MX2011006118A - Neutral grey glass composition. - Google Patents

Abstract

The invention relates to a neutral grey glass composition having a base composition comprising a silicon-sodium-calcium glass containing the following main colouring agents: 0.3 - 0.7 wt.-% Fe2O3; 0 - 30 ppm CO3O4; 1 - 20 ppm Se; and 20 - 200 ppm CuO. The glass has a transmission value in relation to illuminating light "A" greater than 65%, solar energy transmission of less than or equal to 60%, ultraviolet solar transmission of less than 46%, a dominant wavelength of between 490 nm and 600 and an excitation purity of at least 6.

Description

COMPOSITION OF NEUTRAL GRAY GLASS BACKGROUND OF THE INVENTION.

A. FIELD OF THE INVENTION.

The present invention relates to a glass composition for the commercial production of a neutral gray glass for use in the automotive industry, such as windshields and side windows, having a light transmission (TLA), illuminant "A", greater than 65%, a total solar energy transmission (Ts) of less than or equal to 60%, and a solar transmission (Tuv) of less than 46%; a dominant wavelength of 490? p? to 600 ???; and a purity of excitation of less than 6.

B. DESCRIPTION OF THE RELATED ART.

Several patents have been developed to obtain gray glass, for "automotive" purposes, which have a light transmission greater than 70, which meets the requirements of the Federal Motor Vehicle Safety Standard of the United States (US Federal Motor Standard Vehicle Safety). In the case of the construction industry, there is no restriction and small values can be used, as well as a thickness between 1.6 and 12 mm.

The glasses described in almost all prior art patents refer to a type of neutral gray glass for automotive purposes, which are based on three basic components: iron oxide, cobalt oxide and selenium. These components are additionally combined nickel oxide or manganese oxide commonly called Manganese Dioxide using different proportions and, together with the typical formulation of a silica-sodium-calcium glass, constitute the basic composition of the glass.

This is the case of the glasses of the North American Patent No. 7071133 of Arbab, et al, granted on July 4, 2006, which has a redox glass value of 0.2 to 0.675; U.S. Patent No. 6821918 to Boulos, et al, issued November 23, 2004, in which iron oxide, cobalt oxide, selenium and manganese are used as the main components. The manganese compound is present in an amount of 0.1 to 0.5% by weight based on MnO2 in the glass composition. The presence of manganese substantially prevents the formation of the amber color. This manganese compound can be added to the glass loading components in a variety of ways, for example, but not limited to MnOi, MroCk, MnO, MnCC-3, MnSO, MNF2, MnCh, etc.

Some other glasses described in other patents, such as those mentioned in the following paragraphs, in addition to the three mentioned components, different metallic elements confer the characteristics to the final product, which allow them a TLA > 70%, in order to be used in the construction and automotive industry.

This is the case of the glass of the North American Patent No. 6114264 of Krumwiede, et al, granted on September 5, 2000, in which the color of the glass is characterized by dominant wavelengths in the range of 480 to 555 nanometers, a excitation purity of no more than 8 percent and a factor of light transmission of 70 percent or more in a thickness of 3.9 millimeters; US Patent No. 6998362 to Higby, et al, issued February 14, 2006, in which the color of the glass is characterized by a dominant wavelength of less than 560 nanometers, with a color purity of no more than 6 percent and a visible light transmission of 70 percent or greater at a thickness of 4 millimeters, and where the percentage of reduction of the total iron is between 21% and 34%; US Patent No. 7,179,763 to Teyssédre, et al, issued on February 20, 20 2007, the glass having a general light transmission under illuminant A greater than 67 for a glass thickness equal to 3.85 mm; and U.S. Patent No. 5,958,811 to Sakaguchi, et al. issued September 28, 1999, wherein an infrared and ultraviolet radiation absorption glass composition has a visible light transmission of 70% or more, measured with a standard of the illuminating CIE, when said glass has a thickness of 3.25 to 6.25 mm. The composition of the glass includes CoO, SE and Fe203 as main components, as well as rare earth Ce02 and La2Ü3.

U.S. Patents Nos. 6235666 (Cochran, et al), 6,403,509 (Cochran, al), and 6,498,118 (Landa, al), 6,573,207 (Landa, al), 6,521,558 (Landa, others), 6,716 .780 (Landa, et al), 7135425 (Thomsen, AL) and 7,151,065 (Thomsen, et al.) Are related to glasses with a light transmission greater than 70 percent. Its main colorants are CoO, Se, and Fe203. Se and CoO can be partially or totally substituted by a combination of rare earths, such as Er203, Y203, Ho203, Ce02. However, a disadvantage in the use of rare earth oxides in glass compositions is the high cost In addition, US Patent No. 5308805 to Baker et al., Issued May 4, 1994, describes a neutral gray glass with a low transmission, in which one of the elements claimed is nickel oxide in proportions of 100 to 500. ppm.

In the past, the absorption of gray heat-absorbing glass that contained nickel in its structure, often formed, during the melting of glass, nickel inclusions in the form of sulfur, which appeared as small invisible particles that were impossible to distinguish once formed the glass. These nickel sulfide inclusions are due to their high coefficient of thermal expansion that can cause thermal stresses sufficient to fracture a glass plate. This is a unique problem when glass pieces are subjected to a heat treatment such as tempering, in which the presence of nickel sulphide causes an excessive percentage of broken pieces during or as a consequence of the tempering process.

A further disadvantage of the glasses containing nickel is the color change they undergo after the thermal process, such as, for example, after tempering.

Additionally, U.S. Patent No. 5,308,805 to Baker et al., Issued May 4, 1994, discloses a low-transmission neutral gray glass, in which one of the claimed components is nickel oxide in proportions of 100 to 500 ppm.

In the past, gray heat-absorbing glass containing nickel in its structure often had nickel inclusions in the form of sulfur that, during the melting of the glass, formed until they appeared as small invisible particles that could not be distinguished by the naked eye in a glass already formed. These inclusions of nickel sulphide are due to their high coefficient of thermal expansion that can cause sufficient thermal stresses to fracture a glass plate. This is a singular problem in glass pieces that are subjected to a thermal treatment such as tempering, in which the presence of nickel sulphide causes an excessive percentage of parts breaking during or as a consequence of the tempering process.

An additional disadvantage of the glasses containing nickel is the color change suffered by these after the thermal process, as for example, after tempering.

U.S. Patent No. 5,023,210 to Krumwide et al., Issued June 11, 1991, describes a composition of a low-transmission neutral gray glass (glass having a luminous transmittance of less than 20%) that does not use nickel. In order to achieve the characteristics similar to those of a neutral gray glass, Krumwide uses chromium oxide in quantities of 220 to 500 ppm of Cr203, of its composition, which in these proportions produces a gray tone and adjusts the levels of selenium and oxide of cobalt to make it neutral tone. However, in prior references a preference for not using these compounds is mentioned due to the problems presented by the difficulty of melting the chromium compounds (U.S. Patent No. 4,837,206), and additionally because they have difficulties in discarding the solid materials containing said compounds. Likewise, in North American Patent No. 5,308,805 the drawback of chromium oxide used as a coloring agent is mentioned, since it requires the use of operations and apparatus additional to the conventional ones inside the foundry furnaces, in order to reach the necessary conditions for produce the desired glasses.

U.S. Patent No. 5,346,867 to Jones et al., Issued September 13, 1994, discloses a composition of a heat-absorbing glass, having a neutral gray color, which uses manganese and titanium oxide to increase the selenium retention (which it is a high-cost component), during the production process. The neutral gray glass having a thickness control of 4 mm, a light transmission using an "A" illuminant from 10.0% to 55.0%. Although from previous references (US Patent No. 4,873,206), it is known that the use of manganese has a tendency to form a yellowish-brown coloration when exposed to ultraviolet radiation, making it difficult to maintain the uniformity of the product, and the use of the same. Titanium causes a yellowing when the glass comes into contact with the liquid tin of the float process. This is what makes these two aspects undesirable during glass production because it makes color control critical to obtain the desired shade during manufacturing. Jones and others mention in their '867 patent that the solarization process is a phenomenon associated with the change from Fe3 + to Fe2 + which causes an undesirable change in color, mentioning that they found that this does not happen in the glass described and additionally The use of titanium oxide is incorporated into the glass to obtain the desired range of dominant wavelength, as well as to reduce the transmission of ultraviolet radiation.

On the other hand, it is well known to those skilled in the art, that the addition or substitution of one or more dyes by another or others, or by the change of the relative proportional amount in the composition of the glass, affects not only the color of the product, such as for example the dominant wavelength of the color or the purity of excitation, but also the light transmission, the absorption of heat and additional properties such as the transmission of ultraviolet and infrared radiation.

It is well known that copper has played an important aspect in the production of glass, ceramics and colored pigments. It has been recognized, for example, the coloring of Persian ceramics by its tonality conferred by Copper. Of particular interest to ceramics artists are turquoise blue and especially dark blue Egyptian and Persian (Waldemar A. Weil, Colored Glasses, Society of Glass Technology, Great Bretain, P.154-167, 1976).

Copper has been used in glass compositions, not only in those of the silica-sodium-calcium type, but in some others, such as those containing for example borosilicate. Therefore, the color developed depends on the base of the glass, its concentration and its state of oxidation.

For the case of the glass mentioned as a base, the copper in the form of oxide imparts a blue coloration of a greenish tone, specifically turquoise, however, in the glass, the copper may be in its monovalent state, which does not impart color. Thus, the blue-green coloration depends not only on the amount of copper present, but on the ionic balance between the cuprous and cupric states. The maximum absorption of copper oxide is in a band centered at 780? P? and a secondary weak peak is present at 450 nm, which disappears at high soda contents (about 40% weight) (CR Bamford Color Generation and Control in Glass, Glass Science and Technlogy, Elsevier Scientific Publishing Company, P. 48-50, Amsterdam, 1977).

In the production of ruby red glass, a mixture containing copper oxide together with some reducing agent (SnO is commonly used), is melted under reducing conditions. The initial mix shows the characteristic blue color of copper II, but as soon as the melting begins, the color changes to a pale straw yellow, which is produced during this stage. Due to a thermal treatment at a temperature between the annealing point and the softening point, the ruby red color develops. Yes, during the merger, the reduction state is carried beyond a critical stage, the color changes to coffee and appears opaque or "off". On the other hand, if the copper is insufficiently reduced, some blue traces remain and the ruby red color does not develop (Amal Paul, Chemistry of Glasses, Chapman and Hall, P.264-270, London, 1982).

U.S. Patent No. 2,922,720 to Parks et al., Issued June 20, 1957, mentions the use of copper in glass as: "... Copper has been used as a coloring agent for glass by developing a ruby red coloration. , but to be able to obtain the color in an open melting furnace, it is necessary to use cyanogens as a reducing agent ... ", he also mentions the effect of copper on the coloration of the glass, as due to the colloidal suspension of copper particles metallic in the glass, and by analogy it is believed that a particle size produces ruby red colors, depending on the intensity of the color, the concentration of the copper. For smaller particle sizes, the color effect is zero.

In the present application, the incorporation of copper oxide (CuO), in combination with iron oxide, cobalt oxide and selenium, is used as an alternative for obtaining a gray shade with a light transmission > 70% for use in the automotive industry. This prevents intentional addiction of some dyes such as nickel, manganese, T1O2 or the rare earth combination.

In addition, cobalt oxide (expressed as C03O4) is partially replaced by copper oxide (CuO) and in some examples is avoided. This substitution is possible because the CuO and the C03O4 provide a blue hue for the glass.

% Redox or% ferrous =% FeO (expressed as Fe203) / (% total Fe203) Neutral tonality is obtained with the combination of iron oxide (Fe203), which causes a color change of the crystal from yellow to yellow-green ( low redox) to a blue (high redox) depending on the% reduction. If redox is greater, it is possible to avoid cobalt oxide (blue) and only add selenium (pink to red-brown coloration) and copper oxide (turquoise blue). On the other hand, if the redox is smaller, a combination of copper oxide-cobalt oxide is necessary. In the last combination, cobalt is partially replaced by copper.

In addition, a reduction in the transmission of ultraviolet radiation and a reduction in the near infrared region are also provided for the absorption bands around 800 nanometers, which helps reduce infrared solar transmission.

It has been proven that industrial production is feasible to add CuO, in concentrations lower than 120 ppm for a glass thickness of 4.0 mm and less than 100 ppm for a glass thickness of 6.0 mm.

The glass can also be manufactured with a thickness of about 1.6 millimeters to about 12 millimeters. If high CuO concentrations are present inside the flotation chamber, a reduction process could occur in the atmosphere, presenting a red coloration on the glass surface. This effect related to the residence time and the speed of advance of the glass sheet can be intense and observable on the glass surface.

Thus, in the present invention, a neutral gray glass composition has a light transmission (TLA), illuminant "A", greater than 70%, a total solar energy transmission (Ts) of less than or equal to 60 %, and a solar transmission (Tuv) less than 46%.

OBJECTIVES OF THE INVENTION It is therefore a principal objective of the present invention to provide a composition of a neutral gray glass, wherein the Cobalt Oxide (expressed as C03O4) is partially replaced by Copper Oxide (CuO), which in combination with the Oxide of Iron and Selenium (Se), allows to obtain a neutral tone in the glass for use in the automotive and construction industry.

It is a primary objective of the present invention to provide a neutral gray glass composition which includes additional components selected from carbon or sodium nitrate to modify the reduction state of the iron.

It is a further object of the present invention to provide a composition of a neutral gray glass, having a light transmission, "A" illuminant, greater than 65%, a total solar energy transmission of less than or equal to 60%, and a solar transmission less than 46%; a dominant wavelength of 490 m to 600 nm; and an excitation purity of less than 6. The glass having a redox% of between about 15 to about 50.

These and other objects and advantages of the neutral gray glass of the present invention will be apparent to those skilled in the art from the following detailed description thereof.

DETAILED DESCRIPTION OF THE INVENTION The typical composition of a silica-sodium-calcium glass used in the automotive industry, and formed by means of a well-known glass float process, is characterized by the following formulation based on percentage by weight with respect to the total weight of the glass: Components% weight Si02 68 to 75 A1203 0 to 5 CaO 5 to 15 MgO 0 to 10 Na20 10 to 18 K20 0 to 5 S03 0.05 to 0.3 The neutral gray glass composition of the present invention is based on the composition described above to which the following coloring compounds have been added, to obtain a gray color: Components% weight Fe203 0.3 to 0.07 C03O4 0.020 to 0.030 Ppm components C03Ü4 0 to 30 It's 1 to 20 CuO 20 to 200 The following are specific examples of the silica-sodium-calcium composition according to the present invention, having the corresponding physical properties of visible transmission, of infrared and ultraviolet radiation, for a glass having a thickness of 4 mm.

TABLE 1 Examples 1 to 8 show the results of the silico-sodium-calcium composition with the addition of Iron Oxide (Fe203), Selenium (Se), Cobalt Oxide (expressed as C03O4) and Copper Oxide (CuO). Sodium nitrate (NaN03) was added as an oxidizing agent to modify the reduction state of the iron for low values. The properties and color are for a glass with a thickness of 4 mm.

Additionally, a reduction in the transmission of ultraviolet radiation and a near reduction to the infrared region is provided for the bands of absorption around 800 ???, which help reduce infrared solar transmission.

For industrial production, it is feasible to add CuO at concentrations lower than 120 ppm for glass thicknesses of 4.0 mm and less than 100 ppm for a glass thickness of 6.0 mm.

TABLE 1 Example 1 2 3 4 5 6 7 8 Colorants % by weight Fe203 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 % REDOX (% Ferrous) 15.2 16.4 13.7 12.7 17.3 18.5 18.1 19.7 Se (ppm) 7.8 6.4 5.8 2.9 17.5 1 1.9 11.5 7.7 Co304 (ppm) 10 10 10 10 12 12 12 12 CuO (ppm) 100 100 100 100 50 50 50 50 Sodium Nitrate (NaN03) 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 % UV transmission (TUV) 39.8 40.7 44.2 45.0 34.0 35.8 36.3 37.7 % Illuminant A, Light Transmission (TLA) 74.6 73.6 76.1 78.3 64.7 71.3 71.3 72.7 % Total Solar Transmission (Ts) 59.9 58.7 62.6 64.6 52.8 55.2 55.8 55.1 % Infrared Transmission (IRR) 49.4 47.5 52.5 54.2 45.3 43.8 44.8 41.7 Transmitted Color, Illuminant 'D65' Y TABLES 2 TO 4 Examples 9 to 26 in Tables 2, 3 and 4 show the results of the silica-sodium-calcium composition considering the addition of ferric oxide (Fe203), Selenium (Se), Cobalt Oxide (expressed as C03O4) and Oxide of Copper (CuO). Carbon was added as a reducing agent, in order to modify the iron reduction state to the highest values. The addition of sodium nitrate (NaN03) in Examples 1 to 8 and Carbon in Examples 9 to 26 resulted in a gray glass, with optimized values of% UV Transmission (TUV),% of total solar transmission (TS) and maintenance of the TLA greater than 70%. All glass compositions can be produced in a commercial glass float process well known in the art.

TABLE 2 Example 9 10 11 12 13 14 15 Colorants % by weight Fe203 0.62 0.62 0.62 0.62 0.62 0.62 0.62 % REDOX (% Ferrous) 25.4 22.3 22.2 24.3 21.1 20.9 20.2 Se (ppm) 11.3 4.1 6.8 7.3 5.2 6.4 5.3 Co304 (ppm) 12 12 12 12 10 10 10 CuO (ppm) 50 50 50 50 50 50 50 % Carbon 0.027 0.027 0.027 0.027 0.027 0.027 0.027 % UV transmission (TUV) 32.4 39.3 37.1 34.1 38.1 38.6 37.9 % Illuminant A, Light Transmission (TLA) 63.7 72.9 68.7 67.1 73.4 71.0 71.2 % Solar Transmission Total (Ts) 46.7 53.5 51.2 48.8 54.1 52.9 53.6 % Transmission Infrared (IRR) 34.1 38.0 37.6 34.7 39.3 39.0 39.9 Transmitted Color, TABLE 3 Example 16 17 18 19 20 21 22 Colorants % by weight Fe203 0.62 0.60 0.60 0.55 0.55 0.55 0.55 % REDOX (% Ferrous) 20.9 21.9 20.8 32.4 36.7 33.0 38.3 Se (ppm) 7.8 5.5 5.6 9.4 13.1 3.6 3.9 Co304 (ppm) 10 5 5 0 0 0 0 CuO (ppm) 50 75 75 75 75 75 75 % Carbon 0.027 0.027 0.027 0.053 0.053 0.053 0.053 % UV transmission (TUV) 36.8 41.5 39.3 39.5 34.4 42.5 41.8 % Illuminant A, Light Transmission (TLA) 69.7 73.1 73.8 68.8 62.9 72.8 70.5 % Solar Transmission Total (Ts) 52.5 53.6 54.6 45.9 40.4 47.7 46.0 % Transmission Infrared (IRR) 39.7 38.4 39.9 27.9 23.2 27.2 26.1 Transmitted Color, TABLE 4 % Carbon 0.053 0.053 0.053 0.053 % UV transmission (TUV) 40.8 41.1 44.2 42.0 % Illuminant A, Transmission of Light (TLA) 69.6 70.3 73.6 71.3 % Total Solar Transmission (Ts) 45.2 44.9 47.6 45.7 % Infrared Transmission (IRR) 25.9 24.6 26.6 25.1 Transmitted Color, Illuminant 'D65' And 10th Obs. (ASTM E308) L * 82.0 84.5 86.5 85.2 a * -6.1 -6.6 -6.5 -6.7 b * 2.4 2.1 1.4 1.6 % Purity of excitation (Pe) 2.0 1.8 1.9 1.9 Dominant wavelength (??) 523 51 1 502 504 In the four tables, cobalt oxide (expressed as Co304) is partially replaced by copper oxide (CuO), which in combination with iron oxide and selenium (Se), allows to obtain a neutral tone in the glass for use in the automotive industry and the construction industry.

The physical properties such as the transmission of light correspond to variables calculated based on internationally accepted standards. So that the transmission of light is evaluated using the illuminant "A" and standard observer of 2 ° also known as of 1931 [Publication C.I.E. 15.2, ASTM E- 308 (1990)]. The range of wavelength used for these purposes is 380 to 780 ???, integrating values in numerical form with intervals of 10? P ?. The transmission of solar energy represents the heat that glass gains directly, being evaluated from 300 ??? until 2150 ??? with intervals of 50, 10, 50? p ?, the numerical form of calculation uses ISO / DIS 13837 as the recognized standard.

The calculation of the transmission of ultraviolet (UV) radiation, involves only the participation of solar UV radiation, so it is evaluated in the range of 300nm to 400 ??? at intervals of 5 ???, the numerical form of calculation uses ISO / DIS 13837 as the recognized standard or the transmission of infrared (IR) radiation, only the range in which the solar spectrum is considered, like UV radiation, is contemplated has influence, so the range of the near infrared region is used from 800 to 2150 ???, with intervals of 50 ???. Both calculations employ the aforementioned ISO / DIS 13837 solar radiation values.

The amount of solar heat that is transmitted through the glass, can also be calculated by the contribution of thermal energy with which it participates in each of the regions where the solar spectrum has influence, which is from the ultraviolet region (280? p?), to the region of the near infrared (2150 ???), which is 3% for UV, 44% for the visible and in the order of 53% for IR, however, the values of solar energy transmission direct, in the present invention, are calculated based on a numerical integration taking into account all the range of the solar spectrum from 300 to 2150 ???, with intervals of 50? p? and using the solar radiation values reported by the ISO / DIS 13837 standard.

The specifications for the determination of color such as the dominant wavelength and the purity of excitation, have been derived from the Tristimulus values (X, Y, Z) that have been adopted by the International Lighting Commission (C.I.E.), as a direct result of experiments involving many observers. These specifications can be determined by calculating the trichromatic coefficients x, y, z of the Tristimulus values that correspond to the colors red, green and blue respectively. The trichromatic values are plotted in the chromaticity diagram and compared with the coordinates of the illuminant "C" considered as the lighting standard. The comparison provides the information to determine the color excitation purity and its dominant wavelength. The dominant wavelength defines the wavelength of the color and its value is in the visible range, from 380 to 780 ???, while for the purity of excitation, the lower its value, the closer it tends to be a neutral color A deeper understanding of these issues can be obtained in the "Handbook of Colorimetry" published by the "Massachusetts Institute of Technology" by Arthur C. Hardy, issued in 1936.

From the above, a neutral gray glass composition has been described and it will be apparent to experts in the field that other possible advances or improvements can be made, which may be considered within the determined field. following claims.

Claims (10)

CLAIMS:

1. A composition of neutral gray glass having a base composition of a silica-sodium-calcium glass containing: SiO2 of between 68 to 75%; AI2O3 from 0 to between 5%; CaO between 5 to 15%; MgO between 0 to 10%; Na2Ü of between 10 to 18%; K2O from 0 to between 5%; SO3 between 0.05 to 0.30% and main dyes comprising: Fe2Ch between 0.30 and between 0.70 weight percent; C03O4 from 0 to between 30 ppm; It is between 1 to between 20 ppm; CuO between 20 a between 200 ppm where the glass has a light transmission, "A" illuminant, greater than 65%, a solar energy transmission of less than or equal to 60%, a solar ultraviolet transmission of less than 46% , a dominant wavelength of 490? p? at 600? p ?, and an excitation purity of less than 6.

2. The glass composition according to claim 1 further includes, an additional component selected from carbon or sodium nitrate to modify the reduction state of the iron.

3. The glass composition according to claim 2, wherein the carbon comprises from about 0.01 to about 0.07 percent by weight of the glass composition.

4. The glass composition according to claim 2, wherein the sodium nitrate is added from about 0.2 to about 1.2 percent by weight of the glass composition.

5. The glass composition according to claim 1, wherein said glass is produced with a thickness of between about 4 millimeters to about 6 millimeters.

6. The glass composition according to claim 1, wherein said glass is produced with a thickness of between about 1.6 millimeters to about 12 millimeters.

7. The glass composition according to claim 1, wherein the glass thickness is preferably between 1.6 and 6 mm.

8. The glass composition according to claim 1, wherein the CuO is less than 120 ppm for a glass thickness of 4.0 mm.

9. The glass composition according to claim 1, wherein the CuO is less than 100 ppm for a glass thickness of 6.0 mm.

10. The glass composition according to claim 1, wherein the glass has a redox% of between about 15 to about 50.