JP3266957B2 - Colored polyethylene coating with excellent weather resistance - 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 corrosion-resistant coated steel material in which the surface of a base material such as steel is coated with a thick corrosion-resistant polyethylene layer.
For example, the present invention relates to a heavy-corrosion-resistant coated steel pipe, a steel pipe sheet pile, a steel sheet pile, and the like, and more particularly, to a colored polyethylene-coated steel material having excellent weather resistance and a surface coated with a colored polyethylene layer.

[0002]

2. Description of the Related Art Steel materials used for a long time outdoors may be exposed to severe corrosive environments. For example, steel sheet piles and steel pipe sheet piles are continuously driven into the ground to form protective fences, mainly for the protection of rivers, coasts, harbors, etc. Has been used for Steel pipes are also often used as gas pipes and water pipes.

[0003] These steel materials are used in outdoor natural environments.
It is exposed to river water, drainage water, rainwater, seawater, and the like, the atmosphere, sunlight, and the like, and it comes into direct strong contact with earth, sand, mud, rubble, etc., and thus is extremely prone to corrosion. Therefore, long term (about 40
) Effective anticorrosion measures were desired.

In recent years, as a countermeasure against this, a resin is used as a thick film (1 to 1).
(3 mm) Heavy corrosion-resistant coated steel materials that have been provided with excellent corrosion resistance by being coated are being used. As this coating resin,
Polyethylene is widely used in consideration of economy and various characteristics.

[0005] However, polyethylene resin is liable to be deteriorated by the influence of ultraviolet light contained in sunlight. Therefore, when it is used outdoors, as in the present application, carbon black is used as one resin.
It is common to add about 3% by weight to improve the weather resistance, and the color tone is limited to black. However, in places where the living environment and natural environment are to be maintained comfortably and neatly, it is required to color steel sheet piles, steel pipe sheet piles, steel pipes for piping, etc. so as to be adapted to the environment.

[0006] Therefore, a colored polyethylene-coated steel material which is colored with a coloring pigment after adding various kinds of deterioration preventing agents such as an ultraviolet absorber and an antioxidant instead of carbon black to polyethylene as a measure against ultraviolet light deterioration has been proposed.

[0007] Examples of such a deterioration inhibitor include a substance which absorbs ultraviolet rays and converts it into low energy (ultraviolet absorber) represented by a benzotriazole compound, a hindered amine light stabilizer generally abbreviated as HALS, a hinder Examples include antioxidants such as dophenolic compounds and sulfuric compounds. In this specification, additives effective for improving weather resistance, such as an ultraviolet absorber, a light stabilizer, and an antioxidant, are collectively referred to as a deterioration inhibitor.

[0008] Addition formulas of these deterioration preventing agents include:
A method of adding an ultraviolet absorber, a phenolic antioxidant and / or carbon black (Japanese Patent Laid-Open No. 63-60712)
No.) is known, but even when combined with a polyethylene resin by combining an ultraviolet absorber and a phenolic antioxidant, about 15 years of weather resistance (sunshine weather meter black panel temperature 63 hours at 63 ° C. 3000 hours) It was not too much.

In addition, an uncolored polyethylene anticorrosion layer (1 mm
Thickness), 0.1% by weight or more of antioxidant and weathering stabilizer
Colored polyethylene anticorrosion layer containing 0.3% by weight or more
(0.4 mm thick), a heavy duty anticorrosion coated steel pipe in which only the surface layer of polyethylene coating is a colored coating layer has been proposed (JP-A-4-80029). However, even if the deterioration inhibitor is added to the surface polyethylene as described above,
It has weather resistance of about 25 years (5000 hours at 63 ° C sunshine weather meter black panel temperature). in this way,
Each of the colored coated steel materials proposed so far is about 40 years
(Sunshine Weather Meter Black Panel Temperature 63
(8000 hours at ℃).

[0010]

In order to improve the weather resistance, it may be effective to increase the amount of a deterioration inhibitor, but these deterioration inhibitors are expensive and require a polyethylene resin as a base. The price is at least several times higher than that of, and the increase in the compounding cost leads to a rise in the product cost. In particular, the outer coating of outdoor piping such as water supply and gas, steel pipe resistance,
In heavy corrosion protection coating of steel sheet piles, steel pipe sheet piles, and the like, the production scale is large, so the addition of a deterioration inhibitor increases, and the excessive addition of the deterioration inhibitor impairs the economics of the product.

An object of the present invention is to provide a steel sheet pile, a steel pipe sheet pile, a steel pipe or the like having a long-term weather resistance of at least about 40 years without impairing the economic efficiency and without adding a deterioration inhibitor. An object of the present invention is to provide a colored polyethylene-coated steel material provided with a colored polyethylene coating.

[0012]

Means for Solving the Problems As a result of repeated studies to achieve the above object, the present inventors have found that long-term weather resistance of about 40 years can be ensured without using a large amount of a deterioration inhibitor. It was concluded that the addition of carbon black to the anticorrosion layer was essential. Therefore, in order to achieve the object by a colored polyethylene coating in which a colored polyethylene layer containing a colored pigment was laminated on a polyethylene anticorrosive layer to which carbon black was added, the weather resistance of the laminated polyethylene coating was examined.

As a result, if carbon black is added in an amount of 0.5% by weight or more to the lower anticorrosion layer polyethylene and the thickness of the upper colored polyethylene layer is reduced to 10 to 200 μm, appearance problems are caused on the surface of the colored polyethylene layer. It was found that, although fine cracks were generated, no substantial decrease in weather resistance was caused by the cracks, and a long-term weather resistance of about 40 years could be achieved as a whole of the coating.

Here, the present invention provides an adhesive layer and an adhesive layer provided thereon.
And anticorrosion polyethylene layer containing only carbon black or 0.5 wt%, the resin layer formed by laminating a colored polyethylene layer having a thickness of 100 to 200 DEG [mu] m containing a coloring pigment provided on the its is, the adhesive layer The present invention provides a colored polyethylene coating material, which is coated on the surface of a base material via a base material.

[0015]

In the present invention, the base material coated with polyethylene in the present invention is generally steel, but the material of the base material is not limited to iron and steel. , Ceramics and the like are also possible. In the following, a description will be given of a case where a steel material, which is a typical material, is used as a base material, but the same applies to a case where a base material other than a steel material is used. The shape of the steel material (or base material) is not particularly limited, and may be a tubular material such as a steel pipe or a steel pipe,
A plate material such as a steel sheet pile, a steel bar, a deformed material, or the like may be used. The surface of the steel material is desirably cleaned in advance by appropriately combining physical means such as shot blasting and chemical means such as pickling and alkali degreasing.

The steel material may be subjected to plating and / or chemical conversion treatment (chromate treatment, zinc phosphate treatment) as a base treatment for improving adhesion and corrosion resistance. Also,
In order to enhance the adhesion of the polyethylene layer, the surface of the steel material may be previously treated with a suitable primer. As the primer, for example, an epoxy primer can be used. The primer is thinly applied and then dried or cured by irradiating ultraviolet rays or the like. These ground treatments can be carried out as required in the conventional manner.

Since the polyethylene resin has relatively low adhesiveness, an adhesive layer is interposed at the interface between the steel material and the resin layer, and the resin material is coated on the steel material via the adhesive. Maleic anhydride-modified polyethylene resin is a preferred adhesive because it exhibits particularly high adhesiveness. In addition, adhesives based on ethylene copolymers (eg, ethylene / vinyl acetate copolymer) and hot melt adhesives based on polyethylene can also be used. The thickness of the adhesive layer is not particularly limited and varies depending on the type of the adhesive, but is generally about 0.1 to 0.5 mm.

The resin layer coated on the steel material according to the present invention comprises:
It is a resin layer obtained by laminating a thick anticorrosive polyethylene layer containing carbon black and a thin colored polyethylene layer serving as a surface layer.

The thickness of the lower anticorrosion polyethylene layer is not particularly limited as long as it is a sufficient thickness as the anticorrosion layer.
Generally, it is 0.5 to 5 mm. In order to realize long-term weather resistance of about 40 years, the range of 2-3 mm is preferable. The polyethylene resin used may be any of high, medium and low density polyethylene, and may be copolymerized with small amounts of other olefins or vinyl monomers (e.g., propylene, vinyl acetate, acrylic acid, acrylates, etc.). Is also good.

The anticorrosion polyethylene layer (anticorrosion layer) is a black resin layer containing carbon black in an amount of 0.5% by weight or more. If the content of carbon black is less than 0.5% by weight, a sufficient ultraviolet shielding effect cannot be obtained, surface deterioration proceeds to the anticorrosion layer, and the physical properties of the entire coating resin layer are significantly reduced. On the other hand, since excessive addition of carbon black lowers the economic efficiency and mechanical properties of the product, the upper limit of the carbon black content is preferably 5% by weight.

Since carbon black alone imparts sufficient weather resistance to the anticorrosion layer, it is not necessary to add another antioxidant, ultraviolet absorber or other deterioration inhibitor to the anticorrosion layer in addition to carbon black. However, if desired, a small amount of a deterioration inhibitor may be added to the anticorrosion layer together with carbon black in a small amount.

Colored polyethylene layer (colored layer) serving as a surface layer
May be the same as the anticorrosion layer. The thickness of the coloring layer is 100 to 200 μm, and particularly preferably 100 to 150 μm in order to realize long-term weather resistance. When the thickness of the colored layer is less than 100 μm, it is difficult to remove the black color of the anticorrosion layer, and the colored polyethylene layer on the surface is darkened. If the thickness of the colored layer exceeds 200 μm, the depth and size of surface cracks caused by surface deterioration are proportional to the thickness of the colored layer. Significantly decreases. In addition, since the cracks become large, the appearance also deteriorates. On the other hand, the thickness of the colored layer is 100 to 200 μm, especially 100 to 200 μm.
When the thickness is within the range of 150 μm, the black color of the anticorrosion layer containing carbon black can be easily erased, and cracks that occur even after surface deterioration are limited to only the surface layer. As a result, cracks do not increase, the physical properties of the entire resin coating layer including the anticorrosion layer do not decrease, and long-term weather resistance can be maintained.

The coloring pigment for coloring the polyethylene resin may be any of known organic or inorganic pigments. Specifically, organic pigments such as azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, dioxazine, perinone, quinophthalone, and perylene pigments, ultramarine, titanium dioxide, iron oxide
(Pegs), inorganic pigments such as chromium oxide and carbon black can be used.

The compounding amount of the coloring pigment may be an amount sufficient for coloring, and cannot be limited because it varies depending on the kind of the pigment.
Will be in the range of 0.1 to 5 parts by weight. In addition to coloring pigments,
One or more known additives such as extenders, rust preventive pigments, dispersants, softeners, and flame retardants may be further added. These additives can also be added to the anticorrosion layer.

Since long-term weather resistance can be ensured without adding a deterioration inhibitor to the colored layer, it is not always necessary to add a deterioration inhibitor to the colored layer. However, when the deterioration inhibitor is added to the colored layer, the time until the occurrence of surface fine cracks is extended. Accordingly, if desired, one or more known deterioration inhibitors may be added to the colored layer, whereby the weather resistance can be further improved. However, even in that case, it is difficult to completely prevent surface cracks.
In addition, excessive addition of the deterioration inhibitor not only impairs the economics of the product, but also causes bleed out of the deterioration inhibitor in some cases, leading to deterioration in quality. Therefore, when adding a deterioration inhibitor, the total amount of
It is preferable that the content be 2 parts by weight or less for 100 parts by weight.

When the colored polyethylene resin used for the colored layer is produced, a color pigment is added to the polyethylene resin in an amount of 3 to 50.
It is easy to obtain a homogeneous composition by preparing a masterbatch in which the masterbatch is blended at about a percentage by weight, and blending the masterbatch and a polyethylene resin containing no pigment at a predetermined ratio to prepare a colored polyethylene resin composition. It is also economically advantageous.

The colored polyethylene coating comprising a laminate of a thick anticorrosive layer and a thin colored layer according to the present invention is not necessarily expensive because the carbon black is added to the anticorrosive layer which occupies most of the layer. The desired long-term weather resistance of about 40 years can be exhibited without adding a deterioration inhibitor. This makes it possible to obtain a polyethylene coating whose surface can be colored in any color according to the use environment and which exhibits long-term weather resistance at low cost.

The colored polyethylene coating is applied to a steel material via an adhesive layer by, for example, the method described below, whereby the colored polyethylene-coated heavy corrosion-resistant steel material of the present invention is produced. The coating of the polyethylene resin may be applied only to the surface of the steel material requiring corrosion protection, and it is not necessary to cover the entire surface.

As a method for coating the steel material with polyethylene, for example, the following method is possible. A: a method based on a melt extrusion method, B: a method based on an electrostatic powder method, C: a method based on a fluidized immersion method, D: a method based on a thermal spraying method, E: a sheet laminating method Based method.

In each of the methods A to D, the surface of the steel material is cleaned by pickling or blasting, preheated to about 120 to 300 ° C. by an appropriate heating means such as induction heating, and then the adhesive resin is heated.
(Eg, maleic anhydride-modified polyethylene resin) by coating the steel surface with any one of the methods A to D. Next, while the adhesive resin is still in a molten state, an anticorrosion layer containing carbon black in the polyethylene resin is coated on the adhesive layer by any of the methods A to D, and the anticorrosion layer is further melted. , A colored layer made of a polyethylene resin containing a colored pigment is coated on the anticorrosion layer by any one of the methods A to D. Adhesive resin,
The anticorrosion layer and the colored layer can be coated by different methods, but the method of coating by the same method will usually be easier to manufacture.

In the laminating method E, an adhesive resin film, a carbon black-containing polyethylene sheet serving as an anticorrosion layer, and a colored polyethylene film serving as a colored layer are prepared, and these three layers are separately or previously laminated. Laminate on the surface of the cleaned preheated steel so that the adhesive layer is on the inside. In a more preferable method, a multi-layer sheet composed of three layers of an adhesive layer, an anticorrosion layer, and a colored layer is formed by a three-layer co-extrusion method or an extrusion lamination method, and the adhesive is placed inside the sheet. At the same time or later, lamination is performed by sticking to the steel surface.

In the case of the present invention, the coating layer is constituted by coating a resin layer formed in advance on the steel material surface. This is a method based on the extrusion method of A or the lamination method of E in the above classification.

Further, steel products (eg, steel sheet piles, steel pipes, etc.) coated with heavy corrosion protection with a black polyethylene layer containing 0.5% by weight or more of carbon black are already commercially available. Using such a product (or other steel material already coated with an anticorrosion layer) as a base material, heating it to about 80 ° C. to soften the polyethylene anticorrosion coating, and then adding a colored polyethylene layer
It is also possible to produce the colored polyethylene-coated steel material of the present invention by extrusion coating at 0 to 250 ° C. Thereby, resin exchange of the extruder is reduced, which is economically advantageous.

[0034]

[Example] The surface of a steel sheet pile (Sumitomo Metal Co., Ltd .; SKSP-II type) was adjusted by shot blasting (Sa. 2.
After that, chromate treatment was performed using a coating type chromate solution (manufactured by Kansai Paint Co., Ltd .; Cosmer 100) so that the chromium adhesion amount was 200 mg / m ² . This steel sheet pile is coated with an epoxy-based primer (Nippon Paint Co., Ltd .;
No. 66 primer) was applied so that the dry film thickness became 30 μm, and the steel material was heated to 190 ° C. using an induction heating device, so that the primer was baked and the steel material was preheated.

On the other hand, as a resin of the anticorrosion layer to be coated, a medium-low pressure polyethylene resin (manufactured by Showa Denko; Shorex S4
002 EX) was blended with carbon black in the amount shown in Table 1 to prepare a carbon black-containing polyethylene resin composition. The resin composition of the colored layer was obtained by adding the pigment shown in Table 1 to the same medium-to-low pressure method polyethylene resin as the anticorrosion layer (addition amount: 0.1 to 3 parts by weight based on 100 parts by weight of the resin) and melt-kneading. .

By extruding three layers of the maleic anhydride-modified polyethylene (Admer manufactured by Mitsui Petrochemical Co., Ltd.) as the adhesive layer together with the anticorrosive layer polyethylene resin composition and the colored layer polyethylene resin composition, the adhesive layer / anticorrosive layer was extruded. A multilayer polyethylene sheet having a width of 900 mm and a three-layered colored layer was obtained. The thickness of this sheet was 0.3 mm for the adhesive layer, and the thicknesses of the anticorrosion layer and the colored layer were as shown in Table 1. After heating this sheet to about 80 ° C. with an infrared heater, the modified polyethylene resin is fused and coated while rolling the steel sheet pile with a press roll on the convex part of the preheated steel sheet pile, thereby coating the colored polyethylene-coated steel sheet pile. Obtained.

Tensile elongation of the resin-coated portion of the colored polyethylene-coated steel sheet pile after 8000 hours at a black panel temperature of 63 ° C. (WOM 8000 hours is equivalent to about 40 years in a real environment) by a sunshine weather meter (WOM accelerated weathering test). The retention was measured. The results are shown in Table 1.

[0038]

[Table 1]

As can be seen from Table 1, in Examples 1 to 14 according to the present invention, the amount of carbon black added to the anticorrosion layer is 0.5% by weight or more, and the color layer has a thickness of 100 to 200 μm.
In this case, the tensile elongation retention was WOM even though no deterioration inhibitor was added to either the anticorrosion layer or the colored layer.
After 8000 hours it hardly dropped. Even if the color tone is changed by changing the type of the coloring pigment, if the thickness of the coloring layer is within the above range, the tensile elongation retention after WOM 8000 hours is almost 80.
% And no significant decrease.

On the other hand, as can be seen from Comparative Examples 1 to 8, when the thickness of the colored layer was greater than 200 μm, the tensile elongation retention after 8000 hours of WOM was remarkably reduced to 20% or less. As shown in Comparative Example 9, when the thickness of the colored layer is less than 10 μm,
No decrease in the tensile elongation retention after 8000 hours of WOM was observed, but since the colored layer was thin, the anticorrosive layer containing carbon black was transparent and the appearance was darkened. Further, as shown in Comparative Example 10, the amount of carbon black added in the anticorrosion layer was
If the amount is less than 0.5% by weight, deterioration of the anticorrosion layer progresses, and as a result, the elongation retention after 8000 hours of WOM is also significantly reduced.

[0041]

As described above, the colored polyethylene-coated steel material of the present invention has a thick anticorrosion layer containing 0.5% by weight or more of carbon black in polyethylene and a film thickness of 100 to 100 % in which a colored pigment is contained in polyethylene. By laminating with a 200 μm colored layer, a very long-lasting weather resistance of about 40 years can be exhibited without adding a deterioration inhibitor. Further, since the product can be directly colored, it is possible to greatly reduce the time required for resin replacement and the like. This allows
It is possible to use polyethylene-coated steel materials colored in any color according to the usage environment outdoors for more than 40 years, extending the range of use to various materials such as steel sheet piles and other materials, and ensuring durability. The period is extended. Therefore, the economic effect of the present invention is remarkable.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B32B 15/08

Claims (1)

(57) [Claims] 1. An adhesive layer and an anticorrosion polyethylene layer containing 0.5% by weight or more of carbon black provided thereon.
When the film thickness 100-200 which contains a coloring pigment provided on the its
resin layer formed by laminating a colored polyethylene layer of μm is,
A colored polyethylene coating material, which is coated on the surface of the base material via the adhesive layer.