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

Abstract

To provide a surface-treated galvanized steel sheet, a resin film-coated steel sheet, and a building panel that have excellent corrosion resistance and processing adhesion to a resin film.SOLUTION: The surface-treated galvanized steel sheet comprises: a steel sheet; a galvanized layer that is formed on the steel sheet; a first chemically-converted covered film layer that is formed on the galvanized layer and that contains 5 mg / m2 or more and less than 30 mg / m2 of cobalt metal; and a second chemically-converted covered film layer that is formed on the first chemically-converted covered film and that contains (a) a zirconium component, (b) a binding component originating from dehydration condensation of a silanol group, and (c) a urethane binding component.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a surface-treated galvanized steel sheet and a resin film-coated steel sheet. It also relates to a building panel using the surface-treated galvanized steel sheet and the resin film-coated steel sheet. Furthermore, it relates to a method for manufacturing the surface-treated galvanized steel sheet and a method for manufacturing the resin film-coated steel sheet.

Background Art

[0002] In recent years, for example, there has been a call for reducing the environmental impact of surface-treated steel sheets for building panel applications such as bathroom panels and kitchen panels. Specifically, from the viewpoints of preventing water pollution and countermeasures against soil pollution, surface-treated steel sheets that do not contain a chromate film are required.

[0003] For example, in Patent Document 1 below, as a method for manufacturing a zinc-based plated steel sheet excellent in flat part corrosion resistance, paint adhesion, etc., a first surface treatment liquid containing an ionic bond salt containing a predetermined cation, a predetermined chelating agent, and water is used to form a first film on the surface of the zinc-based plated steel sheet. Then, a second surface treatment liquid containing a silane coupling agent having a glycidyl group, tetraalkoxysilane, zirconium carbonate compound, a predetermined anionic polyurethane resin, a vanadium compound, a molybdic acid compound, and water in a predetermined amount is used to form a second film on the surface of the first film. A manufacturing method is disclosed.

[0004] Patent Document 2 discloses a pre-coated steel sheet excellent in corrosion resistance and workability, in which a chromium-free base treatment is provided on both sides of a zinc-based plated steel sheet, and on one side which is the front surface, a bottom coating film layer containing at least one of an ion-exchange type oxide rust preventive pigment or a phosphoric acid-based rust preventive pigment with a polyester resin and / or an epoxy-modified polyester resin as a binder is provided on the base treatment, and further one or more top coating film layers are provided on the upper layer of the bottom coating film layer. Also, on the other side which is the back surface, a bottom coating film layer containing at least one of an ion-exchange type oxide rust preventive pigment or a phosphoric acid-based rust preventive pigment with a polyester resin and / or an epoxy-modified polyester resin as a binder is provided, and further one or more top coating film layers are provided on the upper layer of the bottom coating film layer.

[0005] Patent Document 3 discloses a chromium-free surface-treated metal material that satisfies corrosion resistance, heat resistance, etc. As a metal material with a chromium-free surface treatment, a trace amount of Co-containing Zn-Co plating film is coated on the metal material, and further thereon, an organic silicon compound (W) obtained by blending a silane coupling agent (A) containing one amino group in the molecule and a silane coupling agent (B) containing one glycidyl group in the molecule at a solid content mass ratio [(A) / (B)] of 0.5 to 1.7, at least one fluorine compound (X) selected from titanium hydrogen fluoride or zirconium hydrogen fluoride, phosphoric acid (Y), and a vanadium compound (Z) are applied and dried to form a composite film containing each component, and a chromate-free surface-treated metal material is disclosed.

[0006] Patent Document 4 discloses a coated steel sheet with sufficiently enhanced corrosion resistance and adhesion of the processed part. As the coated steel sheet, it includes a steel sheet, a zinc-based plating layer, and the total adhesion amount of Ni and Co is 20 mg / m 2 or more and 100 mg / m 2 or less, and the adhesion amount of the treatment layer is 2.0 g / m 2 or more and 7.0 g / m 2Disclosed is a painted steel sheet in which a phosphate treatment layer, a chromium-free sealing film containing an oxyacid salt of a Group 4 metal and a Group 1 metal or a salt thereof, and an organic film are arranged in this order.

[0007] Patent Document 5 discloses a chemical conversion treated steel sheet excellent in coating film adhesion and film adhesiveness after processing, which is based on a galvanized steel sheet or a zinc alloy galvanized steel sheet, and on the surface of the galvanized steel sheet, a chemical conversion film composed of an oxide or hydroxide of a valve metal having a high insulation resistance of the oxide and a fluoride and a polyvalent phenol resin has a film thickness of 0.01 to 0.5 μm.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, all of the above Patent Documents 1 to 5 had room for improvement with respect to the current demand for materials for building panels. That is, in recent years, in surface-treated steel sheets for building panel applications where various appearance variations are required, a resin film having design properties is pasted on the surface subjected to chemical conversion treatment.

[0010] In addition, surface-treated steel sheets laminated with resin films such as polyester and polyvinyl chloride are subjected to press working or the like to obtain various shapes. Therefore, for example, excellent corrosion resistance that can withstand severe environments such as bathroom use and high processing adhesion of the resin film are required.

[0011] As a result of earnestly studying the constitution of the material of the building panel having higher processing adhesion with the resin film, the present invention has been conceived. That is, the present disclosure intends to provide a surface-treated galvanized steel sheet having corrosion resistance equivalent to that of a conventional chromate film and processing adhesion with a resin film.

Means for Solving the Problems

[0012] In order to solve the above problems, a surface-treated galvanized steel sheet according to an embodiment of the present disclosure includes a steel sheet, a galvanized layer formed on the steel sheet, and a first chemical conversion coating layer formed on the galvanized layer and containing cobalt metal at 5 mg / m 2 or more and less than 30 mg / m 2 and a second chemical conversion coating layer formed on the first chemical conversion coating and containing (a) a zirconium component, (b) a bonding component starting from dehydration condensation of a silanol group, and (c) a urethane bonding component.

[0013] In addition, a resin film-coated steel sheet according to an embodiment of the present disclosure includes the above surface-treated galvanized steel sheet, an adhesive layer formed on the surface-treated galvanized steel, and a resin film formed on the adhesive layer.

[0014] Furthermore, a building panel according to an embodiment of the present disclosure is characterized by using the above resin film-coated steel sheet.

[0015] The manufacturing method of a surface-treated galvanized steel sheet according to an embodiment of the present disclosure includes applying an alkaline treatment agent containing a metal chelating agent containing cobalt nitrate and ferric nitrate to the galvanized steel sheet, so that the cobalt metal is 5 mg / m 2 or more and 30 mg / m 2 less, and forming a first chemical conversion coating layer on the galvanized layer in a first treatment step; and applying an aqueous treatment agent containing a coupling agent, a metal oxide, a blocked isocyanurate, and a polyester polyol as constituent components to the first chemical conversion coating layer, and drying at 60° C. or higher in a second treatment step.

[0016] The manufacturing method of a resin film-coated steel sheet in an embodiment of the present disclosure includes a third treatment step of applying a polyester-based adhesive to the surface-treated galvanized steel sheet with a thickness of 1 μm to 4 μm; and heating the surface-treated galvanized steel sheet coated with the polyester-based adhesive to 180° C. or higher, and covering a resin film on the polyester-based adhesive in a fourth treatment step.

Advantages of the Invention

[0017] According to the present disclosure, it is possible to provide a surface-treated galvanized steel sheet, a resin film-coated steel sheet, and a building panel that do not contain a chromate film and have excellent corrosion resistance and processing adhesion to a resin film.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0019] <Galvanized Steel Sheet with Surface Treatment 100> Hereinafter, the galvanized steel sheet with surface treatment according to this embodiment will be described in detail. As shown in FIG. 1, the galvanized steel sheet with surface treatment 100 according to this embodiment includes a galvanized steel sheet 10 and a chemical conversion 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. The chemical conversion treatment film 20 includes a first chemical conversion treatment coating layer 21 on the galvanized layer 13 and a second chemical conversion treatment coating layer 23 covering both the galvanized layer 13 and the first chemical conversion treatment coating layer 21.

[0020] <Galvanized Steel Sheet 10> As the galvanized steel sheet 10 used in this embodiment, it is possible to use a galvanized steel sheet generally used in laminated metal sheets. For example, a hot-dip galvanized steel sheet, a hot-dip zinc alloy galvanized steel sheet, an alloyed hot-dip galvanized steel sheet, an electro-galvanized steel sheet, an electro-galvanized zinc alloy steel sheet, etc. can be mentioned. Among these, from the viewpoints of easy availability and price, etc., a hot-dip galvanized steel sheet (JIS G3302) can be preferably used.

[0021] There is no particular limitation on the thickness of the galvanized steel sheet 10, but for example, a thickness of 0.10 mm to 1.20 mm is preferable from the viewpoints of ease of construction and appearance. If the thickness of the galvanized steel sheet is less than 0.1 mm, it may not be possible to obtain preferable corrosion resistance and weather resistance. On the other hand, if the thickness of the galvanized steel sheet exceeds 1.2 mm, the weight increases, which may cause problems during construction, and it is not preferable from the cost viewpoint.

[0022] As the steel sheet 11 included in the galvanized steel sheet 10, for example, a normal steel cold-rolled steel sheet with a thickness of about 0.05 mm to 1.20 mm can be mentioned. Among cold-rolled steel sheets, a low-carbon or extra-low-carbon aluminum-killed steel sheet with a carbon content of less than 0.01% by mass is preferably used as the steel sheet 11 from the viewpoint of workability and the like.

[0023] Although there is no particular limitation on the zinc plating adhesion amount of the zinc plating layer 13 formed on the steel sheet 11, as an example, it can be set to about 60 g / m 2 ~600 g / m 2 degree. More specifically, when the galvanized steel sheet 10 is a hot-dip galvanized steel sheet, it is preferably within the range of Z06 to Z60 as the plating adhesion amount display symbol shown in JIS G3302:2019.

[0024] <Conversion treatment film 20> As described above, the conversion treatment film 20 is formed on at least one side of the galvanized steel sheet 10. The conversion treatment film 20 includes a first conversion treatment coating layer 21 that covers at least a part of the surface of the galvanized steel sheet 10, and a second conversion treatment coating layer 23 that is formed on the first conversion treatment coating layer 21 and covers the entire surface of the galvanized steel sheet 10.

[0025] <First conversion treatment coating layer 21> The first conversion treatment coating layer 21 is a metal film containing cobalt metal of 5 mg / m 2 or more and less than 30 mg / m 2 As shown in FIG. 1, the first conversion treatment coating layer 21 is in contact with the surface of the galvanized steel sheet 10. The first conversion treatment coating layer 21 does not need to cover the entire surface of the galvanized steel sheet 10, and it may exist on at least a part of the surface of the galvanized steel sheet 10.

[0026] The effects of the first chemical conversion coating layer 21 on the surface of the zinc-plated steel sheet 10 are as follows. That is, since cobalt (Co), which has a smaller ionization tendency than zinc (Zn), becomes the oxygen reduction reaction point (cathode), microcells of Co (cathode) and Zn (anode) are formed under the film of the formed first chemical conversion coating layer 21. As a result, the generation amount of OH - below can be reduced, and cathodic delamination and corrosion under the film can be suppressed.

[0027] Note that the method for forming the first chemical conversion coating layer 21 will be described in detail later, but it is performed by applying a cobalt-containing alkaline treatment solution to the surface of the zinc-plated steel sheet 10. When the alkaline treatment solution is applied to the surface of the zinc-plated steel sheet 10, zinc (Zn) on the zinc-plated steel sheet 10 dissolves, and at this time, electrons are released, so that Co 2+ ions are reduced (replacement electroless plating).

[0028] <Second chemical conversion coating layer 23> The second chemical conversion coating layer 23 is (a) an organic-inorganic composite film containing a zirconium component. The film amount of the second chemical conversion coating layer is preferably 4 mg / m 2 ~600 mg / m 2 and more preferably 30 mg / m 2 ~70 mg / m 2 . The dry film amount of the second chemical conversion coating layer can be measured with a known fluorescent X-ray analyzer.

[0029] The thickness of the second chemical conversion coating layer is preferably 1 μm or less. The amount of zirconium contained in the second chemical conversion coating layer 23 is preferably 1.2 mg / m 2 or more and 171.4 mg / m 2 or less, and more preferably 8.6 mg / m 2 ~20.0 mg / m 2 . Note that the dry film amount of the above-mentioned second chemical conversion coating layer can be calculated from the above zirconium amount. More specifically, it can be calculated by the following calculation formula. Dry film amount (mg / m 2 ) = Zirconium amount (mg / m 2 ) × 3.5

[0030] The second chemical conversion treatment coating layer 23 further includes (b) a bonding component starting from the dehydration condensation of silanol groups and (c) a urethane bonding component. The bonding component starting from the dehydration condensation of silanol groups includes siloxane bonds and the like 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 conversion treatment coating layer 23 has a structure in which siloxane bonds (-Si-O-Si-) are dispersed in the urethane resin component and is considered to be bonded (-Si-O-metal-) to the metal oxide and the cobalt metal of the first chemical conversion treatment coating layer or zinc on the zinc-plated steel sheet.

[0031] <Resin film-coated steel sheet 200> As shown in FIG. 2, the resin film-coated steel sheet 200 in the present disclosure includes an adhesive layer 30 formed on at least one surface of the above-described surface-treated zinc-plated steel sheet 100 and a resin film 40 formed on the adhesive layer 30.

[0032] <Adhesive layer 30> The adhesive layer 30 is preferably an adhesive mainly composed of a polyester resin, and more preferably a polyester urethane-based adhesive. The adhesive layer 30 may be an adhesive mainly composed of an acrylic resin. The type of the adhesive may be one type or a mixture of multiple types, and an acrylic-based adhesive or an olefin-based adhesive may be mixed with the polyester-based adhesive for use.

[0033] The thickness of the adhesive layer 30 is preferably 1 μm to 4 μm. Further, from the viewpoint of improving the processing adhesion between the second chemical conversion treatment coating layer 23 and the resin film 40, the adhesive layer 30 may contain an adhesion improver. Examples of the adhesion improver include silane coupling agents having a trimethoxysilyl group, an amino group, and an epoxy group.

[0034] <Resin film 40> As the resin film 40, a film used for building materials can be used. Examples of the material of the resin film 40 include a polyvinyl chloride film, a polyester film, an acrylic film, an olefin film, and the like. The resin film 40 may be a transparent film or a colored film. Further, the resin film 40 may be a film having a design property, for example, a film provided with embossing or the like on the surface. The resin film 40 may be a film formed by laminating films made of a plurality of different materials. For example, a film obtained by laminating 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. Although there is no particular limitation on the upper limit of the thickness of the resin film 40, it is preferably 0.5 mm or less from the viewpoint of cost.

[0035] Generally, when a resin film having a thickness of 0.06 mm or more is laminated on a surface-treated steel sheet and then subjected to a forming process, peeling of the resin film may occur due to internal stress. However, the resin film-coated steel sheet in the present disclosure can significantly improve the processing adhesion. The reason is generally as follows.

[0036] When the steel sheet is stretched by processing, a stress load is applied to the chemical conversion treatment layer containing an inorganic component. When the thickness of the chemical conversion treatment layer is equal to or more than a predetermined value, it cannot follow the processing, and the force concentrates at the interface between the chemical conversion treatment layer and the zinc plating. As a result, the chemical conversion treatment layer undergoes cohesive failure and peeling of the resin film occurs. The above is the reason for the peeling of the chemical conversion treatment layer in a general resin film-coated steel sheet.

[0037] On the other hand, in the present disclosure, by forming the chemical conversion treatment layer into a two-layer structure including a first chemical conversion treatment coating layer containing cobalt metal and a second chemical conversion treatment coating layer containing a coupling agent component, it has been possible to improve the processing adhesion.

[0038] <Building Panel 300> Next, the building panel 300 in the present embodiment will be described. As shown in FIG. 3, the building panel 300 in the present embodiment is characterized by using the above-described surface-treated galvanized steel sheet 100 or resin film-coated steel sheet 200. More specifically, the building panel 300 in the present embodiment is provided with a back paint layer 50 on the surface of the resin film-coated steel sheet 200 on the side opposite to the resin film 40. The thickness of the back paint layer 50 is not particularly limited, but for example, it may be 5 μm to 20 μm. As the type of the back paint layer 50, known paints generally used for building applications can be applied, and examples thereof include epoxy paints and polyester paints.

[0039] Furthermore, the building panel 300 in the present embodiment may be provided with a metal layer, a resin layer, a gypsum board layer, a volcanic glass multi-layer board, etc. (not shown) on at least one surface of the back paint layer 50.

[0040] The building panel 300 in the present embodiment can be applied to interior materials such as bathroom panels and kitchen panels. More specifically, it can be applied to unit bathroom interior materials, composite magnetic panels in the kitchen, panels that can be attached to indoor walls, etc. It can also be applied to exterior materials such as entrance doors.

[0041] <Manufacturing Method of Surface-Treated Galvanized Steel Sheet> Subsequently, the manufacturing method of the surface-treated galvanized steel sheet 100 of the present embodiment will be described. As shown in FIG. 4, the manufacturing method of the surface-treated galvanized steel sheet 100 of the present embodiment includes the following first treatment step and second treatment step. Note that the manufacturing method of the surface-treated galvanized steel sheet 100 of the present embodiment may include a known degreasing step. Since the zinc plating step for the steel sheet can be appropriately applied with known steps, the description thereof is omitted here.

[0042] <Degreasing Step> First, the degreasing process of the galvanized steel sheet will be described. Note that this degreasing process is not an essential process and can be omitted as appropriate. Specifically, in order to remove the oxide film and coating oil on the surface of the galvanized steel sheet to be used, this degreasing process may be passed through.

[0043] Specifically, the degreasing process can be carried out by applying a known alkaline treatment agent to the surface of the galvanized steel sheet. Specifically, as the known alkaline treatment agent, a silicate-type alkaline treatment agent containing 35-40% sodium metasilicate and 0.1-1.0% potassium hexafluorotitanate as the composition concentration can be used. During the degreasing process, this alkaline treatment agent can be adjusted to a concentration of 2.0% or less and a liquid temperature of 60°C to 75°C for use. As the method for applying the alkaline treatment agent to the galvanized steel sheet, known methods such as the spray method and the dipping method can be applied. As the treatment time in the degreasing process, in the case of the spray method or the dipping method, the treatment time can be 9 to 13 seconds. Also, after the treatment, it is preferable to remove the treatment agent by washing the galvanized steel sheet with water.

[0044] <First treatment step> Following any degreasing process, the first treatment step can be carried out. The first treatment step is a step of forming a first chemical conversion coating layer on the galvanized steel sheet. The first chemical conversion coating layer contains 5 mg / m 2 or more and less than 30 mg / m 2 of cobalt metal. The first chemical conversion coating layer can be formed by applying an alkaline treatment agent containing a cobalt metal component on the galvanized steel sheet. Note that as the alkaline treatment agent, it can be one containing a metal chelating agent containing cobalt nitrate and ferric nitrate.

[0045] More specifically, as the alkaline treatment agent in the first treatment step, an alkaline treatment agent containing 20-25% sodium hydroxide, 1-5% cobalt nitrate, and 1-5% ferric nitrate as the composition concentration can be used. Also, in the first treatment step, the above alkaline treatment agent can be adjusted to a liquid temperature of 60°C to 75°C for use.

[0046] In the first treatment step, as a method for applying the alkali treatment agent to the galvanized steel sheet, known methods such as the spray method and the dipping method can be applied. In the case of the spray method or the dipping method, the treatment time in the first treatment step can be set to 8 to 16 seconds. In the first treatment step, after the treatment, the by-products and the treatment liquid components remaining on the surface of the galvanized steel sheet can be removed by water washing. Further, after the water washing, the surface of the galvanized steel sheet can be dried with hot air to form a cobalt metal film as the first chemical conversion treatment film layer on the surface of the galvanized steel sheet. The cobalt metal contained in the first chemical conversion treatment film layer is 5 mg / m 2 or more and 30 mg / m 2 less than that.

[0047] In the first treatment step, the mechanism for forming the cobalt metal film as the first chemical conversion treatment film layer is generally as follows. That is, on the galvanized steel sheet, zinc (Zn), which is a base metal, dissolves, and the Co of the alkali treatment agent is reduced by the electrons released at that time and precipitates on the galvanized steel sheet. In other words, a cobalt metal film as the first chemical conversion treatment film layer can be formed by a substitution-type electroless plating method using the ionization tendency. 2+ In other words, a cobalt metal film as the first chemical conversion treatment film layer can be formed by a substitution-type electroless plating method using the ionization tendency.

[0048] <Second treatment step> In the manufacturing method of the surface-treated galvanized steel sheet in the present embodiment, after the above-described first treatment step, a second treatment step is performed. The second treatment step is a step of forming a second chemical conversion treatment film layer on the above-described first chemical conversion treatment film layer. In the second treatment step, a second chemical conversion treatment film layer can be formed by applying an aqueous treatment agent containing a coupling agent and a metal oxide.

[0049] As the coupling agent contained in the aqueous treatment agent used in the second treatment step, a silane coupling agent is preferably used, and more preferably a silane coupling agent containing aminoalkylsilane. Since the amino group of the aminoalkylsilane binds to the ester group in the adhesive layer and the second chemical conversion treatment film layer described later, it is considered to contribute to the processing adhesion. More specifically, the aminoalkylsilane is considered to contribute to the processing adhesion by forming a siloxane bond (-Si-O-Si-) by dehydration condensation and binding (-Si-O-metal-) to the metal oxide and the first chemical conversion treatment film layer described later.

[0050] Specific examples of the aminoalkylsilane include 3-aminopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldiethoxymethylsilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethylamino)-propyldimethoxymethylsilane, 3-(2-aminoethylamino)-propyltrimethoxysilane, 3-(2-aminoethylamino)-propyltriethoxysilane, [3-(6-aminohexaa mino)-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, trimethyl[3-(trimethoxysilyl)-propyl]ammonium chloride, trimethyl[3-(triethoxysilyl)-propyl]ammonium chloride, and the like. Among these, 3-aminopropyltriethoxysilane is particularly preferably used from the viewpoints of processing adhesion, weather resistance, and easy availability.

[0051] The coupling agent contained in the aqueous treatment agent may be used alone or in combination of two or more. Further, the silane coupling agent containing aminoalkylsilane may be partially hydrolyzed or dehydrated and condensed.

[0052] The content rate of the coupling agent in the above aqueous treatment agent is not particularly limited, but 1 to 5 wt% is preferably used.

[0053] Examples of the metal oxide contained in the above aqueous treatment agent include zirconium oxide, silicon oxide, titanium oxide, etc. Examples of zirconium oxide include zirconium dioxide. Examples of silicon oxide include silicon dioxide. Examples of titanium oxide include titanium oxide. These metal oxides may be used alone or in combination of two or more.

[0054] These metal oxides preferably exist as particles, and their average particle size is preferably 1 μm or less. In addition, the average particle size of these metal oxide particles is more preferably 10 to 300 nm.

[0055] The content rate of the metal oxide contained in the above aqueous treatment agent is not particularly limited, but it is preferably 1.0 to 5.0 wt% based on the whole aqueous treatment agent. By setting the content rate of the metal oxide to 0.1 wt% or more, the heat resistance and corrosion resistance of the obtained second chemical conversion treatment film layer tend to improve. On the other hand, by setting the content rate of the metal oxide component to 5.0 wt% or less, the processing adhesion of the obtained second chemical conversion treatment film layer to the zinc-plated steel sheet tends to improve.

[0056] The aqueous treatment agent in the second treatment step may contain a component that forms a urethane bond. Specifically, the aqueous treatment agent in the second treatment step preferably contains blocked isocyanurate and polyester polyol.

[0057] The blocked isocyanurate contained in the above water treatment agent is more preferably, specifically, pyrazole-blocked isocyanurate. Specifically, as the pyrazole-blocked isocyanurate, it is preferable to introduce a pyrazole compound as a blocking agent to the isocyanate group in the trimer of an aliphatic polyisocyanate monomer (for example, an isocyanurate-modified product). The blocking agent blocks and inactivates the isocyanate group, while de-blocking by heating to activate the isocyanate group.

[0058] Specific examples of the aliphatic polyisocyanate include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, tetramethylene diisocyanate, 3-methyl-1,5-pentane diisocyanate, and the like. Among these, from the viewpoints of reactivity and availability, it is preferable to use 1,6-hexamethylene diisocyanate.

[0059] On the other hand, specific examples of the pyrazole compound include pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, 3-ethylpyrazole, 3,5-diethylpyrazole, 3-propylpyrazole, and the like. Among these, it is more preferable to use 3,5-dimethylpyrazole, which has excellent solubility in solvents and is frequently used in the production of pyrazole-blocked isocyanurate.

[0060] In the second treatment step, the polyester polyol contained in the aqueous treatment agent reacts with the isocyanurate after the release of the blocking agent to form a urethane bond, thereby having a function of improving the processing adhesion of the second chemical conversion coating layer. Specifically, the polyester polyol can be obtained by subjecting a dibasic acid alone or a mixture of two or more kinds thereof and a polyhydric alcohol alone or a mixture of two or more kinds thereof to a condensation reaction. 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 polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane. As the polyester polyol, a polycaprolactone polyol obtained by ring-opening polymerization of ε-caprolactone using a low molecular weight polyol can also be used.

[0061] In the aqueous treatment agent in the second treatment step, the content of the component forming the urethane bond is not particularly limited, but is preferably 0.1 to 0.5 wt%.

[0062] The aqueous treatment agent in the second treatment step may further contain known substances such as a solvent, a catalyst, a stabilizer, and a pH adjuster.

[0063] The pH of the aqueous treatment agent in the second treatment step is preferably 7 or less, and more preferably 5 to 7. By setting the pH of the aqueous treatment agent to 7 or less, the storage stability is further improved.

[0064] As a method for applying the above aqueous treatment agent, it can be applied by a roll coating method on the above first chemical conversion treatment film layer. Thereafter, the applied aqueous treatment agent is dried in a hot air drying furnace at a plate temperature of 80°C to 100°C to form an organic-inorganic composite film as the second chemical conversion treatment film layer. Note that the dry film amount of the second chemical conversion treatment film layer is 4mg / m 2 ~600mg / m 2 It is preferably, and more preferably 30mg / m 2 ~70mg / m 2 The dry film amount of the second chemical conversion treatment film layer can be measured with a known fluorescent X-ray analyzer. Also, the thickness of the second chemical conversion treatment film layer is preferably 1μm or less.

[0065] Note that the amount of zirconium contained in the second chemical conversion treatment film layer after drying is 1.2mg / m 2 ~171.4mg / m 2 It is preferably, and even more preferably 8.6mg / m 2 ~20.0mg / m 2 From the above zirconium amount, the dry film amount of the above second chemical conversion treatment film layer can be converted. More specifically, it can be calculated by the following calculation formula. Dry film amount (mg / m 2 ) = Zirconium amount (mg / m 2 ) × 3.5

[0066] <Method for manufacturing resin film-coated steel sheet> Subsequently, the method for manufacturing the resin film-coated steel sheet 200 of the present embodiment will be described. As shown in FIG. 4, the method for manufacturing the resin film-coated steel sheet 200 of the present embodiment includes the following third treatment step and fourth treatment step following the above first treatment step and second treatment step.

[0067] <Third treatment step> In the third treatment step, an adhesive layer is formed on the above-mentioned second chemical conversion treatment coating layer. The thickness of the formed adhesive layer 30 is preferably 1 μm to 4 μm. In the third treatment step, a known adhesive used for building materials can be applied onto the second chemical conversion treatment coating layer using a known method. For example, a solvent-based adhesive containing a polyester urethane resin and a silane coupling agent composed of a trimethoxysilyl group and an amino group can be applied with a roll coater and then heat-dried to obtain an adhesive layer with a thickness of 1 μm to 4 μm.

[0068] <Fourth Treatment Step> In the fourth treatment step, a resin film is laminated on the above-mentioned adhesive layer. Specifically, after the above-mentioned third treatment step, the surface-treated zinc-plated steel sheet with the adhesive layer formed is heated to a temperature equal to or higher than the curing temperature of the adhesive, and after bringing the adhesive layer into contact with the resin film, it is passed between a pair of rolls to laminate the resin film. Also, after the above-mentioned third treatment step, a method of extruding the molten resin may be applied.

[0069] <Fifth Treatment Step> In addition, as a method for manufacturing the building panel in the present disclosure, it may include a step (fifth treatment step) of forming a back surface coating layer on the surface of the resin film-coated steel sheet obtained as described above, which is opposite to the resin film. As a method for forming the back surface coating layer, a known method can be applied. The formation of the back surface coating layer may be performed simultaneously with the above-mentioned third treatment step or fourth treatment step.

Examples

[0070] Hereinafter, the present invention will be described more specifically with reference to examples.

[0071] <Manufacture of Surface-Treated Zinc-Plated Steel Sheet> An untreated hot-dip galvanized steel sheet (thickness: 0.45 mm) specified in JIS G3302 was prepared. When white rust or the like had occurred on the surface of the hot-dip galvanized steel sheet due to storage, degreasing treatment was performed by the following known method (degreasing step). The degreasing treatment was carried out by spray immersion treatment (11 ± 2 seconds) with a silicate-type alkaline treatment agent containing an aqueous sodium metasilicate solution (concentration: 2%, liquid temperature: 65 ± 5°C). After the degreasing treatment, the treatment agent was removed by washing with water.

[0072] Next, a first chemical conversion coating layer was formed on the surface of the hot-dip galvanized steel sheet using an alkaline treatment agent having the following composition (first treatment step). Solvent: 25% aqueous sodium hydroxide solution Metal component: 5 wt% cobalt nitrate Liquid temperature: 60 to 75°C pH: 11.5 Conductivity: 115 mS Treatment method: Spray immersion treatment (12 ± 4 seconds) After the treatment, the alkaline treatment agent was removed by washing with water to form the first chemical conversion coating layer.

[0073] Next, a second chemical conversion coating layer was formed on the first chemical conversion coating layer using an aqueous treatment agent having the following composition (second treatment step). Solvent: 95 wt% water, 1.5 wt% ethanol Coupling agent (1.3 wt% 3-aminopropyltriethoxysilane) Metal oxide (1.1 wt% zirconium oxide, 0.02 wt% hafnium oxide, 0.6 wt% silicon dioxide), Block isocyanurate (0.15 wt% 1,6-hexamethylene diisocyanate, 0.06 wt% 3,5-dimethylpyrazole,) Polyester polyol 0.2 wt% pH: 5 to 7

[0074] In the second treatment step, after applying the aqueous treatment agent with a roll coater, it was dried at 80°C or higher and 100°C or lower to form the second chemical conversion coating layer.

[0075] <Manufacture of Resin Film-Coated Steel Sheet> A resin film was laminated (laminated) via an adhesive layer on the surface-treated galvanized steel sheet obtained as described above.

[0076] An adhesive layer was formed on the above-described second chemical conversion treatment coating layer (third treatment step). As the adhesive, a solvent-based adhesive containing a polyester urethane-based resin and a silane coupling agent composed of a trimethoxysilyl group and an amino group was used.

[0077] Next, a resin film was laminated (laminated) on the adhesive layer (fourth treatment step). As the type of resin film, the following (A) or (B) was used. (A) PET / vinyl chloride multilayer resin film (PET / PVC) Multilayer film of stretched PET film (0.025 mm) and vinyl chloride (0.10 mm) (B) PET / PBT multilayer resin film (PET / PBT) Multilayer film of stretched PET film (0.025 mm) and PBT (0.075 mm)

[0078] The surface-treated galvanized steel sheet with the adhesive layer formed was heated to the target plate temperature and laminated with the resin film to obtain a resin film-coated steel sheet. The target plate temperature was set at 200 °C for the PET / vinyl chloride multilayer resin film and 230 °C for the PET / PBT multilayer resin film.

[0079] <Measurement and Evaluation of Adhesion of Resin Film Processing According to Cobalt Amount in First Chemical Conversion Treatment Coating Layer> Regarding the resin film-coated steel sheets of the examples and comparative examples, the adhesion during the processing of the resin film according to the cobalt amount in the first chemical conversion treatment coating layer was evaluated based on the results of the cruciform Erichsen bulge test. Specifically, it was carried out according to the adhesion test of "JIS K 6744 2019: Polyvinyl Chloride Coated Metal Sheets and Metal Strips, Item 9". The measurement conditions are shown below. The measurement results are shown in Table 1.

[0080] Test method (1) A test piece with a size of about 75×150 mm or more was cut out from the resin film-coated steel sheet in each example or comparative example. (2) Using a cutting tool, two straight cuts, one vertical and one horizontal, reaching the steel sheet were made on both sides of the center line of the cut-out test piece at a distance of 2.5 mm. The length of each cut was 50 mm. The intersection of the vertical and horizontal center lines was defined as the test position. The test piece with the above cuts was set on an Erichsen testing machine (device according to JIS B 7729). (3) Specifically, the surface of the test piece with the cuts was placed on the die side of the testing machine, and the test position was set at a position that coincides with the center of the punch, die, and wrinkle presser. (4) The punch was pushed in by 8 mm at as uniform a speed as possible. The pushing speed was in the range of 30 to 120 mm per minute, and the test was conducted at a test environment temperature of 25 ± 5°C.

[0081] Evaluation method (5) After the pushing-in was completed, the test piece was taken out from the Erichsen testing machine. Regarding the part of the test piece with the cuts, the presence or absence of peeling of the resin film was visually confirmed. (6) Based on the following judgment criteria, the test pieces after the test were evaluated in five grades. The evaluation criteria for the test pieces after the test are schematically shown in Fig. 5. A: No abnormality in the resin film (no lifting) B: Slight lifting at the edge of the resin film. C: Clearly lifted at the edge of the resin film. D: Large lifting from the edge of the resin film. E: Lifting throughout the resin film. Regarding the above A and B as ○ (usable in practice), C as △ (difficult to use in practice), and D and E as × (impossible to use in practice), the results were entered in a table.

[0082] <Test and Evaluation of Corrosion Resistance of Resin Film-Coated Steel Sheet According to Cobalt Content of the First Chemical Conversion Coating Layer> In accordance with JIS Z2371, a salt spray test was conducted to evaluate the corrosion resistance of the resin film-coated steel sheet. Test pieces similar to those for the resin film processing adhesion test were prepared, cross-cuts reaching the steel sheet were made on the resin film-coated surface, and a neutral salt spray test (5% NaCl aqueous solution) was carried out for 1000 hours. For the test pieces after the test, the blister widths at the cross-cut parts and the flat parts were measured. The results were evaluated as follows. ○: The peeling of the resin film at the cross-cut part was less than 10 mm at most, and no blisters were observed from the flat part. △: The peeling of the resin film at the cross-cut part was 10 mm or more at most, and no blisters were observed from the flat part. ×: The entire resin film at the cross-cut part was peeled off, or blisters were observed overall from the flat part.

[0083] <Measurement and Evaluation of Resin Film Processing Adhesion According to the Coating Amount of the Second Chemical Conversion Coating Layer> Regarding the resin film-coated steel sheets of the examples and comparative examples, the adhesion during the processing of the resin film according to the coating amount of the second chemical conversion coating layer was evaluated based on the results of the Erichsen cupping test. The measurement method and evaluation method were carried out in the same manner as the evaluation according to the cobalt amount, and the results are shown in Table 2.

[0084] <Measurement and Evaluation of Accelerated Damp Heat Adhesion According to the Coating Amount of the Second Chemical Conversion Coating Layer> In accordance with JIS K6744 2019: Polyvinyl Chloride Coated Metal Sheets and Strips, Clause 9, a damp heat adhesion test was conducted to evaluate the adhesion of the resin film under damp heat conditions. Test pieces similar to those for the resin film processing adhesion test were prepared, cross-cuts reaching the steel sheet were made on the resin film-coated surface, and the test pieces were immersed in boiling water for 20 hours. After taking out the test pieces and drying them, the resin film of the test pieces was forcibly peeled off, the peeling length was measured, and the evaluation was carried out as follows. ○: Peeling length less than 10 mm △: Peeling length exceeding 10 mm to 20 mm or less ×: Peeling length exceeding 20 mm

[0085] (Examples 1 to 10, Comparative Examples 1 to 6) The types of resin films were as shown in Table 1, and resin film-coated steel sheets were produced by varying the cobalt metal content in the first chemical conversion coating layer. As a method for varying the cobalt deposition amount in the first chemical conversion coating layer, the number of seconds of spray immersion treatment and the liquid temperature of the treatment solution were varied. The liquid temperature of the treatment solution is shown in Table 1. In the first chemical conversion coating layer, when the cobalt metal content is 5 mg / m 2 or more and less than 30 mg / m 2 , it was confirmed that a resin film-coated steel sheet having both work adhesion and corrosion resistance could be obtained.

[0086] (Examples 11 to 19, Comparative Examples 7 to 9) The types of resin films were as shown in Table 2, and resin film-coated steel sheets were produced by varying the film thickness of the second chemical conversion coating layer. Specifically, as a method for varying the film thickness of the second chemical conversion coating layer, it was carried out by changing the gauge number of the coating bar coater when applying the aqueous treatment agent. When the type of resin film is a PET / vinyl chloride multilayer film, when the film thickness of the second chemical conversion coating layer is 4 mg / m 2 to 600 mg / m 2 , it was confirmed that good work adhesion could be obtained. Also, when the type of resin film is a PET / PBT multilayer film, when the film thickness of the second chemical conversion coating layer is 10 mg / m 2 to 600 mg / m 2 , it was confirmed that good work adhesion could be obtained.

[0087] (Reference Example 1) A surface-treated steel sheet having an inorganic chromium-free chemical conversion coating film (film thickness: 300 mg / m 2 ) formed on a hot-dip galvanized steel sheet (thickness: 0.45 mm) of JIS G3302 (basis weight: Z18) was prepared. 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. Table 2 shows the results of the I-beam Erichsen cupping test conducted in the same manner as in Example 1.

[0088] (Reference Example 2) Except that the chemical conversion treatment film was an organic chromium-free chemical conversion treatment film (coating amount: 700 mg / m 2 ), it was carried out in the same manner as in Reference Example 1. The results are shown in Table 2.

[0089] (Reference Example 3) Except that the chemical conversion treatment film was an organic-inorganic chromium-free chemical conversion treatment film (coating amount: 700 mg / m 2 ), it was carried out in the same manner as in Reference Example 1. Note that the chemical conversion treatment film of this Reference Example 3 does not have a layer containing cobalt metal. Also, although a Zr-based treatment film is formed, it does not contain Si. The results are shown in Table 2.

[0090] (Consideration of Reference Examples 1 to 3) In any of Reference Examples 1 to 3, it was confirmed that the resin film peeled off during processing in the I-beam Erichsen bulge test. This is presumably because the chemical conversion treatment film could not follow the processing, and the stress acting on the interface between the chemical conversion treatment film and the plating at the Erichsen cut portion was concentrated.

[0091]

Table 1

[0092]

Table 2

[0093] The above-described embodiments and each example can be variously modified without departing from the gist of the present invention.

Industrial Applicability

[0094] It can be suitably used as a bathroom wall material such as a unit bath, an exterior material or an interior magnetic panel as a housing member, and an interior member such as a system kitchen.

Explanation of Signs

[0095] 100: Surface-treated zinc-plated steel sheet 10: Zinc-plated steel sheet 200: Resin film-coated steel sheet 20: Chemical conversion treatment film 21: First chemical conversion treatment film layer 30: Adhesive layer 40: Resin film 300: Building panel

Claims

1. A steel sheet, A zinc plating layer formed on the steel sheet, formed on the zinc plating layer, the first chemical conversion treatment film layer containing cobalt metal of 5 mg / m ２ or more and less than 30 mg / m ２ and; A second chemical conversion coating layer formed on the first chemical conversion coating film and containing (a) a zirconium component, (b) a bonding component starting from the dehydration condensation of a silanol group, and (c) a urethane bonding component, A surface-treated zinc-plated steel sheet composed of the above.

2. The film thickness of the second chemical conversion treatment film layer is 4 mg / m ２ to 600 mg / m ２ The surface-treated galvanized steel sheet according to claim 1, wherein the film thickness is in this range.

3. The amount of zirconium contained in the second chemical conversion coating layer is 1.2 mg / m ２ or more and 171.4 mg / m ２ or less. The surface-treated galvanized steel sheet according to claim 2.

4. The surface-treated zinc-plated steel sheet according to any one of Claims 1 to 3, An adhesive layer formed on the surface-treated zinc-plated steel, A resin film formed on the adhesive layer, A resin film-coated steel sheet comprising the above.

5. The resin film contains at least one of a polyvinyl chloride film, a polyester film, an acrylic film, and an olefin film, The thickness of the resin film is 0.06 mm or more, The resin film-coated steel sheet according to Claim 4.

6. The resin film-coated steel sheet according to Claim 5, wherein the adhesive layer is mainly composed of a polyester resin or an acrylic resin.

7. An architectural panel using the resin film-coated steel sheet according to Claim 5.

8. By applying an alkaline treatment agent containing a metal chelating agent containing cobalt nitrate and ferric nitrate to the zinc-plated steel sheet, a cobalt metal of 5 mg / m ２ or more and less than 30 mg / m ２ A first treatment step of forming a first chemical conversion treatment coating layer contained on the zinc plating layer; A second treatment step of applying an aqueous treatment agent containing a coupling agent, a metal oxide, a blocked isocyanurate, and a polyester polyol as constituent components onto the first chemical conversion coating layer and drying at 60°C or higher, A method for manufacturing a surface-treated zinc-plated steel sheet having the above.

9. In the first treatment step, The alkaline treatment agent has a pH of 12 or more and is applied to the zinc-plated steel sheet at a liquid temperature of 60°C or higher and 75°C or lower, A method for manufacturing a surface-treated zinc-plated steel sheet according to Claim 8.

10. The pH of the aqueous treatment agent is 5 to 7, the coupling agent contains an aminoalkylsilane, and the blocked isocyanurate is a pyrazole-blocked isocyanurate, A method for manufacturing a surface-treated zinc-plated steel sheet according to Claim 9.

11. A third treatment step of applying a polyester-based adhesive to the surface-treated zinc-plated steel sheet according to any one of Claims 1 to 3 with a thickness of 1 μm to 4 μm, A fourth treatment step of heating the surface-treated zinc-plated steel sheet coated with the polyester-based adhesive to 180°C or higher and covering the polyester-based adhesive with a resin film, A method for manufacturing a resin film-coated steel sheet having the above.

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