Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Patent
1996-06-27
1998-11-17
Group, Karl
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
501 71, 501 57, C03C 3087
Patent
active
058376291
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition of silica-soda-calcium glass apt for the making of glass windows notably susceptible of being used in the automobile industry or in the architectural field.
2. Description of the Background
The glass windows used in these fields present characteristics of transmission very much different in regard to effects much sought after.
One of the effects actively sought is the greatest reduction possible of the energetic transmission of glass windows, i.e., its transmission in the visible be weak or raised. This effect is obtained by increasing the absorption of infrared radiations of glass of which it is constituted. The study of this effect will often go in pair with the study of the other effects as a weak transmission of ultraviolet radiations and a particular coloring.
If the constituents susceptible to obtain such effects are generally known, the study of a combination of particular characteristics, for example, the luminous transmission factors and the energetic transmission presenting a predetermined relation, associated to a domain of a well defined wavelength and at a specific gravity, is difficult.
Therefore, to maintain a luminous transmission raised in the visible part of the spectrum by all absorbing the most possible, i.e., the rest of the solar energy, it is known to introduce iron in the composition of glass.
At the same time, it is present in the glass in the form of ferric oxide (Fe.sub.2 O.sub.3) and ferrous oxide (FeO).
The presence of Fe.sub.2 O.sub.3 permits the absorption of UV radiations and those which possess short wavelengths in the visible part of the spectrum. On the contrary, the presence of FeO permits the absorption close to IR radiations and those corresponding to long wavelengths in the visible region.
If the increase of iron content under two of its oxide forms accentuates the absorption of radiations at two ends of the visible spectrum, this effect is obtained at the expense of the luminous transmission.
Till this day, different solutions were proposed to use in a better way, the aptitude of iron oxides to absorb the radiations by conserving nevertheless the biggest luminous transmission possible. The preferred solutions to absorption of radiation belonging closely to infrared may consist in modifying in an important manner, the glass composition or else to manufacture much reduced glasses whose composition is relatively classic.
The first category of solutions may be illustrated by requesting for the patent JP-60-215546, the second category by the EP-297404.
According to the Japanese patent, the glasses which present the characteristics of transmission and of absorption much sought after, contain at least 4% in weight of BaO. This oxide, introduced in sufficient quantity has the effect of shifting the absorption band due to FeO close to infrared towards the longer wavelengths. This effect may be accentuated by the introduction of K.sub.2 O in these glasses.
The introduction of BaO according to the contents relatively raised in these glasses has in the meantime effects which are negative: the non-negligible increase of cost of the composition, the diminution of hydrolytic resistance of the glass. A strong percentage of BaO can accentuate the phenomenon of devitrification and render the obtaining of homogenous glass more difficult.
The glasses described in the European patent mentioned above are traditional silica-soda-calcium glasses whose total iron content, expressed under the form of Fe.sub.2 O.sub.3 is understood between 0.45 and 0.65%. These glasses are made in the conditions such that less than 35% and preferably at least 50% of total iron is in the form of FeO. The increase of the FeO content thus obtained is to accentuate the absorption of glasses in the infrared and to reduce the T.sub.E factor. However, when a glass is made in the presence of sulphur in the reduced conditions, this last one takes on an amber color due to the formation of chromophores which results from
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Combes Jean-Marie
Mazon-Ramos Pedro Pablo
Group Karl
Saint-Gobain Vitrage
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