JPS6145513B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an antifouling method for the surfaces of steel or concrete objects that come into contact with seawater, particularly for various types of ships such as engineering ships, pulp ships, and offshore oil storage vessels, offshore structures such as quays, offshore airports, coastal oil drilling towers, and underwater structures. The present invention relates to a surface antifouling method whose main purpose is to prevent corrosion and adhesion of marine organisms to the surfaces of various steel or concrete objects used in contact with seawater, such as pipes and seawater drainage pipes. Various ship bottom paints have been used for this purpose, but none of them can maintain an antifouling effect for a long period of more than one year, and the stains grow on the paint film at least once a year. After cleaning the surface by removing various marine organisms such as barnacles, oysters, scale insects, and seaweed (hereinafter referred to as underwater sessile organisms), the bottom paint must be applied again to form a new antifouling film surface. Must be. Conventionally, cuprous oxide or cuprous oxide mixed with a small amount of mercury oxide has been used as an active antifouling ingredient in ship bottom paints as a poisonous substance to prevent the attachment of aquatic organisms. They previously reported that while cupric sulfide is an effective toxic component, the copper sulfate produced when it is oxidized by oxygen in water comes into contact with the steel surface, precipitates metallic copper, and severely corrodes the steel. proposed an antifouling method for the surfaces of steel or concrete objects that come into contact with seawater by using polymer cement in a safe and long-term manner (Japanese Patent Application No. 54-29369). We have recently developed a more effective antifouling method that uses metallic copper powder as an effective toxic ingredient. It has been known for a long time that if the surface of a structure attached to the sea, such as the bottom of a real ship, is coated with a copper plate, underwater sessile organisms cannot inhabit this area, and this state can be maintained for a long period of time. It is being However, when a steel surface comes in contact with not only a copper plate but also copper powder or fine particles of metallic copper, a local battery is formed, and the steel in the area where the metallic copper comes into contact is severely corroded. Therefore, it has been considered completely impossible to use metallic copper as an antifouling agent for conventional ship bottom paints. The present invention effectively prevents corrosion of steel by metallic copper by using the polymer cement coating agent described in detail below as an adhesive concrete coating on the steel surface, and furthermore, the metallic copper powder itself is also separately coated with polymer cement. By incorporating it into a coating agent and applying it to the surface of a polymer cement protective coating, a long-lasting antifouling effect can be achieved. Therefore, the present invention provides a polymer cement coating agent for the surface of a steel or concrete object that comes into contact with seawater, which is prepared by blending a water-based polymer emulsion with Portland cement or blast furnace cement alone or in a mixture with fine aggregate of the cement. To provide an antifouling method for the surface of a steel or concrete object that comes into contact with seawater, which comprises applying and curing a mixture of metallic copper powder and the polymer cement coating agent to the coated surface. It is something. The essential feature of the present invention is that metallic copper powder is used as a toxic component for preventing the adhesion of aquatic spores, and its severe corrosivity to steel is effectively inhibited in combination with a polymer cement coating agent. That is, according to the present invention, by first applying a polymer cement coating agent as a primer to the steel surface to an appropriate thickness, for example, 3 to 10 mm, the strong alkalinity of cement with a pH of 11 or higher is maintained and the corrosion protection of the steel is achieved. A highly effective tough film is formed and then a mixture of metallic copper powder and polymer cement coating is further applied. The use of such a primer in the present invention not only has the physical effect of blocking the metallic copper powder-containing film from coming into direct contact with the steel surface, but also has the effect that the metallic copper is oxidized by underwater oxygen and Copper ions produced by the action of salt are captured by alkaline calcium to form a double salt, which has the chemical effect of protecting the steel surface from electrolytic corrosion. The powder part of the polymer cement coating agent used in the present invention (hereinafter referred to as the polymer cement powder part) may be composed of Portland cement or blast furnace cement alone, but more generally it is composed of a cement mortar base, that is, cement and silica sand. ,
A mixture containing fine aggregate such as river sand is used. The particle size of the aggregate is preferably fine, about 1 mm or less. The blending ratio of aggregate may be one commonly used for cement mortar bases and is not particularly limited. Usually, a mixing ratio of 20 to 50 parts by weight of cement and 80 to 50 parts by weight of fine aggregate is used. The aqueous polymer emulsion for the polymer cement coating may be aqueous emulsion based on various synthetic resins, including acrylic, vinyl acetate, epoxy, etc., natural or synthetic rubber latex, or mixtures thereof. In particular, for the purpose of the present invention, impact resistance, bending workability, abrasion resistance, weather resistance, water resistance, seawater resistance, heat resistance, etc. are important, and long-term durability is required for these. Of course, appropriate additives may be added depending on the individual case. As such additives, polyvinyl alcohol aqueous solutions, petroleum resins derived from by-products during naphtha decomposition, polyisobutylene emulsions, and the like have been found to be particularly effective. Therefore, an example of a formulation of a polymer cement coating particularly suitable for use in the present invention is 20 to 50 parts by weight of Portland cement, 70 to 95 parts of polymer cement powder consisting of 80 to 50 parts by weight of silica sand, and an aqueous polymer emulsion. 30-5 parts by weight and 0-15 parts of fresh water
A particularly preferred example of the aqueous polymer emulsion is a polyvinyl alcohol aqueous solution (concentration 10% or less), petroleum resin or its diluted product in the presence of a nonionic or cationic surfactant. An example is an aqueous emulsion obtained by mixing the mixture at the bottom, adding SBR latex to this, and stirring. As mentioned above, it is important to use a polymer cement coating agent as the coating base for the coating agent containing metallic copper powder.
It is possible to obtain an antifouling coating film that can exhibit a desired antifouling effect over a long period of time against adhesion of aquatic sessile organisms without fear of adhesion and falling off. Furthermore, as mentioned above, the copper ion trapping effect due to the formation of double salts is also noteworthy. Even if a conventional paint-type vehicle is used for this purpose, such an effect cannot be expected.Due to the strong alkalinity of the polymer cement coating applied as a primer, it swells, peels off, and falls off while immersed in seawater for a long period of time. the desired effect is not achieved. As the metallic copper powder, any powdered copper including scale-like, dendritic, crushed-like, etc. forms can be used, and commercially available powders can be used without particular limitations on the form, particle size, etc. For example, commercially available particles with a particle size of 100 mesh or less, for example, as a particle size distribution.
325 meters or less 20-90%, 200-325 meters 40
-20%, 100-200 meshes and 50-1%. One feature of the present invention is that a large amount of metallic copper powder can be incorporated into the polymer cement coating, and generally a ratio of metallic copper powder to polymer cement powder portion in the range of 70:30 to 20:80 can be used. By appropriately selecting this ratio, the copper ion concentration in the coating film, that is, the degree of toxicity, can be adjusted; of course, the higher the proportion of metallic copper powder, the greater the toxicity. The ratio of the metallic copper powder to the polymer cement coating agent in the coating agent containing metallic copper powder is not particularly critical, but it is usually 20 to 20 parts by weight of the coating base per 100 parts by weight of the metallic copper powder.
It is used at a ratio of about 100 parts by weight. If the proportion of the coating base is too low, the coating film formation will be unstable and peeling will occur in seawater, while if it is too large, the outflow of copper ions will be too low, making it impossible to obtain sufficient antifouling effects. do not have. In addition, after forming the first polymer cement coating, that is, the primer coating, and before forming the coating containing metallic copper powder, a thin film of synthetic resin coating such as epoxy or acrylic is formed as an intermediate film. , it is possible to prevent the calcium-based strong alkaline component in cement from being lost to water, the formation of pinholes, etc. Furthermore, in a preferred embodiment of the present invention, when mixing the metallic copper powder with the polymer cement coating agent, the toxicity of the metallic copper is enhanced by simultaneously incorporating a small amount of calcium chloride or magnesium chloride in the form of an aqueous solution. I can do it. The amount of alkaline earth metal chloride added is 0.1 to 1% based on the total amount of polymer cement powder containing metallic copper powder.
That's about it. Next, the present invention will be explained with reference to Examples, but of course the present invention is not limited to these Examples. In the examples, parts are by weight unless otherwise specified. Example 1 A polymer cement coating agent prepared as below was applied to a steel plate measuring 60 cm in length, 20 cm in width, and 3.2 mm in thickness to a film thickness of 4 mm, and after curing for 1 week, an acrylic resin emulsion (trade name: Suncoat) was applied. CN-78)
A primer-coated test piece (hereinafter referred to as a test piece) was prepared by applying the primer to a thickness of 100 μm and drying and curing it. A polymer cement coating was prepared as follows. A mixture of 30 parts by weight of Portland cement and 70 parts by weight of silica sand was used as the powder part of the polymer cement, while an aqueous polymer emulsion for polymer cement was prepared by adding 300 parts by weight of petroleum resin and 90 parts by weight of ethylene pyrolysis by-product oil as a diluent. Add part,
After heating and stirring, add a stirred solution of 12 parts by weight of a nonionic surfactant to 700 parts by volume of a 10% polyvinyl alcohol aqueous solution.
An emulsion obtained by adding and stirring 500 parts by volume of SBR latex and 200 parts by weight of polyisoptylene emulsion was used. 85 parts by weight of this powder, 12 parts by weight of emulsion, and 5 parts by weight of water were further mixed and stirred and used as the polymer cement coating agent. Various coating agents containing metallic copper powder shown in (a) to (c) below were applied to the coated surface of the polymer cement coating agent of Test Specimen I, and the antifouling effects were observed by conducting a seawater immersion test on these coating agents. . The test results are summarized in Section 1 below.
Shown in the table. (a) Test Specimen I was mixed with 150 parts of metallic copper powder and 150 parts of powder of the same polymer cement used in the primer, and then mixed with 90 parts of the same aqueous polymer emulsion water (50% active ingredient) and A coating agent prepared by mixing 50 parts of water was applied to a thickness of 1 to 1.2 mm, and dried and cured to form a coating. (b) A coating obtained by mixing 60 parts of metallic copper powder with 150 parts of the powder part of the polymer cement, and then 27 parts of the water-based polymer emulsion (active ingredient 50%) and 15 parts of water. The agent was applied to specimen I to a thickness of 1 to 1.2 mm and dried and cured to form a coating. (c) 200 parts of metallic copper powder is mixed with 100 parts of the powder part of the polymer cement, and then the water-based polymer emulsion (50% active ingredient) is added.
81 parts, silicone resin emulsion (Toray Silicone SR2404) (active ingredient 40%) 9 parts and water 50 parts
The coating agent obtained by mixing the parts was applied to a thickness of 1 to 1.2 mm, and dried and cured to form a coating. Comparative example Length 60 cm, width 20 cm, same as used in Example 1,
After thoroughly removing the rust on a 3.2mm thick iron plate, apply commercially available ship bottom paint Primer AF (manufactured by Nippon Paint) three times with a brush, and after drying, apply a rubber coat.
I applied three coats of AC (manufactured by Nippon Paint) with a brush. Seawater Immersion Test Each of the test pieces of Examples 1 (a) to (c) and Comparative Example was fixed to a pillar of a bridge on the Goi coast in Chiba Prefecture, immersed in seawater, kept for about 12 months, and observed. The results are shown in Table 1.

[Table] * After the test, the paint film on the test piece was removed with a chisel and the state of rust was observed.

Claims (1)

[Claims] 1. A polymer cement coating consisting of a water-based polymer emulsion mixed with Portland cement or blast furnace cement alone or a mixture of the cement and fine aggregate was applied to the surface of a steel or concrete object that would come into contact with seawater, and the coating was cured. A method for preventing stains on the surface of an object made of steel or concrete that comes into contact with seawater, the method comprising: thereafter applying a mixture of metallic copper powder and the polymer cement coating agent to the applied surface.