TILES OR SLABS OF COMPACTED CERAMIC MATERIAL

Abstract

The disclosure relates to tiles or slabs comprising a fired ceramic material which has a chemical composition with a particular combination of oxides; to a method for the manufacture of said tiles or slabs; and to the use thereof for construction or decoration applications.

Claims

1. A tile or slab comprising a fired ceramic material, wherein the fired ceramic material has a length of at least 1.2 m and a width of at least 0.6 m, and has a chemical composition comprising a combination of oxides according to: TABLE-US-00014 SiO.sub.2 from 54.0 wt %-64.0 wt % Al.sub.2O.sub.3 from 17.5 wt %-23.0 wt % CaO from 2.7 wt %-6.8 wt % MgO from 1.0 wt %-5.5 wt % ZrO.sub.2 from 2.0 wt %-6.6 wt % based on the total weight of the fired ceramic material.

2. The tile or slab according to claim 1, wherein the weight percentage of ZrO.sub.2 ranges from 3.1 wt %-5.8 wt %, based on the total weight of the fired ceramic material.

3. The tile or slab according to claim 1, wherein a sum of the weight percentages of CaO+MgO ranges from 4.3 wt %-7.3 wt %, based on the total weight of the fired ceramic material.

4. The tile or slab according to claim 1, wherein the fired ceramic material has a chemical composition comprising one or more of: from 56.0 wt %-62.0 wt % of SiO.sub.2; from 18.3 wt %-22.3 wt % of Al.sub.2O.sub.3; from 3.2 wt %-5.5 wt % of CaO; and from 1.2 wt %-3.8 wt % of MgO; based on the total weight of the fired ceramic material.

5. The tile or slab according to claim 1, wherein the fired ceramic material has a chemical composition further comprising one or more of: from 1.5 wt %-3.8 wt % of Na.sub.2O; from 1.0 wt %-4.2 wt % of K.sub.2O; from 0.05 wt %-0.6 wt % of Fe.sub.2O.sub.3; and from 0.05 wt %-0.3 wt % of TiO.sub.2; based on the total weight of the fired ceramic material.

6. The tile or slab according to claim 1, wherein the fired ceramic material has a chemical composition comprising a combination of oxides according to: TABLE-US-00015 SiO.sub.2 from 56.0 wt %-62.0 wt % Al.sub.2O.sub.3 from 18.3 wt %-22.3 wt % CaO from 3.2 wt %-5.5 wt % MgO from 1.2 wt %-3.8 wt % ZrO.sub.2 from 3.1 wt %-5.8 wt % Fe.sub.2O.sub.3 from 0.05 wt %-0.6 wt % TiO.sub.2 from 0.05 wt %-0.3 wt % based on the total weight of the fired ceramic material.

7. The tile or slab according to claim 1, wherein the fired ceramic material comprises less than 10 wt % of mullite as crystalline phase based on the total weight of the fired ceramic material.

8. The tile or slab according to claim 1, wherein the fired ceramic material comprises at least 40 wt % of amorphous phase, based on the total weight of the fired ceramic material.

9. The tile or slab according to claim 1, wherein the fired ceramic material has a length of at least 2.4 m and a width of at least 1.2 m.

10. The tile or slab according to claim 1, wherein the tile or slab further comprises a layer or deposit of one or more of porcelain, glaze, engobe, ink, frit, and grit.

11. A kitchen or vanity countertop, kitchen splashback, shower tray, wall or floor covering, furniture cladding, tabletop, ventilated façade tile, stovetop, stair step, or fireplace made from the title or slab as according to claim 1.

12. A method for manufacturing the tile or slab according to claim 1, comprising: a) preparing discrete agglomerates of ceramic raw materials; b) shaping and compacting the agglomerates to provide a shaped and compacted material, the shaped and compacted material having a length of at least 1.2 m and a width of at least 0.6 m; and c) firing the shaped and compacted material with a temperature profile having a maximum between 1,100° C. and 1,300° C.; wherein the ceramic raw materials of step a) comprise: (i) from 25 wt %-45 wt % of clay materials, wherein the clay materials comprise one or more of kaolin, bentonite clays, fire clays, stoneware clays, ball clays, and mixtures thereof; and (ii) from 55 wt %-75 wt % of non-clay materials, wherein the non-clay materials comprise one or more of of feldspars, nepheline syenite, talc, corundum, quartz minerals, and mixtures thereof, based on the total weight of said ceramic raw materials; and wherein the non-clay materials (ii) comprise: from 4 wt %-12 wt % of a calcium containing material chosen from wollastonite, diopside, tremolite, garnet, and mixtures thereof, and from 2 wt %-10 wt % of a zirconium containing material comprising from 45 wt %-100 wt % of ZrO.sub.2, based on the total weight of the ceramic raw materials in a).

13. The method according to claim 12, wherein the non-clay materials (ii) comprise, based on the total weight of the ceramic raw materials, from 0 wt %-5 wt % of a quartz mineral with a quartz content higher than 70 wt %.

14. The method according to claim 12, wherein the compacting in step b) is performed by applying a pressure ranging from 350 kg/cm.sup.2-600 kg/cm.sup.2.

15. The method according to claim 12, further comprising providing a layer, deposit or a precursor thereof, of a glaze, pigment, engobe, grit, frit, ink or a combination thereof on the shaped and compacted material obtained after step b).

Description

EXAMPLES ACCORDING TO THE DISCLOSURE AND COMPARATIVE EXAMPLES

Example 1

[0157] One mixture A (with a composition comprising a combination of oxides according to the disclosure) and two different comparative mixtures B and C were similarly separately prepared by adding raw materials and water to a ball grinding mill and then collecting the slip formed after the mixtures are homogeneous and the particle size is predominantly under 63 micrometers (with a maximum of 1.0% of particles above this size). The slip mixtures were then partially dried to a humidity content of approximately 7.5 wt %, molded and pre-compacted with a pressure of 450 kg/cm.sup.2 to 100×50 mm.sup.2 shaped test samples with a thickness of 7.0 mm.

[0158] The raw materials of the mixtures A, B and C included clay materials in an amount of from 30 wt %-40 wt %, and non-clay materials in an amount from 60 wt %-70 wt %. The wt % did not consider any humidity or water content of the raw materials. The sum of clay and non-clay materials added up 100 wt %.

[0159] The clay materials comprised different amounts of bentonites, ball clays, and/or kaolins. The non-clay materials included different amounts of feldspars, talc minerals, and/or alumina. The clay and non-clay raw materials were commercially available products obtained from suppliers known to the skilled person. The amount of each raw material is adjusted, taking their compositions into account, to result in the fired composition after firing listed in Table 1 below.

[0160] Mixtures A, B and C comprised 5.0 wt %-6.0 wt % bentonite, related to the total weight of raw materials in those mixtures.

[0161] The raw materials for mixture A comprised also 7.0 wt %-8.0 wt % wollastonite, while mixtures B and C did not comprise any wollastonite. In the other hand, mixture A did not comprise any quartz mineral with a quartz content higher than 70 wt % (that is, a mineral mixture where quartz is predominant, such as quartz mineral or feldspathic sands), while mixtures B and C comprised from 3 wt %-10 wt % of feldspathic sand having from 80 wt %-85 wt % of quartz.

[0162] Mixture A comprised additionally 8.0 wt % of zircon, mixture B comprised 12.0 wt % of zircon, and mixture C comprised 17.0 wt % zircon.

[0163] The mixtures A, B and C comprised 3.5 wt %-5.0 wt % of talc, the talc comprising >30 wt % of MgO.

[0164] The molded test samples were then pressed with a pressure reaching 450 kg/cm.sup.2 before they were dried at 110° C. to decrease humidity content to <1.0% wt % and then, they were fired in a muffle furnace for 110 minutes reaching a maximum temperature of 1,190° C., resulting in corresponding fired test samples A, B and C.

[0165] The compositions of the fired test samples A, B and C obtained determined by XRF are depicted in table 1.

TABLE-US-00008 TABLE 1 Test sample Test sample Test sample B (wt %) C (wt %) Component A (wt %) comparative comparative SiO.sub.2 57.2 57.6 56.9 Al.sub.2O.sub.3 21.6 19.8 18.8 CaO 4.9 0.5 0.5 MgO 1.5 1.4 1.5 ZrO.sub.2 3.9 6.6 9.4 Fe.sub.2O.sub.3 0.3 0.3 0.3 TiO.sub.2 0.1 0.1 0.1 Na.sub.2O 2.4 2.2 2.1 K.sub.2O 3.0 3.2 3.3 Other oxides 0.3 0.5 0.5 L.O.I..sup.‡ 4.8 7.8 6.6 Ratio 2.6 2.9 3.0 SiO.sub.2/Al.sub.2O.sub.3 CaO + MgO 6.4 1.9 2.0 Fe.sub.2O.sub.3 + TiO.sub.2 0.4 0.4 0.4 .sup.‡Weight lost on ignition

[0166] The different crystalline phases formed during firing for the three test samples A, B and C, and their relative concentration, as measured by XRD are listed in Table 2.

TABLE-US-00009 TABLE 2 Test sample Test sample Test sample B (wt %) C (wt %) Phase A (wt %) comparative comparative Quartz [SiO.sub.2] 5.2%  9.9%  8.7% Zircon [ZrSiO.sub.4] 7.1% 11.3% 16.8% Anorthite 15.1%  — — [CaAl.sub.2Si.sub.2O.sub.8] Mullite [Al.sub.6Si.sub.2O.sub.13] — 14.1% 11.8% Albite [NaAlSi.sub.3O.sub.8] 6.4%  1.4% — Amorphous phase  66% .sup. 63% .sup. 63%

[0167] The XRD results in Table 2 evidence the differences in crystalline mineral phases formed during firing for the different compositions. The mullite phase goes from being majoritarian among the crystalline phases in test sample B, to being not measurable in test sample A. In exchange, the crystalline mineral phases dominant in test sample A are from mineral phases containing calcium.

[0168] Table 3 shows a comparison of properties of the test samples before and after firing:

TABLE-US-00010 TABLE 3 Test Test Test sample B sample C Parameter sample A comparative comparative Mechanical stability of 10.3 9.4 9.9 compacted sample before drying [kg/cm.sup.2] Mechanical stability of 40.7 39.5 42.1 compacted sample before firing [kg/cm.sup.2] Pyroplastic Index (PI) [cm.sup.−1] 3.4 × 10.sup.−5 6.2 × 10.sup.−5 6.8 × 10.sup.−5 Shrinkage during firing 6.8% 9.2% 9.8% Apparent density after firing 2.39 2.57 2.63 (ISO 10545-3: 2018) [g/cm.sup.3] Water absorption after firing ≤0.01% ≤0.01% ≤0.01% (ISO 10545-3: 2018) Breaking strength after firing 672 670 688 (ISO 10545-4: 2019) [kg/cm.sup.2] Colorimetry L* 89.29 88.78 90.80 a* −0.32 −0.01 0.18 b* 4.63 5.60 5.55

[0169] Compared with test samples B and C, the test sample A shows a significantly reduced apparent density after firing, together with an importantly lower firing shrinkage. The reduction in firing shrinkage is an advantage of great relevance when considering the industrial production of tiles in large format of more than 3.0 m length and 1.2 m width, where significantly more square meters of fired tiles can be obtained from unfired pressed tiles of same size with the composition of test sample A compared to B and C.

[0170] Without wanting to be bound by theory, it seems the formation of crystalline phases containing calcium and/or sodium during firing, which have a lower packing density than mullite and zircon, helps reducing the density and shrinkage of the test sample A compared to samples B and C.

[0171] Simultaneously, the decreased Pyroplastic Index for test sample A compared to B and C indicates a lower tendency to deformation of the molded sample during firing. This parameter is again of special relevance when considering the manufacture of large format tiles with thickness of up to 3.0 cm, where deformation during firing translates into defects and internal material stresses.

[0172] The advantages mentioned are obtained for test sample A, without the mechanical stability being compromised (either before or after firing), and while still achieving an outstanding whiteness and colorimetry. The water absorption in all three cases remains negligible, below 0.01%, indicating a nearly absent open porosity.

Example 2

[0173] Mixture D (with a composition comprising a combination of oxides according to the disclosure) and three different mixtures E, F and G were prepared following the same general process as for samples A-C.

[0174] Mixture D, E and F were prepared following what has been described above for Mixture A in Example 1, however, while mixture D (as mixture A) comprised about 3 wt %-5 wt. % of talc (having a MgO content of >30 wt %), mixtures E and F did not comprise any talc. Additionally, mixture F did not comprise any bentonite. Mixture D comprised about 8 wt % zircon, mixture E about 8.4 wt % zircon, and mixture F about 8.9 wt % zircon.

[0175] Mixture G comprised about 18 wt % of illitic clay, and about 10 wt % kaolin. Mixture G further comprised about 10 wt % feldspathic sand (having 80 wt %-85 wt % of quartz), about 5 wt % zircon, 2 wt % calcite, 10 wt % of a frit (having 26 wt % CaO, 12 wt % ZrO.sub.2, 55 wt % SiO.sub.2 and 2 wt % Al.sub.2O.sub.3 relative to the weight of the frit), and 45 wt % sodium feldspar. Different to Mixture D, Mixture G did not comprise any wollastonite, bentonite or talc. Mixture G comprised about 28 wt % clay materials and about 72 wt % of non-clay materials.

[0176] As in Example 1, molded test samples from mixtures D-G were pressed with a pressure reaching 450 kg/cm.sup.2 before they were dried at 110° C. to decrease humidity content to <1.0 wt % and then, they were fired in a muffle furnace for 110 minutes reaching a maximum temperature of 1,190° C., resulting in corresponding fired test samples D, E, F and G.

[0177] The compositions of the fired test samples D, E, F and G obtained determined by XRF are depicted in table 4.

TABLE-US-00011 TABLE 4 Test sample Test sample Test sample Test sample Component D (wt %) E (wt %) F (wt %) G (wt %) SiO.sub.2 60.2 61.4 59.6 64.9 Al.sub.2O.sub.3 20.6 21.7 22.0 17.8 CaO 3.8 3.8 4.1 4.4 MgO 1.9 0.3 0.2 0.2 ZrO.sub.2 4.7 4.8 5.2 4.1 Fe.sub.2O.sub.3 0.4 0.3 0.3 0.2 TiO.sub.2 0.1 0.1 0.1 0.3 Na.sub.2O 2.6 2.8 3.0 4.8 K.sub.2O 3.4 4.0 3.7 0.9 Other oxides 0.5 0.3 0.3 0.3 L.O.I..sup.‡ 1.8 0.5 1.5 2.1 Ratio 2.9 2.8 2.7 3.6 SiO.sub.2/Al.sub.2O.sub.3 CaO + MgO 5.7 4.1 4.3 4.6 Fe.sub.2O.sub.3 + TiO.sub.2 0.5 0.4 0.4 0.5 .sup.‡Weight lost on ignition

[0178] Table 5 shows a comparison of properties of the test samples D-G before and after firing:

TABLE-US-00012 TABLE 5 Test Test Test Test Parameter sample D sample E sample F sample G Mechanical stability 43.6 36.8 19.3 11.3 of compacted sample before firing [kg/cm.sup.2] Water absorption ≤0.01% 0.94% 3.2% 12.9% after firing at 1,190° C. (ISO 10545-3: 2018) Breaking strength 699 594 473 232 after firing (ISO 10545-4: 2019) [kg/cm.sup.2] Colorimetry L* 87.8 88.8 90.1 91.6 a* −0.03 0.6 0.86 0.4 b* 5.6 5.4 5.6 7.5

[0179] Test samples E, F and G present low concentration of MgO in their composition, since no talc or bentonite was used in their corresponding mixtures. Compared with test sample D, samples E-G show a marked reduction in the mechanical stability of the compacted sample before firing.

[0180] The mechanical stability of the unfired ceramic material is of critical importance especially when manufacturing large format slabs or tiles, i.e. with dimensions larger than 1.2 m×0.6 m. The large format compacted unfired ceramic material needs to be transported by belts, rollers, through different stations in the production line, before they are fired. Such stations between the press and the firing kiln normally include stations for application of layers (e.g. glazes, decorative layers), drying kilns, etc. A lower value of mechanical stability before firing means that the compacted unfired ceramic material is more prone to deform, crack or break during its transport, causing lower production efficiency and higher waste ratio.

[0181] Simultaneously, the test samples E-G present high values of water absorption and reduced mechanical strength against fracture. In contrast, the composition comprising a combination of oxides according to the disclosure (sample D) led to very low values of water absorption and high mechanical strength against fracture even when the firing was performed at a temperature lower than 1,200° C., which represents at least an economic advantage compared to other methods for manufacture that require higher temperatures.

[0182] In view of the low mechanical stability of the unfired ceramic material, and their reduced mechanical strength and elevated water absorption after firing, the compositions of mixtures E-G are considered not suitable for the industrial manufacture of tiles or slabs of large format.

Example 3

[0183] The formulations for the test sample A and comparative test sample B in Example 1 were employed as base for the manufacture at industrial scale of tiles of approximately 3.2 m length and 1.4 m width, and with a thickness of about 2 cm. Tiles A comprised a fired ceramic layer based on the formulation for the test sample A, while comparative Tiles B comprised a fired ceramic layer based on the formulation of the test sample B.

[0184] In the industrial production of the fired ceramic layers in Tiles A and B, the same basic steps as for the preparation of the test samples A and B were followed. However, in the industrial manufacture, after wet grinding of the raw materials in the ball mill, the slips were partially dried in an industrial spray-drier to obtain powders having a humidity content of 8.5% and with particle sizes predominantly<800 micrometers. The powders are then shaped by dispensing them as a uniform layer on a forming belt and pre-compacted before they are subjected to compaction to a pressure of at least 450 kg/cm.sup.2. The compacted (unfired) ceramic layer was cut to a length of 3.55 m and a width of 1.63 m, and were further dried until a humidity content of from 0.0 wt %-1.0 wt % was reached, before they were fired in a roller kiln reaching a maximum temperature of around 1,190° C. and a residence time at this maximum temperature of about 10 minutes-30 minutes.

[0185] Table 6 shows the average composition of the fired ceramic layer in the Tiles A and B obtained.

TABLE-US-00013 TABLE 6 Tiles B (wt %) Component Tiles A (wt %) comparative SiO.sub.2 59.8 60.8 Al.sub.2O.sub.3 20.4 20.3 CaO 4.1 0.5 MgO 2.0 1.4 ZrO.sub.2 4.8 6.8 Fe.sub.2O.sub.3 0.4 0.4 TiO.sub.2 0.1 0.1 Na.sub.2O 2.7 2.4 K.sub.2O 3.2 3.6 Other oxides 0.4 0.4 L.O.I. 2.1 3.3 Ratio SiO.sub.2/Al.sub.2O.sub.3 2.9 3.0 Sum CaO + MgO 6.1 1.9 Sum Fe.sub.2O.sub.3 + TiO.sub.2 0.5 0.5

[0186] The fired ceramic layer of Tile A had a length and width after firing of 3.34*1.52 m, while the fired ceramic layer of Tile B had a length and width of 3.24*1.47 m, meaning the fired ceramic layer of Tile A had a 6.6% surface increase in relation to the fired ceramic layer of Tile B.

[0187] The apparent density of the fired ceramic layer was 2.35 g/cm.sup.3 and 2.57 g/cm.sup.3 for Tile A and Tile B, respectively. In both cases of Tile A and Tile B, the water absorption of the fired ceramic layer was 0.01%.

[0188] Tiles A and B were cut at 90° and 45° angles with a CNC bridge saw provided with a commercial freshly sharpened disk appropriate for porcelain stoneware. The maximum speed was recorded, at which the disk can be moved as it cuts through the tile at 2400 rpm producing clean cuts, without chipping or tile cracking. While Tile B maximum cutting speed could not be increased beyond 0.8 m/min, since it would either chip or crack, Tile A could be cut to 1.3 m/min without problems.

[0189] In another example, Tiles A and B were cut at 90° C. using a CNC bridge saw provided with commercial unused disks appropriate for porcelain stoneware. The cuts were done at 2400 rpm, longitudinally along the length of the tile, and separated 2 cm apart. In total, cuts extended for more than 200 linear meters. While Tile B could not be cut at speeds over 0.8 m/min without the appearance of chipping or even fracture of the tile, the Tile A could be cut at speed of 1.6 m/min or even higher without presenting similar problems.