JP2000355671A - Topcoating material for imparting scratch resistance, galling resistance, and snow-slipping properties to metal sheet, surface treatment method for metal sheet, and coated metal sheet excellent in scratch resistance, galling resistance, and snow-slipping properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a topcoating material which forms a coating film improved in scratch resistance, galling resistance, and snow-slipping properties by compounding a vinylidene fluoride resin as the matrix resin with a ceramic-base inorganic aggregate, polyacrylonitrile beads, and a fluororesin powder. SOLUTION: This topcoating material comprises 100 pts.wt. vinylidene fluoride resin, 1-40 pts.wt. ceramic-base inorganic aggregate having an average particle size (r1) of 0.6-40 μm, 1-40 pts.wt. polyacrylonitrile beads having an average particle size (r2) of 0.6-40 μm, and 0.1-20 pts.wt. fluororesin powder having an average particle size (r3) of 0.6-40 μm. The topcoating material is applied to the surface of a metal sheet which has been subjected to cleaning by alkali degreasing, warm water washing, water washing, etc., and then to undercoating. The topcoating material is applied so that the resultant coating film after drying has a thickness (T1) satisfying the relations: 0.04<=r1/T1<1.0, 0.04<=r2/T1<=1.0, and 0.04<=r3/T1<=1.0. After applied, the topcoating material is baked by heating at a temperature high enough and for a time long enough for the matrix resin to form a film and then dried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated metal plate, a top coat for the same, and a method for treating the surface of the metal plate.
More specifically, the present invention relates to a vinylidene fluoride-based fluororesin coated metal sheet suitable for outdoor building materials in snowfall areas.

[0002]

2. Description of the Related Art Currently, fluororesin-coated metal sheets having excellent weather resistance, corrosion resistance, workability, chemical resistance, abrasion resistance, stain resistance, and the like are widely used as outdoor building materials. Among them, a vinylidene fluoride-based fluororesin-coated metal sheet has excellent snow sliding properties in addition to the above-mentioned properties, and is therefore frequently used particularly for roofing materials in snowfall areas. However, the vinylidene fluoride-based fluororesin has a low coating strength, so that when frozen snow on the roof slides down, the coating surface is easily damaged. Further, there is a problem that when water enters the inside from the damaged portion of the coating film, the metal plate under the coating film is corroded.

Therefore, in order to improve the strength of the coating film, for example, an inorganic aggregate is added as a reinforcing material to the coating film of the vinylidene fluoride-based fluororesin used for the roof material in snowfall areas. Strategies have been devised. That is, a method of adding an inorganic aggregate of glass fiber as a reinforcing material to the coating film (JP-A-61-236869, JP-A-61-269).
No. 37636), or an inorganic aggregate of spherical glass beads is added as a reinforcing material to the coating film, and the average particle size (r) and coating film thickness (T) of the beads are adjusted to 0.5 ≦ r /
A method for defining the range of T ≦ 1.5 (JP-A-7-256)
821). However, the above glass fibers tend to be oriented vertically in the baked and dried topcoat, and the glass fibers protrude from the coating surface. Also, when using a spherical glass bead that is larger than the coating thickness and projecting beyond the coating surface, if the coatings rub against each other during transportation of the coated metal plate, etc. The coating surface of the other metal plate is shaved off by the protruding inorganic aggregate to give a whitish appearance, or a so-called whitening phenomenon occurs, or in a more remarkable case, the coating peels off, so-called coating galling occurs. Serious problems occur. Furthermore, if unevenness occurs on the surface of the coating film, the slipperiness is reduced as compared with the case where no inorganic aggregate is added, and the original advantage of the vinylidene fluoride-based fluororesin coated metal plate is impaired. Occurs.

Therefore, in order to improve the drawbacks caused by the inorganic aggregate, in addition to the hard inorganic aggregate which is a reinforcing material in the coating film, organic polymer beads and fluorine which are as soft as the matrix resin are added. A method of adding resin powder in combination has been devised. That is, the inorganic aggregate of silicon carbide in the coating film, acrylic polymer beads as organic polymer beads and polytetrafluoroethylene resin powder as a fluororesin powder in a composite addition, the inorganic aggregate of the coating film The strength of the matrix resin can be increased, and at the same time, the organic polymer beads and the fluororesin powder can alleviate the mechanical strain generated between the inorganic aggregate and the matrix resin of the coating film (Japanese Patent Application Laid-Open No. H08-08380). 183925
JP-A-9-221621, JP-A-9-221162
No. 2). However, the acrylic polymer beads are inferior in wettability and dispersibility in paint,
It has the disadvantage that it tends to settle in the paint. Therefore, it was necessary to separately perform surface treatment on the acrylic polymer beads using a coupling agent to improve wettability and dispersibility. By performing this processing, the number of manufacturing steps increases, and the manufacturing cost increases. Furthermore, when the acrylic polymer beads protrude even slightly from the coating surface,
When the coated metal plate is roll-formed, stress concentrates on the beads protruding from the coating film surface, and as a result, the coating film covering the beads peels off or falls off, or the beads and the coating film There was a problem that cracks and peeling occurred between the portions, and the corrosion resistance of the processed portion was reduced.

[0005]

The vinylidene fluoride-based fluororesin coating film has excellent snow sliding properties, but is insufficient in abrasion resistance and scratch resistance. Thus, as described above, when inorganic aggregate is added to the coating film to increase the strength of the coating film, the scratch resistance of the coating film is improved, but the inorganic aggregate is coated with the inorganic coating material. When projecting to the membrane surface,
The unevenness of the coating film surface becomes large, the anti-galling property of the coating film is reduced, and the snow sliding property, which is the original advantage of the vinylidene fluoride-based fluororesin coated metal plate, is also impaired. Therefore, in addition to the inorganic aggregate in the coating film, when the organic resin beads and the fluororesin powder as soft as the matrix resin are added in combination, the coating film galling resistance and the snow sliding property are relatively good. However, it is hard to say that it has reached a sufficient level. Also,
In order to prevent the organic polymer beads from settling in the paint, it is necessary to separately perform a surface treatment of the additive, which causes a problem of increasing the cost.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a coated metal sheet having a coating film galling resistance, a scratch resistance, and a snow-sliding property which is remarkably superior to the conventional one at a low manufacturing cost. And

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and have obtained a vinylidene fluoride-based fluororesin-coated metal sheet having excellent scratch resistance, coating galling resistance, and snow sliding property. To produce the above-mentioned coated metal plate having an undercoat and an overcoat, at the same time as optimizing the overcoat, furthermore, there is a limit only to the countermeasure of the overcoat, By combining the countermeasure and the countermeasure of the undercoat coating, without increasing the number of processes,
The inventors have found that it is possible to dramatically improve the above characteristics, and have led to the creation of the present invention.

[0008] That is, a first aspect of the present invention is to provide an undercoat formed on a metal plate by adding a vinylidene fluoride-based fluororesin as a matrix resin, adding a ceramic-based inorganic aggregate, organic polymer beads, and a fluororesin powder. The present invention relates to a topcoat applied on a coating film. In the above top coating,
The organic polymer beads are polyacrylonitrile beads, and a ceramic inorganic aggregate having an average particle size of 0.6 to 40 μm is added in an amount of 1 to 100 parts by weight of the matrix resin.
40 parts by weight of polyacrylonitrile beads having an average particle size of 0.6 to 40 μm are mixed with the matrix resin in an amount of 1 to 4 parts.
It is preferable to add 0.1 to 20 parts by weight of a fluororesin powder having 0 parts by weight and an average particle diameter of 0.6 to 40 μm to the matrix resin.

In a second aspect of the present invention, the ratio of the above-mentioned top coating composition to the above-mentioned additives and the coating film thickness after drying is as follows:
The above-mentioned additives do not protrude from the coating film, and are coated on a metal plate so as to be in a specified range so that the strength of the coating film is not impaired, and a temperature sufficient for the above-mentioned matrix resin to form a film. For a sufficient time for baking and drying to form a film.

A third aspect of the present invention is a vinylidene fluoride-based fluororesin-coated metal, comprising an undercoat and an overcoat formed on the undercoat using the above-mentioned overcoat. Regarding the board. Furthermore, the above-mentioned top coat, the above-mentioned top coat, the ratio of the average particle size of the additive and the thickness of the top coat after drying, the additive in the coat does not protrude from the coat and the film strength Is preferably formed on the above-mentioned undercoating film so as to be within a specified range so as not to be impaired.

[0011] A fourth aspect of the present invention relates to a vinylidene fluoride-based fluororesin-coated metal plate in which the undercoat film contains a ceramic-based inorganic aggregate. The undercoating film, the content of the ceramic-based inorganic aggregate is 1 to 40 parts by weight based on 100 parts by weight of the matrix resin, and the ratio of the average particle size and the thickness of the undercoating film is such that the inorganic aggregate is undercoating. It is preferably formed on a metal plate that does not protrude from the coating film and falls within a specified range so that the strength of the coating film is not impaired.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. (Topcoat) The topcoat of the vinylidene fluoride-based fluororesin coated metal plate of the present invention is obtained by forming an undercoat on a metal plate on which a chemical conversion coating is formed, and then forming an overcoat thereon. An inorganic aggregate that reinforces the topcoat, organic polymer beads for reinforcing the topcoat and improving lubricity, and fluorine for lowering the surface energy of the topcoat and improving snow sliding properties Contains resin powder.

(Inorganic aggregate) Vinylidene fluoride according to the present invention
Ceramics that are added to
Inorganic aggregates are formed by applying paint and drying by heating.
Added to increase the strength of the matrix resin film
It does not hinder matrix resin film formation
It is not particularly limited as long as it is one. like this
As a ceramic inorganic aggregate, for example, spherical glass beads
Size, fibrous ceramic or spherical ceramic
Can be In addition, these inorganic aggregates, the purpose of the present invention,
In the technical field of ceramics as long as the effect is not impaired
Various known additives may be added. The inventors have found that inorganic bone
Between the content of the material and the adhesion and scratch resistance of the topcoat
When we investigated the relationship, the content of inorganic aggregate
Less than 1 part by weight per 100 parts by weight of matrix resin
If there is, the strength of the coating film is reduced, the scratch resistance is insufficient, and 40
If the amount exceeds the above range, the adhesion of the topcoat film will decrease and the coating film will be processed.
It was also found that the properties were insufficient. Therefore, these
The machine aggregate is 100 parts by weight of the matrix resin of the coating film.
It is preferable to add in an amount of about 1 to 40 parts by weight.
No. Furthermore, the average particle size (r₁) And coating thickness
(T₁) To make the inorganic aggregate protrude from the coating surface.
Conditions and the range of conditions that can secure coating strength
Upon detailed investigation, the average particle size (r₁) And coating thickness
Sa (T₁) Ratio is related to the presence or absence of inorganic aggregate
Turned out to be key parameters. First, inorganic
When the shape of the aggregate is spherical, the protrusion of the inorganic aggregate can be prevented.
The range that can be obtained is as follows. Average particle size of inorganic aggregate (r
₁) And the thickness of the top coat (T₁) Ratio r₁/ T ₁But
If it is larger than 1.0, the inorganic aggregate is higher than the surface of the top coat.
It is necessary to keep this ratio to 1.0 or less because it protrudes
It is. Also, this ratio r₁/ T₁Is less than 0.04
In this case, the ratio cannot be increased because the coating film strength cannot be sufficiently obtained.
It is necessary to make it 04 or more. Therefore, inorganic aggregate
Average particle size (r₁) And the thickness (T₁)But,
0.04 ≦ r₁/ T₁Paint so that ≦ 1.0
Is preferred. Next, when the shape of the inorganic aggregate is fibrous
The range that can prevent the protrusion of inorganic aggregates is as follows
Become. When the inorganic aggregate is fibrous, the fiber cross section diameter is 5μ
m or more, the inorganic aggregate becomes
There is a tendency to orient perpendicular to the coating surface,
In order to prevent the inorganic aggregate from protruding to the surface,
The diameter of the fiber cross section must be smaller than 5 μm. Ma
In addition, just like the spherical inorganic aggregate, the fiber cross section of the inorganic aggregate
If the average diameter is defined as the average particle diameter, this average particle diameter
(R₁) And the thickness of the top coat (T₁) Ratio r₁/ T₁
Needs to be 1.0 or less. Also, this ratio
r₁/ T₁Is less than 0.04, sufficient film strength is obtained.
This ratio must not be less than 0.04.
It is important. Therefore, the average particle size (r₁) And above
Thickness of top coat (T₁) Is 0.04 ≦ r₁/ T₁≤
It is preferable that the coating be performed so as to be 1.0.

(Organic Polymer Beads) The organic polymer beads to be added in the top coat of the vinylidene fluoride-based fluororesin coated metal plate of the present invention are polyacrylonitrile selected from the viewpoint of wettability and dispersibility in the paint. Beads (hereinafter referred to as PAN beads) are used. This PA
N-beads have excellent dispersibility in paint and do not settle in the paint when added as they are, and thus have the advantage that surface treatment with a coupling agent, which has been performed on conventional acrylic polymer beads, becomes unnecessary. Further, since the PAN beads are more resilient and have an appropriate hardness than the conventional acrylic polymer beads, the PAN beads are used during molding.
Even when stress is concentrated on the N beads, a larger mechanical strain relaxation effect is exhibited as compared with conventional acrylic polymer beads.
For this reason, compared with the above-mentioned coated metal plate to which the conventional acrylic polymer beads are added, the coated metal plate to which the PAN beads are added has a remarkable ability to prevent the top coat coated on the PAN beads from peeling and falling off. Higher
In addition, cracking and peeling between the PAN beads and the matrix resin of the overcoat film are sufficiently suppressed. The present inventors have investigated the relationship between the content of PAN beads and the scratch resistance, coating galling resistance, and coating processability of the overcoating film. If the amount is less than 1 part by weight relative to 100 parts by weight of the resin, sufficient coating strength and lubricity cannot be obtained, so that the scratch resistance and the galling resistance of the coating are insufficient. It was found that the scratch resistance and the galling resistance of the coating film were secured, but the workability of the coating film was insufficient. Therefore, the content of the PAN beads is
1 to 100 parts by weight of the matrix resin of the coating film
Preferably, it is added in an amount of about 40 parts by weight. Furthermore, the average particle size (r ₂ ) of the PAN beads and the thickness (T ₁ ) of the above-mentioned top coat were variously changed, and conditions under which the film strength was secured were examined in detail. (R ₂ ) and the ratio r ₂ / r of the above top coat thickness (T ₁ )
If T ₁ is larger than 1.0, the PAN beads protrude from the surface of the top coating film, and the snow sliding property and the coating processability are reduced.
It is necessary to make this ratio 1.0 or less. Also,
If the ratio r ₂ / T ₁ is smaller than 0.04, the strength of the coating film is reduced. Therefore, it is necessary to set the ratio to 0.04 or more. Therefore, the average particle size (r ₂ ) of the PAN beads and the thickness (T ₁ ) of the coating film are 0.04 ≦ r ₂ / T ₁ ≦ 1.
It is preferable that the coating be performed so as to be 0.

(Fluorine Resin Powder) Vinyl Fluoride of the Present Invention
Added to the top coat of fluorinated resin coated metal plate
Fluororesin powder is used for lubrication and snow
And to increase the coating whitening resistance.
And does not hinder the formation of a matrix resin film.
It is not particularly limited. As such aggregate
For example, polytetrafluoroethylene resin, ethylene tetrafluoride
Ethylene resin and the like. Also these
The fluororesin powder does not impair the object and effects of the present invention.
Various additions known in the technical field for fluororesins
Agents may be added. The inventors have included fluororesin powder
The relationship between the amount and the adhesion and scratch resistance of the topcoat
Investigations revealed that the content of fluororesin powder was
Less than 0.1 parts by weight per 100 parts by weight of Rix resin
If any, the above-mentioned overcoating film has anti-galling properties,
If the whitening resistance of the coating film cannot be sufficiently obtained and exceeds 20 parts by weight,
The coating film adhesion and processability of the above-mentioned top coating film may decrease.
It turned out. Therefore, these fluororesin powders
0.1 to 100 parts by weight of the matrix resin of the coating film
It is preferably added in an amount of about 20 parts by weight. Furthermore,
Average particle size of fluororesin powder (r_Three) And the above top coat
Thickness (T₁), The fluororesin powder is coated
Condition that does not protrude into the
Investigating in detail that the fluororesin powder has moderate hardness
And moderate lubricity and excellent lubricity
Even if it protrudes more, like the inorganic aggregate,
No damage, no paint galling, no paint white
From the standpoint of ensuring chemical compatibility, the upper limit of the average particle size is regulated.
Although not specified, the particle size of the fluororesin powder is
If the film thickness is larger than the above, the coating adhesion of the above-mentioned top coat decreases.
However, at the same time, the workability also decreases. Furthermore, this fluororesin powder
When the powder protrudes from the surface of the coating film,
The size of the fluororesin powder increases due to
Uniform particle size (r_Three) And the thickness of the top coat (T ₁) Ratio r_Three
/ T₁Needs to be 1.0 or less. Also,
Ratio r _Three/ T₁Less than 0.04
This ratio is 0.1% because the water resistance and the whitening resistance of the coating film decrease.
04 or more is required. Therefore, fluororesin
Average particle size of powder (r_Three) And coating thickness (T₁) Is 0.
04 ≦ r_Three/ T₁Painting so that ≦ 1.0
Is preferred.

(Method of Surface Treatment of Metal Plate) A method of performing a surface treatment of a metal plate using the overcoating material according to the present invention in which each additive is prepared and blended in a prescribed range as described above will be described below. I do. The metal plate used in the present invention,
The metal plate is not particularly limited as long as it can form a chemical conversion coating.
n-Al-based alloy-plated steel sheet, hot-dip Zn-Al-Mg-based alloy-plated steel sheet, hot-dip Al-coated steel sheet, stainless steel sheet,
An aluminum plate or the like can be used.

(Pretreatment) In the surface treatment method for a metal plate according to the second aspect of the present invention, it is preferable to firstly clean the metal plate to be coated as a pretreatment by alkali degreasing, hot water washing, water washing, or the like. . This cleaning method is not particularly limited as long as a necessary chemical conversion coating can be formed because the vinylidene fluoride-based fluororesin coating according to the present invention is properly formed.

(Chemical conversion treatment) The surface of the metal plate thus cleaned is subjected to chemical conversion treatment. The chemical conversion treatment method is not particularly limited, and either a chromate-based film or a non-chromate-based film may be used. it can. For example, in the case of a chromate-based film, the amount of chromium is 5 to 100 mg / m in terms of the total amount of Cr in order to ensure corrosion resistance and coating film adhesion.
Preferably it is ² . The amount of chromium deposited should be the same even when the chromate film contains a water-soluble or water-dispersible resin or silica, or when the chromate film is formed with a phosphoric acid-chromic acid treatment solution. preferable.

(Undercoating Film) An undercoating film is formed on the chemical conversion film thus formed. There is no particular limitation on the type of matrix resin of the undercoating film. And polyester-based, epoxy-urethane-based, or phenoxy-based resins. As an additive of the undercoat, an inorganic aggregate such as ceramic beads is used, and the inorganic aggregate does not protrude from the undercoat and is in a range defined so as to ensure sufficient film strength. Add an appropriate amount and apply with an appropriate film thickness. The thickness of the undercoat film is about 3 to 10 μm in the related art. Further, as a rust preventive pigment for the undercoat coating film, chromic acid rust preventive pigments such as strontium chromate, calcium chromate, barium chromate, zinc chromate, or aluminum phosphate, zinc phosphate, calcium phosphate,
Non-chromate rust preventive pigments such as calcium carbonate may be used alone or in combination.

(Overcoat film) On the undercoat film formed in this manner, the above-mentioned topcoat material is coated with each additive and the ratio of the film thickness after drying is determined so that the additive protrudes from the coating film. Without coating, and coated on a metal plate so that the strength of the coating film is not impaired, and heated at a temperature and for a sufficient time so that the matrix resin of the top coating film is formed into a film. The present invention relates to a method for treating a surface of a metal plate, which includes a step of baking and drying to form a film. The film thickness of the overcoat film is 15 to 40 μm, which is the same as a conventional ordinary fluororesin-coated metal plate.
Degree. The reason for this is that if the film thickness is less than 15 μm, sufficient weather resistance and corrosion resistance cannot be obtained, and if the film thickness exceeds 40 μm, the baking tends to occur during baking and drying and the production cost increases. Therefore, the film thickness needs to be 15 to 40 μm. Further, the thickness of the undercoating film is 3 to 10 μm as in the case of a conventional ordinary fluororesin-coated metal plate. The reason is that if the thickness is less than 3 μm, sufficient corrosion resistance cannot be secured.
If it exceeds μm, it is not preferable because aside is likely to occur during baking and drying, and the workability of the undercoat film is also reduced. As the drying temperature, the coating is heated to a temperature not lower than the boiling point of the solvent of the paint and not lower than the melting point of the solute of the resin. For example, in a paint in which glass beads, PAN beads, and polytetrafluoroethylene resin powder are added to vinylidene fluoride-based fluororesin, the heating temperature is preferably set to 250 ± 10 ° C.

[0021]

[Example 1] (Chemical treatment of metal sheet) Hot-dip galvanized steel sheet
(Sheet thickness: 0.35 mm, coating weight on one side: 140 g /
m ^TwoGI) and molten zinc 5% Al
Coated steel sheet (thickness: 0.35mm, coating weight on one side:
140g / m^Two, GT)
And then wash the coated steel sheet with hot water and water.
And dried. In addition, molten Zn-55% Al-1.6
% Si-plated steel sheet (Thickness: 0.35mm, with one side plating)
Landing amount: 75 g / m^Two, GS).
It was degreased, washed with hot water and water, and dried. this
Later, the coating type chromate treatment liquid (day
Product name: Surfcoat NRC30, manufactured by Hon Paint Co., Ltd.
0NS) with a roll coater without washing with water
Dried at 100 ° C, total Cr content is 40mg / m^TwoBlack
A mate film was formed.

(Painting) Next, strontium chromate as a rust preventive was applied on the chromate film to a non-volatile content of 1%.
An undercoat paint of 25 parts by weight was added to 00 parts by weight, and an epoxy resin-based undercoat to which titanium oxide and silica were added as pigments was applied so as to have a dry film thickness of 5 μm.
Dry at ℃. Thereafter, the inorganic aggregate of glass beads, fibrous ceramic, ceramic beads, a combination of glass beads and fibrous ceramics, a combination of glass beads and ceramic beads, a PAN bead, and a fluororesin powder of polytetrafluoroethylene powder were fluorinated. The vinylidene fluoride-based fluororesin overcoat paint added to have a predetermined content with respect to the vinylidene fluoride-based fluororesin, respectively, and to have a predetermined average particle size, respectively, to have a dry film thickness of 22 μm. Painted and dried at 250 ° C. For comparison, a topcoat of vinylidene fluoride-based fluororesin and a topcoat of enamel-based resin without additives were added to the above-mentioned undercoat, respectively. Coating was performed on the membrane in the same manner as above. Table 1 shows the coating compositions of Example 1 of the present invention and Comparative Examples according to the conventional method.

[0023]

[Table 1]

(Note) 1) The specifications of the metal plate are as follows. GT: Hot-dip zinc 5% Al-plated steel sheet (sheet thickness: 0.35 m
m, one surface coating weight: 140g / m ²⁾ GI: hot-dip galvanized steel sheet (sheet thickness: 0.35 mm, one surface coating weight: 140g / m ²⁾ GS: molten zinc 55% Al-1.6% Si-plated Steel plate (thickness: 0.35 mm, coating weight on one side: 75 g / m
² ) 2) PAN beads (polyacrylonitrile beads) 3) Polytetrafluoroethylene 4) Formulations A to G of the top coating composition containing an inorganic aggregate are as follows. A: 5 parts by weight of glass beads having an average particle size of 12 μm was added. B: 20 parts by weight of glass beads having an average particle size of 12 μm were added. C: 10 parts by weight of a fibrous ceramic having an average particle size of 3 μm and a length of 30 μm was added. D: 20 parts by weight of ceramic beads having an average particle size of 2 μm were added. E: 5 parts by weight of glass beads having an average particle diameter of 12 μm and 5 parts by weight of a fibrous ceramic having an average particle diameter of 3 μm and a length of 30 μm were added. F: 5 parts by weight of glass beads having an average particle size of 12 μm and 5 parts by weight of ceramic beads having an average particle size of 2 μm were added. G: 10 parts by weight of a fibrous ceramic having an average particle diameter of 3 μm and a length of 30 μm and 1 ceramic bead having an average particle diameter of 2 μm
0 parts by weight added. H: 45 parts by weight of glass beads having an average particle size of 12 μm were added. I: 5 parts by weight of glass beads having an average particle size of 25 μm were added. J: A glass fiber having an average particle size of 13 μm and a length of 35 μm
Add by weight. K: Inorganic aggregate, organic aggregate, no PTFE powder added (enamel paint). 5) Indicated in parts by weight. 6) r: average particle size, T: coating thickness 7) unit: μm

(Evaluation) The following characteristics were evaluated for the coated steel sheet prepared as described above. Table 2 shows the test results.

(1) Evaluation of Coating Adhesion 0 to 10 t in a room at 20 ° C. so that the coating is on the outside.
(T: thickness of the material) is sequentially bent at 180 degrees, and each time the adhesiveness of the bent portion is evaluated by a coating film peeling test using a pressure-sensitive adhesive tape. The symbol ◎ indicates that no coating occurred, the symbol ○ indicates that the coating was separated at 2t, the symbol △ indicates that the coating was stripped at 3t, and the symbol indicates that the coating was stripped at 4t. It evaluated by x. In addition, the use of building materials is required to have a symbol of “記号” or more in this evaluation.

(2) Evaluation of moisture resistance The test was performed for 3000 hours under the test conditions of a temperature of 70 ° C. and a relative humidity of 98% in accordance with JIS K 2246. As a result, those with no swelling of the coating film on the flat portion were evaluated with a symbol ◎, and those with swelling of the coating film were evaluated with a symbol x.

(3) Evaluation of processability In a room at 20 ° C., 1 to 10 t
The 80-degree bending process was sequentially performed, and the state of crack generation at the bent portion was observed with a stereoscopic microscope (magnification: 30 times). If no bending occurred even when the bending process was 0 to 4 t, the symbol ◎ indicates that a crack occurred at 5 t. With the symbol ○,
When a crack occurred at 6t, the symbol △ was used, and when a crack occurred at 7t, the symbol × was used. In addition, the use of building materials is required to have a symbol of “記号” or more in this evaluation.

(4) Evaluation of Scratch Resistance In a room at 20 ° C., the surface of the coating film was scratched with a 10-yen coin having no cracks with a pressing force such that the scratch reached the undercoat film, and then the exposed state of the undercoat film was observed. The undercoating film is not exposed by the symbol ◎, the undercoating film having an exposed area of less than 30% is represented by the symbol ○, and the undercoating film having the exposed area of 30 to 50% is represented by the symbol 、. Those with more than 50% were evaluated with the symbol x. In addition, the use of building materials is required to have a symbol of “記号” or more in this evaluation.

(5) Evaluation of scratch resistance Clemens type scratch paint hardness tester (Toyo Seiki Co., Ltd.)
) At room temperature of 20 ° C. to form a coating having a tip diameter of 125.
Scratch resistance with a diamond needle of μm until the plating layer of the base steel sheet is exposed (Since the minimum load of the weight is 50 g, for example, when the plating layer of the base steel sheet is exposed with a load of 500 g, The evaluation was 450 g), and the load was evaluated.

(6) Evaluation of anti-galling property of coating film A coated steel plate having a size of 70 × 70 mm was bent in a room at 20 ° C. so that the coating film was on the outside and the radius of curvature was 5 mm, and both ends of the bent portion were bent. It was scraped off and used as a sliding test piece.
Next, the apex of the bent portion of the sliding test piece was brought into contact with the coating film surface of a flat plate test piece having a size of 70 × 90 mm attached to a fixing table and fixed. Then, the plate test piece was slid 50 times to the left and right (a distance of one reciprocation: 70 mm) with a load of 10 kg applied to the sliding test piece. The symbol ◎ indicates that the steel sheet (plating layer) is not exposed, the symbol を indicates that the exposed area is 10% or less of the whole, and the symbol を indicates that the exposed area is 11 to 30%.
Those exceeding 0% were evaluated with the symbol x. In this evaluation, the coating film whitening resistance was also evaluated at the same time, and those with almost no whitening observed on the coating film surface after the test were visually observed with a symbol ◎, and those with mild whitening were represented with a symbol ○. Was evaluated with a symbol を when the surface was conspicuous on the entire surface, and evaluated with a symbol X when the whitening significantly occurred on the entire surface. In addition, the use of building materials is required to have a symbol of “記号” or more in this evaluation.

(7) Evaluation of snow-sliding property 1 cc of water was dropped on the center of a coated steel plate having a size of 70 × 150 mm, and the height, width and height were 35 mm each thereon.
And placed in a freezer at −20 ° C. for 24 hours. After that, the painted steel sheet with frozen ice is taken out of the freezer and placed on a roof type model (cooled to 4 ° C) with a 30 ° inclination angle in a room at 20 ° C, and the time until the ice slides off the painted surface. (Retention time) was measured and evaluated. Also,
Similarly, the time (retention time) until the ice completely dropped from the center to the lowermost part of the coated steel sheet was measured and evaluated.

(8) Evaluation of weather resistance Accelerated weather resistance test was carried out for 5000 hours using a sunshine weather meter tester in which a black panel temperature was set to 80 ° C. in accordance with JIS A1415. The symbol ◎ indicates that lightness was observed and no peeling or blistering was observed, and the degree of color tone change was larger than that of the conventional aggregate-free enamel coating. Those in which at least one occurrence was observed were evaluated with the symbol x.

(9) Corrosion resistance evaluation Using a Clemens type scratch hardness tester, a load of 4
By scratching the coating film surface with a length of 50 mm at 50 g, a test piece was prepared in which the topcoat film, the undercoat film and the plating layer of the base steel plate were damaged. The depth of the scratch differs depending on the scratch resistance of the top coat and the undercoat. Thereafter, the coated steel sheet was immersed in a 1% sulfuric acid solution for 24 hours, and further subjected to 30 cycles of acid rain combined corrosion test (1 cycle: 0.1% NaCl corrosion liquid spray (temperature: 35 ° C., pH: 4 , Adjust the pH with sulfuric acid))
For 1 hour, then dried for 4 hours (temperature: 50 ° C.)
Next, after the sample was placed in a humid environment for 3 hours (temperature: 50 ° C., relative humidity: 98%), the swelling of the coating film generated from the scratched portion (one-side creep of the scratched portion) was measured. The symbol ◎ indicates that the coating film swelling did not occur from the damaged portion, and the symbol ○ indicates that the maximum coating swelling width was 0.5 mm or less.
Those having a diameter of 1.0 mm were evaluated with a symbol △, and those exceeding 1.0 mm were evaluated with a symbol x. Table 2 shows the evaluation results of Example 1 and Comparative Example by the conventional method.

[0035]

[Table 2]

(Note) 1) The specifications of the metal plate are as follows. GT: Hot-dip zinc 5% Al-plated steel sheet (sheet thickness: 0.35 m
m, one surface coating weight: 140g / m ²⁾ GI: hot-dip galvanized steel sheet (sheet thickness: 0.35 mm, one surface coating weight: 140g / m ²⁾ GS: molten zinc 55% Al-1.6% Si-plated Steel plate (thickness: 0.35 mm, coating weight on one side: 75 g / m
² ) 2) Ice falling start time (seconds) / time required for ice to fall to the bottom (seconds)

As shown in Table 2, the content and average particle size of each inorganic aggregate, PAN beads and polyvinylidene fluoride-based fluororesin to which polytetrafluoroethylene was added were defined as a predetermined range. In the painted test pieces, the evaluation results were ◎ for all of the coating film adhesion, moisture resistance, scratch resistance, scratch resistance, coating galling resistance, coating whitening resistance, and corrosion resistance. Regarding the properties, the evaluation results are ◎ to ○, which sufficiently satisfy the required level for building materials. On the other hand, in the topcoat paint containing only the inorganic aggregate or the topcoat paint without any additive, X was observed in regard to workability, coating galling resistance, coating whitening resistance, and corrosion resistance. Some materials do not meet the required standards for building materials. In addition, as for the snow sliding property, the test pieces of the top-coat paint to which the additives specified in the specified conditions were added were all the same as those in which the additives were not specified or those in which no additives were specified. It has excellent performance as described above.

[0038]

EXAMPLE 2 Ceramics in which 25 parts by weight of strontium chromate was added as a rust preventive to 100 parts by weight of non-volatile components and titanium oxide and silica were added as pigments to an epoxy resin having an average particle diameter of 2 μm. The undercoat paint containing 5 to 20 parts by weight of the inorganic aggregate of the beads with respect to 100 parts by weight of the epoxy resin is applied so as to have a dry film thickness of 5 μm, and then the top coat paint is applied in the same manner as in Example 1. Painted. For comparison, the epoxy resin to which the rust inhibitor and the pigment were added had an average particle size of 2 to 10 μm.
A test piece was prepared by applying an undercoat paint containing 5-45 parts by weight of the inorganic aggregate of the ceramic beads to 100 parts by weight of the epoxy resin to a dry film thickness of 5 μm. Thereafter, each coated steel sheet was evaluated in the same manner as in Example 1. Table 3 shows the coating composition of Example 2 and the comparative example by the conventional method, and Table 4 shows the test results of Example 2 and the comparative example by the conventional method.

[0039]

[Table 3]

(Note) 1) The specification of the metal plate is as follows. GT: Hot-dip zinc 5% Al-plated steel sheet (sheet thickness: 0.35 m
m, one surface coating weight: 140g / m ²⁾ GI: hot-dip galvanized steel sheet (sheet thickness: 0.35 mm, one surface coating weight: 140g / m ²⁾ GS: molten zinc 55% Al-1.6% Si-plated Steel plate (thickness: 0.35 mm, coating weight on one side: 75 g / m
² ) 2) Ceramic beads 3) Example 2 and Comparative Examples 1 and 2 were made of PTFE powder (polytetrafluoroethylene, average particle size: 5 μm, content 1 part by weight, r / T (particle size / coating thickness) : 0.23) was added. 4) Polyacrylonitrile beads (PAN beads) 5) Unit: μm 6) Shown in parts by weight. 7) r / T: radius / coating thickness 8) Formulation A, B, C, D, E, of top coat of inorganic aggregate
F, G, and K are as follows. A: 5 parts by weight of glass beads having an average particle size of 12 μm was added. B: 20 parts by weight of glass beads having an average particle size of 12 μm were added. C: 10 parts by weight of a fibrous ceramic having an average particle size of 3 μm and a length of 30 μm was added. D: 20 parts by weight of ceramic beads having an average particle size of 2 μm were added. E: 5 parts by weight of glass beads having an average particle diameter of 12 μm and 5 parts by weight of a fibrous ceramic having an average particle diameter of 3 μm and a length of 30 μm were added. F: 5 parts by weight of glass beads having an average particle size of 12 μm and 5 parts by weight of ceramic beads having an average particle size of 2 μm were added. G: 10 parts by weight of a fibrous ceramic having an average particle diameter of 3 μm and a length of 30 μm and 1 ceramic bead having an average particle diameter of 2 μm
0 parts by weight added. K: Inorganic aggregate, organic aggregate, no PTFE powder added (enamel paint).

[0041]

[Table 4]

(Note) 1) The specifications of the metal plate are as follows. GT: Hot-dip zinc 5% Al-plated steel sheet (sheet thickness: 0.35 m
m, one surface coating weight: 140g / m ²⁾ GI: hot-dip galvanized steel sheet (sheet thickness: 0.35 mm, one surface coating weight: 140g / m ²⁾ GS: molten zinc 55% Al-1.6% Si-plated Steel plate (thickness: 0.35 mm, coating weight on one side: 75 g / m
² ) 2) Ice falling start time (seconds) / time required for ice to fall to the bottom (seconds)

As shown in Table 4, in the test piece of the undercoat coating film in which the average particle size and the content of the inorganic aggregate of the ceramic beads were defined, the coating film adhesion, moisture resistance, scratch resistance, scratch resistance, All of the evaluation results were ◎, and the evaluation results were ◎ to ○ for all of the coating film galling resistance, the coating whitening resistance, and the corrosion resistance. ing. On the other hand, in the case of the topcoat paint containing only the inorganic aggregate and the topcoat paint without any additives, the workability, the galling resistance of the coating film, the whitening resistance of the coating film, and the corrosion resistance are unsatisfactory.
And some of them did not meet the required standards for building materials. In addition, regarding the snow-slip property, the test piece of the top-coat paint containing the additives specified in the predetermined conditions is equal to or greater than those of the additives not specified or those without additives. Has excellent performance.

[0044]

As described above, according to the present invention, a vinylidene fluoride-based fluororesin is used as a matrix resin,
An overcoating material containing the ceramic inorganic aggregate, polyacrylonitrile beads, and the content of the fluororesin powder in an appropriate amount and with an appropriate average particle size is added thereto, and the average particle size of the content and the film thickness of the dried coating film are determined. So that the ratio of
A coated metal with excellent scratch resistance, coating resistance to galling, and snow slippage compared to conventional coatings by applying it on the undercoat coating on a metal plate, heating and drying in an appropriate temperature range to form a coating. A plate can be obtained.

Further, a proper amount of a ceramic inorganic aggregate having an optimized average particle size is contained in the undercoat film,
And if the undercoat is formed such that the ratio of the average particle size of the inorganic aggregate and the thickness of the undercoat after drying is within an appropriate range, the protrusion of the aggregate from the overcoat is prevented. Thus, it is possible to obtain a coated metal plate which is sufficiently excellent in scratch resistance, coating film galling resistance and snow sliding property as compared with conventional ones.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B32B 15/08 B32B 15/08 G 102 102B (72) Inventor Katsuhisa Osaki 7th of Takayashinmachi, Ichikawa-shi, Chiba 1 Within Nisshin Steel Co., Ltd. Technical Research Laboratory (72) Inventor Hiroshi Enya 1-Nisshin Steel Co., Ltd. Technical Research Laboratory, 7-chome, Takayashinmachi, Ichikawa-shi, Chiba F-term (reference) 4D075 BB28Z CA02 CA09 DA06 DB01 DC01 DC10 EB16 EC05 EC13 EC24 4F100 AB01A AB03 AD00B AD00C AG00 AK17B AK18 AK19B AK19C AK27B AL01B BA02 BA03 BA07 BA10A BA10B CA24B CA24C CC00B DE01B DE01C DE04B DG01 EJ64 JA20 JK16 YY00 4J007 CD111 CG162 NA111

Claims (4)

[Claims] 1. A matrix resin comprising a vinylidene fluoride-based fluororesin, 1 to 40 parts by weight of a ceramic inorganic aggregate having an average particle diameter of 0.6 to 40 μm per 100 parts by weight of a matrix resin, and an average particle diameter of 0.1 to 40 parts by weight. 1 to 40 parts by weight of polyacrylonitrile beads of 6 to 40 μm per 100 parts by weight of the matrix resin, and an average particle diameter of 0.6 to 40 μm
A topcoat paint for a metal plate that imparts scratch resistance, coating resistance to galling, and snow-slidability, containing 0.1 to 20 parts by weight of a fluororesin powder of 100 m per 100 parts by weight of a matrix resin. 2. A vinylidene fluoride-based fluororesin
Resin and the average particle size (r₁) 0.6-40 μm
100 parts by weight of matrix resin with ceramic inorganic aggregate
1 to 40 parts by weight with respect to the average particle size (r_Two) 0.6-4
0 μm polyacrylonitrile beads were added
1 to 40 parts by weight per 100 parts by weight of fat, and average grain
Diameter (r_Three) 0.6 to 40 µm fluororesin powder
0.1 to 20 parts by weight per 100 parts by weight of resin
Film thickness (T ₁) Is 0.04 ≦ r₁/ T₁≦ 1.0, 0.04 ≦ r_Two/ T₁≦ 1.0, 0.04 ≦ r_Three/ T₁≦ 1.0, painted on a metal plate and the matrix resin
Bake by heating at a temperature sufficient for a sufficient time to form a film
Scratch resistance, characterized by drying and film formation
Surface treatment of metal sheet to provide galling resistance and snow sliding resistance
Method. 3. A coated metal plate having a chemical conversion coating, an undercoat, and an overcoat on a metal surface, wherein the overcoat uses a vinylidene fluoride-based fluororesin as a matrix resin, and comprises a ceramic. 1 to 40 parts by weight based on 100 parts by weight of matrix resin, 1 to 40 parts by weight of polyacrylonitrile beads per 100 parts by weight of matrix resin, and 0 to 40 parts by weight of fluororesin powder relative to 100 parts by weight of matrix resin. 0.1 to 20 parts by weight, and the average particle size (r ₄ ) and the thickness of the overcoat film (T ₁ ) of the ceramic-based inorganic aggregate, polyacrylonitrile beads and fluororesin powder are 0.04 ≦ r ₄ / T A coated metal sheet excellent in scratch resistance, coating film galling resistance and snow sliding property, wherein ₁ ≦ 1.0. 4. The undercoating film contains a ceramic inorganic aggregate, the content of which is 1 to 40 parts by weight based on 100 parts by weight of a matrix resin, and the average particle size of the ceramic inorganic aggregate (r ₅ ) And the thickness of the undercoating film (T ₂ ) are 0.05
≦ r ₅ / T ₂ ≦ 1.0, The coated metal sheet excellent in scratch resistance, coating galling resistance and snow sliding property according to claim 3, characterized in that: ≦ r ₅ / T ₂ ≦ 1.0.