JPH08318218A - Organic composite covering steel sheet with excellent press moldability and corrosion resistance - Google Patents

Abstract

PURPOSE: To enhance press moldability and corrosion resistance by providing a chromate layer on the surface of a galvanized steel sheet as a first layer and providing an organic film layer consisting of polymer resin and a rust inhibitor thereon as a second layer and specifying the components, component ratio and thickness of the films of the respective layers. CONSTITUTION: A chromate layer of adhesive amount 5-200mg/m<2> expressed in terms of metallic chromium is provided as a first layer on the surface of a galvanized steel sheet. An organic film is provided as the upper layer thereof. The organic film contains organic polymer resin and a rust inhibitor at the weight percentage of nonvolatile matter and contains 30-80wt.% organic polymer resin and 3-50wt.% rust inhibitor. Herein, in the organic film, polyisocyanate compound is mixed at the rate of 5-80 pts.wt. for 100 pts.wt. base resin having OH group or COOH group. Film thickness C satisfies the following formula. 0.1(Ra<3> +2)<=C<=3.0 (but, Ra denotes centerline mean roughness of surface of galvanized steel sheet) Thereby, press moldability and corrosion resistance are enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic composite coated steel sheet based on a zinc-based plated steel sheet used for automobile bodies, home electric appliances and the like, which is excellent in press formability and corrosion resistance. It is a thing.

[0002]

2. Description of the Related Art In a press working process of an automobile body, workability, degreasing property, and chemical conversion processability are required, so that it is rare that a high-viscosity press oil is used. Used as it is as press oil. In addition, particularly in the press working of the outer panel of the vehicle body, a cleaning oil (lubricity is further inferior to the rust preventive oil) is used to prevent a pressing flaw. Therefore, there is a problem that problems such as press cracking are likely to occur when processing a part having a complicated shape.
Therefore, there is a demand for the development of a material having excellent press formability that enables stable press forming even in the processing of a portion having a complicated shape.

On the other hand, in the field of home electric appliances, the material is often molded and processed using a press oil, and after being processed, it is used after degreasing with a chlorofluorocarbon solvent. However, CFC-based solvents cause ozone layer depletion of the earth, and the working environment in which press oil is used is poor for workers. Is being developed. Under the above background, conventionally, the following organic composite coated steel sheets have been proposed.

(1) In Japanese Patent Laid-Open No. 64-8033, Z
Having a chromate layer on the surface of the n-Ni alloy plated steel sheet,
An organic composite-coated steel sheet in which an organic film composed of an amine-modified epoxy resin containing silica or chromate is coated as a second layer on the upper layer is shown. (2) Japanese Patent Application Laid-Open No. 3-284942 discloses an organic resin containing silica or fluororesin fine powder in an organic film in order to improve the powdering resistance and flaking resistance of a galvannealed steel sheet. A coated alloyed hot-dip galvanized steel sheet is shown.

(3) Japanese Unexamined Patent Publication No. 5-255587 discloses that
An organic composite coated steel sheet having an organic coating containing water-dispersed polyurethane resin, silica, polyolefin wax and / or fluororesin fine powder on the upper surface of the cold-rolled steel sheet or the zinc-based plated steel sheet is subjected to some surface treatment. It is shown. (4) JP-A-5-65666 discloses that a zinc-based plated steel sheet has a chromate layer on its surface, and an aqueous resin is formed on the chromate layer.
Silica, a molecular weight of 1000 to 4000 with a polar group,
An organic composite-coated steel sheet having an organic coating containing a polyolefin wax dispersion (particle size 3.0 μm or less) and a Teflon dispersion (particle size 3.0 μm or less) having a softening temperature of 150 ° C. or less is shown.

(5) Japanese Patent Laid-Open No. 6-173037 discloses that
An organic composite coated steel sheet having an organic coating containing an ether ester type urethane resin, an epoxy resin, silica and a polyolefin wax is shown. (6) JP-A-6-57440 has a chromate layer on the surface of a zinc-based or aluminum-plated steel sheet, and a carboxyl-modified epoxy resin or polyvinyl butyral resin, silica, polyethylene wax and polytetrafluoride as the upper layer. An organic composite coated steel sheet having an organic coating containing fine ethylene resin powder is shown.

(7) JP-A-2-43040 discloses a zinc-based plated steel sheet having a chromate layer on the surface thereof, and a carboxyl-modified epoxy resin or polyvinyl butyral resin, silica, and a polyolefin wax having a melting point of 70 ° C. or higher as the upper layer. And fluororesin fine powder (particle size 1.0 to 7.0 μ
An organic composite coated steel sheet having an organic coating containing m) is shown. (8) JP-A-3-2257 discloses that a cold-rolled steel sheet or a zinc-based plated steel sheet has a phosphate coating or a chromate coating on the surface, and an epoxy resin, silica, 11
Polyolefin wax having a melting point of 0 ° C. or higher (average particle size 2.0 to 5.0 μm, specific gravity 0.94 to 0.9
8) and an organic composite-coated steel sheet having an organic coating containing a fluororesin fine powder.

[0008]

[Problems to be Solved by the Invention] However, the above-mentioned (1)
Although the organic composite coated steel sheets of (8) to (8) have excellent lubrication characteristics in press formability with a die that does not have a drawing bead like drawn parts of small items, they have excellent lubrication properties. Sufficient lubrication characteristics cannot be obtained by press molding with a beaded mold, and excellent press moldability cannot be obtained.

Further, recently, corrosion resistance (corrosion rust resistance) in a special environment where iron rust coexists in a corrosive environment has begun to be a problem (CAMP-ISIJ Vol.5 (1992), p. 169
3). That is, when the organic composite-coated steel sheet is used in such an environment, iron rust adheres to the surface of the organic coating, significantly lowering the original excellent corrosion resistance of the organic composite-coated steel sheet, and as a result, the organic coating is applied. It has been pointed out that there is a problem of decreasing the superiority to non-galvanized steel sheet, and improvement of such rust resistance is required.
The corrosion resistance of the organic composite coated steel sheets of (8) to (8) is not at a sufficient level.

[0010] Regarding the improvement of rust resistance, "GALVATECH '
92, p372 ", describes that when the cross-linking density is reduced by reducing the amount of the cross-linking agent added to the organic resin, the rust rust resistance of the organic composite coated steel sheet is reduced. It does not show any specific means for improving the sex. The present invention has been made in view of the above problems of the prior art, and is excellent in press molding using a mold provided with a squeezing bead as typified by large automobile parts by improving the lubricity of an organic film. An object of the present invention is to provide an organic composite-coated steel sheet which has press formability and is excellent in corrosion resistance.

[0011]

[Means for Solving the Problems] The inventors have found that the film composition of the organic composite coated steel sheet, the film thickness of the organic coating, the surface roughness of the base plated steel sheet of the organic composite coated steel sheet, the press formability, the corrosion resistance, etc. As a result of repeated studies on the relationship, the following findings were obtained. First, for improving the rust resistance, use a polyisocyanate compound as a curing agent, to increase the crosslink density of the organic film by polyfunctionalizing the polyisocyanate compound, and silica as a rust preventive additive. It has been found that the combined addition of the sparingly soluble chromate in a specific ratio is extremely effective in obtaining excellent resistance to rust.

Further, for the purpose of improving the press forming using a die provided with a drawing bead represented by a large automobile part, a factor of deterioration of formability in the press forming with an organic composite coated steel sheet with a drawing bead was investigated. , The organic composite coated steel sheet peels off the organic film due to sliding accompanied by plastic deformation such as bending and bending back when passing through the bead, and the exposed area of the plating layer after passing the bead is extremely increased compared with that before passing through the bead. For this reason, it was found that the sliding property after passing through the bead significantly increased the area where the plating layer and the press die were in direct contact with each other, resulting in deterioration of lubricity and no satisfactory press formability. Therefore, as a result of further studies on improving the lubricity of the steel sheet after passing through the beads, the following facts have been found regarding the improvement of lubricity.

(1) By setting the thickness of the organic coating to a certain thickness Co or more, good lubricity can be obtained even after passing through the beads. (2) Depending on the surface roughness of the base plated steel sheet of the organic composite coated steel sheet and the lubricant content in the organic coating, the minimum film thickness Co of the organic coating required to have good lubricity even after passing through the beads.
In contrast, between the minimum required film thickness Co of the organic film to have good lubricity, the lubricant content in the organic film and the surface roughness Ra of the base-plated steel plate of the organic composite-coated steel plate, There exists the relationship of the following empirical formula (i), and if the film thickness of the organic film is not less than this film thickness Co, good lubricity can be obtained. 0.1 [Ra ³ +1.5 {2 / (D + 2)} + 0.5] = Co (i) where Ra: center line average roughness (μm) of zinc-based plated steel surface D: lubrication in organic coating Content of agent (nonvolatile) (wt
%) Co: Minimum film thickness required to have good lubricity (μ
m)

(3) As a polyolefin wax added as a lubricant, a polyolefin wax produced by a coordinated anionic polymerization method using a Ziegler type catalyst has excellent lubricity, and among them, a specific softening agent is used. The lubricity is remarkably improved by using the polyethylene wax having the point and the molecular weight. (4) As the fluororesin fine powder, tetrafluoroethylene resin fine powder has particularly excellent lubricity, and among them, low molecular weight tetrafluoroethylene resin fine powder exhibits particularly excellent lubricity, and further, By using the tetrafluoroethylene resin fine powder having a specific melting point, the lubricity is remarkably improved.

The present invention has been made on the basis of such findings, and is characterized by having the following configuration. (1) As a first layer on the surface of a zinc-based plated steel sheet, a chromate layer having an adhesion amount of 5 to 200 mg / m ^{2 in} terms of metallic chromium is provided, and as a second layer above the chromate layer, the organic layer shown in (i) below is used. Polymer resin and rust preventive additive in a weight ratio of non-volatile content, organic polymer resin: 30 to 80 wt%, rust preventive additive:
An organic composite-coated steel sheet having an organic coating contained in a proportion of 3 to 50 wt% and having a film thickness of the organic coating satisfying the following (ii), which is excellent in press formability and corrosion resistance. (i) Base resin having OH group or COOH group [A]
(However, excluding epoxy resin in which at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the end of the epoxy resin) 100 parts by weight (solid content),
Organic polymer resin in which polyisocyanate compound [B] is mixed in a proportion of 5 to 80 parts by weight (solid content) (ii) The film thickness of the organic film satisfies the following formula (1). 0.1 (Ra ³ +2) ≦ C ≦ 3.0 (1) where C: thickness of organic coating (μm) Ra: center line average roughness (μm) of zinc-based plated steel surface

(2) As a first layer on the surface of a zinc-based plated steel sheet, the amount of adhesion is 5 to 200 mg / m in terms of metal chromium.
^It has a chromate layer of ² and, as a second layer on top of it, an organic polymer resin shown in (i) below, a lubricant shown in (ii) below, and an anticorrosive additive are added in a weight ratio of non-volatile content of organic matter. Polymer resin: 30-80 wt%, lubricant: 50 wt% or less (excluding 0 wt%), anti-rust additive: 3-50 wt
%, An organic composite-coated steel sheet excellent in press formability and corrosion resistance, wherein the organic coating film contains the organic coating film in a proportion of%. (i) Base resin having OH group or COOH group [A]
(However, excluding epoxy resin in which at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the end of the epoxy resin) 100 parts by weight (solid content),
Organic polymer resin in which polyisocyanate compound [B] is mixed in a ratio of 5 to 80 parts by weight (solid content) (ii) Fluorine resin fine powder, polyolefin wax, 1
At least one lubricant selected from the group consisting of a mixture of polyolefin and fluororesin in one particle, graphite, boron nitride, or fluorocarbon (iii) The film thickness of the organic film is (2) Satisfy the formula. 0.1 [Ra ³ +1.5 {2 / (D + 2)} + 0.5] ≦ C ≦ 3.0 (2) where C: thickness of organic coating (μm) Ra: center of zinc-based plated steel surface Line average roughness (μm) D: Content of lubricant (nonvolatile component) in organic film (wt)
%)

(3) In the organic composite coated steel sheet according to (2) above, the lubricant contained in the organic coating is polyolefin wax (E) and fluororesin fine powder (F) in a weight ratio of E.
/ F = 90/10 to 10/90, which is a composite lubricant, is an organic composite-coated steel sheet having excellent press formability and corrosion resistance. (4) In the organic composite-coated steel sheet according to (2) or (3) above, the polyolefin wax (E) contained in the organic coating is a polyolefin wax produced by a coordinated anionic polymerization method using a Ziegler-based catalyst. And an organic composite coated steel sheet with excellent corrosion resistance. (5) In the organic composite coated steel sheet according to any one of (2) to (4) above, the polyolefin wax (E) contained in the organic coating has a polyethylene wax having an average molecular weight of 700 to 4500 and a softening point of 100 to 140 ° C. An organic composite coated steel sheet excellent in press formability and corrosion resistance.

(6) In the organic composite coated steel sheet according to any one of the above (2) to (5), the fluororesin fine powder (F) contained in the organic coating satisfies the condition (a) below. An organic composite coated steel sheet that is an ethylene resin fine powder and has excellent press formability and corrosion resistance. (a) In the flow characteristic test method using a capillary rheometer according to JIS K 7199, the apparent melt viscosity measured under the following measurement conditions satisfies the following expression (3) with the apparent shear rate. .

(Equation 3) Measurement conditions Test temperature: 330 ° C Barrel diameter: 9.55 mm Capillary dimensions: Diameter d = 1 mm, length 1 = 10 mm Capillary inlet: Flat

(7) In the organic composite coated steel sheet according to any one of (2) to (6) above, the fluororesin fine powder (F) contained in the organic coating has a melting point of 300 to 330 ° C. An organic composite coated steel sheet that is fine powder and has excellent press formability and corrosion resistance. (8) In the organic composite-coated steel sheet according to (2), the lubricant particles contained in the organic film are a mixture of polyolefin (E ′) and fluororesin (F ′) in one particle. Or a composite lubricant in which the lubricant (G) is blended with the polyolefin wax (E) and / or the fluororesin fine powder (F), and constitutes the lubricant (G). Polyolefin (E ')
An organic composite coated steel sheet excellent in press formability and corrosion resistance, which is a lubricant or a composite lubricant in which a fluororesin (F ′), a polyolefin wax (E) and a fluororesin fine powder (F) are blended in the following weight ratios. (E + E ') / (F + F') = 10/90 to 90/10

(9) In the organic composite-coated steel sheet according to (8) above, the polyolefin (E ') and the polyolefin wax (E) constituting the lubricant (G) contained in the organic film.
Is a polyolefin or polyolefin wax produced by a coordinated anionic polymerization method using a Ziegler-based catalyst, which is an organic composite-coated steel sheet excellent in press formability and corrosion resistance. (10) In the organic composite-coated steel sheet according to (8) or (9), the polyolefin (E ′) and the polyolefin wax (E) that form the lubricant (G) contained in the organic coating have an average molecular weight of 700 to 4500. , Softening point: 1
An organic composite coated steel sheet having excellent press formability and corrosion resistance, which is polyethylene or polyethylene wax at 00 to 140 ° C.

(11) In the organic composite coated steel sheet according to any one of the above (8) to (10), the fluororesin (F ') and the fluororesin fine powder (F) constituting the lubricant (G) contained in the organic film. ) Is an organic composite coated steel sheet excellent in press formability and corrosion resistance, which is a tetrafluoroethylene resin or tetrafluoroethylene resin fine powder satisfying the following condition (a). (a) In the flow characteristic test method using a capillary rheometer according to JIS K 7199, the apparent melt viscosity measured under the following measurement conditions satisfies the following expression (3) with the apparent shear rate. .

[Equation 4] Measurement conditions Test temperature: 330 ° C Barrel diameter: 9.55 mm Capillary dimensions: Diameter d = 1 mm, length 1 = 10 mm Capillary inlet: Flat

(12) In the organic composite coated steel sheet according to any one of the above (8) to (11), the fluororesin (F ') and the fluororesin fine powder (F) which constitute the lubricant (G) contained in the organic film. ) Is a tetrafluoroethylene resin or a fine powder of tetrafluoroethylene resin having a melting point of 300 to 330 ° C., which is an organic composite coated steel sheet excellent in press formability and corrosion resistance. (13) In the organic composite-coated steel sheet according to any one of (1) to (12), the polyfunctional polyisocyanate compound contained in the organic coating has at least three isocyanate groups in one molecule. The organic composite coated steel sheet which is excellent in press formability and corrosion resistance. (14) In the organic composite-coated steel sheet according to any one of (1) to (13), the polyfunctional polyisocyanate compound contained in the organic coating has at least four isocyanate groups in one molecule. The organic composite coated steel sheet which is excellent in press formability and corrosion resistance.

(15) In the organic composite coated steel sheet according to any one of (1) to (12), the polyfunctional polyisocyanate compound contained in the organic coating has at least 6 isocyanate groups in one molecule. An organic composite coated steel sheet that is a polyisocyanate compound and has excellent press formability and corrosion resistance. (16) In the organic composite-coated steel sheet according to any one of (1) to (12), the polyfunctional polyisocyanate compound contained in the organic coating is a hexamethylene diisocyanate having at least 6 isocyanate groups in one molecule. Organic composite coated steel sheet with excellent press formability and corrosion resistance, which is a functional material.

(17) In the organic composite coated steel sheet according to any one of the above (1) to (16), OH group or COOH
The base resin having a group is an epoxy resin, a modified epoxy resin (excluding an epoxy resin in which at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the terminal of the epoxy resin) and polyhydroxypolyether. An organic composite-coated steel sheet which is one or more organic polymer resins selected from ether resins and is excellent in press formability and corrosion resistance. (18) In the organic composite-coated steel sheet according to any one of (1) to (17), the rust preventive additive contained in the organic coating is
An organic composite coated steel sheet which is made of silica and / or a poorly soluble chromate and has excellent press formability and corrosion resistance.

(19) In the organic composite coated steel sheet according to any one of the above (1) to (17), the rust preventive additive contained in the organic coating is composed of silica and a sparingly soluble chromate in the following proportions by weight. Organic composite coated steel sheet with excellent press formability and corrosion resistance. Silica / Slightly soluble chromate = 90/10 to 2/98 (20) In the organic composite-coated steel sheet according to any one of the above (1) to (19), the adhesion amount is 0 as a third layer on the upper layer of the organic film. An organic composite coated steel sheet excellent in press formability and corrosion resistance having a rust preventive oil layer of 0.01 to 10 g / m ² .

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below together with the reasons for limitation. As the original plate of the zinc-based plated steel sheet used in the present invention, cold-rolled steel sheet for general processing (CQ) to cold-rolled steel sheet for deep drawing (DQ), cold-rolled steel sheet for high deep drawing (DD)
Q), all cold-rolled steel sheets for soft working up to cold-rolled steel sheets for ultra-deep drawing (EDDQ) can be applied, and when used for electroplating, the annealing method can be either box annealing or continuous annealing. Good. Further, as the original plate, a high-strength steel plate having a relatively low strength level having bake hardenability, a general high-strength steel plate exceeding 390 MPa, a descaled hot-rolled steel plate and the like can be used. When a cold-rolled steel sheet for soft working, such as a cold-rolled steel sheet for high-deep drawing (DDQ) or a cold-rolled steel sheet for ultra-deep drawing (EDDQ), which has excellent press formability, is used as a base plate for a zinc-based plated steel sheet, In particular, a particularly excellent effect can be obtained.

As the plating layer of the zinc-based plated steel sheet, Z
n plating, Zn-Ni alloy plating (Ni content 10 to 1
5 wt%), Zn-Fe alloy plating (Fe content ratio 5 to 2)
5 wt% or Fe content 60 to 90 wt%), Zn-
Mn alloy plating (Mn content 30-80 wt%), Zn
-Co alloy plating (Co content ratio 3 to 15 wt%), Zn
-Cr alloy plating (Cr content 5 to 30 wt%), Zn
-Al alloy plating (Al content rate 3 to 60 wt%) and the like. Further, for the purpose of improving corrosion resistance, each of the above plating components may contain alloy elements such as Co, Fe, Ni and Cr, oxides or salts such as silica, alumina and sparingly soluble chromate, and polymers. .

Further, it is also possible to make a multi-layer plating in which two or more kinds of the same or different kinds of the above plating layers are plated. As the plating method, any of the electrolytic method, the melting method and the vapor phase method which can be carried out can be adopted, but the electrolytic method is most advantageous from the viewpoint of the selectivity of the material of the base steel sheet. If the coating weight is less than 10 g / m ² , there is a problem because the corrosion resistance is poor. Further, in the case of Zn-Ni alloy plating, Zn-Fe alloy plating, Zn-Mn alloy plating, Zn-Co alloy plating, and Zn-Cr alloy plating, the powdering resistance is inferior if it exceeds 60 g / m ^2. The coating weight is preferably 10 to 60 g / m ^2, and in order to ensure higher corrosion resistance and powdering resistance, the coating weight is 15 to 50 g / m ^2.
It is preferably m ² .

Further, regarding Zn-Ni alloy plating, Ni is formed at the interface between the base steel sheet and the Zn-Ni alloy plating layer.
By providing the plating layer, excellent low temperature chipping resistance can be secured. The Ni plating layer, the amount of plating adhesion can not be obtained a sufficient low temperature chipping resistance is less than 0.05 g / m ^2, whereas, since the powdering resistance exceeds 1 g / m ² is deteriorated, plating coating weight is preferably set to 0.05 to 1 g / m ^2, also to ensure a more advanced low temperature chipping resistance and powdering resistance shall be 0.1 to 0.5 g / m ² It is preferable.

The chromate layer formed on the surface of the zinc-plated steel sheet has a passivation effect due to hexavalent chromate ions contained in the chromate layer and chromium water of trivalent chromium which is a reduction product of chromate ions. The effect of reducing the anode area by covering the surface with a hydrated oxide film, and 3
The corrosion of the steel sheet is suppressed by the effect that the chromium hydrated oxide film of valent chromium acts as a diffusion barrier for water and oxygen. The amount of the chromate layer deposited is 5 to 200 mg / m in terms of metal chromium.
^{Assume 2} . If the adhesion amount is less than 5 mg / m ² , sufficient corrosion resistance cannot be obtained, while if it exceeds 200 mg / m ² , the weldability deteriorates. Further, in order to obtain higher corrosion resistance and weldability, the range is preferably 10 to 150 mg / m ² .

As the chromate treatment for forming the chromate layer, any of reaction type, electrolytic type and coating type methods can be applied. From the viewpoint of corrosion resistance, a coating type in which the chromate layer contains a large amount of hexavalent chromate ions is preferable. As the coating type chromate treatment, a partially reduced chromic acid aqueous solution is the main component, and the following (1)
A treatment liquid containing one or more of the components (7) to be added as required is applied to a zinc-based plated steel sheet and dried without washing with water.

(1) Organic resins such as water-soluble or water-dispersible acrylic resins and polyester resins (2) Oxide colloids of silica, alumina, titania, zirconia and / or powders (3) Molybdic acid, tungstic acid , Acids such as vanadic acid and / or salts thereof (4) Phosphoric acids such as phosphoric acid and polyphosphoric acid (5) Fluorides such as zirconium fluoride, silicofluoride and titanium fluoride (6) Metal ions such as zinc ion (7 ) Conductive fine powder of iron phosphide, antimony-doped tin oxide, etc.In the coating type chromate treatment, the treatment liquid is usually applied by the roll coater method, but after coating by the dipping method or the spray method, the air knife method or the roll squeezing method is applied. It is also possible to adjust the coating amount by the method.

The organic film formed as the second layer on the chromate layer suppresses the excessive elution of hexavalent chromate ions in the chromate layer into the corrosive environment and maintains the anticorrosion effect. Anticorrosion additives such as silica and sparingly soluble chromate added in the organic film further improve the corrosion resistance. Further, the lubricant added to the organic film improves the lubrication characteristics of the zinc-based plated steel sheet during press forming. This organic film is formed by applying a resin solution containing an organic polymer resin having an OH group or a COOH group and baking it.

The base resin having an OH group or a COOH group is, for example, an epoxy resin or a modified epoxy resin (provided that at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the terminal of the epoxy resin. Epoxy resin), polyhydroxypolyether resin, acrylic copolymer resin, ether-acrylic acid copolymer resin, alkyd resin, polybutadiene resin, phenol resin, polyurethane resin, polyamine resin, polyphenylene resin and these Examples include a mixture or addition condensation product of two or more kinds of resins. Examples of the epoxy resin include bisphenol A, bisphenol F, novolac, and the like, glycidyl etherified epoxy resin, bisphenol A to which propylene oxide, ethylene oxide, or polyalkylene glycol is added to form a glycidyl etherified epoxy resin, and an aliphatic epoxy resin. An alicyclic epoxy resin, a polyether epoxy resin, etc. can be used.

It is desirable that these epoxy resins have a number average molecular weight of 1500 or more, especially when curing at a low temperature is required. The epoxy resins may be used alone or as a mixture of different types. Examples of the modified epoxy resin include resins obtained by reacting various modifying agents with the epoxy group or hydroxyl group in the epoxy resin. For example, epoxy ester resin obtained by reacting a carboxyl group in a drying oil fatty acid, acrylic acid,
Epoxy acrylate resin modified with methacrylic acid, etc.
Examples thereof include a urethane-modified epoxy resin obtained by reacting an isocyanate compound and an amine-added urethane-modified epoxy resin obtained by adding an alkanolamine to a urethane-modified epoxy resin obtained by reacting an epoxy resin with an isocyanate compound.

The above polyhydroxypolyether resin is
A polymer obtained by polycondensing a mononuclear or dinuclear dihydric phenol or a mixed dihydric phenol of a mononuclear type and a divalent type with an approximately equimolar amount of epihalohydrin in the presence of an alkali catalyst. . Representative examples of mononuclear dihydric phenols include resorcin, hydroquinone and catechol, and representative examples of binuclear phenols include bisphenol A. These may be used alone or in combination of two or more. May be.

The above-mentioned acrylic copolymer resin is a resin synthesized by a solution polymerization method, an emulsion polymerization method, a suspension polymerization method or the like using an unsaturated monomer, and includes acrylic acid ester, methacrylic acid ester, Acrylotril,
It can be obtained by polymerizing one or more monomers such as styrene, acrylic acid, methacrylic acid, acrylamide and vinyltoluene. Further, this resin may be a resin modified with other alkyd resin, epoxy resin, phenol resin or the like. Further, the alkyd resin may be a known one obtained by a usual synthesis method, for example, oil-modified alkyd resin, rosin-modified alkyd resin, phenol-modified alkyd resin, styrenated alkyd resin, silicone-modified alkyd resin, Examples thereof include acrylic modified alkyd resin and oil-free alkyd resin (polyester resin).

The method of curing the base resin is preferably a urethanization reaction between an isocyanate and a hydroxyl group in the base resin, but in order to stably store the coating composition before film formation, a curing agent is used. It is necessary to protect the isocyanate. As a method of protecting the isocyanate, a protecting method in which the protecting group is eliminated during the heat treatment and the isocyanate group is regenerated can be adopted. The polyisocyanate compound used in the present invention is an aliphatic, alicyclic (including heterocyclic) or aromatic isocyanate compound having at least two isocyanate groups in one molecule, or a polyhydric alcohol part of these compounds. Compounds that have been reacted chemically, or compounds such as buret type adducts and isocyanuric ring type adducts of these compounds. For example,

M- or p-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, or p-xylylene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate, isophorone diisocyanate, triphenylmethane-4,4 ′ , 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene,
A polyisocyanate compound having three or more isocyanate groups such as 2,4,6-triisocyanatotoluene and 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate,

The above compounds alone or in combination with polyhydric alcohols (dihydric alcohols such as ethylene glycol and propylene glycol: trihydric alcohols such as glycerin and trimethylolpropane; tetrahydric alcohols such as pentaerythritol; sorbitol, dipenta Hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylene diisocyanate, 4,4'-diphenylmethane diisocyanate, which is a reaction product of erythritol and other hexahydric alcohols) in which at least two isocyanate groups remain in one molecule. , 4,4′-methylenebis (cyclohexyl isocyanate) and the like, buret type adducts, isocyanuric ring type adducts, and the like.

In particular, when iron rust coexists in a corrosive environment and the resin barrier property in the organic coating greatly contributes to the suppression of corrosion, a polyisocyanate compound having at least three isocyanate groups in one molecule, More preferably 4
It is preferable to use a polyisocyanate compound having one or more, and more preferably six or more isocyanate groups as a curing agent.

Examples of the polyfunctional polyisocyanate compound having at least 3 isocyanate groups in one molecule include compounds having 3 or more isocyanate groups in one molecule, and isocyanate compounds having at least 2 isocyanate groups in one molecule. There are compounds such as those obtained by reacting with a polyhydric alcohol, or compounds such as buret type adducts and isocyanuric ring type adducts thereof. For example, triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4'.
-Polyisocyanate compounds having three or more isocyanate groups such as dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate; ethylene glycol, propylene glycol, 1,4-butylene glycol, polyalkylene glycol, trimethylolpropane , An adduct obtained by reacting a polyisocyanate compound in an amount such that an isocyanate group is in excess with respect to a hydroxyl group of a polyol such as hexanetriol; hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate,
4,4'-diphenylmethane diisocyanate, 4,
4'-methylenebis (cyclohexyl isocyanate)
And the like, and isocyanuric ring type adducts.

In the adduct obtained by reacting the polyisocyanate compound in an amount such that the isocyanate group is in excess with respect to the hydroxyl group of the polyol, the polyisocyanate compound is the polyisocyanate compound having three or more isocyanate groups. And aliphatic diisocyanate compounds such as hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, dimer acid diisocyanate and lysine diisocyanate; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-
2,4- (or -2,6-) diisocyanate, 1,3
Alicyclic diisocyanate compounds such as-(or 1,4-) di (isocyanatomethyl) cyclohexane; and xylylene diisocyanate, tolylene diisocyanate, m
Examples thereof include aromatic diisocyanate compounds such as-(or p-) phenylene diisocyanate, diphenylmethane diisocyanate, and bis (4-isocyanatophenyl) sulfone.

Among the polyfunctional polyisocyanate compounds having at least 6 isocyanate groups in one molecule (6-functional polyisocyanate compound),
The polyfunctional hexamethylene diisocyanate is most effective in resisting rust. The polyfunctional polyisocyanate compound used in the present invention may be a mixture of homologous compounds having different numbers of isocyanate groups in one molecule.
Moreover, you may use together 2 or more types of the said polyfunctional polyisocyanate compound.

As described above, as a method for protecting the isocyanate of the curing agent in order to stably store the film-forming product, the protecting group (blocking agent) is desorbed during heat curing and the isocyanate group is regenerated. As the protective agent (blocking agent), there are, for example, the following ones. By reacting one or more of these with the polyisocyanate compound, stable protection is achieved at least at room temperature. The obtained isocyanate compound can be obtained.

(1) Aliphatic monoalcohols such as methanol, ethanol, propanol, butanol and octyl alcohol (2) Monoethers of ethylene glycol and / or diethylene glycol, for example, methyl, ethyl, propyl (n-, iso) , Ethers such as butyl (n-, iso, sec) (3) Phenols such as phenol and cresol (4) Oximes such as acetoxime and methyl ethyl ketone oxime

The polyisocyanate compound (B) as a curing agent is 5 to 80 parts by weight (solid content), preferably 10 to 50 parts by weight with respect to 100 parts by weight (solid content) of the base resin (A).
It is mixed in a ratio of parts by weight (solid content). If the compounding amount of the curing agent is less than 5 parts by weight, the cross-linking density of the formed film will be insufficient and the effect of improving the rust resistance will be small. On the other hand, 80
If blended in excess of parts by weight, unreacted residual isocyanate absorbs water and not only has no effect on resisting rust, but on the contrary, corrosion resistance (perforation resistance) and adhesion are impaired.
For this reason, the amount of the polyisocyanate compound is 5-80 parts by weight with respect to 100 parts by weight of the base resin (A).

Further, part or all of the methylol compound obtained by reacting one or more selected from melamine, urea and benzoguanamine as a curing agent with formaldehyde is reacted with a monohydric alcohol having 1 to 5 carbon atoms. The alkyl etherified amino resin may be used in combination with an isocyanate compound. The resin is sufficiently cross-linked with the above-mentioned curing agents, but it is desirable to use a known curing-accelerating catalyst in order to further increase the low temperature cross-linking property. Examples of the curing acceleration catalyst include N-ethylmorpholine, dibutyltin dilaurate, cobalt naphthenate, stannous chloride, zinc naphthenate, and bismuth nitrate.

The content of the organic polymer resin in the organic film is
The weight ratio of the nonvolatile content is 30 to 80 wt%. When the amount of organic polymer resin is less than 30 wt%, press moldability,
Corrosion resistance and paint adhesion deteriorate. On the other hand, if it exceeds 80 wt%, the effect of the added lubricant or rust preventive additive is not sufficiently exerted, and press formability and corrosion resistance deteriorate. Further, in order to obtain higher press moldability, corrosion resistance and paint adhesion, it is preferable that the range is 40 to 70 wt%.

By adding a lubricant to the organic film,
The press formability is remarkably improved. Further, as compared with an organic film without addition of a lubricant, a better film formability can be obtained with a smaller film thickness. This is because the addition of a lubricant to the organic coating improves the lubricity of the organic coating itself, and as a result, sufficient lubricity can be imparted to the organic coating that remains without peeling off when the beads pass. Conceivable. If the amount of lubricant added to the organic film exceeds 50 wt%, the adhesion with the cationic electrodeposition coating will deteriorate, so the amount of lubricant added will be 50 wt%.
Below. Further, in order to obtain higher press moldability and higher paint adhesion, it is preferably in the range of 5-40 wt%.

As the lubricant, fluororesin fine powder (eg, tetrafluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, tetrafluoride Ethylene-ethylene copolymer resin, trifluorochloroethylene resin,
Fine powder such as vinylidene fluoride resin), polyolefin wax (for example, polyethylene wax, polypropylene wax, etc.), lubricant containing mixed polyolefin and fluororesin in one particle, graphite, boron nitride, carbon fluoride At least one lubricant selected from the above is used. Here, by adding the polyolefin wax (E) and the fluororesin fine powder (F) in combination at a weight ratio of nonvolatile components of E / F = 90/10 to 10/90, lubricity is remarkably improved. To do.

The mechanism by which the excellent lubricity is obtained by the combined addition of the polyolefin wax (E) and the fluororesin fine powder (F) is not always clear, but
The polyolefin wax has a semi-melting lubrication mechanism by melting and softening during sliding, while the fluorocarbon resin fine powder has a self-lubricating property due to weak intermolecular interaction due to small polarization of C—F bond. In addition, since it has a cleaving lubrication mechanism due to cleavage, it is considered that excellent lubricity can be obtained by the synergistic effect of the composite addition of lubricants having different lubrication mechanisms.

The weight ratio of the polyolefin wax (E) to the fluororesin fine powder (F) is E / F = 90/10 to 10
The range is / 90. If the weight ratio of polyolefin wax / fluorine resin fine powder is less than 10/90, 90 /
Even if it exceeds 10, the synergistic effect due to the composite addition becomes insufficient and sufficient lubricity cannot be obtained. Further, when the E / F weight ratio is in the range of 70/30 to 30/70, particularly excellent lubricating performance is obtained.

In the present invention, as the polyolefin wax used as a lubricant, a polyolefin wax produced by a coordinated anionic polymerization method using a Ziegler type catalyst is preferable because it has particularly excellent lubricity.
The following are the main methods for producing a polyolefin wax. (a) A method for producing by a coordinated anionic polymerization method using a Ziegler type catalyst (b) A method for producing by a radical polymerization method using a radical catalyst (c) A method for thermally decomposing a general molding polyolefin

Of these, the polyolefin waxes produced by the methods (b) and (c) have a branched structure having long chain branches as shown in FIG. On the other hand, the polyolefin wax produced by the method (a) does not have long-chain branching as shown in FIG. Is less likely to cause steric hindrance due to branching. Therefore, compared to the one produced by the method of (b) or (c), it is easy to concentrate in the outermost layer of the organic film,
Since the area where the tool and the polyolefin wax directly contact each other increases, it is presumed that the tool has better lubricity than the polyolefin wax produced by the methods (b) and (c).

As the polyolefin wax added as a lubricant, it is preferable to use one produced by the coordinated anionic polymerization method using the above-mentioned Ziegler type catalyst. Among them, polyethylene wax is most preferable. It is preferable because it has excellent lubricity. Also,
Among polyethylene waxes, the molecular weight is 700-450
0, a softening point of 100 ° C. to 140 ° C. shows particularly excellent lubricity, and a molecular weight of 1000 to 3500, a softening point of 1
Those having a temperature of 10 ° C to 130 ° C show the most excellent lubricity.

FIG. 3 shows a zinc-based plated steel sheet (No.
The surface of 6) has a chromate layer as the first layer, and the second layer
As a layer, an organic polymer resin (No. 15 in Table 5) is added to a rust-preventive additive (silica + sparingly soluble chromate) and a polyethylene wax having a different molecular weight from the production method (softening point 110 ° C to 130 ° C).
For an organic composite-coated steel sheet having an organic coating (film thickness 0.8 μm) added with (° C.), the relationship between the molecular weight of polyethylene wax added in the organic coating and press formability is shown. The press formability shown in the figure corresponds to the press formability condition 2 (press mold condition stricter than the condition 1) in the examples described later.

FIG. 4 shows a zinc-based plated steel sheet (No.
The surface of 6) has a chromate layer as the first layer, and the second layer
As a layer, an organic polymer resin (No. 15 in Table 5), a rust-preventive additive (silica + sparingly soluble chromate), a tetrafluoroethylene resin fine powder (No. 17 in Table 7), a manufacturing method and a molecular weight are used. Different polyethylene wax (softening point 110 ℃ ~ 130
For an organic composite-coated steel sheet having an organic coating (film thickness 0.8 μm) added with (° C.), the relationship between the molecular weight of polyethylene wax added in the organic coating and press formability is shown. The press formability shown in the figure corresponds to the press formability condition 2 (press mold condition stricter than the condition 1) in the examples described later.

According to FIGS. 3 and 4, excellent press moldability is exhibited when polyethylene wax having a molecular weight of 700 to 4500, which is produced by a coordinated anionic polymerization method using a Ziegler type catalyst, is used. It can be seen that those having a molecular weight of 1,000 to 3,500 exhibit particularly excellent press moldability. Further, it is understood that the press moldability is remarkably improved by adding the polyethylene wax together with the fluororesin fine powder.

FIG. 5 shows a zinc-based plated steel sheet (No.
The surface of 6) has a chromate layer as the first layer, and the second layer
As a layer, an organic polymer resin (No. 15 in Table 5) is added to a rust-preventive additive (silica + sparingly soluble chromate) and a polyethylene wax having a different softening point from the production method (molecular weight 1000 to 350).
The relationship between the softening point of the polyethylene wax added to the organic coating and the press formability of the organic composite-coated steel sheet having the organic coating (film thickness 0.8 μm) added with 0) is shown. The press formability shown in FIG. 5 also corresponds to the press formability condition 2 (a press form condition severer than the condition 1) in the examples described later.

FIG. 6 shows a zinc-based plated steel sheet (No.
The surface of 6) has a chromate layer as the first layer, and the second layer
Organic polymer resin (No. 15 in Table 5) as a layer, anti-rust additive (silica + sparingly soluble chromate), tetrafluoroethylene resin fine powder (No. 17 in Table 7), manufacturing method and softening point Different polyethylene waxes (Molecular weight 1000-350
The relationship between the softening point of the polyethylene wax added to the organic coating and the press formability of the organic composite-coated steel sheet having the organic coating (film thickness 0.8 μm) added with 0) is shown. The press formability shown in FIG. 6 corresponds to the press formability condition 2 (press mold condition stricter than the condition 1) in the examples described later.

According to FIGS. 5 and 6, excellent press moldability is exhibited when polyethylene wax produced by a coordinated anionic polymerization method using a Ziegler type catalyst and having a softening point of 100 ° C. to 140 ° C. is used. I understand. If the softening point is less than 100 ° C, the polyethylene wax will completely liquefy and flow during sliding and will mix with the applied oil, failing to exhibit the original lubricating properties of the polyethylene wax, and therefore sufficient press formability can be obtained. Absent. On the other hand, when the softening point is higher than 140 ° C., on the contrary, since the polyethylene wax does not soften during sliding, the inherent semi-melting lubrication mechanism of polyethylene wax does not function, and the press formability is not improved in this case as well. Also, FIG.
Also, according to FIG. 6, it can be seen that those having a softening point of 110 ° C. to 130 ° C. exhibit particularly excellent press moldability. It is also found that the press moldability is remarkably improved by adding the polyethylene wax together with the fine powder of fluororesin.

A polyethylene wax produced by the coordinated anionic polymerization method using a Ziegler type catalyst is provided with a polar group such as a carboxyl group, a hydroxyl group or a carbonyl group by oxidation, and also by an acid, an ester, an aromatic group or the like. Polyethylene wax produced by modification, copolymerization with α-olefin or the like during coordinated anionic polymerization using a Ziegler-based catalyst, even if the softening point and the molecular weight are in the above ranges, provides lubricity. It has no problems and shows excellent press formability.

As the fluororesin fine powder used as a lubricant, tetrafluoroethylene resin fine powder having a small molecular weight is preferable because it has excellent lubricating properties. Since it is difficult to directly measure the molecular weight of the tetrafluoroethylene resin fine powder, the apparent shear rate dependence of the apparent melt viscosity measured by the flow characteristic test method by the capillary rheometer specified in JIS K 7199. Can be used as a measure of the molecular weight. The larger the molecular weight, the larger the apparent melt viscosity at a certain apparent shear rate, and conversely, the smaller the molecular weight, the smaller the apparent melt viscosity.

Then, in the flow characteristic test method using the capillary rheometer in accordance with JIS K 7199, the apparent melt viscosity measured under the following measurement conditions and the apparent shear rate are expressed by the following equation (3). Satisfactory tetrafluoroethylene resin fine powder is preferable because it has particularly excellent lubricating properties.

(Equation 5) Measurement conditions Test temperature: 330 ° C Barrel diameter: 9.55 mm Capillary dimensions: Diameter d = 1 mm, length 1 = 10 mm Capillary inlet: Flat

It is particularly preferable that the tetrafluoroethylene resin fine powder has an average particle diameter in the range of 0.1 to 6 μm.
When the average particle size is less than 0.1 μm, the tetrafluoroethylene resin fine powder is completely hidden in the organic film, and sufficient lubricity cannot be exhibited. On the other hand, if the average particle size exceeds 6 μm, the organic resin cannot hold the tetrafluoroethylene resin fine powder, and is easily lost during press molding, resulting in poor lubricity. Further, among the tetrafluoroethylene resin fine powders having an average particle diameter in this range and satisfying the above formula (3), the tetrafluoroethylene resin fine powders having a melting point of 300 to 330 ° C.
Particularly excellent in press formability.

FIG. 7 shows a zinc-based plated steel sheet (No.
The surface of 6) has a chromate layer as the first layer, and the second layer is an organic polymer resin (No. 15 in Table 5) and a rust preventive additive (silica + slightly soluble chromate) and the above (3). Organic film (film thickness 0.8μ) with addition of tetrafluoroethylene resin fine powder with different melting points satisfying the formula (average particle size 3-5μm)
m)) and a zinc-based plated steel sheet (No. 6 in Table 4) having a chromate layer as the first layer on the surface and an organic polymer resin as the second layer (No. 1 in Table 5).
In 5), rust preventive additive (silica + sparingly soluble chromate), polyethylene wax (No. 3 in Table 6) and tetrafluoroethylene resin fine powder with different melting points satisfying the formula (3) (average particle size 3) ~ 5μm) added organic film (film thickness 0.8μ
With respect to the organic composite coated steel sheet having m), the relationship between the melting point of the tetrafluoroethylene resin fine powder added to the organic coating and the press formability is shown. The press formability shown in FIG. 7 corresponds to the press formability condition 2 in Examples described later. According to FIG. 7, excellent press formability is obtained in the melting point range of 300 to 330 ° C. Therefore, it is preferable to use a fine powder of tetrafluoroethylene resin having a melting point of 300 to 330 ° C.

As described above, the organic composite-coated steel sheet of the present invention exhibits excellent lubricity even in oil-lubrication molding because the polyolefin wax (preferably polyethylene wax) and the fluororesin fine powder (preferably 4) are used. This is due to a synergistic effect obtained by adding a plurality of lubricants having different lubrication mechanisms such as fluorinated ethylene resin fine powder). Therefore, even when a lubricant composed of lubricant particles produced in a form in which a polyolefin component and a fluororesin component are mixed in one particle by so-called melt blending is used, the above-mentioned polyolefin wax and fluororesin fine powder are used. A lubricity equal to or close to that of the case of adding and is added. The same applies to the case where such a lubricant and the polyolefin wax and / or the fine powder of fluororesin are added in combination.

When using the lubricant (G) composed of lubricant particles in which the polyolefin (E ') and the fluororesin (F') are mixed and contained in one particle as described above,
Alternatively, when the lubricant (G) and the polyolefin wax (E) and / or the fluororesin fine powder (F) are added in combination, the polyolefin (E ′) and the fluororesin forming the lubricant (G) are used. The compounding ratio of (F '), polyolefin wax (E) and fluororesin fine powder (F) is (E + E') / (F + F ') = 1 in weight ratio.
It is set to 0/90 to 90/10. Similar to the weight ratio of E / F described above, the weight ratio of (E + E ') / (F + F') is 10
If it is less than / 90 or more than 90/10, the synergistic effect of the composite addition is insufficient, and sufficient lubricity cannot be obtained. Also, from the viewpoint of obtaining better lubricity,
The above weight ratio is particularly preferably in the range of 30/70 to 70/30.

Further, regarding the lubricant (G) composed of lubricant particles in which the polyolefin and the fluororesin are mixed in one particle, the preferable conditions for the polyolefin and the fluororesin which are the constituents are It is the same as the polyolefin wax and the fluororesin fine powder described above.
That is, the fluororesin that constitutes the lubricant (G) is
It is preferable to use a tetrafluoroethylene resin which has an apparent shear rate dependence of the apparent melt viscosity that satisfies the formula (3). Further, the polyolefin which constitutes the lubricant (G) also uses a Ziegler type catalyst. It is preferably produced by an anionic polymerization method, and among them, in particular, molecular weight: 700 to 4500, softening point: 100 to 1
40 ° C, more preferably molecular weight: 1000 to 3500,
Polyethylene having a softening point of 110 to 130 ° C. is preferable.

The amount of the rust preventive additive added to the organic film is 3 to 5
It is set to 0 wt%. If the addition amount is less than 3 wt%, the effect of improving the rust resistance is insufficient, while if it exceeds 50 wt%, the film peels off during press molding and press moldability deteriorates. Further, in order to obtain higher corrosive rust resistance and press formability, it is preferably in the range of 5 to 40 wt%. As the anticorrosive additive, fine powder or colloid of silica, sparingly soluble chromate, aluminum tripolyphosphate dihydrogen phosphate, aluminum phosphomolybdate, zinc phosphate and the like can be used, but among them, from the viewpoint of corrosion resistance. Are most preferably silica and sparingly soluble chromate.
It is presumed that silica is dissolved in a trace amount in a corrosive environment, and the silicate ion functions as a film-forming corrosion inhibitor, so that the anticorrosive effect is exhibited. Further, it is considered that the sparingly soluble chromate releases a hexavalent chromate ion by dissolving in a trace amount in a corrosive environment, and suppresses corrosion of the zinc-based plated steel sheet by a mechanism similar to that of the chromate layer.

Further, it is possible to obtain higher corrosion resistance by adding silica and a sparingly soluble chromate together. That is, silica and a sparingly soluble chromate are contained in an organic film in a weight ratio of silica / poorly soluble chromate of 90 /
By adding in the range of 10 to 2/98, the most excellent corrosion resistance can be obtained due to the synergistic anticorrosion effect of both components. Even if the weight ratio of silica / hardly soluble chromate exceeds 90/10, and if it is less than 2/98, the synergistic effect is insufficient and the corrosion resistance is slightly inferior.

FIG. 8 shows an organic composite obtained by adding a hexamethylene diisocyanate-based 6-functional polyisocyanate compound as a curing agent to an organic film and adding silica and a sparingly soluble chromate as a rust preventive additive in different weight ratios. Regarding the coated steel sheet, the relationship between the weight ratio of silica / hardly soluble chromate and unpainted corrosion resistance (evaluation after 200 cycles of puncture resistance test) and rust resistance (evaluation after 15 cycles of rust resistance test) About. The rust-proof rust resistance shown in the figure is the condition 2 of the rust-proof rust resistance in Examples described later.
(Corresponding to stricter rust resistance test conditions than Condition 1).

According to FIG. 8, if the weight ratio of silica / poorly soluble chromate exceeds 90/10, the rust resistance deteriorates, whereas if it is less than 2/98, normal unpainted corrosion resistance (perforation resistance) Sex) has deteriorated. Therefore, the mixing ratio of silica / slightly soluble chromate is preferably 90/10 to 2/98, and more preferably 50/50 to 10/70.

Furthermore, the embodiment described later (No. 1 and N)
o. As is clear from 307), when a hexamethylene diisocyanate-based 6-functional polyisocyanate compound and an isophorone diisocyanate-based 6-functional polyisocyanate compound are compared, when the silica / slightly soluble chromate compounding ratio is the same, In the case of using a hexamethylene diisocyanate-based hexafunctional polyisocyanate compound, more excellent resistance to rust can be obtained.

The silica used in the present invention is dry silica (eg, AEROSI manufactured by Nippon Aerosil Co., Ltd.).
L 130, AEROSIL 200, AEROSIL
300, AEROSIL 380, AEROSIL R9
72, AEROSIL R811, AEROSIL R8
05 etc.), organosilica sol (for example, MA-CT, IPA-ST, NBA-ST, manufactured by Nissan Chemical Industries, Ltd.).
IBA-ST, EG-ST, XBA-ST, ETC-S
T, DMAC-ST, etc.), precipitated wet silica (eg,
Tokuyama Soto Co., Ltd. T-32 (S), K-41, F-8
0, etc.), gel wet silica (for example, Syroid 244, Syloid 150, Syloid 72, Syloid 65, SHIELDEX, etc., manufactured by Fuji Davison Chemical Co., Ltd.)
Etc. can be used. It is also possible to use a mixture of two or more of the above silicas.

The silica includes hydrophilic silica and hydrophobic silica. Of these, hydrophilic silica can be expected to have an effect of improving rust resistance, but hydrophobic silica significantly improves rust resistance. Hydrophilic silica has a hydroxyl group (

Embedded image ), It is hydrophilic. Since this silanol group is highly reactive, it easily reacts with various organic compounds, and the surface of silica can be organized. On the other hand, the hydrophobic silica is obtained by substituting a part or most of the silanol groups on the surface of the hydrophilic silica with a methyl group or an alkyl group,
The silica surface is hydrophobized.

There are various methods for producing the hydrophobic silica, and the representative ones are reaction of organic solvents such as alcohols, ketones and esters, silanes, silazanes, polysiloxanes and the like. Examples of the method include a reaction pressurization method in an organic solvent and a catalyst heating method. Silica has an excellent anticorrosion effect, but as described above, hydrophobic silica is more effective in improving rust resistance than hydrophilic silica. Due to its strong hydrophilicity, hydrophilic silica is apt to cause permeation of iron ions and iron oxides in iron rust, and it is presumed that this is the reason why it is less effective in improving rust resistance. Therefore, in the present invention, it is preferable to use hydrophobic silica as the rust preventive additive.

The sparingly soluble chromate used in the present invention includes barium chromate (BaCrO ₄ ), strontium chromate (SrCrO ₄ ), and calcium chromate (C
aCrO ₄ ), zinc chromate (ZnCrO ₄ .4Zn (O
H) ₂ ), zinc potassium chromate (K ₂ O ・ 4ZnO ・ 4
Fine powders such as CrO ₃ .3H ₂ O) and lead chromate (PbCrO ₄ ) can be used. It is also possible to use a mixture of two or more of the above-mentioned hardly soluble chromates. However, from the viewpoint of corrosion resistance, barium chromate, which can be expected to have a self-repairing effect by hexavalent chromate ions over a long period of time,
Preference is given to using strontium chromate.

In addition, in the pretreatment process for painting automobiles,
From the viewpoint of minimizing the elution of water-soluble chromium from the sparingly soluble chromate added to the organic film, it is preferable to use barium chromate, which has a low solubility in water. The average particle diameter of the sparingly soluble chromate is preferably in the range of 0.1 to 1.0 μm. If the average particle size is less than 0.1 μm, the solubility of the sparingly soluble chromate in water becomes excessive, so that the self-repairing effect of hexavalent chromate ions is lost, while if it exceeds 1 μm, electrodeposition coating is performed. This is because the smoothness of the surface tends to decrease and the image clarity tends to deteriorate.

In the present invention, the above-mentioned lubricant and rust-preventive additive are the main addition components to the resin composition, but in addition to these, conductive substances (for example, iron phosphide, graphite, antimony-doped oxidation) are used. Tin, antimony-doped tin oxide-coated titanium oxide, antimony-doped indium oxide, carbon black, titanium black, metal powder, etc., silane coupling agents, color pigments (for example, condensed polycyclic organic pigments, phthalocyanine organic pigments, etc.) ), Coloring dyes (for example, azo dyes, azo metal complex salt dyes, etc.),
It is also possible to blend one or more kinds of surfactants and the like.

The organic film has the following (2) on the chromate film.
It is formed with a film thickness within a range that satisfies the formula. 0.1 [Ra ³ +1.5 {2 / (D + 2)} + 0.5] ≦ C ≦ 3.0 (2) where C: thickness of organic coating (μm) Ra: center of zinc-based plated steel surface Line average roughness (μm) D: Content of lubricant (nonvolatile component) in organic film (wt)
%) 0 ≦ D ≦ 50

First, the lower limit of the organic film is defined by the lubricity after passing through the beads. As described above, for the purpose of improving the press forming by a die with a drawing bead as typified by large automobile parts, an investigation was made of a formability deterioration factor in the beaded press forming of the organic composite coated steel sheet, The organic composite coated steel sheet peels off the organic film due to sliding accompanied by plastic deformation such as bending and bending back when passing the bead, and after passing the bead, the plating layer is more exposed than before it passed the bead. The area of direct contact between the plating layer and the press die is extremely increased as compared with that before passing through the beads. As a result, it was found that the lubricity deteriorates after passing the beads, and good press formability cannot be obtained.
Therefore, the present inventors have investigated the surface roughness Ra (center line average roughness) of the base-coated steel sheet of the organic composite-coated steel sheet and the lubricant content in the organic coating in order to improve the lubricity of the steel sheet after passing through the beads. The relationship between the amount D, the film thickness C of the organic film, and the lubricity after passing the beads was examined.

9 to 15 show that a zinc-plated steel sheet (No. 1 in Table 3) having different surface roughness has a chromate layer as the first layer and an organic polymer resin (as the second layer) on the surface thereof. In Table 5, No. 15), a rust preventive additive (silica + slightly soluble chromate), a lubricant (tetrafluoroethylene fine powder (No. 17 in Table 7)) + a polyolefin wax (N in Table 6)
o. 3)): 0-50% added organic film (film thickness 0.
The surface roughness R of the base-plated steel sheet of the organic composite-coated steel sheet is about 0.5-4.0 μm)
a, lubricant content D in the organic film and film thickness C of the organic film
An example of the result of investigation of the relationship between the lubricity after passing through the bead and the bead is shown. According to this, the film thickness of the organic film is a certain value C
By setting it to be o or more, the lubricity after passing the beads is improved, and the surface roughness Ra of the base plated steel sheet of the organic composite-coated steel sheet and the lubricant content D in the organic film provide good lubrication even after passing the beads. It was found that the film thickness Co of the organic film, which is the minimum required to have the property, is different. That is, as the surface roughness Ra of the base-plated steel sheet becomes finer or the lubricant content D increases, the film thickness Co of the organic coating, which is the minimum required to obtain good lubricity even after passing through the beads, decreases.

From these experimental results, the surface roughness Ra of the base-plated steel sheet of the organic composite coated steel sheet, the lubricant content C in the organic film, and the minimum required to have good lubricity even after passing the beads. As a result of regression analysis of the experimental results of the film thickness Co of the organic film, the minimum film thickness Co of the organic composite coated steel plate required to have good lubricity, the lubricant content D in the organic film and the surface of the base plated steel plate It was found that there was a relationship of the following empirical formula (i) with the roughness Ra, and this was defined as the lower limit film thickness of the organic film. 0.1 [Ra ³ +1.5 {2 / (D + 2)} + 0.5] = Co (i) where Ra: center line average roughness (μm) of zinc-based plated steel surface D: lubrication in organic coating Content of agent (nonvolatile) (wt
%) Co: Minimum film thickness (μm) required to have good lubricity

Thus, the lower limit of the thickness of the organic coating depends on the surface roughness of the base plated steel sheet because the force applied to the organic coating varies depending on the surface roughness of the base plated steel sheet even if the organic coating is the same. It is believed that there is. This will be explained based on the schematic diagram shown in FIG. 16. When a constant load is applied to the organic film by the bead, the surface roughness of a rough surface is locally concentrated on the convex portion of the surface. This means that the organic coating is subjected to a very large surface pressure as compared with a material having a small thickness. As a result, peeling of the film is likely to occur, and it is considered that the minimum film thickness required to have good lubricity increases as the surface roughness increases. It is considered that the effect of adding the lubricant is that the lubricity of the organic coating itself is improved, so that sufficient lubricity can be imparted even to the organic coating remaining without being peeled off when passing through the beads.

On the other hand, the upper limit of the film thickness C of the organic film is defined by the weldability, and if the film thickness of the organic film exceeds 3 μm, the weldability (particularly continuous spotting property) deteriorates. FIG. 17 shows the result of examining the relationship between the film thickness C of the organic film and the spot weldability (continuous spotting property). According to this, it can be seen that the spot weldability deteriorates when the film thickness exceeds 3.0 μm. 18 and 19 show the range of the film thickness of the organic film defined by the present invention. When obtaining an organic film, the coating composition is usually applied by a roll coater method, but it is also possible to adjust the application amount by an air knife method or a roll drawing method after applying by a dipping method or a spray method.

The heat treatment after applying the coating composition can be carried out using a hot air oven, a high frequency induction heating oven, an infrared oven or the like. The heat treatment is the ultimate plate temperature of 80 ° C to 25 ° C.
It is desirable to carry out at 0 ° C, preferably in the range of 100 ° C to 200 ° C. If the heating temperature is lower than 80 ° C., sufficient corrosion resistance cannot be obtained because crosslinking of the coating does not proceed. on the other hand,
Corrosion resistance deteriorates at high temperature baking exceeding 250 ° C.
This is due to the volatilization of water contained in the chromate film components and the hydroxyl groups (

Embedded image ) Due to the rapid progress of dehydration condensation reaction between them, the destruction of the chromate film due to cracking of the film progresses, and the reduction of hexavalent chromium progresses to reduce the passivation effect of hexavalent chromium. It is estimated that

When the present invention is applied to a zinc-based plated steel sheet having BH property, heat treatment at 170 ° C. or lower is preferable. Further, although the car body is subjected to cationic electrodeposition coating, if the wet electric resistance of the chromate film + organic film exceeds 200 kΩ / cm ² , there is a problem that the cationic electrodeposition coating cannot be properly formed. In the steel sheet of the present invention mainly used for vehicle bodies, it is preferable to form both films so that the wetting resistance of the chromate + organic film is suppressed to 200 kΩ / cm ² or less.

The present invention includes a steel sheet having the coating structure as described above on both sides or one side. Therefore, examples of the aspects of the present invention are as follows. (1) One side: plating layer-chromate layer-organic film, one side:
Fe side (2) One side: plating layer-chromate layer-organic film, one side:
Plating surface (3) One side: plating layer-chromate layer-organic film, one side
Plating Layer-Chromate Layer (4) Both Sides: Plating Layer-Chromate Layer-Organic Film The organic composite-coated steel sheet of the present invention is not limited to automobiles,
It can also be applied to home appliances and building materials.

A rust preventive oil layer can be provided as a third layer on the organic film. As the rust preventive oil, a rust preventive additive (eg oil-soluble surfactant), a petroleum base (eg
Mineral oil, solvent), oil film modifier (eg mineral oil, crystalline substance, viscous substance), antioxidant (eg phenolic antioxidant), lubricant (eg extreme pressure additive) as main constituents Ordinary rust preventive oil, cleaning rust preventive oil, lubricating rust preventive oil and the like can be mentioned. As normal rust preventive oil, fingerprint removal type rust preventive oil in which the base is dissolved / decomposed in petroleum solvent, solvent diluted rust preventive oil, petrolactam, lubricating oil type rust preventive oil based on wax, Evaporative rust preventive oil and the like can be mentioned.

The amount of rust preventive oil film adhered is 0.01 to 10 g / m.
^{Assume 2} . If the adhesion amount is less than 0.01 g / m ² , the steel sheet and the mold are likely to adhere to each other, and the press formability tends to be poor. On the other hand, if it exceeds 10 g / m ² , it becomes difficult to completely remove the rust preventive oil during degreasing in the pretreatment process of coating. In order to obtain higher press moldability and degreasing property, it is preferable that the adhesion amount be in the range of 0.05 to 5 g / m ² .

[0093]

[Example] Zinc-based plated steel sheet was alkali degreased and washed with water,
After drying, chromate treatment was performed, and then the coating composition was applied by a roll coater and baked, and then rust preventive oil or cleaning oil was applied. Regarding the organic composite coated steel sheet thus obtained, lubricity, press formability, powdering resistance, corrosion resistance (perforation resistance), streak rust resistance,
Each test of paint adhesion and weldability was performed.

(1) Zinc-based galvanized steel sheet (1-1) Plating material steel sheet Tables 1 and 2 show the plating material steel sheet (plate thickness 0.8 mm) used in this example. (1-2) Zinc-based plating Table 3 shows the plating composition and the amount of the applied plating of the zinc-based plated steel sheet used in this example. (1-3) Zinc-based plated steel sheet Table 4 shows the zinc-based plated steel sheet used in this example together with its surface roughness (center line average roughness Ra).

(2) Chromate Treatment (a) Coating Chromate Treatment: A chromate treatment liquid having the following liquid composition was applied by a roll coater and dried without washing with water. The amount of the chromate layer attached was adjusted by changing the peripheral speed ratio of the pickup roll of the roll coater and the applicator roll. Chromic anhydride: 20 g / L Phosphate ion: 4 g / L Zirconium fluoride ion: 1 g / L Zinc ion: 1 g / L Hexavalent chromate ion / Trivalent chromate ion: 3/3 (weight ratio) Chromic anhydride / Zirconium fluoride ion: 20/1
(Weight ratio)

(B) Electrolytic chromate treatment: Chromic anhydride:
Using a treatment liquid of 30 g / L, sulfuric acid: 0.2 g / L, bath temperature: 40 ° C., a zinc-based plated steel sheet was subjected to cathodic electrolysis treatment at a current density of 10 A / dm ² , washed with water and dried. The amount of the chromate layer deposited was adjusted by controlling the amount of electricity applied during cathodic electrolysis. (c) Reactive chromate treatment: Chromic anhydride: 30 g /
L, phosphoric acid: 10 g / L, NaF: 0.5 g / L, K ₂
TiF _6: 4g / L, bath temperature: Spray process on zinc-based plated steel sheet with a 60 ° C. of the processing solution, washed with water and dried. The adhesion amount of the chromate layer was adjusted by changing the treatment time.

(3) Organic resin Table 5 shows the organic resin used for the organic film (base resin + curing agent).
Indicates. The base resins A to G and the curing agents a to
e (polyisocyanate compound) was prepared by the following method. [Synthesis Example of Base Resin] 1. Resin A A general resin, Epicoat 1007 (molecular weight 2900) manufactured by Yuka Shell Epoxy Co., Ltd. is dissolved in a mixed solvent of xylene / methyl ethyl ketone = 6/4 (weight ratio) to prepare a resin liquid A having a solid content of 20% by weight. did. 2. Resin B As a polyhydroxypolyether resin, a commercially available phenoxy resin Phenoto YP-50 (molecular weight 36,000) manufactured by Tohto Kasei Co., Ltd. is dissolved in a mixed solvent of cellosolve acetate / cyclohexanone = 1/1 (weight ratio), Solid content 2
A resin liquid B of 0% by weight was prepared.

3. Production of Resin C (I) Isocyanate Compound Hexamethylene diisocyanate: 168 parts and methyl isobutyl ketone: 213 parts were taken and uniformly dissolved in a reactor equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing device. After the temperature was raised to ℃, 45 parts of trimethylolpropane was gradually added dropwise over 1 hour, and then 120
The reaction was conducted at 4 ° C. for 4 hours to obtain an isocyanate compound having a nonvolatile content of 50%. The isocyanate equivalent of this compound X is 7
It was 1. (II) Production of Resin C A reaction apparatus equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing apparatus was placed in Epicoat 1007 (Yukaka Shell Epoxy Co., Ltd .: epoxy equivalent 2000) 2000.
Parts and 1000 parts of toluene were added and the temperature was raised to 80 ° C. to uniformly dissolve them. Next, this isocyanate compound X60
0 part (solid content) was gradually added dropwise over 1 hour, and further 8 parts were added.
The reaction was carried out at 0 ° C for 3 hours. The end point of the reaction is determined by absorption of an isocyanate group by an infrared spectrophotometer (

(Equation 6) ) Disappeared. In this way, a urethanized epoxy resin having an epoxy equivalent of 2600 was obtained. Subsequently, 105 parts of diethanolamine was added to the urethanized epoxy resin and reacted at 80 ° C. for 2 hours to obtain a resin C.

4. Resin D Epicoat 1009 (Epoxy resin manufactured by Yuka Kagaku Shell Epoxy Co., Ltd., molecular weight: about 3750) in a reactor equipped with a stirrer, a reflux condenser, a thermometer, and a liquid dropping device 1
After adding 880 g (0.5 mol) and 1000 g of a mixed solvent of methyl isobutyl ketone / xylene = 1/1 (weight ratio), the mixture was heated with stirring and uniformly dissolved at the boiling point of the solvent. Then, the mixture was cooled to 70 ° C., and 70 g of the collected di (n-propanol) amine was added dropwise to the liquid dropping device over 30 minutes. During this period, the reaction temperature was maintained at 70 ° C. After completion of dropping, the temperature was maintained at 120 ° C. for 2 hours to complete the reaction.
The active ingredient of Resin D thus obtained was 66%.

5. Resin E Polyethylene glycol diglycidyl ether (Nagase Kasei Co., Ltd., trade name "Denacol EX-83"
0 ", epoxy equivalent 262) 100 g and bisphenol A type epoxy resin (Yukaka Shell Epoxy Co., Ltd., trade name" Epicoat 1001 ", epoxy equivalent 500) 10
Add 50 g of bisphenol A to the mixture with 0 g and add
After reacting at 0 ° C. for 6 hours, after confirming that the unreacted phenolic hydroxyl group disappeared, 125 g of xylol and 125 g of methyl ethyl ketone were added and cooled to obtain a product X. Next, after heating the product X at 80 degreeC, it was made to react, dropping 20 g of tolylene diisocyanate over 1 hour.
After completion of the dropping, the reaction was further continued for 3 hours while maintaining the temperature at 80 ° C. The end point of the reaction is determined by absorption of an isocyanate group (

(Equation 7) ) Disappeared. This gives an epoxy equivalent of 17
85 urethanized epoxy resins were obtained. Subsequently, 14.7 g of diethanolamine was added and reacted at 80 ° C. for 2 hours to obtain resin E.

6. Resin F (I) Production of Isocyanate Compound In a reactor equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing device, 168 parts of hexamethylene diisocyanate and 168 parts of methyl isobutyl ketone are uniformly dissolved and heated to 80 ° C. After warming, a solution of 87 parts of methyl ethyl ketone oxime and 87 parts of methyl isobutyl ketone was gradually added dropwise over 1 hour, and further reacted at 80 ° C. for 3 hours,
An isocyanate compound having a nonvolatile content of 50% was obtained. The isocyanate equivalent weight of this compound X was 510. (II) Production of Resin F In a reactor equipped with a reflux condenser, a stirrer, a thermometer, and a nitrogen gas blowing device, 250 parts of Epicoat 1001 (produced by Yuka Shell Epoxy Co., Ltd .: epoxy equivalent 500) and 50 parts of xylol And 63 parts of cellosolve acetate, and then added with 39.2 parts of azelaic acid and 4.3 parts of diethanolamine and reacted at 145 ° C. for 6 hours,
When the acid value of the resin solid content reached 1.1, 110 parts of xylol and 68 parts of methyl ethyl ketone were added and cooled. Next, 200 parts of isocyanate compound (solid content)
And add 200 parts of cellosolve acetate, 100 ℃
After reacting for 3 hours, isopropyl alcohol 1
00 parts was added and cooled to obtain a urethane-modified epoxy ester resin F.

7. Resin G 15% of monomers having OH groups, 5% of monomers having COOH groups, and (weight of monomers having OH groups / C
Ethylene-acrylic acid copolymer resin copolymerized so that the weight of the monomer having an OOH group) = 3

[Curing agent] (a) Hexafunctional isocyanate (curing agent a) 222 parts of isophorone diisocyanate and 34 parts of methyl isobutyl ketone were weighed in a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser with a dropping funnel. After being taken and uniformly dissolved, 87 parts of methyl ethyl ketone oxime was added dropwise from the dropping funnel to the stirred isocyanate solution kept at 70 ° C. over 2 hours. Then, 30.4 parts of sorbitol was added, the temperature was raised to 120 ° C., and the reaction was carried out at 120 ° C. After that, IR measurement of this reaction product is performed,

(Equation 8) It was confirmed that there was no absorption due to the isocyanate group, and 50.4 parts of butyl cellosolve was added to obtain a curing agent a. The effective component of this curing agent a was 80%.

(B) Tetrafunctional isocyanate (curing agent b) 222 parts of isophorone diisocyanate and 34 parts of methyl isobutyl ketone were weighed in a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser equipped with a dropping funnel, and uniformly mixed. Then, 87 parts of methyl ethyl ketone oxime was added dropwise from the dropping funnel to the stirred isocyanate solution kept at 70 ° C. over 2 hours. Then, 34 parts of pentaerythritol was added and the temperature was raised to 120 ° C.
The reaction was carried out at ° C. After that, IR measurement of this reaction product is performed,

[Equation 9] It was confirmed that there was no absorption due to the isocyanate group of, and 52 parts of butyl cellosolve was added to obtain a curing agent b. The effective component of this curing agent b was 80%.

(C) Trifunctional isocyanate (curing agent c) In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser with a dropping funnel, Duranate TPA-100 (HMD
Isocyanuric ring type I; manufactured by Asahi Kasei Co., Ltd., 550 parts and methyl isobutyl ketone 34 parts were weighed and uniformly dissolved, and then 270 parts of methyl ethyl ketone oxime was stirred from the dropping funnel at 70 ° C. to obtain isocyanate. It dripped in the solution over 2 hours. After that, IR measurement of this reaction product is performed,

[Equation 10] After confirming that there was no absorption due to the isocyanate group, 47 parts of butyl cellosolve was added to obtain a curing agent c. The active ingredient of this curing agent c was 90%.

(D) Bifunctional isocyanate (curing agent d) Takenate B-870N (MEK oxime block of IPDI; manufactured by Takeda Pharmaceutical Co., Ltd.) was used as a curing agent d.

(E) Hexamethylene diisocyanate system 6
Functional isocyanate (curing agent e) Hexamethylene diisocyanate-based 6-functional isocyanate compound Duranate MF-B80M (HMD
An I-type hexafunctional isocyanate oxime block: manufactured by Asahi Chemical Industry Co., Ltd. was used as a curing agent e.

(4) Lubricants Tables 6 to 8 show the lubricants added to the organic coating in this example. In addition, FIG. 18, N
o. 19, No. 21-No. The apparent melt viscosity of 28 fluororesin fine powders measured by a flow characteristic test method (based on JIS K 7199) by a capillary rheometer is shown. Based on this result, Table 7 shows whether or not each fluororesin fine powder satisfies the condition of the above-mentioned formula (3). In addition, in Table 7, No. 17, N
o. The fluororesin fine powder of No. 29 had an apparent melt viscosity low enough to exceed the measurement limit of the test apparatus, and therefore satisfied the condition of the expression (3). In addition, No. Two
The fluororesin fine powder of 0 did not melt completely because it had a higher melting point than the measurement conditions, and therefore did not satisfy the condition of formula (3).

(5) Anticorrosion Additives Tables 9 and 10 show the antirust additives added to the organic coating in this example. (6) Coating Composition A lubricant and a rust preventive additive were dispersed in the above organic resin using a sand mill to prepare a coating composition. The constitution of the coating composition is shown in Tables 11 to 20. (7) Anti-rust oil Table 21 shows the anti-rust oil used in this example.

Composition of the organic composite coated steel sheet prepared as described above and their lubricity, hat formability with beads, press formability (deep drawability), powdering resistance, corrosion resistance (perforation resistance) Tables 22 to 59 show the evaluation results of the rust resistance, paint adhesion and weldability. In addition,
The evaluation method of each characteristic is as follows.

(A) Lubricity (friction after draw bead) The test material was sheared to a width of 28.5 mm and a draw bead test as shown in FIG. 21 (triangular bead, bead tip radius:
0.5 mm, bead height: 4 mm, pressing force: 500
kgf, pulling speed: 200 mm / min), and then a flat plate sliding test shown in FIG. 22 (bead: 3 × 10 mm, pressing force: 400 Kgf, pulling speed: 1.0 m / se
c) was performed, the pulling force (F) at that time was measured, and the friction coefficient (μ = F / 400) was measured. The evaluation criteria are as follows. ◎: Less than 0.06 ○ +: 0.06 or more, less than 0.08 ○: 0.08 or more, less than 0.12 △: 0.12 or more, less than 0.13 ×: 0.13 or more

(B) Hat Type Molding Test with Beads The test piece was sheared to 280 × 60 mm, and the hat type molding test with beads shown in FIG. By doing so, the BHF at which cracking first occurred was measured as the fracture limit BHF, and cold-rolled steel sheets with different material levels (sheet thickness: 0.8 mm)
The fracture limit BHF was compared. Test conditions Punch diameter: square cylinder 100 mm, punch shoulder radius 5 mm, die: bead radius 5 mm, bead height 2 mm, blank: 280 × 60 mm molding height: 50 mm The evaluation criteria are as follows. ⊚: Superior to cold-rolled steel sheet for ultra deep drawing (No. 8 in Table 1). ◯ +: Equivalent to cold rolled steel sheet for ultra deep drawing (No. 8 in Table 1). ◯: Equivalent to cold-rolled steel sheet for high deep drawing (No. 6 in Table 1). Δ: Equivalent to cold-rolled steel sheet for deep drawing (No. 4 in Table 1). X: Equal to or inferior to the cold-rolled steel sheet for general processing (No. 1 in Table 1).

(C) Press Formability (Condition 1) The test material was processed into a circle with a diameter of 115φ, the punch diameter was 50 mm, the punch shoulder radius was 5 mm, and the die diameter was:
53mm, die shoulder radius 5mm, BHF: 3.5 tons, perform deep drawing of the cylinder, measure the deep drawing height at the time of cracking, and use cold-rolled steel sheets with different material levels (sheet thickness: 0.8mm ) Compared with the deep drawing height. (Condition 2) The test material was processed into a circle with a diameter of 115φ, the punch diameter was 50 mm, the punch shoulder radius was 5 mm, and the die diameter was:
Cylindrical deep drawing was performed at 53 mm, die shoulder radius 3 mm, and BHF: 5.0 tons, and the deep drawing forming height at the time of cracking was measured, and cold-rolled steel sheets with different material levels (sheet thickness: 0.8 mm ) Compared with the deep drawing height. Condition 1
The evaluation criteria under Condition 2 are as follows. ⊚: Superior to cold-rolled steel sheet for ultra deep drawing (No. 8 in Table 1). ◯ +: Equivalent to cold rolled steel sheet for ultra deep drawing (No. 8 in Table 1). ◯: Equivalent to cold-rolled steel sheet for high deep drawing (No. 6 in Table 1). Δ: Equivalent to cold-rolled steel sheet for deep drawing (No. 4 in Table 1). X: Equal to or inferior to the cold-rolled steel sheet for general processing (No. 1 in Table 1).

In the example No. 1, No. 4 to No.
Regarding No. 16, in order to see the influence of the material more conspicuously, the forming height under the (Condition 2) of the present example is set to that of the cold-rolled steel sheets (plate thickness: 0.8 mm) having different material levels (Condition 1). ) Was compared with the deep-drawing height under the measurement conditions of). 5: Cold rolled steel sheet for ultra deep drawing under the condition 1 (No.
8) Better. 4: Cold rolled steel sheet for ultra deep drawing under the condition 1 (No.
Equivalent to 8). 3: Cold-rolled steel sheet for high deep drawing under the condition 1 (No.
Equivalent to 6). 2: Cold-rolled steel sheet for deep drawing under the condition 1 (No.
Equivalent to 4). 1: Cold-rolled steel sheet for general processing under Condition 1 (No.
Equal to or less than 1). (In the examples, in the column of press moldability condition 2, the above 5
The index of ~ 1 is described together with the evaluation of ◎ ~ x).

(D) Powdering resistance The test material was sheared to a width of 30 mm, and the bead tip radius: 0.
5mm, bead height: 4mm, pressing force; 500kg
After the draw bead test shown in FIG. 21 was performed at a pull-out speed of 200 mm / min, the portion that was slid at the bead portion was peeled off with an adhesive tape, and the amount of plating peeling per unit area before and after the test was measured. .. The evaluation criteria are as follows. ◎: Less than 2 g / m ² ○: 2 g / m ² or more and less than 3 g / m ² ○-: 3 g / m ² or more, less than 4 g / m ² △: 4 g / m ² or more, less than 6 g / m ² ×: 6 g / M ² or more

(E) Corrosion resistance (perforation resistance) The test material was FCL-446 manufactured by Nippon Parkerizing Co., Ltd.
After degreasing at 0 (standard condition) and tape-sealing the end and back, put a cross cut on the lower half of the test piece with a cutter knife, and perform a corrosion promotion test of the following complex corrosion test cycle, and after 200 cycles The degree of red rust was evaluated. 5% NaCl spray, 35 ° C., 4 hours ↓ dry, 60 ° C., 2 hours ↓ 95% RH wet, 50 ° C., 4 hours The evaluation criteria are as follows. ◎: No red rust generation ○ +: Red rust area ratio less than 5% ○: Red rust area ratio 5% or more and less than 10% ○-: Red rust area ratio 10% or more and less than 20% △: Red rust area ratio 20% or more, 50% Less than ×: Red rust area ratio 50% or more

(F) Anti-corrosion rust resistance The test material was FCL-446 manufactured by Nippon Parkerizing Co., Ltd.
After degreasing at 0 (standard condition) and tape-sealing the end and back surface, the corrosion acceleration test of the following complex corrosion test cycle in the presence of iron rust was performed, and after 7 cycles (condition 1) and 1
The degree of red rust generation after 5 cycles (condition 2) was evaluated. In the presence of iron rust (* Note) 5% NaCl immersion, 50 ° C, 18 hours ↓ 95% RH wet, 50 ° C, 3 hours ↓ Dry, 60 ° C, 3 hours (* Note) Iron rust supply method: salt water 1. A cold rolled steel sheet having an area of 10 cm ² per 0 L was immersed. The evaluation criteria are as follows. ◎: No red rust generation ○ +: Red rust area ratio less than 5% ○: Red rust area ratio 5% or more and less than 10% ○-: Red rust area ratio 10% or more and less than 20% △: Red rust area ratio 20% or more, 50% Less than ×: Red rust area ratio 50% or more

(G) Paint Adhesion The test material was subjected to electrodeposition coating (25 μm) with U-600 manufactured by Nippon Paint Co., Ltd., and then K manufactured by Kansai Paint Co., Ltd.
Intermediate coating (30 μm) was performed with PX-36, and top coating (35 μm) was further performed with Lugerbake B-531 manufactured by Kansai Paint Co., Ltd. 40 of these test materials
After immersing in ion-exchanged water at ℃ for 240 hours, the test piece was taken out and left at room temperature for 24 hours, and then the coating film was cut into 100 squares, and the adhesive tape was adhered and peeled off. The residual rate was evaluated. The evaluation criteria are as follows. ◎: No peeling ○: Peeling rate less than 3% △: Peeling rate 3% or more and less than 10% ×: Peeling rate 10% or more

(H) Weldability DR type alumina-dispersed copper having a tip diameter of 6 mm was used as the electrode, and the applied pressure was 200 kgf and the energization time was 10 cycles /
A continuous spotting property test was performed at 50 Hz and a welding current of 10 kA, and the continuous spotting number was evaluated. The evaluation criteria are as follows. ◎: 3000 points or more ○: 2000 points or more and less than 3000 points Δ: 1000 points or more, less than 2000 points ×: less than 1000 points

[0120]

[Table 1]

[0121]

[Table 2]

[0122]

[Table 3]

[0123]

[Table 4]

[0124]

[Table 5]

[0125]

[Table 6]

[0126]

[Table 7]

[0127]

[Table 8]

[0128]

[Table 9]

[0129]

[Table 10]

[0130]

[Table 11]

[0131]

[Table 12]

[0132]

[Table 13]

[0133]

[Table 14]

[0134]

[Table 15]

[0135]

[Table 16]

[0136]

[Table 17]

[0137]

[Table 18]

[0138]

[Table 19]

[0139]

[Table 20]

* 1 to * 6 described in Tables 11 to 20
Indicates the following contents. * 1: Organic resin Nos. Shown in Table 5 * 2:% by weight of non-volatile content * 3: Lubricant No. shown in Table 6 to Table 8. * 4: Nonvolatile content weight ratio * 5: Rust preventive additive No. * 6: Rust preventive additive No. shown in Table 10

[0141]

[Table 21]

[0142]

[Table 22]

[0143]

[Table 23]

[0144]

[Table 24]

[0145]

[Table 25]

[0146]

[Table 26]

[0147]

[Table 27]

[0148]

[Table 28]

[0149]

[Table 29]

[0150]

[Table 30]

[0151]

[Table 31]

[0152]

[Table 32]

[0153]

[Table 33]

[0154]

[Table 34]

[0155]

[Table 35]

[0156]

[Table 36]

[0157]

[Table 37]

[0158]

[Table 38]

[0159]

[Table 39]

[0160]

[Table 40]

[0161]

[Table 41]

[0162]

[Table 42]

[0163]

[Table 43]

[0164]

[Table 44]

[0165]

[Table 45]

[0166]

[Table 46]

[0167]

[Table 47]

[0168]

[Table 48]

[0169]

[Table 49]

[0170]

[Table 50]

[0171]

[Table 51]

[0172]

[Table 52]

[0173]

[Table 53]

[0174]

[Table 54]

[0175]

[Table 55]

[0176]

[Table 56]

[0177]

[Table 57]

[0178]

[Table 58]

[0179]

[Table 59]

* 1 to * 5 described in Tables 22 to 59
Indicates the following contents. * 1: Evolution ... Inventive example, ratio ... Comparative example * 2: Plated steel sheet No. * 3: Chromate adhesion amount in terms of metallic chromium (mg /
m ² ) * 4: Coating composition No. 1 shown in Table 11 to Table 20. * 5: Rust preventive oil No. shown in Table 21.

[0181]

The organic composite-coated steel sheet of the present invention described above exhibits excellent press formability and corrosion resistance, and is excellent in various characteristics such as paint adhesion and weldability, and is therefore used for automobiles and home appliances. It is extremely useful as a surface-treated steel sheet for buildings and building materials.

[Brief description of drawings]

FIG. 1 A molecular structure model of polyethylene wax produced by radical polymerization using a radical catalyst or polyethylene wax produced by thermally decomposing polyethylene for general molding.

FIG. 2 Molecular structure model of polyethylene wax produced by coordination anionic polymerization method using Ziegler type catalyst

FIG. 3 is a graph showing the relationship between the average molecular weight of polyethylene wax added to an organic film and the press formability of an organic composite-coated steel sheet.

FIG. 4 is a graph showing the relationship between the average molecular weight of polyethylene wax added to the organic coating and the press formability of the organic composite-coated steel sheet.

FIG. 5 is a graph showing the relationship between the softening point of polyethylene wax added to the organic film and the press formability of the organic composite-coated steel sheet.

FIG. 6 is a graph showing the relationship between the softening point of polyethylene wax added to the organic film and the press formability of the organic composite-coated steel sheet.

FIG. 7 is a graph showing the relationship between the melting point of the tetrafluoroethylene resin fine powder added to the organic film and the press formability of the organic composite-coated steel sheet.

FIG. 8 is a graph showing the relationship between the weight ratio of silica and sparingly soluble chromate added in the organic coating, and the usual unpainted corrosion resistance (perforation resistance) and rust resistance of the organic composite-coated steel sheet.

FIG. 9 is a graph showing the lubricity of an organic composite-coated steel sheet having a lubricant content of 0% in an organic coating after passing through a bead as a relation between the surface roughness of a base-plated steel sheet and the organic coating thickness.

FIG. 10 is a graph showing the lubricity of an organic composite-coated steel sheet having a lubricant content of 2% in the organic coating after passing through a bead as a relationship between the surface roughness of the base-plated steel sheet and the organic coating thickness.

FIG. 11 is a graph showing the lubricity of an organic composite-coated steel sheet having a lubricant content of 3% in the organic coating after passing through beads, as a relationship between the surface roughness of the base-plated steel sheet and the organic coating thickness.

FIG. 12 is a graph showing the lubricity of an organic composite coated steel sheet having a lubricant content of 5% in the organic coating after passing through a bead as a relation between the surface roughness of the base plated steel sheet and the organic coating thickness.

FIG. 13 is a graph showing the lubricity of an organic composite-coated steel sheet having a lubricant content of 10% in the organic coating after passing through beads, as a relationship between the surface roughness of the base-plated steel sheet and the organic coating thickness.

FIG. 14 is a graph showing the lubricity of an organic composite-coated steel sheet having a lubricant content of 18% in the organic coating after passing through a bead as a relation between the surface roughness of the base-plated steel sheet and the organic coating thickness.

FIG. 15 is a graph showing the lubricity of an organic composite-coated steel sheet having a lubricant content of 50% in an organic coating after passing through beads, as a relationship between the surface roughness of a base-plated steel sheet and the organic coating thickness.

FIG. 16 is a model diagram showing the relationship between the surface roughness of the base plated steel sheet of the organic composite coated steel sheet and the film thickness of the organic film.

FIG. 17 is a graph showing the relationship between the film thickness of the organic coating and the weldability of the organic composite coated steel sheet.

FIG. 18 is a graph showing the range of the film thickness of the organic coating specified by the present invention in relation to the surface roughness of the base plated steel sheet in the organic composite coated steel sheet in which the lubricant is not added to the organic coating.

FIG. 19 is a graph showing the range of the film thickness of the organic coating specified by the present invention in relation to the surface roughness of the base plated steel sheet in the organic composite coated steel sheet in which a lubricant is added to the organic coating.

FIG. 20 is a graph showing the apparent melt viscosity of the tetrafluoroethylene resin described in Table 7 in relation to the apparent shear rate, which is measured by a flow characteristic test method using a capillary rheometer according to JIS K 7199.

FIG. 21 is an explanatory diagram showing a draw bead test method performed in Examples.

FIG. 22 is an explanatory view showing a flat plate sliding test method performed in Examples.

FIG. 23 is an explanatory diagram showing a hat-type molding test method performed in Examples.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B32B 15/08 B32B 15/08 G C23C 22/24 C23C 22/24 28/00 28/00 C ( 72) Inventor Takahiro Kubota 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan KK (72) Inventor Masaaki Yamashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan KK (72) Inventor Kentaro Sato 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihonkokan Co., Ltd. (72) Inventor Yasuhiko Haruta 4-17-1, Higashihachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd.

Claims (20)

[Claims] 1. A zinc-based plated steel sheet has, as a first layer, a chromate layer having an adhesion amount of 5 to 200 mg / m ^{2 in} terms of metal chromium, and a second layer above the chromate layer.
An organic film containing the organic polymer resin shown in (i) and a rust preventive additive in a weight ratio of non-volatile content of organic polymer resin: 30 to 80 wt% and rust preventive additive: 3 to 50 wt%. An organic composite coated steel sheet having excellent press formability and corrosion resistance, wherein the organic coating film thickness satisfies the following (ii). (i) Base resin having OH group or COOH group [A]
(However, excluding epoxy resin in which at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the end of the epoxy resin) 100 parts by weight (solid content),
Organic polymer resin in which polyisocyanate compound [B] is mixed in a proportion of 5 to 80 parts by weight (solid content) (ii) The film thickness of the organic film satisfies the following formula (1). 0.1 (Ra ³ +2) ≦ C ≦ 3.0 (1) where C: thickness of organic coating (μm) Ra: center line average roughness (μm) of zinc-based plated steel surface 2. A zinc-plated steel sheet has a chromate layer having a deposition amount of 5 to 200 mg / m ^{2 in} terms of metallic chromium as a first layer on the surface thereof, and a second layer as a second layer above the chromate layer.
The organic polymer resin shown in (i), the lubricant shown in (ii) below, and the rust-preventive additive are added in a weight ratio of the nonvolatile content of the organic polymer resin:
30-80 wt%, lubricant: 50 wt% or less (however, 0
(not including wt%), an anticorrosive additive: an organic film having an organic film content of 3 to 50% by weight, the organic film having a film thickness satisfying the following (iii) and having excellent press formability and corrosion resistance Composite coated steel sheet. (i) Base resin having OH group or COOH group [A]
(However, excluding epoxy resin in which at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the end of the epoxy resin) 100 parts by weight (solid content),
Organic polymer resin in which polyisocyanate compound [B] is mixed in a ratio of 5 to 80 parts by weight (solid content) (ii) Fluorine resin fine powder, polyolefin wax, 1
At least one lubricant selected from the group consisting of a mixture of polyolefin and fluororesin in one particle, graphite, boron nitride, or fluorocarbon (iii) The film thickness of the organic film is (2) Satisfy the formula. 0.1 [Ra ³ +1.5 {2 / (D + 2)} + 0.5] ≦ C ≦ 3.0 (2) where C: thickness of organic coating (μm) Ra: center of zinc-based plated steel surface Line average roughness (μm) D: Content of lubricant (nonvolatile component) in organic film (wt)
%) 3. A composite lubricant in which a lubricant contained in an organic film is a mixture of a polyolefin wax (E) and a fluororesin fine powder (F) in a weight ratio of E / F = 90/10 to 10/90. An organic composite-coated steel sheet excellent in press formability and corrosion resistance according to claim 2, which is an agent. 4. The press moldability and corrosion resistance according to claim 2 or 3, wherein the polyolefin wax (E) contained in the organic film is a polyolefin wax produced by a coordinated anionic polymerization method using a Ziegler type catalyst. Organic composite coated steel sheet. 5. The press moldability according to claim 2, 3 or 4, wherein the polyolefin wax (E) contained in the organic film is a polyethylene wax having an average molecular weight of 700 to 4500 and a softening point of 100 to 140 ° C. Organic composite coated steel sheet with excellent corrosion resistance. 6. The press according to claim 2, 3, 4 or 5, wherein the fluororesin fine powder (F) contained in the organic film is a tetrafluoroethylene fine resin powder satisfying the following condition (a). Organic composite coated steel sheet with excellent formability and corrosion resistance. (a) In the flow characteristic test method using a capillary rheometer according to JIS K 7199, the apparent melt viscosity measured under the following measurement conditions satisfies the following expression (3) with the apparent shear rate. . [Equation 1] Measurement conditions Test temperature: 330 ° C Barrel diameter: 9.55 mm Capillary dimensions: Diameter d = 1 mm, length 1 = 10 mm Capillary inlet: Flat 7. The press according to claim 2, 3, 4, 5 or 6, wherein the fluororesin fine powder (F) contained in the organic film is a tetrafluoroethylene resin fine powder having a melting point of 300 to 330 ° C. Organic composite coated steel sheet with excellent formability and corrosion resistance. 8. A lubricant (G), wherein the lubricant contained in the organic film comprises lubricant particles containing a mixture of a polyolefin (E ′) and a fluororesin (F ′) in one particle,
Alternatively, it is a composite lubricant in which the lubricant (G) is blended with a polyolefin wax (E) and / or a fluororesin fine powder (F), and the polyolefin (E ′) and fluorine constituting the lubricant (G). The organic material excellent in press moldability and corrosion resistance according to claim 2, wherein the resin (F '), the polyolefin wax (E), and the fluororesin fine powder (F) are a lubricant or a composite lubricant compounded in the following weight ratios. Composite coated steel sheet. (E + E ') / (F + F') = 10/90 to 90/10 9. A polyolefin or a polyolefin wax produced by a coordinated anionic polymerization method using a Ziegler type catalyst, wherein the polyolefin (E ′) and the polyolefin wax (E) constituting the lubricant (G) contained in the organic coating are The organic composite-coated steel sheet excellent in press formability and corrosion resistance according to claim 8. 10. The polyolefin (E ′) and the polyolefin wax (E) constituting the lubricant (G) contained in the organic film have an average molecular weight of 700 to 4500 and a softening point:
The organic composite-coated steel sheet excellent in press formability and corrosion resistance according to claim 8 or 9, which is polyethylene or polyethylene wax at 100 to 140 ° C. 11. A fluororesin (F ′) and a fluororesin fine powder (F) constituting a lubricant (G) contained in an organic film.
Is a tetrafluoroethylene resin or tetrafluoroethylene resin fine powder that satisfies the following condition (a), and the organic composite-coated steel sheet excellent in press formability and corrosion resistance according to claim 8, 9, or 10. (a) In the flow characteristic test method using a capillary rheometer according to JIS K 7199, the apparent melt viscosity measured under the following measurement conditions satisfies the following expression (3) with the apparent shear rate. . [Equation 2] Measurement conditions Test temperature: 330 ° C Barrel diameter: 9.55 mm Capillary dimensions: Diameter d = 1 mm, length 1 = 10 mm Capillary inlet: Flat 12. A tetrafluoroethylene resin or a tetrafluoroethylene resin having a melting point of 300 to 330 ° C. of the fluororesin (F ′) and the fluororesin fine powder (F) constituting the lubricant (G) contained in the organic film. It is a resin fine powder.
Alternatively, the organic composite-coated steel sheet having excellent press formability and corrosion resistance according to item 11. 13. The polyfunctional polyisocyanate compound contained in the organic coating is a polyfunctional polyisocyanate compound having at least three isocyanate groups in one molecule, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1
The organic composite coated steel sheet having excellent press formability and corrosion resistance according to 0, 11 or 12. 14. The polyfunctional polyisocyanate compound contained in the organic coating is a polyfunctional polyisocyanate compound having at least 4 isocyanate groups in one molecule. 7, 8, 9, 1
The organic composite coated steel sheet having excellent press formability and corrosion resistance according to 0, 11 or 12. 15. The polyfunctional polyisocyanate compound contained in the organic coating is a polyfunctional polyisocyanate compound having at least 6 isocyanate groups in one molecule, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1
The organic composite coated steel sheet having excellent press formability and corrosion resistance according to 0, 11 or 12. 16. The polyfunctional polyisocyanate compound contained in the organic film is a polyfunctional hexamethylene diisocyanate having at least 6 isocyanate groups in one molecule. 6, 7,
The organic composite-coated steel sheet having excellent press formability and corrosion resistance according to 8, 9, 10, 11 or 12. 17. The base resin having an OH group or a COOH group is an epoxy resin or a modified epoxy resin (provided that at least one basic nitrogen atom is present at the terminal of the epoxy resin,
An epoxy polymer added with at least two primary hydroxyl groups is excluded) and one or more organic polymer resins selected from polyhydroxypolyether resins 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1
The organic composite coated steel sheet having excellent press formability and corrosion resistance according to 2, 13, 14, 15 or 16. 18. The rust preventive additive contained in the organic film comprises silica and / or a sparingly soluble chromate.
2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13,
An organic composite coated steel sheet having excellent press formability and corrosion resistance according to 14, 15, 16 or 17. 19. The rust preventive additive contained in the organic film comprises silica and a sparingly soluble chromate in the following proportions by weight. 10, 1
The organic composite coated steel sheet having excellent press formability and corrosion resistance according to 1, 12, 13, 14, 15, 16 or 17. Silica / Slightly soluble chromate = 90/10 to 2/98 20. A rust preventive oil layer having an adhesion amount of 0.01 to 10 g / m ² as a third layer on the upper layer of the organic film. , 8, 9, 10, 1
The organic composite coated steel sheet having excellent press formability and corrosion resistance according to 1, 12, 13, 14, 15, 16, 17, 18 or 19.