Surface-treated galvanized steel sheet, resin film coated steel sheet, construction panel, method for manufacturing surface-treated galvanized steel sheet, and method for manufacturing resin film coated steel sheet

Abstract

[Problem] To provide a surface-treated galvanized steel sheet, a resin film-coated steel sheet, and a building panel having excellent corrosion resistance or processing adhesion with a resin film. [Solution] A surface-treated galvanized steel sheet comprising a steel sheet, a zinc plating layer formed on the steel sheet, a first chemical treatment coating layer formed on the zinc plating layer containing cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m², and a second chemical treatment coating layer formed on the first chemical treatment coating layer comprising (a) a zirconium component, (b) a bonding component based on the dehydration condensation of a silanol group, and (c) a urethane bonding component.

Description

Technology Field

[0001] The present disclosure relates to surface-treated galvanized steel sheets and resin film-coated steel sheets. Furthermore, it relates to architectural panels using surface-treated galvanized steel sheets and resin film-coated steel sheets. Moreover, it relates to a method for manufacturing surface-treated galvanized steel sheets and a method for manufacturing resin film-coated steel sheets. Background Technology

[0002] Recently, there has been a growing demand for surface-treated steel sheets used for architectural panels, such as bathroom or kitchen panels, to reduce environmental burden. Specifically, surface-treated steel sheets that do not contain chromate coatings are in demand from the perspective of preventing water pollution and addressing soil contamination.

[0003] For example, the following patent document 1 discloses a method for manufacturing a zinc-plated steel sheet having excellent corrosion resistance and paint adhesion of the flat portion, wherein a first surface treatment solution containing an ionic bonding salt containing a predetermined cation, a predetermined chelating agent, and water is used to form a first film on the surface of the zinc-plated steel sheet, and then a second surface treatment solution containing a predetermined amount of a silane coupling agent having a glycidyl group, tetraalkoxysilane, zirconium carbonate compound, a predetermined anionic polyurethane resin, vanadium compound, molybdic acid compound, and water is used to form a second film on the surface of the first film.

[0004] Patent Document 2 discloses a pre-coated steel sheet having excellent corrosion resistance and processability, wherein a chrome-free undercoat treatment is formed on both sides of a zinc-plated steel sheet, and on one side which is the surface, a primer coating layer is formed on the undercoat treatment, wherein the primer coating layer contains at least one of an ion-exchange type oxide anti-corrosion pigment or a phosphate-based anti-corrosion pigment and uses a polyester-based resin and / or an epoxy-modified polyester-based resin as a binder, and furthermore, one or more topcoat coating layers are formed on the upper layer of the primer coating layer, and on the other side which is the back side, a primer coating layer is formed, wherein the primer coating layer contains at least one of an ion-exchange type oxide anti-corrosion pigment or a phosphate-based anti-corrosion pigment and uses a polyester-based resin and / or an epoxy-modified polyester-based resin as a binder, and furthermore, one or more topcoat coating layers are formed on the upper layer of the primer coating layer.

[0005] Patent Document 3 discloses a chromate-free surface-treated metal material that has undergone a chrome-free surface treatment satisfying corrosion resistance, heat resistance, etc., wherein a Zn-Co plating film containing a small amount of Co is coated on the metal material, and thereon, a water-based metal surface treatment agent comprising a silane coupling agent (A) containing one amino group in its molecule and a silane coupling agent (B) containing one glycidyl group in its molecule are mixed in a ratio of 0.5 to 1.7 in solid mass ratio [(A) / (B)] to form a composite film containing each component.

[0006] Patent Document 4 discloses a coated steel plate having sufficiently high corrosion resistance and adhesion of the processed part, wherein the steel plate, a zinc-based plating layer, a phosphate treatment layer having a total adhesion amount of Ni and Co of 20 mg / m² or more and 100 mg / m² or less and an adhesion amount of the treatment layer of 2.0 g / m² or more and 7.0 g / m² or less, a chrome-free sealing film containing an oxylate of a group 4 metal and a group 1 metal or its salt, and an organic film are arranged in this order.

[0007] Patent Document 5 discloses a chemical treatment steel sheet having excellent coating adhesion and film adhesion after processing, wherein the steel sheet is a zinc-plated steel sheet or a zinc alloy-plated steel sheet, and the thickness of the chemical treatment film formed by an oxide or hydroxide and fluoride of a valve metal, in which the oxide exhibits high insulation resistance, and a polyphenol resin is 0.01 to 0.5 μm on the surface of the plated steel sheet. Prior art literature

[0008] Japanese Patent Publication No. 2022-39097 Japanese Patent Publication No. 2007-119858 Japanese Patent Publication No. 2008-184659 Japanese Patent Publication No. 2020-152986 Japanese Patent Publication No. 2008-163364 The problem to be solved

[0009] However, the above patent documents 1 to 5 all had room for improvement regarding the current demand for materials for architectural panels. That is, in the case of surface-treated steel sheets for architectural panels where various exterior variations are required recently, a resin film having an ornamental quality is attached to a surface that has undergone chemical treatment.

[0010] In addition, surface-treated steel sheets laminated with resin films, such as polyester or polyvinyl chloride, are formed into various shapes by press processing. Therefore, excellent corrosion resistance and high processing adhesion of the resin film are required to withstand harsh environments, such as bathroom applications.

[0011] As a result of carefully examining the composition of materials for architectural panels that possess higher processing adhesion to resin films, the present invention was conceived. Specifically, the present disclosure aims to provide a surface-treated galvanized steel sheet that possesses processing adhesion to resin films in addition to corrosion resistance equivalent to that of conventional chromate films. means of solving the problem

[0012] To solve the above problem, a surface-treated galvanized steel sheet according to one embodiment of the present disclosure is characterized by comprising a steel sheet, a zinc plating layer formed on the steel sheet, a first chemical treatment film layer formed on the zinc plating layer containing cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m², and a second chemical treatment film layer formed on the first chemical treatment film layer comprising (a) a zirconium component, (b) a bonding component based on the dehydration condensation of a silanol group, and (c) a urethane bonding component.

[0013] In addition, a resin film coated steel sheet according to one embodiment of the present disclosure is characterized by being composed of the surface-treated galvanized steel sheet, an adhesive layer formed on the surface-treated galvanized steel sheet, and a resin film formed on the adhesive layer.

[0014] In addition, a building panel according to one embodiment of the present disclosure is characterized by being formed using the resin film-coated steel plate.

[0015] A method for manufacturing a surface-treated galvanized steel sheet according to one embodiment of the present disclosure is characterized by having a first treatment process of forming a first chemical treatment film layer containing cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m² on the galvanized steel sheet by applying an alkaline treatment agent containing a metal chelating agent containing cobalt nitrate and ferric nitrate to the galvanized steel sheet, and a second treatment process of applying a water-based treatment agent containing a coupling agent, a metal oxide, a block isocyanurate, and a polyester polyol as constituents to the first chemical treatment film layer and drying at 60°C or higher.

[0016] A method for manufacturing a resin film-coated steel sheet according to one embodiment of the present disclosure is characterized by having a third treatment process of applying a polyester-based adhesive to the surface-treated galvanized steel sheet to a thickness of 1 μm to 4 μm, and a fourth treatment process of heating the surface-treated galvanized steel sheet coated with the polyester-based adhesive to 180°C or higher and coating a resin film on the polyester-based adhesive. Effects of the invention

[0017] According to the present disclosure, a surface-treated galvanized steel sheet, a resin film-coated steel sheet, and a building panel can be provided, which do not include a chromate film and have excellent corrosion resistance or processing adhesion with a resin film. Brief explanation of the drawing

[0018] Figure 1 is a schematic cross-sectional view of a surface-treated galvanized steel sheet according to an embodiment. FIG. 2 is a schematic cross-sectional view of a resin film coated steel plate according to an embodiment. FIG. 3 is a schematic cross-sectional view of a building panel according to an embodiment. Figure 4 is a drawing showing a method for manufacturing surface-treated galvanized steel sheets and resin film-coated steel sheets. FIG. 5 is a diagram schematically showing the test evaluation criteria in the present embodiment. Specific details for implementing the invention

[0019] Surface-treated galvanized steel sheet (100)

[0020] Hereinafter, a surface-treated galvanized steel sheet according to the present embodiment will be described in detail. As shown in FIG. 1, the surface-treated galvanized steel sheet (100) according to the present embodiment has a galvanized steel sheet (10) and a chemical treatment film (20) coated on at least one side of the galvanized steel sheet (10). The galvanized steel sheet (10) includes a steel sheet (11) and a galvanized layer (13) formed on the steel sheet (11). In addition, the chemical treatment film (20) includes a first chemical treatment film layer (21) on the galvanized layer (13), and a second chemical treatment film layer (23) covering both the galvanized layer (13) and the first chemical treatment film layer (21).

[0021] <Galvanized steel sheet (10)>

[0022] In this embodiment, the galvanized steel sheet (10) used can be a galvanized steel sheet generally used in laminated metal sheets. Examples include hot-dip galvanized steel sheets, hot-dip galvanized steel sheets, alloyed hot-dip galvanized steel sheets, electro-galvanized steel sheets, electro-galvanized steel sheets, etc. Among these, hot-dip galvanized steel sheets (JIS G3302) can be preferably used from the perspective of ease of availability and price.

[0023] There are no specific restrictions on the thickness of the galvanized steel sheet (10), but for example, a thickness of 0.10 mm to 1.20 mm is desirable from the perspective of ease of construction and appearance. If the thickness of the galvanized steel sheet is less than 0.1 mm, there is a possibility that desirable corrosion resistance or weather resistance cannot be obtained. On the other hand, if the thickness of the galvanized steel sheet exceeds 1.2 mm, the weight increases, which increases the likelihood of causing difficulties during construction, and is not desirable from the perspective of cost.

[0024] As for the steel plate (11) included in the galvanized steel plate (10), for example, a cold-rolled steel plate of ordinary steel with a thickness of about 0.05 mm to 1.20 mm can be used. Among the cold-rolled steel plates, a low-carbon or ultra-low-carbon aluminum-killed steel plate with a carbon content of less than 0.01 mass% is preferably used as the steel plate (11) in terms of workability, etc.

[0025] There is no particular limitation on the zinc plating amount of the zinc plating layer (13) formed on the steel plate (11), but as an example, it can be 60 g / m² to 600 g / m². More specifically, when the zinc-plated steel plate (10) is a hot-dip galvanized steel plate, it is preferable that it be within the range of Z06 to Z60 as the plating amount indication symbol shown in JIS G3302:2019.

[0026] <Mars treatment membrane (20)>

[0027] As described above, the chemical treatment film (20) is formed on at least one side of the galvanized steel sheet (10). The chemical treatment film (20) includes a first chemical treatment film layer (21) that covers at least a portion of the surface of the galvanized steel sheet (10), and a second chemical treatment film layer (23) that is formed on the first chemical treatment film layer (21) and covers the entire surface of the galvanized steel sheet (10).

[0028] <First chemical treatment film layer (21)>

[0029] The first chemical treatment film layer (21) is a metal film containing cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m². As shown in FIG. 1, the first chemical treatment film layer (21) is in contact with the surface of the galvanized steel sheet (10). The first chemical treatment film layer (21) does not need to cover the entire surface of the galvanized steel sheet (10), but is present on at least a part of the surface of the galvanized steel sheet (10).

[0030] The effect of the first chemical treatment film layer (21) on the surface of the galvanized steel sheet (10) is as follows. That is, since cobalt (Co), which has a lower ionization tendency than zinc (Zn), becomes the oxygen reduction reaction site (cathode), microcells of Co (cathode) and Zn (anode) are formed under the film of the formed first chemical treatment film layer (21). As a result, OH under the film - It can reduce the amount of [product] produced and inhibit cathodic delamination or corrosion under the film.

[0031] In addition, the method for forming the first chemical treatment film layer (21) is performed by applying a cobalt-containing alkaline treatment solution to the surface of the galvanized steel sheet (10), although this will be described in detail later. When the alkaline treatment solution is applied to the surface of the galvanized steel sheet (10), the zinc (Zn) on the galvanized steel sheet (10) is dissolved, and at that time, electrons are emitted, thereby the Co in the alkaline treatment solution 2+ Ions are reduced (substitutional electroless plating).

[0032] <Second chemical treatment film layer (23)>

[0033] The second chemical treatment film layer (23) is (a) an organic-inorganic composite film containing a zirconium component. The film amount of the second chemical treatment film layer is preferably 4 mg / m² to 600 mg / m², and more preferably 30 mg / m² to 70 mg / m². The dry film amount of the second chemical treatment film layer can be measured using a known fluorescent X-ray analyzer.

[0034] It is preferable that the thickness of the second chemical treatment film layer be 1 μm or less. It is preferable that the amount of zirconium contained in the second chemical treatment film layer (23) be 1.2 mg / m² or more and 171.4 mg / m² or less, and more preferable that it be 8.6 mg / m² to 20.0 mg / m². In addition, the amount of dry film of the second chemical treatment film layer described above can be calculated from the amount of zirconium. More specifically, it can be calculated by the following formula.

[0035] Dry film weight (mg / m²) = Zirconium weight (mg / m²) × 3.5

[0036] The second chemical treatment film layer (23) further includes (b) a bonding component based on the dehydration condensation of silanol groups and (c) a urethane bonding component. (b) The bonding component based on the dehydration condensation of silanol groups includes siloxane bonds, etc., and is a silane coupling agent component. The silane coupling agent reacts with the surface of the metal and the resin under heat curing. That is, the second chemical treatment film layer (23) is composed of siloxane bonds (-Si-O-Si-) dispersed within the urethane resin component, and is also thought to be bonded (-Si-O-metal-) with the metal oxide and the cobalt metal of the first chemical treatment film layer or the zinc on the galvanized steel sheet.

[0037] <Resin film coated steel plate (200)>

[0038] The resin film coated steel plate (200) in the present disclosure comprises, as shown in FIG. 2, an adhesive layer (30) formed on at least one side of the surface of the surface-treated galvanized steel plate (100) described above, and a resin film (40) formed on the adhesive layer (30).

[0039] <Adhesive layer (30)>

[0040] The adhesive layer (30) is preferably an adhesive with polyester resin as the main component, and furthermore, is preferably a polyester-urethane adhesive. The adhesive layer (30) may also be an adhesive with acrylic resin as the main component. One type of adhesive may be used, multiple types may be mixed and used, and an acrylic adhesive or an olefin adhesive may be mixed and used with a polyester adhesive.

[0041] It is preferable that the thickness of the adhesive layer (30) be 1 μm to 4 μm. In addition, the adhesive layer (30) may contain an adhesion enhancer in order to improve the processing adhesion between the second chemical treatment film layer (23) and the resin film (40). Examples of adhesion enhancers include silane coupling agents having trimethoxysilyl groups, amino groups, and epoxy groups.

[0042] <Suzy Film (40)>

[0043] The resin film (40) may be a film used for construction materials. Examples of materials for the resin film (40) include polyvinyl chloride film, polyester film, acrylic film, olefin film, etc. The resin film (40) may be a transparent film or a colored film. In addition, the resin film (40) may be a film with decorative properties, and may be, for example, a film with embossing processing on its surface. The resin film (40) may be a laminate of films made of multiple different materials. For example, a film laminated with a polyethylene terephthalate film and a polyvinyl chloride film may be used as the resin film (40). The thickness of the resin film (40) is preferably 0.06 mm or more. In addition, there is no particular limit on the upper limit of the thickness of the resin film (40), but for cost-effectiveness, it is preferable to be 0.5 mm or less.

[0044] Generally, when a resin film with a thickness of 0.06 mm or more is laminated onto a surface-treated steel plate and then subjected to forming processing, delamination of the resin film may occur due to internal stress. However, the resin film-coated steel plate of the present disclosure can significantly improve processing adhesion. The reasons for this are approximately as follows.

[0045] When a steel sheet is elongated during processing, a stress load is applied to the chemical treatment layer containing inorganic components. If the thickness of the chemical treatment layer exceeds a certain limit, it cannot keep up with the processing, and forces become concentrated at the interface between the chemical treatment layer and the galvanizing layer. As a result, the chemical treatment layer undergoes cohesive fracture, causing delamination of the resin film. This is the reason for the delamination of the chemical treatment layer in general resin film-coated steel sheets.

[0046] Meanwhile, in the present disclosure, by configuring the chemical treatment layer into a two-layer structure consisting of a first chemical treatment film layer containing cobalt metal and a second chemical treatment film layer containing a coupling agent component, it was possible to realize improved processing adhesion.

[0047] <Architectural panel (300)>

[0048] Next, the architectural panel (300) in this embodiment will be described. The architectural panel (300) in this embodiment is characterized by using the surface-treated galvanized steel sheet (100) or the resin film-coated steel sheet (200) described above, as shown in FIG. 3. More specifically, the architectural panel (300) in this embodiment is formed by providing a back-side paint layer (50) on the surface opposite to the resin film (40) in the resin film-coated steel sheet (200). The thickness of the back-side paint layer (50) is not particularly limited, but, for example, it may be 5㎛ to 20㎛. In addition, as for the type of back-side paint layer (50), known paints generally used for architectural purposes may be applied, and examples include epoxy-based paints or polyester-based paints.

[0049] In addition, the architectural panel (300) in this embodiment may have a metal layer, resin layer, gypsum board layer, volcanic glass multilayer plate, etc., not shown on at least one side of the back paint layer (50).

[0050] The architectural panel (300) in this embodiment can be applied to interior materials such as bathroom panels or kitchen panels. More specifically, it can be applied to unit bathroom interior materials, composite magnetic panels in kitchens, panels that can be attached to indoor walls, etc. In addition, it can be applied to exterior materials such as entrance doors.

[0051] Method for manufacturing surface-treated galvanized steel sheets

[0052] Next, a method for manufacturing a surface-treated galvanized steel sheet (100) of the present embodiment will be described. As shown in FIG. 4, the method for manufacturing a surface-treated galvanized steel sheet (100) of the present embodiment includes the following first treatment process and second treatment process. Additionally, the method for manufacturing a surface-treated galvanized steel sheet (100) of the present embodiment may include a known degreasing process. Furthermore, since a suitable known process can be applied to the process of galvanizing the steel sheet with zinc, a description is omitted here.

[0053] Degreasing Process

[0054] First, the degreasing process for galvanized steel sheets will be explained. Furthermore, this degreasing process is not mandatory and can be omitted as appropriate. Specifically, this degreasing process may be performed to remove oxide films or oil coatings from the surface of the galvanized steel sheets used.

[0055] Specifically, the degreasing process can be performed by applying a known alkali treatment agent to the surface of a galvanized steel sheet. Specifically, as a known alkali treatment agent, a silicate-type alkali treatment agent containing 35–40% sodium metasilicate and 0.1–1.0% potassium hexafluoride titanate as a compositional concentration may be used. During the degreasing process, this alkali treatment agent may be used by adjusting the concentration to 2.0% or less and the liquid temperature to 60°C–75°C. As a method of applying the alkali treatment agent to the galvanized steel sheet, known methods such as the spray method or the immersion method may be applied. In the case of the spray method or the immersion method, the treatment time during the degreasing process may be 9–13 seconds. Furthermore, it is preferable to remove the treatment agent by rinsing the galvanized steel sheet with water after treatment.

[0056] <First Process>

[0057] Following any degreasing process, a first treatment process may be performed. The first treatment process is a process of forming a first chemical treatment film layer on a galvanized steel sheet. The first chemical treatment film layer contains cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m². The first chemical treatment film layer can be formed by applying an alkaline treatment agent containing a cobalt metal component onto the galvanized steel sheet. Additionally, the alkaline treatment agent may include a metal chelating agent containing cobalt nitrate and ferric nitrate.

[0058] As an alkaline treatment agent in the first treatment process, more specifically, an alkaline treatment agent containing 20-25% sodium hydroxide, 1-5% cobalt nitrate, and 1-5% ferric nitrate as a compositional concentration may be used. In addition, in the first treatment process, the alkaline treatment agent may be used by adjusting the liquid temperature to 60°C to 75°C.

[0059] In the first treatment process, known methods such as spraying or immersion can be applied as the method of applying the alkali treatment agent to the galvanized steel sheet. In the case of the spraying or immersion method, the treatment time in the first treatment process can be 8 to 16 seconds. In the first treatment process, after treatment, by-products and treatment solution components remaining on the surface of the galvanized steel sheet can be removed by washing with water. In addition, after washing with water, a cobalt metal film as a first chemical treatment film layer can be formed on the surface of the galvanized steel sheet by drying the surface of the galvanized steel sheet with hot air. In addition, the cobalt metal contained in the first chemical treatment film layer is 5 mg / m² or more and less than 30 mg / m².

[0060] In the first treatment process, the mechanism by which a cobalt metal film is formed as the first chemical treatment film layer is approximately as follows. That is, on a galvanized steel sheet, the base metal zinc (Zn) is dissolved, and by the electrons emitted at that time, the Co of the alkali treatment agent 2+ Ions are reduced and precipitated on the galvanized steel sheet. In other words, a cobalt metal film can be formed as a first chemical treatment film layer using a substitutional electroless plating method that utilizes the ionization tendency.

[0061] <Second Process>

[0062] In the method for manufacturing a surface-treated galvanized steel sheet according to the present embodiment, a second treatment process is performed after the first treatment process. The second treatment process is a process of forming a second chemical treatment film layer on the first chemical treatment film layer described above. In the second treatment process, the second chemical treatment film layer can be formed by applying a water-based treatment agent containing a coupling agent and a metal oxide.

[0063] As for the coupling agent included in the water-based treatment agent used in the second treatment process, it is preferable that it be a silane coupling agent, and more preferable that it be a silane coupling agent containing aminoalkylsilane. It is believed that aminoalkylsilane contributes to processing adhesion because the amino group of the amino silane combines with the ester group in the adhesive layer and the second chemical treatment film layer described later. More specifically, it is believed that aminoalkylsilane contributes to processing adhesion by forming siloxane bonds (-Si-O-Si-) through dehydration condensation and also by combining with the metal oxide and the first chemical treatment film layer described later (-Si-O-metal-).

[0064] As aminoalkylsilanes, specifically, 3-aminopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldiethoxymethylsilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethylamino)-propyldimethoxymethylsilane, 3-(2-aminoethylamino)-propyltrimethoxysilane, 3-(2-aminoethylamino)-propyltriethoxysilane, [3-(6-aminohexaamino)-propyl]trimethoxysilane, trimethoxy[3-(methylamino)-propyl]silane, [3-(N,N-dimethylamino)-propyl]trimethoxysilane, N-[3-(trimethoxysilyl)-propyl]-1-butanamine, trimethoxy[3-(phenylamino)-propyl]silane, bis[3-(trimethoxysilyl)-propyl]amine, Examples include trimethyl[3-(trimethoxysilyl)-propyl]ammonium chloride and trimethyl[3-(triethoxysilyl)-propyl]ammonium chloride. Among these, 3-aminopropyltriethoxysilane is particularly preferred in terms of processing adhesion, weather resistance, and ease of availability.

[0065] The coupling agent included in the above-mentioned water-based treatment agent may be used as a single type or in combination of two or more types. In addition, the silane coupling agent containing aminoalkylsilane may be partially hydrolyzed or dehydrated and condensed.

[0066] The content of the coupling agent in the above-mentioned water-based treatment agent is not particularly limited, but 1 to 5 wt% is preferably used.

[0067] Examples of metal oxides included in the above-mentioned water-based treatment agent include zirconium oxide, silicon oxide, titanium oxide, etc. Examples of zirconium oxide include zirconium oxide. Examples of silicon oxide include silicon dioxide. In addition, examples of titanium oxide include titanium oxide. These metal oxides may be used as a single type or as a combination of two or more types.

[0068] It is preferable that these metal oxides exist as particles, and it is preferable that their average particle size be 1 μm or less. In addition, it is more preferable that the average particle size of these metal oxide particles be 10 to 300 nm.

[0069] The content of the metal oxide included in the above-mentioned aqueous treatment agent is not particularly limited, but it is preferably 1.0 to 5.0 wt% relative to the total aqueous treatment agent. By making the content of the metal oxide 0.1 wt% or more, the heat resistance and corrosion resistance of the second chemical treatment film layer obtained tend to be improved. On the other hand, by making the content of the metal oxide component 5.0 wt% or less, the processing adhesion of the second chemical treatment film layer obtained to the galvanized steel sheet tends to be improved.

[0070] The water-based treatment agent in the second treatment process may include a component that forms a urethane bond. Specifically, the water-based treatment agent in the second treatment process preferably includes a blocked isocyanurate and a polyester polyol.

[0071] The blocked isocyanurate included in the above-mentioned aqueous treatment agent is preferably, more specifically, a pyrazole blocked isocyanurate. Specifically, as for the pyrazole blocked isocyanurate, it is preferable to introduce a pyrazole compound as a blocking agent to the isocyanate group in a trimer of an aliphatic polyisocyanate monomer (e.g., an isocyanurate modified agent). The blocking agent blocks the isocyanate group to inactivate it, while deblocking it by heating to activate the isocyanate group.

[0072] Examples of the above-mentioned aliphatic polyisocyanates include, specifically, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, tetramethylene diisocyanate, 3-methyl-1,5-pentane diisocyanate, etc. Among these, it is preferable to use 1,6-hexamethylene diisocyanate from the perspective of reactivity and availability.

[0073] Meanwhile, specific examples of the above-mentioned pyrazole compounds include pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, 3-ethylpyrazole, 3,5-diethylpyrazole, 3-propylpyrazole, etc. Among these, it is more preferable to use 3,5-dimethylpyrazole, which has excellent solubility in solvents and is frequently used in the manufacture of pyrazole block isocyanurates.

[0074] The polyester polyol included in the water-based treatment agent in the second treatment process reacts with the isocyanurate after the blocking agent dissociates to form a urethane bond, thereby having the function of improving the processing adhesion of the second chemical treatment film layer. Specifically, the polyester polyol can be obtained by condensing a dibasic acid alone or a mixture of two or more types with a polyhydric alcohol alone or a mixture of two or more types. Examples of the dibasic acid include carboxylic acids such as succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid. Examples of the above polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, ethoxylated trimethylolpropane, etc. As the above polyester polyol, polycaprolactone polyol obtained by ring-opening polymerization of ε-caprolactone using a low molecular weight polyol may be used.

[0075] In the water-based treatment agent for the second treatment process, the content of the component forming the urethane bond is not particularly limited, but it is preferably 0.1 to 0.5 wt%.

[0076] The water-based treatment agent in the second treatment process may further include known substances such as solvents, catalysts, stabilizers, and pH adjusters.

[0077] In the second treatment process, the pH of the aqueous treatment agent is preferably 7 or lower, and more preferably 5 to 7. By making the pH of the aqueous treatment agent 7 or lower, storage stability is further improved.

[0078] As a method for applying the above-described water-based treatment agent, it may be applied by a roll coating method onto the first chemical treatment film layer described above. Subsequently, by drying the applied water-based treatment agent in a hot air drying oven at a plate temperature of 80°C to 100°C, an organic-inorganic composite film is formed as a second chemical treatment film layer. Furthermore, the dry film amount of the second chemical treatment film layer is preferably 4 mg / m² to 600 mg / m², and more preferably 30 mg / m² to 70 mg / m². The dry film amount of the second chemical treatment film layer can be measured using a known fluorescent X-ray analyzer. Additionally, the thickness of the second chemical treatment film layer is preferably 1 μm or less.

[0079] In addition, the amount of zirconium contained in the second chemical treatment film layer after drying is preferably 1.2 mg / m² to 171.4 mg / m², and more preferably 8.6 mg / m² to 20.0 mg / m². From the above amount of zirconium, the amount of the dried film of the second chemical treatment film layer described above can be calculated. More specifically, it can be calculated by the following formula.

[0080] Dry film weight (mg / m²) = Zirconium weight (mg / m²) × 3.5

[0081] Method for manufacturing resin film coated steel sheets

[0082] Next, a method for manufacturing a resin film coated steel plate (200) of the present embodiment will be described. As shown in FIG. 4, the method for manufacturing a resin film coated steel plate (200) of the present embodiment includes the following third and fourth processing steps, which follow the first and second processing steps described above.

[0083] <Third Process>

[0084] In the third treatment process, an adhesive layer is formed on the second chemical treatment film layer described above. The thickness of the formed adhesive layer (30) is preferably 1 μm to 4 μm. In the third treatment process, a known adhesive used for construction materials can be applied to the second chemical treatment film layer using a known method. For example, a solvent-based adhesive containing a polyester urethane-based resin and a silane coupling agent composed of a trimethoxysilyl group and an amino group can be applied with a roll coater and then heated and dried to obtain an adhesive layer with a thickness of 1 μm to 4 μm.

[0085] <4th Processing Process>

[0086] In the fourth processing step, a resin film is laminated onto the adhesive layer described above. Specifically, after the third processing step described above, the surface-treated galvanized steel sheet having the adhesive layer formed thereon can be heated above the curing temperature of the adhesive, and after bringing the adhesive layer and the resin film into contact, passed between a pair of rolls to laminate the resin film. Additionally, after the third processing step described above, a method of extruding molten resin may be applied.

[0087] <5th Processing Process>

[0088] In addition, the method for manufacturing a building panel in the present disclosure may include a process (fifth processing step) of forming a back-side paint layer on the surface opposite to the resin film of the resin film-coated steel sheet obtained as described above. As a method for forming the back-side paint layer, a known method may be applied. The formation of the back-side paint layer may be performed simultaneously with the third processing step or the fourth processing step described above.

[0089] Examples

[0090] The present invention will be explained in more detail below with reference to examples.

[0091] Manufacture of Surface-Treated Galvanized Steel Sheets

[0092] An untreated hot-dip galvanized steel sheet (sheet thickness 0.45 mm) as specified in JIS G3302 was prepared. If white rust or the like had formed on the surface of the hot-dip galvanized steel sheet due to storage, degreasing treatment was performed by the following known method (degreasing process). The degreasing treatment was performed by spray immersion treatment (11 ± 2 seconds) with a silicate-type alkali treatment agent (concentration 2%, liquid temperature 65 ± 5°C) containing an aqueous solution of sodium metasilicate. After degreasing treatment, the treatment agent was removed by rinsing with water.

[0093] Next, a first chemical treatment film layer was formed on the surface of a hot-dip galvanized steel sheet using an alkaline treatment agent of the following composition (first treatment process).

[0094] Solvent: 25% aqueous sodium hydroxide solution

[0095] Metal component: Cobalt nitrate 5wt%

[0096] Liquid temperature: 60–75°C

[0097] pH: 11.5

[0098] Conductivity: 115 mS

[0099] Treatment method: Spray immersion treatment (12±4 seconds)

[0100] After treatment, the alkaline treatment agent was removed by washing with water to form a first chemical treatment film layer.

[0101] Next, a second chemical treatment film layer was formed on the first chemical treatment film layer using a water-based treatment agent of the following composition (second treatment process).

[0102] Solvent: Water 95wt%, Ethanol 1.5wt%

[0103] Coupling agent (3-aminopropyltriethoxysilane 1.3wt%)

[0104] Metal oxide (zirconium oxide 1.1wt%, hafnium oxide 0.02wt%, silicon dioxide 0.6wt%),

[0105] Block isocyanurates (1,6-hexamethylene diisocyanate 0.15 wt%, 3,5-dimethylpyrazole 0.06 wt%)

[0106] Polyester polyol 0.2wt%

[0107] pH: 5–7

[0108] In the second treatment process, after applying a water-based treatment agent by a roll coater, the mixture was dried at a temperature of 80°C or higher and 100°C or lower to form a second chemical treatment film layer.

[0109] Manufacture of Resin Film Coated Steel Sheets

[0110] A resin film was laminated onto the surface-treated galvanized steel sheet obtained as described above, with an adhesive layer interposed therein.

[0111] An adhesive layer was formed on the second chemical treatment film layer described above (third treatment process). The adhesive used was a solvent-based adhesive containing a polyester-urethane resin and a silane coupling agent composed of trimethoxysilyl and amino groups.

[0112] Next, a resin film was laminated onto the adhesive layer (4th processing step). As for the type of resin film, the following (A) or (B) was used.

[0113] (A) PET / vinyl chloride multilayer resin film (PET / vinyl chloride)

[0114] A multilayer film of stretched PET film (0.025 mm) and vinyl chloride (0.10 mm)

[0115] (B) PET / PBT multilayer resin film (PET / PBT)

[0116] Multilayer film of stretched PET film (0.025 mm) and PBT (0.075 mm)

[0117] A surface-treated galvanized steel sheet having an adhesive layer formed thereon was heated to a target plate temperature and bonded with a resin film to obtain a resin film-coated steel sheet. In addition, the target plate temperature was set to 200°C for a PET / vinyl chloride multilayer resin film and 230°C for a PET / PBT multilayer resin film.

[0118] <Measurement and Evaluation of Resin Film Processing Adhesion According to Cobalt Content in the First Chemical Treatment Coating Layer>

[0119] For the resin film-coated steel plates of the examples and comparative examples, the adhesion during processing of the resin film according to the amount of cobalt in the first chemical treatment coating layer was evaluated based on the results of the well-shaped Erichsen protrusion test. Specifically, the test was conducted in accordance with the adhesion test of “JIS K 6744 2019: Polyvinyl chloride coated metal plates and metal plates, Clause 9”. The measurement conditions are shown below. In addition, the measurement results are shown in Table 1.

[0120] Test method

[0121] (1) A test specimen of about 75×150 mm or larger was cut from the resin film coated steel plate in each example or comparative example.

[0122] (2) Using a knife, two straight cuts were made in each direction, both vertical and horizontal, at a distance of 2.5 mm from both sides of the center line of the cut test specimen. Each cut was made 50 mm long. Additionally, the intersection of the vertical and horizontal center lines was set as the test position. The test specimen with the cuts was set in an Erichsen testing machine (a device according to JIS B 7729).

[0123] (3) Specifically, the cut surface of the test specimen was positioned toward the die side of the test machine, and the test position was placed at a position that coincided with the center of the punch, die, and blank holder.

[0124] (4) The punch was pressed 8 mm at the same speed as possible. The pressing speed was in the range of 30 to 120 mm per minute, and the test environment temperature was 25 ± 5℃.

[0125] Evaluation method

[0126] (5) After the indentation was finished, the test specimen was removed from the Ericsson tester. The peeling of the resin film was visually checked on the indented part of the test specimen.

[0127] (6) Based on the following judgment criteria, the test specimens after testing were evaluated in 5 stages. In addition, the evaluation criteria for the test specimens after testing are schematically shown in Fig. 5.

[0128] A: No abnormalities in the resin film (no peeling)

[0129] B: Slight lifting at the edge of the resin film.

[0130] C: Clear lifting at the edge of the resin film.

[0131] D: The lifting from the edge of the resin film is large.

[0132] E: Lifting is present throughout the resin film.

[0133] The above A and B were marked as ○ (possible to provide for practical use), C as △ (difficult to provide for practical use), and D and E as × (impossible to provide for practical use), and the results were entered in a table.

[0134] <Test and Evaluation of Corrosion Resistance of Resin Film Coated Steel Sheets According to Cobalt Content in the First Chemical Treatment Coating Layer>

[0135] In accordance with JIS Z2371, a salt spray test was performed to evaluate the corrosion resistance of a resin film-coated steel sheet. Test specimens identical to those used in the resin film processing adhesion test were prepared, cross cuts reaching the steel sheet were made on the resin film coating surface, and a neutral salt spray test (5% NaCl aqueous solution) was performed for 1,000 hours. After the test, the blister widths of the cross cut section and the flat section of the test specimen were measured. The results were evaluated as follows.

[0136] ○: The peeling of the resin film from the cross-cut section was less than 10 mm at most, and no blisters were observed from the flat section.

[0137] △: The peeling of the resin film from the cross-cut section was more than 10 mm, and no blisters were observed from the flat section.

[0138] ×: The entire surface of the resin film in the cross-cut section was peeled off, or a blister from the flat section was confirmed to be present throughout.

[0139] <Measurement and Evaluation of Resin Film Processing Adhesion According to the Amount of Second Chemical Treatment Coating Layer Attachment>

[0140] For the resin film coated steel sheets of the examples and comparative examples, the adhesion of the resin film during processing according to the amount of the second chemical treatment coating layer was evaluated based on the results of the well-shaped Erichsen protrusion test. The measurement and evaluation methods were performed in the same manner as the evaluation according to the amount of cobalt, and the results are shown in Table 2.

[0141] <Measurement and Evaluation of Accelerated Moist-Heat Adhesion According to the Amount of the Second Chemical Treatment Film Layer>

[0142] In accordance with Article 9 of JIS K6744 2019: Polyvinyl chloride coated metal plate and metal plate, a moist heat adhesion test was performed to evaluate the adhesion of the resin film under moist heat. A test specimen identical to the one used in the resin film processing adhesion test was prepared, a cross cut reaching the steel plate was made on the resin film coating surface, and the specimen was immersed in boiling water for 20 hours. After removing the specimen and drying it, the resin film on the specimen was forcibly peeled off, the peel length was measured, and the evaluation was performed as follows.

[0143] ○: Peel length less than 10mm

[0144] △: Peel length greater than 10mm to 20mm or less

[0145] ×: Peel length exceeding 20mm

[0146] (Examples 1–10, Comparative Examples 1–6)

[0147] As shown in Table 1, the type of resin film was varied, and a resin film coated steel sheet was produced by varying the cobalt metal content of the first chemical treatment coating layer. As a method to vary the amount of cobalt deposited in the first chemical treatment coating layer, the initial number of spray immersion treatments and the liquid temperature of the treatment solution were varied. The liquid temperature of the treatment solution is shown in Table 1. It was confirmed that when the cobalt metal content in the first chemical treatment coating layer was 5 mg / m² or more and less than 30 mg / m², a resin film coated steel sheet with both processing adhesion and corrosion resistance was obtained.

[0148] (Examples 11–19, Comparative Examples 7–9)

[0149] As shown in Table 2, the type of resin film was varied, and a resin film coated steel sheet was produced by varying the amount of the second chemical treatment coating layer. Specifically, the method for varying the amount of the second chemical treatment coating layer was carried out by changing the number of coating bar coaters when applying the water-based treatment agent. When the type of resin film was a PET / vinyl chloride multilayer film, it was confirmed that good processing adhesion was obtained in the range of 4 mg / ㎡ to 600 mg / ㎡ for the amount of the second chemical treatment coating layer. In addition, when the type of resin film was a PET / PBT multilayer film, it was confirmed that good processing adhesion was obtained in the range of 10 mg / ㎡ to 600 mg / ㎡ for the amount of the second chemical treatment coating layer.

[0150] (Reference Example 1)

[0151] A surface-treated steel sheet was prepared by forming an inorganic chrome-free chemical treatment film (film amount: 300 mg / m²) on a hot-dip galvanized steel sheet (sheet thickness 0.45 mm) of JIS G3302 (weight per unit area: Z18). A polyester-based adhesive (thickness 3 μm) was applied to the surface, and a resin film was laminated. The resin film was a multilayer film (total thickness 0.10 mm) of stretched PET and colored vinyl chloride. The results of the well-shaped Erichsen protrusion test, performed in the same manner as in Example 1, are shown in Table 2.

[0152] (Reference Example 2)

[0153] Except for using an organic chromium-free chemical treatment film (film amount: 700 mg / m²), the procedure was carried out in the same manner as Reference Example 1. The results are shown in Table 2.

[0154] (Reference Example 3)

[0155] The procedure was carried out in the same manner as Reference Example 1, except that the phosphating film was an organic-inorganic chromium-free phosphating film (film amount: 700 mg / m²). Furthermore, no layer containing cobalt metal was formed in the phosphating film of Reference Example 3. Additionally, a Zr-based phosphating film was formed, but it did not contain Si. The results are shown in Table 2.

[0156] (Consideration of Reference Examples 1–3)

[0157] In all of Reference Examples 1 to 3, it was confirmed that the resin film peeled off during processing in the well-shaped Erichson protrusion test. This is thought to be because the chemical treatment film could not keep up with the processing, and stress acting on the chemical treatment film and the plating interface of the Erichson cut portion was concentrated.

[0158]

[0159]

[0160] The above-described embodiments and each example may be modified in various ways without departing from the spirit of the present invention.

[0161] Industrial applicability

[0162] It can be preferably used as a bathroom wall material for unit baths, an exterior material or interior magnetic panel as a housing component, or an interior component for system kitchens. Explanation of the symbols

[0163] 100: Surface-treated galvanized steel sheet 10: Galvanized steel sheet 200: Resin film coated steel sheet 20: Mars treatment membrane 21: First chemical treatment film layer 30: Adhesive layer 40: Resin film 300: Architectural panels

Claims

Claim 1 A surface-treated galvanized steel sheet comprising: a steel sheet; a zinc plating layer formed on the steel sheet; a first chemical treatment coating layer formed on the zinc plating layer and containing cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m²; and a second chemical treatment coating layer formed on the first chemical treatment coating layer and comprising (a) a zirconium component, (b) a bonding component based on the dehydration condensation of a silanol group, and (c) a urethane bonding component. Claim 2 A surface-treated galvanized steel sheet according to claim 1, wherein the film amount of the second chemical treatment film layer is 4 mg / ㎡ to 600 mg / ㎡. Claim 3 A surface-treated galvanized steel sheet according to claim 2, wherein the amount of zirconium contained in the second chemical treatment film layer is 1.2 mg / m² or more and 171.4 mg / m² or less. Claim 4 A resin film coated steel sheet comprising a surface-treated galvanized steel sheet described in any one of claims 1 to 3, an adhesive layer formed on the surface-treated galvanized steel sheet, and a resin film formed on the adhesive layer. Claim 5 A resin film coated steel plate according to claim 4, wherein the resin film comprises at least one of a polyvinyl chloride film, a polyester film, an acrylic film, and an olefin film, and the thickness of the resin film is 0.06 mm or more. Claim 6 In claim 5, the adhesive layer is a resin film coated steel plate having a polyester resin or an acrylic resin as the main component. Claim 7 A building panel using a resin film-coated steel sheet as described in Clause 5. Claim 8 A method for manufacturing a surface-treated galvanized steel sheet, comprising: a first treatment process of forming a first chemical treatment film layer containing cobalt metal in an amount of 5 mg / m² or more and less than 30 mg / m² on a galvanized steel sheet by applying an alkaline treatment agent containing a metal chelating agent containing cobalt nitrate and ferric nitrate to the galvanized steel sheet; and a second treatment process of applying a water-based treatment agent containing a coupling agent, a metal oxide, a block isocyanurate, and a polyester polyol as constituents to the first chemical treatment film layer and drying at 60°C or higher. Claim 9 A method for manufacturing a surface-treated galvanized steel sheet according to claim 8, wherein in the first treatment process, the alkaline treatment agent has a pH of 12 or higher and is applied to the galvanized steel sheet at a liquid temperature of 60°C or higher and 75°C or lower. Claim 10 A method for manufacturing a surface-treated galvanized steel sheet according to claim 9, wherein the pH of the aqueous treatment agent is 5 to 7, the coupling agent comprises an aminoalkylsilane, and the block isocyanurate is a pyrazol block isocyanurate. Claim 11 A method for manufacturing a resin film coated steel sheet, comprising: a third treatment process of applying a polyester-based adhesive to a surface-treated galvanized steel sheet described in any one of claims 1 to 3 to a thickness of 1 μm to 4 μm; and a fourth treatment process of heating the surface-treated galvanized steel sheet coated with the polyester-based adhesive to 180°C or higher and coating a resin film on the polyester-based adhesive.

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