DE752357C - Process for the production of magnesia cements - Google Patents

Description

Process for the preparation of magnesia cements There are repeated Suggestions have been made, common magnesia cement masses, especially the stone wood, by changing the usual compositions and using new ones Magnesia grades have greater resistance to water and very humid air to lend. The proposed modified mixtures have proven themselves in practice usually cannot introduce either because of the increased levels contained in them Part of magnesia made the laying of such floors uneconomical, or because the dimensional stability did not meet the standards, or because the good sound absorption and thermal insulation of the stone wood is not achieved when processing these mixtures became.

As is well known, the preservation of the magnesia cement is primarily based Line on the hydration of the burnt magnesia and secondarily on the Formation of oxychlorides. The latter never happens so quantitatively that not a considerable part of the magnesium chloride after setting still left over and thus remains water-soluble. Any leaching of free magnesium chloride however, water causes the cement to rot.

It has now been found that the portion of the soluble. permanent magnesium chloride decreases by over half if you use the mortar powder in a special form Basic magnesium carbonate produced by magnesium hydroxide is added. The strength the cements provided with this additive at least decrease when soaked Surprisingly, the still existing leaching of magnesium chlorine is not as usual off, but even significantly too.

It is true that there is always some basic carbonate in normally fired magnesite before; it is known, however, that the magnesia contains a considerable amount of this compound, z. B. 101 / o, for driving and reducing the normal strength of the cement leads. As has been shown, the burning of the Magnesite has no effect on the later water resistance, as does an additive of ground magnesite, limestone powder and other natural carbonates without Influence remains.

In contrast, the new method differs in that the basic carbonate from hydroxide through the action of carbonic acid or reaction with carbonates and added to the burned magnesia. The hydroxide becomes appropriate Obtained by the wet route from mineral acid salts of magnesium. The precipitation of the Hydroxyds and its carbonization can optionally in the same vessel and at the same time take place. The precipitated and carefully dried basic magnesium carbonate is evidently more active than a mixture of burnt with the same gross composition Magnesia and natural carbonates; it contains about 30-1 / o water of crystallization.

The method also has the further advantage that it does Magnesium hydroxide that is sometimes unusable for the stone wood industry makes also applicable. If you burn the hydroxide without prior treatment Carbonic acid or reaction with carbonates, this is how you get one for this industry Much too light product that requires too much water when mixing the mortar and has only about 3o 1 / o of the usual strength values after setting.

Finally, the addition described provides a Reduction of the corrosive effect of the stone wood, as is particularly evident from the lower layers of the laid floor can be observed. In a period in which a stonewood laid in the usual way already dangerous pitting corrosion on unprotected Iron causes normal fluctuations in relative humidity, one can found no serious damage when adding basic carbonate.

The surprisingly good water resistance can also be achieved if the basic carbonate obtained from hydroxide described above briefly, but at extremely high. Temperature (e.g. 1200 ° C) glows well above the usual temperature of burning magnesite, and the fired product alone or mixed with common burnt magnesia with chlorine magnesium lye. The strength Even such cement masses are practically not changed by water after they have set. The use of the commercially available magnesia can be wholly or partially be waived.

As an inorganic filler that can be added to the magnesium mortar in addition to the organic, blast furnace slag has also become known. It was found that this additive alone reduced the strength of the cement under water can only reduce it, but not prevent it. If you replace part of the inorganic However, filler by a mixture of acidic blast furnace slag with the above-mentioned basic Carbonate. this gives particularly good water resistance; one then observes even after storage under water, an increase compared to the samples that were only stored in air the compressive strength by about 181/0.

The described better durability and strength by adding the Annealed and unannealed basic carbonates mentioned above are most pronounced, if in the preparation of the latter from hydroxide and carbonic acid in the presence some ammonia works, e.g. B. with a 10 to 30% suspension of hydroxide in n / 2o ammonium hydroxide solution.

You also get an effect that is at least as good if you click on the filter on which the hydroxide is still from the previous washing, applying a solution of ammonium bicarbonate, or when using solid ammonium carbonates kneads into the hydroxide dough. After carbonization is complete and any Filtration, the basic carbonate is dried at temperatures below 100 ° C.

It is known to use magnesium chloride-containing magnesia mortar in the manner to prepare that from magnesium oxide and magnesium chloride a present in solid form Mixture is produced, which is made with water at the construction site. It has now further shown that one can also do the above-mentioned Dry mix Incorporate sufficient amounts of chloride with basic magnesium carbonates for setting can, whereby powder mixtures are obtained, which after mixing with water harden and then particularly water-insensitive masses, z. B. waterproof stone wood, result. Receives the required chloride content in the carbonate mixture either by adding solid or dissolved chloride to the basic carbonate or by carefully introducing less, appropriately concentrated Hydrochloric acid before drying.

But you can also dry and ground basic carbonates in move a slow stream of dry hydrochloric acid gas and this reaction product then add burnt magnesia.

It is known to use fired products to slow down the setting process Carbonize magnesia, d. h to absorb carbonic acid. Here, however not a basic carbonate of particularly good quality as in the present process Setting ability and masses of particularly high strength obtained therefrom, and in addition, the masses produced afterwards are not sufficiently stable in space. It is coming on the other hand, for the present process, the fact that the carbonic acid is not after the fire the magnesia is absorbed by it, but on the magnesium hydroxide acts before it is fired.

It has also been suggested to use basic magnesium carbonates burn between 55o and 75o '° C; before the firing temperature is exceeded of 75o ° C, however, was expressly warned, because this reduces the setting properties of cement get worse. The procedure mentioned has not been introduced can, because if you keep these firing temperatures, z. B. 735 ° C, a powder which, similar to non-carbonized hydroxide, only has a bulk weight (unshaken) of o, 152 '. To use such a magnesia to become a smoothable To get mortar, its water content must normally be from 31 to 35 0 / ö 39% can be increased. The consequence is that the normal compressive strength of the bound Mortar of about 3oo. kg / cm 'is then not reached, and surprisingly drops this firmness even after three days of soaking, in contrast to higher fired ones basic carbonates according to the present invention, by 2.3.6%.

In contrast, it was in no way to be expected that by short-term Annealing of the basic carbonate to about z2oo! ° C a sufficient density and thereby Magnesia which is particularly reactive and produces good cement compounds is available.

Examples 1. The table below shows seven stone wood mixtures same mortar consistency, of which samples 3 days below after a setting time of 16 days distilled water from 9 to 24 ° C. Along with the unwatered Samples were watered after a further 5 days of compressive strength testing subjected. Setting and drying took place under 6o to 8o% relative humidity. Talc and slate powder were used as inorganic fillers. The composition and the absolute strength values of the mixtures show certain fluctuations, because the mortar consistency is always easy to spread despite the changing densities of some components had to be.

Mixture i shows how, with this treatment, a stone wood manufactured according to the current state of the art loses about 20% of its compressive strength (KD) due to the influence of water; Mixture 2 shows the same behavior to a greater extent for an artificial magnesia; Mixture 3 shows the improvement in water resistance through blast furnace slag, but this does not lead to the solidification of the stone wood under water; Mixture q. shows how the watering remains practically without influence, which is achieved by adding 19.51 / a of a powder obtained from basic Mg C 03 and H Cl gas, corresponding to 9.6% Mg C12; Mixture 5 shows the best consolidation under water, achieved by adding a mixture of 4.7% basic Mg C 03 and iz, 8% of an acidic blast furnace slag; Mixture 6 shows how the strength is practically not impaired by water if the magnesia was obtained via the basic carbonate as an intermediate; Mixture 7 shows a "further improvement of the mixture 6 when 4.2% unfired basic carbonate is added to it; Mixture 8 shows a mixture in which a burnt magnesia is assumed which is carbonized after the firing, i. h: has still absorbed some carbonic acid. This initially gives favorable strength properties, but this mass is not water-resistant and also shows an impermissibly high shrinkage; Mixture 9 shows a mixture that is produced in the same way as Mixture 6, but with the Magnesia is annealed at 7301 ° C. Mixture 1 2 3 4 5 6 7 3 9 from burned MG0 like iristal-bas. (with 2115 C02) at 6, Kind of as baselines from Mg like like like Car- like carbonized after Substance-serving producer (OH) 2 at at bonat at French but at patent specification Magnesia nis des i2oo "C i II I2oo ° C £ '499 314 by 730' C Trade briefly inclusion of annealed 2.7% CO2 gas annealed Min. Glow time ... - 45 - - - 35 35 - 45 01 J ° MAO, techn. . 27.0 25.8 27.0 29.2 27.2 26.6 27.0 29.2 24.8 °% MgCl @ ....... 10.1 8.4 9.4 9.6 10, o 1o, 1 10.2 9.5 9.6 °; '° Hz 0 ......... 33.8 35.9 31.4 37.2 33.5 34.0 34.3 31.9 38.7 ° inorganic ink pen including color fabric ......... 18.5 20.8 8, o 2.6 2.1 18.6 13.9 17.9 16.9 °, j ° bas. Carbonate - - - 9.9 4.7 - 4.2 - - °; @ ° acidic high furnace slag .. - - 13.5 - 11.8 - - - - °;, wood flour .... 1o, 6 9, i 10.7 11.5 10.7 10.7 10.4 11.5 10.0 °,;, ° longitude- ration in 6 days 1 -I- 1.5 - z, 251 -i- 0.5 +0.75 +0.5 -I- 1.0 -f- 1.0 -3.25 1 -I- 11, O Compressive strength after 24 days in kg, cm = not watered ..... 311 145 327 298 261 290 336 311 28o watered ....... 249 43 299 30 24 308 287 362 255 214 % Change by water tion ......... -19.9 - 70.5 - 8.6 -; - 1.3 -E- 18.0 -1.0 -E- 7.8 - 18.0 - 23.6 2. A stone wood mortar according to example i, mixture 1, was molded into a sheet iron can with a wall thickness of 0.3 mm to form a 30 mm thick layer. On the same day and in the same way, a mortar containing 13.30 / 0 basic magnesium carbonate, which had been dried together with 11.30 / 0 magnesium chloride, was molded into a can of the same type. Both cans were stored open next to one another in normal room air. After a year the mixture had eaten through the sheet metal in numerous places on the lower half of the height; the mixture described last did not cause any defects.

Claims (6)

PATENT CLAIMS: i. Process for the production of magnesia cement compounds, characterized in that the magnesia used to mix the cements is still Basic magnesium carbonate produced from magnesium hydroxide by absorption of carbonic acid is added. 2. The method according to claim i, characterized in that the usual Magnesia fired from magnesite is wholly or partly replaced by those which by briefly annealing at i2oo ° C of basic produced from magnesium hydroxide Carbonate was obtained and still partially contains basic carbonate, if appropriate with the addition of further, but unannealed, basic magnesium carbonate. 3. Procedure according to claim i and 2, characterized in that the cement masses apart from basic, contain carbonate produced from magnesium hydroxide, ground blast furnace slag. .I. Process according to Claims 1 to 3, characterized by the use of one made from magnesium hydroxide and basic carbonic acid produced in the presence of ammonia or amniotic salts Carbonate or a magnesium hydroxide treated with carbonates of ammonia. 5. The method according to claim i to 1, characterized in that basic magnesium carbonate with hydrochloric acid solution in the lower amount and / or chlorine magnesium solution stirred, whereby the carbonic acid present in the powder is only partially driven out, then dried and, after mixing with magnesia, mixed with water. 6. The method according to claim 5, characterized in that the basic carbonate in the already dried and ground state with a deficit of hydrogen chloride gas is treated. To differentiate the subject matter of the invention from the prior art are The following publications were considered in the granting procedure: German Patent Specification No. 37a 566; French patent specification No. 499 314-