Method for repairing steel structure, and adhesive sheet for repairing steel structure

Abstract

[Problem] To provide a method whereby a steel structure having a deteriorated part can be repaired in a short period of time. [Solution] A method for repairing a steel structure that has a deteriorated part, said method including: a first step for preparing an adhesive sheet comprising a support body and an adhesive layer which is provided on one surface of the support body; a second step for subjecting the deteriorated part of the steel structure to surface preparation to form a surface-prepared surface which may have an active film; a third step for subjecting the surface-prepared surface of the steel structure to a rust-proofing treatment to form a rust-proof surface; and a fourth step for disposing the adhesive sheet on the rust-proof surface of the steel structure.

Description

Steel structure repair method and adhesive sheet for steel structure repair

[0001] The present disclosure relates to a method for repairing a steel structure and an adhesive sheet for repairing a steel structure.

[0002] Steel structures such as bridges are primarily made of steel. Deterioration of the steel material necessitates the repair of the steel structure. Various repair methods have been studied (see, for example, the background art of Patent Document 1). Known repair methods for steel structures with deteriorated portions include, for example, performing surface preparation such as blasting on the deteriorated portion of the steel structure, applying a corrosion-resistant base coat, applying an epoxy resin paint or the like that has excellent barrier properties against corrosion factors (water or oxygen), and then applying a fluororesin paint or the like that has excellent weather resistance.

[0003] Japanese Patent Application Laid-Open No. 2018-193739

[0004] However, the above-mentioned methods require a long construction period and multiple painting processes. An object of the present disclosure is to provide a method that enables repair of a steel structure having deteriorated portions in a short period of time.

[0005] The steel structure repair method disclosed herein is a method for repairing a steel structure having a deteriorated portion, and includes the following steps: a first step of preparing a support and an adhesive sheet having an adhesive layer provided on one surface of the support; a second step of performing a surface preparation on the deteriorated portion of the steel structure to form a surface preparation surface that may have an active film; a third step of performing a rust prevention treatment on the surface preparation of the steel structure to form a rust prevention treated surface; and a fourth step of placing an adhesive sheet on the rust prevention treated surface of the steel structure.

[0006] According to the present disclosure, it is possible to provide a method that enables repair of a steel structure having deteriorated portions in a short period of time.

[0007] Fig. 1 is a schematic cross-sectional view showing the steps of a steel structure repair method. Fig. 2A is a diagram showing a method for measuring the storage modulus of an adhesive layer. Fig. 2B is a schematic cross-sectional view showing a laminate provided in an adhesive sheet. Fig. 3 is a schematic cross-sectional view showing a support provided in an adhesive sheet. Fig. 4 is a schematic cross-sectional view showing a method for weather resistance testing. Fig. 5 is a schematic cross-sectional view showing a method for weather resistance testing.

[0008] In this specification, when multiple upper limit candidate values ​​and multiple lower limit candidate values ​​are listed for a certain parameter, the numerical range of the parameter may be formed by combining any one upper limit candidate value and any one lower limit candidate value. As an example, consider the following statement: "Parameter B is preferably A1 or more, more preferably A2 or more, even more preferably A3 or more, and preferably A4 or less, more preferably A5 or less, and even more preferably A6 or less." In this example, the numerical range of parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each layer more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each drawing, elements similar to those already described with reference to the previous drawings will be designated by the same reference numerals, and detailed description may be omitted as appropriate.

[0010] The steel structure repair method disclosed herein is a method for repairing a steel structure having a deteriorated portion, and includes the following steps: a first step of preparing a support and an adhesive sheet having an adhesive layer provided on one surface of the support; a second step of performing surface preparation on the deteriorated portion of the steel structure to form a surface preparation surface that may have an active film; a third step of performing rust prevention treatment on the surface preparation surface of the steel structure to form a rust prevention treated surface; and a fourth step of placing an adhesive sheet on the rust prevention treated surface of the steel structure.

[0011] In one embodiment, the steel structure repair method of the present disclosure further includes a step 3a of forming a coating resin layer on the rust-proofed surface (e.g., rust-proof coating film) of the steel structure. In one embodiment, the steel structure repair method of the present disclosure further includes a step 5 of forming a topcoat coating film on the surface of the adhesive sheet placed on the rust-proofed surface of the steel structure.

[0012] In the first step, an adhesive sheet is prepared. In the first step, a steel structure having a deteriorated portion may be prepared. The steel structure to be repaired is a structure having a steel material as its base material. Examples of steel structures include bridges, bridge piers, steel towers, steel pipes, chimneys, tanks, plants, pipelines, rolled plates, and roofs. Examples of steel materials include alloy steels such as nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, and manganese steel, as well as carbon steel. The steel structure may be, for example, an architectural structure or a civil engineering structure.

[0013] The steel structure to be repaired has a portion on its surface where rust, such as red rust (e.g., iron oxide (Fe2O3)), has developed due to corrosion factors such as water and oxygen. Generally, during the manufacture of a steel structure, a coating (hereinafter also referred to as the "pre-repair coating" or "old coating") is applied to the steel material to prevent rusting. Such coatings may crack or blister due to aging, construction or repair work performed on the steel structure, or other factors. In this specification, such rusted portions or portions where cracks and blisters have developed in the coating are referred to as "deteriorated portions" of the steel structure. FIG. 1A shows a schematic cross-sectional view of a deteriorated portion of a steel structure. In FIG. 1A, a pre-repair coating (old coating) 20 is applied to a steel material 10, and rust 30 has developed.

[0014] The steel structure to be repaired has a deteriorated portion. In the present disclosure, the deteriorated portion is subjected to surface preparation, a surface preparation surface that may have an active film is formed, a rust prevention treatment is performed on the surface preparation surface, a rust prevention treated surface is formed, and an adhesive sheet is placed on the rust prevention treated surface. In this manner, the steel structure having the deteriorated portion can be repaired. This repair method allows repair treatment of the steel structure to be performed in a shorter period of time and at lower cost than, for example, heavy-duty corrosion protection coating.

[0015] The adhesive sheet includes a support and an adhesive layer provided on one surface of the support.

[0016] The support is preferably, for example, a resin film. Examples of resin materials constituting the resin film include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, vinylidene chloride-vinyl chloride copolymers, polyesters such as polyethylene terephthalate, polycarbonates, polyarylates, styrene resins, acrylic resins, acrylic urethane resins, urethane resins, fluororesins, acetyl cellulose, polyamides, and polyimides. The support may be a single layer or a multilayer, and may be, for example, a laminated film of resin films.

[0017] The support may contain additives. Examples of additives include pigments, dyes, colorants, antistatic agents, flame retardants, mildew inhibitors, ultraviolet absorbers, antioxidants, light stabilizers, plasticizers, leveling agents, flow control agents, antifoaming agents, and dispersants. From the viewpoint of suppressing deterioration of the steel structure after repair and from the viewpoint of suppressing deterioration of the adhesive layer and other parts, the support preferably has excellent weather resistance. From this viewpoint, the support may contain weather resistance agents such as ultraviolet absorbers, antioxidants, and light stabilizers. This, for example, allows for a thinner topcoat coating film, as described below, and also allows for the omission of the formation of a topcoat coating film.

[0018] Taking into consideration the finish of the steel structure after repair, i.e., the finish after the adhesive sheet is applied to the steel structure, and the ease of handling and application of the adhesive sheet, the thickness of the support is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, still more preferably 50 μm or more, and particularly preferably 100 μm or more, and is preferably 5000 μm or less, more preferably 4000 μm or less, even more preferably 3000 μm or less, still more preferably 2000 μm or less, and particularly preferably 1000 μm or less.

[0019] The support may include a fiber-reinforced resin layer. An adhesive sheet including such a support has, for example, excellent impact resistance. The fiber-reinforced resin layer is, for example, a layer containing a resin material and reinforcing fibers. Examples of the resin material include the resin materials described above. The reinforcing fibers may be inorganic fibers or organic fibers. Examples of inorganic fibers include glass fibers, carbon fibers, silicon-titanium-carbon fibers, boron fibers, and metal fibers. Examples of organic fibers include aramid fibers, vinylon fibers, polyester fibers, and polyamide fibers. The reinforcing fibers may be in a mesh (network) shape. The fiber-reinforced resin layer may contain glass mesh as the reinforcing fiber.

[0020] The thickness of the fiber-reinforced resin layer is preferably 50 μm or more, more preferably 75 μm or more, even more preferably 100 μm or more, still more preferably 125 μm or more, particularly preferably 150 μm or more, and is preferably 550 μm or less, more preferably 525 μm or less, even more preferably 500 μm or less, still more preferably 475 μm or less, particularly preferably 450 μm or less. An adhesive sheet having a fiber-reinforced resin layer of such a thickness has, for example, excellent impact resistance.

[0021] The support may include, for example, a laminate including a fiber-reinforced resin layer and a resin layer in this order in the thickness direction, or a laminate including a first resin layer, a fiber-reinforced resin layer, and a second resin layer in this order in the thickness direction. Examples of resin materials constituting the resin layer, the first resin layer, and the second resin layer include the resin materials described above. The support may include, for example, a laminate including, in this order, a fiber-reinforced resin layer containing polyethylene and a glass mesh and a polyethylene layer, or a laminate including, in this order, a first polyethylene layer, a fiber-reinforced resin layer containing polyethylene and a glass mesh, and a second polyethylene layer. The thickness of the resin layer, the first resin layer, and the second resin layer is each independently preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, still more preferably 50 μm or more, particularly preferably 100 μm or more, and preferably 1000 μm or less, more preferably 800 μm or less, even more preferably 600 μm or less, still more preferably 500 μm or less, particularly preferably 400 μm or less.

[0022] The support may include a gas barrier layer such as a vapor-deposited film. Such a support may include, for example, a gas barrier film, particularly a vapor-deposited film, comprising a resin film and a gas barrier layer such as a vapor-deposited film provided on the resin film. Adhesive sheets comprising such a support have excellent gas barrier properties, particularly oxygen and water vapor barrier properties, and can, for example, suppress rusting and deterioration of coatings on steel structures after repair. Examples of the resin film in the gas barrier film include the resin films described above. The thickness of the resin film is preferably 5 μm or more, more preferably 10 μm or more, and preferably 100 μm or less, more preferably 50 μm or less. Examples of vapor-deposited films include vapor-deposited films containing one or more metals, vapor-deposited films containing one or more inorganic oxides, and vapor-deposited films containing one or more metals and one or more inorganic oxides. Examples of metals include aluminum, chromium, tin, nickel, copper, silver, gold, and platinum. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, barium oxide, and silicon carbide oxide (carbon-containing silicon oxide). Among these, aluminum vapor deposition films, aluminum oxide (alumina) vapor deposition films, and silicon oxide (silica) vapor deposition films are preferred. The thickness of the vapor deposition film is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more, and preferably 150 nm or less, more preferably 100 nm or less, and even more preferably 80 nm or less. Examples of methods for forming the vapor deposition film include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. Examples of vapor-deposited films include vapor-deposited polyester films such as vapor-deposited polyethylene terephthalate films, and vapor-deposited polyamide films.

[0023] The support provided with a gas barrier layer may be, for example, a laminate provided with a gas barrier film, a fiber-reinforced resin layer, and a resin layer in this order, or a laminate provided with a gas barrier film, a first resin layer, a fiber-reinforced resin layer, and a second resin layer in this order. From the viewpoint of interlayer adhesion, a laminate provided with a gas barrier film, a first resin layer, a fiber-reinforced resin layer, and a second resin layer in this order is preferred, and the gas barrier film is preferably arranged so that the gas barrier layer faces the first resin layer.

[0024] The oxygen transmission rate (OTR, unit: cc / (m2·day·atm)) of an adhesive sheet provided with a gas barrier layer is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. The lower limit of the OTR is preferably as low as possible, but may be, for example, 0.01, 0.05, or 0.1. In this specification, the OTR is measured in accordance with JIS K7126-2:2006 in an environment at a temperature of 23°C and a humidity of 60% RH. The oxygen transmission rate can be measured using an oxygen transmission rate measuring device (OX-TRAN2 / 20, manufactured by MOCON Corporation).

[0025] The water vapor transmission rate (WVTR, unit: g / (m2·day)) of an adhesive sheet provided with a gas barrier layer is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. The lower limit of the WVTR is preferably as low as possible, but may be, for example, 0.01, 0.05, or 0.1. In this specification, the WVTR is measured in accordance with JIS K7129-2:2019 in an environment at a temperature of 40°C and a humidity of 90% RH. The WVTR can be measured using a water vapor transmission rate measuring device (PERMATRAN-w 3 / 33, manufactured by MOCON Corporation).

[0026] The layer constituting the surface of the support opposite to the surface facing the adhesive layer is preferably a resin layer such as a polyolefin, acrylic resin, acrylic urethane resin, or urethane resin, from the viewpoint of adhesion to the topcoat coating film described below.

[0027] The support may have a surface resin layer as the surface layer opposite to the surface layer facing the adhesive layer. This, for example, improves the weather resistance of the repaired steel structure and ensures rust prevention even long after construction. A colored surface resin layer may also be formed. In this case, the fifth step described below may be omitted.

[0028] Examples of resin materials constituting the surface resin layer include fluororesins, urethane resins, acrylic resins, butadiene resins, silicone resins, vinyl ester resins, and epoxy resins. Among these, fluororesins are preferred. Examples of fluororesins include polyvinyl fluoride, polytetrafluoroethylene, perfluoroalkoxyalkanes, and ethylene-tetrafluoroethylene copolymers. The surface resin layer may contain additives such as pigments, dyes, dispersants, antifoaming agents, thickeners, leveling agents, anti-settling agents, anti-sagging agents, anti-algae agents, anti-fungal agents, preservatives, UV absorbers, antioxidants, and light stabilizers.

[0029] The thickness of the surface resin layer is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0030] The adhesive layer contains a component having adhesive properties. Examples of adhesive components include acrylic resins, vinyl chloride-vinyl acetate copolymers, vinyl acetate resins, polyolefins, polyesters, polyurethanes, silicone resins, and rubber-based resins. In this specification, "adhesion" refers to adhesion in a broad sense, and the concept of "adhesion" also includes cohesion.

[0031] In one embodiment, the adhesive layer is a pressure-sensitive adhesive layer, i.e., a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is a layer formed of a pressure-sensitive adhesive (pressure-sensitive adhesive) and exhibits a tacky adhesive feeling at room temperature (e.g., 23°C). Examples of pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, silicone pressure-sensitive adhesives, and rubber pressure-sensitive adhesives. Among these, acrylic pressure-sensitive adhesives are preferred in terms of the need for long-term protection, the adhesion between the pressure-sensitive adhesive layer and the adherend surface (e.g., anti-rust coating film) having a large step, and the adhesion between the pressure-sensitive adhesive layer and the support.

[0032] The adhesive layer may contain additives such as pigments, dyes, colorants, antistatic agents, flame retardants, mildew inhibitors, ultraviolet absorbers, antioxidants, light stabilizers, crosslinking agents, tackifiers, plasticizers, leveling agents, flow control agents, antifoaming agents, and dispersants.

[0033] The storage modulus (G') at 40°C of the adhesive layer, preferably the pressure-sensitive adhesive layer, which comes into contact with the adherend when the adhesive sheet is attached to the adherend, is preferably 0.05 MPa or more and 1 MPa or less, and may be, for example, 0.1 MPa or more and 0.8 MPa or less. When the storage modulus is equal to or more than the lower limit, excessive elongation of the adhesive layer when subjected to an impact tends to be suppressed. When the storage modulus is equal to or less than the upper limit, breakage of the adhesive layer when subjected to an impact tends to be suppressed.

[0034] The storage modulus is measured by the following method: Two test pieces 90 are prepared from an adhesive sheet according to the test piece preparation method described in 6.2 of JIS K7244-1:1998. Because the test piece 90 is prepared from the adhesive sheet, it has a support 91 corresponding to the support of the adhesive sheet and an adhesive layer 92 corresponding to the adhesive layer of the adhesive sheet.

[0035] Next, the two prepared test pieces 90 are attached to a measuring device 70 as shown in FIG. 2A . As shown in FIG. 2A , the measuring device 70 includes a plate 71 and a jig 72. The jig 72 includes a pair of plate-like portions 73 that sandwich the plate 71. The plate 71 and the pair of plate-like portions 73 extend vertically. The distance between the pair of plate-like portions 73 can be adjusted by rotating nuts 75 threaded onto bolts 74 that pass through the pair of plate-like portions 73. The bolts 74 do not pass through the plate 71 and the test pieces 90 attached to the measuring device 70. The bolts 74 are located at different positions from the plate 71 and the test pieces 90 in the direction perpendicular to the paper surface of FIG. 2A . When attaching the two test pieces 90 to the measuring device 70, the two test pieces 90 are first adhered to the plate 71 by the action of an adhesive layer 92 so that the plate 71 is sandwiched between the two test pieces 90. Next, the nut 75 is rotated to reduce the distance between the pair of plate-like portions 73, thereby sandwiching the plate 71 and the two test pieces 90 between the pair of plate-like portions 73, as shown in Fig. 2A. This fixes the two test pieces 90 to the jig 72.

[0036] The thickness w1 of the test specimen 90 is also determined. The thickness w1 of the test specimen 90 can be determined by the following method. Before fixing the two test specimens 90 to the jig 72, the dimensions of the plate 71 and the jig 72 are determined. As the dimensions of the plate 71 and the jig 72, the thickness w2 of the plate 71 shown in FIG. 2A and the thicknesses w3 and w4 of each of the pair of plate-like portions 73 can be determined. The thicknesses w2, w3, and w4 can be determined by measuring with a vernier caliper. Furthermore, after fixing the two test specimens 90 to the jig 72 as shown in FIG. 2A, the dimensions of the jig 72 with the two test specimens 90 sandwiched between them are determined. As the dimension of the jig 72 with the two test specimens 90 sandwiched between them, the distance w5 from one outer surface of the pair of plate-like portions 73 to the other outer surface of the pair of plate-like portions 73 shown in FIG. 2A can be determined. The distance w5 can be determined by measuring with a vernier caliper. Next, the thickness w1 of the test piece 90 is determined from the dimensions of the plate 71 and the jig 72 and the dimensions of the jig 72 sandwiching the two test pieces 90. The thickness w1 of the test piece 90 can be calculated by subtracting the thicknesses w2, w3, and w4 from the distance w5 and dividing the result by 2. The determined thickness w1 of the test piece 90 is used to measure the storage modulus (G').

[0037] As shown in Fig. 2A, two test pieces 90 are fixed to a jig 72, and then the jig 72 is vibrated in the vertical direction. As a result, vertical vibrations are input to the adhesive layers 92 of the test pieces 90. By detecting the movement of the plate 71 when vertical vibrations are input to the adhesive layers 92 of the test pieces 90, the storage modulus (G') of the adhesive layers 92 can be measured.

[0038] The storage modulus (G') is measured under the following conditions: Atmospheric gas: nitrogen Attachment mode: solid shear mode Temperature dependency measurement (heating is performed using a temperature program, and the modulus is measured at each temperature at 10 Hz) Fundamental frequency: 10 Hz Measurement program: starting temperature = 30°C, step temperature = 1°C, end temperature = 150°C, heating rate: 3°C / min Sine wave, stop vibration Manual static load: adjusted to 0 g when fixing the two test pieces 90 to the jig 72 Strain: value automatically set when the sample length is input, 0.05 Automatic adjustment mode

[0039] The storage modulus (G') can be measured using a solid viscoelasticity measuring device, such as Rheogel E4000 manufactured by UBM Corporation.

[0040] The thickness of the adhesive layer is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, still more preferably 40 μm or more, particularly preferably 50 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less, still more preferably 250 μm or less, even more preferably 200 μm or less, still more preferably 180 μm or less, particularly preferably 150 μm or less. The same applies to the thickness of the first adhesive layer such as the first adhesive layer and the second adhesive layer such as the second adhesive layer described below.

[0041] The adhesive sheet may have a colorant layer, for example, on the surface of the support opposite to the surface on which the adhesive layer is provided. By using an adhesive sheet having a colorant layer, for example, it is possible to easily form a repaired portion with a beautiful finish. The colorant layer may have a color that is the same as or similar to the color of the object to be repaired.

[0042] The adhesive sheet may, for example, comprise a composite adhesive layer having a first adhesive layer, a base layer, and a second adhesive layer in this order in the thickness direction, or preferably a composite adhesive layer having a first adhesive layer, a base layer, and a second adhesive layer in this order in the thickness direction. Such adhesive sheets tend to have excellent conformability to uneven surfaces and impact resistance when the surface of the adherend has unevenness. For example, the surface preparation of a steel structure after type 3 cleaning usually has an active film, and therefore the rust-proofed surface also has significant unevenness. Such adhesive sheets have excellent conformability to uneven surfaces of the rust-proofed surface of the steel structure and can adhere well to the rust-proofed surface.

[0043] Examples of materials constituting the substrate layer include acrylic resins, urethane resins, polyolefins, and rubbers including acrylic rubber and other elastomers, and in one embodiment, the substrate layer is an acrylic resin. The substrate layer may contain the above-mentioned additives.

[0044] The substrate layer may have a cellular structure (cell structure). The cellular structure (cell structure) may be a closed-cell structure, an open-cell structure, or a semi-open or semi-closed-cell structure in which a closed-cell structure and an open-cell structure are mixed. Examples of the substrate layer having a cellular structure include a foam layer, and specific examples include acrylic resin foam (acrylic foam), urethane resin foam (urethane foam), polyolefin foam, and rubber foam including acrylic rubber and other elastomers, and in one embodiment, the substrate layer is an acrylic resin foam.

[0045] From the viewpoint of step-following ability and impact resistance, the thickness of the base layer is preferably 300 μm or more, more preferably 400 μm or more, even more preferably 500 μm or more, particularly preferably 600 μm or more, and is preferably 2000 μm or less, more preferably 1800 μm or less, even more preferably 1500 μm or less, particularly preferably 1200 μm or less.

[0046] The thickness of the composite adhesive layer comprising the first adhesive layer, the base layer, and the second adhesive layer, preferably the thickness of the composite adhesive layer comprising the first pressure-sensitive adhesive layer, the base layer, and the second pressure-sensitive adhesive layer, is preferably 350 μm or more, more preferably 450 μm or more, even more preferably 550 μm or more, particularly preferably 650 μm or more, and is preferably 2050 μm or less, more preferably 1850 μm or less, even more preferably 1550 μm or less, particularly preferably 1250 μm or less. If the thickness of the composite adhesive layer is equal to or greater than the lower limit, the adhesive sheet can adhere well to the surface of the adherend, for example, even if the surface of the adherend has large irregularities.

[0047] When an adhesive sheet having a composite adhesive layer is used, for example, even without providing the step 3a (e.g., unevenness adjustment step) described below, the adhesive sheet can adequately conform to the unevenness of the rust-proofed surface, and good adhesion tends to be ensured.

[0048] Specific examples of adhesive sheets include an adhesive sheet comprising, in this order, a resin layer, a fiber-reinforced resin layer, a first adhesive layer, a substrate layer, and a second adhesive layer; an adhesive sheet comprising, in this order, a second resin layer, a fiber-reinforced resin layer, a first resin layer, a first adhesive layer, a substrate layer, and a second adhesive layer; an adhesive sheet comprising, in this order, a resin layer, a fiber-reinforced resin layer, a gas barrier film, a first adhesive layer, a substrate layer, and a second adhesive layer; and an adhesive sheet comprising, in this order, a second resin layer, a fiber-reinforced resin layer, a first resin layer, a gas barrier film, a first adhesive layer, a substrate layer, and a second adhesive layer. In these examples, each resin layer is, for example, a polyethylene layer, the fiber-reinforced resin layer is, for example, a glass-net-containing polyethylene layer, and the substrate layer is, for example, an acrylic resin layer.

[0049] Specific examples of adhesive sheets include a pressure-sensitive adhesive sheet comprising, in this order, a resin layer, a fiber-reinforced resin layer, a first adhesive layer, a substrate layer, and a second adhesive layer; a pressure-sensitive adhesive sheet comprising, in this order, a second resin layer, a fiber-reinforced resin layer, a first resin layer, a first adhesive layer, a substrate layer, and a second adhesive layer; a pressure-sensitive adhesive sheet comprising, in this order, a resin layer, a fiber-reinforced resin layer, a gas barrier film, a first adhesive layer, a substrate layer, and a second adhesive layer; and a pressure-sensitive adhesive sheet comprising, in this order, a second resin layer, a fiber-reinforced resin layer, a first resin layer, a gas barrier film, a first adhesive layer, a substrate layer, and a second adhesive layer. In these examples, each resin layer is, for example, a polyethylene layer, the fiber-reinforced resin layer is, for example, a glass-net-containing polyethylene layer, each adhesive layer is, for example, an acrylic pressure-sensitive adhesive layer, and the substrate layer is, for example, an acrylic resin layer.

[0050] The adhesive sheet may have a release film on the adhesive layer. This protects the adhesive layer from dust and the like. Before using the adhesive sheet, the release film is peeled off from the adhesive layer. This exposes the adhesive layer, making the adhesive sheet ready for application. Examples of release films include paper substrates and resin films, as well as those coated with a release agent. Examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents.

[0051] Since the adhesive sheet has an adhesive layer, it can be applied by hand, for example. It is also possible to apply the adhesive sheet using a machine. Before application, the adhesive sheet may be cut to an appropriate size to fit the shape and size of the deteriorated part of the steel structure.

[0052] In the second step, the deteriorated parts of the steel structure are subjected to surface preparation (priming) to form a surface preparation surface that may have an active film. Examples of methods for preparing the surface of a steel structure include scraping. Scraping generally involves removing old paint films, rust, dust, dirt, etc., using blasting, power tools, or manual tools. Scraping is classified into grades of Class 1, Class 2, Class 3, and Class 4. The lower the grade number, the higher the level of surface preparation.

[0053] "Type 1 scraping" is a surface preparation method in which all rust and old paint films are removed to expose the steel surface, and surface preparation is mainly performed by blasting. "Type 2 scraping" is a surface preparation method in which rust and old paint films are removed to expose the steel surface, and surface preparation is mainly performed using power tools and / or manual tools. "Type 3 scraping" is a surface preparation method in which the active film of the old paint film (a film in a healthy state) is left, but other defective parts (rust and dead film of the old paint film (a film with cracks and blisters)) are removed, and surface preparation is mainly performed using power tools and / or manual tools. Type 3 scraping has the advantage of requiring fewer work areas and lower labor costs than Type 1 and Type 2 scraping, but because the active film of the old paint film remains, the surface preparation after Type 3 scraping tends to have significant unevenness. Rust may remain on the surface preparation after Type 3 scraping. The height of the unevenness is, for example, 10 μm to 1000 μm, or may be 30 μm to 500 μm, or 50 μm to 300 μm. Figure 1B shows a schematic cross-sectional view of a deteriorated portion of a steel structure subjected to surface preparation using Type 3 scraping. In Figure 1B, the old paint film 20 has been removed except for the active film 22, and rust 30 has also been removed. "Type 4 scraping" is a surface preparation method that removes powdered matter (including loose rust) and dirt adhering to the surface, and is mainly performed using manual tools and / or brushes.

[0054] Examples of power tools include disc sanders and wire wheels, and examples of hand tools include wire brushes, scrapers, scraping rods, and sandpaper.

[0055] In the present disclosure, it is preferable to perform at least type 3 surface preparation. The surface preparation surface after type 3 surface preparation may have an active film and a rusted surface. In the present disclosure, it is also possible to perform type 1 or type 2 surface preparation, but type 1 and type 2 surface preparation tend to be more expensive from the standpoints of securing work space, construction period, cost, etc. According to the repair method of the present disclosure, there is no need to perform costly type 1 and type 2 surface preparation, and steel structures can be repaired using low-cost type 3 surface preparation.

[0056] In the third step, the surface preparation of the steel structure is subjected to a rust-preventive treatment to form a rust-preventive treated surface. Examples of methods for rust-preventive treatment of the surface preparation of the steel structure include applying a rust inhibitor or rust-preventive paint to form a rust-preventive coating film. Examples of painting methods include brush painting, roller painting, and spray painting (e.g., air spray, airless spray). Figure 1C shows a schematic cross-sectional view of a steel structure surface that has been subjected to a rust-preventive treatment to form a rust-preventive coating film. In Figure 1C, a rust-preventive coating film 40 is formed on the steel material 10 and the active film 22.

[0057] In the repair method disclosed herein, the rust prevention treatment and the application of an adhesive sheet are performed separately. By providing the adhesive layer of the adhesive sheet with rust prevention properties, the repair method disclosed herein can more clearly achieve the effects of the rust prevention treatment itself compared to when rust prevention treatment is not performed before applying the adhesive sheet to the steel structure's surface preparation surface. Furthermore, the rust prevention coating film formed by the rust prevention treatment can fill in the unevenness of the surface preparation surface to some extent, improving the adhesion of the adhesive sheet. Furthermore, the disclosed method of applying an adhesive sheet allows repairs to be performed in a shorter time than methods that require multiple painting and drying treatments on-site, and is superior in terms of ease of work, repair costs, and quality control of the repaired steel structure.

[0058] The thickness (dry film thickness) of the rust-preventive coating film formed by the rust-preventive treatment is preferably 10 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, still more preferably 100 μm or more, particularly preferably 150 μm or more, and preferably 1000 μm or less, more preferably 800 μm or less, even more preferably 600 μm or less, particularly preferably 500 μm or less. If the thickness is equal to or greater than the lower limit, a sufficient rust-preventive effect tends to be obtained, and if the thickness is equal to or less than the upper limit, workability and economy tend to be excellent.

[0059] Rust inhibitors include inorganic rust inhibitors and organic rust inhibitors.Inorganic rust inhibitors include, for example, inorganic acids and their salts, specifically, red lead, lead suboxide, basic lead chromate, lead dianamide, calcium plumbate, basic lead sulfate, zinc chromate, zinc powder, red iron oxide, nitrite, sulfite, silicate, metasilicate, phosphate, polyphosphate, hypophosphite, phosphite, molybdate, phosphomolybdate, borate, metaborate, tungstate, carbonate, and chromate, and also include phosphate compounds, vanadium compounds, niobium compounds, zirconium compounds, and zinc oxide.In these cases, salts include, for example, ammonium salt, calcium salt, magnesium salt, aluminum salt, zinc salt, manganese salt, and barium salt.

[0060] Examples of organic rust inhibitors include organic amine compounds, organic amine salts, tannic acid, carboxylic acids and esters or salts of these acids, sulfonates, organic phosphates, benzotriazole compounds, benzothiazole compounds, mercaptan compounds, guanidino group-containing compounds, pyruguanidino group-containing compounds, thiocarbonyl group-containing compounds, alkylphenol compounds, diisopropylammonium nitrite, and dicyclohexylammonium nitrite.

[0061] Examples of anti-rust paints include epoxy resin paints, urethane resin paints, acrylic resin paints, silicone acrylic resin paints, styrene resin paints, fluororesin paints, and zinc-rich paints containing an organic binder and zinc powder. In one embodiment, the anti-rust paint contains a binder and, if desired, the above-mentioned rust inhibitor. Examples of binders in anti-rust paints include organic binders such as epoxy resins, urethane resins, acrylic resins, silicone acrylic resins, styrene resins, and fluororesins; and inorganic binders such as alkyl silicates.

[0062] Anti-rust agents and anti-rust paints can be classified by their anti-rust mechanisms into, for example, rust conversion types and salt and iron ion neutralizing types, and either can be used.

[0063] As the rust inhibitor and the rust-preventive paint, a type of rust inhibitor and a rust-preventive paint that prevents rust by stabilizing iron ions with a two-component curing ion trapping agent may be used, in terms of the rust prevention mechanism.

[0064] Rust conversion-type rust inhibitors and rust prevention paints produce black rust when they provide rust prevention to steel materials. As a result, rust conversion-type rust inhibitors and rust prevention paints become colored when they provide rust prevention. In contrast, rust inhibitors and rust prevention paints that neutralize salt and iron ions and those that rely on iron ion stabilization with a two-component curing ion trapping agent do not become colored when they provide rust prevention to steel materials. Therefore, the use of rust inhibitors or rust prevention paints that neutralize salt and iron ions or those that rely on iron ion stabilization with a two-component curing ion trapping agent makes it easier to visually inspect the steel material through the rust prevention coating when a rust prevention coating film is formed on the surface of the steel material. In particular, when an adhesive sheet and a rust prevention coating film cover the steel material as shown in FIG. 1D , it makes it easier to visually inspect the steel material through the adhesive sheet and the rust prevention coating film. This allows inspectors to inspect the steel material without peeling off the adhesive sheet or removing the rust prevention coating. In particular, it becomes easier to check whether cracks or the like have occurred on the surface of the steel material.

[0065] The anti-rust paint may be a one-component curing anti-rust paint, or may be a two-component curing anti-rust paint consisting of a base agent and a curing agent.In the case of a two-component curing anti-rust paint, the base agent containing a binder and optionally a rust inhibitor and the curing agent that promotes crosslinking reaction are generally stored in separate containers, and the two are mixed just before use.For example, from the viewpoint of high adhesion to the surface preparation surface, high coating film strength, and the ability to form a dense anti-rust coating film, and from the viewpoint of adhesion to the adhesive sheet, a two-component curing anti-rust paint is preferred, a two-component curing epoxy resin paint and a two-component curing urethane resin paint are more preferred, and a two-component curing epoxy resin paint is even more preferred.

[0066] In one embodiment, the two-component curing epoxy resin paint contains an epoxy resin as a binder and an epoxy resin curing agent as a curing agent. Examples of the curing agent include amine-based curing agents, phenol-based curing agents, acid anhydride-based curing agents, and mercaptan-based curing agents. Urethane resin paints include two-component curing types consisting of a polyol compound and an isocyanate compound, and one-component curing types that cure due to moisture in the air, with two-component curing urethane resin paints being preferred.

[0067] The anti-rust paint may contain a moisture-curable resin. The moisture-curable resin has an isocyanate group as a reactive group. The isocyanate group of the moisture-curable resin reacts with water and cures according to the reaction shown in formula (I) below. That is, first, the isocyanate group of the moisture-curable resin reacts with water to produce carbamic acid. Next, the carbamic acid is decomposed to produce an amine. Next, the amine reacts with the isocyanate group of the moisture-curable resin, causing a crosslinking reaction that produces a urea bond. This crosslinking reaction cures the moisture-curable resin. By including a moisture-curable resin in the anti-rust paint, water, which can be a corrosion factor, is removed, thereby achieving a rust-preventing effect.

[0068] For example, the moisture-curing resin contained in the anti-rust paint is a urethane resin. In this case, the anti-rust paint may be a two-component curing urethane resin paint that neutralizes salt and iron ions.

[0069] When an anti-rust paint contains a moisture-curing resin, carbon dioxide gas can be generated by the moisture-curing resin reacting with water, as shown in formula (I) above. When an adhesive sheet and an anti-rust coating film are covering a steel material as shown in FIG. 1D , it is preferable that the adhesive sheet not be endowed with oxygen barrier properties in order to prevent the generated carbon dioxide gas from passing through the adhesive sheet and remaining in the adhesive sheet as bubbles. The lack of oxygen barrier properties in the adhesive sheet allows carbon dioxide gas to easily pass through the adhesive sheet, preventing it from remaining in the adhesive sheet as bubbles. This makes it less likely that bubbles will obstruct the visibility of the anti-rust coating film and steel material through the adhesive sheet. Therefore, when an anti-rust paint containing a moisture-curing resin is used, it is preferable that the adhesive sheet not be endowed with oxygen barrier properties in order to allow the anti-rust coating film and steel material to be visible through the adhesive sheet. Furthermore, when an anti-rust paint containing a moisture-curing resin and not colored is used, it is preferable that the adhesive sheet not be endowed with oxygen barrier properties in order to allow the steel material to be visible through the adhesive sheet and the anti-rust coating film.

[0070] On the other hand, particularly when an anti-rust paint that does not contain a moisture-curing resin is used, it is preferable to impart oxygen barrier properties to the adhesive sheet in order to prevent oxygen, which can be a corrosion factor, from reaching the anti-rust coating film and the steel material. In particular, when an anti-rust paint that does not contain a moisture-curing resin is used, even if the adhesive sheet is imparted with oxygen barrier properties, it is possible to prevent the formation of air bubbles in the adhesive sheet. Therefore, when an anti-rust paint that does not contain a moisture-curing resin and is not colored is used, imparting oxygen barrier properties to the adhesive sheet makes it difficult for oxygen to reach the anti-rust coating film and the steel material, while making the anti-rust coating film and the steel material visible through the adhesive sheet. In particular, when an anti-rust paint that does not contain a moisture-curing resin and is not colored is used, imparting oxygen barrier properties to the adhesive sheet makes it difficult for oxygen to reach the anti-rust coating film and the steel material, while making the steel material visible through the adhesive sheet and the anti-rust coating film. An anti-rust paint that does not contain a moisture-curing resin and is not colored may be, for example, the type of anti-rust paint that prevents rust by stabilizing iron ions with the two-component curing ion trapping agent described above.

[0071] As an example, the oxygen transmission rate (OTR) of an adhesive sheet to which oxygen barrier properties have been imparted is 6.57 cc / (m 2 ·day·atm) or less.

[0072] Regardless of whether the anti-rust coating contains a moisture-curing resin, the adhesive sheet may be provided with water vapor barrier properties, which makes it difficult for water, which can be a corrosive factor, to reach the anti-rust coating film and the steel material. For example, the water vapor transmission rate (WVTR) of an adhesive sheet provided with water vapor barrier properties is 3.0 g / (m²-day) or less.

[0073] As described above, from the viewpoint of making it possible to visually recognize the anti-rust coating film and the steel material through the adhesive sheet, it is preferable that the adhesive sheet is not colored, as will be described later, and it is more preferable that it is transparent.

[0074] The anti-corrosion coating may optionally contain additives such as rosins, plasticizers, extender pigments, coloring pigments, solvents, curing accelerators, coupling agents, corrosive ion fixing agents, anti-sagging agents, and anti-settling agents. Examples of coupling agents include silane-based coupling agents, titanium-based coupling agents, aluminum-based coupling agents, and zirconium-based coupling agents. Examples of corrosive ion fixing agents include hydrotalcite and hydrocalumite.

[0075] The anti-rust coating film provided on the surface preparation surface of a steel structure preferably has an 85° specular gloss of 3 or more. The 85° specular gloss of the anti-rust coating film is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, even more preferably 20 or more, and particularly preferably 23 or more. Such an anti-rust coating film has a high specular gloss, so it can be said to be a dense film, and therefore the adhesion of an adhesive sheet to the anti-rust coating film tends to be high. The upper limit of the 85° specular gloss is not particularly limited, but it may be, for example, 60, 50, or 40.

[0076] The adhesion of the anticorrosive coating to the surface preparation of a steel structure is preferably high. The anticorrosive coating provided on the surface preparation of a steel structure preferably has an 85° specular gloss retention rate of 50% or more. Here, the 85° specular gloss retention rate refers to the 85° specular gloss retention rate of the anticorrosive coating surface before and after a 90° tape peel test. Specifically, if the 85° specular gloss of the anticorrosive coating surface before the 90° tape peel test is designated "Gsb" and the 85° specular gloss of the anticorrosive coating surface after the 90° tape peel test is designated "Gsa," the retention rate is expressed as Gsa × 100 / Gsb. The 85° specular gloss retention rate of the anticorrosive coating is more preferably 60% or more, even more preferably 70% or more, even more preferably 80% or more, particularly preferably 90% or more, and particularly preferably 95% or more. A rust-preventive coating film with a high retention rate means that it is difficult to peel off from the surface preparation surface in a 90-degree tape peel test, and therefore such a rust-preventive coating film has excellent adhesion to the surface preparation surface of a steel structure.

[0077] <90-Degree Tape Peel Test> 25 cm of 24 mm-wide cellophane adhesive tape conforming to JIS Z1522:2009 was unwound from a roll at 23°C and 50% RH. The adhesive surfaces of the 10 cm sections were bonded together to create a handle. A 5 cm section of the adhesive surface was then adhered to the rust-preventive coating of a steel structure using a 2 kg pressure roller, with two passes back and forth. The adhesive was then re-adhered using finger pressure to prevent air from entering the structure. Next, the cellophane adhesive tape was manually peeled once at a speed of 5 cm / s at a 90-degree angle relative to the rust-preventive coating. Cellotape® (manufactured by Nichiban, Model No. 405-1P, 24 mm wide) was used as the cellophane adhesive tape. If this product was not available, a 24 mm-wide cellophane adhesive tape conforming to JIS Z1522:2009 with equivalent adhesive strength was used. <85° Specular Gloss> The 85° specular gloss of the anti-rust coating film surface is measured at an incident angle of 85° and an observation angle of 85° in accordance with JIS Z8741-1997, Method 1. Using a gloss meter, the 85° specular gloss is measured three times and the average value is calculated.

[0078] In step 3a, a coating resin layer is formed on the rust-proofed surface (e.g., a rust-proof coating film) of the steel structure. Examples of resin materials constituting the coating resin layer include fluororesin, acrylic resin, silicone resin, urethane resin, urea resin, and epoxy resin. The coating resin layer can be formed using, for example, a paint. The paint may be a one-component curing paint or a two-component curing paint.

[0079] The coating resin layer may contain additives such as pigments, dyes, dispersants, antifoaming agents, thickeners, leveling agents, anti-settling agents, anti-sagging agents, anti-algae agents, anti-mold agents, preservatives, UV absorbers, antioxidants, and light stabilizers. The paint used to form the coating resin layer may contain an organic solvent and / or water for the purpose of adjusting viscosity, etc. Examples of organic solvents include aromatic hydrocarbons, aliphatic hydrocarbons, ketones, acetate esters, ethers, alcohol-based solvents, and mineral spirits.

[0080] The coating resin layer, for example, smooths unevenness on the rust-prevented surface of a steel structure. In one embodiment, step 3a is a so-called unevenness adjustment process. The unevenness adjustment process refers to a process of filling and smoothing unevenness in the base with a putty-like unevenness adjustment agent. For example, the surface preparation surface of a steel structure after type 3 cleaning has an active film, resulting in unevenness on the surface. These unevennesses tend to remain even after rust prevention treatment. When an adhesive sheet is applied to an uneven rust-prevented surface in step 4 described below, corrosion and peeling may progress due to corrosion factors (water or oxygen) present in the space between the rust-prevented surface and the adhesive sheet. When the unevenness in the base is filled and smoothed with the unevenness adjustment agent, the adhesive sheet can be applied without gaps to the unevenly adjusted steel structure. Therefore, the intrusion of corrosion factors (water or oxygen) into the repaired steel structure can be reduced.

[0081] The thickness of the coating resin layer is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 300 μm or more, and is preferably 5000 μm or less, more preferably 3000 μm or less, and even more preferably 1000 μm or less.

[0082] The coating resin layer can be formed by, for example, a conventional coating method. Examples of the coating method include brush coating, roller coating, and spray coating (e.g., air spray, airless spray). For example, a paint is applied to the rust-proofed surface (e.g., the rust-proof coating surface) of a steel structure, and then air-dried or dried to form a coating resin layer.

[0083] In the fourth step, an adhesive sheet is placed on the rust-preventive surface of the steel structure. For example, the adhesive sheet is attached to the rust-preventive surface of the steel structure, or to the surface of the coating resin layer if a coating resin layer is formed on the rust-preventive surface. Figure 1D shows a schematic cross-sectional view of an adhesive sheet placed on a rust-preventive coating film of a steel structure. In Figure 1D, adhesive sheet 50 includes a support 52 and an adhesive layer 54 provided on support 52. Adhesive sheet 50 is placed so that adhesive layer 54 contacts rust-preventive coating film 40.

[0084] For example, the adhesive sheet is applied to the steel structure under pressure at room temperature so that the adhesive layer of the adhesive sheet is in contact with at least the rust-proofed surface or the coated resin layer surface of the steel structure. For example, the adhesive sheet is pressed from above using a roller or the like. This allows the adhesive layer of the adhesive sheet to adhere closely to the rust-proofed surface or the coated resin layer surface of the steel structure.

[0085] If the adhesive sheet has a release film, the release film is peeled off from the adhesive layer. This exposes the adhesive layer, making the adhesive sheet ready for application. The adhesive sheet may also be applied so as to cover, for example, the rust-proofed surface and the periphery of the rust-proofed surface. The adhesive sheet may also be folded up to the end face of the steel structure and applied.

[0086] According to the repair method of the present disclosure described above, repair treatment of steel structures can be performed in a shorter time than, for example, heavy-duty coating. Furthermore, according to the present disclosure, multiple painting processes are not particularly required, and the adhesive sheet can be used. Therefore, repair treatment can be performed at low cost. Furthermore, because the adhesive sheet is a factory-manufactured product, pinholes are less likely to occur compared to heavy-duty coating. Therefore, the adhesive sheet can improve the repair effect of steel structures compared to heavy-duty coating.

[0087] In the fifth step, a topcoat paint (paint composition) is applied to the surface of the adhesive sheet placed on the rust-proofed surface of the steel structure to form a topcoat paint film. This improves the weather resistance of the repaired steel structure, ensuring rust prevention even long after application. A colored topcoat paint film may also be formed.

[0088] Examples of resin materials constituting the topcoat film include fluororesins, urethane resins, acrylic resins, butadiene resins, silicone resins, vinyl ester resins, and epoxy resins. Among these, fluororesins are preferred. Examples of fluororesins include polyvinyl fluoride, polytetrafluoroethylene, perfluoroalkoxyalkanes, and ethylene-tetrafluoroethylene copolymers. The topcoat film can be formed using, for example, a topcoat paint. The topcoat paint may be a one-component paint or a two-component paint.

[0089] The topcoat coating film may contain additives such as pigments, dyes, dispersants, antifoaming agents, thickeners, leveling agents, anti-settling agents, anti-sagging agents, anti-algae agents, anti-mold agents, preservatives, UV absorbers, antioxidants, and light stabilizers. The topcoat paint may contain organic solvents and / or water for purposes such as adjusting viscosity. Examples of organic solvents include aromatic hydrocarbons, aliphatic hydrocarbons, ketones, acetate esters, ethers, alcohol-based solvents, and mineral spirits.

[0090] The thickness of the topcoat coating is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0091] The topcoat film can be formed by, for example, a conventional coating method. Examples of coating methods include brush coating, roller coating, and spray coating (e.g., air spray, airless spray). For example, a topcoat paint is applied to the surface of the adhesive sheet, and the applied paint is allowed to dry naturally or undergoes a drying treatment to form a topcoat film.

[0092] In the present disclosure, by applying the above-described steel structure repair method of the present disclosure to a steel structure having a deteriorated portion, a repaired steel structure can be manufactured. The details are as described above, and therefore will not be described here.

[0093] In one embodiment, the repaired steel structure of the present disclosure comprises a steel structure having a surface preparation surface which may have an active film, a rust-preventive coating film provided on the surface preparation surface, and an adhesive sheet placed on the rust-preventive coating film. The repaired steel structure may further comprise a coating resin layer between the rust-preventive coating film and the adhesive sheet. The repaired steel structure may further comprise a topcoat coating film on the surface of the adhesive sheet. Details of each element are as described above, and will not be described here.

[0094] When an adhesive sheet placed on a rust-preventive coating film of a repaired steel structure is subjected to a 180-degree peel test at a speed of 300 mm / min in accordance with JIS Z0237:2022, cohesive failure is preferably observed in the adhesive sheet, for example, in the adhesive layer or the above-mentioned base layer. In such cases, it can be said that there is good adhesion between the surface preparation surface and the rust-preventive coating film, and between the rust-preventive coating film and the adhesive sheet.

[0095] With regard to adhesive sheets, examples have been described above in which the layers of the adhesive sheet are colored. For example, examples have been described above in which the surface resin layer of the support is colored. In addition, examples have been described in which the adhesive sheet is provided with a color material layer. However, the form of the adhesive sheet is not limited to this. The layers of the adhesive sheet do not have to be colored. All of the layers of the adhesive sheet may be uncolored and transparent. This may make the adhesive sheet transparent as a whole.

[0096] Materials and components referred to as transparent in this specification may have a total light transmittance of 70% or more. For example, the transmittance of the adhesive sheet as a whole may be 70% or more. The total light transmittance is measured in accordance with JIS K7361-1:1997. When the adhesive sheet has a transmittance of 70% or more, the steel material and the rust-preventive coating film can be visually recognized through the adhesive sheet when the adhesive sheet covers the steel material and the rust-preventive coating film as shown in FIG. 1D. This allows a person inspecting the steel material and the rust-preventive coating film to inspect the steel material and the rust-preventive coating film without removing the adhesive sheet. This facilitates repeated inspection of the steel material and the rust-preventive coating film over a long period of time. Furthermore, it facilitates inspection of the steel material and the rust-preventive coating film from various angles.

[0097] When the adhesive sheet is transparent, the haze of the adhesive sheet is, for example, 97% or less. Haze is measured in accordance with JIS K7136:2000. When the adhesive sheet has a haze of 97% or less, when the adhesive sheet covers a steel material and a rust-preventive coating film as shown in FIG. 1D , the steel material and the rust-preventive coating film can be more easily viewed through the adhesive sheet.

[0098] The surface of the adhesive sheet that faces the steel structure when the adhesive sheet is placed on the steel structure is referred to as the second surface of the adhesive sheet. In this embodiment, the second surface is the surface that faces the steel structure when the adhesive sheet is placed on the rust-proofed surface of the steel structure. The surface of the adhesive sheet opposite the second surface is referred to as the first surface of the adhesive sheet. When the adhesive sheet is transparent, the image clarity (%) measured by the reflection method on the first surface of the adhesive sheet is 20% or less when the comb width is 1.0 mm, for example. The image clarity (%) measured by the reflection method on the first surface of the adhesive sheet as measured by the above method may be 7% or less. By setting the upper limit of the image clarity (%) as described above, and particularly by setting the image clarity (%) to 7% or less, reflection of external objects on the surface of the adhesive sheet is suppressed. This makes it easier to view the steel material and the rust-proof coating through the adhesive sheet when the adhesive sheet covers them as shown in FIG. 1D.

[0099] Image clarity is also called DOI or image clarity. Image clarity is measured in accordance with JIS K7374:2007 unless otherwise specified. The incident surface during measurement is the first surface of the cover sheet. The incident angle of light incident on the incident surface during measurement is 60°. The incident angle is the angle (°) between the incident direction and the normal direction of the incident surface. Therefore, the incident angle can take a value between 0° and 90°. An image clarity measuring instrument ICM-1T manufactured by Suga Test Instruments Co., Ltd. can be used to measure image clarity (%) using the reflection method on the first surface of the adhesive sheet.

[0100] When measuring image clarity, the sample to be measured is placed on a black mount. The image clarity is measured with the back surface (second surface) of the sample, which is opposite to the incident surface (first surface), in contact with the black mount.

[0101] The measurement environment for measuring image clarity is set to a temperature of 23° C.±2° C. and a relative humidity of 50%±5%. The measurement sample is placed in the measurement environment for 16 hours before starting the measurement.

[0102] The image clarity is the arithmetic mean value of five measurements taken at five measurement positions on the adhesive sheet to be evaluated, the five measurement positions being at least 10 mm apart from each other.

[0103] For example, when the adhesive sheet includes an adhesive layer and a base layer, the adhesive layer and the base layer may be transparent rather than colored, thereby making the adhesive sheet transparent.

[0104] When the adhesive sheet comprises an adhesive layer, a substrate layer, and a surface resin layer, the adhesive layer, the substrate layer, and the surface resin layer may be transparent and not colored. This allows the adhesive sheet to be transparent. In this case, the surface resin layer may contain an ultraviolet absorber. This allows the adhesive sheet to be transparent while protecting the rust-preventive coating film and the portion of the adhesive sheet covered by the surface resin layer from ultraviolet light by the surface resin layer.

[0105] When the adhesive sheet is transparent, as described above, a topcoat film may be provided on the surface of the adhesive sheet 50. In this case, the adhesive sheet is made transparent, and the topcoat film can protect the rust-preventive coating film 40 and the adhesive sheet 50 from ultraviolet rays.

[0106] In the following examples, the adhesion of the anti-rust coating was confirmed. A steel plate with rusted areas (red rust) was prepared. Type 3 scraping was performed on the steel plate. After Type 3 scraping, the steel plate had a surface preparation including an active film (approximately 150 μm thick) of the previous coating and a rusted surface. The surface preparation of the steel plate was subjected to anti-rust treatment using anti-rust paints A to F to form an anti-rust coating film approximately 50 μm thick. The anti-rust coating surface was subjected to the following 90-degree tape peel test. After the 90-degree tape peel test, the anti-rust coating film on the surface preparation of the steel plate was visually observed. Cases where no peeling of the anti-rust coating film was observed were marked "AA," and cases where partial peeling of the anti-rust coating film was observed were marked "BB." The 85-degree specular gloss of the anti-rust coating surface was measured before and after the 90-degree tape peel test according to the following conditions. The results are shown in Table 1.

[0107] <90-Degree Tape Peel Test> Cellotape (registered trademark) (manufactured by Nichiban, model number 405-1P, 24 mm width, adhesive strength: 3.93 N / 10 mm, tensile strength: 41.6 N / 10 mm, elongation: 23%, all physical property values ​​are catalog values) was prepared as a cellophane adhesive tape conforming to JIS Z1522:2009. 25 cm of the cellophane adhesive tape was unwound from the roll at a temperature of 23°C and a humidity of 50% RH. 10 cm of the adhesive surfaces were bonded together to form a handle. 5 cm of the adhesive surface was then adhered to the rust-preventive coating surface using a 2 kg pressure roller, with two passes back and forth, and then again with finger pressure to ensure no air was trapped. Next, the cellophane adhesive tape was manually peeled once at a 90-degree angle to the rust-preventive coating surface at a speed of 5 cm / s. <85° Specular Gloss> The 85° specular gloss of the anti-rust coating film surface was measured at an incident angle of 85° and an observation angle of 85° in accordance with JIS Z8741-1997, Method 1. Using a gloss meter (manufactured by BYK, trade name: micro-TRI-gloss gloss meter), the 85° specular gloss was measured three times and the average value was calculated.

[0108] Anti-rust paint A Alpha Paint Co., Ltd. Select Coat N300 Water-based silicone acrylic resin, one-component curing type, rust conversion type Anti-rust paint B Mie Toryo Co., Ltd. Earth Coat Organic acid / inorganic acid, one-component curing type, rust conversion type Anti-rust paint C Eco Clean Co., Ltd. Sabi Barrier Epoxy resin, two-component curing type, rust conversion type Anti-rust paint D Eco Clean Co., Ltd. DecK Epoxy resin, two-component curing type, rust conversion type Anti-rust paint E Dai Nippon Toryo Co., Ltd. Sabi Shut Urethane resin, two-component curing type, salt and iron ion neutralizing type Anti-rust paint F Nippon Paint Co., Ltd. Hypon Savista Epoxy resin, two-component curing type, two-component curing type with ion trapping agent to stabilize iron ions

[0109] The urethane resin contained in Anti-Rust Paint E is a moisture-curing resin. Anti-Rust Paint E is a two-component curing urethane resin paint that neutralizes salt and iron ions. Anti-Rust Paint F is a type of anti-rust paint that does not contain a moisture-curing resin and prevents rust by stabilizing iron ions with a two-component curing ion-trapping agent.

[0110]

[0111] As described above, a steel plate having a rusted portion (red rust) was prepared. The steel plate was subjected to the Type 3 cleaning. After the Type 3 cleaning, the steel plate had a surface preparation surface including an active film (approximately 150 μm thick) of the old paint film and a rusted surface. The surface preparation surface of the steel plate was subjected to a rust prevention treatment using anti-rust paints A to F, forming an anti-rust coating film approximately 50 μm thick.

[0112] A pressure-sensitive adhesive sheet was prepared that included, in this order, a 300 μm-thick polyethylene layer, a glass-net-containing polyethylene layer, a 300 μm-thick polyethylene layer, and a 1000 μm-thick acrylic composite adhesive layer (3M® VHB® Tape for Glass, High Transparency Y-4910J). The acrylic composite adhesive layer included, in this order, an acrylic adhesive layer, an acrylic resin layer, and an acrylic adhesive layer. The storage modulus (G') of the outermost acrylic adhesive layer at 40°C was 0.369 MPa. The storage modulus was measured using a solid viscoelasticity analyzer (RSA-III, manufactured by TA Instruments) using a dynamic viscoelasticity measurement method in accordance with JIS K7244-1:1998 (attachment mode: compression mode, frequency: 1 Hz, temperature: -50 to 200°C, heating rate: 5°C / min).

[0113] In accordance with JIS Z0237:2022, a 10 mm wide adhesive sheet was attached to the surface of a steel plate on which an anti-rust coating had been formed, under conditions of 23°C and 50% RH. At this stage, the adhesive sheet's ability to conform to the unevenness of the coating surface was confirmed, and it was found to adhere well to the unevenness. After leaving the sheet stationary for three days under the above conditions, the adhesive sheet was peeled at a 180° angle at a speed of 300 mm / min to confirm the peeling state of the adhesive sheet. A Tensilon universal testing machine RTG-1250 was used as the testing equipment. When the peeling state was confirmed, it was confirmed that cohesive failure had occurred in the acrylic composite adhesive layer.

[0114] Further tests were conducted to evaluate the support body of the adhesive sheet used in the steel structure repair method of the present disclosure. In the tests, a laminate 55 having the layer structure shown in FIG. 2B was fabricated, and a support body 52 having the layer structure shown in FIG. 3 was fabricated using the laminate 55. Evaluation tests were then conducted on the fabricated laminate 55 and support body 52. ​​In the example shown in FIG. 2B , the laminate 55 includes a resin layer 62 and a surface resin layer 63, in this order, in the thickness direction. In the example shown in FIG. 3 , the support body 52 includes a gas barrier film 61, a resin layer 62, and a surface resin layer 63, in this order, in the thickness direction. The support body 52 further includes an adhesive layer 64 located between the gas barrier film 61 and the resin layer 62, bonding the gas barrier film 61 and the resin layer 62 together.

[0115] The laminate 55 shown in FIG. 2B and the support 52 shown in FIG. 3 were produced as follows. First, 95 parts by mass of a base resin was mixed with 5 parts by mass of a weathering agent master batch to obtain a resin composition. The base resin was a 0.901 g / cm3 resin having a density of 0.901 g / cm3. 3 A metallocene linear low-density polyethylene resin (M-LLDPE) having a melting point of 93°C and an MFR of 2.0 g / 10 min at 190°C was used. The weather-resistant agent masterbatch was prepared by mixing 0.6 parts by mass of HALS (KEMISTAB62 manufactured by Chemipro Chemical Co., Ltd.), 3.5 parts by mass of a first ultraviolet absorber, and 0.6 parts by mass of a second ultraviolet absorber with 100 parts by mass of the low-density polyethylene resin. The density of the low-density polyethylene resin in the weather-resistant agent masterbatch was 0.880 g / cm. 3 The melt flow rate (MFR) at 190°C was 3.5g / 10min. As the HALS, "KEMISTAB62" manufactured by Chemipro Chemical Co., Ltd. was used. As the first ultraviolet absorber, "KEMISORB12" manufactured by Chemipro Chemical Co., Ltd. was used. As the second ultraviolet absorber, "KEMISORB79" manufactured by Chemipro Chemical Co., Ltd. was used.

[0116] Next, the resin composition was sheeted at an extrusion temperature of 210°C using a film molding machine equipped with a φ30 mm extruder and a 200 mm wide T-die. This resulted in a resin layer 62 with a thickness of 300 μm. The take-up speed during this sheeting was adjusted so that the thickness of the resin layer 62 formed was 300 μm. A chrome-plated cooling roll with a surface roughness Rz of 1.5 μm was used as the cooling roll immediately below the T-die. A silicone rubber roll with a hardness of 70 degrees was used as the rubber roll immediately below the T-die. The resin layer 62 was not colored and was transparent.

[0117] Next, one surface of the resin layer 62 was subjected to a corona discharge treatment. Subsequently, 100 parts by mass of the mixture, 5 parts by mass of a curing agent, 20 parts by mass of an ultraviolet absorber, and a dilution solvent were mixed to prepare a primer layer resin composition. The 100 parts by mass of the mixture was a mixture consisting of a polycarbonate-based urethane-acrylic copolymer and an acrylic polyol. 5 parts by mass of the curing agent was hexamethylene diisocyanate. The prepared primer layer resin composition was applied to the corona discharge-treated surface of the resin layer 62. When applying the primer layer resin composition, the primer layer resin composition was applied to the treated surface by gravure printing and then dried. This formed a 4 μm-thick primer layer on the treated surface of the resin layer 62.

[0118] Next, an ionizing radiation-curable resin composition containing 100 parts by mass of a urethane acrylate oligomer, 4 parts by mass of a hydroxyphenyltriazine-based ultraviolet absorber as an ultraviolet absorber, and 3 parts by mass of a hindered amine-based non-reactive light stabilizer was prepared. The prepared ionizing radiation-curable resin composition was applied to a primer layer to form an uncured resin layer on the primer layer. The uncured resin layer was then cured by irradiating it with an electron beam. The electron beam used had an acceleration voltage of 165 kV and an exposure dose of 5 Mrad (50 kGy). This resulted in a surface resin layer 63 with a thickness of 5 μm being formed from the uncured resin layer. The surface resin layer 63 and the resin layer 62 were bonded via a primer layer not shown in FIGS. 2B and 3 . This produced the laminate 55 shown in FIG. 2B .

[0119] Furthermore, a transparent urethane resin adhesive was applied to the surface of the resin layer 62 opposite to the surface on which the primer layer and surface resin layer 63 were formed, and then dried to form a 3 μm-thick adhesive layer 64. Furthermore, a gas barrier film 61 was prepared. IB-PET-UB (manufactured by Dai Nippon Printing Co., Ltd.) was used as the gas barrier film 61. IB-PET-UB can be said to be a gas barrier film 61 comprising a resin film and a gas barrier layer, which is a vapor-deposited film. Next, the resin layer 62 and the gas barrier film 61 were bonded together by dry lamination via the adhesive layer 64. At this time, the resin layer 62 and the gas barrier film 61 were bonded together so that the surface of the gas barrier film 61 comprising the gas barrier layer and the surface of the resin layer 62 faced each other. In this manner, a support 52 was produced.

[0120] <Weather Resistance Test> The support 52 and the adhesive sheet 50 including the support 52 preferably have weather resistance. Specifically, the support 52 may be able to protect the rust-preventive coating film 40 from ultraviolet rays when the support 52 covers the rust-preventive coating film 40 as shown in FIG. 1D . In particular, the support 52 may be able to suppress deterioration of the materials contained in the rust-preventive coating film 40 due to ultraviolet rays. The support 52 may be able to suppress discoloration, particularly yellowing, of the rust-preventive coating film 40 due to ultraviolet rays. The support 52 may be resistant to ultraviolet rays so that the materials contained in the adhesive sheet 50 do not deteriorate due to ultraviolet rays. As described above, when a topcoat coating is provided on the surface of the adhesive sheet 50, the topcoat coating can protect the rust-preventive coating film 40 and the adhesive sheet 50 from ultraviolet rays. However, it is also conceivable that no topcoat coating is provided on the surface of the adhesive sheet 50. In this case, it is particularly preferable that the support 52 be able to suppress deterioration of the materials contained in the rust-preventive coating film 40 due to ultraviolet rays. Furthermore, in this case, it is particularly preferable that the support 52 be resistant to ultraviolet rays. As described above, the support 52 may contain an ultraviolet absorber as an additive. In this case, the surface resin layer 63 may contain an ultraviolet absorber, as described above. As described above, the resin layer 62 of the support 52 as shown in FIG. 3 may contain an ultraviolet absorber. As described above, the primer layer that bonds the surface resin layer 63 and the resin layer 62 of the support 52 as shown in FIG. 3 may contain an ultraviolet absorber. When the support 52 contains an ultraviolet absorber, the rust-preventive coating film 40 can be protected from ultraviolet rays. Furthermore, resistance to ultraviolet rays can be imparted to the support 52. In particular, when the surface resin layer 63 contains an ultraviolet absorber, the surface resin layer 63 can protect the rust-preventive coating film 40 and the portions of the adhesive sheet 50 covered by the surface resin layer 63 from ultraviolet rays.

[0121] A weathering test was conducted on the laminate 55 shown in FIG. 2B prepared as described above. For this weathering test, a steel material 110 having a rust-preventive coating film 140 formed thereon, as shown in FIG. 4, was prepared. The thickness of the rust-preventive coating film 140 was approximately 25 μm. Next, as shown in FIG. 5, the laminate 55 and the rust-preventive coating film 140 were bonded together via an adhesive layer 154 to prepare a sample for the weathering test. The laminate 55 and the rust-preventive coating film 140 were bonded together so that the surface of the rust-preventive coating film 140 faced the surface of the laminate 55 formed by the resin layer 62. An acrylic adhesive was used as the adhesive layer 154. The thickness of the adhesive layer 154 was 80 μm.

[0122] Next, a 408-hour weather resistance test was conducted on the weather resistance test sample. The weather resistance test was conducted using a weather resistance test device. The 408-hour weather resistance test was conducted as follows. The weather resistance test sample was subjected to a cycle consisting of a 20-hour irradiation process in which ultraviolet light was irradiated from the side formed by the surface resin layer 63 in FIG. 5 and a 4-hour condensation process, and this cycle was repeated until 408 hours were reached. After the irradiation process and before the condensation process began, a 30-second shower process was conducted, and after the condensation process and before the irradiation process began. In the shower process, the sample held in the weather resistance test device was exposed to a water shower.

[0123] The weather resistance test equipment used was the "Eye Super UV Tester SUV-W261," an ultra-accelerated weather resistance test equipment manufactured by Iwasaki Electric Co., Ltd. The UV lamp, lamp jacket, and illuminance meter included in the weather resistance test equipment were as follows: UV lamp: Product name: M04-L21WB / SUV, manufactured by Iwasaki Electric Co., Ltd. Lamp jacket: Product name: WJ50-SUV, manufactured by Iwasaki Electric Co., Ltd. Illuminance meter: Product name: UVD-365PD, manufactured by Iwasaki Electric Co., Ltd.

[0124] The conditions for the irradiation process were as follows: <Irradiation conditions> Black panel temperature: 63°C Illuminance: 100 mW / cm ２ ・Inside tank humidity: 50%RH ・Time: 20 hours

[0125] The conditions for the condensation process were as follows: <Condensation conditions> Illuminance: 0 mW / cm ２・Humidity inside the tank: 98%RH ・Time: 4 hours

[0126] Then, the color difference ΔE of the anti-rust coating film 140 was measured before and after the weather resistance test. The measured color difference ΔE is the L ＊ a ＊ b ＊ In the color system, the color before the weather resistance test is L ＊ １ a ＊ １ b ＊ １ , the color after the weather resistance test is L ＊ ２ a ＊ ２ b ＊ ２ and are defined by the following formulas (1) to (4).

[0127] Color L before weather resistance test ＊ １ a ＊ １ b ＊ １ , and color L after weather resistance test ＊ ２ a ＊ ２ b ＊ ２ was the color when the rust-preventive coating film 140 was observed through the laminate 55.

[0128] Furthermore, as a comparative sample, a steel material 110 having a rust-preventive coating film 140 formed thereon was prepared as shown in Fig. 4. For the comparative sample, a weathering test was carried out for 408 hours in the same manner as for the sample shown in Fig. 5 described above, without covering the rust-preventive coating film 140 with the laminate 55, and the color difference ΔE of the rust-preventive coating film 140 before and after the weathering test was measured. In the irradiation step of the weathering test for the comparative sample, ultraviolet light was irradiated from the side of the sample that was formed by the rust-preventive coating film 140.

[0129] As a result of measuring the color difference ΔE, in the sample in which the rust-preventive coating film 140 was covered with the laminate 55 as shown in Figure 5, the color difference ΔE before and after ultraviolet irradiation was 4.3. In contrast, in the comparative example in which the rust-preventive coating film 140 was not covered with the laminate 55, the color difference ΔE before and after ultraviolet irradiation was 14.7. This shows that by covering the rust-preventive coating film 140 with the laminate 55 as shown in Figure 5, the rust-preventive coating film 140 can be protected from ultraviolet rays and discoloration of the rust-preventive coating film 140 can be suppressed. This result also reveals that when the rust-preventive coating film 140 is covered with the support 52 including the gas barrier film 61 and the adhesive layer 64 in addition to the laminate 55, the rust-preventive coating film 140 can be protected from ultraviolet rays and discoloration of the rust-preventive coating film 140 can be suppressed.

[0130] <Test for resistance to repeated wetting, cooling, and heat> The support 52 preferably has resistance to repeated wetting, cooling, and heat. More specifically, it is preferably evaluated as "able to withstand repeated wetting, cooling, and heat" in the "test for resistance to repeated wetting, cooling, and heat" described in 7.18 of JIS K5659:2018.

[0131] The support 52 shown in FIG. 3 prepared as described above was subjected to a "Test for Resistance to Repeated Wet and Cooling" as described in JIS K5659:2018, 7.18. As a result, the support 52 was evaluated as "resistant to repeated wetting and cooling." Specifically, two test pieces were prepared from the support 52 according to the method described in JIS K5659:2018, 7.16, a) and b). The two prepared test pieces were immersed in water at 23°C ± 1°C for 18 hours, immediately cooled in a thermostatic chamber maintained at -20°C ± 3°C for 3 hours, and then humidified in another thermostatic chamber maintained at 50°C ± 3°C for 3 hours. This operation was repeated 10 times. The two test pieces were visually observed. No swelling, cracking, or peeling was observed in the coating film. Furthermore, when the gloss retention was calculated by the method described in JIS K5659:2018, 7.18, b)2), it was 80% or more.

[0132] The two test pieces that had been subjected to the above-described procedure 10 times were visually inspected, and no peeling was observed between the layers contained in the support 52.

[0133] A T-peel test was performed on the test piece that had undergone the above-described operation 10 times in accordance with JIS K6854-3:1999, "Adhesives - Testing Methods for Peel Adhesion Strength - Part 3: T-peel." This measured the maximum strength of the peel adhesive strength of the adhesive layer 64. When the material of the test piece broke during the test, the breaking strength was measured; when the material of the test piece did not break during the test, the maximum peel strength was measured. Furthermore, as a comparative example, a test piece that had not undergone the above-described operation 10 times was subjected to the same T-peel test as the test piece that had undergone the above-described operation 10 times. This measured the maximum strength of the peel adhesive strength of the adhesive layer 64 for the comparative example test piece. As a result, the maximum strength of the test piece that had undergone the above-described operation 10 times was 90% or more of the maximum strength of the comparative example test piece. From the above, it was found that even when the support 52 shown in FIG. 3 was subjected to a test for resistance to repeated hot and cold cycles, the decrease in peel strength of the adhesive layer 64 was small.

[0134] <Test for Topcoat Compatibility> As described above, it may be desirable to apply a topcoat paint to the surface of the adhesive sheet 50 to form a topcoat film. In this case, the support 52 that forms the surface of the adhesive sheet 50 preferably has topcoat compatibility. In this specification, the "topcoat compatibility" of the support 52 means the property that allows a topcoat paint to be applied to the surface of the support 52 without hindrance to form a topcoat film.

[0135] A test for overcoat compatibility was conducted on the support 52 shown in FIG. 3 prepared as described above. In this overcoat compatibility test, two test plates measuring 150 mm x 70 mm were prepared from the support 52. A topcoat paint was applied to the surface of one of the test plates, which was composed of the surface resin layer 63. A Baker-type applicator was used to apply the topcoat paint. A test specimen was thus prepared. Aside from the test plate to which the topcoat paint was applied, one test plate was left as is without the topcoat paint applied.

[0136] Using the prepared test specimens, the substrate 52 was evaluated for suitability for overcoating according to the method described in "Evaluation and Judgment" regarding "Overcoat Suitability" in JIS K5551:2018, Section 7.11, c). That is, the following three points 1) to 3) were confirmed: 1) When applying a topcoat paint to the surface of one test plate formed by the surface resin layer 63, there was no interference with the overcoat work. 2) When the topcoat paint was left for 48 hours (after application of the topcoat paint to the surface formed by the surface resin layer 63) and the appearance of the formed topcoat paint film was visually observed, no repellency, cracking, blistering, or peeling of the topcoat paint was observed. 3) When the test specimens left for 48 hours after overcoating were compared with the original test specimens prepared at the same time, there was no significant degree of stickiness when checked by touch and no significant degree of wrinkling when checked visually. When all three points 1) to 3) above are satisfied, it is judged that there is "no problem" in applying a topcoat paint to the surface of the substrate 52 to form a topcoat coating film. In other words, when all three points 1) to 3) above are satisfied, the substrate 52 is judged to have topcoat compatibility.

[0137] The above-mentioned topcoat compatibility test was conducted using a stain-resistant fluororesin topcoat paint (manufactured by Dai Nippon Toryo Co., Ltd., product name "V-Flon #100H Smile Topcoat IG") as the topcoat paint. The target film thickness of the topcoat paint film was 25 μm. The measured film thickness of the formed topcoat paint film was 23.8 μm. Furthermore, the above-mentioned topcoat compatibility test was conducted using a weak-solvent ultra-thick film epoxy resin paint (manufactured by Dai Nippon Toryo Co., Ltd., product name "Eponics H-R Smile") as the topcoat paint. The target film thickness of the topcoat paint film was 150 μm. The measured film thickness of the formed topcoat paint film was 164.5 μm.

[0138] As a result of the topcoat compatibility test, it was determined that whether a stain-resistant fluororesin topcoat paint or a weak-solvent ultra-thick film epoxy resin paint was used as the topcoat paint, there was no problem in applying the topcoat paint to the surface of the substrate 52 to form a topcoat film. In other words, it was determined that the substrate 52 was suitable for topcoating whether a stain-resistant fluororesin topcoat paint or a weak-solvent ultra-thick film epoxy resin paint was used as the topcoat paint.

[0139] Furthermore, the above-mentioned 90-degree tape peel test was performed on the topcoat coating film of the test piece prepared in the topcoat compatibility test, which had been coated with a topcoat paint and left for 48 hours after topcoating. That is, 25 cm of a 24 mm wide cellophane adhesive tape conforming to JIS Z1522:2009 was unwound at a temperature of 23 ° C and a humidity of 50% RH. To prepare a handle, 10 cm adhesive surfaces were bonded together. In this state, 5 cm of the adhesive surface was adhered to the surface of the topcoat coating film using a 2 kg pressure roller, which was then rolled back and forth twice, and then again with finger pressure to prevent air from being trapped. Next, the cellophane adhesive tape was manually peeled off once at a speed of 5 cm / s in a 90-degree direction relative to the surface of the topcoat coating film. The cellophane adhesive tape used was Cellotape (registered trademark) (manufactured by Nichiban, model number 405-1P, 24 mm width, adhesive strength: 3.93 N / 10 mm, tensile strength: 41.6 N / 10 mm, elongation: 23%, all physical property values ​​are catalog values). If this product cannot be used, a 24 mm wide cellophane adhesive tape conforming to JIS Z1522:2009, which has adhesive strength equivalent to that of this product, can be used to perform a 90-degree tape peel test on the topcoat coating film.

[0140] As a result of a 90° tape peeling test on the topcoat film, the topcoat film did not peel off even after one strong peeling of cellophane adhesive tape.

[0141] <Image clarity> From the viewpoint of suppressing the reflection of external objects on the surface of the adhesive sheet, it is preferable that the image clarity (%) measured by the reflection method on the first surface of the adhesive sheet is small. An image clarity measurement test was conducted on the laminate 55 shown in FIG. 2B prepared as described above. In this image clarity measurement test, a sample was prepared using the same method as described above for the weather resistance test, which included a steel material 110, an anti-rust coating film 140 formed on the steel material 110, and a laminate 55 covering the anti-rust coating film 140, as shown in FIG. 5. The anti-rust paint F described above was used to form the anti-rust coating film 140.

[0142] The image clarity (%) of this sample was measured by a reflection method on the surface formed by the surface resin layer 63. The image clarity (%) was measured in accordance with JIS K7374:2007. The image clarity (%) was measured when the comb width was 1.0 mm. During measurement, the angle of incidence of light incident on the incident surface (the surface of the sample formed by the surface resin layer 63) was 60°. An image clarity measuring instrument ICM-1T manufactured by Suga Test Instruments Co., Ltd. was used to measure the image clarity (%).

[0143] The image clarity (%) was measured to be 12.8%, which indicates that the image clarity on the surface of the laminate 55 formed by the surface resin layer 63 when the comb width is 1.0 mm is suppressed to 20% or less.

[0144] The present disclosure relates to, for example, the following items [1] to

[13] . [1] A method for repairing a steel structure having a deteriorated portion, the method comprising: a first step of preparing an adhesive sheet including a support and an adhesive layer provided on one surface of the support; a second step of performing surface preparation on the deteriorated portion of the steel structure to form a surface preparation surface that may have an active film; a third step of performing rust prevention treatment on the surface preparation surface of the steel structure to form a rust prevention treated surface; and a fourth step of placing the adhesive sheet on the rust prevention treated surface of the steel structure. [2] The method for repairing a steel structure as described in [1], wherein the second step is a step of performing at least surface preparation using a three-step cleaning method on the deteriorated portion of the steel structure. [3] The method for repairing a steel structure as described in [1] or [2], wherein the third step is a step of applying an anti-rust paint to the surface preparation surface of the steel structure to form an anti-rust coating film. [4] The method for repairing a steel structure according to [3], wherein the anticorrosive paint is a two-component curing anticorrosive paint. [5] The method for repairing a steel structure according to [3] or [4], wherein, when the 85-degree specular gloss of the anticorrosive coating surface before a 90-degree tape peel test is performed on the anticorrosive coating surface, which is the surface of the anticorrosive coating film, is designated as Gsb, and the 85-degree specular gloss of the anticorrosive coating surface after a 90-degree tape peel test is designated as Gsa, the maintenance rate (Gsa x 100 / Gsb) is 95% or more. [6] The method for repairing a steel structure according to any one of [1] to [5], further comprising, between the third step and the fourth step, a step 3a of forming a coating resin layer on the anticorrosive treated surface. [7] The method for repairing a steel structure according to any one of [1] to [6], further comprising a step 5 of forming a topcoat coating on the surface of the adhesive sheet placed on the anticorrosive treated surface. [8] The method for repairing a steel structure according to any one of [1] to [7], wherein the adhesive sheet comprises a composite adhesive layer comprising a first adhesive layer, a base layer, and a second adhesive layer in that order in the thickness direction. [9] The method for repairing a steel structure according to any one of [1] to [8], wherein the support of the adhesive sheet comprises a gas barrier layer.

[10] The steel structure repair method according to [9], wherein the adhesive sheet has an oxygen permeability of 6.57 cc / (m2·day·atm) or less, measured in accordance with JIS K7126-2:2006 at a temperature of 23°C and a humidity of 60%.

[11] The steel structure repair method according to [9] or

[10] , wherein the adhesive sheet has a water vapor permeability of 3.0 g / (m2·day) or less, measured in accordance with JIS K7129-2:2019 at a temperature of 40°C and a humidity of 90%.

[12] The steel structure repair method according to any one of [1] to

[11] , wherein the adhesive sheet has a total light transmittance of 70% or more.

[13] The steel structure repair method according to

[12] , wherein the adhesive sheet has a haze of 97% or more.

[14] The steel structure repair method according to

[12] or

[13] , wherein the adhesive sheet has a first side that is the side opposite to the side that faces the steel structure when the adhesive sheet is placed on the rust-proofed surface of the steel structure, and the image clarity (%) on the first side of the adhesive sheet measured by a reflection method is 20% or less when the comb width is 1.0 mm.

[15] A steel structure manufacturing method, comprising applying the steel structure repair method according to any one of [1] to

[14] to a steel structure having a deteriorated portion to manufacture a repaired steel structure.

[16] An adhesive sheet for repairing a steel structure, comprising a support and an adhesive layer provided on one surface of the support, the adhesive sheet being intended to be placed on a rust-proofed surface of a steel structure having a deteriorated portion, where the deteriorated portion has been subjected to surface preparation and rust-proofing treatment.

[17] An adhesive sheet for repairing steel structures as described in

[16] , wherein the adhesive sheet has a composite adhesive layer having a first adhesive layer, a base layer, and a second adhesive layer in that order in the thickness direction.

[0145] 10: Steel material, 20: Paint film before repair (old paint film), 22: Active film, 30: Rust, 40: Anti-rust paint film, 50: Adhesive sheet, 52: Support, 54: Adhesive layer

Claims

1. A method for repairing a steel structure having a deteriorated portion, comprising: a first step of preparing an adhesive sheet having a support and an adhesive layer provided on one surface of the support; A second step of performing a surface preparation process on the deteriorated portion of the steel structure to form a surface preparation surface which may have an active film; A third step of performing a rust-proofing treatment on the base preparation surface of the steel structure to form a rust-proofed surface; A fourth step of placing the adhesive sheet so as to be in direct contact with the rust-proofing surface of the steel structure; A method for repairing a steel structure, comprising:

2. 2. The method for repairing a steel structure according to claim 1, wherein the second step is a step of at least performing surface preparation using a three-type surface preparation method on the deteriorated portion of the steel structure.

3. 2. The method for repairing a steel structure according to claim 1, wherein the third step is a step of applying an anti-rust paint to the base preparation surface of the steel structure to form an anti-rust coating film.

4. 4. The method for repairing a steel structure according to claim 3, wherein the anti-rust paint is a two-component curing type anti-rust paint.

5. 4. The method for repairing a steel structure as described in claim 3, wherein the 85 degree specular gloss of the anti-rust coating film surface before a 90 degree tape peel test is performed on the anti-rust coating film surface is designated as Gsb, and the 85 degree specular gloss of the anti-rust coating film surface after a 90 degree tape peel test is performed on the anti-rust coating film surface is designated as Gsa, and the maintenance rate (Gsa x 100 / Gsb) is 95% or more.

6. 2. The method for repairing a steel structure according to claim 1, further comprising a step 3a between the third step and the fourth step of forming a coating resin layer on the rust-proofed surface.

7. 2. The method for repairing a steel structure according to claim 1, further comprising a fifth step of forming a topcoat film on the surface of the adhesive sheet placed on the rust-proofed surface.

8. The method of repairing a steel structure according to claim 1 , wherein the support of the adhesive sheet comprises a gas barrier layer.

9. 9. The method for repairing a steel structure according to claim 8, wherein the adhesive sheet has an oxygen permeability of 6.57 cc / (m2·day·atm) or less, measured in accordance with JIS K7126-2:2006 at a temperature of 23°C and a humidity of 60% RH.

10. The method for repairing a steel structure according to claim 8, wherein the adhesive sheet has a water vapor permeability of 3.0 g / (m2·day) or less, measured in accordance with JIS K7129-2:2019 at a temperature of 40°C and a humidity of 90% RH.

11. The method for repairing a steel structure according to claim 1 , wherein the adhesive sheet has a total light transmittance of 70% or more.

12. The method for repairing a steel structure according to claim 11 , wherein the adhesive sheet has a haze of 97% or less.

13. the adhesive sheet has a first surface which is a surface opposite to a surface which faces the steel structure when the adhesive sheet is placed on the rust-proofing surface of the steel structure; 12. The method for repairing a steel structure according to claim 11, wherein an image clarity (%) on the first surface of the adhesive sheet by a reflection method is 20% or less when the comb width is 1.0 mm.

14. A manufacturing method for a steel structure, comprising applying the steel structure repair method according to any one of claims 1 to 13 to a steel structure having a deteriorated portion to manufacture a repaired steel structure.

15. An adhesive sheet for repairing a steel structure, comprising a support and an adhesive layer provided on one surface of the support, the adhesive sheet being intended to be placed in direct contact with a rust-proofing treated surface of a steel structure having a deteriorated portion, the rust-proofing treatment having been performed on the deteriorated portion.