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

Abstract

Provided are: a separation solution for an aluminum foil laminate, the separation solution being capable of reducing the elution of an aluminum foil into the separation solution while having the ability to separate the aluminum foil laminate into a resin and an aluminum foil; and a method for separating an aluminum foil laminate using the same. The present invention provides a separation solution for an aluminum foil laminate, the separation solution being characterized by comprising a carboxylic acid metal salt, an acid, and a polar solvent, wherein the content of the carboxylic acid metal salt is 1.1-50 mass%, and said separation solution has a pH of 0.5-4 at 25ºC.

Description

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

[0001] The present invention relates to a separating 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 an aluminum foil laminate using the same.

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

[0003] Furthermore, the resin to be laminated in the aluminum foil laminate must satisfy various requirements such as heat sealability, strength, and puncture resistance, and therefore many types of resins such as epoxy resins, acrylic resins, and vinyl chloride-vinyl acetate copolymer resins are used.

[0004] However, with the recent rise in awareness of the SDGs and global environment, high recyclability is also required for laminates containing resin, but the combination of various materials and materials including the resin has been an obstacle to the recycling of laminates. In particular, in the case of aluminum foil laminates containing aluminum foil, the aluminum foil and the resin cannot be easily separated, so recycling has not progressed.

[0005] In view of this situation, for example, in JP-A No. 2020-515655 (Patent Document 1), a method has been developed for separating a metal layer from a resin by using a separation fluid (separation solution) containing a mixture of water, a short-chain carboxylic acid, phosphoric acid, and an alkali metal hydroxide.

[0006] Special Publication No. 2020-515655

[0007] Therefore, the present inventors confirmed the separation of the aluminum foil laminate using the technology described in Patent Document 1 and found that it had a certain effect in separating the resin from the aluminum foil laminate. However, at the same time, it was found that after the resin separation began, the aluminum foil exposed in the separation solution was eluted into the separation solution.

[0008] However, in the separation method described in Patent Document 1, the aluminum foil and the resin do not separate instantly, but rather take a certain amount of time to separate, making it extremely difficult to remove the aluminum foil from the separation solution immediately after separation without exposing it. In addition, in the case of an aluminum foil laminate in which a resin is laminated only on one side of the aluminum foil, the other side of the aluminum foil is always exposed, so it will be in contact with the separation solution from the beginning during separation. Furthermore, even in the case of an aluminum foil laminate in which a resin is laminated on both sides of the aluminum foil, if the resin laminated on one side separates first, the aluminum foil exposed in the separation solution will be in contact with the separation solution throughout the separation of the other side of the aluminum foil and other parts of the resin.

[0009] Therefore, the separation method described in Patent Document 1 has the problem that it is extremely difficult to avoid contact between the aluminum foil surface and the separation solution and to suppress elution into the separation solution.

[0010] Furthermore, the elution of aluminum into the separation solution means a decrease in the yield of recovered aluminum and an increase in the amount of aluminum accumulated in the separation solution. Therefore, even a yield reduction of a few percent results in a large recycling loss on an industrial scale, while the latter poses problems of reduced production efficiency due to a decrease in the separation ability of the separation solution and an increase in the purification load (environmental load) when the separation solution is repeatedly used or discarded.

[0011] Therefore, in the method of separating an aluminum foil laminate using a separation solution as described in Patent Document 1, it is strongly required from both an industrial and environmental perspective to minimize the elution of the aluminum foil into the separation solution. There was also a strong demand.

[0012] Therefore, the present invention is a separation solution for an aluminum foil laminate that has the ability to separate an aluminum foil laminate into a resin and aluminum foil while reducing the elution of aluminum foil into the separation solution. An object of the present invention is to provide a separation solution and an aluminum foil laminate separation method using the same.

[0013] In order to solve the above problems, the present inventors have conducted intensive research into methods for separating an aluminum foil laminate into a resin and an aluminum foil. As a result, in a separation solution containing a carboxylic acid metal salt, an acid, and a polar solvent, the content of the carboxylic acid metal salt is adjusted and the pH of the separation solution is controlled within a predetermined range. It has been found that the aluminum foil laminate can be easily separated into aluminum foil and resin while reducing the elution of the aluminum foil into the separation solution, and the present invention has been completed.

[0014] That is, according to the present invention, a separation solution for an aluminum foil laminate is provided, which contains a metal carboxylate, an acid, and a polar solvent, and is characterized in that the content of the metal carboxylate is 1.1% by mass or more and 50% by mass or less, and the pH at 25 ° C. is 0.5 or more and 4 or less.

[0015] Further, according to the present invention, as a method for separating an aluminum foil laminate into resin and aluminum foil using the above-mentioned aluminum foil laminate separation solution, a step of preparing an aluminum foil laminate containing aluminum foil and resin, and crushing and / or pulverizing the aluminum foil laminate to a size of 1 mm to 70 mm to obtain a crushed and / or pulverized product, and a step of immersing the crushed and / or pulverized product in the above-mentioned aluminum foil laminate separation solution, and leaving or stirring at a temperature of 0 ° C. to 99 ° C. for 1 minute to 24 hours to separate into aluminum foil and resin.

[0016] In the present invention, the carboxylic acid generated by the reaction of a carboxylic acid metal salt with an acid in a solution functions to separate the aluminum foil laminate into a resin and an aluminum foil, and a portion of the carboxylic acid metal salt suppresses the ionization of the generated carboxylic acid, thereby reducing the elution of the aluminum foil into the separation solution. Therefore, the separation solution of the present invention can easily separate the aluminum foil laminate into a resin and an aluminum foil while reducing the elution of the aluminum foil into the separation solution.

[0017] In the present invention, it is preferable to use water as the polar solvent in order to further enhance the separation effect of the aluminum foil laminate and the effect of reducing elution of the aluminum foil into the separation solution.

[0018] In order to further enhance the effect of the separation solution of the present invention, it is preferable to use one or more acids selected from the group consisting of inorganic acids, sulfonic acids, carboxylic acids, vinyl carboxylic acids, and nucleic acids, such as sulfuric acid, citric acid, formic acid, acetic acid, tartaric acid, malic acid, lactic acid, maleic acid, oxalic acid, phosphoric acid, nitric acid, and hydrochloric acid. Furthermore, it is preferable to use an acid that does not contain a halogen element.

[0019] It is also preferable to use one or more carboxylic acid metal salts selected from the group consisting of sodium formate, potassium formate, calcium formate, zinc formate, sodium acetate, potassium acetate, calcium acetate, zinc acetate, and basic aluminum acetate.

[0020] According to the separation solution for aluminum foil laminates of the present invention and the method for separating aluminum foil laminates using the same, the separation solution of the present invention functions in such a way that the carboxylic acid generated by the reaction of a carboxylic acid metal salt with an acid in the solution separates the aluminum foil laminate into resin and aluminum foil, and a portion of the carboxylic acid metal salt suppresses the ionization of the generated carboxylic acid, thereby reducing the elution of the aluminum foil into the separation solution. Therefore, the aluminum foil laminate can be easily separated into resin and aluminum foil while reducing the elution of the aluminum foil into the separation solution.

[0021] Hereinafter, a separating solution for an aluminum foil laminate according to one embodiment of the present invention and a method for separating an aluminum foil laminate using the same will be described in detail. Note that the present invention is not limited to the following examples, and various modifications are possible within the scope of the technical idea of ​​the present invention.

[0022] <Aluminum foil laminate separating solution> The aluminum foil laminate separating solution of the present invention contains a metal carboxylate, an acid, and a polar solvent, and is characterized in that the content of the metal carboxylate is 1.1 mass% or more and 50 mass% or less, and the pH at 25° C. is 0.5 or more and 4 or less. Hereinafter, each component of the aluminum foil laminate separating solution of the present invention will be described in detail.

[0023] <Carboxylate Metal Salt> The carboxylate metal salt used in the present invention is a metal salt of a carboxylic acid having from 1 to 4 carbon atoms. Specifically, one or more selected from the group consisting of metal formates, metal acetates, metal propionates, metal butyrates, metal acrylates, metal methacrylates, metal oxalates, metal malonates, metal succinates, metal maleates, metal fumarates, metal lactates, metal malates, and metal tartarates are used. In one embodiment of the present invention, a metal formate or a metal acetate is used.

[0024] The metal carboxylate used in the present invention may be, for example, one or more selected from the group consisting of sodium carboxylate, potassium carboxylate, calcium carboxylate, zinc carboxylate, nickel carboxylate, and aluminum carboxylate, but is not necessarily limited to these.

[0025] In the present invention, from the viewpoint of suppressing aluminum elution, it is preferable to use a salt of a metal having a higher ionization tendency than aluminum or an aluminum salt. When a salt of a metal having a higher ionization tendency than aluminum is used, aluminum and ions of the other metal are simultaneously present in the solution, and the ions of the other metal react preferentially with aluminum, thereby exhibiting the effect of suppressing aluminum ionization, i.e., aluminum elution. Specifically, it is preferable to use one or more salts selected from the group consisting of sodium carboxylates, potassium carboxylates, and calcium carboxylates. From the viewpoint of further suppressing aluminum elution, it is more preferable to use sodium carboxylates and / or potassium carboxylates, which are salts of metals having a higher ionization tendency.

[0026] When an aluminum salt is used as the metal salt, the elution of aluminum can be further suppressed based on Le Chatelier's principle. The aluminum salt dissolves in the separation solution and exists as aluminum ions, which acts to suppress excess aluminum ions and reduces the ionization of aluminum in the aluminum foil laminate. When an aluminum salt is used, a basic aluminum carboxylate is preferred. A basic aluminum carboxylate exhibits basicity when dissolved alone, and therefore exhibits a buffering effect with the acid described below, stabilizing the pH and further suppressing the ionization of aluminum.

[0027] The metal carboxylate reacts with an acid in the separation solution to produce a carboxylic acid and an acid salt. The produced carboxylic acid ionizes in the separation solution, and the interaction between the carboxylic acid ion and the hydrogen ion promotes the separation of the aluminum foil and the resin. Some metal carboxylates suppress the ionization of the produced carboxylic acid based on Le Chatelier's principle, thereby exhibiting the effect of reducing the leaching of the aluminum foil into the separation solution (hereinafter referred to as the "leaching reduction effect").

[0028] In the separation solution of the present invention, the content of the carboxylic acid metal salt is preferably 1.1% by mass or more and 50% by mass or less. If the content of the carboxylic acid metal salt in the separation solution is less than 1.1% by mass, the amount of carboxylic acid produced decreases, resulting in an insufficient effect of separating the aluminum foil and the resin (hereinafter referred to as the "separation effect").

[0029] On the other hand, the separation solution of the present invention exhibits excellent separation effect in proportion to the content of the metal carboxylate in the separation solution, and the separation effect of the separation solution itself does not fundamentally change even if the content of the metal carboxylate continues to increase after saturation. However, if the amount of the metal carboxylate in the separation solution continues to increase after saturation, the formation of precipitates begins to be observed in the separation solution, and if the content of the metal carboxylate exceeds 50 mass%, some of the solution becomes gel-like, reducing the fluidity of the solution.

[0030] Therefore, from the viewpoint of exhibiting the separation effect, the content of the carboxylate metal salt in the separation solution can be more than the saturated amount or more than 50% by mass without any problem, and there is no particular upper limit. However, in practice, it is preferable to be able to immerse the aluminum foil laminate in the separation solution and stir it, etc., so that in order to exhibit an excellent separation effect while ensuring fluidity as a liquid and having high handleability, the content of the carboxylate metal salt in the separation solution is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less.

[0031] <Acid> The acid used in the present invention may be, for example, one or more selected from the group consisting of sulfuric acid, citric acid, formic acid, acetic acid, tartaric acid, malic acid, lactic acid, maleic acid, oxalic acid, phosphoric acid, nitric acid, and hydrochloric acid, but is not necessarily limited thereto. As will be described later, it is preferable to use an acid that does not contain a halogen element. Therefore, among the above acids, hydrochloric acid is an acid that contains a halogen element, and therefore, it is more preferable to use one or more acids selected from the group consisting of sulfuric acid, citric acid, formic acid, acetic acid, tartaric acid, malic acid, lactic acid, maleic acid, oxalic acid, phosphoric acid, and nitric acid.

[0032] The acid reacts with the carboxylic acid metal salt in the separation solution to form a salt of the carboxylic acid and the acid. The resulting carboxylic acid ionizes in the separation solution, and the interaction between the carboxylic acid ion and the hydrogen ion promotes separation of the aluminum foil from the resin.

[0033] A strong acid such as sulfuric acid can supply a large amount of hydrogen ions with a small amount, which contributes to further improving the separation effect, reducing the environmental load, and reducing the separation cost. A weak acid such as citric acid can separate the aluminum foil laminate at a pH close to neutral, which contributes to further improving the elution reduction effect and reducing the environmental load. The acid used in the separation solution can be selected appropriately depending on the purpose.

[0034] The acid containing a halogen element ionizes in the separation solution to generate ions of the halogen element. The ions of the halogen element have strong oxidizing power, which promotes the destruction of the aluminum oxide layer that functions as a protective layer on the surface of the aluminum foil. Therefore, the acid used in the present invention is preferably an acid that does not contain a halogen element.

[0035] The content of the acid in the separation solution is not particularly limited as long as the separation solution satisfies the pH range (0.5 to 4) at 25 ° C., but is preferably 1% by mass to 50% by mass. From the viewpoint of further enhancing the effect of separating the aluminum foil laminate into the resin and the aluminum foil while reducing the elution of the aluminum foil into the separation solution, the content of the acid in the separation solution is more preferably 3% by mass to 20% by mass, and even more preferably 5% by mass to 15% by mass.

[0036] <Polar Solvent> The polar solvent used in the present invention is not limited, and a protic polar solvent and / or an aprotic polar solvent can be used. Examples of protic polar solvents include water, methanol, ethanol, and isopropanol, and examples of aprotic polar solvents include acetone, acetonitrile, and dimethyl sulfoxide (DMSO). From the viewpoints of safety, solution cost, and environmental impact, it is preferable to use water as the polar solvent used in the present invention.

[0037] The polar solvent has the effect of promoting the reaction between the metal carboxylate and the acid and the ionization of the resulting carboxylic acid and acid salt. The content of the polar solvent in the separation solution is not particularly limited as long as the content of the metal carboxylate (2% by mass or more and 50% by mass or less) and the pH range of the separation solution at 25°C (0.5 to 4) are satisfied, but it is preferably 32% by mass or more and 96% by mass or less.

[0038] In the separation solution of the present invention, if the polar solvent content is less than 32% by mass, the fluidity of the separation solution will decrease, and the separation effect may be insufficient. If the polar solvent content is more than 96% by mass, the contents of the metal carboxylate and acid will be low, and the separation effect may be insufficient. Therefore, the polar solvent content in the separation solution is more preferably 50% by mass or more and 92% by mass or less, and even more preferably 70% by mass or more and 88% by mass or less. The total content of the metal carboxylate, acid, and polar solvent is 100% by mass or less.

[0039] <pH of Separation Solution at 25°C> In the separation solution of the present invention, the pH at 25°C (hereinafter simply referred to as "pH") is preferably 0.5 or more and 4 or less. If the pH of the separation solution is lower than 0.5, the elution-reducing effect becomes insufficient, and if the pH is higher than 4, the separation effect becomes insufficient. In order to maximize the separation effect and elution-reducing effect of the separation solution under an optimal balance, the pH is more preferably 1 or more and 3.7 or less, and even more preferably 1.5 or more and 3.5 or less.

[0040] <Surfactant> The separation solution of the present invention may contain a surfactant. The type of surfactant is not particularly limited, and one or more surfactants selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants are preferably used. The surfactant contributes to smooth separation by imparting lubricity to the separated resin surface, thereby suppressing entanglement with the aluminum foil, and also contributes to further improving the leaching reduction effect by protecting the aluminum foil surface.

[0041] <Heavy liquefaction additive> The separation solution of the present invention may contain an additive (hereinafter referred to as "heavy liquefaction agent") for increasing the specific gravity of the separation solution (e.g., relative to water), i.e., for heavy liquefaction of the separation solution. By adjusting the specific gravity of the separation solution using the heavy liquefaction agent to be between the specific gravity of the aluminum foil and the specific gravity of the resin, the difference in specific gravity between the aluminum foil and the resin can be utilized to promote separation of the two. The type of heavy liquefaction agent is not particularly limited, and for example, sodium polytungstate or a mixture of thallium formate and thallium malonate (raw material for the Clerici solution) is preferably used. From the viewpoints of safety and ease of handling, it is preferable to use non-toxic sodium polytungstate as the heavy liquefaction agent used in the present invention.

[0042] <Other Additives> The separation solution of the present invention may contain one or more additives selected from the group consisting of ketones, esters, ethers, dioxolanes, cycloalkanes, and alkylbenzenes. These additives permeate the resin of the aluminum foil laminate immersed in the separation solution, thereby contributing to further improving the separation effect.

[0043] Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone, acetophenone, and benzophenone. Methyl ethyl ketone is often used as a true solvent for resin coating agents, and is also preferred from the standpoint of solubility.

[0044] Examples of ethers include dimethyl ether, ethyl methyl ether, diethyl ether, diphenyl ether, ethylene oxide, tetrahydrofuran (THF), furan, 1,4-dioxane, anisole, benzofuran, dibenzofuran, and crown ether. Specific examples of dioxolanes include 1,3-dioxolanes. Examples of alkylbenzenes include xylene, toluene, ethylbenzene, cumene, and p-cymene. Examples of cycloalkanes include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane.

[0045] Separation solutions according to examples of the present invention and separation solutions according to comparative examples were prepared and evaluated, and will be described in detail below.

[0046] 1. Preparation of Separation Solution [Example 1] To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 10.9 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 78.9 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40°C for 30 minutes to prepare the separation solution of Example 1.

[0047] Example 2 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 15.1 g of citric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: food additive, 99.5% by mass), and 74.7 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 2.

[0048] Example 3 To a 100 mL glass bottle were added 2.6 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 2.7 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 94.8 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 3.

[0049] Example 4 To a 100 mL glass bottle were added 51.0 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 28.1 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 20.9 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 4.

[0050] Example 5 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 14.1 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 75.7 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 5.

[0051] Example 6 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 3.1 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 86.7 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 6.

[0052] Example 7 To a 100 mL glass bottle were added 10.3 g of potassium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: Wako Special Grade, 97% by mass), 7.8 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd., 64% by mass), and 81.9 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 7.

[0053] Example 8 To a 100 mL glass bottle were added 5.1 g of calcium formate (manufactured by Thermo Scientific, 98% by mass), 4.7 g of sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 64% by mass), and 90.2 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 8.

[0054] Example 9 To a 100 mL glass bottle were added 13.0 g of zinc formate (II) dihydrate (Kanto Chemical Co., Ltd.: Grade 1, 95% by mass), 7.8 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd., 64% by mass), and 79.2 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 9.

[0055] Example 10 To a 100 mL glass bottle were added 13.8 g of nickel (II) formate dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 90% by mass), 7.8 g of sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 64% by mass), and 78.4 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 10.

[0056] Example 11 To a 100 mL glass bottle were added 20.3 g of sodium acetate (Fujifilm Wako Pure Chemical Industries, Ltd.: special reagent grade, 98.5% by mass), 15.6 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 64.1 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40°C for 30 minutes to prepare a separation solution of Example 11.

[0057] Example 12 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 6.6 g of formic acid (Asahi Chemical Industry Co., Ltd.: special grade reagent, 76% by mass), and 83.2 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 12.

[0058] Example 13 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special reagent grade, 98% by mass), 15.0 g of acetic acid (Fujifilm Wako Pure Chemical Industries, Ltd.: special reagent grade, 99.7% by mass), and 74.8 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 13.

[0059] Example 14 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 15.1 g of L(+)-tartaric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 99.5% by mass), and 74.7 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 14.

[0060] Example 15 To a 100 mL glass bottle were added 10.2 g of sodium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 15.2 g of DL-malic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: Wako special grade reagent, 99% by mass), and 74.6 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 15.

[0061] Example 16 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 16.9 g of lactic acid (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 88.5% by mass), and 72.8 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 16.

[0062] Example 17 To a 100 mL glass bottle were added 10.2 g of sodium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 10.1 g of maleic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 99% by mass), and 79.7 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 17.

[0063] Example 18 To a 100 mL glass bottle were added 4.1 g of sodium formate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 5.6 g of oxalic acid dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 100% by mass), and 90.3 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 18.

[0064] Example 19 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 11.8 g of phosphoric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: Wako Grade 1, 85% by mass), and 78.0 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 19.

[0065] Example 20 To a 100 mL glass bottle were added 7.9 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 7.0 g of nitric acid (1.42) (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 69% by mass), and 85.1 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 20.

[0066] Example 21 To a 100 mL glass bottle were added 10.0 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 8.3 g of hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 36% by mass), and 81.7 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40°C for 30 minutes to prepare a separation solution of Example 21.

[0067] Example 22 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 10.9 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), 77.9 g of purified water (AS ONE Corporation: ASSWS-20), and 1.0 g of a surfactant (Kao Corporation: Emulgen LS-106), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 22.

[0068] Example 23 To a 100 mL glass bottle were added 11.1 g of basic aluminum acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 90% by mass), 5.8 g of nitric acid (1.42) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 69% by mass), and 83.1 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 23.

[0069] Example 24 To a 100 mL glass bottle were added 5.6 g of basic aluminum acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 90% by mass), 15.8 g of formic acid (manufactured by Asahi Chemical Industry Co., Ltd.: special grade reagent, 76% by mass), and 78.7 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 24.

[0070] Example 25 To a 100 mL glass bottle were added 1.2 g of basic aluminum acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 90% by mass), 1.4 g of nitric acid (1.42) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 69% by mass), 5.3 g of formic acid (manufactured by Asahi Chemical Industry Co., Ltd.: special grade reagent, 76% by mass), and 92.2 g of purified water (manufactured by AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution of Example 25.

[0071] Comparative Example 1 To a 100 mL glass bottle were added 59.2 g of formic acid (Asahi Chemical Industry Co., Ltd.: special grade reagent, 76% by mass), 30.5 g of purified water (AS ONE Corporation: ASSWS-20), 3.5 g of phosphoric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: Wako First Grade, 85% by mass), and 6.8 g of sodium hydroxide (Fujifilm Wako Pure Chemical Industries, Ltd.: Wako First Grade, 93% by mass), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution for Comparative Example 1.

[0072] Comparative Example 2 To a 100 mL glass bottle were added 13.2 g of formic acid (Asahi Chemical Industry Co., Ltd.: special grade reagent, 76% by mass) and 86.8 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution for Comparative Example 2.

[0073] Comparative Example 3 To a 100 mL glass bottle were added 1.0 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 1.6 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 97.4 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution for Comparative Example 3.

[0074] Comparative Example 4 To a 100 mL glass bottle were added 61.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 34.4 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 4.4 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution for Comparative Example 4.

[0075] Comparative Example 5 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 1.6 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 88.2 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution for Comparative Example 5.

[0076] Comparative Example 6 To a 100 mL glass bottle were added 10.2 g of sodium formate (Fujifilm Wako Pure Chemical Industries, Ltd.: special grade reagent, 98% by mass), 15.6 g of sulfuric acid (Fujifilm Wako Pure Chemical Industries, Ltd.: 64% by mass), and 74.2 g of purified water (AS ONE Corporation, ASSWS-20), and the mixture was stirred at 40° C. for 30 minutes to prepare a separation solution for Comparative Example 6.

[0077] The compositions of the separation solutions of Examples 1 to 25 and Comparative Examples 1 to 6 are shown in Table 1 below.

[0078] 2. Evaluation of Separation Solution <Preparation of Aluminum Foil Laminate A> A 20 μm 1N30 material (manufactured by Toyo Aluminum Co., Ltd.) was used as the aluminum foil. Subsequently, a nitrocellulose-based coating agent (manufactured by DIC Graphics Corporation: SF1009 Clear NT, solid content 20% by mass) was applied to the glossy side of the aluminum foil using a bar coater #18 so that the weight after drying was 5.0 g / m ２ The coating was then dried at 150°C for 1 minute to form a resin layer. Further, a vinyl chloride-vinyl acetate copolymer coating agent (LD#S837G Clear, manufactured by Leader Co., Ltd., solid content 21% by mass) was applied to the poppy side of the aluminum foil using a bar coater #18 so that the weight after drying was 5.0 g / m ２ The resin layer was formed by drying at 150° C. for 1 minute, thereby preparing a test specimen A having a resin layer composed of nitrocellulose / aluminum foil / vinyl chloride / vinyl acetate copolymer.

[0079] <Preparation of Aluminum Foil Laminate B> A 20 μm 1N30 material (manufactured by Toyo Aluminum K.K.) was used as the aluminum foil. Subsequently, a polyolefin-based white coating agent (manufactured by T&K TOKA: PPZ-C 96 white, solid content 34 mass%) was applied to the glossy side of the aluminum foil using a bar coater #8 so that the weight after drying was 1.5 g / m ２ Then, an epoxy-based overprint coating agent (PT-OP varnish manufactured by T&K TOKA Corporation, solid content 33% by mass) was applied onto the white layer using a bar coater #5 so that the weight after drying was 1.5 g / m ２ The white layer and overprint layer were applied to the poppy side of the aluminum foil in the same manner as the glossy side, and a test specimen B was prepared in which resin layers were formed on both sides of the structure epoxy / polyolefin / aluminum foil / polyolefin / epoxy.

[0080] <Measurement of pH of Separation Solution at 25°C> The pH of the separation solution was measured by keeping the separation solution at 25°C using a glass electrode hydrogen ion concentration indicator (TPX-999i, manufactured by Toko Chemical Research Institute) and a composite electrode (PCE108CW-SR, manufactured by Toko Chemical Research Institute).

[0081] <Evaluation of Peelability (Separation Effect)> 50 mL of each separation solution prepared in Examples 1 to 25 and Comparative Examples 1 to 6 was measured and placed in a 100 mL glass bottle (mouth inner diameter 31.9 mm, body diameter 48.5 mm, height 87 mm), and the glass bottle was placed in a heating and stirring dry bath (manufactured by AS ONE Corporation: HDBS-6) and heated so that the temperature of the separation solution reached 70° C. Next, one aluminum foil laminate cut into a square shape (20 mm x 20 mm) and a rotor (manufactured by AS ONE Corporation: tapered shape, length 25 mm, diameter 8 mm, material PTFE) were placed in the glass bottle, and the temperature of the separation solution was maintained at 70° C. while stirring with the rotor at 200 RPM.

[0082] The time until the resin on both sides separated from the aluminum foil was measured, and the peelability (separation effect) of the separation solution was evaluated as follows: "A" for separation within 60 minutes, "B" for separation within 720 minutes, "C" for separation within 1440 minutes, and "F" for no separation within 1440 minutes.

[0083] <Evaluation of elution (elution reduction effect)> 100 mL of each separation solution prepared in Examples 1 to 25 and Comparative Examples 1 to 6 was measured into a 100 mL glass bottle (mouth inner diameter 31.9 mm, body diameter 48.5 mm, height 87 mm), and the glass bottle was placed in a heating and stirring dry bath (manufactured by AS ONE Corporation: HDBS-6), and the temperature of the separation solution was heated to 70 ° C. Next, 20 μm thick aluminum foil (manufactured by Toyo Aluminum Co., Ltd.: 1N30 material) cut into a square shape (40 mm x 40 mm) was immersed in each separation solution at 70 ° C. for 10 minutes, and the weight before and after immersion was measured. The weight loss rate of the aluminum foil was calculated.

[0084] Since it is virtually impossible to remove the aluminum foil from the separation solution immediately after the resin is separated without exposing it, the immersion time was set to 10 minutes. In addition, in order to eliminate the influence of trace components attached to the aluminum foil surface on the weight loss rate, the weight of the aluminum foil before immersion in the separation solution was measured after immersing the aluminum foil in hexane (Fujifilm Wako Pure Chemical Industries, Ltd.: Reagent Grade) for 1 minute to degrease and clean it, and then drying it for 10 minutes in a constant temperature oven maintained at 100 ° C. 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, and drying it for 10 minutes in a constant temperature oven maintained at 100 ° C.

[0085] The leaching (leaching reduction effect) was evaluated by assigning a weight loss rate of 0.3% or less to "A", 0.4% or less to "B", 0.5% or less to "C", and more than 0.5% to "F".

[0086] Table 2 shows the evaluation results of stripping properties (separation effect) and elution properties (elution reduction effect) using the separation solutions of Examples 1 to 25 and Comparative Examples 1 to 6.

[0087] <Discussion> As shown in Table 2, the separation effects of the separation solutions of Examples 1 to 25 were rated "A," "B," or "C," and the leaching reduction effect was rated "A," "B," or "C," indicating that all of the separation solutions had excellent separation effects and excellent leaching reduction effects. On the other hand, the separation solutions of Comparative Examples 1 to 6, except for those whose fluidity as liquids had decreased to the point where measurement was impossible, were rated "F" for separation effect or "F" for leaching reduction effect, indicating that good results were not obtained in the evaluation of at least one of the separation effect and leaching reduction effect.

[0088] From the above results, it was found that the separation solutions of Examples 1 to 25 effectively exhibit excellent separation effects and excellent elution reduction effects by containing a metal carboxylate, an acid, and a polar solvent, with the content of the metal carboxylate being 1.1% by mass or more and 50% by mass or less, and having a pH at 25°C of 0.5 or more and 4 or less.

Claims

1. A separation solution for aluminum foil laminates, comprising a metal carboxylate, an acid, and a polar solvent, wherein the content of the metal carboxylate is 1.1% by mass or more and 50% by mass or less, and the pH at 25°C is 0.5 or more and 4 or less.

2. The separating solution for aluminum foil laminates according to claim 1, wherein the polar solvent is water.

3. The separation solution for aluminum foil laminates according to claim 1, wherein the acid is one or more selected from the group consisting of inorganic acids, sulfonic acids, carboxylic acids, vinyl carboxylic acids, and nucleic acids.

4. The separating solution for aluminum foil laminates according to claim 1, wherein the acid does not contain any halogen element.

5. The separation solution for aluminum foil laminates according to claim 1, wherein the metal carboxylate is one or more selected from the group consisting of sodium formate, potassium formate, calcium formate, zinc formate, sodium acetate, potassium acetate, calcium acetate, zinc acetate, and basic aluminum acetate.

6. The separation solution for aluminum foil laminates according to claim 1, wherein the acid is one or more selected from the group consisting of sulfuric acid, citric acid, formic acid, acetic acid, tartaric acid, malic acid, lactic acid, maleic acid, oxalic acid, phosphoric acid, and nitric acid.

7. A method for separating an aluminum foil laminate, comprising: a step of preparing an aluminum foil laminate containing aluminum foil and resin; a step of crushing and / or pulverizing the aluminum foil laminate to obtain a crushed and / or pulverized product; and a step of immersing the crushed and / or pulverized product in the separating solution for aluminum foil laminates described in any one of claims 1 to 6, and leaving or stirring the solution at a temperature of 0°C to 99°C for 1 minute to 24 hours, thereby separating the aluminum foil and the resin.

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