WO2025134539A1 - Aqueous metal surface treatment agent and method for producing metal foil laminate - Google Patents

Abstract

The present disclosure provides an aqueous surface treatment agent which is capable of improving adhesion and electrolyte solution resistance when laminating a metal. An aqueous metal surface treatment agent according to one embodiment of the present invention is used for surface treatment of a metal and includes a trivalent chromium compound (A), a water-soluble or water-dispersible acrylic resin (B), and a phosphoric acid compound (C). The water-soluble or water-dispersible acrylic resin (B) has a weight average molecular weight of 50,000 to 1,000,000 inclusive, and a solid acid value of more than 740 mgKOH/g.

Description

Aqueous metal surface treatment agent and method for producing metal foil laminate

The present invention relates to an aqueous metal surface treatment agent and a method for producing metal foil laminates.

Traditionally, metal has been laminated by adhering a laminate film to the metal to protect it and add a design.

In order to maintain the aesthetic appearance and corrosion resistance of the laminated metal, it is important to improve the adhesion of the laminate film. For example, a method is known in which a chemical conversion coating layer is formed on one or both sides of the aluminum foil.

A method for forming a chemical conversion coating layer on an aluminum surface is known that uses a surface treatment agent that contains a water-soluble trivalent chromium compound and a water-soluble organic polymer compound (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 53-037550

When using laminated metals as exterior materials for batteries, it is desirable to improve adhesion and electrolyte resistance.

The present invention aims to provide an aqueous surface treatment agent that can improve adhesion and electrolyte resistance when laminating metals.

(1) The present disclosure relates to an aqueous metal surface treatment agent used for metal surface treatment, the aqueous metal surface treatment agent comprising a trivalent chromium compound (A), a water-soluble or water-dispersible acrylic resin (B), and a phosphoric acid compound (C), the water-soluble or water-dispersible acrylic resin (B) having a weight-average molecular weight of 50,000 or more and 1,000,000 or less, and an acid value of the solid content exceeding 740 mg KOH/g.

(2) The aqueous metal surface treatment agent according to (1), in which the mass ratio of trivalent chromium contained in the trivalent chromium compound (A) to the total solid content of the aqueous metal surface treatment agent is 5% or more and 15% or less in terms of trivalent chromium, and the mass ratio of solid content of the phosphate compound (C) to the total solid content of the aqueous metal surface treatment agent is 5% or more and 40% or less in terms of phosphate ion.

(3) The aqueous metal surface treatment agent according to (1) or (2), further comprising nitrate ions (D), and the molar ratio (A/D) of the trivalent chromium compound (A) to the nitrate ions (D) is 0.3 or more and 0.4 or less.

(4) The present disclosure also relates to a method for producing a metal foil laminate, comprising a surface treatment step of treating at least one surface of a metal foil, and a lamination step of laminating a film onto the surface of the metal foil treated by the surface treatment step, in which the aqueous metal surface treatment agent used in the surface treatment step comprises a trivalent chromium compound (A), a water-soluble or water-dispersible acrylic resin (B), and a phosphoric acid compound (C), and the water-soluble or water-dispersible acrylic resin (B) has a weight average molecular weight of 50,000 or more and 1,000,000 or less and an acid value of the solid content of more than 740 mg KOH/g.

(5) The method for producing a metal foil laminate according to (4), wherein the mass ratio of trivalent chromium contained in the trivalent chromium compound (A) to the total solid content of the aqueous metal surface treatment agent is 5% or more and 15% or less in terms of trivalent chromium, and the mass ratio of solid content of the phosphate compound (C) to the total solid content of the aqueous metal surface treatment agent is 5% or more and 40% or less in terms of phosphate ion.

(6) The method for producing a metal foil laminate according to (4) or (5), wherein the aqueous metal surface treatment agent further contains nitrate ions (D), and the molar ratio (A/D) of the trivalent chromium compound (A) to the nitrate ions (D) is 0.3 or more and 0.4 or less.

The present invention provides an aqueous surface treatment agent that can improve adhesion and electrolyte resistance when laminating metals.

The following describes an embodiment of the present invention. The present invention is not limited to the description of the following embodiment.

[Aqueous surface treatment agent]
The aqueous surface treatment agent of the present embodiment is used for treating the surface of a metal.

The metal to be surface-treated is not particularly limited, but examples thereof include iron, zinc, aluminum, copper, nickel, etc., and two or more of them may be used in combination. That is, the metal may be an alloy. The alloy components may include, for example, carbon, nitrogen, oxygen, phosphorus, sulfur, silicon, manganese, chromium, titanium, molybdenum, etc. Among these, from the viewpoint of workability and adhesion, aluminum or aluminum alloys, iron or iron alloys, or copper or copper alloys are preferred, and aluminum or aluminum alloys are more preferred. Examples of aluminum alloys include Al-Cu alloys, Al-Mn alloys, Al-Si alloys, Al-Mg alloys, Al-Mg-Si alloys, Al-Zn-Mg alloys, aluminum die-cast (ADC material), etc. When the surface-treated metal of this embodiment described later is used as a battery exterior material, it is preferable to use 8079 material or the like as the aluminum alloy. Examples of aluminum alloys that can be used for other applications include 3004, 3104, and 3005 materials for beverage and food can bodies, 5052 and 5182 materials for beverage and food can lids, 1050, 1100, and 1200 materials for dry battery containers, and 8021 materials for electrodes. Examples of iron alloys include cold-rolled steel sheets such as SPCC, SPCD, and SPCE, and stainless steel (SUS). Examples of SUS include austenitic stainless steels such as SUS304, SUS301, and SUS316, ferritic stainless steels such as SUS430, and martensitic stainless steels such as SUS410. Examples of zinc alloys include Zn-Al alloys. Examples of copper alloys include brass. Examples of nickel alloys include Ni-P alloys.

The metal, which may be an alloy, may be plated. Examples of the metals to be plated include nickel, zinc, chromium, iron, tin, copper, silver, platinum, and gold, and two or more metals may be used in combination. Examples of plating methods include electroplating, electroless plating, hot-dip plating, vacuum deposition, sputtering, and ion plating. Examples of plated metals include Ni-plated steel, Ni-plated copper, Zn-plated steel, and Zn-Ni-plated steel. Examples of the metal to be plated (base material) include cold-rolled steel sheets such as SPCC, SPCD, and SPCE, and copper sheets.

The aqueous metal surface treatment agent according to this embodiment contains a trivalent chromium compound (A), a water-soluble or water-dispersible acrylic resin (B), and a phosphoric acid compound (C). It is preferable that the aqueous metal surface treatment agent further contains nitrate ions (D).

The aqueous surface treatment agent of this embodiment may contain hexavalent chromium. In this case, the content of hexavalent chromium in the aqueous surface treatment agent of this embodiment is, for example, less than 0.04 mass%, less than 0.02 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, less than 0.00001 mass%, or less than 0.000001 mass%. The content of hexavalent chromium in the aqueous surface treatment agent of this embodiment is preferably minimized, i.e., a trace amount, and most preferably 0 mass%. The film formed by surface treating a metal with the aqueous surface treatment agent of this embodiment preferably contains substantially no hexavalent chromium, and most preferably contains no hexavalent chromium.

(Trivalent chromium compound (A))
The trivalent chromium compound (A) is contained in the aqueous surface treatment agent, and improves the electrolyte resistance when laminating metal. The electrolyte may contain a fluorine compound such as _LiPF6 . The fluorine compound reacts with water to generate hydrofluoric acid, which causes corrosion of metals such as aluminum. The trivalent chromium compound (A) can form a film having excellent electrolyte resistance against the above electrolyte.

Trivalent chromium compounds (A) are not particularly limited, but examples include chromium (III) fluoride, chromium (III) nitrate, chromium (III) phosphate, chromium (III) acetate, chromium (III) chloride, chromium (III) sulfate, chromium (III) oxalate, chromium (III) formate, chromium (III) hydroxide, chromium (III) oxide, chromium (III) bromide, and chromium (III) iodide.

The content of the trivalent chromium compound (A), calculated as the trivalent chromium content (chromium concentration) of the trivalent chromium compound (A), is preferably 5% or more and 15% or less of the total solid content of the aqueous surface treatment agent. This improves the electrolyte resistance when laminating to metal. It is more preferable that the trivalent chromium concentration in the aqueous surface treatment agent is 5% or more and 10% or less.

The concentration of the trivalent chromium compound (A) is preferably 0.1% or more and 0.45% or less in the aqueous surface treatment agent, calculated as the trivalent chromium contained in the trivalent chromium compound (A) (chromium concentration). This improves the electrolyte resistance when laminating to metal. It is more preferable that the trivalent chromium concentration in the aqueous surface treatment agent is 0.15% or more and 0.45% or less.

(Water-soluble or water-dispersible acrylic resin (B))
The water-soluble or water-dispersible acrylic resin (B) improves adhesion when laminating metal by being contained in the aqueous surface treatment agent. The water-soluble or water-dispersible acrylic resin (B) contains, for example, a structural unit derived from a monomer having a carboxyl group. The monomer having a carboxyl group is not particularly limited, but examples thereof include (meth)acrylic acid, crotonic acid, isocrotonic acid, (meth)acrylic acid dimer, and ε-caprolactone adduct of (meth)acrylic acid. Other examples of monomers having a carboxyl group include unsaturated dibasic acids such as maleic acid, fumaric acid, and itaconic acid, and their half esters, half amides, and half thioesters, and two or more of them may be used in combination.

The water-soluble or water-dispersible acrylic resin (B) is preferably poly(meth)acrylic acid, and more preferably polyacrylic acid, from the viewpoint of electrolyte resistance when laminating metal.

Commercially available polyacrylic acid products include Jurimer AC-10L, AC-10H, AC-20L, and SH-5 (all manufactured by Toagosei).

The water-soluble or water-dispersible acrylic resin (B) may further contain a structural unit derived from a monomer having a hydroxyl group.

The monomer having a hydroxyl group is not particularly limited, but examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, glycerin mono(meth)acrylate, (meth)allyl alcohol, N-methylol (meth)acrylamide, N-(2-hydroxyethyl)acrylamide, N-(2-hydroxypropyl)acrylamide, and ε-caprolactone adduct of 2-hydroxyethyl (meth)acrylate, and two or more of these may be used in combination.

The water-soluble or water-dispersible acrylic resin (B) may further contain structural units derived from monomers other than those mentioned above (other monomers).

Other monomers include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, 1-methylethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, dihydrodicyclopentadienyl (meth)acrylate, methoxypolyethylene (meth)acrylate, and the like. Other monomers besides those mentioned above include styrene, α-methylstyrene, vinyl ketone, t-butylstyrene, p-chlorostyrene, vinylnaphthalene, acrylonitrile, methacrylonitrile, ethylene, propylene, vinyl acetate, vinyl propionate, butadiene, isoprene, etc., and two or more of them may be used in combination.

The weight average molecular weight of the water-soluble or water-dispersible acrylic resin (B) is 50,000 or more and 1,000,000 or less. This allows the formation of a film with excellent adhesion and electrolyte resistance. The weight average molecular weight of the water-soluble or water-dispersible acrylic resin (B) is preferably 50,000 or more and 250,000 or less. If the weight average molecular weight of the water-soluble or water-dispersible acrylic resin (B) is less than 50,000, the adhesion of the laminate film decreases when laminating to metal, and if it exceeds 1,000,000, the aqueous surface treatment agent is prone to gelation, making handling difficult.

In this specification and claims, the weight average molecular weight of the water-soluble or water-dispersible acrylic resin (B) is the molecular weight determined by the GPC method using polyethylene oxide as the standard substance.

The acid value of the solid content of the water-soluble or water-dispersible acrylic resin (B) is greater than 740 mg KOH/g. This allows the formation of a film with excellent adhesion and electrolyte resistance. The acid value of the solid content of the water-soluble or water-dispersible acrylic resin (B) may be 779 mg KOH/g or less.

In this specification and claims, the acid value of the solid content of the water-soluble or water-dispersible acrylic resin (B) refers to the theoretical value of the acid value of the solid content, calculated by calculating the amount of potassium hydroxide (unit: mg) required to neutralize the acid groups contained in 1 g of the solid content of the acrylic resin based on the charge ratio of each monomer used in the polymerization of the acrylic resin. The acid value of the solid content of the water-soluble or water-dispersible acrylic resin (B) can be controlled to a desired value by adjusting the type and charge ratio of each monomer constituting the monomer composition used in the polymerization.

(Phosphate Compound (C))
The phosphoric acid compound (C) is contained in the aqueous surface treatment agent, and when laminating metal, it improves the electrolyte resistance. The phosphoric acid compound (C) is not particularly limited, but for example, phosphoric acid, condensed phosphoric acid, phosphate, condensed phosphate, etc. may be used in combination of two or more. Among these, phosphoric acid is preferred. For example, condensed phosphoric acid includes pyrophosphoric acid, tripolyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, ultraphosphoric acid, etc. For example, salt of phosphate or condensed phosphate includes alkali metal salt, ammonium salt, etc.

The ratio of the solid mass of the phosphate compound (C) to the total solid mass of the aqueous metal surface treatment agent is preferably 5% or more and 40% or less in terms of phosphate ions. This improves the electrolyte resistance when laminating to metal. It is more preferable that the content of the phosphate compound (C) in the aqueous surface treatment agent is 10% or more and 40% or less.

The concentration of the phosphoric acid compound (C) in the aqueous metal surface treatment agent is preferably 0.2% or more and 0.8% or less as phosphate ions. This improves electrolyte resistance when laminating to metal. The concentration of the phosphoric acid compound (C) in the aqueous surface treatment agent is more preferably 0.2% or more and 0.5% or less.

(Nitrate ion (D))
Nitrate ions (D) are preferably contained in the aqueous metal surface treatment agent as counter ions of trivalent chromium in the trivalent chromium compound (A). The inclusion of nitrate ions (D) and/or phosphate ions in the aqueous metal surface treatment agent can improve the corrosion resistance and adhesion of the coating formed. For example, when chromium nitrate (III) is used as the trivalent chromium compound (A), chromium nitrate (III) can be a source of nitrate ions (D). In addition to the above, a substance that can be a source of nitrate ions (D) may be blended into the aqueous surface treatment agent. Examples of such substances include nitric acid. When chromium nitrate (III) is used as the trivalent chromium compound (A), it is preferable that the source of nitrate ions (D) is only chromium nitrate (III).

When the aqueous surface treatment agent according to this embodiment contains nitrate ions (D), it is preferable that the molar ratio (A/D) of the trivalent chromium compound (A) to the nitrate ions (D) is 0.3 or more and 0.4 or less. When the molar ratio (A/D) is less than 0.3, there is a risk that the nitrate ions will be in excess and adhesion will be poor, and when the molar ratio (A/D) is more than 0.4, there is a risk that the liquid will not be stable and precipitation will be more likely to occur due to a shortage of nitrate ions, which are counter ions necessary to stabilize trivalent chromium.

The concentration of nitrate ions (D) in the aqueous metal surface treatment agent is preferably 0.3% or more and 1.7% or less. This ensures solution stability and electrolyte resistance. It is more preferable that the concentration of nitrate ions (D) in the aqueous surface treatment agent is 0.5% or more and 1.6% or less.

The pH of the aqueous surface treatment agent of this embodiment is not particularly limited, but is, for example, 1 or more and 4 or less.

(Other ingredients)
The content of water in the aqueous surface treatment agent of the present embodiment is not particularly limited, but is, for example, 50% by mass or more and 99.9% by mass or less. In addition, the aqueous surface treatment agent may further contain an organic solvent miscible with water, as necessary, in order to adjust the solid content concentration and drying speed. The organic solvent miscible with water is not particularly limited, but examples thereof include ketone-based solvents such as acetone and methyl ethyl ketone; amide-based solvents such as N,N'-dimethylformamide and dimethylacetamide; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol and 1-methoxy-2-propanol; ether-based solvents such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether; and pyrrolidone-based solvents such as 1-methyl-2-pyrrolidone and 1-ethyl-2-pyrrolidone.

The aqueous surface treatment agent of this embodiment may further contain known additives such as crosslinking agents, surface conditioners, defoamers, plasticizers, antioxidants, antibacterial agents, and colorants, as necessary.

[Surface-treated metal]
By surface treating a metal with the aqueous surface treatment agent of this embodiment, a surface-treated metal having a coating formed on the surface can be obtained. The shape of the metal is not particularly limited, but examples thereof include foil and plate shapes. When using a foil-shaped or plate-shaped metal, one side may be surface-treated with the aqueous surface treatment agent of this embodiment, or both sides may be surface-treated with the aqueous surface treatment agent of this embodiment. When both sides are surface-treated with the aqueous surface treatment agent of this embodiment, both sides may be surface-treated with the same aqueous surface treatment agent, or both sides may be surface-treated with different aqueous surface treatment agents.

The surface-treated metal of this embodiment may be a metal having a coating that has been laminated. That is, a laminate film may be adhered to the coating formed by surface-treating the metal. When a foil- or plate-shaped metal is used, the laminate film may be adhered to one side, or the laminate film may be adhered to both sides. Also, when the laminate film is adhered to both sides, the same laminate film may be adhered to both sides, or different laminate films may be adhered to both sides.

　Materials constituting the laminate film are not particularly limited, but examples include polyethylene resins, polypropylene resins, polycarbonate resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyvinylidene chloride resins, polyvinyl acetate resins, polyethylene terephthalate resins, polyethylene naphthalate resins, polybutylene terephthalate resins, polyethylene isophthalate resins, copolymer polyester resins, polyester resins, polyamide resins, polyimide resins, polyetherimide resins, polyphenylene sulfide resins, fluorine resins, silicone resins, nylon resins, phenolic resins, (meth)acrylic resins, epoxy resins, polymetaxylylene azibamide resins, etc., and two or more of these may be used in combination.

As the laminate film, a single layer film or a multilayer film may be used. In the multilayer film, multiple films may be laminated with an adhesive or without an adhesive. The adhesive may be a one-component curing adhesive or a two-component curing adhesive. Resin components constituting the adhesive include polyester resins, polyether resins, polyurethane resins, epoxy resins, phenol resins, polyamide resins, polyolefin resins, polyvinyl acetate resins, cellulose resins, (meth)acrylic resins, polyimide resins, amino resins, rubber, and silicone resins. Methods for laminating multiple films without an adhesive include, but are not limited to, co-extrusion, sand lamination, and thermal lamination.

The surface-treated metal of this embodiment may have layers other than the coating and the laminate film (hereinafter referred to as other layers). The other layers may be present between the coating and the laminate film, or may be present on the laminate film. Also, the surface-treated metal of this embodiment may have other layers present on the coating, without the laminate film adhering to the metal having the coating.

The other layers are not particularly limited, but examples include known layers such as an adhesive layer, a coating film, a hard coat layer, an antifouling layer, an antiglare layer, a design layer, a printing layer, a polarizing plate, a colored layer, a liquid crystal layer, a light guide plate, a transparent conductive film, and a spacer, and two or more of these layers may be used in combination.

The adhesive layer may be formed from a one-component adhesive or a two-component adhesive.

　Resins constituting the adhesive that can be used to form the adhesive layer include polyolefin resins, polyester resins, polyether resins, polyurethane resins, polycarbonate resins, epoxy resins, phenol resins, polyamide resins, polyvinyl acetate resins, cellulose resins, (meth)acrylic resins, polyimide resins, amino resins, chloroprene rubber resins, nitrile rubber resins, styrene-butadiene rubber resins, silicone resins, fluorinated ethylene-propylene copolymer resins, etc., and two or more of these may be used in combination. Examples of combinations of resins that can be used in combination include polyurethane resins and modified polyolefin resins, polyamide resins and acid-modified polyolefin resins, polyamide resins and metal-modified polyolefin resins, polyamide resins and polyester resins, polyester resins and acid-modified polyolefin resins, polyester resins and metal-modified polyolefin resins, etc.

Polyolefin resins include acid-modified polyolefin resins and metal-modified polyolefin resins. Examples of acid-modified polyolefin resins include polyolefin resins that have been acid-modified with unsaturated carboxylic acids such as maleic anhydride-modified polypropylene or their anhydrides. Commercially available acid-modified polypropylene resins include Admer (NB508, NF518, LB548, QB510, QB550, LB458, NF528, LF128, LF308, NF308, NF548, NF558, SF600, SF700, SF731, SF715, SE800, NE060, NE065, NE090, XE070, HE040, QE060, QF500, QF551, QF570, NR106, NS101, etc.) manufactured by Mitsui Chemicals, and Unistall (R-200X, R-303XE, E-200EM, A-2 00PM, A-201PM, H-100, H-200, XP01A, XP01B/11B, XP03F, XP04A, etc.), Mitsubishi Chemical's Modic (P502, P512VB, P553A, P674V, P565, P555, P908H511, H503, H514, L502, L504, M142, M512, M522, M545, A543, F502, F573, F534A, etc.), Unitika's Arrowbase (SB-1200, SE-1200, SD-1200, DA1010, DC-1010, YA-6010, etc.), etc.

The method for forming the adhesive layer is not particularly limited, but examples include the extrusion molding method and the dispersion method.

Applications of the surface-treated metal of this embodiment include, for example, exterior materials for batteries, food packaging materials, bodies or lids for food cans, bodies or lids for beverage cans, soft packaging materials or surface protection materials containing metal foil such as aluminum pouches, battery separators, tab leads, condenser cases, heat exchangers, electronic device housings, metal building materials, vehicle bodies, engine parts or chassis parts, aircraft bodies, main wings, frames, fuel tanks, engine turbines, engine fans or parts, railroad car bodies, bogies or parts, ships, rocket parts, bicycle parts, vending machines, elevator car side panels, governors or hoists, escalator steps or interior panels, machine tools, injection molding machines, structural or driving parts for industrial robots, semiconductor manufacturing equipment, displays, submarines, traffic lights, automatic looms, tunnel boring machines, pipelines, road signs, generators, waste incinerators, exhaust gas treatment devices, motors, transformers, electronic circuits, light bulbs, photomultiplier tubes, golf clubs, antennas, bolts, nuts, screws, etc. Among these, from the viewpoint of electrolyte resistance, exterior materials for batteries are preferred, and exterior materials for lithium ion batteries are particularly preferred.

[Method of manufacturing metal foil laminate]
The method for producing a metal foil laminate according to this embodiment includes a surface treatment step and a lamination step.

(Surface treatment process)
The surface treatment step is, for example, a step of applying the aqueous surface treatment agent of the above embodiment to at least one surface of the prepared metal foil, and then drying the applied surface.

　The method for applying the aqueous surface treatment agent of this embodiment is not particularly limited, but examples include roll coater coating, gravure coater coating, reverse coater coating, slot die coater coating, lip coater coating, knife coater coating, blade coater coating, chamber doctor coater coating, air knife coater coating, curtain coat coating, spin coat coating, brush coating, roller coating, bar coater coating, dip coating, applicator coating, spray coating, flow coating, and combinations thereof.

The drying method is not particularly limited, but any known method can be used, and examples of such heat drying methods include drying using an oven, drying by forced circulation of hot air, and drying in an electromagnetic induction heating furnace using an IH heater or the like. The conditions for the heat drying method can be, for example, a temperature of 40°C or higher and 230°C or lower for 2 seconds or longer and 180 seconds or shorter. Here, the conditions such as the air volume and air speed set during heat drying can be set as desired.

The surface treatment process may involve applying the aqueous surface treatment agent of this embodiment to the surface of the metal foil while drying. For example, the aqueous surface treatment agent of this embodiment may be applied to the surface of a preheated metal foil and then dried.

The amount of the coating formed after drying in the surface treatment step is preferably 0.1 mg/ ^m2 or more and 5000 mg/ ^m2 or less, and more preferably 1 mg/ ^m2 or more and 500 mg/ ^m2 or less.

(Lamination process)
The lamination step is a step of laminating a film on the surface of the metal foil treated by the surface treatment step. The lamination method is not particularly limited, but may be any known method such as a dry lamination method, a heat lamination method, or an extrusion lamination method.

The method for manufacturing the metal foil laminate according to this embodiment may include steps other than those described above as long as they do not impair the effects of the present invention.

The following describes examples of the present invention, but the present invention is not limited to these examples.

[Preparation of aqueous metal surface treatment agent]
The aqueous metal surface treatment agents according to each Example and Comparative Example were prepared by mixing with pure water so that the amount of each component was as shown in Table 1. In Table 1, (A) means the trivalent chromium compound (A), and the content means the ratio (mass%) of the mass of trivalent chromium to the total solid content of the aqueous metal surface treatment agent. Similarly, (B) means a resin such as a water-soluble or water-dispersible acrylic resin (B), and the content means the ratio (mass%) of the mass to the total solid content of the aqueous metal surface treatment agent. Similarly, (C) means a phosphoric acid compound (C), and the content means the ratio (mass%) of the solid content as phosphate ions to the total solid content of the aqueous metal surface treatment agent. (A/D) means the molar ratio (A/D) of the trivalent chromium compound (A) and the nitrate ions (D).

In each of the Examples and Comparative Examples, a 35% chromium nitrate solution was used as the trivalent chromium compound (A). A 75% aqueous phosphoric acid solution was used as the phosphate compound (C). In Comparative Example 9, nitric acid was also used as a source of nitrate ions (D).

The definitions of the abbreviations in Table 1 are as follows.
B1: JURYMER AC-10L (manufactured by Toagosei) Polyacrylic acid Weight average molecular weight 50,000 Solid content acid value 779 mg KOH/g
B2: Polyacrylic acid manufactured by Wako Pure Chemical Industries, Ltd. Weight average molecular weight: 250,000 Acid value of solid content: 779 mg KOH/g
B3: JURYMER AC-10H (manufactured by Toagosei) Polyacrylic acid Weight average molecular weight 800,000 Solid content acid value 779 mg KOH/g
B4: JURYMER AC-10H (manufactured by Toagosei) Polyacrylic acid Weight average molecular weight 3,000,000 Solid content acid value 779 mg KOH/g
B5: Aron A-10SL (manufactured by Toagosei) Polyacrylic acid Weight average molecular weight 5,000 Solid content acid value 779 mg KOH/g
B6: Arialic HL-415 (manufactured by Nippon Shokubai) Polyacrylic acid Weight average molecular weight 10,000 Solid content acid value 779 mg KOH/g
B7: Haricoat G-51 (Harima Chemicals) Acrylamide B8: PVA-HC (Kuraray) Polyvinyl alcohol B9: A-12SL (Toagosei) Sulfonic acid copolymer B10: Addibond 021 (Solvay) Phosphonic acid modified acrylic acid B11: K-30 (Nippon Shokubai) Polyvinylpyrrolidone

[Application of water-based metal surface treatment agent (surface treatment)]
The aqueous metal surface treatment agents according to the Examples and Comparative Examples prepared above were applied to aluminum foil using a 0.8 nylon bar (bar coater), and then baked at 190° C. for 2 minutes.

[Dry lamination (lamination processing)]
XP01A (modified polyolefin, manufactured by Mitsui Chemicals) and D-370N (isocyanate, manufactured by Mitsui Chemicals) were mixed and stirred in a mass ratio of 100:0.59 to prepare an adhesive liquid. Next, the adhesive liquid was applied to each sample coated with the above-mentioned aqueous metal surface treatment agent using a #20 stainless steel bar (bar coater). Then, baking was performed at 100°C for 60 seconds to form an adhesive layer. A CPP film was placed on the prepared sample, sandwiched between PET films, and passed through a laminator for heat and pressure bonding. Then, the sample was aged at 60°C for 3 days to obtain samples according to each Example and Comparative Example.

<Evaluation>
[Peel strength test (initial stage) (adhesion of laminate film)]
The samples of each Example and Comparative Example were adjusted to a width of 15 mm, and a cut was made from the back side about 1 cm below the film adhesion part with a cutter, and the sample was folded. Next, the film of the folded part was pulled about 2 mm in the direction of the remaining part of the sample (180° direction), and the seal strength (N/15 mm) was measured to evaluate the adhesion. For the test, a tension and compression tester: LST-200N-S100 (manufactured by MinebeaMitsumi Inc.) was used. The measurement was performed with n=2, and the average value is shown in Table 1.

[Peel strength test (electrolyte) (electrolyte resistance)]
10000 ppm of deionized water was added to an electrolyte solution in which 1M _LiPF6 was dissolved in a mixed solvent of ethylene carbonate/dimethyl carbonate/diethyl carbonate (volume ratio 1/1/1) to obtain a test electrolyte solution. The samples according to the above examples and comparative examples were immersed in the test electrolyte solution at 85°C for one day, and then the peel strength was measured in the same manner as above to evaluate the electrolyte resistance. Note that the film of the sample of Comparative Example 8 was completely peeled off, and the peel strength could not be measured.

[handling]
The aqueous metal surface treatment agents according to the respective Examples and Comparative Examples were prepared, and left to stand at room temperature for one day, after which the presence or absence of gelation and precipitation was visually confirmed. The cases in which neither gelation nor precipitation occurred were rated as "pass", and the cases in which gelation or precipitation occurred were rated as "fail". The results are shown in Table 1 as "pass" (A) or "fail" (B).

The results shown in Table 1 show that when a metal plate is surface-treated with the aqueous surface treatment agent of each Example, the adhesion and electrolyte resistance of the laminate film of the laminated metal plate is higher than when the metal plate is surface-treated with the aqueous surface treatment agent of each Comparative Example. Note that although the aqueous surface treatment agent of Comparative Example 1 provided a laminate film with high adhesion and electrolyte resistance, it had poor handleability and was not suitable for practical use.

Claims (6)

An aqueous metal surface treatment agent for use in surface treatment of metals, comprising:
The composition comprises a trivalent chromium compound (A), a water-soluble or water-dispersible acrylic resin (B), and a phosphoric acid compound (C),
The water-soluble or water-dispersible acrylic resin (B) has a weight average molecular weight of 50,000 or more and 1,000,000 or less and an acid value of the solid content of more than 740 mgKOH/g. a mass ratio of trivalent chromium contained in the trivalent chromium compound (A) to a total solid content of the aqueous metal surface treatment agent is 5% or more and 15% or less, calculated as trivalent chromium;
2. The aqueous metal surface treatment agent according to claim 1, wherein the ratio of the solid content mass of the phosphate compound (C) to the total solid content mass of the aqueous metal surface treatment agent is 5% or more and 40% or less in terms of phosphate ions. The aqueous metal surface treatment agent further contains nitrate ions (D),
3. The aqueous metal surface treatment agent according to claim 1, wherein a molar ratio (A/D) of the trivalent chromium compound (A) to the nitrate ions (D) is 0.3 or more and 0.4 or less. A method for producing a metal foil laminate, comprising the steps of:
a surface treatment step of treating at least one surface of the metal foil;
A lamination step of laminating a film on the surface of the metal foil treated by the surface treatment step,
the aqueous metal surface treatment agent used in the surface treatment step comprises a trivalent chromium compound (A), a water-soluble or water-dispersible acrylic resin (B), and a phosphoric acid compound (C);
The water-soluble or water-dispersible acrylic resin (B) has a weight average molecular weight of 50,000 or more and 1,000,000 or less and an acid value of the solid content of more than 740 mgKOH/g. a mass ratio of trivalent chromium contained in the trivalent chromium compound (A) to a total solid content of the aqueous metal surface treatment agent is 5% or more and 15% or less, calculated as trivalent chromium;
5. The method for producing a metal foil laminate according to claim 4, wherein a ratio of a solid content mass of the phosphate compound (C) to a total solid content mass of the aqueous metal surface treatment agent is 5% or more and 10% or less in terms of phosphate ions. The aqueous metal surface treatment agent further contains nitrate ions (D),
6. The method for producing a metal foil laminate according to claim 4, wherein a molar ratio (A/D) of the trivalent chromium compound (A) to the nitrate ions (D) is 0.3 or more and 0.4 or less.