Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-11-20
2002-10-15
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C428S403000, C428S404000, C428S462000, C428S468000, C428S472000, C428S466000
Reexamination Certificate
active
06464772
ABSTRACT:
The present invention relates to bismuth-based pigments exhibiting greatly improved coloring and resistance characteristics.
The invention also relates to the process for producing these pigments and to their application, in particular in the coloring of paints, lacquers and/or plastics.
Technological Background and State of the Art
Bismuth vanadate is a yellow inorganic pigment well known (DE 422447, U.S. Pat. No. 3,843,554, U.S. Pat. No. 4,115,142, JP 62277485 and DE 19733584) for coloring plastics and paints, as a catalyst in the oxidation of olefins, as a contrast-enhancing pigment for television screens and as a reversible temperature indicator.
However, pure bismuth vanadate (named PY184) does not make it possible to directly obtain orange colors. There thus currently exists an obvious need to have available bismuth-based inorganic pigments exhibiting, on the one hand, a color range extending from greenish yellow to orange yellow and having, on the other hand, resistance at least equal to or even superior to those of pure bismuth vanadate.
Pigments based on bismuth vanadate are nontoxic, have a vivid yellow color, have a high coloring strength and have excellent opaqueness; they are readily dispersed in their medium of use and they can be easily used in all kinds of paints (conventional, industrial, powdered).
Bismuth-based pigments with the chemical composition BiOCl are also known (U.S. Pat. No. 2,974,053, DE 3738114 and U.S. Pat. No. 3,917,671). However, these pigments are very different from pigments based on pure bismuth vanadate since they are pearlescent, off-white and rather unresistant to light. They are mainly used in the cosmetics industry for pearlescent and metallic effects.
It is also known, by Patent Application EP-A-632 110, to precipitate a fine layer of bismuth vanadate on a synthetic mica-based pearlescent pigment in order to obtain highly dispersible and very glossy pigments with a yellow hue.
A description has also been given, in Patent Application EP-A-839 874, of basic bismuth vanadates BiVO
4
.xBi
2
O
3
, the yellow color of which verges on orange, either by calcining a very homogeneous mixture of bismuth and vanadium oxides or by calcining a precipitate obtained by the aqueous route in the presence of phosphate.
Other attempts have been made to obtain bismuth vanadates with a reddish hue, by doping the BiVO
4
crystal with very small amounts of metals (iron, rare earth metals), but the purity of color and the coloring strength of which leave something to be desired (DE 19529837).
It is also known, by Patent Application DE 197481423, to crystallize bismuth oxide Bi
2
O
3
in a special metastable &bgr; variety by carrying out the process very rapidly in a refluxing aqueous medium in the presence of alkaline hydroxides, to isolate a reddish yellow.
A description is given, in Patent Application EP-A-816 440, of a mixture of pigmentary bismuth vanadate powders and of orange, red or orange yellow organic pigments, to obtain an orange powder which is a pigment with a hybrid inorganic-organic nature.
There also exist other possibilities for obtaining bismuth-based compounds with a darker color, for example by calcining bismuth, zirconium and chromium coprecipitates (DE 4002943).
However, none of these attempts to obtain bismuth-based orange pigments succeed in simultaneously combining the various characteristics desired for an application of a pigment, namely a pure orange color, easy application, nontoxicity and improved resistance to light, to weathering and to heat.
Aims of the Invention
The present invention aims to provide bismuth-based pigments which exhibit a sufficiently pure color of yellow to orange type and which have excellent qualities of resistance.
Another aim of the present invention is to provide bismuth-based pigments, which are easy to apply, in conventional formulations (solvents) and modern formulations (powdered, dispersed in water, with a high solids content, and the like).
An additional aim of the present invention is to provide a process for the manufacture of such pigments which is simple in conception and applicable industrially.
Characteristic Components of the Invention
The invention relates to bismuth-based pigments exhibiting a yellow to orange color composed of a yellow component based on bismuth vanadate and of an orange component based on bismuth oxyhalides which are very intimately combined.
The pigments of the invention correspond to the following general formula:
BiV(1−n)XnO(4−3n),
or more particularly to the formula:
(1−n){BiVO4}.n{BiOX},
where:
X denotes a halogen selected from the group consisting of chlorine, bromine and iodine, preferably bromine or iodine, or a mixture thereof, preferably a mixture of bromine and iodine (this mixture furthermore being preferred to bromine alone or to iodine alone)
n is greater than zero and less than one (0<n<1), preferably between 0.25 and 0.40,
more particularly with n=0.3, that is to say BiV(0.7)X(0.3)O(3.1),
Xn can be written [Cl(p)Br(q)I(1−p−q)]n, in which the situation will preferably be:
between 0 and 0.3,
q between 0 and 0.8 and
p+q between 0.1 and 0.8,
more particularly p=0 and q is between 0.35 and 0.55.
Consequently, in addition to the orange color not possessed by pure bismuth vanadate, the intimate mixing of the two compounds BiVO
4
and BiOX gives the pigment of the invention [BiV(1−n)XnO(4−3n)], which has durabilities (especially to light) which are improved with respect to the known properties alone of the compounds BiVO
4
and BiOX used alone.
In the case where n=1, the compounds present are bismuth oxyhalides BiOX, such as disclosed in U.S. Pat. No. 4,252,570, exhibiting white, yellow, orange and red colors according to the respective contents of various halogens. These contents are given by the coefficients p and q in the following formula BiOCl(p)Br(q)I(1−p−1), preferably with p=0.
In this case, the greater the content of iodine, the more the color tends towards orange and reddish. Often, q is taken between 0.35 and 0.55 and preferably between 0.40 and 0.45.
In the case where n=0, the compound present is pure bismuth vanadate BiVO
4
(PY184) with a greenish yellow color.
Another aspect of the present invention relates to a pigment having the abovementioned general formula where n=1, that is to say a bismuth oxyhalide BiOX, stabilized and coated with additional protective layers, that is to say comprising one or more successive coating deposits based on oxides, hydroxides, hydrates, carbonates, phosphates, borates, molybdates and/or silicates of elements from Groups II, III and IV (IIIa, IIIb, IVa and IVb) of the Periodic Table, in particular on various compounds based on titanium, aluminum, calcium, zinc, rare earth metals and/or silicon.
The pigments of the invention advantageously corresponding to the abovementioned general formula can also comprise one or more stabilizing or coating layers composed of one or more successive deposits of these said oxides, hydroxides, hydrates, carbonates, phosphates, borates, molybdates or silicates of elements from Groups II, III and IV, in particular those mentioned above.
Said pigments can comprise one or more layers particularly suited to improving the resistances to light, to weathering and to heat of pigments, in particular a final layer based on zinc and boron which makes it possible to improve the resistance to heat and which makes possible its application in materials subjected to high temperatures.
The various inorganic compounds used in the coating layers of the invention can also be prepared from other preferred elements, such as titanium, aluminum, zinc, antimony, silicon, boron, calcium, zirconium, niobium, rare earth metals, in particular cerium, lanthanum, neodymium, praseodymium, samarium or yttritim, or a mixture of these. The proportion (calculated with respect to the total weight of the pigment obtained) of the coating layer or layers is generally between abo
Buyse Emile Joseph
Vermoortele Frank
Gebroeders Cappelle N.V.
Knobbe Martens Olson & Bear LLP
Wood Elizabeth D.
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