Composite filter material and method for manufacturing the same

Abstract

A composite filter material consisting of a precision fabric of the type having weft and warp threads, on whose surface nanofibers are deposited by electrospinning. A method for producing a composite filter material, comprising a step of electrospinning to form nanofibers, followed by a step of depositing said nanofibers on a substrate; the method comprises establishing a potential difference between a nozzle and an electrode; the nanofibers are formed as a result of evaporation of a solvent or mixture of solvents by an electric field and stretching of a polymer deposited on the electrode by the nozzle; the nanofibers thus formed are then stretched and deposited on said substrate.

Description

[Technical Field]

[0001] The present invention relates to a composite filter material and a method for manufacturing the same.

[0002] The present invention relates in particular to a composite filter material in the form of a fabric for use as a protective material for electroacoustic components in the field of consumer electronics such as speakers, receivers, and microphones. [Background technology]

[0003] Various fabrics are known that are used to protect acoustic devices, with the aim of providing adequate protection from external factors while simultaneously offering sufficient acoustic performance.

[0004] Conventional composite fabrics used in the aforementioned fields have a mesh coated with a layer of nanofibers, but they have the drawback of not being able to withstand temperatures up to 300°C. In fact, the fibers that make up the fabric tend to degrade with heat and basically do not have suitable thermal properties to ensure the required performance.

[0005] Further drawbacks of existing composite materials include poor adhesion between nanofibers and monofilaments that form the mesh of the fabric. [Overview of the project]

[0006] The objective of the present invention is to provide a composite filter material that is improved and exhibits higher performance compared to conventionally known filter materials.

[0007] In particular, the object of the present invention is to provide a novel composite fabric with filtering properties for electroacoustic components that can withstand temperatures up to 300°C, exhibiting filtering performance equivalent to or better than that of composite fabrics of the prior art.

[0008] A further object of the present invention is to provide the above-described type of composite fabric that can improve adhesion between the filaments of the fabric mesh and the nanofibers of the coating without the use of adhesive additives.

[0009] Within the scope of the above objectives, an object of the present invention is to provide a filter material particularly useful for the manufacture of hearing aids and acoustic devices.

[0010] Another object of the present invention is to provide a filter material that can ensure sufficient functionality at least similar to conventional fabrics, while also having improved protective capabilities.

[0011] A further object of the present invention is to provide a filter material that can simultaneously ensure better acoustic performance and better protection against the intrusion of fine particles.

[0012] Another object of the present invention is to provide a filter material that can guarantee at least the same breathability and acoustic impedance values ​​as conventional fabrics, but has a better degree of protection against the intrusion of metal dust, fibrous dust, etc. than conventional fabrics.

[0013] A further object of the present invention is to provide a filter material that can be advantageously used for protecting electroacoustic components in the consumer electronics field, such as speakers, receivers, and microphones.

[0014] A further objective of the present invention is to provide a filter material that can guarantee reliability and safety during use as broadly as possible.

[0015] These and other objectives are made apparent below, but are achieved by the composite filter material and method for manufacturing the same as specified in the attached claims. [Brief explanation of the drawing]

[0016] Further features and advantages of the subject matter of the present invention will become more apparent by considering the description of preferred embodiments of the present invention, which are illustrated in the accompanying drawings as explanatory and non-limiting examples.

[0017] [Figure 1] The composite filter material according to the present invention is a PEEK71.35 monofilament base fabric, i.e., composed of polyether ether ketone monofilaments with 71 weft and warp threads per 1 cm of fabric and a nominal diameter of 35 μm. The base fabric has a coating of polyimide nanofibers deposited in solution by an electrospinning process. A suitable solvent is a weight ratio of DMAc (dimethylacetamide) to NMP (N-methyl-2-pyrrolidone) of 40:60. In this mixed solvent, a polyimide solution for nanofiber formation by electrospinning is prepared. [Figure 2] Graph showing Rub & Buzz analysis of standard composite fabric (Aethex25), PROTO1, and Acoustex025 (Ac025) fabric: ·Rub & Buzz analysis is an acoustic type analysis regarding the undesirable effects of irregular nonlinear distortion; ·Aethex25 is a conventional composite fabric (nanomesh with an acoustic impedance of 25 MKS rayls) and is not suitable for high temperatures; ·PROTO1 is a composite fabric according to the present invention, which also has an acoustic impedance of 25 MKS rayls; ·Acoustex025 is a non-composite fabric, i.e., a fabric without nanofiber coating, with an acoustic impedance of 25 MKS rayls. [Figure 3] Figure 1 shows the untreated PEEK 71.35 substrate used in the preparation of the composite material. [Figure 4] Figure 3 shows the PEEK71.35 base fabric, illustrating the surface of the PEEK monofilaments of the base fabric during electrospinning using DMAc-NMP solvent in a 40:60 weight percentage ratio. Nanofibers are not included. [Figure 5] Unlike the filter material according to the present invention, this shows a fabric from the prior art that does not exhibit swelling. [Figure 6] This figure shows the composite filter material of FIG. 1, and is a view of the surface of the PEEK monofilament of the base fabric in an electrospinning process using a DMAc-NMP solvent and polyimide nanofibers at a weight percentage ratio of 40:60, before (A) and after (B - F) various thermal recycling cycles: · B: Each cycle is 260°C for 1 minute with 2 reflow cycles; · C: Each cycle is 260°C for 10 minutes with 2 reflow cycles; · D: Each cycle is 260°C for 30 minutes with 2 reflow cycles; · E: Each cycle is 260°C for 1 hour with 2 reflow cycles; · F: Each cycle is 260°C for 2 hours with 2 reflow cycles. [Figure 7] This shows the energy required to completely remove oil from the composite fabric according to the present invention, compared with the energy required for a filter material according to the prior art having equivalent air permeability characteristics: PROTO1, 2, 3 are composite fabrics according to the present invention, having air permeabilities of 4500, 2350, 980 (l / m2s-1) 200 Pa respectively; Aethex25, 70, 160 are filter materials according to the prior art, having air permeabilities of 4500, 2350, 980 (l / m2s-1) 200 Pa respectively.

Embodiments for Carrying out the Invention

[0018] Referring particularly to the numbers present in the aforementioned figures, the composite filter material 1 according to the present invention is composed of a type of fabric having warp and weft, preferably PEEK yarns or monofilaments 2, and polyimide nanofibers 3 are deposited on its surface by electrospinning. According to the present invention, the monofilament 2 can be replaced with another type of yarn formed of a polymer suitable for withstanding high temperatures, such as a fabric made of glass fiber, polyphenylene sulfide, polyimide, polyethersulfone, sulfonated polyaryl ether sulfone. The nanofibers themselves can further be made of materials resistant to high temperatures different from polyimide, such as polybenzimidazole, sulfonated polyether ether ketone, polyethersulfone, sulfonated polyaryl ether sulfone, etc.

[0019] Suitable for the present invention are monofilaments and nanofibers characterized by good heat resistance represented by melting temperature and / or glass transition temperature in the heat range from room temperature to 300 °C.

[0020] The base fabric used for the preparation of the composite filter material according to the present invention is generally selected from a wide range of synthetic monofilament fabrics with 3 to 200 filaments / cm, a diameter of 24 to 600 μm, and different chemical properties of the monofilaments used for weaving.

[0021] Specifically, a base fabric that can withstand high process temperatures (up to 300 °C) in both one-step heat processes and thermal recycling or reflow processes, i.e., processes with a large number of continuous cooling / heating cycles, is suitable for the present invention.

[0022] For finishing and further surface treatment, it is possible to use fabrics subjected to metallization, washing and heat-set "white" fabrics, colored fabrics, plasma treatment, hydrophobic treatment, hydrophilic treatment, antibacterial treatment, antistatic treatment, etc.

[0023] Preferred for the present invention is a monofilament fabric made of polyether ether ketone (PEEK) with 71 filaments / cm, a diameter of 35 μm, a base fabric mesh opening of 102 μm, a basis weight of 20 g / m

[0026] , , and a thickness of 65 μm.

[0024] Suitable for the present invention are polymer nanofibers with a nanofiber diameter of 50 to 500 nm that can withstand high process temperatures up to 300 °C in both one-step heat processes and reflow cycles.

[0025] Preferred for the present invention are polyimide (PI) nanofibers with a diameter of 100 to 220 nm.

[0026] The electrospinning process for the formation of nanofibers and subsequent deposition onto a substrate includes injecting a nanofiber-forming material, dissolved in a suitable solvent or mixture of solvents, through a nozzle to spread it onto an electrode.

[0027] Thanks to the potential difference between the nozzle and the electrode, nanofibers are formed as a result of the evaporation of the solvent or mixed solvent due to the electric field and the stretching of the polymer deposited on the electrode by the nozzle.

[0028] The nanofibers formed in this way are then stretched and subsequently deposited onto a substrate.

[0029] Furthermore, the nanofibers 3 thus formed are not only deposited on the base fabric in an innovative manner compared to prior art, but also adhere firmly to the base fabric without the help of adhesives and / or tacks applied to the base fabric and / or nanofiber layer, thanks to the use of several process parameters, which are revealed below, that promote the partial and superficial swelling 4 of the yarns 2 forming the base fabric.

[0030] This swelling phenomenon of the base yarn 2, which does not affect the structural properties of the base fabric, promotes strong adhesion of the nanofibers 3 placed on the base yarn 2, enabling the formation of a more stable product in terms of the integrity of adhesion between the base fabric and the nanofibers during the various processing steps the filter material undergoes.

[0031] According to the present invention, this result is achieved by subjecting a solution of polyimide for the formation of nanofibers 3 in a mixed solvent of dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP) to an NMP-rich electrospinning process. In the electrospinning process, polyimide nanofibers are obtained, which precipitate on a polyether ether ketone (PEEK) yarn 2. During this precipitation step, the aforementioned solvent solution remains carried by the nanofibers 3, wetting the yarn 2 on the surface in contact with the nanofibers, resulting in the formation of softened portions and swelling 4 on the surface itself. This swelling 4 incorporates a portion of the nanofibers 3 in the electrospinning process, thereby contributing to adhesion or fixation to the yarn 2 (Figure 1).

[0032] As a result, according to the present invention, during the electrospinning process, not only are nanofibers 3 deposited on monofilaments 2, but adhesion or relative fixation phenomena occur between the yarn and nanofibers, contributing to the stability of the composite fabric 1. A solvent suitable for this purpose is a mixed solvent of DMAc and NMP in a ratio of 40:60, with NMP present in excess, especially in an amount of 50% by weight or more in the solvent mixture. Thus, the adhesion of nanofibers is promoted without impairing the structural properties of the base fabric. Figures 1, 3, and 4 are SEM images illustrating the phenomenon described above.

[0033] Table 1 provides a comparison of the heat resistance characteristics of the filter material according to the present invention and the filter material according to the prior art, in terms of the rate of change in air permeability (Δ%) before and after one or more reflow cycles, at different temperatures and different operating times, specifically, 120 hours at 130°C (temperature and operating time generally required for the filter material according to the prior art); and a time range of 1 minute to 2 hours at 260°C (temperature and operating time generally required for the filter material operating at high temperatures).

[0034] in particular Aethex25 is a composite fabric based on prior art that is not suitable for withstanding high temperatures (nanomesh with acoustic impedance of 25 MKS rays). PROTO1 is a composite fabric according to the present invention, formed from a PEEK71.35 base fabric coated with polyimide nanofibers obtained by electrospinning a polyimide solution in DMAc / NMP in a 40:60 ratio, and it also has an acoustic impedance of 25 MKS rays.

[0035] Next, Table 1 shows a comparison of the percentage difference in air permeability measured before and after one or more reflow cycles from 25°C to 130°C and from 25°C to 260°C between the filter material according to the present invention PROTO1 and the filter material according to the prior art Aethex25. Air permeability is measured in l / m at a pressure of 200 Pa. 2 s -1 It was measured using [this method].

[0036] This table shows that the filter material according to the present invention has the same filtering capacity as the filter material according to the prior art in the temperature range of 25-130°C and the typical usage time of the latter, and that only the filter material according to the present invention can be used at high temperatures, for different durations, and for multiple reflow cycles. For this reason, data measured at 260°C for the composite fabric Aethex25 is unavailable as it cannot be measured. It is known that signs of damage to the filter material during or after use are an increase or decrease in permeability that is higher than the normal tolerance of the process compared to the initial state of non-use. This behavior suggests that damage to the morphology of the filter material may occur during use, and this is generally considered to be within the acceptable range of 8% or less. Conversely, excessive or defective permeability fluctuations with respect to the initial state of non-use, which is within the tolerance of the process itself, indicate that the protective capacity of the filter material has not changed during use. In a specific example, a decrease in permeability of the filter material, i.e., a decrease in permeability of less than 5%, which is within the tolerance of the process, can be observed, and the filtering capacity of the composite material according to the present invention can be confirmed.

[0037] [Table 1]

[0038] Figure 6 shows a composite filter material according to the present invention, illustrating the surface of the PEEK monofilament of the base fabric before (A) and after (B-F) various thermal recycling cycles in an electrospinning process using a 40:60 weight percentage DMAc-NMP solvent and polyimide nanofibers. Specifically, B: Reflow cycle of 260°C for 1 minute each, twice; C: Two reflow cycles of 10 minutes each at 260°C; D: Two reflow cycles of 30 minutes each at 260°C; E: Two reflow cycles of 1 hour each at 260°C; F: Two reflow cycles of 2 hours each at 260°C.

[0039] From the images presented, it should be noted that in all thermal recycling research cases from B to F, the morphological appearance of the filter material according to the present invention, which is understood to be due to the formation of bulges on the surface of the fabric itself as described above, resulting in the homogeneity of the mesh coating and the adhesion of polyimide nanofibers to the PEEK fabric, remains unchanged compared to the morphological appearance of the filter material itself before use, and the heat resistance of the filter material according to the present invention was confirmed in relation to the thermal recycling tests conducted.

[0040] Table 2 below shows the permeability, pore size, and acoustic impedance characteristics of various prototypes of the filter material according to the present invention, compared to the corresponding characteristics of PEEK71.35 base fabric alone, i.e., without nanofiber coating.

[0041] In this table, pores refer to the pores of the fabric, consisting of a combination of pores present in the base fabric and pores formed in the nanofiber coating. Permeability is expressed as l / m at a pressure of 200 Pa. 2 s -1 It is measured in units of [unit]. moreover: PEEK71.35 is the base fabric used in this invention, with a thread count of 71 threads / cm, a diameter of 35 μm, a mesh opening of 102 μm, and a basis weight of 20 g / m². 2 , having a thickness of 65 μm; PROTO1 is a composite fabric according to the present invention, formed from a PEEK71.35 base fabric having a coating of polyimide nanofibers obtained by electrospinning a polyimide solution in a 40 / 60 ratio DMAc / NMP; PROTO2-5 are composite fabrics according to the present invention, similar to PROTO1 but obtained with different parameters in the electrospinning process.

[0042] [Table 2]

[0043] From Table 2 above, it should be noted that, in terms of breathability, in the electrospinning process used to prepare PROTO1-5 according to the present invention, the PEEK fabric mesh is coated in a manner that gradually increases with nanofibers, resulting in a decrease in pore size and an increase in acoustic impedance.

[0044] Instead, Table 3 below shows the breathability properties of a standard fabric (if any) having pore sizes equivalent to those of various prototypes according to the present invention. PES38 / 20 and PES15 / 09 have mesh openings of 38 μm and 15 μm, respectively, and are suitable for fabrics up to 1 cm². 2 This is a polyester with free surface areas of 20% and 9%, respectively.

[0045] [Table 3]

[0046] Table 3 emphasizes that for PROTO1 and 2 with comparable pore sizes, they have much greater air permeability than the fabric, and as a result, more excellent acoustic properties are ensured. Instead, since there is no standard reference fabric for comparison with PROTO3 and PROTO4, it is clear that only the composite fabric according to the present invention can ensure the described properties of air permeability and protection against fine particles.

[0047] Finally, a further object of the present invention is to provide a novel composite fabric having a filtering action for electroacoustic components, which can withstand temperatures up to 300 °C and has filtering performance equal to or better than that of the composite fabrics of the prior art.

[0048] In the case under consideration, different prototypes having the same air permeability as the composite fabric according to the prior art were prepared, and considering the same characteristics of air filtering, a filter material having a pore size comparable to or smaller than that of the corresponding composite fabric according to the prior art was obtained.

[0049] In combination with the use of polyimide nanofiber 3, by adding plasma treatment to the filter material according to the present invention, in addition to increasing the water column resistance already known in the case of filter materials belonging to the prior art, the energy required to remove the oil adhered to the surface of the filter material is significantly reduced compared to the prior art, and better protection performance than the prior art is obtained.

[0050] FIG. 7 shows the pressure required to completely remove the oil deposited on the surface of the filter materials according to the prior art and the present invention, and this filter material has an air permeability comparable to that of various prototypes according to the present invention.

[0051] In FIG. 7: · Aethex25 and PROTO1 are the composite fabrics according to the prior art and the present invention respectively, with pore sizes of 60 and 36 μm respectively, and about 4500 (l / m 2 s -1It has a breathability of 200 Pa. Aethex70 and PROTO2 are a conventional composite fabric and a composite fabric according to the present invention, respectively, with pore sizes of 12 and 19 μm and a density of approximately 2350 (l / m²). 2 s -1 It has a breathability of 200 Pa. Aethex160 and PROTO3 are a composite fabric according to the prior art and a composite fabric according to the present invention, respectively, with pore sizes of 14 and 5 μm and approximately 980 (l / m²). 2 s -1 It has a breathability of 200 Pa.

[0052] Figure 7 clearly shows that, in particular, the pressure required to completely remove oil from the composite fabric according to the present invention is lower than that of the prior art, making the fabric easier and faster to clean.

[0053] This invention has a wide range of advantageous applications.

[0054] One example of a practical application of the present invention is filtering even at high temperatures.

[0055] Compared to conventional nanomesh types, filter materials made of PEEK and polyimide can be used in several other applications. For example, they can be used in applications where the filter material must be exposed to high process temperatures and its properties must not change; that is, where the fabric and nanofibers must not be affected by temperature changes.

[0056] The innovative application of the filter material according to the present invention relates to MEMS (Micro Electro-Mechanical Systems) technology.

[0057] Specifically, MEMS devices have two ventilation openings to overcome problems such as overheating and pressure equalization of electronic components during use: one is located inside the MEMS device and uses protective filtering material that is not necessarily post-processed by the die-cutting process, and the other is located outside the device itself and uses protective filtering material that is always post-processed by the die-cutting process.

[0058] This allows the device to withstand extremely high process temperatures of nearly 300°C at various stages of assembly and use, and facilitates the passage of air between the inside and outside of the MEMS device.

[0059] The need to protect both of these vents with a protective film that is air-permeable and can withstand temperatures close to 300°C is essential because it prevents contamination by moisture, particulate matter, dust, oil, etc., generally prevents a decrease in acoustic transmission performance, allows for recirculation of airflow, and lastly, because their high temperature resistance is advantageous for assembling MEMS devices with the protective layer pre-integrated, and is a technical choice that makes the manufacture of MEMS devices that are assembled without protecting the vents and could be damaged during assembly easier and more economical.

[0060] In the current technological landscape, protection of internal and external vents in MEMS devices is carried out in two ways: i) without applying a protective layer, which results in a very short device lifespan, or ii) by applying protective adhesive tape.

[0061] Using protective adhesive tape is not as satisfactory as not protecting the ventilation port itself. Because these tapes are impermeable to air, they can protect the device from some contaminants, but they cannot allow proper air recirculation, resulting in problems such as overheating and uneven pressure distribution within the MEMS.

[0062] Therefore, the use of filter materials made from known types of nanomesh, with the added advantage of heat resistance according to the present invention, represents an advancement over the current state of MEMS technology in both internal and external protection of MEMS devices.

[0063] In acoustic applications, the present invention can be used in situations where the filter material is co-molded with a high-melting-point polymer, thereby ensuring thermal resistance during the process.

[0064] In addition to its use in high-temperature applications where conventional nanomesh could not be used due to obvious physical limitations, a second advantage of the present invention lies in the improved, tighter adhesion between the support fabric and the nanofibers.

[0065] In this case, this characteristic actually makes the following possible: • Post-processing of the material prevents potential damage to the material and resulting performance degradation (see typical die-cutting process for providing packaged nanomesh components assembled with a layer of adhesive). While the fact that nanofibers and standard fabrics are not tightly bonded is a significant advantage in terms of acoustic properties, the passage of sound, i.e., airflow at a given velocity, can cause minute vibrations in the nanofiber layer on the substrate, resulting in sound distortion and undesirable noise.

[0066] If the nanofibers are firmly adhered to the substrate, the aforementioned vibration problem will be eliminated, and therefore the sound will be clearer.

[0067] Typically, acoustic analysis known as "Rub & Buzz" can be used to investigate sound distortion and unwanted noise generation caused by minute vibrations resulting from the electrospun nanofiber layer on the substrate.

[0068] Figure 2 is a graph showing the rub and buzz analysis of a standard nanomesh sample (Aethex25), a PROTO1 sample (i.e., the filter material according to the present invention), and a sample of Acoustex025, a fabric having the same acoustic impedance as Aethex25 and PROTO1.

[0069] The graph shown in Figure 2 generally indicates that for all measured test specimens of Aethex25, PROTO1, and Acoustex025, the percentage of vibration induced by the filter material is less than 0.8% (the standard target for commercially available acoustic devices).

[0070] Furthermore, comparing PROTO1 with the two reference specimens, it can be seen that the superior adhesion of the nanofiber layer on the base fabric resulted in lower Rub & Buzz percentage values ​​in all PROTO1 specimens compared to Aethex25 and Acoustex025, indicating an improvement.

[0071] The filter material according to the present invention can be subjected to plasma treatment, which provides the following two advantages. • Water resistance is improved, especially for materials with low permeability. • In the case of highly permeable materials, the non-wetting properties of the nanomesh are ensured.

[0072] Furthermore, plasma treatment reduces the energy required to remove oil adhering to the surface of the filter material.

[0073] It has been found that the intended purposes and objectives of this invention have been achieved.

[0074] In fact, a filter material was obtained that consisted of polymer nanofibers deposited on a monofilament fabric by electrospinning.

[0075] During deposition, nanofibers are positioned on the threads, at the intersections between threads, and within the mesh of the fabric. By being positioned within the mesh, they reduce the average opening and free surface area of ​​the fabric.

[0076] In this way, it is possible to obtain moisture permeability and acoustic impedance values ​​equivalent to those of standard fabrics.

[0077] If the moisture permeability / impedance values ​​are equal, composite fabrics offer better protection against dust (metal dust, fiber dust, etc.) penetration than standard fabrics.

[0078] This is due to the random, three-dimensional structure of nanofiber layers arranged in a mesh, which, unlike fabrics that only employ their own mesh openings to reduce and / or prevent dust passage, allows for a reduction in the surface area through which dust can pass. Thanks to the nanoscale size of the fibers, it is also possible to minimize the proportion of sealed or unfiltered volume.

[0079] Thus, by replacing standard fabrics with equivalent permeability in specific applications with composite fabrics, it becomes practically possible to guarantee the same pressure loss for the same flow, significantly improving protection against ingress.

[0080] In specific cases where composite fabrics are used as protective materials for electroacoustic components (speakers, receivers, microphones) in the consumer electronics sector, it is possible to guarantee the same acoustic performance as conventionally used fabrics, while offering improved protective capabilities. In some cases, it is possible to obtain both superior acoustic performance and protection against particle intrusion simultaneously.

Claims

1. A method for producing a composite filter material having a base fabric having weft and warp threads of polyetheretherketone (PEEK) yarn or monofilament (2), The method is characterized by comprising the steps of electrospinning to form polyimide (PI) nanofibers (3) and a subsequent step of depositing the nanofibers (3) onto the base fabric, The method includes injecting a material for forming nanofibers (3), dissolved in a solvent mixture of dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP) in an NMP-rich ratio, through a nozzle to spread it onto an electrode. The above method includes providing a potential difference between the nozzle and the electrode, The nanofibers (3) are formed as a result of the evaporation of the solvent mixture by an electric field and the extension of the polymer deposited on the electrode by a nozzle. The nanofibers (3) formed in this manner are then stretched and deposited on the base fabric. The solvent mixture carried by the nanofiber (3) moistens the yarn or monofilament (2) on the surface in contact with the nanofiber (3), and as a result, a swollen portion (4) is formed on the surface of the yarn or monofilament (2), and the swollen portion (4) incorporates a portion of the nanofiber (3). A method for adhering the nanofibers (3) to the base fabric without the help of an adhesive and / or tack applied to the base fabric and / or the nanofiber layer, at the swollen portion (4) of the yarn or monofilament (2) of the base fabric, which is formed on the contact surface of the yarn or monofilament (2) itself with the nanofibers (3).

2. A composite filter material obtained by the method described in claim 1, A composite filter material characterized in that the yarn or monofilament (2) has a swelling portion (4) on its surface that contacts the nanofiber (3) that incorporates the nanofiber (3) itself and holds them on the surface of the yarn or monofilament (2) itself.

3. The composite filter material according to claim 2, characterized in that the base fabric is selected from synthetic monofilament fabrics having a thread count of 3 to 200 threads / cm and a diameter of 24 to 600 μm.

4. The composite filter material according to claim 3, characterized in that the base fabric is selected from a synthetic monofilament base fabric having a diameter of 24 to 600 μm and a yarn count of 3 to 200 yarns / cm.

5. The composite filter material according to claim 4, characterized in that, as a finishing treatment and further surface treatment, a fabric selected from metallized, washed and heat-set white fabric, colored fabric, plasma-treated, hydrophobic, hydrophilic, antibacterial, and antistatic fabric is used.

6. The base fabric is a monofilament fabric made of polyetheretherketone (PEEK), with a thread count of 71 threads / cm, a diameter of 35 μm, a mesh opening of 102 μm, and a basis weight of 20 g / m². ２ A composite filter material according to any one of claims 2 to 5, characterized in that it has a thickness of 65 μm.

7. The composite filter material according to claim 2, characterized in that the nanofiber (3) is a polyimide (PI) nanofiber having a diameter of 100 to 220 nm.

Images