Separation solution for aluminum foil laminate, and method for separation and recovery of aluminum foil laminate using same

Abstract

Provided are: a separation solution for an aluminum foil laminate, which can reduce elution of an aluminum foil into the separation solution and reduce the amount of impurities when a recovered aluminum foil is melted and cast, and which has sufficient ability to separate an aluminum foil laminate into a resin and an aluminum foil; and a method for separation and recovery of an aluminum foil laminate using same. The present invention is capable of providing a separation solution for an aluminum foil laminate, which contains an ammonium salt comprising at least one of ammonium formate and ammonium acetate, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid and acetic acid, and water, the separation solution being characterized in that a content ratio obtained by dividing the content (mass%) of the ammonium salt in the separation solution by the content of the acid (mass%) in the separation solution is 0.1-40.0.

Description

Separation solution for aluminum foil laminates and method for separating and recovering aluminum foil laminates using the same

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

[0002] Traditionally, laminates in which resin is laminated on at least one side of aluminum foil (hereinafter referred to as "aluminum foil laminates") have been widely used in applications where a function to protect the contents from external environmental factors such as oxygen, moisture, and ultraviolet rays, i.e., barrier properties, is required, such as in packaging materials for food and pharmaceuticals. Furthermore, due to their excellent electrical properties and processability, aluminum foil laminates are also widely used in industrial applications such as electronic components.

[0003] Furthermore, since the resin used in the aluminum foil laminate needs to meet various requirements such as heat sealing properties, strength, puncture resistance, and design aesthetics, many types of resins are used, including epoxy resins, olefin resins, nitrocellulose resins, vinyl chloride-vinyl acetate copolymer resins, and polyethylene resins.

[0004] However, with the recent rise in awareness of SDGs and the global environment, there is a growing demand for high recyclability in laminates containing resin. The diverse materials and combinations of materials, including the aforementioned resin, have been hindering the recycling of these laminates. In particular, in the case of aluminum foil laminates containing aluminum foil, recycling has been slow because the aluminum foil and 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. In addition, since the passivating agent added contains sodium (Na), an alkali metal, there was a problem that sodium could be mixed in when the peeled aluminum foil was recovered, melted and cast into ingots, potentially reducing the purity and quality of the aluminum.

[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 further reducing impurities when the separated aluminum is reused, as well as 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 ammonium salt to the acid to a specific range in a separation solution containing at least one of ammonium formate and ammonium acetate, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, and water, it is possible to easily separate the aluminum foil laminate into aluminum foil and resin while reducing the elution of aluminum foil into the separation solution. Furthermore, they found that impurities can be reduced when the recovered aluminum foil is melted and cast, thus completing the present invention.

[0010] In other words, the present invention provides a separation solution for aluminum foil laminates containing an ammonium salt consisting of at least one of ammonium formate and ammonium acetate, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, and water, characterized in that the content ratio obtained by dividing the content of the ammonium salt (mass%) in the separation solution by the content of the acid (mass%) in the separation solution is 0.1 or more and 40.0 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 can peel the resin from the laminate while reducing the elution of exposed aluminum foil through the synergistic effect of the peeling effect of one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, and the effect of reducing the amount of aluminum eluted by an ammonium salt consisting of at least one of ammonium formate and ammonium acetate.

[0013] Furthermore, the aforementioned ammonium salt is released in aqueous solution as formate ions and acetate ions, which also has the effect of promoting the peeling effect. In addition, because it is an ammonium salt rather than a metal salt as has been used conventionally, CO2 is released when the recovered aluminum is dissolved. ２ H ２ O, NO Ｘ It does not gasify and become mixed into the aluminum, thus not degrading the purity or quality of the aluminum ingot.

[0014] 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 set the ammonium salt content in the separation solution to 1.2% by mass or more and 75% by mass or less, and the acid content to 2% by mass or more and 30% by mass or less.

[0015] Furthermore, in order to further enhance the elution reduction effect of the separation solution of the present invention, the separation solution may contain 10% by mass or less of one or more acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polycarboxylic acid salts, and hydroxy acid salts.

[0016] Furthermore, in order to further enhance the peeling effect of the separation solution of the present invention, the separation solution may contain 50% by mass or less of one or more organic solvents selected from the group consisting of ketones, ethers, alkylbenzenes, dioxolanes, cycloalkanes, and carboxylic acid esters.

[0017] 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 leaching of exposed aluminum foil while peeling the resin from the laminate through the synergistic effect of the peeling effect of one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, and the effect of reducing the amount of aluminum leached by an ammonium salt consisting of at least one of ammonium formate and ammonium acetate. Furthermore, it can reduce the amount of impurities when the recovered aluminum foil is melted and cast.

[0018] 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.

[0019] <Separation Solution for Aluminum Foil Laminates> The separation solution for aluminum foil laminates of the present invention is characterized in that it contains an ammonium salt consisting of at least one of ammonium formate and ammonium acetate, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, and water, wherein the content ratio obtained by dividing the content of the ammonium salt (mass%) in the separation solution by the content of the acid (mass%) in the separation solution is 0.1 or more and 40.0 or less.

[0020] 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.

[0021] 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, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid function 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.

[0022] <Acid> The acid used in this invention is an acid consisting of at least one of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic 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 from the aluminum foil, using nitric acid alone leads to the undesirable result of dissolving a large amount of aluminum foil. The same is true for sulfuric acid, which is also a strong acid. Therefore, in this invention, by using an ammonium salt, which will be described later, the ammonium salt is attached to the aluminum surface to suppress the dissolution of aluminum, and by adjusting the content ratio of the acid to the ammonium salt within a specific range, both the peeling effect of the acid and the effect of reducing the amount of aluminum dissolved by the ammonium salt can be achieved.

[0023] 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 elution of aluminum. Therefore, even if an ammonium salt is added, hydrochloric acid will react even more violently with aluminum and dissolve it, making it unsuitable for stripping aluminum foil laminates.

[0024] Phosphoric acid is an acid with a moderate acid dissociation constant pKa of 2.2, falling between a weak and a strong acid. Like strong acids such as nitric acid and sulfuric acid, it has a stripping effect, but it also dissolves aluminum. Therefore, when using phosphoric acid, it is necessary to add an ammonium salt, similar to nitric acid, to reduce the elution of aluminum.

[0025] 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.

[0026] 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, similar to nitric acid, it is necessary to add an ammonium salt to formic acid to reduce aluminum leaching.

[0027] Acetic acid is a weak acid with an acid dissociation constant pKa of 4.8 (pKa 3-7). Therefore, acetic acid has a lower ability to break the adhesion between the aluminum interface and the resin layer interface and separate the aluminum foil and the resin layer compared to formic acid and nitric acid. On the other hand, when ammonium formate or ammonium acetate is present in the aqueous acetic acid solution, the dissociated formate ions or acetate ions combine with the protons released by acetic acid, releasing formic acid or acetic acid. This release of formic acid or acetic acid is advantageous in breaking the adhesion between the aluminum interface and the resin layer interface. Therefore, even though there is little aluminum elution, the separation of the aluminum foil and the resin layer by the acid is promoted.

[0028] In the separation solution for aluminum foil laminates of the present invention, the acid content in the separation solution is preferably 2% by mass or more and 30% by mass or less. If the acid content is less than 2% by mass, the above-mentioned peeling effect may not be sufficiently obtained. On the other hand, if the acid content exceeds 30% by mass, the elution of aluminum will proceed further, and the effect of reducing the amount of aluminum eluted by the ammonium salt may not be sufficiently obtained.

[0029] Therefore, the acid content in the separation solution is not particularly limited as long as the content ratio (hereinafter also referred to as the "ammonium salt / acid content ratio") obtained by dividing the ammonium salt content (mass%) by the acid content (mass%) is 0.1 or more and 40.0 or less, but it is preferably 2% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 15% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less.

[0030] In the separation solution for aluminum foil laminates of the present invention, the acid must have an ammonium salt / acid content ratio of 0.1 or more and 40.0 or less. If the ammonium salt / acid content ratio exceeds 40.0, the effect of reducing the amount of aluminum eluted by the ammonium salt (aluminum protective effect) will be excessively advanced, and the peeling effect of the acid will not be sufficiently obtained. On the other hand, if the ammonium salt / acid content ratio is less than 0.1, the peeling effect of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid will be excessively advanced, leading to the undesirable result of an excessive increase in the amount of aluminum eluted. Therefore, in the present invention, the ammonium salt / acid content ratio is preferably 0.1 or more and 40.0 or less, more preferably 0.2 or more and 4.5 or less, and even more preferably 0.3 or more and 1.0 or less.

[0031] The acid in this invention may consist of one component (single component) from among nitric acid, sulfuric acid, phosphoric acid, formic acid, or acetic acid, or it may be a mixture of two or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic 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 mixing ratio of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid is not particularly limited as long as the ammonium salt / acid content ratio is within the range of 0.1 to 40.0 and can be freely set.

[0032] <Ammonium Salt> The ammonium salt used in this invention is an ammonium salt consisting of at least one of ammonium formate and ammonium acetate. The effect of reducing aluminum elution by the ammonium salt is due to the fact that the ammonium ions and carboxylate ions of the ammonium salt form hydrates with water (water molecules), which will be described later, and then adsorbed onto the aluminum foil surface.

[0033] The ammonium salt of the present invention not only reduces the amount of aluminum leached but also promotes peeling. Specifically, protons released by acids such as acetic acid liberate formic acid and acetic acid from the ammonium salt, and these liberated acids promote the separation of the resin and the aluminum foil. As mentioned above, formic acid and acetic acid are weak acids but have the ability to peel aluminum foil from the resin, so the ammonium salt plays a role in replenishing the acid components consumed during peeling with the acid liberated from the ammonium salt.

[0034] In the separation solution for aluminum foil laminates of the present invention, the content of ammonium salt in the separation solution is not particularly limited as long as the ammonium salt / acid content ratio is 0.1 or more and 40.0 or less, but is preferably 1.2% by mass or more and 75% by mass or less, more preferably 5 to 75% by mass, and even more preferably 5 to 45% by mass. If the ammonium salt content is less than 1.2% by mass, the above-mentioned effect of reducing the amount of aluminum eluted may not be sufficiently obtained. Also, if the ammonium salt content exceeds 75% by mass, the adhesion of ammonium salt to the aluminum foil may become excessive, and the peeling effect between the aluminum foil and the resin may not be sufficiently obtained.

[0035] In the present invention, the ammonium salt is ammonium formate and / or ammonium acetate. Formic acid, which is released from ammonium formate in the presence of an acid, has a greater peeling effect on aluminum foil and resin than acetic acid, which is released from ammonium acetate in the presence of an acid. Therefore, it is more preferable to use ammonium formate as the ammonium salt in the present invention.

[0036] Other salts besides ammonium salts include alkali metal salts such as sodium and potassium salts, calcium salts, and salts of polycarboxylic acids and hydroxy acids such as ammonium salts. However, if these salts are used, there is a risk that the metals may become impurities in the aluminum when the aluminum separated and recovered from the aluminum laminate is dissolved and reused as aluminum ingots.

[0037] For example, sodium, an alkali metal, is incorporated into aluminum as an impurity when aluminum is heated and melted. Aluminum is usually cast to a high purity of 98-99.9% by mass and then rolled to become aluminum foil, so even the incorporation of trace amounts of metal salt impurities will reduce its purity and quality. Therefore, in this invention, the salt used to adjust (reduce) the amount of aluminum leached out does not contain metal components other than aluminum, such as alkali metals or alkaline earth metals, and does not decompose during casting to produce NO. Ｘ Ya CO ２An ammonium salt, which is a salt that becomes a gas such as this, is most preferable.

[0038] In the present invention, the effect of reducing the elution amount of aluminum by the ammonium salt is manifested because ammonium ions and carboxylic acid ions of the ammonium salt form hydrates with water (water molecules) described later and then adsorb on the surface of the aluminum foil. Since functional groups such as carboxyl groups, carbonyl groups, and hydroxyl groups exist on the surface of the aluminum foil, the reaction of acid with aluminum is suppressed by the attachment of the above-mentioned hydrates to these functional groups.

[0039] <Water> In the present invention, it is preferable that the separation solution for the aluminum foil laminate contains 23% by mass or more and 96.8% by mass or less of water. However, the total of the acid, ammonium salt, and water needs to be 100% by mass or less in the separation solution.

[0040] When water is present in the separation solution, the ammonium salt forms a hydrate with water molecules, and the elution amount reduction effect of aluminum is manifested by the attachment of the hydrate to the surface of the aluminum foil. Furthermore, the ammonium salt can be dissolved in water and can also dissociate the protons of the acid in water. Therefore, 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 water is more preferably 45% by mass or more and 90% by mass or less in the separation solution, and even more preferably 65% by mass or more and 90% by mass or less. When the amount of water is within the above range, the ammonium salt is sufficiently dissolved in water to make the elution amount reduction effect of aluminum sufficient, and furthermore, the peeling of the aluminum foil and the resin by the acid can be effectively performed, which is preferable.

[0041] <Remainder> In the separating solution for the aluminum foil laminate of the present invention, when the total of the acid, ammonium salt, 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 the effect of promoting the peeling of the resin layer from the aluminum foil.

[0042] Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone, acetophenone, benzophenone, etc. They are often used as true solvents for resin coating agents, and from the perspective of excellent peeling solubility of the resin, it is preferable to use methyl ethyl ketone.

[0043] Examples of ethers include 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] Examples of alkylbenzenes include xylene, toluene, ethylbenzene, cumene, p - cymene, etc. They are often used as true solvents for resin coating agents, and from the perspective of excellent peeling solubility of the resin, it is preferable to use xylene or toluene.

[0045] Specific examples of dioxolane include 1,3 - dioxolane. Since it has high miscibility with water and penetrates well into the resin layer, it can be preferably used.

[0046] Cycloalkanes include, for example, cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, and cyclooctanecyclododecane, which are cycloalkanes having 5 to 12 carbon atoms. They are often used as true solvents in resin coating agents, and methylcyclohexane is preferred from the viewpoint of excellent resin peeling and dissolution properties.

[0047] As carboxylic acid esters, carboxylic acid esters consisting of formic acid esters having 9 or fewer carbon atoms and / or acetate esters having 9 or fewer carbon atoms can be used. Specifically, examples include 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, and heptyl acetate. These carboxylic acid esters are carboxylic acid derivatives that generate carboxylic acids in heated water and are preferably used because they exhibit an effect of reducing the amount of aluminum eluted by adhering to the surface of aluminum foil, as described later. In particular, butyl acetate, ethyl acetate, and isoamyl formate can be used more preferably because they have excellent resin solubility.

[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 ammonium salt / acid content ratio is 0.1 to 40.0, but it is preferable that the total amount of additives be 0.1% to 50% by mass in the separation solution, and more preferably 0.1% to 10% by mass in order to uniformly mix them in the separation solution.

[0049] <Other Additives> The separation solution for aluminum foil laminates of the present invention contains an ammonium salt, an acid, and water, and as long as the ammonium salt / acid ratio is 0.1 or more and 40.0 or less, further reduction of aluminum elution can be achieved by mixing in a polycarboxylic acid.

[0050] Polycarboxylic acids adhere to the aluminum foil surface via carboxyl and hydroxyl groups, exhibiting a reduction in aluminum leaching similar to ammonium salts. In particular, tricarboxylic acids such as citric acid, which also possess hydroxyl groups, adhere favorably to aluminum foil after forming hydrates, thus effectively reducing aluminum leaching. While dicarboxylic acids, tricarboxylic acids, and their salts all exhibit similar effects, in the case of salts, it is necessary to use ammonium salts that do not become impurities during aluminum dissolution. Examples of metal salts include alkaline earth metals such as sodium, potassium, and calcium salts; however, using metal salts is unsuitable because they become impurities other than aluminum during aluminum ingot production.

[0051] A polycarboxylic acid is one or more components selected from the group consisting of hydroxy acids, polycarboxylic acid salts, and hydroxy acid salts. For example, lactic acid, citric acid, malic acid, tartaric acid, glycolic acid, mandelic acid, glyceric acid, salicylic acid, ascorbic acid, and gluconic acid can be used as hydroxy acids. Among these, citric acid, lactic acid, malic acid, tartaric acid, and gluconic acid are more preferable as they readily exhibit a chelating effect, as will be described later. As polycarboxylic acids, for example, dicarboxylic acids such as oxalyl acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, and fumaric acid can be used, and tricarboxylic acids such as aconitic acid and trimesic acid can be used. Among these, those with a structure in which carboxylic acids are close together, such as maleic acid, are more preferable as they readily produce a chelating effect.

[0052] In the present invention, the amount of polycarboxylic acid added can be within a range that does not impair the peeling effect. For example, when a polycarboxylic acid is added to assist in reducing the amount of aluminum eluted, it is preferable that the amount is 10% by mass or less in the separation solution.

[0053] 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.

[0054] 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.

[0055] 1. Preparation of Separation Solution [Example 1] 7.25 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 87.8 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.

[0056] [Example 2] In a 100 mL glass bottle, 17.39 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 1.2 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 3 g of diammonium hydrogen citrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 78.4 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 2.

[0057] [Example 3] 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 75 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 22.1 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 3.

[0058] [Example 4] 13.16 g of formic acid (manufactured by Asahi Chemical Industries, Ltd., reagent grade, 76% by mass), 45 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 41.8 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 4.

[0059] [Example 5] 2.90 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 1.2 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 95.9 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.

[0060] [Example 6] 7.81 g of sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 64% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 87.2 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 6.

[0061] [Example 7] 17.65 g of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 85% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 77.4 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.

[0062] [Example 8] 30.1 g of acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 99.7% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 64.9 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.

[0063] [Example 9] 6.58 g of formic acid (manufactured by Asahi Chemical Industries, Ltd., reagent grade, 76% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 88.4 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.

[0064] [Example 10] 7.25 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 5 g of ammonium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 87.8 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.

[0065] [Example 11] 7.25 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 2.5 g of ammonium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 2.5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 87.8 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 11.

[0066] [Example 12] In a 100 mL glass bottle, 2.9 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), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 86.8 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 12.

[0067] [Example 13] 7.25 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 3 g of ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 84.8 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.

[0068] [Example 14] 7.25 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), 3 g of methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 84.8 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.

[0069] [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).

[0070] [Comparative Example 2] 17.39 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 69% by mass) and 82.6 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.

[0071] [Comparative Example 3] 15.79 g of formic acid (manufactured by Asahi Chemical Industry Co., Ltd., reagent grade, 76% by mass) and 84.2 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.

[0072] [Comparative Example 4] 18.75 g of sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent, 64% by mass) and 81.3 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.

[0073] [Comparative Example 5] 14.12 g of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, reagent grade, 85% by mass) and 85.9 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.

[0074] [Comparative Example 6] 5 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade) and 95.0 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.

[0075] [Comparative Example 7] 17.39 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 1 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 81.6 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.

[0076] [Comparative Example 8] 1.45 g of nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade, 69% by mass), 75 g of ammonium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako special grade), and 23.6 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.

[0077] 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. ２ The 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.

[0078] [Test Specimen 2] (Vinyl Chloride-Vinyl Acetate Copolymer / Aluminum Foil) For the aluminum foil, 1N30 material with a thickness of 20 μm (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 using a bar coater #8 such that the weight after drying was 1.5 g / m ２ Then it was dried at 150°C for 1 minute to form a green layer. Next, a green layer was similarly formed on the matte side of the aluminum foil. After that, from above the green layer on the glossy side of the aluminum foil, a vinyl chloride-vinyl acetate copolymer-based coating agent (manufactured by Leader Co., Ltd.: LD#S837G clear, solid content 21% by mass) was applied using a bar coater #12 such that the weight after drying was 3.0 g / m ２ Then it was dried at 150°C for 1 minute to form a heat-seal layer. Next, a heat-seal layer was similarly formed from above the green layer on the matte side of the aluminum foil, and Test Specimen 2 with resin layers formed on both sides was produced. The structure of Test Specimen 2 was vinyl chloride-vinyl acetate copolymer / vinyl chloride-vinyl acetate copolymer / aluminum foil / vinyl chloride-vinyl acetate copolymer / vinyl chloride-vinyl acetate copolymer.

[0079] [Test Specimen 3] (PE / Aluminum Foil) For the aluminum foil, 1N30 material with a thickness of 35 μm (manufactured by Toyo Aluminum Co., Ltd., soft foil) was used. Subsequently, using a polyethylene melt extrusion machine, a urethane-based anchor coating agent (manufactured by Mitsui Chemicals, Inc., Olivine EL-557A / Olivine EL-557B = weight ratio 1 / 2) was applied to the glossy side of the aluminum foil using a boss roll at 0.05 g / m ２ Then it was dried at 70°C for 3 seconds. From above the anchor coating layer, a polyethylene coating (manufactured by Sumitomo Chemical Co., Ltd., Sumika Sen L705) was applied to a thickness of 20 μm to form a resin layer, and it was cured at 40°C for 24 hours to produce Test Specimen 3. That is, the structure of Test Specimen 3 was polyethylene layer / urethane layer / aluminum foil.

[0080] 3. Evaluation of Separation Solutions <Evaluation of Peelability (Separation Effect)> 100 g of each separation solution prepared in Examples 1-14 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.

[0081] 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.

[0082] 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".

[0083] <Evaluation of Elution Properties (Elution Reduction Effect)> 100 mL of each separation solution prepared in Examples 1-14 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

[0084] 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.

[0085] The elution properties (elution reduction effect) of aluminum foil were evaluated as follows: those with a weight retention rate of 99% or more were classified as "A", those with a weight retention rate of 97% or more but less than 99% as "B", those with a weight retention rate of 95% or more but less than 97% as "C", and those with a weight retention rate of less than 95% as "F".

[0086] <Evaluation of Residual Amount of Metal Salt> 100 g of each separation solution prepared in Examples 1-14 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 specimen 1 was cut into a 20 mm × 20 mm square shape, the lid was removed, the test specimen was submerged in each separation solution, and the lid was replaced. The test specimens were immersed in each separation solution for one hour, then removed, dried at 40°C for 24 hours, and subsequently heated in a heating furnace under an argon atmosphere at 350°C for one hour.

[0087] 0.5 g of each test specimen treated as described above was weighed and placed in a 200 mL tall beaker. 8 ml of hydrochloric acid (20% by mass, manufactured by Hayashi Pure Chemical Industries, Ltd.) and 3.7 ml of nitric acid (61% by mass, manufactured by Hayashi Pure Chemical Industries, Ltd.) were added to the tall beaker, and the mixture was heated to 200°C on a hot plate. Subsequently, the acid solution and the tall beakers containing each test specimen were heated at 200°C for 60 minutes until the test specimen dissolved. After the acid solution was allowed to cool naturally, deionized water was added to bring the solution to 100 mL, and measurements were performed using inductively coupled plasma mass spectrometry (Shimadzu Science Corporation ICPS-8100) under the following conditions: (a) High-frequency output: 1.2 kW (b) Plasma gas flow rate: 14.0 L / min (c) Auxiliary gas flow rate: 1.2 L / min (d) Carrier gas flow rate: 0.7 L / min

[0088] The presence or absence of metal contamination from the stripping solution was determined by calculating the background S / N ratio of the ICPS measurement results at 6σ, and if a peak above this level was detected, it was judged that metal contamination was "present". Since aluminum foil originally contains components other than aluminum, such as silicon and iron, a separate test specimen 1 that was not immersed in the stripping solution was prepared, the resin was stripped off, and these impurity metals were qualitatively analyzed based on the test specimen 1 that was carefully washed with water, and these impurity metals were not counted as impurity metals in each 0.5g weighed test specimen. As a result, for each 0.5g weighed test specimen, those in which no metals other than aluminum and metals derived from aluminum foil were detected were evaluated as "A", and those in which metals other than those detected were evaluated as "F".

[0089] Table 1 shows the evaluation results for peelability (separation effect), elution (elution reduction effect), and residual amount of metal salt using the separation solutions of Examples 1 to 14 and Comparative Examples 1 to 8.

[0090] <Discussion> As shown in Table 1, the peelability (separation effect) evaluation of the separation solutions of Examples 1 to 14 was "A", "B", or "C", the elution effect (elution reduction effect) evaluation was "A", "B", or "C", and the metal salt residue evaluation was "A", 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 effect (elution reduction effect), indicating that good results were not obtained in at least one of the evaluations of separation effect, elution reduction effect, and metal salt residue.

[0091] From the above results, it was found that the separation solutions of Examples 1 to 14 exhibited excellent elution properties (elution reduction effect), and in order to reduce impurities when aluminum foil is recovered and melted and cast, it is effective to have a content ratio of ammonium salt content (mass%) in the separation solution to acid content (mass%) in the separation solution of water, in a separation solution for aluminum foil laminates containing an ammonium salt consisting of at least one of ammonium formate and ammonium acetate, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, where the content ratio is 0.1 or more and 40.0 or less.

Claims

1. A separation solution for aluminum foil laminates comprising an ammonium salt consisting of at least one of ammonium formate and ammonium acetate, one or more acids selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, and acetic acid, and water, characterized in that the content ratio obtained by dividing the content (mass%) of the ammonium salt in the separation solution by the content (mass%) of the acid in the separation solution is 0.1 or more and 40.0 or less.

2. The separation solution for aluminum foil laminates according to claim 1, characterized in that the content of the ammonium salt in the separation solution is 1.2% by mass or more and 75% by mass or less, and the content of the acid in the separation solution is 2% by mass or more and 30% by mass or less.

3. The separation solution for aluminum foil laminates according to claim 1, characterized in that the separation solution contains, as a remainder, 10% by mass or less of one or more acids selected from the group consisting of polycarboxylic acids, hydroxy acids, polycarboxylic acid salts, and hydroxy acid salts.

4. The separation solution for aluminum foil laminates according to claim 3, characterized in that the separation solution contains 50% by mass or less of one or more organic solvents selected from the group consisting of ketones, ethers, alkylbenzenes, dioxolanes, cycloalkanes, and carboxylic acid esters.

5. 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 4; 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.

Images