Hard oxide-based particles coated with ceramic pigments, process for manufacturing them and their use.

The present invention relates to hard material particles, based on oxide, in particular corundum, which are coated with ceramic color bodies, and a method for their preparation. It also relates to the use of these particles as a colorant, and verschleisshemmende roughening component, especially in ceramic glazes, enamels, paints and coating compositions.

To improve the mechanical properties, especially the wear resistance and slip resistance, hard particles are incorporated into highly stressed surfaces often. Examples of such surfaces include ceramic floor tiles or their glazes, particularly for floor surfaces in wet areas, such as public or private bathrooms, or outdoor, or flooring made of other materials such as plastics or synthetic stone, exposed to similar pressures. especially Korundkörnungen be used as hard material particles for this purpose, as opposed to non-oxide hard materials such as hard metals or silicon carbide can be incorporated without disturbing chemical reactions in glazes and enamels and at reasonable prices have satisfactory hardness and wear resistance.

A disadvantage of the commercial Korundkörnungen lies in the fact that only limited color schemes and surface appearances are possible, which in the living area and public buildings in particular leads to severe restrictions. The reason for this lies in the intrinsic color of these Korundkörnungen, the white to brown or gray to blue or with special corundum also are pink to ruby ​​and also may change during the firing process when used in ceramic glazes. Satisfactory results are therefore only obtained if the glaze has approximately the same color, whereby the color palette is very concentrated and intense colors are all excluded. Increasing the pigment amount in the glaze on the usual value addition brings this does not help, because the corundum have their purpose are correspondingly on the surface of the glaze, and also leads to a substantial increase in the price. Possibly desired surface appearances such as mottle with different colors between glaze and hard material, also have only very limited possible.

Object of the present invention was therefore to provide oxidic hard material particles are available which can be incorporated in any colored glazes and other surfaces without affecting the color impression and an extension of the color palette for generating homogeneous coloring and special surface appearances such as mottle, dulling let mottling, marbling and other patterns.

According to the invention this object is achieved by the covered with ceramic coloring bodies hard particles according to claim. 1

It has been found that it is possible to provide hard particles, based on oxide with a coating of one or more ceramic coloring bodies and a binder.

In this way, the good mechanical properties of the hard material particles can be used without having to accept limitations in color or deterioration in the number of possible appearances of these objects, in which the particles come to application.

Among ceramic coloring bodies are here, (inorganic) oxides produced an annealing process, inorganic compounds (eg. As Rutile, spinels, chromites, aluminates, ferrites, etc.) to understand which are used as a colorant was in ceramic glazes, and are characterized by that they can not solve or in ceramic glazes little. In addition, depending on application specific requirements, the use of inorganic pigments, such as. For example, single-phase or multi-phase metal oxides, metal powders, etc., as well as frits of color is possible.

An overview is provided as example Römpp, Chemie-Lexikon, 9th Edition, Volume 4, 1991, G. Thieme Verlag, Stuttgart, or W. Heinz, silicate Encyclopedia, 1st edition, 1985, Akademie-Verlag Berlin, S. 226th

In general, for surfaces that are not exposed to temperatures above about 300 ° C, such as paints, plastic surfaces and concrete, all ceramic stains are easily usable by the above definition. When using colored glasses especially in glazes of tiles a melt blending of colored glasses with the glaze to the hard nucleus takes place, which can lead to a desired part Melierungseffekt. When using inorganic pigments in glazes to be checked in each individual case, to what extent an inert behavior of the inorganic pigments present in the glaze firing.

The basic material for the novel coated hard particles on oxide are preferably alumina, zirconia, silica, spinels, or mixtures thereof, optionally with the usual impurities and / or additives, such as stabilizers or sintering aids. A particularly preferred base material is corundum, in particular melting or sintered. The particle size of the inventive coated hard material particles is 0.03 to 3 mm, preferably 0.06 to 0.5 mm. Particular preference narrow grain bands, as described in the FEPA standard 42-D-1984 and 43-D-1984th

Due to its size, coated hard particles are very easy to work with because they are free-flowing and dust-free and do not agglomerate. They can therefore be used both in Trockenglasierverfahren and in the common Nassglasierverfahren and can be good support by automatic devices and metering.

The ceramic pigments is used in an amount of 2 to 20 wt.%, Preferably 5 to 10 wt.%, Based on the amount of particles in front of the sheath, are used. The amount to be applied depends on the particle size of the color solid, the desired color strength, color depth and the grain size of the hard particles.

When using finer grits (z. B. F 220 according to FEPA) ceramic glazes may be colored so as to give a homogeneous visual color impression, as it is with a conventional glaze coloring achieved by direct pigment additive. However, it has shown that use of the inventive coated hard particles have a substantially smaller amount of color bodies is sufficient to achieve the same color saturation as in the conventional glaze color. For example,% color coated corundum the same color saturation So was an addition of 7 wt. with a pigment content of at most 10 wt.%, with weight not more than 0.7.% pigment, based on the total dry glaze mix, achieved as a direct addition from 5 wt.% pigment at the same glaze.

This makes it possible to reduce the heavy metal content of glazes dramatically without having to resort to other pigment compositions.

The binder used for the coating is basically any binder that sufficiently wetted both the hard material and the color bodies, constitutes a sufficiently adherent layer and the intended use of the coated particles, for example, the glaze firing of tiles, does not interfere.

Preferred binders are silica, silica salts, with or without addition of colorless glass frits, aluminum monophosphate or mixtures of these substances. Particularly preferred alkali metal silicates are ( "water glass"), such as sodium silicate.

The inventive coated hard material particles can be produced in a simple and inexpensive manner. For this purpose, for example, to be coated hard material particles are initially wetted with a solution or suspension of the binder. This can be carried out, for example, by simple mixing in a conventional mixer or by spraying onto the particles in motion. As a solution or suspension, a solution or a suspension is preferably used with water or other readily volatile liquid. Advantageously, not substantially more binder solution or suspension used as for the uniform wetting of the particles and the binding of the provided pigment amount is required. The required amount depends on the specific surface area or the size of the particles and the viscosity of the solution or suspension and the color bodies from.

The so-wetted particles are then thoroughly mixed with the required amount of finely powdered color body, so as to form a uniform coating. Preferably, the proportions between binder and pigment are selected such that the coating outside being substantially free of excess binder, otherwise stick together, the particles easily and form agglomerates. After the application of the color solid, the particles are first dried. The further thermal treatment is highly dependent on the desired application and covers a temperature range of<ul><li>at least 300 ° C for use in plastic surfaces, concrete, and especially when using coated with colored glass tiles in corundum to produce a Melierungseffektes up</li><li>a maximum of 1200 ° C for use in tiles, if an absolutely inert behavior of the coated corundum is required.</li></ul> Recently optionally deagglomerating and / or sieved to destroy agglomerates formed and / or to remove.

A preferred use of the inventive coated hard particles is their addition to ceramic glazes or enamels. Primarily, the particles are there to increase the wear resistance and to roughen the surface and thus reducing the risk of slipping. For this purpose, the particles are preferably incorporated into the surface of the glaze or enamel layer. This can be done before firing or during firing by sprinkling on the already applied as a slurry or powdered glaze or enamel composition. Besides the addition of the particles can also be used to affect the appearance of the finished glaze or enamel layer, for example, to achieve a modified surface structure in the form of a matt effect, or to produce mottle and similar color effects when or for Glaze . email matrix and the particle shell, different shades and / or color intensities can be selected. In this case it may be, depending on the degree of transparency of the glaze or enamel also advantageous evenly distribute the particles in the glaze or similar to the so-called underglaze first applied to the substrate and to cover with the glaze.

Particularly preferred is the use of the inventive coated hard material particles in the glaze of ceramic floor tiles in the outdoor area, in wet rooms and for strong verschleissbelastete floors, particularly in public buildings and in industry.

Another preferred use of the inventive coated hard particles is their addition to plastics and coating materials, for example, for floor and wall coverings. Also suitable here are its advantages, namely the combination of wear and color, to wear.

Also, a preferred use of the inventive coated hard particles is their addition to paints for mechanically loaded paints.

In addition, the inventive coated hard material particles can be used as an additive to synthetic stone materials, concrete or plaster.

The following examples illustrate the present invention.

example 1

To 1 kg of corundum (corundum, grit F-120 (d₅₀ ≃ 110 microns))% sodium silicate solution (34.2, 25 ml of a mixture of 60 vol. Percent.% Solids content, 8 wt.% Na₂O, 26.2 wt.% where SiO₂, viscosity about 70 mPa.s) and 40 vol.% of water and about 20 min mixed in a paddle mixer. To the thus uniformly wetted corundum (100% &lt;63 micron particle size) was added) and continue the mixing for a further 20 min 100 g color bodies, eg spinel. The thus obtained coated corundum particles were at 150 ° C up to a residual moisture content of max. 0.1% dried (with convection h in the tumble dryer during 4). After drying, a control screening was held at 212 micron. Subsequently, the dried particles with the exception of grain over at 1000 ° C in an oxidizing atmosphere (air) were burned in the rotary kiln. The mean residence time here was 2 h. After cooling, the particles were deagglomerated on a vibrating screen using hard rubber balls and sieved at 212 microns at the same time to separate remaining agglomerates. The product is a flowable grain that visually conveys a homogeneous color impression.

example 2

Analogously to Example 1 Korundkörnungen% of a ceramic color body were each with 10 wt. Jacketed. were used pigments of the following colors and compositions (in wt.%):<dl id="dl0001"><dt>Green:</dt><dd>Cr₂O₃ 95% Al₂O₃ 3% SiO₂ 2%</dd><dt>Brown:</dt><dd>ZnO 50% Fe₂O₃ 25% Cr₂O₃ 25%</dd><dt>Blue:</dt><dd>Co₃O₄ 20% Al₂O₃ 80%</dd><dt>Yellow:</dt><dd>Pb₃O₄ 40% Sb₂O₃ 40% ZnO 10% CaO 10%</dd></dl> The following table shows the comparison with the conventional coloring glaze possible reduction of the content of environmentally relevant compounds in the glaze (in wt.%) Through use of the inventive hard material particles. <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="4" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">color</entry><entry namest="col2" nameend="col2" align="center">Environmental Connection</entry><entry namest="col3" nameend="col3" align="center">For direct staining with 5% Farbk wt. Örper (wt.%) *)</entry><entry namest="col4" nameend="col4" align="center">When coloring with 7 wt.% Of the inventive particles (wt.%)</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">green</entry><entry namest="col2" nameend="col2" align="left">Cr₂O₃</entry><entry namest="col3" nameend="col3" align="char" char=",">4.75</entry><entry namest="col4" nameend="col4" align="char" char=",">0.67</entry></row><row><entry namest="col1" nameend="col1" morerows="1" rowsep="1" align="left">brown</entry><entry namest="col2" nameend="col2" align="left">ZnO</entry><entry namest="col3" nameend="col3" align="char" char=",">2.50</entry><entry namest="col4" nameend="col4" align="char" char=",">0.35</entry></row><row><entry namest="col2" nameend="col2" align="left">Cr₂O₃</entry><entry namest="col3" nameend="col3" align="char" char=",">1.25</entry><entry namest="col4" nameend="col4" align="char" char=",">0.18</entry></row><row><entry namest="col1" nameend="col1" align="left">blue</entry><entry namest="col2" nameend="col2" align="left">Co₃O₄</entry><entry namest="col3" nameend="col3" align="char" char=",">1.00</entry><entry namest="col4" nameend="col4" align="char" char=",">0.14</entry></row><row><entry namest="col1" nameend="col1" morerows="2" rowsep="1" align="left">yellow</entry><entry namest="col2" nameend="col2" align="left">Pb₃O₄</entry><entry namest="col3" nameend="col3" align="char" char=",">2.00</entry><entry namest="col4" nameend="col4" align="char" char=",">0.28</entry></row><row><entry namest="col2" nameend="col2" align="left">Sb₂O₃</entry><entry namest="col3" nameend="col3" align="char" char=",">2.00</entry><entry namest="col4" nameend="col4" align="char" char=",">0.28</entry></row><row><entry namest="col2" nameend="col2" align="left">ZnO</entry><entry namest="col3" nameend="col3" align="char" char=",">0.50</entry><entry namest="col4" nameend="col4" align="char" char=",">0.07</entry></row></tbody></tgroup><tgroup cols="4" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><tbody valign="top"><row><entry namest="col1" nameend="col4" align="justify">*) The difference between the stated 5% are part of the color solid, which are themselves not environmentally relevant (eg. As Al₂O₃, SiO₂, Fe₂O₃ ....)</entry></row></tbody></tgroup></table></tables>