Patent Application
20240317634
The present invention relates to a glass with low transmittance, of a neutral gray color and more specifically to a gray glass composition to produce glass for use in the automotive industry, for the manufacture of both laminated and temperate panoramic roofs, rear windows and rear doors.
Colored glass is a material to which, during the fusion process, metal oxides are incorporated. As a result of previous research, it is known that the addition of iron-cobalt oxides in combination with selenium gives the glass shades from greenish gray-neutral gray to yellowish gray depending on the ratio thereof. By increasing the concentrations of iron oxide, cobalt oxide and selenium and controlling the redox conditions in the glass melting atmosphere and/or in the mixture (mainly carbon and sodium nitrate concentration), a glass with low light transmission, good direct solar transmission blocking and privacy gray coloration, which is widely used in roofs, rear windows and rear doors of motor vehicles can be obtained.
Solar control is the ability to modify the amount of solar radiation transmitted or reflected, in the spectral ranges of near ultraviolet (UV; 300-380 nm), visible (VIS; 380-780 nm) and infrared (IR; 780-2500 nm). In its automotive use, this is achieved with the addition of various absorbent coloring agents in the initial mixture, so that the glass has properties to absorb both infrared (IR) and ultraviolet (UV) solar radiation, to reduce the passage of excess heat towards the interior of the vehicle caused by radiation from the sun, as well as to protect the interiors from the degradation of UV radiation coming therefrom.
The glasses described in almost all patents that refer to a type of neutral gray glass are based on three main dyes: iron oxide, cobalt oxide and selenium, whose main function is to provide solar control properties to the glass.
The following prior art patents use various metal oxides as main dyes to obtain a gray glass and provide the final characteristics of the product. These components, such as nickel oxide, manganese oxide, chromium oxide or rare earth oxides, are mixed in a base formulation of a silica-sodium-calcium glass.
For example, U.S. Pat. No. 5,352,640 (U.S. RE37,998 E) to Combes et al. mentions the obtaining of gray glasses used mainly in the automotive industry, whose composition of coloring agents ranges from 1.4 to 4% of iron oxide (Fe2O3) and from 0 to 0.05% of cobalt oxide, with around 0.02% of excess cobalt oxide when Fe2O3 is less than 2%, optionally having a combination of CoO+Se+Cr2O3 with a content of less than 0.24% by weight. The physical properties of the glass such as light transmission and energy transmission are equal to or less than 20% under illuminant A and equal to or less than 12% at a thickness of 3.85 mm, respectively.
U.S. Pat. No. 5,545,596 to Alvarez Casariego, et al, discloses the use of dyes is mentioned in concentrations of 0.45 to 2.5% for Fe2O3 (total iron), from 0.001 to 0.02% for CoO, from 0 to 0.0025% for Se and from 0 to 0.1% for Cr2O3, for gray glass having a light transmission with illuminant A of 20 to 60%, used in side and rear windows for vehicles.
U.S. Pat. No. 7,393,802 B2 to Seto, et al, describes the use of Fe2O3, CoO, Se and NiO as dyes, but also adds the use of CeO2 and TiO2 in amounts no greater than 2.0% by weight to increase ultraviolet absorption.
For the glasses obtained in U.S. Pat. No. 7,622,410 assigned to Longobardo et al, nickel oxide is used in concentrations of 500 to 1000 ppm, erbium oxide from 0.1 to 0.8% and chromium oxide in contents of 1 to 20 ppm, in addition to a total content of iron oxide of 0.15 to 0.45%, selenium less than or equal to 3 ppm and cobalt oxide of 120 to 240 ppm. The mixture of these oxides is used for the general adjustment of the gray coloration of the glass. The light transmission of the glass of this patent is 8 to 25%, with a dominant wavelength of 435 to 570 nm, using a cobalt oxide/nickel oxide ratio of 0.22 to 0.30 and FeO/Fe2O3 redox values of from 0.20 to 0.40.
The main disadvantage of these glasses is the high cost of using rare earth oxides in their composition.
In U.S. Pat. No. 8,017,538 B2 to Teyssedre, et al, the glasses disclosed are known to use nickel oxide in concentrations of 400 to 700 ppm or 1500 to 1900 ppm, iron oxide 0.7 to 0.95% with a redox value of 0.40 or less, plus cobalt oxide at 200 to 300 ppm, to obtain a gray color adjustment and obtain the following physical properties: light transmission under illuminant A (TLA) of 50% or less and an average energy transmission (TE) less than 45%, for a glass thickness of 3.85 mm.
The use of nickel oxide, used as a dye in some of the previous patents, has the disadvantage that nickel sulfide inclusions can form (a defect that is not easily detectable) that can cause the glass sheets to break due to the difference in the thermal expansion coefficient of this material with the rest of the glass matrix.
The glasses described in U.S. Pat. No. 8,551,899 to Kim, et al., have a dark gray-neutral green color, given by the dyes used such as Fe2O3 in 1.4 to 2.5%, CoO from 0.02 to 0.04%, Se from 0.0001 to 0.004%, MnO from 0.005 to 0.5 and CeO from 0.05 to 1% with a light transmission of illuminant A less than 15%. These glasses are used as privacy glass or panoramic roofs in automobiles, as well as used in construction.
U.S. Pat. No. 7,754,632 Delmotte, et al, uses concentrations of MnO up to 600 ppm and TiO2 less than 0.1% in addition of other oxides such as Fe2O3 1.1 to 1.5% (total iron), Co 150 to 200 ppm, Cr2O3 25 at 100 ppm and Se 10 at 50 ppm, to achieve optical characteristics of light transmission of illuminant A less than 20% for thicknesses of 4 mm.
U.S. Pat. No. 8,785,338 to Tsuzuki, et al refers to a composition of a silica-sodium-calcium glass with contents of 0.70 to 1.70% by mass of Fe2O3 (total iron), 0.15 to 0.45% by mass of FeO (oxide ferrous), 0-0.8% by mass of TiO2, 100 to 350 ppm of CoO, 0 to 60 ppm of Se, 100 to 700 ppm of Cr2O3 and 3 to 150 ppm of MnO, which has a ratio (Fe2+/Fe3+) of ferrous ion to ferric ion of from 0.20 to 0.80. This patent claims that this glass has superior ultraviolet radiation absorption and infrared radiation absorption performance (thermal insulation performance), as well as adequate transparency, achieved thanks to the use of TiO2 preferably in ranges from 0 to 0.5%.
U.S. Pat. No. 9,120,695 to Lee, et al., features the following glass composition: 1.4 to 2% Fe2O3 with an FeO content of 10 to 30% (with respect to total iron), 0.02 to 0.035% CoO, 0.0015 to 0.004% Se and 0.005 to 0.5% MnO. Optical characteristics of light transmission of illuminant A of less than 15% and ultraviolet ray transmission of 2% or less are reported.
The dark green glasses of U.S. Pat. No. 9,617,182 by Cho, et al. (Apr. 11, 2017), use as dye 1.2 to 2% of total Fe2O3, 0.0220 to 0.04% of CoO, 0.002 to 0.0035% of Se and 0.01 to 0.04% of Cr2O3, wherein the weight ratio of (CoO+Cr2O3) to Se (=[CoO+Cr2O3]/Se) is 13 to 25 and the weight ratio of CoO to Cr2O3 (=CoO/Cr2O3) is 0.9 to 1.8. The glass exhibits a visible light transmittance (TLA) of 15% or less, a direct solar energy transmittance (TDS) of 16% or less, and an ultraviolet radiation transmittance (TUV) of 3% or less, measured for a 4 mm reference thickness.
U.S. Pat. No. 7,902,097 B2 to Cid-Aguilar et al., uses concentrations of: 0 to 30 ppm of Co3O4, 1 to 20 ppm of Se, 20 to 200 ppm of CuO and 0.30 to 0.70% of Fe2O3 to obtain a neutral gray glass, with optical characteristics of light transmission with illuminant A greater than 65%, total solar energy transmission equal to or less than 60%, ultraviolet radiation transmission less than 46% and a dominant wavelength of 490 to 600 nm. This patent adds components such as carbon from 0.01 to 0.07% or sodium nitrate from 0.2 to 1.2% for modifying the redox state of iron and copper oxide, since, in combination with the other dyes, it is used as an alternative to obtain the gray tone, partially replacing the addition of titanium oxide and cobalt oxide.
As can be read from the above, iron is present in glass (silica-sodium-calcium) in two compounds that depend on the oxidation state of the iron: if the iron is present as Fe2+, the compound formed is ferrous oxide (FeO). If iron is present as Fe3+, ferric oxide (Fe2O3) would be present. Each ion confers different properties; the ferrous ion has a wide and strong absorption band centered at 1050 nm, which results in a decrease in infrared radiation. Furthermore, this band extends into the visible region, decreasing light transmission and imparting a bluish coloration to the glass. On the other hand, the ferric ion features a strong absorption band located in the ultraviolet region, which evidently prevents its transmission through the glass and, in addition, it shows two other weak bands in the visible region located between 420 and 440 nm, which cause a slight decrease in light transmission and a yellowing of the glass.
Generally, the iron in glass and its amount of ferrous oxide are expressed in the form of Fe2O3. It is common in the industry to express the amount of ferrous or ferric oxide as a percentage of total iron. The balance between ferrous and ferric oxide has a direct effect on the color and
transmittance characteristics of the glass, represented as:
The above means that the greater the amount of ferric ion (Fe3+) present in the glass, the greater the absorption of ultraviolet radiation and the light transmission will increase; as well as the yellowish tone; but, if the content of ferrous ion (Fe2+) increases as a result of chemical reduction of Fe2O3, the absorption of infrared radiation will increase, but the absorption of ultraviolet radiation will decrease and so will the light transmission.
The variation in the concentration of FeO in relation to Fe2O3 gives rise to a color change in the glass. The hue shift can be modified from yellow through green, blue to amber. The color changes as follows (according to experimental results):
To control the balance between ferrous oxide and ferric oxide necessary to achieve solar control glass, it is necessary to establish the mixing and melting atmosphere conditions; for the former case, the concentration of reducing agents such as carbon and oxidizing agents, such as sodium sulfate and sodium nitrate, is adjusted. Regarding fusion conditions, it is necessary to adjust the atmosphere with greater or lesser oxygen content depending on the thermal performance and shade of the desired glass.
Additionally, it is well known that titanium oxide also acts as a dye and when used in combination with Fe2O3, it is possible to obtain a further reduction of the transmission of ultraviolet radiation to a point where the desired visibility transmission is achieved.
K. M. Fyles in the article Modern Automotive Glasses, Glass Technology, vol 37, February 1996, pp. 2-6, considers that iron is the most important dye in automotive glass since it is a component available at a low price that absorbs undesirable ultraviolet radiation (ferrous ion) and, in addition, a large amount of infrared radiation (ferrous ion).
Gordon F. Bresterm et al, in the article “The color of iron-containing glasses of varying composition”, Journal of the Society of Glass Technology, New York, USA, April 1950, pp. 332-406, mentions color changes caused by systematically varying the composition of iron-containing silicate and non-silica glasses evaluated in terms of visual color, spectral transmission and chromaticity.
Other articles also describe the importance of the balance between ferrous and ferric oxides in glasses, such as the one written by N. E. Densem; The equilibrium between ferrous and ferric oxides in glasses; Journal of the Society of Glass Technology, Glasgow, England, May 1937, pp. 374-389; J. C. Hostetter and H. S. Roberts, “Note on the dissociation of Ferric Oxide dissolved in glass and its relation to the color of iron-bearing glasses”; Journal of the American Ceramic Society, USA, September 1921, pp. 927-938.
Many books and scientific articles have been published on the composition of colored glass with infrared and ultraviolet radiation absorption characteristics.
C. R. Bamford, in the book Color Generation and Control in Glass, Glass Science and Technology (Elsevier Science Publishing Co., Amsterdam, 1977) describes the principle of glass coloring methods and applications. In this book the author considers that three elements govern the color of the light transmitted by a glass, being the color of the incident light, the interaction of the glass with that light and the interaction of the transmitted light with the eye of the observer. The procedures require the spectral transmission data of the glass with the corresponding glass thickness and viewing angle.
With respect to titanium oxide (TiO2) in silica-sodium-calcium glasses, the most stable form of titanium in glasses is the tetravalent (Ti4+). The trivalent form could confer coloration however, this effect is not observed in silica-sodium-calcium glass. In the document “Effects of titanium dioxide on glass” written by Beals MD, The Glass Industry, September 1963, pp 495-531, he describes the interest that titanium dioxide has been shown as a glass component. The effects produced by the use of titanium dioxide include comments that TiO2 greatly increases the refractive index, increases the absorption of light in the ultraviolet region, and that viscosity and surface tension are reduced. From data on the use of titanium dioxide in enamels, it was observed that TiO2 increases chemical durability and acts as a flux. In general, clear glasses containing titanium dioxide can be found in all common glass-forming systems (borates, silicates and phosphates). The various glass-forming regions for titanium dioxide-containing systems are not grouped together in one place, as the organization of the discussion is based more on the properties of a use of titanium dioxide-containing glasses rather than their own constitution.
On the other hand, the addition of selenium to silica-sodium-calcium glass can produce a pink color due to the presence of atomic selenium. Selenium is one of the most used physical bleaches for glass with traces of iron coming as an undesirable impurity in the raw materials, because its coloring neutralizes the ferrous and ferric ions present in the glass.
The combination of iron oxide and selenium in silica-sodium-calcium glass confers a reddish-brown coloration and a decrease in light transmission, due to an absorption band located in the visible region between 490 and 500 nm (band similar to atomic selenium). This band extends towards the ultraviolet region, also causing a decrease in this type of transmission in the glass.
The intensity of the coloration and the final properties of the glass are a function of the concentration of iron oxide and selenium in the glass.
It is well known that copper has played an important aspect in the production of glass, ceramics and colored pigments. For example, the coloring of Persian ceramics has been recognized by its tone conferred by copper. Of special interest to ceramic artists are turquoise blue and especially dark Egyptian and Persian blue (Waldemar A. Weil; Colored Glasses, Society of Glass Technology, Great Britain, 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 that contain, for example, borosilicate. Therefore, the color developed depends on the base of the glass, its concentration and its oxidation state.
In the case of a sodium-silica-calcium base glass, copper in oxide form imparts a blue coloration of a greenish tone, specifically turquoise, however, in glass, copper can 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 also on the ionic balance between the cuprous and cupric states. The maximum absorption of copper oxide is found in a band centered at 780 nm and a secondary weak maximum peak is present at 450 nm, which disappears at high soda contents (around 40 wt %) (C. R. Bamford Color Generation and Control in Glass, Glass Science and Technology, Elsevier Scientific Publishing Company, pp. 48-50, Amsterdam, 1977).
The incorporation of copper oxide (CuO), in combination with iron oxide, cobalt oxide, selenium and titanium oxide proves to be an alternative in order to obtain a gray tone with low light transmission for use in the automotive or construction industry, where a glass having a low light transmission of illuminant A (TLA) no greater than 15%, direct solar energy transmission (TDS) no greater than 14%, near infrared radiation transmission (TIR) no greater than 14%, an ultraviolet radiation transmission (TUV) no greater than 8%, a total solar energy transmission (TTS) no greater than 38%, a purity no greater than 50% and a dominant wavelength of 480-590 nm when it has a nominal thickness of 3.85 mm is needed.
It has been proven in the industrial production that the addition of CuO is feasible in concentrations of less than 120 ppm for a thickness of 4 mm and less than 100 ppm for thicknesses of 6 mm.
Glass can also be manufactured in smaller thicknesses, as is the case with glass used in the manufacture of laminated systems. If higher concentrations of CuO are present, during the formation process within the float chamber, a reduction process attributable to the process atmosphere could occur, with the presence of a reddish color on the glass surface, which is observed in reflection. This effect is related to the residence time and the advancing speed of the glass ribbon, which means that, at lower speeds, it will be necessary to reduce the CuO content in glass or adjust the reducing conditions in the float chamber.
A main object of the present invention is a gray glass with low light transmission of illuminant A (TLA) no greater than 15%, a direct solar energy transmission (TDS) no greater than 14%, a near infrared radiation transmission (TIR) no greater than 14%, an ultraviolet radiation transmission (TUV) no greater than 8%, a total solar energy transmission (TTS) no greater than 38%, a purity no greater than 50% and a dominant wavelength of 480-590 nm when it has a nominal thickness of 3.85 mm, manufactured by the float process.
Another object of the present invention is the use of copper oxide as a partial replacement for cobalt oxide (Co3O4). The feasibility of its addition in flat glass manufactured by the float process has been demonstrated to levels close to 120 ppm without a reduction effect due to the conditions of the tin chamber. Likewise, TiO2 is incorporated as an additional element to the iron oxide to provide an additional reduction in the transmission of ultraviolet radiation.
An additional object of the present invention is also to obtain a gray glass composition with low light transmission, which includes additional elements such as carbon or sodium nitrate to modify the redox state of the iron oxide.
The glass of this invention avoids the use of coloring compounds such as nickel, chromium, manganese or rare earth oxides, mainly erbium oxide (Er2O3).
The present invention refers to a gray glass composition that, although its use in the automotive industry is mentioned as its main application, said use is not limited to other fields such as the construction industry or other applications such as, for example, as a substrate to be coated by one or more thin layers applied via cathodic vacuum erosion process (MSVD), chemical vapor deposition (CVD) or other techniques.
The typical composition of a silica-sodium-calcium glass formed by the float glass process for the automotive industry is characterized by the following formulation based on the percentage by weight with respect to the total weight of the glass:
The glass composition of the present invention is based on a silica-sodium-calcium glass to which the following dyes were added in order to obtain a gray color:
The main purpose of adding sodium nitrate (NaNO3) and carbon to the composition is to modify the oxidation state of iron so as to achieve the optimal level of direct heat transfer (TDS). Also, sodium nitrate helps optimizing retention of selenium in the glass.
This gray glass has an illuminating light transmission A (TLA) of no more than 15%, a direct solar energy transmission (TDS) of no more than 14%, a near-infrared radiation transmission (TIR) of no more than 14%, a ultraviolet radiation transmission (TUV) no greater than 8%, a total solar energy transmission (TTS) no greater than 38%, a purity no greater than 50% and a dominant wavelength of 480-590 nm when it has a thickness for example between 1.4 to 6 mm, from 1.6 to 5 mm, and more preferably 3.85 mm. The glass of the present invention avoids the use of coloring compounds such as nickel, chromium, manganese or rare earth oxides, mainly erbium oxide (Er2O3).
The following examples show the physical properties of illuminant light A transmission (TLA), direct solar energy transmission (TDS), near-infrared radiation transmission (TIR), ultraviolet radiation transmission (TUV), total solar energy transmission (TTS). The color transmission (L*, a* and b*), color purity and a dominant wavelength (λ), for a 3.85 glass.
Tables 1 and 2 (Examples 1 to 14) show the experimental results of the composition of the present invention with the combination of iron oxide (Fe2O3), cobalt oxide (Co3O4), selenium (Se), copper oxide, and titanium oxide (TiO2). In addition, they contain 0.66% sodium nitrate (NaNO3) as an oxidizing agent in the mixture, without the addition of carbon.
Table 3 (Examples 15 to 18) shows the experimental results of the composition of the present invention with the combination of iron oxide (Fe2O3), cobalt oxide (Co3O4), selenium (Se), copper oxide, and titanium oxide 5 (TiO2). In addition, 0.16% sodium nitrate (NaNO3) and 0.04% carbon (coke type) are incorporated into the mixture.
Tables 4 and 5 Tables 4 and 5 (Examples 19 to 31) show the experimental results of the composition of the present invention with the combination of iron oxide (Fe2O3), cobalt oxide (Co3O4), selenium (Se), copper oxide, and titanium oxide (TiO2). Likewise, they contain 0.16% sodium nitrate (NaNO3) and 0.02% carbon in the mixture.
Table 6 (Examples 32 to 34) shows the experimental results of the composition of the present invention with the combination of iron oxide (Fe2O3), cobalt oxide (Co3O4), selenium (Se), copper oxide, and titanium oxide (TiO2). In addition, they contain 0.16% sodium nitrate (NaNO3) and 0.030% carbon.
The main purpose of adding sodium nitrate (NaNO3) and carbon to the composition is to modify the oxidation state of iron in order to achieve the optimal level of direct heat transfer (TDS). Color and privacy are adjusted by optimizing the percentages of dyes described in this invention.
The physical properties of the glasses obtained were evaluated in accordance with internationally accepted standards. Specifications for color determination, such as dominant wavelength and excitation purity, have been derived from the Tristimulus values (X, Y, Z) that have been adopted by the International Commission on Illumination (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 graphed on the chromaticity diagram and compared with the coordinates of the D65 illuminant, considered the lighting standard. The comparison provides the information to determine the purity of color excitation 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 nm, while for the excitation purity, the lower its value, the closer it tends to be a neutral color.
The calculation of the ultraviolet radiation transmission (TUV) is adjusted to the range of solar UV radiation, so it was evaluated in the range of 300 to 400 nm in intervals of 10 nm, according to what is indicated in the ISO/DIS 13837 standard.
For the evaluation of light transmission, illuminant “A” (TLA) was used, in the wavelength range of 400 to 800 nanometers, integrating values in intervals of 10 nm. Color transmission (L*, a* and b*) was calculated according to ASTM E308 (C.I.E. D65 observer at 10°).
The direct solar energy transmission (TDS) values were evaluated in the range of 300 to 2500 nm with intervals of 5, 10 and 50 nm, according to the ISO/DIS 13837 standard.
In infrared transmission (TIR), the range included in the radiation of the solar spectrum is contemplated, having a range of 800 to 2500 nm, with intervals of 50 nm, using the values of the ISO/DIS 13837 standard.
The total solar energy transmission (TTS) was evaluated in the range of 300 to 2500 nm considering (stationary) wind speed of 4 m/s, according to the ISO/DIS 13837 standard.
The neutral gray glass of this invention can be manufactured by the float glass process from a thickness of 1.4 mm to 6 mm, however, it is not limited only to this range of thicknesses and can be processed as tempered, in double window glazing systems, lamination process or as a substrate covered by one or more layers.
This glass has the following properties: light transmission with illuminant A (TLA) no greater than 15%, direct solar energy transmission (TDS) no greater than 14%, near infrared radiation transmission (TIR) no greater than 14%, ultraviolet radiation transmission (TUV) no greater than 8%, total solar energy transmission (TTS) no greater than 38% and purity no greater than 50%.
This application is the United States national phase of International Application No. PCT/MX2021/050029 filed Jun. 18, 2021, the disclosure of which is hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/MX2021/050029 | 6/18/2021 | WO |
