JP2023128968A - Method for recovering polyester support and method for producing polyester film - Google Patents

Abstract

To provide a method for the stable transportation of a polyester film and the efficient removal of various functional layers from a polyester support in a short time.SOLUTION: A method for recovering a polyester support includes applying ultraviolet rays to a polyester film that includes a polyester support composed of a polyester composition and one or more functional layers and then treating the polyester film with alkali treatment liquid.SELECTED DRAWING: None

Description

The present invention relates to a method for recovering a polyester support from a polyester film having at least one functional layer, and a method for producing a polyester film.

Polyester films are used in a variety of industrial applications from the viewpoint of mechanical properties, thermal properties, etc. Functional layers having various functions are coated on many surfaces of these polyester films.

The above-mentioned polyester film is generally discarded or incinerated after use, and in order to effectively utilize resources, it is being considered to recycle the polyester film support by peeling off the functional layer.

As such a technique, for example, Patent Document 1 can be cited. In Patent Document 1, a film having a release layer is subjected to corona treatment, and then brought into contact with a solution containing an alkaline substance and alcohol, and then brought into contact with an organic solvent to remove the release layer.

JP2009-291690A

However, the above method has the problem that if a conductive substance exists or is attached to the film, sparks may be generated during corona treatment and the film may be burned out, making it inapplicable to peeling off various functional layers. There is.

The present invention has been made in view of the above reasons, and its purpose is to provide a method that can transport a polyester film stably and efficiently peel various functional layers from a polyester support in a short time. It is in.

The present inventors conducted extensive studies to solve the above problems. As a result, they discovered that the desired objective could be achieved by irradiating the polyester film with ultraviolet rays and then contacting it with an alkaline treatment solution, thereby completing the present invention.

The configuration of the present invention is as follows.
(1) A method for recovering a polyester support, which comprises irradiating a polyester film comprising a polyester support made of a polyester composition and at least one functional layer with ultraviolet light, and then treating the film with an alkaline treatment liquid.
(2) The method for recovering a polyester support according to (1) above, wherein the ultraviolet irradiation intensity is 0.5 to 40 mW/cm ² and the ultraviolet irradiation time is 3 to 210 seconds.
(3) The method for recovering a polyester support according to (1) or (2) above, wherein the interval between the ultraviolet ray irradiation and the treatment with the alkaline treatment liquid is 1 second to 24 hours.
(4) The alkaline treatment liquid is an alkaline aqueous solution at a temperature of 40 to 95°C and a concentration of 1 to 25 wt%, and the treatment time with the alkaline treatment liquid is 30 to 600 seconds, (1) to (3) above. ) A method for recovering a polyester support according to any one of the above.
(5) A method for producing a polyester film, which comprises producing a polyester film by extrusion molding a polyester support recovered by the polyester support recovery method described in any one of (1) to (4) above.

According to the present invention, a polyester film having at least one functional layer can be transported stably, various functional layers can be efficiently peeled off from a polyester support in a short time, and the recovered polyester support can be recycled. can do.

Embodiments of the present invention will be described in detail below.
In addition, in this specification, "~" indicating a numerical range is used to include the numerical values described before and after it as a lower limit value and an upper limit value, unless otherwise specified.

The method for recovering a polyester support of the present invention includes irradiating a polyester film comprising a polyester support made of a polyester composition and at least one functional layer with ultraviolet light, and then treating it with an alkaline treatment liquid.

<Polyester film>
(Polyester support)
The polyester support is formed from a polyester composition.
Examples of the polyester constituting the polyester support include polyester obtained by polycondensing a dicarboxylic acid component and a diol component.

As the dicarboxylic acid component, various dicarboxylic acid components such as aromatic dicarboxylic acid, chain aliphatic dicarboxylic acid, and alicyclic dicarboxylic acid can be used.

Various diols can be used as the diol component. For example, aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexane Diethanol, decahydronaphthalene dimethanol, decahydronaphthalene diethanol, norbornane dimethanol, norbornane dimethanol, tricyclodecane dimethanol, tricyclodecaneethanol, tetracyclododecane dimethanol, tetracyclododecane diethanol, decalin dimethanol, decalin diethanol, etc. Alicyclic diols such as saturated cycloaliphatic primary diols, 2,6-dihydroxy-9-oxabicyclo[3,3,1]nonane, 3,9-bis(2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro[5,5]undecane (spiroglycol), 5-methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3- Saturated heterocyclic primary diols containing cyclic ethers such as dioxane and isosorbide, other cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-diol) Various alicyclic diols such as -(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, and adamanediol, and bisphenol A Examples include aromatic cyclic diols such as , bisphenol S, styrene glycol, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9'-bis(4-hydroxyphenyl)fluorene. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used.

The polyester may be a homopolyester or a copolyester. Further, the polyester may contain a third component other than the dicarboxylic acid component and the diol component as a copolymer component.

Specific examples of polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polybutylene-2,6-naphthalate, and among these, polyethylene terephthalate is preferred. Moreover, these may be copolymerized polyesters.

The polyester composition may be made of polyester, or may contain additives other than polyester. Examples of additives include terminal capping agents, antioxidants, flame retardants, optical brighteners, matting agents, plasticizers, and antifoaming agents.

The polyester support can be produced by the following method.

For example, after drying a polyester composition in vacuum, it is supplied to an extruder, melted at 260 to 300°C, extruded into a sheet from a T-shaped nozzle, and then cast to a surface temperature of 10 to 60°C using an electrostatic casting method. The unstretched polyester support is produced by winding it around a mirror casting drum and cooling and solidifying it. The unstretched polyester support is stretched 2.5 to 5 times in the machine direction between rolls heated to 70 to 130°C. Subsequently, it was continuously stretched 2.5 to 5 times in the width direction in a hot air zone heated at 70 to 150 °C, and then led to a heat treatment zone at 190 to 240 °C, and heat treated for 5 to 40 seconds. The crystal orientation is completed through a cooling zone at ~200°C to obtain a polyester support. Further, during the above heat treatment, a relaxation treatment of 0.1 to 12% may be performed in the width direction or longitudinal direction, if necessary.

(Functional layer)
At least one side of the polyester support has a functional layer. Here, the functional layer is a layer that can impart various functions to the polyester support, and includes, but is not limited to, an easy-adhesion layer, a release layer, a hard coat layer, and the like.

These functional layers may be provided on at least one side of the polyester support, or may be provided on both sides. Further, the functional layer may have a single layer, or may have two or more types of layers laminated. Further, the functional layer may have not only a single function but also a plurality of functions in one layer.

The resin constituting the above adhesive layer is not particularly limited as long as it is a resin commonly used for adhesive layers, and examples include polyester resins, polycarbonate resins, epoxy resins, alkyd resins, acrylic resins, and urea resins. Examples include resins and urethane resins. Further, these resins may be used alone or in combination of two or more.

The resin constituting the above mold release layer is not particularly limited as long as it is a resin commonly used for mold release layers, and examples include various silicone resins, fluorosilicone resins, modified silicone resins, amide alkyd resins, and olefin resins. Examples include resins, long-chain alkyl resins, and urethane resins. Further, these resins may be used alone or in combination of two or more.

The resin constituting the hard coat layer is not particularly limited as long as it is a resin commonly used for hard coat layers, and examples thereof include acrylic resins, polycarbonate resins, vinyl chloride resins, polyester resins, urethane resins, etc. Can be mentioned. These resins may be used alone or in combination of two or more.

The functional layer can be formed on the polyester support using a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a wire bar coating method, a die coating method, a spray coating method, etc., although the functional layer is not particularly limited.

<Recovery of polyester support>
(Ultraviolet irradiation)
The method for recovering a polyester support of the present invention includes the step of irradiating a polyester film with ultraviolet rays. It is thought that by irradiating the polyester film with ultraviolet rays, the affinity with the alkaline treatment liquid described below increases, thereby increasing the decomposition of the functional layer by the alkaline treatment liquid.

The ultraviolet rays irradiated in the present invention are electromagnetic waves of invisible light having a wavelength of 10 to 400 nm, that is, shorter than visible light and longer than soft X-rays.

The irradiation intensity of ultraviolet rays is preferably 0.5 to 40 mW/cm ² , more preferably 10 to 40 mW/cm ² , even more preferably 15 to 40 mW/cm ² . If the irradiation intensity is too high, the polyester support tends to be easily damaged, and if the irradiation intensity is too low, the time for the alkali treatment described below increases, and the polyester support tends to be easily damaged. When the irradiation intensity of ultraviolet rays is 0.5 to 40 mW/cm ² , the polyester support can be processed with good productivity without being damaged.

The irradiation time of ultraviolet rays to the polyester film is preferably 3 to 210 seconds, more preferably 30 to 100 seconds, and even more preferably 50 to 70 seconds. When the irradiation time of ultraviolet rays becomes longer, the size of the apparatus needs to be increased, which increases manufacturing costs, and the polyester support tends to be easily damaged. If the irradiation time of ultraviolet rays is too short, there is a possibility that the functional layer cannot be sufficiently peeled off. When the ultraviolet ray irradiation time is 3 to 210 seconds, a peeling effect of the functional layer can be obtained and damage to the polyester support can be suppressed.

As a source of ultraviolet rays, for example, known lamps such as an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a metal halide lamp, etc. can be used, and it is preferable to use a low pressure mercury lamp.

(Treatment with alkaline treatment liquid)
The method for recovering a polyester support of the present invention includes a step of treating with an alkaline treatment liquid after irradiation with ultraviolet rays. By bringing the alkaline treatment liquid into contact with the polyester film after UV irradiation (hereinafter also referred to as "treated polyester film"), the functional layer, whose affinity with the alkaline treatment liquid has been increased by the UV irradiation, will easily decompose. , it is presumed that it becomes easier to peel off from the polyester support.

As the alkaline treatment liquid, a solution in which an alkaline substance is dissolved can be used.
Examples of the alkaline substance include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc., which may be used alone or in combination of two or more.

Examples of the solvent for dissolving the alkaline substance include water, alcohol, and the like. Among them, water is preferable from the viewpoint of economy.

The content of the alkaline substance in the alkaline treatment liquid is preferably 1 to 25 wt%, more preferably 2 to 8 wt%, and even more preferably 3.5 to 4.5 wt%. If the content of the alkaline substance is too high, the polyester support tends to be easily damaged, and if the content is too low, there is a possibility that the functional layer cannot be peeled off sufficiently. When the content of the alkaline substance is 1 to 25 wt%, a peeling effect of the functional layer can be obtained and damage to the polyester support can be suppressed.

It is preferable that the alkaline treatment liquid contains a surfactant.
The surfactant is not particularly limited, and examples include cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants. Surfactants may be used alone or in combination of two or more.

Examples of the cationic surfactant include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyldimethylbenzylammonium chloride.

Examples of anionic surfactants include alkyl sulfate sodium salt, alkylbenzene sulfonate sodium salt, succinic acid dialkyl ester sulfonate sodium salt, alkyldiphenyl ether disulfonic acid sodium salt, polyoxyethylene alkyl ether sulfate sodium salt, polyoxyethylene Examples include alkyl phenyl ether sulfate sodium salt.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and the like.

Examples of the amphoteric surfactant include lauryl betaine, hydroxyethylimidazoline sulfate sodium salt, and imidazoline sulfonic acid sodium salt.

The alkaline treatment liquid may contain other additives as long as they do not impede the effects of the present invention. Examples of additives include antioxidants, pH adjusters, antifoaming agents, and the like.

The method of treatment with the alkaline treatment liquid is not particularly limited as long as the polyester film after ultraviolet irradiation (treated polyester film) can come into contact with the alkaline treatment liquid. Examples include a method of immersing the treated polyester film in a cleaning tank containing an alkaline treatment liquid, a method of applying the alkaline treatment liquid to the treated polyester film, a method of spraying the alkaline treatment liquid onto the treated polyester film, and the like. Among these, the immersion method is preferred from the viewpoint of permeability of the alkaline treatment liquid into the functional layer.

In the present invention, it is more preferable to use an alkaline aqueous solution having a temperature of 40 to 95°C and a concentration of 1 to 25 wt% as the alkaline treatment liquid.

The temperature of the alkaline treatment liquid when treating the treated polyester film is preferably 40 to 95°C, more preferably 60 to 85°C, and even more preferably 75 to 80°C. By using an alkaline treatment liquid within the above temperature range, peeling of the functional layer is promoted and the time required to recover the polyester support can be shortened.

The treatment time of the treated polyester film with the alkaline treatment liquid is preferably 30 to 600 seconds, more preferably 90 to 180 seconds, and even more preferably 100 to 140 seconds. If the treatment time is too long, the polyester support tends to be easily damaged; if the treatment time is too short, the functional layer may not be sufficiently peeled off. When the treatment time with the alkaline treatment liquid is 30 to 600 seconds, a peeling effect of the functional layer can be obtained and damage to the polyester support can be suppressed.

(Interval between ultraviolet irradiation and alkali treatment)
In the present invention, treatment with an alkaline treatment liquid may be performed immediately after irradiation with ultraviolet rays, or may be performed after a desired period of time.
The interval between ultraviolet irradiation and alkali treatment is preferably 1 second to 24 hours. If the interval between ultraviolet irradiation and alkali treatment is too long, the effect of ultraviolet irradiation will be weakened and it will take a long time to peel off the functional layer, which may result in insufficient peeling of the functional layer. It is preferable to carry out the alkali treatment within 24 hours. When the interval between ultraviolet irradiation and alkali treatment is 1 second to 24 hours, the functional layer can be peeled off in a short time due to the effect of ultraviolet irradiation. The interval between ultraviolet irradiation and alkali treatment is more preferably 1 second to 5 hours, even more preferably 1 second to 1 hour, from the viewpoint of the peeling effect of the functional layer.

(Multiple processing)
It is preferable to perform the above ultraviolet irradiation and alkali treatment multiple times. By performing the treatment multiple times, the polyester support can be treated in a short time without suffering damage such as a decrease in intrinsic viscosity. When performing multiple treatments, for example, repeat the process of irradiating with ultraviolet rays for 3 to 50 seconds and then treating with alkaline treatment liquid for 10 to 90 seconds about 2 to 5 times, for a total of 6 seconds or more of ultraviolet rays and treatment with alkaline treatment liquid. It is preferable to process for 30 seconds or more.

(Water washing process)
After the treatment with the alkaline treatment liquid, a water washing step is preferably performed in order to remove the residue of the functional layer and the alkaline treatment liquid remaining on the polyester support after the functional layer has been peeled off.

Examples of the washing method include a method of spraying water onto the polyester support from which the functional layer has been peeled off, a method of immersing the polyester support in a water tank, and the like.

(drying process)
After washing with water, it is preferable to go through a drying process. The drying step can remove water remaining on the polyester support.

The drying method is not particularly limited, and examples include a method of blowing hot air and a method of heating with a non-contact heater.

The drying time is preferably 50 to 150 seconds. If the drying time is too short, drying may be insufficient and blocking may occur. On the other hand, if the drying time is too long, the polyester support tends to be easily damaged.

(pelletizing process)
It is preferable to pelletize the recovered polyester support to obtain pelletized polyester.

The pelletizing method is not particularly limited, and examples include a method in which the recovered polyester support is pulverized, put into an extruder, melted, and pelletized.

<Production of polyester film>
The method for manufacturing a polyester film of the present invention includes manufacturing a polyester film by extrusion molding the polyester support recovered by the above-mentioned method for recovering a polyester support.
Specifically, a polyester film can be formed by a known film forming method using a raw material containing the above pelletized polyester produced from the recovered polyester support.

Although the thickness of the polyester film is not limited, it can usually be set appropriately within the range of 10 to 50 μm. In addition, if necessary, it can be used as a laminate by laminating it with other layers (for example, a release layer, an adhesive layer, a heat seal layer, a surface protection layer, a printing layer, a design layer, etc.). By molding the laminate, it can also be used as various molded products as described above.

Hereinafter, the present invention will be explained in more detail based on Examples and Comparative Examples. However, the present invention is not limited to the embodiments described below.

(Ultraviolet irradiation intensity measurement)
An ultraviolet intensity meter (“UM-10” manufactured by Konica Minolta, Inc.) was used to measure the ultraviolet irradiation intensity.

(Evaluation of peeling of functional layer)
1. Evaluation of processability After cutting the recovered polyester support into small pieces, it was molded into a cylindrical shape using a melt press machine, and the silicon (Si) content was measured using a fluorescent X-ray analyzer (“Model 3270” manufactured by Rigaku Co., Ltd.). was measured.
The processability of the present invention was evaluated based on the obtained Si content using the following criteria.
〔Evaluation criteria〕
○: Si content is below the detection limit (100 ppm) △: Si content is more than 100 ppm and less than 300 ppm ×: Si content is 300 ppm or more

2. Evaluation of damage to polyester support Add 0.1 g of pellets obtained from the recovered polyester support to 10 ml of o-chlorophenol and dissolve at 100°C for 30 minutes. The intrinsic viscosity (intrinsic viscosity of the pellet after treatment) was measured.
Furthermore, using pellets obtained from untreated polyethylene terephthalate, the intrinsic viscosity at 25°C (intrinsic viscosity of the pellet before treatment) was measured in the same manner.
The intrinsic viscosity of the treated pellets was compared with the intrinsic viscosity of the pellets before treatment, and evaluated based on the following criteria.
〔Evaluation criteria〕
○: Compared with the intrinsic viscosity of the pellet before treatment, the intrinsic viscosity of the pellet after treatment decreased by less than 0.005. Δ: Compared with the intrinsic viscosity of the pellet before treatment, the intrinsic viscosity of the pellet after treatment decreased by 0.005. A decrease of 0.05 or more and less than 0.01 ×: A decrease of 0.01 or more in the intrinsic viscosity of the pellet after treatment compared to the intrinsic viscosity of the pellet before treatment.

<Preparation of sample film>
(1) Preparation of polyester support (polyester film) having functional layer A polyethylene terephthalate film having a thickness of 38 μm manufactured by a conventional method was prepared as a polyester support. A 5 wt % toluene solution of a curable silicone resin composition was coated on this film using a reverse kiss coater so that the coating amount after drying was 0.2 g/m ² , and heated at 130°C in a tunnel oven. A release layer was formed and wound up.
The curable silicone resin composition contains 100 parts by mass of silicone resin ("LTC-300B" manufactured by Toray Dow Corning Silicone Co., Ltd.) and a curing agent ("SRX-212" manufactured by Toray Dow Corning Silicone Co., Ltd.). ) 0.8 parts by mass of the mixture.

(2) Preparation of ceramic green sheet layer and internal electrodes Using the polyester support having the above-mentioned functional layer as a carrier sheet, a ceramic slurry having the composition below is uniformly applied on the surface of the release layer using a blade coater, and tunneling is performed. A ceramic green sheet layer with a thickness of 20 μm was produced on the mold release layer by drying in an oven at 85° C. Next, a conductive paste having the composition shown below was screen printed on the ceramic green sheet, dried at 80°C for 10 minutes to form internal electrodes, and then left at 20°C for 1 hour.

《Ceramic slurry composition》
Ceramic powder (barium titanate) 100 parts by mass Binder (polyvinyl butyral) 10 parts by mass Plasticizer (dioctyl phthalate) 5 parts by mass Solvent (toluene/isopropyl alcohol = 1/1 (mass ratio)) 100 parts by mass <<Conductivity Paste composition》
Ni-based powder 90 parts by mass Organic vehicle 10 parts by mass Terpineol 30 parts by mass

(3) Peeling of the ceramic green sheet layer After making a 10 cm x 10 cm slit in the ceramic green sheet layer on which the internal electrodes are formed on the release film, the ceramic green sheet layer is sucked with a vacuum suction machine. The film was peeled off from the release layer to obtain a sample film. Note that a portion of the ceramic slurry and conductive paste that could not be peeled off were still attached to the surface of the release layer of the sample film.

[Example 1]
<Ultraviolet irradiation>
The above sample film was irradiated with ultraviolet light for 60 seconds at an irradiation intensity of 30 mW/cm ² using an ultraviolet irradiation device.
Three minutes after the ultraviolet irradiation, the alkali treatment described below was performed.

<Alkali treatment>
A mixed aqueous solution of 4 wt % of sodium hydroxide and 0.01 wt % of a nonionic surfactant ("polyoxyethylene (10) octylphenyl ether" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was heated to 80°C and exposed to ultraviolet light. By immersing the irradiated sample film in the aqueous solution for 120 seconds and treating it, the release layer was peeled off and a sample film (recovered polyester support) was obtained. The above-mentioned "evaluation of processability" was performed using the sample film.

<Washing/drying/pelletization>
The sample film (recovered polyester support) was immersed in a water tank for 120 seconds, and then dried by blowing hot air. The sample film after drying was crushed and put into an extruder to be melted and pelletized. The above-described "evaluation of damage to polyester support" was performed using the obtained pellets.

<Manufacture of polyester film>
The pellets obtained from the sample film were dried at 150°C for 3 hours, fed to an extruder, melt extruded at 285°C, and cast onto a cast drum at 20°C to which an electrostatic charge was applied to obtain an unstretched sheet. This unstretched sheet was stretched 3.1 times in the longitudinal direction with a stretching roll heated to 90°C, then stretched 3.7 times in the width direction at 120°C with a tenter-type stretching machine, and then heat-set at 230°C. and wound it into a roll.

[Examples 2 to 4]
A polyester film was produced in the same manner as in Example 1 except that the ultraviolet irradiation intensity was changed to the conditions listed in Table 1.

[Examples 5 to 10]
A polyester film was produced in the same manner as in Example 1 except that the ultraviolet irradiation time was changed to the conditions listed in Table 1.

[Examples 11 to 13]
A polyester film was produced in the same manner as in Example 1, except that the interval from UV irradiation to alkali treatment was changed to the conditions listed in Table 1.

[Examples 14 to 19]
A polyester film was produced in the same manner as in Example 1 except that the temperature of the alkaline treatment liquid in the alkali treatment was changed to the conditions listed in Table 2.

[Examples 20 to 25]
A polyester film was produced in the same manner as in Example 1 except that the concentration of the alkaline treatment liquid in the alkali treatment was changed to the conditions listed in Table 2.

[Examples 26 to 31]
A polyester film was produced in the same manner as in Example 1, except that the immersion time in the alkaline treatment liquid in the alkali treatment was changed to the conditions listed in Table 3.

[Example 32]
The sample film was irradiated with ultraviolet light for 3 seconds at an irradiation intensity of 30 mW/cm ² . Three minutes after UV irradiation, the sample film was immersed in the same alkaline treatment solution as in Example 1 for 30 seconds. After carrying out this operation again, it was washed with water and dried in the same manner as in Example 1 to produce a polyester film.

[Example 33]
A polyester film was produced in the same manner as in Example 32, except that the ultraviolet irradiation time, alkali immersion time, and the number of treatment repetitions were changed to the conditions listed in Table 3.

[Comparative Examples 1 and 2]
The sample film was immersed in the same alkaline treatment solution as in Example 1 for the predetermined time listed in Table 3 without irradiating with ultraviolet rays, and then washed with water and dried in the same manner as in Example 1 to produce a polyester film.

These results are shown in Tables 1 to 3.

From Tables 1 to 3, according to the method of the present invention, it is possible to peel off the functional layer from a polyester film having a functional layer, and it is possible to recover the polyester support and use this polyester support as part of the raw material. We were able to produce a polyester film that

Furthermore, from the results of Examples 32 and 33, it was found that by performing ultraviolet irradiation and alkali treatment multiple times, it was possible to peel off the functional layer in a short time without suffering damage such as a decrease in intrinsic viscosity. Ta.

In Comparative Examples 1 and 2 in which no ultraviolet rays were irradiated, the functional layer could not be peeled off in a short time.

As described above, according to the method of the present invention, the functional layer can be peeled off according to the conditions of ultraviolet irradiation and alkali treatment, and the polyester support can be recovered and a polyester film using this polyester support as part of the raw material can be produced. It is possible to manufacture Further, by performing ultraviolet irradiation and alkali treatment multiple times, it is possible to peel off the functional layer in a short time without suffering damage such as a decrease in intrinsic viscosity, which is extremely useful.

Claims (5)

A method for recovering a polyester support, which comprises irradiating a polyester film comprising a polyester support made of a polyester composition and at least one functional layer with ultraviolet rays, and then treating the film with an alkaline treatment liquid. The method for recovering a polyester support according to claim 1, wherein the ultraviolet irradiation intensity is 0.5 to 40 mW/cm ² and the ultraviolet irradiation time is 3 to 210 seconds. The method for recovering a polyester support according to claim 1 or 2, wherein the interval between the ultraviolet ray irradiation and the treatment with the alkaline treatment liquid is 1 second to 24 hours. Any one of claims 1 to 3, wherein the alkaline treatment liquid is an aqueous alkaline solution at a temperature of 40 to 95°C and a concentration of 1 to 25 wt%, and the time for treatment with the alkaline treatment liquid is 30 to 600 seconds. A method for recovering a polyester support described in . A method for producing a polyester film, which comprises producing a polyester film by extrusion molding a polyester support recovered by the method for recovering a polyester support according to any one of claims 1 to 4.