JP4197164B2 - Thermosetting powder paint, painted iron-based material, and method for producing painted iron-based material - Google Patents

Description

  The present invention relates to a thermosetting powder coating material, a coated iron-based material coated with the thermosetting powder coating material, and a method for producing the coated iron-based material. Specifically, the edge portion, particularly mechanically cut. Thermosetting powder coating with excellent edge coverage when coating ferrous materials having edge portions with burrs, and edge portions, particularly machines coated with the thermosetting powder coating TECHNICAL FIELD The present invention relates to a coated iron-based material in which generation of rust from an edge portion having a burr and corrosion are suppressed, and a method for manufacturing the coated iron-based material.

  In powder coating, a powder coating material in a powder state is applied to an object to be coated, heated to melt and cure the powder coating material, thereby forming a coating film. The material of the object to be coated with powder is usually metal, and cold-rolled steel sheets and hot-rolled steel sheets are used in addition to cast iron as iron-based materials. Powder coating is performed. In the case of a cold-rolled steel plate or a hot-rolled steel plate, the cutting process is performed by a mechanical cutting machine, so that burrs are unavoidable at the edge portion. When powder coating is applied to an object having this burr, the film is pulled by the surface tension at the time of baking at this burr part, and the film is very thin at the stage of complete curing. It will be in a state close to the bare state. As a matter of course, the product value of such an object to be coated is lowered due to the generation of rust from the burr portion and the progress of corrosion. In order to prevent this, by removing the burrs after mechanical cutting, and then applying the powder coating, the generation of surface tension due to baking after the coating of the powder coating is suppressed as much as possible. I tried to cover it with. However, in this case, there is a problem that one process is increased by machining and the machining cost is increased.

  Various powder coatings with improved edge coverage have also been proposed. For example, an epoxy resin that is solid at normal temperature with a softening point of 60 ° C. to 150 ° C. is an essential component, and 2 to 30 parts by weight of the (meth) acrylate polymer fine particle component in 100 parts by weight of the epoxy resin component Is uniformly dispersed in an epoxy resin composition for powder coating (see Patent Document 1), high-density polyethylene 10 to 50% by weight, linear low-density polyethylene 20 to 80% by weight, unsaturated carboxylic acid-modified polyethylene Resin composition for powder coatings comprising 2 to 20% by weight and 3 to 20% by weight of elastomer compound (see Patent Document 2), epoxy resin, curing agent, curing accelerator and components having a particle size of 20 μm or less are contained in the filler. Epoxy resin-based powder coating material containing 80% by weight or more filler as an essential component (see Patent Document 3), copolymerized polyamide resin containing hydrogenated dimer acid units In an epoxy resin powder coating comprising a copolyamide resin for powder coating (see Patent Document 4), an epoxy resin, a curing agent and an inorganic filler as essential components, negatively charged inorganic particles and negative There has been proposed an epoxy resin powder coating (see Patent Document 5) blended with chargeable inorganic particles. However, no powder coating that can eliminate the need for deburring has been proposed.

JP-A-6-329955 JP-A-9-143400 JP-A-9-279060 Japanese Patent Laid-Open No. 10-120942 JP 2002-348528 A

  The present invention has been made to solve the above-described problems, and covers the edge part, particularly, the edge part when coating a ferrous material having a burred edge part that is mechanically cut. Is excellent in thermosetting powder coating, and it is coated with the thermosetting powder coating, and the occurrence of rust and corrosion from the edge portion, especially the edge portion with burrs that are mechanically cut, is suppressed. The object is to provide a coated iron-based material and a method for producing the painted iron-based material.

As a result of intensive studies to achieve the above object, the present inventors have found that the powder coating is in a semi-molten state when the temperature is increased from 110 ° C. at a rate of 10 ° C./min. of there viscosity characteristics within a specific range, found that the above object is achieved by and thermosetting powder coating with a volume average particle diameter of the individual particles of the powder coating material within a specific range, the Completed the invention.

In other words, thermosetting powder coating of the present invention is a thermosetting polyester resin powder coating or epoxy resin powder coating, the temperature of the powder coating temperature at a rate of 10 ° C. / min from 110 ° C. When it is warmed, it has the characteristic that the minimum viscosity during the semi-molten state is 150 Pa · s or more and less than 500 Pa · s, and the temperature of the powder coating is increased from 110 ° C. at a rate of 10 ° C./min. When it is heated, the viscosity is 300 Pa · s or less while it is in a semi-molten state , and the volume average particle size of individual fine particles of the powder coating is 20 to 200 seconds. It is characterized by being 150 μm.

  The coated iron-based material of the present invention is characterized by being coated with the above thermosetting powder coating material.

  Furthermore, the method for producing a coated iron-based material according to the present invention includes performing the necessary pretreatment without performing deburring after mechanically cutting the iron-based material, and then performing the above thermosetting powder. It is characterized by being painted with paint.

  The thermosetting powder coating material of the present invention is excellent in the edge portion, in particular, the cover property of the edge portion when coating a ferrous material having a burred edge portion that is mechanically cut, and the manufacturing method of the present invention The coated iron-based material of the present invention coated with the thermosetting powder coating manufactured in the above-mentioned manner has suppressed the generation of rust and corrosion from the edge portion, particularly the edge portion having burrs that are mechanically cut. .

The present invention is described in detail below.
In the thermosetting powder coating of the present invention, when the temperature of the powder coating is raised from 110 ° C. at a rate of 10 ° C./min, the minimum viscosity during the semi-molten state is 150 Pa · s or more. It is an essential requirement to have a characteristic of less than 500 Pa · s, and it is preferable that this minimum viscosity is 180 Pa · s or more and 400 Pa · s or less. When this minimum viscosity is less than 150 Pa · s, when powder coating is performed on an article having burrs using such a powder coating, the coating film is applied to the burrs due to surface tension during baking. At the stage of being pulled and completely cured, the coating film is very thin, and this burr portion tends to be in a state close to being exposed while remaining in the burr state. Naturally, such a coated article tends to have a reduced commercial value due to the generation of rust from the burr portion and the progress of corrosion. On the contrary, when the minimum viscosity is 500 Pa · s or more, a sufficient flowability of the coating cannot be obtained at the time of baking and melting, and the appearance of the coating film tends to be remarkably deteriorated.

  In the thermosetting powder coating of the present invention, when the temperature of the powder coating is increased from 110 ° C. to 10 ° C./min, the viscosity is 300 Pa · s or less while it is in a semi-molten state. It is preferable to have a characteristic that a certain time is 300 seconds or less, and it is more preferable to have a characteristic that a time that the viscosity is 200 Pa · s or less is 150 seconds or less. Even when powder coating is performed on an object having burrs using such a powder coating, the coating film becomes thin when it is completely cured by being pulled by surface tension at the burr portion during baking. There is no such thing.

  When the temperature of the powder coating is raised from 110 ° C. at a rate of 10 ° C./min, the minimum viscosity during the semi-molten state is 150 Pa · s or more and less than 500 Pa · s. When the temperature of the thermosetting powder coating material, preferably the powder coating material is raised at a rate of 110 ° C. to 10 ° C./min, the viscosity is 300 Pa · s or less while it is in a semi-molten state. Is a thermosetting powder coating having a property that the viscosity is 300 seconds or less, more preferably a thermosetting powder coating having a property that the viscosity is 200 Pa · s or less and the time is 150 seconds or less. It can obtain by selecting appropriately the kind of resin used for, the combination of 2 or more types of resin used, and the combination of used resin and a hardening | curing agent.

  The above melt viscosity is measured using a cone plate type viscosity measuring apparatus equipped with a temperature program controller (for example, Mettler-Toledo (currently Waters Technologies Corporation / TA Instruments) equipped with Shimaden's temperature program controller FP21). It is a numerical value measured by a rheometer RM260 (numerical calculation software SWR-37) of a cone plate type viscosity measuring apparatus.

  Further, in the thermosetting powder coating of the present invention, it is an essential requirement that the volume average particle size of individual fine particles of the powder coating is 20 to 150 μm, and the volume average particle size is 25 to 120 μm. Preferably there is. When the volume average particle size is less than 20 μm, the total surface area per unit mass of such powder coating particles increases, and the electrostatic charge per unit volume of the powder coating increases in electrostatic coating. Therefore, the electrostatic ionization phenomenon occurs even in a relatively thin film in electrostatic coating. Once the deionization phenomenon occurs at the edge part, the powder falls from the part due to the phenomenon of electricity release. Therefore, a coating film cannot be formed on the edge portion, and the target edge cover cannot be sufficiently achieved. Further, when the volume average particle diameter exceeds 150 μm, the coating film surface becomes uneven when coated with such a powder coating material, and the coating film appearance is remarkably deteriorated. As a result, a concave portion is generated in the edge portion, the coating film is partially thinned, and rust generation and corrosion progress are caused.

  The volume average particle size in the present invention is the volume average particle size under the conditions for measuring a normal powder coating using a wet particle size distribution measuring machine (for example, using an aperture tube of 280 μm with a Coulter Counter Multisizer 3 manufactured by BECKMAN COULTER). It is the numerical value which measured the diameter.

The thermosetting powder coating of the present invention contains a thermosetting polyester resin or epoxy resin, and is in a semi-molten state when the temperature of the powder coating is raised from 110 ° C. to 10 ° C./min. As long as the viscosity characteristics during going on to satisfy the above conditions, further curing agent, pigment, Ru can contain without particular limitation additives.

  As a hardening | curing agent, the hardening | curing agent normally used for the thermosetting resin can be used without a restriction | limiting in particular, for example. Examples of such curing agents include amide compounds, acid anhydrides, dibasic acids, glycidyl compounds, aminoplast resins, blocked isocyanates, uretdione isocyanates, hydroxyalkylamides, and the like. Typical examples of the curing agent include dicyandiamide, acid hydrazide, triglycidyl isocyanurate, and isophorone diisocyanate block. For example, as a dibasic acid, adipic acid, pimelic acid, suberic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,20-eicosanedicarboxylic acid, hexahydrophthalic acid, malee Examples include acid, phthalic acid, and cyclohexene 1,2-dicarboxylic acid.

Examples of pigments include titanium dioxide, bengara, iron oxide, zinc powder, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments, azo pigments, isoindolinone pigments, various calcined pigments, silica, talc, etc. And extender pigments such as barium sulfate, calcium carbonate and glass flakes, aluminum powders, aluminum powders such as aluminum paste, bright pigments called white mica or silver mica showing a cloudy color from white to silver .
Examples of other additives include an anti-sagging agent, a surface conditioner, an ultraviolet absorber, a light stabilizer, an antioxidant, and the like, and can be arbitrarily blended as necessary.

  In the method for producing a coated iron material of the present invention, iron materials such as cast iron, cold rolled steel plate, hot rolled steel plate are mechanically cut using a shearing cutter or the like. Thereafter, the necessary pretreatment such as degreasing and chemical conversion treatment is performed without performing deburring, and then the thermosetting powder coating of the present invention is applied by electrostatic coating or the like, The coated iron-based material is manufactured by forming a coating film by heating and curing in an induction heating furnace or the like to an object temperature of 120 to 250 ° C.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. In the following examples and comparative examples, “part” is based on mass.

<Example 1>
30 parts of thermosetting polyester resin “CRYLCOAT340” (manufactured by Daicel UCB) having an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” having an epoxy resin equivalent of 750 g / eq (manufactured by Japan Epoxy Resin) 1 part silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” (manufactured by Monsanto) as additive, 0.3 part benzoin as defoaming agent, 1 part carbon black as pigment, 35 parts calcium carbonate, titanium oxide 5 parts and 1 part of synthetic finely divided silica “RY200 (average primary particle size 12 nm)” (manufactured by Nippon Aerosil Co., Ltd.) were stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, classified by 180 mesh, and volume. A powder coating material having an average particle size of 35 μm was prepared.

<Example 2>
30 parts of thermosetting polyester resin “CRYLCOAT340” with an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” with an epoxy resin equivalent of 750 g / eq, silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive "1 part, 0.3 part of benzoin as defoaming agent, 2 parts of masterbatch resin" CRYLCOAT164 "(manufactured by Daicel UCB) as catalyst, 1 part of carbon black as pigment, 35 parts of calcium carbonate, titanium oxide 5 parts and 1 part of synthetic finely divided silica “RY200 (average primary particle size 12 nm)” were stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, classified with 180 mesh, and powder with a volume average particle size of 35 μm. A body paint was prepared.

<Example 3>
30 parts of thermosetting polyester resin “CRYLCOAT340” with an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” with an epoxy resin equivalent of 750 g / eq, silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive 1 part, 0.3 part of benzoin as defoaming agent, 4 parts of masterbatch resin “CRYLCOAT164” as catalyst, 1 part of carbon black as pigment, 35 parts of calcium carbonate, 5 parts of titanium oxide and synthetic fine silica “RY200” 1 part (average primary particle diameter: 12 nm) was stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, and classified with 180 mesh to prepare a powder coating material having a volume average particle diameter of 35 μm.

<Example 4>
30 parts of thermosetting polyester resin “CRYLCOAT340” with an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” with an epoxy resin equivalent of 750 g / eq, silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive ”1 part, 0.3 part of benzoin as a defoaming agent, 4 parts of masterbatch resin“ CRYLCOAT164 ”as a catalyst, 1 part of carbon black as a pigment, 50 parts of calcium carbonate and 5 parts of titanium oxide were stirred with a Henschel mixer. After mixing, the mixture was kneaded with an extruder, pulverized, and classified with 180 mesh to prepare a powder coating material having a volume average particle size of 35 μm.

<Example 5>
57 parts of thermosetting polyester resin “CRYLCOAT7636” (manufactured by Daicel UCB) having an acid value of 33 mg KOH / g, 3 parts of hydroxyalkylamide “XL-552” (manufactured by EMS Showa Denko) as a curing agent, and additive 1 part of silica adsorbed acrylic acid oligomer “Modaflow Powder 2000”, 0.3 part of benzoin as defoaming agent, 1 part of carbon black as pigment, 35 parts of calcium carbonate, 5 parts of titanium oxide and synthetic fine silica “RY200 ( An average primary particle size of 12 nm) was stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, and classified with 180 mesh to prepare a powder coating material having a volume average particle size of 35 μm.

<Example 6>
55 parts of bisphenol A type epoxy resin “Epicoat 1004” (manufactured by Japan Epoxy Resin Co., Ltd.) with an epoxy resin equivalent of 925 g / eq, 5 parts of “adipic acid dihydrazide” (manufactured by Nippon Hydrazine Kogyo Co., Ltd.), and silica as an additive 1 part of adsorbed acrylic acid oligomer “Modaflow Powder 2000”, 0.3 part of benzoin as defoaming agent, 0.3 part of 2-undecylimidazole “Curazole C11Z” (manufactured by Shikoku Kasei Kogyo Co., Ltd.) as a catalyst, and pigment 1 part of carbon black, 35 parts of calcium carbonate, 5 parts of titanium oxide and 1 part of synthetic fine silica “RY200 (average primary particle size 12 nm)” were stirred and mixed with a Henschel mixer, kneaded with an extruder, and pulverized. A powder coating having a volume average particle size of 35 μm was prepared by classification with 180 mesh. .

<Example 7>
35 parts of bisphenol A type epoxy resin “Epicoat 1004” with an epoxy resin equivalent of 925 g / eq, 20 parts of bisphenol A type epoxy resin “Epicoat 1007” (manufactured by Japan Epoxy Resin Co., Ltd.) with an epoxy resin equivalent of 2000 g / eq, “ 5 parts adipic acid dihydrazide (manufactured by Nippon Hydrazine Kogyo), 1 part silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as additive, 0.3 part benzoin as defoaming agent, 2-undecyl as catalyst 0.3 parts of imidazole "Curazole C11Z", 1 part of carbon black as a pigment, 35 parts of calcium carbonate and 5 parts of titanium oxide are stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, and classified with 180 mesh Powder with a volume average particle size of 35 μm A paint was prepared.

<Comparative Example 1>
30 parts of thermosetting polyester resin “CRYLCOAT340” with an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” with an epoxy resin equivalent of 750 g / eq, silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive 1 part, 0.3 part of benzoin as defoaming agent, 4 parts of masterbatch resin “CRYLCOAT164” as catalyst, 1 part of carbon black as pigment, 35 parts of calcium carbonate, 5 parts of titanium oxide and synthetic fine silica “RY200” 1 part (average primary particle diameter 12 nm) ”was stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, and classified with 300 mesh to prepare a powder coating material having a volume average particle diameter of 18 μm.

<Comparative example 2>
30 parts of thermosetting polyester resin “CRYLCOAT340” with an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” with an epoxy resin equivalent of 750 g / eq, silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive 1 part, 0.3 part of benzoin as defoaming agent, 4 parts of masterbatch resin “CRYLCOAT164” as catalyst, 1 part of carbon black as pigment, 35 parts of calcium carbonate, 5 parts of titanium oxide and synthetic fine silica “RY200” 1 part (average primary particle diameter 12 nm) ”was stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, and classified with 40 mesh to prepare a powder coating material having a volume average particle diameter of 175 μm.

<Comparative Example 3>
30 parts of thermosetting polyester resin “CRYLCOAT340” with an acid value of 71 mg KOH / g, 30 parts of bisphenol A type epoxy resin “Epicoat 1003F” with an epoxy resin equivalent of 750 g / eq, silica adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive ”1 part, 0.3 part of benzoin as a defoaming agent, 1 part of carbon black as a pigment, 35 parts of calcium carbonate and 5 parts of titanium oxide were stirred and mixed with a Henschel mixer, then kneaded with an extruder and pulverized. Then, classification was performed with 180 mesh to prepare a powder coating material having a volume average particle size of 35 μm.

<Comparative example 4>
57 parts of thermosetting polyester resin “CRYLCOAT7636” having an acid value of 33 mg KOH / g, 3 parts of hydroxyalkylamide “XL-552” as a curing agent, 1 part of silica-adsorbed acrylic acid oligomer “Modaflow Powder 2000” as an additive, 0.3 parts of benzoin as a defoaming agent, 1 part of carbon black as a pigment, 35 parts of calcium carbonate and 5 parts of titanium oxide were stirred and mixed with a Henschel mixer, kneaded with an extruder, pulverized, and 180 mesh Classification was performed to prepare a powder coating material having a volume average particle diameter of 35 μm.

<Comparative Example 5>
55 parts of bisphenol A type epoxy resin “Epicoat 1004” with an epoxy resin equivalent of 925 g / eq, 5 parts of “adipic acid dihydrazide” (manufactured by Nippon Hydrazine Kogyo Co., Ltd.) as a curing agent, silica adsorbed acrylic acid oligomer “Modaflow” as an additive 1 part of Powder 2000 ", 0.3 part of benzoin as a defoaming agent, 0.3 part of 2-undecylimidazole" Cuazole C11Z "as a catalyst, 1 part of carbon black as a pigment, 35 parts of calcium carbonate, and titanium oxide 5 The parts were stirred and mixed with a Henschel mixer, then kneaded with an extruder, pulverized, and classified with 180 mesh to prepare a powder coating having a volume average particle size of 35 μm.

  Tables 1 and 2 show the blending compositions and volume average particle diameters of the powder coating materials prepared in the above Examples and Comparative Examples. Further, for each of the powder coating materials prepared in the above examples and comparative examples, the minimum viscosity when the temperature is increased from 110 ° C. at a rate of 10 ° C./min, the temperature is increased at a rate of 110 ° C. to 10 ° C./min. The time during which the viscosity was 300 Pa · s or less when measured and the time during which the viscosity was 200 Pa · s or less when the temperature was raised from 110 ° C. to 10 ° C./min was measured as follows. The results were as shown in Tables 1 and 2.

<Minimum viscosity when the temperature is raised from 110 ° C. at a rate of 10 ° C./min>
Cone plate type viscosity measuring device equipped with a temperature program controller (Rheometer RM260 (numerical calculation software SWR-37) of Mettler-Toledo's cone plate type viscosity measuring device equipped with Shimaden's temperature program controller FP21) The powder coating is placed in a state where the temperature of the apparatus is 110 ° C., and the temperature of the powder coating is kept at 110 ° C. for 60 seconds, and the temperature of the powder coating is set to 110 ° C., and then at a rate of 10 ° C./min. Of the viscosity data measured up to 220 ° C. by raising the temperature, the lowest viscosity value was selected from the viscosity data after 1 minute. In addition, the measurement conditions by this apparatus this time were measurement frequency: 25 times / minute, used cone type: MS-CP8, and shear rate: 20 (S ⁻¹ ).

<Time when viscosity is 300 Pa · s or less and time is 200 Pa · s or less when the temperature is raised from 110 ° C. at a rate of 10 ° C./min>
Cone plate type viscosity measuring device equipped with a temperature program controller (Rheometer RM260 (numerical calculation software SWR-37) of Mettler-Toledo's cone plate type viscosity measuring device equipped with Shimaden's temperature program controller FP21) The powder coating is placed in a state where the temperature of the apparatus is 110 ° C., and the temperature of the powder coating is kept at 110 ° C. for 60 seconds, and the temperature of the powder coating is set to 110 ° C., and then at a rate of 10 ° C./min. Of the viscosity data measured up to 220 ° C. by raising the temperature, the time of the viscosity of 300 Pa · s or less and the time of 200 Pa · s or less from the viscosity data after 1 minute were defined as the current time. In addition, the measurement conditions by this apparatus this time were measurement frequency: 25 times / minute, used cone type: MS-CP8, and shear rate: 20 (S ⁻¹ ).

  SPCC-B (manufactured by Nippon Test Panel Co., Ltd.) having a length of 150 mm, a width of 70 mm, and a plate thickness of 0.8 mm was cut in the width direction using a shearing cutter and degreased with xylene, but no chemical conversion treatment was performed. Using an electrostatic powder coating machine (PG-1 type, manufactured by Asahi Sunac Co., Ltd.), each of the powder coatings prepared in the above examples and comparative examples at a voltage of −60 kV is coated on both sides so that the coating film thickness is 60 μm. did. Thereafter, the test plate was prepared by heat curing at 180 ° C. for 20 minutes in an electric furnace. The state of the coating film was observed for each of the obtained coating test plates, and the following various tests were performed to obtain the results shown in Tables 1 and 2.

<State of coating film>
The state of the coating film on each of the above coating test plates was visually evaluated according to the following criteria.
○: Good ×: Bad

<Weight drop resistance>
The resistance of each of the above-mentioned coating test plates to the drop of the weight of the coating conforms to JIS K5600-5-3 (DuPont type), and there is no cracking or peeling of the coating at a weight of 500 g and a drop height of 50 cm. It was evaluated with.
○: No cracking / peeling of coating film ×: Cracking / peeling of coating film

<Edge cover rate>
Each of the above-mentioned coating test plates was cut, the cut surface was polished so that the edge portion was covered with a coating film, and the film thickness of the coating film on the edge portion was measured with a microscope. . Moreover, the film thickness of the coating film of the normal part measured the part 10 mm away from the edge part with the film thickness meter. The edge coverage was determined according to the following formula.
Edge coverage (%) = (thickness of coating film of edge part film / film thickness of coating film of normal part) × 100

<Edge rusting test>
Each of the above-mentioned coating test plates is placed in a neutral-resistant salt spray tester for 96 hours, the number of rust generated from the edge portion and a peel test using a cellophane tape are performed, and the peel width (average value) from the edge portion is calculated. Asked.

Claims (4)

While a thermosetting polyester resin powder coating or epoxy resin powder coating, has become semi-molten state when the temperature of the powder paint was raised at a rate of 10 ° C. / min from 110 ° C. When the temperature of the powder coating material is raised from 110 ° C. at a rate of 10 ° C./min, it is in a semi-molten state with a minimum viscosity of 150 Pa · s or more and less than 500 Pa · s . And a viscosity of 300 Pa · s or less for a time of 300 seconds or less , and the volume average particle size of individual fine particles of the powder coating is 20 to 150 μm paint. When the temperature of the powder coating is raised from 110 ° C. at a rate of 10 ° C./min, the time during which the viscosity is 200 Pa · s or less during the semi-molten state is 150 seconds or less Item 2. The thermosetting powder coating material according to item 1 . A coated iron-based material which is coated with the thermosetting powder coating material according to claim 1 or 2 . After mechanically cutting the iron-based material, the necessary pretreatment is carried out without carrying out deburring, and then the coating is applied with the thermosetting powder coating according to claim 1 or 2. To manufacture painted iron-based materials.