Method for removing functional layer from laminated polyester film

Abstract

To provide a method for removing a functional layer from a laminated polyester film, which has the functional layer on the surface of a polyester film.SOLUTION: A method according to the present invention includes a polishing step for removing a functional layer, with a transportable polisher 11, from a laminated polyester film F, which has the functional layer on the surface of a polyester film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for removing a functional layer of a laminated polyester film.

Background Art

[0002] Conventionally, waste plastics have been treated by landfilling, ocean dumping, incineration, etc. However, it is becoming difficult to secure landfill sites, and ocean dumping has become a problem in terms of the environment because plastics do not decompose. In addition, 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 such as reuse and regeneration of waste plastics is required, and research and development for this purpose are being actively carried out. In addition, since many plastics are produced from fossil fuels, the construction of a recycling method is also 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 polyester 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 release layer, a decorative layer, a light-shielding layer, an ultraviolet shielding layer, and an easy-adhesion layer, and a laminated polyester film in which a material corresponding to the functional layer is laminated on the polyester film is used.

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

[0006] Even if a laminated polyester film with a functional layer is directly remelted and recycled, since the material constituting the functional layer is mixed into the molten polymer, it generates an abnormal odor during extrusion, or the melt viscosity of the polymer decreases, which causes breakage during film formation. Moreover, even if film formation were possible, deterioration in quality due to coloring of the obtained film or contamination with foreign matter would be inevitable.

[0007] As a method for recycling a laminated polyester film, for example, there is a technique disclosed in Patent Document 1. This technique is a laminated polyester film in which a readily soluble resin layer and a surface functional layer are laminated in this order on at least one surface of a base film. After such a configuration, after use, only the readily soluble resin layer can be dissolved, and the base film is separated and recovered from the laminated polyester film by washing with a solvent that does not dissolve the base film. What is separated and recovered is remelted, enabling the resin composition that constituted the base film to be recycled.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The method disclosed in Patent Document 1 is premised on a laminated polyester film in which a readily soluble resin layer and a surface functional layer are laminated in this order on the surface of a base film, and attempts to remove the functional layer by dissolving the readily soluble resin layer. That is, it cannot be used for most laminated polyester films that do not have a readily soluble resin layer, and is a technology with no versatility. In view of the above circumstances, an object of the present invention is to propose a method for removing a functional layer of a laminated polyester film that can peel off the functional layer even in a laminated polyester film that does not have a readily soluble resin layer.

Means for Solving the Problems

[0010] As a result of intensive studies, the present inventors have found that by using a conveyor type polishing machine, the functional layer can be easily removed from a laminated polyester film having a functional layer on the surface of the polyester film. The present invention has been completed based on such findings. That is, the present invention has the following aspects. [1] A method for removing a functional layer of a laminated polyester film, comprising a polishing step of removing the functional layer from the laminated polyester film having a functional layer on the surface of the polyester film with a conveyor type polishing machine. [2] The method for removing a functional layer of a laminated polyester film according to [1] above, wherein the polishing step is performed in a wet method. [3] The method for removing a functional layer of a laminated polyester film according to [1] or [2] above, wherein the abrasive in the polishing step is a buff roll. [4] The method for removing a functional layer of a laminated polyester film according to [3] above, wherein the buff roll itself vibrates laterally. [5] The method for removing a functional layer of a laminated polyester film according to [3] or [4] above, wherein the rotation direction of the buff roll is opposite to the conveyance direction of the laminated polyester film. [6] The method for removing a functional layer of a laminated polyester film according to any one of [1] to [5] above, wherein the functional layer is a silicone release layer. [7] Further, a method for removing a functional layer of a laminated polyester film according to any one of [1] to [6] above, including a cleaning step of cleaning with a cleaning agent containing an alkalizing agent. [8] The method for removing a functional layer of a laminated polyester film according to [7] above, wherein the cleaning agent further contains (b) a compound having at least one hydroxyl group. [9] The method for removing a functional layer of a laminated polyester film according to at least any one of [1] to [8] above, further comprising a rinsing step of washing away at least any one of the dust generated in the polishing step and the cleaning agent attached to the polyester film. A recycled polyester product containing at least a part of a polyester film raw material regenerated by the method for removing a functional layer of the laminated polyester film according to any one of [1] to [9] above.

[11] A recovery step of recovering a polyester film from which the functional layer has been removed by the functional layer removal method according to any one of [1] to [9] above, A method for producing a recycled polyester product, comprising a production step of producing a recycled polyester product using the recovered polyester film as a raw material.

[12] A functional layer removing device for a laminated polyester film, comprising a transport type polishing machine for removing a functional layer from a laminated polyester film having a functional layer on the surface thereof.

[13] (a) The functional layer removing device according to

[12] above, comprising a cleaning agent containing an alkalizing agent and a cleaning device for cleaning the laminated polyester film with the cleaning agent.

[14] The functional layer removing device according to

[12] or

[13] above, comprising a rinsing device for rinsing at least one of dust and cleaning agent adhering to the polyester film from which the functional layer has been removed.

[15] A recycling device comprising the functional layer removing device according to any one of

[12] to

[14] above, a recovery device for recovering a polyester film from which the functional layer has been removed by the functional layer removing device, and a production device for producing a recycled polyester product using the recovered polyester film as a raw material.

Advantages of the Invention

[0011] According to the method for removing a functional layer of the laminated polyester film of the present invention, the functional layer can be easily removed from the laminated polyester film having a functional layer.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0013] The method for removing a functional layer of a laminated polyester film of the present invention (hereinafter, also referred to as "this functional layer removing method") includes a polishing step of removing a functional layer from a laminated polyester film having a functional layer on the surface of a polyester film with a conveyor type polishing machine.

[0014] <Laminated Polyester Film> The laminated polyester film in the present invention refers to a polyester film which is a base film and has a functional layer such as a resin layer laminated on the surface thereof. The polyester film may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, it may have a two-layer structure, a three-layer structure, etc., or may be a multilayer of four layers or more, and the number of layers is not particularly limited. Further, 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 formed by polycondensing dicarboxylic acids and diols can be mentioned. As the dicarboxylic acid, aromatic dicarboxylic acids are preferable, and as the diol, aliphatic glycols are preferable.

[0015] Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, etc. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. The polyester may be a homopolyester or a copolyester. Further, the polyester may contain a third component other than aromatic dicarboxylic acid and glycol as a copolymer component.

[0016] Specific examples of the polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polybutylene-2,6-naphthalate, etc. Among these, polyethylene terephthalate is preferred. Also, these may be copolymer polyesters. For example, polyethylene terephthalate may have dicarboxylic acid units other than terephthalic acid units at about 30 mol% or less of the dicarboxylic acid units, and may also have diol units other than ethylene glycol units at about 30 mol% of the diol units.

[0017] The constituent components of the functional layer are not particularly limited, but from the viewpoint of being removed by this functional layer removal method, it is preferably composed of a resin. Examples of the functional layer include a hard coat layer, an adhesive layer, a release layer, a decorative layer, a light-shielding layer, an ultraviolet shielding layer, an easy adhesion layer (primer layer), an antistatic layer, a refractive index adjustment layer, an oligomer sealing layer, etc.

[0018] The hard coat layer is a layer provided to impart scratch resistance, etc. to the polyester film. The material for forming the hard coat layer is not particularly limited, but examples include cured products of monofunctional (meth)acrylates, polyfunctional (meth)acrylates, reactive silicon compounds such as tetraethoxysilane, etc.

[0019] The adhesive layer is a layer provided for adhesion to other devices, etc. The material for constituting the adhesive layer is not particularly limited, but for example, known pressure-sensitive resins such as acrylic, rubber, silicone, etc. can be used.

[0020] The release layer is a layer provided to impart releasability to a polyester film, and is, for example, a layer provided on a release film used for a process paper for forming a green sheet used in the manufacture of ceramic electronic components, an adhesive separator for an optical member used in the manufacture of flat panel displays such as a polarizing plate and an optical filter. There is no particular limitation on the material constituting the release layer, and examples thereof include those mainly composed of a curable silicone resin, or a modified silicone resin obtained by graft polymerization with a urethane resin, an epoxy resin, etc., various release agents such as long-chain alkyl group-containing compounds, fluorine compounds, and hydrocarbon-based waxes. Among these, a silicone release layer is preferred. The silicone release layer is a release layer using a silicone resin such as a curable silicone resin or a modified silicone resin as a release agent.

[0021] The decorative layer is a layer provided to impart design properties. There is no particular limitation on the material constituting the decorative layer, and examples thereof include polyurethane-based resins, vinyl-based resins, polyamide-based resins, polyester-based resins, acrylic-based resins, polyvinyl acetal-based resins, etc. Pigments, dyes, etc. are added to these resins for decoration.

[0022] The light-shielding layer or ultraviolet-shielding layer is a layer provided to protect the contents from ultraviolet rays, visible light, etc. There is no particular limitation on the material constituting the light-shielding layer or ultraviolet-shielding layer, and examples thereof include various resins described in the decorative layer, inorganic fillers such as calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, barium sulfate, etc., organic fillers such as wood powder, pulp powder, and cellulose powder.

[0023] The easy-adhesion layer (primer layer) is a layer provided to adhere other layers or films onto the polyester film. There is no particular limitation, and examples thereof include polyurethane-based resins, vinyl-based resins, polyamide-based resins, polyester-based resins, acrylic-based resins, polyvinyl acetal-based resins, etc., various cross-linking agents, particles, etc.

[0024] The antistatic layer is a layer provided to prevent electrostatic charging generated by contact with or separation from other materials. The antistatic agent used in the antistatic layer is not particularly limited, and examples include nonionic, cationic, anionic, amphoteric surfactants, conductive polymers such as polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate), metal oxide fillers such as SnO2 (Sb-doped), In2O3 (Sn-doped), ZnO (Al-doped), and carbon compounds such as graphene, carbon black, and carbon nanotubes (CNT). These may be used alone or in combination of two or more. Further, the antistatic layer may be formed from a resin composition containing an antistatic agent. Examples of the resin contained 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 material constituting the refractive index adjustment layer is not particularly limited, and examples include polyester resins, acrylic resins, urethane resins, polycarbonate resins, epoxy resins, alkyd resins, urea resins, fluororesins, and metal oxides such as zirconium oxide and titanium oxide. These may be used alone or in combination of two or more.

[0026] The oligomer sealing layer is a layer provided to prevent film whitening and foreign matter after the heating process, and is not particularly limited. For example, examples of the material constituting the oligomer sealing layer include amine compounds and ionic resins. Further, the oligomer sealing layer may be a crosslinked coating film or the like.

[0027] These functional layers may be single layers or two or more types of layers may be laminated. When two or more types of layers are laminated, it is preferable that at least one layer is a layer constituted by a resin.

[0028] <Polishing process> The method for removing the functional layer of the laminated polyester film of the present invention is a method of removing the functional layer by a polishing process of polishing the functional layer on the surface of the laminated polyester film with a conveyor type polishing machine. The conveyor type polishing machine is a machine that conveys the laminated polyester film to a predetermined polishing position by moving it with a belt conveyor or by providing a pay-off device and a take-up device and moving it by the driving force of these, and polishing the surface of the functional layer of the laminated polyester film with an abrasive material at the polishing position.

[0029] The polishing process may be performed in a dry method without using a liquid or in a wet method using a liquid. However, from the viewpoint of suppressing the resistance and heat generation due to polishing, the wet method is preferable. Also, by polishing in a wet method, it is possible to prevent the scattering of a large amount of dust generated in the polishing process.

[0030] In the polishing process in the wet method, as the liquid to be used, water, a known polishing liquid, a cleaning agent described later, etc. can be used. However, considering the necessity of recovering, circulating, and discharging the used liquid, it is preferable to use water. The temperature of the liquid to be used is not particularly limited as long as it is equal to or higher than room temperature (20°C) and equal to or lower than the boiling point.

[0031] As the abrasive material used in the polishing process, for example, those in the form of a buff, a brush, a scrubbing brush, a paper, a mesh, a comb, etc. can be used, and a plurality of abrasive materials may be used in combination. Also, the abrasive material is preferably one in which a known abrasive such as silicon carbide or alumina is adhered with an adhesive to form a grindstone shape. From the viewpoint of widely adhering the abrasive to the abrasive material, it is preferable to use a buff-shaped abrasive material. Note that the abrasive has a number called "mesh number" that represents coarseness and fineness, and is expressed as #240, #600, #1500, etc. The smaller the number, the coarser, and the larger the number, the finer. In the present invention, there is no particular limitation on the mesh number, and those commercially available can be appropriately used.

[0032] Examples of the form of such an abrasive include a roll shape, a flat shape, etc., and examples of the material of the abrasive include resin and metal. Among them, from the viewpoint of improving the polishing efficiency for a roll-shaped laminated polyester film, a resin roll-shaped buff (hereinafter also referred to as "buff roll") is preferable. By disposing a rotating buff roll at a position in contact with the laminated polyester film, efficient polishing becomes possible. Note that one buff roll may be disposed, or a plurality of buff rolls may be disposed, but disposing a plurality of buff rolls can improve the functional layer removal rate.

[0033] In the polishing step, the laminated polyester film may be polished by the abrasive while being conveyed. When using the buff roll, the rotation direction of the buff roll may be either the forward direction or the reverse direction with respect to the conveyance direction of the laminated polyester film, but the reverse direction is preferable. By setting it to the reverse direction, the peripheral speed of the buff roll is relatively added to the conveyance speed of the laminated polyester film, so the polishing property becomes stronger than in the case of the forward direction.

[0034] When using the buff roll, the larger the speed ratio (Va / Vb) of the peripheral speed (Va) of the buff roll to the conveyance speed (Vb) of the laminated polyester film, the greater the polishing effect. Also, the peripheral speed (Va) of the buff roll and the conveyance speed (Vb) of the laminated polyester film are not particularly limited, but they may be conveyed at the normal peripheral speed of the buff roll and the conveyance speed of the resin film. Generally, as is well known, the peripheral speed (Va) and the conveyance speed (Vb) are larger as the size of the conveyance-type polishing machine is larger.

[0035] The abrasive preferably vibrates laterally by itself. By vibrating laterally, the polishing efficiency can be improved and the functional layer can be removed more efficiently. Here, the "lateral vibration" refers to vibration in a direction perpendicular to the conveyance direction of the laminated polyester film. In the case of a buff roll, the buff roll itself may be vibrated laterally, for example, by vibrating the axis of the buff roll along the axial direction.

[0036] The conveying type polishing machine according to the present invention may have a function of adjusting how close the abrasive is to the laminated polyester film, that is, the adhesion between the abrasive and the laminated polyester film. The above-mentioned adhesion is called the pressing pressure (mm). The smaller the pressing pressure is, the lower the adhesion to the laminated polyester film is, and the higher the pressing pressure is, the higher the adhesion to the laminated polyester film is. The pressing pressure (mm) is not particularly limited as long as it does not prevent the conveyance of the laminated polyester film and is in contact with the laminated polyester film. However, the higher the pressing pressure is, the higher the removal rate of the functional layer is.

[0037] Note that the number of times of performing the polishing process (hereinafter referred to as "the number of passes") may be once or a plurality of times.

[0038] As a specific embodiment of the polishing process, it is preferable to install an unwinding device in the front stage of the conveying type polishing machine, unwind the laminated polyester film from the device, and polish the functional layer on the surface with the conveying type polishing machine. In such an embodiment, the roll-shaped laminated polyester film, which is waste material, can be efficiently polished.

[0039] <Cleaning process> In addition to the polishing process, this functional layer removal method may further have a cleaning process of cleaning the laminated polyester film with a cleaning agent containing an alkalizing agent. By having such a cleaning process, the removal rate of the functional layer is improved. When the functional layer can be sufficiently removed only by the polishing process, the cleaning process can be omitted. However, for a functional layer having particularly high adhesion to the base film or a functional layer having a thick film thickness, it is preferable to have the above cleaning process.

[0040] The cleaning process may be performed either before or after the polishing process, or simultaneously with the polishing process. However, for the purpose of avoiding contamination of the conveyor - type polishing machine used in the polishing process by the cleaning agent described below, it is preferable to have a cleaning process after the polishing process. Note that performing simultaneously with the polishing process means using the liquid used in the wet - type polishing process as the cleaning agent according to the present invention.

[0041] (Alkalizing agent) The (a) alkalizing agent constituting the cleaning agent according to the present invention makes the cleaning agent alkaline and can also be called an alkali agent. As the alkalizing agent, it may be an inorganic alkalizing agent or an organic alkalizing agent. However, from the viewpoint of suitability for combination with (b) a compound having at least one hydroxyl group and (c) a compatibilizer described below, it is preferably an inorganic alkalizing agent.

[0042] Examples of inorganic alkalizing agents include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide; hydroxides of alkaline earth metals such as calcium hydroxide, barium hydroxide; carbonates of alkali metals such as sodium carbonate, potassium carbonate; phosphates of alkali metals such as trisodium phosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, tripotassium phosphate, potassium pyrophosphate, potassium tripolyphosphate; silicates of alkali metals such as sodium orthosilicate, sodium metasilicate, potassium silicate; ammonia, etc.

[0043] Among the inorganic alkalizing agents in this cleaning agent, hydroxides of alkali metals are preferred. From the viewpoint of easy availability, sodium hydroxide and potassium hydroxide are more preferred, and potassium hydroxide is particularly preferred from the viewpoint of cleaning performance.

[0044] As the inorganic alkalizing agent in this cleaning agent, one kind can be used alone or two or more kinds can be used in combination. In particular, using a combination of potassium hydroxide and sodium hydroxide is preferable from the viewpoints of effect and handleability.

[0045] Examples of the organic alkaline agent 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. Note that as the organic alkaline agent, a compound having at least one hydroxyl group may be included. If the acidity constant (pKa) of the compound is 30 or more, it is handled as an alkaline agent.

[0046] Among the organic alkaline agents in this detergent, monoethanolamine, diethanolamine, and triethanolamine are preferred from the viewpoint of versatility, monoethanolamine and diethanolamine are more preferred from the viewpoint of easy availability, and monoethanolamine is particularly preferred from the viewpoint of detergency.

[0047] In addition, the content of the (a) alkaline agent in the entire detergent is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass. When within the above range, a sufficient effect as a detergent can be obtained.

[0048] (Compound having at least one hydroxyl group) The detergent according to the present invention preferably contains, in addition to the component (a), a (b) compound having at least one hydroxyl group. Regarding the mechanism by which the functional layer can be effectively removed by using the above components (a) and (b) in combination, it is not clear, but it is presumed as follows. It is presumed that the reaction described below proceeds at the interface of the polyester film as the base material and / or the functional layer, and the functional layer can be efficiently peeled off from the laminated polyester film.

[0049] When a laminated polyester film having a functional layer that undergoes hydrolysis, such as an acrylic adhesive layer or an acrylic hard coat layer, is washed, (b) a transesterification reaction occurs at the ester bond portion of the functional layer and / or the base material by an alkoxide generated from the hydroxyl group of a compound having at least one hydroxyl group to obtain a low molecular weight compound. Next, with respect to the ester bond of the above low molecular weight compound, (a) a saponification reaction proceeds by a nucleophilic attack of a hydroxyl group ionized from an alkalizing agent to obtain a carboxylate (ionization). Based on this, it is presumed that the functional layer elutes.

[0050] Even when a laminated polyester film having a functional layer that does not undergo hydrolysis, such as a silicone release layer, is washed, the polyester film as the base material undergoes depolymerization by transesterification, saponification, and elution due to the above reaction mechanism, so that the functional layer laminated on the film can be peeled off and removed. Therefore, it is considered that the combination of components (a) and (b) enables the functional layer to be efficiently peeled off from the laminated polyester film.

[0051] Examples of the compound (b) having at least one hydroxyl group include alcohols and phenols.

[0052] Examples of alcohols include monohydric alcohols such as hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; dihydric alcohols such as ethylene glycol, diethylene glycol, and propylene glycol; and polyhydric alcohols such as glycerin.

[0053] Examples of phenols include phenol, xylenol, salicylic acid, picric acid, naphthol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, dibutylhydroxytoluene, bisphenol A, cresol, estradiol, eugenol, gallic acid, guaiacol, phenolphthalein, serotonin, dopamine, adrenaline, noradrenaline, thymol, tyrosine, hexahydroxybenzene, and the like.

[0054] These may be used alone or in combination of two or more. Among these, alcohols are preferred from the viewpoint of maintaining the detergency without impairing the alkalinity of the detergent.

[0055] From the viewpoint of detergency, the acidity constant (pKa) of 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, still more preferably 9.0 or more and 16.0 or less, particularly preferably in the range of 9.3 or more and 15.6 or less, and most preferably 14.0 or more and 15.4 or less. If the acidity constant (pKa) of alcohols is within the above range, alkoxide is generated without impairing the alkalinity of the detergent, so that the detergency of the detergent is improved.

[0056] The acidity constants (pKa) of some alcohols are shown below. 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), tert-butanol (pKa = 18.0).

[0057] Among the above-mentioned alcohols, from the viewpoint of detergency, hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, propyl alcohol, and benzyl alcohol are more preferable. Among these, from the viewpoints of low volatility and the usable temperature range, the use of benzyl alcohol is even more preferable. These alcohols have high detergency because protons are easily ionized to form alkoxides.

[0058] In addition, a dihydric alcohol or a polyhydric alcohol may be used in combination with the above-mentioned suitable alcohols.

[0059] In the cleaning agent, the content of the compound (b) having at least one hydroxyl group 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, since the amount of the alkalizing agent (a) is appropriate, foreign matter contamination due to precipitation of the alkalizing agent component can be suppressed when the polyester film is recovered, and the quality of the recycled polyester film can be maintained. Further, when the component (c) is used in combination in addition to the components (a) and (b) in the cleaning agent, or when the cleaning agent is an aqueous cleaning agent, the content of the component (b) in the cleaning agent is preferably 10 to 90% by mass, more preferably 20 to 75% by mass, even more preferably 30 to 65% by mass, and particularly preferably 35 to 50% by mass. Within the above range, in addition to the alkalizing agent (a), the amount of the compatibilizer can also be made appropriate. Also, in the case of an aqueous system, a certain amount or more of water can be contained.

[0060] (Compatibilizer) The cleaning agent according to the present invention preferably further contains (c) a compatibilizer. (c) The compatibilizer has a function of assisting the elution of the functional layer from the laminated polyester film when used in combination with the components (a) and (b), and has a function of solubilizing the components (a) and (b) and other optionally added additives. In addition, by containing the (c) compatibilizer, even when the cleaning agent contains water as a single component, the compatibility between the (a) component and the (b) component becomes good.

[0061] (c) As the compatibilizer, there is no particular limitation, and any of anionic compatibilizers, cationic compatibilizers, nonionic compatibilizers, and amphoteric compatibilizers can be used. Note that since the compatibilizer includes a compound corresponding to the above-mentioned alkalizing agent, in the detergent of the present invention, when the (c) compatibilizer is used in combination with the components (a) and (b), a different one from the components (a) and (b) is used.

[0062] Examples of the anionic compatibilizer include alkyl sulfonic acid, alkylbenzene sulfonic acid, alkyl carboxylic acid, aromatic carboxylic acid, alkyl naphthalene sulfonic acid, α-olefin sulfonic acid, dialkyl sulfosuccinic acid, α-sulfonated fatty acid, N-methyl-N-oleyl taurine, petroleum sulfonic acid, alkyl sulfuric acid, sulfated oil and fat, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene styrenated phenyl ether sulfuric acid, alkyl phosphoric acid, polyoxyethylene alkyl ether phosphoric acid, polyoxyethylene alkyl phenyl ether phosphoric acid, naphthalene sulfonic acid formaldehyde condensate, and salts thereof.

[0063] Examples of the cationic compatibilizer include quaternary ammonium, tetraalkyl ammonium, trialkyl benzyl ammonium, alkyl pyridinium, 2-alkyl-1-alkyl-1-hydroxyethyl imidazolinium, N,N-dialkyl morpholinium, polyethylene polyamine fatty acid amide, urea condensate of polyethylene polyamine fatty acid amide, quaternary ammonium of urea condensate of polyethylene polyamine fatty acid amide, and salts thereof.

[0064] Examples of nonionic compatibilizers include polyoxyalkylene ethers such as polyoxyethylene alkyl ether and polyoxyethylene-polyoxypropylene alkyl ether; polyoxyethylene alkyl phenyl ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene-polyoxypropylene glycol, partial esters of polyhydric alcohol fatty acids, partial esters of polyoxyethylene polyhydric alcohol fatty acids, polyoxyethylene fatty acid esters, polyglycerin fatty acid esters, polyoxyethylenated castor oil, fatty acid diethanolamides, monomethylamine, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, triisopropanolamine, polyoxyethylene alkylamine, partial esters of triethanolamine fatty acids, and organic amine compounds such as trialkylamine oxides.

[0065] Examples of amphoteric compatibilizers 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 ester betaine, and 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine; and aminocarboxylic acids such as N,N-dialkylaminoalkylene carboxylates.

[0066] Note that as a compatibilizer, the compound having at least one hydroxyl group in the above (b) may be included. However, alkanolamine compounds, alkanolamide compounds, and hydroxy compounds having 12 or more carbon atoms corresponding to the following are treated as (c) compatibilizers. Examples of alkanolamine compounds include monoethanolamine, diethanolamine, and triethanolamine; and examples of alkanolamide compounds include monoethanolamide, diethanolamide, and triethanolamide. In addition, examples of the hydroxy compound having 12 or more carbon atoms include polyoxyethylene alkyl ether-based, thioether-based, polyoxyalkylene glycol-based, acetylene glycol-based, ester-based, and glycoside-based hydroxy compounds having 12 or more carbon atoms.

[0067] Among the (c) compatibilizers in this detergent, from the viewpoints of compatibility and handleability, it is preferable to use aromatic sulfonates and amine compounds containing a hydroxyl group. Specific compounds include sodium benzenesulfonate, sodium toluenesulfonate, sodium 2,4-dimethylbenzenesulfonate, sodium 2-naphthalenesulfonate, alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. Among these, from the viewpoint of raising the upper limit of the heating temperature of the detergent, it is more preferable to use the above-mentioned aromatic sulfonates having a high boiling point. Here, it is premised that a compound different from the (a) alkalizing agent is used as described above.

[0068] Specific examples of the combination of the (a) alkalizing agent and the (c) compatibilizer are as follows: When an inorganic alkalizing agent is used as the (a) alkalizing agent, as the (c) compatibilizer, at least one of an anionic compatibilizer, a cationic compatibilizer, a nonionic compatibilizer, and an amphoteric compatibilizer may be used. When an organic alkalizing agent is used as the (a) alkalizing agent, as the (c) compatibilizer, at least one of an anionic compatibilizer, a cationic compatibilizer, a nonionic compatibilizer other than an organic amine compound, and an amphoteric compatibilizer may be used.

[0069] In addition, in this detergent, it is preferable to use an inorganic alkalizing agent as the (a) alkalizing agent and at least one selected from aromatic sulfonates and amine compounds containing a hydroxyl group as the (c) compatibilizer. Among these, a combination of at least one inorganic alkaline agent such as sodium hydroxide and potassium hydroxide and an aromatic sulfonate such as sodium 2,4-dimethylbenzenesulfonate is preferable. Further, a combination of at least one inorganic alkaline agent such as sodium hydroxide and potassium hydroxide and at least one hydroxyl group-containing amine compound selected from monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, and triisopropanolamine is preferable. Among these, a combination of at least one inorganic alkaline agent selected from sodium hydroxide and potassium hydroxide and at least one hydroxyl group-containing amine compound selected from monoethanolamine and diethanolamine used in combination is particularly preferable.

[0070] Further, from the viewpoint of comprehensively dissolving various additives in the detergent, two or more of the above solubilizers may be used in combination. Also, the content of the solubilizer in the detergent is preferably in the range of 1 to 30% by mass. When it is within the above range, sufficient detergency can be obtained. From the above viewpoints, the content of the solubilizer in the detergent is more preferably in the range of 5 to 25% by mass, and even more preferably in the range of 8 to 20% by mass.

[0071] The detergent according to the present invention is preferably an aqueous detergent. The aqueous detergent is obtained by dissolving the components (a) to (c) etc. in water and diluting them. The aqueous detergent can raise the flash point and thus has relatively high safety, and is also advantageous in that water can be used in the rinsing step described later.

[0072] The detergent according to the present invention can contain various additives in addition to the components (a) to (c) above. For example, antioxidants, rust inhibitors, pH adjusters, preservatives, viscosity adjusters, antifoaming agents, etc. can be added.

[0073] The cleaning process according to the present invention is one of the processes for removing the functional layer of the laminated polyester film using the above-mentioned cleaning agent. The cleaning process can use, for example, an immersion method of immersing in a cleaning tank containing the cleaning agent, a coating method of applying the cleaning agent in a solution state, a spraying method of spraying the cleaning agent in a solution state or the vaporized cleaning agent, etc. Among these, from the viewpoint of the permeability of the cleaning agent into the functional layer, the immersion method is preferable.

[0074] The temperature of the cleaning agent in the immersion method is preferably room temperature (20°C) or higher. When it is room temperature (20°C) or higher, the viscosity of the cleaning agent is low and it easily penetrates into the functional layer, so good detergency can be obtained. From the above viewpoints, the temperature of the cleaning agent in the immersion method is more preferably 40°C or higher, further preferably 50°C or higher, and particularly preferably 60°C or higher. Also, as the upper limit value of the temperature of the cleaning agent, when the cleaning agent is used in a solution state, a temperature below the boiling point is preferable. In the case of the aqueous cleaning agent which is a preferred embodiment of the present application, 100°C or lower is preferable, and 90°C or lower is more preferable. In addition, even in cases other than the immersion method, the temperature of the cleaning agent during cleaning is the same as above. Also, in the peeling cleaning by the immersion method, microwave irradiation may be performed for the purpose of promoting the hydrolysis reaction.

[0075] The pH of the cleaning agent is preferably 12 or higher, and more preferably 13 or higher, from the viewpoint of detergency.

[0076] Regarding the immersion time, it is preferably adjusted as appropriate as follows depending on the type of the object to be cleaned.

[0077] When a polyester film provided with an acrylic adhesive layer as a functional layer is to be cleaned, it is preferably for 1 second or more and 30 minutes or less. If it is 1 second or more, the cleaning agent can sufficiently penetrate into the functional layer and the detergency can be exhibited. On the other hand, if it is within 30 minutes, the amount of polyester obtained when recovered can be ensured without excessive dissolution of the polyester film as the base material. From the above viewpoints, it is more preferably 15 seconds or more and 20 minutes or less, further preferably 30 seconds or more and 15 minutes or less, and particularly preferably 1 minute or more and 10 minutes or less.

[0078] When a polyester film provided with an acrylic hard coat layer as a functional layer is to be cleaned, it is preferably for 1 second or more and 30 minutes or less. If it is 1 second or more, the cleaning agent can sufficiently penetrate into the functional layer and the detergency can be exhibited. On the other hand, if it is within 30 minutes, the amount of polyester obtained when recovered can be ensured without excessive dissolution of the polyester film as the base material. From the above viewpoints, it is more preferably 15 seconds or more and 30 minutes or less, further preferably 30 seconds or more and 25 minutes or less, and particularly preferably 1 minute or more and 20 minutes or less.

[0079] When a polyester film provided with a silicone release layer as a functional layer is to be cleaned, it is preferably for 1 second or more and 30 minutes or less. If it is 1 second or more, the cleaning agent can sufficiently penetrate into the functional layer and the detergency can be exhibited. On the other hand, if it is within 30 minutes, the amount of polyester obtained when recovered can be ensured without excessive dissolution of the polyester film as the base material. From the above viewpoints, it is more preferably 15 seconds or more and 20 minutes or less, further preferably 30 seconds or more and 10 minutes or less, and particularly preferably 1 minute or more and 5 minutes or less.

[0080] The cleaning step is a step of removing the functional layer by immersing it in a cleaning tank containing a cleaning agent. The specific mode of the cleaning step depends on the order with the polishing step. When the cleaning step is performed after the polishing step, it is preferable to remove the functional layer in the roll-to-roll method in the order of the polishing step and the cleaning step. On the one hand, when a cleaning step is performed before the polishing step, it is preferable to unwind the laminated polyester film from the unwinding device at the front stage of the conveyor-type polishing machine and remove the functional layer in a roll-to-roll manner in sequence through the cleaning step and the polishing step. In each of the above aspects, the functional layer can be efficiently removed from the roll-shaped laminated polyester film which is waste material, and the steps involved in removing the functional layer can be minimized.

[0081] <Recovery step> After removing the functional layer from the laminated polyester film using the present functional layer removal method, there may be a recovery step of recovering the polyester film which is the base film. Further, the functional layer removal method may have a rinsing step and a drying step, which will be described later, at the front stage of the recovery step, and can be continuously performed in a roll-to-roll manner, and can be efficiently recovered by winding after appropriately passing through the polishing step, the cleaning step, the rinsing step and the drying step. The polyester film recovered as described above is advantageously made into pellets after recovery in terms of handling.

[0082] <Rinsing step> In the present invention, after removing the functional layer and before the recovery step, there may be a rinsing step of washing away the dust and / or cleaning agent generated in the polishing step. This step is a step of washing away the dust and / or cleaning agent adhering to the polyester film from which the functional layer has been removed with a rinsing liquid. Water is preferably used as the rinsing liquid, but the rinsing step can be omitted when it is not necessary to wash away the dust and / or cleaning agent.

[0083] In the rinsing step, the functional layer peeled off from the polyester film may be washed away simultaneously with the dust and / or cleaning agent. The water and the material that constituted the functional layer are separated thereafter, and the water can be reused in the rinsing step. Also, the material that constituted the functional layer can be reused.

[0084] The rinsing step may be performed after at least one of the above-described polishing step and washing step, but it is preferably performed after both the polishing step and the washing step. Therefore, it is more preferable to perform the steps in the order of the polishing step, the washing step, and the rinsing step. When the rinsing step is performed after both the polishing and washing steps, it is possible to efficiently remove both dust and the cleaning agent in the rinsing step. However, the order of the steps is not particularly limited, and they may be performed in the order of the washing step, the polishing step, and the rinsing step, or in the order of the polishing step, the rinsing step, and the washing step. Also, the rinsing step may be performed two or more times. For example, they may be performed in the order of the polishing step, the rinsing step, the washing step, and the rinsing step. Also, when the washing step is omitted, it is preferable to perform the steps in the order of the polishing step and the rinsing step.

[0085] <Drying step> After the rinsing step, there may be a drying step. The conditions of the drying step are not particularly limited, and it is usually dried at 70 to 150 °C for about 1 to 30 minutes. As the drying method, general methods such as heat drying using an infrared heater or an oven, hot air drying using a hot air dryer, or microwave heating drying can be used. When the rinsing step is omitted, the drying step is preferably performed after the washing step. Also, as described above, when the rinsing step is performed multiple times, drying may be performed after each rinsing step, but it is not necessary to perform drying after each rinsing step. For example, the drying step may be performed only after the last rinsing step.

[0086] <Recycled polyester product and its manufacturing method> The polyester film obtained by the functional layer removing method of the present invention can be reused as a polyester raw material for manufacturing so-called recycled polyester products. Specifically, the recovered polyester can be pelletized and stored as pellet-shaped polyester (polyester products). Further, the recovered polyester can also be formed into various polyester products such as polyester films by melt extrusion or the like. Note that, from the viewpoint of ease of production, it is preferable that the recovered polyester be formed into various products after being once pelletized.

[0087] As for the use, it can be used for the same uses as ordinary polyester products. For example, it can be used as a polyester film which is a base film. By forming a functional layer on the base film, it is also possible to reuse it as a laminated polyester film. Recycled polyester can also be mixed with polyester produced by a conventional method and used, and a multilayer film using recycled polyester and polyester produced by a conventional method can also be formed. As recycled polyester products, in addition to films, they can be used for various applications. For example, PET bottles, polyester fibers, polyester sheets, polyester containers, etc. can also be manufactured. Note that, regarding the peeled functional layer, it can also be recovered and reused as necessary.

[0088] <Functional layer removing device for laminated polyester film> Next, the functional layer removing device for the laminated polyester film will be described with reference to FIG. 1. Note that the device shown in FIG. 1 is an example schematically shown for explaining the embodiment, and is not limited to the configuration of FIG. 1. For example, the configuration of FIG. 1 shows an aspect of a so-called roll-to-roll method in which a roll-shaped laminated polyester film is unwound and further wound up by a roll, but it may be performed by other methods. (Conveyor type polishing machine) The functional layer removing device 10 includes a conveyor type polishing machine 11. An unwinding device 12 is installed in front of the conveyor type polishing machine 11. The laminated polyester film F is unwound from the device 12 and moved by the belt conveyor as described above, or the unwinding device 12 and the winding device 17 are provided, and the laminated polyester film may be conveyed to a predetermined polishing position by being moved by the driving force of these devices. The unwinding device 12 unwinds the roll-shaped laminated polyester film F into a sheet shape and supplies it to the conveyor type polishing machine 11. The conveyor type polishing machine 11 has an abrasive 11A at a predetermined polishing position. The abrasive 11A may be arranged at a position in contact with the laminated polyester film F, and the number of abrasives 11A arranged may be one or more.

[0089] As described above, the conveyor type polishing machine 11 may be either a wet type or a dry type. In the case of the wet type, as shown in FIG. 1, it may have a spraying device 11B for spraying a liquid such as water described above onto the laminated polyester film F. The spraying device 11B may be arranged so that the above liquid can be sprayed at a position where the abrasive 11A contacts the laminated polyester film F or at a position in front of that.

[0090] Also, while moving the conveyor type polishing machine with a belt conveyor, for example, the laminated polyester film may be polished by bringing the laminated polyester film into contact with the abrasive on the belt conveyor. Also, in a roll-to-roll system where an unwinding device and a winding device are provided, the laminated polyester film may be polished by bringing it into contact with an abrasive. Further, in the roll-to-roll system, when the abrasive 11A is a buff roll, a backup roll and / or a guide roll are provided on the side opposite to the buff roll, that is, on the side opposite to the functional layer of the laminated polyester film, and the laminated polyester film is preferably polished while passing between the buff roll and the backup roll and / or the guide roll, and preferably polished on the backup roll. However, the backup roll is provided at a position facing the buff roll, and the guide roll is provided at a position where they do not face each other. By providing one or more of the backup roll and / or the guide roll, the functional layer of the laminated polyester film can be pressed against the buff roll, and the removal rate of the functional layer is improved. In addition, in FIG. 1, the abrasive 11A is shown assuming a buff roll, but the abrasive 11A may be other than the buff roll as described above.

[0091] The functional layer removing device according to the present invention may further include a cleaning device 13.

[0092] (Cleaning device) The cleaning device 13 is a device that includes a cleaning agent containing the above-described compound and cleans the laminated polyester film F with the cleaning agent. Typically, as shown in FIG. 1, a cleaning tank filled with the above-described cleaning agent is exemplified, and the laminated polyester film F, which is waste material, is introduced therein and immersed for cleaning. In addition, there are a coating device for applying a cleaning agent in a solution state, a cleaning agent in a solution state or vaporized state, and a spraying device for forming a mist of the cleaning agent and spraying the mist.

[0093] The cleaning agent is as described above, and as the cleaning agent, an aqueous cleaning agent is preferable. By using an aqueous cleaning agent, rinsing with water can be performed by a rinsing device 14 described later, which is preferable.

[0094] Furthermore, the functional layer removing device according to the present invention is preferably used in combination with a rinsing device 14 and a drying device 15, which will be described in detail below as appropriate.

[0095] (Rinsing device) The rinsing device 14 is a device for washing away dust and / or cleaning agent adhering to the polyester film after removing the functional layer with the transport type polishing machine 11 and the cleaning device 13. Specifically, there are mentioned a spraying device for spraying a rinsing liquid, an immersion device for immersing in the rinsing liquid, and the like. As described above, by using an aqueous cleaning agent as the cleaning agent, water can be used in the rinsing process, which is highly safe and does not require an explosion-proof device, etc., so it is also preferable in terms of cost. In addition, the functional layer removing device may include a separating device (not shown) for separating the rinsing liquid used in the rinsing device 14 into the material that constituted the functional layer and water. The separating device may be of any method, such as a device for filtering and separating with a filter, a solid-liquid separating device such as a centrifuge, an oil-water separating device, or a device for vaporizing and separating water such as a distiller. Also, the separating device may be used alone or in combination of two or more separating devices. By providing the separating device, the functional layer removing device can reuse the water used as the rinsing liquid and the material that constituted the functional layer.

[0096] As shown in FIG. 1, the rinsing device 14 is preferably arranged at a later stage than either the transport type polishing machine 11 or the cleaning device 13. Therefore, it is preferable to arrange them in the order of the transport type polishing machine 11, the cleaning device 13, and the rinsing device 14 from the front stage. However, the rinsing device 14 only needs to be arranged at a later stage than at least one of the transport type polishing machine 11 and the cleaning device 13. Therefore, it may be arranged in the order of the transport type polishing machine 11, the rinsing device 14, and the cleaning device 13 from the front stage. Also, if a plurality of rinsing devices 14 are provided, they may be arranged in the order of the transport type polishing machine 11, the rinsing device 14, the cleaning device 13, and the rinsing device 14. Furthermore, the rinsing device 14 may be omitted.

[0097] (Drying device) The drying device 15 is for drying the polyester film F from which the functional layer has been removed and the cleaning agent has been rinsed away by the rinsing device 14. The drying conditions are as described above. Examples of the drying device 15 include an infrared heater, an oven, a hot air dryer, and a microwave heating dryer. Through the drying process in the drying device, the polyester base material is recovered. When the rinsing device 14 is omitted, the drying device 15 may be provided downstream of the cleaning device 13 to dry the polyester film after cleaning with the cleaning agent. Also, when multiple rinsing devices 14 are provided, multiple drying devices may be provided, and a drying device may be provided downstream of each rinsing device 14. However, one drying device may be sufficient, and it is preferable that the drying device 15 is provided further downstream of the rinsing device 14 on the rearmost side.

[0098] <Recycling device> The above-described functional layer removing device may be used in the recycling device. The recycling device 16 includes the above-described functional layer removing device 10 and a device (recovery device) for recovering the polyester film from which the functional layer has been removed. The device for recovering the polyester film is not particularly limited, but it is preferably a winding device 17 that winds up the polyester film from which the functional layer has been removed in a roll form. It is also preferable that the recycling device 16 further has a pellet manufacturing device 18. The recovered polyester film is preferably pelletized by the pellet manufacturing device 18 to facilitate handling. The polyester film can have even better handling properties by being pelletized. Also, instead of the pellet manufacturing device 18, the recycling device 16 may be equipped with a manufacturing device other than a pellet manufacturing device such as an extruder. The recovered polyester film may be made into a polyester product in a form other than pellets as described above, for example, in the form of a film as a recycled polyester product. The recycling device 16 may be equipped with both a pellet manufacturing device and a manufacturing device other than a pellet manufacturing device, and the pellets manufactured by the pellet manufacturing device may be made into various recycled polyester products by the other manufacturing device.

[0099] In the functional layer removing device 10 shown in FIG. 1 described above, the conveying polishing machine 11 and the cleaning device 13 are arranged in this order from the front stage, but they may be arranged in the order of the cleaning device 13 and the conveying polishing machine 11. In this case, it is preferable to arrange them in the order of the cleaning device 13, the conveying polishing machine 11, and the rinsing device 14 from the front stage, but they may be arranged in the order of the cleaning device 13, the rinsing device 14, and the conveying polishing machine 11 from the front stage. A plurality of rinsing devices 14 may be provided and they may be arranged in the order of the cleaning device 13, the rinsing device 14, the conveying polishing machine 11, and the rinsing device 14.

[0100] Further, as shown in FIG. 2, the cleaning device 13 of the functional layer removing device 10 may be omitted. When the cleaning device is omitted, the rinsing device 14 becomes a device for washing away the dust attached to the polyester film.

[0101] Also, as described above, the cleaning process and the polishing process may be performed simultaneously. In that case, the above-described cleaning agent may be sprayed from the spraying device 11B. Therefore, the spraying device 11B provided in the conveying polishing machine 11 will be used as a cleaning device. Also in that case, as shown in FIG. 2, the cleaning device in the subsequent stage of the conveying polishing machine 11 may be omitted. Note that the other configurations of the functional layer removing device 10 and the recycling device 16 shown in FIG. 2 are as described above. Also in the functional layer removing device 10 shown in FIG. 2, the rinsing device 14 and the drying device 15 may be omitted as appropriate.

[0102] <<Explanation of terms>> In the present invention, when referring to a "film", it includes a "sheet", and when referring to a "sheet", it includes a "film". In the present invention, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", and also includes the meaning of "preferably larger than X" or "preferably smaller than Y". In addition, when it is described as "X or more" (X is any number), unless otherwise specified, it includes the meaning of "preferably greater than X", and when it is described as "Y or less" (Y is any number), unless otherwise specified, it also includes the meaning of "preferably less than Y".

Examples

[0103] 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.

[0104] <Evaluation method> (1) Intrinsic viscosity 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (mass ratio) was added and dissolved, and the measurement was carried out at 30°C.

[0105] (2) Evaluation of removal rate of functional layer: Fluorescent X-ray analysis The surface of the laminated polyester film after removing the functional layer was subjected to quantitative analysis of Si element using a fluorescent X-ray analyzer (XRF, "XRF-1800" manufactured by Shimadzu Corporation). By setting the Si element amount on the surface of the laminated polyester film before removing the functional layer as 100% and the Si element amount of the plain film without the functional layer of the laminated polyester film as 0%, the removal rate of the functional layer was measured.

[0106] (3) Polishing experiment Using a conveyor type polishing machine A or B with different overall dimensions and specifications, an A4 (300×225 mm) size laminated polyester film was polished according to the conditions shown in Table 1 below. Note that both the conveyor type polishing machine A and B are laboratory test machines, and the overall dimensions of the conveyor type polishing machine A are larger than those of the conveyor type polishing machine B. The conveyor type polishing machine A does not have a function to adjust the pressing pressure, and the conveyor type polishing machine B has such a specification. In addition, the conveyor type polishing machines A and B were used in a wet method using water at a water temperature of 25°C. Also, as the abrasive, a resin buff roll in which silicon carbide is adhered with an adhesive to form a grindstone shape was used, and the rotating buff roll was pressed against the laminated polyester film to be conveyed to remove the functional layer.

[0107] (4) Cleaning experiment The following cleaning agent 1 or 2 was placed in a 30 ml container, and a laminated polyester film with a size of 40×30 mm was immersed. When using cleaning agent 1, the immersion was carried out at 60°C for 1 minute, and when using cleaning agent 2, the immersion was carried out at 80°C for 1 minute. (Cleaning agent 1) (a) component: 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide (b) component: 37 parts by mass of benzyl alcohol, 3 parts by mass of propylene glycol (c) component: 18 parts by mass of monoethanolamine Other components: 32 parts by mass of water (Cleaning agent 2) (a) component: 5 parts by mass of potassium hydroxide (b) component: 41 parts by mass of benzyl alcohol (c) component: 18 parts by mass of sodium 2,4-dimethylbenzenesulfonate Other components: 36 parts by mass of water

[0108] <Laminated polyester film having a functional layer> A laminated polyester film having the following functional layers (I) to (II) was prepared as a sample. (I) Laminated polyester film (a laminated polyester film having a silicone release layer); commercially available product ("MRF38" manufactured by Mitsubishi Chemical Corporation), thickness of the polyethylene terephthalate film; 38 μm, intrinsic viscosity of the polyethylene terephthalate film; 0.57 dl / g.

[0109] (II) Laminated polyester film (laminated polyester film having a silicone release layer); commercially available product ("MRF19" manufactured by Mitsubishi Chemical Corporation), thickness of polyethylene terephthalate film; 19 μm, intrinsic viscosity of the polyethylene terephthalate film; 0.57 dl / g.

[0110] [Example 1] Using the laminated polyester film described in Table 1, a polishing experiment was carried out with a conveyor type polishing machine under the conditions described in Table 1. After the polishing experiment, quantitative analysis of the Si element on the surface of the laminated polyester film was performed to evaluate the removal rate of the functional layer.

[0111] [Examples 2 to 11] Except for using the laminated polyester film and polishing conditions described in Table 1, the removal rate evaluation after the polishing experiment was carried out in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0112] [Examples 12 to 17] Except for using the laminated polyester film and polishing conditions described in Table 1, the removal rate evaluation after the polishing experiment was carried out in the same manner as in Example 1. Next, cleaning experiments were carried out using Detergents 1 and 2, and the removal rate of the functional layer after the cleaning experiments was calculated.

[0113]

Table 1

[0114] As shown in Table 1, by polishing the functional layer on the surface of the laminated polyester film with a conveyor type polishing machine, the functional layer can be easily removed from the laminated polyester film. In addition, the functional layer removal method of the present invention can further improve the removal rate of the functional layer by including a cleaning step.

Explanation of Signs

[0115] 10 Functional layer removal device 11 Conveyor type polishing machine 11A Abrasive 11B Spraying device 12 Unwinding device 13 Cleaning device 14 Rinsing device 15 Drying device 16 Recycling device 17 Rewinding device 18 Pellet manufacturing device F Laminated polyester film

Claims

1. A method for removing a functional layer from a laminated polyester film, comprising a polishing step of removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film using a conveyor-type polishing machine.

2. The method for removing a functional layer from a laminated polyester film according to claim 1 , wherein the polishing step is carried out in a wet manner.

3. 3. The method for removing a functional layer from a laminated polyester film according to claim 1, wherein the abrasive used in the polishing step is a buff roll.

4. The method for removing a functional layer from a laminated polyester film according to claim 3, wherein the buff roll itself is laterally vibrated.

5. 5. The method for removing a functional layer from a laminated polyester film according to claim 3, wherein the buff roll rotates in a direction opposite to a transport direction of the laminated polyester film.

6. The method for removing a functional layer from a laminated polyester film according to any one of claims 1 to 5, wherein the functional layer is a silicone release layer.

7. The method for removing a functional layer from a laminated polyester film according to any one of claims 1 to 6, further comprising (a) a cleaning step of cleaning with a cleaning agent containing an alkalizing agent.

8. The method for removing a functional layer from a laminated polyester film according to claim 7 , wherein the cleaning agent further contains (b) a compound having at least one hydroxyl group.

9. The method for removing a functional layer from a laminated polyester film according to any one of claims 1 to 8, further comprising a rinsing step of washing away at least one of the dust generated in the polishing step and the cleaning agent that adheres to the polyester film.

10. A recycled polyester product comprising, at least in part, a polyester film raw material regenerated by the method for removing a functional layer from a laminated polyester film according to any one of claims 1 to 9.

11. A recovery step of recovering the polyester film from which the functional layer has been removed by the functional layer removal method according to any one of claims 1 to 9; A manufacturing method for a recycled polyester product, comprising a manufacturing step of manufacturing a recycled polyester product using the recovered polyester film as a raw material.

12. An apparatus for removing a functional layer from a laminated polyester film, comprising a conveying polishing machine for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film.

13. A recycling apparatus comprising the functional layer removal device described in claim 12, a recovery device for recovering a polyester film from which the functional layer has been removed by the functional layer removal device, and a manufacturing device for producing recycled polyester products using the recovered polyester film as a raw material.

Images