Abstract: A composite porous media for either gas or liquid flow is strong and efficient, and can readily be formed in or into a wide range of different shapes and configurations. In particular, the porous media is a composite of a metal, aerogel or ceramic foam (i.e., a reticulated inter-cellular structure in which the interior cells are interconnected to provide a multiplicity of pores passing through the volume of the structure, the walls of the cells themselves being substantially continuous and non-porous, and the volume of the cells relative to that of the material forming the cell walls being such that the overall density of the intercellular structure is less than about 30 percent theoretical density) the through pores of which are impregnated with a sintered powder or aerogel. The thickness, density, porosity and porous characteristics of the final composite porous media can be varied to conform with what is demanded by the intended use.

Abstract: An improved two-step replication process for fabrication of porous metallic membranes is provided. A negative of a porous non-metallic template is made by infiltration of a liquid precursor into the template, curing the precursor to form a solid negative, and removing the template to expose the negative. Metal is deposited to surround the exposed negative. Removal of the negative provides a porous metallic membrane having pores which replicate the pores of the original template membrane. The negative is kept immersed in a liquid at all times between removing the template and depositing the metal. This immersion eliminates damage to the negative that would be incurred in drying the negative out between these processing steps. Another aspect of the invention is metallic membranes prepared according to the preceding method. For example, metallic membranes having pores smaller on one side than on the other side of the membrane are provided.

Abstract: A process and apparatus for the collection of biological materials from air. Collection and separation devices utilize a novel membrane structure formed from a functionalized inorganic mesoporous membrane supported by porous substrate.

Abstract: A porous ceramic laminate has a porous silicon nitride substrate and a porous silicon nitride separation film supported thereon and having minute pores of sizes capable of Knudsen separation or molecular sieve by sintering a porous silicon nitride substrate supporting a formed layer containing polysilazane at 800° C. in a nitrogen atmosphere.

Abstract: The present invention provides improved synthetic polymer hydrogel permeation layers for use on active electronic matrix devices for biological assays. The permeation layers have a defined porous character, with mesopores in a size range between about 100 nanometers and about 1000 nanometers, and may also have micropores in the micrometer size range. The mesoporous synthetic hydrogel permeation layers demonstrate improved signal intensity and linearity characteristics as compared to nanoporous synthetic hydrogel permeation layers on active electronic matrix devices. In addition, the present invention also provides synthetic polymer hydrogel permeation layers which contain copolymerized attachment sites for nucleic acid probes or other biomolecules.

Abstract: A microporous membrane comprising a highly electropositive hydrophilic material capable of irreversibly binding one or more nucleic acids, the membrane being useful for isolating, amplifying and detecting nucleic acids is disclosed. Methods of making the membrane and using the membrane for amplifying nucleic acids are also disclosed.

Abstract: A claim is laid to a permeable composite, a process of production of the composite as well as the use of this composite. The composite essentially contains a perforated and permeable carrier, on and in or on or in which another component that essentially contains metallic compounds with elements from group III to VI of the periodic system is stabilized. Stabilization of the component on or in the carrier is carried out by heating a suspension consisting of the component suspended in a metallic oxide sol that has been applied onto or into or onto and into the carrier. In this way, it is possible to produce a permeable composite that is ideally suited for use in filtration and membrane technologies under very mild conditions either by heating for a short time or warming for a longer time.

Abstract: A porous inorganic membrane comprises at least one inorganic phase having separating properties. Said membrane has a carbon content representing 0.05% to 25% by weight with respect to the mass of said inorganic phase and is selective to non-condensable gases. It is obtained by means of a selectivation treatment of a porous carbon-free inorganic membrane using a hydrocarbon feed. It is used in processes for separating non-condensable molecules such as hydrogen, and in association with a catalyst in a catalytic membrane reactor.

Abstract: The invention relates to semipermeable membranes comprising organically modified silicic-acid polycondensates, to a process for preparing them and to their use in gas exchange and in separation techniques, especially in gas separation, dialysis, pervaporation, and other filtration. The membranes of the invention can be flat or tubular and can be manufactured by conventional methods from viscous liquids obtained by hydrolytic polycondensation of organically modified, hydrolyzable silicon compounds containing C═C double bonds. The membranes are cured by addition polymerization and/or polyaddition of the C═C double bonds.

Abstract: Microporous hydrophobic inorganic membrane having an average pore size of less than 2 nm and a hydrophobicity index octane/water of at least 2 can be obtained by a process comprising hydrolyzing a metal alkoxide in the presence of a hydrocarbyl metal alkoxide having at least one non-hydrolyzable group in an organic solvent to produce a metal (hydr)oxide sol, and precipitating metal (hydr)oxide from said sol and drying the precipitate. In this process, at least 50% of the amount of hydrocarbyl metal alkoxide is introduced into the solvent after 20% of the hydrolysis period has lapsed.

Abstract: The present invention relates to a super water-repellent organic/inorganic composite material, more particularly to a new-concept super water-repellent organic/inorganic composite material with superior separation property having skin layer chemically immobilized with functional polymer on the porous inorganic support surface with fractal surface structure and pores of nanometers to micrometers, using grafting-from surface polymerization method.

Abstract: Gas-impermeable membranes containing a molten salt electrolyte in an electron-conducting matrix provide for mixed ion and electron conduction across the membrane. The membranes mediate transport of a selected ion for gas separation and or catalytic reactions at the membrane surface. The membranes are useful in catalytic membrane reactors, particularly for gas separation and full or partial oxidation reactions. The membranes are of particular interest for mediation of oxide ions, such as carbonate, for carbon dioxide separation or for partial oxidation reactions. Catalytic membrane reactors can incorporate catalyst layers on the membrane surfaces and or three-dimension catalysts, e.g., packed-bed catalysts, in the oxidation zone or the reduction zone of the reactor. The invention also relates to methods of gas separation and method for generating products employing the membranes and catalytic membrane reactors of this invention.

Abstract: A laminar structure (17) comprising a deposited metal, the structure having microholes (17a) extending between a first surface and a second surface thereof, each microhole having a wall which meets the first surface with a rounded edge or tapered configuration in such a manner that the first surface is substantially smooth.

Abstract: A membrane structure comprising a silicon film having a grain structure including grains defining pores therebetween.

Abstract: The invention provides a membrane for cross-flow filtering of a fluid to be treated, said membrane comprising an inorganic rigid porous support defining at least one flow channel for the fluid to be treated flowing in a given direction, the surface of the channel being covered in at least one separator layer separating out from the fluid to be treated a fraction referred to as the permeate which passes through the layer and the support. According to the invention, the separator layer presents a thickness gradient that decreases in the flow direction of the fluid to be treated.

Abstract: Method for the removal of particulate matter from aqueous suspension comprising steps of establishing value of pH and of Zeta potential of particles in the suspension; providing a porous filter having a membrane layer consisting of at least a metal-oxide with a Zeta potential at the pH value of the suspension having same polarity of the Zeta potential as the particles in the suspension; passing the suspension through the porous filter; and withdrawing a filtrate.

Abstract: The present invention relates to metallic filter units 1, in particular, although not exclusively, for use in industrial environments, with improved resistance to degradation. The metallic filtration material 2 is coated with a protective material to reduce degradation thereof during use.

Abstract: A filter device (1) is provided for microfiltration and/or ultrafiltration, preferably for varnishes, such as cathodic dipping varnishes, for connection to a conduit, having a pressure housing (2) and at least one ceramic membrane filter element (3) located in the pressure housing (2). In order to make a filter device of the previously mentioned type available which is also suitable for the recycling of varnishes, particularly cathodic dipping varnishes, the ceramic membrane filter element (3) is electrically connected with at least one electrical conductor (5) and is grounded via the electrical conductor (5).

Abstract: The invention relates to a membrane module in order to filter media which are capable of flowing. Said module incorporates an integrated heat exchanger. According to the invention, the membrane module has the following characteristics: a plurality of rod-shaped, porous, ceramic filter elements (1) (ceramic rods); the ceramic rods (1) are provided with continuous bores (1.1) located parallel to an axis; the ceramic rods are arranged parallel to each other and a lid (3, 4) covers the end thereof: the ceramic rods (1) are sealed at their circumferences against the lid (3, 4); a lid (3) located at one of the membrane modules is provided with an inlet (2.1) for the medium to be treated and a lid (4) located at the other end is provided with an outlet (2.

Abstract: The present invention is directed to a filtration system including filter media that use diffusion as a method of particulate reduction that balances the contact time required for a desirable level of interception and filter performance. The filter system of the present invention includes a filter medium that removes particulate contaminants by diffusion, means for providing sufficient contact time for an influent to contact the filter medium such that the filter medium can intercept sub-micron particulates at an average flow rate below that of an on-demand or instantaneous flow rate; and a storage buffer for providing a filtered effluent at a rate independent of the average flow rate required to achieve adequate particulate reduction through the filter medium.

Abstract: Structures treated with a microbiological interception enhancing agent comprising of a water-soluble cationic material having a counter ion associated therewith at specific sites on the cationic material, in combination with a biologically active metal salt, wherein the counter ion associated with the cationic material preferentially precipitates with at least a portion of the cation of the biologically active metal salt such that precipitation of the biologically active metal cation and the counter ion associated with the cationic material occurs in proximity to the cationic material are disclosed herein. The microbiological interception enhancing agent may be incorporated into articles of commerce by treating the starting materials of the structure or by applying the microbiological interception enhancing agent on to at least one surface of the article.

Abstract: A mordenite (MOR) zeolite membrane is formed on a porous substrate and has crystals that are substantially oriented in a specific crystalline direction. A method for producing the mordenite (MOR) zeolite membrane includes the steps of: immersing a porous substrate in a gel of raw materials which contains zeolite constitution elements in molar ratios of 40-400 of SiO2/Al2O3, 10-120 of H2O/Na2O, and 10-40 of H2O/SiO2; and subjecting the gel in the presence of the porous substrate to hydrothermal synthesis at 150° C. or more to crystallize the MOR zeolite constitution elements and form a MOR zeolite membrane on the porous substrate.

Abstract: An article and method for producing extremely small pore inorganic membranes. The method enables reduction of the pore size of a porous inorganic membrane, such as metal oxides, metal carbides, metal nitrides and cermets. Mean pore diameters of below about 10 Å. Can readily and efficiently be achieved. After the conventional formation of an inorganic membrane, the pore size of the membrane is progressively reduced in a controlled manner to deposit one or more layers of an inorganic compound on the pore walls. This is done by exposing the membrane to the vapor of an inorganic precursor compound. The compound reacts with hydroxyl groups and or absorbed water molecules on the surface of the membrane and is thus bonded to the surface. Water vapor, oxygen, or vapors containing one or more oxygen ligands such as an alcohol are used to hydrolyze the deposited material to the inorganic membrane.

Abstract: The invention is directed to a microbiological interception enhanced filter medium, preferably having an adsorbent prefilter located upstream from the filter medium. Preferably, the prefilter is adapted to remove natural organic matter in an influent prior to the influent contacting the microbiological interception enhanced filter medium, thereby preventing loss of charge on the filter medium. The microbiological interception enhanced filter medium is most preferably comprised of fibrillated cellulose fibers, in particular, lyocell fibers. At least a portion of the surface of the at least some of the fibers have formed thereon a microbiological interception enhancing agent comprising a cationic metal complex. A filter medium of the present invention provides greater than about 4 log viral interception, and greater than about 6 log bacterial interception.

Abstract: The invention is directed to a microbiological interception enhanced filter medium, preferably having an adsorbent prefilter located upstream from the filter medium. Preferably, the prefilter is adapted to remove natural organic matter in an influent prior to the influent contacting the microbiological interception enhanced filter medium, thereby preventing loss of charge on the filter medium. The microbiological interception enhanced filter medium is most preferably comprised of fibrillated cellulose fibers, in particular, lyocell fibers. At least a portion of the surface of the at least some of the fibers have formed thereon a microbiological interception enhancing agent comprising a cationic metal complex. A filter medium of the present invention provides greater than about 4 log viral interception, and greater than about 6 log bacterial interception.

Abstract: A device for separating liquid and/or gas components from each other, which device includes a ceramic membrane comprising a porous layer of &ggr;-alumina which is present on top of a porous layer of supporting material, wherein an alkali-free, phosphorous material is provided between said supporting material and said layer of &ggr;-alumina, and wherein said material preferably consists of monoaluminium phosphate.

Abstract: The invention relates to an ion-conducting composite which is permeable to matter, to a method for producing an ion-conducing composite which is permeable to matter, and to the use of this composite in various processes. Membranes or ion-conducting materials are used for various chemical and physical process, e.g., electrolysis, electrodialysis. The membranes used are often polymer-based. These polymers are relatively non-resistant to solvents and high temperatures. Therefore, the aim of the invention is to provide an ion-conducting composite. The inventive composite consists of inorganic constituents or at least mainly of inorganic constituents, and is characterised in that is very stable in relation to acids and high temperatures. According to the invention, ion-conducting materials or materials which will be ion-conducting after an additional treatment are added to a composite which is permeable to matter during production. Alternatively, the finished composite is treated with said materials.

Abstract: The invention is directed to a microbiological interception enhanced filter medium, preferably having an adsorbent prefilter located upstream from the filter medium. Preferably, the prefilter is adapted to remove natural organic matter in an influent prior to the influent contacting the microbiological interception enhanced filter medium, thereby preventing loss of charge on the filter medium. The microbiological interception enhanced filter medium is most preferably comprised of fibrillated cellulose fibers, in particular, lyocell fibers. At least a portion of the surface of the at least some of the fibers have formed thereon a microbiological interception enhancing agent comprising a cationic metal complex. A filter medium of the present invention provides greater than about 4 log viral interception, and greater than about 6 log bacterial interception.

Abstract: A bacterial fluid filter includes a filter element supported by a backing member. The filter element and backing member are sealed, e.g., with one or more o-ring seals, in a housing to provide a filter assembly capable of filtering fluid under relatively high pressure. In one embodiment, a filter element, backing member, and seal are disposed in a removable and disposable housing that is sized to fit within a filter housing.

Abstract: The invention concerns an inorganic filtering membrane characterized in that it comprises a support made of an inorganic material coated with at least a membrane separating layer consisting of metal hydroxide and/or oxide particles and at the surface of which organomineral and/or mineral units are covalently grafted. The invention also concerns a method for preparing said membranes and their use for filtering.

Abstract: The present invention provides a nonwoven metal fabric for various uses, such as a filter used for purification of exhaust gas from automobiles or semiconductor manufacturing gas, a catalyst carrier of fuel cell, and so forth, in which the corrosion resistance is improved without compromising the property in terms of pressure loss. The nonwoven metal fabric of the present invention is formed with the metal fibers wherein the relation of the fiber diameter Da at the surface part of the gas inlet side and the fiber diameter Db at the central part of the thickness direction is expressed as the equation Da≧1.5×Db and the fiber diameter Da at the surface part of the gas inlet side is not less than 15 &mgr;m and not more than 60 &mgr;m.

Abstract: A process for producing a composite, containing at least one shrinkage-matched ceramic layer, wherein a starting material for the ceramic layer(s) has shrinkage behavior on sintering which is matched to remaining layer(s), and which is selected such that the ceramic-forming constituent of the same contains at least one ceramic powder of a specific size, and which process entails joining the layers of the composite by sintering.

Abstract: An asymmetric membrane comprising a tubular polymer film in combination with a tubular braid on which the film is supported, requires the braid be macroporous and flexible, yet sufficiently strong to withstand continuous flexing, stretching and abrasion during use for microfiltration (MF) or ultrafiltration (UF). The specifications for a braid of a long-lived membrane are provided. A membrane is formed by supporting a polymer film in which particles of calcined &agr;-alumina are dispersed, on the defined tubular braid.

Abstract: A reverse osmosis membrane having excellent antifouling property, which is advantageous in terms of fundamental prevention of fouling generated by inorganic crystalloids, organic contaminants, and microorganisms, and a method for preparing the same. The membrane can be manufactured by hydrolyzing a titanium compound in an acidic aqueous solution to produce TiO2 particles of nano scale; dispersing the produced TiO2 particles in an acidic aqueous solution of pH 1-6 or an alkaline aqueous solution of pH 9-13 to yield a stable TiO2 dispersed solution; and immersing a reverse osmosis membrane prepared by a known method in the TiO2 dispersed solution to incorporate TiO2 into the membrane.

Abstract: The invention provides a membrane for cross-flow filtering of a fluid to be treated, said membrane comprising an inorganic rigid porous support defining at least one flow channel for the fluid to be treated flowing in a given direction, the surface of the channel being covered in at least one separator layer separating out from the fluid to be treated a fraction referred to as the permeate which passes through the layer and the support. According to the invention, the separator layer presents a thickness gradient that decreases in the flow direction of the fluid to be treated.

Abstract: The present invention relates to the field of ceramics and to a ceramic network which can, for example, be applied as a deep-bed filter and a method for the production and utilization thereof. The present invention provides a ceramic network in which the mechanical stability is improved and/or an application-dependent structure can be specifically adjusted. To this end, a ceramic network is provided which comprises two or three dimensional ceramic struts that are connected to one another. The cavities in the ceramic struts have a cross-sectional area with a circular or approximately circular or extensively circular or a convex or multiply convex contour. In addition, a method is provided in which a fiber network is produced. The fiber network comprises polymer fibers and/or natural fibers and/or other fibers, with the fibers each having cross-sectional area with a circular or approximately circular or extensively circular or a convex or multiply convex contour.

Abstract: The present invention provides for a dual-layer inorganic microporous membrane capable of molecular sieving, and methods for production of the membranes. The inorganic microporous supported membrane includes a porous substrate which supports a first inorganic porous membrane having an average pore size of less than about 25 Å and a second inorganic porous membrane coating the first inorganic membrane having an average pore size of less than about 6 Å. The dual-layered membrane is produced by contacting the porous substrate with a surfactant-template polymeric sol, resulting in a surfactant sol coated membrane support. The surfactant sol coated membrane support is dried, producing a surfactant-templated polymer-coated substrate which is calcined to produce an intermediate layer surfactant-templated membrane.

Abstract: A cold isopressing method in which two or more layers of material are formed within an isopressing mold. One of the layers consists of a tape-cast film. The layers are isopressed within the isopressing mold, thereby to laminate the layers and to compact the tape-cast film. The isopressing mold can be of cylindrical configuration with the layers being coaxial cylindrical layers. The materials used in forming the layers can contain green ceramic materials and the resultant structure can be fired and sintered as necessary and in accordance with known methods to produce a finished composite, ceramic structure. Further, such green ceramic materials can be of the type that are capable of conducting hydrogen or oxygen ions at high temperature with the object of utilizing the finished composite ceramic structure as a ceramic membrane element.

Abstract: This invention relates to advanced composite filtration media comprising a functional filtration component and a matrix component, and methods for preparing and using same. More particularly, this invention pertains to advanced composite filtration media and advanced composite filtration media products comprised of a functional filtration component, such as a biogenic silica product (e.g., diatomite), a natural glass product (e.g., expanded perlite), or a natural or synthetic crystalline mineral (e.g., titanium dioxide), which is thermally sintered to a matrix component, such as an engineering polymer (e.g., glasses, natural or synthetic crystalline minerals, thermoplastics, and metals) or a suitable natural material (e.g., rice hull ash, sponge spicules) that has a softening temperature below that of the functional filtration component. This invention also relates to advanced composite media and advanced composite media products, generally, which are also useful in non-filtration applications.

Abstract: A hydrophilic membrane that includes a hydrophobic polymer and a water-soluble polymer-metal complex is provided. This membrane is made by heating a mixture of a hydrophobic polymer, a metal compound, and a water-soluble polymer. The water-soluble polymer forms complexes with the metal compound and homogeneously entangles with the dissolved hydrophobic polymer to form a viscous dope. The dope is extruded through an annular orifice to form a hollow fiber. The fiber is put in an environment having a controlled humidity so that it becomes partially solidified, and then, the fiber is put in a coagulation bath. The hollow fiber is formed by phase inversion in the coagulation bath and is collected using a take-up wheel that is partially immersed in a leaching bath.

Abstract: Powdered nickel-based alloys having substantial amounts of chromium and molybdenum are molded and sintered to form tubular filter supports. Metal oxide particulates, preferably titanium oxide, are impregnated into the interior surfaces of the tubular elements and sintered to create 0.1 micron filter membranes. Hastelloy C-22 is a preferred nickel-based alloy for forming the porous metal support, while rutile is preferred as a starting material for forming the filter membrane. The resultant porous metal/metal oxide filter elements have superior resistance to chemical attack in high chloride, low pH environments.

Abstract: The invention provides a membrane for cross-flow filtering of a fluid to be treated, said membrane comprising an inorganic rigid porous support defining at least one flow channel for the fluid to be treated flowing in a given direction, the surface of the channel being covered in at least one separator layer separating out from the fluid to be treated a fraction referred to as the permeate which passes through the layer and the support. According to the invention, the separator layer presents a thickness gradient that decreases in the flow direction of the fluid to be treated.

Abstract: The invention concerns an inorganic nanofiltration membrane with a detachment threshold between 100 and 200 daltons and comprising: a multichannel ceramic monolith support consisting of a mixture of Al2O3 and of TiO2, a microfiltration membrane separating layer, an ultrafiltration membrane separating layer, preferably consisting of ZrO2, a nanofiltration membrane separating layer, preferably consisting of ZrO2, and obtained by a sol-gel type method. This inorganic nanofiltration membrane is designed for use in the sugar industry, more particularly for treating saline effluents derived from the regeneration of ion exchanging resins used if the refining of cane sugar.

Abstract: A fuel filter having a formulation of a stable intermetallic compound of materials such as tin and antimony. The filter may have an integral porous structure or may be in the form of particles. It removes trace metal ions such as Ca and Na ions.

Abstract: Powdered nickel-based alloys having substantial amounts of chromium and molybdenum are molded and sintered to form tubular filter supports. Metal oxide particulates, preferably titanium oxide, are impregnated into the interior surfaces of the tubular elements and sintered to create 0.1 micron filter membranes. Hastelloy C-22 is a preferred nickel-based alloy for forming the porous metal support, while rutile is preferred as a starting material for forming the filter membrane. The resultant porous metal/metal oxide filter elements have superior resistance to chemical attack in high chloride, low pH environments.

Abstract: A filter media structure, which is capable of operating in the micro- and nanofiltration regime, offers: low cost, durability, high temperature and chemical resistance, high permeability, high flow rate, low pressure drop across the filter media, high mechanical strength, separation efficiency, and biocompatibility. The filter media structure is comprised of mixture of carbon or ceramic fibers and inorganic fiber whiskers generally having a diameter of from about 0.03 to about 5 microns. The present invention further provides a method of preparing a filter media structure comprising mixing together a) inorganic fibers; b) inorganic fiber whiskers; c) a water soluble binder, and optionally depositing a thin layer of pyrolytic carbon on the surface of the inorganic fibers and inorganic fiber whiskers comprising the filter media structure. The filter media structure is selected from the group consisting of a paper, felt and fabric.

Abstract: A porous composite structure, and in particular a membrane, for separating fluids is described. The composite structure comprises at least a porous support and a zeolite layer applied to the support and the zeolite is a zeolite of the T type or of an erionite type.

Abstract: The invention relates to a hydrophobic permeable composite, to a method for producing a hydrophobic permeable composite and to the use of said composite in various processes. Hydrophobic, permeable materials have been known for some time. Plastic materials especially, for example Gore-Tex®, but also materials consisting of other organic polymers are used whenever a material is required to be gas- and steam-permeable but not liquid-permeable. These materials have the disadvantage that they can only be used within a certain temperature range. The inventive composite is characterised by a higher temperature resistance since it consists mainly of inorganic materials. It is also relatively easy to produce since it can be obtained using the sol-gel technique. The inventive composite can be used as a membrane in the oxidation of aromatics, for example in the direct oxidation of benzene to phenol.

Abstract: A liquid solid separation apparatus having a porous metal pipe sealed inside a non-porous metal pipe which allows a portion of the liquids, e.g., hydrocarbons and water to pass through the first pipe into the non porous pipe from which they are removed while solids are retained within the porous pipe. In the process there is a system pressure which aids in the filtration and a circulating velocity which removes the detained solids. Preferably a portion of these solids with reduced liquid content are recycled back to the system, mixed with fresh feed. By recycling a porion of the recovered solid concentrate the velocity of the flow in the system kept constant and the system itself is stabilized.

Abstract: It is a metal filter 1 including a fine filtering layer 3 and a supporting member 2 sintered to be porous and having a covering surface 4 to integrate the fine filtering layer 3 into a laminate to maintain its shape. The average pore diameter of the fine filtering layer 3 is set to be smaller than an average pore diameter of the supporting member 2. The covering surface 4 is formed in an uneven shape so as to allow a filtering surface of the fine filtering layer 3 to be an undulating filtering surface 3A such that the area ratio S1/S0 of its real filtration area S1 to the standard filtration area S0 of the case where it is not formed in an uneven shape, is larger than or equal to 1.3. The average thickness of the fine filtering layer 3 at valley portions 6 of the uneven shape is set to be larger than the average thickness of the fine filtering layer 3 at the crest portions 5 of the uneven shape, and the undulating filtering surface 3A is formed in a smoothly curved surface shape.