Salt bath additive and method for manufacturing the same

Abstract

The present invention provides a salt bath additive with a small dosage and suitable for on-line use, and a manufacturing method thereof. The salt bath additive, with its components expressed in weight percentages, contains: SiO2: 20-60%; Na2O: 10-45%; CeO2: 5-30%. Through reasonable component design, the present invention obtains a salt bath additive with a small dosage and suitable for on-line use. In some embodiments, by utilizing the crystallization and other phenomena in a specific glass melting process, the lithium ion absorption rate of the salt bath additive is increased, the lithium ion equilibrium concentration in the salt bath under on-line use conditions is reduced, and the use effect of the salt bath additive is significantly improved.

Description

Technical Field

[0001] The present invention relates to a salt bath additive, in particular to a salt bath additive suitable for a chemical strengthening salt bath of lithium-containing glass. Background Art

[0002] Chemically strengthened glass is a kind of glass that through an ion exchange process, replaces the network external alkali metal ions in the glass with alkali metal ions having a larger diameter, provides a compressive stress on the glass surface, and thus has significantly improved comprehensive mechanical strength. The key properties of chemically strengthened glass include the magnitude of the surface compressive stress and the strength of the glass matrix. To meet the high requirements such as anti-drop and anti-scratch of thin and light devices such as smart wearable devices and smartphones, high-performance chemically strengthened glass often contains lithium (Li) components. On the one hand, lithium is the alkali metal with the smallest ionic radius, and can achieve a larger surface compressive stress through lithium-sodium and sodium-potassium ion exchanges; on the other hand, the interaction force between lithium and the glass network is greater than that of sodium and potassium, which is beneficial to improving the strength of the glass matrix and also conducive to the formation of microcrystalline glass with a crystal dispersion strengthening effect.

[0003] However, the presence of lithium in the glass leads to the problem of shortened life of the chemical strengthening salt bath. During the chemical strengthening process, lithium ions (Li + ) in the lithium-containing glass continuously exchange ions with sodium ions (Na + ) in the salt bath, resulting in the appearance of lithium ion impurities in the salt bath. In the chemical strengthening sodium nitrate salt bath, the activity of lithium ions per unit concentration is much higher than that of sodium ions, resulting in that the presence of only about 100 ppm level of lithium ions in the salt bath significantly changes the equilibrium concentration of lithium ions-sodium ions on the glass surface, significantly reduces the sodium ion content on the glass surface after ion exchange, and leads to a significant reduction in the surface compressive stress of the glass after the salt bath, and cannot achieve the effect of inhibiting the unstable expansion of microcracks on the glass surface.

[0004] Conventional methods to solve the problem of salt bath failure caused by lithium ion impurities include changing the salt or using additives. After a fixed number of ion exchanges, all the molten salts in the salt bath are discarded, and new sodium nitrate raw materials are used for the salt bath, which can solve the problem of lithium ion impurities, but this will significantly increase the cost of the salt bath raw materials and the burden of waste treatment. Using a salt bath additive to absorb lithium ion impurities in the salt bath can play a role in extending the service life of a single salt bath. For example, CN108290781B and CN110981219A disclose adding phosphates to the salt bath, and removing lithium ion impurities by heating the salt bath to form precipitates such as lithium phosphate in the salt bath. However, the phosphate precipitates formed by this method are fine and difficult to precipitate in the salt bath, resulting in turbidity of the salt bath and affecting the uniformity of the ion exchange process on the surface of the glass to be strengthened; moreover, this method results in the presence of variable amounts of phosphates in the salt bath, and different phosphate contents lead to a large range of changes in the pH value of the aqueous solution of the salt bath substances, which results in OH in the salt bath -The content fluctuates, while OH - has a strong interaction with the surface of the glass to be strengthened, resulting in difficulty in achieving a consistent chemical strengthening effect for different batches of glass based on the same salt bath process. CN112645608A and CN104743866B disclose glass ion sieves for absorbing lithium ions in a salt bath, that is: placing glass containing a large amount of sodium ions into the salt bath to enable lithium ions in the salt bath to enter such glass. Through glass composition design, it is possible to prevent silicon in such glass additives from entering the salt bath in the form of silicic acid and other forms, which is an adverse factor causing a reduction in the salt bath effect. The problem with such glass additives is that the efficiency and cost need to be optimized. In the case of "online use", the entry and adsorption of lithium ions in the salt bath occur simultaneously. "Online use" means that the glass additive is used while the chemical strengthening process is in progress. In this case, the process of lithium ions entering the salt bath from the glass to be chemically strengthened and entering the additive from the salt bath occurs simultaneously, and a dynamic equilibrium is reached at an equilibrium concentration. If this equilibrium concentration is too high, it still causes poisoning of the salt bath and cannot achieve a good chemical strengthening effect for the glass to be chemically strengthened. A large amount of salt bath additives need to be used online to avoid this salt bath poisoning, and the salt bath additives also need to be updated after a short period, resulting in the generation of a large amount of salt bath additive waste residues. If the salt bath additive is placed into the salt bath after the chemical strengthening process is completed and allowed to adsorb lithium ions in the salt bath for a certain period of time, on the one hand, it increases additional processes, wastes time and energy, and on the other hand, the effect of the glass additive decreases rapidly after repeated use, and it is necessary to extend the placement time or use a new glass additive. The above methods are not economical. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a salt bath additive with a small dosage and suitable for online use and its manufacturing method.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] (1) A salt bath additive, the components of which are expressed in weight percentages and contain: SiO2: 20 - 60%; Na2O: 10 - 45%; CeO2: 5 - 30%.

[0008] (2) The salt bath additive according to (1), the components of which are expressed in weight percentages and further contain: Al2O3: 0 - 30%; and / or B2O3: 0 - 15%; and / or K2O: 0 - 20%; and / or P2O5: 0 - 5%; and / or MgO + CaO + BaO + ZnO: 0 - 2%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 2%.

[0009] (3) A salt bath additive, the components of which contain SiO2, Na2O and CeO2. The components are expressed in weight percentages and contain 0 - 30% of Al2O3, where CeO2 / (3×Al2O3 + SiO2) is 0.05 - 1.0.

[0010] (4) The salt bath additive according to (3), the components of which are expressed in weight percentages and contain: SiO2: 20 - 60%; and / or Na2O: 10 - 45%; and / or CeO2: 5 - 30%; and / or B2O3: 0 - 15%; and / or K2O: 0 - 20%; and / or P2O5: 0 - 5%; and / or MgO + CaO + BaO + ZnO: 0 - 2%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 2%.

[0011] (5) A salt bath additive, the components of which contain Na2O, and the salt bath additive is a composition containing a glass phase and a crystal phase.

[0012] (6) The salt bath additive according to (5), the components of which are expressed in weight percentages and contain: SiO2: 20 - 60%; and / or Na2O: 10 - 45%; and / or CeO2: 5 - 30%; and / or Al2O3: 0 - 30%; and / or B2O3: 0 - 15%; and / or K2O: 0 - 20%; and / or P2O5: 0 - 5%; and / or MgO + CaO + BaO + ZnO: 0 - 2%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 2%.

[0013] (7) The salt bath additive according to any one of (1) - (6), the components of which are expressed in weight percentages, where: SiO2: 25 - 55%, preferably SiO2: 30 - 50%; and / or Na2O: 12.5 - 42.5%, preferably Na2O: 15 - 40%; and / or CeO2: 7.5 - 27.5%, preferably CeO2: 10 - 25%; and / or Al2O3: 0 - 27.5%, preferably Al2O3: 0 - 25%; and / or B2O3: 0 - 12.5%, preferably B2O3: 0 - 10%; and / or K2O: 0 - 5%; and / or P2O5: 0 - 4%, preferably P2O5: 0 - 3%; and / or MgO + CaO + BaO + ZnO: 0 - 1%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 1%.

[0014] (8) The salt bath additive according to any one of (1) to (6), wherein the components are expressed in weight percentages, and: (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.3 to 1.0, preferably (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.4 to 0.9, more preferably (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.5 to 0.8.

[0015] (9) The salt bath additive according to any one of (1) to (6), wherein the components are expressed in weight percentages, and: CeO2 / (3×Al2O3 + SiO2) is 0.05 to 1.0, preferably CeO2 / (3×Al2O3 + SiO2) is 0.08 to 0.9, more preferably CeO2 / (3×Al2O3 + SiO2) is 0.1 to 0.8.

[0016] (10) The salt bath additive according to any one of (1) to (6), wherein the components do not contain K2O; and / or do not contain ZrO2; and / or do not contain La2O3; and / or do not contain Y2O3; and / or do not contain TiO2; and / or do not contain Fe2O3; and / or do not contain MgO; and / or do not contain CaO; and / or do not contain BaO; and / or do not contain ZnO; and / or do not contain Li2O; and / or do not contain As2O3; and / or do not contain PbO.

[0017] (11) The salt bath additive according to any one of (1) to (4), wherein the salt bath additive is a glass composition.

[0018] (12) The salt bath additive according to any one of (1) to (6), wherein the salt bath additive is a composition containing a glass phase and a crystal phase, preferably the crystal phase is a crystal without alkali metal components, more preferably the crystal phase is a CeO2 crystal.

[0019] (13) The salt bath additive according to any one of (1) to (6) has a salt bath erosion resistance of class II or above, preferably class I; and / or the salt bath optimization effect E is 1.05 or above, preferably 1.06 or above, more preferably 1.07 or above.

[0020] (14) A method for manufacturing a salt bath additive, the method comprising the following steps:

[0021] 1) Mix the raw materials of the salt bath additive according to the composition ratio of the salt bath additive, and then melt and homogenize the raw materials using a glass melting device;

[0022] 2) Pour the molten raw materials into a clean cooling medium to obtain a lump-shaped composition;

[0023] 3) Dry and crush the lump-shaped composition.

[0024] (15) The manufacturing method of the salt bath additive according to (14), wherein the cooling medium is air, vacuum or water, and preferably the cooling medium is deionized water.

[0025] The beneficial effects of the present invention are as follows: Through reasonable component design, the present invention obtains a salt bath additive with a small dosage and suitable for on-line use. In some embodiments, by utilizing the crystallization and other phenomena in a specific glass melting process, the lithium ion absorption rate of the salt bath additive is increased, the lithium ion equilibrium concentration in the salt bath under on-line use conditions is reduced, and the use effect of the salt bath additive is significantly improved. Specific Embodiments

[0026] Next, the embodiments of the salt bath additive of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and appropriate changes can be made within the scope of the object of the present invention for implementation. In addition, regarding the repeated description part, although there are cases where the description is appropriately omitted, the gist of the invention will not be limited thereby. In this specification, the salt bath additive is sometimes referred to as an additive or a glass additive.

[0027] [Salt Bath Additive]

[0028] The salt bath additive described in the present invention is a composition composed of one, or two, or more than two phases. In some embodiments, the salt bath additive of the present invention is a single phase, namely the glass phase, also known as the glass composition. In some embodiments, the salt bath additive of the present invention contains two phases, namely the glass phase and the crystal phase. In some embodiments, when the salt bath additive is two-phase, the crystal phase is preferably a crystal without alkali metal components (Li, Na, K), and more preferably the crystal phase is CeO2 crystal.

[0029] The presence of the crystal phase is beneficial to the excellent performance of the salt bath additive of the present invention for "on-line use", especially when it contains CeO2 crystal. On the one hand, the precipitation process of the crystal phase causes stress in the additive due to the volume change during the crystallization process. At the same time, the thermal expansion coefficients of the crystal phase and the additive glass phase are mismatched. During the cooling process that the additive needs to experience, due to the different volume changes of the crystal phase and the additive glass phase, stress is generated in the additive. During the ion adsorption process using the additive, the process of lithium ions entering the additive can relax the residual stress in the additive and reduce the Gibbs free energy of the additive. The tendency of the additive to reduce the Gibbs free energy provides additional driving force for the adsorption of lithium ion impurities, which is beneficial to reducing the lithium ion equilibrium concentration in the salt bath under on-line use conditions. On the other hand, the above stress causes a large number of microcracks inside the glass additive, increasing the surface area of the additive, enhancing the exchange efficiency and the service life of the additive.

[0030] The scope of each component of the salt bath additive of the present invention will be described below. In the present invention, unless otherwise specified, the contents and total contents of each component are all expressed in weight percentage (wt%), that is, the contents, total contents, and total contents of each component are expressed as weight percentages relative to the total amount of the salt bath additive substance in the composition converted to oxides. Here, the "composition converted to oxides" means that when oxides, double salts, hydroxides, etc. used as raw materials for the composition of the salt bath additive of the present invention decompose and transform into oxides when melted, the total amount of the oxides is taken as 100%.

[0031] Unless otherwise indicated in specific cases, the numerical ranges listed herein include upper and lower limit values, "above" and "below" include endpoint values, and all integers and fractions within the range, rather than being limited to the specific values listed when defining the range. The term "about" as used herein means that the formulations, parameters, and other quantities and characteristics are not and need not be exact, and if necessary, can be approximate and / or greater or lower, which reflects tolerances, conversion factors, measurement errors, etc. As used herein, "and / or" is inclusive, for example, "A; and / or B" means only A, or only B, or both A and B.

[0032] SiO2 belongs to the network former and plays a major framework role in the salt bath additive of the present invention. If the content of SiO2 is too high, the network structure of the additive will be too dense, which is not conducive to the ion exchange with lithium ions in the salt bath. Therefore, the content range of SiO2 is 20-60%, preferably 25-55%, and more preferably 30-50%. In some embodiments, it may contain about 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60% of SiO2.

[0033] Na2O belongs to the network modifier and plays a role in ion exchange with lithium ion impurities in the salt bath and adsorbing lithium ion impurities in the additive of the present invention, and is an essential component of the additive of the present invention. The higher the content of Na2O, the more beneficial it is to increase the amount of lithium ions adsorbed by the salt bath additive per unit mass. However, if the glass contains too much Na2O, sodium-containing crystals that do not participate in ion exchange may precipitate during the cooling process. Therefore, the use efficiency of the salt bath additive cannot be infinitely improved by increasing the content of Na2O. At the same time, too high a content of Na2O also causes the additive to be eroded in the salt bath, resulting in silicon and the like entering the salt bath or forming suspended particles, which in turn leads to surface contamination and surface damage of the glass after chemical strengthening. Therefore, the content range of Na2O is 10-45%, preferably 12.5-42.5%, and more preferably 15-40%. In some embodiments, it may contain about 10%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5%, 20.0%, 20.5%, 21.0%, 21.5%, 22.0%, 22.5%, 23.0%, 23.5%, 24.0%, 24.5%, 25.0%, 25.5%, 26.0%, 26.5%, 27.0%, 27.5%, 28.0%, 28.5%, 29.0%, 29.5%, 30.0%, 30.5%, 31.0%, 31.5%, 32.0%, 32.5%, 33.0%, 33.5%, 34.0%, 34.5%, 35.0%, 35.5%, 36.0%, 36.5%, 37.0%, 37.5%, 38.0%, 38.5%, 39.0%, 39.5%, 40.0%, 40.5%, 41.0%, 41.5%, 42.0%, 42.5%, 43.0%, 43.5%, 44.0%, 44.5%, 45% of Na2O.

[0034] CeO2 is an essential component of the additive of the present invention. CeO2 has a limited glass-forming range in silicate glass. If its content exceeds the glass-forming range, it has the characteristic that it is a homogeneous glass melt in the molten state but rapidly crystallizes after cooling. In some embodiments, within the composition range of the additive of the present invention, the crystals precipitated after cooling of the glass are CeO2 crystals. However, too much CeO2 will cause an excessive amount of CeO2 crystals to precipitate in the additive, hindering the ion exchange between the additive and the salt bath and being unfavorable for the realization of the functions of the additive. Therefore, the content range of CeO2 is 5-30%, preferably 7.5-27.5%, and more preferably 10-25%. In some embodiments, it may contain about 5%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5%, 20.0%, 20.5%, 21.0%, 21.5%, 22.0%, 22.5%, 23.0%, 23.5%, 24.0%, 24.5%, 25.0%, 25.5%, 26.0%, 26.5%, 27.0%, 27.5%, 28.0%, 28.5%, 29.0%, 29.5%, 30% of CeO2.

[0035] P2O5 is a non-essential component of the additive of the present invention. P2O5 is beneficial to improving the ion diffusion rate of the additive, beneficial to improving the working efficiency of the additive, prolonging the time required for the absorption efficiency of the additive to drop to an unacceptable range, and prolonging the service life of the additive. However, too high a content of P2O5 causes phase separation of the glass, and the phosphorus-rich phase therein has very low chemical stability and is easily introduced into the salt bath, resulting in fluctuations in the ion exchange effect. Therefore, the content range of P2O5 is 0-5%, preferably 0-4%, and more preferably 0-3%. In some embodiments, it may contain about 0%, greater than 0%, 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5% of P2O5.

[0036] Al2O3 belongs to the network former and is a non-essential component of the additive in the present invention. Compared with SiO2, Al2O3 can consume the free oxygen introduced by Na2O, which is beneficial to improving the chemical stability of the additive. However, too high content of Al2O3 will significantly increase the high-temperature viscosity of the glass and the surface tension of the glass melt, which is not conducive to the preparation of the additive in the present invention. Therefore, the content of Al2O3 is 0-30%, preferably 0-27.5%, more preferably 0-25%. In some embodiments, it may contain about 0%, greater than 0%, 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5%, 20.0%, 20.5%, 21.0%, 21.5%, 22.0%, 22.5%, 23.0%, 23.5%, 24.0%, 24.5%, 25.0%, 25.5%, 26.0%, 26.5%, 27.0%, 27.5%, 28.0%, 28.5%, 29.0%, 29.5%, 30% of Al2O3.

[0037] In some embodiments, to achieve the characteristic that the additive in the present invention contains an appropriate content of CeO2 crystals and improve the adsorption capacity of the additive for lithium ion impurities in the salt bath, it is preferably to control the range of CeO2 / (3×Al2O3 + SiO2) within 0.05-1.0, more preferably CeO2 / (3×Al2O3 + SiO2) is 0.08-0.9, and further preferably CeO2 / (3×Al2O3 + SiO2) is 0.1-0.8. In some embodiments, the value of CeO2 / (3×Al2O3 + SiO2) can be 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0.

[0038] B2O3 is a non-essential component of the additive of the present invention. B2O3 can reduce the high-temperature viscosity of the glass melt. At the same time, it can also consume the free oxygen generated due to the presence of Na2O in the glass, which is beneficial to improving the erosion resistance of the additive in the salt bath. However, the presence of B2O3 in the glass will significantly reduce the ionic diffusion coefficient of the glass. Therefore, the content of B2O3 is 0-15%, preferably 0-12.5%, and more preferably 0-10%. In some embodiments, it may contain about 0%, greater than 0%, 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15% of B2O3.

[0039] K2O is a non-essential component of the additive of the present invention. In some cases, the additive containing K2O is beneficial to absorbing lithium ion impurities in the potassium nitrate salt bath. Due to the too large radius difference between lithium ions and potassium ions, the ion exchange between lithium and potassium is not easy to carry out. In the ion exchange process, the salt bath of lithium-containing glass generally also adopts a two-step salt bath, that is, the first step is lithium-sodium exchange and the second step is sodium-potassium exchange process, and generally there is no need to absorb lithium ion impurities in the potassium nitrate salt bath. Therefore, the content of K2O is 0-20%, preferably 0-5%, and more preferably does not contain K2O. In some embodiments, it may contain about 0%, greater than 0%, 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5%, 20% of K2O.

[0040] In some embodiments, the ratio (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) of the total content of Na2O and K2O (Na2O + K2O) to the total content of SiO2, Al2O3, and B2O3 (SiO2 + Al2O3 + B2O3) is in the range of 0.3 to 1.0, which can endow the additive of the present invention with good ion exchange ability and resistance to salt bath erosion simultaneously. Therefore, it is preferred that (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.3 to 1.0, more preferably 0.4 to 0.9, and further preferably 0.5 to 0.8. In some embodiments, the value of (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) can be 0.3, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0.

[0041] ZrO2, La2O3, Y2O3, TiO2, and Fe2O3 are non-essential components of the additive of the present invention. ZrO2, La2O3, Y2O3, TiO2, and Fe2O3 all belong to network intermediates, and can improve the chemical stability of the additive within a certain content range. Therefore, without affecting the function of the additive of the present invention, the total content of ZrO2, La2O3, Y2O3, TiO2, and Fe2O3 (ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3) is 0 to 2%, preferably 0 to 1%, and more preferably does not contain ZrO2, and / or does not contain La2O3, and / or does not contain Y2O3, and / or does not contain TiO2, and / or does not contain Fe2O3. In some embodiments, ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3 is 0%, greater than 0%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%.

[0042] MgO, CaO, BaO, and ZnO are non-essential components of the additive of the present invention. Although MgO, CaO, BaO, and ZnO all have certain disadvantages of tending to be outside the glass network and reducing the ion diffusion coefficient of the additive, the presence of a small amount of MgO, CaO, BaO, and ZnO does not significantly affect the performance of the additive of the present invention. Therefore, the total content of MgO, CaO, BaO, and ZnO, i.e., MgO + CaO + BaO + ZnO, is 0 to 2%, preferably 0 to 1%, and more preferably does not contain MgO, and / or does not contain CaO, and / or does not contain BaO, and / or does not contain ZnO. In some embodiments, MgO + CaO + BaO + ZnO is 0%, greater than 0%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%.

[0043] Preferably, the additive of the present invention does not contain Li2O, and / or does not contain As2O3, and / or does not contain PbO.

[0044] The "not containing" and "0%" described herein mean that the compound, molecule, element, etc. are not deliberately added as raw materials to the additive of the present invention. However, as raw materials and / or equipment for producing the additive, there may be certain impurities or components that are not deliberately added and will be contained in small amounts or traces in the final additive. Such a situation is also within the scope of protection of this invention patent.

[0045] Next, the performance of the salt bath additive of the present invention will be described.

[0046] <Resistance to salt bath erosion>

[0047] The salt bath additive with a polished surface is placed in a 450°C pure sodium nitrate salt bath for 48 hours and then taken out. Observe the surface of the salt bath additive and the state of the salt bath additive, and evaluate the resistance of the additive to salt bath erosion according to the criteria shown in Table 1.

[0048] Table 1. Criteria for resistance to salt bath erosion

[0049] Level Additive condition I The polished surface of the additive is smooth Ⅱ A distinguishable decrease in the glossiness of the polished surface of the additive occurs Ⅲ The polished surface of the additive is significantly eroded and becomes a matte surface Ⅳ A distinguishable decrease in the external dimensions of the additive occurs Ⅴ The additive completely disappears

[0050] In some embodiments, the salt bath additive of the present invention has a resistance to salt bath erosion of Class II or above, preferably Class I.

[0051] <Salt bath optimization effect>

[0052] For lithium-containing glass, the influencing factors for the ion-exchange process to achieve chemical strengthening mainly include the lithium-ion / sodium-ion equilibrium concentration on the glass surface and the glass ion diffusion rate. When the salt bath temperature and glass composition are fixed, the glass ion diffusion rate is the same. Therefore, when the ion diffusion time is the same, the depth of the glass stress layer is basically unchanged, and the surface compressive stress value and the total ion exchange amount mainly depend on the lithium-ion / sodium-ion equilibrium concentration on the glass surface, while the lithium-ion / sodium-ion equilibrium concentration on the glass surface mainly depends on the lithium-ion impurity content in the salt bath. Therefore, the adsorption capacity of the salt bath additive for lithium ions in the salt bath, i.e., the salt bath optimization effect, can be characterized by comparing the mass difference of the glass before and after strengthening with and without the salt bath additive.

[0053] The test method for the salt bath optimization effect is as follows:

[0054] Polish the two major surfaces of the glass sample to be strengthened with dimensions of 45mm×40mm×1mm, and weigh the mass of the glass sample to be strengthened using an analytical balance. Place 50 glass samples to be strengthened and 1 kg of the salt bath additive into a salt bath with a total mass of 50 kg. The salt bath temperature is 450 °C, and the salt bath composition is sodium nitrate added with 200 ppm lithium nitrate. After the salt bath treatment for 8 h, take out the strengthened glass sample, wait for it to cool to room temperature, clean, and dry it. Weigh the mass of the strengthened glass sample, and record the mass difference before and after strengthening, denoted as Δm1.

[0055] Polish the two major surfaces of the glass sample to be strengthened with dimensions of 45mm×40mm×1mm, and weigh the mass of the glass sample to be strengthened using an analytical balance. Place 50 glass samples to be strengthened into a salt bath with a total mass of 50 kg. The salt bath temperature is 450 °C, and the salt bath composition is sodium nitrate added with 200 ppm lithium nitrate without adding the salt bath additive. After the salt bath treatment for 8 h, take out the strengthened glass sample, wait for it to cool to room temperature, clean, and dry it. Weigh the mass of the strengthened glass sample, and record the mass difference before and after strengthening, denoted as Δm2.

[0056] Take the ratio between the mass differences Δm1 and Δm2 of the glass samples before and after strengthening obtained twice as the salt bath optimization effect of the salt bath additive, denoted as E, i.e.:

[0057]

[0058] In some embodiments, the salt bath optimization effect (E) of the salt bath additive of the present invention is 1.05 or more, preferably 1.06 or more, and more preferably 1.07 or more.

[0059] [Manufacturing method of the salt bath additive]

[0060] The salt bath additive of the present invention can be manufactured by the following method:

[0061] Step 1: Mix various salt bath additive raw materials (such as oxides, salts, hydroxides, simple substances, etc.) according to the composition ratio of the salt bath additive of the present invention, and use any available glass melting equipment to melt and homogenize the raw materials of the glass. The purpose of this step is to evenly mix the raw materials and provide a basis for obtaining the glass phase in the salt bath additive;

[0062] Step 2: Pour the molten raw material obtained in step 1 into a clean cooling medium. The optional cooling medium includes air, vacuum, water, etc. The preferred cooling medium is deionized water. The purpose of this step is to cool the glass liquid to room temperature at a very fast speed, so that the structure of the glass can be kept as much as possible at its high temperature state, to obtain a larger network gap, that is, a higher virtual temperature, thereby obtaining a larger ion diffusion coefficient and improving the efficiency of absorbing lithium ion impurities in the salt bath. After step 2, a lump-shaped composition with a large number of cracks inside can be obtained;

[0063] Step 3: drying and crushing the agglomerated composition obtained in step 2 to obtain the salt bath additive of the present invention.

[0064] The method for manufacturing the salt bath additive of the present invention has the following three characteristics. First, the method is simple in process and does not require additional material forming and cold processing processes. In addition, the additional stress in the rapid cooling process of the glass liquid makes the product easy to break into glass fragments of suitable size and with suitable stacking gaps. Second, the rapid cooling process of the glass liquid can greatly avoid the relaxation of stress of the glass through its own structural changes. The obtained additional stress makes the fragments have more microcracks that are conducive to ion exchange, increases the specific surface area of the fragments, and is conducive to the ion exchange between the additive and the lithium ion impurities in the salt bath. Third, the rapid cooling process of the glass liquid can keep the glass structure at a higher temperature, that is, a higher virtual temperature, and obtain a glass phase with a larger network gap, which is beneficial to increase the ion diffusion coefficient of the glass phase in the additive and improve the performance of the salt bath additive.

[0065] Under the concept of the present invention, those skilled in the art can conceive of precipitating other crystals containing no alkali metal elements in addition to CeO2 in the glass through glass component design to achieve the function of the salt bath additive similar to or the same as that of the present invention, which is also within the spirit and scope of the present invention.

[0066] The salt bath additive of the present invention can also be formed by other methods. Other forming methods in the field of inorganic material (such as glass) manufacturing, including but not limited to strip forming, rod forming, sheet forming, sintering and the like, are also within the scope of protection of the present invention to obtain the salt bath additive with the same component range of the present invention.

[0067] The salt bath additive of the present invention can be used in the chemical strengthening salt bath of glass, and is particularly suitable for the chemical strengthening salt bath of lithium-containing glass. The glass described in the present invention is inclusive and can include glass having a single glass phase, as well as glass-ceramics containing a glass phase and a crystal phase.

[0068] [Examples]

[0069] To further clearly illustrate and explain the technical solutions of the present invention, the following non-limiting Examples 1 to 11 are provided. In this example, the salt bath additives having the compositions shown in Tables 2 to 3 were obtained by using the manufacturing method of the above salt bath additive. In addition, the characteristics of each salt bath additive were measured by the test method described in the present invention, and the measurement results are shown in Tables 2 to 3.

[0070] Table 2.

[0071]

[0072]

[0073] Table 3.

[0074]

[0075]

[0076] Comparative Example 1 is a sodium aluminosilicate glass frit. According to the test results of Examples 1 to 11, when the salt bath additive of the present invention is added, the chemically strengthened glass has a greater mass change after salt bath treatment, indicating that more sufficient ion exchange has been achieved. Although sodium aluminosilicate glass belongs to a glass system with a large ion diffusion coefficient, the salt bath additive of the present invention can maintain a lower lithium ion concentration in the salt bath under "online use" compared to Comparative Example 1.

Claims

1. Salt bath additive, characterized in that, Its components are expressed in weight percentages and contain: SiO2: 20 - 60%; Na2O: 10 - 45%; CeO2: 5 - 30%.

2. The salt bath additive according to claim 1, wherein Its components are expressed in weight percentages and further contain: Al2O3: 0 - 30%; and / or B2O3: 0 - 15%; and / or K2O: 0 - 20%; and / or P2O5: 0 - 5%; and / or MgO + CaO + BaO + ZnO: 0 - 2%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 2%.

3. Salt bath additive, characterized in that, Its components contain SiO2, Na2O and CeO2. Its components are expressed in weight percentages, contain 0 - 30% of Al2O3, and CeO2: 5 - 30%, where CeO2 / (3×Al2O3 + SiO2) is 0.05 - 1.

0.

4. The salt bath additive according to claim 3, wherein, Its components are expressed in weight percentages and contain: SiO2: 20 - 60%; and / or Na2O: 10 - 45%; and / or B2O3: 0 - 15%; and / or K2O: 0 - 20%; and / or P2O5: 0 - 5%; and / or MgO + CaO + BaO + ZnO: 0 - 2%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 2%.

5. Salt bath additive, characterized in that, Its components contain Na2O and CeO2: 5 - 30%. The salt bath additive is a composition containing a glass phase and a crystal phase.

6. The salt bath additive according to claim 5, characterized in that, Its components are expressed in weight percentages and contain: SiO2: 20 - 60%; and / or Na2O: 10 - 45%; and / or Al2O3: 0 - 30%; and / or B2O3: 0 - 15%; and / or K2O: 0 - 20%; and / or P2O5: 0 - 5%; and / or MgO + CaO + BaO + ZnO: 0 - 2%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 2%.

7. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, where: SiO2: 25 - 55%; and / or Na2O: 12.5 - 42.5%; and / or CeO2: 7.5 - 27.5%; and / or Al2O3: 0 - 27.5%; and / or B2O3: 0 - 12.5%; and / or K2O: 0 - 5%; and / or P2O5: 0 - 4%; and / or MgO + CaO + BaO + ZnO: 0 - 1%; and / or ZrO2 + La2O3 + Y2O3 + TiO2 + Fe2O3: 0 - 1%.

8. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, where: SiO2: 30 - 50%; and / or Na2O: 15 - 40%; and / or CeO2: 10 - 25%; and / or Al2O3: 0 - 25%; and / or B2O3: 0 - 10%; and / or P2O5: 0 - 3%.

9. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, where: (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.3 - 1.

0.

10. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, where: (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.4 - 0.

9.

11. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, wherein: (Na2O + K2O) / (SiO2 + Al2O3 + B2O3) is 0.5 to 0.

8.

12. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, wherein: CeO2 / (3×Al2O3 + SiO2) is 0.05 to 1.

0.

13. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, wherein: CeO2 / (3×Al2O3 + SiO2) is 0.08 to 0.

9.

14. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components are expressed in weight percentages, wherein: CeO2 / (3×Al2O3 + SiO2) is 0.1 to 0.

8.

15. The salt bath additive according to any one of claims 1 to 6, characterized in that, Its components do not contain K2O; and / or do not contain ZrO2; and / or do not contain La2O3; and / or do not contain Y2O3; and / or do not contain TiO2; and / or do not contain Fe2O3; and / or do not contain MgO; and / or do not contain CaO; and / or do not contain BaO; and / or do not contain ZnO; and / or do not contain Li2O; and / or do not contain As2O3; and / or do not contain PbO.

16. The salt bath additive according to any one of claims 1 to 4, characterized in that, The salt bath additive is a glass composition.

17. The salt bath additive according to any one of claims 1 to 6, characterized in that, The salt bath additive is a composition containing a glass phase and a crystal phase.

18. The salt bath additive according to any one of claims 1 to 6, characterized in that, The salt bath additive is a composition containing a glass phase and a crystal phase, and the crystal phase is a crystal without alkali metal components.

19. The salt bath additive according to any one of claims 1 to 6, characterized in that, The salt bath additive is a composition containing a glass phase and a crystal phase, and the crystal phase is a CeO2 crystal.

20. The salt bath additive according to any one of claims 1 to 6, characterized in that, The salt bath additive has a salt bath erosion resistance of class II or above; and / or the salt bath optimization effect E is 1.05 or above.

21. The salt bath additive according to any one of claims 1 to 6, characterized in that, The salt bath additive has a salt bath erosion resistance of class I; and / or the salt bath optimization effect E is 1.06 or above.

22. The salt bath additive according to any one of claims 1 to 6, characterized in that, The salt bath optimization effect E is 1.07 or above.

23. The manufacturing method of the salt bath additive according to any one of claims 1 to 6, characterized in that, The method includes the following steps: 1) Mix the raw materials of the salt bath additive according to the composition ratio of the salt bath additive, and then use glass melting equipment to melt and homogenize the raw materials. 2) Pour the molten raw materials into a clean cooling medium to obtain a lump-shaped composition. 3) Dry and crush the lump-shaped composition.

24. The manufacturing method of the salt bath additive according to claim 23, characterized in that, The cooling medium is air, vacuum or water.

25. The manufacturing method of the salt bath additive according to claim 23, characterized in that, The cooling medium is deionized water.

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