DE19651757C2 - Filled alumina sol mass and uses therefor - Google Patents

Description

The present invention relates to a filled organic aluminum oxide Sol and uses for this.

There have been a number of attempts recently to produce ceramic masses via a sol-gel route.

A purely inorganic aluminum oxide gel is known from EP 406 847 A1 known. Abrasives in particular can be produced from this.

Shaped bodies can be made from organic lead-zirconium-titanate sols generate by mixing lead carboxylate with zirconium and titanium alcoholates are stable under certain conditions (see DE-PS 43 32 831 C1). Furthermore, you can also Produce organic aluminum oxide brine. DE OS 19 35 722 describes a process for producing aluminum aerogels using aluminum 2-butylet and 2-butanol. A solid with a highly developed pore structure can be obtained from this. Other organic aluminum oxide brines are suitable for example for the production of polycrystalline fibers (see EP 591 812 A1). For this, an aluminum alkoxide with an alkoxyamino or keto alcohol or the like Connections implemented. The sol can with a carboxylic acid be diluted. Controlled insertion of a small amount Water leads to controlled partial hydrolysis and -condensation. The product so obtained is tough and sticky, so that it is suitable for spinning through fine nozzles. By The organic part of the mass can be removed by heating, and you get a purely inorganic ceramic fiber.

However, the mass described above is desirable for many other applications cannot be used. Larger when heated Molded parts and surfaces made of this material appear strong Shrinkage, so that molded articles with larger dimensions in more than one dimension at least unstable under loads are.

The object of the invention is to provide a sol with which succeeds in producing molded articles that not only in one dimension dimensions above the millimeter range can have.  

Surprisingly, this task was solved by that an organic alumina sol that can be made, for example can, as described in EP 591 812 A1, aluminum oxide powder is added.

This gives you a highly viscous, viscous and sticky mass that Surprisingly, none or only a small amount when heated Shows shrinkage.

The particle size of the alumina powder can be varied. Smaller particles (e.g. below 0.2 µm) are due to the Overcoming the surface energy of the particles is more difficult to incorporate while sedimenting too large particles. A usable particle size is in the range from 0.1 to 50 μm, preferably up to 10 μm and in particular in the range from 0.3 to 3 µm.

The alumina powder can be in depending on the intended application an amount of up to about 50 or even 60% by mass will. The quantity range depends on the desired Viscosity. Since the sol can also be used with solvents up to one can be diluted to a certain degree, can be relatively broad Set parameter ranges. However, the thinnability limited; if too much diluent is added (e.g. ethanol) sedimentation of Alumina. Furthermore, the amount of workable Alumina powder up by reaching a high Viscosity, if not limited, not anymore useful if above this viscosity no longer with usual mixing units and without using excessive energy can be worked.

In a particularly preferred embodiment, additional Fibers worked into the filled sol. The fibers are preferably short fibers (e.g. in the length range of 200 µm). By their use will continue to shrink the molded article reduced. They can also improve the strength properties improve the molded body. The fibers are preferred  also made of aluminum oxide, but others can temperature-resistant fibers, for example silicon carbide or Glass fibers can be used.

For incorporating the aluminum oxide powder and possibly the fibers the components are preferably first in a polar and / or protic solvent suspended. Will the resulting mixture of a not yet condensed sol- Added precursor and immediately afterwards at least one partially initiated hydrolysis, an immediate one is obtained Viscosity increase of the sol, so that the suspension opposite Sedimentation is particularly stable.

After the filled sol has been produced, it can be shaped of the later shaped body are transferred. It can be three-dimensional bodies such as plates or the like or else to deal with fabrics. Due to the high stickiness of the filled mass is this especially as a high-temperature Suitable for glue. In this particular embodiment filled sol applied to one of the parts to be glued, the connection with the other part is established, and the Junction is dried at room temperature. After Drying has the adhesive bond for normal handling sufficiently high strength.

After drying, the removed organic components. In contrast to one Adhesive connection from a corresponding unfilled sol, at that when heated above 200 ° C by removing the chemically bound organic components and the associated Shrinkage the adhesive connection is lost and the glue crumbles, the adhesive as described above remains stable at high temperatures. Further heating to 1000 ° C causes the conversion of the amorphous components into α-aluminum oxide. Above this temperature is additionally hardened by Formation of sinter necks instead.  

In principle, any stable organic is an usable sol Alumina sol suitable. For this, organic Aluminum compounds used, possibly together with others hydrolytically condensable metal compounds such as calcium, Magnesium, boron, silicon, transition metal, lanthanide and / or actinide compounds. These elements can be the Sol in doping quantities or in larger quantities be attached.

A is preferred as the organic aluminum compound Aluminum alcoholate, for example aluminum isopropylate or sec-butoxide used. Regarding suitable solvents in particular reference is made to EP 591 813 A1. Preferred Solvents are low molecular weight carboxylic acids, whereby Alkoxy alcohols or keto, sulfo, or amino alcohols are added should be. The sol can with z. B. diluted with an alcohol will.

The sol according to the invention and the ones produced from it Molding compounds and adhesives can be obtained from commercially available Establish output connections. It can be non-toxic Select components that can be easily mixed with each other. The reactions can be carried out easily since they are without major Heat development that should be dissipated. The filled sol is a homogeneous mass that lasts for several months is stable in storage.

The specific embodiment of the adhesive offers the advantage that the adhesive effect in the entire temperature range of about Room temperature is well above 1600 ° C, so that the parts to be joined at room temperature and then can be brought to the desired temperature. With Objects connected to the adhesive can be extremely tall Exposed to temperatures without the adhesive bond would be attacked.  

Examples

• 1. 1 mol of aluminum sec-butoxide was in 1.5 mol Isopropoxyethanol and 2 mol propionic acid dissolved. The Solution was diluted with 5 mol of ethanol and then partially hydrolyzed with 0.5 mol water. It came into being a viscous, sticky mass (unfilled mass).
• 2. 30 g of aluminum oxide powder (A16SG, manufacturer Alcoa) were in 50 g of a sol prepared as described under 1. registered, but no partial hydrolysis had been subjected. The suspension was made using Ultrasound dispersed. Then one Partial hydrolysis with 50 mol% water, based on the Aluminum alcoholate component. Under strong Viscosity rose (from 0.005 to 10 Pas) filled sol (filled sol A).
• 3. 30 g aluminum oxide powder (A16SG, manufacturer Alcoa) and 3 g alumina short fibers (Saffil, manufacturer ICI) were introduced into 50 g of a sol which was obtained from the same as for the above unfilled sol described under 1. Components manufactured, but no hydrolysis yet had been subjected. The suspension was made using Ultrasound dispersed. Then one Partial hydrolysis with 50 mol% water, based on the Aluminum alcoholate component. Under strong A filled sol formed as the viscosity increased (filled sol B).

The unfilled and both filled brine were used as glue between an alumina tube and an alumina crucible used. After assembling the objects to be glued the adhesive bond was 30 minutes at room temperature dried and then exposed to rising temperatures. Above 200 ° C the adhesive connection from the unfilled sol. Both the filled Sol A and the filled Sol B retained its adhesive effect. Above 600 ° C  no more organic components could be detected. At about 1000 ° C you could convert the amorphous parts observe in α-alumina. The strength increased above 1000 ° C continues to increase what the formation of sinter necks is attributed. The adhesive effect could be up to 1650 ° C be detected.

The adhesive was in layer thicknesses of 0.5 to 3 mm, u. a. from 1 or 2 mm.

Claims (11)

1. Organic filled with alumina powder Alumina sol. 2. Filled organic alumina sol according to claim 1, wherein the alumina powder has a particle size of 0.1 to 50 µm. 3. Filled organic alumina sol according to claim 2, wherein the alumina powder has a particle size of 0.3 to 3 µm. 4. Filled organic alumina sol according to one of the The preceding claims, wherein the alumina powder in an amount of up to 60% by mass, preferably from 40 to 50 Mass% is used. 5. Filled organic alumina sol according to one of the preceding claims, which additionally fibers, contains in particular aluminum oxide fibers as filler. 6. Filled organic alumina sol according to claim 5, wherein the alumina fibers are short alumina fibers and / or in an amount of 3 to 8, preferably about 5 mass %, are used. 7. Filled organic alumina sol according to one of the preceding claims obtainable by generating of an alumina sol by reacting Aluminum alkoxide with an alkoxy alcohol and / or one Keto, sulfo or amino alcohol and at least one 1 to 6 Carboxylic acid containing carbon atoms, filling the sol with the appropriate aluminum oxide powder and possibly one further filler (s) and subsequent partial or complete hydrolysis and condensation.   8. Filled organic alumina sol according to claim 7, wherein the alumina sol by reacting aluminum sec-butoxide with isopropoxyethanol and propionic acid, Dilute with ethanol and then partial hydrolysis and Condensation with about 50 mol% water, based on that Aluminum butylate is available. 9. Filled organic alumina sol according to claim 7 or 8, characterized in that the implementation of Aluminum alkoxide with an alkoxy alcohol and / or one Keto, sulfo or amino alcohol and at least one 1 to 6 Carbonic acid-containing carboxylic acid with addition further alkoxides or carboxylates, selected from Compounds of calcium, magnesium, boron, silicon, the Transition metals, the lanthanides and the actinides, is carried out. 10. Use a filled organic alumina sol according to one of claims 1 to 9 for the production of Molded articles. 11. Using an organic filled alumina sol according to one of claims 1 to 9 as high temperature resistant adhesive.