JPH11152423A - Aluminum flake figment, coating composition containing the same and coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum flake pigment high in mechanical shear- resistance and excellent in brightness by making the pigment include an aluminum flake having a specific mean thickness, mean particle size, aspect ratio and uniformity number. SOLUTION: This pigment is obtained by making it include an aluminum flake with the following properties: a mean thickness (t) (resulted from the steps of; adding 1 g of stearic acid to 1 g of aluminum flake; heating the mixture together with a little amount of xylene to thereby perform a leafing treatment; powdering it by acetone for measuring its water surface diffusion area; and calculating from the equation t=4,000/the water surface diffusion area) = 0.2 to 0.7 μm; a mean particle size (D50 ) (by the laser diffraction method) = 4 to 20 μm; an aspect ratio (D50/t )=15 to 50; and a uniformity number (n) (obtained by determining a particle size distribution on an area basis by using a laser diffraction type particle size distribution detector, plotting the cumulative distributions corresponding to the obtained respective particle sizes on a Rosin- Rammler diagram, translating the resultant line, and drawing an extrapolation line from the pole) >=2.4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum flake pigment for use in, for example, automobiles, motorcycles and other industrial coatings, a coating composition containing the same, and a formed coating film. Resistance (circulation resistance: Circulation Resi
stance) related to aluminum flake pigments for metallic paints.

[0002]

2. Description of the Related Art Aluminum flakes have conventionally been used as paint pigments for imparting a high metallic feeling. Generally, when a paint containing aluminum flakes is actually applied, it is necessary to circulate the paint by stirring or a gear pump or a plunger pump so that the pigment does not settle. In such agitation or circulation, an intense turbulence near the agitating blades or the pump or inside the pipe exerts an excessive impact on the aluminum flakes, resulting in deformation or breakage. Finishing of a coating film using a paint using a deformed or broken aluminum flake pigment causes difficulty in lowering light brightness and brightness.

As prior arts related to this problem, Japanese Patent Nos. 2905590 and 2506609 can be exemplified, but these attempt to solve the problem by limiting the shape factor of aluminum flakes to a specific range. It is. However, in order to limit the shape factor of aluminum flakes to a specific range, it is necessary to increase the flake thickness at each particle size, and as a result, the number of flakes in the coating film decreases, the flake surface becomes insufficient. As a result, the degree of polishing or the decrease in the parallel arrangement of flakes in the coating film, etc., was consequently reduced, and the reduction in the brightness of the coating film was still inevitable, and the black finish could not be sufficiently avoided.

Accordingly, an object of the present invention is to provide a paint and a coating film formed product which are resistant to mechanical shear and which have excellent light brightness.

[0005]

According to the present invention, there is provided an image forming apparatus comprising:
(t) 0.2 to 0.7 [mu] m, an average particle diameter (D ₅₀₎ 4~20μm, the aspect ratio (D ₅₀ / t) 15~50 and aluminum flake pigment containing aluminum flakes are equivalent number (n) ≧ 2.4, It can be solved effectively. The above features and the like of the aluminum flake of the present invention will be described in detail below.

[0006] 1. Flake Shape Conventional aluminum flakes (see Comparative Example 2 shown in FIGS. 3 and 4) often have fine particles adhered to the surface of the flakes, especially when the average particle size is 25 μm or less. Is remarkable. These fine particles do not come off under the condition of ordinary paint, but they come off under strong shear such as circulation, and when formed into a coating film, cause black change. Further, the attachment of fine particles is one of the causes of impairing the surface smoothness, and lowers the light brightness of aluminum flakes. The smoothness of the surface and the smoothness of the periphery have an important role in the circulation resistance of the paint. That is, flakes that are jagged at the periphery and are not smooth are easily deformed or broken by a mechanical shear, resulting in a significant color change.

These will be described in detail with reference to the accompanying drawings (Example 3 shown in FIGS. 1 and 2 and Comparative Example 2 shown in FIGS. 3 and 4). In (Example 3), the average number of fine particles attached was about 0.3 /
It is a flake, and both the surface and the edge smoothness are extremely good. On the other hand, the number of attached fine particles of Comparative Example 2 which is a conventional product is an average of about 5 or more / flake, and the surface and the edge smoothness are Very bad. In the aluminum flake pigment of the present invention, the number is preferably 2 / flake or less.

[0008] 2. Average particle diameter, aspect ratio and uniform number If the average particle diameter is less than 4 μm, black-grained finish will result due to the incorporation of ultra-fine particles. The smoothness of the film is deteriorated, and the sharpness is impaired.

The aspect ratio is a factor that affects the resistance to circulation. If the aspect ratio exceeds 50, the flakes are cut or deformed by the shear during circulation due to flattening. Under such a phenomenon, the arrangement of flakes in the coating film is significantly disturbed, and the glitter of the coating film is impaired. On the other hand, if it is less than 15, a parallel arrangement of flakes in the coating film cannot be obtained, and the glitter of the coating film is similarly impaired.

If the uniform number is less than 2.4, the particle size distribution becomes wide, and the light luminance and lightness of the coating film are reduced. In addition, by uniformizing the particle size distribution under each particle size and thickness,
A remarkable improvement in circulation resistance is obtained.

The uniform number n of the present invention is obtained by obtaining the area-based particle size distribution using a laser diffraction type particle size distribution analyzer, plotting the obtained cumulative distribution for each particle size on a rosin-Rammler diagram, The straight line is translated and an extrapolation line is drawn from the pole (Pol P) to obtain n.

3. Flame Brightness The most distinctive feature of the metallic paint finish is the metallic sensation of aluminum flakes, and therefore, it is most important in practical use to increase the brightness of the aluminum flakes themselves.

In conventional products, attempts have been made to make the aluminum flakes more scaly in order to increase the brightness. However, such scalying is equivalent to increasing the aspect ratio. It may cause a decrease in circulation.

In the present invention, the brightness of the aluminum flake has been successfully improved by smoothing the surface of the aluminum flake and smoothing the peripheral shape.

Aluminum flakes having a luminance (L ₁₅ value) of 140 or more are those which the present invention can provide for the first time.
The flakes appropriately flaked in this way not only enable excellent finish as a metallic coating color, but also straight silver (silver color by aluminum alone)
It has a remarkable effect that it can also be used in light-colored (metallic color colored by a light-colored organic pigment) coating.

4. Coating composition In the coating composition, if the amount of the aluminum flake pigment is less than 1 part by weight, based on 100 parts by weight of the resin solid content, the amount of flakes present in the coating film is extremely small, and the luster as a metallic coating is lacking. . If it exceeds 20 parts by weight, the flake content in the coating film becomes excessive,
Extrusion of the flakes onto the surface of the coating film impairs its smoothness, which not only reduces the sharpness, but also gives rise to the possibility of delamination.

As the resin used in the present invention, resins generally used for paints are used. For example, an acrylic resin, a polyester resin, an alkyd resin, a fluororesin, and the like can be given, and the mixture is usually used after being mixed with a crosslinking agent such as an amino resin or a blocked polyisocyanate compound. Further, these resins are not limited to one kind, and two or more kinds can be used in combination. In addition, a lacquer which can be usually cured by drying, a two-pack type polyurethane resin or a silicone resin is also used.

5. Additives Usually, in metallic coating, atomized paint mist reaches an object to be coated, and there is coalescence of paint droplets and shrinkage of the coating film due to evaporation of a solvent. The aluminum flakes incorporated in the paint achieve their parallel alignment during the coalescence of the paint and shrinkage due to evaporation of the solvent. That is, the non-volatile content of the paint on the object to be coated during that time increases, the viscosity also increases, and the arrangement of the aluminum flakes is determined. Volatiles are composed of the type of solvent used (aromatic, ketone, ester, glycol, etc.) and affect the solubility and workability of the paint resin.

In the present invention, the increase in viscosity due to the volatilization of the solvent is delayed by the addition of an additive, and the dispersion of aluminum flakes in the coating film is facilitated to improve the parallel arrangement characteristics. .

More remarkable effects can be obtained by simultaneously adding three kinds of additives such as fatty acid amide wax, cellulose acetate butyrate, and a transparent or translucent inorganic filler.

The fatty acid amide wax is usually used as a thixotropic agent in metallic coatings as an anti-settling agent or an anti-sagging agent. However, it alone has little effect for the purpose of arranging aluminum flakes in parallel in a coating film. Fatty acid amide wax is 5 to resin solids
15 parts by weight are preferred. Outside of this range, the effect of arranging aluminum flake pigments in parallel in the coating film cannot be obtained significantly. Cellulose acetate butyrate is said to be effective in controlling the viscosity of aluminum flakes and therefore has an effect on the orientation of aluminum flakes. Cannot be said to be obtained. Cellulose acetate butyrate is preferably used in an amount of 2 to 8 parts by weight based on the solid content of the resin. Outside this range, the effect of orientation of the aluminum flakes is not easily obtained. It is known that the addition of boron nitride or barium sulfate can improve the glitter of coating films, but the use of inorganic fillers is limited because the amount of these additives must be extremely large. was there. Even opaque inorganic fillers should be avoided from being used to reduce the brightness of the aluminum flakes, and transparent or translucent ones are preferred.

Examples of the transparent or translucent inorganic filler include aluminum silicate, calcium carbonate, precipitated barium sulfate and the like.

The amount of the transparent or translucent inorganic pigment is preferably 3 to 10 parts by weight based on the solid content of the resin. Outside this range, the brightness of the aluminum flakes is hardly remarkably exhibited.

As other pigments used in the paint of the present invention, other flake pigments, coloring pigments, various additives and the like can be used as needed. Examples of the flake pigment include plate-like iron oxide, phthalocyanine flake, graphite, mica coated with titanium dioxide, and colored mica. These are used in an amount that does not impair the glitter of the aluminum flake pigment. As the coloring pigment, those conventionally used for paints are conventionally used.For example, as an organic pigment, an azo lake pigment, a phthalocyanine pigment, an indigo pigment, a perinone pigment, a perylene pigment, a quinophthalone pigment, a dioxazine pigment, Examples thereof include quinacridone-based pigments, isoindolinone-based pigments, metal complex pigments, and the like, and examples of inorganic-based pigments include yellow lead, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide.
The addition amount of the coloring pigment is arbitrarily set according to the hue of the coating color.

6. As a coating method such as a coating method, a conventional air gun coating, a two-coat one-bake method using electrostatic coating, or the like is preferable. Further, as the coating color, a silver color of aluminum flake alone, a metallic color colored with an organic pigment, and the like can be exemplified as preferable ones.

Method for measuring various characteristic values The method for measuring various characteristic values of the aluminum flake in the present invention is as follows.

1. Average particle diameter (D ₅₀ ) By a laser diffraction method using a laser diffractometer SALD1100 manufactured by Shimadzu Corporation.

2. Average thickness (t) To 1 g of aluminum flakes, add 1 g of stearic acid, heat with a small amount of xylene, perform leafing treatment, powder with acetone, measure the water surface diffusion area, and calculate the thickness by the following formula (Aluminum Paint and Powder,
JDEdwards and I. Wray, third edition, Reinhold Pu
blishing Corp., New York (1955), pages 16-22).

Average thickness (t: μm) = 4000 / water surface diffusion area (cm ² / g) Brightness (L ₁₅ value) Painted plate Aluminum flake pigment Net Al 1.5g Acrylic lacquer * 48.5g (*: Nippon Paint Co., Ltd., Auto Clear) And dried at room temperature.

Colorimetric method : The coated plate was coated with X-Rite MA-68 type (X-Rite Incorporated).
L ₁₅ (L value at an incident angle of 45−reflection angle of 30 °) is measured at.

(Remarks) In order to measure the brightness of the aluminum flake itself as much as possible, a transparent acrylic lacquer was used as a vehicle, and the aluminum flake was coated with a doctor blade as a coating method capable of parallel arrangement of flakes.

4. Shape of flake Observation using a scanning electron microscope.

[0033] 5. 240 g of Acrydic A-322 containing circulation-resistant paint Uban 20SE-60 50 g manufactured by Dainippon Ink and Chemicals, Inc. Aluminum flake pigment net Al 24 g manufactured by Mitsui Chemicals, Inc. And the viscosity is adjusted with a thinner for 20 seconds at Ford cup # 4. ⇒ Paint before Circulation (Paint A) 300 g of this paint was transferred into a vessel equipped with a jacket for circulating cooling water, and stirred for 1 hour with a stirrer having stirring blades of turbine blades. ⇒ Paint after circulation
(Paint B) The paints A and B were spray-coated on an undercoated steel sheet by an automatic coating machine so that the dry coating thickness became about 15 μm. Then, a clear coat (acrylic / melamine resin-based paint “Super Rack 0: 150”, manufactured by Nippon Paint Co., Ltd.) on the coating film
Was baked at 140 ° C. for 30 minutes after being coated by a wet-on-wet method so that the dry coating film thickness became 35 μm. The: (wet-on-wet after metallic paint, clear coating to baking and drying methods without baking and drying) colorimetric method described above coated plate to measure the L ₁₅ in the X-Rite MA-68 type. Circulation resistance (CR property) is calculated by the following equation.

[0034] CR resistance (%) = (light intensity L ₁₅ of light brightness L ₁₅ / circulation after the coating of circulation before coating)
If the x100 rating is 80% or more, it is within the range that can be used without any practical problems.

[0035]

According to the present invention, there is provided a novel aluminum flake pigment, a coating composition and a coating film which are resistant to mechanical shear and have excellent light brightness.

[0036]

Example 1 Example 1 Ball mill Inner diameter 500 mm φ, length 180 mm Raw material D ₅₀ 4.5 μm spherical powder 800 g Mineral spirit 5000 ml Oleic acid 100 g Number of revolutions 34 rpm Operating time 5:30 (5 hours 30 minutes) Screen 400 mesh (2) Step) Fine particles of 10% were cut by decantation, separated into solid and liquid by a filter, and the cake was mixed for 30 minutes to obtain an aluminum flake pigment (heating residue: 65%).

[0037] Except Example 2 material D ₅₀ same embodiment spherical powder milling time 6:00 except the above Example 1 of 7.0 .mu.m 3 raw material D ₅₀ 6.5 [mu] m spherical powder milling time 4:30 above Examples the same example 4 material D ₅₀ 5.5 [mu] m than spherical powder milling time 6:30 above except same example 5 starting material D ₅₀ 5.0 .mu.m spherical powder milling time 6:00 above example 1 example of the 1 1 and the same embodiment 6 material D ₅₀ 8.7 .mu.m same Comparative example 1 inner diameter 500mm spherical powder milling time 5:00 except the above example 1, in a ball mill of length 180 mm, atomized aluminum spherical powder (Toyal Amer
ica, Inc. X-81) filled with a composition consisting of 1.0 kg, mineral spirit 5.01 and oleic acid 500 g, and operated at 38 rpm (corresponding to 64% of the critical rotation speed) for 3.5 hours using 50 kg of steel balls having a diameter of 2 mm. did.

After the completion of the pulverization, the slurry in the mill was washed out with mineral spirits, sequentially passed through a 150, 350, and 400 mesh (37 μm) vibrating screen, and the passed slurry was solid-liquid separated with a pan filter. The obtained cake (NV 85%) was transferred into a kneader mixer and kneaded for 1 hour to obtain an aluminum flake pigment (NV 80%).

Comparative Example 2 7640NS (manufactured by Toyo Aluminum) Comparative Example 3 TF3645 (manufactured by Silver Line) In Examples 1 to 6 and Comparative Examples 1 to 3, the circulating resistance was evaluated by the paint formulation described in the above item 5. .

Example 11 Using the aluminum flake pigment of Example 5, a paint for a test for resistance to circulation was prepared.

However, the following additives were further added.

CAB-381-05 10 g Eastman Chemical Japan K.K. Furonon SP-1000 3 g Kyoeisha Chemical Co., Ltd. Aluminum silicate ASP-200 5 g Engelhard Co. Example 12 In place of the aluminum flake pigment of Example 5, A coating for a test for resistance to circulation was prepared in the same manner as in Example 11, except that the aluminum flake pigment of Example 6 was used.

Example 13 Using the aluminum flake pigment of Example 6, a paint for a test for resistance to circulation was prepared.

However, only the following additives were added in Example 11.

CAB-381-05 10 g Eastman Chemical Japan Co., Ltd.

[0046]

[Table 1]

[0047]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph of an aluminum flake of Example 3 of the present invention.

FIG. 2 is another scanning electron micrograph of the aluminum flake of Example 3 of the present invention.

FIG. 3 is the same photograph of the aluminum flake of Comparative Example 2.

FIG. 4 is another photograph of the same aluminum flake of Comparative Example 2.

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[Submission date] November 25, 1997

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 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Okuma 3-6-8 Kutarocho, Chuo-ku, Osaka-shi, Osaka Toyo Aluminum Co., Ltd. (72) Inventor Akiyuki Yoneda 1 Nihookicho, Minami-ku, Hiroshima-shi, Hiroshima No. 30 Nippon Paint Co., Ltd. Hiroshima Office (72) Inventor Masahiko Togo 4-1-1 Minami Shinagawa, Shinagawa-ku, Tokyo Japan Paint Co., Ltd. Tokyo Office

Claims (5)

[Claims] An aluminum flake having an average thickness (t)
0.2-0.7 μm, average particle diameter (D ₅₀ ) 4-20 μm, aspect ratio (D ₅₀ / t) 15-50, and uniform number (n) ≧ 2.4, high luminance and high circulation resistance Aluminum flake pigment with excellent properties. 2. The aluminum flake pigment according to claim 1, wherein the aluminum flake has a luminance of 140 or more. 3. 1 to 100 parts by weight of resin (solid content)
A coating composition comprising 20 parts by weight of the aluminum flake pigment according to claim 1 or 2. 4. 1-2 parts per 100 parts by weight of resin (solid content)
A coating composition comprising 0 parts by weight of the aluminum flake pigment according to claim 1, a fatty acid amide wax, cellulose acetate butyrate, and a transparent or translucent inorganic filler. 5. A coating film formed by applying the coating composition according to claim 3 or 4.