| Molecular Formula | CoO·Al2O3 |
| Density | 4.26[at 20℃] |
| Physical and Chemical Properties | The main composition of cobalt blue is CoO, Al2O3, or cobalt aluminate [CoAl2O4], according to the chemical formula theory, Al2O3 content is 57.63%, CoO content is 42.36%, or Co content is 33.31%, but the actual composition of cobalt blue pigment Al2O3 in 65% ~ 70%, CoO between 30% ~ 35%, some cobalt blue pigment containing cobalt oxide content is lower by one or one and a half, because it is also possible to contain small amounts of oxides of other elements, such as Ti, Li, Cr, Fe, Sn, Mg, Zn, etc. As the analysis of a cobalt blue pigment species shows that its CoO is 34%, Al2O3 is 62%,ZnO is 2% and P2O5 is 2%. It is also possible for cobalt blue to contain small amounts of alumina, Cobalt green (CoO · ZnO) and cobalt violet [Co2(PO4)2] In addition to the main composition to change the hue of the cobalt blue pigment. This kind of pigment belongs to the spinel class, is a cube with spinel crystallization. The relative density is 3.8~4.54, the hiding power is very weak, only 75~80g/m2, the oil absorption is 31% ~ 37%, the specific volume is 630 ~ 740g/L, the quality of cobalt blue produced in modern times is essentially different from that of early products. Cobalt blue pigment has a bright color, excellent weather resistance, alkali resistance, resistance to various solvents, heat resistance up to 1200. The main weak poof is less than the color strength of phthalocyanine blue pigment, because it is calcined at high temperature, although after grinding, but the particles still have a certain hardness. |
| Use | cobalt blue is a non-toxic pigment. Cobalt blue pigment is mainly used for high temperature resistant coatings, ceramics, enamel, Glass coloring, high temperature resistant engineering plastic coloring, and as an art pigment. The price is more expensive than the general inorganic pigment, the main reason is the higher price of cobalt compounds. The varieties of ceramic and enamel coloring are quite different from those of plastics and coatings. |
| EPA chemical substance information | information provided by: ofmpeb.epa.gov (external link) |
| Use | cobalt blue is a non-toxic pigment. Cobalt blue pigment is mainly used for high temperature resistant coatings, ceramics, enamel, Glass coloring, high temperature resistant engineering plastic coloring, and as an art pigment. The price is more expensive than the general inorganic pigment, the main reason is the higher price of cobalt compounds. The varieties of ceramic and enamel coloring are quite different from those of plastics and coatings. |
| production method | There are three methods for producing cobalt blue: carbonate method, sulfate method and cobalt oxide method. Cobalt carbonate method. Reaction equation: CoSO4 Na2CO3 → Na2SO4 Co3 ↓ 2K al(SO4)2 3NaCO3 3H2O → K2SO4 2Na2SO4 3co2 ↑ 2Al(OH)3 ↓ operation method: potassium alum [Kal(SO4)2 · 12H2O]: Cobalt sulfate (CoSO4 · 7H2O): zinc sulfate (ZnSO4 · 7H2O): sodium carbonate (NaCO3): disodium hydrogen phosphate (Na2HPO4 · 12H2O) 100:18.6:1.2:85:4.2. Cobalt sulfate and potassium alum are added together to dissolve in water and then sodium carbonate solution is added to produce a precipitate containing cobalt carbonate and aluminum hydroxide. The precipitate was washed, filtered, dried, and calcined at a high temperature of 1100 to 1200 ° C. For 2 to 2.5h, and the end point was judged by the color of the pigment. After completion of calcination and cooling, water is added to form slurry, and the finished product is obtained by grinding in a magnetic ball mill to achieve the required fineness, and then vacuum suction filtration, drying and grinding. Cobalt sulfate method. Reaction equation: CoSO4 Al2(SO4)3 → CoO · Al2O3 4SO3 operation method: 61 parts of aluminum sulfate (Al2(SO4)3 · 18H2O) and 18 parts of cobalt sulfate (CoSO4 · 7H2O) the charge was prepared by thorough mixing, dehydrated at 300 to 350 ° C., and then calcined at a high temperature of 1100 to 1200 ° C. For 2.5h, and the end point was judged by the color of the pigment. After completion of calcination and cooling, water is added to form slurry, and the finished product is obtained by grinding in a magnetic ball mill to achieve the required fineness, and then vacuum suction filtration, drying and grinding. Cobalt oxide method. Reaction equation: 2Co3O4 12Al(OH)3 → 6CoO · Al2O3 O2 ↑ 18H2O operation method: 72 parts of aluminum hydroxide [Al(OH)3] and 22 parts of cobalt oxide (Co3O4) and a small amount of zinc oxide (ZnO, such as 6 parts) are mixed into a charge, and then calcined at a high temperature of 1100~1200 C for 2.5h, and the end point is judged by the color of the pigment. After completion of calcination and cooling, water is added to form slurry, and the powder is ground in a magnetic ball mill to achieve the required fineness, and then vacuum suction filtration, drying and crushing are used to obtain a cobalt blue finished product. |