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WO2019064276A1 - Procédé de renforcement de substrats en verre - Google Patents

Procédé de renforcement de substrats en verre Download PDF

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Publication number
WO2019064276A1
WO2019064276A1 PCT/IB2018/057589 IB2018057589W WO2019064276A1 WO 2019064276 A1 WO2019064276 A1 WO 2019064276A1 IB 2018057589 W IB2018057589 W IB 2018057589W WO 2019064276 A1 WO2019064276 A1 WO 2019064276A1
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WO
WIPO (PCT)
Prior art keywords
glass substrate
salt
solution
glass
ionic salt
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2018/057589
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English (en)
Inventor
Mario Arturo MANNHEIM ASTETE
Mauricio Fernando CORNEJO POL
Iván Arturo CORNEJO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AGP America SA
Original Assignee
AGP America SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AGP America SA filed Critical AGP America SA
Publication of WO2019064276A1 publication Critical patent/WO2019064276A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
    • C03C21/008—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in solid phase, e.g. using pastes, powders
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
    • C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
    • C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions

Definitions

  • the present disclosed invention relates to a method of strengthening chemically glass substrates, and more particularly to a method of strengthening glass substrates by an ion exchange process using saturated solutions.
  • Chemical strengthening is a process that toughens the surface of a glass by substituting smaller ions in the glass composition (e.g. sodium ions) with larger ions in a molten ionic salt (e.g. potassium ions), and thus the process is called "ion exchange” or "stuffing".
  • the ion exchange process creates a thin layer of high compression on the surface which results in a layer of tension in the center.
  • Conventional ion exchange technique is performed by submerging the glass into an ionic bath for several hours at temperatures usually below the strain point of the glass. This technique is widely used today to strengthen glass that are used in mobile phones, televisions and automobiles, among others.
  • FIG. 1 shows an example of a production process of chemically strengthened glass substrates according to the conventional ion exchange technique, in which soda-lime glass substrates 1 are mounted on a support structure 2 with several slots 3 that are spaced apart, each slot 3 configured to receive and retain one glass substrate 1.
  • An ionic bath composition 4 is prepared into a vessel 5 by melting ionic salt KN0 3 with heat.
  • the glass substrates 1 are preheated at 350°C inside a furnace 6 for two hours, and the temperature of the ionic bath composition 4 prepared is adjusted to 450°C for chemical strengthening, wherein the glass substrates preheating temperature depends on the temperature at which the glass substrates 1 will be immersed in the ionic bath 4.
  • the glass substrates 1 are immersed in the ionic bath composition 4 for eight to twelve hours to allow the ion exchange to take place.
  • the glass substrates 1 are removed from the vessel 5 to cool them gradually to room temperature inside furnace 6 for three hours.
  • the ion exchanged glass substrates 1 will have a compressive stress (CS) of about 650-700MPa and a depth of layer (DOL) of about 10-15 ⁇ .
  • a problem with this conventional technique is that the process is potentially dangerous for the following reasons: (a) it produces large amounts of nitrogen oxides (NOx) because of the decomposition of the salt at the high temperature during the ion exchange process; (b) the salt could react violently with water at high temperature (e.g. a badly dried glass); and (c) the rate of vessel corrosion is elevated because of the high salt concentration.
  • NOx nitrogen oxides
  • Another problem that arises with conventional technique is the salt cross contamination, i.e. as the salt is continuously used, the bath is progressively enriched with the original ions from the glass. The rate of ion exchange tends to decrease, and so does the compressive stress. At some point, the salt must be changed.
  • the conventional technique is a very time-consuming process that consumes a considerable amount of energy not only because of the preheating and heating steps, which last several hours, but also because of the bath preparation step. It is especially significant when different types of glasses are needed, each type of glass requiring different ionic bath compositions. Thus, between the processing of two different types of glasses, it is required to remove the current ionic bath composition from the vessel, clean the vessel and reload the vessel with the following ionic bath composition, which could take several days. Therefore, the ionic exchange process becomes the bottle neck of the entire production chain.
  • U.S. Pat. No. 3,498,773 discloses a method of strengthening glass containers, wherein a glass container is coated with an aqueous solution that changes its salt to water concentration due to the vaporization of water to provide a solid film on the glass surface, followed by heating the glass container at an elevated temperature at or above the strain point for a period of time of about 5 to 30 minutes, so that the ion exchange can be carried out.
  • 4,206, 253 discloses a method of strengthening soda- lime glass containers, which comprises forming a coating film of a metal oxide at an elevated temperature on the outer surface of the glass container and then applying to the outer and inner surface of the glass container an aqueous solution containing a surfactant, a potassium nitrate and others potassium salts, the temperature of the glass container being lower than that of the aqueous solution, thereby depositing out the potassium salts on the outer surface and inner surface of the glass, then holding the glass container at an elevated temperature below the strain point of the glass but near said strain point for a period of time sufficient to form a compressive stress layer on the outer surface and inner surface of the glass container.
  • both mentioned methods have some drawbacks.
  • the former method requires preheating the glass at a temperature above the boiling point of water (temperatures between 150 - 485 °C are preferred) to allow water evaporation from the aqueous solution when applied to the preheated glass. Accordingly, as the conventional ion exchange technique, the preheating step is a time-consuming process that consume a considerable amount of energy. In addition, as ion exchange is carried out at an elevated temperature at or above the strain point of soda-lime glass, the resulting compressive stress would be attenuated by both viscoelasticity and structural relaxation of the glass.
  • the latter method has some limitations: (a) since the solution is an aqueous solution, solvents without water are not allowed; (b) the use of mixed potassium salts in the aqueous solution is mandatory, therefore only glass containing sodium metal ions could be used in this method; (c) glass containers are made with soda-lime glass (soda- lime glass having a strain point of about 510 °C is preferred), therefore this method is limited to soda-lime glass; (d) the aqueous solution contains a surfactant, which together with the elevated temperature used for ion exchange, affect the resulting compressive stress (max.
  • CS obtained is 120MPa); and (e) the glass container requires a coating film of a metal oxide on the outer surface to protect the compressive stress layer formed by ion exchange treatment. Consequently, there is a need in the art for methods of strengthening glass that be broad in application scope and optimize the use of resources without compromising the degree of chemical strengthening.
  • a method of strengthening a glass substrate which comprises the steps of applying a saturated solution at temperature Ti on the glass substrate at temperature T 2 , wherein the saturated solution contains an ionic salt and a liquid solvent, and wherein Ti > T 2 ; allowing the solution on the glass substrate to cool, thereby precipitating the ionic salt as soon as the solution temperature decrease, leaving a crust of salt adhered to the surface of the glass substrate; and heating the glass substrate to a predetermined temperature T3 for a predetermined period of time ⁇ 3, wherein the temperature T 3 ranges from the melting point of the ionic salt to preferably temperatures below the strain point of the glass substrate, and the time t 3 is enough to allow an ion exchange process.
  • the saturated solution is prepared as it is needed and the preheating/heating time is dismissed/reduced, not as much NOx is produced as in other methods.
  • the solution is a saturated solution, there is no probability of salt reacting violently with water as in the conventional method.
  • each of them could be prepared in a short time, even a previous saturated solution could be re-used to prepare new ones.
  • Another advantage of this method is that since the temperature for ion exchange ranges from the melting point of the ionic salt to preferably temperatures below the strain point of the glass substrate, there is minimal compressive stress attenuation by both viscoelasticity and structural relaxation. Additionally, as the resulting compressive stress is satisfactory, there is no necessity for applying an extra film on the glass. Finally, there is no particular limitation on the ionic salt, solvent and type of glass that could be used in the present invention and, therefore, it is possible to take advantage of the chemical strengthening process to change others glass surface properties.
  • FIG. 1 shows a schematic view of a production process of chemically strengthened glass substrates according to conventional method.
  • FIG. 2 shows a schematic view of a production process of chemically strengthened glass substrates according to one embodiment of the present invention.
  • FIG. 3 shows a saturated solution application process according to one embodiment of the present invention.
  • FIG. 4 shows the furnace temperature as a function of time according to the process of Example 1.
  • a saturated solution 7 is prepared into a vessel 8 by dissolving ionic salt in a liquid solvent (e.g. deionized water) at a temperature T 1; wherein the solubility of the salt is higher as Tl increases according to the solubility curve of said salt which plots the changes of the solubility of a salt at different temperatures in a solvent.
  • the ionic salt is a salt with the generic formula ANO 3 , or a mixed ionic salt (A, B)NC>3, or a mixture thereof; wherein both A and B are an alkali metal (e.g. NaNC>3, KNO 3 and L1NO3, among others).
  • glass substrates 9 are immersed in the saturated solution 7, and immediately extracted from said saturated solution 7, allowing the solution 7 on the glass substrates 9 to cool at a cooling rate from l°C/min to 100°C/min, preferably from l°C/min to 50°C/min, thereby precipitating the ionic salt as soon as the solution temperature decrease along the solubility curve of said ionic salt, i.e. as temperature decreases it precipitates as much ionic salt as corresponds to the change of temperature at the curve.
  • each glass substrate 9 is evenly coated with a recrystallized salt, forming a crust of salt 10 on the surface of the glass substrate.
  • the glass substrates 9 are heating inside a heat source 11 at a predetermined temperature T 3 for a predetermined period of time ⁇ 3, wherein the temperature T3 ranges from the melting point of the ionic salt to preferably temperatures below the strain point of the glass substrates 9, and the time ⁇ 3 is enough to allow an ion exchange process.
  • the glass substrates 9 are cooling inside the heat source 11, preventing the glass substrates 9 from shattering due to sudden temperature change.
  • the heat source 11 is a furnace.
  • the heat source is provided with at least one heat transfer mechanism selected from the group consisting of convection, radiation and conduction.
  • the thickness of the crust 10 lies between 20 and 60 ⁇ .
  • the thickness of the crust lies between 16 and 600 um, preferably between 20 and 400 ⁇ , and even more preferably between 20 and 200 ⁇ .
  • the glass substrates 9 are immersed in the saturated solution 7 (dipping).
  • the saturated solution is applied to the glass substrates by others means.
  • FIG. 3 shows an embodiment wherein the application step is performed by atomizing a saturated solution 12 to a windshield glass 13 via spray means 14.
  • the saturated solution is applied to glass substrates by painting a saturated solution via paint application means.
  • the present invention is not limited to a particular shape, geometry or size of the glass substrate.
  • the invention can be used independently of the glass type and/or composition used, provided that the glass substrate contains alkalis or transition metals in its composition.
  • the present invention is able to take advantage of the chemical strengthening process to change others glass surface properties such as luminescence, index of refraction, antimicrobial properties and antibacterial properties, among others. Therefore, in the embodiments in which at least one of these properties are required, the ionic salt is a mixed ionic salt of the form (C, D)N0 3 ; wherein C is an alkali metal and D is selected from the group consisting of transition metals and rare-earth metals.
  • the ionic salt contains at least one salt selected from the group consisting of sulfides, chlorides, halides or hydrates.
  • the glass substrates are made of soda-lime, alkali aluminosilicate, lithium aluminosilicate, alkali alkaline earth aluminosilicate or another silicate.
  • the liquid solvent is water or at least one organic solvent (e.g. ammonia and glycerol, among others).
  • the liquid solvent is selected from the group consisting of deionized water, distilled water and potable water.
  • a mixture of 30g of KNO 3 was mixed at 60°C with 30 cm 3 of deionized water. The mixture was then applied to a 10cm 2 soda-lime glass at room temperature with a spray bottle, forming a crust of salt adhered to the surface of the glass. Afterwards, the glass was heated in a furnace to 450°C for 6 hours and then cooled gradually inside the furnace for three hours. The result of the sprayed glass is reported as follow:
  • a mixture of lOOg of KNO 3 was mixed at 60°C with 100 cm 3 of deionized water.
  • Three different types of glass substrates (100x100 mm 2 ) of: soda lime glass (SLG), lithium aluminosilicate (LAS), and alkali aluminosilicate (AAS), were then immersed in the solution at 60°C and extracted rapidly from the solution, allowing the salt to precipitate on the glass substrates surfaces at room temperature. All three types of glasses were then heated in a furnace at different temperatures from 380 to 480°C for four hours for the ion exchange to take place and then cooled inside the furnace to room temperature. The results are reported as follow:
  • FIG. 4 shows that proposed method has a process time improvement of more than 40% over the conventional method by dismissing the preheating step and reducing by half the heating step time. As it was mentioned above, this process time improvement also leads to an improvement in energy consumption.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Surface Treatment Of Glass (AREA)

Abstract

L'invention concerne un procédé de renforcement d'un substrat en verre, dans lequel une solution saline saturée est appliquée sur un substrat en verre, ladite application étant suivie d'une variation rapide de la température, permettant au sel de précipiter. Le substrat en verre est ensuite revêtu uniformément d'un sel recristallisé. Ensuite, le substrat en verre est soumis à un échange d'ions à une température prédéfinie pendant une période prédéfinie.
PCT/IB2018/057589 2017-09-29 2018-09-29 Procédé de renforcement de substrats en verre Ceased WO2019064276A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201762566150P 2017-09-29 2017-09-29
US62/566,150 2017-09-29
US201762595563P 2017-12-06 2017-12-06
US62/595,563 2017-12-06

Publications (1)

Publication Number Publication Date
WO2019064276A1 true WO2019064276A1 (fr) 2019-04-04

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CO (1) CO2017012695A1 (fr)
WO (1) WO2019064276A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498773A (en) 1966-02-23 1970-03-03 Owens Illinois Inc Method of strengthening glass by ion exchange
JPS5443221A (en) * 1977-09-13 1979-04-05 Yamamura Glass Co Ltd Chemical strengthening of glass container
US4206253A (en) 1976-06-04 1980-06-03 Yamamura Glass Kabushiki Kaisha Method of strengthening chemically a glass container
US4218230A (en) * 1978-08-04 1980-08-19 Brockway Glass Company, Inc. Method of glass strengthening by ion exchange
JPS5632350A (en) * 1979-08-17 1981-04-01 Shin Nippon Glass Kk Glass product tempering method
US20040221615A1 (en) * 2003-04-22 2004-11-11 Dennis Postupack Method and apparatus for strengthening glass

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498773A (en) 1966-02-23 1970-03-03 Owens Illinois Inc Method of strengthening glass by ion exchange
US4206253A (en) 1976-06-04 1980-06-03 Yamamura Glass Kabushiki Kaisha Method of strengthening chemically a glass container
JPS5443221A (en) * 1977-09-13 1979-04-05 Yamamura Glass Co Ltd Chemical strengthening of glass container
US4218230A (en) * 1978-08-04 1980-08-19 Brockway Glass Company, Inc. Method of glass strengthening by ion exchange
JPS5632350A (en) * 1979-08-17 1981-04-01 Shin Nippon Glass Kk Glass product tempering method
US20040221615A1 (en) * 2003-04-22 2004-11-11 Dennis Postupack Method and apparatus for strengthening glass

Also Published As

Publication number Publication date
CO2017012695A1 (es) 2018-02-28

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