JPH0554823B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a resin-coated steel sheet with excellent paintability, corrosion resistance, chemical resistance, and scratch resistance, which is preferably used for home appliances, building materials, etc., and a method for manufacturing the same. BACKGROUND ART Conventionally, zinc-based galvanized steel sheets have been widely used in household electrical appliances, building materials, and the like. Since these zinc-based plated steel sheets have insufficient corrosion resistance and paintability as they are, they have conventionally been subjected to chromate treatment or phosphate treatment. Among these, chromate-treated steel sheets are used for parts of audio equipment, chassis, etc., but in these applications, they are not necessarily coated and are sometimes used in a so-called bare state. In this way, when the chromate coating is exposed, the characteristics of the coating such as corrosion resistance, color tone, appearance due to fingerprint stain resistance, etc. are very important. Also,
In addition to the above-mentioned required properties, when used in applications where paint is applied, a high degree of performance in terms of paint film adhesion is required. Therefore, for example, increasing the thickness of the chromate film has been proposed for the purpose of improving corrosion resistance. However, when using this method, the resulting coating exhibits a yellow to brown color characteristic of chromate coatings, and is susceptible to stains such as fingerprints. In recent years, it has been proposed in JP-A-58-100685 to improve the corrosion resistance and paintability of the resulting chromate film by adding various compounds to the chromate treatment agent. It is being done. However, even with this method, when a water-soluble chromium compound is added to carboxylated polyethylene resin, it is difficult to disperse it uniformly, and it tends to separate and precipitate during use and storage. Furthermore, in applications where secondary adhesion is required, such as steel plates for washing machines, there still remains the problem of reduced adhesion. Furthermore, in recent years, as galvanized steel sheets have become more diverse in their uses for computer parts, microwave oven bottom plates, etc., the required properties have also become more sophisticated, and chromate treatment and phosphate treatment have become more difficult. ,
It is becoming difficult to respond adequately. Therefore, recently, Japanese Patent Application Laid-Open No. 58-100685
As described in Japanese Patent Laid-Open Nos. 58-153785 and 1977-177476, resin-coated steel sheets in which a resin coating is further applied on the chromate coating have come to be used. However, with such resin-coated steel sheets, the resin coating may swell or peel due to press oil or quick-drying oil during press working, or alkali or solvent used in the next degreasing process. , performance such as corrosion resistance and paintability deteriorates significantly. Furthermore, since the resin coating is soft, the surface of the steel plate is likely to be scratched during handling or the like. Problems to be Solved by the Invention The present invention has been made in order to solve the above-mentioned problems with conventional resin-coated steel sheets, and includes:
In particular, it is an object of the present invention to provide a resin-coated steel sheet with improved paintability, corrosion resistance, chemical resistance to alkalis, solvents, etc., and further improved scratch resistance, and a method for manufacturing the same. Means for Solving the Problems The resin-coated steel sheet of the present invention, which has excellent paintability and corrosion resistance, contains 5 to 50% ethylenically unsaturated carboxylic acid.
A resin coating containing 40% by weight of ethylene copolymer resin and 5 to 30% by weight of silica particles is formed on the surface of the steel plate at a coating weight of 0.2 to 2.5g/ ^m2 . shall be. Such a resin-coated steel sheet is the first resin-coated steel sheet according to the present invention.
According to the method described above, a water-soluble or water-acidic resin paint containing 5 to 30 weight % of silica particles, mainly consisting of an ethylene copolymer resin containing 5 to 40 weight % of ethylenically unsaturated carboxylic acid, is applied to the surface of the steel plate. It can be obtained by applying the resin coating to the surface of the steel plate and drying it to form a resin coating on the surface of the steel plate with a coating weight of 0.2 to 2.5 g/m ² . Furthermore, according to the present invention, as the second method for producing a resin-coated steel sheet, the ethylene copolymer resin containing 5 to 40 weight % of ethylenically unsaturated carboxylic acid is used as a main ingredient, and 5 to 30 weight % of silica particles and 5 to 30 weight % of silica particles and A water-soluble or water-dispersible resin paint containing 1 to 30% by weight of an organic compound having an aziridinyl group is applied to the surface of a steel plate, dried, and the coating weight is 0.10 to 2.5 g/
Provided is a method for producing a resin-coated steel sheet with excellent paintability, corrosion resistance, chemical resistance, and scratch resistance, which comprises forming a resin film on the surface of the steel sheet at m ² . In the first and second methods according to the present invention, the resin coating used is mainly composed of an ethylene copolymer resin containing an ethylenically unsaturated carboxylic acid, and a water-soluble resin containing silica particles (and an organic compound having an aziridinyl group). It is a water-based resin paint that is water-based or water-dispersible. The ethylene copolymer resin is a copolymer of ethylene and 5 to 40% by weight of an ethylenically unsaturated carboxylic acid, and the ethylenically unsaturated carboxylic acid used as a water-dispersible or water-soluble resin includes: For example, (meth)acrylic acid, maleic acid,
One or more kinds of itaconic acid and the like are preferably used. In such an ethylene copolymer resin, when the content of ethylenically unsaturated carboxylic acid is more than 40% by weight, the resulting resin coating still does not have sufficient corrosion resistance. In the method of the present invention, the ethylene copolymer resin is dissolved or dispersed in an aqueous dispersion medium to form an aqueous solution or dispersion, and silica particles (and an organic compound having an aziridinyl group), which will be described later, are blended into this. A water-based resin paint is applied to the surface of the steel plate and dried to form a resin film. Here, when the content of ethylenically unsaturated carboxylic acid is less than 5% by weight, it is difficult to make the resulting copolymer resin water-soluble or water-dispersible, and it is not suitable for use in the method of the present invention. do not have. As the aqueous dispersion medium, water or a mixture of water and a hydrophilic organic solvent is used. Examples of hydrophilic organic solvents include methanol, ethanol,
Lower aliphatic alcohols such as n-propanol,
Glycol ethers such as ethylene glycol methyl ether, glycol esters such as ethylene glycol acetate, ethers such as tetrahydrofuran and dioxane, dimethylformamide, diacetone alcohol, etc. are used. Furthermore, in the present invention, the ethylene copolymer resin contains a third monomer other than ethylene and ethylenically unsaturated carboxylic acid, such as (meth)
Methyl acrylate, ethyl (meth)acrylate,
(meth)acrylic acid esters such as propyl (meth)acrylate; styrenic monomers such as styrene, vinyltoluene, and chlorostyrene; (meth)acrylates such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; N-substituted (meth)acrylamide such as hydroxyalkyl acrylate, N-methylol (meth)acrylamide,
One or more of epoxy group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate, (meth)acrylonitrile, etc. may be contained. The resin coating used in the present invention contains silica particles in a range of 5 to 30% by weight, and the silica particles are
It is effective in imparting excellent corrosion resistance to the resulting resin coating. However, in resin paints, when the amount of silica is less than 5% by weight, the corrosion resistance of the resin coating obtained is insufficient, while when it exceeds 30% by weight, silica begins to act as a lubricant. This increases the coefficient of friction of the coating, lowering the lubricity, which in turn deteriorates the corrosion resistance after processing, and further deteriorates the paintability. In particular, in the present invention, the amount of silica particles in the resin coating is 5
A range of 10% by weight is preferred. In order to maximize the effects of silica as described above, the particle size of silica is preferably in the range of 1 to 20 mμ. The smaller the particle size of silica, the better the corrosion resistance and paintability of the coating. This effect of silica appears to be due to the fact that the resin coating is dense and has excellent adhesion, thereby further enhancing the corrosion resistance of the resin coating. From this point of view, the smaller the particle size of the silica used, the better; however, even if extremely small particles are used, the above-mentioned effects will not be particularly enhanced. In the invention, the silica may have a particle size of 1 mμ or more. On the other hand, when it exceeds 20 mμ, the surface of the coating becomes rough, making it impossible to form a dense coating and deteriorating the corrosion resistance of the coating. In particular, in the present invention, the silica particles used preferably have a particle size in the range of 4 to 6 mμ. Such silica particles are generally known as colloidal silica, and are commercially available as, for example, Snowtex-XS and SS (manufactured by Nissan Chemical Industries, Ltd.). According to the method of the present invention, a resin coating as described above is applied to the surface of a steel plate and dried to form a resin coating. Here, in the first method according to the present invention, the amount of the resin coating deposited on the steel plate is in the range of 0.2 to 2.5 g/m ² . When the amount of the resin coating is less than 0.2 g/m ² , the resin coating cannot sufficiently exhibit its desired performance such as paintability and corrosion resistance. On the other hand,
When the amount of the resin coating on the steel plate is more than 2.5 g/m ² , although corrosion resistance is excellent, the manufacturing cost increases, which is not economically preferable. Furthermore, in the second method of the present invention, the water-based resin coating used contains an organic compound having an arizidinyl group in a range of 1 to 30% by weight. Organic compounds having such an arizidinyl group include:
For example, the following formula Trimethylolpropane tris (β
-aziridinylpropionate), the following formula: tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, Tris[1-(2-methyl)aziridinyl]phosphine oxide represented by the above formula, or commercially available glycidylamine type epoxy resins are preferably used. Such an organic compound having an aziridinyl group performs a crosslinking reaction with the carboxyl group contained in the ethylene copolymer resin as shown in the following formula, thereby improving the corrosion resistance and scratch resistance of the resin coating. In the resin coating, when the content of the above-mentioned organic compound having an arizidinyl group is less than 1% by weight, not only the above-mentioned crosslinking reaction with the carboxyl group of the ethylene copolymer is insufficient; As mentioned above, it reacts with sodium and potassium in the alkaline compounds used in the degreasing process after press working, making the coating hydrophilic and significantly deteriorating its corrosion resistance and paintability. On the other hand, 30
When the weight percentage is exceeded, the crosslinking density becomes excessively high and the film hardness increases.As a result, it is unable to follow deformation due to press working etc., cracks etc. occur, and the chemical resistance deteriorates. Deteriorates corrosion resistance, paintability, etc. In particular, in the present invention, the blending amount of the organic processed material having an aziridinyl group in the resin coating is preferably in the range of 5 to 10% by weight. According to the method of the present invention, a resin coating as described above is applied to the surface of a steel plate and dried to form a resin coating. Here, in the second method according to the present invention, the amount of such resin coating applied to the steel plate is in the range of 0.10 to 2.5 g/m ² . When reducing the amount of resin coating less than 0.10g/ ^m2 ,
The resin paint cannot be applied uniformly to the steel plate,
In addition, the resin coating cannot fully exhibit the desired properties such as chemical resistance, corrosion resistance, and scratch resistance. On the other hand, when the amount of resin coating attached to the steel plate is more than 2.5 g/m ² , the coating will peel off more during intense press working, and the peeled coating will accumulate on the mold, causing problems in press forming. In addition, it increases manufacturing costs. From a practical point of view,
In particular, the amount of resin film deposited is preferably in the range of 0.30 to 1.0 g/m ² . In the present invention, the steel sheet material is not particularly limited, but for example, zinc or zinc alloy plated steel sheets, or those steel sheets subjected to chemical conversion treatment such as chromate treatment or phosphate treatment, etc. are preferably used. It will be done. Effects of the Invention As described above, according to the first method of the present invention,
A resin coating is formed by applying an aqueous resin coating containing silica particles to a steel plate together with an ethylene copolymer resin containing an ethylenically unsaturated carboxylic acid and drying the coating. Here, since silica particles make the film dense and have excellent adhesion, according to the present invention, even if it is a thin film, it has excellent paintability and corrosion resistance. A resin-coated steel sheet with excellent properties can be obtained. Furthermore, according to the second method of the present invention, a water-based resin paint containing silica particles and an organic compound having an aziridinyl group is applied to a steel plate together with an ethylene copolymer resin containing an ethylenically unsaturated carboxylic acid. By drying, a resin film is formed. Here, the silica particles make the coating dense and have excellent adhesion, and the organic compound having an aziridinyl group reacts with the carboxyl group of the ethylene copolymer resin to form a crosslinked structure. According to the method, it is possible to obtain a resin-coated steel sheet with particularly improved chemical resistance, corrosion resistance, and scratch resistance. Therefore, the resin-coated steel sheet according to the present invention can be suitably used, for example, in home appliances, building materials, etc. that require high paintability, corrosion resistance, chemical resistance, scratch resistance, and the like. EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, in the examples, electrogalvanized steel sheets subjected to chromate treatment (zinc coating amount 20g/
m ² , chromium adhesion amount 20 mg/m ² ) was used as the material steel sheet. Example 1 Colloidal silica with a particle size of 4 to 6 mμ was added to an aqueous dispersion of an ethylene copolymer resin containing acrylic acid in a range of 5 to 40% by weight as an ethylenically unsaturated carboxylic acid in a solid content of 10% by weight. In addition, a water-dispersible resin paint was prepared. This resin coating was applied to the surface of the steel plate and dried to obtain a resin-coated steel plate with a coating weight of 0.5 g/m ² . Table 1 shows the corrosion resistance and paintability of the resin-coated steel sheet obtained. Corrosion resistance is 1% white rust according to JIS Z 2371.
Evaluation was made based on the time taken to occur. Erichsen is shown in the results after 6 mm of Erichsen extrusion. In addition, for paintability, melamine-based paint is applied to a film thickness of 20 μm.
Bake at 150℃ for 30 minutes, soak in boiling water for 1 hour,
Evaluated after hours.

[Table] ◎: Very good, ○: Good, △: Fair
Poor, ×: Poor Example 2 Colloidal silica with a particle diameter of 4 to 6 mμ was added to an aqueous dispersion of an ethylene copolymer resin containing 20% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid at a solid content of 0 to 6 mμ. 40% by weight was added to prepare a water-dispersible resin paint, and in the same manner as in Example 1, it was applied to the surface of the steel plate and dried to give a coating weight of 0.5g/m ²
A resin-coated steel plate was obtained. Table 2 shows the corrosion resistance and paintability of the resin-coated steel sheet obtained.

[Table] ◎: Very good, ○: Good, △: Fair
Poor, ×: Poor Example 3 10% by weight of colloidal silica with a particle size of 4 to 50 mμ was added to an aqueous solution of ethylene copolymer resin containing 20% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid. In addition, a water-dispersible resin coating was prepared and applied to the surface of the steel plate in the same manner as in Example 1, and dried to obtain a resin-coated steel plate with a coating weight of 0.5 g/m ² . Table 3 shows the corrosion resistance and paintability of the resin-coated steel sheet obtained.

[Table] ○: No peeling, △: Partial peeling,
×: A large amount of peeling,
Example 4 To an aqueous dispersion of an ethylene copolymer resin containing 20% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid, 10% by weight of colloidal silica with a particle size of 4 to 6 mμ was added as a solid content, and the mixture was water-dispersed. Prepare a plastic resin paint, apply it to the surface of the steel plate in the same manner as in Example 1, and dry it to obtain a film adhesion amount of 0.1 to 3.0 g/m ²
A resin-coated steel plate was obtained. Table 4 shows the corrosion resistance and paintability of the resin-coated steel sheet obtained.

[Table] ◎: Very good, ○: Good, △: Fair
Poor, ×: Poor Example 5 Colloidal silica with a particle size of 4 to 6 mμ was solidified in an aqueous dispersion of an ethylene copolymer resin containing 5 to 40% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid. Trimethylolpropane tris(β-aziridinylpropionate) as a compound with aziridinyl group and 10% by weight in min.
A water-dispersible resin paint was prepared by adding 5% by weight of the following. This resin coating was applied to the surface of the steel plate and dried to obtain a resin-coated steel plate with a coating weight of 0.5 g/m ² . Table 5 shows the corrosion resistance and paintability of the resin-coated steel sheet obtained. Example 6 Colloidal silica with a particle size of 4 to 6 mμ was added to an aqueous dispersion of an ethylene copolymer resin containing 20% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid.

【table】

[Table] ◎: Very good, ○: Good, △: Fair
Fairly poor, ×: poor 0 to 40% by weight in terms of solid content, and 5% by weight of trimethylolpropane tris (β-aziridinylpropionate) as a compound having an aziridinyl group was added to form a water-dispersible resin. A paint was prepared, applied to the surface of the steel plate and dried in the same manner as in Example 1, to obtain a resin-coated steel plate with a coating weight of 0.5 g/m ² . Table 6 shows the corrosion resistance and paintability of the resin-coated steel sheet obtained. Example 7 As an ethylenically unsaturated carboxylic acid, colloidal silica with a particle size of 4 to 50 mμ was added to an aqueous solution of an ethylene copolymer resin containing 20% by weight of acrylic acid as a solid content of 10% by weight and an aziridinyl group. As a compound, 5% by weight of trimethylolpropane tris (β-aziridinylpropionate)
In addition, a water-dispersible resin coating was prepared and applied to the surface of the steel plate in the same manner as in Example 1, and dried to obtain a resin-coated steel plate with a coating weight of 0.5 g/m ² .
The corrosion resistance and paintability of the obtained resin-coated steel sheet were evaluated in the 7th test.
Shown in the table.

[Table] ◎: Very good, ○: Good, △: Fair
Or inferior, ×: inferior

[Table] ◎: Very good, ○: Good, △: Fair
Or inferior, ×: inferior
Example 8 In an aqueous dispersion of ethylene copolymer resin containing 20% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid, 10% by weight of colloidal silica with a particle size of 4 to 6 mμ in solid content and aziridinyl groups were added. A water-dispersible resin coating was prepared by adding 0 to 40% by weight of trimethylol proponent tris (β-aziridinyl propionate) as a compound containing The coating was applied and dried to obtain a resin-coated steel plate with a coating weight of 0.5 g/m ² . Table 8 shows the chemical resistance and scratch resistance of the resin-coated steel sheet obtained. For chemical resistance, the corrosion resistance and paintability of the obtained resin-coated steel sheets before degreasing and after alkaline degreasing or solvent degreasing using trichlene were compared. The evaluation of corrosion resistance and paintability was the same as above. In addition, the scratch resistance was measured by sandwiching a test piece (40 x 300 mm) 2 between flat dies 1 and 1, and pressuring one of the dies at 240 Kgf/cm ² with a hydraulic cylinder 3, as shown in Figure 1. Tsutsu,
Pull the test piece upwards and place it on the test piece.

[Table] ◎: Very good, ○: Good, △
: Slightly inferior, ×: Inferior

[Table] ◎: Very good, ○: Good, △: Fair
Or inferior, ×: inferior
The occurrence of defects was investigated. Example 9 An aqueous solution of an ethylene copolymer resin containing 20% by weight of acrylic acid as an ethylenically unsaturated carboxylic acid and 10% by weight of colloidal silica having a particle size of 4 to 6 mμ in solid content and having an aziridinyl group. A resin coating was prepared by adding 5% by weight of a glycidylamine type epoxy resin as a compound, and applied to the surface of the steel plate in the same manner as in Example 1, and dried to obtain a coating weight of 0.05 to 3.0 g/ ^m2. A range of resin-coated steel sheets were obtained. Regarding the obtained resin-coated steel plate,
Its corrosion resistance, paintability and scratch resistance are shown in Table 9.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing a method for evaluating the scratch resistance of a resin-coated steel sheet. 1... Flat die, 2... Test piece, 3... Hydraulic cylinder.

Claims (1)

[Claims] 1. 5 to 40% by weight of ethylenically unsaturated carboxylic acid
A coating characterized in that a resin coating containing 5 to 30% by weight of silica particles is formed on the surface of a steel plate at a coating weight of 0.2 to 2.5 g/ ^m2 , mainly containing ethylene copolymer resin. Resin-coated steel sheet with excellent durability and corrosion resistance. 2. A resin-coated steel sheet with excellent paintability and corrosion resistance according to claim 1, wherein the ethylene copolymer resin is an ethylene-acrylic acid copolymer resin. 3. A resin-coated steel sheet with excellent paintability and corrosion resistance according to claim 1, wherein the silica particles have a particle size of 1 to 20 mμ. 4 5-40% by weight of ethylenically unsaturated carboxylic acid
A water-soluble or water-dispersible resin coating mainly containing ethylene copolymer resin and 5 to 30% by weight of silica particles is applied to the surface of the steel plate, dried, and coated with a coating weight of 0.2 to 2.5 g/m. 2. A method for producing a resin-coated steel sheet with excellent paintability and corrosion resistance, which comprises forming a resin film on the surface of the steel sheet in ^{step 2} . 5. The method for producing a resin-coated steel sheet with excellent paintability and corrosion resistance according to claim 4, wherein the ethylene copolymer resin is an ethylene-acrylic acid copolymer resin. 6. The method for producing a resin-coated steel sheet with excellent paintability and corrosion resistance according to claim 4, wherein the silica particles have a particle size of 1 to 20 mμ. 7 5-40% by weight of ethylenically unsaturated carboxylic acid
A water-soluble or water-dispersible resin coating mainly containing ethylene copolymer resin, 5 to 30% by weight of silica particles, and 1 to 30% by weight of an organic compound having an aziridinyl group is applied to the surface of the steel plate and dried. Manufacturing a resin-coated steel sheet with excellent paintability, corrosion resistance, chemical resistance, and scratch resistance, characterized by forming a resin film on the surface of the steel sheet with a film adhesion amount of 0.10 to 2.5 g/ ^m2 . Method. 8. Production of a resin-coated steel sheet with excellent paintability, corrosion resistance, chemical resistance, and scratch resistance according to claim 7, wherein the ethylene copolymer resin is an ethylene-acrylic acid copolymer resin. Method. 9. The method for producing a resin-coated steel sheet with excellent paintability, corrosion resistance, chemical resistance, and scratch resistance according to claim 7, wherein the silica particles have a particle size of 1 to 20 mμ.