Polyester recycling systems and recycling methods

Abstract

To propose a recycling system or method for laminated polyester film that can be used for general purposes. [Solution] The polyester recycling system includes a functional layer removal means for removing the functional layer from the recovered waste material, which is a laminated polyester film having a functional layer on the surface of the polyester film, using a cleaning agent that dissolves the polyester film, a recovery means for recovering the polyester film from which the functional layer has been removed, and a manufacturing means for producing recycled polyester products using the recovered polyester film as a raw material.

Description

Technical Field

[0001] The present invention relates to a polyester recycling system and a recycling method.

Background Art

[0002] Conventionally, waste plastics have been treated by landfill, ocean dumping, incineration, etc. However, it is becoming difficult to secure landfill sites, and ocean dumping is causing environmental problems because plastics do not decompose. Also, although it can be used as heat by incineration, there is a problem that it leads to global warming due to the emission of carbon dioxide.

[0003] Therefore, due to the increasing environmental problems in recent years, recycling of waste plastics such as reuse and regeneration is required, and research and development for this purpose are being actively conducted. Also, since many plastics are produced from fossil fuels, construction of a recycling method is required from the viewpoint of effective use of resources.

[0004] By the way, a polyester film, which is a kind of plastic film, is useful as a base film and is often used as a laminated film in which various functional layers are laminated on one or both sides. As the functional layer, there are various functional layers such as a hard coat layer, an adhesive layer, a decorative layer, a light shielding layer, a polarizing layer, an ultraviolet shielding layer, etc., and a laminated film in which a material corresponding to the functional layer is laminated on the polyester film is used.

[0005] Such laminated films are hardly reused after use and are discarded, incinerated, etc.

[0006] Even if an attempt is made to recycle a laminated film with a functional layer by remelting it as it is, since the material constituting the functional layer is mixed into the molten polymer, it generates a strange odor during extrusion, or the melt viscosity of the polymer decreases, which causes breakage during film formation. Also, even if a film can be formed, deterioration in quality due to coloring of the obtained film, foreign matter inclusion, etc. cannot be avoided.

[0007] Furthermore, even if the functional layer is physically removed by scraping or other means and then melt-extruded, problems can arise during the filtration process of extrusion, such as the filter becoming clogged by the remaining functional layer, preventing proper film formation.

[0008] One example of a method for recycling laminated films is the technology disclosed in Patent Document 1. This technology involves a laminated film in which an easily soluble functional layer and a surface functional layer are laminated in that order on at least one side of a base film. With this configuration, after use, the base film is separated and recovered from the laminated film by washing it with a solvent that can dissolve only the easily soluble functional layer and does not dissolve the base film. The separated and recovered material is then remelted, making it possible to regenerate the resin composition that constituted the base film. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2004-169005 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The method disclosed in Patent Document 1, as described above, is based on a laminated film in which an easily soluble resin layer and a surface functional layer are laminated in that order on the surface of a base film, and attempts to remove the functional layer by dissolving the easily soluble functional layer. In other words, it cannot be used with most laminated polyester films that do not have an easily soluble functional layer, making it a technology with limited versatility. In view of the above circumstances, the object of the present invention is to propose a general-purpose recycling system or recycling method for polyester film. [Means for solving the problem]

[0011] As a result of diligent research, the inventors have found that the above problem can be solved by recovering laminated polyester film, which is waste material, removing the functional layer using a specific cleaning agent, recovering the polyester film from which the functional layer has been removed, and manufacturing recycled products using the recovered polyester film as a raw material. The present invention was completed based on this finding. That is, the present invention has the following aspects. (1) A polyester recycling system comprising: a functional layer removal means for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film, which is a collected waste material, using a cleaning agent that dissolves the polyester film; a recovery means for recovering the polyester film from which the functional layer has been removed; and a manufacturing means for manufacturing a recycled polyester product using the recovered polyester film as a raw material. (2) The polyester recycling system according to (1) above, wherein the manufacturing means comprises a pellet manufacturing means for pelletizing the polyester film from which the functional layer has been removed. (3) The polyester recycling system according to (1) or (2) above, wherein the cleaning agent is a cleaning agent containing an alkaline agent. (4) A polyester recycling system according to any one of (1) to (3) above, further comprising a rinsing means for washing away the cleaning agent adhering to the polyester film from which the functional layer has been removed by the functional layer removal means. (5) A polyester recycling system according to any one of (1) to (4) above, wherein the waste material is a roll-shaped or block-shaped laminated polyester film. (6) A polyester recycling system according to any one of (1) to (5) above, further comprising an unwinding means or a cutting means prior to the functional layer removal means. (7) A polyester recycling system described in any one of (1) to (6) above, to which the roll-to-roll method is applied. (8) A method for recycling polyester, comprising: a recovery step (A) for recovering a laminated polyester film which is waste material and has a functional layer on the surface of the polyester film; a functional layer removal step for removing the functional layer from the laminated polyester film using a cleaning agent that dissolves the polyester film; a recovery step (B) for recovering the polyester film from which the functional layer has been removed; and a manufacturing step for manufacturing a recycled polyester product using the polyester film recovered in the recovery step (B) as a raw material. (9) The method for recycling polyester according to (8) above, wherein the manufacturing process includes a pellet manufacturing process that pelletizes the polyester film from which the functional layer has been removed. (10) The method for recycling polyester according to (8) or (9) above, wherein the cleaning agent is a cleaning agent containing an alkaline agent. (11) A method for recycling polyester according to any one of (8) to (10) above, further comprising a rinsing step of washing away the detergent adhering to the polyester film from which the functional layer has been removed in the functional layer removal step. (12) A method for recycling polyester according to any one of (8) to (11) above, wherein in the recovery step (A), the waste polyester film is recovered in roll form or in block form. (13) A method for recycling polyester according to any one of (8) to (12) above, further comprising an unwinding step or a cutting step prior to the functional layer removal step. (14) A method of recycling polyester described in any one of (8) to (13) above, performed in a roll-to-roll manner. [Effects of the Invention]

[0012] According to the recycling system and recycling method of the present invention, the functional layer can be removed from a laminated polyester film having a functional layer, and the polyester (polyester film substrate) can be efficiently recovered and recycled. [Brief explanation of the drawing]

[0013] [Figure 1]It is a conceptual diagram showing one aspect of the recycling system of the present invention. [Figure 2] It is a conceptual diagram showing another aspect of the recycling system of the present invention.

Mode for Carrying Out the Invention

[0014] The recycling method of the present invention includes a recovery step (A) of recovering a laminated polyester film that is waste material and has a functional layer on the surface of the polyester film, a functional layer removal step of removing the functional layer using a cleaning agent that dissolves the polyester film from the laminated polyester film, a recovery step (B) of recovering the polyester film from which the functional layer has been removed, and a manufacturing step of manufacturing a recycled polyester product using the polyester film recovered in the recovery step (B). It is a recycling method of polyester.

[0015] <Recovery Step (A) of Laminated Polyester Film> The recovery step of the laminated polyester film in the present invention is to recover the used laminated polyester film from the market. More specifically, for example, a method of recovering the used laminated polyester film, which is waste material, in exchange for the delivery of the next new laminated polyester film for the laminated polyester film with a functional layer sold to customers can be considered. In the present invention, by grasping the type, delivery amount, and delivery frequency of the laminated polyester film delivered in the customer list, etc., the type and recovery amount of the laminated polyester film to be recovered can be predicted. The recycling method of the present invention can make a more accurate prediction from this prediction and the recovery record, and can grasp the type and required amount of the cleaning agent necessary for peeling the functional layer in advance, and is a consistent recycling method. Note that the laminated polyester film that has become waste material may be stored in a roll form as it was at the time of delivery, or it may be in a lump form. In the recycling method of the present invention, depending on the shape of the waste material, by making full use of the unwinding method and cutting method described later, it can be recycled efficiently. Here, since the shape of the waste material usually depends on the use of the laminated film, in the recycling method of the present invention, it is also possible to predict how much of each shape (roll form or lump form) will be recovered.

[0016] (Laminated polyester film) The laminated polyester film in the present invention refers to a film in which a functional layer such as a resin layer is laminated on the surface of a polyester film that is a base film. The polyester film may have a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, it may have a two-layer structure, a three-layer structure, etc., or it may be a four-layer or more multi-layer, and the number of layers is not particularly limited. Also, the polyester film may be a stretched film such as a biaxially stretched film or an unstretched film. The polyester constituting the polyester film is not particularly limited, and those commercially available can be appropriately used. Specifically, polyesters obtained by polycondensing a dicarboxylic acid and a diol can be mentioned. As the dicarboxylic acid, an aromatic dicarboxylic acid is preferable, and as the diol, an aliphatic glycol is preferable. Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, etc. Examples of the aliphatic glycol component include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. The polyester may be a homopolyester or a copolyester. Also, the polyester may contain a third component other than the aromatic dicarboxylic acid and glycol as a copolymer component. Specific examples of polyesters include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, and polybutylene-2,6-naphthalate, with polyethylene terephthalate being preferred among these. These may also be copolymer polyesters; for example, polyethylene terephthalate may have dicarboxylic acid units other than terephthalic acid in an amount of about 30 mol% or less of dicarboxylic acid units, and may also have diol units other than ethylene glycol in an amount of about 30 mol% of diol units.

[0017] The functional layer is not particularly limited in its constituent components, but from the viewpoint of removal by the recovery method of the present invention, it is preferably composed of resin. Examples of functional layers include adhesive layers, hard coat layers, release layers, decorative layers, light-shielding layers, ultraviolet shielding layers, easy-adhesion layers (primer layers), antistatic layers, refractive index adjusting layers, and oligomer encapsulation layers.

[0018] The adhesive layer is a layer provided for adhesively adhering to other equipment, etc., and the material constituting the adhesive layer is not particularly limited, but for example, known adhesive resins such as acrylic, rubber, or silicone can be used.

[0019] The hard coat layer is a layer provided to the polyester film to impart scratch resistance and other properties. The material used to form the hard coat layer is not particularly limited, but examples include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, and cured products of reactive silicon compounds such as tetraethoxysilane.

[0020] The release layer is a layer provided to impart release properties to the polyester film. For example, it is a layer provided in release films used in process paper for green sheet molding used in the manufacture of ceramic electronic components, polarizing plates, and adhesive separators for optical components used in the manufacture of flat panel displays such as optical filters. There are no particular restrictions on the materials that constitute the release layer. Examples include those mainly composed of curable silicone resin, modified silicone resins produced by graft polymerization with urethane resin, epoxy resin, etc., long-chain alkyl group-containing compounds, fluorine compounds, hydrocarbon waxes, etc.

[0021] The decorative layer is a layer provided to enhance the design, and the materials constituting the decorative layer are not particularly limited, but include polyurethane resins, vinyl resins, polyamide resins, polyester resins, acrylic resins, polyvinyl acetal resins, etc. Pigments, dyes, etc. are added to these resins to create the decoration.

[0022] The light-shielding layer or UV-shielding layer is a layer provided to protect the contents from ultraviolet light, visible light, etc. The materials constituting the light-shielding layer or UV-shielding layer are not particularly limited, but examples include the various resins described in the decorative layer section, inorganic fillers such as calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, and barium sulfate, and organic fillers such as wood flour, pulp flour, and cellulose powder.

[0023] The easy-adhesion layer (primer layer) is a layer provided to adhere other layers or films onto the polyester film, and is not particularly limited, but examples include polyurethane resins, vinyl resins, polyamide resins, polyester resins, acrylic resins, polyvinyl acetal resins, and various crosslinking agents and particles.

[0024] An antistatic layer is a layer provided to prevent static electricity generated by contact with other materials or peeling. While not particularly limited, the antistatic agents used in the antistatic layer include nonionic, cationic, anionic, and amphoteric surfactants, conductive polymers such as polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), and poly(4-styrene sulfonate), metal oxide fillers such as SnO2 (Sb-doped), In2O3 (Sn-doped), and ZnO (Al-doped), and carbon compounds such as graphene, carbon black, and carbon nanotubes (CNTs). These may be used individually or in combination of two or more. Furthermore, the antistatic layer may be formed from a resin composition containing the antistatic agent. Examples of resins included in the resin composition include polyester resins, acrylic resins, and urethane resins.

[0025] The refractive index adjustment layer is a layer provided to adjust the refractive index. The materials constituting the refractive index adjustment layer are not particularly limited, but examples include polyester resin, acrylic resin, urethane resin, polycarbonate resin, epoxy resin, alkyd resin, urea resin, fluororesin, and metal oxides such as zirconium oxide and titanium oxide. These may be used individually or in combination of two or more types.

[0026] The oligomer encapsulation layer is a layer provided to prevent film whitening and foreign matter after the heating process. While not particularly limited, examples of materials constituting the oligomer encapsulation layer include amine compounds and ionic resins. The oligomer encapsulation layer may also be a highly crosslinked coating or the like.

[0027] These functional layers can be single layers or stacked in pairs or layers. When two or more layers are laminated, it is preferable that at least one layer is made of resin.

[0028] <Functional layer removal process> The functional layer removal process is the process of removing the functional layer from the laminated polyester film. The functional layer removal process involves either dissolving the functional layer itself by washing with a cleaning agent, or dissolving a portion of the surface of the polyester film substrate and peeling the functional layer off at the interface with the polyester film substrate. More specifically, these methods include immersion, where the cleaning agent is submerged in a cleaning tank containing the cleaning agent; application, where the cleaning agent is applied in solution; and spraying, where the cleaning agent is sprayed in solution or vaporized. Of these, the immersion method is preferred due to the penetration of the cleaning agent into the functional layer.

[0029] In the immersion method, the temperature of the cleaning agent is preferably room temperature (20°C) or higher. At room temperature (20°C) or higher, the viscosity of the cleaning solution is low, allowing it to penetrate the functional layer easily, thus providing good cleaning performance. From this viewpoint, the temperature of the cleaning agent in the immersion method is more preferably 40°C or higher, even more preferably 50°C or higher, and particularly preferably 60°C or higher. Furthermore, as for the upper limit of the temperature of the detergent, when the detergent is used in solution form, a temperature below the boiling point is preferable. In the case of an aqueous detergent, which is a preferred embodiment of the present invention, a temperature of 100°C or lower is preferable, and 90°C or lower is more preferable. Furthermore, the temperature of the cleaning solution during cleaning is the same as described above, even in methods other than immersion. In addition, microwave irradiation may be performed during stripping cleaning in the immersion method in order to promote the hydrolysis reaction.

[0030] The pH of the cleaning agent is preferably 12 or higher, and more preferably 13 or higher, from the viewpoint of cleaning performance.

[0031] The immersion time needs to be adjusted as appropriate depending on the type of object being cleaned, as follows:

[0032] When a polyester film with an acrylic adhesive layer as a functional layer is to be cleaned, a cleaning time of 1 second to 30 minutes is preferable. If the cleaning time is 1 second or longer, the cleaning agent can sufficiently penetrate the functional layer and exhibit its cleaning ability. On the other hand, if the cleaning time is 30 minutes or less, the polyester film base material will not dissolve excessively, and the amount of polyester recovered can be secured. From these viewpoints, a cleaning time of 15 seconds to 20 minutes is more preferable, 30 seconds to 15 minutes is even more preferable, and 1 minute to 10 minutes is particularly preferable.

[0033] When a polyester film with an acrylic hard coat layer as a functional layer is to be cleaned, a cleaning time of 1 second to 30 minutes is preferable. If the cleaning time is 1 second or longer, the cleaning agent can sufficiently penetrate the functional layer and achieve its cleaning performance. On the other hand, if the cleaning time is 30 minutes or less, the polyester film base material will not dissolve excessively, and the amount of polyester recovered can be secured. From these viewpoints, a cleaning time of 15 seconds to 30 minutes is more preferable, 30 seconds to 25 minutes is even more preferable, and 1 minute to 20 minutes is particularly preferable.

[0034] When a polyester film with a silicone release layer as a functional layer is to be cleaned, a cleaning time of 1 second to 30 minutes is preferable. If the cleaning time is 1 second or longer, the cleaning agent can sufficiently penetrate the functional layer and exhibit its cleaning ability. On the other hand, if the cleaning time is 30 minutes or less, the polyester film, which is the base material, will not dissolve excessively, and the amount of polyester obtained when recovered can be secured. From the above viewpoint, a cleaning time of 15 seconds to 20 minutes is more preferable, a cleaning time of 30 seconds to 10 minutes is even more preferable, and a cleaning time of 1 minute to 5 minutes is particularly preferable.

[0035] The specific details of the functional layer removal process depend on the shape of the laminated polyester film that is being used as waste material.

[0036] (In the case of roll form) If the waste laminated polyester film is in roll form, it is preferable to install an unwinding device before the washing tank containing the cleaning agent, unwind the laminated film from the device, and introduce it into the washing tank for washing. It is then preferable to proceed continuously to the next recovery process (B). Furthermore, in the rinsing process described later, following the functional layer removal process, equipment equipped with physical means such as a roll brush, ultrasonic waves, micro / nanobubbles, water jets, and compressed cold air may be provided for the purpose of efficiently removing the functional layer from the laminated polyester film.

[0037] (In the case of a lump) If the waste laminated polyester film is in the form of a lump, it is preferable to install a cutting device before the washing process to break it into flakes before introducing it into the washing tank. Breaking it into flakes increases the contact area between the laminated polyester film and the cleaning agent, allowing the cleaning agent to penetrate more easily and efficiently remove the functional layer. In this embodiment, it is preferable to use a belt conveyor or the like to continuously introduce the flake-shaped laminated polyester film into the washing tank. By adopting this embodiment, washing can be performed in a batch manner.

[0038] <Recovery process (B)> After the functional layer removal step, the polyester film, which is the base film, is recovered. Preferably, the recovery step is preceded by a rinsing step and a drying step, which will be described later. As for the recovery method, an appropriate method can be selected depending on the shape of the laminated polyester film that is the waste material.

[0039] When the waste laminated polyester film is in roll form, it can be efficiently recovered by continuously processing it using a roll-to-roll method, followed by appropriate washing, rinsing, and drying processes, before being wound up.

[0040] If the waste laminated polyester film is in the form of a block, it is preferable to have a cutting step before the functional layer removal step, as described above. In this embodiment, it is preferable to use a belt conveyor or the like to continuously pass the film through the rinsing and drying steps to recover the flake-shaped polyester.

[0041] As described above, it is advantageous in terms of handling to process the recovered polyester film into pellets after collection.

[0042] <Rinsing process> In the present invention, it is preferable to have a rinsing step to wash away the detergent after the functional layer removal step and before the recovery step (B). Specifically, this refers to a step in which the detergent adhering to the polyester film from which the functional layer has been removed is washed away with a rinsing solution.

[0043] The rinsing solution is not particularly limited as long as it can wash away the detergent, but when using a water-based detergent, which is a preferred embodiment of the present invention, water can be used in the rinsing step.

[0044] The temperature of the rinsing process is preferably around room temperature, more preferably 5 to 50°C, and more preferably 5 to 30°C, from the viewpoint of efficient rinsing.

[0045] Methods for rinsing off the cleaning agent include a spray method, where rinsing solution is sprayed onto the polyester film from which the functional layer has been removed, and an immersion method, where the polyester film is immersed in a rinsing tank containing rinsing solution. However, if a cleaning agent that does not require rinsing is used, the rinsing step can be omitted.

[0046] Along with the cleaning agent, the functional layer that has been peeled off from the polyester film may also be washed away at the same time. The organic solvent or water used in the rinsing process and the material that made up the functional layer are then separated, and the organic solvent and water can be reused in the rinsing process, and the material that made up the functional layer can also be reused.

[0047] <Drying process> It is preferable to follow the rinsing step with a drying step. The drying step removes any remaining detergent and / or rinsing solution from the polyester film. If the rinsing step is omitted, the drying step may be performed after the functional layer removal step (A).

[0048] The drying process conditions are not particularly limited, but are usually 70-150°C for 1-30 minutes. Common drying methods can be used, such as heating with an infrared heater or oven, hot air drying with a hot air dryer, or microwave heating drying.

[0049] <Recycled Polyester Product Manufacturing Process> The polyester film recovered in the above recovery process (B) is recycled (reused) as a raw material to manufacture recycled polyester products. Preferably, in the preceding step of this manufacturing process, the polyester is pelletized in the pellet manufacturing process described later, and the recycled polyester products described later are used with these pellets.

[0050] <Pellet Manufacturing Process> It is preferable that the dried polyester film be processed into pellets through a pellet manufacturing process. In particular, if the waste laminated polyester film is in the form of a block, it is cut as described above, and the resulting recycled polyester is in the form of flakes. The handling of flake polyester is greatly improved by pelletizing it. Pellets offer advantages not only in terms of handling but also in terms of ease of storage and subsequent processing.

[0051] <Recycled polyester products> The polyester film obtained by the recovery method of the present invention can be used as a polyester raw material and can be reused as a so-called recycled polyester product. Specifically, the recovered polyester can be pelletized and stored as pelletized polyester (polyester product). The recovered polyester can also be molded into various polyester products such as polyester film by melt extrusion or the like. However, due to its ease of manufacture, it is preferable to pelletize the recovered polyester first and then mold it into various products.

[0052] In terms of applications, it can be used in the same ways as ordinary polyester products, for example, as a polyester film used as a base film. By forming a functional layer on the base film, it can also be reused as a laminated film.

[0053] Recycled polyester can be used in combination with conventionally manufactured polyester, or it can be used to create multilayer films using recycled polyester and conventionally manufactured polyester.

[0054] Recycled polyester products can be used for various purposes other than film, such as manufacturing PET bottles, polyester fibers, polyester sheets, and polyester containers.

[0055] Furthermore, the detached functional layer can also be recovered and reused as needed.

[0056] <Cleaning agent> The cleaning agent used in the functional layer removal process is not particularly limited as long as it has the function of dissolving the polyester film of the base material, but it is preferable that it contains an alkaline agent. Depending on the type of functional layer, there is a suitable cleaning agent, and it is preferable to prepare it in advance. Furthermore, in this recycling system, it is preferable that various information such as the customer list mentioned above is consistently managed, which allows for the preparation of cleaning agents and cleaning tanks without waste.

[0057] (Detergent containing an alkalizing agent) Detergents containing an alkalizing agent are effective, for example, on adhesive films and hard coat films having an acrylic functional layer. Specifically, a detergent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group is preferred.

[0058] Even in laminated films having a functional layer that is not decomposed or dissolved by the cleaning agent, such as the above-mentioned silicone-based functional layer release film, the polyester film base itself undergoes transesterification, saponification, ionization, etc., causing dissolution, which allows the functional layer on top to be peeled off and removed.

[0059] (Alkalinizing agent) The alkalizing agent (hereinafter also referred to as component (a)) is a substance that makes the cleaning solution alkaline, and can also be called an alkaline agent. The alkalizing agent may be an inorganic alkalizing agent or an organic alkalizing agent.

[0060] Examples of inorganic alkalizing agents include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and barium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal phosphates such as trisodium phosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, tripotassium phosphate, potassium pyrophosphate, and potassium tripolyphosphate; alkali metal silicates such as sodium orthosilicate, sodium metasilicate, and potassium silicate; and ammonia.

[0061] Among the inorganic alkalizing agents in this detergent, alkali metal hydroxides are preferred, sodium hydroxide and potassium hydroxide are more preferred due to their availability, and potassium hydroxide is particularly preferred due to its cleaning properties.

[0062] In this detergent, one inorganic alkalizing agent can be used alone or in combination of two or more. In particular, the combination of potassium hydroxide and sodium hydroxide is preferred in terms of effectiveness and ease of handling.

[0063] Examples of organic alkalizing agents include organic amine compounds such as N,N-bis(2-hydroxyethyl)-N-cyclohexylamine, diazabicycloundecene, diazabicyclononene, monomethylamine, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, and triisopropanolamine. Furthermore, while organic alkalizing agents may include compounds having at least one hydroxyl group, if the acidity constant (pKa) of such compounds is 30 or higher, they shall be treated as alkalizing agents.

[0064] Organic alkalizing agents may include compounds having at least one hydroxyl group, but if the acidity constant (pKa) of such compound is 30 or higher, it should be treated as an alkalizing agent.

[0065] Among the organic alkalizing agents in this detergent, monoethanolamine, diethanolamine, and triethanolamine are preferred due to their versatility, monoethanolamine and diethanolamine are more preferred due to their availability, and monoethanolamine is particularly preferred due to its cleaning properties.

[0066] Furthermore, using both an inorganic alkalizing agent and an organic alkalizing agent is preferable from the viewpoint of cleaning performance. Specifically, a combination of at least one inorganic alkalizing agent, such as sodium hydroxide and potassium hydroxide, and at least one organic alkalizing agent selected from monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, and triisopropanolamine is more preferable. A combination of at least one inorganic alkalizing agent selected from sodium hydroxide and potassium hydroxide, and at least one organic alkalizing agent selected from monoethanolamine and diethanolamine is particularly preferable.

[0067] The content of the alkaline agent in the total detergent is more preferably 1 to 50% by mass, even more preferably 2 to 45% by mass, and particularly preferably 3 to 40% by mass. If it falls outside the above range, the detergent may not be sufficiently effective.

[0068] (A compound having at least one hydroxyl group) Detergents containing an alkaline agent preferably contain a compound having at least one hydroxyl group (hereinafter also referred to as component (b)). Examples of compounds having at least one hydroxyl group include alcohols and phenols.

[0069] Examples of alcohols include monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and hexafluoro-2-propanol; dihydric alcohols such as ethylene glycol, diethylene glycol, and propylene glycol; and polyhydric alcohols such as glycerin.

[0070] Examples of phenols include phenol, xylenol, salicylic acid, picric acid, naphthol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, dibutylhydroxytoluene, bisphenol A, cresol, estragyl, eugenol, gallic acid, guaiacol, picric acid, phenolphthalein, serotonin, dopamine, adrenaline, noradrenaline, thymol, tyrosine, and hexahydroxybenzene.

[0071] These can be used individually or in combination of two or more types, but in particular, from the viewpoint of enhancing the stripping and cleaning effect, it is preferable to use two or more types in combination, and among these, it is even more preferable to use two or more types of alcohols in combination.

[0072] Among these, alcohols are preferred from the viewpoint of maintaining the cleaning performance without impairing the alkalinity of the cleaning agent, and from the viewpoint of promoting the dissolution of the polyester film substrate. A transesterification reaction occurs at the ester bonds of the polyester film due to alkoxides generated from the hydroxyl groups of alcohols, yielding a low molecular weight compound. Subsequently, a saponification reaction proceeds, in which hydroxyl groups dissociated from the alkalizing agent (b) nucleophilically attack the ester bonds of the low molecular weight compound to obtain a carboxylate (ionization). This is presumed to accelerate the dissolution of the polyester film.

[0073] From the viewpoint of cleaning performance, the acidity constant (pKa) of the alcohols is preferably in the range of 8.0 or more and 20.0 or less, more preferably 8.0 or more and 18.0 or less, even more preferably 9.0 or more and 16.0 or less, particularly preferably in the range of 9.0 or more and 15.6 or less, and most preferably 9.3 or more and 15.4 or less. If the acidity constant (pKa) of the alcohols is within the above range, alkoxides are generated without impairing the alkalinity of the cleaning agent, thus improving the cleaning ability of the cleaning agent.

[0074] The acidity constants (pKa) of some alcohols are as follows: Hexafluoro-2-propanol (pKa=9.3), benzyl alcohol (pKa=15.4), methanol (pKa=15.5), ethanol (pKa=16.0), 1-propanol (pKa=16.1), 2-propanol (pKa=17.1), 1-butanol (pKa=16.1), and tert-butanol (pKa=18.0). In the case of the acidity constants (pKa) of alcohols shown above, alcohols with an acidity constant (pKa) of 15.4 or less can be said to be alcohols with an acidity constant (pKa) smaller than methanol. Furthermore, alcohols with an acidity constant (pKa) of 9.3 or higher can be defined as alcohols with an acidity constant (pKa) equal to or greater than that of hexafluoro-2-propanol.

[0075] (Preferred embodiment of component (b) 1) Among the above, hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, propyl alcohol, and benzyl alcohol are more preferred from the viewpoint of cleaning properties. These alcohols readily produce alkoxides through proton ionization and have high cleaning properties. Among them, hexafluoro-2-propanol is preferred due to its high cleaning power.

[0076] Furthermore, it is preferable to use hexafluoro-2-propanol in combination with other alcohols to adjust the cleaning ability. When used in combination, it is preferable to use hexafluoro-2-propanol with methyl alcohol, hexafluoro-2-propanol with ethyl alcohol, or hexafluoro-2-propanol with benzyl alcohol.

[0077] When hexafluoro-2-propanol and other monohydric alcohols are used as alcohols, the mass ratio of these alcohols (hexafluoro-2-propanol: other monohydric alcohols) is preferably 1:1 to 1:100, more preferably 1:3 to 1:41, even more preferably 1:4 to 1:20, and particularly preferably 1:5 to 1:10.

[0078] Furthermore, even when using two or more monohydric alcohols in combination, dihydric alcohols and polyhydric alcohols may also be used in combination.

[0079] (Preferred embodiment of component (b) 2) Furthermore, from the viewpoint of low volatility and usable temperature range, the use of benzyl alcohol is preferred among the above.

[0080] (Preferred embodiment of component (b) 3) Furthermore, from the viewpoint of enhancing the peeling and cleaning effect, it is preferable to use two or more types in combination, and when using two or more types in combination, a combination of hydrophobic monovalent alcohol and water-soluble monovalent alcohol is preferable from the viewpoint of exhibiting a broad and synergistic peeling and cleaning effect regardless of the properties of the coating film. Here, hydrophobic monovalent alcohol refers to monovalent alcohol that separates into two layers without mixing with water, and water-soluble monovalent alcohol refers to monovalent alcohol that mixes with water to form a single layer. Furthermore, it is more preferable to use benzyl alcohol as the hydrophobic monovalent alcohol and hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, and propyl alcohol as water-soluble monovalent alcohols in combination, with the combination of benzyl alcohol and hexafluoro-2-propanol and benzyl alcohol and methyl alcohol being the most preferable.

[0081] When two or more of the aforementioned alcohols are used in combination, the mixing ratio is not particularly limited, but from the viewpoint of particularly enhancing the peeling and cleaning effect, the mass ratio of hydrophobic monovalent alcohol to water-soluble monovalent alcohol is preferably 1:1 to 10:1, and more preferably 1.5:1 to 10:1.

[0082] Furthermore, even when using two or more monohydric alcohols in combination, dihydric alcohols and polyhydric alcohols may also be used in combination.

[0083] The content of compound (b) in the cleaning agent containing the alkalizing agent is preferably 10 to 99% by mass, more preferably 20 to 98% by mass, and even more preferably 30 to 97% by mass. Within the above range, the amount of alkalizing agent (a) is appropriate, so when the polyester film is recovered, contamination by foreign matter due to precipitation of alkalizing agent components is suppressed, and the quality of the recycled polyester film can be maintained.

[0084] From the viewpoint of cleaning performance, a particularly preferred embodiment of the cleaning agent in the present invention is a combination of (W) or (X) and (Y) or (Z). (W)(a) Contains alkali metal hydroxides, particularly sodium hydroxide or potassium hydroxide, as an alkalining agent (alkaline agent). (X)(a) The alkalizing agent (alkalinizing agent) includes an alkali metal hydroxide, particularly sodium hydroxide or potassium hydroxide, and also includes an organic alkalizing agent. (Y)(b) The compound having at least one hydroxyl group includes at least hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, propyl alcohol, or benzyl alcohol, particularly benzyl alcohol. (Z)(b) The compounds having at least one hydroxyl group include alcohols whose acidity constant (pKa) is in the range of 9.3 or higher and 15.4 or lower, that is, at least alcohols whose acidity constant (pKa) is greater than or equal to that of hexafluoro-2-propanol and less than that of methanol.

[0085] The cleaning agent containing the alkalizing agent according to the present invention is preferably an aqueous cleaning agent. An aqueous cleaning agent is obtained by dissolving or diluting the above components (a) and (b) in water. A aqueous cleaning agent is relatively safe because its flash point can be raised, and it is also advantageous because water can be used in the rinsing step described later.

[0086] In addition to components (a) and (b) above, various other additives can be added to the cleaning agent. For example, surfactants, antioxidants, rust inhibitors, pH adjusters, preservatives, viscosity modifiers, and defoamers may be added.

[0087] (Surfactants) There are no particular restrictions on the surfactant used; any of anionic surfactants, cationic surfactants, nonionic surfactants, or amphoteric surfactants can be used.

[0088] Examples of anionic surfactants include alkyl sulfonic acid, alkylbenzene sulfonic acid, alkyl carboxylic acid, alkylnaphthalene sulfonic acid, α-olefin sulfonic acid, dialkyl sulfosuccinic acid, α-sulfonated fatty acid, N-methyl-N-oleyl taurine, petroleum sulfonic acid, alkyl sulfate, sulfated oils and fats, polyoxyethylene alkyl ether sulfate, polyoxyethylene styrene-phenyl ether sulfate, alkyl phosphoric acid, polyoxyethylene alkyl ether phosphoric acid, polyoxyethylene alkylphenyl ether phosphoric acid, naphthalene sulfonic acid formaldehyde condensate, and salts thereof.

[0089] Cationic surfactants include quaternary ammonium compounds, tetraalkylammonium compounds, trialkylbenzylammonium alkylpyridinium compounds, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium compounds, N,N-dialkylmorpholinium compounds, polyethylene polyamine fatty acid amides, urea condensates of polyethylene polyamine fatty acid amides, quaternary ammonium compounds of polyethylene polyamine fatty acid amides, and salts thereof.

[0090] Examples of nonionic surfactants include polyoxyalkylene ethers such as polyoxyethylene alkyl ethers and polyoxyethylene-polyoxypropylene alkyl ethers; polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrenephenyl ethers, polyoxyethylene-polyoxypropylene glycols; polyhydric alcohol fatty acid partial esters; polyoxyethylene polyhydric alcohol fatty acid partial esters; polyoxyethylene fatty acid esters; polyglycerin fatty acid esters; polyoxyethylene castor oil; fatty acid diethanolamide; polyoxyethylene alkylamines; triethanolamine fatty acid partial esters; and trialkylamine oxides.

[0091] Examples of amphoteric surfactants include betaines (such as N,N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N,N,N-trialkyl-N-sulfoalkyleneammonium betaine, N,N-dialkyl-N,N-bispolyoxyethyleneammonium sulfate betaine, and 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine) and aminocarboxylic acids (such as N,N-dialkylaminoalkylene carboxylates).

[0092] (Antioxidant) The antioxidant is not particularly limited, and amine-based antioxidants, phenol-based antioxidants, etc., can be used.

[0093] (Rust inhibitor) Examples of rust inhibitors include inorganic compounds such as chromates, molybdates, and sodium nitrite.

[0094] (pH adjuster) Examples of pH adjusters include lactic acid, carbon dioxide, succinic acid, gluconic acid, citric acid, trisodium citrate, malic acid, and phosphoric acid.

[0095] (Preservative) Examples of preservatives include parabens, benzoic acid, sodium benzoate, sorbic acid, propionates, dehydroacetic acid, sulfur dioxide, and sodium pyrosulfite.

[0096] (Viscosity modifier) Examples of viscosity modifiers include polymer compounds and layered inorganic particles.

[0097] (Antifoaming agent) Examples of defoaming agents include fluorine compounds, silicone compounds, polyether compounds, acetylene glycol compounds, and chelating agents such as EDTA.

[0098] <Polyester Recycling System> The polyester recycling system according to the present invention comprises means for removing a functional layer, means for recovering the polyester film from which the functional layer has been removed, and means for manufacturing recycled polyester products using the polyester film as a raw material. This system is a system for recycling laminated polyester film, which is recovered waste material. The method for recovering the waste material is as described above. Furthermore, depending on the shape of the waste polyester film, it is also preferable to provide an unwinding mechanism, a cutting mechanism, etc., in front of the washing device, as described above, in this system. When the waste polyester film is in roll form, it is preferable to have a means for unwinding, and furthermore, a so-called roll-to-roll method, where winding is also done on a roll, is preferable in terms of efficiently obtaining recycled polyester. Furthermore, if the waste polyester film is in the form of a block, it is preferable to have a cutting means. Cutting breaks the waste into flakes, which, as mentioned above, makes the washing means more efficient.

[0099] The polyester recycling system of the present invention will be described in detail below with reference to the conceptual diagrams shown in Figures 1 and 2. Figure 1 shows the case where the waste laminated polyester film is in roll form, and Figure 2 shows the case where the waste laminated polyester film is in block form. When the waste material is in roll form, it is preferable to have an unwinding means (unwinding roll) 14 for unwinding the roll of laminated polyester film, as shown in Figure 1. The unwinded laminated film 16 is washed with a cleaning agent by a functional layer removal means 11, and the functional layer is peeled off and removed. In Figure 1, the functional layer removal means 11 is illustrated as an immersion device in which a cleaning agent is filled into an immersion tank and the laminated film is immersed in it, but it may also be an application device for applying the cleaning agent to the laminated polyester film, or a spraying device for spraying the cleaning agent onto the laminated polyester film. Among these, the immersion method using an immersion device is preferred.

[0100] Next, it is preferable to use the rinsing means 12 to wash away the cleaning agent adhering to the polyester film substrate used in the functional layer removal means 11. Figure 1 shows an immersion apparatus in which a immersion tank is filled with rinsing liquid and the polyester film is immersed in it, similar to the functional layer removal means. However, a spraying apparatus that sprays rinsing liquid onto the polyester film substrate from which the functional layer has been removed may also be used.

[0101] The polyester film substrate from which the functional layer has been removed is dried by the drying means 13 to remove the rinse solution. However, the rinsing means 12 may be omitted, and if the rinsing means 12 is omitted, the detergent is removed by the drying means. The drying means is not particularly limited, and known drying devices such as ovens that perform heat drying and hot air dryers can be used.

[0102] If the waste material is a roll of laminated polyester, it is preferable that it be wound up by a winding means (winding roll) 15. In other words, it is efficient and preferable to use the so-called roll-to-roll method shown in Figure 1.

[0103] The dried and wound polyester film substrate is preferably then pelletized in a pellet manufacturing apparatus 18. The pellet manufacturing apparatus 18 is not particularly limited as long as it can melt the polyester film substrate and pelletize it, but for example, a known extruder can be used, in which case the polyester film substrate can be melted in the extruder and the extruded polyester can be pelletized. Alternatively, after the polyester film substrate is unwound from the winding means, it may be appropriately pulverized before being fed into the extruder, and known pulverizers, cutters, etc., can be used as pulverizers.

[0104] Next, using Figure 2, we will explain the case where the waste laminated polyester film is in the form of a block. When the waste laminated polyester film is in the form of a block 26, it is preferable to cut it into flake-shaped laminated polyester film 27 using the cutting means 24. The flaked polyester film is transported by a belt conveyor 25 to a functional layer removal means 21, where it is washed with a cleaning agent and the functional layer is removed. In Figure 2, the functional layer removal means 21 is illustrated by filling an immersion tank with a cleaning agent and immersing the laminated film in it. Subsequently, the cleaning agent used in the functional layer removal means 21 is preferably washed away by the rinsing means 22, and then dried by the drying means 23 to obtain flake-shaped recycled polyester. The obtained flake-shaped polyester is then made into pellets in the pellet manufacturing apparatus 28. The pellet manufacturing apparatus 28 is similar to the pellet manufacturing apparatus 18, but since the polyester is already in flake form, the micronization means may be omitted. In the embodiment shown in Figure 2, performing the series of steps using the belt conveyor 25 is advantageous in terms of productivity, but other conveying means may also be used. The polyester recycling system described above is just one embodiment, and each of the means in this system can be modified or altered as appropriate, as long as it does not impair the effects of the present invention.

[0105] <Wastewater treatment system for stripping and cleaning solutions> The wastewater from the stripping and cleaning solution used in this invention may be disposed of by isolating each active ingredient using conventionally known separation and purification methods and reusing it as a raw material for the stripping and cleaning solution, or it may be disposed of from an operational standpoint. When disposing of wastewater, one method is to dispose of it in a sewage treatment tank equipped with a biological oxidation layer, aeration layer, sedimentation tank, chlorine disinfection tank, sludge tank, etc., which are capable of purifying the wastewater. In the case of wastewater treatment using sewage treatment tanks, the wastewater cannot be disposed of unless the chemical oxygen demand (COD) and biochemical demand (BOD) levels are below specified values, so some degree of wastewater purification is required beforehand. Alternatively, the amount of wastewater may be reduced beforehand by concentrating it or performing other methods. The aforementioned pretreatment methods include the coagulation-sedimentation method, in which a coagulant is added to separate the treated water and coagulated material, and then each is discarded; the filter filtration separation method, in which the waste liquid is separated into treated water and concentrated liquid using a UF membrane filter, etc., and then each is discarded; the reduced-pressure distillation method or evaporation concentration method, in which the waste liquid is heated under reduced pressure or atmospheric pressure to volatilize the solvent and separate it into treated water and concentrated liquid, and then each is recovered or discarded; the oxidation-reduction method (such as ozone decomposition) that decomposes organic matter in the waste liquid into CO2 and water by oxidation treatment, etc.; and the biological treatment method that decomposes organic matter in the waste liquid by biological treatment. [Examples]

[0106] Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples described below.

[0107] <Evaluation Method> (1) Immersion test The cleaning agents prepared in each example and comparative example were placed in a 30 ml water bath, and the laminated films were immersed in the solution. The temperature of the cleaning agent, the immersion time, and the sample size are as shown in the table.

[0108] (2) Evaluation of delamination of the functional layer (2-1) Visual inspection (Laminated polyester film having an adhesive layer, and laminated polyester film having a hard coat layer) The immersed laminated films were removed and their surfaces were visually inspected and evaluated according to the following criteria. ◎(very good); The functional layer is dissolved or peeled off, which is particularly preferable in practical terms. ○(good); The functional layer is partially dissolved or peeled off, but this does not pose a practical problem. △(fair); A small portion of the functional layer is dissolved or peeled off. ×(bad); The functional layer remains, which poses practical problems.

[0109] (2-2) X-ray fluorescence analysis (Laminated polyester film with silicone release layer) The surface of the washed laminated film was subjected to quantitative analysis of the Si element using an X-ray fluorescence analyzer (XRF, Shimadzu Corporation "XRF-1800"). The removal rate of the functional layer was measured by setting the Si element content of the laminated polyester film surface before washing to 100% and the Si element content of the plain film without the functional layer coating of the laminated film to 0%. ◎(very good) ;Removal rate 90~100% ○(good); Removal rate 70~89% ×(bad); Removal rate 0~69%

[0110] (3) Evaluation of intrinsic viscosity (IV) 1 g of polyester was accurately weighed, dissolved in 100 ml of a phenol / tetrachloroethane mixed solvent (50 / 50 by weight ratio), and measured at 30°C.

[0111] (4) Evaluation of dissolution of polyester film Polyethylene terephthalate film was immersed in a cleaning agent under the conditions shown in Table 1, and the thickness change of the polyester film substrate was measured by measuring the thickness using a Mitutoyo Corporation "Thickness Gauge ID-C112X / 1012X". Cases where the thickness change was 3 μm or more were classified as A, and cases where the thickness change was less than 3 μm were classified as B. When the thickness change was 3 μm or more, it is presumed that the dissolution of the polyester film substrate progressed due to immersion in the cleaning agent, and the functional layer peeled off.

[0112] (Laminated polyester film with a functional layer) Laminated polyester films having the following functional layers (I) to (III) were prepared as samples. (I) Laminated film (laminated polyester film with an acrylic adhesive layer); commercially available product ("PET75-H120(10) Blue" manufactured by Nichiei Shinka Co., Ltd.), polyethylene terephthalate film thickness: 75 μm, acrylic adhesive layer thickness: 10 μm.

[0113] (II) Laminated film (laminated polyester film having an acrylic hard coat layer); A laminated polyester film having an acrylic hard coat layer was obtained by the following procedure. (Preparation of acrylic hard coat solution) An acrylic hard coat solution was obtained by mixing 24 parts by weight of dipentaerythritol hexaacrylate, 6 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 1.5 parts by weight of a photopolymerization initiator (trade name: Omnirad 184, manufactured by IGM Resins BV), and 70 parts by weight of toluene. (Preparation of acrylic hard coat film) A polyethylene terephthalate film (commercially available product, "Diafoil" manufactured by Mitsubishi Chemical Corporation) was coated with the above-mentioned acrylic hard coat solution to a dry film thickness of approximately 9 μm, and cured by irradiation with ultraviolet light to obtain a laminated polyester film having an acrylic hard coat layer.

[0114] (III) Laminated film (laminated polyester film with a silicone release layer); commercially available product (Mitsubishi Chemical Corporation's "MRF38"), polyethylene terephthalate film thickness: 38 μm. The intrinsic viscosity of the polyethylene terephthalate film is 0.67.

[0115] [Example 1] A detergent (pH=13 or higher) was prepared by mixing 5 parts by mass of potassium hydroxide (a), 40 parts by mass of benzyl alcohol and 10 parts by mass of xylenol (b), and 45 parts by mass of water as the other component. The cleanability of laminated films (I) to (III) was evaluated under the conditions described in Table 1. The results are shown in Table 1.

[0116] [Example 2] A detergent (pH=13 or higher) was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 19 parts by mass of ethanolamine as components, (b) 40 parts by mass of benzyl alcohol and 1 part by mass of propylene glycol as components, and 30 parts by mass of water as other components. The cleanability of laminated films (I) to (III) was evaluated under the conditions described in Table 1. The results are shown in Table 1.

[0117] [Example 3] A detergent (pH=13 or higher) was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 10 parts by mass of diethanolamine as components, (b) 16 parts by mass of benzyl alcohol as component, and 64 parts by mass of water as other components. The cleanability of laminated films (I) and (III) was evaluated under the conditions described in Table 1. The results are shown in Table 1.

[0118] [Example 4] A detergent (pH=13 or higher) was prepared by mixing (a) 5 parts by mass of potassium hydroxide and (b) 95 parts by mass of benzyl alcohol. The cleanability of laminated films (I) and (III) was evaluated under the conditions described in Table 1. The results are shown in Table 1.

[0119] [Example 5] A detergent (pH=13 or higher) was prepared by mixing potassium hydroxide (5 parts by mass) as component (a) and methanol (95 parts by mass) as component (b). The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0120] [Example 6] A cleaning agent was prepared by mixing (a) 5 parts by mass of potassium hydroxide and (b) 95 parts by mass of ethanol. The cleanability of laminated films (I) and (III) was evaluated under the conditions described in Table 1. The results are shown in Table 1.

[0121] [Example 7] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of ethanolamine as components, (b) 33.8 parts by mass of benzyl alcohol, 3.8 parts by mass of methanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0122] [Example 8] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of ethanolamine as components, (b) 28.1 parts by mass of benzyl alcohol, 9.4 parts by mass of methanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0123] [Example 9] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as components, (b) 18.8 parts by mass of benzyl alcohol, 18.8 parts by mass of methanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0124] [Example 10] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as components, (b) 33.8 parts by mass of benzyl alcohol, 3.8 parts by mass of hexafluoro-2-propanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0125] [Example 11] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as components, (b) 28.1 parts by mass of benzyl alcohol, 9.4 parts by mass of hexafluoro-2-propanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0126] [Example 12] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as components, (b) 18.8 parts by mass of benzyl alcohol, 18.8 parts by mass of hexafluoro-2-propanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0127] [Example 13] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as components, (b) 28.1 parts by mass of benzyl alcohol, 9.4 parts by mass of ethanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0128] [Example 14] A detergent was prepared by mixing (a) 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as components, (b) 28.1 parts by mass of benzyl alcohol, 9.4 parts by mass of 2-propanol, and 2.9 parts by mass of propylene glycol as components, and 31.7 parts by mass of water as other components. The washability was evaluated using laminated film (III) under the conditions described in Table 1. The results are shown in Table 1.

[0129] [Comparative Example 1] (a) A cleaning agent was prepared by mixing 30 parts by mass of potassium hydroxide as one component and 70 parts by mass of water as another component. The cleaning performance was evaluated using laminated films (I) and (III) under the conditions described in Table 1. The results are shown in Table 1.

[0130] [Reference example 1] As a reference example, a base film (IV) without a functional layer (polyethylene terephthalate film, 52 μm thick) was prepared as a sample. Using a cleaning agent with the same composition as in Example 1, the sample was immersed in the cleaning agent for 5 minutes, and the change in the thickness of the substrate was measured by measuring the thickness with a Mitutoyo Corporation "Thickness Gauge ID-C112X / 1012X". Cases where the thickness change was 3 μm or more were classified as A, and cases where the thickness change was less than 3 μm were classified as B. The results are shown in Table 1.

[0131] [Table 1]

[0132] [Reference example 2] To determine the optimal form of alcohols in the cleaning agent, the cleaning conditions were changed in Examples 2 and 7-12 to a cleaning temperature of 40°C and an immersion time of 1.2 minutes, and the cleaning was evaluated according to the following criteria. The results are shown in Table 2. Similarly, the cleaning performance of the laminated film after cleaning was evaluated by quantitative analysis of the Si element on the surface using an X-ray fluorescence analyzer. The removal rate of the functional layer was determined based on the following criteria. ○(good); Removal rate 50~100% △(fair); Removal rate 0~49%

[0133] [Table 2]

[0134] According to the recycling system or recycling method of the present invention, the functional layer can be peeled off from the laminated polyester film using a cleaning agent that dissolves the polyester film, and the polyester film can be recycled efficiently.

[0135] From the results of Reference Example 1, it can be seen that the base film (IV), which is a polyester film, has been partially melted on its surface and thinned. Therefore, the recycling system of the present invention effectively removes the functional layer by partially dissolving the surface of the polyester film base using a cleaning agent. [Explanation of Symbols]

[0136] 10 Recycling System 11 Functional layer removal means 12. Rinsing method 13 Drying means 14. Unwinding mechanism 15. Winding mechanism 16 Laminated polyester film 18. Pellet manufacturing method 20 Recycling Systems 21 Functional layer removal means 22 Rinsing method 23 Drying means 24 Cutting means 25 Belt conveyor 26. Bulk laminated polyester film (waste material) 27 Flake-like laminated polyester film 28. Pellet manufacturing method

Claims

1. A method for manufacturing recycled polyester film, which involves removing the functional layer from a laminated polyester film having a functional layer on the surface of a polyester film, using a cleaning agent that dissolves the polyester film to dissolve a portion of the surface of the polyester film, wherein the functional layer is removed from the laminated polyester film having a functional layer on the surface of the polyester film, which is a collected waste material. The aforementioned functional layer is a silicone-based functional layer, The removal rate of the functional layer in the polyester film from which the functional layer has been removed is 70% or more. The aforementioned cleaning agent is a cleaning agent containing an alkaline agent and alcohols (excluding ethanol), A method for producing recycled polyester film, wherein the amount of inorganic alkaline agent in the entire cleaning agent is 10 parts by mass or less.

2. The method for producing a recycled polyester film according to claim 1, wherein the cleaning agent contains one or more of the following components (a) to (c). (a) Inorganic alkalizing agents and organic alkalizing agents (b) Alkalinizing agents and alcohols with an acidity constant (pKa) of 9.3 or higher and 15.4 or lower (c) Alkalinizing agents and two or more types of alcohols

3. A method for producing a recycled polyester film according to claim 1 or 2, wherein two or more inorganic alkalizing agents are used as the alkalizing agent.

4. A method for producing a recycled polyester film according to any one of claims 1 to 3, wherein the cleaning agent contains benzyl alcohol.

5. A method for producing a recycled polyester film according to any one of claims 2 to 4, wherein the two or more alcohols include a hydrophobic monovalent alcohol and a water-soluble monovalent alcohol.

6. A method for recycling polyester, comprising using a cleaning agent that dissolves the polyester film to dissolve a portion of the surface of a laminated polyester film having a functional layer on its surface, which is a collected waste material, thereby removing the functional layer, The aforementioned functional layer is a silicone-based functional layer, The removal rate of the functional layer in the polyester film from which the functional layer has been removed is 70% or more. The aforementioned cleaning agent is a cleaning agent containing an alkaline agent and alcohols (excluding ethanol), A method for recycling polyester, wherein the amount of inorganic alkaline agent in the entire cleaning agent is 10 parts by mass or less.

7. The method for recycling polyester according to claim 6, comprising pelletizing the polyester film from which the functional layer has been removed.

8. The method for recycling polyester according to claim 6 or 7, wherein the cleaning agent comprises one or more of the following components (a) to (c). (a) Inorganic alkalizing agents and organic alkalizing agents (b) Alkalinizing agents and alcohols with an acidity constant (pKa) of 9.3 or higher and 15.4 or lower (c) Alkalinizing agents and two or more types of alcohols

9. A method for recycling polyester according to any one of claims 6 to 8, wherein two or more inorganic alkaline agents are used as the alkalizing agent.

10. The method for recycling polyester according to any one of claims 6 to 9, wherein the cleaning agent comprises benzyl alcohol.

11. A method for recycling polyester according to any one of claims 8 to 10, wherein the two or more types of alcohols include a hydrophobic monovalent alcohol and a water-soluble monovalent alcohol.

12. A method for recycling polyester according to any one of claims 6 to 11, comprising washing away the cleaning agent adhering to the polyester film from which the functional layer has been removed.

13. A method for recycling polyester according to any one of claims 6 to 12, comprising recovering waste polyester film in roll form or in block form.

14. A method for recycling polyester according to any one of claims 6 to 13, further comprising an unwinding means or a cutting means.

15. A method for recycling polyester according to any one of claims 6 to 14, performed in a roll-to-roll manner.

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