JP3166901B2 - Heavy-duty coated steel sheet pile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty anti-corrosion coated steel sheet pile having a heavy duty anti-corrosion coating formed on the surface of a steel sheet pile by attaching a polyolefin sheet. The present invention relates to a heavy duty anticorrosion coated steel sheet pile having excellent adhesion.

[0002]

2. Description of the Related Art Steel sheet piles forming quays of oceans, ports, rivers, etc. are exposed to a severe corrosive environment. Therefore, a sheet made of a polyolefin resin such as polyethylene or polypropylene is attached to the sheet pile surface via an adhesive layer. As a result, so-called heavy-corrosion-coated steel sheet piles provided with a corrosion-resistant coating have been increasingly used.

[0003] This heavy-corrosion coated steel sheet pile is disclosed in
As disclosed in Japanese Patent No. 058, etc., a chemical conversion treatment layer, a primer layer, a modified polyolefin layer, and a corrosion-resistant polyolefin layer are sequentially formed on a steel sheet pile whose base material has been adjusted. A method is known in which a sheet in which a polyolefin layer is integrated is attached to a preheated steel sheet pile to produce the sheet.

[0004]

However, polyolefin-coated steel sheet piles manufactured by sticking sheets are more likely to be exposed to the marine environment after casting than other heavy-duty corrosion-resistant steel materials, such as polyolefin-coated steel pipe piles. In particular, there is a problem that there is a high possibility that the sheet will be peeled off from the end portion, particularly in the undersea area.

[0005] Since the repair cost and the like when the sheet of the heavy-corrosion-coated steel sheet pile is peeled off is extremely large, it is extremely important to ensure the long-term adhesion of the sheet of the polyolefin-coated steel sheet pile, especially in seawater. ing.

The present invention has been made in order to solve the above-mentioned problems, and relates to a heavy-duty corrosion-resistant coated steel sheet pile having a polyolefin sheet adhered to the surface of the steel sheet pile, and to a 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 having excellent resistance.

[0007]

In the case of polyolefin-coated steel sheet piles, the cause of the above-mentioned peeling is that, due to the characteristic that a sheet is stuck to one side of the steel sheet pile, invasion of environmental substances from the end of the sheet or cathodic protection. Cathode separation easily occurs when used together with
Further, it is considered that the residual stress of the sheet acts in a direction to promote a decrease in the adhesion at the end portion due to the above-described factors.

The inventor of the present invention has conducted intensive studies in order to solve the problem of edge peeling. As a result, a sheet in which a modified polyolefin layer and an anticorrosion polyolefin layer are integrated with each other is applied to a heated steel sheet pile subjected to base treatment. In the heavy-corrosion-coated steel sheet pile to be attached, the modified polyolefin layer has a Vicat softening point in the range of 50 ° C. or more and 90 ° C. or less, so that the long-term adhesion of the sheet in seawater is extremely excellent. Have been obtained, and the present invention has been completed.

The heavy corrosion resistant coated steel sheet pile of the present invention has a modified polyolefin layer having a Vicat softening point in the range of 50 to 90 ° C.,
It is considerably lower than a general coated steel sheet pile. For example, Japanese Patent Application Laid-Open No. 60-8058 specifies that the difference between the melting points of the modified polyolefin layer and the anticorrosion polyolefin layer is less than 20 ° C., and a resin having a melting point of 120 ° C. is used as an example.

However, the present inventors have found that it is very important to minimize the difference between the softening point of the modified polyolefin layer and the temperature in the actual use environment, especially in order to ensure long-term adhesion of the sheet in seawater. Has been found to have a significant effect.

Although the reason for this is unknown, one of the possible causes is an effect of reducing the residual stress. That is, when a polyolefin sheet is fused to a heated steel sheet pile, the polyolefin sheet is heated to a fusible temperature and adheres to a steel material in a thermally expanded state. In the cooling process after fusing, the sheet shrinks until the modified polyolefin layer reaches the softening point, causing a gap between the steel material and the sheet, and in the cooling process after the modified polyolefin layer is solidified, the steel material and the polyolefin Internal stress due to the difference in linear expansion coefficient from the sheet remains. Therefore, it is expected that the smaller the difference between the softening point of the modified polyolefin layer and the temperature in the actual use environment, the smaller the residual stress.

If the residual stress of the sheet is large, particularly during long-term use in seawater, the peeling of the cathode and the decrease in the adhesiveness of the edge due to the invasion of environmental substances are remarkably promoted, and this is a factor that enlarges the peeling. It is expected that. Therefore, lowering the residual stress led to a significant reduction in these factors of peeling, and as a result, the heavy duty corrosion-resistant steel sheet pile of the present invention is expected to have excellent long-term adhesion.

However, the softening point of the modified polyolefin layer is
If the temperature is too low, there is a danger that the modified polyolefin layer reaches the softening point in the aerial part particularly in the sunshine in summer and the adhesive strength is lowered. Therefore, in the present invention, the lower limit of the softening point is set to 50 ° C.

[0014]

Embodiments of the present invention will be described below in detail. As shown in FIG. 1, the heavy-corrosion-coated steel sheet pile of the present invention includes a steel sheet pile 1, a primer layer 2, a modified polyolefin layer 3, and a corrosion-resistant polyolefin layer 4.

The steel sheet piles used in the present invention include harbors, rivers,
Used for revetment of landfills, etc.
U-type, Z-type, I-type specified in 5528, and those having a shape conforming thereto can be used. There are no particular restrictions on its dimensions. In the present invention, heavy anticorrosion coating is applied to a portion where anticorrosion needs to be applied. For example, when used for seawall protection in a port, the coating is often applied mainly to the side facing the sea.

The steel sheet pile used in the present invention is previously subjected to a known base treatment such as degreasing, pickling, shot blasting, grit blasting, and sand blasting to remove oil, scale and the like on the surface of the steel material. It is desirable. The level of the underlayer treatment is preferably, for example, about Sa 2 1/2 or more in Swedish standard (SIS). If the undercoating treatment is insufficient, the long-term anticorrosion of the heavy duty anticorrosion coating is significantly impaired. Further, it is preferable to perform a known chemical conversion treatment such as a chromate treatment from the viewpoint of long-term adhesion and corrosion resistance.

The primer layer used in 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 subjected to the base treatment and the modified polyolefin layer. Used.
The primer layer is formed by a known coating method such as air spraying, airless spraying, brush coating, or the like, and if necessary, heated after coating to form a complete cured film. The thickness of the primer layer is about 10 to 200 μm, particularly 20 to 200 μm.
It is preferably about 100 μm. If the thickness is less than 10 μm, the adhesion between the polyolefin sheet and the steel material is reduced.
There is a problem that the polyolefin sheet is peeled off, and if the thickness exceeds 200 μm, the residual stress of the primer layer itself increases, which adversely affects the long-term adhesion of the sheet.

The modified polyolefin used in the present invention is obtained by modifying a polyolefin resin such as polyethylene or polypropylene with an unsaturated carboxylic acid such as maleic acid, acrylic acid or methacrylic acid or an anhydride thereof by a graft reaction or the like. Refers to a resin whose adhesiveness to other substances is remarkably improved as compared with a polyolefin alone.
Modified polyolefins are known to have various thermal properties depending on the type and amount of functional groups to be grafted, but the modified polyolefin used in the present invention has a Vicat softening point of 5%.
0 ° C or more and 90 ° C or less. If the softening point is 50 ° C. or less, the adhesiveness of the sheet is lowered in the aerial part of the heavy-duty corrosion-resistant steel sheet pile due to a rise in temperature due to sunshine or the like. In this case, the effect of improving the long-term adhesion of the sheet is unfavorably deteriorated. The preferred Vicat softening point is 55-80 ° C, particularly preferably 55-70 ° C. Although other physical properties of the modified polyolefin are not particularly limited, the melt index is about 0.2 to 10 g / 10 min, preferably about 0.5 to 5 g / 10 min, and the density is 0.85 to 0.98 g.
/ Cm ³ , melting point 60-135 ° C, preferably 6
Those having a temperature of about 0 to 100 ° C are suitable. The thickness of the modified polyolefin layer is about 0.1 to 1.5 mm, preferably about 0.2 to 1 mm.

The polyolefin resin of the anticorrosion polyolefin layer used in the present invention is a low-density polyethylene,
Known polyolefins such as medium density polyethylene, high density polyethylene, linear low density polyethylene and polypropylene, and known polyolefin copolymers such as ethylene-propylene random or block copolymers. The preferred softening point difference from the modified polyolefin layer is 10
About 70 ° C. In order to improve long-term properties such as weather resistance, various additives such as carbon black, coloring pigments and antioxidants are often added to the anticorrosive polyolefin layer. The thickness of the anticorrosion polyolefin 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 maintenance of the mechanical strength of the coating layer.

Next, a method for manufacturing a heavy-corrosion-coated steel sheet pile according to the present invention will be described. The scale is completely removed by blasting, and a chemical treatment such as a chromate treatment is performed to apply a base treatment to the steel material. Further, the primer coating is applied by a spray coating method or another method, and cured by standing or heating to form a primer layer.

The steel sheet pile that has been subjected to the base treatment and the primer coating is heated by a heating device such as a heating furnace. The heating temperature is required to be a temperature necessary for fusing the polyolefin sheet, and therefore, a temperature higher than the melting point of the modified polyolefin layer, preferably about 10 to 100 ° C. higher than the melting point,
Usually, the temperature range is about 100 to 200 ° C.

A sheet in which the modified polyolefin layer and the anticorrosion polyolefin layer are integrated with the heated steel sheet pile is supplied onto the steel sheet pile so that the modified polyolefin layer side is in contact with the sheet pile. After the supply, the sheet is sequentially pressed from a central portion to a peripheral portion by a pressing device such as a roll to fuse the sheet to the steel sheet pile.
After fusion, the steel sheet is cooled by standing cooling or forced cooling, and the necessary edge treatment is performed to obtain the heavy-duty corrosion-resistant steel sheet pile of the present invention.

[0023]

Embodiments of the present invention will be described below.

U-shaped steel sheet pile (effective width 500 mm, height 22
5mm, thickness 24.3, length 6m)
A sand blast treatment was performed until a 2 1/2 was reached, and a chromate treatment agent was applied to the surface in contact with the sea at the time of use and baked to form a chromate film having a total chromium adhesion of 500 mg / m ² . After curing the unpainted part, an epoxy-based primer was spray-coated on the surface so as to have a thickness of 40 μm, and was cured by heating.

Thereafter, the steel sheet pile was heated to 140 ° C. in a heating furnace to form a sheet formed by integrating a modified polyolefin layer having a thickness of 0.5 mm and a corrosion-resistant polyolefin layer having a thickness of 2.0 mm with the steel sheet pile in a high temperature state. Was placed and pressed to fuse. Thereafter, the steel sheet was allowed to cool and subjected to an edge treatment to produce five types of heavy duty anticorrosion coated steel sheet piles having different modified Vicat softening points of the modified polyolefin layer.

A cut was made at the end of the heavy-corrosion-coated steel sheet pile, and the steel sheet pile was cast on a quay in a state where artificial peeling of about 1 cm was generated. Covered area is the average low tide surface (LWL)
In the following, the range was set to 1.5 m, and the portion below that range was subjected to cathodic protection by a galvanic anode method. The anticorrosion potential was set to an over-corrosion prevention state of -1.5 V on the basis of a saturated luster electrode, so that the influence of cathode peeling was intentionally excessively increased.

After the casting, the state of peeling of the coating layer was observed over time. Table 1 shows the types of steel sheet piles tested and the observation results.

[0028]

[Table 1]

As described above, it can be seen that the heavy-corrosion-coated steel sheet pile of the present invention exhibits extremely excellent adhesion even in long-term exposure in the sea.

[0030]

As described above, the heavy duty anticorrosion coated steel sheet pile of the present invention has the characteristics that it has excellent long-term adhesion of a sheet particularly in seawater in actual use and has little possibility of peeling of the sheet. Is shown. Therefore, it is possible to prevent the loss of the repair cost and the like due to the peeling of the coating of the coated steel sheet pile, and a remarkable economic effect is obtained. Further, there is also an effect of reducing energy cost by lowering the heating temperature of the steel sheet pile due to lowering of the softening point of the modified polyolefin.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heavy-corrosion-coated steel sheet pile of the present invention.

[Explanation of symbols]

 Reference Signs List 1 steel sheet pile 2 primer layer 3 modified polyolefin layer 4 anticorrosion polyolefin layer

Claims (1)

(57) [Claims] 1. A heavy-duty corrosion-coated steel sheet pile wherein at least one surface of the steel sheet pile is coated with a corrosion-resistant polyolefin layer via a modified polyolefin layer, the modified polyolefin has a Vicat softening point of 50 ° C. or more and 90 ° C. or less. Characteristic heavy-duty coated steel sheet pile