JP5658536B2 - Painted aluminized steel sheet - Google Patents

Description

  The present invention relates to a coated aluminum-plated steel sheet excellent in heat resistance and non-adhesiveness.

  Painted steel sheet with a coating containing fluororesin is excellent in heat resistance, non-adhesiveness, stain resistance, etc., such as food cooking utensils such as frying pans and baking molds, microwave ovens and gas tables It is used for cooking utensils and sliding members. A coated steel sheet that is excellent in both heat resistance and non-adhesiveness is formed by forming a heat-resistant primer film on the surface of the steel sheet, and further forming a top film on which the fluororesin is unevenly distributed. Manufactured (for example, see Patent Documents 1 to 3).

  Patent Document 1 describes a method of manufacturing a coated steel sheet in which a fluororesin is unevenly distributed on the surface of a coating film by a short baking process. In this method, a paint for primer coating (hereinafter referred to as “primer paint”) is based on a heat-resistant resin having a hydroxyl group at both ends of a molecular chain (polyethersulfone resin, polyphenylsulfide resin or polyamideimide resin). You are using paint. A heat resistant resin having hydroxyl groups at both ends of the molecular chain undergoes dehydration condensation polymerization during baking. Therefore, even if the paint for the top coating (hereinafter referred to as “top paint”) is applied onto the primer coating after the primer coating is baked, the heat-resistant resin in the primer coating remains in the solvent contained in the top coating. It does not dissolve and the viscosity of the top paint does not increase. As a result, the fluororesin can be smoothly transferred to the surface of the coating film when baking the top paint, and a coated steel sheet having heat resistance and non-adhesiveness can be produced by a short baking process.

  Patent Document 2 describes a method of improving the adhesion of the fluororesin layer by making the interface shape between the fluororesin layer and the heat resistant resin layer in the top coating film wavy. In this method, the top coating is baked at a high temperature exceeding 400 ° C., whereby the interface shape between the fluororesin layer and the heat resistant resin layer is made wavy. Thus, by making the interface shape between the fluororesin layer and the heat resistant resin layer wavy, the contact area between the fluororesin layer and the heat resistant resin layer can be increased, and an anchor effect can be imparted to the fluororesin layer. it can. As a result, the adhesion of the fluororesin layer to the heat resistant resin layer is improved.

  Patent Document 3 describes a method for producing a coated steel sheet that is excellent not only in heat resistance and non-adhesiveness but also in corrosion resistance. In this method, a fluoroacid film is formed as a chemical conversion film on the surface of a hot-dip aluminized steel sheet (painted original sheet), and a primer coating and a top coating based on a heat resistant resin are formed thereon. Moreover, the primer coating film contains a phosphate-based anticorrosive pigment.

JP 2006-168251 A JP 2005-262465 A JP 2005-186287 A

  As described in Patent Document 2, peeling of the fluororesin layer can be suppressed by making the interface shape between the fluororesin layer and the heat resistant resin layer in the top coating wave (see FIG. 2A). ). In the method described in Patent Document 2, the interface shape is made wavy by baking the top coating at a high temperature exceeding 400 ° C. However, even if the top coating is baked at a high temperature exceeding 400 ° C., the interface shape is partially It became smooth and the fluororesin layer sometimes peeled off during processing (see FIG. 2B). Moreover, it was unpreferable from a viewpoint of energy saving to set it as high temperature exceeding 400 degreeC.

  This invention is made | formed in view of this point, and it aims at providing the coating aluminum plating steel plate which can suppress peeling of a fluororesin layer even if a top coating is baked by comparatively low temperature heating. .

  The present inventor examined the cause of peeling of the fluororesin layer, and found that by increasing the baking temperature of the primer coating, the interface shape was prevented from becoming smooth and the peeling of the fluororesin layer could be prevented. As a result of further detailed investigation based on this result, it was found that the fluororesin layer is easily peeled off when a rust preventive pigment containing crystal water is blended in the primer paint.

  And this inventor discovered that the said subject could be solved by using the compound which does not contain crystallization water as a rust preventive pigment mix | blended with a primer coating film, added further examination, and completed this invention. .

That is, this invention relates to the following heat-resistant non-adhesive coating steel plates.
[1] An aluminum-plated steel sheet; a primer coating film formed on the surface of the aluminum-plated steel sheet and containing a heat-resistant resin and an antirust pigment; and a heat-resistant resin and tetrafluoroethylene A coated aluminum-plated steel sheet comprising: a perfluoroalkyl vinyl ether copolymer, wherein the tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer is unevenly distributed on the surface side of the coating film; The heat-resistant resin contained in the primer coating and the heat-resistant resin contained in the top coating are a polyethersulfone resin, polyphenylsulfide resin, polyamideimide resin or a combination thereof having hydroxyl groups at both ends of the molecular chain. A dehydration condensate of Ribuden zinc, are calcium or zirconium phosphate, or a combination thereof molybdate; coated aluminum-plated steel sheet.
[2] The painted aluminized steel sheet according to [1], wherein the rust preventive pigment is zinc molybdate.
[3] The painted aluminum plated steel sheet according to [1] or [2], which is a precoated steel sheet for food cooking utensils or cooking utensils.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the coated aluminum plating steel plate which is excellent in heat resistance and non-adhesiveness, and a fluororesin layer cannot peel easily. Further, when zinc molybdate is blended as a rust preventive pigment, it is possible to provide a coated aluminum plated steel sheet that is further excellent in corrosion resistance. The coated aluminum-plated steel sheet of the present invention is useful as a pre-coated steel sheet for food cooking utensils or heat cooking utensils, for example.

1A is a photograph showing a cross section of a coated steel sheet of Reference Example 3. FIG. 1B is a photograph showing a cross section of the coated steel sheet of Comparative Example 1. FIG. FIG. 2A is a schematic cross-sectional view of a coated steel sheet having a wavy interface shape between the fluororesin layer and the heat-resistant resin layer. FIG. 2B is a schematic cross-sectional view of a coated steel plate having a smooth interface shape between the fluororesin layer and the heat resistant resin layer.

1. The coated aluminum-plated steel sheet of the present invention The coated aluminum-plated steel sheet of the present invention was formed on the surface of the aluminum-plated steel sheet (coated raw sheet), the primer coating film formed on the surface of the aluminum-plated steel sheet, and the primer coating film. And a top coating. One feature of the coated steel sheet of the present invention is that the rust preventive pigment blended in the primer coating is a compound containing no water of crystallization (zinc molybdate, calcium molybdate or zirconium phosphate).

[Painted original plate]
As the coating original plate, an aluminum plated steel plate having an aluminum plating layer formed on the steel plate surface, which is excellent in heat resistance and corrosion resistance, is used. The aluminum plating layer may contain Si, Zn, Mg, Ti, Ni, Cu, or the like as necessary.

  Moreover, in addition to heat resistance and corrosion resistance, when processed part corrosion resistance is also requested | required, as a steel plate used as a coating original plate, the molten Al-Si plating steel plate which annealed after forming the plating layer is preferable. In a portion subjected to bending processing such as 180-degree bending processing, defects such as cracks and peeling may occur in the plating layer, and the base steel may be exposed. If the base steel is exposed in this way, under severe corrosive environments such as the inside of a microwave oven having a steam function, red rust may occur in the part where the base steel is exposed, and the appearance may deteriorate. There is. Thus, when a process part corrosion resistance becomes a problem, what is necessary is just to use the hot-melted Al-Si plated steel plate which annealed after forming the plating layer. By further annealing after forming the molten Al-Si plating layer, the molten Al-Si plating layer can be softened. As a result, the molten Al—Si plating layer does not generate cracks or peels off even when combined with compression and tension, and can be deformed following the processing. Therefore, even if composite processing is performed, defects such as cracks and peeling that expose the underlying steel do not occur, and the processed portion corrosion resistance can be improved.

  In order to anneal the molten Al—Si plated layer, the molten Al—Si plated steel sheet on which the plated layer is formed may be held at 350 to 500 ° C. for 30 minutes or longer (see Japanese Patent Application Laid-Open No. 62-50454). At this time, the film thickness of the alloy layer formed at the interface between the plating layer and the base steel can be reduced by adjusting the cooling rate from when the molten Al-Si plating bath is pulled up to annealing. The workability of the Al—Si plating layer can be further improved. Specifically, a steel plate (steel strip) pulled up from a molten Al—Si plating bath (bath temperature of 640 ° C. or higher) is cooled to 400 ° C. at an average cooling rate of 10 ° C./second or higher, and then at 350 to 500 ° C. It is preferable to heat for more than a minute (refer Unexamined-Japanese-Patent No. 2000-256816).

The aluminum-plated steel sheet may be formed with a chemical conversion film that improves coating film adhesion. The type of chemical conversion treatment is not particularly limited. Examples of the chemical conversion treatment include phosphate treatment, chromate treatment, chromium-free treatment, and the like. The film thickness of the chemical conversion film is not particularly limited as long as it is within a range effective for suppressing corrosion of the coating original sheet and improving the adhesion of the coating film. For example, in the case of a chromate film, the film thickness may be adjusted so that the total Cr equivalent adhesion amount is 5 to 100 mg / m ² . In the case of a phosphate film, the film thickness may be adjusted so that the adhesion amount is 5 to 500 mg / m ² . In the case of a Ti—Mo composite film, the film thickness may be adjusted so that the adhesion amount is 10 to 500 mg / m ² .

The type of chemical conversion treatment is preferably chromium-free treatment from the viewpoint of environmental protection. Among the chromium-free treatments, treatment using an aqueous fluoroacid solution is preferable from the viewpoint of corrosion resistance and coating film adhesion. Examples of fluoroacids include H ₂ TiF ₆ , H ₂ ZrF ₆ , H ₂ HfF ₆ , H ₂ SiF ₆ , H ₂ GeF ₆ , F ₂ SnF ₆ , HBF _{4 and the} like. Among these, H ₂ TiF ₆ shows the most excellent rust prevention effect. These compounds may be used independently and may be used in combination of 2 or more type.

The fluoroacid aqueous solution has a strong etching property and can also activate the eutectic portion of Al—Si contained in the aluminum plating layer, which is difficult to activate with a general inorganic acid. In addition, the fluorine component reacts with Al in the aluminum plating layer to form hardly soluble AlF ₃ . The fluoroacid film formed by the reaction with the aluminum plating layer exhibits coating film adhesion comparable to the conventional chromate treatment. In addition, since the fluoroacid film is dense, it has an excellent environmental barrier ability.

The film thickness of the fluoroacid film is not particularly limited as long as it is within a range effective for inhibiting corrosion of the coating original plate and improving coating film adhesion. For example, the film thickness may be adjusted so that the element equivalent deposition amount of total metals (Ti, Zr, Hf, Si, Ge, Sn, B) or the element equivalent deposition amount of fluorine is 1 to 500 mg / m ² . When the adhesion amount is less than 1 mg / m ² , the corrosion resistance, the coating film adhesion and the heat resistance cannot be sufficiently exhibited. Moreover, when the adhesion amount exceeds 500 mg / m ² , the rust preventive effect corresponding to the blending amount cannot be obtained, and the processability and adhesion of the coating film are deteriorated.

[Primer coating]
The primer coating film is formed on the surface of the aluminized steel sheet. Here, the “surface of the aluminum-plated steel sheet” includes not only the surface of the aluminum-plated steel sheet but also the surface of the chemical conversion film. That is, the primer coating film may be formed on the chemical conversion film. The primer coating film contains a rust preventive pigment based on a heat resistant resin.

As the base heat-resistant resin, a dehydration condensate of a polyethersulfone resin, a polyphenylsulfide resin, a polyamideimide resin, or a combination thereof having a hydroxyl group at both ends of the molecular chain is used. A polyethersulfone resin having a hydroxyl group at both ends of the molecular chain is represented by, for example, formula (1). A polyphenyl sulfide resin having hydroxyl groups at both ends of the molecular chain is represented by, for example, the formula (2). A polyamideimide resin having a hydroxyl group at both ends of the molecular chain is represented by, for example, formula (3). What is necessary is just to adjust l-n in Formula (1)-(3), and to adjust to the below-mentioned resin molecular weight.

  Polyether sulfone resin, polyphenyl sulfide resin, and polyamide-imide resin are excellent in preventing blisters and rust starting from the cut end face of the coated steel sheet and coating film defects, and improve the corrosion resistance of the coated steel sheet. As described later, by using a dehydration condensate of a heat-resistant resin having hydroxyl groups at both ends of the molecular chain, it is possible to prevent the primer coating from dissolving in the solvent when forming the top coating, As a result, the shape of the interface between the fluororesin layer and the heat-resistant resin layer in the top layer can be changed to a desired shape.

  The molecular weight (number average molecular weight) of the heat resistant resin before baking is not particularly limited, but is preferably in the range of 5000 to 50000, and more preferably in the range of 15000 to 30000. When the molecular weight is too small, the cross-linking density between molecules by dehydration condensation polymerization becomes too high, the workability of the primer coating film is lowered, and the adhesion between the primer coating film and the top coating film is lowered. On the other hand, when the molecular weight is too large, the solubility in a solvent is lowered, making it difficult to form a coating material, and the softening point is increased to increase the baking temperature of the coating material.

As the anticorrosive pigment, zinc molybdate, calcium molybdate, zirconium phosphate or a combination thereof is used. As will be described later, since these compounds do not contain crystallization water, they are more preferable than rust preventive pigments (such as zinc magnesium phosphate) containing crystallization water from the viewpoint of suppressing peeling of the fluororesin layer. From the viewpoint of the antirust effect (suppression of red rust), zinc molybdate is preferable to calcium molybdate and zirconium phosphate. Zinc molybdate elutes molybdate ions (MoO ₄ ²⁻ ) stably in any of acidic, neutral and alkaline environments. This molybdate ion (MoO ₄ ²⁻ ) is a strong oxidant and reacts with Fe ²⁺ derived from the coating original plate to form insoluble molybdate (FeMoO ₃ ). This insoluble molybdate forms a barrier film on the surface of the iron base and suppresses the occurrence of red rust. On the other hand, since calcium molybdate and zirconium phosphate have low solubility, they cannot be expected to have the same rust prevention effect as zinc molybdate.

  The particle size (average particle size) of the rust preventive pigment is not particularly limited, but is preferably in the range of 0.1 to 10 μm. When the average particle size is less than 0.1 μm, the rust preventive pigment tends to aggregate in the paint, and it becomes difficult to uniformly disperse the rust preventive pigment. On the other hand, when the average particle size is more than 10 μm, the original properties of the primer coating film are impaired, the smoothness is lowered, and the coating film surface becomes cocoon skin-like and the appearance is remarkably deteriorated. The amount of the rust preventive pigment is preferably in the range of 5 to 150 parts by mass with respect to 100 parts by mass of the resin solid content in the primer coating. When the amount of the rust preventive pigment is less than 5 parts by mass, the corrosion resistance cannot be sufficiently exhibited. Moreover, when the amount of the rust preventive pigment is more than 150 parts by mass, a rust preventive effect corresponding to the blending amount cannot be obtained, and the workability and adhesion of the coating film are deteriorated.

  The primer coating film may be transparent, but may be colored by adding an arbitrary coloring pigment. Examples of the color pigment include titanium oxide, carbon black, chromium oxide, iron oxide and the like. Further, the primer coating film may be added with scaly inorganic additives, inorganic fibers, etc. to improve the coating film hardness and wear resistance. Examples of the scale-like inorganic additive include glass flake, barium sulfate flake, graphite flake, synthetic mica flake, synthetic alumina flake, silica flake and the like. Examples of the inorganic fiber include potassium titanate fiber, wollastonite fiber, silicon carbide fiber, alumina fiber, alumina silicate fiber, silica fiber, rock wool, slag wool, glass fiber, carbon fiber and the like.

  The thickness of the primer coating film is not particularly limited, but is preferably in the range of 0.5 to 30 μm. When the film thickness is less than 0.5 μm, the effects of corrosion resistance and coating film adhesion may not be sufficiently obtained. Moreover, when a primer coating film is a colored coating film, in order to conceal a coating original plate, the film thickness of 3 micrometers or more is preferable. On the other hand, when the film thickness is more than 30 μm, the surface of the coating film becomes a cocoon skin shape and the appearance is deteriorated, and a crack is easily generated when baking.

[Top coating film]
The top coating film is formed on the surface of the primer coating film. The top coating film contains a fluororesin based on a heat resistant resin. The fluororesin is unevenly distributed on the surface of the top coating film to form a fluororesin layer.

  The heat resistant resin is the same as the primer coating film, but it is not necessarily the same as the primer coating film. That is, the heat-resistant resin contained in the top coating is a primer coating as long as it is a dehydration condensate of a polyethersulfone resin, a polyphenylsulfide resin, a polyamideimide resin, or a combination thereof having hydroxyl groups at both ends of the molecular chain. The heat-resistant resin contained in the film may be the same or different.

  As the fluororesin, a heat-meltable fluororesin having a melting point of 270 ° C. or higher is preferable from the viewpoint of imparting heat resistance and non-adhesiveness. Examples of such fluororesins include polymers or copolymers such as tetrafluoroethylene, hexafluoroethylene, perfluoroalkyl vinyl ether, and chlorotrifluoroethylene. Among these, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer is particularly preferable from the viewpoint of non-adhesive durability and heat resistance.

  The amount of the fluororesin is preferably in the range of 10 to 200 parts by mass with respect to 100 parts by mass of the resin solid content in the top coating film. When the amount of the fluororesin is less than 10 parts by mass, non-adhesiveness cannot be exhibited sufficiently. On the other hand, when the amount of the fluororesin is more than 200 parts by mass, the adhesion of the top coating to the primer coating tends to decrease. From the viewpoint of achieving both non-adhesive durability and adhesion, the amount of the fluororesin is more preferably in the range of 50 to 150 parts by mass with respect to 100 parts by mass of the resin solid content in the top coating film, and 80 to A range of 120 parts by mass is particularly preferable.

  You may mix | blend a rust preventive pigment with a top coating film. In this case, it is preferable to blend a rust preventive pigment that does not contain crystal water as in the primer coating film. For example, as the anticorrosive pigment, zinc molybdate, calcium molybdate, zirconium phosphate or a combination thereof is used.

  The top coating film may be transparent, but may be colored by adding an arbitrary coloring pigment. Examples of the color pigment include titanium oxide, carbon black, chromium oxide, iron oxide and the like.

You may mix | blend a dark color type | system | group (black type | system | group) near-infrared reflective pigment with a top coating film as a coloring pigment. For example, when the coated aluminum-plated steel sheet of the present invention is applied to the interior material of the microwave oven, a dark color tone is often preferred as the interior material of the microwave oven from the viewpoint of design. However, when the top coating film of dark color is formed on the interior of the microwave oven, the infrared radiation radiated when the oven is heated is absorbed by the top coating film. This leads to an increase in power. Thus, when applying the coated aluminum-plated steel sheet of the present invention to the interior material of a microwave oven or the like, from the viewpoint of improving heating efficiency while maintaining a dark color tone, a wavelength region of 400 to 750 nm (visible light) ) And a dark (black) near-infrared reflective pigment having an average reflectance of 20% or more in the wavelength range of 750 to 2500 nm (near infrared) in the top coating film. It is preferable. Examples of dark (black) near-infrared reflective pigments include calcined pigments containing Fe ₂ O ₃ , Cr ₂ O ₃ , CoO or combinations thereof. The content of the dark color (black) near infrared reflective pigment is preferably in the range of 5 to 35 parts by mass with respect to the heat resistant resin. When the content is less than 5 parts by mass, a dark color tone cannot be imparted. On the other hand, when the content is more than 35 parts by mass, the cohesive force of the coating film is lowered, and the processability may be deteriorated.

  Moreover, a scale-like inorganic additive, an inorganic fiber, etc. may be added to a top coating film, and coating-film hardness and abrasion resistance may be improved. Examples of the scale-like inorganic additive include glass flake, barium sulfate flake, graphite flake, synthetic mica flake, synthetic alumina flake, silica flake and the like. Examples of the inorganic fiber include potassium titanate fiber, wollastonite fiber, silicon carbide fiber, alumina fiber, alumina silicate fiber, silica fiber, rock wool, slag wool, glass fiber, carbon fiber and the like.

  Although the film thickness of a top coating film is not specifically limited, The inside of the range of 5-40 micrometers is preferable. When the film thickness is less than 5 μm, non-adhesiveness cannot be sufficiently maintained. On the other hand, when the film thickness is more than 40 μm, the surface of the coating film becomes a cocoon skin shape and the appearance is deteriorated, and a crack is easily generated when baking. From the viewpoint of workability, the film thickness of the top coating film is preferably in the range of 5 to 20 μm.

  The fluororesin is unevenly distributed on the surface of the top coating film to form a fluororesin layer. On the other hand, the heat resistant resin forms a heat resistant resin layer under the fluororesin layer. The shape of the interface between the fluororesin layer and the heat resistant resin layer is preferably wavy (see FIG. 2A). More specifically, the maximum height difference at the interface between the fluororesin layer and the heat resistant resin layer is preferably 0.4 μm or more. By making the interface shape wavy, the contact area between the fluororesin layer and the heat-resistant resin layer can be increased, and an anchor effect can be imparted to the fluororesin layer. As a result, the adhesion of the fluororesin layer to the heat resistant resin layer can be improved, and the fluororesin layer is difficult to peel off. When the interface shape is smooth, the adhesion of the fluororesin layer to the heat-resistant resin layer is low, and the fluororesin layer is easy to peel (see FIG. 2B). As will be described later, in order to make the shape of the interface between the fluororesin layer and the heat-resistant resin layer more easily (even if the baking temperature of the top paint is low), the anti-corrosion pigment containing no crystallization water is prevented. What is necessary is just to mix | blend a rust pigment with a primer coating film.

  The coated aluminum-plated steel sheet of the present invention can exhibit heat resistance, non-adhesiveness, and contamination resistance over a long period of time because the fluororesin layer is difficult to peel off. In addition to the above properties, the coated aluminum plated steel sheet of the present invention containing zinc molybdate as a rust preventive pigment can also exhibit corrosion resistance over a long period of time.

  Although the manufacturing method of the coated aluminum plating steel plate of this invention is not specifically limited, For example, it can manufacture with the following method.

2. Manufacturing method of coated aluminum-plated steel sheet of the present invention The manufacturing method of coated steel sheet of the present invention includes 1) a first step of preparing an aluminum-plated steel sheet (painted original sheet), and 2) a second step of forming a primer coating film. And 3) a third step of forming a top coating film.

[Preparation of original coating]
In the first step, an aluminized steel sheet is prepared as a coating original sheet. As described above, in the case where processed part corrosion resistance is required in addition to heat resistance and corrosion resistance, a molten Al—Si plated steel sheet that is further annealed after forming a plating layer is preferable as the coating original sheet. The coated original plate is preferably degreased before coating to improve the coating film adhesion. The degreasing method is not particularly limited. For example, a weak alkaline or neutral degreasing solution may be applied by a roll coating method or a dip-up method. Moreover, you may improve the wettability of the plating layer surface by a pickling, a phosphate process, etc. as needed.

  Moreover, it is preferable that the coating original plate is subjected to a chemical conversion treatment in order to improve coating film adhesion before being coated. For example, the chemical conversion treatment may be performed at 80 to 200 ° C. without washing with water after applying a chemical conversion treatment liquid to the surface of the steel sheet by a roll coating method, a curtain flow method, a dip pulling up method, etc. As described above, the type of chemical conversion treatment is not particularly limited, but treatment using an aqueous fluoroacid solution is preferable. Further, the film thickness of the chemical conversion film is not particularly limited as long as it is within a range effective for suppressing corrosion of the coating original plate and improving coating film adhesion.

[Formation of primer coating]
In the second step, a primer coating film is formed on the surface of the aluminized steel sheet. As described above, “the surface of the hot-dip aluminized steel sheet” includes not only the surface of the aluminized steel sheet but also the surface of the chemical conversion film.

  In order to form the primer coating film, a primer paint containing a predetermined heat resistant resin and a rust preventive pigment is applied to the surface of the aluminum-plated steel sheet and baked. The method for applying the primer paint is not particularly limited, and may be appropriately selected from the methods used for the production of precoated steel sheets. Examples of such a coating method include a roll coating method, a flow coating method, a curtain flow method, a spray method, and the like.

  As the heat-resistant resin to be blended in the primer coating, a polyethersulfone resin, a polyphenylsulfide resin, a polyamideimide resin, or a combination thereof having hydroxyl groups at both ends of the molecular chain is used. Further, as the rust preventive pigment, zinc molybdate, calcium molybdate, zirconium phosphate or a combination thereof is used. Coloring pigments, scale-like inorganic additives, inorganic fibers, etc. may be added to the primer paint.

  As a solvent for the primer coating, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N, N-dimethylimidazolidinone (DMI), Aprotic polar solvents such as methyl isobutyl ketone (MIBK); ethers such as diethylene glycol dimethyl ether (DMDG) and diethylene glycol diethyl ether (DEDG); chlorides of aliphatic hydrocarbons such as methylene chloride and carbon tetrachloride are used. . These solvents may be used alone or in combination of two or more. Moreover, you may add solvents, such as hydrocarbons, such as xylene, halogenated hydrocarbon, alcohol, in the range which does not reduce the solubility of resin to these solvents.

  After applying the primer coating to the surface of the hot-dip aluminized steel sheet, the primer coating film can be formed by baking at 300 to 400 ° C. for 30 to 180 seconds. At this time, the heat-resistant resin is increased in molecular weight and cured by a dehydration condensation polymerization reaction between hydroxyl groups at both ends of the molecular chain of the heat-resistant resin. That is, the heat resistant resin contained in the primer coating is a thermosetting resin. The heat-resistant resin having a high molecular weight as described above does not dissolve in the solvent of the top paint and forms a stable primer coating film.

  When a rust preventive pigment containing crystallization water is added to the primer paint as in the conventional method, heat energy is consumed to remove the crystallization water in the rust preventive pigment, resulting in insufficient dehydration condensation polymerization reaction. was there. In addition, since water molecules exist around the heat-resistant resin molecules, the dehydration polycondensation reaction in which the water molecules are generated is difficult to proceed (Le Chatelier's law). As a result, the primer coating film may be insufficiently cured. These problems can be solved to some extent by raising the baking temperature of the primer paint, but are not preferable from the viewpoint of energy saving.

  On the other hand, in the production method of the present invention, a rust preventive pigment not containing crystallization water is blended in the primer paint, heat energy is not consumed for the removal of crystallization water, and water molecules are surrounded around the heat-resistant resin molecules. Therefore, the dehydration condensation polymerization reaction can be advanced efficiently. Therefore, the primer coating film can be sufficiently cured without increasing the baking temperature of the primer coating more than necessary.

[Formation of top coating]
In the third step, a top coating film is formed on the primer coating film. In order to form the top coating film, a top coating containing a predetermined heat resistant resin and fluororesin particles may be applied to the surface of the primer coating film and baked. The method for applying the top coating is not particularly limited, and may be the same as the method for applying the primer coating. Moreover, you may add a rust preventive pigment, a color pigment, a near-infrared reflective pigment, a scale-like inorganic additive, an inorganic fiber, etc. to a top coating material. When adding a rust preventive pigment to the top paint, a rust preventive pigment not containing crystallization water is added to the top paint in the same manner as the primer paint.

  As the heat resistant resin to be blended in the top coating, a polyethersulfone resin, a polyphenylsulfide resin, a polyamideimide resin or a combination thereof having hydroxyl groups at both ends of the molecular chain is used.

  As the fluororesin particles, particles containing a heat-meltable fluororesin having a melting point of 270 ° C. or higher are used. As described above, the heat-meltable fluororesin is preferably a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer. The particle diameter (average particle diameter) of the fluororesin particles is not particularly limited, but is preferably 1 μm or less, and particularly preferably 0.5 μm or less. The fluororesin particles having an average particle size of 1 μm or less are easily melted when baking the top paint, and form a fluororesin layer on the surface of the top coating film. The fluororesin particles can be produced by a suspension polymerization method or an emulsion polymerization method. For example, if an emulsion polymerization method is used, fluororesin particles having a small average particle size can be produced (for example, an average particle size of 0.05 to 1 μm).

  As the solvent for the top coating, as with the primer coating, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N, N- Aprotic polar solvents such as dimethylimidazolidinone (DMI) and methyl isobutyl ketone (MIBK); ethers such as diethylene glycol dimethyl ether (DMDG) and diethylene glycol diethyl ether (DEDG); aliphatic carbonization such as methylene chloride and carbon tetrachloride Hydrogen chloride or the like is used. These solvents may be used alone or in combination of two or more. Moreover, you may add solvents, such as hydrocarbons, such as xylene, halogenated hydrocarbon, alcohol, in the range which does not reduce the solubility of resin to these solvents. The solvent of the top paint may be the same as or different from the solvent of the primer paint.

  After the top coating is applied to the surface of the primer coating, baking is performed at 350 to 400 ° C. for 60 to 300 seconds, so that the heat resistant resin is made high molecular weight (cured) to form the top coating. At this time, the fluororesin particles in the top coating melt while moving in the direction of the coating film surface, and the heat resistant resin moves in the direction of the primer coating film. Therefore, a fluororesin layer is formed on the coating film surface, and a heat resistant resin layer is formed thereunder.

  The solvent for the top coating is also a good solvent for the heat resistant resin of the primer coating. Therefore, when the heat resistant resin of the primer coating is not sufficiently cured, when the top coating is applied onto the primer coating, the surface portion of the primer coating is dissolved in the top coating. If the surface part of the primer coating dissolves in the top paint in this way, the heat resistant resin in the top paint is highly compatible with the dissolved heat resistant resin, and therefore the primer coating is more likely to move to the primer coating. Promoted. On the other hand, since the fluororesin in the top paint has low compatibility with the dissolved heat-resistant resin, the transition toward the coating film surface is further promoted. Thus, when the transfer rate of a fluororesin is too high, since a fluororesin will transfer completely before a heat resistant resin hardens | cures, the interface of a fluororesin layer and a heat resistant resin layer will become smooth.

  On the other hand, in the production method of the present invention, since the heat resistant resin of the primer coating is sufficiently cured, even if the top coating is applied on the primer coating, the surface portion of the primer coating is dissolved in the top coating. do not do. When the primer coating is stable as described above, the transfer rate of the fluororesin in the top paint becomes an appropriate rate, and the interface between the fluororesin layer and the heat resistant resin layer becomes wavy.

  Moreover, in the manufacturing method of this invention, the rust preventive pigment which does not contain crystal water as a rust preventive pigment is mix | blended with primer paint and / or top paint. Thereby, heat energy is not consumed for the removal of crystallization water, and water molecules do not exist around the heat-resistant resin molecules, so that the dehydration condensation polymerization reaction of the heat-resistant resin can be efficiently advanced. Therefore, the top coating can be quickly cured without raising the baking temperature of the top coating to a high temperature exceeding 400 ° C. As a result, since the top coating film can be cured before the fluororesin completely shifts, the interface between the fluororesin layer and the heat resistant resin layer becomes wavy.

  According to the above procedure, even if the top coating is baked at a low temperature (400 ° C. or lower), a coated aluminum-plated steel sheet that is excellent in heat resistance and non-adhesiveness and hardly peels off the fluororesin layer can be produced.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

[Experiment 1]
1. Preparation of coated steel sheets Preparation of 12 sheets of molten Al-9Si plated steel sheets with a plate thickness of 0.5 mm and single-sided plating coverage of 40 g / m ² (Example 1 , Reference Examples 2, 3, Comparative Examples 1-9) did. After degreasing the surface of the coating original plate, a chromium-free chemical conversion treatment liquid having the composition shown in Table 1 is applied with a bar coater so that the amount in terms of fluorine is 20 mg / m ² and the total amount of metal is 17.5 mg / m ^2. did. The steel plate was heated at 100 ° C. to dry the chemical conversion treatment liquid.

Next, a primer coating was applied to the surface of the chemical-treated coating original plate and baked at 380 ° C. for 120 seconds to form a primer coating film having a dry film thickness of 5 μm. The primer paint is composed of a solvent (N-methyl-2-pyrrolidone (NMP) 25%, N, N-dimethylacetamide (DMAc) 35%, methyl isobutyl ketone (MIBK) 10%, xylene 30%), It was prepared by adding a rust pigment. Table 2 shows the compositions of the primer paints (Example 1 , Reference Examples 2 and 3, and Comparative Examples 1 to 9). Of the six types of anticorrosive pigments, zirconium phosphate, calcium molybdate and zinc molybdate do not contain crystal water. On the other hand, zinc magnesium phosphate, trihydrogen dihydrogen AlMg, and zinc phosphite all contain crystal water.

  The number average molecular weight of the polyethersulfone resin having hydroxyl groups (—OH groups) at both ends is 22000 to 24000, and the number average molecular weight of the polyethersulfone resin having chlorine groups (—Cl groups) at both ends is 17000. ~ 19000. The compounding quantity of the antirust pigment was 65 mass parts with respect to 100 mass parts of heat resistant resins.

Next, a top coating was applied on the primer film and baked at 400 ° C. for 120 seconds to form a top coating film having a dry film thickness of 10 μm. The top paint was prepared by adding a heat-resistant resin and a heat-meltable fluororesin to the same solvent as the primer paint. Table 3 shows the composition of the top coating (Example 1 , Reference Examples 2, 3, and Comparative Examples 1 to 9). In each example , reference example, and comparative example, the type and blending amount of the heat resistant resin are the same as those of the primer paint. The average particle diameter of the heat-meltable fluororesin particles (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) is 0.2 μm. The compounding amount of the heat-meltable fluororesin particles was 50 parts by mass with respect to 100 parts by mass of the heat-resistant resin.

2. Cross-sectional analysis For each coated steel sheet, the cross-section of the top coating film was observed with a microscope. 1A is a cross-sectional photograph of a coated steel sheet of Reference Example 3. FIG. 1B is a cross-sectional photograph of the coated steel sheet of Comparative Example 1. FIG. The interface between the fluororesin layer and the heat resistant resin layer was observed with a field of view of 500 times. As shown in FIG. 2A, when the maximum height difference at the interface between the fluororesin layer 100 and the heat-resistant resin layer 200 was 0.4 μm or more, it was determined that the shape of the interface was wavy. On the other hand, as shown in FIG. 2B, when the maximum height difference of the interface was less than 0.4 μm, it was determined that the shape of the interface was smooth.

3. Contamination resistance test A specimen was cut out from each coated steel sheet and a contamination resistance test was performed. On the surface of each test piece, 0.5 mL of a contaminated liquid (soy sauce: sugar: egg = 1: 1: 1 (mass ratio)) was dropped. Each test piece was placed in a heating furnace at 260 ° C. for 1 hour, sufficiently cooled, and then washed with a neutral detergent. After washing, it was confirmed whether or not the burning of the contaminants could be removed for each test piece. The above procedure was taken as one cycle, and the number of cycles until scorch could no longer be removed was counted.

4). Coating Film Adhesion Test A test piece was cut out from each coated steel sheet and a coating film adhesion test was performed. Each test piece was subjected to 180-degree contact folding. A pressure-sensitive adhesive tape was applied to the bent part of each test piece, and the tape was peeled off instantaneously. After tape peeling, it was observed whether the coating film (fluororesin layer) was peeled off.

5. Processed part corrosion resistance test The test piece was cut out from each coated steel plate, and the corrosion resistance test was implemented. After performing 180 degree | times adhesion bending process, the end surface of each test piece was sealed. Each test piece after processing was subjected to a wet test at 70 ° C. for 120 hours in accordance with JIS K2246. After the test, it was observed whether red rust was generated on the surface of each test piece.

6). Analysis result Table 4 is a table | surface which shows the analysis result of each coated steel plate. In the column of “coating state (swell)”, the case where the shape of the interface between the heat-resistant resin layer and the fluororesin layer is wavy is indicated by “◯”, and the case where it is flat is indicated by “X”. In the “contamination resistance” column, “◯” indicates that scoring can be removed even after 10 cycles, and “X” indicates that it cannot be burned. In the “fluorine peeling” column, “o” indicates that no peeling of the coating film (fluororesin layer) was detected, and “x” indicates that peeling was detected. In the column of “corrosion resistance (red rust)”, the case where no red rust was generated was indicated as “◯”, and the case where red rust was generated was indicated as “X”.

The coated steel sheets of Example 1 , Reference Examples 2 and 3, and Comparative Examples 1 to 3 in which a coating film based on a polyethersulfone resin (thermosetting resin) having hydroxyl groups at both ends of the molecular chain is formed are resistant to contamination. It was excellent in nature. This is because in these coated steel sheets, the fluororesin moved to the surface when the top paint was baked to form a fluororesin layer (see FIG. 1A). On the other hand, in the coated steel sheets of Comparative Examples 4 to 9 in which a coating film based on a polyethersulfone resin (thermoplastic resin) having chlorine groups at both ends of the molecular chain was formed, it was not possible to remove scoring within 10 cycles. . This is because with these coated steel sheets, when the top coating is applied, the primer coating re-dissolves in the top coating and the viscosity of the top coating increases, so the fluororesin cannot migrate to the surface when baking the top coating. This is probably because the fluororesin layer could not be formed.

Among the coated steel sheets (Example 1 , Reference Examples 2 and 3, Comparative Examples 1 to 3) on which the fluororesin layer was formed, the peeling of the fluororesin layer was observed in the coated steel sheets of Example 1 , Reference Examples 2 and 3. Was not. This is because the compound containing no water of crystallization was used as a rust preventive pigment, so that the shape of the interface between the fluororesin layer and the heat resistant resin layer could be made wavy even when the top coating was baked at 400 ° C. or lower. is there. On the other hand, in the coated steel sheets of Comparative Examples 1 to 3, peeling of the fluororesin layer was observed. This is because the shape of the interface between the heat resistant resin layer and the fluororesin layer has become smooth. The reason why the shape of the interface has become smooth is thought to be because the primer coating film could not be sufficiently cured because a compound containing water of crystallization was used as an anticorrosive pigment.

Further, among the coated steel sheets of Example 1 and Reference Examples 2 and 3 having excellent coating film adhesion, red rust did not occur at all in the coated steel sheet of Reference Example 3. This is considered to be because the molybdate ions derived from zinc molybdate formed a barrier film on the exposed portion of the iron base.

From the above results, it can be seen that the coated steel sheets of Example 1 and Reference Examples 2 and 3 are excellent in non- adhesiveness and stain resistance, and the fluororesin layer is hardly peeled off.

[Experiment 2]
In Experiment 2, by annealing the plated layer of paint original plate, indicating that the processing unit corrosion resistance of the coated steel plate can also be improved.

1. Preparation of Painted Steel Sheets The following two types of molten Al-9Si plated steel sheets were prepared as painted original sheets. The coating original plate A and the coating original plate B are different only in that an annealing treatment is performed after the plating layer is formed.
[Paint original plate A]
-Molten Al-9Si plated steel sheet (plate thickness 0.5 mm, single-sided plating adhesion 40 g / m ² )
・ No annealing after forming the plating layer [Paint original B]
-Molten Al-9Si plated steel sheet (plate thickness 0.5 mm, single-sided plating adhesion 40 g / m ² )
-After the plating layer is formed, there is an annealing treatment (heated at 420 ° C for 30 hours)

After degreasing the surface of the coating original plate (painting original plate A or coating original plate B), the above-mentioned chromium-free chemical conversion treatment liquid has a fluorine conversion adhesion amount of 20 mg / m ² and a total metal adhesion amount of 17.5 mg / m ^2. It was coated with a bar coater. The steel plate was heated at 100 ° C. to dry the chemical conversion treatment liquid.

  Next, a primer coating was applied to the surface of the chemical-treated coating original plate and baked at 380 ° C. for 120 seconds to form a primer coating film having a dry film thickness of 5 μm. The primer coating is prepared by adding a heat-resistant resin (polyethersulfone resin having hydroxyl groups (—OH groups) at both ends; number average molecular weight: 22000 to 24000) and a rust preventive pigment (zirconium phosphate) to the solvent described above. did. The compounding amount of the rust preventive pigment was 65 parts by mass with respect to 100 parts by mass of the polyethersulfone resin.

  Next, a top coating was applied on the primer film and baked at 400 ° C. for 120 seconds to form a top coating film having a dry film thickness of 10 μm. The top paint was prepared by adding the same heat-resistant resin and heat-melting fluororesin (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) as the primer paint to the same solvent as the primer paint. The blending amount of the polyethersulfone resin is the same as that of the primer paint. The compounding amount of the heat-meltable fluororesin particles was 50 parts by mass with respect to 100 parts by mass of the polyethersulfone resin.

2. Processed part corrosion resistance test A test piece was cut out from each coated steel sheet (Examples 4 and 5), and a processed part corrosion resistance test was performed. After performing 180 degree | times adhesion bending process, the end surface of each test piece was sealed. Each test piece after processing was subjected to a wet test at 70 ° C. for 120 hours in accordance with JIS K2246. After the test, it was observed whether red rust was generated on the surface of each test piece.

3. Analysis result Table 5 is a table | surface which shows the analysis result of each coated steel plate. In the column of “corrosion resistance (red rust)”, the case where no red rust was generated was indicated as “◯”, and the case where red rust was generated was indicated as “X”. In addition, the coated steel plate of Example 4 using the coating original plate A is the same as the coated steel plate of Example 1. Moreover, the coated steel plate of Example 4 (Example 1) and the coated steel plate of Example 5 differ only in the kind of coating original plate (whether the annealing process was performed after forming the plating layer).

  As shown in Table 5, in the coated steel sheet of Example 4 (Example 1) using the coating original sheet A in which the plating layer was not annealed, red rust was generated in the processed portion. This is presumably because cracks occurred in the plating layer or the like during processing, and the base steel was exposed. On the other hand, red rust did not occur at all in the coated steel sheet of Example 5 using the coating original sheet B having the plated layer annealed. This is considered to be because the plating layer was annealed and softened to suppress cracks in the plating layer during processing.

  From the above results, it can be seen that the coated steel sheet of the present invention can also improve the corrosion resistance of the processed part by using the coated original sheet with the plated layer annealed.

[Experiment 3]
In Experiment 3, by blending the near-infrared reflecting pigment in the top coating, indicating that the heat reflecting properties of the coated steel plate can also be improved.

1. Preparation of coated steel plate As a coating original plate, a molten Al-9Si plated steel plate having a thickness of 0.5 mm and a single-side plating coating amount of 40 g / m ² was prepared.

After degreasing the surface of the coating original plate, the above-mentioned chromium-free chemical conversion treatment solution was applied with a bar coater so that the fluorine conversion adhesion amount was 20 mg / m ² and the total metal adhesion amount was 17.5 mg / m ² . The steel plate was heated at 100 ° C. to dry the chemical conversion treatment liquid.

  Next, a primer coating was applied to the surface of the chemical-treated coating original plate and baked at 380 ° C. for 120 seconds to form a primer coating film having a dry film thickness of 5 μm. The primer coating is prepared by adding a heat-resistant resin (polyethersulfone resin having hydroxyl groups (—OH groups) at both ends; number average molecular weight: 22000 to 24000) and a rust preventive pigment (zirconium phosphate) to the solvent described above. did. The compounding amount of the rust preventive pigment was 65 parts by mass with respect to 100 parts by mass of the polyethersulfone resin.

  Next, a top coating was applied on the primer film and baked at 400 ° C. for 120 seconds to form a top coating film having a dry film thickness of 10 μm. The top paint is the same solvent as the primer paint, the same heat-resistant resin as the primer paint, heat-meltable fluororesin (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) and black pigment (iron / chromium near-infrared reflective pigment or Carbon black pigment) was added. The blending amount of the polyethersulfone resin is the same as that of the primer paint. The compounding amount of the heat-meltable fluororesin particles was 50 parts by mass with respect to 100 parts by mass of the polyethersulfone resin. The compounding amount of the black pigment was 20 parts by mass with respect to 100 parts by mass of the polyethersulfone resin.

  42-706A (Dongguan Material Technology Co., Ltd.) was used as the iron / chromium near-infrared reflective pigment. MA-100 (Mitsubishi Carbon Corporation) was used as the carbon black pigment.

2. Heat reflectivity test About each coated steel plate (Example 6, 7), the heat reflectivity test was implemented. A heating chamber (width 34 cm × depth 36 cm × height 23 cm) was prepared using the coated steel plate of Example 6 or Example 7 as a wall material, and a glass ceramic plate was installed in the heating chamber. The heating chamber was heated by infrared using a glass ceramic plate, and the temperature of the wall surface of the heating chamber was measured over time. Table 6 shows the measurement results of the ceiling surface temperature of the heating chamber.

  As shown in Table 6, in the coated steel sheet of Example 6 in which a general black pigment (carbon black) was blended in the top coating film, the wall surface temperature reached 100 ° C. after 3 minutes from the start of heating. After 5 minutes, the temperature rose to 134.2 ° C. This is considered because the black pigment absorbed near infrared rays. On the other hand, in the coated steel plate of Example 7 in which a black heat-reflecting pigment was blended in the top coating film, the wall surface temperature did not reach 80 ° C. even after 5 minutes and had excellent heat-reflecting properties. . Comparing the rate of temperature rise of the wall surface, the rate of temperature rise of the wall surface of the coated steel plate of Example 7 blended with the black heat reflecting pigment was the same as that of the coated steel plate of Example 6 blended with a general black pigment. About 50% of the rate of temperature increase.

  From the above results, it can be seen that the coated steel sheet of the present invention can also improve the heat reflection characteristics of the coated steel sheet by blending the top coating film with a heat reflecting pigment.

  The coated aluminized steel sheet of the present invention can maintain heat resistance, non-adhesiveness, and contamination resistance over a long period of time. Therefore, the coated aluminum-plated steel sheet of the present invention is useful as a pre-coated steel sheet used for food cooking utensils such as frying pans and baking molds, and heating cooking utensils such as microwave ovens and gas tables.

100 Fluorine resin layer 200 Heat resistant resin layer

Claims (2)

An aluminum-plated steel sheet;
Formed on the surface of the aluminum-plated steel sheet, and a primer coating film containing a heat-resistant resin and a rust preventive pigment;
Formed on the surface of the primer coating, comprising a heat resistant resin and a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, wherein the tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer is unevenly distributed on the surface of the coating A coated aluminized steel sheet having a top coating,
The heat resistant resin contained in the primer coating and the heat resistant resin contained in the top coating are a polyethersulfone resin, polyphenylsulfide resin or polyamideimide resin having hydroxyl groups at both ends of the molecular chain, or these A dehydration condensate in combination,
The anti-rust pigment is a re-phosphate zirconium-time,
Painted aluminized steel sheet.   The coated aluminized steel sheet according to claim 1, which is a precoated steel sheet for food cooking utensils or cooking utensils.