JPH03293427A - Angular steel tubular pile with heavy rustproof covering and its manufacture - Google Patents

Abstract

PURPOSE:To greatly raise water-resistant adhesive between a color paint film and a heavy rustproof covering by a method in which a polyolefin-covered angular steel tubular pile is treated by corona discharge and coated with a urethane primer and a fluoro resin paint. CONSTITUTION:A polyolefin-covered angular steel tube 3, having a polyolefin film 2 containing 0.05-5.0wt.% antioxidant and having a thickness of 1-10mm on its outermost layer, is treated by corona discharge using 4 roll electrodes 6 turning continuously. The tube 3 so treated is coated with a urethane primer or a modified polyolefin primer 16 and then with a color paint 4 such as various color fluoro resin paints, having a thickness of 10-100mum. The steel tube 1 so formed is free of blistering in the fluoro resin paint film and has sufficiently high adhesion between the fluoro resin paint film and the low-density polyethylene covering. The water-resistant adhesion between the color paint film and the heavy rust-proof covering can thus be greatly enhanced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a square steel pipe pile with a heavy anti-corrosion coating used for steel structures used in the ocean, rivers, ports, etc. This invention relates to a heavy corrosion-resistant coated rectangular steel pipe pile that has a colored coating film in various colors with excellent weather resistance, has an excellent appearance, and has excellent water-resistant adhesion between the colored coating film and the heavy-duty anticorrosive coating, and a method for manufacturing the same. .

(Prior Art) Conventional polyolefin-coated steel materials, such as polyolefin-coated steel pipe piles, are coated with black polyethylene, which has excellent corrosion resistance. However, due to the recent increase in market needs for beautiful landscapes of steel structures such as urban landscapes, rivers, and ports, steel piles have been made into square shapes and colored in various colors to harmonize with the environment and are weather resistant. The development of heavy-duty corrosion-resistant coated square steel pipe piles is desired. To meet such needs, for example, as shown in FIG. 3, a urethane primer layer 14 and a fluororesin layer containing a colored pigment are added to the surface of a polyolefin-coated steel material having a polyolefin coating layer 13 subjected to flame treatment on the outer surface. There is a heavily corrosion-protected N steel material that is characterized by sequentially laminating layers of No. 15.

(Problems to be Solved by the Invention) However, in the conventional heavy anti-corrosion coated steel material shown in FIG. There is a problem in that the adhesive force between the fluororesin layer 15 containing the color pigment gradually decreases and blisters occur in the fluororesin layer 15 containing the colored pigment.

(Means for Solving the Problems) As a result of intensive studies to solve the above-mentioned problems, the present inventors added 0.05 to 5% of an antioxidant to the outermost layer of the outer surface of the square steel pipe.
0% by weight and whose outer surface is corona discharge treated with polyolefin, or after applying a urethane primer or modified polyolefin primer to the outer surface, fluorine-based paints of various colors, acrylic - The inventors have discovered that the above-mentioned problems can be solved by laminating colored paint films such as silicone paints and acrylic-urethane paints, leading to the present invention.

That is, as shown in Figure 'fS1, the present invention provides an outer surface of a square steel pipe 1 having a polyolefin 2 containing 0.05 to 5.0% by weight of an antioxidant in the outermost layer of the outer surface and having the outer surface treated with a corona discharge. A heavy anti-corrosion coated square steel pipe pile characterized in that a colored paint coating 4 of various colors such as fluorine paint, acrylic-silicon paint, acrylic-urethane paint, etc. is laminated on the outer surface of the polyolefin-coated square steel pipe pile; and , as shown in Figure 2, the antioxidant in the outermost layer of the outer surface of the square steel pipe is 0.05%.
A rectangular steel pipe pile 3 whose outer surface is coated with polyolefin having a polyolefin content of ~50% by weight is transferred and conveyed on a table roller, and each of the four sides of the outer surface is continuously rotated 4.
Heavy corrosion-resistant coated square steel pipe piles are coated with colored paints such as fluorine paints, acrylic-silicon paints, acrylic-urethane paints, etc. in various colors after corona discharge treatment with a roll-type electrode 6. As shown in FIG.
A urethane primer or a modified polyolefin primer 16, a fluorine-based paint in various colors, an acrylic-silicon paint, etc. are applied to the outer surface of the square steel pipe pile coated with an external polyolefin, which has a polyolefin 2 containing 5 to 50% by weight and whose outer surface has been subjected to a corona discharge treatment. , a square steel pipe pile with a heavy anti-corrosion coating characterized by sequentially laminating colored paint coatings 4 such as acrylic-urethane paint, and as shown in FIG. A rectangular steel pipe pile 3 coated with polyolefin on the outer surface having a polyolefin content of 05 to 580% by weight is corona discharged using four roll-type electrodes 6 that continuously rotate each of the four sides of the outer surface while being transferred and conveyed on a table roller 5. After treatment, a urethane primer or a modified polyolefin primer is applied, and then colored paints such as fluorine paints, acrylic-silicon paints, acrylic-urethane paints, etc. in various colors are applied. This is a method for manufacturing piles.

Hereinafter, the present invention will be explained in detail.

The square steel tube used in the present invention is a square tube made of alloy steel such as carbon steel and stainless steel. In addition, for the purpose of improving the corrosion resistance of square steel pipe piles, the outer and inner surfaces of square steel pipes are plated with zinc, aluminum, nickel, etc., alloy plating such as zinc-iron, zinc-aluminum, zinc-nickel-cobalt, etc. It is also possible to use alloy plating coated with dispersion plating in which inorganic fine particles such as silica or titanium oxide are dispersed.

For square steel pipe piles coated with external polyolefin, the outside surface of the square steel pipe is blasted using grid blasting, sandblasting, etc. to remove rust, and then the base is treated with a chromate treatment agent and epoxy primer, and then the polyolefin is modified with maleic anhydride, etc. modified polyolefin adhesive? ! ! After covering, a polyolefin-coated rectangular steel pipe pile can be used, but from the point of view of the present invention, it is sufficient that the outermost layer of the coated rectangular steel pipe pile has polyolefin, and conventionally known chromate is used for surface treatment. It is also possible to use square steel pipe piles coated with polyolefin on the outside that have been treated with a treatment agent, epoxy brimer phosphate treatment, silane coupling agent, etc. alone, or a combination of these surface treatments.

The polyolefin coated on the outermost layer of the square steel pipe pile covered with external polyolefin contains an antioxidant of 0.05 to 5.0.
Polyolefins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, and ethylene-propylene block or random copolymers, polyamide-propylene block or random copolymers, containing within the range of weight% Polyolefin copolymers such as the following can be used. If the antioxidant content of the polyolefin coating is less than 0.05% by weight or more than 5.0% by weight, the polyolefin coating and fluorine-based, acrylic-silicon-based, or acrylic-urethane-based paints of various colors may be used after a marine practical test. The adhesive force between the paint film and the paint film decreases, and blisters occur in the paint film.

Next, the corona discharge treatment applied to the polyolefin-coated outer surface of the polyolefin-coated square steel pipe pile will be described. For corona discharge treatment, colored paints of various colors can be applied to the surface of the polyolefin coating after discharge treatment without repelling and cured to form a coating film, and the key is to apply discharge treatment uniformly to the outer surface of the polyolefin coating. is necessary. For this purpose, a method using a roll-type electrode coated with a silicone resin that rotates continuously can be used. If the outer surface of the polyolefin coating is not uniformly treated with corona discharge, the adhesion between the polyolefin coating and the colored paint coating of various colors will decrease after the marine practical test, and blisters will occur in the paint coating. Regarding the degree of corona discharge treatment, for example, in the case of low-density polyethylene, high-density polyethylene, or ethylene propylene block copolymer coating, corona discharge [ffi The "wetting index (surface tension)" after treatment is 36 dyn.
It is desirable to carry out the discharge treatment so that the thickness is equal to or higher than /cm.

If the "wetting index (surface tension)" is 36 dyn/cm and the groove is not grooved, the adhesion between the polyolefin coating and the colored paint film of various colors decreases after the marine practical use test, and the colored paint film Blisters occur.

Next, the urethane primer and modified polyolefin primer to be laminated on the surface of the corona discharge-treated polyolefin-coated square steel pipe pile will be explained. The urethane primer used in the present invention has a molecular weight of 400 to 20 from the viewpoint of water resistance.
A urethane prepolymer containing a terminal isocyanate group obtained by reacting a polyol compound having 00 and two or more hydroxyl groups in the molecule with a polyisocyanate compound having an isocyanate group in the molecule is desirable. In addition, from the viewpoint of water resistance, the modified polyolefin primer is preferably a liquid primer made by diluting with a solvent a modified polyolefin whose main component is a polyolefin modified with an acid anhydride such as ethylene-vinyl acetate copolymer or maleic anhydride. As a general commercial product, for example, Thermotack E manufactured by Chugoku Paint Co., Ltd.
200, Thermotac E300, Thermotac E500
etc. can be used.

Next, the colored paint to be laminated on the outer surface of the polyolefin-coated square steel pipe pile that has been subjected to corona discharge treatment will be explained. From the viewpoint of weather resistance, the paints include commercially available acrylic-urethane paints such as NY Porin in various colors manufactured by Shinto Paint Co., Ltd., Silica Lac in various colors manufactured by Chugoku Paint Co., Ltd., and silica lacquer in various colors manufactured by Shinto Paint Co., Ltd. General commercially available acrylics such as Ceraforte in various colors.
It is desirable to use commercially available fluorocarbon paints such as silicone paints, Duflon in various colors manufactured by Nippon Paint Co., Ltd., and Syntoflon in various colors manufactured by Shinto Paint Co., Ltd.

Next, a method for manufacturing a square steel pipe pile with heavy corrosion protection coating according to the present invention will be explained.

As shown in FIG. 2, a polyolefin-coated square steel pipe pile having polyolefin 2 containing 0.05 to 5.0% by weight of an antioxidant on the outermost layer of the outer surface of the square steel pipe is transferred on a table roller while the outer surface of the square steel pipe pile is being transferred on a table roller. After corona discharge treatment is performed on each of the four sides of the plate using four roll-type electrodes 6 that rotate continuously,
Alternatively, after the treatment, a urethane primer or modified polyolefin is applied, and then colored paints such as fluorine paints, acrylic-silicon paints, acrylic-urethane paints, etc. in various colors are applied to obtain heavy corrosion-resistant coated square steel pipe piles according to the present invention. . Regarding the degree of corona discharge 38 embedding on the polyolefin coated surface, for example, in the case of low density polyethylene, high density polyethylene, and ethylene propylene block copolymer coatings, the "wetting test method for polyethylene and polypropylene films" specified in JIS 6768 is used. The "wetting index (surface tension)" after corona discharge treatment is 36 dyn.
/cm or more. In Figure 2, a roll-type electronic 8i coated with silicone resin that rotates! However, if it is difficult to achieve uniform corona discharge treatment due to the transportation speed of square steel pipe piles, five or more roll-type electrodes 6 may be arranged to measure the wettability index (surface tension). )" is 36
It should be 6 yn/cm or more and uniform. The roll-type electrode 6 that is driven and rotated is effective in making the corona discharge treatment uniform.

(Function of the invention) As shown in FIGS. 1 and 4, the heavy corrosion-proof coated square steel pipe pile of the present invention has a square steel pipe 1 coated with 0 to 0% antioxidant on the outermost layer of the outer surface.
5 to 5.0% by weight of polyolefin 2 and whose outer surface has been subjected to corona discharge treatment.The outer surface of an outer polyolefin-coated square steel pipe pile is coated with urethane primer or modified polyolefin primer 16, and then various types of primers are applied. Colored paint film 4 such as colored fluorine paint, acrylic-silicon paint, acrylic-urethane paint, etc.
This is a square steel pipe pile with heavy corrosion protection coating that is laminated in sequence. Furthermore, in the method for producing a square steel pipe pile with a heavy anti-corrosion coating of the present invention, as shown in FIG.
After corona discharge treatment is performed on the square steel pipe pile 3 coated with polyolefin on the outer surface having a polyolefin containing % by weight using four roll-type electrodes 6 that continuously rotate each of the four sides of the outer surface while being transferred on a table roller, or After the corona group' has been treated, a urethane primer or a modified polyolefin primer 16 is applied, and colored paints such as fluorine paints, acrylic-silicon paints, acrylic-urethane paints, etc. in various colors are then applied.

In addition, the Kuninaka polyolefin 2 has a film thickness of 1 to 10 mm, and the colored paint film 4 has a film thickness of 1 to 10 mm, such as fluorine paints of various colors, acrylic-silicon paints, acrylic-urethane paints, etc.
Good results can be obtained with a film thickness of 00μ.

(Example) Example 1 Outer diameter 200 mm x 200 mm, wall thickness 5.8 mm
While transporting a square steel pipe with a length of 5500 mm on a table roller, the outer surface was subjected to grid blasting to remove rust, and a chromate treatment agent was applied so that the total amount of chromium deposited was 350 mg/m2 as shown in Figure 1. The chromate treatment agent film 7 is coated by baking, and the epoxy primer is spray-coated to a film thickness of 50μ, heated and cured to coat the epoxy primer coating 8, and then the powdered maleic anhydride-modified linear A low-density polyethylene adhesive is electrostatically applied to a film thickness of 200μ, heated and melted to cover the modified polyolefin adhesive 9, and a molten black low-density polyethylene sheet is extruded from a square die and coated on the surface. Then, a square steel pipe pile with external low-density polyethylene coating was obtained. The antioxidant content in the low density polyethylene coating is 0.3
In weight%, the film thickness of low density polyethylene coated N2 is 2.5m.
It was m. The outer surface of the square steel pipe pile coated with low-density polyethylene obtained as described above was transferred by table rollers 5 (conveying speed: 2.75 m/win), as shown in Fig. 2.
After applying corona discharge treatment to each of the four surfaces of the outer surface using four roll-type electrodes 6 (silicone resin coating thickness: 10 mm) that rotate electrically (peripheral speed: 2.75 m/win) while The colored paint type M4 was coated by spray painting a type paint (Duflon manufactured by Nippon Paint Co., Ltd., color tone Marcel value: IOB 5/10 (blue)) to a film thickness of 30μ, and the heavy corrosion protection coating angle according to the present invention was applied. A steel pipe pile ■ was obtained. The "wetting index (surface tension)" of the low-density polyethylene coated surface after corona discharge treatment is 55 dyn/cm
Met.

As a comparative material, the outer surface of the square steel pipe pile coated with external low-density polyethylene obtained as described above was heated with a propane burner for 5 minutes to raise the surface temperature to 70 to 80°C, and a urethane primer (urethane polymer 50 % by weight, toluene 50% by weight), and then apply 5 to 10μ of fluororesin paint (60% by weight of fluororesin, 26% by weight of pigment, 14% by weight of isocyanate, Marsene value of color tone: IOB).
5/10) was coated with 30 μm of paint to obtain a comparatively heavy corrosion-resistant coated square steel pipe pile ■.

Comparison of the heavy anti-corrosion coated square steel pipe pile of the present invention obtained as described above The heavy anti-corrosion coated square steel pipe pile ■ was subjected to a three-year marine practical test, and after the test, fluorine-based paint coating or fluorine resin In addition to observing the presence or absence of blisters in the paint coating, an adhesion test between these colored coatings and the low-density polyethylene coating [substrate test: according to JIS 5400, the adhesion was evaluated on a scale of 0 to 10 (10 (10 points)] was carried out. The test results are shown in Table 1.

As is clear from the results in Table 1, the heavy corrosion-resistant coated rectangular steel pipe pile according to the present invention shows a higher level of fluorine-based paint coating even after a three-year marine practical use test compared to the comparative heavy-duty corrosion-proof coated square steel pipe pile. No blistering occurs, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high, and the water-resistant adhesion between the colored coating and the heavy-duty anti-corrosion coating is extremely excellent.

Example 2 The content of antioxidant in the low-density polyethylene coating of the external low-density polyethylene-coated square steel pipe pile used for manufacturing the heavy corrosion-proof coated square steel pipe pile of the present invention in Example 1 was 0.05 to 5% by weight.
Heavy-duty anti-corrosion coated square steel pipe piles (1) to (2) according to the present invention were manufactured in the same manner as in Example 1, with changes made within the following ranges. As a comparative example, the content of the antioxidant was 0.01 using the same method as in Example 1.
Comparative heavy corrosion protection coated rectangular steel pipe pile (2) with a content of 6% by weight of the antioxidant and comparative heavy corrosion protection coated square steel pipe pile (2) with an antioxidant content of 6% by weight were manufactured. Comparison of the heavy-duty anti-corrosion coated square steel pipe pile obtained as described above The heavy-duty anti-corrosion coated square steel pipe pile was subjected to the same 3-year ocean service test as in Example 1, and after the test was completed, the fluorine-based paint coating or fluoro-resin coating IIEIM was applied. In addition to observing the presence or absence of blisters, an adhesion test was conducted between these colored coatings and the low-density polyethylene coating [base grain test JIS 54].
00, the adhesive strength is expressed as a rating from 0 to 1o (out of 10 points)]. The test results are shown in Table 1.

As is clear from the results in Table 1, if the antioxidant content in the polyolefin coating of the heavy corrosion protection coated square steel pipe pile according to the present invention is in the range of 0.05 to 5% by weight, Fluorine thread paint even after use test! ! ! No blistering occurs in the film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high. However, when the content of the antioxidant is 0.01% by weight and 6% by weight,
Blisters occur in the fluorine-based paint film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating also decreases.

Example 3 In the same manner as in Example 1, the degree of corona discharge treatment applied to the outer low-density polyethylene coating was determined by "wetting index (surface tension)".
Heavy duty corrosion-proof coated square steel pipe piles 1 to 2 according to the present invention were manufactured by changing the corrosion resistance to 36 to 70 dyn/cm in terms of . As a comparative example, a comparative heavy-duty anti-corrosion coated square steel pipe pile (2) was manufactured using the same method as in Example 1, in which the degree of corona discharge treatment was 346 yn/cm in terms of "wetting index (surface tension)". Comparison of the heavy anti-corrosion coated rectangular steel pipe pile obtained as described above The heavy anti-corrosion coated rectangular steel pipe pile was subjected to the same 3-year marine service test as in Example 1, and after the test, fluorine-based paint coating or fluororesin coating was applied. In addition to observing the presence or absence of blisters in the paint coatings, we conducted an adhesion test between these colored coatings and the low-density polyethylene coating [
Base test: According to JIS 5400, adhesive strength is 0~
A score of 10 (out of 10) was given. The test results are shown in Table 1.

As is clear from the results in Table 1, when the degree of corona discharge treatment used in the present invention is 36 to 70 dyn/cm in terms of "wetting index (surface tension)", fluorine-containing There is no occurrence of blisters in the paint film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high. However, the "wetting index (surface tension)" is 3
At 4 dyn/cm, blisters occur in the fluorine-based paint film, and the adhesive force between the fluorine-based paint film and the low-density polyethylene coating also decreases.

Example 4 In the same manner as in Example 1, the square steel pipe pile covered with low-density polyethylene on the outside was replaced with a square steel pipe pile coated on the outside with high-density polyethylene, and the square steel pipe pile covered with ethylene-propylene block copolymer on the outside were used to obtain heavy corrosion protection according to the present invention. Covered square steel pipe piles ■ to ■ were manufactured.

Comparison of the heavy anti-corrosion coated square steel pipe piles obtained as described above The heavy anti-corrosion coated square steel pipe piles were subjected to the same 3-year marine service test as in Example 1, and after the test was completed, the piles were coated with fluorine-based paint or fluororesin paint. In addition to observing the presence or absence of blisters on the film, an adhesion test was conducted between these colored coatings and the low-density polyethylene coating [base test: according to JIS K5400, the adhesion was rated from 0 to 10 (out of 10). I did the display in . The test results are shown in Table 1.

As is clear from the results in Table 1, the heavy corrosion protection coated rectangular steel pipe pile according to the present invention retains fluorocarbons even after three years of actual marine use tests, regardless of the type of polyolefin in the external polyolefin coated square steel pipe pile used in its manufacture. There is no occurrence of blisters in the fluorine-based paint film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high.

Example 5 A fluorine-based paint (Duflon manufactured by Nippon Paint Co., Ltd., Marcel value of color tone: 1085/10) was applied in the same manner as in Example 1.
(Blue)) was replaced with the acrylic-silicon and acrylic-urethane colored paints shown in Table 3 to produce heavy corrosion-resistant coated square steel pipe piles 1 to 0 according to the present invention. Comparison of the heavy-duty anti-corrosion coated square steel pipe pile obtained as described above The heavy-duty anti-corrosion coated square steel pipe pile was subjected to the same 3-year marine service test as in Example 1, and after the test was completed, it was coated with a fluorine coating $4 coating or a fluorine resin coating. In addition to observing the presence or absence of blisters in the paint coating, the adhesion test between these colored coatings and the low-density polyethylene coating [substrate test/according to JIS K5400, the adhesion strength was rated from 0 to 10 (out of 10). ) was performed. The test results are shown in Table 1.

As is clear from the results in Table 1, even when acrylic-silicon-based or acrylic-urethane-based colored paints were used, there was no occurrence of blisters in the colored paint film even after three years of actual marine usage tests. Moreover, the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high.

Example 6 Outer diameter 200 mm x 200 mm, wall thickness 5.8 mm
While transporting a square steel pipe with a length of 5,500 mm on a table roller, the outer surface was subjected to grid blasting to remove rust, and as shown in Figure 4, the total chromium adhesion amount was 350 mg/m'' with a chromate treatment agent. The chromate treatment agent solution 11!7 is coated by coating and baking, and the epoxy primer is spray-coated to a film thickness of 50 μm and cured by heating to coat the epoxy primer coating 8. A maleic acid-modified straight-sided low-density polyethylene adhesive is electrostatically coated to a film thickness of 200μ, heated and melted to coat the modified polyolefin adhesive 9, and the surface is coated with molten black-density polyethylene from a square die. The sheet was extruded and coated to obtain a square steel pipe pile with an external low-density polyethylene coating.The content of antioxidant in the low-density polyethylene coating was 0.
, 3% by weight, and the film thickness of the low-density polyethylene coating 2 was 2°5 ma+.The square steel pipe pile coated with external low-density polyethylene obtained in the above manner was rolled with a table roller 5 as shown in FIG. (conveying speed: 2.75m/mi
n) Each of the four sides of the outer surface was subjected to corona discharge treatment using four roll-type electrodes 6 (silicon resin coating thickness: 10 mm) that rotated electrically (peripheral speed: 2.75 m/win) while , modified polyolefin primer (
``Thermotac E300J'' made by Chugoku Paint Co., Ltd. 5 to 1
0μ coating, and then fluorine-based paint (Duflon manufactured by Nippon Paint Co., Ltd., Marcel value of color tone: IOB 5710)
(blue)) was spray-painted to a film thickness of 30 μm to cover the colored paint film 4 to obtain a heavy anti-corrosion coated square steel pipe pile [phase] according to the present invention. The "wetting index (surface tension)" of the low-density polyethylene coated surface after corona discharge treatment is 55 dy
n/cm.

As a comparative material, the outer surface of the square steel pipe pile coated with external low-density polyethylene obtained as described above was heated with a propane burner for 5 minutes to raise the surface temperature to 70 to 80°C, and a urethane primer (urethane polymer 50 % by weight, toluene 50% by weight), and then apply 5 to 10μ of fluororesin paint (60% by weight of fluororesin, 26% by weight of pigment, 14% by weight of isocyanate, Marcel value of color tone: IOB).
5/10) was coated with 30 μm of paint to obtain a comparatively heavy corrosion-resistant coated square steel pipe pile ■.

The heavy-duty anti-corrosion coated square steel pipe pile [phase] of the present invention obtained as described above and the comparative heavy-duty anti-corrosion coated square steel pipe pile ■ were subjected to a three-year marine practical use test. In addition to observing the presence or absence of blisters in the fluororesin paint coating, an adhesion test between these colored coatings and the low-density polyethylene coating [base test: JIS K540
0, the adhesive strength was evaluated on a scale of 0 to 10 (out of 10 points). The test results are shown in Table 2.

As is clear from the results in Table 2, the heavy corrosion-resistant coated rectangular steel pipe pile according to the present invention shows a higher level of fluorine-based paint coating even after three years of marine practical use tests than the comparative heavy-duty corrosion-proof coated square steel pipe pile. No blistering occurs, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high, and the water-resistant adhesion between the colored coating and the heavy anti-corrosion coating is extremely excellent.

Example 7 The content of antioxidant in the low-density polyethylene coating of the external low-density polyethylene-coated square steel pipe pile used for manufacturing the heavy corrosion-proof coated square steel pipe pile of the present invention in Example 6 was set in the range of 0.05 to 5% by weight. Instead, heavy anti-corrosion coated square steel pipe piles 1 to 0 according to the present invention were manufactured in the same manner as in Example 6. As a comparative example, the same method as in Example 6 was carried out to prepare a comparative heavy duty coated square steel pipe pile ■ in which the content of the antioxidant was 0.01% by weight and a comparison in which the content of the antioxidant was 6% by weight. Heavy-duty anti-corrosion coated square steel pipe pile■
was manufactured. Comparison of the heavy anti-corrosion coated square steel pipe piles obtained as described above The heavy anti-corrosion coated square steel pipe piles were subjected to the same 3-year ocean service test as in Example 6, and after the test was completed, the piles were coated with fluorine-based paint or fluororesin paint. In addition to observing the presence or absence of blisters on the film, an adhesion test between these colored coating films and a low-density polyethylene coating [baseline test: JIS K540
0, the adhesive strength was expressed on a scale of 0 to 10 (out of 10). The test results are shown in Table 12.

As is clear from the results in Table 2, if the antioxidant content in the polyolefin coating of the heavy corrosion protection coated square steel pipe pile according to the present invention is in the range of 0.05 to 5% by weight, it will last for three years in the ocean. Even after practical tests, no blistering occurred in the fluorine-based paint film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating was sufficiently high. However, when the antioxidant content is 0.01% by weight and 6% by weight, blisters occur in the fluorine-based paint film, and the fluorine-based paint film and low-density polyethylene coating The adhesive strength between them also decreases.

Example 8 In the same manner as in Example 6, the degree of corona discharge treatment applied to the outer low-density polyethylene coating was determined by "wetting index (surface tension)".
36 to 70 dyn/ca+ in terms of 36 to 70 dyn/ca+, and a heavy corrosion-proof coated square steel pipe pile @~0 according to the present invention was manufactured. As a comparative example, the degree of the corona discharge treatment was calculated as 346 yn/cm in terms of "wetting index (surface tension)" using the same method as in Example 6.
A comparative heavy-duty anti-corrosion coated rectangular steel pipe pile ■ manufactured as described above and a comparative heavy-duty anti-corrosion coated square steel pipe pile obtained as above were subjected to the same 3-year ocean service test as in Example 6, and After the test, the presence or absence of blisters on the fluorine-based paint film or fluororesin paint film was observed, and an adhesion test between these colored paint films and the low-density polyethylene coating [
Base test: According to JIS K5400, adhesive strength is 0
- Displayed on a scale of 10 (out of 10)]. The test results are shown in Table 2.

As is clear from the results in Table 2, if the degree of corona discharge treatment used in the present invention is 36 to 70 dyn/cm in terms of "wetting index (surface tension)", fluorine-based There is no blistering of the paint film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high.However, the "wetting index (surface tension)" is 3.
At 4 dyn/cm, blisters occur in the fluorine-based paint film, and the adhesive force between the fluorine-based paint film and the low-density polyethylene coating also decreases.

Example 9 The same method as in Example 6 was used to replace the square steel pipe pile coated with low-density polyethylene on the outside with a square steel pipe pile coated on the outside with high-density polyethylene, and the square steel pipe pile coated with ethylene-propylene block copolymer on the outside to obtain heavy corrosion protection according to the present invention. Covered square steel pipe piles [phases] ~■ were manufactured.

Comparison of the heavy anti-corrosion coated square steel pipe piles obtained as described above The heavy anti-corrosion coated square steel pipe piles were subjected to the same 3-year ocean service test as in Example 6, and after the test was completed, the piles were coated with fluorine-based paint or fluororesin paint. In addition to observing the presence or absence of blisters on the film, an adhesion test was conducted between these colored coatings and the low-density polyethylene coating [base test: according to JIS K5400, the adhesion was rated from 0 to 10 (out of 10). I did the display in . The test results are shown in Table 2.

As is clear from the results in Table 2, the heavy corrosion protection coated square steel pipe pile according to the present invention has a polyolefin coated square steel pipe pile on the outside, regardless of the fl H of the polyolefin used in its manufacture.
Even after three years of actual marine use tests, no blisters occurred in the fluorine-based paint film, and the adhesion between the fluorine-based paint film and the low-density polyethylene coating was sufficiently high.

Example 10 A fluorine-based paint (Duflon manufactured by Nippon Paint Co., Ltd., Marcel value of color tone: IOB 5/1) was applied in the same manner as in Example 6.
0 (blue)) was replaced with the acrylic-silicon-based and acrylic-urethane-based colored pigments shown in Table 3, heavy anti-corrosion coated square steel pipe piles [phase] to [phase] according to the present invention were manufactured. Comparison of the heavy-duty anti-corrosion coated rectangular steel pipe piles obtained as described above was subjected to a three-year marine practical test in the same manner as in Example 6.
After the test, the presence or absence of blisters on the fluorine-based paint film or fluororesin paint film was observed, and an adhesion test was conducted between these colored paint films and the low-density polyethylene coating [base test: JIS 5400]. in accordance with
Adhesive strength was expressed on a scale of 0 to 10 (out of 10). The test results are shown in Table 2.

As is clear from the results in Table 2, even when acrylic-silicon-based or acrylic-urethane-based colored paints were used, there was no occurrence of blisters in the colored paint film even after three years of actual marine usage tests. Moreover, the adhesion between the fluorine-based paint film and the low-density polyethylene coating is sufficiently high.

Example 11 The present invention was carried out in the same manner as in Example 6, except that the modified polyolefin primer (Thermotac E300J manufactured by China Paint Co., Ltd.) was replaced with a urethane primer (50% by weight of urethane prepolymer containing terminal isocyanate groups, 50% by weight of toluene). A square steel pipe pile with a heavy corrosion protection coating was manufactured.The square steel pipe pile O with a heavy corrosion protection coating obtained in the above manner was subjected to the same 3-year marine practical test as in Example 6, and after the test was completed, a fluorine-based paint coating was applied. Alternatively, the presence or absence of blisters in the fluororesin paint film is observed, and an adhesion test between the colored paint film and the low-density polyethylene coating [substrate test: according to JIS 5400, the adhesion strength is measured from 0 to 10]. The test results are shown in Table 2.

As is clear from the results in Table tj & 2, even when a urethane primer was used instead of a modified polyolefin primer, there was no blistering of the colored paint film even after a three-year marine use test, and there was no problem with fluorine-based paint coating. The adhesion between the membrane and the low density polyethylene coating is also sufficiently high.

Sword 3 Table (Effects of the Invention) As is clear from the above examples, polyolefin containing 0.05 to 5.0% by weight of an antioxidant in the outermost layer of the outer surface of the square steel pipe and whose surface was subjected to corona discharge treatment was used. A urethane primer or a modified polyolefin primer is applied to the outer surface of the square steel pipe pile coated with polyolefin, or to the outer surface, and then colored paints such as fluorine-based paints, acrylic-silicon-based paints, acrylic-urethane-based paints, etc. of various colors are applied. The heavy-duty anti-corrosion coated square steel pipe piles of the present invention obtained by coating the present invention can be coated with colored paints such as fluorine-based paints, acrylic-silicon-based paints, and acrylic-urethane-based paints in various colors, compared to conventional heavy-duty anti-corrosion coated steel materials. The water-resistant adhesion between the paint film and the polyolefin coating is outstanding.

[Brief explanation of the drawing]

1 and 4 are partial cross-sectional views of a square steel pipe pile with heavy corrosion protection coating according to the present invention, FIG. FIG. 3 is a diagram showing a partial cross section of heavy anti-corrosion coated steel material. In the figure, 1 is a square steel pipe or steel material, 2 is an antioxidant of 0.0
3 is a polyolefin-coated square steel pipe pile in which the outermost layer of the outer surface of a square steel pipe is coated with a polyolefin containing 0.05 to 50% by weight of an antioxidant, 4 5 is a colored paint film such as fluorine paint, acrylic-silicon paint, acrylic-urethane paint in various colors, 5 is a table roller,
6 is a continuously rotating roll electrode, 7 is a chromate treatment agent coating, 8 is an epoxy brimer coating, 9 is a modified polyolefin adhesive, 10 is an inorganic brimer, 11 is an organic brimer, 12 is an adhesive layer, 13 is a polyolefin resin layer, 14 is a urethane primer layer, 5 is a fluororesin layer containing a colored pigment, and 16 is a urethane primer or modified polyolefin primer layer. 4. Square steel pipe, polyolefin containing 0.05 to 50% by weight of antioxidant and having corona discharge treatment on the outer surface: Coloring of fluorine-based paints of various colors, acrylic-urethane paints on acrylic-silicon-based coatings, etc. Paint Coating Film Chromate Treatment Agent Coat Epoxy Brimer Modified Polyolefin Adhesive Inorganic Brimer Organic Brimer Adhesive Layer Polyolefin Resin Layer Urethane Primer Layer Fluororesin Layer Containing Color Application Urethane Primer or Modified Polyolefin Primer figure

Claims (1)

[Claims] 1. Add 0.05 to 5.0% of an antioxidant to the outermost layer of the outer surface of the square steel pipe.
Colored paints such as fluorine-based paints, acrylic-silicon-based paints, acrylic-urethane-based paints, etc. in various colors are applied to the outer surface of square steel pipe piles coated with external polyolefin, which contains polyolefin containing 0% by weight and whose outer surface has been subjected to corona discharge treatment. Heavy duty anti-corrosion coated square steel pipe pile characterized by laminated membrane. 2 Add 0.05 to 5.0% of antioxidant to the outermost layer of the outer surface of the square steel pipe.
A rectangular steel pipe pile coated with polyolefin on its outer surface and having a polyolefin content of 0% by weight is subjected to corona discharge treatment using four roll-type electrodes that continuously rotate each of the four sides of the outer surface while being transferred on a table roller, and is then treated with various colors. A method for manufacturing a square steel pipe pile with heavy corrosion protection coating, characterized by coating with a colored paint such as a fluorine paint, an acrylic-silicon paint, or an acrylic-urethane paint. 3 Add 0.05 to 5.0% of antioxidant to the outermost layer of the outer surface of the square steel pipe.
The outer surface of the square steel pipe pile coated with outer polyolefin, which contains polyolefin containing 0% by weight and whose outer surface has been subjected to corona discharge treatment, is coated with urethane primer or modified polyolefin primer, fluorine-based paint in various colors, acrylic-silicon-based paint, acrylic-urethane. A square steel pipe pile with a heavy anti-corrosion coating, characterized by sequentially laminating colored paint films such as paints. 4 Add 0.05 to 5.0% of antioxidant to the outermost layer of the outer surface of the square steel pipe.
A rectangular steel pipe pile coated with polyolefin on the outside having a polyolefin content of 0% by weight was subjected to corona discharge treatment using four roll-type electrodes that continuously rotated each of the four sides of the outside surface while being transferred and conveyed on a table roller. A square steel pipe pile with a heavy anti-corrosion coating, characterized in that the outer surface is coated with a urethane primer or a modified polyolefin primer, and colored paints such as fluorine paints, acrylic-silicon paints, and acrylic-urethane paints in various colors are applied. Manufacturing method.