SODA-LIME-SILICA GLASS COMPOSITION

Abstract

A soda-lime-silica glass composition, includes the optical absorbers below in contents varying within the following weight limits: Fe.sub.2O.sub.3 (total iron) 100 to 1600 ppm, Cr.sub.2O.sub.3 20 to 100 ppm, S.sup.2 10 to 50 ppm. The composition has a redox, defined by the molar ratio between the ferrous iron and the total iron, of less than 0.7.

Claims

1. A soda-lime-silica glass composition, comprising the optical absorbers below in contents varying within the following weight limits: TABLE-US-00006 Fe.sub.2O.sub.3 (total iron) 100 to 1600 ppm, Cr.sub.2O.sub.3 20 to 100 ppm, S.sup.2 10 to 50 ppm, the composition having a redox, defined by the molar ratio between the ferrous iron and the total iron, of less than 0.7.

2. The composition as claimed in claim 1, such that the content of iron oxide (Fe.sub.2O.sub.3) is between 500 and 1500 ppm.

3. The composition as claimed in claim 1, such that the content of chromium oxide (Cr.sub.2O.sub.3) is indeed between 20 and 80 ppm.

4. The composition as claimed in claim 1, such that the content of sulfide ions (S.sup.2) is between 20 and 40 ppm.

5. The composition as claimed in claim 1, such that the redox is less than 0.68.

6. The composition as claimed in claim 1, such that the glass has, for a thickness of 5 mm, a dominant wavelength between 574 and 578 nm, a purity of from 45% to 70%, and a light transmission factor of greater than 50%.

7. The composition as claimed in claim 1, such that the glass has, for a thickness of 5 mm, a screening power of greater than or equal to 80%.

8. A hollow glass article formed by molding, pressing or blowing, such that its chemical composition are defined by claim 1.

9. The composition as claimed in claim 2, such that the content of iron oxide (Fe.sub.2O.sub.3) is between 800 and 1400 ppm.

10. The composition as claimed in claim 5, such that the redox is less than 0.67.

11. The composition as claimed in claim 10, such that the redox is less than 0.66.

12. A hollow glass article formed by molding, pressing or blowing, such that its optical properties are defined by claim 6.

13. A hollow glass article formed by molding, pressing or blowing, such that its optical properties are defined by claim 7.

Description

[0032] The present invention will be better understood on reading the detailed description below of nonlimiting exemplary embodiments below.

[0033] The following glass composition according to the invention was prepared from a batch mix comprising 25% by weight of half-white cullet, the contents being expressed as weight percentages:

TABLE-US-00004 SiO.sub.2 73.6% Na.sub.2O 12.4% K.sub.2O 0.8% CaO 10.3% MgO 1.1% Al.sub.2O.sub.3 0.35% Fe.sub.2O.sub.3 (total) 1430 ppm Cr.sub.2O.sub.3 30 ppm S.sup.2 36 ppm Redox 0.65

[0034] The weight contents of iron oxides and chromium oxides and also of sulfide ions are measured by chemical analysis.

[0035] The redox is defined as being the molar ratio of FeO to total iron expressed in the form of Fe.sub.2O.sub.3. The total iron content is measured by x-ray fluorescence and the FeO content is measured by wet chemistry.

[0036] The values of the following optical properties were calculated for a glass thickness of 5 mm from experimental spectra: [0037] the light transmission factor, calculated between 380 and 780 mm, and also the dominant wavelength and the purity. These calculations are made using the illuminant C as defined by the ISO/CIE 10526 standard and the C.I.E. 1931 colorimetric reference observer, as defined by the ISO/CIE 10527 standard. [0038] the screening power defined as being equal to the value of 100% minus the arithmetic mean of the transmission between 330 and 450 nm.

[0039] The results are presented below:

TABLE-US-00005 Dominant wavelength 576 nm Purity 63% Light transmission factor 56%