of tetraisobutyl titanate was added thereto, and ester exchange reaction was carried out at 230 to 250 ℃ for 3 hours at 1.3hPa to 2.6hPa under a gradual reduced pressure to obtain polyester 1 as a polyester polyol having a number average molecular weight of 11,000, a weight average molecular weight of 24,000, a molecular weight distribution of 2.18, a hydroxyl value of 11.6mgKOH/g, an acid value of 0.2mgKOH/g and a resin Tg of-8 ℃. Assuming that the excessive polyol component was distilled off almost equally, and the total of the polybasic acid component and the polyol component was set to 200mol%, the composition of the obtained polyester 1 became isophthalic acid, terephthalic acid, adipic acid, ethylene glycol, neopentyl glycol, butylethylpropanediol = 30: 25: 45: 35: 50: 15 (mol%) as shown in table 1. The phenolic antioxidant, lyonol (Irganox) 1010, was 0.3 mass% based on the total mass of the polyester raw materials.

(confirmation of covalent bond between phenol antioxidant and hydroxyl group-containing polyurethane resin)

The presence or absence of the covalent bond was confirmed by measuring 1H-Nuclear Magnetic Resonance (NMR). The measurement conditions were: fourier Transform-Nuclear Magnetic Resonance (FT-NMR) apparatus (JNM-ECZ 400R); the resonance frequency is 400MHz; the probe is a 10mm Super-cooling probe (Super cool probe); the measuring temperature is room temperature; the pulse interval was 15 seconds; the solvent is deuterated chloroform; a sample obtained by dissolving 0.6g of the dried sample in 4g of deuterated chloroform was used. The unreacted phenol antioxidant (C-1: irganox 1010) had a peak at 6.98ppm of hydrogen bonded to a carbon adjacent to a carbon bonded to a tert-butyl group, whereas the peak intensity was reduced in the polyester 1, and a broad peak was observed at 6.80ppm to 6.86 ppm. Similarly, the peak intensity of the unreacted hydrogen also decreased, and a broad peak after the reaction appeared in the vicinity. Thus, it was confirmed that the phenolic antioxidant and the hydroxyl group-containing polyurethane resin were covalently bonded.

(polyesters 2 to 22)

Polyesters 2 to 22 were obtained by reacting a polybasic acid component and a polyhydric alcohol component in the same manner as in polyester 1 except that the mol% of each component was changed to the composition shown in table 1, with the total amount of the polybasic acid component and the polyhydric alcohol component of the obtained polyester polyol being 200 mol%.

[ Table 1]

The abbreviations in table 1 are as follows.

IPA: isophthalic acid (isophthalic acid)

TPA: terephthalic acid (terephthalic acid)

PA: phthalic acid (phthalic acid)

AdA: adipic acid (adipic acid)

And (5) SeA: sebacic acid (sebac acid)

AzA: azelaic acid (azelaic acid)

TMA: trimellitic anhydride (trimellitic anhydride)

EG: ethylene glycol (ethylene glycol)

NPG: neopentyl glycol (neopentyl glycol)

BEPG: butyl ethyl propylene glycol (butyl ethyl propylene glycol)

MPO: 2-methyl-1,3-propanediol (2-methyl-1, 3-propanediol)

DEG: diethylene glycol (diethylene glycol)

1,6-HD:1, 6-hexanediol (1, 6-hexanediol)

C-1: tetrakis- [ methylene-3- (3 ',5' -di-tert-butyl-4 ' -hydroxyphenyl) propionate ] methane (phenolic antioxidant, irganox 1010, manufactured by BASF corporation)

C-2:1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene (phenol antioxidant, irganox 1330, manufactured by BASF corporation)

C-3:1,3, 5-tris (3 ',5' -di-tert-butyl-4 ' -hydroxybenzyl) -S-triazine-2, 4,6- (1H, 3H, 5H) trione (phenolic antioxidant, irganox 3114, manufactured by BASF corporation)

< Synthesis of hydroxyl group-containing polyurethane resin >

(Carbamate (a) -1)

1100 parts of the obtained polyester and 43 parts of ethyl acetate were charged into a four-necked flask, heated to 85 ℃ and stirred until the solution became homogeneous. To this mixture were added 2.5 parts of toluene diisocyanate and 0.02 part of dibutyltin dilaurate, and a reaction was carried out for 4 hours. After the reaction, 59 parts of ethyl acetate was added to obtain a urethane (a) -1 solution as a hydroxyl group-containing polyurethane resin having a urethane bond concentration of 0.29mmol/g, an Mw of 82,000, a resin Tg of-7 ℃, a hydroxyl group value of 1.6mgKOH/g and a nonvolatile content of 50%.

(Carbamate (a) -2-Carbamate (a) -23)

Except for changing the blending amounts shown in table 2, the polyester polyol and the polyisocyanate were reacted in the same manner as in the case of urethane (a) -1 to obtain urethane (a) -2 to urethane (a) -23 as the hydroxyl group-containing polyurethane resin.

[ Table 2]

The abbreviations in table 2 are as follows.

1,4BD:1, 4-butanediol (1, 4-butandediol)

TMP: trimethylolpropane (trimethylol propane)

TDI: toluene diisocyanate (tolylene diisocyanate) (manufactured by Crosstide T-80 Tosoh Co., ltd.)

MDI:4,4 '-diphenylmethane diisocyanate (4, 4' -diphenylmethyl diisocyanate) (manufactured by Millinonote (MILLIONATE) MT Tosoh Co., ltd.)

IPDI: isophorone diisocyanate (manufactured by Desmodur I scientific Co., ltd.)

HDI: hexamethylene diisocyanate (hexamethylene diisocyanate) (manufactured by Desmodur Kosteken (Desmodur) H scientific Co., ltd.)

< production of packaging Material for Electrical storage device >

[ example 1]

200 parts (100 parts in terms of solid content) of the urethane (a) -1 solution and 0.05 part of 3-aminopropyltrimethoxysilane as a silane coupling agent having an amino group were charged, and after stirring for 10 minutes, 47 parts (35 parts in terms of solid content) of crotonate L (manufactured by tokyo corporation, having a solid content of 75% and an NCO content of 13.2%) were charged and diluted with ethyl acetate to prepare an adhesive solution having a solid content of 25%. One surface of an aluminum foil with the thickness of 40 mu m is coated with 0.03g/m ² Coating type chromate treatment agent (Surfcoat manufactured by Nippon paint, ltd.) of SurfcoatNR-X) is baked at 230 ℃. Then, the adhesive solution was applied as an outer layer side adhesive layer (2) to the surface of the aluminum foil having a thickness of 40 μm using a dry laminator, and after volatilizing the solvent, a stretched polyamide film having a thickness of 25 μm was laminated to obtain an intermediate laminate. The amount of the adhesive applied after drying was 3g/m ² . Then, an adhesive for an inner layer side adhesive layer described later was applied to the other surface of the aluminum foil of the obtained intermediate laminate using a dry laminator, the solvent was evaporated, and an unstretched polypropylene film having a thickness of 25 μm was laminated to obtain a laminate. The coating weight of the adhesive after drying was set to 3g/m ² . Then, the outer layer side and inner layer side adhesive layers were hardened by aging at 60 ℃ for 5 days to obtain a packaging material for an electricity storage element having a structure comprising an outer layer side resin film layer (1)/an outer layer side adhesive layer (2)/a metal foil layer (3)/an inner layer side adhesive layer (4)/a heat-seal layer (5).

(adhesive for inner layer side adhesive layer)

AD-502 (polyester polyol manufactured by Toyo Morton corporation) was used as a main agent, CAT-10L (isocyanate-based curing agent manufactured by Toyo Morton corporation) was used as a curing agent, the main agent/curing agent =100/10 (mass ratio) was blended, the solid content concentration was adjusted to 25% by ethyl acetate, and the obtained mixture was used as an adhesive for the inner layer side adhesive layer.

Examples 2 to 25 and comparative examples 1 to 9

The same operation as in example 1 was performed except that the amount (parts) was changed to those in table 3, to obtain a packaging material for an electric storage device.

< evaluation of packaging Material for Power storage device >

The obtained packaging material for an electric storage element was evaluated as follows. The results are shown in table 3.

[ evaluation of coating Property of packaging Material ]

The appearance of each of the electric storage element packaging materials was visually observed and evaluated according to the following criteria.

A: no coating omission or longitudinal streaking (good) was observed.

B: although there was slight coating omission, no longitudinal streaks were observed (could be used).

C: coating omission or longitudinal streaks (unusable) were observed.

[ Adhesivity (before durability test) ]

The packaging materials for electric storage elements were each cut into a size of 200mm × 15mm, and a T-peel test was performed using a tensile tester to measure the peel strength (N/15 mm width) between the stretched polyamide film and the aluminum foil. The measurement was carried out at a load rate of 50 mm/min in an environment of 20 ℃ and 65% RH, and the average value of three test pieces was evaluated according to the following criteria.

S: the average value of the peel strength was 5N or more (very good).

A: the average value of the peel strength was 4N or more and less than 5N (good).

B: the average value of the peel strength is 3N or more and less than 4N (usable).

C: the average value of the peel strength was less than 3N (unusable).

[ evaluation of moldability ]

The surface of the packaging material for the electricity storage element was coated at a ratio of 0.02g/m ² Erucamide was applied and then cut into 60mm × 60mm pieces to prepare a billet. The preform was subjected to one-stage molding by drawing with a straight mold having no limitation on the molding height so that the stretched polyamide film was located on the outer side, and the moldability was evaluated according to the following criteria based on the maximum molding height at which the aluminum foil did not break or the lifting between the layers did not occur. The punch shape of the die used was a square with a side of 29.4mm, a corner R of 1mm and a punch shoulder R of 1mm. The die hole shape of the die used was a square with one side of 30.0mm, the die hole corner R was 1mm, the die hole shoulder R was 1mm, and the clearance between the punch and the die hole was 0.3mm. An inclination corresponding to the molding height is generated due to the gap. The following four-stage evaluation was performed according to the molding height.

S: the maximum molding height was 7mm or more (very good).

A: the maximum molding height was 6mm or more and less than 7mm (good).

B: the maximum molding height is 5mm or more and less than 6mm (usable).

C: the maximum molding height is less than 5mm (cannot be used).

[ Heat-resistant sealing Properties of deformed moldings ]

Similarly, the following four-stage evaluation was performed based on the highest temperature at which floating between the layers did not occur, by performing one-stage molding by drawing at a molding height of 5mm, directly recessing the drawing center of the molded product, forming valley fold wrinkles at four drawing corners and deforming the valley fold wrinkles, and then performing heat sealing at each temperature, 2kgf, and 5 seconds on the surface of the flange 4. The reason for deforming the molded article is: the molded product is deformed during the production of the battery container and the filling of the electrolyte solution, and the center of the square convex portion is depressed, and the dimple-like wrinkles are brought close to the corners of the convex portion, whereby the layers at the corners of the convex portion are likely to float during the heat sealing.

S: there was no floating at 210 ℃ (very good).

A: there was no floating at 200 ℃ but floating (good) at 210 ℃.

B: there was no floating at 190 ℃ but floating (usable) at 200 ℃.

C: it floats (cannot be used) at 190 ℃.

[ Wet Heat durability of molded article ]

The packaging material for an electric storage element was cut into a size of 60mm × 60mm to prepare a blank. The preform was stretched at a molding height of 5mm using a straight die not limited to the molding height so that the stretched polyamide film was located on the outer side, and one-stage molding was performed to obtain a molded article. Then, the molded article was placed in a constant temperature and humidity chamber at 85 ℃ and 85% RH, taken out from the constant temperature and humidity chamber at 200-hour intervals, and the occurrence of floating was visually checked to evaluate it according to the following criteria.

S: there was no floating after 1000 hours (very good).

A: there was no floating after 800 hours, but there was floating (good) after 1000 hours.

B: after 600 hours, there was no floating, but after 800 hours, there was floating (usable).

C: after 600 hours, the film floated (could not be used).

[ high temperature durability of molded article ]

The conditions of standing were changed from 85 ℃ and 85% RH to 120 ℃ and, similarly to the moist heat durability of the molded article, whether or not floating occurred was visually checked and evaluated according to the following criteria.

S: there was no floating after 1000 hours (very good).

B: after 600 hours, there was no floating, but after 800 hours, there was floating (usable). C: after 600 hours, the floating (unusable) was observed.

[ Table 3]

The abbreviations in table 3 are as follows.

C-1: tetrakis- [ methylene-3- (3 ',5' -di-tert-butyl-4 ' -hydroxyphenyl) propionate ] methane (Irganox 1010, manufactured by BASF corporation)

EP-1: bisphenol A type epoxy resin (JER 1002, manufactured by Mitsubishi chemical corporation, epoxy equivalent of 650, molecular weight of about 1,200)

EP-2: bisphenol A type epoxy resin (JER 834, manufactured by Mitsubishi chemical corporation, epoxy equivalent of 250, molecular weight of about 470)

SC-1: 3-aminopropyltrimethoxysilane

SC-2: 3-aminopropyltriethoxysilane

NCO-1: trimethylolpropane adduct of tolylene diisocyanate (Crosstide, L Tosoh Co., ltd., nonvolatile content of 75%, NCO content of 13.2%)

NCO-2: isocyanurate structural body of isophorone diisocyanate (VESTANT (registered trademark) T1890/100 Yingchu (Evonik) Inc., NCO content 17.3%)

NCO-3: isocyanurate Structure of hexamethylene diisocyanate and isophorone diisocyanate (Duranate MHG-80B Asahi Kasei Co., ltd. Having NCO content of 15.0%)

As is clear from the results in table 3, even in the case of the packaging material using the hydroxyl group-containing polyurethane resin containing a predetermined amount of the phenolic antioxidant as the main agent for forming the outer layer side adhesive layer, thermal oxidation degradation is suppressed in the adhesive layer which is stretched and the outer layer side adhesive layer is a thin film and is plastically deformed, and the molded product is excellent in high-temperature durability. Further, the polyester polyol contained in the hydroxyl group-containing polyurethane resin and the phenolic antioxidant are integrated through a covalent bond, whereby thermal oxidative degradation can be efficiently suppressed, and thermal decomposition degradation can be suppressed also by multidimensional branching. Further, by adjusting the content of the phenolic antioxidant, both adhesiveness and high-temperature durability of the molded product can be achieved. In particular, in examples 5, 11, and 12, since the content of the phenolic antioxidant was appropriate and the phenolic antioxidant and the hydroxyl group-containing polyurethane resin were integrated by covalent bonding, a tough adhesive layer that can suppress thermal oxidative degradation and thermal decomposition degradation was obtained, and the moldability, the heat-resistant sealing properties of the deformed molded article, and the high-temperature durability of the molded article were excellent.

On the other hand, in comparative example 1, the content of the phenolic antioxidant was small, and the high-temperature durability of the molded article was lowered. In comparative example 2, the content of the phenolic antioxidant was too large, and the adhesive layer became brittle and the adhesiveness was reduced. In comparative examples 3 to 9, the molded article had low durability at high temperature because the phenolic antioxidant was not contained. Further, comparative example 3 was obtained based on the example of International publication No. 2018/117082, comparative example 4 was obtained based on the example of Japanese patent laid-open publication No. 2019-156925, comparative example 5 was obtained based on the example of Japanese patent laid-open publication No. 2016-196580, comparative example 6 was obtained based on the example of Japanese patent laid-open publication No. 2019-117706, comparative example 7 was obtained based on the example of Japanese patent laid-open publication No. 2017-25287, and comparative example 8 was obtained based on International publication No. 933202I/038. In comparative example 5, since the hydroxyl group-containing polyurethane resin had a high aromatic polybasic acid content and a low molecular weight, the adhesive layer became hard and brittle, and adhesiveness and moldability were significantly reduced. Therefore, a molded article having a molding height of 5mm could not be obtained, and the heat-resistant sealing property of the deformed molded article and the durability of the molded article could not be evaluated. In comparative example 7, the hydroxyl group-containing polyurethane resin had a high urethane bond concentration and contained no phenol antioxidant, and therefore the molded article had a reduced high-temperature durability. In comparative example 9, since the main agent did not contain a hydroxyl group-containing polyurethane resin, the wet heat durability and high temperature durability of the molded article were reduced.

Claims

1. A polyurethane adhesive for a power storage element packaging material, which contains a polyol main agent (A) and a polyisocyanate curing agent (B),

the polyol main agent (A) contains a polyurethane resin having a hydroxyl group as a reaction product of a polyester polyol and a polyisocyanate, and contains 0.03 to 3 mass% of a phenol-based antioxidant (C) based on the mass of the polyol main agent (A).

2. The polyurethane adhesive for electricity storage element packaging material according to claim 1, wherein

The polyol main agent (A) further contains an epoxy resin.

3. The polyurethane adhesive for electricity storage element packaging material according to claim 1 or 2, wherein

The polyol main agent (A) further contains a silane coupling agent having an amino group.

4. The polyurethane adhesive for electricity storage element packaging material according to claim 3, wherein

The content of the silane coupling agent having an amino group is 0.05 to 5% by mass based on the mass of the polyol base (a).

5. The polyurethane adhesive for power storage element packaging material according to any one of claims 1 to 4, wherein

The hydroxyl group-containing polyurethane resin has a structure in which at least a part of the phenolic antioxidant (C) is bonded via a covalent bond.

6. The polyurethane adhesive for power storage element packaging material according to any one of claims 1 to 5, wherein

The urethane bond concentration of the hydroxyl group-containing polyurethane resin is 0.10mmol/g to 0.90mmol/g.

7. The polyurethane adhesive for power storage element packaging material according to any one of claims 1 to 6, wherein

The weight average molecular weight of the polyurethane resin having a hydroxyl group is 30,000 to 100,000.

8. The polyurethane adhesive for power storage element packaging material according to any one of claims 1 to 7, wherein

The polyester polyol constituting the hydroxyl group-containing polyurethane resin is a reaction product of a polybasic acid and a polyhydric alcohol, and the polybasic acid component is contained in an amount of 55 to 80mol% based on 100mol% of the polybasic acid component.

9. A packaging material for an electricity storage element, comprising a structure in which at least an outer layer side resin film layer, an outer layer side adhesive layer, a metal foil layer, an inner layer side adhesive layer and a heat-seal layer are laminated in this order from the outside, wherein in the packaging material for an electricity storage element, the outer layer side adhesive layer is a cured product of the polyurethane adhesive for an electricity storage element packaging material according to any one of claims 1 to 8.

10. A container for an electric storage device, which is formed from the electric storage device packaging material according to claim 9, wherein the outer layer side resin film layer forms a convex surface and the heat sealing layer forms a concave surface.

11. An electricity storage element comprising the electricity storage element container according to claim 10.