JP7619255B2 - Polyester film recovery method, recovery device, and functional layer remover - Google Patents

Description

The present invention relates to a method for recovering polyester film, a recycled polyester product, a polyester film recovery device, and a functional layer remover for polyester film.

Traditionally, waste plastic has been disposed of by landfilling, dumping at sea, incineration, etc., but it is becoming increasingly difficult to secure landfill sites, and dumping at sea is an environmental problem because plastic does not decompose. In addition, while it can be used to generate heat by incineration, there is the problem that carbon dioxide emissions contribute to global warming.

In light of the recent heightened environmental concerns, there is a need to reuse, regenerate, and recycle waste plastics, and research and development into this area is being actively carried out. Furthermore, since most plastics are produced using fossil fuels, there is a need to develop recycling methods to make effective use of resources.

By the way, polyester film, which is a type of plastic film, is useful as a base film, and is often used as a laminate film with various functional layers laminated on one or both sides. There are various functional layers, such as a hard coat layer, adhesive layer, decorative layer, light-shielding layer, polarizing layer, and ultraviolet ray shielding layer, and laminate films are used in which materials appropriate for the functional layer are laminated on polyester film.

Such laminated films are rarely reused after use, but are instead discarded or incinerated.

Even if an attempt is made to recycle a laminated film with a functional layer laminated thereon by simply remelting it, the material that constitutes the functional layer will be mixed into the molten polymer, causing an unpleasant odor during extrusion or a decrease in the melt viscosity of the polymer, which can lead to breakage during film production.
Even if it were possible to produce a film, degradation of quality due to discoloration of the resulting film or contamination with foreign matter would be unavoidable.

Even if the functional layer is physically removed by scraping it off and then melt extrusion is performed, the remaining functional layer can cause the filter to become clogged during the filtration process during extrusion, resulting in problems such as failure to produce a normal film.

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 a readily soluble resin 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 with a solvent that dissolves only the readily soluble resin layer but does not dissolve the base film. The separated and recovered material is remelted, making it possible to regenerate the resin composition that constituted the base film.

JP 2004-169005 A

The method disclosed in Patent Document 1, as described above, is based on a laminated film in which a readily soluble resin layer and a surface functional layer are laminated in that order on the surface of a base film, and aims to remove the functional layer by dissolving the readily soluble resin layer.
That is, the technique cannot be used for most laminated polyester films that do not have an easily soluble resin layer, and is therefore not versatile.
In view of the above circumstances, an object of the present invention is to propose a method for recovering polyester films, which enables peeling off of the functional layer and recovery of the base film, even in the case of a laminated polyester film that does not have a readily soluble resin layer.

As a result of intensive research, the present inventors have found that by using a cleaning agent containing an alkalizing agent and a compound having at least one hydroxyl group, the functional layer can be removed and the polyester film substrate can be efficiently recovered. The present invention has been completed based on this finding. That is, the present invention has the following aspects.
(1) A method for recovering a polyester film, comprising: a functional layer removal step (A) of washing a laminated polyester film having a functional layer on the surface of the polyester film with a cleaning agent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group, thereby removing the functional layer; and a recovery step (B) of recovering the polyester film from which the functional layer has been removed.
(2) The method for recovering polyester film according to the above (1), wherein the cleaning agent is a water-based cleaning agent.
(3) The method for recovering a polyester film according to the above (1) or (2), wherein the alkalizing agent (a) contains an alkali metal hydroxide.
(4) The method for recovering polyester film according to the above (3), wherein the alkali metal hydroxide contains potassium hydroxide.
(5) The method for recovering a polyester film according to any one of (1) to (4) above, wherein the compound (b) having at least one hydroxyl group is an alcohol.
(6) The method for recovering a polyester film according to the above (5), wherein the alcohol has an acidity constant (pKa) of 10.0 or more and 20.0 or less.
(7) The method for recovering a polyester film according to (5) or (6) above, wherein two or more kinds of the alcohols are used in combination.
(8) The method for recovering a polyester film according to any one of (1) to (7) above, wherein the temperature of the cleaning agent in the functional layer removal step (A) is 20° C. or higher.
(9) A recycled polyester product, which contains, as a raw material, at least a polyester film recovered by the recovery method according to any one of (1) to (8).
(10) A polyester film recovery apparatus having a cleaning device, characterized in that in the cleaning device, a laminated polyester film having a functional layer on the surface of the polyester film is washed with a cleaning agent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group, and the polyester film from which the functional layer has been removed is recovered.
(11) The polyester film recovery apparatus according to (10) above, further comprising a rinsing device for washing away any cleaning agent adhering to the polyester film from which the functional layer has been removed.
(12) The polyester film recovery apparatus according to (11) above, wherein the cleaning agent is a water-based cleaning agent, and the water-based cleaning agent is washed away with water in the rinsing device.
(13) The polyester film recovery device according to any one of (10) to (12) above, further comprising a drying device for drying the polyester film from which the functional layer has been removed.
(14) The polyester film recovery apparatus according to any one of (10) to (13) above, further comprising an unwinding device disposed upstream of the cleaning device.
(15) The polyester film recovery device according to (14) above, which recovers the polyester film using a roll-to-roll method.
(16) The polyester film recovery apparatus according to any one of (10) to (13) above, further comprising a cutting device provided upstream of the cleaning device.
(17) A remover for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film, the remover comprising (a) an alkalizing agent and (b) a compound having at least one hydroxyl group.
(18) The functional layer remover for polyester film according to the above (17), wherein the remover is an aqueous remover.
(19) The functional layer remover for polyester film according to the above (17) or (18), wherein the (a) alkalizing agent contains an alkali metal hydroxide.
(20) The functional layer remover for polyester film according to the above (19), wherein the alkali metal hydroxide contains potassium hydroxide.
(21) The functional layer remover for polyester film according to any one of (17) to (20) above, wherein the compound (b) having at least one hydroxyl group is an alcohol.
(22) The functional layer remover for polyester film according to the above (21), wherein the alcohol has an acidity constant (pKa) of 10.0 or more and 20.0 or less.
(23) The functional layer remover for polyester film according to the above (21) or (22), wherein two or more kinds of the alcohols are used in combination.

According to the recovery method of the present invention, the functional layer can be easily removed from a laminated polyester film having a functional layer, and the base film (polyester film) can be efficiently recovered.

The method for recovering a laminated polyester film of the present invention includes a functional layer removal step (A) of washing a laminated polyester film having a functional layer on the surface of the polyester film with a cleaning agent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group, thereby removing the functional layer, and a recovery step (B) of recovering the polyester film from which the functional layer has been removed.
Here, in the functional layer removal step (A), it is important to use (a) an alkalizing agent and (b) a compound having at least one hydroxyl group in combination, and by using them in combination, the functional layer on the polyester film can be effectively removed.

The mechanism by which the combined use of the above-mentioned components (a) and (b) enables the functional layer to be effectively removed is not clear, but is presumed to be as follows.
It is believed that the reaction described below proceeds at the interface between the polyester film substrate and/or the functional layer, making it possible to efficiently peel the functional layer from the laminate film.

When a laminated film having a functional layer that undergoes hydrolysis, such as an acrylic adhesive layer or an acrylic hard coat layer, is washed, (b) an alkoxide generated from the hydroxyl group of a compound having at least one hydroxyl group causes an ester exchange reaction at the ester bond of the functional layer and/or substrate to obtain a low molecular weight compound. Next, (a) a hydroxyl group ionized from an alkalizing agent attacks the ester bond of the low molecular weight compound in a nucleophilic manner, causing a saponification reaction to obtain a carboxylate (ionization). It is presumed that this causes the functional layer to dissolve.

Even when a laminated film having a functional layer that does not undergo hydrolysis, such as a silicone-based release layer, is cleaned, the polyester film substrate undergoes the above-mentioned reaction mechanism, causing the functional layer laminated on the film to be peeled off and removed, as a result of which the polyester film undergoes molecular weight reduction, saponification, and leaching due to the ester exchange reaction.
Therefore, it is believed that the combination of components (a) and (b) makes it possible to efficiently peel the functional layer from the laminate film.

<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 multilayer structure. In the case of a multilayer structure, it may have a two-layer structure, a three-layer structure, or a four-layer structure or more, and the number of layers is not particularly limited. In addition, 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 any polyester available on the market can be appropriately used. Specifically, polyesters obtained by polycondensation of dicarboxylic acids and diols can be mentioned, and the dicarboxylic acid is preferably an aromatic dicarboxylic acid, and the diol is preferably an aliphatic glycol.
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 copolymer polyester, and may contain a third component other than the aromatic dicarboxylic acid and the glycol as a copolymer component.
Specific examples of polyesters include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polybutylene-2,6-naphthalate, etc., among which polyethylene terephthalate is preferred. These may also be copolymer polyesters, and for example, polyethylene terephthalate may have dicarboxylic acid units other than terephthalic acid at about 30 mol % or less of the dicarboxylic acid units, and may have diol units other than ethylene glycol at about 30 mol % of the diol units.

The functional layer is not particularly limited in terms of its constituent components, but is preferably composed of a resin from the viewpoint of removal by the recovery method of the present invention. Examples of functional layers include a hard coat layer, a tacky 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, and an oligomer sealing layer.

The hard coat layer is a layer provided to impart scratch resistance to the polyester film. The material for forming 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.

The adhesive layer is a layer that is provided to adhesively adhere to other devices, etc., and the material that constitutes the adhesive layer is not particularly limited, but for example, known adhesive resins such as acrylic, rubber, and silicone-based adhesive resins can be used.

The release layer is a layer provided to impart releasability to a polyester film, and is provided, for example, in release films used in forming green sheets used in the manufacture of ceramic electronic components, and in adhesive separators for optical components used in the manufacture of flat panel displays such as polarizing plates and optical filters. There are no particular limitations on the material that constitutes the release layer, and examples include those mainly composed of cured silicone resin, modified silicone resins obtained by graft polymerization with urethane resins, epoxy resins, etc., compounds containing long-chain alkyl groups, fluorine compounds, and hydrocarbon waxes.

The decorative layer is a layer provided to impart design, and the material constituting the decorative layer is not particularly limited, but examples include polyurethane resin, vinyl resin, polyamide resin, polyester resin, acrylic resin, polyvinyl acetal resin, etc. Pigments, dyes, etc. are added to these resins to create decoration.

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

The easy-adhesion layer (primer layer) is a layer provided to adhere other layers or films onto the polyester film, and may be made of, but is not limited to, polyurethane resins, vinyl resins, polyamide resins, polyester resins, acrylic resins, polyvinyl acetal resins, and the like, as well as various crosslinking agents and particles.

The antistatic layer is a layer provided to prevent static electricity caused by contact with or peeling off from other materials. The antistatic agent used in the antistatic layer is not particularly limited, but includes nonionic, cationic, anionic, and amphoteric surfactants, conductive polymers such as polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), and poly(4-styrenesulfonate), metal oxide fillers such as SnO ₂ (Sb-doped), In ₂ O ₃ (Sn-doped), and 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. The antistatic layer may be formed from a resin composition containing an antistatic agent. Examples of resins contained in the resin composition include polyester resins, acrylic resins, and urethane resins.

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

The oligomer sealing layer is a layer provided to prevent film whitening and foreign matter after the heating process. Although there is no particular limitation, examples of materials constituting the oligomer sealing layer include amine compounds and ionic resins. The oligomer sealing layer may also be a highly cross-linked coating film, etc.

These functional layers may be a single layer, or two or more kinds of layers may be laminated.
When two or more kinds of layers are laminated, it is preferable that at least one layer is made of a resin.

<Cleaning agent>
The method of the present invention is characterized in that the functional layer removal step (A) involves cleaning with a cleaning agent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group.

(Alkalizing agent)
The (a) alkalizing agent constituting the cleaning agent of the present invention is a component that makes the cleaning liquid alkaline and can also be called an alkaline agent. The alkalizing agent may be an inorganic alkalizing agent or an organic alkalizing agent.

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.

Among the inorganic alkalizing agents used in this cleaning agent, alkali metal hydroxides are preferred, with sodium hydroxide and potassium hydroxide being more preferred due to their ease of availability, and potassium hydroxide being particularly preferred due to its cleaning properties.

The inorganic alkalizing agent in this cleaning agent may be used alone or in combination of two or more. In particular, it is preferable to use a combination of potassium hydroxide and sodium hydroxide in terms of effectiveness and ease of handling.

Examples of the organic alkalizing 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.
In addition, organic alkalizing agents may include compounds having at least one hydroxyl group, and if the acidity constant (pKa) of the compound is 30 or more, it is treated as an alkalizing agent.

Of the organic alkalizing agents used in this cleaning agent, monoethanolamine, diethanolamine, and triethanolamine are preferred from the perspective of versatility, monoethanolamine and diethanolamine are more preferred from the perspective of availability, and monoethanolamine is particularly preferred from the perspective of cleaning properties.

Furthermore, from the viewpoint of cleaning properties, it is also preferable to use an inorganic alkalizing agent in combination with an organic alkalizing agent. Specifically, 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, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, and triisopropanolamine is more preferable, and 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.

The content of the alkalizing agent in the entire cleaning agent is preferably 1 to 50% by mass, more preferably 2 to 45% by mass, and even more preferably 3 to 40% by mass. If it is within the above range, the cleaning agent will be sufficiently effective.

(Compound having at least one hydroxyl group)
Examples of the compound (b) having at least one hydroxyl group that constitutes the present cleaning agent include alcohols and phenols.

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, and propylene glycol monoethyl ether; dihydric alcohols such as ethylene glycol, diethylene glycol, and propylene glycol; and polyhydric alcohols such as glycerin.

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, and hexahydroxybenzene.

These may be used alone or in combination of two or more types, but from the viewpoint of enhancing the peeling and cleaning effect, it is preferable to use two or more types in combination, and it is more preferable to use two or more types of alcohols in combination.

Among these, monohydric alcohols are preferred from the viewpoint of not impairing the alkalinity of the cleaner and maintaining the cleaning properties.
In particular, from the viewpoint of cleaning properties, methyl alcohol, ethyl alcohol, propyl alcohol and benzyl alcohol are more preferable. These alcohols have high cleaning properties because protons are easily ionized to generate alkoxides.
From the viewpoints of low volatility and usable temperature range, benzyl alcohol is particularly preferred.

Specifically, the monohydric alcohols contribute to the penetration and swelling of the coating film, and when two or more types of the monohydric alcohols are used in combination, a combination of a hydrophobic alcohol and a water-soluble alcohol is preferred from the viewpoint of achieving a wide and synergistic peeling and cleaning effect regardless of the properties of the coating film. Here, the hydrophobic alcohol refers to an alcohol that does not mix with water and separates into two layers, and the water-soluble alcohol refers to an alcohol that mixes with water to form one layer.
As the hydrophobic alcohol, benzyl alcohol is particularly preferred, and as the water-soluble alcohol, any one or more selected from methyl alcohol, ethyl alcohol and propyl alcohol are particularly preferred.
From the above, it is particularly preferable to use benzyl alcohol as the hydrophobic alcohol in combination with at least one of methyl alcohol, ethyl alcohol and propyl alcohol as the water-soluble alcohol, and among these, the combination of benzyl alcohol and methyl alcohol is most preferable.

When two or more of the monohydric alcohols are used in combination, the blending ratio of the hydrophobic alcohol:water-soluble alcohol is preferably from 1:1 to 10:1, more preferably from 1.5:1 to 9:1, and even more preferably from 2:1 to 8:1, from the viewpoint of particularly enhancing the stripping and cleaning effect.
In addition, even when two or more kinds of monohydric alcohols are used in combination, a dihydric alcohol and a polyhydric alcohol may be further used in combination.

From the viewpoint of cleaning properties, the acidity constant (pKa) of the alcohol is preferably in the range of 10.0 or more and 20.0 or less, more preferably 10.0 or more and 18.0 or less, even more preferably 12.0 or more and 16.0 or less, particularly preferably 14.0 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 the alcohol is within the above range, the alkoxide is generated without impairing the alkalinity of the cleaning agent, and therefore the cleaning ability of the cleaning agent is improved.

The acidity constants (pKa) of some alcohols are as follows: 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).
From the values of the acidity constants (pKa) of alcohols shown above, it can be said that alcohols having an acidity constant (pKa) of 15.4 or less are alcohols having an acidity constant (pKa) smaller than that of methanol.

The content of the (b) compound in the cleaning 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 the (a) alkalizing agent is appropriate, so that when the polyester film is recovered, contamination with foreign matter due to precipitation of the alkalizing agent components is suppressed, and the quality of the recycled polyester film can be maintained.

In view of cleaning properties, a particularly preferred embodiment of the cleaning agent of the present invention is a combination of (W) or (X) and (Y) or (Z).
(W) (a) As an alkalizing agent (alkaline agent), an alkali metal hydroxide, in particular sodium hydroxide or potassium hydroxide, is included.
(X) (a) As an alkalizing agent (alkaline agent), it includes an alkali metal hydroxide, in particular 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 methyl alcohol, ethyl alcohol, propyl alcohol, or benzyl alcohol, particularly benzyl alcohol.
(Z) (b) The compound having at least one hydroxyl group includes an alcohol having an acidity constant (pKa) in the range of 14.0 or more and 15.4 or less, that is, includes at least an alcohol having an acidity constant (pKa) smaller than that of methanol.

The cleaning agent according to the present invention is preferably a water-based cleaning agent. A water-based cleaning agent is obtained by dissolving the above-mentioned components (a) and (b) in water and diluting them. Water-based cleaning agents are relatively safe because they can increase the flash point, and are also advantageous in that water can be used in the rinsing step described below.

The cleaning agent according to the present invention can contain various additives in addition to the above-mentioned components (a) and (b), such as surfactants, antioxidants, rust inhibitors, pH adjusters, preservatives, viscosity adjusters, and defoamers.

(Surfactant)
The surfactant is a component that solubilizes the above-mentioned components (a) and (b) and any other additives that are added arbitrarily, and representative examples thereof include the compounds described below.

There are no particular limitations on the surfactant, and any of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants can be used.

Examples of anionic surfactants include alkyl sulfonic acids, alkyl benzene sulfonic acids, alkyl carboxylic acids, alkyl naphthalene sulfonic acids, α-olefin sulfonic acids, dialkyl sulfosuccinic acids, α-sulfonated fatty acids, N-methyl-N-oleyl taurine, petroleum sulfonic acids, alkyl sulfuric acids, sulfated oils and fats, polyoxyethylene alkyl ether sulfates, polyoxyethylene styrenated phenyl ether sulfates, alkyl phosphoric acids, polyoxyethylene alkyl ether phosphoric acids, polyoxyethylene alkyl phenyl ether phosphoric acids, naphthalene sulfonic acid formaldehyde condensates, and salts thereof.

Examples of cationic surfactants include quaternary ammonium, tetraalkylammonium, trialkylbenzylammonium, alkylpyridinium, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium, N,N-dialkylmorpholinium, 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.

Nonionic surfactants include polyoxyalkylene ethers such as polyoxyethylene alkyl ethers and polyoxyethylene-polyoxypropylene alkyl ethers; polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl 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, polyoxyethylated castor oil, fatty acid diethanolamides, polyoxyethylene alkylamines, triethanolamine fatty acid partial esters, trialkylamine oxides, etc.

Examples of amphoteric surfactants include betaines (N,N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N,N,N-trialkyl-N-sulfoalkyleneammonium betaine, N,N-dialkyl-N,N-bispolyoxyethyleneammonium sulfate betaine, 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine, etc.) and aminocarboxylic acids (N,N-dialkylaminoalkylenecarboxylate, etc.).

(Antioxidants)
The antioxidant is not particularly limited, and an amine-based antioxidant, a phenol-based antioxidant, or the like can be used.

(Rust inhibitor)
The rust inhibitor includes inorganic compounds such as chromates, molybdates, and sodium nitrite.

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

(Preservatives)
Preservatives include parabens, benzoic acid, sodium benzoate, sorbic acid, propionate salts, dehydroacetic acid, sulfur dioxide, and sodium pyrosulfite.

(Viscosity modifier)
Examples of the viscosity modifier include polymer compounds and layered inorganic particles.

(Antifoaming agent)
Examples of the antifoaming agent include fluorine-based compounds, silicone-based compounds, polyether-based compounds, acetylene glycol-based compounds, and chelating agents such as EDTA.

<Functional layer removal step (A)>
The functional layer removal step according to the present invention is a step of removing the functional layer of the laminated film using the cleaning agent. Examples of the removal method include an immersion method in which the laminated film is immersed in a cleaning tank containing a cleaning agent, Examples of such methods include a coating method in which a cleaning agent in a solution state is applied, and a spraying method in which a cleaning agent in a solution state or a vaporized cleaning agent is sprayed. Among these, the immersion method is preferred from the viewpoint of the permeability of the cleaning agent into the functional layer. preferable.

The temperature of the cleaning agent in the immersion method is preferably room temperature (20° C.) or higher. At room temperature (20° C.) or higher, the viscosity of the cleaning solution is low and it is easy to penetrate into the functional layer, so that good cleaning properties can be obtained. From the above viewpoints, 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.
The upper limit of the temperature of the cleaning agent is preferably a temperature equal to or lower than the boiling point when the cleaning agent is used in a solution state. In the case of an aqueous cleaning agent, which is a preferred embodiment of the present application, the upper limit is preferably 100° C. or lower, and more preferably 90° C. or lower.
In addition, the temperature of the cleaning solution during cleaning is the same as that described above even in the case of a method other than the immersion method. In addition, in the peeling cleaning in the immersion method, microwave irradiation may be performed for the purpose of promoting the hydrolysis reaction.

From the standpoint of cleaning performance, the pH of the cleaning agent is preferably 12 or higher, and more preferably 13 or higher.

It is preferable to adjust the immersion time as follows, depending on the type of object being cleaned:

When the polyester film having an acrylic adhesive layer as a functional layer is to be cleaned, the cleaning time is preferably 1 second or more and 30 minutes or less. If it is 1 second or more, the cleaning agent will sufficiently penetrate into the functional layer, and cleaning properties can be exhibited. On the other hand, if it is 30 minutes or less, the polyester film as the base material will not be excessively dissolved, and the amount of polyester obtained when recovered can be secured. From the above viewpoints, it is more preferable that it is 15 seconds or more and 20 minutes or less, even more preferable that it is 30 seconds or more and 15 minutes or less, and particularly preferable that it is 1 minute or more and 10 minutes or less.

When the polyester film having an acrylic hard coat layer as a functional layer is to be cleaned, the cleaning time is preferably 1 second or more and 30 minutes or less. If it is 1 second or more, the cleaning agent will sufficiently penetrate into the functional layer, and cleaning properties can be exhibited. On the other hand, if it is 30 minutes or less, the polyester film as the base material will not be excessively dissolved, and the amount of polyester obtained when recovered can be secured. From the above viewpoints, it is more preferable that it is 15 seconds or more and 30 minutes or less, even more preferable that it is 30 seconds or more and 25 minutes or less, and particularly preferable that it is 1 minute or more and 20 minutes or less.

When the object to be cleaned is a polyester film having a silicone release layer as a functional layer, the cleaning time is preferably 1 second or more and 30 minutes or less. If it is 1 second or more, the cleaning agent will sufficiently penetrate into the functional layer, and cleaning properties can be exhibited. On the other hand, if it is within 30 minutes, the polyester film substrate will not be excessively dissolved, and the amount of polyester obtained when recovered can be secured. From the above viewpoints, it is more preferable that it is 15 seconds or more and 20 minutes or less, even more preferable that it is 30 seconds or more and 10 minutes or less, and particularly preferable that it is 1 minute or more and 5 minutes or less.

The specific aspects of the functional layer removal process depend on the shape of the laminated film waste material.

When the waste laminated polyester film is in the form of a roll, it is preferable to provide a winding device in front of the cleaning tank containing the cleaning agent, and to wind the laminated film from the device and introduce it into the cleaning tank for cleaning. Then, it is preferable to continuously proceed to the next recovery step (B).
In addition, in order to efficiently remove the functional layer from the laminated polyester film from the functional layer removal step to the rinsing step described below, equipment equipped with physical means such as a roll brush, ultrasonic waves, micro/nano bubbles, water flow, or compressed cold air may be provided.

When the laminated polyester film waste is in a lump form, it is preferable to install a cutting device before the cleaning process and cut the laminated polyester film into flakes before introducing them into the cleaning tank. By cutting the laminated polyester film into flakes, the contact area between the laminated polyester film and the cleaning agent is increased, making it easier for the cleaning agent to penetrate, and the functional layer can be removed efficiently. In this embodiment, a method is preferable in which the laminated polyester film in flake form is continuously introduced into the cleaning tank using a belt conveyor or the like. By adopting such an embodiment, cleaning can be performed with high productivity. In this embodiment, cleaning can also be performed in a batch manner.

<Recovery process (B)>
After the functional layer removing step (A), the polyester film, which is the base film, is recovered. It is preferable to have a rinsing step and a drying step, which will be described later, before the recovery step. As the recovery method, an appropriate method can be selected depending on the shape of the laminated polyester film, which is the waste material.

If the waste laminated polyester film is in roll form, it can be efficiently recovered by continuously processing it from roll to roll, passing it through the appropriate cleaning, rinsing and drying processes, and then winding it up.

When the waste laminated polyester film is in a lump form, as described above, it is preferable to have a cutting process before the functional layer removal process. In this embodiment, it is preferable to use a belt conveyor or the like to continuously pass the film through a rinsing process and a drying process to recover the flake-like polyester.

The polyester film recovered as described above is advantageously pelletized after recovery in terms of handling.

<Rinsing process>
In the present invention, it is preferable to have a rinsing step of washing away the cleaning agent after the functional layer removing step (A) and before the recovery step (B). Specifically, this refers to a step of washing away the cleaning agent adhering to the polyester film from which the functional layer has been removed with a rinsing liquid.

There are no particular limitations on the rinsing liquid as long as it can wash away the cleaning agent, but when using a water-based cleaning agent, which is a preferred embodiment of the present invention, water can be used in the rinsing step.

The temperature for the rinsing step is preferably around room temperature, more specifically 5 to 50°C, and more preferably 5 to 30°C, from the viewpoint of efficient rinsing.

Methods for rinsing off the cleaning agent include a spraying method in which a rinsing liquid is sprayed onto the polyester film from which the functional layer has been removed, and an immersion method in which the polyester film is immersed in a rinsing tank containing a rinsing liquid. However, if a cleaning agent that does not need to be washed off is used, the rinsing process can be omitted.

<Drying process>
After the rinsing step, a drying step is preferably performed. The drying step can remove the cleaning agent and/or the rinsing liquid remaining on the polyester film. When the rinsing step is omitted, the drying step is preferably performed after the functional layer removing step (A).

The conditions for the drying process are not particularly limited, and drying is usually performed at 70 to 150°C for about 1 to 30 minutes. As for the drying method, a general method such as heating and drying using an infrared heater or oven, hot air drying using a hot air dryer, or microwave heating and drying can be used.

<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 films by melt extrusion or the like. In addition, the recovered polyester is preferably pelletized once and then molded into various products because of its ease of production.

It can be used in the same applications as ordinary polyester products, for example, as a polyester film, which is a base film. By forming a functional layer on the base film, it can also be reused as a laminate film.

Recycled polyester can be mixed with polyester produced by conventional methods, and multilayer films can be made using recycled polyester and polyester produced by conventional methods.

Recycled polyester products can be used for a variety of purposes other than film, such as producing PET bottles, polyester fibers, polyester sheets, and polyester containers.

In addition, the peeled functional layer can also be recovered and reused if necessary.

<Functional layer remover>
According to another aspect of the present invention, there is provided a remover (hereinafter also referred to as "the remover") for removing a functional layer from a laminated polyester film having a functional layer on the surface of a polyester film.
The functional layer remover for polyester film according to the present invention is a cleaning agent used in the functional layer removal step (A) in the above-mentioned polyester film recovery method, which is used to remove the functional layer from the polyester film.
Specific and preferred aspects of the present remover are the same as those of the above-mentioned cleaning agent, and all of these can be used.
The removing agent of the present invention can easily remove the functional layer from the polyester film, and can efficiently recover the polyester film from the laminated polyester film.

<Polyester film recovery device>
The polyester film recovery device according to the present invention includes a cleaning device, and recovers the polyester film that has been cleaned by the cleaning device and from which the functional layer has been removed.

The means for recovering the polyester film is not particularly limited. In the case of a roll, a take-up roll for recovering the polyester film from which the functional layer has been removed may be used.
In the case of a lump, the polyester film from which the functional layer has been removed may be transported to a predetermined recovery position by a transport device such as a belt conveyor and recovered.

The means for unwinding and cutting the polyester film is not particularly limited, but in the case of a roll, it is preferable that the polyester film has an unwinding device, and further, it is preferable that the winding is also performed on a roll, that is, a so-called roll-to-roll method, in which the polyester film can be recovered efficiently.
If in chunk form, it is preferred to have a shredding device, which breaks the waste material into flakes, which, as mentioned above, makes the cleaning process more efficient.

It is also preferable that the recovery device has a pellet manufacturing device, and the recovered polyester film is preferably pelletized in the pellet manufacturing device to facilitate handling. In particular, polyester film recovered from chunky waste materials can be made even easier to handle by pelletizing it.

Furthermore, the recovery device preferably includes a rinsing device and a drying device, as described in more detail below.

(Cleaning device)
The cleaning device is a device for cleaning with a cleaning agent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group. A typical example is a cleaning tank filled with the above-mentioned cleaning agent, into which the waste laminated polyester film is introduced and immersed for cleaning. Other examples include a coating device that coats the cleaning agent in a solution state, a spraying device that forms a mist of the cleaning agent in a solution state or vaporized state, or the cleaning agent, and sprays the mist.

The cleaning agent is as described above, and a water-based cleaning agent is preferable as the cleaning agent. By using a water-based cleaning agent, rinsing with water can be performed using the rinsing device described below, which is preferable.

(Rinsing device)
The rinsing device is a device for washing away the cleaning agent attached to the polyester film after removing the functional layer with the cleaning agent. Specifically, it can be a spraying device for spraying the rinsing liquid, an immersion device for immersing the polyester film in the rinsing liquid, etc. As described above, by using a water-based cleaning agent as the cleaning agent, water can be used in the rinsing step, which is highly safe and does not require an explosion-proof device, which is also preferable in terms of cost.

The functional layer that has peeled off from the polyester film may also be washed away together with the cleaning agent. The water and the material that constituted the functional layer are then separated, and the water can be reused in the rinsing step, and the material that constituted the functional layer can also be reused. The rinsing device may be omitted.

(Drying device)
The drying device is for drying the polyester film from which the functional layer has been peeled off and the cleaning agent has been washed away, and the drying conditions are as described above. Examples of the drying device include an infrared heater, an oven, a hot air dryer, and a microwave heating dryer. After the drying process in the drying device, the polyester substrate is recovered. Note that even when the rinsing device is omitted, the drying device may be used to dry the polyester film from which the functional layer has been peeled off.

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.

<Evaluation method>
(1) Immersion test The cleaning agent prepared in each Example and Comparative Example was placed in a 30 ml water tank, and the laminated film was immersed in the cleaning agent. The temperature of the cleaning agent, the immersion time, and the sample size are as shown in the table.

(2) Evaluation of peeling of 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 film was taken out and the surface was visually observed and evaluated according to the following criteria.
⊚ (very good): The functional layer was dissolved or peeled off, and the polyester film substrate was not significantly damaged, which is particularly preferable from a practical standpoint.
◯ (good): The functional layer is partially dissolved or peeled off, but there is no problem in practical use.
Δ (fair): A small part of the functional layer was dissolved or peeled off.
× (bad): The functional layer remains, and there is a problem in practical use.

(2-2) X-ray fluorescence analysis (laminated polyester film having a silicone release layer)
The surface of the laminated film after cleaning was subjected to a quantitative analysis of the Si element using an X-ray fluorescence analyzer (XRF, "XRF-1800" manufactured by Shimadzu Corporation).
The removal rate of the functional layer was measured by setting the amount of Si element on the surface of the laminated polyester film before cleaning to 100% and the amount of Si element on a plain film of the laminated film not coated with a functional layer to 0%.
◎(very good); Removal rate 90-100%
○ (good); Removal rate 70-89%
× (bad); Removal rate 0-69%

(3) Intrinsic Viscosity 1 g of polyester was precisely weighed, dissolved in 100 ml of a mixed solvent of phenol/tetrachloroethane = 50/50 (mass ratio), and the intrinsic viscosity was measured at 30°C.

(Laminated polyester film having a functional layer)
A laminated polyester film having the following functional layers (I) to (III) was prepared as a sample.
(I) Laminated film (laminated polyester film having an acrylic adhesive layer);
Commercially available product ("PET75-H120(10) Blue" manufactured by Nichiei Shinka Co., Ltd.), thickness of polyethylene terephthalate film: 75 μm, thickness of acrylic adhesive layer: 10 μm

(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 (product name: Omnirad 184, manufactured by IGM Resins BV), and 70 parts by weight of toluene.
(Preparation of Acrylic Hard Coat Film)
The above acrylic hard coat solution was applied onto a polyethylene terephthalate film; a commercially available product ("Diafoil" manufactured by Mitsubishi Chemical Corporation) to a dry film thickness of about 9 μm, and cured by exposure to ultraviolet light to obtain a laminated polyester film having an acrylic hard coat layer.

(III) Laminated film (laminated polyester film having a silicone release layer): commercially available product ("MRF38" manufactured by Mitsubishi Chemical Corporation), thickness of polyethylene terephthalate film: 38 μm, intrinsic viscosity of the polyethylene terephthalate film was 0.67.

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

[Example 2]
A cleaning agent (pH = 13 or more) was prepared by mixing 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 19 parts by mass of monoethanolamine as component (a), 40 parts by mass of benzyl alcohol and 1 part by mass of propylene glycol as component (b), and 30 parts by mass of water as another component.
Using the laminated films (I) to (III), cleaning property evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.
The laminated film (III) was washed at a temperature condition of 60°C for an immersion time of 1 minute, and the intrinsic viscosity of the polyester film from which the silicone release layer had been removed was measured. The intrinsic viscosity was 0.67, and there was no change in the intrinsic viscosity of the polyester film before and after washing.

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

[Example 4]
5 parts by mass of potassium hydroxide as component (a) and 95 parts by mass of benzyl alcohol as component (b) were mixed together to prepare a cleaning agent (pH = 13 or more).
Using the laminated films (I) and (III), cleaning property evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 5]
Five parts by mass of potassium hydroxide as component (a) and 95 parts by mass of methanol as component (b) were mixed together to prepare a cleaning agent (pH = 13 or more).
Using the laminated film (III), cleaning performance evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 6]
A cleaning agent was prepared by dissolving 5 parts by mass of potassium hydroxide as component (a) and 95 parts by mass of ethanol as component (b) in water.
Using the laminated films (I) and (III), cleaning property evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 7]
A cleaning agent was prepared by mixing 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as component (a), 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 component (b), and 31.7 parts by mass of water as another component.
Using the laminated film (III), cleaning property evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 8]
A cleaning agent was prepared by mixing 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as component (a), 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 component (b), and 31.7 parts by mass of water as another component.
Using the laminated film (III), cleaning performance evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 9]
A cleaning agent was prepared by mixing 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as component (a), 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 component (b), and 31.7 parts by mass of water as another component.
Using the laminated film (III), cleaning performance evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 10]
A cleaning agent was prepared by mixing 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as component (a), 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 component (b), and 31.7 parts by mass of water as another component.
Using the laminated film (III), cleaning property evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Example 11]
A cleaning agent was prepared by mixing 5 parts by mass of potassium hydroxide, 5 parts by mass of sodium hydroxide, and 17.9 parts by mass of monoethanolamine as component (a), 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 component (b), and 31.7 parts by mass of water as another component.
Using the laminated film (III), cleaning performance evaluation was carried out under the conditions shown in Table 1. The results are shown in Table 1.

[Comparative Example 1]
A cleaning agent was prepared by mixing 30 parts by mass of potassium hydroxide as component (a) and 70 parts by mass of water as the other component. Using the laminated films (I) and (III), cleaning performance evaluation was performed under the conditions shown in Table 1. The results are shown in Table 1.

[Comparative Example 2]
Except for changing the temperature conditions as shown in Table 1, the cleaning performance evaluation was carried out in the same manner as in Comparative Example 1. The results are shown in Table 1.

As reference examples, a base film (IV) (polyethylene terephthalate film, thickness 52 μm) not provided with a functional layer and a base film (V) (unstretched polypropylene film, thickness 56 μm) were prepared as samples.
The sample was immersed in the cleaning agent for 5 minutes, and the thickness was measured using a thickness gauge ID-C112X/1012X manufactured by Mitutoyo Corporation to measure the change in thickness of the substrate.
A case where the thickness change was 3 μm or more was rated A, and a case where the thickness change was less than 3 μm was rated B.

[Reference Example 1]
A cleaning test was carried out on the base film (IV) and the base film (V) under the conditions shown in Table 1 using a cleaning agent having the same composition as in Example 1, and the thickness after cleaning was measured. The results are shown in Table 1.

[Reference Example 2]
Using a cleaning agent having the same composition as in Example 2, cleaning tests were carried out on the base film (IV) and the base film (V) under the conditions shown in Table 1, and the thicknesses after cleaning were measured. The results are shown in Table 1.

[Reference Example 3]
In order to confirm the best form of the monohydric alcohol in the cleaning agent, the cleaning conditions were changed to 40° C. and 1.2 minutes for the immersion time in Examples 2, 7, 8 and 9, and the cleaning performance was evaluated according to the following criteria. The results are shown in Table 2.
As in the above, the cleaning evaluation was performed by quantitatively analyzing the Si element on the surface of the laminated film after cleaning using an X-ray fluorescence analyzer.
The removal rate of the functional layer was judged according to the following criteria.
○ (good); Removal rate 50-100%
△ (fair); Removal rate 0-49%

As can be seen from the results shown in Table 1, the method of the present invention made it possible to peel the functional layer from any of the adhesive film, hard coat film, and release film, and to recover the polyester film.
Furthermore, from the results of Example 2, it can be seen that according to the method of the present invention, the intrinsic viscosity (IV) of the polyester film does not decrease before and after the functional layer removal process (cleaning process), and therefore recycled polyester products made from the recovered polyester film are also likely to have excellent mechanical properties, etc.
Furthermore, from the results of Examples 7 to 11, it was found that according to the method of the present invention, by using two or more types of alcohols in combination as a compound having at least one hydroxyl group, it is possible to peel off the functional layer at a lower temperature and in a shorter time, which is less likely to affect the film.

It can be seen that Comparative Example 1 and Comparative Example 2, which contain only component (a) and no component (b) as cleaning agents, do not exhibit the effects of the present invention.

The results of Reference Examples 1 and 2 show that the surface of the base film (IV), which is a polyester film, is partially melted and thinned, while the surface of the base film (V), which does not have ester bonds, is not melted and is not thinned. In other words, it is believed that the cleaning agent according to the present invention effectively peels off the functional layer by partially dissolving the surface of the polyester film, which is the base material.

The results of Reference Example 3 (Table 2) also show that by using a monohydric alcohol as component (b) and setting the mass ratio of hydrophobic alcohol:water-soluble alcohol to be 2:1 to 8:1, an extremely excellent cleaning effect can be obtained.

As described above, according to the present invention, various functional layers can be peeled off with one type of cleaning agent, so even in the case of a laminated polyester film having multiple different functional layers, it is possible to peel off all of the functional layers with one solution. Furthermore, even in the case of a laminated polyester film having, for example, a hard coat layer on the front side and an adhesive layer on the back side, the functional layers can be peeled off from both sides with a single cleaning operation, and the polyester film substrate can be recovered.

Claims (27)

The method includes a functional layer removing step (A) and a recovery step (B),
The functional layer removal step (A) is a step of removing a functional layer of a laminated polyester film having a functional layer on a surface of a polyester film using a cleaning agent,
The cleaning agent contains : (a) an alkalizing agent; and (b) a compound having at least one hydroxyl group;
the functional layer is any one of a hard coat layer, a tacky adhesive layer, and a release layer, the hard coat layer is an acrylic hard coat layer, the tacky adhesive layer is an acrylic tacky adhesive layer, and the release layer is a silicone release layer;
The (b) compound having at least one hydroxyl group includes at least one of the following (i) and (ii):
The method for producing a recycled polyester product, wherein the recovery step (B) is a step of recovering the polyester film from which the functional layer has been removed.
(i) Two or more types of alcohols including a hydrophobic alcohol and a water-soluble alcohol
(ii) Alcohols having an acidity constant (pKa) of 15.4 or less The method for producing a recycled polyester product according to claim 1, wherein the mass ratio of the hydrophobic alcohol to the water-soluble alcohol is 2:1 to 8:1. The method for producing a recycled polyester product according to claim 1 or 2 , wherein the detergent is a water-based detergent. The method for producing a recycled polyester product according to any one of claims 1 to 3, wherein two or more inorganic alkalizing agents are used as the alkalizing agent (a). The method for producing a recycled polyester product according to any one of claims 1 to 4, wherein the alcohols include benzyl alcohol. The method for producing a recycled polyester product according to any one of claims 1 to 5 , wherein the (a) alkalizing agent contains an alkali metal hydroxide. The method for producing a recycled polyester product according to any one of claims 1 to 6 , wherein the (a) alkalizing agent contains potassium hydroxide. The method for producing a recycled polyester product according to any one of claims 1 to 7 , wherein the temperature of the cleaning agent in the functional layer removal step (A) is 20°C or higher . A polyester film recovery device having a cleaning device, the cleaning device having a cleaning tank containing a cleaning agent , and a laminated polyester film having a functional layer on a surface of the polyester film is immersed in the cleaning agent containing (a) an alkalizing agent and (b) a compound having at least one hydroxyl group to clean the laminated polyester film,
the functional layer is any one of a hard coat layer, a tacky adhesive layer, and a release layer, the hard coat layer is an acrylic hard coat layer, the tacky adhesive layer is an acrylic tacky adhesive layer, and the release layer is a silicone release layer;
The (b) compound having at least one hydroxyl group includes at least one of the following (i) and (ii):
A polyester film recovery device comprising a means for recovering the polyester film that has been washed in the washing device and from which the functional layer has been removed .
(i) Two or more types of alcohols including a hydrophobic alcohol and a water-soluble alcohol
(ii) Alcohols having an acidity constant (pKa) of 15.4 or less The apparatus for recovering a polyester film according to claim 9, wherein the ratio of the hydrophobic alcohol to the water-soluble alcohol is from 2:1 to 8:1 by weight. The apparatus for recovering a polyester film according to claim 9 or 10, wherein the alkalizing agent (a) comprises two or more inorganic alkalizing agents. The polyester film recovery device according to any one of claims 9 to 11, wherein the alcohols include benzyl alcohol. The apparatus for recovering a polyester film according to any one of claims 9 to 12, wherein the alkalizing agent (a) comprises an alkali metal hydroxide . The apparatus for recovering a polyester film according to any one of claims 9 to 13, wherein the alkalizing agent (a) comprises potassium hydroxide. The polyester film recovery device according to any one of claims 9 to 14 , further comprising a rinsing device that washes away any cleaning agent adhering to the polyester film from which the functional layer has been removed. The polyester film recovery apparatus according to claim 15 , wherein the cleaning agent is a water-based cleaning agent, and the water-based cleaning agent is washed away with water in the rinsing device. The polyester film recovery device according to any one of claims 9 to 16 , further comprising a drying device for drying the polyester film from which the functional layer has been removed. The polyester film recovery apparatus according to any one of claims 9 to 17 , further comprising an unwinding device upstream of the cleaning device. The polyester film recovery device according to claim 18 , which recovers the polyester film by a roll-to-roll method. The polyester film recovery apparatus according to any one of claims 9 to 17 , further comprising a cutting device provided upstream of the cleaning device. A remover for removing a functional layer from a laminated polyester film having a functional layer on a surface of the polyester film, comprising:
(a) an alkalizing agent; and (b) a compound having at least one hydroxyl group,
The (b) compound having at least one hydroxyl group includes at least one of the following (i) and (ii):
The functional layer remover for polyester film, wherein the functional layer is any one of a hard coat layer, an adhesive layer, and a release layer, the hard coat layer is an acrylic hard coat layer, the adhesive layer is an acrylic adhesive layer, and the release layer is a silicone release layer .
(i) Two or more types of alcohols including a hydrophobic alcohol and a water-soluble alcohol
(ii) Alcohols having an acidity constant (pKa) of 15.4 or less The remover according to claim 21, wherein the mass ratio of the hydrophobic alcohol to the water-soluble alcohol is 2:1 to 8:1. The functional layer remover for a polyester film according to claim 21 or 22 , wherein the remover is a water-based remover. The functional layer remover for a polyester film according to any one of claims 21 to 23, wherein the (a) alkalizing agent comprises two or more inorganic alkalizing agents. The functional layer remover for a polyester film according to any one of claims 21 to 24 , wherein the (a) alkalizing agent comprises an alkali metal hydroxide. The functional layer remover for polyester film according to any one of claims 21 to 25 , wherein the (a) alkalizing agent contains potassium hydroxide. The functional layer remover for polyester film according to any one of claims 21 to 26, wherein the alcohol comprises benzyl alcohol.