Resin-coated metal sheet and method for manufacturing a resin-coated metal sheet

Abstract

Provided is a resin-coated metal sheet which comprises a metal base and a resin layer provided on the metal base, and in which a protruding peak height Rpk on the surface of the resin layer is at least 0.46 μm.

Description

Technical Field

[0001] The present invention relates to a resin-coated metal plate and a method for manufacturing the resin-coated metal plate.

Background Art

[0002] A coated metal plate formed with a resin coating layer on a metal plate is widely used in building exterior members, automobile members, etc. For example, a joint material used in a joint part is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the coated metal plate disclosed in Patent Document 1, there is a problem that air bubbles may enter between the metal plate and the coating layer, which may cause poor appearance. Further, the coated metal plate disclosed in Patent Document 1 has a specification in which a coating layer is provided on top of a chromate treatment. On the other hand, there is a technique in which a chromate treatment is not performed in order to reduce the environmental load, and an adhesive layer is provided between the metal plate and the coating layer, but there is room for improvement in adhesion, and there is a problem that the metal plate and the coating layer may peel off.

[0005] An object of the present invention is to provide a resin-coated metal plate that is excellent in adhesion to an adhesive resin used for adhesion to a coating layer and has a good appearance.

Means for Solving the Problems

[0006] As a result of diligent research to achieve the above objective, the present inventors have found that the above objective can be achieved by a resin-coated metal plate having a metal substrate and a resin layer provided on the metal substrate, wherein the height Rpk of the protruding peaks on the surface of the resin layer is 0.46 μm or more, and have completed the present invention.

[0007] [1] That is, according to a first aspect of the present invention, a resin-coated metal plate is provided, comprising a steel plate, a metal substrate, and a resin layer provided on the metal substrate, wherein the height Rpk of the protruding peaks on the surface of the resin layer is 0.46 μm or more.

[0008] [2] According to a second aspect of the present invention, a resin-coated metal plate is provided according to aspect 1, wherein the height Spk of the protruding peaks on the surface of the resin layer is 0.6 μm or more.

[0009] [3]According to aspect 3 of the present invention, a resin-coated metal plate according to aspect 1 or 2 is provided, wherein the resin layer is composed of a resin material including an olefin-based and / or urethane-based resin.

[0010] [4]According to aspect 4 of the present invention, a resin-coated metal plate according to any one of aspects 1 to 3 is provided, wherein the arithmetic mean height Sa1 of the resin layer is 0.5 μm or more.

[0011] [5]According to aspect 5 of the present invention, a resin-coated metal plate is provided which has a height Rpk of the protruding peaks on the surface of the resin layer of 0.6 μm or more.

[0012] [6]According to aspect 6 of the present invention, a resin-coated metal plate according to any one of aspects 1 to 5 is provided, wherein the metal substrate comprises a metal base plate and a metal plating layer containing zinc, and the resin layer is formed on the metal plating layer.

[0013] [7]According to aspect 7 of the present invention, a resin-coated metal plate is provided in which the arithmetic mean height Sa2 of the surface on which the metal plating layer is formed in the metal base plate is 0.5 μm or more, as described in any of aspects 1 to 6.

[0014] [8]According to aspect 8 of the present invention, a method for manufacturing a resin-coated metal plate according to any one of aspects 1 to 7 is provided, comprising the steps of: applying an aqueous dispersion containing a resin material at a solid content concentration of 15% by weight or more onto a metal substrate by a direct roll coating method; and drying the layer made of the aqueous dispersion to form the resin layer.

[0015] [9]According to aspect 9 of the present invention, a method for manufacturing a resin-coated metal plate as described in aspect 8 is provided, wherein the solid content concentration of the aqueous dispersion is 15% by weight or more and less than 70% by weight, the metal substrate consists of a metal base plate and a metal plating layer containing zinc, and the arithmetic mean height Sa2 of the surface on which the metal plating layer is formed on the metal base plate is 0.75 μm or more.

[0016]

[10] According to aspect 10 of the present invention, a method for manufacturing a resin-coated metal plate according to aspect 8 or 9 is provided, wherein the resin material comprises an olefin-based and / or urethane-based resin. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a resin-coated metal plate that has excellent adhesion to adhesive resins and a good appearance. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a cross-sectional view showing the structure of a resin-coated metal plate in an embodiment of the present invention. [Figure 2] Figure 2(a) is a diagram illustrating a method for coating an aqueous dispersion by direct roll coating according to an embodiment of the present invention, and Figure 2(b) is a cross-sectional view showing the surface shape of a resin layer 20 formed by coating an aqueous dispersion with a solid content of 15% by weight or more by direct roll coating. [Figure 3] Figure 3 is a reference diagram showing a resin layer formed by coating an aqueous dispersion with a solid content of less than 15% by weight using the direct roll coating method.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0020] FIG. 1 is a cross-sectional view showing the configuration of the resin-coated metal plate 1 in the present embodiment. The resin-coated metal plate 1 in the present embodiment includes a metal base material 10 and a resin layer 20 provided on the metal base material 10. The resin-coated metal plate 1 in the present embodiment is used for joint materials, automotive interior materials, etc. by forming a coating layer made of a resin material using an adhesive resin on the resin layer 20.

[0021] <Metal base material 10> The metal base material 10 in the present embodiment is a plated sheet including a metal base plate 11 and a metal plating layer 12 containing zinc formed on the metal base plate 11.

[0022] The metal base plate 11 is not particularly limited, and examples thereof include metal base plates based on iron or aluminum. As the metal base plate based on iron, carbon steel plates or stainless steel plates can be used. As the carbon steel plate, low-carbon steel such as low-carbon aluminum-killed steel (carbon content 0.01 to 0.15 wt%), extra-low-carbon steel with a carbon content of less than 0.01 wt%, or non-ageing carbon steel obtained by adding Ti, Nb, etc. to extra-low-carbon steel can be used. When using a steel plate as the metal base plate 11, it is preferable to use a hot-rolled sheet of these steels pickled to remove the surface scale (oxide film), then cold-rolled, and then annealed and temper-rolled after electrolytic cleaning. The annealing method may be either continuous annealing or box annealing, and is not particularly limited.

[0023] From the viewpoint of controlling the height of the protruding peaks of the resin layer 20, which will be described later, the arithmetic mean height Sa2 of the surface on which the metal plating layer 12 is formed on the metal base sheet 11 is preferably 0.5 μm or more, and more preferably 0.75 μm or more. A method for making the arithmetic mean height Sa2 of the metal base sheet 11 within the above range is to roll the steel using a rolling roll having a predetermined surface roughness when rolling the steel to form the metal base sheet 11. The arithmetic mean roughness Ra of the rolling roll, measured along the central axis of the rolling roll (a direction perpendicular to the rolling direction of the metal base sheet 11), is preferably 0.8 μm or more, more preferably 2.5 μm or more, and even more preferably 3.2 μm or more. While there is no particular upper limit to the arithmetic mean roughness Ra of the rolling roll, if the arithmetic mean height Sa2 of the metal base plate 11 is too large, the thickness may become uneven when forming the metal plating layer 12 or the resin layer 20 on the metal base plate 11. Therefore, from the viewpoint of improving the uniform stability of the metal plating layer 12 and the resin layer 20, the arithmetic mean roughness Ra of the rolling roll is preferably 8.0 μm or less, and more preferably 6.0 μm or less. From a similar viewpoint, the upper limit of the arithmetic mean height Sa2 of the metal base plate 11 is preferably 2.0 μm or less. The arithmetic mean height Sa2 can be measured according to ISO 25178, and the arithmetic mean roughness Ra can be measured according to JIS B 0671:2002.

[0024] The thickness of the metal base plate 11 in this embodiment is not particularly limited, but is preferably 0.04 to 2.0 mm, and more preferably 0.04 to 1.5 mm.

[0025] The metal plating layer 12 is a zinc-containing layer provided on the metal base plate 11. Examples of metal plating constituting the metal plating layer 12 include zinc plating, zinc-cobalt-molybdenum alloy plating, zinc-nickel alloy plating, zinc-iron alloy plating, alloyed hot-dip galvanizing, and zinc-aluminum-magnesium alloy plating. Among these zinc-based platings, zinc-cobalt-molybdenum alloy plating or pure zinc plating (hereinafter also referred to as pure zinc plating), in which the weight percentage of zinc is 99.9% or more, is more preferable from the viewpoint of improving the corrosion resistance of the resin-coated metal plate 1. The metal plating layer can be formed by electroplating the surface of the metal base plate 11 using a plating bath of a predetermined composition.

[0026] For example, if the metal plating layer 12 is composed of a zinc-cobalt-molybdenum alloy plating, it can be formed by electroplating using a plating bath with a composition of 150-300 g / L zinc sulfate, 5-60 g / L cobalt sulfate, 0.01-0.5 g / L ammonium molybdate, 5-60 g / L ammonium sulfate, and 50 g / L or less sodium sulfate. The electroplating conditions are preferably pH 2.5-4.0, bath temperature 30-60°C, and current density 5-50 A / dm². 2 Furthermore, if the metal plating layer 12 is composed of pure zinc plating, it can be formed by electroplating using a plating bath with a composition of 150-300 g / L zinc sulfate and 10-100 g / L sodium sulfate. The electroplating conditions are preferably pH 0.5-2.5, bath temperature 30-60°C, and current density 5-80 A / dm². 2 That is the case.

[0027] When the metal plating layer 12 is composed of a zinc-cobalt-molybdenum alloy plating, the preferred content ratio of zinc, cobalt, and molybdenum in the metal plating layer 12 is 0.1 to 5% by weight of cobalt, 0.001 to 1% by weight of molybdenum, and the remainder being zinc. The metal content ratio in the metal plating layer 12 can be adjusted by setting the composition of the plating bath and the electroplating conditions to a suitable range.

[0028] The thickness of the metal plating layer 12 is not particularly limited, but is preferably 0.3 to 8.0 μm. The thicker the metal plating layer 12, the smoother the surface roughness of the metal plating layer 12 becomes, which may affect the subsequent formation of the resin layer 20. In particular, in the case of zinc-based plating, the crystals precipitate in a plate-like manner, so the surface roughness of the metal plating layer 12 tends to become smoother. For this reason, the thickness of the metal plating layer 12 is more preferably 0.3 to 5.0 μm from the viewpoint of controlling the surface roughness of the metal plating layer 12 and controlling the height of the protruding peaks of the resin layer 20. The thickness of the metal plating layer 12 is even more preferably 0.6 to 5.0 μm from the viewpoint of corrosion resistance. The thickness of the metal plating layer 12 is particularly preferably 0.7 μm to 4.5 μm from the viewpoint of achieving both corrosion resistance and suppression of surface roughness reduction due to metal plating.

[0029] In this embodiment, the metal substrate 10 has a metal plating layer 12 formed on both sides of the metal base plate 11. However, the configuration of the metal substrate 10 is not limited to this, and the metal plating layer 12 may be formed on only one side of the metal base plate 11. Alternatively, the metal substrate 10 may not have a metal plating layer 12 and may consist only of the metal base plate 11.

[0030] <Resin layer 20> The resin layer 20 is a layer formed on the metal plating layer 12. The resin layer 20 is provided to improve the adhesion between the metal substrate 10 and the adhesive resin used in conjunction with the resin-coated metal plate 1 in this embodiment. In this embodiment, the resin layer 20 is formed on both sides of the metal substrate 10, but it is not limited to this, and the resin layer 20 may be formed on only one side of the metal substrate 10.

[0031] The resin contained in the resin layer 20 is not particularly limited, but examples include olefin resins and urethane resins. Examples of olefin resins include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer, with ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer being more preferred. Examples of urethane resins include reaction products of polyols such as polyacrylic polyol, polyester polyol, and polyether polyol with polyisocyanates such as aliphatic diisocyanates, aromatic diisocyanates, and aromatic aliphatic diisocyanates. Olefin resins and urethane resins may be used individually or both may be used simultaneously. The resin layer 20 is formed by coating an aqueous dispersion containing the resin material, as will be described later, but it is preferable that the resin layer 20 substantially contains no other components other than the resin material, except for unavoidable components derived from additives contained in the aqueous dispersion. The resin content in the resin layer 20 is preferably 90% by weight or more, and more preferably 99% by weight or more. In other words, it is preferable that the resin layer 20 is substantially composed of the above-mentioned resin alone.

[0032] When an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer is used as the resin contained in the resin layer 20, the weight-average molecular weight is preferably 20,000 to 150,000, more preferably 30,000 to 100,000, and even more preferably 40,000 to 80,000.

[0033] Furthermore, the proportion of the polar component in the surface free energy of the resin layer 20 is preferably 3% to 35%, more preferably 10% to 35%, and even more preferably 20% to 35%. The proportion of the polar component in the surface free energy can be calculated from the surface free energy obtained by applying the Kitazaki-Hata theoretical formula to the contact angles of ion-exchanged water, ethylene glycol, and diiodomethane measured using a fully automatic contact angle meter (DM-701 manufactured by Kyowa Interface Science). Specifically, after determining the surface free energies of the dispersion component, dipole component, and hydrogen bonding component, the proportion of the polar component can be determined by the ratio of the sum of the surface free energies of the dipole component and the hydrogen bonding component to the total value of these components. There is no particular limit to the method for setting the proportion of the polar component in the surface free energy of the resin layer 20 surface within the above range, but one method is to select the resin material constituting the resin layer 20. For example, when an ethylene-acrylic acid copolymer is used as the resin constituting the resin layer 20, the proportion of the polar component in the surface free energy of the resin layer 20 surface can be controlled by adjusting the content ratio of acrylic acid units in the ethylene-acrylic acid copolymer. Furthermore, when an ethylene-methacrylic acid copolymer is used as the resin constituting the resin layer 20, the proportion of polar components in the surface free energy of the resin layer 20 can be controlled by adjusting the content ratio of methacrylic acid units in the ethylene-methacrylic acid copolymer.

[0034] The thickness of the resin layer 20 is not particularly limited, but is preferably 0.3 to 3.0 μm. From the viewpoint of facilitating the formation of convex shapes across the entire surface to set the height Rpk (described later) of the protruding peaks on the surface of the resin layer 20 to a specific range, the thickness of the resin layer 20 is preferably 0.5 μm or more, and more preferably 0.6 μm or more. The upper limit of the thickness of the resin layer 20 is not particularly limited, but if it is too thick, the adhesion strength of the resin layer 20 to the adhesive resin may weaken, so it is preferably 2.0 μm or less.

[0035] In this embodiment, the resin layer 20 of the resin-coated metal plate 1 has a surface protrusion height Rpk of 0.46 μm or more, preferably 0.60 μm or more, as measured according to JIS B 0671:2002. The upper limit of the protrusion height Rpk is not particularly limited, but is preferably 2.0 μm or less, and more preferably 1.5 μm or less from the viewpoint of stable ease of manufacturing. The protrusion height Rpk is one of the parameters for evaluating the roughness curve as defined in JIS B 0671-1, and represents the height of the protruding peaks in the roughness curve. More specifically, Rpk is the average height of the protruding peaks above the core, calculated by dividing the surface shape into three stages: peaks, cores, and valleys, based on the roughness curve. The larger the protrusion height Rpk of the resin layer 20, the higher the average height of the protrusions on the surface of the resin layer 20, and by setting Rpk to 0.46 μm or more, it is possible to sufficiently form the protruding convex parts corresponding to the protruding peaks. Furthermore, by setting the height Rpk of the protruding peaks within this range, it is presumed that when the coating layer is applied to the resin layer 20 using adhesive resin, the adhesive resin flows along the protrusions and spreads, thereby improving adhesion. By having the height Rpk of the protruding peaks of the resin layer 20 within the above range, the resin-coated metal plate 1 can be made to have excellent adhesion with the adhesive resin.

[0036] Conventionally, when using a metal substrate with a zinc-containing metal plating layer formed on a metal base plate, and when chromium-free is used for environmental reasons, it was sometimes difficult to improve the adhesion to the adhesive resin even when a resin layer was formed on the metal substrate. With the resin-coated metal plate 1 of this embodiment, by controlling the height Rpk of the protruding peaks on the surface of the resin layer 20, it is possible to improve the adhesion of the resin layer 20 to the adhesive resin even when using a metal substrate 10 on which a zinc-containing metal plating layer 12 is formed.

[0037] While the height Rpk of the protruding peaks on the surface of the resin layer 20 can be measured at any point on the surface of the resin layer 20, it is more preferable that the height Rpk of the protruding peaks along a line parallel to the width direction of the resin-coated metal sheet 1 (a direction perpendicular to the direction in which the metal sheet 11 was rolled on the surface of the resin layer) is within the above range, in order to evaluate a more average roughness including the rolling marks, considering the influence of the protrusions formed on the resin layer 20 due to the streak shape (rolling marks) formed on the surface of the metal sheet 11 by the rolling of the metal sheet 11.

[0038] In this embodiment, the resin layer 20 of the resin-coated metal plate 1 preferably has a surface protrusion height Spk of 0.60 μm or more, more preferably 0.70 μm or more, and even more preferably 0.80 μm or more, as measured according to ISO 25178. While the protrusion height Rpk is calculated from the line roughness load curve, the protrusion height Spk is calculated from the surface roughness load curve, and captures the average height of the protrusions on the resin layer surface from a more overall perspective. The larger the protrusion height Spk, the more pronounced the protrusions are throughout the entire resin layer 20. When the protrusion height Spk is within the above range, when the coating resin is applied to the resin layer 20 using adhesive resin, air bubbles that form between the resin layer 20 and the adhesive resin can escape to the outside through the gaps in the protrusions. More specifically, when the adhesive resin and the coating layer are simultaneously and continuously poured onto the resin layer 20 and bonded together, air bubbles can escape through the gaps in the protrusions present across the entire surface. This allows for a good appearance of the coated metal sheet manufactured using the resin-coated metal sheet 1.

[0039] In this embodiment, the resin-coated metal plate 1 can achieve even greater adhesion, particularly by setting the height Rpk of the protruding peaks Rpk and the height Spk of the protruding peaks Spk of the resin layer 20 to 0.6 μm or more. The reason for this is not entirely clear, but it is thought that by setting the height Rpk and Spk of the protruding peaks within the above range, the adhesive resin can be wetted and spread more uniformly, and air bubbles can escape more easily, thereby reducing unevenness in the thickness of the adhesive resin and suppressing the formation of air bubbles.

[0040] The arithmetic mean height Sa1 of the surface of the resin layer 20, measured according to ISO 25178, is preferably 0.5 μm or more, and more preferably 0.6 μm or more, from the viewpoint of improving adhesion with the adhesive resin by forming a convex shape on the surface of the resin layer 20 to set the protruding peak height Rpk within a specific range. The upper limit of the arithmetic mean height Sa1 of the resin layer 20 is not particularly limited, but if it is too large, the thickness of the resin layer 20 may become uneven, so it is preferably 2.0 μm or less.

[0041] Generally speaking, the concept of surface roughness and adhesion strength is that the greater the arithmetic mean height of the material's surface, the greater the adhesion strength of the resin to that material. On the other hand, while diligently studying how to improve the adhesion strength between a metal substrate coated with a resin layer and an adhesive resin, the inventors noticed that the strength of the adhesion strength of the adhesive resin to the resin layer does not depend on the arithmetic mean height of the resin layer. They found that the adhesion strength can be improved by controlling the surface shape of the resin layer 20 and setting the height Rpk of the protruding peaks within a specific range.

[0042] As described above, the resin-coated metal plate 1 in this embodiment exhibits excellent adhesion to the adhesive resin because the height Rpk of the protruding peaks on the surface of the resin layer 20 is within the above range. Examples of such adhesive resins include olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer, as well as urethane resins.

[0043] The resin-coated metal plate 1 in this embodiment can be manufactured by the following method. Specifically, the resin-coated metal plate 1 can be manufactured by the steps of: coating a metal substrate 10 with an aqueous dispersion containing a resin material at a solid content concentration of 15% by weight or more using a direct roll coating method; and drying the layer made of the aqueous dispersion to form a resin layer 20.

[0044] The aqueous dispersion used in the manufacture of the resin-coated metal sheet 1 is an aqueous dispersion in which the above-mentioned olefin resin and / or urethane resin are dispersed in a medium such as water. The solid content concentration of the aqueous dispersion is 15% by weight or more. By setting the solid content concentration to 15% or more, when the aqueous dispersion that has come into contact with the surface of the metal substrate 11 is pushed out of the roll together with the metal substrate 11 by the direct roll coating method, the aqueous dispersion can be pulled by the roll and lifted relative to the metal substrate 10. As a result, in addition to the surface irregularities derived from the surface morphology of the metal substrate 10, it becomes possible to form protrusions unique to the resin layer 20 on the surface of the resin layer 20, and the Rpk and Spk of the resin layer 20 can be controlled within the above range. According to the present invention, by forming the resin layer 20 by direct roll coating using an aqueous dispersion containing resin with a solid content concentration of 15% by weight or more, the height of the protruding peaks Rpk and Spk on the surface of the resin layer 20 can be controlled within the above range.

[0045] Furthermore, the solid content concentration of the aqueous dispersion is preferably adjusted according to the arithmetic mean height Sa2 of the surface on the metal base plate 11 where the metal plating layer 12 is formed. For example, when the arithmetic mean height Sa2 of the metal base plate 11 is 0.75 to 2.0 μm, the solid content concentration of the aqueous dispersion is preferably 15% by weight or more, and more preferably 20% by weight or more, from the viewpoint of making it easier to form the unique protrusions of the resin layer 20, or making it easier to make the protrusions higher. In this case, the upper limit of the solid content concentration of the aqueous dispersion is not particularly limited, but from the viewpoint of making it easier to suppress deterioration and solidification of the aqueous dispersion in continuous production and to stably form the surface shape of the resin layer 20, it is preferably less than 70% by weight, more preferably 65% ​​by weight or less, and even more preferably 55% by weight or less. Furthermore, when the arithmetic mean height Sa2 of the metal base plate 11 is 0.65 μm or more and less than 0.75 μm, that is, when the arithmetic mean height Sa2 of the metal base plate is relatively small, it is preferable to set the solid content concentration of the aqueous dispersion to 20% by weight or more and less than 70% by weight in order to facilitate the formation of the unique protrusions of the resin layer 20 or to facilitate the height of the protrusions. When the arithmetic mean height Sa2 of the metal base plate 11 is 0.65 μm or more and less than 0.75 μm, the lower limit of the solid content concentration of the aqueous dispersion is more preferably 25% by weight or more, and even more preferably 30% by weight or more. Thus, it is preferable from the viewpoint of improving adhesion strength to set the arithmetic mean height Sa2 of the metal base plate 11 to any of the above ranges, use an aqueous dispersion with a solid content concentration corresponding to the arithmetic mean height Sa2, and form the resin layer 20 by the direct roll coating method. In addition, by such a manufacturing method, the Rpk and Spk of the surface of the resin layer 20 can be controlled, and the arithmetic mean height Sa1 of the surface of the resin layer 20 can also be set to a preferred range.

[0046] The method for producing such an aqueous dispersion is not particularly limited, but examples include producing the above-mentioned olefin resin and / or urethane resin by known emulsion polymerization or solution polymerization methods, and then preparing the dispersion by vigorously stirring the polymer solution.

[0047] Furthermore, the minimum film forming temperature (MFT) of the aqueous dispersion is preferably 0 to 200°C, and more preferably 5 to 150°C. The minimum film forming temperature of the aqueous dispersion can be adjusted by selecting the type of resin material contained in the aqueous dispersion.

[0048] Furthermore, the pH of the aqueous dispersion is preferably 3 to 11, and more preferably 4 to 10.

[0049] The viscosity of the aqueous dispersion used to form the resin layer 20 at 25°C is not particularly limited as long as the solid content concentration of the aqueous dispersion is within the above range, but is preferably 10 to 150 mPa·s, and more preferably 20 to 100 mPa·s. Note that many aqueous dispersions change their viscosity significantly depending on external forces applied, and the viscosity of the aqueous dispersion and the solid content concentration are not necessarily proportional.

[0050] The aqueous dispersion used to form the resin layer 20 may, in addition to the resin described above, optionally contain surfactants, emulsifying agents, colloidal silica, etc. On the other hand, in order to form protruding peaks on the surface of the resin by lifting with a roll as described above, it is preferable that the aqueous dispersion does not contain metal oxides, and it is also preferable that the resin layer 20 does not contain metal oxides.

[0051] Drying of the layer consisting of the aqueous dispersion is preferably carried out under conditions of a temperature of 50°C to 200°C and a drying time of 1 second to 60 seconds.

[0052] <Method for manufacturing resin-coated metal plate 1> The resin-coated metal plate 1 in this embodiment can be manufactured by the steps of: applying an aqueous dispersion containing a resin material at a solid content concentration of 15% by weight or more onto a metal substrate 10 using a direct roll coating method; and drying the layer consisting of the aqueous dispersion to form a resin layer 20. The above-mentioned aqueous dispersion can be used.

[0053] Figure 2(a) is a diagram illustrating the direct roll coating method for an aqueous dispersion in this embodiment, and Figure 2(b) is a cross-sectional view showing the surface shape of a resin layer 20 formed by coating an aqueous dispersion with a solid content of 15% by weight or more using the direct roll coating method. Figure 3 is a reference diagram showing a resin layer formed by coating an aqueous dispersion with a solid content of less than 15% by weight using the direct roll coating method.

[0054] This section describes a process for coating a metal substrate 10 with an aqueous dispersion containing a resin material using a direct roll coating method. In the direct roll coating method, as shown in Figure 2(a), the roll is rotated so that the direction of the roll's rotation and the direction of the metal substrate 10's movement are the same (so that the direction of movement of the part of the roll that contacts the metal substrate 10 is the same as the direction of movement of the metal substrate 10), thereby coating the metal substrate 10 with the aqueous dispersion. In this embodiment, by setting the solid content concentration of the aqueous dispersion containing the resin material to 15% by weight or more, a portion of the aqueous dispersion extruded onto the metal substrate 10 is lifted away from the metal substrate 10 towards the roll as the roll rotates. As a result, as shown in Figure 2(b), protrusions can be formed on the surface of the resin layer 20 formed from the aqueous dispersion, and the heights Rpk and Spk of the protruding peaks on the surface of the resin layer 20 can be controlled within a predetermined range. On the other hand, in reverse roll coating, where the direction of the roll's rotation is opposite to the direction of the metal substrate 10's movement, the aqueous dispersion is applied to the metal substrate 10 by the roll, making it difficult to form protrusions.

[0055] On the other hand, if the solid content concentration of the aqueous dispersion is less than 15% by weight, the aqueous dispersion is not lifted by the roll, even when using the direct roll coating method, and a resin layer with a smooth surface shape is formed, as shown in Figure 3.

[0056] As described above, it is preferable to use a metal base plate 11 that has been rolled using rolling rolls with an arithmetic mean roughness Ra of 0.8 μm or more, and has an arithmetic mean height Sa2 of 0.5 m or more, and then coated with a zinc-based metal plating to form a metal plating layer 12.

[0057] The resin-coated metal sheet 1 obtained in this manner has appropriately controlled protruding peak heights Rpk and Spk of the resin layer 20, exhibits excellent adhesion to the adhesive resin, and can produce a good appearance for joint materials, automotive interior materials, etc., made from coated metal sheets manufactured using the resin-coated metal sheet 1. [Examples]

[0058] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0059] <Weight-average molecular weight of resin> The weight-average molecular weight of the resin was measured using a high-temperature GPC-IR method with an aqueous dispersion containing the resin material used in the examples.

[0060] <Height and arithmetic mean height of the protruding peaks of the resin layer, and the arithmetic mean height of the metal base plate> Using a laser microscope (Olympus LEXT OLS5000 3D measuring laser microscope), an analysis image with a field of view of 645 μm × 645 μm was obtained with a 20x objective lens (lens name: MPLAPON20XLEXT). Next, the obtained analysis image was subjected to automatic correction processing, namely noise reduction and tilt correction, using an analysis application. After that, the line roughness measurement and surface roughness measurement icons were clicked to perform the analysis and determine the protruding peak heights Rpk and Spk, and the arithmetic mean height Sa1 of the resin layer 20 of the resin-coated metal plate 1. The protruding peak height Rpk was determined in the width direction of the resin-coated metal plate 1, that is, in the cross section along the direction perpendicular to the rolling direction (RD) of the metal base plate 11 on the surface of the resin-coated metal plate 1. The arithmetic mean height Sa2 of the metal base plate 11 was measured in the same manner.

[0061] <Percentage of polar components in the surface free energy of the resin layer surface> Using a fully automatic contact angle meter (DM-701, manufactured by Kyowa Interface Science), the contact angles of ion-exchanged water, ethylene glycol, and diiodomethane with respect to the surface of the resin layer 20 of a resin-coated metal plate 1 were measured, respectively. By applying the measured contact angle values ​​to the Kitazaki-Hata theoretical formula, the surface free energies of the dispersion component, dipole component, and hydrogen bonding component were determined, respectively. The ratio of the sum of the surface free energies of the dipole component and the hydrogen bonding component to the total value of these components was determined as the proportion of the polar component.

[0062] <Peel strength against adhesive resins> To evaluate the adhesion to the adhesive resin, a T-peel peel test (hereinafter also referred to as a peel test) was performed in accordance with JIS K 6854-3 to measure the peel strength of the resin-coated metal plate 1. Specifically, two resin-coated metal plates 1, each 25 mm wide and 80 mm long, were placed facing each other, and nine granules of olefin-based adhesive resin (product name Mersen, manufactured by Tosoh Corporation) were sandwiched between the two resin-coated metal plates 1. The resin-coated metal plates 1 and the olefin-based adhesive resin were heat-pressed together under conditions of 150°C, 0.5 MPa pressure, and 2 minutes to obtain a laminate. A peel test was performed on the prepared laminate using a tensile testing machine (product name "AGX-V", manufactured by Shimadzu Corporation) at a peel speed of 200 mm / min, and the maximum peel strength [unit: N / 25 mm] was measured.

[0063] <Appearance (presence or absence of air bubbles), wettability of the adhesive resin> The prepared resin-coated metal plate 1 is heated on a hot plate set to 130°C, and one granule of olefin-based adhesive resin (product name Mersen, manufactured by Tosoh Corporation) is placed on the resin layer 20 of the resin-coated metal plate 1. A 3.5g, 9cm diameter piece is placed on top of the olefin-based adhesive resin. 2A Teflon plate (Teflon is a registered trademark) was placed on top of the Teflon plate, and a 150g weight was placed on top of the Teflon plate and maintained for 2 minutes. After 2 minutes, the Teflon plate and weight were removed, and after air cooling, it was visually inspected to see if there were any air bubbles between the adhesive resin and the resin layer 20. If there are no air bubbles, it indicates that the coated metal plate manufactured using the resin-coated metal plate 1, as well as joint materials and automotive interior materials made from the coated metal plate, can have an excellent appearance. Furthermore, to confirm the difference in wettability, the same procedure as above was used, except that the hot plate temperature was changed to 100°C and 110°C. After air cooling, the roundness c (c=b / a), which is the ratio of the major axis length a to the minor axis length b of the adhesive resin that has wetted and spread on the resin layer, was determined. A higher roundness c indicates that the adhesive resin has wetted and spread more uniformly.

[0064] <Example 1> As the metal base sheet 11, a cold-rolled sheet (thickness 0.16 mm) of low-carbon aluminum-killed steel was prepared. This metal base sheet 11 was rolled using rolling rolls with an arithmetic mean roughness Ra of 2.5 to 5.5 μm, and the arithmetic mean height Sa2 of the metal base sheet 11 was set to 0.95 μm. Next, the metal base sheet 11 was subjected to alkaline electrolytic degreasing and pickling by sulfuric acid immersion, followed by treatment at a bath temperature of 40°C and a current density of 15 A / dm². 2 By plating under these conditions, a metal substrate 10 was obtained in which a 1.5 μm thick metal plating layer 12 made of zinc-cobalt-molybdenum alloy plating was formed on both sides of the metal base plate 11. When the composition ratio of the metal plating layer was measured by fluorescent X-ray, it was found to be Co: 0.16 wt%, Mo: 0.02 wt%, and the remainder being Zn.

[0065] Next, a layer of aqueous dispersion (solid content concentration 20% by weight, viscosity 70 mPa·s, pH 9.3, MFT 12℃) containing an olefin resin (ethylene-acrylic acid copolymer) was applied to the metal plating layer 12 of the metal substrate 10 by direct roll coating, thereby forming an aqueous dispersion layer. Subsequently, drying was performed at a temperature of 150℃ for 10 seconds to form a resin layer 20 containing the olefin resin. The thickness of the resin layer 20 was 0.6 μm. The resin layer 20 was formed on both sides of the metal substrate 10. In this way, a resin-coated metal plate 1 with resin layers 20 formed on both sides of the metal substrate 10 was obtained. For the obtained resin-coated metal plate 1, the height and arithmetic mean height of the protruding peaks of the resin layer were measured, the proportion of the polar component in the surface free energy of the resin layer surface was measured, and the peel strength to the adhesive resin, appearance (presence or absence of bubbles), and wettability of the adhesive resin were evaluated. The results are shown in Tables 1 to 3. Furthermore, the weight-average molecular weight of the ethylene-acrylic acid copolymer, as measured by the high-temperature GPC-IR method, was 49,900.

[0066] <Example 2> A resin-coated metal plate 1 was obtained in the same manner as in Example 1, except that an aqueous dispersion containing an olefin resin (ethylene-methacrylic acid copolymer) (solid content concentration 44.5% by weight, viscosity 40 mPa·s, pH 4.8, MFT 100℃) was used instead of an aqueous dispersion containing an olefin resin (ethylene-acrylic acid copolymer). The height of the protruding peaks and the arithmetic mean height of the resin layer were measured, and the peel strength against the adhesive resin, appearance (presence or absence of bubbles), and wettability of the adhesive resin were evaluated. The results are shown in Tables 1 to 3. The weight-average molecular weight of the ethylene-methacrylic acid copolymer, measured by high-temperature GPC-IR, was 69300. The thickness of the resin layer 20 was 0.6 μm.

[0067] <Comparative Example 1> A resin-coated metal sheet 1 was obtained in the same manner as in Example 1, except that the metal base sheet 11 used was rolled using rolling rolls with an arithmetic mean roughness Ra of 0.01 to 0.5 μm and had an arithmetic mean height Sa2 of 0.3 μm. The height of the protruding peaks and the arithmetic mean height of the resin layer were measured, and the appearance (presence or absence of bubbles) was evaluated. The results are shown in Table 1. The thickness of the resin layer 20 was 0.6 μm.

[0068] <Comparative Example 2> A resin-coated metal sheet 1 was obtained in the same manner as in Example 1, except that the metal base sheet 11 used was rolled using rolling rolls with an arithmetic mean roughness Ra of 0.8 to 2.3 μm and had an arithmetic mean height Sa2 of 0.73 μm. The height of the protruding peaks and the arithmetic mean height of the resin layer were measured, and the peel strength against the adhesive resin and appearance (presence or absence of bubbles) were evaluated. The results are shown in Table 1. The thickness of the resin layer 20 was 0.6 μm.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] As shown in Table 1, the resin-coated metal plates 1 of Examples 1 and 2 had a protruding peak height Rpk of 0.46 μm or more, exhibiting high peel strength against the adhesive resin and excellent adhesion to the adhesive resin. Furthermore, it was shown that no air bubbles were incorporated into the adhesive resin that spread on the resin layer 20, resulting in a joint material with an excellent appearance.

[0073] On the other hand, the resin-coated metal plates of Comparative Examples 1 and 2 had a protruding peak height Rpk of less than 0.46 μm, resulting in low peel strength against the adhesive resin and poor adhesion to the adhesive resin. Furthermore, the resin-coated metal plate of Comparative Example 1 had air bubbles mixed into the adhesive resin that had spread on the resin layer, resulting in an unsightly appearance when used as a jointing material.

[0074] Furthermore, as can be seen from comparing Examples 1 and 2 with Comparative Examples 1 and 2, no correlation was observed between the arithmetic mean height Sa1 of the resin layer 20 and the peel strength. This indicates that simply increasing the arithmetic mean height of the resin layer 20 is not sufficient to improve adhesion to the adhesive resin, and that adhesion to the adhesive resin can only be improved by controlling the height Rpk of the protruding peaks of the resin layer 20 to 0.46 μm or higher.

[0075] Furthermore, the resin-coated metal plate 1 in Example 2 exhibited superior peel strength compared to Example 1. This is thought to be because, as shown in Table 2, Example 2 had a higher roundness than Example 1, allowing the adhesive to wet and spread more uniformly.

[0076] <Reference Experiment Example 1> As the metal base sheet 11, a cold-rolled sheet (thickness 0.16 mm) of low-carbon aluminum-killed steel was prepared by cold-rolling, annealing, and then temper-rolling with rolls having an arithmetic mean roughness Ra of 2.5 to 5.5 μm. A pure zinc plating bath was used with a bath temperature of 50°C and a current density of 30 A / dm². 2 A resin-coated metal sheet 1 was obtained by the direct roll coating method in the same manner as in Example 1, except that zinc plating was performed under the specified conditions to form a zinc-plated layer made of pure zinc as the metal plating layer 12. The height Rpk of the protruding peaks of the obtained resin-coated metal sheet 1 was measured in the same manner as in Example 1.

[0077] <Reference Experiment Example 2> A resin-coated metal plate 1 was obtained in the same manner as in Reference Experiment Example 2, except that an aqueous dispersion containing an olefin resin (ethylene-methacrylic acid copolymer) (solid content concentration 44.5% by weight, viscosity 40 mPa·s, pH 4.8, MFT 100℃) was used instead of an aqueous dispersion containing an olefin resin (ethylene-acrylic acid copolymer), and the height Rpk of the protruding peaks was measured.

[0078] <Reference Example 1> A resin-coated metal plate was obtained in the same manner as in Reference Experiment Example 1, except that an aqueous dispersion was applied using a bar coater instead of the direct roll coating method, and the height Rpk of the protruding peaks was measured. The coating conditions using the bar coater were as follows: a wireless bar coater (Select-Roller / A-Bar, manufactured by OSG System Products Co., Ltd.) was used, with a wireless bar size of 0 (OSP-00), aiming for a film thickness of 1 μm.

[0079] <Reference Comparison Example 2> A resin-coated metal plate was obtained in the same manner as in Reference Experiment Example 2, except that the aqueous dispersion was applied by a bar coater instead of the direct roll coating method, and the height Rpk of the protruding peaks was measured. Table 4 shows the measurement results of Rpk for Reference Experiment Examples 1 and 2 and Reference Comparative Examples 1 and 2, with Reference Comparative Example 1 as the standard.

[0080] [Table 4]

[0081] Compared to Reference Comparative Examples 1 and 2, which were coated using a bar coater with an aqueous dispersion, Reference Experimental Examples 1 and 2, which were coated using the direct roll coating method, all showed significantly higher Rpk values. In contrast to coating with a bar coater, where the liquid is not lifted during coating, the direct roll coating method lifts the aqueous dispersion as the metal substrate 11 is fed out of the roll, as shown in Figure 2(a), which is thought to have allowed for a higher protruding peak height Rpk. [Explanation of Symbols]

[0082] 1…Resin-coated metal plate 10...Metal base material 11… Metal plate 12…Metal plating layer 20… Resin layer

Claims

1. It comprises a metal substrate and a resin layer provided on the metal substrate, The aforementioned metal substrate consists of a metal base plate and a metal plating layer containing zinc. The resin layer is formed on the metal plating layer, In the aforementioned metal base plate, the arithmetic mean height Sa2 of the surface on which the metal plating layer is formed is 0.5 μm or more. A resin-coated metal plate in which the height Rpk of the protruding peaks on the surface of the resin layer is 0.46 μm or more.

2. A resin-coated metal plate according to claim 1, A resin-coated metal plate in which the height Spk of the protruding peaks on the surface of the resin layer is 0.6 μm or more.

3. A resin-coated metal plate according to claim 1 or 2, A resin-coated metal plate in which the resin layer is composed of a resin material containing an olefin-based and / or urethane-based resin.

4. A resin-coated metal plate according to claim 1 or 2, The arithmetic mean height Sa of the resin layer １ However, it is a resin-coated metal plate with a thickness of 0.5 μm or more.

5. A resin-coated metal plate according to claim 1 or 2, A resin-coated metal plate in which the height Rpk of the protruding peaks on the surface of the resin layer is 0.6 μm or more.

6. A method for manufacturing a resin-coated metal plate according to claim 1 or 2, A method for manufacturing a resin-coated metal plate, comprising the steps of: coating a metal substrate with an aqueous dispersion containing a resin material at a solid content concentration of 15% by weight or more by a direct roll coating method; and drying the layer made of the aqueous dispersion to form the resin layer.

7. A method for manufacturing a resin-coated metal plate according to claim 6, The solid content concentration of the aqueous dispersion is 15% by weight or more and less than 70% by weight. The aforementioned metal substrate consists of a metal base plate and a metal plating layer containing zinc. In the aforementioned metal base plate, the arithmetic mean height Sa of the surface on which the metal plating layer is formed ２ A method for manufacturing a resin-coated metal plate having a thickness of 0.75 μm or more.

8. A method for manufacturing a resin-coated metal plate according to claim 6, A method for manufacturing a resin-coated metal plate, wherein the resin material includes an olefin-based and / or urethane-based resin.

Images