JP2002038280A - Metal plate with chromium-free coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal plate with a coating of an ingredient material including no chromium, superior in not only corrosion resistance but also formability and moisture resistance. SOLUTION: This coating on the metal plate comprises sequentially from a surface of the metal plate, (1) an organic-inorganic composite coating including a titanium compound and fluoride, (2) a primer coating with a film thickness of 5 μm or more containing a silica-base rust preventive pigment of 15-60 weight %, and (3) an over coating with a film thickness of 10-300 μm. The organic- inorganic composite coating includes a titanium compound of 3-25 mg/m2 by coating weight converted to titanium, fluoride of 7-57 mg/m2 by coating weight converted to fluorine, and a zirconium compound, if necessary, of 0.8-6.4 mg/m2 by coating weight converted to zirconium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-chromium film which is used for an exterior material, an interior material, an outer plate for home electric appliances, various kinds of articles, etc. and has a coating film formed thereon via a chemical conversion coating film having excellent corrosion resistance. The present invention relates to a coated metal sheet.

[0002]

2. Description of the Related Art A coated metal sheet using a Zn-plated steel sheet, a Zn-A1 alloy-plated steel sheet, an alloyed Zn-plated steel sheet, an A1-plated steel sheet, an A1 sheet, etc. as a coating base sheet is used as a pre-coating treatment.
Chromate treatment is applied. Next, an undercoat film is formed using a paint containing a chromium-based rust-preventive pigment such as strontium chromate and calcium chromate, and then an overcoat is applied. However, in recent years, where environmental protection is important, chromium regulations have tended to be greatly strengthened.
Chromium-free undercoat paint is being developed.

[0003] As a coating base for aluminum, an aqueous base coating composition containing a water-soluble zirconium compound or the like (Japanese Patent Publication No. 7-81097);
A non-chromium-based chemical conversion treating agent containing a component selected from Ti oxides (Japanese Patent Application Laid-Open No. 10-102264) is known, but no mention is made of a non-chromium-based rust preventive pigment for an undercoat.

[0004] Surface-treated steel sheets that do not use chromium have also been proposed. For example, Japanese Patent Application Laid-Open No. Hei 8-283609 discloses a paint in which phosphoric acid and heavy metal ions such as Cu, Co, and Fe are mixed with an organic resin, or further various colloids are added. Further, Japanese Patent Application Laid-Open No. Hei 8-209038 introduces a chromium-free coating composition containing a crosslinking system of acrylic acid or a derivative thereof as a binder and a hydroxide of a polyvalent metal.

Japanese Unexamined Patent Publication (Kokai) No. 63-248873 introduces a water-dispersible silica-alkoxysilane-acrylic resin-based non-chromium chemical conversion treating agent. Did not mention. JP 11
In JP-A-222575, a coating composition and a coated steel sheet using calcium ion-exchanged amorphous silica fine particles as a rust preventive pigment for an undercoat paint are introduced. Chromate treatment is used for pre-painting treatment.

[0006]

As described above, as for the non-chromium-based rust-preventive pigments to be incorporated in the non-chromium-based chemical conversion treatment and the undercoat film, those which sufficiently satisfy the requirements regarding the corrosion resistance are still in practical use. Not. The present invention has been devised to solve such a problem, and provides a coated metal sheet using a raw material that does not contain chromium and having excellent not only corrosion resistance but also processability and moisture resistance. With the goal.

[0007]

Means for Solving the Problems The non-chromium-based coated metal sheet of the present invention, on the surface of the metal sheet,
An organic-inorganic composite film containing a titanium compound and a fluoride, an undercoat film having a thickness of 5 μm or more containing 15 to 60% by mass of a modified silica-based rust preventive pigment, and an overcoat film having a thickness of 10 to 300 μm are sequentially laminated. The titanium compound of the organic-inorganic composite coating is 3 to 25 mg /
m ² , the amount of fluoride is 7 to 57 mg in terms of fluorine.
/ M ² .

[0008] The organic-inorganic composite coating may further contain a zirconium compound in an amount of 0.8 to 6.4 mg / m ^{2 in} terms of zirconium. In addition, the base metal plate and the organic
A nickel adhesion layer having an adhesion amount of 1 to 20 mg / m ² may be interposed between the inorganic composite film and the inorganic composite film. The content of the modified silica-based rust-preventive pigment contained in the undercoat film and the glass transition point temperature of the overcoat film are shown by A (15,0) and B (15,
65), C (35, 65), D (60, 31), E (6
(0, 0) is preferably set in the range enclosed by (0, 0).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a non-chromium coated metal sheet according to the present invention, a Zn-plated steel sheet, a Zn-A1 alloy-plated steel sheet, an alloyed Zn-plated steel sheet, an A1-plated steel sheet, an A1 sheet or the like is used as a base plate for coating. After the surface of the coated original plate is cleaned by degreasing, pickling or the like, a chemical conversion treatment using a non-chromium chemical conversion treatment agent is performed. As the non-chromium chemical conversion treating agent, an aqueous solution of 72 g / l of aminomethyl-substituted polyvinyl phenol (as a solid) dissolved in propoxypropanol as an organic resin of 57 g / l of hexafluorotitanic acid can be used. Due to the acid component in the processing solution, metal ions elute from the metal surface and the pH of the metal surface rises, and the eluted metal ions, titanium compound, fluoride and organic resin in the processing solution are combined to form an organic-inorganic material. Formed at the interface as a composite film.

As the organic resin, JP-A-4-26308
No. 3, published in detail, and obtained by reacting a 4-vinylphenol polymer with formaldehyde and methylethanolamine. If the organic resin contains a large amount of hydroxyl groups and amino groups, it is convenient to make the bond with the eluted metal ions and the titanium compound in the treatment liquid strong. Preferably, the non-chromium chemical conversion treatment liquid may contain 10 g / 1 hexafluorozirconic acid.

The non-chromium-based chemical conversion treatment solution is preferably applied to a metal plate so as to form an organic-inorganic composite film having a dry film amount of 25 to 200 mg / m ² . Dry film amount 25
When the coating amount is less than mg / m ^2, the effect of the organic-inorganic composite film is not sufficiently exhibited, and conversely, the dry film amount is 200 mg / m ^2.
If the coating amount exceeds the above range, the processability will decrease. The organic-inorganic composite film has a titanium compound adhesion of 3 to 25 mg / m ² in terms of titanium and a coating amount of 7 to 57 mg / m ² in terms of fluorine.
It is necessary to include m ² fluoride. The titanium compound reacts with the organic resin together with the metal ions eluted from the metal base to form a poorly soluble organic-inorganic composite film. If the amount of the titanium compound is small, the effect of forming an organic-inorganic composite film is insufficient, and workability after coating cannot be obtained. If the amount is too large, not only the effect is saturated, but also the workability after painting is reduced, the cost is increased, and it is economically wasteful.

Fluoride dissociates into fluorine ions in the processing solution, and has an effect of etching the metal substrate together with the acid component in the processing solution. If the amount is small, the etching of the metal substrate by the fluorine ions becomes poor, and the adhesion to the metal substrate becomes insufficient. If the amount is large, the metal eluted by etching increases in the film, weakens the organic-inorganic composite film, and the adhesion to the metal substrate becomes insufficient. Further, when the pH of the interface increases, the fluorine ions form poorly soluble fluorides with the metal ions eluted from the metal base, and contribute to the formation of the organic-inorganic composite film. When the titanium compound and the fluoride coexist, they form a fluoride complex of titanium and suppress the dissociation of fluorine ions, so that excessive reaction with the metal material and rapid deterioration of the treatment bath are reduced. It is convenient because both the titanium component and the fluoride can be simultaneously introduced into the treatment bath.

The organic-inorganic composite coating may further contain a zirconium compound in an amount of 0.8 to 6.4 mg / m ^{2 in} terms of zirconium. The zirconium compound has the same effect as the titanium compound, and forms a hardly soluble organic-inorganic composite film by reacting with the organic resin together with the metal ions eluted from the metal base. When the metal ions eluted from the metal base contain a large amount of aluminum, a better organic-inorganic composite film is formed by the zirconium compound. When the zirconium compound is small, the effect is insufficient, and when the zirconium compound is large, not only the effect is saturated, but also on the contrary, the workability after painting is reduced, the cost is increased, and the cost is economically wasteful.

Prior to the formation of the organic-inorganic composite film, a nickel adhesion layer may be formed if necessary. The nickel adhesion layer also acts on an inactive portion of the metal surface remaining after degreasing, and adheres nickel, thereby helping the adhesion between the metal surface and the organic-inorganic composite film. The nickel adhesion layer
It is formed by a method such as spray treatment using an aqueous solution of nickel silicofluoride and silicic hydrofluoric acid.
/ M ² . The treatment liquid is commercially available as NPC500 (manufactured by Nippon Paint Co., Ltd.). If the amount of nickel deposited is small, a large amount of inactive portions will remain, and if the amount is large, the effect will be saturated and only the cost will be increased, which is economically wasteful.

An undercoat is applied to the original coating plate on which the organic-inorganic composite coating has been formed. The undercoat is prepared by blending a modified silica-based rust preventive pigment with a thermosetting epoxy-modified polymer polyester resin paint or the like. The modified silica-based rust-preventive pigment is produced, for example, by introducing calcium ions into a fine porous wet silica carrier, and includes SHIELDEX (manufactured by Fuji Silysia Chemical Ltd.), SC610, TC710 (manufactured by Teica Corporation). )). The modified silica-based rust preventive pigment is blended so as to be dispersed in the undercoating film at a ratio of 15 to 60% by weight. If the amount is less than 15% by weight, a sufficient rust-preventing effect is not exhibited, and if the amount exceeds 60% by weight, the workability of the coating film tends to deteriorate. Next, a top coat is applied to form a top coat of 10 to 300 μm in dry film thickness. As the top coat, a high-molecular polyester resin paint or the like is used, and the glass transition temperature of the top coat is in the range of 0 to 65 ° C. depending on the mixing ratio of the main resin and the curing agent and the use of the main resins having different glass transition temperatures. It is adjusted to.

[0016] The glass transition temperature of the overcoating film is different from the content of the modified silica-based rust-preventive pigment contained in the undercoating film.
It is preferable to adjust the relationship shown in FIG. That is, with respect to the undercoat film in which a relatively large amount of the modified silica-based rust preventive pigment is dispersed, an overcoat film having a lowered glass transition temperature according to the content of the modified silica-based rust preventive pigment is formed. As a result, the osmotic pressure of the modified silica-based rust-preventive pigment caused by the ions escapes from the overcoat film, thereby preventing the moisture-resistant swelling. On the other hand, when an overcoat having a high glass transition temperature is overlaid on an undercoat having a large content of the modified silica-based rust-preventive pigment, osmotic swelling caused by ions of the modified silica-based rust-proof pigment does not escape from the overcoat, It becomes swelling of moisture resistance and causes defects on the coating film surface.

[0017]

[Example 1] As a coating base plate, the basis weight was 250 g / m ² ,
A zinc-4% aluminum alloy-plated steel sheet having a thickness of 0.5 mm was prepared. After degreased paint base plate, hexafluorotitanic acid-based non-chromium chemical conversion treatment agent (Bonderite 14
53: manufactured by Henke 1) to be targeted.
Dried. Next, a modified silica-based rust preventive pigment (SHIEL
A polyester resin paint (KP8110: manufactured by Kansai Paint Co., Ltd.) blended with DEX (manufactured by Fuji Silysia Ltd.) was applied as an undercoat paint to the coated base plate after the chemical conversion treatment, and baked at a reached plate temperature of 225 ° C. for 40 seconds. Further, a polyester overcoat (AT2000: manufactured by Kansai Paint Co., Ltd.) was applied and baked at an ultimate plate temperature of 225 ° C. for 50 seconds. Table 1 shows the layer configuration of each of the obtained coated steel sheets. The adhesion amounts of the titanium compound, the fluoride, and the zirconium compound contained in the organic-inorganic composite coating are represented by a titanium equivalent, a fluorine equivalent, and a zirconium equivalent, respectively. The organic component was contained in the organic-inorganic composite coating as aminomethyl-substituted polyvinylphenol.

[0018]

A test piece was cut out from each coated steel sheet and subjected to a workability test, a moisture resistance test, and a corrosion resistance test. For comparison,
A coating was prepared in which the amount of the non-chromium-based chemical conversion coating film, the content of the modified silica-based rust-preventive pigment in the undercoat film, the thickness of the overcoat film, etc. were out of the ranges specified in the present invention. In the workability test, after sandwiching two steel plates of the same thickness in the bent part, bending the painted metal plate by 180 degrees, applying adhesive tape to the bent part and peeling it off, the peeling state of the coating film was measured. Observed (2t bending test). The adhesion of the coating film was evaluated on a 6-point scale from 0 to 5, with 5 points where no peeling was detected and 0 points where the coating film was completely peeled off. Generally 4
The above points are treated as coating films having good adhesion. In the moisture resistance test, after exposing the test piece to saturated steam at 80 ° C. for 72 hours, the coating film surface was observed, and the sample having no abnormality was evaluated as ○, and the sample with blistering was evaluated as ×, to evaluate the moisture resistance. In the corrosion resistance test, a test piece having a cut end face reaching the base steel sheet from the top coat film side was used, and after a salt water spray test for 250 hours in accordance with JIS Z-2371, the state of occurrence of corrosion of the cut end face was observed. Then, the peeling of the coating film due to the corrosion of the cut end surface was evaluated by the maximum swollen width of the coated film from the cut end surface.

As can be seen from the examination results in Table 2, the coated steel sheets of Test Nos. 1 to 8 in which the organic-inorganic composite coating, the undercoat and the topcoat were formed according to the present invention were all workability and moisture resistance. Excellent in corrosion resistance and corrosion resistance. On the other hand, Test No. 9 in which the amount of the titanium compound and fluoride in the organic-inorganic composite coating is small is poor in workability and corrosion resistance, and Test Nos. 10 and 14 in which the thickness of the undercoat is insufficient and the test in which the top coat is thin. Test No. 11 in which the corrosion resistance was insufficient and excessively modified silica-based rust preventive pigment was dispersed in the undercoating film was used. Test No. 12 was inferior in workability and test No. 1 in which the amount of the modified silica-based rust preventive pigment was small.
Test No. 3 was inferior in corrosion resistance, and Test No. 15 in which the titanium compound and the fluoride of the organic-inorganic composite film were excessive was inferior in workability.

[0021]

[0022]

Example 2 An A1-plated steel sheet was used as a base material for coating, and after degreasing, a hexafluorotitanic acid-based non-chromium chemical conversion treatment agent (Bonderite 1453: manufactured by Henke 1) was applied to a titanium compound in an amount of 13 mg / m in terms of titanium.
^{In 2 above} , the fluoride was applied so that the amount of fluoride was 28 mg / m ² in terms of fluorine, and was dried. Next, a 7 μm-thick undercoat film and a 15 μm-thick overcoat film were formed.
The use of a modified silica-based rust-preventive pigment as a base coat and a top coat that is adjusted to have various glass transition temperatures of a top coat by using paints having various contents of modified silica-based rust-preventive pigments have an effect on the properties of the resulting coated steel sheet. The effects of the rust-preventive pigment content and the glass transition temperature of the overcoat film were investigated. As shown in Table 3 and FIG. 1 showing the results of the investigation, A (15,0) and B (15,6) were plotted on the coordinate with the content of the modified silica-based rust preventive pigment on the horizontal axis and the glass transition temperature on the vertical axis.
5), C (35, 65), D (60, 31), E (6
Test Nos. 1 to 11, in which the modified silica-based rust-preventive pigment and the glass transition temperature were set in the range surrounded by (0, 0), showed excellent moisture resistance, and both workability and corrosion resistance were good.

[0023]

[0024]

As described above, the non-chromium-coated metal sheet of the present invention is obtained by forming an organic-inorganic composite film containing a titanium compound and a fluoride on a coating original sheet and then forming a modified silica-based rust-preventive pigment. The top coat is laminated via the undercoat containing. With this coating composition, a coated steel sheet having workability, corrosion resistance, and moisture resistance comparable to chromate-coated steel sheets can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the modified silica-based rust preventive pigment content of an undercoat film and the glass transition temperature of an overcoat film on moisture resistance.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Koji Mori, Inventor 7-1, Takatani-Shimmachi, Ichikawa-shi, Chiba Nisshin Steel R & D Co., Ltd. (72) Inventor Hiromitsu Fukumoto 7-1, Takatani-Shimmachi, Ichikawa-shi, Chiba F-term (Reference) 4D075 CA33 DB05 DB07 DC10 EB16 EB42 EB56 EC02 EC15 4F100 AA05B AA17B AA20C AA21B AA34B AB01A AB03 AB10 AB18 AB31 AK41 BA04 BA10A BA10D BA25D CA13C CC00E CC00D E00B 002 AB02 BA10 BA14 BA20 BA21 BB04 BB05 BC02 BC05 CA11 CA16 CA53

Claims (4)

[Claims] 1. An undercoating film having a thickness of 5 μm or more, comprising an organic-inorganic composite film containing a titanium compound and a fluoride on the surface of a metal plate, containing 15 to 60% by weight of a modified silica-based rust preventive pigment, and a film. A top coat having a thickness of 10 to 300 μm is sequentially laminated, and the titanium compound of the organic-inorganic composite film is 3 to 25 mg / m ² in terms of titanium equivalent, and the fluoride is 7 to 57 mg in terms of fluorine equivalent in terms of fluorine. / M ² , a non-chromium coated metal plate. 2. The non-chromium-coated metal sheet according to claim 1, wherein the organic-inorganic composite film contains a zirconium compound in an amount of 0.8 to 6.4 mg / m ^{2 in} terms of zirconium. 3. The non-chromium-coated metal sheet according to claim 1, wherein an organic-inorganic composite film is formed via a nickel adhesion layer having an adhesion amount of 1 to 20 mg / m ² . 4. The relationship between the content of the modified silica-based rust-preventive pigment contained in the undercoating film and the glass transition temperature of the overcoating film is shown by A (15,0) and B (15,65) in FIG. , C
The non-chrome-based coated metal sheet according to any one of claims 1 to 3, wherein the metal sheet is in a range surrounded by (35, 65), D (60, 31), and E (60, 0).