JPH0757849B2 - Powder coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a powder coating composition for electrostatic coating which has improved electrostatic coating properties, fluidity, blocking resistance and the like.

<Prior Art and Problems> Conventional powder paints have been widely adopted as pollution-free paints that do not use organic solvents. Of these, thermosetting powder coatings are usually manufactured by a method such as melting and kneading a resin, a curing agent, and if necessary, components containing a pigment, an additive, etc., cooling and pulverizing, Some of them are hardened (blocking) or have poor fluidity during coating work. Therefore, such problems are solved by methods such as dry blending of fine silica powder with thermosetting powder coating. It was

On the other hand, as a coating method for such a thermosetting powder coating material, electrostatic spray coating with high coating efficiency is widely adopted.

However, if a thermosetting powder paint dry-blended with silica fine powder is electrostatically spray-coated with a thick film, the adhesion of the paint may deteriorate, and the paint may adhere to the edges of the object to be coated. There is a problem that it is difficult, that is, the electrostatic coating property is poor.

The present invention has been made as a result of intensive studies in view of the above circumstances, and as a result, not only the flowability and blocking resistance of the thermosetting powder coating are improved, but also the electrostatic coating property is good. That is, the present invention has been achieved.

<Means for Solving Problems> That is, in the present invention, a thermosetting powder coating composition is mixed with an aluminum oxide fine powder in an amount of 0.01 to 0.01
The present invention relates to a powder coating composition for electrostatic coating, which is characterized by containing 1.0% by weight.

The thermosetting powder coating used in the present invention is a conventionally known resin, a curing agent, and further various pigments, if necessary, consisting of components containing additives, for example, polyester resin system, epoxy resin system, Acrylic resin-based thermosetting powder coating material is a typical example. As a method for producing the same, a method in which the mixture of the components is melt-kneaded with an extruder, a heat roll, a kneader or the like at a temperature at which the resin and the curing agent do not cause a crosslinking reaction, and a method of pulverizing after cooling is used. Although typical examples thereof are given, the present invention is not limited to these, and it goes without saying that other conventionally known manufacturing methods can be adopted.

As a resin which is a constituent component of the thermosetting powder coating material, a polyester resin, an epoxy resin, an acrylic resin, or the like can be given as a typical resin. Polyester resins include terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutanoic acid, adipic acid, sebacic acid, β-oxypropionic acid and other carboxylic acids, and ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neo Those obtained by reacting a polyhydric alcohol such as pentyl glycol, trimethylolpropane, pentaerythritol and the like by a usual method are typically used.

Epoxy resin is a compound having two or more epoxy groups in the molecule, and is represented by a condensate of bisphenol A and epichlorohydrin, a glycidyl ether type resin, a glycidyl ester type resin, a glycidyl amine type resin, an alicyclic epoxy resin. A linear aliphatic epoxy resin is typically used.

Examples of the acrylic resin include monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and styrene, and glycidyl acrylate, Those obtained by polymerizing a glycidyl group-containing monomer such as glycidyl methacrylate and 2-methylglycidyl methacrylate by a usual method are typically used.

The curing agent, which is a constituent of the thermosetting powder coating composition, is appropriately selected depending on the type of the resin. For example, 2 equivalents or more per molecule of blocked polyisocyanate, adipic acid, succinic acid, sebacic acid, etc. Compounds containing a carboxyl group or acid anhydride, aminoplast resin, epoxy resin, etc. are typically used.

Examples of pigments include titanium dioxide, red iron oxide, iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments, azo pigments, isoindolinone pigments, and other coloring pigments, silica, talc, precipitated barium sulfate, calcium carbonate. Extender pigments such as are typically used.

As the additive, an anti-sagging agent, a surface conditioner, a crosslinking accelerating catalyst and the like are used.

The thermosetting powder coating material of the present invention is obtained by dry blending a fine powder of aluminum oxide when a composition comprising these components is melt-kneaded and then pulverized. Dry blending is performed by uniformly mixing a fixed amount of aluminum oxide fine powder with melt-kneaded pellets, and then supplying the powder in a so-called batch system before pulverizing, or continuously using an electromagnetic feeder or the like in the pulverizing path. It is carried out by supplying a fine powder of aluminum oxide.

The amount of fine aluminum oxide powder blended is 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight, in the powder coating composition. If the addition amount is less than the above range,
Electrostatic paintability, fluidity, blocking resistance, etc. cannot be improved, and conversely, if too much, it adversely affects the coating surface condition, which is not preferable.Also, aluminum oxide fine powder is not suitable for powder coating powders. It is desirable that the surface is evenly sprinkled, so that the average particle size is preferably 100 mμm or less.

<Effects of the Invention> The present invention improves electrostatic coating properties, fluidity, blocking resistance and the like by adding aluminum oxide fine powder to a thermosetting powder coating composition, and is suitable for electrostatic coating. A fine powder coating can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, "parts" and "%" are shown by weight.

Example 1 Note 1) Polyester resin 54.0 parts Note 2) Blocked polyisocyanate 11.0 parts Titanium dioxide 35.0 parts Note 3) Additive 0.9 parts Note 1) "ER-6610" (trade name of Nippon Ester Co., Ltd.) Note 2) " Kurelan Ui ”(Bayer's trade name) Note 3) Surface conditioner 0.7: Curing accelerator 0.2 After mixing the above components with a Henschel Mississor for about 1 minute, extractor (Busco Kneader) under a temperature condition of 100 to 120 ° C.
Melt kneading with PR46), and after cooling, 0.2% of aluminum oxide fine powder [“Aluminium Oxide C” (trade name, manufactured by Nippon Aerosil Co., Ltd., average particle size 20 mμm, particles 99.9% or more with a particle size of 60 mμm or less) to the mixed component) Addition: The powder pulverized with a bantam mill was sieved through a wire mesh of 200 mesh to prepare a powder coating.

Example 2 Note 4) Polyester resin 58.0 parts Note 5) Blocked polyisocyanate 8.0 parts Note 6) Epoxy resin 3.0 parts Heavy calcium carbonate 10.0 parts Titanium dioxide 20.0 parts Carbon black 0.2 parts Note 7) Additives 0.7 parts Note 4) "Findick M8000" (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) * 5) "Adduct B-1530" (trade name, manufactured by Hyurus, Inc.) * 6) "Epiclon 4050" (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) Note 7) Surface modifier 0.5: Curing accelerator 0.2 The above components were mixed, melt-kneaded in the same manner as in Example 1, and after cooling, 0.2% of aluminum oxide fine powder was added and pulverized to prepare a powder coating. .

Example 3 Note 8) Polyester resin 32.0 parts Note 9) Epoxy resin 32.0 parts Precipitating barium sulfate 20.0 parts Titanium dioxide 15.0 parts Phthalocyanine blue 0.5 parts Yellow iron oxide 2.0 parts Note 10) Additives 0.6 parts Note 8) "Ester resin ER" −8101 ”(trade name of Nippon Ester Co., Ltd.) Note 9)“ Epototo YD-014 ”(trade name of Toto Kasei Co., Ltd.) Note 10) Surface modifier 0.5: curing accelerator 0.1 The same components as in Example 1 were used. After mixing, melt kneading, and cooling, 0.1% of aluminum oxide fine powder was added and pulverized to prepare a powder coating material.

Example 4 In Example 3, 0.8 parts of aluminum oxide fine powder was added.
A powder coating material was prepared in the same manner except that the addition amount was 0.1%.

Example 5 Note 11) Epoxy resin 60.0 parts Dicyandiamide 3.0 parts Silica powder 20.0 parts Titanium dioxide 10.0 parts Carbon black 0.1 parts Note 12) Additives 0.6 parts Note 11) "Epicoat 1004" (trade name of Yuka Shell Epoxy Co., Ltd.) Note 12) Surface Conditioner 0.5: Curing Accelerator 0.1 The above components were mixed, melt-kneaded in the same manner as in Example 1, and after cooling, 0.2% of aluminum oxide fine powder was added and pulverized to prepare a powder coating material.

Example 6 Note 13) Acrylic resin 52.0 parts Dodecanedioic acid 8.0 parts Note 14) Epoxy resin 3.0 parts Titanium dioxide 30.0 parts Phthalocyanine blue 0.1 parts Quinacridone red pigment 0.2 parts Note 15) Additives 0.5 parts Note 13) "Almatex PD −7210 ”(trade name, manufactured by Mitsui Toatsu Chemicals, Inc.) Note 14)“ Epicoat 1002 ”(trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) Note 15) Surface modifier 0.5 The above components were mixed and melted in the same manner as in Example 1. After kneading and cooling, 0.2% of aluminum oxide fine powder was added and pulverized to prepare a powder coating material.

Comparative Example 1 In Example 3, 1.5 parts of aluminum oxide fine powder was used.
A powder coating material was prepared in the same manner except that the addition amount was 0.1%.

Comparative Example 2 A powder coating material was prepared in the same manner as in Example 3, except that 0.2% of silica fine powder (average particle size: 3.3 μm) was used instead of the aluminum oxide fine powder.

Comparative Example 3 A powder coating material was prepared in the same manner as in Example 3 except that the aluminum oxide fine powder was not added.

The powder coating material manufactured in each Example and Comparative Example was applied to a 0.8 mm-thick polished soft steel plate with an electrostatic powder coating gun (Type 721 manufactured by Gema Co., Ltd.)
It was coated at a voltage of 0 KV to a film thickness of 60 μm and baked in a hot air drying oven.

Various tests were conducted on the obtained coating film, and the results are shown in Table 1.

As is clear from Table 1, the powder coating material of the present invention was good in fluidity (smoothness), blocking resistance and electrostatic coating property.

On the other hand, Comparative Example 1 in which the aluminum oxide fine powder is excessive
In Comparative Example 2 in which the fluidity is poor, the smoothness of the coating film is poor, and the aluminum oxide fine powder is not added, and the conventional silica fine powder is added, and the aluminum oxide fine powder is poor. In Comparative Example 3 in which neither fine silica powder was added, the electrostatic coating property and blocking resistance were poor.

Claims (2)

[Claims] 1. A powder coating composition for electrostatic coating, comprising 0.01 to 1.0% by weight of aluminum oxide fine powder added to a thermosetting powder coating composition by a dry blending method. 2. The powder coating composition for electrostatic coating according to claim 1, wherein the average particle size of the aluminum oxide fine powder is 100 mμm or less.