MXPA97004095A - Reduction of nickel sulfide stones in vid - Google Patents

Abstract

The invention is a method to prevent the formation of nickel sulphide stones in soda-lime-silica glass. Nickel compounds are often added as dyes or enter the glass batch as an impurity of the raw materials. It involves mixing together raw materials of batch, melting and refining them to form a molten glass, the improvement comprising the step of reducing the formation of nickel sulphide stones by adding to the batch materials 0.01-2.0% step of a manganese compound that contains oxygen calculated as manganese dioxide. The manganese compound can be manganese oxide or permanganic acid salts, such as sodium permanganate or potassium

Description

REDUCTION OF NICKEL SULFIDE STONES IN GLASS BACKGROUND OF THE INVENTION Nickel is often included in soda-lime-silica glass as a coloring agent or through pre-existing impurities in batch materials. It can also be inadvertently included because stainless steel equipment, which generally contains large amounts of nickel, is often used when mining or handling batch materials or making glass. As is well known in the industry, the presence of nickel in the glass can lead to the formation of nickel sulphide "stones" which can seriously degrade the quality of the glass. Sulfur comes from sulfates such as sodium sulfate which is used in They are commonly referred to as refining agents during melting and processing of glass. Normally, in the early stages of glass melting, sodium nitrate is included in the batch to achieve oxidizing conditions under which the sulfate is not converted into nickel-reduced nickel sulphide or oxide. Therefore, b oxidizing conditions the formation of ñi sulfide stone that is essentially prevented. The problem arises later in the melting process when conditions can change from oxidants to reducing agents and the sulfate would be reduced to sulfur or reduced nickel oxide to nickel. The nickel-in-glass-sulfide stones are usually too soft to be seen without help and are very difficult to detect by optical inspection elements. The nitrogen sulphide stones pass through a change in the phase of the glass product. during the time that is accompanied -by a volumetric expansion of approximately 4%. When this happens, and if the glass product has been tempered, it may experience spontaneous breakage. This can not happen until a long time after the glass has been installed in a vehicle or in a building. Therefore, the prevention of nickel sulphide stones is an important goal for glass manufacturers. Obviously, one of the easiest ways to prevent the formation of nickel sulphide stone is to not use nickel compounds as a coloring component in glass or to let it in as an impurity. However, nickel oxide is considered a very effective dye and due to this reason it is -used frequently. To prevent the formation of nickel sulfide stone in glass containing nickel oxide as a dye, Cramer, and Col., in the U.S. patent. 3,881,905, describes complex processing conditions to maintain an oxidizing environment through the glassmaking process. In US Pat. No. 4,919,598, Knavish suggests another approach comprising electrically imposing oxidizing conditions near the bottom of the furnace. It would be commercially valuable if glassmakers could use nickel as a coloring component without having to employ complex processing to prevent the formation of nickel sulphide stone. To avoid the formation of nickel sulfide pidra in glass compositions in which nickel is not used as a colorant, glass companies typically specify that their primary materials are free of nickel compounds. And raw material suppliers try to avoid using stainless steel equipment when exploiting or handling raw materials to prevent nickel contamination from stainless steel. Glass manufacturers are also cautious about using stainless steel equipment in their glass making to prevent nickel from penetrating the glass. Even with all these precautions, nickel sometimes finds its way to the composition of glass. In U.S. Patent No. 5,401,287, Pecoraro, and Col. suggest that one way to limit the number of nickel sulfide stones is to add to the batch charge of raw material a material from the group consisting of molybdenum, arsenic, antimony, bismuth, copper, silver, potassium dichromate and iron chromite. All the above materials such as copper oxides and chromium contain materials that can color the glass even when used in small quantities. It would be desirable to have a less expensive and more desirable way of reducing the formation of nickel sulphide stones when nickel is present in the glass materials either as a dye or as an impurity. The present invention provides said solution.

SUMMARY OF THE INVENTION The present invention is a method for reducing the formation of nickel sulphide stones during the manufacture of soda-lime-silica glass having nickel compounds added as a component of the glass batch or entering as an impurity. as with the raw materials of the lot. It involves mixing the raw materials of the batch together, melting and refining them to form a molten glass, the improvement comprising the step of reducing the formation of nickel sulphide stones by adding 0.01-2.0% by weight of a compound to the batch materials. manganese containing oxygen calculated as manganese dioxide. Example of manganese compound containing oxygen is sodium or potassium oxide permanganate. If iron (such as Fe203) is present in the glass, the weight ratio of the manganese compound as calculated as MnO2 to FeOg is desirably less than 6 to 1. Advantageously, the manganese compounds containing oxygen are all oxidants. strong and thus have the distinctive advantage over conventional oxidants such as sodium or potassium nitrates in that these manganese compounds maintain their oxidizing effect on glass at much higher temperatures than that of nitrates. Manganese dioxide, as an example, is relatively inexpensive as a glass batch material and maintains oxidizing conditions through the glassmaking process. It has been found in accordance with this invention that the manganese compounds can be used to replace all or some of these conventional oxidizing materials. Much previous literature has taught that manganese compounds should not be added to glass compositions because the glass is discolored ("suns") during exposure to UV light. However, we have found that mangan compounds can be used without causing sunburn. If iron oxide (such as Fe203) is present in the glass, we have found that by desirably maintaining a ratio of 6/1 or less of a manganese compound containing oxygen calculated as Mn02 / Fe203, sun exposure is impeded.

DESCRIPTION OF THE PREFERRED MODALITIES The typical float glass of soda lime-1 can be characterized by the following composition on a weight percent basis of the total glass: 68-75% SiOp, 10-18% Na20, 5-15% CaO, 0-10% MgO, 0-5% A1203, and 0.5% K20. When nickel is present as a trap material, it is usually in very small amounts generally less than 0.00 weight percent. When the nickel is purposely added to be a colorant for the glass, then the amount is generally greater than 0.002% by weight as Ni. The batch materials blended to produce this glass typically include sand, soda ash, dolomite, limestone, nitrate or sodium nitrite, carbozite and gypsum or salt cake (Na2S04). As will be appreciated by those skilled in the art, process aids such as carbocite are added to maintain the proper balance of oxidation reduction conditions. For example, the carbocite when added to the glass composition has the effect of reducing dyes such as iron oxide to achieve lower infrared transmission, that is, reducing the Fe203 to FeO.

In the method of the invention, the batch materials would add to a typical glass melting furnace and would ignite to melt the molten glass forming components. The oxygen-containing manganese compound can be added together with the initial batch materials or added a little later during melting, depending on whether other oxidizing agents such as sodium nitrate have been added. If it has been done, the manganese compound can be added later. It is preferred to use in its most part or all of the manganese compounds containing oxygen as the oxidizing agents since they maintain their oxidizing capacity through the complete melting process and, therefore, the formation of nickel sulphide stones in the glass melt is reduced. Preferably, it is desirable to add the manganese compound to the melt with the other batch materials. The manganese compound containing oxygen is added to the melt components in an amount of 0.01-2.0% by weight, caulculated as manganese dioxide based on the total weight of the batch materials. Preferably, the amount added is at least 0.02% by weight of the total weight of the materials, of the tea. The amount of manganese compound to be added to the batch will be determined by the color of the glass product. Since the glass transmittance is reduced, more manganese dioxide can be added to the batch with minimal color effect. By "manganese containing oxygen" in this invention is meant a manganese compound that includes oxygen (0) in its chemical formula. This compound includes, for example, manganese oxides such as manganese dioxide (Mn02) or manganese oxide s (MN203); or perganic acid salts such as sodium permanganate or potassium permanganate; carbonates with manganese carbonate, etc. It is preferred that the maj ganeso compound be added as Mn02 because more oxygen is available than with Mn203. The manganese compound may be added to the batch in the form of a partially refined mineral such as pyrolusite containing manganese dioxide. Another way that you can add to the batch is as a component of a processed material, an example of a pio being Brickox from Prince Manufacturing Company. In this processed material, the manganese compound present is approximately 78% Mn02. Using a process material like this is useful because the cost of MnO on a per pound basis is cheaper. However, any manganese compound containing oxygen incorporated into the glass during the fusion process will provide the benefit of the invention by reducing the nickel sulphide stone formations.

Generally, glasses made by the flotation process include iron oxide in some amount, the higher the amount the glass is darker. Iron oxide is often included in commercial glass as automotive or architectural glass because it has the ability to block some of the ultraviolet and infrared radiation from passing through the glass. For example, U.S. Patents 5,346.8 and 5,521,128 filed by Iso present inventors and commonly assigned with the present invention, we describe that in high iron neutral gri glass manganese dioxide can be added to increase selenium retention, a colorant prone to vaporize out of the composition. We have found, in accordance with one aspect of the present invention, that if iron oxide is included as a colorant in the glass, the ratio of the manganese compound containing oxygen (calculated as MnO2 desirably should not exceed six times the oxide). of iron (calculated as total Fe203) We have found that above this level, the ravaged (discoloration) of the glass can occur when it is exposed for a significant time to UV radiation such as sunlight. It is well known to cause rains in glasses that contain iron oxide.The sunny involves chemical reactions in the glass that occur during exposure to UV, a reaction is the displacement of Fe + to Fe +, as the iron moves from the species oxidized (Fe203) to the reduced respect (FeOO is coupled by an undesirable color shift towards blue in the glass product.) Advantageously, we have found that the conditions oxidize These can be maintained through the glassmaking process using manganese compounds containing oxygen not in the glass batch. By maintaining these oxidant conditions, the formation of nickel sulphide stones can be reduced or prevented. We have found that manganese compounds when included in the melt batch in accordance with this invention continue to provide an oxygen source in the glass melt through the glassmaking process. Compared to the invention of Pecoraro 5,401,287, the present invention uses manganese compounds which in themselves provide the oxygen to maintain the oxidizing conditions in the vineyard lot. Manganese compounds are much cheaper in comparison with the materials suggested in the patent, 5,401,287 pa to reduce the formation of nickel sulphide stone. In addition, we have found that manganese compounds tend not to color glass by sunlight unless the glass is very low in iron oxide. By adding very large amounts of manganese, it is necessary to act as a colorant for the glass, they are much larger than those seen in the invention currently described. We formulated several glass samples in accordance with embodiments of the present invention to show the reduction of nickel sulfide stones, when oxygen-containing manganese compounds are added to the glass during the melting process. In addition, in the tables below we show the impaction about physical properties such as color (wavelength) or purge of excitation of these samples by inclusion of manganese compounds. In particular, Table I lists six glass compositions in accordance with the present invention and shows the color shift (based on the length of dominant wave) after the samples were subjected to an accelerated exposure of 1500 hours in a meter. of time Model C i 65, Atlas using a UV lampa of Xenon. This 1500-hour exposure is approximately equivalent to the sun in Arizona for 3 years.

TABLE I- Exposed Wavelength 1500 Original Difference Original in nm. Ex. 1: 556.6 543.7 12.9 0.1T by weight Fe203, 0.2% by weight of Mn02 Ex. 2: 520.1 509.4 10.7 0.3% by weight Fe2 ° 3, 0.2% by weight of Mn02 Ex. 3: 514.1 511.6 -2.5 0.6% by weight Fe203, 0.6% by weight of Mn02 .Ej. 4: 570.6 598.7 -28.1 0.1% by weight of Fe203, 0.6% by weight of Mn02 Ex. 5: 559.5 561.0 + 1.5 0.3% by weight of Fe203, 0.6% by weight of Mn02 Ex 6: 553.5 553.8 +0.3 06. % by weight of Fe203, 0.6% by weight of Mn02 in Table II below, the same six samples were evaluated for changes in purity of excitation. Table I below shows the difference in the 5 of excitation purity before and after 1500 hours of exposure to the previous Xenon light. The exhibition of 1500 hours under the conditions. Severe Light Xenon represents approximately 3 years of real-time exposure in Arizona. The small change to the excitation purity percentage in Examples 1 and 2 is not considered significant and coupled with the low original percentage of purity of excitation for Examples 1 and 2, the color shifts are not considered to have any impact practical about color. Examples 1, 2 and 4 will show a shift in the -color based on the dominant wavelength alone; however, Example 4 is the only glass sample that shows a significant change in color once the change in excitation purity percentage is examined. Example 4 is considered to have made a significant color change under strong ultraviolet exposure and is determined to be "sunny". Therefore, if the molar ratio of Mn02 / Fe203 is 6/1 or greater then we would expect the glass to have the potential to remain sunny and this ratio of 6/1 should not be exceeded for those glasses expected to be used for a prolonged term. UV light. The data in Tables I and II suggest that a molar ratio of 3/1 of n02 / Fe203 will be more acceptable to avoid a color change during the use of the glass. In other applications it may still be desired to maintain the Mn02 / Fe203 ratio to less than 3/1. That is, at low concentrations of Fe203, the glasses of the invention would have a greater tendency to sun when the molar ratio of Mn02 / Fe203 is greater than 3/1.

TABLE II Purity of Exci Exposure of Difference% OriaT 1500 hours nal Ex. 1: 0.6 0.2 -0.4 0. 1% by weight of Fe203, 0.2% by weight of Mn02 Ex. 2: 0.7 0.6 -0.1 0. 3% by weight of Fe203. 0.2% by weight of Mn02 Ex. 3: 1.4 1.4 0.0 0. 6% by weight of Fe203, 0.2% by weight of Mn02 Ex. 5: 2.3 1.4 -0.9 0. 3% by weight of Fe203, 0.6% by weight of Mn02 Ex. 6: 3.5 3.1 0.4 0. 6% by weight of Fe203, 0.6% by weight of Mn02 The Pecoraro patent '287 et al. mentioned above describes in the column, lines 15-25 a procedure to generate nickel sulfide stones in laboratory fusions and using the Pecoraro fusion program we made mergers of the laboratory to demonstrate the improvement by reducing nickel sulfide stones. created when manganese dioxide is used in an area prone to the formation of nickel sulphide stones. New test results, given in Table IV below, show that we reduced the incidence of nickel sulfide stones significantly when manganese dioxide additions are used to the batch. Table III shows the components of base batch melting, without additives, based on weight in grams: TABLE III Sand 500 Sosa Ash 73 Dolomite 121 Limestone 45 Salt Cake 7.5 Paint (grass green only) 3.6 Nickel Powder 0.5 The merger test results made in the same way as Pecoraro's' 287 patent using the base viral lot of Table III are listed in Table IV and these results easily demonstrate the ability of man-made dioxide to suppress formation of nickel sulfide stones: TABLE IV Additive Number of nickel sulfide stones by melting Normal, without additive, without paint 64 0.1% by weight of Mn02, without paint 25 0.4% by weight of Mn02, without paint 5 0.4% by weight of Mn02, with paint 0 From Table IV it can be seen that when 0.1% by weight of MnO2 is added to the batch, a significant drop occurs in the number of nickel sulphide stones. As Mn02 is increased to the level of 0.4% by weight, the formation of nickel-sulfide stones is further reduced. It can be seen that the addition of paint, Fe203, reduces the propensity of glass to form nickel sulphide stones. This result is consistent with the fact that Fe203 is the oxidized species of iron oxide. The paint or carmine typically contains about 93-97% by weight of Fe203 with less than 0.1% by weight of FeO (the reduced concentration). During the manufacture of glass, the proportion - of FeO increases in the melting to 20-30% of the total iron oxide and this also generates oxygen that helps to prevent the formation of nickel oxide stones. It is not desirable to include carmine alone for the purpose of preventing the formation of nickel sulphide stone, however, since even relatively large amounts of iron oxide are not necessary. amente -elvi dr i o-. Because manganese dioxide is a dye d bil, it can be advantageously used to prevent sulphite nickel stones without significantly affecting the color of the glass that could be provided by dyes such as cobalt oxide or selenium. In this discussion, manganese dioxide is intended to be exemplary of any manganese compound that remains oxygenated that may also be employed. Being a weak dye, manganese doxide can be used in relatively large amounts, particularly when cobalt agents such as cobalt oxide are also included in large amounts, without impairing the desired color. Typically as the concentration of dye in the glass increases, the transmittance of glass light will be reduced which helps in masking any color impact by manganese dioxide. In this way, as the concentration of dye is increased, so the concentration of manganese dioxide can be increased to prevent the formation of nickel sulphide stones without this added manganese dioxide significantly affecting the optical properties. desired of glass products. Therefore, this particularity of manganese dioxide as a weak co-agent is important for the present method of the invention.

Claims (6)

CLAIMS:

1. - In a method for manufacturing soda-lime-silica glass in which the raw materials are mixed together, melted and refined to form a molten glass and nickel compounds are added as a component of the lot or which is present as an -impurity in the same capable of forming nickel sulfide stone defects, the improvement comprising the step of reducing the formation of nickel sulphide stones by adding 0.01-2.0% by weight of manganese compound containing oxygen calculated as manganese dioxide to batch materials.

2. The method according to claim 1, wherein the manganese compound comprises at least 0.02% by weight of the batch materials.

3. The method according to claim 1, wherein the manganese compound is added to the lot materials in the form of an oxide.

4. The method according to claim 3, wherein the manganese compound is added to the lot materials such as manganese dioxide, Mn02.

5. The method according to claim 1, wherein the manganese compound is added in the form of permaj manganese or manganese carbonate.

6. The method according to claim 1, wherein the manganese compound is added as a component of a partially refined ore. 1 . - The method according to claim 1, wherein the manganese compound is added as a component of a processed material. 8. The method according to claim 1, wherein the dolote materials include sand, soda ash, limestone, dolomite and salt cake. 9. The method of conformance with rei indication 1, where the batch materials include sand, soda ash, limestone, dolomite and gypsum. 10. The method of confomrity with claim 1, wherein the batch materials include nitrates or nitrites.