JPH081085A - Coated steel excellent in antifouling property - Google Patents

Abstract

PURPOSE:To provide a safe and pollution-free coated steel excellent in antifouling property and anticorrosive property. CONSTITUTION:The coated steel excellent in antifouling property is provided with an under coating layer formed by applying a pure epoxy resin containing 10-60wt.% flake shaped pigment (talc, mica, glass flake or the like) and no tar component on the surface of a steel, an intermediate layer formed by applying a coating material (resin of urethane, epoxy, vinyl chloride, polyester or the like) containing >=3wt.% silicone rubber on the under coating layer and a top coating layer formed by applying a silicone rubber coating material on the intermediate layer. Since antifouling components such as an organic tin or cuprous oxide are not contained, the coated steel is safe and pollution-free and excellent in antifouling property and anticorrosive property and is used suitably for equipment materials using sea water such as heat exchangers or sea water intake pipes. And a process necessary for coating is simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be applied to facilities / devices that use seawater, such as cooling seawater intake pipes for power plants, heat exchangers, etc.
The present invention relates to a coated steel material having no toxicity and good corrosion resistance.

[0002]

2. Description of the Related Art For example, in facilities and apparatuses that use seawater, such as heat exchangers and seawater intake pipes, there is a problem due to adhesion of barnacles, mussels and other marine organisms. Specific examples thereof include a decrease in heat transfer efficiency and a decrease or blockage in the pipe flow efficiency due to adhesion of large organisms. As a technique for preventing such damage due to the adhesion of marine organisms, conventionally, the surface of a steel material is coated with an antifouling coating containing an antifouling component such as organic tin or cuprous oxide, which is effective in preventing the adhesion of marine organisms. Various methods such as a chemical treatment method such as chlorine injection into seawater have been devised and put into practical use.

However, in recent years, the problem of accumulation toxicity due to bioconcentration of organotin in a marine ecosystem has been revealed, and many organotin compounds are "laws concerning the examination and the regulation of chemical substances (Chemical Substances Control Law)". It is defined as a specific substance and a designated substance of, and their production and use are regulated. Since the restrictions on chlorine injection in seawater intake pipes, etc. are gradually becoming strict and disadvantageous in terms of cost, it is desired to develop a pollution-free biofouling prevention technique that replaces these conventional methods.

Recently, as a non-toxic antifouling paint, a method has been proposed in which a steel material surface is coated with a water-repellent substance consisting of silicone rubber alone or a mixture of silicone rubber and silicone oil. However, it is pointed out that this method has various problems such as adhesion of the coating, corrosion resistance, and durability.

As a measure for solving these problems, for example,
Japanese Examined Patent Publication No. 55-41666 discloses a coating composition for intermediate coating in which polyvinyl butyral is mixed with 1.5 to 5% by weight of silicone rubber together with other additives. this is,
The above intermediate coating composition is present between the undercoating anticorrosive coating and the top silicone rubber coating to act as a binder layer for strengthening the mutual adhesion of both the undercoat and topcoat. It improves the adhesion.

Japanese Unexamined Patent Publication (Kokai) No. 4-262724 discloses a method of coating aquatic fishing nets with a silicone synthetic resin coating on a chlorinated rubber base coating. It has been shown that the antifouling effect of the silicone rubber-based synthetic resin coating is enhanced by using the chlorinated rubber-based base coating, but the details of the reason have not been clarified.

Further, various studies have been made on the maintenance of the antifouling effect of the silicone coating film for a long period of time, that is, the antifouling durability. For example, JP-A-4-142373 discloses silicone rubber and polyether-modified silicone oil. An antifouling paint containing the above is disclosed. This is because the polyether-modified silicone oil migrates to the surface of the coating film at an appropriate rate, so that the antifouling property is exhibited for a long period of time. Further, JP-A-4-45170 discloses that the antifouling effect can be enhanced by adding / combining a quaternary ammonium salt having an antifouling effect to a silicone resin.

As described above, it is desired to develop a pollution-free biofouling prevention technique that does not cause accumulated toxicity in consideration of the influence on the environment. As one of them, various methods using a silicone resin coating have been studied. Is the current situation.

[0009]

Since the coated steel material utilizing the water repellency of silicone for preventing the adhesion of marine organisms is inferior in anticorrosion property, the anticorrosion property is usually imparted by using an anticorrosion paint as the undercoat. As an anticorrosion paint for this undercoat, a tar epoxy paint is generally used and is often used in seawater piping. However, the tar component in this tar-epoxy coating penetrates to the top coat layer, which adversely affects the antifouling property of the silicone resin. Therefore, in general, a method of applying a paint that prevents the permeation of tar as an intermediate coating layer is adopted, but since the number of steps required for coating increases,
It is not very advantageous to apply a paint for preventing the penetration of tar as an intermediate coating layer.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a coated steel material which is safe and pollution-free, has excellent antifouling and anticorrosion properties, and has a simplified process required for coating. To do.

[0011]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that a tar-free epoxy resin containing 10 to 60% by weight of a scaly pigment as an undercoat layer ( Hereinafter, it was found that by using this as a "pure epoxy resin" as an anticorrosion paint, it is possible to effectively prevent base corrosion and ensure long-term corrosion resistance. Further, by interposing a layer coated with a coating material containing 3% by weight or more of silicone rubber as a binder between the undercoat layer and the silicone resin coating material as the topcoat layer as an intermediate coating layer, the pure epoxy resin as the undercoat layer and the topcoat layer are provided. It has been found that the adhesiveness with the silicone resin coating, which is a layer, can be improved, there is no adverse effect due to the penetration of tar content, the durability is excellent for a long period of time, and a stable antifouling effect is obtained.

Since a pure epoxy resin containing no tar is applied to the undercoat layer, the coating for preventing the penetration of tar, which has been indispensable for maintaining the antifouling effect of the silicone rubber paint as the topcoat, is omitted. This also contributes to simplification of the process required for painting.

The present invention has been made on the basis of such knowledge, and its gist resides in the following coated steel material.

10 to 60% by weight of scale-shaped pigment on the surface of the steel material
Of an undercoat layer formed by applying a pure epoxy resin containing no contained tar component, an intermediate coat layer formed by applying a paint containing 3% by weight or more of silicone rubber on the undercoat layer, and an intermediate coat layer A coated steel material with excellent antifouling properties that has an overcoat layer with a silicone rubber coating applied on top.

[0015]

The coated steel material of the present invention comprises a steel material having a surface coated with an undercoat which is an anticorrosive coating layer, an intermediate coating which is a binder layer and an upper coating which is an antifouling coating layer. There is no particular limitation on the type and shape of the steel material for the base, and there are plates, bars,
Pipes and steel sheet piles can be used.

In the coated steel material of the present invention, a tar-free pure epoxy resin containing a scale-shaped pigment in an amount of 10 to 60% by weight is used as an anticorrosive coating as an undercoat. Since the pure epoxy resin does not contain tar, it is slightly inferior in anticorrosion property to the case of using the tar epoxy paint which is generally used as an undercoating anticorrosion paint for anticorrosion coating such as ship bottom and seawater piping. .
Therefore, in the present invention, the scale-like pigment is added to enhance the anticorrosion effect.

The scale-shaped pigments include talc, mica,
Glass flakes and MIO (mica-like iron oxide) can be used. When these scale-shaped pigments are contained in a pure epoxy resin, when the resin is applied to the surface of the steel material, the scale-shaped substances are arranged in parallel with the surface of the steel sheet. Therefore, it is possible to remarkably suppress the permeation of water and chlorine ions and improve the anticorrosion property. At the same time, since the hardness of the film is improved, damage to the film due to the bite of the organism and the corrosion due to the invasion of the organism can be prevented even if the organism adheres.

The content of the scale-like pigment is set to 10 to 60% by weight because when the content is less than 10% by weight, sufficient corrosion resistance cannot be obtained, and when it exceeds 60% by weight, the viscosity of the coating increases and the coating This is because it has poor properties, and when it is diluted with a solvent, the dry curability deteriorates. Therefore, it is particularly preferable to use 30 to 50% by weight.

The scale (major axis) of the scale-shaped pigment is 2 to 500.
It is preferable that the diameter is μm and the minor axis is 5 times or more the thickness. If the size of the pigment is less than 2 μm, the effect is small, and if it exceeds 500 μm, the coating property is deteriorated.

Further, since the pure epoxy resin has higher adhesion to the steel surface than the chlorinated rubber type anticorrosive paint, the one using the pure epoxy resin as the undercoat uses the chlorinated rubber type anticorrosive paint with the same film thickness. It has a higher anticorrosion property than the existing one and is advantageous.

In the coated steel material of the present invention, since a pure epoxy resin containing no tar is used as the undercoating anticorrosive paint, the tar resin contained in the tar epoxy paint conventionally used as an anticorrosion paint is overcoated with a silicone resin. It is possible to prevent deterioration of the antifouling effect due to penetration into the layer. On the other hand, as compared with the case where a paint for preventing the permeation of the tar component is applied as the intermediate layer, the intermediate layer can be omitted, which can contribute to simplification of the process at the time of painting. .

The coating thickness of this undercoat paint (pure epoxy resin containing scale-shaped pigment) is 300 μm to 3 mm.
Is preferred. If it is thinner than 300 μm, sufficient corrosion resistance cannot be obtained, and if it is thicker than 3 mm, it is economically disadvantageous.

As the intermediate coating material, a coating material containing 3% by weight or more of silicone rubber is applied. If the content of silicone rubber is less than 3% by weight, the adhesion with the topcoat layer will be reduced. On the other hand, if it exceeds 30% by weight, the adhesion to the undercoat layer will be deteriorated, so it is preferably 3 to 30% by weight. The silicone rubber contained in the intermediate coating is
It is preferable to use the same silicone rubber paint used for the top coat.

As the resin which is the base of the intermediate coating,
Although various resins such as urethane, epoxy, vinyl chloride, and polyester can be used, it is preferable to use those having good adhesiveness to the pure epoxy resin used as the undercoat. The thickness of the intermediate coating layer is preferably 20 μm or more, and if it is thinner than this, the adhesiveness is lowered. Also, the thickness
If it exceeds 100 μm, it is not preferable in terms of economy.

Silicone rubber paint is used as the top coat paint. Generally, when attached organisms such as barnacles and mussels adhere to normal solid surfaces during the juvenile period, they secrete viscous proteins immediately afterwards, and produce adhesive cement to adhere and grow on the solid surfaces. . However, it has a low surface tension like silicone rubber (the contact angle with water is
Since the solid surface has water repellency, it reduces the adherence of the secretions of the above-mentioned adherent organisms. Further, even if organisms adhere to the surface, the adhesion force is very weak, so that they easily peel off by a physical action such as a slight increase in the flow velocity of the fluid in contact with the surface.

As the silicone rubber paint, 100% silicone rubber may be used, but the coating tends to deteriorate when used for a long period of time. Therefore, silicone oil, paraffin or the like is added in an amount of 5 to 30% by weight. Is preferably used. Thereby, the excellent antifouling property can be maintained for a long period of time. This is thought to be because the antifouling effect is increased due to the decrease in surface tension due to silicone rubber, and silicone oil and paraffin are appropriately eluted from the coated surface to keep the coated surface always active. To be

The thickness of the overcoat is preferably 50 μm or more, and if it is less than this, the antifouling property is deteriorated. Further, from the viewpoint of economy, it is preferable that the thickness is less than 300 μm.

The coated steel material of the present invention is a coated steel material having the above-mentioned constitution, but the coating method is not particularly limited, and various conventionally used methods can be applied.

Generally, the interval between each of the undercoating, the intermediate coating and the topcoating is preferably 24 hours, but when a solvent type coating is used for the lower layer, it may be longer than the dry curing time. Further, this time can be shortened by heating.

As in the present invention, by applying a pure epoxy resin containing no tar content to the undercoat layer, an intermediate layer for preventing the penetration of tar content is not required, and the coating process is simplified, so that it can be applied locally. Is advantageous to. Furthermore, the conventional coated steel material with an intermediate layer interposed to prevent the penetration of tar components requires at least four layers of coating, which makes it difficult to perform line coating in a factory, but the coated steel material of the present invention requires three layers of coating. Therefore, it is possible to coat the steel material using the line in the factory and ship it as a product.

[0031]

Example A blasted SS-41 steel plate having a thickness of 200 mm × 100 mm and a thickness of 4 mm was coated by air spray coating so that the coating composition shown in Table 1 was obtained. The interval between each of the undercoat, middle coat and top coat was 24 hours.

Seawater immersion tests and accelerated corrosion resistance tests were carried out using the test pieces thus manufactured. The seawater immersion test is a test to evaluate the antifouling property.
The sample was taken out after 1 year and 2 years, and the state of biofouling on the surface of the test piece was visually observed. The accelerated corrosion resistance test is a test to evaluate the corrosion resistance. The coated part of the test piece immersed in artificial seawater at 60 ° C for 2 years is mechanically peeled off with a chisel or a cutter knife, and the interface between the steel plate and the undercoat paint. That is, the steel material (base) surface was observed.

The test results are shown in Table 2. In the seawater immersion test, the state of biofouling was evaluated according to the following four grades: ◎, ○
And Δ were considered good.

◎: No biofouling or slight ○: Little biofouling (slime formation in part) △: Larger fouling in part ×: Larger fouling in whole surface Also, in the accelerated corrosion resistance test, steel ( The occurrence of rust on the (base) surface was evaluated according to the following three grades, and ◯ and Δ were evaluated as good.

◯: No abnormality Δ: Spot rusting on a part of the substrate X: Spot rusting on the entire surface of the substrate As is clear from the results in Table 2, in any of the test pieces of Examples 1 to 6 of the present invention, the prevention of corrosion was observed. The stain resistance (seawater immersion test result) and corrosion resistance (accelerated corrosion resistance test result) were good.

On the other hand, in Comparative Example 7, since the scale-like pigment was not contained in the undercoat layer which was the anticorrosion layer, rust was generated on the entire surface of the base. In Comparative Example 8, since the silicone content in the intermediate layer, which is the binder layer, was less than that specified in the present invention, the adhesion between the undercoat and the topcoat was poor, peeling of the topcoat layer was observed, and antifouling durability was poor. Met. In Comparative Example 9, only the undercoat was applied, and there was no antifouling effect. In Comparative Example 10, since silica was used as an extender pigment to be added to the undercoat layer, the corrosion resistance was insufficient. In addition, Comparative Example 11
However, since the tar epoxy coating was used as the undercoat, the tar content penetrated into the silicone rubber overcoat layer, and the antifouling property deteriorated. In Comparative Example 12, a chlorinated rubber was used as the undercoat, but the corrosion resistance was inferior to that of Inventive Example 1 having the same film thickness.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

EFFECTS OF THE INVENTION The coated steel material of the present invention does not contain antifouling components such as organic tin and cuprous oxide, so it is safe and non-polluting, and has excellent antifouling properties and anticorrosion properties, and heat exchangers, seawater intake pipes, etc. It is suitable as a material for facilities and equipment that uses seawater.
In addition, since tar epoxy resin is not used as an anticorrosion paint for the undercoat, it is possible to omit the coating of the intermediate layer to prevent the penetration of tar and simplify the process required for painting. Instead, it is possible to paint using the line in the factory.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C09D 183/04

Claims (1)

[Claims] 1. A scale-shaped pigment of 10 to 60% by weight on the surface of a steel material.
An undercoat layer formed by applying an epoxy resin containing no contained tar component, an intermediate coat layer formed by applying a paint containing 3% by weight or more of silicone rubber on the undercoat layer, and an intermediate coat layer formed on the intermediate coat layer. A coated steel material with an excellent antifouling property, which has an overcoat layer formed by coating a silicone rubber paint on.