Patent Application
20190338135
The invention relates to ceramic colours comprising effect pigments and a sol-gel based glassy matrix for decoration of metallic, ceramic and glassy articles and to a process for the preparation of a ceramic glaze.
In general, decorative applications in ceramic glazes use mixtures of pigments, for example effect pigments, and ceramic frits/frit mixtures. The firing temperature and the composition of the frit are determined by the article to be coated. Typical firing temperature ranges for different applications are for example:
enamel at 500-850° C.,
glass at 550-650° C.,
triple-fired crockery at 740-900° C.,
triple-fired tiles at 900-1150° C.,
single-fired crockery at 1000-1300° C.,
single-fired tiles at 1100-1250° C.
The temperature of the firing process has to be sufficiently high for the respective application to ensure that abrasion-resistant and closed coatings are made from the ceramic colour. The firing temperature is oriented towards the softening or melting temperature of the respective glass frit. The glass particles being present at the beginning soften then and form a continuous matrix and a smooth surface. Here the problem occurs that the pigments, in particular the representatives from the class of the pearlescent pigments, generally do not survive the aggressive conditions consisting of oxidic melt (frit components) and high temperatures during the firing process without damage.
It is known from the prior art that a significant loss in tinting strength and pearlescent effect must be expected on use of pearlescent pigments in ceramic or glassy coatings.
In order to prevent this, these pigments must either be encapsulated in additional protective layers, or alternatively the use of pearlescent pigments in this high-temperature area of application is limited to special combinations of pearlescent pigments and modified engobes or fluxes.
Efforts have therefore been made in the past to optimise the pearlescent effect in decorative applications on ceramic articles by application-technical modifications, e.g. varying particle form and size of frit particles, varying the chemical composition of frit particles or enhancing pigment concentration. Furthermore, efforts have been made to stabilise the effect pigments, in particular pearlescent pigments, by sheathing with insulating protective layers for such thermally and chemically extremely highly demanding applications of this type.
This is described in EP 3 159 380 A1, EP 220 509 A1, EP 307 771 A1, EP 307 771 A1, DE 39 32 424 C1, GB 2 096 592 A, U.S. Pat. Nos. 5,783,506, 4,353,991, EP 0 419 843 A1, CN 101462895A, and DE 198 59 420 A1.
These solutions known from the prior art, such as, for example, the encapsulation of the pigments, are complex in production, since a further process step for application of the protective layer must be carried out in production. In addition, disadvantageous effects, such as, for example, clouding of the glaze and colour changes in the pigment or poorer control of the colour effect in the application medium, may occur, depending on the composition of the protective layer.
The second approach by application-technical modifications such as pigment concentration, composition and form of frit particles always require a sufficiently high temperature to ensure film formation of the ceramic colour. A smooth and mechanically stable layer can be insured by a high alkali concentration of the frit or by a sufficiently high temperature. Both variants might negatively influence the effect pigment, tending to decompose under such harsh conditions.
EP 1 218 202 B1 describes the use of a pigments comprising sol-gel based colour for the preparation of fine printed circuit lines that do not melt away during a firing process using low process temperatures of 400-800° C.
The decoration of glass, glass ceramics or metallic work pieces at low process temperatures with mixtures comprising sol-gel derived systems, pigments and further components are described in the following patent applications: DE102012109808, WO 2013182356, WO 2013156617, DE102011050872, DE202011110029, DE102010045149, DE102010031866, EP 2223900, DE102008031426, DE102008031428, EP 1978055, DE102008020895, DE102005036427, DE102005018246, US 20050129959, DE 20005461.
Although several methods and mixtures are known in the state of the art, yet none of them serves all needs for forming ceramic glazes on ceramic, metallic or glasslike bodies like tiles or porcelain, especially not at firing temperatures between 700° C. and 1300° C. respectively on metallic bodies like enamel at firing temperatures between 450° C. and 850° C.
It was therefore the object of the present invention to provide a process for the preparation of ceramic glazes and to develop a ceramic colour containing pearlescent pigments which do not show the disadvantages of state of the art methods and compositions.
Surprisingly, it has now been found that by use of a ceramic colour comprising effect pigments and a sol-gel component in a process according to the invention, disadvantages of the combination of a particulate frit and pearlescent pigments can be avoided.
The invention therefore relates to a process for the preparation of a ceramic glaze and glazed articles comprising the following steps:
(a) preparing a ceramic colour by mixing at least one effect pigment based on flake-form substrates and/or at least one uncoated flake-form substrate with a refractive index R.I.>1.5, at least one sol-gel component, optionally a solvent, optionally a binder, optionally an absorptive ceramic pigment and optionally at least one additive,
(b) printing or coating the ceramic colour obtained in step (a) on a ceramic or metallic body,
(c) drying the ceramic or metallic body obtained in step (b),
(d) firing the ceramic or metallic body obtained in step (c) at a temperature in the range of 450° C.-1300° C.
The present invention preferably relates to a process for the preparation of a ceramic glaze and glazed articles wherein a ceramic colour comprising at least one effect pigment based on flake-form substrates and/or at least one uncoated flake-form substrate with a refractive index>1.5 and at least one sol-gel based component, and optionally a solvent, optionally a binder, optionally an absorptive ceramic pigment and optionally at least one additive is applied to a ceramic article and fired at a temperature≥700° C. respectively on a metallic body at a temperature≥450° C., preferably ≥500° C.
In ceramic colours according to the invention, effect pigments based on flake-form substrates as well as uncoated flake-form substrates with a refractive index>1.5 may be used alone or in combination with each other. Preferably, effect pigments based on flake-form substrates are used.
The present invention also relates to a ceramic colour comprising at least one sol-gel based component and at least one effect pigment based on flake-form substrates like e.g. synthetic mica flakes, natural mica flakes, glass flakes and silica flakes. Preferably the effect pigments are based on high-temperature-resistant flakes, such as, for example, Al2O3 flakes, SiC flakes, SixNyCz flakes (with x=0.5-1.0; y=0.25-0.5; z=0.25-0.5), B4C flakes, BN flakes, graphite flakes, TiO2 flakes, and Fe2O3 flakes, especially Al2O3 flake, SiC flakes, B4C flakes, BN flakes, graphite flakes, TiO2 flakes, and Fe2O3 flakes. Preferably, the proportion of effect pigment in the ceramic colour is at least 0.1% by weight based on the sol-gel component.
Flake-form substrates with refractive index larger than that of the applied ceramic glaze (approx. >1.5) can also be used or added in pure form (without any coating). In this case an attractive sparkle effect can be obtained. Preferably, uncoated flake-form substrates with R.I.>1.5 selected from the group consisting of Al2O3 flake, SiC flakes, SixNyCz (with x=0.5-1.0; y=0.25-0.5; z=0.25-0.5), flakes; B4C flakes, BN flakes, graphite flakes, TiO2 flakes, and Fe2O3 flakes are used, especially Al2O3 flake, SiC flakes, B4C flakes, BN flakes, graphite flakes, TiO2 flakes, and Fe2O3 flakes. The proportion of uncoated flake-form substrates in the ceramic colour may be at least 0.1% by weight based on the sol-gel component.
Surprisingly, the ceramic colours and the process according to the invention are suitable for the decoration of ceramic articles like tiles or porcelain at temperatures in the range of 700° C.-1300° C., preferably 720° C.-1150° C., in particular 740° C.-900° C. The ceramic colours and the process according to the invention are also suitable for the decoration of metallic articles like enamel at temperatures in the range of 450° C.-950° C., preferably 500° C.-900° C., in particular 550° C.-850° C.
It is an advantage of the present invention that the loss of pearlescent effect and tinting strength can be reduced. Preferably, a considerably strong pearlescent effect and a higher tinting strength can be achieved compared to methods of the state of the art.
Ceramic articles comprising a glaze made according to the invention can preferably provide the advantage that the desired optical effects are stable and accessible in a reproducible manner in high-temperature applications up to 1100° C.
The sol-gel component preferably consists of pre-hydrolysed alkoxides of at least one metal or semi-metal selected from rubidium, caesium, beryllium, magnesium, calcium, strontium, barium, boron, aluminum, silicon, vanadium, germanium, titanium, zirconium, tin, and zinc. Preferred sol-gel systems consist of pure or organo-functionalized metal-alkoxides and/or silicon compounds. Without limiting the general use of metal-oxide precursors the preferred metal-oxide precursors are selected from the group of metal-alkoxides.
Sol-gel components and the process for their preparation are known in the art. The glassy matrix-forming sol-gel components are preferably obtainable by partial hydrolysis and condensation of at least one metal-organic metal-oxide precursor. Preferred examples are alkoxysilanes, especially tetraethoxysilane (TEOS) and/or tetramethoxysilane and/or organofunctional silanes such as 3-aminopropyltriethoxysilane, preferably tetramethoxysilane and/or 3-aminopropyltriethoxysilane. But also pure or organo-functionalized alkoxymetallates may be used, preferably tetra-ethoxy-titanate, titanium(IV) i-propoxide, germanium(IV) ethoxide; lanthanum(III) i-propoxide; tin(IV) t-butoxide; vanadium (V) tri-i-propoxide; zirconium(IV) ethoxide. As known from literature in the sol-gel chemistry a wide variation of metal oxide precursors can be combined. By proper selection of the combination of metal-oxide precursors the final property of the ceramic glaze can be widely adjusted. The sol-gel system can be further modified by the addition of metal-halogenides like e.g. CaCl2, SnCl4 or CeCl3 or other metal salts, preferably CaCl2, SnCl4 or CeCl3. The final conversion into a glassy matrix takes place during the firing process.
Additionally, the ceramic colour may comprise binders for example silicon containing polymers or silicon containing resins. Commercial resins are for example available by Wacker under the tradename Silres® silicone resins or by Arkema under the tradename Synolac® silicone-modified alkyd resins. However, the selection of binder is generally not limited to silicon containing resins. As long as the compatibility between resin and sol-gel system is provided, all kinds of organic binders can be used, like e.g. polyester, polyurethane, epoxy, alkyd, acrylate etc.
Besides these components, the ceramic color may comprise further fillers, additives (e.g. dispersing additives, rheology additives, thickener, defoamer), solvents such as screen printing oils or ceramic absorptive pigments like e.g. green chromium-oxide pigments, black spinel pigments, buff-rutile-pigments, cadmium red and yellow, cobalt-blue pigments, commercially available by Shepperd or Ferro. Additives are available by BYK or other manufacturers. Examples for possible additives are: Aerosil fumed silica, Byk 405 solution of polyhydroxycarboxylic acid amides, Byk 410 solution of a modified urea, Mowital B 30 H Polyvinyl butyral (Kuraray), Crayvallac PA3 BA 20 Polyamide Paste (Arkema), Byk 065 Silicone defoamer, Koralision Entschäumer FG 100, TEGO Dispers 652 fatty acid derivative wetting/dispersing additive.
For the preparation of fine colour grids and relief-like prints on ceramic substrates by means of ceramic colours, use is made of screen printing oils, which prevent running of the colour pastes after printing and give rise to prints with sharp contours. Furthermore, screen printing oils ensure suitability of the ceramic colour for application on transfer printing paper. Examples of screening printing oil are the commercially available 221-ME and Screenprint Bulk 803035 MR by Ferro.
The proportion of effect pigment in the ceramic colour is preferably at least 0.1%, especially 0.1-99.9%, by weight based on the pre-ceramic sol-gel component. Further preferred ranges may be 0.1-98%, 0.5-95%, and 1-91% by weight based on the pre-ceramic sol-gel component. Especially in these embodiments of the invention, the preferred sol-gel components may be used.
The proportion of uncoated flake-form substrates in the ceramic colour may be the same as for the effect pigments.
Preferably, ceramic colours according to the invention comprise 0.1-99.9% by weight of at least one effect pigment and/or at least one uncoated flake-form substrate, 0.1-99.9% by weight of at least one sol-gel component, 0-50% by weight of at least one solvent, 0-90% by weight of at least one binder, 0-20% by weight of at least one additive, where percentages are based on the weight of the ceramic colour and total to 100%.
The temperature at which a closed and mechanically stable glassy film on the work piece is formed, lies preferably below the temperature that is necessary for usual methods by glass frits. Since in the process according to the invention the glass layer forms during the firing process and a temperature near the melting point of the glass can be avoided, there is no danger that the pigment decomposes at high temperatures in the oxidic melt and the pearlescent effect is lost.
Furthermore, this route helps to avoid aggressive and counterproductive alkali glass components. A certain amount of alkali is necessary for the state of the art methods to adopt the glass melting point to the respective temperature window of the firing process of the work piece to be coated.
This limitation does not exist for the ceramic colour according to the invention. As already described above the range of variation for the selection of the sol-gel components is very wide. Therefore, advantageously the temperature window can also be widely adjusted by the choice of sol-gel components and a high chromatic pearlescent effect or pure sparkle effect (when pure flakes of R.I.>1.5 are used) can be achieved in a much wider temperature range of firing temperature than by using classical particulate frits or glazes.
All known effect pigments are suitable for the invention, in particular pearlescent pigments (e.g. single or multilayered effect pigments of various oxides) and pure flakes of R.I.>1.5. The effect pigments may preferably be based on substrates selected from synthetic mica flakes, silica flakes, glass flakes, natural mica flakes and very particularly preferably based on high-temperature-resistant flakes, such as, for example, Al2O3 flakes, SiC flakes, SixNyCz flakes (with x=0.5-1.0; y=0.25-0.5; z=0.25-0.5), B4C flakes, BN flakes, graphite flakes, TiO2 flakes, and Fe2O3 flakes, especially Al2O3 flakes.
Finally, particularly high temperature stability is generally achieved if use is made of pearlescent pigments based on flake-form substrates which are stable at high temperatures. Examples which may be mentioned here are: corundum—Al2O3, carborundum—SiC, siliconcarbonitride—SiC, SixNyCz (with x=0.5-1.0; y=0.25-0.5; z=0.25-0.5), boron nitride—BN, graphite and haematite—Fe2O3.
It is also possible to employ pigment mixtures of pigments based on different substrates or pigment mixtures of pigments based of the same substrates or mixtures of pigments and pure flakes having different particle sizes. The composition of the above-mentioned blends may vary in their weight ratio. 10:1 to 1:10 mixtures are preferably employed, in particular 1:1 mixtures. Particular preference is given to mixtures consisting of substrate flakes having different particle sizes, in particular mixtures of S fraction (10-200 μm), N fraction (10-60 μm) and F fraction (5-25 μm), but also of F fraction (5-25 μm) and M fraction (1-15 μm).
The size of the base substrates is not crucial per se and can be matched to the particular application and desired target effect/target texture: for example, satin or strong sparkle.
In general, the flake-form substrates have a thickness of 0.05-5 μm, preferably 0.1-2 μm, in particular 0.1-1 μm. The size in the two other dimensions is usually 1-500 μm, preferably 1-250 μm and in particular 1-60 μm.
Uncoated flake-form substrates may be used in the ceramic colour according to the invention in same or similar embodiments like substrates used for the effect pigments.
The thickness of at least one individual layer on the base substrate of the pearlescent pigment is essential for the optical properties of the pigment, as already described in numerous patents and patent applications, for example in DE 14 67 468, DE 19 59 988, DE 20 09 566, DE 22 14 545, DE 22 15 191, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 11 602, DE 32 35 017 or also in further patent documents and other publications known to the person skilled in the art.
The pigment must have at least one optically active layer, preferably a high-refractive-index layer (for example TiO2, Fe2O3, SnO2, etc.). High-refractive-index layers here are taken to mean all layers which have a refractive index of n≥1.8, preferably of n≥2.0.
Suitable substrate flakes for the pearlescent pigments may be doped or undoped. If they are doped, the doping is preferably Al, N, B, Ti, Zr, Si, In, Sn or Zn or mixtures thereof. Furthermore, further ions from the group of the transition metals (V, Cr, Mn, Fe, Co, Ni, Cu, Y, Nb, Mo, Hf, Ta, W) and ions from the group of the lanthanides may serve as dopants.
In the case of Al2O3, the substrate is preferably undoped or doped with TiO2, ZrO2 or ZnO. The Al2O3 flakes are preferably corundum. Suitable Al2O3 flakes are preferably doped or undoped α-Al2O3 flakes, in particular TiO2-doped α-Al2O3 flakes. If the substrate is doped, the proportion of the doping is preferably 0.01-5.00% by weight, in particular 0.10-3.00% by weight, based on the substrate.
Suitable Al2O3 flakes have an equivalence diameter distribution according to which 90% of the particles are in the range 5-45 μm, preferably 5-40 μm.
The D50 values of the Al2O3 flakes are preferably in the range 15-30 μm, very particularly preferably in the range from 15-25 μm.
The D10 values are preferably in the range 5-15 μm, very particularly preferably in the range 6-10 μm.
Throughout the application, the D10, D50 and D90 values are determined using a Malvern MS 2000.
The thickness of the Al2O3 flakes is preferably 50-1200 nm preferably 150-800 nm and in particular 200-450 nm.
In a very particularly preferred embodiment, the thickness of the Al2O3 flakes is <500 nm, preferably 150-450 nm and in particular 150-400 nm.
The aspect ratio (diameter/thickness ratio) of the Al2O3 flakes is preferably 10-1000, in particular 50-500.
In a further preferred embodiment, the aspect ratio of the Al2O3 flakes is 30-200, in particular 50-150.
In a preferred embodiment, the flake-form substrate is coated with one or more transparent, semi-transparent and/or opaque layers comprising metal oxides, metal oxide hydrates, metal silicates, metal suboxides, metals, metal fluorides, metal nitrides, metal oxynitrides or mixtures of these materials. The metal oxide, metal oxide hydrate, metal silicate, metal suboxide, metal, metal fluoride, metal nitride or metal oxynitride layers or the mixtures thereof can have a low refractive index (refractive index<1.8) or a high refractive index (refractive index≥1.8). Suitable metal oxides and metal oxide hydrates are all metal oxides or metal oxide hydrates known to the person skilled in the art, such as, for example, aluminium oxide, aluminium oxide hydrate, silicon oxide, silicon oxide hydrate, iron oxide, tin oxide, cerium oxide, zinc oxide, zirconium oxide, chromium oxide, zirconium silicate ZrSiO4, mullite, titanium oxide, in particular titanium dioxide, titanium oxide hydrate and mixtures thereof, such as, for example, ilmenite or pseudobrookite. Metal suboxides which can be employed are, for example, the titanium suboxides (for example Ti2O3 or γ-Ti3O5). Suitable metal silicates are aluminium silicate, Mg silicate, C silicate or Ba silicate; mixed alkaline-earth metal silicates, such as, for example, Ca/Mg silicate, Zr silicate or mixtures of the said silicates. Suitable metals are, for example, chromium, aluminium, nickel, silver, gold, titanium, copper or alloys, and a suitable metal fluoride is, for example, magnesium fluoride. Metal nitrides or metal oxynitrides which can be employed are, for example, the nitrides or oxynitrides of the metals titanium, zirconium and/or tantalum. Metal oxide, metal, metal fluoride and/or metal oxide hydrate layers and very particularly preferably metal oxide and/or metal oxide hydrate layers are preferably applied to the support. Furthermore, multilayered structures comprising high- and low-refractive-index metal oxide, metal oxide hydrate, metal or metal fluoride layers may also be present, with high- and low-refractive-index layers preferably alternating. Particular preference is given to layer packages comprising a high-refractive-index layer and a low-refractive-index layer, where one or more of these layer packages may be applied to the support. The sequence of the high- and low-refractive-index layers here can be matched to the support in order to incorporate the support into the multilayered structure. In a further embodiment, the metal oxide, metal silicate, metal oxide hydrate, metal suboxide, metal, metal fluoride, metal nitride or metal oxynitride layers may be mixed or doped with colorants or other elements. Suitable colorants or other elements are, for example, inorganic coloured pigments, such as coloured metal oxides, for example magnetite, chromium(III) oxide or coloured pigments, such as, for example, Thenard's Blue (a Co/Al spinel) or elements, such as, for example, yttrium or antimony, and generally pigments from the structural class of the perovskites, pyrochlores, rutiles and spinels. Pearlescent pigments comprising these layers exhibit great colour variety with respect to their mass tone and may in many cases exhibit an angle-dependent change in colour (colour flop) due to interference.
In a preferred embodiment, the outer layer on the support is a high-refractive-index metal oxide. This outer layer may additionally be on the above-mentioned layer packages or, in the case of high-refractive-index supports, may be part of a layer package and consist, for example, of TiO2, titanium suboxides, Fe2O3, SnO2, ZnO, ZrO2, Ce2O3, CoO, Co3O4, V2O5, Cr2O3 and/or mixtures thereof, such as, for example, ilmenite or pseudobrookite.
The thickness of the metal oxide, metal oxide hydrate, metal silicate, metal suboxide, metal, metal fluoride, metal nitride or metal oxynitride layers or a mixture thereof is usually 3 to 300 nm and, in the case of the metal oxide, metal oxide hydrate, metal suboxide, metal fluoride, metal nitride or metal oxynitride layers or a mixture thereof, preferably 20 to 200 nm. The thickness of the metal layers is preferably 4 to 50 nm.
The optical layer preferably consists of TiO2, ZrO2, Fe2O3, Fe3O4, SnO2, ZnO, or mixtures or combinations thereof. The layer may be undoped or doped. Suitable dopants are, for example, alkaline-earth metals or compounds thereof, in particular calcium and magnesium. The doping proportion is generally a maximum of 5% by weight, based on the respective layer.
The optical layer is particularly preferably a TiO2 layer, an Fe2O3 layer, a TiO2/Fe2O3 mixed layer, a pseudobrookite layer (Fe2TiO5) or a combination of these layers in a multilayered system, such as, for example, TiO2—SiO2—TiO2 or Fe2O3-SiO2-Fe2O3.
The titanium dioxide may be present in the high-refractive-index coating in the rutile or anatase modification, preferably in the form of rutile. The processes for the preparation of rutile are described, for example, in the prior art in U.S. Pat. Nos. 5,433,779, 4,038,099, 6,626,989, DE 25 22 572 C2 and EP 0 271 767 B1. A thin tin oxide layer (<10 nm), which serves as additive in order to convert the TiO2 into rutile, is preferably applied to the substrate flakes before the TiO2 precipitation.
The thickness of the optically active layer is preferably in each case 30 to 350 nm, in particular 50 to 250 nm.
Pearlescent pigments based on flake-form substrates which are particularly preferred for the ceramic colour according to the invention are indicated below:
substrate flake+FeO2
substrate flake+Fe2O3
substrate flake+Fe3O4
substrate flake+TiO2/Fe2O3
substrate flake+FeTiO3
substrate flake+Fe2TiO5
substrate flake+ZrO2
substrate flake+ZnO
substrate flake+SnO2
substrate flake+Cr2O3
substrate flake+Ce2O3
substrate flake+TiOx (reduced), where x=1.50-1.95
substrate flake+TiO2+Fe2O3
substrate flake+TiO2+Fe3O4
substrate flake+Fe2O3+TiO2
substrate flake+TiO2+SiO2+TiO2
substrate flake+TiO2+SnO2+TiO2
substrate flake+TiO2+Al2O3+TiO2
substrate flake+Fe2O3+SiO2+TiO2
substrate flake+TiO2/Fe2O3+SiO2+TiO2
substrate flake+TiO2/Fe2O3+SiO2+TiO2/Fe2O3
substrate flake+TiO2/Fe2O3+SiO2+TiO2+TiO2/Fe2O3
substrate flake+TiO2+SiO2+TiO2/Fe2O3
substrate flake+TiO2+SiO2
substrate flake+TiO2+Al2O3
substrate flake+TiO2+MgO x SiO2+TiO2
substrate flake+Fe2O3+MgO x SiO2+TiO2
substrate flake+TiO2/Fe2O3+MgO x SiO2+TiO2
substrate flake+TiO2/Fe2O3+MgO x SiO2+TiO2/Fe2O3
substrate flake+TiO2/Fe2O3+MgO x SiO2+TiO2+TiO2/Fe2O3
substrate flake+TiO2+MgO x SiO2+TiO2/Fe2O3
substrate flake+SnO2+TiO2+SiO2+SnO2+TiO2
substrate flake+SnO2+TiO2+SnO2+TiO2
substrate flake+SnO2+TiO2+Fe2O3+SiO2+SnO2+TiO2+Fe2O3
substrate flake+Fe2O3+SnO2+TiO2
substrate flake+Fe2O3+SnO2+Fe2O3
substrate flake+TiO2+SnO2+TiO2
substrate flake+TiO2/Fe2O3+SnO2+TiO2
substrate flake+TiO2/Fe2O3+SnO2+TiO2/Fe2O3
substrate flake+SnO2+TiO2+Fe2O3+SnO2+TiO2+Fe2O3.
substrate flake+Fe2TiO5+SnO2+Fe2TiO5
substrate flake+Fe2TiO5+SiO2+Fe2TiO5
In a further preferred embodiment, a first low-refractive-index layer is firstly applied to the substrate flake. Low-refractive-index layer in this application is taken to mean a layer which has a refractive index of <1.8.
The low-refractive-index layer on the substrate is preferably selected from the group Al2O3, SiO2, zirconium silicate ZrSiO4, mullite 3Al2O3 x 2SiO2 or 2Al2O3 x SiO2 (sintered or fused mullite) or alkaline-earth metal silicate (MSiO3, where M=Mg2+, Ca2+, Sr2+ or Ba2+, or M2Si3O8, where M=Mg2+, Ca2+, Sr2+ or Ba2+).
Preferred pigments having a low-refractive-index layer (LRL) on the substrate surface are distinguished by the following structure:
substrate flake+LRL+TiO2
substrate flake+LRL+Fe2O3
substrate flake+LRL+Fe3O4
substrate flake+LRL+TiO2/Fe2O3
substrate flake+LRL+FeTiO3
substrate flake+LRL+Fe2TiO5
substrate flake+LRL+ZrO2
substrate flake+LRL+ZnO
substrate flake+LRL+SnO2
substrate flake+LRL+Cr2O3
substrate flake+LRL+Ce2O3
substrate flake+LRL+TiOx (reduced), where x=1.50-1.95
substrate flake+LRL+TiO2+Fe2O3
substrate flake+LRL+TiO2+Fe3O4
substrate flake+LRL+Fe2O3+TiO2
substrate flake+LRL+TiO2+SiO2+TiO2
substrate flake+LRL+TiO2+SnO2+TiO2
substrate flake+LRL+TiO2+Al2O3+TiO2
substrate flake+LRL+Fe2O3+SiO2+TiO2
substrate flake+LRL+TiO2/Fe2O3+SiO2+TiO2
substrate flake+LRL+TiO2/Fe2O3+SiO2+TiO2/Fe2O3
substrate flake+LRL+TiO2/Fe2O3+SiO2+TiO2+TiO2/Fe2O3
substrate flake+LRL+TiO2+SiO2+TiO2/Fe2O3
substrate flake+LRL+TiO2+SiO2
substrate flake+LRL+TiO2+Al2O3
substrate flake+LRL+TiO2+MgO x SiO2+TiO2
substrate flake+LRL+Fe2O3+MgO x SiO2+TiO2
substrate flake+LRL+TiO2/Fe2O3+MgO x SiO2+TiO2
substrate flake+LRL+TiO2/Fe2O3+MgO x SiO2+TiO2/Fe2O3
substrate flake+LRL+TiO2/Fe2O3+MgO x SiO2+TiO2+TiO2/Fe2O3
substrate flake+LRL+TiO2+MgO x SiO2+TiO2/Fe2O3
substrate flake+LRL+SnO2+TiO2+SiO2+SnO2+TiO2
substrate flake+LRL+SnO2+TiO2+SnO2+TiO2
substrate flake+LRL+SnO2+TiO2+Fe2O3+SiO2+SnO2+TiO2+Fe2O3
substrate flake+LRL+Fe2O3+SnO2+TiO2
substrate flake+LRL+Fe2O3+SnO2+Fe2O3
substrate flake+LRL+TiO2+SnO2+TiO2
substrate flake+LRL+TiO2/Fe2O3+SnO2+TiO2
substrate flake+LRL+TiO2/Fe2O3+SnO2+TiO2/Fe2O3
substrate flake+LRL+SnO2+TiO2+Fe2O3+SnO2+TiO2+Fe2O3
substrate flake+LRL+Fe2TiO5+SnO2+Fe2TiO5
substrate flake+LRL+Fe2TiO5+SiO2+Fe2TiO5
It is also possible to use different pearlescent pigments as a mixture in the ceramic colour according to the invention. Preferably, only one type of pearlescent pigment is employed.
Preferred embodiments of the invention comprise the preferred effect pigments and/or uncoated flake-form substrates and the preferred sol-gel components. Especially preferred are combinations wherein all components are used in their particularly preferred variants. Particularly preferred are combinations of preferred effect pigments and preferred sol-gel components in their preferred proportions. Formulations comprising such combinations and screen printing oils are also preferred.
Layer or coating in this application is taken to mean the complete covering of the flake-form substrate.
The pearlescent pigments can be prepared relatively easily. The covering of substrate flakes is preferably carried out by wet-chemical methods, where the wet-chemical coating methods developed for the preparation of pearlescent pigments can be used. Methods of this type are described, for example, in DE 14 67 468, DE 19 59 988, DE 20 09 566, DE 22 14 545, DE 22 15 191, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 11 602, DE 32 35 017 or also in further patent documents and other publications known to the person skilled in the art.
Furthermore, the coating of the substrates can also be carried out by gas-phase coating in a fluidised-bed reactor, where, for example, the processes proposed for the preparation of pearlescent pigments in EP 0 045 851 A1 and EP 0 106 235 A1 can be used correspondingly.
In the case of wet coating, the substrate particles are suspended in water, and one or more soluble metal salts are added at a pH which is suitable for hydrolysis, which is selected so that the metal oxides or metal oxide hydrates are precipitated directly onto the flakes without secondary precipitations occurring. The pH is usually kept constant by simultaneous metered addition of a base or acid. The pigments are subsequently separated off, washed and dried and optionally calcined, where the calcination temperature can be optimised with respect to the coating present in each case. In general, the calcination temperatures are between 250 and 1000° C., preferably between 350 and 900° C. If desired, the pigments can be separated off after application of individual coatings, dried and optionally calcined and then resuspended for precipitation of the further layers.
If, for example, a TiO2 or TiO2/Fe2O3 layer is to be reduced, the reduction of the finished pearlescent pigment is preferably carried out after drying by subsequently calcining the pigment at 500 to 1200° C., preferably at 500-1000° C., in particular at 500-800° C., for 0.5-5 h, preferably for 0.5-2 h, under reducing conditions, preferably under forming gas (N2/H2). On use of pigments which have been calcined under reducing conditions in the glaze, however, it has proven helpful likewise to select reducing conditions under the firing conditions for the workpiece to be glazed.
In order to improve the wettability and/or compatibility with the printing medium, it is frequently advisable, depending on the area of application, to subject the finished pearlescent pigment to inorganic or organic post-coating or post-treatment. Suitable post-coatings or post-treatments are, for example, the processes described in DE patent 22 15 191, DE-A 31 51 354, DE-A 32 35 017 or DE-A 33 34 598. This post-coating simplifies handling of the pigment, in particular incorporation into various media. In order to improve the wettability, dispensability and/or compatibility with the application media, functional coatings comprising organic or combined organic/inorganic post-coatings may be possible, for example with silanes, as described, for example, in DE 10348174, EP 0090259, EP 0 342 533, EP 0 632 109, EP 0 888 410, EP 0 634 459, EP 1 203795, WO 94/01498, WO 96/32446, WO 99/57204, WO 2004/092284, U.S. Pat. Nos. 5,759,255, 5,571,851, WO 01/92425 or in J. J. Ponjeé, Philips Technical Review, Vol. 44, No. 3, 81 ff. and P. H. Harding J. C. Berg, J. Adhesion Sci. Technol. Vol. 11 No. 4, pp. 471-493. The post-coating merely comprises a proportion by weight of 0.1 to 5% by weight, preferably 0.5 to 3% by weight, based on the pearlescent pigment.
In a particular embodiment of the invention, the pearlescent pigments are hydrophobically or amphiphilically post-coated, which, on application via printing pastes, results in the advantage of more homogeneous distribution in the print medium and thus more homogeneous colour distribution on the workpiece.
The invention expands the range of colours of pigmented ceramic glazes on fired or unfired bricks, floor and wall tiles for indoor or outdoor use, sanitary ceramics, such as bathtubs, washbasins and toilet pans, porcelain crockery, earthenware and ceramicware by attractive interference colours (silver, gold, bronze, copper, red, violet, blue, turquoise, green), and with so-called mass tone pearlescent pigments, which are distinguished by a combination of interference and absorption colour, in particular in the region of gold, brass, bronze, copper, red and green shades. It furthermore also facilitates entirely novel colour effects, such as viewing angle-dependent so-called colour flop effects. The choice of the pearlescent pigment furthermore facilitates novel optical effects, such as sparkle/glitter effects and coarse or fine structures.
The invention also relates to the use of the ceramic colour according to the invention for ceramic glazes on fired or unfired bricks, floor and wall tiles for indoor or outdoor use, sanitary ceramics, porcelain, enamel, metallic workpieces, earthenware and ceramicware. The ceramic colour can be applied onto the unglazed, the glazed or the glazed and fired body.
The invention also relates to the use of a ceramic colour according to the invention for the manufacture of decorative elements on articles exhibiting an outer surface of porcelain, china, bone china, ceramic, glass or enamel.
The invention thus also relates to formulations comprising the ceramic colour according to the invention. Especially mentioned are transfer media for transfer printing on workpieces described.
The invention also relates to glazed articles such as fired or unfired bricks, floor and wall tiles for indoor or outdoor use, sanitary ceramics, porcelain, enamel, metallic workpieces, earthenware and ceramicware comprising a ceramic glaze based on the ceramic colours according to the invention.
According to the invention, the ceramic colours can preferably be prepared by combining the pearlescent pigments with a respective amount of sol-gel component and printing medium. After homogenisation of the mixture, it can be applied to a workpiece by conventional methods. The ceramic colour may be applied as printed image in order to produce optical patterns or over a large area.
The ceramic colour obtained can be applied to workpieces by standard printing processes such as slip processes, spray application or transfer printing.
The ceramic colours are preferably applied by screen printing on ceramic articles. For flat surfaces direct printing can be used and for uneven surfaces transfer printing with transfer media can be used. In principal, the ceramic colour may be applied by all printing processes usable for the workpiece (i.e. ink-jet printing, thermoplastic transfer printing, flexographic printing, intaglio printing, tampon printing). Furthermore, the ceramic can also be applied by methods used for coating like spraying, by doctor blade, painting, dip coating, waterfall application. Especially in enamel techniques, dip or bath coating are also common. Preferred examples are screen printing in direct or transfer print. However, hand decoration by brush, stamping or by writing with a pencil can also be used.
After application of the ceramic colour, the coated workpiece can preferably be dried by heating in a drying cabinet or fume hood at temperatures in the range of 60-110° C. in order to evaporate the solvent present.
The printed or coated and dried ceramic articles are then fired at a temperature in the range of 700° C.-1300° C., preferably 800° C.-1200° C., in particular 850-1150° C.
The printed or coated and dried metallic articles are then fired at a temperature in the range of 450° C.-950° C., preferably 500° C.-900° C., in particular 550° C.-850° C.
The printed or coated and dried ceramic or metallic articles are then fired with firing cycles (heating+holding+cooling) of 0.5-72 hour, preferably 0.5-30 hours, in particular 0.5-3 hours.
Holding time itself varies from 1 minute-68 hours, preferably 1 min-25 hours, in particular 1 minute-2 hours.
Heating time itself varies from 0.2-36 hours, preferably 0.25-15 hours, in particular 0.25-4 hours.
Cooling time itself varies from 0.2-36 hours, preferably 0.25-15 hours, in particular 0.25-4 hours.
Preferably, the printed and dried articles are fired in a firing furnace by means of a temperature profile, for example:
180 min: heating to 1100° C.,
3 min: holding at 1100° C.,
120 min: rapid cooling to 600° C.,
300 min: slow cooling to room temperature.
Preferred embodiments of the invention comprise the components, especially the effect pigment and the sol-gel component, and/or the process conditions in their preferred, especially in their particularly preferred variants. Especially preferred are combinations wherein all components and features are in their particularly preferred variants.
The following examples are intended to explain the invention, but without limiting it.
For the preparation of ceramic colours, the effect pigments according to Examples 1 to 298 are weighed out and homogenised with the corresponding amount of sol-gel component having at solid content of 3.6% SiO2 and printing oil (221-ME Ferro). The so-gel-component is received by hydrolysis of TEOS.
The pearlescent pigments used in the examples are all commercially available and have the compositions listed in Table 2 (in the “Particle size” column, the d10-d90 value is measured using a Malvern is indicated in each case):
The printing paste obtained is applied to tiles by means of doctor blade and screen printing. In all cases, the printed tile is dried in a drying cabinet or fume hood at temperatures of 60-110° C. in order to evaporate the solvent present in the printing oil.
The printed and dried tiles are then fired in a firing furnace by means of a temperature profile in accordance with
180 min: heating to 1100° C.,
3 min: holding at 1100° C.,
120 min: rapid cooling to 600° C.,
300 min: slow cooling to room temperature.
The temperature programme as a function of time is depicted in
The glazed tiles of the examples according to the invention are distinguished by the fact that the desired optical effects are stable and accessible in a reproducible manner in respective high-temperature applications 500-1300° C.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.
The entire disclosures of all applications, patents and publications, cited herein and of corresponding Singapore application No. 10201803807.X, filed May 4, 2018, are incorporated by reference herein.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10201803807.X | May 2018 | SG | national |
