JP2024011052A - Recovery method of polyester-based support and manufacturing method of polyester product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for safely and efficiently recovering, with good profitability and in a short time, a polyester-based support with high purity from a polyester-based substrate having at least one layer of a coating film on a polyester-based support.

SOLUTION: Disclosed is a method for recovering a polyester-based support by removing a coating film from a polyester-based substrate having at least one layer of a coating film on at least a part of a polyester-based support. The method for recovering a polyester-based support includes: a first step of bringing at least a surface of the polyester-based substrate having the coating film into contact with a surfactant or an aqueous solution dissolving a surfactant; and a second step of bringing, after the first step, the polyester-based support into contact with an alkaline processing liquid.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for recovering a polyester support from a polyester base material having at least one coating film on at least a portion of the polyester support, and a method for producing a polyester product.

Polyester supports have excellent mechanical, physical, and chemical properties, and are therefore used in a variety of applications for fibers, films, and other molded products. Coating films having various functions are laminated on one or both surfaces of many of these polyester supports.

As the above-mentioned polyester supports are used for various purposes, the amount of waste materials and used products being generated is increasing, which leads to deterioration of the global environment. In order to solve this problem and recycle the polyester support, it is preferable to remove the coating film from the polyester base material and use it again as a polyester support.

As such a technique, for example, Patent Document 1 can be cited. In Patent Document 1, the coating film on at least one side of the base film is removed by contacting it with a 20 to 60% by mass alkaline treatment liquid heated to a temperature of 90 to 140°C. ing.

Japanese Patent Application Publication No. 2020-90094

However, the method described in Patent Document 1 has a problem in that the polyester support deteriorates in quality due to contact with a high-temperature, high-concentration alkaline treatment liquid. Furthermore, since high temperature and high concentration alkali is used, there is also the problem that safety and profitability are reduced.

The present invention has been made in view of the above reasons, and its purpose is to obtain a polyester support with high purity from a polyester base material having at least one coating film on the polyester support. The objective is to provide a safe, profitable, and efficient collection method in a short period of time.

Therefore, as a result of studies to solve the above-mentioned problems, the surface of the polyester base material was made hydrophilic by contacting the polyester base material with a surfactant or an aqueous solution containing a surfactant, and then the surface of the polyester base material was made hydrophilic. The present invention was completed based on the discovery that the desired objective can be achieved by treating a polyester base material with an alkaline treatment liquid. By dividing the process into a first step in which the surface of the polyester base material is made hydrophilic with a surfactant or an aqueous solution containing a surfactant, and a second step in which the surface of the polyester base material is treated with an alkaline treatment liquid, the first The step and the second step can be performed at different temperatures. By making the surface of the polyester base material hydrophilic in the first step and removing the coating film in the second step under optimal temperature conditions, the polyester support material can be efficiently recovered in a short time. becomes possible.

The configuration of the present invention is as follows.
(1) A method for recovering the polyester support by removing the coating film from a polyester base material having at least one coating film on at least a portion of the polyester support, the method comprising: A first step of bringing a surfactant or an aqueous solution containing a surfactant into contact with at least the surface of the polyester base material having the coating film, and alkaline treatment of the polyester base material after the first step. A method for recovering a polyester support, the method comprising: a second step of contacting a liquid.
(2) Before the first step, at least the surface of the polyester base material having the coating film is subjected to a treatment selected from the group consisting of corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment. The method for recovering a polyester support according to (1) above, which comprises performing at least one surface modification treatment.
(3) The method for recovering a polyester support according to (2) above, which comprises washing with water after the second step.
(4) The method for recovering a polyester support according to (3) above, wherein in the first step, the surfactant or an aqueous solution in which the surfactant is dissolved is brought into contact for within 300 seconds. .
(5) The method for recovering a polyester support according to (4) above, wherein the surfactant is a nonionic surfactant.
(6) In the second step, the alkaline treatment liquid is an alkaline treatment liquid having a temperature of less than 100°C and an alkaline concentration of 0.04% by mass to 15% by mass; The method for recovering a polyester support according to (5) above, characterized in that the contact is carried out for a period of seconds or more and 180 seconds or less.
(7) The method for collecting a polyester support according to (6) above, characterized in that the polyester support is collected in a long form.
(8) A method for producing a polyester product, comprising extruding a polyester support recovered by the method for recovering a polyester support according to any one of (1) to (7) above to produce a polyester product.

According to the present invention, since the coating film can be efficiently removed from the polyester base material having at least one coating film on at least a portion of the polyester support, the used polyester base material, which was conventionally discarded, can be removed efficiently. A highly pure polyester support can be recovered from the base material in a short time and efficiently.

The present invention will be explained 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 involves removing a coating film from a polyester base material including a polyester support and at least one coating film provided on at least a portion of the polyester support. A method for recovering a polyester support, comprising: a first step of contacting at least a surface of a polyester base material having a coating film with a surfactant or an aqueous solution in which the surfactant is dissolved; After that, there is a second step of bringing an alkaline treatment liquid into contact with the polyester base material.

<Polyester support>
The polyester support in the present invention is formed containing a polyester composition. The polyester composition is not particularly limited, but includes, for example, 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. For example, terephthalic acid, 2,6-naphthalene dicarboxylic acid, isophthalic acid Examples include acids, phthalic acid, etc.

The diol component is preferably an aliphatic glycol, such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used.

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

As the polyester support, a polyester support containing polyethylene terephthalate or polyethylene naphthalate as a main component is preferably used. More preferred is polyethylene terephthalate. Moreover, these may be copolymerized polyesters.

The polyester support may be made of a polyester composition, or may contain additives other than polyester in the composition. 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. It is wound around a mirror-surfaced casting drum and cooled and solidified to produce an unstretched polyester support. The unstretched polyester support is stretched 2.5 to 5 times in the longitudinal 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. 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.

The thickness of the polyester support is not particularly limited, but in consideration of handleability such as strength and rigidity, it is preferably 5 μm or more and 500 μm or less. The thickness of the polyester support is more preferably 10 μm or more and 200 μm or less, particularly preferably 20 μm or more and 100 μm or less.

In addition, in the present invention, in the recovery of the polyester support described later, the polyester base material may be in a long shape or in a cut state. If it is long, the length will vary depending on the type of equipment used, etc., but it generally means 100 m or more and 10,000 m or less, and means that it can be directly collected without being crushed. Further, as long as the polyester base material is in a cut state, there is no particular limitation, but it means, for example, that a polyester base material cut into square pieces of 1 mm or more and 10 mm or less is recovered.

According to the method of the present invention, if the polyester base material is handled in a long form, the first step is to contact the polyester base material wound into a roll with a surfactant or an aqueous solution in which the surfactant is dissolved. The second step of contacting with an alkaline treatment liquid can be carried out in series, and the coating film can be efficiently removed in a short time. Preferably, after carrying out the surface modification treatment described below on the elongated polyester base material, it is brought into contact with a surfactant or an aqueous solution in which the surfactant is dissolved, and then brought into contact with an alkaline treatment liquid, and then subjected to the surface modification treatment described below. It is recommended that the product be directly introduced into the next process (washing, drying) and then wound up in a roll, that is, using a roll-to-roll method. The roll-to-roll method is an unwinding and unwinding method in which a flexible base material wound into a roll is continuously conveyed via multiple guide rolls, subjected to predetermined processing during conveyance, and then wound again into a roll. This is the transportation method of the formula. By processing in a roll-to-roll manner, a series of coating film removal steps can be performed continuously in a short time, which is very efficient.

<Coating film>
The polyester support in the present invention has at least one coating film on at least a portion thereof. The coating film herein refers to a film that can impart various functions to the polyester support, and includes, for example, a release film, an adhesive film, a hard coat film, an easily adhesive film, an antistatic film, and the like. These coating films may be provided on at least one side of the polyester support, and may be provided on both sides. Furthermore, the coating film may be provided alone, or two or more types may be laminated. Further, the coating film may have not only a single function but also a plurality of functions.

The resin constituting the mold release film is not particularly limited as long as it is a resin commonly used for mold release films, and examples include silicone resins such as polydimethylsiloxane, amino resins such as melamine resin and urea resin, and acrylic resins. Examples include resin, epoxy resin, and alkyd resin. Further, these resins may be used alone or in combination of two or more. Further, the release film may contain a release agent such as silicone or wax.

The resin constituting the adhesive film includes an adhesive commonly used for adhesive films. The type of the adhesive is not particularly limited, and examples thereof include acrylic adhesives, rubber adhesives, polyurethane adhesives, silicone adhesives, and the like. Further, the adhesive film may further contain a tackifier (tackifying resin) or the like.

The resin constituting the hard coat film is not particularly limited as long as it is a resin commonly used for hard coat films, and examples thereof include acrylic resins, urethane resins, and epoxy resins. These resins may be used alone or in combination of two or more. The resin constituting the hard coat film is not particularly limited as long as it is a resin commonly used for hard coat films, and examples thereof include acrylic resins, urethane resins, and epoxy resins. These resins may be used alone or in combination of two or more.

The resin constituting the above adhesive film is not particularly limited as long as it is a resin commonly used for adhesive films, and examples include polyester resin, acrylic resin, polycarbonate resin, polyurethane resin, polyvinyl alcohol resin, polyamide resin, and polyacetic acid resin. Examples include vinyl resin. These resins may be used alone or in combination of two or more.

The resin constituting the antistatic film is not particularly limited as long as it is a resin commonly used for antistatic films. It is preferable that the antistatic film further contains an antistatic agent. Examples of the antistatic agent include nonionic, cationic, anionic, or amphoteric surfactants (conductive polymers such as polypyrrole and polyaniline, metal oxide fillers, carbon-based substances), and the like. These antistatic agents may be used alone or in combination of two or more.

The coating film is not particularly limited, but can be formed on the polyester support using, for example, 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. .

The thickness of the coating film (in the case of a plurality of functional films, the total thickness thereof) is preferably 0.005 μm or more and 50 μm or less. In order to effectively exhibit a predetermined function, the thickness is more preferably 0.01 μm or more. On the other hand, if the thickness of the coating film exceeds 50 μm, it may take time to remove the coating film.

<Recovery of polyester support>
The method for recovering a polyester support of the present invention includes a first step of bringing a surfactant or an aqueous solution containing the surfactant into contact with at least the surface of the polyester base material having the coating film; The method is characterized in that it subsequently includes a second step of bringing an alkaline treatment liquid into contact with the polyester base material.

(First step: Step of bringing into contact a surfactant or an aqueous solution containing a surfactant)
In the first step, at least the surface of the polyester base material having the coating film is brought into contact with a surfactant or an aqueous solution in which the surfactant is dissolved. The surface of the polyester base material is made hydrophilic by directing the hydrophobic region of the surfactant toward the polyester support or coating film and the hydrophilic region of the surfactant toward the solution side. In the first step, the surface of the polyester base material is made hydrophilic in advance, and in the second step described later, an alkaline treatment liquid is brought into contact with the surface of the polyester base material, so that the hydrophobic region of the surfactant is Since the hydrophilic region of the surfactant moves toward the solution side of the coating film, penetration of the alkaline treatment liquid is promoted, and the coating film can be easily removed from the polyester support in a short time and efficiently. A surfactant is a typical example of a compound having a hydrophilic region and a hydrophobic region, but any compound having both a hydrophilic region and a hydrophobic region can be used.

The method of contacting the surfactant or the aqueous solution in which the surfactant is dissolved is not particularly limited as long as at least the surface of the polyester base material having the coating film can be brought into contact with the surfactant or the aqueous solution in which the surfactant is dissolved. For example, a method of immersing a polyester base material in a cleaning tank containing a surfactant or an aqueous solution containing a surfactant, a method of applying a surfactant or an aqueous solution containing a surfactant to a polyester base material, a method of applying a surfactant or an aqueous solution containing a surfactant to a polyester base material, Examples include a method of spraying a surfactant or an aqueous solution containing a surfactant onto the base material. Among these, the immersion method is preferred from the viewpoint of permeability of the surfactant or an aqueous solution containing the surfactant into the coating film.

The surfactant is not particularly limited, but may include at least one surfactant selected from the group consisting of nonionic surfactants, cationic surfactants, and anionic surfactants. Can be done. Particularly preferred are nonionic surfactants. Surfactants may be used alone or in combination of two or more.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, and polyoxyethylene oleyl ether. Polyoxyethylene alkylphenol ethers such as oxyethylene nonylphenol ether, polyoxyethylene alkylaryl ether, polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, Sorbitan fatty acid esters such as sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, and polyoxyethylene sorbitan tristearate. Examples include polyoxyethylene sorbitan fatty acid esters such as ester, polyoxyethylene sorbitan moreoleate, and polyoxyethylene sorbitan trioleate, and glycerin fatty acid esters such as stearic acid monoglyceride.

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

Examples of anionic surfactants include alkyl sulfate sodium salt, alkylbenzenesulfonate sodium salt, succinic acid dialkyl ester sulfonate sodium salt, alkyldiphenyl ether disulfonic acid sodium salt, polyoxyethylene alkyl ether sulfate sodium salt, polyoxy Examples include ethylene alkylphenyl ether sulfate sodium salt.

The contact time between the polyester base material and the surfactant or the aqueous solution containing the surfactant is preferably within 300 seconds, more preferably 0.001 to 10 seconds, and still more preferably 0.1 to 10 seconds. preferable. If the contact time between the polyester base material and the surfactant or an aqueous solution in which the surfactant is dissolved is too short, there is a risk that the coated film cannot be removed sufficiently, and if the contact time is too long, the equipment size will increase, making it difficult to maintain economic efficiency. , there is a risk that operability will deteriorate. When the contact time between the polyester base material and the surfactant or the aqueous solution in which the surfactant is dissolved is within 300 seconds, economic efficiency and operability are good, and the coating film removal effect can be enhanced.

The concentration of the surfactant or the aqueous solution containing the surfactant is preferably 0.00001 wt% to 100 wt%, more preferably 0.0001 wt% to 100 wt%, and even more preferably 0.001 wt% to 50 wt%. , 0.01 wt% to 1 wt% is particularly preferred. If the surfactant concentration is too low, there is a possibility that the coating film cannot be removed sufficiently. When the concentration of the surfactant or the aqueous solution containing the surfactant is 0.00001 wt% to 100 wt%, a sufficient coating film removal effect can be obtained.

The temperature of the surfactant or the aqueous solution in which the surfactant is dissolved may be adjusted depending on the surfactant used, but it is preferably 50° C. or lower. When the temperature of the surfactant or the aqueous solution in which the surfactant is dissolved is 50° C. or lower, the surfactant can be concentrated at a high concentration, so that the coating film removal effect is promoted. In addition, since nonionic surfactants will not dissolve in water if the temperature is too high, it is preferable to perform the treatment at a temperature below the clouding point of the surfactant.

(Surface modification treatment)
The surface of the coating film may be subjected to a surface modification treatment for the purpose of increasing the compatibility with a surfactant or an aqueous solution containing a surfactant, and further with an alkaline treatment liquid to be described later. The surface modification treatment is not particularly limited, and any known method can be adopted, such as corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, ultraviolet treatment, etc. It is preferable to perform at least one process selected from:

The surface modification treatment may be carried out before the second step of contacting with the alkaline treatment liquid, but in order to increase the affinity with the surfactant or an aqueous solution containing the surfactant, It is more preferable to carry out before the first step.

If the ratio of C-C bonds and C-H bonds has decreased by 0.1% or more in analysis using X-ray photoelectron spectroscopy after surface modification treatment, the surfactant or an aqueous solution containing the surfactant Alternatively, the effect of increasing the affinity with the alkaline processing liquid described later can be obtained.

In the case of corona discharge treatment, the treatment intensity is preferably 10 to 1000 Wmin/m ² or higher, more preferably 20 to 200 Wmin/m ² , and even more preferably 40 to 120 Wmin/m ² . If the treatment strength becomes too high, the polyester support tends to be easily damaged, and if the treatment strength is too low, the time for the alkali treatment described later becomes longer, and the polyester support tends to be more susceptible to damage. be. Further, if the power density of the corona discharge machine used is 4 to 20 W/cm ² , uniform surface treatment can be performed.

In the case of ultraviolet treatment, the irradiation intensity is preferably 0.5 to 40 mW/cm ² , more preferably 10 to 40 mW/cm ² , and 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 tends to be longer, making the polyester support more susceptible to damage. . The ultraviolet irradiation time is preferably 3 to 210 seconds, more preferably 30 to 100 seconds, and even more preferably 50 to 70 seconds. If the ultraviolet irradiation time is too long, the size of the device 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 coating film cannot be removed sufficiently. Further, the wavelength of the ultraviolet rays to be irradiated is preferably 10 to 400 nm, that is, electromagnetic waves of invisible light shorter than visible light and longer than soft X-rays are preferably used. 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.

(Second step: step of contacting with alkaline treatment liquid)
In the method for recovering a polyester support of the present invention, a second step of contacting with an alkaline treatment liquid is performed after the first step. After making the surface of the polyester base material hydrophilic in the first step, by contacting it with a hydrophilic alkaline treatment liquid, the penetration of the alkaline treatment liquid into the polyester support or coating film is promoted. , the coating film is dissolved and swollen to weaken the bond at the interface between the polyester support and the coating film, and the coating film that dissolves in the alkaline processing liquid can be removed from the polyester support in a short time.

In the present invention, the treatment with the alkaline treatment liquid may be performed immediately after the first step, or may be performed after a desired period of time.

As the alkaline processing liquid used in the present invention, a solution in which an alkaline substance is dissolved can be used. Examples of alkaline substances include, but are not limited to, sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide; sodium silicate, potassium silicate, ammonium silicate; dibasic sodium phosphate, dibasic Potassium phosphate, diammonium phosphate; Sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate; Sodium carbonate, potassium carbonate, ammonium carbonate; Sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate; Sodium borate, potassium borate, boron Examples include inorganic alkaline agents such as ammonium acid. Preferred among these are alkali metal hydroxide salts, and more preferred are sodium hydroxide and potassium hydroxide. The above alkaline substances may be used alone or in combination of two or more.

The solvent for dissolving the alkaline substance is not particularly limited, but includes, for example, water.

The content of the alkaline substance in the alkaline treatment liquid is preferably 0.01 to 15% by mass, more preferably 0.04 to 15% by mass, and even more preferably 1 to 10% by mass. 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 coating film cannot be removed sufficiently. When the content of the alkaline substance is within the above range, a coating film removal effect can be obtained and damage to the polyester support can be suppressed.

As a method for bringing the alkaline treatment liquid into contact with the polyester base material, various methods such as a dipping method, an ultrasonic method, a spray method, and a shaking method can be employed. The above conditions can be appropriately selected depending on the type and thickness of the polyester support and coating film, but in order to obtain a high quality polyester support with few impurities, it is necessary to It is preferable to contact the alkaline treatment liquid heated to a temperature of 0.01 to 15% by mass for a period of more than 0 seconds and less than 700 seconds.

The temperature of the alkaline treatment liquid is preferably less than 100°C, more preferably 50 to 95°C. In order to shorten the treatment time with the alkaline treatment liquid in the second step, it is better to have the alkaline treatment liquid at a higher temperature, so it is preferable to carry out the treatment at a temperature equal to or higher than the treatment temperature in the first step. Specifically, when the temperature of the alkaline treatment liquid is 50°C or higher, the physicochemical properties of the polyester support will not change, and high-quality polyester with few impurities can be produced without taking an excessive amount of time. A system support can be obtained. Furthermore, since the temperature of the alkaline treatment liquid cannot exceed 100° C. under normal pressure, this leads to an increase in the size of the equipment and also causes hydrolysis and dissolution of the polyester support due to heating.

The contact time with the alkaline treatment liquid is preferably more than 0 seconds and less than 700 seconds, more preferably more than 0 seconds and less than 600 seconds, even more preferably more than 0 seconds and less than 180 seconds, and more preferably more than 0 seconds and less than 120 seconds. Particularly preferred. If the treatment time is too long, the polyester support tends to be easily damaged, and since the polyester support is eluted into the alkaline treatment liquid, there is a risk that the load when treating the alkaline treatment liquid as waste water will increase. There is. The treatment time with the alkaline treatment liquid is sufficient as long as the coating film can be sufficiently dissolved and swollen; if the treatment time is too short, the coating film may not be removed sufficiently, so it is more preferably 1 second or more, and 5 seconds or more. More preferred. When the treatment time with the alkaline treatment liquid is within the above range, the effect of removing the coating film can be obtained and damage to the polyester support can be suppressed.

In the present invention, the treatment with an alkaline treatment liquid in the second step is performed by treating the polyester base material with a It is more preferable that the contact be carried out for at least 180 seconds.

The alkaline treatment liquid may contain a surfactant or ultra-fine bubbles as an auxiliary agent in order to prevent the removed coating film from re-adhering and improve the efficiency of removing the coating film. The surfactant is not particularly limited, but for example, nonionic surfactants, cationic surfactants, anionic surfactants, etc. can be used. Surfactants may be used alone or in combination of two or more.

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

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

Examples of anionic surfactants include alkyl sulfate sodium salt, alkylbenzenesulfonate sodium salt, succinic acid dialkyl ester sulfonate sodium salt, alkyldiphenyl ether disulfonic acid sodium salt, polyoxyethylene alkyl ether sulfate sodium salt, polyoxy Examples include ethylene alkylphenyl ether sulfate 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.

(Water washing process)
After the second step, it is preferable to perform a water washing treatment. Washing with water is performed to remove a trace amount of the coating film remaining on the polyester support after the above treatment and to remove the alkaline treatment liquid remaining on the polyester support after the above treatment.

Although the temperature of the water washing treatment is not particularly limited, for example, washing with warm water at a temperature of about 40° C. or more and 100° C. or less brings out the above effects more effectively.

Examples of the washing method include a method of spraying water onto the polyester support from which the coating film has been removed, a method of immersing the polyester support in a water tank, and the like. During the water washing process, physical washing using a roll brush, micro bubbles, water jet, etc. may be performed.

(drying process)
After washing with water, it is preferable to perform a drying process to remove water remaining on the polyester support.

The drying time is preferably 10 seconds or more and 5 minutes or less. If the drying time is less than 10 seconds, drying may be insufficient and blocking may occur. More preferably, it is 30 seconds or more. On the other hand, if the drying time exceeds 5 minutes, there is a risk that the polyester support will be deformed.

The drying method is not particularly limited, and examples thereof include hot air drying by blowing hot air, heating drying by heating with a non-contact type heater, and the like.

(Multiple processing)
The above surface modification treatment step, the first step of contacting with a surfactant or an aqueous solution containing a surfactant, and the second step of contacting with an alkaline treatment liquid may be performed 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.

<Molding of recovered polyester support>
The method for manufacturing a polyester product of the present invention includes manufacturing a polyester product by extrusion molding the polyester support recovered by the above method for recovering a polyester support.

Specifically, the recovered polyester support can be once pelletized and then molded into various polyester products such as polyester films by melt extrusion or the like.

The polyester product is not particularly limited and can be used for ordinary polyester purposes, and can also be used to produce polyester films, PET bottles, polyester fibers, polyester sheets, polyester containers, etc. For example, it can be used as a polyester film.

The thickness of the polyester film is not particularly limited, but can usually be set appropriately within the range of 10 to 50 μm. Further, a coating film can be formed as necessary. Examples include a release film, an adhesive film, a hard coat film, an easily adhesive film, and an antistatic film. Further, the coating film can be removed from the recovered polyester support, the polyester support can be recovered again, and a polyester product can be manufactured by extrusion molding. Polyester products manufactured from the recycled polyester support are not particularly limited and can be used for normal polyester applications, such as polyester films, plastic bottles, and polyester fibers similar to those mentioned above. , polyester sheets, polyester containers, etc.

Hereinafter, embodiments of the present invention will be described in more detail based on Examples, but the present invention is not necessarily limited thereto. Note that the usefulness of the coating film removal method according to the present invention can be expressed by the ability to remove the coating film. In the following, unless otherwise specified, "%" means % by mass, and "part" means parts by mass. The characteristics were measured as follows.

(Evaluation of coating film removal)
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 (“3270 model” manufactured by Rigaku Co., Ltd.). The amount was measured. Quantification was performed using a fluorescence X-ray measurement method using a calibration curve of fluorescence X-ray intensity prepared in advance.
The processability of the present invention was evaluated based on the obtained Si content using the following criteria. Note that "◎", "○", and "△" indicate a pass, and "x" indicates a fail.
〔Evaluation criteria〕
◎ (Excellent): Si content is below the detection limit (100 ppm) ○ (Good): Si content is more than 100 ppm and less than 300 ppm △ (Acceptable): Si content is 300 ppm or more and less than 500 ppm × (Not acceptable): Si The content of is 500ppm or more

2. Evaluation of damage to polyester support 0.1 g of pellets obtained from the recovered polyester support was added to 10 ml of o-chlorophenol, dissolved at 100°C for 30 minutes, and then evaluated using an Ubbelohde viscometer for 25 minutes. The intrinsic viscosity (intrinsic viscosity of the pellet after treatment) at °C was measured.
Furthermore, the intrinsic viscosity at 25° C. (intrinsic viscosity of the pellet before treatment) was similarly measured using pellets obtained from polyester before laminating the coating film.
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. Note that "○" and "△" indicate a pass, and "x" indicates a fail.
〔Evaluation criteria〕
○ (Good): Compared to the intrinsic viscosity of the pellet before treatment, the intrinsic viscosity of the pellet after treatment decreased by less than 0.005. △ (Acceptable): Compared to the intrinsic viscosity of the pellet before treatment, the intrinsic viscosity of the pellet after treatment decreased by less than 0.005. A decrease in the intrinsic viscosity of 0.005 or more and less than 0.01 × (Not allowed): A decrease in the intrinsic viscosity of the pellet after treatment of 0.01 or more compared to the intrinsic viscosity of the pellet before treatment.

3. Evaluation of treatment time with alkaline treatment liquid The treatment time with the alkaline treatment liquid used in the second step was evaluated based on the following criteria. Note that "◎", "○", and "△" indicate a pass, and "x" indicates a fail.
〔Evaluation criteria〕
◎ (Excellent): Processing time with alkaline processing liquid is 120 seconds or less ○ (Good): Processing time with alkaline processing liquid is more than 120 seconds but less than 300 seconds △ (Acceptable): Processing time with alkaline processing liquid is 300 seconds or more and less than 700 seconds × (not allowed): Processing time with alkaline processing liquid is 700 seconds or more

(Preparation of sample film)
Laminated polyester films A to C each having a release film, an adhesive film, and a hard coat film were prepared as sample films as follows.

<Film A: Film having a silicone release film>
1. Preparation of polyester support having coating film A polyethylene terephthalate film (Toray "Lumirror" T60, thickness 38 μm, intrinsic viscosity 0.61) was prepared as a polyester support. One side of the film was coated with a 5% toluene solution of a curable silicone resin (containing 100 parts of Toray Dow Corning Silicone LTC-350B and 0.8 parts of a curing agent SRX-212) using a bar coater. A release film was prepared by heating at 100° C. in a tunnel oven and wound up.

2. Application of Ceramic Slurry and Conductive Paste A ceramic slurry having the following composition was uniformly applied to the surface of the release layer of the above release film using a blade coater. This was dried in a tunnel oven at 85° C. to form a ceramic layer with a thickness of 20 μm on the release film. Next, a conductive paste having the composition shown below was screen printed on the ceramic layer, dried at 80°C for 10 minutes to form an electrode, and then left at 20°C for 1 hour.
《Ceramic slurry composition》
Ceramic powder (barium titanate): 100 parts Binder (polyvinyl butyral): 10 parts Plasticizer (dioctyl phthalate): 5 parts Solvent (toluene/isopropyl alcohol = 1/1 (mass ratio)): 100 parts <<Conductivity Paste composition》
Ni-based powder: 90 parts Organic vehicle: 10 parts Terpineol: 30 parts

3. Peeling off the ceramic film and internal electrodes After making a slit in the shape of 10 cm x 10 cm only in the part of the coating film where the ceramic layer and electrodes were formed on the release film on which the ceramic layer and electrodes were formed, The ceramic layer and the electrode were separated from the release film by suction to obtain Film A. It should be noted that the ceramic layer and electrode, which could not be peeled off, were partially attached to the surface of the release layer of Film A.

<Film B: Film with acrylic adhesive film>
A polyethylene terephthalate film (Toray "Lumirror", thickness 31 μm, intrinsic viscosity 0.62) was prepared as a polyester support. One side of the film was coated with an acrylic adhesive film having a thickness of 10 μm to prepare a film B having an adhesive film.

<Film C: Film having an acrylic hard coat film>
A polyethylene terephthalate film (Toray "Lumirror" T60, thickness 38 μm, intrinsic viscosity 0.61) was prepared as a polyester support. An acrylic hard coat solution having the following composition was uniformly applied onto one side of the film using a blade coater to form an acrylic hard coat film with a thickness of 9 μm. Subsequently, the film was cured by irradiation with ultraviolet rays to produce a film C having an acrylic hard coat film.
《Acrylic hard coat solution》
Dipentaerythritol hexaacrylate: 95 parts 2-hydroxy-3-phenoxypropyl acrylate: 5 parts Photoinitiator (Irgacure 184, manufactured by BASF Corporation): 4 parts Solvent (methyl ethyl ketone): 100 parts

[Example 1]
(Surface modification treatment)
Using a film (film A) having a silicone release film as a sample film, the release film side surface of film A was subjected to corona discharge using a corona discharge treatment device at a power density of 8 W/cm ² and a treatment intensity of 60 Wmin/m ² . processed.

(First step)
The sample film subjected to the corona discharge treatment was placed in an aqueous solution of 0.03 wt% of a nonionic surfactant (“Polyoxyethylene (10) Octylphenyl Ether” manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at 25° C., which is room temperature. It was immersed for 1 second.

(Second process)
A mixed aqueous solution of 3 wt % of sodium hydroxide and 0.03 wt % of a nonionic surfactant ("polyoxyethylene (10) octylphenyl ether" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was heated to 80°C and corona discharged. After the treatment, the sample film that had been brought into contact with the aqueous surfactant solution was immersed in the mixed aqueous solution for 45 seconds and treated to remove the release layer and obtain a sample film (recovered polyester support). The above-mentioned "evaluation of processability" was performed using the sample film.

(washing, drying, pelletizing)
The sample film (recovered polyester support) was immersed in a water tank for 45 seconds, and then dried by blowing hot air onto it. The sample film after drying was crushed and put into an extruder to be melted and pelletized. The above-mentioned "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.

[Example 2]
A polyester film was produced in the same manner as described in Example 1 except that the sample film used was a film having an acrylic adhesive film (film B).

[Example 3]
A polyester film was produced in the same manner as described in Example 1 except that the sample film used was a film having an acrylic hard coat film (film C).

[Example 4]
After carrying out corona discharge treatment as a surface modification treatment, a polyester film was produced in the same manner as described in Example 1 except that the sample film used was cut into flakes.

[Example 5]
A polyester film was produced in the same manner as described in Example 1 except that the surface modification treatment was not performed.

[Example 6]
A polyester film was produced in the same manner as described in Example 1, except that as surface modification treatment, ultraviolet irradiation was performed for 60 seconds at an irradiation intensity of 30 mW/cm ² using an ultraviolet irradiation device.

[Example 7]
A polyester film was produced in the same manner as described in Example 1 except that both surfaces of the film were subjected to corona discharge treatment as a surface modification treatment to avoid transfer of the release film to the back surface of the film.

[Example 8]
A polyester film was prepared in the same manner as described in Example 1, except that the surfactant used in the first step and the second step was an anionic surfactant (Nukol 290 series manufactured by Nippon Nyukazai Co., Ltd.). was created.

[Examples 9-10]
A polyester film was produced in the same manner as in Example 1, except that the contact time with the aqueous surfactant solution in the first step was changed to the conditions listed in Table 2.

[Examples 11-12]
A polyester film was produced in the same manner as in Example 1, except that the concentration of the surfactant aqueous solution in the first step was changed to the conditions listed in Table 2.

[Examples 13-14]
A polyester film was produced in the same manner as in Example 1, except that the temperature of the surfactant aqueous solution in the first step was changed to the conditions listed in Table 3.

[Examples 15-16]
A polyester film was produced in the same manner as in Example 1, except that the temperature of the alkaline treatment liquid in the second step was changed to the conditions listed in Table 3.

[Example 17]
A polyester film was produced in the same manner as in Example 1, except that the temperature of the aqueous surfactant solution in the first step was changed to the conditions listed in Table 3, which was a temperature equal to or higher than the clouding point of the surfactant (64°C).

[Example 18]
A polyester film was produced in the same manner as in Example 1, except that the concentration of the alkaline treatment liquid and the contact time in the second step were changed to the conditions listed in Table 3.

[Example 19]
A polyester film was produced in the same manner as in Example 1, except that the concentration of the alkaline treatment liquid and the contact time in the second step were changed to the conditions listed in Table 4.

[Examples 20-21]
A polyester film was produced in the same manner as in Example 1, except that the concentration of the alkaline treatment liquid and the contact time in the second step were changed to the conditions listed in Table 4.

[Example 22]
A polyester film was produced in the same manner as in Example 1, except that the alkaline treatment liquid in the second step was changed to potassium hydroxide shown in Table 4.

[Comparative Examples 1-2]
The sample film was subjected to the same surface modification treatment as in Example 1 and the second step without performing the first step, and then washed with water and dried in the same manner as in Example 1 to produce a polyester film. . In Comparative Example 1, the processing time in the second step was 45 seconds, and in Comparative Example 2, the processing time in the second step was 900 seconds.

[Comparative example 3]
The sample film was subjected to the same surface modification treatment as in Example 1 and the second step without performing the first step, and then washed with water and dried in the same manner as in Example 1 to produce a polyester film. . In Comparative Example 3, the concentration of sodium hydroxide in the second step was 25 wt%, and the treatment time was 45 seconds.

[Comparative example 4]
The sample film was subjected to the same surface modification treatment as in Example 1 and the first step without performing the second step, and then washed with water and dried in the same manner as in Example 1 to produce a polyester film. .

[Comparative example 5]
A polyester film was produced in the same manner as in Example 1 except that the order was changed so that the first step was performed after the second step.

The evaluation results for Examples 1 to 22 and Comparative Examples 1 to 5 are listed in Tables 1 to 6 below.

From Tables 1 to 6, according to the method of the present invention, it is possible to remove the coating film from a polyester support having at least one coating film, and it is possible to recover the polyester support and to recover the polyester support. It was possible to produce a polyester product using the support as part of the raw material.
In addition, from the results of Example 1, by carrying out the surface modification treatment, the first step of contacting with a surfactant or an aqueous solution containing a surfactant, and the second step of contacting with an alkaline treatment liquid, It was found that the coating layer could be removed in a short time without suffering damage such as a decrease in intrinsic viscosity.
On the other hand, in Comparative Examples 1, 2, and 3 in which the first step was not performed, the coating film could not be removed in a short time.

As described above, according to the method of the present invention, if the first step of contacting with a surfactant or an aqueous solution in which the surfactant is dissolved and the second step of contacting with an alkaline treatment liquid, the coating layer It is possible to recover the polyester support and to produce polyester products using this polyester support as part of the raw material. In addition, by performing the first and second steps after surface modification treatment, it is possible to remove the coating film efficiently in a short time without suffering damage such as a decrease in intrinsic viscosity. Therefore, it is extremely useful.

Claims (8)

A method for recovering the polyester support by removing the coating film from a polyester base material having at least one coating film on at least a portion of the polyester support, the method comprising:
A first step of bringing a surfactant or an aqueous solution containing a surfactant into contact with at least the surface of the polyester base material having the coating film; and after the first step, applying an alkaline solution to the polyester base material. A method for recovering a polyester support, comprising a second step of contacting with a treatment liquid. Before the first step, at least the surface of the polyester base material having the coating film is treated with at least one selected from the group consisting of corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment. 2. The method for recovering a polyester support according to claim 1, which comprises performing a surface modification treatment. The method for recovering a polyester support according to claim 2, characterized in that washing with water is performed after the second step. 4. The method for recovering a polyester support according to claim 3, wherein in the first step, the surfactant or an aqueous solution in which the surfactant is dissolved is brought into contact for within 300 seconds. 5. The method for recovering a polyester support according to claim 4, wherein the surfactant is a nonionic surfactant. In the second step, the alkaline treatment liquid is an alkaline treatment liquid having a temperature of less than 100° C. and an alkali concentration of 0.04% by mass or more and 15% by mass or less, and the alkaline treatment solution is heated for 1 second or more and 180% by mass. 6. The method for recovering a polyester support according to claim 5, wherein the contact is carried out for less than a second. 7. The method for collecting a polyester support according to claim 6, wherein the polyester support is collected in a long form. A method for producing a polyester product, comprising extruding a polyester support recovered by the method for recovering a polyester support according to any one of claims 1 to 7 to produce a polyester product.