Cleaning method and cleaning station for cleaning a product surface after an ion exchange process, and ion exchange method having such a cleaning method

Abstract

The present invention relates to a cleaning method and a cleaning station for cleaning a surface of a product or body consisting of glass or glass-ceramic after at least one ion exchange process, and to an ion exchange method having such a cleaning method.

Description

[0001] Cleaning process and cleaning station for cleaning a product surface after an ion exchange process as well as ion exchange process with such a cleaning process

[0002] The present invention relates to a cleaning method and a cleaning station for cleaning a surface of a product or body made of glass or glass ceramic after at least one ion exchange process, as well as an ion exchange method using such a cleaning method. Ion exchange of glass or glass ceramic products is used, for example, for chemical hardening and is described, for example, in the publication S. Karlsson, B. Jonson and C. Stalhandske, "The technology of chemical glass strengthening - a review," Glass Technol.: Eur.J. Glass Sci. Technol. A, pp. 51 (2), 41-54, 2010, the publication AK Varshneya, "Chemical Strengthening of Glass: Lessons Learned and Yet To Be Learning," International Journal of Applied Glass Science 1 , p. [2] 131-142, 2010 and the publication D.-l. M. Patschger, “Process development for chemical tempering of thin glasses,” Dissertation, Friedrich Schiller University, 2014.

[0003] During chemical hardening, the alkali ions of the glass or glass-ceramic (usually sodium, sometimes also lithium) located close to the surface of the product to be hardened are replaced by larger ions (usually potassium) ("crowding"; "ion stuffing"). The exchange occurs at the same points in the glass network without significantly altering the silicon-oxygen bonds of the original network structure. Furthermore, the exchange occurs at temperatures below the glass transition temperature Tg. This is a thermally activated interdiffusion process. The ion exchange near the surface creates compressive stress, which leads to the strengthening of the product. As with the also established thermal tempering of glass products, strengthening occurs through the buildup of compressive residual stress to a certain depth below the surface.This is compensated for by a tensile stress state in the inner layers of the product. Chemical toughening can increase the product's impact strength, fracture strength, scratch resistance, flexural strength, and thermal shock resistance.

[0004] Chemical hardening can be achieved, for example, by immersing the product in a molten alkali salt. During the immersion, the alkali ions of the glass or glass-ceramic are exchanged for those of the molten salt.

[0005] As an alternative to immersing the product in molten salt, it can also be sprayed with the molten salt. Other options include applying salt pastes to the surface of the product to be hardened or coating the surface with aqueous salt solutions. In the next step, the product is heated to create a molten salt solution on the surface and perform the ion exchange.

[0006] Ion exchange can also occur above the transformation temperature Tg. This can produce a glass or crystals with other (lower) expansion coefficients near the surface, which induces compressive stress near the surface after cooling. However, the ion exchange temperature must not be so high that the product could deform during the exchange process.

[0007] The glass products to be tempered include, for example, flat glass products, in particular displays for mobile phones, touch panels, car windows or aircraft cockpits.

[0008] A flat glass product is any glass product in the form of sheets or panes.

[0009] They are referred to as "tables", regardless of the manufacturing process used. However, they can also be hollow glass products (glass containers). Hollow glass products are known to be glass containers that can be filled due to their shape. A distinction is made between container glass products (glass packaging), commercial glass products, and construction hollow glass products. Container glass products are hollow glass products that are used for the packaging, storage, preservation, and transport of beverages and other liquids (e.g., perfume), foodstuffs, chemicals, pharmaceuticals, and cosmetics. Container glass products are manufactured in glassworks. Commercial glass products (restaurant glass products or everyday glass products) are hollow glass products that are found on the "set table."Examples include drinking glasses, ashtrays, vases, bowls, and measuring cups. Hollow glass construction products include, in particular, glass blocks, concrete glass, and glass roof tiles.

[0010] They can also be tube glass products. Tube glass products consist of glass produced in tubular form.

[0011] Furthermore, it can be an optical glass product. Optical glass products are glass products used to manufacture optical components (such as lenses, prisms, and mirrors) for optical systems such as objectives, microscopes, or telescopes.

[0012] The above definitions for the different glass products apply analogously to the different glass ceramic products within the scope of the invention.

[0013] Glass-ceramic is known to consist of a polycrystalline and a glassy phase. During the production of glass products, the glass solidifies upon cooling without crystallizing. To produce glass-ceramic products, the formation of crystallites in the glass melt is specifically promoted by the addition of nucleating agents, resulting in controlled partial crystallization. Glass-ceramic products are typically manufactured by casting and subsequent heat treatment.

[0014] Furthermore, it is known that ion exchange, e.g. of alkali ions by silver and / or copper ions, can also produce (additional) coloration near the surface of a product.

[0015] Following the respective ion exchange process, the products are cooled.

[0016] Regardless of the specific variant of the ion exchange process, a residue of hardened molten salt remains on the surface of the product, which must be removed by subsequent washing. Washing is described, for example, in DE 11 2014 003 338 T5.

[0017] This typically multi-stage washing process produces wash water contaminated with salts such as nitrates, sulfates, and / or chlorides. Sometimes the wastewater is sent to receiving waters or sewage treatment plants without removing the salt load. This leads to significant water pollution. Alternatively, the salts are partially or completely separated. However, this significantly increases process costs.

[0018] Furthermore, it is generally known to clean component surfaces of particulate dirt or dust by blowing them off, in particular with compressed air, for example from DE 10 2006 034 309 A1 and DE 10 2019 116 307 A1. According to DE 10 2019 116 307 A, the temperature of the cleaning gas is between 10 and 80°C, preferably between 15 and 60°C.

[0019] The object of the present invention is to provide a cleaning method for the surface cleaning of a glass or glass-ceramic product that has a surface molten salt residue after at least one ion exchange process, wherein the cleaning method is to be cost-effective and environmentally safe. A further object is to provide an ion exchange process with such a cleaning method and a cleaning station for carrying out such a cleaning method.

[0020] These objects are achieved by a cleaning method having the features of claim 1, an ion exchange method having the features of claim 18, and a cleaning station having the features of claim 26. Advantageous developments of the invention are characterized in the respective subsequent subclaims.

[0021] The invention is explained in more detail below using a drawing as an example. The drawings show:

[0022] Figure 1: A first embodiment of a cleaning station according to the invention, greatly simplified and schematic

[0023] Figure 2: Another embodiment of a cleaning station according to the invention, greatly simplified and schematic

[0024] Figure 3: Another embodiment of a cleaning station according to the invention

[0025] Figure 4: Another embodiment of a cleaning station according to the invention, greatly simplified and schematic

[0026] Figure 5: Another embodiment of a cleaning station according to the invention, greatly simplified and schematic

[0027] Figure 6: Another embodiment of a cleaning station according to the invention, greatly simplified and schematic

[0028] Within the scope of the invention, it was discovered that it is possible to at least partially blow off the surface molten salt residue that a glass or glass-ceramic product or glass or glass-ceramic body 1 has after ion exchange using hot gas. Thus, according to the invention, this involves dry cleaning with hot gas. The hot gas stream impinging on a product or body surface 1a to be cleaned causes the molten salt residue to be blown off the product or body surface 1a through momentum transfer.

[0029] The hot gas stream may also contain solid particles, such as carbon particles, to assist the cleaning effect. However, these should be softer than the glass or glass-ceramic product 1 to avoid damage. Furthermore, the glass or glass-ceramic product 1 may need to be subsequently freed of the solid particles.

[0030] The glass or glass ceramic product 1 to be cleaned is preferably a flat glass or flat glass ceramic product 2 (Fig. 1) or a hollow glass or hollow glass ceramic product 3 (Figs. 2-4) or a tubular glass or tubular glass ceramic product or an optical glass or glass ceramic product.

[0031] The flat glass or flat glass ceramic product 2 is preferably a flat flat glass or flat glass ceramic pane 4 (Fig. 1). The flat flat glass or flat glass ceramic pane 4 has two opposing pane surfaces 4a;b and four adjacent pane edges 4c. The flat glass or flat glass ceramic pane 4 is also, in particular, a float glass pane or a display pane, preferably for mobile phones or tablets.

[0032] Furthermore, the flat glass or flat glass ceramic product 2 can also be a curved flat glass or flat glass ceramic pane, preferably a car window or a window of an aircraft cockpit (not shown).

[0033] The hollow glass or hollow glass ceramic product 3 is preferably a container glass or container glass ceramic product 5 (Figs. 2 to 5) or a household glass or household glass ceramic product 6 (Fig. 6) or a construction hollow glass or construction hollow glass product. The container glass or container glass ceramic product 5 is preferably a bottle 7 with an outer bottle surface 7a and an inner bottle surface 7b. The bottle 7 also has a bottle neck 8, a bottle belly 9, and a bottle bottom 10.

[0034] The household glass or household glass ceramic product 6 is preferably a bowl 11. The bowl 11 has an inner and an outer bowl surface 11a;b.

[0035] Furthermore, the glass product 1 consists of inorganic, non-metallic glass, preferably of oxidic glass, preferably of silicate glass or phosphate glass. The silicate glass is preferably borosilicate glass, aluminosilicate glass, or alkali silicate glass, preferably alkali-alkaline earth silicate glass, in particular soda-lime glass.

[0036] The glass-ceramic product 1 preferably consists of glass-ceramic from the MAS system (MgO x AI2O3 x nSiÜ2) or the ZAS system (ZnO x AI2O3 x nSiÜ2) or the LAS system (LiO x AI2O3 x nSiÜ2).

[0037] As already explained, the glass or glass-ceramic product 1 to be cleaned also has a surface molten salt residue due to at least one previously performed ion exchange process or ion exchange.

[0038] The ion exchange process can be carried out using one of the possible methods described above. Preferably, the ion exchange process increases the strength of the glass or glass-ceramic product 1. The ion exchange process therefore preferably leads to the chemical hardening of the glass or glass-ceramic product 1.

[0039] For ion exchange, the surface of the glass or glass-ceramic product 1 to be treated is brought into contact with a molten salt for a specific period of time. The molten salt contains at least one molten salt, preferably at least one molten alkali salt. The alkali salt is preferably potassium nitrate (KNO3). During contact, the alkali ions of the glass or glass-ceramic are exchanged for ions of the molten salt.

[0040] The molten salt can also contain at least one additive that influences, for example, the melting temperature and / or the ion exchange process. For example, the at least one additive can be K2CO3, Na2CO3, KHCO3, NaHCO3, K3PO4, or Na3PO4.

[0041] The ion exchange process can be carried out, as described above, by immersing the glass or glass-ceramic product 1 in the molten salt. Alternatively, the glass or glass-ceramic product 1 is sprayed with the molten salt. Alternatively, a salt paste is applied to the surface of the glass or glass-ceramic product 1 to be treated, or the surface of the glass or glass-ceramic product 1 to be treated is coated with an aqueous salt solution. In the next step, the glass or glass-ceramic product 1 is heated to create a molten salt on the surface and perform the ion exchange.

[0042] During the ion exchange, the glass or glass-ceramic product 1 preferably has a temperature below the softening temperature, preferably below the glass transition temperature Tg. The temperature of the glass or glass-ceramic product 1 during the ion exchange is preferably between 300°C and 600°C, preferably between 400°C and 500°C. It depends, among other things, on the glass or glass-ceramic composition.

[0043] However, the temperature of the glass or glass-ceramic product 1 can also be above the glass transition temperature Tg during the ion exchange, especially for a short time. After the ion exchange process, the cleaning process according to the invention is carried out with hot gas. For this purpose, the still-hot glass or glass-ceramic product 1 is first allowed to drip off, so that a portion of the molten salt present on the product surface 1a drips off.

[0044] A residue of the molten salt remains as molten salt residue on the product surface 1a. The molten salt residue thus comprises at least one salt, preferably at least one alkali salt. The molten salt residue is formed, in particular, as a superficial molten salt film, although the film need not be continuous.

[0045] In addition, cleaning is preferably carried out directly after draining, without cooling the glass or glass-ceramic product 1.

[0046] During cleaning, the temperature of the glass or glass-ceramic product 1 is below the softening temperature, preferably below the respective glass transition temperature Tg, but high enough that the molten salt residue is still liquid or molten or can be quickly remelted by the energy input of the hot gas. The temperature of the glass or glass-ceramic product 1 during cleaning is preferably between 200°C and 700°C, preferably between 300°C and 650°C, particularly preferably between 400°C and 500°C.

[0047] The temperature of the glass or glass-ceramic product 1 is measured in particular by means of an infrared pyrometer.

[0048] Furthermore, the molten salt residue is blown off by means of at least one hot gas jet directed at the product surface 1a to be cleaned, preferably with several hot gas jets. The hot gas jet emerges, in particular, from a nozzle 17 in a manner known per se.

[0049] The at least one hot gas jet also preferably has a pressure of

[0050] > 1 to 6 bar, preferably 1.1 to 4 bar, particularly preferably 1.1 to 3 bar. The pressure is determined in a conventional manner before the hot gas jet exits the nozzle 17.

[0051] In addition, the at least one hot gas jet preferably has a gas velocity of 5 to 20 m / s when exiting the nozzle 17.

[0052] The distance of a nozzle outlet of the nozzle 17 to the product surface 1a is also preferably 5 to 15 mm.

[0053] In addition, the at least one hot gas jet preferably has a blowing force of 1 to 8 N, preferably 2 to 5 N. A high blowing force is generally preferable, as it improves cleaning performance. However, this also increases the hot gas requirement, which impairs the cost-effectiveness of the process.

[0054] In addition, at least one hot gas jet is continuous or pulsed.

[0055] Preferably, the temperature of the hot gas exiting the nozzle 17 is between 350 and 650°C, preferably between 400 and 500°C.

[0056] The temperature of the hot gas is determined in a conventional manner using sensors, preferably by means of a thermocouple.

[0057] The hot gas is preferably air or nitrogen or oxygen or argon or CO2 or a CO2-containing combustion gas or a gas mixture, in particular a gas mixture of several of the aforementioned gases.

[0058] After hot gas cleaning, the glass or glass-ceramic product 1 may also be subjected to a superficial flame or plasma treatment.

[0059] Preferably, the cleaning also takes place in a cleaning station 12. According to a first embodiment of the invention (Fig. 1), the cleaning station 12 according to the invention serves to clean flat glass or flat glass ceramic panes 4.

[0060] The cleaning station 12 has two transport tracks 13a; b with transport rollers 14 for transporting the flat glass or flat glass-ceramic pane 4 in a transport direction 15. A nozzle arrangement 16 with a plurality of nozzles 17 is arranged above each of the two transport tracks 13a; b. The nozzles 17 are arranged next to one another in a direction perpendicular to the transport direction 15. The nozzles are preferably flat jet nozzles 18. The nozzles 17 each provide a hot gas jet. Consequently, the nozzles 17 are high-temperature-resistant nozzles 17, preferably made of stainless steel. Furthermore, the nozzles 17 are preferably arranged such that the hot gas jet impinges on the pane surface 4a; b to be cleaned at an acute angle.

[0061] The hot gas jet preferably forms an angle of 0 to 90°, more preferably 10 to 35°, with the product surface 1a to be cleaned. An acute angle has the advantage that the molten salt residue is removed. The at least one hot gas jet thus forms an air blade (also called an air sword, air knife, or air knife). The cleaning station 12 also has a turning device 19 for transferring the flat glass or flat glass-ceramic pane 4 from one transport track 13 to the other while simultaneously turning the flat glass or flat glass-ceramic pane 4.

[0062] In addition, the cleaning station 12 preferably has a housing 20 surrounding the transport tracks 13, the nozzle arrangements 16, and the turning device 19. The housing 20 serves, among other things, to prevent emissions of aerosols or nitrous gases from the decomposition of the salts in the molten salt residue and to reduce noise pollution from the nozzles 17.

[0063] In addition, the cleaning station 12 has a compression device 21 for compressing the cleaning gas and a gas superheater 22 for heating the cleaning gas to the desired temperature, i.e. for generating the hot gas.

[0064] Instead of the compression device 21 or in addition thereto, a blower 29 may also be present.

[0065] Furthermore, the cleaning station 12 preferably has an extraction device 23 for extracting the hot exhaust gas contaminated with salt after cleaning. After the hot exhaust gas has been extracted, it is treated. Preferably, the salt is first separated in a cyclone before the exhaust gas is fed to an exhaust gas purification system suitable for the gas composition.

[0066] The cleaning of the flat glass or flat glass ceramic pane 4 in the cleaning station 12 is then carried out as follows:

[0067] After the ion exchange process, the drained, still hot flat glass or flat glass ceramic sheet 4 is placed on the first conveyor track 13a and transported in the transport direction 15 by means of the transport rollers 14. The flat glass or flat glass ceramic sheet 4 passes the nozzle arrangement 16 or passes underneath it. The first sheet surface 4a and the sheet edges 4c are irradiated with the hot gas from the nozzles 17, and the molten salt residue is blown off. The flat glass or flat glass ceramic sheet 4 is then turned over and, with the already cleaned first sheet surface 4a, placed on the second conveyor track 13b and transported in the transport direction 15 by means of the transport rollers 14. The flat glass or flat glass ceramic sheet 4 passes the nozzle arrangement 16 or passes underneath it.The second disc surface 4b and the disc edges 4c are now exposed to hot gas from the nozzles 17 and the molten salt residue is blown off.

[0068] It is, of course, also within the scope of the invention that the nozzle arrangement 16 is moved relative to the flat glass or flat glass ceramic pane 4 and is guided over the pane surface 4a;b to be cleaned. This can be done in addition to or alternatively to the transport of the flat glass or flat glass ceramic pane 4.

[0069] Furthermore, the transport of the flat glass or flat glass ceramic pane 4 can also be carried out by other means of transport, e.g. by means of an air cushion track.

[0070] After cleaning both pane surfaces 4a;b, the flat glass or flat glass ceramic pane 4 is slowly cooled to room temperature, preferably in a preheated oven.

[0071] If traces of the molten salt residue remain on the pane surfaces 4a;b and / or the pane edges 4a after the hot gas cleaning, these can be removed, for example, during a subsequent fire polishing of the surfaces 4a;b;c. In this case, too, the resulting exhaust gases are preferably subjected to suitable treatment.

[0072] According to a further embodiment (Fig. 2), the cleaning station 12 according to the invention serves to clean container glass or container glass ceramic products 5, in particular bottles 7.

[0073] The cleaning station 12 comprises a robot with a robot arm 24 for handling the bottle 7, an annular nozzle 25, and a circular jet nozzle 26. The annular nozzle 25 has, in a conventional manner, an annular slotted opening from which the hot gas emerges. The generated hot gas jet is thus annular. Alternatively, the annular nozzle 25 can also have several outlet openings, particularly slotted ones, from each of which a hot gas jet emerges.

[0074] The nozzles 25;26 can also each be designed as Laval nozzles.

[0075] The cleaning of the bottle 7 in the cleaning station 12 is then carried out as follows:

[0076] After the ion exchange process, the bottle 7 is pulled from the melt by the robot arm 24 and allowed to drain over the molten salt bath. The bottle 7 is then transported to the cleaning station 12 and positioned centrally within the annular nozzle 25. The robot arm 24 then guides the bottle 7 through the annular nozzle 25 in a direction parallel to the bottle's longitudinal axis to blow off the molten salt residue from the outside of the bottle's belly 9. The outer bottle surface 7a is irradiated with the hot gas jet emerging from the annular nozzle 25. Alternatively or in addition to the movement of the bottle 7, the annular nozzle 25 is moved in a direction parallel to the bottle's longitudinal axis.

[0077] This process is preferably repeated twice. Subsequently, the bottle neck 8 and the bottle base 10 are cleaned from the outside with the hot gas jet emerging from the round jet nozzle 26. The corresponding positioning of the bottle 7 is also carried out with the robot arm 24. Preferably, the bottle 7 is rotated around its longitudinal axis to clean the bottle neck 8.

[0078] According to the embodiment shown in Figure 3, the cleaning station 12 according to the invention also serves to clean container glass or container glass ceramic products 5, in particular bottles 7. The cleaning station 12 has the robot with the robot arm 24 and the housing 20.

[0079] In addition, the cleaning station 12 has a protective housing 36 surrounded by thermal insulation 35, which is made of metal, preferably steel. The protective housing 36 preferably has a cylindrical peripheral wall 36a and a housing base 36b.

[0080] In addition, the protective housing 36 is open at the top and is closed at the top by the annular nozzle 25. The annular nozzle 25 is also covered at the top by the insulation 35.

[0081] The annular nozzle 25 has a circumferential annular gap 34 from which the hot gas exits in the manner of an air knife. The annular gap 34 preferably extends at an acute angle to a housing longitudinal axis 36c. The annular nozzle 25 is also connected to a hot gas inlet 31, which extends through the insulation 35. In the region of the annular nozzle 25, the insulation 35 has an inlet and outlet opening 30 for the container glass or container glass-ceramic product 5, in particular the bottle 7.

[0082] The housing bottom 36b has a molten salt drain opening 32. And the housing peripheral wall 36a has, near the housing bottom 36b, an exhaust opening 33 for exhausting the exhaust gas.

[0083] The cleaning of the bottle 7 in the cleaning station 12 is then carried out as follows:

[0084] After the ion exchange process, the bottle 7 is pulled from the melt by the robot arm 24 and allowed to drain over the molten salt bath. The bottle 7 is then transported to the cleaning station 12, inserted through the inlet and outlet opening 30 into the protective housing 36, and positioned centrally within the annular nozzle 25. The robot arm 24 then guides the bottle 7 through the annular nozzle 25 in a direction parallel to the bottle's longitudinal axis in order to blow off the molten salt residue from the outside of the bottle's belly 9. The outer bottle surface 7a is irradiated with the hot gas jet emerging from the annular gap 34 of the annular nozzle 25.

[0085] Preferably, this process is repeated twice and the bottle 7 is then guided out of the protective housing 36 through the inlet and outlet opening 30.

[0086] The hot exhaust gas contaminated with salt is also extracted through the extraction opening 33 during cleaning. Furthermore, removed molten salt particles sink downward, and a portion of the molten salt residue is thrown from the inside against the housing peripheral wall 36a and drains down it toward the housing bottom 36b. At the housing bottom 36b, the removed molten salt residue drains through the molten salt drain opening 32. According to a further embodiment (Fig. 4), the cleaning station 12 according to the invention also serves to clean container glass or container glass-ceramic products 5, in particular bottles 7.

[0087] Instead of the ring nozzle 25 and the round jet nozzle 26 as shown in Figure 2, the cleaning station 12 only has a flat jet nozzle 18.

[0088] To clean the outer bottle surface 7a in the area of ​​the bottle belly 9 and the bottle neck 8, the bottle 7 is then guided past the flat jet nozzle 18 parallel to the bottle's longitudinal axis and rotated about the bottle's longitudinal axis. Alternatively or additionally, the flat jet nozzle 18 is moved in a direction parallel to the bottle's longitudinal axis. The bottle bottom 10 is also cleaned from the outside by means of the hot gas jet emerging from the flat jet nozzle 18, for which purpose the bottle 7 and / or the flat jet nozzle 18 are positioned accordingly.

[0089] The cleaning station 12 can also be used to clean the bottle 7 from the inside (Fig. 5). This is necessary if an ion exchange has also been performed on the inner bottle surface 7b.

[0090] For this purpose, the cleaning station 12 has holding means 27 for holding the bottle 7 in the area of ​​the bottle bottom 10. In addition, a ball nozzle 28 with several outlet openings is provided.

[0091] To clean the inner bottle surface 7b, the ball nozzle 28 is then inserted into the bottle 7 parallel to the bottle's longitudinal axis and rotated about the bottle's longitudinal axis. Alternatively or additionally, the bottle 7 is also moved in the direction parallel to the bottle's longitudinal axis and / or rotated about the bottle's longitudinal axis. The inner bottle surface 7b is exposed to the hot gas jets emerging from the ball nozzle 28 and cleaned, both in the area of ​​the bottle bottom 10 and in the area of ​​the bottle belly 9 and the bottle bottom 10. According to a further embodiment (Fig. 6), the cleaning station 12 according to the invention serves to clean glass or glass ceramic products 6, in particular bowls 11.

[0092] The cleaning station 12 has a flat jet nozzle 18 for cleaning the outer shell surface 11b and a round jet nozzle 26 for cleaning the inner shell surface 11a.

[0093] For cleaning, the shell 11 is rotated about its shell rotation axis and the outer shell surface 11b is exposed to the hot gas jet from the flat jet nozzle 18 and the inner shell surface 11a is exposed to the hot gas jet from the round jet nozzle 26.

[0094] The advantage of the purification process according to the invention is that the cleaning takes place in a dry state, thus producing no wastewater. This makes the purification process according to the invention significantly more environmentally friendly. The salts from the exhaust gas can be easily separated, and the salt can be reused. This also saves costs.

[0095] When washing off the molten salt residue, the water also attacks the glass and penetrates the product surface. This, too, is avoided by the cleaning process according to the invention.

[0096] It is also within the scope of the invention that several ion exchange processes are carried out consecutively on a glass or glass-ceramic product 1, and that a cleaning process according to the invention takes place after each ion exchange process. The different ion exchange processes are carried out with different compositions of the molten salt. By cleaning between the individual ion exchange processes, contamination of the different molten salts is avoided. Furthermore, the glass or glass-ceramic product 1 does not have to be cooled for cleaning between the ion exchange processes. This improves the entire process economically and ecologically. However, cleaning can also take place only after several ion exchange processes.

[0097] Example 1:

[0098] A 2.7 mm thick float glass sheet (50 mm x 100 mm) made of soda-lime glass is heated to 400°C in one hour and then immersed in a 430°C KNO3 melt for 3 hours. During this time, ion exchange takes place to increase strength. The float glass sheet is then withdrawn from the melt bath and held above it for 20 seconds to allow some of the molten salt residue to drip off.

[0099] The float glass pane, which is approximately 400°C hot, is then cleaned from one side with hot air that has previously been preheated to approximately 500°C in an air heater. When the hot gas hits the pane, the temperature is still approximately 420°C. Several flat jet nozzles are passed over the float glass pane at an angle of 45° at a speed of approximately 10 seconds. The gas velocity is 15 m / s. The distance between the flat jet nozzles and the float glass pane is 5 mm. In this first step, the first surface of the pane and the edges of the pane are cleaned. Immediately afterwards, the float glass pane is rotated and the process is repeated. Finally, the float glass pane is cooled to room temperature in an oven preheated to 400°C.

[0100] Example 2:

[0101] A soda-lime glass bottle (430g, 0.6 l volume) is preheated to 590°C and then fire-polished for 20 seconds before being immersed by a robot arm for 2 hours in a molten salt bath consisting primarily of a KNO3 melt. The bottle is immersed in the melt so deeply that ion exchange takes place only on the outside. The robot arm then pulls the bottle out of the melt, lets it drip briefly over the molten salt bath (20 seconds), before transferring it to a cleaning station with a suction device to remove the film of molten salt residue. The robot arm guides the bottle through a ring nozzle at a depth of approximately 5 seconds to blow off the molten salt film. This process is repeated twice. The bottle neck and bottom are cleaned with a circular jet nozzle. The hot air used is heated in an air heater to about 500°C and the gas velocity is 15 m / s.

[0102] To remove any remaining traces of molten salt residue, the bottle surface is briefly treated with a natural gas flame. This causes the nitrate to decompose and diffuse into the surface of the glass. The bottle is then subjected to controlled cooling in a muffle furnace. The bottle can then be further processed using typical processes (e.g., labeling or cold-end coating).

[0103] Finally, it is pointed out that all mentioned, particularly claimed, features of the cleaning method and / or the cleaning station are particularly advantageous in themselves and in any combination and are the subject of the present invention.

[0104] In addition, the upper and lower limits specified for each individual range can all be combined with one another according to the invention.

Claims

Claims 1 . Cleaning method for cleaning a product surface (1a) of a glass or glass-ceramic product (1) which has a superficial molten salt residue after an ion exchange, characterized in that the molten salt residue is at least partially blown off the product surface (1a) with hot gas.

2. Cleaning method according to claim 1, characterized in that a) the temperature of the glass or glass-ceramic product (1) during cleaning is below the softening temperature, preferably below the glass transition temperature Tg, or b) the temperature of the glass or glass-ceramic product (1) during cleaning is 200°C to 700°C, preferably 300°C to 650°C, particularly preferably 400°C to 500°C.

3. Cleaning process according to claim 1 or 2, characterized in that the molten salt residue is blown off in liquid form.

4. Cleaning method according to claim 3, characterized in that the molten salt residue is still liquid when the hot gas hits the product surface (1a) or is melted by the energy input of the hot gas.

5. Cleaning method according to one of the preceding claims, characterized in that the molten salt residue is blown off by means of at least one hot gas jet directed onto the product surface (1a) to be cleaned, preferably with several hot gas jets.

6. Cleaning method according to claim 5, characterized in that a) the at least one hot gas jet has a pressure of > 1 to 6 bar, preferably 1.1 to 4 bar, particularly preferably 1.1 to 3 bar, and / or b) the at least one hot gas jet has a gas velocity of 5 to 20 m / s.

7. Cleaning method according to claim 5 or 6, characterized in that the at least one hot gas jet has a blowing force of 1 to 8 N, preferably 2 to 5 N.

8. Cleaning method according to one of claims 5 to 7, characterized in that the at least one hot gas jet is provided by a nozzle (17), preferably a round jet nozzle (26) or an annular nozzle (25) or a flat jet nozzle (18) or a spherical nozzle (28), wherein the nozzle (17) is preferably a Laval nozzle.

9. Cleaning method according to one of claims 5 to 8, characterized in that the at least one hot gas jet encloses an angle of 0 to 90°, preferably 10 to 35°, with the product surface (1a) to be cleaned.

10. Cleaning method according to one of claims 5 to 9, characterized in that the at least one hot gas jet and the glass or glass-ceramic product (1) move relative to one another during cleaning.

11. Cleaning method according to one of claims 5 to 10, characterized in that the at least one hot gas jet is continuous or pulsed.

12. Cleaning method according to one of claims 5 to 11, characterized in that the at least one hot gas jet forms an air knife.

13. Cleaning method according to one of the preceding claims, characterized in that the hot gas is hot air or nitrogen or oxygen or argon or CO2 or a CO2-containing combustion gas or a gas mixture, in particular a gas mixture of several of the aforementioned gases.

14. Cleaning method according to one of the preceding claims, characterized in that the glass or glass ceramic product (1) is a flat glass or flat glass ceramic product (2), preferably a flat glass or flat glass ceramic disc (4), or a hollow glass or hollow glass ceramic product (3), preferably a container glass or container glass ceramic product (5) or a household glass or household glass ceramic product (6), or a tubular glass or tubular glass ceramic product or an optical glass or glass ceramic product.

15. Cleaning method according to one of the preceding claims, characterized in that the glass product (1) consists of inorganic, non-metallic glass, preferably of oxidic glass, preferably of silicate glass or phosphate glass, wherein the silicate glass is preferably borosilicate glass or aluminosilicate glass or alkali silicate glass, particularly preferably alkali-alkaline earth silicate glass, in particular soda-lime glass.

16. Cleaning method according to one of the preceding claims, characterized in that the glass-ceramic product (1) consists of glass-ceramic from the MAS system (MgO x AI2O3 x nSiÜ2) or the ZAS system (ZnO x AI2O3 x nSiÜ2) or the LAS system (LiO x AI2O3 x nSiÜ2).

17. Cleaning process according to one of the preceding claims, characterized in that the molten salt residue comprises at least one salt, preferably at least one alkali salt, preferably potassium nitrate (KNO3).

18. Ion exchange method, preferably for chemical hardening, in which at least one ion exchange process is carried out on a glass or glass-ceramic product (1), wherein for the ion exchange a product surface (1a) of the glass or glass-ceramic product (1) to be treated is brought into contact with a molten salt and then a molten salt residue remaining on the product surface (1a) after the ion exchange process, in particular a remaining molten salt film, is removed, characterized in that the removal of the molten salt residue takes place by means of the cleaning method according to one of the preceding claims.

19. Ion exchange process according to claim 18, characterized in that During ion exchange, ions of the glass or glass-ceramic product (1 ) are exchanged for ions of the molten salt.

20. Ion exchange process according to claim 18 or 19, characterized in that the glass or glass-ceramic product (1) has a temperature below or above the glass transition temperature Tg during ion exchange.

21. Ion exchange process according to one of claims 18 to 20, characterized in that for the ion exchange a) the glass or glass ceramic product (1) is immersed in a molten salt bath, or b) the glass or glass ceramic product (1) is sprayed with the molten salt, or c) a salt paste or an aqueous salt solution is applied to the product surface (1a) of the glass or glass ceramic product (1) to be treated and then the glass or glass ceramic product (1) is heated so that the molten salt is generated on the product surface (1a).

22. Ion exchange method according to one of claims 18 to 21, characterized in that the glass or glass ceramic product (1) is allowed to drip off after the ion exchange process and before cleaning, so that a part of the molten salt located on the product surface (1a) drips off, wherein the cleaning preferably takes place directly after dripping, without the glass or glass ceramic product (1) being actively cooled beforehand.

23. Ion exchange process according to one of claims 18 to 22, characterized in that the glass or glass-ceramic product (1) is subjected to a superficial flame or plasma treatment after cleaning with hot gas.

24. Ion exchange process according to one of claims 18 to 23, characterized in that hot exhaust gas contaminated with the molten salt residue is sucked off after cleaning and the molten salt residue is separated from the exhaust gas, preferably in a cyclone.

25. Ion exchange process according to one of claims 18 to 24, characterized in that several ion exchange processes are carried out successively with salt melts of different composition and cleaning is preferably carried out after each ion exchange process.

26. Cleaning station (12) for cleaning a product surface (1a) of a glass or glass-ceramic product (1) which has a superficial molten salt residue after an ion exchange, preferably a cleaning station (12) for carrying out the cleaning method according to one of claims 1 to 17, characterized in that the cleaning station has means for blowing the molten salt residue off the product surface (1a) with hot gas.

27. Cleaning station (12) according to claim 26, characterized in that the cleaning station (12) has a nozzle arrangement (16) with at least one nozzle (17) for providing at least one hot gas jet directed onto the product surface (1a) to be cleaned.

28. Cleaning station (12) according to claim 26 or 27, characterized in that the cleaning station (12) has a compression device (21) for compressing the gas and / or a blower (29) as well as a gas superheater (22) for heating the gas to the desired temperature before cleaning.

29. Cleaning station (12) according to one of claims 26 to 28, characterized in that the cleaning station (12) has a suction device (23) for sucking off the hot exhaust gas contaminated with the salt after cleaning.

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