Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Producing microporous article
Patent
1995-11-29
1998-01-13
Derrington, James
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Producing microporous article
264634, 26411711, 264DIG19, C04B 3800
Patent
active
057075840
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for the production of ceramic hollow fibre membranes for microfiltration, ultrafiltration and gas separation, said filter membranes having an external diameter of 0.5-3 mm and a wall thickness of 30-500 .mu.m.
BACKGROUND OF THE INVENTION
Separation processes are of great economic importance for the concentration and separation of gases and liquids. Membrane technology is being used to an ever increasing extent in this field. The use of hollow fibre membranes in a separation or concentration process has a number of concomitant advantages: concentration or separation process will be high; and the process is also easy to carry out and to adapt to the needs.
The abovementioned surface area/volume ratio is of vital importance to be able to compete with other types of membranes.
Hollow fibre membranes have already been available for years and are widely used. Commercially available hollow fibre membranes consist of a polymer material and consequently are sensitive to corrosive conditions and higher temperatures. In order to solve this problem attempts have been made to produce ceramic hollow fibre membranes, for example by condensing vapour on a carbon wire and then removing the wire. A sol-gel method for the production of ceramic thin membranes on a porous ceramic hollow fibre substrate has also been described in the "Journal of Membrane Science", 59 (1991), pp 81-99. However, these attempts have not led to a situation where ceramic fibres are commercially obtainable.
Dry and wet spinning are together with melt spinning the most commonly used spinning processes in the field of fibre production. Despite the fact that melt spinning is the most economical for fibre production (see Encyclopaedia of Polymer Science and Engineering, volume 6, John Wiley and sons, 1986, page 805) to the best of our knowledge this method was never used before to produce ceramic hollow fibre membranes.
SUMMARY OF THE INVENTION
The aim of the invention is to provide a method by means of which ceramic hollow membrane fibres for microfiltration, ultrafiltration and gas separation can be produced on an industrial scale.
According to the invention this method is characterised in that a paste is made by filling a thermoplastic polymer binder system with a ceramic powder, the said thermoplastic binder system is made plastic by heating and the paste is processed by melt extruding through a spinneret to give ceramic hollow fibre membranes, that the binder system is removed with the aid of thermal diffusion and that the powder particles are sintered to each other to obtain single layer hollow fibre membranes without an additional microporous layer.
For the ceramic powder, use is preferably made of silicon nitride (Si.sub.2 N.sub.4), but aluminium oxide, silicon carbide and other substances can also be used.
The thermoplastic binder system will he filled with ceramic powder to 40 to 60% V/V.
It has been found that a thermoplastic binder system of the following composition leads to good results: 37% m/m polyethylene vinyl acetate, 23% m/m ethylenebisstearylamide, 15% m/m dioctyl phthalate, 11% m/m oleic acid, 12% m/m polyglycol ester and 2% m/m polyglycol ether.
Use of the method according to the invention can lead to fibre membranes having a surface area/volume ratio of at least 1000 m.sup.2 /m.sup.3.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic of an apparatus for practicing the present method .
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FR-A-2466269 discloses a method for the production of ceramic support tubes. Several pastes are made by mixing a mineral of inorganic powder with a binder, for instance an organic binder. From each of the pastes a layer is made and the layers are simultaneously extruded or spun to form tubes. The obtained tubes are subject to a sintering operation. Finally a microporous layer is deposited on the tubes. There is no talk of a thermoplastic binder, there is no heating to make the binder plastic, the paste is not processed by me
REFERENCES:
patent: 4222977 (1980-09-01), Dobo
patent: 4571414 (1986-02-01), Renlund
patent: 5135895 (1992-08-01), Frechette
Feenstra Frits Kornelis
Terpstra Rinse Alle
Van Eijk Joost Petrus Gerardus Maria
Derrington James
Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk On
LandOfFree
Method for the production of ceramic hollow fibres 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 the production of ceramic hollow fibres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the production of ceramic hollow fibres will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-323858