JPH09201902A - Polyolefin coated steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin coated steel material excellent in hot water resistance, cathode separation resistance and thermal shock resistance even in the long-term use in the hot water over 80 deg.C and containing salt water. SOLUTION: By applying a chromate treating agent on the surface of a steel, pipe 1 and then firing the pipe, a chromate treating layer 4 is formed. Next, by applying a primer prepared by mixing an epoxy resin made from glycidyl ether of bisphenol A or F or of the mixture of them with hardener made of the mixture of modified heterocyclic amine prepared by reactively adding phenylglycidyl ether to heterocyclic amine and in-xylylenediamine and by thermally curing the primer layer 7 is formed on the resultant surface of the steel pipe 1. Then, by extruding a modified polyethylene resin 9 and a polyethylene resin 10 through a circular die 8 in two layers on the surface, on which the primer layer 7 is formed, for covering and finally cooling the surface in order to obtain a polyethylene resin coated steel pipe 1c.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin-coated steel material, and more particularly to a polyolefin-coated steel material excellent in hot water resistance, high temperature cathode peeling resistance, heat shock resistance and the like.

[0002]

2. Description of the Related Art Polyolefin-coated steel materials are used for steel pipes, steel pipe piles, steel sheet piles, etc. because of their excellent long-term corrosion resistance.

In recent years, polyolefin-coated steel pipes have come to be used also in pipelines for transporting crude oil, heavy oil, and natural gas, which are premised on use in the seabed, extremely cold regions, and tropical regions.

Therefore, it has become an important subject for the polyolefin-coated steel material to improve its performance under a wide temperature range environment or a high temperature water contact environment. The properties required for the polyolefin-coated steel material used under these environments include improvement in hot water resistance and heat shock resistance, especially over a long period of time.

Further, in an environment in which cathodic protection is used in combination, cathodic peeling occurs due to over-corrosion current, and therefore improvement in cathodic peeling resistance is also required.

Conventionally, in order to improve the above performance,
A method of performing chromate treatment between the steel material and the modified polyolefin resin adhesive layer (JP-A-54-120681, JP-A-1-280545) (Prior Art 1) and a method of interposing an epoxy primer (JP-A-SHO) 56-143
No. 223, JP-A-59-222275) (Prior Art 2), a method of applying an epoxy primer after chromate treatment (JP-A-60-245544) (Prior Art 2), and the like.

[0007]

However, in the methods shown in the prior art 1 and the prior art 2, the adhesive force between the resin and the steel material of the polyolefin-coated steel material is long-term use in a high temperature water contact environment exceeding 60 ° C. Is difficult to hold, and in that case, the decrease in adhesion is a problem.

When the chromate treatment and the epoxy primer treatment are used in combination as in the prior art 3, 60
In water contact environment up to ℃, hot water resistance and cathode peeling resistance are good, but when used for a long time in high temperature water contact environment requiring hot water resistance over 80 ℃, the adhesive strength decreases. However, it is difficult to maintain anticorrosion performance.

Therefore, it has been desired to develop a polyolefin-coated steel material which is excellent in hot water resistance, cathode peeling resistance, and heat shock resistance even when it is used for a long time in hot water exceeding 80 ° C. or salt water.

The present invention is intended to solve the above problems, and is excellent in hot water resistance, cathode peeling resistance, and heat shock resistance even when used for a long time in hot water exceeding 60 ° C. or salt water. An object of the present invention is to provide a polyolefin-coated steel material.

[0011]

The present invention is a polyolefin-coated steel material in which a chromate treatment layer, a primer layer, a modified polyolefin adhesive layer and a polyolefin resin layer are sequentially laminated on the surface of a steel material, wherein the primer layer is ) And (b), it is a polyolefin-coated steel material characterized by comprising the composition.

(A) Epoxy resin consisting of glycidyl ether of bisphenol A, glycidyl ether of bisphenol F, or a mixture thereof, (b) modified heterocyclic amine obtained by reaction-adding phenylglycidyl ether to heterocyclic amine, and metaxylylene diamine A mixture of amines.

[0013]

Embodiments of the present invention will be described below.

The steel materials used in the present invention are carbon steel, Mo,
Steel pipes and shaped steels made of alloy steels containing V, Nb, Cr, etc.
Steel plates, steel bars, and molded products and structures made of steel that are widely used outdoors, in the ground, on the ground, and on the seabed.

The coating layer in the present invention is formed on the surface of the steel material,
A chromate-treated layer, an epoxy primer layer containing the compositions (a) and (b) as essential components, a modified polyolefin resin layer, and a polyolefin resin layer are sequentially laminated.

The epoxy primer for forming the epoxy primer layer of the present invention comprises an epoxy resin which is the composition of (a) and a mixture of modified heterocyclic amine and metaxylylenediamine which is the composition of (b). The ratio of the epoxy equivalent of the composition (1) to the active hydrogen equivalent of the composition (2) is 1:
It is a mixture of 0.7 to 1: 1.1.

The composition of (a) above is bisphenol A.
Epoxy resin of glycidyl ether of bisphenol F or glycidyl ether of bisphenol F, alone or in a mixture. The glycidyl ether of bisphenol A has a molecular structure represented by the following chemical formula (1), and preferably has an epoxy equivalent in the range of 170 to 250 in terms of hot water resistance. ) Epicoat 828 and the like.

[0018]

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The glycidyl ether of bisphenol F has a molecular structure represented by the following chemical formula (2) and preferably has an epoxy equivalent of 170 to 185 from the viewpoint of hot water resistance. Epoxy Co., Ltd.
Manufactured by Epicoat 807.

[0020]

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The composition (b) comprises a mixture of modified heterocyclic amine obtained by addition reaction of alkyl glycidyl ether with heterocyclic amine and metaxylylenediamine.

That is, the composition (b) is a modified heterocyclic compound obtained by reaction-adding a phenylglycidyl ether having a molecular structure represented by the following chemical formula (4) to a heterocyclic amine having a molecular structure represented by the following chemical formula (3). A curing agent composed of a mixture of an amine and metaxylylenediamine having a molecular structure represented by the following chemical formula (5).

[0023]

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[0024]

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[0025]

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The mixture ratio of the modified heterocyclic amine and metaxylylenediamine is practically 90/1 by weight.
It is a mixture of 0 to 50/50.

Further, titanium oxide, silica, talc, muscovite, chromium oxide, zinc phosphate or the like may be used as an inorganic pigment in addition to the epoxy resin.

Further, in order to improve the wettability with the epoxy resin, chemical treatment such as silane coupling treatment may be applied.

Next, the chromate-treating agent used in the present invention is a polymeric organic reducing agent, and chromic acid partially reduced such that the weight ratio of hexavalent chromium to total chromium is in the range of 0.35 to 0.65. Examples thereof include silica-based chromate treatment agents in which fine silica powder is added to an aqueous solution. As a commercially available product, there is Cosmer 100 manufactured by Kansai Paint Co., Ltd.

Next, the polyolefin resin and the modified polyolefin resin used for forming the polyolefin resin layer and the modified polyolefin resin layer of the present invention will be described.

The polyolefin resin used in the present invention is a conventionally known polyolefin resin such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene and polypropylene.

The modified polyolefin resin is obtained by modifying the above-mentioned polyolefin resin with an unsaturated carboxylic acid such as maleic acid, acrylic acid or methacrylic acid or an acid anhydride thereof, or by appropriately modifying the modified product with a polyolefin resin. It is a conventionally known modified polyolefin resin such as.

Next, a method for producing a polyolefin-coated steel material according to the present invention will be described using a polyethylene-coated steel pipe as a representative.

The polyethylene-coated steel pipe can be obtained by the manufacturing process as shown in FIG. In FIG. 1, a chromate treatment agent coating device 2 applies a chromate treatment agent to the surface of a steel pipe 1 from which rust and the like have been removed, and a heating device (for chromate) 3 is baked to form a chromate treatment layer 4. Reference numeral 12 is a chromate treatment agent supply container.

In the above, the chromate treatment agent coating device 2
An ironing jig 19 is provided at the outlet of the chromate treatment layer 4 to make the surface of the chromate treatment layer 4 uniform.

Then, a primer is applied to the surface of the steel pipe 1a on which the chromate-treated layer 4 is formed by the primer application device 5 and is heated and cured by the heating device (for primer) 6 to form the primer layer 7. Reference numeral 13 denotes a primer supply container, which has a predetermined ratio from the epoxy resin supply container 14 of the composition (a) and the curing agent supply container 15 of the mixture of the modified heterocyclic amine and metaxylylenediamine which is the composition (b). The epoxy resin and the curing agent supplied in 1 are mixed in a mixing container (for primer) 16 and supplied to the primer supply container 13.

The modified heterocyclic amine, which is one of the compositions in (b) above, is the heterocyclic amine from the heterocyclic amine supply container 20 and the phenylglycidyl ether supply container 21.
The phenyl glycidyl ether from the above was supplied to the reaction container 22 at a predetermined ratio to carry out an addition reaction.

The modified heterocyclic amine thus produced is mixed with metaxylylenediamine supplied from the metaxylylenediamine supply container 23 in a mixing container (for curing agent) 24 at a predetermined ratio and then supplied to the curing agent supply container 15. ing.

In the above, an ironing jig 19 is provided at the exit of the primer coating device 5 to make the surface of the primer layer 7 uniform.

Next, the steel pipe 1 on which the primer layer 7 is formed
After the modified polyethylene resin 9 and the polyethylene resin 10 are extruded and coated as two layers on the surface of b by the round die 8,
It is cooled by the cooling device 11 to obtain a polyethylene resin-coated steel pipe 1c. 17 is a polyethylene resin supply container,
18 is a modified polyethylene resin supply container.

In the above, a T die may be used instead of the round die 8. Alternatively, the modified polyethylene resin 9 and the polyethylene resin 10 may be extrusion-coated as single layers.

In the case of the above manufacturing method, the surface of the steel pipe 1 is coated with a chromate treatment agent, baked, and then the steel pipe 1a is formed.
It is sufficient that the primer layer 7 is formed on the surface of the steel pipe 1a by the time it reaches the round die 8 and it is sufficiently cured. The epoxy primer can be applied by spray coating by the spray coating device 5 described above. It can be appropriately selected from conventionally known methods such as roll coating and ironing.

The method of heating the steel pipes 1a and 1b by the heating device 3 and the heating device 6 can be appropriately selected and used from conventionally known methods such as high frequency induction heating, far infrared heating and gas heating.

[0044]

The present invention will be described below in detail with reference to examples. The test methods in the examples are as follows. (1) Hot water immersion test Test temperature: 95 ° C., immersion time: 2500 hours After immersing the sample, the adhesion is measured (measurement temperature: room temperature, peeling angle: 90 degrees, peeling speed: 10 mm / min, peeling off the coating). When measuring the peel strength).

(2) High temperature cathode peeling test Test temperature: 80 ° C., electrolyte: 3% saline, voltage: 1.5
V, (Cu / CuSO _Four, Standard electrode), initial holiday
Diameter: diameter 9 mm, test days 30 days, peeling of coating film after the test
Measure the separation area.

(3) Heat cycle test The heat shock resistance is examined. Test conditions: −45 ° C. (holding for 8 hours) → 15 ° C. (holding for 8 hours) in the air for 15 cycles to check for edge peeling.

In the examples of the present invention, steel pipes (SGP80A) were prepared by shot blasting epoxy primers having the compositions shown in Tables 1 and 2 in advance and applying a chromate treatment agent (Cosmer 100: Kansai Paint Co., Ltd.) and baking. ) To 40 to 50 μm thick and heat-cured at 130 ° C., and a maleic anhydride-modified polyethylene resin layer and a polyethylene resin layer are melt-extruded as two layers on the surface with a circular die, 0.5 mm and 3. A coating layer of 0 mm was formed to obtain a polyethylene-coated steel pipe. A polyethylene-coated steel pipe was processed into a test piece of a specified size, and a test piece N
o. 1 to No. No. 18, a hot water immersion test, a cathode peeling test, a heat cycle test and the like were performed.

Specimen No. 1 to No. No. 9 is a sample in which glycidyl ether of bisphenol A (commercially available Epicoat 828) is used as the epoxy resin, and the sample No. 9 ~
No. No. 18 uses glycidyl ether of bisphenol F (commercially available Epicoat 807).

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

As a comparative example, an epoxy resin primer having the composition shown in Table 3 was applied in the same manner, and the test piece No.
1 to No. 6 was prepared and subjected to a hot water immersion test, a cathode peeling test, a heat cycle test and the like. The results are shown in Table 4.

[0053]

[Table 4]

As is clear from Table 4, the test piece Nos. 1 to No. No. 18 is a test piece No. according to a comparative example in all tests. 1 to No. 6, a good result was obtained.

As described above, the present invention is a hot water immersion test (95 ° C., 25 ° C.) under severe conditions for evaluating a long-term use condition.
Good results were obtained with respect to the cathode peeling test (80 ° C., initial Holiday diameter: diameter 9 mm, test days 30 days, etc.) and thermal cycle test.

[0056]

As described above, according to the present invention, by forming a specific primer layer on the underlayer, as compared with the conventional polyolefin-coated steel material, warm water resistance capable of withstanding long-term severe use conditions, It is possible to obtain a polyolefin-coated steel material that is excellent in both high-temperature cathode peel resistance and heat shock resistance.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a manufacturing process of a polyethylene-coated steel pipe of the present invention.

[Explanation of symbols]

 1 Steel Pipe 1a Steel Pipe with Chromate Treatment Layer 1b Steel Pipe with Primer Layer 1c Polyethylene Coated Steel Pipe 2 Chromate Treatment Agent Coating Device 3 Heating Device (for Chromate) 4 Chromate Treatment Layer 5 Primer Coating Device 6 Heating Device (for Primer) ) 7 primer layer 8 round die 9 modified polyethylene resin 10 polyethylene resin 11 cooling device 12 chromate treatment agent supply container 13 primer supply container 14 epoxy resin supply container 15 curing agent supply container 16 mixing container (for epoxy resin) 17 polyethylene resin supply container 18 Modified polyethylene resin supply container 19 Ironing jig 20 Heterocyclic amine supply container 21 Phenyl glycidyl ether supply container 22 Reaction container 23 m-Xylylenediamine supply container 24 Mixing container (for curing agent)

Claims (1)

[Claims] 1. A polyolefin-coated steel material in which a chromate treatment layer, a primer layer, a modified polyolefin adhesive layer and a polyolefin resin layer are sequentially laminated on the surface of the steel material, and the primer layer has the following composition (a) and (b): (B) glycidyl ether of bisphenol A, epoxy resin consisting of glycidyl ether of bisphenol F alone or in a mixture, (b) phenylglycidyl ether was reacted and added to heterocyclic amine A mixture of modified heterocyclic amine and metaxylylenediamine.