Static structures (e.g. – buildings) – Ornamental: color – thickness variation – or dissimilar...
Reexamination Certificate
2000-06-21
2001-09-11
Brunsman, David (Department: 1755)
Static structures (e.g., buildings)
Ornamental: color, thickness variation, or dissimilar...
C428S454000, C106S287180, C106S453000
Reexamination Certificate
active
06286278
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions suitable for coloring ceramic manufactured articles and the relevant coloring process. In particular, the compositions of the invention consist of aqueous solutions of tungsten and chromium salts or organic complexes which impart a particular colour to ceramic manufactured articles, when used on supports modified with an addition of TiO2. Furthermore, to obtain particular shades, said solutions may be mixed with solutions of other cations.
STATE OF THE ART
The use of coloured ceramic manufactured articles as well as the compositions and procedures adopted to obtain the relevant colours have been known since long time. One of the methods most commonly used consists in the addition of powdered pigments, in particular inorganic oxides and other mineral pigments, to the ceramic mixture (vitrified stoneware) before firing. The ceramic manufactured article is thus coloured through its whole thickness, although with large consumption of colouring matter, which is the most expensive component. Being superfluous to colour the inside of the ceramic manufactured article, due to the material non-transparency, efforts have been made to find new methods for colouring only the surface of the ceramic material, with considerable saving of costly materials.
A procedure consists in making the surface of the ceramic material absorb, either after partial burning (as disclosed e.g. in German patent 2,012,304) or simply after molding pressing and before burning (as disclosed e.g. in Swiss patent 575,894), an aqueous solution of inorganic salts or metal complexes (as disclosed e.g. in Sprechsal, vol. 119, No. 10, 1986, in EP 0 704 411 and in patent PCT WO 97/38952), which become stable colours at high temperature during the firing cycle of the ceramic manufactured article.
The aqueous solution is applied to the ceramic material, e.g. by immersion, spraying, disk, and silk-screen techniques, before final firing.
This procedure is particularly advantageous because it allows the colouring of very thin layers: therefore, it is widely used for flat manufactured articles (such as e.g. floor and wall tiles).
Of great importance is the application technique: in particular, the quantity of colouring solution that may be applied by disk and spraying techniques is as high as 400 to 600 g/m2; by silk-screen type techniques it usually amounts to 100 to 200 g/m2 and sometimes even to 400 g/m2.
Silk-screen type techniques are very much in demand, being the only techniques allowing graphic decorations and drawings, and requiring lower quantities of colouring matter.
Colour penetration into the ceramic material before firing is obtained with relatively high quantities of water or of other liquids after application of the colouring solution. However, the resulting colours are less intense than those obtained using other techniques.
Colour penetration into the material is of cardinal importance in the case of “smoothed” vitrified stoneware tiles.
The term “smoothed” means that the vitrified stoneware surface has been abraded with diamond wheels by 0.8 to 1.5 mm, smoothed and polished with appropriate felt until obtaining a glassy surface.
It follows that colour penetration into stoneware articles to be smoothed after burning must reach a depth of at least 1.6 mm.
In other cases, only a very thin surface layer (1 to 10 &mgr;) can be smoothed and then polished.
TECHNICAL PROBLEM
Considering that it is very simple to colour ceramic materials by disk and spraying techniques, the ceramic industry is highly interested in finding new substances to be used therewith.
As concerns said new substances, the technical problems to be solved are: they must become stable colours at a high temperature; the manufactured article has to be coloured in the desired shades without too high consumption of colouring matter; the colouring matter has to penetrate deeply into the ceramic manufactured article.
Unfortunately, very few are the colours available so far. In particular, the lack of various shades of red, green, yellow and yellow ocher is deeply felt, especially by the industry of vitrified stoneware, which must propose ever new aesthetic solutions.
Furthermore, since yellow is a primary colour, the lack of substances producing it in its various shades makes it impossible to obtain other colours.
REFERENCES:
patent: 4908065 (1990-03-01), Tanitsu et al.
patent: 2012304 (1971-09-01), None
patent: 2605651 (1977-08-01), None
patent: 197 01 080 (1997-01-01), None
patent: 0704411 (1996-04-01), None
patent: 1071659 (1984-02-01), None
patent: 9738952 (1997-10-01), None
English abstract of Swiss patent 575,894 (May 1976).
English abstract of Sprechsal, vol. 119, No. 10 (1986) No month provided.
Brunsman David
Hedman & Costigan ,P.C.
LandOfFree
Composition based on tungsten and chromium aqueous solutions... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composition based on tungsten and chromium aqueous solutions..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composition based on tungsten and chromium aqueous solutions... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2450354