JP3385607B2 - Heavy-duty coated steel sheet pile - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heavy anticorrosion coated steel sheet pile in which a heavy anticorrosion coating is formed on the surface of a steel sheet pile by sticking a polyethylene sheet, and more specifically, to long-term adhesion between the sheet and the steel material. The present invention relates to a heavy anticorrosion coated steel sheet pile having excellent properties.

[0002]

2. Description of the Related Art Steel sheet piles that form the quay of the ocean, harbors, rivers, etc. are exposed to a severe corrosive environment. Therefore, a sheet made of polyolefin resin such as polyethylene or polypropylene is attached to the surface of the steel sheet pile through an adhesive layer. By doing so, so-called heavy anticorrosion coated steel sheet piles, which have been anticorrosion coated, have been increasingly used.

This heavy-duty anticorrosion coated steel sheet pile is disclosed in JP-A-59-2.
As disclosed in Japanese Unexamined Patent Publication No. 24717 or Japanese Unexamined Patent Publication No. 60-8058, a base sheet-treated steel sheet pile is formed with an undercoating layer consisting of a chemical conversion treatment layer, a primer layer, etc., and then a modified polyethylene or the like is bonded. An anticorrosion polyethylene layer is formed via an agent layer. As a manufacturing method, there is known a method in which a sheet-shaped anticorrosion polyethylene layer is attached to a preheated steel sheet pile to manufacture. When pasting the anti-corrosion polyethylene sheet after forming the modified polyethylene layer by a method such as powder coating in advance,
It is also known to cover a sheet in which a modified polyethylene layer and an anticorrosion polyethylene layer are integrated. Cross-linked polyethylene is generally used as the anticorrosion polyethylene layer (Japanese Patent Laid-Open No. 59-224717).

[0004]

However, when a polyethylene-coated steel sheet pile manufactured by attaching a sheet is exposed to the marine environment for a long time after being placed, the adhesion between the sheet and the steel material is reduced especially in the undersea area. In the worst case, there is a possibility that the coating may float or turn over.

Considering the present situation in which the design life of port facilities and the like has become longer in recent years and it is desired to reduce the maintenance cost during that period, the long-term adhesion of the coating of the heavy anticorrosion coated steel sheet pile is further improved. This will be a very significant issue that will produce extremely large economic effects.

The cause of the decrease in the adhesion strength of the heavy anticorrosion coated steel sheet pile in seawater is that it is exposed to seawater for a long period of time, and therefore the deterioration of the adhesive layer and the base treatment layer due to the moisture and oxygen that permeate the anticorrosion polyethylene layer of the coating. First, it is considered that the adhesion between the coating layer and the steel material decreases. Furthermore, because the sheet is attached to one side of a steel sheet pile having a curved surface, deterioration of the adhesive layer or the undercoat layer due to invasion of environmental substances from the edge of the sheet is likely to occur.

In order to prevent the deterioration due to moisture penetrating the coating, for example, in Japanese Patent Laid-Open No. 61-72127, the density of polyethylene and the film thickness are set within a predetermined relational expression so that A technique for reducing the water vapor transmission rate of the coating is disclosed, and it is said that the higher the density of polyethylene, the lower the water vapor transmission rate. However, in the study by the present inventors, it is sufficient to use only high-density polyethylene. It was found that excellent long-term adhesion cannot be obtained.

The present invention has been made to solve the above problems, and relates to a heavy anticorrosion coated steel sheet pile formed by sticking a polyethylene sheet to the surface of a steel sheet pile, and long-term adhesion of the coating layer in seawater. It is an object of the present invention to provide a heavy-duty anticorrosion coated steel sheet pile that is excellent in

[0009]

Means for Solving the Problems The present inventor has diligently studied in order to eliminate the cause of the above-mentioned decrease in adhesion and to develop a heavy-corrosion-coated steel sheet pile excellent in long-term adhesion of polyethylene sheet in seawater. went. As a result, the heavy anticorrosion coated steel sheet pile having a specific density and molecular structure as the anticorrosion polyethylene layer and controlling the residual stress of the coating layer within a specific range is remarkably excellent in long-term adhesion in seawater. And finally came to complete the present invention.

That is, according to the present invention, in a heavy anticorrosion coated steel sheet pile in which at least one surface of a steel sheet pile subjected to a surface treatment is covered with a modified polyethylene layer through a modified polyethylene layer, the anticorrosion polyethylene layer has a density of 0.940 g / cm
^The present invention relates to a heavy-corrosion-coated steel sheet pile, which has a residual stress of ³ or more and a coating stress of 20 kgf / cm ² or less.

Further, the present invention relates to the heavy anticorrosion coated steel sheet pile, wherein the polyethylene resin of the anticorrosion polyethylene layer is non-crosslinked polyethylene.

In the above heavy anticorrosion coated steel sheet pile, the anticorrosion polyethylene layer is formed of a polyethylene resin having a density of 0.940 g / cm ³ or more. Density is 0.940g / c
Polyethylene of m ³ or more is generally referred to as high-density polyethylene, and is a type having extremely high density among polyethylene. These are produced by a medium- and low-pressure polymerization method using a high-performance catalyst such as a Ziegler type catalyst, and have a structure in which the degree of branching of polyethylene molecules is extremely small and branching is small. Due to this characteristic of the molecular structure, not only is it excellent in mechanical strength and impact resistance, but it also has the property of having very low moisture and oxygen permeability due to its high density. Originally polyethylene is a resin with excellent moisture permeation resistance,
In terms of water vapor permeability, which is a measure of water permeability, of the polyethylene, high-density polyethylene has a permeability of only 1/3 to 1/5 as compared with low-density polyethylene. Therefore, when the high-density polyethylene is used as the anticorrosion polyethylene layer, the permeation rate of water into the coating is extremely smaller than that of the low-density polyethylene. In addition, the amount of oxygen permeation is much smaller than that of low density polyethylene. In the case of heavy anticorrosion steel sheet pile, the thickness of the anticorrosion polyethylene layer is usually 2.0 mm or more, but if it is such a thickness, it is extremely slow for moisture and oxygen to permeate and reach the steel surface. Even if it arrives, the amount thereof is so small that it is considered that it does not lead to deterioration of the adhesive layer or the undercoat layer.

However, the density as described above is 0.940 g / c.
Even if a high-density polyethylene of m ³ or more is used as the anti-corrosion polyethylene for heavy anti-corrosion coated steel sheet pile, when it is immersed in seawater for a long time, the adhesive strength at the center of the coated area does not decrease, but the edge of the coating May peel off from the area or turn over. It is considered that this is because the high-density polyethylene has a high elastic modulus, and therefore the thermal stress when coating the steel sheet pile with the polyethylene becomes extremely large.

On the other hand, the present inventors have found that the density is 0.940 g /
As a result of studying a heavy-corrosion-coated steel sheet pile, which is resistant to peeling and swelling from the edge of the coating while taking advantage of the low permeability of high-density polyethylene of cm ³ or more to water and oxygen, the residual stress of the coating is 20 kgf / It has been found that, if it is cm ² or less, regardless of the manufacturing method, it exhibits high resistance to coating permeation moisture and permeation moisture from the end, and exhibits extremely excellent long-term adhesiveness.

A steel sheet pile having a high-density polyethylene having a density of 0.940 g / cm ³ or more as an anticorrosion layer has a residual stress of at least 30 kgf / cm when coated by a conventional method.
² or more, and in many cases 40 kgf / cm ² or more. Therefore, a special material and manufacturing method are required to reduce the residual stress of the coating to 20 kgf / cm ² or less.

One method is to use high density polyethylene as non-crosslinked polyethylene. Several cross-linking methods such as electron beam cross-linking, silane cross-linking, and chemical cross-linking are known for polyethylene, and these cross-linked polyethylenes may be used for heavy-corrosion steel sheet piles. It is preferred to use non-crosslinked polyethylene, not used. This is because the thermal stress generated in the cooling process after the polyethylene is adhered is effectively relieved by promoting the displacement between the molecules without forming a cross-linking structure between the molecular chains of polyethylene.

Further, the Vicat softening point of the modified polyethylene layer which is the adhesive layer is lowered, specifically, 50 ° C. to 90 ° C.
Setting the temperature in the range of ° C is also effective in reducing the residual stress of the coating. Furthermore, it is also effective to make the cooling rate on the polyethylene side higher than the cooling rate on the steel material side by adopting a specific cooling method in the cooling process after the polyethylene is attached. All of these methods make it possible to reduce the thermal stress generated by lowering the temperature of the anticorrosion polyethylene layer at the adhesive layer solidifying stage.

There are several methods for reducing the residual stress of the coating as described above, and they may be combined appropriately. Further, regardless of the above method, the method is not particularly limited as long as the residual stress of the coating can be 20 kgf / cm ² or less.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. As shown in FIG. 1, the heavy anticorrosion coated steel sheet pile of the present invention comprises a steel sheet pile 1, a base treatment layer 2, a modified polyethylene layer 3, an anticorrosion polyethylene layer 4, and an end seal layer 5.

The steel sheet pile used in the present invention means a harbor, a river,
It is used for revetment of landfills, etc., JIS A
U-shaped, Z-shaped, I-shaped, and shapes conforming to these can be used. There are no particular restrictions on its dimensions. In the present invention, the heavy anticorrosion coating is applied to a portion where anticorrosion needs to be applied. For example, in the case of being used as a seawall for a harbor, a coating is often applied mainly to the side facing the sea, but it goes without saying that a heavy anticorrosion coating can be applied to both sides of the steel sheet pile. Also used in combination with cathodic protection, the heavy anticorrosion coating is LW from the sea atmosphere.
L. It is also commonly applied to a limited area of about -1 m.

The steel sheet pile according to the present invention should be preliminarily subjected to known substrate adjustment such as degreasing, pickling, shot blasting, grit blasting, sand blasting, etc. to remove oil, scale and the like on the surface of the steel material. is necessary. It is preferable that the level of substrate adjustment is, for example, about Sa2 1/2 or more according to the Swedish standard (SIS). If this foundation adjustment is insufficient, the long-term anticorrosion property of the heavy anticorrosion coating is significantly impaired. Further, it is preferable to perform a chemical conversion treatment such as a known chromate treatment from the viewpoints of long-term adhesion and anticorrosion.

The primer layer of the steel sheet pile of the present invention is
An epoxy resin-based or urethane resin-based organic resin-based primer having excellent adhesion between the surface of the steel sheet pile that has been subjected to substrate conditioning and chemical conversion treatment and the modified polyethylene layer is used. The primer layer is formed by a known coating method such as air spray, airless spray, brush coating,
If necessary, heating after coating may be performed to form a completely cured coating. The thickness of the primer layer is 10 to 200 μm,
20 to 100 μm is particularly preferable. If the thickness is less than 10 μm, the adhesion of the polyethylene sheet to the steel material is weakened, and there is a problem such as peeling of the polyethylene sheet. If the thickness exceeds 200 μm, the residual stress of the primer layer itself increases, and the sheet Adversely affects the long-term adhesion of.

In the heavy-duty anticorrosion coated steel sheet pile of the present invention, the modified polyethylene layer is obtained by modifying a polyethylene resin by a graft reaction of an unsaturated carboxylic acid such as maleic acid, acrylic acid or methacrylic acid or an anhydride thereof. In comparison with polyethylene alone, it means a resin layer with significantly improved adhesion to other substances. The modified polyethylene is known to have various thermal properties depending on the kind and amount of the functional group to be grafted. The modified polyolefin used in the present invention has a Vicat softening point of 50 ° C. or higher and 90 ° C. or higher.
The following is preferable. If the softening point is 50 ° C or lower, the adhesion of the sheet will be deteriorated in the aerial part of the heavy anticorrosion steel sheet pile due to temperature rise due to sunlight, and if it is 90 ° C or higher, the residual stress of the sheet will be remarkably high. It is not preferable because it becomes large, the long-term adhesion of the coating is poor, and the energy cost is increased by raising the required heating temperature of the steel sheet pile. A more preferable Vicat softening point is 55 to 70 ° C. Among other physical properties of the modified polyethylene, the melt index is about 0.2 to 10 g / 10 minutes, preferably about 0.5 to 5 g / 10 minutes, and the melting point is 60.
A temperature of about -100 ° C, preferably about 60-80 ° C is suitable. The modified polyethylene layer functions as an adhesive layer of the anticorrosion polyethylene layer and has a layer thickness of 0.
About 1 to 1.5 mm, preferably about 0.2 to 1 mm is suitable.

In the heavy anticorrosion coated steel sheet pile of the present invention, the anticorrosion polyethylene layer has a density of 0.940 g / cm ^3.
These are so-called high-density polyethylene. Propylene for the purpose of improving environmental stress crack resistance, impact resistance, and toughness,
A copolymer having a polyolefin-based component such as butene-1 or hexene-1 as a copolymerization component may be used. The preferred softening point difference from the modified polyethylene layer is about 10 to 70 ° C. In order to improve long-term properties such as weather resistance, it is preferable to add various additives such as carbon black, color pigments and antioxidants to the anticorrosion polyethylene layer. The thickness of the anticorrosion polyethylene layer is preferably in the range of about 1 to 6 mm, particularly about 1 to 4 mm, from the viewpoint of long-term adhesion, long-term anticorrosion, and retention of mechanical strength of the coating layer. By the way, the standard of the anticorrosion polyethylene of the heavy anticorrosion steel sheet pile is defined as 2.0 mm or more, and in general, the thickness of the anticorrosion polyethylene layer is often 2.0 mm or more.

Several cross-linking methods such as electron beam cross-linking, silane cross-linking, and chemical cross-linking are known for polyethylene, and these cross-linked polyethylene may be used for heavy-corrosion steel sheet pile, but in the present invention, , These crosslinked polyethylenes are not used, and non-crosslinked polyethylenes are used. This is because the stress relaxation effect after cooling is not impaired, and since high density polyethylene is used, it has sufficient mechanical strength, and therefore it is not necessary to take a crosslinked structure.

Next, a method of manufacturing the heavy anticorrosion coated steel sheet pile according to the present invention will be described. The scale is completely removed by blasting, and chemical conversion treatment such as chromate treatment is performed. Further, a primer coating is applied by a spray coating method or another method, and left standing or heated to be cured to form a primer layer.

The steel sheet pile, which has been subjected to the blasting, chemical conversion treatment, and primer coating and the like, is heated by a heating device such as a heating furnace. The heating temperature needs to be a temperature necessary for fusion bonding of the polyethylene sheet, and therefore is a temperature above the melting point of the modified polyethylene layer, preferably about 10 to 100 ° C. higher than the melting point, and usually a temperature range of about 80 to 200 ° C. Is.

A heated steel sheet pile is coated with a corrosion-resistant polyethylene sheet through a modified polyethylene layer. As the coating method, it is preferable that a modified polyethylene layer and an anticorrosion polyethylene layer are integrally formed in advance to form a polyethylene sheet, and the integrated sheet is supplied to the steel sheet pile so that the modified polyethylene layer side is in contact with the steel sheet pile. However, it does not necessarily have to be integrated, and only the modified polyethylene layer is formed on the steel sheet pile that has been pretreated in advance,
A sheet consisting only of the anticorrosion polyethylene layer may be attached thereon. In that case, the modified polyethylene layer may be formed by melt extrusion coating, powder coating, fluidized dipping, thermal spraying, sheet sticking, or the like. In order to heat-bond the anticorrosion polyethylene sheet, the modified polyethylene layer needs to be in a molten state at least.

The sheet supplied on the steel sheet pile is attached by pressing the sheet against the steel sheet pile with a pressure device such as a roll. At that time, it is preferable to sequentially press the steel sheet pile from the central portion to the curved surface portion and then to the peripheral portion in order to prevent bubbles and the like from being mixed into the sheet and to efficiently attach the sheet.

After the fusion is completed, the extra length of the sheet is trimmed and the steel sheet pile to which the sheet is attached is cooled. In the present invention, cooling from the polyethylene side is preferable from the viewpoint of reducing residual stress. Cooling is performed by water cooling, air cooling, or another cooling medium, but it is most efficient to sprinkle water from the polyethylene side for cooling. Further, this cooling is preferably performed at least until the modified polyethylene layer as the adhesive layer is solidified from the viewpoint of the residual stress reducing effect. After that, the residual stress reducing effect does not change even if cooling is performed from both the polyethylene side and the steel material side, and the cooling time can be shortened, which is preferable.

After cooling, it is preferable to seal the ends of the coating with a sealing material. As shown in FIG. 1, the shape of the end seal is preferably applied so that the gap between the end and the steel material is filled and the end seal does not protrude much from the plane of the sheet.

[0032]

EXAMPLES Examples of the present invention will be described below. U-shaped steel sheet pile (effective width 500 mm, height 225 mm, thickness 24.
The surface of the concave surface (3, length 6 m) is sandblasted until it becomes SIS Sa2 1/2, and a chromate treatment agent is applied to the surface on the side in contact with the sea during use and baked to give a total chromium adhesion of 500 mg / m ² Formed a chromate film. After curing the unpainted portion, an epoxy primer was spray-coated on the surface so as to have a film thickness of 40 μm, and heated to cure.

Thereafter, the steel sheet pile was heated to 140 ° C. in a heating furnace, and a sheet made by integrally forming a modified polyethylene layer having a thickness of 0.5 mm and an anticorrosion polyethylene layer having a thickness of 2.0 mm on the high temperature steel sheet pile. Was placed, and pressure was applied to fuse. Modified polyethylene is maleic anhydride modified polyethylene. The density of the anticorrosion polyethylene and the Vicat softening point of the modified polyethylene used are shown in Table 1.

Cooling was performed by the method shown in Table 1. After that, the entire side edges of the sheet were sealed with a moisture-curable urethane resin composition to prepare a heavy corrosion-resistant steel sheet pile of the present invention. The following evaluation was performed on this steel sheet pile.

(1) Investigation of residual stress of coating After cooling, part of the coating was peeled off from the steel sheet pile while preventing deformation of the coating, and the dimensional difference between the coating before and after peeling and the polyethylene used for coating The residual stress of the coating was calculated from the Young's modulus. (2) Hot salt water immersion test Cut the obtained steel sheet pile into an appropriate size, 50 ℃, 3%
Immersed in salt water for a long time, the adhesive strength of the coating after immersion is 90 °
It was evaluated by the peel strength method (JIS G 3469). In addition, the coated end of the end seal part was forcibly peeled off, and the state of deterioration such as rust at the peeled part and exposure of the iron material was investigated. (3) Salt spray test The obtained steel sheet pile is cut into an appropriate size, and JIS K 5
The salt spray test defined in 400 was carried out to investigate the progress of rust from the end.

[0036]

[Table 1]

[0037]

[Table 2]

From the results of this acceleration test, 0.940 g /
The high-density polyethylene system of cm ³ or more shows almost no decrease in peel strength due to the water permeating the coating,
In addition, the heavy anticorrosion coated steel sheet pile having a residual stress of coating of 20 kgf / cm ² or less is deteriorated at the end due to permeation of a corrosive substance from the end particularly in a test conducted at a temperature close to an environmental temperature such as a salt spray test. It turned out that I can control. Further, in a system using a high-density polyethylene as a coating material such as the present invention, it is possible to use modified polyethylene having a low Vicat softening point or to cool from the polyethylene side after sticking, because the residual stress of the coating is low. It was effective in obtaining a sheet pile.

Further, in the marine exposure test of the steel sheet pile carried out by the group of the present inventors, the steel sheet piles having the configurations of Example 2 and Comparative Example 4 were tested. In the steel sheet pile having the configuration of Comparative Example 4, the coating had already peeled off around the corners of the end portion in the sea portion after the lapse of 5 years. However, Example 2
In the steel sheet pile having the above structure, the end seals remained completely even after 10 years, and no progress of deterioration from the end was observed. The peel strength of the coating is the same as the initial value, 30 kgf /
It was at least cm ² and was not deteriorated at all. this is,
The high-density polyethylene has a high barrier effect against water penetration, and the residual stress of the coating is 20 kgf / cm.
It was considered that the reason for this is that since it was small at ² , the permeation of water from the edges was suppressed, and peeling and curling from the edges were effectively suppressed.

As described above, the heavy anticorrosion coated steel sheet pile of the present invention was found to exhibit extremely excellent adhesion even in various accelerated tests and long-term exposure in the sea.

[0041]

As described above, the heavy anticorrosion coated steel sheet pile of the present invention exhibits very excellent long-term adhesion in accelerated tests and exposure tests in the marine environment. Therefore, the long-term life of the coating of coated steel sheet pile can be significantly extended, the maintenance cost of the port facility can be reduced, and the loss of repair costs due to peeling can be prevented, and its economic effect is immeasurable. Absent.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (enlarged view of a side end portion) of a heavy anticorrosion coated steel sheet pile according to the present invention.

[Explanation of symbols]

1 steel sheet pile 2 Undercoat layer 3 Modified polyethylene layer 4 Anticorrosion polyethylene layer 5 Edge sealing layer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiro Saito Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Tube Co., Ltd. (72) Yoshihiro Okano Marunouchi 1-2-2 Nippon-Kobe, Chiyoda-ku, Tokyo Within the corporation (56) Reference JP-A-4-336113 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A heavy anticorrosion coated steel sheet pile in which at least one surface of a steel sheet pile subjected to a base treatment is coated with a modified polyethylene layer through a modified polyethylene layer, wherein the polyethylene resin of the anticorrosion polyethylene layer has a density of 0.940 g / c
Heavy duty coated steel sheet pile, characterized in that in m ³ or more, and the residual stress of the coating is 20 kgf / cm ² or less. 2. The polyethylene resin of the anticorrosion polyethylene layer is non-crosslinked polyethylene.
The described heavy-duty anticorrosion coated steel sheet pile.