CS237365B1 - Mixture for preparation of pink ceramic zirconium-type pigment - Google Patents

Abstract

Preparation of pink ceramic pigment zirconia type - with the addition of £ - EepOx at temperatures of 600 to 630 ° C, ie 150 to 35ΟC lower than the temperature so far used, allows the composition of the mineralizer added to the base feed mixture oxides (zirconium and silica) and ferric oxide hydroxide 5 is employed the beneficial effect of lithium hydroxide which has been found in combination with sodium hexafluorosilicate even sodium chloride reduces the temperature of formation pigment below 700 ° C. Further temperature reduction then adds molybdate ammonium, respectively. molybdenum oxide when hexavalent molybdenum is converted to tetravalent with release of active oxygen, with strong oxygen mineralizing effects pigment formation temperature up to 600 ° C. The blank is usable without further modification as a pigment in glazes and no need for it to wash because it contains only a small amount soluble components. The invention may be of use in the ceramic industry where it would allow simple preparation of quality pigment under favorable conditions.

Description

The invention relates to a composition for the preparation of a pink ceramic zirconium pigment; it allows pigment synthesis at temperatures substantially lower than those used in prior art methods.

The pink ceramic zirconium pigment is a synthetic zirconium silicate in which microspheres with a zirconium structure retain particles of < - &gt; - Fe2O4 which give them a pink hue. The ferric oxide staining particles are coated (sealed) with the synthesized silicate so that, when the pigment is applied to the ceramic glazes, they are protected from the aggressive environment of the molten glaze; otherwise, the oxide would react with the components in the glaze to lose color.

The pigment according to the prior art is prepared by firing of the starting mixture containing the basic starting oxides ZrCl 2 and θ 2 ^{in a} molar ratio equal (or at least close to one), further comprising so-called chromophore and mineralizers. Sodium or potassium halides are most commonly used as mineralizers, and iron compounds are used as chromophore for the formation of dC-Fe2O4 (most often ferrous sulphate or iron oxide-hydroxide) when calcining the mixture. As a rule, however, when preparing a high-quality pigment, either the chromophore or the compounds in the mineralizer contain sulfate ions in sufficient quantities. The firing temperatures used in the individual processes are in the range of 800 to 1000 [deg.] C. and are generally operated at temperatures in the upper half (930 to 950 [deg.] C.) with a firing time of 0.5 to 5 hours. Due to the relatively high content of sulphate component, it is usually necessary, before application to the glaze, to wash the stillage with water, ev. dilute mineral acid.

The essence of the process according to the invention is that the mixture for

237 365 preparation of a pink zirconium-type ceramic pigment based on zirconium dioxide, silica, sodium chloride and ferric oxide, containing by weight 49.5 to 52.5% zirconia, 22.5 to 24% silica, 1.3 up to 2.0% sodium chloride, 5 to 12% ferric oxide hydroxide (formula FeO (OH)), and 4.8 to 6.2% sodium hexafluorosilicate, 2.3 to 3.1% lithium hydroxide (formula LiOH · 6 to 10% of ammonium molybdate (formula (NH 4 gMOyOg 4 · 4 1 ^ 0) or 5 to 8.2% molybdenum oxide, preferably the mixture contains 50.4 to 51.4% zirconium oxide , 23.0 to 23.5% silica, 1.55 to 1.7% sodium chloride, 7.0 to 10.0% ferric oxide (FeO (OH)), and 5.35 to 5, 5% sodium hexafluorosilicate,

2.73 to 2.8% lithium hydroxide (LiOH · 4 O);

8.5% ammonium molybdate (formula (ΝΗ ^) ^ Μθγθ2 ^ · 4 ^ 0), or

5.7 to 6.9% molybdenum trioxide. The ingredients are dry blended and baked at a temperature of 600 to 630 ° C (depending on the type of zirconia used) for 1 to 3 hours (depending on the type of oxide and the firing temperature within the range). In calcining the mixture, lithium hydroxide first reacts with sodium hexafluorosilicon to release lithium and fluoride ions, which have strong mineralization effects. Further, the silica component is released from hexafluorosilicate both in the form of gaseous silica tetrafluoride and in the form of a liquid glass phase of the sodium silicate type; these are movable components in the calcined mixture and by means of which the transfer of the silica component to the ZrCl3 grains takes place at the beginning of the reaction. This is also due to the water vapor released in the reaction of lithium hydroxide with hexafluorosilicon; it also permits the transition of a small fraction of fluoride ions to hydrogen fluoride, which also acts on the grain surface of the parent starting oxides, thereby promoting their entry into the reaction. The iron (III) component is also partially converted to the halide, which reacts with SiCl 2 to form silica and iron (III) hematite; tetra then reacted with ZrO ₂ to form the microcrystals of the zircon ZrSiO ^ structure in which the resulting particles <£ -Γβ2θβ capture. Said actions of the individual components of the fired mixture reduce the temperature of the formation reaction

- 3 237 365 zirconium silicate at 670 to 680 ° C. A further decrease in temperature is due to the addition of ammonium molybdate, respectively. directly molybdenum trioxide (to the molybdenum in calcination anyway). Indeed, at temperatures above 500 ° C, this oxide gradually releases oxygen along with the transition of Mo ^VI to Mo ^IV ; the released active oxygen is manifested by a strong mineralization action, which further lowers the silicate formation reaction temperature up to 600 ° C. Mo ^gg incorporates pigment into the resulting zirconium structure as a substitute uncharged disorder at the zirconium site - Mo ^ p. The lime after cooling does not need to be leached to remove the soluble components of the mineralizer, because their proportion in the lime is very low compared to the previous methods. After easy spreading (baking has little cohesiveness) it can be applied directly into ceramic glazes.

The inventive method is advantageous in that, to prepare a pink ceramic pigments can be used as a zirconia type firing temperature of 150 to 350 ° C _and lower than the methods currently used in technological practice. The quality of the obtained pigment is in terms of color shade corresponding to the pigments prepared by the prior art. The lime has a high degree of conversion to zirconium silicate, is not diluted with sulphate ions (as in the prior art) and, therefore, does not need to be washed with water prior to application to the ceramic glaze. mineral acid.

The following are examples of implementation:

Example 1 g of zirconia (synthetic ZrO ₂ ), 9.1 g of silica (SiO ₂ ), 2.1 g of sodium hexafluorosilicate (Na ₂ SiFg),

1.1 g of lithium hydroxide (LiOH. H ₂ 0), 0.7 g of sodium chloride (NaCl), 3.5 g of ferric oxide hydroxide (FeO (OH)) and 3.5 g of ammonium molybdate ((^ ΝΗ) Μθγ0 ^ ^ _2. 4H ₂ 0) were dry mixed and heated 5 ° C / min. to 630 ° C. This temperature was maintained for 2 h. After cooling and trituration of the stillage, a pigment containing 85% zirconium silicate was obtained, directly using 37 365

- 4 digestible for coloring ceramic glazes to a pink color, including high-temperature glazes (with a glazing temperature of about 1300 ° C).

Example 2 g of zirconia (ZrO ₂ - purified mineral baddeleyite)

8.8 g silica (SiO ₂ ), 2.5 g sodium hexafluorosilicate (Na ₂ SiFg), 1.3 g lithium hydroxide (LiOH, H ₂ O), 0.9 g sodium chloride (NaCl) 3 6 g of ferric oxide (FeO (DH)) and 3.0 g of molybdenum oxide (MoO 4) were dry mixed, heated at 10 ° C / min to 610 ° C, which was maintained for 2h. The pigment obtained contained 83% zirconium silicate.

Claims (1)

D δ E D ME D OF THE INVENTION 237 365 A composition for the preparation of a pink zirconium-type ceramic pigment based on zirconium dioxide, silica, sodium chloride and ferric oxide, characterized in that it contains by weight 49.5 to 52.5% of zirconia, 22.5 to 24% of silica 1.3 to 2.0% sodium chloride, 5.0 to 12.0% ferric oxide hydroxide of the formula FeO (OH), 4.8 to 6.2% sodium hexafluorosilicate, 2.3 to 3.1% hydroxide LiOH · H ₂ O and 6.0 to 10.0% ammonium molybdate of formula (ΝΗ ^) γθγO ₂ ^. 4 H ₂ 0 ev. 5.0 to 8.2% molybdenum dioxide, preferably 50.4 to 51.4% zirconia, 23.0 to 23.5% silica, 1.55 to 1.7% sodium chloride, 7.0 up to 10.0% FeO (OH), 5.35 to 5.5% sodium hexafluorosilicate, 2.73 to 2.8% lithium hydroxide (LiOH · H ₂ O), and 7.0 to 8% 5% ammonium molybdate of the formula (NH?) GMO 0 ^ ₂ ^. 4 H ₂ 0 ev. 5.7 to 6.9% molybdenum trioxide.