Use of iron oxide coated aluminum flakes having red 1.SUP.st .order interference color in coatings

Abstract

The use of an effect pigment (a) comprising an aluminum-based substrate and an iron oxide coating having a red 1.sup.st order interference color in combination with a colored absorption pigment (b) for producing a coating having enhanced coloristic properties, in particular enhanced chroma, lightness and hiding power, is provided. The pigment combination of (a) and (b) is suitable for coloring plastics, a fiber, a film and a coating composition such as a paint, a printing ink, a varnish or a powder coating, preferably an automotive, an architectural or an industrial coating composition.

Claims

1. A method for producing a coating having an enhanced coloristic property, the method comprising: coating an article with an effect pigment (a) and a colored absorption pigment (b), wherein the effect pigment (a) comprises an aluminum-based substrate and an iron oxide coating having a red 1.sup.st order interference color, the colored absorption pigment (b) comprises an organic transparent pigment, an inorganic transparent pigment, or both, where the organic transparent pigment is at least one red-hued pigment selected from the group consisting of an anthraquinone pigment, a diketopyrrolopyrrole pigment, an isoindolinone pigment, a metal complex pigment, a perylene pigment, and an indigo pigment, a weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 95:5 to 5:95, and the effect pigment (a) and the colored absorption pigment (b) are in a dispersed form.

2. The method according to claim 1, wherein the weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 90:10 to 30:70.

3. The method according to claim 1, wherein the colored absorption pigment (b) is the organic transparent pigment and is a perylene pigment.

4. The method according to claim 1, wherein the colored absorption pigment (b) is the inorganic transparent pigment and is a yellow or red iron oxide.

5. The method according to claim 1, wherein the effect pigment (a) is coated by a chemical vapor deposition process.

6. The method according to claim 1, wherein the effect pigment (a) comprises an aluminum substrate which is optionally passivated with a layer of a metal phosphate, silica, aluminum oxide, hydrated aluminum oxide or a combination thereof.

7. The method according to claim 1, wherein the coating is an automotive coating, an architectural coating or an industrial coating.

8. A process for enhancing a coloristic property of a coating, comprising: contacting an effect pigment (a) and a colored absorption pigment (b) in the coating, wherein the effect pigment (a) comprises an aluminum-based substrate and an iron oxide coating having a red 1.sup.st order interference color, the colored absorption pigment (b) comprises an organic transparent pigment, an inorganic transparent pigment, or both, where the organic transparent pigment is at least one red-hued pigment selected from the group consisting of an anthraquinone pigment, a diketopyrrolopyrrole pigment, an isoindolinone pigment, a metal complex pigment, a perylene pigment, and an indigo pigment, a weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 95:5 to 5:95, and the effect pigment (a) and the colored absorption pigment (b) are in a dispersed form.

9. A pigment combination, comprising: (a) an effect pigment comprising an aluminum-based substrate and an iron oxide coating having a red 1.sup.st order interference color; and (b) a colored absorption pigment comprising an organic transparent pigment, an inorganic transparent pigment, or both, where the organic transparent pigment is at least one red-hued pigment selected from the group consisting of an anthraquinone pigment, a diketopyrrolopyrrole pigment, an isoindolinone pigment, a metal complex pigment, a perylene pigment, and an indigo pigment, wherein a weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 95:5 to 5:95, and the effect pigment (a) and the colored absorption pigment (b) are in a dispersed form.

10. The pigment combination according to claim 9, wherein the weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 90:10 to 30:70.

11. A method for coloring an article, comprising: contacting the article with the pigment combination according to claim 9, wherein the article is a plastic, a fiber, a film or a coating composition.

12. An article coated with a composition comprising the pigment combination of claim 9.

13. An automotive coating, comprising: the pigment combination of claim 9.

14. The method according to claim 1, wherein the method is suitable for enhancing chroma, lightness and/or hiding power.

15. The method according to claim 1, wherein the weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 75:25 to 20:80.

16. The method according to claim 3, wherein the organic transparent pigment is in the form of a solid solution or a mixed crystal.

17. The method according to claim 11, wherein the coating composition is a paint, a printing ink, a varnish or a powder coating.

18. The pigment combination according to claim 9, wherein a weight ratio of the effect pigment (a) to the colored absorption pigment (b) is from 90:10 to 30:70, and the colored absorption pigment (b) is the organic transparent pigment and is a red perylene pigment.

19. The method according to claim 1, wherein the coating has enhanced chroma, lightness and/or hiding power as compared to a coating produced by a method comprising coating the article with an effect pigment having an orange 2.sup.nd order interference color and the colored absorption pigment (b).

20. The method according to claim 1, wherein the effect pigment (a) consists of a pigment having the aluminum-based substrate and the iron oxide coating having the red 1st order interference color.

Description

EXAMPLES

(1) In order to determine the CIELAB values of hue h [ ], chroma C* and lightness L*, the coating films obtained (in masstone) are measured as follows: the pigment(s) is/are incorporated by stirring with a level of total pigmentation of 5% by weight (based on the total weight of the wet varnish) into a conventional solvent-borne, medium solids cellulose acetobutyrate (CAB)/polyester varnish (pigment/binder 20/100), until the pigments are finally dispersed. The completed varnish is applied onto aluminum panels with a wet film thickness of about 150 to 160 m and subsequently dried at room temperature to a thickness of about 20 m. The color data are determined using a multi-angle colorimeter BYK-MAC (from BYK Gardner) with a constant incident angle of 45. The values C*, L*, a*, b* and h* are measured at 15 and 15 (relative to the specular angle).

(2) In order to determine the opacity (hiding power), the coating films obtained (in masstone) are measured as follows: The basecoat is sprayed in form of a wedge on a panel with black and white contrasts like a chess game. It is visually determined where the hiding zone starts. At that point the basecoat thickness is determined with a coating thickness gauge (DeFelsko PosiTector 6000).

Synthesis Example 1

(3) In a laboratory fluidized bed reactor 1000 g of aluminum platelets with an average particle size d50=18 m are fluidized with nitrogen and heated up to 180 C. within 1 hour. After reaching that temperature water vapor and air are dosed with 400 L/h and 150 L/h, respectively. The oxygen content is adjusted to be below 3%. Subsequently, gaseous Fe(CO).sub.5 (produced by heating the liquid material outside the reactor to 60 C.) is dosed with 50 mL/h using a nitrogen stream. The process reaches the desired red color of 1.sup.st order interference at an amount of around 390 ml of Fe(CO).sub.5. The aluminum content determined by chemical analysis of the product is about 80% by weight, whereas the iron oxide content is about 20% by weight.

Synthesis Example 2

(4) 75 g of SiO.sub.2 coated aluminum platelets (prepared according to step (a) of Example 1 of EP-A-0708154) are dispersed in 700 mL of water. The suspension is heated to 80 C., and the pH is adjusted to pH3. Simultaneously, an aqueous 50% iron nitrate solution and NaOH are added in order to keep the pH constant. The addition is stopped when the color of 2.sup.nd order orange to red is achieved. The pigment composition according to chemical analysis is Al:SiO.sub.2:Fe.sub.2O.sub.3=32:11:57.

Examples 1-4 and Comparative Example 1

(5) A pigment combination comprising Synthesis Example 1 and Paliogen Red L 3885 (C.I. Pigment Red 179) in the following weight ratios is formed:

(6) TABLE-US-00001 (Synthesis Example 1:Pigment Red 179) Comparative Example 1 100:0 Example 1 90:10 Example 2 70:30 Example 3 50:50 Example 4 30:70

Comparative Examples 2-7

(7) A pigment combination comprising Synthesis Example 2 and Paliogen Red L 3885 in the following weight ratios is formed:

(8) TABLE-US-00002 (Synthesis Example 2:Pigment Red 179) Comparative Example 2 100:0 Comparative Example 3 90:10 Comparative Example 4 70:30 Comparative Example 5 50:50 Comparative Example 6 30:70

(9) The results are demonstrated in Tables 1 to 3.

(10) TABLE-US-00003 TABLE 1 Examples h C* L* a* b* h* C* L* E* Observation angle 15 Comp. Ex. 2 56.68 127.6 94.48 70.08 106.6 Comp. Ex. 1 56.92 123.6 104.5 67.46 103.6 0.5 4 10 10.8 Observation angle 15 Comp. Ex. 2 53.97 117.6 87.67 69.18 95.12 Comp. Ex. 1 56.42 114.0 96.61 63.61 95.00 5 3.6 8.9 10.8

(11) TABLE-US-00004 TABLE 2 Example h C* L* a* b* h* C* L* E* Observation angle 15 Comp. Ex. 3 51.03 130.4 80.52 82.00 101.4 Example 1 50.95 126.2 88.87 79.48 97.97 0.2 4.2 8.3 9.4 Comp. Ex. 4 46.88 114.7 62.65 78.39 83.72 Example 2 46.30 118.0 71.28 81.52 85.31 1.2 3.3 8.6 9.3 Comp. Ex. 5 43.56 100.9 51.52 73.1 69.52 Example 3 44.06 110.7 60.31 79.53 76.97 0.9 9.8 8.8 13.2 Comp. Ex. 6 39.53 83.35 41.99 64.29 53.05 Example 4 40.76 92.82 48.58 70.31 60.6 1.9 9.8 6.6 11.7 Observation Angle 15 Comp. Ex. 3 49.23 121.6 74.25 79.4 92.09 Example 1 50.53 116.6 81.67 74.13 90.02 2.7 5 7.4 9.3 Comp. Ex. 4 45.7 108.8 58.21 76.00 77.88 Example 2 45.92 109.9 65.45 76.42 78.91 0.4 1 7.2 7.3 Comp. Ex. 5 42.81 96.41 47.79 70.73 65.51 Example 3 43.66 103.1 55.06 74.58 71.17 1.5 6.7 7.3 10.0 Comp. Ex. 6 39.28 80.27 38.65 62.13 50.81 Example 4 40.58 87.25 44.11 66.27 56.76 1.9 7 5.5 9.1

(12) A difference of 1 unit in C* may already be recognized by a person skilled in the art.

(13) TABLE-US-00005 TABLE 3 Thickness of a hiding basecoat layer Example Comp. Ex. 3 19-21 m Example 1 15-17 m Comp. Ex. 4 25-27 m Example 2 21-23 m Comp. Ex. 5 34-36 m Example 3 22-24 m Comp. Ex. 6 42-44 m Example 4 35-38 m

(14) The smaller the values in m the higher the hiding power.