Process for making a microfiltration, ultrafiltration, pervaporation or reverse osmosis membrane for suspensions, emulsions or gas separation.

The invention relates to a method for producing a membrane for microfiltration, ultrafiltration, pervaporation or reverse osmosis of suspensions, emulsions or gas separation with the features of the preamble of claim 1.

There are known methods and devices for micro-filtration filter particles from gases or suspensions using a tubular wire wound membrane. Here, the membrane windings are wound under pretension. The feed is fed under pressure through the membrane. The slot-shaped membrane pores between adjacent turns of the membrane allow the separation of the particles to be filtered from the feed. A disadvantage is that such a process for the microfiltration permits not the separating particles for ultrafiltration, pervaporation or gas / gas separation.

From EP-A-0,213,941 a filtering method and a filter is known, wherein a tubular, wound from a wire filter is used, one side of which is firmly connected to a holder part, which is adjoined by an actuating rod, which obtained by filter is guided. With the actuating rod, the tubular wound filter can be stretched or compressed. Changing the filter is only used to change the pore size to the particular circumstances accordingly.

From DE-A-38 17 578 a method and an apparatus for microfiltration and ultrafiltration and reverse osmosis is known. This preferably takes a membrane using, which is formed by a tubular body made of prestressed wire wound. This membrane can with a decreasing pore size, be provided limited elastically stretchable material application. This membrane is used in a filtration device. The filtration process can be carried out both in the flow-through method with cross-flow effect and in Deadend method.

From DE-A-35 22 725 a spirally wound wire, with or without bias from membrane is known which is provided with a material application. The material is applied can be applied before or after the winding process. It can be made from the finest, organic or inorganic particles. This can increase their crystalline or latticed structures and their interstices and exercise appropriate for the specific application filter effects. As particles of graphite, Graphitoxid-, metal, metal oxide, ceramic and other particles, applied alone or together with a carrier material (suspension, z. B. from water, grease or oil) on the wires or fibers or in the interstices of the spiral are inserted and then fixedly connected to the membrane. The filter effect of the particles is caused by their porosity. A disadvantage is that the production of such membranes is complex. Since the particles are firmly attached to the membrane, there is a danger that the passages are clogged by this material application in filtration and a Rückflußreinigung is difficult to carry out. In addition, the particles used for the application of material act only on the basis of which they form passages, so the resulting porosity, but not due to other effects, such as affinity for certain substances or the like.

EP-A-0319893 describes a method for manufacturing a filter in the form of a disc, wherein the filter disc is firmly connected to a membrane, the pore size determined.

The GB-A-926 138 discloses a filter in which filter residues, which could lead to blockage, are weitgehenst avoided.

The US Patent 4,693,835 describes a filter in which the filter with a filter active layer is firmly covered.

The invention has for its object to reduce easily the separation limits of these known filter membranes significantly, so that the size of the particles to be separated from a feed to the ultra range (mol. Separating region) is possible and pervaporation and gas / gas separation, optionally with the use of composite membranes or separation membranes, are feasible.

The invention solves this object with the characterizing features of claim 1.

The invention offers the advantage of reducing the pore size between adjacent turns of a tubular membrane of a filter device directly by reducing the winding distances and indirectly by incorporation of fine separating layers. This makes it possible to enter the ultrafiltration range and perform well, pervaporation and gas / gas separations. Here, the fine separating layer acts as a filter, phase or gas separation element, whereas the tubular membrane serves as a scaffold with microfiltration properties for further fine separation layer substantially. Thus, the diameter of the wire for the membrane turns can be large. The application of high filtration pressures and achieving high filter performance are possible. The fine separation layers are formed of substances which are present in the feed or added during filtration. Due to the cross-flow effect these substances are supplied to the pores to form the fine separating layer. The fine separating layer is in the form of loose substances, maintained by the cross flow effect, optionally under running exchange of the substances. The fine separating layer can be made porous or transport active depending on the substances used.

Further embodiments of the invention result from the dependent claims. The invention is explained in more detail with reference to an embodiment shown in the drawing. In the drawings:<dl id="dl0001"><dt>Fig. 1</dt><dd>a vertical section of a tubular membrane, which is used in a conventional, not shown filter apparatus;</dd><dt>FIG. 2</dt><dd>a plan view of the diaphragm of FIG. 1;</dd><dt>Fig. 3</dt><dd>a greatly enlarged fragmentary sectional view of a Windungsspaltes with a loosely with the membrane overlying porous, or homogeneous, transport active separating layer and</dd><dt>Fig. 4</dt><dd>a partial view in section.</dd></dl>

A common, not shown filter apparatus comprises one or more tubular membrane first For this, a wire is spirally, preferably with a large bias wound. As wire material finds of metal, plastic, glass or other material use. The wire cross-section may be circular, oval or polygonal.

The diameter, in particular of the metal wire is so large that the tubular membrane withstands a filtration pressure in the medium and high pressure range from 1 to&gt; 1000 bar.

The resulting between adjacent turns of the membrane 1 slit-shaped pores 3 can not be reduced below 0.5 »m due to production irregularities of the wire surface. By correspondingly high axial pressure on the membrane 1, this unevenness can be planarized. Thereby, it is possible to reduce the pore size down to 1 nm.

Such a membrane is wound with or without bias, may be provided for filtration of a liquid or gaseous feeds to an associated transport or porous active separation layer.

To form the porous layer 4 inorganic components, such. As glass powder m, ceramic body, metal powder or other powdered materials in such a small scale, up to the grain size range of 0.1 "are introduced into the feed, that resulted in the case of filtration prevailing cross-flow effect in the effective filter area of ​​the pores 3 can only form a layer having one to two grain layers. The inorganic components can be sorted before it is introduced by screening in wound metal membranes with defined pore size.

At correspondingly lower distribution of the components in the feed an accumulation only in the narrowest region of the spacing of the windings 2. The pore slot formed by the spacings of the turns 2 of 5, which can permeate larger, disc-shaped or rod-shaped particles without aforesaid separation layer 4, is carried out so interrupted , Disc-shaped or rod-shaped particles can not permeate.

The pores formed by the slit 5, original pore size decreases - depending on the size of the non-incorporated particles - on.

It is also possible to form the separation layer 4 caused by the presence of a suspension or an aerosol substances. For this purpose, the membrane 1 is used with such a pore size that forms a separating layer 4 by deposits of the substances from the pores of the third

After formation of the separation layer 4, the diaphragm 1, z. B. can be so stretched by a micrometer-pulling device, that the separating layer 4, the enlarged pore 3 just bypassed.

By stretching an enlarged pore 3 is desirable, so that an increase in power is possible.

Since the filtering performance not only depends on the cross-flow, but also on the pressure, the turns 2 wire forming so strongly selected to filter pressures from 1 to&gt; 1000 are bar bar possible. High-pressure applications of the aforementioned type lead to significant performance enhancement and quality improvement of the permeate in cases where the porous fine separating layer 4 is made of non-compressible material (eg. As already included in the Feed undissolved or precipitated metals, absorbent materials such as activated carbon, diatomaceous earth or zeolites or catalysts, which are introduced in the form of granules).

When using a polygonal, for example rectangular wire cross-section of Fig. 4 is produced at the edges of adjacent windings 2 due to the small edge radii a small crotch region. This can take a few layers of free components that constantly renew themselves whirling through the action of the longitudinal current and the cross current of the feed. These components form a separating layer 4 whose pores are not clogged.