JP3231455B2 - Pretreatment method for inorganic paint coating of stainless steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for applying an inorganic paint, for example, a silicon alkoxide-based inorganic paint, an alkali silicate-based inorganic paint, a phosphate-based inorganic paint, etc. on the surface of a stainless steel sheet. The present invention relates to a novel inorganic paint pretreatment method capable of stably forming a high-quality coating film having no coating defects such as blisters, cracks, and peeling, and having excellent adhesion of the coating film, particularly excellent secondary adhesion to water. Things.

[0002]

2. Description of the Related Art Stainless steel sheets have much better corrosion resistance than ordinary steel sheets, but when used unpainted, dirt easily adheres to them, and in the long term corrosion occurs from contaminated stains. However, there is a problem in terms of functionality as well as a decrease in design. In order to solve these problems, a painted stainless steel plate obtained by applying a coating to a stainless steel plate is being used as a building material. However, in order to increase the corrosion resistance of stainless steel sheets and to provide long-term durability, alkyds,
Conventional paints mainly composed of polyester-based or acrylic-based resins are not sufficient, and fluorine-based paints and inorganic paints having long-term durability are increasingly used.

[0003] Inorganic paints such as silicon alkoxides have high corrosion resistance, chemical resistance, abrasion resistance, weather resistance, heat resistance, mold resistance, and antibacterial properties. Because of its high quality, it has an extremely high coating film hardness as compared with an organic resin coating film, and thus has extremely excellent scratch resistance. Accordingly, inorganic paints have received great attention in the fields of building materials and structural materials.

In general, it is known that the surface of a stainless steel plate is covered with a chemically stable metal oxide and has low adhesion to a coating film. Therefore, there is a demand for a stainless steel sheet coated with an inorganic paint having coating film adhesion that can withstand practical use. In particular, the silicon alkoxide-based inorganic coating has a polysiloxane as a basic skeleton, so that the coating is brittle compared to general organic resin-based coatings, and the resin itself has a strong polarity, so that the water permeability of the coating is high. When a metal material, in particular, a stainless steel plate is used as an object to be coated, the adhesion to the material, particularly the water-resistant secondary adhesion, is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawback of the inorganic paint coating using a stainless steel sheet as an object to be coated, in particular, the lack of water-resistant secondary adhesion. By solving this drawback, the corrosion resistance, which is an excellent property of stainless steel plates, is enhanced, and
Conventional organic resin-based coatings that fully demonstrate the excellent chemical stability, chemical resistance, abrasion resistance, weather resistance, heat resistance, mold resistance, antibacterial properties, and scratch resistance of inorganic coatings. , An inorganic paint-coated stainless steel sheet exhibiting much higher durability than that of a coated steel sheet is provided.

[0006]

Means for Solving the Problems The present inventors have found that the adhesion of a coating film, which is a drawback in exhibiting long-term durability when a stainless steel sheet coated with an inorganic coating is used outdoors, is particularly problematic. As a result of intensive studies to improve the next adhesion, the surface of the stainless steel sheet was first treated with a chromate solution in advance, and then a solution containing at least one selected from silica sol and a specified organic silicon compound group was applied. It has been found that by performing the pretreatment described above, the adhesion to inorganic coatings, particularly the secondary adhesion to water, can be greatly improved, and the present invention has been completed.

In the present invention, the pretreatment for coating with an inorganic paint is carried out by chromate treatment, silica sol and one or two or more compounds selected from the specified organosilicon compounds.
It consists of two steps of a process of applying a liquid containing at least% by weight. First, the chromate treatment in the present invention will be described.

The chromate treatment is adopted in the present invention because a reactive chromate treatment in which a chromate solution is applied and then washed with water is easily applied to a molded product. The reactive chromate treatment is not particularly limited, such as phosphoric acid chromate treatment, chromate chromate treatment, and the like.

The composition of the chromate solution used in the present invention is not particularly limited, but preferred compositions are chromic acid 0.4 to 10 g / liter and phosphoric acid 1.5.
-50 g / liter and fluorine ion 0.05-5 g
Per liter. In this composition system, stainless steel can be treated with a dilute solution of less than 0.4 g / L of chromic acid, less than 1.5 g / L of phosphoric acid, and less than 0.05 g / L of fluorine ions, even if it is an aqueous chromate solution. It is not preferable because the time required for forming an effective treated surface as a pre-stage of the treatment of silica sol or the like becomes long and the productivity decreases. Chromic acid 1
Even with a concentrated chromate solution having a concentration of more than 0 g / l, phosphoric acid of more than 50 g / l, and fluoride ion of more than 5 g / l, there is no problem in the chromate treatment of stainless steel itself, but the effect reaches saturation, which is not economical. .

A composition containing 0.4 to 10 g / l of chromic acid, 0.1 to 10 g / l of nitric acid and 0.05 to 5 g / l of fluorine ions can also be preferably used. In this composition system, chromic acid 0.1.
Although it is possible to treat stainless steel even with a dilute aqueous chromate solution of less than 4 g / liter, less than 0.1 g / liter of nitric acid, and less than 0/05 g / liter of fluorine ions, it can be used as a pre-stage for the subsequent treatment of silica sol or the like. The time required to form an effective treated surface is prolonged and productivity is undesirably reduced. Also, chromic acid more than 10 g / liter,
Even if a concentrated aqueous chromate solution containing more than 10 g / liter of nitric acid and more than 5 g / liter of fluorine ion does not cause any problem in the treatment itself, it is not economical because the effect of the chromate treatment reaches saturation.

[0011] One or more acids selected from hydrofluoric acid, hydrosilicic acid, hydrofluoroboric acid, titanium hydrofluoric acid and zircon hydrofluoric acid contained in these chromate aqueous solutions are used. Can be supplied. These fluorine ions do not refuse to use water-soluble salts of the acids, for example, salts with alkali metals such as sodium and potassium, salts with alkaline earth metals such as magnesium, salts with ammonium and the like. . These aqueous chromate solutions can further contain 0.1 to 10 g / l of sulfuric acid. It is presumed that sulfuric acid contained in the aqueous chromate solution has an effect of assisting dissolution of the oxide film on the stainless steel plate.

The chromate treatment method in the present invention is not particularly limited, and a method of applying an aqueous chromate solution by a usual spray method, dipping method, or the like can be used. After application in this manner, the chromate treatment is completed by washing with water in a usual manner. The temperature of the aqueous chromate solution used in the chromate treatment is not particularly limited, but is usually preferably in the range of 10 to 60 ° C. from the viewpoint of economy and workability.

The solution containing one or more compounds selected from the group consisting of silica sol and organosilicon compounds, which is used in the subsequent step following the chromate treatment in the present invention, will be specifically described. First, a specific example of silica sol will be described. A fumed product produced by oxidizing colloidal silica or silane chloride in an aqueous solution of an alkali silicate such as water glass using an ion exchange resin or the like in the air. A liquid in which silica or the like is uniformly dispersed in a solvent can be used. Although the average particle size of these silica sols is not particularly limited, it is 5 to 500 nm.
Is preferred.

As the organosilicon compound used in the present invention, the following organosilicon compound group (A) containing at least two alkoxy groups in one molecule is used. Vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycid Xypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, n-β- (aminoethyl) γ-aminopropyltrimethoxysilane, n-β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ -Aminopropyltriethoxysilane, n-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane.

The solution applied to the treated surface after the chromate treatment is a solution containing one or more compounds selected from the group consisting of silica sol and (A) an organosilicon compound. Their content (in the case of two or more types, the total amount) needs to be 0.01% by weight or more. If these contents are less than 0.01% by weight, the effect of improving the adhesion is insufficient. On the other hand, the upper limit of the content is not particularly limited, but is 5% by weight.
If it is excessive, the effect of improving the adhesion reaches saturation and is not economical. The type of the solvent used for dissolving and / or dispersing the silica sol and the organosilicon compound is not limited at all, and is not limited to water, but also alcohols, aromatics such as toluene and xylene, Cellosolve,
Organic solvents such as acetates and esters can be used. The method for applying this solution is not particularly limited, and a usual method such as spraying, dipping, or brushing can be used. After application, preferably 50 to 200
Dry at a temperature of ° C.

[0016]

The present inventors presume the chemical action of the pretreatment of the chemical solution used in the present invention on a stainless steel plate as follows. Usually, the surface of the stainless steel sheet is covered with a metal oxide that is chemically stable in the air, and it is described that the corrosion resistance of the stainless steel sheet is due to the metal oxide film. On the other hand, it is known that the adhesion of a coating film such as a coating material applied to a metal to a substrate depends on a polar group in the coating material. However, since the surface of the stainless steel sheet is covered with a stable metal oxide film, it has a property that it is difficult to exert the adhesion due to the polar group in the paint when it is painted.

Therefore, when the effect of the chromate treatment in the present invention is presumed, the metal oxide film is activated by dissolving the metal oxide film on the stainless steel plate or adsorbing chromic acid, etc.
Further, it is considered that the silica sol and the organosilicon compound of the present invention strongly bind to the surface of the activated stainless steel sheet. The silica sol and the organosilicon compound of the present invention thus strongly bonded have a structure very close to the siloxane skeleton, which is a main component of the inorganic coating, so that the adhesive force with the silicon alkoxide-based inorganic coating is remarkably increased. It is supposed to improve.

[0018]

The present invention will be described in detail with reference to the following examples, but the scope of the present invention is not limited by these examples.

A commercially available stainless steel sheet (SUS304) having a thickness of 0.3 mm was used as a material, and after performing the pretreatment of the following Examples (1) to (8) and Comparative Examples (1) to (4), Various performance tests were conducted by coating with an inorganic paint.

EXAMPLE 1 Alkaline degreasing of a stainless steel plate (Note 1), washing with water (Note 2)
After that, chromic acid 0.4 g / liter, phosphoric acid 1.5 g
/ Liter, Fluorine ion to supply hydrofluoric acid 0.05
After being immersed in a 50 ° C. aqueous solution containing g / liter for 20 minutes, it was washed with water (Note 2), further coated with an aqueous solution containing 0.1% by weight of silica sol (Note 3), and dried at 80 ° C.

Example 2 Alkaline degreasing of stainless steel sheet (Note 1), washing with water (Note 2)
After immersion for 10 minutes in a 50 ° C. aqueous solution containing 4 g / l of chromic acid, 8 g / l of phosphoric acid, and 0.3 g / l of fluoride ions from a source of hydrofluoric acid as a source, washing with water (Note 2) Then, an ethanol solution containing 0.01% by weight of vinyltrichlorosilane was applied, and dried at 80 ° C.

Example 3 Alkaline degreasing of a stainless steel plate (Note 1), washing with water (Note 2)
After immersion for 5 minutes in a 50 ° C. aqueous solution containing 2.6 g / l of chromic acid, 10 g / l of nitric acid, and 0.2 g / l of fluorine ions using hydrosilicic acid as a source, washing with water (note 2) Then, an ethanol solution containing 0.1% by weight of γ-methacryloxypropyltrimethoxysilane was applied and dried at 80 ° C.

Example 4 A stainless steel plate was alkali-degreased (Note 1) and washed with water (Note 2)
After that, chromic acid 0.4 g / liter, phosphoric acid 1.5 g
/ Liter, fluorine ion from hydrofluoric acid as a source 0.0
50 ° C. containing 5 g / l and sulfuric acid 5 g / l
Immersed in an aqueous solution for 5 minutes, washed with water (Note 2), and then γ
An aqueous solution containing 1% by weight of glycidoxypropyltrimethoxysilane was applied and dried at 80 ° C.

Example 5 Alkaline degreasing of a stainless steel plate (Note 1), washing with water (Note 2)
After that, 0.4 g / liter of chromic acid and 0.1 g /
Immersion for 5 minutes in a 50 ° C. aqueous solution containing 0.05 g / l of fluorine ion and 0.2 g / l of sulfuric acid using zircon hydrofluoric acid as a supply source, followed by washing with water (Note 2) and further n-β -(Aminoethyl) γ-aminopropyltrimethoxysilane was coated with an ethanol solution containing 5% by weight, and dried at 80 ° C.

Example 6 Alkaline degreasing of a stainless steel plate (Note 1), washing with water (Note 2)
After immersion for 2 minutes in a 30 ° C. aqueous solution containing 10 g / l of chromic acid, 10 g / l of nitric acid, and 5 g / l of fluoride ions using a magnesium salt of hydrosilicofluoric acid as a source, washing with water (Note 2) Then, an aqueous solution containing 0.5% by weight of γ-aminopropyltriethoxysilane was applied, and dried at 80 ° C.

Example 7 Alkaline degreasing of a stainless steel plate (Note 1), washing with water (Note 2)
After immersion for 2 minutes in a 30 ° C. aqueous solution containing 10 g / l of chromic acid, 50 g / l of phosphoric acid, and 5 g / l of fluoride ions using an ammonium salt of hydrofluoric acid as a source, washing with water (Note 2) ) And further applied a xylene solution containing 5% by weight of vinyltrimethoxysilane, and dried at 80 ° C.

Example 8 A stainless steel plate was alkali-degreased (Note 1) and washed with water (Note 2)
After immersion for 2 minutes in a 30 ° C. aqueous solution containing 10 g / l of chromic acid, 50 g / l of phosphoric acid, and 5 g / l of fluoride ion using titanium hydrofluoric acid as a source, washing with water (Note 2), Further, a methanol solution containing 0.01% by weight of n-phenyl-γ-aminopropyltrimethoxysilane was applied and dried at 80 ° C.

EXAMPLE 9 Alkaline degreasing of stainless steel sheet (Note 1), washing with water (Note 2)
After that, 0.4 g / liter of chromic acid and 0.1 g /
Immersion for 5 minutes in a 50 ° C. aqueous solution containing 0.05 g / l of fluorine ions and 0.2 g / l of sulfuric acid using borofluoric acid as a supply source, followed by washing with water (Note 2)
Then, an ethanol solution containing 5% by weight of n-β- (aminoethyl) γ-aminopropyltrimethoxysilane was applied, and dried at 80 ° C.

EXAMPLE 10 Alkaline degreasing of a stainless steel plate (Note 1), washing with water (Note 2)
After that, chromic acid 0.4 g / liter, phosphoric acid 1.5 g
Per liter, with hydrofluoric acid as the source, fluorine ion 0.0
After immersion in a 50 ° C. aqueous solution containing 5 g / liter for 20 minutes, washing with water (Note 2), 0.06% by weight of silica sol (Note 3) and 0.04% by weight of γ-aminopropyltriethoxysilane The aqueous solution contained was applied and dried at 80 ° C.

Comparative Example 1 A stainless steel plate was alkali-degreased (Note 1) and washed with water (Note 2)
After that, it was dried at 80 ° C.

Comparative Example 2 A stainless steel plate was alkali-degreased (Note 1) and washed with water (Note 2)
After that, 4 g / l of chromic acid, 8 g / l of phosphoric acid, 0.3 g of fluorine ions using hydrofluoric acid as a source
After immersion for 10 minutes in a 50 ° C./liter aqueous solution containing water / liter, washed with water (Note 2) and dried at 80 ° C.

Comparative Example 3 A stainless steel plate was alkali-degreased (Note 1) and washed with water (Note 2)
After immersion for 20 minutes in a 50 ° C. aqueous solution containing 10 g / l of chromic acid, 50 g / l of phosphoric acid, and 5 g / l of fluoride ions using zircon hydrofluoric acid as a source, washing with water (Note 2), Dried at 80 ° C.

Comparative Example 4 A stainless steel plate was alkali-degreased (Note 1) and washed with water (Note 2)
After drying, an aqueous solution containing 1% by weight of γ-glycidoxypropyltrimethoxysilane was applied and dried at 80 ° C.

(Note 1) Alkaline degreasing: A test stainless steel plate was treated with an alkali degreasing agent (trade name: Nippon Parkerizing Co., Ltd., Fine Cleaner 4360, concentration: 20 g /
Liter) of an aqueous solution at 60 ° C. for 2 minutes to carry out alkali degreasing. (Note 2) Rinse: Tap water was sprayed on the test stainless steel plate for 20 seconds and rinsed. (Note 3) Silica sol: Snowtex N (silica sol concentration = 20%) manufactured by Nissan Chemical Industries, Ltd. was used.

1. Preparation of Inorganic Paint-Coated Plate A silicon alkoxide-based inorganic paint was applied to the test stainless steel plates subjected to the pretreatment in Examples 1 to 10 and Comparative Examples 1 to 4, and baked at 200 ° C. for 30 minutes to form a film having a thickness of 7 μm. A coated plate was prepared, and performance tests shown in the following (1) to (3) were performed. The results are shown in Table 1.

2. Performance Test (1) Observation of Coating Appearance The coating film after coating and baking was observed, and the occurrence of peeling, bumps, blisters, and cracks was visually observed. (2) Primary adhesion test Draw 100 squares of 1 mm square on the painted surface with an NT cutter so as to reach the substrate, and peel off with cellophane tape. The following ranks were evaluated according to the number of crosses remaining after the tape was peeled off. ◎: No abnormalities ○: Number of remaining grids 95/100 or more △: Number of remaining grids 80/100 or more ×: Number of remaining grids less than 80/100 (3) Secondary adhesion test Inorganic paint-coated boards were placed in boiling water After soaking for 2 hours, 100 squares of 1 mm square are drawn on the painted surface with an NT cutter so as to reach the base material, and peeled off with cellophane tape. The following ranks were evaluated according to the number of crosses remaining after the tape was peeled off. ：: No abnormality ○: Number of remaining crosses 95/100 or more △: Number of remaining crosses 80/100 or more ×: Number of remaining crosses less than 80/100

From the results of the performance test, Examples 1 to 10 according to the present invention were excellent in the appearance of the coating film, primary adhesion and secondary adhesion, whereas Comparative Example 1 showed cracks in the appearance of the coating film itself and was completely It cannot be put to practical use. In Comparative Examples 2 and 3, the appearance of the coating film was good, but the primary adhesion and the secondary adhesion were poor. Comparative Example 4 has relatively good primary adhesion, but is inferior in secondary adhesion, and does not achieve long-term durability.

[0038]

TABLE 1 Performance Test Results Symbol film appearance primary adhesion secondary adhesion Example 1 No abnormalities ◎ ◎ Example 2 No abnormality ◎ ◎ Example 3 No change ◎ ◎ Example 4 No change ◎ ◎ Example 5 No abnormality ◎ ◎ Example 6 No abnormality ◎ ◎ Example 7 No abnormality ◎ ◎ Example 8 No abnormality ◎ ◎ Example 9 No abnormality ◎ ◎ Example 10 No abnormality ◎ ◎ Comparative example 1 Slight crack × × Comparative example 2 No abnormality △ × Comparative Example 3 No abnormality △ × Comparative Example 4 No abnormality ○ ×

[0039]

As described above, according to the method for pre-treating stainless steel sheet with inorganic paint according to the present invention, not only beautiful inorganic paint free of coating film defects can be obtained, but also
Since extremely high primary adhesion and secondary adhesion can be imparted to the inorganic paint film, it is possible to easily produce an inorganic paint-coated stainless steel sheet excellent in long-term durability, which is the main object of the present invention. It is.

Continuation of the front page (56) References JP-A-49-123446 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 C23C 28/00 C23C 28 / 04

Claims (5)

(57) [Claims] In a pre-coating method carried out before applying an inorganic paint to the surface of a stainless steel sheet, the surface of the stainless steel sheet is treated with a chromate solution, washed with water, and the treated surface is treated with silica sol and the following organic silicon compound group. A method for pretreating a stainless steel sheet with an inorganic coating, comprising applying a liquid containing at least 0.01% by weight of one or more compounds selected from (A). (A) Organosilicon compound group: vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,
4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropylmethyldiethoxysilane, n-
β- (aminoethyl) γ-aminopropyltrimethoxysilane, n-β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, n-phenyl-γ-aminopropyltrimethoxysilane, gamma-chloropropyltrimethoxysilane. 2. The method according to claim 1, wherein the chromate solution contains chromic acid 0.4 to 0.4.
The method for pretreating a stainless steel sheet with inorganic paint according to claim 1, comprising 10 g / l, phosphoric acid 1.5 to 50 g / l, and hydrofluoric acid ion 0.05 to 5 g / l. 3. The method according to claim 1, wherein the chromate solution has a chromic acid concentration of 0.4 to 0.4
The method for pretreating a stainless steel sheet with inorganic paint according to claim 1, comprising 10 g / l, nitric acid 0.1 to 10 g / l, and hydrofluoric acid ion 0.05 to 5 g / l. 4. The chromate solution further comprises 0.1 to 10 sulfuric acid.
The method for pretreating a stainless steel sheet with an inorganic paint according to claim 2 or 3, which comprises g / liter. 5. The fluorine ion is supplied from one or more fluorine compounds selected from hydrofluoric acid, hydrosilicofluoric acid, hydrofluoric acid, titanium hydrofluoric acid and zircon hydrofluoric acid. The pretreatment method for coating stainless steel plates according to claim 2 or 3, wherein