A high-white frit opal glaze containing zirconia or coexisting zirconia and zircon silicate and a preparation method thereof

Abstract

The present invention discloses a high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate and a preparation method thereof. The raw material composition of the high-white frit opacifying glaze is as follows: clay 2-11 wt%, potassium feldspar 10-30 wt%, quartz 5-30 wt%, zinc oxide 1-5 wt%, calcined talc 1-5 wt%, calcium carbonate 10-20 wt%, glass powder 2-8 wt%, zirconium silicate 2-8 wt%, phase separation agent 3-12 wt%; the phase separation agent is one or a combination of P2O5, TiO2, and B2O3. By introducing one or more phase separation agents P2O5 / TiO2 / B2O3 into the glaze to form a phase separation region, the present invention promotes the crystallization of zirconia while inhibiting its conversion to zirconium silicate, and finally obtains a low-zircon high-white opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate, achieving the purposes of cost savings, reduction of the radioactivity of the glaze, and improvement of the glaze surface properties.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic glazes, and particularly relates to a low-zirconium high-white frit opacifying glaze and a preparation method thereof. Background Art

[0002] Opacifying glazes can cover the poor coloring of the green body and expand the source of raw materials, and are widely used in the building ceramics and sanitary ceramics industries. The key to obtaining an opacifying effect with an opacifying glaze is the presence of a second phase in the glaze that is different in nature (especially refractive index) from the base glass, thereby causing phenomena such as light reflection, refraction, and diffuse scattering, resulting in the devitrification of the glaze layer.

[0003] Zircon-based opacifying glazes are the most widely used opacifying glazes in the ceramic industry at present. Their main opacifier is zirconium silicate (ZrSiO4) crystals. The refractive index of zirconium silicate is 1.94, which is greater than that of the base glass (1.50 - 1.55), so an ideal opacifying effect can be obtained. Moreover, the Mohs hardness of zirconium silicate is about 7.5, which can also endow the glaze surface with excellent mechanical properties. To achieve the desired opacifying effect, the addition amount of zirconium silicate generally needs to reach 12 - 20 wt%. However, due to the relatively scarce zircon resources in China, the price of zirconium silicate has increased significantly. In addition, the raw ore of zirconium silicate is often associated with radioactive impurities such as Ra 226 , K 40 and other radioactive impurities. When a large amount of zirconium silicate is added, the radioactivity of the product will exceed the standard, which is harmful to the health of consumers. Therefore, it is of great significance to develop low-zirconium or zirconium-free opacifying glazes that are environmentally friendly and have good opacifying effects.

[0004] According to the technological requirements, the opacifying glaze can be prepared by using raw glaze or fritted glaze. Among them, the raw glaze is obtained by directly mixing the raw materials according to the ratio and then ball-milling to obtain the glaze slurry for standby. The fritted glaze is prepared by pre-melting the uniformly mixed raw materials at a high temperature (≥1400 °C), pouring them into water for quenching to obtain frit, and then mixing the frit with certain raw materials such as clay, zinc oxide or calcium carbonate with good suspension in a certain proportion and ball-milling to obtain a glaze slurry with a certain particle size for standby. Since the fritted glaze is pre-melted at a high temperature, it can quickly melt and spread on the surface of ceramics or tiles when fired again on the surface of the green body, obtaining a more ideal decorative effect. Research shows that the whiteness and lightness of the zirconium-based opacifying glaze prepared by the fritted glaze are higher than those prepared by the raw glaze method. And further research finds that when preparing the zirconium-based opacifying glaze by the fritted glaze, zirconia (ZrO2) crystals will precipitate preferentially during the heating process, and when heating continues, ZrO2 will react with silica (SiO2) in the glaze to finally form zirconium silicate (ZrSiO4). Considering that the refractive index of ZrO2 is 2.13 - 2.20, which is higher than 1.94 of ZrSiO4, therefore, if the conversion of ZrO2 to ZrSiO4 can be inhibited and the crystal phase in the glaze is ZrO2 or the coexistence of ZrO2 and ZrSiO4, its whiteness will be higher than that of the glaze containing only ZrSiO4. This means that it is theoretically feasible to prepare a low-zirconium and high-whiteness opacifying glaze. However, it is also found in research that no matter whether the zirconium source in the glaze is ZrO2, ZrSiO4 or other zirconium salts (such as CaZrSiO6, ZnZrSiO6, etc.), it will be converted to ZrSiO4 after heat treatment. Therefore, it is technically difficult to prepare a glaze containing only zirconia (ZrO2) or the coexistence of zirconia and zirconium silicate (ZrSiO4), which is also the difficulty in preparing the low-zirconium and high-whiteness opacifying glaze at present. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a high-whiteness fritted opacifying glaze containing zirconia or the coexistence of zirconia and zirconium silicate. By introducing one or more phase separation agents P2O5 / TiO2 / B2O3 into the glaze to form a phase separation region, while promoting the crystallization of zirconia and inhibiting its conversion to zirconium silicate, a low-zirconium and high-whiteness opacifying glaze containing zirconia or the coexistence of zirconia and zirconium silicate is obtained, achieving the purposes of cost saving, reducing the radioactivity of the glaze, and improving the glaze surface performance. Another purpose of the present invention is to provide a preparation method for the above-mentioned high-whiteness fritted opacifying glaze containing zirconia or the coexistence of zirconia and zirconium silicate.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate, and the raw material composition thereof is: clay 2-11 wt%, potassium feldspar 10-30 wt%, quartz 5-30 wt%, zinc oxide 1-5 wt%, calcined talc 1-5 wt%, calcium carbonate 10-20 wt%, glass powder 2-8 wt%, zirconium silicate 2-8 wt%, phase separation agent 3-12 wt%; the phase separation agent is one or a combination of P2O5, TiO2, and B2O3.

[0008] Furthermore, the chemical composition of the high-white frit opacifying glaze of the present invention is SiO2 55-70%, Al2O3 5-13%, CaO 8-16%, MgO 0.5-4.5%, ZnO 1.5-6%, K2O 1-6%, Na2O 1-3%, ZrO2 1-7%, P2O5 / TiO2 / B2O3 3.5-14%.

[0009] Another object of the present invention is achieved by the following technical solutions:

[0010] The preparation method of the above-mentioned high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate provided by the present invention is characterized by including the following steps:

[0011] (1) Weigh the raw materials according to the above composition, and after dry or wet ball milling and mixing, obtain a mixed material;

[0012] (2) Heat the mixed material until it is fully melted, then pour it into water for quenching to obtain a frit; crush the frit and dry it to obtain frit particles;

[0013] (3) Mix 90-95 wt% of the frit particles and 5-10 wt% of the clay to obtain a mixed material; then add water, sodium carboxymethyl cellulose, and sodium tripolyphosphate to the mixed material, and after ball milling and sieving, obtain a glaze; add water to the glaze for adjustment to obtain a glaze slurry;

[0014] (4) Apply the glaze slurry to the surface of a green ceramic body or a bisque-fired ceramic body; after firing the obtained glazed body at a temperature of 1000-1250 °C, a high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate is obtained.

[0015] Furthermore, in step (2) of the preparation method of the present invention, the heating temperature of the mixed material is 1450-1550 °C; the particle size range of the frit particles is 0.1-150 μm. In step (3), the amounts of water, sodium carboxymethyl cellulose, and sodium tripolyphosphate are 50-60 wt%, 0.1-0.3 wt%, and 0.1-0.3 wt% of the mixed material respectively; the median diameter D50 of the glaze is 0.8-2.5 μm; the density of the glaze slurry is 1.50-1.80 g / cm 3, the flow rate is 22 to 32 s / 100 mL. In the step (4), when used for architectural ceramics, the firing temperature is 1000 to 1220 °C and the firing cycle is 40 to 80 min; when used for sanitary ceramics, the firing temperature is 1150 to 1250 °C and the firing cycle is 10 to 24 h.

[0016] In the above solution, the zirconia crystals contained in the high-white frit opacifying glaze prepared by the preparation method of the present invention are nearly spherical, with a size of 100 to 500 nm; the zirconium silicate crystals contained are needle-shaped or rod-shaped, and the aspect ratio is 12 to 20:1.

[0017] The present invention has the following beneficial effects:

[0018] (1) By introducing one or more phase separation agents P2O5 / TiO2 / B2O3 into the glaze, the present invention forms a SiO2-rich phase and a P2O5 / TiO2 / B2O3-rich phase in the glaze. On the one hand, the phase separation interface can reduce the nucleation barrier and promote the crystallization of ZrO2 at low temperature. On the other hand, due to the lack of SiO2 in the P2O5 / TiO2 / B2O3-rich phase, the reaction between ZrO2 and SiO2 to form ZrSiO4 will be inhibited; at the same time, the phase separation interface can also play a role of diffusion hindrance, preventing the migration of SiO2 from the SiO2-rich phase to the P2O5 / TiO2 / B2O3-rich phase, so that the ZrO2 crystals cannot be transformed or only partially transformed into ZrSiO4, and finally a low-zirconium high-white frit opacifying glaze containing only ZrO2 or coexisting ZrO2 and ZrSiO4 is obtained.

[0019] (2) The present invention uses a phase separation agent to form a phase separation region in the glaze, promoting the crystallization of zirconia while inhibiting its transformation into zirconium silicate, obtaining a low-zirconium high-white opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate, thereby saving costs and reducing the radioactivity of the glaze. At the same time, the high-hardness zirconia can also improve the hardness of the glaze surface, endow the glaze surface with excellent mechanical properties, and extend the service life of architectural ceramics and sanitary ceramics. The whiteness of the high-white frit opacifying glaze surface of the present invention is 72 to 82, the surface glossiness is 65 to 80°, and the hardness of the glaze surface measured by a Vickers hardness tester is 6.98 to 7.22 MPa.

[0020] (3) The preparation process of the present invention is simple and easy to operate, the product performance is stable, and it is suitable for industrial production. Description of the Drawings

[0021] The present invention will be further described in detail below in conjunction with the embodiments and the drawings:

[0022] Figure 1 is a high-white frit opacifying glaze coexisting zirconia and zirconium silicate prepared in Example 1 of the present invention ((a): XRD pattern; (b): SEM image);

[0023] Figure 2It is the high-white frit opacifying glaze containing only zirconia prepared in Example 3 of the present invention ((a): XRD pattern; (b): SEM image). Detailed implementation manners

[0024] Example 1:

[0025] 1. A high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate in this example, and its raw material composition is: clay 8wt%, potassium feldspar 28wt%, quartz 25wt%, zinc oxide 3wt%, calcined talc 3wt%, calcium carbonate 15wt%, glass powder 5wt%, zirconium silicate 7wt%, phase separation agent B2O3 6wt%. Its chemical composition is SiO2 62.0%, Al2O3 8.1%, CaO 9.2%, MgO 1.4%, ZnO 3.2%, K2O 2.8%, Na2O 1.6%, ZrO2 5.2%, B2O3 6.5%.

[0026] 2. A preparation method of a high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate in this example, and its steps are as follows:

[0027] (1) Weigh the raw materials according to the above composition, and obtain a mixture through dry mixing.

[0028] (2) Put the above mixture into an alumina crucible, heat it to 1550 °C and keep it warm for 1 h until it is fully melted, then pour it into water for quenching to obtain a frit; crush the frit and dry it to obtain frit particles with a particle size range of 0.1 - 100 μm.

[0029] (3) Mix 95wt% of the frit particles and 5wt% of clay to obtain a mixed material; then add water, sodium carboxymethyl cellulose, and sodium tripolyphosphate to the mixed material, and their dosages are 60wt%, 0.2wt%, and 0.2wt% of the mixed material respectively. Place it in a planetary ball mill for ball milling for 1 h, and obtain a glaze with a median diameter D50 of 2.5 μm after sieving; add water to the glaze for adjustment to obtain a glaze slurry with a density of 1.80 g / cm 3 and a flow rate of 32 s / 100 mL.

[0030] (4) Apply the above glaze slurry to the surface of a green building ceramic by the method of pouring glaze; put the glazed green body into a roller hearth kiln and fire it at a temperature of 1180 °C, and the firing cycle is 58 min, then a high-white frit opacifying glaze surface containing zirconia or coexisting zirconia and zirconium silicate is obtained.

[0031] The crystal phases existing in the high-white frit opacifying glaze surface obtained in this example are ZrO2 and ZrSiO4 (see Figure 1 ), the whiteness of the glaze surface is 78, the surface glossiness is 72°, and the hardness of the glaze surface measured by a Vickers hardness tester is 6.98 MPa.

[0032] Example Two:

[0033] 1. A high - white frit opacifying glaze containing zirconia or co - existing zirconia and zirconium silicate in this example has the following raw material composition: clay 8wt%, potassium feldspar 28wt%, quartz 25wt%, zinc oxide 3wt%, calcined talc 3wt%, calcium carbonate 15wt%, glass powder 5wt%, zirconium silicate 7wt%, phase - separating agent P2O5 + B2O3 (by mass ratio P2O5∶B2O3 = 2∶1) 6wt%. Its chemical composition is SiO2 62.0%, Al2O3 8.1%, CaO 9.2%, MgO 1.4%, ZnO 3.2%, K2O 2.8%, Na2O 1.6%, ZrO2 5.2%, P2O5 + B2O3 6.5% (P2O5 4.3%, B2O3 2.2).

[0034] 2. A preparation method of a high - white frit opacifying glaze containing zirconia or co - existing zirconia and zirconium silicate in this example is as follows:

[0035] (1) Weigh the raw materials according to the above composition, mix them dry to obtain a mixed material;

[0036] (2) Put the above - mentioned mixed material into an alumina crucible, heat it to 1500 °C and keep it for 1 h until it is fully melted, then pour it into water for quenching to obtain a frit; crush and dry the frit to obtain frit particles with a particle size range of 0.1 - 100 μm;

[0037] (3) Mix 95wt% of the frit particles and 5wt% of clay to obtain a mixed material; then add water, sodium carboxymethyl cellulose, and sodium tripolyphosphate to the mixed material, and their dosages are 60wt%, 0.3wt%, and 0.3wt% of the mixed material respectively. Place it in a planetary ball mill and ball - mill for 2 h, and then sieve it to obtain a glaze with a median diameter D50 of 1.1 μm; add water to this glaze for adjustment to obtain a glaze slurry with a density of 1.55 g / cm 3 and a flow rate of 24 s / 100 mL;

[0038] (4) Apply the above - mentioned glaze slurry to the surface of the green body of sanitary ceramics by spraying; put the obtained glazed body into a tunnel kiln and fire it at 1200 °C for 12 h to obtain a high - white frit opacifying glaze surface containing zirconia or co - existing zirconia and zirconium silicate.

[0039] The crystal phases existing in the high - white frit opacifying glaze surface obtained in this example are ZrO2 and ZrSiO4. The whiteness of the glaze surface is 72, the surface glossiness is 78°, and the hardness of the glaze surface measured by a Vickers hardness tester is 7.12 MPa.

[0040] Example Three:

[0041] 1. A high-white fritted opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate in this embodiment has the following raw material composition: clay 5wt%, potassium feldspar 30wt%, quartz 20wt%, zinc oxide 5wt%, calcined talc 5wt%, calcium carbonate 18wt%, glass powder 7wt%, zirconium silicate 5wt%, and phase separation agent P2O5 5wt%. Its chemical composition is SiO2 59.7%, Al2O3 7.3%, CaO 11.2%, MgO 2.2%, ZnO 5.5%, K2O 3.0%, Na2O 1.9%, ZrO2 3.7%, and P2O5 5.5%.

[0042] 2. A preparation method of a high-white fritted opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate in this embodiment is as follows:

[0043] (1) Weigh the raw materials according to the above composition, and obtain a mixed material through dry mixing.

[0044] (2) Put the above mixed material into an alumina crucible, heat it to 1500 °C and keep it warm for 1 h until it is fully melted, then pour it into water for quenching to obtain a frit; crush the frit and dry it to obtain frit particles with a particle size range of 0.2 - 90 μm.

[0045] (3) Mix 95wt% of the frit particles and 5wt% of clay to obtain a mixed material; then add water, sodium carboxymethyl cellulose, and sodium tripolyphosphate to the mixed material, with their dosages being 55wt%, 0.2wt%, and 0.2wt% of the mixed material respectively, place it in a planetary ball mill for ball milling for 1 h, and obtain a glaze with a median diameter D50 of 1.8 μm after sieving; add water to adjust this glaze to obtain a glaze slurry with a density of 1.50 g / cm 3 and a flow rate of 22 s / 100 mL.

[0046] (4) Apply the above glaze slurry to the surface of a green body of building ceramics by spraying; put the glazed green body into a roller hearth kiln and fire it at a temperature of 1120 °C for a firing cycle of 40 min to obtain a high-white fritted opacifying glaze surface containing zirconia or coexisting zirconia and zirconium silicate.

[0047] The crystal phase existing in the high-white fritted opacifying glaze surface obtained in this embodiment is ZrO2 (see Figure 2 ), the whiteness of the glaze surface is 77, the surface glossiness is 65°, and the hardness of the glaze surface measured by a Vickers hardness tester is 7.08 MPa.

[0048] Example 4:

[0049] 1. In this embodiment, a high-white fritted opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate has the following raw material composition: 8 wt% clay, 30 wt% potassium feldspar, 22 wt% quartz, 3 wt% zinc oxide, 3 wt% calcined talc, 15 wt% calcium carbonate, 5 wt% glass powder, 8 wt% zirconium silicate, and 6 wt% phase-separating agent P2O5 + B2O3 + TiO2 (by mass ratio P2O5∶B2O3∶TiO2 = 3∶2∶1). Its chemical composition is 60.8% SiO2, 8.4% Al2O3, 9.2% CaO, 1.4% MgO, 3.2% ZnO, 3.0% K2O, 1.6% Na2O, 5.9% ZrO2, and 6.5% P2O5 + B2O3 + TiO2 (3.2% P2O5, 2.2% B2O3, 1.1% TiO2).

[0050] 2. The preparation method of a high-white fritted opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate in this embodiment is as follows:

[0051] (1) Weigh the raw materials according to the above composition, and obtain a mixed material through dry mixing.

[0052] (2) Put the above mixed material into an alumina crucible, heat it to 1500 °C and keep it for 1 h until it is fully melted, then pour it into water for quenching to obtain a frit; after crushing and drying the frit, frit particles with a particle size range of 0.1 - 150 μm are obtained.

[0053] (3) Mix 92 wt% of the frit particles and 8 wt% of clay to obtain a mixed material; then add water, sodium carboxymethyl cellulose, and sodium tripolyphosphate to the mixed material, with their dosages being 58 wt%, 0.2 wt%, and 0.2 wt% of the mixed material respectively, and ball-mill in a planetary ball mill for 3 h. After sieving, a glaze with a median diameter D50 of 0.8 μm is obtained; add water to adjust this glaze to obtain a glaze slurry with a density of 1.51 g / cm 3 and a flow rate of 28 s / 100 mL.

[0054] (4) Apply the above glaze slurry to the surface of a green sanitary ceramic body by spraying; put the glazed body into a tunnel kiln and fire it at 1220 °C for 15 h to obtain a high-white fritted opacifying glaze surface containing zirconia or coexisting zirconia and zirconium silicate.

[0055] The crystal phases existing in the high-white fritted opacifying glaze surface obtained in this embodiment are ZrO2 and ZrSiO4. The whiteness of the glaze surface is 82, the glossiness is 80°, and the hardness of the glaze surface measured by a Vickers hardness tester is 7.22 MPa.

Claims

1. A preparation method of a high-white frit opacifying glaze containing zirconia crystals or coexisting zirconia crystals and zirconium silicate crystals, characterized in that: The raw material composition of the opacifying glaze is as follows: clay 2-11wt%, potassium feldspar 10-30wt%, quartz 5-30wt%, zinc oxide 1-5wt%, calcined talc 1-5wt%, calcium carbonate 10-20wt%, glass powder 2-8wt%, zirconium silicate 2-8wt%, phase separation agent 3-12wt%; the phase separation agent is one or a combination of P2O5, TiO2, and B2O3; the method includes the following steps: (1) Weigh the materials according to the above raw material composition, and obtain a mixture after dry or wet ball milling and mixing. (2) Heat the mixture until it is fully melted, then pour it into water for quenching to obtain frit; crush the frit and dry it to obtain frit particles. (3) Mixing is carried out according to 90-95 wt% of fritted particles and 5-10 wt% of clay to obtain a mixed material; then water, sodium carboxymethyl cellulose, and sodium tripolyphosphate are added to the mixed material, and after ball milling and sieving, a glaze is obtained; water is added to the glaze for adjustment to obtain a glaze slurry with a density of 1.50-1.80 g / cm 3 and a flow rate of 22-32 s / 100 mL; (4) Apply the glaze slurry on the surface of the green ceramic body or the bisque-fired ceramic body; the obtained glazed body is fired at a temperature of 1150-1250°C for a firing cycle of 10-24h. The opacifying glaze is used for sanitary ceramics; a SiO2-rich phase and a P2O5 / TiO2 / B2O3-rich phase are formed in the glaze. The phase separation interface can reduce the nucleation barrier and promote the crystallization of ZrO2 at low temperature. The phase separation interface can also act as a diffusion barrier to prevent the migration of SiO2 from the SiO2-rich phase to the P2O5 / TiO2 / B2O3-rich phase, so that the ZrO2 crystals cannot be transformed or only partially transformed into ZrSiO4, obtaining a high-white frit opacifying glaze containing zirconia or coexisting zirconia and zirconium silicate. The zirconia crystals contained are nearly spherical with a size of 100-500nm, and the zirconium silicate crystals contained are needle-shaped or rod-shaped with an aspect ratio of 12-20:1; the whiteness of the surface of the high-white frit opacifying glaze is 72-82, the surface glossiness is 65-80°, and the hardness of the glaze surface measured by a Vickers hardness tester is 6.98-7.22MPa.

2. The preparation method according to claim 1, characterized in that: In the step (2), the heating temperature of the mixture is 1450-1550°C; the particle size range of the frit particles is 0.1-150μm.

3. The preparation method according to claim 1, characterized in that: In the step (3), the dosages of water, sodium carboxymethyl cellulose, and sodium tripolyphosphate are 50-60wt%, 0.1-0.3wt%, and 0.1-0.3wt% of the mixture respectively; the median diameter D50 of the glaze is 1.1-2.5μm.

4. The preparation method according to claim 1, wherein: The chemical composition of the high-white frit opacifying glaze is SiO2 55-70%, Al2O3 5-13%, CaO 8-16%, MgO 0.5-4.5%, ZnO 1.5-6%, K2O 1-6%, Na2O 1-3%, ZrO2 1-7%, P2O5 / TiO2 / B2O3 3.5-14%.

Images