Method for recovering polyester-based support and method for manufacturing polyester product

Abstract

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

Description

Technical Field

[0001] The present invention relates to a method for recovering a polyester-based support from a polyester-based substrate having at least one coating film on at least a part of the polyester-based support, and a method for manufacturing a polyester product.

Background Art

[0002] Due to its excellent mechanical, physical, and chemical properties, polyester-based supports are used in various applications for fibers, films, and other molded articles. Coating films having various functions are laminated on one or both sides of many of these polyester-based supports.

[0003] With the increasing use of the above polyester-based supports in various applications, the amount of waste objects and used products generated is also increasing, which is leading to the deterioration of the global environment. In order to solve this problem and recycle polyester-based supports, it is preferable to remove the coating film from the polyester-based substrate and then use it again as a polyester-based support.

[0004] As such a technique, for example, Patent Document 1 can be cited. In Patent Document 1, the coating film provided on at least one surface of the base film is removed by bringing it into contact with an alkaline treatment liquid of 20 to 60% by mass heated to a temperature of 90 to 140°C.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the method described in Patent Document 1 has a problem that the polyester-based support is deteriorated by contact with a high-temperature and high-concentration alkaline treatment liquid. Further, since a high-temperature and high-concentration alkali is used, there is also a problem that safety and profitability are reduced.

[0007] The present invention has been made in view of the above reasons, and an object thereof is to provide a method for efficiently recovering a highly pure polyester-based support from a polyester-based substrate having at least one coating film on the polyester-based support safely and with good profitability in a short time.

Means for Solving the Problems

[0008] Therefore, as a result of investigations to solve the above problems, after hydrophilizing the surface of the polyester-based substrate by bringing a surfactant or an aqueous solution in which a surfactant is dissolved into contact with the polyester-based substrate, it was found that the intended object can be achieved by treating the polyester-based substrate with an alkaline treatment liquid, and the present invention was completed. By dividing the steps into a first step of hydrophilizing the surface of the polyester-based substrate with a surfactant or an aqueous solution in which a surfactant is dissolved and a second step of treating with an alkaline treatment liquid, the first step and the second step can be treated at different temperatures. By performing the hydrophilization of the surface of the polyester-based substrate in the first step and the removal of the coating film in the second step under optimal temperature conditions, it becomes possible to efficiently recover the polyester-based support in a short time.

[0009] The configuration of the present invention is as follows. (1) A method for recovering the polyester-based support by removing the coating film from a polyester-based substrate having at least one coating film on at least a part of the polyester-based support, the method comprising: a first step of bringing a surfactant or an aqueous solution in which a surfactant is dissolved into contact with at least the surface of the polyester-based substrate having the coating film; and a second step of bringing an alkaline treatment liquid into contact with the polyester-based substrate after the first step. A method for recovering a polyester-based support, characterized by including the steps. (2) Before the first step, at least one surface modification treatment selected from the group consisting of corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment is performed on at least the surface of the polyester-based substrate having the coating film, and the method for recovering the polyester-based support according to (1) above is characterized in that. (3) After the second step, the method for recovering the polyester-based support according to (2) above is characterized in that washing with water is performed. (4) In the first step, the method for recovering the polyester-based support according to (3) above is characterized in that an aqueous solution in which the surfactant or the surfactant is dissolved is brought into contact within 300 seconds. (5) The method for recovering the polyester-based support according to (4) above is characterized in that 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 or more and 15% by mass or less, and the alkaline treatment liquid is brought into contact for 1 second or more and 180 seconds or less. The method for recovering the polyester-based support according to (5) above is characterized in that. (7) The method for recovering the polyester-based support according to (6) above is characterized in that the polyester-based support is recovered in a long shape. (8) A method for producing a polyester product, wherein the polyester-based support recovered by the method for recovering the polyester-based support according to any one of (1) to (7) above is extrusion-molded to produce a polyester product.

Effect of the Invention

[0010] According to the present invention, since the coating film can be efficiently removed from the polyester-based substrate having at least one layer of coating film on at least a part of the polyester-based support, the used polyester-based substrate that has been conventionally discarded can be efficiently removed in a short time. A highly pure polyester-based support can be recovered.

Modes for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. In this specification, the symbol "~" indicating a numerical range is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0012] The method for recovering a polyester-based support of the present invention is a method for recovering a polyester-based support by removing a coating film from a polyester-based substrate including a polyester-based support and at least one layer of coating film provided on at least a part of the polyester-based support, the method having: a first step of bringing a surfactant or an aqueous solution in which a surfactant is dissolved into contact with at least the surface of the polyester-based substrate having the coating film; and a second step of bringing an alkaline treatment liquid into contact with the polyester-based substrate after the first step.

[0013] 〈Polyester-based support〉 The polyester-based support in the present invention is formed including a polyester composition. The polyester composition is not particularly limited, and examples thereof include polyesters obtained by polycondensing a dicarboxylic acid component and a diol component.

[0014] As the above dicarboxylic acid component, various dicarboxylic acid components such as aromatic dicarboxylic acids, chain aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids can be used, and examples thereof include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, and phthalic acid.

[0015] As the above diol component, aliphatic glycols are preferable, and examples thereof include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, and neopentyl glycol. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used.

[0016] 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 copolymerization component.

[0017] As the polyester support, a polyester support mainly composed of polyethylene terephthalate or polyethylene naphthalate is preferably used. More preferably, it is polyethylene terephthalate. Also, these may be copolyester.

[0018] The polyester support may be composed of a polyester composition, or may contain additives other than polyester in the composition. Examples of the additives include end-capping agents, antioxidants, flame retardants, fluorescent brighteners, matting agents, plasticizers, or defoaming agents, etc.

[0019] The polyester support can be produced by the following method. For example, after vacuum-drying the polyester composition, it is supplied to an extruder, melted at 260 to 300 °C, extruded in a sheet shape from a T-shaped die, wound around a mirror casting drum with a surface temperature of 10 to 60 °C using an electrostatic application casting method, and cooled and solidified to produce an unstretched polyester support. The unstretched polyester support is longitudinally stretched 2.5 to 5 times between rolls heated to 70 to 130 °C. Subsequently, it is continuously stretched 2.5 to 5 times in the width direction in a hot air zone heated to 70 to 150 °C, then led to a heat treatment zone at 190 to 240 °C, subjected to heat treatment for 5 to 40 seconds, passed through a cooling zone at 100 to 200 °C to complete the crystal orientation, and a polyester support is obtained. Also, during the above heat treatment, a relaxation treatment of 0.1 to 12% may be performed in the width direction or the longitudinal direction as necessary.

[0020] The thickness of the above polyester-based support is not particularly limited, but considering handleability such as strength and rigidity, it is preferably 5 μm or more and 500 μm or less. The thickness of the polyester-based support is more preferably 10 μm or more and 200 μm or less, and particularly preferably 20 μm or more and 100 μm or less.

[0021] In the present invention, in the recovery of the polyester-based support described later, the polyester-based substrate may be in a long shape or in a cut state. If it is in a long shape, the length varies depending on, for example, the type of equipment used, etc., but generally means 100 m or more and 10,000 m or less, and it means directly performing a recovery process without crushing or the like. Also, if it is in a cut state, although not particularly limited, for example, it means recovering a polyester-based substrate cut into a square with a side length of 1 mm or more and 10 mm or less.

[0022] According to the method of the present invention, if handling in a long shape, for a polyester-based substrate wound in a roll shape, a first step of contacting a surfactant or an aqueous solution in which a surfactant is dissolved and a second step of contacting an alkaline treatment liquid can be carried out in series, and the coating film can be removed efficiently in a short time. Preferably, after performing the surface modification treatment described later on the long polyester-based substrate, it is contacted with a surfactant or an aqueous solution in which a surfactant is dissolved, further contacted with an alkaline treatment liquid, and then directly introduced into the next step (water washing, drying) described later and wound in a roll shape, that is, it is recommended to perform a roll-to-roll method. The roll-to-roll method is a winding and unwinding type conveying method in which a flexible substrate wound in a roll shape is continuously conveyed through a plurality of guide rolls, a predetermined treatment is performed during conveyance, and it is wound again in a roll state. By processing in the roll-to-roll method, a series of coating film removal steps can be continuously performed in a short time, which is very efficient.

[0023] 〈Coating film〉 The polyester-based support in the present invention has at least one coating film on at least a part thereof. Here, the coating film is a film that can impart various functions to the polyester-based support, and examples include a release film, an adhesive film, a hard coat film, an easy adhesion film, an antistatic film, and the like. These coating films may be provided on at least one side of the polyester-based support, or may be provided on both sides. Further, the coating film may be provided alone, or two or more types may be laminated. Also, the above coating film may have not only a single function but also a plurality of functions.

[0024] The resin constituting the above release film is not particularly limited as long as it is a resin generally used for release films. Examples include silicone-based resins such as polydimethylsiloxane, amino resins such as melamine resins and urea resins, acrylic resins, epoxy resins, alkyd resins, and the like. Also, these resins may be used alone, or two or more types may be used in combination. Further, the above release film may contain a release agent such as silicone or wax.

[0025] The resin constituting the above adhesive film contains an adhesive generally used for adhesive films. The type of the above adhesive is not particularly limited, and examples include acrylic adhesives, rubber adhesives, polyurethane adhesives, silicone adhesives, and the like. Also, the above adhesive film may further contain a tackifier (adhesion-imparting resin) or the like.

[0026] The resin constituting the above hard coat film is not particularly limited as long as it is a resin generally used for hard coat films. Examples include acrylic resins, urethane resins, epoxy resins, and the like. These resins may be used alone, or two or more types may be used in combination. The resin constituting the above hard coat film is not particularly limited as long as it is a resin generally used for hard coat films. Examples include acrylic resins, urethane resins, epoxy resins, and the like. These resins may be used alone, or two or more types may be used in combination.

[0027] The resin constituting the easily adherable film is not particularly limited as long as it is a resin generally used for easily adherable films. For example, polyester resins, acrylic resins, polycarbonate resins, polyurethane resins, polyvinyl alcohol resins, polyamide resins, polyvinyl acetate resins, etc. may be mentioned. These resins may be used alone or in combination of two or more.

[0028] The resin constituting the antistatic film is not particularly limited as long as it is a resin generally used for antistatic films. The antistatic film preferably 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, carbonaceous substances), etc. These antistatic agents may be used alone or in combination of two or more.

[0029] The coating film is not particularly limited, but can be formed on a polyester-based support using, for example, the reverse coating method, the gravure coating method, the rod coating method, the bar coating method, the wire bar coating method, the die coating method, the spray coating method, etc.

[0030] The thickness of the coating film (when having 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, it is more preferably 0.01 μm or more. On the other hand, when the thickness of the coating film exceeds 50 μm, it may take time to remove the coating film.

[0031] 〈Recovery of polyester-based support〉 The method for recovering the polyester-based support of the present invention is characterized by having a first step of bringing a surfactant or an aqueous solution in which a surfactant is dissolved into contact with at least the surface of the polyester-based substrate having the coating film, and a second step of bringing an alkaline treatment liquid into contact with the polyester-based substrate after the first step.

[0032] (First step: Step of bringing a surfactant or an aqueous solution in which a surfactant is dissolved into contact) In the first step, a surfactant or an aqueous solution in which a surfactant is dissolved is brought into contact with at least the surface of the polyester-based substrate having the coating film. By orienting the hydrophobic region of the surfactant towards the polyester-based support or the coating film and the hydrophilic region of the surfactant towards the solution side, the surface of the polyester-based substrate is rendered hydrophilic. In the first step, with the surface of the polyester-based substrate being made hydrophilic in advance, in the second step described later, by bringing an alkaline treatment liquid into contact therewith, since the hydrophobic region of the surfactant faces the polyester-based support or the coating film and the hydrophilic region of the surfactant faces the solution side, the penetration of the alkaline treatment liquid is promoted, and the coating film can be efficiently removed from the polyester-based support in a short time and easily. Surfactants are representative examples of compounds having a hydrophilic region and a hydrophobic region, but any compound having both a hydrophilic region and a hydrophobic region can be used.

[0033] The method of bringing the surfactant or the aqueous solution in which the surfactant is dissolved into contact is not particularly limited as long as at least the surface of the polyester-based substrate having the coating film can be brought into contact with the surfactant or the aqueous solution in which the surfactant is dissolved. For example, methods include immersing the polyester-based substrate in a cleaning tank containing the surfactant or the aqueous solution in which the surfactant is dissolved, applying the surfactant or the aqueous solution in which the surfactant is dissolved to the polyester-based substrate, and spraying the surfactant or the aqueous solution in which the surfactant is dissolved onto the polyester-based substrate. Among these, from the viewpoint of the permeability of the surfactant or the aqueous solution in which the surfactant is dissolved into the coating film, the immersion method is preferred.

[0034] The surfactant is not particularly limited, and examples thereof include at least one surfactant selected from the group consisting of nonionic surfactants, cationic surfactants, and anionic surfactants. In particular, nonionic surfactants are preferred. The surfactant may be used alone or in combination of two or more.

[0035] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkylphenol ethers such as polyoxyethylene octylphenol ether and polyoxyethylene nonylphenol ether; polyoxyethylene alkylaryl ethers; polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate; and glycerin fatty acid esters such as monoglyceride stearate.

[0036] Examples of cationic surfactants include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyldimethylbenzylammonium chloride.

[0037] Examples of anionic surfactants include sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl succinate sulfonate, sodium alkyl diphenyl ether disulfonate, sodium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkylphenyl ether sulfate.

[0038] The contact time between the polyester-based substrate and the surfactant or the aqueous solution in which the surfactant is dissolved is preferably within 300 seconds, more preferably 0.001 to 10 seconds, and even more preferably 0.1 to 10 seconds. If the contact time between the polyester-based substrate and the surfactant or the aqueous solution in which the surfactant is dissolved is too short, there is a risk that the coating film cannot be sufficiently removed. If the contact time is too long, the size of the apparatus increases, and there is a risk that the economy and operability deteriorate. When the contact time between the polyester-based substrate and the surfactant or the aqueous solution in which the surfactant is dissolved is within 300 seconds, the economy and operability are good, and the removal effect of the coating film can be enhanced.

[0039] The concentration of the surfactant or the aqueous solution in which the surfactant is dissolved is preferably 0.00001 wt% to 100 wt%, more preferably 0.0001 wt% to 100 wt%, even more preferably 0.001 wt% to 50 wt%, and particularly preferably 0.01 wt% to 1 wt%. If the surfactant concentration is too low, there is a risk that the coating film cannot be sufficiently removed. When the concentration of the surfactant or the aqueous solution in which the surfactant is dissolved is 0.00001 wt% to 100 wt%, a sufficient removal effect of the coating film can be obtained.

[0040] The temperature of the surfactant or the aqueous solution in which the surfactant is dissolved may be adjusted according to the surfactant used, but 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 made to have a high concentration, so the removal effect of the coating film is promoted. In addition, in the case of a nonionic surfactant, if the temperature is too high, it becomes insoluble in water, so it is preferable to perform the treatment at a temperature below the cloud point of the surfactant.

[0041] (Surface modification treatment) For the purpose of enhancing the affinity with a surfactant or an aqueous solution in which the surfactant is dissolved and an alkaline treatment liquid described later, a surface modification treatment may be performed on the surface of the coating film. The surface modification treatment is not particularly limited, and known methods can be adopted. For example, corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, ultraviolet treatment, etc. can be mentioned, and it is preferable to perform at least one treatment selected from the group consisting of these.

[0042] The surface modification treatment may be carried out before the implementation of the second step of bringing the alkaline treatment liquid into contact, but in order to enhance the affinity with the surfactant or the aqueous solution in which the surfactant is dissolved, it is more preferable to carry out the treatment before the first step.

[0043] In the analysis by X-ray photoelectron spectroscopy after the surface modification treatment, if the ratio of C-C bonds and C-H bonds decreases by 0.1% or more, the effect of enhancing the affinity with the surfactant or the aqueous solution in which the surfactant is dissolved, or the alkaline treatment liquid described later can be obtained.

[0044] In the case of corona discharge treatment, the treatment intensity is preferably 10 to 1000 Wmin / m 2 or more, more preferably 20 to 200 Wmin / m 2 and even more preferably 40 to 120 Wmin / m 2 If the treatment intensity becomes too high, the polyester-based support tends to be damaged. If the treatment intensity is too weak, the time of the subsequent alkali treatment becomes long, and the polyester-based support tends to be damaged. Also, if the power density of the corona discharge machine used is 4 to 20 W / cm 2 surface treatment can be performed uniformly.

[0045] 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 even more preferably 15 to 40 mW / cm 2is more preferable. If the irradiation intensity is too high, the polyester-based support tends to be damaged. If the irradiation intensity is too low, the time for the subsequent alkali treatment becomes long, and the polyester-based support tends to be damaged. The irradiation time of ultraviolet rays is preferably 3 to 210 seconds, more preferably 30 to 100 seconds, and even more preferably 50 to 70 seconds. If the irradiation time of ultraviolet rays becomes too long, it is necessary to increase the size of the apparatus, so the manufacturing cost becomes high, and the polyester-based support also tends to be damaged. If the irradiation time of ultraviolet rays is too short, there is a risk that the coating film cannot be sufficiently removed. Further, the wavelength of the irradiated ultraviolet rays is preferably 10 to 400 nm, that is, an invisible electromagnetic wave shorter than visible light and longer than soft X-rays. As the ultraviolet ray source, for example, known lamps such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, metal halide lamps, etc. can be used, and it is preferable to use a low pressure mercury lamp.

[0046] (Second step: Step of bringing an alkaline treatment liquid into contact) The method for recovering the polyester-based support of the present invention performs a second step of bringing an alkaline treatment liquid into contact after the first step. After hydrophilizing the surface of the polyester-based substrate in the first step, by bringing the hydrophilic alkaline treatment liquid into contact, the penetration of the alkaline treatment liquid into the polyester-based support or the coating film is promoted, the coating film is dissolved and swollen, the bond at the interface between the polyester-based support and the coating film is weakened, and the coating film dissolved in the alkaline treatment liquid can be removed from the polyester-based support in a short time.

[0047] In the present invention, the treatment with the alkali treatment liquid may be performed immediately after the first step, or may be performed after a desired time.

[0048] As the alkaline treatment liquid used in the present invention, a solution in which an alkaline substance is dissolved can be used. The alkaline substance is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide; sodium silicate, potassium silicate, ammonium silicate; disodium phosphate, dipotassium phosphate, diammonium phosphate; sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate; sodium carbonate, potassium carbonate, ammonium carbonate; sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate; sodium borate, potassium borate, ammonium borate and other inorganic alkaline agents. Among these, an alkali metal hydroxide salt is preferable, and sodium hydroxide and potassium hydroxide are more preferable. The above alkaline substances may be used alone or in combination of two or more.

[0049] The solvent for dissolving the alkaline substance is not particularly limited, and examples thereof include water.

[0050] The content of the alkaline substance in the above 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. When the content of the alkaline substance is too high, the polyester-based support tends to be damaged. When the content is too low, there is a risk that the coating film cannot be sufficiently removed. When the content of the alkaline substance is within the above range, the effect of removing the coating film can be obtained, and damage to the polyester-based support can be suppressed.

[0051] As a method for bringing the alkaline treatment liquid into contact with the polyester-based substrate, various methods such as an immersion method, an ultrasonic method, a spray method, and a rocking method can be adopted. The above conditions can be appropriately selected according to the type and thickness of the polyester-based support and the coating film. However, in order to obtain a high-quality polyester-based support with few impurities, for example, it is preferable to contact with an alkaline treatment liquid having a concentration of 0.01 to 15% by mass heated to a temperature of less than 100°C for a period exceeding 0 seconds and less than 700 seconds.

[0052] The temperature of the above-mentioned 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, since a higher temperature of the alkaline treatment liquid is better, it is preferably carried out 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-based support are not changed, and a high-quality polyester-based support with few impurities can be obtained without spending excessive time. Also, since it is impossible to achieve a temperature of the alkaline treatment liquid exceeding 100°C under normal pressure, it leads to an increase in the size of the equipment, and hydrolysis, dissolution, etc. of the polyester-based support may occur due to heating.

[0053] The contact time with the above-mentioned alkaline treatment liquid is preferably more than 0 seconds and less than 700 seconds, more preferably more than 0 seconds and 600 seconds or less, even more preferably more than 0 seconds and 180 seconds or less, and particularly preferably more than 0 seconds and 120 seconds or less. When the treatment time is too long, the polyester-based support tends to be damaged, and there is a risk that the polyester-based support elutes into the alkaline treatment liquid, increasing the load when treating the alkaline treatment liquid for wastewater treatment. The treatment time with the alkaline treatment liquid only needs to be such that the coating film can be sufficiently dissolved and swollen. If the treatment time is too short, there is a risk that the coating film cannot be sufficiently removed, so it is more preferably 1 second or more, and even more preferably 5 seconds or more. When the treatment time with the alkaline treatment liquid is within the above range, the removal effect of the coating film can be obtained, and damage to the polyester-based support can be suppressed.

[0054] In the present invention, in the second step, the treatment with the alkaline treatment liquid is more preferably carried out by bringing the polyester-based substrate into contact with an alkaline treatment liquid having a temperature of less than 100°C and an alkaline concentration of 0.04% by mass or more and 15% by mass or less for 1 second or more and 180 seconds or less.

[0055] The above-mentioned alkaline treatment liquid may contain a surfactant or ultrafine bubbles as an auxiliary agent in order to prevent the reattachment of the removed coating film and enhance the removal efficiency of the coating film. There is no particular limitation on the surfactant, and for example, a nonionic surfactant, a cationic surfactant, an anionic surfactant, etc. can be used. The surfactant may be used alone or in combination of two or more kinds.

[0056] Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, etc.

[0057] Examples of the cationic surfactant include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, alkyldimethylbenzylammonium chloride, etc.

[0058] Examples of the anionic surfactant include sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl succinate sulfonate, sodium alkyl diphenyl ether disulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, etc.

[0059] The above-mentioned alkaline treatment liquid may contain other additives within a range that does not interfere with the effects of the present invention. Examples of the additives include antioxidants, pH adjusters, antifoaming agents, etc.

[0060] (Water washing treatment) After the above-mentioned second step, it is preferable to perform a water washing treatment. Washing with water is carried out to remove the coating film remaining in trace amounts on the polyester-based support after the above treatment and to remove the alkaline treatment liquid remaining on the polyester-based support after the above treatment.

[0061] The temperature of the above-mentioned water washing treatment is not particularly limited. For example, when washing with warm water at about 40°C or higher and 100°C or lower, the above-mentioned effect is more effectively exerted.

[0062] Examples of the water washing method include a method of spraying water onto the polyester-based support from which the coating film has been removed, and a method of immersing the polyester-based support in a water tank. During the water washing treatment, physical cleaning such as a roll brush, microbubbles, or a water flow may be performed.

[0063] (Drying treatment) After water washing, it is preferable to perform a drying treatment to remove the water remaining on the polyester-based support.

[0064] The drying time is preferably 10 seconds or more and 5 minutes or less. If the drying time is less than 10 seconds, the drying may be insufficient, and there is a risk of causing blocking. More preferably, it is 30 seconds or more. On the other hand, if the drying time exceeds 5 minutes, there is a risk of deformation of the polyester-based support.

[0065] The drying method is not particularly limited, and examples include hot air drying by blowing hot air and heating drying by heating with a non-contact heater.

[0066] (Multiple treatments) The above-mentioned surface modification treatment step, the first step of bringing the surfactant or an aqueous solution in which the surfactant is dissolved into contact, and the second step of bringing the alkaline treatment liquid into contact may be performed multiple times. By performing the multiple treatments, the polyester-based support can be processed in a short time without being damaged such as a decrease in intrinsic viscosity.

[0067] 〈Molding of the recovered polyester-based support〉 The method for manufacturing a polyester product of the present invention includes extruding and molding the polyester-based support recovered by the above-mentioned method for recovering a polyester-based support to manufacture a polyester product.

[0068] Specifically, after the recovered polyester support is once pelletized, it can be formed into various polyester products such as polyester films by melt extrusion or the like.

[0069] The polyester products are not particularly limited and can be used for ordinary polyester applications. It is also possible to manufacture polyester films, PET bottles, polyester fibers, polyester sheets, polyester containers, etc. For example, it can be used as a polyester film.

[0070] The thickness of the polyester film is not particularly limited, but it can usually be appropriately set within the range of 10 to 50 μm. Also, a coating film can be formed as needed. For example, a release film, an adhesive film, a hard coat film, an easy adhesion film, an antistatic film, etc. can be mentioned. Also, from the recovered polyester support, the coating film can be removed, the polyester support can be recovered again, and it can be extrusion molded to manufacture a polyester product. The polyester products manufactured from the polyester support recovered again are also not particularly limited and can be used for ordinary polyester applications. For example, the same polyester films, PET bottles, polyester fibers, polyester sheets, polyester containers, etc. as described above can be mentioned.

Examples

[0071] Hereinafter, based on the examples, the embodiments of the present invention will be described in more detail, but it is not necessarily limited thereto. The usefulness of the coating film removal method according to the present invention can be represented by the ability to remove the coating film. Hereinafter, unless otherwise specified, “%” means mass %, and “part” means part by mass. The characteristics were measured as follows.

[0072] (Evaluation of Coating Film Removal) 1. Evaluation of Processability After finely cutting the recovered polyester support, 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 type" manufactured by Rigaku Corporation). Quantification was performed from a calibration curve of fluorescent X-ray intensity created in advance by the fluorescent X-ray measurement method. The processability of the present invention was evaluated based on the obtained Si content according to the following criteria. Note that "◎", "○", and "△" indicate passing, and "×" indicates failing. 〔Evaluation Criteria〕 ◎ (Excellent): The Si content is below the detection lower limit (100 ppm) ○ (Good): The Si content is more than 100 ppm and less than 300 ppm △ (Fair): The Si content is 300 ppm or more and less than 500 ppm × (Poor): The Si content is 500 ppm or more

[0073] 2. Evaluation of Damage to the Polyester Support 0.1 g of the pellets obtained from the recovered polyester support was added to 10 ml of o-chlorophenol and dissolved at 100 °C for 30 minutes. Then, the intrinsic viscosity at 25 °C (intrinsic viscosity of the treated pellets) was measured using an Ubbelohde viscometer. Also, using the pellets obtained from the polyester before laminating the coating film, the intrinsic viscosity at 25 °C (intrinsic viscosity of the pellets before treatment) was measured in the same manner. The intrinsic viscosity of the treated pellets was compared with that of the pellets before treatment and evaluated according to the following criteria. Note that "○" and "△" indicate passing, and "×" indicates failing. 〔Evaluation Criteria〕 ○ (Good): The decrease in the intrinsic viscosity of the treated pellets is less than 0.005 compared to the intrinsic viscosity of the pellets before treatment △ (Fair): The decrease in the intrinsic viscosity of the treated pellets is 0.005 or more and less than 0.01 compared to the intrinsic viscosity of the pellets before treatment × (Poor): The decrease in the intrinsic viscosity of the treated pellets is 0.01 or more compared to the intrinsic viscosity of the pellets before treatment

[0074] 3. Evaluation of the Treatment Time in the Alkaline Treatment Liquid The treatment time with the alkaline treatment liquid used in the second step was evaluated according to the following criteria. Note that "◎", "○", and "△" indicate passing, while "×" indicates failing. 〔Evaluation Criteria〕 ◎ (Excellent): The treatment time with the alkaline treatment liquid is 120 seconds or less. ○ (Good): The treatment time with the alkaline treatment liquid exceeds 120 seconds and is less than 300 seconds. △ (Fair): The treatment time with the alkaline treatment liquid is 300 seconds or more and less than 700 seconds. × (Poor): The treatment time with the alkaline treatment liquid is 700 seconds or more.

[0075] (Preparation of Sample Film) As follows, laminated polyester films A to C each having a release film, an adhesive film, and a hard coat film were prepared as sample films.

[0076] (Film A: A film having a silicone-based release film) 1. Preparation of a polyester-based support having a coating film A polyethylene terephthalate film (Toray "Lumirror" T60, thickness 38 μm, intrinsic viscosity 0.61) was prepared as the polyester-based support. On one side of the film, a 5% toluene solution of a curable silicone resin (100 parts of Toray Dow Corning Silicone Co., Ltd. LTC-350B and 0.8 part of curing agent SRX-212) was coated with a bar coater and heated at 100 °C in a tunnel oven to prepare a release film, which was then wound up.

[0077] 2. Coating of Ceramic Slurry and Conductive Paste On the release layer surface of the above release film, a ceramic slurry having the following composition was uniformly coated with a blade coater. This was dried at 85 °C in a tunnel oven to form a ceramic layer with a thickness of 20 μm on the release film. Next, a conductive paste having the following composition 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 《Conductive paste composition》 Ni-based powder: 90 parts Organic vehicle: 10 parts Terpineol: 30 parts

[0078] 3. Peeling of the ceramic film and the internal electrode On the release film on which the above ceramic layer and electrode were formed, a slit was made in the shape of 10 cm × 10 cm only in the coating film of the portion where the ceramic layer and electrode were formed, and then the ceramic layer and electrode were sucked by a vacuum suction machine and peeled from the release film to obtain Film A. Note that on the surface of the release layer of Film A, the ceramic layer and electrode that could not be partially peeled were adhered.

[0079] <Film B: Film having an acrylic adhesive film> A polyethylene terephthalate film (Toray "Lumirror", thickness 31 μm, intrinsic viscosity 0.62) was prepared as a polyester-based support. An acrylic adhesive film was coated on one side of the film at 10 μm to produce Film B having an adhesive film.

[0080] <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-based support. An acrylic hard coat solution having the following composition was uniformly coated on one side of the film with a blade coater so as to form an acrylic hard coat film having a thickness of 9 μm. Subsequently, ultraviolet rays were irradiated for curing to produce 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 Co., Ltd.): 4 parts Solvent (methyl ethyl ketone): 100 parts

[0081] [Example 1] (Surface modification treatment) A film having a silicone-based release film as a sample film (Film A) was used, and the surface on the release film side of Film A was treated with a corona discharge treatment apparatus at a power density of 8 W / cm 2 , and a corona discharge treatment was performed at a treatment intensity of 60 Wmin / m 2 .

[0082] (First step) The sample film subjected to the corona discharge treatment was immersed in an aqueous solution of a nonionic surfactant (Polyoxyethylene (10) octylphenyl ether, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) at 0.03 wt% at room temperature of 25°C for 1 second.

[0083] (Second step) A mixed aqueous solution of 3 wt% sodium hydroxide and 0.03 wt% of a nonionic surfactant (Polyoxyethylene (10) octylphenyl ether, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was heated to 80°C, and the sample film that had been brought into contact with the surfactant aqueous solution after the corona discharge treatment was immersed in the mixed aqueous solution for 45 seconds and treated to remove the release layer, thereby obtaining a specimen film (recovered polyester-based support). Using the specimen film, the above-mentioned "evaluation of processability" was performed.

[0084] (Washing, drying, and pelletizing) The specimen film (recovered polyester-based support) was immersed in a water tank filled with water for 45 seconds and then dried by blowing hot air. The dried specimen film was pulverized and put into an extruder for melting and pelletizing. Using the obtained pellets, the above-mentioned "evaluation of damage to the polyester-based support" was performed.

[0085] (Manufacture of polyester film) The pellets obtained from the specimen film were dried at 150 °C for 3 hours, supplied to an extruder, melt-extruded at 285 °C, and cast onto a 20 °C casting drum with electrostatic application to obtain an unstretched sheet. This unstretched sheet was stretched 3.1 times in the longitudinal direction by a stretching roll heated to 90 °C, then stretched 3.7 times in the width direction at 120 °C by a tenter-type stretching machine, and then heat-fixed at 230 °C and wound onto a roll.

[0086] [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).

[0087] [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).

[0088] [Example 4] After performing 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.

[0089] [Example 5] A polyester film was produced in the same manner as described in Example 1, except that no surface modification treatment was performed.

[0090] [Example 6] As a surface modification treatment, ultraviolet irradiation was performed for 60 seconds at an irradiation intensity of 30 mW / cm 2 A polyester film was produced in the same manner as described in Example 1.

[0091] [Example 7] Since transfer of the release film to the back surface of the film occurred, a polyester film was produced in the same manner as described in Example 1, except that corona discharge treatment was performed on both sides of the film as a surface modification treatment.

[0092] [Example 8] A polyester film was produced 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 ("Newcol 290 series" manufactured by Nippon Emulsion Co., Ltd.).

[0093] [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 described in Table 2.

[0094] [Examples 11 - 12] A polyester film was produced in the same manner as in Example 1, except that the concentration of the aqueous surfactant solution in the first step was changed to the conditions described in Table 2.

[0095] [Examples 13 - 14] 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 described in Table 3.

[0096] [Examples 15 - 16] A polyester film was produced in the same manner as in Example 1, except that the temperature of the alkaline treatment solution in the second step was changed to the conditions described in Table 3.

[0097] [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 described in Table 3, which is a temperature equal to or higher than the cloud point (64°C) of the surfactant.

[0098] [Example 18] A polyester film was produced in the same manner as in Example 1, except that the concentration and contact time of the alkaline treatment solution in the second step were changed to the conditions described in Table 3.

[0099] [Example 19] A polyester film was produced in the same manner as in Example 1, except that the concentration and contact time of the alkaline treatment liquid in the second step were changed to the conditions described in Table 4.

[0100] [Examples 20 - 21] A polyester film was produced in the same manner as in Example 1, except that the concentration and contact time of the alkaline treatment liquid in the second step were changed to the conditions described in Table 4.

[0101] [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 described in Table 4.

[0102] [Comparative Examples 1 - 2] A surface modification treatment similar to that of Example 1 was carried out on the sample film without performing the first step. After performing the second step, it was washed with water and dried in the same manner as in Example 1 to produce a polyester film. Note that in Comparative Example 1, the treatment time in the second step was 45 seconds, and in Comparative Example 2, the treatment time in the second step was 900 seconds.

[0103] [Comparative Example 3] A surface modification treatment similar to that of Example 1 was carried out on the sample film without performing the first step. After performing the second step, it was washed with water and dried in the same manner as in Example 1 to produce a polyester film. Note that in Comparative Example 3, the concentration of sodium hydroxide in the second step was 25 wt% and the treatment time was 45 seconds.

[0104] [Comparative Example 4] A surface modification treatment similar to that of Example 1 was carried out on the sample film without performing the second step. After performing the first step, it was washed with water and dried in the same manner as in Example 1 to produce a polyester film.

[0105] [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 carried out after the second step.

[0106] For Examples 1 to 22 and Comparative Examples 1 to 5, the evaluation results are shown in Tables 1 to 6 below.

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] [Table 4]

[0111] [Table 5]

[0112] [Table 6]

[0113] From Tables 1 to 6, according to the method of the present invention, it is possible to remove the coating film from the polyester-based support having at least one layer of coating film, and to recover the polyester-based support and manufacture a polyester product using this polyester-based support as part of the raw material. In addition, from the results of Example 1, it was found that by performing the first step of contacting with a surface modification treatment, a surfactant or an aqueous solution in which a surfactant is dissolved, and the second step of contacting with an alkaline treatment liquid, it is possible to remove the coating layer in a short time without being damaged 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.

[0114] As described above, according to the method of the present invention, by performing the first step of bringing into contact with an aqueous solution in which a surfactant or a surfactant is dissolved and the second step of bringing into contact with an alkaline treatment liquid, the coating layer can be removed, and it is possible to recover the polyester-based support and manufacture a polyester product using this polyester-based support as part of the raw materials. Further, after performing the surface modification treatment, by performing the first step and the second step, it is possible to efficiently remove the coating film in a short time without being damaged such as a decrease in the intrinsic viscosity, which is extremely useful.

Claims

1. A method for recovering a polyester support by removing a coating film from a polyester-based substrate having at least one layer of coating film on at least a part of a polyester-based support, comprising: a first step of bringing a surfactant or an aqueous solution in which the surfactant is dissolved into contact with at least the surface of the polyester-based substrate having the coating film; and a second step of bringing an alkaline treatment liquid into contact with the polyester-based substrate after the first step, The method for recovering a polyester support according to claim 1, characterized in that the alkaline treatment liquid is brought into contact in the second step in a state where the surface of the polyester-based substrate has been hydrophilized in advance in the first step.

2. The method for recovering a polyester support according to claim 1, characterized in that at least one surface modification treatment selected from the group consisting of corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment is carried out on at least the surface of the polyester-based substrate having the coating film before the first step.

3. The method for recovering a polyester support according to claim 2, characterized in that washing with water is carried out after the second step.

4. The method for recovering a polyester support according to claim 3, characterized in that in the first step, the surfactant or the aqueous solution in which the surfactant is dissolved is brought into contact within 300 seconds.

5. The method for recovering a polyester support according to claim 4, characterized in that 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 alkali concentration of 0.04% by mass or more and 15% by mass or less, and the alkaline treatment liquid is brought into contact for 1 second or more and 180 seconds or less. The method for recovering a polyester support according to claim 5, characterized by the above.

7. The method for recovering a polyester-based support according to claim 6, characterized in that the polyester-based support is recovered in a long shape.

8. A method for manufacturing a polyester product, wherein the polyester-based support recovered by the method for recovering a polyester-based support according to any one of claims 1 to 7 is extrusion molded to produce a polyester product.

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