JP2000239856A - Precoated steel sheet excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a precoated steel sheet subjected to rust preventing treatment instead of chromate treatment and excellent in corrosion resistance. SOLUTION: The surface of a steel sheet is provided with a film layer contg. a resin of 100 pts.wt. expressed in terms of the solid content and at least a vanadic compd. of 0.1 to 100 pts.wt. and furthermore optionally contg. at least one kind among a thiocarbonyl group-contg. compd. of 0.1 to 300 pts.wt., a phosphoric compd. of 0.01 to 300 pts.wt. (as PO4) and particulate silica of 1 to 2000 pts.wt. as a substrate treated layer, moreover, the surface is provided with a colored upper film layer, or with an under coat layer contg. rust preventive pigment and a colored upper film layer or with an upper film layer contg. rust preventive pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-coated steel sheet having excellent corrosion resistance, and more particularly to a pre-coated steel sheet having excellent corrosion resistance using a zinc-plated steel sheet as an original sheet, and also having excellent corrosion resistance, excellent fingerprint resistance, and excellent formability. It relates to a precoated steel sheet.

[0002]

2. Description of the Related Art Pre-coated steel sheets coated with a colored organic film have been used for home appliances, building materials, automobiles, and the like, instead of post-painted products which have been conventionally coated after processing. This steel sheet has, in particular, a zinc-based plating film as an underlayer and an organic film coated on it, and has the characteristics of having good workability, good workability, and good corrosion resistance. are doing.

For example, Japanese Patent Application Laid-Open No. 08-168723 discloses a technique for obtaining a precoated steel sheet having excellent workability, stain resistance and hardness by defining the structure of a film. Japanese Patent Application Laid-Open No. 03-100180 discloses a precoated steel sheet having improved end face corrosion resistance by using a specific chromate treatment solution.

[0004] For example, JP-A-3-39485 discloses that a zinc-plated steel sheet is subjected to a chromate film treatment, and a resin paint in which silica and a wax having a glass transition temperature of 40 ° C or more are dispersed in an aqueous resin is dried. 0.3 to 3 in film thickness
g / m ² coatings are disclosed. Japanese Patent Application Laid-Open No. 3-28380 discloses that a coating composed of a carboxylated polyethylene resin and a Teflon lubricant is coated on an electrogalvanized steel sheet at a dry film thickness of 0.5 to 4 g / m2. ^Two coatings are disclosed. These pre-coated steel sheets are plated, chromated,
Due to the combined effect of the organic film, it has not only corrosion resistance, but also workability, weldability, and paint adhesion, and aims to improve productivity and quality by omitting painting after processing.

[0005]

In such a precoated steel sheet, chromate-based rust prevention treatment is mainly performed to impart corrosion resistance. Chromate treatment, when treated with water-soluble hexavalent chromium, forms a poorly soluble film of trivalent chromium and has a barrier effect, and when the film is damaged, hexavalent chromium elutes to repair the barrier. And therefore has the characteristic of being excellent in corrosion resistance,
In particular, in the rust-prevention application of a zinc-based plated steel sheet, a chromate treatment has been exclusively performed to date as a corrosion resistance imparting film.

However, recently, there has been an increasing demand for a chromium-free rust preventive treatment due to the toxicity problem of hexavalent chromium which may be eluted from the chromate treatment. Therefore,
An object of the present invention is to provide a pre-coated steel sheet excellent in corrosion resistance or a pre-coated steel sheet excellent in corrosion resistance and having workability, lubricity, fingerprint resistance and the like in response to such a demand.

[0007]

SUMMARY OF THE INVENTION The present invention provides the above object,
On a steel sheet, 100 parts by weight of a resin and at least 0.1 to 100 parts by weight of a vanadate compound and optionally 0.1 to 3000 parts by weight of a thiocarbonyl group-containing compound, and 0.01 to 300 parts by weight of a phosphoric acid compound are contained on a steel sheet. Parts (as PO ₄ ) and 1 to 2000 parts by weight of finely divided silica as a base treatment layer, and a colored coating layer thereon as an upper layer. Achieved by pre-coated steel sheet.

According to the present invention, there is also provided a precoated steel sheet having a coating layer containing a rust-preventive pigment as an undercoat layer between the undercoating layer and the colored coating layer. Furthermore, there is provided a precoated steel sheet having, as an upper layer, a coating layer to which a rust preventive pigment is added on the base treatment layer. This pre-coated steel sheet has the same corrosion resistance as a conventional chromate-treated pre-coated steel sheet, and does not use chromium.
Alternatively, there is an advantage that the amount of chromium can be reduced.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The rust-prevention treatment of a pre-coated steel sheet of the present invention was developed mainly for the purpose of rust-prevention treatment of a galvanized steel sheet. The present invention is not limited to galvannealed steel sheets and the like, and can be suitably applied to any of cold-rolled steel sheets, hot-rolled steel sheets, various types of plated steel sheets, stainless steel, and the like.

[0010] The steel sheet can be subjected to ordinary treatments such as hot water washing and alkali degreasing before the base treatment. The precoated steel sheet of the present invention is characterized in that the undercoat layer contains a vanadium compound. The undercoat layer is a coating layer based on an aqueous resin. Here, the term "aqueous resin" includes not only a water-soluble resin but also a resin (a water-dispersible resin) which is originally water-insoluble but can be in a finely dispersed state in water, such as an emulsion or a suspension. Examples of resins that can be used as such an aqueous resin include, for example, polyolefin resins, acrylic olefin resins, polyurethane resins, acrylic resins, polycarbonate resins, epoxy resins, polyester resins, alkyd resins, phenol resins, Other heat-curable resins can be exemplified, and a crosslinkable resin is more preferable. Particularly preferred resins are acrylic olefin-based resins, polyurethane-based resins, and mixed resins of both. Two or more of these aqueous resins may be used as a mixture or as a copolymer. Further, an amino resin such as a melamine resin, a phenol resin, a blocked isocyanate resin, or the like may be added as a crosslinking agent.

It has been found that the vanadate compound has the same rust-preventing action as the chromic acid compound. Like the chromic acid compound, the vanadate compound forms a passivation film on the surface of the steel sheet (particularly zinc) at the time of application, and exhibits a rust-preventive effect. Furthermore, even when a corrosion site is generated on the surface of a steel plate (particularly zinc), it is considered that vanadate ions present in the coating act on the corrosion site to suppress the corrosion reaction.

As the vanadate compound used for the undercoat layer, for example, ammonium vanadate, sodium vanadate, potassium vanadate and the like can be used. The amount of the vanadate compound is preferably in the range of 0.1 to 100 parts by weight based on 100 parts by weight of the resin (solid content). If less than this, the rust prevention effect is not sufficient,
If it is more than this, the rust prevention effect is saturated and uneconomical.

The undercoating layer of the present invention can contain, in addition to a vanadate compound, one or more of a thiocarbonyl group-containing compound, a phosphate compound, and finely divided silica as an additive exhibiting a rust preventive effect. . The thiocarbonyl group-containing compound is a sulfide, is easily adsorbed on the metal surface, and has excellent oxidizing power, so that the metal surface is passivated and exhibits a rust prevention effect. In particular, it is considered that thiol group ions in the thiocarbonyl group-containing compound are adsorbed to active sites on the steel sheet surface (particularly, zinc surface) and exhibit a rust-preventive effect.

Further, the thiocarbonyl group-containing compound acts as a crosslinking accelerator for the resin film, has the effect of reducing micropores in the resin film and efficiently blocking harmful ions such as water and chloride ions. Is also considered to contribute to the rust prevention effect. In the present invention, the thiocarbonyl group-containing compound is a thiocarbonyl group (formula 1)

[0015]

Embedded image A compound having the following formula: Typically,

[0016]

Embedded image Thioureas and derivatives thereof represented by, for example, methylthiourea, dimethylthiourea, ethylthiourea, diethylthiourea, diphenylthiourea, thiopental, thiocarbazide, thiocarbazones, thiocyanuric acids,
Thiohydantoin, 2-thiouramil, 3-thiourazole and the like;

[0017]

Embedded image A thioamide compound represented by, for example, thioformamide, thioacetamide, thiopropionamide, thiobenzamide, thiocarbostyril, thiosaccharin and the like;

[0018]

Embedded image A thioaldehyde compound represented by, for example, thioformaldehyde, thioacetaldehyde and the like;

[0019]

Embedded image Carbothioic acids represented by, for example, thioacetic acid, thiobenzoic acid, dithioacetic acid and the like;

[0020]

Embedded image And thiocarbonates represented by the following formulas; and other compounds having the structure of formula 1, such as thiocouzone, thiocumothiazone, thionin blue J, thiopyrone, thiopyrine, and thiobenzophenone.

The content of the thiocarbonyl group-containing compound is as follows:
0.1 to 3000 parts by weight, based on 100 parts by weight of the resin,
More preferably, the content of the thiocarbonyl group-containing compound is 0.5 to 30 parts by weight. If the content of the thiocarbonyl group-containing compound is less than this, the rust-preventing effect is not improved, and if it is more than this, the adhesion of the overcoat film may be poor and it is not economical.

The rust-preventing effect of the undercoating layer of the present invention is remarkably improved by containing a phosphate compound together with a vanadate compound or a thiocarbonyl group-containing compound. The vanadate compound or thiocarbonyl group-containing compound is adsorbed to active sites on the steel sheet surface (especially zinc surface) and exerts a rust-preventive effect, but phosphoric acid acts on the inactive surface of the steel plate (especially zinc). An active surface is formed, and a vanadate compound or a thiocarbonyl group-containing compound is adsorbed on the active surface, so that the rust-preventing effect is exerted on the entire surface of the steel sheet (particularly zinc), and the rust-preventing effect is considered to be improved. . Phosphoric acid compounds also act as a cross-linking accelerator for the resin film, reducing micropores in the resin film and effectively blocking harmful ions such as water and chloride ions, which also contributes to the rust prevention effect. It is thought that.

As the phosphate compound, phosphate ions may be included, and for example, phosphoric acid, polyphosphoric acid, ammonium phosphate, sodium phosphate, potassium phosphate, various phosphate esters and the like can be used. The amount of the phosphoric acid compound in the undercoating layer is determined as the solid content of the aqueous resin 1
With respect to 00 parts by weight, 0.01 to 3 as a phosphate ion
00 parts by weight, more preferably 0.5 to 10 parts by weight. If the amount of the phosphate compound is less than 0.01 part by weight, the rust-preventing effect is not sufficiently exhibited, while if it exceeds 300 parts by weight, the rust-preventing effect is rather reduced, or the resin is gelled in the state of the coating solution. There may be.

Further, even if fine silica is added to the undercoat layer, the rust-preventing action (corrosion resistance) is promoted. Moreover, in addition to the corrosion resistance, the drying property, the scratch resistance, and the coating film adhesion can be improved.
In the present invention, finely divided silica is a generic term for silica having properties such that when it is dispersed in water, it has a fine particle size and can maintain a stable aqueous dispersion state, and semipermanently no sedimentation is observed. It is. The finely divided silica is not particularly limited as long as it has a small amount of impurities such as sodium and is weakly alkaline. For example, "Snowtex N", "Snowtex NS", "Snowtex NXS" (manufactured by Nissan Chemical Industries, Ltd.), "Adelite AT-
Commercially available silica sols such as "20N" (manufactured by Asahi Denka Kogyo KK),
Alternatively, commercially available Aerosil (powder silica, manufactured by Degussa Co., Ltd.) or the like can be used. The smaller the silica particle size, the better the corrosion resistance.

When the vanadate compound is used in combination with the fine silica, the vanadate compound is adsorbed on the surface of the fine silica, and the rust-preventive effect is synergistically exhibited. In this sense, when the fine silica particles are of the ammonium adsorption type or the aluminum oxide coating type, the silica particles are easily adsorbed and the rust prevention effect is improved, which is preferable. The content of fine silica is 100
It is preferably from 1 to 2000 parts by weight, more preferably from 10 to 400 parts by weight, based on parts by weight. If it is less than 1 part by weight, the effect of addition is small, and if it is more than 2,000 parts by weight, the effect of improving corrosion resistance is saturated and uneconomical. In addition, the film becomes too hard and cracks and peeling of the film occur, which may lower the corrosion resistance. is there.

The combination of a rust preventive agent used for the undercoat layer may be a vanadate compound and fine silica, a vanadate compound and a thiocarbonyl group-containing compound, a vanadate compound and a thiocarbonyl group-containing compound and fine silica,
A combination of a vanadate compound, a thiocarbonyl group-containing compound, finely divided silica and a phosphate compound is preferred,
It is not limited to these.

Further, the undercoat layer of the present invention may contain other components. For example, a content, a surfactant and the like can be mentioned. Further, in order to improve the affinity between the aqueous resin and the silica particles and the pigment, and further to improve the adhesion between the aqueous resin and the phosphor layer of zinc or iron, a silane coupling agent or a hydrolyzed condensate thereof or Both of them may be blended. Here, the “hydrolysis condensate of a silane coupling agent” refers to an oligomer of a silane coupling agent obtained by subjecting a silane coupling agent to a raw material and hydrolyzing and polymerizing the same. Examples of such other component pigments include titanium oxide (TiO ₂ ),
Zinc oxide (ZnO), zirconium oxide (ZrO), calcium carbide (CaCO ₃ ), barium sulfate (BaSO
₄ ) Inorganic pigments such as alumina (Al ₂ O ₃ ), kaolin clay, carbon black, iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ) and various coloring pigments such as organic pigments can be used.

The above-mentioned silane coupling agent that can be used in the present invention is not particularly limited, but preferred examples include the following: vinylmethoxysilane, vinyltrimethoxysilane, vinylethoxysilane, Vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N- (1,3-dimethylbutylidene) ) -3-
(Triethoxysilyl) -1-propanamine, N,
N′-bis [3- (trimethoxysilyl) propyl] ethylenediamine, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ
-Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane,
N- [2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane.

Particularly preferred silane coupling agents are vinyltrimethoxysilane, vinylethoxysilane, 3-
Aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N- (1,3-dimethylbutylidene)
-3- (triethoxysilyl) -1-propanamine,
N, N'-bis [3- (trimethoxysilyl) propyl] ethylenediamine. One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

In the present invention, the silane compound is selected from the group consisting of resin 1
Desirably, the content is 0.1 to 100 parts by weight based on 00 parts by weight. When the content of the silane compound is less than 0.1 part by weight, the effect of adding the silane compound is not recognized, the effect of improving the corrosion resistance and the adhesion of the top coating is insufficient, and when the content exceeds 100 parts by weight, the storage stability as a chemical decreases. And is not preferred.

In order to form a base treatment layer on a steel sheet, a base treatment agent (coating agent) containing the above components is prepared in water, applied to the steel sheet, and the coating film is heated and dried. Crosslinkable and curable resins are crosslinked and cured by this heating. The heating and drying of the coating film may be performed by heating and drying the steel sheet coated with the base treatment agent with hot air, induction heating or the like, or by applying the base treatment agent to the heated steel sheet and drying. The heating temperature is preferably 50 to 250C. If the temperature is less than 50 ° C., the evaporation rate of water is too slow to obtain a sufficient film-forming property, so that the rust-preventing ability is insufficient. On the other hand, when the temperature exceeds 250 ° C., thermal decomposition of the aqueous resin occurs, and thus there is a problem that the SST property and the water resistance are reduced and the appearance is yellowed. 70-160 ° C is more preferred. In hot air drying, a drying time of 1 second to 5 minutes is preferable.

The thickness (dry) of the undercoat layer is 0.05 μm.
m or more is preferred. If the thickness is less than 0.05 μm, rust prevention and adhesion are insufficient. When a coating layer (described later) to which a rust-preventive pigment is added is not provided between the colored coating layer and the base treatment layer, the dry thickness of the base treatment layer is 3 μm or more, more preferably 5 μm or more, from the viewpoint of ensuring corrosion resistance. It is good. On the other hand, if the film thickness is too thick, it is uneconomical as a base treatment layer, and is inconvenient for painting. Therefore, the upper limit of the film thickness is 10
μm or less is preferred.

The method of applying the undercoat layer is not particularly limited, and may be a commonly used air knife, curtain coat, roll coat, air spray, airless spray, dipping, or the like. Drying and baking of the base treatment layer may be performed by a known method such as a hot blast furnace, an induction heating furnace, a near-infrared furnace, or a combination thereof. Depending on the type of aqueous resin used, the resin can be cured by energy rays such as ultraviolet rays and electron beams. Alternatively, natural drying may be performed without using forced drying, or a steel sheet may be preheated in advance, and then naturally dried after being applied to the steel sheet.

[0034] The precoated steel sheet of the present invention is characterized by having a colored coating layer on the base-treated steel sheet. This colored coating layer is an essential layer for imparting design properties to the steel sheet and obtaining a coated steel sheet that can be used without further coating on the steel sheet. This coating layer contains pigments and dyes necessary for coloring. Organic pigments include
Inorganic type, known ones can be used regardless of the composite type of both, titanium white, zinc white, alumina white, zinc yellow, cyanine blue, and other cyanine pigments, such as carbon black, iron black, black iron, yellow Examples include iron oxide, molybdate orange, Hansa yellow, pyrazolone orange, azo pigments, navy blue, condensed polycyclic pigments, and the like. In addition, additives such as metal pieces / powder, pearl pigment, mica pigment, resin beads, and the like for imparting functionality such as design properties and conductivity may be added.

As the dyes, azo dyes, anthraquinone dyes, indigoid dyes, sulfur dyes, phthalocyanine dyes, diphenylmethane and triphenylmethane dyes,
Other known dyes such as nitro dye and acridine dye are used. As a binder for the coating layer, an organic or inorganic binder can be used. As an organic resin,
Examples include polyolefin resin, acrylic resin, urethane resin, epoxy resin, polyester resin, vinyl chloride resin, fluorine resin, butyral resin, polycarbonate resin, and phenol resin. These mixtures and copolymers can also be used. In addition, an isocyanate resin, an amino resin, a silane, a titanium coupling agent, or the like can be used in combination as a crosslinking agent or an auxiliary component. Since the coated steel sheet according to the present invention is premised on being used as it is after being formed, the colored layer is required to be free from cracking or peeling during bending or press forming. From such a viewpoint, a resin system in which a polyester resin is cross-linked with a melamine resin, a resin system in which a polyester resin is cross-linked with a urethane resin (isocyanate, isocyanate resin), a vinyl chloride resin system, a fluorine resin system (solvent-soluble, acrylic) Resin-dispersion type). The resin may be in any form of a water-based, solvent-based, powder-based, or solvent-free resin.

In addition, pigments and additive components not directly related to coloring, for example, pigments such as barium sulfate, calcium carbide, and kaolin clay; additives such as defoaming agents, leveling agents, and dispersion aids; In addition, a diluent, a solvent, water, or the like for lowering the viscosity of the paint, such as an organic wax component such as ester, paraffin, and fluorine, and an inorganic wax component such as molybdenum disulfide can be added.

The amount of the coloring component in the resin is not particularly limited.
What is necessary is just to determine by the required color and hiding power. For example,
When carbon black is blended for coloring black, it is sufficient to add 1 to 5% by weight of the pigment in terms of solid content. For example, when titanium white is blended for coloring white, solid 30-55% by weight in terms of pigment
Need a degree.

The colored coating layer is coated on the undercoating layer by a known method such as a roll coater, curtain coater, electrostatic coating, spray coating, dip coating, and the like, and then heated air, induction heating, near infrared rays, far infrared rays Drying and curing by heating such as If the resin of the colored coating layer is of a type that can be cured by radiation such as an electron beam or ultraviolet light, it is cured by electron beam irradiation or ultraviolet irradiation. These may be used in combination. A drying and curing method can be selected according to the type of the colored film layer. Drying and baking sheet temperatures are also determined according to the type of film layer. In a general coated steel sheet continuous production line, the sheet temperature is 150 to 250 ° C.

The thickness of the colored coating layer is not particularly limited.
In order to obtain a uniform colored appearance, it is desirable to have a dry film thickness of 5 μm or more. More preferably, it is 8 μm or more. Although there is no upper limit on the film thickness, when the coating is continuously performed with the coil on the production line of the coated steel sheet, the dry film thickness in one coating is often about 50 μm. This upper limit is mainly governed by the occurrence of defects that occur when the viscosity of the coating is too high when volatiles in the coating called `` Waki '' volatilize out of the system from inside the coating. Many. In the case of manufacturing while intermittently coating the cut plate, baking can be performed under mild conditions, and the upper limit dry film thickness increases to about 200 μm. Further, when processing is performed for each sheet by spray coating or the like, the upper limit film thickness further increases.

The precoated steel sheet of the present invention may further have, as an undercoat layer, a coating layer containing a rust preventive pigment between the undercoating layer and the colored coating layer, if necessary.
Alternatively, a coating layer to which a rust-preventive pigment is added can be provided as an upper layer on the base treatment layer without a colored coating layer. This undercoat layer is a layer mainly for the purpose of improving corrosion resistance, but is designed in consideration of other properties such as moldability and chemical resistance. The upper layer can be typically a layer for the purpose of imparting lubricity, fingerprint resistance, scratch resistance, moldability, and the like. Since the rust-preventive pigment is contained in the undercoat layer on the undercoat layer, the corrosion resistance is significantly improved due to a synergistic effect with the undercoat layer.

Since the undercoat layer of the present invention is non-chromium,
The rust preventive pigment of the undercoat layer or the upper layer is also preferably non-chromium, but is not limited thereto. The base of the undercoat layer or the upper layer may be in any form such as a water-based, solvent-based, or powder form, or may be an adhesive layer. Further, an organic film, an inorganic film, or a composite of both may be used. As the water-based resin, those similar to the water-based resin of the undercoat layer can be used.For example, polyacryl-based, polyolefin-based, polyurethane-based, polyepoxy-based, polyester-based, polybutyral-based, polyamide-based, and polyamino-based resins can be used. Systems and their copolymers and mixtures can be mentioned.

The resin forming the solvent-based or powder-based film can be the same as the undercoating layer or the colored film layer. As the inorganic coating, lithium silicate, water glass, inorganic resin, inorganic-organic composite resin, or the like may be used. In most cases, the precoated steel sheet is used after being formed and processed, and thus it is required that the coating film does not crack or peel during this processing. From this point, a resin system that crosslinks a polyester resin with a melamine resin, a resin system that crosslinks a polyester resin with a urethane resin (isocyanate, isocyanate resin), a vinyl chloride resin system, a fluororesin system (solvent-soluble, acrylic resin, etc.) Dispersion-mixing type) is desirable.

The rust preventive pigment contained in the undercoat layer and the upper layer means a solid rust preventive in the present invention, not a colorant. For example, zinc phosphate, iron phosphate, zinc phosphate such as aluminum phosphate, calcium molybdate, aluminum molybdate, molybdate such as barium molybdate, vanadium such as vanadium oxide, strontium chromate, zinc chromate, Chromium-based such as calcium chromate, potassium chromate and barium chromate; finely divided silica such as water-dispersed silica and fume silica; and finely divided titanium oxide, phosphite, calcium silicate and the like.

In particular, finely divided silica having a primary average particle diameter of 100 nm or less is preferred. Further, the rust preventive used for the undercoat treatment can also be used as a rust preventive pigment or an additional rust preventive in the undercoat layer. The amount of such rust preventive pigments
The content is preferably 1 to 40% by weight based on the solid content of the film. If the amount is less than this, the corrosion resistance is not sufficiently improved, and if it exceeds 40% by weight, the workability is reduced, the film becomes brittle, and chipping occurs during molding.

The thickness of the undercoat layer is preferably in the range of 0.05 to 60 μm. Below this, the desired properties of providing an undercoat layer as well as corrosion resistance cannot be obtained sufficiently, and if it is too thick, the cost increases. The formation of the undercoat layer can be performed in the same manner as the undercoating or the colored film layer, but the heating temperature is appropriately selected according to the film.

The undercoating layer, the undercoating layer containing the rust-preventive pigment, and the colored coating layer are usually formed one by one by repeating coating, drying and curing, but the coating is repeated without drying each layer. You may dry and harden three layers collectively or two layers collectively. Further, a plurality of layers may be formed as necessary. Further, the colored film layer may contain a rust preventive pigment, and the undercoat layer containing the rust preventive pigment may contain a component for coloring.

In order to impart properties such as lubricity, fingerprint resistance, scratch resistance and moldability to the upper layer, if necessary,
The film can be devised and additives can be added.
For example, wax is added. The thickness of the upper layer is not limited, but is preferably in the range of 0.3 to 10 μm. Below this, the desired properties of providing the upper layer in addition to corrosion resistance cannot be obtained sufficiently, and if too thick, the cost increases.

The formation of the upper layer can be performed in the same manner as in the base treatment, but the heating temperature is appropriately selected according to the film.

[0049]

The present invention will be described below with reference to examples.

(Example 1) Zinc plating adhesion amount is 2 per side
A 0.6 mm thick electrogalvanized steel sheet plated on both sides at 0 g / m ² , and the galvanized coating weight is 60 g per side
A hot-dip galvanized steel sheet having a thickness of 0.6 mm and plated on both sides at / m ² was degreased with a 2% by weight solution of FC-364S (manufactured by Nippon Parkerizing) at 60 ° C. for 10 seconds, washed with water, and dried. Next, a surface treatment agent having the composition shown in Table 1 was applied by a roll coater and dried in a hot air drying oven. At the time of drying, the reached plate temperature was 150 ° C. The same evaluation as in Table 1 was performed with the ultimate plate temperature at the time of drying set at 70 ° C. and 220 ° C., and the same result was obtained with the ultimate plate temperature of 150 ° C. in each case.

Next, Nippon Paint's P641 primer paint (polyester resin, described in Table 1 as polyester), Nippon Paint P108 primer paint (epoxy resin, described in Table 1 as epoxy), Nippon Paint P304 paint (urethane resin type, described as urethane in Table 1) in which the rust preventive pigment is changed to the rust preventive pigment described in Table 1. After removing the rust-preventive pigment, titanium white was added to that extent) and dried with a roll coater, and the applied amount was adjusted to the value shown in Table 1. After that, the sheet temperature reached in an induction heating furnace blown with hot air. It was cured and dried to 220 ° C.

Next, Nippon Paint FLC200HQ
(Polyester resin type, color is white)
And then cured and dried in an induction heating furnace into which hot air was blown so that the reached plate temperature was 230 ° C. After each curing and drying process,
The plate was water cooled. The following evaluation was performed on the coated steel sheet prepared in this manner. 1. Coating film adhesion The coated plate was cut into a 1 mm square base plate with a cutter knife and extruded 7 mm with an Erichsen tester so that the coated surface became convex, and then subjected to a tape peeling test. The method of inserting the base, the method of extruding Erichsen, and the method of peeling the tape were based on 8.2 and 8.5 of JISK5400. In addition, the evaluation after the tape was peeled was performed according to the figures of the evaluation examples described in 8.5. When the score was 10 points, it was evaluated as 、, when it was 6 or more and less than 10 points, it was evaluated as Δ, and when it was less than 6 points, it was evaluated as ×. Further, the coated steel sheet was immersed in boiling water according to the method of 8.20 of JIS K5400, taken out, and allowed to stand for 24 hours. Ratings were given as described above. 2. Adhesion of bent portion of coating film The coated plate was bent at 180 degrees, and the coated film of the processed portion was observed with a 10-fold loupe to check for cracks in the coating film.
In addition, a pressure-sensitive adhesive tape was stuck to the processed portion, and when the tape was vigorously peeled off, the remaining state of the coating film was visually observed. The bending process is performed at 20 ° C. with close bending (0T) and thickness of 0.
It carried out by two methods (1T) which sandwich one spacer of 6 mm. ○: when the coating film is not cracked, △: when the coating film is slightly cracked, ×: when the coating film is clearly cracked visually.
And In the case where the coating film of the processed portion of the portion peeled off with the tape remains without peeling at all (good adhesion),
The case where partial peeling was observed was evaluated as Δ, and the case where peeling was observed over almost the entire surface was evaluated as x. 3. Corrosion resistance The coated plate was tested according to the method described in 9.1 of JIS K5400. The test time was 120 hours for the electrogalvanized steel sheet (EG) and 240 hours for the galvanized steel sheet (GI). When the maximum swelling width on one side of the cross-cut of the coating film in the cross-cut portion was less than 1 mm, it was evaluated as ○, when it was 1 mm or more and less than 3 mm, and when it was 3 mm or more, it was evaluated as x.
Further, the flat plate was directly placed in a salt spray tester, and after the same test time as above, the swollen width of the coating film from the end face (upper burr portion) was observed. ○ when the swollen width from the end face is within 3mm, 3mm
When it was 5 mm or more, it was evaluated as x when it was 5 mm or more.

The evaluation results are shown in Table 1. The coating film adhesion, bending workability, adhesion of the bent portion, and corrosion resistance of the precoated steel sheet according to the present invention are No. 1 and No. 2 respectively. It is equal to or better than the pre-coated steel sheets with chromate pretreatments of 43 to 45 (Comparative Example). On the other hand, No. In 36 to 42 (Comparative Examples), any of the performances was inferior. No. In the case of No. 37, all the performances could not be ensured because there was no base treatment. No. In the case of No. 39, the amount of the V-based rust inhibitor was small and the corrosion resistance and coating film adhesion were poor. N
o. In the case of No. 40, the adhesion amount of the base is small, and the corrosion resistance and the adhesion are inferior. No. 41 has too much ammonium phosphate,
The processing bath gelled and could not be processed. No. 42 is V
Since no rust preventive is added, adhesion and corrosion resistance are poor. No. Nos. 43 to 45 use a base treatment containing chromium, and have a toxicity problem.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

[Table 6]

(Example 2) The amount of plating applied was 20 g per side.
/ M ² electrogalvanized steel sheet with 0.8 mm thickness (referred to as EG), galvanized steel sheet with a coating weight of 60 g / m ² per side with 0.8 mm thickness (referred to as GI), coating weight Prepared a galvannealed steel sheet (referred to as GA) having a thickness of 0.8 mm with a thickness of 60 g / m ² per side by FC-36.
It was degreased with a 2% by weight solution of 4S (manufactured by Nippon Parkerizing) at 60 ° C. for 10 seconds, washed with water and dried. Next, a base treatment agent for forming a base treatment layer having the composition shown in Table 2 was applied by a roll coater, and the reached plate temperature was 1 in a hot air drying furnace.
It was dried to 40 ° C.

The types of resin, silica, vanadate compound, thiocarbonyl compound and phosphate compound used for the undercoating agent are as follows. 1. Resin type Acrylic olefin: "HI-TECH S-7024"
1. Urethane type: "Bon Titer HUX-320" (manufactured by Asahi Denka Co., Ltd.) Epoxy type: "Polysol 8500" (manufactured by Showa Polymer Co., Ltd.) Colloidal silica ST-N: "Snowtex N" (manufactured by Nissan Chemical Co., Ltd., indicated as N in the table) ST-NS: "Snowtex NS" (manufactured by Nissan Chemical Co., Ltd.)
2. ST-NXS: "Snowtex NXS" (manufactured by Nissan Chemical Industries, Ltd., indicated as NXS in Table 2). 3. Vanadate compound Ammonium vanadate 4. Thiocarbonyl group-containing compound Thiourea Phosphate compounds Ammonium phosphate Solids concentration in these baths (solids concentration / water volume)
Is shown in Table 2 (unit: g / l). In addition, the amount of adhesion of the base treatment layer is also shown.

After forming the undercoating layer, a coating layer to which a rust-preventive pigment is added (hereinafter referred to as an upper layer; referred to as a rust-preventive pigment-containing coating layer in Table 2) is formed. The formation method is the same as that of the base treatment layer. As the upper layer treatment agent for forming the upper layer, the same type of acrylic olefin resin used as the resin as the substrate treatment agent was used as the resin, and as the rust preventive pigment, the same type of silica (N , NS,
NSX) was used. In addition, No. A base using the base treating agent shown as 101 (Example) as it was as an upper layer forming agent was also prepared (in Table 2, "base" is written in the column of pigment type). The thickness of the upper layer is described in the table.

For comparison, a coating type chromate treatment solution obtained by mixing a reduced chromic acid (a starch having a reduction ratio of 30%) / Snowtex N = 1/3 (weight ratio of solid content) to a plated steel sheet was applied to a roll coater. No. 1 was prepared by applying a steel sheet and drying at a sheet temperature of 70 ° C. 135, 137 (comparative example). 0.15g / m adhesion amount by coating type chromate treatment
^{And 2} . Further, a steel sheet in which a coating mainly composed of trivalent chromium was deposited by electrolysis was also prepared. 136 (comparative example). The adhesion amount of this electrolytic chromate treatment was 0.05 g / m ² .

The following evaluation was performed on the coated steel sheet thus prepared. 1. Adhesion of Film The flat plate was evaluated by the cross-cut tape method (clearance interval: 1 mm) described in 8.5.2 of JIS K 5400 (described as “flat” in the table). In addition, coated steel
The film to be tested by an Erichsen tester specified in 8.2 of SK 5400 was extruded 7 mm so as to be a convex portion, and the extruded portion was peeled off with a tape to examine the adhesion of the film (in the table, "Er"). When it is difficult to visually determine, the film is dyed with a 3% acetone solution of methyl violet, and the dyed portion has a film,
Adhesion was determined on the assumption that no film was present on the unstained portion. The same test was performed after the coated steel sheet was immersed in boiling water for 30 minutes, pulled up, and left for 24 hours. In Table 2, the test results of the adhesion of the coating of the coated steel sheet after immersion in boiling water are shown (the column of "Secondary adhesion"). ：: No coating peeling, Δ: Part of the coating peeled, ×: Film completely peeled

2. Fingerprint resistance Fingerprints were attached to the film of the surface-treated steel sheet, and the visibility of the fingerprints was visually judged and scored. The evaluation was as follows: 指紋: Fingerprint scarcely appeared, Δ: Fingerprint scar was visible, ×: Fingerprint scar was conspicuous. 3. Corrosion resistance Flat plate (sealed end and back of steel plate as cut)
A salt water spray test (specified in JIS Z 2371) was performed on a 7 mm Erichsen machined part (the end face and the back face of a steel sheet extruded by 7 mm with an Erichsen test machine), and the area ratio of generated white rust (%) ) Was determined visually.
The salt spray test was performed for 168 hours and 360 hours. Table 2
Among them, those not described in the column of 360 hours indicate that red rust has occurred. 4. Cylindrical drawing test Wrinkle holding pressure 1.0 ton, drawing ratio 2.2, die shoulder R4.
Under the condition of 0 mm, each coated steel sheet was cylindrically drawn. A cross cut was made in the lower part of the cylinder with a cutter knife, and the tape was peeled off to examine the adhesion of the film. In addition, the coated steel sheet drawn by cylindrical drawing was immersed in boiling water for 30 minutes and then pulled up.
After standing for 24 hours, the coating adhesion test was performed in the same manner. Table 2 shows the test results of the adhesion of the coating of the coated steel sheet after immersion in boiling water (the column of “cylindrical drawing”). ：: No peeling of coating, 一部: Partial peeling of coating, ×: Peeling of film entirely

Table 2 shows the test results. In the present invention example,
All have good corrosion resistance, film adhesion, and cylindrical drawability. When the thicknesses of the base treatment layer and the upper layer (rust prevention film layer) are increased, the corrosion resistance is improved (Nos. 101 to 109). N
o. When the same undercoat layer is formed on the upper layer as in 106, corrosion resistance is particularly good. As the type of silica, the use of NS having a smaller particle size and NXS having a smaller particle size than that of using N improves the corrosion resistance as the particle size decreases (No. 107, 110 to 112). The higher the amount of silica, the better the corrosion resistance (Nos. 107 and 11).
8-120). When the thiocarbonyl group-containing compound and the phosphate compound are used in combination with the vanadate compound, the corrosion resistance is improved (Nos. 116, 117, 121, 126). Even if the resin is changed, the corrosion resistance does not significantly change according to the examples of the present invention (Nos. 122 and 123). The plated steel sheet is GI
And GA, the corrosion resistance, the film adhesion,
Excellent moldability (Nos. 125 to 131).

No. 124 (Example of the present invention), in addition to N, the polyethylene-based wax “Chempearl WF”
640 (manufactured by Mitsui Chemicals, Inc.) and acrylic olefin resin 10
8 (solid parts by weight) is added to 0, but corrosion resistance,
Both moldability is good. In addition, the film adhesion before immersion in boiling water and the film adhesion of the cylindrical drawing body were all good (except for No. 132 (Comparative Example)).

The anti-fingerprint property of No. 3 which could not be applied due to the gelling of the treating agent. With the exception of 132 (Comparative Example), all had a good score of 4 points. No. 133 (comparative example)
Since the undercoating layer does not contain a vanadate compound, the corrosion resistance and the adhesion of the film are poor. No. 132 (Comparative Example) was excessive in the content of the vanadate compound, and the treatment liquid was not uniform and could not be applied. No. 134 (Comparative Example) shows that even when the plating type is GI, if the vanadate compound is not contained, the corrosion resistance and adhesion are inferior.

No. 135 to 137 (Comparative Example) are coated steel sheets using a chromate treatment, and have a problem of elution of hexavalent chromium. Further, although the corrosion resistance is good, the adhesiveness of the coating and the moldability (the adhesiveness of the coating after molding) are not always sufficient.

[0070]

[Table 7]

[0071]

[Table 8]

[0072]

As described above, the pre-coated steel sheet according to the present invention has a coating base in which a water-based resin is combined with a vanadate compound containing no hexavalent chromium, so that the pre-coated steel sheet is equal to or more than the one using the conventional chromate treatment. Film adhesion and corrosion resistance. That is, a pre-coated steel sheet having low pollution and excellent rust prevention performance is provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C23C 22/17 C23C 22/17 (72) Inventor Yujiro Miyauchi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation (72) Inventor Atsushi Morishita 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation (72) Inventor Hiroyasu Furukawa 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Inside the steelworks (72) Inventor Kohei Ueda 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Toshiaki Shimakura 4-1-15-1 Minamishinagawa, Shinagawa-ku, Tokyo Japan Paint Stock Inside the company (72) Inventor Katsuyoshi Yamazoe 4-1-1-15 Minamishinagawa, Shinagawa-ku, Tokyo Inside Japan Paint Co., Ltd. (72) Inventor Motoo Kamiya, Shinagawa, Tokyo 4-1-1-15 Minami Shinagawa, Ward Japan Paint Co., Ltd. (72) Inventor Tetsu Kobori 4-1-1-15 Minami Shinagawa, Shinagawa Ward, Tokyo Japan Paint Co., Ltd. (72) Inventor Masateru Takimoto Minami, Shinagawa Ward, Tokyo Shinagawa 4-1-1-15 Japan Paint Co., Ltd.

Claims (3)

[Claims] 1. A steel sheet containing 100 parts by weight of resin and at least 0.1 to 100 parts by weight of a vanadate compound as a solid component and optionally containing 0.1 to 100 parts by weight of a thiocarbonyl group-containing compound.
3000 parts by weight, 0.01 to 300 parts by weight of phosphoric acid compound (as PO ₄₎ and the coating layer further contains at least one of fine silica 1-2000 parts by weight has a surface treatment layer, further thereon A precoated steel sheet having a colored coating layer as an upper layer. 2. A steel sheet containing 100 parts by weight of a resin and at least 0.1 to 100 parts by weight of a vanadate compound as a solid content and optionally containing 0.1 to 100 parts by weight of a thiocarbonyl group-containing compound.
3000 parts by weight, 0.01 to 300 parts by weight of phosphoric acid compound (as PO ₄₎ and the coating layer further contains at least one of fine silica 1-2000 parts by weight has a surface treatment layer, further thereon A coated layer containing a rust-preventive pigment as an undercoat layer, and a colored coating layer thereon as an upper layer. 3. A steel sheet containing 100 parts by weight of resin and at least 0.1 to 100 parts by weight of a vanadate compound in terms of solid content and optionally 0.1 to 100 parts by weight of a thiocarbonyl group-containing compound.
3000 parts by weight, 0.01 to 300 parts by weight of phosphoric acid compound (as PO ₄₎ and the coating layer further contains at least one of fine silica 1-2000 parts by weight has a surface treatment layer, further thereon A coated steel sheet comprising, as an upper layer, a coating layer to which a rust-preventive pigment is added.