Compositions: ceramic – Ceramic compositions – Pore-forming
Reexamination Certificate
2002-09-09
2004-06-22
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Pore-forming
C501S134000, C264S043000, C264S117000, C264S125000, C264S628000
Reexamination Certificate
active
06753282
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for producing a monolithic, porous, ceramic shaped body which is predominantly used as a supporting material for porous, inorganic and/or organic membranes for the flow filtration (cross flow) of liquids and gases.
According to the prior art, porous oxide ceramic filter materials are produced by ceramic mixing and shaping methods and subsequent sintering. To obtain a porosity of >30% and pore sizes of 1-20 &mgr;m two basic methods are common use:
a) A coarse ceramic powder granulation of a mean grain size between 3-500 &mgr;m is mixed with a fine ceramic powder granulation of a mean grain size between 0.01-7 &mgr;m, whereby the fine-grained powder material envelopes the coarse-grained particles. The fine-grained material, due to its low melting point, acts as a flux during the sintering process. Such methods are described in, for example, EP 0 450 899, EP 0 585 152 or in the U.S. Pat. No. 5,223,318.
b) A fine ceramic powder granulation of a mean grain size between 0.01-7 &mgr;m is mixed, shaped and sintered with organic material, whereby the organic material is burnt out during sintering and leaves open pores in the shaped body. Such methods are described in, for example, EP 0 354 721, and EP 0 549 873.
The use of the method to b) is problematic for environmental reasons and, moreover, this method does not ensure the required purity of the material for the porous filters. The prior art methods do not permit a manufacture of a ceramic filter material under use of TiO
2
-powder of sufficiently large grain sizes, whereby the filter material shall consist of nearly 100% TiO
2
and shall have an open porosity of >20%. When TiO
2
-powder of a mean grain size of between 0.1-1 &mgr;m is tempered, a sintering at a temperature of >1100° C. starts which is accompanied by a structural densification and an increase of strength. Hence, it is not possible to achieve a sufficiently open porosity in this manner in ranges of temperature >1200° C.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for producing monolithic, porous, ceramic shaped body which is adapted for use as support for inorganic and/or organic membranes for the separation of solids, liquids and gases by way of flow filtration, whereby
the material for these shaped bodies has to be TiO
2
>99.9% and
commercially available TiO
2
-powder can be utilized, and the shaped body shall have the following properties:
open porosity: >10%
mean pore size: 1-50 &mgr;m, preferably 3-5 &mgr;m,
mechanical strength: >20N/mm
2
, preferably >30N/mm
2
.
The object is realized by the features of the first claim. The strong structural compaction of the material in the course of sintering in the range of temperature >1200° C. as typical for the prior art is eliminated in that a considerable part of the initial TiO
2
-powder is pre-sintered at temperatures >1200° C., whereby the powder particles are sintered to agglomerates. In a subsequent process this pre-compacted material is reduced in size such that mean grain sizes of <100 &mgr;m will result. The thermally pre-compacted powder obtained in this manner is mixed with a further smaller part of the thermally not pretreated initial TiO
2
-powder, shaped and sintered at temperatures which lie below the pre-sintering temperatures. Thus, a sintering of the thermally not pretreated powder with the thermally pretreated powder is obtained, whereby the here occurring structural compaction is only the result of the sintering of the smaller part of the thermally not pretreated initial TiO
2
-powder. As a result of this proceeding, a monolithic porous ceramic shaped body is obtained exhibiting the properties which are to be obtained according to the task set by the present invention.
REFERENCES:
patent: 5069697 (1991-12-01), Hamaguchi et al.
patent: 5183608 (1993-02-01), Guile
patent: 5185110 (1993-02-01), Hamaguchi et al.
patent: 5223318 (1993-06-01), Faber et al.
patent: 5415775 (1995-05-01), Castillon et al.
patent: 0354721 (1990-02-01), None
patent: 0450899 (1991-10-01), None
patent: 0549873 (1993-07-01), None
patent: 0585152 (1994-03-01), None
Fleischmann Thomas
Kastner Heike
Group Karl
Jordan and Hamburg LLP
TAMI Deutschland GmbH
LandOfFree
Method for producing monolithic, porous, ceramic shaped bodies does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing monolithic, porous, ceramic shaped bodies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing monolithic, porous, ceramic shaped bodies will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3301183