JPH0454746B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a molten aluminum plated steel sheet that has improved corrosion resistance, roll-forming properties, etc. by forming a resin film with excellent corrosion resistance and adhesion directly or through a chromate film on the surface of a molten aluminum plated steel plate. Regarding plated steel sheets. (Prior art) In the past, hot-dip aluminum coated steel sheets were often used for applications that required heat resistance, but in recent years, they have been increasingly used in building materials due to their beautiful appearance with a silvery white luster and excellent corrosion resistance. I'm getting used to it. Conventionally, materials for non-heat resistant uses such as building materials have been treated with chromate treatments such as chromic acid or chromium phosphate to improve their corrosion resistance. Forming would destroy the chromate film and reduce corrosion resistance. In addition, since aluminum is soft, the aluminum of the plating layer adheres to the forming roll during roll forming (hereinafter referred to as "pickup") and the surface layer of the plating layer is peeled off, and the picked up aluminum builds up on the forming roll. This caused damage to the molded product. For this reason, a resin film is formed on the chromate film using an aqueous solution of a resin having water-soluble hydroxyl groups to prevent destruction of the chromate film, peeling of the surface layer of the plating layer, and build-up of the forming roll. It is. (Problems to be Solved by the Invention) However, although this method solves the problems caused by using only a chromate film, improvement in corrosion resistance must be achieved through a chromate film. There were limits to that improvement. Therefore, in order to further improve the corrosion resistance, it was necessary to improve the corrosion resistance of the resin film. An industrially inexpensive method to improve the corrosion resistance of a resin film is to include hexavalent chromium in the resin film, but in order to incorporate hexavalent chromium using this method, it is necessary to treat the resin film containing hexavalent chromium. Must be treated with liquid. However, if chromic anhydride or chromate is added to contain hexavalent chromium in the resin coating treatment solution, the hydroxyl groups of the resin molecules will be oxidized, and the treatment solution will become a gel, making it impossible to apply it to the steel plate. It is reduced to valent chromium and no longer exhibits corrosion resistance. For this reason, it has conventionally been difficult to incorporate hexavalent chromium into a resin film. (Means for Solving the Problems) The present invention provides an organically coated hot-dip aluminum plated steel sheet that makes it possible to incorporate hexavalent chromium into the resin film, which has been difficult in the past. The molten aluminum plated steel sheet of the present invention uses a water-dispersible copolymer that does not have hydroxyl groups as the resin for the resin coating, thereby preventing the resin from being oxidized in the treatment solution stage, and the acid value of the copolymer. The water resistance, adhesion, and physical properties of the film are improved by adding a silane coupling agent and/or a titanate coupling agent. That is, the present invention uses (A) the general formula CH ₂ = CR ₁ −COOR ₂ (wherein R ₁ is H, CH ₃ , R ₂
1 to 95% by weight of one or more monomers represented by (C is an alkyl group having 1 to 8); (B) 3 to 20% by weight of an α,β unsaturated carboxylic acid monomer; (C) A solid obtained by emulsion polymerization of these monomers and 0.1 to 50% by weight of a copolymerizable monomer [however, the total of (A), (B) and (C) is 100% by weight] Acid value per minute 10-200
Copolymer resin with silane coupling agent or/
and a titanate coupling agent are used. Here, the general formula that constitutes the copolymer resin is CH ₂ =
Examples of CR ₁ -COOR ₂ monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of α, β unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and examples of monomers that can be copolymerized with these monomers include styrene. ,α−
Examples include methylstyrene, vinyl acetate, vinyl chloride, and vinylidene chloride. The reason for using the above-mentioned copolymer resin in the present invention is that a film having the desired physical properties can be obtained and the industrial production of the copolymer resin is easy. The reason why the acid value of the copolymer resin is set to 10 to 200 per solid content is that if it is less than 10, the water resistance is good but the adhesion to the steel plate is poor, and if it exceeds 200, the water resistance is poor. This is because corrosion resistance decreases. When the acid value is set to 15 to 100, the film will have good water resistance and adhesion, so it is preferable to set it within that range. Even if one or both of the silane coupling agent and the titanate coupling agent are blended, it is preferable to blend them in an amount of 0.05 to 10 parts by weight per 100 parts by weight of the copolymer resin. There are various types of silane coupling agents, but as long as they are water-dispersible or water-soluble, monomer types [e.g. vinyltri(β-methoxyethoxy)silane, γ
-glycidoxypropyltrimethoxysilane],
Oligomer type (e.g. glycide type),
Either a resin-modified type (for example, an acrylic-modified or epoxy-modified type) or a cationic type can be used. Titanate coupling agents can also be used as long as they are water-dispersible or water-soluble. Preferred examples include tetra(2,2-diallyloxymethyl-1-butyl).
Examples include bis(di-tridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, and bis(dioctyl pyrophosphate) ethylene titanate. In the present invention, the resin film is formed as described above, and the film contains chromate as a source of hexavalent chromium, and further contains silica sol to improve the physical properties and corrosion resistance of the film. The chromate to be contained here is preferably water-soluble and inexpensive, such as ammonium chromate, magnesium chromate, potassium dichromate, calcium chromate, zinc chromate, manganese chromate, nickel chromate, and chromate. Cobalt acid, strontium chromate, etc. are suitable. The amount of chromate and silica sol contained in the resin film is preferably 0.1 to 50 parts by weight in the case of chromate and 0.5 to 100 parts by weight in the case of silica sol per 100 parts by weight of the copolymer resin. Further, the thickness of the resin film is preferably 1 to 5 μm in order to provide a uniform film. this is
This is because if the thickness is less than 1 μm, it is difficult to form a uniform film, resulting in a spotty film, poor corrosion resistance, and no effect of preventing aluminum from picking up during roll forming processing. A resin film with such a content and film thickness may be made of, for example, 200 to 400 g of copolymer resin, 0.1 to 40 g of silane coupling agent or/and titanate coupling agent.
It can be formed using a treatment liquid containing 0.2 to 200 g of chromate, and 1 to 400 g of silica sol. Since the resin film contains chromate, it exhibits corrosion resistance even if it is formed directly on a molten aluminum plated steel plate, but in order to exhibit even more corrosion resistance, it is necessary to form a chromate film on a molten aluminum plated steel plate. , form on it. In this case, the type of chromate film generally does not matter, such as reactive type or coating type, but the total amount of chromate film is 5 to 5%.
Preferably it is 200 mg/m ² . The hot-dip aluminum-plated steel sheets of the present invention are not limited to those plated in a bath of industrially pure aluminum, but also those plated in a bath containing industrially pure aluminum with silicon, zinc, etc. Includes 50% or more. Next, the present invention will be explained by examples. (Example) 50% by weight of methyl methacrylate, 40% by weight of butyl acrylate, 9.8% by weight of acrylic acid,
Acrylic emulsion obtained by emulsion polymerization with 0.2% by weight of styrene [resin content: 40% by weight, PH2.3,
viscosity 25 cps (25°C, B-type viscometer), acid value per solid content of about 78, hereinafter the copolymer resin in this emulsion will be referred to as X], 55% by weight of methyl acrylate, 40% by weight of butyl acrylate. , an acrylic emulsion obtained by emulsion polymerization of 4.7% by weight of acrylic acid and 0.3% by weight of vinyl chloride [resin content: 40% by weight]
% by weight, PH2.6, viscosity 150 cps (same as above), acid value per solid content of about 40, hereinafter the copolymer resin in this emulsion will be referred to as Y], a silane coupling agent or/and a titanate coupling agent, and chromium. After adjusting the resin coating treatment solution by adding various acid salts and silica sol (Snowtex-O, manufactured by Nissan Chemical), this treatment solution was applied directly to the surface or on molten aluminum plating with a thickness of 0.8 mm on which a chromate coating was formed. It was applied on a steel plate. The process of applying the treatment liquid and the conditions for forming the chromate film were as follows. (B) Coating process Steel plate → Degreasing → (Chromate treatment) → Applying resin film treatment solution → Drying (150℃, 10 seconds) (B) Chromate film formation conditions: CrO ₃ 20g/, Na ₂ SiF ₆ 1g/ After being immersed in the treatment solution at 60° C. for 5, 10, 15, and 20 seconds, roll squeezing was performed. On the other hand, as a comparative example, a treatment liquid containing both chromate and silica sol and a treatment liquid containing neither of them were prepared without containing a silane coupling agent and a titanate coupling agent in the same emulsion as above. It was applied on the same hot-dip aluminum plated steel plate in the same manner. These steel plates were then tested for roll forming workability and corrosion resistance in the following manner. (1) Roll forming processability test High-speed automatic duct forming machine (manufactured by Kojima Kogyo Co., Ltd.)
A test piece with a size of 100 x 300 mm was formed by cross-folding using a molding machine, and after forming, the state of the aluminum attached to the forming roll was observed with the naked eye and evaluated using the following criteria. ◎ Items with no aluminum attached ○ Items with a very small amount of aluminum attached △ Items with a large amount of aluminum attached × Items with a significant amount of aluminum attached (2) Corrosion resistance test Flat areas, cross-cut areas (reaching the plating layer on the resin film) (with a notch), end face,
Erichsen extrusion part (6mm extrusion) and
We prepared a test piece for a 180 degree bend (4 steel plates of the same thickness sandwiched inside and bent in a vise) and conducted a salt spray test for 500 hours in accordance with JISZ2371 to determine the occurrence of white rust. The condition was evaluated based on the following criteria. ◎ No white rust at all ○ Very little white rust △ Significant white rust × Significant white rust Table 1 shows resin film formation conditions and test results. However, the molten aluminum plated steel sheet of the present invention has excellent roll forming workability and corrosion resistance. In particular, in terms of corrosion resistance, even a steel plate in which a resin film is directly formed is superior to a conventional chromate film in which a resin film is formed alone.

【table】

[Table] (Effects) As explained above, since the resin of the coating resin film of the molten aluminum plated steel sheet of the present invention does not have hydroxyl groups, even if the treatment liquid contains chromate during manufacturing, The resin does not oxidize and does not gel. In addition, since the resin film contains chromate and silica sol, corrosion resistance is improved compared to a case where they are not contained, and since it also contains a silane coupling agent and/or a titanate coupling agent, The adhesion and physical properties of the resin film and the adhesion with the paint film when applied with paint are improved. Furthermore, since the molten aluminum plated steel sheet of the present invention is coated with a resin film, destruction of the chromate film, peeling of the surface layer of the plating layer, and picking up of aluminum by forming rolls during roll forming are prevented. . As a result, a molded product with a silver-white luster characteristic of molten aluminum-plated steel sheets can be obtained, and the quality and yield of the molded product are further improved.

Claims (1)

[Claims] 1. On the surface of a molten aluminum plated steel sheet, (A) general formula CH ₂ = CR ₁ -COOR ₂ (wherein R ₁ is H, CH ₃ and R ₂ are alkyl groups with 1 to 8 C). ) 1 of the monomers shown in
1-95% by weight of one or more species, (B) 3-20% by weight of an α,β-unsaturated carboxylic acid monomer, and (C) 0.1-95% of a monomer copolymerizable with these monomers. A silane coupling agent is added to a copolymer resin with an acid value of 10 to 200 per solid content obtained by emulsion polymerization of 50% by weight [however, the total of (A), (B) and (C) is 100% by weight]. An organically coated molten aluminum plated steel sheet, characterized in that it is coated with a resin film containing chromate and silica sol in the resin film blended with or/and a titanate coupling agent. 2 A chromate film is formed on the surface of the molten aluminum plated steel sheet, and on top of the chromate film (A) general formula CH ₂ = CR ₁ −COOR ₂ (wherein R ₁ is H, CH ₃ , R ₂ are C 1 to 95% by weight of one or more monomers represented by (1 to 8 alkyl groups)
, (B) 3 to 20% by weight of an α,β unsaturated carboxylic acid monomer, and (C) a monomer copolymerizable with these monomers.
A silane cup is added to a copolymer resin with an acid value of 10 to 200 per solid content obtained by emulsion polymerization of 0.1 to 50% by weight [however, the total of (A), (B) and (C) is 100% by weight]. An organic coated fused aluminum plating characterized in that a resin film containing a ring agent and/or a titanate coupling agent is formed and coated with a chromate and silica sol. steel plate.