JPH0143696B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new process for producing silica and metal silicates from solutions of alkali metal silicates. The invention relates in particular to the product obtained during the manufacture of glass and to its uses. It has long been known to produce precipitated silicas by the action of acidifying agents such as silicate organic or inorganic acids. It is also known to produce single or composite silicates in multiple solutions. However, several problems pose significant difficulties with both the product and the process. Such difficulties include product purity, particle size and density, and ease of handling, selection of materials used, and, in addition to those covered above, energy savings related to the process. Thus, for example, in the case of glass manufacturing, although the process has been operating for a long time, the compositions used are produced by melting the various components, which requires the use of high temperatures for long periods of time. In addition to the energy and operational issues associated with
This causes serious problems with regard to the control of the homogeneity of the preparation for glass production, in particular its homogeneity. French Patent No. 6B512292, filed in 1938, discloses that the components of the mixture are not brought into the form of a solid powder by suitable chemical processes in order to lower the melting temperature and shorten the melting time. has already proposed precipitation from solution. However, such a process suffers from a priori difficulties resulting from the necessity, on the one hand, to remove by-products and, on the other hand, to evaporate large amounts of water. In Patent Application No. 804001972 filed on February 8, 1980, the applicant uses a solution of a soluble alkali metal silicate to carry out at least partial substitution with at least one oxide of another metal. A method using reactants in solution form has already been proposed. In practical terms, the process is carried out using solutions of sodium and/or potassium, and the treatment operation can be prepared by metal treatment, i.e. dissolution of metal oxides or hydroxides with nitric acid. Performed with metal nitrates. Although this method provides highly advantageous amorphous and isotropic compositions, it nevertheless produces a variety of metal silicates that are included in the composition. This incurs a disadvantage, and this makes it difficult to ignore the level of energy consumption. By the way, silica and metal silicates are produced by treating an aqueous solution of alkali metal silicate with a water-miscible polar organic liquid so as to make the alkali metal silicate in an insoluble separated form. I recently discovered a new method. According to a first embodiment of the method of the invention, the organic liquid is added directly to the silicate solution and the resulting insoluble form of the silicate is easily separated and optionally ground. Can be done. According to another embodiment, the organic liquid is first dissolved in a solution of metal oxides and salts of metal oxides, so as to produce an organic solution of metal oxides and salts of metal oxides, in particular a methanol-containing solution. and then a solution of alkali metal silicate is added to the organic solution. It is then found that a solution of one or several silicates can be rapidly added to an organic solution, such as, for example, a methanol-containing solution of lead silicate. It will be clearly appreciated that the type of base material and its amount can be varied and intermediate methods of operation can be used. Generally, an alkaline solution containing silica and an acidic solution of an oxide or salt of the modifier oxide group, such as calcium, barium, zinc, etc., are made and either together with one of the two solutions or separately. In the presence of a miscible polar organic liquid that can be added, the two solutions are allowed to react.
In the case of glass-making compositions, alkaline solutions contain glass former oxides such as silica, boron, alumina, etc., whereas acidic solutions contain other oxides, in particular glass modifier oxides. are doing. According to the invention, by carrying out the exchange of multiple cations, very intimate compositions of metal silicates can be produced, which from a product point of view are chemical in nature and This results in a state of homogeneity that is no longer merely physical, while from a processing point of view this results in a single step with inevitable savings both in the cost of invested capital and in the cost of operation. can be operated. The invention is particularly advantageous when two-component, three-component or even multi-component silicates with a high degree of homogeneity are to be produced in a very simple manner. Moreover, it is also pointed out that impurities can be removed more easily than when using prior art methods, if necessary by transferring them in the form of soluble complexes to the aqueous phase. The aqueous solution of silicate used as raw material is
In particular, it consists of sodium and potassium silicates. Such solutions may optionally contain special complexing agents, such as tiron, i.e. 1,2 Certain adjuvants and additives and adjuvants can be included, such as sodium -dihydroxybenzene-3,5-disulfonate. The water-miscible polar organic liquid used is alcohol, especially methyl alcohol. As already mentioned, if silica is to be produced, methanol is added to an aqueous solution of an alkali metal silicate and treated with an acidifying agent. The acidifying agent may be a mineral acid or an organic acid. Mixtures according to the invention having eutectic properties can be prepared in the following simple manner. First, determine the molar ratio of the alkali metal silicate solution that precipitates the alkali metal silicate forming the mixture. The above molar ratios are: Rm = molar concentration of the former oxide SiO ₂ / K ₂ O, Na ₂ O, ... PbO,
It is the total molar concentration of CaO, ZnO... Preparation of alkaline solutions, i.e. solutions of sodium borate, sodium phosphate, or sodium aluminate, if other forming oxides such as B ₂ O ₃ , P ₂ O ₅ or Al _{2 O} 3 are present. , or the addition of solutions of boric acid or phosphoric acid in acid form can be tried. For Al ₂ O ₃ the situation is different as the acid form of this is not soluble, in this case water soluble aluminum nitrate can be used and the molar ratio calculations are as follows: Modify based on selected requirements. Following this, a solution of an alkaline solution of the molar ratio Rm=SiO ₂ /Na ₂ O or K ₂ O and a mixture of oxides dissolved in an acidic medium, for example nitric acid, is prepared. The overall reaction scheme is as follows: Metal salt + alkali metal silicate methanol -> Metal silicate + alkali metal salt This results in a suspension that simply has to be filtered. The solid matter is collected by filtration, and the solid matter is washed to remove dissolved alkali metal salts.
It is observed that the metal elements were combined in the same molar ratio in the form of silicate. If the mixture consists of borates, phosphates, or aluminates, the borates, phosphates, or aluminates of metals that are generally insoluble in the mother liquor are produced in the same manner. The solids described above can be used in wet form or can be dried or vitrified depending on the intended use. In order to vitrify it, it must be heated to a temperature slightly above that at which it can be irreversibly converted to glass. Since there is no need for an excess of salt of one or more substituting metals, and the exchange reaction is complete, salts can even be present in an insufficient state, which means that lead-based compositions In this case, the excess of lead required for the reaction is no longer present in the mother liquor, so
A considerable advantage is that it is possible to achieve full reaction efficiency, eliminate the risk of contamination, and easily recover by-products, e.g. alkali metal nitrates in a highly pure state. You will also be able to do things. Generally, the reactants must be added in such a way that a very fine suspension preparation of the silicate is obtained. According to a first non-limiting embodiment of the invention:
A silicate solution is first formed as a base, then a polar organic liquid is added and then optionally an aqueous solution of an acid and a salt of a substituted metal. The concentration of reactants is preferably near ambient temperature;
It is only limited by the degree of saturation of the reactants in the medium at a given temperature. Furthermore, the solid and liquid phases can be separated, for example by filtration, and then the polar liquid can be recycled. In this embodiment, the amount of methanol relative to the alkali metal feedstock is advantageously substantially equal to or greater than the amount of solids produced. Another embodiment refers to the preparation of an organic solution, in particular a methanol solution, of a group of salts of one or more metal oxides to which a solution of one or more alkali metal silicates is added. . It then turns out that it is possible to quickly add a solution of one or more silicates to an organic solution, such as a methanolic solution of lead nitrate, for example. Furthermore, from an industrial operational point of view, it can be seen that less substantial agitation is sufficient, which results in energy savings. In this embodiment, for the metal, preferably one (or several) alkali metals, the amount corresponds to between one and a half times and three times the amount of solids produced.
It has also been shown that by operating with an excess of polar organic liquid it is possible to improve the homogeneity of the product and reduce the water content of the product. The invention also relates to compositions produced by the method according to the invention. It is particularly known that in common compositions for glass manufacture, the various components tend to behave as if they were present alone, and that the composition becomes homogeneous only at the moment of melting at high temperatures. It is. Now, the composition according to the present invention is in a homogeneous form, and as can be imagined from the differential thermal analysis, it is believed that a complete eutectic mixture is produced in this case. Moreover, the melting point is low compared to conventional mixtures. Now, a critical problem in glass production is the complete melting of silica particles, and this is known to be achieved by adding melting aids, particularly in the form of alkali metal derivatives, in large quantities. The process according to the invention can be adapted to large amounts of molten components in a simple and completely novel manner. In this case, it is sufficient to refer to the figures which indicate the desired melting temperature to be obtained for a given composition. Moreover, as soon as the melting temperature of the eutectic is reached, the glass is already formed, indicating that phase fining begins earlier. It has therefore been found that by adding a finning agent which decomposes at a temperature slightly above the melting temperature, a large amount of foam is rapidly formed and such foam is removed very easily; Because of the phenomenon
The size of the bubbles is such that glass finning operations can be carried out at high viscosity levels and thus at lower temperatures, thus allowing much lower finning temperatures to be used. The products according to the invention can be recommended for many uses. As mentioned above, the products according to the invention enable the glass manufacturing industry to produce glasses of very high quality, homogeneous, free from impurities and of very precise composition. The simplicity of the manufacturing method and the required manufacturing time, which is much shorter than that used in current methods, result in substantial energy savings. Moreover, a wider range of natural raw materials can be used in the above manufacturing method. In fact, a large number of modifier oxides exist in the natural state, but the bonding ratio is highly variable and they contain undesirable impurities. A simple processing operation involving firstly a wet process or gold and then a filtration or separation step makes it possible to directly prepare solutions of the oxides mentioned for use in the proposed process. In this case, the operating method for producing high-quality glass is completely new. In particular, the proportion of oxides has to be determined in advance, based on the ore and possible chemical treatments, firstly taking into account economic criteria. The basic properties of glass, in particular the properties necessary for good quality and for conversion operations, either manual or mechanical, in other words:
Consideration should also be given to refractive index, color, working range or constant coefficient range, and safety against cutting and engraving or etching. Taking the production of crystalline articles containing more than 24% PbO as an example, the raw material used must be lead ore or lead concentrate produced after flotation. However, there are various ores of different quality, so the first step is to study the appropriate wet and gold treatments, and to measure the precise composition of the solution obtained from the wet treatments. A separation treatment is then performed to remove undesirable oxides - generally these are colored oxides, Fe ₂ O ₃ , FeO, CuO, NiO, etc. after that
Obtain a solution with a high content of PbO, which can play an advantageous role during glass production
It also contains other oxides such as ZnO, CaO, BaO, etc. This results in a composition appropriate to the ore investigated. The economical attractiveness of the process of the invention lies in the direct use of this solution. next,
In order to meet the characteristics of the crystal, other oxides,
It is sufficient to determine the proportions of SiO ₂ , B ₂ O ₃ , Na ₂ O, K ₂ O, and LiO, and the properties of the viscosity curve of the glass versus temperature can be used as an index for this selection. If the final composition of the glass has been selected, an alkaline solution of good molar ratio is prepared, which may or may not be modified depending on the circumstances, or a purified solution obtained by wet or gold treatment. It is sufficient to use the method and follow the method already described above. For glasses based on toxic substances such as lead, there is virtually no risk of contamination in vitrified products. Finally, new glass formulations containing smaller amounts of alkali metal elements can be attempted. Coatings or topcoats based on mineral substances - ceramics, glass steels, etc.
In the manufacturing industry, new production methods can be used with mixtures of this type and the hydrated glass can be chemically combined with the carrier to improve the mechanical properties. In the industry that manufactures mineral catalysts based on silica, there are
One of the properties of silicate mixtures can be used. Niwaka Industries can use the above products as high temperature binders. They can be used very advantageously in the treatment of toxic mineral wastes which can be vitrified easily and quickly. However, the invention will be more easily appreciated by the following examples, which are given by way of reference and not by way of limitation. Example 1 Preparation of sodium silicate in powder form with a molar ratio of 3.45. 366 kg of sodium silicate solution containing 23.1% SiO ₂ and 6.9% Na ₂ O are placed in a 600 reaction vessel.
At a temperature of 20°C, add 150 kg of methanol with stirring and filter the resulting suspension, the suspension contains 18.4% precipitated sodium silicate. On the one hand, 356 Kg of mother liquor, 221.3 Kg of water, 5.01 Kg of dissolved sodium silicate, 130.0 Kg of methanol, on the other hand, 160 Kg of wet precipitate containing:
Collect 104Kg of solid sodium silicate and 56Kg of mother liquor. After washing, wet grinding and drying, approximately 110 Kg of sodium silicate in powder form is collected. The ignition loss of this is about 5.4%. This product is sifted and
Rejected material can also be recycled. The mother liquor is treated and distilled to recover methanol. The distillation residue can be recycled to the operation for dissolving the vitreous silicate. Example 2 Example 1 was repeated except that this example added 500 g of Tyron to the initial sodium silicate solution.
is the same as The iron present in the silicate solution dissolves and remains in the mother liquor. In this way, iron-free silicates are produced in a simple manner. Example 3 Powdered Silica 366 Kg of a sodium silicate solution containing 23.1% SiO ₂ and 6.9% Na ₂ O are placed in a 600 reaction vessel.
Add 150 kg of methanol at a temperature of 20°C while stirring. The suspension is then slowly neutralized by adding 51.3 kg of pure nitric acid. Nitric acid may be diluted to 30% or 60%. The resulting suspension consists of 84.5 Kg precipitated silica, 69.2 Kg dissolved sodium nitrate, 150.0 Kg methanol, 256.2 Kg water, or more if the acid has been diluted. Filtration, substantial washing, and drying yield silica in powder form. The characteristics of this are as follows: Ignition residual amount 6% NaNO ₃ 100ppm or less. If necessary, sieving may be performed. The selection of acid is determined by the solubility of the salt in methanol water. Neutralization can be carried out with other organic or inorganic acids, but nitrates have the advantage of high solubility. The mother liquor can first be distilled to recover the methanol and then the salt can be crystallized in an evaporator. Example 4 183 kg of a sodium silicate solution containing powdered calcium silicate with a molar ratio of 3.45, 23.1% SiO ₂ and 6.9% Na ₂ O was placed in a 600-mm reaction vessel, and 75.0 kg of methanol was added thereto at a temperature of 20° C. while stirring. and a 30% solution of 33.4Kg of Ca( _NO3 ) ₂ . The resulting suspension has the following composition: 53.8 kg of solid calcium silicate, 34.6 kg of dissolved sodium nitrate, 75.0 kg of methanol, 205.1 kg of water, filtered, washed and dried to obtain calcium silicate powder. Gain about 58Kg. As in the previous example, the mother liquor is partially distilled and then the sodium nitrate is crystallized. Example 5 200 kg of potassium silicate solution containing trisilicate of potassium, lead and calcium, 21.2% SiOB and 8.8% K ₂ O was placed in a reaction vessel at 600 °C and the temperature
At 20°C, add 80Kg of methanol with stirring and add a solution of lead nitrate and calcium, each containing 19.4Kg of Pb( _NO3 ) ₂ , 9.6Kg of Ca( _NO3 ) ₂ , 71.0Kg of water, The resulting suspension consisted of: 19.5Kg solid potassium silicate, 17.4Kg solid calcium silicate, 27.2Kg solid lead silicate, 0.5Kg potassium silicate dissolved; Potassium nitrate 23.7Kg, water 211.0Kg, methanol 80.0Kg, after filtering, washing with methanol water (methanol 26%) and drying, consisting of a very intimate mixture of potassium, lead and calcium silicates, Obtain a homogeneous powder. When this powder is suspended in a liquid with a specific gravity of 3, whose specific gravity is between that of potassium and calcium silicates on the one hand, and that of lead silicates on the other hand, it does not separate under gravity but completely spreads to the surface. stay It is also shown that the silicates are in the same molar ratio. The present invention is not limited to the above five embodiments,
Other soluble silicates, namely lithium silicate,
potassium, sodium, or quaternary ammonium;
It also applies to solutions of other anionic and cationic metal salts, such as barium nitrate, aluminum nitrate, calcium chloride, ferrous sulfate. Example 6 Manufacture of glass with the following composition: SiO ₂ 57%, PbO 29.5%, K ₂ O 12.1%, Na ₂ O 2.0%, Sb ₂ O ₃ 0.4%, using this composition, alkali metals used as raw materials Determine the properties of the silicate solution. Furthermore, a value of 1% K _{2 O} is selected as the amount of the component to be introduced in the form of nitrate for the finning operation.
Therefore, the molar ratio is Rm=29.5/223.19/11.1/94.2+2/61.9
It is a mixture of metal silicates with a ratio of 8+3.3. In this way, a first solution containing 20.3% SiO ₂ and 9.66% K ₂ O, and 26.7% SiO ₂ and 8.33% Na ₂ O
Two alkali metal silicate solutions are prepared, a second solution containing %. In this method, lead oxide is added in the form of a lead nitrate solution, either by directly dissolving the metallic lead with 15% to 25% dilute nitric acid, or by dissolving the oxide in nitric acid. . In order to produce 25 kg of glass, the operation method for producing glass is carried out in the following manner at ambient temperature. Pour 31.27 kg of lead nitrate solution containing 35% lead nitrate into 200 reaction vessels equipped with stirrer equipment.
Add 50Kg of methanol. Stir the mixture for a few minutes, then add the potassium silicate solution specified above.
Inject 60.8Kg over 60 minutes. Stirring was continued for a further 2 hours and the suspension was filtered to form: On the one hand, after washing, a wet cake consisting of 21.6 Kg of mixed potassium silicate and lead, 0.54 Kg of potassium nitrate, and 22.0 Kg of methanol water; On the other hand, collect the mother liquor and after washing, namely 6.14 kg of potassium nitrate and 120 kg of methanol water. Dry the cake in a drying oven at a temperature of 200°C to take 24Kg of product, then prepare the following mixture in a malaxator: 24Kg of mixed potassium silicate and lead, 0.1Kg of antimony oxide, and 6.0Kg of the sodium silicate solution specified above, then pressurize the mixture into a lump to give it a non-friable form. In some cases, lumps are
Can be dried in a drying oven at a temperature of 200°C. The mass is then placed in a crucible maintained at a temperature of 1350°C. After 5 hours of melting, the bubble content of the glass was less than 1 bubble/cm ³ , indicating the fast rate of the finning operation. In this case, 2 hours is sufficient to produce a very good, very homogeneous glass. In the drawings: Figure 1 shows the finning curve at 1350°C, showing the very short time for this type of operation, Figure 2 shows the differential thermal analysis curve, and Figure 3 shows the infrared absorption curve. shows. Physicochemical analysis of the powder before melting shows unique properties. In detail, in differential thermal analysis, 20
In addition to the separation of bound and unbound water, which prevails between 500 °C and 500 °C, we show that a slightly endothermic transformation occurs at about 700 °C, corresponding to complete vitrification of the powder. There is. Contains 2% powder according to the invention
Infrared spectra produced with KBr pellets clearly show that the structure is close to that of glass, except for the presence of water and potassium nitrate.
Similarly, chemical analysis of amorphous mixtures when raised to different temperatures for 12 hours shows physicochemical transformations. Actually, based on the drying and firing temperature, 100℃
Examining the solubility of the formulation in nitric acid, a substantial decrease in solubility is observed between 600°C and 700°C.

[Table] The values are also these values.
Example 7 The raw material is sulfur or carbonate ore concentrate containing mainly PbO 75% ZnO 3% CaO 2% MgO 1% CuO 0.1% Fe ₂ O ₃ 0.1% and traces of silica and insoluble materials and impurities. It is. This concentrate is treated with nitric acid. A very large proportion of oxides are dissolved. An excess of acid is necessary because of the unavoidable reduction reaction between sulfide and acid that is often present. 120g of concentrate was placed in 410g of 20% diluted nitric acid, and after filtering, a solution containing 24% lead nitrate, 1.5% zinc nitrate, 1.3% calcium nitrate, 0.8% magnesium nitrate, 220ppm CuO, and 220ppm Fe ₂ O ₃ was collected. do. Copper oxide is removed by electrolytic precipitation on lead, and iron oxide is removed by precipitating hydroxide at pH 3.5. Thus, one obtains a solution containing a modifier oxide without coloring properties. This solution can be used in the process of manufacturing the desired glass.

[Brief explanation of drawings]

Figure 1 is a finning curve at 1350°C, Figure 2 is a differential thermal analysis curve, and Figure 3 is an infrared absorption curve before and after melting.

Claims (1)

[Claims] 1. Production of metal silicates from alkali metals and at least one other metal by reaction of an aqueous solution of the alkali metal silicate with a solution of at least one other metal. A method characterized in that said reaction is carried out by mixing said two solutions under stirring in the presence of sufficient methanol so that the metal silicate produced forms a suspension in the methanol medium. A method for producing a metal silicate for a glass-forming composition comprising silica. 2. The metal silicate according to item 1 above, wherein the reaction is carried out by preparing a methanol solution of at least one other metal and adding thereto an aqueous solution of the alkali metal silicate. Production method. 3. The method for producing a metal silicate according to item 1 above, wherein the methanol medium is directly added to the silicate solution. 4. The method for producing a metal silicate according to any one of items 1 to 3, wherein the source of the other metal is a natural mineral substance. 5 The molar ratio of SiO ₂ /alkali metal oxide in the initial silicate results in a
The metal silica according to any one of paragraphs 1 to 4 above, wherein the molar ratio of SiO ₂ to the sum of molar concentrations of metal oxides such as K ₂ O, Na ₂ O, PbO, CaO and ZnO is equal to Method for producing acid salts.