Method for recovering polyester-based film, polyester-based film processing device, and method for manufacturing polyester product

Abstract

To provide a method for recovering a high purity polyester-based film from a long polyester-based film substrate having at least one coating film on a long polyester-based film profitably and efficiently in a short time.SOLUTION: A method for recovering a polyester-based film by removing a coating film from a long polyester-based film substrate having at least one coating film at least partially on a long polyester-based film, comprises the step (1) of making the plurality of long polyester-based film substrates contact a solvent simultaneously.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Polyester films are used in a variety of applications due to their excellent mechanical, physical, and chemical properties. Many of these polyester films have coating films with various functions laminated on one or both sides of the surface.

[0003] As the polyester film is used in various applications, the amount of waste and used products generated is also increasing, which leads to the deterioration of the global environment. In order to solve this problem and recycle the polyester film, it is preferable to remove the coating film from the polyester film substrate and reuse it as a polyester film.

[0004] Examples of such techniques include Patent Documents 1, 2, and 3. These patent documents describe a technique for recovering a polyester film by contacting a long polyester film substrate having a coating film while still in a long state with an alkaline treatment liquid to remove the coating film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-90094 A [Patent Document 2] Patent Publication No. 2022-31256 [Patent Document 3] JP 2022-36124 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, release films used for forming green sheets used in the manufacture of ceramic electronic components, and adhesive separators for optical components used in the manufacture of flat panel displays such as polarizing plates and optical filters are cut from large-area films to a predetermined film width for use. Therefore, in the methods described in Patent Documents 1, 2, and 3, when recycling polyester-based film substrates with narrow film widths, the amount of film that can be recovered with one equipment line is small, making the profitability low, and further improvements in the recovery method are required.

[0007] The present invention has been made in consideration of the above, and its object is to provide a method for efficiently recovering a high-purity polyester film from a long-length polyester film substrate having at least one coating film thereon, in a short period of time, in a profitable manner. [Means for solving the problem]

[0008] As a result of investigations to solve the above problems, the inventors of the present invention have come up with a technique of simultaneously conveying multiple long polyester film substrates and contacting them with a solvent. This technique allows multiple long polyester film substrates with narrow film widths to be simultaneously contacted with a solvent, so that the amount of film that can be recovered by one device can be significantly increased, and the present invention has been completed based on the findings.

[0009] In the recovery of polyester films, when recycling narrow polyester film substrates, the process includes a step of simultaneously contacting multiple long polyester film substrates with a solvent, which increases the amount of film that can be recovered using one equipment line and enables recovery with good profitability.

[0010] In addition, in the recovery of polyester films, when the long polyester film substrate is arranged on a roller, transported, and contacted with a solvent, the long polyester film substrate is provided with a meandering travel prevention function and a skewed travel prevention function, which prevents the film substrates from overlapping with each other during solvent treatment, thereby preventing deterioration of processability, and enables the recovery of high-purity polyester films efficiently in a short time with good profitability.

[0011] The present invention is configured as follows. 1. A method for recovering a polyester film by removing a coating film from a long polyester film substrate having at least one coating film on at least a portion of the long polyester film, the method comprising the following step (1): (1) contacting a plurality of the long polyester film substrates with a solvent at the same time 2. The method according to claim 1, wherein in step (1), the solvent is an alkaline processing liquid. 3. The method according to claim 2, further comprising the following step (4) after step (1): (4) A step of washing the long polyester film substrate with water 4. The method according to claim 3, further comprising the following step (2) prior to step (1): (2) A step of contacting the long polyester film substrate with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol dissolved therein. 5. The method according to claim 4, further comprising the following step (3) prior to step (1): (3) A step of performing at least one surface modification treatment selected from corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment. 6. A polyester film processing device that prevents meandering and skewed travel of multiple long polyester film substrates when the long polyester film substrates are arranged on rollers, transported, and contacted with a solvent. 7. A method for producing a polyester product, comprising extruding a polyester film recovered by the treatment device according to any one of 1 to 5 above or 6 above to produce a polyester product. Effect of the Invention

[0012] According to the polyester film recovery method of the present invention, a coating film can be efficiently removed from a long polyester film substrate having at least one coating film on at least a portion of the long polyester film, so that a high-purity polyester film can be recovered profitably from used polyester film that would previously have been discarded. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the present invention will be described in detail based on embodiments. In this specification, unless otherwise specified, the use of "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0014] The method for recovering a long polyester film of this embodiment (hereinafter also referred to as the method of this embodiment) is a method for recovering a long polyester film by removing a coating film from a long polyester film substrate including a long polyester film and at least one coating film provided on at least a portion of the long polyester film, and includes a step (1) of simultaneously transporting multiple long polyester film substrates and contacting them with a solvent.

[0015] <Polyester film> The polyester film in the present embodiment is formed by containing a polyester composition. The polyester composition is not particularly limited, but examples thereof include polyesters obtained by polycondensation of a dicarboxylic acid component and a diol component.

[0016] Examples of the dicarboxylic acid component include various dicarboxylic acid components such as aromatic dicarboxylic acids, linear aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, etc. Specific examples include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, and phthalic acid.

[0017] The diol component is preferably an aliphatic glycol, such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used.

[0018] The polyester film may be a homopolyester film or a copolymer polyester film, and may contain a third component other than the dicarboxylic acid component and the diol component as a copolymer component.

[0019] As the polyester-based film, a polyester-based film mainly composed of polyethylene terephthalate or polyethylene naphthalate is preferably used, more preferably polyethylene terephthalate. These may also be copolymerized polyesters.

[0020] The polyester film may be made of a polyester composition, or the composition may contain additives other than polyester, such as an endblocking agent, an antioxidant, a flame retardant, a fluorescent brightening agent, a matting agent, a plasticizer, or an antifoaming agent.

[0021] The polyester film may be a commercially available product, or when it is produced, it can be produced, for example, by the following method. For example, a polyester film is vacuum dried, fed to an extruder, melted at 260-300°C, extruded into a sheet from a T-shaped die, and wound around a mirror-finished casting drum with a surface temperature of 10-60°C using an electrostatic casting method, and cooled and solidified to produce an unstretched polyester film. The unstretched polyester film is stretched 2.5-5 times in the longitudinal direction between rolls heated to 70-130°C. Then, the film is continuously stretched 2.5-5 times in the width direction in a hot air zone heated to 70-150°C, and then introduced into a heat treatment zone at 190-240°C, where it is heat-treated for 5-40 seconds, and passed through a cooling zone at 100-200°C to complete the crystal orientation, thereby obtaining a polyester film. In addition, during the heat treatment, a relaxation treatment of 0.1-12% may be performed in the width direction or longitudinal direction as necessary.

[0022] In this embodiment, the thickness of the polyester film is not particularly limited, but is preferably 5 μm to 500 μm in consideration of handleability such as strength, rigidity, etc. The thickness of the polyester film is more preferably 10 μm to 200 μm, and particularly preferably 20 μm to 100 μm.

[0023] In this embodiment, the polyester film substrate in the polyester film recovery described later is a long polyester film substrate. In this specification, "long" means that the length of the long side is about twice or more longer than the length (width) of the short side in a plan view. If the polyester film substrate is long, its length can be about 100 m or more and 10,000 m or less, although it varies depending on, for example, the type of device used, and it can be directly recovered without crushing.

[0024] According to the method of the present embodiment, a plurality of polyester film substrates wound in a long shape (long polyester film substrates) can be simultaneously transported and contacted with a solvent at the same time, and the coating film can be efficiently removed from the long polyester film substrate. Preferably, a plurality of long polyester film substrates are simultaneously transported and contacted with a solvent described below, and then introduced directly into the next process (washing and drying) described below, and wound in a roll, that is, a roll-to-roll method is recommended.

[0025] The roll-to-roll method is a method of continuous transport of a flexible substrate wound in a roll via multiple guide rolls, where it is subjected to a specified treatment during transport and then wound up again in a roll. By processing multiple long polyester film substrates using the roll-to-roll method, the amount of polyester film that can be recovered in one series of equipment for the coating film removal process can be increased, and the process can be carried out continuously in a short time, which is very efficient.

[0026] <Coating film> In the polyester-based film substrate in this embodiment, the polyester-based film 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 film, such as a release film, an adhesive film, a hard coat film, an easy-adhesion film, and an antistatic film. In the polyester-based film substrate, these coating films may be present on at least one side of the polyester-based film, and may be present on both sides. Furthermore, in the polyester-based film substrate, the coating film may be contained alone, or two or more types may be laminated. In addition, the coating film may have not only a single function but also multiple functions.

[0027] The resin constituting the release film is not particularly limited as long as it is a resin generally used for release films, and examples thereof include silicone resins such as polydimethylsiloxane, amino resins such as melamine resins and urea resins, acrylic resins, epoxy resins, and alkyd resins. These resins may be used alone or in combination of two or more. The release film may contain a release agent such as silicone or wax.

[0028] The resin constituting the adhesive film includes an adhesive that is generally used for adhesive films. The type of the adhesive is not particularly limited, and examples thereof include acrylic adhesives, rubber adhesives, polyurethane adhesives, and silicone adhesives. The adhesive film may further contain a tackifier (tackifier resin).

[0029] The resin constituting the hard coat film is not particularly limited as long as it is a resin generally used for hard coat films, and examples thereof include acrylic resins, urethane resins, epoxy resins, etc. These resins may be used alone or in combination of two or more kinds.

[0030] The resin constituting the easy-adhesion film is not particularly limited as long as it is a resin generally used for easy-adhesion films, and examples thereof include polyester resin, acrylic resin, polycarbonate resin, polyurethane resin, polyvinyl alcohol resin, polyamide resin, polyvinyl acetate resin, etc. These resins may be used alone or in combination of two or more kinds.

[0031] 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 materials, etc.). These antistatic agents may be used alone or in combination of two or more.

[0032] The method for forming a coating film on a polyester-based film substrate is not particularly limited, but for example, the coating film can be formed on a polyester-based film using a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a wire bar coating method, a die coating method, a spray coating method, or the like.

[0033] The thickness of the coating film (when multiple functional films are present, the total thickness of these films) is preferably 0.005 μm or more and 50 μm or less. In order to effectively exert a predetermined function, the thickness is more preferably 0.01 μm or more. On the other hand, if the coating film is too thick, it may take a long time to remove the coating film.

[0034] <Recycling of polyester film> The method of the present embodiment is characterized by including a step (1) of simultaneously contacting a plurality of long polyester film substrates with a solvent. In the step (1), it is preferable to simultaneously transport a plurality of long polyester film substrates and contact at least the surface of each long polyester film substrate having a coating film with the solvent.

[0035] In addition, the processing device used in the method of this embodiment may be equipped with a function to prevent the long polyester film substrates from meandering and running obliquely, in order to prevent the long polyester film substrates from overlapping each other when the long polyester film substrates are arranged on a roller, transported, and contacted with a solvent.

[0036] (Simultaneous conveyance of multiple long polyester film substrates) By pulling out each film end from multiple long polyester film substrates and transporting them side by side on the same roller, it is possible to process multiple long polyester film substrates simultaneously using one line of equipment.

[0037] The method of simultaneously conveying a plurality of long polyester-based film substrates is not particularly limited as long as two or more rolls of long polyester-based film substrates can be conveyed side by side on the same roller. From the viewpoint of preventing meandering and oblique travel, it is preferable to convey two or more and ten or less rolls of long polyester-based film substrates side by side on the same roller. In addition, the upper limit of the conveying speed for conveying two or more rolls of long polyester-based film substrates is not particularly limited, but from the viewpoint of preventing meandering and oblique travel, it is preferably 250 m / min or less, more preferably 230 m / min or less, and even more preferably 200 m / min or less. The lower limit of the conveying speed is not particularly limited, but from the viewpoint of reducing the amount of processing in a processing device of the same size when the conveying speed is slow, or increasing the size of the processing device to maintain the same amount of processing, it is usually preferably 10 m / min or more, more preferably 50 m / min or more, and even more preferably 70 m / min or more.

[0038] Examples of the method for unwinding two or more rolls of the long polyester film substrate include a method of unwinding on the same axis in the unwinding section, and a method of unwinding on a separate axis for each roll in the unwinding section. Examples of the method for winding up two or more rolls of the long polyester film substrate include a method of winding on the same axis in the winding section, and a method of winding on a separate axis for each roll in the winding section. Among these, the method of unwinding on a separate axis for each roll and the method of winding on a separate axis for each roll are preferred from the viewpoint of preventing meandering and oblique running.

[0039] The method of the present embodiment includes a process of simultaneously conveying a plurality of long polyester film substrates and then contacting at least the coated surface of the polyester film substrate with a solvent, so that if the long polyester film substrates overlap each other, the processability will be poor. Therefore, the processing device used in the method of the present embodiment is preferably equipped with a meandering prevention function and a skewed travel prevention function. The meandering prevention function and the skewed travel prevention function are not particularly limited, but examples thereof include a method of guiding at least one side of the conveying roll, a method of making the film conveying roll into a conical surface shape and tilting the long polyester film substrate to one side, a method of providing grooves, cutting, or ridges on the conveying roll or belt, or a method of adjusting the rotation speed between two or more driving devices to keep the tension applied to the long polyester film substrate constant.

[0040] [Step (1) of contacting a long polyester film substrate with a solvent] The method of the present embodiment includes a step (1) of simultaneously transporting multiple long polyester film substrates and contacting at least the surface of the long polyester film substrate having a coating film with a solvent. This increases the amount of polyester film that can be recovered in a single series of coating film removal devices, and allows the processes to be carried out continuously in a short period of time, making the method extremely efficient.

[0041] The solvent used in step (1) of the method of the present embodiment is not particularly limited, but may be an alkaline treatment liquid. The above solvents may be used alone or in combination of two or more. In addition, the solvent may contain a surfactant, ultrafine bubbles, alcohol, etc.

[0042] In step (1), the solvent treatment may be carried out in one tank or in multiple tanks. When the treatment is carried out in multiple tanks, the types of solvents used may be different or the same.

[0043] The alkaline treatment liquid used in step (1) may be a solution in which an alkaline substance is dissolved. The alkaline substance is not particularly limited, but may be, for example, an inorganic alkaline agent such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide; sodium silicate, potassium silicate, ammonium silicate; sodium dibasic phosphate, potassium dibasic phosphate, ammonium dibasic 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, etc. Among these, alkali metal hydroxide is preferred, and sodium hydroxide and potassium hydroxide are more preferred. The alkaline substances may be used alone or in combination of two or more.

[0044] The solvent for dissolving the alkaline substance is not particularly limited, but may be, for example, water.

[0045] The concentration of the alkaline substance in the alkaline processing liquid is preferably 0.01% by mass to 15% by mass, more preferably 0.04% by mass to 15% by mass, and even more preferably 1% by mass to 10% by mass. If the concentration of the alkaline substance is too high, the polyester film tends to be easily damaged, and if the concentration is too low, there is a risk that the coating film cannot be sufficiently removed. If 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 film can be suppressed.

[0046] The solvent may contain a surfactant or ultrafine bubbles as an auxiliary agent to prevent reattachment of the removed coating film and to increase the efficiency of removing the coating film. The surfactant is not particularly limited, and examples thereof include nonionic surfactants, cationic surfactants, and anionic surfactants. The surfactants may be used alone or in combination of two or more kinds.

[0047] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

[0048] Examples of the cationic surfactant include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyldimethylbenzylammonium chloride.

[0049] 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, and sodium polyoxyethylene alkyl phenyl ether sulfate.

[0050] The solvent may contain other additives within the range that does not impair the effects of the present invention. Examples of the additives include antioxidants, pH adjusters, and antifoaming agents.

[0051] The temperature of the solvent is preferably less than 100°C, more preferably 65°C or more and less than 100°C, and even more preferably 65 to 95°C. When the temperature of the solvent is 65°C or more, it is preferable because the physicochemical properties of the polyester film are not changed and a high-quality polyester film with few impurities can be obtained without spending excessive time. In addition, by making the temperature of the solvent less than 100°C, it is possible to achieve the above at normal pressure, prevent the equipment from becoming large-sized, and suppress the occurrence of hydrolysis or dissolution of the polyester film due to heating.

[0052] The contact time between the solvent and the long polyester film substrate 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 particularly preferably more than 0 seconds and less than 120 seconds. If the treatment time is too long, the polyester film tends to be easily damaged, and the polyester film dissolves in the alkaline treatment liquid, which may increase the load when the alkaline treatment liquid is discharged. The treatment time with the solvent is sufficient so that the coating film can be sufficiently dissolved and swollen, and if the treatment time is too short, the coating film may not be sufficiently removed, so 1 second or more is more preferable, and 5 seconds or more is even more preferable. If the treatment time with the solvent is within the above range, the effect of removing the coating film can be obtained and damage to the polyester film can be suppressed.

[0053] In step (1), the treatment with a solvent can be appropriately selected depending on the type and thickness of the long polyester film or coating film. In order to obtain a high-quality polyester film with few impurities, specifically, for example, it is preferable to contact the long polyester film substrate 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 more than 0 seconds and less than 700 seconds, and it is more preferable to contact the polyester film substrate with an alkaline treatment liquid having a temperature of 65°C or higher and lower than 100°C and an alkaline concentration of 0.04% by mass or higher and 15% by mass or lower for 1 second or higher and 180 seconds or lower.

[0054] [Step (2) of contacting with a surfactant, an alcohol, or an aqueous solution containing a surfactant or an alcohol] The method of the present embodiment may include a step (2) of contacting at least the surface of the long polyester film substrate having a coating film with a surfactant, alcohol, or an aqueous solution of a surfactant or alcohol, prior to the step (1) of contacting the long polyester film substrate with a solvent. The surface of the polyester film substrate is hydrophilized by contacting the surface of the long polyester film substrate with a surfactant, alcohol, or an aqueous solution of a surfactant or alcohol and allowing the surfactant, alcohol, or the aqueous solution of a surfactant or alcohol to penetrate into the coating film of the long polyester film substrate. By contacting the surface of the long polyester film substrate with a solvent in a previously hydrophilized state, the penetration of the solvent is promoted, and the coating film can be easily and efficiently removed from the polyester film substrate in a short time.

[0055] The method of contacting the surfactant, alcohol, or an aqueous solution of a surfactant or alcohol is not particularly limited as long as the surface of the long polyester film substrate having at least a coating film can be contacted. For example, a method of immersing the long polyester film substrate in a cleaning tank containing a surfactant, alcohol, or an aqueous solution of a surfactant or alcohol, a coating method, a spraying method, etc. can be mentioned. Among these, the immersion method is preferred from the viewpoint of the permeability of the surfactant, alcohol, or an aqueous solution of a surfactant or alcohol into the coating film.

[0056] The alcohol is not particularly limited, and may be a monohydric alcohol or a polyhydric alcohol, and may be a lower alcohol or a higher alcohol.

[0057] Examples of monohydric alcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonylnol, decylnol, undecylnol, dodecylnol, methoxyethanol, methoxypropanol, methoxybutanol, methoxyethoxyethanol, ethoxyethanol, ethoxyethoxyethanol, ethoxypropanol, ethoxybutanol, butoxyethanol, butoxypropanol, and butoxybutanol.

[0058] Examples of polyhydric alcohol solvents include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, glycerin, and polyoxyalkylene polyols.

[0059] Among these, monohydric lower alcohols such as methanol, ethanol, 1-propanol (normal propanol), and 2-propanol (isopropanol) are more preferred, at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol is even more preferred, and methanol and ethanol are particularly preferred. The alcohols may be used alone or in combination of two or more kinds.

[0060] The concentration of the alcohol or the aqueous solution in which the alcohol is dissolved is preferably 0.1% by mass to 100% by mass, and the lower limit is more preferably 30% by mass or more. If the alcohol concentration is too low, there is a risk that the coating film cannot be sufficiently removed. If the concentration of the alcohol or the aqueous solution in which the alcohol is dissolved is 30% by mass or more, a sufficient coating film removal effect can be obtained.

[0061] The temperature of the alcohol or the aqueous solution containing the alcohol may be adjusted depending on the alcohol used, but is preferably 50° C. or less, and more preferably room temperature of 5 to 30° C. If the temperature of the alcohol or the aqueous solution containing the alcohol is too high, the alcohol may boil. If the temperature of the alcohol or the aqueous solution containing the alcohol is 50° C. or less, the alcohol is below the boiling point, and therefore the effect of removing the coating film is promoted.

[0062] The surfactant is not particularly limited, but may be at least one surfactant selected from the group consisting of nonionic surfactants, cationic surfactants, and anionic surfactants. In particular, nonionic surfactants are preferred. The surfactants may be used alone or in combination of two or more.

[0063] 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 moreoleate, and polyoxyethylene sorbitan trioleate; and glycerin fatty acid esters such as stearic acid monoglyceride.

[0064] Examples of the cationic surfactant include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyldimethylbenzylammonium chloride.

[0065] 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, and sodium polyoxyethylene alkyl phenyl ether sulfate.

[0066] The concentration of the surfactant or the aqueous solution in which the surfactant is dissolved is preferably 0.00001% by mass to 100% by mass, more preferably 0.0001% by mass to 100% by mass, further preferably 0.001% by mass to 50% by mass, and particularly preferably 0.01% by mass to 1% by mass. If the surfactant concentration is too low, there is a risk that the coating film cannot be sufficiently removed. If the concentration of the surfactant or the aqueous solution in which the surfactant is dissolved is 0.00001% by mass to 100% by mass, a sufficient coating film removal effect can be obtained, which is preferable.

[0067] The temperature of the surfactant or the aqueous solution in which the surfactant is dissolved may be adjusted depending on the surfactant used, but is preferably 50° C. or lower. If 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 to a high concentration, which promotes the removal effect of the coating film. In addition, since nonionic surfactants do not dissolve in water if the temperature is too high, it is preferable to treat them at a temperature below the cloud point of the surfactant.

[0068] The contact time between the long polyester film substrate and the surfactant, alcohol, or the aqueous solution in which the surfactant or alcohol is dissolved is preferably within 120 seconds, more preferably 0.001 to 60 seconds, even more preferably 0.001 to 10 seconds, and particularly preferably 0.1 to 10 seconds. If the contact time with the long polyester film substrate is too short, there is a risk that the coating film cannot be sufficiently removed, and if the contact time is too long, there is a risk that the device size becomes large, resulting in poor economic efficiency and operability. If the contact time with the polyester film substrate is within 120 seconds, economic efficiency and operability are good, and the effect of removing the coating film can be enhanced.

[0069] The surfactant, alcohol, or the aqueous solution containing the surfactant or alcohol may contain ultra-fine bubbles as an auxiliary agent to enhance the efficiency of removing the coating film. The alcohol or the aqueous solution containing the alcohol may contain the surfactant, and the surfactant or the aqueous solution containing the surfactant may contain the alcohol.

[0070] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

[0071] Examples of the cationic surfactant include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyldimethylbenzylammonium chloride.

[0072] 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, and sodium polyoxyethylene alkyl phenyl ether sulfate.

[0073] [Surface modification process (3)] The method of the present embodiment may include a step (3) of performing a surface modification treatment on the surface of the coating film on the long polyester film substrate prior to step (1) in order to increase the affinity with a surfactant, alcohol, or an aqueous solution in which a surfactant or alcohol is dissolved, and further with the solvent. The surface modification treatment is not particularly limited, and a known method can be adopted, such as a corona discharge treatment, a plasma treatment, a glow discharge treatment, a flame treatment, or an ultraviolet treatment, and it is preferable to perform at least one treatment selected from the group consisting of these.

[0074] The surface modification treatment may be carried out before step (1), in which the long polyester film substrate is contacted with a solvent. However, in order to increase the affinity with a surfactant, alcohol, or an aqueous solution in which a surfactant or alcohol is dissolved, it is more preferable to carry out the surface modification treatment before step (2), in which the substrate is contacted with a surfactant, alcohol, or an aqueous solution in which a surfactant or alcohol is dissolved.

[0075] If an analysis using X-ray photoelectron spectroscopy after the surface modification treatment shows that the proportion of C-C bonds and C-H bonds has decreased by 0.1% or more, the effect of increasing the affinity with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol, or an alkaline treatment liquid can be obtained.

[0076] For corona discharge treatment, the treatment intensity is 10 to 1000 Wmin / m 2 More than 20 to 200 Wmin / m is preferable. 2 More preferably, 40 to 120 Wmin / m 2 If the treatment intensity is too high, the polyester film tends to be easily damaged, and if the treatment intensity is too low, the alkali treatment time becomes long, and the polyester film tends to be easily damaged. The power density of the corona discharge machine used is preferably 4 to 20 W / cm. 2 If so, the surface treatment can be performed uniformly.

[0077] For UV treatment, the irradiation intensity is 0.5 to 40 mW / cm 2 is preferably 10 to 40 mW / cm 2 More preferably, 15 to 40 mW / cm 2is more preferable. If the irradiation intensity is too high, the polyester film tends to be easily damaged, and if the irradiation intensity is too weak, the alkali treatment time becomes long, and the polyester film tends to be easily damaged. 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 the manufacturing cost and also tends to cause the polyester film to be easily damaged. If the ultraviolet irradiation time is too short, there is a risk that the coating film cannot be sufficiently removed. In addition, it is preferable to use an electromagnetic wave of invisible light that is shorter than visible light and longer than soft X-rays, with a wavelength of 10 to 400 nm for the ultraviolet light to be irradiated. Examples of sources of ultraviolet light include known lamps such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, and metal halide lamps, and low pressure mercury lamps are preferred.

[0078] [Step (4) of performing water washing treatment] The method of the present embodiment preferably includes a step (4) of washing the long polyester film substrate with water after the step (1) of contacting the long polyester film substrate with a solvent. The washing with water is performed to remove a trace amount of the coating film remaining on the polyester film after the step (1) and to remove the solvent remaining on the polyester film after the above treatment.

[0079] The temperature for the water washing treatment in step (4) is not particularly limited, but for example, washing with warm water of about 40° C. to 100° C. will more effectively exhibit the above effects.

[0080] Examples of the method of washing with water include a method of spraying water onto the polyester film from which the coating film has been removed, a method of immersing the polyester film in a water tank, etc. During the water washing treatment, physical washing using a roll brush, microbubbles, water flow, etc. may be performed.

[0081] [Drying treatment] After washing with water, it is preferable to carry out a drying treatment in order to remove water remaining on the polyester film.

[0082] The drying time is preferably 10 seconds or more and 5 minutes or less. When the drying time is 10 seconds or more, the drying is sufficient and blocking can be suppressed. It is more preferably 30 seconds or more. In addition, when the drying time is 5 minutes or less, deformation of the polyester film can be prevented.

[0083] The drying method is not particularly limited, and examples thereof include hot air drying in which hot air is blown onto the substrate, and heat drying in which a non-contact heater is used.

[0084] (multiple processing) The above steps (1) to (3) may be carried out multiple times. By carrying out these treatments multiple times, the polyester film can be treated in a short time without being damaged, such as by a decrease in intrinsic viscosity.

[0085] <Molding of Recycled Polyester Film> The method for producing a polyester product of the present embodiment includes extruding the polyester film recovered by the method of the present embodiment to produce a polyester product.

[0086] Specifically, the recovered polyester film can be pelletized and then molded into various polyester products such as polyester films by melt extrusion or the like.

[0087] The polyester product is not particularly limited, and can be used for ordinary polyester applications, such as polyester films, PET bottles, polyester fibers, polyester sheets, polyester containers, etc. Specifically, it can be used as polyester films, for example.

[0088] The thickness of the polyester film is not particularly limited, but can be set appropriately within the range of 10 to 50 μm. In addition, a coating film can be formed as necessary. Examples of the coating film include a release film, an adhesive film, a hard coat film, an easy-adhesion film, and an antistatic film. In addition, the coating film can be removed from the recovered polyester film, and the polyester film can be recovered again and extrusion-molded to produce a polyester product.

[0089] The polyester products produced from the recycled polyester films are not particularly limited, and can be used for ordinary polyester applications, such as the polyester films, PET bottles, polyester fibers, polyester sheets, and polyester containers described above.

[0090] As described above, the present specification discloses the following configurations. <1> A method for recovering a polyester film by removing a coating film from a long polyester film substrate having at least one coating film on at least a portion of the long polyester film, the method comprising the following step (1): (1) contacting a plurality of the long polyester film substrates with a solvent at the same time <2> In the step (1), the solvent is an alkaline processing liquid. <1> The method described above. <3> The method further comprises the following step (4) after the step (1): <1> or <2> The method described above. (4) A step of washing the long polyester film substrate with water <4> The method further comprises the following step (2) before the step (1): <1> ~ <3> 2. The method according to claim 1 , (2) A step of contacting the long polyester film substrate with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol dissolved therein. <5> The method further comprises the following step (3) before the step (1): <1> ~ <4> 2. The method according to claim 1 , (3) A step of performing at least one surface modification treatment selected from corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment. <6> A polyester film processing apparatus that prevents meandering and skewed travel of a plurality of long polyester film substrates when the long polyester film substrates are arranged on a roller, transported, and contacted with a solvent. <7> The above <1> ~ <5> 2. The method according to claim 1 , <6> 2. A method for producing a polyester product, comprising extruding a polyester film recovered by the treatment device according to claim 1 to produce a polyester product. EXAMPLES

[0091] Hereinafter, the embodiment of the present invention will be described in more detail based on examples, but the present invention is not necessarily limited thereto. The usefulness of the coating film removal method according to the present invention can be expressed by the coating film removal ability. In the following, unless otherwise specified, "%" means % by mass, and "parts" means parts by mass.

[0092] (Evaluation of coating film removal) Each characteristic was measured as follows.

[0093] 1. Evaluation of meandering and diagonal running properties The transport state of the polyester film substrate was photographed with a camera, the right and left end positions of the film during transport were confirmed, and the difference between the right and left end positions of the film at the unwinding section was measured to evaluate the meandering and skewed running properties. The meandering and oblique running properties were compared and evaluated according to the following criteria, where "◯" and "Δ" are acceptable and "×" is unacceptable. [Evaluation Criteria] ○ (Good): The difference between the right and left ends of the film at the unwinding section and the right and left ends of the film being transported is 0.5 cm or less △ (Acceptable): The difference between the right and left ends of the film at the unwinding section and the right and left ends of the film being transported is more than 0.5 cm and less than 1.5 cm. × (Not acceptable): The difference between the right and left ends of the film at the unwinding section and the right and left ends of the film being transported is 1.5 cm or more.

[0094] 2. Evaluation of treatability The collected polyester film was cut into small pieces, then molded into a cylindrical shape using a melt press, and the silicon (Si) content was measured using an X-ray fluorescence analyzer (Rigaku Corporation, "Model 3270"). The Si content was quantified using the X-ray fluorescence measurement method, based on a calibration curve of X-ray fluorescence intensity that had been prepared in advance. The processability of each Example or Comparative Example was evaluated based on the obtained Si content according to the following criteria, where "◎", "◯" and "△" are acceptable, and "×" is unacceptable. [Evaluation Criteria] ◎ (Excellent): The Si content is below the detection limit (100 ppm by mass). ○ (Good): Si content is more than 100 mass ppm and less than 300 mass ppm △ (OK): Si content is 300 mass ppm or more and less than 500 mass ppm × (Not acceptable): Si content is 500 mass ppm or more

[0095] 3. Evaluation of treated and recovered amount The amount of pellets obtained from one series of equipment was evaluated according to the following criteria, where "◎", "◯" and "△" are acceptable, and "×" is unacceptable. [Evaluation Criteria] ◎ (Excellent): The amount of pellets obtained is 1100g / min or more per one equipment line. ○ (Good): The amount of pellets obtained is 1100 g / min or more and less than 700 g / min per one equipment line. △ (Acceptable): The amount of pellets obtained is 700g / min or more and less than 300g / min per one equipment line. × (Not acceptable): The amount of pellets obtained is 300 g / min or less per one equipment line.

[0096] (Preparation of sample film) A laminated polyester film having a release film was prepared as a sample film as follows.

[0097] 1. A polyethylene terephthalate film (Toray Industries, Inc.'s "Lumirror" T60, thickness 38 μm, intrinsic viscosity 0.61) was prepared as a polyester film. One side of the film was coated with a 5% toluene solution of a curable silicone resin (containing 100 parts of Toray Dow Corning Silicones Co., Ltd.'s LTC-350B and 0.8 parts of the same company's curing agent SRX-212) using a bar coater, and heated at 100°C in a tunnel oven to produce a release film, which was then wound up.

[0098] 2. Application of ceramic slurry and conductive paste A ceramic slurry having the following composition was uniformly applied to the release layer surface of the release film using a blade coater. This was dried in a tunnel oven at 85°C to form a ceramic layer having 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

[0099] 3. Peeling off of ceramic film and internal electrodes On the release film on which the ceramic layer and electrodes were formed, a 10 cm x 10 cm slit was made only in the coating film on the part on which the ceramic layer and electrodes were formed, and then the ceramic layer and the electrode were sucked with a vacuum suction machine and peeled off from the release film to obtain a long sample film. Note that some of the ceramic layer and the electrode were still attached to the surface of the release layer of the sample film, and could not be peeled off.

[0100] [Example 1] (Surface modification treatment) The release film side of the sample film was treated with a corona discharge treatment device at a power density of 8 W / cm 2 , Processing intensity 60Wmin / m 2 A corona discharge treatment was carried out.

[0101] (Transportation method) Four rolls of long polyester-based film substrate were unwound on separate shafts at the unwinding section, lined up on the same roller, transported at a speed of 70 m / min, and each treatment described below was carried out during transport, after which each roll was wound up on a separate shaft at the winding section. Method 1: A transport roller with plates on both sides was installed, and the film was transported, and the above-mentioned "evaluation of meandering running property and oblique running property" was performed.

[0102] (Step of contacting with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol) The corona discharge-treated sample film was immersed for 1 second in a 0.03 wt % aqueous solution of a nonionic surfactant ("Polyoxyethylene (10) Octylphenyl Ether" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at room temperature (25°C).

[0103] (Step of Contacting with Alkaline Processing Liquid) 1000 L of a mixed aqueous solution of 3% sodium hydroxide and 0.03% nonionic surfactant ("Polyoxyethylene (10) octylphenyl ether" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was heated to 80°C. The sample film was conveyed at 70 m / sec and exposed to the alkaline processing solution for 60 seconds to remove the release layer and obtain a recovered polyester film. The recovered polyester film was used to carry out the above-mentioned "evaluation of processability".

[0104] (Washing, drying, pelletizing) The sample film (recovered polyester film) was immersed in a water tank for 45 seconds, and then dried by blowing hot air onto it. The dried sample film was crushed, put into an extruder, melted, and pelletized. The obtained pellets were used to perform the "evaluation of the amount of processed and recovered" described above.

[0105] (Manufacture of polyester film) 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 an electrostatically charged casting drum at 20°C to obtain an unstretched sheet. This unstretched sheet was stretched 3.1 times in the longitudinal direction using a stretching roll heated to 90°C, then stretched 3.7 times in the transverse direction at 120°C using a tenter-type stretching machine, and then heat-set at 230°C and wound up on a roll.

[0106] [Example 2] A polyester film was produced in the same manner as in Example 1, except that two rolls of the long polyester film substrate were transported side by side on the same roller.

[0107] [Example 3] A polyester film was produced in the same manner as in Example 1, except that six rolls of the long polyester film substrate were transported side by side on the same roller.

[0108] [Example 4] A polyester film was produced in the same manner as in Example 1, except that eight rolls of the long polyester film substrate were transported side by side on the same roller.

[0109] [Example 5] A polyester film was produced in the same manner as in Example 1, except that 10 rolls of the long polyester film substrate were transported side by side on the same roller.

[0110] [Example 6] A polyester film was produced in the same manner as in Example 1, except that, as a measure to prevent meandering and skewed travel, method 2 was used: the film transport roll was made to have a conical surface, and the film was transported while being shifted to one side by inclination.

[0111] [Example 7] A polyester film was produced in the same manner as in Example 1, except that, as a measure to prevent meandering and skewed running, method 3 was used: conveying rolls and belts were provided with grooves for conveyance.

[0112] [Example 8] A polyester film was produced in the same manner as in Example 1, except that, as a measure to prevent meandering and skewed running, method 4: transport was performed with ridges provided on the transport rolls or belts.

[0113] [Example 9] A polyester film was produced in the same manner as in Example 1, except that, as a measure to prevent meandering and skewed traveling, Method 5 was used: The rotation speed between two or more driving devices was adjusted to keep the tension applied to the film substrate constant during transportation.

[0114] [Example 10] A polyester film was produced in the same manner as in Example 1, except that the conveyance was carried out without carrying out any of Methods 1 to 5, which are measures for preventing meandering and skewed transport.

[0115] [Example 11] A polyester film was produced in the same manner as in Example 1, except that 4 rolls of the long polyester film substrate were transported at 50 m / min.

[0116] [Example 12] A polyester film was produced in the same manner as in Example 1, except that four rolls of the long polyester film substrate were transported at 200 m / min.

[0117] [Example 13] A polyester film was produced in the same manner as in Example 1, except that the surface modification treatment was not carried out.

[0118] [Example 14] A polyester film was prepared in the same manner as in Example 1, except that the step of contacting the film with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol was not carried out.

[0119] [Comparative Example 1] Except for the fact that only one roll of the long polyester film substrate was arranged on a roller and transported, the same surface modification treatment as in Example 1 and the process of contacting with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol were carried out, and then the polyester film was contacted with an alkaline treatment liquid, washed with water, and dried in the same manner as in Example 1 to produce a polyester film.

[0120] [Comparative Example 2] As in Example 1, four rolls of long polyester film substrate were lined up on the same roller and transported, and the steps of surface modification treatment and contact with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol were carried out. After that, the step of contact with an alkaline treatment liquid described in Example 1 was not carried out, and the substrate was washed with water and dried to produce a polyester film.

[0121] The evaluation results for Examples 1 to 14 and Comparative Examples 1 and 2 are shown in Tables 1 to 4 below.

[0122] [Table 1]

[0123] [Table 2]

[0124] [Table 3]

[0125] [Table 4]

[0126] As shown in Tables 1 to 4, the method of the present invention makes it possible to efficiently remove a coating film from a long polyester film substrate having at least one coating film, and to efficiently recover the polyester film and produce polyester products using this polyester film as part of the raw material.

[0127] In addition, the results of Example 1 showed that by simultaneously transporting multiple long polyester film substrates and then carrying out a process of contacting at least the surface of the long film substrate having a coating film with a solvent, it is possible to remove a large amount of the coating layer from the film in a short period of time.

[0128] In contrast, in Comparative Example 1, in which only one roll of long polyester film substrate was transported, the amount of film from which the coating film could be removed using the same equipment for the same period of time was smaller than that of Example 1. Also, in Comparative Example 2, in which the contact step with the alkaline processing solution was not performed, the coating film could not be removed.

[0129] As described above, according to the method of the present invention, the coating layer can be efficiently removed by simultaneously contacting the multiple long polyester film substrates with a solvent, and it is possible to recover the polyester film and efficiently manufacture polyester products using the polyester film as a part of the raw material. In addition, by taking measures to prevent meandering and oblique running, the coating film can be efficiently removed in a short time without reducing the processability in the solvent due to the films overlapping each other, which is extremely useful.

Claims

1. A method for recovering a polyester film by removing a coating film from a long polyester film substrate having at least one coating film on at least a portion of the long polyester film, the method comprising the following step (1): (1) A step of simultaneously contacting a plurality of the long polyester film substrates with a solvent

2. The method according to claim 1 , wherein in step (1), the solvent is an alkaline processing liquid.

3. The method according to claim 2, further comprising the following step (4) after step (1): (4) A step of washing the long polyester film substrate with water

4. The method according to claim 3, further comprising the following step (2) prior to step (1): (2) A step of contacting the long polyester film substrate with a surfactant, alcohol, or an aqueous solution containing a surfactant or alcohol dissolved therein.

5. The method according to claim 4, further comprising the following step (3) prior to step (1): (3) A step of performing at least one surface modification treatment selected from a corona discharge treatment, a plasma treatment, a glow discharge treatment, a flame treatment, and an ultraviolet treatment.

6. A polyester film processing apparatus that prevents meandering and skewed travel of a plurality of long polyester film substrates when the long polyester film substrates are arranged on a roller, transported, and contacted with a solvent.

7. A method for producing a polyester product, comprising extruding a polyester film recovered by the method according to any one of claims 1 to 5 or the treatment device according to claim 6 to produce a polyester product.

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