NL8200598A - SHAPED PRODUCTS OF HIGH MECHANICAL STABILITY AT HIGH TEMPERATURES, METHOD OF MANUFACTURING THEREOF AND USE THEREOF. - Google Patents

Description

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Br / Bl / lh / 75

Molded articles with high mechanical stability at high temperatures, method of manufacture and use thereof.

The invention relates to molded articles having a high mechanical stability at high temperatures, a method for their manufacture and the use thereof.

Thermally insulating ceramic fiber bodies of refractory fibers, organic or inorganic binder with, on the one hand, low strength and high compressibility and, on the other hand, increased values of strength, density and stability. For example, DE-AS'12 74 10 490 describes a furnace combustion chamber, which is formed by shaping the binder-associated fiber mass and the binder concentration will decrease across the cross-section of the wall. As a suitable binder, clays, alkali metal silicates, aluminum phosphate, colloidal silica with a weight percentage of 5-35, optimally 10%, are mentioned. However, the fiber body is not sufficiently suitable for high loads due to its dense hardwall wall surface and the opposite soft flexible wall surface.

In the method according to DE-AS 27 32 387, the mineral fiber plate, which is pre-bonded with an organic-plastic binder, must be reinforced by impregnation with an aqueous suspension of a binder clay and then by tempering. 0 006 362 plates are known which contain glassy inorganic fibers as reinforcement in a matrix of a plastic clay. The amounts of clay in this case are within a range of 29-80% by weight and the amount of the glassy inorganic fibers within the range of 15-55% by weight of the plate.

The object of the invention is formed articles with improved mechanical and thermal properties, which in particular can also serve as a replacement for light flame plates.

The molded articles with high mechanical stability serve to solve this objective.

5 at high temperatures and good insulating properties, as further defined in claim 1.

Advantageous embodiments of the shaped articles according to the invention are further described in claims 2-5.

The production of the shaped articles according to the invention takes place according to the method, which is further defined in the characterization of claim 6. Preferred embodiments of the method are further explained in claims 7-9.

The shaped articles according to the invention can be used for many purposes, in particular as a replacement for known light flame plates. They have the advantage that they have a lower density than the known plates and that they have a very narrow pore size distribution and a small pore size. Despite the densification, the thermal conductivity is in the same order of magnitude as that of per se known glass fiber molded articles, which are not compacted during their manufacture and are produced by a vacuum-molding method. However, relative to these molded articles, the molded articles according to the invention exhibit considerably greater strength.

Due to their high mechanical strength, the shaped yeast articles according to the invention are particularly suitable as filler elements of expansion joints between the bricks of rotary kilns. Asbestos has hitherto been used for this purpose, but the use of asbestos is increasingly being rejected due to its harmful health effects.

As inorganic fibers, in the molded articles according to the invention, all conventional ceramic fibers, such as rock wool or aluminum silicate-based fibers with an A 2 O 3 content of about 40 to 95% by weight, can be used. applied.

The other refractory additives used in the molded articles according to the invention are the additives usually used for molded fiber articles, such as porcelain flour, chamotte, corundum spheres or vermiculite.

The binders present in the shaped articles according to the invention are phosphate-containing binders, for example boron phosphate, aluminum phosphate or sodium poly-10 phosphate with a polymerization content of n ^ 4 and in particular n = 6 to 10.

The organic binders present in the molded articles according to the invention are the binders usually used in refractory or flame-resistant molded articles, such as starch, sulphite phthalate, molasses, but in particular methyl cellulose. The amount of binder mentioned refers to the solid organic binder, i.e. without water content.

Both the phosphate binder and the organic binder can be added in both dissolved and solid form, however, using methyl cellulose, which is usually added as a 5 wt% aqueous solution, advantageously a portion of this methyl cellulose, in particular with larger amounts of methyl cellulose to be added, is used as an organic binder in solid finely divided form, because otherwise the amount of water incorporated in the composition via such a binder solution becomes too large for 20 hours.

The clay and / or the extra fine Al2O3 and / or the extra fine SiC> 2 and / or the aluminum hydroxides and / or the extra fine magnesium oxide and / or the extra present in the composition of the shaped articles 30 according to the invention fine titanium dioxide and / or the extra fine chromium oxide are components used in known manner in the field of refractories. If clay is used, this is a conventional binder clay or also a preferred special clay, such as, for example, bentonite. By the term "extra 8200598 · # * -4-fine" as used herein, in relation to the above constituents it is understood that these constituents are in extremely finely ground or even in a colloidal state. In particular when using such a colloidal one. conditional materials, such as colloidal SiO4, resp. colloidal alumina it is possible to use only small amounts of binder, namely near the lower limit of 2 wt. parts of such a binder. The binder can be either only a phosphate binder or only an organic binder, but advantageously, however, a mixture of both phosphate binder and organic binder is used, the use of approximately equal amounts of phosphate binder in methyl cellulose as the organic binder in particular 15 is preferred.

Advantageously, the composition of the shaped articles according to the invention contains 5-15 parts by weight of clay, respectively. of the other ingredients mentioned per 100 parts by weight of the ceramic fibers. Of particular advantage is the use of a mixture of clay and in particular bentonite and 1-3 parts by weight of one of the above-mentioned other ingredients, in particular of colloidal silica.

In the manufacture of the shaped articles according to the invention, a burned fiber granulate, the clay and the clay, respectively, are formed from the ceramic fibers or the mixture of ceramic fibers. the other aforementioned ingredients, the optionally present phosphate binder, the optionally used other refractory additives and the optionally used organic binder, a mixture is prepared with the addition of water. If the phosphate binder and / or the organic binder are already in the form of a solution, usually an aqueous solution, the addition of water may be unnecessary. In the preparation in step a) of the process according to the invention, usually 5-25 parts by weight of water per 100 parts by weight of the ceramic fibers are present in the mixture. Phosphate binders, such as sodium polyphosphate and monoaluminum phosphate, as well as organic binders, such as, sulfite phthalate or methyl cellulose, can be used in solid ground form, while it is also possible to use part of these binders in the form of a solution and add the remainder in solid form 5.

The roasted fiber granulate used in the production of the molded articles according to the invention is described in detail in patent application .......

in the name of the applicant of the same date. The preparation thereof takes place in such a way that a) 100 parts by weight of ceramic fibers, 2-15 parts by weight of clay and / or extra fine and / or extra fine SiCl and / or aluminum hydroxide and / or extra fine magnesium oxide and / or extra fine titanium dioxide and / or extra fine chromium oxide, possibly at most 10 parts by weight of other refractory additives and 1-8 parts by weight of phosphate binder, optionally with the addition of a plasticizer in a mixing device. are mixed with about 2-25 parts by weight of water, b) the mixture obtained in step a} is compacted with a volume factor of at least 3, and c) the product obtained in step b) is optionally dried and at temperatures of 80 ° C. 1500 ° C is fired and then comminuted to the desired grain size.

The materials used in the preparation of this fiber granulate are ceramic fibers, clay, or. the other ingredients mentioned, the refractory additives and the phosphate binder correspond to the materials as described above. Methyl cellulose is preferably used as plasticizer. In the preparation of the fiber granulate, the compaction in step b) can be carried out in an extruder, a turntable press or a briquetting machine. The mixing of the components in step a> in the preparation of this fiber granulate can take place in any suitable mixing device, for example in a Drais mixer. Advantageously, 8 2 0 0 5 9 8 4 to 6 fibers prepared as ceramic fibers are used in the preparation of such a fiber granulate, as can also be used in the manufacture of the shaped articles according to the invention. Crushing in step c) in the preparation of this fiber granulate can take place in any device, the maximum grain size usually being 6 mm. However, this comminution can also be adjusted to a specific range, for example, a product with a grain size between 2 and 3 mm can be obtained by comminuting in conventional crushers and optionally sieving the desired grain sizes. The granular material obtained hereby has a density of 0.7-1.75 g / cm and has a pore volume in the order of magnitude of 35-75%. The amount of plasticizer optionally added in step a} in the preparation of this fiber granulate depends on the compaction device used in step b). For example, when using methyl cellulose and densifying in an extruder, an amount of 4 wt. parts of methyl cellulose are added, half of this amount of methyl-20 cellulose as 5% solution. water and the other half is added as dry methyl cellulose. If the compaction is carried out in an extruder, then the step a). amount of water used, however, may not exceed 100 parts by weight.

However, the amount of water used in the manufacture of the shaped articles according to the invention should be kept as small as possible and advantageously only a maximum of 15 parts by weight of water per 100 parts by weight of the ceramic fibers and in particular 30 only 10 parts by weight of water per 100 parts by weight of the ceramic fibers are incorporated in the mixture, so that a dough-like mass is obtained.

The advantage of using a mixture of ceramic fibers and a fiber granulate lies in the fact that a smaller amount of water must be used in the production of the shaped articles according to the invention. The amount of water depends on the content of ceramic fibers and roasted fiber granulate 82 0 0 5 9 8

* V

In the mixture, the required amount of water decreasing the smaller, the greater the amount of burnt fiber granulate in the mixture. The use of a mixture of 50% by weight of ceramic fibers and 50% by weight of the roasted fiber granulate has proved to be of particular advantage.

The dough-like mass obtained in step a) in the production of the shaped articles is introduced into a suitable press, for example a storey press or a table press or also an isostatic press, in step b) of the method according to the invention and for a suitable period of time pressed, this period depending on the type of press used. On a storey press, the pressing time is usually 5-20 seconds.

It is essential that in the manufacture of the molded article according to the invention in step b) the compaction is carried out with a volume factor of at least 3 when using only ceramic fibers or with a volume factor of at least 1.5 when using a a mixture of 80 parts by weight of burnt fiber granulate and 20 parts by weight of ceramic fibers takes place. When a mixture of ceramic fibers and burnt fiber granulate is used in other mixing ratios, this minimum compaction factor lies at values between 3 and 1.5. Favorable values for the compaction factor when using ceramic fibers only are values between 5 and 8 and when using one. mixture of 80 parts by weight of fiber granulate and 20 parts by weight of ceramic fibers at 2.5-4. Of course, with other amounts of ceramic fibers and roasted fiber granulate in a mixture, the favorable compaction factors lie between the above-mentioned limit values.

The maximum volume factor of the compaction when using ceramic fibers only is about 12-14, while when using a mixture of 80 parts by weight of fiber granulate and 20 parts by weight of ceramic fibers, it is at values of 6-8.

If the shaped articles according to the invention are manufactured in the form of fiber plates, they can have a thickness of 1-50 mm.

8200598 ♦ -8-

After pressing, the molded articles in step c) of the process according to the invention are dried at higher temperatures, advantageously between 110 and 18 ° C and can subsequently be tempered at temperatures between 250 ° C and 600 ° C or also at temperatures between 800 and 1650 ° C are baked. However, the maximum baking temperature as well as the maximum operating temperature depend mainly on the starting mixture of ceramic fibers used and to a small extent on any other refractory additives that may be present.

On delivery, ceramic fibers are in the form of a loose wool, which may however be partly densely compacted: In order to allow a better adhesion between the fibers and the binder used and a good wetting of the surface by liquids in small concentrations. the fibers are advantageously prepared to impart the shape.

Mixing units with rapidly rotating mixing heads, so-called turbo mixers, can be used for this purpose, which make the larger agglomerates present in the fiber state available in the delivered state, without shattering the fibers inadmissibly strongly.

In the method according to the invention, if no burnt fiber granulate is used, it is possible to perform stage a) in such a turbo mixer, ie a mixer with rapidly rotating knife heads, which means that the digestion of the fibers and mixing with the further constituents added in this step a), namely clay and / or other aforementioned constituents, optionally phosphate binder, other refractory additives, optionally the organic binder, is carried out. In this case, however, only dry solids are added to effect on the one hand the digestion of the agglomerated fibers and, on the other hand, the homogeneous mixing of the added substances. Subsequently, water and optionally binders used in the form of solution are sprayed onto the mass in the mixing vessel and mixed earlier.

8200598 ψ -9-

Obviously, however, it is also possible to decompose the ceramic fibers first. to carry out a turbo mixer and then add the other additives in another mixer, for example a Drais mixer or an Eirich mixer. This method of operation is used in particular when using vermiculite or corundum hollow spheres as further refractory additives, because otherwise crushing of these materials would occur, and also when using a. roasted fiber granulate 10 mixed with the ceramic fibers.

The molded articles according to the invention have the special advantage that they have very good thermal insulating properties due to the relatively high ceramic fiber content and thanks to the compaction with a volume factor of at least 3 resp. 1.5 nevertheless exhibit relatively good mechanical stability in their manufacture. Furthermore, the resistance to temperature changes (TWBl) is excellent and exceeds 25 cycles.

The invention is further elucidated by means of the following examples. .

In the examples, ceramic fibers of the system A ^ O ^ -SiC ^ are used, i.e. a fiber x material of A with 47% A ^ O ^, 53% SiO2, operating temperature up to 1260 ° C and a fiber material B suitable for higher operating temperatures with 95% Al2 (> 3 and 5% SiO2

The mixtures were partly prepared in a curbo-mixer equipped with a fast rotating blade head (3000 rpm). In this mixer, on the one hand, the fiber material 30 is readily decomposed and, on the other hand, a bulkable or flowing fiber granulate is formed, which contains the raeng components evenly distributed thereover. The fiber granulate mixture appears during further processing to form fiber materials with a low to high apparent density and a particularly homogeneous structure. On the other hand, with a mixer, which has circulating memg arms at relatively low speed, for example an Eirich mixer, less intensive digestion of the fibers and a not so homogeneous 8200598 • ·.

-10- composition of the mixture achieved. The 50% monoaluminium phos faa toplosing is added in the blender near the fast rotating blade head as a spray mist. As a result, with a liquid volume as small as possible, for example 10% by weight of MAP = 6.6 liters, complete wetting of the agglomerate surfaces is achieved. Water is then sprayed onto the mixture in the same manner. The water attacks any dry methyl cellulose present and thereby achieves good green strength of the shaped articles.

Preparation of roasted fiber granules: al In an Eirich mixer, 100 parts by weight of the ceramic fibers Al, 10 parts by weight of binder clay with an Al 2 O 2 content of 35% by weight and 1.5 parts by weight of dry methyl-15 powdered cellulose and mixed together for 10 minutes. Thereafter, 10 parts by weight of 50% by weight of monoaluminum phosphate solution and 2 parts by weight of water were sprayed onto the mass in the mixer under continuous mixing and mixing was continued for 30 minutes.

The product taken out of the mixer was pressed in a multi-stage press at a press pressure of 30 N / mm into a plate-shaped product with a thickness of 30 mm, whereby a compaction with a factor of 5.5 was achieved.

The resulting plate-shaped product was then dried in an oven at 110 ° C for 24 hours and then burned at different temperatures for 24 hours each and then comminuted to a maximum grain size of 3 mm.

The granulate had the following properties:

30 · 'TABLE · · A

Burning temperature (° C) 800 135Q 1510

Apparent density of grains R (g / cm3) 1.34 1.52 1.77 3

Density S (g / cm} 2.60 2.70 2.75 35 Pg (vol.% 1 47.7 43.7 35.6 b) The procedure of preparation a) was repeated, but with a turbo mixer was used, which opened up the fibers. The pressure at stage b) was 10 = 8200598 2? -11- t resp. 15 N / mm, the compaction was at a factor of 4 resp. 5.

After firing at 1350 ° C for 24 hours and comminuting, a granulate with the following properties was obtained:

TABLE B

Compression pressure (N / mm2) 10 15 R (g / cm3) 0.7 1.02 3

Density (g / cm} 2.7 2.7 10 Pg (vol.%) 74 63 4 c) The procedure of preparation a) was repeated, but with the amount of monoaluminum phosphate solution up to Φ5 parts by weight and the amount of water up to 5 parts by weight were increased at a mixing period shortened to 20 minutes. After burning for 24 hours at. JL350 ° C and comminution to the desired grain size, the granules had the following properties:

TABLE C

20 R (g / cm3) 1.29 5 (g / cm3) 2.69

Pg (vol.%) 53.8 d) The procedure of preparation a) was repeated, but an additional 8 parts by weight of chamotte flour were added in the first step. Furthermore, only 8.3 parts by weight of 50% by weight monoaluminum phosphate solution, but, however, 4 parts by weight of water were added at the mixing stage.

2

The compression pressure at the compaction step was 30 N / mm, yielding a compaction with a volume factor of 5.2.

The resulting plate-shaped product was dried at 180 ° C and samples were fired at the different temperatures listed in Table D below. Then the dried resp. roasted product comminuted to a maximum grain size of 3 mm.

The obtained granulate had the following properties: 8200598 -12-

TABLE D

Treatment temperature (° C) 180 800 1200 1300 1500

Apparent density of grains, R, (g / cm3) 1.30 1.26 1.31 1.34 1.48 5 Specific gravity (g / cm ^) 2.60 2.60 2.65 2.68 2.72

Pg (vol.%) 50.0 51.5 50.5 50.0 45.6

The invention is further elucidated by reference to the following examples,

Example I

The following recipe was used

Parts by weight

Ceramic fibers A (with 47 wt.% A ^ O ^} 100

Binder clay (with 35 wt.% A ^ O ^) 10 15 Methyl cellulose, dry 1.5 -

Monoaluminum phosphate solution, 50 wt% fs 10

Water 2

The ceramic fibers A were placed in the Eirich mixer with the binder clay and the dry methyl cellulose and treated therein for 20 minutes, achieving a homogeneous mixing. Then, while the mixer was in operation, the monoaluminum phosphate solution and then the water was sprayed on the mass and mixed thoroughly.

Stones with a size of 405 x 135 x 50 mm were then pressed therefrom at a pressure of 30 N / mm. The compaction factor was 6.0.

After this, the bricks were dried at 110 ° C for 4 hours and then at different temperatures for different temperatures. baked for periods.

The properties measured on the bricks after firing at different temperatures before firing were as follows: / 8200598 '-13- "

TABLE E

800 ° C / 8 h 1350 ° C / 6 h 1510 ° C / 6 h E (g / cm3) 1.34 1.52 1.77

Pg (Tol .- *) 47.7 43.7 35.6 VU (N / mm2) 1408 1303 5291

Cold flexural strength, KBF (N / rrun) 5.0 4.4. 8.2

Resistance to temp. difference-> 25 a »25> 25

Hot flexural strength, HBF (1000 ° σΗΐ? Ιηιη2) 4, 7 6.6 11.6 HEF, 1200 ° C (H / mm2) 6.2 5.9 9.6

Shrinkage after 24 h at 1400 ° C -3.19 -1.89 1500 ° C -6.94 -3.35 -0.16 1600 ° C -10.32 -7.70 -5.45

Chemical analysis: A1205 (Jé) 44.7

SiO2 (jé) 50.7 P205 (*) 2.95

Thermal conductivity, WJiF

(W / m ° K at 700 ° C) 0.45 8200598 -14-

Example II

The same mixture, upon digestion in the turbo-mixer and a lower pressing pressure after firing at 1350 ° C, led to stones with the following properties, with the properties at a pressing pressure of 30 N / mirt from table E also being mentioned for comparison.

TABLE F

Example I Example II

Compression pressure (N / mm2) 30 20 15 10 10 Thickening factor 6.0 5.4 .4.4 3.5

Baking temperature (° C) 1350 1350 1350 1350

Baking time (h) 6 24 24 24 R (g / cm3) 1.52 1.34 1.02 0.7

Pg (vol.%) 4.4 4.1 0.9 0.7 15 HBF, 1000 ° C (N / mm2) 6.6 - 2.0 '0.3 HBF, 1200 ° C (N / mm2) - 5.9 5.6 HBF, 1400 ° C (N / mm2) - - 2.3 0.3 WLF, (W / m ° K at 700 ° C) 0.45 0.25 0.20 0.16 20 Example III '

The following recipe was used

Wt. share

Ceramic fibers A (with 47% by weight Al ^ O ^ J 100

Binder clay (with 35 wt.% A ^ O ^} 10 25 Methyl cellulose, dry 1.5

Monoaluminum phosphate solution, 50% by weight 15

Water 5

An Eirich mixer was used in step a) of the method according to the invention. First, the dry ingredients were placed in the Eirich mixer and mixed for 10 minutes, after which the monoaluminum phosphate solution and then the water were sprayed on the mass. After mixing for another 20 minutes, the mass was taken out of the mixer.

As in Example 1 above, the mixture was pressed into bricks in a press at a compression pressure of 30 N / mm. The compaction factor was 5.2.

The pressed stones were dried at 0 ° C for 4 hours and then baked at 1350 ° C for 6 hours.

; 8 2 0 0 5 9 8 -15-

The properties measured on the resulting stones were as follows:

TABLE G

R (g / cm3) 1.29 5 Pg (vol.%) 53.8 HBP at 1000 ° C (N / mm2) 2.1 KBF (N / mm2) -2.6 WLF (W / m ° K at 700 ° C) 0.35

In comparison with the according to examples I, II

resp. It has been found that bricks produced in III are produced with a higher cold flexural strength when produced in a turbo-mixer and at the same pressing pressure. When prepared in an Eirich mixer, ie without decomposition of the ceramic fibers, it is expedient to slightly increase the amount of phosphate binder and also the amount of water, the water content being advantageously at 8-10%.

Examples IV and V

20 The following recipes were used:

Parts by weight

Ceramic fibers B (with 95% by weight A ^ O ^) 100 100

Binder clay (with 35 wt% A ^ O ^ 10 10 10

Methyl cellulose, dry 1.5 1.5 25 Monoaluminum phosphate solution, 50% by weight 12 15

Water 3 5

The preparation of the mixture in step a); took place in accordance with the procedure of Example II, i.e. using a turbo mixer.

The mixture obtained in step a) was, in accordance with the procedure of Example II, at a pressure of 9 resp. 20 'N / imn pressed into bricks, then dried at 110 ° C for 4 hours and then baked at 1350 ° C for 24 hours. The properties of the bricks obtained were as follows: 8200598 -16- TABLE Η

Example_ IV_V_ R (g / cm2) 0.52 1.01

Compaction factor 3.5 6.7 5 Pg (vol.%) 84.2 69.4 KBF (N / mm2) 0.9 1.9 HBF, 900 ° C (N / mm2) 3.4 HBF, 1000 ° C (N / mm2) 0.8 HBF, 1400 ° C (N / mm2) 0.7 10 WLF (W / m ° K at 700 ° C) 0.19 0.35

Examples VI to IX

The following recipe was used:

Wt. parts 15 Ceramic fibers A (with 47% by weight Al ^ O ^) 25

Ceramic fibers B (with 95% by weight Al ^ O ^) 75

Binder clay (with 35 wt% A ^ O ^) 5

Extremely finely ground pipe clay, <L 44 pm 5

Methyl cellulose, dry 1.5 20 Monoaluminum phosphate solution, 50 wt% 10

Water 2

In accordance with the procedure of Example II, the mixture of Example VI was prepared in a turbo-mixer and at the pressure specified in Table I below to. stones pressed according to the procedure of example I. In examples VII-IK an Eirich mixer was used.

After drying at 110 ° C for 4 hours, baking was done for 24 hours at various temperatures, also indicated in the table. The properties of the resulting stones are shown in the table.

Instead of stones of the dimensions mentioned in example I, the mixtures described here were also pressed on plates with dimensions of 360 x 360 x 18 mm on a hydraulic press. Such plates form excellent aids in baking, for example in the baking of fine ceramic products or porcelain.

8200598 -17-

TABLE I

Example_ VI_VII VIII IX

Pressing pressure (N / mm2) 8 30 30 30

Compaction factor 3/8 5.3 5.3 5.3 5 Drying (° C) 110 110 110 110

Baking temperature control (° C) 1350 1520 1580 1620

Properties: 10 R (g / cm3) 0.57 1.22 1.22 1.31

Pg (vol.%) 79.9 62.1 62.2 59.3 KBF (N / ijim 0.4 3.5 3.6 4.2 HBF, 1000 ° C (N / mm2) 0.8 'HBF , 1400 ° C (N / mm2) 0.8 4.5 4.9 5.6 15 WLF (W / m ° K at 700 ° C) 0.22 0.47 0.49 0.53

Example X.

The following recipe was used:

Parts by weight 20 Fiber granulate a) 80

Ceramic fibers B 20

Binder clay with 35% A ^ O ^ 5

Extremely finely ground pipe clay, <44 µm 5

Extremely finely ground chromium oxide, <44 / um 2 Monoaluminum phosphate solution (50% by weight). 5

Sodium polyphosphate, solid 0.5

Water 5

The fiber granulate, the clay, the pipe clay and the chromium oxide were placed with the solid sodium polyphosphate in a 30. Eirich mixer, after which 5 parts by weight of water were sprayed on and mixed for 5 minutes. Then the 20 parts by weight of the ceramic fibers B were added and mixed for an additional 10 minutes, then the monoaluminum phosphate solution was added and mixed for an additional 10 minutes.

The mixture taken out of the mixer was pressed at a compression pressure of 30 N / mm into plates of 405 x 135 x 15 mm, then dried for 24 hours at 11 ° C and then each time for 8 hours at 800 ° C, respectively. Baked at 1350 ° C. The following properties were measured on the product obtained: 8200598 -18-

TABLE J

Baking temperature (° C) 800 1350 R (g / cm2) 1.8 1.8

Compaction factor 2.0 2.0 5 Pg (vol.%) 35.8 35.8 KBF (N / nrni2) 2.65 6.4 HBF, 1000 ° C (N / mm2) 4.5 7.0 WLF (W / m ° K at 700 ° C) 0.70 0.65

Example XI

The following recipe was used

Parts by weight

Ceramic fibers A 100

Hollow corundum spheres, <3 mm 10.

15 Clay with 35% A ^ O ^ 5

Magnesium oxide 2

Boron phosphate, solid 4.2

Water 9

The fibers were first exposed in a turbo-mixer for 10 minutes. The corundum spheres, the clay and the water were then placed in an Eirich mixer and mixed for 5 minutes, after which the magnesium oxide and the boron phosphate were added and mixed for a further 5 minutes. Then, the fibers released in the turbo mixer were introduced into the Eirich mixer and mixing was continued for an additional 20 minutes.

Plates were prepared from the resulting mixture according to the procedure of Example X. After drying at -120 ° C at 800 ° C, resp. Baked at 1350 ° C.

The following properties were determined on the yerkregen product:

TABLE K

Baking temperature (° C) 800 1350 R: (g / cin2) 1.15 1.1.8 35 Compaction factor 4.1 4.1

Pg (vol.%) 51.9 54.6 HBF, 1000 ° C (N / mm2) 2.8 4.1 WLF (W / m ° K at 700 ° C); 0.63 0.65 - 8200 598 -19-

Example XII

The following recipe was used:

Wt. share

Ceramic fibers A 100 5 Bindraiddel clay 10

Sulphite phalog, dry 9

Water9

In an Eirich mixer, the ceramic fibers, the clay and the solid sulfite phalog were mixed for 10 sainuten 10, after which the water was sprayed on and mixed for a further 2 10 minutes. Stones were pressed as in Example 1 at a compression pressure of 30 N / mrn. After drying for 24 hours at 110 ° C, these stones were pressed at 800 ° C, respectively. Baked at 1350 ° C. The following 15 properties were determined on the stones.

TABLE L

Baking temperature (° C) 800 1350R (g / cm3) 1.18 1.28

Compaction factor 5.1 5.1 20 Pg (vol.%) 54.6 52.6 HBF, 1000 ° C (N / mm2) 1.5 2.9 WLF (W / m ° K at 700 ° C) 0r27 0 , 28 8200598

Claims (10)

1. Molded article with high mechanical stability at high temperatures, made from the following composition: 100 parts by weight of either ceramic fibers or a mixture consisting of at least 20% by weight of fibers and at most 80% by weight of burnt fiber granulate , 2-20 wt. parts of clay and / or extra fine A1203 and / or extra fine SiC> 2 and / or aluminum hydroxides and / or 10 extra fine magnesium oxide and / or extra fine titanium dioxide and / or extra fine chromium oxide, 0-8 parts by weight of phosphate binder, calculated as 0-10 parts by weight of an organic binder, 0-10 parts by weight of other refractory additives, however at least 2 parts by weight of a binder are present, with a density of 0.5 to 1.8, a hot flexural strength at 1000 ° C of at least 0.8 N / mm 2, 20 and resistance to temperature changes of at least 25 times quenching with air. Shaped article according to claim 1, characterized in that it contains bentonite as clay. Shaped article according to claim 1, characterized in that the further refractory additive contains porcelain flour, chamotte or corundum corundum spheres. Molded product according to claim 1, characterized in that it contains sodium polyphosphate or monoaluminum phosphate as the phosphate binder. Molded product according to claim 1, characterized in that it contains methyl cellulose as organic binder. A method of manufacturing a molded article according to claim 1, characterized in that 35 parts by weight of either ceramic fibers or a mixture consisting of at least 20% by weight of fibers and at most 80% by weight of a roasted fiber granulate with 2-20 8200598 a - -21- parts by weight of clay and / or extra fine and / or extra fine SiCl and / or aluminum hydroxides and / or extra fine magnesium oxide and / or extra fine titanium dioxide and / or extra fine chromium oxide, 0-8 parts by weight of phosphate binder, calculated as P2 ° 5, 0-10 parts by weight of an organic binder, however a 2 parts by weight of a binder must be present, as well as 0-10 parts by weight other refractory additives as well as water are thoroughly mixed in a mixer, 10 b) the mixture obtained in step a) with a volume factor of at least 3 when using only ceramic fibers or with a volume factor of at least 1.5 when using a mixture of 80 parts by weight of fiber granulate and 20 parts by weight of ceramic the fibers are densified while imparting the shape, and c) the shaped article produced in step b) is dried and / or tempered and / or baked. 7. Method according to claim 6, characterized in that the compaction in step b) is carried out with a factor of 5-8 when using only ceramic fibers or with a factor of 2.5 to 4 when using a mixture of 80 parts by weight of fiber granulate and 20 parts by weight of ceramic fibers. 8. Method according to claim 6 or 7, characterized in that the compaction at step b.) Is carried out with the production of fiber boards. Method according to claim 5, characterized in that prepared fibers are used as ceramic fibers. Use of the molded articles according to any one of claims 1 to 5 as a baking aid, i.e. underlayers for articles to be baked. 8200598