JPH02217242A - Coated steel structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a covering structure for steel structures such as steel pipe piles, steel sheet piles, and steel pipe sheet piles that require heavy corrosion protection.

[Prior art] Steel pipe piles, steel sheet piles, steel pipe sheet piles, etc. (hereinafter abbreviated as piles and sheet piles) are widely used as civil engineering construction materials for marine (port) structures, structure foundations, and seawall construction. There is. Although these piles and sheet piles are used in highly corrosive environments where they are constantly exposed to water, oxygen, sunlight, or salt, they are required to have heavy corrosion resistance that can withstand years of use. ing.

In order to meet these demands, in recent years, piles and sheet piles coated with polyurethane have been developed as a coating system with emphasis on heavy corrosion protection. This pile/sheet pile is constructed as shown in FIG. 2, in which a base treatment layer 10 is provided on the surface of a steel material 1, and then a polyurethane layer 11 is formed. Specifically, the polyurethane layer 11 is formed by applying a main agent consisting of a polyol and a curing agent consisting of an isocyanate compound using an airless coating machine.

By the way, piles and sheet piles are often used in places where people can see them, such as in port facilities, so in addition to the corrosion resistance that is required as an original property, there is also a demand for aesthetically pleasing materials, such as colored materials. It has become. In response to this demand for aesthetics, a technique is disclosed in Japanese Patent Application Laid-open No. 183838/1983. As shown in FIG. 3, the technique disclosed in Japanese Patent Application Laid-Open No. 63-183838 is to form a base treatment layer 12 on the surface of the steel material 1 by applying a primer or the like, and then
A colored polyurethane elastomer layer 13 is provided, and an acrylic urethane resin layer 14 containing a colored pigment is provided thereon.

[Problem to be solved by the invention] However, the above conventional technology has the following problems.

Polyurethane coatings on piles and sheet piles are generally made black by adding carbon black in addition to antioxidants and ultraviolet absorbers to improve weather resistance, so that discoloration and fading are hardly noticeable, but other colors If carbon black is not added to improve the appearance, discoloration or fading may be severe or chalking may occur, which may impair the appearance. Aromatic isocyanate was used. However, polyurethane coatings cured with aromatic isocyanates tend to yellow regardless of the type of polyol used as the main ingredient, and when colored in colors other than black, such as blue or green, The color fades after just a few months of outdoor exposure, and the initial beauty is lost.To address this problem, it is possible to cure with a so-called non-yellowing type aliphatic isocyanate, but in general, aliphatic Isocyanates are expensive and have low NGO concentrations, so they must be reacted with polyols in high proportions, or the curing reaction is slow, resulting in sagging when applied in thick films, and it takes a long time to form thick films with multiple coats. There are problems such as requiring , and its use is not appropriate.

A technique disclosed in Japanese Unexamined Patent Publication No. 183838/1983 was proposed as a method for solving this problem. However, although the acrylic urethane resin that is the colored layer shows good performance in terms of discoloration and fading due to weather resistance deterioration, it cannot be said to be sufficient in terms of long-term maintenance of flexibility. Due to deterioration of weather resistance, cracks will occur in the layer even if only a few percent of bending strain is applied, resulting in a coating layer that lacks flexibility.The cracks will propagate to the polyurethane coating layer that is integrated with the acrylic urethane resin. However, it becomes unable to function as a covering layer.

This colored urethane-based coating layer may suffer brittle fracture when subjected to external forces such as collisions with floating objects after several years of use, and improvements have been desired.

An object of the present invention is to solve the problems of the above-mentioned conventional techniques and provide a colored coated steel structure that has excellent long-term durability, particularly weather deterioration resistance (resistance to discoloration and fading, and maintenance of flexibility).

[Means for solving the problem] In order to achieve the above object, in the present invention, a base agent containing a difunctional and/or trifunctional polyol as a main component is applied to the surface of a steel structure that has been subjected to a base treatment. and an aromatic isocyanate-based curing agent with an NC010H ratio of 0.
A first cured film is formed by mixing and coating reaction in such a manner that the amount of the fluorine resin becomes 8 to 1.2, and a second cured film made of a fluororesin is formed on this first cured film.

The second cured coating can contain a colored pigment to form a colored coating layer.

Further, as the fluororesin forming the second cured film, a main agent mainly composed of a copolymer of fluoroolefin and vinyl ethyl and a curing agent mainly composed of an aliphatic isocyanate and/or an alicyclic isocyanate are used. It can also be made into a reaction.

It is desirable to use at least three kinds of vinyl ethers that form copolymers with fluoroolefins: those having hydroxyl groups, those having alkyl groups, and those having carboxyl groups.

[Operation No. 10 is a sectional view showing the covering structure of the steel structure according to the present invention. In FIG. 1, reference numeral 1 is a steel material, and a first hardened coating 3 of urethane elastomer is formed on the surface of the steel material 1, which represents piles and sheet piles, and has a surface treatment layer 2. A second cured film 4 is formed by the following methods.

Examples of the urethane elastomer forming the first hardening liquid 11a3 include polyether-based, polyester-based, polyalcohol-based, bossesteramide-based polyols, epoxy-modified or castor oil-modified polyols, or polybutadiene having a terminal OH group. A mixture of a main agent mainly composed of bifunctional and/or trifunctional polyols, such as, and a curing agent mainly composed of aromatic isocyanates, such as tolylene diisocyanate and diphenylmethane diisocyanate, or modified derivatives thereof, is used. When mixing the base resin and curing agent, the OH groups and NGO groups that form urethane bonds have an NGO lo H ratio of 0.8 to 1.
It is desirable to set it to 2.

This first hardened coating is formed to provide the coated structure with comprehensive corrosion protection properties, that is, electrical insulation, mechanical strength, material shielding properties, and long-term durability, but these properties are It varies depending on the NGO10H ratio. N
If the GO10H ratio is less than 0.8, the mechanical strength will be extremely reduced, and if it exceeds 1.2, it will result in a decrease in material shielding properties and lack of flexibility, which is not preferable.Also, the above characteristics can be obtained. Therefore, it is desirable that the thickness of the coating is 2 m1 or more.

The purpose of forming the second hardening liquid llI4 is to give the coated steel structure an aesthetic appearance, but in order to maintain the aesthetic appearance for many years, this coating must have weather resistance, water resistance, heat resistance and In the present invention, where it is necessary to have stain resistance, a fluororesin is used as the material in order to obtain a coating having the above-mentioned properties. There are various fluororesins such as polyvinylidene fluoride, polyvinyl fluoride, polytetrafluoroethylene, polyfluorotrifluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer, all of which have chemical stability and low surface energy properties. Equipped with: However, coating with these thermoplastic fluororesins requires heating, and it is difficult to coat the first cured film without changing its properties.

In response to this problem, the present inventors focused on the fact that by introducing a vinyl ether having a specific functional group into a fluororesin and making it an isocyanate-curing type, it would be possible to form a coating at room temperature, and the above problem would be solved. We have discovered a fluororesin that can be used. That is, the fluororesin used in the present invention is
Taking into account solvent solubility, room temperature curability, adhesion with the first urethane cured film, and compatibility with pigments, at least three types of vinyl ethers, one having a hydroxyl group, one having an alkyl group, and one having a carbosyl group, were used. It is a copolymer of fluoroolefin cured with an aliphatic and/or alicyclic isocyanate.

The coated steel structure of the present invention first has a first layer on the surface of the pile/sheet pile.
A second hardened film is formed on the hardened film, and the function of the second hardened film is to maintain the aesthetic appearance. Therefore, for example, the second hardened film does not necessarily have to be formed on the part that is always underwater or under the sea after pouring, and the second hardened film is not formed on the part of the first hardened film. The color is preferably black so as not to discolor or fade during outdoor storage before pouring.

The second cured film is a mixture of various colored pigments, but in order to hide the first cured film, its thickness must be 3.
0 Jim or more is required, and considering durability and workability, it is desirable to set the thickness to 50 to 200 μm.

As the colored pigment to be mixed into the second cured film, inorganic and organic ones such as titanium oxide, chromium oxide, red lead, red iron oxide, and phthalocyanine blue can be used.

Surface treatment is performed after rust removal treatment such as shot blasting is applied to the steel material. Surface treatment is necessary to maintain long-term adhesion between the steel material and the first hardened coating. In addition to acid-based chemical conversion treatment, epoxy resin-based primer coating, urethane resin-based brimer coating, etc. are applied.

[Example] Examples of the present invention will be described below.

(Example) 3m long U-shaped steel sheet pile (Nippon Kokan, NKSPlla)
Two sheets were prepared, their convex sides were sandblasted, and an epoxy resin primer was applied. The film thickness is approximately 5 after drying.
The thickness was set to 0 μm.

Next, a bifunctional polyol and a trifunctional polyol were mixed in a weight ratio of 1:1, a main resin containing 1% by weight of carbon black, and a curing agent containing a modified monodiphenylmethane diisocyanate as a main component so that the NC010H ratio was 1.0. Coating was performed using a two-component Ares coating machine to form a black urethane elastomer coating layer having a thickness of about 2.5 mm, which would become the first cured coating. After the urethane elastomer coating layer is cured, the hydroxyl value is 5011gKON7g, and the acid value is 5I.
The main ingredients are vinyl ether having OH/g of hydroxyl, carboxyl, and alkyl groups per 1g, and a fluoroolefin copolymer, and there are two types: one containing titanium oxide and cobalt blue as coloring pigments, and the other containing titanium yellow. (a, b) are mixed, a fluororesin paint consisting of a curing agent whose main component is a hexamethylene diisocyanate derivative, and 20% of each of these two types of base ingredients.
Approximately 70% each, painted with a liquid mold construction Ares spray paint machine.
A colored coating layer with a thickness of μm was obtained. In this way, the appearance (
Corrosion-proof coated steel sheet piles having a blue colored layer (Al) and corrosion-proof coated steel sheet piles having a yellow colored layer (BL) were obtained. The test results of these corrosion-proof coated steel sheet piles are shown in the table.

(Comparative Example 1) The coating with black urethane elastomer was carried out in the same manner as in the example, and after curing, a commercially available acrylic urethane colored paint (blue color) was applied as a top coat to a thickness of about 70 μm.
A colored coated steel sheet pile was obtained.

The test results for this anti-corrosion coated steel sheet pile are shown in the table.

(Comparative Example 2) In the same manner as in the example, a primer was applied to the steel sheet pile, and on top of that, the same urethane elastomer as in the example was used, except that phthalocyanine pull and titanium oxide were added as coloring pigments instead of carbon book. Painted using a liquid type Ares spray paint machine. In this way, a steel sheet pile having a blue colored coating with a thickness of about 2.5 mm was obtained. The test results for this anti-corrosion coated steel sheet pile are shown in the table.

A marine exposure test, a weather resistance acceleration test, and an adhesion test were conducted on the anti-corrosion coated steel sheet piles obtained in the above Examples and Comparative Example 1.2.

In the marine exposure test, 2m length of the above steel sheet pile was exposed to the marine environment (tidal zone) for 1 year at J%iL, and the rest was exposed to 150u+ x 7.
A test piece of 0 sn was cut out and an accelerated weather resistance test was conducted. The accelerated weather resistance test was carried out by attaching the sample to a carbon arc sunshine weather meter (black panel temperature 63°C, pure water spray for 12 minutes/2 hours), and testing for 1000 hours, 20 minutes.
The situation after 00 hours of irradiation was compared. In the adhesion test, vertical shear adhesion force was measured using the pull-off method. The test results were as shown in the table.

As is clear from the table, in Examples +a+ and TBL, there was no deterioration in aesthetics due to marine biofouling, the color difference was small, and there was no discoloration or fading due to the action of ultraviolet rays and oxygen, and there were no abnormalities in the bending test. It was observed that flexibility was maintained. Furthermore, the adhesive strength was as strong as that of the single layer coating (Comparative Example 2). On the other hand, in Comparative Example 1.2, the aesthetic appearance deteriorated due to the adhesion of marine organisms, and in Comparative Example 1, cracks were further generated in the bending test, and the flexibility was impaired.

[Effects of the Invention] The present invention is a coated steel structure in which a coating layer made of a fluororesin is formed on the outer surface, and has the following effects.

(The coating layer on the outer surface of No. 11 has a low surface energy similar to that of general hexafluorine-based dark fat, so it is difficult to be contaminated.

In addition, when the outer surface coating layer is a colored layer to which pigments are added, the color hardly changes or fades over many years, and the aesthetic appearance can be maintained for a long period of time.

(2) If the fluororesin that forms the outer coating layer is an isocyanate-curing type, it can be cured at room temperature, making coating construction easier.In addition, it has excellent interlayer adhesion with the urethane elastomer that is the lower coating layer. During construction or use, the outer coating layer does not peel or break due to external force.

[Brief explanation of the drawing]

FIG. 1 shows fRII! according to the present invention! FIGS. 2 and 3 are cross-sectional views showing the structure of the object, and FIGS. 2 and 3 are cross-sectional views showing the covering structure according to the prior art. DESCRIPTION OF SYMBOLS 1... Steel material, 2... Base treatment layer, 3... First hardened film, 4... Second hardened film.

Claims (4)

[Claims] (1) Apply NCO/O to the surface of the steel structure that has been subjected to surface treatment, a main agent containing a difunctional and/or trifunctional polyol as a main component, and a curing agent containing an aromatic isocyanate as a main component.
A first cured film is formed by mixing and coating so that the H ratio is 0.8 to 1.2, and a second cured film made of a fluororesin is formed on this first cured film. coated steel structures. (2) The fluororesin forming the second cured film is made by reacting a main agent mainly composed of a copolymer of fluoroolefin and vinyl ether with a curing agent mainly composed of aliphatic isocyanate and/or alicyclic isocyanate. The coated steel structure according to claim 1, which is a coated steel structure. (3) The coated steel structure according to claim 2, wherein the vinyl ether comprises at least three types: one having a hydroxyl group, one having an alkyl group, and one having a carboxyl group. (4) The coated steel structure according to claim 1, wherein the second hardened coating contains a colored pigment.