JP2023026456A - Polyester film recovery method, recovery device, and functional layer removal agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film recovery method, a recovery device and a functional layer removal agent that capable of peeling a functional layer and recovering a substrate film.

SOLUTION: A polyester film recovery method includes: a functional layer removal step (A) of cleaning, with a cleaning agent containing (a) an alkalinizing agent and (b) a compatibilizing agent, a layered polyester film comprising a functional layer on a surface of a polyester film, thereby removing the functional layer; and a recovery step (B) of recovering the polyester film from which the functional layer has been removed.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a polyester film recovery method, a recycled polyester product, a polyester film recovery device, and a polyester film functional layer removing agent.

Conventionally, waste plastics have been disposed of by landfill, ocean dumping, incineration, etc., but it is becoming difficult to secure a landfill site, and ocean dumping is becoming an environmental problem 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 gas.

Therefore, due to the recent heightening of environmental problems, there is a need for recycling such as reuse and regeneration of waste plastics, and research and development for this purpose are being actively carried out. In addition, most plastics are produced using fossil fuels, and from the point of view of effective use of resources, construction of a recycling method is required.

By the way, a polyester film, which is a type of plastic film, is useful as a base film and is often used as a laminated film in which various functional layers are laminated on one side or both sides. There are various functional layers such as hard coat layer, adhesive layer, decorative layer, light shielding layer, polarizing layer, and UV shielding layer. is used.

Such laminated films are hardly reused after use, and are discarded, incinerated, or the like.

Even if you attempt to re-melt and recycle the laminated film with the functional layer laminated as it is, the materials that make up the functional layer will be mixed into the molten polymer, causing an offensive odor during extrusion and a decrease in the melt viscosity of the polymer. As a result, it causes breakage during film formation.
In addition, even if the film can be formed, it is inevitable that the resulting film will be colored and the quality will be deteriorated due to contamination with foreign matter.

In addition, even if the functional layer is removed physically by scraping it off and then melted and extruded, the remaining functional layer clogs the filter during the filtration process during extrusion, making normal film formation impossible. problem arises.

As a method for recycling laminated films, for example, there is a technique disclosed in Patent Document 1. This technique is a laminated film formed by laminating a readily soluble resin layer and a surface functional layer in this order on at least one side of a substrate film. With such a structure, after use, the substrate film is separated and recovered from the laminated film by washing with a solvent that can dissolve only the easily soluble resin layer but does not dissolve the substrate film. be. The separated and collected material is remelted, making it possible to regenerate the resin composition constituting the base film.

Japanese Patent Application Laid-Open No. 2004-169005

As described above, the method disclosed in Patent Document 1 is based on the premise of a laminated 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. is intended to remove the functional layer by dissolving the
That is, it cannot be used for most laminated polyester films that do not have a readily soluble resin layer, and it is a technique without versatility.
In view of the above circumstances, it is an object of the present invention to propose a polyester film recovery method capable of peeling off the functional layer and recovering the base film even in the case of a laminated polyester film that does not have a readily soluble resin layer. do.

As a result of intensive studies, the present inventors have found that the functional layer can be removed by using a cleaning agent containing an alkalinizing agent and a compatibilizing agent, and the polyester film of the substrate can be efficiently recovered. found to get. The present invention has been completed based on such findings. That is, the present invention has the following aspects.
(1) A functional layer removing step of washing a laminated polyester film having a functional layer on the surface of the polyester film with a detergent containing (a) an alkalinizing agent and (b) a compatibilizing agent to remove the functional layer. A method for recovering a polyester film comprising (A) and a recovery step (B) for recovering the polyester film from which the functional layer has been removed.
(2) The method for recovering a polyester film according to (1) above, wherein the cleaning agent is a water-based cleaning agent.
(3) The method for recovering a polyester film according to (1) or (2) above, wherein (a) the alkalinizing agent contains an alkali metal hydroxide.
(4) The method for recovering a polyester film according to (3) above, wherein the alkali metal hydroxide contains potassium hydroxide.
(5) The polyester film recovery method according to any one of (1) to (4) above, wherein the cleaning agent further contains (c) at least one compound having a hydroxyl group.
(6) The method for recovering a polyester film according to (5) above, wherein the (c) compound having at least one hydroxyl group is an alcohol.
(7) The polyester film recovery method according to (6) above, wherein the alcohol has an acidity constant (pKa) of 8.0 or more and 20.0 or less.
(8) The method for recovering a polyester film according to (6) or (7) above, wherein two or more alcohols are used in combination.
(9) The compatibilizing agent (b) is at least one selected from the group consisting of aromatic sulfonates and hydroxyl group-containing amine compounds, according to any one of (1) to (8) above. A method for recovering a polyester film.
(10) The polyester film recovery method according to any one of (1) to (9) above, wherein the temperature of the cleaning agent in the functional layer removing step (A) is 20° C. or higher.
(11) A recycled polyester product containing, as a raw material, at least a part of the polyester film recovered by the recovery method according to any one of (1) to (10) above.
(12) A polyester film recovery apparatus having a washing device, in which a laminated polyester film having a functional layer on the surface of the polyester film is coated with (a) an alkalinizing agent and (b) a compatibilizing agent. 1. A recovery apparatus for a polyester film, characterized in that the polyester film is recovered from which the functional layer has been removed by washing with a cleaning agent.
(13) The apparatus for recovering a polyester film according to (12) above, further comprising a rinsing device for washing off the cleaning agent adhering to the polyester film from which the functional layer has been removed.
(14) The polyester film recovery apparatus according to (13) 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.
(15) The polyester film recovery apparatus according to any one of (12) to (14) above, which includes a drying device for drying the polyester film from which the functional layer has been removed.
(16) The polyester film recovery apparatus according to any one of (12) to (15) above, which has an unwinding device upstream of the cleaning device.
(17) The apparatus for collecting the polyester film according to (16) above, which is collected by a roll-to-roll system.
(18) The polyester film recovery apparatus according to any one of (12) to (15) above, further comprising a cutting device in a stage preceding the cleaning device.
(19) A removing agent for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film, the polyester film containing (a) an alkalinizing agent and (b) a compatibilizing agent Functional layer remover.
(20) The functional layer removing agent for a polyester film as described in (19) above, wherein the removing agent is a water-based removing agent.
(21) The functional layer removing agent for a polyester film as described in (19) or (20) above, wherein the (a) alkalinizing agent contains an alkali metal hydroxide.
(22) The functional layer removing agent for polyester film as described in (21) above, wherein the alkali metal hydroxide contains potassium hydroxide.
(23) The functional layer removing agent for polyester film as described in any one of (19) to (22) above, which further contains (c) a compound having at least one hydroxyl group.
(24) The functional layer removing agent for a polyester film as described in (23) above, wherein (c) the compound having at least one hydroxyl group is an alcohol.
(25) The functional layer removing agent for polyester film as described in (24) above, wherein the alcohol has an acidity constant (pKa) of 8.0 or more and 20.0 or less.
(26) The polyester film functional layer removing agent according to (24) or (25) above, wherein two or more of the alcohols are used in combination.
(27) The polyester according to any one of (19) to (26), wherein the compatibilizer (b) is at least one selected from the group consisting of aromatic sulfonates and hydroxyl-containing amine compounds. Functional layer remover for films.

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

The method for recovering the laminated polyester film of the present invention includes washing a laminated polyester film having a functional layer on the surface of the polyester film with a detergent containing (a) an alkalinizing agent and (b) a compatibilizing agent, and removing the functional layer and a recovery step (B) for recovering the polyester film from which the functional layer has been removed.
Here, in the functional layer removing step (A), it is important to use (a) an alkalinizing agent and (b) a compatibilizing agent in combination, and the combination effectively removes the functional layer on the polyester film. be able to.

Although the mechanism by which the functional layer can be effectively removed by the combined use of the above components (a) and (b) is not clear, it is presumed as follows.

That is, at the interface between the polyester film as the base material and the functional layer, the saponification reaction by the hydroxyl groups ionized from the alkalinizing agent progresses to generate carboxylate (ionization), which causes the functional layer to swell and peel off or dissolve. I'm guessing.
It is believed that the use of the compatibilizing agent improves the compatibility of the cleaning agent components, thereby facilitating the above-described reaction and facilitating the separation of the functional layer.

<Laminated polyester film>
The laminated polyester film in the present invention means a film in which a functional layer such as a resin layer is laminated on the surface of a polyester film which 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 be a two-layer structure, a three-layer structure, or a multilayer structure of four or more layers, and the number of layers is not particularly limited. Moreover, 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. Specific examples thereof include polyesters obtained by polycondensation of dicarboxylic acids and diols. Dicarboxylic acids are preferably aromatic dicarboxylic acids, and diols are preferably aliphatic glycols.
Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, and phthalic acid. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like.
The polyester may be a homopolyester or a copolyester. Moreover, the polyester may contain a third component other than the aromatic dicarboxylic acid and the glycol as a copolymer component.
Specific examples of polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polybutylene-2,6-naphthalate, etc. Among these, polyethylene terephthalate is preferred. These may also be copolymer polyesters. For example, polyethylene terephthalate has dicarboxylic acid units other than terephthalic acid at about 30 mol % or less of the dicarboxylic acid units, and 30 mol % of the diol units. It may have diol units other than ethylene glycol to some extent.

The constituents of the functional layer are not particularly limited, but from the viewpoint of removal by the recovery method of the present invention, the functional layer is preferably made of a resin. Functional layers include, for example, 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 adjusting layer, an oligomer sealing layer, stopping layer, and the like.

The hard coat layer is a layer provided to impart abrasion resistance and the like to the polyester film, and the material forming the hard coat layer is not particularly limited, but examples include monofunctional (meth)acrylates, polyfunctional ( Examples include cured products of reactive silicon compounds such as meth)acrylates and tetraethoxysilane.

The adhesive layer is a layer provided for adhesion to other devices or the like, and the material constituting the adhesive layer is not particularly limited, but for example, known acrylic, rubber, silicone A tackifying resin such as a system can be used.

The release layer is a layer provided to impart releasability to the polyester film. For example, it is used in the production of flat panel displays such as green sheet forming process paper, polarizing plates, and optical filters used in the production of ceramic electronic components. It is a layer that is provided on a release film that is used as an adhesive separator for optical members that are sometimes used. The material constituting the release layer is not particularly limited. For example, a material containing a curable silicone resin as a main component, a modified silicone resin obtained by graft polymerization with a urethane resin, an epoxy resin, or the like, a long-chain alkyl group, etc. Containing compounds, fluorine compounds, hydrocarbon waxes and the like can be mentioned.

The decorative layer is a layer provided for imparting design properties, and the material constituting the decorative layer is not particularly limited, but examples thereof include polyurethane-based resins, vinyl-based resins, polyamide-based resins, and polyester-based resins. , acrylic resins, polyvinyl acetal resins, and the like. Pigments and dyes are added to these resins for decoration.

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

The easy-adhesion layer (primer layer) is a layer provided for adhering other layers or films onto the polyester film, and is not particularly limited, but may be polyurethane-based resin, vinyl-based resin, polyamide-based resin, polyester-based resin, Examples include acrylic resins, polyvinyl acetal resins, various cross-linking agents, and particles.

The antistatic layer is a layer provided to prevent electrification caused by contact with or peeling off from other materials. The antistatic agent used in the antistatic layer is not particularly limited, but nonionic, cationic, anionic, amphoteric surfactants, polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), poly( 4-styrene sulfonate), conductive polymers such as SnO ₂ (Sb-doped), In ₂ O ₃ (Sn-doped), metal oxide fillers such as ZnO (Al-doped), graphene, carbon black, carbon nanotubes ( CNT) and other carbon compounds. These may be used alone or in combination of two or more. Also, 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 adjusting layer is a layer provided for adjusting the refractive index, and the material constituting the refractive index adjusting layer is not particularly limited, but polyester resin, acrylic resin, urethane resin, polycarbonate resin, epoxy resin, Examples include alkyd resins, urea resins, fluorine resins, and metal oxides such as zirconium oxide and titanium oxide. 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 prevention after a heating process, and is not particularly limited. Examples of materials constituting the oligomer sealing layer include amine compounds and ionic resins. mentioned. Also, the oligomer sealing layer may be a highly crosslinked coating film or the like.

A single layer may be sufficient as these functional layers, and two or more types of layers may be laminated|stacked.
When two or more layers are laminated, at least one layer is preferably a layer made of resin.

<Cleaning agent>
The method of the present invention is characterized in that in the functional layer removing step (A), cleaning is performed with a cleaning agent containing (a) an alkalinizing agent and (b) a compatibilizing agent.

(Alkalizing agent)
The (a) alkalinizing agent, which constitutes the cleaning agent of the present invention, makes the cleaning liquid alkaline, and can also be called an alkaline agent. The alkalinizing agent may be an inorganic alkalizing agent or an organic alkalizing agent, but the inorganic alkalizing agent is preferred because it is suitable for combination with the compatibilizing agent (b) described later. is preferred.

Examples of inorganic alkalinizing 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 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.

Of the inorganic alkalinizing agents in the cleaning agent, alkali metal hydroxides are preferred, sodium hydroxide and potassium hydroxide are more preferred from the standpoint of availability, and potassium hydroxide is particularly preferred from the standpoint of detergency.

As the inorganic alkalinizing agent in the cleaning agent, one type can be used alone, or two or more types can be used in combination. In particular, it is preferable to use potassium hydroxide and sodium hydroxide in combination from the viewpoint of effect and handling.

Examples of organic alkalinizing agents include N,N-bis(2-hydroxyethyl)-N-cyclohexylamine, diazabicycloundecene, diazabicyclononene, monomethylamine, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, tri Examples include organic amine compounds such as ethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, triisopropanolamine, and the like.
A compound having at least one hydroxyl group may be included as an organic alkalinizing agent, and if the acidity constant (pKa) of the compound is 30 or more, it is treated as an alkalizing agent.

Of the organic alkalinizing agents in the cleaning agent, monoethanolamine, diethanolamine and triethanolamine are preferred from the viewpoint of versatility, monoethanolamine and diethanolamine are more preferred from the viewpoint of availability, and monoethanolamine is particularly preferred from the viewpoint of detergency.

Also, the content of the alkalinizing agent in the entire cleaning agent is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass. Within the above range, a sufficient effect as a cleaning agent can be obtained.

(Compatibilizer)
In the cleaning agent according to the present invention, the (b) compatibilizing agent has a function of assisting the elution of the functional layer from the laminated polyester film by being used in combination with the (a) component. It has the function of solubilizing the component (c), which can be suitably added, and other optional additives.
The compatibilizer (b) is not particularly limited, and any of anionic compatibilizers, cationic compatibilizers, nonionic compatibilizers and amphoteric compatibilizers can be used.
Since the compatibilizer includes a compound corresponding to the alkalinizing agent, the (b) compatibilizing agent in the cleaning agent of the present invention, when used in combination with the (a) alkalinizing agent, A different component from the component (a) is used.

Examples of anionic compatibilizers include alkylsulfonic acids, alkylbenzenesulfonic acids, alkylcarboxylic acids, aromatic carboxylic acids, alkylnaphthalenesulfonic acids, α-olefinsulfonic acids, dialkylsulfosuccinic acids, α-sulfonated fatty acids, N-methyl- N-oleyl taurine, petroleum sulfonic acid, alkyl sulfuric acid, sulfated fat, polyoxyethylene alkyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphoric acid, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkylphenyl ether Phosphoric acid, naphthalenesulfonic acid formaldehyde condensate, salts thereof, and the like.

Cationic compatibilizers 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, salts thereof and the like.

Examples of nonionic compatibilizers include polyoxyalkylene ethers such as polyoxyethylene alkyl ethers and polyoxyethylene-polyoxypropylene alkyl ethers; Oxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, fatty acid diethanolamide, monomethylamine, dimethylamine, trimethylamine , monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, triisopropanolamine, polyoxyethylenealkylamine, triethanolamine fatty acid Examples include organic amine compounds such as partial esters and trialkylamine oxides.

Amphoteric compatibilizers include N,N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N,N,N-trialkyl-N-sulfoalkylene ammonium betaine, N,N-dialkyl-N,N- Examples include betaines such as bispolyoxyethylene ammonium sulfate betaine and 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine, and aminocarboxylic acids such as N,N-dialkylaminoalkylene carboxylates.

The compatibilizing agent may include (c) a compound having at least one hydroxyl group, which will be described later. , (b) are treated as compatibilizers.
Examples of alkanolamine compounds include monoethanolamine, diethanolamine and triethanolamine, and examples of alkanolamide compounds include monoethanolamide, diethanolamide and triethanolamide.
Examples of hydroxy compounds 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.

Of the (b) compatibilizing agents in the cleaning agent, aromatic sulfonates and hydroxyl group-containing amine compounds are preferred from the viewpoint of compatibility and handling. Specific compounds include alkanolamines such as sodium benzenesulfonate, sodium toluenesulfonate, sodium 2,4-dimethylbenzenesulfonate, sodium 2-naphthalenesulfonate, monoethanolamine, diethanolamine and triethanolamine. . Among these, the aromatic sulfonate having a high boiling point is more preferably used from the viewpoint of raising the upper limit of heating of the cleaning liquid.
Here, as described above, it is assumed that a compound other than (a) the alkalinizing agent is used.

Specific examples of the combination of (a) an alkalinizing agent and (b) a compatibilizing agent include, when an inorganic alkalinizing agent is used as the alkalinizing agent, and (b) an anionic compatibilizing agent is used as the compatibilizing agent. , a cationic compatibilizer, a nonionic compatibilizer, and an amphoteric compatibilizer. (a) When an organic alkalinizing agent is used as the alkalinizing agent, (b) the compatibilizing agent may be an anionic compatibilizing agent, a cationic compatibilizing agent, or a nonionic phase other than an organic amine compound. At least one of a solubilizing agent and an amphoteric compatibilizing agent may be used.

In the cleaning agent, (a) an inorganic alkalinizing agent is used as an alkalinizing agent, and (b) at least one selected from aromatic sulfonates and hydroxyl group-containing amine compounds is used as a compatibilizing agent. It is preferred to use
Among them, a combination of at least one inorganic alkalinizing agent selected from sodium hydroxide and potassium hydroxide and an aromatic sulfonate such as sodium 2,4-dimethylbenzenesulfonate is preferred. In addition, at least one inorganic alkalinizing agent selected from sodium hydroxide and potassium hydroxide, monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino -A combination of at least one hydroxyl group-containing amine compound selected from 2-propanol and triisopropanolamine is preferred, and among these, at least one inorganic alkalinizing agent selected from sodium hydroxide and potassium hydroxide, A combination of at least one hydroxyl group-containing amine compound selected from monoethanolamine and diethanolamine is particularly preferred.

Two or more of the compatibilizing agents may be used in combination from the viewpoint of comprehensively compatibilizing various additives in the detergent.
Also, the content of the compatibilizer in the detergent is preferably in the range of 1 to 30% by mass. Sufficient detergency can be obtained within the above range. From the above viewpoints, the content of the compatibilizing agent in the cleaning agent is more preferably in the range of 5 to 25% by mass, more preferably in the range of 8 to 20% by mass.

The cleaning agent according to the present invention preferably contains (c) a compound having at least one hydroxyl group.

(Compound with at least one hydroxyl group)
Examples of (c) the compound having at least one hydroxyl group include alcohols and phenols.

Alcohols include monovalent 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.

Phenols include phenol, xylenol, salicylic acid, picric acid, naphthol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, dibutylhydroxytoluene, bisphenol A, cresol, estradil, eugenol, gallic acid, guaiacol, phenolphthalein. , serotonin, dopamine, adrenaline, noradrenaline, thymol, tyrosine, hexahydroxybenzene and the like.

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

Among these, alcohols are preferable from the viewpoint of maintaining the detergency without impairing the alkalinity of the detergent.

From the viewpoint of detergency, the alcohol preferably has an acidity constant (pKa) of 8.0 or more and 20.0 or less, more preferably 8.0 or more and 18.0 or less. It is more preferably 0 or more and 16.0 or less, particularly preferably 9.0 or more and 15.6 or less, and most preferably 9.3 or more and 15.4 or less.
If the acidity constant (pKa) of the alcohol is within the above range, the alkoxide is generated without impairing the alkalinity of the cleaning agent, thereby improving the cleaning ability of the cleaning agent.

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).
From the values of the acidity constants (pKa) of alcohols shown above, alcohols having an acidity constant (pKa) of 15.4 or less can be said to be alcohols having an acidity constant (pKa) smaller than that of methanol.
Alcohols having an acidity constant (pKa) of 9.3 or more can be said to be alcohols having an acidity constant (pKa) of hexafluoro-2-propanol or more.

(Preferred embodiment 1 of component (c))
Among the above, hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, propyl alcohol and benzyl alcohol are more preferable from the viewpoint of detergency. These alcohols easily ionize protons to form alkoxides and have high detergency. Among them, hexafluoro-2-propanol, which has high detergency, is preferred.

Furthermore, it is also preferable to use hexafluoro-2-propanol in combination with other alcohols for the purpose of adjusting the cleaning ability. When used in combination, hexafluoro-2-propanol and methyl alcohol, hexafluoro-2-propanol and ethyl alcohol, and hexafluoro-2-propanol and benzyl alcohol are preferably used in combination.

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

In addition, even when two or more monovalent alcohols are used in combination, a dihydric alcohol and a polyhydric alcohol may be used in combination.

(Preferred embodiment 2 of component (c))
Among the above, benzyl alcohol is preferred from the viewpoint of low volatility and usable temperature range.

(Preferred embodiment 3 of component (c))
Furthermore, in particular, from the viewpoint of enhancing the peeling and cleaning effect, it is preferable to use two or more types in combination, and when two or more types are used together, the viewpoint of broadly and synergistically expressing the peeling and cleaning effect regardless of the properties of the coating film. Therefore, a combination of a hydrophobic monovalent alcohol and a water-soluble monovalent alcohol is preferred. Hydrophobic monovalent alcohol refers to monovalent alcohol that separates into two layers without being mixed with water, and water-soluble monovalent alcohol refers to monolayer alcohol that forms one layer when mixed with water.
Among them, it is more preferable to use benzyl alcohol as a hydrophobic monovalent alcohol and at least one selected from hexafluoro-2-propanol, methyl alcohol, ethyl alcohol and propyl alcohol as a water-soluble monovalent alcohol. Combinations of benzyl alcohol and hexafluoro-2-propanol and benzyl alcohol and methyl alcohol are most preferred.

When two or more alcohols are used in combination, the blending ratio is not particularly limited, but from the viewpoint of particularly enhancing the peeling and cleaning effect, the weight ratio of hydrophobic monovalent alcohol:water-soluble monovalent alcohol is 1:1 to 20:1. 1:1 to 10:1 is more preferred, and 1.5:1 to 10:1 is even more preferred.

In addition, even when two or more monovalent alcohols are used in combination, a dihydric alcohol and a polyhydric alcohol may be used in combination.

In the detergent, the content of (c) the compound 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, (a) the amount of the alkalinizing agent is appropriate, so that when the polyester film is recovered, contamination by foreign matter due to precipitation of the alkalinizing agent component is suppressed, and the quality of the recycled polyester film can be maintained. .

The cleaning agent according to the present invention is preferably a water-based cleaning agent. The water-based detergent is obtained by dissolving and diluting the above components (a) to (c) in water. Aqueous detergents are relatively safe because they can raise the flash point, and are also advantageous in that water can be used in the rinsing step, which will be described later.

The cleaning agent according to the present invention can contain various additives other than the above components (a) to (c). Modifiers, defoamers, and the like can be added.

(Antioxidant)
The antioxidant is not particularly limited, and amine-based antioxidants, phenol-based antioxidants, and the like can be used.

(anti-rust)
Rust inhibitors include inorganic compounds such as chromates, molybdates, and sodium nitrite.

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

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

(Viscosity modifier)
Viscosity modifiers include polymer compounds and layered inorganic particles.

(Antifoaming agent)
Antifoaming agents include fluorine-based compounds, silicone-based compounds, polyether-based compounds, acetylene glycol-based compounds, and chelating agents represented by EDTA.

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

The temperature of the cleaning agent in the immersion method is preferably room temperature (20° C.) or higher. When the temperature is above room temperature (20° C.), the viscosity of the cleaning liquid is low and it easily permeates into the functional layer, so 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, further preferably 50° C. or higher, and particularly preferably 60° C. or higher.
As for the upper limit of the temperature of the cleaning agent, when the cleaning agent is used in the form of a solution, a temperature below the boiling point is preferable. In the case of a water-based cleaning agent, which is a preferred embodiment of the present application, the temperature is preferably 100°C or lower, more preferably 90°C or lower.
In addition, the temperature of the cleaning liquid during cleaning is the same as described above even in methods other than the immersion method. Further, in the peeling cleaning in the immersion method, microwave irradiation may be performed for the purpose of advancing the hydrolysis reaction.

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

The immersion time is preferably adjusted as follows depending on the type of object to be cleaned.

When a polyester film provided with an acrylic pressure-sensitive adhesive layer as a functional layer is to be cleaned, the cleaning time is preferably 1 second or more and 30 minutes or less. When the time is 1 second or more, the cleaning agent sufficiently permeates into the functional layer, and cleaning performance can be exhibited. On the other hand, when it is within 30 minutes, the amount of polyester obtained when recovered can be ensured without excessive dissolution of the polyester film as the substrate. 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.

When a polyester film provided with an acrylic hard coat layer as a functional layer is to be washed, it is preferably 1 second or more and 30 minutes or less. When the time is 1 second or more, the cleaning agent sufficiently permeates into the functional layer, and cleaning performance can be exhibited. On the other hand, when it is within 30 minutes, the amount of polyester obtained when recovered can be ensured without excessive dissolution of the polyester film as the substrate. From the above viewpoints, the time is more preferably 15 seconds or more and 30 minutes or less, more preferably 30 seconds or more and 25 minutes or less, and particularly preferably 1 minute or more and 20 minutes or less.

When a polyester film provided with a silicone release layer as a functional layer is to be cleaned, the cleaning time is preferably 1 second or more and 30 minutes or less. When the time is 1 second or more, the cleaning agent sufficiently permeates into the functional layer, and cleaning performance can be exhibited. On the other hand, when it is within 30 minutes, the amount of polyester obtained when recovered can be ensured without excessive dissolution of the polyester film as the substrate. From the above viewpoints, the time is more preferably 15 seconds or more and 20 minutes or less, more preferably 30 seconds or more and 10 minutes or less, and particularly preferably 1 minute or more and 5 minutes or less.

A specific aspect of the functional layer removing step depends on the shape of the laminated film, which is a waste material.
When the waste laminated polyester film is in the form of a roll, an unwinding device is installed in front of the cleaning tank containing the detergent, and the laminated film is unwound from the device and introduced into the cleaning tank. It is preferable to wash with And the aspect which transfers to the following collection|recovery process (B) continuously is preferable.
In addition, in the rinsing process to be described later from the functional layer removal process, equipment equipped with physical means such as roll brushes, ultrasonic waves, micro/nano bubbles, water flow, compressed cold air, etc. for the purpose of efficiently removing the functional layer from the laminated polyester film. may be provided.

When the waste laminated polyester film is in the form of lumps, it is preferable to set up a cutting device before the washing step to make flakes and introduce them into the washing tank. By forming flakes, the contact area between the laminated polyester film and the cleaning agent is increased, the cleaning agent can easily permeate, and the functional layer can be removed efficiently. In this embodiment, it is preferable to use a belt conveyor or the like to continuously introduce the flaky laminated polyester film into the washing tank. By adopting such an aspect, cleaning can be performed with high productivity. In addition, in the case of this aspect, cleaning can also be performed in a batch system.

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

When the waste laminated polyester film is in the form of a roll, it can be efficiently collected by continuously performing a roll-to-roll process, appropriately washing, rinsing, and drying, and then winding it up.

When the waste laminated polyester film is in the form of a block, it is preferable to have a cutting step before the functional layer removing step, as described above. In the case of this embodiment, it is preferable to use a belt conveyor or the like to continuously pass through the rinsing process and the drying process to recover the polyester flakes.

It is advantageous in terms of handling that the polyester film recovered as described above is pelletized after recovery.

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

The rinsing liquid is not particularly limited as long as it can wash away the cleaning agent, but water can be used in the rinsing step when using an aqueous cleaning agent, which is a preferred embodiment of the present invention.

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

Examples of the method for washing away the cleaning agent include a spraying method of spraying a rinse liquid onto the polyester film from which the functional layer has been removed, and an immersion method of immersing the polyester film in a rinse tank containing the rinse liquid. However, the rinsing step can be omitted when using a cleaning agent that does not require rinsing.

<Drying process>
After the rinsing process, it is preferable to pass through a drying process. The drying process can remove the detergent and/or rinse liquid remaining on the polyester film. When the rinsing process is omitted, the drying process is preferably performed after the functional layer removing process (A).

Conditions for the drying step are not particularly limited, and drying is usually carried out at 70 to 150° C. for about 1 to 30 minutes. As a drying method, general methods such as heat drying using an infrared heater or an oven, hot air drying using a hot air dryer or the like, and microwave heat 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 pelleted 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 view of ease of production, the recovered polyester is preferably pelletized once and then molded into various products.

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

Recycled polyester can be used by mixing with conventionally produced polyester, or a multilayer film using recycled polyester and conventionally produced polyester can be used.

Recycled polyester products can be used for various purposes other than films, such as PET bottles, polyester fibers, polyester sheets, and polyester containers.

It should be noted that the separated functional layer can also be recovered and reused as necessary.

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

<Polyester film recovery device>
The polyester film collecting device according to the present invention has a washing device. The collecting device collects the polyester film from which the functional layer has been removed by washing with the washing device.

The means for collecting the polyester film is not particularly limited, but in the case of a roll, a take-up roll for collecting the polyester film from which the functional layer has been removed may be used.
In the case of lumps, the polyester film from which the functional layer has been removed may be transported to a predetermined collection position by a conveying device such as a belt conveyor and collected.

The means for unwinding and cutting the polyester film is not particularly limited, but in the case of a roll, it is preferable to have an unwinding device, and further, the so-called roll-to-roll system in which winding is also performed by a roll. is preferable in that the polyester film can be recovered efficiently.
In the case of lumps, it is preferable to have a cutting device. Shredding flakes the waste material and, as mentioned above, makes the cleaning process more efficient.

The recovering device preferably also has a pelletizing device, and the recovered polyester film is preferably pelletized by the pelletizing device in order to facilitate handling. In particular, the polyester film recovered from bulky waste materials can be pelletized to make it easier to handle.

Furthermore, the recovery device preferably comprises a rinsing device and a drying device, as detailed below.

(Washing equipment)
The cleaning device is a device that cleans with a cleaning agent containing (a) an alkalinizing agent and (b) a compatibilizing agent. Typically, the washing tank includes a washing tank filled with the above cleaning agent, and the waste laminated polyester film is introduced into the washing tank and immersed therein for washing. In addition, there are a coating device that applies a cleaning agent in a solution state, and a spraying device that forms a mist of a cleaning agent in a solution state or vaporized state and sprays the mist.

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

(Rinse device)
The rinsing device is a device for washing off the detergent adhering to the polyester film after removing the functional layer with the detergent. Specifically, a spraying device for spraying the rinse solution, an immersion device for immersing the substrate in the rinse solution, and the like can be used. As described above, by using a water-based cleaning agent as the cleaning agent, it is possible to use water in the rinsing process, which is highly safe, and is preferable in terms of cost because an explosion-proof device is unnecessary.

In some cases, the functional layer peeled off from the polyester film is also washed away together with the detergent. The water and the material that made up the functional layer are then separated, the water can be reused in the rinsing step, and the material that made up the functional layer can also be reused. Note that the rinse 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. Drying devices include infrared heaters, ovens, hot air dryers, microwave heating dryers, and the like. The polyester base material is recovered through the drying process in the drying device. Even when the rinsing device is omitted, it is preferable to dry the polyester film from which the functional layer has been removed using a drying device.

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. The cleaning agent temperature, immersion time, and sample size are as described in the table.

(2) Detachment evaluation of functional layer (2-1) Visual observation (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 is dissolved or peeled off, and the polyester film as the base material is not significantly damaged, which is particularly preferable for practical use.
○ (good); the functional layer is partially dissolved or peeled off, and there is no practical problem.
Δ (fair); A small part of the functional layer is dissolved or peeled off.
x (bad); the functional layer remains and is problematic in practice.

(2-2) X-ray fluorescence analysis (laminated polyester film with silicone release layer)
The surface of the laminated film after washing was quantitatively analyzed for Si element using an X-ray fluorescence spectrometer (XRF, "XRF-1800" manufactured by Shimadzu Corporation).
The removal rate of the functional layer was measured by setting the Si element content of the surface of the laminated polyester film before washing to 100% and the Si element content of the plain film not coated with the functional layer of the laminated film to 0%.
◎ (very good); removal rate 90-100%
○ (good); removal rate 70 to 89%
× (bad); removal rate 0 to 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 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);
Commercial product (“PET75-H120 (10) Blue” manufactured by Nisei 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)
Dipentaerythritol hexaacrylate 24 parts by mass, 2-hydroxy-3-phenoxypropyl acrylate 6 parts by mass, photopolymerization initiator (trade name: Omnirad 184, manufactured by IGM Resins B.V.) 1.5 parts by mass, toluene 70 parts by mass to obtain an acrylic hard coating solution.
(Preparation of acrylic hard coat film)
Polyethylene terephthalate film; commercially available product (Mitsubishi Chemical Co., Ltd. "Diafoil"), the above acrylic hard coat solution is applied so that the dry film thickness is about 9 μm, and cured by irradiating ultraviolet rays to form an acrylic film. A laminated polyester film having a hard coat layer was obtained.

(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 polyethylene terephthalate film of 0.67 Met.

[Example 1]
5 parts by mass of potassium hydroxide and 5 parts by mass of sodium hydroxide as components (a), 19 parts by mass of monoethanolamine as component (b), 40 parts by mass of benzyl alcohol as component (c), 1 part by mass of propylene glycol, and other components and 30 parts by mass of water to prepare a cleaning agent (pH = 13 or more).
Washability was evaluated under the conditions shown in Table 1 using the laminated films (I) to (III). Table 1 shows the results.
Laminated film (III) was immersed for 1 minute and washed at a temperature of 60 ° C., and the intrinsic viscosity of the polyester film after removing the silicone release layer was measured. As a result, the intrinsic viscosity was 0.67. The intrinsic viscosity of the film was unchanged.

[Example 2]
5 parts by mass of potassium hydroxide and 5 parts by mass of sodium hydroxide as components (a), 10 parts by mass of diethanolamine as component (b), 16 parts by mass of benzyl alcohol as component (c), and 64 parts by mass of water as other components. A detergent (pH = 13 or more) was prepared by mixing as follows.
Detergency evaluation was performed under the conditions shown in Table 1 using the laminated films (I) and (III). Table 1 shows the results.

[Example 3]
5 parts by mass of potassium hydroxide as component (a), 17.6 parts by mass of sodium 2,4-dimethylbenzenesulfonate as component (b), 41.3 parts by mass of benzyl alcohol as component (c), and water as other components were mixed so as to be 36.1 parts by mass to prepare a cleaning agent.
Washability was evaluated under the conditions shown in Table 1 using the laminated film (III). Table 1 shows the results.

[Example 4]
5 parts by mass of potassium hydroxide as component (a), 17.6 parts by mass of sodium 2,4-dimethylbenzenesulfonate as component (b), 37.2 parts by mass of benzyl alcohol as component (c), and 4.1 parts by mass of methanol parts, and 36.1 parts by mass of water as another component to prepare a cleaning agent.
Washability was evaluated under the conditions shown in Table 1 using the laminated film (III). Table 1 shows the results.

[Example 5]
5 parts by mass of potassium hydroxide as component (a), 17.6 parts by mass of sodium 2,4-dimethylbenzenesulfonate as component (b), 31.0 parts by mass of benzyl alcohol as component (c), and 10.3 parts by mass of methanol parts, and 36.1 parts by mass of water as another component to prepare a cleaning agent.
Washability was evaluated under the conditions shown in Table 1 using the laminated film (III). Table 1 shows the results.

[Example 6]
5 parts by mass of potassium hydroxide as component (a), 17.6 parts by mass of sodium 2,4-dimethylbenzenesulfonate as component (b), 20.7 parts by mass of benzyl alcohol and 20.7 parts by mass of methanol as component (c) parts, and 36.1 parts by mass of water as another component to prepare a cleaning agent.
Washability was evaluated under the conditions shown in Table 1 using the laminated film (III). Table 1 shows the results.

[Example 7]
5 parts by mass of potassium hydroxide as component (a), 17.6 parts by mass of sodium 2,4-dimethylbenzenesulfonate as component (b), 37.2 parts by mass of benzyl alcohol as component (c), hexafluoro-2- A detergent was prepared by mixing 4.1 parts by mass of propanol and 36.1 parts by mass of water as another component.
Washability was evaluated under the conditions shown in Table 1 using the laminated film (III). Table 1 shows the results.

[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 other components. Detergency evaluation was performed under the conditions shown in Table 1 using the laminated films (I) and (III). Table 1 shows the results.

[Comparative Example 2]
Detergency evaluation was carried out in the same manner as in Comparative Example 1, except that the temperature conditions were changed as shown in Table 1. Table 1 shows the results.

As reference examples, a substrate film (IV) (polyethylene terephthalate film, thickness 52 μm) having no functional layer and a substrate 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 by Mitutoyo's "Thickness Gauge ID-C112X/1012X" to measure the thickness change of the substrate.
A was given when the thickness change was 3 μm or more, and B was given when the thickness change was less than 3 μm.

[Reference example 1]
A cleaning test was performed on the substrate film (IV) and the substrate film (V) under the conditions shown in Table 1 using the cleaning agent having the same composition as in Example 1, and the thickness after cleaning was measured. Table 1 shows the results.

[Reference example 2]
In order to confirm the best mode of monovalent alcohols in the cleaning agent, the cleaning conditions were changed to 55°C for the cleaning temperature and 1 minute for the immersion time in Examples 3 to 6, and the cleaning evaluation was performed according to the following criteria. rice field. Table 2 shows the results.
In the same manner as described above, cleaning evaluation was performed by quantitatively analyzing the Si element on the surface of the laminated film after cleaning using a fluorescent X-ray spectrometer.
The removal rate of the functional layer was judged according to the following criteria.
○ (good); removal rate 50 to 100%
△ (fair); removal rate 0 to 49%

From the results shown in Table 1, according to the method of the present invention, the functional layer could be peeled off from any of the adhesive film, hard coat film, and release film, and the polyester film could be recovered. .
Further, from the results of Example 1, according to the method of the present invention, the intrinsic viscosity (IV) of the polyester film before and after the functional layer removal step (washing step) does not decrease, so the recovered polyester film is used as a raw material. Recycled polyester products are also highly likely to have excellent mechanical properties.

It can be seen that Comparative Examples 1 and 2, in which only component (a) is used as a detergent and does not contain component (b), do not exhibit the effects of the present invention.

From the results of Reference Example 1, the surface of the base film (IV), which is a polyester film, is partially melted and thinned, and the surface of the base film (V) having no ester bonds is not melted and is not thinned. I understand. That is, it is considered that the cleaning agent according to the present invention effectively peels off the functional layer by partially dissolving the surface of the polyester film that is the substrate.

Furthermore, from the results of Reference Example 2 (Table 2), according to the method of the present invention, the combined use of two or more alcohols as (c) a compound having at least one hydroxyl group can affect the film. It has been found that the functional layer can be peeled off at a lower temperature and in a shorter period of time with less resistance.
Further, it was found that a very good cleaning effect can be obtained by setting the weight part ratio of hydrophobic alcohol:water-soluble alcohol to 1.5:1 to 10:1.

As described above, according to the present invention, various functional layers can be peeled off with one kind of cleaning agent. It is possible to peel off the layers. In addition, for example, even with a laminated polyester film having a hard coat layer on the surface and an adhesive layer on the back surface, the functional layer can be peeled off from both sides by one washing operation, and the polyester film as the substrate can be removed. can be recovered.

Claims (27)

A functional layer removing step (A) of washing a laminated polyester film having a functional layer on the surface of the polyester film with a detergent containing (a) an alkalinizing agent and (b) a compatibilizing agent to remove the functional layer. and a recovery method for a polyester film having a recovery step (B) for recovering the polyester film from which the functional layer has been removed. 2. The method for recovering a polyester film according to claim 1, wherein the cleaning agent is a water-based cleaning agent. The method for recovering a polyester film according to claim 1 or 2, wherein the (a) alkalinizing agent contains an alkali metal hydroxide. 4. The method for recovering a polyester film according to claim 3, wherein the alkali metal hydroxide contains potassium hydroxide. The method for recovering a polyester film according to any one of claims 1 to 4, wherein the cleaning agent further contains (c) a compound having at least one hydroxyl group. 6. The method for recovering a polyester film according to claim 5, wherein the (c) compound having at least one hydroxyl group is an alcohol. The method for recovering a polyester film according to claim 6, wherein the alcohol has an acidity constant (pKa) of 8.0 or more and 20.0 or less. The method for recovering a polyester film according to claim 6 or 7, wherein two or more of the alcohols are used in combination. The method for recovering a polyester film according to any one of claims 1 to 8, wherein the (b) compatibilizer is at least one selected from the group consisting of aromatic sulfonates and hydroxyl-containing amine compounds. The method for recovering a polyester film according to any one of claims 1 to 9, wherein the temperature of the cleaning agent in the functional layer removing step (A) is 20°C or higher. A recycled polyester product containing at least a part of the polyester film recovered by the recovering method according to any one of claims 1 to 10 as a raw material. A polyester film recovery apparatus having a washing device, wherein a laminated polyester film having a functional layer on the surface of the polyester film is washed with a washing agent containing (a) an alkalinizing agent and (b) a compatibilizing agent. wash with
An apparatus for recovering a polyester film, characterized by recovering a polyester film from which a functional layer has been removed. 13. The apparatus for recovering a polyester film according to claim 12, further comprising a rinsing device for washing away a cleaning agent adhering to the polyester film from which the functional layer has been removed. 14. The apparatus for recovering a polyester film according to claim 13, 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 apparatus for recovering a polyester film according to any one of claims 12 to 14, comprising a drying device for drying the polyester film from which the functional layer has been removed. 16. The polyester film collecting apparatus according to any one of claims 12 to 15, further comprising an unwinding device in front of the cleaning device. 17. The apparatus for recovering a polyester film according to claim 16, wherein the polyester film is recovered by a roll-to-roll system. The polyester film recovery apparatus according to any one of claims 12 to 15, further comprising a cutting device in a stage preceding the cleaning device. A removing agent for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film, the removing agent containing (a) an alkalinizing agent and (b) a compatibilizing agent. agent. 20. The polyester film functional layer removing agent according to claim 19, wherein the removing agent is a water-based removing agent. The functional layer removing agent for a polyester film according to claim 19 or 20, wherein the (a) alkalinizing agent contains an alkali metal hydroxide. The functional layer removing agent for polyester film according to claim 21, wherein the alkali metal hydroxide contains potassium hydroxide. The functional layer removing agent for polyester film according to any one of claims 19 to 22, wherein the removing agent further contains (c) a compound having at least one hydroxyl group. 24. The functional layer removing agent for a polyester film according to claim 23, wherein (c) the compound having at least one hydroxyl group is an alcohol. 25. The functional layer removing agent for polyester film according to claim 24, wherein the alcohol has an acidity constant (pKa) of 8.0 or more and 20.0 or less. 26. The functional layer removing agent for polyester film according to claim 24 or 25, wherein two or more of said alcohols are used in combination. The polyester film functional layer removing agent according to any one of claims 19 to 26, wherein the compatibilizer (b) is at least one selected from the group consisting of aromatic sulfonates and hydroxyl group-containing amine compounds. .