Non-metallic pigments having metal properties

Patent metadata

Field	Value
Publication number	US-10240045-B2
Application number	US-201515534716-A
Country	US
Kind code	B2
Filing date	Nov 23, 2015
Priority date	Dec 12, 2014
Publication date	Mar 26, 2019
Grant date	Mar 26, 2019

Abstract

The present invention relates to non-metallic interference pigments, in particular laminar interference pigments, which comprise a thin high-refractive layer and an outermost layer that contains crystalline carbon in the form of graphite and/or graphene. The invention also relates to a method for producing such pigments and the use of the thus produced pigments.

First claim

The invention claimed is:

1. Non-metallic interference pigments based on a flake-form non-metallic support, wherein the pigments have a particle size having a volume-weighted d 90 value of <25 μm and a volume-weighted d 50 value of <15 μm, the support has a coating comprising one or more successive layers of a colourless material having a refractive index n of n≥1.8 with a geometrical overall layer thickness of at most 70 nm, wherein the pigments have an outermost layer which consists of at least 95% by weight, based on the weight of this layer, of carbon and comprises crystalline carbon in the form of graphite and/or graphene, wherein the outermost, crystalline carbon-containing layer has a geometrical thickness in the range of from 1-3 nm and the proportion of the outermost crystalline carbon-containing layer, based on the weight of the interference pigment, is 1 to 3% by weight, and wherein the pigments have a specific powder resistance of less than 1×10 6 ohm*cm.

2. Interference pigments of claim 1 , wherein the pigments have a volume-weighted d 50 value of less than 10 μm.

3. Interference pigments of claim 1 , characterised in that the outermost, crystalline carbon-containing layer consists of at least 98% by weight of carbon.

4. Interference pigments of claim 1 , wherein the flake-form support is natural or synthetic mica flakes, kaolin, sericite or talc flakes, BiOCl flakes, TiO 2 flakes, glass flakes, borosilicate flakes, SiO 2 flakes, Al 2 O 3 flakes, boron nitride flakes, or mixtures of two or more thereof.

5. Interference pigments of claim 1 , wherein the layer or layers of a colourless material having a refractive index n in the range n ≥1.8 is/are arranged between the support and the crystalline carbon-containing outermost layer and the pigments have no further layers.

6. Interference pigments of claim 1 , wherein the colourless material having a refractive index n in the range n≥1.8 is selected from the group consisting of titanium dioxide, titanium dioxide hydrate, zirconium dioxide, zirconium dioxide hydrate, tin oxide, tin oxide hydrate, zinc oxide, zinc oxide hydrate and/or mixed phases thereof.

7. Interference pigments of claim 6 , wherein the layer comprising materials having a refractive index n in the range n≥1.8 consists of titanium dioxide and/or titanium dioxide hydrate.

8. Interference pigments of claim 1 , wherein the specific powder resistance is less than 100 ohm*cm.

9. A process for the preparation of non-metallic interference pigments of claim 1 , in which flake-form support particles which have been coated with one or more successive layers of a colourless material having a refractive index n of n≥1.8 with a geometrical overall layer thickness of at most 70 nm and have a particle size having a volume-weighted d 90 value of <25 μm and a volume-weighted d 50 value of <15 μm are coated with an outermost layer which consists of at least 95% by weight, based on the weight of this layer, of carbon and comprises crystalline carbon in the form of graphite and/or graphene, the crystalline carbon-containing layer having a geometrical thickness in the range of from 1-3 nm and exhibiting a proportion, based on the weight of the interference pigment, of 1 to 3% by weight, in a reactor in a stream of carrier gas with feed of a gaseous, carbon-containing compound by pyrolytic decomposition of the carbon-containing compound at a temperature in the range of from 500° C. to 700° C.

10. The process of claim 9 , wherein the gaseous, carbon-containing compound employed is acetone or 2-methyl-3-butyn-2-ol.

11. The process of claim 9 , wherein the flake-form support particles are kept in motion in the reactor.

12. A paint, coating, printing ink, coating composition, security application, plastic, ceramic material, glass, paper, film, heat protection composition, floorcovering, laser marking composition, dry preparation or pigment preparation comprising a non-metallic interference pigment of claim 1 .

Assignees

• Merck Patent Gmbh

Inventors

• Rueger Reinhold
• Kleist Bjoern

Classifications

• C09D17/008

  Titanium dioxide · CPC title

• C09C2200/302

  Thickness of a layer with high refractive material · CPC title

• C09C2200/306

  Thickness of an absorbing layer · CPC title

• C01P2006/40

  Electric properties · CPC title

• C09D5/29

  for multicolour effects · CPC title