A high-strength antibacterial ceramic glaze and its preparation method

Abstract

This invention discloses a high-strength antibacterial ceramic glaze and its preparation method, belonging to the field of glaze preparation technology. By mass, the glaze comprises the following raw materials: 45-55 parts potassium feldspar, 12-17 parts quartz powder I, 8-12 parts kaolin, 4-6 parts alumina, and 18-22 parts zinc borophosphorus silicate glass frit. First, potassium feldspar, quartz powder I, kaolin, alumina, and zinc borophosphorus silicate glass frit are mixed to obtain a mixture. Then, a dispersant and binder are added to the mixture, followed by ball milling. After ball milling, the mixture is filtered to obtain a glaze slurry. Finally, the specific gravity of the glaze slurry is adjusted, and after aging, the final product is obtained. The glaze provided by this invention can release Zn, which has a membrane-disrupting effect, when in a weakly acidic microenvironment produced by bacterial metabolism. 2+ It achieves synergistic antibacterial effects with phosphate ions, which can interfere with bacterial energy metabolism, and generates permeable channels in the functional phase of the glaze to achieve long-term release of zinc ions, thus exhibiting long-lasting antibacterial properties.

Description

Technical Field

[0001] This invention relates to the field of glaze preparation technology, specifically to a high-strength antibacterial ceramic glaze and its preparation method. Background Technology

[0002] In modern society, with the increasing public awareness of health and hygiene, higher demands are being placed on the hygienic performance of everyday contact items, especially daily-use ceramic products (such as ceramic bowls, plates, and chopsticks). As the interface that directly contacts food, the human body, and the environment, the easy-to-clean properties of ceramic glaze are no longer sufficient to meet the needs of high-end applications. Endowing daily-use ceramic glazes with intrinsic, long-lasting antibacterial functions, capable of actively inhibiting or killing bacteria, mold, and other microorganisms attached to the surface, is of vital importance for preventing cross-infection and ensuring public health safety.

[0003] To achieve antibacterial properties in daily-use ceramic glazes, existing technologies primarily employ the addition of various antibacterial agents to the glaze. These technologies can be broadly categorized into two types: one involves adding inorganic metal ion-based antibacterial agents, such as silver-, copper-, or zinc-loaded zeolites or zirconium phosphate; the other involves adding photocatalytic nanomaterials, such as nano-titanium dioxide. For instance, the "Negative Ion Easy-Clean Functional Ceramic Additive" technology described in patent CN104129996B involves physically compounding various natural minerals (tourmaline, halite, and shale), nano-titanium dioxide, and nano-zinc oxide to create a functional additive, which is then mixed into the glaze. The antibacterial mechanism mainly relies on the self-polarization effect of the mineral crystals to continuously generate negative ions, and the catalytic effect of nano-titanium dioxide under light, indirectly altering the microbial environment and achieving a hydrophilic and easy-clean surface.

[0004] However, existing technologies in this area still have some shortcomings in achieving antibacterial properties in glazes. First, the antibacterial mechanism is indirect, passive, and inefficient. Antibacterial methods, such as negative ions and photocatalysis, rely on environmental conditions (such as airflow and light) and the process is relatively slow. They are broad-spectrum, indirect antibacterial methods that improve the microenvironment, and their contact killing efficiency against specific pathogens may not meet the requirements of high-standard catering scenarios. Second, the introduction of functional components has a negative impact on the properties of the glaze itself. Most existing technologies directly mix functional components (such as mineral crystals and nanoparticles) into the glaze as physical fillers. These second-phase particles differ from the glaze glass matrix in physicochemical properties. During high-temperature firing, problems such as insufficient reaction, poor compatibility, or thermal expansion mismatch may lead to a decrease in the density of the glaze layer and an increase in microstructural defects. This can easily lead to a decrease in the hardness and wear resistance of the glaze, a deterioration in chemical stability, and even stress points introduced by particle residue or aggregation, reducing the overall strength of the glaze. In addition to the above, both ion-releasing and mineral-effect antibacterial glazes are prone to decline in antibacterial performance after the initial stage due to surface passivation, consumption of active sites, or blockage of diffusion channels, failing to meet the requirements of long-lasting antibacterial effects in high-end applications. Therefore, it is essential to propose a new high-strength antibacterial ceramic glaze and its preparation method. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a high-strength antibacterial ceramic glaze and its preparation method.

[0006] The first aspect of the present invention is to provide a high-strength antibacterial ceramic glaze, which, by mass parts, comprises the following raw materials: 45-55 parts of potassium feldspar, 12-17 parts of quartz powder I, 8-12 parts of kaolin, 4-6 parts of alumina, and 18-22 parts of zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate are mixed to obtain a premix; (2) The premixed materials are melted and mixed to obtain molten glass; (3) The glass melt is subjected to water quenching and rapid cooling to obtain glass particles, which are then dried and ground to obtain zinc borophosphosilicate glass frit.

[0007] It should be noted that this invention innovatively uses zinc oxide, boric acid, quartz, strontium carbonate, lithium carbonate, and ammonium dihydrogen phosphate as raw materials, which are melted at high temperature. During this process, P₂O₅ produced by the decomposition of ammonium dihydrogen phosphate enters the melt, and P… 5+ It participates in the construction in the form of [PO4] tetrahedron, because P 5+ High charge density and Zn 2+The strong electrostatic interaction between the network modification properties and the zinc phosphate clusters facilitates localized enrichment under thermodynamic driving, forming zinc phosphate clusters. During the subsequent water quenching process, the structure of the high-temperature melt is rapidly frozen, allowing the zinc phosphate clusters to distribute within the borosilicate matrix.

[0008] In some embodiments, the mass ratio of zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate is 30-35:35-40:15-20:5-7:2-4:2-4.

[0009] In some embodiments, mixing in step (1) takes 1.5-2.5 h; melting in step (2) involves heating to 1200-1300 °C at a rate of 4-6 °C / min and holding for 1-2 h; drying in step (3) involves drying at 105-115 °C for 22-26 h and grinding to D90 < 90 μm.

[0010] A second aspect of this invention is to provide a method for preparing a high-strength antibacterial ceramic glaze, comprising the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add dispersant and binder to the mixture and ball mill it. After ball milling, filter to obtain glaze slurry; S3: Adjust the specific gravity of the glaze slurry, and after aging, a high-strength antibacterial ceramic glaze is obtained.

[0011] In some embodiments, the dispersant is selected from at least one of sodium tripolyphosphate and sodium hexametaphosphate; the binder is selected from at least one of sodium carboxymethyl cellulose and hydroxypropyl methyl cellulose.

[0012] In some embodiments, the mass amount of dispersant is 0.2-0.4% of the mass of the mixture; the mass amount of binder is 0.08-0.12% of the mass of the mixture.

[0013] In some embodiments, ball milling is performed using alumina balls as the grinding medium for 8-10 hours.

[0014] In some embodiments, the ball milling is a wet ball milling, with the weight ratio of material, balls and water being 0.8-1.2:1.2-1.7:0.6-0.7.

[0015] In some embodiments, the specific gravity of the glaze slurry is adjusted to 1.45-1.5 g / cm³. 3 .

[0016] In some implementations, aging is performed by placing the container in a sealed container at room temperature for 26-30 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The zinc borosilicate phosphate glass frit provided by this invention disperses chemically active zinc phosphate nanoregions (rich in antibacterial zinc ions) within a highly stable borosilicate continuous phase, thereby achieving microenvironment-responsive, long-lasting antibacterial action. When the glaze is in a weakly acidic microenvironment generated by bacterial metabolism, the PO-Zn bonds in the phosphate microregions preferentially undergo selective dissolution, rapidly releasing Zn with membrane-disrupting properties. 2+ It achieves synergistic antibacterial effects with phosphate ions, which can interfere with bacterial energy metabolism. At the same time, due to the preferential solubility of phosphate microregions in weak acid, permeation channels are generated in situ in the functional phase of the glaze, allowing zinc ions to be released slowly and controllably over a long period of time through the channels, avoiding the defect that the release rate decreases with surface passivation.

[0018] 2. The high-strength antibacterial ceramic glaze provided by this invention exhibits high mechanical strength after high-temperature sintering. The alumina in the glaze formulation forms a dense aluminosilicate glass framework after firing, imparting high microhardness and excellent scratch and wear resistance to the glaze surface. Furthermore, the zinc borosilicate glass frit completely melts at the glaze firing temperature, uniformly dissolving with the base glaze components to form a dense and continuous composite glass network, collectively constituting a high-strength glaze layer. The main body of the glaze layer is a chemically stable amorphous glass phase with uniform internal stress distribution, making it less prone to cracking and peeling during friction. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to specific embodiments.

[0020] Example 1 A high-strength antibacterial ceramic glaze, by mass parts, comprises the following raw materials: 50 parts potassium feldspar, 15 parts quartz powder, 10 parts kaolin, 5 parts alumina, and 20 parts zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate in a mass ratio of 32:37:18:6:3:3 were mixed for 2 hours to obtain a premix. (2) The premixed material is heated to 1250℃ at a rate of 5℃ / min and kept at that temperature for 1.5h to obtain glass melt; (3) The glass melt is subjected to water quenching and rapid cooling to obtain glass particles, which are dried at 110°C for 24 hours and ground to D90<90μm to obtain zinc borosilicate glass frit.

[0021] The above-mentioned high-strength antibacterial ceramic glaze is prepared by the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add sodium tripolyphosphate and sodium carboxymethyl cellulose to the mixture and perform wet ball milling with alumina balls as the grinding medium. The weight ratio of material, balls, and water is 1:1.5:0.65. Ball mill for 9 hours and filter to obtain a glaze slurry. The mass of sodium tripolyphosphate is 0.3% of the mass of the mixture, and the mass of sodium carboxymethyl cellulose is 0.1% of the mass of the mixture. S3: Adjust the specific gravity of the glaze slurry to 1.48 g / cm³. 3 A high-strength antibacterial ceramic glaze is obtained by placing it in a sealed container at room temperature for 28 hours.

[0022] Example 2 A high-strength antibacterial ceramic glaze, by mass parts, comprises the following raw materials: 55 parts potassium feldspar, 17 parts quartz powder, 12 parts kaolin, 6 parts alumina, and 22 parts zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate in a mass ratio of 35:40:20:7:4:4 were mixed for 2.5 h to obtain a premix; (2) The premixed material is heated to 1300℃ at a rate of 6℃ / min and kept at that temperature for 1h to obtain glass melt; (3) The glass melt was subjected to water quenching and rapid cooling to obtain glass particles, which were dried at 115℃ for 22h and ground to D90<90μm to obtain zinc borophosphosilicate glass frit.

[0023] The above-mentioned high-strength antibacterial ceramic glaze is prepared by the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add sodium hexametaphosphate and hydroxypropyl methylcellulose to the mixture and perform wet ball milling with alumina balls as the grinding medium. The weight ratio of material, balls, and water is 1.2:1.7:0.7. Ball mill for 10 hours and filter to obtain a glaze slurry. The mass of sodium hexametaphosphate is 0.4% of the mass of the mixture, and the mass of hydroxypropyl methylcellulose is 0.12% of the mass of the mixture. S3: Adjust the specific gravity of the glaze slurry to 1.5 g / cm³. 3 A high-strength antibacterial ceramic glaze is obtained by placing it in a sealed container at room temperature for 30 hours.

[0024] Example 3 A high-strength antibacterial ceramic glaze, by mass parts, comprises the following raw materials: 45 parts potassium feldspar, 12 parts quartz powder, 8 parts kaolin, 4 parts alumina, and 18 parts zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate in a mass ratio of 30:35:15:5:2:2 were mixed for 1.5 h to obtain a premix; (2) The premixed material is heated to 1200℃ at a rate of 4℃ / min and kept at that temperature for 2h to obtain glass melt; (3) The glass melt was subjected to water quenching and rapid cooling to obtain glass particles, which were dried at 105℃ for 26 hours and ground to D90<90μm to obtain zinc borosilicate glass frit.

[0025] The above-mentioned high-strength antibacterial ceramic glaze is prepared by the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add sodium tripolyphosphate and sodium carboxymethyl cellulose to the mixture and perform wet ball milling with alumina balls as the grinding medium. The weight ratio of material, balls, and water is 0.8:1.2:0.6. Ball mill for 8 hours and filter to obtain a glaze slurry. The mass of sodium tripolyphosphate is 0.2% of the mass of the mixture, and the mass of sodium carboxymethyl cellulose is 0.08% of the mass of the mixture. S3: Adjust the specific gravity of the glaze slurry to 1.45 g / cm³. 3 A high-strength antibacterial ceramic glaze is obtained by placing it in a sealed container at room temperature for 26 hours.

[0026] Example 4 A high-strength antibacterial ceramic glaze, by mass parts, comprises the following raw materials: 46 parts potassium feldspar, 14 parts quartz powder, 9 parts kaolin, 4 parts alumina, and 19 parts zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate in a mass ratio of 31:39:16:6:2:3 were mixed for 2 hours to obtain a premix. (2) The premixed material is heated to 1230℃ at a rate of 5℃ / min and kept at that temperature for 1.5h to obtain glass melt; (3) The glass melt is subjected to water quenching and rapid cooling to obtain glass particles, which are dried at 110°C for 23 hours and ground to D90<90μm to obtain zinc borophosphosilicate glass frit.

[0027] The above-mentioned high-strength antibacterial ceramic glaze is prepared by the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add sodium hexametaphosphate and sodium carboxymethyl cellulose to the mixture and perform wet ball milling with alumina balls as the grinding medium. The weight ratio of material, balls, and water is 0.9:1.4:0.65. Ball mill for 8 hours and filter to obtain a glaze slurry. The mass of sodium hexametaphosphate is 0.4% of the mass of the mixture, and the mass of sodium carboxymethyl cellulose is 0.09% of the mass of the mixture. S3: Adjust the specific gravity of the glaze slurry to 1.45 g / cm³. 3 A high-strength antibacterial ceramic glaze is obtained by placing it in a sealed container at room temperature for 26 hours.

[0028] Example 5 A high-strength antibacterial ceramic glaze, by mass parts, comprises the following raw materials: 52 parts potassium feldspar, 16 parts quartz powder, 11 parts kaolin, 6 parts alumina, and 21 parts zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate in a mass ratio of 34:38:18:6:4:2 were mixed for 2.5 h to obtain a premix; (2) The premixed material is heated to 1280℃ at a rate of 6℃ / min and kept at that temperature for 2h to obtain glass melt; (3) The glass melt is subjected to water quenching and rapid cooling to obtain glass particles, which are dried at 115℃ for 25h and ground to D90<90μm to obtain zinc borosilicate glass frit.

[0029] The above-mentioned high-strength antibacterial ceramic glaze is prepared by the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add sodium tripolyphosphate and hydroxypropyl methylcellulose to the mixture and perform wet ball milling with alumina balls as the grinding medium. The weight ratio of material, balls, and water is 1.1:1.6:0.65. Ball mill for 10 hours and filter to obtain a glaze slurry. The mass of sodium tripolyphosphate is 0.3% of the mass of the mixture, and the mass of hydroxypropyl methylcellulose is 0.11% of the mass of the mixture. S3: Adjust the specific gravity of the glaze slurry to 1.48 g / cm³. 3 A high-strength antibacterial ceramic glaze is obtained by placing it in a sealed container at room temperature for 29 hours.

[0030] Comparative Example 1 It is basically the same as Example 1, except that: no ammonium dihydrogen phosphate is added.

[0031] Comparative Example 2 The process is basically the same as in Example 1, except that: instead of preparing zinc borophosphorus silicate glass frit, zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate in the same amounts as in Example 1 are directly added to the high-strength antibacterial ceramic glaze step S1, i.e., a physical mixing method is used.

[0032] Comparative Example 3 It is basically the same as Example 1, except that zinc oxide is not added.

[0033] Comparative Example 4 It is basically the same as Example 1, except that zinc borophosphosilicate glass frit is not added.

[0034] The glazes prepared in Examples 1-5 and Comparative Examples 1-4 were applied to ceramic bodies and fired in a kiln at an oxidizing atmosphere of about 1300°C. The performance of the fired glazes was tested, and the test results are shown in Table 1.

[0035] Antimicrobial activity test: Following standard ISO 22196, the bacterial strains were *Escherichia coli* (ATCC 25922) and *Staphylococcus aureus* (ATCC 6538); inoculum size: 5 × 10⁻⁶. 5 CFU / mL; contact time 24h; temperature: 35±1℃, relative humidity ≥90%, calculate antibacterial rate.

[0036] Antibacterial durability test: According to standard JC / T 897-2014, the sample was placed in a 1% neutral detergent solution and aged in a constant temperature water bath at 60℃ for 24 hours. After aging, it was taken out, washed and dried, and the antibacterial rate was tested.

[0037] Microhardness test: Refer to standard GB / T 16534, use a micro Vickers hardness tester, apply a test force of 4.903 N (HV0.5) for 15s, and take the average value of 10 points.

[0038] Abrasion resistance test: Refer to standard GB / T 3810.7, use a glaze abrasion resistance tester, the abrasive is standard white corundum, and observe the wear revolutions visible on the glaze surface.

[0039] Table 1

[0040] As can be seen from Table 1, the glazes provided in Examples 1-5 of the present invention have excellent antibacterial properties and glaze strength, with an initial antibacterial rate of over 99.99%. When the glaze comes into contact with the acidic microenvironment of bacteria, it can rapidly release a high concentration of Zn. 2+This invention achieves highly efficient contact sterilization, and the antibacterial rate remains above 99.9% even after durable aging treatment. This is because the invention selectively dissolves phosphate microregions to form nanopores, controlling the zinc ion release rate and making the antibacterial performance long-lasting and stable. In addition, the glaze provided by this invention has high hardness and wear resistance after glazing. The alumina reinforcing phase in the formula is uniformly dispersed, and the frit reacts with the base glaze at high temperature to form a dense and continuous glass network, which together constitute a high-strength glaze skeleton.

[0041] As can be seen from the comparative examples, Comparative Example 1, without the addition of ammonium dihydrogen phosphate, yielded a phosphorus-free frit. This glaze exhibited good initial antibacterial properties, but its antibacterial durability decreased. This is because after immersion aging, a silicon / boric acid gel passivation layer forms on the surface of the zinc borosilicate glass, blocking the subsequent release of zinc ions and causing the antibacterial function to fail rapidly. Comparative Example 2, using a physical mixing method, showed a decrease in both initial and post-aging antibacterial rates. The physically mixed raw materials could not form a uniform and highly active glass phase during firing. Zinc oxide might agglomerate, volatilize, or react insufficiently with the matrix, resulting in fewer and unevenly distributed effective antibacterial phases. Comparative Example 3, without the addition of zinc oxide, resulted in a significant decrease in the antibacterial rate, demonstrating that zinc ions are an indispensable core source of antibacterial function in this scheme. Comparative Example 4, lacking the zinc borosilicate glass frit, showed a significant decrease in both antibacterial properties and glaze strength.

[0042] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A high-strength antibacterial ceramic glaze, characterized in that, By mass fractions, it includes the following raw materials: 45-55 parts potassium feldspar, 12-17 parts quartz powder I, 8-12 parts kaolin, 4-6 parts alumina, and 18-22 parts zinc borophosphorus silicate glass frit. The zinc borophosphosilicate glass frit is prepared by the following steps: (1) Zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate are mixed to obtain a premix; (2) The premixed material is melted and mixed to obtain molten glass; (3) The glass melt is subjected to water quenching and rapid cooling to obtain glass particles, which are then dried and ground to obtain zinc borosilicate glass frit.

2. The high-strength antibacterial ceramic glaze according to claim 1, characterized in that, The mass ratio of zinc oxide, boric acid, quartz powder II, strontium carbonate, lithium carbonate and ammonium dihydrogen phosphate is 30-35:35-40:15-20:5-7:2-4:2-4.

3. The high-strength antibacterial ceramic glaze according to claim 1, characterized in that, In step (1), the mixing is carried out for 1.5-2.5 hours; in step (2), the melting is carried out by heating to 1200-1300℃ at a rate of 4-6℃ / min and holding for 1-2 hours; in step (3), the drying is carried out at 105-115℃ for 22-26 hours and the grinding is carried out until D90 < 90μm.

4. A method for preparing a high-strength antibacterial ceramic glaze according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Mix potassium feldspar, quartz powder I, kaolin, alumina and zinc borophosphorus silicate glass frit to obtain a mixture; S2: Add dispersant and binder to the mixture and ball mill it. After ball milling, filter to obtain glaze slurry. S3: Adjust the specific gravity of the glaze slurry, and after aging, the high-strength antibacterial ceramic glaze is obtained.

5. The method for preparing the high-strength antibacterial ceramic glaze according to claim 4, characterized in that, The dispersant is selected from at least one of sodium tripolyphosphate and sodium hexametaphosphate; the binder is selected from at least one of sodium carboxymethyl cellulose and hydroxypropyl methyl cellulose.

6. The method for preparing the high-strength antibacterial ceramic glaze according to claim 5, characterized in that, The mass amount of the dispersant is 0.2-0.4% of the mass of the mixture; the mass amount of the binder is 0.08-0.12% of the mass of the mixture.

7. The method for preparing the high-strength antibacterial ceramic glaze according to claim 4, characterized in that, The ball milling process uses alumina balls as the grinding medium and lasts for 8-10 hours.

8. The method for preparing the high-strength antibacterial ceramic glaze according to claim 7, characterized in that, The ball mill is a wet ball mill, and the weight ratio of material, balls and water is 0.8-1.2:1.2-1.7:0.6-0.

7.

9. The method for preparing the high-strength antibacterial ceramic glaze according to claim 4, characterized in that, The specific gravity of the glaze slurry is adjusted to 1.45-1.5 g / cm³. 3 .

10. The method for preparing the high-strength antibacterial ceramic glaze according to claim 4, characterized in that, The aging process involves placing the container in a sealed container at room temperature for 26-30 hours.

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