Process for the preparation of composite pigments

• US 5,562,763 A
• Filed: 04/07/1993
• Issued: 10/08/1996
• Est. Priority Date: 04/07/1992
• Status: Expired due to Fees

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Subrod, Ines, Bruckner, Hans-Dieter
• Primary Examiner(s): Group, Karl
• Assistant Examiner(s): Hertzog, Scott L.
• Application Number:
  US08/043,912
• Time in Patent Office: 1,280 Days
• Field of Search: 106/403, 106/417, 106/415, 106/493, 106/494
• US Class Current: 106/403
• CPC Class Codes: C01P 2004/54 Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• CPC Class Codes: C09B 63/00 Lakes
• CPC Class Codes: C09B 67/0033 Blends of pigments; Mixtured crystals; Solid solutions
• CPC Class Codes: C09C 1/0021 comprising a core coated with only one layer having a high or low refractive index
• CPC Class Codes: C09C 1/0081 Composite particulate pigments or fillers, i.e. containing at least two solid phases, except those consisting of coated particles of one compound C09C1/0015, C09C1/0078 take precedence
• CPC Class Codes: C09C 2200/102 the core consisting of glass or silicate material like mica or clays, e.g. kaolin
• CPC Class Codes: C09C 2200/1062 the core consisting of an organic compound, e.g. Liquid Crystal Polymers [LCP], Polymers or natural pearl essence
• CPC Class Codes: C09C 2200/505 Inorganic particles, e.g. oxides, nitrides or carbides
• CPC Class Codes: C09C 3/006 Combinations of treatments provided for in groups C09C3/04 - C09C3/12
• CPC Class Codes: C09C 3/043 Drying, calcination
• CPC Class Codes: C09C 3/063 Coating
• CPC Class Codes: C09C 3/08 Treatment with low-molecular-weight non-polymer organic compounds C09C3/006, C09C3/048 take precedence

Abstract

The invention relates to a process for the preparation of composite pigments containing a substrate having an average diameter of 3-200 μm as support for small organic or inorganic pigment particles having an average diameter of less than 1 μm, characterized in that the pigment particles are applied by spray-drying an aqueous suspension containing the substrates and the pigment particles without addition of additives.

Claims

1. A process for the preparation of a composite pigment containing a substrate having an average diameter of about 3-200 μ

m and supported thereon organic or inorganic pigment particles having an average diameter of less than about 1 μ

m, said process comprising spray-drying an aqueous suspension consisting essentially of discrete particles of the substrate and the pigment particles in the absence of wetting, dispersing or deflocculating agents.

2. A process according to claim 1, comprising spray drying the aqueous suspension in the absence of polycarboxylate, silane or silicone oil additives.

3. A process according to claim 1, comprising spray drying the aqueous suspension in the absence of additives.

4. A process according to claim 1, wherein the substrate is a platelet-shaped substrate having an average diameter of between 3 and 200 μ

m and an aspect ratio of at least 5.

5. A process according to claim 4, wherein the platelet-shaped substrate is mica, talc, glass platelets, platelet-shaped polymer particles, metal platelets or platelet-shaped metal oxides.

6. A process according to claim 1, wherein the pigment particles are pigments which cannot be precipitated in an aqueous medium.

7. A composite pigment obtained by a process according to claim 1.

8. A composite pigment according to claim 7, wherein the pigment particles cannot be precipitated in an aqueous medium.

9. A composite pigment obtained by a process according to claim 1, in which the weight proportion of the pigment particles, relative to the weight of the composite pigment, is 5%-50% and in which the composite pigment has substantially the same geometrical structure as the substrate.

10. A composite pigment obtained by a process according to claim 1, in which the weight proportion of the pigment particles, relative to the weight of the composite pigment, is 30%-60% and in which the composite pigment has substantially the same geometrical structure as the substrate.

11. A pigment according to claim 9, wherein the weight proportion of the pigment particles, relative to the weight of the composite pigment, is not more than 30%.

12. A composite pigment consisting essentially of a substrate, having an average diameter of about 3-200 μ

m and supported thereon on the substrate surface organic or inorganic pigment particles having an average diameter of less than about 1 μ

m, in which the composite pigment has substantially the same shape as the substrate.

13. A pigment according to claim 12, wherein the weight proportion of the pigment particles, relative to the weight of the composite pigment, is not more than 30%.

14. A pigment according to claim 12, having a ratio of the average diameter of the composite pigment to the average diameter of the corresponding substrate at a coverage of about 30% by weight, relative to the weight of the composite pigment, of not more than 2.