JPH1028928A - Polyolefin coated steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesion strength by using a thermosetting resin compsn. containing a mixture of a bisphenol-A epoxy resin having a specified epoxy equiv., a modified polyamine and an ethyltrismethane for a primer layer. SOLUTION: A primer layer 7 is formed on a steel pipe 1 by using a primer coating device, and two layers of a modified polyethylene resin 10 and a polyethylene resin 9 are formed through a round die 8 at one time to coat the pipe. When the primer layer 7 is formed, a thermosetting resin compsn. described below is used. This compsn. contains a mixture of an epoxy resin comprising either a bisphenol-A epoxy resin having 156 to 280 epoxy equiv. or a bisphenol-F epoxy resin or a mixture of these, a modified polyamine as the reaction product of xylilene diamine and unsatd. carboxylic acid or unsatd. carboxylic acid alkylester, and ethyltris(aminopropyl oxymethyl)methane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-coated steel material having high adhesion between a polyolefin resin layer and a steel material and having excellent anticorrosion performance.

[0002]

2. Description of the Related Art Steel materials coated with polyolefin resin on their surfaces (hereinafter referred to as polyolefin-coated steel materials) have excellent anticorrosion performance over a long period of time.
In addition to applications such as steel sheet piles, in recent years it has also been used as a steel material for construction materials used on the seabed, in extremely cold regions, and in the tropics, and for pipelines that transport crude oil, heavy oil, and natural gas. Have been.

[0003] Because of their use in a wide temperature environment or a high-temperature water-contact environment as described above, there is a demand for improved anticorrosion performance, that is, improved hot water resistance and heat shock resistance. Have been. In addition, in an environment in which cathodic protection is also used, cathode peeling due to excessive corrosion protection current becomes a problem.

[0004] As a prior art relating to polyolefin-coated steel, Japanese Patent Application Laid-Open No. 54-120681 and Japanese Patent Application Laid-Open
Japanese Patent Publication No. 280545 (referred to as Reference Document 1) discloses a method of providing a chromate treatment layer between a steel material and a modified polyolefin resin adhesive layer, as disclosed in JP-A-56-143223 and JP-A-59-222275. Reference 2) discloses a method of interposing an epoxy primer layer.

[0005] Japanese Patent Application Laid-Open No. 60-245544 (referred to as Reference 3) discloses a method for further improving the anticorrosion performance by interposing a primer layer on a chromate-treated layer. In this method, polypropylene is used as the anticorrosion layer. There is no specific description about the primer layer, but only vaguely an aromatic amine-based curing agent.

[0006]

However, the method of applying the chromate treatment disclosed in the prior art document 1 and the method of applying the epoxy primer treatment disclosed in the prior art document 2 are not suitable for use in a wet environment of 60 ° C. or lower. However, in a water-contact environment exceeding 60 ° C., satisfactory performance in hot water resistance and cathode peeling resistance cannot be obtained.

[0007] The method disclosed in Patent Document 3 using both the chromate treatment and the primer treatment provides satisfactory performance in a wet environment of 80 ° C or lower, but in a wet environment of over 80 ° C. Satisfactory performance in hot water resistance and cathodic peeling resistance cannot be obtained. In particular, the adhesion between the polyolefin resin layer and the steel material is significantly reduced, and it is difficult to maintain the anticorrosion performance for a long time.

The present invention has been proposed in order to solve the above-mentioned problems of the prior art, in which the adhesion between the polyolefin resin layer and the steel material can be improved, and in a high-temperature water-contact environment exceeding 80 ° C. It is an object of the present invention to provide a polyolefin-coated steel material having excellent hot water resistance, cathodic peeling resistance, and heat shock resistance, and excellent in anticorrosion performance.

[0009]

The invention according to claim 1 is a coated steel material in which a chromate treatment layer, a primer layer, a modified polyolefin adhesive layer, and a polyolefin resin layer are sequentially coated on the steel material surface from the steel material surface. A polyolefin-coated steel material characterized by using a thermosetting resin composition containing the following (1) and (2) when forming a layer.

(1) An epoxy resin comprising one of a bisphenol A epoxy resin and a bisphenol F epoxy resin having an epoxy equivalent of 156 to 280, or a mixture of both.

(2) A mixture of a modified polyamine, which is a reaction product of xylylenediamine with an unsaturated carboxylic acid or an unsaturated carboxylic acid alkyl ester, and ethyltris (aminopropyloxymethyl) methane.

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, the coating layer according to the present invention is composed of a steel material surface, a chromate-treated layer, a primer layer formed from a thermosetting resin composition obtained by blending the above (1) and (2), and an adhesive formed from a modified polyolefin resin. A layer (this is called a modified polyolefin adhesive layer) and a polyolefin resin layer are laminated in this order.

The reason why the coating layer is formed in such a configuration and in order is as follows. First, since the polyolefin resin is non-polar, it does not directly adhere to the steel surface. Therefore, in the present invention, the modified polyolefin adhesive layer having a polar group and having adhesiveness is interposed between the steel material and the polyolefin resin layer to improve the adhesion between the two.

Next, by providing a chromate treatment layer and a primer layer between the modified polyolefin adhesive layer and the steel material, the adhesion between them is further improved. That is, by providing the chromate treatment layer, the resistance to cathodic peeling is improved, and by forming the primer layer, it is possible to ensure a certain degree of long-term anticorrosion performance in a high-temperature water-contact environment. Here, the term "cathode peeling" means that the coating resin easily peels from a coating defect as a starting point due to an excessive corrosion protection current in an environment where the electrolytic protection is performed.

The primer layer according to the present invention comprises the epoxy resin shown in (1) as a main agent and the (2) epoxy resin as a curing agent.
Is a layer formed by blending and curing with the amines shown in (1).

The epoxy resin (1) is an epoxy resin composed of one of a bisphenol A epoxy resin and a bisphenol F epoxy resin having an epoxy equivalent of 156 to 280, or a mixture of both. Further, they are materials having the molecular structures of Chemical Formulas 1 and 2.

[0017]

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[0018]

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The epoxy resin (1) made of the above material has a highly symmetric and rigid bisphenol skeleton, and therefore has stable high-temperature characteristics (hot water resistance). Also, it has moderate flexibility because it has an ether bond in the skeleton. Furthermore, as a result of the reaction of the epoxy group, a hydroxyl group is generated, so that the adhesive strength is increased.

Similarly, the present inventors have studied the curing agent to obtain a material having hot water resistance and flexibility. As a result, it has been found that simply using xylylenediamine as the curing agent has high temperature properties (warm water resistance) but lacks flexibility.

Therefore, as a result of further intensive studies, it was found that a mixture of a modified polyamine obtained by reacting xylylenediamine with an unsaturated carboxylic acid or an alkyl ester of an unsaturated carboxylic acid and ethyltris (aminopropyloxymethyl) methane was used as a curing agent. It was found that a cured product (primer layer) having high flexibility could be obtained by using as a. Further, it has been found that the coated steel material having the primer layer is excellent in hot water resistance and heat shock resistance over a long period of time. Here, the modified polyamine and ethyltris (aminopropyloxymethyl) methane are materials having the molecular structures of Chemical Formulas 3 and 4, respectively.

[0022]

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[0023]

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The invention according to claim 2 is characterized in that the unsaturated carboxylic acid or unsaturated carboxylic acid alkyl ester is acrylic acid or acrylic acid alkyl ester, or methacrylic acid or methacrylic acid alkyl ester. Item 4. A polyolefin-coated steel material according to item 1.

There are various unsaturated carboxylic acids and esters thereof. When the above-mentioned acrylic acid, methacrylic acid, alkyl acrylate and alkyl methacrylate are used, they easily react with xylylenediamine and have side reactions. It produces few impurities. When the resulting modified polyamine is used as a curing agent, it gives a sufficient flexibility effect.

Using such a modified polyamine as a curing agent,
By using an epoxy resin having the above-described properties as a main component, a primer layer having excellent hot water resistance and heat shock resistance exceeding 80 ° C. is formed.

As described above, in the present invention, the steel material surface is coated with the above-described structure, and the adhesion between the polyolefin resin layer and the steel material is improved by using the above-described composition as the primer layer. A polyolefin-coated steel material having excellent anti-corrosion performance with good hot water resistance, cathodic peeling resistance, and heat shock resistance in a water-contact environment is obtained.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The steel material according to the present invention is carbon steel,
For low-alloy steel, etc. processed into shaped steel, steel plates, steel bars, steel pipe piles, steel sheet piles, steel pipes for transporting crude oil / heavy oil, natural gas, etc., used outdoors, underground, in seawater, etc. Target

Inorganic pigments such as titanium oxide, silica, talc, muscovite, chromium oxide and zinc phosphate may be added to the epoxy resin of the material (1). In addition, a chemical treatment such as a silane coupling treatment may be performed on the inorganic pigment in order to improve the adhesiveness with the epoxy resin. Further, another epoxy resin may be added as long as the performance is not changed.

As the bisphenol A-based epoxy resin, those having an epoxy equivalent of 170 to 280 can be used, and preferably those having an epoxy equivalent of 184 to 194 (for example, oiled shell epoxy) in consideration of workability. Epicoat 828 (trade name, manufactured by Co., Ltd.)
Is desirable.

As the bisphenol F-based epoxy resin, those having an epoxy equivalent of 156 to 280 can be used. However, in consideration of handling workability, those having an epoxy equivalent in the range of 160 to 175 (for example, oiled shell epoxy ( Epicoat 807) (trade name, manufactured by KK) is desirable.

The modified polyamine constituting the curing agent of the material (2) is mainly a modified product of xylylenediamine having a molecular structure represented by the chemical formula 3, and impurities and unreacted products generated when synthesizing the modified product are as follows. Xylylenediamine may remain. In addition, xylylenediamine is O-
Any of isomers of (ortho-), m- (meta-), and p- (para-) may be used, but metaxylylene diylene is preferable from the viewpoint of easy handling (workability) and good reactivity. Amines are preferred.

The modified polyamine may have a molecular structure represented by the following chemical formula 3. In order to synthesize the modified polyamine, an unsaturated carboxylic acid or an unsaturated carboxylic acid alkyl ester may be used. Acid anhydrides and acid halides may be used.

Here, when synthesizing a modified polyamine using an unsaturated carboxylic acid alkyl ester as a raw material, the raw material ester is decomposed by a reaction with the amine to produce an alcohol. The reaction proceeds smoothly when the alcohol goes out of the system. Therefore, it is preferable that the generated alcohol has a low boiling point, and the unsaturated carboxylic acid alkyl ester as the raw material is preferably a methyl ester or an ethyl ester. When the epoxy equivalent of the epoxy resin is smaller than the above range, satisfactory performance cannot be obtained, and when the epoxy equivalent is larger, handling operability deteriorates.

Ethyl tris (aminopropyloxymethyl) methane may have an active hydrogen equivalent of 70 to 85.

Regarding the compounding, the ratio (b) of the mole number (b) of the total active hydrogen in the mixture (curing agent) of the mixture (curing agent) of (2) to the epoxy group (a) in the epoxy resin (base) of (1) b /
It is blended so that a) is in the range of 0.7 to 1.2. Further, the mixing ratio (c / d) of the modified polyamine (weight c) and ethyltris (aminopropyloxymethyl) methane (weight d) constituting the mixture (curing agent) of (2) is 1
00/0 <c / d <60/40, preferably 90/1
By mixing so as to be in the range of 0 <c / d <70/30, a primer layer excellent in warm water resistance exceeding 80 ° C., cathode peeling resistance and heat shock resistance can be obtained.

When the molar ratio (b / a) is less than 0.7 or exceeds 1.2, the mixing ratio (c / d) is 1
When it is out of the range of 00/0 <c / d <60/40,
Or ethyl tris (aminopropyloxymethyl)
When the active hydrogen equivalent of methane is out of the range of 70 to 85, the glass transition temperature of the cured product decreases, and the warm water resistance decreases, which is not preferable.

As the chromate treating agent, the weight ratio of hexavalent chromium to total chromium is determined by using a high molecular organic reducing agent.
A silica-based chromate treating agent obtained by adding fine silica powder to an aqueous solution of chromic acid partially reduced so as to be in the range of 0.35 to 0.65 can be used.

The polyolefin resin used as the material of the polyolefin resin layer according to the present invention is a conventionally known polyolefin such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and polypropylene.

The modified polyolefin resin used as the material of the modified polyolefin adhesive layer is obtained by modifying the above polyolefin resin with an unsaturated carboxylic acid such as maleic acid, acrylic acid, methacrylic acid or an acid anhydride thereof.
Alternatively, a modified product thereof is appropriately diluted with a polyolefin resin or the like, and is a conventionally known modified polyolefin.

Next, as one embodiment of the polyolefin-coated steel material of the present invention, a method for producing a polyethylene-coated steel pipe will be described. FIG. 1 is a diagram showing a configuration of a coated steel pipe manufacturing apparatus. Here, 1 is a steel pipe, 2 is a chromate treatment coating device, 3 is a heating device, 4 is a chromate treatment layer, 5 is a primer coating device, 6 is a post-heating device, 7 is a primer layer,
8 is a round die, 9 is a polyethylene resin, 10 is a modified polyethylene resin, 11 is a cooling device, 12 is a chromate treatment agent supply container, 13 is a primer supply container, 14 is an epoxy resin supply container, 15 is a modified polyamine and polyoxygen. A mixture supply container with propylene triamine (hereinafter, referred to as a curing agent supply container), 16 is a mixing container, 17 is a polyethylene resin supply container, 18 is a modified polyethylene resin supply container, and 19 is an ironing jig.

First, a chromate treatment agent is applied to the surface of the steel pipe 1 from which rust has been removed by a chromate treatment agent application device 2 and heated by a heating device 3 to bake the chromate treatment agent to form a chromate treatment layer 4. An ironing jig 19 is provided at the outlet of the chromate treatment agent application device 2 to make the surface of the chromate treatment layer uniform.

Next, from the epoxy resin supply container 14, the epoxy resin as the material (1) is supplied to the curing agent supply container 1.
From 5, the curing agent as the material of (2) is cut out at a predetermined ratio (weight ratio), supplied to the mixing container 16, and mixed to produce a primer. The generated primer is supplied to the primer coating device 5 via the primer supply container 13.

The primer generated as described above is
On the surface of the steel pipe 1a on which the chromate treatment layer 4 is formed,
The coating is performed by the primer coating device 5 and the post-heating device 6
To form a primer layer 7.

An ironing jig 19 is provided at the outlet of the primer coating device 5 to make the surface of the primer layer 7 uniform. Next, two layers of the modified polyethylene resin 10 and the polyethylene resin 9 are simultaneously extruded and coated on the surface of the steel pipe 1b on which the primer layer 7 is formed by the round die 8 (or a T-type die). Thereafter, cooling is performed by the cooling device 11 to obtain the polyethylene-coated steel pipe 1c. At this time, the modified polyethylene resin 10 and the polyethylene resin 9 may be respectively extruded and coated in a single layer.

In the case of the above-mentioned manufacturing method, a primer layer 7 is formed on the surface of the steel pipe 1a after the chromate treating agent is applied to the surface of the steel pipe 1 and baked and before the steel pipe 1a reaches the round die 8. Suffice if it is sufficiently cured. The method for applying the epoxy primer can be appropriately selected from conventionally known methods such as spray coating using a spray coating machine, roll coating, and ironing. The method of heating the steel pipe 1b by the post-heating device 6 can be appropriately selected from conventionally known methods such as high-frequency induction heating, far-infrared heating, and gas heating.

[0047]

EXAMPLES In order to confirm the effect of the present invention, a polyethylene-coated steel pipe was manufactured by the above-described coated steel pipe manufacturing method, and a test piece was taken therefrom to confirm the anticorrosion performance.

In the production of a polyethylene-coated steel pipe, first, a steel pipe (SGP 80A) was shot blasted in advance, and a chromate treatment agent was applied and baked. On this chromate-treated layer, a primer composed of a main agent and a curing agent shown in Table 1 described below was applied to a thickness of 40 to 50 μm, and cured by heating at 130 ° C. to form a primer layer.

Thereafter, two layers were simultaneously melt-extruded on the primer layer using a round die in the order of a maleic anhydride-modified polyethylene resin layer and a polyethylene resin layer to form a coating layer. At this time, the thicknesses of the modified polyethylene adhesive layer and the polyethylene resin layer were 0.5 mm and 3.0 mm, respectively.

Table 1 shows the epoxy resin (base resin), the curing agent and the mixing ratio thereof used for producing the above-mentioned epoxy primer.

[0051]

[Table 1]

In the examples, two types of the above-mentioned Epicoat 828 and Epicoat 807 were used as the epoxy resin (main agent), and the modified polyamine A was a modified polyamine A (active hydrogen equivalent) obtained by reacting xylylenediamine with acrylic acid. 65), modified polyamine B produced by reacting xylylenediamine and methacrylic acid (active hydrogen equivalent 6
8) and ethyl tris (aminopropyloxymethyl) methane (active hydrogen equivalent: 80) were used.

Further, the mixing ratio (c / d) of the modified polyamine (weight c) and ethyltris (aminopropyloxymethyl) methane (weight d) was 95/5, 80/20,
Three levels of 60/40 were set.

In the comparative example, one kind of Epicoat 828 was used as the epoxy resin (base), and B002 or P002 was used as the curing agent. Here, B002 is disclosed in
As disclosed in JP-143223, it is a modified heterocyclic amine obtained by reacting 1 mol of butyl glycidyl ether with 2 mol of a heterocyclic amine having a molecular structure of Chemical Formula 5. P002 is a modified heterocyclic amine obtained by reacting 1 mol of phenylglycidyl ether with 2 mol of a heterocyclic amine having a molecular structure of Chemical Formula 5.

[0055]

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The compounding ratio = main agent / curing agent is defined as (1)
(2) with respect to 100 parts by weight of the epoxy resin (base resin)
Is a ratio of the weight of the mixture (curing agent). B / a indicates the ratio of the mole number (a) of the epoxy group in the epoxy resin (base) of (1) to the mole number (b) of the active hydrogen of the mixture (curing agent) of (2). It is.

A test piece having a predetermined size was sampled from the manufactured polyethylene-coated steel pipe and subjected to a hot water immersion test, a cathode peeling test, and a heat cycle test. Table 2 shows the test results. The details of each test method will be described later.

[0058]

[Table 2]

In Examples 1 to 36, the peel strength in the hot water immersion test exceeded 10 kg / cm, the coating film peeling area in the high temperature cathode peeling test was 8 cm ² or less, and edge peeling in the heat cycle test was observed. Did not. Therefore, 8
All of the hot water resistance exceeding 0 ° C., the resistance to cathodic peeling, and the resistance to heat shock were all good, and the polyethylene-coated steel pipe excellent in anticorrosion performance could be evaluated.

In Comparative Example 1, the peel strength was 1 kg / cm, the peeling area value of the coating film exceeded 8 cm ² , and edge peeling was observed in the heat cycle test. Therefore, it is impossible to judge that the resistance to hot water exceeding 80 ° C., the resistance to cathodic peeling and the resistance to heat shock are good, and a polyethylene-coated steel pipe excellent in anticorrosion performance cannot be obtained.

In Comparative Example 2, the peel strength was 3 kg / cm
, The hot water resistance exceeding 80 ° C is good, but the peeling area of the coating film exceeds 8 cm ² , edge peeling was observed by a heat cycle test, and the cathode peeling resistance and heat shock resistance could not be judged to be good. However, a polyethylene-coated steel pipe having excellent anticorrosion performance cannot be obtained.

(Details of Test Method) Hot water immersion test This test is for evaluating hot water resistance.

From the manufactured polyethylene-coated steel pipe, a width of 10
A test piece having a thickness of 200 mm, a length of 200 mm and a thickness of 20 mm was cut out to obtain a sample.

After this test piece was immersed in a water bath at a test temperature of 85 ° C. for a dipping time of 10,000 hours, the coating resin layer was slightly peeled off, and this was gripped as a margin to be pulled by a tensile tester to be peeled off. The strength (this is called peel strength) is measured. The measurement conditions of the tensile test are as follows: temperature: room temperature,
Peeling angle: 90 degrees, peeling speed: 10 mm / min, unit: kg / cm.

When the peel strength exceeds 2 kg / cm, 8
It is judged that the hot water resistance exceeding 0 ° C. is good.

2. High Temperature Cathodic Peeling Test A test for evaluating the cathodic peeling resistance.

Test temperature: 85 ° C., electrolyte: 3% saline,
Applied voltage: -1.5V, (standard electrode: Cu / CuSO ₄
), Initial holiday diameter: diameter 11 mm, test time:
After 50 days, the coating peeled area after the test is measured.

If the coating resin peeling area is 8 cm ² or less, it is judged that the cathode peeling resistance is good.

3. Heat cycle test This is a test for evaluating heat shock resistance.

Test conditions: -70 ° C (8Hr) → 23 ° C water (8Hr) → + 45 ° C (8Hr) as one cycle,
After repeating 25 cycles, the presence or absence of end peeling of the test piece is visually observed. If there is no edge peeling, it is determined that the heat shock resistance is good.

[0071]

According to the polyolefin-coated steel material of the present invention, a coating layer having the above-described structure and laminated in order is formed on the steel material surface, so that the adhesion between the polyolefin resin layer and the steel material is improved, and A polyolefin-coated steel material having excellent hot water resistance, cathodic peeling resistance and heat shock resistance, and excellent corrosion protection performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a manufacturing apparatus for a polyolefin-coated steel pipe.

[Explanation of symbols]

 Reference Signs List 1 steel pipe 4 chromate treatment layer 7 primer layer 9 polyethylene resin 10 modified polyethylene resin 12 chromate treatment agent supply container 13 primer supply container 14 epoxy resin supply container 15 hardener supply container 16 mixing container 17 polyethylene resin supply container 18 modified polyethylene resin supply container

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B32B 27/32 B32B 27/32 Z C08L 63/00 NJD C08L 63/00 NJD C23C 28/00 C23C 28 / 00 C

Claims (2)

[Claims] 1. A coated steel material in which a chromate treatment layer, a primer layer, a modified polyolefin adhesive layer, and a polyolefin resin layer are sequentially coated on the steel material surface from the steel material surface, and when forming the primer layer, the following (1) (2)
A polyolefin-coated steel material characterized by using a thermosetting resin composition containing: (1) Bisphenol A epoxy resin or bisphenol F having an epoxy equivalent of 156 to 280
An epoxy resin comprising one or a mixture of both. (2) A mixture of a modified polyamine, which is a reaction product of xylylenediamine with an unsaturated carboxylic acid or an unsaturated carboxylic acid alkyl ester, and ethyltris (aminopropyloxymethyl) methane. 2. The polyolefin coating according to claim 1, wherein the unsaturated carboxylic acid or unsaturated carboxylic acid alkyl ester is acrylic acid, acrylic acid alkyl ester, methacrylic acid or methacrylic acid alkyl ester. Steel.