Effect pigments

Abstract

The present invention relates to silver-colored effect pigments having a strong sparkle effect based on Al2O3 flakes and to the use thereof in paints, button pastes, automotive paints, automotive refinish paints, powder coatings, printing inks, security printing inks, plastics, ceramic materials, glasses, paper, for coating seed, in security applications, as dopant for the laser marking of plastics and papers, as additive for the laser welding of plastics, in cosmetic formulations and for the preparation of pigment preparations and dry preparations.

Claims

1. An effect pigment comprising: Al.sub.2O.sub.3 flakes as substrate having an equivalent diameter distribution according to which 90% of the particles are in the range from 5-45 m, the Al.sub.2O.sub.3 flakes as substrate being doped with TiO.sub.2, ZrO.sub.2, SiO.sub.2, In.sub.2O.sub.3, SnO.sub.2, or ZnO or mixtures thereof, wherein the pigment has two highly refractive layers each having a refractive index n>1.9 on the substrate, wherein one of said two highly refractive layers consists of titanium dioxide and the other of said two highly refractive layers contains ilmenite (FeTiO.sub.3) or TiO.sub.2/Fe.sub.2O.sub.3 and FeTiO.sub.3, wherein said one of said two highly refractive layers consisting of titanium dioxide has a layer thickness of 15-200 nm, and wherein said effect pigment is a silver-colored effect pigment.

2. The effect pigment according to claim 1, wherein the form factor (aspect ratio: diameter/thickness ratio) of the Al.sub.2O.sub.3 flakes is 30-200.

3. The effect pigment according to claim 1, wherein the Al.sub.2O.sub.3 flakes are corundum.

4. The effect pigment according to claim 1, wherein the Al.sub.2O.sub.3 flakes are doped with TiO.sub.2.

5. The effect pigment according to claim 1, wherein the proportion of the doping is <5%, based on the substrate.

6. The effect pigment according to claim 1, wherein the other of said two highly refractive layers is an FeTiO.sub.3 layer.

7. The effect pigment according to claim 6, wherein the highly refractive layer consisting of titanium dioxide is in the rutile modification.

8. The effect pigment according to claim 1, wherein the other of said two highly refractive layers has a thickness of 5-100 nm.

9. The effect pigment according to claim 1, wherein the proportion of the doping is 0.05-3%, based on the substrate.

10. The effect pigment according to claim 1, wherein the Al.sub.2O.sub.3 flakes have a D.sub.50 value in the range from 15-30 m.

11. The effect pigment according to claim 1, wherein the Al.sub.2O.sub.3 flakes have a D.sub.50 value in the range from 15-25 m.

12. The effect pigment according to claim 1, wherein the Al.sub.2O.sub.3 flakes have a D.sub.10 value in the range from 5-15 m.

13. The effect pigment according to claim 1, wherein the Al.sub.2O.sub.3 flakes have a D.sub.10 value in the range from 6-10 m.

14. The effect pigment according to claim 1, wherein the form factor (aspect ratio: diameter/thickness ratio) of the Al.sub.2O.sub.3 flakes is 50-150.

15. The effect pigment according to claim 1, wherein said one of said two highly refractive layers consisting of titanium dioxide is applied to the substrate, and the other of said two highly refractive layers is a colored layer which is applied to said layer consisting of titanium dioxide and is a mixture of TiO.sub.2/Fe.sub.2O.sub.3 and FeTiO.sub.3 or is a pure ilmenite layer, said colored layer having a layer thickness of 5-100 nm.

16. The effect pigment according to claim 15, wherein said layer consisting of titanium dioxide has a layer thickness of 20-150 nm and said colored layer has layer thicknesses of 8-80 nm.

17. The effect pigment according to claim 15, wherein said layer consisting of titanium dioxide has a layer thickness of 20-100 nm and said colored layer has layer thicknesses of 8-50 nm.

18. A formulation comprising one or more effect pigments according to claim 1.

19. The formulation according to claim 18, further comprising at least one constituent selected from absorbents, astringents, antimicrobial substances, antioxidants, antiperspirants, antifoaming agents, antidandruff active compounds, antistatics, binders, biological additives, bleaches, chelating agents, deodorants, emollients, emulsifiers, emulsion stabilizers, dyes, humectants, film formers, fragrances, flavors, insect repellents, preservatives, anticorrosion agents, cosmetic oils, solvents, oxidants, vegetable constituents, buffer substances, reducing agents, surfactants, propellant gases, opacifiers, UV filters and UV absorbers, denaturing agents, viscosity regulators, perfume and vitamins.

20. A pigment preparation or paste comprising one or more binders, optionally one or more additives, and one or more effect pigments according to claim 1.

21. A dry preparation comprising one or more effect pigments according to claim 1, wherein said preparation is in the form of pellets, granules, chips, briquettes, beads- or sausages.

22. A process for the preparation of the effect pigments according to claim 1, said process comprising forming said layers by coating the Al.sub.2O.sub.3 flakes by a wet-chemical method of precipitation from metal salts in aqueous medium, and subsequent calcining the coated flakes in a reducing gas atmosphere.

23. An effect pigment comprising: Al.sub.2O.sub.3 flakes as substrate having an equivalent diameter distribution according to which 90% of the particles are in the range from 5-45 m, the Al.sub.2O.sub.3 flakes as substrate being doped with TiO.sub.2, ZrO.sub.2, SiO.sub.2, In.sub.2O.sub.3, SnO.sub.2, or ZnO or mixtures thereof, wherein the pigment has two highly refractive layers each having a refractive index n>1.9 on the substrate, wherein one of said two highly refractive layers consists of titanium dioxide and the other of said two highly refractive layers contains ilmenite (FeTiO.sub.3) or TiO.sub.2/Fe.sub.2O.sub.3 and FeTiO.sub.3, wherein said one of said two highly refractive layers consisting of titanium dioxide has a layer thickness of 15-200 nm, wherein said other of said two highly refractive layers has layer thicknesses of 5-100 nm, wherein the thickness of the Al.sub.2O.sub.3 flakes is 150-450 nm and the form factor (aspect ratio: diameter/thickness ratio) of the Al.sub.2O.sub.3 flakes is 30-200, and wherein the Al.sub.2O.sub.3 flakes have a D.sub.50 value in the range from 15-30 m and a D.sub.10 value in the range from 5-15 m, and wherein said effect pigment is a silver-colored effect pigment.

Description

EXAMPLES

Example 1

(1) 100 g of Al.sub.2O.sub.3 flakes of particle size 5-40 m having a thickness of 220-400 nm are heated to 75 C. in 1 l of demineralised water with stirring. The pH of the suspension is subsequently adjusted to 1.8 using 10% hydrochloric acid. This is followed by the metered addition of a 2% tin tetrachloride solution (5.6 g of SnCl.sub.4 (50%) dissolved with 17.2 g of 32% HCl and 110 ml of demineralised water), during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred for a further 15 min. Addition of 30% titanium tetrachloride solution (68 g of TiCl.sub.4 (25%) dissolved in 58.6 g of demineralised water) subsequently follows, during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred for a further 15 min.

(2) The pH of the suspension is then set to 2.8 using 32% sodium hydroxide solution. 72.8 g of an FeCl.sub.3 solution w=7.0% are subsequently metered in, during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred again for a further 15 min. The pH value of pH 5.0 is set using 32% sodium hydroxide solution, and the mixture is stirred again for a further 10 min.

(3) The product is filtered off, washed, dried, calcined at 650 C. under reducing conditions (N.sub.2/H.sub.2) for 2 h and sieved through a sieve, giving a bluish silver-coloured effect pigment having high lustre and an intense sparkle effect.

(4) The particle size distribution of the pigment according to Example 1 determined using Malvern MS 2000 gives:

(5) D.sub.10=8.6 m

(6) D.sub.50=18.2 m

(7) D.sub.90=33.3 m

Example 2

(8) 100 g of Al.sub.2O.sub.3 flakes of particle size 5-40 m having a thickness of 220-400 nm are heated to 75 C. in 1 l of demineralised water with stirring. The pH of the suspension is subsequently adjusted to 1.8 using 10% hydrochloric acid. This is followed by the metered addition of a 2% tin tetrachloride solution (5.6 g of SnCl.sub.4 (50%) dissolved with 17.2 g of 32% HCl and 110 ml of demineralised water), during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred for a further 15 min.

(9) A 30% titanium tetrachloride solution (92 g of TiCl.sub.4 (25%) dissolved in 79.2 g of demineralised water) is subsequently added, during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred for a further 15 min.

(10) The pH of the suspension is then set to 2.8 using 32% sodium hydroxide solution. 72.8 g of an FeCl.sub.3 solution w=7.0% are subsequently metered in, during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred again for a further 15 min. The pH value of pH 5.0 is set using 32% sodium hydroxide solution, and the mixture is stirred again for a further 10 min.

(11) The product is filtered off, washed, dried, calcined at 650 C. under reducing conditions (N.sub.2/H.sub.2) for 2 h and sieved through a sieve, giving a neutral silver-coloured effect pigment having high lustre and an intense sparkle effect.

(12) The particle size distribution of the pigment according to Example 2 determined using Malvern MS 2000 gives:

(13) D.sub.10=8.8 m

(14) D.sub.50=18.5 m

(15) D.sub.90=33.5 m

Example 3

(16) 100 g of Al.sub.2O.sub.3 flakes of particle size 5-40 m having a thickness of 220-400 nm are heated to 75 C. in 1 l of demineralised water with stirring. The pH of the suspension is subsequently adjusted to 1.8 using 10% hydrochloric acid. This is followed by the metered addition of a 2% tin tetrachloride solution (5.6 g of SnCl.sub.4 (50%) dissolved with 17.2 g of 32% HCl and 110 ml of demineralised water), during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred for a further 15 min. A 30% titanium tetrachloride solution (120 g of TiCl.sub.4 (25%) dissolved in 103.3 g of demineralised water) is now added, during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred for a further 15 min.

(17) The pH of the suspension is subsequently set to 2.8 using 32% sodium hydroxide solution. 72.8 g of an FeCl.sub.3 solution w=7.0% are then metered in, during which the pH is kept constant by simultaneous dropwise addition of 32% sodium hydroxide solution. When the addition is complete, the mixture is stirred again for a further 15 min. The pH value of pH 5.0 is set using 32% sodium hydroxide solution, and the mixture is stirred again for a further 10 min.

(18) The product is filtered off, washed, dried, calcined at 650 C. under reducing conditions (N.sub.2/H.sub.2) for 2 h and sieved through a sieve, giving a goldish silver-coloured effect pigment having high lustre and an intense sparkle effect.

(19) The particle size distribution of the pigment according to Example 3 determined using Malvern MS 2000 gives:

(20) D.sub.10=8.9 m

(21) D.sub.50=18.6 m

(22) D.sub.90=33.6 m

Examples 4-6: Post-Coating

(23) In order to increase the light, water and/or weather stability or for improved incorporation of the pigments into the respective application medium, the effect pigments of Examples 1-3 are subjected to a post-coating. The post-coating is carried out as described in the following patent applications and patents:

(24) DE 22 15 191, DE 31 51 354, DE 32 35 017, DE 33 34 598, DE10348174, EP 0090259, EP 0 342 533, EP 0632109, EP 0 888 410, EP 1203795, WO94/01498, WO 96/32446, WO 99/57204, WO 02/064682, WO 2004/092284 and U.S. Pat. No. 5,759,255. The proportion of the post-coating in the case of the pigments of Examples 1-3 is in each case 2%, based on the effect pigment.

USE EXAMPLES

Examples A1:Paint System

(25) 90% by weight of Hydroglasur BG/S colourless (water-borne paint from Ernst Diegel GmbH) 10% by weight of bluish silver-coloured effect pigment from Example 1 Painting by spraying on at 80 C. 5 min pre-drying at 80 C. 20 min baking at 180 C.

(26) Example A2 is carried out analogously to Example A1, but the uncoated pigment from Example 1 is replaced by the corresponding post-coated pigment of Example 1.

Example B:Plastic

(27) 1 kg of polystyrene granules are uniformly wetted with 5 g of coupling agent in a tumble mixer. 42 g of effect pigment from Example 2 are then added and mixed for 2 min. These granules are converted into stepped plates having the dimensions 430.5 cm under conventional conditions in an injection-moulding machine. The stepped plates are distinguished by their pronounced sparkle effect.

(28) The products of Use Examples A1, A2 and B are distinguished by their high lustre, their silver colour and an intense sparkle effect.