Separation solution for aluminum foil laminate and method for separating and collecting aluminum foil laminate using same

Abstract

Provided are: a separation solution for an aluminum foil laminate, the separation solution having a sufficient ability to separate the aluminum foil laminate into a resin and an aluminum foil while being capable of reducing elution of the aluminum foil into the separation solution; and a method for separating and collecting an aluminum foil laminate using the separation solution. The present invention provides a separation solution for an aluminum foil laminate, the separation solution comprising: a first acid that comprises at least one of nitric acid and formic acid; one or more second acids that are selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts; and water. The separation solution is characterized in that the content ratio obtained by dividing the content (mass%) of the first acid in the separation solution by the content (mass%) of the second acids in the separation solution is 0.05-30.

Description

Separation Solution for Aluminum Foil Laminate and Method for Separating and Recovering Aluminum Foil Laminate Using the Same

[0001] The present invention relates to a separation solution for an aluminum foil laminate for separating an aluminum foil laminate in which a resin is laminated on at least one side of an aluminum foil into an aluminum foil and a resin, and a method for separating and recovering the aluminum foil laminate using the same.

[0002] Conventionally, in applications where functions such as protecting contents from external environmental factors such as oxygen, moisture, and ultraviolet rays, that is, barrier properties, are required, such as packaging materials for foods and pharmaceuticals, laminates in which a resin is laminated on at least one surface of an aluminum foil (hereinafter referred to as "aluminum foil laminates") are widely used. In addition, aluminum foil laminates are widely used in industrial applications such as electronic components because of their excellent electrical properties and workability.

[0003] In addition, as the resin laminated in the aluminum foil laminate, since it is necessary to satisfy various requirements such as heat sealability, strength, puncture resistance, and designability, many types of resins such as epoxy resins, olefin resins, nitrocellulose resins, vinyl chloride-vinyl acetate copolymer resins, and polyethylene resins are used.

[0004] However, with the recent increase in SDGs and awareness of the global environment, high recyclability has been required for laminates containing resins. However, various combinations of materials and materials containing the resin have been an inhibiting factor that hinders the recycling of the laminate. Particularly in the case of aluminum foil laminates containing aluminum foil, there has been a situation where recycling has not progressed because the aluminum foil and the resin cannot be easily separated.

[0005] Therefore, in order to take advantage of the properties of aluminum foil while also achieving high recyclability, methods are being considered to improve the separation of aluminum foil from the laminated resin layer. For example, Japanese Patent Publication No. 47-034572 (Patent Document 1) discloses a method for separating the resin layer from the aluminum foil by dissolving at least a portion of the aluminum foil. Also, Japanese Patent Publication No. 2021-526091 (Patent Document 2) discloses a method for separating the metal layer from the resin by using a separation fluid (separation solution) containing a mixture of water, a carboxylic acid, a carboxylic acid salt, and a passivating agent.

[0006] JP-A-47-034572 Publication Special Publication No. 2021-526091

[0007] However, the separation technology described in Patent Document 1 had the problem that a large amount of aluminum foil was leached out by nitric acid, making it impossible to recover enough aluminum useful for recycling. Furthermore, although the separation technology described in Patent Document 2 suppressed the leaching of aluminum to some extent, the peeling speed was insufficient, and the peeling efficiency was too low for practical use on an industrial scale, which could hinder the recovery, melting, and casting of the peeled aluminum foil for reuse.

[0008] Therefore, the present invention aims to provide a separation solution for aluminum foil laminates that has sufficient ability to separate the aluminum foil laminate into resin and aluminum foil while reducing the elution of aluminum into the separation solution, and a method for separating and recovering aluminum foil laminates using the same.

[0009] To solve the above problems, the present inventors diligently researched methods for separating aluminum foil laminates into resin and aluminum foil. As a result, they discovered that by controlling the content ratio (mass%) of the first acid to the second acid (mass%) in a separation solution containing a first acid consisting of nitric acid and / or formic acid, a second acid consisting of a polycarboxylic acid, and water, the aluminum foil laminate can be easily separated into aluminum foil and resin while reducing the elution of aluminum foil into the separation solution. This led to the completion of the present invention.

[0010] In other words, the present invention provides a separation solution for aluminum foil laminates containing a first acid consisting of at least one of nitric acid and formic acid, one or more second acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts, and water, characterized in that the content ratio obtained by dividing the content (mass%) of the first acid in the separation solution by the content (mass%) of the second acid in the separation solution is 0.05 or more and 30 or less.

[0011] Furthermore, according to the present invention, a method for separating an aluminum foil laminate into resin and aluminum foil using the above-mentioned separation solution for aluminum foil laminates is provided, characterized by comprising the steps of: preparing an aluminum foil laminate containing aluminum foil and resin; crushing and / or cutting the laminate containing aluminum foil and / or resin with a crusher and / or cutter to obtain crushed and / or pulverized material; immersing the crushed and / or cut material in the above-mentioned separation solution for aluminum foil laminates; and separating the aluminum foil and resin by letting it stand or stirring at a temperature of 15°C to 99°C for a period of 1 second to 24 hours.

[0012] The separation solution for aluminum foil laminates of the present invention reduces the elution of exposed aluminum foil while peeling the resin from the laminate through the synergistic effect of a first acid consisting of at least one of nitric acid and formic acid and a second acid selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts, which reduces the amount of aluminum eluted. In other words, in the present invention, the second acid suppresses the reaction between nitric acid or formic acid and aluminum foil by its adhesion effect to the surface of the aluminum foil, thereby reducing the elution of aluminum into the separation solution.

[0013] In the present invention, in order to further enhance the separation effect of the aluminum foil laminate and the effect of reducing the amount of aluminum foil eluted into the separation solution, it is preferable to have a first acid content of 2% by mass or more and 35% by mass or less, and a second acid content of 0.1% by mass or more and 35% by mass or less.

[0014] Furthermore, in order to further enhance the effectiveness of the separation solution of the present invention, as described above, it is preferable to use one or more second acids selected from the group consisting of citric acid, tartaric acid, lactic acid, malic acid, maleic acid, phthalic anhydride, sodium citrate, diammonium hydrogen citrate, ethylenediaminetetraacetic acid (ethylenedinitrilo)tetraacetic acid, triglycolamic acid, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, diethylenetriaminepentaacetic acid, glycine, and aspartic acid.

[0015] According to the separation solution for aluminum foil laminates and the method for separating and recovering aluminum foil laminates using the present invention, the separation solution of the present invention can reduce the elution of exposed aluminum foil while peeling the resin from the laminate through the synergistic effect of the peeling effect of a first acid consisting of at least one of nitric acid and formic acid and the effect of reducing the amount of aluminum eluted by one or more second acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts and aminocarboxylic acid salts.

[0016] The following describes in detail a separation solution for aluminum foil laminates according to one embodiment of the present invention and a method for separating and recovering aluminum foil laminates using the same. It should be noted that the present invention is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the invention.

[0017] <Separation Solution for Aluminum Foil Laminates> The separation solution for aluminum foil laminates of the present invention contains a first acid consisting of at least one of nitric acid and formic acid, one or more second acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts, and water, characterized in that the content ratio obtained by dividing the content (mass%) of the first acid in the separation solution by the content (mass%) of the second acid in the separation solution is 0.05 or more and 30 or less.

[0018] Furthermore, the method for separating an aluminum foil laminate into resin and aluminum foil according to the present invention is characterized by comprising the steps of: crushing, pulverizing, and / or cutting an aluminum foil laminate of any size so that the maximum length in a plane is 1 mm or more and 50 mm or less to obtain crushed material, pulverized material, and / or cut material; and immersing the crushed material, pulverized material, and / or cut material in the above-mentioned separation solution for aluminum foil laminates, and separating it into aluminum foil and resin by standing or stirring at a temperature of 15°C or more and 99°C or less for a time of 1 second or more and 24 hours or less.

[0019] The surface of aluminum foil is typically rich in functional groups such as carboxyl groups, carbonyl groups, and hydroxyl groups. These polar groups bond with the polar groups on the resin surface, causing adhesion and forming an aluminum foil laminate in which the resin and aluminum foil are combined. In this invention, a first acid, consisting of nitric acid and / or formic acid, functions to break the bond between the functional groups of the resin and the aluminum foil, thereby separating the aluminum foil from the resin. The components of the separation solution for aluminum foil laminates of this invention will be described in detail below.

[0020] <First Acid> The first acid used in this invention is an acid consisting of at least one of nitric acid and formic acid. Nitric acid is a strong acid with an acid dissociation degree constant pKa of -1.4 at 25°C. Nitric acid penetrates from the resin side or edge of the aluminum foil laminate and eventually reaches the interface between the resin and the aluminum foil, where it breaks the bonds between the functional groups on the aluminum foil surface and the resin surface. Subsequently, the nitric acid reacts violently with the aluminum, dissolving it. Therefore, while nitric acid has the effect of peeling the resin and the aluminum foil, using nitric acid alone leads to the undesirable result of dissolving a large amount of aluminum foil. For this reason, in this invention, by using a second acid described later, the second acid is attached to the aluminum surface to suppress the dissolution of aluminum, and by adjusting the content ratio of nitric acid to the second acid within a specific range, both the peeling effect of nitric acid and the effect of reducing the amount of aluminum dissolved by the second acid are made possible.

[0021] Hydrochloric acid, like nitric acid and formic acid, is a strong acid, but because it contains chloride ions, using it as the primary acid will more strongly accelerate the dissolution of aluminum. Therefore, even if a second acid is added, hydrochloric acid will react violently with the aluminum and dissolve it further, making it unsuitable for stripping aluminum foil laminates.

[0022] Unlike strong acids such as hydrochloric acid and nitric acid, formic acid does not react violently with aluminum foil, thus not causing the aluminum to disappear during separation from the resin layer. Furthermore, although formic acid is a weak acid with an acid dissociation constant pKa of 3.75 (pKa 3-7), it exhibits the strongest acidity among monovalent aliphatic carboxylic acids and has the property of readily dissociating protons. Therefore, in the separation solution for aluminum foil laminates of the present invention, formate ions and other substances break the adhesion between the aluminum interface and the resin layer interface, further promoting the separation of the aluminum foil and the resin layer.

[0023] Thus, formic acid has the effect of separating aluminum foil from resin in aluminum foil laminates. On the other hand, formic acid alone also has the undesirable effect of leaching aluminum, although not to the same extent as nitric acid. Therefore, as with nitric acid, it is necessary to add a second acid to formic acid to reduce the leaching of aluminum.

[0024] In the separation solution for aluminum foil laminates of the present invention, the content of the first acid, which is a combination of nitric acid and formic acid, in the separation solution is preferably 2% by mass or more and 35% by mass or less. If the content of the first acid is less than 2% by mass, the above-mentioned peeling effect may not be sufficiently obtained. On the other hand, if the content of the first acid exceeds 35% by mass, the dissolution of aluminum will proceed further, and the effect of reducing the amount of aluminum dissolved by the second acid may not be sufficiently obtained.

[0025] Therefore, the content of the first acid in the separation solution is not particularly limited as long as the content ratio (hereinafter also referred to as the "first acid / second acid content ratio") obtained by dividing the content of the first acid (mass%) by the content of the second acid (mass%), as described later, is 0.05 or more and 30 or less. However, it is preferably 2% by mass or more and 35% by mass or less, more preferably 3% by mass or more and 10% by mass or less, and even more preferably 4% by mass or more and 10% by mass or less.

[0026] In the separation solution for aluminum foil laminates of the present invention, the content ratio of the first acid to the second acid must be 0.05 or more and 30 or less. If the content ratio of the first acid to the second acid is less than 0.05, the effect of reducing the amount of aluminum eluted by the second acid (the protective effect of aluminum) will be excessively advanced, and the peeling effect of the first acid will not be sufficiently obtained. On the other hand, if the content ratio of the first acid to the second acid exceeds 30, the peeling effect of nitric acid or formic acid will be excessively advanced, which will lead to the undesirable result of an excessive increase in the amount of aluminum eluted. Therefore, in the present invention, the content ratio of the first acid to the second acid is preferably 0.05 or more and 30 or less, more preferably 0.3 or more and 6.0 or less, and even more preferably 0.3 or more and 2.3 or less.

[0027] The first acid may consist of either nitric acid or formic acid as a single component, or it may be a mixture of nitric acid and formic acid. When formic acid, a weak acid, is mixed with nitric acid, a strong acid, the formic acid also functions as a weak base, which has the effect of suppressing the elution of aluminum. The ratio of nitric acid to formic acid is not particularly limited as long as the ratio of the content of the first acid to the second acid is within the range of 0.05 to 30 and can be freely set.

[0028] <Second Acid> The second acid used in this invention refers to a multi-functional acid or a multi-functional salt, specifically a polycarboxylic acid, hydroxy acid, polyaminocarboxylic acid, aminocarboxylic acid, or salts thereof. A typical example is citric acid. The effect of the second acid in reducing the elution of aluminum occurs because the hydroxyl group, carboxyl group, or amino group of the second acid generates hydrates with water (water molecules), which will be described later, and then adsorbs onto the aluminum foil surface. In addition, the carboxyl group, hydroxyl group, and amino group themselves also have the ability to adsorb onto the aluminum foil surface, with the adsorption strength increasing in the order of carboxyl group > hydroxyl group > amino group. This is because the carboxyl group can form a bidentate ligand with two oxygen atoms, the hydroxyl group has monodentate coordination with one oxygen atom or a hydrogen bond, and the amino group has weak Lewis basicity of nitrogen and forms a coordinate bond, but hydrogen bonding is the main contributor.

[0029] Citric acid is a hydroxy acid having three carboxyl groups and one hydroxyl group. These functional groups form hydrates, which adhere to the functional groups on the aluminum surface, thereby inhibiting the reaction of aluminum with nitric acid and formic acid. Therefore, tartaric acid, which has two carboxyl groups and two hydroxyl groups, and lactic acid, a hydroxy acid with one carboxyl group and one hydroxyl group, exhibit similar effects to citric acid. Maleic acid, a dicarboxylic acid, and polycarboxylic acid derivatives (e.g., fumaric anhydride), as well as polyfunctional acid salts that become polyfunctional acid ions when dissolved in water, also exhibit similar effects. Furthermore, polyaminocarboxylic acids such as diethylenetriaminepentaacetic acid (commonly known as DTPA), which has five carboxyl groups and three amino groups, and aminocarboxylic acids such as aspartic acid, which has two carboxyl groups and one amino group, also exhibit similar effects.

[0030] In the separation solution for aluminum foil laminates of the present invention, the content of the second acid in the separation solution is not particularly limited as long as the content ratio of the first acid to the second acid is 0.05 or more and 30 or less, but it is preferably 0.1% by mass or more and 35% by mass or less. If the content of the second acid is less than 0.1% by mass, the above-mentioned effect of reducing the amount of aluminum eluted may not be sufficiently obtained. Also, if the content of the second acid exceeds 35% by mass, the adhesion of the second acid to the aluminum foil will be excessive, and the peeling effect between the aluminum foil and the resin may not be sufficiently obtained.

[0031] In the present invention, the second acid consists of one or more components selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts. For example, hydroxy acids include lactic acid, citric acid, malic acid, tartaric acid, glycolic acid, mandelic acid, glyceric acid, salicylic acid, ascorbic acid, and gluconic acid. Among these, it is preferable to use citric acid, lactic acid, malic acid, tartaric acid, and gluconic acid, which readily exhibit a chelating effect as described later.

[0032] Furthermore, examples of polycarboxylic acids include dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, and fumaric acid, and examples of tricarboxylic acids such as aconitic acid and trimesic acid. Among these, those with structures in which carboxylic acids are in close proximity to each other, such as maleic acid, readily produce a chelating effect and are therefore preferred for use.

[0033] In this invention, as the second acid, salts of polycarboxylic acids or hydroxy acids such as sodium salts, potassium salts, calcium salts, and ammonium salts, which are alkaline earth metals, can be used. Among these, it is preferable to use a salt that is not a metal salt, such as diammonium hydrogen citrate. This is because aluminum separated and recovered from aluminum laminates is usually melted down and reused as aluminum ingots, but if the second acid is a metal salt containing sodium, calcium, etc., there is a risk that the metal may be mixed into the aluminum as an impurity.

[0034] Furthermore, if the second acid of the present invention is a dicarboxylic acid derivative, for example, maleic anhydride, phthalic anhydride, phthalate ester, maleate ester, dimethyl adipate, dibutyl sebacate, diethyl glutarate, dimethyl fumarate, dioctyl adipate, and glyoxylic acid can be used. Among these, substances that readily hydrolyze in heated water to produce a dicarboxylic acid are preferred, and for example, phthalic anhydride is suitably used.

[0035] If the second acid of the present invention is a polyaminocarboxylic acid, for example, ethylenediaminetetraacetic acid (ethylenedinitrilo)tetraacetic acid (commonly known as DTPA), triglycolamic acid (commonly known as NTA), N-(2-hydroxyethyl)ethylenediamine-N,N',N'--triacetic acid (commonly known as HEDTA), and diethylenetriaminepentaacetic acid (commonly known as DTPA) can be used. Among these, DTPA, which has five carboxyl groups and three amino groups and exhibits excellent adsorption to aluminum, is the most preferred.

[0036] Furthermore, if the second acid of the present invention is an aminocarboxylic acid, for example, glycine, alanine, serine, aspartic acid, lysine, hydroxyproline, and cysteine ​​can be used. Among these, aspartic acid, which has two carboxyl groups and one amino group and exhibits excellent adsorption to aluminum, is the most preferred.

[0037] In this invention, as the second acid, salts of polyaminocarboxylic acids or aminocarboxylic acids, such as sodium salts, potassium salts, calcium salts, or ammonium salts, which are alkaline earth metals, can be used. Among these, it is preferable to use a salt that is not a metal salt, such as monoammonium asparaginate. This is because aluminum separated and recovered from aluminum laminates is usually melted down and reused as aluminum ingots, but if the second acid is a metal salt containing sodium, calcium, etc., there is a risk that the metal may be mixed into the aluminum as an impurity.

[0038] The effect of the second acid in this invention on reducing the amount of aluminum eluted is thought to be due to physical adsorption, chemical adsorption, chelating effects, etc. The chelating effect occurs when bidentate or more ligands form a complex in which metal ions are sandwiched between them. Since the chelating effect involves carboxyl groups, hydroxyl groups, and amino groups in forming the complex structure, it is necessary to have multiple functional groups in order to exhibit the effect of this invention. Therefore, hydroxy acids such as citric acid and tartaric acid, which have both hydroxyl and carboxyl groups, exhibit a large effect on reducing the amount of aluminum eluted. In addition, polycarboxylic acids with multiple carboxyl groups exhibit a similar effect. Furthermore, polyaminocarboxylic acids with carboxyl and amino groups also exhibit a similar effect.

[0039] <Water> In the present invention, it is preferable that the separation solution for the aluminum foil laminate contains 40% by mass or more and 97.7% by mass or less of water. However, the total amount of the first acid, the second acid, and water must be 100% by mass or less of the separation solution.

[0040] When water is present in the separation solution, the hydroxyl group or carboxyl group of the second acid forms a hydrate with water molecules, and the attachment of the hydrate to the surface of the aluminum foil exhibits the effect of reducing the elution amount of aluminum. In the second acid, polyvalent carboxylate salts, hydroxy acid salts, and other polyfunctional group acid salts are also dissolved in water, dissociated into polyfunctional group acid ions, and attached to the surface of the aluminum foil, so the effect of reducing the elution amount of aluminum is exhibited. Therefore, when the polyfunctional group acid is a solid crystal, it needs to be dissolved in water. Accordingly, the separation solution for the aluminum foil laminate of the present invention is preferably a separation solution in which water is moderately present, and the amount of the water is more preferably 53.0% by mass or more and 97.7% by mass or less in the separation solution, and even more preferably 63% by mass or more and 91% by mass or less. When the amount of water is within the above range, when the second acid is a solid crystal, it is sufficiently dissolved in water to make the effect of reducing the elution amount of aluminum sufficient, and further, since the separation of the aluminum foil and the resin by the first acid can be effectively performed, it is preferable.

[0041] <Remainder> In the separation solution for the aluminum foil laminate of the present invention, when the total of the first acid, the second acid, and water is less than 100% by mass, the remainder may contain one or more organic solvents selected from the group consisting of ketones, ethers, alkylbenzenes, dioxolanes, cycloalkanes, and carboxylic acid esters. This is because ketones, ethers, alkylbenzenes, dioxolanes, cycloalkanes, and carboxylic acid esters also penetrate into the resin layer and have an effect of promoting the separation of the resin layer from the aluminum foil.

[0042] Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone, acetophenone, benzophenone, etc. It is often used as a true solvent for the resin coating agent, and it is preferable to use methyl ethyl ketone from the viewpoint of excellent peeling solubility of the resin.

[0043] Ethers include, for example, dimethyl ether, ethyl methyl ether, diethyl ether, diphenyl ether, ethylene oxide, tetrahydrofuran (THF), furan, 1,4-dioxane, anisole, benzofuran, dibenzofuran, crown ether, etc. Considering the miscibility with water, it is preferable to use tetrahydrofuran (THF), furan or 1,4-dioxane.

[0044] Alkylbenzenes include, for example, xylene, toluene, ethylbenzene, cumene, p-cymene, etc. They are often used as true solvents for resin coating agents. From the perspective of excellent stripping solubility of the resin, it is preferable to use xylene or toluene.

[0045] Dioxolane specifically includes 1,3-dioxolane. It has high miscibility with water and can penetrate well into the resin layer, so it can be preferably used.

[0046] Cycloalkanes include cycloalkanes having 5 to 12 carbon atoms such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, cyclododecane, etc. They are often used as true solvents for resin coating agents. From the perspective of excellent stripping solubility of the resin, it is preferable to use methylcyclohexane.

[0047] As the carboxylic acid ester, a carboxylic acid ester composed of a formate ester having 9 or less carbon atoms and / or an acetate ester having 9 or less carbon atoms can be used. Specifically, for example, methyl formate, ethyl formate, propyl formate, butyl formate, pentyl formate, hexyl formate, isoamyl formate, heptyl formate, octyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, heptyl acetate, etc. These carboxylic acid esters are carboxylic acid derivatives that generate carboxylic acids in warm water and are also preferably used because they exhibit an effect of reducing the elution amount of aluminum by adhering to the surface of the aluminum foil described later. In particular, butyl acetate, ethyl acetate, and isoamyl formate can be more preferably used because of their excellent solubility in resins.

[0048] Thus, when the separation solution for aluminum foil laminates of the present invention contains additives such as ketones, ethers, alkylbenzenes, dioxolanes, cycloalkanes, and carboxylic acid esters, it is not particularly limited as long as the content ratio of the first acid to the second is 0.05 or more and 30 or less, but it is preferable that the total amount of additives be 0.1% by mass or more and 50% by mass or less in the separation solution, and it is more preferable that it be 0.1% by mass or more and 10% by mass or less in order to uniformly mix with the separation solution.

[0049] <Other Additives> In the separation solution for aluminum foil laminates of the present invention, in the case of monodentate ligand carboxylic acids such as formic acid and acetic acid, the chelating effect does not manifest due to the physical structure, but a slight reduction in the amount of aluminum eluted can be obtained due to the physical adsorption effect on aluminum. Therefore, as long as the solution contains the first acid, the second acid, and water, and the ratio of the content of the first acid to the second acid is 0.05 or more and 30 or less, further reduction of aluminum elution can be achieved by mixing acetic acid with the first acid.

[0050] The effect of reducing the amount of aluminum leaching can also be achieved by using formate or acetate salts, and examples of these salts include alkaline earth metals such as sodium salts, potassium salts, calcium salts, and ammonium salts. Among these, it is preferable to use salts that are not metal salts, such as ammonium formate or ammonium acetate. This is because the aluminum separated and recovered from the aluminum laminate is usually melted down and reused as aluminum ingots, but if the second acid is a metal salt containing sodium or calcium, there is a risk that the metal will be mixed into the aluminum as an impurity. Therefore, if the other additives are salts that are not metal salts as described above, the amount added can be within a range that does not impair the peeling action, and for example, if it is added for the purpose of assisting the effect of reducing the amount of aluminum leaching, it is preferable that it be 10% by mass or less in the separation solution.

[0051] The separation solution for aluminum foil laminates of the present invention may contain other additives, such as buffer solutions, as long as they do not impair the peeling action. For example, buffer solutions can be expected to stabilize the pH of the separation solution, but adding an excessive amount of buffer solution may cause an excessive peeling effect. Therefore, in the separation solution for aluminum foil laminates of the present invention, it is preferable that the amount of buffer solution added is 3% by mass or less of the separation solution.

[0052] The separation solutions of the examples and comparative examples according to the present invention were prepared and evaluated, and their results will be described in detail below.

[0053] 1. Preparation of Separation Solution [Example 1] 14.49 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 30 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 55.51 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 1.

[0054] [Example 2] 14.49 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 30 g of diammonium hydrogen citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 55.51 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 2.

[0055] [Example 3] 13.16 g of formic acid (manufactured by Asahi Chemical Industries, Ltd., reagent grade, 76% by mass), 30 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 56.84 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 3.

[0056] [Example 4] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 4.

[0057] [Example 5] 4.35 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 0.1 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 95.55 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 5.

[0058] [Example 6] 3.95 g of formic acid (manufactured by Asahi Chemical Industries, Ltd., reagent grade, 76% by mass), 0.1 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 95.95 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 6.

[0059] [Example 7] 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 35 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 62.10 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 7.

[0060] [Example 8] 50.72 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 15 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 10 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 34.28 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 8.

[0061] [Example 9] 46.05 g of formic acid (manufactured by Asahi Chemical Industries, Ltd., reagent grade, 76% by mass), 15 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 38.95 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 9.

[0062] [Example 10] 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 0.3 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 96.80 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 10.

[0063] [Example 11] In a 100 mL glass bottle, 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 5.26 g of formic acid (manufactured by Asahi Chemical Industries, Ltd., reagent grade, 76% by mass), 1 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 90.84 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 11.

[0064] [Example 12] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3 g of L(+)-tartaric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 12.

[0065] [Example 13] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3.4 g of lactic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade, 88.5%), and 87.91 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 13.

[0066] [Example 14] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3.0 g of malic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 14.

[0067] [Example 15] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3.0 g of maleic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 15.

[0068] [Example 16] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3.0 g of phthalic anhydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 16.

[0069] [Example 17] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3.0 g of trisodium citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., food additive), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 17.

[0070] [Example 18] In a 100 mL glass bottle, 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 1.5 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 1.5 g of trisodium citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., food additive), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 18.

[0071] [Example 19] 5.80 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 1 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 4 g of acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 89.20 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 19.

[0072] [Example 20] In a 100 mL glass bottle, 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 35 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 10 g of butyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 52.10 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 20.

[0073] [Example 21] In a 100 mL glass bottle, 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 35 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 10 g of methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 52.10 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 21.

[0074] [Example 22] In a 100 mL glass bottle, 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass), 3 g of ethylenediaminetetraacetic acid (ethylenedinitrilotetraacetic acid, commonly known as EDTA, manufactured by Tokyo Chemical Industry Co., Ltd., >98.0% by mass), and 88.30 g of purified water (manufactured by AS ONE, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 22.

[0075] [Example 23] In a 100 mL glass bottle, 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass), 3 g of triglyceramicin (commonly known as NTA, manufactured by Tokyo Chemical Industry Co., Ltd., >98.0% by mass), and 88.30 g of purified water (manufactured by AS ONE, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 23.

[0076] [Example 24] In a 100 mL glass bottle, 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass), 3 g of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (commonly known as HEDTA, manufactured by Tokyo Chemical Industry Co., Ltd., >98.0% by mass), and 88.30 g of purified water (manufactured by AS ONE, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 24.

[0077] [Example 25] In a 100 mL glass bottle, 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass), 3 g of diethylenetriaminepentaacetic acid (commonly known as DTPA, manufactured by Tokyo Chemical Industry Co., Ltd., >98.0% by mass), and 88.30 g of purified water (manufactured by AS ONE, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Example 25.

[0078] [Example 26] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass), 3 g of glycine (manufactured by Fujifilm Wako Pure Chemical Industries, molecular biology grade reagent, >99.0% by mass), and 88.30 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 26.

[0079] [Example 27] 8.70 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 3 g of L-aspartic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, >99.0% by mass), and 88.30 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 27.

[0080] [Comparative Example 1] In a 100 mL glass bottle, 42.5 g of acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 99.7% by mass), 3.5 g of sodium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 1.1 g of disodium hydrogen phosphate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 52.9 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added and stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 1 (the separation solution of Example 1 (composition 1) of Patent Document 2, which is prior art).

[0081] [Comparative Example 2] 14.49 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass) and 85.51 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 2.

[0082] [Comparative Example 3] 13.16 g of formic acid (manufactured by Asahi Chemical Industry Co., Ltd., reagent grade, 76% by mass) and 86.84 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 3.

[0083] [Comparative Example 4] 27.78 g of hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 36% by mass) and 72.22 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 4.

[0084] [Comparative Example 5] 33.33 g of hydrogen peroxide (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 30% by mass) and 67.67 g of purified water (manufactured by AS ONE, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 5.

[0085] [Comparative Example 6] 35 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade, 99.5% by mass) and 65.0 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 6.

[0086] [Comparative Example 7] 1.45 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 35 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 63.55 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 7.

[0087] [Comparative Example 8] 5.80 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 0.1 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 94.10 g of purified water (manufactured by AS ONE Corporation, ASSWS-20) were added to a 100 mL glass bottle, and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Comparative Example 8.

[0088] 2. Preparation of Test Specimens [Test Specimen 1] (Epoxy / Aluminum Foil) For the aluminum foil, 20 μm 1N30 material (manufactured by Toyo Aluminum Co., Ltd., hard foil) was used. Subsequently, a polyolefin-based white coating agent (manufactured by T&K TOKA Co., Ltd.: PPZ-C 96 white, solid content 34% by mass) was applied to the glossy side of the aluminum foil using a bar coater #8 until the weight after drying was 1.5 g / m². ２ The material was applied in this manner and dried at 150°C for 1 minute. Next, a nitrocellulose coating agent (DIC Graphics: TF842 805 Sumi, solid content 29% by mass) was applied over the white layer using a bar coater #3 until the weight after drying was 0.5 g / m². ２The material was applied in this manner and dried at 150°C for 1 minute. Furthermore, an epoxy-based overprint coating agent (T&K TOKA Co., Ltd.: PT-OP varnish, solid content 33% by mass) was applied over the black layer using a bar coater #5 until the weight after drying was 1.5 g / m². ２ The material was applied in this manner and dried at 150°C for 1 minute to form an overprint layer. The matte side of the aluminum foil was also coated with a white layer, a black layer, and an overprint layer in the same way as the glossy side, creating test specimen 1 with a composition of epoxy / nitrocellulose / polyolefin / aluminum foil / polyolefin / nitrocellulose / epoxy, in which resin layers were formed on both sides.

[0089] [Test Specimen 2] (Vinyl chloride vinyl acetate copolymer / aluminum foil) For the aluminum foil, 20 μm 1N30 material (manufactured by Toyo Aluminum Co., Ltd., hard foil) was used. Subsequently, a vinyl chloride vinyl acetate copolymer-based green coating agent (manufactured by T&K TOKA Co., Ltd.: MSP-N 53 Kusa, solid content 27% by mass) was applied to the glossy side of the aluminum foil with a bar coater #8 until the weight after drying was 1.5 g / m². ２ The coating was applied in this manner and dried at 150°C for 1 minute to form a green layer. Next, a green layer was formed on the matte aluminum surface in the same manner. After that, a vinyl chloride vinyl acetate copolymer coating agent (Leader Co., Ltd.: LD#S837G Clear, solid content 21% by mass) was applied over the green layer on the glossy aluminum surface using a bar coater #12 until the weight after drying was 3.0 g / m². ２ The material was applied in this manner and dried at 150°C for 1 minute to form a heat-seal layer. Next, a heat-seal layer was similarly formed on top of the green layer on the aluminum frosted side to create test specimen 2 with resin layers on both sides. The composition of test specimen 2 was vinyl chloride vinyl acetate copolymer layer / vinyl chloride vinyl acetate copolymer layer / aluminum foil / vinyl chloride vinyl acetate copolymer layer / vinyl chloride vinyl acetate copolymer layer.

[0090] [Test Specimen 3] (PE / Aluminum Foil) For the aluminum foil, 35 μm 1N30 material (manufactured by Toyo Aluminum Co., Ltd., soft foil) was used. Subsequently, a polyethylene melt extruder was used to apply a urethane-based anchor coating agent (manufactured by Mitsui Chemicals, Olivine EL-557A / Olivine EL-557B = weight ratio 1 / 2) to the glossy side of the aluminum foil using a boze roll at a rate of 0.05 g / m ２ After applying the coating and drying it at 70°C for 3 seconds, a polyethylene coating (Sumitomo Chemical Co., Ltd., Sumikasen L705) was applied to the anchor coat layer to a thickness of 20 μm to form a resin layer, and the rest was cured at 40°C for 24 hours to prepare test specimen 3. In other words, the composition of test specimen 3 was polyethylene layer / urethane layer / aluminum foil.

[0091] 3. Evaluation of Separation Solutions <Evaluation of Peelability (Separation Effect)> 100 g of each separation solution prepared in Examples 1-27 and Comparative Examples 1-8 was placed in a 100 mL glass bottle (mouth diameter × body diameter × height: φ31.9 × φ48.5 × 87 mm). Next, one rotor (AS ONE Corporation, tapered shape, length 25 mm, diameter 8 mm, material PTFE) was placed inside, and the opening of the glass bottle was covered to prevent the separation solution from evaporating. Furthermore, the glass bottles containing the separation solutions were placed in a 6-way heated stirring dry bath (AS ONE Corporation: HDBS-6) and heated while stirring at 200 rpm until the temperature reached 70°C. After confirming that the separation solution had reached 70°C with a thermometer, test specimens 1-3 were cut into 20 mm × 20 mm squares, the lids were removed, each test specimen was submerged in the respective separation solution, and the lids were replaced.

[0092] For test specimens 1 and 2, the time it took for the resin on both sides to peel off the aluminum foil was measured. Specimens that peeled off within 10 minutes were classified as "A", those that peeled off within 30 minutes as "B", those that peeled off within 60 minutes as "C", and those that did not peel off even after 60 minutes as "F". The peelability (separation effect) of the separation solution was evaluated.

[0093] For test specimen 3, the time it took for the resin to peel off the aluminum foil was measured, and the peelability (separation effect) of the separation solution was evaluated as follows: specimens that peeled off within 60 minutes were classified as "A", those that peeled off within 120 minutes as "B", those that peeled off within 240 minutes as "C", and those that did not peel off even after 240 minutes as "F".

[0094] <Evaluation of Elution Properties (Elution Reduction Effect)> 100 mL of each separation solution prepared in Examples 1-27 and Comparative Examples 1-8 was measured into a 100 mL glass bottle (mouth diameter 31.9 mm, body diameter 48.5 mm, height 87 mm). The glass bottle was placed in a heated and stirred dry bath (AS ONE Corporation: HDBS-6) and heated until the temperature of the separation solution reached 70°C. Next, a 20 μm thick aluminum foil (Toyo Aluminum Co., Ltd.: 1N30 material, hard foil) cut into a 100 mm x 100 mm square was gently folded into thirds to minimize creases, and then folded in half again to a size that would allow the entire foil to be immersed in the separation solution. The foil was immersed in each separation solution at 70°C for 60 minutes, and the weight before and after immersion was measured to calculate the weight retention rate (%) of the aluminum foil (see formula below). (Formula) [Weight retention rate of aluminum foil (%)] = [Weight of aluminum foil after immersion] / [Weight of aluminum foil before immersion] × 100

[0095] Furthermore, to eliminate the influence of trace components adhering to the aluminum foil surface on the weight retention rate of the aluminum foil before immersion in the separation solution, the aluminum foil was first immersed in methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: reagent grade) for 1 minute, the surface was gently wiped with a Kimwipe to degrease and clean it, and then measured after being air-dried at room temperature for 15 minutes. The weight of the aluminum foil after immersion in the separation solution was measured after immersion in the separation solution, washing the aluminum foil with water, immersing it in methyl ethyl ketone for 1 minute, removing it, wiping the surface with a Kimwipe, and then air-drying at room temperature for 15 minutes.

[0096] The elution properties (elution reduction effect) of aluminum foil were evaluated as follows: those with a weight retention rate of 97.3% or higher were classified as "A", those with a weight retention rate of 95% or more but less than 97% were classified as "B", and those with a weight retention rate of less than 95% were classified as "F".

[0097] Table 1 shows the evaluation results for peelability (separation effect) and elution (elution reduction effect) using the separation solutions of Examples 1 to 27 and Comparative Examples 1 to 8.

[0098] <Discussion> As shown in Table 1, the peelability (separation effect) evaluation of the separation solutions of Examples 1 to 27 was "A", "B", or "C", and the elution (elution reduction effect) evaluation was "A" or "B", indicating that all of the separation solutions had excellent separation and elution reduction effects. On the other hand, the separation solutions of Comparative Examples 1 to 8 were "F" in the evaluation of peelability (separation effect) and / or elution (elution reduction effect), indicating that good results could not be obtained in at least one of the evaluations of separation effect and elution reduction effect.

[0099] From the above results, it was found that in order for the separation solutions of Examples 1 to 27 to exhibit excellent elution (elution reduction effect), the separation solution for aluminum foil laminates contains a first acid consisting of at least one of nitric acid and formic acid, one or more second acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts, and water, and it is effective when the content ratio obtained by dividing the content (mass%) of the first acid in the separation solution by the content (mass%) of the second acid in the separation solution is 0.05 or more and 30 or less.

Claims

1. A separation solution for aluminum foil laminates comprising: a first acid consisting of at least one of nitric acid and formic acid; one or more second acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polyaminocarboxylic acids, aminocarboxylic acids, polycarboxylic acid salts, hydroxy acid salts, polyaminocarboxylic acid salts, and aminocarboxylic acid salts; and water, characterized in that the content ratio obtained by dividing the content (mass%) of the first acid in the separation solution by the content (mass%) of the second acid in the separation solution is 0.05 or more and 30 or less.

2. The separation solution for aluminum foil laminates according to claim 1, characterized in that the content of the first acid in the separation solution is 2% by mass or more and 35% by mass or less, and the content of the second acid in the separation solution is 0.1% by mass or more and 35% by mass or less.

3. The separation solution for aluminum foil laminates according to claim 1, characterized in that the second acid is one or more selected from citric acid, tartaric acid, lactic acid, malic acid, maleic acid, phthalic anhydride, sodium citrate, diammonium hydrogen citrate, ethylenediaminetetraacetic acid (ethylenedinitrilo)tetraacetic acid, triglycolamic acid, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, diethylenetriaminepentaacetic acid, glycine, and aspartic acid.

4. A method for separating and recovering an aluminum foil laminate, comprising the steps of: preparing an aluminum foil laminate containing aluminum foil and resin; crushing and / or cutting the laminate containing aluminum foil and / or resin with a crusher and / or cutter to obtain crushed material and / or pulverized material; immersing the crushed material and / or the cut material in a separation solution according to any one of claims 1 to 3; and separating the aluminum foil and resin by standing or stirring at a temperature of 15°C to 99°C for a period of 1 second to 24 hours.

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