JP3389061B2 - Painted metal plate with excellent galling and grounding properties - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to home electric appliances, especially electronic parts and the like which are required to have a good grounding property, in particular, having excellent workability and grounding property. To a coated metal plate. Heretofore, various performances such as galling, corrosion resistance and fingerprint resistance have been required for painted metal sheets for home appliances. For example, in the home appliance industry, there is a demand for a metal plate having excellent galling, corrosion resistance, and fingerprint resistance, which can be omitted in its own process and can be omitted from the viewpoint of saving steps and costs. Various studies have been made to satisfy these performances, and many products have been developed. Among them, a coated metal plate that has undergone chromate treatment on a plated metal plate and further formed an organic composite film based on a special resin on the top layer has been developed, and currently the most effective metal plate that satisfies the above performance It has become mainstream as a component for home appliances. For example, Japanese Patent Publication No. 4-14191 discloses that an organic composite film in which a colloidal sol having a specific fine particle size is additionally adjusted to an aqueous organic resin is formed on a chromate-coated plated steel sheet to improve corrosion resistance and fingerprint resistance. A method for producing a surface-treated steel sheet having an organic film is disclosed. Further, Japanese Patent Application Laid-Open No. 5-65666 discloses a paint in which a wax is added to an organic composite film for the purpose of improving the galling property. [0003] In recent years, with the worldwide demand for electronic equipment parts, new characteristics have been required for the coated metal plate itself. The requirement is an electromagnetic wave shielding property which is indispensable for electronic device parts and the like, and in order to satisfy this performance, a good grounding property is required for the metal plate itself. In order to impart a good grounding property to a conventionally developed coated metal plate, it is effective means to make the organic composite film coated on the outermost layer of the metal plate into a thin film. However, it has been difficult to simply provide a thinner film and to impart a better grounding property while maintaining the inherent properties of the coated metal plate such as galling, corrosion resistance, and fingerprint resistance. Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve such problems, and as a result, have found that a metal plate, a chromate-coated metal plate, or a chromate-coated plated metal plate (hereinafter referred to as an uncoated original plate) By controlling the center line average roughness and the amount of coating applied, the coated area ratio of the coating is controlled, and the inherent performance of the coated metal plate such as galling, corrosion resistance and fingerprint resistance By adding a lubricant to the organic composite coating, it is possible to impart lubrication to the coating surface and improve processing galling while ensuring good grounding. -Findings that can also impart a good performance. That is, the gist of the present invention is as follows.
A solid lubricant having a surface roughness of not more than 1.0 μm in center line average roughness Ra defined by JIS-B0601 or a chromate-coated metal plate or a chromate-coated plated metal plate is coated with a solid lubricant in an amount of 1% by weight. An organic composite film having a coating weight of 0.25 to 30%.
1 g / m ² and the covering area ratio to the metal plate surface is 7
It is a coated metal plate excellent in processing galling and grounding, characterized in that it is formed to be 0 to 99%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the case of a thin coated metal plate, the effects of the area ratio of the organic composite coating on the metal plate are greatly affected by the grounding properties, processing galling, corrosion resistance, fingerprint resistance and the like. receive. The larger the area of the organic composite coating, the higher the organic composite coating on the outermost layer, such as fingerprint resistance, processing galling, and corrosion resistance. However, the grounding property is degraded because of the interruption of the power supply. Conversely, the smaller the coverage area ratio of the organic composite film, the greater the number of current-carrying points obtained in the uncoated portion of the film, and the better the grounding properties, but the performance such as fingerprint resistance, galling resistance, and corrosion resistance deteriorates. . To ensure grounding while maintaining the inherent performance of the metal plate coated with organic composite coating such as galling, fingerprint resistance and corrosion resistance, the amount of organic composite coating and the area ratio of coating must be within the appropriate range. Found that it is necessary to control. [0007] The area ratio of the organic composite coating is greatly affected by the surface roughness of the original plate before painting. In particular, when an original plate having a rough surface roughness is used, the organic composite film enters into the concave portions of the roughness when the coating is applied, so that the coating area ratio of the coating film is extremely low. On the other hand, when an unpainted original plate having a low surface roughness is used, the coating area ratio of the coating film increases. Based on this finding, an appropriate range of the amount of the organic composite coating after drying and the appropriate range of the coating area ratio was determined, and the present invention was completed. FIG. 1 schematically shows a cross section of a coated metal plate having the plating and chromate of the present invention. The lower layer is composed of a metal plate 1, a plating 2, a chromate 3, and an organic composite film 4. Hereinafter, each film will be described. The metal plate targeted by the present invention is iron, iron-based alloy, aluminum,
Includes aluminum-based alloys, copper, and copper-based alloys. Also,
The plated metal sheet contains a galvanized metal sheet, a zinc alloy plated metal sheet, aluminum and an aluminum alloy plated metal sheet, and uses any of electroplating, hot dipping, vapor deposition plating, dispersion plating, and lap plating. Manufactured. In particular, a zinc alloy plated metal sheet has excellent performance in terms of work galling and corrosion resistance. The plating amount is not particularly limited, but is preferably 5 g / m ² or more in consideration of corrosion resistance. After plating on the metal plate and on the metal plate by the above-mentioned existing method, a chromate treatment is performed if necessary. It is not necessary to specifically limit the amount of chromate attached,
If it is less than 5 mg / m ^{2 in} terms of Cr, it is difficult to obtain corrosion resistance, and if it is more than 100 mg / m ² , the cohesive failure of the chromate itself occurs, and the adhesion of the coating film cannot be obtained. 5 to 100 mg / m ²
Is desirable. Regarding the type of chromate treatment, any of electrolytic chromate, etching chromate, and coating chromate can be applied to the present invention. In particular, when importance is placed on uniformity of appearance and adhesion of a top coat, electrolytic chromating is most suitable. When importance is attached to corrosion resistance, coating chromate is most suitable. The surface roughness of a metal plate before painting or a chromate-coated metal plate or a chromate-coated plated metal plate (original plate before painting) manufactured by the above-mentioned existing method has a surface roughness of JIS-B.
The center line average roughness Ra defined by 0601 is 1.0
It is necessary to be less than μm. Surface roughness is 1.0μ in Ra
m, the coating area ratio of the thin film coating decreases,
Sufficient fingerprint resistance, corrosion resistance, and galling may not be obtained. The resin component in the organic composite film is not particularly limited, but may be an acrylic resin, an olefin resin, an acrylic olefin resin, a urethane resin, an epoxy resin, a polyester resin, a phenol resin, a polycarbonate resin, a polyolefin ionomer, And one or a mixture or copolymer of two or more melamine resins. Acrylic resin is most suitable for cost consideration, epoxy and polyester resin is best suited for top coatability, and urethane resin is best suited for workability. The pigment is not particularly limited, but may be SiO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ ,
₃ O ₄ , MgO, ZrO ₂ , SnO ₂ , Al ₂ O ₃ , S
One or a mixture of two or more of b ₂ O ₅ can be used. In particular, SiO ₂ is economically optimal.
It is also advantageous for improving corrosion resistance. 1-30% by weight of a solid lubricant is added to the organic composite film. If it is less than 1%, the lubricating performance is insufficient, and if it exceeds 30%, the surface properties, particularly the adhesion of the top coating material, are reduced, and the earth property is further deteriorated. As the lubricant, an emulsion obtained by emulsion polymerization of the following lubricant having hydrophilic carboxyl groups and hydroxyl groups is used. Specifically, low-density polyethylene (density 0.9 to 0.95, softening temperature 90 to 120 ° C.), high-density polyethylene (density 0.95 to 1.2, softening temperature 10
0-130 ° C), polypropylene (density 0.95-1.
2, a polyolefin-based wax such as a softening temperature of 150 to 190 ° C., and a Teflon-based lubricant (density of 1.0 to 1.2, softening temperature of 300 to 400 ° C.) are desirable. In particular, a fine spherical polyethylene wax dispersion having an average particle diameter of 4 μm or less exhibits the best lubrication performance. The polyethylene and polypropylene dispersions are those obtained by making the emulsifier concentration as low as possible and not more than 5%, preferably without using an emulsifier, and having a molecular weight of 1,000 to 4,000 having substantially no polar group and an ethylene-based dispersion. It has a polar group containing a saturated carboxylic acid or an anhydride thereof, or a carboxyl group-containing derivative as a binding component, and preferably has an acid value of 10 to 150 and a molecular weight of 100
A dispersion of a high melting point lubricant having a shape close to a true sphere obtained by dispersing a modified polyolefin of 0 to 4000 in water or an aqueous solution from the molten state of melt mixing.
The acid value of the polyolefin wax after melt mixing is 1 to 20.
Is preferable. As a method for forming a coating film, any method such as roll coating, spray coating, curtain flow coating, or a method of controlling the amount of adhesion with an air knife after applying a coating solution may be used. After forming the coating film, the coating film is dried and cured as necessary. The conditions for drying and curing are appropriately selected depending on the type of the paint. Drying and curing may be performed by a known method, for example, a hot air drying furnace, an induction heating furnace, a near-infrared heating furnace, an electric furnace, a direct fire furnace, or the like. If the paint is a radiation-curable paint, a radiation furnace may be used. The organic composite film is coated in an amount of 0.25 to 1 g / m ² after drying. 0.
If it is less than 25 g / m ² , sufficient galling, corrosion resistance and fingerprint resistance cannot be obtained, and if it is more than 1 g / m ² , sufficient grounding properties cannot be obtained. [0014] The coated area ratio of a metal plate coated with an organic composite film is CMA (Computer Aided).
X-ray Micro Analyzer (manufactured by JEOL Ltd.). CMA analysis conditions are: analysis diameter 2 μm, irradiation current 0.05 μA, irradiation time 30 ms
At ec, an acceleration voltage of 15 kV, 500,000 × 500 points were analyzed at 250,000 points (1 mm square), and the detection strength of elemental Si contained in the coating film at each analysis point was measured. The measurement element for determining the coating film coverage ratio is
A sensitive heavy element is desirable. The silica content is the same as the measurement sample, and the average coating weight is 1.25 g /
The average strength of 250,000 points of the coated metal plate of m ² was obtained, and 1/10 of the average strength was determined as the threshold value. The rate (%) can be obtained from the following formula. Coating film area ratio (%) = (N / 250,000) × 100 It is necessary that the coating film covering area ratio be 70% or more. When it is less than 70%, when the painted metal plate is directly touched with a hand, fingerprint marks become conspicuous, the appearance is impaired, and the corrosion resistance is also deteriorated. Conversely, in order to secure the grounding property, it is necessary to reduce the coating film coverage area ratio to 99% or less. If it exceeds 99%, the grounding property is reduced, and a sufficient electromagnetic wave shielding property cannot be obtained. Next, an embodiment of the present invention will be described. The bath components in the examples are concentration ratios as nonvolatile components. The symbols and contents of the examples are as shown in Table 1. The particle size is determined by a laser light scattering method or a transmission electron microscope. (Example 1) The chromate-coated plated steel sheets having different surface roughnesses have Ra of 0.6 μm and 0.8 μm.
m, 1.0 μm, 1.2 μm) Electroplating of 20 g / m ² on 4 types of cold-rolled steel sheet (sheet thickness 0.8 mm) by the existing method After applying the paint shown in Table 2 with a roll coater after washing with water, put it in a gas open flame furnace within 2 seconds and bake it to the reached plate temperature of 150 ° C. It was created. The resulting organic composite film-coated plated steel sheet was evaluated for fingerprint resistance, corrosion resistance, processing galling, grounding properties, and paint adhesion. [Table 1] The fingerprint resistance was evaluated by pressing a real finger against each steel plate for 3 seconds and rating the degree of conspicuousness of the fingerprint trace. The following indicators were used for scoring. Fingerprint traces are completely unknown: Score 5 Fingerprint traces are hardly understood: Score 4 Fingerprint traces are clearly observed by observing: Score 3 Fingerprint traces are somewhat noticeable: Score 2 Fingerprint traces are very noticeable: Score 1 For practical application of fingerprint resistance, a rating of 3 or more is required. The grounding property is based on JIS-C25 of each painted metal plate.
According to the measurement method specified in No. 50, the interlayer resistance (Ω · c
m ² / sheet). For practical application, it is necessary to suppress the interlayer resistance to 2.5 or less (Ω · cm ² / sheet). The corrosion resistance was measured by measuring the time during which 5% of the area of white rust occurred in a flat salt spray corrosion test. The workability was evaluated by a press square cylinder crank press. Crank press conditions were as follows: a blank plate (0.8 × 220
× 180mm) into a 65 × 115mm, 50mm height, peel off the side with adhesive tape, paste on imitation paper, measure lightness (L) with color difference system, and directly apply the adhesive tape to imitation paper (L2-L) from the brightness (L2) of the blank pasted on
Was shown by ΔL value. Paint adhesion was measured by applying a commercially available melamine alkyd resin paint at a dry adhesion amount of 20 g / m ² , baking for 20 minutes at 120 ° C. with hot air, and measuring 9 m with an Erichsen tester.
After squeezing m, the sample was peeled off with an adhesive tape and visually evaluated (peeling area ratio). [Table 2] Table 2 shows the evaluation results. No. Nos. 1 to 3 are examples of the present invention in which the weight ratio of the lubricant is changed to 10, 20, and 30%. The larger the content of the lubricant, the better the process galling property and the better the earth property. showed that. No. 3
No. has a large lubricant content, and Compared with Nos. 1 and 2, it was superior in processing galling. No. Nos. 4 and 5 are examples of the present invention in which the chromate adhesion amount was changed to ²⁰ , 80 mg / m ² , Sample No. 4 had sufficient corrosion resistance, but was sufficiently practical. In addition, N
o. 5 was excellent in corrosion resistance. No. 6 to 8 have a coating film adhesion amount of 0.3, 0.
7, In the example of the present invention changed to 1.0 g / m ² , the larger the amount of coating film applied, the larger the coating film area ratio, and the better the processing galling property and corrosion resistance. No. Sample No. 6 had a low coating film area ratio due to a small amount of the coating film attached, and was excellent in grounding properties. No. In Nos. 7 and 8, since the amount of the coating film was large, both the corrosion resistance and the galling property were good.
No. Nos. 9 to 12 are examples of the present invention in which the type of the lubricant was changed, and showed good processing galling and earth properties regardless of the type of the lubricant. No. 13 to 15 are 0.6 μm in surface roughness Ra
In the present invention, a chromate-coated plated steel sheet of m and 1.0 μm was used as an original plate, and the coating weight was changed to 0.3 and 0.5 g / m ^2. As the size became larger, the coating film coverage ratio decreased, and the grounding property tended to be excellent. No. Nos. 16 and 17 are comparative examples in which the weight ratio of silica was not added and was changed to 40%. No. 16 is inferior in processing galling. No. No. 17 has a high lubricant content and good work galling,
Poor paintability and paint adhesion. No. 18 to 20 are chromate-coated plated steel sheets without painting and the coating weight is 0.2,
In a comparative example in which the ratio was changed to 1.2 g / m ² , No. 19 has a small coating film coating area ratio and a good grounding property due to a small coating film adhesion amount, but is inferior in fingerprint resistance, corrosion resistance and processing galling. No. No. 20 has a large coating film coverage ratio due to a large coating film adhesion amount, and has good fingerprint resistance, corrosion resistance, and galling property, but has poor grounding properties. No. No. 18 was a level without an organic composite film, and the grounding property was very excellent, but the fingerprint resistance, corrosion resistance and processing galling property were very poor. No. Reference numeral 21 is a comparative example in which the coating amount was changed to 0.3 g / m ² using a chromate-coated plated steel sheet having a surface roughness Ra of 1.2 μm as a base plate, and the coating amount was low and the surface roughness was low. When it becomes, the coating area ratio of the coating film decreases,
Poor fingerprint resistance, corrosion resistance, and galling. No. 22 ~
No. 24 is the present invention in which the type of resin is changed. The resin of No. 22 using a urethane epoxy emulsion showed very good processing galling. In each case, good fingerprint resistance, corrosion resistance, processing galling and grounding properties were obtained. Example 2 Cold rolled steel sheet having a thickness of 0.8 mm (Ra of chromate-coated steel sheet after chromate treatment)
Is 0.8 μm) and the plating amount is 20 g /
It performed 10% Ni-Zn alloy plating m ^2, current density 1 the surface with chromic acid / sulfuric acid = 30 / 0.3 g / l bath
0 A / dm ² , electrolysis for 2 seconds, washing with water, 40 m of Cr adhesion
g / m ² , and a water-based paint having a different resin as shown in Table 2 was applied by a roll coater.
It was baked at 170 ° C. and subjected to water aging to prepare an organic composite film-coated plated steel sheet. The evaluation was performed according to Example 1, and the obtained results are also shown in Table 2. In each of the Ni—Zn alloy platings, the corrosion resistance was relatively improved as compared with Example 1. No. 25 to 28 have a coating film adhesion amount of 0.3,
In the example of the present invention in which the coating amount was changed to 0.5, 0.7, and 1.0 g / m ² , the larger the amount of the coating film applied, the larger the coating film coverage ratio, and the corrosion resistance, processing galling property, and grounding property were all high. It was good. No. 29, 30: 0.2, 1.2 g of coating film adhesion amount
/ M ² in the comparative example. No. 29 has a small coating film coverage and therefore a small coating film coverage area ratio and good grounding properties, but is inferior in corrosion resistance, corrosion resistance, and processing galling. N
o. No. 30 has a large coating film coverage area ratio due to a large coating film adhesion amount, and has good fingerprint resistance, corrosion resistance, and processing galling, but has poor grounding properties. No. Nos. 31 and 32 are examples of the present invention in which the baking temperature was changed to 110 and 170 ° C. 3
In No. 1, the coating film adhesion and the like were slightly lowered, but at a practically usable level. No. No. 32 obtained good fingerprint resistance, corrosion resistance, processing galling and grounding properties. (Example 3) 20% Fe-Zn electro-zinc alloy-coated steel sheet (Ra 0.8 of chromate-coated steel sheet)
μm, plating amount 20 g / m ² )
o. 33), a commercially available coated chromate is coated on the surface of a hot-dip galvanized steel sheet (Ra 0.8 μm of a chromate-coated steel sheet, a coating amount of 40 g / m ² ) with a Cr adhesion amount of 40 mg / m ^2.
(No. 34). Under the conditions of 2, an organic composite film-coated plated steel sheet was prepared. Evaluation is Example 1
The results obtained are also shown in Table 2. No. 3
Sample No. 3 obtained very excellent results in corrosion resistance and processing galling.
No. No. 34 obtained good fingerprint resistance, processing galling and grounding properties. According to the above results, the surface roughness is JIS-B0
1.0 μm in center line average roughness Ra specified in 601
m, a solid lubricant on top of a metal plate or a chromate-coated metal plate or a chromate-coated plated metal plate
0.25 to 1 g / m ^{2 of} the organic composite coating containing
The coated metal plate coated with the organic composite coating having a coating amount of 70 to 99% with respect to the surface of the metal plate has excellent processing galling and grounding properties, and is further excellent. It also has excellent fingerprint and corrosion resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a film of a surface-treated metal plate when there is plating of the present invention. [Explanation of Signs] 1 Metal plate 2 Plating 3 Chromate 4 Organic film

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C23C 22/82 C23C 22/82 (56) References JP-A-8-224830 (JP, A) JP-A 8-318218 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 B05D 7/14 B05D 7/24 301 B32B 15/08

Claims (1)

(57) [Claim 1] A metal plate or a chromate-coated metal plate or a chromate-coated plating having a surface roughness of 1.0 μm or less in center line average roughness Ra specified in JIS-B0601. 1 to 30% by weight of solid lubricant on top of metal plate
%, And the organic composite film is formed so that the amount of adhesion is 0.25 to 1 g / m ² and the coverage of the metal plate surface is 70 to 99%. A coated metal plate with excellent galling and grounding characteristics.