Coating film removal method

Abstract

To provide a coating film removal method which enables significant reduction of powder dust and noise and enables a coating film to be peeled in a short time.SOLUTION: A coating film removal method includes: a first removal step in which a steel material 1 is heated by electromagnetic induction to remove a part as seen in a thickness direction of a coating film 2; and a second removal step in which the remaining coating film 2, from which the part as seen in the thickness direction has been removed, is removed from the steel material 1 by radiation of a laser beam. Accordingly, an undercoat layer 2b, a middle coat layer 2c, and a topcoat layer 2d, which exclude a corrosion-proofing ground layer 2a formed by an inorganic paint, of the coating film 2 are quickly removed by electromagnetic induction heating in the first removal step, and then the remaining corrosion-proofing ground layer 2a formed by the inorganic paint is completely removed by radiation of the laser beam in the second removal step. Therefore, the coating film 2 containing a rust-proof paint which cannot be removed by heating can be quickly and completely removed. Thus, the coating film 2 can be peeled in a short time. Further, the method rarely causes powder dust and noise and thus is very effective for environmental impact reduction measures at a site such as an urban area.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a coating film removal method for removing a coating film of paint applied to steel structures such as bridges, steel towers, and steel-frame buildings. [Background technology]

[0002] Conventionally, in bridges on ordinary roads, expressways, and the like, the surfaces of the steel materials that make up the bridge girders are painted to prevent corrosion and to add color, but because the paint film deteriorates and becomes dirty over time, the paint is periodically repainted. In this case, the paint film is peeled off the surface of the steel material, the old paint film is removed from the steel material, and a new paint film is applied.

[0003] A commonly known method for removing a coating film is the so-called blasting method, in which an abrasive material is collided with the coating film to grind it off (see, for example, Patent Document 1). Other known methods include a method in which the coating film is ground off using an electric tool such as a grinder (see, for example, Patent Document 2), a method in which a release agent is applied to the coating film, and the coating film is chemically swollen by the penetration of the release agent, and then removed with a scraper or the like (see, for example, Patent Document 3), a method in which the substrate is heated by electromagnetic induction to soften the coating film, and then the coating film is removed with a scraper or the like (see, for example, Patent Document 4), and a method in which the coating film is irradiated with high-power laser light to evaporate and remove the coating film (see, for example, Patent Document 5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Utility Model Registration No. 3169505 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-56333 [Patent Document 3] Patent No. 3985966 [Patent Document 4] Patent No. 5896849 [Patent Document 5] Japanese Patent Application Publication No. 11-28900 Summary of the Invention [Problem to be solved by the invention]

[0005] The blasting method is widely used as a paint removal method because it can remove paint all the way down to the base material, can form an anchor pattern (surface roughness that improves paint adhesion) on the surface of the base material, and can be completed in a short period of time.

[0006] However, the blasting method generates dust and noise during construction, which means that it cannot be used in urban areas, etc., due to the environmental impact it places on the surrounding area. Furthermore, the equipment is large, and it requires the installation of special protective equipment to prevent the scattering of dust, as well as the collection and disposal of used abrasives, which means that the on-site work requires a great deal of labor.

[0007] In addition, the method using power tools is easy to work with as it does not require large-scale equipment, but like the blasting method, it generates dust and noise, and the unevenness of the base surface is also cut flat, leaving no anchor pattern behind.

[0008] On the other hand, methods that use release agents, electromagnetic induction, and lasers can all significantly reduce the generation of dust and noise, making them effective in reducing environmental impact.

[0009] However, the method using a stripping agent requires a drying (curing) period after application, which results in a longer application period. In addition, in the method of applying a stripping agent, the coating is chemically swollen by the components that have penetrated the coating, and then removed with a scraper or the like. However, if the bottom layer of the coating (the anti-corrosion base layer) is made of an anti-rust paint that cannot be chemically swelled by the stripping agent (for example, inorganic paint such as inorganic zinc-rich paint), there is a problem in that the bottom layer of the coating cannot be removed.

[0010] In addition, with the electromagnetic induction method (IH method), the base material underneath the coating is heated to soften the resin components of the coating, allowing the coating to be quickly peeled off with a scraper, shortening construction time. However, if an inorganic paint with very little resin content is used as the bottom layer of the coating (corrosion-resistant base layer), the bottom layer of the coating cannot be removed.

[0011] For this reason, in the methods using a release agent or electromagnetic induction, the coating remaining on the surface of the substrate must be removed using a blasting method or power tools, which results in the generation of dust and noise, and also poses the problem that the anchor pattern cannot be formed because the power tools cut into the substrate.

[0012] On the other hand, while laser-based methods cannot form new anchor patterns on the surface of the substrate like blasting methods, they can evaporate the coating by irradiating it with laser light, thereby removing the coating all the way down to the interior of the irregularities without damaging the surface of the substrate, allowing the anchor pattern to be reproduced by the irregularities from which the coating has been removed.

[0013] However, in the laser method, the entire coating film is evaporated and removed by irradiation with laser light, which has the problem that it takes a long time to remove the coating film compared to other methods.

[0014] The present invention has been made in view of the above-mentioned problems, and its object is to provide a coating removal method that can significantly reduce dust and noise and can remove the coating in a short period of time. [Means for solving the problem]

[0015] In order to achieve the above-mentioned object, the present invention provides a coating removal method for removing a coating from a metal member having a coating formed on its surface, characterized in that it comprises a first removal step in which the metal member is heated by electromagnetic induction to remove a portion of the coating in the thickness direction, and a second removal step in which the remaining coating from which the portion in the thickness direction has been removed by the first removal step is removed from the metal member by irradiating it with laser light.

[0016] As a result, the metal member is heated by electromagnetic induction to remove a portion of the coating film in the thickness direction, and then the remaining coating film from which the portion in the thickness direction has been removed is removed from the metal member by irradiation with laser light.Therefore, after the portion of the coating film in the thickness direction is quickly removed by electromagnetic induction heating, the remaining coating film is completely removed by irradiation with laser light.

[0017] In order to achieve the above-mentioned object, the present invention provides a coating film removal method for removing a coating film from a metal member having a coating film formed on its surface, characterized in that it comprises a first removal step of removing a portion of the coating film in the thickness direction by applying a stripping agent to the coating film, and a second removal step of removing the remaining coating film from the metal member after the portion in the thickness direction has been removed by the first removal step by irradiating it with laser light.

[0018] As a result, after a portion of the coating film in the thickness direction is removed by the release agent, the remaining coating film from which the portion in the thickness direction has been removed is removed from the metal member by irradiation with laser light, so that after a portion of the coating film in the thickness direction is quickly removed by the release agent, the remaining coating film is completely removed by irradiation with laser light. [Effects of the Invention]

[0019] According to the present invention, a portion of the coating film can be rapidly removed in the thickness direction using electromagnetic induction heating or a stripping agent, and then the remaining coating film can be completely removed by irradiating it with laser light. Therefore, even coating films containing paints that cannot be removed by heating or a stripping agent can be quickly and completely removed, and the coating film can be stripped in a short period of time. In this case, laser light irradiation can remove the coating film without damaging the substrate, leaving an anchor pattern on the substrate and improving the quality of repainting. Furthermore, dust and noise generation can be significantly reduced, making this method extremely effective in addressing environmental impacts in urban and other areas. [Brief explanation of the drawings]

[0020] [Figure 1] A cross-sectional side view of a steel material and a coating film showing a first embodiment of the present invention. [Figure 2] Side cross-sectional view of steel and paint showing the paint removal process [Figure 3] Cross-sectional side view of steel showing paint removal [Figure 4] Schematic side view showing the coating removal process [Figure 5] Schematic side view showing a coating film removal step according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 and 2 show a first embodiment of the present invention, which illustrates a paint film removal method for removing a paint film applied to a steel structure such as a bridge.

[0022] The steel material 1 shown in the figure is made of a metal member forming, for example, a steel girder, and has a coating film 2 formed on its surface to prevent corrosion and to impart color.

[0023] The coating film 2 is formed from a corrosion-resistant base layer 2a as the bottom layer applied to the base surface of the steel material 1, a base coat layer 2b applied on top of the corrosion-resistant base layer 2a, an intermediate coat layer 2c applied on top of the intermediate coat layer 2b, and a top coat layer 2d applied on top of the intermediate coat layer 2c.

[0024] The anti-corrosion base layer 2a is made of an inorganic paint such as inorganic zinc-rich paint, red lead or lead-based anti-rust paint, and is a paint whose main purpose is to strengthen adhesion to the base material of the steel material 1, protect the base material from corrosion, and assist in adhesion to the intermediate layer 2b.

[0025] The undercoat layer 2b is made of a resin paint, a chlorinated rubber paint or the like, and is a paint whose main purpose is to strengthen adhesion to the anticorrosion base layer 2a and to prevent the penetration of corrosive substances such as moisture and salts.

[0026] The intermediate coating layer 2c is made of a resin coating material, a chlorinated rubber coating material, or the like, and is a coating material whose main purpose is to strengthen the adhesion between the undercoat layer 2b and the topcoat layer 2d and to aid in the hiding power of the topcoat layer 2d.

[0027] The top coat layer 2d is made of a resin paint, a chlorinated rubber paint or the like, and is a paint whose main purpose is to protect the substrate from ultraviolet rays, heat and rainwater, and to obtain a decorative effect by adding color.

[0028] The coating film removal method of this embodiment includes a first removal step of removing the coating film 2 by electromagnetic induction and a second removal step of removing the coating film 2 by laser, in which a portion of the coating film 2 in the thickness direction is peeled off from the surface side in the first removal step, and then the remaining coating film 2 is peeled off in the second removal step.

[0029] The first removal step uses an induction heating device 10 that heats the steel material 1 by electromagnetic induction. The induction heating device 10 is a well-known IH (Induction Heating) heating device, and includes a heating unit 11 that can be held with fingers, and a cylindrical heating head 12 attached to the heating unit 11. The heating unit 11 is connected to a high-frequency power source or the like (not shown), and supplies an alternating current to the coil of the heating head 12, causing the heating head 12 to generate an electromagnetic field.

[0030] The second removal step uses a laser irradiation device 20 that vaporizes the coating film 2 by irradiating it with laser light. The laser irradiation device 20 includes a laser irradiation head 21 that irradiates the laser light and a suction nozzle 22 that sucks in the vaporized material; although not shown, the suction nozzle 22 is integrally provided with the laser irradiation head 21. The laser irradiation head 21 has a well-known configuration that generates plasma on the object to be irradiated by irradiating it with high-power laser light, and vaporizes (ablates) and thermally fragments the object to be irradiated by shock waves and thermal expansion generated when the plasma expands. The suction nozzle 22 sucks in the vaporized material generated at the laser irradiation site and discharges it to the outside.

[0031] In the paint film removal method of this embodiment, in the first removal step, as shown in FIG. 4(a), the heating head 12 of the induction heating device 10 is moved along the surface of the paint film 2 on the steel material 1, and the steel material 1 is heated to a predetermined temperature (240°C or less). This generates eddy currents in the steel material 1 by the heating head 12, and the eddy currents are converted into heat by the electrical resistance components of the steel material 1 due to the magnetic field. During this process, heat is generated below the paint film 2, penetrating, for example, up to 0.3 mm from the surface of the steel material 1. However, since the induction heat heats and softens the resin or rubber components of the paint film 2, the corrosion-protective base layer 2a, which is made of an inorganic zinc-rich paint or the like with an extremely low resin content, does not soften. Instead, the interfacial bond between the corrosion-protective base layer 2a and the primer layer 2b is destroyed by the softening of the primer layer 2b.

[0032] Next, the undercoat layer 2b and topcoat layer 2d of the coating film 2 that have softened and floated are peeled off with a scraper 13, thereby peeling off a portion of the coating film 2 in the thickness direction (the undercoat layer 2b, the intermediate coat layer 2c, and the topcoat layer 2d).

[0033] Subsequently, in the second removal step, as shown in FIG. 4(b), the coating film 2, from which the undercoat layer 2b, intermediate layer 2c, and topcoat layer 2d have been removed in the first removal step, leaving only the corrosion-resistant base layer 2a, is removed from the steel material 1 using a laser irradiation device 20. Specifically, by irradiating the coating film 2 with laser light from a laser irradiation head 21, even if the corrosion-resistant base layer 2a is an inorganic paint such as inorganic zinc-rich paint, it can be vaporized by the laser light and completely removed from the steel material 1, as shown in FIG. 3. Because the coating film 2 is vaporized by irradiation with laser light, the coating film 2 can be removed down to the unevenness 1a of the steel material 1 without damaging the surface of the substrate. The unevenness 1a from which the coating film 2 has been removed forms an anchor pattern. Furthermore, the vaporized material resulting from the evaporation of the coating film 2 is sucked in by a suction nozzle 22 and does not scatter into the surrounding area.

[0034] Thus, the coating film removal method of this embodiment includes a first removal step in which the steel material 1 is heated by electromagnetic induction to remove a portion of the coating film 2 in the thickness direction, and a second removal step in which the remaining coating film 2 after the portion in the thickness direction has been removed is removed from the steel material 1 by irradiating it with laser light. Therefore, the primer layer 2b, the intermediate layer 2c, and the topcoat layer 2d of the coating film 2, excluding the corrosion-protective base layer 2a made of inorganic paint, can be rapidly removed by electromagnetic induction heating in the first removal step, and then the remaining corrosion-protective base layer 2a made of inorganic paint can be completely removed by irradiating it with laser light in the second removal step. This allows for rapid and complete removal of the coating film 2 containing inorganic paint, which cannot be removed by heating. This allows for the coating film 2 to be peeled off in a short period of time. Since the laser light irradiation in the second removal step removes the coating film 2 without damaging the substrate, an anchor pattern can be left on the substrate, improving the quality of recoating. Furthermore, the first removal process using electromagnetic induction and the second removal process using lasers generate almost no dust or noise, making them extremely effective in reducing environmental impact in urban areas and other locations.

[0035] FIG. 5 shows a second embodiment of the present invention, and components equivalent to those in the previous embodiment are designated by the same reference numerals.

[0036] In this embodiment, instead of the first removing step of the first embodiment, a step of removing the coating film with a stripping agent serves as the first removing step.

[0037] That is, the coating film removal method of this embodiment includes a first removal step of removing the coating film 2 using a stripping agent and a second removal step of removing the coating film 2 using a laser, and after a portion of the coating film 2 in the thickness direction is peeled off from the surface side in the first removal step, the remaining coating film 2 is peeled off in the second removal step.

[0038] The stripping agent used in this embodiment is a well-known stripping agent that contains, for example, an organic solvent or a surfactant and softens the paint or coating to remove it from the surface.

[0039] In the paint film removal method of this embodiment, in the first removal step, a release agent is applied to the surface of the paint film 2 on the steel material 1 using a spray nozzle 30, as shown in Figure 5(a). A brush or an application roller may be used to apply the release agent. As a result, the paint film 2 swells as the release agent penetrates the surface. However, because the release agent swells the resin or rubber components, the corrosion-protective base layer 2a, which is made of an inorganic zinc-rich paint or the like with an extremely low resin content, does not swell, but the primer layer 2b, intermediate layer 2c, and top coat layer 2d swell.

[0040] Next, the primer layer 2b, intermediate layer 2c, and top coat layer 2d of the coating film 2, which have swelled and floated due to the release agent, are peeled off with a scraper 31 as shown in Figure 5(b), thereby peeling off a portion of the coating film 2 in the thickness direction (the intermediate layer 2b and the outermost layer 2c).

[0041] Subsequently, in the second removal step, as shown in FIG. 5(c), the coating film 2, which has been stripped of the undercoat layer 2b, intermediate layer 2c, and topcoat layer 2d in the first removal step, leaving only the corrosion-resistant base layer 2a, is removed from the steel material 1 using a laser irradiation device 20. Specifically, by irradiating the coating film 2 with laser light from a laser irradiation head 21, even if the corrosion-resistant base layer 2a is an inorganic paint such as inorganic zinc-rich paint, it can be vaporized by the laser light and completely removed from the steel material 1, as shown in FIG. 3. Because the coating film 2 is vaporized by irradiation with laser light, the coating film 2 can be removed down to the unevenness 1a of the steel material 1 without damaging the surface of the substrate. The unevenness 1a from which the coating film 2 has been removed forms an anchor pattern. Furthermore, the vaporized material resulting from the evaporation of the coating film 2 is sucked in by a suction nozzle 22 and does not scatter into the surrounding area.

[0042] Thus, the coating film removal method of this embodiment includes a first removal step in which a portion of the coating film 2 is removed in the thickness direction using a stripping agent, and a second removal step in which the remaining coating film 2 is removed from the steel material 1 by irradiating it with laser light. Therefore, the primer layer 2b, intermediate layer 2c, and topcoat layer 2d of the coating film 2, excluding the corrosion-protective base layer 2a made of inorganic paint, can be rapidly removed using the stripping agent in the first removal step, and then the remaining corrosion-protective base layer 2a made of inorganic paint can be completely removed by irradiating it with laser light in the second removal step. This allows for rapid and complete removal of the coating film 2 containing inorganic paint, which cannot be removed by heating. This allows for the coating film 2 to be removed in a short period of time. Since the laser light irradiation in the second removal step removes the coating film 2 without damaging the substrate, an anchor pattern can be left on the substrate, as in the first embodiment, thereby improving the quality of recoating. Furthermore, the first removal process using electromagnetic induction and the second removal process using lasers generate almost no dust or noise, making them extremely effective in reducing environmental impact in urban areas and other locations.

[0043] In the above-described embodiments, the coating film 2 has a corrosion-resistant base layer 2a made of an inorganic paint such as inorganic zinc-rich paint as the bottom layer, but the present invention can also be applied to removing coating films that use resin-based anti-rust paint or coating films that do not use anti-rust paint. That is, even if a coating film can be removed by electromagnetic induction heating or a stripping agent, if the coating film cannot be completely removed with a scraper or the like in the first removal step and remains on the unevenness of the substrate, such a coating film can be removed in the second removal step.

[0044] Furthermore, the above-described embodiments are examples of the present invention, and the present invention is not limited to those described in these embodiments. [Explanation of symbols]

[0045] 1...steel material, 2...paint film, 2a...corrosion-resistant base layer, 2b...primer layer, 2c...intermediate coat layer, 2d...top coat layer, 10...induction heating device, 11...heating unit, 12...heating head, 13...scraper, 20...laser irradiation device, 21...laser irradiation head, 22...suction nozzle, 30...spray nozzle, 3...scraper.

Claims

1. A coating film removal method for removing a coating film from a metal member having a coating film formed on its surface, comprising: a first removing step of heating the metal member by electromagnetic induction to remove a portion of the coating film in a thickness direction; and a second removing step of removing the remaining coating film from the metal member by irradiating the metal member with laser light, the remaining coating film being partially removed in the thickness direction by the first removing step. A coating film removal method characterized by:

2. A coating film removal method for removing a coating film from a metal member having a coating film formed on its surface, comprising: a first removal step of removing a portion of the coating film in a thickness direction by applying a release agent to the coating film; and a second removing step of removing the remaining coating film from the metal member by irradiating the metal member with laser light, the remaining coating film being partially removed in the thickness direction by the first removing step. A coating film removal method characterized by:

3. The coating film is made up of multiple layers of paint, with the bottom layer being made up of an inorganic paint.

3. The coating film removal method according to claim 1 or 2.

Images