JPH08183926A - Coating composition excellent in scratch resistance, stain resistance, and durability and metal plate coated therewith - Google Patents

Abstract

PURPOSE: To obtain the composition free from the breaking of the base resin and the detachment of the aggregates, excellent in scratch resistance and abrasion resistance due to the high film hardness of 9H or higher as pencil hardness, and also excellent in processability, impact resistance, and durability such as weathering resistance, and staining resistance. CONSTITUTION: This coating composition comprises, as the major component, on a solid basis, a vehicle composed of 50 to 75 pts.wt. of an acrylic resin with a hydroxyl value ranging from 60 to 110mgKOH/g and a glass transition temperature ranging from 70 to 110 deg.C and 50 to 25 pts.wt. of a melamine resin, and inorganic aggregates with an average particle diameter ranging from 3 to 30μm at 5 to 60 pts.wt. based on 100 pts.wt. of the solid content of the vehicle. The inorganic aggregates are preferably at least one kind of inorganic fine powder selected from fused alumina and glass beads. The other objective coated metal plate has on at least one side thereof a chemically treated film, on which there is an undercoating film, on which there is a coating film obtained by application and baking of the coating composition.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention provides a coating film having extremely high hardness, excellent scratch resistance and abrasion resistance as well as excellent stain resistance, chemical resistance, impact resistance and weather resistance. The present invention relates to a coating composition and a coated metal plate coated with this coating composition, and in particular, when applied to building materials used for building exterior walls, roads, tunnels, and other structures, it is damaged by wind and sand, exhaust gas, etc. The present invention relates to a coating composition and a coated metal plate having durability for a long period of time against stains, stains, chemical erosion due to NOx, SOx, and the like.

[0002]

2. Description of the Related Art In recent years, coated metal plates used for roofing materials and exterior wall materials for buildings, interior and exterior wall materials for buildings, etc. Higher performance has been achieved by improving corrosion resistance and weather resistance. In addition, the design characteristics such as color tone and luster are pursued from the consideration of matching the appearance of buildings with the local environment. Problems such as the above-mentioned stain resistance, corrosion resistance, weather resistance, etc. are scratches of the coating film that occurs during the transportation and processing of the coated metal plate, abrasion and scratches of the coating film due to wind sand after construction, etc. Deposition of pollutants. For this reason, recently, there is an increasing need for higher hardness of the coating film surface. For example, a conventional pencil hardness of 9H or more is required in a place where the pencil hardness is 5H or more, or where the coating film is severely scratched. The hardness that could not be obtained is now required.

As one measure to meet such demands, there has been proposed a method of electron beam curing an acrylic resin coating material, which is easy to obtain a coating film having a high hardness, to make it highly crosslinked (for example, JP-B-55). -5422, Japanese Patent Publication No. 56-
No. 8070, Japanese Patent Publication No. 1-229622, Japanese Patent Publication No. 2-242863). However, since this electron beam curing method cures the paint in the electron beam irradiation equipment, it is difficult to continuously treat the metal plate, and the oxygen concentration in the electron beam irradiation atmosphere must be controlled. There are many disadvantages to line production, and there are major problems in productivity and production costs. Also, in terms of coating film performance, the coating film cured by electron beam is inferior in flexibility, so that there is a problem in workability and impact resistance when bounced stones collide, and inferior in weather resistance. Therefore, it has a drawback that it is not suitable for outdoor use.

As another measure, a method of continuously photopolymerizing a photocurable resin to continuously obtain a coating film having a high hardness has been proposed (Japanese Patent Publication No. 3-261551).
Compared with the bake-curing method, this method has a significantly higher equipment cost, and since the coating material is also expensive, the production cost is high and the productivity is low. Further, the coating performance itself is inferior in flexibility as in the coating by the electron beam curing method, and is also inferior in workability and impact resistance.

On the other hand, many attempts have been made so far to meet the above requirements by the bake hardening method which is advantageous in terms of productivity and production cost. Most of these are intended to increase the hardness and improve the performance by adding an aggregate to the coating film. For example, Japanese Patent Publication No.
Publication, Japanese Patent Publication No. 51-8128, Japanese Patent Publication No. 56-4
In Japanese Patent No. 0544, Japanese Patent Publication No. 59-210980, Japanese Patent Publication No. 63-5938, and Japanese Patent Publication No. 4-11671, glass fibers and glass beads are added to the uppermost coating film to improve the hardness of the coating film. There is disclosed a technique for enhancing the scratch resistance and abrasion resistance, and treating these additives with a silane coupling agent, which have poor adhesion to a coating film due to the smooth surface, with a silane coupling agent to compensate for the defects. There is.

[0006]

However, in these conventionally proposed coating films, the strength of the base resin is insufficient with respect to the aggregate or glass beads to be added, so that the coating film is rubbed with a hard object. If this happens, the base resin will be destroyed, resulting in the problem that the aggregate falls off from the coating film. Further, as the amount of aggregate in the coating film increases, defects in the resin such as voids and cracks increase, so that the addition of the aggregate conversely decreases the scratch resistance. Further, since dirt and corrosive substances are accumulated in the aggregate dropout portion, there is a problem that this defective portion is easily exposed. Therefore, in the conventional bake-hardening method, there is a limit in increasing the hardness of the coating film by adding the aggregate, and the coating film hardness (pencil hardness) is at most 5H.
However, the coated metal plate having a coating film hardness of 9H or higher could not be obtained.

Therefore, an object of the present invention is to provide a coating composition in which the coating film is made to have a high hardness by containing an aggregate, without causing destruction of the base resin or dropping of the aggregate.
Moreover, a coating composition having excellent scratch resistance and abrasion resistance by obtaining a high coating hardness of 9H or more in pencil hardness, and further excellent in durability such as processability, impact resistance, weather resistance and stain resistance. And to provide a coated metal plate coated with this coating composition.

[0008]

[MEANS FOR SOLVING THE PROBLEMS] From the viewpoint of scratch resistance and abrasion resistance, the coating film of a coated metal plate must have sufficient strength and hardness so that the resin constituting the coating film can hold the aggregate. In addition, it is necessary to have both durability such as weather resistance, corrosion resistance, chemical resistance and stain resistance.
Further, it must be stable as a paint and excellent in paintability and bake hardenability.

As a result of examining a resin having these characteristics,
Optimizing the strength and hardness of the resin constituting the coating film by using as a main component a color-developing agent in which an acrylic resin having a specific hydroxyl value and a glass transition temperature and a melamine resin are blended in a specific ratio. And, by limiting the average particle size and content of the inorganic aggregate contained therein to a specific range, scratch resistance, stain resistance, durability, flexibility,
It was found that the paintability and bake hardenability can be maximized.

The structure of the present invention based on such knowledge is as follows. (1) As a solid content, the hydroxyl value is 60 to 110 mg KOH
/ G, a glass transition temperature of 70-110 ℃ 50-75 parts by weight of an acrylic resin and 50-25 parts by weight of a melamine resin as a main component, and an average particle size of 3-30μ
m inorganic aggregate to 5 parts by weight per 100 parts by weight of the solid content of the color spreader
A coating composition containing 60 to 60 parts by weight.

(2) The coating composition according to claim 1, wherein the inorganic aggregate is one or more kinds of inorganic fine powder selected from fused alumina and glass beads. (3) At least one surface of the metal plate has a chemical conversion treatment film, has an undercoat coating film on its upper layer, and further coating and baking the coating composition of (1) or (2) on its upper layer. A coated metal plate having a coating film obtained by the above.

[0012]

The details and reasons for limitation of the present invention will be described below. In the coating composition of the present invention, the main components of the color-developing agent are an acrylic resin having a specific hydroxyl value and a glass transition temperature and a melamine resin. An acrylic resin can react with a melamine resin to form a very high-hardness crosslinked structure, and such an acrylic resin has a hydroxyl group in a side chain or a hydroxyl group and a carboxyl group in a side chain. It is necessary.

For introducing a hydroxyl group into the acrylic resin,
As the acrylic monomer having a hydroxyl group, for example,
Hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, N-
Examples include methylol acrylic amine. Further, for introducing a carboxyl group into the acrylic resin, as the acrylic monomer having a carboxyl group, for example,
Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, and substituted derivatives thereof.

Further, as an acrylic monomer to be copolymerized with the above-mentioned acrylic monomer containing a hydroxyl group or a carboxyl group in order to form a crosslink structure having an extremely high hardness, for example, (meth) acrylic Methyl acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n- (meth) acrylate
Butyl, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, isobornyl (meth) acrylate, etc. And (meth) acrylic acid alkyl ester type ethylenic monomers, ethylenic monomers copolymerizable with these monomers, and (meth) acrylonitrile and styrene.

In the production of the acrylic resin of the present invention, for example, a mixture of each component of the acrylic monomer and a radical polymerization initiator is dropped into a heated organic solvent over a predetermined period of time and then kept constant for a predetermined period of time. By maintaining the temperature, the radical polymerization reaction can be carried out to obtain an acrylic resin having a desired composition. Acrylic resin has a hydroxyl value of 60-110
It is necessary that mgKOH / g and the glass transition temperature are in the range of 70 to 110 ° C. When the hydroxyl value of the acrylic resin is less than 60 mgKOH / g, the strength and hardness of the coating film are insufficient because the crosslink density of the coating film is low, while when the hydroxyl value exceeds 110 mgKOH / g, the flexibility of the coating film is low. Results in poor impact resistance, inferior bake hardenability, and unreacted groups remain in the coating film even after curing, resulting in poor durability such as chemical resistance and corrosion resistance.

The acrylic resin has a glass transition temperature of 7
If the temperature is lower than 0 ° C, the strength and hardness of the coating film are insufficient. On the other hand, if the glass transition temperature exceeds 110 ° C, the flexibility of the coating film is inferior and the impact resistance is insufficient, and the coating property and baking are not sufficient. It is also inferior in curability. Furthermore, the acrylic resin has a number average molecular weight of 3
The range of 000 to 10,000 is particularly preferable. When the number average molecular weight is less than 3,000, bake hardenability is poor and the coating film hardness tends to be insufficient, while the number average molecular weight is 1
When it exceeds 0000, the resin becomes difficult to dissolve in the solvent, and the coating solid content becomes low, resulting in poor coatability.

The melamine resin is an alkyl etherified melamine obtained by reacting melamine with formaldehyde, and then using a monohydric alcohol such as methanol, ethanol, propanol or butanol, and etherifying some or all of the methylol groups. is there. As the melamine resin, a methylated melamine resin, a butylated melamine resin, and a methylated-butylated mixed melamine resin are particularly suitable.

The coating composition of the present invention comprises the above acrylic resin (A) and melamine resin (B) as the main components of the color-developing agent.
As solids, (A): 50-75 parts by weight and (B): 5
0 to 25 parts by weight, particularly preferably (A): 60 to 70 parts by weight and (B): 40 to 30 parts by weight.
When the amount of the component (B) is less than 25 parts by weight, the coating film hardness is insufficient, and the chemical resistance and stain resistance are poor. On the other hand, when the amount of the component (B) exceeds 50 parts by weight, the flexibility is poor. There is a problem with impact resistance.

In the present invention, an inorganic aggregate is added to the resin composition in order to secure excellent scratch resistance and abrasion resistance which cannot be obtained only by the resin component. As the inorganic aggregate, ceramic aggregate or glass aggregate can be used. The ceramic aggregate may have any shape such as a granular shape or a fibrous shape. For example, one kind or two or more kinds of aggregates made of silica, titania, alumina, zirconia or a composite material thereof can be used. As the glass aggregate, soda lime-based, borosilicate-based, alumina-silica-based glass beads or the like can be used. Among these inorganic aggregates, fused alumina and glass beads are most preferable in terms of durability of the aggregate itself and hardness balance with the resin forming the coating film. Further, in order to improve the wettability and adhesion with the coating film, the inorganic aggregate may be subjected to a surface treatment such as a silane coupling agent treatment or a titanium coupling agent treatment.

The particle size of the inorganic aggregate is 3 to 30 μm in average particle size. If the average particle size is less than 3 μm, the aggregate is barely exposed on the surface of the coating film, so the effect of improving scratch resistance is small, while if the average particle size exceeds 30 μm, the dispersibility in the paint is poor and Since the material tends to settle in the paint, poor coating is likely to occur. The amount of the inorganic aggregate added is 5 to 60 parts by weight based on 100 parts by weight of the solid content of the color developing agent. If the addition amount of the inorganic aggregate is less than 5 parts by weight, the scratch resistance and abrasion resistance are insufficient, while if the addition amount exceeds 60 parts by weight, the flowability of the coating material is deteriorated and the coating workability is hindered. ,
It reduces the flexibility of the coating film. From the above viewpoints, the more preferable addition amount of the inorganic aggregate is 5 to 30 parts by weight.

Next, a coated metal plate coated with the above-mentioned coating composition will be described. The coated metal plate used in the coated metal plate of the present invention, cold rolled steel plate, stainless steel plate,
In addition to aluminum plates, copper plates, etc., various metal plates such as zinc, zinc alloys, plated steel plates plated with aluminum, chromium, nickel or these alloys can be used.
A chemical conversion treatment film is formed on the surface of the metal plate in order to ensure adhesion with the coating film. The chemical conversion coating may be formed by a pre-coating treatment suitable for each metal plate, such as coating or spraying with a chromate, a phosphate or a silane coupling agent, or an acid such as phosphoric acid, nitric acid or hydrofluoric acid or an alkali. In addition to those formed by activation treatment or the like, those formed by electrolytic treatment may be used.

An undercoating film is formed on the upper layer of the above chemical conversion treatment film, and an overcoating film formed by applying and baking the coating composition of the present invention on the upper layer is formed. The undercoating film is formed in order to enhance the adhesion between the metal plate and the topcoating film, or to improve durability and impact resistance in a special environment such as high humidity. As the undercoating film, lacquer-based or oil-based undercoating paints can be used. For synthetic resin-based paints, in addition to epoxy resin-based paints, generally used undercoating paints such as urethane resin-based paints and polyester resin-based paints are used. be able to.

Further, when high corrosion resistance and coating adhesion are required, it is preferable to add a chromate compound as a rust preventive pigment in the undercoat coating. As chromate compounds, zinc chromate, strontium chromate, calcium chromate, barium chromate and the like are preferable, and the content thereof is 1 to 60 of the solid content in the coating film.
It is suitable to set it in the range of% by weight. Further, the dry coating film thickness of the undercoat film is 5 to 20 in order to obtain the above-mentioned effects.
It is preferably about μm.

The top coating film is formed by applying the above-mentioned coating composition and then baking it. The dry coating film thickness of the top coating film is preferably 15 to 50 μm. When the coating film thickness is less than 15 μm, the hard coating film layer becomes thin, and durability such as abrasion resistance, corrosion resistance, and weather resistance is deteriorated.
On the other hand, if the coating thickness exceeds 50 μm, the coating becomes brittle, and the coating adhesion and impact resistance are poor, and appearance defects such as foaming occur depending on the coating conditions. Further, more preferably, the thickness of the coating film is adjusted to 70 to 150% of the average particle diameter of the inorganic aggregate contained. In this range, the coating appearance is most beautiful and the coating film performance is the maximum. If the coating thickness is too small with respect to the average particle size of the aggregate, the aggregate is exposed to the coating surface to a large extent, resulting in poor smoothness of the coating film. If the value is too large, the aggregate sinks deeply into the coating film, so that the scratch resistance, abrasion resistance, etc. are reduced, and the coating film performance may be insufficient.

The baking treatment after applying the coating composition is, for example, 30 times in the case of performing short-time drying in a coil coating line.
It is preferable to perform the heating for about 180 seconds to reach the metal plate temperature of 220 to 300 ° C. If the temperature of the metal plate is less than 220 ° C, the drying and curing of the resin component is insufficient, while if it exceeds 300 ° C, thermal deterioration including the undercoat paint component begins. In addition, if the baking time is less than 30 seconds, the drying and curing of the resin component is insufficient, and since the curing speed of the resin exceeds the evaporation speed of the solvent, defects such as cracking occur in the coating film, and the appearance tends to deteriorate. If it exceeds 180 seconds, thermal deterioration including the components of the undercoating material will start, and in any case, the original performance of the coating material will not be exhibited, which is not preferable. In addition, when performing drying for a long time in a cutting plate coating line such as a post coat line, the metal plate temperature is 150 to
It is preferable to hold at 240 ° C. for 10 to 30 minutes. The reason is the same as in the case of short-time drying. There is no particular limitation on the heating method at the time of baking, and hot air heating method, high frequency heating method and the like can be applied.

In the above-mentioned top coating film and undercoat coating film, if necessary, a plasticizer, a desiccant, a dispersant, a curing catalyst,
A pigment or the like can be added, and it is effective to add an antioxidant especially when performing high temperature baking. Also,
As the pigment, in addition to various color pigments, an extender pigment and a rust preventive pigment can be added. The coating method is not particularly limited, and conventionally-used coating methods such as a roll coater method, a curtain flow coater method, and a spray method can be applied.

[0027]

[Example] A stainless steel plate or a hot-dip galvanized steel plate (each having a plate thickness of 0.5 mm) was subjected to a coating-type chromate treatment or a phosphate treatment, and then an epoxy resin-based paint (a product manufactured by NOF Corporation) as an undercoat paint. Name "pre-color WP-3"), followed by baking at an ultimate plate temperature of 190 ° C. and baking time of 40 seconds, and then applying a coating composition prepared as follows as a topcoat paint and baking ( Baking time: 90 seconds), the obtained coated metal plate was subjected to the following various tests. Tables 1 and 2 show the production conditions and characteristics of the acrylic resin copolymer used in the coating composition, and Tables 3 to 8
Table 9 to Table 13 show the composition of the coating composition, and Table 9 to Table 13 show the production conditions of the coated metal plates of the examples and the results of various tests.

[Production of Acrylic Resin Copolymer] Thermometer,
Into a four-necked flask equipped with a reflux condenser, a stirrer, a dropping funnel and a nitrogen gas introduction tube, 20 parts by weight of Solvesso # 100 and 10 parts by weight of n-butanol were charged under a nitrogen gas stream, and heated under reflux with stirring. In addition, a mixture of the monomer and the polymerization initiator having the compositions shown in Tables 1 and 2 (dropping component) 5
5 parts by weight was added dropwise at a constant rate from a dropping funnel over 24 hours. After the completion of the dropping, the mixture was kept under reflux for 2 hours, 15 parts by weight of Solvesso # 100 was added thereto, and the mixture was cooled, and then filtered through a 200-mesh wire mesh to obtain an acrylic resin having the characteristics shown in Table 1 and Table 2, respectively. Resin copolymer A-
Solutions 1 to A-8 were obtained. The number average molecular weight of each acrylic resin copolymer was measured by gel permeation chromatography using a calibration curve of standard polystyrene.

[Production of coating composition] A part of the acrylic resin copolymer and a part of the mixed solvent are mixed according to the blending ratios shown in Tables 3 to 8, and then titanium dioxide is added to obtain a uniform mixture. Particle size 10μm using an attritor
Dispersed below. Furthermore, after adding the remainder of the acrylic resin copolymer, the melamine resin and the acid catalyst and adding and mixing the inorganic aggregate with stirring, the remaining mixed solvent is appropriately added to adjust the viscosity to Ford Cup No. 4 to 120 ± 10 seconds (25 ° C.), and the coating composition T- shown in Tables 3 to 8
1 to T-22 were obtained. In Tables 3 to 8, T-
1 to T-12 are coating compositions of the present invention, and T-13
-T-22 are coating compositions of comparative examples.

[Test / Evaluation Method] (1) Pencil Hardness Test According to the method of JIS-K 5400, 8.4.1 (1993), the scratch resistance of a coating film was measured by changing the hardness of the pencil lead. The coating was examined for scratches, and the highest hardness at which no scratch was found on the coating was defined as the pencil hardness of the coating. Pencil hardness is 9H in this test
The above-mentioned items were regarded as pass, and those of less than 9H were regarded as fail. (2) Abrasion resistance test (Taber method) According to JIS-K 5400, 8.9 (1993) method, the sample was 9.8.
A wear loss (mg) was measured when the CS10 wear wheel was rotated 1000 times while applying a load of 1N. In this test, those with a wear loss of 30 mg or less were accepted, and those with an abrasion loss of more than 30 mg were rejected.

(3) Coating film adhesion test (cross-cut tape method) According to the method of JIS-K 5400, 8.5.2 (1993), 1 mm was applied to the test piece coating film using a cutter knife in a room at 20 ° C.
After making a grid of 10 × 10 squares and firmly sticking the adhesive tape on the grid, immediately peel off the adhesive tape from the coating surface immediately, and leave the remaining grid of the coating without peeling. Adhesion was evaluated by the number. In this test, the number of cross-cuts remaining without peeling was 100, and the number of 99 or less was rejected.

(4) Impact deformation test (DuPont type) The method of JIS-K 5400, 8.3.2 (1993) is applied and a weight of 500 is applied.
Under the conditions of g and height of 50 cm, the test piece was tested with the coating surface facing upward and downward, and evaluated according to the following criteria. ⊚: No peeling of adhesive tape (pass) ◯: Adhesive tape peeling area is 10% or less (pass) Δ: Adhesive tape peeling area exceeds 10% and less than 50% (fail) ×: Adhesive tape peeling area 50% or more (fail)

(5) Chemical resistance test According to the method of JIS-A 5707, 1% aqueous 5% nitric acid solution, 5% aqueous sulfuric acid solution and 5% aqueous sodium hydroxide solution were applied on the coating film.
After being dropped in ml, the mixture was allowed to stand in a thermo-hygrostat at 20 ° C. and 50 RH% for 24 hours, washed with water and dried, and the change in the coating film surface was visually observed and evaluated according to the following criteria. ◯: No change at all on the coating surface (pass) Δ: Slight discoloration or swelling is recognized on the coating surface (fail) X: Clear discoloration, swelling or peeling is recognized on the coating surface (fail)

(6) Carbon Contamination Resistance Test 1 ml of a dispersion of carbon black / water = 5/95 (weight ratio) was placed on the coating film and left in a constant temperature and humidity room at 20 ° C. and 50 RH% for 24 hours. Then, it was washed with water, and the degree of discoloration on the surface of the coating film on which the dispersion liquid was placed was visually observed and evaluated according to the following criteria. ◎: No traces (pass) ○: Slight traces are recognized (pass) △: Marks are slightly conspicuous (fail) X: Dark traces remain (fail) (7) Accelerated weathering test (Sunshine carbon Arc lamp type) According to the method of JIS-K 5400 9.8.1 (1993), the gloss retention rate (%) of the coating surface after 2,000 hours of sunshine weatherometer is evaluated, and 80% or more passes. , Less than 80% was rejected.

As is clear from the results of the above examples,
The coated metal plates of Comparative Examples 1 to 10, which are out of the conditions of the present invention,
Fails in any of the coating hardness, impact resistance and other properties. On the other hand, the paint metal sheets of Examples 1 to 14 of the present invention all have a coating film hardness of 9H or more and are excellent in all properties including impact resistance. Further, among them, in particular, Examples 1 to 3 of the present invention using only fused alumina, glass beads or a mixture thereof as the inorganic aggregate.
Particularly excellent wear resistance was obtained in Nos. 5, 8, and 10-12.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

[Table 7]

[0043]

[Table 8]

[0044]

[Table 9]

[0045]

[Table 10]

[0046]

[Table 11]

[0047]

[Table 12]

[0048]

[Table 13]

Note that * 1 to * 6 in Tables 3 to 8 indicate the following contents. * 1: Melamine resin manufactured by Mitsui Cyanamide Co., Ltd., trade name "Cymel 212" (nonvolatile content 100 wt%) * 2: Melamine resin manufactured by Mitsui Cyanamide Co., Ltd., trade name "Cymel 254" (nonvolatile content 80 wt%) * 3: Butyl cellosolve / isophorone = 1/1 * 4: Titanium dioxide manufactured by Ishihara Sangyo Co., Ltd., trade name “Taipec CR93” * 5: 20 wt% solution of p-toluenesulfonic acid * 6: GA; glass beads (( Made by Union Co., Ltd. Product name "SPM
-20 ", average particle size 22 μm AL: fused alumina (trade name" White Morundum WA # 2500 "manufactured by Fujimi Polishing Industry Co., Ltd., average particle size 5 μm)
m) MI; mica (product name “WG manufactured by English Mica”)
-1000 ", average particle size 10 µm) SI; Silicic anhydride (trade name" Cyloid 244 "manufactured by Fuji Divison Co., average particle size 3 µm) PT: Potassium titanate fiber (fiber length 10 to 30 µm, fiber diameter 0.5 to 2.0 μm, manufactured by Kubota Iron Works Co., Ltd. GB; Glass beads (manufactured by Union Co., Ltd.)
-30 ", average particle size 30 µm) SA; nepheline syenite powder (trade name" MINEX-4 white powder "manufactured by Indusmin, average particle size 2.3 µm) GC; glass beads (trade name" manufactured by Union Corporation " SPM
-40 ", average particle diameter 41 μm)

Further, * 1 to * 3 in Tables 9 to 13 indicate the following contents. * 1: Kind of metal plate SUS; SUS304 stainless steel plate GI; Hot dip galvanized steel plate (coating amount; Z-25) * 2: Kind of chemical conversion treatment Cr; Coating chromate treatment P; Zinc phosphate treatment * 3: Reach Plate temperature

[0051]

As described above, according to the coating composition of the present invention, the base resin is not destroyed and the aggregate is not dropped, and the coating film hardness as high as 9H or more in pencil hardness is obtained, so that it is scratch-resistant. It is possible to obtain a coating film having excellent properties and abrasion resistance as well as excellent processability, impact resistance, weather resistance and other durability, chemical resistance and stain resistance. Therefore, the coated metal sheet of the present invention exhibits excellent scratch resistance, durability, stain resistance and the like as a material for exterior building materials, tunnel interior boards and the like.

Front Page Continuation (72) Inventor Ryoji Okamura 2-33, Enzo, Chigasaki City, Kanagawa Prefecture (72) Inventor Yoshitomo Takeuchi 2130 Kamikurata Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture (72) Inventor Tomohiro Mizukami Yokohama City, Kanagawa Prefecture 4-36 Nakazato, Minami-ku

Claims (3)

[Claims] 1. A hydroxyl value of 60 to 110 as a solid content.
50 to 75 parts by weight of an acrylic resin having a mgKOH / g and a glass transition temperature of 70 to 110 ° C. and a melamine resin of 50 to 25
A coating composition comprising a color-developing agent as a main component, and an inorganic aggregate having an average particle size of 3 to 30 μm in an amount of 5 to 60 parts by weight based on 100 parts by weight of the solid content of the color-developing agent. . 2. The coating composition according to claim 1, wherein the inorganic aggregate is at least one kind of inorganic fine powder selected from fused alumina and glass beads. 3. A metal plate having a chemical conversion treatment film on at least one surface thereof, an undercoating film as an upper layer thereof, and the coating composition according to claim 1 or 2 applied and baked on the upper layer thereof. A coated metal plate having a coating film obtained by the above.