Patent ID: 12201972

DETAILED DESCRIPTION

As used herein, “have,” “having,” “include,” “including,” “comprise,” “comprising” or the like are used in their open ended sense, and generally mean “including, but not limited to.”

All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

The present disclosure is described below, at first generally, then in detail on the basis of several exemplary embodiments. The features shown in combination with one another in the individual exemplary embodiments do not all have to be realized. In particular, individual features may also be omitted or combined in some other way with other features shown of the same exemplary embodiment or else of other exemplary embodiments.

Embodiments of the present disclosure relate to an ion exchange tank having a processing chamber and an additive chamber separated by a weir system. The additive chamber includes a solids-absorbing material and at least one glass article is at least partially immersed in a salt bath within the processing chamber where an ion exchange process is performed. Embodiments of the present disclosure advantageously reduce the concentration of solid additives in the processing chamber where ion exchange processing is performed on glass articles. As such, as compared to tanks used in conventional ion exchange processing, ion exchange tanks as described herein facilitate faster draining and refilling of the processing chamber. Embodiments of the present disclosure also advantageously allow for ion exchange processing to be performed in the processing chamber at the same time that fresh salt is added to the additive chamber and that heat is applied to the additive chamber106bmelt the fresh salt to form molten salt. As compared to tanks used in conventional ion exchange processing where the fresh salt added to the tank must first be heated to form molten salt prior to beginning ion exchange processing, ion exchange tanks as described herein allow for the processing chamber to be filled with molten salt and for the ion exchange process to begin in the processing chamber once the filling of the chamber is complete.

As used herein, the term “conventional ion exchange process” refers to an ion exchange process in which smaller alkali metal ions in a glass article are exchanged for larger alkali metal ions to impart a compressive stress in the glass article, wherein the ion exchange process is carried out for a sequence of glass articles or a sequence of batches of pluralities of glass articles, in the same salt bath.

With reference toFIG.1, a cross section of an ion exchange tank in accordance with embodiments of the present disclosure is shown. The ion exchange tank100includes a bottom102and sidewalls104which define an interior space106configured to hold a molten salt bath. The interior space106of the ion exchange tank includes an additive chamber106aand a processing chamber106bseparated by a weir system110. As shown, the weir system110includes a first partition112extending from the top of the tank100toward the bottom102of the tank100and a second partition114extending from the bottom102of the tank100toward the top the tank100. A flow channel116is disposed between the first partition112and the second partition114. The first partition112divides the additive chamber106bfrom the flow channel116and the second partition114divides the processing chamber106afrom the flow channel116. An opening118between the bottom102of the ion exchange tank100and the first partition112fluidly connects the additive chamber106bto the flow channel116of the weir system110.

FIG.1illustrates an ion exchange tank100including a second partition114of the weir system110having a height that is substantially similar to the height of the sidewalls104of the ion exchange tank100. However, it should be appreciated that the second partition114may have any height such as, for example, any height that is less than the height of the sidewalls104of the ion exchange tank100.FIG.2illustrates an ion exchange tank100including a second partition114of the weir system110having a height that is less than the height of the sidewalls104of the ion exchange tank100.

The ion exchange tank100may further include an inlet122through which fresh salt and/or solid additives may be introduced into the additive chamber106b. The ion exchange tank100may further include a processing chamber outlet120athrough which molten salt may be removed from the processing chamber106a. The processing chamber outlet120amay be fluidly connected to the processing chamber106avia an opening disposed in the bottom102of the ion exchange tank100within the processing chamber106a. Alternatively, the opening may be disposed in a sidewall104of the ion exchange tank100within the processing chamber106a. Additionally, the system may also include an additive chamber outlet120bthrough which the contents of the additive chamber106b, including solid additives, may be removed from the additive chamber106b. The additive chamber outlet120bmay be fluidly connected to the additive chamber106bvia an opening disposed in the bottom102of the ion exchange tank100within the additive chamber106b. Alternatively, the opening may be disposed in a sidewall104of the ion exchange100within the additive chamber106b.

As further shown inFIG.1, the ion exchange tank100as described herein may include a plurality of heating apparatuses130a,130bconfigured to heat the salt bath to an ion exchange temperature, the ion exchange temperature generally being a temperature in which both the first and second metal salts are molten. The ion exchange temperature may be, for example but without limitation, between about 380° C. to about 570° C.; however, it will be appreciated by those skilled in the art that other temperatures may be used. According to embodiments of the present disclosure, first heating apparatus130amay be positioned and configured to heat the processing chamber106aand second heating apparatus130bmay be positioned and configured to heat the additive chamber106b. It is contemplated herein that each of the first heating apparatus130aand second heating apparatus130bmay include a plurality of heating apparatuses. The first and second heating apparatuses130a,130bmay have the same operating power or heating apparatus130amay have a different operating power than heating apparatus130b. As one non-limiting example, the second heating apparatus130bmay heat the additive chamber106bto a temperature at which molten salt is formed. In contrast, the first heating apparatus130amaintain an ion exchange temperature in the processing chamber106awhere the ion exchange temperature is less than the temperature at which molten salt is formed. In such an example, because less energy would be required to maintain the ion exchange temperature, the first heating apparatus130a, as compared to the second heating apparatus130b, may be a smaller, less expensive apparatus having a lower operating power. This effectively reduces the overall costs of the ion exchange tank100and also leads to a reduction in ion exchange processing costs as compared to a conventional ion exchange process.

The ion exchange tank100may further include a solids-absorbing material140disposed within the additive chamber106b. The solids-absorbing material140selectively absorbs solids or reduces the concentration of the solids in the additive chamber106b. In particular, the solids-absorbing material140may selectively absorb the solid additives as a result of, for example, reaction of the solids-absorbing material140with the solid additives being thermodynamically and/or kinetically more favorable than reaction of the solids-absorbing material with the other salt ions in the additive chamber106b. The solids-absorbing material140may be disposed at or near the bottom of the additive chamber106b. As the contents of the additive chamber106bmove over the solids-absorbing material140and toward the flow channel116of the weir system110, solids are separated from the molten salt and prevented from traveling through the flow channel116and into the processing chamber106a. Optionally, at least a portion of the solids-absorbing material140may be disposed in the flow channel116of the weir system110.

As shown inFIG.1, the solids-absorbing material140may be disposed at or near the bottom of the additive chamber106b.FIG.6illustrates an alternative configuration of the additive chamber106bwhere the solids-absorbing material140is positioned in the opening118between the bottom102of the ion exchange tank100and the first partition112. As shown inFIG.7, the additive chamber106bmay further include a porous container160where the solids-absorbing material140is disposed in the porous container160. In operation, the contents of the additive chamber106bmay flow through the pores of the porous container160to contact the solids-absorbing material140.

Optionally, the ion exchange system may further include a stirring apparatus150disposed in the additive chamber106band configured to stir the contents of the additive chamber106b. The stirring apparatus150may advantageously aid in the formation of molten salt and reaction of the molten salt with the solid additives within the additive chamber. The stirring apparatus150may also reduce or eliminate stratification, or concentration non-uniformity, of the components of the contents of the additive chamber.

FIG.1further illustrates a glass article302that may be at least partially immersed in the salt bath within the tank100. For example, the glass article302may be a glass container and, as shown inFIG.1, may be a plurality of glass containers. Merely for purposes of illustrating the ion exchange tank100, the glass containers are shown contained in a magazine apparatus400which will be described in more detail below. The glass article302includes a plurality of substrate metal ions which are alkali metal ions (e.g., Li+, Na+, K+). The salt bath304includes a plurality of first metal cations (e.g., K+) at a first metal ion concentration, and a plurality of second metal cations (e.g., Na+) at a second metal ion concentration. The first metal cations and second metal cations may be introduced into the salt bath as first and second metal salts (e.g., KNO3and NaNO3respectively).

In operation of the ion exchange tank100described herein, fresh salt is introduced into the additive chamber106beither through the inlet122or by being introduced through an opening at the top of the ion exchange tank100. Similarly, additives as described herein may also be added to the additive chamber either through the inlet122or by being introduced through an opening at the top of the ion exchange tank100. Heat is applied to the additive chamber106bby heating apparatus130bto melt the fresh salt and form molten salt. Optionally, a stirring apparatus150is operated to stir the contents of the additive chamber106b.

Due to hydrostatic pressure present in the additive chamber106b, molten salt is driven from the additive chamber106b, through opening118and along the flow channel116of the weir system110, over the top of the second partition114of the weir system110and into the processing chamber106a. In the processing chamber106a, an ion exchange process is performed in the molten salt bath with at least one glass article302in the processing chamber106b. Due to the solids-absorbing material140in the additive chamber106b, solid additives are retained in the additive chamber106band substantially all of the solid additive is prevented from passing through opening118and along the flow channel116of the weir system110, over the top of the second partition114of the weir system110and into the processing chamber106a.

Generally during ion exchange processing, a glass article302is placed in the processing chamber106aof the ion exchange tank at an ion exchange temperature, for a predetermined period of time, for example, in the range of about 1 hour to about 10 hours. The entire glass article302, or only a portion of the glass article302, may be immersed in the molten salt during the ion exchange process. Optionally, a single glass article302may be immersed in the molten salt during the ion exchange process, or a plurality of glass articles302may be immersed in the molten salt at the same time. Where a plurality of glass articles302are processed, the plurality of glass articles302may be subdivided into smaller groups, “runs,” or lots, which undergo ion exchange in the molten salt in succession.

Glass articles302as described herein may be formed from alkali aluminosilicate glass compositions which are amenable to strengthening by ion exchange. Such composition generally includes a combination of SiO2, Al2O3, at least one alkaline earth oxide, and one or more alkali oxides, such as Na2O and/or K2O. The glass composition may be free from boron and compounds containing boron. The glass compositions may further comprise minor amounts of one or more additional oxides such as, for example, SnO2, ZrO2, ZnO, TiO2, As2O3, or the like. These components may be added as fining agents and/or to further enhance the chemical durability of the glass composition. For example, glass articles as described herein my be formed from the ion exchangeable glass composition described in granted U.S. Pat. No. 8,980,777 filed Oct. 25, 2012 entitled “Glass Compositions with Improved Chemical and Mechanical Durability” the contents of which are incorporated herein by reference in their entirety.

Exemplarily glass compositions that glass articles302as described herein may be formed from include glass compositions which meet the criteria for pharmaceutical glasses described by regulatory agencies such as the USP (United States Pharmacopoeia), the EP (European Pharmacopeia), and the JP (Japanese Pharmacopeia) based on their hydrolytic resistance. Per USP 660 and EP 7, borosilicate glasses meet the Type I criteria and are routinely used for parenteral packaging. Examples of borosilicate glass include, but are not limited to Corning® Pyrex® 7740, 7800 and Wheaton 180, 200, and 400, Schott Duran, Schott Fiolax, KIMAX® N-51A, Gerrescheimer GX-51 Flint and others. Soda-lime glass meets the Type III criteria and is acceptable in packaging of dry powders which are subsequently dissolved to make solutions or buffers. Type III glasses are also suitable for packaging liquid formulations that prove to be insensitive to alkali. Examples of Type III soda lime glass include Wheaton 800 and 900. De-alkalized soda-lime glasses have higher levels of sodium hydroxide and calcium oxide and meet the Type II criteria. These glasses are less resistant to leaching than Type I glasses, but more resistant than Type III glasses. Type II glasses can be used for products that remain below a pH of 7 for their shelf life. Examples include ammonium sulfate treated soda lime glasses. These pharmaceutical glasses have varied chemical compositions and have a coefficient of linear thermal expansion (CTE) in the range of 20-85×10−7° C.−1.

Generally, the molten salt bath may include a first cation and a second cation wherein the first cation is larger than the second cation. At the beginning of the ion exchange process, the bath may include only the first cation. Optionally, the second cation may be intentionally included in the bath at the beginning of the ion exchange process. In either case, the second cation is introduced into the bath during the ion exchange process. The ion exchange bath may include, for example, a potassium salt such as potassium nitrate (KNO3) and a small amount of the corresponding sodium salt (NaNO3), which may be present as a contaminant or intentionally added to the bath, with the K+ ion being the first cation and the Na+ ion being the second cation. After the ion exchange is considered to be complete the glass article302is removed and washed to remove excess salt from the ion exchange bath. This process is repeated for additional glass articles in the same ion exchange bath until the salt in the ion exchange bath no longer provides a high enough surface concentration to achieve a CS above a targeted CS, a CT above a targeted CT, or a DOL above the targeted DOL. As ion exchange processing is performed on each glass article302, the concentration of smaller cations in the ion exchange bath increases while the concentration of larger cations in the ion exchange bath decreases, eventually reaching a concentration in which too few larger cations are available to be exchanged for the smaller cations in the glass article. This phenomenon is referred to as “poisoning” of the bath. As used herein, the terms “poisoning ions” and “poisoning cations” refer to the smaller cations that leave the glass and enter the ion exchange/salt bath during the ion exchange process and “poisoning salt” refers to the salts of such cations. The increase in concentration of poisoning cations as ion exchange progresses causes gradual deterioration of the CS, CT and DOL over time for glass articles that are subsequently ion exchanged in the same salt bath. Prior to reaching a concentration in which too few larger cations are available to be exchanged for the smaller ions in the glass article, the entire contents of the ion exchange bath may be replaced.

As described above,FIG.4, schematically depicts a cross-sectional view of a cassette assembly410which may include a plurality of magazine apparatuses400stacked adjacently and secured together in a cassette608. The magazine apparatuses400are configured to retain glass articles302, such as glass vials, during ion exchange processing while allowing for acceptable levels of fluid contact by the molten salt in the processing chamber106awith all areas (interior and exterior) of the glass articles302when the magazine apparatus400is partially or fully submerged in the molten salt. Each magazine apparatus400generally includes a bottom support floor500, a plurality of glassware-securing members420, a cover plate440and vertical supports430that securely connect the bottom support floor500, the glassware-securing members420, and may removably secure the cover plate440.

According to embodiments of the present disclosure, the operation of the ion exchange tank100described herein may further include recirculating salt from the processing chamber106aof the ion exchange tank100. Dragout, or salt which adheres to the surface of the glass article302, or to the surface of any fixture or carrier which contacts the glass article302in the ion exchange tank100, exits the molten salt bath when the glass article302and/or the fixture or carrier is removed from the ion exchange tank100. Dragout is conventionally washed off the glass article302and/or the fixtures without being recirculated.

However, according to embodiments of the present disclosure, a robotic lift system210including a rotation tool215may be configured to move the glass article302and/or the fixture or carrier out of the processing chamber106ato a position over the additive chamber106b. The rotation tool215may include engagement features, such as a plurality of prongs219as shown inFIG.5, which are configured to engage with a portion of the magazine apparatus400so that the magazine apparatus400can be rotated. Thus, in operation, the robotic lift system210may be controlled to mount the magazine apparatus400onto the rotation tool215. The rotation tool215may be motorized such that the rotation tool215can perform a rotation sequence to substantially drain the magazine apparatus400of molten salt into the additive chamber106b.

FIG.3illustrates an ion exchange tank100in accordance with embodiments of the present disclosure. As shown inFIG.3, the ion exchange tank100may include a pump device250configured to transfer molten salt from the processing chamber106ato the additive chamber106b. In operation, molten salt is recirculated from the processing chamber106aby way of the pump device250. According to embodiments of the present disclosure, the molten salt may be circulated continuously. Alternatively, the molten salt may be circulated at predetermined intervals for predetermined periods of time. As shown inFIG.3, molten salt is pumped by way of the pump device250out of the processing chamber106a, over the top of the weir system110, and into the additive chamber106b. As an alternative, the processing chamber106amay be fluidly connected via a pipe to the additive chamber106band the pump device250may be configured to pump molten salt from a recirculation outlet (not shown) in the processing chamber106a, through the pipe, and into the additive chamber106b.

According to the embodiments of the present disclosure, ion exchange processing may be performed in the processing chamber106aat the same time that fresh salt is added to the additive chamber106band that heat is applied to the additive chamber106bmelt the fresh salt and form molten salt. As compared to tanks used in conventional ion exchange processing where the fresh salt added to the tank must first be heated to form molten salt prior to beginning ion exchange processing, ion exchange tanks as described herein allow for the processing chamber106ato be filled with molten salt and for the ion exchange process to begin once the filling of the chamber106ais complete.

According to embodiments of the present disclosure, molten salt in the processing chamber106amay be drained through processing chamber outlet120awhile the contents of the additive chamber106bremain unaltered. Because solid additives are confined to the additive chamber106bof the ion exchange tank described herein, embodiments of the present disclosure prevent a concentration of solids forming at the bottom of the tank, such as frequently occurs in conventional ion exchange processing, which in turn facilitates faster draining and refilling of the processing chamber106athan in tanks used in conventional ion exchange processing. The additive chamber106bmay also be drained through additive chamber outlet120b. Because the processing chamber106aand the additive chamber106bare drained through separate outlets, the chambers may be drained with different frequencies and at different times.

While the present disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the present disclosure.