Method for recovering polyester-based supports and method for manufacturing polyester products

Abstract

To provide an optimal method for recovering a polyester-based support, including removing and recovering the coating layer from a polyester film having at least one coating layer. [Solution] Using a polyester film having a polyester support and at least one coating layer, the depth profile of the polyester film was measured by time-of-flight secondary ion mass spectrometry, and Si2HO5 was detected at a position 1 nm deep from the surface of the coating layer. - Ionic strength of 0.1 or higher, Si2CH3O4 - A method for recovering a polyester support by treating the polyester film with an alkaline treatment solution and then performing a water-washing and peeling procedure, with the ion strength set to 0.5 or higher. (The ion strength in the depth profile is determined by the ions (C) derived from the polyester of the base material.) 10 H7O4 - (Normalized by setting the average ionic intensity in the region where the intensity is constant to 1.)

Description

[Technical Field]

[0001] The present invention provides a method for recovering a polyester film-based support that is optimal for removing and recovering a coating layer from a polyester film having at least one coating layer on a polyester-based support, and a method for manufacturing a polyester product. [Background technology]

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

[0003] As the aforementioned polyester film is used in a wide variety of applications, the amount of waste and used products generated is increasing, leading to a deterioration of the global environment. To resolve this problem and promote the recycling of polyester film, it is preferable to remove the coating layer from the polyester support and reuse it as polyester film.

[0004] Examples of such technologies include Patent Documents 1, 2, 3, and 4. Patent Documents 1 to 3 describe a technique for recovering a polyester support by contacting a long polyester film having a coating layer with an alkaline treatment solution to remove the coating layer. Furthermore, it is described that by performing corona treatment before the step of removing the coating layer with the alkaline treatment solution, the surface of the coating layer can be made hydrophilic and chemical bonds can be broken, thereby effectively removing the coating layer. Patent Document 4 describes a method for removing a functional layer by a polishing step of polishing the surface of a laminated polyester film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-291690 [Patent Document 2] Japanese Patent Publication No. 2020-90094 [Patent Document 3] Japanese Patent Publication No. 2023-79089 [Patent Document 4] Japanese Patent Publication No. 2022-130226 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, after treatment with an alkaline treatment solution, residue from the coating layer remains, resulting in insufficient removal of the coating layer and preventing the rapid recovery of the polyester support. Further improvements are needed.

[0007] The present invention has been made in view of the above, and its objective is to provide a method for recovering polyester-based supports that facilitates the removal and recovery of coating layers from polyester films having at least one coating layer during the recycling process. [Means for solving the problem]

[0008] As a result of studies conducted to solve the above-mentioned problems, the inventors focused on the Si oxide and siloxane from which the methyl group has been removed contained in the coating layer when removing the coating layer from a polyester film. By adjusting these components and treating the polyester film with an alkaline treatment solution followed by a water-wash stripping treatment, they discovered that the remaining coating layer residue could be sufficiently removed, thus completing the present invention.

[0009] Furthermore, the inventors discovered that in polyester films, the mineralization of polydimethylsiloxane progresses not only on the outermost surface of the coated layer but also within the coated layer itself. In other words, in this invention, Si2HO5 - Ions, Si2CH3O4 - By using a polyester film with adjusted ion strength, the coated layer can be removed efficiently in a short time, and the polyester support can be recovered.

[0010] The structure of the present invention is as follows. (1) Using a polyester film having a polyester support and at least one coating layer, the Si2HO5 at a position with a detection depth of 1 nm from the coating layer surface in the measurement of the depth profile by time-of-flight secondary ion mass spectrometry of the polyester film - The intensity of the ions is 0.1 or more, and the intensity of the Si2CH3O4 - ions is 0.5 or more. A method for recovering a polyester-based support, which comprises treating the polyester film with an alkaline treatment solution and subjecting it to a water washing and peeling treatment. (The intensity of the ions in the depth profile is normalized with the average ion intensity in the region where the intensity of the ions derived from the polyester of the substrate (C 10 H7O4 - ) becomes constant as 1) (2) In the measurement of the depth profile by time-of-flight secondary ion mass spectrometry, the ratio of the ion intensity at a position of 1 nm to the ion intensity at a position of 10 nm from the coating layer surface for the Si2HO5 - ions and the Si2CH3O4 - ions is 1.0 or less. The method for recovering a polyester-based support according to (1), which comprises treating the polyester film. (3) The method for recovering a polyester-based support according to (1) or (2), which comprises performing at least one surface treatment selected from the group consisting of corona treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment. (4) The method for recovering a polyester-based support according to (1), which comprises treating with a sponge roll in the water washing and peeling treatment. (5) The method for recovering a polyester-based support according to (4), wherein the speed ratio V1 / V2 of the peripheral speed (V1) of the sponge roll to the conveyance speed (V2) of the polyester film is less than 2.0. (6) A method for manufacturing a polyester product, which comprises using the polyester-based support recovered by the method for recovering a polyester-based support according to (1) or (5) in extrusion molding.

Effects of the Invention

[0011] According to the method for recovering the polyester-based support of the present invention, by focusing on the Si oxide contained in the coating layer and the siloxane from which the methyl group has been removed, the polyester film in which the inorganicization of polydimethylsiloxane, which is the main component of the coating layer, has progressed is treated with an alkaline treatment liquid, and a water washing and peeling treatment is performed, so that the remaining coating layer residue can be sufficiently removed, and the polyester-based support can be efficiently recovered.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail based on embodiments. In this specification, "~" indicating a numerical range is used to mean including the numerical values described before and after as the lower limit value and the upper limit value unless otherwise specified.

[0013] The method for recovering the polyester-based support in the present invention has at least one coating layer, and in the measurement of the depth profile by time-of-flight secondary ion mass spectrometry, Si2HO5 at a detection depth of 1 nm from the coating layer surface - The intensity of the ions is 0.1 or more, and Si2CH3O4 - The polyester film in which the intensity of the ions is 0.5 or more is treated with an alkaline treatment liquid and subjected to a water washing and peeling treatment.

[0014] 〈Polyester-based support〉 The polyester-based support in the present invention is formed by 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.

[0015] Examples of the dicarboxylic acid component include various dicarboxylic acid components such as aromatic dicarboxylic acids, chain aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. Specifically, for example, terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, etc. are mentioned.

[0016] The diol component is preferably an aliphatic glycol, such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, or neopentyl glycol. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used.

[0017] The polyester support may be a homopolyester support or a copolymerized polyester support. Furthermore, the polyester support may contain a third component other than the dicarboxylic acid and diol components as a copolymerized component.

[0018] As the polyester support, a polyester support mainly composed of polyethylene terephthalate or polyethylene naphthalate is preferably used. More preferably, polyethylene terephthalate is used. These may also be copolymerized polyesters.

[0019] The polyester support may consist of a polyester composition, or it may contain additives other than polyester. Examples of additives include end-capping agents, antioxidants, flame retardants, fluorescent whitening agents, matting agents, plasticizers, or defoaming agents.

[0020] A commercially available polyester support can be used, or if it is to be manufactured, it can be produced by, for example, the following method. For example, after vacuum drying the polyester composition, it is fed into an extruder, melted at 260-300°C, extruded into a sheet through a T-shaped die, and wound onto a mirror-finish casting drum with a surface temperature of 10-60°C using an electrostatic casting method, where it is cooled and solidified to produce an unstretched polyester support. The unstretched polyester film is stretched 2.5-5 times in the longitudinal direction between rolls heated to 70-130°C. Subsequently, it is continuously stretched 2.5-5 times in the width direction in a heated hot air zone at 70-150°C, then led to a heat treatment zone at 190-240°C, subjected to heat treatment for 5-40 seconds, and then completed crystal orientation through a cooling zone at 100-200°C to obtain a polyester film. In addition, a relaxation treatment of 0.1-12% in the width direction or longitudinal direction may be applied as needed during the above heat treatment.

[0021] In the present invention, the thickness of the polyester support is not particularly limited, but considering handling properties such as strength and rigidity, it is preferably 5 μm to 500 μm. More preferably, the thickness of the polyester support is 10 μm to 200 μm, and particularly preferably 20 μm to 100 μm.

[0022] <Coated layer> The polyester film in this invention has at least one coating layer. Here, the coating layer is a layer that can impart various functions to the polyester support, and examples include a release layer, an adhesive layer, a hard coat layer, an easy-adhesion layer, and an antistatic layer. These coating layers may be present on at least one side of the polyester film, or on both sides. Furthermore, the coating layer may be present alone, or two or more layers may be laminated together. In addition, the coating layer may have not only a single function but also multiple functions.

[0023] The resin constituting the release layer is not particularly limited as long as it is a resin commonly used for release layers. Examples include silicone resins such as polydimethylsiloxane, amino resins such as melamine resin and urea resin, acrylic resins, epoxy resins, and alkyd resins. These resins may be used individually or in combination of two or more. The release layer may also contain release agents such as silicone and wax. Among these, it is preferable to include a silicone resin in order to determine the degree of mineralization of polydimethylsiloxane.

[0024] The resin constituting the above-mentioned adhesive layer includes an adhesive commonly used in adhesive layers. The type of adhesive is not particularly limited, and examples include acrylic adhesives, rubber adhesives, polyurethane adhesives, and silicone adhesives. Furthermore, the above-mentioned adhesive layer may further contain a tackifier (tackifying resin), etc.

[0025] The resin constituting the hard coat layer is not particularly limited as long as it is a resin commonly used for hard coat layers, and examples include acrylic resins, urethane resins, and epoxy resins. These resins may be used individually or in combination of two or more.

[0026] The resin constituting the easy-adhesion layer is not particularly limited as long as it is a resin commonly used for easy-adhesion layers, and examples include polyester resin, acrylic resin, polycarbonate resin, polyurethane resin, polyvinyl alcohol resin, polyamide resin, and polyvinyl acetate resin. These resins may be used individually or in combination of two or more.

[0027] The resin constituting the antistatic layer is not particularly limited as long as it is a resin commonly used for antistatic layers. Preferably, the antistatic layer further contains an antistatic agent. Examples of such antistatic agents include nonionic, cationic, anionic, or amphoteric surfactants (conductive polymers such as polypyrrole and polyaniline, metal oxide fillers, and carbon-based materials). These antistatic agents may be used alone or in combination of two or more.

[0028] The method for forming the coated layer is not particularly limited, but for example, it can be formed on a polyester support using methods such as reverse coating, gravure coating, rod coating, bar coating, wire bar coating, die coating, or spray coating.

[0029] The thickness of the coating layer (or the total thickness of multiple functional layers if applicable) is preferably 0.005 μm or more and 50 μm or less. More preferably, it is 0.01 μm or more in order to effectively perform the desired function. On the other hand, if the coating layer is too thick, it may take time to remove it.

[0030] The polyester film in this invention is characterized by the presence of Si2HO5 at a detection depth of 1 nm from the surface of the coated layer, as measured by time-of-flight secondary ion mass spectrometry. - Ionic strength of 0.1 or higher, Si2CH3O4 - The ion intensity is adjusted to 0.5 or higher. Here, the depth profile is the ion (C) derived from the polyester substrate. 10 H7O4 - The average intensity in the region where the intensity of ) becomes constant was normalized to 1. - and Si2CH3O4 - The increased ionic strength indicates that mineralization of the polydimethylsiloxane constituting the coating layer is occurring, which can be achieved by applying a surface treatment to the coating layer as described later.

[0031] In the measurement of the depth profile of the polyester film by time-of-flight secondary ion mass spectrometry in the present invention, Si2HO5 is detected at a position 1 nm deep from the surface of the coated layer. - The ion intensity is adjusted to 0.1 or higher, more preferably 0.3 or higher. Furthermore, Si2CH3O4 - The ionic strength is 0.5 or higher, more preferably 0.6 or higher. If it is outside this range, the degree of mineralization of polydimethylsiloxane is small, and when removing the coating layer from the polyester film, it takes a long time and becomes inefficient. - and Si2CH3O4 - As a means of achieving ionic strength, it is preferable to apply a surface treatment to the coating layer, as described later.

[0032] In measuring the depth profile of the polyester film, Si2HO5 - Ions and Si2CH3O4 - Preferably, the ratio of the ionic intensity at a position of 1 nm to the ionic intensity at a detection depth of 10 nm from the surface of the coated layer is 1.0 or less, and more preferably 0.7 or less. If the ratio of ionic intensity is 1.0 or more, the degree of mineralization of polydimethylsiloxane on the outermost surface and inside the coated layer is small, resulting in a long and inefficient process when removing the coated layer from the polyester film.

[0033] <Surface treatment> In the present invention, the method for recovering a polyester support preferably involves applying a surface treatment to the surface of the coating layer of the polyester film. By applying the surface treatment, not only is the hydrophilicity of the polyester film surface improved, but the amount of Si oxide increases due to the degradation of polydimethylsiloxane contained in the coating layer, and a decomposition reaction due to the detachment of methyl groups proceeds simultaneously, leading to the mineralization of polydimethylsiloxane. By removing the coating layer using the polyester film, the affinity with water is increased during treatment with alkaline treatment solutions and water washing stripping treatments, making it possible to remove the coating layer efficiently in a short time. The surface treatment is not particularly limited, and known methods can be used, such as corona discharge treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment. It is preferable to perform at least one treatment selected from the group consisting of these, and among them, corona discharge treatment is preferred from the viewpoint of processability.

[0034] For corona discharge treatment, the treatment intensity is 60-1000 Wmin / m 2 Preferably, the value is above 80-200 Wmin / m². 2 If the treatment strength is too high, the polyester support tends to be easily damaged, and if the treatment strength is too low, the degree of mineralization of polydimethylsiloxane, the main component of the coating layer, is small, and a sufficient modification effect cannot be obtained. In addition, the power density of the corona discharge machine used is 4-20 W / cm². 2 Therefore, a uniform surface treatment can be applied.

[0035] The irradiation intensity for UV treatment is 10-50 mW / cm². 2 Preferably, it is 15-50 mW / cm². 2 More preferably, 20-50 mW / cm² 2More preferably, the irradiation intensity is too high, which tends to damage the polyester support, and if the irradiation intensity is too low, the alkali treatment time described later will be longer, which also tends to damage the polyester support. 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 will need to be increased, which will increase the manufacturing cost, and the polyester support will also tend to be damaged. If the ultraviolet irradiation time is too short, there is a risk that the coating film will not be sufficiently removed. Furthermore, it is preferable to use electromagnetic waves of invisible light with a wavelength of 10 to 400 nm, that is, shorter than visible light and longer than soft X-rays. As a source of ultraviolet light, known lamps such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, and metal halide lamps can be used, and it is preferable to use low pressure mercury lamps.

[0036] <Treatment with alkaline treatment solution> The polyester film in the present invention undergoes treatment with an alkaline treatment solution, and the Si2HO5 - Ions, Si2CH3O4 - It is hypothesized that adjusting the ion strength promotes the penetration of the alkaline treatment solution into the coating layer, thereby easily decomposing the coating layer and making it easier to peel off from the polyester support.

[0037] In the present invention, treatment with an alkaline treatment solution may be performed immediately after surface treatment, or after a desired period of time has elapsed.

[0038] The alkaline treatment solution used in the present invention can be a solution in which an alkaline substance is dissolved. The alkaline substance is not particularly limited, but examples include: sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide; sodium silicate, potassium silicate, ammonium silicate; sodium distodium phosphate, potassium distodium phosphate, ammonium distodium phosphate; sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate; sodium carbonate, potassium carbonate, ammonium carbonate; sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate; sodium borate, potassium borate, ammonium borate, and other inorganic alkaline agents. Of these, alkali metal hydroxide salts are preferred, with sodium hydroxide and potassium hydroxide being more preferred. The above alkaline substances may be used individually or in combination of two or more.

[0039] While there are no particular limitations on the solvent used to dissolve alkaline substances, water is one example.

[0040] The alkaline substance content in the alkaline treatment solution is preferably 0.01 to 15% by mass, more preferably 0.04 to 15% by mass, and even more preferably 1 to 10% by mass. If the alkaline substance content is too high, the polyester support tends to be easily damaged, and if the content is too low, there is a risk that the coating layer cannot be sufficiently removed. When the alkaline substance content is within the above range, the coating layer can be removed effectively, and damage to the polyester support can be suppressed.

[0041] Various methods can be used to bring the polyester film into contact with an alkaline treatment solution, such as immersion, ultrasonic, spray, and agitation. The above conditions can be appropriately selected depending on the type and thickness of the polyester support and coating layer, but in order to obtain a high-quality polyester support with few impurities, it is preferable to contact the film with an alkaline treatment solution heated to a temperature of less than 100°C, in which the concentration of the alkaline substance is 0.01 to 15% by mass, for a period of more than 0 seconds but less than 700 seconds.

[0042] The temperature of the alkaline treatment solution is preferably less than 100°C, and more preferably between 50°C and 95°C. Specifically, if the temperature of the alkaline treatment solution is 50°C or higher, it does not cause any changes in the physicochemical properties of the polyester support, and a high-quality polyester support with few impurities can be obtained without taking excessive time. Furthermore, since it is not possible to achieve a temperature of over 100°C in the alkaline treatment solution at atmospheric pressure, it would lead to the need for larger equipment, and heating would cause hydrolysis or dissolution of the polyester support.

[0043] The contact time with the alkaline treatment solution is preferably between 0 and 700 seconds, more preferably between 0 and 600 seconds or less, and even more preferably between 0 and 300 seconds or less. If the treatment time is too long, the polyester support tends to be more susceptible to damage, and the polyester support dissolves in the alkaline treatment solution, which may increase the load when treating the alkaline treatment solution as wastewater.

[0044] The alkaline treatment solution may contain surfactants or ultrafine bubbles as auxiliary agents to prevent the re-adhesion of the removed coating layer and to improve the efficiency of coating layer removal. There are no particular restrictions on the surfactant, but for example, nonionic surfactants, cationic surfactants, anionic surfactants, etc., can be used. Surfactants may be used alone or in combination of two or more types.

[0045] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

[0046] Examples of cationic surfactants include alkylpyridinium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyldimethylbenzylammonium chloride.

[0047] Examples of anionic surfactants include sodium alkyl sulfate salts, sodium alkylbenzene sulfonate salts, sodium dialkyl succinate sulfonate salts, sodium alkyl diphenyl ether disulfonate salts, sodium polyoxyethylene alkyl ether sulfate salts, and sodium polyoxyethylene alkylphenyl ether sulfate salts.

[0048] The alkaline treatment solution described above may contain other additives, to the extent that they do not interfere with the effects of the present invention. Examples of additives include antioxidants, pH adjusters, and defoaming agents.

[0049] <Multiple Processing> The aforementioned surface treatment and treatment with an alkaline treatment solution may be performed multiple times. By performing the treatment multiple times, the polyester support can be processed in a short time without suffering damage such as a decrease in its intrinsic viscosity.

[0050] <Water-based stripping treatment> After treatment with an alkaline treatment solution, a water-wash stripping process is performed. To remove any remaining coating residue on the polyester support after the coating layer has been stripped, a rotating sponge roll or similar device is placed and brought into contact with the surface of the coating layer of the polyester film. Furthermore, water washing is performed to remove the alkaline treatment solution.

[0051] The temperature of the water washing and stripping treatment is not particularly limited, but for example, washing with warm water at a temperature of approximately 40°C to 100°C will further enhance the effects described above.

[0052] Methods for water-based stripping include, in the first step, contacting the polyester film with a sponge roll or rubber roll. Multiple sponge rolls may be used. In the second step, methods for water washing include spraying water onto the polyester support from which the coating layer has been removed, or immersing the polyester support in a water tank. Microbubbles or water flow may be used during water washing.

[0053] As a means of the above-mentioned water-washing stripping, for example, a sponge or rubber roll with a hardness of Hs20 to 80 is preferable because it increases the contact area. Of these, a chloroprene rubber sponge with a hardness of Hs20 is preferred.

[0054] When using a sponge roll, it is preferable from a processability standpoint that the rotation direction of the sponge roll be opposite to the conveying direction. Furthermore, it is preferable that the speed ratio V1 / V2 between the peripheral speed of the sponge roll (V1) and the conveying speed of the polyester film (V2) be less than 2. If the speed ratio is too large, the adhesion between the roll and the polyester film will decrease, resulting in insufficient removal of the coated layer and potentially causing the film to tear.

[0055] The rinsing time is preferably 0 to 60 seconds, more preferably 0 to 30 seconds or less, and even more preferably 0 to 15 seconds or less. If the rinsing time is too long, the size of the device will increase, making it inefficient.

[0056] <Drying process> After rinsing, a drying process is carried out to remove any remaining water from the polyester support. It is preferable to do so.

[0057] The drying time is preferably 10 seconds to 5 minutes. If the drying time is less than 10 seconds, drying will be insufficient and blocking may occur. More preferably, it is 30 seconds or more. On the other hand, if the drying time exceeds 5 minutes, the polyester support may deform.

[0058] The drying method is not particularly limited and can include, for example, hot air drying, which involves blowing hot air onto the material, or heat drying, which involves heating with a non-contact heater.

[0059] <Molding of recovered polyester-based support> The present invention's method for producing polyester products includes using the polyester-based support recovered by the above-described method for recovering polyester-based support in extrusion molding to produce polyester products.

[0060] Specifically, the recovered polyester support can be pelletized and then molded into various polyester products such as polyester films using methods such as melt extrusion.

[0061] The polyester product is not particularly limited and can be used for general polyester applications, including the manufacture of polyester films, PET bottles, polyester fibers, polyester sheets, and polyester containers. For example, it can be used as a polyester film.

[0062] The thickness of the polyester film is not particularly limited, but can usually be set appropriately within the range of 10 to 50 μm. Furthermore, it can be laminated with other layers (e.g., release layer, adhesive layer, heat seal layer, surface protection layer, printing layer, design layer, etc.) as needed to form a laminate, and this laminate can also be molded to produce various molded products as described above.

[0063] The embodiments of the present invention will be described in more detail below based on examples, but are not necessarily limited thereto. The usefulness of the coating layer removal method according to the present invention can be expressed by the coating layer removal ability. Unless otherwise specified below, "%" means mass percent and "parts" means parts by mass. The properties were measured as follows.

[0064] [Evaluation Method] 1. Depth profile measurement by time-of-flight secondary ion mass spectrometry Depth profile measurements were performed using TOF-SIMS 5 (manufactured by ION-TOF) under the following conditions. • Secondary ion polarity ·Mass range (m / z): 0~200 • Raster size: 300 μm • Scan rate: 1 scan / cycle • Pixel count (per side): 128 pixels • Measured vacuum level (before sample introduction): 4 × 10 -7 Pa(4×10 -9 mbar) or less • Neutralization of static charge: Yes ·Late acceleration: 9.5kV Pulse width: 11.3 ns • Primary ion species: Bi3 ++ • Primary ion acceleration voltage: 30kV • Bunching: Yes (High mass resolution measurement) • Etching ions: Ar-GCIB • Etching ion acceleration voltage: 5.0 kV Measurements were taken in the depth direction from the surface of the coated layer, and Si2HO5 was detected at depths of 1 nm and 10 nm. - Ions, Si2CH3O4 - Ion depth profile measurements were performed. The ratio of ion intensity at a position of 1 nm to the detection depth at a position of 10 nm from the surface of the coated layer was calculated using the following formula. (Ratio of ionic intensities) = (Ionic intensity at a depth of 10 nm) / (Ionic intensity at a depth of 1 nm)

[0065] Furthermore, the ion intensity in the depth profile is determined by the ions (C) derived from the polyester substrate in the depth analysis. 10 H7O4 - This value is normalized by setting the average ionic strength of the region where the strength of the material is constant (the region where the strength of the polyester layered beneath the coating layer is high) to 1.

[0066] 2. Evaluation of processing efficiency After removing the coating layer and finely cutting the recovered polyester support, it was 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 silicon content was quantified using the X-ray fluorescence measurement method from a pre-prepared calibration curve of X-ray fluorescence intensity.

[0067] The processability of the present invention was evaluated based on the obtained Si content according to the following criteria. "◎" and "○" indicate a pass, while "△" and "×" indicate a fail. The Si content was used as the evaluation criterion for the removal rate of polydimethylsiloxane, the main component of the coating layer. [Evaluation Criteria] ◎: Si content is 20 ppm by mass or less ○: Si content is between 20 ppm by mass and less than 50 ppm by mass △: Si content is greater than 50 ppm by mass but less than 100 ppm by mass. ×: Si content is 100 ppm by mass or more.

[0068] As described below, a laminated polyester film having a release layer was prepared as the sample film.

[0069] [Preparation of sample film] 1. Preparation of a polyester film having a coating layer A polyethylene terephthalate film (Toray Industries, Inc.'s "Lumirror" T60, 38 μm thick, with an intrinsic viscosity of 0.61) was prepared as a polyester-based support. A 5% toluene solution of curable silicone resin (containing 100 parts of Toray Dow Corning Silicone Co., Ltd.'s LTC-350B and 0.8 parts of the company's curing agent SRX-212) was coated onto one side of the film using a bar coater, and a release film was prepared by heating it at 100°C in a tunnel oven and then wound up.

[0070] 2. Application of ceramic slurry and conductive paste A ceramic slurry with the following composition was uniformly applied to the release layer surface of the above-mentioned release film using a blade coater. This was dried in a tunnel oven at 85°C to form a 20 μm thick ceramic layer on the release film. Next, a conductive paste with the following composition was screen printed onto the ceramic layer, dried at 80°C for 10 minutes to form electrodes, and then left at 20°C for 1 hour. 《Ceramic Slurry Composition》 Ceramic powder (barium titanate): 100 parts by mass Binder (polyvinyl butyral): 10 parts by mass Plasticizer (dioctyl phthalate): 5 parts by mass Solvent (toluene / isopropyl alcohol = 1 / 1 (mass ratio)): 100 parts by mass 《Composition of conductive paste》 Ni-based powder: 90 parts by mass Organic vehicle: 10 parts by mass Terpineol: 30 parts by mass.

[0071] 3. Delamination of the ceramic layer from the internal electrodes. On the release film on which the ceramic layer and electrodes were formed, a 10cm x 10cm slit was made only in the coated layer where the ceramic layer and electrodes were formed. Then, the ceramic layer and electrodes were removed from the release film by vacuum suction, obtaining a long sample film. Some of the ceramic layer and electrodes that could not be completely removed remained attached to the surface of the release layer of the sample film. [Examples]

[0072] [Example 1] (Surface treatment) The release layer side surface of the sample film is subjected to corona discharge treatment at a power density of 8 W / cm² using a corona discharge device. 2 Processing intensity 100W min / m 2 Corona discharge treatment was performed.

[0073] The obtained film was used to perform the "depth profile measurement by time-of-flight secondary ion mass spectrometry" described above.

[0074] (Removal of the coating layer and recovery of the polyester-based support) A sample film treated with corona discharge was set in a winding machine, and a mixed aqueous solution of 3 wt% sodium hydroxide and 0.01 wt% nonionic surfactant ("Polyoxyethylene (10) Octylphenyl Ether" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was introduced into a bath heated to 80°C. The sample film was then immersed and transported in the aqueous solution for 30 seconds. A sponge roll was then brought into contact with the release layer side surface of the removed sample film. The peripheral speed of the sponge roll (V1) was set to 50 m / min, and the film transport speed (V2) was set to 40 m / min. The speed ratio V1 / V2 was 1.3. Subsequently, the film was introduced into a water bath containing 18°C ​​water and immersed and transported for 10 seconds. After drying by blowing hot air, a sample film (recovered polyester support) with the release layer removed was obtained. The "evaluation of processability" described above was performed using the sample film.

[0075] (Manufacturing of polyester film) The pellets obtained from the sample film were dried at 150°C for 3 hours, fed into an extruder, melt-extruded at 285°C, and cast onto a 20°C cast 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 using a tenter stretching machine, and then heat-set at 230°C and wound onto a roll.

[0076] [Examples 2-3] A polyester film was prepared in the same manner as in Example 1, except that the corona discharge treatment intensity was changed to the conditions shown in Table 1.

[0077] [Example 4] For surface treatment, use an ultraviolet treatment device at 40 mW / cm². 2 A polyester film was prepared in the same manner as in Example 1, except that ultraviolet irradiation was performed for 60 seconds at the specified irradiation intensity.

[0078] [Example 5] A polyester film was prepared in the same manner as in Example 1, except that a rubber roll with Hs80 was brought into contact with the film during the water-washing and stripping process.

[0079] [Example 6] A polyester film was prepared in the same manner as in Example 1, except that two layers of sponge rolls were installed for the water-washing and stripping process.

[0080] [Example 7] A polyester film was prepared in the same manner as in Example 1, except that the peripheral speed (V1) of the sponge roll was set to 80 m / min for the water-washing and stripping process.

[0081] [Example 8] A polyester film was prepared in the same manner as in Example 1, except that the water-washing and stripping process was performed using water at 80°C.

[0082] [Example 9] A polyester film was prepared in the same manner as in Example 1, except that the film was immersed in a water tank for 45 seconds as part of the water-washing and stripping treatment.

[0083] [Comparative Example 1] A polyester film was prepared in the same manner as in Example 1, except that no surface treatment was performed.

[0084] [Comparative Example 2] A polyester film was prepared in the same manner as in Example 1, except that the corona discharge treatment intensity was changed to the conditions shown in Table 1.

[0085] [Comparative Example 3] A polyester film was prepared in the same manner as in Example 1, except that a sponge roll was not used in the water-washing and stripping process.

[0086] [Comparative Example 4] A polyester film was prepared in the same manner as in Example 1, except that a brush roll was applied during the water-washing and stripping process.

[0087] [Reference example 1] For the sample film obtained in [Comparative Example 2], any areas where release layer residue remained were rubbed with a sponge, the film was immersed in a water bath for 10 seconds, and then dried by blowing hot air on it.

[0088] The evaluation results for Examples 1-9, Comparative Examples 1-4, and Reference Example 1 are shown in Table 2 below.

[0089] [Table 1]

[0090] [Table 2]

[0091] As shown in Tables 1 and 2, according to the polyester support recovery method of the present invention, it is possible to remove the coating layer from a polyester film having at least one coating layer in which the mineralization of polydimethylsiloxane has progressed by treating it with an alkaline treatment solution and performing a water washing and stripping treatment, and a polyester product can be manufactured using this polyester support as part of the raw material.

[0092] In Comparative Example 1, where no surface treatment was performed; Comparative Example 2, where the corona treatment strength was weak; Comparative Example 3, where no water-wash stripping treatment was performed; and Comparative Example 4, where a brush roll was used, the removal of the coating layer was insufficient. Furthermore, in Reference Example 1, where the sample film with insufficient removal of the coating layer was subjected to water-wash stripping treatment again, an improvement in processability was observed.

[0093] As described above, the method of the present invention is extremely useful because, by focusing on the Si oxide and siloxane from which the methyl group has been removed contained in the coating layer, the degree of mineralization of polydimethylsiloxane, which is the main component of the coating layer, can be determined, and the coating layer can be efficiently removed from the polyester film.

Claims

1. Using a polyester film having a polyester support and at least one coating layer, the Si at a position with a detection depth of 1 nm from the surface of the coating layer in the measurement of the depth profile by time-of-flight secondary ion mass spectrometry of the polyester film ２ HO ５ － The intensity of the ion is 0.1 or more, and the intensity of the Si ２ CH ３ O ４ － The intensity of the ion is 0.5 or more, and the polyester film is treated with an alkaline treatment solution and then subjected to a water washing and peeling treatment to recover the polyester-based support. (The intensity of the ion in the depth profile is normalized with the average ion intensity in the region where the intensity of the ions derived from the polyester of the substrate (C １０ H ７ O ４ － ) becomes constant as 1)

2. In measuring depth profiles using time-of-flight secondary ion mass spectrometry, Si ２ HO ５ － Ions and Si ２ CH ３ O ４ － A method for recovering a polyester support according to claim 1, wherein the ions process a polyester film in which the ratio of the ionic intensity at a position of 1 nm to the ionic intensity at a detection depth of 10 nm from the surface of the coated layer is 1.0 or less.

3. A method for recovering a polyester support according to claim 1 or 2, wherein the surface treatment is performed by selecting at least one surface treatment from the group consisting of corona treatment, plasma treatment, glow discharge treatment, flame treatment, and ultraviolet treatment.

4. A method for recovering a polyester support according to claim 1, wherein the treatment is performed with a sponge roll in a water washing and stripping treatment.

5. A method for recovering a polyester support according to claim 4, wherein the speed ratio V1 / V2 of the peripheral speed of the sponge roll (V1) and the conveying speed of the polyester film (V2) is less than 2.

0.

6. A method for producing a polyester product, comprising extruding a polyester support recovered by the polyester support recovery method described in claim 1 or claim 5.

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