Processing method for laminated film

Abstract

To provide a method for processing laminated film.SOLUTION: The present invention provides a method for treating a laminated film formed from multiple resin layers, comprising applying a solution containing a radical source to the laminated film and generating radicals to decompose the bonding interfaces between the films within the laminated film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for treating a laminated film. [Background technology]

[0002] Laminated films, which are widely used in refill packs and food packaging, are important base materials that can be given functionality by combining multiple resins with different compositions and metal compositions such as aluminum. For example, by layering polyethylene terephthalate (PET) or polypropylene (PP), which have excellent printability, as the outermost layer, and aluminum layers with excellent gas barrier and light blocking properties, or polyethylene (PE), which has excellent heat-sealing properties, on the inside, it is possible to give the film a variety of functions that cannot be achieved with films made of a single composition.

[0003] However, recycling these laminated films is difficult and presents a major challenge. Functional laminated films are made of multiple resin films with different compositions laminated together via adhesive layers, making them difficult to recycle through material or chemical means. In particular, laminated films with aluminum layers, which are commonly found in refill packs, contain a mixture of resin and metal, making them difficult to disassemble and recycle, and most are incinerated.

[0004] In recent years, efforts toward material recycling of laminated films such as refill packs have been expanding, and conventional techniques for recycling laminated films including metal-containing layers are described in, for example, Patent Documents 1 to 4 below.

[0005] Patent Document 1 describes a method of recycling resin containing crushed aluminum foil by feeding a multilayer film formed by laminating aluminum foil on a resin layer into a twin-screw extruder and melt-kneading the film.

[0006] Furthermore, Patent Document 2 describes a method in which packaging waste is separated into aluminum foil laminated packaging material in which aluminum foil is laminated and aluminum vapor-deposited packaging material in which aluminum is vapor-deposited, and the aluminum foil laminated packaging material and the aluminum vapor-deposited packaging material are each subjected to reflux treatment at different temperatures to thermally decompose each packaging material and recover aluminum.

[0007] Furthermore, Patent Document 3 describes a method for producing a resin composition having dispersed therein particles of the metal, by removing the resin waste material having a resin layer having a metal foil layer from a resin waste material mixture comprising a resin waste material having a resin layer with a metal foil layer and a resin waste material having a resin layer with a metal vapor deposition layer, and then melt-molding the resin waste material mixture.

[0008] Furthermore, Patent Document 4 describes a method for producing a resin composition using recycled resin obtained by recycling resin containers having a metal layer as a raw material. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-192748 [Patent Document 2] JP 2012-21200 A [Patent Document 3] JP 2013-35272 A [Patent Document 4] International Publication No. 2022 / 124146 Summary of the Invention [Problem to be solved by the invention]

[0010] In particular, recycled resin obtained from resin containers containing metal layers poses recycling challenges due to the presence of residual metals present in the original container. For example, when film is formed from recycled resin containing metals, the metals can interfere with the forming process and potentially reduce the strength and physical properties of the resulting film. Conventional methods for dissolving metals, such as aluminum, include treatment with acids, alkalis, and hypochlorite. However, these methods have limited penetration into the film's laminate interface, resulting in poor penetration and removal of the aluminum-vaporized layer, leading to insufficient film separation and residual aluminum-vaporized layer issues. Furthermore, these methods are likely to hydrolyze the resin layer, depending on the type of resin in the film. This makes the hydrolyzed resin layer itself difficult to reuse. Therefore, these methods are considered inferior to the proposed method in terms of raw material recovery for material recycling.

[0011] The technologies described in the above Patent Documents 1 to 4 focus on the recycling of resin containers having a metal layer, and do not take into consideration the quality of resin molded articles, particularly film materials, made from recycled resin obtained by recycling.

[0012] Furthermore, Patent Document 4 describes a method for producing a resin composition using recycled resin obtained by recycling resin containers having a metal layer as a raw material. However, in this production method, resin waste materials having a metal foil layer are removed using a metal detector, which is an inaccurate method for separating metal vapor deposition layers, and it is thought that a large amount of resin waste materials having such resin layers are produced. Therefore, there has been a demand for the development of a more appropriate material recycling method.

[0013] Therefore, conventional techniques for material recycling of laminated films, especially laminated films containing metal layers, have many issues with the raw materials and quality of the recycled films, and no clear usefulness has been demonstrated. Therefore, new processing methods for recycling recovered laminated films are being considered. [Means for solving the problem]

[0014] If it were possible to peel off used laminated films and separate them into their respective resin materials, the recycling of laminated films would be greatly improved. However, in this technical field, conventional techniques for recycling laminated films have mainly involved thermally decomposing the films by melting or the like, and therefore an appropriate method for peeling laminated films has not yet been developed.

[0015] As a result of investigations to solve the above problems, it was found that by applying a solution containing a radical source to a laminated film, radicals derived from chlorous acid, which is the radical source, can penetrate into the resin layer, and that the radicals that penetrate from the surface layer to the inside of the laminated film can oxidatively decompose the bonding interface between films that were originally separate and independent before lamination in each laminated film, thereby separating the films into layers, which led to the completion of the present invention. Note that the bonding interface here means the interface between materials formed in a film form, for example, the portion where films that were originally formed separately and independently before lamination come into contact with each other, or the interface between a film that serves as a substrate and a layer that is vapor-deposited on the film, and the material that forms the interface in part or the entirety can be decomposed by the radicals.

[0016] The present invention includes: [1] A method for treating a laminated film formed from multiple resin layers, comprising applying a solution containing a radical generating source to the laminated film to generate radicals and thereby decompose the bonding interfaces between the films within the laminated film. [2] The method of claim 1, wherein the laminated film has a metal-containing layer at the bonding interface between the films. [3] The method according to item 1 or 2, wherein the metal-containing layer is a metal vapor deposition layer, a metal foil layer, or both. [4] The method according to any one of items 1 to 3, wherein the metal-containing layer is an aluminum vapor deposition layer, an aluminum foil layer, or both. [5] The method according to any one of items 1 to 4, comprising dissolving the metal-containing layer by applying the solution. [6] The method according to any one of items 1 to 5, comprising applying the solution to dissolve the metal-containing layer and separate the resin layer. [7] The method according to item 1, wherein the laminated film has an adhesive layer at the bonding interface between the films. [8] The method of claim 7, wherein the adhesive layer is an adhesive resin, an adhesive, or both. [9] The method according to item 7 or 8, wherein the adhesive resin comprises one or more resins selected from the group consisting of polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and copolymers of ethylene with an α-olefin polymerized using a metallocene catalyst; ethylene-unsaturated carboxylic acid copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-maleic acid copolymer; and ionomer resins.

[10] The method according to any one of items 7 to 9, wherein the adhesive is an adhesive composition obtained by mixing, for example, a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent.

[11] The method according to any one of items 7 to 10, comprising dissolving the adhesive layer by applying the solution.

[12] The method according to any one of items 7 to 11, comprising applying the solution to dissolve the adhesive layer and separate the resin layer.

[13] The method according to Item 1, wherein the laminated films are bonded to each other by melting together at the bonding interface and / or by intermolecular forces.

[14] The method of claim 13, comprising dissolving the bonding interface by applying the solution.

[15] The method according to item 13 or 14, comprising applying the solution to dissolve the bonding interface and separate the resin layer.

[16] The method according to any one of items 1 to 15, wherein the laminated film includes a resin layer formed from a polymer compound.

[17] The method according to Item 16, wherein the laminated film includes two or more resin layers formed of the same or different polymer compounds, and the resin layers are bonded to the upper and lower layers of the metal-containing layer.

[18] The method according to Item 17, wherein the polymer compound is one or more polymer compounds selected from the group consisting of polyolefin, polyethylene terephthalate (PET), and polyamide.

[19] The method according to any one of items 1 to 18, wherein the radical generating source is one or more compounds selected from the group consisting of a haloid acid, a haloid ion, or a haloid salt.

[20] The method according to any one of items 1 to 19, wherein the solution further comprises an additive.

[21] The method according to item 20, wherein the additive is hydrochloric acid.

[22] The method according to any one of items 1 to 21, further comprising, in applying the solution, performing an external treatment on the surface of the laminated film to improve penetration of the solution containing the radical source into the laminated film.

[23] The method according to Item 22, wherein the external treatment is a means for treating the surface of the laminated film to improve penetration of the solution containing the radical source into the laminated film.

[24] The method according to Item 22 or 23, wherein the external treatment is irradiating the reaction system with light.

[25] The method according to Item 22 or 23, wherein the external treatment is heating the reaction system. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a simple and highly efficient method for treating a laminated film, which can specifically remove bonded interfaces from a laminated film formed from a plurality of resin layers. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the embodiments of the present invention will be described in more detail.

[0019] One embodiment of the method for treating a laminated film of the present invention comprises applying a solution containing a radical generating source to the laminated film.

[0020] A. Laminated film The laminated film of the present invention may be a laminated structure formed from a plurality of resin layers via a metal-containing layer and / or an adhesive layer, or may be a laminated structure formed by melting and / or bonding by intermolecular forces at the bonding interface between the laminated films, and may further include a resin layer formed from a polymer compound.

[0021] Examples of materials for the resin layer formed into the film include polyolefin, polyester, polyamide, and polyimide.

[0022] Examples of polyolefins include polyethylene, polypropylene, ethylene-α-olefin copolymers, etc. Polymer materials derived from biomass, such as biopolyethylene and biopolypropylene, may also be used.

[0023] Examples of polyethylene include low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene.

[0024] Examples of polypropylene include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene.

[0025] Examples of the α-olefin constituting the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene.

[0026] Examples of polyester include polyethylene terephthalate and polybutylene terephthalate.

[0027] Examples of polyamides include nylon 6, nylon 6,6, and nylon 4,6.

[0028] An example of the polyimide is poly(4,4'-oxydiphenylenepyromellitimide).

[0029] These materials can be used alone or in combination of two or more.

[0030] The laminated film of the present invention may contain two or more resin layers formed of the same or different polymer compounds, and the metal-containing layer may be formed on the resin layer by vapor deposition or the like.

[0031] For example, by laminating stretched polyethylene terephthalate on the outer side of the laminate film, a laminate film with high strength and excellent heat resistance can be obtained. From the viewpoint of promoting the recycling of resins that are widely used as resin materials for packaging containers, it is more preferable that the material for the resin layer contains polyethylene as a main component.

[0032] Other resins include, for example, ethylene-vinyl alcohol copolymer. Ethylene-vinyl alcohol copolymers are resins with excellent barrier properties against various gases, including oxygen. Therefore, a laminated film obtained by laminating a resin layer containing an ethylene-vinyl alcohol copolymer onto the resin film material of the present invention has excellent gas barrier properties. Therefore, this laminated film is suitable as a packaging container for storing various liquid or powder contents.

[0033] In one embodiment, the laminate film used in the present invention may be a laminate in which multiple layers, such as an ink layer, an adhesive layer, or another resin film, are laminated onto a resin film. Examples of such laminates include, without limitation, laminate films laminated with reactive adhesives used for food packaging and household goods. However, laminate films laminated with non-reactive adhesives, such as thermoplastic resin adhesives, and laminate films obtained by heat fusion using an extrusion lamination method can also be separated and recovered into their respective monolayer films using the separation and recovery method of the present invention. Furthermore, the laminate may be in the form of a sheet or container.

[0034] Laminated films bonded by a reactive adhesive often have an adhesive layer made of the reactive adhesive laminated between at least two resin film layers or metal foil or vapor-deposited film layers. Specifically, in the laminate film, if the resin film layer is represented as (F), the metal-containing layer of the metal foil or vapor-deposited film layer is represented as (M), and the adhesive layer of the reactive adhesive or the like is represented as (AD), specific embodiments of the laminate film include, but are not limited to, the following configurations. (F) / (AD) / (F), (F) / (AD) / (F) / (AD) / (F), (F) / (AD) / (F) / (AD) / (F), (F) / (AD) / (M), (F) / (AD) / (M) / (F), (F) / (AD) / (F) / (AD) / (M) / (AD) / (F), (F) / (AD) / (M) / (AD) / (F) / (AD) / (F), (M) / (AD) / (F) / (AD) / (M), (AD) / (F) / (AD) / (M), (AD) / (F) / (AD) / (F) / (AD), etc. In addition, it may be a laminated film that does not include decoration or printing, for example, a cast film (sheet) that is melt-laminated using an extrusion molding machine and uniaxially or biaxially stretched, and has a pattern that does not use an adhesive between layers. In this case, for example, (F) / (F) (F) / (M) / (F) Patterns without adhesives, such as the following, are also conceivable. That is, laminated structures can be formed by the bonding interface between laminated films melting and / or bonding via intermolecular forces. In (F) / (F) systems, particularly (F) / (F)' systems using different resins, a melt-mixed layer at the lamination interface, for example, F and F', may be mixed, or the bonded layers, for example, F and F', may be physically bonded (the so-called anchor effect) or may be bonded via intermolecular forces. It is believed that layer separation can be achieved by the action of a radical generating source at the interface, decomposing the bonding interface. Furthermore, even in the case of (F) / (M) / (F), for example, the radical generating source may dissolve the aluminum vapor deposition layer, thereby achieving layer separation via a mechanism similar to that of an adhesive layer.

[0035] As the material for the adhesive layer, an adhesive resin or adhesive that can provide the required adhesive strength is appropriately selected and used depending on the material of the layer to be adhered thereto.

[0036] The adhesive resin may be one or more resins selected from polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and copolymers of ethylene with an α-olefin polymerized using a metallocene catalyst; ethylene-unsaturated carboxylic acid copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-maleic acid copolymer; and ionomer resins.

[0037] The adhesive is, for example, an adhesive composition obtained by mixing a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent. The adhesive layer obtained from this adhesive contains a cured product produced by reaction between the base agent and the curing agent in the adhesive composition.

[0038] Examples of the base agent include polyols. Examples of the curing agent include isocyanate compounds. Examples of the adhesive include two-component ether-based reactive adhesives and two-component ester-based reactive adhesives.

[0039] An example of a cured product of an ether-based two-component reactive adhesive is polyether polyurethane, which is produced by reacting a polyether polyol as a base agent with an isocyanate compound as a curing agent.

[0040] Examples of cured products of ester-based two-component reactive adhesives include polyester polyurethane and polyester. Polyester polyurethane is produced by reacting a polyester polyol as a base resin with an isocyanate compound as a curing agent.

[0041] In the two-component reactive adhesive, an acrylic polyol may be used as a main component. The adhesive composition may not contain a solvent as long as it melts or has a low viscosity when heated.

[0042] The metal-containing layer may be a metal vapor deposition layer, a metal foil layer, or both. Metals used in the metal vapor deposition layer include various metals commonly used in metal vapor deposition in the art, such as aluminum, magnesium, chromium, zinc, gold, silver, platinum, nickel, copper, tin, iron, or lead. Two or more metals may also be used in combination. Furthermore, a vapor deposition film of a metal oxide such as aluminum oxide or an inorganic oxide such as silicon oxide may also be provided. In a preferred embodiment of the present invention, aluminum is used as the metal used in the metal vapor deposition layer.

[0043] The layer that serves as the base material for the metal vapor deposition layer can be a resin layer formed from a polymer compound such as polyolefin, polyester, polyamide, or polyimide. Specific examples of these resins are as described above.

[0044] The metal foil layer is formed by rolling various metals into foil. As the metal foil, various single metal foils having barrier properties, such as aluminum, chromium, zinc, gold, silver, platinum, nickel, copper, tin, iron, or lead, can be used. Two or more metals may also be used in combination. In a preferred embodiment of the present invention, aluminum is used as the metal used in the metal foil layer.

[0045] A used laminate film including a metal-containing layer can also be used. For example, a used two-dimensional or three-dimensional molded body having a resin layer with a metal-containing layer can be used as is, or crushed bodies of the used molded body can be used as the laminate film including a metal-containing layer to be subjected to the treatment of the present invention.

[0046] Alternatively, scraps that are generated in the process of producing a two-dimensional or three-dimensional molded product and that have no value as a product themselves can also be used as a laminate film containing a metal-containing layer.

[0047] In the following explanation, used goods and scrap materials are collectively referred to as "scrap materials." In other words, in this specification, "scrap materials" is a concept that encompasses both used goods and scrap materials that are generated in the process of manufacturing products and that have no value as products in themselves.

[0048] Of these laminate films containing a metal-containing layer, from the viewpoint of reducing the environmental load, it is preferable to use a used two-dimensional or three-dimensional molded body as a laminate as is, or to use crushed pieces of the used molded body as a laminate, rather than using a virgin laminate.

[0049] From the same viewpoint, it is also preferable to use scraps generated during the production of a two-dimensional molded body or a three-dimensional molded body as a laminated film including a metal-containing layer.

[0050] B. Liquid reaction system for radical generation

[0051] The present invention may further include, for example, a radical generation step. The radical generation step may be carried out, for example, before or simultaneously with the treatment step. The method for generating radicals in the radical generation step is not particularly limited, and, for example, the radicals may be generated using a radical generation reaction system. For example, the radical generation reaction system may be used as a liquid reaction system in the treatment step after generating the halogen oxide radicals.

[0052] The radical generating reaction system may be, for example, an aqueous phase containing a radical generating source. The aqueous phase generates radicals from the radical generating source in the radical generating step. The aqueous phase may be, for example, an aqueous solvent phase, and the aqueous solvent may be water such as HO or DO. Examples of water include purified water, ion-exchanged water, distilled water, filtered water, and sterilized water.

[0053] The radical-generating reaction system may be, for example, an aqueous phase only, or may be a two-phase reaction system including an aqueous phase and an organic phase. When the radical generated in the aqueous phase is hydrophobic, the radical can be transferred to the organic phase by using a two-phase reaction system including the organic phase and the aqueous phase.

[0054] Examples of the radical generating source include halogen ions, hypohalite ions, halite ions, halide ions, and perhalide ions, and it is preferable to include at least one selected from the group consisting of these.

[0055] The radical generating source may include, for example, an oxoacid or its salt (e.g., a halogen oxoacid or its salt). Examples of the oxoacid include boric acid, carbonic acid, orthocarbonic acid, carboxylic acid, silicic acid, nitrous acid, nitric acid, phosphorous acid, phosphoric acid, arsenic acid, sulfurous acid, sulfonic acid, sulfinic acid, chromic acid, dichromate, and permanganic acid. Examples of halogen oxoacids include chlorine oxoacids such as chlorous acid, chloric acid, and perchloric acid; bromine oxoacids such as hypobromous acid, bromous acid, bromic acid, and perbromic acid; and iodine oxoacids such as hypoiodous acid, iodous acid, iodic acid, and periodic acid. Examples of these salts include alkali metal salts such as sodium and potassium.

[0056] Among these, the radical generating source is more preferably at least one selected from the group consisting of halous acid, halous ion, and halous salt, and even more preferably at least one selected from the group consisting of chlorous acid, chlorous ion, and chlorite, because the reactivity with the additives described below is mild and the reaction is easy to control. Specifically, sodium chlorite is preferred.

[0057] The aqueous phase may further contain one or more additives that enhance the oxidation action of the radicals derived from the radical source, and thus the phase separation effect.

[0058] In the present invention, the additive can be a liquid agent having a function of lowering pH, so-called protonic acid. For example, citric acid, acetic acid, hydrochloric acid, etc. can be used as the protonic acid. Preferably, the same halogen as the radical generating source is used, and for example, when chlorous acid is used, it is preferable to use hydrochloric acid.

[0059] The content of the radical generating source in the aqueous phase is preferably 0.01 to 1500 ppm by mass. If the concentration of the radical generating source in the solution is too low, the amount of radicals generated will be too small, which may prevent the oxidation action and, ultimately, the layer separation effect from being obtained. Furthermore, the higher the concentration of the radical generating source, the better the layer separation effect, but from the viewpoint of ensuring safety, it is preferably 1500 ppm by mass or less. The content of the radical generating source in the solution is more preferably 1 to 1000 ppm by mass, even more preferably 10 to 500 ppm by mass, and particularly preferably 50 to 250 ppm by mass.

[0060] The aqueous phase preferably contains, for example, the halogen oxide ions and the additive, and is, for example, an aqueous phase in which the compound and the additive are dissolved in an aqueous solvent. As a specific example, when the halogen oxide radical is a chlorine dioxide radical, the aqueous phase preferably contains, for example, chlorite ions (ClO - ) and hydrochloric acid, for example, an aqueous phase in which the sodium chlorite (NaClO2) and the hydrochloric acid are dissolved in an aqueous solvent is preferred.

[0061] In the aqueous phase, for example, the additive and the radical generating source may be dissolved or insoluble in the aqueous solvent. In the latter case, they may be dispersed or precipitated in the aqueous solvent.

[0062] The halogen oxide radical generation step is not particularly limited, and for example, by adding the radical generation source to the aqueous solvent, the halogen oxide radicals (e.g., chlorine dioxide radicals) can be spontaneously generated from the halogen oxide ions (e.g., chlorite ions). The aqueous phase preferably contains the generation source dissolved in the aqueous solvent, and is preferably allowed to stand. In the halogen oxide radical generation step, the generation of the halogen oxide radicals can be further promoted by, for example, further containing one or more additives. In the halogen oxide radical generation step, the halogen oxide radicals can be generated by, for example, irradiating the aqueous phase with light. However, the halogen oxide radicals can also be generated without light irradiation, for example, by simply allowing the aqueous phase to stand.

[0063] In the solution used in the present invention, the content of the additive is preferably 0.01 to 1500 ppm by mass. If the additive concentration in the solution is too low, radical generation may be suppressed, which may result in the oxidation action and, ultimately, the phase separation effect, etc. not being obtained. Furthermore, an additive content of 1500 ppm by mass or less is preferable because safety can be ensured. The additive content in the solution is more preferably 0.1 to 1000 ppm by mass, more preferably 0.1 to 500 ppm by mass, even more preferably 1 to 200 ppm by mass, and most preferably 1 to 100 ppm by mass. Note that, from the viewpoint of preventing the phase separation effect, etc. from being impaired due to micelle formation, the additive concentration is preferably equal to or less than the micelle limit concentration.

[0064] The solution used in the present invention may contain components other than the above-mentioned additives, radical generating source, and water, such as organic solvents and pH adjusters, as long as the effects of the present invention are not impaired.

[0065] Examples of organic solvents include ketones such as acetone, nitrile solvents such as acetonitrile, and alcohol solvents such as ethanol and propylene glycol. These may be used alone or in combination of two or more.

[0066] Examples of pH adjusters include potassium dihydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, trishydroxymethylaminomethane, trishydroxymethylaminomethane hydrochloride, ethylenediaminetetraacetic acid, etc. These may be used alone or in combination of two or more.

[0067] The solution used in the present invention can be prepared by sequentially mixing and dissolving the radical generating source, any additives, water, and, if desired, other components to a uniform degree.

[0068] C. Laminated film processing method

[0069] One embodiment of the method of treating a laminated film including a metal-containing layer of the present invention comprises applying a solution containing a radical generating source to the laminated film.

[0070] The radicals generated by the method of the present invention are permeable to the polymer resin layer, and by penetrating the polymer resin layer, they can act on the adhesive layer and / or metal-containing layer present inside the laminate film from a direction perpendicular to the laminate film. As a result, efficient decomposition of the adhesive layer and / or metal-containing layer not exposed on the surface of the laminate film can be achieved. Therefore, by applying the treatment method of the present invention, it is possible to obtain a laminate film having a lower residual rate of the adhesive layer and / or metal-containing layer, and as a result, the resin layers of the laminate film can be separated.

[0071] The solution containing the radical generating source of the present invention is typically in the form of a dispersion containing an active ingredient and has appropriate fluidity, which means that it does not require complex processing (pre-mixing, shape adjustment, etc.) before use and is easy to handle.

[0072] The laminate film may be treated by applying the solution using a method selected from the group consisting of immersion, dripping, spraying, and painting. This oxidatively decomposes and dissolves the adhesive layer and / or metal-containing layer in the laminate film, successfully separating the resin film layer bonded to the adhesive layer and / or metal foil layer. Preferably, the laminate film is immersed completely in the solution. The treatment process may be batch or continuous. In the case of a continuous process, the adhesive layer and / or metal foil layer can be oxidatively decomposed by, for example, placing the laminate film on a belt conveyor or the like and immersing it in a tank containing the solution for a predetermined period of time. If necessary, the laminate film may be cut into small pieces to make the adhesive layer and / or metal foil layer more accessible to the solution, thereby accelerating the oxidative decomposition rate of these layers. The solution containing the metal ions dissolved by oxidative decomposition may be collected or discarded as appropriate.

[0073] When applying the solution, the reaction temperature is not particularly limited as long as it is within a temperature range in which the oxidative decomposition of the adhesive layer and / or metal foil layer in the laminate film proceeds efficiently. For example, it may be 0°C to 200°C, preferably 10°C to 100°C. The treatment time of the laminate film with the solution depends on various factors, such as the concentration and type of radical source and radical catalyst in the solution, the type and thickness of the adhesive layer and / or metal foil layer desired to be oxidatively decomposed, and the type and thickness of the resin layer to which it is attached. For example, when the treatment is performed at room temperature and the metal foil has a thickness of approximately 0.001 to 0.1 mm, the treatment time is approximately 0.5 to 24 hours, preferably 1 to 12 hours, and more preferably 3 to 6 hours. The oxidative decomposition of the adhesive layer and / or metal foil layer can be performed at approximately room temperature, which saves energy during industrial waste disposal and is preferable from the viewpoints of equipment and the environment. On the other hand, oxidative decomposition can also be promoted by heating, so appropriate temperature treatment conditions can be selected by balancing equipment and environmental considerations with efficiency.

[0074] Furthermore, the oxidative decomposition of the adhesive layer and / or metal foil layer can be accelerated by treating the exposed surface of the laminate film, i.e., the outermost layer, so as to promote the penetration of the radical-generating solution into the laminate film. There are no particular limitations on the means for such surface treatment, but examples include scratching the surface with a file or piercing the surface with a needle.

[0075] When the solution is applied by immersion, the method may further include stirring the reaction system including the solution and the laminated film.

[0076] The application of the solution may further include an external treatment for treating the surface of the laminated film to improve penetration of the solution containing the radical source into the laminated film. The external treatment may be heating the reaction system or irradiating the reaction system with light as a means for enhancing the oxidizing action of radicals derived from the radical source and thus the layer separation effect. In particular, the application of light irradiation can enhance the oxidizing power of the solution.

[0077] The temperature for heating is not particularly limited and may be, for example, about 40 to 100° C., and preferably about 60 to 90° C. The wavelength of the irradiated light is not particularly limited and the lower limit may be, for example, 200 nm or more and the upper limit may be, for example, 800 nm or less, and the light irradiation time is not particularly limited and the lower limit may be, for example, 1 second or more and the upper limit may be, for example, 24 hours.

[0078] The light source for the light irradiation is not particularly limited, and for example, visible light contained in natural light such as sunlight can be used. The use of natural light allows, for example, easy excitation. Furthermore, as the light source, for example, a xenon lamp, a halogen lamp, a fluorescent lamp, a mercury lamp, an LED lamp, or the like can be used instead of or in addition to the natural light. In the light irradiation, for example, a filter that cuts off wavelengths other than the required wavelength can also be used as appropriate.

[0079] The solution treatment step may further include applying an organic solvent to the laminated film, if necessary. Examples of organic solvents include ketones (e.g., acetone), nitrile solvents (e.g., acetonitrile), and alcohol solvents (e.g., ethanol and propylene glycol). These may be used alone or in combination of two or more.

[0080] The organic solvent may be added as an additive to the solution containing the radical source and applied simultaneously, or may be applied alone to the laminated film after the solution containing the radical source has been applied by a method selected from the group consisting of dropping, spraying, coating, and immersion.

[0081] In one embodiment, the application of the solution can dissolve part or all of the metal-containing layer contained in the laminate film.

[0082] In one embodiment, by dissolving a part or all of the metal-containing layer contained in the laminate film, different types of resin layers and adhesive layers constituting the laminate film can be separated from each other, which makes it possible to separate and recover the resin layers and adhesive layers by type, thereby facilitating the recycling of each layer. [Example]

[0083] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples.

[0084] <Example 1: Radical permeability test through polymer resin film>

[0085] (Example) 30 ml of distilled water was added to a glass container, and a polyethylene film bag (Unipack with an area of ​​85 mm x 60 mm and a thickness of 0.04 mm) was immersed in the water. Thereafter, the bag was filled with 20 ml of a radical-generating liquid: a liquid in which a 10% aqueous solution of sodium chlorite and 35% hydrochloric acid were mixed in a ratio of 100:1. The reaction vessel was covered with aluminum foil to shield the system from light, and then allowed to stand at room temperature for approximately 90 minutes. The distilled water in the glass vessel was collected at 0 and 90 minutes after the reaction time, and UV-vis spectrum was measured and evaluated using a UV-Vis Spectrometer (V-750 (Jasco)) by measuring the 280 nm spectrum derived from ClO2 ions and the 360 ​​nm spectrum derived from ClO2 radicals. (Comparative Example) As a comparative example, UV-vis spectrum measurement was carried out in the same manner as in Example 1, except that instead of the radical-generating liquid preparation, 20 ml of a 10% aqueous solution of sodium chlorite alone was filled into the pair of bags.

[0086] result (Example) For the radical-generating liquid preparation, the absorbance at 280 nm was 0.06 at 0 minute of reaction time, and 0.07 after 90 minutes of reaction time. Furthermore, the absorbance at 360 nm was 0.050 at 0 minute of reaction time, but was 0.876 after 90 minutes. (Comparative Example) The absorbance at 280 nm was 0.01 at 0 minutes of reaction time, and 0.01 after 90 minutes. The absorbance at 360 nm was 0.00 at 0 minutes of reaction time, and 0.01 after 90 minutes.

[0087] From the above, it was found from the Examples and Comparative Examples that ClO2 radicals permeate from the inside of the polyethylene film bag (i.e., equivalent to the resin film) into the distilled water. Specifically, the spectrum of ClO2 radicals generated from sodium chlorite, the radical source, became approximately 17.5 times stronger after 90 minutes of standing, which revealed that they permeate the resin layer, and that ClO2 ions in the radical source cannot permeate the resin layer.

[0088] <Example 2: Oxidative decomposition test of laminated film using a solution containing a radical source>

[0089] material The laminated film samples used in this example were selected from commercially available refill pouches with different film layer compositions. 1cm squares were cut from the pouches and used as the immersion samples. Before and after the test, IR analysis was performed on the front, each peeled surface, and the back of each sample using a PerkinElmer Spectrum FT-IR Spectrometer. The obtained IR spectra were analyzed using Spectrum software. This analysis identified the polymer compounds contained in the film, resulting in the composition shown in Table 1.

[0090] [Table 1]

[0091] Preparation of NaClO2 solution A NaClO2 solution was prepared by placing sodium chlorite (3.0 g), hydrochloric acid (3 ml), and purified water (300 ml) in a reaction vessel shielded from light by aluminum foil and leaving it to stand for 1 hour.

[0092] Test 1 Each laminated film sample 1 to 6 was immersed in a NaClO2 solution to allow ClO2 radicals generated from the NaClO2 solution to act on each sample. After immersion in the NaClO2 solution, each sample was stirred for 4 hours and then left to stand overnight.

[0093] In addition, in Test 1, samples 1 to 6 taken from the same refill pouch were subjected to the same reaction system as above, with an illumination intensity of 20 mW / cm from above the reaction system during stirring. 2 The sample was obtained by irradiating it with UV light adjusted to 1000 kJ / cm.

[0094] evaluation After leaving the sample to stand overnight, the sample was removed from the solution, washed with purified water, and then dried. After the sample dried, the peeling state of the film layer was classified as either peeled or not, and rated as "++" if the film peeled naturally after standing, "+" if it could be peeled by hand after standing, and "-" if it could not be peeled by hand after standing. The results are summarized in Table 2.

[0095] [Table 2]

[0096] Test 2 In Test 1, separation by ClO2 radicals generated from the NaClO2 solution was confirmed, so a test was conducted in which heating was performed to enhance the action of film separation by ClO2 radicals.

[0097] The targets were laminated film samples 1, 2, 5, and 6. Each sample was newly cut out from the refill pouch used in Test 1 and immersed in a NaClO2 solution. The reaction system was then placed on a hot plate set to 80°C and heated.

[0098] Two types of each sample were prepared, distinguished by the presence or absence of UV irradiation under the same conditions as in Test 1. One was heated for one hour, and the other was heated and UV irradiated for one hour. The reaction system was then stirred for three hours and then left to stand overnight. After leaving it to stand overnight, the samples were evaluated by peeling using the same procedure as in Test 1, and the results are summarized in Table 3.

[0099] [Table 3]

[0100] Test 3 In Test 2, it was confirmed that heating increases the decomposition ability of the ClO2 radicals generated from the NaClO2 solution. Based on this, in Test 3, in order to further enhance the film separation effect of the ClO2 radicals, a test was conducted in which defects (so-called physical scratches) were made on the non-laminated side of the film to assist penetration.

[0101] For laminated film samples 2 and 6, samples newly cut from the refill pouches used in Test 1 were scratched with a wire brush or tweezers. The treated samples were reacted for 1 hour under the same conditions as in Test 2. After 1 hour, the heating and UV irradiation were stopped, and the reaction system was stirred for 3 hours and then left to stand overnight. After leaving the samples to stand overnight, a peel test was performed on the samples using the same procedure as in Tests 1 and 2. The results are summarized in Table 4.

[0102] [Table 4]

[0103] From the results of Tests 1 to 3, layer separation was observed in all samples. Furthermore, because IR analysis could be performed before and after the tests, the films were recovered in a state that allowed for consistent composition analysis.

[0104] Therefore, taking into account the results of Example 1, it was demonstrated that radicals generated from a radical source can penetrate the resin layer itself in laminated films having various polymer layers. In addition, even between resins, for example, there are irregularities on the resin film surface that would occur at the interface of independently formed films, and there are inconsistencies or modified areas due to the adhesive layer at the interface of the adhesive. Therefore, it is suggested that the radicals that penetrated one of the resin films caused decomposition originating from these inconsistencies or modified areas in the composition (i.e., present at the bonding interface between the films), which resulted in the films being able to separate from each other at the bonding interface.

[0105] In other words, it is suggested that under the conditions of this test, radicals that have penetrated into the resin layer may cause decomposition of the adhesive.

[0106] Furthermore, the results of Tests 2 and 3 showed that for samples where no peeling was observed, peeling could be achieved by adding UV irradiation, heat treatment, abrasion, or pitting. In other words, adding a structure that adds thermodynamic energy or physical treatment, such as UV, heat, abrasion, or pitting, can promote decomposition. This suggests that the addition of such a structure can control the oxidative decomposition reaction.

[0107] In particular, it was confirmed that the aluminum vapor deposition contained in each film completely disappeared for Samples 1, 2, 4, and 5. The aluminum vapor deposition layer disappeared for Samples 1 and 5 under conditions of 80°C and UV irradiation, and for Sample 4 under conditions of UV irradiation only. In other words, aluminum is dissolved in the NaClO2 solution, and by combining this with a technology to appropriately extract this aluminum, the possibility of recycling aluminum is suggested.

Claims

1. A method for treating a laminated film formed from a plurality of resin layers, the method comprising applying a solution containing a radical generating source to the laminated film to generate radicals and thereby decompose the bonding interfaces between the films in the laminated film.

2. The method of claim 1 , wherein the laminated film has a metal-containing layer at the bonding interface between the films.

3. The method of claim 1 , wherein the laminated film has an adhesive layer at the film-to-film bonding interface.

4. The method according to claim 1, wherein the laminated film comprises two or more resin layers formed of the same or different polymer compounds, and the resin layers are bonded to the upper and lower layers of the metal-containing layer.

5. A liquid for treating a laminated film formed from a plurality of resin layers, the liquid containing a radical generating source, wherein radicals generated from the radical generating source are applied to the laminated film so as to decompose the bonding interfaces between the films that make up the laminated film.

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