Coated metal sheet and method for manufacturing coated metal sheet

Abstract

To suppress the occurrence of a pressure mark and to suppress the falling of beads even if a coating film is not formed.SOLUTION: Coated metal sheet 30 includes metal base 40 and bead-containing coating film 46. The bead-containing coating 46 is formed on either surface of the metal base 40. The beads-containing coating film 46 has a mother phase 70 and beads 72. The mother phase 70 contains an epoxy resin. A part of the bead 72 protrudes from the mother phase 70. A portion of the bead 72 embedded in the mother phase 70 is fused with the mother phase 70. The beads 72 contain a polyamide resin. The polyamide resin has an aliphatic skeleton.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coated metal sheet and a method for producing the coated metal sheet. [Background technology]

[0002] Some coated metal sheets are used without further painting or other processes after being pressed or otherwise processed. Such coated metal sheets are stored in a coiled state or stacked. During such storage, the appearance of one surface of the coated metal sheet may be damaged. One cause of such damage to the appearance is that a location on one of the coatings on the coated metal sheet is crushed. This location may be pressed against another location on the same coated metal sheet, or against a location on another coated metal sheet. In the following description, the shape of the crushed location is referred to as a "pressure mark."

[0003] A coated metal sheet that is used without further painting after processing may have a coating film containing a synthetic resin formed on one side. While such a coating film has the advantage of easily adhering some object to it, it also has the problem of being very hard. When a coating film with high hardness comes into contact with a coating film formed on another side during the above-mentioned storage, pressure marks often form on the surface of the coating film that comes into contact with the other side.

[0004] To solve this problem, a measure has been taken to mix soft synthetic resin beads into a hard coating. Patent Documents 1 and 2 disclose coated metal sheets that solve this problem.

[0005] The coated metal sheet disclosed in Patent Document 1 has a decorative coating film formed on one surface of a metal base, a non-cosmetic coating film formed on the other surface of the metal base, and beads formed of a polyurethane resin. The beads are contained in the non-cosmetic coating film. The non-cosmetic coating film has a primer coating film formed on the surface of the metal base and a top coating film formed on the surface of the primer coating film. The top coating film contains beads. The ratio of the bead protrusion amount to the primer coating film thickness is 2.0 or more and 8.0 or less. The bead protrusion amount in Patent Document 1 is the amount of beads protruding from the surface of the top coating film. The bead protrusion amount in Patent Document 1 is expressed as the difference between the film thickness of the top coating film and the average particle size of the beads. The base resin of the primer coating film and the top coating film is a polyester resin or an epoxy resin. The bead-containing top coating film is a cured product of a mixture containing beads and a paint containing a polyester resin or an epoxy resin. The average particle size of the beads is 10 to 30 micrometers. According to the invention disclosed in Patent Document 1, it is possible to suppress the occurrence of pressure marks and the falling off of beads.

[0006] The coated metal sheet disclosed in Patent Document 2 has a decorative coating film formed on one surface of a metal base, a non-cosmetic coating film formed on the other surface of the metal base, and resin beads contained in the non-cosmetic coating film. The non-cosmetic coating film is formed on the surface of the metal base. The non-cosmetic coating film includes a primer coating film containing beads and a coating film covering the surface of the beads and the primer coating film. The ratio of the bead protrusion amount to the coating film thickness is 3.0 or more and 9.0 or less. The bead protrusion amount is the amount of beads protruding from the surface of the primer coating film. The bead protrusion amount is expressed as the difference between the thickness of the primer coating film and the average particle size of the beads. The invention disclosed in Patent Document 2 can suppress the occurrence of pressure marks while also suppressing bead shedding. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7229756 [Patent Document 2] Patent No. 7094864 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the invention disclosed in Patent Document 1 has a problem in that it does not sufficiently prevent beads from falling off. The invention disclosed in Patent Document 2 can further prevent beads from falling off. However, the invention disclosed in Patent Document 2 has a problem in that a coating film must be formed in addition to a primer coating film containing beads. In addition, the invention disclosed in Patent Document 2 has a problem in that the coating film covers the beads, so the amount of protrusion of the beads from the surface of the coating film is reduced.

[0009] The present invention aims to solve the above-mentioned problems by providing a coated metal sheet that can suppress the occurrence of pressure marks and the dropping off of beads even without the formation of a coating film. [Means for solving the problem]

[0010] The coated metal sheet and the method for manufacturing the coated metal sheet of the present invention will be described with reference to the drawings. Note that the reference numerals used in this section are intended to facilitate understanding of the invention, and are not intended to limit the invention to the scope shown in the drawings.

[0011] In order to solve the above-mentioned problems, according to one aspect of the present invention, the painted metal sheet 30 has: steel plate 40 and a bead-containing coating 46. The bead-containing coating 46 includes steel plate 40. The bead-containing coating film 46 has a matrix 70 and beads 72. The matrix 70 contains an epoxy resin. Some of the beads 72 protrude from the matrix 70. The portion of the beads 72 that is embedded in the matrix 70 floats within the matrix 70 .The portions of the beads 72 that are embedded in the matrix 70 are fused to the matrix 70. The beads 72 contain a polyamide resin. The polyamide resin is nylon 12. The diameter of the beads 72 is greater than 15 micrometers and equal to or less than 40 micrometers. The protruding height of the beads 72 from the matrix 70 is equal to or greater than 15 micrometers and equal to or less than 30 micrometers.

[0012] Because portions of the beads 72 protrude from the matrix 70, even when the bead-containing coating 46 overlaps a coating 44 different from the bead-containing coating 46, contact between a large area of ​​the bead-containing coating 46 and the coating 44 is avoided. Additionally, the polyamide resin nylon 12 exhibits excellent flexibility. This facilitates suppression of crushing at the contact points of the coating 44 different from the bead-containing coating 46, even when the bead-containing coating 46 overlaps a coating 44 different from the bead-containing coating 46. Because crushing is more easily suppressed, the occurrence of pressure marks on the coating 44 different from the bead-containing coating 46 is also suppressed. Furthermore, because the portions of the beads 72 buried in the matrix 70 are fused to the matrix 70, the beads 72 are prevented from falling off even when not covered by a coating. Furthermore, nylon 12 has the lowest melting point among nylon 6, nylon 11, nylon 12, and nylon 66. This allows the polyamide resin to be most easily thermally welded to the epoxy resin of the matrix 70 when forming the bead-containing coating film 46 .

[0013] Furthermore, it is desirable that the content of beads in the bead-containing coating film 46 be 10% by mass or more.

[0014] According to another aspect of the present invention, the method for manufacturing a coated metal sheet 30 includes a bead-containing paint application step S506 and a bead-containing paint drying step S508. steel plate 40. In the bead-containing paint drying step S508, steel plateThe paint applied to 40 is dried to form a bead-containing coating film 46 having a matrix 70 and beads 72. The paint contains a solvent, an epoxy resin, a curing agent for the epoxy resin, and beads 72. The beads 72 contain a polyamide resin. The polyamide resin is nylon 12. The diameter of the beads 72 is greater than 15 micrometers and not greater than 40 micrometers. After the bead-containing paint drying step S508, the portions of the beads 72 that were embedded in the matrix 70 float in the matrix 70. After the bead-containing paint drying step S508, the portions of the beads 72 that were embedded in the matrix 70 are fused to the matrix 70. The protrusion height of the beads 72 from the matrix 70 after the bead-containing paint drying step S508 is 15 micrometers or more and 30 micrometers or less. The drying temperature of the paint in the bead-containing paint drying step S508 is 473.15 Kelvin or more and 523.15 Kelvin or less. [Effects of the Invention]

[0015] According to the coated metal sheet and the method for manufacturing the coated metal sheet of the present invention, the occurrence of pressure marks can be suppressed, and the falling off of beads can be suppressed even without the formation of a coating film. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of a coated metal plate according to an embodiment of the present invention. [Figure 2] 1 is a flowchart showing a method for manufacturing a coated metal plate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0018] <Configuration of painted metal sheet> Fig. 1 is a cross-sectional view of a coated metal sheet 30 according to this embodiment. The configuration of the coated metal sheet 30 according to this embodiment will be described based on Fig. 1.

[0019] As is clear from FIG. 1, the coated metal sheet 30 according to this embodiment has the following features: steel plate 40, a design surface primer layer 42, an other surface primer layer 43, a design surface forming coating film 44, and a bead-containing coating film 46.

[0020] steel plate 40 is the base of the coated metal sheet 30 according to this embodiment. steel plate Reference numeral 40 denotes a known hot-dip zinc-aluminum alloy plated steel sheet having a known chemical conversion treatment applied to both the front and back surfaces.

[0021] The design surface base layer 42 is steel plate The design surface base layer 42 according to this embodiment is formed by drying a known base paint. The other surface base layer 43 is steel plate The other-side base layer 43 according to this embodiment is formed by drying a well-known base paint. Note that in this embodiment, the base paint used to form the other-side base layer 43 is different from the base paint used to form the design-side base layer 42.

[0022] Design surface forming coating film 44 steel plate The decorative surface forming coating film 44 according to this embodiment is formed so as to overlap the decorative surface base layer 42. The decorative surface forming coating film 44 according to this embodiment is formed by drying a well-known topcoat paint.

[0023] The bead-containing coating 46 is steel plate The bead-containing coating film 46 according to this embodiment is formed on the other surface of the substrate 40 so as to overlap the other surface underlayer 43. The bead-containing coating film 46 according to this embodiment has a matrix 70 and a plurality of beads 72.

[0024] The matrix 70 includes an epoxy resin. The matrix 70 according to this embodiment includes an epoxy resin to facilitate adhesion of an optional component to the bead-containing coating film 46. An example of such an optional component is a heat insulating material. Examples of heat insulating material include urethane and rock wool. The components of the matrix 70 according to this embodiment are not particularly limited, except that it includes an epoxy resin.

[0025] The beads 72 according to this embodiment are particles made of the following material: a polyamide resin, particularly nylon 12, having an aliphatic skeleton.

[0026] Polyamide resins with an aliphatic skeleton are highly elastic and soft, which reduces the risk of damaging another coating when the beads 72 come into contact with the other coating (the type of coating formed on the object is not particularly limited. For example, the coating may be the decorative surface-forming coating 44 of the coated metal sheet 30 having the beads 72 or a coating of another coated metal sheet 30).

[0027] The melting point of polyamide resins with an aliphatic skeleton (primarily 200°C ± 50°C, i.e., primarily 473.15°C ± 50°C) is close to the temperature range described below. This temperature range is suitable for baking and drying epoxy resin-containing paints (200°C to 250°C, i.e., 473.15°C to 523.15°C). This facilitates melting of the surfaces of the beads 72 as the paint forming the matrix 70 bakes and dries. When the surfaces of the beads 72 melt, the portions of each bead 72 embedded in the matrix 70 tend to fuse strongly with the matrix 70. In addition, this prevents the beads 72 from melting completely and thus failing to fuse with the matrix 70, and also prevents excessively melted beads 72 from protruding from the matrix 70. If the beads 72 do not melt completely and thus fail to fuse with the matrix 70, this can cause the beads 72 to fall off the bead-containing coating film 46.

[0028] Examples of polyamide resins having an aliphatic skeleton include nylon 6, nylon 11, nylon 12, and nylon 66. Among polyamide resins having an aliphatic skeleton, nylon 12 is particularly suitable as a component of the beads 72 according to this embodiment. Among nylon 6, nylon 11, nylon 12, and nylon 66, nylon 12 has the lowest melting point. This allows nylon 12 to more easily thermally weld with the epoxy resin of the matrix 70 during the formation of the bead-containing coating film 46. Additionally, the melting point of nylon 12 (176°C, 449.15 Kelvin) is not too low compared to the temperature range in which epoxy resins polymerize (200°C to 250°C, i.e., 473.15 Kelvin to 523.15 Kelvin). This helps prevent excessive dissolution of the beads 72 during the formation of the matrix 70. Furthermore, nylon 12 has the lowest density among nylon 6, nylon 11, nylon 12, and nylon 66. This low density means that nylon 12 floats more easily in a high-density liquid. Because they tend to float, when the thickness of the bead-containing coating film 46 is thick, the beads 72 tend to protrude from the liquid that becomes the mother phase 70, compared to when the beads 72 contain nylon 6, nylon 11, nylon 12, and nylon 66 other than nylon 12. 。

[0029] A portion of each bead 72 protrudes from the matrix 70 . The portion of the beads 72 that is embedded in the matrix 70 floats within the matrix 70 . The portion of each bead 72 that is embedded in the matrix 70 is fused to the matrix 70. In this embodiment, the protruding height of the beads 72 relative to the surface of the matrix 70 is 15 micrometers or more and 30 micrometers or less.

[0030] In this embodiment, the diameter of the beads 72 is 15 micrometers or more and 40 micrometers or less, and may be 20 micrometers or more and 30 micrometers or less.

[0031] In this embodiment, there is no particular limitation on the content of the beads 72 in the bead-containing coating film 46. For example, the content is 3% by mass or more. The content may be 10% by mass or more.

[0032] <Manufacturing method of coated metal sheet> 2 is a flowchart showing a method for manufacturing the coated metal sheet 30 according to this embodiment. The method for manufacturing the coated metal sheet 30 according to this embodiment will be described with reference to FIG.

[0033] The manufacturing method of the painted metal plate 30 according to this embodiment includes a primer coating process S500, a primer coating drying process S502, a design surface forming paint coating process S504, a bead-containing paint coating process S506, and a bead-containing paint drying process S508.

[0034] In the primer coating process S500, steel plate A primer coat is applied to one of the front and back surfaces of 40. steel plate Another base paint is applied to the other surface of the front or back of 40. steel plate 40 is a hot-dip zinc-aluminum alloy plated steel sheet on both sides of which a known chemical conversion treatment is applied.

[0035] In the base paint drying step S502, steel plate The primer paints applied to the front and back of the 40 are dried. steel plate Each 40 is dried in a drying device. When the primer paint dries, steel plate A design surface base layer 42 and an other surface base layer 43 are formed on the front and back surfaces of the sheet 40.

[0036] In the design surface forming paint application step S504, steel plate A top coat paint is applied onto the design surface base layer 42 formed on one of the front and back surfaces of the sheet 40 .

[0037] In the bead-containing paint application step S506, steel plate A paint is applied onto the other-side base layer 43 formed on the other side of the front or back surface of 40. The paint contains a solvent, an epoxy resin dissolved in the solvent, a curing agent for the epoxy resin, and beads 72.

[0038] In the bead-containing paint drying step S508, steel plate The paint applied to the other of the front and back surfaces of 40 is dried. This paint is the paint applied in the bead-containing paint application step S506. In this embodiment, steel plate The top coat paint applied to one of the front and back surfaces of 40 is also dried. In this embodiment, the drying temperature of these paints is 200 degrees Celsius (473.15 Kelvin) or higher and 250 degrees Celsius (523.15 Kelvin) or lower. In this embodiment, the drying time of these paints is 20 seconds or higher and 60 seconds or lower.

[0039] <How to use painted metal sheets> The method of using the coated metal sheet 30 according to this embodiment is similar to that well known, and therefore, detailed description thereof will not be repeated.

[0040] [Effect description] In the coated metal sheet 30 according to this embodiment, some of the beads 72 protrude from the matrix 70. This prevents a large area of ​​the bead-containing coating 46 from contacting the design-surface-forming coating 44, even if the bead-containing coating 46 of another coated metal sheet 30 overlaps the design-surface-forming coating 44 of this coated metal sheet 30. Additionally, polyamide resins with aliphatic skeletons exhibit excellent flexibility. This prevents the bead-containing coating 46 from collapsing at the contact points of the design-surface-forming coating 44, even if the bead-containing coating 46 overlaps the design-surface-forming coating 44 of another coated metal sheet 30. This minimizes the risk of crushing the design-surface-forming coating 44, thereby preventing pressure marks from appearing on the design-surface-forming coating 44. Furthermore, because the portions of the beads 72 that are buried in the matrix 70 are fused to the matrix 70, the beads 72 are prevented from falling off even when the bead-containing coating 46 is not covered by a coating.

[0041] Furthermore, nylon 12 has the lowest melting point among nylon 6, nylon 11, nylon 12, and nylon 66. As a result, when forming the bead-containing coating film 46 on the coated metal sheet 30 according to this embodiment, nylon 12 is the most likely to undergo thermal welding with the epoxy resin of the matrix 70 among nylon 6, nylon 11, nylon 12, and nylon 66. Furthermore, the beads 72 are more likely to protrude from the matrix 70 than when the beads 72 contain any of nylon 6, nylon 11, nylon 12, and nylon 66 other than nylon 12. This is because nylon 12 has the lowest density among nylon 6, nylon 11, nylon 12, and nylon 66.

[0042] [Description of Modifications] The above-described coated metal sheet 30 is an example used to embody the technical concept of the present invention. The shape and structure of the metal base 40, the composition of the decorative surface primer layer 42, the composition of the other surface primer layer 43, the composition of the decorative surface-forming coating film 44, and the composition of the bead-containing coating film 46 are not limited to those in the above-described embodiment. Various modifications can be made to these. [Explanation of symbols]

[0043] 30...painted metal plate 40...Metal base 42...Design surface base layer 43…Other side base layer 44...Design surface forming coating film 46...Bead-containing coating 70...Mother phase 72...Beads

Claims

1. A steel plate, a bead-containing coating film formed on any surface of the steel plate, The bead-containing coating film is a matrix containing an epoxy resin; A coated metal sheet having beads partially protruding from the matrix, a portion of the beads that is embedded in the matrix is ​​floating in the matrix, a portion of the bead that is embedded in the matrix is ​​fused to the matrix, the beads comprise a polyamide resin; the polyamide resin is nylon 12, The diameter of the beads is greater than 15 micrometers and less than or equal to 40 micrometers; A coated metal sheet characterized in that the protrusion height of the beads from the parent phase is 15 micrometers or more and 30 micrometers or less.

2. 2. The coated metal sheet according to claim 1, wherein the content of the beads in the bead-containing coating film is 10% by mass or more.

3. a bead-containing paint application step in which paint is applied to the steel plate; A method for producing a coated metal plate, comprising a bead-containing paint drying step in which the paint applied to the steel plate is dried to form a bead-containing paint film having a matrix and beads, The paint is A solvent, Epoxy resin, a curing agent for the epoxy resin; beads; the beads comprise a polyamide resin; the polyamide resin is nylon 12, The diameter of the beads is greater than 15 micrometers and less than or equal to 40 micrometers; After the bead-containing paint drying step, the part of the beads that is embedded in the matrix floats in the matrix, After the bead-containing paint drying step, the portions of the beads that are embedded in the matrix are fused to the matrix, a protrusion height of the beads from the matrix after the bead-containing paint drying step is 15 micrometers or more and 30 micrometers or less; A method for producing a coated metal sheet, wherein the drying temperature of the paint in the bead-containing paint drying step is 473.15 Kelvin or more and 523.15 Kelvin or less.

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