DE2923586A1 - METHOD FOR PRODUCING HEAT-INSULATING, IN PARTICULAR CERAMIC, FASTENED FIBERBODY, FIBERBODY PRODUCED BY THE METHOD AND THE USE THEREOF - Google Patents

Description

- 3 - Case 3028

VXR / P / Lo / Sc

DIDIER-WERKE AG
Lessingstrasse 16-18 6200 Wiesbaden

"Process for the production of heat-insulating, in particular ceramic, consolidated fiber bodies, fiber bodies produced by the process and their use "

The invention relates to a method for producing heat-insulating, especially ceramic, possibly under Use of other binders for solidified fiber bodies.

Heat-insulating ceramic fiber bodies made of refractory fibers, organic or inorganic binders with, on the one hand, low strength and high compressibility and, on the other hand, increased values for strength, density and dimensional stability are known. For example, DE-AS 12 74 490 describes a combustion chamber for ovens, which is formed by shaping the fiber mass mixed with binder, and in which the binder concentration is to decrease over the cross-section of the wall. Clays, alkali metals, aluminum phosphate, colloidal silica with a weight fraction of 5 to 35, optimally 10 % , are mentioned as suitable binders. However, because of its dense hard wall surface and the opposite soft, flexible wall surface, the fiber body is not sufficiently suitable for high loads.

In the method according to DE-AS 27 32 387 should .die with a Mineral fiber board pre-bonded with organic plastic binder by impregnation with an aqueous slurry of a Binding clays and subsequent tempering are solidified. That

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The method according to DE-OS 16 46 696 sees the stiffening of thermal insulation from a fiber layer through the Treatment of the surface and partially the underlying First coat with silicate sol. The thermal insulation treated in this way is also used as a lining for a gutter Molten metal provided. According to DE-AS 20 49 054 Shaped bodies made of refractory heat-insulating material with a homogeneous structure can be obtained by applying microwave drying, e.g. for insulation of turbine housings, for lining gas convectors and for lining stoves. As preferred Mixtures of colloidal silicon dioxide sol and aluminum silicate fibers are called compositions. These but have already known heat insulating fiber bodies the disadvantage that they are insufficient at high temperatures Dimensions are stable, corrosion-resistant and dimensionally stable.

The object of the invention is to avoid the disadvantages previously occurring in thermally insulating, solidified, in particular ceramic fiber bodies, and to create fiber bodies which have a high degree of spatial stability and resistance to erosion as well as high chemical resistance to hot and aggressive, in particular acidic, gases with practically unchanged bulk density and have thermal conductivity. Such aggressive gases contain, for example, SO ₂ , CL, F, as acidic reacting constituents, which in some cases severely attack or corrode the fibers used to manufacture the fiber bodies, in particular ceramic fibers.

This object is achieved by a method, which is characterized in that the shaped in a manner known fibrous body impregnated with a wässriqen monoaluminum phosphate solution, dried, heat-treated at at least 400 ⁰ C and optionally fired.

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A 20 to 50%, preferably 30 to 40%, aqueous monoaluminum phosphate solution is advantageously used for the impregnation of the fiber bodies. It has been shown that with such a concentration, the solidification and also the dimensional stability of the fiber bodies is achieved in an optimal manner at high temperatures. With a higher concentration there is already the risk of a noticeable structural change when the fiber bodies are used. Thus, showed fiber body of aluminum silicate fiber 47 wt .-% Al? ^ 3 ^NaCN hour treatment with a 40% mono aluminum phosphate solution and firing at 1000 ⁰ C for 4 hours while a linear stretch was found from about 1% no Schw1ndung _s with 50 Xiger monoaluminium phosphate solution .

Preferably, the fiber bodies are fired at 800 to 1400 ⁰ C, whereby a further improvement of the soundness of the body can be achieved. Firing the tempered fiber bodies is not necessary in every case, however, since this firing or heating to higher temperatures can only take place when the fiber bodies are used, for example as feed in an oven or a reaction vessel.

Furthermore, it has been found to be advantageous in to add a small amount of sodium polyphosphate to the manufacture of the fiber bodies. According to an advantageous embodiment the sodium polyphosphate can be added to the monoaluminum phosphate solution in solid or dissolved form be, and it is here expediently in an amount of 0 to 15% by weight, based on the monoaluminum phosphate present, is present. According to another advantageous embodiment the sodium polyphosphate can also be used in an amount of 0-5% by weight, based on the amount used for production of the fiber body used, ceramic fibers to the aqueous slurry of fibers during manufacture of the fiber body are added, in which case it is expediently added in solid, finely divided form will. 030051/0224

292358a

Known methods, such as shaking in, can be used in the production or shaping of the fiber bodies and pressing a moist mixture of ceramic Fiber and binder or the pouring of a corresponding suspension into a mold provided with a sieve bottom and Aspirating the liquid. Reference is made to DE-AS 19 46 018 for the procedure in the latter process.

According to a further advantageous embodiment of the invention it is provided that in the presence of a further binder, not yet set fiber bodies with the fully saturated with aqueous monoaluminium phosphate solution and then the excess solution is removed. In this way, a more uniform one is advantageously achieved Structure of the fiber body and, on the other hand, the concentrated one Use of a relatively small amount of monoaluminum phosphate solution achieved. It can, however, also be proceeded in such a way that the tied and dried fiber bodies with the fully saturated with aqueous monoaluminium phosphate solution and then remove excess solution.

The fiber materials used to manufacture the fiber bodies, in particular ceramic fiber materials, are the known materials in particular on the basis of aluminum silicate with in particular high A ^ Og content in the range of 45 to 95% by weight.

In the method according to the invention, however, mineral fibers can also be used such as rock wool or glass fibers are used. These glass fibers are advantageously used in chopped form, i.e. with a length of 1 to 5 mm, but it is also possible to use so-called ground fibers, which range in length from 100 to 500 µm. The diameter the fiber material is generally of the order of magnitude from 1 to 25 µm, in particular in the range from 2 to 8 µm.

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Of course, however, it is also possible to use fiber material to use with other dimensions.

In the production of fiber bodies according to the prior art it is already known to use binders, which can be of an inorganic or organic nature. Examples For inorganic binders, clays, finely ground chamotte, bauxite, clay or bentonite are an example of an organic one Binder is starch. In the method according to the invention however, it is not absolutely necessary to use such a binder in addition to the monoaluminum phosphate which acts as a binder to be used, i.e. it is easily possible to produce a fiber body from the fiber material suspended in water in the usual way, for example by means of a suction box, and to remove this fiber body (before or after it is dried) according to the invention with the monoaluminum phosphate solution treat.

Monoaluminium phosphate is understood to mean the compound Al (HpPO ₄ )., Which is commercially available as a 50% strength aqueous solution. Such a 50% aqueous solution can be further diluted with water as required.

Since the fiber materials used to manufacture the fiber bodies are partially attacked and corroded by phosphates and also monoaluminum phosphate, the use was not considered such fiber materials together with monoaluminum phosphate solution is not close, surprisingly, however, it has been found that obtained by the method according to the invention fiber bodies in which, in addition to good consolidation, the structure and the application limit temperature of the fiber material at the same time remain.

The fiber bodies produced according to the invention can be in the usual forms, for example as mats, plates, Pipes or any fittings.

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The fiber bodies made by the method of the invention Because of their high resistance to erosion and chemical resistance, they are particularly suitable as a lining for Pipelines for using under high pressure and high temperature gases flowing at high speeds are suitable. The fiber bodies can also be used as heat-insulating and little heat storing material can be used in furnaces as a layer facing the combustion chamber. The strength of the fiber body can be further improved by adding sodium polyphosphate and adjusted.

To be performed in the invention process annealing at a temperature of at least 400 ⁰ C is a function of the size and shape of the fiber body prepared for a period of generally from 0.5 to 4 hours, preferably 1 was carried out to 3 hours, wherein the maximum temperature tempering usually does not exceed 600 ⁰ C and 550 ⁰ C advantageously.

The firing of the tempered fiber body, which may have to be carried out, is also dependent on the size and shape of the fiber body carried out for a period of 0.5 to 4 hours.

Naturally, it is however also possible that the annealing treatment and the firing treatment merge into one another and that, particularly when fiber bodies of small dimensions, in which a temperature equilibrium in the fiber body is quickly reached, only one heating up to firing temperatures, in particular 800 to 1400 ⁰ C in the following the drying of the fiber bodies takes place so that the tempering treatment and the firing treatment continuously merge into one another.

When impregnating the fiber bodies usually produced with the monoaluminum phosphate solution, adsorption thereof takes place within the fiber body, so that a certain Amount of monouminophosphate remaining on the fibers. This forms a protective layer for the fibers. Depending on the

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Concentration of the monoaluminum phosphate solution used and, depending on the diameter and length of the fibers, a more or less large amount of monoaluminum phosphate will remain on the fibers. However, by changing the concentration of the monoaluminum phosphate solution used for the impregnation and the strength of the suction of the impregnated fiber body, it is possible on the basis of simple preliminary tests to regulate the amount of monoaluminum phosphate remaining in the fiber body. This can be determined chemically in a simple manner after the fiber body has been completed and is usually given as P ₂ 0, - 6 content. The fiber bodies produced according to the invention generally contain contents of 5 to 38% by weight of P ₂ O _5, advantageously of 10 to 32% by weight of P 2 O 5.

The invention is illustrated in more detail by means of the following examples.

example 1

In a batch with 1800 l of water, 30 kg of ceramic silicate _{fibers with 52% by weight of Al 2} O _{3 and 48% by weight of SiO 2 were used} as the main components in addition to the usual impurities with a length of 2 to 3 mm and a diameter of 2 to 3 fim mixed in together with 1.5 kg of starch and 2.2 kg of bentonite at ambient temperature. A mat with a thickness of 25 mm was formed from this suspension in a suction box measuring 500 × 1000 mm. After the water had been suctioned off, the mat was dried at 120 ° C. for one hour. After drying, a piece was cut out of this mat as a comparison sample.

0s rest of the dried mat was washed with 7 1 of a 33 weight Xi gen mono-aluminum phosphate solution at ambient temperature for ten minutes completely soaked and then excess mono-aluminum phosphate solution of the mat using was aspirated a screen as a support, the mat was again dried at about 130 ⁰ C and then the two mats an annealing treatment at 420 ⁰ C for two hours were subjected.

The mat treated and tempered according to the invention with "monoaluminum phosphate solution" showed in the analysis a content of 27% by weight P ₂ O ₅ -

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The following table shows the properties determined for this mat together with those of the comparative mat, which had not been treated with monoaluminophosphate solution.

Tabel:

according to the invention without treatment

with monoaluminium phosphate solution

Bulk density (g / cm ³ ) 0.48 0.26 Cold bending strength (N / mm ² ) 1.0 0.3

'Flexural strength according to

4 h firing at 1000 ^° C. 1.0 0.06

Shrinkage after 24 hours

at 1000 ⁰ C - 0.75 - 1.83

at 125O ⁰ C - 1.1-3.25

From these values it can be seen that the inventive fiber body treated with monoaluminophosphate solution ■ · has better properties than the comparison sample.

It was also found that the gas permeability of the fiber body according to the invention remained practically unchanged was.

Example 2

The procedure described above was repeated except that a slurry of the fibers was used which only 30 kg of the fibers used in Example 1 in 1800 liters of water

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contained. From this, in accordance with the procedure of Example 1, a fiber body in the form of a mat was produced, which was soaked with 7 liters of the monoaluminum phosphate solution used in Example 1. After heat treatment at 45O ⁰ C in a very stable mat was obtained.

Example 3

The procedure of Example 1 was repeated, except that ceramic fibers with 95% by weight of Al ₉ O ₁ and 5% by weight of SiO _{9 were} used, which had a diameter of 1 to 2 µm and a length of 1 to 2 mm . A mat with excellent mechanical properties was obtained.

Example .4

In this example, milled fibers were used which were 1 to 2 µm in diameter and 200 to 200 in length possessed. A mat with a somewhat lower density and excellent gas permeability was obtained.

Example 5

Following the procedure of Example 2, a mat of ceramic fibers with 62% by weight of Al ₂ O ₃ and 38% by weight of SiO _{2 was} produced. The mat was heat-treated for two hours at 440 C and showed after a two-hour firing at 1000 ⁰ C an excellent gas permeability and good mechanical properties.

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Example 6

The procedure of Example 2 was repeated, except that the suspension of 35 kg used in Example 2 was used Fibers in 1,600 l of water was run out. To this, 1.5 kg of starch and 0.75 kg of solid, finely ground sodium polyphosphate were added and then the fiber suspension obtained immediately poured onto the sieve.

After impregnation with the mono-aluminum phosphate solution, and tempering at a temperature of 400 ⁰ C a fiber body in mat form with a slightly lower porosity was, however, increased obtained mechanical strength.

Example 7

The procedure of Example 6 was repeated, except that 0.75 kg of solid, finely ground sodium polyphosphate was not added the fiber suspension, but to the monoaluminum phosphate solution used for impregnation.

There was also a fiber mat with lower porosity, but get better adhesion of the individual fibers together after firing the mat at 950 ⁰ C.

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Claims (11)

2323588 Case 3028 VXR / P / Lo / Sc DIDIER-WERKE AG
Lessingstrasse 16-18 6200 Wiesbaden "Process for the production of heat-insulating, in particular ceramic, solidified fiber bodies produced by the method Fiber bodies and their use " Claims ι Iy process heat insulating for the production, in particular ceramic, further optionally using binder solidified fiber body, characterized in that are that the shaped in a manner known fibrous body impregnated with an aqueous mono-aluminum phosphate solution, dried, heat-treated at at least 400 ⁰ C and optionally fired. 2. The method according to claim 1, characterized in that the fiber body with a 20 to 50% strength, in particular 30 to 40% aqueous monoaluminum phosphate solution to be soaked. 3. The method of claim 1 or 2, characterized in that the fiber bodies are fired at 800 to 1400 ⁰ C. 4. The method according to any one of the preceding claims, characterized in that the not yet set fiber body with the aqueous monoaluminium phosphate solution are soaked, and that then the excess solution is removed. 030 "05 Ϊ / 0224 292358Θ -z- 5. The method according to any one of claims 1 to 3, characterized in, da3 the bound and dried fiber bodies with the aqueous monoaluminium phosphate solution are completely soaked, and that then the excess solution is removed. 6. The method according to any one of the preceding claims, characterized in that a monoaluminium phosphate solution for impregnation which contains a small amount of sodium polyphosphate is used. 7. The method according to any one of claims 1 to 5, characterized in that that a shaped fiber body is used for impregnation, sodium polyphosphate in its production has been used. 8. Heat insulating, especially ceramic fiber body, produced by the method of one of the preceding claims. 9. Use of the fiber body according to claim 8 for thermal insulation of pipelines for those flowing under high pressure, high temperature and / or at high speed Gases. 10. Use of the fiber body according to claim 8 for the lining of reaction rooms in particular ovens with an acidic atmosphere. 11. Use of the fiber body according to claim 8 as a wear lining into liquid metals, especially aluminum melts, Containing vessels in particular in the case of transport vessels. 030051/0224