JP2011020006A - Rust preventive coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rust preventive coating method capable of forming a coating film excellent in a rust prevention effect and even more excellent in durability, on a metal surface using lead-free and chromium-free paint. <P>SOLUTION: The rust preventive coating method includes coating a metal surface 3 with paint composed of an epoxy resin containing a rust preventive agent free of lead and chromium to form an undercoat layer 1, and subsequently coating the surface of the undercoat layer 1 with rubber-based paint that yields a coating film exhibiting an elongation of at least 20% and water-vapor permeability of not higher than 400 g/m<SP>2</SP>×24 hr after drying, to form an undercoat protective layer 2. An undercoat protective layer 3 formed of highly elastic rubber-based paint exhibits capability of following the behavior of the metal surface part and prevents the exposure of cracks and scars appearing on the undercoat layer 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rust-proof coating method, and in particular, relates to a rust-proof coating method for forming a coating film excellent in rust prevention effect and excellent in durability on a metal surface.

  In the coating of metal surfaces for the purpose of rust prevention, an epoxy resin paint containing tar is applied to the metal surface as a rust prevention paint, and from the viewpoint of protection of the rust prevention paint and improvement of design, urethane resin paint is used. By applying it as a surface protective layer on the surface of the rust preventive paint, at least two layers of coating films are formed to exhibit rust prevention performance. In coating with an epoxy resin or urethane resin paint as described above, a high-hardness coating film is formed to increase the impact resistance of the coating film itself (see Patent Document 1).

  However, epoxy resin paints containing tar become hard in winter, unable to follow the movement of the underlying metal, and the paint film is cut off. Becomes worse. In addition, the epoxy resin for the underlayer and the urethane resin for the surface protective layer have high hardness and are resistant to mechanical impacts, but on the other hand, behavior such as expansion / contraction of the metal surface part due to temperature change or external force, bending deformation, etc. However, the coating film tends to have minute cracks and scratches. And by the penetration | invasion of the water | moisture content from a crack and a crack, generation | occurrence | production and proliferation of rust progress on a metal surface, and the float and peeling of a coating film are caused.

  In addition, anti-corrosion paints containing lead and chromium such as lead tan, lead suboxide and basic lead chromate are mainly used as anti-corrosion pigments, but there are restrictions on harmful heavy metals such as lead and chromium. As a result, there is a need for coating with lead / chromium-free rust-proof paint that does not affect people and the environment.

JP-A-10-157004

  The present invention has been made in view of the above circumstances, and the purpose thereof is to use a lead / chromium-free paint, and to form a coating film having excellent rust prevention effect and further excellent durability on a metal surface. It is to provide a rust-proof coating method.

  As a result of intensive studies, the inventor has a water vapor barrier property and a behavior of the metal surface portion with respect to an underlayer formed by an epoxy resin containing a lead / chromium-free anticorrosive agent that mainly exhibits an antirust effect. By applying a highly elastic rubber-based paint that exhibits followability to the surface of the base layer to form a base protective layer, moisture intrusion from the surface layer is suppressed, and cracks and scratches that occur in the base layer are exposed. The wisdom is that it can be prevented by the base protective layer, and the occurrence of cracks etc. in the base protective layer itself can be reduced, so that even if the base protective layer is damaged, the penetration of moisture into the metal surface side can be suppressed. The present invention has been completed.

That is, the rust preventive coating method of the present invention is a rust preventive paint method for forming a rust preventive coating on a metal surface, and a coating made of an epoxy resin containing a lead / chromium free rust preventive agent is applied to the metal surface. After forming the base layer, a rubber-based paint having an elongation rate of 20% or more and a water vapor transmission rate of 400 g / m ² · 24 hr or less is applied to the surface of the base layer after drying. It is characterized by forming.

  According to the present invention, since a paint containing lead / chromium-free rust preventive agent is used, there is no influence on people and the environment, and the coating film formed on the metal surface has a high water vapor barrier property. A base protective layer made of an elastic rubber-based paint suppresses the ingress of moisture from the surface layer and follows expansion, contraction, and deformation of the metal surface. Therefore, the penetration of moisture into the underlayer can be suppressed. Therefore, according to the present invention, it is possible to form a coating film having excellent rust prevention effect and further excellent durability on the metal surface by the lead / chromium-free paint.

It is the longitudinal cross-sectional view which showed typically the layer structure and function of the coating film formed by the antirust coating method of this invention.

  An embodiment of a rust preventive coating method according to the present invention (hereinafter abbreviated as “coating method”) will be described. The coating method of the present invention is a method of forming a rust-preventive coating on a metal surface, and not only a metal surface that is not coated with paint or various plating, but also rust-prevention coating or plating of zinc, tin, aluminum, etc. It is also applied to a metal surface that is rusted as a change with time and is raised. However, when the metal surface is coated with rust-proof and the coating film is cracked or cracked due to rust generation / proliferation, the active film is utilized to remove the deteriorated coating film, The present invention is applied after removing the rust of the rusted portion with a nonwoven fabric abrasive, paper sand, disk sander, wire brush, etc. to reveal the metal surface. Further, even when various plating is performed and rust is generated, the present invention is applied after the rust of the rust portion is similarly removed to reveal the metal surface. In the following description, the portion of the gold surface to be painted is referred to as “base material” as appropriate.

  In the present invention, as shown in FIG. 1 (a), first, a base layer 1 is formed by applying a coating material made of an epoxy resin containing a lead / chromium-free rust inhibitor to the base material 3. The above lead / chromium-free rust preventives include sacrificial anodizing substances such as zinc phosphate, zinc potassium phosphite, zinc aluminum phosphite, zinc calcium phosphite, and various chelating substances capable of fixing rust. And rust converting substances such as tannic acid that convert red rust to black rust, and scaly substances such as mica and iron oxide. The epoxy resin paint is preferably a cross-linked epoxy resin paint from the viewpoint of a water vapor barrier, a chlorine ion barrier, and an oxygen barrier.

  The epoxy resin coating is applied by a normal application method using a brush, roller, reiki, spraying machine, etc., and the thickness of the underlying layer 1 formed thereby depends on the type of the resin, but is usually 10 to 10. It is about 300 μm. When the thickness of the underlayer 1 is less than 10 μm, the rust prevention effect decreases, and when it is thicker than 300 μm, the number of times of coating increases, which is not realistic, and when thickly applied at once, sink marks and cracks enter the surface, It is not preferable.

After the epoxy resin coating is applied, a rubber coating having an elongation rate of 20% or more and a water vapor transmission rate of 400 g / m ² · 24 hr or less is applied to the surface of the base layer 1 after drying. Then, the base protective layer 2 is formed. Examples of the rubber-based paint having the above characteristics include paints made of urethane rubber or paints made of acrylic rubber. As the acrylic rubber paint, for example, “MY Rufer HG / nt” (trade name) manufactured by Mitsubishi Plastics, which contains an acrylic emulsion as a main component and is blended with a crosslinking agent, an antifoaming agent, a filler, and the like is preferable. The urethane rubber paint is preferably a urethane coating waterproof material comprising a main agent and a curing agent.

  In the present invention, it is important to select a rubber-based paint such that the elongation percentage of the coating film constituting the base protective layer 2 is 20% or more. In other words, in the present invention, the base protective layer 2 is formed by an elastic coating film.

  The reason for prescribing the elongation percentage of the coating film to the above value is as follows. That is, when the elongation percentage of the coating film is less than 20%, when a large number of cracks occur in the underlayer 1, the total deformation amount of the underlayer 1 exceeds the range of elastic deformation of the undercoat protective layer 2, and the undercoat protective layer Cracks are likely to occur in 2 itself. Although there is no restriction | limiting in particular about the upper limit of the elongation rate of a coating film, since a softness | flexibility will become high and the function as a protective film will be impaired when elongation rate becomes large too much, it is about 22 to 800% practically. The elongation rate of the coating film is measured by a method in accordance with JIS A6021 (dumbbell shape No. 3, 20 mm between marked lines, 60 mm between grips, tensile speed: 200 mm / min for acrylic rubber and 500 mm / min for urethane rubber). it can.

In the coating film as the base protective layer 2 formed of the rubber-based paint, the water vapor permeability is preferably 400 g / m ² · 24 hr or less from the viewpoint of enhancing the rust prevention effect as the characteristic of the coating film alone. By providing the base protective layer on the base layer 1 described above, it is possible to greatly reduce moisture intrusion from the surface layer, and the rust prevention effect is greatly improved.

Further, from the viewpoint of enhancing the durability and the rust-preventing effect, the adhesive force (40 × 40 mm) with the coating film forming the above-described base layer 1 is preferably 0.10 N / mm ² or more. The rubber-based paint is applied by an application method using a brush, a roller, a reiki, a spraying machine, or the like. And although it depends on the kind of resin, the thickness of the base protective layer 2 is usually 20 to 4000 μm. If it is thinner than 20 μm, the rust prevention effect will be reduced, and if it is thicker than 4000 μm, the number of times of coating will increase, which is not realistic. It is not preferable because it may cause cracks, sink marks, and cracks.

  The water vapor permeability can be measured by JIS K7129 (cup method, 40 ° C./90% RH). The adhesive strength of the coating film was determined by attaching a 40 x 40 mm jig to the surface of the base protective layer 2 with a two-component epoxy adhesive, and after drying, Kenken adhesive strength tester (Sanko Techno Techno Tester R-30000ND) ) Can be measured.

  In the present invention, by providing the base protective layer 2 as described above, the base protective layer 3 exhibits followability to the behavior of the base material 3 such as vibration, expansion / contraction, deflection, etc. Even if cracks or scratches are generated, the underlying protective layer 2 can prevent the cracks and scratches from being exposed, and oxygen and moisture can be prevented from entering the base material 3 from the cracks and scratches.

  Furthermore, although not shown in the drawings, in the present invention, in order to further improve the rust prevention, improve the impact resistance, and improve the contamination resistance, rain dripping resistance, algae proofing, fungicidal properties, heat shielding properties, etc. From the resin selected from urethane urea resin, polyurethane resin, epoxy resin, chlorinated rubber resin, alkyd resin, phthalic acid resin, fluororesin, phenol resin, acrylic resin and acrylic silicon resin with respect to the surface of the base protective layer 2 The surface protective layer may be formed by applying a coating material. Usually, an acrylic resin or urethane resin paint is used as the paint for forming the surface protective layer. As the acrylic resin paint, a common acrylic resin paint, acrylic-styrene, acrylic-urethane, silicone-modified acrylic resin and the like used for the top coat layer of the conventional coating film can be used. In addition, as the urethane resin paint for forming the surface protective layer, a water-soluble paint, a terpene-soluble weak solvent type or a strong solvent type petroleum solvent paint of an aromatic solvent may be used. From the viewpoint of rust prevention, a weak solvent type or a strong solvent type petroleum solvent paint is preferred. Furthermore, among these, the self-crosslinking type is preferable.

  As described above, in the coating by the coating method of the present invention, two layers of the anticorrosive coating film of the base layer 1 and the base protective layer 2 on the metal surface (base material 3), preferably the base layer 1, the base protective layer 2 and A three-layer rust preventive coating film is formed as a surface protective layer. At that time, the base protective layer 2 made of a highly elastic rubber-based paint is deformed following the expansion and contraction or deformation of the base material 3 to prevent exposure of cracks and the like generated in the base layer 1, and the base protective layer. Since the occurrence of cracks and scratches in 2 itself is small, the penetration of moisture into the base material 3 side is suppressed. As a result, it is possible to prevent rust generation, diffusion and floating of the underlayer 1 over a long period of time. That is, according to this invention, the coating film excellent in the antirust effect and much more excellent in durability can be formed on a metal surface.

  In particular, in the present invention, by forming the base protective layer 2 with the above-mentioned specific rubber-based paint, an excellent rust prevention effect can be maintained even when cracks or the like occur in the base protective layer 3 itself. . This is because, as shown in FIGS. 1B to 1C, even if a crack or a flaw occurs in the base protective layer 2 itself, the crack or the like is blocked by the swelling property of the base protective layer 2 with respect to moisture. It is considered that moisture permeation into the underlayer 1 can be prevented by the property that moisture is captured by the binding property to moisture. The arrow in FIG.1 (b) has shown the water of the coating-film surface.

  A rust-proof coating film was formed on the sample steel plate (coating object), and the rust-proof performance of the coating film was confirmed by the difference in the combination of the coating materials. As a sample steel plate, a steel plate in which rust was generated was prepared, and as a base treatment, keren (about three types of keren) was applied to the surface with a # 60 paper file. The antirust performance was confirmed by a salt water combined cycle test. In the salt water combined cycle test, the sample was sprayed with salt water with a water temperature of 50 ° C. and a concentration of 3% for 4 days, and then dried in an environment of a temperature of 50 ° C. and a humidity of 30% for 3 days (7 days is one cycle). The occurrence of this was visually confirmed, and the same test was carried out three cycles for each sample. In addition, the elongation percentage of the coating film is measured by a method in accordance with the above-mentioned JIS A6021, and the adhesion force of the coating film is obtained by attaching a 40 × 40 mm jig to the surface of the base protective layer 2 with a two-component epoxy adhesive. After attaching and drying, it was measured with a Kenken-type adhesive strength tester (manufactured by Sanko Techno, trade name: Techno Tester R-30000ND).

Example 1:
First, as a base layer, an epoxy resin paint (manufactured by Mitsubishi Plastics Co., Ltd., trade name: “MY Rufer Antirust Primer K”) was applied to a sample and dried to form a coating film having a thickness of 55 μm. The epoxy resin contains 5% by weight of zinc phosphate and a rust converting substance as a lead / chromium-free rust inhibitor. Next, an acrylic rubber paint (Mitsubishi Resin Co., Ltd., trade name: “MY Rufer HG / nt”) is applied to the surface of the base layer as a base protective layer and dried to form a coating film having a thickness of 180 μm. did. The elongation percentage of the coating film of the undercoat protective layer was 80%, the water vapor permeability was 90 g / m ² · 24 hr, and the adhesive strength with the undercoat layer was 0.60 N / mm ² . And about the sample which gave said coating, when the generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, generation | occurrence | production of rust was not confirmed at all.

Example 2:
After forming the same base layer as in Example 1, the same acrylic rubber paint as in Example 1 was used, and a 70 μm thick coating film was formed as the base protective layer. The elongation of the base protective layer was 30%, the water vapor permeability was 180 g / m ² · 24 hr, and the adhesive strength with the base layer was 0.60 N / mm ² . And like Example 1, when generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, generation | occurrence | production of rust was not confirmed at all.

Example 3:
After forming a base layer similar to that in Example 1, urethane rubber paint (trade name: “Saraseine C”, main agent: curing agent = 1: 1) manufactured by Asahi Glass Co., Ltd., having a thickness of 370 μm as the base protective layer was used. A coating film was formed. The elongation of the base protective layer was 160%, the water vapor permeability was 250 g / m ² · 24 hr, and the adhesive strength with the base layer was 0.80 N / mm ² . And like Example 1, when generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, generation | occurrence | production of rust was not confirmed at all.

Comparative Example 1:
A coating film similar to the base layer of Example 1 was formed. The base protective layer was not formed, and only one layer corresponding to the base layer was formed. And like Example 1, when the generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, the rust floating phenomenon was confirmed.

Comparative Example 2:
First, as an undercoat layer, an epoxy resin paint (Mitsubishi Resin Co., Ltd., trade name: “MY Rufer Primer AP”) that does not contain a rust preventive agent is applied to a sample and dried to form a 55 μm thick coating film Formed. Subsequently, the same coating film as Example 1 was formed as a base protective layer. The elongation of the undercoat protective layer was 80%, the water vapor permeability was 90 g / m ² · 24 hr, and the adhesion with the underlayer was 0.60 N / mm ² . And like Example 1, when the generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, the rust floating phenomenon was confirmed.

Comparative Example 3:
After forming the base layer similar to Example 1, the coating material similar to Example 1 was used as the base protective layer to form a coating film having a thickness of 15 μm. The elongation of the base protective layer was 10%, the water vapor permeability was 430 g / m ² · 24 hr, and the adhesive strength with the base layer was 0.60 N / mm ² . And like Example 1, when the generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, the rust floating phenomenon was confirmed.

Comparative Example 4:
After forming the same underlayer as in Example 1, a urethane rubber paint (manufactured by Asahi Glass Co., Ltd., trade name: “Sarah Seine C”, main agent: curing agent = 1: 1) was used, and the thickness of the base protective layer was 50 μm. A coating film was formed. The elongation of the base protective layer was 40%, the water vapor permeability was 480 g / m ² · 24 hr, and the adhesive strength with the base layer was 0.80 N / mm ² . And like Example 1, when the generation | occurrence | production of rust (rust floating phenomenon) was confirmed by the salt water combined cycle test, as shown in Table 1, the rust floating phenomenon was confirmed.

1: Base layer 2: Base protective layer 3: Metal surface (base material)

Claims (3)

A rust-proof coating method for forming a rust-preventive coating on a metal surface. A coating made of an epoxy resin containing lead and chromium-free rust-preventive agent is applied to the metal surface to form an underlayer, and then dried. Rust-proof coating characterized in that a base protective layer is formed by applying a rubber-based paint having an elongation rate of 20% or more and a water vapor permeability of 400 g / m ² · 24 hr or less to the surface of the base layer. Method.   The rust preventive coating method according to claim 1, wherein the rubber-based paint is an acrylic rubber-based or urethane rubber-based paint.   In addition, the surface of the base protective layer is coated with a resin selected from urethane urea resin, polyurethane resin, epoxy resin, chlorinated rubber resin, alkyd resin, phthalic acid resin, fluororesin, phenol resin, acrylic resin and acrylic silicon resin. The rust preventive coating method according to claim 1, wherein the surface protective layer is formed by applying to a surface.

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