Molten salt purifying agent as well as preparation method and application thereof

Abstract

The invention relates to the field of glass chemical strengthening, and discloses a molten salt purifying agent and a preparation method and application thereof.The molten salt purifying agent is prepared from, by mass, 35%-65% of SiO2, 5%-40% of Al2O3, 0-5% of MgO, 20%-45% of Na2O and 0.01%-2% of CeO2; wherein the mass ratio of the (MgO + CeO2) to the (SiO2 + Al2O3) is 0.001 to 0.1. According to the molten salt purifying agent provided by the invention, SiO2, Al2O3, MgO, Na2O and CeO2 in a certain proportion are added, the proportion of MgO + CeO2 to SiO2 + Al2O3 is strictly controlled in a specific range, and the effect of each component in purifying molten salt is fully utilized, so that the molten salt purifying agent is high in purification reaction activity and purification efficiency, the phenomena of softening and purification activity failure of the molten salt purifying agent in the molten salt can be avoided, and the service life of the molten salt purifying agent is prolonged. The stability and the service life of the molten salt purifying agent are improved, the proportion of the molten salt is not affected, the situation that alkaline matter is attached to the surface of glass to affect the surface flatness of the glass is avoided, the service life of the molten salt can be prolonged, and the consistency of the glass strengthening performance is improved.

Description

Technical Field

[0001] The invention relates to the field of glass chemical strengthening, and in particular to a molten salt purifier and a preparation method and application thereof. Background Art

[0002] In the field of consumer electronics, lithium aluminum silicon glass is gradually becoming the mainstream material choice in the glass cover processing industry due to its excellent heat resistance, chemical corrosion resistance and mechanical strength.

[0003] During the chemical strengthening process of lithium aluminum silicon glass, Li in the chemical strengthening molten salt + The concentration (exchanged from the glass) will gradually increase. + When a certain concentration is reached, the enhanced surface compressive stress and the depth of the enhanced stress layer will exceed the quality control standards, and new mixed molten salt will need to be replaced regularly to meet the strengthening requirements.

[0004] The current solution to the problem of Li + The concentration can be increased by adding trisodium phosphate (Na 3 PO 4 ), using Na 3 PO 4 Absorbing Li in molten salt + The specific principle is Na 3 PO 4 With salt bath Li + The reaction generates a mixed alkali phosphate precipitate, which removes Li from the molten salt. + However, this method introduces a large amount of Na into the molten salt. + and PO 4 3- , breaking the original molten salt ratio balance and affecting the quality of the enhanced product (Na 3 PO 4 It will react with the sodium ions on the surface of the glass substrate to form phosphate crystals. After the phosphate crystals are cleaned, they will leave tiny depressions, protrusions, cracks and other defects on the glass surface. The precipitates will be deposited at the bottom of the molten salt bath, which is extremely difficult to clean when replacing the molten salt bath. In addition, Na 3 PO 4 It has severe hygroscopicity. Since phosphate is weakly acidic, adding a salt bath will change its pH value from neutral to alkaline, which can easily corrode the glass surface at high temperatures. Summary of the invention

[0005] The purpose of the present invention is to provide a molten salt purifier with high purification efficiency and good thermal stability to solve the current problem of reducing the Li + The concentration affects the quality of glass chemical strengthening and makes the molten salt inconvenient to clean and replace.

[0006] In order to achieve the above object, the first aspect of the present invention provides a molten salt purifier, which contains 35-65% SiO 2 , 5-40% Al 2 O 3 , 0-5% MgO, 20-45% Na 2 O, 0.01-2% CeO 2 ;

[0007] Among them, (MgO+CeO 2 ) / (SiO 2 +Al 2 O 3 )The mass ratio is 0.001-0.1.

[0008] The second aspect of the present invention provides a method for preparing the molten salt purifier described in the first aspect, the method comprising:

[0009] The composition A is subjected to melting treatment and molding treatment in sequence to obtain a molten salt purifier; the composition A contains a silicon oxide source, an aluminum oxide source, a sodium oxide source, a cerium oxide source and an optional magnesium oxide source.

[0010] The third aspect of the present invention provides the use of the molten salt purifier described in the first aspect or the molten salt purifier prepared by the preparation method described in the second aspect in the chemical strengthening of lithium aluminum silicon glass.

[0011] The technical solution provided by the present invention has at least the following advantages:

[0012] The molten salt purifier provided by the present invention is prepared by adding a certain proportion of SiO 2 、Al 2 O 3 ,MgO,Na 2 O and CeO 2 , and strictly control MgO+CeO 2 With SiO 2 +Al 2 O 3 The ratio of sodium ions to molten salt is within a specific range, making full use of the role of each component in purifying molten salt, such as controlling the concentration of sodium ions in the purifier network former so that it can fully participate in the glass network former (SiO 2 With Al 2 O 3 ) to ensure that the molten salt purifier is in high purification reaction activity and purification efficiency. At the same time, MgO+CeO 2 With SiO 2 +Al 2 O 3 The specific ratio of MgO+CeO2 It combines with silicon oxide and aluminum oxide in the purifier to form cross-linked silicon-oxygen bonds and aluminum-oxygen bonds, reducing or eliminating tiny bubbles, lattice defects and impurities, improving the low-temperature viscosity and elastic modulus of the product, reducing the high-temperature viscosity of the product, avoiding the softening of the molten salt purifier in the molten salt and the failure of the purification activity, improving the stability and service life of the molten salt purifier, preventing the appearance of extremely small particles in the product during the production, transportation and use of the molten salt purifier, and improving the environmental adaptability of the product.

[0013] In addition, the molten salt purifier provided by the present invention will not affect the ratio of the molten salt, will not produce alkaline substances attached to the glass surface to affect the surface flatness of the glass, can extend the service life of the molten salt, and improve the consistency of the glass strengthening performance. For example, the surface compressive stress of the strengthened glass produced in the same batch is more uniform, thereby improving the stability of the product's mechanical properties.

[0014] The method for preparing a molten salt purifier of the present invention has a wide range of raw material sources, simple operating steps, low cost, and is conducive to industrial production.

[0015] The molten salt purifier provided by the present invention can be used in the chemical strengthening process of lithium aluminum silicon glass (including lithium aluminum silicon ordinary glass and lithium aluminum silicon glass-ceramics) to reduce the Li + concentration, and has good application prospects. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] As mentioned above, the first aspect of the present invention provides a molten salt purifier, which contains, by mass percentage, 35-65% SiO 2 , 5-40% Al 2 O 3 , 0-5% MgO, 20-45% Na 2 O, 0.01-2% CeO 2 ;

[0018] Among them, (MgO+CeO 2 ) / (SiO 2 +Al 2 O 3 )The mass ratio is 0.001-0.1.

[0019] In the molten salt purifier provided by the present invention, a certain proportion of SiO 2 、Al 2 O 3 ,MgO,Na 2 O and CeO 2 , where SiO 2 and Al 2 O 3 As the main body of the network structure, SiO 2 As the first network former, Al 2 O 3 As the second network former, it plays a role in adjusting the oxygen atom content and increasing the ion migration rate; Na 2 O is the ion release source of the purifier; MgO is located in the octahedron and belongs to the glass network outer body, which regulates the purification activity of the product at high temperature; CeO 2 Reacting with silicon oxide and aluminum oxide to improve stability, the components of the molten salt purifier of the present invention cooperate with each other to achieve high purification efficiency and good thermal stability, and do not affect the quality of glass chemical strengthening. The present invention controls the concentration of sodium ions in the purifier network former so that it fully participates in the glass network former (SiO 2 With Al 2 O 3 ) to ensure that the molten salt purifier is in high purification reaction activity and purification efficiency. At the same time, the present invention strictly controls MgO+CeO 2 With SiO 2 +Al 2 O 3 The specific ratio of MgO+CeO 2 It combines with silicon oxide and aluminum oxide in the purifier to form cross-linked silicon-oxygen bonds and aluminum-oxygen bonds, reducing or eliminating tiny bubbles, lattice defects and impurities, improving the low-temperature viscosity and elastic modulus of the product, reducing the high-temperature viscosity of the product, avoiding the softening of the molten salt purifier in the molten salt and the failure of the purification activity, improving the stability and service life of the molten salt purifier, preventing the appearance of extremely small particles in the product during the production, transportation and use of the molten salt purifier, and improving the environmental adaptability of the product.

[0020] In addition, the molten salt purifier provided by the present invention will not affect the ratio of the molten salt, will not produce alkaline substances attached to the glass surface to affect the surface flatness of the glass, can extend the service life of the molten salt, and improve the consistency of the glass strengthening performance. For example, the surface compressive stress of the strengthened glass produced in the same batch is more uniform, thereby improving the stability of the product's mechanical properties.

[0021] In the embodiments of the present invention, Na 2 O / Al 2 O 3 The mass ratio is 0.6-10, Na2 O / (SiO 2 +Al 2 O 3 ) mass ratio is 0.2-1.7, controlling Na 2 O、SiO 2 、Al 2 O 3 The specific ratio between Al and Mg can ensure sufficient ion exchange source and high purification efficiency, reduce energy consumption in producing molten salt purifier, and reduce costs, because Al 2 O 3 High melting temperature, too much Al 2 O 3 Increase the production difficulty and energy consumption of products.

[0022] In a specific embodiment of the present invention, control Na 2 O / Al 2 O 3 The mass ratio is 0.6-6, Na 2 O / (SiO 2 +Al 2 O 3 ) mass ratio is 0.2-0.9, which can further ensure sufficient ion exchange source and high purification efficiency while reducing the energy consumption and cost of producing molten salt purifier.

[0023] In a specific embodiment of the present invention, control (MgO+CeO 2 ) / (SiO 2 +Al 2 O 3 ) mass ratio is 0.001-0.03. Because the glass is chemically strengthened at high temperature, and the molten salt purifier is placed in the chemically strengthened molten salt for a long time, it can further make full use of the purification activity of MgO at high temperature, and CeO 2 Combined with silicon oxide and aluminum oxide, the elastic modulus of the product is improved to avoid the phenomenon of high-temperature softening and loss of purification activity of the molten salt purifier in the molten salt, and further improve the stability, service life and environmental adaptability of the molten salt purifier.

[0024] In the embodiment of the present invention, the molten salt purifier contains, by mass percentage: 35-63% SiO 2 , 5-35% Al 2 O 3 , 0.01-5% MgO, 20-45% Na 2 O, 0.01-2% CeO 2 The inventors have found that the molten salt purifier that meets the preferred conditions has a better purification efficiency.

[0025] In an embodiment of the present invention, the purification coefficient of the molten salt purifier 530°C / 4h is 5.0-20.0, preferably 5.0-12.0.

[0026] Preferably, the purification coefficient of the molten salt purifier 530°C / 8h is 3.0-15.0, preferably 3.5-10.0.

[0027] Preferably, the strengthening temperature applicable to the molten salt purifier is 380-600°C, for example, it can be 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C or any value between 380-600°C; preferably 400-600°C, more preferably 500-600°C.

[0028] In the present invention, the test method of the purification coefficient is: to add a content of Li + Add a molten salt purifier with a content of b to 1 kg of molten salt. After reacting for a certain time and temperature, the purified molten salt is obtained. The Li content in the purified molten salt is tested. + The corresponding mass percentage of nitrate is c. Then the purification coefficient x = b / (ac), where a, b, and c are all mass percentages.

[0029] In an embodiment of the present invention, the molten salt purifier is in the shape of particles and / or flakes.

[0030] In some specific embodiments, the molten salt purifier is in the shape of particles, and the average particle diameter is ≥ 0.1mm. In some specific embodiments, the molten salt purifier is in the shape of a sheet, and the thickness is 0.2-0.7mm, preferably 0.4-0.6mm. The inventors found that the molten salt purifier under the preferred conditions will neither form a sludge-like precipitation at the bottom, nor affect the ratio of the molten salt, nor produce alkaline substances attached to the glass surface to cause surface defects, which can not only extend the service life of the molten salt and improve the consistency of the glass strengthening performance. And the molten salt purifier provided by the present invention does not need to stand still and wait, which improves production efficiency and reduces production costs.

[0031] In some embodiments, the molten salt purifier is in the form of a sheet and has a specific surface area of ​​0.001-1.2 m 2 / g.

[0032] As mentioned above, the second aspect of the present invention provides a method for preparing the molten salt purifier described in the first aspect, the method comprising:

[0033] The composition A is subjected to melting treatment and molding treatment in sequence to obtain a molten salt purifier; the composition A contains a silicon oxide source, an aluminum oxide source, a sodium oxide source, a cerium oxide source and an optional magnesium oxide source.

[0034] The method for preparing the molten salt purifier of the present invention only requires melting and molding the components to obtain the molten salt purifier, the preparation process is simple, the raw materials are widely available, the cost is low, and it is conducive to industrial production.

[0035] Preferably, the conditions of the melt treatment include: a temperature of 1400-1600° C. and a time of 2-4 hours.

[0036] Preferably, the molding process is selected from at least one of tablet extruder roller molding, water quenching molding or compression molding. The present invention preferably adopts tablet extruder roller molding to carry out the molding process. Compared with the other two molding methods, the inventors found that the molding method under this preferred condition can increase the specific surface area of ​​the product and retain the high activity of the product.

[0037] The silicon oxide source described in the present invention refers to a substance that can be converted into silicon dioxide through the preparation method of the molten salt purifier provided by the present invention; the aluminum oxide source, sodium oxide source, cerium oxide source and magnesium oxide source have similar definitions, and the present invention will not be repeated here.

[0038] The present invention has no particular limitation on the specific types of the silicon oxide source, the aluminum oxide source, the sodium oxide source, the cerium oxide source and the magnesium oxide source. Those skilled in the art can make their selections based on the types of substances known in the art. However, in order to obtain a molten salt purifier with higher purification efficiency and longer life, the present invention provides preferred types of substances below.

[0039] Preferably, the silicon oxide source is selected from at least one of quartz sand and silicon dioxide. More preferably, the quartz sand is ultra-white silica sand.

[0040] Preferably, the alumina source is selected from at least one of aluminum oxide, aluminum hydroxide and aluminum carbonate.

[0041] Preferably, the sodium oxide source is selected from at least one of sodium carbonate, sodium hydroxide and sodium bicarbonate.

[0042] Preferably, the cerium oxide source is selected from at least one of cerium dioxide, cerium carbonate and cerium nitrate.

[0043] Preferably, the magnesium oxide source is selected from at least one of magnesium oxide, magnesium hydroxide and magnesium carbonate.

[0044] As mentioned above, the third aspect of the present invention provides the use of the molten salt purifier described in the first aspect or the molten salt purifier prepared by the preparation method described in the second aspect in the chemical strengthening of lithium aluminum silicon glass.

[0045] The molten salt purifier provided by the present invention can be used in the chemical strengthening process of lithium aluminum silicon glass to reduce the Li + concentration, and has good application prospects.

[0046] It should be noted that lithium aluminum silicon glass includes but is not limited to lithium aluminum silicon ordinary glass and lithium aluminum silicon glass-ceramics. + It is suitable for scenes with high concentration.

[0047] According to a preferred embodiment, relative to 1 cm 2 The lithium aluminum silicate glass, the amount of the molten salt purifier used is 0.05-0.3g.

[0048] Preferably, the strengthening conditions include: a temperature of 380-600°C, for example, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C or any value between 380-600°C; and a time of 4-10h.

[0049] The molten salt purifier provided by the present invention can be applied to a wider range of strengthening temperatures, still has excellent purification efficiency at higher strengthening temperatures, and has stronger stability.

[0050] The molten salt purifier provided by the present invention has no particular limitation on the specific type of molten salt, and is applicable to the purification of a variety of molten salts. For example, the molten salt includes at least one of sodium nitrate, potassium nitrate, and lithium nitrate. The present invention is not described in detail here, and those skilled in the art should not be construed as limiting the present invention.

[0051] According to a particularly preferred specific embodiment, the present invention also provides a method for chemically strengthening lithium aluminum silicate glass, the method comprising: introducing a molten salt purifier into the molten salt for ion strengthening of the lithium aluminum silicate glass, the molten salt purifier being the molten salt purifier described in the first aspect above.

[0052] Preferably, the molten salt purifier and the glass to be strengthened are placed together in molten salt to perform ion strengthening treatment to obtain strengthened lithium aluminum silicon glass.

[0053] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available. The normal temperature in the present invention refers to 15-25°C.

[0054] The mass of the molten salt purifier product prepared in the following examples and comparative examples is 5 kg.

[0055] Purification coefficient test method: add molten salt purifier with content b to 1kg of molten salt containing lithium nitrate with content a, the molten salt component is a mixture of potassium nitrate and sodium nitrate, and react at a certain time and temperature to obtain purified molten salt, and test the content c of lithium nitrate in the purified molten salt. Then the purification coefficient x = b / (ac), where a, b, and c are all mass percentages, and the initial Li in the molten salt is + is 200-300ppm, b is 3%.

[0056] Example 1

[0057] (1) weighing quartz sand, aluminum oxide, sodium carbonate, magnesium oxide and cerium oxide according to a set ratio, and stirring them at room temperature for 30 minutes using a micro mixer to obtain a mixture;

[0058] (2) adding the mixed material into a crucible, heating the mixture to a preset melting temperature of 1500° C., and maintaining the temperature for 3 hours after the temperature reaches the target temperature to obtain a melt;

[0059] (3) Pour the uniformly melted molten liquid onto a sheet extruder roller to form a molten salt purifier.

[0060] The material composition of the molten salt purifier is listed in Table 1.

[0061] Embodiment 2-9

[0062] The process is similar to that of Example 1, except that the amount of each raw material in step (1) is changed to prepare molten salt purifiers with different material compositions. See Table 1 for details.

[0063] Comparative Examples 1-5

[0064] The process is similar to that of Example 1, except that the amount of each raw material in step (1) is changed to prepare molten salt purifiers with different material compositions. See Table 1 for details.

[0065] Table 1

[0066]

[0067] Table 1

[0068]

[0069] Test Case

[0070] The flake molten salt purifiers of the above-mentioned embodiments and comparative examples are placed in a long stainless steel cage and placed inside a strengthening frame together with a sheet basket containing lithium aluminum silicon glass to be strengthened. After preheating, entering the strengthening tank, slow cooling and taking out the cage containing the molten salt purifier from the strengthening frame, the use of the molten salt purifier is completed. 2 For lithium aluminum silicate glass, the dosage of molten salt purifier is 0.1g and the strengthening time is 8h.

[0071] The standard deviation of CS value refers to: taking 20 samples from the same batch of products, testing the chemically strengthened surface compressive stress (CS value) of the glass respectively, and calculating the standard deviation value.

[0072] The test method is: use the fully automatic stress meter FSM-6000Le and place the sample on the prism for testing.

[0073] The lithium absorption performance of the molten salt purifier under different strengthening conditions is listed in Table 2.

[0074] Table 2

[0075] Molten salt purifier source Strengthening temperature / ℃ Strengthening time / h Purification coefficient CS value standard deviation / Mpa Example 1 450 8 5.2 +1.5 Example 4 450 8 8.3 ±2.3 Comparative Example 3 450 8 96 ±11 Comparative Example 5 450 8 99 ±16 Example 1 500 8 4.1 +1.4 Example 4 500 8 7.6 ±2.9 Comparative Example 3 500 8 101 ±12 Comparative Example 5 500 8 99 ±15 Example 1 550 8 3.0 +1.3 Example 4 550 8 6.7 ±2.7 Comparative Example 3 550 8 88 ±11.4 Comparative Example 5 550 8 110 ±19

[0076] It can be seen from the above results that the molten salt purifier prepared by the technical scheme provided by the present invention has excellent purification effect, high purification efficiency and good thermal stability, longer service life, can meet production needs to a higher degree, and has low cost and better market value and economic value.

[0077] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A molten salt purifier, characterized in that: The molten salt purifier contains, in terms of mass percentage, 35-65% SiO2, 5-40% Al2O3, 0-5% MgO, 20-45% Na2O, and 0.01-2% CeO2; Among them, the mass ratio of (MgO+CeO2) / (SiO2+Al2O3) is 0.001-0.

1.

2. The molten salt purifier according to claim 1, characterized in that: In the molten salt purifier, the mass ratio of Na2O / Al2O3 is 0.6-10, and the mass ratio of Na2O / (SiO2+Al2O3) is 0.2-1.

7.

3. The molten salt purifier according to claim 1, characterized in that: In the molten salt purifier, the mass ratio of (MgO+CeO2) / (SiO2+Al2O3) is 0.001-0.

03.

4. The molten salt purifier according to claim 2, characterized in that: The mass ratio of Na2O / Al2O3 is 0.6-6, and the mass ratio of Na2O / (SiO2+Al2O3) is 0.2-0.

9.

5. The molten salt purifier according to claim 1, characterized in that: Calculated by mass percentage, the molten salt purifier contains: 35-63% SiO2, 5-35% Al2O3, 0.01-5% MgO, 20-45% Na2O, and 0.01-2% CeO2.

6. The molten salt purifier according to claim 1, characterized in that: The purification coefficient of the molten salt purifier at 530°C / 4h is 5.0-20.0; And / or, the purification coefficient of the molten salt purifier at 530°C / 8h is 3.0-15.

0.

7. The molten salt purifier according to claim 1, characterized in that: The molten salt purifier is in the form of granules and / or flakes; Preferably, the molten salt purifier is in the form of particles, and the average particle diameter is ≥ 0.1 mm; Preferably, the molten salt purifier is in the shape of a sheet and has a thickness of 0.2-0.7 mm.

8. A method for preparing the molten salt purifier according to any one of claims 1 to 7, characterized in that: The method includes: The composition A is subjected to melting treatment and molding treatment in sequence to obtain a molten salt purifier; the composition A contains a silicon oxide source, an aluminum oxide source, a sodium oxide source, a cerium oxide source and an optional magnesium oxide source.

9. The method according to claim 8, characterized in that The silicon oxide source is selected from at least one of quartz sand and silicon dioxide; And / or, the alumina source is selected from at least one of aluminum oxide, aluminum hydroxide, and aluminum carbonate; And / or, the sodium oxide source is selected from at least one of sodium carbonate, sodium hydroxide and sodium bicarbonate; And / or, the cerium oxide source is selected from at least one of cerium dioxide, cerium carbonate and cerium nitrate; And / or, the magnesium oxide source is selected from at least one of magnesium oxide, magnesium hydroxide and magnesium carbonate.

10. Use of the molten salt purifier according to any one of claims 1 to 7 or the molten salt purifier prepared by the preparation method according to any one of claims 8 to 9 in chemical strengthening of lithium aluminum silicon glass.

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