Composition for colouring glass and uses thereof
View Patent ↗The present invention relates to a coloring composition free of nickel oxide. In particular, the coloring composition for glass comprises manganese dioxide (MnO 2 ), chromium oxide (III) (Cr 2 O 3 ), cobalt oxide (Co 3 O 4 ) and a glass medium. Furthermore, the present invention relates to the process for producing the coloring composition and the use thereof for the purpose of imparting a dark color (black), in particular a blue-violet-black color, to the glass.
1. A coloring composition for glass, free of nickel oxide, comprising:
35-50% by weight of MnO 2 ;
4-10% by weight of Cr 2 O 3 ;
0.5-1.5% by weight of Co 3 O 4 ; and
40-60% of a glass matrix.
2. The composition in accordance with claim 1 , comprising:
40-45% by weight of MnO 2 ;
5-8% by weight of Cr 2 O 3 ;
0.8-1.2% by weight of Co 3 O 4 ; and
45-55% of a glass matrix.
3. The composition in accordance with claim 1 , wherein said glass matrix is silica, a silicate, or an anhydrous silicate.
4. The composition in accordance with claim 3 , wherein said at least one silicate is a sodium silicate.
5. The composition in accordance with claim 1 , wherein said glass matrix comprises 42-48% sodium silicate 1:3 by weight relative to the glass medium or 2-8% sodium silicate 1:2 by weight relative to the glass matrix.
6. The composition in accordance with claim 1 , wherein the chromium oxide is in the form of a powder, crystals or crystal powder.
7. The composition in accordance with claim 1 in powder form, or in the form of pellets, tablets or granules.
8. A process for producing the composition according to claim 1 , in the form of granules, said process comprising the following steps:
(i) providing a composition for coloring glass according to claim 1 ;
(ii) humidifying the coloring composition;
(iii) reducing the composition into granules;
(iv) humidifying the colorant granules; and
(v) drying the granules.
9. The process according to claim 8 , wherein the humidification step is carried out in an atmosphere comprising from 15 to 35% by weight of water.
10. A granule of the composition according to claim 1 , wherein the granule has a density which ranges from 1 to 5 g/cm 3 , a size which ranges between 1 and 15 mm, and a humidity of less than 5% w/w.
11. A colored glass made from the composition of claim 1 , having a light reflectance percentage of between 0 and 40.
12. A colored glass made from the granule according to claim 10 , characterized by a light reflectance percentage of between 0 and 40.
13. A process for producing colored glass, comprising the following steps:
(i) providing a molten glass matrix;
(ii) adding a composition according to claim 1 ; and
(iii) forming the glass.
14. A food or cosmetic grade article, comprising colored glass according to claim 13 .
15. A process in accordance with claim 14 , wherein said composition or granule is added at a concentration which ranges between 1 and 6%, relative to the molten glass matrix.
16. The composition in accordance with claim 4 , wherein said sodium silicate is selected from the group consisting of sodium silicate 1:2 (Na 2 O*2SiO 2 ), sodium silicate 1:3 (Na 2 O*3SiO 2 ) and mixtures thereof.
17. The composition in accordance with claim 1 , wherein the chromium oxide has a particle size ranging from 3 to 10 microns.
18. The process in accordance with claim 9 , wherein the atmosphere comprises from 20 to 30% by weight water.
19. The granule of the composition according to claim 10 , having a density which ranges between 2 to 3 g/cm 3 .
20. A granule of the composition according to claim 10 , having a size which ranges between 2 and 10 mm.