Surface-catalytically finished polymer fibres and / or polymeric sheets, method for surface-catalytically finishing same, and use thereof for producing an air purification filter

Abstract

The present invention relates to a method for surface-catalytically finishing polymer fibres and / or polymeric sheets, said method comprising the steps: a) providing a polymer fibre or a polymeric sheet; b) providing an aqueous dispersion of a catalyst support particle; and c) contacting the polymer fibre or the polymeric sheet with the aqueous dispersion of the catalyst support particle, the method being characterised in that the catalyst support particle has a particle size in a range of between at least 0.5pm and at most 20µm, and in that the contacting in step c) takes place at a temperature in a range of between at least 15°C and at most 60°C above the glass transition temperature TG of the polyester, and wherein the catalyst support particle is impregnated with a catalytically active metal or metal oxide. The invention also relates to: a polyester fibre or polyester sheet with a corresponding finish; and the use of same for producing a filter for particle separation in an air purification system.

Description

[0001] Surface-catalyzed polymer fibers and / or polymer sheet structures, processes for their surface-catalyzed treatment, and the use thereof for producing an air purification filter

[0002] The present invention relates to a process for the surface catalytic treatment of polymer fibers and / or polymer sheet materials with catalyst particles and to the use of the fibers and / or sheet materials thus treated.

[0003] Heterogeneous catalysis is the reaction of gaseous or liquid substances on the surface of a solid partner, the catalyst. The presence of a catalyst increases the reaction rate or decreases the activation energy. The externally measurable reaction rate, r, is eff depends on several influencing factors, e.g. the phase interface, the bulk density of the catalyst and the pore structure. The choice of catalyst depends on the desired reactions to be catalyzed. The catalysts used in gas purification processes, for example, are usually metals or metal compounds, as well as their oxides. These metals are applied to an otherwise inactive support material with a large external and internal surface area. A catalyst should exhibit high activity and selectivity with regard to the desired reactions. A second requirement is high stability, i.e. resistance to mechanical influences such as abrasion, and chemical resistance. For example, platinum can be used as a catalyst for the oxidative conversion of CO to CO2.The conversion of toxic carbon monoxide into the less harmful carbon dioxide occurs on a platinum surface, which catalyzes the reaction. Oxygen and carbon monoxide molecules first bind to the platinum surface before reacting to form carbon dioxide. They simultaneously detach from the platinum, leaving the platinum unchanged. Approximately 99 percent of the platinum surface consists of smooth surfaces, while just over one percent consists of steps between the individual smooth layers of platinum atoms. Both surface types are catalytically active, with the steps exhibiting more catalytic activity than the smooth surfaces.

[0004] For effective heterogeneous catalysis, especially for gases, the largest possible phase interface between the gas to be converted and the catalyst is necessary. Catalytic treatment of fibers or fabrics is a suitable approach for this.

[0005] A practical example of an application of such heterogeneous gas catalysis is the use of particulate matter filters, such as bag filters, for product separation during the pneumatic conveying of organic dusts. However, as a side effect, these processes can, at elevated temperatures, result in the formation of fire pockets in which harmful gases such as carbon monoxide are formed. The resulting carbon monoxide must be oxidized to carbon dioxide before it can be released into the exhaust air. Compliance with corresponding carbon monoxide limits will pose a challenge for industrial applications in the future. In particular, relatively low temperatures are possible for catalytic exhaust air purification.

[0006] One problem here is the so-called fixation of the catalyst on the fabric or fiber surface. This is usually achieved using a binder, such as an adhesive. However, such a fixation of the catalyst or catalytically active particles often does not meet the mechanical requirements placed on corresponding fabrics or fibers, so that the applied catalyst particles are rubbed off the surface and the catalytic activity of the fabrics or fibers decreases accordingly. Furthermore, the binder covers a not insignificant part of the catalytically active surface. Furthermore, with a corresponding surface catalytic treatment of a woven fabric, knitted fabric or nonwoven, the flow resistance should remain as unchanged as possible compared to a woven fabric, knitted fabric or nonwoven without a surface catalytic treatment.

[0007] Document EP 1738823 A1 discloses a catalytically active unit with a support material, wherein the catalytically active unit or the support material comprises polymer particles, in particular polymeric nanoparticles, and / or wherein the support material is coated with polymer particles, in particular polymeric nanoparticles, wherein the polymer particles comprise at least one catalytically active component. The catalytically active unit according to the present invention is particularly suitable for removing pollutants, odors, and toxic substances of all kinds, in particular from air and / or gas streams, and for protecting against chemical toxins, in particular warfare agents, for example in NBC protective materials (e.g., protective clothing).

[0008] JP 2004024937A discloses a manufacturing apparatus for a catalytic bag filter comprising a catalytic slurry tank, a catalytic slurry circulation pump in the catalytic slurry tank, a catalytic slurry viscosity sensor in the catalytic slurry tank, a catalytic slurry supply device whose operation is controlled by readings from the viscosity sensor, a flat base on which the bag filter is placed, a press plate for pressing the bag filter onto a surface of the flat base and impregnating the bag filter with the catalytic slurry, a press plate drive device, and a pair of squeeze rollers installed at an upper part of the catalytic slurry tank.

[0009] Document RU 2399391 CI discloses a filter-catalyst composite material for air purification of aerosols and carbon monoxide, which contains two layers of a fibrous filter medium and a layer of catalytic material. The catalytic material layer consists of needle felt with a surface density of 220-250 g / m² 3 , filled with a finely ground palladium-containing low-temperature carbon monoxide oxidation catalyst with a particle size of 100 nm in the following weight ratio: catalyst - 15-50%, fibrous filter medium - the rest, and is arranged between the layers of the filter medium made of electrostatic fine-filament polymer fibers.

[0010] US 2021 069621 A1 discloses a filter capable of removing particles with a size of 2.5 pm and / or other air pollutants, wherein the filter comprises fibers with an average diameter of no more than 500 nm, wherein the fibers consist of at least 90 wt.% polyacrylonitrile, based on all fibers in the filter; and a catalyst with at least 90 wt.% TiCh, based on all catalytic metals in the filter, dispersed on the fibers. The fibers do not need to be loaded. The TiCh can be condensed or precipitated onto the fibers using simple methods from a liquid containing the TiCh and the fibers. The catalyst can be activated by UV irradiation to decompose particles with an average particle size of 2.5 pm or less and / or other air pollutants from the air. Such filters can be used near areas with vehicle traffic, e.g.as elements of traffic lights, and can be used for the controlled purification of polluted air.

[0011] US 2009235625 A1 discloses a filter comprising a membrane with pores that are permeable to air. A nanoparticle precursor is dispersed in the pores, and the nanoparticle precursor responds to a stimulus to form a catalytically active nanoparticle. A corresponding method is also provided.

[0012] BE 883343 A discloses a textile material containing polyester fibres having excellent opacity and haptic properties, the material being characterized in that it comprises a substrate containing polyester fibres, the fibres having been treated with up to about 20% by weight of the textile material with titanium dioxide particles having an average particle size of at least about 0.18 microns, the durability of the bonding of the particles to the textile fibres being such that at least 50% of the particles remain fixed to the surface of the textile fibres after five AATCC standard washes.

[0013] JP 2009191369 A1 discloses that a coating film of a diallyldimethylammonium salt polymer is formed on the surface of a polyester fiber constituting a curtain fabric, and porous fine particles carrying a metal oxide catalyst and / or a metal catalyst are adsorbed on the coating film.

[0014] US 2002197396 A1 discloses a method and apparatus for treating yarn to improve the performance characteristics, such as odor adsorption capacity, of the yarn while maintaining the physical properties associated with the yarn, such as hand and feel. Yarn treatment methods incorporate solid particles, such as activated carbon, into the yarn using an air dispersion technique or a cushioning technique. In the air dispersion technique, the solid particles are dispersed over the yarn in a controlled air stream. In the cushioning method, the solid particles are incorporated into the yarn as the yarn passes through a bath of solid particles. In the yarn treatment method, a binder may be applied to the yarn. The binder binds the solid particles to the yarn without impairing the performance characteristics of the solid particles.The yarn treatment process further includes curing the binder to permanently bond the solid particles to the yarn.

[0015] It is therefore the object of the present invention to provide a process for providing a surface-catalytically active polymer fiber or a polymer sheet, which has high mechanical stability with consistently good catalytic activity. According to a further aspect, the object of the invention is to provide a catalytically active polyester sheet with high mechanical stability and consistently good catalytic activity, and the use thereof. This object is achieved by a process according to claim 1. With regard to the catalytically active polymer sheet, the object is achieved by a polymer fiber or a polymer sheet according to claim 8. With regard to the use of a corresponding polyester sheet, the object is achieved by a use according to claim 10.

[0016] The invention proposes a method for the surface catalytic treatment of polymer fibers and / or sheetlike structures, comprising the steps of: a) providing a polymer fiber or a polymer sheetlike structure made of an amorphous or partially amorphous polymer; b) providing an aqueous dispersion of a catalyst support particle; c) contacting the polymer fiber or the polyester sheetlike structure with the aqueous dispersion of the catalyst support particle, wherein the catalyst support particle has a particle size in a range between >0.5pm and <20pm, preferably between >1pm and <10pm, in particular between >1.5pm and <5pm and that the contacting in step c) takes place at a temperature in a range between >15°C and <60°C, preferably between >20°C and <50°C, in particular between >30°C and <40°C above the glass transition temperature TG of the polymer and wherein the catalyst support particle is impregnated with a catalytically active metal or metal oxide.

[0017] A fabric within the meaning of the invention is a woven fabric, knitted fabric, nonwoven fabric, film or membrane.

[0018] Surface catalytic treatment in the sense of the invention is understood to mean the application of a catalytically active substance to the surface of the polymer fiber or the polymer sheet, so that fluids such as gas or liquids passing by the surface come into contact with the catalytically active substance and a conversion reaction of the fluid or of a substance contained in the fluid can take place heterocatalytically.

[0019] According to a preferred embodiment of the invention, the amorphous or partially amorphous polymer is a polyester or a polyamide, a copolymer or a blend thereof.

[0020] Polyesters within the meaning of the invention are in particular polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylacid (PLA), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polycarbonate (PC), polyarylate (PAR), polyester carbonate (PEC) or copolymers or blends thereof.

[0021] Surprisingly, it has been shown that the process according to the invention makes it possible to bond catalyst support particles impregnated with a catalytically active metal or metal oxide to an amorphous or partially amorphous polymer in a mechanically stable manner. Mechanically stable within the meaning of the invention means that the catalyst support particles are only washed off or mechanically abraded to a very small extent. In particular, mechanically stable within the meaning of the invention means that a polymer fiber or a polymer sheet correspondingly treated according to the invention results in detachments of the catalytic particles of < 5% in relation to the total mass of the catalytic particles after > 500 compressed air pulses at an overpressure of 6 bar, each lasting 1 second. In this respect, the process according to the invention enables dispersion fixation of catalytically active particles on a polymer fiber or a polymer sheet.It was surprisingly found that the catalyst support particles partially penetrate into the polymer structure and are thus mechanically stably bonded to the polymer structure. The only partial penetration into the structure allows a predominant part of the catalyst support particle surface and thus the catalytically active metals or metal oxides applied to the catalyst support particle to be available for heterogeneous catalysis. According to a preferred embodiment of the process according to the invention, the polymer fiber or the polymer sheet is contacted at the stated temperature for a period of between > 30 min and < 360 min, preferably between > 60 min and < 240 min, in particular between > 90 min and < 120 min. It has been shown that such a contact period is, on the one hand, sufficient to ensure sufficient migration of the catalyst support particles impregnated with a catalytically active metal into the fiber structure orto ensure the surface structure without causing the polymer to swell too much.

[0022] According to a preferred embodiment of the method according to the invention, the polymer fiber or the polymer sheet is contacted with the aqueous dispersion of a catalyst support particle while providing a temperature gradient. It can preferably be provided that the polymer fiber or the polymer sheet and the aqueous dispersion of a catalyst support particle are heated together from a lower temperature, such as room temperature, to the intended temperature in a range between >15°C and <60°C above the glass transition temperature To of the polymer. A heating rate in a range of >1°C / min <10°C / min, preferably between >2°C / min <5°C / min, such as 3°C / min, can preferably be provided.After a holding time of between > 30 min and < 360 min, preferably between > 60 min and < 240 min, in particular between > 90 min and < 120 min, cooling to a lower temperature can preferably take place. The target temperature for cooling is preferably in a range between > 5°C below the glass transition temperature TG of the polymer and room temperature. During cooling, a cooling rate in a range between > 1°C / min and < 20°C / min, preferably between > 2°C / min and < 10°C / min, such as 6°C / min, can preferably be provided. It is preferably provided that the cooling rate is greater than the heating rate.

[0023] According to a further preferred embodiment of the method, the catalyst support particle is porous and preferably has a porosity in a range between >10% and <60%. Such porosity advantageously increases the specific surface area of ​​the catalyst support particle and thus the contact area available for heterogeneous catalysis, and on the other hand, it allows for improved fixation of the

[0024] Catalyst support particles on the polyester fibers or fabrics. The porosity in the sense of this invention is 1 minus the quotient of the bulk density of the

[0025] Catalyst support particle and the true density of the catalyst support particle material according to the formula = (1 - p / po)* 100%, where p is the bulk density and po is the true density and where p = m / (Vfest + Vpor) and o = m / Vfest.

[0026] According to a further embodiment of the process according to the invention, the catalyst support particle is selected from the group consisting of titanium dioxide, cordierite, zeolites, magnesium silicate, or aluminum silicate. In the case of a magnesium silicate, talc is preferred. It has been advantageously shown that these compounds exhibit good impregnability while simultaneously exhibiting chemical and mechanical stability.

[0027] According to a further embodiment of the method, the catalytically active metal can be at least one metal selected from the group consisting of metals from the group of outer transition metals of the periodic table, preferably platinum, nickel, gold, silver, rhenium, cobalt, vanadium, chromium, copper, palladium, iridium, rhodium, and zirconium, or an oxide or mixed oxide thereof. Advantageously, the metals mentioned have good redox-catalytic properties, which can be advantageously utilized in the context of the application of appropriately treated polyester fibers or polyester fabrics.

[0028] In one embodiment of the process according to the invention, the aqueous dispersion is preferably adjusted to a pH in a range > pH 1 and < pH 5. It has been shown that providing a correspondingly acidic environment facilitates the bonding of the catalyst support particles to the polymer structure. In particular, it can be provided that a pH gradient is established during the course of the process, i.e. during the period in which the polymer fiber or the polymer sheet is contacted with the aqueous dispersion. It is particularly preferred if the pH decreases over the course of the contact time. This makes it possible to achieve a more uniform bonding and distribution of the catalyst support particles in the polymer structure.

[0029] According to a further embodiment of the invention, the aqueous dispersion of the catalyst support particle can contain a dispersant. The dispersant can preferably be present in the dispersion at a concentration between >0.01 g / l and <0.04 g / l, based on the total dispersion. According to a further preferred embodiment, between >50 ml and <250 ml, preferably between >80 ml and <150 ml, such as 100 ml of dispersion, are used per 10 g of polymer fiber / polymer sheet.

[0030] According to a further preferred embodiment of the invention, the dispersant can be an agent selected from the group consisting of XHT-S SDB, SMS, SDB from CHT Germany GmbH, Tübingen. To prepare a dispersion, a stock solution of a dispersant can first be prepared, which is then added to the dispersion in a ratio of <1:50 to >1:250, preferably <1:80 to >1:150, such as 1:100.

[0031] According to a further embodiment of the invention, it can be provided that the dispersion comprises the catalyst support particle in a concentration in a range between >5 g / l and <100 g / l, preferably between >15 g / l and <40 g / l, based on the total dispersion. Such a concentration has proven to be particularly suitable for ensuring uniform deposition of the catalyst support particle onto the polymer fiber or the polymer sheet. According to a preferred embodiment of the process, the polymer fiber or the polymer sheet is loaded with between 5 wt.% and 20 wt.% of catalyst support particles. The loading rate can be calculated from the quotient of the difference between the weight of the polymer fiber or the polymer sheet after the dispersion fixation of the catalyst support particle and the weight of the polymer fiber orof the polymer sheet before the dispersion fixation of the catalyst support particle, and the weight of the polymer fiber or the polymer sheet before the dispersion fixation of the catalyst support particle.

[0032] According to one embodiment of the invention, the preferably used TiCh catalyst particles or other metallic or metal oxide catalyst support particles can be impregnated with another metal salt or noble metal salt solution in the sense of wet impregnation and thermally treated. The thermal treatment can comprise heating to a temperature of, for example, 400°C at a high heating rate of up to 20 K / min. The impregnated catalyst support particles can be held at this temperature for a period of 30 minutes and then cooled in a defined manner at a cooling rate of, for example, 2-5 K / min.

[0033] With regard to the surface-catalytically equipped polymer fiber or surface-catalytically equipped polymer sheet, the object underlying the invention is achieved by the fiber or sheet, wherein said fiber has catalyst support particles on the surface, wherein the catalyst support particles have as catalyst at least one metal from the group of the outer transition metals of the periodic table, preferably platinum, nickel, gold, silver, rhenium, cobalt, vanadium, chromium, copper, palladium, iridium, rhodium and zirconium, or an oxide or a mixed oxide thereof, and wherein the catalyst support particles have at least partially penetrated into the polymer fiber or the polymer sheet and are thus bound to the polymer fiber or the polymer sheet without an additional fastening means.It has surprisingly been shown that the process according to the invention makes it possible, on the one hand, to mechanically stably fix catalyst support particles to the surface of a polymer fiber or a polymer sheet without the need for a separate binder such as an adhesive. On the other hand, the catalyst support particles penetrate into the polymer fibers or the polymer sheet, or their surface, only to the extent that a predominant portion of the particles protrudes from the surface, allowing any redox-active catalyst metals applied thereto to come into sufficient contact with the catalyst metal, or any gas passing past the surface of the polymer fiber or the polymer sheet, to be catalytically converted.

[0034] Surprisingly, it has been shown that the catalyst support particles are mechanically immobilized on the surface of the fiber or the sheet so stably that > ​​500 compressed air pulses with an overpressure of 6 bar with a duration of 1 second each lead to detachments of the catalytic particles of < 5% in relation to the total mass of the catalytic particles.

[0035] With regard to the use, the invention proposes using the polymer fibers surface-catalytically treated according to the invention or a corresponding surface-catalytically treated polymer sheet to produce a filter for particle separation in an air purification system. In particular, the invention proposes using the polymer fibers surface-catalytically treated according to the invention or a corresponding surface-catalytically treated polymer sheet to produce a gas / solid filter for catalytic carbon monoxide degradation.

[0036] For example, it is possible to provide a bag filter for a particle separator for separating organic dust from a gas stream. This bag filter is capable of catalytically converting any carbon monoxide (CO) formed in the separated organic dust or the forming filter cake into carbon dioxide (CO2), thus removing it from the filtered gas stream. This can overcome a problem in mechanical exhaust gas purification that occurs when, for example, fire or ember pockets form in the separated filter cake and CO is formed during the thermal decomposition of the filter dust. However, such CO formation is undesirable because the filtered gas stream is contaminated by this CO, and regulatory requirements for the exhaust gas stream may not be met.Thanks to the polymer fibers or polymer sheet structures catalytically treated according to the invention, relatively low temperatures are possible for catalytic exhaust air purification. A further advantage of the inventive use of the surface-catalytically treated polymer fibers or polymer sheet structures is that the catalytically active substance is mechanically and stably bonded to the fibers or sheet structures, so that any mechanical stresses that can occur in filter systems during operation and particularly during countercurrent cleaning can prevent erosion of the catalytically active substance. Such erosion can be observed when catalytically active substances are applied using a binder, such as an adhesive, so that the catalytic activity of corresponding filters decreases significantly over the course of use.

[0037] Furthermore, a disadvantage of applying catalytically active substances to a polymer fiber or polymer sheet using a binder is that the woven, knitted, or nonwoven fabrics produced from them often exhibit significantly increased air permeability resistance compared to untreated woven, knitted, or nonwoven fabrics. When these materials are used as filters, a significant pressure drop occurs across the filter. This is detrimental to flow and is therefore generally undesirable because overcoming the pressure difference requires energy. In contrast, the polymer fibers or polymer sheet structures treated according to the invention, and the woven, knitted, or nonwoven fabrics produced therefrom, exhibit significantly lower pressure drop and are therefore advantageous in terms of flow. The specific surface area of ​​a textile is directly dependent on the fiber diameter.While most commercially available bag filters today utilize needle-punched PET nonwovens with a titer of approximately 5 dtex, there are also newer generation bag filters with significantly lower titers, e.g., based on microfilament nonwovens (see DE102007023806). The technical advantage of these newer bag filters lies in the fact that good separation performance can be achieved with comparatively significantly lower surface weights. This is because the pore-forming filaments have smaller diameters than conventional fibers and because they are not mechanically needled, which leads to damage and thus a reduction in mechanical properties, but are hydromechanically bonded. At the same time, the microfilaments of the "segmented pie" type have a comparatively much larger surface area, as demonstrated by the following example calculation.

[0038] The surface area per 100g of nonwoven fabric is calculated as follows:

[0039] Case 1, 5dtex, PET: 13.5m 2

[0040] Case 2, 2.4dtex PIE 16 with 70% PET and 30% PA6: for PET 65m 2 , for PA6 57 m 2

[0041] That is, with the same basis weight, namely 100g (per m 2 ), the needle felt has 13.5m per 100g 2 PET surface, while the spunbonded nonwoven, segmented PIE 70 / 30 at 2.4dtex before splitting, has about 5 times the PET surface after splitting by hydroentanglement.

[0042] Fig. 1 shows a scanning electron micrograph of the cross section of a polymer fiber treated according to the invention.

[0043] The bright spots shown in Fig. 1 show TiO2 particles with a diameter of 2pm to 4pm. The particles were impregnated with a platinum-containing solution so that catalytically active platinum atoms or agglomerates are present on the surface of the TiO2 particles. The TiO2 particles partially penetrate into the fiber structure and are thus firmly bound to the fiber surface. The fiber diameter remains almost unchanged compared to an unfinished fiber, so that the hydraulic resistance of a woven, knitted or nonwoven fabric made from a correspondingly finished fiber also remains almost unchanged compared to an unfinished woven, knitted or nonwoven fabric. The same applies to woven, knitted or nonwoven fabrics which are subsequently finished according to the invention. These also show an almost unchanged air permeability resistance compared to unfinished comparative woven, knitted or nonwoven fabrics.

[0044] The invention is explained in more detail below using exemplary embodiments.

[0045] Example 1 :

[0046] Four 10g samples of a polyester fabric (PET needle-punched nonwoven fabric with approx. 5dtex and 550g / m 2 ) was individually contacted with dispersion liquor containing 1.5 wt.%, 2.0 wt.%, 3.0 wt.% or 4.0 wt.% platinum-impregnated TiCh particles. 0.3 g of a dispersant (CHT Dispergator SMS) was added to each dispersion liquor, and the pH of the dispersion liquor was adjusted to 4.5 using dilute acetic acid. The dispersion liquors were made up to 100 ml with softened water (soft water), and the dispersion liquor was homogenized. The fabric samples were then heated to 135°C with the appropriate dispersion liquors in dye bombs (autoclaves) with mechanical agitation in a glycol bath at a heating rate of 3°C / min, and then held at this temperature for 60 min. This was followed by cooling to 60°C at a cooling rate of 6°C / min. Before opening the autoclaves, they were cooled to room temperature using running water.The fabric samples were removed and washed with 2 l of softened water for 1 minute each. The samples were then dried by spinning for 1 minute. After final drying at 40°C in a drying cabinet, the load of the respective samples was determined by weighing them and comparing them to the sample weight before treatment. The following loads were determined:

[0047] Example 2: A 10g sample of a PET / PA6 microfilament nonwoven fabric with a basis weight of 80g / m 2 made of PET / PA6 with a volume ratio of approximately 70 / 30 and a titer after splitting of approximately 0.2 dtex for PET and approximately 0.1 dtex for PA6 was treated analogously to Example 1 and contacted with a dispersion liquor containing 4 wt.% platinum-impregnated TiCb particles. A loading of 3.05 g was determined, which corresponds to approximately twice the loading, of which 0.2 g were detached after 500 pressure shock tests and a further 0.08 g after 1000 pressure shocks. The fact that not five times the amount of Pt / TiCb was absorbed can be explained by the fact that in the spunbond process, comparatively high stretching leads to higher crystallinity of the polymer filaments and accordingly fewer amorphous regions are available for fixation of the catalyst particles. Furthermore, the fixation on the polyamide is not quite as stable as on PET.The fact that a portion of the deposited catalyst particles can be repelled by the compressed air pulses can be explained by the fact that some of the particles are filtered out but not fixed due to the smaller pore size of the microfilament material. At higher basis weights with more layers (tortuosity) and increasing density after hydroentanglement, the filtration of catalyst particles becomes even more significant. However, it has been demonstrated that it is also possible, in principle, to achieve such highly stretched microfilament nonwovens using dispersion fixation.

Claims

Patent claims Process for the surface catalytic treatment of polymer fibers and / or sheetlike structures, comprising the steps of: a) providing a polymer fiber or a polymer sheetlike structure made of an amorphous or partially amorphous polymer; b) providing an aqueous dispersion of a catalyst support particle; c) contacting the polymer fiber or the polymer sheetlike structure with the aqueous dispersion of the catalyst support particle, characterized in that the catalyst support particle has a particle size in a range between >0.5pm and <20pm, preferably between >1pm and <10pm, in particular between >1.5pm and <5pm and that the contacting in step c) takes place at a temperature in a range between >15°C and <60°C, preferably between >20°C and <50°C, in particular between >30°C and <40°C above the glass transition temperature TG of the polymer and wherein the catalyst support particle is impregnated with a catalytically active metal or metal oxide. Process according to claim 1, wherein the polymer fiber or the polymer sheet is contacted at the stated temperature for a period of time between >30 min and <360 min, preferably between >60 min and <240 min, in particular between >90 min and <120 min. Process according to claim 1 or 2, characterized in that the catalyst support particle is porous and preferably has a porosity . in a range between >10% and <60%.

4. The process according to claim 3, characterized in that the catalyst support particle is selected from the group consisting of titanium dioxide, cordierite, zeolites, magnesium silicate or layered silicate.

5. Process according to one of the preceding claims, characterized in that the catalytically active metal is at least one metal selected from the group consisting of metals of the group of the outer transition metals of the periodic table, preferably platinum, nickel, gold, silver, rhenium, cobalt, vanadium, chromium, copper, palladium, iridium, rhodium and zirconium, or an oxide or a mixed oxide thereof.

6. Process according to one of the preceding claims, characterized in that the polymer is selected from the group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylacid (PLA), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polycarbonate (PC), polyamide (PA), polyarylate (PAR), polyester carbonate (PEC), or copolymers or blends thereof.

7. Process according to one of the preceding claims, wherein the aqueous dispersion is adjusted to a pH in a range > pH 1 and < pH 5.

8. A surface-catalytically equipped polymer fiber or surface-catalytically equipped polymer sheet, characterized in that the fiber or the sheet has redox-active catalyst support particles on the surface, wherein the catalyst support particles have at least one metal from the group of the outer transition metals of the periodic table, preferably platinum, nickel, gold, silver, rhenium, cobalt, vanadium, chromium, copper, palladium, iridium, rhodium and zirconium, or an oxide or a mixed oxide thereof, and wherein the catalyst support particles are at least partially incorporated into the polymer fiber or the Polymer sheet material and are thus bonded to the polymer fiber or the polymer sheet material without an additional fastening agent. Surface-catalytically treated polyester fiber or surface-catalytically treated polyester sheet material according to claim 8, wherein the Catalyst support particles are mechanically stably immobilized on the surface of the fiber or sheet, and at least > 500 compressed air pulses with an overpressure of 6 bar, each lasting 1 second, result in detachment of the catalytic particles by < 5% of the total mass of the catalytic particles. Use of a surface-catalytically treated polymer fiber and / or a surface-catalytically treated polymer sheet for producing a filter for particle separation in an air purification system.

Images