Method for forming a 2mm or less thick rolled glass

Abstract

The application provides a method for forming a calendered glass with a thickness of less than 2mm, and belongs to the technical field of calendering of glass. The method comprises the following steps: flowing a glass melt with a viscosity of less than 10 4 Pa·s into a closed container containing a metal liquid; when the viscosity of the glass melt increases to 10 5.3 -10 5.8 Pa·s, the glass melt is formed into a viscoelastic glass ribbon with a certain width and a thickness of H1 by horizontal drawing, and H1<4mm; when the viscosity of the viscoelastic glass ribbon increases to 10 5.8 -10 6.3 Pa·s, the viscoelastic glass ribbon is introduced between an upper calendering roller and a lower calendering roller through a guide roller; after being drawn and extruded by the upper calendering roller and the lower calendering roller, the viscosity of the viscoelastic glass ribbon is greater than 10 6.8 Pa·s, the thickness is H2, H1>H2, and H2≤2mm; and the viscoelastic glass ribbon is annealed and cooled to obtain a product. The method is used for producing calendered glass with a thickness of less than 2mm.

Description

Technical Field

[0001] This invention belongs to the field of glass rolling technology, specifically relating to a method for forming rolled glass with a thickness of less than 2 mm. Background Technology

[0002] Solar glass, also known as ultra-clear glass, low-iron glass, or new energy glass, is a general term for glass used in the solar energy industry. Ultra-clear glass, a type of soda-lime-silicon glass, has a significantly different manufacturing process compared to ordinary glass. In the production of ultra-clear glass, the total Fe2O3 content does not exceed 0.015%. Based on manufacturing processes, solar glass can be divided into solar rolled glass and ultra-clear float glass. Ultra-clear float glass is mainly used in thin-film solar cell modules, lenses or reflectors in solar thermal power generation systems, etc. Solar rolled glass is mainly used in cover plates and backsheets for silicon crystal solar cell modules, solar smart agriculture sunrooms, and flat-plate solar collectors, etc.

[0003] Rolled glass is named for the way molten glass is pressed and stretched between the upper and lower rollers of a rolling mill. The forming process is called the rolling process. The rolling process originated in 16th-century France, and by the 20th century, glass produced using this method was widely used around the world. In 1956, my country's first rolled glass production line was built and put into operation at the Zhuzhou Glass Factory in Hunan Province.

[0004] Due to the unique nature of the calendering process, the thickness of calendered solar glass on the market is currently mainly 3.2mm. Controlling thickness variations is difficult when producing ultra-thin glass below 3mm, and any inherent defects on the surface are amplified during production. To increase sunlight transmittance, patterns are pressed onto the glass during the calendering process to enhance light transmission. This is also done to reduce the weight of silicon-based solar cell modules and increase sunlight transmittance through the module cover. The calendering method primarily relies on calendering rollers to directly shape the molten glass. This method makes it difficult to produce solar glass thinner than 2mm. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for forming rolled glass with a thickness of less than 2 mm, in order to overcome the shortcomings of the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for forming rolled glass with a thickness of less than 2mm, comprising the following steps: Make the viscosity less than 10 4 A glass melt with a viscosity of Pa·s flows into a sealed container holding molten metal. When the viscosity of the glass melt increases to 10… 5.3 -10 5.8At Pa·s, the glass melt is formed into a viscoelastic glass strip of a certain width and thickness H1 by horizontal pulling method, where H1 < 4 mm; When the viscosity of the viscoelastic glass ribbon increases to 10 5.8 -10 6.3 At a pressure of 10 Pa·s, the viscoelastic glass strip is guided between the upper and lower calendering rolls by the guide rollers; after being pulled and squeezed by the upper and lower calendering rolls, the viscosity of the viscoelastic glass strip is greater than 10 Pa·s. 6.8 Pa·s, thickness H2, H1>H2, and H2≤2mm, annealing, cooling, to obtain the product.

[0007] Optionally, the distance between the upper calendering roll and the lower calendering roll is 0.7~2.0mm, the design pressure is 480000N, and the effective length is not less than 3000mm.

[0008] Optionally, the viscoelastic glass strip is located above the guide roller, the highest point of the guide roller is higher than the horizontal plane of the overflow port of the sealed container, and the horizontal height of the guide roller is higher than that of the lower calendering roller.

[0009] An apparatus for forming rolled glass with a thickness of less than 2 mm includes: a sealed container, an upper calendering roll, a lower calendering roll, and an edge-pulling machine. It also includes a guide roll, which is disposed at the overflow port of the sealed container. The upper calendering roll and the lower calendering roll are disposed at the exit end of the guide roll. The highest point of the guide roll is higher than the horizontal plane where the overflow port of the sealed container is located, and the horizontal height of the guide roll is higher than that of the lower calendering roll.

[0010] In the calendering process of solar glass, the adjusted high-temperature molten glass flows out from the overflow port. As it passes through the gap between the rollers, the friction and stretching caused by the rotation of the calendering rollers create a clear calendered surface. After cooling, the high-temperature glass strip is quickly shaped and flattened. The technical difficulty of glass calendering lies in the high temperature involved and the exceptionally complex heat transfer conditions, which easily lead to various forming defects. Defects in solar glass significantly reduce its quality, potentially affecting further forming and processing, and even generating a large amount of waste. Common defects caused during the forming process include internal defects such as bubbles, inclusions, streaks, and crystallization, and external defects such as optical deformation, scratches, thickness deviations, and end-face defects (edge ​​bursting, corner missing). If defects such as crystallization and bubbles appear in the glass, they will affect the refraction and reflection of the glass, impacting the high-quality optical and mechanical properties required for photovoltaic glass.

[0011] During the calendering process, high-temperature molten glass flows into the gap between the two rollers. As it passes through the gap, it is rapidly rolled, rubbed, and stretched to form the shape. One calendering roller is a smooth roller, and the other is a patterned roller. The friction and stretching caused by the rotation of the rollers create a clear calendering pattern. Cooling water channels are connected inside the calendering rollers, allowing heat exchange between the calendering rollers and the molten glass on their surfaces, forming a calendering roller cooling system that enables the high-temperature glass strip to quickly set and flatten. Factors such as the temperature and rotational speed of the calendering rollers, the roller gap, and the distance between the two rollers have a significant impact on the forming quality of photovoltaic glass.

[0012] The surface temperature of the calender roll is controlled by the cooling system inside the calender roll. It is mainly affected by the structure of the calender roll cooling chamber, the temperature and speed of the cooling water. If the calender roll temperature is too high, it will cause the roll to stick, resulting in deformation of the photovoltaic glass during calendering and unclear patterns on the glass surface. If the calender roll temperature is too low, it will cause cold lines to appear on the surface of the glass plate.

[0013] The surface temperature of the calender rolls and their rotational speed need to be coordinated and adjusted accordingly. Under high-speed operation, the surface temperature of the calender rolls should be lower; otherwise, the shortened calendering time will cause the glass melt temperature to rise and the adhesion force to the calender rolls to decrease, resulting in glass sticking to the rolls or a thicker product. Conversely, under low-speed operation, the surface temperature of the calender rolls should be higher; otherwise, the glass thickness will decrease due to increased adhesion. Insufficient heat in the glass melt can also lead to a rough surface, bubbles, pattern deformation, and even voids. Uniform and consistent surface temperature of the calender rolls is essential for accurate glass forming control during the photovoltaic glass calendering process.

[0014] The gap between the calender rolls is roughly the same as the thickness of the required product. The calender rolls are subjected to great lateral pressure during operation, which may cause elastic deformation of the calender rolls. The deflection caused by the deformation of the calender rolls causes the gap between the rolls to change along the length of the roll, so that the calendered glass will have a cross-sectional shape with different thicknesses.

[0015] Therefore, it is evident that the quality problems of rolled glass are closely related to its forming process. Factors affecting the quality of rolled parts include the glass melt temperature, the surface temperature of the rolling rolls, the rolling roll speed, the rolling roll gap, and the feeding and working conditions during the rolling process. Glass production conditions will vary accordingly with changes in these factors. Although glass rolling has long been industrialized, some forming processes and parameters still rely heavily on experience, resulting in significant instability.

[0016] The current method for producing solar photovoltaic glass involves pressing and stretching qualified molten glass (1000-1100℃) through calendering rollers, followed by rapid cooling to obtain rolled glass of a certain thickness, typically 3.2±0.2mm, with a minimum thickness variation of 0.25mm for the original sheet. The surface temperature of the 3.2mm rolled glass after forming is 700-730℃, and the designed pressure between the upper and lower calendering rollers is between 90,000-150,000N. The gap and pressure between the upper and lower calendering rollers directly affect the glass thickness; a smaller gap and higher pressure result in thinner glass, and vice versa. The solar photovoltaic glass calendering process is essentially a dynamic heat exchange process. In a typical production line, the glass sheets advance at a speed of 5-10 m / min, while the temperature difference between the glass before and after the calendering rolls exceeds 300℃. A large amount of heat is transferred to the calendering rolls in a short time, rapidly changing the physical state from a quasi-liquid to a solid. The calendering rolls then complete the next work cycle in a circular motion. During this cyclical process, the calendering rolls are constantly under harsh production conditions of alternating thermal stress, with the surface temperature fluctuating periodically between 100℃ and 300℃. The long-term, cyclical, and high-load production stamping places extremely stringent quality requirements on the calendering rolls.

[0017] Existing direct rolling production methods require rapid cooling of the molten glass from a quasi-liquid state to a solid state during pressing and stretching. In this process, the temperature T of the upper surface of the glass... 上 and lower surface temperature T 下 At around 500℃, the core temperature T 中 Maintaining a temperature of around 1000℃ is crucial; it is precisely this temperature difference that allows the glass to be pressed and stretched to the required thickness. When using this method for glass less than 2mm thick, T... 上 and T 下 At 500℃, and T 中 However, it rapidly decreased in thickness, forming a solid state, so the thickness could no longer be reduced.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a two-step method to produce rolled glass with a thickness of less than 2mm. The first step is to flatten the glass, and the second step is to slightly thin and roll it. Specifically, qualified molten glass is poured into a sealed container filled with liquid metal. During the gradual cooling process, the glass is flattened and thinned to obtain a viscoelastic glass strip of a certain thickness. The viscoelastic glass strip is then fed between upper and lower rolling rollers. Under the pressure, tension, and cooling effect of the rolling rollers, the viscoelastic glass is transformed into a rolled glass strip of even smaller thickness.

[0019] This invention, through the aforementioned technical solution, enables the production of solar rolled glass with a thickness of less than 2mm. This effectively reduces the weight of solar power generation modules, expanding their application scenarios, such as building-integrated photovoltaics (BIPV). The reduced thickness decreases the amount of raw materials used in the glass, lowering costs and reducing carbon emissions. While maintaining the same solar transmittance, the iron content can be appropriately increased. For example, 3.2mm thick glass requires an iron content of less than 150ppm to achieve a solar transmittance of 91.5%, while 1.5mm thick glass with an iron content of less than 200ppm can achieve the same 91.5% transmittance. Increasing the iron content effectively reduces the procurement cost of glass raw materials.

[0020] The product produced by this invention is superior to GB / T30984.1-2015 Solar Glass Part 1: Ultra-clear Rolled Glass, with a thickness deviation of ±0.1mm, a maximum allowable thickness difference of 0.15, and a solar transmittance (the ratio of solar flux transmitted through the sample to incident solar flux in the solar spectrum range of 380nm~1100nm) ≥91.8%, which is significantly better than existing products.

[0021] The calendering method of this invention can produce solar calendered glass with a thickness of 0.7mm-2mm; it reduces the design pressure of the calendering roll, increases the service life and design difficulty of the calendering roll, and at the same time reduces the ineffective operation time in the glass production process. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 : A schematic diagram of the structure of a roller calendering device in the existing glass calendering process; Figure 2 : A schematic diagram of the apparatus for forming rolled glass with a thickness of less than 2 mm according to the present invention; Among them, 1. glass melt; 2. liquid metal; 3. viscoelastic glass belt; 4. guide roller; 5. upper calendering roller; 6. lower calendering roller; 7. solar rolled glass. Detailed Implementation

[0024] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0025] For ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn to actual scale. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0026] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0027] The numerical ranges and parameters shown in this invention are approximate values, but the values ​​shown in specific embodiments are recorded as accurately as possible. However, all numerical values ​​inherently contain specific errors that are necessarily caused by the standard deviations observed in the various experimental measurements. The term "about" means, as would be considered by those skilled in the art, within the permissible standard error.

[0028] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain any unspecified components other than unavoidable impurities.

[0030] Figure 1 The diagram shows a schematic of a roll calendering device in the existing glass calendering process. The calendering process corresponding to this device is as follows: molten glass at a temperature of 1000-1100℃ flows from the overflow port between the upper and lower calendering rolls. After being pressed and stretched by the calendering rolls, it becomes a glass strip with a surface temperature of 700-750℃. After annealing and cooling, qualified glass sheets are produced. A front guide roller is provided at the bottom of the glass sheet to guide the transport direction of the glass sheet.

[0031] The 3.2mm product obtained by the existing method is tested according to GB / T30984.1-2015 Solar Glass Part 1: Ultra-white Rolled Glass, with a thickness deviation of ±0.2mm, a maximum allowable thickness difference of 0.25, and a solar transmittance (the ratio of solar flux transmitted through the sample to the incident solar flux in the solar spectrum range of 380nm~1100nm) ≥91.5%.

[0032] like Figure 2 As shown, the apparatus for forming rolled glass with a thickness of less than 2mm includes: a sealed container, a guide roller disposed at the overflow port of the sealed container, and a rolling roller disposed at the outlet end of the guide roller. The rolling roller includes an upper rolling roller 5 and a lower rolling roller 6, which are positioned correspondingly. The highest point of the guide roller is higher than the horizontal plane where the overflow port of the sealed container is located, and the horizontal height of the guide roller is higher than that of the lower rolling roller 6. Several sets of edge-pulling machines are symmetrically arranged on both sides of the sealed container along the flow direction of the glass melt 1.

[0033] The head of the edge-pulling machine presses against the edge of the glass melt 1 at a certain angle to the flow direction of the glass melt 1, transmitting the force of the rotation of the head to the glass melt 1; wherein, the certain angle is an acute angle.

[0034] Therefore, several pairs of edge-pulling machines are symmetrically arranged on both sides of the sealed container. The machine head of the edge-pulling machine is tilted at a certain angle and rotates on the edge of the glass melt 1. The machine head applies a pulling force to the left and right front on both sides of the glass melt 1, and transmits the force of the machine head rotation to the glass melt 1, flattening the glass melt 1 to the expected thickness.

[0035] like Figure 2 As shown, a method for forming 1.5mm thick Na-Ga-Si series rolled glass includes the following steps: The glass batch is mixed evenly, then melted and clarified at high temperature in a glass melting furnace to obtain a viscosity of 10. 3.8 Glass melt at Pa·s 1; Make the viscosity 10 3.8 A glass melt 1 with a viscosity of Pa·s (approximately 1048°C) flows into a sealed container holding molten metal. When the viscosity of the glass melt 1 increases to 10... 5.5 At Pa·s (temperature approximately 830℃), the glass melt 1 is formed into a viscoelastic glass strip 3 with a width of 3000mm and a thickness of 2mm using a horizontal pulling method; When the viscosity of viscoelastic glass strip 3 increases to 10 6.0 At a temperature of approximately 800°C (Pa·s), the viscoelastic glass strip 3 is guided between the upper calendering roll 5 and the lower calendering roll 6 via the guide roller; After being drawn and extruded by the upper calendering roller 5 and the lower calendering roller 6, the viscosity of the viscoelastic glass strip 3 is 10. 6.9Pa·s (temperature approximately 720℃), thickness reaching 1.5mm, annealed, cooled, and cut to obtain ultra-white rolled glass sheet.

[0036] The distance between the upper calendering roll 5 and the lower calendering roll 6 is 1.5 mm, the design pressure is 480000 N, and the effective length is 3000 mm.

[0037] The diameters of the guide roller, upper calendering roller 5, and lower calendering roller 6 are all 300 mm.

[0038] The temperature of the glass melt 1 inside the sealed container is controlled by local heating and cooling methods; the guide roller, upper calendering roller 5 and lower calendering roller 6 have internal cooling systems, and the cooling medium is water.

[0039] The viscoelastic glass strip 3 is located above the guide roller, which is located above the level of the overflow port of the sealed container, and the horizontal height of the guide roller is higher than that of the lower calendering roller 6.

[0040] In this invention, tin liquid can be conventionally selected as the metal liquid.

[0041] The product obtained by this invention was tested in accordance with GB / T30984.1-2015 Solar Glass Part 1: Ultra-white Rolled Glass. The thickness deviation was ±0.1mm, the maximum allowable thickness difference was 0.15, and the solar transmittance (the ratio of solar flux transmitted through the sample to incident solar flux in the solar spectrum range of 380nm~1100nm) was ≥91.8%, which is significantly better than the 3.2mm product.

[0042] Furthermore, the forming method of this invention can be used to produce solar rolled glass with a thickness of less than 2mm, which can effectively reduce the weight of solar power generation modules and increase the application scenarios of power generation modules, such as the application of building-integrated photovoltaics. The reduction in thickness can reduce the use of glass raw materials, reduce costs, and reduce carbon emissions. Under the same solar transmittance, the iron content can be appropriately increased. For example, the iron content of 3.2mm thick glass must be less than 150ppm to achieve a solar transmittance of 91.5%, while for 1.5mm thick glass, the solar transmittance can reach 91.5% with an iron content of less than 200ppm. The increase in iron content can effectively reduce the procurement cost of glass raw materials. It also reduces the design pressure of the rolling rolls, increases the service life and design difficulty of the rolling rolls, and reduces the ineffective operation time in the glass production process.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

A method for forming rolled glass with a thickness of less than 1.2 mm, characterized in that: Includes the following steps: Make the viscosity less than 10 4 A glass melt with a viscosity of Pa·s flows into a sealed container holding molten metal. When the viscosity of the glass melt increases to 10… 5.3 -10 5.8 At Pa·s, the glass melt is formed into a viscoelastic glass strip of a certain width and thickness H1 by horizontal pulling method, where H1 < 4 mm; When the viscosity of the viscoelastic glass ribbon increases to 10 5.8 -10 6.3 At a pressure of Pa·s, the viscoelastic glass strip is guided between the upper and lower calendering rolls by the guide rollers; after being pulled and squeezed by the upper and lower calendering rolls, the thickness of the viscoelastic glass strip is H2, H1>H2, and H2≤2mm, and the viscosity is greater than 10. 6.8 Pa·s, annealing, cooling, to obtain the product; The distance between the upper and lower calendering rolls is 0.7~2.0mm, the design pressure is 480000N, the effective length is not less than 3000mm, the viscoelastic glass strip is located above the guide roll, the highest point of the guide roll is higher than the horizontal plane of the overflow port of the sealed container, and the horizontal height of the guide roll is higher than that of the lower calendering roll.

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