EP1587607A2

EP1587607A2 - Flexible, breathable polymer film and method for production therof

Info

Publication number: EP1587607A2
Application number: EP04702279A
Authority: EP
Inventors: Dietmar Fink; Udo Küppers; Jose Rojas-Chapana; Helmut Tributsch
Original assignee: Hahn Meitner Institut Berlin GmbH
Current assignee: Hahn Meitner Institut Berlin GmbH
Priority date: 2003-01-15
Filing date: 2004-01-15
Publication date: 2005-10-26
Also published as: WO2004064478A3; WO2004064478A2; DE10301984B4; DE10301984A1; US20060194037A1; JP2006518287A

Abstract

The invention relates to an economical, flexible, breathable polymer film, modified in the region of the pores opening out in a funnel shape at the surface thereof, with a nanoscale particle system and which is particularly suitable for packaging purposes. The modification comprises at least one composite layer construction made from a binding agent film of chemically inert inorganic nanoparticles and a coating film of hydrophilic non-toxic metal oxide particles which are photocatalytically active to short-wave light radiation, which have an anti-bacterial and self-cleaning effect. The efficacy thereof is dependent on the selection of opening angle of the funnel-shaped opening of the pores. Various layer adjuncts are possible for increasing the functionality. Production occurs with a polymer film provided on both sides with funnel-shaped capillary pores by means of high-energetic ion radiation and single- or double-sided etching, by means of an economical surface treatment carried out at ambient conditions in a sol-gel system with colloidal nanoparticle dispersions, in particular based on ceramics.

Description

Flexible, breathable polymer film and process for its manufacture.

description

The invention relates to a flexible, breathable polymer film with a spatially ordered structure from the gas exchange through the

Polymer film enable capillary pores and a method for producing such polymer films.

Such a polymer film is a functional, porous membrane. Nature has developed a large number of such functional membranes for all life to come. This also includes the organic / inorganic composite systems of egg shells. Its structure is designed in such a way that it guarantees the vital gas exchange processes (Cθ ₂ / θ ₂ exchange) and danger prevention for future life (microorganisms) through the entire structural structure of the eggshell. This efficient biological property is used as a model for the technical development of a functional membrane, as will be described below. Based on the bioanalogous evaluation of the ultrastructure of an ostrich eggshell as a bionic model system and its suitability for the selection of surface-active agents, a polymer film is to be developed which, however, in contrast to the eggshell, is flexible, which results in a significantly larger area of application and a significantly lower risk of destruction , An ostrich egg is characterized by high stability due to optimized composite layers with the participation of microparticles of the CaCO ₃ type and spatially ordered structures. It shows the ability to skillfully control gas exchange processes as a breathing membrane and has an effect as antibacterial protection against the penetration of microorganisms (antifouling properties). In addition, the ostrich egg has high reflection properties. An application-oriented outlook for such breathable bionic membranes primarily leads to packaging of all kinds. Higher demands on comfort, logistics and environmental protection require high-quality packaging. It is no longer enough that packaging only protects the product and makes it transportable. In addition, they must be environmentally friendly to produce, usable for recycling and must be disposed of safely at the end of their product life. The material that meets all of these ecological and economic requirements should also be particularly light, stable, unbreakable, transparent and also tasteless. Hardly any packaging material can currently combine all of these criteria and even more. Packaging of the future can set standards if it is not the "product" packaging but the "system" packaging including its environmental and economic constraints as a whole that is optimized. This applies to packaged food and plants, which are perishable and short-lived, as the largest area of application as well as for "packaging" everyday useful goods, capital goods or others. Other fields of application for such breathable bionic membranes are: Packs in the medical and pharmaceutical sector, biocompatible, antibacterial and breathable implants, breathable films for "cladding" in construction and design, flexible covers, sensor-integrated films for controlling gas transport, active membranes with self-diagnosis system, intelligent encapsulations on a molecular or nanoscale size as a depot for active substances, flexible elements or covers for applications in vehicle and traffic technology, active covers (cell covers) as functional parts of new robot generations, active covers (membranes) in the field of environmental technology, active covers in filter technology, Hazard protection, mouth filters and textile and clothing technology.

In addition to its breathability, its functionality with regard to the antibacterial effect is important for the new material type to be designed (Sterilization) and self-cleaning. A relatively new, known process for combining these two functions is "photocatalysis". Here, a light-stimulable material, usually a semiconductor, is exposed to long-wave UV radiation. This generates reactive OH radicals that destroy microorganisms and dirt or neutralize decomposition gases or liquids. Photoactivity is also considered to be the cause of hydrophilic properties. Surface tension measurements on small drops of liquid have shown that UV light reduces the contact angle. This confirms a photocatalytic decomposition of organic substances on the coated film. The advantages of this process can be seen in the fact that the catalyst can be reused and that the UV radiation required for the chemical reaction can be taken from both artificial light and sunlight otocatalytically active material (doped or micro-heterogeneous material) towards a long-wave sensitivity, blue light can be used for irradiation. Overall, short-wave light irradiation in a wavelength range from 300 nm to 600 nm is suitable for producing the described photocatalytic effect.

It is generally known from the prior art to impregnate membranes with inhibitors, antibiotics or salts, for example breathable film for extending the freshness of food or bacteria-repellent packaging for food. With these membranes, however, a controlled gas exchange cannot be guaranteed at the same time. From US 6,114,024, monolithic, breathable polymer films are known as solid, homogeneous fluid barriers, which, however, permit gas transport by adsorption, absorption, diffusion or desorption. The polymers used are highly hygroscopic, which means that they tend to absorb water. In a saturated state, they prefer to allow water vapor to pass into an unsaturated environment over oxygen and other gases. US 6,187,696 B1 is a layered composite known with a fibrous substrate on which a film is laminated, which is vapor-permeable but liquid-blocking. However, the layer composite is preferably free of micropores. From US 6,228,480 B1, a flexible structure coated with a photocatalytic material is known for the moisture-regulating packaging of foods, in which a resin layer is arranged between the substrate and the photocatalytic layer in order to improve adhesion and to protect the substrate and catalytic activity of the photocatalytic material. In particular, it is known from this US patent that titanium dioxide as an n-conducting semiconductor material is a good photocatalytic material with disinfectant and antimicrobial properties, which can activate various chemical reactions under UV radiation, in particular can decompose ethylene gas as a fermentation gas from food. It is also known that a high catalytic activity is achieved if the titanium oxide is involved in powder form or as a suspension in a solution. The activity can be increased further if the substrate has a porous structure on its surface in order to increase the contact areas of the substrate with the reactant. A penetration of the flexible substrate with a photocatalytically active material to increase the catalytic activity is not apparent from the US patent.

However, this deals with the publication by JC Hulteen and CRMartin: "Template Synthesis of Nanoparticles in Nanoporous Membranes" (from the book by JH Feudler et al.: "Nanoparticles and Nanostructured Films", Chapter 10, pp. 235-262, 1998) , which the chapter 10.3.4. "Sol-gel deposition" (p. 242) 10.8.2 "Photocatalysis" (pp. 258/259) can be found. This also discloses the use of titanium dioxide using its photocatalytic sterilizing effects, which is, however, well known. Furthermore, the titanium dioxide is embedded in a porous structure (“template”). However, the known template is rigid Al ₂ θ ₃ ceramic membranes, in the pores of which the titanium dioxide is embedded. Such ceramic membranes are highly fragile and therefore not suitable as packaging material. The titanium dioxide is filled into the pores using the sol-gel process and then fired at high temperatures and converted into ceramic. By completely filling the pores, small solid rods made of hard ceramic ("fibrilles"; typically a few 10 μm long, approx. 1 μm diameter) are formed after firing. Then the AI ₂ θ3 membrane is dissolved and glued to the ceramic rods on an epoxy resin. The known arrangement thus has the only function of that of photocatalytic activity. The difference to the massive titanium dioxide can be seen in the much larger surface of the many ceramic rods, which causes an increase in the reaction rate. A controlled gas exchange in a film-like structure cannot be guaranteed with this known arrangement.

The task for the present invention is therefore, based on the last-mentioned publication as the closest prior art and the model of ostrich ice cream from nature, to be seen in a porous material that optimally implements photocatalysis and a method based on the sol-gel method Specify production in which the control and neutralization of microorganisms while maintaining gas exchange is guaranteed. In addition, the polymer film should be watertight and a wide range of uses should be achieved while at the same time being inexpensive to produce with regard to the materials and process steps used.

The solution according to the invention for this task provides the following structure: flexible, breathable polymer film with a spatially ordered structure from capillary pores that can be selected from the gas exchange through the polymer film, with funnel-shaped extensions in at least one surface of the polymer film and with at least in the area of the funnel-shaped extensions the capillary pores applied composite layer structure of at least one transparent, the polymer film protective binder film made of chemically inert, inorganic nanoparticles and at least one lining film adhering to the binder film made of short-wave light irradiation, photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles, which are antibacterial and self-cleaning, the effectiveness of which is based on the choice of the opening angle of the funnel-shaped extensions the capillary pores is adjustable. Advantageous configurations of the polymer film according to the invention can be found in the subclaims. A preferred process for producing such a polymer film and embodiments thereof can be found in the corresponding process claims. All claims are explained in more detail in the context of the invention in the following general and special description part.

With the present invention, based on the bioanalogous evaluation of the ultrastructure of the ostrich eggshell and its suitability for the selection of surface-active agents, it is possible to provide a flexible polymer film in the function of a functional ceramic porous membrane with modification by a nanoscale particle system. A technically applicable packaging film is produced with the physicochemical properties, which allows breathability and protects the potential, breathing packaged goods against bacterial attack and thus against premature aging and early spoilage. Packaged "living" food, such as As fruit, can be kept fresh longer by the bionic membrane packaging according to the invention and protected from drying out or loss of aroma. The modified polymer film itself can be easily recycled or disposed of. For this purpose, according to the invention, porous polymer films whose funnel-shaped enlarged pores with a diameter of only a few micrometers beforehand, for example by high-energy heavy ion irradiation of large film rolls and subsequent etching (one-sided etching to achieve funnel-shaped extensions in only one surface - single cone -, two-sided etching to achieve this) from funnel-shaped extensions in both surfaces - double cone -) were subjected to a nanotechnologically functional design of the specially funnel-shaped pores in the form of a special lining. In contrast to ostrich egg, the lining is not in a large, hard form, but in the form of tiny particles in the nanometer range (5 nm-100 nm) both inside and outside the pore volume in a largely homogeneous distribution that does not impair the flexibility of the polymer film. A composite layer structure in which a lining layer with the required properties has been applied to a binder layer to improve adhesion and protect the substrate film has proven to be particularly favorable. Adequate homogeneity of the pores and chemical resistance of the end product are two of several quality properties. Thus, with the invention in the form of a sterilizing and breathable film, bionic packaging can be made available as an environmentally friendly and inexpensive packaging alternative. The polymer film according to the invention represents an artificial eggshell membrane with a functional nanoparticle lining in a bio-analogous structure and shows the structural appearance of a photocatalytic, breathable, smooth and evenly shiny packaging prototype in almost any form of application.

One criterion for the realization of the required quality properties is the interactions at the interfaces between the substrate, binder and lining film or nanoparticles. Knowledge of the interface phenomena and the internal structure of the ostrich egg shell allows a targeted selection of the components with the aim of optimizing the bionic prototype to be developed (pore membrane in foil form) depending on the particle size and the specific surface properties of the porous membrane. In analogy to the eggshell, well-defined pores with an antibacterial and self-cleaning lining, which is also referred to below as “functional lining”, thus ensure effective gas exchange in the polymer film according to the invention through the porous film as a breathing function with simultaneous antibacterial effect of the inorganic surface. In this way, for example, the life of foods packaged with the film according to the invention without additives can be significantly extended. In contrast to the eggshell, the polymer film according to the invention with membrane function is flexible and thus robust and versatile. The functional lining is produced with a photocatalytically active material, this is a short-wave light irradiation, usually UV light irradiation, photocatalytically active, hydrophilic, non-toxic metal oxide in the form of nanoparticles. As a rule, these criteria meet ceramic materials, for example zinc oxide or trivalent iron oxide. The best known is titanium dioxide, which is approved as non-toxic in the food industry. Photoactivity is believed to be the cause of the required hydrophilic properties. The photoactivity is a semiconductor effect that occurs in relation to titanium dioxide on anatase crystallites, but also rutile and other crystallite forms as well as mixed forms thereof show photoactivity. The band gap of the anatase modification of Eg = 3.2 eV and the high oxidation potential of the valence band of approx. VVB = 3.1 eV (pHO) make it possible to oxidize almost any organic molecule under UV radiation (wavelength <390 nm) , Titanium dioxide is extremely resistant to chemicals and only soluble in very strong acids. In contrast, it is stable in bases. Catalysts and carrier materials made of titanium dioxide do not release any interfering ions in their special applications. They are ideally suited as carriers in conventional pH ranges, but especially for use in strongly alkaline media (see publication "Easy-to-clean and self-cleaning smooth surfaces" by A. Biedermann, available on the Internet at http: //home.t- online.de/home/titam/rein.htm, as of December 9, 2002)

A brief outlook on the economic prospects of the polymer film according to the invention is intended to underline its importance. In 2000, approx. 1.8 million tons of packaging films were made in Germany Made of plastic. Comparable products made from biodegradable materials are estimated to be just 10,000 tonnes across Europe, according to experts. High technical requirements must be met for these technical packaging, depending on the specific application. Among other things, they must be tear-resistant, flexible, odor-tight, they must not form any kind of connections to the packaged goods - the majority are foodstuffs - and last but not least, the extension of the lifespan of a packaged food has a very high economic importance due to the specific properties of packaging films. For plastic packaging films as well as for biodegradable packaging films, however, it has not yet been possible to achieve a - with regard to specific applications, e.g. packaging of flowers or fresh breathing foods such as apples - waterproof and at the same time against 0 ₂ , C0 ₂ and Water vapor breathable packaging film structure with the economic aim of extending the life of the packaged goods. Such a technical film has functional analog properties, such as those sought after according to the bio-analog model and realized for the first time with the present invention. With the developed packaging technology, technical polymer films can be easily perforated in a first practical approach and coated with ceramic nanoparticles so that they are breathable and get various functional properties (antibacterial, self-cleaning, waterproof, etc.). The extended keeping of food fresh, the longer protection against drying out and against loss of aroma are important economic target criteria that a functionally optimized, bionic packaging film based on the ostrich egg model should achieve. In the case of fresh, packaged food, packaging chemistry does the following: the ripening products, such as fruits, vegetables and flowers, release ethylene gas, a gaseous plant product, which in turn stimulates further ripening. For long-term storage of the maturation-related products, it is important to remove the formation of ethylene gas from the packaging space as effectively as possible. The photocatalytically active contained in the polymer film according to the invention Particle material breaks down the ethylene gas so that the food can be transported and stored longer without the addition of inhibitors.

For the purpose of preserving the aroma and extending the life of perishable goods which can be packaged with the coated polymer film according to the invention, further modifications of the polymer film also serve to further develop it into an active packaging material for objects and spaces. The modifications include, for example, sensors integrated in the polymer film for measuring gases which are relevant to the ripening process, for example button-shaped oxygen sensors. The measured values determined can then be displayed qualitatively, for example, via integrated indicators. These can be fields with possible color changes. Microencapsulated oxygen storage depots can also be integrated into the polymer film. For example, these can be nanoparticles that release oxygen. The storage depots serve as a fresh-keeping reservoir in the event of the membrane structure of the polymer film not functioning, so that a significant increase in the fresh-keeping time can be achieved. Finally, actuators can be integrated into the polymer film, which interact with existing sensors and storage depots in control loops. The actuators are usually valves, for example in the form of swellable nanoparticles, which close the pores when necessary. However, they can also be expandable and shrinkable tubes that are embedded in the polymer film and receive chemical control commands.

The described surface modification of a flexible, well-defined porous polymer film according to the invention, which can be carried out on one or both sides, has found a way to a functional membrane for a variety of possible uses. In the case of a surface modification on both sides, a polymer film which can be used on both sides is produced, and when used it does not relate to a specific film orientation with respect to modified surface must be observed. A production can be carried out for one or both surfaces of the polymer film used in accordance with the procedure mentioned in the process claim. Chemically inert nanoparticles are applied in a composite layer or mixed structure with controlled coating rates using a one-sided or double-sided sol-gel process. If water-based particle sols are used to form the layer, the particles condense (gel), since the particle concentration rises sharply when the water evaporates. During the drying process, transparent films are formed with a largely homogeneous particle distribution, the flexibility of which increases with decreasing thickness. Alternatively, colloidal particle solutions can also be applied to the polymer film, using stabilizing, highly concentrated particle dispersions for homogeneous coating of the films. Further details on the claimed production method according to the invention and on preferred embodiments thereof can be found in the special description part.

Forms of embodiment of the invention, in particular also with regard to the different materials and layer structures that can be used, are explained in more detail below in the special description part using individual exemplary embodiments. For further clarification, SEM images of differently parameterized layer structures on polymer films are used in the figures, the representation and meaning of which are explained in a direct connection.

Production of the porous polymer films with ion radiation

The practical applications of well-known filter films with capillary pores are diverse. They are often produced by irradiating gap fragments with impermeable foils and converting the damaged traces of the fragment webs into capillary openings by subsequent alkaline etching. Instead of the split fragments you can also use heavy ions from an accelerator. At the applicant's institute (Hahn-Meitner Institute HMI), the fact that plasma tubes are formed in different plastics - even if only in different amounts - is used to produce suitable foils. When an ion flies through a polymer film with high energy, a plasma tube forms for a very short time along the ion's path. Chemical bonds of the high-molecular substances are broken, free chemical bonds are formed, cross-links and new molecules can form in the polymer. These processes are extremely diverse and complicated. After the ion has flown through, the plasma tube collapses and an area of changed chemical structure remains, which is called the “nuclear trace”.

These core traces can be made visible if the plastics are etched, since the etching rates in the area of the core trace are generally orders of magnitude higher than for the unirradiated material (approx. 103 for Krlones). In polymers, such as polyethylene terephthalate PET or polyimide PI, the irradiated areas are therefore detached from the film. Capillary pores (traces) are formed, the diameter (a few hundred nm to 2 μm) of which is given by the duration of the etching process and the number of which is given by the number of projectile ions during the irradiation. By varying the ratio of the trace etching rate to the polymer etching rate (choice of heavy ion type / choice of etching process), funnel-shaped traces with different opening angles can be produced. The etching can be done on one side (one-sided funnel) or on both sides to create pores with funnels at each pore end (double cone). The particles then accumulate in the highest concentration in the funnel area, since in the case of curved surfaces, the potential energy is reduced by the surface difference that occurs. In this way, where the photocatalytic effect of the nanoparticles is essential, namely at the entrance to the pores, the best possible photocatalytic effect can be achieved through the highly concentrated addition. Furthermore, the funnel shape also proves to be from This is an advantage because it enables extensive access of the short-wave light into the interior of the capillary, thus ensuring the sterilizing and self-cleaning effect of the lining layer. In the case of transparent polymer films with funnel extensions on both sides (double cone), the short-wave light also passes through the film and thus falls into both funnel areas, so that a great catalytic activity of the lining film is achieved. If, on the other hand, a reflective silver layer is evaporated onto one side of the polymer film, only funnels on that side are also irradiated. The light is reflected and does not pass through the film. In this case, a polymer film modified on one side can be used, but its orientation in use must then be observed, which is not necessary in the case of a film modified on both sides.

For the porous structure, FIG. 1 shows an SEM overview image of the surface of an irradiated and subsequently etched polyethylene terephthalate film with a representation of funnel-shaped micropores. The polymer film has approximately 30 million pores per cm ² . The pore diameter is 500 nm.

Fission products from reactors or ions from heavy ion accelerators can be used to irradiate the film, whereby the radiation at the accelerator offers some decisive advantages: the activation of the film inherent in a reactor by gap fragments is avoided, the higher intensity of the accelerator jets enables high pore densities to be achieved, Due to the defined incidence, the same size and energy of the ions, defined pore sizes can be achieved and, due to the higher ion energies, thicker films can also be used. For this purpose, both a 300 MeV ³⁶ Ar ¹⁴⁺ beam at 3x10 ⁷ cm ^"2 and a 250 MeV ⁷⁸ Kr ¹²⁺ beam at 1x10 ⁶ cm ^{" 2} were applied to the heavy ion accelerator at ISL-HMI Berlin through a metallic mask on three different polymer films (compare below), consisting of polyethylene terephthalate PET, Polyimide Pl and cereal starch shot. The polymer films were then etched. As Etchants were taken from those that have long been proven for etching ion traces, namely 5 Moi / I NaOH at 450 ° C for PET and corn starch, and NaOCI solution at 50 ° C for pH concentrated 8 with Pl -10. Etching the polymer film with NaOH or NaOCI is absolutely necessary in order to create the pores, whereby the surface bonds are broken. It is known that the OH attack breaks up the (-O -) groups connecting the monomers and replaces them with (OH) end groups.

Selected analysis methods

The SEM examinations were carried out in the HMI. SEM investigations allow the qualitative and, under defined conditions, quantitative detection of the surface of porous films of fixed species. A computer-controlled scanning electron microscope (Oxford 440) is available in a conventional three-lens version with acceleration voltages up to 40 kV with a maximum sample size of 250 mm diameter, a maximum theoretical resolution of 200,000 times and a maximum practical resolution depending on the sample up to 50,000 times. The SEM investigation of the surface changes in the interaction of the solid active phase (porous polymer film) with the inorganic binder components (nanoparticles) provides information about the binding and the morphology of the coatings on the surface of the films. For the SEM investigations, the foil samples to be examined are scanned in a grid-like manner by a strongly bundled electron beam with a diameter of a few nm. The number of secondary electrons released in the surface area and that of the reflected beam electrons are influenced by the surface geometry and result in the topography contrast. The average atomic number of the existing elements gives the material contrast. The gray scale value of each pixel correlates with the number of electrons generated at the corresponding scanning point. With vertical radiation, inclined surfaces appear brighter than horizontal ones. Surface levels appear bright. Pores and gaps appear dark. Sample locations with predominantly light elements appear darker than those with heavier elements. Example: In a Ti0 ₂ / Siθ ₂ coating, the Ti0 ₂ phase appears darker than the Si0 ₂ phase.

Selected polymer systems

In general, it should be stated that almost all known polymer systems are suitable as a carrier film for the invention. These include inorganic polymer films, for example made of silicon rubber or polysilicon, and organic polymer films, for example made of polyethylene terephthalate PET, polyethylene PE, polyimide PI, polycarbonate PC or polyamide PA. Composite composite materials made from mixtures or with block or copolymers can also be used. Furthermore, films made from renewable raw materials such as cereal or potato starch can also be realized, which are of ecological importance as biodegradable packaging. A material is said to be biodegradable if all organic components are subject to degradation caused by biological activity. Films in which a renewable raw material is only added as a filler to a conventional plastic (PE or PP) cannot be described as biodegradable in the aforementioned sense. Biodegradable films for the packaging sector are mainly made from natural starch due to the then relatively low price (e.g. corn starch, potato starch). Other biodegradable films contain cellulose, sugar or lactic acid. However, biodegradable films are currently about four to five times more expensive than PE films and are therefore not of great interest for an inexpensive packaging film.

Polyethylene terephthalate PET, which is derived from petroleum, has long been known among plastics because the base material was developed in 1941 as a polyester in the USA and has been used as a high-quality synthetic fiber in the textile industry ever since. Today's PET is a refined polyester with further improved material properties. As an extremely resilient plastic, PET is suitable for packaging, containers, foils, Fibers and much more. PET packaging is characterized by a low raw material requirement. The high strength of PET makes it possible to produce very thin-walled containers and foils. Constant further developments mean that PET packaging is becoming ever lighter. Since products made of PET meet the strictest hygienic requirements and their use is very widespread in the cosmetics and food sector and especially in medicine, PET films are particularly suitable as polymer films for the present invention.

Polyimide Pl is a normally non-meltable, colored (often amber-colored) high-performance polymer with above all aromatic molecules with high heat resistance. Pl have excellent high-temperature properties and excellent resistance to radiation. They are inherently flame retardant and produce little smoke when burned. Creep occurs only to a small extent, wear resistance is very good. Pl are however very expensive. Their water absorption capacity is moderate, they tend to hydrolise and are attacked by alkalis and concentrated acids. Because of these excellent properties, Pl can be used as an alternative polymer film for the invention for high quality goods. The same applies to polyamide PA as a polymer film.

Selected composite layer structure

The polymer film according to the invention was tested on various prototypes. The composite layer system built up consisted of an alternating layer structure of titanium dioxide and silicon dioxide with a total thickness of less than 500 nm. The layer thickness distribution was determined by SEM investigations. Silicon dioxide acts as a binder. It serves to bind the photocatalytically active substances to the pore surface, but at the same time also protects the unmodified polymer film from a harmful influence of the active substance. Selected nanoscale species

Ti0 ₂ powder (P25, Degussa) was used for the photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles. The titanium dioxide is in the crystal forms anatase and rutile or P25 (mixture of anatase and rutile, Degussa-Hüls AG). A SiO ₂ dispersion (Levasil, Bayer) was chosen to provide the chemically inert, inorganic nanoparticles. Si0 ₂ -Levasil products are aqueous colloidally dispersed solutions of amorphous silicon dioxide particles with excellent stability against sedimentation. The silicon dioxide is in the form of spherical individual particles which are not cross-linked with one another. A significant product feature of the Levasil types is the irreversible transition of the colloidally dissolved silicon dioxide into solid water-insoluble silicon dioxide. The following Levasil types are suitable for film treatment: Levasil 100/45%, particle size 30 nm, pH 10, concentration 45%; Levasil 200/30%, particle size 15 nm, pH 9.0, concentration 30%.

Selected additional functional layers

The advantage of a composite layer system is that it can easily be expanded with layer cycles or additional layers. For example, embedded precious metals, such as gold or silver, have an antibacterial effect. They are chemically active and contribute to sterilization. However, metals from the iron group, for example iron, cobalt or nickel, which have other functional properties, are also suitable. Nickel, for example, has an algicidal effect and is also active in the dark without light. Mixtures of the elements are also possible. A sol-gel addition of natural dyes can lead to highly wash-resistant stains. Furthermore, entire layers or only partial island areas can be built up. The additionally stored substances only appear in relatively low concentrations. Due to its properties, silver can also be used as a binder layer. As a precursor to the lining, metallic silver has therefore been tested as an alternative to SiO _2. Chemical precipitation ensures nanoscale silver particles, which shield the film substrate untreated by the etching against photocatalytic TiO ₂ activity. Chemical precipitation using AgN0 ₃ , NaOH, glucose or NH ₄ OH while reducing the size of the particles ensures continuous nanoscale layers of silver particles. If such layers are used, however, the modified polymer film loses its transparency and assumes a metallic sheen. Regardless of whether a transparent layer formation with Ti0 ₂ / Si0 ₂ occurs or whether an Ag layer is deposited as a precursor, the porous property of the films, which is essential to the invention, is retained.

Furthermore, the photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles themselves can also be modified before they are processed. To this end, they can be coated with a low concentration of a swelling layer of an additional substance, for example calcium hydroxyapatite or just calcium apatite. The additional substance is used in particular to dock living substances and to destroy them. In contrast, silver only kills as an additional substance, but does not destroy it.

Selected layer systems The substances for the alternating layer structure applied to the polymer films, which was produced by the sol-gel process, were at atmospheric pressure by hydrolysis and condensation of compounds soluble in the reaction medium of at least one element from the group Si, Al, Ti and Zr , optionally in combination with a biocompatible binder aminosilane (N-2-aminoethyl) -3-aminopropyltrimethoxysilane) and subsequent heat treatment (60 ° C., 1 hour). The combination Ti / Si is always used in the following, since these components are known in detail in their effects. However, other compounds such as zinc oxide (known from medicine for anti-inflammatory dressings) or cerium oxide can also be used. When coating the films with TiO ₂ as a colloidal solution (pH 3.5), a primary substance takes part in the reaction, namely SiO ₂ . The Ti0 ₂ Sedimentation mainly takes place after the Si0 _{2 is} already on the substrate surface (foil). This process can therefore provide excellent film protection against the photocatalytic activity of Ti0 ₂ . Silicon dioxide is known to react with alkalis to form silicates, so SiO ₂ levasil dispersions were selected which are alkaline stabilized.

The process conditions that enable homogeneous and durable porous film coatings were then determined by means of tests. The process was therefore standardized for the intended purpose: All porous films were treated with the ceramic dispersions by the “dip coating” process (step I). The coating runs at normal pressure in air and at room temperature (22 ° C.). At a deposition rate A coating rate of 5 nm / min and 10 nm / min was assumed for an individual coating of 200 nm in one hour After a sufficiently long time (1 hour reaction time), an equilibrium is established between particle binding and excess SiO ₂ , the coating rate being kept so low is that the replenishment of Si0 ₂ can reach the surface by diffusion and therefore an all-round coating is possible around the pores In this phase, monodisperse SiO ₂ nanoparticles bind as a closed 200 nm layer to the surface of the films Reaction with the SiO ₂ dispersion on the films at room temperature was carried out by thermal treatment (1 hour at 60 ° C; sol-gel method) and repeated rinsing with distilled water. A longer duration of the Dip Coating I process leads to the formation of larger particles (aggregates). However, such particle formation is detrimental to the coating because it leads to cloudy, non-sticky deposits.

As the next step to the TiO ₂ lining coating, the polymer film sample already treated with SiO _{2 was} brought into the second reaction zone (Dip-Coating II). This reaction is completely analogous to Si0 ₂ (dip Coating II) carried out. With a coating using Ti0 ₂ powder, which is dissolved in a stabilizing, Si0 ₂ -containing Levasil solution (type 200S / 30%, pH 3.8; Ti0 ₂ 20g / 100 ml Levasil), there is both an electrostatic and also an interaction with the existing Si0 ₂ layer instead.

The use of cationically charged Ti0 nanoparticles using aminosilane was carried out according to known guidelines. This makes it possible to coat TiO ₂ nanoparticles with a swelling layer based on an aminoalkylsilane such as aminosilanes (N-2-aminoethyl) -3-aminopropyltrimethoxysilane (AHAPS) covalently by means of a controlled modification. As a result, the surface charge (zeta potential) of the resulting particles with hydrodynamic diameters in the range from 50 nm-100 nm could be increased from negative values to +33 mV at pH 5.4. The basis of this process is the well-known fact that silicon and titanium are not reluctant to combine with organic groups, thus creating a whole class of silanes or hybrid titanium dioxide-silanes, in which many compounds have significant stability. The process runs through various intermediate stages. The application of the aminosilane-modified Ti0 ₂ layer was carried out completely analogously to the process for the transparent layer formation with Ti0 / SiO ₂ .

Selected sol-gel process

The additional and decisive sol-gel process depends in particular on the furnace temperature and the controlled temperature gradient. Significant gelation is already observed at 30 ° C. This is due to the extreme water and temperature sensitivity of the Ti0 ₂ / Si0 _{2 system} . If the oven temperature is lower, the dispersion will not condense. On the other hand, if the temperature is too high, the temperature-sensitive polymer films will be destroyed. In this respect, the sol-gel transition was carried out under air and normal pressure at moderate oven and substrate temperatures. From a temperature of 60 ° C they show Films have stable properties after treatment, while films that have been treated above 100 ° C suffer from poor stability (tears). A sol-gel process of approx. 1 hour at 60 ° C thus already represents a suitable process for film coating. After the thermal treatment, it is necessary to rinse all of the samples repeatedly with distilled water until the condensed deposits have completely dissolved. The process steps mentioned can also be repeated cyclically to expand the composite layer system.

Results of the investigations

Nanoscale porous layers

The use of well-adhering nanoscale agents as binders on the active surface of the solid active phase (porous film) promotes the interaction of the components in the sense of deposition using the sol-gel process. The investigations of the Ti0 ₂ / Si0 ₂ layers showed a reduction in the surface tension of the porous foils as a function of the layer thickness with a simultaneous increase in hydrophilicity. The appearance of a photocatalytic, breathable, smooth and evenly shiny surface was achieved.

Levasil silica is very prone to appear in a colloidal state and to form gels with heat treatment. The thin SiO ₂ layers that are to be used as protective layers practically behave as a closed, monodisperse layer. No aggregates can be seen in the Si0 coating. This picture of the chemical behavior of silicon dioxide shows in connection with the secondary Ti0 ₂ coating that the use of SiO ₂ as a binder and protective agent is a suitable process for film coating. FIG. 2 shows an SEM overview picture to show an Ar-irradiated polyimide (PI) film which is coated with Ti0 ₂ / Si0 ₂ nanoparticle Levasil (200/30%; pH: 9.0; particle size: 10 nm - 20 nm) coated is: there are approximately 30 million pores per cm ² with a pore diameter of 3 μm. The white rings correspond to heavily coated zones.

When coating the pre-coated Si0 ₂ porous films with additive positively charged TiO ₂ nanoparticles, the photocatalytic coating must have a good shelf life, because incomplete or irregular layers cannot be repaired afterwards. The reason for this can be seen in the fact that even with a layer thickness of a few nm in the order of a few dozen atomic layers, uncoated areas also occur due to the probability distribution of the particle deposition. FIG. 3 shows a SEM photograph of an Ar-irradiated polyimide (PI) film which has been precoated with a primary SiO nanoparticle Levasil solution (200/30%; pH: 9.0; particle size: 10 nm). 20 nm; reaction time 30 min) and with Ti0 ₂ powder, which was dissolved in Levasil (200S / 30% Si02 colloidal dispersion, pH: 3.8; particle size 10-20 nm; reaction time 30 min). The foils are provided with approx. 30 million pores per cm ² with a pore diameter of 2.0 μm. Depletion zones can be seen on the surface around the heavily coated openings (white rings), which indicates the interaction between mass transfer (transport process) and chemical reaction.

A layer thickness of a few hundred nm seems to be optimal. FIG. 4 shows an SEM photograph of a Kr-irradiated polyethylene terephthalate (PET) film which was coated with a primary SiO ₂ nanoparticle Levasil solution (200/30%; pH: 9.0; particle size: 10 nm -20 nm ; Reaction time: 60 min) and coated with TiO 2 powder, which was dissolved in Levasil (200S / 30% Si0 ₂ colloidal dispersion, pH: 3.8; particle size 10 nm-20 nm; reaction time 60 min). The films have approximately 20 million pores per cm ² with a pore diameter of 3.0 μm. Thicker layers require a longer reaction time (»1 hour). As a rule, layer thicknesses of approximately 200 nm were observed. With the help of electron microscopic examinations, typical layer formation, particle formation and division and layer thickness are examined. A narrowing of the pores could be determined by the capillary, homogeneous particle arrangement, which is connected to the entire surface layer thickness of the film. In such investigations, layer thicknesses of approximately 200 nm-300 nm were observed. The direct measurement of the layer thickness can only be carried out on specifically produced cross sections. This measurement requires consideration of various side influences and their applicability depends heavily on the mechanical properties of the film.

The use of stabilized, highly concentrated TiO ₂ / SiO ₂ dispersions facilitates a homogeneous coating of the films. Depletion of the coating material due to larger particle formation (aggregate) practically leads to the coating coming to a standstill. In this respect, it is advantageous that a large number of small particles, even if they form only a small mass overall, have a very large surface area. FIG. 5 shows a high-resolution SEM image of an Ar-irradiated polyimide (Pl) film (coated with a primary SiO ₂ nanoparticle-Levasil solution (200/30%; pH: 9.0; particle size: 10 nm -20 nm ) and after-coated with Ti0 powder, dissolved in Levasil 200S / 30% Si0 ₂ colloidal dispersion, pH: 3.8; particle size 10 nm -20 nm). The film is provided with approx. 20 million pores per cm ² with a pore diameter of 2.0 μm). The porous PI film was completely covered with nanoparticles (TiO ₂ / SiO ₂ ) by the sol-gel process. With this polymer film, an optimal TiO ₂ / SiO ₂ layer formation of approx. 200 nm thickness (coating rate approx. 5 nm / min) was carried out using the sol-gel process (60 ° C., 60 min, heat-treated). A homogeneous coating with good optical and SEM quality is formed (no cracks, hydrophilic, stable). The inner structure of the pores (capillary walls) was also coated evenly and without the formation of aggregates. With this process it is possible to produce stable layers of binder and lining. Shape and distribution of the coated pores in the foils

The following examples are shown to clearly demonstrate the porosity of the films after coating. FIG. 6 shows a high-resolution SEM image of an Ar-irradiated polyimide (PI) film, which was coated with a primary SiO ₂ nanoparticle-Levasil solution (200/30%; pH: 9.0, particle size: 10 nm - 20 nm) precoated and post-coated with Ti0 ₂ powder, dissolved in Levasil (200S / 30% -SiO ₂ colloidal dispersion, pH: 3.8; particle size 10 nm -20 nm). The film is provided with approx. 20 million pores per cm ² with an inner pore diameter of 2.0 μm. The image shows 3 pores with a diameter of approx. 3 μm in the funnel area, which have been coated by nanoparticles. The small particles indicate Si0 ₂ («20 nm), the large particles indicate TiO ₂ (» 30 nm). Thus, the Ti0 ₂ and Si0 ₂ particles are clearly recognizable both inside and outside the pore volume. The built-in building blocks indicate that a capillary reaction takes place between the inner wall of the pores and the nanoparticles. A connection between the NaOH-etched edges of the pore openings and the number of fixed particles is clearly recognizable. Because of their reduced potential as cylindrical surfaces, these regions in particular offer better adhesion than the smooth surfaces for the Ti0 ₂ particles. The Si0 ₂ layer underneath is also clearly recognizable due to its particle size. With a longer duration of the dip coating process, the foils show a complete, closed TiO ₂ layer on the zones immediately near the pore openings.

FIG. 7 shows a SEM image of a pore opening (approx. 2 μm diameter) in the case of a Kr-irradiated polyethylene terephthalate (PET) film (coated with a primary SiO ₂ nanoparticle-Levasil solution (200/30%; pH: 9 , 0; particle size: 10 nm -20 nm; reaction time: 60 min) and coated with Ti0 ₂ powder, dissolved in Levasil 200S / 30% Si0 ₂ colloidal dispersion, pH: 3.8; particle size 10 nm-20 nm) The picture shows the opening of a coated capillary tube that shows a strong affinity for nanoparticles. The region around the capillary opening, however, shows a rather modest one Ti0 ₂ - enrichment. By maximizing the depth of field, it was possible to look inside the capillary at depths of 21.6 μm. The total film thickness is 30 μm. The figure thus shows the strong affinity of the nanoparticles to the pores (particle incorporation). Different layer formation mechanisms work together under the conditions mentioned above.

Morphology of the pores

Usually, the etched pores have a cylindrical shape with a funnel-shaped expansion area on the film surface. As a result, the light (daylight or artificial light) required for the photoactivity of the Ti0 can penetrate into greater capillary depths. FIG. 8 shows an enlarged SEM image of a Kr-irradiated polyethylene terephthalate (PET) film (precoated with a primary SiO ₂ nanoparticle-Levasil solution (200/30%; pH: 9.0; particle size: 10 nm-20 nm and coated with Ti0 ₂ powder, dissolved in Levasil 200S / 30% Si0 ₂ colloidal dispersion, pH: 3.8; particle size 10 nm-20 nm. The picture shows a capillary tube (approx. 6.5 μm diameter at the outer edge) and 2.5 μm diameter in the interior at a distance of approximately 21.6 μm from the surface to the narrowest point) with a funnel-shaped structure This morphology shows the closed and homogeneous incorporation of particles into the walls of the capillary structure a conical opening, which is important for the functional effect of the claimed polymer films It can be seen that the inner walls coated with TiO ₂ already have an increased reflectivity due to their construction alone Due to the difference in refractive index between the different angles within the pore walls, the degradation of harmful organic material can be carried out very efficiently. It is noteworthy that the inner diameter of the funnel-shaped tapering pores becomes so narrow that bacterial contamination by loose bacteria is prevented by design. Silver layer on the polymer films

Silver deposition as the precursor of the Ti0 ₂ / Si0 coating is advisable for technical and functional reasons. The reason for a silver coating of foils is that the etched ion traces (pores) are protected against the photocatalytic activity of Ti0 ₂ and the light is better guided into the capillary interior. This is achieved by applying a very highly reflective silver mirror to the surface of the porous film, which is obtained after chemical precipitation. Silver nitrate, NaOH, glucose, and NH ₄ OH are used. In fact, silver nitrate creates a very homogeneous and stable coating on both PET and PI films. According to SEM measurements, the Ag coating has a thickness of approx. 50 nm-100 nm. Thicker layers require longer process times without improving the protective effect: on the contrary, the protective effect is reduced here because comparatively thick layers of up to a few μm have considerable residual stresses develop, show cracks and flake off. Figure 9 shows one. SEM image of a porous polyimide film irradiated with Ar and coated with a 100 nm thick Ag film. The picture shows a closed, homogeneous Ag layer on the PI surface of the film. The pores of the film structure have remained after the coating (1.0 μm diameter). Ag-coated films promote the fixation of anionically charged particles. In the aftertreatment of the Ag-coated films by means of additive SiO ₂ / aminosilane-modified TiO ₂ dispersion, it was found that an Ag layer as the precursor of the TiO ₂ / SiO ₂ coating achieves an optimal coating and layer thickness.

FIG. 10 shows an SEM image of a Kr-irradiated polyethylene terephthalate (PET) film, which is provided with a primary Ag layer as a precursor layer and with TiO ₂ powder, dissolved in Levasil solution 200S / 30% SiO 2 colloidal dispersion, pH: 3.8; Particle size 10 nm -20 nm is coated. The use of a well-adhering silver mirror on the PET surface promotes the interaction of the ceramic components (Ti0 / Si0 ₂ ) in the sense of Stabilization of the monodisperse particles (50 nm -100 nm) against aggregating particle formation while maintaining the porosity of the film. In the case of an Ag coating on porous films, the production of a smooth and uniform anti-bacterial interface between the film surface and the environment (Ti0 / Si0 ₂ / water / air) is also realized. Due to the large surface area of the particles, a sufficiently high concentration of antibacterial silver ions is ensured in the contact area. The presence of colloidal silver near a virus, fungus, bacterium or other unicellular pathogen inactivates its oxygen metabolism enzyme, its "chemical lung". The pathogen suffocates, dies and is then broken down by the photocatalytic Ti0 activity.

Summary conclusions from the SEM studies

• By varying the ratio of trace etching rate to polymer etching rate, funnel-shaped traces with different opening angles can be produced as capillary pores in the preparation of polymer films.

• During the treatment there is a colloidal dispersion film (water-containing Ti0 ₂ / Si0 oxide hydrate film) on the film surface, which only changes into stable Ti0 ₂ / Si0 ₂ layers after the sol-gel process and thermal treatment. With the so-called "sol-gel process", a gelatinous network (gel) of inorganic or inorganic / organic substances can be assembled from a liquid mixture (sol).

• The quality of the porous polymer films is decisively determined by the properties and the thickness of the TiO ₂ / SiO ₂ layers. The film coatings that can be achieved remain transparent if the addition of particles is of the order of nanometers. • The thickness and quality of the Ti0 ₂ / Si0 layers is strongly influenced by the material of the film substrates, by the slightest surface contamination, by aging of the surface due to the temperature and humidity of the air and by the interface chemistry of various film substrates (transport processes ).

• Silicon dioxide or silicon dioxide-containing Ti0 ₂ layers were used in the present invention both as an insulation layer to keep the photocatalytic activity of the Ti0 ₂ away from the polymer substrate of the films and as a template (binder) of the TiO ₂ coating to the Ti0 Apply ₂ sol evenly on the foils.

• The formation of the nanoscale TiO 2 / SiO 2 layers on porous foils requires the use of a very clean reaction space, because the smallest, invisible dust particles in the air or, for example, fingerprints and other impurities act as a repellent nucleation surface (artifact) in the sense of the reaction. These artifacts very quickly lead to local growth of the layer or to a standstill of the deposition process.

• Ag coatings should act both as an insulation layer and as an antibacterial. Silver particles are said to shield the polymer structure of the films from photocatalysis. Then the foils are no longer sensitive to TiO2, however the transparency of the foils is replaced by a silver surface. On the other hand, the thin silver film on the surface of capillary pores with a funnel-shaped entrance area with an optimized opening angle enables high light intensity even in deeper foil areas. Apart from the Ag coating and the irradiation of the films, the present invention can provide an inexpensive method for producing the functional polymer films, since the costs for the polymer films, the layer material, the agents and the costs for the necessary heat treatment are comparatively low ,

• It was shown that polymer films, for example PET, which consist only of petrochemical materials, can be coated very well with nanoparticles. According to the results available to date, biodegradable polymers such as cereal starch show other physicochemical properties, which does not yet optimally design both the pore generation and the sol-gel treatment. Only when the conditions lead to standardized treatment through experiments and subsequent quantitative and qualitative analyzes will these new materials also become suitable substrates for ceramic-nanoscale coatings.

Claims

claims

1. Flexible, breathable polymer film with a spatially ordered structure of capillary pores selectable from gas exchange through the polymer film with funnel-shaped extensions in at least one surface of the polymer film and with a composite layer structure of at least one transparent layer applied at least in the area of the funnel-shaped extensions of the capillary pores , the polymer film-protecting binder film made of chemically inert, inorganic nanoparticles and at least one lining film adhering to the binder film made of hydrophilic, non-toxic metal oxide nanoparticles which are photocatalytically active under short-wave light radiation and which are antibacterial and self-cleaning, their effectiveness being based on the choice the opening angle of the funnel-shaped extensions of the capillary pores is adjustable.

2. Flexible, breathable polymer film according to claim 1 with funnel-shaped extensions of the capillary pores in both surfaces of the polymer film.

3. Flexible, breathable polymer film according to claim 1 or 2 with an organic structure, in particular of polyethylene terephthalate PET, polyimide Pl or polyamide PA

4. Flexible, breathable polymer film according to one of claims 1 to 3 with silicate particles, noble metal particles, in particular silver particles or particles made of a metal of the iron group, in particular nickel particles, or a particle mixture as a chemically inert, inorganic nanoparticles for the binder film.

5. Flexible, breathable polymer film according to one of claims 1 to 4 with ceramic nanoparticles, in particular titanium dioxide, or a particle mixture as photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles for the lining film.

6. Flexible, breathable polymer film according to one of claims 1 to 5 with a mixture of the nanoparticles for the binder and the lining film.

7. Flexible, breathable polymer film according to one of claims 1 to 6 with a further type of nanoparticles for fulfilling further functions, in particular anchor functions, the further nanoparticles, in particular calcium hydroxyapatite or silver nanoparticles, as an additional film in at least island-shaped formation or as Mixture to the other nanoparticles are introduced.

8. Flexible, breathable polymer film according to one of claims 1 to 7 with a non-toxic color additive for coloring the polymer film.

9. Flexible, breathable polymer film according to one of claims 1 to 8 with a capillary diameter of the capillary pores in a size range of 100 nm - 2 microns and a size of the nanoparticles in a size range of 5 nm - 100 nm, with capillary and nanoparticle diameter in their Size to maintain the respiratory function are coordinated, and a thickness of the composite layer structure in a range below 500 nm.

10. Flexible, breathable polymer film according to one of claims 1 to 9 with integrated sensors that detect the chemical and physical measured values of objects and spaces surrounded by the polymer film and indicators that display the measured values.

11. Flexible, breathable polymer film according to one of claims 1 to 10 with integrated, microencapsulated oxygen storage depots.

12. Flexible, breathable polymer film according to claim 10 or 11 with integrated actuators, which interact in control loops with existing sensors and storage depots.

13. A method for producing a flexible, breathable polymer film with a spatially ordered structure from capillary pores that can be selected from the gas exchange through the polymer film, with funnel-shaped extensions in at least one surface of the polymer film and with a composite layer structure applied at least in the region of the funnel-shaped extensions of the capillary pores from at least one transparent binder film protecting the polymer film from chemically inert, inorganic nanoparticles and at least one lining film adhering to the binder film from hydrophilic, non-toxic metal oxide nanoparticles which are photocatalytically active under short-wave light irradiation, the antibacterial and self-cleaning effect being effective the choice of the opening angle of the funnel-shaped extensions of the capillary pores is adjustable, in particular according to one of claims 1 to 12, with the process steps that can be repeated cyclically under clean room conditions:

Dip-coating step I: wetting at least one surface of the porous polymer film with a water-based dispersion of chemically inert, inorganic nanoparticles in colloidal solution to form the binder film at normal pressure in an air atmosphere and room temperature. Sol-gel step I: moderate thermal treatment of the formed Binder film in a temperature range which does not impair the polymer film for condensation of the solution. Rinsing step I: repeated rinsing of the solidified binder film with distilled water to remove unbound nanoparticles

Dip-coating step II: wetting the surface of the porous polymer film coated with the binder film with a water-based one Dispersion of photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles in colloidal solution for the formation of the lining film at normal pressure under an air atmosphere and room temperature. Sol-gel step II: moderate thermal treatment of the formed lining film in a temperature range which does not impair the polymer film to condense the solution

Rinsing step II: repeated rinsing of the solidified lining film with distilled water to remove unbound nanoparticles.

14. The method according to claim 13 with a treatment of both surfaces of the polymer film used.

15. The method according to claim 13 or 14 with a solution of the photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles in powder form in a colloidal dispersion with the chemically inert, inorganic nanoparticles

16. The method according to any one of claims 13 to 15 with a porous polymer film made of polyethylene terephthalate PET, polyimide PI or polyamide PA, silicon dioxide powder as chemically inert, inorganic nanoparticles and titanium dioxide powder as photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles.

17. The method according to any one of claims 13 to 16 with a controlled modification of the photocatalytically active, hydrophilic, non-toxic metal oxide nanoparticles by sufficiently permanent coating with a swelling layer, in particular based on an aminoalkylsilane.

18. The method according to any one of claims 13 to 17 with an upstream of the dip coating step I or alternative process step for applying a silver layer to the polymer film.

19. The method according to any one of claims 13 to 18 with an integrated or the upstream or alternative process step for applying the silver layer to the polymer film upstream process step for applying further functional layers or parts thereof made of nanoparticles.

20. The method according to claim 19 with an upstream process step for applying a layer with an anchor function, wherein the nanoparticles used consist in particular of calcium hydroxyapatite.

21. The method according to any one of claims 13 to 20 with an integrated non-toxic color additive for coloring the composite layer structure.

22. The method according to any one of claims 13 to 21 with a preparatory process step for producing the capillary pores in the polymer film by high-energy irradiation with gap fragments or ions to produce chemically modified traces and subsequent nanotechnological surface treatment by etching the irradiated polymer film, whereby by varying the Ratio of trace etching rate to polymer etching rate capillary pores with funnel-shaped extensions of different opening angles can be produced.