JP2534938B2 - Polyurethane coated structure - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating structure formed on the surface of a steel material, particularly a steel structure such as a steel pipe pile, a steel sheet pile, a steel pipe sheet pile, an H-shaped steel, etc., which requires heavy anticorrosion. The present invention provides a colored coating of a polyurethane-based composition that maintains corrosion resistance even when used as a steel, and aesthetically has little discoloration during and after construction of a steel structure.

[0002]

2. Description of the Related Art Steel pipe piles, steel pipe sheet piles, and steel sheet piles (hereinafter abbreviated as piles and sheet piles) are widely used as materials for civil engineering and construction such as marine structures, foundations of structures, and seawall construction. Since the environment in which these piles and sheet piles are used is always in contact with corrosive environments such as water, oxygen, and ultraviolet rays, a heavy anticorrosion coating is required to prevent corrosion of steel for a long period of time.
Moreover, aesthetics is an important theme because it has many uses such as piers, piers, and port facilities that are visible to the public.

Conventionally applied anticorrosion methods for piles and sheet piles include asphalt and coal tar enamel coating,
Although there have been tar epoxy coatings and the like, it is difficult to maintain the heavy anticorrosion property for many years, so in recent years, polyethylene coatings and polyurethane coatings that emphasize heavy anticorrosion property have been developed.

The former is a steel material surface 1 having a pretreatment layer 2 such as a chromate or a thermosetting epoxy plumer as shown in FIG.
Is coated with adhesive polyethylene 5 and polyethylene 6 by a polyethylene sheet pressure bonding method, a powder coating method, and a melt extrusion method. The latter is provided with a pretreatment layer 2 of chromate and urethane type primer as shown in FIG. After that, the polyurethane layer 3 is formed.
As in Japanese Patent Laid-Open No. 3-57234, a single polyurethane layer is formed by coating a main agent made of a polyol and a curing agent made of an isocyanate with a two-liquid mixing type spray coating machine.

[0005]

The polyethylene coating having the structure as shown in FIG. 2 has an advantage of exhibiting excellent corrosion resistance.
However, there is a problem that coating work becomes difficult on the surface of a steel material having a deformed portion, a bent portion such as a sheet pile, or around a site where welding is performed on site.

Further, in order to apply polyethylene coating, it is necessary to raise the temperature of the steel material to 150 to 200 ° C.,
Its main application is limited to mass-produced steel pipe piles and steel sheet piles. A colored coating layer can be formed by adding a coloring pigment to polyethylene, but when it is deteriorated by ultraviolet rays or oxygen, fine cracks are formed on the surface, so the pigment falls off and white with fine cracks appears. There is a drawback in that polyethylene remains on the surface, which is aesthetically unfavorable.

Further, the polyurethane coating is coated as shown in FIG. 3 and is excellent in anticorrosion property.
No. 234 and Japanese Patent Publication No. 63-13826, since an aromatic isocyanate curing agent is used, carbon black is added so that yellowing and chalking easily occur and the discoloration and discoloration of the coating is not noticeable. Black is the mainstream. Coatings with a color other than black, such as green or blue color pigments added at about 0.5%, have faded due to outdoor exposure for several months, losing their initial aesthetic appearance, resulting in different construction periods for different construction periods. However, there is a drawback in that the gloss tone is different and the color tone of the entire structure becomes muddy.

In order to solve this problem, curing with an aliphatic isocyanate, which is a well-known yellowing-resistant isocyanate, is considered to cure, but the curing reaction is slow, so that a thick film is formed. There are drawbacks such as sagging and requiring a long time. Further, since the NCO content is small, the curing agent ratio is high, which leads to an increase in the cost of the coating.

Further, as in Japanese Patent Publication No. 63-13826, a method of applying a coating layer 7 made of a colored acrylic urethane resin on the black polyurethane coating layer 3 in FIG. 4 and JP-A-2-217242. As in the publication, there is a method of applying a coating 8 made of a colored fluororesin on the black polyurethane coating layer 3 of FIG.

The paint for forming the coating of the colored acrylic urethane resin and the fluorine-based resin is a solvent type paint, and as a matter of experience, the dry coating thickness that can be applied once is 30.
It is about 70 μ. The steel used in the steel structure is difficult to handle, so it is preferably 0.3-1.5 mm.
If it is not so large, it will be flawed during handling. Therefore, the above resin has a drawback that it has to be painted many times.

[0011]

According to the present invention, as a result of various studies to solve the problems in the conventional steel coating as described above, by using a proper combination of a weather resistant color pigment and an ultraviolet stabilizer, The present inventors have found that even a polyurethane coating using an aromatic isocyanate that causes yellowing and chalking can reduce discoloration and fading to such an extent that there is no problem in terms of appearance.

That is, in order to obtain a coated steel structure in which the first polyurethane coating layer is first formed on the surface of the steel structure which has been pretreated as required, and the second polyurethane coating layer is further formed. Accordingly, the first polyurethane coating layer comprises a curing agent containing an aromatic isocyanate as a main component, a polyol having two or more hydroxyl groups, and an inorganic filler so that the NCO / OH ratio becomes 0.9 to 1.2. (A) aromatic isocyanate and / or so that the second polyurethane coating layer has a NCO / OH ratio of 0.9 to 1.2. A curing agent composed of an aliphatic isocyanate, (b) a polyol having two or more hydroxyl groups, (c) an inorganic filler (excluding color pigments), and (d) 8% by weight or more of a weather resistant inorganic in terms of a cured coating film. A color pigment, and (e A coating steel structure, characterized in that the base resin containing 1.5 wt% or more UV stabilizers in the cured coating film in terms of mixing is obtained by reacting.

The present invention will be specifically described below.
FIG. 1 is an enlarged cross-sectional view showing a coating structure of a steel material. If necessary, the surface of the steel material 1 to which the pretreatment layer 2 has been applied is coated with the polyurethane composition 3 of the first layer, and the colored polyurethane composition 4 of the second layer is coated thereon. The steel material 1 is an offshore structure, a steel pipe pile, a steel sheet pile, a steel pipe sheet pile, an H-shaped steel, etc., which is a civil engineering material such as a foundation revetment work.

As the aromatic isocyanate forming the first polyurethane layer 3, tolylene diisocyanate (TDI), crude diphenylmethane diisocyanate (crude MDI), liquid diphenylmethane diisocyanate (liquid MDI), tolyl phenyl methane triisocyanate, and the like. It is a modified derivative, and the main component of the curing agent may be selected from these.

Further, in order to form the second polyurethane layer 4, besides the above-mentioned aromatic isocyanate, an aliphatic isocyanate can be used. Aliphatic isocyanates also include alicyclic isocyanates, such as hexamethylene diisocyanate, isophorodiisocyanate, xylene diisocyanate, methylene bis (cyclohexyl isocyanate), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate and derivatives thereof. A curing agent may be selected from these aromatic isocyanates and aliphatic isocyanates.

Polyols having two or more hydroxyl groups which react with these isocyanates to form the coatings of the first layer and the second layer include terminal OH polybutadiene, polyoxyalkylene polyol, polytetramethylene ether glycol and castor oil. And polyols such as its derivatives, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexanediol,
Bisphenol A, trimethylolpropane, bis (2
-Hydroxypropyl) aniline and alkylene oxide adducts thereof. Further, a polyamine having two or more amino groups such as diaminodiphenylmethane, methylenebis (octochloroaniline, phenylenediamine, tolylenediamine, ethylenediamine) may be used in part.

The inorganic filler used in the present invention is a colored pigment, and its kind and addition amount are not limited. The inorganic filler is generally called an extender pigment and includes silicon oxide, alumina, aluminum silicate, magnesium silicate, calcium carbonate, zinc oxide and the like.

A feature of the present invention is to add a weather resistant inorganic colorant to the polyol forming the second layer so that the cured coating film contains 8% by weight or more, preferably 10% by weight or more,
In addition, the light stabilizer is added so as to be contained in the cured coating film in an amount of 1.5% by weight or more, preferably 2% by weight or more. The inventors of the present invention have made the present invention by discovering the following facts by earnestly studying the color pigments / types and addition amounts, UV stabilizers, etc. by an accelerated test using a sunshine weather meter and an outdoor exposure test.

Whether a polyurethane coating cured with an aliphatic isocyanate that does not easily turn yellow or an aromatic isocyanate that tends to yellow easily loses its luster due to sunlight and causes chalking. Particularly, when the polyurethane coating using a curing agent that tends to be yellow contains 1.5% by weight or more of an ultraviolet stabilizer, yellowing chalking is reduced even if a pigment is present. When the polyurethane coating contains 8% by weight or more of the weather-resistant inorganic coloring pigment, the change in color difference after the gloss disappears is small, and the change in color difference can be suppressed to 5 or less so that the appearance is not noticed. A weather-resistant organic color pigment has a smaller specific gravity than an inorganic pigment, and therefore, when it is contained in the polyurethane coating in an amount of 2% by weight or more, the change in color difference similarly becomes 5 or less.

The weather-resistant inorganic coloring pigment used in the present invention includes red iron oxide (valve pattern), yellow iron oxide (yellow walker), chrome green (Cr ₂ O ₃ ) and the like, as well as calcined pigments and the like. For example calcined pigment brown (ZnO-Fe ₂ O
_{3, ZnO-Fe 2 O 3} -Cr 2 O 3), titanium yellow _{(TiO 2 -Sb 2 O 3 -NiO} ), calcined pigment green (TiO ₂ -CoO-ZnO), cobalt blue (CoO-Al ₂ O ₃ ) Etc.

The weather resistant organic color pigments used in the present invention include copper phthalocyanine green, copper phthalocyanine blue,
Quinacridone, such as isoindolinone and slene.
The UV stabilizer used in the present invention refers to a mixture of a benzophenone-based, benzotriazole-based, benzoate-based UV absorber and a hindered amine-based light stabilizer. In particular, for polyurethane, a benzotriazole-based ultraviolet absorber (TINUVIN 171 T manufactured by Ciba-Gigi Japan Ltd.
INUVIN1130, CGL-384) and a hindered amine light stabilizer (TINUVIN2 manufactured by Nippon Ciba Kaigi)
92. A mixture of CGL-123 and Sankyo LS-292) is effective.

Examples of the pretreatment applied to the steel material include phosphoric acid-based chemical conversion treatment, chromic acid-based chemical conversion treatment, silane compound treatment, various epoxy-based primer treatments, and urethane-based primer treatments, in order to maintain anticorrosion performance for a long period of time. Is necessary for.

As described above, the present invention provides a polyurethane-based two-layer coating having a different composition. More specifically, in order to ensure the anticorrosion performance, the first polyurethane layer is applied to ensure a good appearance. A two-layer coating having a second polyurethane layer containing a weather-resistant inorganic color pigment and an ultraviolet stabilizer. The thickness of each layer is 1.5 to 3.0 mm for the first layer and 0.3 for the second layer in consideration of the material cost and coating workability.
It is desired to be ~ 1.5 mm. 2.0 as a whole
When the thickness is at least mm, a coating structure having excellent mechanical properties such as impact resistance can be obtained.

[0024]

EXAMPLES The present invention will be described below with reference to examples. Examples and Comparative Examples A convex surface of a U-shaped steel sheet pile (FSP-III type manufactured by Nippon Steel) was sandblasted, and a urethane primer was applied so that the film thickness after drying was 50 μm. Then, the main agent having the composition shown in Table 1 and a curing agent which is a crude MDI are mixed in a two-liquid type spray coating machine in a volume ratio of 3.4: 1 (NCO / OH = 1.05).
Was applied to form a first polyurethane coating layer having a thickness of 2.0 mm.

[0025]

[Table 1]

Then, after 30 minutes, 0.5 m of the main agent having the composition shown in Table 2 and the curing agent were applied using a two-component mixed spray coating machine.
m second polyurethane coating layer was formed. Sample number 1
10 to 10 are examples, and sample numbers 11 to 15 are comparative examples.

After coating these polyurethane 2-layer-coated steel sheet piles for 7 days after coating, a test piece was cut out, and the test piece was attached to a carbon arc sunshine weather meter for 250 hours, 1000 hours, 2000 hours, 300 hours.
After irradiation for 0 hour, the degree of discoloration and fading was determined as a color difference using a spectrophotometer 250 hours after the wesometer as a reference. In addition, an adhesion test by an elcometer atheation tester, an impact test by ASTMG-14, and an insulation resistance measurement by DIN 30670 were carried out. Table 3 shows the above inspection and test results.

It is clear that the examples have less change in color difference than the comparative examples. Even when visually observed, the examples showed little discoloration. Also, adhesive strength (initial value is 100 kg / cm
² ), insulation resistance (initial value> 10 ¹¹ Ω-m ² ) and impact resistance (initial value> kg-m) were unchanged and good.

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

EFFECTS OF THE INVENTION The polyurethane resin of the present invention contains a specific weather-resistant colored pigment in an amount of 8% by weight, which is unprecedented, and an ultraviolet stabilizer is used in an amount of 1.5% by weight or more to form a colored polyurethane coating layer on the outer surface. A urethane-based two-layer coating structure is provided. According to the present invention, it is possible to obtain a urethane coating of a color other than black, which exhibits almost no discoloration and fading and is excellent in impact resistance while making the best use of the anticorrosion property of the urethane coating, which is extremely significant industrially.

[Brief description of drawings]

1 is a partial cross-sectional view of a coated steel structure constructed in accordance with the present invention.

FIG. 2 is a partial cross-sectional view of a conventional coated steel structure.

FIG. 3 is a partial cross-sectional view of a conventional coated steel structure.

FIG. 4 is a partial cross-sectional view of a conventional coated steel structure.

FIG. 5 is a partial cross-sectional view of a conventional coated steel structure.

[Explanation of symbols]

 1 Steel Material 2 Primer Layer 3 First Polyurethane Coating Layer 4 Second Polyurethane Coating Layer 5 Adhesive Polyethylene 6 Polyethylene 7 Acrylic Urethane 8 Fluorine Resin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B32B 27/40 B32B 27/40

Claims (2)

(57) [Claims] 1. A coated steel structure in which a first polyurethane coating layer is first formed on the surface of a steel structure, and a second polyurethane coating layer is further formed on the surface of the steel structure.
The polyurethane coating layer has a NCO / OH ratio of 0.9-
The second polyurethane coating is prepared by mixing a curing agent containing an aromatic isocyanate as a main component to a ratio of 1.2, a polyol having two or more hydroxyl groups, and a main agent composed of an inorganic filler, and reacting them. The layer has an NCO / OH ratio of 0.
(A) a curing agent composed of an aromatic isocyanate and / or an aliphatic isocyanate so as to be 9 to 1.2, (b) a polyol having two or more hydroxyl groups, and (c) an inorganic filler (excluding color pigments). And (d) 8 in terms of cured coating
A coated steel obtained by mixing and reacting at least wt% of a weather-resistant inorganic color pigment and (e) a main agent containing at least 1.5 wt% of a UV stabilizer in terms of a cured coating film, and reacting them. Structure. 2. In forming the second polyurethane coating layer, 2% instead of 8% by weight or more of the weather resistant inorganic coloring pigment is used.
2. The coated steel structure according to claim 1, wherein the weather-resistant organic coloring pigment is used in an amount of at least wt%.