Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2002-12-13
2004-10-05
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S403000, C106S404000, C106S417000, C106S418000, C106S442000, C106S456000, C106S480000, C428S403000, C428S404000
Reexamination Certificate
active
06800125
ABSTRACT:
BACKGROUND OF THE INVENTION
The provision of metallic effects in surface coatings, plastics coloration, cosmetic preparations and the like is well known. To achieve this effect, one approach has been to disperse both a metallic pigment and a transparent colored pigment in the composition. The metallic pigment is usually aluminum flake and the colored pigment can be, for instance, iron oxide. The art has also combined the two pigments into a single entity by precipitating the colored material on the aluminum flake.
The precipitation of, for instance, iron oxide on the aluminum flake was often carried out from an aqueous solution but that gave rise to various difficulties. Aluminum readily reacts in aqueous media, very dilute solutions of the iron oxide were required, complexing additives were necessary and the procedure had to be carried out in a limited pH range.
An alternate, non-aqueous procedure is described in U.S. Pat. No. 4,328,042. Here, iron pentacarbonyl is oxidized to iron oxide and carbon dioxide in a fluidized bed of the aluminum flake with oxygen at elevated temperature. To obtain reproducible results, the carbonyl cannot exceed 5 volume percent of the fluidizing gas. The use of the low concentration carbonyl and fluidized bed operation are obvious drawbacks of this approach.
It is desirable to provide a metallic oxide color effect material which has the same or better pigment properties as the products just mentioned but without encountering the production and materials limitations of that prior art. The present invention is directed to satisfying that desire.
SUMMARY OF THE INVENTION
The present invention provides an oxide metallic color effect material comprising a platelet-shaped substrate encapsulated with a highly light reflective first layer of silver and a layer of iron oxide. The product, where necessary, can be given a post-treatment for specific attributes such as weather stability, polymeric dispersability and cosmetic compatibility. The method of producing the effect material is also a part of this invention.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide novel oxide metallic effect materials which can also be prepared in a reliable, reproducible and technically efficient manner. This object is achieved by an effect material comprising a platelet-shaped substrate coated with (a) a highly light reflective first layer of silver; and (b) an iron oxide layer.
Any encapsulatable smooth platelet can be used as the substrate in this invention. Examples of usable platelets include mica, aluminum oxide, bismuth oxychloride, boron nitride, glass flake, iron oxide-coated glass flake, titanium oxide-coated glass flake, iron oxide-coated mica, silicon dioxide and titanium dioxide-coated mica. The size of the platelet-shaped substrate is not critical per se and can be adapted to the particular use. In general, the particles have average largest major dimensions of about 5-250 microns, in particular 5-100 microns. Their specific free surface area (BET) is in general from 0.2 to 25 m
2
/g.
The degree of reflectivity for the first encapsulating layer, the highly reflective layer, should be at least about 75% and is preferably at least about 90% reflectivity. This layer is constituted by highly reflective silver.
The thickness of the first layer is not critical so long as it is sufficient to make the layer highly reflective. If desirable, the thickness of the first layer can be varied to allow for some selective transmission of light. The mass percent of this coating can vary considerably because it is directly related to the surface area of the particular substrate being utilized and the thickness necessary to achieve the desired reflectivity. In general, the silver thickness should be at least about 5 nm, preferably from about 10 to 75 nm. A thickness of the silver layer outside of the above-mentioned ranges will typically be either completely opaque or allow for substantial transmission of light.
As a result of the high reflectivity, the silver encapsulated substrate is substantially opaque and much more light is reflected than with conventional effect pigments. The amount of fight reflected in the case of, for instance, iron oxide-coated mica is on the order of about 18% whereas the amount of light in the effect pigment of the instant invention is on the order of 35%.
The effect material of the present invention contains an iron oxide layer directly encapsulated onto the first encapsulating layer. The thickness of this layer can vary considerably. As the thickness increases, interference colors are realized. In general, the layer thickness is about 40 to 200 nm, and preferably about 60 to 180 nm.
If desired, an additional outer layer can be provided. The optional outer encapsulating layer, when present, is a material providing a transparency of about 25-75% transmission. More preferably, one would prefer to have about 40-60% transparency for the outer encapsulating layer. The degree of reflectivity and transparency for the different layers can be determined using a variety of methods such as ASTM method E1347-97, E1348-90 (1996) or F1252-89 (1996), all of which are substantially equivalent for the purposes of this invention.
The material employed as the outer layer can be silver, gold, platinum, palladium, rhodium, ruthenium, osmium, iridium and alloys thereof. Alternatively, the outer layer may also be a metal oxide provided that it is not iron oxide, and may also constitute a nitride or carbide.
The effect materials of the invention are notable for multiple encapsulation of the platelet-shaped substrate. In one embodiment, the first layer and the iron oxide layer are further encapsulated by a selectively transparent outer layer that allows for partial reflection of light directed thereon. Preferably, the outer encapsulating layer is selected from the group consisting of silicon, chromium oxide, a mixed metal oxide, titanium dioxide, titanium nitride and aluminum. More preferably, the outer layer is one or more of the precious metals or alloys.
The optional outer layer is, of course, a part of the optical package. Its thickness can vary but must always allow for partial transparency. For instance, the layer has a preferable thickness of about 5 to 20 nm for silicon; about 2 to 15 nm for aluminum; about 1-15 nm for titanium nitride; about 10 to 60 nm for chromium oxide; about 10-100 nm for titanium dioxide; about 5 to 60 nm for a mixed metal oxide, about 5 to 20 nm for silver; about 3 to 20 nm for gold; about 3-20 nm for platinum; and about 5 to 20 nm for palladium. The metal alloys generally have a similar film thickness compared to the pure metal. It is recognized that a film thickness out of the above range may be applicable depending on the desired effect.
All the encapsulating layers of the effect material of the invention are altogether notable for a uniform, homogeneous, film-like structure that results from the manner of preparation according to the invention.
One advantage of the present invention is that one does not have to start with a traditional metal flake which may have structural integrity problems, hydrogen outgassing problems and a host of other perceived issues (pyrophoric and environmental concerns) typically associated with metal flakes. The substrate provides structural integrity and the silver used in this invention is much more chemically stable than aluminum and generally prefers to be in its non-oxidized metallic ground state. Furthermore, silver can maximize the chromaticity of the reflected color(s) of the end product. In addition, when silver is used as the final (outer) layer of the particle, it may impart electrical conductivity to the effect material, which may be desirable in some applications such as powder coatings.
While the metal layers can be deposited by any known means, they are preferably deposited by electroless deposition or reduction and the non-metal layers preferably by aqueous or non-aqueous sol-gel deposition. An advantage of electroless deposition (Egypt. J. Anal. Chem., Vol. 3, 11
Jones Steven A.
Zimmermann Curtis J.
Brown Melanie L.
Engelhard Corporation
Koslow C. Melissa
Manlove Shalie A.
LandOfFree
Oxide metallic effect materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oxide metallic effect materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oxide metallic effect materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3295929