MXPA98002173A

MXPA98002173A - Low transmittance glass, neu

Info

Publication number: MXPA98002173A
Application number: MXPA/A/1998/002173A
Authority: MX
Inventors: L Higby Paige; V Goodwin Kevin
Original assignee: Libbeyowensford Co
Priority date: 1995-09-21
Filing date: 1998-03-19
Publication date: 1998-11-12

Abstract

A silicon-lime-soda glass with neutral, or low transmittance, generally green gray (no more than 50 percent brightness transmittance), which has a reduced solar energy transmittance and a reduced ultra violet radiation transmittance when provides with the following coloring constituents in percentages by weight: Fe203 (total iron) 1.3 - 2, NiO 0.01 - 0.05, CoO 0.02 - 0.04, Se 0.0002 - 0.003, TiO2 0.09 - 3. The glass has a ferrous value in an average of 18 up

Description

GLASS OF TRANSMITANCA BAJA, NEUTRA FIELD OF THE INVENTION The present invention relates to a dark colored, neutral glass having a low visible light transmittance, particularly a low ultraviolet radiation transmittance, and a low total solar energy transmittance. Although it does not have a limit of use, the glass presents a combination of properties that makes it highly desirable for use in crystals that allow privacy as for example in the later portions of vehicles such as vans. These properties include a low transmittance of visible light to reduce the visibility of vehicle contents, low transmittance for sunlight and infrared rays, in order to reduce the heat that occurs inside when closed, low radiation transmittance ultraviolet to protect the fabric and other components inside the degradation, preferably with a neutral greenish-gray color for the consideration of the coordination with a wide variety of exterior colors and the interior finishes of the vehicles and a composition compatible with the methods production of flat glass, for example the commercial floating glass processes. BACKGROUND OF THE INVENTION Glasses with good infrared absorption are usually produced by reducing the iron present in the glass in the ferrous state or by adding copper. These materials give the glass a blue color. The materials added to achieve a good absorption of ultraviolet radiation are Fe3 +, Ce, Ti or V. The amounts added to cause the desired level of ultraviolet absorption are such that they tend to color the glass yellow. The combination in the same glass of a good UV absorption as well as IR absorption gives the glasses the colors either green or blue. The proposals have been made to produce a glass for vehicles with a good protection against UV and IR radiation in gray or bronze, but the proposed glasses tend to have a yellowish green tone. Glasses to absorb the heat of the prior art that are neutral and of a blue, green, gray or bronze tint tend to have a considerable transmittance of sunlight higher than that desired in glasses for privacy. For example, the new issuance of U.S. Patent No. 25,312 is directed to a gray glass composition containing 0.2 to 1 percent Fe203, 0.003 to 0.05 percent NiO, 0.003 to 0.02 percent CoO and 0.003 up to 0.02 percent Se and that it has a visible transmittance of between 35 and 45 percent in a thickness of 0.25 of an inch. The typical dark gray glass, of the prior art, has the following composition: 72.9% SiO2, 13.7% Na20, 0.03% K20, 8.95% CaO, 3.9% MgO, .10% A1203, .27% S03, .06% Fe203, .015% CoO and .95% NiO. The solar energy absorption of this type of glass is not as low as would be desired for the purposes of the present invention. More recently, gray glass has been proposed, free of nickel, which absorb heat, for use in low transmittance glasses. Examples of these glasses can be found in U.S. Patent Nos. 4,104,076 and 5,023,210. However, these two patents that include chromic oxide as a dyeing agent, may require the use of melting apparatus / operations other than melting furnaces of the conventional fire tank type to provide the reduction conditions during the melting necessary for produce the desired glasses, and have dye concentrations of iron oxide, cobalt oxide and selenium which will not produce the particular combination of the properties desired herein. SUMMARY OF THE INVENTION We have identified a requirement for excellent neutral privacy glasses so that, in the CIELAB system, they have a color coordinate in a range: a * of -5 ± 5, preferably -4 ± 3, more desirably -4; b * of 10 ± 20, preferably O ± IO, more desirable + 4 ± 1; and L * of 50 + 10, preferably 50 ± 5, more desirable 48 ± 2, in visible light transmittance not greater than 50%. More particularly, at a nominal reference thickness of 4 mm, the glass of the present invention exhibits a visible light transmittance (CIE Illuminant A) of not more than 50%, preferably not greater than 25% and more desirably not greater than 20%. %; the total transmittance of solar energy of at least 15 percent of points below the visible light transmittance when the transmittance of visible light is in a range of 40 to 50 percent, and the total transmittance of total solar energy below 25 percent when the transmittance of visible light is below 40 percent, and in any case it does not mark the transmittance of visible light; and the transmittance of the ultraviolet radiation is not greater than 25%, preferably not greater than 18%, and more preferably not greater than 15% 1. Generally, these greenish, neutral gray glasses, which have a surplus coefficient not greater than .53 and preferably not greater than .46, are produced with a composition based on a float glass of soda-lime-silicon, normal, to the which is added iron oxide, cobalt oxide, nickel oxide, titanium oxide and selected in certain critical proportions. 1 The values of the transmittance of the radiation that is presented are based on the following wavelength ranges: Ultraviolet 300-400 nanometers Visible 380-780 nanometers Solar total 300-2130 nanometers As is common in the glass industry, the total iron content in the glass or batch composition will be referred to herein as the "total iron expressed as Fe203". However, when a batch of glass is melted, a part of this total amount of iron is reduced to FeO, while the remainder remains Fe203. The balance between the ferrous and ferric oxides in the fusion is the result of the oxidation-reduction equilibrium. The reduction of Fe203 produces not only FeO, but also oxygen as gas, so that the combined weight of the two iron compounds in the resulting glass product decreases. Accordingly, the actual combined weight of FeO and Fe203 contained in the resulting glass composition will be less than the weight of the total iron batch expressed as Fe203. By this, it will be understood that "total iron" or "total iron expressed as Fe203", as used herein, refers to the total weight of the iron contained in the glass batch before reduction. In addition, it will be understood that "ferrous value", which term is used in the present invention, is defined as ferrous oxide percent, by weight, in the resulting glass divided by the weight percent of total iron expressed as Fe203. Unless otherwise specified, the terms "percentage (%)" and "parts", as used herein and in the appended claims, refer to the percentage (%) and parts by weight. The fluorescence of the dispersive X-ray of the wavelength is used to determine the percentages of weight of NiO, Co304, Ti02 and Se and the total iron expressed as Fe203. The percentage of total iron reduction was determined first by the measurement of the radiant transmission of the sample at a wavelength of 1060 nanometers, using a spectrometer. The transmission value of 1060 nanometers was then used to calculate the optical density, using the following formula: Optical density = Log10 J ^ (T0 = 100 minus the estimated loss T of reflection = 92, T = transmission at 1060 nm) The density optics is then used to calculate the reduction percentage: % reduction = (110) x (optical density) (thickness of the glass in mm) x (% of total weight Fe203) The dark colored colored glass according to the invention can be produced using iron, cobalt, nickel, titanium and selected as colorants in the following ranges: The neutral greenish-gray co marked by the low purity of excitation. The glasses of the invention have an excitation purity of less than 15%, and preferably less than 10%. The glasses of the invention fall within a relatively narrow range of wavelengths ranging from 490 to 580 nanometers, and preferably from 545 to 570. DETAILED DESCRIPTION Silica-lime-soda glass can be characterized essentially by the following composition in base to percentage by weight of the total glass: Si02 68 - 75% Na20 10 - 18% CaO 5 - 15% MgO 0 - 5% A1203 0 - 5% K20 0 - 5% BaO 0 - 5% Other minor ingredients, including aid for melting and refining such as S03, may also appear in the glass composition. Sometimes small amounts of B203 are also included in the flat glass and can be considered as optional. The colorant constituents of the present invention are added to this base glass, as specified above. In accordance with the present invention, the use of Ilmenite is suitable as an ingredient in the composition of the glass. Ilmenite is used, optionally, as a source of titanium and to supply at least a partial amount of Fe203. Essentially, the glasses of the invention are free of colorants unless they are specifically mentioned, with the exception of some residual amounts of these dyes that may be present as an impurity. These glasses can be continuously melted and refined in a conventional tank-type melting furnace and formed into sheets of flat glass of varying thicknesses by means of the flotation method in which the molded glass rests on a pool or pool of molten metal, usually tin, as it takes the form of a tape and cools. Examples 1 to 6 are all satisfactory embodiments of the invention, which have a pleasant neutral greenish gray appearance and provide an excellent reduction of the transmittance of solar energy and a very desired surplus coefficient. The Shade Coefficient was calculated with the Window 3.1 program of Lawrence Berkely Laboratories, which is based on the external temperature of 89 ° F (32 ° C), an indoor temperature of 75 ° F (24 ° C), a solar intensity of 248 Btu (hr s square foot), (789 P / m squared) and 7.5 mph (12 kph) of wind speed. Thus, the transmittance of brightness ("111 A") is less than 20% for all examples at a reference thickness of 4 mm. The total transmittance of solar energy ("TS") for each example is less than 18% and in all cases it is less than the transmittance of the luminosity. The transmittance of ultraviolet radiation is exceptionally low in each of the examples, where no amount exceeds 16.5%. the excess coefficient of each example is in no case greater than .47.

TABLE I Typically, the glass that is made by means of the flotation process has an average thickness from about 2 to 10 millimeters. For the preferred solar radiation control features of the present invention, it is preferred that the transmittance properties described herein are obtained in a thickness ranging from 3 to 5 millimeters.

Claims

1. A neutral, silicon-lime-soda glass composition, comprising on the basis of the weight percentage: S02 68-75%; Na20 10 - 18% CaO 5 - 15% MgO 0 - 5% A1203 0 - 5% K20 0 - 5% BaO 0 - 5% and dyes consisting essentially of about 1.2 to 2 percent by weight of Fe203 ( total iron), from about 0.01 to 0.05 percent by weight of NiO, from about 0.02 to 0.04 percent by weight of Co304, from about 0.09 to 3 percent by weight of Ti02 and from 0.0002 to 0.005 percent by weight of , and that has a ferrous value in the range that goes from 18 to 30 percent.

2. The glass according to claim 1, wherein the glass, at a nominal thickness of 4 mm, has a total solar energy transmittance of at least 15 percentage points below the visible light transmittance (Illuminant A) when the Visible light transmittance is in the range from 40 to 50 percent, and the total transmittance of solar energy is below 25 percent when the transmittance of visible light is below 40 percent.

3. The glass according to claim 1, which has a color defined by the following CIELAB coordinates: a * = -5 ± 5; b * = 10 + 20; L * = 50 + 10.

4. The glass according to claim 1, having a color defined by the following CIELAB coordinates: a * = -4 + 3; b * = + 0 + 10; L * = 50 ± 5.

5. The glass according to claim 1, having a dominant wavelength in the range from 490 to 580 and an excitation purity less than 15.

6. The glass according to claim 1, having a dominant wavelength in the range from 570 to an excitation purity less than 10.

7. The glass according to claim 1, wherein the glass has a shade coefficient that is not greater than 0. 53

8. The glass according to claim 1, wherein this glass has a transmittance of ultraviolet radiation not greater than 25 percent.

9. A neutral, silicon-lime-soda glass composition, comprising on the basis of the weight percentage: S02 68-75%; Na20 10 - 18% CaO 5 - 15% MgO 0 - 5% A1203 0 - 5% K20 0 - 5% BaO 0 - 5% and dyes consisting essentially of about 1.2 to 2 percent by weight of Fe203 (total iron), from about 0.01 to 0.05 percent by weight of NiO, from about 0.02 to 0.04 percent by weight of Co304, from about 0.09 to 3 percent by weight of Ti02 and from 0.0002 to 0.005 percent by weight of Se, and that it has a ferrous value in the range that goes from 18 to 30 percent; glass with a nominal thickness of 4 mm, has a total solar energy transmittance of at least 15 percentage points below the visible light transmittance (Illuminant A) when the visible light transmittance is in the range of 40 up to 50 percent, and the total transmittance of solar energy is below 25 percent when the transmittance of visible light is below 40 percent.

10. The glass according to claim 9, wherein the percentage by weight of Fe203 (total iron) is in the range from 1.3 to 1.6 percent.

11. The glass according to claim 9, wherein the NiO is present in a range ranging from 0.0225 to 0.285 percent by weight.

12. The glass according to claim 9, wherein the Co304 is present in a range ranging from 0.020 to 0.026 percent by weight.

13. The glass according to claim 9, wherein the Se is present in a range ranging from 0.0010 to 0. 0020 percent by weight.

14. The glass according to claim 9, wherein the Ti02 is present in a range ranging from 0.4 to 1 percent by weight.

15. The glass according to claim 9, which has a ferrous value in an average of about 19 to 24 percent.

16. The glass according to claim 9, which has a color defined by the following CIELAB coordinates: a * = -4 ± 3; b * = + 0 ± 10; L * = 50 ± 5.

17. The glass according to claim 9, which has a shadow coefficient that is not greater than .46.

18. The glass according to claim 9, which has a transmittance of ultraviolet radiation no greater than 18 percent.

19. A neutral, silicon-lime-soda glass composition, comprising on the basis of the weight percentage: S02 68-75%; Na20 10 - 18% CaO 5 - 15% MgO 0 - 5% A1203 0 - 5% K20 0 - 5% BaO 0 - 5% and dyes consisting essentially of approximately 1.3 to 1.6 percent by weight of Fe203 (total iron), from about 0.0225 to 0.0285 percent by weight of NiO, from about 0.020 to 0. 026 percent by weight of Co304, from about 0.4 to 1 percent by weight of Ti02 and from 0.0010 up 0. 0020 percent by weight of Se, and that has a ferrous value in the range that goes from 18 to 30 percent; the glass has a visible light transmittance that is not greater than 25 percent, a total solar energy transmittance of no more than 25 percent, and an ultraviolet radiation transmittance that is not more than 15 percent at a nominal thickness of 4 millimeters .

20. The glass according to claim 1, wherein it has a shadow coefficient that is not greater than 0.46.