DE2215047C2 - Process for the production of vitreous, porous moldings - Google Patents

Description

was possible, the method according to the invention offers the possibility, by varying the state conditions, to produce glass-like, porous moldings of very different nature, namely one Series of moldings with increasing density and increasing compressive strength as a function of the respective excess steam pressure reached in the conversion vessel at which the conversion had been canceled and which is decisive for the content of the conversion product of Zeolinh. This is because, depending on the level of the excess steam pressure, precipitates of the sodium aluminum silicates are formed in gel or crystal form. In the crystal form, it is zeolites that are hydrothermal, i.e. H. from sodium aluminum silicate gels, or primarily through precipitation from the melt. In the In gel form, they are sodium aluminum silicates, which can be produced both by precipitation of the gels and by glassy ones May have formed solidification.

Ao is therefore important for the method according to the invention the fact that the nature of the conversion product depends essentially on the excess steam pressure so that the nature of the finished products, which depend on the properties of the conversion products, is controlled by the water as steam overpressure can be influenced.

In preferred embodiments of the invention The process is similar to the previously proposed process except for hydrous alkali silicates also used other silicate material. Preferably used as a silicate Material ground rocks rich in agirine, natural or artificial zeolites and / or other easily fusible ones Silicates are used, but in general all natural and artificial silicates are included under silicate material, such as silicate rocks, quartzite, fly ash, blast furnace slag and also common building sand to understand. If the silicate material does not contain aluminum, the one used as the starting material must be used Mixture of aluminum hydroxide are added, so that in each case alkali aluminum silicates during the conversion arise in gel form or in the form of crystallized compounds.

The silicate material can either be added to the mixture in comminuted form, similar to the method already proposed, before heating. The amount to be used can be in a ratio of 2 to 6: 1 to the water-containing alkali metal silicates. According to another variant of the method according to the invention, however, the silicate material is added to the conversion product. In this case the ratio of the silicate material to the conversion product can be 0.02 to 6: 1. The addition of silicate material to the conversion product has the considerable economic advantage that this material does not have to be subjected to the pretreatment in the closed vessel, so that only a fraction of the mass required for the production of the shaped body has to undergo such a pretreatment. Furthermore, the conversion product, which is obtained from a mixture free of silicate material, can be comminuted particularly easily. The already comminuted silicate material is only dry mixed with the likewise comminuted conversion product before the mixture is heated ^{to 700 to 95O 0 C to produce the molded body.}

That the conversion products formed in the process according to the invention are not as in the already proposed method crushed down to a grain size between 0.1 and 1 mm, but are ground finely, has its reason that the conversion product of the invention Process predominantly from crystals and not, like the conversion products of the proposed process, consist primarily of gels.

The examples discussed below are intended to further illustrate the invention.

example 1

500 g of basic, plagioclase-rich rock (basalt, bytownite, anorthosite) were finely ground and then _{mixed with 212 g of sodium metasilicate 5 hydrate and 82 g of boric acid (H 3} BO ₃ ). The mixture was then heated ^{to 200 °} C. in a closed vessel with a capacity of 1.3 l, which was equipped with a manometer and a pressure valve. The excess steam pressure in the vessel rose slowly. This process step was terminated when a specified excess steam pressure was reached. The conversion product obtained in this way was ^{dried at 200 °} C., then finely ground and heated ^{to 700 to 900 ° C. in a mold.} This procedure was repeated several times and the conversion process was stopped at various pressures. In this way, moldings of different compressive strength and different density were obtained, which are given in the table below:

Steam
overpressure
aiii Compressive strength
kg / cm ² Volume weight
g / cm ³ Obis I 10 to 20 0.15 to 0.18 2 25.6 0.21 5 37 0.27 8.75 47.5 0.32 10.5 57 0.37 11.3 65.6 0.41 11.6 73.3 0.4S 12th 80 0.50

Example 2

50 g of ground sand, 20 g of sodium metasilicate 5 hydrate, 7.5 g of boric acid and 7.5 g of aluminum hydroxide (alumina gel) were mixed and then heated to 200 ° C. for 2 hours in a closed vessel. The conversion product obtained in this way was then ^{dried at 200 °} C., ground and filled into a metal mold. When heated to about 950 ⁰ C, a fine-bubble foam body was cooled in the glass relaxation oven of 500 ° C in the course of 2 hours to temperatures below 5oC formed.

Example 3

82 g of boric acid, 212 g of sodium metasilicate-5-hydrate and 80 g of aluminum hydroxide were mixed together and heated ^{to 200 ° C. in a closed vessel.} In this way, an alkali aluminum silicate containing boric acid with the composition HiMe ₂ O · Al ₂ O ₃ · nSiO ₂ · pH ₂ O + qH ₃ BO _{3 is} obtained. The conditions for the formation of this conversion product are the specific alkaline environment established by the addition of boric acid, the reaction temperature in the vessel and the excess steam pressure. The conversion product obtained is

then dried at 200 ^° C. and finely ground. In this embodiment, the gel form is preferred for the conversion product, which leads to finished products with a lower density. The gel powder obtained as a conversion product was further processed in detail as follows:

a) The gel powder was heated without admixtures in a metal mold at 800 ⁰ C. Glass-like, porous moldings with a very low density of about 0.2 g / cm ³ were formed with foaming.

b) The gel powder was mixed with old powder in a weight ratio of 1: 1 and heated ^{to 90O 0 C in a metal mold.} In this way a foam body was created which had about the chemical composition of normal glass, namely 72.2% glass formers (SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ ), 12.9% oxides of divalent metals (CaO, MgO ' , FeO) and 14.3% NeuO. The density of the foam body was between 0.2 and 0.3 g / cm ³ .

c) The gel powder was mixed with basalt powder in a weight ratio of 3: 4. By heating to 900 ° C., a shaped body with a density of about 0.3 g / cm ^{3 is obtained} .

d) By mixing the gel powder with basalt powder in a ratio of 1: 2 and then heating the mixture to 950 ° C, a molded article with a density of 0.5 g / cm ^{3 was obtained} .

Example 4

The process according to Example 3 was repeated, but instead of basalt an aegirin-rich rock material was used. The shaped bodies produced from the mixtures of the gel powder and it from a rock material rich in aegirin had a density of between 0.08 and 0.20 g / cm ³ . Similar results are also achieved if, instead of the rock material rich in aegiri η, another easily meltable silicate material is used.

Claims (5)

Ratio is achieved that the humidity of the Claims: Mass during the entire conversion process remains constant. Compliance with this condition is at Process for the production of vitreous, po- the proposed process the prerequisite for red shaped bodies, in which a water-containing 5 for that a product with constitutionally bound alkali metal silicates-containing mixture is made possible by water. It is this water contained in the conversion product in the closed vessel to 140 to 50O ⁰ C, which dries when the converted and the conversion product ground conversion product is heated in the form, ground and finally in a form to temperatures between 700 and 95O ⁰ C Temperatures between 700 and 950 ⁰ C are released and the foaming of the at these temperatures takes place, characterized in that the molten conversion product causes
the mixture before heating polybasic, the moisture constancy for a longer weak to at most medium strong, oxygen- time span is also required in the proposed method about the same amount of acids of non-metals to dissolve silicate material or molar ratio to the alkali silicates and / or 15 at least to be dissolved, so that a water-containing Nafeinverteiites aluminum hydroxide (alumina gel) trium-aluminum-silicate can arise. The invention is added, the conversion in a water dung takes place in an improved form of the earlier pre-charge steam overpressure, which is allowed to rise up to at most a specific method, which consists in 12 atmospheres, so that the conversion in the mixture before heating Polybasic, product at an overpressure of about 1 atm. ao weak to at most medium strength, oxygen-containing sodium-aluminum silicate gels and, in the case of acids of non-metals, about an equimolar increase in pressure from the sodium-aluminum ratio to the alkali silicates and / or finely divided silicate gels how aluminum hydroxide (alumina gel) is added, and contains zeolites, and that the dried conversion product is ground finely at a water vapor pressure conversion product. 25 follows, which is allowed to rise to a maximum of 12 atmospheres, 2. The method according to claim 1, characterized in that the conversion product is at an excess pressure shows that the mixture was crushed by sodium-aluminum-silicon before heating to about 1 atm silicate material in the ratio katgele and with increasing pressure from the sodium of 2 to 6: 1 crystals formed in the hydrous alkali silicates, aluminum silicate gels, such as anal added will. 30 cim and zeolites, and that finally the dried 3. The method according to claim 1, characterized in that the conversion product is milled as fine as a flour, draws that the conversion product silicate- While in the proposed process the cal material in the ratio of 0.02 to 6: 1 with constant moisture content during the conversion mixture will. Process by choosing an optimal filling 4. The method according to claim 2 or 3, characterized in that 35 degrees was achieved, according to the present characterized in that as the silicate material invention, the formation of water-containing sodium-alumiaegirin-rich Rock flour, natural or artificial silicates by adding one of the alkali silicates borrowed zeolites and / or other easily fusible equimolar amounts of polybasic, weak ones Silicates are used. to at most medium-strength, oxygen-containing acids 5. Achieved the method according to any one of the preceding 40 of non-metals. Thereby arise depending on Claims, characterized in that the level of the excess water vapor pressure failure of the pen oxygen-containing acid of a non-metal boric acid sodium aluminum silicates in gel or crystal form, is used. Instead of a polybasic, weak acid can In some cases, finely divided aluminum hydroxide (clay 45 earth gel) can also be used. When heating the mixture in the vessel creates melts, which are caused by a very considerable lowering of the melting point come about, depending on the content of water and acid The discovery relates to a process to be attributed. For example, the pure production of vitreous, porous moldings melts at 50 K ₂ Si ₂ O ₅ at 1015 ° C. while an addition of about 8% to the water containing a hydrous alkali silicate lowers the melting point to about 500 ° C. by heating the mixture in a closed vessel on and a further addition of an acid, for example of up to 500 C converted and the conversion boric acid, the melting in the range of after the product dried, ground and finally in a method according to the invention for application kom-form to temperatures between 700 and 950 C 55 changing transition temperatures enables
is heated. The resulting in the method according to the invention Such a method is the subject of the current melt is in particular able to solve larger, older patent application P 2121 574.7 (German open quantities of plagioclase and by imposing it with application 2 121574). In the process proposed in this older of the melt the Na ₂ O-Al ₂ O ₃ -4SiO ₂ molecule to bil patent application, a mixture is used which, in addition to the water-containing z. B. Increase of the water vapor overpressure, as alkali silicates contains natural silicates in the ratio of analcime (Na ₂ O · Al ₂ O ₃ · 4SiO ₂ · H ₂ O) to a ratio of 6: 1. The heating takes place at constant separation. The primarily crystallized, magna volume of the system, which bypasses the vaporous analcime, also exists in nature, even if a specific phase is selected from which the genuinely hydrothermal formation is more frequent.
temperature and the composition of the mixture. In contrast to the already proposed ratio of vascular volume to volume, which only takes place with fixed, optimal amounts of the mixture. By choosing the right condition, the alkali silicates will dissolve