JP5547364B2 - Epoxy powder coating composition for steel and coated steel - Google Patents

Description

  The present invention relates to an epoxy powder coating composition useful as a primer for steel materials, particularly polyolefin-coated steel pipes for pipelines.

  Conventionally, steel pipes for pipelines are used for transportation of oil and natural gas. Since steel pipes for pipelines are laid and used in corrosive environments such as the atmosphere, the ground, and the sea, they are usually subjected to anticorrosion treatment. For example, anticorrosive treatment of steel pipes for pipelines used in natural gas, asphalt, coal tar, enamel, coal tar pitch and petroleum bitumen coatings, polyolefins, epoxy And plastic coatings such as three-layer coating systems. Among these anticorrosion treatments, a three-layer coating system is currently the mainstream for anticorrosion treatment of steel pipes for pipelines because of its excellent anticorrosion performance.

  The general anticorrosion treatment of the three-layer coating system has a configuration in which the outer peripheral surface of a chromate-treated pipe steel pipe is coated with an epoxy powder coating composition, a polyolefin adhesive, and a polyolefin coating resin in this order. Pipeline steel pipes subjected to such anticorrosion treatment are called polyolefin-coated steel pipes. As an epoxy powder coating composition used for such a polyolefin-coated steel pipe, for example, Patent Document 1 discloses an epoxy resin component containing a bisphenol A type epoxy resin and an o-cresol novolac type epoxy resin in a specific ratio, a phenolic type. An invention relating to an epoxy powder coating composition comprising a curing agent, an imidazole curing accelerator and / or an imidazoline curing accelerator and an inorganic filler is disclosed. Patent Document 2 discloses that tannin or tannic acid is 20 parts by mass or less with respect to 100 parts by mass of the main agent made of a cured product obtained by curing a bisphenol A or F type epoxy resin and a curing agent in the presence of a catalyst. An invention relating to an epoxy powder coating composition characterized in that it is contained in an amount is disclosed.

JP 2000-191954 A JP 2002-105393 A

  Although the epoxy powder coating compositions of these inventions satisfy the properties such as anticorrosion, adhesion, cathode peelability, and low temperature impact required for polyolefin coated steel pipes used in normal environments, they are thick films. When used in the above, the adhesion performance under an extremely low temperature environment of about −60 ° C. is not sufficiently satisfied.

  This invention is made | formed in view of said situation, The place made into the objective is to provide the epoxy powder coating composition for steel materials excellent in the adhesiveness in very low temperature also in a thick film.

In the present invention , (1) a coating film composed of an epoxy powder coating composition for steel materials having the following characteristics, (2) a polyolefin adhesive layer, and (3) a polyolefin-coated resin layer are sequentially laminated on the steel material surface. It is related with the covering steel material characterized by these.
Epoxy powder coating composition for steel:
Epoxy powder for steel containing epoxy resin component (A) and phenolic curing agent (B)
A coating composition comprising 1 to 70% by weight of bisphenol A type epoxy resin (a-1) having an epoxy equivalent of 300 to 750 g / eq and an epoxy equivalent of 1,
200 to 5,500 g / eq of bisphenol A type epoxy resin (a-2) 30 to 99% by weight, in phenolic curing agent (B) with respect to 1 equivalent of epoxy group in epoxy resin component (A) Epoxy powder coating composition for steel, wherein the group that reacts with the epoxy group is in the range of 0.5 to 1.5 equivalents

According to the onset bright, it is possible to obtain low-temperature impact resistance, excellent adhesion durability, the coating steel also has sufficient resistance to further thermal cycling test was intended for use under cryogenic environment.

The epoxy powder coating composition for steel materials of the present invention comprises a bisphenol A type epoxy resin (a-1) having an epoxy equivalent of 300 to 750 g / eq and a bisphenol A type epoxy having an epoxy equivalent of 1,200 to 5,500 g / eq. A powder coating composition containing an epoxy resin component (A) containing a resin (a-2) and a curing agent (B) , wherein the epoxy resin component (A) contains a bisphenol A type epoxy resin (a-2) 30 to 99% by weight .

  The epoxy resin component (A) includes, as essential components, a bisphenol A type epoxy resin (a-1) having an epoxy equivalent of 300 to 750 g / eq and a bisphenol A type epoxy resin having an epoxy equivalent of 1,200 to 5,500 g / eq ( a-2).

  The bisphenol A type epoxy resin (a-1) contributes to the curability of the formed coating film and the adhesion to the steel material. The bisphenol A type epoxy resin (a-1) is not particularly limited and conventionally known ones can be used. For example, as commercially available products, jER-1001 (manufactured by Japan Epoxy Resin, epoxy equivalent 450 to 500 g / eq), jER-1002 (manufactured by Japan Epoxy Resin, epoxy equivalent 600 to 700 g / eq), Epototo YD-011 (Toto Kasei) Manufactured by the company, epoxy equivalent 450-500 g / eq), Epototo YD-901 (manufactured by Toto Kasei Co., Ltd., epoxy equivalent 450-500 g / eq), Epototo YD-012 (manufactured by Toto Kasei Co., Ltd., epoxy equivalent 600-700 g / eq), Epototo YD-902 (manufactured by Tohto Kasei Co., Ltd., epoxy equivalent: 600 to 700 g / eq) and the like.

  The content of the bisphenol A type epoxy resin (a-1) is not particularly limited. A preferable content is in the range of 1 to 70% by weight, more preferably in the range of 5 to 60% by weight, and particularly preferably in the range of 10 to 50% by weight in the epoxy resin component (A). The lower limits of these ranges are significant in terms of heat cycle resistance and adhesion durability. Moreover, the upper limit of these ranges is significant in terms of storage stability and heat cycle resistance.

  The bisphenol A type epoxy resin (a-2) contributes to the flexibility of the formed coating film. It does not specifically limit as a bisphenol A type epoxy resin (a-2), A conventionally well-known thing can be used. For example, as commercial products, jER-1007 (Japan Epoxy Resin, epoxy equivalent 1,750-2,200 g / eq), jER-1009 (Japan Epoxy Resin, epoxy equivalent 2,400-3,300 g / eq) , JER-1010 (manufactured by Japan Epoxy Resin, epoxy equivalent 3,000 to 5,000 g / eq), Epototo YD-907 (manufactured by Tohto Kasei Co., Ltd., epoxy equivalent 1,300 to 1,700 g / eq), Epototo YD- 017 (manufactured by Tohto Kasei Co., Ltd., epoxy equivalent 1,750-2,100 g / eq), Epototo YD-909 (manufactured by Toto Kasei Co., Ltd., epoxy equivalent 1,800-2500 g / eq), Epototo YD-019 (Toto Kasei) Epoxy equivalent 2,400-3,300 g / eq), Epototo YD-7019 (Toto Kasei) , Epoxy equivalent 3,000 to 4,000 g / eq), Epototo YD-6020 (manufactured by Tohto Kasei Co., Ltd., epoxy equivalent 3,000 to 5,000 g / eq), Epototo YD-020N (manufactured by Toto Kasei Co., epoxy equivalent) 3,800 to 4,000 g / eq).

  The content of the bisphenol A type epoxy resin (a-2) is not particularly limited. A preferable content is in the range of 30 to 99% by weight in the epoxy resin component (A), more preferably in the range of 40 to 95% by weight, and particularly preferably in the range of 50 to 90% by weight. These ranges are significant in terms of the flexibility of the formed coating film and the heat cycle resistance.

  Moreover, as an epoxy resin component (A), in addition to the above epoxy resin, other epoxy resins can be used in combination as long as the effects of the present invention are not impaired. For example, bisphenol A type epoxy resins other than the above (a-1) and (a-2) are mentioned. In addition, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, polyhydric alcohol type epoxy resin, glycidyl ester type epoxy resin and the like can also be mentioned. These may be used alone or in combination of two or more.

  If a hardening | curing agent (B) is a hardening | curing agent which reacts with the epoxy group of an epoxy resin component (A), it will not specifically limit and a conventionally well-known thing can be used. Examples include amine curing agents, acid curing agents, acid anhydride curing agents, polyamide curing agents, phenol curing agents, dicyandiamide curing agents, cationic polymerization reaction curing agents, and hydrazine curing agents. Among these, phenol-based curing agents are preferable from the viewpoints of curability and resistance to cathode peeling. These can be used alone or in combination of two or more.

  The content of the curing agent (B) is not particularly limited. The preferred content is in the range of 0.5 to 1.5 equivalents of the group that reacts with the epoxy group in the curing agent with respect to 1 equivalent of the epoxy group in the epoxy resin component (A), more preferably 0.8 to The range is 1.3 equivalents. These ranges are significant in terms of cold cycle resistance, low temperature impact resistance, and storage stability.

  The steel powder epoxy powder coating composition of the present invention can further contain a filler (C). The filler is not particularly limited, and a conventionally known filler can be used. For example, coloring pigments (titanium oxide, carbon black, bengara, iron oxide, etc.), extender pigments (calcium carbonate, silica, barium sulfate, calcium metasilicate, alumina, clay, talc, mica, etc.), anti-rust pigments (zinc phosphate) , Aluminum phosphate, etc.).

  The content of the filler (C) is not particularly limited. The preferred content is in the range of 10 to 60% by weight, more preferably in the range of 20 to 50% by weight, based on the epoxy resin component (A). These ranges are significant in terms of storage stability and heat cycle resistance.

The epoxy powder coating composition for steel used for the coated steel material of the present invention can further contain a curing catalyst. The curing catalyst is not particularly limited, and a conventionally known catalyst can be used. Specifically, for example, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2,4 -Imidazole compounds such as diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-S-triazine; 2-methylimidazoline, 2-ethylimidazoline, 2-heptyluimidazoline, 2-heptadecylimidazoline, 2 -Imidazoline compounds such as -phenylimidazoline, 2-phenylimidazoline-isocyanuric acid adduct, 1-cyanoethyl-2-phenylimidazoline, and the like. These can be used alone or in combination of two or more.

  The content of the curing catalyst is not particularly limited. The preferred content is 0.1 to 10% by weight, more preferably 1 to 5% by weight, based on the curing agent (B). These ranges are significant in terms of curability and coating workability.

Furthermore, the epoxy powder coating composition for steel materials used for the coated steel material of the present invention can contain additives such as a dispersant, a surface conditioner, and a thixotropic agent.

The epoxy powder coating composition for steel materials used in the coated steel material of the present invention has a Young's modulus at 20 ° C. of 15,000 kgf / cm ² or less, an elongation at break of 10% or more, and a heat shrinkage stress of 130 kgf / cm. It is preferable that it is cm ² or less. A more preferable range is a range in which the formed coating film has a Young's modulus at 20 ° C. of 8,000 to 12,000 kgf / cm ² , an elongation at break of 13 to 35% and a heat shrinkage stress of 60 to 130 kgf / cm ² . If it is in these ranges, it can be expected to further improve the thermal cycle resistance. Coating satisfying these physical properties can be formed by appropriately selecting the above-described components and content of the steel material for epoxy powder coating composition.

Here, the Young's modulus is obtained by the following method. An epoxy powder coating composition for steel is applied on a glass plate so that the film thickness is 150 μm, heated and cured under predetermined conditions, and then the coating film is peeled off from the glass plate, and the length is 30 mm, the width Cut into 5 mm strips. Using “Tensilon UTM-II-20” (trade name, manufactured by Orientec Co., Ltd.) as the measuring instrument, the coating film is attached to the measuring instrument so that the measurement length is 20 mm, and the tensile speed is 8 mm / min at a temperature of 20 ° C. Measure with The slope of the stress-strain curve at the rise of the measurement result is the Young's modulus, and the unit is kgf / cm ² .

The elongation at break is measured using the equipment used to measure the Young's modulus. A coating film having a thickness of 150 μm, a length of 30 mm, and a width of 5 mm prepared in the same manner as described above is attached to a measuring device so that the measured length of the coating film is 20 mm, and pulled at a temperature of 20 ° C. and a pulling speed of 8 mm / min. The measured elongation when the coating film is broken is compared with the measured length before the test, and the elongation at break is determined by the following formula.
Elongation at break (%) = [(measured length of coating film when fractured) − (measured length of coating film before measurement)] / [(measured length of coating film before measurement) × 100]

  The heat shrinkage stress is obtained by the following method. A coating film having a film thickness of 150 μm, a length of 30 mm, and a width of 5 mm is prepared by the same production method as that for measuring the Young's modulus. The heat shrinkage stress measuring device “RS-20C” (manufactured by Reska Co., Ltd., product name) is attached so that the measurement length of the coating film is 20 mm, and the heat shrinkage stress is measured. In the measurement, the stress measurement value at an atmospheric temperature of 100 ° C. is adjusted to 0 kgf, and then the temperature is lowered to 40 ° C. by natural cooling. The stress value indicated on the recorder is plotted against the temperature, and a straight line α is obtained from the points of 40 ° C., 50 ° C. and 60 ° C. by the least square method. A stress value at 20 ° C. is read from the obtained straight line α, and set as a heat shrinkage stress value.

The manufacturing method of the epoxy powder coating composition for steel materials used for the coated steel material of the present invention is not particularly limited, and can be manufactured by a conventionally known method. For example, after dry-mixing each of the above components with a Henschel mixer, etc., and then melt-mixing using a melt mixing and dispersing machine such as a twin screw extruder, then cooling, coarse pulverization, atomizer, jet mill, etc. And then filtered. The average particle size of the produced epoxy powder coating composition for steel materials is preferably in the range of 10 to 100 μm, more preferably in the range of 40 to 70 μm. The lower limit of these ranges is significant in terms of coating workability. Moreover, the upper limit of these ranges is significant in terms of the smoothness of the coating film.

  The coated steel material of the present invention is formed by sequentially laminating a coating film made of the above-described epoxy powder coating composition for steel materials, a polyolefin adhesive layer, and a polyolefin-coated resin layer on the surface of the steel material.

  The steel material is a steel material made of alloy steel such as carbon steel or stainless steel, and the shape may be any of a plate shape, a pipe shape, and a box shape. Further, the surface of the steel material may be subjected to rust removal treatment such as alkali degreasing / pickling treatment or blast treatment as necessary. Furthermore, surface treatment such as chromate treatment or phosphate treatment may be applied in order to impart excellent corrosion resistance.

  On the steel material, a coating film made of the epoxy powder coating composition for steel material of the present invention is laminated. The film thickness of a coating film can be suitably selected according to the use of steel materials. Preferably it is the range of 30-1000 micrometers, More preferably, it is the range of 40-600 micrometers.

  The coating and curing method is not particularly limited and can be performed by a conventionally known method. When the steel material is a pipe-shaped steel pipe, for example, the surface of the steel pipe is preheated by high frequency induction heating or burner heating, and the epoxy powder coating composition for steel material of the present invention is electrostatically coated or frictionally charged on the outer surface. Or application | coating and hardening can be performed by fluid dip coating etc. Moreover, after applying the epoxy powder coating composition for steel material to the outer surface of the steel pipe at room temperature, the steel pipe may be heated and cured. Curing conditions are not particularly limited, and can usually be performed at 120 to 400 ° C. for 1 to 40 minutes.

  A polyolefin adhesive layer is laminated on the coating film formed as described above. The polyolefin adhesive used for the polyolefin adhesive layer is not particularly limited, and a conventionally known one can be used. For example, it is preferable to use a modified polyethylene resin from the viewpoint of adhesion to the coating film and fusion with the polyolefin-coated resin layer.

  The thickness of the polyolefin adhesive layer is not particularly limited, and can be appropriately selected according to the application of the coated steel material. Preferably it is 50-400 micrometers, More preferably, it is the range of 100-300 micrometers.

  A polyolefin-coated resin layer is laminated on the adhesive layer. Resin used for a polyolefin coating resin layer is not specifically limited, A conventionally well-known thing can be used. Examples thereof include polyethylene resins such as low density polyethylene resin, medium density polyethylene resin, and high density polyethylene resin; polypropylene resin and the like. These resins may be a small amount of a vinyl monomer such as acrylic acid or a copolymer with another olefin.

  If necessary, the above-mentioned polyolefin-coated resin includes, for example, color pigments (titanium oxide, carbon black, etc.), extender pigments (calcium carbonate, barium sulfate, clay, etc.), reinforcing materials (glass flakes, etc.), silane coupling agents, ultraviolet rays Absorbers, antioxidants and the like can be added.

  The thickness of the polyolefin-coated resin layer is not particularly limited, and can be appropriately selected according to the application of the coated steel material. Preferably it is 2-20 mm, More preferably, it is the range of 3-10 mm.

  The method for forming the polyolefin adhesive layer and the polyolefin-coated resin layer is not particularly limited, and can be performed by a conventionally known method. For example, when laminating to a steel pipe, the steel pipe surface is preheated by high frequency induction heating or burner heating in advance, and the epoxy powder coating composition for steel of the present invention is applied thereto, and further, a polyolefin adhesive layer and a polyolefin coating Examples include a method of forming a resin layer. The polyolefin adhesive layer and the polyolefin-coated resin layer can each be formed by a melt round die extrusion coating method or a melt T-die extrusion coating method. Further, both layers can be formed at once by a melt round die coextrusion coating method or a melt T die coextrusion coating method. In addition, a sheet comprising a layer in which a polyolefin adhesive layer and a polyolefin-coated resin layer are integrated in advance is used, and the sheet is coated on the coating film composed of the epoxy powder coating composition for steel material of the present invention laminated on the steel material. In addition, the polyolefin adhesive layer may be laminated so as to be in contact therewith. The temperature at the time of lamination can be arbitrarily set depending on the preheating temperature or the like, but the steel material surface temperature is usually 150 to 230 ° C.

  Hereinafter, the present invention will be described in more detail with reference to examples. “Part” and “%” indicate “part by weight” and “% by weight” unless otherwise specified.

Example 1
Manufacture of epoxy powder coating composition 7 parts by weight of bisphenol A type epoxy resin (a-1) (Note 1), 93 parts by weight of bisphenol A type epoxy resin (a-2) (Note 2), phenolic curing agent (Note) 3) 13 parts by weight, imidazole catalyst (Note 4) 0.39 part by weight and surface conditioner (Note 5) 1 part by weight were premixed with a Henschel mixer, then melt-kneaded with Busconyder PLK-46, cooled, The epoxy powder coating composition of Example 1 having an average particle diameter of 50 μm was produced by pulverization and filtration.
(Note 1) Bisphenol A type epoxy resin (a-1): jER-1002, manufactured by Japan Epoxy Resin, epoxy equivalent of about 650 g / eq
(Note 2) Bisphenol A type epoxy resin (a-2): jER-1007, manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent of about 1,975 g / eq
(Note 3) Phenolic curing agent: jER Cure 171N, manufactured by Japan Epoxy Resin Co., Ltd., about 4.5 meq / g of phenolic OH group
(Note 4) Imidazole-based catalyst: 2-methylimidazole, manufactured by Shikoku Kasei Kogyo Co., Ltd. (Note 5) Surface conditioner: Regiflow P-67, manufactured by ESTRON CHEMICAL

Measurement of Young's Modulus The epoxy powder coating composition produced above was applied to a glass plate to a thickness of 150 μm, heated at 200 ° C. for 10 minutes and cured, and then the coating film was peeled off from the glass plate. And was cut into strips having a length of 30 mm and a width of 5 mm. Using “Tensilon UTM-II-20” (trade name, manufactured by Orientec Co., Ltd.) as the measuring instrument, the coating film is attached to the measuring instrument so that the measurement length is 20 mm, and the tensile speed is 8 mm / min at a temperature of 20 ° C. Measured with The slope of the stress-strain curve at the rise of the measurement result is the Young's modulus, and the unit is kgf / cm ² . The measurement results are shown in Table 1.

Measurement of elongation at break It was measured using the equipment used for the measurement of Young's modulus. A coating film having a thickness of 150 μm, a length of 30 mm, and a width of 5 mm, prepared in the same manner as in the measurement of Young's modulus, is attached to a measuring device so that the measured length of the coating film is 20 mm, and is pulled at a temperature of 20 ° C. It pulled at a speed of 8 mm / min. The measured elongation when the coating film was broken was compared with the measured length before the test, and the elongation at break was determined by the following formula.
Elongation at break (%) = [(measured length of coating film when fractured) − (measured length of coating film before measurement)] / [(measured length of coating film before measurement) × 100]
The measurement results are shown in Table 1.

Measurement of Heat Shrinkage Stress A coating film having a thickness of 150 μm, a length of 30 mm, and a width of 5 mm was prepared by the same production method as the measurement of Young's modulus. The film was attached to a thermal contraction stress measuring device “RS-20C” (trade name, manufactured by Reska Co., Ltd.) so that the measured length of the coating film was 20 mm, and the thermal contraction stress was measured. In the measurement, the stress measurement value at an atmospheric temperature of 100 ° C. was adjusted to 0 kgf, and then the temperature was lowered to 40 ° C. by natural cooling. The stress values shown on the recorder were plotted against temperature, and a straight line α was determined from the points of 40 ° C., 50 ° C. and 60 ° C. by the least square method. The stress value at 20 ° C. was read from the obtained straight line α and used as the heat shrinkage stress value. The measurement results are shown in Table 1.

Low temperature impact test Cosmer 100 (trade name, manufactured by Kansai Paint Co., Ltd., chromate treatment agent) is applied to a blasted steel plate (size 9 mmT × 100 mm × 150 mm) preheated to 200 ° C. The test piece was prepared by coating the object with an electrostatic coating machine to a film thickness of 350 μm. The test was conducted in accordance with the weight drop resistance test (DuPont type) of JIS K-5600 5-3 under the conditions of a falling weight of 2,000 g, a tip diameter of 1/2 inch, and a falling weight height of 50 cm. The coating film was impacted at a temperature of -30 ° C.
The test results were visually evaluated according to the following criteria. The evaluation results are shown in Table 1.
○: No cracking or lifting was observed on the coating surface. Δ: There was no cracking on the coating surface, but the coating film was slightly lifted. ×: Cracking was observed on the coating surface.

Bond durability test First, a simple overlay test piece defined in JIS K6850 was prepared by the following method. A blasted steel plate a (coating with Cosmer 100) (thickness 2.3 mm × width 25 mm × length 100 mm) is preheated to 200 ° C., and the epoxy powder coating composition produced above is used with an electrostatic coating machine. It coated on the fixed area (width 25mm, length 13mm) of the said blast steel plate a edge part. The film thickness at this time is 300 μm. Next, after overlapping the end portion of the blasted steel plate b coated with the same size Cosmer 100 preheated to 200 ° C. and the coated portion of the blasted steel plate a, it is held at 200 ° C. for 10 minutes, and the bonded portion is 25 mm wide and long. A simple overlap test piece having a thickness of 13 mm was prepared.
Subsequently, an adhesion durability test was performed using the test piece prepared above. “AUTOGRAPH AG-200B” (manufactured by Shimadzu Corporation, trade name) was used as a test device, and both ends of the test piece were pulled at a temperature of 20 ° C. at a pulling speed of 10 mm / min, and the force when the adhesive surface peeled was measured. The measurement results are shown in Table 1.

Cold cycle test First, a coated steel plate was prepared by the following process using a blasted steel plate (thickness 9 mm × 100 mm × 150 mm) coated with Cosmer 100. The blasted steel sheet was preheated to 200 ° C., and the epoxy powder coating composition produced above was applied to a predetermined film thickness (100 μm or 350 μm) using an electrostatic coating machine. About 1 minute after painting, a sheet (thickness 5 mm) consisting of a layer in which the modified polyethylene resin adhesive layer and the polyethylene-coated resin layer are integrated is pressure-bonded onto the coating film so as not to contain air bubbles. Created.
Subsequently, the prepared coated steel sheet was immersed in ethanol cooled to −60 ° C. with dry ice for 8 hours, immediately after being taken out, immersed in water at 25 ° C. for 15 hours, and further taken out and left in a room at 23 ° C. for 1 hour. The cooling / heating cycle test was conducted with one cycle as one cycle. The evaluation was performed by visually confirming every cycle whether the blast steel sheet and the epoxy coating layer were peeled off, and the number of cycles until peeling was used as a test result. The test was conducted up to 15 cycles. The measurement results are shown in Table 1.

Examples 2-8, Comparative Examples 1-6
The epoxy powder coating compositions of Examples 2 to 8 and Comparative Examples 1 to 6 were prepared in the same manner as in Example 1 except that the composition of the epoxy powder coating composition was changed to the compositions of Examples and Comparative Examples in Table 1. A composition was produced and subjected to each of the above measurements and tests. The evaluation and test results are shown in Table 1.

（注６）ビスフェノールＡ型エポキシ樹脂（ａ−３）：ｊＥＲ−１００４、ジャパンエポキシレジン社製、エポキシ当量約９２０ｇ／ｅｑ
（注７）ｏ−クレゾールノボラック型エポキシ樹脂：ｊＥＲ−１５７Ｓ７０、ジャパンエポキシレジン社製、エポキシ当量約２２０ｇ／ｅｑ

(Note 6) Bisphenol A type epoxy resin (a-3): jER-1004, manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent of about 920 g / eq
(Note 7) o-cresol novolac type epoxy resin: jER-157S70, manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent of about 220 g / eq

Claims (2)

It is characterized in that (1) a coating film made of an epoxy powder coating composition for steel materials having the following characteristics, (2) a polyolefin adhesive layer, and (3) a polyolefin-coated resin layer are sequentially laminated on the steel surface. Coated steel.
Epoxy powder coating composition for steel:
An epoxy powder coating composition for steel materials containing an epoxy resin component (A) and a phenolic curing agent (B), wherein an epoxy equivalent is 300 to 750 g / e in the epoxy resin component (A).
1 to 70% by weight of bisphenol A type epoxy resin (a-1) of q and an epoxy equivalent of 1,
200 to 5,500 g / eq of bisphenol A type epoxy resin (a-2) 30 to 99% by weight, in phenolic curing agent (B) with respect to 1 equivalent of epoxy group in epoxy resin component (A) Epoxy powder coating composition for steel, wherein the group that reacts with the epoxy group is in the range of 0.5 to 1.5 equivalents The coated steel material according to claim 1, wherein the epoxy powder coating composition for steel material contains a filler (C).