COLOURLESS SODA-LIME GLASS COMPOSITION

Abstract

A colorless soda-lime glass composition comprising by weight from 68 to 78% SiO.sub.2, from 8 to 18% Na.sub.2O, from 0 to 10% K.sub.2O, from 7 to 12% CaO, from 0 to 10% MgO, from 0 to 10% ZnO, from 0 to 10% BaO, from 0 to 3% Al.sub.2O.sub.3, from 0 to 1% B.sub.2O.sub.3, from 0 to 1% SrO, less than 0.078% total sulfur expressed in the form of SO.sub.3, at most 0.12% total cerium expressed in the form of CeO.sub.2, from 50 to 1200 ppm total iron expressed in the form of Fe.sub.2O.sub.3, without the intentional addition of Mo, As, Sn and Sb species, and with a redox lower than 45.

Claims

1. A colourless soda-lime glass composition, comprising, by weight, from 68 to 78% SiO.sub.2, from 8 to 18% Na.sub.2O, from 0 to 10% K.sub.2O, from 7 to 12% CaO, from 0 to 10% MgO, from 0 to 10% ZnO, from 0 to 10% BaO, from 0 to 3% Al.sub.2O.sub.3, from 0 to 1% B.sub.2O.sub.3, from 0 to 1% SrO, less than 0.078% total sulphur expressed in the form of SO.sub.3, at most 0.12% total cerium expressed in the form of CeO.sub.2, from 50 to 1,200 ppm total iron expressed in the form of Fe2O3, without intentional addition of the Mo, As, Sn and Sb species, and with a redox lower than 45.

2. The composition according to claim 1, comprising, by weight, less than 0.074% total sulphur expressed in the form of SO.sub.3.

3. The composition according to claim 1, comprising, by weight, from 0 to 1% TiO.sub.2 and from 0 to 0.3% F.

4. The composition according to claim 1, comprising, by weight, from more than 8 to less than 15% Na.sub.2O, from 0 to 1% ZnO, from 0 to 2%, preferably less than 0.10%, BaO, from 0 to 2%, preferably from 1.0 to 1.90%, Al.sub.2O.sub.3, at most 0.1% total cerium expressed in the form of CeO.sub.2, less than 0.10%, preferably less than 0.05%, ZrO.sub.2, less than 200 ppm Er.sub.2O.sub.3, and with a redox lower than 40.

5. The composition according to claim 1, comprising, by weight, from 0 to 0.5%, preferably from 0 to 0.2%, K.sub.2O and from 1 to 2% MgO.

6. The composition according to claim 1, comprising, by weight, from 71.0 to 73.0% SiO.sub.2 and from 9 to less than 12% CaO.

7. The composition according to claim 1, comprising, by weight, from 10.0 to 11.4% CaO.

8. The composition according to claim 1, comprising, by weight, less than 150 ppm Er.sub.2O.sub.3.

9. The composition according to claim 1, comprising, by weight, from 13.0 to 14.0% Na.sub.2O.

10. The composition according to claim 1, without intentional addition of the Ti, Ce, B, Zn, Sr and Sn species.

11. The composition according to claim 1, comprising, by weight, from 0 to 0.06%, preferably from 0 to 0.05%, BaO.

12. The composition according to claim 1, comprising, by weight, from 100 to 300 ppm total iron expressed in the form of Fe2O3, preferably from 100 to 250 ppm.

13. The composition according to claim 1, comprising, by weight, more than 300 to 900 ppm total iron expressed in the form of Fe.sub.2O.sub.3, preferably less than 700 ppm.

14. (canceled)

15. The composition according to claim 1, comprising a luminance value L* according to CIE1976 in total transmission higher than 94, preferably 95.

16. The composition according to claim 1, comprising, by weight, from 0.0405 to 0.0731% total sulphur expressed in the form of SO.sub.3.

17. The composition according to claim 1, wherein the redox is higher than 30 and lower than 40.

18. The composition according to claim 1, comprising at least one from among Se, Co and Er, preferably the total amount of zinc selenite, CoO and Er.sub.2O.sub.3 is comprised between 50 and 200 ppm.

19. The composition according to claim 1, wherein the ZrO.sub.2 content is comprised between 335 and 961 ppm, the CaO content is comprised between 9.03 and 11.36%, the MgO content is comprised between 1.13 and 1.51%, the K.sub.2O content is comprised between 0.04 and 0.36%, the SiO.sub.2 content is comprised between 71.48 and 72.74%, the Al.sub.2O.sub.3 content is comprised between 1.39 and 2%, the Na.sub.2O content is comprised between 13.03 and 14.37%, the CeO.sub.2 content is comprised between 827 and 1,000 ppm, the redox is comprised between 18 and 36, the luminance L* is comprised between 94.35 and 95.75.

20. The composition according to claim 1, wherein the ZrO.sub.2 content is comprised between 102 and 136 ppm, the CaO content is comprised between 10.83 and 11.23%, the MgO content is comprised between 1.38 and 1.42%, the K.sub.2O content is comprised between 0.03 and 0.04%, the SiO.sub.2 content is comprised between 72.60 and 72.77%, the Al.sub.2O.sub.3 content is comprised between 1.50 and 1.52%, the Na.sub.2O content is comprised between 13.31 and 13.36%, the CeO.sub.2 content is comprised between 337 and 362 ppm, the redox is comprised between 33 and less than 40, the luminance L* is comprised between 95.36 and 95.58.

21. (canceled)

22. (canceled)

23. The composition according to claim 1, comprising, by weight, from 69.0 to 75.0% SiO.sub.2, from 12.0 to 16.0% Na.sub.2O+K.sub.2O, from 10.0 to 15.5% CaO+MgO+BaO, from 0.5 to 3.0% Al.sub.2O.sub.3, and from 0 to 1.0% B.sub.2O.sub.3.

Description

[0031] In one embodiment, the composition comprises, by weight, less total sulphur expressed in the form of SO.sub.3 than the maximum allowed by the redox and the composition of the glass.

[0032] In one embodiment, the composition comprises, by weight, less than 0.074% total sulphur expressed in the form of SO.sub.3. The condensation is reduced. The reactivity of the glass with the components of the production line is reduced.

[0033] In one embodiment, the composition comprises, by weight, from 0 to 1% TiO.sub.2.

[0034] In one embodiment, the composition comprises, by weight, from 0 to 0.3% F. Beyond 0.3%, the corrosion of the moulds is increased.

[0035] In one embodiment, the composition comprises, by weight, from 71.0 to 73.0% SiO.sub.2, from more than 8 to less than 15% Na.sub.2O, from 0 to 0.5% K.sub.2O, from 9 to less than 12% CaO, from 1 to 2% MgO, from 0 to 1% ZnO, from 0 to 2% BaO, from 0 to 2% Al.sub.2O.sub.3, at most 0, 1% total cerium expressed in the form of CeO.sub.2, less than 0.10% ZrO2, less than 200 ppm Er.sub.2O.sub.3, and with a redox lower than 40.

[0036] In a preferred embodiment, the composition comprises, by weight, 13.0 to 14.0% Na.sub.2O.

[0037] In a preferred embodiment, the composition comprises, by weight, from 0 to 0.2% K.sub.2O.

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

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

[0040] In a preferred embodiment, the composition comprises, by weight, from 1.0 to 1.90% Al.sub.2O.sub.3. Below 1% Al.sub.2O.sub.3, the finished glass has a lower chemical resistance.

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

[0042] In a preferred embodiment, the composition comprises, by weight, less than 150 ppm Er.sub.2O.sub.3. The discolouration could be obtained by Selenium, for example in the form of zinc selenite ZnSeO.sub.3 CAS 13597.sub.-46-1.

[0043] In one embodiment, the composition does not involve an intentional addition of any Ti species.

[0044] In one embodiment, the composition does not involve an intentional addition of any B species.

[0045] In one embodiment, the composition does not involve an intentional addition of any Zn species.

[0046] In one embodiment, the composition does not involve an intentional addition of any Sr species.

[0047] In one embodiment, the composition does not involve an intentional addition of any Sn species.

[0048] In one embodiment, the composition does not involve an intentional addition of any Ce species.

[0049] In one embodiment, the composition does not involve an intentional addition of any Cr species.

[0050] In one embodiment, the composition comprises, by weight, from 0 to 0.06%, preferably from 0 to 0.05%, BaO. The optical properties are obtained by other chemical species.

[0051] In one embodiment, the composition comprises, by weight, from 100 to 300 ppm total iron expressed in the form of Fe.sub.2O.sub.3.

[0052] In a preferred embodiment, the composition comprises, by weight, from 100 to 250 ppm total iron expressed in the form of Fe.sub.2O.sub.3.

[0053] In one embodiment, the composition comprises, by weight, more than 300 to 900 ppm total iron expressed in the form of Fe.sub.2O.sub.3.

[0054] In a preferred embodiment, the composition comprises, by weight, from 300 to less than 700 ppm total iron expressed in the form of Fe.sub.2O.sub.3.

[0055] In one embodiment, the composition is intended for household or culinary use.

[0056] In one embodiment, the composition comprises a lightness value L* according to CIE1976 in total transmission higher than 94, preferably higher than 95. These values correspond to a transparent glass also so-called white glass.

[0057] In one embodiment, the redox is at least 18.

[0058] In one embodiment, the redox is at least 20.

[0059] In one embodiment, the composition comprises, by weight, from 69.0 to 75.0% SiO.sub.2, from 12.0 to 16.0% Na.sub.2O+K.sub.2O, from 10.0 to 15.5% CaO+MgO+BaO, from 0.5 to 3.0% Al.sub.2O.sub.3, and from 0 to 1.0% B.sub.2O.sub.3.

[0060] In general, the mixture of raw materials should be understood as glass raw materials.

[0061] Other features and advantages of the invention will become apparent upon examining the detailed description hereinafter.

[0062] The refining of the glass is a very important step in glass production. This step is described in various structures, the refining agents and their behaviour being detailed in the context of a furnace conventional operation. [0063] 1. Le VerreSciences et TechnologieJames BARTON and Claude GUILLEMET. [0064] 2. Glass Science (Second edition)Robert H. DOREMUS (Rensselaer Polytechnic Institute)Wiley-Interscience publication John Wiley & Sons Inc. [0065] 3. GlassScience and TechnologyVolume 2 Processing IEdited by D. R. UHLMANN and N. J. KREIDL. [0066] 4. Elaboration du verre (fusion et affinage)Etude bibliographiqueSymposium de l'Union Scientifique Continentale du verre (Belgium)Madrid, 11-14 Sep. 1973.

[0067] On the other hand, these structures do not allow revealing approaches for reducing sulphates. It is generally accepted that the residual sulphate content in the glass is strongly related to the redox state of the produced glass. Thus, without modification of the Redox, there cannot be any reduction in the concentration of SO.sub.3 in the finished glass; and such a reduction would be vain because the SO.sub.3 content is a guarantee for the quality of the produced items, in particular the refining of the final glass.

[0068] The soda-lime glass is refined by adding sulphates. A particular attention is given to the following points: glass working temperature, glass working level, corrosion of the refractories, temperatures in the fume extraction circuit and the filtration system, filtration temperatures higher than the dew point of hydrochloric acid, quality of the filtration on the existing filtration equipment, potential impact on the corrosion of the steel moulds used for the production of glassware items.

[0069] Platinum coatings are often used in glassware to avoid the phenomena of enrichment of the glass by various pollutions, which are at the origin of creation of heterogeneous glass. For example, in the field of table arts, this enrichment could be revealed in the dishwasher by apparition of fine yarns, in the form of a wig. These yarns are specific to a localised enrichment of zirconia, a chemical compound present in the refractories used for the construction of the furnaces and the feeders, i.e. the flow channels of glass towards the shaping machines. Platinum, which is a neutral element with respect to the glass, allows avoiding this glass/refractory interface detrimental to the quality of the glass.

[0070] The platinum may also serve as a protective coating for metals subject to sublimation at the temperatures of use in the glass or structural material process, cf. WO2016135084.

[0071] The Applicant estimates that lowering the residual sulphate in the glass could allow reducing the use of platinum.

[0072] The Applicant has conducted several production tests by testing several compositions. These tests have been conducted with the same raw materials, the amounts of which have been adjusted to obtain the desired final composition.

[0073] The use of toxic components, like arsenate, or with the risk of pollution, like nitrate, has been avoided. In order to promote refining despite the reduction of sulphates, an addition of halogens has been considered. Yet, their presence in a soda-lime glass has risks. Thus, the chlorine has a problem of solubility in soda-lime glass thereby a substantial dose to be considered in order to obtain an effect on refining.

[0074] The discolouration of the glass can be performed with zinc selenite for a redox from 20 to 45.

[0075] In a test of a first industrial furnace over more than 15 days, the daily production has varied from 17% to +18% relative to the average. The ZrO2 content is comprised between 335 and 961 ppm. The CaO content is comprised between 9.03 and 11.36%. The MgO content is comprised between 1.13 and 1.51%. The K.sub.2O content is comprised between 0.04 and 0.36%. The SiO.sub.2 content is comprised between 71.48 and 72.74%. The Al.sub.2O.sub.3 content is comprised between 1.39 and 3.01%. The Na.sub.2O content is comprised between 13.03 and 14.37%. The CeO.sub.2 content is comprised between 827 and 1,007 ppm. The redox is comprised between 18 and 36 with an average equal to 26. The luminance L* is comprised between 94.35 and 95.75, with an average equal to 95.38. The glass is of commercial grade with a significant refining duration without change. This results in a correct refining. In particular, the average total refining over the retained period is lower than 0.7 glass broth/cm.sup.3 visible to the binocular magnifier at 20 magnification and lower than 0.55 broth at more than 100 m per cm.sup.3. The daily production is stable.

[0076] Se, Co, Er additions have been performed with a positive effect on individual addition discolouration. The preferred mode is an addition of the three species Se, Co and Er in the form of an oxide. The amount of zinc selenite may be comprised between 0.5 and 5 ppm. The amount of CoO may be comprised between 0.5 and 5 ppm. The amount of Er.sub.2O.sub.3 may be comprised between 50 and 200 ppm. The total amount of zinc selenite, CoO and Er.sub.2O.sub.3, may be comprised between 50 and 200 ppm.

[0077] There is no intentional introduction of the Zn, Ba, B, Sr, Mo, As, Sn, Sb, Ti and F species.

[0078] Table 1 below contains glass composition data measured at the production output during production tests on an industrial furnace conducted over a sufficient period of time for a change in the composition of the raw materials to be reflected in a stable manner in the composition of the produced glass. Moreover, the measurements No. 1 to 12 are spaced apart by several hours for a regular monitoring of the production. The CaO, K.sub.2O, SiO.sub.2, Al.sub.2O.sub.3, MgO, Na.sub.2O, CeO.sub.2, Er.sub.2O.sub.3, ZnSeO.sub.3 and CoO contents originate from the introduced raw materials. In this configuration, these species have proved to be not very subject to evaporation in the furnace. Their contents are well controlled to the extent that the composition of the introduced raw materials is constant over time.

[0079] The ZrO2 content depends on the operating conditions of the furnace and of the channels downstream as zirconia in the glass originates from the refractories forming the vessel of the furnace and the channels. The zirconia is absent from the raw materials. The presence of zirconia reflects the wear of the furnace and of the channels. A high zirconia content indicates a short service life of the furnace between two replacements of refractories and a high cost price of the produced glass tonne. The zirconia content is in particular sensitive to the temperature of the glass bath and to the operating incidents, for example a modification of the movements within the glass bath.

[0080] The iron oxide total content depends on the quality and the consistency of the introduced raw materials. Hence, this parameter is difficult to control. The redox depends on the degree of oxidation of the glass and is correlated with the colour of the glass in the absence of colourants. At an identical redox, the colour of the glass may be modified by colouring materials.

[0081] The SO.sub.3 content depends on the amount of sulphates introduced into the glass bath, the redox, the heating mode and constructive parameters of the furnace. The Applicant has sought to produce a soda-lime glass for household or culinary use that is transparent and has a low SO.sub.3 content. The daily production of the furnace is equal or close to that of the same furnace with a higher sulphate content, which was not expected.

[0082] In general, the composition measurements may be performed according to the standard ASTM C169.

[0083] The measurement of the sulphates content is performed by X-ray fluorescence according to DIN 51001. For a higher accuracy, a method can be performed by HF and then HNO.sub.3 acid digestion, followed by an analysis using an ICP spectrometer which has shown a reduced dispersion of 35%.

TABLE-US-00001 TABLE 1 ZrO2 CaO K2O SO3 SiO2 Al2O3 MgO Na2O CeO2 Er2O3 FeO Fe2O3 Fe tot redox Se CoO Date PPM % % PPM % % % % PPM PPM PPM PPM PPM % PPM PPM L* 1 776 9.4 0.36 423 71.5 3.01 1.13 13.0 998 173 38 206 248 18.4 1.55 0.87 95.61 2 366 9.0 0.23 421 72.4 2.36 1.19 13.4 1,007 208 40 175 219 22.9 2.40 0.90 95.16 3 829 11.4 0.08 429 72.1 1.66 1.46 13.4 938 219 44 153 202 28.8 2.08 0.96 95.15 4 644 10.0 0.07 639 72.7 1.62 1.34 13.6 981 164 33 165 193 21.2 1.94 0.84 95.48 5 709 10.2 0.07 633 72.6 1.64 1.36 13.6 967 181 35 155 194 22.6 1.85 1.14 94.35 6 890 11.1 0.11 405 72.1 1.76 1.44 13.3 950 216 41 160 206 25.6 1.99 0.95 95.25 7 872 10.7 0.05 707 72.4 1.54 1.46 13.6 925 89 41 160 206 25.6 0.91 0.76 95.75 8 784 10.9 0.05 699 72.3 1.54 1.51 13.6 926 94 40 162 206 24.7 0.75 0.81 95.71 9 961 10.9 0.05 675 72.3 1.56 1.49 13.6 921 96 50 154 209 32.5 0.89 0.89 95.50 10 383 10.2 0.04 726 72.4 1.40 1.45 14.4 835 82 51 173 230 29.5 0.90 0.90 95.48 11 335 10.2 0.04 731 72.3 1.39 1.45 14.3 827 86 58 162 226 35.8 0.83 1.08 95.42 12 938 10.9 0.05 691 72.2 1.53 1.51 13.7 894 85 50 178 233 28.1 0.65 0.95 95.72 Min 335 9.0 0.04 421 71.5 1.39 1.13 13.0 827 82 53 153 193 18.4 0.65 0.84 94.35 Max 961 11.4 0.36 731 72.7 3.01 1.51 14.4 1,007 219 58 206 248 35.8 2.40 1.14 95.72

[0084] In a test of a second industrial furnace, the daily production has varied from 5% to +10% relative to the average. The ZrO.sub.2 content is comprised between 102 and 136 ppm. The CaO content is comprised between 10.83 and 11.23%. The MgO content is comprised between 1.38 and 1.42%. The K.sub.2O content is comprised between 0.03 and 0.04%. The SiO.sub.2 content is comprised between 72.60 and 72.77%. The Al.sub.2O.sub.3 content is comprised between 1.50 and 1.52%. The Nao content is comprised between 13.31 and 13.36%. The CeO.sub.2 content is comprised between 337 and 362 ppm. The redox is comprised between 33 and 43 with an average equal to 37. The glass is of commercial grade with a significant refining duration without change. This results in a correct refining. In particular, the average total refining over the retained period amounts to 0 glass broth/cm.sup.3 visible to the binocular magnifier at 20 magnification. The daily production is very stable.

[0085] Se, Co, Er additions have been performed with a positive effect on individual addition discolouration. The preferred mode is an addition of the three species Se, Co and Er in the form of an oxide. The amount of zinc selenite may be comprised between 0.5 and 5 ppm. The amount of CoO may be comprised between 0.5 and 5 ppm. According to the introduced raw materials, the amount of Er.sub.2O.sub.3 may be comprised between 50 and 200 ppm. The total amount of zinc selenite, CoO and Er.sub.2O.sub.3, may be comprised between 50 and 200 ppm.

[0086] There is no intentional introduction of the Zn, Ba, B, Sr, Mo, As, Sn, Sb, Ti and F species.

[0087] Table 2 below contains glass composition data measured at the production output during production tests on an industrial furnace conducted for a sufficient period of time for a change in the composition of the raw materials to be reflected in a stable manner in the composition of the produced glass. Moreover, the measurements No. 1 to 4 are spaced apart by at least 24 hours for a regular monitoring of the production. The CaO, K.sub.2O, SiO.sub.2, Al.sub.2O.sub.3, MgO, Na.sub.2O, CeO.sub.2, Er.sub.2O.sub.3 and CoO contents originate from the introduced raw materials. In this configuration, these species have proved to be not very subject to evaporation in the furnace. Their contents are well controlled to the extent that the composition of the introduced raw materials is constant over time.

[0088] Zirconia is absent from the raw materials.

[0089] The total content of iron oxides depends on the quality and on the consistency of the introduced raw materials.

[0090] The SO.sub.3 content depends on the amount of sulphates introduced into the glass bath, the redox, the heating mode and the constructive parameters of the furnace. The Applicant has sought to produce a soda-lime glass for household or culinary use that is transparent and has a low SO.sub.3 content. The daily production of the furnace is equal or close to that of the same furnace with a higher sulphate content, which was not expected.

TABLE-US-00002 TABLE 2 ZrO2 CaO K2O SO3 SiO2 Al2O3 MgO Na2O CeO2 FeO Fe2O3 Fe tot redox Se CoO Date PPM % % PPM % % % % PPM PPM PPM PPM 33.4 PPM PPM L* 1 102 10.98 0.03 0.07 72.77 1.52 1.42 13.33 337 50 150 205.0 34.4 0.98 0.83 95.57 2 107 11.23 0.03 0.07 72.60 1.51 1.41 13.32 344 51 148 204.0 36.2 0.82 0.83 95.58 3 133 11.12 0.03 0.07 72.61 1.52 1.41 13.36 362 56 138 200.0 43.2 0.99 0.91 95.58 4 136 10.83 0.04 0.07 72.69 1.50 1.38 13.31 340 69 159 236.0 43.2 0.89 1.16 95.36 Min 136 11.23 0.04 0.07 72.77 1.52 1.42 13.36 362 69 159 236.0 33.4 0.99 1.16 95.58 Max 102 10.83 0.03 0.07 72.60 1.50 1.38 13.31 337 50 138 200.0 33.4 0.82 0.83 95.36