DE10254718A1 - Hydrophobic, permeable composite material with self-cleaning properties - Google Patents

Abstract

The present invention relates to a composite material based on a substrate provided with a plurality of openings with a porous inorganic coating located on and in this substrate, which is characterized in that the inner and / or outer surfaces of the composite material at least partially have a structure with elevations has an average height of the elevations of 1 nm to 100 mum and an average distance between the elevations of 1 nm to 100 mum, which are formed by hydrophobic particles, which has self-cleaning properties. DOLLAR A The composite material can be obtained by applying and fixing suitable hydrophobic particles to a composite material. B. can be used as a membrane in filtration applications or as technical textiles.

Description

Object of the present invention is a composite material that rests on at least part of an inner and / or outer surface Has a structure that shows self-cleaning properties, a method for the production of this composite material and its use.

Hydrophobic permeable materials have been known for a long time. Mainly membranes made of Teflon (Goretex), but also from other organic polymers should be mentioned here. These are suitable for a big Field of application where it matters that the material passage through the porous Material only in the form of gas or steam, but not as a liquid takes place. These materials are manufactured, for example by stretching Teflon foils, causing the smallest cracks, which then allow the passage of steam or gas. Because of the hydrophobic Material becomes water droplets retained because of the large surface tension and the lack of wettability of the surfaces of the hydrophobic materials cannot penetrate the pores.

Such hydrophobic materials are suitable for gas and vapor permeation, but also for membrane filtration. moreover they are used in many areas as inert filter materials. A disadvantage of these materials is always the limited temperature range, in which they can be used.

This disadvantage can be avoided by using ceramic membrane films such as z. B. from DE 19741498 . DE 19811708 and WO 99/15262 are known. In contrast to the polymer membranes mentioned, they are stable to high temperatures and also very stable to many chemicals. For this reason, these ceramic membrane foils can be used well in filtration. However, the inorganic membranes have the disadvantage that they are often (due to the ceramic components) hydrophilic and therefore z. B. are not suitable for vapor permeation.

As a further development of the ceramic A hydrophobic ceramic membrane is known from WO 99/62624. This membrane is used during the manufacture of the membrane or after the manufacture of the membrane a water repellent used for water repellency. through of the hydrophobicizing reagent are hydrophobic layers on the inner or outer surfaces of the Membrane generated. However, these layers have the disadvantage that they at least partially clog the pores of the membrane and thus limit the flow through the membrane.

These membranes also show only a comparatively low hydrophobicity and none at all self-cleaning properties. For applications in filtration, in which it is easy to block the pores with the separable one Well, these materials are unsuitable. Most of all also because the membranes are not easily cleaned (e.g. with water) can be. Such membranes must then often with aggressive cleaning agents (acidic, alkaline, with tensides) costly be cleaned, which damages the environment and is expensive and time-consuming.

Object of the present invention it was therefore to provide hydrophobic ceramic composites, which are not only hydrophobic but also only slowly pollute (block) or are easy to clean.

Surprisingly it was found that composite materials, with a surface structure can be equipped with self-cleaning properties from hydrophobic particles can. Such composites have a hydrophobicity that frequently also as super hydrophobicity referred to as. Such composites can by their self-cleaning Properties particularly well used as a membrane in filtration because they block less (quickly) and are cleaned more easily can be. In addition, despite their hydrophobicity, such composites have the same effect Pores that do not or only to a small extent with water repellents are clogged.

The invention is based on the so-called Lotus effect, i.e. the principle of self-cleaning, which is general is known. To achieve good self-cleaning (super hydrophobicity) of a Surface must the surface in addition to a very hydrophobic surface, also a certain roughness exhibit. A suitable combination of structure and hydrophobicity make it possible, that even small amounts of moving water stick to the surface Take dirt particles with you and clean the surface (WO 96/04123).

State of the art is according to EP 0 933 388 that an aspect ratio of> 1 and a surface energy of less than 20 mN / m is required for such self-cleaning surfaces. The aspect ratio is defined here as the quotient of the height and the width of the structure. The aforementioned criteria are realized in nature, for example in the lotus leaf. The surface formed from a hydrophobic wax-like material surface of the plant has elevations that are a few μm apart. Water drops essentially only come into contact with the tips of the elevations. Such water-repellent surfaces have been widely described in the literature.

EP 0 909 747 teaches a method of creating a self-cleaning surface. The surface has hydrophobic elevations with a height of 5 to 200 μm. Such a surface is produced by applying a dispersion of powder particles and an inert material in a siloxane solution and then curing. The structure-forming particles are thus fixed to the substrate by an auxiliary medium.

WO 00/58410 comes to the conclusion that it's technically possible is, surfaces of objects artificially to make self-cleaning. The surface structures required for this from elevations and depressions have a distance between the Surveys of the surface structures in the range of 0.1 to 200 µm and an elevation in the range 0.1 to 100 μm. The one for this used materials must made of hydrophobic polymers or permanently hydrophobic material consist.

In DE 101 18 348 describes polymer fibers with self-cleaning surfaces in which the self-cleaning surface is obtained by the action of a solvent which has structure-forming particles, dissolving the surface of the polymer fibers by the solvent, adhering the structure-forming particles to the dissolved surface and removing the solvent. The disadvantage of this method is that when the polymer fibers are processed (spinning, knitting, etc.), the structure-forming particles and thus the structure which causes the self-cleaning surface can be damaged or, under certain circumstances, can even be lost entirely and the self-cleaning effect can also be lost goes.

In DE 101 18 346 are textile fabrics with a self-cleaning and water-repellent surface, made up of at least one synthetic and / or natural textile base material A and an artificial, at least partially hydrophobic surface with elevations and depressions made of particles that are firmly bonded to the base material A without adhesives, resins or lacquers , which are obtained by treating the base material A with at least one solvent which contains the particles in undissolved form and removing the solvent, at least some of the particles being firmly bonded to the surface of the base material A.

None of the items or Documents describing materials with self-cleaning properties it can be seen that the hydrophobicity of porous ceramic surfaces due to equipment with a hydrophobic structure with self-cleaning properties can be increased without reducing the porosity of the ceramic coating impaired must become.

Object of the present invention is therefore a composite material based on one with a multitude of openings provided substrate with one on and in this substrate porous inorganic coating, which is characterized by that the inner and / or outer surfaces of the Composite material at least partially a structure of surveys with a medium height the elevations from 1 nm to 100 μm and an average distance between the elevations of 1 nm up to 100 μm, which are formed by hydrophobic particles, and that these surfaces have self-cleaning properties.

Also the subject of the present The invention is a process for the production of, in particular, composite materials according to the invention based on a substrate provided with a plurality of openings with a porous inorganic located on and in this substrate Coating, the surface of the composite material, at least partially, a structure of elevations with a medium height the elevations from 1 nm to 100 μm and an average distance between the elevations of 1 nm up to 100 μm have, which are formed by hydrophobic particles, which characterized in that on the outer and / or inner surfaces of the Composite microparticles are applied and fixed, which have hydrophobic properties or by subsequent treatment be made hydrophobic with a water repellent.

It is also the subject of the present Invention the use of composite materials according to the invention as Membranes for filtration, vapor and gas permeation and for the production of objects exposed to the high levels of dirt and water.

The composite materials according to the invention are versatile. As membranes, they have compared to conventional ones purely organic membranes have the advantage that they have a significantly higher temperature stability, even if as a carrier material polymeric materials are used. Through the self-cleaning Properties of the composite surface have those as a membrane Composites used have a significantly longer service life than membranes without self-cleaning surfaces. Through the hydrophobization of the surfaces of the membrane by the hydrophobic particles, the pores of the inorganic layer, in particular, the number of pores and their size are essentially not determined by affects the hydrophobization, which is why a composite material according to the invention almost the same flow or retention properties has like the corresponding untreated composite material.

The composite materials according to the invention also have considerable advantages as technical textiles on. The water vapor permeability is not reduced, although the permeability for the liquid phase is reduced. This effect is also used in steam permeation, which is why the composite materials according to the invention are particularly suitable as membranes in such processes. The composite materials according to the invention have high abrasion stability and have excellent self-cleaning properties due to moving water. The process for producing the composite materials has the advantage that it can be carried out on commercially available machines for coating nonwovens with ceramic.

The method according to the invention has the advantage that the application of the hydrophobic particles to the ceramic Composites are technically easier to carry out than with polymers Materials. In particular can the inorganic hydrophobic microparticles on the purely thermal inorganic coating of the composite material "sintered". To increase the Adhesion can additionally on simple way adhesion-promoting inorganic substances are used.

The composite material according to the invention and a Process for its production is described below without that the invention be limited to these implementations should.

The composite material according to the invention one with a variety of openings provided substrate with one on and in this substrate porous inorganic coating, is characterized in that the inner and / or outer surfaces of the Composite material at least partially a structure of surveys with a medium height the elevations from 1 nm to 100 μm and an average distance between the elevations of 1 nm up to 100 μm, preferably with an average elevation of 50 nm up to 4 μm and / or an average distance of 50 nm to 4 μm, which by hydrophobic particles are formed, and that these surfaces or the parts of the surfaces equipped with the structure, self-cleaning Have properties. Under the inner surfaces of the Composite material, the surfaces of the pores, in particular understood the open pores of the composite material. Make the outer surfaces the outer surfaces of the Composite material. Is it the composite material to a flat Membrane or a flat Formations, so one side (surface) or both sides of the Membrane or all sides and all or part of the inner surfaces be equipped with a corresponding structure from surveys. Preferably both the inner and outer surfaces are one Membrane equipped with a structure from surveys in the area mentioned. The Presence of structures with elevations only on parts of the surface (s) can be advantageous if there is no superhydrophobicity at these points required is because z. B. allow water to pass through should. Usually are the surfaces but completely equipped with the structure with surveys in the area mentioned.

The very particularly preferably have surfaces structures of the composite material according to the invention with elevations with an average height of 0.3 to 1 μm and a average distance from 0.3 to 1 μm on. In the sense of the present invention the distance of the highest elevation of an elevation to the next highest Survey understood. An elevation has the shape of a cone like this represents the top of the cone the highest elevation of the elevation If the elevation is a cuboid, then posed the top surface the highest of the cuboid Survey of the survey. The average width of the surveys is preferably from 1 nm to 100 μm, preferably from 50 nm to 4 μm and very particularly preferably 0.3 to 1 μm. The average width of the surveys will be halfway up the Surveys measured and over the smallest and largest width averaged. The average width of a cone or cylinder corresponds to the diameter of the cylinder or cone in half Height. The average width of a cube is the mean of length the side surface plus length of the area diagonals. It has proven to be particularly advantageous if the surface of the Composite particles at a distance of 0 to 10, in particular 0 to 3 particle diameters to each other.

Those forming the surveys according to the invention hydrophobic microparticles can selected be made of hydrophobic or hydrophobic particles that are a material selected from the silicates, minerals, metal oxides, metal powders, silicas and / or Polymers. The particles can particularly preferably contain silicates, doped silicates, minerals, metal oxides, aluminum oxide, silicas or pyrogenic silicates, aerosils or powdered polymers, such as. B. spray dried and have agglomerated emulsions or cryomilled PTFE or be. The hydrophobic particles can very particularly preferably silicas his.

Preferably, the surface of the Composite material particles that have an average particle diameter from 0.02 to 100 μm, particularly preferably from 0.01 to 50 μm and very particularly preferably from 0.1 to 30 μm exhibit. The surface but can also have particles that form primary particles Store agglomerates or aggregates with a size of 0.2 to 100 μm.

The hydrophobic properties of the particles may be inherent due to the material used for the particles, such as, for example, in the case of polytetrafluoroethylene (PTFE). However, the microparticles can also be those particles which, after suitable treatment, have hydrophobic properties, such as, for. B. after treatment with at least one compound from the group of alkylsilanes, fluoroalkylsilanes or disilazanes. Particularly suitable particles are hydrophobicized pyrogenic silicas, see above called aerosils. Examples of hydrophobic particles are e.g. B. the Aerosil VPR 411, Aerosil ^® VPLE 8241 or Aerosil R 8200. Examples of particles which can be rendered hydrophobic by treatment with perfluoroalkylsilane and subsequent tempering are, for. B. Aeroperl 90/30, Sipernat silica 350, aluminum oxide C, vanadium-doped zirconium silicate or Aeroperl P 25/20.

It can be advantageous if the microparticles have a structured surface. Preferred composite materials have microparticles on their surface which have an irregular fine structure in the nanometer range, that is to say with elevations and intervals in the range from 1 to 1000 nm, preferably from 2 to 750 nm and very particularly preferably from 10 to 100 nm, on the surface. Fine structure is understood to mean structures which have heights, widths and distances in the areas mentioned. Such particles preferably have at least one compound selected from pyrogenic silica, precipitated silica, aluminum oxide, silicon dioxide, pyrogenic and / or doped silicates or powdered polymers. The microparticles with the irregular, airy, fissured fine structure in the nanometer range preferably have elevations with an aspect ratio in the fine structures of greater than 1, particularly preferably greater than 1.5. The aspect ratio is defined as the quotient from the maximum height to the maximum width of the survey. In 1 the difference between the elevations formed by the particles and the elevations formed by the fine structure is illustrated schematically. The figure shows the surface of a substrate X which has particles P (only one particle is shown to simplify the illustration). The elevation formed by the particle itself has an aspect ratio of approx. 0.71, calculated as the quotient from the maximum height of the particle mH, which is 5, since only the part of the particle that contributes to the elevation protrudes from the surface of the composite material X, and the maximum width mB, which is 7 in relation to it. A selected elevation of the elevations E, which are present on the particles due to the fine structure of the particles, has an aspect ratio of 2.5, calculated as a quotient from the maximum height of the elevation mH ′, which is 2.5 and the maximum width mB ', which is 1 in proportion.

The bumps caused by the particles themselves, preferably have an aspect ratio of 0.3 to 1, preferably from 0.5 to 0.95 and particularly preferably from 0.75 to 0.9. Due to the inorganic porous coating on which the microparticles are fixed, there is almost no possibility for the Particles in the surface penetrate the coating (in contrast to particle layers which are attached to them by melting plastic surfaces), which results in an almost ideal aspect ratio of almost 1.

The fact that the ratio is often slightly below 1 can result from the way the particles are fixed to the inorganic porous coating. The microparticles can be fixed to the inorganic porous coating in different ways. On the one hand, the fixation can be achieved using pure adhesive forces. However, the microparticles are preferably fixed to the surface by a chemical bond, preferably by at least partial sintering. The microparticles can be chemically bound or sintered directly with particles of the inorganic porous coating. It is also possible that the microparticles are bound to the surface via adhesion-promoting particles or layers. In the simplest case, such adhesion-promoting particles can be nanoscale, that is to say sizes from 0.1 to 50 nm, metal oxide particles such as B. SiO ₂ , TiO ₂ , ZrO ₂ or Al ₂ O ₃ particles. The adhesion-promoting particles or layers / films can also organic groups, such as. B. have alkyl or alkoxy groups. This can be the case in particular if a temperature was selected during the fixing process at which the adhesion promoter containing organic groups, such as, for. B. silanes or metal alkoxides, have not been completely converted into the corresponding oxides. Functionalized alkyltrialkoxysilanes are preferably used as adhesion promoters.

The adhesion-promoting particles or Layers / films can the surface of the composite material and / or the surface of the structuring microparticles cover all or part. Preferably there is so much adhesion promoter present that surface a maximum of 15% of the microparticles, preferably a maximum of 10% and very particularly preferably from 1 to 5% of adhesion-promoting particles or layers / films are covered. Are significantly more shares of the Microparticle surface covered by adhesion-promoting particles or layers / films, so the self-cleaning properties of the surface deteriorate noticeably. All the adhesion-promoting alkyltrialkoxysilanes form particularly preferably or their hydrolysis products from monolayers.

Suitable as a composite material itself all composite materials that are made of a porous inorganic on a porous substrate Have coating. Are particularly suitable as composite materials Membranes, such as B. ceramic membranes or hybrid membranes. Particularly preferred composite materials are e.g. B. such as them in documents WO 99/15262, WO 99/62620, WO 99/62624, WO 02/47801 and WO 02/47802, to which expressly is referred to have been described.

Preferred composite materials have woven and / or non-woven fibers or filaments of metals, natural fibers, glasses, ceramics or polymers as the substrate. The substrate comprising fibers or filaments can e.g. B. a woven, knitted and / or nonwoven. Particularly preferred composite fabric have a substrate that is selected from polymer fiber nonwovens, metal wire mesh or glass fiber fabrics. Very particularly preferred composite materials have a polymer fleece. The polymer fibers are preferably selected from polyacrylonitrile, polyamides, polyimides, polyacrylates, polytetrafluoroethylene, polyester, such as. B. polyethylene terephthalate and / or polyolefins, such as. B. polypropylene, polyethylene or mixtures of these polymers. The membrane according to the invention preferably has polymer fibers which have a softening temperature of greater than 100 ° C. and a melting temperature of greater than 110 ° C. The application areas are also reduced for polymer fibers with lower temperature limits. Preferred membranes can be used up to a temperature of up to 150 ° C., preferably up to a temperature of 120 to 150 ° C. and very particularly preferably up to a temperature of 121 ° C. It can be advantageous if the polymer fibers of the substrate of the composite material have a diameter of 1 to 25 μm, preferably 2 to 15 μm. If the polymer fibers are significantly thicker than the ranges mentioned, the flexibility of the substrate and thus that of the membrane suffers.

The substrate particularly preferably has of the composite material used has a thickness of less than 200 μm. It can be particularly advantageous if the composite material according to the invention has a substrate which has a thickness of 25 to 100 microns and particularly preferably from 30 to 70 μm having.

The porous, inorganic, ceramic Coating has interconnected particles. The particles can be chemically or physically linked. Preferably are the particles by sintering or inorganic gluing connected with each other. The size and size distribution the particle determines the porosity of the coating. Preferably there is at least one inorganic component in the coating in a grain size fraction with an average grain size of 1 to 250 nm, preferably 10 to 100 nm or with a medium Grain size of 251 up to 10000 nm, preferably 1000 to 5000 nm. It can be beneficial be when the composite material according to the invention has a coating that has at least two grain size fractions one or more inorganic components. Likewise can it may be advantageous if the coating has at least two grain size fractions of at least two inorganic components. The grain size ratio can from 1: 1 to 1: 10000, preferably from 1: 1 to 1: 100. The quantitative ratio the grain size fractions in the composite material can preferably be from 0.01: 1 to 1: 0.01 be.

The inorganic coating preferably has an oxide of the metals Ti, Si, Zr or Al. The inorganic porous coating preferably has oxides selected from TiO ₂ , SiO ₂ , ZrO ₂ or Al ₂ O ₃ . In addition to one or more of these oxides, the inorganic coatings can have further compounds or elements.

The composite material according to the invention preferably has a porosity from 10% to 70%, preferably from 20% to 60% and particularly preferred from 30% to 50%. The composite materials according to the invention have preferably an average pore size of 5 to 5000 nm, particularly preferably from 10 to 1000 nm and very particularly preferably from 100 up to 800 nm. The determination of the mean pore size and the porosity by means of mercury porosimetry z. B. with a porosimeter 4000 by Carlo Erba Instruments. The method of mercury porosimetry be on the Washburn equation (E. W. Washburn, "Note on a Method of Determining the Distribution of Pore Sizes in a Porous Material, "Proc. Natl. Acad. Sci., 7, 115-16 (1921)) as well as publications referring to this quote.

Composites according to the invention have a particularly high hydrophobicity. As a measure of the hydrophobicity of the composite materials according to the invention can z. B. the height a water column that can be built on these composite materials become. The height the water column is not only from the hydrophobicity but also from the porosity of the composite material dependent. preferred composite materials according to the invention are characterized by the fact that a water column acc. DIN EN13562 of preferably at least 4 cm, preferably of at least 10 cm, particularly preferably at least 50 cm and very particularly preferably at least 100 cm high can be built.

The composite materials according to the invention are preferably flexible and can preferably be set up without damage to every radius down to 100 mm, preferably down to Bend 50 mm and very particularly preferably down to 2 mm. The good flexibility of the membrane according to the invention has the advantage that when used in filtration or gas separation sudden Pressure fluctuations through the membrane can be easily tolerated can, without damaging the membrane becomes. Furthermore, you can the membranes can be brought into almost any shape by the application needed (winding modules, pocket modules etc.). The high flexibility guarantees also the usability of the composite materials according to the invention in textiles for applications in industry, in the leisure sector and in the clothing industry.

The composite material according to the invention is preferably obtainable by a process for the production of composite materials on the basis of a substrate provided with a multiplicity of openings with a porous inorganic coating located on and in this substrate, the surface of the composite material at least partially having a structure of elevations with an average height the survey gene from 1 nm to 100 microns and an average distance of the elevations from 1 nm to 100 microns, which are formed by hydrophobic particles, which is characterized in that microparticles are applied and fixed on the inner and / or outer surfaces of the composite material which have hydrophobic properties or are rendered hydrophobic by subsequent treatment with a hydrophobicizing reagent. The particles are preferably applied by applying a dispersion in which the particles are dispersed. The application can take place in such a way that only partial areas of the inner and / or outer surfaces of the composite material or the entire inner and / or outer surfaces of the composite material are brought into contact with the microparticles.

The application of the particles can by doctoring, spraying or rolling a dispersion comprising the particles onto at least one a surface (Side) of the composite material or parts thereof. As well Is it possible, the application of the particles by immersing the composite material in a dispersion containing the particles.

The dispersion containing particles preferably has an alcohol or hydrocarbon as the dispersant, especially ethanol, toluene or cyclohexane. In addition to the dispersant and the structure-forming microparticles, the dispersion can further Components have. In particular, the dispersion can be an adhesion promoter or precursors thereof and chemical reaction components, such as. B. water or acids, or have dispersing agents. Dispersions are preferred used from 1 to 25% by weight, preferably 5 to 20% by weight and particularly preferably 7.5 to 12.5% by weight of structure-forming Have microparticles.

It’s not imperative that an adhesion promoter is present in the dispersion. It is also possible the bonding agent in an upstream step on the composite material apply and then to treat the composite material pretreated according to the invention, z. B. by applying a dispersion which has microparticles.

As an adhesion promoter in the method according to the invention preferably those selected from silanes and / or polymeric or particulate sols of alkyltrialkoxysilanes or silicon, zirconium or titanium alkoxides used. Especially Functionalized alkyltrialkoxysilanes are preferably used as adhesion promoters.

Such brines are hydrolyzed at least one metal compound, preferably selected from Metal nitrate, metal chloride, metal carbonate, metal alcoholate produced. The sols are preferably obtained by hydrolysis of an alcoholate compound of the elements Zr, Al, Si, Ti, Sn, and Y. The hydrolysis takes place preferably in the presence of water, steam, ice, or one Acid or a combination of these connections.

In a special version are polymerized by hydrolysis of the compounds to be hydrolyzed Brine made. These polymer sols are characterized by that the compounds formed in the sol by hydrolysis are polymeric (i.e. chain-like over one larger space networked). The polymeric sols usually have less than 50 % By weight, preferably very much less than 20% by weight, of water and / or aqueous Acid on. To the preferred proportion of water and / or water Acid too come the hydrolysis is preferably carried out so that the compound to be hydrolyzed with 0.5 to 10 times the molar ratio and preferably with half the molar ratio Water, steam or ice, based on the hydrolyzable group, the hydrolyzable compound is hydrolyzed. One up to 10 times the amount of water can be used with very slow hydrolyzing compounds, such as B. in tetraethoxysilane (TEOS) or alkyltrialkoxysilanes, be used. Hydrolysis with less than the preferred one Amount of water, water vapor, or ice also gives good results. With a fall below the preferred amount of half molar ratio possible by more than 50% but is not very useful, because if this value is fallen below the hydrolysis is no longer complete is and the adhesion-promoting effect is no longer so good. to Production of this polymeric brine with the desired very small proportion of water and / or acid in the sol it can be advantageous if the compound to be hydrolyzed in an organic solvent, in particular ethanol, isopropanol, butanol, amyl alcohol, hexane, Cyclohexane, ethyl acetate and or mixtures of these compounds, solved before the actual hydrolysis is carried out.

As adhesion promoting silanes in particular hydrolyzed or non-hydrolyzed compounds selected from the alkylalkoxysilanes, the fluorinated alkylalkoxysilanes, the Vinylalkoxysilanes, the amine-functionalized alkoxysilanes and / or the glycidyl-functionalized alkoxyilanes, such as. B. the Dynasilane Degussa or TEOS can be used.

The following table contains one exemplary overview of this and other usable adhesion promoters based on organofunctional ones Si compounds.

With:

• AMEO = 3-aminopropyltriethoxysilane
• DAMO = 2-aminoethyl-3-aminopropyltrimethoxysilane
• GLYMO = 3-glycidyloxytrimethoxysilane
• MEMO = 3-methacryloxypropyltrimethoxysilane
• Silfin = vinylsilane + initiator + catalyst
• VTEO = vinyl triethoxysilane
• VTMO = vinyl trimethoxysilane
• VTMOEO = vinyl tris (2-methoxyethoxy) silane

The adhesion promoter should be selected so that at the chosen one Fixation temperature a secure fixation of the particles by the adhesion promoter on the surface of the composite material guaranteed is. In particular, may the substances used after fixation no longer hydrolysis be sensitive.

The dispersions used according to the invention preferably have from 0.1 to 5% by weight, particularly preferably from 0.5 to 2.5% by weight of adhesion-promoting component (based on the proportion of particles, i.e. without solvent or the like) on.

That after applying the particles fixation is preferably carried out by heating of the composite material with the dispersion applied to a temperature from 100 to 700 ° C, preferably from 100 to 400 ° C. By warming up may be Remaining residues of the dispersant removed. Are not adhesion promoters present in the dispersion, it has proven to be advantageous if the temperature so chosen is that the structure-forming particles sinter at least partially or at least superficial Form chemical bonds to the composite. Are in the Dispersion coupling agent present, the temperature is preferred chosen so that by heating chemical bonds formed between adhesion promoter, particles and / or surface become or a sintering of adhesion promoter, particles and / or surface he follows. The temperature at which fixation is performed can, in addition to the requirements for the fixation and the type of Adhesion promoter essentially depends on that in the composite material existing materials. Has the composite as a substrate or particles of polymers, the maximum temperature is in which the particles are fixed, depending on the polymer from 100 to 300 ° C. Only inorganic materials are included, all of which have a melting point above from 700 ° C have, the maximum temperature can be up to 700 ° C.

Fixing the on the composite applied particles are preferably carried out by heating a temperature of 100 to 400 ° C, preferably from 150 to 350 ° C and particularly preferably from 200 to 300 ° C. Very particularly preferred solidification takes place by heating for 10 min. up to 5 hours for one Temperature from 100 to 350 ° C or for 0.5 to 5 minutes at a temperature of 150 to 400 ° C, preferably 200 to 250 ° C.

As hydrophobic microparticles can in the inventive method those are used that have at least one material selected from Silicates, minerals, metal oxides, metal powders, silicas, pigments or high temperature resistant Have (HT) polymers. The particles can particularly preferably contain silicates, doped silicates, minerals, metal oxides, aluminum oxide, silicas or Aerosile or powdery Polymers such as B. spray dried and be agglomerated emulsions or cryomilled PTFE. Especially silicas are preferably used as hydrophobic particles.

Particles are preferably used, which have an average particle diameter of 0.01 to 100 μm, especially preferably from 0.02 to 50 μm and very particularly preferably have from 0.1 to 30 μm. But are suitable also particles that are made up of primary particles Store together to form agglomerates or aggregates with a size of 0.2 to 100 μm.

It can be advantageous if the particles used have a structured surface. Particles which have an irregular fine structure in the nanometer range with elevations with an average distance of 1 to 1000 nm and an average height of 1 to 1000 nm, preferably in each case from 2 to 750 nm and very particularly preferably in each case from 10 to 100 nm, are preferred Have surface used. Fine structure is understood to mean structures which have heights, widths and distances in the areas mentioned. Such particles preferably have at least one compound selected from pyrogenic silica, precipitated silica, aluminum oxide, silicon dioxide, pyrogenic and / or doped silicates or powdery high-temperature-resistant polymers. The particles with the irregular, airy, fissured fine structure in the nanometer range preferably have elevations with an aspect ratio in the fine structures of greater than 1, particularly preferably greater than 1.5. The aspect ratio is defined as the quotient from the maximum height to the maximum width of the survey. In 1 the difference between the elevations formed by the particles and the elevations formed by the fine structure is illustrated schematically. The figure shows the surface of a composite material X which has particles P (only one particle is shown to simplify the illustration). The elevation formed by the particle itself has an aspect ratio of approx. 0.71, calculated as the quotient from the maximum height of the particle mH, which is 5, since only the part of the particle that contributes to the elevation protrudes from the surface of the composite material X, and the maximum width mB, which is 7 in relation to it. A selected elevation of the elevations E, which are present on the particles due to the fine structure of the particles, has an aspect ratio of 2.5, calculated as a quotient from the maximum height of the elevation mH ′, which is 2.5 and the maximum width mB ', which is 1 in proportion.

The hydrophobic properties of the particles may be inherent due to the material used for the particles, such as, for example, in the case of polytetrafluoroethylene (PTFE). However, it is also possible to use hydrophobic particles which, after suitable treatment, have hydrophobic properties, such as, for example, B. treated with at least one compound from the group of fluoroalkylsilanes, alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes. Particularly suitable particles are hydrophobicized pyrogenic silicas, so-called aerosils. Examples of hydrophobic particles are e.g. B. the Aerosil ^® VPR 411, Aerosil ^® R202, Aerosil ^® VPLE 8241 or Aerosil ^® R 8200. Examples of particles which can be rendered hydrophobic by treatment with perfluoroalkylsilane and subsequent heat treatment include B. Aeroperl 90/30, Sipernat silica 350, aluminum oxide C, vanadium-doped zirconium silicate or Aeroperl P 25/20. The use of such hydrophobized particles is usually possible without problems up to a temperature of 350 ° C. without the hydrophobicity being significantly impaired.

It may be advantageous to change the surfaces of the Composite material that has been equipped with the surface structure are, afterwards to hydrophobize (again). This can be done by treating the surfaces with the for the hydrophobization of the particles specified compounds take place.

As a usable composite material Even all composite materials that are on a porous substrate are suitable a porous have inorganic coating. Are particularly suitable as Composite membranes, such as B. ceramic membranes or Hybrid membranes. Particularly preferred composite materials are e.g. B. those as described in documents WO 99/15262, WO 99/62620 WO 99/62624, WO 02/47801 and WO 02/47802, to which express reference is made will be described. Preferred usable composite materials have average pore sizes of 5 to 5000 nm, particularly preferred from 10 to 1000 nm and very particularly preferably from 100 to 800 nm on.

The method according to the invention can be used one flat, flexible composite material as the starting material z. B. be carried out that the composite material is unrolled from a roll with a Speed from 1 m / h to 2 m / s, preferably at one speed of 0.5 m / min. up to 20 m / min and very particularly preferably with a Speed of 1 m / min to 5 m / min through at least one apparatus, which the dispersion on one or both sides of the composite or else on and in the composite material, such as. Legs Roller, a spray apparatus, a squeegee or a plunge pool, and at least one other piece of equipment, which is the fixing of the particles to the surface of the composite by heating allows such as B. an electrically heated oven, and the so produced Composite material is rolled up on a second roll. To this Way it is possible the composite material according to the invention manufactured in a continuous process. Any necessary post-treatment steps (e.g. a subsequent Hydrophobization) also be carried out in a continuous process.

The composite materials according to the invention can be used as Membranes for the filtration, steam and Gas permeation and for the production of objects that have high loads exposed to dirt and water. Such objects can z. B. selected be made of textiles, technical textiles, awnings, tents, convertible tops, advertising and workwear.

The superhydrophobic ceramic composites according to the invention with self-cleaning surfaces can be used particularly well in filtration. Because of the very good temperature stability, the composite materials according to the invention are very well suited as membranes for gas and vapor permeation. However, the self-cleaning composites are also better suited for conventional filtration tasks than polymer membranes, as they show a significantly better fouling behavior. In addition, composite materials used as membranes can be easily removed with pure water be cleaned, so that cleaning agents that are harmful to the environment and to some extent to health (usually very acidic or alkaline as well as containing surfactants and solvents) can ideally be dispensed with.

Based on the figure 1 the method according to the invention and the composite material according to the invention are explained in more detail without being limited thereto.

In 1 the difference between the elevations formed by the particles and the elevations formed by the fine structure is illustrated schematically. The figure shows in simplified form the surface of a composite material X which has particles P (only one particle is shown to simplify the illustration). The elevation formed by the particle itself has an aspect ratio of approx. 0.71, calculated as the quotient from the maximum height of the particle mH, which is 5, since only the part of the particle that contributes to the elevation protrudes from the surface of the composite material X, and the maximum width mB, which is 7 in relation to it. A selected elevation of the elevations E, which are present on the particles due to the fine structure of the particles, has an aspect ratio of 2.5, calculated as a quotient from the maximum height of the elevation mH ′, which is 2.5 and the maximum width mB ', which is 1 in proportion.

The inventive method is based on the following examples described, without the invention thereon limited should be.

Example 1.1: Production an S450P membrane

15 g are initially added to 160 g of ethanol g of a 5 wt .-%, aqueous HCl solution, 10 g tetraethoxysilane, 2.5 g methyltriethoxysilane and 7.5 g dynasilane GLYMO (Degussa AG). In this sol, initially for some Hours stirred was then 125 g of the aluminum oxides Martoxid MZS-1 and Martoxid MZS-3 (manufacturer: Martinswerke) suspended. This suspension (Slip) is for Homogenized for at least another 24 h with a magnetic stirrer, the Mixing vessel covered must be so that there is no loss of solvent comes.

A PET fleece with a thickness of approx. 30 μm and a basis weight of about 20 g / m2 in a continuous rolling process (Belt speed approx. 8 m / h, T = 200 ° C) coated with this slip. In this rolling process, the slip is treated with a roller, the opposite to the direction of the belt (direction of movement of the fleece) Fleece rolled on. The fleece is running then through an oven at the specified temperature. In the following The same method or arrangement is used for experiments. It becomes a microfiltration membrane with a medium pore size of 450 nm, which is not hydrophobic and not self-cleaning Has properties. The determination of the average pore size was carried out by means of mercury porosimetry with a porosimeter 4000 by Carlo Erba Instruments.

Example 2.1:

A PET supported membrane according to Example 1.1 (S450P, Creavis GmbH) is reacted with a suspension of 25 g of Aerosil ^® VPLE 8241 (Degussa AG) in 100 g of ethanol and 60 g of water is coated. For this purpose, the suspension is continuously rolled onto the ceramic membrane films and dried at a temperature of 210 ° C.

Then the behavior of the characterized membrane thus produced. The membrane showed one very good lotus effect. Water droplets dripped off very well. The Roll angle, i.e. the angle to the horizontal at which a drop independent rolls off, was for a 60 μl drop of water 8 ± 5.7 °. After pollution the membrane with soot could this is almost completely removed by sprinkling with water become. The water penetration through the membrane equipped in this way took place as the water column built up a height exceeded 4 cm (measured according to DIN EN13562). On the membrane not equipped with microparticles according to example 1.1 could not have a water column being constructed.

Example 2.2:

A PET supported membrane according to Example 1.1 (S450P, Creavis GmbH) is reacted with a suspension of 10 wt .-% Aerosil ^® VPLE coated in ethanol 8241 purpose, the suspension is coated onto the ceramic membrane foil and dried at a temperature of 150 ° C.

The behavior of the membrane produced in this way was then characterized. The membrane showed a very good lotus effect. Water droplets dripped off very well. The roll angle, i.e. the angle to the horizontal at which a drop rolls off independently, was 0.6 ± 0.5 ° for a 60 μl drop of water. According to Ver soiling of the membrane with soot could be almost completely removed by sprinkling with water. The water penetration through the membrane equipped in this way did not take place until the built-up water column exceeded a height of 50 cm (measured according to DIN EN13562). No water column could be built up on the membrane not equipped with microparticles according to Example 1.1. The comparison of the products of Examples 2.1 and 2.2 clearly shows that the use of a non-aqueous dispersion can better prevent the passage of the membrane.

Example 2.3

A steel mesh-supported membrane (Z450S, Creavis GmbH) is mixed with a suspension of 40 g Aerosil ^® VPLE 8241 (Degussa AG), 2 g tetraethyl (ortho) silicate (TEOS) and 0.5 g of a 0.5% HCl solution Water coated in 356 g of ethanol. For this purpose, the suspension is rolled onto the ceramic membrane film in a continuous process and dried at a temperature of 250 ° C.

Then the behavior of the characterized membrane thus produced. The membrane showed one very good lotus effect. Water droplets dripped off very well. The Roll angle, i.e. the angle to the horizontal at which a drop independent rolls off, was for a 60 μl drop of water 1.2 ± 0.3 °. After pollution the membrane with soot could this is almost completely removed by sprinkling with water become. The water penetration through the membrane thus equipped only occurred than the water column built up a height exceeded 50 cm (measured according to DIN EN13562). On the membrane not equipped with microparticles couldn't have a water column being constructed.

Example 2.4

A polymer supported non-woven membrane (foil) (S450P, Creavis GmbH) is reacted with a suspension of 40 g of Aerosil ^® VPLE 8241, 2 g MEMO and 0.5 g of a 0.5% HCl solution in water in 360 g of ethanol coated. For this purpose, the suspension is rolled onto the ceramic membrane film in a continuous process and dried at a temperature of 150 ° C.

Then the behavior of the characterized membrane thus produced. The membrane showed one very good lotus effect. Water droplets dripped off very well. The Roll angle, i.e. the angle to the horizontal at which a drop independent rolls off, was for a 60 μl drop of water 2.1 ± 0.6 °. After pollution the membrane with soot could this is almost completely removed by sprinkling with water become. The water penetration through the membrane thus equipped only occurred than the water column built up a height exceeded> 160 cm (measured according to DIN EN13562). On the membrane not equipped with microparticles according to example 1.1 could not have a water column being constructed.

Claims (21)

Composite material based on a substrate provided with a plurality of openings with a porous inorganic coating on and in this substrate, characterized in that the inner and / or outer surfaces of the composite material at least partially have a structure of elevations with an average height of the elevations of 1 nm to 100 microns and an average distance between the elevations of 1 nm to 100 microns, which are formed by hydrophobic microparticles, and that these surfaces have self-cleaning properties. Composite material according to claim 1, characterized in that the hydrophobic microparticles are selected from hydrophobic or hydrophobized particles that are a material selected from the silicates, minerals, metal oxides, metal powders, silicas and / or Polymers. Composite material according to claim 1 or 2, characterized characterized that the surveys have an average height of 50 nm to 4 μm and / or have an average distance of 50 nm to 4 μm. Composite material according to at least one of claims 1 to 3, characterized in that the elevations caused by the microparticles themselves, have an aspect ratio of 0.3 to 1. Composite material according to at least one of claims 1 to 4, characterized in that the microparticles are nanostructured Microparticles are a fine structure with bumps with a aspect ratio of greater than 1. Composite material according to at least one of claims 1 to 5, characterized in that the substrate is woven and / or non-woven fibers or filaments of metals, natural fibers, glasses, ceramics or have polymers. Composite material according to claim 6, characterized in that the substrate comprising fibers or filaments is a woven fabric, Has knitted fabrics and / or fleece. Composite material according to one of claims 6 or 7, characterized in that the substrate is selected made of polymer fiber fleece, metal wire mesh or glass fiber mesh. Composite material according to at least one of claims 1 to 8, characterized in that the porous inorganic, ceramic Coating has at least one oxide of the metals Ti, Si, Zr or Al. Process for the production of composite materials based on a substrate provided with a plurality of openings with a porous inorganic located on and in this substrate Coating, the surfaces of the composite material, at least partially, a structure of elevations with a medium height the elevations from 1 nm to 100 μm and an average distance between the elevations of 1 nm up to 100 μm have, which are formed by hydrophobic particles, thereby characterized in that on at least one inner and / or outer surface of a Composite microparticles are applied and fixed, which have hydrophobic properties or by subsequent treatment be made hydrophobic with a water repellent. A method according to claim 10, characterized in that the application of the particles by doctoring, spraying or Rolling a dispersion containing the particles onto at least one side of the composite material is made. A method according to claim 10, characterized in that applying the particles by dipping the composite in a dispersion containing the particles. Procedure according to a of claims 11 or 12, characterized in that the dispersion as a dispersant has an alcohol. Procedure according to at least one of the claims 11 to 13, characterized in that the dispersion contains an adhesion promoter, selected from solutions and / or polymeric or particulate Sols of functionalized alkyltrialkoxysilanes or silicon, Has zirconium or titanium alkoxides. Method according to at least one of claims 10 to 14, characterized in that the fixing of the particles by Heat to a temperature of 100 to 400 ° C. Procedure according to at least one of the claims 10 to 15, characterized in that microparticles that a have an average particle diameter of 0.01 to 100 μm. Method according to at least one of claims 10 to 16, characterized in that microparticles selected from Silicates, minerals, metal oxides, metal powders, silicas, pigments or polymers. Method according to at least one of claims 10 to 17, characterized in that microparticles that have a fine structure with elevations with an average distance of 1 to 1000 nm and a medium height have from 1 to 1000 nm, are used. Method according to at least one of claims 10 to 18, characterized in that the particles by treatment with at least one compound from the group of alkylsilanes, fluoroalkylsilanes and / or Disilazane can be endowed with hydrophobic properties. Use of composite materials according to one of claims 1 to 9 as membranes for filtration, vapor and gas permeation and for the production of objects exposed to the high levels of dirt and water. Use according to claim 20, characterized in that the objects are selected from textiles, technical Textiles, textiles for leisure needs, awnings, tents, convertible tops, advertising media and Workwear.