DD140573A5 - WAERMEDAEMMPLATTE - Google Patents

Description

209 583 - + ·

Application de3? Invention;

The invention relates to a only; a mixture of hochdis].) Cr3cr pyrogenic silica (silica airgel) and aluminum silicate wool with the addition of a turbid agent pressed thermal insulation board. For the definition of the term "pyrogenic silicic acid" cf. I & mpps Chemic-Lxxikon,?. Edition, Dd. 5, page 3220 1st column center.

Characteristic of the known technical solutions:

In the known thermal insulation panels find as opacifiers TiO, rutile, ilmenite, chromium oxide, manganese oxide, iron oxide, but also graphite or carbon black use.

Of the opacifiers listed, graphite and carbon black can only be used at higher temperatures if the permanent absence of oxygen is ensured. In the other case, namely, the turbidity properties of graphite and carbon black were lost by decomposition,. Likewise, a part of the enumerated oxides, in particular, for example, manganese oxide.

But also the otherwise used opacifiers, such as TiO, rutile or ilmenite do not lead to the desired success. Namely, under atmospheric pressure, thermal insulation panels made with such opacifiers have a relatively high dependence of their thermal conductivity on the mean temperature

Aim of the invention;

This is where the invention comes in and wants to create a heat-insulating plate, in which the dependence of their thermal conductivity of the average temperature is much lower and beyond better turbidity properties, especially in the upper temperature range of about 400 ⁰ C can be expected.

Explanation of the essence of the invention:

The object underlying the invention is achieved in that a carbide of silicon, boron, tantalum or tungsten are used alone or in the mixture as opacifiers.

Of course, both silicon carbide and boron carbide at the same fineness more expensive than, for example, the above-enumerated previously used opacifiers. However, it has been shown that in the case of carbides, in particular silicon carbide, it is possible to resort to the use of filter dusts of grinding systems that are no longer usable in the level. This makes a product of economic usability available, which was previously classified as a waste

product, and the elimination of which was not easy due to its poor water quality. The use of such carbides thus makes a useful contribution to environmental protection in addition to achieving the desired technical effects, because now these carbides can be supplied to a useful use.

The specified carbides are characterized by high thermal and chemical stability even at higher temperatures and also have the required low- ^! rige transmission in a wide IR spectral range.

In the accompanying graphical representation the typical behavior of thermal insulation panels is shown using TiO ₂ (curve 1), silicon carbide (curve 2) and boron carbide (curve 3).

• It is apparent from the graph readily that particularly at the high temperature means doors over 100 ⁰ C, the use of silicon and in particular of boron carbide, a significant improvement in the thermal conductivity of the Äbhäiigigkeit 7 \ of the mean temperature t has the consequence.

Of course, it is possible for Wärmedärnnplatten containing TiO "as opacifiers to improve the thermal conductivity in the upper temperature range by increasing the density. Again, however, the proposal according to the invention of the use of carbides as opacifiers so far has an advantage, as thermal insulation boards at the same thickness by about 60% easier, which is desirable in many cases. Of course, the thermal insulation panels made with silicon or boron carbide as opacifier can be improved by increasing the density in the dependence of their thermal conductivity A of the average temperature t.

The clouding agent used according to the invention in the form of a carbide should expediently have a particle size such that the residue is less than 5% mesh on a 10 μm mesh.

For insulations at the atomic level, i. thermal insulation used in nuclear installations on nuclear reactors of various types and on

209 583 -a

In addition to insulating parts of treatment plants, especially when in this area a neutron radiation with thermal energy is present, there are further advantages in the use of boron carbide in that due to its large cross-section against thermal neutrons, the thermal insulation of the corresponding parts with the " It is advantageous if the boron carbide has a proportion of between 20 and 35% by weight.

Example Example:. ·.

  In the following, two embodiments will be given: A thermal insulation board was produced from the following composition:

59.6% by weight of pyrogenic silica 34.8% by weight of silicon carbide "'5.6% by weight of mineral wool.

•

Another embodiment has been used

68.4% by weight of pyrogenic silica 26.04% by weight of earbarbide 5.6% by weight of mineral wool.

The use of carbides for refractory insulating compositions is already known in the art. Thus, for example, a silicon carbide addition to a refractory Faserisolierzusammensetzung consisting essentially of aluminum silicate fiber has already become known from DT-OS 25 57 741 or from its corresponding US Patent 4,014,704. With this mass in particular casting funnels for molten metal are to be produced. Apart from the fact that the grain size of the silicon carbide used there is much higher than in the silicon carbide used in the invention, also missing in this Faserisolierzusammensetzung the use of fumed silica or silica airgel as an essential component of the thermal insulating molding.

From DT-OS 20 05 838 a protective cover for spacecraft has become known, which is intended to peel off under thermal stress. Here are organo-polyoxysilanes "silicon carbide, silicon dioxide and high temperature resistant fibers

added, but the silicon carbide should only serve to improve the Abblattiv-Eigenscliaften the coating. Also, in this case, the grain size of silicon carbide is much higher than that of the thermal barrier plate of the present invention.

Claims (3)

209 583 -s : Claim for invention, 1. .Aus from a mixture of highly dispersed fumed silica / and aluminum silicate wool with the addition of a turbidity compressed heat insulation board, characterized in that a carbide of silicon, boron, tantalum or tungsten alone or in admixture is used as the opacifier. 2. Thermal insulation board according to item 1, characterized in that the opacifier has such a particle size that the residue on the DIN sieve 10μπι mesh size is less than 5%. 3. Use of a thermal insulation board according to point 1 with boron carbide as opacifier in amounts between 20 and 35 wt .-% in nuclear installations. For this yf Page drawing