JPS637879A - Method for painting steel structure in water - Google Patents

Abstract

PURPOSE:To facilitate work and to enhance the corrosion resistance of a film to a large extent, by applying an underwater curable composition containing a specific amount of a specific metal powder as the first layer of a film and subsequently applying an underwater curable composition containing no metal powder as the second layer of the film. CONSTITUTION:A two-layered structure is formed using paint being a two-pack type resin compound system consisting of a compound system based on an epoxy resin and a compound system containing an under water curable curing agent capable of curing said epoxy resin compound system even in water. In this case, a metal powder having ionization tendency larger than that of iron such as a zinc powder of an aluminum powder is added to the composition of a first layer in a range of 5-75wt% on the basis of a total composition and a glass flake is added to the composition of a second layer along with coloring pigment such as chromium oxide, iron oxide or carbon black. As a result, a film having excellent film capacity due to the epoxy resin, a good underwater coating property and high anticorrosion effect in obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an underwater coating method for steel structures, and more specifically, to a method for coating steel structures underwater or under humid conditions as a means of anticorrosion repair. This article concerns an underwater painting method used to effectively prevent corrosion and staining. [Conventional technologies and problems] Oil drilling rigs or oil stockpile purging accompanying offshore development in recent years, steel structures such as offshore plant ships, piers of long bridges constructed on the ocean, underwater steel structures at offshore airports, etc. The number of buildings and constructions continues to increase. When performing anti-corrosion repairs on these steel structures, it is almost impossible to move them from the installation location to another location, and the work must be carried out under poor working conditions such as underwater or splash areas. For this reason, there is a need for corrosion protection that can be easily implemented at sea and under the sea. ! Development of a repair method is required. As one means for solving this problem, for example, as seen in Japanese Patent Application Laid-Open No. 54-137034, a simple and easy method similar to that used on land can be applied to the underwater parts and splash zones of underwater structures. A coating method that forms a film with excellent corrosion resistance is considered. Conventionally known compositions used for such underwater coatings are based on epoxy resin and use polyamide or polyamine as a curing agent, as seen in JP-A No. 51-67400, for example. There are compositions in which a filler is added to. However, conventional compositions have the disadvantage that they not only have poor underwater applicability, but also have weak adhesion and are extremely easily washed away by waves, etc. during curing. Furthermore, even if cured, the adhesion of the cured product is insufficient and long-term corrosion protection cannot be expected. [Means for solving the problem] Therefore, the present inventors have developed a page that advantageously solves the above-mentioned problems.
As a result of various studies, we found that when painting steel structures underwater, by applying a paint containing a predetermined amount of a specific metal powder as the first layer, and a paint that does not contain the metal powder as the second layer, it is possible to paint steel structures underwater. The present invention was developed based on the discovery that coating can be easily performed using the same operations as those used on land, and that a coating with excellent adhesion and corrosion resistance can be formed. In particular, the phenomenon that the adhesion of epoxy resin to iron in water is significantly improved by using metal powder in the coating for forming the first layer is completely unknown, and the inventors of the present invention This is a completely new finding discovered for the first time as a result of many years of research. [Structure and operation of the invention] That is, the present invention has been made based on the above-mentioned knowledge, and its gist is to provide a compound system containing an epoxy resin as a main component and a system that can be cured even in water. A two-component resin compounding system consisting of a compounding system containing an underwater curing agent,
After applying as a first layer an underwater curable composition containing 5 to 75% by weight of a metal powder with a greater ionization tendency than iron based on the total composition, a desired coloring pigment and glass are added to the two-component resin blend system. The present invention provides an underwater coating method for steel structures, which is characterized in that an underwater curable composition containing flakes is top coated as a second layer. In the above, the metal powder content can be calculated using the following formula. Two-component + lII compounding system (including additives) (g) Ten metal powders (g) The present invention will be explained in detail below. First, the epoxy resin as used in the present invention refers to an epoxy resin or a mixed resin consisting of an epoxy resin and another resin that is compatible with the epoxy resin. That is, among the two compounding systems constituting the two-component epoxy resin composition of the present invention, one is mainly composed of an epoxy resin or a mixed resin consisting of an epoxy resin and another resin that is compatible with the epoxy resin. Other ingredients such as fillers such as calcium carbonate, silica, talc, and perlite, and additives such as other finely powdered non-silica and fluidity modifiers such as montmorillonite are mixed according to the purpose of use. ．． These other components are usually 1000 parts by weight of the main component 100! It is blended in a proportion of less than 1 part by weight, preferably 1 to so many parts by weight, and in particular, by using a large amount of filler, a blended system with a relatively high viscosity can be obtained. As the epoxy resin, bisphenol type epoxy resin is suitable, but other cycloaliphatic epoxy resins, phenol or talezol novolac type epoxy resins, phthalate glycidyl ester type epoxy resins, β-methylepichlorohydrin type epoxy resins, dimer acid type epoxy resins Examples include resins, polyglycol type epoxy resins, etc. These epoxy resins may be used alone or in combination of two or more. At this time, the epoxy resin is not particularly limited, but those having an epoxy equivalent of 70 to too much, preferably 100 to 700 are used. In addition, other resins that can be mixed with the above-mentioned epoxy resin include thermosetting resins and thermoplastic resins.
Typical thermosetting resins include phenoxy resin, phenol resin, xylene resin, acrylic resin, unsaturated polyester resin, etc. Examples of thermoplastic resin include polyester resin, ethylene-vinyl acetate copolymer,
Examples include thiocol resin, ionomer resin, modified butadiene-acrylonitrile resin, vinyl acetate resin, coal such as coal tar and asphalt pitch, and petroleum residue resin. One or more of these resins can be used together with the above-mentioned epoxy resin.

At this time, other resins compatible with the epoxy resin may be used in place of the epoxy resin in an amount of 50% by weight or less, preferably 30% by weight or less. Another compounding system in the composition used in the present invention is one in which the main component is a curing agent containing an underwater curing agent that can cure the epoxy resin even in water, and other ingredients. Additives such as the fillers and fluidity regulators mentioned above are mixed according to the purpose of use. These other components are usually blended in a ratio of 1000 parts by weight or less, preferably 1 to 500 parts by weight, per 100 parts by weight of the main component, and in particular, by using a large amount of filler, a relatively high viscosity can be achieved. It can be done as follows. As the underwater curing agent, it is possible to use an epoxy resin curing agent that is hardly soluble in water and contains active hydrogen that can replace water molecules. Examples of these include aromatic amines, polyalkylene polyamines, cycloaliphatic polyamines, modified polyamines, amine curing agents for epoxy resins such as ketemine, and borimel butane. Use more than one species.

A room-temperature curing agent that is normally used in the atmosphere can be used together with this underwater curing agent, and examples of these curing agents include aliphatic polyamines, polyamidoamines, amine-containing adducts, and separated adducts. It can be done.
The above-mentioned room temperature curing agent used in normal atmosphere is generally used in place of the underwater curing agent used in an amount of 40% by weight or less, preferably 30% by weight or less.

Next, examples of metal powders having a greater ionization tendency than iron to be included in the composition of the first layer used in the present invention include zinc powder, aluminum powder, magnesium powder, chromium powder, zirconium powder, etc., or alloy powders thereof. There are also composite powders plated or vapor-deposited with the above metals, and one or more of these may be used. Composite powder is
It is sufficient if the particle surface is made of the above-mentioned metals, for example, a metal powder (including iron) that has a smaller ionization tendency than iron.
Alternatively, it can be obtained by coating the surface of plastic powder with the metals by plating or vapor deposition. By using such metal powder in combination, the adhesion of epoxy resin to iron in water is significantly improved. Among these, particularly preferred are zinc powder and aluminum powder. The average particle size of the powder is preferably in the range of 1 to 300 μm; if it is less than 1, crm, it will not have a sufficient effect on improving underwater adhesion, and if it exceeds 300 μm, the appearance of the coating film will deteriorate, so it is not suitable. be. Regardless of the shape of the powder, such as flat, spherical, or acicular, the effect on improving underwater adhesion is the same, and any shape is acceptable. As mentioned above, the amount of these additives is 5 to 75% by weight based on the total composition.
It is necessary to add within the range of . If the amount is less than 5% by weight, it will not be effective in improving underwater adhesion, and if it exceeds 75% by weight, the cohesive force of the composition and the adhesion to the steel substrate will decrease, making it unsuitable. The mixing ratio of the above formulation system and the formulation system containing an underwater curing agent is such that the active amine hydrogen equivalent of the underwater curing agent component is 0.0.
It is generally 2 to 2.0 equivalents, preferably 0.5 to 1.5 equivalents. If this ratio is too low, curing will be slow, and if it is too high, the properties of the cured product will deteriorate, so both are unfavorable. The metal powder may be mixed in advance into either or both of a blending system containing an epoxy resin as a main component or a blending system containing an underwater curing agent as a main component for curing an epoxy resin. It may be added when mixing a compound system containing a resin as a main component and a compound system containing an underwater curing agent as a main component. For the first layer of undercoat using the above composition, adhesion to iron is the most important point in construction, and a composition containing metal powder is essential, but on the other hand, coloring is limited due to the metal powder. Ru. Therefore, for the second layer of the top coat, an underwater curable composition prepared by adding a colored pigment to the two-component resin composition system can be used.
The underwater curable composition used at this time does not substantially contain metal powder. On the other hand, a coloring pigment may be added to the metal powder-free composition used for coating the first layer described above, if necessary. Further, it is preferable that the epoxy resin and underwater curing agent constituting the metal powder composition for coating the first layer and those for coating the second layer are the same or similar, but they may be of different M classes. You can. Coloring pigments used to adjust the composition for the second layer coating include oxide coloring pigments such as chromium oxide, iron oxide, and titanium dioxide, pigments such as carbon blank, and graphite, as well as lid cyanine blue and phthalocyanine. All the coloring pigments used in ordinary paints, such as organic coloring pigments such as green, can be used, but it is especially desirable to add II-soluble pigments to water. Furthermore, the coloring pigment may be mixed in either or both of a compounding system containing an epoxy resin as a main component or a compounding system containing an underwater curing agent as a main component. When adding pigments to both, it is possible to add pigments of different tones to each and use this as a guide for the degree of mixing when mixing and stirring the two. Furthermore, in the present invention, in the second layer of the top coat, glass flakes are added to the two-component resin formulation system together with a colored pigment. This glass flake is added to enhance the anti-corrosion effect. The glass flakes used in the present invention pass through a 32 mesh (500 μm) with a standard sieve specified in JIS Z 8801.
The main component is that which does not pass through the 0-mensch (45 μm). The main component I means 50% by weight or more of the total amount of glass flakes, preferably 60% by weight or more, particularly preferably 70% by weight or more. Further, the glass flakes used are generally those whose total amount passes through 16 mesoches (l O O Qμm) within the above-mentioned specific range.

Further, the thickness of the glass flakes is preferably 0.5 to 10 μ
It is m. The amount of glass flakes added is 5 to 30% by weight, preferably 10 to 25% by weight, based on the total composition. By using glass flakes within the above numerical range,
Excellent anti-corrosion effect can be obtained. In the present invention, a compounding system mainly composed of epoxy resin (
A two-component epoxy resin composition is composed of a combination of a compound system containing a water-curable curing agent (hereinafter referred to as a hardening agent) as a main component and a water-curable curing agent as a main component. By mixing the base resin and curing agent, the curing reaction progresses and a cured epoxy resin product is obtained. Two-component epoxy resin compositions have properties such as those in which the base agent and curing agent are made into a high-viscosity compound (putty-like) in advance so that they can be mixed and applied by a wet hand method, and low-viscosity compounds (such as paint drop, viscosity, etc.). (approximately 3,000 ps or less) is used, and depending on the properties, it can be brushed, troweled, or
You can use a spatula, roller, etc. The coating thickness also varies depending on the viscosity properties, but the total thickness of the two layers can usually be coated in the range of 100 μm to 10+s+. The thickness of the single layer is generally 50 μm to 80 μm for both the first layer undercoat and the second layer top coat. When applying, first a first layer of an underwater curable composition containing metal powder is applied to the steel surface after removing rust, marine organisms, etc. from the steel surface under the sea by means such as disk sanguine, water jet, sand water jet, etc. After coating as a second layer, the above-mentioned underwater curable composition containing a colored pigment and glass flakes is applied as a second layer. These two layers may be applied either with the undercoat uncured or after it has hardened. In this way, in the present invention, by using an epoxy resin, a curing agent that hardens it even in water, and a metal powder that has a greater tendency to ionize than iron, the original excellent coating film of the epoxy sealant can be improved. In addition to maintaining its properties and hardenability, it has excellent underwater coating properties due to interaction with metal powder, and its underwater adhesion properties are significantly improved. For this reason, it hardens as it is without being washed away by waves, etc., and the hardened film has a strong adhesive force, so it firmly adheres to underwater steel structures. Furthermore, since the cured coating film retains the excellent properties inherent to epoxy resin, in combination with the above properties, it exhibits an extremely excellent anti-corrosion effect and effectively protects underwater structures. In addition, when the main component of the second layer topcoat composition used is the same as or similar to the first layer undercoat composition, it is not only extremely easy to recoat, but also has excellent glabella adhesion after curing. ing. Another advantage is that coating defects such as pinholes are extremely reduced due to multi-layer coating. Furthermore, in the present invention, since glass flakes are contained in the second layer of the top coat, the anticorrosion effect is further improved. Although the method of the present invention is an underwater coating method, it can of course be applied to wet surfaces such as the splash zone and tidal zone of structures, and can also be applied to structures on land. Next, the effects of the present invention will be explained in more detail with reference to Examples. The parts in the examples are parts by weight. Examples 1 to 4 90 parts of bisphenol A epoxy resin with an epoxy equivalent of 185 to 192, 10 parts of phenyl glycidyl ether as a reactive diluent, 40 parts of calcium carbonate, and ultrafine anhydrous silica as an anti-sag agent (specific surface area 200 m2/g)
) were stirred and mixed at 50°C to form an epoxy resin blend system. On the other hand, 50 parts of a modified aromatic polyamine (modified diaminodiphenylmethane) having an active hydrogen equivalent of 95, 15 parts of calcium carbonate, and 1 part of ultrafine anhydrous silica (specific surface area 200 m2/g) as an anti-sag agent were added in a stirring mixing pot.
The mixture was mixed at ℃ to form a curing agent. Epoxy resin blend system 1
42g and 66g of the curing agent combination system were weighed out, and zinc powder (
Undercoat compositions 1, 2, and 3 used for the first layer are prepared by adding and mixing 50 μm (average particle size) in the proportions shown in Table 1.
A mixture of Table 1 The numbers in Table 1 indicate the blending proportions in parts by weight. However, () indicates the weight percent of zinc powder in the compound. In addition, the topcoat composition used for the second layer uses colored pigments titanium oxide and glass flakes for the epoxy resin blend system, and color pigments phthalocyanine blue B and glass flakes for the hardener blend system, and as with the undercoat composition, Each was mixed in a mixing pot at 50°C. Table 2 shows the mixing ratio of each. The glass flakes used were those whose main component (70% by weight) was one that passed through 32 meshes but did not pass through 350 meshes (the thickness of the glass flakes was 3% by weight).
μm) passed through 16 mesh). Table 2 Next, as a steel sample to be coated, a 9x100x100sa SS41 steel plate prepared with a disc sanguo was immersed in seawater for 4 hours, and then the undercoating composition l shown in Table 1 was applied.
Apply the mixture of 2 and 3 as the first layer with a spatula in the sea,
After 30 hours had passed, top coating compositions 1 and 2 shown in Table 2 were applied as a second layer using a roller. The coating film thickness is approximately 200μm for the first layer and approximately 200μm for the second layer, total approximately 4
It was 00μm. Table 3 shows the coating workability during application, the appearance of the coating film surface after application, and the coating film adhesion strength after curing. Table 3 (Note 1) O: The entire surface can be easily and evenly coated with a few coats with a spatula. Δ: When applying multiple coats, the initial coat may peel off, but the entire surface can be coated by repeating spatula coats. ×: Even after repeated coating, peeling occurs from the steel surface and the entire surface cannot be coated. (Note 2) Adhesion bull-off test Paint samples that had been immersed for one month or one year were taken out into the atmosphere, allowed to dry for a day and night, and then adhesion strength was measured using an adhesion tester. Almost the same results were obtained when aluminum powder was used instead of the zinc powder used in the above example.
[Effects of the Invention] As is clear from the above examples, the present invention provides excellent corrosion protection for steel structures with excellent underwater coating workability and excellent long-term corrosion protection. ! It is possible to provide a means of repair, and the industrial effect is extremely remarkable. (that's all)

Claims (2)

[Claims] (1) A two-component resin compounding system consisting of an epoxy resin-based compounding system and a compounding system containing an underwater curing agent that can harden it even in water, and a metal powder with a higher ionization tendency than iron. After applying an underwater curable composition containing 5 to 75% by weight as the first layer, a second layer of an underwater curable composition prepared by adding a desired color pigment and glass flakes to the two-component resin formulation system. An underwater painting method for steel structures, characterized by applying a topcoat as a topcoat. (2) The underwater coating method for steel structures according to claim 1, wherein the metal powder is zinc powder or aluminum powder.