JPH0797534A - Undercoating material excellent in corrosion resistance and resin-coated metal plate - Google Patents

Abstract

PURPOSE:To provide an undercoating material capable of forming a resin-coated layer excellent in corrosion resistance and processability, therefore, producing a resin-coated metal plate excellent in corrosion resistance and processability by using this coating material and of improving the whiteness and applicable especially to a part requiring a high whiteness. CONSTITUTION:(1) An undercoating material containing inhibitors (an alkyne, an alkynol, an amine, etc.) in an amount of 0.05 to 20wt.% in total based on the total weight of the solid matter of the coating material. (2) A resin-coated metal plate having a plating film (zinc-based one, aluminium-based one or zinc- aluminium-based one), a chromate coating film or a zinc phosphate coating film, an undercoating film formed by using (1) the above-mentioned coating material (1 to 15mum thickness) and one or more layers of resin coating films in order from the lower layer on the surface of a metal plate such as a steel plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an undercoat paint having excellent corrosion resistance, high workability, high hardness, and high whiteness, which is suitable for home appliances and building materials, and a resin-coated metal using the paint. Regarding the board.

[0002]

2. Description of the Related Art The purpose of applying a coating to the surface of a metal plate, for example, a steel plate, is originally to improve aesthetics and corrosion resistance. Except for the case where a steel plate is used as a structural member, it is considered that the improvement of corrosion resistance also leads to the improvement of aesthetic appearance in the sense that the material surface is prevented from being damaged by corrosion.

A coated steel sheet (precoated steel sheet) is handed over to a user and then subjected to processing such as punching, bending, and drawing to form the outer surface of the product as it is. Compared with the above, the exposure rate of the end surface of the steel sheet is higher and the end surface corrosion resistance is required to be excellent. In addition, in recent years, the pursuit of high functionality and high designability has become more active due to the trend toward high-grade products or individualization.For example, in household appliances, in addition to excellent corrosion resistance, good workability and high hardness, etc. In addition, it is required to have a high functionality and to be excellent in design, such as a beautiful pattern and excellent image clarity.

In order to impart such various functions to the steel sheet in a well-balanced manner, conventionally, a method of forming two or more resin coating layers on the surface of the steel sheet has been carried out. That is, an undercoat paint containing an anticorrosive pigment is applied on a plated steel sheet that has been subjected to coating-type chromate treatment or zinc phosphate treatment to secure end face corrosion resistance and workability, and one or more resin coating layers By providing the above, various functions such as high hardness, excellent image clarity, stain resistance, and beautiful pattern have been improved.

However, in the production of such a coated steel sheet, in the case of using a solvent type paint which has been conventionally used, it is generally impossible to make workability and end face corrosion resistance compatible with each other, and in order to improve the end face corrosion resistance, When the amount of the rust preventive pigment is increased, the workability of the undercoat film tends to decrease, and the workability of the coated steel sheet as a whole tends to decrease. Therefore, a coated steel sheet for building materials that requires high corrosion resistance is inferior in workability, and a coated steel sheet for home electric appliances having improved workability generally tends to be inferior in end face corrosion resistance.

Further, for example, lighting equipment such as a reflector of a fluorescent lamp is required to have a very high degree of whiteness from the viewpoint of energy saving. Therefore, an undercoat paint using white titanium dioxide as a pigment is often used. However, corrosion resistance is not always sufficient because no rust preventive pigment is added to enhance whiteness. In addition to lighting fixtures, there are many parts that require high whiteness in order to improve the design, and steel plates conventionally used for such parts sacrifice corrosion resistance or workability, or It was dealt with by painting later.

Therefore, if the corrosion resistance and the workability are both excellent and the whitening is possible, it is expected that the application site of the coated steel sheet will be further expanded in the future.

[0008]

SUMMARY OF THE INVENTION The present invention provides an undercoat paint capable of forming a resin coating layer excellent in corrosion resistance, particularly end face corrosion resistance and workability, and having high whiteness on the surface of a metal plate, and such a paint. The object is to provide a resin-coated metal plate used.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to find a method for improving the end face corrosion resistance and workability of a resin-coated metal plate in a well-balanced manner and for achieving high whiteness. It was found that it is effective to include an organic inhibitor having a corrosion inhibiting effect in the undercoat paint.

The present invention was made on the basis of this finding, and has as its gist the following undercoat paint and the following resin-coated metal plate.

1 of alkynes, alkynols, amines or salts thereof, thio compounds, heterocyclic compounds, polycarboxylic acid compounds or salts thereof, aromatic carboxylic acid compounds or salts thereof, and ligninsulfonic acid or salts thereof. An undercoating coating excellent in corrosion resistance, characterized by containing at least 0.05 to 20% by weight based on the total solid weight of the coating.

A metal plate has a zinc-based, aluminum-based, or zinc-aluminum-based plating film on at least one surface, and the amount of the adhesion is 10 to 100 mg / mm in terms of chromium.
It has a chromate film of m ² or a zinc phosphate film of which the amount of adhesion is 0.1 to 2.0 g / m ² , and a resin coating layer having a thickness of 1 to 15 μm formed on the undercoat paint described above. And a resin-coated metal plate having excellent corrosion resistance, further comprising one or more resin coating layers thereon.

[0013]

The function of the present invention and its function and effect will be described below.

As described above, the above invention is an undercoat paint to which an organic inhibitor such as an alkyne or amine is added, and the invention of the above is a plating film (first layer) on the surface of a metal plate in order from the bottom layer. Layer), chromate film or zinc phosphate film (second layer), undercoat resin coating layer (third layer)
And a resin-coated metal sheet having one or more resin coating layers (fourth layers), characterized in that an inhibitor is added to the coating material, and the resin-coated metal sheet is coated with the inhibitor. It has the undercoat resin coating layer formed by.

In the resin-coated metal plate of the invention, the metal plate is a steel plate conventionally used as a base material of a resin-coated steel plate (for example, SPCC, SPCD, SP specified in JIS G 3141).
It is usually a steel plate such as CE, or an ultra-low carbon Ti-added steel, P-added steel or other high-strength steel plate, but is not particularly limited to these steel plates and is an aluminum plate used for weight reduction. For example, a metal plate other than a steel plate may be used depending on the purpose of use of the material and the site of use.

The first layer plating film is a zinc-based, aluminum-based or zinc-aluminum-based plating film having excellent corrosion resistance. For example, pure Zn (zinc), Zn-Fe (iron) alloy, Zn-Co (cobalt) alloy, Zn-Ni (nickel) alloy, Zn-Mn (manganese) alloy, Zn-Cr (chromium) alloy,
Zn-Mg (magnesium) alloy, Zn-Al (aluminum)
It is a plating film of an alloy, pure Al, an Al-Mn alloy, etc., and as a plating method, any of electroplating, hot dipping, vapor deposition plating and the like can be applied. Plating metal is Zn, Zn−
In the case of Fe alloy and Zn-Al alloy, when the metal plate is a steel plate,
Generally, hot dip galvanized steel sheets are mainly used rather than electrogalvanized steel sheets. This is because the electroplated steel sheet has high workability even if it has a high weight per unit area, although the workability is good, and the corrosion resistance is insufficient with the thin weight per unit area.

The plating may be either single-sided plating or double-sided plating. The coating weight is not particularly limited, but from the balance of workability and corrosion resistance, 10 to 120 g per side
A range of / m ² is preferred.

In the second layer of chromate film or zinc phosphate film (base treatment film), the chromate film may be formed by any of a coating type, a reaction type and an electrolytic type. A type chromate film is particularly preferable because it has excellent corrosion resistance. The type of coating type chromate solution is not particularly limited, and a commercially available partially reduced chromate solution may be used. If the amount of chromate film adhered is small, the adhesion of the film and by extension the corrosion resistance of the resin-coated metal plate will decrease, and if it is large, the workability will decrease. Converted to the amount of metal chromium (Cr), 10-100 mg / m Must be ² . 30 ~
A range of 80 mg / m ² is preferred.

The zinc phosphate coating may be a coating formed by a conventional method such as a spray method or a dipping method, using a chemical solution used for the chemical conversion treatment of ordinary coated steel sheets. For the same reason as the chromate film, the amount of zinc phosphate film deposited is
It may be within the range of ^{0.1~2.0mg / m 2, 0.4~1.2mg / m} 2
Is preferred.

The third undercoat resin coating layer is a layer having a thickness of 1 to 15 μm formed by applying and baking the undercoat paint (primer paint) of the invention.

The undercoat paint contains a pigment, various additives and an organic solvent in addition to the resin and the crosslinking agent. The undercoat paint of the present invention contains an organic inhibitor in addition to these components. Has been done.

The resin used in the undercoat paint is not particularly limited as long as it is a resin used in ordinary paints such as polyester, epoxy, acrylic and urethane.

The cross-linking agent is also melamine, isocyanate or the like used in ordinary paints and is not particularly limited. The addition amount is also not particularly limited, but in order to maintain the balance of hardness and workability, it is preferable that 5 to 50 g is added to 100 g of the resin.

The pigment is usually a rust preventive pigment, titanium oxide, or an extender pigment (for reinforcing the coating film such as silica) which is added to the undercoat paint, and is not particularly limited. The addition ratio and total addition amount of each pigment may be appropriately determined according to the performance required for the resin film to be formed.

The additive is a crosslinking catalyst, a lubrication-contributing component, a defoaming agent, a surface-hardening modifier, etc., and is appropriately selected and added according to the resin and crosslinking agent used.

The organic solvent may also be appropriately selected depending on the type of resin and crosslinking agent and the production conditions.

Examples of organic inhibitors include alkynes, alkynols, amines or salts thereof, thio compounds, heterocyclic compounds, polycarboxylic acid compounds or salts thereof, aromatic carboxylic acid compounds or salts thereof, and ligninsulfonic acid. Alternatively, one or more of its salts are used.

Alkynes are carbon-carbon triple bonds (-C
≡C-) is an organic compound containing, for example, pentin,
Hexin, heptin, octyne and the like can be mentioned.

Alkynols are organic compounds in which one or more hydroxyl groups are bonded to the above alkynes, and include propargyl alcohol, 1-hexyne-3-ol, 1-heptin-.
3-ol etc. are mentioned.

The amines are organic compounds containing one or more nitrogen atoms in the molecule, which may be aliphatic or aromatic, and laurylamine, octylamine, propenylamine, cyclohexylamine and the like can be used. The salt is, for example, a nitrate, a hydrochloride, or a sulfate thereof. When the resin that is the base of the paint is a thermoplastic resin,
It is particularly suitable.

The thio compound is an organic compound containing at least one sulfur atom in the molecule, and examples thereof include thiourea and its derivatives, decyl mercaptan and dimethyl sulfide.

The heterocyclic compound is an organic compound containing an element other than carbon as a ring-constituting atom in a cyclic molecule, and examples thereof include thiophene, indole and benzimidazole.

The polycarboxylic acid compound is a compound containing two or more carboxyl groups in the molecule, and includes citric acid, succinic acid,
Examples thereof include adipic acid and sebacic acid. Examples of the salt include potassium dihydrogen citrate and disodium adipate.

The aromatic carboxylic acid compound is a compound having a carboxyl group bonded to an aromatic hydrocarbon, and examples thereof include benzoic acid and salicylic acid. The salt includes sodium benzoate, sodium salicylate and the like.

In addition to the above compounds, lignin sulfonic acid and its salts (such as sodium lignin sulfonate) can also be used as inhibitors.

The undercoat paint of the invention of the present invention contains at least one compound selected from the above inhibitors in a total amount of 0.05 to 20% by weight based on the total weight of the solid content in the paint. If the content is less than 0.05% by weight, the effect of improving the corrosion resistance of the undercoat paint is poor, and if it exceeds 20% by weight, the mechanical properties of the resin are impaired.

The above-mentioned inhibitor may be appropriately selected depending on the types and addition amounts of the resin and the cross-linking agent, for example, so that the inhibitor is not thermally decomposed in the bake-curing process after the coating material is applied.

When the thickness of this resin coating layer is less than 1 μm, the anticorrosion effect is insufficient, the underlying plating film does not show through and the so-called hiding property is not sufficient, and when it exceeds 15 μm, the workability decreases. Therefore, it is 1 to 15 μm.

Fourth layer organic resin film (upper layer resin film)
Is required to be at least one layer, and is not particularly limited, but it is preferably three layers or less in consideration of workability, adhesion between layers, and the like. Although the film thickness is not particularly limited, it is preferably in the range of 10 to 40 μm in consideration of the balance of hiding property, hardness, stain property, processability and the like.

The resin used as the upper resin film is not particularly limited, as long as it is a polyester-based, acrylic-based, urethane-based, epoxy-based, vinyl chloride-based, or fluorine-based resin that is usually used as a top coating composition or film. Further, there are no particular restrictions on the crosslinking agent, pigment, additive, or organic solvent added to the resin.

To produce the resin-coated metal sheet of the present invention having the above-mentioned constitution, the first layer of the plating film and the second layer of the chromate film or the zinc phosphate film are produced on the surface of the metal plate. After the formation, the undercoat paint is applied and baked and cured to form a third undercoat resin coating layer. A conventional means such as a roll coater or a curtain flow coater may be used for coating, and a method such as a hot air oven, an induction heating oven or the like may be used for baking and curing, or ultraviolet curing, electron beam curing or the like. For bake hardening, for example, in the case of heat hardening, the maximum temperature reached is 200 to 220 ° C.
It is preferable to heat it for about 30 seconds to about 70 seconds. The chromate film or zinc phosphate film of the second layer, the undercoat resin film of the third layer and the upper resin film of the fourth layer may be formed on one side or both sides of the plated metal plate depending on the purpose of use of the material. May be.

An upper resin film for the fourth layer is formed on the undercoat resin coating layer for the third layer.

The formation of the upper resin film may be carried out by applying a conventional method such as a roll coater in the case of a coating material and then baking it at a temperature of 80 to 250 ° C. A line or the like may be used. Further, in the case of a film, it may be formed by an ordinary laminating method.

The resin-coated metal sheet of the present invention thus obtained, for example, a resin-coated steel sheet, contains an organic substance (inhibitor) having a corrosion-inhibiting effect in the undercoating resin film of the third layer, so that the workability is improved. The corrosion resistance, especially the end surface corrosion resistance, can be improved without impairing the corrosion resistance. This is because when the metal plate is exposed to a corrosive environment, the inhibitor in the primer dissolves and adsorbs to the active portion of the plated metal on the end face, thereby suppressing the dissolution of that portion. Moreover, since the corrosion resistance can be improved without adding a rust preventive pigment, the whiteness of the resin-coated steel sheet can be increased.

[0045]

[Example 1] Cold-rolled steel sheet having a thickness of 0.5 mm (material: JIS G 3141
The SPCD material specified in 1) is subjected to the chromate treatment shown in Table 1 on both sides of the plated steel sheet on which various plating shown in Table 1 is applied to form an undercoat resin coating layer on the surface, and the resin of the upper layer is formed thereon. A resin-coated steel sheet having a film formed was produced.

A commercially available coating type chromate treatment liquid was used for the chromate treatment, and the coating liquid was applied by a roll coater so that the adhesion amount was 50 mg / m ² in terms of Cr and then dried to obtain a chromate film. The undercoat resin film should have a dry film thickness of 8 μm, and the maximum steel plate temperature (hereinafter referred to as PMT) 21
It was baked and cured at 0 ° C. The upper resin film is a commercially available polyester resin paint (FLC1001 manufactured by Nippon Paint Co., Ltd.).
HQ) was applied by a roll coater to a dry film thickness of about 18 μm, and then baked and cured at PMT 220 ° C. In addition,
An epoxy resin paint (Vinizol 1000 manufactured by Nippon Paint Co., Ltd.), which is a commercially available paint for service coat, was applied to the back surface so that the dry film thickness was 5 μm, and then baked and cured at PMT 220 ° C.

The end face corrosion resistance and workability of the resin-coated steel sheet thus obtained were evaluated by the following methods.

[Endface Corrosion Resistance] A 70 mm × 150 mm test piece is cut out with a shear so that the burrs on both sides of the end face toward the surface side, and a salt spray test (5% NaCl, 35 ° C.) is performed, and after 500 hours, the end face The degree of blister occurring in the burrs part of No. 3 was evaluated by classifying it into the following 5 grades.

◎: When the blister width is less than 1.0 mm ○: When the blister width is 1.0 mm or more and less than 2.0 mm △: When the blister width is 2.0 mm or more and less than 3.0 mm ×: Blister width is 3.0 mm or more and less than 4.0 mm XX: When the blister width is 4.0 mm or more [Workability] A 50 mm x 150 mm test piece was cut out, and the bending surface was subjected to a bending test in a constant temperature room at 25 ° C. The evaluation was carried out by observing the presence or absence of cracks in the resin film in the processed portion with a magnifying glass 10 times, and performing the number of bends (0T to 6T below) until no crack occurred. 0T is the best, 1T,
The workability decreases as it increases to 2T.

0T: 180 degree close contact bending 1T: 180 degree close contact bending with one 0.5 mm thick steel sheet sandwiched between them 2T: 180 degree close contact bending with 2 0.5 mm thick steel sheet sandwiched 3T: 0.5 mm thick 180 degree close bending with 3 sheets of steel plate sandwiched between them 4T: 180 degree close contact bending with 4 sheets of 0.5mm thick steel sheet 5T: 180 degree close contact bending with 5 sheets of 0.5mm thick steel sheet sandwiched 6T : The results of 180 degree close contact bending test with 6 sheets of 0.5 mm thick steel plates sandwiched between are also shown in Table 1. Comparing the present invention examples and comparative examples by type of plating film and type of resin, by containing an inhibitor having a corrosion inhibitory effect in the undercoat resin film, the end face corrosion resistance is enhanced, and further without impairing the workability, It can be seen that the end face corrosion resistance and workability can be improved in a well-balanced manner.

[0051]

[Example 2] A commercially available zinc phosphate treatment liquid was applied to the surface (both sides) of a hot-dip galvanized steel sheet having a thickness of 0.5 mm (coating adhesion amount: 60 g / m ² per side, the base steel sheet is low carbon aluminum killed steel). Apply so that the adhesion amount is 0.8 g / m ² and dry,
The undercoat resin film having the film structure shown in Table 2 was baked and cured at PTM 210 ° C. so that the dry film thickness was 10 μm. Furthermore, a commercially available high-white paint (Arestech # 100 manufactured by Kansai Paint Co., Ltd.) was baked and cured at 230 ° C. at PTM so that the dry film thickness was 20 μm.

The end face corrosion resistance, workability and color tone of the resin-coated steel sheet thus obtained were evaluated. The end face corrosion resistance and workability were evaluated in the same manner as in Example 1, and the color tone was evaluated by measuring the L value, which is a measure of whiteness. The larger the L value, the higher the whiteness.

The test results are also shown in Table 2. As shown in these results, the materials shown as comparative examples have corrosion resistance,
It was difficult to achieve both processability and whiteness, but it became possible to improve the balance between corrosion resistance, processability and whiteness by using an undercoat paint containing an inhibitor.

[0054]

[Table 1 (1)]

[0055]

[Table 1 (2)]

[0056]

[Table 2]

[0057]

The undercoat paint of the present invention can form a resin coating layer having excellent corrosion resistance and processability. The resin-coated metal plate of the present invention using this paint has excellent corrosion resistance and workability, and can increase the whiteness, and thus can be applied to a site where particularly high whiteness is required. .

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location // B32B 15/08 G (72) Inventor Shinya Hikino 4-53-3 Kitahama, Chuo-ku, Osaka-shi, Osaka (72) Inventor Kiyoyuki Fukui Sumitomo Metal Industry Co., Ltd. 4-53-3 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture

Claims (2)

[Claims] 1. Among alkynes, alkynols, amines or salts thereof, thio compounds, heterocyclic compounds, polycarboxylic acid compounds or salts thereof, aromatic carboxylic acid compounds or salts thereof, and ligninsulfonic acid or salts thereof. One or more of them in total with respect to the total solid weight of the paint
An undercoat paint with excellent corrosion resistance, characterized by containing 0.05 to 20% by weight. 2. A metal plate having a zinc-based, aluminum-based or zinc-aluminum-based plating film on at least one surface, and a chromate film or an adhesion amount of 10-100 mg / m ² converted to chromium on the plating film. A zinc phosphate coating having an amount of 0.1 to 2.0 g / m ² , a resin coating layer having a thickness of 1 to 15 μm formed by the undercoat paint according to claim 1 thereon, and further thereon. A resin-coated metal plate having excellent corrosion resistance, which has one or more resin coating layers.