JPH11245335A - Polyethylene-coated steel material and polyethylene for coated steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a weather resistance of a polyethylene-coated steel material by sequentially laminating a primer layer, an adhesive polyethylene layer and a polyethylene layer made of a non-crosslinked linear low-density ethylene having a specific flexural modulus and density and added with a specific substance on a surface of a steel material. SOLUTION: In this polyethylene-coated steel material 10, a primer layer 13, an adhesive polyethylene layer 12 and a polyethylene layer 11 are sequentially laminated on a surface of a steel material 14. As the polyethylene used for the layer 11, a non-crosslinked linear low-density polyethylene having a density of less than 0.930 g/m<3> and a flexural modulus of less than 300 MPa is used. To the layer 11, 0.1 to 0.5 pt.wt. of a specific undecane derivative, 0.02 to 0.5 pt.wt. of a specific phosphite compound, 0.15 to 1.4 pt.wt. of a specific sebacate compound, 0.15 to 1.4 pt.wt. of a specific iminole derivative and 0.3 to 2.8 pts.wt. of specific chrolobenzotriazole to 100 pts.wt. of the polyethylene are added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene-coated steel material and a polyethylene for the coated steel material, and more particularly, to a weather-resistant material which is used for revetment work in rivers and marine areas, and for structural materials such as piers and piers. The present invention relates to a polyethylene-coated heavy-corrosion-resistant steel material and a polyethylene suitable for this.

[0002]

2. Description of the Related Art Steel pipe piles, steel pipe sheet piles, and organically coated heavy-corrosion-protected steel sheets with steel sheet piles organically coated have been widely used as structural materials for structures such as piers and piers in rivers and marine areas. In such applications, since long-term corrosion resistance of steel is expected, a polyethylene resin having excellent water resistance has been used as a coating material. However, when these materials are exposed outdoors for a long period of time, they cause photo-oxidative degradation due to ultraviolet rays. That is, the polyethylene resin undergoes a molecular cutting reaction due to photo-oxidation degradation, and as a result, the polyethylene layer is embrittled and the coating layer is cracked.

[0003] In order to prevent the photo-oxidative deterioration of the polyethylene layer, carbon black is usually added to the polyethylene layer to convert light energy into heat energy to provide long-term weather resistance. However, in recent years, harmony with the surrounding environment has been demanded even for such structural materials, and an organic heavy duty anticorrosion coated steel material which is not only conventional black but also has various colors and has excellent landscape properties has been required. Was. Therefore, an antioxidant in the polyethylene layer,
By adding a light stabilizer, an ultraviolet absorber, and the like, the weather resistance of the polyethylene layer was improved, and as a result, it became possible to color using a pigment other than carbon black. As for this technique, for example, a method in which a hindered phenol-based antioxidant, a hindered amine-based light stabilizer, a benzotriazole-based ultraviolet absorber, and a color pigment are blended with an electron beam cross-linked polyethylene (Japanese Unexamined Patent Publication No.
No. 92514), a one-sided hindered phenol-based antioxidant, a sulfur-based antioxidant having an ester bond in polyethylene, a hindered amine-based light stabilizer, an ultraviolet absorber,
A compound containing a color pigment or the like (Japanese Patent Laid-Open No. 6-39976); a phenol-based antioxidant, a phosphorus-based antioxidant, a hindered amine-based light stabilizer;
Compounded with an ultraviolet absorber and a color pigment (JP-A-5-252)
No. 69950). These technologies are weather resistance tests using a sunshine weather meter,
Weather resistance of about 8000 to 12000 hours has been obtained.

Since the durability of a structure is generally expected to be about 40 years, the polyethylene layer must be provided with at least 40 years of weather resistance. JP-A-5-9251
4, JP-A-6-39976 and JP-A-5-39976.
JP-A-269950 considers that irradiation for 8000 to 12000 hours in a sunshine weather meter test is equivalent to 40 years of an outdoor exposure test.
JP-A-39976 describes that irradiation for 200 hours corresponds to one year of actual outdoor exposure. In this case, the acceleration factor of the sunshine weather meter test was set to about 44 times, and the reason for this was that the amount of light near a wavelength of 300 nm, which would mainly contribute to the photooxidative degradation of polyethylene,
This is probably because it is about 40 times the actual sunlight. However, photo-oxidation degradation of polyethylene is a complicated chain reaction consisting of a plurality of reaction processes, and in fact, light having a wavelength longer than 300 nm also contributes to the promotion of oxidation degradation of polyethylene. Although the details will be described in the examples, the inventors conducted a comparative test using the same sample outdoors and a sunshine weather meter, and found that irradiation for 800 hours with the sunshine weather meter was equivalent to one year of outdoor exposure. Was. That is, the promotion rate of the sunshine weather meter is about 11 times, and in order to obtain the weather resistance of 40 years, it is necessary to have the weather resistance of 32,000 hours or more in the sunshine weather meter test. Therefore,
It is clear that the conventional technology can provide only about 10 to 15 years of weather resistance.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyethylene-coated steel material having excellent weather resistance and a polyethylene for coating the steel material.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by combining the density, structure, mechanical properties and specific additives of polyethylene, the weather resistance has been improved. It has been found that excellent polyethylene-coated steel can be obtained.

That is, the present invention relates to a polyethylene-coated steel material in which a primer layer, an adhesive polyethylene layer, and a polyethylene layer are sequentially laminated on the surface of a steel material, wherein the polyethylene of the polyethylene layer has a flexural modulus of 300 MPa.
And a non-crosslinked linear low-density polyethylene having a density of less than 0.930 g / cm ³ , and the polyethylene layer further comprises the following (A), (B), (C), (D),
It contains the components (E) and (F), and the content is 0.1 to 0.5 parts by weight, and the component (B) is 0.02 to 100 parts by weight based on 100 parts by weight of the polyethylene. 0.5 parts by weight (C) 0.15 to 1.4 parts by weight of component (D) 0.15 to 1.4 parts by weight of component (E) 0.3 to 2.8 parts by weight of component (A) 3,9-bis [2- {3- (3-t-butyl-4)
-Hydroxy-5-methylphenyl) propionyloxy {-4,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane (B) tris (mixed mono / di-nonylphenyl)
-Phosphite (C) bis (2,2,6,6-tetramethyl-4-piperidine) sepagate (D) poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3] , 5-Triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -4-piperidyl} Iminol] (E) 2- (2'hydroxyl-3'-t-butyl-
5'-methylphenyl) -5-chlorobenzotriazole (F) pigment.

[0008] The present invention is also a polyethylene for a coated steel material in which a primer layer, an adhesive polyethylene layer, and a polyethylene layer are sequentially laminated on the surface of a steel material, wherein the polyethylene has a flexural modulus of less than 300 MPa and A non-crosslinked linear low-density polyethylene having a density of less than 0.930 g / cm ³ , and the polyethylene layer further comprises the following (A), (B), (C), (D), (E) and (F)
Component (A) is 0.1 to 0.5 part by weight, component (B) is 0.02 to 0.5 part by weight with respect to 100 parts by weight of the polyethylene. ) 0.15 to 1.4 parts by weight of the component (D) 0.15 to 1.4 parts by weight of the component (E) 0.3 to 2.8 parts by weight of the component (E). (A) 3,9-bis [2- {3- (3-t-butyl-4)
-Hydroxy-5-methylphenyl) propionyloxy {-4,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane (B) tris (mixed mono / di-nonylphenyl)
-Phosphite (C) bis (2,2,6,6-tetramethyl-4-piperidine) sepagate (D) poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3] , 5-Triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -4-piperidyl} Iminol] (E) 2- (2'hydroxyl-3'-t-butyl-
5'-methylphenyl) -5-chlorobenzotriazole (F) pigment. Further, the present invention provides a polyethylene-coated steel material, wherein the polyethylene is a polyethylene having a weather resistance of 32,000 hours or more in a sunshine weathermeter test.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present invention relates to a polyethylene-coated steel excellent in weather resistance (hereinafter, referred to as a coated steel of the present invention) and a polyethylene for the coated steel. FIG. 1 shows a cross-sectional view of one example of the polyethylene-coated steel material of the present invention. As shown in FIG. 1, a polyethylene-coated steel material 10 includes a polyethylene layer 11, an adhesive polyethylene layer 12, a primer layer 13, and a steel material 1.
It consists of four. Polyethylene coated steel 10 of the present invention
In the surface of the steel material 14, a primer layer 13, an adhesive polyethylene layer 12, and a polyethylene layer 11 are laminated, and the molecular structure of the polyethylene layer 11 is specified, and the density, mechanical properties, and composition are specified in a specific range. By doing so, it is a coated steel material having water resistance, eventually corrosion resistance and weather resistance.

[0010] The primer layer 13 is laminated directly on the steel material 14, and protects the surface of the steel material 14 by exhibiting adhesion to the steel material and anticorrosion, thereby improving the appearance quality and durability of the coated steel material 10. It works. The adhesive polyethylene layer 12 is laminated directly on the primer layer 13 and has excellent adhesion with the primer layer 13 and also has excellent adhesion with the polyethylene layer 11 laminated directly on the adhesive polyethylene layer 12. It acts to ensure interlayer adhesion between the layer and the polyethylene layer. The polyethylene layer 11 is the outermost layer of the coated steel material 10 and contains the specific components (A) to (F),
It works to provide corrosion resistance and weather resistance. Primer layer 1
The adhesive layer 3 and the adhesive polyethylene layer 12 both ensure interlayer adhesion, but further support the polyethylene layer 11 containing this specific component to maximize the coating properties such as weather resistance. Work to do The coated steel material of the present invention may have a coating layer of steel such as one example of the coated steel material of the present invention shown in FIG. A coating layer different from the coat, for example, a chemical conversion film formed by roughening, degreasing, chromate treatment or the like may be formed on the surface of a steel material, and an adhesive polyethylene layer and a polyethylene layer may be formed directly on the chemical conversion film.

As a method for manufacturing such a coated steel material 10, the following method can be exemplified. In general,
In order to improve the bonding strength between the steel material and the primer layer,
It is important to keep the steel surface clean. In the present invention,
The specific means is not limited as long as the oxidized layer and oil on the steel surface can be removed, but Rz (ten-point average roughness) = 20
Optimally, a steel blast treatment or a steel grid treatment of １００100 μm is performed. When Rz (ten-point average roughness) is less than 20 μm,
If the anchor effect is reduced, the adhesion strength of the primer is reduced. If it exceeds 100 μm, the steel cannot be completely covered with the primer, and the long-term corrosion-resistant performance of the polyethylene-coated steel is reduced. Rz (ten-point average roughness) is 3
More preferably, it is 0 to 60 μm. Next, a primer is applied to the steel material to form a primer layer.Before applying the primer, for the purpose of imparting corrosion resistance to the steel material surface,
Chromate treatment may be performed. In the present invention, a chromate solution and a method for coating the chromate solution are not particularly specified. Is mentioned. By baking the painted chromate at a steel temperature of 80 ° C or higher,
It is preferable to evaporate the water to form a strong film. Next, a primer is applied by spraying or the like and baked to form a primer layer. Next, an adhesive polyethylene obtained by imparting an adhesive property to the polyethylene by modification with maleic anhydride or the like and a polyethylene containing specific components (A) to (F) described below, each processed into a sheet, are laminated in advance. Form the layer sheet. After heating the steel material coated with the primer to 150 ° C. or more in an oven, the two-layer sheet is pressure-bonded so that the adhesive polyethylene layer and the primer layer are in contact with each other to form a coated steel material of the present invention. Further, the coated steel material of the present invention can be obtained by forming an adhesive polyethylene layer once on the primer layer and then forming a polyethylene layer.

(Steel Material) Examples of the steel material 14 include a steel pipe, a steel pipe sheet pile, a steel sheet pile, an H-shaped steel, and a steel sheet. Specifically, steel pipes used for underground pipes, undersea pipes, above-ground pipes, steel plates used for fuel storage tanks and chemical plants, shaped steel, steel pipes, and offshore structures,
Examples include pile steel pipes, steel pipe sheet piles, steel sheet piles, and H-section steels used for structures installed outdoors such as harbor river revetment structures and bridges.

(Primer Layer) The primer layer 13 is laminated directly on the steel material 14, has excellent adhesion to the steel material 14, and functions to protect the surface of the steel material by exhibiting corrosion resistance. The primer used for the primer layer 13 is not particularly limited, and any primer such as an epoxy-based or epoxy-modified polyester may be used. An example is an epoxy primer obtained by curing a bisphenol A type epoxy resin with a predetermined amount of an alicyclic amine. For example, when the above-mentioned epoxy primer is used, the coating thickness of the primer layer 13 is preferably 10 to 100 μm,
0 to 60 μm is more preferable. When the thickness is less than 10 μm, the adhesive strength is remarkably reduced. For the purpose of suppressing cathodic peeling and providing corrosion resistance,
Phosphoric acid-based, chromic acid-based and molybdic acid-based rust preventive pigments may be added to the primer resin in an amount of 20 to 50% by weight based on the primer resin. In order to further improve the cathode peeling resistance, a chromate treatment for forming a stable chromium oxide film on the surface of the steel material 14 may be performed before applying the primer layer 13 to the steel material 14.

(Adhesive polyethylene layer) Primer layer 1
The adhesive polyethylene layer 12 laminated immediately above 3 is made of polyethylene having an adhesive property by being modified with carboxylic anhydride. The polyethylene is not particularly limited, but preferably has a density of 0.89 to 0.93.
g / cm ³ of low density polyethylene is used. Preferred examples of the carboxylic acid anhydride for modifying such polyethylene include maleic anhydride and succinic anhydride. Among them, maleic anhydride-modified polyethylene is more preferred because of its high adhesive strength. The thickness of the adhesive polyethylene layer 12 is preferably 50 to 500 μm, more preferably 100 to 400 μm. 50μ
If less than 500 m, sufficient adhesive strength cannot be obtained.
In the case described above, the manufacturing cost increases.

(Polyethylene layer) Polyethylene layer 11
Is laminated directly on the adhesive polyethylene layer 12 and coated.
This is a layer that functions as a corrosion protection layer of the steel sheet 10. Po
The polyethylene used for the ethylene layer 11 has a density of
0.930 g / cm ^ThreeNon-crosslinked linear low density polye less than
It is styrene and the flexural modulus is less than 300 MPa
Use polyethylene. Photo-oxidation degradation of polyethylene
Deterioration from the outermost surface with the largest amount of sunlight and oxygen concentration
Start. Degraded polyethylene is caused by a molecular cleavage reaction.
Therefore, the molecular weight is reduced, the elongation at break disappears, that is,
Embrittlement has occurred. Therefore, for some reason external
Hair shock on the outermost surface
Occurs and propagates inside the anticorrosion layer. Density 0.9
30g / cm^ThreeWhen the above polyethylene is used for the anticorrosion layer
In this case, stress concentrates on the tip of the resulting hair crack
Therefore, even if the surface slightly deteriorates,
The crack propagates at. On the other hand, the anticorrosion layer has a density of 0.930.
g / cm^ThreeWhen using linear low density polyethylene of less than
The stress at the tip of the crack on the surface is sufficiently relaxed
Cracks do not propagate to the inside of the anticorrosion layer.
No. The density is 0.930 g / cm^ThreeLess than polyethylene
Even if len is used, if it is not linear low density polyethylene
Is inferior in environmental stress crack resistance (crack resistance). Density
0.930 g / cm^ThreeWith less than cross-linked polyethylene
In some cases, due to its high modulus, polyethylene
Non-crosslinking of heat shrinkage stress generated when pressed and cooled on the material surface
And the adhesion durability is inferior. Also poly
When conducting electronic crosslinking of ethylene, use antioxidants or
After kneading the excipient into polyethylene and forming it into a sheet,
Irradiation with electron beam, generated by electron beam
The radical reacts with the additive to reduce the weather resistance.
Therefore, electron beam crosslinked polyethylene cannot be used. density
Is 0.890-0.928 g / cm^ThreeIs more preferred
No.

As described above, the polyethylene used for the polyethylene layer 11 has a flexural modulus of less than 300 MPa. When the flexural modulus of polyethylene is 300 MPa or more, the heat shrinkage stress after the polyethylene melts and adheres to the steel material surface increases, and not only the adhesion durability of the coating layer decreases, but also the cracks due to the photo-oxidation deterioration of the polyethylene. Outbreak occurs early. Therefore, the flexural modulus of polyethylene must be less than 300 MPa. The bending elastic modulus of polyethylene is more preferably from 200 to 299 MPa. The thickness of the polyethylene layer 11 is preferably from 1 to 4 mm, more preferably from 1.5 to 3 mm. When the film thickness is less than 1 mm, impact resistance and long-term corrosion resistance are poor, and
If it is more than mm, an anticorrosion effect worth the production cost cannot be obtained.

(Polyethylene additive) Polyethylene layer 1
The following (A) to (F) are essential components as additives to be blended in 1. (A) 3,9-bis [2- {3- (3-t-butyl-4)
-Hydroxy-5-methylphenyl) propionyloxy {-4,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane (B) tris (mixed mono / di-nonylphenyl)
-Phosphite (C) bis (2,2,6,6-tetramethyl-4-piperidine) sepagate (D) poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3] , 5-Triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -4-piperidyl} Iminol] (E) 2- (2'hydroxyl-3'-t-butyl-
5'-methylphenyl) -5-chlorobenzotriazole (F) pigment

(Components (A) and (B)) In the step of processing polyethylene into a sheet or the step of pressing a formed polyethylene sheet on the surface of a steel material, the polyethylene must be melted and softened. When polyethylene is kept in a high temperature state in an environment where oxygen is present, a thermal oxidative degradation reaction of polyethylene occurs, and a peracid or a carbonyl group generated at that time becomes a starting point of the photooxidative degradation reaction. Therefore, in order to impart long-term weather resistance to polyethylene, it is necessary to suppress thermal oxidative degradation during heating. For this reason, the polyethylene for coated steel used for the polyethylene layer of the coated steel of the present invention contains, as essential components, a component (A) which is a phenolic antioxidant and a component (B) which is a phosphorus antioxidant. I do.

It is widely known that when a phenolic antioxidant and a thioether-based antioxidant are used in combination to prevent thermal oxidative deterioration of polyethylene, particularly excellent effects are exhibited. However, a thioether antioxidant and a hindered amine light stabilizer (C) component described below,
The use of thioether-based antioxidants is not preferred, irrespective of the compounding amount, since the components (D) exhibit an antagonistic effect of reducing the effects of each other.

The phenolic antioxidant to be added is 3,
9-bis [2- {3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -4,
1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane, and the phosphorus-based antioxidant is tris (mixed mono / di-nonylphenyl)
-Phosphite. This is because the coated steel material of the present invention obtained by using these phenol-based and phosphorus-based antioxidants is excellent in weather resistance and can provide a weather resistance life of 40 years or more. Here, the weathering life refers to the time required until the polyethylene layer on the surface of the coated steel material deteriorates by photooxidation and cracks begin to occur.

((C) component, (D) component, (E) component)
In the polyethylene forming the polyethylene layer of the coated steel material of the present invention, in addition to the components (A) and (B), the components (C) and (D), which are hindered amine light stabilizers, and benzotriazole Component (E), which is a system ultraviolet absorber, is contained as an essential component. These components (C) to (E) function to suppress the photooxidative degradation of polyethylene. The hindered amine-based light stabilizer has an action of capturing and stabilizing radicals generated in the process of photooxidative degradation of polyethylene. The benzotriazole-based ultraviolet absorber consumes the absorbed light energy in the intramolecular photoisomerization reaction. As an additive having a similar function, a benzophenone-based or salicylate-based ultraviolet absorber may be mentioned, but the performance is inferior to any of the benzotriazole-based ones, and the photoisomerized substance exhibits a yellow color. It is not preferable because it causes discoloration.

The hindered amine light stabilizer to be added is
Bis (2,2,6,6-tetramethyl-4-piperidine) sepagate and poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-
2,4-diyl {(2,2,6,6-tetramethyl-
4-piperidyl) imino {hexamethylene} (2,2
6,6-tetramethyl) -4-piperidyldiiminor]. This is because the coated steel material of the present invention using these hindered amine-based light stabilizers in combination has excellent weather resistance and can provide a weather resistance life of 40 years or more.

(C) As a hindered amine light stabilizer
When only the component is used, the molecular weight of the component (C) is 48.
Since it is so small as to be 0 and diffuses out of the polyethylene layer, it is difficult to provide long-term weather resistance. When only the component (D) is used as the hindered amine light stabilizer, the molecular weight of the light stabilizer is as large as 2500 or more, and the light stabilizer is supplied from the inside according to the speed at which the light stabilizer is consumed in the outermost layer. Is slow, the polyethylene in the outermost layer deteriorates, and the weather resistance decreases. The mixing ratio of the component (C) to the component (D) is preferably 3: 1 to 1: 3 by weight, more preferably 1: 1.

The added benzotriazole ultraviolet absorber is 2- (2'hydroxyl-3'-t-butyl-
5'-Methylphenyl) -5-chlorobenzotriazole is used. This is because the use of this benzotriazole-based ultraviolet absorber provides a weathering life of 40 years or more.

(Component (F)) The type and amount of the pigment to be added to the polyethylene of the anticorrosion layer are not particularly limited, and may be blended so as to obtain a desired color. For example, titanium oxide,
Titanium yellow, iron oxide black, phthalocyanine green,
Examples thereof include phthalocyanine blue, quinacridone red, and perinoso orange, and one or more of these can be added to obtain a desired color.

(Blending amount of additive) The blending amount of each additive is 0.1 to 0.5 part by weight, and the blending amount of component (B) is 100 parts by weight of polyethylene. The amount is 0.02 to 0.5 parts by weight, and the amount of the component (C) is 0.1
5 to 1.4 parts by weight, the compounding amount of the component (D) is 0.15 to
1.4 parts by weight, and the compounding amount of the component (E) is 0.3 to 2.8 parts by weight. When the amount is less than each of the above ranges, the weather resistance is reduced. If the amount is larger than the above range, a bleed-out phenomenon occurs in which additives kneaded into polyethylene are deposited on the surface, which not only significantly impairs the appearance but also improves the weather resistance. Therefore, the intended sufficient weather resistance cannot be obtained. Additives used for imparting long-term weather resistance are extremely expensive as compared with polyethylene, and are difficult to use in large quantities in industrial production.
The preferred range of the amount of each additive is 0.1 to 0.3 parts by weight of component (A) and 0.02 to 0.2 parts by weight of component (B) based on 100 parts by weight of polyethylene. ) The component is 0.5 to 1.0 part by weight. The component (D) is 0.5 to 1.0 part by weight. The component (E) is 1.0 to 2.0 parts by weight. The method of blending the additive with the polyethylene is not particularly limited, and it can be performed by a usual melting and kneading method.

The polyethylene coated steel material of the present invention has excellent weather resistance in addition to water resistance and corrosion resistance and has a weather life equivalent to 40 years or more by adopting the above-mentioned structure. In addition, since the outermost polyethylene layer is excellent in weather resistance, a pigment can be blended instead of blending carbon black or the like, and the design is excellent. Further, the production cost is in a range suitable for industrial production. Therefore, the polyethylene-coated steel material of the present invention is a steel pipe used for underground buried piping, submarine piping, above-ground piping, a steel plate used for a fuel storage tank or a chemical plant, a shaped steel, a steel pipe, or an offshore structure, It is suitably used for steel pipes for piles, steel pipe sheet piles, steel sheet piles, H-section steels and the like used for structures installed outdoors such as harbor river revetment structures and bridges. Also,
The polyethylene for coated steel of the present invention has excellent adhesion durability, corrosion resistance, and weather resistance by adopting the above-described configuration, and has excellent corrosion resistance and weather resistance to the coated steel using the polyethylene for coated steel of the present invention. give.

[0028]

(Example) (Method of manufacturing a polyethylene-coated steel sample) A steel plate having a thickness of 6 mm was coated with Rz (ten-point average roughness) of 50 μm.
The rust was removed by performing a mastic plasting process, the surface thereof was subjected to a chromate treatment, and baked at 120 ° C. A primer using a bisphenol A-type epoxy resin as a base material and an alicyclic amine as a curing agent, and having a dry film thickness of 30 to 50
It was applied to a thickness of μm and gelled at 120 ° C.

A maleic anhydride-modified polyethylene (adhesive polyethylene) film and a polyethylene film blended with a predetermined additive were laminated on the upper layer of the primer, and pressed under a pressure of 1 kgf / cm ^{2 at} a temperature of 180 ° C. for 10 minutes. . The film thickness of the adhesive polyethylene layer was 200 μm, and the film pressure of the polyethylene layer was 2.0 mm.

A test specimen of 150 mm × 70 mm was cut out from the sample, and an outdoor exposure test (test place: Mizushima, Kurashiki-shi, Okayama) and a weather resistance test (using a sunshine weather meter, carbon arc furnace type, black panel temperature 63)
C., 50% relative humidity).

In each of the test methods, after the test was performed for a predetermined time, the polyethylene layer was peeled off from the test piece, and a tensile test of polyethylene was performed. The conditions of the tensile test are such that polyethylene is punched into a JIS type 2 1/2 test piece, and the tensile speed is 20 mm / min. When the elongation at break reached 50% of the elongation at break before the test, the polyethylene was considered to be photooxidatively degraded, and the time to reach it was defined as the weatherable life of the polyethylene in the test method.

(Correlation between outdoor exposure test and weather resistance test)
For the purpose of investigating the correlation between the outdoor exposure test and the weather resistance test (sunshine weather meter), a test was conducted using polyethylene having the composition shown in Table 1. In order to clarify the results at an early stage, the test was performed in a region where the amount of the additive was small. The results are shown in FIG. The correlation between the two tests is high, and it can be seen that the weather life of 800 hours in the weather resistance test is equivalent to about one year in the outdoor exposure test. Therefore, in order to obtain the weather resistance of 40 years outdoors, it is understood that the weather resistance life in a weather resistance test (sunshine weather meter) is 32000 hours or more. Further, from the results of FIG. 2, it can be seen that, even when the same additive is blended in the same amount, the polyethylene having lower density and flexural modulus has longer weathering life.

[0033]

[Table 1]

Symbol of additive in Table 1 (A) 3,9-bis [2- {3- (3-t-butyl-4)
-Hydroxy-5-methylphenyl) propionyloxy {-4,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane (B) tris (mixed mono / di-nonylphenyl)
-Phosphite (C) bis (2,2,6,6-tetramethyl-4-piperidine) sepagate (D) poly [{6- (1,1,3,3-tetramerbutyl) imino-1,3] , 5-Triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -4-piperidyl} Iminol] (E) 2- (2'-hydroxyl-3'-t-butyl-
5'-methylphenyl) -5-chlorobenzotriazole

(Examples 1 to 17, Comparative Examples 1 to 25) Test pieces were prepared from polyethylene containing additives in the proportions shown in Tables 2 and 3 and subjected to a weather resistance test (sunshine weather meter). And the weather resistance life was measured. The results are shown in Tables 2 and 3.

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

[Table 7]

[0042]

[Table 8]

In Comparative Examples 9 to 13 and Comparative Examples 17 to 37, in addition to the combinations of the respective additives shown in the table, 1.0 parts by weight of titanium white and titanium yellow were blended as coloring pigments (color is ivory). . Comparative Example 14, in addition to the combinations of additives described in the table, as a coloring pigment titanium white,
1.0 part by weight of reinforced graphite and phthalocyanine green were blended (color is green). Comparative Example 15 had titanium white as a coloring pigment, in addition to the combinations of additives described in the table.
1.0 part by weight of phthalocyanine green and phthalocyanine blue were blended (the color was blue). Comparative Example 16
In addition, in addition to the combinations of additives described in the table, 1.0 parts by weight of titanium white, titanium yellow, red iron oxide and carbon black were blended as coloring pigments (color is gray). In Comparative Examples 9 to 37, a linear low-density polyethylene having a density of 0.922 g / cm ³ and a flexural modulus of 260 MPa was used.

The symbols (A), (B), (C), (D) and (E) of the additives in Tables 2 and 3 correspond to (A), (B), (C) and ( D) and (E). G: 4,4'-thiobis (3-methyl-6-t-butylphenol) H: 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane I: triethylene glycol -Bis- [3- (3-t-
Butyl-5-methyl-4-hydroxyphenyl) propionate] J: 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl)
Benzene K: Tris (2,4-di-t-butylphenyl) phosphite L: Tris (biphenyl) phosphite M: Pentaerythritol-tetrakis (β-lauryl-thiopropionate) N: Distearyl-3,3 '-Thiodipropionate O: dilauryl-3,3'-thiodipropionate P: phenyl-4-piperidinyl carbonate Q: bis (N-methyl-2,3,6,6-tetramethyl-4- Piperidinyl) sepagate R: 4-hydroxy-2,2,6,6-tetramethyl-
Polyester conjugate of 1-piperidineethanol and succinic acid S: 2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) -5-chlorobenzotriazole T: 2- (2'-hydroxy- 3 ', 5'-di-t-butylphenyl) benzotriazole U: 2-hydroxy-4-methoxybenzophenone V: 2,4-di-t-butylphenyl-3', 5'-di-t-butyl- 4-hydroxybenzoate W: ethyl-2-cyano-3,3-diphenylacrylate

From these results, it is understood that the polyethylene-coated steel material of the present invention has a weathering life of 32,000 hours or more and can be used for 40 years or more even outdoors.
On the other hand, even one additive essential for the present invention is missing (Comparative Examples 1 to 5), the density is 0.930 g / cm ³ or more (Comparative Example 7), and the flexural modulus is 300 MPa or more (Comparative Examples 6 and 7).
In the case of, it can be seen that the weather life is short. In addition, when the polyethylene used for the polyethylene layer is a medium density polyethylene (Comparative Example 7) or an electron beam crosslinked linear low density polyethylene (Comparative Example 8), the weathering life is short.

[0046]

Industrial Applicability The polyethylene coated steel material of the present invention has excellent weather resistance, a long weather life, and can be used outdoors.
It can be used for 0 years or more without cracking or rusting, and therefore, it is most suitable for steel pipe piles, steel pipe sheet piles, steel sheet piles and the like used in piers, piers and the like. Further, the polyethylene for coated steel of the present invention is excellent in environmental stress crack resistance (crack resistance) and adhesion durability, and as a result, it is possible to impart excellent weather resistance to the coated steel.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a polyethylene-coated steel material of the present invention.

FIG. 2 is a graph showing a relationship between an outdoor exposure test and a weather resistance life obtained by a weather resistance test (sunshine weather meter).

[Explanation of symbols]

 Reference Signs List 10 polyethylene-coated steel material 11 polyethylene layer 12 adhesive polyethylene layer 13 primer layer 14 steel material

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23/06 C08L 23/06

Claims (2)

[Claims] 1. A polyethylene-coated steel material in which a primer layer, an adhesive polyethylene layer and a polyethylene layer are sequentially laminated on the surface of a steel material, wherein the polyethylene of the polyethylene layer has a flexural modulus of 3
A non-crosslinked linear low-density polyethylene having a density of less than 00 MPa and a density of less than 0.930 g / cm ³ , and the polyethylene layer further comprises the following (A), (B),
(C) It contains the components (D), (E) and (F), and the content is 0.1 to 0.5 parts by weight of the component (A) with respect to 100 parts by weight of the polyethylene. Component B) 0.02 to 0.5 part by weight Component (C) 0.15 to 1.4 part by weight Component (D) 0.15 to 1.4 part by weight Component (E) 0.3 to 0.5 part by weight 2.8 parts by weight: (A) 3,9-bis [2- {3- (3-t-butyl-4)
-Hydroxy-5-methylphenyl) propionyloxy {-4,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane (B) tris (mixed mono / di-nonylphenyl)
-Phosphite (C) bis (2,2,6,6-tetramethyl-4-piperidine) sepagate (D) poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3] , 5-Triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -4-piperidyl} Iminol] (E) 2- (2'hydroxyl-3'-t-butyl-
5'-methylphenyl) -5-chlorobenzotriazole (F) pigment. 2. A polyethylene for a coated steel in which a primer layer, an adhesive polyethylene layer, and a polyethylene layer are sequentially laminated on a surface of the steel, wherein the polyethylene has a flexural modulus of less than 300 MPa and a density of 0. A non-crosslinked linear low-density polyethylene of less than 0.930 g / cm ³ , and the polyethylene layer further comprises the following (A), (B),
(C) It contains the components (D), (E) and (F), and the content is 0.1 to 0.5 parts by weight of the component (A) with respect to 100 parts by weight of the polyethylene. Component B) 0.02 to 0.5 part by weight Component (C) 0.15 to 1.4 part by weight Component (D) 0.15 to 1.4 part by weight Component (E) 0.3 to 0.5 part by weight 2.8 parts by weight of polyethylene: (A) 3,9-bis [2- {3- (3-t-butyl-4)
-Hydroxy-5-methylphenyl) propionyloxy {-4,1-dimethylethyl] -2,4,8,10-
Tetraoxaspiro [5,5] undecane (B) tris (mixed mono / di-nonylphenyl)
-Phosphite (C) bis (2,2,6,6-tetramethyl-4-piperidine) sepagate (D) poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3] , 5-Triazine-2,4-diyl {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -4-piperidyl} Iminol] (E) 2- (2'hydroxyl-3'-t-butyl-
5'-methylphenyl) -5-chlorobenzotriazole (F) pigment.