JPH01259074A - Powder coating composition - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in electrostatic coating workability, by incorporating a powder coating with particulate igneous alumina in a specified amount. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100pts.wt. of a powder coating <=100mu (pref. 10-40mu) in mean particle size, pref. <=300mu in maximum particle size and pref. 0.1-0.4m<2>/g in specific surface area with (B) 0.03-2 (pref. 0.1-1.5)pts.wt. of igneous alumina consisting (mainly) of that <=50mmu in particle size. Said alumina is pref. 15-25mmu in mean particle size and 55-115m<2>/g in specific surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder coating composition K (hereinafter sometimes abbreviated as "this composition") which has excellent coating workability, particularly electrostatic coating workability.

Powder coatings are powder coatings that do not contain volatile components such as organic solvents or water, and are applied to the surface of the object to be coated and thermally fused, making it possible to prevent air pollution and save resources. Powder coatings are often used in a wide range of applications because of their ease of reuse.Although powder coating methods include thermal spraying and fluidized dipping, the electrostatic coating method It is widely used because it is easy to control, is not limited by the size and shape of the object to be coated, can be sprayed by hand or automatically, and has excellent coating efficiency.

However, when powder coating is applied with an electrostatic coating machine, the powder coating adheres to the vicinity of the powder coating discharge port at the tip of the gun of the coating machine due to electrostatic force, moisture, attraction between powder particles, etc. It is easy to accumulate, and the deposits often come off in a coarse-grained state and disappear from the coated surface, and if they are baked as they are, protrusions will appear on the coated surface, causing a deterioration in the finished appearance. In an attempt to eliminate this defect, the inventors of Zero analyzed the powder paint deposited on the tip of the gun and found that most of the paint was fine powder with a particle size of 20 microns or less.

Therefore, in powder paints, the amount of deposited 1 ton at the tip of the gun is reduced by removing fine powders of about 20 microns or less, but as the average particle size becomes larger, the smoothness of the coating film decreases. In particular, in order to reduce painting costs in recent years, fun (approximately 40 to 80μ
), but the problem is that the smoothness of the thin film deteriorates.

The purpose of the present invention is to be useful in fields where painted surface smoothness is required as an important function, such as the exterior panels of private cars, without impairing paint properties such as storage stability and film performance.
To make a paint film smooth by pulverizing the paint, and to eliminate problems such as adhesion of the paint to the tip of the gun of an electrostatic coating machine and deterioration of paint @wJ properties, which tend to occur as a result. As a result, the objective was achieved by mixing a specific large-sized alumina into a finely powdered powder coating, and the present invention was completed.

In other words, for zero-filling, igneous alumina with a particle size of 50 mm or less is used as the main fraction, with an average particle size m' 1 (
1 (Regarding a powder paint composition which is characterized in that it is made by mixing 100 parts of sodium bicarbonate powder paint with 90.03 to 2 parts of sodium bicarbonate to a powder paint adjusted to 1 micron or less.

Taisei alumina used in the present invention has aluminum oxide (AtzOa) as its main component, and is produced, for example, by high-temperature (flame) hydrolysis of anhydrous aluminum chloride.
) etc. (2 to 3% by weight or less) may be included. As a commercially available product, Aluminum manufactured by Degussa, Germany
There is Oxide C (product name).

In the present invention, the main component of the large-sized alumina is particles with a particle size of 50 mm or less, more specifically, particles with a particle size of 50 mm or less in an amount of 80% by weight or more, preferably 90% by weight or more. Especially preferably, daisei alumina containing 100% is used.

Regarding this large-sized alumina, the average particle size is lO~3
0 millimicrons, especially 15 to 25 millimicrons, and a specific surface area of 50 to 150? F1″/f, especially 85~l 15
rr? /? It is more preferable that

The specific surface area is a value measured by the BET method.

For this purpose, the average particle size is the average particle size that is the particle size when the content rate is accumulated from the smallest particle size in the powder to 50%. If the diameter is 20 microns, powder with a particle size of 20 microns or less is 501
%. These measurements were carried out using a light transmission type particle size analyzer, Micro Photosizer SK model (manufactured by Seishin Enterprise ■).

Next, powder coatings in which Taisei alumina is mixed and dispersed can be those already known per se; for example, thermosetting resins whose base components are epoxy resins, acrylic resins, polyester resins, etc., or polyethylene resins, polyamide resins. The main component is a thermoplastic resin such as vinyl chloride resin, with cross-linking agents, additives, fillers, and other additives added as necessary, and then melted, cross-wired, and pulverized into powder. In particular, in the present invention, there is no need to remove the fine powder part, and specifically, the maximum particle size is 500 microns or less,
Preferably 300 microns or less, average particle size 100 microns or less, preferably Fi 10-40 microns, specific surface area (measured by light transmission method) 0.1-0.4rr? It is preferable to use a powder coating of /f 0. Mixing and dispersion of large alumina into a powder coating involves adding fine powder of large alumina to the powder coating that also contains fine powder of 20 microns or less produced as described above. These same components can be mixed and dispersed using a Henschel mixer, a super mixer, etc., or large alumina can be continuously mixed and dispersed using a quantitative feeder while the powder coating is being conveyed in air. After mixing, it is preferable to sieve through a screen with appropriate openings to remove coarse particles.

In the present invention, the blending amount of Taisei alumina is as follows:
0.00 parts by weight and 0.03 to 2 parts by weight, preferably 0.00 parts by weight.
A range of 1 to 1.5 parts by weight is suitable.

If the number of double-tone parts increases, the smoothness of the coating film may deteriorate.

The present composition of the present invention, which is made by mixing Taisei alumina with a powder coating, does not adhere to the powder near the powder discharge port at the tip of the gun of an electrostatic coating machine, even though it contains fine powder with a particle size of 20 microns or less. There was almost no deposition of this composition, and the smoothness of the coating film was also good.

Furthermore, this composition has improved flowability and anti-blocking properties, resulting in further improved storage stability. In other words, Taisei alumina has the property of being positively charged due to frictional electrification, which makes it easy to attach a name to the particle surface of powder coating.
As a result, the powder paint particles adhered to Taisei Aluminum and were electrically repelled, preventing agglomeration and deposition at the tip of the gun, and improving anti-waking properties.

Although this composition fully exhibits the above-mentioned technical effects when applied with an electrostatic coating machine, it can also be applied by other methods (fluidized dipping method, thermal spraying method, etc.).

Examples and Comparative Examples (1) Table 1 shows the particle size characteristics of powder coatings containing Taisei alumina. The percentage is 88% (the same applies below).

(Table 2 shows the properties of Taisei alumina that is blended into the powder coating.

Table 2 (3) Taisei alumina was added to the above powder coating, and the coating was applied using an electrostatic coating machine, and the amount of powder coating that adhered to the tip of the gun and the coating film performance were examined. The results are shown in Table 3.

In Table 23, ■Mixing method of powder coating and Taisei alumina: Powder coating】0
Add Taisei alumina in the amount (frt parts) listed in Table 3 per 0 parts by weight, and mix with a Henschel mixer for 2 minutes/1
000 rpm and passed through a 74-mesh sieve.

(Electrostatic coating method: Apply the above powder coating to the steel plate that has been coated with cationic N coating and intermediate coating using an electrostatic powder coating gun (Onoda Cement Fuki GX).
-501 type), applied voltage -70a1 powder discharge 1100
Coating was carried out under conditions of f'/min and temperature and humidity of 25° C./70% RH.

(3) Measuring sound for the amount of adhesion on the tip of the gun: Measure the weight of the plastic cap on the tip of the gun in advance, and after electrostatically painting in four directions under the above conditions, remove the cap to avoid dropping any deposits and measure the weight. I do.

■Performance test results of coating film: The following performance was obtained by discharging under the above conditions for 4 minutes, then painting the above steel plate as it was so that the cured coating film was 60μ, and heating and curing at 160℃ for 30 minutes. I looked into it.

(+) Smoothness Visual judgment C): Good △: Yuzu skin occurrence (1) Painted surface condition Visual judgment C): Good △：Putu occurrence (1) Light Sawa Visual 'j'lJ determination ○: Good (rv) Adhesiveness cross cut cheese test ○: Good Patent applicant: Kansai Paint Co., Ltd.

Claims (1)

[Claims] A powder characterized by blending 0.03 to 2 parts by weight of igneous alumina, the main component of which is particles with a particle size of 50 millimicrons or less, per 100 parts by weight of a powder coating with an average particle size of 100 microns or less. Paint composition.