JPH07233337A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain a coating composition useful for coating galvanized steel, excellent in corrosion resistance by allowing to contain a chromate based anticor rosive pigment and a phosphate pigment in a specific ratio based on a solid component of a coating forming resin. CONSTITUTION:This composition contains (A) 10-100 pts.wt. preferably 30 80 pts.wt. chromate based anticorrosive pigment (preferably, a combination of strontium chromate and zinc chromate, or one of strontium chromate and barium chromate and (B) 5-50 pts.wt., preferably 15-40 pts.wt. phosphate pigment (preferably, at least one of zinc phosphate, aluminum phosphate and calcium phosphate) based on 100 pts.wt. solid resin component in a coating forming resin (e.g., an epoxy resin, an epoxy-urethane resin, a polyester resin, etc. preferably a combination of the polyester resin and amino resin). Here, the total pigment is preferably 60-180pts. based on 100pts. resin solid component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition and a coated steel sheet using the same, and more particularly, to a coating composition effective for improving corrosion resistance, particularly corrosion resistance of an end surface of an object to be coated such as a steel sheet, and It relates to a coated steel sheet using the same.

[0002]

2. Description of the Related Art Conventionally, galvanized steel sheets such as galvanized steel sheets, aluminum-zinc alloy plated steel sheets, and aluminized steel sheets have been subjected to chemical conversion treatment such as phosphate treatment or chromate treatment. ,
Applying a primer, then applying a top coat paint on the primer coating film, as a so-called precoated steel plate,
Widely used for building roofing materials, wall materials, shutters, and various home appliances.

However, when the above-mentioned coated steel sheet is used in a corrosive environment such as outdoors, the coating film may blister at the cut end face portion or the like. The occurrence of blistering on the end face is remarkable especially in the aluminum-zinc alloy-plated steel sheet, and its solution has been a problem.

To solve this problem, for example, Japanese Patent Publication No. 2
No. 32355, a coating film-forming resin, an extender pigment, calcium chromate, and strontium chromate are mixed on a chromate-based chemical conversion-treated aluminum-zinc alloy-plated steel sheet, and an undercoat paint is applied on the resin. A coated steel sheet coated with a top coating is disclosed. In addition,
In No. 36384, a strontium chromate or calcium chromate is coated on the surface of the aluminum-zinc alloy-plated steel sheet subjected to chemical conversion treatment with an undercoat paint containing 30 to 70% by weight of the non-volatile content, and an overcoat paint is applied on this. A coated steel sheet is disclosed. In each of the coated steel sheets disclosed above, the corrosion resistance is improved to some extent, but the corrosion resistance of the end face portion (hereinafter, also referred to as “edge creep resistance”) is still insufficient. Therefore, the present inventors have conducted earnest studies to obtain a coating composition capable of improving the corrosion resistance of the above steel sheet, particularly the corrosion resistance of the end face portion, and a coated plate using this composition as a primer.

[0005]

As a result of the above research, the inventors of the present invention have found that by using a coating composition containing a specific amount of a chromate-based rust preventive pigment and a phosphate pigment, corrosion resistance, particularly end face part The present invention has been completed by finding out that the corrosion resistance of can be improved.

That is, the present invention provides the following coating composition and coated plate. 1. To 100 parts by weight of the resin solid content of the film-forming resin, (a) 10 to 100 parts by weight of a chromate-based rust preventive pigment and (b) 5 to 50 parts by weight of a phosphate pigment are contained. A characteristic coating composition. 2. (1) 30 to 80 parts by weight of a chromate-based rust preventive pigment, and (b) 15 to 40 parts by weight of a phosphate pigment, relative to 100 parts by weight of a resin solid content. The coating composition described. 3. 3. The coating composition according to item 1 or 2, wherein the pigment component contains a coloring pigment and / or an extender pigment in addition to (a) a chromate-based rust preventive pigment and (b) a phosphate pigment. . 4. The total pigment content is 60 with respect to 100 parts by weight of the resin solid content.
The coating composition according to any one of items 1 to 3, which is ˜180 parts by weight. 5. Item 5. The coating composition according to any one of Items 1 to 4, wherein the resin composition uses a polyester resin as a base resin. 6. The coating composition according to the above item 5, wherein the resin composition comprises a polyester resin and an amino resin. 7. (A) The chromate-based rust preventive pigment is at least one selected from strontium chromate, zinc chromate, and barium chromate.
The coating composition according to any one of 6 above. 8. Item 7. The chromate-based rust preventive pigment (a) is a combination of both strontium chromate and zinc chromate.
The coating composition described. 9. 8. The coating composition according to the above item 7, wherein the chromate-based anticorrosive pigment (a) is a combination of both strontium chromate and barium chromate. 10. (B) The phosphate pigment is at least one selected from zinc phosphate, aluminum phosphate, and calcium phosphate, and the coating composition according to any one of items 1 to 9 above. 11. 20 to 60 parts by weight of strontium chromate, zinc chromate and / or chromic acid as a pigment component, relative to 100 parts by weight of resin solid content of a resin consisting of 60 to 95 parts by weight of polyester resin and 5 to 40 parts by weight of amino resin. 10-40 parts by weight of barium, 15-40 parts by weight of at least one phosphate pigment selected from zinc phosphate, aluminum phosphate and calcium phosphate, 0-50 parts by weight of titanium white, and 0-50 parts by weight of extender pigment. The coating composition according to item 1, wherein the coating composition is contained and the total amount of all pigments is 60 to 180 parts by weight. 12. A coated plate comprising a coating film of the coating composition according to any one of items 1 to 11 formed on an aluminum-zinc alloy plated steel sheet. 13. The coated plate according to claim 12, wherein an overcoat coating film is formed on the coating film of the coating composition according to any one of claims 1 to 11.

[0007]

In the coating composition of the present invention, examples of the film-forming resin include resins usually used in the coating field. Specific examples include epoxy resin, epoxy-urethane resin, modified epoxy resin, phenoxy resin, acrylic resin, modified acrylic resin, polyester resin, modified polyester resin, alkyd resin, urethane resin, amino resin, phenol resin, and block isocyanate group-containing Resins, acid-modified polypropylene resins, chlorinated polyethylene, chlorinated polypropylene, vinyl chloride resins, chlorinated rubber resins and the like can be mentioned, and these can be used alone or as a mixture of two or more kinds. The coating film-forming resin may be thermosetting or thermoplastic, and may be a resin that is cured by an actinic ray such as ultraviolet rays.

When the film-forming resin in the composition of the present invention is used for precoating, epoxy resins and polyester resins of the above resins are used for crosslinking amino resins, isocyanate group-containing resins and phenol resins, respectively. It is preferable to use it in combination with a resin (curing agent), and among them, a combination of a polyester resin and an amino resin is preferable from the viewpoint of edge creep resistance.

Examples of the chromate-based rust preventive pigment (a) to be incorporated in the composition of the present invention include strontium chromate, zinc chromate, barium chromate, calcium chromate and the like, which have edge creep resistance. From the viewpoint, at least one selected from strontium chromate, zinc chromate, and barium chromate is particularly preferable, and among them, a combination of strontium chromate and zinc chromate and / or barium chromate is preferable.

Examples of the (b) phosphate pigment blended in the composition of the present invention include zinc phosphate, aluminum phosphate, calcium phosphate, magnesium phosphate, potassium phosphate, ammonium phosphate, barium phosphate and phosphoric acid. Sodium, chromium phosphate, manganese phosphate, boron phosphate,
Examples thereof include cobalt phosphate, zirconium phosphate, calcium ammonium phosphate, ammonium hydrogen phosphate, potassium hydrogen phosphate and the like. Of these, at least one selected from zinc phosphate, aluminum phosphate and calcium phosphate is particularly preferable.

In the composition of the present invention, the compounding amounts of the above (a) chromate-based rust preventive pigment and (b) phosphate pigment are
It is in the following range with respect to 100 parts by weight of the resin solid content of the film-forming resin. Component (a): 10 to 100 parts by weight, preferably 30 to 80 parts by weight, Component (b): 5 to 50 parts by weight, preferably 15 to 40 parts by weight. If the compounding amount of the component (a) is less than 10 parts by weight, the edge creep resistance is poor, while if it exceeds 100 parts by weight, blisters occur in the coating film part. If the amount of the component (b) is less than 5 parts by weight, the edge creep resistance is poor, and blister at the end face cannot be prevented. On the other hand, if it exceeds 50 parts by weight, the pigment precipitates in the paint and the gloss of the coating film decreases. Problem occurs.

The coating composition of the present invention has a pigment content of
In addition to the components (a) and (b), coloring pigments such as titanium white, phthalocyanine blue and carbon black, body pigments such as calcium carbonate, barium sulfate, clay, mica and silica powder, other than the components (a) and (b) Anti-rust pigments, etc. can be added as required. In this case, the sum of all pigments is 60 to 100 parts by weight of the resin solid content of the film-forming resin.
It is preferably in the range of 180 parts by weight from the viewpoint of the corrosion resistance, moisture resistance, workability and the like of the coating film.

In a particularly preferred embodiment of the composition of the present invention, the resin solid content of the resin is 60 to 95 parts by weight of polyester resin and 5 to 40 parts by weight of amino resin.
At least one selected from 20 to 60 parts by weight of strontium chromate, 10 to 40 parts by weight of zinc chromate and / or barium chromate, zinc phosphate, aluminum phosphate and calcium phosphate as a pigment component with respect to 0 part by weight. 15 to 40 parts by weight of phosphate pigment, 0 to 50 parts by weight of titanium white, and 0 to 50 parts by weight of extender pigment, and the sum of all pigments is 60 to 180 parts by weight. A coating composition can be mentioned.

The composition of the present invention comprises, in addition to the above-mentioned film-forming resin and pigment, if necessary, an organic solvent, water; an additive for paints such as an anti-settling agent, a pigment dispersant, a defoaming agent and a leveling agent; Curing catalyst; a neutralizing agent such as amine may be contained.

In the composition of the present invention, the mixing of each component is
It can be carried out by appropriately using the apparatus used for producing the paint. Examples of this apparatus include an attritor, a sand mill, a pebble mill, a paint shaker, a dissolver, a steel ball mill, a kneader, and a three-roll mill.

The coating composition of the present invention is a coating for metal plates such as steel plates, aluminum plates, and various plated steel plates such as galvanized steel plates, aluminum-zinc alloy plated steel plates, and aluminum plated steel plates, for example, one-coat finishing paint. It can be suitably used as an undercoat paint for 2 coat 2 bake finishing.

The coating of the composition of the present invention is carried out by degreasing a metal plate such as an aluminum-zinc alloy-plated steel sheet to be coated and subjecting it to chemical conversion treatment, and then coating the composition of the present invention thereon. You can As the chemical conversion treatment, phosphate treatment such as zinc phosphate treatment, chromate treatment,
Among chemical conversion treatments such as phosphoric acid-chromium treatment and composite oxide film treatment, a treatment suitable for each metal plate can be selected and performed. When the object to be coated is an aluminum-zinc alloy plated steel sheet, chromate treatment is usually suitable.

The coating composition of the present invention is applied by roll coating,
Known coating methods such as spray coating, brush coating, and dip coating can be used. In the case of precoating, roll coating is suitable for both coil coating and cutting board coating. When used as a precoat 1-coat paint or a paint for making a primer steel sheet, the dry film thickness is usually about 3 to 25 μm, preferably 5 to 20 μm, and when it is used as an undercoat paint for 2 coat 2 bake. ,Normal,
The dry coating thickness is about 2 to 10 .mu.m, preferably 3 to 8 .mu.m.

The baking condition of the coating composition of the present invention is that the maximum temperature (PMT) reached by the material is 80 to 240 ° C. and the baking time is 3
It is in the range of 0 minutes to 10 seconds, and in the precoat coating line, the PMT is usually 180 to 230 ° C. and the baking time is 6
The range of 0 to 15 seconds is preferable.

When the coating composition of the present invention is used as an undercoat for a two-coat, two-bake finish, examples of the overcoat to be applied on this undercoat include those commonly used in the paint field. You can As this top coating, alkyd resin, oil-free polyester resin, fluororesin, acrylic resin, silicone polyester resin,
Examples thereof include silicone acrylic resin and vinyl chloride resin-based paints. These paints may contain an amino resin such as a melamine resin, a polyisocyanate compound which may be blocked, and a chelate compound as a crosslinking agent.

The coating composition of the present invention comprises:
In addition to the undercoat paint for finishing the coat 2 bake, the undercoat paint for the 2 coat 1 bake, the undercoat paint for the 3 coat 3 bake, etc. can be effectively used for the purpose of being directly coated on the metal surface which may be subjected to the chemical conversion treatment.

The coating composition of the present invention exhibits a remarkable effect in improving the corrosion resistance, particularly the edge creep resistance, of a metal plate, particularly an aluminum-zinc alloy plated steel plate. Although the reason for this is not clear, the present inventors believe that the phosphate pigment controls the elution of chromium ions.

[0023]

The present invention will be described in more detail with reference to the following examples. Examples 1 to 12 and Comparative Examples 1 to 6 Each paint was prepared with the composition shown in Table 1 below. The quantities in Table 1 are expressed in parts by weight (solid content). When manufacturing each paint, mix the pigment with a part of the resin and solvent,
After the dispersion, the remaining resin was added and the viscosity was adjusted with a solvent to 70 seconds (Ford cup No. 4/25 ° C.) to obtain coating materials of Examples and Comparative Examples. As the solvent, a mixed solvent of [xylene / ethylene glycol monoethyl ether acetate / butanol = 5/3/2 (weight ratio)] was used.

[0024]

[Table 1]

[Note] in Table 1 has the following meanings. (Note 1): Product name "Byron 296", Toyobo Co., Ltd.
Made, solid content 40% by weight. (Note 2): Product name "Epicoat 1010", manufactured by Shell Chemical Co., solid content 35% by weight. (Note 3): Product name "Sumimar M-55", Sumitomo Chemical Co., Ltd., methylated melamine resin, solid content 70% by weight. (Note 4): Product name "Beckamine P-196-M", manufactured by Dainippon Ink and Chemicals, Inc., solid content 60% by weight. (Note 5): Trade name "Takenate B-870N", manufactured by Takeda Pharmaceutical Co., Ltd., solid content 60%.

The coating composition obtained in each of the above examples was applied to the following chemical conversion treated material with a bar coater so that the dry coating film weight would be 8 g / m ^2, and the maximum material temperature reached 220 ° C. and baking time Baking was performed under the condition of 30 seconds. Furthermore, an oil-free polyester-based paint KP Color 1580 Blue (manufactured by Kansai Paint Co., Ltd.) was applied on this coating film with a bar coater so that the dry coating film weight would be 15 g / m ^2, and the material reached the maximum. Baking was performed under the conditions of a temperature of 220 ° C. and a baking time of 45 seconds to obtain a test coated plate.

The chemical conversion treatment material thickness 0.4 mm, typically being commonly called "Galvalume", high aluminum aluminum content - zinc alloy plated steel sheet (. Aluminum content in the alloy plating is from about 55 wt%) to the coating Type Chromate Treatment "Cosmer 15
0 "(trade name, manufactured by Kansai Paint Co., Ltd.) in a dry coating amount of 1
What was coated so as to be 50 mg / m ² (abbreviated as “GL” in Table 3) 0.4 mm thick aluminum-zinc alloy plated steel plate with a low aluminum content, commonly called “Galfan” (Aluminum content in alloy plating is about 5% by weight
Is. ) "Cosmer 150" dry coating amount 150mg
What was coated so that it would be / m ² (in Table 3, "G
Abbreviated as "F". ). A hot-dip galvanized steel sheet having a thickness of 0.4 mm and treated with zinc phosphate (abbreviated as "HDG" in Table 3).

The test coated plates thus obtained were tested according to the following test method. The test results are shown in Table 3 below.

Gloss: JIS K-5400 7.6 (1
990), and the 60-degree specular reflectance was measured.

Workability: At a temperature of 20 ° C., the test plate was bent 180 ° with the coated surface facing outward (no bending of the inside of the bent portion without any pinching, OT bending), and then the bent portion. The cellophane adhesive tape was brought into close contact, and the tape was immediately peeled off, and the degree of peeling of the coating film at the bent portion was evaluated. The evaluation criteria are as follows. 5: No peeling 4: Less than 20% of the area of the bent portion peeled. 3: 20% or more and less than 40% of the bent area is peeled off. 2: 40% or more and less than 80% of the bent area is peeled off. 1: 80% or more of the bent area is peeled off.

Corrosion resistance: A test coated plate was cut into a size of 75 mm × 150 mm, three sides other than one side of 150 mm and the back surface were sealed with anticorrosive paint, and the unsealed side was cut to obtain a 70 mm × 150 mm piece. The size A cross cut is put in the center of this coated plate, and this coated plate is used as a test piece.
1,50 in salt spray test according to IS Z-2371
A 0 hour test was conducted. In the general department, the degree of blistering (the degree of blistering according to ASTM D714-87) was evaluated. In the cross-cut part and the cut end face part,
The maximum width of blisters or rust was visually evaluated. The width at the cross-cut portion was the width on one side from the cross-cut. The evaluation was performed according to Table 2 below.

[0032]

[Table 2]

Moisture resistance: JIS K5400 was used by using a test piece prepared in the same manner as the test piece used for the above corrosion resistance test.
A moisture resistance test was conducted according to 9.2.2. The temperature in the box was 49 ° C., and the test time was 1,500 hours. The evaluation was performed according to the same criteria as in the above corrosion resistance test.

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

The coating composition of the present invention is effective in improving the corrosion resistance of the object to be coated such as a steel plate, especially the corrosion resistance of the end face portion. A coated plate obtained by applying the composition of the present invention to an aluminum-zinc alloy-plated steel sheet, which has hitherto been a big problem in the corrosion resistance of the end surface portion, has good performance also in the corrosion resistance of the end surface portion.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B05D 7/14 101 A 7/24 302 V 7717-4D B32B 15/08 C09D 5/00 PPF 7 / 12 PSK 161/20 PHK 167/02 PKW

Claims (13)

[Claims] 1. A coating material having a resin solid content of 100 parts by weight, wherein (a) a chromate-based rust preventive pigment (10 to 100 parts by weight) and (b) a phosphate pigment (5 to 50 parts by weight). A coating composition comprising: 2. It is characterized by containing (a) 30 to 80 parts by weight of a chromate-based rust preventive pigment and (b) 15 to 40 parts by weight of a phosphate pigment with respect to 100 parts by weight of a resin solid content. The coating composition according to claim 1. 3. The pigment component contains a coloring pigment and / or an extender pigment in addition to (a) the chromate-based rust preventive pigment and (b) the phosphate pigment.
Or the coating composition according to 2. 4. The coating composition according to claim 1, wherein the total pigment content is 60 to 180 parts by weight with respect to 100 parts by weight of the resin solid content. 5. The coating composition according to claim 1, wherein the resin composition comprises a polyester resin as a base resin. 6. The coating composition according to claim 5, wherein the resin composition comprises a polyester resin and an amino resin. 7. The chromate-based rust preventive pigment (a) is at least one selected from strontium chromate, zinc chromate and barium chromate, according to any one of claims 1 to 6. The coating composition described. 8. The coating composition according to claim 7, wherein the chromate-based rust preventive pigment (a) is a combination of both strontium chromate and zinc chromate. 9. The coating composition according to claim 7, wherein the chromate-based rust preventive pigment (a) is a combination of both strontium chromate and barium chromate. 10. (b) The phosphate pigment is zinc phosphate,
It is at least 1 sort (s) chosen from aluminum phosphate and calcium phosphate, It is characterized by the above-mentioned.
The coating composition according to any one of 1. 11. Strontium chromate 20 to 60 parts by weight and zinc chromate as a pigment component based on 100 parts by weight of a resin solid content of a resin comprising 60 to 95 parts by weight of a polyester resin and 5 to 40 parts by weight of an amino resin. And / or barium chromate 10-
40 parts by weight, at least one phosphate pigment selected from zinc phosphate, aluminum phosphate and calcium phosphate 15-
40 parts by weight, titanium white 0 to 50 parts by weight, and extender pigment 0 to 50 parts by weight, and the sum of all pigment components is 60 to 180 parts by weight.
The coating composition described. 12. A coated plate comprising a coating film of the coating composition according to any one of claims 1 to 11 formed on an aluminum-zinc alloy plated steel plate. 13. A coated plate according to claim 12, wherein an overcoat coating film is formed on the coating film of the coating composition according to any one of claims 1 to 11.