Composition of Colorless Soda-Lime Glass

Abstract

To provide a colorless soda-lime glass composition which reduces the amount of sulfate to be added to a bath while maintaining the quality of the glass without prolonging the refining time. [Solution] The composition of the present invention contains, by weight, 68-78% SiO2, 8-18% Na2O, 0-10% K2O, 7-12% CaO, 0-10% MgO, 0-10% ZnO, 0-10% BaO, 0-3% Al2O3, 0-1% B2O3, 0-1% SrO, a total sulfur content expressed in the form of SO3: less than 0.078%, a total cerium content expressed in the form of CeO2: 0.12% or less, and a total iron content expressed in the form of Fe2O3: 50-1,200 ppm; Mo, As, Sn, and Sb are not intentionally added; and the redox is less than 45.

Description

[Technical field]

[0001] The present invention relates to the field of glass industry. To melt the constituent substances of glass, a large supply of energy is required. The temperature of the glass bath is in the range of 1,300-1,500°C. Depending on its composition, glasses are intended for domestic use, e.g. drinking glasses, or for culinary use, e.g. cooking vessels. [Background technology]

[0002] The furnace is exposed to extreme thermal and mechanical stresses. The furnace is constructed with high quality refractory coatings. Such refractory coatings are not only expensive but also prone to react with some of the highly chemically reactive components of the glass. Due to the poor thermal conductivity of the refractory coatings, the heating of the molten glass bath is carried out in the furnace, for example from above or inside the glass bath.

[0003] For example, there is a liquid or gaseous fueled flame burner between the glass bath and the top of the furnace, the so-called vault. The glass bath is essentially heated by radiation. The gas outlet temperature is 1,300-1,600°C, depending on the type of glass.

[0004] The production of glass also releases large amounts of gas. The glass bath is degassed for several hours to prevent bubbles from forming in the glass. Refining additives such as sulfates may be used to aid in degassing. The furnace runs successive batches of glass with a defined composition, which may vary within a batch. Summary of the Invention [Problem to be solved by the invention]

[0005] The applicant has found that sulfates can be disadvantageous in terms of contamination, in particular of the outlet gases and the glass bath. [Means for solving the problem]

[0006] The applicant has conducted tests to reduce the amount of sulfate added to the bath while maintaining glass quality without increasing refining time.

[0007] The present invention proposes a colorless soda-lime glass composition containing, by weight, 68-78% SiO2, 8-18% Na2O, 0-10% KO, 7-12% CaO, 0-10% MgO, 0-10% ZnO, 0-10% BaO, 0-3% Al2O3, 0-1% B2O3, 0-1% SrO, a total sulfur content expressed in the form of SO3 of less than 0.078%, a total cerium content expressed in the form of CeO2 of 0.12% or less, and a total iron content expressed in the form of Fe2O3 of 50-1,200 ppm, wherein Mo species, As species, Sn species, and Sb species are not intentionally added, and the composition has a redox of less than 45.

[0008] When the SiO2 content falls below 68%, the viscosity of the glass decreases and the expansion coefficient increases.

[0009] When the SiO2 content is above 78%, melting becomes more difficult.

[0010] When the Na2O content is below 8%, the melting kinetics deteriorate.

[0011] If the Na2O content exceeds 18%, the wear of the furnace refractories increases and the expansion coefficient increases.

[0012] If the K2O content exceeds 10%, the viscosity of the glass bath increases significantly.

[0013] When the CaO content falls below 7%, the slope of the temperature-viscosity curve decreases and the rate of glass formation in the molding machine slows.

[0014] If the CaO content exceeds 12%, there is a risk of devitrification due to crystallization.

[0015] If the MgO content exceeds 10%, the softening point of the glass decreases.

[0016] When the ZnO content is greater than 10%, the softening point of the glass decreases and the density of the glass increases.

[0017] If the BaO content exceeds 10%, the softening point of the glass decreases and the density of the glass increases.

[0018] When the Al2O3 content exceeds 3%, the melting point increases.

[0019] If the B2O3 content exceeds 1%, it will evaporate with downstream deposits and increase refractory corrosion.

[0020] When the total cerium content, expressed in the form of CeO2, exceeds 0.12%, the glass becomes colored due to metamerism.

[0021] When the total iron content, expressed in the form of Fe2O3, falls below 50 ppm, silicon, calcium and sodium sources are generally not available with low iron content, making raw material selection more difficult and limiting cullet recycling.The glass bath becomes transparent to infrared radiation, causing increased temperatures near the hearth and furnace walls, accelerating refractory wear.

[0022] Total iron in the form Fe2O3 above 1,200 ppm results in color that is difficult to counteract, specifically, without the addition of an oxidizing agent to oxidize the FeO to the less colored Fe2O3.

[0023] Intentional addition of As is undesirable for reasons related to its toxicity.

[0024] The intentional addition of Sb is undesirable for toxicity-related reasons.

[0025] Applicants have found that redox, which corresponds to the ferrous / ferric ratio, is important for successful smelting when sulfate content is low. Redox affects the solubility of SO3. As redox approaches 55, solubility is at a minimum.

[0026] Redox is defined herein as the molar ratio of FeO (ferrous) / Fe2O3 (ferric).

[0027] The applicant has found that in air-natural gas fired furnaces, the mass content of SO3 in the glass is about 0.20% or less at redox=40. That is, the more sulfate degassing occurs, the more it is present in the glass bath. On the other hand, it is difficult to reduce the mass content of SO3 in the glass without changing the production conditions. In fact, by increasing the refining time, the amount of refining agent can be reduced, but at the expense of a decrease in production inversely proportional to the refining time and an increase in furnace energy consumption and wear relative to the tonnage of glass produced.

[0028] In an oxygen-natural gas fired furnace, the mass content of SO3 in the glass was about 0.10% or less at redox = 40. Redox can be reduced to values ​​in the range of 10-15.

[0029] However, refining glasses with a high degree of oxidation requires longer refining times and lower tonnage, so that for reasons related to refining speed as well as decolorization of the glass to obtain so-called white glass (i.e., transparent, nearly colorless glass), a redox of 18 or more, or even 25 or more, is preferred. In this redox range, the higher the degree of oxidation of the glass, the higher the maximum relative amount of sulfate that will remain in the glass.

[0030] The redox range is preferably 20 to 45. The redox range is more preferably 25 to 40. The redox range is even better if it is 30 to 40.

[0031] In one embodiment, the composition has a total sulfur content, expressed in the form of SO3, by weight, that is lower than the maximum allowed by the redox and glass composition.

[0032] In one embodiment, the composition contains less than 0.074% total sulfur, by weight, expressed in the form of SO3. Condensation is reduced. Reactivity of the glass with production line components is reduced.

[0033] In one embodiment, the composition contains, by weight, TiO2: 0-1%.

[0034] In one embodiment, the composition contains, by weight, 0 to 0.3% F. If it exceeds 0.3%, corrosion of the mold increases.

[0035] In one embodiment, the composition contains, by weight, 71.0-73.0% SiO2, greater than 8% and less than 15% Na2O, 0-0.5% KO, 9-12% CaO, 1-2% MgO, 0-1% ZnO, 0-2% BaO, 0-2% Al2O3, 0.1% or less total cerium in the form of CeO2, less than 0.10% ZrO2, and less than 200 ppm Er2O3; and has a redox of less than 40.

[0036] In a preferred embodiment, the composition contains, by weight, Na2O: 13.0 to 14.0%.

[0037] In a preferred embodiment, the composition contains, by weight, K2O: 0 to 0.2%.

[0038] In a preferred embodiment, the composition contains, by weight, CaO: 10.0 to 11.4%.

[0039] In one preferred embodiment, the composition contains, by weight, less than 0.10% BaO.

[0040] In a preferred embodiment, the composition contains, by weight, Al2O3: 1.0 to 1.90%. If Al2O3 is less than 1%, the chemical resistance of the final glass decreases.

[0041] In one preferred embodiment, the composition contains, by weight, less than 0.05% ZrO2.

[0042] In a preferred embodiment, the composition contains less than 150 ppm Er2O3 by weight. -46-1 ) or other forms of selenium.

[0043] In one embodiment, the composition does not have any intentionally added Ti species.

[0044] In one embodiment, the composition has no intentionally added B species.

[0045] In one embodiment, the composition does not have any intentionally added Zn species.

[0046] In one embodiment, the composition does not contain any intentionally added Sr species.

[0047] In one embodiment, the composition does not have any intentionally added Sn species.

[0048] In one embodiment, the composition does not have any intentionally added Ce species.

[0049] In one embodiment, the composition has no intentionally added Cr species.

[0050] In one embodiment, the composition contains, by weight, BaO: 0-0.06%, preferably 0-0.05%. Optical properties are provided by other chemical species.

[0051] In one embodiment, the composition contains, by weight, 100 to 300 ppm total iron, expressed in the form of Fe2O3.

[0052] In a preferred embodiment, the composition contains, by weight, 100 to 250 ppm of total iron, expressed in the form of Fe2O3.

[0053] In one embodiment, the composition contains, by weight, a total iron content, expressed in the form of Fe2O3, of greater than 300 ppm to 900 ppm.

[0054] In a preferred embodiment, the composition contains, by weight, 300 to less than 700 ppm total iron, expressed in the form of Fe2O3.

[0055] In one embodiment, the composition is intended for home or cooking use.

[0056] In one embodiment, the composition has a luminance value L of total transmitted light according to CIE 1976. * is more than 94, preferably more than 95. Such a value corresponds to transparent glass, also known as white glass.

[0057] In one embodiment, the redox is 18 or greater.

[0058] In one embodiment, the redox is 20 or greater.

[0059] In one embodiment, the composition contains, by weight, SiO2: 69.0-75.0%, Na2O+K2O: 12.0-16.0%, CaO+MgO+BaO: 10.0-15.5%, Al2O3: 0.5-3.0%, and B2O3: 0-1.0%.

[0060] Generally, a mixture of raw materials is understood to be a glass raw material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] Other features and advantages of the present invention will become apparent from the following detailed description.

[0062] Glass refining is one of the most important steps in glass production. This process is described in various publications detailing the refining agents and their behavior during typical furnace operation:

[0063] Publication 1: Le Verre - Sciences et Technologie - James BARTON and Claude GUILLEMET.

[0064] Publication 2: Glass Science (Second edition) - Robert H. DOREMUS (Rensselaer Polytechnic Institute) - Wiley-Interscience publication John Wiley & Sons Inc.

[0065] Publication 3: Glass - Science and Technology - Volume 2 Processing I - Edited by D. R. UHLMANN and N. J. KREIDL.

[0066] Publication 4: Elaboration du verre (fusion et affinage) - Etude bibliographique - Symposium de l'Union Scientifique Continentale du verre (Belgium) - Madrid, 11 - 14 September 1973.

[0067] However, the above publications fail to elucidate measures to reduce sulfates. It is generally believed that the residual sulfate content in the glass is strongly related to the redox state of the produced glass. Thus, without redox modification, it is not possible to reduce the concentration of SO3 in the final glass. Moreover, such a reduction would be futile, since the SO3 content is a guarantee for the quality of the product, specifically for the refinability of the final glass.

[0068] Soda lime glass is refined by the addition of sulfates. Particular considerations are the effect on glass working temperature, glass working rate, refractory corrosion, fume exhaust and filtration system temperatures, filtration temperatures above the dew point of hydrochloric acid, the filtration quality of existing filtration equipment, and corrosion of steel moulds used in the production of glass products.

[0069] In glass products, platinum coatings are often used to avoid the phenomenon of concentration in the glass of various contaminants, which can lead to the formation of foreign glass. For example, in the field of tableware, such concentration is manifested in the dishwasher by the appearance of fine threads in the form of wigs. These threads are characteristic of local concentrations of zirconia, a compound present in the refractories used to build furnaces and feeders (i.e. the glass flow path towards the forming machine). Platinum, an element neutral to glass, is able to prevent such glass / refractory contacts, which are detrimental to the quality of the glass.

[0070] Platinum can also act as a protective coating for metals that tend to sublime at the temperatures used in glass and structural material processing (see WO2016135084).

[0071] Applicants have determined that by reducing the amount of sulfate remaining in the glass, platinum usage can be reduced. EXAMPLES

[0072] The applicants of the present application have conducted a number of production trials, testing several compositions, using the same raw materials and adjusting the amounts to arrive at the final desired composition.

[0073] Toxic ingredients such as arsenates and ingredients that may cause pollution such as nitrates were avoided. The addition of halogens was considered to promote refining while reducing sulfates. However, there are concerns about the incorporation of halogens into soda-lime glass. In other words, chlorine has a problem with its solubility in soda-lime glass, so a significant amount of it must be added to achieve any effect on refining.

[0074] When the redox is between 20 and 45, decolorization of the glass can be achieved by zinc selenite.

[0075] Tests over 15 days in the first industrial furnace showed that the daily production change with respect to the average was -17% to +18%. The ZrO2 content is 335-961 ppm. The CaO content is 9.03-11.36%. The MgO content is 1.13-1.51%. The K2O content is 0.04-0.36%. The SiO2 content is 71.48-72.74%. The Al2O3 content is 1.39-3.01%. The Na2O content is 13.03-14.37%. The CeO2 content is 827-1,007 ppm. The redox is 18-36 (average = 26). Luminance L * is 94.35-95.75 (average = 95.38). This glass is commercial grade and The refinement time is long without change. In this way, refinement is adequate. Specifically, the average overall refinement for the holding period is 1 cm of glass bubbles visible with a binocular magnifier (magnification = 20 times). 3 The number of bubbles per cm is less than 0.7 and more than 100 μm. 3 The daily production is stable.

[0076] Addition of Se, Co and Er was performed, and good results were obtained for decolorization of each addition. It is preferable to add these three elements, Se, Co and Er, in the form of oxides. The amount of zinc selenite can be 0.5 to 5 ppm. The amount of CoO can be 0.5 to 5 ppm. The amount of Er2O3 can be 50 to 200 ppm. The total amount of zinc selenite, CoO and Er2O3 can be 50 to 200 ppm.

[0077] Zn, Ba, B, Sr, Mo, As, Sn, Sb, Ti and F are not intentionally added.

[0078] Table 1 below contains glass composition data measured at the production output of a production test in an industrial furnace, which was conducted over a period of time sufficient to allow changes in the composition of the raw materials to be stably reflected in the composition of the produced glass. In addition, measurements No. 1 to 12 were spaced several hours apart for regular monitoring of production. The contents of CaO, K2O, SiO2, Al2O3, MgO, Na2O, CeO2, Er2O3, ZnSeO3 and CoO are derived from the raw materials charged. It was found that in this configuration, these species are unlikely to volatilize in the furnace. Their contents are well controlled within a range in which the composition of the charged raw materials remains constant over time.

[0079] The ZrO2 content depends on the operating conditions of the furnace and downstream flow channels, since the zirconia in the glass comes from the refractories that make up the furnace vessel and flow channels. Zirconia is not included in the raw materials. Its presence reflects wear of the furnace and flow channels. High zirconia content represents a shorter furnace life between two refractory changes and a higher glass tonnage cost. The zirconia content is highly sensitive to the temperature of the glass bath and to operational events, such as changes in the motion within the glass bath.

[0080] The total iron oxide content depends on the quality and consistency of the input raw materials. Therefore, this parameter is difficult to control. Redox depends on the oxidation degree of the glass and correlates with the color of the glass in the absence of colorants. If the redox is the same, the color of the glass can be changed by the coloring substances.

[0081] The SO3 content depends on the amount of sulfates added to the glass bath, the redox, the heating mode and the construction parameters of the furnace. The applicant has attempted to produce a soda-lime glass for domestic or cooking use that is transparent and has a low SO3 content. Unexpectedly, the daily production of the furnace is comparable to that of the furnace with a higher sulfate content without changing the furnace.

[0082] Generally, the composition can be measured according to the ASTM C169 standard.

[0083] The sulfate content is determined by X-ray fluorescence in accordance with DIN 51001. For greater accuracy, a method of acid dissolution with HF and then HNO3 followed by analysis with an ICP analyzer can also be used, which has been shown to reduce the variance to 35%.

[0084] [Table 1]

[0085] Tests on the second industrial furnace showed that the variation in daily production relative to the average was -5% to +10%. The ZrO2 content is 102-136 ppm. The CaO content is 10.83-11.23%. The MgO content is 1.38-1.42%. The K2O content is 0.03-0.04%. The SiO2 content is 72.60-72.77%. The Al2O3 content is 1.50-1.52%. The Na2O content is 13.31-13.36%. The CeO2 content is 337-362 ppm. The redox is 33-43 (average = 37). The glass is of commercial grade with a long refining period without change. Thus, the refining is adequate. Specifically, the average overall refinement for the holding period was 1 cm for glass bubbles visible through a binocular magnifier (magnification = 20x). 3 Per 0 (bouillon / cm 3 ) Daily production is extremely stable.

[0086] The preferred method is to add the three species Se, Co, and Er in the form of their oxides. The amount of zinc selenite can be 0.5-5 ppm. The amount of CoO can be 0.5-5 ppm. The amount of Er2O3 can be 50-200 ppm depending on the input raw materials. The total amount of zinc selenite, CoO and Er2O3 can be 50-200 ppm.

[0087] Zn, Ba, B, Sr, Mo, As, Sn, Sb, Ti and F are not intentionally added.

[0088] Table 2 below contains glass composition data measured at the production output of a production test in an industrial furnace, which was carried out over a period of time sufficient to ensure that changes in the composition of the raw materials were stably reflected in the composition of the produced glass. In addition, measurements No. 1 to 4 were separated by at least 24 hours to allow for regular monitoring of production. The contents of CaO, K2O, SiO2, Al2O3, MgO, Na2O, CeO2, Er2O3 and CoO are derived from the raw materials charged. It was found that in this configuration, these species are unlikely to volatilize in the furnace. Their contents are well controlled within the range in which the composition of the charged raw materials remains constant over time.

[0089] Zirconia is not included in the raw materials.

[0090] The total iron oxide content depends on the quality and consistency of the input raw materials.

[0091] The SO3 content depends on the amount of sulfates added to the glass bath, the redox, the heating mode and the construction parameters of the furnace. The applicant has attempted to produce soda-lime glass for domestic or cooking use that is transparent and has a low SO3 content. Unexpectedly, the daily production of the furnace is comparable to that of the furnace with a higher sulfate content without any change.

[0092] [Table 2]

Claims

1. 1. A colorless soda-lime glass composition comprising, by weight: Yes ２ :68~78%, Na ２ O:8~18%、 K ２ O: 0~10%, CaO: 7-12%, MgO: 0-10%, ZnO: 0-10%, BaO: 0-10%, Al ２ O ３ :0~3%、 B ２ O ３ :0~1%、 SrO: 0 to 1%, SO ３ Total sulfur content expressed in the form of: less than 0.078%; CeO ２ Total cerium content expressed in the form: 0.12% or less, and Fe ２ O ３ Total iron content expressed in the form: 50 to 1,200 ppm, Contains Mo species, As species, Sn species, and Sb species are not intentionally added, A composition having a redox of less than 45.

2. 10. The composition of claim 1, comprising, by weight: SO ３ Total sulfur content expressed in the form of: less than 0.074%; A composition comprising:

3. 3. The composition of claim 1 or 2, comprising, by weight: TiO ２ : 0 to 1%, and F: 0 to 0.3%, A composition comprising:

4. 10. The composition of claim 1, comprising, by weight: Na ２ O: More than 8% to less than 15% ZnO: 0 to 1%, BaO: 0 to 2%, Al ２ O ３ :0~2%、 CeO ２ Total cerium content expressed in the form: 0.1% or less, ZrO ２ : Less than 0.10%, and Er ２ O ３ : Less than 200 ppm, Contains A composition having a redox of less than 40.

5. 10. The composition of claim 1, comprising, by weight: K ２ O: 0 to 0.5%, and MgO: 1 to 2%, A composition comprising:

6. 10. The composition of claim 1, comprising, by weight: SiO ２ : 71.0 to 73.0%, and CaO: 9 to less than 12% A composition comprising:

7. 7. The composition of claim 6, comprising, by weight: CaO: 10.0-11.4%, A composition comprising:

8. 5. The composition of claim 4, comprising, by weight: Er ２ O ３ : Less than 150 ppm, A composition comprising:

9. 5. The composition of claim 4, comprising, by weight: Na ２ O:13.0~14.0%、 A composition comprising:

10. 2. The composition of claim 1, wherein Ti species, Ce species, B species, Zn species, Sr species, and Sn species are not intentionally added.

11. 5. The composition of claim 4, comprising, by weight: BaO: 0-0.06%, A composition comprising:

12. 10. The composition of claim 1, comprising, by weight: Fe ２ O ３ A composition comprising: 100 to 300 ppm of total iron expressed in the form of:

13. 10. The composition of claim 1, comprising, by weight: Fe ２ O ３ Total iron content expressed in the form of: more than 300 ppm to 900 ppm, A composition comprising:

14. 10. The composition of claim 1, intended for home or cooking use.

15. The composition according to claim 1, wherein the luminance value L of total transmitted light is determined in accordance with CIE 1976. ＊ is greater than 94.

16. 10. The composition of claim 1, comprising, by weight: SO ３ Total sulfur content expressed in the form: 0.0405 to 0.0731%, A composition comprising:

17. The composition according to claim 4, wherein the redox is greater than 30 and less than 40.

18. 10. The composition of claim 1, at least one of Se, Co, and Er; A composition comprising:

19. 10. The composition of claim 1, ZrO ２ The content is 335 to 961 ppm, The CaO content is 9.03 to 11.36%, The content of MgO is 1.13 to 1.51%, K ２ The content of O is 0.04 to 0.36%, SiO ２ The content is 71.48 to 72.74%, Al ２ O ３ The content is 1.39 to 2%, Na ２ The content of O is 13.03 to 14.37%, CeO ２ The content is 827 to 1,000 ppm, Redox is 18 to 36, Brightness L ＊ is 94.35 to 95.

75.

20. 10. The composition of claim 1, ZrO ２ The content is 102 to 136 ppm, The CaO content is 10.83 to 11.23%, The content of MgO is 1.38 to 1.42%, K ２ The content of O is 0.03 to 0.04%, SiO ２ The content is 72.60 to 72.77%, Al ２ O ３ The content of is 1.50 to 1.52%, Na ２ The content of O is 13.31 to 13.36%, CeO ２ The content is 337 to 362 ppm, Redox is less than 33 to 40, Brightness L ＊ is 95.36 to 95.

58.

21. The composition of claim 1, wherein the redox is 18 or greater.

22. 22. The composition of claim 21, wherein the redox is 20 or greater.

23. 10. The composition of claim 1, comprising, by weight: Yes ２ :69.0~75.0%, Na ２ 2000 ２ O:12.0~16.0%、 CaO + MgO + BaO: 10.0 to 15.5%, Al ２ O ３ : 0.5 to 3.0%, and B ２ O ３ :0~1.0%、 A composition comprising: