CERAMIC ARTICLE AND METHOD FOR PRODUCING SAME

Abstract

A ceramic article in the form of a sanitary, culinary or laboratory article, comprising a ceramic base body and also a fired glaze applied on said base body, the fired glaze comprising SiO2 at 45-55 mass %, Al2O3 at 6-12 mass %, ZnO at 15-35 mass %, and additionally PbO at 0.1-15 mass % and/or CuO at 0.025-2 mass % and/or Bi2O3 at 0.25-7 mass %.

Claims

1. A ceramic article in the form of a sanitary, culinary or laboratory article, comprising a ceramic base body and also a fired glaze applied on said base body, the fired glaze comprising SiO.sub.2 at 45-55 mass %, Al.sub.2O.sub.3 at 6-12 mass %, ZnO at 15-35 mass %, and additionally PbO at 0.1-15 mass % and/or CuO at 0.025-2 mass % and/or Bi.sub.2O.sub.3 at 0.25-7 mass %.

2. The ceramic article according to claim 1, wherein the PbO content is between 0.5-12 mass % and/or the CuO content is between 0.05-1.5 mass % and/or the Bi.sub.2O.sub.3 content is between 0.35-6 mass %.

3. The ceramic article according to claim 2, wherein the PbO content is between 0.75-10 mass % and/or the CuO content is between 0.075-1.25 mass % and/or the Bi.sub.2O.sub.3 content is between 0.5-5 mass %.

4. The ceramic article according to claim 3, wherein the PbO content is between 1-8 mass % and/or the CuO content is between 0.1-1 mass %.

5. The ceramic article according to claim 1, wherein either both PbO and CuO, but not Bi.sub.2O.sub.3, or Bi.sub.2O.sub.3, but not PbO and CuO, are included.

6. The ceramic article according to claim 1, wherein the ZnO content is between 18-32 mass %.

7. The ceramic article according to claim 6, wherein the ZnO content is between 20-30 mass %.

8. The ceramic article according to claim 7, wherein the ZnO content is between 22-28 mass %.

9. The ceramic article according to claim 1, wherein the glaze has a layer thickness between 0.1-3 mm.

10. The ceramic article according to claim 9, wherein the layer thickness is between 0.5-1 mm.

11. A method for producing a ceramic article according to claim 1, comprising the following steps: providing a ceramic base body which is unfired or has undergone preliminary firing, applying a glaze coating using a slip comprising a lead frit containing at least 80 mass % of PbO, at 0.12-18 mass % and/or CuO powder at 0.025-2 mass % and/or Bi.sub.2O.sub.3 powder at 0.25-7 mass %, and carrying out firing to form a fired glaze at a temperature of 1100-1350 C.

12. The method according to claim 11, wherein a slip comprising lead frit at 0.6-14.4 mass % and/or CuO powder at 0.05-1.5 mass % and/or Bi.sub.2O.sub.3 powder at 0.35-6 mass % is used.

13. The method according to claim 12, wherein a slip comprising lead frit at 0.9-12 mass % and/or CuO powder at 0.075-1.25 mass % and/or Bi.sub.2O.sub.3 powder at 0.5-5 mass % is used.

14. The method according to claim 13, wherein a slip comprising lead frit at 0.12-9.6 mass % and/or CuO powder at 0.1-1 mass % is used.

15. The method according to claim 11, wherein a slip is used in which either both PbO and CuO, but not Bi.sub.2O.sub.3, or Bi.sub.2O.sub.3, but not PbO and CuO, are included.

16. The method according to claim 11, wherein a slip comprising ZnO at 18-32 mass % is used.

17. The method according to claim 16, wherein a slip comprising ZnO at 20-30 mass % is used.

18. The method according to claim 17, wherein a slip comprising ZnO at 22-28 mass % is used.

19. The method according to claim 11, wherein the glaze coating is applied with a layer thickness between 0.1-3 mm.

20. The method according to claim 19, wherein the layer thickness is between 0.5-1 mm.

21. The method according to claim 11, wherein the glaze coating is applied in a printing, more particularly screen printing, casting, injecting, spraying, spreading or dipping process or in a combination of at least two of the stated processes.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0038] In the drawing:

[0039] FIG. 1 shows a table for illustrating the antibacterial effect of three test bodies containing ZnO, PbO and CuO, where the PbO content is varied and the ZnO and CuO content is substantially constant,

[0040] FIG. 2 shows a table for illustrating the antibacterial effect of three test bodies containing ZnO, PbO and CuO, where the CuO content is varied and the ZnO and PbO content is substantially constant, and

[0041] FIG. 3 shows a table for illustrating the antibacterial effect of all the test bodies including a standard glaze without ZnO, PbO, CuO, a comparative glaze based on the standard glaze but additionally containing ZnO, and a particularly effective glaze containing ZnO, PbO and CuO.

DETAILED DESCRIPTION OF THE INVENTION

[0042] A series of inventive glazes and comparative glazes were produced as part of the experimental procedure outlined below.

[0043] Each test body consisted of a ceramic base body in the form of a ceramic plate, which was then coated in a spraying process with a slip made up accordingly and produced in accordance with the glaze composition to be investigated. The test bodies were then each fired in an oxidizing atmosphere at a temperature of approximately 1280 C. for a time of 19 hours.

[0044] The individual test bodies were subsequently investigated for the antimicrobial activity of the respective glaze applied, in accordance with the JIS Z 2801: 2010 test standard Antibacterial productsTest for antibacterial activity and efficacy. As part of the investigation, a defined amount of Escherichia coli test microbes was applied to each glaze surface. The same quantity of test microbes was also applied to the glass surface of a glass body. Both bodies were incubated under defined test conditions for 24 hours. This was followed by a count of the number of colony-forming units on both test surfaces (glaze surface and glass surface). Addition of the amount of the reduction rate of microbes on the glaze surface to the amount of the growth rate of the microbes on the glass area gives the reduction rate, which is expressed in log.sub.10 steps. One log.sub.10 step corresponds to the reduction of the microbes by one power of ten. An antibacterial effect is said to be present when the reduction is 2 log.sub.10 steps or more; a reduction of 5 log.sub.10 steps or more is referred to as disinfection.

[0045] First of all, a standard glaze SG without ZnO, PbO, CuO and Bi.sub.2O.sub.3 was prepared. The slip contained the following raw materials:

TABLE-US-00001 Raw material mass % Quartz 29.10 Calcium carbonate 21.30 Feldspar 17.80 Chamotte 12.50 Zirconium silicate 10.50 Glass frit 4.60 Kaolin 4.20

[0046] The raw materials listed were used to prepare a slip, for which the raw materials are dispersed in water.

[0047] This slip was applied by spraying to a ceramic base body in plate form which had been subjected to preliminary firing (prefired), the layer thickness being approximately 1 mm. The sample body was then fired at approximately 1280 C. for 19 h in order to form the fired glaze.

[0048] The composition of the fired standard glaze SG was as follows:

TABLE-US-00002 Oxide mass % SiO.sub.2 62.61 Al.sub.2O.sub.3 11.50 TiO.sub.2 0.16 Fe.sub.2O.sub.3 0.21 CaO 12.60 K.sub.2O 0.43 MgO 1.11 Na.sub.2O 2.58 B.sub.2O.sub.3 (ICP) 0.53 P.sub.2O.sub.5 0.05 SrO 0.02 ZnO 0.03 ZrO.sub.2 8.00 HfO.sub.2 0.16

[0049] The differences relative to the initial weighings derive, as is known, from a certain loss on ignition during firing.

[0050] This standard glaze SG was then investigated for its antibacterial effect on the basis of the JIS test. Following evaluation of the test, a reduction in the formation of test microbes on the standard glaze SG of around 0.76 log.sub.10 steps was found, this being synonymous with no antibacterial effect at all. This means that the standard glaze SG without ZnO or one of the other stated metal oxides has no antimicrobial properties.

[0051] A further comparative glaze HG1 was then prepared. The relevant slip was produced from the following raw materials:

TABLE-US-00003 Raw materials mass % Quartz 32.72 Chamotte 8.71 Kaolin 4.24 Calcium carbonate 6.56 Dolomite 1.90 Zinc oxide 26.40 Glass frit 2.86 Tin oxide 0.62 Feldspar 6.83 Zirconium silicate 9.16

[0052] This slip as well was then applied by spraying to a prefired ceramic body, with the layer thickness here again being approximately 1 mm. The sample body was subsequently fired.

[0053] The composition of the fired glaze HG1 was as follows:

TABLE-US-00004 Oxide mass % SiO.sub.2 50.17 Al.sub.2O.sub.3 7.25 TiO.sub.2 0.10 Fe.sub.2O.sub.3 0.16 CaO 4.52 K.sub.2O 0.33 MgO 0.50 Na.sub.2O 5.62 B.sub.2O.sub.3 (ICP) 0.84 Li.sub.2O (ICP) 0.05 P.sub.2O.sub.5 0.02 SnO.sub.2 0.61 ZnO 24.00 ZrO.sub.2 5.74 HfO.sub.2 0.10

[0054] The differences relative to the initial weighings derive, as is known, from a certain loss on ignition during firing.

[0055] This glaze as well, already improved through the addition of ZnO, was subjected to the JIS test. An antibacterial effect emerged which was already good. A test microbe reduction by 3.82 log.sub.10 steps was measured.

[0056] A test body with a glaze HG2 was then produced, originating from a slip in accordance with the glaze HG1 in its raw materials composition. This slip was admixed with PbO at approximately 5 mass %, in the form of a lead frit containing at least 80% PbO. The CuO was added in the form of CuO powder at 0.25 mass %. The fractions of the other slip raw materials were reduced accordingly, the reduction taking place in particular in relation to the quartz.

[0057] The slip prepared was sprayed onto a prefired ceramic base body, the layer thickness being approximately 1 mm. The test body was subsequently fired in order to form the fired glaze.

[0058] The composition of the glaze HG2 was as follows:

TABLE-US-00005 Oxide mass % SiO.sub.2 48.87 Al.sub.2O.sub.3 7.12 TiO.sub.2 0.10 Fe.sub.2O.sub.3 0.15 CaO 4.44 K.sub.2O 0.31 MgO 0.53 Na.sub.2O 2.16 B.sub.2O.sub.3 (ICP) 0.84 Li.sub.2O (ICP) 0.04 CuO 0.24 P.sub.2O.sub.5 0.05 SnO.sub.2 0.64 ZnO 24.79 ZrO.sub.2 5.79 HfO.sub.2 0.09 PbO 3.86

[0059] The differences relative to the initial weighings derive, as is known, from a certain loss on ignition during firing.

[0060] For this test body as well, its antibacterial activity was then ascertained in accordance with the JIS standard test. The glaze of the invention, or its surface, displayed an outstanding antibacterial quality. A test microbe reduction of 6.9 log.sub.10 steps was ascertained. The activity was a massive improvement on the HG1 glaze, which already displays good antibacterial properties. The glaze layer produced exhibits not only an antibacterial but also a disinfectant effect. Consequently, no microbes at all were found any longer on the glazed surface.

[0061] This means that, evidently, a combination of PbO and CuO in a ZnO-containing glaze exhibits outstanding antibacterial and disinfectant properties, respectively.

[0062] In order to clarify the effect of a varying PbO content, three different slips were prepared, again starting from the raw materials batch as per the HG1 glaze.

[0063] These slips were each admixed with a constant CuO content of approximately 0.25 mass %. The PbO fraction, however, varied. It was approximately 1 mass % in the first glaze slip HG-P1, approximately 2 mass % in the second slip HG-P2, and approximately 8 mass % in the third glaze slip HG-P3. The fractions of the other raw materials, particularly of the quartz, were adapted accordingly.

[0064] The respective slips were applied in turn by spraying to a prefired ceramic test body, in each case with a layer thickness of 1 mm. The test bodies were subsequently fired in order to produce three different glazes HG-P1, HG-P2 and HG-P3.

[0065] The compositions of the fired glazes HG-P1, HG-P2 and HG-P3 were as follows:

TABLE-US-00006 Oxide HG-P1 mass % HG-P2 mass % HG-P3 mass % SiO.sub.2 49.54 49.58 48.14 Al.sub.2O.sub.3 8.85 8.67 7.47 TiO.sub.2 0.10 0.10 0.10 Fe.sub.2O.sub.3 0.15 0.15 0.15 CaO 5.12 4.83 4.51 K.sub.2O 0.31 0.31 0.31 MgO 0.53 0.53 0.53 Na.sub.2O 2.16 1.93 2.08 B.sub.2O.sub.3 (ICP) 0.84 0.82 0.87 Li.sub.2O (ICP) 0.04 0.05 0.04 CuO 0.24 0.26 0.25 P.sub.2O.sub.5 0.05 0.05 0.05 SnO.sub.2 0.64 0.68 0.61 ZnO 24.79 24.52 23.21 ZrO.sub.2 5.79 5.84 5.43 HfO.sub.2 0.09 0.09 0.09 PbO 0.77 1.59 6.16

[0066] The respective glazes or test bodies were then again subjected to the JIS test for determining the antibacterial effect. The values ascertained were as follows:

TABLE-US-00007 Glaze log.sub.10 steps HG-P1 4.7 HG-P2 5.8 HG-P3 6.7

[0067] The results are illustrated in FIG. 1 in the form of a diagram.

[0068] It is seen that an increase in the PbO content leads to an improvement in the reduction performance and hence in the disinfection performance. It is found that at and above a relatively low PbO fraction of just approximately 2 mass %, a log.sub.10 step significantly greater than 5 is achieved, and therefore there is already a disinfectant effect even with a low PbO fraction and likewise a low CuO fraction.

[0069] The results, moreover, correlate very well with the result for the glaze HG2, for which approximately 5 mass % of PbO and 0.25 mass % of CuO were weighed out and a reduction rate of 6.9 log.sub.10 steps was found.

[0070] A further increase in the PbO fraction to approximately 8 mass % in the slip did not lead to a further increase in the reduction rate, with the reduction capacity instead remaining virtually constant, at 6.7 log.sub.10 steps.

[0071] In order to shed further light on the properties of PbO and CuO, in the next step, three sample bodies with constant PbO content but varying CuO content were produced.

[0072] The starting point again was the slip batch as per the HG1 glaze. Each slip of the various sample bodies contained PbO at approximately 4 mass %. The CuO content of the slip varied: in the slip of the first sample body, it was approximately 0.1 mass %, in the slip of the second sample body approximately 0.5 mass %, and in the slip of the third sample body approximately 1 mass %.

[0073] Therefore, three different slips were made up, each with varying CuO content but constant PbO content.

[0074] The three different slips were then again sprayed onto a prefired ceramic base body, with a layer thickness of approximately 1 mm. The sample bodies were subsequently fired in order to form the respective fired glazes.

[0075] Investigation of the glazes resulted in the following oxide fractions, with the glaze containing 0.1 mass % of CuO in the slip being designated HG-C1, the glaze containing 0.5 mass % of CuO in the slip HG-C2, and the glaze containing 1 mass % of CuO in the slip HG-C3:

TABLE-US-00008 Oxide HG-C1 mass % HG-C2 mass % HG-C3 mass % SiO.sub.2 48.34 48.72 48.84 Al.sub.2O.sub.3 8.03 7.84 7.73 TiO.sub.2 0.10 0.10 0.10 Fe.sub.2O.sub.3 0.15 0.15 0.15 CaO 4.78 4.83 4.69 K.sub.2O 0.31 0.31 0.31 MgO 0.53 0.53 0.53 Na.sub.2O 2.13 2.02 2.03 B.sub.2O.sub.3 (ICP) 0.83 0.84 0.85 Li.sub.2O (ICP) 0.04 0.05 0.05 CuO 0.12 0.48 1.02 P.sub.2O.sub.5 0.05 0.05 0.05 SnO.sub.2 0.61 0.63 0.64 ZnO 24.54 24.21 24.28 ZrO.sub.2 5.43 5.21 5.21 HfO.sub.2 0.09 0.09 0.09 PbO 3.92 3.94 3.97

[0076] For each test body, then, the antibacterial activity of the glazes HG-C1, HG-C2 and HG-C3 was ascertained, again based on the JIS 2801 test method. The results obtained were as follows:

TABLE-US-00009 Glaze log.sub.10 steps HG-C1 5.6 HG-C2 5.9 HG-C3 6.3

[0077] The results are illustrated in FIG. 2 in the form of a diagram.

[0078] It is found that for a constant PbO content of approximately 3.9-4 mass % in the fired glaze, an increase in the antibacterial effect sets in as the CuO content goes up.

[0079] The CuO content can be increased still further; however, at CuO contents which are in the vicinity of the maximum value of 2 mass %, the glaze may acquire a green coloration, which is unwanted particularly in the area of sanitary products, in spite of the outstanding antimicrobial action.

[0080] With regard to the specified oxides of each of the glazes investigated, the presence of these oxides having been determined in each case by a spectral analysis, it can be stated that they include not only fluxes but also opacifiers and also components not specifically added, primarily in the form of impurities. Fluxes of note include, in particular, CaO, K.sub.2O and Na.sub.2O; opacifiers, primarily ZrO.sub.2 and SnO.sub.2. TiO.sub.2 acts as a whitener, but is not added separately. The other constituents, such as Fe.sub.2O.sub.3, MgO or HfO.sub.2, primarily represent impurities.

[0081] In the table shown in FIG. 3, again, all of the reduction rates ascertained are depicted in summary form. Plotted along the abscissa are the respective glazes (standard glaze SG, HG1, HG2, HG-P1, HG-P2, HG-P3, HG-C1, HG-C2, HG-C3), with the respective reduction rate in log.sub.10 steps along the ordinate. Quite clearly apparent is the outstanding disinfectant effect of the glazes of the invention comprising not only ZnO but also the metal oxides PbO and CuO, which are evidently responsible for the significantly improved effect, in different mixing proportions or quantitative proportions.

[0082] Lastly, a test body with a glaze containing Bi.sub.2O.sub.3 was also produced. This glaze contained no PbO and CuO.

[0083] Here again, the slip was prepared on the basis of the raw materials batch as per the glaze HG1, and therefore contained ZnO. A Bi.sub.2O.sub.3 content of 0.5 mass % was added in powder form. This slip as well was applied by spraying to a prefired ceramic body, with a layer thickness of approximately 1 mm, and was then fired to form the fired glaze.

[0084] When the test body was completed, here again, the antimicrobial effect of the glaze surface was investigated in accordance with the JIS standard. A reduction rate of 4.3 log.sub.10 steps was ascertained. This reduction rate as well is well above that of the HG1 glaze containing only ZnO. This means that the addition simply of a small amount of Bi.sub.2O.sub.3, leads to a significant improvement in the antibacterial glaze quality.

[0085] While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.