EFFECT PIGMENTS

Abstract

The present invention relates to silver-coloured 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. Effect pigments, characterised in that Al.sub.2O.sub.3 flakes having an equivalence diameter distribution according to which 90% of the particles are in the range from 5-45 m have on the surface two highly refractive coatings having a refractive index n>1.9, where the layers consist of titanium dioxide and ilmenite (FeTiO.sub.3) or TiO.sub.2/Fe.sub.2O.sub.3 and FeTiO.sub.3.

2. Effect pigments according to claim 1, characterised in that the form factor (aspect ratio: diameter/thickness ratio) of the Al.sub.2O.sub.3 flakes is 30-200.

3. Effect pigments according to claim 1, characterised in that the Al.sub.2O.sub.3 flakes are corundum.

4. Effect pigments according to claim 1, characterised in that the Al.sub.2O.sub.3 flakes are doped with TiO.sub.2, ZrO.sub.2, SiO.sub.2, In.sub.2O.sub.3, SnO.sub.2, or ZnO or mixtures thereof.

5. Effect pigments according to claim 1, characterised in that the proportion of the doping is <5%, based on the substrate.

6. Effect pigments according to claim 1, characterised in that the Al.sub.2O.sub.3 flakes have on the surface firstly a layer of titanium dioxide and subsequently an FeTiO.sub.3 layer.

7. Effect pigments according to claim 1, characterised in that the layer of titanium dioxide is in the rutile modification.

8. Effect pigments according to claim 1, characterised in that the TiO.sub.2 layer has a thickness of 15-200 nm.

9. Effect pigments according to claim 1, characterised in that the ilmenite layer has a thickness of 5-100 nm.

10. Process for the preparation of the effect pigments according to claim 1, characterised in that the coating of the Al.sub.2O.sub.3 flakes is carried out by wet-chemical methods by precipitation from metal salts in aqueous medium and subsequent calcination in a reducing gas atmosphere.

11. Use of the effect pigments according to claim 1 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.

12. Formulations comprising one or more effect pigments according to claim 1.

13. Formulations according to claim 12, that they additionally comprise at least one constituent selected from the group of the absorbents, astringents, antimicrobial substances, antioxidants, antiperspirants, antifoaming agents, antidandruff active compounds, antistatics, binders, biological additives, bleaches, chelating agents, deodorants, emollients, emulsifiers, emulsion stabilisers, dyes, humectants, film formers, fragrances, flavours, 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.

14. Pigment preparations and pastes comprising one or more binders, optionally one or more additives and one or more effect pigments according to claim 1.

15. Dry preparations in the form of pellets, granules, chips, briquettes, beads, sausages comprising one or more effect pigments according to claim 1.

Description

EXAMPLES

Example 1

[0066] 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.

[0067] 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.

[0068] The pH of the suspension is then set to 2.8 using 32% sodium hydroxide solution. 72.8 g of an FeCl3 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.

[0069] 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.

[0070] The particle size distribution of the pigment according to Example 1 determined using Malvern MS 2000 gives:

[0071] D.sub.10=8.6 m

[0072] D.sub.50=18.2 m

[0073] D.sub.90=33.3 m

Example 2

[0074] 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 (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.

[0075] 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.

[0076] 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.

[0077] The particle size distribution of the pigment according to Example 2 determined using Malvern MS 2000 gives:

[0078] D.sub.10=8.8 m

[0079] D.sub.50=18.5 m D.sub.90=33.5 m

Example 3

[0080] 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. 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.

[0081] 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.

[0082] The particle size distribution of the pigment according to Example 3 determined using Malvern MS 2000 gives: D.sub.10=8.9 m

[0083] D.sub.50=18.6 m D.sub.90=33.6 m

Examples 4-6

Post-Coating

[0084] 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:

[0085] 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

[0086] 90% by weight of Hydroglasur BG/S colourless (water-borne paint from Ernst Diegel GmbH)

[0087] 10% by weight of bluish silver-coloured effect pigment from Example 1

[0088] Painting by spraying on at 80 C.

[0089] 5 min pre-drying at 80 C.

[0090] 20 min baking at 180 C.

[0091] 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

[0092] 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.

[0093] The products of Use Examples A1, A2 and B are distinguished by their high lustre, their silver colour and an intense sparkle effect.