CN1556873A - Precoated metal sheet having excellent press formability and manufacturing method thereof - Google Patents

Abstract

As a precoated metal sheet having excellent press formability and a production method thereof, there is provided a precoated metal sheet having excellent press formability, comprising a metal sheet having on one surface or both surfaces thereof a chemical conversion coating layer simultaneously containing, as solid contents, a silane coupling agent, fine particles of silica and at least either one of tannin and a tannic acid, and further having thereon a coating layer containing from 1 to 140 parts by mass of an aluminum phosphate-base pigment per 100 parts by mass of resin solid contents, and a production method thereof. It is preferred that the chemical conversion coating layer further contains a polyester resin and the coating layer further contains an antirust pigment. The aluminum phosphate-base pigment is optimally aluminum dihydrogen tripolyphosphate and the antirust pigment is optimally calcium ion-exchanging silica.

Description

Precoated metal sheet having excellent press formability and manufacturing method thereof

field of invention

The present invention relates to a surface-treated metal material having excellent press formability and corrosion resistance. The material is rust-resistant and exhibits coating adhesion when pressed, and in particular does not use hexavalent chromium, which is an environmental concern. The material can be used in household appliances, building materials, structural materials, machines, motor vehicles, furniture or containers.

Background technique

In order to replace conventional post-coated products obtained by coating resin after processing, which are used in household appliances, structural materials, and automobiles, pre-coated metals coated with colored coatings have been used. Such a precoated metal sheet can be obtained by forming a layer of the resin coating composition on a pretreated metal sheet. After applying the resin coating composition, the pre-coated metal sheet is cut and press-formed. Therefore, the cut end face portion of the precoated metal sheet has problems in corrosion resistance, the metal on this portion is exposed because it is not covered by the resin coating, and there is a problem of separation of the resin layer during press molding. However, these problems can be resolved when pre-treating the metal with chromates and using resin coatings containing hexavalent chromium-based anti-rust pigments. Such metal plates are currently available for general use.

However, hexavalent chromium, which can be leached from chromate films, and resin coatings containing hexavalent chromium-based antirust pigments have environmental problems. Therefore, there has been an increasing demand for chromate-free chemical conversion treatments and chromate-free resin coating materials that do not contain hexavalent chromium. Japanese Unexamined Patent Publication (Kokai) No. 2001-89868 discloses a method for providing a precoated metal sheet in which the processed portion of the metal sheet has excellent adhesion and high corrosion resistance, the Methods The chemical conversion treatment containing tannin, tannin acid, silane coupling agent and silica fine particles was used instead of chromate treatment. On the other hand, Japanese Unexamined Patent Publication No. 9-12931 discloses a method for providing a precoated metal sheet in which the cut end portion has excellent corrosion resistance, using a polyester-based And an epoxy-based coating composition, wherein the composition combines a phosphoric acid-based antirust pigment and an ion-exchanged silica-based antirust pigment instead of a hexavalent chromium-based antirust pigment.

The chemical conversion method disclosed in Japanese Unexamined Patent Publication No. 2001-89868 can ensure that the processed parts have excellent adhesion in the Erichsen test or the T-bend test, but it has a problem in that when press molding (such as deep When stretch forming), the coating is scratched by the die and peeled off easily compared to chromated pre-coated sheet metal. On the other hand, the method disclosed in Japanese Unexamined Patent Laid-Open Publication No. 9-12931 uses zinc phosphate for chemical conversion treatment, and has a problem in that the processed part The adhesion of the coating is not enough, and when press molding, the coating will be scratched by the mold and easily peeled off.

The object of the present invention is to solve those problems in the conventional methods, and to provide a precoated metal sheet having excellent corrosion resistance even without hexavalent chromium, which sheet is also excellent in press formability, and to provide method.

Summary of the invention

The present inventors have found that when a chemical conversion coating is formed containing both a silane coupling agent and silica fine particles and at least one of tannin and tannic acid, a resin containing an aluminum phosphate-based pigment is additionally formed thereon When coating, the obtained composite coating film can not only have excellent corrosion resistance, but also can have excellent press formability. The present invention was accomplished based on this finding. Main points of the present invention are as follows:

(1) A precoated metal sheet having excellent press-formability, comprising a metal sheet having a chemical conversion coating on one or both sides, the chemical conversion coating simultaneously containing a silane coupling agent, two Silica fine particles and at least one of tannin and tannin, and the chemical conversion coating is additionally coated with a resin coating comprising 1-140 parts by mass of aluminum phosphate-based pigment per 100 parts by mass of resin solid content.

(2) The precoated metal sheet having excellent press formability as described in (1) above, wherein the chemical conversion coating further contains a polyester resin as a solid component.

(3) The precoated metal sheet having excellent press formability as described in (1) or (2) above, wherein the aluminum phosphate-based pigment contained in the resin coating layer is aluminum dihydrogen tripolyphosphate.

(4) The precoated metal sheet having excellent press-formability as described in any one of (1) to (3) above, wherein the resin coating further contains an antirust pigment, and the antirust pigment and an aluminum phosphate-based The total content of the pigments is 140 parts by mass or less per 100 parts by mass of resin solid content.

(5) The precoated metal sheet having excellent press formability as described in (4) above, wherein the antirust pigment contained in the resin coating layer is calcium ion-exchanged silica.

(6) The precoated metal sheet having excellent press-formability as described in any one of (1) to (5) above, wherein the metal sheet is a metal sheet having a plating layer on one or both sides.

(7) A method of producing a precoated metal sheet having excellent press-formability, comprising treating a treatment liquid simultaneously containing a silane coupling agent, silica fine particles, and at least one of tannin and tannin Coating on one or both sides of the metal plate, drying the treatment liquid to form a chemical conversion coating, and coating the aluminum phosphate-based pigment containing 1-140 parts by mass per 100 parts by mass of resin solid content on the chemical conversion coating The resin coating composition, and drying and curing the coating material.

(8) The method of producing a precoated metal sheet excellent in press formability as described in (7) above, wherein the treatment liquid further contains a polyester resin.

(9) The method for producing a precoated metal sheet having excellent press formability as described in (7) or (8) above, wherein the coating composition further contains an antirust pigment, and the antirust pigment and an aluminum phosphate-based The total content of the pigments is 140 parts by mass or less per 100 parts by mass of resin solid content.

(10) A press-formed precoated metal article comprising a press-formed precoated metal sheet which is the metal sheet described in (1) to (9).

Brief description of the drawings

1 is a schematic cross-sectional view of a press-formed precoated metal sheet, wherein a chemical conversion coating 2, a resin coating 3 and an optional top coating 4 are formed on the surface of the metal sheet 1, the chemical conversion coating Layer 2 contains at least one of tannin and tannin, a silane coupling agent, and silica fine particles, and resin coating 3 contains an aluminum phosphate-based pigment. Coatings 2-4 can be formed on both sides of the metal plate.

Embodiments of the present invention

The present invention can be realized in the following manner: on one or both sides of a metal plate or a plated metal plate, a silane coupling agent, silicon dioxide fine particles, and at least one of tannin and tannic acid are formed as solid components. A chemical conversion coating, and additionally formed thereon a resin coating containing 1 to 140 parts by mass of an aluminum phosphate-based pigment. The aluminum phosphate based pigment is preferably aluminum dihydrogen tripolyphosphate, as this coating is more scratch resistant during press molding. Furthermore, the chemical conversion coating used in the precoated metal sheet of the present invention preferably also contains a polyester resin as a solid component, since this improves the adhesion of the coating and makes the coating more durable during press-forming. Scratch resistant.

The resin coating layer formed in the precoated metal sheet of the present invention preferably contains an antirust pigment in addition to the aluminum phosphate-based pigment, since this can improve the corrosion resistance of the precoated metal sheet. A suitable addition amount of these pigments is 140 parts by mass or less per 100 parts by mass of resin solid content based on the total content of the aluminum phosphate-based pigment and the antirust pigment. In addition, the antirust pigment is preferably calcium ion-exchanged silica, since this improves corrosion resistance.

It is preferable to apply a coating liquid containing a silane coupling agent, silica fine particles, and at least one of tannin and tannin at the same time, or such a coating liquid additionally containing a polyester resin, and dry the coated The coating liquid is used to form the chemical conversion coating in the precoated metal sheet of the present invention, whereby the precoated metal sheet of the present invention can be produced more efficiently. In addition, it is preferable to form the precoat of the present invention by applying a resin coating composition containing an aluminum phosphate-based pigment or a resin coating material containing both an aluminum phosphate-based pigment and an antirust pigment, and drying and curing the resin coating composition. Resin coating of clad metal sheets, whereby the precoated metal sheets of the present invention can be produced more efficiently.

As a result of conducting various studies on chromate-free precoated metal sheets in which the coating is hardly scratched by the die during press-forming, the present inventors have found that when formed on a metal sheet or a plated metal sheet When a chemical conversion coating containing tannin and/or tannin, a silane coupling agent, and silica fine particles is formed at the same time, and a coating containing an aluminum phosphate-based pigment is additionally formed thereon, it can significantly prevent the During the process, the coating peeling phenomenon occurs due to the scraping of the mold. The reason why the coating is scraped and peeled by the die during the press-forming process is considered to be that the die scrapes the coating of the pre-coated metal sheet under heavy load and the resulting shear force acts on the die. caused by the coating. Therefore, it is considered that the following two methods can solve this problem. The first method is to increase the bond strength between the coating and the metal. The second method is to make it difficult for the shear force acting on the coating to be transmitted to the peeled surface of the coating (the interface between the coating and the original metal plate). The reason why the coating of the precoated metal sheet of the present invention has mold scratch resistance during press-forming is not fully understood, but it is thought to contain tannins and/or tannins, silane coupling agents and silica The chemical conversion coating with fine particles and excellent adhesion properties is combined with the resin coating layer containing aluminum phosphate-based pigments, thereby significantly improving the adhesion of the coating due to the synergistic effect, and can prevent mechanical damage caused by the aluminum phosphate-based pigment itself. The shear force generated in the coating at the time of press-forming due to its nature is easily transmitted to the interface between the coating and the metal plate.

The metal sheet used in the precoated metal sheet of the present invention may be a generally known metal sheet or a coated metal sheet, such as cold-rolled steel sheet, hot-rolled steel sheet, hot-dip galvanized steel sheet, electro-galvanized steel sheet, molten alloyed coated Zinc steel plate, aluminum plated steel plate, aluminum-zinc alloy plated steel plate, aluminum-magnesium-zinc plated steel plate, aluminum-magnesium-silicon-zinc plated steel plate, stainless steel plate and aluminum plate. These metal plates may be subjected to conventional treatments such as hot water washing and degreasing with alkali prior to chemical conversion treatment.

The chemical conversion coating formed in the precoated metal sheet of the present invention is characterized in that it contains tannin and/or tannic acid, a silane coupling agent, and silica fine particles.

The tannins or tannins used may be hydrolyzable tannins, concentrated tannins or partial decomposition products thereof. Tannins and tannins are not particularly limited, and examples thereof include witch hazel tannins, Chinese gall tannins, galla tannins, myrobalan tannins, tannins, algarobillatannic , valonia tannic and catechol tannic. When "Tannin: AL" (manufactured by Fuji Kagaku Kogyo) is used, the bonding performance of the processed part of the coating can be particularly improved. The amount of at least one of tannin or tannic acid added is not particularly specified, but is preferably 2-80 g/L in the chemical conversion solution to be coated on the metal plate to form a coating. If the amount of at least one of tannin or tannin added is less than 2 g/l, the antirust effect or coating adhesion of the coating cannot be ensured, whereas if it exceeds 80 g/l, the Decrease the anti-rust effect or coating adhesion to a certain extent or the tannin or tannin cannot be dissolved in the aqueous solution.

Examples of usable silane coupling agents include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-( 2-Aminoethyl)aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropylmethyldiethoxysilane, γ-(2-aminoethyl)aminopropylmethyldi Methoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane , γ-methacryloxypropylmethyldiethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(N -vinylbenzylaminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltriethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl Methyldimethoxysilane, γ-Glycidoxypropyltriethoxysilane, γ-Glycidoxypropylmethyldiethoxysilane, γ-Mercaptopropyltrimethoxysilane, γ- Mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldiethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane , Methyltriethoxysilane, Dimethyldiethoxysilane, Vinyltriacetoxysilane, γ-Chloropropyltrimethoxysilane, γ-Chloropropylmethyldimethoxysilane, γ- Chloropropyltriethoxysilane, γ-chloropropylmethyldiethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, γ-anilinopropylmethyldimethoxy ylsilane, γ-anilinopropyltriethoxysilane, γ-anilinopropylmethyldiethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxy Silane, Vinylmethyldiethoxysilane, Octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, Octadecyldimethyl[3-(methyl Dimethoxysilyl)propyl]ammonium chloride, octadecyldimethyl[3-(triethoxysilyl)propyl]ammonium chloride, octadecyldimethyl[3 -(methyldiethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane , dimethyldichlorosilane and trimethylchlorosilane. In particular, when γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropyltriethoxysilane having a glycidyl ether group is used, the adhesion of the coating processing part can be improved performance. In addition, when a triethoxy-type silane coupling agent is used, the storage stability of the surface treatment agent can be improved. This is believed to be due to the relative stability of triethoxysilane in aqueous solution and the low rate of polymerization.

The amount of the silane coupling agent added is not particularly specified, but its content in the chemical conversion solution to be coated on the metal plate to form a chemical conversion coating is preferably 2-80 g/L. If the content of the silane coupling agent is less than 2 g/L, a coating with sufficiently high adhesion during processing cannot be obtained, and the corrosion resistance is insufficient, whereas if it exceeds 80 g/L, it will be damaged at a certain Reduce the adhesion of the coating to a certain extent.

The silica fine particles used in the present invention generally refer to silica having a minute particle size so that it can stably maintain a water-dispersed state when dispersed in water. Examples of usable silica fine particles include commercially available silica gels such as "Snowtex N", "Snowtex C", "Snowtex Up", "Snowtex pS (all manufactured by Nissan Chemicals Industries, Ltd.) and "Adelite AT- 20Q" (manufactured by Asahi Denka Kogyo K.K.), and powdered silica such as "Aerosil #300" (manufactured by Nippon Aerosil). Silica fine particles can be appropriately selected according to the required properties. When used even at pH=4 The storage stability of the surface treatment agent can be improved when using fine silica particles such as "Snowtex C" that can be stably dispersed when it is larger or larger. This is considered to be because the pH of the chemical solution can be adjusted to 4 or larger, Therefore, the reaction of the silane coupling agent, which has a high activity at low pH, can be suppressed.

The amount of silica fine particles to be added is also not particularly specified, but is preferably 1 to 40 g/liter in the chemical conversion solution to be coated on a metal plate to form a chemical conversion coating. If the content is less than 1 g/l, the processed portion of the coating is poor in adhesiveness, whereas if it exceeds 40 g/l, the adhesiveness and corrosion resistance of the processed portion become saturated, which is disadvantageous.

It is preferable that the chemical conversion coating also contains polyester resin as a solid component, because it can better improve the processing adhesion performance. There is no special regulation on the amount of polyester resin added, but when its content in the chemical conversion solution to be coated on the metal plate to form a chemical conversion coating is 1-60 g/liter, it can be greatly improved. Adhesive properties of processed parts. If the content is less than 1 g/L, the effect of adding polyester cannot be achieved; on the contrary, if it exceeds 60 g/L, the bonding performance of the coating processing part will be reduced to a certain extent. Examples of usable polyester resins include "FINETEXES-650", "FINETEX ES-611", "FINETEX ES-670", "FINETEXES-675" (all manufactured by Dai-Nippon Ink & Chemicals, Inc.), "VILONALMD- 1200", "VILONAL MD-1220", "VILONAL MD-1250", "VILONAL MD-1100", "VILONAL MD-1330" and "VILONAL MD-1930" (all manufactured by Toyobo Co., Ltd.).

In the chemical conversion solution to be coated when used to form the chemical conversion coating of the present invention, acid, alkali, etc. may be added to adjust the pH within a range that does not impair performance.

It is preferable to form a chemical conversion coating on a metal plate by applying the above-mentioned chemical conversion agent to the metal plate and firing or heating/drying the chemical conversion agent, because this can improve production efficiency. The firing temperature is preferably 50-250°C. If the roasting temperature is lower than 50°C, the evaporation rate of water is slow, and satisfactory film-forming properties cannot be obtained, resulting in insufficient rust resistance. The alkyl moiety of nitric acid or silane coupling agent will be denatured such as thermally decomposed, and will reduce the adhesion performance or corrosion resistance. The firing temperature is more preferably 70-160°C. In hot air drying, it is preferable to dry for 1-5 seconds because it can improve production efficiency.

The coating method of the chemical conversion solution is not particularly limited, and generally known methods such as roll coating, ring roll coating, air spray coating, airless spray coating, or dipping can be employed. It is preferable to apply the chemical conversion solution by an ordinary continuous coating line (referred to as a coil coating line or a plate coating line) fully equipped with these coating equipment, because it can be coated with good efficiency and large-scale production can be realized .

The solids content of the formed chemical conversion coating is preferably 10-500 mg/m ² . If the formed amount is less than 10 mg/m ² , sufficiently high bonding performance of the processed portion cannot be ensured, whereas if the amount exceeds 500 mg/m ² , the bonding performance of the processed portion may be impaired to some extent.

In the precoated metal sheet of the present invention, the resin used to form the coating on the chemical conversion coating may be in any form of aqueous type, solvent type, powder type, or the like. As for the type of resin, generally known resins such as polyacryl-based resins, polyolefin-based resins, polyurethane-based resins, epoxy-based resins, polyester-based resins, polybutyral resins, etc. can be used by themselves or in combination. based resins and melamine based resins.

The resin coating of the precoated metal sheet of the present invention must contain 1-140 parts by mass of aluminum phosphate-based pigment per 100 parts by mass of resin solid content. If the added amount of the aluminum phosphate-based pigment is less than 1 part by mass, the coating has no effect of resisting scratches during the press molding process, which is unfavorable. With the increase of the added amount of aluminum phosphate-based pigments, the effect of the coating against scratches during processing and molding can be advantageously improved, but if the added amount exceeds 140 parts by mass, the machinability of the pre-coated metal sheet is greatly reduced , which is inappropriate.

Examples of usable aluminum phosphate-based pigments include generally known pigments such as aluminum dihydrogen tripolyphosphate and aluminum metaphosphate. Among these pigments, aluminum dihydrogen tripolyphosphate is easily available and is preferred. Examples of usable aluminum dihydrogen tripolyphosphate include commercially available products such as "K-WHITE" manufactured by Tayca Corporation.

In the coating layer of the precoated metal sheet of the present invention, it is preferable to add an antirust pigment capable of exerting an antirust function in addition to the aluminum phosphate-based pigment, because this improves corrosion resistance. As the added amount of the antirust pigment increases, its effect can be advantageously improved, however, a suitable total content of the antirust pigment and the aluminum phosphate-based pigment is 140 parts by mass or less per 100 parts by mass of resin solid content. If the total added amount of the aluminum phosphate-based pigment and the rust-preventive pigment exceeds 140 parts by mass, problems arise, such as when the precoated metal sheet is bent, its processability is greatly reduced, which is not preferable.

The antirust pigment added to the resin coating of the precoated metal sheet of the present invention may be a generally known antirust pigment. Examples thereof include (1) phosphoric acid-based antirust pigments such as zinc phosphate and iron phosphate, (2) molybdic acid-based antirust pigments such as calcium molybdate, aluminum molybdate, and barium molybdate, (3) vanadium-based antirust pigments such as oxide Vanadium, (4) chromate-based antirust pigments such as strontium chromate, zinc chromate, calcium chromate, potassium chromate, and barium chromate, and (5) fine particle silica such as water-dispersible silica , fumed silica and calcium ion-exchanged silica. However, it is preferable not to use the chromate antirust pigment of (4) because of its environmental problems. Among the silica-based pigments in (5), calcium ion-exchanged silica is preferred because this silica is environmentally friendly and has a good antirust effect, which can be exerted when added as an antirust pigment. A higher anti-rust effect. Examples of calcium ion-exchanged silica that can be used include "Shieldex" manufactured by Grace. The added antirust pigment can be a composition of various pigments.

In the coating of the precoated metal sheet of the present invention, known pigments generally called "extender pigments" or coloring pigments for coloring can be used, and they can be combined with those aluminum phosphate-based pigments and antirust pigments use. The term "pigment extender" refers to pigments added to enhance various properties that a coating must have, such as coating brittleness or masking properties. Examples include talc to fill or matt the coating, titanium white (titanium oxide) to improve the hiding properties of the coating, and silica to matt the coating or improve its scratch properties. When the extender pigment is added, the various properties mentioned above can be advantageously improved. Examples of usable coloring pigments include commonly known coloring pigments including inorganic pigments such as titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), calcium carbonate (CaCO ₃ ), barium sulfate ( BaSO ₄ ), aluminum oxide (Al ₂ O ₃ ), kaolin, carbon black and iron oxides (Fe ₂ O ₃ , Fe ₃ O ₄ ), and organic pigments. It is preferable to use a plurality of extender pigments and coloring pigments having different effects in combination, because the respective effects can be exerted. When the extender pigment and the color pigment are added, the added amount of all the pigments, i.e. the sum of the aluminum phosphate-based pigment, the antirust pigment, the extender pigment and the color pigment, is suitably 140 parts by mass or less per 100 parts by mass of the resin solids of the coating composition Element. If all the pigments are added in an amount exceeding 140 parts by mass, problems arise such as greatly reduced workability of the precoated metal sheet when it is bent.

In the precoated metal sheet of the present invention, there is no special regulation to the thickness of the coating containing aluminum phosphate-based pigments, but the various properties of the coating can vary with the thickness of the layer, so it must be properly adjusted according to the situation. Choose layer thickness.

In the precoated metal sheet of the present invention, it is preferable to prepare a coating composition containing a pigment in advance (the amount thereof is the amount specified in the present invention based on the solid content of the resin), and apply, dry and cure the coating composition materials to form resin coatings containing aluminum phosphate-based pigments, thereby increasing production efficiency even more. The coating composition can be in the form of a solvent coating composition, an aqueous coating composition, a melt coating composition, a powder coating composition, an electrodeposition coating composition, an ultraviolet curable coating composition, and Use in any form of electron beam curable coating composition. It can be coated by generally known coating methods such as roll coating, curtain flow coating, roller curtain coating, die coating, air spray coating, airless spray coating, electric coating, etc. The coating composition is applied by deposition coating, powder coating, dipping, rod coating or brush coating. Preferably, the coating composition is applied by a conventional continuous coating line (known as a coil coating line or a panel coating line) equipped with roll coating, curtain coating flow coating or roll curtain coating equipment, because it can Coating is performed with good efficiency and mass production is possible. The coating composition may be dried, fired and cured by a generally inhibited dry curing method such as a hot air oven, a direct fired oven, a far infrared oven or an induction heating oven. When the coating composition is a UV curable coating composition, commonly known ultraviolet radiation equipment can be used, and when the coating composition is an electron beam curable coating composition, commonly known electron radiation equipment can be used. beam radiation equipment.

In the precoated metal sheet of the present invention, a top coat layer may be additionally provided on the resin coat layer containing an aluminum phosphate-based pigment. The coating appearance, color appearance, design appearance and other coating properties of the precoated metal sheet can advantageously be further enhanced by providing a top coat. The top coat layer may be formed by applying a generally known top coat composition and drying, firing, and curing the coating composition. Examples of commonly known top coating compositions include polyester-based top coating compositions, epoxy-based top coating compositions, polyurethane-based top coating compositions, acryl-based resins, and melamine-based top coating compositions. The top coating composition can be in the form of a solvent coating composition, an aqueous coating composition, a powder coating composition, an electrodeposition coating composition, an ultraviolet curable coating composition and an electron beam curable coating composition. Use in any form of layer composition. The topcoat composition may contain commonly known coloring pigments and extenders such as titanium oxide ( _TiO2 ), zinc oxide (ZnO), zirconium oxide ( _ZrO2 ), calcium carbonate ( _CaCO3 ), barium sulfate ( _BaSO4 ) , aluminum oxide (Al ₂ O ₃ ), kaolin, carbon black and iron oxides (Fe ₂ O ₃ , Fe ₃ O ₄ ), talc and silica. For the topcoat composition, generally known designer coating compositions can also be used, such as orange peel topcoat compositions, crepe topcoat compositions, hammer topcoat compositions, A matted tone top coating composition, a metallic top coating composition, a pearly top coating composition or a textured tone coating composition.

It can be applied by generally known coating methods such as roll coating, curtain coating flow coating, roll curtain coating, die coating, air spray coating, airless spray coating, electrodeposition coating, powder coating, dipping, Rod coating or brush coating is used to apply the topcoat composition. The top coat coating is preferably applied by a conventional continuous coating line (known as a coil coating line or a panel coating line) equipped with roll coater, curtain flow coater or roll curtain coater equipment, as this can Coating is performed with good efficiency and mass production is possible. The top coating composition may be dried, fired and cured by a generally known drying and curing method such as a hot air oven, a direct-fired oven, a far-infrared oven, or an induction heating oven. When the topcoat composition is a UV curable coating composition, commonly known UV radiation equipment can be used, and when the topcoat composition is an electron beam curable coating composition, commonly known UV radiation equipment can be used. electron beam radiation equipment.

Example

The materials utilized in the experiments will be described in detail below.

1. Metal plate

The following metal plates were used as materials tested in the experiments.

Hot-dip galvanized steel sheet (GI)

Plate thickness: 0.6 mm, application amount of zinc: 60 g/cm ² on each surface (both surfaces are plated).

Galvanized Steel Sheet (EG)

Plate thickness: 0.6 mm, application amount of zinc: 20 g/cm ² on each surface (both surfaces are plated).

55% aluminum-zinc alloy steel plate (GL)

Plate thickness: 0.6 mm, amount applied as zinc: 90 g/cm ² on each surface (both surfaces are plated).

Zinc-11% Aluminum-3% Magnesium-0.2% Silicon-coated steel sheet (SD)

Plate thickness: 0.6 mm, amount applied as zinc: 60 g/cm ² on each surface (both surfaces are plated).

Cold Rolled Steel Sheet (CR)

Plate thickness: 0.6mm.

2. Chemical conversion solution

The following solutions were prepared as chemical conversion solutions for the test materials in the experiments.

Chemical conversion solution (A)

An aqueous solution containing 20 g/L of tannic acid, 40 g/L of a silane coupling agent, and 20 g/L of silica fine particles was prepared and used as a pretreatment agent for metals. The tannin used was "Tannin: AL" manufactured by FujiKagaku Kogyo, the silane coupling agent was γ-glycidoxypropyltrimethoxysilane, and the silica fine particles were manufactured by Nissan Chemicals Industries, Ltd. "Snowtec-N".

Chemical conversion solution (B)

An aqueous solution containing 20 g/L of tannic acid, 40 g/L of a silane coupling agent, 20 g/L of silica fine particles, and 20 g/L of polyester was prepared and used as a pretreatment agent for metal. The tannin used was "Tannin: AL" manufactured by Fuji Kagaku Kogyo, the silane coupling agent was γ-glycidoxypropyltrimethoxysilane, and the silica fine particles were manufactured by Nissan Chemicals Industries, Ltd. "Snowtec-N", and the polyester resin is FINETEX ES-650 manufactured by Dai-Nippon Ink & Chemicals, Inc.".

Chemical conversion solution (C)

For comparison, a commercially available chromate treatment liquid "ZM-1300AN" manufactured by Nihon Parkerizing Co., Ltd. was used.

Chemical conversion solution (D)

For comparison, a commercially available zinc phosphate treatment liquid "PALBOND" manufactured by Nihon Parkerizing Co., Ltd. was used.

3. Coating compositions containing aluminum phosphate

To each of commercially available completely pigment-free polyester-based, polyurethane-based, and epoxy-based clear coating compositions, an aluminum phosphate-based pigment and, if desired, an anti-rust pigment were added and stirred to prepare a coating combination. The aluminum phosphate-based pigment used was "K-G105" manufactured by Tayca Corporation. The antirust pigments used were zinc phosphate-based antirust pigment "NP-530" manufactured by Toho Ganryo (indicated as "zinc phosphate" in the table), calcium ion-exchanged silica "Shieldex-C303" manufactured by Grace (indicated in the table is "Ca-Si") or commercially available strontium chromate (indicated as "Sr-Cr" in the table) as a chromium-based anti-rust pigment. Table 1 shows the respective addition amounts of these pigments. In addition, if necessary, an extender pigment can be used, and the pigment extender used is "Aerosil #300" manufactured by Nippon Aerosil (indicated as "silica" in the table) as a commercially available fine particle silica, or as white The pigment is titanium oxide "CR-95" manufactured by Ishihara Sangyo Kaisha Ltd. (indicated as "titanium white" in the table). Table 1 shows the respective addition amounts of these pigments.

4. Top coat composition

A commercially available polyester-based top coating composition "FL100HQ" manufactured by Nippon Paint Co., Ltd. was used. The color is white.

5. Back coating composition

A commercially available polyester-based top coating composition "FL100HQ" manufactured by Nippon Paint Co., Ltd. was used. The color is gray.

6. Manufacture of pre-coated metal sheets

Each metal plate was degreased by dipping in an aqueous FC-364S solution (manufactured by Nihon Parkerizing Co., Ltd.) having a concentration of 2% by mass and a temperature of 60° C. for 10 seconds, washed with water, and dried. The chemical conversion solution (A), (B), (C) or (D) is coated on both sides of each metal plate by a roll coater, and dried in a hot air drying oven to obtain a chemical conversion coating. Regarding the amount of the chemical conversion solution, when the chemical conversion solution is (A), (B) or (D), the amount of the chemical conversion solution of the entire dry film applied is 200 mg/m ² . The amount of the chemical conversion solution applied was 50 mg/m ² in terms of metallic chromium. In the samples using the chemical conversion solution (E), a chemical conversion coating was obtained by immersing a degreased metal plate in the chemical conversion solution (E) for 2 minutes, and drying in a hot air drying oven. The chemical conversion solution (E) was applied such that the applied amount of zinc phosphate was 2 mg/m ² . The final plate temperature during chemical conversion and drying was set at 60°C. After that, a resin coating solution containing an aluminum phosphate-based pigment was applied to a dry thickness of 5 micrometers on one side of the metal plate by a roll coater, and coated on the other side of the metal plate by a roll coater. The back resin coating composition reaches a dry thickness of 5 microns. These resin coating compositions were dried and cured in an induction heating furnace while blowing hot air into the furnace under the condition that the final plate temperature of the metal plate was 210°C to obtain a coating. The dried and cured coated metal panels were cooled with water by spraying the panels with water. Subsequently, a topcoat composition with a dry thickness of 15 microns was applied on the resin coating containing aluminum phosphate-based pigments by a roll coater, which was then dried and cured in an induction heating furnace while blowing into the furnace Hot air, provided that the final plate temperature of the metal plate is 230°C. The dried and cured coated metal panels were cooled with water by spraying the panels with water. Precoated metal panels were thus obtained as test material.

The following evaluation tests were performed on the precoated metal sheets thus obtained. In either test, the surface of the resin coating formed by the resin coating composition containing the aluminum phosphate-based pigment was used as the evaluation surface.

1. Test of the adhesion performance of the coating processing part

Each precoated metal plate was bent 180°, and the coating of the processed portion was observed through a magnifying glass of 20 times to detect the presence or absence of cracks in the coating. In the bend test, the bend should be such that the surface coated with the resinous coating composition comprising the aluminum phosphate-based pigment faces outward. In addition, a pressure-sensitive tape was fixed on the processed part, and it was peeled off forcefully, and the remaining state of the coating was visually inspected. In this test, two tape peels were performed. The bending operation was performed by OT bending (ECCA-27) in an atmosphere of 20°C.

In evaluating coating cracks, the case where the coating had no cracks at all was rated as ◎, the case where the coating had about 1-3 very small cracks was rated as ○, and the case where very small cracks appeared on the entire coating was rated as ◎ △, the case where large cracks clearly visible even by visual inspection occurred in the entire processed portion of the coating was rated as ×.

In evaluating the remaining state of the coating after tape peeling, the case where the coating was not peeled off and remained on the steel sheet was rated as ◎, the case where a part of the coating was slightly peeled off was rated as ○, and the case where a part of the coating was severely peeled off was rated as ◎ A case where the coating was observed to be peeled off almost throughout the processed portion was rated as x.

Each OT bent precoated metal panel was dipped in hot water for 1 hour, then removed, left for 24 hours, and tape stripped. In evaluating the remaining state of the coating, the case where the coating was not peeled off at all and remained on the plated steel sheet was rated as ◎, the case where a part of the coating was slightly peeled off was rated as ○, and the case where a part of the coating was severely peeled off The case where the coating was observed to be peeled off almost throughout the processed portion was rated as x.

2. The coating is scratched by the ball (bead) test

Carry out "Test Method of Coating Scratching by bead" (see Technical Disclosure Publication (Kokai-Giho) No. 95-1078), this test method is: in the process of pressing and forming of pre-coated metal sheets produced by scraping by the die The coating of the pre-coated metal sheet is repeatedly stripped. First, the prepared precoated metal sheet was cut into 30 mm (width)×300 mm (length) samples. The sample was sandwiched between a flat metal mold and a metal mold with 3mmR balls on it. At this time, the sample was clamped so that the balls of the metal mold were pressed against the aluminum phosphate-based pigment-containing resin-coated surface (evaluation surface) of the sample, and a load of 1 ton was applied so that the balls of the metal mold were partially pressed against the pre-pressed surface. Evaluation surface of coated metal sheet. In this state, the precoated metal sheet was pulled out at a speed of 200 mm/min, and the peeling state of the coating on the evaluation surface of the precoated metal sheet scratched by the ball was visually observed and evaluated.

In the evaluation, the case where the coating was not peeled off at all was rated as ◎, the case where the coating was peeled off in a very small part was rated as ○, and about 20% or more of the coating area in the part scratched by the ball was rated as ◎ The case of peeling was rated as Δ, and the case where the coating was completely peeled off was rated as x.

3. Test of corrosion resistance

On the surface of the prepared precoated metal sheet coated with the aluminum phosphate-based pigment coating composition, a cutting tool is used to cut the coating and pass through the coating to the metal sheet. Also, cut the edge portion of the board so that the burrs formed by the cutting reach the surface coated with the back resin coating (less burrs). Samples for the corrosion resistance test were thus prepared. The samples were then subjected to a salt spray test according to the method described in JIS K5400-9.1. Salt water was sprayed on the surface of the metal plate coated with the aluminum phosphate-based pigment coating composition. When the original blank of the pre-coated metal sheet is a cold-rolled steel sheet, the test time is 120 hours. When the comparison sample is an electro-galvanized steel sheet, the test time is 240 hours. For zinc alloyed steel sheets or zinc-11% aluminum-3% magnesium-0.2% silicon-coated steel sheets, the test time is 360 hours.

In the evaluation of the cut part of the coating, when the maximum blistering width on the cut side is less than 1 mm, it is rated as ◎, when the width is 2 mm - less than 3 mm, it is rated as ○, when the width is 3 mm - less than 5 mm was rated as Δ, and was rated as x when the width was 5 mm or more.

In the evaluation of the cut end face portion, it was rated as ◎ when the maximum blister width from the end face was 2 mm or less, and ○ when the width was 2 mm - less than 3 mm, and when the width was 3 mm - less than 5 mm was rated as Δ, and was rated as x when the width was 5 mm or more.

surface serial number Metal plate Metal Pretreatment Coating compositions containing aluminum phosphate-based pigments resin type Addition amount of aluminum phosphate-based pigment paint (parts per 100 parts by mass of resin solid content) Antirust Pigment Extender pigment type Amount added (parts by mass/100 parts by mass resin) type Amount added (parts by mass/100 parts by mass resin) The total amount of all pigments added (parts by mass/100 parts by mass resin) Embodiment of the invention 1 GI A Polyester 20 Ca-Si 50 not added - 80 2 GI B Polyester 1 not added - not added - 1 3 GI B Polyester 10 not added - not added - 10 4 GI B Polyester 20 not added - not added - 20 5 GI B Polyester 50 not added - not added - 50 6 GI B Polyester 100 not added - not added - 100 7 GI B Polyester 140 not added - not added - 140 8 GI B Polyester 20 Ca-Si 10 not added - 30 9 GI B Polyester 20 Ca-Si 20 not added - 40 10 GI B Polyester 20 Ca-Si 50 not added - 70 11 GI B Polyester 20 Ca-Si 100 not added - 120 12 GI B Polyester 20 Ca-Si 50 silica 10 80 13 GI B Polyester 20 Ca-Si 100 silica 40 160 14 GI B Polyester 20 Ca-Si 50 Titanium dioxide 10 80 15 GI B Polyester 20 Zinc phosphate 50 not added - 70 16 GI B Polyester 20 Sr-Cr 50 not added - 70 17 GI B Polyurethane 20 Ca-Si 50 not added - 70 18 GI B epoxy resin 20 Ca-Si 50 not added - 70 19 EG B Polyester 20 Ca-Si 50 not added - 70 20 GL B Polyester 20 Ca-Si 50 not added - 70 twenty one SD B Polyester 20 Ca-Si 50 not added - 70 twenty two CR B Polyester 20 Ca-Si 50 not added - 70 comparative example twenty three GI B Polyester not added not added - not added - 0 twenty four GI B Polyester 0.5 not added - not added - 0.5 25 GI B Polyester 150 not added - not added - 150 26 GI C Polyester 20 Ca-Si 50 not added - 70 27 GI C Polyester 20 Sr-Cr 50 not added - 70 28 GI D. Polyester 20 Ca-Si 50 not added - 70 29 GI E. Polyester 20 Ca-Si 50 not added - 70

Table (continued) serial number Evaluate test results Remark Processing adhesion performance test of coating Scratching of the coating by the ball Corrosion resistance test Crack Evaluation Stripping assessment cutting part End part Embodiment of the invention 1 ◎ ◎ ○ △ x - 2 ◎ ◎ △ x x - 3 ◎ ◎ ○ △ x - 4 ◎ ◎ ◎ △ x - 5 ◎ ◎ ◎ △ x - 6 ◎ ◎ ◎ △ x - 7 ○ ◎ ◎ △ x - 8 ◎ ◎ ◎ ○ △ - 9 ◎ ◎ ◎ ◎ ○ - 10 ◎ ◎ ◎ ◎ ◎ - 11 ◎ ◎ ◎ ◎ ◎ - 12 ◎ ◎ ◎ ◎ ◎ Improved scratch performance 13 △ ◎ ◎ ◎ ◎ Improved scratch performance 14 ◎ ◎ ◎ ◎ ◎ Whiteness has improved 15 ◎ ◎ ◎ ○ △ - 16 ◎ ◎ ◎ ◎ ◎ - 17 ◎ ◎ ◎ ◎ ◎ - 18 ◎ ◎ ◎ ◎ ◎ - 19 ◎ ◎ ◎ ◎ ◎ - 20 ◎ ◎ ◎ ◎ ◎ - twenty one ◎ ◎ ◎ ◎ ◎ - twenty two ◎ ◎ ◎ ◎ ◎ - comparative example twenty three ◎ ◎ x x x - twenty four ◎ ◎ x x x - 25 △ ◎ ◎ △ x - 26 ◎ ◎ ◎ ◎ ◎ - 27 ◎ ◎ ◎ ◎ ◎ - 28 ◎ ◎ x ◎ ◎ - 29 ○ ○ x △ △ -

The evaluation results are described in detail below.

The table gives the evaluation test results of the pre-coated metal panels. The precoated metal panels of the present invention (Examples 1-22) were scratch coated with balls compared to the metal panels treated with a conventional chromate-free chemical conversion treatment such as zinc phosphate (Comparative Example 28). The coating was less peeled off in the test, which shows that the performance of the precoated metal sheet of the present invention is excellent. In addition, compared with the case where no aluminum phosphate-based pigment coating (Comparative Example 23) is added to the resin coating on the chemical conversion coating or the addition of aluminum phosphate-based pigment coating is less than 1 mass part/100 mass parts resin solid content (Comparative Example 23) Compared with Example 24), the coating was less peeled off in the test of scratching the coating with a ball, which shows that the precoated metal sheet of the present invention has excellent performance. In the precoated metal sheet of the present invention, when the chemical conversion coating contains a polyester resin, the bonding performance of the coating processed part is improved, and the coating is difficult to peel off in the test of scratching the coating with a ball (Compare Example 1 and Example 10 of the present invention), therefore it is more preferred that the chemical conversion coating contains polyester resin. When (embodiment 8-22 of the present invention) when also adding antirust pigment except aluminum phosphate-based pigment paint in coating material, with the coating material (embodiment 2-7 of the present invention) that does not add antirust pigment ) compared to improved corrosion resistance, it is therefore preferred to additionally add antirust pigments to the coating composition. In particular, when the anti-rust pigment is calcium ion-exchanged silica (Example 1, 8-14 and 17-22 of the present invention), the corrosion resistance is greatly improved, and the corrosion resistance is the same as that of adding traditional chromate-based The performance of the antirust pigment (comparing Example 16 of the present invention with Comparative Example 26) is comparable, therefore, the antirust pigment is preferably calcium ion-exchanged silica.

Industrial applicability

According to the present invention, it is possible to obtain a precoated metal sheet which is excellent in adhesion and corrosion resistance of the processed part of the coating and is very suitable for press forming without using hexavalent chromium which is harmful to the environment. Therefore, the present invention has high industrial value.

Claims (10)

1. precoat metal plate with excellent compression moulding, it is included in the metal sheet that has chemical conversion coating on the one or both sides, this chemical conversion coating contains at least a in silane coupling agent, silicon-dioxide fine particle and tannin and the tannic acid as solids component simultaneously, and scribbling resin coating thereon in addition, this resin coating contains the resin solid composition of aluminophosphate-based pigment/100 mass parts of 1-140 mass parts.

2. the precoat metal plate with excellent compression moulding according to claim 1, wherein said chemical conversion coating also contains the vibrin as solids component.

3. the precoat metal plate with excellent compression moulding according to claim 1 and 2, the aluminophosphate-based pigment that contains in the wherein said resin coating is aluminium dihydrogen tripolyphosphate.

4. according to each described precoat metal plate in the claim 1 to 3 with excellent compression moulding, also contain rust-stabilising pigment in the wherein said resin coating, and the total content of described rust-stabilising pigment and aluminophosphate-based pigment is 140 mass parts or the resin solid composition of mass parts still less/100.

5. the precoat metal plate with excellent compression moulding according to claim 4, the rust-stabilising pigment that contains in the wherein said resin coating is a calcium ion-exchanged silicon-dioxide.

6. according to each described precoat metal plate with excellent compression moulding in the claim 1 to 5, wherein metal sheet is the metal sheet that one or both sides have coating.

7. a manufacturing has the method for the precoat metal plate of excellent compression moulding, it comprises with the one or both sides that contain at least a treatment solution metallic sheet in silane coupling agent, silicon-dioxide fine particle and tannin and the tannic acid simultaneously, dry this treatment solution is to form chemical conversion coating, on chemical conversion coating, apply the resin coating composition of the resin solid composition of aluminophosphate-based pigment/100 mass parts that contain the 1-140 mass parts in addition, and dry and this coated material of curing.

8. manufacturing according to claim 7 has the method for the precoat metal plate of excellent compression moulding, and wherein said treatment solution also contains vibrin.

9. has the method for the precoat metal plate of excellent compression moulding according to claim 7 or 8 described manufacturings, wherein said coating composition also contains rust-stabilising pigment, and the total content of described rust-stabilising pigment and aluminophosphate-based pigment is 140 mass parts or the resin solid composition of mass parts still less/100.

10. the precoating metal products of the compression moulding of a precoat metal plate that comprises compression moulding, described precoat metal plate is the metal sheet of describing in the claim 1 to 6.

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