Method for producing recycled resin

Abstract

This method for producing a recycled resin comprises, in order, a first treatment step in which a laminated resin film is treated with a treatment liquid 1 containing potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, and a second treatment step in which the laminated resin film is treated with a treatment liquid 2 containing an amide-based solvent. The laminated resin film includes an adhesive layer and a printing layer.

Description

Recycled resin manufacturing method

[0001] The present invention relates to 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 Documents 1 and 2.

[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 method for producing recycled resin that can remove an adhesive layer and a printed layer from a laminated resin film and can shorten the processing time.

[0007] According to the present invention, there is provided a method for producing recycled resin as follows.

[0008] [1] A method for producing recycled resin, comprising: a first treatment step of treating a laminate resin film with a treatment liquid 1 containing potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent; and a second treatment step of treating the laminate resin film with a treatment liquid 2 containing an amide-based solvent, in this order, wherein the laminate resin film comprises an adhesive layer and a printed layer. [2] The method for producing recycled resin according to [1], wherein the amide-based solvents contained in the treatment liquid 1 and the treatment liquid 2 each contain N-methyl-2-pyrrolidone. [3] The method for producing recycled resin according to [1] or [2], wherein the treatment liquid 2 further contains a surfactant. [4] The method for producing recycled resin according to any of [1] to [3], wherein the treatment liquid 2 further contains a high-boiling point solvent. [5] The method for producing recycled resin according to any of [1] to [4], wherein in the first treatment step, the laminate resin film is treated with the treatment liquid 1 while ultrasonically vibrating the laminate resin film. [6] The method for producing a recycled resin according to any one of [1] to [5], wherein in the second treatment step, the laminate resin film is treated with the treatment liquid 2 while ultrasonically vibrating the laminate resin film. [7] The method for producing a recycled resin according to any one of [1] to [6], further comprising an amide-based solvent regeneration step of recovering one or more treatment liquids selected from the group consisting of the treatment liquid 1 after the first treatment step and the treatment liquid 2 after the second treatment step, and regenerating the amide-based solvent. [8] The method for producing a recycled resin according to any one of [1] to [7], wherein the content of the amide-based solvent in the treatment liquid 1 is 1% by mass or more and 60% by mass or less, when the total amount of the treatment liquid 1 is taken as 100% by mass. [9] The method for producing a recycled resin according to any one of [1] to [8], wherein the content of potassium hydroxide in the treatment liquid 1 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 having 3 or less carbon atoms is taken as 100 parts by mass.

[10] The method for producing a recycled resin according to any one of [1] to [8], wherein the content of potassium hydroxide in the treatment solution 1 is 0.1 parts by mass or more and 20 parts by mass or less when the total content of the potassium hydroxide and the alcohol having 3 or less carbon atoms is 100 parts by mass.

[11] The method for producing a recycled resin according to any one of [1] to

[10] , wherein the content of the amide-based solvent in the treatment liquid 2 is 90% by mass or more when the total amount of the treatment liquid 2 is taken as 100% by mass.

[12] The method for producing a recycled resin according to any one of [1] to

[10] , wherein the content of the amide-based solvent in the treatment liquid 2 is 70% by mass or more when the total amount of the treatment liquid 2 is taken as 100% by mass.

[13] The method for producing a recycled resin according to any one of [1] to

[12] , further comprising, after the first treatment step, a separation step of separating the treatment liquid 1 from a mixture of the laminate resin film and the treatment liquid 1.

[14] The method for producing a recycled resin according to any one of [1] to

[13] , further comprising, after the second treatment step, a granulation step of granulating the laminate resin film.

[15] The method for producing a recycled resin according to any one of [1] to

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

[16] The method for producing a recycled resin according to any one of [1] to

[15] , wherein the adhesive layer contains a polyurethane resin.

[17] The method for producing recycled resin according to any one of [1] to

[16] , wherein the film constituting the laminated resin film contains a polyolefin resin.

[0009] According to the present invention, it is possible to provide a method for producing recycled resin that can remove an adhesive layer and a printed layer from a laminated resin film and can shorten the processing time.

[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 method for producing recycled resin of this embodiment includes, in this order, a first treatment step of treating a laminated resin film with treatment liquid 1 containing potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, and a second treatment step of treating the laminated resin film with treatment liquid 2 containing an amide-based solvent, and the laminated resin film includes an adhesive layer and a printing layer.

[0012] In the recycled resin manufacturing method of this embodiment, the first treatment step is a step of immersing a laminate resin film in treatment liquid 1 to peel off each layer. The potassium hydroxide contained in treatment liquid 1 decomposes the adhesive layer and printed layer of the laminate resin film and allows them to be removed from the laminate resin film. The alcohol having 3 or fewer carbon atoms contained in treatment liquid 1 can improve the solubility of potassium hydroxide. Furthermore, the amide-based solvent contained in treatment liquid 1 can further improve the penetration of treatment liquid 1 into the spaces between the layers of the laminate resin film. The second treatment step is a step of dissolving the adhesive layer and printed layer decomposed in the first treatment step in treatment liquid 2 and cleaning them. By containing the amide-based solvent, treatment liquid 2 can improve the cleanability of the adhesive layer and printed layer decomposed in the first treatment step. Furthermore, by performing the second treatment step in addition to the first treatment step, the cleanability of the adhesive layer and printed layer of the laminate resin film can be improved, thereby shortening the treatment times of the first and second treatment steps and shortening the overall treatment time of the recycled resin manufacturing method of this embodiment. In addition, the method for producing recycled resin in this embodiment is a method for obtaining recycled resin raw material by peeling, dissolving, and removing the adhesive layer and printed layer from the laminated resin film, and recovering the resin contained in each layer (e.g., base layer, etc.) of the laminated resin film.

[0013] (Treatment Solution 1 and Treatment Solution 2) Treatment solution 1 of this embodiment contains potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, and treatment solution 2 of this embodiment contains an amide-based solvent. The components of treatment solution 1 and treatment solution 2 will be described below.

[0014] The content of the amide solvent in treatment liquid 1 of this embodiment is preferably 1% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 60% by mass or less, and even more preferably 40% by mass or more and 55% by mass or less, when the total amount of treatment liquid 1 is taken as 100% by mass. When the content of the amide solvent in treatment liquid 1 is equal to or greater than the above-mentioned lower limit, the removability of the adhesive layer and the printed layer can be further improved. Furthermore, when the content of the amide solvent in treatment liquid 1 is equal to or less than the above-mentioned upper limit, the solubility of potassium hydroxide in treatment liquid 1 can be further improved, and the removability of the adhesive layer and the printed layer can be further improved.

[0015] The content of potassium hydroxide in treatment liquid 1 of this embodiment, when the total amount of treatment liquid 1 is taken as 100% by mass, is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.2% by mass or more and 20% by mass or less, even more preferably 0.5% by mass or more and 20% by mass or less, even more preferably 1.0% by mass or more and 10% by mass or less, and even more preferably 1.5% by mass or more and 5% by mass or less. When the content of potassium hydroxide in treatment liquid 1 is equal to or greater than the above-mentioned lower limit, the decomposition of the resin (e.g., polyurethane) contained in the adhesive layer described below can be further improved, and the removability of the adhesive layer and the printed layer can be further improved. Furthermore, when the content of potassium hydroxide in treatment liquid 1 is equal to or greater than the above-mentioned lower limit, the removability of the adhesive layer and the printed layer can be further improved, and the time required for the first treatment step described below can be further shortened. Furthermore, when the content of potassium hydroxide in treatment liquid 1 is equal to or less than the above-mentioned upper limit, the solubility of potassium hydroxide in alcohol can be further improved, and waste liquid treatment after the stripping treatment can be more efficiently performed.

[0016] Furthermore, the content of potassium hydroxide in treatment liquid 1 is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.2 parts by mass or more and 20 parts by mass or less, even more preferably 1 part by mass or more and 20 parts by mass or less, even more preferably 1.5 parts by mass or more and 15 parts by mass or less, even more preferably 2 parts by mass or more and 10 parts by mass or less, and even more preferably 2 parts by mass or more and 5 parts by mass or less, when the total content of potassium hydroxide and the alcohol having 3 or less carbon atoms is 100 parts by mass.

[0017] In treatment liquid 1, the total content of potassium hydroxide, the alcohol having 3 or less carbon atoms, and the amide-based solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 98% by mass or more, when the total amount of treatment liquid 1 is taken as 100% by mass, from the viewpoint of sufficiently treating the laminated resin film with the treatment liquid and further improving the removability of the adhesive layer and the printed layer, and may be, for example, 100% by mass or less, or may be less than 100% by mass.

[0018] Treatment liquid 1 of this embodiment contains potassium hydroxide. Potassium hydroxide can be dissolved in alcohols having 3 or less carbon atoms, which makes it possible to reduce the water content in treatment liquid 1. Reducing the water content in treatment liquid 1 makes it possible to further improve the removability of the adhesive layer and the printed layer when the laminate resin film includes a substrate layer, which will be described later, and further includes a highly hydrophobic substrate layer.

[0019] The water content in the treatment liquid 1 of this embodiment is preferably 10.0% by mass or less, more preferably 5.0% by mass or less, and even more preferably 3.0% by mass or less, from the viewpoint of further improving the removability of the adhesive layer and the printing layer, when the total amount of the treatment liquid 1 is 100% by mass.

[0020] The treatment liquid 1 of this embodiment contains an alcohol having three or fewer carbon atoms. The alcohol having three or fewer carbon atoms preferably contains one or more selected from the group consisting of methanol, ethanol, propyl alcohol (1-propanol), and isopropyl alcohol (2-propanol) in order to further improve the solubility of potassium hydroxide. Ethanol is more preferably contained in order to further improve the removability of the adhesive layer and the printed layer. The alcohol containing ethanol as the main component is not particularly limited, but examples include absolute ethanol, aqueous ethanol, and denatured alcohol obtained by adding a denaturant to ethanol. The water content of the aqueous ethanol is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less in order to further improve the removability of the adhesive layer and the printed layer. 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 in order to further improve the removability of the adhesive layer and the printed layer. 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 1 of this embodiment may further contain a water-soluble organic solvent other than alcohols or amide-based solvents in order to adjust the content of potassium hydroxide or the content of alcohols or amide-based solvents.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; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol; etc. These can be used alone or in combination of two or more.

[0021] The content of the amide solvent in treatment liquid 2 of this embodiment 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, and even more preferably 98% by mass or more, when the total amount of treatment liquid 2 is taken as 100% by mass. There is no upper limit for the content of the amide solvent in treatment liquid 2, but it may be, for example, 100% by mass or less, or 99.5% by mass or less. Furthermore, the content of the amide solvent in treatment liquid 2 of this embodiment may be 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 98% by mass or more and 99.5% by mass or less, when the total amount of treatment liquid 2 is taken as 100% by mass. By having the content of the amide solvent in treatment liquid 2 be equal to or greater than the above-mentioned lower limit, the cleanability of the adhesive layer and the printing layer decomposed in the first treatment step can be further improved.

[0022] Furthermore, it is preferable that treatment liquid 2 does not contain alcohol. By not containing alcohol, the solubility of the adhesive layer and the printed layer decomposed in the first treatment step in treatment liquid 2 is further improved, and the cleanability with treatment liquid 2 can be further improved. The alcohol content in treatment liquid 2 is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, when the total amount of treatment liquid 2 is taken as 100% by mass, and may be 0% by mass or more, preferably 0% by mass. Note that the above alcohol does not include alcohols that fall under the category of high-boiling point solvents (e.g., glycols, described below).

[0023] The amide-based solvents contained in Treatment Liquid 1 and Treatment Liquid 2 in this embodiment each preferably contain one or more solvents selected from the group consisting of β-alkoxy-N-substituted propanamides and N-methyl-2-pyrrolidone, more preferably one or more solvents 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 solvents selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide and N-methyl-2-pyrrolidone. By including the amide-based solvent in Treatment Liquid 1, the penetration of Treatment Liquid 1 into the spaces between the layers of the laminated resin film, which is insufficient when using only an alcohol having 3 or fewer carbon atoms, can be further improved, thereby further improving the removability of the adhesive layer and the printed layer. By including the amide-based solvent in Treatment Liquid 2, the cleanability of the adhesive layer and the printed layer decomposed in the first treatment step can be further improved. More preferably, the amide solvents contained in treatment liquid 1 and treatment liquid 2 each contain N-methyl-2-pyrrolidone. By containing N-methyl-2-pyrrolidone in both treatment liquid 1 and treatment liquid 2, the efficiency of the amide solvent regeneration step and the reuse of the resulting regenerated amide solvent, which will be described later, can be further improved.

[0024] Treatment liquid 2 in this embodiment preferably further contains a surfactant. By including a surfactant, the cleanability of the decomposed adhesive layer and printed layer in the second treatment step can be further improved. The surfactant is not particularly limited in composition as long as it is dissolved or mixed in N-methyl-2-pyrrolidone, but one or more surfactants selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used. Of these, one or more surfactants selected from the group consisting of nonionic surfactants and anionic surfactants are preferably used.

[0025] In this embodiment, the treatment liquid 2 preferably further contains a high-boiling-point solvent. A high-boiling-point solvent is a solvent with a high boiling point, and its boiling point is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher. There is no particular upper limit to the boiling point of the high-boiling-point solvent, but it may be, for example, 300°C or lower, or 290°C or lower. By including a high-boiling-point solvent in the treatment liquid 2, the efficiency of distillation of the amide-based solvent in the amide-based solvent regeneration step described below can be further improved, and thus the efficiency of reuse of the obtained regenerated amide-based solvent can be further improved. Specific examples of high-boiling-point solvents include one or more selected from the group consisting of glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol.

[0026] The content of the high-boiling point solvent in the treatment liquid 2 of this embodiment is preferably 0% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 20% by mass or less, even more preferably 3% by mass or more and 15% by mass or less, and even more preferably 5% by mass or more and 12% by mass or less, when the total amount of the treatment liquid 2 is taken as 100% by mass. When the content of the high-boiling point solvent in the treatment liquid 2 is within the above range, the efficiency of distillation of the amide solvent in the amide solvent regeneration step can be further improved, and therefore the efficiency of reuse of the obtained regenerated amide solvent can be further improved.

[0027] The content of the high-boiling point solvent in treatment liquid 2 of this embodiment is preferably 0 to 40 parts by mass, more preferably 1 to 30 parts by mass, even more preferably 3 to 20 parts by mass, and even more preferably 5 to 15 parts by mass, when the total amount of the amide-based solvent in treatment liquid 2 is taken as 100 parts by mass. When the content of the high-boiling point solvent in treatment liquid 2 is within the above range, the efficiency of distillation of the amide-based solvent in the amide-based solvent regeneration step can be further improved, and thus the efficiency of reuse of the obtained regenerated amide-based solvent can be further improved.

[0028] (First Processing Step and Second Processing Step) Hereinafter, the conditions for the first processing step and the second processing step will be described.

[0029] In the method for producing recycled resin according to this embodiment, it is preferable to treat the laminate resin film with treatment liquid 1 while ultrasonically vibrating the laminate resin film in the first treatment step, and then treat the laminate resin film with treatment liquid 2 while ultrasonically vibrating the laminate resin film in the second treatment step. By using ultrasonic vibration in the first treatment step, the permeability of treatment liquid 1 between the layers of the laminate resin film and the removability of the adhesive layer and printed layer can be improved, and the time required for the first treatment step can be further shortened. By using ultrasonic vibration in the second treatment step, the cleanability of the adhesive layer and printed layer decomposed in the first treatment step can be further improved, and the time required for the second treatment step can be further shortened. Furthermore, by using ultrasonic cleaning in both the first and second treatment steps, the efficiency of dissolving, decomposing, cleaning, etc. of the laminate resin film can be further improved in the method for producing recycled resin according to this embodiment, and the time required for the entire process can be further shortened. When ultrasonic vibration is used, ultrasonic vibration can be applied using an ultrasonic oscillator, for example, at a frequency of 20 kHz to 150 kHz.

[0030] In addition, in the method for producing recycled resin of this embodiment, it is preferable that in the first treatment step, the laminate resin film is treated with treatment liquid 1 while being agitated, and in the second treatment step, the laminate resin film is treated with treatment liquid 2 while being agitated. More preferably, in both the first treatment step and the second treatment step, the laminate resin film is subjected to both ultrasonic treatment and agitation. This can further improve the efficiency of the removability of the adhesive layer and the printed layer in the method for producing recycled resin of this embodiment, and further shorten the time required for all steps.

[0031] In addition, it is preferable that the ultrasonic treatment and stirring in the first treatment step and the second treatment step be carried out throughout the treatment time in each of the first treatment step and the second treatment step, while maintaining the temperature in each of the first treatment step and the second treatment step, as described below.

[0032] In the first treatment step, the temperature when treating the laminated resin film with treatment liquid 1 is preferably 20°C or higher and 80°C or lower, more preferably 20°C or higher and 60°C or lower, and even more preferably 40°C or higher and 60°C or lower, from the viewpoint of further improving the removability of the adhesive layer and the printed layer.

[0033] In the first treatment step, the concentration of the laminate resin film relative to the total amount of treatment liquid 1 is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 9% by mass or less, and even more preferably 3% by mass or more and 8% by mass or less. When the concentration of the laminate resin film relative to the total amount of treatment liquid 1 in the first treatment step is at least the above-mentioned lower limit, the treatment efficiency of the laminate resin film in the first treatment step can be further improved. Furthermore, when the concentration of the laminate resin film relative to the total amount of treatment liquid 1 in the first treatment step is at most the above-mentioned upper limit, the removability of the adhesive layer and the printed layer can be further improved.

[0034] In the second treatment step, the temperature when treating the laminated resin film with treatment liquid 2 is preferably 20°C or higher and 80°C or lower, more preferably 20°C or higher and 60°C or lower, and even more preferably 40°C or higher and 60°C or lower, from the viewpoint of further improving the removability of the adhesive layer and the printed layer.

[0035] In the second treatment step, the concentration of the laminate resin film relative to the total amount of treatment liquid 2 is preferably 1% by mass or more and 15% by mass or less, more preferably 3% by mass or more and 12% by mass or less. When the concentration of the laminate resin film relative to the total amount of treatment liquid 2 in the second treatment step is equal to or more than the above-mentioned lower limit, the treatment efficiency of the laminate resin film in the second treatment step can be further improved. Furthermore, when the concentration of the laminate resin film relative to the total amount of treatment liquid 2 in the second treatment step is equal to or less than the above-mentioned upper limit, the removability of the adhesive layer and the printed layer can be further improved.

[0036] The treatment times in the first and second treatment steps in the recycled resin manufacturing method of this embodiment can be adjusted appropriately depending on the treatment volume (amount of laminate resin film and amount of treatment solution) to be treated in each step. Increasing the treatment volume requires a longer treatment time. The recycled resin manufacturing method of this embodiment can shorten the treatment time required for the entire process even when the treatment volume in the first and second treatment steps is increased. Furthermore, the treatment times in the first and second treatment steps in the recycled resin manufacturing method of this embodiment need to be extended if the ink in the printed layer of the laminate resin film contains a curing agent. The recycled resin manufacturing method of this embodiment can shorten the treatment time required for the entire process even if the ink in the printed layer of the laminate resin film contains a curing agent.

[0037] (Amide-Based Solvent Regeneration Step) The method for producing a recycled resin according to this embodiment preferably further includes an amide-based solvent regeneration step in which one or more treatment liquids selected from the group consisting of treatment liquid 1 after the first treatment step and treatment liquid 2 after the second treatment step are recovered and the amide-based solvent is regenerated. After being regenerated, the amide-based solvent in the one or more treatment liquids selected from the group consisting of treatment liquid 1 and treatment liquid 2 can be reused in one or more treatment liquids selected from the group consisting of treatment liquid 1 and treatment liquid 2. This allows for a further reduction in the amount of amide-based solvent discarded in all steps of the method for producing a recycled resin.

[0038] Specifically, the method for regenerating an amide-based solvent from one or more treatment liquids selected from the group consisting of recovered treatment liquid 1 and treatment liquid 2 (hereinafter collectively referred to as "treatment liquids") can be carried out as follows. First, the potassium hydroxide in the recovered treatment liquid is neutralized. For example, the potassium concentration in the treatment liquid is measured by titration with hydrochloric acid, and an acid (e.g., 85% aqueous phosphoric acid) equivalent to the potassium concentration is added. The resulting neutralized liquid is then filtered. Filtration removes salts (e.g., potassium phosphate) resulting from the neutralization of the potassium hydroxide in the treatment liquid and solids such as pigments contained in the printed layer of the laminated resin film. Filtration can be carried out, for example, using filter paper with a retention particle size of approximately 1 μm. The resulting filtrate is then distilled to obtain a regenerated amide-based solvent. For example, the distillation can be carried out by heating the resulting filtrate above the boiling point of the amide-based solvent and distilling it under reduced pressure. The content of the amide-based solvent in the regenerated amide-based solvent is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0039] In addition, the alcohol having 3 or less carbon atoms in the treatment solution 1 can also be regenerated in the same manner as the amide solvent in the treatment solution 1.

[0040] (Separation Step) The recycled resin manufacturing method of this embodiment preferably further includes a separation step of separating treatment liquid 1 from a mixture of the laminate resin film and treatment liquid 1 after the first treatment step. By recovering treatment liquid 1 after the first treatment step in the separation step, the aforementioned amide-based solvent regeneration step can proceed more smoothly. Furthermore, by removing treatment liquid 1 from the laminate resin film after the first treatment step, the subsequent second treatment step can proceed efficiently. Specifically, by separating treatment liquid 1 from the laminate resin film in the first treatment step, the alcohol in treatment liquid 1 can be removed, further improving the solubility of each layer of the laminate resin film peeled in the first treatment step in treatment liquid 2, and further improving the cleanability of the adhesive layer and printed layer decomposed in the first treatment step with treatment liquid 2. Specifically, the separation step can be performed by filtering the mixture of the laminate resin film and treatment liquid 1. Filtration can be performed, for example, using a filter cloth with a mesh size of approximately 200. Alternatively, the separation step can be performed by solid-liquid separation through a dewatering device such as a screw press.

[0041] (Small Pieces Forming Step) The recycled resin manufacturing method of this embodiment preferably further includes a step of small pieces forming the laminate resin film, from the viewpoint of further improving the removability of the adhesive layer and the printed layer. The small piece forming step is preferably performed before the first treatment step, from the viewpoint of thoroughly contacting the laminate resin film with treatment liquid 1 and further improving the removability of the adhesive layer and the printed layer. Small pieces can be formed, for example, by crushing and cutting the laminate resin film into square shapes using a crusher or a cutter. The size of the small pieces is preferably 3 mm x 3 mm or more, more preferably 5 mm x 5 mm or more, and preferably 15 mm x 15 mm or less, more preferably 12 mm x 12 mm or less. When small pieces are collected through a screen using a crusher or the like, the mesh size of the screen is preferably 3 mm φ or more, more preferably 5 mm φ or more, and preferably 15 mm φ or less, more preferably 12 mm φ or less.

[0042] (Granulation step) The method for producing recycled resin of this embodiment preferably further includes a granulation step of granulating the laminate resin film after the second treatment step. Specifically, the granulation step is a step of producing a recycled resin raw material from one or more resins selected from the group consisting of the substrate layer, sealant layer, and intermediate layer described below in the laminate resin film obtained by dissolving and washing in the second treatment step. Examples of methods for producing the recycled resin raw material include a method of pelletizing by extrusion, a method of forming into a film or sheet, etc.

[0043] Furthermore, the recycled resin manufacturing method of this embodiment may further include, after the second treatment step and before the granulation step, an ethanol washing step in which the laminate resin film is washed with ethanol, a water washing step in which the laminate resin film is washed with water, and a drying step in which the washed laminate resin film is dried, in this order. The recycled resin manufacturing method of this embodiment may further include a separation step in which the laminate resin film is separated after each of the second treatment step, the ethanol washing step, and the water washing step, and this can be performed in the same manner as the separation step after the first treatment step described above. By performing the ethanol washing step and the water washing step, the amount of organic solvent adhering to the pieces of laminate resin film can be further reduced before the granulation step of the recycled resin manufacturing method. Furthermore, by performing the drying step, the subsequent granulation step can be carried out more efficiently.

[0044] (Laminated Resin Film) The laminated resin film treated in the recycled resin manufacturing method of this embodiment includes an adhesive layer and a printed layer. The laminated resin film may further include one or more layers selected from the group consisting of a substrate layer and a sealant layer. When the laminated resin film includes the substrate layer and the sealant layer, it may further include an intermediate layer between the substrate layer and the sealant layer.

[0045] When recycling printed films, the recycled materials can be colored black or gray due to the presence of ink. This problem is particularly evident when the printed layer is an inner layer of a laminated structure. Because the treatment solution 1 of this embodiment contains potassium hydroxide, an alcohol having 3 or fewer carbon atoms, and an amide-based solvent, the first treatment step can simultaneously remove the adhesive layer from the substrate layer and the printed layer (deinking). More specifically, the synergistic effect of potassium hydroxide, the alcohol having 3 or fewer carbon atoms, and the amide-based solvent in the treatment solution 1 effectively dissolves the adhesive layer of the laminated resin film, thereby enabling the substrate layer and the like that were adhered by the adhesive layer to be removed. This removal exposes the printed layer that was previously an inner layer of the laminated resin film, allowing the printed layer to be removed (deinked). Therefore, the resulting recycled resin can be colorless (white). Here, "colorless (white)" means "colorless or white."

[0046] Known printing inks can be used for the printed layer of the laminated resin film. 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 removability (deinking) of the printed layer, inks that do not contain a curing agent are preferred, but the treatment liquid 1 of this embodiment can remove (deink) the printed layer regardless of whether the ink contains a curing agent.

[0047] The adhesive used in the adhesive layer of the laminated resin film preferably contains a polyurethane resin. The polyurethane resin preferably contains a polyisocyanate compound and a polyol compound. The polyisocyanate compound is not particularly limited, but may be a polyisocyanate 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.

[0048] Examples of the polyisocyanate compound include polyisocyanate derivatives derived from the above polyisocyanate monomers, such as dimers, trimers, biuret, and allophanates. Examples of the polyisocyanate compound include 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.

[0049] 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.

[0050] 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 treatment liquid 1 of this embodiment, good removability can be achieved regardless of the composition of the adhesive layer, such as the presence or absence of hydrolyzable ester bonds.

[0051] The film constituting the laminate resin film preferably contains a polyolefin resin. Here, the film constituting the laminate resin film refers to one or more types selected from the group consisting of the substrate layer, sealant layer, and intermediate layer described above. The substrate layer in the laminate resin film preferably contains a polyolefin resin. The sealant layer in the laminate resin film preferably contains a polyolefin resin. The intermediate layer in the laminate resin film preferably contains a polyolefin resin. Examples of polyolefin resins include one or more types selected from the group consisting of polyethylene, polypropylene, and ethylene-α-olefin copolymers. The recycled resin production method of this embodiment is preferably a method for producing recycled resin from a polyolefin resin contained in one or more types selected from the group consisting of the substrate layer, sealant layer, and intermediate layer. Treatment liquid 1 of this embodiment is particularly suitable for use with polyolefin substrates that are resistant to alkaline solutions. The substrate layer, sealant layer, and intermediate layer may each be a stretched or unstretched film.

[0052] The laminated resin film to be treated in the recycled resin manufacturing method of this embodiment may be a laminated resin film laminated with an adhesive. Its configuration preferably includes one selected from the group consisting of printed layer / substrate layer / adhesive layer / substrate layer, printed layer / substrate layer / adhesive layer / sealant layer, substrate layer / printed layer / adhesive layer / substrate layer, and substrate layer / printed layer / adhesive layer / sealant layer. Furthermore, if the laminated resin film has an intermediate layer, its configuration may include substrate layer / printed layer / adhesive layer / intermediate layer / adhesive layer / sealant layer. The recycled resin manufacturing method of this embodiment can also be applied to laminated resin films with no printed layer. Examples of layer configurations of laminated resin films without a printed layer include substrate layer / adhesive layer / substrate layer, substrate layer / adhesive layer / sealant layer, and substrate layer / adhesive layer / intermediate layer / adhesive layer / sealant layer. The recycled resin manufacturing method of this embodiment uses treatment liquid 1 of this embodiment, so that the adhesive layer and printed layer can be simultaneously removed from the substrate layer. Even in the case of a laminated resin film having a printed layer as an inner layer in the laminated structure, as described above, the printed layer can be peeled off to expose the printed layer, and the printed layer can be removed (deinked). Furthermore, the laminated resin film may include an inorganic layer such as an aluminum vapor deposition layer, an inorganic vapor deposition layer, or a metal foil layer. Treatment liquid 1 of this embodiment can remove these layers from a laminated resin film that includes an aluminum vapor deposition layer, an inorganic vapor deposition layer, or a metal foil layer.

[0053] When a laminate resin film has a substrate layer and a sealant layer, the substrate layer and the sealant layer are preferably made of the same material. Furthermore, when a laminate resin film has an intermediate layer between the substrate layer and the sealant layer, the substrate layer, the sealant layer, and the intermediate layer are preferably made of the same material. By using the same material for each layer film, each peeled layer is made of a single material or something close to that, making it easier to obtain a recycled resin made of a single material, thereby further improving the efficiency of recycling the laminate resin film.

[0054] The thickness of the entire laminated resin film is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, and preferably 200 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 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, even 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 ２ and preferably 10 g / m ２ Less than 5 g / m, more preferably ２ The thickness of the sealant layer in this embodiment is preferably 5 μm or more, more preferably 10 μm or more, and preferably 180 μm or less. By setting the thickness of the entire laminated resin film and the amount of adhesive applied to within the above numerical ranges, the removability of the adhesive layer and the printed layer can be further improved.

[0055] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0056] Examples of reference embodiments are listed below. 1. A method for producing recycled resin, comprising a first treatment step of treating a laminate resin film with treatment liquid 1 containing potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent, in that order, and a second treatment step of treating the laminate resin film with treatment liquid 2 containing an amide-based solvent, wherein the laminate resin film comprises an adhesive layer and a printed layer. 2. A method for producing recycled resin according to 1., wherein the amide-based solvents contained in treatment liquid 1 and treatment liquid 2 each contain N-methyl-2-pyrrolidone. 3. A method for producing recycled resin according to 1. or 2., wherein treatment liquid 2 further contains a surfactant. 4. A method for producing recycled resin according to any one of 1. to 3., wherein in the first treatment step, the laminate resin film is treated with treatment liquid 1 while ultrasonically vibrating the laminate resin film, and in the second treatment step, the laminate resin film is treated with treatment liquid 2 while ultrasonically vibrating the laminate resin film. 5. The method for producing a recycled resin according to any one of 1. to 4., further comprising an amide solvent regeneration step of recovering one or more treatment liquids selected from the group consisting of treatment liquid 1 after the first treatment step and treatment liquid 2 after the second treatment step, and regenerating the amide solvent. 6. The method for producing a recycled resin according to any one of 1. to 5., wherein the content of the amide solvent in treatment liquid 1 is 1% by mass or more and 60% by mass or less, when the total amount of treatment liquid 1 is taken as 100% by mass. 7. The method for producing a recycled resin according to any one of 1. to 6., wherein the content of potassium hydroxide in treatment liquid 1 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 having 3 or less carbon atoms is taken as 100 parts by mass. 8. The method for producing a recycled resin according to any one of 1. to 7., wherein the content of the amide solvent in treatment liquid 2 is 90% by mass or more, when the total amount of treatment liquid 2 is taken as 100% by mass. 9. 9. The method for producing recycled resin according to any one of 1. to 8., further comprising a separation step of separating the treatment liquid 1 from the mixture of the laminate resin film and the treatment liquid 1 after the first treatment step.10. The method for producing recycled resin according to any one of 1. to 9., further comprising a granulation step of granulating the laminate resin film after the second treatment step. 11. The method for producing recycled resin according to any one of 1. to 10., further comprising a step of cutting the laminate resin film into small pieces. 12. The method for producing recycled resin according to any one of 1. to 11., wherein the adhesive layer contains a polyurethane resin. 13. The method for producing recycled resin according to any one of 1. to 12., wherein a film constituting the laminate resin film contains a polyolefin resin.

[0057] The present embodiment will be described in detail below with reference to examples, etc. However, the present embodiment is not limited to the descriptions of these examples.

[0058] The following materials were used for treatment liquid 1 and treatment liquid 2 in the examples and comparative examples.

[0059] Potassium hydroxide 1: potassium hydroxide Alcohol 1: ethanol (ethanol content: 99.5% by mass) Amide solvent 1: N-methyl-2-pyrrolidone (boiling point: 202°C) Amide solvent 2: recycled N-methyl-2-pyrrolidone obtained by <Production of amide solvent 2> described below Surfactant 1: polyoxyethylene lauryl ether, manufactured by Kao Corporation, Emulgen 108 High boiling point solvent 1: diethylene glycol (boiling point: 245°C)

[0060] <Preparation of Treatment Liquid 1> According to the composition of treatment liquid 1 (unit: parts by mass) shown in Table 1, a mixed solution was prepared by mixing potassium hydroxide and alcohol, and then an amide solvent was added to prepare treatment liquid 1 for each example.

[0061] <Preparation of Treatment Liquid 2> Treatment liquid 2 for each example was prepared by adding a surfactant to an amide solvent and mixing them according to the composition of treatment liquid 2 (unit: parts by mass) shown in Table 1. In Example 10, a surfactant and a high-boiling point solvent were added to the amide solvent.

[0062] <Production of Amide Solvent 2 (Distillative Regeneration of Amide Solvent)> Using the used treatment liquid 1 used in the <First Treatment Step> of Examples 1 to 3 described below, an amide solvent was distilled and regenerated as follows. The potassium concentration of the used treatment liquid 1 was quantified by titration with hydrochloric acid, and an 85% aqueous phosphoric acid solution equimolar to the potassium concentration was added to neutralize the solution, yielding a neutralized solution. The resulting neutralized solution was filtered under reduced pressure at room temperature using filter paper with a retention particle size of 1 μm to obtain a filtrate. The resulting filtrate was distilled under reduced pressure at 200 to 220°C and 30 kPa to obtain regenerated N-methyl-2-pyrrolidone (amide solvent 2). The purity of the resulting amide solvent 2 was 99.8% by mass, and the water and ethanol contents were each 0.1% by mass.

[0063] The laminated resin film was made of the following materials. (Films) OPP film 1: biaxially oriented polypropylene film, 20 μm, U-1, manufactured by RM Tocello Co., Ltd. CPP film: unstretched polypropylene film, 20 μm, Pylen® Film-CT P1128, manufactured by Toyobo Co., Ltd. (Adhesives) Adhesive 1: polyether urethane polyol, Takelac® A-951, manufactured by Mitsui Chemicals, Inc. Adhesive 2: polyisocyanate, Takenate® A-91, manufactured by Mitsui Chemicals, Inc. (Printing layer inks) Ink 1: gravure ink for lamination, LP Bio R92 Black N2, manufactured by Toyo Ink Co., Ltd. Ink 2: gravure ink for lamination, LP Bio R39 Indigo N1, manufactured by Toyo Ink Co., Ltd. Ink 3: gravure ink for lamination, LP Bio F121 Crimson N1, manufactured by Toyo Ink Co., Ltd. Ink 4: Gravure ink for lamination, LP Bio F23 Yellow N1, manufactured by Toyo Ink Co., Ltd. Ink 5: Gravure ink for lamination, LP Bio S R641 White B1, manufactured by Toyo Ink Co., Ltd.

[0064] <Preparation of Laminated Resin Film> A laminated resin film was prepared by the following procedure. The above-mentioned printing layer inks were printed on OPP film 1 in the order of the ink numbers using a gravure printing machine to obtain an OPP film with a printing layer. An adhesive (a mixture of adhesive 1 and adhesive 2, with a mixing mass ratio of adhesive 1:adhesive 2 = 1:1) was applied to the surface of the OPP film on the side of the printing layer at a solid content of 3 g / m ２ The laminated resin film was subjected to an aging reaction at 40° C. for 72 hours to obtain a laminated resin film having a configuration of OPP (with printed layer) / adhesive layer / CPP.

[0065] <Small Pieces Forming Step> The obtained laminated resin film was crushed in a crusher (SRH3-360TRFS, manufactured by HORAI Co., Ltd.) using a screen with a mesh diameter of 6 mmφ or 10 mmφ according to the film size of each example shown in Table 1, and small piece samples that passed through each screen were collected. The shapes of the crushed small pieces were random rectangular.

[0066] <First Treatment Step> According to the conditions for the first treatment step in Table 1, the fragmented laminate resin film was treated with Treatment Solution 1 of each Example. A 500 mL separable flask equipped with a stirrer and a cooling tube was charged with 200 g of the laminate resin film and Treatment Solution 1 so as to achieve the film concentration (mass %) shown in Table 1. The separable flask was immersed in the water bath of a heating ultrasonic cleaner (AS ONE Corporation, model number: US-2) heated to 50°C, and ultrasonic treatment was performed while stirring and maintaining the temperature at 50°C for the treatment time shown in Table 1. The ultrasonic treatment was performed at 38 kHz. Note that ultrasonic treatment was not performed in Examples 8 and 10.

[0067] <Separation Step> The mixture of the fragmented laminate resin film obtained in the first treatment step and treatment liquid 1 was filtered under reduced pressure at room temperature using a 200-mesh filter cloth, and the laminate resin film was recovered.

[0068] <Second Treatment Step> The laminate resin film obtained in the separation step was treated with Treatment Solution 2 of each Example according to the second treatment step conditions in Table 1. The laminate resin film obtained in the separation step and 140 g of Treatment Solution 2 were placed in a 500 mL separable flask equipped with a stirrer and a cooling tube, and the separable flask was immersed in the water bath of a heating ultrasonic cleaner (AS ONE Corporation, model number: US-2) heated to 50°C. Ultrasonic treatment was performed while stirring and maintaining the temperature at 50°C for the treatment time listed in Table 1. The ultrasonic treatment was performed at 38 kHz. Comparative Example 1 did not undergo the second treatment step.

[0069] <Evaluation of peelability of laminate resin film> The small pieces of laminate resin film obtained in the second treatment step were rinsed with ethanol and then with water to completely remove the amide-based solvent, and then dried. The removability of the printed layer was evaluated visually and by FT-IR according to the following criteria. A to C were considered pass. (Criteria) A: In the small piece of laminate resin film, it was visually confirmed that the printed layer had completely disappeared, and FT-IR confirmed that the film was the only film, or that less than 5% of the printed layer remained. B: In the small piece of laminate resin film, it was visually confirmed that 5% or more but less than 30% of the printed layer remained. C: In the small piece of laminate resin film, it was visually confirmed that 30% or more but less than 70% of the printed layer remained. D: In the small piece of laminate resin film, it was visually confirmed that the printed layer had not changed compared to before treatment, or that 70% or more of the printed layer remained.

[0070]

[0071] This application claims priority based on Japanese Patent Application No. 2024-091473, filed on June 5, 2024, the disclosure of which is incorporated herein in its entirety by reference.

Claims

1. A method for producing recycled resin, comprising the steps of: a first treatment step of treating a laminated resin film with treatment liquid 1 containing potassium hydroxide, an alcohol having 3 or less carbon atoms, and an amide-based solvent; and a second treatment step of treating the laminated resin film with treatment liquid 2 containing an amide-based solvent, in this order; wherein the laminated resin film includes an adhesive layer and a printed layer.

2. The method for producing recycled resin according to claim 1, wherein the amide solvent contained in the treatment liquid 1 and the treatment liquid 2 each contains N-methyl-2-pyrrolidone.

3. The method for producing recycled resin according to claim 1 or 2, wherein the treatment liquid 2 further contains a surfactant.

4. The method for producing recycled resin according to any one of claims 1 to 3, wherein the treatment liquid 2 further contains a high-boiling point solvent.

5. A method for producing recycled resin according to any one of claims 1 to 4, wherein in the first treatment step, the laminated resin film is treated with the treatment liquid 1 while being subjected to ultrasonic vibrations.

6. A method for producing recycled resin according to any one of claims 1 to 5, wherein in the second treatment step, the laminated resin film is treated with the treatment liquid 2 while being subjected to ultrasonic vibrations.

7. A method for producing a recycled resin according to any one of claims 1 to 6, further comprising an amide-based solvent regeneration step of recovering one or more treatment liquids selected from the group consisting of treatment liquid 1 after the first treatment step and treatment liquid 2 after the second treatment step, and regenerating the amide-based solvent.

8. A method for producing recycled resin described in any one of claims 1 to 7, wherein the content of the amide-based solvent in the treatment liquid 1 is 1% by mass or more and 60% by mass or less when the total amount of the treatment liquid 1 is 100% by mass.

9. A method for producing recycled resin described in any one of claims 1 to 8, wherein the content of potassium hydroxide in the treatment liquid 1 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 having 3 or less carbon atoms is 100 parts by mass.

10. A method for producing recycled resin described in any one of claims 1 to 8, wherein the content of potassium hydroxide in the treatment liquid 1 is 0.1 parts by mass or more and 20 parts by mass or less when the total content of the potassium hydroxide and the alcohol having 3 or less carbon atoms is 100 parts by mass.

11. A method for producing recycled resin described in any one of claims 1 to 10, wherein the content of the amide-based solvent in the treatment liquid 2 is 90% by mass or more when the total amount of the treatment liquid 2 is 100% by mass.

12. A method for producing recycled resin described in any one of claims 1 to 10, wherein the content of the amide-based solvent in the treatment liquid 2 is 70% by mass or more when the total amount of the treatment liquid 2 is 100% by mass.

13. A method for producing recycled resin according to any one of claims 1 to 12, further comprising a separation step of separating the treatment liquid 1 from the mixture of the laminated resin film and the treatment liquid 1 after the first treatment step.

14. A method for producing recycled resin according to any one of claims 1 to 13, further comprising a granulation step of granulating the laminated resin film after the second treatment step.

15. The method for producing recycled resin according to any one of claims 1 to 14, further comprising a step of cutting the laminated resin film into small pieces.

16. The method for producing recycled resin according to any one of claims 1 to 15, wherein the adhesive layer contains a polyurethane resin.

17. The method for producing recycled resin according to any one of claims 1 to 16, wherein the film constituting the laminated resin film contains a polyolefin resin.

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