JP2002194289A - Powder coating composition and metallic material provided with powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating composition which neither causes a coating film failure such as a coating film crater even when coated on a material such as a magnesium alloy and the like having a defective portion such as a void and a fine groove on its metallic surface nor cause a coating sag on baking, and a metallic material provided with powder coating. SOLUTION: A powder coating composition comprising 0.05-30 mass%, based on the total amount of a thermosetting resin and a curing agent, polypropylene wax composed of a propylene homopolymer and/or copolymer having an average particle diameter (D50) of 0.1-30 μm and a melting point of 150-180 deg.C or a number average molecular weight of 3,000-10,000 and/or a mass average molecular weight of 8,000-20,000 is coated on a metallic material such as a magnesium alloy material and baked to form a metallic material provided with powder coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a powder coating composition suitable for coating on a magnesium alloy or the like in which air bubbles tend to be generated during baking of a powder coating film, and a powder coated metal material.

[0002]

2. Description of the Related Art Materials such as magnesium alloys having defects such as pits and fine grooves on the metal surface are coated with powder paint and then baked. The coating film surface is pushed up or the coating film surface is destroyed to form a hole such as a crater called a coating film crater, thereby causing a coating film defect. Therefore, after coating, it was necessary to sharpen the exposed portion of the coating with sandpaper or the like and re-paint.

[0003] In order to prevent the above-mentioned coating film defects, the viscosity of the conventional powder coating is controlled by melting the powder coating, and a certain effect is obtained by lowering the absolute value of the viscosity and delaying the timing of the viscosity increase. Came. For example, JP-A-2000-2
No. 73390 discloses a melt viscosity of 60 Pa · s / 165.
A powder comprising a film-forming resin having a temperature of not more than 0 ° C. and at least two kinds of fillers having different average particle diameters each having an average particle diameter in the range of 3 to 100 μm for the purpose of design (expression of pattern). A coating composition is disclosed. According to the present invention, it is described that defects on the surface of the metal material are satisfactorily concealed by the coating surface having the design property.

However, Japanese Patent Laid-Open No. 2000-273390 describes
By lowering the viscosity or delaying the timing of the increase in viscosity as described in Japanese Patent Application Laid-Open Publication No. H10-157, dripping of the paint at the time of baking is likely to occur, and defective paint is likely to occur.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for coating a material having a defect such as a cavity or a fine groove on a metal surface, such as a magnesium alloy, to prevent a coating defect such as a coating crack. An object of the present invention is to provide a powder coating composition which does not occur and is less likely to cause paint dripping during baking, and a powder coated metal material.

[0006]

According to the present invention, there is provided a powder coating composition comprising a thermosetting resin and a curing agent as main components, a polypropylene wax, and the resin and the curing agent. 0.1 parts per 100 parts by weight of the total amount of the agent.
0.05 to 30 parts by weight.

The above-mentioned polypropylene wax has an average particle diameter (D50) of 0.1 to 30 μm and a melting point of 150 to 18.
It is preferably a propylene homopolymer and / or copolymer at 0 ° C. Further, the number average molecular weight is 3000 to 10
000 and / or weight average molecular weight 8000-200
It is also preferably a propylene homopolymer and / or a copolymer of No. 00.

[0008] The powder-coated metal material of the present invention contains 0.05 to 30 parts by weight of polypropylene wax on the metal material based on 100 parts by weight of the total amount of the thermosetting resin and the curing agent. The powder coating composition has been painted and baked.

Further, the powder-coated metal material of the present invention contains 0.05 to 30 parts by weight of a polypropylene wax on the metal material based on 100 parts by weight of the total amount of the thermosetting resin and the curing agent. A powder coating composition may be coated and baked as a primer, and an upper layer may be further formed thereon to form a multilayer coating film.

As the above-mentioned metal material, a single or composite material having a defective portion on the metal surface, such as a magnesium alloy material, an aluminum die-cast material, an alloyed galvanized material, a cast iron material, a hot-dip galvanized material, is preferably used. it can.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The polypropylene wax contained in the coating composition of the present invention has an average particle diameter (D50) of 0. 1 to
It is preferably 30 μm, more preferably 1 to 15 μm. In addition, the melting point is 15 so as to be in a molten or semi-molten state when the coating film is baked.
The temperature is preferably 0 to 180 ° C, more preferably 160 to 170 ° C. The polypropylene wax is composed of a propylene homopolymer or a copolymer, and may have any melting point and the following molecular weight. One or two or more of these can be used in combination. 300 if the number average molecular weight of polypropylene
0 to 10000, more preferably 4000 to 7000, if represented by weight average molecular weight 8000 to 20,000,
More preferably, it is 10,000-15,000.

As described above, the content of the polypropylene wax is 0.05 to 30 parts by weight based on the total amount of the resin and the curing agent of 100 parts by weight, but preferably 0.1 to 0.3 parts by weight.
It is 1 to 20 parts by weight, more preferably 0.5 to 5.0 parts by weight. If the content exceeds 30 parts by weight, the curability of the coating film deteriorates and the surface hardness decreases. Will remain.

The powder coating composition of the present invention comprises a thermosetting resin and a curing agent, which are conventionally known components, as main components, except for the above-mentioned polypropylene wax, and optionally contains other pigments and additives. It becomes.

As the thermosetting resin, those which are solid at room temperature can be used. For example, epoxy resin, acrylic resin, polyester resin, polyester / epoxy resin obtained by blending epoxy resin and polyester resin, epoxy resin and acrylic resin And an epoxy resin and a fluororesin which are blended.

Examples of the epoxy resin include a glycidyl ester resin, a glycidyl ether resin which is a condensate of bisphenol A or bisphenol F with epichlorohydrin, an alicyclic epoxy resin, an aliphatic epoxy resin, and a bromine-containing epoxy resin. And compounds containing two or more oxirane groups in one molecule, such as phenol novolak epoxy resin and cresol novolak epoxy resin.

Examples of the acrylic resin include (meth)
Acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, t- (meth) acrylate
tert-butyl, glycidyl (meth) acrylate, 2
-(Meth) such as methylglycidyl (meth) acrylate
Acrylic monomers, styrene, and other radically polymerizable monomers are copolymerized.

Examples of the polyester resin include polyhydric alcohols such as ethylene glycol, diethylene glycol, propanediol, pentanediol, hexanediol, neopentyl glycol, trimethylolpropane, and pentaerythritol, and maleic acid, terephthalic acid, isophthalic acid, and the like. Examples thereof include those obtained by ester polymerization of a carboxylic acid such as succinic acid, glutamic acid, adipic acid, sebacic acid, and β-oxypropionic acid or a carboxylic anhydride.

The above epoxy resin, acrylic resin and polyester resin are appropriately blended to form a polyester / polyester resin.
It can be used as an epoxy resin or an acrylic epoxy resin.

Examples of the fluorine resin include a fluorine-based monomer such as vinylidene fluoride, ethylene trifluoride, and vinyl fluoride; a hydroxyl group-containing alkyl monomer such as 2-hydroxyethyl (meth) acrylate; Examples thereof include those obtained by copolymerizing a monomer used for a resin. As a specific example, "Lubron L-2"
(Made by Daikin Industries, Ltd.).

Examples of the curing agent include blocked polyisocyanate compounds such as alicyclic polyisocyanates blocked with ε-caprolactam, uretdione-type polyisocyanate compounds, aliphatic polycarboxylic acids such as sebacic acid, and aminoplasts. Resins, aliphatic acid anhydrides, amine compounds, polyamide resins, imidazole compounds, imidazoline compounds, phenol resins, epoxy resins, others, triglycidyl isocyanate, triglycidyl isocyanurate, dicyandiamide, hydroxyalkyl Amides and glycoluril can be mentioned, and these curing agents can be appropriately selected according to the functional group of the thermosetting resin to be used.

From the viewpoint of curability, the weight ratio of the thermosetting resin and the curing agent in the powder coating component is 40:60.
The range of -96: 4 is preferred. It is also preferable to use a mixture of two or more of the thermosetting resin and the curing agent. Further, from the viewpoint of the concealability of the coating film and the physical properties of the coating film, the total amount of the thermosetting resin and the curing agent is preferably 40 to 95 parts by weight in 100 parts by weight of the powder coating component. In addition, a thermoplastic resin can be used in addition to the thermosetting resin and the curing agent.

When the pigment is used in consideration of concealing properties, design properties, etc., 5 to 100 parts by weight of all components of the powder coating composition are used.
Preferably, it occupies 60 parts by weight. If the amount of the pigment is less than 5 parts by weight, the concealing property of the coating film is inferior. If the amount of the pigment exceeds 60 parts by weight, the bending property of the coating film and the smoothness of the coating film may be reduced. Examples of pigments include aluminum flakes, interference mica, various glitter pigments such as colored mica, titanium dioxide, red iron oxide, yellow iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments,
Examples include coloring pigments such as azo pigments, extender pigments such as talc, silica, calcium carbonate, and precipitated barium sulfate, and other rust-preventive pigments.

Further, as the above additives, for example, silicones such as dimethyl silicone and methyl silicone;
Surface modifiers such as acrylic oligomers, antifoaming agents such as benzoin and benzoin derivatives, anti-bake agents, curing catalysts,
Examples include a curing accelerator, a plasticizer, an antistatic agent, a charge control agent such as fine-particle aluminum oxide, an ultraviolet absorber, a light stabilizer, an antioxidant, a pigment dispersant, a flame retardant, and a fluidity imparting agent.

A production example of the powder coating composition of the present invention will be described below. First, the above-mentioned polypropylene wax, thermosetting resin, curing agent and other components are blended in a dry state. Then, the mixture is kneaded while being heated and melted by an extruder, cooled after extrusion and coarsely pulverized. After the coarsely pulverized particles thus obtained are further finely pulverized, fine particles and coarse particles are removed using a classifier to obtain a powder coating composition having a predetermined particle size distribution.

The powder coating composition of the present invention produced by the above production method preferably has a volume average particle diameter of 3 to 50 μm, more preferably 15 to 40 μm. The volume average particle diameter can be determined by a particle diameter measuring device using a laser light scattering method generally used in the field of powder coatings. When the volume average particle diameter is less than 3 μm, the coating production process may be complicated, and the efficiency of applying the powder coating to an object to be coated may decrease. On the other hand, when the volume average particle diameter exceeds 50 μm, when the film thickness is small, coating unevenness is conspicuous, and the concealability of the coating film and the smoothness of the coating film may be reduced.

The powder coated metal material of the present invention can be formed, for example, by the following method. In order to apply the powder coating composition to a metal material, it is preferable to employ an electrostatic powder coating method using a powder coating gun. In the electrostatic powder coating method, after a metal material to be coated is grounded, powder coating such as a corona charging type coating gun, a friction charging type coating gun, for example, an electrostatic electric field cloud fluidized immersion coating device manufactured by Mesac, etc. The powder coating composition is sprayed using an apparatus.

When a corona charging type coating gun is used, the charging voltage applied to the powder coating composition by corona discharge treatment is as follows:
It is preferably set to -50 to -100 KV, more preferably -60 to -90 KV from the viewpoint of coating efficiency and appearance. On the other hand, when a triboelectric coating gun is used, it is preferable to perform a triboelectric treatment so that the internally generated current value of the powder coating composition is 1.0 to 8.0 μA from the viewpoint of coating efficiency and appearance. .

The preferred discharge rate of each of the above coating guns is 50 to 400 g / min, and the discharge pressure is 4.9 × 10 ⁴ to
It is 4.9 × 10 ⁵ Pa. Furthermore, the distance from the tip of the coating gun to the object to be coated is preferably 10 to 50 cm. By coating in this range, the particles in the powder coating can be applied efficiently and the conductive object is electrostatically applied to the object. To form a powder coating layer.

Then, this powder coating layer is added
By baking at a temperature of ° C. for a predetermined time, the powder coated metal material of the present invention is formed. The coating thickness (set film thickness) after baking is 10 to 150 μm, and further 20 to 80 μm.
Is preferred. When the coating composition of the present invention is used as a primer, an upper layer is formed on the coated film after baking for the purpose of design and the like. As a material for forming the upper layer, besides the general powder coating not containing the above-mentioned polypropylene wax, a known acrylic-based, polyester-based, fluorine-based, silicon-based solvent-based coating or water-based coating may be used. Can be. In addition to the paint, a film surface as an upper layer can be formed by laminating polyethylene terephthalate, high-density polyethylene, polypropylene film or the like.

The metal material used in the present invention is not limited, but may be magnesium alloy material, aluminum die-cast material, galvannealed material, cast iron material, hot-dip galvanized material,
Various metal plates or processed products obtained by subjecting these metals to surface treatment by degreasing or chemical conversion treatment, and plastic plates or processed products subjected to conductive treatment by applying a conductive primer or the like are included. Examples of such processed products include a notebook computer and a mobile phone.

[0032]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the compounding amount represents a weight part unless there is particular notice.

Example 1 Preparation of powder coating composition 60 parts of thermosetting polyester resin ("FINEDIC M-8020", manufactured by Dainippon Ink and Chemicals, Inc.), 12 parts of curing agent ("Cleran UI", Sumitomo Bayer) Urethane block polyisocyanate), polypropylene wax 0.3 part ("PROPYL MATTE 31",
0.5 parts of benzoin, 1.0 part of anti-crater agent (“Acronal 4F”, BAS
Made by F company. Acrylic oligomer), 30 parts of titanium oxide (“CR-50”, manufactured by Ishihara Sangyo Co., Ltd.), and 0.2 parts of carbon black (“MA-100”, manufactured by Mitsubishi Chemical Corporation) are mixed (“Supermixer”, Nippon Spindle) For about 3 minutes to obtain a mixture.

Next, the above mixture is melt-kneaded at about 100 ° C., and the obtained melt-kneaded product is cooled to room temperature, and then coarsely pulverized by a pulverizer (“Atomizer”, manufactured by Fuji Paudal Co.) and further finely pulverized. Pulverizer jet mill (“IDS-2
Using a mold, manufactured by Nippon Pneumatic Industries, Ltd.).

The powder thus obtained is subjected to an airflow classifier (“D
(S-2 type, manufactured by Nippon Pneumatic Industries Ltd.) to remove fine particles and coarse particles. The obtained polyester resin-based powder coating composition has a volume average particle diameter of 25.
μm.

The volume average particle size and the particle size distribution were measured using a particle size analyzer ("Microtrac HRAX-100", manufactured by Nikkiso Co., Ltd.). The measurement sample at this time is
50 g of a 0.1% by weight aqueous solution of polyoxyethylene (10) octyl phenyl ether and 0.5 g of a powder coating composition to be measured are added to a sample bottle, and the sample bottle is placed in an ultrasonic cleaner (“SILENTSONIC UT-
105 "(manufactured by Sharp Corp.) for 3 minutes, and a powder coating water in which an aqueous solution was immersed was used.

Coating Method The powder coating composition obtained as described above is applied to a magnesium alloy material (hereinafter referred to as “α material”), an alloyed hot-dip galvanized steel sheet material (hereinafter referred to as “β material”), and hot-dip galvanized. Electrostatic coating was performed on a test piece of a steel plate material (hereinafter referred to as “γ material”).

The test piece material of α material is AZ91 (ASTM)
(Alloy symbol) by a thixomolding method. The size is 200 mm × 300 mm and the thickness is 1.0 mm.
In addition, since the coating film baking at the time of baking often occurs at the end of the metal material, the test piece was formed into a shape including a flat portion and a flange portion having a height of 5 mm and provided vertically around the flat portion.

The β material is an SGCC material specified in JIS G 3302 and has a plating weight of F06, a size of 300 mm × 300 mm and a thickness of 0.6 mm. Since the coating of the metal material at the time of baking is likely to be generated in a bent portion, a test piece of the above size was bent at 90 degrees so as to be equally divided.

The γ material is an SGHC material specified in JIS G 3302 and has a plating weight of HDZ35, a size of 300 mm × 300 mm and a thickness of 3.2 mm.

For coating, a test piece was placed on a grounded conductive horizontal belt conveyor, and then the distance from the tip of the gun head of a corona charging coating gun (“PG-1”, manufactured by GEMA) to the steel plate was measured. Is set to 15 cm, the applied voltage of the coating gun is -80 KV, and the set film thickness is 30.
Painted at ５０50 μm. Then, the obtained coated test piece is
The test piece was baked under the condition that the surface temperature could be maintained at 180 ° C. for 15 minutes. Three pieces of each of the test pieces were prepared and evaluated as follows. Table 1 shows the results.

<Evaluation of the number of coatings on the coating film> The test pieces after baking were observed, and the locations where the coating coatings were generated were counted. Then, an average value of three pieces was obtained and evaluated as follows. ◎ Average number of coatings 0 0 1 to 3 4 to 10 × 11 or more

Examples 2 to 13, Comparative Examples 1 and 2 The amounts and types of the polypropylene wax of Example 1, the amounts and types of the thermosetting resin and the curing agent in the powder coating composition, the material of the test piece, Various examples and comparative examples were carried out by changing the shape and the thickness of the coating film. Table 1 shows detailed contents and evaluation results. All parts other than those described in Table 1 were performed in the same manner as in Example 1.

[0044]

[Table 1]

As apparent from the evaluation of the coating film in Table 1,
Each of the coating films formed by the examples has a small number of coatings. That is, it is apparent that there is no problem in appearance or rust prevention because there is no or very few coating film defects.

Example 14 On the α-coated material obtained in Example 12, a silver metallic solvent type paint (Olga Select 300KK Yellowish Silver Metallic, manufactured by Nippon Paint Co., Ltd.) having a design property was further applied as a top coat with a set film thickness of 20. ~ 30μ
m with air spray gun, 130 ℃
Baking was performed in an atmosphere for 20 minutes. As a result, it was possible to obtain a decorative magnesium alloy coated article having a beautiful finished appearance of the coating film without any coating film defects.

Example 15 In the same manner as in Example 14, on the α-coated material obtained in Example 12, a silver metallic powder paint (Powax P60 SM-C, manufactured by Nippon Paint Co., Ltd.) having further design properties was applied. Electrostatic coating was performed with an electrostatic coating gun so as to have a set film thickness of 40 to 50 μm, and baked in a 180 ° C. atmosphere for 20 minutes. As a result, it was possible to obtain a decorative magnesium alloy coated article having a beautiful finished appearance of the coating film without any coating film defects.

Comparative Example 3 A decorative magnesium alloy coated article was formed in the same manner as in Example 15 except that the α-coated article obtained in Comparative Example 2 was used instead of the α-coated article of Example 15. . As a result, since the coating was applied on the coating film in which the coating side was generated, the coating side affects the overcoated decorative coating film, and the coating appearance was poor.

[0049]

Since the powder coating composition of the present invention contains polypropylene and wax, it can be applied to a material such as a magnesium alloy or the like having defects such as burrows or fine grooves on the metal surface, even when baked. It does not leave traces of paint film splats due to the generated air, and does not cause paint dripping due to viscosity adjustment as in the prior art. In addition, the synergistic effect of the effect of the above-mentioned polypropylene wax and the film thickness effect of the powder coating unique thick coating makes it possible to hide cracks and cracks in the metal material (substrate concealment properties) and ensure rust prevention. can do. Furthermore, when the coating composition of the present invention is used as a primer, as described above, it has a high base concealing property and a high rust prevention property, so that the appearance of the upper coating film can be sufficiently enhanced.

Therefore, the powder coated metal material of the present invention
If a magnesium alloy material or an aluminum die-cast material is used as a metal material, it can be suitably used for a notebook computer or a mobile phone, and if an alloyed hot-dip galvanized material, a cast iron material or a hot-dip galvanized material is used, a vending machine, It is useful as an industrial material such as a range hood.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 7/12 C09D 7/12 123/10 123/10 191/06 191/06 F-term (Reference) 4D075 AE03 DB01 DB02 DB05 DB07 EA02 EA19 EA37 EB13 EB16 EB22 EB32. DD002 KA03 MA02 MA12 MA14 NA01 PA02 PA19 PC02

Claims (6)

[Claims] 1. A powder coating composition comprising a thermosetting resin and a curing agent as main components, further comprising a polypropylene wax in an amount of from 0.05 to 100 parts by weight based on the total amount of the resin and the curing agent. A powder coating composition comprising 30 parts by weight. 2. The polypropylene wax has an average particle size (D50) of 0.1 to 30 μm and a melting point of 150 to 180.
The powder coating composition according to claim 1, which is a propylene homopolymer and / or copolymer at a temperature of ℃. 3. The powder coating according to claim 1, wherein the polypropylene wax is a propylene homopolymer and / or copolymer having a number average molecular weight of 3,000 to 10,000 and / or a weight average molecular weight of 8,000 to 20,000. Composition. 4. A powder coating composition containing 0.05 to 30 parts by weight of a polypropylene wax based on 100 parts by weight of a total of a thermosetting resin and a curing agent on a metal material,
Powder coated metal material characterized by being painted and baked. 5. A powder coating composition comprising a metal material and 0.05 to 30 parts by weight of a polypropylene wax based on 100 parts by weight of a total of a thermosetting resin and a curing agent,
A powder-coated metal material characterized by being painted and baked and further having an upper layer formed thereon. 6. The metal material is at least one material selected from a magnesium alloy material, an aluminum die-cast material, a galvannealed material, a cast iron material, and a galvanized material. Powdered metal material as described.