METHOD FOR REMOVING COATING FROM COATED FILM AND EQUIPMENT FOR REMOVING COATING

Provided is a method for removing a coating film from a coated film including a coating film containing a water-soluble resin on at least one side of a base film. The method includes: supplying a cleaning liquid in a form of droplets to a surface of the coating film, and retaining the cleaning liquid in the form of droplets on the surface of the coating film; and subsequently removing the coating film containing the cleaning liquid from the coated film.

FIELD OF THE INVENTION

The present invention relates to a method for removing a coating from a coated film and an equipment for removing the coating, which enable efficient removal of a coating on a surface of a thermoplastic resin film.

BACKGROUND OF THE INVENTION

While plastics are used in a variety of fields, they are considered to be substances causing marine pollution such as microplastics, and the load of plastics on the environment needs to be reduced urgently.

In recent years, as the number of electronic devices such as CPUs installed in computers and smartphones has been increasing with the advance of the Internet of Things (IoT), the number of multilayer ceramic capacitors (MLCCs) required to drive these electronic devices has been rapidly increasing. A common method for manufacturing such an MLCC uses, as a carrier sheet, a release film including a release layer formed on a plastic base film, and includes a step of forming a ceramic green sheet layer on the release film, and a step of peeling the ceramic green sheet layer to obtain a ceramic green sheet. In this step, the release film from which the ceramic sheet has been peeled is discarded as an unwanted substance.

In other words, the increase of release films as waste resulting from the rapid increase in MLCC production volume in recent years has become an environmental issue, and efforts to reuse the base film are gaining momentum. The components of the release layer contained in the release film are generally different in composition from the components of the base film from the viewpoint of releasability. Thus, when a release film with a release layer is remelted without being treated to form a recycled film, this film cannot be formed stably because the components of the release layer are present therein as foreign matter.

Patent Literature 1 discloses, as a method for removing release components from a release film, a method in which a release film including a water-soluble resin layer formed between a base film and a release layer is used, it is immersed in a hot water bath for two seconds or more, and then the release film surface is scraped with a brush roll to remove off the release layer.

PATENT LITERATURE

SUMMARY OF THE INVENTION

However, the method for removing a coating disclosed in Patent Literature 1 has a problem in that, due to elution of the water-soluble resin layer into the hot water bath, the resin concentration in the hot water increases with the passage of treatment time, making it impossible to continuously maintain the initial removability. Even when a method of increasing the amount of supplied water is used to suppress the increase in resin concentration, the amount of wastewater also increases with the increasing amount of supplied water, and thus there is a problem that not only the cleaning cost significantly increases but also load on the environment significantly increases.

In view of this, it is an object of the present invention to provide a coating removing method and a coating removing equipment that, in order to obtain a base film with which a recycled film can be stably formed from a used coated film even when the film is remelted, can efficiently remove a coating from a surface of a coated film including a coating containing a water-soluble resin on at least one side of a base film by dissolving the water-soluble resin with a very small amount of a solvent.

A coating removing method according to embodiments of the present invention to solve the object is a method for removing a coating from a coated film including a coating containing a water-soluble resin on at least one side of a base film. The method includes: supplying a cleaning liquid in a form of droplets to a surface of the coating, and retaining the cleaning liquid in the form of droplets on the surface of the coating; and c removing the coating containing the cleaning liquid from the coated film.

The coating removing method according to the present invention is preferably the following methods.

The cleaning liquid is supplied to the surface of the coating while being heated to 40° C. or higher.

The coated film is heated to 40° C. or higher.

The coating film contains a curable silicone resin.

The cleaning liquid is water.

A diameter of the droplets of the cleaning liquid is 1 mm or less.

A coating removing equipment according to embodiments of the present invention to solve the object is an equipment for removing a coating from a coated film including a coating containing a water-soluble resin on at least one side of a base film. The equipment includes: a cleaning-liquid applying mechanism configured to dispense a cleaning liquid in a form of droplets toward a surface of the coating film such that the cleaning liquid is able to be retained in the form of droplets on the surface of the coating; and a removing mechanism configured to remove the coating film containing the cleaning liquid from the coated film in which the cleaning liquid has been supplied to the surface of the coating.

The coating film removing equipment according to the present invention preferably has the following aspects.

The cleaning-liquid supplying mechanism includes a unit configured to heat the cleaning liquid.

The coating film removing equipment further includes a unit configured to heat the coated film.

By the method for removing a coating film and the equipment for removing a coating film according to embodiments of the present invention, the coating film can be efficiently removed from the coated film including the coating film containing the water-soluble resin on at least one side of the base film with a small amount of the cleaning liquid.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

As a result of diligently studying a method for efficiently removing a coating film from a surface of a coated film including a coating film containing a water-soluble resin on at least one side of a base film, using a very small amount of a cleaning liquid, the inventors of the present invention have come up with a coating film removing method and a coating film removing equipment for a coated film as follows.

[Coated Film to be Processed]

The coating film removing method for a coated film in embodiments of the present invention is a method intended for a coated film including a coating film containing a water-soluble resin on at least one side of a base film, by which the coating film containing a cleaning liquid is removed off from the base film.

As the coated film to be processed, all of coated films can be processed that have coatings containing water-soluble resins for which load on the environment and other factors are considered. The water-soluble resin is more preferably a resin that contains, as a main component, at least one type of water-soluble polyester resins, polyester urethane resins, acrylic resins, ethylene ionomer resins, polyvinyl alcohol resins, polyvinyl pyrrolidone resins, ethylene-vinyl alcohol resins, and starch.

The coating film containing the water-soluble resin may be a single-layer product containing the water-soluble resin, may be a layered product including two or more layers containing the water-soluble resin, or may be a layered product including a layer containing the water-soluble resin and a layer containing no water-soluble resin.

A coated release film containing a release component in addition to the water-soluble resin in part of the coating is particularly preferable, which can efficiently exert the effect of removing the coating film. The release component herein is a component that increases the contact angle of the coating surface to the cleaning liquid, that is, reduces the surface energy of the coating film. Examples thereof include a curable silicone resin compound containing dimethylsiloxane as a main skeleton, a compound having a long-chain alkyl group, and a compound containing fluorine. The coating film may be a layer containing the water-soluble resin and the release component, or may be a coating film in which a layer containing the water-soluble resin and a layer containing the release component are layered together. In the layered coating film, it is preferable that the layer containing the water-soluble resin is formed directly on the base film and the layer containing the release component is then formed on the top surface, and it is particularly preferable to use, as the release component, a curable silicone resin compound containing, as a main skeleton, dimethylsiloxane that has high water permeability and can be suitably used as the cleaning liquid.

[Method for Removing Coating from Coated Film]

The coating film removing method in embodiments of the present invention is a removing method in which the cleaning liquid in the form of droplets is supplied to the coating surface of the above-described coated film, the cleaning liquid is retained in the form of droplets on the coating surface, and then the coating film containing the cleaning liquid is removed from the base film.

As a method of supplying the cleaning liquid to the coating surface, a method of supplying the cleaning liquid in the form of a sheet, or a thin film, as in a general coating process can be easily conceived of. However, for a coated film a coating of which has a surface tension lower than the surface tension of the cleaning liquid, such as a coated film containing a release component in part of the coating film, there is a problem that the cleaning liquid is shed by the coating and flows greatly, the cleaning liquid is unevenly distributed, and the coating fails to be removed in areas where no cleaning liquid is present.

In contrast, according to embodiments of the present invention, by discretely supplying the cleaning liquid to the coating film in the form of droplets, the cleaning liquid can be supplied to substantially the entire surface of the coating film, even to a coated film a coating of which has a surface tension lower than the surface tension of the cleaning liquid, because the cleaning liquid supplied to the coating film surface maintains the form of droplets without flowing. The supplied cleaning liquid spreads around the area while dissolving the water-soluble resin in the coating, and the cleaning liquid is distributed over the entire surface of the coating film, so that the water-soluble resin component dissolves over the entire surface of the coating film, and the coating film containing the cleaning liquid can be easily removed off from the base film. Even if the coating of the coated film to be processed is a layered coating film containing a release component on the top surface, when the curable silicone resin compound containing dimethylsiloxane as a main skeleton in the release component is used, the cleaning liquid will permeate from the coating surface and reach the layer containing the water-soluble resin, and thus the same cleaning effect can be exerted to remove off the coating film.

The size of the droplets of the cleaning liquid to be supplied to the surface of the coating film may be any size that allows the cleaning liquid to be discretely held on the coating film in the form of droplets. However, if the droplet diameter is too large, the discretely supplied cleaning liquid may flow due to tilting or vibration of the coated film and be unevenly distributed. Thus, the droplet diameter is preferably 1 mm or less in order to prevent the droplets from flowing on the coating film. In order to efficiently clean the entire surface of the coating film, it is preferable to supply the cleaning liquid of 1 cm3or more per unit area of 1 m2for a coated film including a coating film thickness of 1 μm or less in total. By doing so, even with the droplets discretely supplied onto the coating film, the cleaning liquid spreads around the area to be distributed entirely while dissolving the water-soluble resin, and thus the coating film containing the cleaning liquid on substantially the entire surface of the coated film can be removed off. The diameter of the droplets of the cleaning liquid described here is a numerical value when droplets at less than one second after the cleaning liquid has been supplied to the coating surface in the form of droplets are observed and measured under a microscope. By using a transparent coated film, for example, and observing the supplied droplets of the cleaning liquid from the back side of the film, the diameter of the droplets can be easily measured. If one second or more has elapsed since the cleaning liquid was supplied to the coating surface in the form of droplets, a phenomenon in which the cleaning liquid spreads while dissolving the water-soluble resin has progressed, and the measurement may be difficult.

In the coating film removing method in embodiments of the present invention, the higher the temperature of the cleaning liquid supplied to the coated film, the faster the dissolution rate of the water-soluble resin, that is, the better the cleaning effect, and thus the temperature of the cleaning liquid supplied to the coated film is preferably 40° C. or higher. To prevent dimensional changes and flatness deterioration of the base film due to heat, the temperature of the cleaning liquid to be supplied to the coated film is preferably 150° C. or lower. Thus, the cleaning liquid is preferably dispensed in the form of droplets the temperature of which is adjusted in accordance with the configuration of the equipment to be used such that the temperature of the cleaning liquid and the film temperature at areas where the cleaning liquid is applied are each set within the range of 40° C. to 150° C.

In the coating film removing method in embodiments of the present invention, raising the temperature of the coated film can also increase the dissolution rate of the water-soluble resin by the cleaning liquid supplied to the coating surface, that is, the cleaning effect is improved, and thus the temperature of the coated film is preferably set to 40° C. or higher and 150° C. or lower similarly to the temperature of the cleaning liquid. The temperature of the coated film described here is the temperature of the coating surface immediately before the cleaning liquid is supplied, and can be measured with a radiation thermometer, for example.

When the temperature of the cleaning liquid to be supplied to the coated film or the coated film is increased as described above, the diameter of the droplets of the cleaning liquid is preferably 10 μm or larger. By doing so, the coating film can be cleaned even if part of the cleaning liquid volatilizes under high temperatures.

As the cleaning liquid for the removing method according to embodiments of the present invention, any solvent exerts its effect if it is a solvent that can dissolve water-soluble resins, but water is preferably used to reduce load on the environment. A surfactant or other agent may be added to the cleaning liquid to improve wettability with the coated film and make it easier for the cleaning liquid to be distributed over the coating surface.

In the coating film removing method according to embodiments of the present invention, the form of the coated film may be in a cut-sheet form, but it is particularly preferable to use the coated film wound in a roll form. By unwinding the coated film in a roll form, performing the coating film removing method according to embodiments of the present invention, and winding the base film after the coating has been removed off, the process of removing coating film can be performed continuously and efficiently.

[Equipment for Removing Coating of Coated Film]

Preferred embodiments of the coating film removing equipment will be described with reference to the drawings. The following description is an example of one of the embodiments according to embodiments of the present invention, which is not limited to this, and various modifications may be made without departing from the gist of the present invention.

FIG.1is a schematic diagram of a coating film removing equipment101according to a first embodiment of the present invention. The coating film removing equipment101includes an unwinding device4that unwinds a coated film2and a winding device5that winds the base film3after the coating film has been removed off. Between the unwinding device4and the winding device5, a drive unit9for conveying the coated film2, a dispense head6for supplying a cleaning liquid11to the coating film of the coated film2, removing equipment7for removing the coating film of the coated film2together with the cleaning liquid11, and a drive unit10for conveying the base film3after the coating film has been removed off are provided. The dispense head6, the removing equipment7, and nozzles14(described later) are enclosed in a booth8.

The coating film removing equipment further includes, as a cleaning-liquid supplying mechanism, a liquid feed pump12for feeding the cleaning liquid11to the dispense head6and a tank (not illustrated) for storing the cleaning liquid in addition to the dispense head6.

The dispense head6only needs to be able to dispense the cleaning liquid11in the form of droplets and supply it to the coating surface of the coated film2, and may be a spray nozzle, for example, but is not limited to this. The amount of the cleaning liquid11to be supplied to the coating surface of the coated film2is preferably set to 1 cm3/m2or more so that the coating film containing the water-soluble resin can be sufficiently dissolved. It is preferable to determine the specifications of the dispense head6and the liquid feed pump12so that the required amount of the cleaning liquid11can be supplied to the coating surface of the coated film2and the form of droplets can be maintained by adjusting the liquid feed pump12in accordance with the conveyance speed of the coated film2.

The cleaning liquid11supplied to the coating surface of the coated film2needs to dissolve the water-soluble resin contained in the coating film before it is then conveyed to the removing equipment7. In other words, to prevent the cleaning liquid11from flowing and dropping off from the coating surface due to vibration or inclination of the coated film2when the coated film2is conveyed, the size of the droplets is preferably set to 1 mm or less in diameter. Thus, the dispense head6is preferably selected that can produce droplets with a diameter of 1 mm or less.

The dispense head6and the removing equipment7only need to be installed so as to face the coating surface of the coated film2, and the installation thereof is not limited to installation on the lower side as illustrated inFIG.1. In order to be able to handle any case whether the coating film of the coated film2wound in a roll form is located on the inside or the outside of the roll, the unwinding device4is more preferably a mechanism that can unwind the coated film from either the upper side or the lower side by changing directions of unwinding the coated film2so that the coating surface of the coated film2can be conveyed in a manner facing the dispense head6and the removing equipment7.

The dispense head6is preferably capable of dispensing a heated cleaning liquid11in order to quickly dissolve the water-soluble resin contained in the coating, and is preferably capable of dispensing the cleaning liquid11heated at 40° C. or higher in particular. For heating the cleaning liquid11, the dispense head6may include a heat source such as a cartridge heater, or the tank (not illustrated) for storing the cleaning liquid may be heated. However, the heating unit is not limited to these, and any unit that can heat the cleaning liquid11may be used.

The material of the dispense head6preferably has heat resistance in order to dispense the heated cleaning liquid11, and metal or a heat-resistant resin is preferably used.

The coating removing equipment101includes a hot-air generator13as a unit of heating the coated film2and the nozzles14connected to the hot-air generator13. By raising the temperature of the coated film2to 40° C. or higher with hot air, the cleaning liquid11supplied to the coating surface quickly dissolves the water-soluble resin contained in the coating film, and the coating film can be more efficiently removed off. As the unit of heating the coated film2, any unit may be used. For example, the coated film2may be brought into direct contact with a heating roll, or an infrared heater may be installed in the booth8for the heating, although the heating unit is not limited to these.

The booth8of the removing equipment101is provided so as to enclose the area from the dispense head6to the removing equipment7to prevent the cleaning liquid11in the form of droplets from dispersing around the area and to prevent the temperature of the heated cleaning liquid and/or the coated film2from decreasing. The material of the booth8preferably has heat resistance because the temperature inside the booth8becomes high, and metal or glass, for example, is preferably used.

In the removing equipment101according to the embodiment of the present invention, as the removing equipment7, a metal plate with a sharp tip that comes into direct contact with the coated film2being conveyed is provided, but the removing equipment is not limited to this. A resin plate with a sharp tip may be provided, or a thin metal plate that is pressed against the coated film2to bend flexibly like a blade may be provided. Alternatively, a mechanism that rotates a brush roll made of metal or resin in the same direction as the conveyance direction or in the opposite direction may be provided to be brought into direct contact with the coating surface of the coated film2, or a waste cloth or a fabric may be used to be pressed against the coated film2and wipe off the coating.

In the removing equipment101according to the embodiment of the present invention, a section from the dispense head6to the removing equipment7is provided such that the booth8encloses the section from the dispense head6to the removing equipment7, because smaller droplets of the cleaning liquid11dispensed from the dispense head6more easily disperse around the area.

The drive units9and10in the present invention preferably have a configuration that can cut the tension in order to stably convey the coated film2and the base film3from which the coating film has been removed off. However, if the tension is cut by a suction roll, a part of the coating film of the coated film2may be sucked in and cause trouble, and thus a configuration nipped by a metal drive roll and a rubber roll is more preferably used. The drive units9and10, to which the cleaning liquid11is likely to adhere, are used preferably with stainless steel or surface treatment being applied as a rust-preventive measure.

It is more preferable to completely remove the cleaning liquid11from the base film3, from which the coating film has been removed off, wound by the winding device5in order to stably form a recycled film after remelting, and a drying device (not illustrated) may be provided between the removing equipment7and the winding device5. The drying device only needs to be provided before winding, and may be provided either upstream or downstream of the drive unit10.

In order to check the quality of the base film3after the coating film has been removed off, an inspection machine (not illustrated) that detects a residue of the coating film and environmental foreign matter attached in the process may be provided upstream of the winding device5. The inspection machine may be selected in accordance with the properties of the base film3, and an inspection machine using transmitted light or reflected light is preferably used. A marking device (not illustrated) for recording the locations of a residue of the coating and environmental foreign matter attached in the process that have been detected by the inspection machine may be provided between the inspection machine and the winding device5. The method of marking by the marking device may be any method, such as using a pen, a sticker, or a laser, that can mark the location of a detection target. Marking the residue of the coating film and environmental foreign matter attached in the process allows such areas to be removed before remelting, and thus a recycled film can be more stably formed and also quality deterioration of the recycled film can be prevented.

FIG.2is a schematic diagram of a removing equipment201according to a second embodiment of the present invention. The removing equipment201is provided with non-contact removing equipment207instead of the removing equipment7provided in the removing equipment101according to the first embodiment. The removing equipment201does not include the hot-air generator13and the nozzles14, but may include the hot-air generator13and the nozzles14. Other than the above, this removing equipment is the same as the removing equipment101illustrated inFIG.1, and thus description is omitted for components that are the same as those of the removing equipment101.

The non-contact removing equipment207only needs to be able to remove off the coating film together with the cleaning liquid11in a non-contact manner, and a method of blowing air or spraying the cleaning liquid11is used, for example. This prevents the conveyance resistance of the coated film2from increasing and the base film3from being damaged by scratches caused by contact, in comparison to the removing equipment7that is brought into direct contact with the coating surface.

FIG.3is a schematic diagram of a removing equipment301that removes coatings from a coated film302including the coatings on both the front and back sides thereof, according to a third embodiment of the present invention. The removing equipment301is provided with, between the unwinding device4and the winding device5, a first discharge head306for supplying the cleaning liquid11to the coating surface of one side of the coated film302, a first removing equipment307for removing this coating film together with the cleaning liquid11, a second dispense head306′ for supplying a cleaning liquid11′ to the coating surface of the other side, and a second removing equipment307′ for removing this coating film together with the cleaning liquid11′. The second removing equipment307′ is provided in a manner being in direct contact with the coating surface on the opposite side of the first removing equipment307with the coated film302interposed therebetween. The removing equipment301further includes, as a cleaning-liquid supplying mechanism, in addition to the first dispense head306and the second dispense heads306′, liquid feed pumps312and312′ for feeding the cleaning liquids11and11′ to the first dispense head306and the second dispense head306′, and a tank (not illustrated) for storing the cleaning liquids11and11′. The removing equipment301does not include the hot-air generator13or the nozzles14, but may include the hot-air generator13and the nozzles14. Other than these, this removing equipment is the same as the removing equipment101illustrated inFIG.1, and thus description is omitted for components that are the same as those of the removing equipment101.

The removing equipment301according to the present embodiment has an equipment configuration in which, to the coating surfaces of the coated film302including coating films on both the front and back sides, the cleaning liquids11and11′ are supplied simultaneously on the front and back sides, and the first removing equipment307and the second removing equipment307′ remove off the coating films together with the cleaning liquids11and11′ in this order. However, the configuration is not limited to this, and any configuration that can remove off the coating films together with the cleaning liquids11and11′ on the front and back sides respectively may be used. For example, this removing equipment may have an equipment configuration including the first dispense head306and the first removing equipment307and, downstream of these, including the second dispense head306′ and the second removing equipment307′, in which the coating films together with the cleaning liquids11and11′ are removed off from one side after another.

The first removing equipment307and the second removing equipment307′ are not limited to the configuration illustrated inFIG.3, and non-contact removing equipment may be used.

In order to efficiently supply the cleaning liquids to the coating surfaces of the coated films2and302, a device for exposing the coating surfaces of the coated films2and302may be provided between the unwinding device4and the drive unit9. For example, when the coating films of the coated films2and302are made of a curable silicone resin compound containing dimethylsiloxane as a main skeleton, the coated film is preferably used as a release film for the process due to characteristics of its surface free energy. Specifically, after a substance to be released has been provided on a coating film of each coated film, the coated film is used as a release film for extracting the substance to be released in a desired shape. In the coated film after being used as such a release film for the process, the substance to be released may remain on the coating surface, and thus a device for exposing a coating surface of a coated film is preferably provided between the unwinding device4and the drive unit9to expose the coating surfaces of the coated films2and302. The device for exposing the coating surfaces may be of a contact type or a non-contact type, and is appropriately selected in accordance with the state of the remaining substance to be released.

Examples of the substance to be released, which is to be appropriately selected in accordance with the characteristics of the coating film, include inorganic materials such as metal provided by vapor deposition, adhesives made of organic material such as acryl provided by a coating process, and ceramic green sheets containing barium titanate as a main component.

EXAMPLES

The following describes Examples of the present invention, but the present invention is not necessarily limited to these.

A polyvinyl alcohol resin having a film thickness of 0.1 μm was formed, as a water-soluble resin, on a base film of polyethylene terephthalate having a thickness of 30 μm, and on top of that, a curable silicone resin having a film thickness of 0.1 μm was formed, as a release component, whereby a coated film was prepared.

Removability was evaluated with commercially available dyne pens (surface energy: 30, 70 mN/m) and measured by the following method. Under the environment of a room temperature of 23° C., a drawing was done on a sample surface with each dyne pen. If the drawing in this state could be retained for 4 seconds or more, the surface energy of the sample surface was determined to be higher than the surface energy of the corresponding dyne pen. If the curable silicone resin of the release component of the coated film remains on the surface, the surface energy thereof is less than 30 mN/m, and thus reagents of both dyne pens are shed by the sample surface and the drawings cannot be retained. If the coating of the curable silicone resin as the release component has been removed off and the polyvinyl alcohol resin has been exposed, the surface energy thereof is 70 mN/m or higher, and thus the drawings by both dye pens can be retained. If both coatings of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin have been removed off and the polyethylene terephthalate has been exposed, the surface energy thereof is 43.8 mN/m, and thus the drawing by 30-mN/m dyne pen can be retained, but the drawing by the 70-mN/m dyne pen cannot be retained. The above evaluation method was used to determine whether the coating of the coated film could be removed off.

<Removing of Coating from Coated Film>

The coated film2was set in the unwinding device4of the removing equipment101illustrated inFIG.1. While the coated film was being conveyed into the booth8by the drive unit9, water (room temperature: 20° C.) was applied as the cleaning liquid11to the coating surface in the form of droplets from a spray nozzle (¼M KB 80063N S303-RW manufactured by Ikeuchi Co., Ltd.) of the discharge head6inside the booth8. Subsequently, a plate with a sharp tip made of SUS630 was brought into contact with the coated film by the removing equipment7, the coating film together with the cleaning liquid11in the form of droplets applied to the coating surface was removed off from the base film3, and the base film3from which the coating film had been removed off was wound by the winding device5. The conveyance speed was increased sequentially from 10 m/min to be set to 10, 30, 50, and 100 m/min. In Example 1, heating of the coated film2by the hot-air generator13and the nozzles14was not performed.

The cleaning liquid11dispensed from the spray nozzle was fed from a Mohno Pump (HEISHIN Ltd. CY08), the feed liquid amount was adjusted in accordance with the speed of conveyance, and the feed liquid amount was set to 30 cm3per 1.0 m2unit area of the coated film2for each conveyance speed. The droplets of the cleaning liquid11applied to the coated film2were observed from the back side, and the diameter of the droplets was confirmed to be 1 mm at the maximum. When the temperature of the coated film was measured with a radiation thermometer from the back side of the coated film2immediately after the droplets had been applied, it was 20° C.

When the base film3, from which the coating film had been removed off, after being wound by the winding device5was collected, the maximum conveyance speed at which both coating films of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin could be removed off was 30 m/min. At the higher conveyance speeds of 50 and 100 m/min, it was observed in the removability evaluation that the coating film of the curable silicone resin or the polyvinyl alcohol resin partially remained.

The operations in Example 1 were performed except that 50° C. water was used as the cleaning liquid11to be dispensed from the spray nozzle (¼M KB 80063N S303-RW manufactured by Ikeuchi Co., Ltd.) of Example 1. 50° C. water, the temperature of which was adjusted by immersing an immersion heater in the tank for storing the cleaning liquid11, was fed to the spray nozzles6by the liquid feed pump12. The droplets of the cleaning liquid11supplied to the coated film2were observed from the back side, and the diameter of the droplets was confirmed to be 1.0 mm at the maximum. When the temperature of the coated film2was measured with the radiation thermometer from the back side of the coated film2immediately after the droplets had been supplied, it was 40° C.

When the base film3, from which the coating film had been removed off, after being wound by the winding device5was collected, the maximum conveyance speed at which both coating films of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin could be removed off was 50 m/min. At the conveyor speed of 100 m/min, it was observed in the removability evaluation that the coating film of the curable silicone resin or the polyvinyl alcohol resin partially remained.

The operations in Example 2 were performed except that the temperature of water used as the cleaning liquid11in Example 2 was set to 90° C. The droplets of the cleaning liquid11supplied to the coated film2were observed from the back side, and the diameter of the droplets was confirmed to be 1.0 mm at the maximum. When the temperature of the coated film2was measured with the radiation thermometer from the back side of the coated film2immediately after the droplets had been supplied, it was 75° C.

When the base film3, from which the coating film had been removed off, after being wound by the winding device5was collected, the maximum conveyance speed at which both coating films of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin could be removed off was 100 m/min.

The operations in Example 1 were performed except that, in the removing equipment101of Example 1, hot air (60° C.) generated by the hot-air generator13(TSK-56 manufactured by Kansai Electric Heat Corp.) was blown from the nozzles14including slit openings onto the back side of the coated film2at substantially the same time as the droplets were supplied. The droplets of the cleaning liquid11applied to the coated film2were observed from the back side, and the diameter of the droplets was confirmed to be 1.0 mm at the maximum. When the temperature of the coated film was measured with the radiation thermometer from the back side of the coated film2immediately after the application of the droplets and the blowing of the hot air, it was 40° C.

When the base film3, from which the coating had been removed off, after being wound by the winding device5was collected, the maximum conveyance speed at which both coatings of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin could be removed off was 50 m/min.

Comparative Example 1

A conventional removing equipment401illustrated inFIG.4was used to remove the coating film of the coated film2. The removing equipment401includes a water tank414that holds water as the cleaning liquid11, a drainage tank415that is adjacent such that the liquid level of the water tank414overflows and drains thereinto, and a filtration filter416for separating removed coating films contained in the drainage.

The coated film2was set on an unwinding device404of the removing equipment401, was conveyed by a drive unit409to the water tank414to be brought into contact with water (room temperature: 20° C.) as the cleaning liquid11, and was then brought into contact with a plate with a sharp tip made of SUS630 by removing equipment407to remove off the coating film together with the cleaning liquid11, and the base film3from which the coating film had been removed off was wound by a winding device405.

The feed liquid amount of a new cleaning liquid11to be fed into the water tank414was confirmed to be the minimum required feed liquid amount by checking the state of the coating being removed. As the water-soluble polyvinyl alcohol resin contained in the coating dissolved and the concentration of the solution increased, the solubility of the polyvinyl alcohol resin decreased. Thus, the cleaning liquid11of 25,000 cm3per unit area (1 m2) of the coated film needed to be fed in order to continuously remove off the coating.

When the base film3, from which the coating film had been removed off, after being wound by the winding device405was collected, the conveyance speed at which both coating films of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin could be removed off was 50 m/min at the maximum. At the conveyance speed of 100 m/min, it was observed in the removability evaluation that the coating films of the curable silicone resin and the polyvinyl alcohol resin partially remained.

Comparative Example 2

A removing equipment501illustrated inFIG.5was used to remove the coating film of the coated film2. The removing equipment501includes a pressure device512and a dispense head506to dispense water as the cleaning liquid11at high pressure.

The operations in Example 1 were performed except that, instead of the spray nozzle6of Example 1, the pressure device512and the discharge head506were used such that the cleaning liquid11became high-pressure water and the conveyance speed was limited to 50 m/min. The high-pressure water (room temperature: 20° C.) was dispensed from the included dispense head506toward the coating film surface of the coated film2by using the pressure device512(K2 Classic high pressure washer manufactured by Kärcher Japan Co., Ltd.). The cleaning liquid11dispensed at high pressure was dispensed continuously and in large amount in order to maintain the high pressure, and thus it did not form droplets at all when it adhered to the coated film2, but rather dripped from the entire surface of the coated film2. Furthermore, the cleaning liquid11that had bounced off the surface of the coated film2accumulated in large amount in the booth8. When the temperature of the coated film2was measured with a radiation thermometer from the back side of the coated film2immediately after the cleaning liquid11had been applied, it was 20° C.

When the base film3, from which the coating film had been removed off, after being wound up by the winding device5was collected and the amount of the high-pressure water that could remove off both coatings of the curable silicone resin as the release component and the water-soluble polyvinyl alcohol resin was checked, the high-pressure water of 800 cm3per 1.0 m2unit area of the coated film was necessary. Herein, the amount of the high-pressure water was derived by collecting the coating film containing the cleaning liquid11, which had been removed off by the removing equipment7, and the cleaning liquid11accumulated in the booth, calculating the amount of the cleaning liquid11from results of weight measurement, and converting it into the amount per unit area of the coated film2.

Comparative Example 3

A removing equipment601illustrated inFIG.6was used to remove the coating film of the coated film2. The removing equipment601includes a steam generator612and a dispense head606for dispensing water as the cleaning liquid11in the form of steam.

The operations in Example 1 were performed except that, instead of the spray nozzle6of Example 1, the steam generator612and the discharge head606were used such that the cleaning liquid11became steam and the conveyance speed was limited to 30 m/min. The steam was dispensed from the dispense head (φ10 bore nozzle) toward the coating film surface of the coated film2by using a steam generator (BOILER.V manufactured by Nihon Dennetsu Co., Ltd.). The dispensed steam was a large amount of steam that had a dispense temperature of 100° C. and the dispense pressure of which was 0.4 MPa. Thus, its behavior could be observed in which, even when it had adhered to the coated film2, the form of droplets could not be maintained, and immediately a large number of droplets joined together to form droplets larger than 1 mm, and ran down from the surface of the coated film2. It could also be observed that areas where no cleaning liquid11remained appeared in areas from which the droplets larger than 1 mm had run down. Furthermore, the cleaning liquid11that had run down from the surface of the coated film2accumulated in large amount in the booth8. When the amount of the cleaning liquid11used was measured, it was determined to be 200 cm3per unit area of 1.0 m2of coated film2. The amount of the cleaning liquid11used for steam was derived by collecting the coating film containing the cleaning liquid11, which had been removed off by the removing equipment, and the cleaning liquid11accumulated in the booth, calculating the amount of the cleaning liquid11from results of weight measurement, and converting it into the amount per unit area of the coated film2. When the temperature of the coated film2was measured with the radiation thermometer from the back side of the coated film2immediately after the cleaning liquid11had been applied, it was 85° C. Similarly, when the film temperature at areas from which the droplets larger than 1 mm had run down was measured, it was 50° C.

As a result of the removability evaluation by taking the base film3, from which the coating film had been removed off, after being wound by the winding device5, it was observed that there were portions in which the coating films of the curable silicone resin and the polyvinyl alcohol resin partially remained in areas, from which the droplets larger than 1 mm had run down, on the surface of the coated film2.

In Examples 1 to 4 of the present invention, the amount of the cleaning liquid used per unit area could be significantly reduced in comparison with Comparative Example 1 using the conventional removing equipment401, Comparative Example 2 using a high-pressure cleaning liquid in the removing equipment501, and Comparative Example 3 using a steam injection in the removing equipment601. Thus, in Examples 1 to 4, the amount of wastewater can be significantly reduced, and thus load on the environment can be reduced and the cleaning cost can be reduced.

In Comparative Example 3, the droplets had run down from the surface of the coated film and it was confirmed that the coating film partially remained at areas from which the droplets had run down. Thus, it could be demonstrated that it is important to retain the droplets on the surface of the coated film as in Examples 1 to 4 in order to remove off the coating film.

Comparison Among Examples 1, 2, and 3

In Example 2, by increasing the temperature of the cleaning liquid to 50° C., the conveyance speed at which the coating film of the coated film could be removed off could be set higher than in Example 1 in which the temperature of the cleaning liquid was 20° C., and the coating film could be removed off even at the conveyance speed of 50 m/min at the maximum. In Example 3, by increasing the temperature of the cleaning liquid to 90° C., the conveyance speed at which the coating film of the coated film could be removed off could be set still higher, and the coating film could be removed off even at the conveyance speed of 100 m/min.

Comparison Among Examples 1, 2, and 4

In Example 2 in which the temperature of the coated film was set to 45° C. by increasing the temperature of the cleaning liquid to 50° C. and in Example 4 in which the temperature of the coated film was increased to 40° C. by applying the cleaning liquid at room temperature (20° C.) the conveyance speeds at which the coating film of the coated film could be removed off were equally 50 m/min at the maximum. In both methods of heating the coated film, by setting the temperature of the coated film to 40° C., the conveyance speed at which the coating film could be removed off could be set higher than in Example 1 in which the temperature of the coated film was set to room temperature (20° C.)

The removing method and removing equipment for a coated film according the present invention can be suitably used for reuse of a film including a release layer. The coated film that can be used in the removing method and the removing equipment for a coated film according to the present invention is not limited to a film including a coating containing a water-soluble resin on one side of a base film, and only needs to be a recyclable resin film, a paper film, or a metal film including a coating containing a readily soluble resin layer.

REFERENCE SIGNS LIST