Method for removing coating layer

Abstract

This method for removing a coating layer involves, in the following order, a preparation step for preparing a laminated film (for example, a roll (50C)) having a base material film and a coating layer, an ultrasonic treatment step for irradiating the laminated film with ultrasonic waves via water (W1), a removal step for removing the coating layer from the laminated film by treating the laminated film using treatment water or steam, and a recovery step for recovering the base material film, wherein: the coating layer includes a hydrophilic and water-insoluble intermediate layer, and a release agent layer; and the intermediate layer is disposed between the base material film and the release agent layer.

Description

Coating layer removal method

[0001] The present invention relates to a method for removing a coating layer.

[0002] In recent years, from the viewpoint of global resource conservation, environmental protection, etc., there has been an increasing movement in various fields to build a recycling-oriented society through efforts to reduce waste generation, reuse, recycle, etc. For example, Patent Document 1 discloses a release sheet that is a laminate having a substrate and, on at least one surface side of the substrate, an intermediate layer and a release agent layer in this order, wherein the intermediate layer is formed from a composition for forming an intermediate layer that contains a silane-based compound (A) that exhibits polycondensability by hydrolysis and an acrylate compound (B).

[0003] Japanese Patent Application Laid-Open No. 2023-148709

[0004] In the release sheet described in Patent Document 1, the substrate is separated from the release sheet by contacting the hydrophilic intermediate layer (containing a silane compound (A) and an acrylate compound (B)) with water. However, depending on the type of release sheet, the substrate may not be separated from the release sheet unless an operation such as stirring the release sheet in a water tank is performed. Furthermore, separating the substrate by leaving the release sheet in a water tank may take time. There is a need for a technology that can more easily remove a coating layer from a release sheet without adding complex means. Here, a release sheet in which multiple layers (e.g., an intermediate layer and a release agent layer) are laminated on a substrate, such as the release sheet described in Patent Document 1, is sometimes referred to as a laminated film.

[0005] An object of the present invention is to provide a method for removing a coating layer that can more easily remove the coating layer from a laminated film.

[0006] [1] A method for removing a coating layer, comprising, in this order: a preparation step of preparing a laminate film having a base film and a coating layer; an ultrasonic treatment step of irradiating the laminate film with ultrasonic waves via water; a removal step of treating the laminate film with treated water or steam to remove the coating layer from the laminate film; and a recovery step of recovering the base film, wherein the coating layer comprises a hydrophilic and water-insoluble intermediate layer and a release agent layer, the intermediate layer being disposed between the base film and the release agent layer. [2] The method for removing a coating layer according to [1], wherein the laminate film in the ultrasonic treatment step is in a sheet, roll, or folded form. [3] The method for removing a coating layer according to [2], wherein, if the laminate film is in a roll or folded form, the method further comprises a cutting step of cutting the laminate film into sheets between the ultrasonic treatment step and the removal step. [4] The method for removing a coating layer according to any one of [1] to [3], wherein the ultrasonic treatment step is performed while the laminate film is immersed in water. [5] The method for removing a coating layer according to any one of [1] to [4], wherein the removing step is a step of placing the laminate film and the treatment water in a pressure vessel, heating the treatment water while immersing the laminate film in the treatment water, and pressurizing the pressure vessel to a pressure higher than 1 atmosphere. [6] The method for removing a coating layer according to any one of [1] to [4], wherein the removing step is a step of placing the laminate film in a treatment vessel and exposing the laminate film to water vapor in the treatment vessel. [7] The method for removing a coating layer according to any one of [1] to [6], wherein the laminate film prepared in the preparing step is a laminate film with a ceramic green sheet, and a ceramic green sheet is attached to the side of the coating layer opposite to the base film.

[0007] According to one aspect of the present invention, a method for removing a coating layer can be provided that allows for easier removal of a coating layer from a laminated film.

[0008] Fig. 3A is a cross-sectional view of a laminated film used in the removal method according to the present embodiment. Fig. 3B is a view showing an example of a roll used in the removal method according to the present embodiment. Fig. 3C is a view showing an example of a folded stack used in the removal method according to the present embodiment. Fig. 3D is a view showing an example of a sheet stack used in the removal method according to the present embodiment. Fig. 3E is a view showing an example of an ultrasonic treatment device used in the ultrasonic treatment step according to the present embodiment. Fig. 3F is a top view of Fig. 3A. Fig. 3C is a view for explaining a cutting step according to the present embodiment. Fig. 3D is a view for explaining a removal step according to the present embodiment. Fig. 3E is a view for explaining a removal step according to the present embodiment. Fig. 3F is a view for explaining a recovery step according to the present embodiment.

[0009] [First embodiment] (Method for removing a coating layer) The method for removing a coating layer according to this embodiment (hereinafter also referred to as the removal method according to this embodiment) includes, in this order, a preparation step of preparing a laminate film having a base film and a coating layer, an ultrasonic treatment step of irradiating the laminate film with ultrasonic waves via water, a removal step of treating the laminate film with treated water or water vapor to remove the coating layer from the laminate film, and a recovery step of recovering the base film. The coating layer includes a hydrophilic and water-insoluble intermediate layer and a release agent layer, and the intermediate layer is disposed between the base film and the release agent layer.

[0010] The present inventors have discovered that in a laminate film having an intermediate layer and a release agent layer (coating layer) laminated in this order on a substrate film, the coating layer naturally separates from the substrate film by subjecting the laminate film to a simple process of irradiating the laminate film with ultrasonic waves through water (ultrasonic treatment process) and then treating the laminate film with treated water or water vapor. The reason for this is believed to be as follows: Generally, when ultrasonic waves are irradiated into a liquid, positive and negative pressures are alternately applied to gas components (oxygen, nitrogen, carbon dioxide, etc.) contained in the water. This repeated compression and expansion generates and disappears tiny bubbles that are difficult to observe with the naked eye, resulting in the following (1) and (2): (1) The generated bubbles push the liquid near the object toward the object. (2) When the bubbles generated near the object disappear, a flow of liquid is generated that tries to enter the space where the bubbles were previously present. The above phenomena (1) and (2) are thought to impact the cross section of the edge (film edge) of the laminate film, forming "peeling triggers" (triggering the coating layer to separate) in various places along the edge. "Peeling triggers" refer to peeling at the edge of the laminate film, resulting in the formation of a small gap between the substrate film and the intermediate layer at that edge. For example, when the laminate film is in a roll form, the above phenomena (1) and (2) also occur on the edge surface in the TD direction of the roll (the direction perpendicular to the flow direction during manufacturing), and water penetrates the interface between the substrate film and the intermediate layer, forming a "peeling trigger." When the laminate film with a "peeling trigger" formed is contacted with treatment water or steam in the subsequent removal process, the treatment water or steam penetrates into the small gap formed at the edge of the laminate film. The treatment water or steam further widens the small gap and continuously weakens the adhesion of the coating layer from the edge to the center of the laminate film, promoting peeling of the coating layer. This is thought to result in spontaneous peeling of the coating layer.As described above, in the removal method according to this embodiment, first, a "peeling trigger" is formed in the laminated film in the ultrasonic treatment step, and then, in the subsequent removal step, the coating layer is peeled from the laminated film using the "peeling trigger" as the starting point. Therefore, it is significant to perform the ultrasonic treatment step and the removal step in this order.

[0011] According to the removal method of this embodiment, even for laminated films for which the coating layer could not be peeled off without operations such as stirring in a water tank in conventional removal processes, natural peeling of the coating layer can be caused by performing the removal process after the ultrasonic treatment process, resulting in easy removal of the coating layer from the laminated film. Therefore, the ultrasonic treatment process of this embodiment can be said to be a means for promoting improved separability of the coating layer. In the removal method of this embodiment, natural peeling of the coating layer is unlikely to occur even when the ultrasonic treatment process is performed after the removal process, but natural peeling of the coating layer occurs when the removal process is performed after the ultrasonic treatment process. The removal method of this embodiment has the effect of this embodiment (easier removal of the coating layer) by having a preparation process, an ultrasonic treatment process, a removal process, and a recovery process in this order.

[0012] In the removal method according to this embodiment, the water used in the ultrasonic treatment step and the treated water used in the removal step will be described later.

[0013] (Laminated Film) FIG. 1 is a cross-sectional view of a laminated film used in the removal method according to this embodiment. The laminated film 50 has a substrate film 51 and a coating layer 52. The coating layer 52 includes an intermediate layer 521 and a release agent layer 522, with the intermediate layer 521 disposed between the substrate film 51 and the release agent layer 522. In FIG. 1, a indicates the surface of the intermediate layer 521 facing the substrate film, b indicates the surface of the intermediate layer 521 facing the release agent layer, d indicates the surface of the release agent layer, and c indicates the surface of the release agent layer 522 facing the intermediate layer. e indicates the surface of the substrate film. In the laminated film according to this embodiment, it is preferable that the substrate film and the intermediate layer are in direct contact. In the case of FIG. 1, the substrate film 51 and the intermediate layer 521 are in direct contact, and the intermediate layer 521 and the release agent layer 522 are in direct contact.

[0014] The laminate film 50 may be a laminate film used in the production of a ceramic green sheet after the ceramic green sheet has been peeled off. Residue of the ceramic green sheet may be attached to the laminate film. The ceramic green sheet is preferably used in the production of a multilayer ceramic capacitor (MLCC). The laminate film 50 is a laminate film with a ceramic green sheet, and a ceramic green sheet may be attached to the surface of the coating layer 52 opposite the substrate film 51 (reference symbol d in FIG. 1). FIG. 2A is a diagram of a roll in which a laminate film 50G with a ceramic green sheet is wound around a shaft core 1G. FIG. 2A shows the state in which the laminate film 50G with a ceramic green sheet has been unwound from the roll. In FIG. 2A, residue 920 of the ceramic green sheet is attached to the surface of the coating layer 52. After the ceramic green sheet is peeled off, a recess 910 is formed, and the coating layer 52 is exposed from the recess 910.

[0015] In the laminate film used in the removal method according to this embodiment, the intermediate layer is hydrophilic and water-insoluble. A hydrophilic intermediate layer allows for easier removal of the coating layer from the laminate film. The reason for this is explained with reference to FIG. 1 . The intermediate layer 521 in the laminate film 50 adheres to the substrate film 51 primarily through hydrogen bonding and the anchoring effect ( FIG. 1 ). If the intermediate layer 521 is hydrophilic, immersing the laminate film in treatment water or exposing the laminate film to water vapor during the removal process facilitates infiltration of treatment water or water vapor into the interface between the substrate film 51 and the intermediate layer 521 from the in-plane edge of the laminate film 50, weakening the hydrogen bonding and anchoring effect between the intermediate layer 521 and the substrate film 51. In the removal method according to this embodiment, "peeling triggers" are formed in various places at the edge of the laminate film during the ultrasonic treatment process prior to the removal process. This is thought to result in natural peeling of the coating layer 52 (the intermediate layer 521 and the release agent layer 522) during the removal process (treatment using treatment water or water vapor).

[0016] Furthermore, since the intermediate layer is water-insoluble, the components of the intermediate layer 521 are prevented from eluting into water during the ultrasonic treatment step. Similarly, in the subsequent removal step, the components of the intermediate layer 521 are prevented from eluting into the treated water. Therefore, since the intermediate layer 521 is water-insoluble, contamination of the water or treated water can be prevented, and the water or treated water can be easily reused after use.

[0017] In this specification, whether an intermediate layer is "hydrophilic" or not is determined to be hydrophilic if the water contact angle of the surface of the intermediate layer facing the substrate film is 55 degrees or less. In the case of the laminate film 50 shown in FIG. 1 , if the water contact angle of the surface of the intermediate layer 521 facing the substrate film (symbol a in FIG. 1 ) is 55 degrees or less, the intermediate layer 521 is hydrophilic. Furthermore, from the viewpoint of promoting the separability of the substrate film, the contact angle is preferably 50 degrees or less, more preferably 45 degrees or less. The contact angle is a value obtained by measuring the water contact angle of the surface of the intermediate layer that was in contact with the substrate film (the peeled surface) after separating the substrate film from the laminate film, i.e., after contacting the intermediate layer with water and peeling the interface between the intermediate layer and the substrate film. Purified water is used as the water that comes into contact with the intermediate layer when measuring the water contact angle.

[0018] Specifically, the intermediate layer is separated from the substrate film by the following method, and the water contact angle of the surface of the intermediate layer facing the substrate film is measured. The obtained value is the water contact angle of the surface of the intermediate layer facing the substrate film. A 50 mm wide adhesive tape (manufactured by Nitto Denko Corporation, product name "Polyester Adhesive Tape No. 31B") is attached to the release agent layer surface of the laminated film, and then cut to a size of 50 mm x 50 mm to prepare a test piece. 2 L of purified water is placed in a 5 L pressure vessel, and the purified water is boiled to 100 °C using a heater. The test piece (cut to a size of 50 mm x 50 mm) is then immersed in boiling water (purified water) at 100 °C. The lid of the pressure vessel is then closed, and heating is resumed until the pressure inside the pressure vessel reaches 2 atmospheres. Boiling (fume) is confirmed to confirm that the pressure inside the pressure vessel has reached 2 atmospheres, and after 15 minutes have passed (held) in this state, the pressure vessel is returned to normal pressure. Thereafter, it is confirmed that the test piece has been separated into a laminate in which the release agent layer and the intermediate layer are integrally supported on the pressure-sensitive adhesive tape, and the base film in the pressure vessel, and the pressure-sensitive adhesive tape supporting the release agent layer and the intermediate layer is removed from the purified water and dried at room temperature for 24 hours. Thereafter, the water contact angle is measured for the surface of the intermediate layer supported on the pressure-sensitive adhesive tape (the surface of the intermediate layer that was in contact with the surface of the base film).

[0019] The water contact angle may be a value measured by the following method. The test piece (cut into a size of 50 mm x 50 mm) is prepared. Next, 300 mL of purified water is filled into a 500 mL glass beaker, and the entire test piece is immersed in purified water heated to 90°C and left for 3 hours. Thereafter, it is confirmed that the test piece has been separated into a laminate in which the release agent layer and the intermediate layer are integrally supported on the adhesive tape, and the substrate film. The adhesive tape carrying the release agent layer and the intermediate layer is removed from the heated purified water and dried at room temperature for 24 hours. The water contact angle is then measured for the surface of the intermediate layer supported on the adhesive tape (the surface of the intermediate layer that was in contact with the surface of the substrate film). The contact angle is measured by the sessile drop method in accordance with JIS R3257:1999 using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701"). Distilled water is used for the droplet.

[0020] In this specification, whether an intermediate layer is "water-insoluble" or not is determined when the difference between the water contact angle of the release agent layer surface (symbol d in Figure 1 ) and the water contact angle of the intermediate layer on the substrate film side (symbol a in Figure 1 ), measured using the following method, is 30 degrees or more. The difference in contact angles is preferably 40 degrees or more, more preferably 50 degrees or more. A small difference indicates that the components constituting the intermediate layer have dissolved in water, resulting in the measurement of a release agent layer that is partially exposed. The water contact angle of the release agent layer surface is not particularly limited, but is usually 80 degrees or more, preferably 85 degrees or more, and more preferably 90 degrees or more. The upper limit of the water contact angle of the release agent layer surface is usually 150 degrees, preferably 140 degrees, and more preferably 130 degrees. The water contact angle of the release agent layer surface is measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701") by the sessile drop method in accordance with JIS R3257: 1999. Distilled water is used as the droplet.

[0021] Each step of the removal method according to this embodiment will be described.

[0022] <Preparation Step> The preparation step is a step of preparing a laminate film having a base film and a coating layer. The laminate film prepared in the preparation step is preferably in the form of a sheet, a roll, or a folded state.

[0023] (Roll-shaped laminate film) The roll-shaped laminate film is, for example, a roll (hereinafter, sometimes simply referred to as a roll) in which a single long laminate film is wound around a core. The dimensions of the roll are, for example, a width (dimension perpendicular to the winding direction) of 100 mm to 1000 mm, preferably 200 mm to 600 mm. The winding diameter of the roll (diameter of the roll including the winding core) is, for example, 100 mm to 1500 mm, preferably 150 mm to 1000 mm. The laminate film constituting the roll is preferably wound so that a first surface of the coating layer opposite the substrate film (in the case of Figure 1, the release agent layer surface (symbol d)) and a second surface of the substrate film opposite the coating layer (in the case of Figure 1, the substrate film surface (symbol e)) directly or indirectly face each other. "Directly facing" means that the first surface of the coating layer and the second surface of the base film face each other without any other material interposed therebetween, whereas "indirectly facing" means that the first surface of the coating layer and the second surface of the base film face each other with another material (e.g., a ceramic green sheet) interposed therebetween (see FIG. 2A ).

[0024] (Folded Laminate Film) A folded laminate film is, for example, a laminate obtained by folding a single sheet-like laminate film using any folding method (hereinafter, sometimes referred to as a folded laminate). The folding method is not particularly limited, but examples include a method of folding in a zigzag pattern so that the edges of the folded portions are aligned (overlapping at the top and bottom) when viewed in a plan view of the folded laminate (see FIG. 2B), and a method of folding in a zigzag pattern so that the edges of the folded portions do not overlap at the top and bottom. FIG. 2B is a diagram showing an example of a folded laminate 50A.

[0025] For example, when a laminate film unwound from a normal roll is folded to form a folded laminate, the size (width, length, and thickness (height)) of the folded laminate is preferably within the following ranges. By folding the laminate film, the folded laminate can be formed into a rectangular parallelepiped block, which makes it easier to load and transport than a roll-shaped laminate. The width of the folded laminate depends on the width of the roll before unwound, but is usually 100 mm to 1000 mm, and preferably 200 mm to 600 mm. The length of the folded laminate is preferably 100 mm to 1000 mm, and more preferably 200 mm to 600 mm. The thickness (height) of the folded laminate is preferably 100 mm to 1000 mm, and more preferably 200 mm to 600 mm.

[0026] (Strip-shaped laminate film) Any number of strip-shaped laminate films are prepared. The shape of the strip-shaped laminate film is not particularly limited, and examples thereof include a rectangular shape and a polygonal shape. The strip-shaped laminate film may have an irregular shape. When the strip-shaped laminate film is rectangular, the dimensions of the laminate film are, for example, 100 mm or more and 1000 mm or less, and preferably 200 mm or more and 600 mm or less on one side.

[0027] The sheet-like laminate film may be prepared as a laminate (hereinafter, sometimes referred to as a sheet-like laminate) in which multiple sheets are stacked in the thickness direction, as shown in FIG. 2C . FIG. 2C is a diagram showing an example of a sheet-like laminate 50B. The stacking method of multiple laminate films is not particularly limited; the laminate films may be stacked in the same direction, or the laminate films may be stacked so that the base films and coating layers face each other between each laminate film. The laminate films may be stacked in any direction. "Stacking in the same direction" refers to stacking the laminate films so that the base films and coating layers face each other between each laminate film. The thickness (height) of the sheet-like laminate is preferably 100 mm or more and 1000 mm or less, more preferably 200 mm or more and 600 mm or less.

[0028] Hereinafter, the term "laminated film" will collectively refer to sheet-shaped, roll-shaped, and folded laminated films.

[0029] <Ultrasonic Treatment Step> In the removal method according to this embodiment, the ultrasonic treatment step is a step of irradiating ultrasonic waves to the laminate film via water. In the ultrasonic treatment step, ultrasonic waves are irradiated to the laminate film prepared in the preparation step via water. Therefore, the laminate film used in the ultrasonic treatment step is preferably in a sheet, roll, or folded form. The ultrasonic treatment step is preferably performed while the laminate film is immersed in water, but may also be performed while only a portion of the laminate film is immersed in water. For example, when the laminate film is in the form of a roll, the ultrasonic treatment step may alternately involve (i) immersing only the vicinity of the top side of the roll in water to perform ultrasonic treatment, and (ii) immersing only the vicinity of the bottom side of the roll in water to perform ultrasonic treatment. In the ultrasonic treatment step, the oscillation frequency when irradiating ultrasonic waves is preferably 10 kHz or more and 300 kHz or less, more preferably 20 kHz or more and 200 kHz or less. In the ultrasonic treatment step, the power density of the ultrasonic waves is preferably 0.1 W / cm. ２ Above, 2.0W / cm ２ or less, more preferably 0.3 W / cm ２ Above, 1.5W / cm ２ The ultrasonic power density is calculated by dividing the ultrasonic power set in the ultrasonic oscillator by the area of ​​the vibration plate. In the ultrasonic treatment step, the ultrasonic irradiation time is preferably 1 minute or more and 60 minutes or less, more preferably 3 minutes or more and 30 minutes or less.

[0030] The water used in the ultrasonic treatment process can be water of the same quality as the "normal water" described below in the "Water Used as Treatment Water" section. It is preferable that the water used in the ultrasonic treatment process is not pure water or purified water, as this facilitates the generation of cavitation. This is because pure water and purified water do not contain dissolved gases, and cavitation does not occur when exposed to ultrasonic waves. Furthermore, water saturated with dissolved gases is also undesirable for use in the ultrasonic treatment process. This is because the diameter of the cavitation bubbles generated by ultrasonic waves tends to be too large, which may prevent the impact from reaching the laminated film as the treated object. The temperature of the water used in the ultrasonic treatment process is preferably 60°C or less from the viewpoint of efficiently generating cavitation and the heat resistance of components such as ultrasonic vibrators. The lower limit of the water temperature is preferably 10°C or higher, as this facilitates the generation of cavitation. The temperature of the water used in the ultrasonic treatment process is preferably lower than the temperature of the treatment water used in the removal process.

[0031] <Cutting Step> In the removal method according to this embodiment, when the laminate film is in a roll or folded form, it is preferable to further include a cutting step of cutting the laminate film into sheets between the ultrasonic treatment step and the removal step. The cutting means for cutting the laminate film into sheets is not particularly limited, but examples thereof include a cutting machine equipped with a cutter. Examples of cutters include a cutter blade, a water jet cutter, a laser cutter, and an ultrasonic cutter. The laminate film unwound from the roll or folded stack is cut into small pieces by passing it between a pair of nip rolls and a pair of cutter blades. The size of the cut laminate film is selected according to the size of the pressure vessel. For example, when the cut laminate film is rectangular, the dimension of one side of the laminate film is preferably 15 cm or less, more preferably 10 cm or less, and even more preferably 5 cm or less. The lower limit of the dimension of one side of the laminate film is preferably 5 mm or more.

[0032] <Removal Step> In the removal method according to the present embodiment, the removal step is a step of removing the coating layer from the laminate film by treating the laminate film with treated water or water vapor. Since the removal step is performed after the ultrasonic treatment step, treating the laminate film with treated water or water vapor causes the coating layer (intermediate layer and release agent layer) to naturally peel off from the substrate film.

[0033] The laminate film is preferably in the form of a sheet laminate film or a sheet stack when the removal step is performed. Specifically, when the ultrasonic treatment step is performed on a rolled or folded laminate film, the rolled or folded laminate film is cut by the cutting step described above after the ultrasonic treatment step. Therefore, the laminate film is in the form of a sheet laminate film when the removal step is performed. The sheet laminate film may be randomly housed in a pressure vessel or the like, may be housed in a holding vessel, or may be fixed (held) using a jig. Examples of the holding vessel include a vessel having multiple holes.

[0034] Hereinafter, the removal step in which the laminated film is treated with treated water may be referred to as a removal step according to embodiment 1, and the removal step in which the laminated film is treated with water vapor may be referred to as a removal step according to embodiment 2.

[0035] (Removal step according to aspect 1 (when treating a laminate film using treatment water)) The removal step according to aspect 1 is preferably a step of removing the coating layer from the laminate film by immersing at least a portion of the laminate film (preferably the entire laminate film) in treatment water. The removal step according to aspect 1 is preferably a step of submerging the substrate film in treatment water and floating the coating layer on the treatment water. The treatment water used in the removal step according to aspect 1 can be water or an alkaline aqueous solution.

[0036] (Treated Water) First, the case where water is used as the treated water will be described. The water used as the treated water refers to the liquid water in which the laminated film is immersed in the removal process. The water used as the treated water refers to "normal water," i.e., preferably industrial water, and may be purified water, distilled water, or water saturated with dissolved gases. Furthermore, the treated water may be recycled wastewater used in various industrial production processes, or recycled wastewater used in the implementation of the present embodiment. When the wastewater is recycled, it may be recycled wastewater, as appropriate. From the viewpoint of improving work efficiency, the water used as the treated water may contain, but preferably does not contain, additives that impart functionality. Examples of additives include surfactants and water-soluble organic solvents. When the water used as the treated water contains an additive, the concentration of the active ingredient of the additive in the treated water is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, relative to the total amount of the treated water. Furthermore, it is preferable that the water used as the treated water does not contain any intentionally added additives. Furthermore, since there is a possibility that wastewater can be recycled simply, the water used as treated water may contain basic substances and acidic substances as additives. In this case, however, it is preferable that the pH of the treated water is 5.8 or more and 8.6 or less, so as to comply with the uniform wastewater standards (other items) based on the Water Pollution Control Act.

[0037] When the treatment water is used as warm water, the temperature of the treatment water is preferably 80°C or higher and 100°C or lower, more preferably 90°C or higher and 100°C or lower. In the removal step, after the water temperature reaches the target temperature, the laminate film is held in the treatment water at this temperature for a predetermined time. In this specification, the holding time of the laminate film in the treatment water from the time when the target temperature is reached is defined as the treatment time of the laminate film. The treatment time of the laminate film is preferably 5 minutes or longer, more preferably 30 minutes or longer. The treatment time of the laminate film is preferably 120 minutes or shorter, more preferably 60 minutes or shorter.

[0038] The water used as the treatment water may be superheated water. Superheated water is liquid water heated under pressure to a temperature exceeding 100°C. When using superheated water as the treatment water, the removal step according to aspect 1 is preferably a step of placing the laminate film and the treatment water in a pressure vessel, heating the treatment water while immersing the laminate film in the treatment water, and pressurizing the pressure in the pressure vessel to a pressure higher than 1 atmosphere. The water contained in the pressure vessel can be water of the same quality as the "normal water" described above in the "Water to be used as treatment water" section. Therefore, the superheated water used as the treatment water in the removal step can be obtained by heating "normal water" under pressure. In the removal step, the pressure in the pressure vessel and the temperature of the heated water (superheated water) are each determined by Boyle's law, and are preferably within the following ranges. The pressure in the pressure vessel is preferably 1.2 atmospheres or more, more preferably 1.4 atmospheres or more, from the viewpoint of facilitating the infiltration of superheated water into the interface between the base film and the release agent layer. The pressure inside the pressure vessel is preferably 9.9 atmospheres or less, more preferably 4.7 atmospheres or less, from the viewpoint of suppressing melting of the resin components contained in the laminate film. The pressure inside the pressure vessel is adjusted using a pressure regulating valve or the like. The temperature of the superheated water is preferably 105°C or more, more preferably 110°C or more, from the viewpoint of facilitating infiltration of the superheated water into the interface between the base film and the release agent layer. The temperature of the superheated water is preferably 180°C or less, more preferably 150°C or less, from the viewpoint of suppressing melting of the resin components contained in the laminate film. In the removal step, the retention time of the laminate film in the superheated water from the time the water temperature reaches the target temperature (the treatment time of the laminate film) is, for example, preferably 5 minutes or more, more preferably 10 minutes or more. The treatment time of the laminate film in the superheated water is preferably 40 minutes or less, more preferably 30 minutes or less.

[0039] An alkaline aqueous solution may be used as the treatment water. When an alkaline aqueous solution is used as the treatment water, the removal step according to aspect 1 involves immersing at least a portion of the laminate film (preferably the entire laminate film) in the alkaline aqueous solution as the treatment water to remove the coating layer from the laminate film. Examples of alkaline aqueous solutions include one or more aqueous solutions selected from sodium hypochlorite aqueous solution, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution. The alkaline aqueous solution is preferably a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution, and more preferably a potassium hydroxide aqueous solution. The alkaline aqueous solution may further contain an auxiliary agent. Examples of the auxiliary agent include surfactants, water-soluble inorganic compounds, water-soluble organic compounds, and water-soluble solvents. Specific examples of the auxiliary agent include nonionic surfactants, water-soluble inorganic salts, water-soluble organic salts, water-soluble polymers, polysaccharides, alcohols, glycols, and water-soluble organic solvents. Examples of glycols include ethylene glycol, diethylene glycol, and propylene glycol. Examples of the water-soluble organic solvent include dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and ethylene glycol ethers (various cellosolves). The auxiliary agents may be used alone or in combination of two or more.

[0040] The temperature of the alkaline aqueous solution is preferably 5° C. or higher, more preferably 20° C. or higher. The temperature of the alkaline aqueous solution is preferably 100° C. or lower, more preferably 80° C. or lower.

[0041] In the removal step, the concentration of the alkaline aqueous solution when the laminated film is immersed in the alkaline aqueous solution is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 3.0% by mass or more. The concentration of the alkaline aqueous solution is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, even more preferably 47% by mass or less, and even more preferably 45% by mass or less. When the alkaline aqueous solution contains an auxiliary, the concentration of the alkaline aqueous solution refers to the total concentration of the alkaline components in the alkaline aqueous solution.

[0042] In the removal step, the time for immersing the laminate film in the alkaline aqueous solution is preferably 5 minutes or more, more preferably 30 minutes or more. The time for immersing the laminate film in the alkaline aqueous solution is preferably 120 minutes or less, more preferably 60 minutes or less. In the removal step, by extending the immersion time of the laminate film, the temperature or concentration of the alkaline aqueous solution can be made mild. After the removal step is performed, the alkaline aqueous solution used as treatment water is neutralized so that it can be disposed of.

[0043] (Removal Step of Aspect 2 (When Treating a Laminated Film Using Water Vapor)) The removal step of Aspect 2 is preferably a step of placing the laminated film in a treatment container and exposing the laminated film to water vapor in the treatment container. The step of exposing to water vapor is carried out without immersing the laminated film in liquid water. The water vapor used in the removal step of Aspect 2 is obtained by evaporating water for generating water vapor (hereinafter, sometimes referred to as "water for water vapor source"). As the water for water vapor source, water of the same water quality as the "normal water" described above in "Water to be used as treatment water" can be used. Examples of methods for exposing the laminated film to water vapor include a method of placing the laminated film in the treatment container and supplying water vapor into the treatment container, and a method of placing the laminated film and water for water vapor source in the treatment container and then heating the water for water vapor source. Alternatively, the method of exposing the laminated film to water vapor may be a method of placing the laminated film in a treatment container filled with water vapor.

[0044] In the step of exposing the laminate film to water vapor, from the viewpoint of facilitating penetration of water vapor into the interface between the base film and the intermediate layer and from the viewpoint of suppressing melting of the resin component contained in the laminate film, the air pressure and temperature within the treatment container in the step of exposing to water vapor are preferably within the following ranges. In the step of exposing to water vapor, the air pressure within the treatment container is preferably 1.2 atmospheres or more, and more preferably 1.4 atmospheres or more. The air pressure within the treatment container is preferably 9.9 atmospheres or less, and more preferably 4.7 atmospheres or less. In the step of exposing to water vapor, the temperature within the treatment container is preferably 105°C or more, and more preferably 110°C or more. The temperature within the treatment container is preferably 180°C or less, and more preferably 150°C or less.

[0045] In the step of exposing the laminated film to water vapor, the time for exposing the laminated film to water vapor is, for example, 5 minutes or more and 40 minutes or less, and preferably 10 minutes or more and 30 minutes or less.

[0046] <Recovery Step> In the removal method according to this embodiment, the recovery step is a step of recovering the substrate film. The recovery means is not particularly limited, but examples include at least one of a mesh-structured tray or container (e.g., a colander), a filter, a container outlet, and a pump. Because the substrate film tends to sink in the treated water and the coating layer tends to float in the treated water, the recovery step is preferably carried out by taking advantage of these properties. For example, as shown in FIG. 5 , after the removal step has been performed in a container (pressure vessel 60A in FIG. 5 ), the substrate film 51D sinks to the bottom of the container, and the coating layer 52D floats on the upper side of the container. Furthermore, for example, FIG. 7 shows the substrate film 51D and coating layer 52D transferred to a recovery container 100 (e.g., a water tank) after the removal step. The recovery container 100 shown in FIG. 7 includes an upper discharge pipe 18 and a lower discharge pipe 19. The upper discharge pipe 18 is connected to an upper discharge port 18A and has an upper discharge valve 21. The lower discharge pipe 19 is connected to a lower discharge port 19A and has a lower discharge valve 22. The upper discharge valve 21 and the lower discharge valve 22 enable the opening and closing of the upper discharge pipe 18 and the lower discharge pipe 19, respectively. By using a recovery container 100 as shown in FIG. 7, the base film 51D can be easily recovered from the lower discharge port 19A. The removal step may also be carried out using a pressure vessel having a sealed and openable base film discharge port on the bottom side. In this case, after the removal step, the base film submerged in the treated water can be easily recovered from the base film discharge port. Water droplets are removed from the recovered base film by a known method.

[0047] The method for recovering the coating layer is not particularly limited, and for example, the coating layer may be recovered directly from the pressure vessel after the air pressure inside the pressure vessel is returned to normal pressure, or the contents inside the pressure vessel may be transferred to a recovery vessel 100 equipped with drainage outlets at the top and bottom, and water may be poured into the pressure vessel, allowing the coating layer 52D in the upper layer portion to be recovered from an upper discharge outlet 18A, as shown in Figure 7. The coating layer 52D (residue of the coating layer) tends to float in the treated water, and therefore can be easily recovered using a tray or container with a mesh structure.

[0048] (Specific Example 1) The removal method according to Specific Example 1 is carried out as follows. A roll of laminated film is prepared, in which the laminated film is wound around a shaft core 3G (preparation step, see FIG. 3A). Hereinafter, the roll of laminated film may be referred to as roll 50C. In Specific Example 1, an ultrasonic treatment step is performed on roll 50C using ultrasonic treatment device 80 shown in FIG. 3A, and a removal step is performed using pressure vessel 60A and treated water shown in FIG. 5. The removal step according to Specific Example 1 is an example of the removal step according to Aspect 1. FIG. 3A is a schematic diagram of ultrasonic treatment device 80, and FIG. 3B is a top view of FIG. 3A. Ultrasonic treatment device 80 includes a water tank 81, a vibration plate 82 equipped with an ultrasonic vibrator therein, a workpiece mounting table 84 provided above vibration plate 82, and an ultrasonic oscillator 40 connected to vibration plate 82. Tap water W1 is contained in water tank 81. As shown in FIG. 3B, workpiece mounting table 84 is composed of multiple rod-shaped members 84A spaced apart at regular intervals. The interval between the rod-shaped members 84A is equal to the diameter D of the roll 50C. １ The roll 50C is held between two rod-shaped members 84A above the vibration plate 82, so that the roll 50C does not come into contact with the vibration plate 82 and interfere with the vibration, and a gap is formed between the roll 50C and the vibration plate 82, which also generates cavitation in the gap, so that an impact is applied to the entire roll 50C. The ultrasonic oscillator 40 supplies high-frequency power to the vibration plate 82 to drive the vibration plate 82. The ultrasonic processing device 80 generates cavities in the tap water W1 by ultrasonic vibrations from the vibration plate 82. The distance D from the upper surface of the vibration plate 82 to the lower surface of the roll 50C is ２ is the diameter D of the roll 50C １ The distance D from the top surface of the vibration plate 82 to the water surface is usually between 10 mm and 500 mm. ３ In the case of Fig. 3A, a rubber band 55 is wound around the end of the roll 50C to prevent the end of the roll 50C from becoming unwound.

[0049] After the roll 50C is placed on the workpiece placement table 84, tap water W1 is placed in the water tank 81, and the roll 50C is immersed in the tap water W1. The roll 50C may be placed on the workpiece placement table 84 with the tap water W1 still placed in the water tank 81. While the roll 50C is immersed in the tap water W1, ultrasonic waves are irradiated to the roll 50C under predetermined conditions (ultrasonic treatment process).

[0050] After the ultrasonic treatment step, roll 50C is removed from water tank 81. Rubber band 55 is removed from roll 50C, and the laminate film is unwound by known means (not shown). The laminate film is then cut into individual laminate film sheets using a cutter (not shown) (see FIG. 4). Hereinafter, the cut laminate film sheets, as well as the substrate film and coating layer constituting the individual laminate film sheets, may be referred to as laminate film 50D, substrate film 51D, and coating layer 52D, respectively.

[0051] Next, a pressure vessel 60A shown in FIG. 5 is used to treat a sheet of laminated film 50D with superheated water to remove the coating layer 52D from the laminated film 50D. FIG. 5 shows the laminated film 50D housed in the pressure vessel 60A together with water TW1 as treatment water. The pressure vessel 60A includes a pressure vessel body 62A and a pressure lid 61A. The pressure lid 61A has a rim 601A formed along its outer periphery. A pressure control unit 70 is disposed above the pressure lid 61A. The pressure control unit 70 controls the internal pressure of the pressure vessel 60A to a first pressure higher than 1 atmosphere. The pressure control unit 70 can be, for example, a pressure control valve (e.g., a safety valve), a pressure control valve (e.g., a relief valve), or a pressure regulating valve (e.g., a weight-type or spring-type) used in a conventional pressure cooker. In the case of FIG. 5, the pressure control unit 70 includes a relief valve 71 and a pressure sensor 72. The relief valve 71 adjusts the air pressure inside the pressure vessel 60A to a predetermined pressure by controlling the opening area of ​​the steam outlet 71A formed in the pressure lid 61A. The opening area of ​​the steam outlet 71A is controlled by a computer control unit in accordance with the air pressure value acquired by the pressure sensor 72. The air pressure inside the pressure vessel 60A can be controlled in other ways. A heater 68 for heating the water TW1 to be treated is disposed at the bottom of the pressure vessel body 62A. A known heater such as an induction heater can be used as the heater 68. Since the removal process according to Example 1 is performed after the ultrasonic treatment process, the coating layer 52D is naturally peeled and separated from the substrate film 51D. After the removal process, the substrate film 51D sinks to the bottom of the pressure vessel 60A, and the coating layer 52D floats on the water TW1. The base film 51D may be recovered directly from the pressure vessel 60A after the air pressure inside the pressure vessel 60A is returned to normal pressure, or the contents inside the pressure vessel 60A may be transferred to a recovery vessel 100 shown in Figure 7 and the base film 51D may be recovered from the lower discharge port 19A (recovery process).

[0052] (Specific Example 2) The removal method according to Specific Example 2 is carried out as follows. The removal method according to Specific Example 2 is similar to the removal method according to Specific Example 1, except that the laminate film is treated using water vapor. The removal step according to Specific Example 2 is an example of the removal step according to Aspect 2. Using the same method as in Specific Example 1, ultrasonic waves are irradiated onto the roll 50C (ultrasonic treatment step). The laminate film is then unwound by known means (not shown) and cut into sheets of laminate film 50D (cutting step). FIG. 6 shows the laminate film 50D housed in a pressure vessel 60A together with water TW2 (water for a steam source) as treatment water. A mounting table 66, whose height is higher than the depth of the water TW2, is installed within the pressure vessel 60A, and the laminate film 50D is housed in a basket 67 on top of the mounting table 66. The removal step is carried out as follows. The water TW2 in the pressure vessel 60A is heated by the heater 68, and the pressure inside the pressure vessel 60A is increased to a pressure higher than 1 atmosphere, generating water vapor within the pressure vessel 60A. The generated water vapor fills the pressure vessel 60A, exposing the laminated film to the water vapor (removal process). The laminated film placed on the mounting table 66 is exposed to water vapor (not shown) without being immersed in water TW2. Because the removal process according to Example 2 is performed after the ultrasonic treatment process, the coating layer 52D naturally peels and separates from the substrate film 51D within the basket 67. After that, the pressure inside the pressure vessel 60A is returned to normal pressure, and the substrate film 51D and coating layer 52D separated within the basket 67 are released into the water W2 in the recovery container 100 shown in FIG. 7 . The substrate film 51D can be recovered from the lower discharge port 19A (recovery process). The coating layer 52D can be recovered from the upper discharge port 18A.

[0053] [Modifications of the Embodiments] The present invention is not limited to the above-described embodiments, and can include modifications and improvements within the scope of achieving the object of the present invention.

[0054] For example, in the removal step according to specific example 1, instead of the pressure vessel 60A, a normal water tank may be used, and the laminate film may be immersed in treatment water (water or an alkaline aqueous solution) for a predetermined time. In the removal step according to this embodiment, the coating layer 52D is naturally peeled off from the substrate film 51D without performing operations such as stirring. Therefore, the removal step according to specific example 1 may be a step of leaving the laminate film in treatment water for a predetermined time. Furthermore, in the removal step according to specific example 2, instead of generating water vapor within the pressure vessel 60A, water vapor generated externally (e.g., in a boiler) may be introduced into the pressure vessel 60A, thereby exposing the laminate film to water vapor.

[0055] The structure of the laminated film used in the above embodiment and modified examples will be described.

[0056] [Laminate Film] The laminate film used in the above embodiment has a substrate film and a coating layer. The laminate film used in the above embodiment may be referred to as a release film. The coating layer includes an intermediate layer and a release agent layer. The intermediate layer is disposed between the substrate film and the release agent layer. The intermediate layer may be a single layer, or a multilayer consisting of two or more intermediate layers of the same or different types. The release agent layer may be a single layer, or a multilayer consisting of two or more release agent layers of the same or different types. From the viewpoint of facilitating removal of the coating layer from the laminate film and recovery of the remaining substrate film, the laminate film preferably has a configuration in which the substrate film and the intermediate layer are directly laminated. Here, "direct lamination" refers to a configuration in which, for example, there is no other layer between the substrate film and the intermediate layer, and the respective layers are in direct contact with each other. Furthermore, as one embodiment of the laminate film, the substrate film, the intermediate layer, and the release agent layer may be directly laminated in this order. That is, the layers may be in direct contact with each other without any other layers being present between the base film, intermediate layer, and release agent layer.

[0057] <Base film> The base film is a resin film formed from a resin component to be recovered. Examples of resin films that can be used include polyester films such as polyethylene terephthalate film, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polyethylene film and polypropylene film; polyimide film; polyamide film; polycarbonate film; polyacetate film; ethylene-vinyl acetate copolymer (EVA) film; ethylene-(meth)acrylic acid copolymer film; ethylene-(meth)acrylic acid ester copolymer film; cycloolefin polymer film; polyurethane film; polyphenylene sulfide film; and cellophane. The density of the base film is preferably greater than the density of water at 40°C, and is 1.0 g / cm. ３ or more is more preferable. This allows the substrate film to sink more easily in the treatment water, facilitating recovery of the substrate film. Among substrate films, polyester film is preferred because it has a density greater than that of water at 40°C and has excellent heat resistance and strength. As the polyester film, a polyester film primarily composed of any of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate is preferred from the viewpoint of easy recovery and recycling of the resin. In this specification, the term "main component" or "principal component" means that the proportion of the total mass of the material is 50% by mass or more. Furthermore, the resin film may contain known fillers, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, etc. Furthermore, the resin film may be transparent or may be colored as desired. Furthermore, at least one surface of the substrate film may be subjected to a surface treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, or etching such as oxidation, as necessary.

[0058] The thickness of the substrate film is not particularly limited, but from the viewpoint of strength, rigidity, etc., it is preferably 10 μm or more and 500 μm or less, more preferably 15 μm or more and 300 μm or less, and even more preferably 20 μm or more and 200 μm or less.

[0059] <Release Agent Layer> The release agent layer is preferably a layer formed from a release agent composition. The release agent composition used to form the release agent layer is not particularly limited as long as it has releasability, and for example, a release agent composition containing as a main component a silicone-based compound; a fluorine compound; a long-chain alkyl group-containing compound; or a thermoplastic resin material such as an olefin-based resin or a diene-based resin; or the like can be used. It is also preferable to use a release agent composition containing as a main component an energy ray-curable or thermosetting resin. These release agent compositions may be used alone or in combination of two or more.

[0060] In the release agent composition containing a silicone compound as a main component, examples of the silicone compound include silicone compounds having an organopolysiloxane as a basic skeleton. Examples of the silicone compound include heat-curable silicone compounds such as addition reaction type and condensation reaction type; and energy beam-curable silicone compounds such as ultraviolet-curable and electron beam-curable types.

[0061] In the release agent composition containing a fluorine compound as a main component, examples of the fluorine compound include fluorine silicone compounds, fluorine boron compounds, and poly(perfluoroalkylene ether) chain-containing compounds.

[0062] In the release agent composition containing a long-chain alkyl group-containing compound as a main component, examples of the long-chain alkyl group-containing compound include polyvinyl carbamate obtained by reacting a polyvinyl alcohol polymer with a long-chain alkyl isocyanate, alkyl urea derivatives obtained by reacting a polyethyleneimine with a long-chain alkyl isocyanate, and copolymers of long-chain alkyl (meth)acrylates. Furthermore, a long-chain alkyl-modified alkyd resin may be used, which is an alkyd resin obtained by the condensation reaction of a polyhydric alcohol and a polybasic acid and which is modified with a long-chain fatty acid as a modifier.

[0063] As a release agent composition mainly composed of an energy ray-curable resin, for example, one containing an energy ray-curable compound having a reactive functional group selected from a (meth)acryloyl group, an alkenyl group, and a maleimide group, and a polyorganosiloxane is preferred. In the release agent layer formed from this release agent composition, an energy ray-curable compound and a polyorganosiloxane having different molecular structures, polarities, and molecular weights are used, so that before curing, components derived from the polyorganosiloxane are segregated near the outer surface of the release agent layer, and then cured by energy rays, and the segregation is fixed. This improves the releasability of the release agent layer. The release agent composition mainly composed of an energy ray-curable resin may further contain a photopolymerization initiator.

[0064] Examples of release agent compositions containing a thermosetting resin as a primary component include release agent compositions containing a melamine resin as a primary component and release agent compositions containing an epoxy resin as a primary component. Release agent compositions containing a melamine resin as a primary component include compositions containing a melamine resin as a primary component, an acid catalyst for thermally curing the melamine resin, and a polyorganosiloxane that imparts release properties to the release agent layer. Furthermore, release agent compositions containing an epoxy resin as a primary component include compositions containing an epoxy resin as a primary component, an acid or basic thermosetting catalyst for thermally curing the epoxy resin, and a polyorganosiloxane that imparts release properties to the release agent layer. Before curing, components derived from the polyorganosiloxane segregate near the outer surface of the release agent layer, and then cure to solidify the segregation. This improves the release properties of the release agent layer.

[0065] The release agent layer may contain other additives in addition to the resin component, such as an antioxidant, a light stabilizer, a flame retardant, a conductive agent, an antistatic agent, and a plasticizer.

[0066] The thickness of the release agent layer can be appropriately selected and is not particularly limited, but is, for example, preferably 0.02 μm or more and 5 μm or less, more preferably 0.03 μm or more and 2 μm or less, and even more preferably 0.05 μm or more and 1.5 μm or less.

[0067] <Intermediate Layer> The intermediate layer is preferably a layer made of a silane-based compound that is hydrophilic and water-insoluble and exhibits polycondensability upon hydrolysis, from the viewpoint of easier removal of the coating layer from the surface of the intermediate layer facing the substrate film.

[0068] The silane-based compound preferably contains, as a main component, at least one selected from tetrafunctional silane-based compounds represented by the following general formula (a) and oligomers thereof: Si(OR) ｐ (X) ４－ｐ (a) [In general formula (a), R represents an alkyl group, and X represents a halogen atom. When multiple Rs are present, the multiple Rs may be the same or different. When multiple Xs are present, the multiple Xs may be the same or different. p represents an integer of 0 to 4.] The number of carbon atoms in the alkyl group is preferably 1 to 4. The silane-based compounds represented by general formula (a) may be used alone or in combination of two or more.

[0069] Furthermore, the silane compound represented by the general formula (a) preferably includes a silane compound in which p in the general formula (a) is 4. The silane compound in which p in the general formula (a) is 4 (i.e., a tetrafunctional silane compound) is preferably a tetraalkoxysilane. More preferred examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Among these, from the viewpoints of ease of availability and reactivity in the hydrolysis reaction, at least one of tetramethoxysilane and tetraethoxysilane, or a mixture of tetramethoxysilane and tetraethoxysilane, is preferred.

[0070] Commercially available products can also be used as the hydrolysis polycondensate of the silane compound, and suitable examples of such commercially available products include "Colcoat (registered trademark) N-103X," "Colcoat (registered trademark) PX," "Methyl silicate 51" which is an average tetramer oligomer of tetramethoxysilane, "Methyl silicate 53A" which is an average heptamer oligomer of tetramethoxysilane, "Ethyl silicate 40" which is an average pentamer oligomer of tetraethoxysilane, "Ethyl silicate 48" which is an average decamer oligomer of tetraethoxysilane, and "EMS-485" which is a mixture of an average decamer oligomer of tetramethoxysilane and an average decamer oligomer of tetraethoxysilane (all manufactured by Colcoat Co., Ltd.).

[0071] The laminate film used in each embodiment is preferably a laminate film after use for a specific purpose. The laminate film used for a specific purpose (in practical use) may have a configuration in which a water-insoluble resin component is blended in the intermediate layer together with the silane compound to improve adhesion between the substrate film and the coating layer (intermediate layer and release agent layer) during use, within a range that does not impair the effects of this embodiment. The intermediate layer may be configured by applying and curing a composition containing a water-insoluble resin component. Examples of water-insoluble resin components include energy ray-curable resins, epoxy resins, and melamine resins. It is preferable that the water-insoluble resin component maintains its water-insolubility even after curing.

[0072] The "water-insoluble resin component" is preferably an energy ray-curable resin, and examples thereof include polyfunctional (meth)acrylates such as dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. When the intermediate layer contains a hydrophilic and water-insoluble resin (preferably the silane-based compound), the content of the hydrophilic and water-insoluble resin is preferably 30% by mass or more and 90% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the total mass of the intermediate layer. The upper limit of the content of the hydrophilic and water-insoluble resin in the intermediate layer is 100% by mass. When the intermediate layer contains a hydrophilic, water-insoluble resin (preferably the silane-based compound) and a "water-insoluble resin component," the content of the hydrophilic, water-insoluble resin is preferably 30% by mass or more and 90% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the total mass of the intermediate layer. The content of the "water-insoluble resin component" is preferably 10% by mass or more and 70% by mass or less, and more preferably 20% by mass or more and 60% by mass or less, relative to the total mass of the intermediate layer. The upper limit of the total content of the hydrophilic, water-insoluble resin and the "water-insoluble resin component" in the intermediate layer is 100% by mass.

[0073] Furthermore, when an energy ray-curable resin is blended in the intermediate layer, it is preferable that the intermediate layer further contains a photopolymerization initiator. Examples of the photopolymerization initiator include 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone. When the intermediate layer contains a photopolymerization initiator, the content of the photopolymerization initiator is preferably 20 parts by mass or less, and more preferably 10% by mass or less, based on 100 parts by mass of the "water-insoluble resin component."

[0074] The thickness of the intermediate layer is preferably 0.01 μm or more and 1 μm or less, more preferably 0.03 μm or more and 0.5 μm or less, and even more preferably 0.05 μm or more and 0.3 μm or less, from the viewpoint of facilitating water penetration when the intermediate layer comes into contact with water.

[0075] The laminated film used in each embodiment of the present invention has a hydrophilic, water-insoluble intermediate layer, so that the removed coating layer residue has a configuration in which the surface of the release agent layer and the surface of the hydrophilic intermediate layer are present. When the residue with this configuration is immersed in cleaning water, the release agent layer surface faces the air due to surface tension, and the intermediate layer surface faces the water, resulting in stability. In other words, the residue with this configuration is more likely to exist at the water-air interface than in water. Here, because the coating layer residue is an extremely thin film, even if it has a slightly high density, the buoyancy due to surface tension is greater, and it is thought that the water-insoluble intermediate layer allows it to continue floating on the surface of the water.

[0076] The laminate film used in each embodiment is generally used for the purpose of protecting the surfaces of other functional sheets or various parts used for specific purposes during the manufacture, transportation, storage, etc. of these functional sheets or parts. In fact, after fulfilling its role of protecting these parts, it is often peeled off from the surface and discarded. Therefore, by using the laminate film, the coating layer and the base film can be easily separated from the laminate film, which is an application that greatly contributes from the viewpoints of resource conservation and environmental protection.

[0077] The present invention is not limited to the above-described embodiment, and may include modifications and improvements within the scope of achieving the object of the present invention.

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0079] (Preparation of Laminated Film) A biaxially stretched polyethylene terephthalate film (thickness: 31 μm) was prepared as a substrate film.

[0080] (Preparation of intermediate layer-forming composition) An alkoxysilane hydrolysis polycondensate (manufactured by Colcoat Co., Ltd., product name "Colcoat (registered trademark) N-103X") and a polyfunctional acrylate, dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd., product name "Aronix M-400"), were mixed in a solids ratio (mass ratio) of 65:35 to obtain a mixture. To the mixture, a photopolymerization initiator (manufactured by IGM Resins B.V., product name "Omnirad 907") and 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one (solids content 100 mass%) were added. Finally, methyl ethyl ketone (MEK) and isopropyl alcohol were mixed in a volume ratio of 3:7 to obtain a composition for forming an intermediate layer with a solids content of 1.0 mass%. The mixing ratios of the photopolymerization initiator and 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one in the mixture were as follows: Photopolymerization initiator: 10% by mass relative to Aronix M-400 (100% by mass solids content); 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one: 10% by mass relative to Aronix M-400 (100% by mass solids content) (formation of intermediate layer).

[0081] Next, the composition for forming an intermediate layer was applied onto the substrate film using a bar coater, and the substrate was passed through a drying oven at 130°C for 1 minute, and then irradiated with ultraviolet light (integrated light amount: 250 mJ / cm ２ ) to obtain a film with an intermediate layer (thickness: 0.04 μm).

[0082] (Preparation of Release Agent Layer-Forming Composition) 94 parts by weight of dipentaerythritol hexaacrylate (solid content 100% by weight), which is a polyfunctional acrylate, 1 part by weight of acrylic-modified polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-22-164A", solid content 100% by weight), and 5 parts by weight of a photopolymerization initiator (manufactured by IGM Resins B.V., trade name "Omnirad (registered trademark) 907" (2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, solid content 100% by weight) were diluted with a mixed solvent of isopropyl alcohol and methyl ethyl ketone to obtain a release agent composition with a solid content concentration of 20% by weight. The mixing ratio of the mixed solvent of isopropyl alcohol and methyl ethyl ketone was isopropyl alcohol:methyl ethyl ketone = 3:1 (mass ratio). Dipentaerythritol hexaacrylate corresponds to the water-insoluble resin component.

[0083] (Formation of Release Agent Layer) The obtained release agent composition was applied onto the intermediate layer formed on the substrate film using a bar coater and dried at 80°C for 1 minute to obtain a coating layer. Next, the coating layer was irradiated with ultraviolet light (integrated light amount: 250 mJ / cm ２ ) to form a release agent layer (thickness: 1 μm), thereby obtaining a laminated film (substrate film / intermediate layer / release agent layer) in which the substrate film, intermediate layer, and release agent layer were laminated in this order. The layer consisting of the intermediate layer and the release agent layer (intermediate layer / release agent layer) constitutes a coating layer. In the obtained laminated film (substrate film / intermediate layer / release agent layer), the water contact angle of the surface of the intermediate layer facing the substrate film was 42 degrees. The water contact angle of the surface of the release agent layer was 93 degrees. From these results, the difference between the water contact angle of the surface of the release agent layer and the water contact angle of the surface of the intermediate layer facing the substrate film was calculated to be 51 degrees.

[0084] [Example 1] The coating layer was removed using the obtained laminated film by the following method. The laminated film was cut into a width of 50 mm and a length of 100 m, and a roll was prepared by winding it around a core with a winding tension of 60 N (preparation step). The obtained roll had a width of 50 mm and a diameter of 110 mm. In addition, the end of the roll was secured with a 50 mm square piece of adhesive tape to prevent it from unwinding.

[0085] (Ultrasonic Treatment Step) Using an ultrasonic treatment device 80 shown in FIG. 3A, ultrasonic waves were irradiated onto the roll obtained in Example 1. First, tap water W1 was placed in a water tank 81. Next, the roll was placed on a treatment object setting table 84, and the roll was immersed in the tap water W1. In this state, ultrasonic waves were irradiated onto the roll. The conditions for ultrasonic irradiation were as follows. (Ultrasonic irradiation conditions) Type of water: tap water Water temperature: 25°C Oscillation frequency: 40 kHz Ultrasonic irradiation time: 10 minutes Power density: 0.70 (W / cm ２ ) Distance D from the top surface of the vibration plate 82 installed in the water tank 81 to the bottom of the roll ２ Distance D from the top surface of the vibration plate 82 installed in the water tank 81 to the water surface: 80 mm ３ : 200 mm

[0086] (Cutting Process and Removal Process) After the ultrasonic treatment process, 3 m of the laminated film was unwound from the roll, and a 50 mm square piece of film was cut from the unwound point. This was used as the evaluation sample (cutting process). Using a pressure vessel with a configuration similar to the pressure vessel 60A shown in FIG. 5, the evaluation sample was treated with treated water in the following manner. The pressure vessel used in this example was a cylindrical stainless steel pressure vessel with a capacity of 5 L. First, 2 L of water as treated water was placed in the pressure vessel body, and the water was boiled to 100°C using an induction heating (IH) heater (heater 68 in the case of FIG. 5). The evaluation sample was then immersed in the boiling water at 100°C, the pressure lid was closed, the relief valve was set to 2 atmospheres, and heating was resumed. After confirming boiling (fume), the pressure inside the pressure vessel reached 2 atmospheres, and the temperature of the superheated water was confirmed to be 120°C. After 15 minutes had passed (held) in this state, the pressure inside the pressure vessel was returned to normal pressure (removal process).

[0087] [Examples 2 to 5] The coating layer removal method in Examples 2 to 5 was carried out in the same manner as in Example 1, except that the ultrasonic irradiation conditions (water temperature and oscillation frequency) in Example 1 were changed to the conditions shown in Table 1.

[0088] Comparative Example 1 The coating layer of Comparative Example 1 was removed in the same manner as in Example 1, except that the ultrasonic treatment step was not performed.

[0089] [Comparative Example 2] The coating layer removal method in Comparative Example 2 involved a cutting process, a removal process, and an ultrasonic treatment process, performed in this order. (Cutting Process) A laminated film was produced in the same manner as in Example 1. A 50 mm square film piece was cut from the resulting laminated film, and this was used as a comparative evaluation sample. (Removal Process) The removal process was performed in the same manner as in Example 1, except that the comparative evaluation sample was used instead of the evaluation sample in Example 1. After the removal process, the comparative evaluation sample was removed from the pressure vessel with tweezers. (Ultrasonic Treatment Process) Using the same ultrasonic treatment device 80 as in Example 1, ultrasonic waves were irradiated to the comparative evaluation sample in the following manner. The comparative evaluation sample was placed in a basket (16 cm long, 16 cm wide, and 2 cm high) with multiple 20 mm square holes. The basket was placed on a workpiece placement table 84 in a water tank 81 containing tap water W1. In this state, ultrasonic waves were irradiated to the comparative evaluation sample under the same conditions as in Example 1.

[0090] [Evaluation] (Separability test of base film) After the removal step, an evaluation sample (50 mm square) was taken from the pressure vessel with tweezers, and the separability of the base film was confirmed visually. Note that the evaluation sample was simply taken with tweezers, and no operations such as stirring the evaluation sample in water were performed on the evaluation sample. In the case of Comparative Example 2, after the ultrasonic treatment step, a comparative evaluation sample (50 mm square) was taken from the basket with tweezers, and the separability of the base film was confirmed visually. As with the evaluation sample, the comparative evaluation sample was also not subjected to operations such as stirring in water. In the separability test, a rating of A was given when the release agent layer / intermediate layer was completely peeled off from the base film, and a rating of F was given when the release agent layer / intermediate layer was not completely peeled off.

[0091] Table 1 shows the ultrasonic irradiation conditions and the results of the separation test for each example.

[0092]

[0093] According to the coating layer removal methods of Examples 1 to 5, by carrying out the ultrasonic treatment step, the coating layer (release agent layer / intermediate layer) was completely peeled off from the substrate film in the subsequent removal step without performing operations such as stirring the laminated film in water. On the other hand, in Comparative Example 1, in which the ultrasonic treatment step was not carried out, and Comparative Example 2, in which the ultrasonic treatment step was carried out after the removal step, the coating layer (release agent layer / intermediate layer) was not completely peeled off from the substrate film.

[0094] 18...upper discharge pipe, 18A...upper discharge port, 19...lower discharge pipe, 19A...lower discharge port, 21...upper discharge valve, 22...lower discharge valve, 40...ultrasonic oscillator, 50, 50D, 50G...laminated film, 50A...folded stack, 50B...sheet stack, 50C...roll, 51, 51D...base film, 52, 52D...coating layer, 55...rubber band, 60A...pressure vessel, 61A...pressure lid, 62A...pressure vessel body, 66...mounting table, 67...basket, 68 heater..., 70...pressure control unit, 71...relief valve, 72...pressure sensor, 80...ultrasonic processing device, 81...water tank, 82...vibration plate, 84...treatment object mounting table, 100...recovery container, 521...intermediate layer, 522...release agent layer.

Claims

1. A method for removing a coating layer, comprising, in this order: a preparation step of preparing a laminated film having a base film and a coating layer; an ultrasonic treatment step of irradiating the laminated film with ultrasonic waves via water; a removal step of treating the laminated film with treated water or water vapor to remove the coating layer from the laminated film; and a recovery step of recovering the base film, wherein the coating layer includes a hydrophilic and water-insoluble intermediate layer and a release agent layer, and the intermediate layer is disposed between the base film and the release agent layer.

2. The method for removing a coating layer according to claim 1, wherein the laminated film in the ultrasonic treatment step is in the form of a sheet, a roll, or a folded film.

3. The method for removing a coating layer according to claim 2, further comprising a cutting step of cutting the laminated film into sheets between the ultrasonic treatment step and the removing step when the laminated film is in a roll or folded form.

4. The method for removing a coating layer according to claim 1 or 2, wherein the ultrasonic treatment step is carried out while the laminated film is immersed in water.

5. A method for removing a coating layer according to claim 1 or claim 2, wherein the removal step is a step of placing the laminated film and the treated water in a pressure vessel, immersing the laminated film in the treated water, heating the treated water, and pressurizing the pressure in the pressure vessel to a pressure higher than 1 atmosphere.

6. The method for removing a coating layer according to claim 1 or claim 2, wherein the removing step is a step of placing the laminated film in a treatment container and exposing the laminated film to water vapor in the treatment container.

7. A method for removing a coating layer according to claim 1 or claim 2, wherein the laminated film prepared in the preparation step is a laminated film with a ceramic green sheet, and a ceramic green sheet is attached to the side of the coating layer opposite the base film.

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