ALPHA-ALUMINA FLAKES

Abstract

The present invention relates to alumina flakes having a defined thickness and particle size distribution and to their use in varnishes, paints, automotive coatings, printing inks, masterbatches, plastics and cosmetic formulations and as substrate for effect pigments.

Claims

1-16. (canceled)

17. An automobile coating, automotive finishing or industrial coating, comprising coated and/or uncoated Al.sub.2O.sub.3 flakes having a particle thickness of less than 500 nm and a D.sub.50-value of 15-30 m and a D.sub.90-value of 30-45 m and one or more further ingredients suitable for an automobile coating, automotive finishing or industrial coating.

18. An automobile coating, automotive finishing or industrial coating according to claim 17, which is a single layer coating or a two-coat system in which the coated and/or uncoated Al.sub.2O.sub.3 flakes are present in a base coat.

19. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the coated and/or uncoated Al.sub.2O.sub.3 flakes are present in an amount of 0.5 to 10% by weight based on the weight of the automobile coating, automotive finishing or industrial coating.

20. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes have a particle thickness of 130-400 nm and a D.sub.50-value of 15-30 m and a D.sub.90-value of 30-45 m and a D.sub.10-value of <9.5 m.

21. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are -alumina flakes.

22. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes have a standard deviation of thickness distribution of less than 80 nm.

23. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are doped with TiO.sub.2, ZrO.sub.2, SiO.sub.2, SnO.sub.2, In.sub.2O.sub.3, or ZnO or a combination thereof.

24. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are coated with at least one layer of a metal oxide, a mixture of at least two metal oxides, a metal, a metal sulphide, a titanium suboxide, a titanium oxynitride, FeO(OH), SiO.sub.2, a metal alloy or a rare earth compound, which form one or more coatings.

25. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are coated with at least one layer of a metal oxide or a mixture of at least two metal oxides.

26. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are coated with the following layer sequence: Al.sub.2O.sub.3 flake+TiO.sub.2 Al.sub.2O.sub.3 flake+TiO.sub.2/Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+TiO.sub.2+Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+TiO.sub.2+Fe.sub.3O.sub.4 Al.sub.2O.sub.3 flake+TiO.sub.2+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+TiO.sub.2/Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+TiO.sub.2+SiO.sub.2+TiO.sub.2/Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+TiO.sub.2+SiO.sub.2 Al.sub.2O.sub.3 flake+TiO.sub.2+SiO.sub.2/Al.sub.2O.sub.3 Al.sub.2O.sub.3 flake+TiO.sub.2+Al.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SnO.sub.2 Al.sub.2O.sub.3 flake+SnO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+SnO.sub.2+Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SiO.sub.2 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2/Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SiO.sub.2+Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+Fe.sub.3O.sub.4 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+SiO.sub.2+Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2/Fe.sub.2O.sub.3+SiO.sub.2+TiO.sub.2 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+SiO.sub.2+TiO.sub.2/Fe.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+SiO.sub.2 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+SiO.sub.2/Al.sub.2O.sub.3 Al.sub.2O.sub.3 flake+SiO.sub.2+TiO.sub.2+Al.sub.2O.sub.3 Al.sub.2O.sub.3 flake+TiO.sub.2+Prussian Blue or Al.sub.2O.sub.3 flake+TiO.sub.2+Carmine Red.

27. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are coated with TiO.sub.2 in the rutile modification.

28. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are coated with TiO.sub.2 in the anatase modification.

29. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes are coated, and which coated flakes consist of 40-90 wt. % of Al.sub.2O.sub.3 flakes and 10-60 wt. % of the one or more coatings.

30. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes have a D.sub.10-value of <9.2 am.

31. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes have a D.sub.10-value of 8.8 to 9.2 am.

32. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes have a particle thickness of 200-250 nm.

33. An automobile coating, automotive finishing or industrial coating according to claim 17, wherein the Al.sub.2O.sub.3 flakes have a particle thickness of 130-400 nm and a D.sub.50-value of 15-30 m and a D.sub.90-value of 30-45 m and a D.sub.10-value of 8.8 to <9.5 am.

34. An automobile coating, automotive finishing or industrial coating composition, comprising coated and/or uncoated Al.sub.2O.sub.3 flakes having a particle thickness of less than 500 nm and a D.sub.50-value of 15-30 am and a D.sub.90-value of 30-45 am and one or more further ingredients suitable for an automobile coating, automotive finishing or industrial coating.

35. An automobile coating, automotive finishing or industrial coating composition according to claim 34, wherein the coated and/or uncoated Al.sub.2O.sub.3 flakes are present in an amount of 0.5 to 10% by weight based on the weight of the automobile coating, automotive finishing or industrial coating.

Description

EXAMPLES

Comparative Example 1 (Example 2 of U.S. Pat. No. 5,702,519)

[0110] 111.9 g of aluminum sulfate 18-hydrate, 57.3 g of anhydrous sodium sulfate and 46.9 g of potassium sulfate are dissolved in 300 ml of deionized water by heating above 60 C. 3.0 g of 34.4% solution of titanyl sulfate solution is added to this solution. The resulting solution is designated as the aqueous solution (a).

[0111] 0.45 g of sodium tertiary phosphate 12-hydrate and 55.0 g of sodium carbonate are added to 150 l of deionized water. The resulting solution is designated as the aqueous solution (b).

[0112] The aqueous solution (b) is added with stirring to the aqueous solution (a) kept at about 60 C. Stirring is continued for further 15 minutes. The resulting mixture of the two solutions (a) and (b) is a gel. This gel is evaporated to dryness, and the dried product is heated at 1200 C. for 5 hours. Water is added to the heated product to dissolve free sulfate. Insoluble solids are filtered off, washed with water, and finally dried. The obtained alumina flake is examined by X-ray diffractometry. The diffraction pattern has only peaks attributed to corundum structure (-alumina structure). D.sub.50 is 13.0 m and D.sub.90 is 22.0 m and the thickness is 200 nm.

[0113] The standard deviation of the thickness distribution of the -Al.sub.2O.sub.3 flake is 83 nm.

Example 1: Production of Al.SUB.2.O.SUB.3 .Flakes

[0114] 74.6 g of aluminum sulfate 18-hydrate, 57.1 g of poly aluminum chloride (PAC: Central Glass Co., LTD, 10% solution as Al.sub.2O.sub.3), 57.3 g of anhydrous sodium sulfate, and 46.9 g of potassium sulfate are dissolved in 300 ml of deionized water by heating above 60 C. 3.0 g of 34.4% of a titanyl sulfate solution are added to the solution. The resulting solution is designated as the aqueous solution (a).

[0115] 0.45 g of sodium tertiary phosphate 12-hydrate and 55.0 g of sodium carbonate are added to 300 ml of deionized water. The resulting solution is designated as the aqueous solution (b).

[0116] The aqueous solution (b) is added with stirring to the aqueous solution (a) and kept at about 60 C. Stirring is continued for 1 h. The obtained mixture of solution (a) and solution (b) is a slurry. This slurry is evaporated to dryness and the dried product is heated at 1150 C. for 6 h. Water is added to the heated product to dissolve free sulfate. Insoluble solids are filtered off and washed with water. Finally, the product is dried.

[0117] The obtained alumina flake is examined by X-ray diffractometry. The diffraction pattern have only peaks attributed to corundum structure (-alumina structure).

[0118] The obtained Al.sub.2O.sub.3 flakes have a D.sub.50 value of 16.0 m and D.sub.90 value of 30.8 m and a thickness of 200 nm.

[0119] The standard deviation of the thickness distribution of the -Al.sub.2O.sub.3 flake is 28 nm.

Example 2: Production of Al.SUB.2.O.SUB.3 .Flakes

[0120] 74.6 g of aluminum sulfate 18-hydrate, 57.1 g of poly aluminum chloride (PAC: Central Glass Co., LTD, 10% solution as Al.sub.2O.sub.3), 57.3 g of anhydrous sodium sulfate, and 46.9 g of potassium sulfate are dissolved in 300 ml of deionized water by heating above 60 C. 3.0 g of 34.4% of a titanyl sulfate solution and 5.5 g of 5.0% indium chloride(III) solution are added to the solution. The resulting solution is designated as the aqueous solution (a).

[0121] 0.45 g of sodium tertiary phosphate 12-hydrate and 55.0 g of sodium carbonate are added to 300 ml of deionized water. The resulting solution is designated as the aqueous solution (b).

[0122] The aqueous solution (b) is added with stirring to the aqueous solution (a) and kept at about 60 C. Stirring is continued for 1 h. The obtained mixture of solution (a) and solution (b) is a slurry. This slurry is evaporated to dryness and the dried product is heated at 1200 C. for 4 h. Water is added to the heated product to dissolve free sulfate. Insoluble solids are filtered off and washed with water. Finally, the product is dried.

[0123] The obtained alumina flake is examined by X-ray diffractometry. The diffraction pattern have only peaks attributed to corundum structure (-alumina structure).

[0124] The obtained Al.sub.2O.sub.3 flakes have a D.sub.50 value of 19.0 m and D.sub.90 value of 35.6 m and a thickness of 250 nm.

[0125] The standard deviation of the thickness distribution of the -Al.sub.2O.sub.3 flake is 32 nm.

Comparative Example 1.1: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0126] 20 g alumina flakes of Comparative Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 125 g of TiCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a silvery color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a whitish and a little glossy pearlescent pigment.

Example 1.1: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0127] 20 g alumina flakes of Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 125 g of TiCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a silvery color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a highly whitish and glossy pearlescent pigment. At the luster angle, the glossy appearance can be seen at a more wider angle compared to Comparative Example 1.1.

Example 2.1: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0128] 20 g alumina flakes of Example 2 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 125 g of TiCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a silvery color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a highly whitish and glossy pearlescent pigment. At the luster angle, the glossy appearance can be seen at a more wider angle compared to Comparative Example 1.1.

Comparative Example 1.2: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0129] 20 g alumina flakes of Comparative Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 75 C.) is added a solution containing 300 g of FeCl.sub.3 per liter. Simultaneously a 10% solution of NaOH was added to keep the pH at 3.0. The addition of the FeCl.sub.3 solution is stopped when the resulting product takes on a most reddish color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 800 C. for 30 minutes to give a moderate luster and brownish red colored pearlescent pigment.

Example 1.2

[0130] 20 g of the alumina flakes of Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 75 C.) is added a solution containing 300 g of FeCl.sub.3 per liter. Simultaneously a 10% solution of NaOH was added to keep the pH at 3.0. The addition of the FeCl.sub.3 solution is stopped when the resulting product takes on a most reddish color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 800 C. for 30 minutes to give a high luster and pure red colored pearlescent pigment. The pigment shows a higher luster and more cleaner red color compared to the appearance of the pigment of Comparative Example 1.2.

Comparative Example 1.3: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0131] 20 g alumina flakes of Comparative Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 50 g of SnCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1 until the total adding volume of SnCl.sub.4 solution become 17 ml. Next the solution containing 125 g of TiCl.sub.4 per liter was added to the resulting suspension. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a silvery color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a whitish and a little glossy pearlescent pigment.

Example 1.3: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0132] 20 g alumina flakes of Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 50 g of SnCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1 until the total adding volume of SnCl.sub.4 solution become 17 ml. Next the solution containing 125 g of TiCl.sub.4 per liter was added to the resulting suspension. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a silvery color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a highly whitish and highly glossy pearlescent pigment. At the luster angle, the glossy appearance can be seen at a more wider angle compared to Comparative Example 1.3

Comparative Example 1.4: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0133] 20 g alumina flakes of Comparative Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 125 g of TiCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a yellowish color. Then a solution containing 50 g of Na.sub.2SiO.sub.3 per liter is added to the resulted suspension. Simultaneously a 10% solution of HCl is added to keep the pH at 7. Next a solution containing 125 g of TiCl.sub.4 per liter is added to the resulted suspension. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a bluish color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a blue-whitish and a little glossy pearlescent pigment.

Example 1.4: Coating of Al.SUB.2.O.SUB.3 .Flakes

[0134] 20 g alumina flakes of Example 1 are suspended in 400 ml of deionized water. To the resulting suspension (kept at about 65 C.) is added a solution containing 125 g of TiCl.sub.4 per liter. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a yellowish color. Then a solution containing 50 g of Na.sub.2SiO.sub.3 per liter is added to the resulted suspension. Simultaneously a 10% solution of HCl is added to keep the pH at 7. Next a solution containing 125 g of TiCl.sub.4 per liter is added to the resulted suspension. Simultaneously a 10% solution of NaOH is added to keep the pH at 2.1. The addition of the TiCl.sub.4 solution is stopped when the resulting product takes on a bluish color. The suspending solids are filtered off, washed with water, and dried. Finally, the dried solids are calcined at 850 C. for 30 minutes to give a highly bluish and glossy pearlescent pigment. At the luster angle, the stronger bluish color and higher glossy appearance can be seen at a more wider angle compared to Comparative Example 1.4.

[0135] Measurements

[0136] Evaluation for Particle Size D.sub.1, D.sub.50 and D.sub.90

[0137] D.sub.10, D.sub.50 and D.sub.90 of the alumina flakes are evaluated by using Malvern MS2000.

[0138] Determination of the Thickness and Particle Size and the Thickness Distribution

[0139] 0.01 g/l of the alumina flake slurry is prepared and 0.1 ml of this slurry is dropped onto a flat substrate like a silicon wafer. The substrate is dried and cut to adequate size. The substrate is set with almost vertically tilted angle on the base of SEM (Scanning electronic microscope) and the thickness of the alumina flake is determined.

[0140] The thickness of more than 100 alumina flakes is measured for the calculation of the thickness distribution. The standard deviation of the thickness is calculated with the Gaussian distribution equation.

[0141] Preparation for a Sprayed Panel

[0142] A base coat paint for automobiles is prepared according to the following formulation.

TABLE-US-00001 <Base coat system> Acrylic-melamine resin system ACRYDIC 47-71 2* 70 pbw SUPERBEKKAMINE G821-60** 30 pbw Toluene 30 pbw Ethyl acetate 50 pbw n-Butanol 110 pbw SOLVESSO#150*** 40 pbw *Acrylic resin from Dainippon Ink & Chemicals, Inc. **Melamine resin from Dainippon Ink & Chemicals, Inc. ***Naphtha (petroleum)

[0143] The above acrylic-melamine resin system (100 pbw) is incorporated with 20 pbw of the pearlescent pigment according to Example 1 or 2. The resulting compound is diluted with a thinner so that the resulting paint has an adequate consistency for spraying (12-15 seconds, for cup #4). This paint is applied to a substrate by spraying to form a base coat layer.

[0144] The base coated layer is coated further with a colorless top clear coat paint, which is prepared according to the following formulation.

TABLE-US-00002 TABLE 1 <Top clear coat system> ACRYDIC 47-712 14 pbw SUPERBEKKAMINE L117-60 6 pbw Toluene 4 pbw MIBK 4 pbw Butyl cellosolve 3 pbw

[0145] The top clear coating is exposed to air at 40 C. for 30 minutes and then cured at 135 C. for 30 minutes.

[0146] Haze-gloss (BYK) is the analyzing equipment to evaluate luster and haze. In this patent application, the value of mirror gloss on 60 is measured by Haze-gloss and represents the value of the luster. Compared to the prior art the coated Al.sub.2O.sub.3 flakes show very high values for the luster. High luster values are necessary to achieve a good appearance in the applications. The haze values measured by this equipment are affected by spreading of the reflection angle. In this patent application, the wider spreading angle is important for the pearlescent appearance. The coated Al.sub.2O.sub.3 flakes according to the present invention show very high haze-gloss values.

[0147] To differentiate the evaluation result, panels are used which are sprayed with a base coat before they are coated with a top clear coat for the haze-gloss measurement.

[0148] Wave-scan dual (BYK) is used as the analyzing equipment to measure the surface flatness of the samples. Wa value represents the cyclic flatness in the range of 0.1-0.3 mm. A smaller value in this patent application represents a flatter surface showing the advantages of the pigments according to the present invention.

[0149] Sprayed panels with a top clear coat are measured for Wa. Flatter surfaces have better finishing appearance.

[0150] The optical properties of the pearlescent pigments according to the above given examples are summarized in the following table:

TABLE-US-00003 TABLE 1 Optical properties TiO.sub.2 Particle size Standard of TiO.sub.2 coated coated distribution of the deviation of Al.sub.2O.sub.3 flakes Al.sub.2O.sub.3 Al.sub.2O.sub.3 Al.sub.2O.sub.3 flakes (m) the Thickness haze- flakes flakes D.sub.10 D.sub.50 D.sub.90 distribution (nm) luster gloss Wa E1 E1.1 9.0 16.0 30.8 28 40 21 9 E2 E2.1 9.1 19.0 35.6 32 46 25 12 CE1 CE1.1 4.8 13.0 22.0 83 11 4 21

[0151] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

[0152] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0153] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

[0154] The entire disclosures of all applications, patents and publications, cited herein and of corresponding European application No. EP 13002293.2, filed Apr. 30, 2013 are incorporated by reference herein.