Oxide-based solid substance particles coated with ceramic dyes, process of their preparation and use

The present invention relates to particles of hard oxide-based solids, in particular corundum, coated with ceramic dyes, as well as a process for their production. The invention further relates to the use of these particles as coloring, roughening and anti-abrasion components, in particular in ceramic glazes, enamels, paints and coatings.

BACKGROUND OF THE INVENTION

To improve mechanical properties, especially abrasion and slip resistance. hard particles are often processed into highly stressed surfaces. Examples of such surfaces are, inter alia, floor tiles or glazes thereof, in particular for floors in wet rooms, such as public or private baths or open baths. Other examples are floor coverings of other materials, such as plastics or artificial stone, which are exposed to similar loads. Above all, corundum grains are used as hard-particle. These, in contrast to non-oxide hard materials such as hard metals or silicon carbide, can be processed into glazes and enamels without disturbing chemical reactions. At favorable prices, it is satisfactorily hard and abrasion resistant.

A disadvantage of commercially available corundum grains is that only limited dye is possible and limited surface patterns are possible. This leads, in particular to housing and public buildings, to great constraints. This is due to the inherent colors of these corundum grains, which are white to brown or gray to blue, or, in the case of special corundums, also pink to ruby, and may also change when added to ceramic glazes during firing. Satisfactory results are only obtained if the glaze is approximately the same color, which makes the color palette very narrow and all intense color tones are also excluded. Nor will an increased amount of dye in the glaze above normal help.

not to be afraid of corundum particles, depending on purpose, must lie on the surface of the glaze and, in addition, this leads to a substantial increase in cost. Possible surface patterns, such as speckled finishes with different colors between the glaze and the hard cloth, are also possible only to a very limited extent.

It is therefore an object of the present invention to provide for the use of solid oxide particles which can be processed into arbitrarily colored glazes and other surfaces without damaging the color impression. The challenge is to further extend the color palette for producing homogeneous dyes and special surface patterns such as speckled, matt, streaked, marbled and other patterns.

SUMMARY OF THE INVENTION

According to the invention, the object is achieved by means of hard solid particles coated with ceramic dyes according to claim 1.

It has been found that it is possible to coat the hard oxide particles with a coating of one or more ceramic dyes and a binder.

In this way, it is possible to exploit the good mechanical properties of the particles of hard matter without having to reduce the color or limit the number of possible image phenomena of the articles in which the particles are used.

Ceramic dyes include (inorganic) oxides prepared by burning, inorganic compounds (for example, rutiles, spinels, chromates, aluminates, ferrites, etc.). which are used as coloring agents in ceramic glazes and are characterized in that they do not dissolve or dissolve little in the ceramic glazes. In addition, inorganic pigments may be used for special needs. such as single or multiphase metal oxides. metal powders, etc., as well as colored frits.

An overview can be obtained for example from B. Rfímppa. ChemieLexikon, 9th edition. Volume 4, 1991, G. Thieme Publishing

Stuttgart, or W. Heinz. Si1ikat-Lexikon, 1st edition 1985, Akademie Berlin, pp. 226.

In general, all of the ceramic dyes as defined above are easy to use for surfaces not exposed to temperatures above 300 ° C, such as paints, plastic surfaces and concrete. When using colored glasses especially in tile glazes, the colored glasses will melt around the hardwood core by melting. This can lead to a partially desired effect of streaking. When using inorganic pigments in galvanized materials, it has to be examined on a case-by-case basis how inert the inorganic pigments behave when glazing is fired.

Alumina, zirconia, silica, spinels or mixtures thereof are preferably used as the base materials for the coated oxide-based solids particles of the invention. optionally with conventional impurities and / or additives, such as stabilizers or sintering aids. A particularly preferred base material is corundum, in particular fused corundum or sintered corundum. The particle size of the coated hard particles according to the invention is 0.03 to 3 mm, preferably 0.06 to 0.5 mm. Particularly preferred are grains within a narrow range as described in the FEEP Standard 42-D-1984 and 43-D-1984, respectively.

The coated particles of hard matter are well processable because of their size, since they are free flowing and dust-free and do not agglomerate. They are therefore applicable both in the dry glazing process and in the conventional wet glazing process and are well conveyed and dosed by automatic devices.

The ceramic paste is used in an amount of from 2 to 20% by weight, preferably 5 to 10% by weight, based on the amount of particles before coating. The application rate depends on the grain size of the dye. the desired color intensity, color depth, as well as the grain size of the particles of hard matter.

When using fine grains (for example F 220 according to FEPft), the ceramic glazes can be stained so that a homogeneous visual color impression is obtained, which is achieved with traditional glaze dyeing by direct addition of dyes. But it turned out. The process according to claim 1, characterized in that using the coated particles of durable substances according to the invention, considerably less dyeing is required in order to achieve the same color saturation as in traditional glaze dyeing. Thus, for example, the same color saturation is achieved by adding 7% by weight of color coated corundum particles with a color content of not more than 10% by weight, i.e. not more than 0.7% by weight of the colorant, based on the total dry glaze composition. .

In this way, it is possible to drastically reduce the proportion of heavy metals in the glazes without having to switch to a different color composition.

Basically, any binder which sufficiently wets both the hard material and the colorants, forms a sufficiently firmly adhering layer and does not interfere with the intended use of the coated particles, for example in the baking of tile glaze, is suitable as coating binder.

Preferred binders are silicic acid, salts of silicic acid, with or without the addition of colorless glass frits, aluminum phosphate or mixtures thereof. Particularly preferred are alkali silicates (waterglass) such as sodium waterglass.

The coated solids particles according to the invention can be produced by a simple a. in a cost-effective way. To this end, for example, the solids particles to be coated are first wetted with a binder solution or suspension. This can be done, for example, by simple mixing in an ordinary mixing device, or by spraying onto the moving particles. The solution or suspension is preferably a solution or suspension with water or other readily evaporable liquid. Preferably, substantially no solution or suspension of binder is used than is necessary to uniformly wet the particles and to bind the expected amount of dye. The amount envisaged depends on the specific surface or particle size and the viscosity of the solution or suspension and color.

The soaked particles are then thoroughly mixed with the pre-screening powder of the dye so. In order to form the ratios of the amount between the binder and the dye, the outside of the coating has no excess otherwise the particles easily stick together and form agglomerates. After application of the dye, the particles are first dried. Further heat treatment depends strongly on the desired application and includes a temperature range from

- at least 300 ° C for use in plastic surfaces, concrete and especially when using corundum with laminated colored glass in tiles for the production of leveling, evenly coated, preferably chosen as iiva, since up to a maximum of 1200 ° C for tile use if absolutely inert behavior of the coated corundum is required.

the agglomerates formed were broken and / or removed.

A preferred use of the coated hard material particles of the invention is their addition to ceramic glazes or enamels. First of all, the particles there serve to increase the abrasion resistance and roughen the surface and thereby reduce the risk of slipping. For this purpose, the particles are preferably placed in the surface of the glaze or enamel layer. This can be done by sprinkling onto the already applied glaze mass or the enamel in the form of a slurry or powder before or during firing. In addition, the addition of particles can also be used to influence the appearance of the finished glaze or enamel layer, for example, to achieve an altered matt surface texture, or to produce a speckled finish and similar color effects therewith. if different color tones and / or colors are chosen for the glaze mass or the enamel and the particle coating. intensity. Depending on the degree of transparency of the glaze or the enamel, it may also be advantageous in this case to distribute the particles evenly in the glaze or the like

And called the colors below the glaze, first apply the particles to the substrate * and then overlay the glaze.

Particularly preferred is the use of the coated hard particles according to the invention in the glazing of ceramic floor tiles in outdoor areas, in wet rooms and for floors with high wear loads, especially in public construction sites and industry.

A further advantageous use of the coated hard material particles according to the invention is their addition to plastics and coatings, for example for floor and wall lining. Here again their advantages, namely the combination of anti-abrasion protection and colourfulness, apply again.

It is also advantageous to use the coated hard material particles according to the invention as an additive to paints for mechanically stressed coatings.

In addition, the coated solids particles according to the invention can, for example, be used as an additive to artificial stone, concrete or plaster materials.

The following examples are intended to illustrate the invention in more detail.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

To 1 kg of corundum (treated corundum, grain size F-120 (d 50 100 pra)) is added 25 ml of a mixture of 60% by volume sodium water glass solution (34.2% by weight solids content, 8% by weight NaaQ, 26% by weight). 2 wt% SiO 2 (viscosity ca 70 mPa.s) and 40 vol% water and stirred for about 20 min. in a paddle stirrer. To this uniformly wetted corundum is added 100 g of dyes, for example of the spinel type (grain size 100% <63 µm) and stirring is continued for another 20 min. The coated corundum particles thus obtained are dried at 150 ° C to a residual humidity of at most 0.1% (in a tumble dryer for 4 hours with ambient air). After drying, screening is carried out on a sieve at 212 µm. Thereafter, the dried particles, except for oversize, are fired at 1000 ° C in an oxidizing atmosphere (in air) in a rotary tube furnace. The mean residence time is about 2 hours. After cooling, the particles are desagglomerated on a vibratory screen using hard rubber beads while screening at 212 µm. to separate the remaining agglomerates. The product is loose grains that give a homogeneous color impression.

Example 2

According to Example 1, corundum grains were coated with 10 wt. ceramic dye. The dyes of the following colors and composition (% w / w) are used:

<td>green:</td><td>Cr2 O3 Al2d3 SiOa</td><td> 95 3 2</td><td> % % %</td>

<td>Brown</td><td>ZnO</td><td> 50</td><td> %</td>

<td></td><td>Fe2 03</td><td> 25</td><td> %</td>

<td></td><td>Cr2 03</td><td> 25</td><td> %</td>

<td>blue =</td><td>C03O4</td><td> 20</td><td> %</td>

<td></td><td>AI2O3</td><td> 80</td><td> %</td>

<td>yellow:</td><td>PbgCM</td><td> 40</td><td> %</td>

<td></td><td>Sb2 03</td><td> 40</td><td> %</td>

<td></td><td>ZnO</td><td> 10</td><td> %</td>

<td></td><td>CaO</td><td> 10</td><td> %</td>

The following table shows a possible reduction of the environmental-friendly compounds in the glaze (% by weight) by using the solids particles of the invention over conventional glaze staining.

<td rowspan="2">color</td><td rowspan="2">and Compound (i) affecting life environment</td><td rowspan="2">Ί- | at | 5 I (¾ 1 1</td><td rowspan="2">direct staining % by weight, dyes wt) *)</td><td colspan="2">j when staining % 7 wt. of the particles according to the invention</td>

<td>| C% 1</td><td>wt.)</td>

<td>ze1ená</td><td>1 CrzCb</td><td> 1 1 1 1 1</td><td> 4.75</td><td>and 1 and 1 1.</td><td> 0,67</td>

<td>Brown</td><td>| ZnO</td><td> 1 1 1</td><td> 2,50</td><td> 1 1</td><td> 0,35</td>

<td></td><td>1 θΓ2θ3</td><td> 1 1</td><td> 1,25</td><td>and</td><td> .0,18</td>

<td>blue</td><td>1 CO3CU</td><td>and 1 1 1</td><td> 1,00</td><td>1 1 1 and</td><td> 0,14</td>

<td>yellow</td><td>1 Pb₃0&lt;</td><td> 1 1 1</td><td> 2,00</td><td>and</td><td> 0.28</td>

<td></td><td>1 Sb2 03</td><td></td><td> 2,00</td><td>and</td><td> 0,28</td>

<td></td><td>i ZnO 1</td><td>1 and 1</td><td> 0,50</td><td> 1 1 !</td><td> 0,07</td>

\

χ) the difference to the mentioned 5% are dye components that do not affect the environment themselves (eg AI2O3, SiO2, Fe2O3 -)

Industrial applicability

The coated solid particles according to the invention can be processed into arbitrarily colored glazes and other surfaces without impairing the color impression. These particles are used as coloring, roughening and abrasion-resistant components, especially in ceramic glazes, enamels, paints and coatings. These particles expand the color palette to produce homogeneous dyes and special surface patterns such as speckled, matt, streaked, marbled and other patterning.

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