EP1047652A1

EP1047652A1 - Method for dying ceramic surfaces

Info

Publication number: EP1047652A1
Application number: EP99969080A
Authority: EP
Inventors: Thomas Staffel; Thomas Klein; Jürgen STRAUB; Jens Schmithüsen
Original assignee: BK Giulini Chemie GmbH
Current assignee: BK Giulini Chemie GmbH
Priority date: 1998-09-10
Filing date: 1999-09-09
Publication date: 2000-11-02
Also published as: BR9906943A; TR200001316T1; WO2000015580A1; DE19841318A1; AU5975699A; DE19841318C2; CN1287549A

Abstract

The invention relates to a method for dying ceramic surfaces, whereby a mixed phase pigment is produced in the surface layer of the ceramic mass. Said pigment consists of a colorless metal oxide which crystallizes in a spinel or rutile grating and which is used as host grating. The pigment also consists of an aqueous dying solution containing a soluble compound of a bivalent or trivalent metal ion which dyes the host grid, and of a soluble compound of a pentavalent or hexavalent metal ion for electrostatic balancing. According to the invention, the pigment is produced in the surface layer by either incorporating the finely dispersed colorless oxide into the ceramic mass and applying the aqueous dying solution to the surface layer, or by mixing the aqueous dying solution with an amount of a soluble compound of the metal ions which form the host grid, said amount being sufficient to form the host grating, and by applying said mixture to the ceramic surface. Once the solvent has dried, the ceramic body is fired at a temperature ranging from 300 to 1400 DEG C during a firing time of 0.5 to 5 hours.

Description

Process for coloring ceramic surfaces

The present invention relates to the use of soluble rare earth compounds in combination with other coloring transition metal compounds of ceramic bodies.

Metal oxides (pigments) are generally used for coloring ceramic materials and are stable at the usual firing temperatures of 700 to 1400 ° C. In the prior art, the colored oxides of iron are used in particular. Chrome. Manganese, pure and mixed phases with spinel structure, for example compounds of Al. Ni. Cr. Zn. Co. Cu, Mn. Fe. U and V. a series of silicates. Sulfides and mixed phases with working cations in colorless host lattices of the rutile type such as Ti0 ₂ . SnO ₂ . Zr0 ₂ . ZrSiO ₄ and PbO ₂ .

The rare earth metals are elements of the 3rd group of the Periodic Table, they belong to the transition metals. The rare earth elements include the elements scandium. Yttriumv and the 14 elements following lanthanum, from lanthanum to lutetium, which are essentially 3+ valued, occur naturally in the form of oxides. At this stage of oxidation they have a wide variety of colors. For example, the compound is Neodym3 + red-violet or Praseodym3 + green-yellow.

These colors are characterized by their intensity; in contrast to the colors produced by the other metals of the transition metals, the rare earth oxides are only weakly colored or staining.

It is also known to use rare earth oxides for this. These oxides are usually water-insoluble and are applied as pigments to the ceramic body by different methods. The use of the rare earth oxides as coloring pigments for ceramics is known from DE 19739124. The use of these oxides to produce purple ceramic decorations is described here. The pigments are based on a burnable carrier material. for example a glass flow, a rare earth oxide hydrate and a gold compound or colloidal gold. In this special process the oxide hydrates of the elements are yttrium. Lanthanum. Cerium and scandium used.

WO 97/08115 describes a further process for the production of ceramic coatings and the coating powders suitable therefor. The coating powders can be rare earth oxides. The process described here is electrostatic coating with oxide powders of a certain size. using specially designed adhesives. The so-called fire-capable substrates are used as substrates, including, in particular, enamelable metals and ceramic materials. e.g. Glass. Fine ceramics (porcelain. Bone China and Vitreous China. Building ceramics (roof tiles. Tiles), as well as sanitary ceramics and decorative ceramics. The advantage of this technique is that the substrates can be coated with powders that are particularly easy to fluidize, ie, liquefy This good fluidization of the coating powder does not give rise to any technical problems during spraying, the surface of the substrate is smooth, not corrugated, and it is also possible to achieve a corresponding coating depth on the surface of 100 to 700 μm.

However, it is also already known in the prior art to replace the coating powder, e.g. the oxide hydrates, so-called staining solutions for coloring the ceramic substrates.

DE-197 01 080 Cl describes a process for coloring ceramic surfaces, which is characterized in that. that a colorless oxide crystallizing in the spinel or rutile lattice is incorporated into a ceramic mass or a surface layer made of the ceramic mass as the host lattice. an aqueous coloring solution, which is a soluble compound of a divalent or trivalent metal ion coloring the host lattice and contains a soluble compound of a pentavalent or hexavalent metal ion for electrostatic compensation, is produced in which. either incorporate the colorless oxide in finely divided form into the ceramic mass and apply the aqueous coloring solution to the surface layer, or the aqueous coloring solution is mixed with a sufficient amount of a soluble compound to form the host lattice of the metal ions forming the host lattice and this mixture is applied to the surface, and after drying the solvent the ceramic body is fired at 300 to 1400 ° C and a burning time of 0.5 to 5 hours.

The advantage of this method is that the coloring solutions can be applied to the surface quite uniformly (sprayed, dipped, etc.) and the color layers produced in this way have a depth of 0.5 to 2 mm. This depth allows it. to subsequently process the ceramic surface by grinding and polishing, but also to create certain surface patterns.

The soluble salts of the transition metals are used as coloring solutions. The combination of antimony and chromium salts used here produces the color yellow; The colors pink or black can be produced in a similar manner, see DE-195 46 325 C1 and DE-196 25 236 Cl.

The colors created here are usually quite intense; it is not possible to use matt or pastel shades with the methods described above. To create chandelier effects without the involvement of precious metals or even color gradations. Often, only a certain lightening or decolorization of the ceramic substrates is desired, which cannot be achieved with these coloring methods. It is also not possible to lighten the colored substrates by applying less concentrated coloring solutions because the low concentration means that the layer thickness of the colored surface layers generated is too small to allow subsequent processing.

The task was therefore to find a method which would make it possible. To create pastel tones on ceramic substrates. lightening or discoloration of the To reach substrates. without using the complex electrostatic pigment application technique.

The problem was solved by using rare earth salts in the form of their solutions or suspensions. Surprisingly, it has been found that it is possible to apply solutions or suspensions of rare earths in combination with other solutions of other coloring metal salts to any type of ceramic substrate in liquid form, to dry them by means of the appropriate drying methods, and then to burn them to give a produce a well-colored colored surface layer on the ceramic substrate.

The process is characterized in that the aqueous solutions or

Rare earth suspensions by diving. Spray or spread on the

Applies ceramic substrate, and after drying the solvent, the ceramic substrate between 300 and 1400 ° C. and burns for 0.5 to 2.5 hours.

Acetates are the water-soluble salts of rare earths. the citrate. Chlorides.

Nitrates. Oxalates and sulfates used.

The combination with other coloring metal salts of the transition metals enables an intensification of the colors.

The use of soluble titanium complex salts has proven to be particularly favorable

Color enhancer proven.

xxxx

The coloring solutions for the production of pigments of the rutile type consist of a water-soluble compound of a divalent or trivalent metal ion, in particular from the group nickel. Cobalt and chromium, as well as another soluble compound of a pentavalent or hexavalent metal ion, especially antimony. Niobium or tungsten, the salts in a concentration of about 1 to 10% by weight. preferably 2 to 5% by weight. are included. Oryanic acids and in particular are preferred as anions complex-forming acids are used, which on the one hand have very good dissolving properties and on the other hand burn in an environmentally friendly manner with the formation of water and CO ₂ . However, inorganic anions such as chloride or nitrate can also be used, provided that the disadvantages associated with this are accepted.

It has also been found that an addition of potassium nitrate. Sodium fluoride or similar substances, which act as mineralizers, also promote the formation of the mixed-phase pigments in the clay matrix.

Furthermore, it has proven to be advantageous for the solution to have complex titanium, in particular potassium titanium oxalate. to add, although the amounts are limited to less than 3% due to the low solubility of this compound. The mixed phase coloring is enhanced by this addition, possibly by promoting the growth of a mixed phase on the existing host lattice.

It has recently become known that titanium (dihydroxy bis [2-hydroxypropanato (2 ^" ) -θ'.0 ² ] titanate (2 ^" )) chelated by lactic acid as the ammonium salt (CA Reg. No. 85104-06-5 ) in up to 50% by weight. corresponding to a titanium content of 8.2% by weight. is stable to hydrolysis in aqueous solution and can be used as a catalyst for crosslinking plastics or as an adhesion promoter.

The Na and K compounds and compounds with other ammonium ions also have corresponding stabilities. Surprisingly, these compounds can be mixed with salts of trivalent and pentavalent ions, as are customary for the mixed phase formation of rutile lattices, in concentrations which are sufficient for direct coloring of ceramic surfaces without the interaction of the different anions leading to incompatibility. Anions in these salts are organic acid residues, such as acetate. Tartrate. Citrate or lactate is preferred because they are oxidized to CO ₂ when burned. Inorganic salts like chlorides. However, sulfates or nitrates can be also use. 1-3% by weight of the tri- and pentavalent ions and 3-8% by weight of the titanium are preferred. Smaller amounts of the trivalent to pentavalent ions lead to pale colors, smaller amounts of titanium or higher amounts of the coloring compounds lead to oxidic mixed colors which do not have the brilliance and the color of the rutile grids. To this extent, preference is given to the formation of a rutile pigment with 10-60%. preferably 20-40% of the coloring ions.

The staining solutions are sprayed. Diving. To paint. Printing etc. only applied to the parts of the surface that are to be colored, whereby the solutions penetrate more or less deeply into the ceramic mass, depending on the amount applied. Discoloration usually occurs to a depth of 0.5 to 2 mm. so that both a patterning of the surface and processing, for example by grinding or polishing, is possible.

Titanium dioxide is preferably used as the host lattice for rutile pigments, but also SnO ₂ . Zr0 ₂ and other oxides customary for this purpose can be used.

MgAl ₂ θ4 compounds are the host lattice for spinels. ZnAl ₂ 0 ₄ or Zn (TiZn) O ₄ , Mg ₂ TiO ₄ , Zn ₂ TiO ₄ can be used.

The organic ligands of the metal compound are burned by burning, or inorganic anions are evaporated, and the remaining metal oxides are incorporated into the silicate phase of the ceramic or, with the formation of colored pigments, into the specified host lattices.

The mixed phase pigments formed according to the invention allow this. to expand the spectrum of subsequent coloring of ceramic surfaces extraordinarily and to apply a multitude of new shades in a targeted manner. The following experiments illustrate the subject of the invention in more detail using the example of the production of rutile pigments, without restricting it.

I. Color measurements:

The color shade obtained was determined using a Minolta Chroma Meter CR 200, using the CIE standard illuminant C (6774K). The L * a * b * color system recommended in ISO and DIN standards was used to determine the values. The L * a * b * color system represents a color body through which three axes have been laid. The vertical axis is the L * axis and represents the brightness of the color. The axes a * and b * are located in the horizontal plane (color wheel), where a * stands for the hue and b * for the saturation.

A typical lemon yellow has, for example, the brightness L * 81, 5; an a * value around 0 and a high b * value of 62.5

II. Results of the burning tests

Experiments with solutions based on the elements Ti, Sb and Cr

Solutions containing antimonate and chromium (III) acetate showed a yellowish hue, which shifted significantly to yellow when titanium was present. The addition of oxidizing agents (KNO ₃ or K ₂ S ₂ θ ₈ ) to improve the color depth resulted in slight color deepening in formulations containing antimony (Ti-Sb-Cr and Ti-Sb-Ni. The latter showed a brown tone).

The influence of mineralizers such as NaF and oxidizing agents such as KNO ₃ has now been investigated in the Ti-Sb-Cr system. It was found that the color was weak, but was clearly present against the blank value and best came out with a formulation with all components (Ti-Sb-Cr. NaF. KNO ₃ ). Cr and Sb are both necessary, the effect of the Ti was weak. just like that of NaF and KNO ₃ . This was also confirmed by a variation in the amount of NaF and KN0 ₃ and the additional formulation of Pr (via Pr ₂ (C0 ₃ ) ₃ and citric acid): in no case was a clear effect obtained.

The following selected formulations are preferred embodiments of the present invention:

III. Selected recipes:

Experiment 3: 21.27% K-Ti oxide oxalate x 2 H ₂ O (2.9% Ti); 8.05% Cr (III) acetate (1.64% Cr); 5.50% K-Sb tartrate (2.00% Sb); 2% Na gluconate; 63.2% dest. Water experiment 4: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb); 2.2% Na gluconate; 84.25% dist. water

Experiment 18: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb); 21.27% K-Ti oxalate (2.87% Ti); 3% KNO ₃

Experiment 19: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb): 21.27% K-Ti oxalate (2.87% Ti); 3% (NH ₄ ) ₂ S ₂ O ₈

Experiment 20: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb); 3% KNO ₃

Experiment 21: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb); 3% (NH ₄ ) ₂ S_O ₈

Experiment 37: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb); 1% NaF; 4.5% KNO ₃

Experiment 39: 8.05% Cr (III) acetate (1.64% Cr); 5.5% K-Sb tartrate (2% Sb); 21.27% K-Ti oxalate: 4.2% Pr ₂ (CO ₃ ) ₃ Table 1 Color values according to the L * a * b * system

The formulations described above were in addition to the usual firing temperature of

1 140 C also fired at 1000 C, whereby no color impression was obtained.

IV. Engobe experiments

A general problem in the experiments mentioned above is the low titanium concentration in aqueous solution (2.9%). which prevents a deepening of the color tone in that no larger portion of the surface is covered with a TiO ₂ grid. The so-called engobing technique offers a solution here. which consists in enriching the surface with TiO ₂ . The engobe clay can either be naturally or artificially enriched with TiO ₂ . For this purpose, an engobing mass from the clay flour FT-A (light-burning) from the company Fuchs ^' see clay pits. Ransbach. with 5 percent by weight of TiO ₂ . The clay flour was processed as follows: The clay was ground in a ball mill and sieved through a sieve with a mesh size of 0.063 mm. The viscosity was regulated by using condensers (max. 0.1%) based on silicate or acrylate. The blanks were then engobed by pouring over and draining. After drying overnight, the moldings thus obtained were sprayed with the appropriate chromophore solution and then fired at 1,140.degree.

Table 4 Addition: TiO ?. ZnO, SnO ?, ZrO "

V. Result:

Only with TiO ₂ did a clear ocher yellowing with a Cr / Sb color body result

Influence of TiO ₂ in other staining solutions:

To a certain extent, other dyeing solutions can also be influenced in their dyeing properties if you add TiO? admixed. For example, one cobalt chloride solution (1) (7 wt.% Co) and one Iron (III) chloride solution (2) (9% by weight Fe) on the Engoben mass with and without 5% TiO ₂ clearly different shades.

Table 5

TiO? brightens the color very clearly and changes its quality in the case of iron, where there is a shift from reddish brown to yellowish.

VI. Incorporation of TiO-> into a ceramic mass:

A ceramic shard with the composition

SiO ₂ 65-72%; Al ₂ O ₃ 18-23%; TiO ₂ <= 1: Fe ₂ O ₃ <= 1: CaO 1-2; MgO <= 1; K ₂ O 2-4; Na ₂ O 1-3; Cr ₂ O ₃ <= 0.1; BaO <= 0.1; P ₂ O ₅ <= 0.1; loss on ignition 4-5.5 was ground, with 5 wt.% TiO? added, pressed and then sprayed with the coloring solution from experiment 37 and fired together with an untreated test specimen. The results of the firing tests are as follows:

Table 6

VII. Staining with a Ti / Cr / Sb solution

Ceramic cullet with a TiO 2 content of <0.1 wt .-% and otherwise the composition corresponding to experiment VI are sprayed with the following solutions, dried and fired at 1,140 ° C.

38.2% Cr (as chromium (III) acetate)

1.4% Sb (as potassium antimony (III) tartrate)

8.8% Ti (as dihydroxybis (ammonium lactato) titanate -

Tyzor LA ^'j - 40% in H ₂ O) balance water

39.1.5% Cr (as chromium (III) acetate)

1.0% Sb (as potassium antimony (III) tartrate)

4.0% Ti (as dihydroxybis (ammonium lactato) titanate -

Tyzor LA "- 40% in H ₂ O) balance water

40.2% Cr (as chromium (III) acetate)

1.4% Sb (as potassium antimony (III) tartrate)

2.5% Ti (as titanium oxalate) balance water

41.2% Cr (as chromium (III) acetate)

1.4% Sb (as potassium antimony (III) tartrate) balance water

42.2% Cr (as chromium (III) acetate)

4.0% Ti (as Dihvdroxybis (ammonium lactato) titanate - TyzorLA "- 40% in H ₂ O) balance water

Table 7

Only the solutions containing the ternary mixture give a rich yellow color due to the rutile mixed phase grid formed. The solution without titanium gives a dirty orange hue, the solution without antimony gives a pale yellow-green color.

Claims

claims

1. A method for coloring ceramic surfaces, characterized in that in the surface layer of the ceramic mass, a mixed phase pigment from a crystalline in the spinel or rutile lattice colorless metal oxide as a host lattice and an aqueous coloring solution which is a soluble compound of a dying the host lattice divalent or trivalent metal ions and contains a soluble compound of a pentavalent or hexavalent metal ion for electrostatic compensation, either by incorporating the colorless oxide in finely divided form into the ceramic mass and applying the aqueous staining solution to the surface layer, or the aqueous staining solution with an adequate one to form the host lattice Amount of a soluble compound of the metal ions forming the host lattice is added and this mixture is applied to the surface, and after drying the solvent, the ceramic body at 300 to 1400 ° C. and a burning time of 0.5 to Burned for 5 hours.

2. The method according to claim 1, characterized in that the host lattice is a rutile lattice made of TiO ₂ , SnO ₂ . ZrÜ ₂ or ZrSiO ₄ is.

3. The method according to claim 1 or 2, characterized in that the host lattice is contained as a fine powder in an amount of 2 to 10%, in particular 5%.

4. The method according to any one of claims 1 to 3, characterized in that the host lattice is produced by one or more impregnations with a solution of a soluble compound of the metal ions forming the host lattice and drying.

5. The method according to any one of claims 1 to 4, characterized in that the coloring solution contains 1 to 10 wt .-%, preferably 5 to 8% of the respective metal compounds.

6. The method according to any one of claims 1 to 5, characterized in that the coloring compounds are selected from the groups Ni, Co and Cr and Sb, Nb and W.

7. The method according to any one of claims 1 to 6, characterized in that the coloring solution additionally contains mineralizers.

8. The method according to any one of claims 1 to 6, characterized in that the coloring solution additionally contains a complex-bound titanium, in particular potassium titanium oxalate.

9. The method according to any one of claim loder 2, characterized in that the impregnation solution to form the mixed phase pigment contains 1-3% of the tri- and pentavalent ions and 3-8% dihydroxybis (ammonium lactato) titanate.

10. Ceramic material produced according to one of claims 1 to 9.