Pigment mixture

Details Pigment mixture Pigment mixture

1999-05-28

2002-12-03

Klemanski, Helene (Department: 1755)

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

C106S417000, C106S410000, C106S482000

Reexamination Certificate

active

06488756

ABSTRACT:

SUMMARY OF THE INVENTION
The present invention relates to pigment mixtures comprising at least two components, component A being SiO
2
flakes coated with one or more metal oxides and/or metals and component B being platelet-shaped, acicular or spherical colorants and/or fillers, and to their use in varnishes, paints, printing inks, plastics, powder coating materials and cosmetic formulations.
With platelet-shaped pigments, hiding power and gloss are often difficult to realize simultaneously to a satisfactory extent. For instance, SiO
2
flakes or mica platelets covered with one or more thin metal oxide layers feature interference colors and a high luster but at the same time, owing to the transparent substrate, feature high transparency and hence a comparatively poor hiding power.
DE-A-42 40 511 discloses a pigment mixture which is composed of an interference pigment and a platelet-shaped color pigment. The interference pigment comprises mica flakes or SiO
2
flakes coated with metal oxides and the color pigment can be colored SiO
2
flakes. This pigment mixture is incorporated into coating materials, printing inks or plastics.
It is an object of the present invention to provide a pigment mixture which is notable for a comparatively high hiding power, which lends itself well to incorporation into the respective system in which it is used and for which at the same time the separation of pigment/colorant in the system is minimal.
Surprisingly, a pigment mixture has now been found which has none of the disadvantages indicated above. The pigment mixture of the invention comprises at least two components, component A being SiO
2
flakes coated with one or more metal oxides and/or metals and component B being platelet-shaped, acicular or spherical colorants or fillers. By admixing the colorant to the coated SiO
2
flakes it is possible to give the systems in which they are used a multiple flop, the color effect is intensified, and new color effects are achieved. As used herein, the term “multiple flop” refer to color changes as a function of viewing angle.
The invention thus provides a pigment mixture comprising at least two components, component A being SiO
2
flakes coated with one or more metal oxides and/or metals and component B being platelet-shaped, acicular or spherical colorants or fillers. By spherical is meant a range of substantially spherical shapes including, e.g., perfect spheres, indented or deformed spheres, etc.
The invention likewise provides formulations, such as paints, varnishes, printing inks, plastics, powder coating materials and cosmetic formulations, which comprise the pigment mixture of the invention.
The coated SiO
2
flakes can be mixed with the colorant and/or filler in any ratio. Preferably, the (wt/wt) ratio of component A to component B is about 1:10 to 10:1, in particular about 1:2 to 2:1.
The SiO
2
flakes produced on a continuous belt in accordance with WO 93/08237 are based on a platelet-shaped, transparent, colored or colorless matrix and typically possess a thickness of about 0.1 to 5 &mgr;m, in particular about 0.2 to 2.0 &mgr;m. The length in the two other dimensions is typically about 1 to 250 &mgr;m, preferably about 2 to 100 &mgr;m and, in particular, about 5 to 40 &mgr;m. The SiO
2
flakes are provided with one or more metal oxide layers an/or metal layers. Examples of suitable metal oxides or metal oxide mixtures are, e.g., titanium oxide, zirconium oxide, zinc oxide, iron oxides and/or chromium oxide, especially TiO
2
and/or Fe
2
O
3
. The SiO
2
flakes can be coated as described, for example, in WO 93/08237 (wet chemical coating) or DE-A-196 14 637 (CVD process).
The outer metal oxide layer can also be a semitransparent metal layer. Metals suitable for this purpose are, for example, Cr, Ti, Mo, W, Al, Cu, Ag, Au and Ni. Metals can be coated on the SiO
2
flakes by conventional methods, e.g., physical vapor deposition (PVD). Preferred pigments have the following layer structure: SiO
2
flakes+metal+SiO
2
+metal oxide.
In order to bring out special color effects, fine particles in the nanometer size range can be introduced into the metal oxide layers of high or low refractive index. Examples of pigments suitable for this purpose are, e.g., finely divided TiO
2
or finely divided carbon (carbon black) with particle sizes in the range of about 10 to 250 nm. Through the light-scattering properties of such particles it is possible to exert a controlled influence on luster and hiding power.
Colorants suitable as component B for the pigment mixture of the invention are all acicular and spherical colorants which are known to the skilled worker and have a particle size of about 0.001 to 10 &mgr;m, preferably about 0.01 to 1 &mgr;m. The pigment mixtures of the invention preferably comprise, as colorants, absorption materials and/or fillers.
The spherical colorants can be, e.g., TiO
2
, colored SiO
2
, CaSO
4
, iron oxides, chromium oxides, carbon black or organic color pigments, such as anthraquinone, quinacridone, diketopyrrolopyrrole, phthalocyanine, azo and isoindoline pigments. The acicular pigments can be, e.g., BiOC1, colored glass fibers, -Fe
3
O
4
, or organic color pigments, such as azo pigments, &bgr;-phthalocyanine CI Blue 15.3, Cromophtal Yellow 8GN (Ciba-Geigy), Irgalith Blue PD56 (Ciba-Geigy), azomethine copper complex CI Yellow 129, and Irgazine Yellow 5GT (Ciba-Geigy).
Cosmetic formulations (especially decorative formulations) preferably comprise, not only colorants and SiO
2
flakes, but also fillers (one or more) or mixtures thereof in amounts (wt/wt) of about 1-50%, preferably about 1-30% and most preferably, about 1-15%, based on the overall solids content of the system.
Suitable fillers can be, e.g., mica, talc, TiO
2
and mica, TiO
2
+BaSO
4
+mica, mica+silica, silica, silica+TiO
2
+Fe
2
SO
3
, BiOC1, BiOC1+mica, or BiOC1+talc. Some of these products are obtainable, e.g., under the trade names of Merck KGaA: Ronasphere®, Ronasphere® LDP, Micronasphere® M, Silk Mica, Satin Mica, Naturaleaf Powder, Low Luster Pigment, Extender W, Talkum feinst gepulvert [finely powdered talc], Biron®, Bital® and Mibiron®. Other fillers can be, e.g., nylon-12 (from Elf Atochem), nylon-6 (from Elf Atochem), boron nitride, Nylon Powder (from Elf Atochem), polyamide 12 (from Kobo), polyethylene (from Kobo), PTFE (from Presperse), lauroyl lysine (from Ikeda), polymethyl methacrylate (from Ikeda) or calcium aluminum borosilicate (from Presperse).
The pigment mixture of the invention is simple and easy to handle. The pigment mixture can be incorporated into the system in which it is used simply by stirring it in. Laborious milling and dispersing of the pigments is not necessary.
The pigment mixture of the invention can be used, e.g., for pigmenting coating materials, printing inks, plastics, agricultural films, the coating of seeds, food colorings, button pastes, medicament coatings or cosmetic formulations. The concentration of the pigment mixture in the system in which it is to be used for pigmenting is typically about 0.1 to 70% by weight, preferably about 0.1 to 50% by weight and, in particular, about 1.0 to 10% by weight, based on the overall solids content of the system. It is generally dependent on the specific application.
Plastics comprising the pigment mixture of the invention in amounts of about 0.01 to 50% by weight, in particular about 0.1 to 7% by weight, based on the overall solids content of the system, are notable for a particular sparkle effect.
In the coating sector, especially in automotive finishing, the pigment mixture can be employed—for 3-coat systems as well—in amounts of about 0.1 to 10% by weight, preferably about 1 to 3% by weight, based on the overall solids content of the system. The proportion in which the coated SiO
2
flakes are mixed with component B depends on the desired effect. The SiO
2
flakes are preferably employed with component B in a proportion (wt/wt) of about 1:4, in particular of about 1:3.
In a coating material, the pigment mixture of the i

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