Boron-free, phosphorus-free high-stability ion sieve and preparation and application thereof

Abstract

The application discloses a kind of boron-free, phosphorus-free high-stability ion sieve and its preparation and application, the present application aims at solving the problem of insufficient lithium ion absorption capacity in salt bath and poor absorption rate in the production process of chemically strengthened glass cover plate under high-temperature salt bath, especially for the absorption of toxic ion lithium.The ion sieve of the present application is based on the mol% of oxide, the first metal oxide is 30mol%-50mol%, SiO2 is 26mol%-50mol%, and Al2O3 is 8mol%-25mol%;Among them, the mol% of SiO2+Al2O3 is greater than 50%, and is greater than the first metal oxide;The content of phosphorus oxide and boron oxide is less than 300ppm or less.The ion sieve of the present application is stable in structure at high temperature, and can continuously and quickly absorb lithium ions at high temperature without increasing the operation cost;Especially for the absorption of toxic ion lithium, it has the characteristics of high absorption rate and controllable absorption rate.It can ensure that the concentration of lithium ions and sodium ions in the salt bath is at a low level, and ensure the stability of the size of the mass production of chemically strengthened glass and the stability of surface stress.

Description

[0001] This application is a divisional application of application number 202010957118.9, filed on September 12, 2020, entitled "A boron-free, phosphorus-free, highly stable ion sieve and its application". Technical Field

[0002] This invention relates to the field of ion sieve technology, specifically to an ion sieve for purifying salt bath compound impurities in glass strengthening processes, and particularly to a boron-free, phosphorus-free, highly stable ion sieve and its preparation process. Background Technology

[0003] In the production process of chemically strengthened glass cover plates, as the amount of strengthening material increases during the strengthening process, the amount of Na in the salt bath increases. + Li + An increase in impurities, even at the ppm level, can severely hinder normal chemical strengthening, leading to a decrease in the CS value of subsequent strengthened samples and making quality control uncontrollable in CG (Cover Glass) factories. After chemical strengthening, the glass undergoes dimensional expansion due to the replacement of smaller ions in the salt bath by larger ions. The increase in impurity ions weakens ion exchange capacity, especially Li. + The increase in sodium-lithium exchange in lithium-aluminum-silicon chemically strengthened glass severely weakens the sodium-lithium exchange capacity, resulting in a rapid decrease in dimensional expansion after strengthening. However, in mobile phone cover glass applications, the dimensional tolerance of the glass is required to be within 20 micrometers. Therefore, the Li in the salt bath... + The increase in the amount of lithium aluminum silicon chemically strengthened glass will lead to an increase in dimensional defects in mass production, which can only be solved by changing the salt bath. However, changing the salt bath will lead to an increase in cost and a decrease in efficiency.

[0004] More importantly, lithium-ion salt baths rapidly affect the stress properties of lithium aluminum silicon glass, especially deep compressive stress. In stress tests, indicators such as CT-LD show a continuous downward trend, causing a gradual decline in the glass's drop resistance and other properties during continuous strengthening, leading to performance instability. Furthermore, the limited lifespan of the salt bath necessitates frequent replacements by glass processing plants, hindering mass production. In microcrystalline glass, due to the very small amount of glass phase, most ion exchange occurs through the glass phase. However, because of its high crystallinity and limited glass phase, it is more sensitive to lithium-ion salt bath poisoning.

[0005] Therefore, it is necessary to provide a material for purifying degraded or impure lithium-ion-containing salt compounds to improve production efficiency, reduce production costs, and be environmentally friendly and pollution-free. In existing technologies, methods for absorbing impure lithium ions mainly involve adding sodium phosphate to a salt bath. The phosphate dissolves in the salt bath, and the phosphate ions react with lithium ions to form lithium phosphate, which precipitates. However, lithium phosphate causes turbidity in the salt bath, requiring a long clarification period before use. Furthermore, excessive lithium phosphate precipitation over time can adhere to the surface of the strengthened glass, causing defects. Additionally, excessive lithium phosphate precipitation at the bottom of the salt bath makes cleaning difficult. For example, the "Method and System for Chemically Strengthening Lithium-Containing Glass" disclosed in WO2020092122A1 addresses salt bath poisoning, where phosphate precipitation produces poisonous cations that crystallize on the glass surface, causing uneven defects. While maintaining a balanced concentration of lithium ions entering and leaving the salt bath—controlling the lithium ion concentration in the salt bath to maintain relative stability—avoids crystallization on the glass surface. However, this method has a limited salt bath life, requiring frequent replacement, which is not conducive to mass production. In addition, the "ion sieve material and its preparation and use method" disclosed in CN201610428113.0 belongs to the ion sieve containing boron and phosphorus, which will cause random corrosion on the surface of glass and microcrystalline glass during high-temperature salt bath exchange at 440℃~600℃. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a boron-free, phosphorus-free, and highly stable ion sieve to solve the problems of insufficient absorption capacity and poor absorption rate of lithium ions in the high-temperature salt bath during the production process of chemically strengthened glass cover plates, especially for the absorption of poisoned lithium ions.

[0007] This invention also provides a preparation process for boron-free and phosphorus-free high-stability ion sieves, solving the problems of existing ion sieves containing boron and phosphorus components having unstable structures at high temperatures, easily decomposing and releasing phosphorus and boron to contaminate the surface of glass substrates and corrode the glass.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A boron-free, phosphorus-free, and highly stable ion sieve is characterized by the following composition: based on the mol% of oxides, the first metal oxide is 30 mol%–50 mol%, SiO2 is 26 mol%–50 mol%, and Al2O3 is 8 mol%–25 mol%. The mol% of SiO2 + Al2O3 is greater than 50% and greater than that of the first metal oxide. The contents of phosphorus oxide and boron oxide are less than 300 ppm or less. The first metal oxide is derived from sodium oxide or potassium oxide. Further, the Al2O3 content is greater than 10 mol%, and the Al2O3 / first metal oxide molar ratio is greater than 0.2. The surface of the ion sieve has pores for absorbing impurity ions from the salt bath.

[0010] This invention also provides a processing method for a boron-free, phosphorus-free, and highly stable ion sieve. The ion sieve is prepared by distributing the materials according to the above-mentioned ion sieve composition, and then melting it at 1000℃ to 1500℃ to form a liquid state. The liquid state is then formed into granular ion sieves with a diameter of 1mm to 10mm, irregularly shaped ion sieves with a thickness of 0.3mm to 1mm, or porous ion sieves with a pore size of 1mm to 10mm. The obtained ion sieve is structurally stable at high temperatures of 430℃ to 650℃, is not easily decomposed, and avoids the precipitation of phosphorus and boron, which contaminate the surface of the glass substrate and corrode the glass.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. The boron-free, phosphorus-free, and highly stable ion sieve provided by this invention uses specific amounts of SiO2 and Al2O3 to form polar covalent and ionic bonds, and incorporates a specific amount of a first metal oxide derived from sodium oxide or potassium oxide. The pores formed on the surface of the ion sieve absorb impurity ions from the salt bath, resulting in a final ion sieve material with excellent adsorption performance for lithium ions. It does not introduce other impurity ions into the molten salt compound, effectively removing metal impurity ions from the molten salt compound in a targeted manner. Furthermore, the used ion sieve does not pollute the environment. More importantly, the ion sieve does not contain boron, phosphorus, or other elements, making its structure more stable. It is particularly suitable for normal use in ultra-high temperature salt baths for glass and microcrystalline glass, exhibiting minimal corrosiveness to glass and preventing contamination of the glass substrate surface; it also does not produce floating matter or turbidity.

[0013] 2. The boron-free, phosphorus-free, and highly stable ion sieve of this invention exhibits structural stability at high temperatures ranging from 430℃ to 650℃, enabling continuous and rapid absorption of lithium ions at high temperatures without increasing operating costs. It is particularly effective for absorbing poisoned lithium ions, featuring high absorption rate and controllable absorption speed. Through ion sieving, it rapidly absorbs lithium and sodium ions generated in the salt bath during the chemical strengthening process of glass production, ensuring low concentrations of lithium and sodium ions in the salt bath and guaranteeing the dimensional and surface stress stability of mass-produced chemically strengthened glass. It can quickly achieve its absorption effect and is easy to remove quickly, avoiding reduced production efficiency.

[0014] 3. The processing method of the boron-free and phosphorus-free high-stability ion sieve of the present invention, due to its diverse manufacturing process and controllable preparation process, can produce ion sieves of different shapes, such as granular (1mm-10mm), irregularly shaped (0.3mm-1mm thick), or porous (1mm-10mm pore size), by selecting different methods. Furthermore, it forms pores on the surface of the ion sieve to increase the absorption area and improve absorption efficiency. Moreover, the obtained ion sieve is structurally stable at high temperatures of 430℃-650℃, is not easily decomposed, and avoids the precipitation of phosphorus and boron, which contaminates the glass substrate surface and corrodes the glass.

[0015] 4. The boron-free and phosphorus-free high-stability ion sieve of the present invention has a wide range of applications. It is not only suitable for normal use in ultra-high temperature salt baths of glass and microcrystalline glass, but also widely applicable to the purification of deteriorated or impure salt compounds containing lithium ions, so as to improve production efficiency, reduce production costs, and be environmentally friendly and pollution-free. Detailed Implementation

[0016] I. The relevant proprietary names and related measurement methods involved in this invention are as follows:

[0017] As used herein, the term "glass and glass articles" is used in their broadest sense, encompassing any object made wholly or partially of glass. Glass articles include laminates of glass and non-glass materials, laminates of amorphous and crystalline materials, and glass-ceramics (including amorphous and crystalline phases). The glass articles described in this invention include strengthened glass or glass-ceramic materials that exhibit improved mechanical properties and reliability compared to known glass articles (particularly known covered glass articles). In this invention, the glass-based substrate is generally unstrengthened, and the glass-based articles generally refer to strengthened glass-based substrates (e.g., through ion exchange). The strengthened glass articles of this invention are generally chemically strengthened by ion exchange and include various types of glass articles, such as aluminosilicate glass, soda-lime glass, etc., and, for example, but not limited to, glass articles comprising alkali metal aluminosilicate glass.

[0018] CTmax: The maximum value of the tensile stress CT region. During chemical strengthening, the tensile stress exhibits a parabolic shape as the strengthening time increases, and its highest point is called CTmax. This paper determines the CTmax of chemically strengthened glass-ceramics using the following method: After determining the appropriate strengthening conditions, the glass-ceramic sample is placed in a fresh salt bath for strengthening. The sample is removed every 30 minutes, and after the sample temperature drops below 100℃, it is washed with room temperature water, then the surface moisture is dried. The CT is then tested using SLP1000 or SLP2000, and the test data is recorded. After the test data is completed, the sample is placed back into the salt bath for strengthening for another 30 minutes before being removed for testing again. When the acquired data exhibits an inverted U-shaped parabolic characteristic, it is fitted to obtain the highest point of the parabola, which is the CTmax.

[0019] Surface compressive stress (CS): After chemical strengthening, the smaller radius alkali metal ions on the surface of the glass are replaced by larger radius alkali metal ions. Due to the crowding effect of the larger radius alkali metal ions, compressive stress is generated on the glass surface.

[0020] Surface compressive stress can be measured using the Orihara FSM6000 and SLP1000 instruments to measure the surface high-pressure stress zone and the deep low-pressure stress zone, respectively, and the stress curves can be fitted using PMC software. Alternatively, other stress testing instruments capable of measuring the surface high-pressure stress zone and the deep low-pressure stress zone can also be used.

[0021] Tensile stress linear density (CT-LD): The ratio of the tensile stress integral to the thickness of glass at its thickness section, obtained from SLP stress meter tests.

[0022] Online purification: Online purification emphasizes continuous operation, where the purification process of lithium-ion concentrate is carried out simultaneously with the strengthening process of glass substrate; it is a process of strengthening and purifying glass products; for example, the continuous operation of several carriers containing glass products and lithium-ion concentrate.

[0023] II. The present invention will be further described in detail below with reference to specific embodiments.

[0024] It should be understood that the following specific embodiments are merely illustrative of the invention and are not intended to limit the invention.

[0025] A boron-free, phosphorus-free, and highly stable ion sieve, based on the mol% of oxides, comprises a first metal oxide of 30 mol%–50 mol%, SiO2 of 26 mol%–50 mol%, and Al2O3 of 8 mol%–25 mol%. The mol% of SiO2 + Al2O3 is greater than 50% and greater than that of the first metal oxide. The contents of phosphorus oxide and boron oxide are less than 300 ppm or less. The first metal oxide is sodium oxide or potassium oxide. The surface of the ion sieve has pores for absorbing impurity ions from a salt bath.

[0026] The ion sieve may also contain a second metal oxide, including magnesium oxide, calcium oxide, and / or zinc oxide, to ensure the high-temperature stability of the ion sieve and reduce the amount of precipitation; in order to avoid weakening the absorption efficiency of the ion sieve, its total amount shall not exceed 5 mol%.

[0027] Table 1 shows some examples of different components of boron-free, phosphorus-free, and highly stable ion sieves.

[0028] Table 1

[0029]

[0030] In the ion sieve of this invention, the first metal oxide includes functional alkali metal oxides such as Na₂O or K₂O. In this invention, K₂O in the ion sieve... + Or Na + The source of the raw materials can also be one or more of KOH, KCl, KHCO3, K2SiO3, K2O, or K2O2; or one or more of NaOH, NaCl, NaHCO3, Na2SiO3, Na2O, or Na2O2. These raw materials can reduce costs and simplify melting.

[0031] The Al2O3 content is controlled between 8 mol% and 25 mol%, for example, 8 mol%, 9 mol%, 11 mol%, 12 mol%, 14 mol%, 15 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, or 25 mol%, etc.; preferably greater than 10 mol%. Furthermore, the molar ratio of Al2O3 to the first metal oxide is greater than 0.2. Higher Al2O3 content results in a better network structure and a faster ion sieve exchange rate; however, excessively high alumina content can lead to difficulties in ion sieve formation.

[0032] SiO2 is an essential component, used to form the framework of the ion sieve network structure through covalent bonds. The choice of its composition and content directly affects the adsorption performance of the ion sieve network structure. Its content is controlled between 26 mol% and 50 mol%; for example, 26 mol%, 27 mol%, 28 mol%, 30 mol%, 33 mol%, 35 mol%, 38 mol%, 40 mol%, 42 mol%, 44 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, or 50 mol%.

[0033] The SiO2+Al2O3 content is controlled to be greater than 50 mol%. Silica and alumina are components of the network structure; the higher their content, the more stable the structure. Ensuring that the network structure content in the ion sieve is greater than 50% is beneficial for obtaining a stable ion sieve structure, which is more resistant to decomposition at high temperatures. The SiO2+Al2O3 content can be 51 mol%, 52 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 62 mol%, 64 mol%, 66 mol%, 67 mol%, 68 mol%, or 69 mol%, etc.

[0034] This invention relates to a boron-free, phosphorus-free, and highly stable ion sieve. "Bron-free" and "phosphorus-free" mean that no phosphorus- or / and boron compounds are actively added, although they may exist as very small amounts of impurities. For example, in the embodiments, the boron and / or phosphorus content is less than 300 ppm, resulting in a more stable structure. This allows for continuous and rapid absorption of lithium ions at high temperatures without increasing operating costs. It is particularly effective for absorbing poisoned lithium ions, exhibiting high absorption rates and controllable absorption speeds. The ion sieve can quickly achieve its absorption effect and is easy and quick to remove, avoiding reduced production efficiency. It is suitable for normal use in ultra-high temperature salt baths for glass and microcrystalline glass, exhibiting minimal corrosiveness to glass and not causing surface contamination of the glass substrate; it also does not produce floating matter or turbidity.

[0035] In the strengthening process of glass products (including glass-ceramics), after a period of use, the impurity metal ions exchanged from the glass products in the ion exchange chemical strengthening salt bath increase in number, thereby deactivating the salt bath and weakening the glass strengthening effect. In these applications, for salt baths that need to remove impurities or deactivate, the ion sieve material described in this invention is added. After reacting at a certain temperature (a temperature higher than the melting point of the molten salt compound) for a period of time, the ion sieve material will adsorb or extract these impurity metal ions, thereby purifying, enhancing or restoring the activity of the salt bath.

[0036] The present invention also provides a processing method for the boron-free, phosphorus-free, and highly stable ion sieve, wherein the ion sieve is assembled according to the above-mentioned ion sieve group and then melted at 1000℃ to 1500℃ to form a liquid state.

[0037] The ion sieve is formed by water quenching, wherein the water quenching temperature is 10℃~80℃, for example 10℃, 15℃, 20℃, 22℃, 25℃, 30℃, 35℃, 45℃, 50℃, 60℃, 65℃, 70℃, 75℃ or 80℃, etc. The size of the ion sieve particles is controlled by controlling the temperature, so that the ion sieve particles meet the requirements of 1mm~10mm, for example 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, etc. Preferably, the size is between 2mm and 5mm.

[0038] The ion sieve is formed into a sheet shape by external force through rolling or drawing. The thickness of the sheet-shaped ion sieve is between 0.3 mm and 1 mm, for example, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm. Preferably, it is between 0.4 mm and 0.6 mm. The ion sieve is irregularly shaped, with its shortest side being at least 0.3 cm and its largest side being less than 1 cm.

[0039] In the ion sieve assembly, a porous ion sieve can also be formed by adding a foaming agent. This invention adjusts the proportion of the foaming agent to make the porous ion sieve pores into fragmented pieces with a pore size of 1mm to 10mm; for example, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm. The diameter of the porous ion sieve block is such that its shortest side is at least 0.5cm and its largest side is less than 10cm. The foaming agent is a conventional foaming agent used to increase the surface area of ​​the ion sieve. The ion sieve obtained by the above method has uniform pores on its surface, used to absorb impurity ions in the salt bath.

[0040] Furthermore, this invention also discloses the application of the boron-free, phosphorus-free, and highly stable ion sieve, which has a wide range of applications. It is not only suitable for normal use in ultra-high temperature salt baths for glass and microcrystalline glass, but also widely applicable for the purification of degraded or impure salt compounds containing lithium ions, thereby improving production efficiency, reducing production costs, and being environmentally friendly and pollution-free. For example, the salt bath used is a salt bath containing at least potassium or sodium, or a mixed salt bath (a salt bath containing at least one of sodium nitrate or potassium nitrate), and the strengthening time is 80% to 150% of the corresponding CTmax time T point under the same chemical strengthening temperature and the same salt bath; for example, at a temperature of 430℃ to 650℃, the reaction time is 4h to 24h. Or, the purification temperature is 430℃ to 480℃, and the strengthening time is 12h to 24h. In actual chemical strengthening processes, even with the same glass substrate, the time to reach CTmax varies depending on the strengthening conditions. For example, if strengthening with 80% sodium salt at 430℃ results in a CTmax of 6 hours, then the determined strengthening time is 80%–150% of 6 hours. Under these conditions, this could be expressed as 6 hours * 80%, 6 hours * 90%, 6 hours * 95%, 6 hours * 100%, 6 hours * 120%, or 6 hours * 150%. Therefore, as long as the absorption rate of the ion sieve is greater than the exchange rate of the glass-ceramic under normal strengthening temperature conditions, the process is successful.

[0041] In addition, the mass of the ion sieve added simultaneously must be less than the mass of the microcrystalline glass; if it is greater, the space in the salt bath device will be excessively occupied by the ion sieve, leaving little space for the glass and resulting in low volume utilization. Furthermore, the total absorption and absorption efficiency per unit mass of ion sieve must be higher than that per unit mass of microcrystalline glass. Typically, the amount of ion sieve added is approximately 3 wt% of the salt bath mass, for example, 2.5 wt%, 2.8 wt%, 3.0 wt%, 3.2 wt%, or 3.3 wt%.

[0042] Based on this, lithium ion sieves are added to the salt bath to purify lithium ions in the salt bath online, ensuring that the lithium ion concentration in the salt bath does not exceed 90 ppm; for example, 80 ppm, 60 ppm, 50 ppm, 40 ppm, 30 ppm, or 20 ppm, etc. The rate of lithium ion release from the glass-ceramic changes with temperature. The ion sieves described in Examples 1-20 are used in the strengthening of glass-ceramics. A comparative analysis of the measurement results before and after strengthening is performed using an atomic absorption spectrophotometer. It can be seen that after the reaction with the addition of the ion sieve, the lithium concentration in the bath salt... + The content can be controlled below 90ppm, 70ppm, or even below 50ppm and 20ppm.

[0043] Table 2 shows the application of the ion sieve of the present invention in a certain microcrystalline glass strengthening process.

[0044] Table 2

[0045]

[0046] Comparative Example Explanation: In Comparative Example 1, the alkali metal oxide content was less than 30 mol%, resulting in lower absorption efficiency and absorption capacity. After final absorption, it still contained 180 ppm Li. + This fails to meet the strengthening requirements for the microcrystalline glass.

[0047] In Comparative Example 2, although its absorption efficiency is very high, the lithium ions in the salt bath can reach below 100 ppm after absorption, but because it contains phosphorus, impurities will be released during high-temperature absorption, resulting in corrosion on the glass surface and white fog on the glass surface.

[0048] In summary, the boron-free, phosphorus-free, and highly stable ion sieve provided by this invention utilizes specific amounts of SiO2 and Al2O3 to form polar covalent and ionic bonds, and incorporates a specific amount of a first metal oxide. The pores of this first metal oxide absorb impurity ions from the salt bath, resulting in an ion sieve material with excellent lithium-ion adsorption performance. It does not introduce other impurity ions into the molten salt compound and effectively removes metallic impurity ions from the molten salt compound. The used ion sieve does not pollute the environment; it has minimal corrosiveness to glass and does not contaminate the surface of the glass substrate; it does not produce floating matter or turbidity; and because it is free of boron and phosphorus, its structure is more stable. Even at high temperatures of 430℃ to 650℃, it can continuously and rapidly absorb lithium ions without increasing operating costs. It is particularly effective for absorbing poisoned lithium ions, exhibiting high absorption rate and controllable absorption rate, allowing for rapid absorption and convenient and quick removal, thus avoiding reduced production efficiency.

[0049] This invention's ion sieve is particularly suitable for normal use in ultra-high temperature salt baths for glass and microcrystalline glass. During the strengthening process of microcrystalline glass, after a period of use in ion exchange chemical strengthening salt baths, the amount of impurity metal ions exchanged from the glass increases, leading to salt bath deactivation and a weakening of the glass strengthening effect. For salt baths requiring impurity removal or deactivation, adding the boron-free, phosphorus-free, and highly stable ion sieve material of this invention, and reacting at a temperature higher than the melting point of the molten salt compound for a period of time, allows the ion sieve material to adsorb or extract impurity metal ions, thereby purifying, enhancing, or restoring the activity of the salt bath.

[0050] Glass-ceramics are materials with a uniform and dense structure composed of microcrystalline and glassy phases. High-crystallinity, high-transparency glass-ceramics are the most valuable type. They are produced by adding nucleating agents to the glass and using heat treatment to induce the uniform precipitation of numerous tiny crystals within the glass, forming a dense multiphase composite of microcrystalline and glassy phases. Glass-ceramics exhibit high internal crystallinity, with grain sizes controllable within a small range. During crystallization, the chemical composition of the crystalline phase and the residual glassy phase are similar, with small differences in refractive index and continuous compositional variation, resulting in high transmittance in the visible light region. Simultaneously, the high content of the crystalline phase ensures the mechanical strength of the glass-ceramics.

[0051] To improve the scratch and drop resistance of glass products (including glass-ceramics), introducing surface compressive stress is a common method for strengthening glass. Chemical strengthening, also known as ion exchange, involves immersing the glass in an alkali ion molten salt for ion exchange. Because the alkali metal ions in the alkali ion molten salt have larger radii than those in the glass, after ion exchange, the larger alkali metal ions create a "squeezing" effect on the glass surface, forming a compressive stress layer of a certain depth. This compressive stress layer can increase the surface hardness of the glass to a certain extent, counteract external impacts, and prevent the propagation of microcracks, thereby improving the scratch and drop resistance of the glass. This invention provides the following specific strengthening method for glass-ceramics to obtain glass-ceramics with better mechanical properties, effectively improving the strengthening level of glass-ceramics to meet the higher drop and scratch resistance requirements of mobile phone cover plates.

[0052] The boron-free, phosphorus-free, and highly stable ion sieve provided by this invention is used to strengthen glass products. During the ion exchange process of chemically strengthened glass, small ions (Li) in the glass... + The sodium salt Li undergoing sodium-lithium exchange will be gradually replaced by large ions. As the number of enhanced batches increases, the pure sodium salt Li undergoing sodium-lithium exchange will be gradually replaced. + The concentration will also increase. The purity of the salt bath is strongly correlated with the strengthening properties of chemically strengthened glass. Li + Impurity ions affect the dynamic equilibrium of ion exchange; Li inside the glass + As sodium-lithium exchange proceeds, it continuously enters the pure sodium salt bath, causing the degree of sodium-lithium exchange to decrease. The ion exchange reaction formula is as follows;

[0053]

[0054] When the number of lithium ions in the salt bath increases, the reaction process proceeds from right to left, shifting the equilibrium to the left. This makes it more difficult for lithium ions in the glass to be exchanged by sodium ions in the salt bath, ultimately leading to salt poisoning and a weakening of the exchange capacity. The weakening of sodium-lithium exchange reduces the depth of stress, which is characterized by a decrease in CT-LD. This results in a decrease in drop resistance, and continuous batch strengthening can cause product instability.

[0055] The quantity of continuously strengthened samples in the unit salt bath is controlled. Since most of the lithium ions in the salt bath are released during the strengthening of glass-ceramics, they are lithium exchanged from the glass interior by sodium in the salt bath. Because the ion exchange is a sodium-lithium exchange, the mass of the glass-ceramics increases due to the mass difference between sodium and lithium ions after the ion exchange. The approximate concentration of lithium ions released in the salt bath can be determined by the increase in mass during continuous strengthening. Furthermore, the concentration of lithium ions in the salt bath is determined through actual control using an atomic absorption spectrometer. Therefore, controlling the lithium ion concentration in the strengthened salt bath at a lower level maximizes the stress performance of the glass-ceramics, better combining it with its high intrinsic properties, improving the glass's drop resistance. The high hardness of the glass-ceramics also provides excellent scratch resistance. Thus, shallow high stress is avoided, preventing performance instability caused by excessive stress differences due to stress unevenness.

[0056] In the aforementioned chemical strengthening process, the glass-ceramic and the ion sieve can be placed in the salt bath sequentially or simultaneously. A slight time difference is allowed for simultaneous entry and exit. For example, simultaneous entry can involve placing the glass-ceramic in the salt bath first, followed by the addition of the lithium-ion purification material; alternatively, the lithium-ion purification material can be added to the salt bath first, followed by the addition of the glass-ceramic. A slight time difference between their entry into the salt bath is permissible, within 10 seconds. A slight time difference is also allowed for simultaneous exit. The mass of the ion sieve added is less than the mass of the glass-ceramic, and the total absorption and absorption efficiency per unit mass of ion sieve are greater than the total lithium ions released per unit mass of glass-ceramic under normal strengthening processes.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A boron-free, phosphorous-free, high-stability ion-sieve for high-temperature purification of salt bath, characterized in that, consisting of the following oxides based on mol% of oxides, the first metal oxide is 41-42 mol%, SiO2 is 40-45 mol%, Al2O3 is 14-18 mol%, the sum of the contents of each oxide component is 100%; wherein the mol% of SiO2+Al2O3 is greater than or equal to 56% and less than or equal to 59%, and is greater than the first metal oxide; the contents of phosphorus oxide and boron oxide are less than 300 ppm; wherein the first metal oxide is sodium oxide or potassium oxide, and the molar ratio of Al2O3 / first metal oxide is greater than or equal to 14 / 41 and less than or equal to 18 / 42; the high temperature temperature is 430-650 DEG C, and the salt bath is an ion exchange chemical strengthening salt bath for strengthening of glass products.

2. The boron-free, phosphorous-free, high-stability ion-sieve of claim 1, wherein, the Al2O3 content is 14 mol%, 15 mol%, 17 mol% or 18 mol%; and / or, the SiO2 content is 40 mol%, 42 mol% or 44 mol%; and / or, the SiO2+Al2O3 content is 56 mol%, 57 mol%, 58 mol% or 59 mol%; and / or, the molar percentage content of the first metal oxide is 41 mol% or 42 mol%; and / or, the molar ratio of Al2O3 / first metal oxide is 14 / 41 or 18 / 42.

3. The boron-free, phosphorous-free, high-stability ion-sieve of claim 1, wherein, consisting of the following oxides based on mol% of oxides, Na2O is 42 mol%, SiO2 is 40 mol%, Al2O3 is 18 mol%.

4. The boron-free, phosphorous-free, high-stability ion-sieve of claim 1, wherein, consisting of the following oxides based on mol% of oxides, K2O is 41 mol%, SiO2 is 45 mol%, Al2O3 is 14 mol%.

5. A boron-free, phosphorous-free, high-stability ion-sieve for high-temperature purification of salt bath, characterized in that, consisting of the following oxides based on mol% of oxides, the first metal oxide is 40-42 mol%, SiO2 is 40-47 mol%, Al2O3 is 12-15 mol%, the second metal oxide consisting of magnesium oxide, calcium oxide and / or zinc oxide, the molar percentage content of which is not more than 4 mol%, the sum of the contents of each oxide component is 100%; wherein the mol% of SiO2+Al2O3 is greater than 54% and less than or equal to 59 mol%, and is greater than the first metal oxide; the contents of phosphorus oxide and boron oxide are less than 300 ppm; wherein the first metal oxide is sodium oxide or potassium oxide, and the molar ratio of Al2O3 / first metal oxide is greater than or equal to 12 / 40 and less than or equal to 13 / 42; the high temperature temperature is 430-650 DEG C, and the salt bath is an ion exchange chemical strengthening salt bath for strengthening of glass products.

6. The boron-free, phosphorus-free high-stability ion sieve according to claim 5, characterized in that, the Al2O3 content is 12 mol%, 14 mol% or 15 mol%; and / or, the SiO2 content is 40 mol%, 42 mol%, 44 mol%, 46 mol% or 47 mol%; and / or, the SiO2 content is 40 mol%, 42 mol% or 44 mol%; and / or, SiO2+Al2O3 is 55 mol%, 56 mol%, 57 mol%, 58 mol% or 59 mol%; and / or, The first metal oxide has a mole percentage content of 40 mol% or 42 mol%; and / or, The Al2O3 / first metal oxide mole ratio is 12 / 40 or 13 / 42; and / or, The second metal oxide has a mole percentage content of 1 mol%, 2 mol% or 4 mol%.

7. The boron-free, phosphorous-free, high-stability ion-sieve of claim 5, wherein, Na2O is 42 mol%, SiO2 is 41 mol%, Al2O3 is 13 mol%, MgO is 2 mol%, CaO is 2 mol% based on mol% of oxide; or, K2O is 40 mol%, SiO2 is 47 mol%, Al2O3 is 12 mol%, ZnO is 1 mol% based on mol% of oxide.

8. A process for the preparation of a boron-free, phosphorus-free high-stability ion-sieve for high-temperature purification salt bath, characterized by, The ion sieve component of any one of claims 1-7 is charged into a crucible, then melted at a temperature of 1000-1500°C to form a liquid state, and then formed into a granular, sheet or porous shape.

9. The method for preparing the boron-free, phosphorus-free, and highly stable ion sieve according to claim 8, characterized in that, The ion sieve is formed into a granular shape by water quenching; the water quenching temperature is 10-80°C, and the ion sieve granule size is 1-10 mm.

10. The method of claim 8, wherein the boron-free, phosphorous-free, high-stability ion-sieve is prepared by the steps of: The ion sieve is formed into a sheet shape by external force rolling or drawing; the sheet-shaped ion sieve has a thickness of 0.3-1 mm. ​ 11. The method of claim 8, wherein the boron-free, phosphorous-free, high-stability ion-sieve is prepared by the steps of: The ion sieve is formed into a porous shape by adding a foaming agent; the porous ion sieve is in the form of a fragment, has a pore size of 1-10 mm, and the porous ion sieve fragment has a shortest side of at least 0.5 cm and a longest side of less than 10 cm. ​ 12. The method of claim 10, wherein the boron-free, phosphorous-free, high-stability ion-sieve is prepared by the steps of: The sheet-shaped ion sieve is in the form of an irregular sheet, has a shortest side of at least 0.3 cm and a longest side of less than 20 cm. ​ 13. Use of a boron-free, phosphorus-free, high-stability ion-sieve for high-temperature purification of salt baths, characterized in that, The boron-free, phosphorus-free ion sieve with high stability according to any one of claims 1-7 or obtained by the method according to any one of claims 8-12 is used for chemical strengthening of glass-ceramics; a salt bath containing at least potassium or sodium or a mixed salt bath is used, and the strengthening time is 80-150% of the time point T at which CTmax is reached under the same chemical strengthening temperature and the same salt bath.

14. Use of the boron-free, phosphorus-free, high-stability ion-sieve according to claim 13, characterized in that, The salt bath is sodium nitrate and / or potassium nitrate, the purification temperature is 430-650°C, and the strengthening time is 4-24 h.

15. Use of the boron-free, phosphorus-free, high-stability ion-sieve according to claim 14, characterized in that, The purification temperature is 430-480°C, and the strengthening time is 12-24 h.

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