Environmentally friendly matting method for soda-lime glasses

Abstract

The invention relates to a glass processing method for giving a matt appearance to tempered glass (10), especially in the white goods sector, wherein it comprises the process steps of preparing a mixture comprising a cation source to facilitate melting; a silica source that is dissolved by potassium ions and bonded to the surface; a filler that binds the mixture to the surface so that the salt does not melt at high temperatures and run off the surface; a thinner as a binder to hold the grains and prevent them from precipitating; printing the prepared mixture onto the surface of the glass (10) by applying wet coating at the inlet of the tempering furnace; after the printing application on the surface of the glass (10), drying it by heat treatment in a drying furnace to remove the part forming the liquid media; after drying, sending the printed glass (10) to the tempering furnace to form a matt surface (11) in the desired areas; under the conditions of the tempering furnace, volatilizing the adhesive contained in the mixture and melting and coating the remainder onto the surface of the glass (10) by forming a layer (12); cleaning the dried residual mixture on the cooled glasses (10) after tempering.

Description

[0001] DESCRIPTION

[0002] ENVIRONMENTALLY FRIENDLY MATTING METHOD FOR SODA-LIME GLASSES

[0003] Technical Field

[0004] The invention relates to a glass processing method for giving a matt appearance to tempered glass used in ovens, stoves, refrigerators, hoods, dishwashers and similar appliances in the white goods sector.

[0005] State of the Art

[0006] The white goods sector is the industry that deals with the production, distribution and sale of basic large electrical appliances used in household and commercial areas. This sector includes products such as refrigerators, washing machines, dryers, dishwashers, ovens, stoves and microwave ovens. White goods are usually made of durable materials and designed for long-lasting use. The sector is constantly evolving in line with technology and design innovations, energy efficiency standards and consumer demands. In addition, the factors such as environmental sustainability, recycling and energy saving have a significant impact on production and product development processes in the sector. The white goods sector is highly competitive in terms of design trends and innovations, which change rapidly with the impact of consumer preferences and market dynamics.

[0007] The tempered glass used in products in the white goods sector is matted for visual aesthetics and design, glare reduction, privacy and confidentiality, durability and protection against scratches. The matted glass provides an aesthetically pleasing appearance and reflects a modern, stylish design approach. Matt surfaces reduce glare and help to achieve a simpler and cleaner appearance. The matting process minimizes glare by diffusing light through the glass. This improves visual comfort and is less uncomfortable for users’ eyes, especially on the surfaces such as screens or glass covers of appliances. Matt glass hides background objects and protects the users’ private spaces. This provides privacy by preventing the contents from being visible from the outside, especially on the products such as refrigerator doors or stove glass. Matt glass makes small scratches and smudges on the surface less obvious. In addition, some matting techniques can increase the physical durability of glass, which can extend the life of products. For these reasons, matting the tempered glass offers various advantages in terms of both aesthetics and functionality and is a preferred application in white goods products.

[0008] Today, five different methods are used to provide glass products with a matt appearance: etching with HF (hydrogen fluoride)-based acid (chemical etching), sandblasting (mechanical etching), film coating, matt paint coating and ion exchange. Acidic / chemical etching is the most commonly used method. However, in this method, the cost increases due to the extra processes such as emulsion printing, foiling, acidic etching, acidic polishing, acid stripping, washing with pure water, washing with caustic and so on. On the other hand, it is known that hazardous acid waste generated by the process is harmful to the environment. This results in high disposal costs. In addition, the acid used to etch the glass is known to be harmful to human health and its use is highly risky in terms of Occupational Health and Safety (OHS), so great care must be taken during the process. The resulting product is not only aesthetically pleasing to the users, but also preferred by the users thanks to the anti-fingerprint property of the matt / si Iky- matt glass. In the sandblasting method, the glass surfaces are mechanically abraded by sandblasting. In this method, it is necessary to use a sandblast-resistant mold (template) for each different pattern to be made on the glass, and the cost of this template is quite high in the current situation such as the white goods sector, in which the designs change frequently and these designs differ on a product / brand / model basis. In addition, the degree of mattness cannot be adjusted in the sandblasting method. Finally, the dust produced in the sandblasting process is known to cause silicosis. In the film coating method, the problems of abrasion, peeling and discoloration of the coating over time arise. The biggest deficiency that arises in the process of giving a matt appearance with enamel paint (temperable) is that only the matt appearance is given, but no matt / silky- matt rough texture can be provided in terms of texture. Therefore, it has a high fingerprint retention rate and does not show anti-fingerprint properties. In addition, since this paint has to be applied to the front surface (the surface that the end user comes into contact with), it must be extremely resistant to abrasion, scratches and chemical materials.

[0009] An example of an ion exchange method for matting a glass is the invention subject to the patent application RU2002135787A. The invention relates to a matting paste containing metal fluoride, barium sulfate and water. The inventive paste comprises 15- 40 g of Barium Sulfate, 5-40 g of Potassium Nitrate, 5-20 g of Lithium Nitrate, 2-30 g of Barium Fluoride, 5-30 g of Dimethyl Sulfoxide, and 1-15 g of Water. Said paste is characterized by the use of barium fluoride as a metal fluoride and also comprises potassium nitrate, lithium nitrate and dimethyl sulfoxide. Said paste is applied at a temperature below 300°C. Since the heat treatment is applied at 300°C, tempering is required after the application. On the other hand, if applied after tempering, heat treatment does not affect the temper of the glass. However, in both cases, the additional heat treatment is required, which results in a significant cost increase. The high proportion of lithium in the mixture, which does not contain any hydrofluoric acid or its derivatives that will etch the surface, creates mechanical stresses by displacing the sodium ion in the glass structure and reducing the volume of the glass surface compared to the beginning. These stresses cause the formation and progression of microcracks. The micro-cracked coating layer created on the glass surface changes the light transmission and reflection, providing the glass with a matt appearance. These microcracks form stress concentration regions on the surface and weaken the mechanical strength of the glass product.

[0010] Another study is the invention subject to the patent application TR200500789A2. The invention relates to a method and equipment for converting a glass into a matt glass in the glass manufacturing industry. The invention consists of a receiving-laying-transport unit, a pre-washing-drying unit, a matting unit, a final washing-drying unit and a receiving- laying-transport unit. The process of matting the glass is completed untouched from start to finish.

[0011] Another study is the invention subject to the patent application W02004078666A2. The present invention relates to a machine or production line for performing a homogeneous matting process on the glass surface, cleaning the surface after matting process and, if necessary, producing the matted glass in different shades; it also relates to a machine for cleaning and washing only the glass surface. The matting machine / production line of the present invention consists of a loading unit, a first washing and drying machine, a foil coating unit (9), a scanning table, a matting conveyor, a screening unit, an absorption unit, a final washing and drying machine, an unloading unit, process tanks and a closed cabin.

[0012] Another study is the invention subject to the patent application CN 110204213A. The invention describes a method for producing an environmentally friendly matt glass. The method comprises the following steps: glass selection, part cutting, edging, cleaning, silk printing, cleaning and drying. Accordingly, soda-lime-silica glass doped with the elements Yb, Cd and Ti is selected, followed by the use of a fluoride-free environmentally friendly matting paste for the glass. Thus, fluoride, which is harmful to human health, is not produced in the matting process and the glass becomes more environmentally friendly and safe.

[0013] Although many studies have been carried out on the matting of glass, these studies use the methods of acidic etching or etching with acid-containing paste, which are known to be harmful to the environment. As a result, the existence of a need for a method for giving a matt appearance to the tempered glass that eliminates the negative effects on the environment and high cost disadvantages of the existing methods in the state of the art and the inadequacy of the existing solutions made it necessary to make a development in the relevant technical field.

[0014] Summary of the Invention

[0015] The invention relates to a glass processing method for giving a matt appearance to tempered glass used in ovens, stoves, refrigerators, hoods, dishwashers and similar appliances in the white goods sector, which meets the above-mentioned requirements, eliminates all disadvantages and brings some additional advantages.

[0016] Based on the state of the art, the object of the invention is to obtain a decorative matt surface on the glass surface by means of the developed method, while minimizing the negative effects and damages of existing applications on the environment and human beings.

[0017] The object of the invention is to reduce the production cost by eliminating the extra processes in the method.

[0018] Another object of the invention is to increase the strength and extend the service life of the glass by penetrating the glass by forming a separate layer on the glass surface in the method. A further object of the invention is to provide adhesion of quartz powders having a low grain size (d90 < 10 mm) to the soda-lime-silica glass surface.

[0019] Another object of the invention is to use crystalline water-containing (hydrated) silica compounds, which show a decomposition reaction around 400°C, so that they can be easily dissolved by K+ ions in potassium nitrate melt at tempering temperatures and adhere homogeneously to the glass surface.

[0020] Another object of the invention is to adjust the viscosity of the mixture as well as to reduce the production cost by means of surface modification with the wet coating application.

[0021] Another object of the invention is that the working temperatures are close to the tempering temperatures and the heat treatment process is carried out in the tempering furnace, so that both surface modification and tempering of the glass can be carried out at the same time without the need for a secondary heat treatment, thus providing a significant cost advantage.

[0022] A further object of the invention is to provide topographic modification of the glass surface at the temperature (500 - 800°C) and time (2 - 10 minutes) ranges, at which the tempering process takes place, by the use of salt and other mixture components to facilitate melting only in the upper layer (100-300 pm).

[0023] Another object of the invention is to provide that the salt contained in the mixture printed on the glass surface by screen printing method at the entrance of the tempering furnace melts rapidly in the tempering furnace and dissociates into its ions and starts to diffuse from the glass surface to the inner parts and that this progress does not occur very quickly in the environment above the glass transition temperature of almost 100°C, so that the softening caused by the high rate of cation increase on the glass surface remains localized.

[0024] Another object of the invention is to provide that the mixture used to change the glass surface topography becomes integral with the glass surface by melting the salts applied by screen printing before the tempering furnace and partial softening on the upper surface. Another object of the invention is to prevent the salt, which has a melting temperature of 334°C and a boiling temperature of 400°C, from melting and running off the surface at high temperatures by adding a filler (AI2O3 or ZrO2) to the mixture to bind the mixture to the surface.

[0025] A further object of the invention is to provide that alumina (AI2O3) or zirconia (ZrO2) used for the surface roughness modification does not adhere to the surface due to its inability to be dissolved by potassium.

[0026] Another object of the invention is to provide that the mixture is spread homogeneously on the surface by preventing the retention and precipitation of the grains by using PVA- containing medium as a thinner and binder.

[0027] Another object of the invention is to provide a more homogeneous spreading by partially dissolving the potassium nitrate (KNO3) used in the mixture in water.

[0028] Another object of the invention is to provide that the prepared mixture does not contain hydrofluoric acid or similar surface abrasives, thereby eliminating the toxic effect contrary to the current applications.

[0029] The structural and characteristic features and all advantages of the invention will be understood more clearly thanks to the figures given below and the detailed description written with reference to these figures, therefore, the evaluation must be made taking into account these figures and detailed descriptions.

[0030] Brief Description of the Drawings

[0031] In order to best understand the embodiment of the present invention and its advantages with additional elements, it should be evaluated together with the figures described below.

[0032] Fig. 1 is a schematic overview of the cross-section of the wet coating-printed glass, Fig. 2 is a schematic overview of a matted glass in a preferred embodiment of the invention. Reference Numbers

[0033] 10. Glass

[0034] 11. Matt surface

[0035] 12. Coating

[0036] 13. Glossy surface

[0037] Detailed Description of the Invention

[0038] In this detailed description, the glass processing method of the invention developed to give a matt appearance to the tempered glass (10) used in ovens, stoves, refrigerators, hoods, dishwashers and similar appliances in the white goods sector is described only as an example for a better understanding of the subject matter and without any limiting effect.

[0039] The glass processing method of the invention has been developed in order to minimize the damage to the environment and people, to reduce the cost by eliminating extra processes, and to increase the strength and extend the service life of the coating (12) by forming a separate layer on the surface of the glass (10) and penetrating in to the glass. In said glass processing method (10), a matting mixture is applied to the desired parts of the surface of the glass (10) by printing method and the matt surfaces (11) are obtained on these parts, while glossy surfaces (13) are obtained on the parts on which the mixture is not applied. The functional matt surface (11), which has both aesthetic and antifingerprint properties, is formed as a result of the coating creating a surface with high surface roughness. The areas that need to be clearly / directly visible, such as the symbol, the digital display, etc., the areas not applied with the mixture are glossy surfaces (13) and have the surface roughness of glass (10). The mixture of salt, silica source, filler, binder and water forms the matt surfaces (11) on the glass (10) after the heat treatment at 500-800°C. The mixture dissolves the silicon in the glass (10) and adheres to the surface, forming a rough structure and revealing the matt surface (11). Said glass processing method does not use acids or corrosive chemicals, providing an environmentally friendly and energy-saving solution thanks to its application during tempering. Said coating provides an adhesion of quartz powders having a low grain size (d90 < 10 mm) to the surface of the soda-lime-silica glass (10). In the temperature range of 400 - 500°C, the K+ cation in the form of ion in the potassium nitrate melt attacks the surface of the silica powder and adheres to the surface of the glass (10) as a result of the dissolution of some silica on the surface. The amount of silica dissolution varies thermodynamically depending on the concentration of K+ ion, temperature and time. When the physical tempering temperatures (between 500-800°C) are approached, due to the time limitation (maximum around 10 minutes), some quartz powder dissolves from the coating (12) under the influence of similar K+ ion and adheres to the surface of the glass (10). In the content of said coating (12), the crystalline water-containing (hydrated) silica compounds, which are easily dissolved by K+ ions in potassium nitrate melt at tempering temperatures to ensure homogeneity, provide adhesion to the surface of the glass (10) and show a degradation reaction around 400°C.

[0040] In said glass processing method, surface modification is performed by the wet coating application. Said glass processing method comprises the steps of coating the prepared mixture on the surface of the glass (10) and heat treatment. The working temperatures are close to tempering temperatures and the heat treatment process is carried out in the tempering furnace. A significant cost advantage is achieved by performing both surface modification process and tempering process of the glass at the same time without the need for a secondary heat treatment as in existing applications. The topographic modification of the surface of the glass (10) at the temperature (500 - 800°C) and time (2 - 10 minutes) ranges, at which the tempering process takes place, is provided by the use of salt and other mixture components to facilitate melting only in the upper layer (100-300 pm). The mixture is screen-printed on the surface of the glass (10) at the inlet of the tempering furnace and then the mixture is dried in a drying furnace. In the tempering furnace, the salt rapidly melts and dissociates into its ions and starts to diffuse from the surface of the glass (10) towards the interior. However, this progress does not take place very quickly in an environment with a glass (10) transition temperature of above almost 100°C and the softening caused by the high rate of cation increase on the surface of the glass (10) remains localized. In the mixture used to modify the surface of glass (10) shown in Fig. 1 , KNO3 salt with a melting temperature of 334°C and a boiling temperature of 400°C was used as a cation source and AI2O3 or ZrC>2 powder that does not melt at 334-400°C, was used as a filler to bind the mixture to the surface so that this salt does not melt at high temperatures and run off the surface. Alumina (AI2O3) or zirconia (ZrC>2), which cannot be dissolved by potassium nitrate (KNO3), is used for surface roughness modification because it does not adhere to the surface. The potassium nitrate (KNO3) used in said mixture is partially soluble in water and thus provides a more homogeneous spreading. At the same time, PVA-containing medium thinner was used as a binder to hold the grains and prevent them from precipitating. The used medium provides homogeneous spreading of the mixture on the surface of the glass (10). The mixture to be used to change the surface topography of the glass (10) is applied by screen printing before the tempering furnace, and the salts melting in the furnace become integral with the surface with partial softening on the upper surface of the glass (10).

[0041] In summary, in the glass processing method of the invention, a water or other solventbased mixture (nitrate, sulfate, carbonate or oxide) which can be produced in paste consistency or in different fluidity values if required, can be applied to the surface of the glass (10) at room temperature as in screen printing, digital printing and all similar glaze and paint applications Since the prepared paste does not contain hydrofluoric acid or similar surface abrasives, it has no toxic effect. After the application to the surface of the glass (10) at room temperature, it is dried at room temperature or at a temperature suitable for the removal of the liquid media. After drying, the printed glass (10) is sent to the tempering furnace to form a matt surface (11) in the desired areas. Under the conditions of the furnace, the organic adhesive contained in the paste mixture volatilizes and the remainder melts and coats the surface of the glass (10) by forming a layer (12). The samples are tempered at a temperature range of 500-800°C for 2-10 minutes. After the heat treatment, the dried residue mixture on the cooled glasses (10) is cleaned with water.

[0042] To explain the glass processing method of the invention in more detail, first, soda-lime glasses (10) taken in the plates shown in Fig. 2 is cut to the desired dimensions and a matting base is formed. The sharp edges of the glass (10) are ground and de-sharpened to prevent damage and reduce stress points. The ground glasses (10) are made ready for the installation of handles, buttons and the like by drilling holes if desired. The glasses (10) are then washed and prepared for printing with a previously prepared matting mixture. The matting mixture comprises potassium nitrate (KNO3) to facilitate melting; a silica source that is dissolved by K ions and bonded to the surface; a filler that binds the mixture to the surface so that the potassium nitrate salt does not melt at high temperatures and run off the surface; a PVA-containing medium thinner as a binder to hold the grains and prevent them from precipitating. The first component in said mixture is potassium nitrate (KNO3). Potassium nitrate salt with a melting temperature of 334°C and a boiling temperature of 400°C melts rapidly and dissociates into its ions in the tempering process (500-800°C). The K+ cation in the potassium nitrate melt begins to diffuse towards the inner parts of the surface of the glass (10) and facilitates melting. This results in a rapid softening of the glass (10). The K+ cation then attacks the surface of the silica powder in the glass (10), dissolves some silica on the surface and thus adheres to the surface of the glass (10). When the different silica sources were tested, it was determined that crystalline water-containing (hydrated) silica compounds, which showed a degradation reaction around 400°C, were easily dissolved by K+ ions in potassium nitrate melt at tempering temperatures and adhered to the glass surface. Therefore, the second important component in the mixture is the silica source to be dissolved by K ions and adhered to the surface. Silica (SiC>2), Zirconium silicate (Zr(SiO4)) or Talc (3MgO, 4SiC>2, H2O) can be used as silica source. Talc, which has a crystalline structure, easily degrades and dissociates into its components in the applied temperature range. Its crystalline structure allows it to degrade at lower temperatures and increases the efficiency of the process. Another component is a filler to bind the mixture to the surface so that the potassium nitrate salt does not melt at high temperatures and run off the surface. Alumina (AI2O3) or Zirconia (ZrC>2) powder that does not melt at the tempering temperature was used as said filler. Alumina or zirconia, which cannot be dissolved by potassium, is used for surface roughness modification because it does not adhere to the surface. At the same time, PVA-containing medium thinner is used as a binder to hold the grains and prevent them from precipitating. The medium used provides that the mixture spreads homogeneously over the surface. In order to be economical, the mixture was prepared as aqueous system and water was added. Water is used to adjust the viscosity of the mixture. In addition, potassium nitrate (KNO3) is partially soluble in water and thus provides a more homogeneous spreading. After the mixture is prepared, it is printed on the front surface of the glass (10) by printing methods such as silk screen printing, digital printing and roller printing. After printing, the glass (10) is dried in drying furnaces to dry the mixture. The glass (10) is then tempered by heat treatment in tempering furnaces in the temperature range of 500-800°C. After tempering, the glass (10) not only gains strength and becomes durable, but also becomes safety glass by breaking into small parts when broken. At the same time, the mixture printed on the glass (10) as a wet coating reacts with silicon to form a rough layer (12) on the surface of the glass (10). This results in the desired matt appearance (11). After the heat treatment, the dried residue mixture on the glass (10) is cleaned with water. In the gloss measurement as a numerical determination of said matt appearance, the gloss of the glass (10) should be between 5-45 Gil.

Claims

CLAIMS1. A glass processing method for giving a matt appearance to tempered glass (10), especially in the white goods sector, wherein it comprises the process steps of; preparing a mixture comprising a cation source to facilitate melting; a silica source that is dissolved by potassium ions and bonded to the surface; a filler that binds the mixture to the surface so that the salt does not melt at high temperatures and run off the surface; a thinner as a binder to hold the grains and prevent them from precipitating; printing the prepared mixture onto the surface of the glass (10) by applying wet coating at the inlet of the tempering furnace; after the printing application on the surface of the glass (10), drying it by heat treatment in a drying furnace to remove the part forming the liquid media; after drying, sending the printed glass (10) to the tempering furnace to form a matt surface (11) in the desired areas; under the conditions of the tempering furnace, volatilizing the adhesive contained in the mixture and melting and coating the remainder onto the surface of the glass (10) by forming a layer (12); cleaning the dried residual mixture on the cooled glasses (10) after tempering.

2. A glass processing method according to claim 1 , wherein the surface modification is performed by the wet coating application.

3. A glass processing method according to claim 1 , wherein the topographic modification of the surface of the glass (10) is carried out only in the top layer, preferably 100-300 pm thick, at a temperature of preferably 500 - 800°C, in which the tempering process takes place, and preferably in the interval of 2-10 minutes, using salt that facilitates melting and other mixture components.

4. A glass processing method according to claim 1 , wherein KNO3 salt is used as a cation source in the mixture to modify the surface of the glass (10).

5. A glass processing method according to claim 1 , wherein silica (SiC>2), zirconium silicate (Zr(SiO4)) or talc (3MgO, 4SiC>2, H2O) are used as silica sources.

6. A glass processing method according to claim 1 , wherein AI2O3 or ZrC>2 is used as a filler to bind the mixture to the surface for the surface roughness modification and to prevent the salt from melting at high temperatures and running off the surface.

7. A glass processing method according to claim 1 , wherein PVA-containing medium thinner is used as a binder to hold the grains and prevent them from precipitating and to spread the mixture homogeneously on the surface of the glass (10).

8. A glass processing method according to claim 1 , wherein water is used to adjust the viscosity of the mixture.

9. A glass processing method according to claim 1 , wherein the water-based or other solvent-based mixture prepared in paste consistency or different fluidity values is applied to the surface of the glass (10) at room temperature as in screen printing, digital printing and all similar glaze and paint applications.

10. A glass processing method according to claim 1 , wherein the soda-lime glasses (10) received in plates are cut to the desired dimensions to form the base to be matted.11 . A glass processing method according to claim 1 , wherein the sharp edges of the glass (10) are ground and de-sharpened to prevent damage and reduce stress points.

12. A glass processing method according to claim 1 , wherein the ground glasses (10) are made ready for the installation of handles, buttons and the like by drilling holes if desired.

13. A glass processing method according to claim 1 , wherein the glasses (10) are washed and prepared for printing the matting mixture.

14. A glass processing method according to claim 1 , wherein after the mixture is prepared, it is printed on the front surface of the glass (10) by the printing methods such as silk screen printing, digital printing, roller printing.

15. A glass processing method according to claim 1 , wherein after the mixture is printed, it is dried in drying furnaces before heat treatment.

16. A glass processing method according to claim 1 , wherein the glass (10) is tempered in tempering furnaces by heat treatment in the temperature range of 500-800°C.

17. A glass processing method according to claim 1 , wherein the mixture, which is printed onto the glass (10) as a wet coating to obtain the matt appearance (11), reacts with silicon to form a rough layer (12) on the surface of the glass (10).

18. A glass processing method according to claim 1 , wherein in the gloss measurement of the matt appearance, the gloss of the glass (10) is between 5- 45 GU.

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