DE102009057257A1 - Rotating body of a sintered material, useful as filtering body for filtering solids or liquids from gases, a packing or a packing bed in a column and a catalytic carrier, comprises an inner cavity and a macropore in a wall - Google Patents

Abstract

Rotating body of a sintered material comprises an inner cavity and at least one macropore in a wall. An independent claim is also included for producing the rotating body, comprising: (i) providing a precursor of the rotating body exhibiting the shape of the subsequent cavity of the rotating body; (ii) coating the precursor with a first slurry comprising burnt out particles, which exhibit at least one dimension along the length corresponding to the thickness of the subsequent wall of the rotating body; (iii) coating the coated precursor with a second slurry containing sinterable particles in a thickness so that the burnt out particles of the first slurry are not completely covered from the layer of the second slurry; (iv) optionally thermally treating for drying the coated precursor; (v) thermally treating for de-binding the coated precursor; and (vi) thermally treating for sintering the sinterable particles to form the rotating body and to remove the precursor of the rotating body and the burnt out articles.

Description

The present invention relates to sintered and macroporous hollow bodies, which can be used preferably in filters or columns as packing and as a catalyst carrier.

Hollow bodies of sintered materials, such as hollow fibers or hollow spheres are known per se.

Such hollow fibers are used for example in EP-A-686 718 . DE-A-19910985 . DE-B-199 10985 . DE-A-10012308 . DE-A-10148768 described.

Out DE-A-10145640 It is known that by modifying the lyocell technology cellulose solutions can be used with different ceramic-forming ingredients and different particle sizes and processed into dimensionally stable hollow fibers of various diameters. The good adaptability of the solutions to each other and their compatibility in the spinning and refining process open up the possibility of producing multilayer hollow or solid filaments with pore gradients in the wall simultaneously.

DE-A-10114496 describes a process for the production of ceramic hollow fibers from nanoscale powders by extrusion or spinning.

DE-A-10155901 describes a method for producing a coating on a hollow fiber which is made porous. The method is characterized in that the hollow fiber is separated on both sides by closures from the coating bath. By applying a negative pressure to a pressure port, the movement of the coating bath through the pores of the membrane is supported, so that well reproducible coatings can be produced in a short time. A decisive advantage of the method described lies in the possibility of being able to coat a large number of hollow fibers simultaneously at high quality.

In DE-A-10114496 Hollow fibers with a porous wall are also mentioned, without their preparation being described in detail.

The production of hollow spheres is known per se. For their preparation, especially methods have proved to be advantageous in which spherical support elements, such as polystyrene balls, by Schlickergießen, immersion in slurry, thermal spraying, and wet powder spraying or fluidized bed process are coated with a metallic, ceramic or inorganic starting material and subsequent pyrolysis and sintering processes hollow balls are formed.

DE-A-19917874 describes a powder metallurgical process to produce hollow spheres of silicides and silicide composites. In this case, a suspension is prepared from the starting powders, an organic solvent and binder, are coated with the polystyrene balls by wet-powder fluidized bed process. After drying, the resulting spheres are debindered by sufficiently slow heating under an argon-hydrogen mixture. After a further thermal treatment, hollow spheres with a wall thickness of 200 μm are present.

DE-C-19929760 describes a process for the production of metallic, oxide or ceramic hollow spheres, in which the starting materials are applied in the presence of a liquid or pasty binder as a coating layer on moving spherical support elements and the green compacts thus produced are subsequently pyrolyzed and sintered.

A process for producing inorganic hollow spheres by thermal spraying is disclosed in US Pat DE-A-19603196 described. The respective starting powders of porous primary particles, porous agglomerates or porous aggregates are introduced into a spray steel. It is possible to use metals, alloys, oxides, silicates, borides, carbides, nitrides, silicides or mixtures thereof as starting materials. The shells of these hollow spheres can be liquid-tight, but also porous.

Metallic hollow spheres in the known form, typically have a largely closed shell or production-related a continuous microporosity and are therefore not suitable as a precursor for the production of open-cell porous structures, since they have only a low flow through in relation to the total porosity.

In summary, it can be stated that no hollow bodies made of sintered materials are known, in which targeted continuous macroporosities have been set in the walls, which contribute to a noticeable improvement in flowability during later use as a porous body.

The object of the present invention is to provide sintered hollow bodies with improved flowability and improved access of media from the surroundings of these hollow bodies in their interior.

The present invention relates to a rotational body of sintered material with inner Cavity and containing at least one macro pore in the wall.

The shapes of the hollow body according to the invention may be arbitrary, as long as they are rotationally symmetric. Preferably, it is hollow cylinder (= hollow fibers) and in particular hollow spheres. But it can also be hollow ellipsoids or other rotationally symmetrical body.

The dimensions of the hollow body according to the invention can vary within wide limits and are limited only by the possibilities of the production process. Typical orders of magnitude of the diameter relative to a rotation axis or in the presence of a plurality of rotation axes, the smallest diameter thereof, are in the range of at least 5 μm, preferably from 500 to 3000 μm.

A characteristic feature of the hollow bodies according to the invention is the presence of macropores. For the purposes of this description, pores are to be understood which pass through the entire wall of the hollow body. Preferably, at least two macropores, in particular two to a hundred macropores, are present; this is conducive to improved flowability. Particular embodiments of the hollow bodies include ten to ninety, ten to seventy, twenty to sixty, twenty to fifty, and thirty to fifty macropores.

Also, the dimensions of the macropores can vary widely and are limited only by the possibilities of the manufacturing process.

Typical magnitudes of the macropores are at least 1 .mu.m, preferably 10 to 200 .mu.m, particularly preferably 30 to 180 .mu.m, particularly preferably 50 to 130 .mu.m.

Preferably, the ratio of the mean diameter of the macropores to the smallest mean diameter of the hollow body relative to the corresponding rotation axis is 0.01: 1 to 0.2: 1. Here, mean diameter is understood to be the d ₅₀ value, that is to say the mean value of the Gaussian distribution of the respective diameters.

The wall thickness of the hollow body according to the invention can vary over wide ranges. Typically, this is in the range of at least 1 .mu.m, preferably from 5 to 500 .mu.m, preferably 5 to 300 .mu.m, particularly preferably 5 to 200 .mu.m or 5 to 100 .mu.m.

The rotary bodies according to the invention may consist of any sintered materials.

Preferred examples of this are sinterable, also called sinterable ceramic materials, sintered metals or sintered metal alloys.

As metal and alloy powder, the standard offered powders can be used, which are prepared by methods known in the art, such as atomization of molten metal, reduction or decomposition of metallic compounds or mechanical comminution and which are commercially available.

Suitable metal powders are commercially available powders prepared by the carbonyl process, especially Fe, Ni and Co metal powders. Also commercially available metal powders of Ni, Cr, Fe, Co, Mo, W and similar eligible metal powder, which were obtained by the reduction of their metal oxides.

Suitable alloy powders are those made by atomizing molten metals by means of gases or water. Their chemical composition depends on the specific stress conditions (temperature, corrosion partner, mechanical stress) of the hollow body. However, the production is often limited by technical limits, which are given by the height of the melting point of the alloy and the reactivity of the melt with respect to crucible materials.

The rotational bodies are particularly preferably derived from highly alloyed, sinter-active powders having mean particle sizes of less than 25 μm. These are for example in DE-10331785 B4 described. These powders can be processed both individually and in combination with commercially available powders. Commercially available powders in this sense are metallic element powders which are obtained from reducible metal oxides by reduction or master alloy powders which only reach the desired target composition by reaction with other metallic and / or alloying constituents.

The basic principle in the production of the rotary bodies according to the invention is based on the fact that a burn-out precursor of the rotary body or a non-burnable precursor of the rotary body, which later becomes a part remaining in the alloy of the wall of the rotary body, is coated with a slurry comprising a burn-out placeholder and that this product is coated with a slurry, which contains sintering powder, which form the wall of the rotating body after the sintering process.

• i) Vorlage eines Vorläufers des Rotationskörpers, der die Form des späteren Hohlraums des Rotationskörpers aufweist,
• ii) Beschichten des Vorläufers mit einer ersten Slurry, die ausbrennbare Teilchen enthält, welche in einer Dimension mindestens eine Länge aufweisen, die der Dicke der späteren Wand des Rotationskörpers entspricht,
• iii) Beschichten des beschichteten Vorläufers mit einer zweiten, sinterfähige Teilchen enthaltenden Slurry in einer Dicke, so dass die ausbrennbaren Teilchen von der Schicht aus der zweiten Slurry nicht vollständig bedeckt werden,
• iv) gegebenenfalls thermische Behandlung zum Trocknen des beschichteten Vorläufers,
• v) thermische Behandlung zum Entbindern des beschichteten Vorläufers, und
• vi) thermische Behandlung zum Sintern der sinterfähigen Teilchen unter Ausbildung des Rotationskörpers und unter Entfernung des Vorläufers des Rotationskörpers sowie der ausbrennbaren Teilchen.

The invention relates to a method for producing the rotary bodies described above comprising the steps:

• i) presentation of a precursor of the rotation body, which has the shape of the later cavity of the rotation body,
• ii) coating the precursor with a first slurry containing burnable particles having in one dimension at least a length equal to the thickness of the later wall of the rotating body,
• iii) coating the coated precursor with a second, sinterable particle-containing slurry in a thickness such that the burn-out particles are not completely covered by the layer of the second slurry,
• iv) optionally thermal treatment for drying the coated precursor,
• v) thermal treatment for debinding the coated precursor, and
• vi) thermal treatment for sintering the sinterable particles to form the rotating body and removing the precursor of the rotating body and the burn-out particles.

The precursor of the rotating body may be a burnout material. In this case, the composition of the wall of the rotary hollow body is determined by the composition of the sintering powder used in the second slurry.

Examples of burnable precursors are the following geometric shapes or shapes:
Balls, cylinders, cuboids or ellipsoids. The materials used for these structures are substances of chemical (organic, inorganic), biological (vegetable, animal) origin.

Examples of organic structures are: polystyrene beads, synthetic hollow and solid fibers, in particular textile fibers, paraffin or wax beads u. ä. Examples of inorganic structures are: crystalline salts, in particular salts which can be decomposed by gas transport reactions, carbon fibers, powdery oxides u. ä.

Examples of plant and animal structures are: fibrous plant constituents, fruits, hair and the like. ä.

The precursor of the rotating body may also be a later component of the alloy which constitutes a chemical constituent of the wall of the rotating hollow body. In this case, the composition of the wall of the precursor of the rotary hollow body is determined both by the composition of the powder used in the second slurry or by the composition of the desired final rotation body, which after thermal treatment, the wall of the rotary hollow body z. B. from a high temperature alloy forms.

Examples of non-burn-out precursors are metallic or ceramic structures of previously produced hollow spheres, hollow cylinders and other non-solid cuboids or ellipsoids.

As burn-out particles in the first slurry any pore-forming agent can be used, which serve as precursors for the macropores in the resulting wall of the rotary hollow body.

Examples of burnable particles for the first slurry are structures of chemical (organic, inorganic), vegetable and animal origin in the form of spheres, cylinders, cuboids or ellipsoids as described above.

Compared to the precursors of the hollow body, the burnable particles are smaller, and arrange themselves during the coating process on the surface of the precursor of the hollow body so that they are subsequently to selectively generated pores. This is preferably done by spraying with the first slurry containing the burnable particles (eg, paraffin beads), or by otherwise applying this slurry followed by a drying step.

After this step, the coating is carried out with a second slurry, which - in addition to low levels of combustible constituents for producing the slurry containing mainly nichtausbennbare metal and / or alloy powders, so as to apply such layer thicknesses that the burnable small, for example, made of paraffin Globules later become permeable pores. For the coating of the hollow body different available on the market reactors or aggregates can be used. Each coating process involves drying to remove the solvent. The coating is preferably, for example, in fluidized bed reactors (Fa. Glatt) or intensive mixers, z. B. a mixer made by Eirich. The coating (processing of the first or second slurry) is carried out at temperatures between 90 ° C and 140 ° C, preferably at 100 to 130 ° C when water-based slurries (dilute slips) are used. In the case of slurries based on organic solvents, e.g. As alcohols such as ethanol, methanol, the process temperature for drying is in the range of the boiling point of the respective alcohol. The In the case of organic solvents, temperatures may also be up to 30 ° C. above the boiling point of the particular alcohol. The coating process is terminated when the residual moisture in the range of 0.1 to 10% by weight, preferably 1 to 5% by weight based on the coated end product. The coating is carried out batchwise or continuously. Suitable process gases are air or inert gases (Ar, N). If slurries containing organic solvents are processed, the processing is always carried out under inert gas for reasons of explosion protection.

The subsequent debindering has the task to remove all volatile (burn-out) components, so that the metal and / or alloy powder leads to a formation of the alloy and compression in a subsequent sintering process, through which the manageable macroporous rotational body with its mechanical, geometric and corrosive properties is illustrated.

Debinding is carried out at temperatures of up to 1000 ° C., preferably of up to 800 ° C., particularly preferably of up to 700 ° C., depending on the burn-out insert components. The debinding takes place in the furnaces where the material to be treated rests and the removal of combustible constituents takes place via flowing process gases. Debinding is carried out predominantly under a protective gas atmosphere (nitrogen, inert gases) or hydrogen or mixtures of inert gases and hydrogen. The heating rate plays a very important role in the debindering process. Too fast heating rates lead to the destruction of the hollow body. Too low heating rates make the process uneconomical. The heating rate is typically between 0.5 and 5 K / min, preferably between 1 and 3 K / min.

The sintering of the hollow body can be carried out in protective gas or vacuum furnaces depending on the alloy or metal powder used. The sintering temperatures depend on the melting point of the materials used. Typical values are 0.7-0.95 times the melting temperature (measured in Kelvin). For example, a Fe alloy having a melting point of 1600 ° C (1873 K) is sintered at about 1250 ° C (1523 K), which corresponds to 0.81 times the melting point of the alloy. The heating rates for sintering processes are between 1 and 30 K / min, preferably between 5 and 10 K / min.

In addition to the alloy, the specific conditions for sintering depend on the particle size of the metal and alloy powders used and on the arrangement (eg, bulk height) of the parts in the furnace. The inventive rotors having macropores can preferably be used as filter bodies, as random packings or as catalyst supports.

These products and uses are also the subject of the present invention.

The following examples illustrate the invention without limiting it.

Example 1: Production of perforated hollow fibers using a burn-out / decomposable precursor, a spacer-containing first slurry, and a particle-loaded second slurry, debindering and thermal treatment

Using a burn-out / decomposable precursor, a spacer-containing first slurry, and a particle-loaded second slurry, as well as at least two coating steps, debindering and thermal treatment (sintering), perforated hollow fibers were produced.

In a first step, the production of a thin liquid first slurry containing placeholders in the form of paraffin beads with a particle size of -75 / + 50 microns and polyvinyl acetate dissolved in methanol. This is done by producing a low-viscosity solution of methanol (65% by volume) and polyvinyl acetate (5% by volume) into which insoluble paraffin beads having a content of 30% by volume have been mixed. The volume fractions of the ingredients used are based on the final mixture. The viscosity of this suspension is adjusted so that gentle stirring ensures a homogeneous distribution of the paraffin pellets.

A thick, particle-loaded second slurry, which mainly contains non-burn-out metal and alloy powders is formed as follows: A first powder fraction (a so-called master alloy) having the composition Fe-49Cr-23Al (d _50: 10 .mu.m) is shared with pure Fe powder (99.5%) (d ₅₀ : 3 microns) mixed. From this powder mixture 150 g are placed in a pad of water (100 g), polyvinyl alcohol (3 g) and Dolapix (0.5 g) and with a mixing-dispersing device (kinematics) at 3000 rev / min for 1 h by treated intense shear. Thereafter, a suspension with pasty, honey-like consistency. The powder mixture used consists of 43.5% of the master alloy powder and 56.5% of iron powder. With these proportions it is achieved that the alloy 67Fe-23Cr-10Al (in% by mass) is produced after the thermal treatment.

An "endless" polyamide hollow fiber with a diameter of 100 microns and a wall thickness of 20 microns is sprayed with the first slurry and then dried. 1 shows the structure of the "green" fiber. This fiber ( 1 ) is with paraffin beads ( 2 ) and with a polyvinyl acetate film ( 3 ) overdrawn.

It is then passed between 2 foam rollers and thereby coated with the second thick slurry that a layer ( 4 ) of about 50 microns is formed, through which pass 50 to 90% of the wax beads. In a following step, the drying of the "green" fiber takes place.

The precursor fibers are then cut to a length of 10 to 15 mm.

The fibrous material is now released. For this purpose, the heating of the fiber bed is carried out with 2 K / min from room temperature to 700 ° C under hydrogen. After a holding time of 1 h, the temperature is raised at 10 K / min from 700 ° C to 1300 ° C and held for 2 h. Thereafter, the cooling to room temperature. As a result of this process arise perforated hollow fibers with an inner diameter of about 60 microns and an outer diameter of about 100 microns with embedded continuous channels or pores that allow a radial flow.

The alloy Fe-23Cr-10Al formed during the thermal process has excellent oxidation properties and is suitable for high-temperature filters due to its good flow properties. 1 shows the section through a sintered fiber (center) and the top view (bottom).

Example 2: Production of Perforated Hollow Fibers Using Diffusion / Enamel Spacers (DSP)

In addition to the burn-out "real" placeholders described in Example 1, it is also possible to use those in the form of diffusion or metallic melting placeholders.

The coating of a burn-out precursor fiber with a powder mixture, which consists of at least 2 components with different melting temperatures. With a suitable combination of these components, the thermal treatment leads to a one-sided (directional) material redistribution and ultimately to pore formation. This occurs due to greatly differing diffusion rates or due to capillary forces when a liquid phase occurs during the thermal treatment and wets the second component. In this way, the centers of the unmelted metal particles are moved apart due to capillary forces as a result of the penetration of melt into the interparticle spaces, whereby the pores are ultimately formed [ Source: A. Böhm: Studies on the reaction sintering of Ti-Al element powder mixtures, dissertation, Mainz-Verlag, Aachen, 2001 ]. The result is a hollow fiber with high porosity in the wall, without burnable placeholders are used.

Such material systems suitable as diffusion / fusion spacers (DSP) may be: Ti and Al, titanium alloys and Al, Ni and Al, nickel alloys and Al, Fe and Al, iron alloys and Al, low nickel Ni-Cr-Mo Alloys and Ni and similar material systems in which one component has a low melting point or preferential diffusion of one component in the second.

As a result of the alloy formation, a hollow fiber with a perforated wall is formed, the composition of which is determined by the starting materials used.

Example 3 Production of perforated hollow spheres using a burn-out / decomposable precursor in the form of polystyrene beads (styrofoam beads), a spacer-containing first slurry, and a particle-loaded second slurry, debindering and thermal treatment

The hollow spheres produced in this process are in 2 shown. The low-viscosity slurry used is the methanol-polyvinyl acetate-paraffin globule dispersion described in Example 1. In the vicinity of "methanol-polyvinyl acetate", paraffin beads and polystyrene are not dissolved, which is important for further processing. [ Source: G. Duve, O. Fuchs, H. Overbeck: Organic Chemicals Hoechst, Solvent Hoechst, "A Handbook for Laboratory and Operations", 5th Edition 1974, Stock and Order Number: B 1166, Print Number: 2 962 130-784 ].

The slurry was adjusted in viscosity so that it could be atomized and applied to polystyrene beads by fluidized bed granulation.

As a result, the spherical polystyrene placeholders ( 1 ) the spherical paraffin particles ( 2 ), due to the forming polyacrylate film ( 3 ). The fact that the "beads" were glued point-like, was formed on the support surface, a capillary active region of importance for a subsequent coating with the second slurry.

A particle-loaded second slurry, which mainly contains non-burn-out of metal and alloy components is formed as follows: A first powder fraction (master alloy) having the composition Fe-49Cr-23Al (d _50: 10 .mu.m) is (together with pure Fe powder 99.5%) (d ₅₀ : 3 μm). 100 g of this powder mixture are placed in a water (100 g) polyvinyl alcohol (3 g) and Dolapix (0.5 g) and treated with a disperser at 3000 rpm for 1 h by intensive shearing (mixing). Thereafter, a suspension with a thin consistency. The powder mixture consists of 43.5% of the master alloy powder and 56.5% of iron powder. With these proportions it is achieved that after the thermal treatment, the alloy Fe-23Cr-10Al (Mass.%) Is formed.

In a next step, the polystyrene beads (diameter 4-5 mm) provided previously with "adhered" paraffin particles (-75 / + 50 μm) are coated in a fluidized bed reactor with the particle-loaded second slurry (layer thickness: 40 to 50 μm). and dried. The coating is carried out so that 50 to 80% of the paraffin beads are not completely embedded in the layer, which is achieved by the layer thickness and the friction effect in the fluidized bed.

The ball bed is now released. This is done by heating the bed at 2 K / min from room temperature to 700 ° C under hydrogen. After a holding time of 1 h, the temperature is raised at 10 K / min from 700 ° C to 1300 ° C and held for 2 h. Thereafter, the cooling to room temperature. As a result of this process arise perforated hollow spheres with a diameter of about 3-4 microns and a layer thickness of about 30 microns. The spherical shell made of Fe-23Cr-10Al creates continuous channels that allow a radial flow.

The alloy Fe-23Cr-10Al formed during the thermal process has excellent oxidation properties and is suitable as a high-temperature filter due to its good flow properties. 2 shows the section through a sintered ball and the top view.

Example 4 Production of Perforated Hollow Balls Using Diffusion / Fusion Spacers (DSP)

A combination of Examples 2 and 3 enables the production of perforated hollow spheres using diffusion-melt spacers.

The coating of a burn-out polystyrene ball with a powder mixture, which consists of at least 2 components with different melting temperatures. With a suitable combination of these components, the thermal treatment leads to a one-sided (directional) material redistribution and ultimately to pore formation. This occurs due to greatly differing diffusion rates or due to capillary forces when a liquid phase occurs during the thermal treatment and wets the second component. In this way, the centers of the unmelted particles are moved apart due to Kapilarkräften, whereby ultimately the pores are formed. The result is a hollow sphere with high porosity in the wall, without burnable placeholders are used.

Such material systems, which may be diffusion / enamel spacers, may be: Ti and Al, titanium alloys and Al, Ni and Al, nickel alloys and Al, Fe and Al, iron alloys and Al, low nickel Ni-Cr-Mo alloys and Ni and similar material systems in which one component has a low melting point or preferential diffusion of one component in the second.

As a result of the alloy formation, a hollow sphere with a perforated wall is produced, the composition of which is determined by the starting materials used.

Example 5: Production of perforated hollow spheres using a foamable spacer

Based on Example 2, it is also possible to use "foamable" or even partially "foamable" and burn-out placeholders for producing a central pore in a hollow sphere, without the use of the paraffin beads used in Examples 1 and 2. In this case, this further foamable placeholder forms the core of the hollow sphere to be perforated. Analogously to Example 2, the particle-loaded second slurry is applied to the foamable and burnable placeholders. In the thermal treatment, cracks in the applied powder layer then form due to foaming of the core, which leads to a high porosity of the spherical shell. After complete debindering and sintering, as described in the examples above, cracks and pores remain as damages in the spherical shell. In this way, a perforated hollow sphere was formed whose composition was determined by the starting powder used.

Example 6: Production of perforated hollow spheres with a sheath of fibers

The process according to Example 5 can be repeated with the difference that in the particle-containing second slurry fibers or hollow fibers made of sintered or otherwise provided material are used in addition to or instead of powder particles. After foaming, a "reinforcement" of the spherical shell is produced which, in the binder-free state, is more stable than the purely powder-containing spherical shells (compare sketch in FIG 3 ). Moreover, these hollow balls coated with a fiber felt show a significantly lower shrinkage than the hollow balls according to Example 5. The sketch in FIG 3 shows the comparison when using powders without fibers (I) and a slurry with powder and / or fibers (II). (II) shows compared to (I) a significantly lower shrinkage during sintering, since the foaming of (II) move the fibers apart, unlike in the case of powders, arise in the case of foaming (II) by sliding the fibers to each other always again new fiber-fiber contacts, which do not lead to noticeable shrinkage during sintering. This is due to the very small radial shrinkage of the fiber-to-fiber contacts and the invariable fiber length during sintering. The result is "fiberballs" according to 3 with high flowability and great damage tolerance to mechanical deformation.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 686718 A [0003]
• DE 19910985 A [0003]
• DE 19910985 B [0003]
• DE 10012308 A [0003]
• DE 10148768 A [0003]
• DE 10145640 A [0004]
• DE 10114496 A [0005, 0007]
• DE 10155901 A [0006]
• DE 19917874 A [0009]
• DE 19929760 C [0010]
• DE 19603196 A [0011]
• DE 10331785 B4 [0028]

Cited non-patent literature

• Source: A. Böhm: Studies on the reaction sintering of Ti-Al element powder mixtures, dissertation, Mainz-Verlag, Aachen, 2001 [0056]
• Source: G. Duve, O. Fuchs, H. Overbeck: Organic Chemicals Hoechst, Solvent Hoechst, "A Handbook for Laboratory and Operations", 5th Edition 1974, Stock and Order Number: B 1166, Print Number: 2 962 130-784 [0059]

Claims (21)

Rotary body of sintered material with internal cavity and containing at least one macropore in the wall. Rotary body according to claim 1, characterized in that it is a hollow fiber. Rotary body according to claim 1, characterized in that it is a hollow ball. Rotary body according to one of claims 1 to 3, characterized in that the smallest diameter relative to a rotation axis is 0.1 to 5 mm. Rotary body according to one of claims 1 to 4, characterized in that in the wall a plurality of macropores are present. Rotary body according to one of claims 1 to 5, characterized in that the macropores have a diameter of 1 to 50 microns. Rotary body according to one of claims 1 to 6, characterized in that the ratio of the average diameter of the macropores to the average diameter of the pores in the wall, based on their axes of rotation, is 0.01: 1 to 0.2: 1. Rotary body according to one of claims 1 to 7, characterized in that the sintered material is a ceramic. Rotary body according to one of claims 1 to 7, characterized in that the sintered material is a sintered metal or a sintered metal alloy. Rotary body according to claim 9, characterized in that the sintered metal or the sintered metal alloy are derived from highly alloyed, sintering powders having average particle sizes of less than 25 microns. Rotary body according to one of claims 1 to 10, characterized in that the rotary body is surrounded by a sheath of short fibers whose length does not exceed the length of the smallest diameter with respect to an axis of rotation of the rotary body. Process for producing the rotary bodies obtainable according to at least one of Claims 1 to 11, comprising the following steps: i) presentation of a precursor of the rotation body, which has the shape of the later cavity of the rotation body, ii) coating the precursor with a first slurry containing burnable particles having in one dimension at least a length equal to the thickness of the later wall of the rotating body, iii) coating the coated precursor with a second sinterable particle-containing slurry in a thickness such that the burn-out particles of the first slurry are not completely covered by the layer of the second slurry, iv) optionally thermal treatment for drying the coated precursor, v) thermal treatment for debinding the coated precursor, and vi) thermal treatment for sintering the sinterable particles to form the rotating body and removing the precursor of the rotating body and the burn-out particles. A method according to claim 12, characterized in that the precursor of the rotary body is a burn-out material, which is preferably in the form of a sphere, a cylinder, a cuboid or an ellipsoid. A method according to claim 12, characterized in that the precursor of the rotating body is a non-burnable substance which is a later component of the alloy forming the wall of the rotary hollow body, preferably in the form of a sphere, cylinder, cuboid or ellipsoid is present. A method according to claim 12, characterized in that are used as ausbrennbare particles in the first slurry pore formers, which have the shape of a ball, a cylinder, a cuboid or ellipsoid, wherein the burnable particles are smaller compared to the precursor of the hollow body, and arrange themselves during the coating process on its surface. Filter body containing rotational body according to one of claims 1 to 11. A packed bed containing a rotary body according to one of claims 1 to 11. Catalyst support comprising a rotary body according to one of claims 1 to 11. Use of the rotary bodies according to one of claims 1 to 11 for the filtration of solids or liquids from gases or from solids from liquids. Use of the rotary body according to one of claims 1 to 11 as packing in columns. Use of the rotary body according to one of claims 1 to 11 as a catalyst support.

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