WO2009058746A1

WO2009058746A1 - Tile glaze

Info

Publication number: WO2009058746A1
Application number: PCT/US2008/081401
Authority: WO
Inventors: Jose Antonio Pascual Herrero; Adolfo Porcar Beltran; Maurizio Ragnetti; Juan Uso Villaneuva
Original assignee: Ferro Corporation
Priority date: 2007-11-01
Filing date: 2008-10-28
Publication date: 2009-05-07

Abstract

A tile glaze composition that can be applied to ceramic tile to form a neutral white glaze composition that does not yellow upon prolonged exposure to UV radiation The tile glaze composition according to the invention generally includes one or more glass components and optional additives Upon firing, the glass component(s) vitrify and form an opaque neutral white glaze that displays excellent physical durability and chemical resistance The glass component of the tile glaze composition includes, by weight, about 40- 80% SiO2, 5-25% CaO, 2-14% A1203, 3-12% TiO2, 0 1 -5% Sb203, and less than or about10% B203, 10% Na20, 10% K20, 6% MgO, and 5% ZrO2

Description

TILE GLAZE

BACKGROUND OF INVENTION [Para 1 ] Field of Invention

[Para 2] The present invention relates to a tile glaze composition and to tiles that have been glazed with the tile glaze composition. More particularly, the present invention relates to a tile glaze composition for forming a non- yellowing opaque white glaze layer on ceramic tile and to tiles that have been glazed with the tile glaze composition. [Para 3] Description of Related Art [Para 4] For the past ten years or so, glaze compositions containing titanium dioxide have been applied to and fired on ceramic tiles to produce a protective and aesthetically pleasing neutral white opaque vitreous glaze layer thereon. Unfortunately, in many cases the glaze layer formed on the ceramic tiles using such compositions has been observed to develop a yellowish appearance upon prolonged exposure to ultraviolet ("UV") radiation such as is present in sunlight. The yellowing of the neutral white opaque vitreous glaze layer on the ceramic tiles is aesthetically undesirable.

BRIEF SUMMARY OF THE INVENTION [Para 5] In view of the foregoing, the present invention is directed toward a tile glaze composition that can be applied to ceramic tile to form an opaque neutral white glaze layer that does not appreciably yellow upon prolonged exposure to UV radiation. The tile glaze composition according to the invention generally comprises a glass component, which is typically in the form of one or more glass frits, and one or more optional additives (as for instance ceramic inorganic raw materials). Upon firing, the glass component vitrifies to form a non-yellowing, opaque neutral white glaze layer on the ceramic tile that displays excellent physical durability and chemical resistance.

[Para 6] The glass component of the tile glaze composition according to the present invention comprises one or more glass frits and one or more optional additives (as for instance ceramic inorganic raw materials) that, collectively, comprise, by weight, from about 40% to about 80% Siθ2, from about 5% to about 25% CaO, from about 2% to about 14% AI2O3, from about 3% to about 1 2% by weight Tiθ2, from about 0.1 % to about 5% Sb2θ3, less than or equal to about 10% B2O3, less than or equal to about 10% Na2θ, less than or equal to about 1 0% K2O, less than or equal to about 6% MgO and less than or equal to about 5% by weight Zrθ2. The glass component can further comprise small amounts of other metal oxides, provided that such metal oxides do not adversely affect the desired non-yellowing properties of the glaze layer formed on the ceramic tile after firing. The present invention also provides tiles that have been glazed using the tile glaze composition.

[Para 7] The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed. DETAILED DESCRIPTION OF THE INVENTION [Para 8] Tile glaze compositions according to the present invention are particularly well-suited for application on ceramic architectural tiles where a long lasting glaze layer having a non-yellowing opaque neutral white appearance is desirable.

[Para 9] Tile glaze composition of the present invention comprises a glass component and one or more optional vehicles and/or additives. Preferably, the glass component comprises one or more glass frits, which provide, in total, a composition as shown in weight percent in Table 1 below (the "~" symbol in Tables 1 -3 means "about"):

TABLE 1

[Para 10] Table 2 lists components that can optionally also be present in the glass component of the tile glaze compositions according to the invention in the amounts shown in weight percentage as shown in Table 2:

TABLE 2

[Para 1 1 ] The presence of small amounts of Sb₂O₃ in the glass component is believed to be essential to the prevention of yellowing of the glaze layer upon prolonged exposure to UV radiation. Glaze layers formed from tile glaze compositions containing TiO₂ and small amounts of Sb₂O₃ tend not to yellow (measured as a color shift) upon prolonged exposure to UV radiation when compared with glaze layers formed from conventional tile glaze compositions that contain TiO₂, but no Sb₂O₃. [Para 1 2] The glass frit or frits that comprise the glass component may be prepared utilizing conventional glass and frit melting techniques. A conventional ceramic refractory, fused silica, or platinum crucible may be used to prepare the glass frit. Typically, selected oxides and/or other raw materials are smelted industrially at temperatures of from about 1400⁰C to about 1 55O°C, either in continuous kilns or in rotary kilns. The molten glass thus formed is then converted to glass frit by pouring the molten glass into water or onto water-cooled steel rollers. The size of the frit can be adjusted using conventional milling equipment. It will be appreciated that the step of producing the glass frit is not per se critical and that any of the various glass frit making techniques well-known to those skilled in the art can be employed.

[Para 1 3] The glass component comprises from about 70% to about 100% by weight of the solids portion of the tile glaze composition. More preferably, the glass component comprises at least 90% by weight of the solids portion of the tile glaze composition. The term "solids portion" as used in the specification and in the appended claims means that portion of the tile glaze composition that does not burn off or evaporate during firing. Thus, solids portion does not include volatile liquid vehicles, carriers or the like. [Para 14] It will be appreciated that the tile glaze composition may further include, in addition to optional vehicles and carriers, additive such as flocculants, antifoaming agents, deflocculants, binders, wetting agents and other mill additions that are commonly used in the preparation of tile glaze compositions. Although one of the primary benefits provided by the tile glaze composition according to the invention is the production of long lasting glaze layers having a non-yellowing opaque neutral white appearance, in alternative embodiments the tile glaze compositions according to the invention could contain ceramic pigments and thus exhibit a color other than white. [Para 1 5] When mill additions are present, the overall composition of the oxides in the solids portion of the glaze composition is preferably within the weight percent ranges shown in Table 3 below (where "Permissible" defines the broad range for the composition and "A", "B" and "C" define the parameters of certain preferred embodiments within the broad range):

TABLE 3 wt% Permissible A B C

SiO, -39 to -81 -49 to - -76 -52 to -73 -54 to - -71

CaO ~5 to ~25 -7 to - 22 -9 to -1 9 -1 1 to - -1 7

ALO. -2 to ~1 5 -4 to -1 4 -5 to -1 3 ~6 to - 1 2

TiO, -2 to -1 3 -3 to - 1 0 -4 to -9 -4 to - -7

SbA -0.05 to ~6 -0.1 to -5 -0.3 to -4 -0.5 to -2.5

BA -0.01 to -1 2 -0.1 to -1 0 -0.5 to -1 0 -0.5 to - -1 0

Na,0 -0.05 to -1 2 -0.05 to -1 0 -0.1 to -8 -0.1 to -6 κ,o -0.1 to -1 2 -0.1 to -1 0 -0.5 to -8 -1 to - -6

MqO -0.05 to -6 -0.07 tc -5 -0.1 to -4 -0.1 to -2

ZrO, -0.1 to -6 -0.1 to -5 -0.5 to -4 -0.5 to -3

[Para 16] The tile glaze composition of the present invention may be applied using any one of a variety of conventional application techniques. For example, the tile glaze composition may be applied wet or dry. Suitable application techniques include, for example, disk and bell applications, spraying, screen-printing, brushing and electrostatic application. It will be appreciated that the ceramic tile can go through a decoration step using any technology prior to and/or after glazing. [Para 1 7] The manner in which the tile glaze composition according to the invention is applied has significant bearing on the manner in which the tile glaze composition is formulated. For example, if the tile glaze composition is to be applied using a wet application technique, the solids portion of the tile glaze composition can be ball milled together with a suitable vehicle such as water, for example, to a fineness whereby from about 1 % to about 8% by weight of the resulting slip is retained on a 45 micron sieve. The resulting slip, which will typically comprise from about 30% to about 50% by weight of vehicle (typically water), is then in condition for application upon a green (i.e., "unfired") or once-fired ceramic tile body. It will be appreciated that milling fineness and the relative amount of vehicle utilized in the formation of the slip is not critical, and such variables can be adjusted to best accommodate the specific application technique being employed. [Para 1 8] When the tile glaze composition is intended for dry or electrostatic application, the tile glaze composition can be dry milled, granulated and/or pelletized. The tile glaze composition can also be wet milled and then dried to obtain a dry material suitable for dry application to a ceramic tile. Other additives, such as, for example, glues, binders, and organopolysiloxanes, may be employed in the dry system. Again, a particular milling fineness is not critical, meaning that the fineness of the material can be varied to optimize application of the tile glaze composition. [Para 1 9] The tile glaze composition according to the invention is preferably applied to engobed green ceramic architectural tiles at a rate of from about 0.25 to about 1 .5 kg/m², and more preferably at a rate of from about 0.4 to about 0.9 kg/m². It will be appreciated that the application rate is not critical, and can be varied to achieve a desired appearance on the fire glazed tile. The tile glaze composition according to the invention can also be applied to once-fired ceramic tile.

[Para 20] Generally, the tile glaze composition of the present invention matures at a firing temperature of from about 1 000⁰C to about 1 230⁰C. Thus, ceramic tile bodies having the glaze composition according to the invention applied thereon are typically fired for a period of from about 1 5 minutes to about 4 hours, and more preferably for a time of from about 25 to about 80 minutes. Firing times and kiln temperatures generally depend on the specific tile body, furnace conditions, and the size of the charge or load placed in the furnace or kiln. After application of the glaze, the tile can be decorated with any technology (e.g., screen printing, ink-jet, spray, decals, cylinder press and so on). Thus, it will be appreciated that the decoration can be applied to a fired glaze layer (in which the decoration is affixed in a second or third firing cycle) or to unfired ceramic tiles (e.g., using KERAjet printing equipment).

[Para 21 ] The present invention further provides a ceramic tile having at least one surface bearing a glaze layer that was formed by firing a tile glaze composition according to the invention on the ceramic tile as described. The ceramic tile can be an architectural tile. The glaze layer formed on the surface of the ceramic tile will exhibit an opaque, neutral white appearance that does not yellow upon prolonged exposure to sunlight and other sources of UV radiation. [Para 22] The following examples are intended only to illustrate the invention and should not be construed as imposing limitations upon the claims.

EXAMPLES

[Para 23] Unless otherwise indicated, all parts and percentages are by weight and all temperatures are in degrees Centigrade (⁰C). The ceramic tile bodies employed in the Examples were conventional in nature, composed principally of clay with silica, feldspar and other conventional additives included.

EXAMPLE 1

[Para 24] To prepare the glass frits, raw materials were mixed together in the amounts shown by weight percent in Table 4 below and melted in a kiln at a temperature above 1400⁰C but less than 1 55O°C. The molten glass was then poured into water to form frit flakes.

TABLE 4

EXAMPLE 2

[Para 25] Tile Glaze Compositions 1 , 2, 3, 4, 5 and 6 were prepared by ball milling the solids shown in parts by weight in Table 5 with water to form aqueous slips. The amount of water in each of the resulting aqueous slips was about 30 to 50 parts by weight, based on the entire weight of each slip (i.e., solids and water). Less than 1 part per weight of conventional aqueous milling additives (sodium carboxymethylcellulose, anti-flocculating, anti-settling agents and preservatives) was added to each slip, which were milled to a fineness of about 1 % to about 8% by weight being retained on a 45 micron sieve.

[Para 26] The final composition of Tile Glaze Compositions 1 , 2, 3, 4, 5 and 6 is shown by weight percent in Table 6 below: TABLE 6

EXAMPLE 3

[Para 27] Tile Glaze Compositions 1 , 2, 3, 4, 5 and 6 were separately applied to engobed conventional green ceramic tile bodies at a rate of 1 kg/m². The coated ceramic tiles were then subjected to a firing cycle of 45 minutes with a maximum temperature as set forth below:

Tile Glaze Compositions 1 and 2: 1 050⁰C ± 2O⁰C; Tile Glaze Compositions 3 and 4: 1 1 20⁰C ± 20⁰C; and Tile Glaze Compositions 5 and 6: 1 200°C ± 20°C [Para 28] After firing, the glazed ceramic tiles were permitted to cool to ambient room temperatures (about 25°C). The CIE*Lab color of the glaze layer formed on the ceramic tiles was measured using a sphere spectrophotometer X-Rite SP60.

[Para 29] The glazed tiles were then subjected to ultraviolet weathering using a QUV Accelerated Weathering Tester, which simulates the effect of sunlight using fluorescent UV lamps and simulates rain and dew through condensing humidity. The tester had 8 fluorescent lamps arranged in two banks of four lamps each, which produced UV radiation primarily in the region from 280 to 31 5 nm (approximating the shortest wavelengths found in sunlight at the Earth's surface). The test cycle used for the weathering testing was: 6 hours UV at 60⁰C and 4 hours condensation at 50 ⁰C during a total time of 24 hours.

[Para 30] Table 7 shows the color measurements using the CIE*Lab colorimetric system for the glaze layer formed on each tile using Tile Glaze Compositions 1 , 2, 3, 4, 5 and 6 before and after exposure to UV radiation. The results shown in Table 7 below show that the glaze layers formed by firing a tile glaze composition according to the invention (i.e., Tile Glaze Compositions 2, 4 and 6) does not yellow upon prolonged exposure to UV radiation as compared to tile glaze compositions that do not contain small amounts of Sb2U3 (i.e., Tile Glaze Compositions 1 , 3 and 5).

[Para 31 ] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and illustrative examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims

What is claimed is:

[Claim 1 ] A tile glaze composition for use in forming a non- yellowing, opaque, neutral white glaze layer on a ceramic body, the tile glaze composition comprising a solids portion comprising: a glass component, the glass component comprising one of more glass frits and optionally, additional ceramic raw materials as mill additions, said glass component comprising by weight, from about 40% to about 80% SiO₂, from about 5% to about 25% CaO, from about 2% to about 14% AI₂O₃, from about 3% to about 1 2% TiO₂, from about 0.1 % to about 5% Sb₂O₃, less than or equal to about 1 0% B₂O₃, less than or equal to about 1 0% Na₂O, less than or equal to about 10% K₂O, less than or equal to about 6% MgO and less than or equal to about 5% by weight ZrO₂;

[Claim 2] The tile glaze composition according to claim 1 wherein the glass component comprises one or more glass frits that, collectively, comprise by weight, from about 55% to about 70% SiO₂, from about 1 0% to about 20% CaO, from about 5% to about 1 1 % AI₂O₃, from about 3% to about 7% TiO₂, from about 0.

3% to about 3% Sb₂O₃, less than about 1 0% B₂O₃, less than about 6% Na₂O, from about 1 % to about 7% K₂O, less than or equal to about 4% MgO and less than or equal to about 5% by weight ZrO₂. [Claim 3] The tile glaze composition according to claim 1 wherein the glass component comprises one or more glass frits that, collectively, comprise by weight, from about 55% to about 70% Siθ2, from about 1 1 % to about 1 7% CaO, from about 6% to about 1 0% AI2O3, from about 4% to about 6% TiO₂, from about 0.5% to about 2% Sb₂O₃, less than about 1 0% B2O3, less than about 5% Na2θ, from about 1 % to about 6% K2O, less than or equal to about 2% MgO and less than or equal to about 2% by weight Zrθ2.

[Claim 4] The tile glaze composition according to claim 1 wherein the glass component further comprises, by weight, less than or equal to about 3% U2O, less than or equal to about 3% BaO, less than or equal to about 3% PbO, less than or equal to about 3% P2O5, less than or equal to about 6% ZnO, less than or equal to about 3% SrO, less than or equal to about 3% La2θ3, less than or equal to about 3% Snθ2, less than or equal to about 3% W2O3, less than or equal to about 0.06% Fe₂O₃ and less or equal to about 3% F.

[Claim 5] The tile glaze composition according to claim 1 wherein the solids portion further comprises one or more inorganic pigments separate from the glass component.

[Claim 6] A tile glaze composition for use in forming a non- yellowing, opaque, neutral white glaze layer on a ceramic body, the tile glaze composition comprising a solids portion comprising: a glass component; and mill additions; wherein the solids portion comprises, by weight, from about 39% to about 81 % SiO₂, from about 5% to about 25% CaO, from about 2% to about 1 5% AI₂O₃, from about 2% to about 1 3% TiO₂, from about 0.05% to about 6% Sb₂O₃, from about 0.01 % to about 1 2% B₂O₃, from about 0.05% to about 1 2% Na₂O, from about 0.1 % to about 1 2% K₂O, from about 0.05% to about 6% MgO, and from about 0.1 % to about 6% ZrO₂.

[Claim 7] The tile glaze composition according to claim 6 wherein the solids portion comprises, by weight, from about 49% to about 76% SiO₂, from about 7% to about 22% CaO, from about 4% to about 14% AI₂O₃, from about 3% to about 10% TiO₂, from about 0.1 % to about 5% Sb₂O₃, from about 0.1 % to about 10% B₂O₃, from about 0.05% to about 1 0% Na₂O, from about 0.1 % to about 1 0% K₂O, from about 0.07% to about 5% MgO, and from about 0.1 % to about 5% ZrO₂.

[Claim 8] The tile glaze composition according to claim 6 wherein the solids portion comprises, by weight, from about 52% to about 73% SiO₂, from about 9% to about 1 9% CaO, from about 5% to about 1 3% AI₂O₃, from about 4% to about 9% TiO₂, from about 0.3% to about 4% Sb₂O₃, from about 0.5% to about 10% B₂O₃, from about 0.1 % to about 8% Na₂O, from about 0.5% to about 8% K₂O, from about 0.1 % to about 4% MgO, and from about 0.5% to about 4% ZrO₂.

[Claim 9] The tile glaze composition according to claim 6 wherein the solids portion comprises, by weight, from about 54% to about 71 % SiO₂, from about 1 1 % to about 1 7% CaO, from about 6% to about 1 2% AI₂O₃, from about 4% to about 7% TiO₂, from about 0.5% to about 2.5% Sb₂θ3, from about 0.5% to about 1 0% B₂O₃, 0.1 % to about 6% Na₂O, from about 1 % to about 6% K₂O, from about 0.1 % to about 2% MgO, and from about 0.5% to about 3% ZrO₂.

[Claim 1 O]A ceramic tile comprising a fired ceramic body having a non-yellowing, opaque, neutral white glaze layer formed on at least a portion of a surface of the ceramic body, wherein the glaze layer is formed by firing a tile glaze composition on the portion of the surface of the ceramic body, and wherein the tile glaze composition comprises a solids portion comprising: a glass component, the glass component comprising one of more glass frits that, collectively, comprise, by weight, from about 40% to about 80% SiO₂, from about 5% to about 25% CaO, from about 2% to about 1 4% AI₂O₃, from about 3% to about 1 2% TiO₂, from about 0.1 % to about 5% Sb₂O₃, less than or equal to about 1 0% B₂O₃, less than or equal to about 1 0% Na₂O, less than or equal to about 1 0% K₂O, less than or equal to about 6% MgO, and less than or equal to about 5% by weight ZrO₂; and optionally, mill additions.

[Claim 1 l ]The ceramic tile according to claim 1 0 wherein the glass component comprises one or more glass frits that, collectively, comprise by weight, from about 55% to about 70% SiO₂, from about 1 0% to about 20% CaO, from about 5% to about 1 1 % AI₂O₃, from about 3% to about 7% TiO₂, from about 0.3% to about 3% Sb₂O₃, less than about 1 0% B₂O₃, less than about 6% Na₂O, from about 1 % to about 7% K₂O, less than or equal to about 4% MgO and less than or equal to about 5% by weight ZrO₂.

[Claim 1 2]The ceramic tile according to claim 1 0 wherein the glass component comprises one or more glass frits that, collectively, comprise by weight, from about 55% to about 70% SiO₂, from about 1 1 % to about 1 7% CaO, from about 6% to about 1 0% AI₂O₃, from about 4% to about 6% TiO₂, from about 0.5% to about 2% Sb₂O₃, less than about 1 0% B₂O₃, less than about 5% Na₂O, from about 1 % to about 6% K₂O, less than or equal to about 2% MgO and less than or equal to about 2% by weight ZrO₂.

[Claim 1 3]The ceramic tile according to claim 1 0 wherein the glass component further comprises, by weight, less than or equal to about 3% Li₂O, less than or equal to about 3% BaO, less than or equal to about 3% PbO, less than or equal to about 3% P₂θ5, less than or equal to about 6% ZnO, less than or equal to about 3% SrO, less than or equal to about 3% La₂O₃, less than or equal to about 3% SnO₂, less than or equal to about 3% W₂O₃, less than or equal to about 0.06% Fe₂O₃ and less or equal to about 3% F.

[Claim 14]The ceramic tile according to claim 1 0 wherein the solids portion further comprises one or more inorganic pigments separate from the glass component.

[Claim 1 5]A ceramic tile comprising a fired ceramic body having a non-yellowing, opaque, neutral white glaze layer formed on at least a portion of a surface of the ceramic body, wherein the glaze layer is formed by firing a tile glaze composition on the portion of the surface of the ceramic body, and wherein the tile glaze composition comprises a solids portion comprising: a glass component; and mill additions; wherein the solids portion comprises, by weight, from about 39% to about 81 % SiO₂, from about 5% to about 25% CaO, from about 2% to about 1 5% AI2O3, from about 2% to about 1 3% TiO₂, from about 0.05% to about 6% Sb₂O₃, from about .01 % to about 1 2% B₂O₃, from about 0.05% to about 1 2% Na₂O, from about 0.1 % to about 1 2% K₂O, from about 0.05% to about 6% MgO, and from about 0.1 % to about 6% ZrO₂.

[Claim 16]The ceramic tile according to claim 1 5 wherein the solids portion comprises, by weight, from about 49% to about 76% SiO₂, from about 7% to about 22% CaO, from about 4% to about 14% AI₂O₃, from about 3% to about 1 0% TiO₂, from about 0.1 % to about 5% Sb₂O₃, from about 0.1 % to about 1 0% B₂O₃, 0.05% to about 10% Na₂O, from about 0.1 % to about 1 0% K₂O, from about 0.07% to about 5% MgO, and from about 0.1 % to about 5% ZrO₂.

[Claim 1 7] The ceramic tile according to claim 1 5 wherein the solids portion comprises, by weight, from about 52% to about 73% SiO₂, from about 9% to about 1 9% CaO, from about 5% to about 1 3% AI₂O₃, from about 4% to about 9% TiO₂, from about 0.3% to about 4% Sb₂O₃, from about 0.5% to about 1 0% B₂O₃, 0.1 % to about 8% Na₂O, from about 0.5% to about 8% K₂O, from about 0.1 % to about 4% MgO, and from about 0.5% to about 4% ZrO₂.

[Claim 1 8]The ceramic tile according to claim 1 5 wherein the solids portion comprises, by weight, from about 54% to about 71 % SiO₂, from about 1 1 % to about 1 7% CaO, from about 6% to about 1 2% AI₂O₃, from about 4% to about 7% TiO₂, from about 0.5% to about 2.5% Sb₂O₃, from about 0.5% to about 1 0% B₂O₃, 0.1 % to about 6% Na₂O, from about 1 % to about 6% K₂O, from about 0.1 % to about 2% MgO, and from about 0.5% to about 3% ZrO₂.