Salt bath system for strengthening glass articles and method for regenerating molten salt

Abstract

This invention provides a salt bath system and a method for regenerating molten salt suitable for use in ion exchange processes. [Solution] A salt bath system and a method for regenerating molten salt comprising: a salt bath defining a first internal volume enclosed by at least one side wall; a salt bath composition containing an alkali metal salt disposed in the first internal volume; a storage device defining a second internal volume enclosed by at least one side wall and containing a regenerating medium disposed in the second internal volume; and a circulation device disposed near the inlet of the storage device, the circulation device operating to circulate the salt bath composition to the storage device.

Description

Description of Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63 / 078,488, filed on September 15, 2020, the content of which is relied upon and incorporated herein in its entirety.

Technical Field

[0002] The present disclosure relates to systems and methods for chemically strengthening glass articles, and more particularly, to salt bath systems for strengthening glass articles and methods for regenerating molten salts.

Background Art

[0003] Tempered or strengthened glass may be used in various applications. For example, strengthened glass articles may be used in household electronic devices such as smartphones and tablets, and pharmaceutical packaging for physical durability and break resistance. In conventional strengthening processes such as conventional ion exchange processes, often, in order to increase the efficiency of the strengthening process, a large number of glass articles are immersed in one salt bath in a batch manner. However, as the batch production of strengthened glass articles continues in the same salt bath, in the ion exchange process, inevitably, the effectiveness of the salt bath will decrease. Numerous methods can be utilized to suppress and / or prevent the decrease in the effectiveness of the salt bath, but these methods may add various complex elements to the ion exchange process.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, there is a need for alternative salt bath systems for strengthening glass articles and alternative methods for regenerating molten salts.

Means for Solving the Problems

[0005] According to a first aspect of the present disclosure, a salt bath system for strengthening glass articles may include: a salt bath defining a first internal volume enclosed by at least one side wall; a salt bath composition comprising an alkali metal salt disposed within the first internal volume; a storage device disposed within the first internal volume, defining a second internal volume enclosed by at least one side wall, and comprising a regenerating medium disposed within the second internal volume; and a circulation device disposed near the inlet of the storage device, which operates to circulate the salt bath composition into the storage device.

[0006] According to a second aspect of the present disclosure, a salt bath system for strengthening glass articles may include: a salt bath defining a first internal volume enclosed by at least one side wall; a salt bath composition comprising an alkali metal salt disposed within the first internal volume; a storage device disposed outside the first internal volume and fluidly connected to the first internal volume, comprising a regenerating medium disposed within the second internal volume, defining a second internal volume enclosed by at least one side wall; and a circulation device disposed within the first internal volume in close proximity to the inlet of the storage device, which operates to circulate the salt bath composition to the storage device.

[0007] A third aspect of this disclosure may include a second aspect in which the temperature of the second internal volume is 3°C or more lower than the temperature of the first internal volume.

[0008] A fourth aspect of this disclosure may include any of the first to third aspects, wherein the regenerated medium includes silicate aggregates, alkali metal phosphates, porous metal oxides, or a combination thereof.

[0009] A fifth aspect of this disclosure may include any of the first to fourth aspects, wherein the average particle size of the recycled medium is between 5 μm and 5,000 μm.

[0010] A sixth aspect of this disclosure may include any of the first to fifth aspects, wherein 90% or more of the recycled medium has a particle size greater than 5 μm.

[0011] A seventh aspect of this disclosure may include any of the first to sixth aspects, wherein the regenerating medium includes particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felts, active layers coated on or impregnated therein on an inert carrier, or a combination thereof.

[0012] An eighth aspect of this disclosure may include any of the first to seventh aspects, wherein the salt bath composition disposed within the first internal volume substantially contains no regenerating medium.

[0013] A ninth aspect of this disclosure may include any of the first to eighth aspects, wherein the circulation device includes an impeller, a pump, a gas injection system, or a combination thereof.

[0014] A tenth aspect of the present disclosure may include any of the first to ninth aspects, wherein the circulation device operates to circulate the salt bath composition to the storage device at a flow rate from 0.001 volumes per hour to 10 volumes per hour.

[0015] An eleventh aspect of the present disclosure may include any of the first to tenth aspects, wherein the inlet of the storage device is surrounded by a sieve having an effective diameter of 15% or less of the average particle size of the recycled medium; the outlet of the storage device is surrounded by a sieve having an effective diameter of 15% or less of the average particle size of the recycled medium; or both the inlet and the outlet of the storage device are surrounded by a sieve having an effective diameter of 15% or less of the average particle size of the recycled medium.

[0016] A twelfth aspect of this disclosure may include any of the first to eleventh aspects, wherein the second internal volume includes a first regeneration area and a second regeneration area located downstream of the first regeneration area.

[0017] A thirteenth aspect of this disclosure may include a twelfth aspect, wherein a first regeneration area includes a first regeneration medium, and a second regeneration area includes a second regeneration medium different from the first regeneration medium.

[0018] A fourteenth aspect of the present disclosure may include a thirteenth aspect, wherein the storage device includes a sieve positioned between a first regeneration area and a second regeneration area, the sieve having an opening having a diameter smaller than the average particle size of at least one of the first regeneration medium and the second regeneration medium.

[0019] According to a 15th aspect of the present disclosure, a method for regenerating a molten salt may include the steps of: circulating the molten salt to a storage device located in a first internal volume of a salt bath, wherein the molten salt contains one or more impurities formed during an ion exchange process, and the storage device contains a regeneration medium located in a second internal volume defined by the storage device; and bringing the molten salt into contact with the regeneration medium in the storage device, wherein the contact reduces the concentration of one or more impurities in the molten salt.

[0020] According to a sixteenth aspect of the present disclosure, a method for regenerating a molten salt may include the steps of: circulating the molten salt to a storage device located outside a first internal volume defined by a salt bath, wherein the molten salt contains one or more impurities formed during an ion exchange process, and the storage device contains a regeneration medium located within a second internal volume defined by the storage device; and bringing the molten salt into contact with the regeneration medium in the storage device, wherein the contact reduces the concentration of one or more impurities in the molten salt.

[0021] A 17th aspect of this disclosure may include a 16th aspect in which the temperature of the second internal volume is 3°C or more lower than the temperature of the first internal volume.

[0022] The eighteenth aspect of this disclosure may include any of the fifteenth to seventeenth aspects, wherein one or more impurities include lithium nitrate, alkali metal nitrites, alkali metal oxides, alkaline earth metal nitrites, alkaline earth metal oxides, or combinations thereof.

[0023] A 19th aspect of this disclosure may include any of the 15th to 18th aspects, wherein the recycled medium includes silicic acid, alkali metal phosphates, alkali metal carbonates, porous metal oxides, or combinations thereof.

[0024] A 20th aspect of this disclosure may include any of the 15th to 19th aspects, wherein the average particle size of the recycled medium is between 5 μm and 5,000 μm.

[0025] A 21st aspect of this disclosure may include any of the 15th to 20th aspects, wherein 90% or more of the recycled medium has a particle size greater than 5 μm.

[0026] A 22nd aspect of this disclosure may include any of the 15th to 21st aspects, wherein the regenerating medium includes particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felt, an active layer coated on or impregnated therein on an inert carrier, or a combination thereof.

[0027] A 23rd aspect of this disclosure may include any of the 15th to 22nd aspects, wherein the salt bath composition disposed within the first internal volume substantially contains no regenerating medium.

[0028] A 24th aspect of this disclosure may include any of the 15th to 23rd aspects, wherein the molten salt is circulated to a storage device at a flow rate of 0.001 volumes per hour to 10 volumes per hour.

[0029] A 25th aspect of the present disclosure may include any of the 15th to 24th aspects, further comprising the steps of: heating a salt bath composition containing an alkali metal salt to an ion exchange temperature to form a molten salt; and immersing a glass article in the molten salt so that ion exchange occurs between the molten salt and the glass article, wherein one or more impurities are formed in the molten salt by ion exchange between the molten salt and the glass article.

[0030] It should be understood that both the general description above and the detailed description below describe various embodiments and are intended to provide an overview or framework for understanding the nature and features of the subject matter of the claims. The accompanying drawings are included and constitute part of this specification to give a further understanding of the various embodiments. The drawings illustrate the various embodiments described herein and, together with the description, serve to illustrate the principles and operation of the subject matter of the claims. [Brief explanation of the drawing]

[0031] The following detailed description in this disclosure will be better understood when read in conjunction with the accompanying drawings. [Figure 1A] A schematic diagram illustrating a portion of the ion exchange process according to one or more embodiments shown and described herein. [Figure 1B] A schematic diagram illustrating a portion of the ion exchange process according to one or more embodiments shown and described herein. [Figure 2A] A schematic diagram illustrating a portion of the ion exchange process according to one or more embodiments shown and described herein. [Figure 2B] A schematic diagram illustrating a portion of the ion exchange process according to one or more embodiments shown and described herein. [Figure 3A] A schematic diagram illustrating a portion of the ion exchange process according to one or more embodiments shown and described herein. [Figure 3B] A schematic diagram illustrating a portion of the ion exchange process according to one or more embodiments shown and described herein. [Figure 4A] A generalized flowchart of a salt bath system for strengthening glass articles, according to one or more embodiments shown and described herein. [Figure 4B] A generalized flowchart of a salt bath system for strengthening glass articles, according to one or more embodiments shown and described herein. [Figure 4C] Schematic diagrams of a storage device for a salt bath system for strengthening glass articles, as shown in Figures 4A and 4C, according to one or more embodiments shown and described herein. [Figure 5A] A graph plotting the volume of surface hydrolysis resistance titrant (mL; Y-axis) as a function of time (days; X-axis) for salt bath systems for strengthening glass articles using various amounts of recycled media, according to one or more embodiments shown and described herein. [Figure 5B] A graph plotting the volume of surface hydrolysis resistance titrant (mL; Y-axis) as a function of the number of strengthened glass articles (number of vials per kilogram of alkali metal salt; X-axis) for a salt bath system for strengthening glass articles using various amounts of recycled medium according to one or more embodiments shown and described herein. [Figure 6A] A graph plotting surface compressive stress (MPa; left Y-axis) and compression depth (μm; right Y-axis) as a function of time (days; X-axis) for a salt bath system for strengthening glass articles, according to one or more embodiments shown and described herein. [Figure 6B] Graphs plotting surface compressive stress (MPa; left Y-axis) and compression depth (μm; right Y-axis) as a function of the number of strengthened glass articles (number of vials per kilogram of alkali metal salt; X-axis) for a salt bath system for strengthening glass articles according to one or more embodiments shown and described herein, may be used when describing the simplified schematic diagrams of Figures 4A-4C, and do not include a number of valves, temperature sensors, electronic control devices, etc., which are well known to those skilled in the art. However, those skilled in the art will understand that these components are included within the scope of this disclosure.

[0032] In addition, the arrows in the simplified schematic diagrams of Figures 4A-4C indicate the movement or flow of material. However, these arrows may also equivalently indicate transfer lines, such as conduits, that can move such material between components of two or more systems. Arrows leading to one or more components of a system represent inlets or outlets in a given system component, while arrows leading to a single component of a system represent system outlets exiting the illustrated system or system inlets entering the illustrated system. The direction of the arrows generally coincides with the main direction of movement of the material or material contained within the physical transfer lines represented by the arrows.

[0033] In the simplified schematic diagrams of Figures 4A-4C, arrows may indicate process steps for transferring material from one system component to another. For example, an arrow pointing from a component of the first system to a component of the second system represents material "passing" from the first system component to the second system component, and this passing material may include material "leaving" or "removed" from the first system component and material "introduced" into the second system component.

[0034] We will now refer in more detail to various embodiments of this disclosure, some of which are shown in the attached drawings. [Modes for carrying out the invention]

[0035] Embodiments described herein relate to a salt bath system for strengthening glass articles and a method for regenerating molten salt. The salt bath system for strengthening glass articles according to this disclosure may generally comprise a salt bath defining a first internal volume enclosed by at least one side wall, a salt bath composition disposed within the first internal volume, a storage device disposed within the first internal volume, and a circulation device disposed near the inlet of the storage device. The salt bath composition may contain an alkali metal salt. The storage device may define a second internal volume enclosed by at least one side wall and may contain a regeneration medium disposed within the second internal volume. The circulation device can be operated to circulate the salt bath composition to the storage device. A method for regenerating molten salt according to this disclosure may comprise the steps of circulating the molten salt to a storage device disposed within the first internal volume of the salt bath, and bringing the molten salt into contact with a regeneration medium in the storage device. The molten salt may contain one or more impurities formed during the ion exchange process. The storage device may contain a regeneration medium disposed within a second internal volume defined by the storage device. This contact can reduce the concentration of one or more impurities in the molten salt. Various embodiments of the systems and methods of this disclosure are described herein with specific reference to the accompanying drawings.

[0036] The directional terms used here—for example, up, down, right, left, front, back, top, bottom—are used only in reference to the depicted drawings and are not intended to imply absolute orientation.

[0037] As used herein, the indefinite articles "a" and "an" mean that, when referring to an element of this disclosure, at least one of these elements is present. While these indefinite articles are traditionally used to indicate that the modified noun is singular, unless otherwise specified, the indefinite articles "a" and "an" also include plural forms in this disclosure. Similarly, the definite article "the" also indicates that, unless otherwise specified, the modified noun may be singular or plural in this disclosure.

[0038] As used herein, the term “or” is inclusive, and in particular, “A or B” refers to “A, B, or A and B.” Alternatively, the term “or” may be used exclusively only when explicitly indicated in this disclosure by terms such as “either A or B” or “one of A or B.”

[0039] As used herein, terms such as “salt bath composition,” “salt bath,” and “molten salt” are synonymous unless otherwise specified and refer to a solution or medium used to carry out an ion exchange process in a glass (or glass-ceramic) article, in which cations within the surface of the glass article are replaced, i.e., exchanged, with cations present in the salt bath. The salt bath may contain at least one alkali metal salt, such as potassium nitrate (KNO3) and / or sodium nitrate (NaNO3), which may be substantially liquefied into a liquid phase by heat or otherwise heated.

[0040] As used herein, the term "chemical durability" refers to the ability of a glass composition to resist degradation when exposed to specific chemical conditions. For more information, see the chemical durability of the glass articles described herein. <600> The evaluation was conducted in water according to the "Surface Glass Test" in "Containers - Glass" (2017).

[0041] It should be understood that material flows may be named in terms of their components, and the component that a material flow is named may be the main component of the material flow (such as constituting 50% by mass, 70% by mass, 90% by mass, 95% by mass, 99% by mass, 99.5% by mass, or 99.9% by mass, up to 100% by mass of the material flow). For example, a flow of a salt bath composition, which may be from a salt bath to a storage device, may constitute 50% by mass to 100% by mass of the salt bath composition, and as a result, the material flow may be named "salt bath composition". It should also be understood that a component is disclosed when a material flow containing that component is disclosed as passing from one component of one system to another component of another system. For example, a disclosed flow of a salt bath composition from a component of a first system to a component of a second system should be understood as equivalently disclosing a salt bath composition passing from the first component of the first system to the second component of the second system.

[0042] Unless otherwise specified, none of the methods described herein are intended to require that the steps be performed in a particular order, nor that any particular orientation be required for any apparatus. Therefore, if a claim for a method does not actually enumerate the order in which the steps should be performed, or if a claim for an apparatus does not actually enumerate the order or orientation of its individual components, or if it is not otherwise specifically stated in the claim or description that the steps should be limited to a particular order, or if no particular order or orientation is enumerated for the components of the apparatus, then neither order nor orientation is ever intended to be implied. This applies to any possible non-expressive criteria of interpretation, including the arrangement of steps, the flow of operations, the order of components, or the orientation of components; the obvious meaning derived from grammatical construction or punctuation; and logical matters relating to the number or type of embodiments described in the specification.

[0043] First, referring to Figures 1A and 1B, a conventional ion exchange process is schematically shown. This ion exchange process includes the step of immersing a glass article 105 in a salt bath 100. The glass article 105 is immersed in relatively small cations 130, such as Li + and / or Na + It may contain alkali metal cations such as cations. Salt bath 100 may contain molten salt 101 containing relatively large cations 120 (i.e., relative to the cations 130 of the glass article). That is, cation 120 may have a larger atomic radius than cation 130. An example of cation 120 is potassium (K + Examples include alkali metal cations such as cations. The larger cation 120 may dissociate from salts such as alkali metal nitrates present in the salt bath 100 when heated to a high temperature to produce the molten salt 101. When the glass article 105 is immersed in the salt bath 100, cations 130 in the glass article 105 may diffuse from the glass article 105 into the molten salt 101. Referring here to Figure 1B, cations 120 from the molten salt 101 may replace cations 130 in the glass article 105 after such diffusion. When the smaller cation in the glass article 105 is thus replaced by the larger cation from the molten salt 101, surface compressive stress (CS) is generated on the surface of the glass article 105, extending to the compression depth (DOC), which will increase the mechanical strength of the glass article 105 and improve its resistance to breakage.

[0044] Generally, to increase the efficiency of the ion exchange process, a large number of glass articles are sometimes immersed in a single salt bath in a batch process. However, as batch production of tempered glass articles continues in the same salt bath, the effectiveness of the salt bath inevitably decreases during the ion exchange process. One reason for this decrease in salt bath effectiveness is likely the formation of undesirable species within the salt bath. Specifically, during the ion exchange process, alkali metal nitrates present in the salt bath may decompose into alkali metal nitrites and / or alkali metal oxides. For example, the decomposition of alkali metal nitrates to alkali metal nitrites is expressed by the following formula: MNO3←→MNO2+1 / 2O2[M:IUPAC Group 1 metal] As shown below, both alkali metal nitrates and alkali metal nitrites are given by the following formula: MNO2 ←→ M2O+NO x [M:IUPAC Group 1 metal] As shown, further decomposition into alkali metal oxides may occur. For example, when potassium nitrate (KNO3) is present in a salt bath, KNO3 decomposes into two main decomposition products: potassium nitrite (KNO2) and potassium oxide (K2O) at temperatures above approximately 400°C. Other alkali metal nitrates, such as sodium nitrate and lithium nitrate, may decompose into their corresponding alkali metal nitrites and alkali metal oxides at even lower temperatures than KNO3 (i.e., below 400°C).

[0045] The presence of alkali metal oxides such as K2O in the molten salt can degrade the properties of glass articles processed within it. Specifically, alkali metal oxides in the molten salt can anharmoniously etch the surface of the glass article during ion exchange. This etching degrades the surface of the glass article, which in turn can adversely affect many of its properties. For example, glass articles subjected to ion exchange in a molten salt containing K2O at a concentration of 0.5% by mass or higher may develop visible etching and surface damage. Even when glass articles undergo ion exchange in a molten salt containing K2O at a significantly lower concentration than 0.5% by mass (i.e., 0.05% by mass or even 0.005% by mass), the presence of K2O can considerably reduce the mechanical strength of the glass article.

[0046] Surface degradation of glass articles during ion exchange can be reduced or prevented by neutralization of the salt bath. That is, surface degradation of glass articles during ion exchange can be reduced or prevented by reducing or eliminating alkali metal oxides present in the salt bath. This can be achieved, at least in part, by including a regenerating medium such as silicic acid in the salt bath. As used here, the term "silicic acid" refers to silicic acid such as orthosilicic acid (Si(OH)4), and its corresponding silicate (the conjugate base of silicic acid). Silicic acid is generally given by the following formula: M2O+SiO2→M2SiO3 [M:IUPAC Group 1 metal] As shown, it reacts with alkali metal oxides to form nonreactive products. Silicic acid reacts with calcium cations (Ca 2+ ) and magnesium cation (Mg 2+ It may also react with common contaminants in molten salts, such as (which can adhere to the surface of glass articles and interfere with the ion exchange process).

[0047] Another reason for this reduced effectiveness of salt baths may be "poisoning" of the molten salt by undesirable cations initially present in the glass article. For example, while lithium-containing glass articles may offer numerous advantages, such as a faster and more efficient ion exchange process, even a difference of about 1 mass% of lithium cations in the molten salt bath (i.e., lithium cations exchanged to leave the glass article and enter the salt bath during ion exchange) can reduce the surface compressive stress and compressive depth that can be achieved in the glass article. Even when the concentration of lithium cations in the molten salt is less than 1 mass%, lithium cations can interfere with the ion exchange process, and as the concentration of lithium cations in the molten salt inevitably increases during the ion exchange process, this can result in tempered glass articles with dramatically different compressive stresses and compressive depths from batch to batch.

[0048] A salt bath contaminated with undesirable cations such as lithium cations can be regenerated by adding a regenerating medium such as phosphate. For example, referring here to Figures 2A and 2B, a salt bath 200 containing a contaminated molten salt 202 is shown. The contaminated molten salt 202 contains lithium cations 230 and relatively larger cations 220 (i.e., relative to the lithium cations 230 of the glass article), such as sodium and / or potassium cations. The contaminated molten salt 202 can be regenerated by adding phosphate 240. When introduced into the contaminated molten salt 202, the phosphate 240 dissociates into cations and phosphoric acid (PO4). -3) can form anions. The phosphate anions present in the contaminated molten salt 202 react with lithium cations 230, allowing them to be selectively precipitated. This selective precipitation reaction produces insoluble lithium phosphates 250, such as trilithium phosphate (Li3PO4), dilithium sodium phosphate (Li2NaPO4), and / or lithium disodium phosphate (LiNa2PO4), and a regenerated molten salt 211 suitable for further ion exchange processes. In other words, the presence of phosphates creates favorable conditions for the removal of lithium cations from the salt bath by precipitation.

[0049] More specifically, the contaminated molten salt can be regenerated by "spiking" phosphate into the salt bath (i.e., introducing phosphate between batches), as shown in Figures 2A and 2B, or the phosphate may be present during the ion exchange process, as shown in Figures 3A and 3B. For example, a glass article 305 containing lithium cations 330 can be immersed in a salt bath 300 containing relatively large cations 320 (i.e., relative to the lithium cations 330 in the glass article), such as sodium and / or potassium cations, and phosphate 340. As the lithium cations 330 diffuse from the glass article 305, the phosphate anions dissociated from the phosphate 340 can react with the dissolved lithium cations 330, selectively precipitating them to produce insoluble lithium phosphate 350 and the regenerated molten salt 311.

[0050] As mentioned above, numerous methods can be used to mitigate and / or prevent the decline in the effectiveness of salt baths. However, while the introduction of regenerating media such as silicates and / or phosphates can mitigate and / or prevent the decline in the effectiveness of salt baths resulting from the ion exchange process, these regenerating media may introduce new challenges to the ion exchange process.

[0051] For example, if excessively large silica particles are added to a salt bath, the silica may fail to effectively neutralize the molten salt. Specifically, if the average size of the silica particles is too large, they may sink more quickly to the bottom of the molten salt, resulting in a reduced chance of interaction and reaction between the silica and alkali metal oxides. Over time, the large silica particles may accumulate as sludge at the bottom of the salt bath, requiring the system to be shut down and the salt bath to be replaced. Conversely, if the average particle size of the silica particles is too small, they may adhere to the surface of glass articles being ion-exchanged in the molten salt. Such adhesion of silica particles to the surface of glass articles can result in the glass articles becoming unsuitable for commercial use, or at the very least, requiring additional processing that increases manufacturing costs and reduces efficiency.

[0052] Similarly, adding phosphate to a salt bath can lead to the formation of phosphate crystals that may adhere to insoluble sludge and / or glass articles that must be removed from the salt bath. For example, lithium cations preferentially bind to phosphate over other alkali metal cations present in the salt bath, such as sodium and potassium cations. However, as the concentration of lithium cations decreases, the phosphate may begin to react with other alkali metal cations to form alkali metal phosphates, which can then dissociate to form phosphate crystals. These phosphate crystals may adhere to the surface of glass articles undergoing ion exchange in the molten salt. The presence of phosphate crystals on the surface of glass articles can disrupt the ion exchange process, reducing the compressive stress and depth achieved, and may also cause depressions and / or protrusions to form on the surface of the glass articles during removal. Even with minimal phosphate crystal formation, insoluble lithium phosphate increases in the salt bath over time, necessitating periodic halting of the process to remove sludge and return the salt bath to its original composition.

[0053] This disclosure relates to a method for regenerating molten salts and a salt bath system for strengthening glass articles, which utilizes regenerating media such as silicates and / or phosphates to effectively regenerate the molten salt while reducing or preventing undesirable effects associated with the presence of these regenerating media in the molten salt.

[0054] Referring here to Figures 4A and 4B, the salt bath system 400 is schematically shown. The salt bath system 400 may include a salt bath 402. The salt bath 402 may define a first internal volume 404 enclosed by at least one side wall 406, and a salt bath composition 408 may be placed in this first internal volume 404. The salt bath system 400 may further include a storage device 410 located within the first internal volume 404. The storage device 410 may define a second internal volume 412 enclosed by at least one side wall 414. One or more types of regenerating media may be placed in this second internal volume 412. The salt bath system may further include a circulation device 416 located adjacent to the inlet 418 of the storage device 410.

[0055] In the embodiment, the salt bath composition 408 may contain alkali metal salts. For example, the salt bath composition 408 may contain alkali metal nitrates such as potassium nitrate (KNO3), sodium nitrate (NaNO3), lithium nitrate (LiNO3), or a combination thereof. In the embodiment, the salt bath composition 408 may contain 90% by mass or more of one or more alkali metal salts based on the total mass of the salt bath composition 408. For example, the salt bath composition 408 may contain 90% to 99.9% by mass, 90% to 99.5% by mass, 90% to 99% by mass, 90% to 97% by mass, 90% to 95% by mass, 90% to 93% by mass, 93% to 99.9% by mass, 93% to 99.5% by mass, 93% to 99% by mass, 93% to 97% by mass, or 93% by mass. It may contain one or more alkali metal salts in amounts of 95% by mass, 95% to 99.9% by mass, 95% to 99.5% by mass, 95% to 99% by mass, 95% to 97% by mass, 97% to 99.9% by mass, 97% to 99.5% by mass, 97% to 99% by mass, 99% to 99.9% by mass, 99% to 99.5% by mass, or 99.5% to 99.9% by mass.

[0056] In the embodiment, the concentration of alkali metal salts in the salt bath composition 408 may be balanced based on the composition of the glass article in order to provide an ion exchange process that increases both the surface compressive stress and the compression depth on the surface of the glass article after the ion exchange process. For example, the salt bath composition 408 may contain potassium nitrate at a higher concentration than sodium nitrate based on the total concentration of the salt bath composition 408, or the salt bath composition 408 may contain sodium nitrate at a higher concentration than potassium nitrate based on the total mass of the salt bath composition 408. A higher concentration of sodium nitrate than potassium nitrate in the salt bath composition, combined with a longer residence time in the molten salt bath, will result in a greater compression depth in the glass article.

[0057] In the embodiment, the salt bath composition 408 may optionally contain lithium nitrate in an amount of 1% by mass or less based on the total mass of the salt bath composition 408. For example, the salt bath composition 408 may contain lithium nitrate in amounts of 0.01% to 1% by mass, 0.01% to 0.8% by mass, 0.01% to 0.6% by mass, 0.01% to 0.3% by mass, 0.01% to 0.2% by mass, 0.01% to 0.1% by mass, 0.1% to 1% by mass, 0.1% to 0.8% by mass, 0.1% to 0.6% by mass, and 0.1% to 0.3% by mass based on the total mass of the salt bath 100. Lithium nitrate may be present in amounts of %, 0.1% to 0.2% by mass, 0.2% to 1% by mass, 0.2% to 0.8% by mass, 0.2% to 0.6% by mass, 0.2% to 0.3% by mass, 0.3% to 1% by mass, 0.3% to 0.8% by mass, 0.3% to 0.6% by mass, 0.6% to 1% by mass, 0.6% to 0.8% by mass, or 0.8% to 1% by mass. If the concentration of lithium nitrate is too high (i.e., more than 1% by mass) due to either the inclusion of lithium nitrate in the salt bath composition and / or the diffusion of lithium cations from the glass article, the molten salt may be considered contaminated, thereby adversely affecting the ion exchange process. A contaminated molten salt will result in reduced compressive stress and compression depth of the glass article compared to a glass article subjected to ion exchange in an uncontaminated molten salt. Conversely, if the lithium nitrate concentration is too low (i.e., less than 0.01% by mass), the molten salt bath may not be suitable for strengthening certain articles, such as glass-ceramic articles. Specifically, excess lithium cations can act as nucleating agents, promoting the formation of one or more crystalline phases, and may diffuse from the glass-ceramic article during the ion exchange process, resulting in reduced crystallization and an increase in sodium-rich areas within the glass-ceramic article. These sodium-rich areas within the glass-ceramic article can cause corrosion and / or crack formation.

[0058] To carry out an ion exchange process, a salt bath composition 408 may be used, in which metal cations of the glass article are exchanged for alkali metal cations of the alkali metal salt of the salt bath composition 408. Once the salt bath composition 408 is contaminated in the first internal volume 404, it may be heated to a temperature (also called the ion exchange temperature) sufficient to create a molten salt and thereby promote the ion exchange process. In the embodiment, the salt bath composition 408 may be heated to a temperature of 350°C to 500°C. For example, the salt bath composition may be heated to temperatures of 350°C to 475°C, 350°C to 450°C, 350°C to 425°C, 350°C to 400°C, 350°C to 375°C, 375°C to 500°C, 375°C to 475°C, 375°C to 450°C, 375°C to 425°C, 375°C to 400°C, 400°C to 500°C, 400°C to 475°C, 400°C to 450°C, 400°C to 425°C, 425°C to 500°C, 425°C to 475°C, 450°C to 500°C, 450°C to 475°C, or 475°C to 500°C. However, if the ion exchange temperature is too high, it may become difficult to properly control the ion exchange process, and for example, the degradation rate of the alkali metal salt in the salt bath composition 408 may increase.

[0059] Referring further to Figure 4A, the salt bath system 400 may include a storage device 410 located within a first internal volume 404. The storage device 410 may define a second internal volume 412 enclosed by at least one side wall 414. One or more types of regeneration media may be placed within the second internal volume 412. The storage device 410 allows contact between the salt bath composition 408 and the regeneration media, thereby suppressing and / or preventing a decrease in the effectiveness of the salt bath composition 408. Furthermore, since all and / or a substantial portion of the regeneration media used in the salt bath system 400 are located within the storage device 410, any undesirable by-products of one or more types of regeneration media remain within the storage device 410.

[0060] As a result, difficult situations associated with the use of the regenerating medium, such as the accumulation of silicic acid and / or insoluble lithium phosphate sludge in the salt bath 402 adhering to the surface of glass articles, will be reduced and / or completely prevented. Next, the storage device 410 can significantly increase the lifespan of the salt bath composition 408 and the overall processing capacity of the strengthening process, thereby significantly reducing operating costs. Furthermore, since the regenerating medium remains separate from the salt bath composition 408, the regenerating medium can be removed, replenished, and / or replaced when depleted without replacing the salt bath composition 408. This further increases the effectiveness of the salt bath system 400 compared to conventional salt bath systems in which the regenerating medium is directly introduced into the salt bath composition.

[0061] In some embodiments, the storage device 410 may include any container suitable for contact with the molten salt (i.e., the salt bath composition 408 heated to a temperature of 350°C to 500°C) on both its inner and outer surfaces. For example, in some embodiments, the storage device 410 may include one or more sections of size 8, schedule 10, Society of Automotive Engineers (SAE) 304 stainless steel pipe. In other embodiments (not shown), the storage device 410 may include one or more containers, such as baskets and / or pouches, made of stainless steel mesh, into which the salt bath composition 408 can flow, but which prevent movement of the regenerating medium.

[0062] As described above, one or more regeneration media can be placed in the second internal volume 412 of the storage device 410. As used herein, the term “regeneration media” refers to any material effective in precipitating, filtering, binding, reducing the concentration of, or removing from the molten salt bath one or more substances (also referred to as impurities and / or contaminants) that are formed during the ion exchange process and / or adversely affect the ion exchange of glass articles, or otherwise are considered undesirable in the salt bath composition. For example, the regeneration media may contain silicic acid, which, as described above, reacts with and removes the decomposition products of alkali metal salts from the salt bath composition 408. Similarly, the regeneration media may contain phosphates, which, as described above, can precipitate excess lithium cations from the salt bath composition 408. The regeneration media may also include alkali metal carbonates such as potassium carbonate (K2CO3), which would be suitable for sodium washing (i.e., reducing sodium nitrate to an appropriate concentration), and filtering media, which would be suitable for removing debris and contaminants from the salt bath composition 408.

[0063] The regeneration medium may be in any form suitable for filling the storage device 410 and capable of allowing the salt bath composition 408 to flow appropriately into the storage device 410. For example, the regeneration medium may include particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felt, active layers coated on or impregnated within an inert carrier, or a combination thereof. As described in detail herein, one or more types of regeneration medium may be contained within the storage device 410 by one or more barriers positioned on the side walls 414 and at both the inlet and outlet of the storage device 410. The barriers may be one or more mesh layers, allowing the salt bath composition 408 to flow into the storage device 410 so that the salt bath composition 408 comes into contact with the regeneration medium but prevents the regeneration medium from moving from the storage device 410 into the first internal volume 404 of the salt bath 402.

[0064] In embodiments where the regeneration medium is granular, the average particle size of the granular regeneration medium may be between 5 μm and 5,000 μm. For example, in embodiments where the regeneration medium is granular, the average particle size of the granular regeneration medium may be between 5 μm and 2,000 μm, 5 μm and 1,000 μm, 5 μm and 500 μm, 5 μm and 100 μm, 5 μm and 50 μm, 50 μm and 5,000 μm, 50 μm and 2,000 μm, 50 μm and 1,000 μm, 50 μm and 500 μm, 50 μm and 100 μm, and 10 The particle sizes may range from 0 μm to 5,000 μm, 100 μm to 2,000 μm, 100 μm to 1,000 μm, 100 μm to 500 μm, 500 μm to 5,000 μm, 500 μm to 2,000 μm, 500 μm to 1,000 μm, 1,000 μm to 5,000 μm, 1,000 μm to 2,000 μm, or 2,000 μm to 5,000 μm. In the embodiment, more than 90% of the recycled medium may have particle sizes greater than 5 μm. For example, more than 92%, 94%, 96%, 98%, 99%, or 99.5% of the recycled medium may have particle sizes greater than 5 μm. If the average particle size of the granular regeneration medium is smaller than that (i.e., less than 5 μm), the regeneration medium may become too densely packed, and the pressure drop across the containment device 410 may be too large for the efficient operation of the salt bath system 400. Conversely, if the average particle size of the granular regeneration medium is larger than that (i.e., greater than 5 μm), some species, such as insoluble lithium phosphate, may conveniently precipitate on the surface of the larger particles. This reduces the amount of relatively small species that could escape from the containment device 410 and contaminate the salt bath composition 408.

[0065] In an embodiment, the playback medium may contain silicic acid aggregates. As used herein, the term "silicic acid aggregates" shall refer to clusters or units formed by the aggregation of single masses of silicic acid nanoparticles. As described above, the silicic acid aggregates can react with the decomposition products of one or more alkali metal salts in the salt bath composition 408 to form non-reactive (e.g., not etching or corroding the surface of the glass article) silicate and water. Therefore, the silicic acid aggregates can reduce the concentration of the decomposition products of the alkali metal salts in the salt bath composition 408 and neutralize the salt bath composition 408.

[0066] In an embodiment, the silicic acid aggregates may have an average particle size of 5 μm to 400 μm as measured by laser diffraction particle size analysis. For example, the silicic acid aggregates may have an average particle size of 5 μm to 350 μm, 5 μm to 300 μm, 5 μm to 250 μm, 5 μm to 200 μm, 5 μm to 50 μm, 50 μm to 400 μm, 50 μm to 350 μm, 50 μm to 300 μm, 50 μm to 250 μm, 50 μm to 200 μm, 200 μm to 400 μm, 200 μm to 350 μm, 200 μm to 300 μm, 200 μm to 250 μm, 250 μm to 400 μm, 250 μm to 350 μm, 250 μm to 300 μm, 300 μm to 400 μm, 300 μm to 350 μm, or 350 μm to 400 μm as measured by laser diffraction particle size analysis. If the silicic acid aggregates have a smaller average particle size (e.g., less than 5 μm), any silicic acid aggregates transferred from the storage device 410 may easily adhere to the surface of the glass article, resulting in making the glass article unsuitable for commercial use due to any situation.

[0067] In an embodiment, the specific surface area of the silicic acid aggregates may be 200 m 2 / g or more as measured by the Brunauer-Emmett-Teller (BET) method. For example, the specific surface area of the silicic acid aggregates may be 200 m 2 / g to 600 m 2 / g, 200 m 2 / g to 550 m 2 / g, 200m 2 / g to 500m 2 / g, 200m 2 / g to 450m 2 / g, 200m 2 / g to 400m 2 / g, 200m 2 / g to 350m 2 / g, 200m 2 / g to 300m 2 / g, 200m 2 / g to 250m 2 / g, 250m 2 / g to 600m 2 / g, 250m 2 / g to 550m 2 / g, 250m 2 / g to 500m 2 / g, 250m 2 / g to 450m 2 / g, 250m 2 / g to 400m 2 / g, 250m 2 / g to 350m 2 / g, 250m 2 / g to 300m 2 / g, 300m 2 / g to 600m 2 / g, 300m 2 / g to 550m 2 / g, 300m 2 / g to 500m 2 / g, 300m 2 / g to 450m 2 / g, 300m 2 / g to 400m 2 / g, 300m 2 / g to 350m 2 / g, 350m 2 / g to 600m 2 / g, 350m 2 / g to 550m 2 / g, 350m 2 / g to 500m 2 / g, 350m 2 / g to 450m 2 / g, 350m 2 / g to 400m 2 / g, 400m2 / g to 600m 2 / g, 400m 2 / g to 550m 2 / g, 400m 2 / g to 500m 2 / g, 400m 2 / g to 450m 2 / g, 450m 2 / g to 600m 2 / g, 450m 2 / g to 550m 2 / g, 450m 2 / g to 500m 2 / g, 500m 2 / g to 600m 2 / g, 500m 2 / g to 550m 2 / g, or 550m 2 / g to 600m 2 It may be / g. The specific surface area of ​​the silicate aggregate is thought to be directly correlated with the reaction rate constant (k) of the reaction between the silicate aggregate and the decomposition products of the alkali metal salt, as described here. That is, the larger the specific surface area of ​​the silicate aggregate, the greater the possibility of reaction with the decomposition products present in the molten salt bath. This will allow for better control of the properties of the salt bath composition 408 while using less silicate aggregate, thereby increasing the chemical durability of the glass articles.

[0068] In the embodiment, the regeneration medium may contain silicate aggregates in an amount sufficient to effectively neutralize the salt bath composition 408. The surface hydrolysis resistance (SHR) of the glass article ion-exchanged in the molten salt bath would be the most reliable and discriminatory criterion for determining the degree to which the salt bath composition 408 is neutralized. The surface hydrolysis resistance of the glass article is a USP <660> This can be measured by the Surface Glass Test, as detailed in [reference]. To measure the surface hydrolysis resistance of a glass article using the Surface Glass Test, the glass vial or container containing the glass article is filled with carbon dioxide-free water or pure water. The filled vial or container is then subjected to an autoclave cycle at approximately 121°C for approximately 1 hour. The resulting leachate in the vial or container is then titrated with weak hydrochloric acid (e.g., 0.01 M HCl) in the presence of methyl red to neutralize it. The volume of titrant per 100 mL of leachate is used to determine the surface hydrolysis resistance of the glass article. Generally, a larger volume of titrant indicates lower chemical durability (i.e., the leachate contains more glass components released by the glass, and therefore more titrant is needed to compensate for the pH change due to the presence of glass components). Lower chemical durability generally corresponds to more surface degradation of the glass article and a higher concentration of alkali metal oxides in the salt bath used for ion exchange.

[0069] For tempered glass articles, particularly those intended for use in pharmaceutical packaging, a small titrant volume and / or high chemical durability are desirable. Generally, for Type I glass, a titrant volume of less than 1.5 mL is desirable. However, as mentioned above, the presence of decomposition products such as alkali hydroxides or alkali metal oxides in the molten salt bath used for ion exchange can corrode and / or etch the surface of the glass article. This etching can increase the titrant volume, which in turn reduces chemical durability. Typically, the titrant volume of a tempered glass article increases as a function of the elapsed time of ion exchange. That is, the longer the glass article is in contact with the molten salt bath, the larger the titrant volume. For example, a glass article undergoing ion exchange for about 3 hours may have a titrant volume of about 0.9 mL, while a glass article undergoing ion exchange for about 10 hours may have a titrant volume of about 1.1 mL. As a result, the chemical durability of tempered glass articles subjected to ion exchange in a neutralized molten salt will be increased compared to those subjected to ion exchange in a conventional molten salt (i.e., a molten salt that is not neutralized by silicate aggregates and consequently contains alkali hydroxides and / or alkali oxides).

[0070] In embodiments, particularly in embodiments where a salt bath system is used to strengthen glass articles for use as pharmaceutical packaging, the regenerated medium may contain silicic acid aggregates in an amount of 0.1% to 10% by mass based on the total mass of the salt bath composition. For example, the regenerating medium may contain approximately 0.1% to 7% by mass, approximately 0.1% to 5% by mass, approximately 0.1% to 3% by mass, approximately 0.1% to 1% by mass, approximately 0.1% to 0.5% by mass, approximately 0.5% to approximately 10% by mass, approximately 0.5% to 7% by mass, approximately 0.5% to 5% by mass, approximately 0.5% to 3% by mass, approximately 0.5% to 1% by mass, approximately 1% to approximately 10% by mass, approximately 1% to 7% by mass, approximately 1% to 5% by mass, approximately 1% to 3% by mass, approximately 3% to approximately 10% by mass, approximately 3% to 7% by mass, approximately 5% to approximately 10% by mass, or approximately 7% to approximately 10% by mass of silica aggregates, based on the total mass of the salt bath composition. If the regeneration medium contains less silicate aggregates (i.e., less than 0.1% by mass), the entire amount of silicate will react with unreacted silicates and water before the molten salt is effectively neutralized.

[0071] In the embodiment, the regeneration medium may contain one or more phosphates capable of precipitating excess lithium cations from the salt bath composition 408. In the embodiment, the phosphates may be trisodium phosphate (Na3PO4), tripotassium phosphate (K3PO4), disodium hydrogen phosphate (Na2HPO4), dipotassium hydrogen phosphate (K2HPO4), and trisodium triphosphate (Na5P3O 10 ), potassium triphosphate (K5P3O 10Examples of alkali metal phosphates include disodium diphosphate (Na2H2P2O7), tetrasodium pyrophosphate (Na4P2O7), potassium pyrophosphate (K4P2O7), sodium trimetaphosphate (Na3P3O9), potassium trimetaphosphate (K3P3O9), or combinations thereof. In embodiments, the phosphate may contain anhydrous phosphates such as anhydrous trisodium phosphate, which may contain 10 percent (%) or less of water and have a chemical purity of at least 97%. As previously described, the phosphate may dissociate with cations such as sodium and / or potassium cations into phosphate anions, thereby selectively precipitating lithium cations to produce insoluble lithium phosphate, which can maintain an appropriate lithium nitrate concentration in the salt bath composition 408.

[0072] In this embodiment, the phosphate may have an average particle size of 5 μm to 400 μm, as measured by laser diffraction particle size analysis. For example, phosphates may have an average particle size of 5 μm to 350 μm, 5 μm to 300 μm, 5 μm to 250 μm, 5 μm to 200 μm, 5 μm to 50 μm, 50 μm to 400 μm, 50 μm to 350 μm, 50 μm to 300 μm, 50 μm to 250 μm, 50 μm to 200 μm, 200 μm to 400 μm, 200 μm to 350 μm, 200 μm to 300 μm, 200 μm to 250 μm, 250 μm to 400 μm, 250 μm to 350 μm, 250 μm to 300 μm, 300 μm to 400 μm, 300 μm to 350 μm, or 350 μm to 400 μm, as measured by laser diffraction particle size analysis. If the phosphate has a smaller average particle size (e.g., less than 5 μm), any phosphate moved from the storage device may easily adhere to the surface of the glass article due to any of the following circumstances, resulting in the glass article being unsuitable for commercial use. Furthermore, with a larger average particle size (e.g., 5 μm or more), the solubility of the phosphate in the salt bath composition 408 at the ion exchange temperature decreases, and consequently, the amount of excess phosphate anions in the molten salt bath decreases, which can lead to the formation of phosphate crystals on the surface of the glass article, as mentioned above.

[0073] In the embodiment, the regeneration medium may contain an amount of phosphate sufficient to effectively maintain the concentration of lithium nitrate in the salt bath composition at an amount of 1% by mass or less based on the total mass of the salt bath composition. The regeneration medium may contain an amount of phosphate from 0.1% by mass to 10% by mass based on the total mass of the salt bath composition. For example, the regenerating medium may contain phosphates in amounts of approximately 0.1% to 7% by mass, approximately 0.1% to 5% by mass, approximately 0.1% to 3% by mass, approximately 0.1% to 1% by mass, approximately 0.1% to 0.5% by mass, approximately 0.5% to approximately 10% by mass, approximately 0.5% to 7% by mass, approximately 0.5% to 5% by mass, approximately 0.5% to 3% by mass, approximately 0.5% to 1% by mass, approximately 1% to approximately 10% by mass, approximately 1% to 7% by mass, approximately 1% to 5% by mass, approximately 1% to 3% by mass, approximately 3% to approximately 10% by mass, approximately 3% to 7% by mass, approximately 3% to 5% by mass, approximately 5% to approximately 10% by mass, or approximately 7% to approximately 10% by mass, based on the total mass of the salt bath composition. If the regeneration medium contains less than 0.1% by mass of phosphate, all or a substantial portion of the phosphate anions dissociated from the phosphate will precipitate before the ion exchange process is complete, increasing the concentration of lithium cations in the molten salt. Consequently, the amount of lithium nitrate in the salt bath composition 408 can increase to more than 1% by mass. Conversely, if the regeneration medium contains more than 10% by mass of phosphate, the concentration of lithium nitrate in the salt bath composition 408 will decrease to less than 0.01% by mass, excess lithium cations will diffuse from the glass article, and the sodium-rich areas in the glass article may increase.

[0074] In embodiments, the regeneration medium may include one or more materials (also referred to as the filtration medium) capable of filtering one or more contaminants from the salt bath composition 408. As used herein, the term “contaminants” refers to the debris introduced into the salt bath composition 408 during normal operation of the salt bath system. That is, contaminants are any material or compound in the salt bath composition that is generally considered undesirable and / or may adversely affect the ion exchange process. Examples of contaminants may include dust / debris, broken glass fragments, particles made from corrosion or wear of components of the salt bath system such as the salt bath, nitrogen oxide species, excess water, or a combination thereof. In embodiments, the filtration medium may include, for example, porous membranes and / or matrices such as porous metal oxides, stainless steel powder molded bodies or screens, porous alumina filters, porous silica filters, or a combination thereof. The filtration medium can bind to and / or capture contaminants while allowing the salt bath composition 408 to flow relatively freely, thereby effectively filtering all or part of the contaminants from the salt bath composition 408.

[0075] In this embodiment, the filtration medium may have an average pore size of 20 μm or less, as measured by mercury intrusion (MIP). For example, a filter medium may have an average pore size measured by MIP of 0.2 μm to 20 μm, 0.2 μm to 16 μm, 0.2 μm to 12 μm, 0.2 μm to 8 μm, 0.2 μm to 4 μm, 0.2 μm to 2 μm, 2 μm to 20 μm, 2 μm to 20 μm, 2 μm to 16 μm, 2 μm to 12 μm, 2 μm to 8 μm, 2 μm to 4 μm, 4 μm to 20 μm, 4 μm to 16 μm, 4 μm to 12 μm, 4 μm to 8 μm, 8 μm to 20 μm, 8 μm to 16 μm, 8 μm to 12 μm, 12 μm to 20 μm, 12 μm to 16 μm, or 16 μm to 20 μm. If the filtration medium has an average pore size smaller than that (e.g., less than 0.2 μm), the pressure drop across the filtration medium will be too large. Conversely, if the filtration medium has an average pore size larger than that (e.g., greater than 20 μm), a considerable amount of contaminants will pass through the filtration medium without being filtered from the salt bath composition 408.

[0076] Referring here to Figure 4C, an enlarged view of the storage device 410 is shown. As shown in Figure 4C, the storage device may include one or more “regeneration areas” located within a second internal volume 412, each containing one or more types of regeneration media. As used herein, the term “regeneration area” refers to a portion of the internal volume that is at least partially separated from the rest of the internal volume by partitions and / or barriers. For example, the storage device 410 shown in Figure 4C includes a first regeneration area 420, a second regeneration area 422, and a third regeneration area 424. The storage device 410 shown in Figure 4C includes sieves 426a to 426d located between these regeneration areas and surrounding the inlet 418 and outlet 428 of the storage device 410. The sieves 426a to 426d can also prevent the movement of regeneration media through the sieves while allowing the flow of the salt bath composition 408. In some embodiments, sieves 426a to 426d may include openings having an effective diameter of 15% or less of the average particle size of the recycled medium. For example, sieves 426a to 426d may include openings having an effective diameter of 10% or less, 5% or less, or 2.5% or less of the average particle size of the recycled medium. In some embodiments, sieves 426a to 426d may be made from a mesh having an average opening size smaller than the average particle size of the recycled medium placed in the second internal volume 412. Therefore, one or more sieves may have a mesh count of 70 or more. In some embodiments, sieves may have a mesh count of 70, 80, 100, 120, 140, 170, 200, 230, 270, 325, 400, 450, 500, or 635, based on the American Standard for Industrial Woven Wire Mesh (ASTM-E11). In other embodiments, the sieves 426a to 426d may be made from a porous filtration device such as sintered porous metal, ceramic, or glass, having an average opening size smaller than the average particle size of the regenerated medium placed in the second internal volume 412.

[0077] In some embodiments, each regeneration area may contain a majority of one regeneration medium. For example, in one embodiment, the first regeneration area 420 may contain more than 50% by mass of phosphate based on the total mass of the regeneration medium in the first regeneration area 420, and the second regeneration area 422 may contain more than 50% by mass of silicate aggregate based on the total mass of the regeneration medium in the second regeneration area 422. In some embodiments, each regeneration area may contain only one type of regeneration medium. For example, the first regeneration area 420 may contain more than 99% by mass of phosphate based on the total mass of the regeneration medium in the first regeneration area 420. In other embodiments, each regeneration area may be a blend and / or gradient of two or more types of regeneration mediums.

[0078] Referring again to Figures 4A-4C, since the regeneration medium cannot leave the regeneration area, the storage device 410 can also prevent undesirable by-products of regeneration from entering the first internal volume 404 while enabling the regeneration of the salt bath composition 408 (e.g., precipitation and / or neutralization of excess lithium cations therefrom). Thus, in the embodiment, the portion of the salt bath composition 408 located within the first internal volume 404 and outside the second internal volume 412 will be substantially free of the regeneration medium. As used herein, the term “substantially free” of a compound may refer to a mixture containing less than 0.1% by mass of that compound. For example, a salt bath composition that would be substantially free of the regeneration medium may contain less than 0.1% by mass, less than 0.08% by mass, less than 0.06% by mass, less than 0.04% by mass, less than 0.02% by mass, or less than 0.01% by mass of the regeneration medium, based on the total mass of the salt bath composition 408.

[0079] Referring again to Figure 4A, the storage device 410 may be located within the first internal volume 404. However, it should be understood that other embodiments are conceivable and possible. Referring to Figure 4B as an example, the salt bath system 400 may, instead of and / or in addition to, include a storage device 410 located outside the first internal volume 404. By locating the storage device 410 outside the first internal volume 404, it becomes possible to regenerate the salt bath composition 408 at a temperature lower than the ion exchange temperature of the salt bath composition 408. Although not bound by any particular theory, it is thought that regenerating the salt bath composition 408 at a temperature lower than the ion exchange temperature of the salt bath composition 408 would increase the efficiency of one or more regeneration media. For example, as described herein, the phosphate anions dissociated from the phosphate can selectively precipitate excess lithium cations to produce lithium phosphate. However, as the temperature of the salt bath composition 408 increases, the solubility and dissociation of lithium phosphate also increase, and the ability of the phosphate anions to precipitate lithium cations decreases. Therefore, the efficiency of one or more regeneration media will be maximized in embodiments where the storage device 410 is located outside the first internal volume 404. However, it should be understood that the salt bath composition 408 should remain liquid (i.e., molten salt) throughout the regeneration process; otherwise, the salt bath system 400 will become inoperable because the salt bath composition 408 cannot flow through the storage device 410. In fact, even if the salt bath composition 408 remains liquid despite having considerable viscosity, the reduction in the flow rate of the salt bath composition 408 through the storage device 410 will outweigh the increase in the efficiency of one or more regeneration media.

[0080] Referring again to Figures 4A-4C, the salt bath system 400 may include a circulation device 416 located near the inlet 418 of the storage device 410. In the inlet 418 of the storage device 410 shown in Figures 4A-4C, the inlet 418 is located near the bottom of the salt bath 402, but it should be understood that in other embodiments, the inlet 418 of the storage device 410 may be located near the top of the salt bath 402. The circulation device 416 can be operated to circulate the salt bath composition 408 into the storage device 410. In operation, the circulation device can be operated to introduce the salt bath composition 408 into the inlet 418, pass it through a first regeneration area 420, a second regeneration area 422 located downstream of the first regeneration area 420, a third regeneration area 424 located downstream of the second regeneration area 422, and discharge it out of the storage device 410 through the outlet 428. As used herein, the term “downstream” refers to the position of a component of the system relative to the flow direction of the material as it flows through the system. For example, a second component of the system can be considered “downstream” of a first component of the system if the material flowing through the system encounters the first component before encountering the second component. Regardless of the circulation of the salt bath composition 408 through the storage device 410, the circulation of the salt bath composition 408 within the first internal volume 404 is expected to improve the uniformity and availability of the desired species throughout the first internal volume 404, and consequently improve the uniformity of the tempered glass articles produced by the salt bath system 400.

[0081] The circulation device 416 may include any device suitable for circulating the salt bath composition 408 to the storage device 410. For example, the circulation device 416 may include a pump such as an electromagnetic pump, an impeller, a gas injection system such as an oxygen bubbler, or a combination thereof. The circulation device 416 may be selected based on various factors, such as the composition of the salt bath composition 408, the location of the storage device 410 (inside and / or outside the first internal volume 404 of the salt bath 402), and / or the location of the inlet 418 of the storage device 410 (for example, an impeller would be more suitable for use if the inlet 418 of the storage device 410 is close to the surface of the salt bath 402). In embodiments, the salt bath composition 408 may be circulated without requiring a mechanical agitator such as a pump or impeller. For example, a local area of ​​the salt bath composition 408 close to the inlet 418 can be selectively heated, thereby thermally inducing circulation of the salt bath composition 408 due to the buoyancy difference of the selectively heated portion of the salt bath. In the embodiment, the storage device 410 can be directly connected to the circulation device 416. For example, in the embodiment in which one or more baskets and / or pouches are made of stainless steel mesh, the storage device 410 can be directly connected to an impeller that rotates the storage device 410 in the first internal volume 404 of the salt bath 402 and circulates the salt bath composition 408 to the storage device 410.

[0082] In this embodiment, the salt bath composition 408 can be circulated to the storage device 410 at a flow rate sufficient to effectively regenerate the molten salt. Therefore, the salt bath composition 408 can be circulated to the storage device 410 at a flow rate of 10 volumes / hour from 0.001 volumes / hour. More simply put, 0.1% to 20000% of the total volume of the salt bath composition 408 can be circulated to the storage device 410 every hour. In this embodiment, the salt bath composition 408 can be circulated to the storage device 410 at flow rates of 0.001 vol / hour to 1 vol / hour, 0.001 vol / hour to 0.1 vol / hour, 0.001 vol / hour to 0.01 vol / hour, 0.01 vol / hour to 10 vol / hour, 0.01 vol / hour to 1 vol / hour, 0.01 vol / hour to 0.1 vol / hour, 0.1 vol / hour to 10 vol / hour, 0.1 vol / hour to 1 vol / hour, and even 1 vol / hour to 10 vol / hour. If the flow rate of the salt bath composition 408 passing through the storage device 410 is too fast (i.e., exceeding 10 vol / hour), the glass articles undergoing ion exchange in the molten salt may be disturbed, which may cause the glass to break. Conversely, if the flow rate of the salt bath composition 408 through the storage device 410 is too slow (i.e., less than 0.001 volumes / hour), the molten salt will not be regenerated fast enough to prevent a decrease in the effectiveness of the molten salt.

[0083] In this embodiment, the circulation device 416 may be positioned close to the bottom of the salt bath 402. While not bound by any particular theory, it is assumed that contaminants and / or regenerated media moved from the containment device will generally become denser than the molten salt and, as a result, settle to the bottom of the salt bath 402 over time. Therefore, if the circulation device 416 is positioned close to the bottom of the salt bath 402, portions of the molten salt likely to contain contaminants and released regenerated media will be preferentially circulated to the containment device 410. This will reduce the number of salt bath exchanges through the containment device before the molten salt is regenerated.

[0084] As previously mentioned, the salt bath composition 408 of the salt bath system may be heated to an ion exchange temperature to form a molten salt, and one or more glass articles may be immersed in the molten salt bath to carry out ion exchange between the molten salt and the glass articles. For example, Figures 1A and 1B show a glass article 105 completely immersed in the salt bath 100, but it should be understood that in embodiments, only a portion of the glass article 105 may be brought into contact with the salt bath 100. The glass article 105 can be brought into contact with the molten salt by immersion in the salt bath 100, or by spraying, dipping, or other similar means that bring the glass article 105 into contact with the salt bath 100. The glass article 105 may be brought into contact with the salt bath 100 multiple times, including but not limited to immersing the glass article 105 in the salt bath 100.

[0085] The glass article may be exposed to a molten salt for a processing time sufficient to generate surface compressive stress extending to the compression depth on the surface of the glass article. In the embodiment, the glass article may be exposed to a molten salt bath for a processing time of about 20 minutes to about 20 hours. For example, the glass article may be exposed to a molten salt bath for a processing time of about 20 minutes to about 15 hours, about 20 minutes to about 10 hours, about 20 minutes to about 5 hours, about 20 minutes to about 1 hour, about 1 hour to about 20 hours, about 1 hour to about 15 hours, about 1 hour to about 10 hours, about 1 hour to about 5 hours, about 5 hours to about 20 hours, about 5 hours to about 15 hours, about 5 hours to about 10 hours, about 10 hours to about 20 hours, about 10 hours to about 15 hours, or about 15 hours to about 20 hours.

[0086] As the ion exchange process progresses, the salt bath composition 408 may be continuously regenerated, as described above. For example, as the ion exchange process progresses, the salt bath composition 408 can be circulated by the circulation device 416 to a storage device 410 located within and / or outside the first internal volume 404 of the salt bath 402. By circulating the salt bath composition 408 to the storage device 410, which may contain one or more types of regeneration media within a predetermined internal volume, one or more types of impurities formed during the ion exchange process can be removed from the salt bath composition 408. More simply, circulating the salt bath composition 408 to the storage device 410 allows the salt bath composition 408 to come into contact with one or more types of regeneration media, thereby reducing the concentration of one or more types of impurities formed during the ion exchange process and continuously regenerating the salt bath composition 408.

[0087] In this embodiment, the glass article is removed from contact with the molten salt after the ion exchange process. The resulting glass article, after ion exchange, may have compressive stress extending to a compressive depth on its surface. This compressive stress and compressive depth increase the glass article's resistance to fracture after mechanical injury, and as a result, the glass article can become a strengthened glass article after the ion exchange process. [Examples]

[0088] The following examples illustrate one feature of the present disclosure. It should be understood that these examples are not intended to limit the scope of the present disclosure or any accompanying claims.

[0089] Example 1 In Example 1, the concept of the present disclosure was evaluated using a 10-kilogram scale. A storage / circulation composite was prepared, including two mesh baskets made of SAE 304 stainless steel, each containing 5 grams of silicate aggregates, mounted on a stainless steel impeller (mounted on a motor). The mesh baskets were then lowered into 10 kilograms of molten salt consisting of industrial potassium nitrate (i.e., more than 98.5% by mass of potassium nitrate) and rotated at a speed sufficient to generate convection through the mesh baskets. Next, ion exchange processes were performed in the molten salt at 470°C for 5.5 hours over a period of 29 days, at a rate of approximately one ion exchange process per day, for each of 20 batches containing 45 Type I glass vials per batch (as described in U.S. Patent No. 8551898). The mesh baskets were removed from the molten salt before each ion exchange process and replaced after each ion exchange process was completed. After the ion exchange process was completed, the SHR of each glass vial was measured using the U.S. Patent No. <660> As detailed in [reference], measurements were taken using the Surface Glass Test. This process was repeated for 10 batches over a period of approximately 13 days, except for those in mesh baskets that did not contain silicate. The results were plotted as a function of time and as a function of the number of glass vials per kilogram of molten salt. These results are shown graphically in Figures 5A and 5B.

[0090] As shown in Figures 5A and 5B, when the mesh basket did not contain silicic acid, the desired titrant volume (approximately 1.3 mL) of the Type I glass was exceeded before 7 days had elapsed. In other words, when the mesh basket did not contain silicic acid, fewer than 25 glass vials per kilogram of molten salt could be effectively strengthened. Conversely, when a total of 10 grams of silicic acid was included, the desired titrant volume of the Type I glass was not exceeded until approximately 20 days had elapsed. In other words, when the mesh basket contained 10 grams of silicic acid, nearly 70 glass vials per kilogram of molten salt could be effectively strengthened. This demonstrates that a regeneration medium containing silicic acid can effectively neutralize the molten salt, even when limited to a single area of ​​the molten salt. In fact, the presence of silicic acid nearly triples the lifetime of the molten salt, which significantly increases the efficiency of the ion exchange process.

[0091] Example 2 In Example 2, the compressive stress and compression depth of the glass vials from Example 1 were measured after an ion exchange process was carried out in the presence of a total of 10 grams of silicate. Specifically, the compressive stress and compression depth of the glass vials from each batch were measured and then plotted as a function of time and as a function of the number of glass vials per kilogram of molten salt. The compressive stress was measured using a surface stress meter (FSM) with commercially available equipment such as the FSM-6000 sold by Orihara Manufacturing Co., Ltd. (Japan). The compression depth was measured at a wavelength of 596 nm using the same commercially available equipment. The results for Example 2 are shown graphically in Figures 6A and 6B.

[0092] As shown in Figures 6A and 6B, the compressive stress and compression depth of the glass vials remained relatively constant over the 30-day usage period of the salt bath, during which more than 85 glass vials were subjected to the ion exchange process. Although the compression depth decreased slightly, the compressive stress achieved after 25 days was almost the same as that achieved on the first day. This further confirms that the regeneration medium containing silica can effectively neutralize the molten salt, even when it is limited to a single area of ​​the molten salt.

[0093] Note that any two quantitative values ​​assigned to a property can constitute a range for that property, and all combinations of ranges formed from all the indicated quantitative values ​​for a given property are considered in this disclosure.

[0094] Note that the term “here” is used as a transitional clause in one or more of the following claims. Note that for the purpose of defining this art, this term is introduced into the claims as an unrestricted transitional clause used to introduce a description of a set of structural features, and should be interpreted similarly to the more commonly used unrestricted predicate “includes.”

[0095] While the subject matter of this disclosure has been described in detail with reference to specific embodiments, it should be noted that various details of such embodiments should not be interpreted as suggesting that these details are integral to those embodiments. Rather, the accompanying claims should be interpreted as a sole expression of the scope of this disclosure and the corresponding scope of the various embodiments described herein. Furthermore, it will be apparent that modifications and alterations are possible without departing from the accompanying claims.

[0096] Preferred embodiments of the present invention are described below in separate sections.

[0097] Embodiment 1 In a salt bath system for strengthening glass articles, A salt bath defining a first internal volume enclosed by at least one side wall, A salt bath composition containing an alkali metal salt disposed within the first internal volume, A storage device disposed within the first internal volume, comprising a second internal volume enclosed by at least one side wall, and including a regenerating medium disposed within the second internal volume, and A circulation device positioned close to the inlet of the storage device, which operates to circulate the salt bath composition in the storage device. A salt bath system is included.

[0098] Embodiment 2 The salt bath system according to Embodiment 1, wherein the regeneration medium includes silicate aggregates, alkali metal phosphates, porous metal oxides, or a combination thereof.

[0099] Embodiment 3 The salt bath system according to Embodiment 1, wherein the average particle size of the regenerated medium is 5 μm to 5,000 μm.

[0100] Embodiment 4 The salt bath system according to Embodiment 1, wherein 90% or more of the regenerated medium has a particle size greater than 5 μm.

[0101] Embodiment 5 The salt bath system according to Embodiment 1, wherein the regenerating medium includes particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felt, an active layer coated on or impregnated therein on an inert carrier, or a combination thereof.

[0102] Embodiment 6 The salt bath system according to Embodiment 1, wherein the salt bath composition disposed within the first internal volume substantially does not contain the regeneration medium.

[0103] Embodiment 7 The salt bath system according to Embodiment 1, wherein the circulation device includes an impeller, a pump, a gas injection system, or a combination thereof.

[0104] Embodiment 8 The salt bath system according to Embodiment 1, wherein the circulation device operates to circulate the salt bath composition to the storage device at a flow rate of 0.001 volumes per hour to 10 volumes per hour.

[0105] Embodiment 9 The entrance to the storage device is surrounded by a sieve that includes an opening having an effective diameter of 15% or less of the average particle size of the regenerated medium. The outlet of the storage device is surrounded by a sieve that includes an opening having an effective diameter of 15% or less of the average particle size of the recycled medium, or Both the inlet and outlet of the storage device are surrounded by a sieve containing an opening having an effective diameter of 15% or less of the average particle size of the recycled medium. A salt bath system according to Embodiment 1.

[0106] Embodiment 10 The salt bath system according to Embodiment 1, wherein the second internal volume includes the first regeneration area and a second regeneration area located downstream of the first regeneration area.

[0107] Embodiment 11 The first regeneration area includes the first regeneration medium, The salt bath system according to Embodiment 10, wherein the second regeneration area includes a second regeneration medium different from the first regeneration medium.

[0108] Embodiment 12 The salt bath system according to Embodiment 11, wherein the storage device includes a sieve positioned between the first regeneration area and the second regeneration area, and the sieve includes an opening having a diameter smaller than the average particle size of at least one of the first regeneration medium and the second regeneration medium.

[0109] Embodiment 13 In a salt bath system for strengthening glass articles, A salt bath defining a first internal volume enclosed by at least one of the aforementioned side walls, A salt bath composition containing an alkali metal salt disposed within the first internal volume, A storage device disposed outside the first internal volume and fluidly connected to the first internal volume, comprising a second internal volume defined by at least one side wall, and containing a regenerating medium disposed within the second internal volume, and A circulation device located within the first internal volume, adjacent to the inlet of the storage device, which operates to circulate the salt bath composition in the storage device, A salt bath system is included.

[0110] Embodiment 14 The salt bath system according to Embodiment 13, wherein the temperature of the second internal volume is 3°C or more lower than the temperature of the first internal volume.

[0111] Embodiment 15 The salt bath system according to Embodiment 13, wherein the regeneration medium comprises silica, alkali metal phosphate, alkali metal carbonate, porous metal oxide, or a combination thereof.

[0112] Embodiment 16 The salt bath system according to Embodiment 13, wherein the average particle size of the regenerated medium is 5 μm to 5,000 μm.

[0113] Embodiment 17 The salt bath system according to Embodiment 13, wherein 90% or more of the regenerated medium has a particle size greater than 5 μm.

[0114] Embodiment 18 The salt bath system according to Embodiment 13, wherein the regenerating medium comprises particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felt, an active layer coated on or impregnated therein on an inert carrier, or a combination thereof.

[0115] Embodiment 19 The salt bath system according to Embodiment 13, wherein the salt bath composition disposed within the first internal volume substantially does not contain the regeneration medium.

[0116] Embodiment 20 The salt bath system according to Embodiment 13, wherein the circulation device includes an impeller, a pump, a gas injection system, or a combination thereof.

[0117] Embodiment 21 The salt bath system according to Embodiment 13, wherein the circulation device operates to circulate the salt bath composition to the storage device at a flow rate of 0.001 volumes per hour to 10 volumes per hour.

[0118] Embodiment 22 The entrance to the storage device is surrounded by a sieve that includes an opening having an effective diameter of 15% or less of the average particle size of the regenerated medium. The outlet of the storage device is surrounded by a sieve that includes an opening having an effective diameter of 15% or less of the average particle size of the recycled medium, or Both the inlet and outlet of the storage device are surrounded by a sieve containing an opening having an effective diameter of 15% or less of the average particle size of the recycled medium. A salt bath system according to Embodiment 13.

[0119] Embodiment 23 The salt bath system according to Embodiment 13, wherein the second internal volume includes the first regeneration area and a second regeneration area located downstream of the first regeneration area.

[0120] Embodiment 24 The first regeneration area includes the first regeneration medium, The salt bath system according to Embodiment 23, wherein the second regeneration area includes a second regeneration medium different from the first regeneration medium.

[0121] Embodiment 25 The salt bath system according to Embodiment 24, wherein the storage device includes a sieve positioned between the first regeneration area and the second regeneration area, and the sieve includes an opening having a diameter smaller than the average particle size of at least one of the first regeneration medium and the second regeneration medium.

[0122] Embodiment 26 In a method for regenerating molten salt, A step of circulating the molten salt to a storage device located within a first internal volume of a salt bath, wherein the molten salt contains one or more impurities formed during the ion exchange process, and the storage device includes a regenerating medium located within a second internal volume defined by the storage device, and A step of bringing the molten salt into contact with the regeneration medium in the storage device, wherein the concentration of one or more impurities in the molten salt decreases as a result of the contact. A method that includes this.

[0123] Embodiment 27 The method according to Embodiment 26, wherein the one or more impurities include lithium nitrate, alkali metal nitrite, alkali metal oxide, alkaline earth metal nitrite, alkaline earth metal oxide, or a combination thereof.

[0124] Embodiment 28 The method according to Embodiment 26, wherein the regenerating medium comprises silica, alkali metal phosphate, alkali metal carbonate, porous metal oxide, or a combination thereof.

[0125] Embodiment 29 The method according to Embodiment 26, wherein the average particle size of the recycled medium is 5 μm to 5,000 μm.

[0126] Embodiment 30 The method according to Embodiment 26, wherein 90% or more of the recycled medium has a particle size greater than 5 μm.

[0127] Embodiment 31 The method according to Embodiment 26, wherein the regenerating medium comprises particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felt, an active layer coated on or impregnated therein on an inert carrier, or a combination thereof.

[0128] Embodiment 32 The method according to Embodiment 26, wherein the salt bath composition disposed within the first internal volume substantially contains the regeneration medium.

[0129] Embodiment 33 The method according to Embodiment 26, wherein the molten salt is circulated to the storage device at a flow rate of 0.001 volumes per hour to 10 volumes per hour.

[0130] Embodiment 34 A step of heating a salt bath composition containing an alkali metal salt to an ion exchange temperature to form the molten salt, and A step of immersing a glass article in a molten salt so that ion exchange occurs between the molten salt and the glass article, wherein the ion exchange between the molten salt and the glass article causes one or more impurities to be formed in the molten salt. The method according to embodiment 26, further including the method described in embodiment 26.

[0131] Embodiment 35 In a method for regenerating molten salt, A step of circulating the molten salt to a storage device located outside a first internal volume defined by a salt bath, wherein the molten salt contains one or more impurities formed during the ion exchange process, and the storage device includes a regenerating medium located within a second internal volume defined by the storage device, and A step of bringing the molten salt into contact with the regeneration medium in the storage device, wherein the concentration of one or more impurities in the molten salt decreases as a result of the contact. A method that includes this.

[0132] Embodiment 36 The method according to Embodiment 35, wherein the temperature of the second internal volume is 3°C or more lower than the temperature of the first internal volume.

[0133] Embodiment 37 The method according to Embodiment 35, wherein the one or more impurities include lithium nitrate, alkali metal nitrite, alkali metal oxide, alkaline earth metal nitrite, alkaline earth metal oxide, or a combination thereof.

[0134] Embodiment 38 The method according to Embodiment 35, wherein the regenerating medium comprises silicic acid, alkali metal phosphate, alkali metal carbonate, porous metal oxide, or a combination thereof.

[0135] Embodiment 39 The method according to Embodiment 35, wherein the average particle size of the recycled medium is 5 μm to 5,000 μm.

[0136] Embodiment 40 The method according to Embodiment 35, wherein 90% or more of the recycled medium has a particle size greater than 5 μm.

[0137] Embodiment 41 The method according to Embodiment 35, wherein the regenerating medium comprises particles, rings, saddles, spheres, artificial monoliths, honeycombs, fibers, felt, an active layer coated on or impregnated therein on an inert carrier, or a combination thereof.

[0138] Embodiment 42 The method according to Embodiment 35, wherein the salt bath composition disposed within the first internal volume substantially does not contain the regeneration medium.

[0139] Embodiment 43 The method according to Embodiment 35, wherein the molten salt is circulated to the storage device at a flow rate of 0.001 volumes per hour to 10 volumes per hour.

[0140] Embodiment 44 A step of heating a salt bath composition containing an alkali metal salt to an ion exchange temperature to form the molten salt, and A step of immersing a glass article in a molten salt so that ion exchange occurs between the molten salt and the glass article, wherein the ion exchange between the molten salt and the glass article causes one or more impurities to be formed in the molten salt. The method according to embodiment 35, further including the method described in embodiment 35.

[0141] Embodiment 36 In a salt bath system for strengthening glass articles, A salt bath defining a first internal volume enclosed by at least one side wall, A salt bath composition containing an alkali metal salt disposed within the first internal volume, A storage device disposed within the first internal volume, comprising a second internal volume enclosed by at least one side wall, and including a regenerating medium disposed within the second internal volume, and A circulation device positioned close to the inlet of the storage device, which operates to circulate the salt bath composition in the storage device. A salt bath system is included.

[0142] Embodiment 37 The salt bath system according to Embodiment 36, wherein the regeneration medium includes silicate aggregates, alkali metal phosphates, porous metal oxides, or a combination thereof.

[0143] Embodiment 38 The salt bath system according to Embodiment 36, wherein the average particle size of the regenerated medium is 5 μm to 5,000 μm.

[0144] Embodiment 39 The salt bath system according to Embodiment 36, wherein 90% or more of the regenerated medium has a particle size greater than 5 μm.

[0145] Embodiment 40 The salt bath system according to Embodiment 36, wherein the salt bath composition disposed within the first internal volume substantially does not contain the regenerating medium.

[0146] Embodiment 41 The entrance to the storage device is surrounded by a sieve that includes an opening having an effective diameter of 15% or less of the average particle size of the regenerated medium. The outlet of the storage device is surrounded by a sieve that includes an opening having an effective diameter of 15% or less of the average particle size of the recycled medium, or Both the inlet and outlet of the storage device are surrounded by a sieve containing an opening having an effective diameter of 15% or less of the average particle size of the recycled medium. A salt bath system according to Embodiment 36.

[0147] Embodiment 42 The salt bath system according to Embodiment 36, wherein the second internal volume includes the first regeneration area and a second regeneration area located downstream of the first regeneration area.

[0148] Embodiment 43 The first regeneration area includes the first regeneration medium, The salt bath system according to Embodiment 42, wherein the second regeneration area includes a second regeneration medium different from the first regeneration medium.

[0149] Embodiment 44 The salt bath system according to Embodiment 43, wherein the storage device includes a sieve positioned between the first regeneration area and the second regeneration area, the sieve including an opening having a diameter smaller than the average particle size of at least one of the first regeneration medium and the second regeneration medium.

[0150] Embodiment 45 In a method for regenerating molten salt, A step of circulating the molten salt to a storage device located within a first internal volume of a salt bath, wherein the molten salt contains one or more impurities formed during the ion exchange process, and the storage device includes a regenerating medium located within a second internal volume defined by the storage device, and A step of bringing the molten salt into contact with the regeneration medium in the storage device, wherein the concentration of one or more impurities in the molten salt decreases as a result of the contact. A method that includes this.

[0151] Embodiment 46 The method according to Embodiment 45, wherein the one or more impurities include lithium nitrate, alkali metal nitrite, alkali metal oxide, alkaline earth metal nitrite, alkaline earth metal oxide, or a combination thereof.

[0152] Embodiment 47 The method according to Embodiment 45, wherein the regeneration medium comprises silicic acid, alkali metal phosphate, alkali metal carbonate, porous metal oxide, or a combination thereof.

[0153] Embodiment 48 The method according to Embodiment 45, wherein the average particle size of the recycled medium is 5 μm to 5,000 μm.

[0154] Embodiment 49 The method according to Embodiment 45, wherein 90% or more of the recycled medium has a particle size greater than 5 μm.

[0155] Embodiment 50 The method according to Embodiment 45, wherein the salt bath composition disposed within the first internal volume substantially does not contain the regeneration medium. [Explanation of symbols]

[0156] 100, 200, 300 salt baths 101, 202, 311 Molten salt 105, 305 Glassware 120, 220, 320 - Relatively large cations 130 Relatively small cations 230, 330 Lithium cations 240, 340 phosphate 250, 350 insoluble lithium phosphate 311 Molten Salt 400 Salt Bath System 402 Salt Bath 404 First internal volume 406, 414 side wall 408 Salt bath composition 410 Storage device 412 Second internal volume 416 Circulation device 418 Entrance 420, 422, 424 Reclamation area 426a~426d Sieve 428 Exit

Claims

1. In a salt bath system for strengthening glass articles, A salt bath defining a first internal volume enclosed by at least one of the aforementioned side walls, A salt bath composition containing an alkali metal salt disposed within the first internal volume, A storage device disposed outside the first internal volume and fluidly connected to the first internal volume, comprising a second internal volume defined by at least one side wall, and including a regenerating medium disposed within the second internal volume, and A circulation device located within the first internal volume, close to the inlet of the storage device, which operates to circulate the salt bath composition through the storage device, Equipped with, The inlet of the storage device is surrounded by a sieve with an opening having an effective diameter of 15% or less of the average particle diameter of the regenerated medium. The outlet of the storage device is surrounded by a sieve with an opening having an effective diameter of 15% or less of the average particle diameter of the regenerated medium, or A salt bath system in which both the inlet and outlet of the storage device are surrounded by a sieve having an opening with an effective diameter of 15% or less of the average particle size of the regenerated medium.

2. The salt bath system according to claim 1, wherein the regeneration medium comprises silicate aggregates, alkali metal phosphates, porous metal oxides, or a combination thereof.

3. The salt bath system according to claim 1, wherein the average particle size of the regenerated medium is 5 μm to 5,000 μm.

4. The salt bath system according to claim 1, wherein 90% or more of the regenerated medium has a particle size greater than 5 μm.

5. The salt bath system according to claim 1, wherein the salt bath composition disposed within the first internal volume substantially does not contain the regeneration medium.

6. The salt bath system according to claim 1, wherein the second internal volume includes a first regeneration area and a second regeneration area located downstream of the first regeneration area.

7. The first regeneration area includes the first regeneration medium, The salt bath system according to claim 6, wherein the second regeneration area includes a second regeneration medium different from the first regeneration medium.

8. The salt bath system according to claim 7, wherein the storage device includes a sieve positioned between the first regeneration area and the second regeneration area, the sieve including an opening having a diameter smaller than the average particle size of at least one of the first regeneration medium and the second regeneration medium.

9. A method for regenerating molten salt in a salt bath system according to claim 1, A step of circulating the molten salt through a storage device located within a first internal volume of a salt bath, wherein the molten salt contains one or more impurities formed during the ion exchange process, and the storage device includes a regenerating medium located within a second internal volume defined by the storage device, and A step of bringing the molten salt into contact with the regeneration medium in the storage device, wherein the concentration of one or more impurities in the molten salt decreases as a result of the contact. A method that includes this.

10. The method according to claim 9, wherein the one or more impurities include lithium nitrate, alkali metal nitrite, alkali metal oxide, alkaline earth metal nitrite, alkaline earth metal oxide, or a combination thereof.

11. The method according to claim 9, wherein the regenerating medium comprises silicic acid, alkali metal phosphate, alkali metal carbonate, porous metal oxide, or a combination thereof.

12. The method according to claim 9, wherein the average particle size of the recycled medium is 5 μm to 5,000 μm.

13. The method according to claim 9, wherein 90% or more of the recycled medium has a particle size greater than 5 μm.

14. The method according to claim 9, wherein the salt bath composition disposed within the first internal volume substantially contains the regeneration medium.

Images