DE102008053231A1 - Concrete-free composite material used for heat and sound insulation contains a hydrophobic aerogel granulate and at least one refractory material - Google Patents

Abstract

Concrete-free composite material contains a hydrophobic aerogel granulate and at least one refractory material. An independent claim is also included for a method for the production of the composite material comprising mixing the aerogel granulate, refractory material and usual dispersant and/or liquefier in water, forming a molded body from the suspension produced and sintering.

Description

The The present invention relates to a particular cyclic thermal loads stable composite, a process for its production and its use.

It There are numerous processes where high temperature insulation (> 800 ° C) is necessary are those with very hot process gases and water vapor come in contact. An example of this are solar reactors, in which is recovered via methane reforming hydrogen gas. Many of the conventional refractory materials (chamotte, granular Oxide mixtures) as well as fiber ceramics (rock wool, high-temperature fiber mats) are hardly suitable for such applications, as they either react with the process gases or at cyclic temperature load mechanically fail.

Heat insulating materials are manufactured on the basis of oxide ceramics and are either dense porous materials or a type of mortar (pasty chamotte) or they are fibrous materials (for example rockwool), fiber fabrics, which may also be soaked with a slurry and sintered or fired (for example also Whipox ^® ). While the massive refractory ceramics are hardly able to cope with rapid cyclic temperature changes, fibrous materials are excellently suited for thermal insulation, light and mechanically almost any loadable. The dense ceramics can react with very hot process gases (depending on the composition of the ceramics and the process gases, here, for example, methane is considered, this can lead to superficial damage). Fiber materials are generally sensitive to hot water vapor, especially when cyclic loads between room temperature and 1000 ° C, the dew point is exceeded.

DE 10 2006 033 061 A1 describes a soundproofing element with an optionally reinforced concrete core and at least one side of the concrete core surface coating, which is characterized in that the surface coating contains fire-resistant lightweight aggregate. One possible alternative for the lightweight aggregate in the surface coating is called airgel granulate.

DE 10 2004 046 495 A1 describes a composite containing hydrophobic airgel particles, inorganic binder and a dispersant, and a method of making such a composite.

It is thus an object of the present invention, a material to develop with low thermal conductivity, the cyclic thermal loads, in particular up to one Temperature of 850 ° C, easily endures.

Solved The object underlying the present invention is in a first embodiment by a concrete-free composite material, which hydrophobic airgel granules and at least one refractory material contains.

Aerogels according to the invention include colloidal substances which are gelled and dried. They have a lower density and high, open porosity. They consist only to about 1 to 15 vol .-% of a solid, while the rest of their volume is filled by the surrounding gas or vacuum, that is, they have a high surface area (up to 1000 m ² / g). Inorganic aerogels are usually hydrophilic aerogels by themselves and are considered one of the lightest materials and one of the best thermal insulators.

Aerogelgranulate are obtained in particular by the milling of airgel monoliths. Hydrophobic in the sense of the present invention means water-repellent, that is, the used airgel granules shows a pronounced Interaction with polar solvents such as water. Have so the hydrophobic airgel granules used have a wetting angle with water of ≥ 160 °.

hydrophobic Airgel granules can often consist of hydrophilic airgel granules be obtained by a hydrophobizing treatment latter. Inorganic, that is usually containing oxidic, aerogels For example, many still free OH groups and are therefore hydrophilic. By a hydrophobizing treatment such as etherification using trimethylsilyl chloride (TMSCI) so hydrophilic converted into hydrophobic aerogels / airgel granulates become.

Refractories are metallic and ceramic materials for operating temperatures (from 300 ° C) over 600 ° C to about optionally 1700 ° C, which are in direct thermal contact with a high-temperature process (for example, melting of metals or glass, firing of ceramics) and its thermal and secondary processes (for example, shaping, heat treatment, et cetera).

Main purpose of the refractories are thus furnace linings of iron and steel, glass, Aluminum, cement and ceramic industries as well as shaping Tools in the mentioned industries. It plays in the Selection of suitable materials for a process not only temperature plays an important role but also the atmosphere, the minimum temporal durability or operational capability, the chemical resistance, the achievable mechanical Strength and other more.

The main components of inorganic nonmetallic refractories (ceramics and glass, glass-ceramic, glass fibers and mineral fibers) are the oxides SiO ₂ , Al ₂ O ₃ , MgO, CaO, ZrO ₂ and Cr ₂ O ₃ . In addition, carbon and silicon carbide (SiC) are important components. In addition, the so-called refractory metals (molybdenum, tungsten) and the platinum group metals (precious metals) and their alloys must be counted among the refractories due to their high melting point and their chemical resistance to many slags and melts. Examples of suitable refractory materials include quartz sand, olivine, chrome ore sand, zircon sand, vermiculites and artificial molding materials such as cerabeads, or aluminum silicate spheres (so-called microspheres).

It has now surprisingly found that such a concrete-free Composite only a low thermal conductivity owns, but at the same time by a special stability distinguished from cyclic temperature changes.

characteristic for the composite material according to the invention is, among other things, the lack of concrete as one of the ingredients, wherein under concrete a mixture of cement, aggregate or concrete surcharge (sand and gravel or split) and mixing water (and, where appropriate, concrete admixtures and concrete admixtures).

Prefers the refractory material has a corundum content of ≥ 80, particularly preferably ≥ 90% by weight.

Prefers the refractory material has a CaO content of ≥ 3, especially preferably ≥ 4 wt .-% on.

Small additions of SiO ₂ , CaO, TiO ₂ (per oxide up to 5 wt .-%) to pure corundum lower the necessary sintering temperature and increase the tightness of the materials.

Prefers the proportion of airgel granules in the composite material is in one Range from 40 to 70, more preferably from 50 to 60% by volume. A higher amount of airgel granules leads to materials with very low strengths, while one too low Quantity of high-density materials produced and a strong Macrosegregation the airgel particle allows.

• a) eine Korngröße in einem Bereich von 0,5 bis 4 mm und/oder
• b) einen Porendurchmesser in einem Bereich von 15 bis 25 nm und/oder
• c) eine Porosität von ≥ 90% und/oder
• d) eine Dichte in einem Bereich von 90 bis 100 kg/m³ und/oder
• e) eine Wärmeleitfähigkeit bei 25°C von ≤ 0,020, bevorzugt ≤ 0,018 W/(m·K), und/oder
• f) eine BET-Oberfläche in einem Bereich von 600 bis 800 m²/g aufweist.

Furthermore, it is preferred that the airgel granules

• a) a grain size in a range of 0.5 to 4 mm and / or
• b) a pore diameter in a range of 15 to 25 nm and / or
• c) a porosity of ≥ 90% and / or
• d) a density in a range of 90 to 100 kg / m ³ and / or
• e) a thermal conductivity at 25 ° C of ≤ 0.020, preferably ≤ 0.018 W / (m · K), and / or
• f) has a BET surface area in a range of 600 to 800 m ² / g.

advantage the low density is that the aerogels in the material act like Reduce pores and thus the total density. The low thermal conductivity causes a low thermal conductivity of the composite material. The hydrophobicity causes a low reactivity of the composite with water vapor.

Prefers the composite has a breaking strength in the 3-point bending test of ≥ 40, more preferably ≥ 45 MPa.

Prefers the composite material has a thermal conductivity in a range of 0.15 to 0.25 W / (m · K).

The composite material preferably has a density of ≦ 1100 kg / m ³ .

in the Composite material of the invention can be up to 50 vol.%, in special cases even up to 70 Vol .-% of the refractory material replaced by hydrophobic airgel granules. Due to the negligible density of the hydrophobic airgel granules Compared to the refractory material can thus reduce the density of the massive refractory material can be achieved by about 50%.

Of the Addition of the hydrophobic airgel granules conditionally about In addition, a significant reduction in thermal conductivity compared to such massive refractories, which are made from the refractory material exist alone (corresponding thermal conductivities here are values around 0.6 W / (m · K)).

Surprised is now that by the addition of hydrophobic airgel granules a significant increase in breaking strength compared to the composite material can be achieved without hydrophobic airgel granules.

In A second embodiment is the basis of the invention solved by a process for manufacturing the composite material according to the invention, which characterized in that the hydrophobic airgel granules and the refractory optionally with the addition of conventional Dispersing agent and / or condenser in water, it produces a shaped body from the resulting suspension and this sinters.

Prefers first drying the shaped body at room temperature and later sinters at a higher temperature, especially at a furnace temperature of ≥ 850 ° C.

The Sintering temperature should be higher if possible its as the later maximum application temperature, with it a change in the geometry of the workpiece during of the operation can be neglected.

In A third embodiment is the basis of the invention lying solved task, by the use of the invention Composite for thermal insulation and / or insulation.

there can in the course of thermal insulation and / or -isolation temperature fluctuations of 500 K or more occur.

This not only proves the excellent thermal insulation Properties of the composite material according to the invention but also its high stability thermal loads.

EXAMPLES

Example 1:

As a refractory material was of lightweight refractory concrete Carath ^® FL-1800 the firm Rath and the translucent airgel TLD used as hydrophobic airgel 302 ^® Cabot Nanogel GmbH.

This hydrophobic airgel had the following physical properties: grain size ≈ 0.5 to 4.0 mm Pore diameter ≈ 20 nm porosity > 90% Density: 90 to 100 kg / m ³ Thermal conductivity: 0.018 W / m · K at 25 ° C BET surface area: 600 to 800 m ² / g

The following table shows the chemical composition of the refractories used in Examples 1 and 2: Carath FL-1800 ^® Carath FL-1450 PR ^® Al ₂ O ₃ 94 > 90 SiO ₂ 0.3 <1.5 Fe ₂ O ₃ 0.3 <0.2 CaO 4.1 5.5

The materials were mixed with tap water and mixed with concrete liquefier (BV) from Remmers. Were used 1200 ml of water, 4 ml of BV 5 kg Carath FL-1800 ^®, so that resulted in a total volume of 2.8 l. To this was added an equal volume of airgel granules. From this plates of dimensions 15 × 15 × 6 cm were poured, 48 hours at room temperature and then dried at 70 ° C for 24 hours in the oven. Thereafter, the plates were turned off and further dried at 100 ° C for 96 hours. Subsequently, the plates were heated to 850 ° C oven temperature in 3 hours and baked at 850 ° C oven temperature for 16 hours. After firing, the plates had a density of 1050 kg / m ³ . The breaking strength in the 3-point bending test was 45 MPa.

Example 2:

As a refractory material, the light-weight concrete Carath ^® FL-1450 PR from Rath was used. The hydrophobic airgel granules were the same as in Example 1. Breaking strengths in the bending test of 35 to 45 MPa are achieved.

In the fired state, similar results were obtained in both cases:
The thermal conductivity was determined to be 0.2 ± 0.05 W / (m · K) for both composites. Compared with the thermal conductivities of the pure refractories, which is 0.6 and 0.7 W / (m · K) respectively, it can be seen that the thermal conductivity in the composite material according to the invention is markedly reduced.

In numerous other tests showed that composites, can be generated without pores and cracks up to a content of 50%, when the mixing ratio is varied, in particular by adding a higher water content. An airgel component up to 70% is also possible, albeit a bit more difficult implement microcrack-free.

With The materials from both examples were thermal cycle test carried out. The following temperature profiles were Periodically repeated 5 to 10 times: heating at room temperature to 850 ° C oven temperature with heating rates of 10 ° C / min and hold at 850 ° C oven temperature for 8 Hours, then oven shutdown was reached until room temperature. Total duration per cycle: 18 hours. The composites had this type of thermal load change survived crack-free.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102006033061 A1 [0004]
• - DE 102004046495 A1 [0005]

Claims (12)

Concrete-free composite material containing hydrophobic Airgel granules and at least one refractory material. Composite material according to claim 1, characterized the refractory material has a corundum content of ≥ 80, preferably ≥ 90 % By weight. Composite material according to one of the claims 1 or 2, characterized in that the refractory material a CaO content of ≥ 3, preferably ≥ 4 wt .-% having. Composite material according to one of the claims 1 to 3, characterized in that the proportion of airgel granules in the composite in a range of 40 to 70, preferably from 50 to 60% by volume. Composite material according to one of claims 1 to 4, characterized in that the airgel granules a) have a particle size in a range of 0.5 to 4 mm and / or b) a pore diameter in a range of 15 to 25 nm and / or c) a Porosity of ≥ 90% and / or d) a density in a range of 90 to 100 kg / m ³ and / or e) a thermal conductivity at 25 ° C of ≤ 0.020, preferably ≤ 0.018 W / (m · K), and / or f) has a BET surface area in a range of 600 to 800 m ² / g. Composite material according to one of the claims 1 to 5, characterized in that it has a breaking strength in 3-point bending test of ≥ 35, in particular ≥ 45 MPa has. Composite material according to one of the claims 1 to 6, characterized in that it has a thermal conductivity in a range of 0.15 to 0.25 W / (m · K). Composite material according to one of claims 1 to 7, characterized in that it has a density of ≤ 1100 kg / m ³ . Method for producing a composite material according to one of claims 1 to 8, characterized if necessary, the hydrophobic airgel granules and the refractory material with the addition of customary dispersants and / or liquefiers in water, mixing, from the resulting suspension, a shaped body produces and sinters this. Method according to claim 9, characterized in that that the moldings first at room temperature and later at a higher temperature, in particular at a temperature of ≥ 850 ° C, dries. Use of a composite material according to one of Claims 1 to 8 for thermal insulation and / or -isolation. Use according to claim 11, characterized that in the course of the thermal insulation and / or insulation temperature fluctuations of 100 K or more occur.