Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1995-01-07
1997-12-02
Marcheschi, Michael
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106401, 423593, 423617, 428403, C09C 100
Patent
active
056931360
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit under 37 USC .sctn.371 of International Patent Application PCT/BE93/00047, international filing date Jul. 8, 1993.
SUBJECT OF THE INVENTION
The present invention relates to a process for the preparation of pigments based on bismuth vanadate exhibiting a purity of hue and a depth of color which are improved. The invention also relates to the products obtained by this process and to their application for the coloring of paints, of lacquers and/or of plastics.
Pure or modified bismuth vanadates are well-known chemical compounds. They can be employed inter alia as a catalyst for obtaining olefins, as a reversible temperature indicator or as a nontoxic yellow pigment for the coloring of paints and of plastics (patent applications GB 237 688--U.S. Pat. No. 3,843,554--JP 6361080--DE 2727863).
Various processes make it possible to manufacture pigments based on bismuth vanadate. It thus is possible to calcine mixtures of oxides or of any salt which decomposes thermally into oxide, for example, nitrate, carbonate, hydroxide, phosphate, etc. (U.S. Pat. Nos. 4,026,722--4,251,283). The calcination temperatures may vary within a wide range of values (200.degree. to more than 1000.degree. C.). The calcined products can be purified by milling in an alkaline medium (patent EP 304399).
It also is possible to mix solutions containing salts of bismuth, vanadium and the like and to calcine the products thus obtained (patent applications BE 9001230--DE 3135281). When starting with finely divided metallic bismuth, the presence of flux may be advantageous (patent application DE 3315850).
It also is possible to carry out the precipitation of a bismuth vanadate gel which is separated from the reaction mixture, which is washed to remove the nitrates and which is then aged without going through an actual calcination stage (patent application U.S. Pat. No. 4,752,460--EP 430888--U.S. Pat. No. 4,063,956).
These processes make it possible to obtain pigments based on bismuth vanadate with a fairly pure yellow hue and whose fastness to light and to heat can be improved by various coating and stabilizing treatments. However, the hue purity and brilliance, the depth of color and the hiding power of these pigments remain limited and restrict their use.
Patent FR-2355779 describes a process for the preparation of a bismuth vanadate, in which a solution of bismuth nitrate in nitric acid is mixed with a solution of alkali metal vanadate (preferably a sodium or potassium vanadate) in an aqueous base chosen from sodium hydroxide and potassium hydroxide, to precipitate a bismuth vanadate gel in suspension in a solution containing a dissolved alkali metal nitrate: the normalities of the acidic and basic solutions being adjusted before the mixing operation so that the pH of the mixture is approximately between 1.0 and 11.0.
The alkali metal vanadate solution is prepared by dissolving a pentavalent vanadium compound such as V.sub.2 O.sub.5, Na.sub.3 VO.sub.4, Na.sub.4 V.sub.2 O.sub.7, Na.sub.4 V.sub.2 O.sub.7 or K.sub.3 VO.sub.4 in an aqueous base chosen from sodium hydroxide and potassium hydroxide.
However, this salt has the disadvantage of being poorly soluble and of giving colored mother liquors of soluble salts based on pentavalent vanadium.
Furthermore, dissolving vanadium pentoxide in caustic soda to obtain a basic solution of sodium vanadate is not a very easy operation because stirring must be continued for a very long time at a temperature which is higher than normal and preferably with pure or distilled water.
In this process, the mixing of bismuth and vanadate solution is performed by "incremental combination," which consists in the simultaneous addition of the reactants under pressure into a mixing tee.
This technique prevents the relatively high gradients and the stoichiometric imbalance which are produced when large quantities of reacting substances are mixed all at once. This imbalance results in undesirable secondary reactions. Equipment which conveniently
REFERENCES:
patent: 4026722 (1977-05-01), Hess
patent: 4063956 (1977-12-01), Higgins
patent: 4115141 (1978-09-01), Piltingsrud
patent: 4115142 (1978-09-01), Hess
patent: 4272296 (1981-06-01), Balducci et al.
patent: 4316746 (1982-02-01), Rustioni et al.
patent: 4455174 (1984-06-01), Wienand et al.
patent: 4752460 (1988-06-01), Herren
patent: 4851049 (1989-07-01), Wienand et al.
patent: 5186748 (1993-02-01), Erkens et al.
Buyse Emile Joseph
Vermoortele Frank
Colour Research Company (CORECO) Ltd.
Marcheschi Michael
LandOfFree
Bismuth vanadate pigments and processes for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bismuth vanadate pigments and processes for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bismuth vanadate pigments and processes for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-797871