Treatment liquid for laminated resin film separation, method for separating laminated resin film, method for manufacturing treatment liquid for laminated resin film separation, and method for manufacturing recycled resin

Abstract

The present invention is a treatment liquid for separating a laminated resin film. The treatment liquid for separating a laminated resin film contains potassium hydroxide, an alcohol having no more than 3 carbons, and an amide-based solvent. The laminated resin film contains a substrate layer and an adhesive agent layer.

Description

Treatment liquid for peeling laminated resin films, method for peeling laminated resin films, method for producing treatment liquid for peeling laminated resin films, and method for producing recycled resin

[0001] The present invention relates to a treatment liquid for stripping a laminated resin film, a method for stripping a laminated resin film, a method for producing a treatment liquid for stripping a laminated resin film, and a method for producing recycled resin.

[0002] In recent years, with the increasing attention being paid to environmental issues, efforts are being made to eliminate the use of plastic in various fields. Demand for recycling technologies is also increasing in the packaging field. Examples of technologies in this field include those described in Patent Document 1.

[0003] Patent Document 1 describes a method for separating and recovering laminated films, which aims to provide a method for separating and recovering laminated films that can easily separate laminated films laminated with a reactive adhesive present in plastic composite waste into single-layer films, and is characterized by comprising: Step 1 of immersing the laminated film laminated with an adhesive in a morpholine solution having a morpholine concentration of 50% by mass or more while heating and stirring the laminated film at 20 to 90°C or subjecting the laminated film to ultrasonic vibration; and Step 2 of recovering the separated single-layer films of each layer.

[0004] Patent Document 2 describes a method for separating and recovering a laminated film laminated with a reactive adhesive having an ester bond that is present in plastic composite waste, with the aim of easily separating the laminated film into single-layer films. The method comprises Step 1 of immersing the laminated film in an alkaline solution while heating and stirring the laminated film at 20 to 90°C or subjecting the laminated film to ultrasonic vibration, and Step 2 of recovering the separated single-layer films of each layer.

[0005] International Publication No. 2020 / 059516 International Publication No. 2020 / 066652

[0006] The present invention provides a treatment liquid for stripping a laminated resin film, a method for stripping a laminated resin film, a method for producing a treatment liquid for stripping a laminated resin film, and a method for producing recycled resin.

[0007] According to the present invention, there are provided a treatment liquid for stripping a laminated resin film, a method for stripping a laminated resin film, a method for producing a treatment liquid for stripping a laminated resin film, and a method for producing a recycled resin, all of which are shown below.

[0008] [1] A treatment liquid for peeling a laminate resin film, the treatment liquid comprising potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, the laminate resin film comprising a substrate layer and an adhesive layer. [2] The treatment liquid for peeling a laminate resin film according to [1], wherein the content of the potassium hydroxide is 1 part by mass or more and 20 parts by mass or less when the total content of the potassium hydroxide and the alcohol in the treatment liquid for peeling a laminate resin film is taken as 100 parts by mass. [3] The treatment liquid for peeling a laminate resin film according to [1] or [2], wherein the content of the amide-based solvent is 1% by mass or more and 60% by mass or less when the total content of the treatment liquid for peeling a laminate resin film is taken as 100% by mass. [4] The treatment liquid for peeling a laminate resin film according to any one of [1] to [3], wherein the amide-based solvent comprises one or more solvents selected from the group consisting of β-alkoxy-N-substituted propanamides and N-methyl-2-pyrrolidone. [5] The treatment liquid for peeling a laminate resin film according to any one of [1] to [4], wherein the potassium hydroxide content is 0.5% by mass or more and 18% by mass or less when the total weight of the treatment liquid for peeling a laminate resin film is taken as 100% by mass. [6] The treatment liquid for peeling a laminate resin film according to any one of [1] to [5], wherein the total content of the potassium hydroxide, the alcohol, and the amide-based solvent is 70% by mass or more and 100% by mass or less when the total weight of the treatment liquid for peeling a laminate resin film is taken as 100% by mass. [7] The treatment liquid for peeling a laminate resin film according to any one of [1] to [6], wherein the treatment liquid for peeling a laminate resin film is obtained by adding the amide-based solvent to a mixed solution of the potassium hydroxide and the alcohol. [8] The treatment liquid for peeling a laminate resin film according to any one of [1] to [7], wherein the water content in the treatment liquid for peeling a laminate resin film is 10.0% by mass or less when the total weight of the treatment liquid for peeling a laminate resin film is taken as 100% by mass. [9] A method for peeling a laminate resin film, comprising a peeling step of treating a laminate resin film including a base layer and an adhesive layer with the treatment liquid for peeling a laminate resin film according to any one of [1] to [8], thereby peeling off at least a part of the laminate resin film.

[10] The method for peeling a laminate resin film according to [9], wherein the laminate resin film further comprises a printed layer.

[11] The method for peeling a laminate resin film according to [9] or

[10] , wherein the adhesive layer comprises a polyisocyanate compound and a polyol compound.

[12] The method for peeling a laminate resin film according to any one of [9] to

[11] , wherein the substrate layer comprises a polyolefin.

[13] The method for peeling a laminate resin film according to any one of

[10] to

[12] , wherein the laminate resin film has one layer structure selected from the group consisting of substrate layer / adhesive layer / substrate layer, printed layer / substrate layer / adhesive layer / substrate layer, and substrate layer / printed layer / adhesive layer / substrate layer.

[14] The method for peeling a laminate resin film according to any one of [9] to

[13] , wherein, when the laminate resin film has two or more substrate layers, the respective substrate layers are made of the same material.

[15] The method for peeling a laminate resin film according to any one of [9] to

[14] , wherein the peeling step involves immersing the laminate resin film in the treatment liquid for peeling a laminate resin film.

[16] The method for peeling a laminate resin film according to any one of [9] to

[15] , wherein the peeling step involves treating at a temperature of 15°C or higher and 60°C or lower.

[17] The method for peeling a laminate resin film according to any one of [9] to

[16] , wherein the peeling step involves stirring or ultrasonically vibrating the laminate resin film and the treatment liquid for peeling a laminate resin film.

[18] The method for peeling a laminate resin film according to any one of [9] to

[17] , further comprising a step of breaking the laminate resin film into small pieces.

[19] A method for producing a treatment liquid for peeling a laminate resin film according to any one of [1] to [8], comprising the steps of preparing a mixed solution of the potassium hydroxide and the alcohol, and adding an amide solvent to the mixed solution.

[20] A method for producing recycled resin, comprising a peeling step of peeling at least a part of a laminated resin film by the method for peeling a laminated resin film according to any one of [9] to

[18] .

[0009] According to the present invention, it is possible to provide a treatment liquid for peeling a laminated resin film, a method for peeling a laminated resin film, a method for producing a treatment liquid for peeling a laminated resin film, and a method for producing recycled resin.

[0010] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0011] The treatment liquid for peeling a laminated resin film of this embodiment (hereinafter also simply referred to as the "treatment liquid") contains potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, and the laminated resin film includes a substrate layer and an adhesive layer.

[0012] The treatment liquid for peeling laminate resin films of this embodiment contains potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide solvent, and the synergistic effect of these components can effectively dissolve (peel) the adhesive layer of the laminate resin film, thereby improving the peelability between the substrate layer and adhesive layer that constitute the laminate resin film. Here, "dissolve (peel)" means "dissolve and peel."

[0013] The treatment liquid for peeling off the laminated resin film will be further explained below.

[0014] <Laminate Resin Film Peel-Off Treatment Liquid> The content of potassium hydroxide in the laminate resin film peel-off treatment liquid is, when the total content of potassium hydroxide and alcohol is taken as 100 parts by mass, preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and even more preferably 13 parts by mass or more, from the viewpoint of further improving the peelability of the laminate resin film, and is preferably 20 parts by mass or less, more preferably 19 parts by mass or less, from the viewpoint of further improving the solubility of potassium hydroxide in the alcohol.

[0015] The content of potassium hydroxide in the treatment liquid for peeling laminate resin films is, when the entire treatment liquid for peeling laminate resin films is taken as 100% by mass, preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of further improving the peelability of the laminate resin film, and is preferably 18% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less, from the viewpoint of further improving the solubility of potassium hydroxide and alcohol. Furthermore, the content of potassium hydroxide in the treatment liquid for peeling laminate resin films is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, from the viewpoint of further improving the peelability of the laminate resin film, when the entire treatment liquid for peeling laminate resin films is taken as 100% by mass, and from the viewpoint of further improving the solubility of potassium hydroxide and alcohol and treating waste liquid after peeling treatment, it is preferably 18% by mass or less, more preferably 15% by mass or less, even more preferably 12% by mass or less, even more preferably 10% by mass or less, even more preferably 8% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0016] The content of the amide solvent in the laminate resin film peeling treatment liquid is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 20% by mass or more, and is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, when the entire laminate resin film peeling treatment liquid is taken as 100% by mass. Having an amide solvent content equal to or greater than the above-mentioned lower limit can further improve the peelability of the printed layer of the laminate resin film, which will be described later. Furthermore, having an amide solvent content equal to or less than the above-mentioned upper limit can further improve the solubility of potassium hydroxide in the laminate resin film peeling treatment liquid, thereby further improving the peelability of the laminate resin film.

[0017] In the treatment liquid for peeling laminate resin films, the total content of potassium hydroxide, alcohol, and amide-based solvent, when the entire treatment liquid for peeling laminate resin films is taken as 100% by mass, is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and preferably 100% by mass or less, from the viewpoint of sufficiently treating the laminate resin film with the treatment liquid and further improving the peelability of the laminate resin film.

[0018] In the laminate resin film peeling treatment solution of this embodiment, the alcohol having 3 or less carbon atoms is preferably one or more selected from the group consisting of methanol, ethanol, propyl alcohol (1-propanol), and isopropyl alcohol (2-propanol) from the viewpoint of further improving the solubility of potassium hydroxide. From the viewpoint of further improving peelability, ethanol is more preferable. Furthermore, from the viewpoint of ease of availability, isopropyl alcohol is more preferable. The alcohol containing ethanol as the main component is not particularly limited, but examples include absolute ethanol, hydrous ethanol, and denatured alcohol obtained by adding a denaturant to ethanol. The water content of the hydrous ethanol is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, from the viewpoint of further improving the peelability of the laminate resin film. The ethanol content of the denatured alcohol is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of further improving the peelability of the laminate resin film. Examples of denaturants that can be used include lower alcohols such as methanol, propyl alcohol, and isopropyl alcohol; and ketone solvents such as acetone and methyl ethyl ketone. Furthermore, the treatment liquid for peeling a laminated resin film of this embodiment may further contain a water-soluble organic solvent other than an alcohol or an amide-based solvent for the purpose of adjusting the content of potassium hydroxide or the content of an alcohol or an amide-based solvent.Specific examples of the water-soluble organic solvent include lower alcohols such as methanol, propyl alcohol, and isopropyl alcohol; ketone solvents such as acetone and methyl ethyl ketone; ethylene glycol ethers such as ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (cellosolve), and ethylene glycol monobutyl ether (butyl cellosolve); diethylene glycol ethers such as diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), and diethylene glycol monobutyl ether (butyl carbitol); propylene glycol ethers such as propylene glycol monobutyl ether; etc. These can be used alone or in combination of two or more.

[0019] The amide solvent may be any compound having an amide bond in the molecule, such as β-alkoxy-N-substituted propanamide, N-methylpyrrolidone (NMP) (N-methyl-2-pyrrolidone), dimethylformamide (DMF), diethylformamide (DEF), etc. The laminate resin film peeling treatment liquid of this embodiment preferably contains one or more selected from the group consisting of β-alkoxy-N-substituted propanamide and N-methyl-2-pyrrolidone, more preferably one or more selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, and N-methyl-2-pyrrolidone, and even more preferably one or two selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide and N-methyl-2-pyrrolidone. This can further improve the peelability of the printed layer of the laminate resin film, as described below. The laminated resin film peeling treatment liquid of this embodiment may further contain a surfactant to the extent that the properties and performance of the liquid are not affected. The surfactant is not particularly limited, but examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. These surfactants may be used alone or in combination of two or more.

[0020] <Method for producing treatment liquid for peeling laminate resin film> The method for producing a treatment liquid for peeling laminate resin film of this embodiment preferably includes a step of preparing a mixed solution of potassium hydroxide and alcohol, and a step of adding an amide solvent to the obtained mixed solution. This allows the potassium hydroxide to be sufficiently dissolved in the alcohol, and then the amide solvent to be dissolved, thereby further improving the solubility of both the potassium hydroxide and the amide solvent.

[0021] <Method for Peeling Laminated Resin Film> The method for peeling a laminated resin film of this embodiment includes a peeling step of treating a laminated resin film including a substrate layer and an adhesive layer with the treatment liquid for peeling a laminated resin film described above, thereby peeling at least a portion of the laminated resin film. The treatment liquid for peeling a laminated resin film dissolves the adhesive layer, thereby peeling the substrate layer and adhesive layer that constitute the laminated resin film, and separating the substrate layer, etc. The method for treating the laminated resin film in the peeling step is preferably a method in which the laminated resin film is immersed in the treatment liquid, from the viewpoint of bringing the laminated resin film into sufficient contact with the treatment liquid and further improving the peelability of the laminated resin film.

[0022] Furthermore, the laminate resin film of the present embodiment may further include a printed layer. When the laminate resin film further includes a printed layer, the peeling method for the laminate resin film may further include a step of peeling off the printed layer of the laminate resin film in the peeling step.

[0023] When recycling printed packaging materials such as laminate resin films, ink contamination can cause the recycled raw materials to turn black or gray. This is particularly true when the printed layer is an inner layer of the laminated structure, making it difficult to peel. The laminated resin film peeling treatment solution of this embodiment contains potassium hydroxide, alcohol, and an amide-based solvent. This solution simultaneously peels the substrate layer and adhesive layer of the laminated resin film and removes the printed layer (deinking) during the peeling process of the laminated resin film peeling method. More specifically, the synergistic effect of potassium hydroxide, alcohol, and amide-based solvent in the laminated resin film peeling treatment solution effectively dissolves the adhesive layer of the laminated resin film, thereby enabling the substrate layer and other layers bonded by the adhesive layer to be peeled off. This peeling process exposes the printed layer that was previously an inner layer of the laminated resin film, allowing the printed layer to be peeled off (deinked). Therefore, the resulting recycled resin can be colorless (white). Here, "colorless (white)" means "colorless or white."

[0024] The laminate resin film peeling treatment liquid of this embodiment also contains a basic compound capable of dissolving the adhesive layer of the laminate resin film, such as a metal hydroxide, including potassium hydroxide. Potassium hydroxide can be dissolved in alcohol, thereby reducing the water content in the solvent of the laminate resin film peeling treatment liquid. Reducing the water content in the laminate resin film peeling treatment liquid improves the peelability of laminate resin films that include highly hydrophobic substrate layers.

[0025] The water content in the treatment liquid for peeling a laminate resin film of the present embodiment, when the entire treatment liquid for peeling a laminate resin film is taken as 100% by mass, is preferably 10.0% by mass or less, more preferably 7% by mass or less, even more preferably 5.0% by mass or less, even more preferably 4.5% by mass or less, even more preferably 3.0% by mass or less, even more preferably 1.0% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less, from the viewpoint of further improving the peelability of the laminate resin film.

[0026] Known printing inks can be used for the printed layer. Typical binder resins for printing inks include one or more selected from the group consisting of cellulose-based resins such as soluble nitrocellulose, urethane resins, polyamide resins, vinyl chloride / vinyl acetate copolymers, rosin-based resins and their modified products, ketone resins, polyester resins, and (meth)acrylic resins. Furthermore, the printed layer may or may not contain a curing agent in the ink, depending on the intended use of the laminated resin film. From the perspective of the releasability (deinking) of the printed layer, inks that do not contain a curing agent are preferred. However, the laminated resin film peeling treatment liquid of this embodiment can peel (deink) the printed layer regardless of whether the ink contains a curing agent.

[0027] The adhesive used in the adhesive layer of this embodiment preferably contains a polyisocyanate compound and a polyol compound. The polyisocyanate compound is not particularly limited, but examples thereof include polyisocyanates having 2 to 4 functional groups. Examples of the polyisocyanate compound include polyisocyanate monomers such as aliphatic diisocyanates such as hexamethylene diisocyanate and pentamethylene diisocyanate; alicyclic diisocyanates such as 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4- or 1,3-bis(isocyanatomethyl)cyclohexane; aromatic diisocyanates such as 4,4'- or 2,4'-diphenylmethane diisocyanate or mixtures thereof, and 2,4- or 2,6-tolylene diisocyanate or mixtures thereof; and araliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or mixtures thereof.

[0028] Examples of the polyisocyanate compound include polyisocyanate derivatives derived from the above polyisocyanate monomers, such as dimers, trimers, biurets, and allophanates. Examples of the polyisocyanate compound include polyisocyanate derivatives such as adducts of the above polyisocyanate monomers with low-molecular-weight polyols having a molecular weight of less than 200, such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, glycerol, and trimethylolpropane; and adducts of the above polyisocyanate monomers with polyester polyols, polyether polyols, and natural oil polyols having a molecular weight of 200 to 200,000.

[0029] The polyol compound is not particularly limited, but examples thereof include polyols having preferably 2 to 6, more preferably 2 to 4, functional groups, a number average molecular weight of preferably 200 to 200,000, more preferably 300 to 100,000, and even more preferably 300 to 50,000, and an acid value of preferably 0 to 280 mgKOH / g, more preferably 0 to 100 mgKOH / g, and even more preferably 0 to 50 mgKOH / g.

[0030] Examples of polyol compounds include polyester polyols, polyether polyols, polyurethane polyols, and mixtures thereof. Polyurethane polyols include polyester urethane polyols and polyether urethane polyols, which are polyols having urethane bonds per molecule, such as polyester polyols or polyether polyols having a number-average molecular weight of 200 to 5,000, obtained by reacting the above-mentioned polyisocyanates with the above-mentioned polyisocyanates at an equivalent ratio (NCO / OH) of isocyanate groups to hydroxyl groups of preferably less than 1, more preferably 0.8 or less. The mixing ratio of the polyisocyanate compound and the polyol compound is preferably such that the equivalent ratio (NCO / OH) of isocyanate groups in the polyisocyanate to hydroxyl groups in the polyol is 0.4 to 10, more preferably 0.5 to 2.0. By using the laminate resin film peeling treatment solution of this embodiment, good peelability can be achieved regardless of the composition of the adhesive layer, such as the presence or absence of hydrolyzable ester bonds.

[0031] The substrate layer of this embodiment preferably contains one or more materials selected from the group consisting of polyolefins, polyesters, and polyamides, and more preferably contains polyolefins. Examples of polyolefins include polyethylene, polypropylene, and ethylene-α-olefin copolymers. The laminated resin film peeling treatment solution of this embodiment is particularly suitable for use with polyolefin substrates that are resistant to alkaline solutions. The substrate layer may be a stretched film or a non-stretched film.

[0032] The laminate resin film to be treated in the laminate resin film peeling method of this embodiment may be a laminate resin film laminated with an adhesive, preferably having one of the following laminate structures: substrate layer / adhesive layer / substrate layer, printed layer / substrate layer / adhesive layer / substrate layer, or substrate layer / printed layer / adhesive layer / substrate layer. The laminate resin film peeling method of this embodiment uses the laminate resin film peeling treatment solution of this embodiment, allowing for simultaneous peeling of the substrate layer, adhesive layer, and printed layer. Even in the case of a laminate resin film having a printed layer as an inner layer in the laminate structure, peeling can be performed to expose the printed layer, and the printed layer can be peeled off (deinked). Furthermore, the laminate resin film of this embodiment may include an inorganic layer such as an aluminum vapor deposition layer, an inorganic vapor deposition layer, or a metal foil layer. The laminate resin film peeling treatment solution of this embodiment can also peel off laminate resin films containing an aluminum vapor deposition layer, an inorganic vapor deposition layer, or a metal foil layer.

[0033] When the laminate resin film of the present embodiment has two or more base layers, it is preferable that each base layer is made of the same material. When the laminate resin film has two or more base layers, by making each base layer of the same material, the peeled base layer etc. is made of a single material or something close to that, making it easier to obtain a recycled resin made of a single material, and further improving the efficiency of recycling the laminate film.

[0034] The overall thickness of the laminated resin film of this embodiment is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less. The thickness of the base layer of this embodiment is preferably 10 μm or more, more preferably 20 μm or more, and preferably 150 μm or less, more preferably 100 μm or less. The thickness of the adhesive layer of this embodiment is preferably 1 μm or more, more preferably 2 μm or more, preferably 3 μm or more, and preferably 10 μm or less, more preferably 5 μm or less. The coating amount of adhesive in the adhesive layer is preferably 1 g / m ２ More preferably, 2 g / m ２and preferably 10 g / m ２ Less than 5 g / m, more preferably ２ By setting the thickness of the laminated resin film and the amount of adhesive applied within the above numerical ranges, the peelability of the laminated resin film can be further improved.

[0035] In the peeling step, the temperature when treating the laminate resin film with the treatment liquid is preferably 15°C or higher, more preferably 20°C or higher, even more preferably 30°C or higher, even more preferably 40°C or higher, and even more preferably 45°C or higher, from the viewpoint of further improving the peelability of the laminate resin film, and is preferably 60°C or lower, more preferably 55°C or lower.

[0036] In the peeling step, the time for treating the laminated resin film with the treatment liquid is, from the viewpoint of further improving the peelability of the laminated resin film, preferably 1 hour or more, more preferably 3 hours or more, even more preferably 5 hours or more, even more preferably 8 hours or more, even more preferably 10 hours or more, and is preferably 48 hours or less, more preferably 36 hours or less, even more preferably 24 hours or less, even more preferably 18 hours or less, even more preferably 15 hours or less.

[0037] In the peeling step, when treating the laminate resin film with the treatment solution, stirring or ultrasonic vibration is preferably performed, more preferably ultrasonic vibration, from the viewpoint of further improving the peelability of the laminate resin film. Furthermore, from the viewpoint of further improving the peelability of the laminate resin film, stirring or ultrasonic vibration is preferably performed while maintaining the temperature in the above-mentioned range. When ultrasonic vibration is performed, ultrasonic vibration can be performed using an ultrasonic oscillator, applying ultrasonic waves of, for example, 20 kHz to 150 kHz.

[0038] The method for peeling a laminate resin film according to this embodiment includes a step of fragmenting the laminate resin film to further improve the releasability of the laminate resin film. Examples of fragmenting include crushing the laminate resin film with a crusher or cutting it with a cutter. The size of the fragments is preferably 3 mm × 3 mm or more, more preferably 5 mm × 5 mm or more, and even more preferably 8 mm × 8 mm or more, and preferably 20 mm × 20 mm or less, more preferably 15 mm × 15 mm or less, and even more preferably 12 mm × 12 mm or less. The size of the fragments is preferably 3 mm diameter or more, more preferably 5 mm diameter or more, and preferably 8 mm diameter or more, and preferably 20 mm diameter or less, more preferably 15 mm diameter or less, and even more preferably 12 mm diameter or less. The fragmenting step is preferably performed before the peeling step to thoroughly contact the laminate resin film with a treatment solution and further improve the releasability of the laminate resin film.

[0039] <Method for Producing Recycled Resin> The method for producing recycled resin of this embodiment includes a peeling step of peeling at least a portion of a laminate resin film using the method for peeling a laminate resin film of this embodiment. A suitable example of the method for producing recycled resin of this embodiment is the following method. First, for example, used or unused laminate resin films in the distribution market, or laminate resin films in the manufacturing stages of printing, laminating, bag making, etc. in molded products, converters, etc., are collected. Next, if necessary, the collected laminate resin film is cut into small pieces. Next, the collected laminate resin film is peeled using the method for peeling a laminate resin film of this embodiment, and resin pieces from which the adhesive layer and printed layer have been removed are extracted. Next, if necessary, the peeled resin pieces are granulated. This allows recycled resin to be produced. Producing recycled resin from laminate resin film using the method for producing recycled resin of this embodiment can reduce waste plastic and the consumption of fossil fuel resources.

[0040] The present invention includes the following aspects: 1. A treatment liquid for peeling a laminate resin film, comprising potassium hydroxide, ethanol, and an amide-based solvent, wherein the laminate resin film comprises a substrate layer and an adhesive layer. 2. The treatment liquid for peeling a laminate resin film according to 1., wherein the content of the potassium hydroxide is 1 part by mass or more and 20 parts by mass or less when the total content of the potassium hydroxide and the ethanol in the treatment liquid for peeling a laminate resin film is taken as 100 parts by mass. 3. The treatment liquid for peeling a laminate resin film according to 1. or 2., wherein the content of the amide-based solvent is 1% by mass or more and 60% by mass or less when the entire treatment liquid for peeling a laminate resin film is taken as 100% by mass. 4. The treatment liquid for peeling a laminate resin film according to any one of 1. to 3., wherein the amide-based solvent comprises a β-alkoxy-N-substituted propanamide. 5. The treatment liquid for peeling a laminate resin film according to any one of 1. to 4., wherein the content of the potassium hydroxide is 0.5% by mass or more and 18% by mass or less, when the total mass of the treatment liquid for peeling a laminate resin film is taken as 100% by mass. 6. The treatment liquid for peeling a laminate resin film according to any one of 1. to 5., wherein the total content of the potassium hydroxide, the ethanol, and the amide-based solvent is 70% by mass or more and 100% by mass or less, when the total mass of the treatment liquid for peeling a laminate resin film is taken as 100% by mass. 7. The treatment liquid for peeling a laminate resin film according to any one of 1. to 6., wherein the treatment liquid for peeling a laminate resin film is obtained by adding the amide-based solvent to a mixed solution of the potassium hydroxide and the ethanol. 8. A method for peeling a laminate resin film, comprising a peeling step of treating a laminate resin film comprising a base layer and an adhesive layer with the treatment liquid for peeling a laminate resin film according to any one of 1. to 7., thereby peeling at least a portion of the laminate resin film. 9. The method for peeling a laminate resin film according to 8., wherein the laminate resin film further comprises a printed layer. 10. The method for peeling off a laminated resin film according to 8. or 9., wherein the adhesive layer contains a polyisocyanate compound and a polyol compound. 11. The method for peeling off a laminated resin film according to any one of 8. to 10., wherein the base layer contains a polyolefin.12. The method for peeling a laminate resin film according to any one of 9. to 11., wherein the laminate resin film has one layer structure selected from the group consisting of substrate layer / adhesive layer / substrate layer, printed layer / substrate layer / adhesive layer / substrate layer, and substrate layer / printed layer / adhesive layer / substrate layer. 13. The method for peeling a laminate resin film according to any one of 8. to 12., wherein, when the laminate resin film has two or more substrate layers, each of the substrate layers is made of the same material. 14. The method for peeling a laminate resin film according to any one of 8. to 13., wherein, in the peeling step, the laminate resin film is immersed in the treatment liquid for peeling a laminate resin film. 15. The method for peeling a laminate resin film according to any one of 8. to 14., wherein, in the peeling step, the treatment is performed at a temperature of 15°C or higher and 60°C or lower. 16. The method for peeling a laminate resin film according to any one of 8. to 15., wherein, in the peeling step, the laminate resin film and the treatment liquid for peeling a laminate resin film are stirred or ultrasonically vibrated. 17. A method for peeling a laminate resin film according to any one of items 8. to 16., further comprising a step of cutting the laminate resin film into small pieces. 18. A method for producing a treatment solution for peeling a laminate resin film according to any one of items 1. to 7., comprising the steps of preparing a mixed solution of potassium hydroxide and ethanol, and adding an amide solvent to the mixed solution. 19. A method for producing recycled resin, comprising a peeling step of peeling at least a portion of a laminate resin film by the method for peeling a laminate resin film according to any one of items 8. to 17.

[0041] The following materials were used in the laminate film peeling treatment solutions of the Examples and Comparative Examples.

[0042] Potassium hydroxide 1: potassium hydroxide Alcohol 1: ethanol (ethanol content: 99.5% by mass) Alcohol 2: ethanol (ethanol content: 90% by mass) Alcohol 3: isopropyl alcohol Amide solvent 1: 3-methoxy-N,N-dimethylpropanamide (CAS.RN: 53185-52-7), KJCMPA (registered trademark)-100 (manufactured by KJ Chemicals Co., Ltd.) Amide solvent 2: N-methyl-2-pyrrolidone Non-amide solvent 1: butyl cellosolve Basic solvent 1: morpholine

[0043] <Preparation of treatment liquid for peeling laminated films> A mixed solution of potassium hydroxide and alcohol was prepared according to the treatment liquid composition (unit: parts by mass) shown in Table 1, and then an amide-based solvent was added to prepare the treatment liquid for peeling laminated films of each example.

[0044] The following materials were used for the laminated resin film. (Films) OPP film 1: biaxially oriented polypropylene film, 20 μm, Pylen (registered trademark) film - OT P2161, manufactured by Toyobo Co., Ltd. OPP film 2: biaxially oriented polypropylene film, 20 μm, U-1, manufactured by Mitsui Chemicals Tohcello, Inc. CPP film: unstretched polypropylene film, 20 μm, Pylen (registered trademark) film - CT P1128, manufactured by Toyobo Co., Ltd. VMCPP film: aluminum-deposited unstretched polypropylene film, 25 μm, MLCP WS, manufactured by Mitsui Chemicals Tohcello, Inc. (Adhesives) Adhesive 1: polyether urethane polyol, Takelac (registered trademark) A-951, manufactured by Mitsui Chemicals, Inc. Adhesive 2: polyisocyanate, Takenate (registered trademark) A-91, manufactured by Mitsui Chemicals, Inc. (Printing layer inks) Ink 1: Gravure ink for lamination, Bellcolor R White 115, manufactured by Sakata Inx Corporation. Ink 2: Gravure ink for lamination, LP Bio R92 Black N2, manufactured by Toyo Ink Co., Ltd.. Ink 3: Gravure ink for lamination, LP Bio R39 Indigo N1, manufactured by Toyo Ink Co., Ltd.. Ink 4: Gravure ink for lamination, LP Bio F121 Red N1, manufactured by Toyo Ink Co., Ltd.. Ink 5: Gravure ink for lamination, LP Bio F23 Yellow N1, manufactured by Toyo Ink Co., Ltd.. Ink 6: Gravure ink for lamination, LP Bio S R641 White B1, manufactured by Toyo Ink Co., Ltd.. Hardener 1: Lamiall R, manufactured by Sakata Inx Corporation.

[0045] <Preparation of Laminated Resin Films> Laminated films 1 to 4 were prepared according to the following procedure. <Printing Method> The above printing ink was printed on an OPP film using a gravure printing machine. When a curing agent was used, the ink was mixed with the curing agent before printing on the OPP film. (Laminated Resin Film 1) A mixture of adhesive 1 and adhesive 2 (mixing mass ratio of adhesive 1:adhesive 2=1:1) was applied to OPP film 1 at a solid content of 3 g / m ２The adhesive was applied in an amount of 100 ppm or more and then laminated to a CPP film. The laminated laminate resin film was subjected to an aging reaction at 40°C for 72 hours to obtain a laminate resin film 1 having an OPP (no printed layer) / adhesive layer / CPP structure. (Laminate Resin Film 2) The above-mentioned ink 1 (no curing agent) was printed on the OPP film 1 using the above-mentioned <Printing Method> to obtain an OPP film 1 with a printed layer (no curing agent). The laminate resin film 1 was produced in the same manner as the laminate resin film 1, except that the OPP film 1 in the laminate resin film 1 was replaced with an OPP film 1 with a printed layer (no curing agent), and an adhesive (a mixture of adhesive 1 and adhesive 2) was applied to the surface of the printed layer, to obtain a laminate resin film 2 having an OPP (with printed layer (no curing agent)) / adhesive layer / CPP structure. (Laminate Resin Film 3) OPP Film 2 was printed with the above-mentioned inks 2 to 5 (without curing agent) and ink 6 (with curing agent) in the order of the ink numbers using the above-mentioned <Printing Method>, thereby obtaining OPP Film 2 with a printed layer (with curing agent). Laminated resin film 1 was produced in the same manner as laminated resin film 1, except that OPP Film 1 in laminated resin film 1 was replaced with OPP Film 2 with a printed layer (with curing agent), and an adhesive (a mixture of Adhesive 1 and Adhesive 2) was applied to the surface of the printed layer, thereby obtaining laminated resin film 3 with an OPP (with printed layer (with curing agent)) / adhesive layer / CPP configuration. (Laminate Resin Film 4) Laminated resin film 4 was produced in the same manner as laminated resin film 3, except that the CPP film in laminated resin film 3 was replaced with a VMCPP film, thereby obtaining laminated resin film 4 with an OPP (with printed layer (with curing agent)) / adhesive layer / VMCPP configuration. (Laminate Resin Film 5) The above inks 1 to 6 (without curing agent) were printed on top of each other in the order of the ink numbers using the above <Printing Method> to obtain OPP Film 3 with a printed layer (without curing agent). Except for changing OPP Film 1 in Laminate Resin Film 1 to OPP Film 3 with a printed layer (without curing agent), and applying an adhesive (a mixture of Adhesive 1 and Adhesive 2) to the surface of the printed layer side, production was performed in the same manner as Laminate Resin Film 1, to obtain Laminate Resin Film 5 having a configuration of OPP (with printed layer (without curing agent)) / adhesive layer / CPP.

[0046] <Slicing of Laminated Resin Film> According to the slicing conditions in Table 1, the obtained laminated resin films 1 and 3 were cut into pieces of 10 mm x 10 mm using a cutter. The cut pieces were approximately square, with each piece measuring 10 mm on a side. Furthermore, laminated resin films 2 to 4 were passed through a pulverizer (SRH3-360TRFS, manufactured by HORAI Co., Ltd.) using a screen with a mesh diameter of 6 mmφ or 10 mmφ, and small piece samples that passed through each screen were collected. The shapes of the crushed small pieces were random.

[0047] Treatment of Laminate Resin Film with Treatment Solution: According to the treatment conditions in Table 1, small pieces of laminate resin films 1 to 4 were treated with the laminate film peeling treatment solution of each example. 0.1 g of laminate resin film and 20 g of the laminate film peeling treatment solution were placed in a glass container, and the sealed glass container was heated to 50°C. For stirring, a magnetic stirrer with a heater was used, stirring was performed with a stirrer tip. For ultrasonic treatment, the temperature was maintained at 50°C in an ultrasonic cleaner with a heating function (As One Corporation, Model US-2), and ultrasonic treatment was performed at 38 kHz. In both cases, stirring or ultrasonic treatment was performed while maintaining the temperature at 50°C, and releasability was evaluated after 2, 6, and 12 hours.

[0048] <Evaluation of peelability of laminate resin film> After treatment with the treatment solution for peeling laminate resin film, peelability of the laminate resin film was evaluated visually and by FT-IR according to the following criteria. A is considered to be pass. (Criteria) A: In a small piece of laminate resin film, it was visually confirmed that the printed layer had completely disappeared, and FT-IR confirmed that it was just the film. B: In a small piece of laminate resin film, it was visually confirmed that part of the printed layer remained. C: In a small piece of laminate resin film, it was visually confirmed that there was no change in the printed layer compared to before treatment.

[0049]

[0050] In each example in Table 1, the laminated resin film marked with "O" was used as the film, and the conditions marked with "O" were used as the fragmentation conditions.

[0051] This application claims priority based on Japanese Patent Application No. 2022-211580, filed December 28, 2022, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A treatment liquid for peeling a laminated resin film, comprising: potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, wherein the laminated resin film includes a base material layer and an adhesive layer, and is a treatment liquid for peeling a laminated resin film.

2. The treatment liquid for peeling a laminated resin film according to Claim 1, wherein when the total content of the potassium hydroxide and the alcohol in the treatment liquid for peeling a laminated resin film is 100 parts by mass, the content of the potassium hydroxide is 1 part by mass or more and 20 parts by mass or less.

3. The treatment liquid for peeling a laminated resin film according to Claim 1 or 2, wherein when the total amount of the treatment liquid for peeling a laminated resin film is 100% by mass, the content of the amide-based solvent is 1% by mass or more and 60% by mass or less.

4. The treatment liquid for peeling a laminated resin film according to Claim 1 or 2, wherein the amide-based solvent includes one or more selected from the group consisting of β-alkoxy-N-substituted propanamide and N-methyl-2-pyrrolidone.

5. The treatment liquid for peeling a laminated resin film according to Claim 1 or 2, wherein when the total amount of the treatment liquid for peeling a laminated resin film is 100% by mass, the content of the potassium hydroxide is 0.5% by mass or more and 18% by mass or less.

6. The treatment liquid for peeling a laminated resin film according to Claim 1 or 2, wherein when the total amount of the treatment liquid for peeling a laminated resin film is 100% by mass, the total content of the potassium hydroxide, the alcohol, and the amide-based solvent is 70% by mass or more and 100% by mass or less.

7. The treatment liquid for peeling a laminated resin film according to Claim 1 or 2, wherein the treatment liquid for peeling a laminated resin film is obtained by adding the amide-based solvent to a mixed solution of the potassium hydroxide and the alcohol.

8. The treatment liquid for peeling a laminated resin film according to Claim 1 or 2, wherein when the total amount of the treatment liquid for peeling a laminated resin film is 100% by mass, the water content in the treatment liquid for peeling a laminated resin film is 10.0% by mass or less.

9. A method for peeling a laminated resin film, comprising a peeling step of peeling at least a part of the laminated resin film by treating the laminated resin film including a base material layer and an adhesive layer with the treatment liquid for peeling a laminated resin film according to Claim 1 or 2.

10. The method for peeling a laminated resin film according to Claim 9, wherein the laminated resin film further includes a printing layer.

11. The method for peeling a laminated resin film according to claim 9, wherein the adhesive layer contains a polyisocyanate compound and a polyol compound.

12. The method for peeling a laminated resin film according to claim 9, wherein the base material layer contains a polyolefin.

13. The method for peeling a laminated resin film according to claim 10, wherein the laminated resin film has one kind of laminated structure selected from the group consisting of a base material layer / adhesive layer / base material layer, a printing layer / base material layer / adhesive layer / base material layer, and a base material layer / printing layer / adhesive layer / base material layer.

14. The method for peeling a laminated resin film according to claim 9, wherein when the laminated resin film has two or more base material layers, each of the base material layers is made of the same material.

15. The method for peeling a laminated resin film according to claim 9, wherein in the peeling step, the laminated resin film is immersed in the treatment liquid for peeling the laminated resin film.

16. The method for peeling a laminated resin film according to claim 9, wherein in the peeling step, the treatment is performed at a temperature of 15°C or higher and 60°C or lower.

17. The method for peeling a laminated resin film according to claim 9, wherein in the peeling step, the laminated resin film and the treatment liquid for peeling the laminated resin film are stirred or ultrasonically vibrated.

18. The method for peeling a laminated resin film according to claim 9, further comprising a step of fragmenting the laminated resin film into small pieces.

19. A method for producing a treatment liquid for peeling a laminated resin film according to claim 1 or 2, comprising: a step of preparing a mixed solution of potassium hydroxide and the alcohol; a step of adding an amide-based solvent to the mixed solution. A method for producing a treatment liquid for peeling a laminated resin film.

20. A method for producing a recycled resin, comprising a peeling step of peeling at least a part of a laminated resin film by the method for peeling a laminated resin film according to claim 9.