Liquid purification or separation – Filter – Material
Reexamination Certificate
1999-08-13
2001-10-30
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Filter
Material
C210S500260, C210S490000, C210S650000, C264S045100, C428S307700, C427S372200, C055S523000
Reexamination Certificate
active
06309545
ABSTRACT:
A claim is laid to a composite, a process of production and use of this permeable composite.
There are several different applications known where composites containing ceramic materials are used.
The advantage of composites containing ceramic material is in the fact that ceramic coatings are chemically inert against most chemical substances such as organic substances and besides this are generally resistant to acids or caustic solutions. For this reason metals are often coated with ceramic materials in order to protect the metal from chemical attack. In addition to this, the porous surface of a composite coated with a ceramic material increases the abrasion resistance of paints or protective coatings that are applied at a later date. Because of their porous surface, ceramic materials themselves are very suitable for use as membranes or filters.
The disadvantage of ceramic materials or composites containing ceramic materials is the brittleness of the ceramic material. Metals coated with ceramic material are therefore very susceptible to shocks, and the ceramic coating rarely survives mechanical stresses without the surface of the ceramic material being damaged. Since bending such a ceramic composite also damages the ceramic coating, the fields of application of such ceramic composites are limited at the present time.
In spite of the disadvantages, ceramic composites are often used in filtration and membrane technology.
EP 0358 338 describes a process in which an aqueous solution containing a metallic oxide sol is applied to and stabilized on a—preferably smooth metallic—surface, thus protecting this surface with a ceramic coating. To improve the bond between the ceramic coating and the surface to be protected a metallic oxide powder and/or a bond-improving agent can be added to the aqueous solution. The process does not describe the coating of permeable carrier materials.
WO 96/00198 shows the production of ceramic coatings on surfaces made from different materials. These coated materials can be used as membranes in nano-filtration. In this process, titanium dioxide sol is dispersed with aluminum oxide powder, whereby hydrochloric acid is used as a peptizing agent.
U.S. Pat. No. 4,934,139 shows a process for the production of ceramic membranes for ultra-filtration and micro-filtration. For the production of such ceramic membranes, a sol or a particle suspension is applied to a metallic carrier and sintered. The porous carrier can be stainless-steel-sintered metal or stainless steel mesh where metallic particles have been sintered into the gaps. Metallic mesh with gaps of more than 100 &mgr;m cannot be produced using this process without sintering in metallic particles. The process prevents the suspension or the sol from penetrating the gaps in the carrier material.
In U.S. Pat. No. 5,376,442 and U.S. Pat. No. 5,605,628 an organic bonding agent is worked into the coating solution to bridge the gaps in the carrier material. This bonding agent must be removed again during stabilization, which can lead to irregularities in the ceramic material surface and/or structure.
Also in DE 4210413, the inorganic powder is fixed with the aid of a polymer resin. This resin must also be removed during stabilization, which can lead to irregularities in the ceramic material surface and/or structure.
With the above-mentioned processes it is not possible to produce composites containing ceramic material, where ceramic material is contained in and on the carrier material, without the ceramic coating being damaged either during production or application.
The basis of the invention at issue is therefore to obtain a composite that contains ceramic components on and in the carrier and to find a simple and economic process of producing such a composite.
Surprisingly, it was found to be the case that a permeable composite based on at least one perforated and permeable carrier containing at least one inorganic component on at least one side of the carrier and inside the carrier, which essentially contains a compound consisting of a metal and at least one element from group III to VII of the periodic system can be produced simply and at a reasonable price.
Subject matter of the invention at issue is therefore a permeable composite based on at least one perforated and permeable carrier containing at least one inorganic component on at least one side of the carrier and inside the carrier, which essentially contains a compound consisting of a metal and at least one element from group III to VII of the periodic system.
Further subject matter of the invention at issue is a permeable composite, which is obtained by application of a suspension that contains at least one inorganic compound, which is a compound of at least one metal with at least one element from group III to VII of the periodic system, and a sol on a perforated and permeable carrier, which is then heated at least once to stabilize the suspension containing at least one inorganic component onto or into or onto and into the carrier.
Further subject matter of the invention at issue is a process to produce a composite as claimed in one of claims
1
to
30
, wherein at least one suspension, which contains at least one inorganic component from at least one compound of at least one metal with at least one of the elements of group III to VII of the periodic system, is applied in and on at least one perforated and permeable carrier and is stabilized in or on or in and on the carrier material when the suspension is subsequently heated at least once.
Subject matter of the invention at issue is furthermore the use of a composite according to at least one of the claims
1
to
30
as a filter separate mixtures.
Permeable composites or carriers respectively are materials that are permeable for substances with a particle size of between 0.5 nm and 500 &mgr;m, depending on the style of execution of the composite or carrier respectively. The substances can be gaseous, liquid or solid or in a mixture of these states of aggregation.
The composite according to invention has the advantage that inorganic components can be stabilized on and in a perforated and permeable carrier, which allow this composite to have permeable properties, without the coating being damaged during production.
The composite according to invention also has the advantage that, although it partly consists of a ceramic material, it can be bent to a radius of up to 1 mm. This property enables an especially simple process of producing this composite, as the composite created by coating with a ceramic material can be wound on or off a roll.
The process of producing the composite according to invention also has the advantage that carriers with perforated surfaces with a maximum gap size of 500 &mgr;m can be coated. The especially careful conditions during stabilization of the suspension in or on the carrier enable carrier materials to be used that cannot be subjected to high temperatures or only subjected to high temperatures for a very short time.
The composite according to invention, which is produced according to the process that is the subject of the invention, is ideally suited for use as a filter or membrane. The possibility of also being able to use carriers that have gaps with a size of up to 500 &mgr;m allows the use of exceptionally reasonably priced materials. The particle size used in combination with the gap size of the carrier material used allows the pore size and/or the pore size distribution to be easily adjusted in the composite so that special membranes can be produced for special applications.
The composite according to invention is described in the following as an example, without the composite according to invention being limited to this style of execution.
The permeable composite according to invention has a basis of at least one perforated and permeable carrier. On at least one side of the carrier and inside the carrier, the carrier contains at least one inorganic component that contains essentially at least one compound consisting of at least one metal, metalloid or compositi
Hoerpel Gerhard
Hying Christian
Penth Bernd
Schmidt Friedrich Georg
Creavis Gesellschaft fuer Technologie und Innovation mbH
Fortuna Ana
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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