Primer composition, coating film obtained therefrom, secondary battery outer casing material containing said coating film, and secondary battery

Abstract

Provided are a primer composition that provides a secondary battery exterior material that has excellent electrolyte resistance and does not lose adhesive strength even in a high-temperature environment, a coating film obtained from the primer composition, a secondary battery exterior material including the coating film, and a secondary battery. [Solution] A primer composition comprising: 100 parts by mass of an acid-modified polypropylene resin aqueous dispersion (A); 0.5 to 3.0 parts by mass of a modified polyvinyl alcohol (B) having a carbonyl group; 1.0 to 5.0 parts by mass of adipic acid dihydrazide (C); 5.0 to 10.0 parts by mass of an oxazoline compound (D); and water, wherein the aqueous dispersion (A) has a melting point of 143 to 148°C as measured in accordance with JIS K 7121 in a nitrogen gas flow at a temperature rise rate of 10°C / min, and an acid value of 20 to 30 mgKOH / g as measured in accordance with JIS K 2501; and the modified polyvinyl alcohol (B) has a degree of saponification of 98 to 99 mol% as measured in accordance with JIS K 6726.

Description

[Technical Field]

[0001] The present invention relates to a primer composition, a coating film obtained from the primer composition, and a secondary battery exterior material including the coating film, and a secondary battery. [Background technology]

[0002] Laminated lithium-ion batteries are widely used as power sources for portable electronic devices such as mobile phones and laptop computers; power sources for electric vehicles and hybrid vehicles; and stationary storage batteries used as backup power sources during power outages in homes, commercial facilities, hospitals, factories, etc. As the range of applications for lithium-ion batteries expands, they are required to maintain long-term functionality in electric vehicles and stationary storage battery applications, and to withstand increases in temperature during charging and discharging and in the ambient temperature of use due to their high functionality (high capacity and high output). To meet these requirements, lithium-ion battery exterior materials are required to have high adhesive strength between the layers, to maintain excellent electrolyte resistance without any loss of adhesive strength even in high-temperature environments, and so on.

[0003] An exterior material typically has a structure in which a substrate layer, a barrier layer made of aluminum foil or the like, an adhesive layer, and a sealant layer are laminated in this order. To improve the heat resistance of an exterior material, it is important to increase the adhesive strength between each layer, and various studies have been conducted, particularly on improving the adhesive layer. For example, Patent Document 1 discloses a battery exterior body in which a substrate layer, a barrier layer, an adhesive layer, and a sealant layer are laminated in this order, in which the adhesive layer contains a specific acid-modified polypropylene resin and a crosslinking agent containing at least one of an oxazoline compound and an epoxy compound in a specific ratio, and the sealant layer is made of polypropylene resin. It has been shown that this exterior material has excellent electrolyte resistance and leakage resistance.

[0004] Patent Document 2 discloses an adhesive composition containing a crystalline modified olefin polymer and a crosslinking agent containing an epoxy compound and / or an oxazoline compound, in which the modified olefin polymer is modified with a monomer having an acid anhydride group, and the ring opening rate of the ring structure derived from the acid anhydride group is 50% or more and 90% or less, and it is shown that the composition has excellent adhesion, usable life, and heat resistance during low-temperature lamination.Patent Document 3 discloses an adhesive composition containing a modified polyolefin (A) having a specific acid value, a polycarbodiimide (B), and an organic solvent (C), and it is shown that the composition has a good pot life and excellent adhesion to both polyolefin resin substrates and metal substrates.

[0005] Furthermore, Patent Document 4 discloses a coating composition containing an acid-modified polyolefin resin, at least one of polyvinyl alcohol and an ethylene-vinyl alcohol copolymer, a hydrazide compound, a basic compound, and an aqueous medium in a predetermined ratio, and shows that the composition can provide a coating film that has excellent adhesion to various substrates, and excellent water resistance and chemical resistance at high temperatures. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-216364 [Patent Document 2] Japanese Patent Publication No. 2023-180312 [Patent Document 3] International Publication No. 2015 / 033703 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-194078 Summary of the Invention [Problem to be solved by the invention]

[0007] The compositions disclosed in Patent Documents 2 and 3 are mainly composed of a solution of modified polyolefin in an organic solvent. However, in order to make the modified polyolefin soluble in a solvent, it is necessary to reduce the crystallinity of the modified polyolefin. Even if a crosslinking agent is added to these compositions, the heat resistance of the resulting coating film is insufficient. The adhesive layer disclosed in Patent Document 1 is obtained by blending an oxazoline compound or an epoxy compound as a crosslinking agent into an aqueous dispersion of an acid-modified polypropylene resin. Furthermore, the coating composition disclosed in Patent Document 4 is obtained by blending polyvinyl alcohol and a hydrazide compound into an aqueous dispersion of an acid-modified polyolefin resin. Exterior materials using coating films obtained from the adhesive layer of Patent Document 1 and the composition of Patent Document 4 exhibit a certain level of adhesive strength and electrolyte resistance in high-temperature environments, but further improvements in these properties are desired.

[0008] The present invention aims to provide a primer composition that provides an exterior material for a secondary battery that has excellent electrolyte resistance and does not lose its adhesive strength even in a high-temperature environment, a coating film obtained from the primer composition, an exterior material for a secondary battery that includes the coating film, and a secondary battery. [Means for solving the problem]

[0009] The present inventors have conducted extensive research into methods for suppressing a decrease in adhesive strength, particularly adhesive strength between a metal foil layer and a sealant layer, in high-temperature environments and improving electrolyte resistance in exterior packaging materials for secondary batteries. As a result, they have found that the problems of the present invention can be solved by using a primer composition for bonding a metal foil layer and a sealant layer, which is prepared by blending a specific resin, a crosslinking agent, and the like in specific proportions with a specific aqueous dispersion of an acid-modified polypropylene resin, and have arrived at the present invention.

[0010] The present invention relates to the following [1] to

[10] . [1] A primer composition comprising: 100 parts by mass of an acid-modified polypropylene resin aqueous dispersion (A); 0.5 to 3.0 parts by mass of a modified polyvinyl alcohol (B) having a carbonyl group; 1.0 to 5.0 parts by mass of an adipic acid dihydrazide (C); 5.0 to 10.0 parts by mass of an oxazoline compound (D); and water, wherein the aqueous dispersion (A) has a melting point of 143 to 148°C as measured in accordance with JIS K 7121 in a nitrogen gas flow at a temperature rise rate of 10°C / min, and an acid value of 20 to 30 mgKOH / g as measured in accordance with JIS K 2501; and the modified polyvinyl alcohol (B) has a degree of saponification of 98 to 99 mol% as measured in accordance with JIS K 6726. [2] The primer composition according to [1], wherein component (A) is an aqueous dispersion of a polypropylene resin modified with maleic anhydride. [3] The primer composition according to [1] or [2], wherein component (B) is polyvinyl alcohol containing diacetone acrylamide units. [4] The primer composition according to any one of [1] to [3], wherein the amount of oxazoline groups in component (D) is 5 to 10 mmol / g. [5] The primer composition according to any one of [1] to [4], wherein the content ratio of component (C) to component (B) is 0.3 to 5 on a mass basis. [6] The primer composition according to claim 1 or 2, which comprises a first agent and a second agent, A primer composition, wherein the first part contains components (A) to (C) and water, but does not contain component (D); and the second part contains component (D) and water, but does not contain components (A) to (C). [7] The primer composition according to any one of [1] to [6], which is used in the production of an exterior material for a secondary battery. [8] A coating film obtained by drying the primer composition according to any one of [1] to [7]. [9] An outer casing material for a secondary battery, which is formed by laminating a substrate layer, an adhesive layer, a metal foil layer, a primer layer, and a sealant layer in this order, wherein the primer layer is the coating film described in [8].

[10] A secondary battery comprising the secondary battery packaging material according to [9] and a power generating element. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a primer composition that provides an exterior material for a secondary battery that does not lose its adhesive strength even in a high-temperature environment and has excellent electrolyte resistance, a coating film obtained from the primer composition, and an exterior material for a secondary battery that includes the coating film, and a secondary battery. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing an example of a laminated battery or capacitor according to the present invention. [Figure 2] FIG. 2 is a diagram showing an example of the layer structure of the packaging material according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The primer composition of the present invention comprises 100 parts by mass of an acid-modified polypropylene resin aqueous dispersion (A); 0.5 to 3.0 parts by mass of a modified polyvinyl alcohol (B) having a carbonyl group; 1.0 to 5.0 parts by mass of an adipic acid dihydrazide (C); 5.0 to 10.0 parts by mass of an oxazoline compound (D); and water, wherein the aqueous dispersion (A) has a melting point of 143 to 148°C as measured in accordance with JIS K 7121 in a nitrogen gas flow at a temperature rise rate of 10°C / min, and an acid value of 20 to 30 mgKOH / g as measured in accordance with JIS K 2501; and the modified polyvinyl alcohol (B) has a degree of saponification of 98 to 99 mol% as measured in accordance with JIS K 6726. The primer composition uses two crosslinking systems, components (A) and (D) and components (B) and (C), in combination, which can further improve the heat resistance of the resulting coating film. By using the primer composition as a primer layer for a secondary battery exterior material, particularly as a primer layer that bonds a metal foil layer and a sealant layer, it is possible to obtain an exterior material for a secondary battery that does not lose adhesive strength even in a high-temperature environment and has excellent electrolyte resistance.

[0014] <Primer composition> The primer composition contains 100 parts by mass of an acid-modified polypropylene resin aqueous dispersion (A), 0.5 to 3.0 parts by mass of a carbonyl-group-containing modified polyvinyl alcohol (B), 1.0 to 5.0 parts by mass of adipic acid dihydrazide (C), 5.0 to 10.0 parts by mass of an oxazoline compound (D), and water. Each component is described in detail below.

[0015] [Aqueous dispersion of acid-modified polypropylene resin (A)] The primer composition contains an acid-modified polypropylene resin aqueous dispersion (A) as a main component. When an organic solvent solution of an acid-modified polypropylene resin is used as the main component of the primer composition, the crystallinity of the resin must be low to make the acid-modified polypropylene resin soluble in the solvent, and even if a crosslinking agent is added, there is a limit to improving the heat resistance of the resulting coating film. By using the acid-modified polypropylene resin aqueous dispersion (A) as the main component of the primer composition, the melting point of the resin is increased, and in combination with the following components (B) to (D), it is possible to improve the heat resistance of the resulting coating film. Component (A) may be used alone or in combination of two or more types.

[0016] Examples of acid-modified polypropylene resins include polypropylene-based resins graft-modified with unsaturated carboxylic acids, unsaturated carboxylic anhydrides, etc.; copolymers of propylene with acrylic acid, methacrylic acid, etc.; and metal-crosslinked polypropylene-based resins. The polypropylene resin before acid modification may be a copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms. Examples of α-olefins having 4 or more carbon atoms include isobutylene, 2-butene, 1-butene, 1-pentene, and 1-hexene. In such a copolymer, the content of polymerized units derived from propylene is 50% by mass or more, preferably 50 to 95% by mass, and more preferably 70 to 95% by mass. When the content of polymerized units derived from propylene is 70 to 95% by mass, good heat resistance and adhesiveness can be exhibited.

[0017] The melting point of component (A) is 143 to 148°C, as measured in a nitrogen stream at a temperature rise rate of 10°C / min according to JIS K 7121. By ensuring that the melting point of aqueous dispersion (A) falls within this range, the heat resistance of the coating film obtained from the primer composition can be enhanced.

[0018] Component (A) has an acid value of 20 to 30 mgKOH / g as measured in accordance with JIS K 2501. By setting the acid value of aqueous dispersion (A) within this range, it is possible to improve the adhesion between the coating film obtained from the primer composition and the acid-resistant treatment layer (metal foil chemical conversion treatment layer).

[0019] From the viewpoints of adjusting the adhesive strength between the resulting primer layer and the acid-resistant treatment layer and sealant layer and of electrolyte resistance when used as an outer casing material for a secondary battery, the acid component content of component (A) is preferably 0.1 to 10 mass%, more preferably 0.3 to 10 mass%, and even more preferably 1 to 9 mass%. If the acid component content is less than 0.1 mass%, it may be difficult to stably produce the aqueous dispersion (A), and sufficient adhesive strength between the primer layer and the acid-resistant treatment layer may not be obtained. On the other hand, if the acid component content exceeds 10 mass%, the adhesive strength between the primer layer and the sealant layer and electrolyte resistance when used as an outer casing material for a secondary battery may be reduced.

[0020] Examples of acid-modified components include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. The manner in which the acid-modified component is introduced is not limited, and examples include random copolymerization, block copolymerization, graft copolymerization (graft modification), and copolymerization by thermal degradation. From the viewpoints of adhesiveness and heat resistance, component (A) is preferably an aqueous dispersion of a polypropylene resin modified with maleic anhydride.

[0021] From the viewpoints of dispersion stability, adhesive strength in a high-temperature environment when used as an outer casing material for a secondary battery, and electrolyte resistance, the weight-average molecular weight of component (A) is preferably 1,000 to 100,000, more preferably 5,000 to 80,000, even more preferably 10,000 to 50,000, and particularly preferably 20,000 to 40,000. The weight-average molecular weight of component (A) can be determined by gel permeation chromatography (GPC).

[0022] The method for dispersing the acid-modified polypropylene resin in an aqueous medium is not particularly limited. For example, the acid-modified polypropylene resin can be stably dispersed in the aqueous medium by placing a predetermined amount of the acid-modified polypropylene resin and water in a sealable container equipped with a stirrer, and heating and stirring the mixture in the presence of a basic compound and, if necessary, an organic solvent. The basic compound may be any compound capable of neutralizing a carboxyl group. Examples of the basic compound include metal hydroxides such as LiOH, KOH, and NaOH; and organic amine compounds such as ammonia, triethylamine, and alkanolamine. From the viewpoint of water resistance of the coating film, volatile organic amine compounds are preferred.

[0023] Component (A) is commercially available, and examples thereof include Arrowbase (registered trademark) YA-6010 (melting point: 145°C, acid value: 20 to 30 mgKOH / g, solid content: 25% by mass, pH: 8 to 11) manufactured by Unitika Ltd.

[0024] [Modified polyvinyl alcohol having carbonyl groups (B)] The primer composition contains 0.5 to 3.0 parts by mass of a modified polyvinyl alcohol (B) having a carbonyl group per 100 parts by mass of an acid-modified polypropylene resin aqueous dispersion (A). Component (B) is a component that improves the heat resistance of the resulting coating film by crosslinking with adipic acid dihydrazide (C). By setting the content of component (B) within the above range, compatibility with component (A) is maintained while appropriate crosslinking with component (C) is achieved, thereby improving the adhesion between the resulting coating film and the acid-resistant layer and further improving heat resistance. Component (B) may be used alone or in combination of two or more types.

[0025] Component (B) can be produced by copolymerizing a fatty acid vinyl ester monomer and a carbonyl group-containing monomer, followed by completely or partially saponifying the resulting polymer. Examples of the fatty acid vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl versatate, with vinyl acetate being preferred. As the saponification method, an alkali saponification method, an acid saponification method, etc. can be used. Among them, an alcoholysis method using an alkali solution in methanol is preferred.

[0026] Component (B) has a degree of saponification of 98 to 99 mol % as measured in accordance with JIS K 6726. By adjusting the degree of saponification of the modified polyvinyl alcohol (B) to fall within the above range, the resulting coating film can be made tougher.

[0027] From the viewpoint of crosslinkability with component (C), component (B) is preferably polyvinyl alcohol containing diacetone acrylamide units.

[0028] Diacetone acrylamide units can be introduced by known methods, such as saponifying a polymer obtained by copolymerizing a fatty acid vinyl ester with diacetone acrylamide. The content of diacetone acrylamide units is preferably 0.1 to 15 mol%, more preferably 0.5 to 10 mol%. If the content of diacetone acrylamide components is less than 0.1 mol%, the heat resistance of the resulting coating film is likely to be insufficient. If the content exceeds 15 mol%, the crosslinking reaction will saturate, and water solubility will decrease, making workability poor. Polyvinyl alcohols containing diacetone acrylamide units are commercially available, and an example is D-Polymer manufactured by Nippon Vaccination & Poval Co., Ltd.

[0029] The average degree of polymerization of component (B) is not particularly limited, but is preferably 100 to 2,000.

[0030] Furthermore, component (B) may be copolymerized with a monomer other than the fatty acid-remaining vinyl ester monomer and the carbonyl group-containing monomer, provided that the effects of the present invention are not impaired. Examples of such other monomers include unsaturated monocarboxylic acids such as crotonic acid, acrylic acid, and methacrylic acid, and their esters, salts, anhydrides, amides, and nitriles; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and their salts; α-olefins having 2 to 30 carbon atoms; alkyl vinyl ethers; and vinylpyrrolidones.

[0031] Component (B) can be made into an aqueous solution by a known method.

[0032] [Adipic acid dihydrazide (C)] The primer composition contains 1.0 to 5.0 parts by mass of adipic acid dihydrazide (C) per 100 parts by mass of acid-modified polypropylene resin aqueous dispersion (A). Component (C) improves the heat resistance of the resulting coating film by crosslinking with component (B). By ensuring that the content of component (C) falls within the above range, it is possible to improve the adhesion between the resulting coating film and the acid-resistant layer and the heat resistance of the coating film.

[0033] The ratio of component (C) to component (B) is preferably 0.3 to 5 by mass, and more preferably 0.3 to 1.0. By keeping the ratio of component (C) to component (B) within the above range, the heat resistance of the resulting coating film can be improved.

[0034] Component (C) can be made into an aqueous solution by a known method.

[0035] [Oxazoline compound (D)] The primer composition contains 5.0 to 10.0 parts by mass of an oxazoline compound (D) per 100 parts by mass of an acid-modified polypropylene resin aqueous dispersion (A). Component (D) improves the heat resistance of the resulting coating film by crosslinking with the acidic groups of component (A). By setting the content of component (D) within the above range, the resulting coating film can be made highly heat-resistant. The content of component (D) is preferably 5.0 to 8.0 parts by mass per 100 parts by mass of component (A). Component (D) may be used alone or in combination of two or more types.

[0036] The amount of oxazoline groups in component (D) is preferably 5 to 10 mmol / g, and the number average molecular weight of component (D) is preferably 30,000 to 50,000.

[0037] Component (D) is commercially available, and examples include the Epocross (registered trademark) series manufactured by Nippon Shokubai Co., Ltd. Specific examples include water-soluble types such as "WS-300," "WS-500," and "WS-700"; and emulsion types such as "K-1010E," "K-1020E," "K-1030E," "K-2010E," "K-2020E," and "K-2030E."

[0038] [water] The primer composition contains water as a medium for dispersing the acid-modified polypropylene resin aqueous dispersion (A). The primer composition may contain a water-soluble organic solvent as the medium. Examples of the water-soluble organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, methyl ethyl ketone, tetrahydrofuran, dioxane, acetone, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether.

[0039] [Other ingredients] The primer composition may contain, within the scope of not impairing the effects of the present invention, resins other than components (A) and (B), crosslinking agents other than components (C) and (D), leveling agents, wetting agents, antifoaming agents, pigments, dyes, dispersants, etc. The content ratio of the other components per 100 parts by mass of the acid-modified polypropylene resin aqueous dispersion (A) is preferably 10.0 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0040] <Preferred Composition> The primer composition may be a one-component composition containing all of components (A) to (D); or, taking into consideration the storage stability of the composition, it may be a two-component composition containing components (A) to (C) and component (D) in separate containers. When a two-part composition is used, it is preferred that the first part contains components (A) to (C) and water but does not contain component (D), and the second part contains component (D) and water but does not contain components (A) to (C).When using a two-part composition, the first and second parts are mixed to prepare the primer composition.

[0041] <Method for preparing primer composition> The one-component primer composition can be produced by dissolving or dispersing components (A) to (D), and optionally other components, in an aqueous medium to form liquids, and then mixing the liquids in a predetermined ratio. In a two-component primer composition, the first and second components are prepared separately. The first component can be produced by dissolving or dispersing components (A) to (C), and optionally other components, in an aqueous medium to form liquids, and then mixing the components in a predetermined ratio. The second component can be produced by dissolving or dispersing component (D), and optionally other components, in an aqueous medium to form liquids, and then mixing the components in a predetermined ratio.

[0042] From the viewpoint of ease of handling, the solid content concentration of the primer composition is preferably 5 to 25 mass %, more preferably 10 to 22 mass %, and the same applies to the solid content concentrations of the first and second parts in a two-component primer composition.

[0043] From the viewpoint of ease of handling, the viscosity of the primer composition measured at 25°C in accordance with JIS Z 8803 is preferably 1 to 100 mPa s, and more preferably 10 to 60 mPa s. The same applies to the viscosities of the first and second parts in a two-component primer composition.

[0044] <Uses of primer composition> The coating film obtained by drying the primer composition has good adhesion to a variety of substrates and excellent heat resistance because it uses two crosslinking systems, components (A) and (D) and components (B) and (C), in combination. In particular, the primer composition can be suitably used for producing an outer casing material for a secondary battery, particularly an outer casing material for a secondary battery used in a high-temperature environment. By using the primer composition as a primer layer of an outer casing material for a secondary battery, particularly as a primer layer that bonds a metal foil layer and a sealant layer, an outer casing material for a secondary battery can be obtained that does not lose adhesion strength even in a high-temperature environment and has excellent electrolyte resistance.

[0045] <Coating film> One aspect of the present invention is a coating film obtained by drying a primer composition. The primer composition can be applied to various substrates by known methods. The substrate is not particularly limited and examples include plastic molded bodies, thermoplastic resin films, fibers, nonwoven fabrics, glass, metals, metal foils, paper, etc., but a substrate made of a material that can withstand the dry heating conditions of 160°C to 180°C for 2 to 5 minutes required for the particles of component (A) to form a film is preferably used.

[0046] After applying the primer composition to a substrate, the solvent contained in the composition is dried to form coating particles of component (A), and the composition is heated to a temperature above the melting point of component (A) to obtain a primer coating. During the drying process, components (A) and (D) and components (B) and (C) undergo crosslinking reactions, respectively, to obtain a coating film with high heat resistance. The drying method and conditions are not particularly limited and can be set appropriately depending on the thickness of the coating film, etc. To efficiently dry the applied primer composition and promote film formation, the drying temperature is preferably 160 to 200°C, more preferably 180 to 200°C.

[0047] The thickness of the coating film after drying is preferably 0.1 to 10 μm, more preferably 1.0 to 8.0 μm, and even more preferably 3.0 to 5.0 μm. By setting the thickness of the coating film within the above range, when the primer composition is used as a primer layer that bonds a metal foil layer and a sealant layer in an outer casing material for a secondary battery, high adhesive strength can be obtained, and even in a high-temperature environment, there is no decrease in adhesive strength, and an outer casing material for a secondary battery having excellent electrolyte resistance can be obtained.

[0048] <Exterior material for secondary batteries> Another aspect of the present invention is an outer casing material for a secondary battery, which is formed by laminating a substrate layer, an adhesive layer, a metal foil layer, a primer layer, and a sealant layer in this order, and the primer layer is a coating film obtained by drying a primer composition.

[0049] FIG. 1 is a diagram showing an example of a laminated battery or capacitor according to the present invention. A laminated battery or capacitor is constructed by enclosing a laminated electrode group, in which positive and negative electrode plates are stacked with a separator interposed therebetween, and an electrolyte (neither of which is shown), in an exterior packaging 3, and then removing a tab lead 9 connected to the positive electrode plate and a tab lead 10 connected to the negative electrode plate, which are hermetically sealed by a sealant layer of the exterior packaging 3 via a tab lead sealing film 2. One longitudinal end of the lead conductor 1 is exposed to the outside from the exterior packaging 3 as a connection terminal to an external device, etc., and the other end is used as a connection portion for connecting to the battery electrode plate lead within the exterior packaging 3. The longitudinal direction of the lead conductor refers to the direction in which the lead conductor is exposed to the outside from the exterior packaging to serve as a connection terminal to an external device, etc.

[0050] The exterior material 3 serves as the exterior case of a laminated battery or capacitor. The exterior material is formed by laminating at least a substrate layer, an adhesive layer, a metal foil layer, a primer layer, and a sealant layer in this order. Fig. 2 is a diagram showing an example of the layer structure of the exterior material according to the present invention. The exterior material of Fig. 2 has acid-resistant layers 13 provided on both sides of a metal foil layer 14, and is formed by laminating a substrate layer 11, an adhesive layer 12, the acid-resistant layer 13, the metal foil layer 14, the acid-resistant layer 13, a primer layer 15, and a sealant layer 16 in this order. The exterior material 3 is sealed in a bag shape by, for example, bonding the peripheral sealant layers of two rectangular exterior material sheets together by heat sealing. The tab leads 9 and 10 are heat sealed to the sealant layer of the exterior material 3 via the tab lead sealing film 2, thereby sealing the tab leads 9 and 10 and the exterior material 3.

[0051] The substrate layer 11 is a layer that imparts mechanical strength to the packaging material. As the substrate layer, a biaxially oriented polyamide film, a biaxially oriented polyester film, a laminate thereof, etc. can be used. The thickness of the substrate layer 11 is preferably 10 to 35 μm, and more preferably 10 to 25 μm.

[0052] The metal foil layer 14 is a layer that prevents water vapor and the like from penetrating from the outside into the interior sealed by the exterior material 3. Metal foils such as aluminum, nickel, and stainless steel can be used as the metal foil layer 14, and aluminum foil is preferred from the viewpoints of light weight, thermal conductivity, processability, etc. The thickness of the metal foil layer 14 is preferably 10 to 100 μm, and more preferably 20 to 60 μm.

[0053] In lithium-ion batteries, the electrolyte in the electrolytic solution contains lithium salts such as LiPF6 and LiBF4. These salts react with moisture that has entered from the outside to generate hydrofluoric acid, which may corrode the aluminum foil that forms the metal foil layer. To prevent corrosion of the metal foil layer 14 by hydrofluoric acid and to improve adhesion between the substrate layer 11 and the metal foil layer 14 and between the metal foil layer 14 and the primer layer 15, it is preferable to provide an acid-resistant layer 13 on at least one side of the metal foil layer 14, and more preferably to provide an acid-resistant layer 13 on both sides of the metal foil layer 14. The acid-resistant layer 13 can be formed, for example, by trivalent chromate conversion treatment. The thickness of the acid-resistant layer 13 is preferably 0.1 to 1.0 μm, and more preferably 0.2 to 0.5 μm.

[0054] The adhesive layer 12 is a layer for bonding the base material layer 11 and the metal foil layer 14, or the base material layer 11 and the acid-resistant layer 13. A polyurethane-based resin or the like can be used as the adhesive layer. The thickness of the adhesive layer is preferably 1.0 to 10.0 μm, and more preferably 3.0 to 5.0 μm.

[0055] The primer layer 15 is a layer for bonding the metal foil layer 14 and the sealant layer 16, or the acid-resistant layer 13 and the sealant layer 16. The primer layer 15 can be formed by applying a primer composition to any one of the metal foil layer 14, the acid-resistant layer 13, and the sealant layer 16, drying the composition, and forming a film. From the viewpoint of adhesion, the primer layer 15 is preferably formed by applying a primer composition to the metal foil layer 14 or the acid-resistant layer 13, drying the composition, and forming a film. The thickness of the primer layer is preferably 0.1 to 10.0 μm, and more preferably 3.0 to 5.0 μm.

[0056] The sealant layer 16 is a layer that adheres to the primer layer 15 and also adheres the surfaces opposite to the adhesion surface with the primer layer 15 (hereinafter also referred to as heat seal layers) to each other, thereby sealing the layers in a bag shape. The sealant layer 16 may be a single-layer film or a laminated film of two or more layers.

[0057] From the viewpoints of adhesion to the primer layer 15, adhesive strength in a high-temperature environment, and resistance to electrolyte, the adhesive surface of the sealant layer 16 to the primer layer 15 is preferably an acid-modified polypropylene resin or a random copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms; more preferably an acid-modified polypropylene resin or a random copolymer of propylene and ethylene and / or 1-butene; and even more preferably an acid-modified polypropylene resin.

[0058] From the viewpoint of adhesion between heat seal layers in a high-temperature environment and resistance to electrolyte, the heat seal layer is preferably a random copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, and more preferably a random copolymer of propylene and ethylene and / or 1-butene.

[0059] From the viewpoint of enhancing heat resistance while maintaining adhesion to the primer layer 15 and adhesion between the heat seal layers, the sealant layer 16 preferably has an intermediate layer made of a high-melting-point resin. That is, the sealant layer 16 is preferably composed of at least three layers, which are formed by sequentially laminating an adhesive layer with the primer layer 15, an intermediate layer, and a heat seal layer. The intermediate layer preferably has a melting point of 150 to 165°C, as measured in accordance with JIS K 7121 in a nitrogen gas flow at a heating rate of 10°C / min, and is selected from the group consisting of a block copolymer of propylene and ethylene and a propylene homopolymer.

[0060] The total thickness of the sealant layer 16 is preferably 21 to 100 μm, and more preferably 32 to 80 μm. When the sealant layer 16 is composed of three layers, namely, an adhesive layer for the primer layer 15, an intermediate layer, and a heat seal layer, laminated in this order, the thickness of the adhesive layer for the primer layer 15 is preferably 1.0 to 30 μm, and more preferably 2.0 to 20 μm. The thickness of the intermediate layer is preferably 10 to 50 μm, and more preferably 20 to 40 μm. The thickness of the heat seal layer is preferably 10 to 40 μm, and more preferably 10 to 30 μm.

[0061] <Method of manufacturing secondary battery exterior packaging material> The method for producing the exterior packaging material for a secondary battery is not particularly limited, and examples thereof include a method including: step 1 of providing an acid-resistant layer 13 on one or both sides of a metal foil layer 14; step 2 of applying a primer composition to the acid-resistant layer 13 obtained in step 1, drying it, and forming a film to form a primer layer 15; step 3 of placing a separately prepared sealant layer 16 opposite the primer layer 15 obtained in step 2 and thermally bonding them together using a hot roll or the like; and step 4 of laminating a base material layer 11 via an adhesive layer 12 provided by a dry lamination method or the like on the side opposite the sealant layer 16 of the obtained laminate (the metal foil layer 14 or the other acid-resistant layer 13 provided on the metal foil layer 14). The conditions for the heated roll in step 3 are not particularly limited, but from the viewpoint of increasing the adhesive strength between the primer layer 15 and the sealant layer 16, the temperature of the roll that comes into contact with the metal foil layer 14 or the other acid-resistant treatment layer 13 provided on the metal foil layer 14 is preferably 160 to 250°C, more preferably 200 to 250°C. The temperature of the roll that comes into contact with the sealant layer 16 is preferably 60 to 100°C, more preferably 80 to 100°C.

[0062] <Secondary battery> Yet another aspect of the present invention is a secondary battery including a secondary battery casing material and a power-generating element, such as a positive electrode formed of a positive electrode active material and a current collector, a separator, a negative electrode formed of a negative electrode active material and a current collector, an electrolyte, and tab leads connected to the positive and negative electrodes and exposed to the outside of the casing material. [Example]

[0063] The present invention will be described in more detail below based on examples and comparative examples.

[0064] [Raw material evaluation method] The evaluation methods for the raw materials used in the examples and comparative examples are as follows.

[0065] 1.DSC measurement For a dried sample of the acid-modified polypropylene resin constituting the primer layer composition and the resin constituting the sealant layer, the sample was heated in a nitrogen gas flow from -50°C to 200°C at a rate of 10°C / min using a differential scanning calorimeter (DSC) in accordance with JIS K 7121, and the melting point was determined as the temperature of the endothermic peak.

[0066] 2. Acid value The acid value of a dried sample of the acid-modified polypropylene resin constituting the primer layer composition was measured in accordance with JIS K 2501.

[0067] 3. Saponification degree The degree of saponification of the carbonyl group-containing modified polyvinyl alcohol (B) was measured in accordance with JIS K 6726.

[0068] [Raw materials used] The raw materials used in the examples and comparative examples are as follows.

[0069] 1. Acid-modified polypropylene resin Maleic anhydride-modified polypropylene aqueous dispersion (A) (Arrowbase (registered trademark) YA-6010, manufactured by Unitika Ltd., melting point: 145°C, acid value: 20 to 30 mgKOH / g, solid content concentration: 25% by mass, pH: 8 to 11 (physical properties are catalog values)) Maleic anhydride-modified polypropylene solution (Hardlen (registered trademark) PMA-TH, manufactured by Toyobo MC Co., Ltd., melting point: 95°C, acid content: 1.1% by mass, solvent: mixed solvent of 90% by mass of cyclohexane and 10% by mass of 2-butanone, solid content: 14% by mass (physical properties are catalog values))

[0070] 2. Modified polyvinyl alcohol having carbonyl groups (B) Diacetone acrylamide-modified polyvinyl alcohol (B) (manufactured by Nippon Vinyl Acetate & Poval Co., Ltd., DF-17, saponification degree: 98 to 99 mol% (catalog value)) A 10% by mass aqueous solution of diacetone acrylamide-modified polyvinyl alcohol (B) was prepared and used to prepare a primer composition.

[0071] 3. Adipic acid dihydrazide (C) Adipic acid dihydrazide (ADH) (Otsuka Chemical Co., Ltd.) A 10% by mass aqueous solution of adipic acid dihydrazide (C) was prepared and used to prepare a primer composition.

[0072] 4. Crosslinking Agent Oxazoline group-containing polymer (D) (manufactured by Nippon Shokubai Co., Ltd., Epocross (registered trademark) WS-300 (aqueous solution), solid content concentration: 10% by mass, pH: 7 to 10, oxazoline group content: 7.7 mmol / g (physical properties are catalog values)) Carbodiimide group-containing polymer (Nisshinbo Chemical Inc., Carbodilite (registered trademark) (aqueous solution), solid content: 40% by mass, pH: 8 to 11 (physical properties are catalog values)) Isocyanate group-containing polymer (Asahi Kasei Corporation, Duranate (registered trademark) TPA-100, solid content concentration: 100% by mass, NCO%: 23.1% by mass (physical properties are catalog values)) Epoxy group-containing polymer (Hardlen (registered trademark) LAE-004 (MEK solution), manufactured by Toyobo Co., Ltd., solid content concentration: 61 to 65% by mass (physical properties are catalog values))

[0073] 5. Sealant layer raw materials (a-1) Maleic anhydride-modified polypropylene (Mitsui Chemicals, Inc., EX005, melting point: 155°C, MFR: 7.0 g / 10 min (physical properties are catalog values)) (b-1) Propylene-ethylene block copolymer (SunAllomer Co., Ltd., SunAllomer (registered trademark) PC480A, melting point: 160°C, MFR: 2.0 g / 10 min (physical properties are catalog values)) (r-1) Propylene random copolymer (SunAllomer Co., Ltd., SunAllomer (registered trademark) PC630S, melting point 142°C, MFR 7.5 g / 10 min (physical properties are catalog values))

[0074] Example 1 To 100.0 parts by mass of the maleic anhydride-modified polypropylene aqueous dispersion (A) based on solids, 5.0 parts by mass of an oxazoline group-containing polymer (D) as a crosslinking agent, 1.0 part by mass of diacetone acrylamide-modified polyvinyl alcohol (B), and 1.0 part by mass of adipic acid dihydrazide (C) were added in that order, and the mixture was stirred and mixed for 10 minutes to obtain a primer composition of Example 1 with a solids concentration of 21.0% by mass.

[0075] Example 2 A primer composition of Example 2 having a solids concentration of 21.1 mass % was obtained in the same manner as in Example 1, except that the blending amount of diacetone acrylamide-modified polyvinyl alcohol (B) was changed to 0.5 parts by mass.

[0076] Example 3 A primer composition of Example 3 having a solids concentration of 20.8 mass % was obtained in the same manner as in Example 1, except that the blending amount of diacetone acrylamide-modified polyvinyl alcohol (B) was changed to 2.0 parts by mass.

[0077] Example 4 A primer composition of Example 4 having a solids concentration of 20.6 mass % was obtained in the same manner as in Example 1, except that the blending amount of diacetone acrylamide-modified polyvinyl alcohol (B) was changed to 3.0 parts by mass.

[0078] Example 5 A primer composition of Example 5 having a solids concentration of 20.2 mass % was obtained in the same manner as in Example 1, except that the blending amount of adipic acid dihydrazide (C) was changed to 5.0 parts by mass.

[0079] Example 6 A primer composition of Example 6 having a solids concentration of 20.0 mass % was obtained in the same manner as in Example 1, except that the blending amount of the oxazoline group-containing polymer (D) was changed to 10.0 parts by mass.

[0080] Comparative Example 1 Using 100.0 parts by mass of the maleic anhydride-modified polypropylene aqueous dispersion (A) as is, a primer composition of Comparative Example 1 having a solid content concentration of 25.0% by mass was obtained.

[0081] Comparative Example 2 A primer composition of Comparative Example 2 having a solids concentration of 21.4 mass % was obtained in the same manner as in Example 1, except that the diacetone acrylamide-modified polyvinyl alcohol (B) and the adipic acid dihydrazide (C) were not blended.

[0082] Comparative Example 3 A primer composition of Comparative Example 3 having a solid content concentration of 22.2 mass % was obtained in the same manner as in Example 1, except that the oxazoline group-containing polymer (D) was not blended.

[0083] Comparative Example 4 A primer composition of Comparative Example 4 having a solid content concentration of 21.2 mass % was obtained in the same manner as in Example 5, except that the oxazoline group-containing polymer (D) was not blended.

[0084] Comparative Example 5 A primer composition of Comparative Example 5 having a solids concentration of 22.6 mass % was obtained in the same manner as in Example 1, except that 5.0 parts by mass of a carbodiimide group-containing polymer was blended instead of the oxazoline group-containing polymer (D).

[0085] Comparative Example 6 A primer composition of Comparative Example 6 having a solids concentration of 23.1 mass % was obtained in the same manner as in Example 1, except that 10.0 parts by mass of a carbodiimide group-containing polymer was blended instead of the oxazoline group-containing polymer (D).

[0086] Comparative Example 7 A primer composition of Comparative Example 7 having a solids concentration of 20.4 mass % was obtained in the same manner as in Example 1, except that the blending amount of diacetone acrylamide-modified polyvinyl alcohol (B) was changed to 4.0 parts by mass.

[0087] Comparative Example 8 To 100.0 parts by mass of the maleic anhydride-modified polypropylene solution (solids content basis), 32.0 parts by mass of an isocyanate group-containing polymer was added as a crosslinking agent, and the mixture was stirred and mixed for 10 minutes to obtain a primer composition of Comparative Example 8 with a solids content of 17.7% by mass.

[0088] Comparative Example 9 To 100.0 parts by mass of the maleic anhydride-modified polypropylene solution (based on solids), 12.1 parts by mass of an epoxy group-containing polymer was added as a crosslinking agent, and the mixture was stirred and mixed for 10 minutes to obtain a primer composition of Comparative Example 9 with a solids concentration of 14.8% by mass.

[0089] [Method for evaluating primer composition] The primer compositions of the examples and comparative examples were evaluated as follows.

[0090] 1. Stability of primer layer composition The viscosity of the primer layer compositions immediately after preparation and after storage for 1 day in environments at 25°C and 40°C was measured at 25°C in accordance with JIS Z 8803 using a TV-200EH viscometer manufactured by Toki Sangyo Co., Ltd. For the compositions immediately after preparation and those stored in an environment at 40°C, the liquid temperature was adjusted to 25°C, and then the viscosity was measured. The formulations and viscosity measurement results for the primer compositions of Examples 1 to 6 and Comparative Examples 1 to 9 are shown in Table 1. The compositions of Comparative Examples 8 and 9 gelled after storage at 25°C and 40°C for 1 day, making it impossible to measure the viscosity.

[0091] [Table 1]

[0092] 2. Adhesion strength 1 (primer coated foil / single layer film / primer coated foil configuration) 1) Preparation of maleic anhydride-modified polypropylene monolayer film Using a single-layer T-die extrusion molding machine, (a-1) maleic anhydride-modified polypropylene was melt-extruded to form a single-layer film having a thickness of 25 μm and a width of 350 mm. A sample having a length of 80 mm and a width of 70 mm was cut out from the single-layer film and used to measure adhesive strength 1. 2) Preparation of primer-coated foil The primer compositions of the Examples and Comparative Examples were applied to one side of an aluminum foil (A1N30, manufactured by UACJ Corporation) measuring 80 mm in length, 70 mm in width, and 0.04 mm in thickness, both sides of which had been treated with trivalent chromate, using a bar coater (OSG System Products Co., Ltd., OSP-22). The applied composition was then dried in an oven set at 180°C for 2 minutes to form a film, yielding an aluminum foil having a primer layer 5 μm thick. For Comparative Examples 8 and 9, the primer layer was applied to one side of the aluminum foil using a bar coater (OSG System Products Co., Ltd., OPS-42), dried for 2 minutes in an oven set at 80°C, and the solvent was evaporated to obtain an aluminum foil having a primer layer with a thickness of 5 μm. 3) Preparation of adhesive test specimens In a 120°C environment, the monolayer film obtained in 1) is stretched by tensile stress, so the adhesive strength cannot be measured using an adhesive test piece between the primer-coated foil and the monolayer film. Therefore, an adhesive test piece consisting of primer-coated foil / monolayer film / primer-coated foil was prepared and used to measure adhesive strength in environments of 25°C and 120°C. Using two sheets of primer-coated foil prepared in 2), a sample of the monolayer film prepared in 1) was sandwiched so that each primer layer was in contact with the monolayer film, and this was sandwiched between upper and lower heat seal bars heated to 180°C, with an 80 μm thick glass cloth-impregnated heat-resistant sheet in between, and bonded under conditions of 0.5 MPa and 5 seconds to prepare an adhesive test specimen. 4) Measurement of T-type peel adhesive strength at 25℃ and 120℃ The prepared adhesive test specimens were stored in an 80°C environment for 18 hours. Subsequently, in 25°C and 120°C environments, a T-peel test was performed in accordance with JIS K 6854-3, with one of the coated foils fixed to one jig and the other fixed to the other jig, at a tensile speed of 100 mm / min. The average value of the central portion of the peel test data, excluding the front and rear 10% of the data, was recorded as the adhesive strength. The adhesive test specimens in the 25°C environment were left in the same environment for 4 hours before measurement. The measurement was repeated five times for each specimen, and the average value was recorded as the adhesive strength of that specimen. An adhesive strength of 14 N / 15 mm or more at 25°C was considered to be excellent. An adhesive strength of 5.0 N / 15 mm or more at 120°C was considered to be excellent in a high-temperature environment.

[0093] The results of measuring adhesive strength 1 for the primer compositions of Examples 1 to 6 and Comparative Examples 3 to 6, 8 and 9 are shown in Table 2.

[0094] [Table 2]

[0095] 3. Adhesion strength 2 (primer layer coated foil / sealant film configuration) 1) Preparation of sealant film Using a three-layer T-die coextrusion molding machine, (a-1) 16 μm of maleic anhydride-modified polypropylene was sequentially coextruded as an adhesive layer for the primer-coated foil, (b-1) 48 μm of propylene-ethylene block copolymer as an intermediate layer, and (r-1) 16 μm of propylene-based random copolymer as a heat-seal layer to produce a three-layer sealant film with a total thickness of 80 μm. 2) Preparation of adhesive test specimens A primer-coated foil having a 5 μm-thick primer layer was obtained in the same manner as in 2.2) Preparation of primer-coated foil above. The foils were stacked with the coated foil on top and the sealant film on the bottom, with the primer layer of the coated foil facing the adhesive layer of the sealant film to the coated foil. This was sandwiched between an upper heat-seal bar heated to 180°C and a lower heat-seal bar heated to 60°C, with an 80 μm-thick glass cloth-impregnated heat-resistant sheet in between, and bonded under conditions of 0.5 MPa and 5 seconds to prepare an adhesion test piece. 3) Measurement of T-type peel adhesive strength in a 25°C environment The prepared adhesive test specimens were stored in an 80°C environment for 18 hours, then left in a 25°C environment for 4 hours. After that, a T-peel test was performed in accordance with JIS K 6854-3, with the coated foil fixed to one jig and the sealant film fixed to the other jig, at a tensile speed of 100 mm / min. The average value of the central portion of the peel test data, excluding the front and rear 10% of the data, was recorded as the adhesive strength. The measurement was repeated five times for each test specimen, and the average value was recorded as the adhesive strength of that test specimen. An adhesive strength of 14 N / 15 mm or more was considered to be excellent.

[0096] The results of measuring adhesive strength 2 for the primer compositions of Examples 1 to 6 and Comparative Examples 1 to 6 are shown in Table 3.

[0097] [Table 3]

[0098] 4. Adhesion strength after immersion in electrolyte Adhesion test specimens were prepared in the same manner as in 3.2) Preparation of Adhesion Test Specimens above, and were stored in an environment at 80°C for 18 hours, and then left in an environment at 25°C for 4 hours. The obtained adhesion test specimens were immersed in a 1 mol / L LiPF6 electrolyte in a 1:1:1 ratio of ethylene carbonate:diethyl carbonate:dimethyl carbonate containing 1,000 ppm of distilled water, and left in a thermostatic bath at 85°C for 3 and 7 days, after which they were removed from the thermostatic bath and washed with a dimethyl carbonate solution, followed by rinsing with water and drying. After immersion in the electrolyte, the adhesive test specimens were stored for 24 hours at 25°C. Under the same conditions, a T-peel test was performed in accordance with JIS K 6854-3, with the coated foil fixed to one jig and the sealant film fixed to the other, at a tensile speed of 100 mm / min. The average value of the central portion of the peel test data, excluding the anterior and posterior 10% of the peel test data, was recorded as the adhesive strength. The measurement was repeated five times for each test specimen, and the average value was recorded as the adhesive strength of that specimen. If the adhesive strength of the adhesive test specimen after 7 days in an 85°C thermostatic bath was 80% or more of the initial value and 12 N / 15 mm or more, the specimen had excellent electrolyte resistance. If the adhesive strength of the adhesive test specimen after 7 days in an 85°C thermostatic bath was 70% or more of the initial value and 12 N / 15 mm or more, the specimen was deemed to have acceptable electrolyte resistance for practical use.

[0099] For the primer compositions of Examples 1 to 6 and Comparative Examples 2 and 4 to 6, the adhesive strength was measured after immersion in the electrolyte solution, and the results are shown in Table 4.

[0100] [Table 4]

[0101] As shown in Tables 1 to 4, the primer compositions of Examples 1 to 6 have excellent storage stability, and a laminate in which a coating film obtained from the composition is used to bond an aluminum foil that has been subjected to a trivalent chromate conversion treatment to a sealant film does not lose adhesive strength even in a high-temperature environment and has excellent electrolyte resistance.

[0102] Comparative Example 1, which used only the maleic anhydride-modified polypropylene aqueous dispersion (A), and Comparative Example 2, which blended only the aqueous dispersion (A) and the oxazoline group-containing polymer (D), showed significantly poor adhesive strength in a 25°C environment. Comparative Examples 3 and 4, which consisted of the three components of the aqueous dispersion (A), diacetone acrylamide-modified polyvinyl alcohol (B), and adipic acid dihydrazide (C), showed poor adhesion at 120°C. Comparative Examples 5 and 6, which used a carbodiimide group-containing polymer instead of the oxazoline group-containing polymer (D), showed poor electrolyte resistance in an 85°C environment. Comparative Example 7, in which the blending amount of diacetone acrylamide-modified polyvinyl alcohol (B) per 100 parts by mass of the aqueous dispersion (A) was 4.0 parts by mass, showed thickening of the composition over time, and the coating amount during application became unstable, resulting in poor coating stability. In Comparative Examples 8 and 9, in which an isocyanate group-containing polymer and an epoxy group-containing polymer were respectively blended with the maleic anhydride-modified polypropylene solution, the compositions had poor storage stability and poor adhesion at 120°C due to the low melting point of the maleic anhydride-modified polypropylene used. [Industrial Applicability]

[0103] The primer composition of the present invention can be suitably used in the production of packaging materials for secondary batteries that are used in high-temperature environments. [Explanation of symbols]

[0104] 1 Lead conductor 2. Tab lead sealing film 3. Exterior materials 9 Positive tab lead 10 Negative electrode tab lead 11 Base material layer 12 Adhesive layer 13 Acid-resistant layer 14 Metal foil layer 15 Primer layer 16. Sealant layer

Claims

1. 100 parts by mass of an aqueous dispersion of acid-modified polypropylene resin (A), 0.5 to 3.0 parts by mass of modified polyvinyl alcohol (B) having a carbonyl group, 1.0 to 5.0 parts by mass of adipic acid dihydrazide (C), 5.0 to 10.0 parts by mass of an oxazoline compound (D), and water A primer composition comprising: The aqueous dispersion (A) has a melting point of 143 to 148°C as measured in accordance with JIS K 7121 in a nitrogen gas flow at a temperature increase rate of 10°C / min, and an acid value of 20 to 30 mgKOH / g as measured in accordance with JIS K 2501, the modified polyvinyl alcohol (B) has a degree of saponification measured in accordance with JIS K 6726 of 98 to 99 mol %, A primer composition having a viscosity of 1 to 60 mPa·s measured at 25°C in accordance with JIS Z 8803 immediately after preparation and after storage for 1 day in a 25°C environment.

2. 2. The primer composition according to claim 1, wherein component (A) is an aqueous dispersion of a polypropylene resin modified with maleic anhydride.

3. 3. The primer composition according to claim 1, wherein component (B) is a polyvinyl alcohol containing diacetone acrylamide units.

4. 3. The primer composition according to claim 1, wherein the amount of oxazoline groups in component (D) is 5 to 10 mmol / g.

5. 3. The primer composition according to claim 1, wherein the content ratio of component (C) to component (B) is 0.3 to 5 on a mass basis.

6. The primer composition according to claim 1 or 2, which comprises a first agent and a second agent, A primer composition, wherein the first part contains components (A) to (C) and water, but does not contain component (D); and the second part contains component (D) and water, but does not contain components (A) to (C).

7. The primer composition according to claim 1 or 2, which is used for producing an exterior material for a secondary battery.

8. A coating film obtained by drying the primer composition according to claim 1 or 2.

9. An outer casing material for a secondary battery, which is formed by laminating a substrate layer, an adhesive layer, a metal foil layer, a primer layer, and a sealant layer in this order, wherein the primer layer is the coating film according to claim 8.

10. A secondary battery comprising the packaging material for a secondary battery according to claim 9 and a power generating element.

Images