Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-04-17
2003-02-11
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S415000, C106S482000, C106S410000, C428S404000
Reexamination Certificate
active
06517628
ABSTRACT:
The present invention relates to pigment mixtures comprising at least two components, component A being multilayer pigments based on mica, SiO
2
flakes, glass flakes, Al
2
O
3
flakes or polymer flakes and component B being platelet-shaped, acicular or spherical colorants and/or fillers, and to their use in varnishes, paints, printing inks, plastics, powder coatings, ceramic glazes, polymer films and cosmetic formulations.
BACKGROUND OF THE INVENTION
With platelet-shaped pigments, hiding power and luster 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, also feature high transparency and hence a comparatively poor hiding power.
DE-A-42 40 511 discloses a pigment mixture composed of an interference pigment and a platelet-shaped color pigment. The interference pigment comprises metal oxide-coated mica or SiO
2
flakes and the color pigment can be colored SiO
2
flakes. This pigment mixture is incorporated into coating materials, printing inks, plastics or cosmetics.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a pigment mixture which is notable for comparatively high hiding power and which lends itself well to incorporation into the respective system in which it is used, and in which, at the same time, pigment/colorant separation in the system is largely ruled out.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
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 comprising multilayer pigments based on mica, SiO
2
flakes, glass flakes, Al
2
O
3
flakes or polymer flakes and component B comprising platelet-shaped, acicular or spherical colorants and/or fillers.
By admixing one or more of the described colorants and/or fillers with the multilayer pigments it is possible to provide application systems with a color flop (strongly angle-dependent color), with intensified color effect, and with new kinds of color effects.
The invention therefore provides a pigment mixture comprising at least two components, component A comprising multilayer pigments based on mica, SiO
2
flakes, glass flakes, Al
2
O
3
flakes or polymer flakes and component B comprising platelet-shaped, acicular or spherical colorants and/or fillers.
The invention likewise provides formulations, such as paints, varnishes, printing inks, plastics, powder coatings, ceramic glazes, polymer films and cosmetic formulations, which comprise the pigment mixture of the invention.
The multilayer pigments can be mixed in any proportion with the colorant and/or filler. The weight ratio of component A to component B is preferably from about 1:20 to about 20:1, in particular from about 1:10 to about 10:1.
The multilayer pigments, including those which are known, for example, from the German laid-open specifications DE 196 18 563, DE 196 18 566, DE 196 18 569, DE 197 07 805, DE 197 07 806 and DE 197 46 067 are based on a platelet-shaped, transparent, colored or colorless matrix consisting of mica (synthetic or natural), SiO
2
flakes, glass flakes, Al
2
O
3
flakes, polymer flakes, and possess in general a thickness of preferably from about 0.3 to 5 &mgr;m, in particular from about 0.4 to 2.0 &mgr;m. The extent in the two other dimensions is preferably from about 1 to 250 &mgr;m, more preferably from about 2 to 100 &mgr;m, and in particular from about 5 to 40 &mgr;m. The multilayer pigments include the matrix (substrate) coated with metal oxides (at least 2). The coating of the substrate flakes of mica, SiO
2
flakes, glass flakes or Al
2O
3
flakes with two or more layers is done so as to give a layer structure having alternating layers of high and low refractive index, i.e., at least two adjacent layers where one is of high refractive index and the other of low refractive index. The multilayer pigments preferably contain 2, 3, 4, 5, 6 or 7 layers, especially 3, 4, or 5 layers. The multilayer coating can be provided on one or both sides of the pigment. Examples of suitable metal oxides of high refractive index are titanium dioxide, zirconium oxide, zinc oxide, iron oxides, iron titanium oxides (iron titanates) and/or chromium oxide, especially TiO
2
and/or Fe
2
O
3
. Metal oxides of low refractive index which are used include SiO
2
and Al
2O
3
. However, it is also possible for this purpose to use MgF
2
or an organic polymer (e.g. acrylate). The substrate flakes can be coated, for example, as in WO 93/08237 (wet-chemical coating) or DE-A-196 14 637 (CVD process).
Preferred multilayer pigments possess the following structure:
substrate+Fe
2
O
3
layer+SiO
2
layer+Fe
2
O
3
layer
substrate+Fe
2
O
3
layer+SiO
2
layer+TiO
2
layer
substrate+TiO
2
layer+SiO
2
layer+Fe
2
O
3
layer
substrate+TiO
2
layer+SiO
2
layer+TiO
2
/Fe
2
O
3
layer
substrate+TiO
2
/Fe
2
O
3
layer+SiO
2
layer+TiO
2
/Fe
2
O
3
layer
substrate+TiO
2
layer+SiO
2
layer+Cr
2
O
3
layer
Instead of the outer metal oxide layer it is also possible to use a semitransparent layer of a metal. Suitable metals for this purpose are, for example, Cr. Ti, Mo, W, Al, Cu. Ag, Au or Ni.
To obtain specific color effects it is also possible to incorporate fine particles in the nanometer size range into the layers of the multilayer pigment, for example, in either the high and low refractive index layers, respectively. Examples of suitable candidates are finely divided TiO
2
or finely divided carbon (e.g., carbon black) with particle sizes from about 10-250 nm. A controlled influence can be exerted on luster and hiding power by virtue of the light-scattering properties of such particles.
In order to improve the light, weathering and chemical stability or to enhance the compatibility in different media, the multilayer pigments can also be provided with a protective layer. Examples of suitable aftercoatings and aftertreatments are the processes described in DE 22 15 191, DE 31 51 354, DE 32 35 017 or DE 33 34 598. The substances applied additionally preferably account for only from about 0.1 to 5% by weight, more preferably from 0.5 to 3.0% by weight of the multilayer pigment.
Suitable components B for the pigment mixture of the invention are all platelet-shaped, acicular and spherical colorants or fillers known to the person skilled in the art, excluding those encompassed by component A. Preferably, they will have a particle size of from about 0.001 to 10 &mgr;m, more preferably from about 0.01 to 1 &mgr;m. The pigment mixtures of the invention preferably include absorption pigments as colorants and platelet-shaped or spherical powders as fillers. Preferable for component B are coated or uncoated spherical SiO
2
particles. SiO
2
particles coated with one or more metal oxides are known, for example, from EP 0 803 550 A2.
Preferred pigment mixtures contain in addition to component A, a colorant as component B, in particular a pearl luster pigment. The pearl luster pigments used are preferably pigments based on platelet-shaped, transparent or semitransparent substrates of, for example sheet silicates, such as mica, synthetic mica, talc, sericite, kaolin, glass or other silicatic materials, which are coated with colored or colorless metal oxides such as, for example TiO
2
, titanium suboxides, titanium oxynitrides, Fe
2
O
3
, Fe
3
O
4
, SnO
2
, Cr
2
O
3
, ZnO, CuO, NiO and other metal oxides, alone or in a mixture in a uniform layer or in successive layers. However, excluded from such component B colorants are those with multilayer pigments having alternating high and low refractive index encompassed by component A. Pearl luster pigments are known, for example, from the German patents and patent ap
Anselmann Ralf
Pfaff Gerhard
Schoen Sabine
Bell Mark L.
Hailey Patricia L.
Merck Patent GmbH
Millen White Zelano & Branigan P.C.
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