Filter insert with improved service life

Abstract

The invention relates to a filter insert (10) for a fluid filter device, comprising: i) at least one particle filter stage (12) for separating solid impurities (14) from the fluid (16) to be filtered, comprising at least one filter medium, ii) at least one coalescer stage (18), which is different from the particle filter stage (12), for agglomerating liquid impurities (20) dispersed in the fluid (16) to be filtered, and iii) at least one separation stage (22) at a distance from the coalescer stage (18) for separating agglomerated liquid impurities (20) from the fluid (16) to be filtered, comprising at least one first more hydrophobic layer (24), wherein the first more hydrophobic layer (24) has a contact angle for water of more than 90.2°, wherein the at least one coalescer stage (18) comprises: ii.1) a more hydrophilic layer (26), wherein the more hydrophilic layer (26) has a contact angle for water of 90.0° or less, and ii.2) a second more hydrophobic layer (28) which contacts the more hydrophilic layer (26) and / or is connected to the more hydrophilic layer (26), wherein the second more hydrophobic layer (28) has a contact angle for water of more than 90.2°.

Description

[0001] Filter insert with improved service life

[0002] Description

[0003] The invention relates to a filter insert for a fluid filter device and a corresponding fluid filter device, as well as a method for filtering a fluid using such a fluid filter device. The invention also discloses the corresponding use of such a fluid filter device for filtering a fluid.

[0004] Fundamentally, there is a continuous need in many industries for high-performance fluid filters with advantageous handling characteristics and high filtration efficiency. Many of the improvements in these properties known from the state of the art are achieved through the selection of suitable materials and / or improved filter designs.

[0005] One area of ​​technology where there is a particularly high demand for high-performance filters is automotive engineering, where corresponding fluid filter systems are used, particularly for filtering fuels such as gasoline or diesel. In addition to separating particulate contaminants, the fluid filter systems used here are often also required to perform other tasks, particularly in the separation of foreign fluids dispersed in the fuel.

[0006] When removing foreign liquids from a fuel, the separation of water is of particular importance, especially in diesel fuel filters. For the separation of water, but potentially also other polar liquids from the fuel, modern diesel fuel filters today generally employ multi-stage systems based on coalescing media. The wettability or surface energy of such coalescing media is designed and matched to the system in such a way that it fulfills its coalescing function for the relevant liquid contaminants, especially water, i.e., it captures small and extremely small droplets dispersed in the liquid and agglomerates or coagulates them into larger droplets.The process occurring in the coalescing stage, in which a large number of smaller liquid contaminants dispersed in the fluid to be filtered are combined to form larger droplets, is referred to synonymously in the present invention as both agglomeration and coagulation, since both terms are used in the prior art to ultimately describe the same process.

[0007] The coalescer media compete with the hydrophobic fuel for the water droplets, which is achieved through a higher degree of hydrophilicity ("better water wettability"). The larger water droplets agglomerated in the coalescer medium are prevented from passing through a separation stage located downstream of and spaced from the coalescer medium. They are retained in the space formed between the coalescer medium and the separation stage, from which they can optionally be removed.

[0008] The use of appropriate combinations of a coalescer stage with a separation stage is established and regularly demonstrates excellent separation performance in new filters for removing liquid contaminants, particularly water, dispersed in the fluid to be filtered. However, for subsequent application in the vehicle, it is essential that the corresponding separation of liquid contaminants not only functions in new condition, but also demonstrates sufficient and, ideally, as consistent a performance as possible over a long period of time, ideally over the entire service life of the respective fluid filter, or during the entire replacement interval of a respective filter insert.

[0009] However, comprehensive studies conducted by the inventors have shown that the long-term separation performance of prior art filter inserts with a coalescing medium and a separation stage deteriorates over time under realistic conditions. In particular, the inventors have found that, given the potentially highly variable fuel compositions internationally, the service life of corresponding separation arrangements in filter inserts can vary considerably. The composition of fuels, especially diesel fuel, can vary noticeably in different regions of the world, particularly with regard to the impurities or secondary components present in the fuel, as well as with regard to the additives deliberately added. Furthermore, different fuel and additive compositions also result in different aging products.The composition of such fuels is regularly subject to certain regulatory requirements internationally, which can lead to differences in composition, for example, between the diesel fuel available in North America and the diesel fuel used in Europe.

[0010] The inventors have recognized that, due to the compositional differences in the fuel, some filter inserts or fluid filter devices which, for example, demonstrate excellent and long-lasting separation performance for dispersed liquid contaminants from the fuel within the European Union can, in other regions of the world, for example in North America or Asia, experience a rapid, undesired deterioration in separation performance. This leads to the separation efficiency required according to the specifications for corresponding liquid contaminants not being guaranteed or no longer being sufficiently guaranteed even before the end of the actually intended replacement interval.Without wishing to be bound by this theory, the inventors, based on their own experiments, assume that regional differences in the impurities contained in the fuel or the additives used are responsible for the very different performance of the corresponding coalescer arrangements. Based on their experiments, they assume that certain additives used in fuels deposit over time on the more hydrophilic surface of the coalescer medium and form more hydrophobic deposits, so that the surface hydrophilicity of the coalescer medium is reduced over time, resulting in a reduction in agglomeration performance.

[0011] According to the inventors, there is still no satisfactory solution available to date that ensures the desired separation performance against liquid contaminants dispersed in the fuel in real operation, especially in all regions of the world, over the entire service life.

[0012] The primary object of the present invention was to eliminate or at least mitigate the disadvantages of the prior art.

[0013] In particular, it was the object of the present invention to provide a filter insert for a fluid filter device and a corresponding fluid filter device which shows an excellent separation of liquid contaminants dispersed in the fluid to be filtered, in particular water, which is particularly suitable for filtering diesel fuel.

[0014] An important objective of the present invention was to maintain the excellent separation efficiency in separating liquid contaminants from the fluid to be filtered for as long as possible, preferably over the entire service life of the filter insert or fluid filter device. Therefore, it was a desirable requirement that the advantageous, long-lasting, high separation efficiency be achievable, particularly under realistic conditions during actual use in vehicles, especially in different regions of the world and when using different fuels that differ in their composition and specifications, particularly with regard to the additives used.

[0015] It was an object of the present invention that the filter insert to be specified and the fluid filter device based thereon should also show an excellent separation performance against solid contaminants.

[0016] It was also a desirable requirement of the present invention that the solution to be provided for the problem described above should ideally be implementable without the use of additional substances that are potentially harmful to health and / or the environment, and it was a further desirable requirement that the advantageous longevity of the separation of liquid contaminants should not require any additional maintenance effort.

[0017] In addition, it was a further object of the present invention that the solution to be specified should allow the production of mechanically highly resilient filter inserts or fluid filter devices, so that the advantageous separation performance against liquid contaminants in the fluid to be filtered is guaranteed in the long term even if the filter insert is subjected to strong mechanical loads during ferry operation.

[0018] The inventors of the present invention have now found that the objects described above can surprisingly be achieved if, in a filter insert starting from a conventional structure with a coalescer stage and a separation stage spaced therefrom, an additional more hydrophobic layer is used in the coalescer stage, as defined in the claims.

[0019] Surprisingly, a corresponding design allows for the creation of high-performance filter inserts in which the separation efficiency for liquid contaminants dispersed in the fluid to be filtered is not only particularly high, but also maintained over a long period of time, advantageously over the entire service life of the corresponding filter inserts. It is considered particularly advantageous that the long-lasting high separation efficiency against corresponding liquid contaminants is also demonstrated under practical conditions, especially in different regions of the world for different fuels.

[0020] Without wishing to be bound by this theory, the inventors assume, based on their own development work, that the additional hydrophobic layer is largely not blocked by deposits from the fuel during operation, as it is largely inert or insensitive to such deposits. The inventors have come to the conclusion that the final layer in particular, i.e. the boundary between the coalescer layer and the fuel phase, is crucial for the desired coalescer function, with the difference in hydrophilicity between the hydrophilic coalescer phase and the adjacent hydrophobic fuel phase being particularly crucial for a beneficial separation effect. In the systems known from the prior art, the degree of this difference decreases due to deposits as the coalescer layer becomes more hydrophobic.

[0021] The multilayer coalescer system used according to the invention, which comprises a deposit-resistant hydrophobic layer in contact with the hydrophilic layer, surprisingly allows a sufficient gradient of hydrophobicity or hydrophilicity to be established at the outlet of the coalescer layer, which can, for example, be made significantly greater than would be possible for the fuel phase. This advantageously ensures the necessary gradient in surface energy at the outlet of the more hydrophilic coalescer layer, even if the hydrophilicity of the coalescer layer is reduced over time due to deposits.In addition, the additional hydrophobic layer at the outlet of the coalescer layer acts advantageously and synergistically as a kind of dam for the liquid contaminants agglomerated in the more hydrophilic coalescer layer, causing many small droplets to converge inside the coalescer layer and only be pushed out as large droplets through the additional hydrophobic layer, for example, when the flow pressure is high enough. Without wishing to be bound by this theory, the inventors assume that harmful deposits hardly form on the additional hydrophobic layer. Based on the inventors' experiments, an additional positive effect is that the downstream hydrophobic (sieve) layer can be cleaned of adhering fuel deposits, particularly by the constantly present water.

[0022] The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0023] Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. Features of preferred fluid filter devices, methods, and uses emerge from the features of preferred filter inserts.

[0024] The invention particularly relates to a filter insert for a fluid filter device, comprising: i) at least one particle filter stage for separating solid contaminants from the fluid to be filtered, comprising at least one filter medium, ii) at least one coalescer stage different from the particle filter stage for agglomerating liquid contaminants dispersed in the fluid to be filtered, and iii) at least one separation stage spaced from the coalescer stage for separating agglomerated liquid contaminants from the fluid to be filtered, comprising at least one first more hydrophobic layer, wherein the first more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°, wherein the at least one coalescer stage comprises:

[0025] 11.1) a more hydrophilic layer, wherein the more hydrophilic layer has a contact angle for water measured by the Washburn method of 90.0° or less, and

[0026] 11.2) a second more hydrophobic layer contacting the more hydrophilic layer and / or connected to the more hydrophilic layer (26), wherein the second more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°.

[0027] The invention particularly relates to a filter insert intended for use in a fluid filter device. Both fluid filter devices and suitable filter inserts are generally known to those skilled in the art, with the filter insert generally making a significant contribution to the filtering capacity of the fluid filter device.Even if it is conceivable to permanently install the filter insert in a fluid filter device, in order to ensure long-term usability of corresponding fluid filter devices and to realize simple maintenance or overhaul of corresponding fluid filter devices for essentially all embodiments, it is preferred if the filter insert is designed as a replaceable filter insert. For this purpose, the filter insert is adapted in particular to the shape of a complementary receptacle in the fluid filter device and can, for example, be provided with a suitable quick-release fastener in order to fix the filter insert in the fluid filter device in a reversible and non-destructively replaceable manner. A filter insert according to the invention is therefore preferred, wherein the filter insert is a replaceable filter insert.

[0028] The above definition of the filter insert also defines the filter insert functionally through the intended effect of the corresponding components on the fluid to be filtered or on the liquid contaminants dispersed in the fluid to be filtered, and thus their corresponding suitability for these purposes. However, those skilled in the art will understand that the fluid to be filtered is not a component of the filter insert according to the invention.

[0029] In accordance with the expert understanding, it follows from the definition that this is a filter insert, as well as the fact that the particle filter stage, the coalescer stage, and the separation stage each act on the fluid to be filtered, that the fluid to be filtered can flow through the corresponding stages. In other words, this is thus a filter insert according to the invention, wherein the filter medium is fluid-permeable, and wherein the first, more hydrophobic layer is partially fluid-permeable, and wherein the second, more hydrophobic layer is partially fluid-permeable, and wherein the more hydrophilic layer is partially fluid-permeable.

[0030] In light of the desired effect of the respective stages, the person skilled in the art will readily understand that the separation stage must be arranged downstream of the coalescing stage in the filter insert with respect to the intended fluid flow direction. Even if it would be theoretically conceivable to also provide a particle filter stage downstream of the separation stage, it is preferred for essentially all embodiments to ensure, by means of a particle filter stage upstream of the coalescing stage, that the coalescing stage is not contaminated by solid particles and that its function is not impaired in the long term. Thus, a filter insert according to the invention is preferred, wherein the filter insert is designed such that a fluid to be filtered can be passed from the outside through the particle filter stage, from the particle filter stage through the coalescing stage, and from the coalescing stage through the separation stage.In other words, a filter insert according to the invention is preferred, wherein the coalescing stage is arranged between the particle filter stage and the separation stage with respect to the flow path of the fluid to be filtered.

[0031] In light of the above disclosure, a person skilled in the art readily understands that the fluid to be filtered in the coalescing stage should first be passed through the more hydrophilic layer, so that the second, more hydrophobic layer in the coalescing stage is arranged downstream of the more hydrophilic layer in the flow direction, so that the liquid agglomerated in the more hydrophilic layer is pushed by the flowing fluid toward the more hydrophobic layer, which exerts a beneficial blocking effect until the agglomerated liquid droplets are large enough that the flow pressure pushes them through the more hydrophobic layer. This is thus a filter insert according to the invention, wherein the filter insert is configured so that the fluid to be filtered can flow through the second, more hydrophobic layer after the more hydrophilic layer and upstream of the first, more hydrophobic layer.In other words, this is a filter insert according to the invention, wherein the second, more hydrophobic layer is arranged on the side of the more hydrophilic layer facing the first, more hydrophobic layer in the fluid direction. For essentially all embodiments, a filter insert according to the invention is preferred, wherein the second, more hydrophobic layer and the more hydrophilic layer are arranged such that the fluid to be filtered cannot pass through the more hydrophilic layer without passing through the second, more hydrophobic layer.

[0032] The first component of the filter insert according to the invention is a particle filter stage which comprises at least one filter medium. This particle filter stage serves to remove solid contaminants from the fluid to be filtered. Within the scope of the present invention, filter stages which are known to the person skilled in the art can in principle be used for the filter stage. Suitable filter media are commercially available from various manufacturers and are already used in numerous filter inserts. Preference is given to a filter insert according to the invention wherein the filter medium is a pleated filter medium, wherein the filter medium preferably comprises a plurality of essentially uniform folds. An example of a filter insert according to the invention is one in which the particle filter stage comprises two or more filter media, or wherein the particle filter stage consists of one filter medium.

[0033] Additionally or alternatively, a filter insert according to the invention is preferred, wherein the filter medium consists at least partially, preferably predominantly, particularly preferably substantially completely, of a thermoplastic selected from the group consisting of polyolefins, polyamides, polyurethanes, polycarbonates, and polyesters, preferably selected from the group consisting of polyolefins and polyesters, particularly preferably selected from the group consisting of polyesters. With regard to the structure of the filter media, a filter insert according to the invention is preferred, wherein the filter medium is selected from the group consisting of textile fabrics, preferably from the group consisting of nonwovens.

[0034] In terms of design, the inventors believe it is conceivable in principle to have the coalescer stage directly connected to the particle filter stage so that the more hydrophilic layer and the filter medium are in contact, in which case the layers of the coalescer stage can preferably be adapted to the shape of the particle filter stage, for example, by appropriate folding. However, the inventors believe it is preferable to arrange the coalescer stage at some distance behind the particle filter stage, which advantageously makes it possible to replace the particle filter stage independently of the coalescer stage. Accordingly, a filter insert according to the invention is preferred, wherein the coalescer stage is spaced from the particle filter stage along the flow path of the fluid to be filtered.

[0035] According to the above definition, the corresponding filter inserts according to the invention are generally suitable for filtering a wide variety of fluids. Since the fluid to be filtered is not inherently a component of the filter insert according to the invention, it is expedient to omit a further definition of the fluid in the above definition.

[0036] According to the above definition, the properties of the hydrophilic and more hydrophobic layers are each defined in accordance with the expert's expectations regarding the contact angle with water, as will be explained further below. In this respect, the expert understands that filter inserts according to the invention are designed to remove polar liquids, such as in particular water, from a less polar liquid, for example a typical fuel, which are present as dispersed liquid contaminants due to the polarity differences in the fuel. In accordance with this statement, the expert understands that filter inserts according to the invention are advantageous for removing polar liquid contaminants from non-polar fluids, even if they would not be able to separate non-polar liquid contaminants from a polar fluid, or would be less efficient at doing so.

[0037] In other words, in practice, for substantially all relevant embodiments, it will be a filter insert according to the invention in which the desired fluid to be filtered is a non-polar liquid, preferably a fuel, particularly preferably a diesel fuel, while the liquid contaminant dispersed in the fluid comprises or consists of a polar liquid, preferably water.

[0038] In the context of the present invention, the wettability of the respective layers, and thus indirectly their surface energy, is expressed by the contact angle with water, as described further below. Those skilled in the art will understand that this characterizes the hydrophilicity or hydrophobicity of the respective layers. According to the inventors' assessment, the qualitative terms "hydrophilic" and "hydrophobic" are associated with different expectations for the contact angle in different industries. A layer that would be considered relatively hydrophilic in the field of filter technology, for example, could already be considered relatively hydrophobic in other industries.To avoid any confusion caused by the use of absolute terms, the present invention uses the relative terms "more hydrophobic" and "more hydrophilic" to clearly identify the layers and emphasize their functionality. These terms refer to the comparison of the corresponding layers. This approach is particularly useful because, in the inventors' opinion, the key is to achieve a desired difference in wettability for the intended application, rather than achieving specific absolute values.However, the person skilled in the art will understand that the terms "hydrophobic" and "hydrophilic", which in the context of the present invention serve in particular to clearly identify the corresponding layers and materials, could alternatively be replaced by the adjectives "hydrophilic" and "hydrophobic", whereby in the context of the present invention a layer or a material is considered to be hydrophilic if its contact angle with water is 90° or less.

[0039] In this respect, the contact angles in the context of the present invention are given with one decimal place, and it is also defined that the contact angle of the more hydrophobic layers is more than 90.2°. This definition serves to clearly separate the range boundaries so that even when applying any rounding conventions, the endpoints do not overlap. In the inventors' opinion, a wider distance in the definition would not do justice to the realities in the field of technology, since both more hydrophobic layers and more hydrophobic layers are available, each of which is quite close to 90°. However, excellent results can be achieved with these materials, particularly in combination with a significantly more hydrophilic or more hydrophobic complementary material.

[0040] In the context of the present invention, the wettability is characterized by measuring the contact angle of the respective layers with water. In accordance with common practice in the field of technology, two different, but established methods are used for the more hydrophilic and the more hydrophobic materials, which are each inherently fluid-permeable. The determination for the more hydrophilic layer is carried out using the so-called Washburn method according to Washburn, EW, Phys. Rev. 17, 374 (1921), which describes the time-dependent penetration of a liquid (here water) into a porous solid and is used in the analysis of the wetting behavior of porous materials such as powders, woven and nonwoven textiles and nonwovens, in particular hydrophilic materials. The Washburn method is known to those skilled in the art, and corresponding devices are commercially available from various suppliers, for example fromKrüss GmbH. The contact angle for the more hydrophobic layers is determined using the so-called drop contour method according to DIN EN ISO 19403:2020, which is also familiar to those skilled in the art. Those skilled in the art understand that the effective contact angle, which is evident for the layers as a whole, is crucial for the reliable definition of the respective layers, which ensures that they can fulfill their intended purpose. In accordance with expert understanding, both the (surface) structure of the layer, for example, its nonwoven design, and the inherent material properties of the processed materials contribute to the overall resulting contact angle.

[0041] In order to achieve the best possible effect, the inventors believe it is particularly advantageous to form the corresponding hydrophilic or hydrophobic layers as largely as possible from a material that is itself hydrophilic or hydrophobic, or to coat them with a material that is itself hydrophilic or hydrophobic to change the surface texture. In this respect, the inventors propose covering the corresponding layers as extensively as possible with the corresponding material, so that, for example, a more hydrophobic layer is equipped as comprehensively as possible with per- and polyfluorinated compounds (PFAS), for example a polyhaloolefin such as polytetrafluoroethylene. In principle, however, other hydrophobic materials are also suitable as alternatives to PFAS and, particularly in light of the increasingly strict regulations on the use of PFAS in many countries, are particularly promising for many future applications.With regard to the choice of materials, in order to achieve the most pronounced effect possible, the inventors believe it is particularly advantageous to use materials that are as hydrophilic as possible for more hydrophilic layers and materials that are as hydrophobic as possible for more hydrophobic layers.

[0042] Against this background, a filter insert according to the invention is preferred for the more hydrophilic layer, wherein the surface of the more hydrophilic layer is formed at least partially by a more hydrophilic material, wherein the more hydrophilic material has a contact angle for water of 90° or less. A filter insert according to the invention is particularly preferred, wherein the surface of the more hydrophilic layer is formed by the more hydrophilic material to the extent of 50% or more, preferably 70% or more, particularly preferably 90% or more, very particularly preferably 95% or more, especially preferably 99% or more, and most preferably essentially completely. Additionally or alternatively, a filter insert according to the invention is also particularly preferred, wherein the more hydrophilic layer consists of the more hydrophilic material or is coated with the more hydrophilic material, preferably is coated with the more hydrophilic material.Additionally or alternatively, a filter insert according to the invention is particularly preferred, wherein the more hydrophilic material has a contact angle for water, measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020, of 89.0° or less, preferably 86.0° or less, particularly preferably 83.0° or less, most preferably 80.0° or less. A filter insert according to the invention is particularly preferred, wherein the more hydrophilic material is selected from the group consisting of synthetic fibers, regenerated fibers, and natural fibers, preferably from the group consisting of viscose fibers, polyester fibers, polyamide fibers, cellulose fibers, and wool fibers.

[0043] With regard to the first more hydrophobic layer, a filter insert according to the invention is preferred, wherein the surface of the first more hydrophobic layer is formed at least partially by a first more hydrophobic material, wherein the first more hydrophobic material has a contact angle for water of more than 90.2°. A filter insert according to the invention is particularly preferred, wherein the surface of the first more hydrophobic layer is formed by the first hydrophobic material to the extent of 50% or more, preferably to the extent of 70% or more, particularly preferably to the extent of 90% or more, very particularly preferably to the extent of 95% or more, especially preferably to the extent of 99% or more, most preferably essentially completely.Additionally or alternatively, a filter insert according to the invention is also particularly preferred, wherein the first more hydrophobic layer consists of the first more hydrophobic material or is coated with the first more hydrophobic material, preferably coated with the first more hydrophobic material, in particular by superficially treating a base material with a hydrophobizing agent, for example perfluorinated carboxylic acid. Additionally or alternatively, a filter insert according to the invention is also particularly preferred, wherein the first hydrophobic material has a contact angle for water, measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020, of more than 95.0°, preferably more than 100.0°, particularly preferably more than 105.0°, particularly preferably more than 110.0°.Particularly preferred is additionally or alternatively a filter insert according to the invention, wherein the first more hydrophobic material is selected from the group consisting of polyhaloolefins, preferably polytetrafluoroethylene. With regard to the second more hydrophobic layer, preferred is a filter insert according to the invention, wherein the surface of the second more hydrophobic layer is at least partially formed by a second more hydrophobic material, wherein the second more hydrophobic material has a contact angle for water of more than 90.2°. Particularly preferred is additionally or alternatively a filter insert according to the invention, wherein the surface of the second more hydrophobic layer is formed by the first more hydrophobic material to the extent of 50% or more, preferably to the extent of 70% or more, particularly preferably to the extent of 90% or more, very particularly preferably to the extent of 95% or more, especially preferably to the extent of 99% or more, most preferably essentially completely.Additionally or alternatively, a filter insert according to the invention is particularly preferred, wherein the second more hydrophobic layer consists of the second more hydrophobic material or is coated with the second more hydrophobic material, preferably coated with the second more hydrophobic material, in particular by superficially treating a base material with a hydrophobizing agent, for example perfluorinated carboxylic acid. Additionally or alternatively, a filter insert according to the invention is particularly preferred, wherein the second more hydrophobic material has a contact angle for water, measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020, of more than 95.0°, preferably more than 100.0°, particularly preferably more than 105.0°, particularly preferably more than 110.0°.Additionally or alternatively, a filter insert according to the invention is also particularly preferred, wherein the second more hydrophobic material is selected from the group consisting of polyhaloolefins, preferably polytetrafluoroethylene.

[0044] The inventors of the present invention have recognized that, with regard to the wettability of the entire layers, i.e., the wettability which results in particular from the interaction between the structure of the respective layer and the material used, surprisingly very noticeable differences arise at the transition from 90.0° or less to more than 90.2°, so that the contact angle transition from 90.0° to 90.2°, which is somewhat broader for reasons of clarity, can be regarded as a relatively sharp dividing line. In particular, it has been found that even with coalescer media in which the overall contact angle of the layer is relatively close to 90.0°, excellent agglomeration effects are achieved in filter inserts according to the invention, in particular also thanks to the retaining effect exerted by the second, more hydrophobic layer.At the same time, it is found that the first, more hydrophobic layer provided in the separation stage is capable of separating the agglomerated liquid contaminants even when the contact angle of the corresponding, more hydrophobic layer is comparatively just above 90.2°. However, the inventors of the present invention have recognized that for the advantageous effect of the invention, in particular to ensure long-term high separation efficiency, the second, more hydrophobic layer adjacent to the more hydrophilic layer should preferably be noticeably more hydrophobic in order to achieve the desired effect sufficiently strongly, so that the minimum hydrophobicity to be implemented and thus the corresponding contact angle, in preferred cases, is significantly above the minimum contact angle that is still functional for the hydrophobic layer.

[0045] Analogous to the above statements regarding the preferred selection of materials that are as hydrophilic or hydrophobic as possible, the inventors consider it highly preferable, despite the advantageous effect that can be achieved even with relatively small differences in wettability, to make the respective layers as hydrophilic or hydrophobic as possible, which can be advantageously achieved by selecting the materials present on the surface and the structure of the layers. Firstly, a filter insert according to the invention is preferred, wherein the more hydrophilic layer has a contact angle for water, measured by the Washburn method, of 89.0° or less, preferably 87.0° or less, particularly preferably 85.0° or less.Additionally or alternatively, a filter insert according to the invention is preferred, wherein the first more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 92.0°, preferably more than 95.0°, particularly preferably more than 100.0°, very particularly preferably more than 105.0°, especially preferably more than 110.0°. Additionally or alternatively, a filter insert according to the invention is also preferred, wherein the second more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 92.0°, preferably more than 95.0°, particularly preferably more than 100.0°, very particularly preferably more than 105.0°, especially preferably more than 110.0°.

[0046] With regard to the difference in surface energy, a filter insert according to the invention is preferred, wherein the contact angle measured for water between the more hydrophilic material and the second more hydrophobic material differs by 5° or more, preferably by 10° or more, particularly preferably by 15° or more, very particularly preferably by 20° or more, particularly preferably by 25° or more, and / or wherein the contact angle measured for water between the more hydrophilic layer and the second more hydrophobic layer differs by 5° or more, preferably by 10° or more, particularly preferably by 15° or more, very particularly preferably by 20° or more, particularly preferably by 25° or more.

[0047] The overall wettability of the corresponding layers can advantageously be adjusted not only by the choice of material but also by their structure. In this respect, the inventors have found that the more hydrophilic layer can particularly preferably be designed as random textile fabrics, in particular nonwovens, in order to promote the desired effect. In contrast, the inventors believe that the more hydrophobic layers can advantageously be realized in particular with sieve- or grid-like structures, for example using woven fabrics, plastic grids or perforated films. A particular feature of these designs is that they have a comparatively smooth surface between the openings open for the passage of fluid, in which the contact angle is not reduced as much by macroscopic and / or microscopic surface structures compared to, for example, nonwovens.With regard to the design of the more hydrophilic layer, a filter insert according to the invention is preferred, wherein the more hydrophilic layer is a porous layer. A filter insert according to the invention is preferred, wherein the more hydrophilic layer is a textile sheet material, preferably a nonwoven or felt, preferably a nonwoven, particularly preferably a meltblown nonwoven, or wherein the more hydrophilic layer is an open-pore foam, an open-pore sponge or an open-pore sintered material. With regard to the design of the first more hydrophobic layer, a filter insert according to the invention is preferred, wherein the first more hydrophobic layer is designed as a sieve-shaped or grid-shaped layer, preferably with an average opening diameter in the range from 10 to 200 pm, preferably in the range from 12 to 150 pm, particularly preferably in the range from 15 to 110 pm.Additionally or alternatively, a filter insert according to the invention is preferred, wherein the first more hydrophobic layer is designed as a fabric, in particular a fabric sieve, as a grid structure, in particular an extruded plastic grid, or as a perforated film, in particular a lasered film.

[0048] With regard to the design of the second more hydrophobic layer, a filter insert according to the invention is preferred, wherein the second more hydrophobic layer is designed as a sieve-shaped or grid-shaped layer, preferably with an average opening diameter in the range from 10 to 200 pm, preferably in the range from 12 to 150 pm, particularly preferably in the range from 15 to 110 pm. Additionally or alternatively, a filter insert according to the invention is preferred, wherein the second more hydrophobic layer is designed as a fabric, in particular a fabric sieve, as a grid structure, in particular an extruded plastic grid, or as a perforated film, in particular a lasered film.

[0049] The first part of the coalescing stage is the more hydrophilic layer. In the course of the development work, the inventors of the present invention have identified, through extensive experiments, particularly advantageous configurations for the structure and the resulting flow properties of the more hydrophilic layer. In this respect, a filter insert according to the invention is preferred, wherein the more hydrophilic layer has an average fiber diameter of 2 μm or more, preferably of 8 μm or more, particularly preferably of 12 μm or more. Additionally or alternatively, a filter insert according to the invention is preferred, wherein the more hydrophilic layer has a basis weight in the range of 20 to 350 g / m 2 , preferably in the range of 25 to 300 g / m 2 , particularly preferably in the range of 30 to 250 g / m 2, is also preferred. Additionally or alternatively, a filter insert according to the invention is preferred, wherein the more hydrophilic layer has an MFP value (mean flow pore size) according to ASTM F 316 from 2019 in the range from 5 to 150 pm, preferably in the range from 7 to 130 pm, particularly preferably in the range from 9 to 110 pm, and / or wherein the more hydrophilic layer has an MFP value (mean flow pore size) according to ASTM F 316 from 2019 of 5 pm or more, preferably of 20 pm or more, particularly preferably of 90 pm or more. In turn, additionally or alternatively, a filter insert according to the invention is preferred, wherein the more hydrophilic layer has an average pore size, determined by optical evaluation, in the range from 200 to 9000 pm 2 , preferably in the range of 250 to 8500 pm 2 , particularly preferably in the range of 300 to 8000 pm 2 , and / or wherein the more hydrophilic layer has an average pore size, determined by optical evaluation, in the range of 200 pm 2or more, preferably 1100 pm 2 or more, most preferably 7000 pm 2 or more. Additionally or alternatively, a filter insert according to the invention is also preferred, wherein the more hydrophilic layer has an air passage in the range of 50 to 4300 L / (s*m 2 ), preferably in the range of 65 to 4000 L / (s*m 2 ), particularly preferably in the range of 80 to 3700 L / (s*m 2 ), and / or wherein the more hydrophilic layer has an air permeability in the range of 65 L / (s*m 2 ) or more, preferably 1000 L / (s*m 2 ) or more, particularly preferably 1700 L / (s*m 2 ) or more.

[0050] In addition to the more hydrophilic layer, the coalescing stage according to the invention also comprises the second, more hydrophobic layer. According to the above definition, this layer is arranged such that it contacts the more hydrophilic layer and / or is connected to the more hydrophilic layer, with the more hydrophilic layer particularly preferably being in contact with it or being connected via a material bond. The inventors assume that direct contact or indirect contact, for example, mediated by an adhesive, is what particularly efficiently enables the advantageous desired retention effect and the desired gradient in wettability. According to the inventors, it is theoretically possible to arrange two separate layers directly one after the other and thus in direct contact with one another using suitable support structures.With a view to ensuring reliable contact even under mechanical stress and thus under real operating conditions, which determines the advantageous separation effect, the inventors consider it preferable to connect the corresponding layers to one another. In addition to mechanical connections, for example, by clamping them in a common frame, adhesive bonding or a similar cohesive connection is particularly preferred. Accordingly, a filter insert according to the invention is preferred, wherein the more hydrophilic layer and the second, more hydrophobic layer are connected to one another at least in sections, preferably cohesively.

[0051] Against this background, it is correspondingly also preferred if the two layers contact each other or are connected to each other to the greatest extent possible. A filter insert according to the invention is preferred, wherein the more hydrophilic layer and the second more hydrophobic layer contact each other over 50% or more, preferably over 70% or more, particularly preferably over 90% or more, very particularly preferably over substantially 100%, of the side surface of the more hydrophilic layer, and / or wherein the more hydrophilic layer and the second more hydrophobic layer are connected over 50% or more, preferably over 70% or more, particularly preferably over 90% or more, very particularly preferably over substantially 100%, of the side surface of the more hydrophilic layer.

[0052] According to the inventors, particularly high-performance coalescer stages are achieved when the more hydrophilic layer and the second, more hydrophobic layer are achieved by different finishing of a material. This takes advantage of the fact that the wetting properties depend significantly on the material present on the surface, making it possible, for example, to coat an inherently hydrophilic textile fabric on one side with a strongly hydrophobic material, such as PTFE, or to finish the surface with other per- and polyfluorinated alkyl compounds, such as perfluorocarboxylic acids. In turn, corresponding finishing with other, PFAS-free hydrophobic materials is also possible. Conversely, although less preferred, hydrophobic base materials can also be provided with a more hydrophilic coating with a more hydrophilic layer.Accordingly, a filter insert according to the invention is preferred, wherein the second more hydrophobic layer is formed by coating a partial layer of the more hydrophilic layer with the second more hydrophobic material, or wherein the more hydrophilic layer is formed by coating a partial layer of the second more hydrophobic layer with the more hydrophilic material, or wherein the second more hydrophobic layer is formed by coating a partial layer of a starting layer with the second more hydrophobic material and wherein the more hydrophilic layer is formed by coating the starting layer with the more hydrophilic material.

[0053] In filter inserts according to the invention, the coalescing stage is followed in the direction of flow by the separation stage, which serves the purpose of retaining the liquid agglomerated in the coalescing stage. With regard to the arrangement, the separation stage can be analogous to the systems known from the prior art, wherein a spacing of the separation stage from the coalescing stage is particularly expedient in order to form an intermediate space for receiving the retained liquid contaminants. A filter insert according to the invention is therefore preferred, wherein the separation stage is spaced from the coalescing stage along the flow path of the fluid to be filtered. A filter insert according to the invention is particularly preferred, wherein the separation stage is spaced from the coalescing stage by 2 mm or more, preferably by 4 mm or more, particularly preferably by 6 mm or more.In other words, a filter insert according to the invention is particularly preferred, wherein an intermediate space is formed in the filter insert between the separation stage and the coalescing stage, wherein the intermediate space is preferably provided for receiving agglomerated liquid contaminants.

[0054] At least theoretically conceivable is a filter insert according to the invention, wherein the separation stage comprises two or more first more hydrophobic layers. With a view to the most efficient production of filter inserts according to the invention, in particular to reduce the required components and thus to simplify procurement and logistics, it is preferable, in the opinion of the inventors, to make the two more hydrophobic layers at least from the same material or to coat them with the same material, with it being very particularly preferable to make the two more hydrophobic layers as a whole essentially similar. Accordingly, a filter insert according to the invention is preferred, wherein the first more hydrophobic material and the second more hydrophobic material are preferably identical.Particularly preferred is a filter insert according to the invention, wherein the first more hydrophobic layer and the second more hydrophobic layer are formed identically, preferably completely, apart from the shape and dimensions of the layer.

[0055] To achieve a simple structure and advantageously easy manufacture, a filter insert according to the invention is preferred, wherein the coalescing stage consists of the more hydrophilic layer and the second more hydrophobic layer, and / or wherein the separation stage consists of the first more hydrophobic layer.

[0056] The more hydrophobic layers can be designed in particular such that no relevant deposits are detectable on them when used in the corresponding fuel over a period of 3 months or more, or, for example, a running time of 50 hours up to 1 year, or preferably 1000 hours or more, particularly preferably 2000 hours or more. Desirably, the more hydrophobic layers are characterized in that the contact angle changes due to hydrophobic deposits over the specified periods by a maximum of 5% or less, preferably 2% or less, particularly preferably 1% or less, relative to the respective contact angle in the new state.

[0057] Particularly preferred filter inserts are disclosed below, which the inventors consider to be particularly advantageous.

[0058] In light of the above statements, particularly preferred, in particular also in combination with further preferred features, is a first preferred filter insert according to the invention for a diesel fuel filter, comprising: i) at least one particle filter stage for separating solid contaminants from the diesel fuel to be filtered, comprising at least one filter medium, ii) at least one coalescer stage different from the particle filter stage for agglomerating liquid water dispersed in the diesel fuel, and iii) at least one separation stage spaced from the coalescer stage for separating agglomerated liquid contaminants from the fluid to be filtered, comprising at least one first more hydrophobic layer, wherein the first more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°,wherein the surface of the first more hydrophobic layer is at least partially formed by a first more hydrophobic material, wherein the first more hydrophobic material has a contact angle for water measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90°, wherein the first more hydrophobic material is preferably selected from the group consisting of polyhaloolefins, wherein the at least one coalescer stage comprises:

[0059] 11.1) a more hydrophilic layer, wherein the more hydrophilic layer has a contact angle for water measured by the Washburn method of 90.0° or less, wherein the surface of the more hydrophilic layer is at least partially formed by a more hydrophilic material, wherein the more hydrophilic material has a contact angle for water measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020 of 90.0° or less, wherein the more hydrophilic material is selected from the group consisting of polyester fibers, polyamide fibers and natural fibers, and

[0060] 11.2) a second more hydrophobic layer contacting the more hydrophilic layer, wherein the second more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°, wherein the surface of the second more hydrophobic layer is at least partially formed by a second more hydrophobic material, wherein the second more hydrophobic material has a contact angle for water of more than 90°, wherein the second more hydrophobic material is preferably selected from the group consisting of polyhaloolefins.

[0061] In light of the above statements, a second preferred filter insert according to the invention for a diesel fuel filter is also particularly preferred, in particular in combination with further preferred features, comprising: i) at least one particle filter stage for separating solid contaminants from the diesel fuel to be filtered, comprising at least one filter medium, ii) at least one coalescer stage different from the particle filter stage for agglomerating liquid water dispersed in the diesel fuel, and iii) at least one separation stage spaced apart from the coalescer stage for separating agglomerated liquid contaminants from the fluid to be filtered, comprising at least one first more hydrophobic layer, wherein the first more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°,wherein the first more hydrophobic layer is formed as a sieve-shaped or grid-shaped layer, wherein the at least one coalescing stage comprises: ii.1) a more hydrophilic layer, wherein the more hydrophilic layer has a contact angle for water measured by the Washburn method of 90.0° or less, wherein the more hydrophilic layer is selected from the group consisting of nonwovens, open-pore foams, open-pore sponges, and open-pore sintered materials, and ii.2) a second more hydrophobic layer contacting the more hydrophilic layer, wherein the second more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°, wherein the second more hydrophobic layer is formed as a sieve-shaped or grid-shaped layer.

[0062] In light of the above statements, a third preferred filter insert according to the invention for a diesel fuel filter is particularly preferred, in particular also in combination with further preferred features, comprising: i) at least one particle filter stage for separating solid contaminants from the diesel fuel to be filtered, comprising at least one filter medium, ii) at least one coalescer stage different from the particle filter stage for agglomerating liquid water dispersed in the diesel fuel, and iii) at least one separation stage spaced from the coalescer stage for separating agglomerated liquid contaminants from the fluid to be filtered, comprising at least one first more hydrophobic layer, wherein the first more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°,wherein the first more hydrophobic layer is formed as a sieve-shaped or grid-shaped layer, wherein the surface of the first more hydrophobic layer is at least partially formed by a first more hydrophobic material, wherein the first more hydrophobic material has a contact angle for water measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°, wherein the first more hydrophobic material is preferably selected from the group consisting of polyhaloolefins, wherein the at least one coalescer stage comprises: ii.1) a more hydrophilic layer, wherein the more hydrophilic layer has a contact angle for water measured by the Washburn method of 90.0° or less, wherein the more hydrophilic layer is selected from the group consisting of nonwovens, open-pore foams, open-pore sponges, and open-pore sintered materials, wherein the surface of the more hydrophilic layer is at least partially formed by a more hydrophilic material,wherein the more hydrophilic material has a contact angle for water measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020 of 90.0° or less, wherein the more hydrophilic material is selected from the group consisting of polyester fibers, polyamide fibers, and natural fibers, and ii.2) a second, more hydrophobic layer contacting the more hydrophilic layer, wherein the second, more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°, wherein the second, more hydrophobic layer is formed as a sieve-shaped or grid-shaped layer, wherein the surface of the second, more hydrophobic layer is at least partially formed by a second, more hydrophobic material, wherein the second, more hydrophobic material has a contact angle for water measured on the solid material according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°,wherein the second more hydrophobic material is preferably selected from the group consisting of polyhaloolefins.,

[0063] The invention also relates to a fluid filter device for filtering a fluid, comprising: i) a filter housing, and ii) a filter insert according to the invention arranged in the filter housing.

[0064] A fluid filter device according to the invention is preferred, wherein the fluid filter device is a fuel filter, preferably a diesel fuel filter

[0065] Additionally or alternatively, a fluid filter device according to the invention is preferred, wherein the filter insert is arranged in the filter housing so that it can be replaced reversibly and without destruction.

[0066] The invention further relates to a method for filtering a fluid with a fluid filter device according to the invention, comprising the method steps: a) separating solid contaminants from the fluid to be filtered with the particle filter stage of the filter insert, b) agglomerating liquid contaminants dispersed in the fluid to be filtered with the coalescing stage to obtain agglomerated liquid contaminants in the fluid to be filtered, and c) separating the agglomerated liquid contaminants from the fluid to be filtered with the separation stage to obtain a filtered fluid.

[0067] A method according to the invention is preferred in which the fluid to be filtered is a fuel, preferably diesel. Additionally or alternatively, a method according to the invention is preferred in which the liquid contaminants comprise water or consist of water, preferably consisting of water.

[0068] Additionally or alternatively, a method according to the invention is also preferred, wherein the fluid to be filtered flows through the coalescer stage after the particle filter stage and the separation stage after the coalescer stage. Additionally or alternatively, a method according to the invention is also preferred, wherein the fluid to be filtered flows through the second, more hydrophobic layer after the more hydrophilic layer and before the first, more hydrophobic layer.

[0069] Also disclosed is the use of a fluid filter device according to the invention for filtering a fluid, in particular diesel fuel, while separating liquid contaminants dispersed in the fluid to be filtered.

[0070] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figures. The figures show:

[0071] Fig. 1 is a schematic cross-sectional view of a filter insert not according to the invention; and

[0072] Fig. 2 is a schematic cross-sectional view of a filter insert according to the invention in a preferred embodiment.

[0073] Fig. 1 and Fig. 2 each show a cross section through a filter insert 10 in a schematic, simplified representation. The embodiment shown in Fig. 1 represents a filter insert 10 not according to the invention, as is basically known from the prior art.

[0074] A fluid 16 to be filtered penetrates into the filter insert 10, which fluid includes not only solid contaminants 14 but also liquid contaminants 20 dispersed in the fluid 16. In the example shown, each filter insert 10 is for a diesel fuel filter, and thus the fluid 16 to be filtered is diesel fuel, with the liquid contaminants 20 consisting essentially entirely of water.

[0075] In the upstream particle filter stage 12, the solid contaminants 14 are separated using a typical filter medium, whereas the liquid contaminants 20 pass largely unhindered through the particle filter stage 12. In the downstream coalescer stage 18, the liquid contaminants 20 are agglomerated into larger water droplets before they exit the coalescer stage 18.

[0076] The coalescer stage 18 is followed by a separation stage 22 which comprises a first more hydrophobic layer 24 and serves to retain the agglomerated liquid contaminants 20 in the space formed between the coalescer stage 18 and the separation stage 22.

[0077] Fig. 1 indicates that the coalescing effect of the coalescing stage 18 is already impaired as a result of prolonged use, which is visualized in the example of Fig. 1 by the fact that even several small liquid droplets that have not been sufficiently agglomerated can enter the space between the coalescing stage 18 and the separation stage 22. Due to the insufficient agglomeration, these liquid contaminants 20 dispersed in the fluid 16 can partially pass through the separation stage 22, so that the desired separation effect in the filter insert 10 of Fig. 1 is not guaranteed due to aging during use.

[0078] In contrast, Fig. 2 visualizes the structure of a filter insert 10 according to the invention. Starting from a structure as described above in Fig. 1, the coalescer stage 18 is now designed according to the invention and comprises, in addition to a more hydrophilic layer 26, which in the example shown is designed as a PET fleece and has a contact angle of less than 90.0°, materially connected to a second, more hydrophobic layer 28, which in the example shown has a contact angle of more than 105.0° for water. The second, more hydrophobic layer 28 is designed in the example shown in Fig. 2 as a woven mesh sieve, the surface of which has been essentially completely hydrophobized with polytetrafluoroethylene and which, in terms of its design, corresponds in the example in Fig. 2 to the layer which is also used further downstream in the flow direction as the first hydrophobic layer 24 of the separation stage 22.

[0079] Fig. 2 visualizes that, due to the damming effect exerted by the second hydrophobic layers 28 and the continued high gradient in wettability at the interface between the more hydrophilic layer 26 and the second more hydrophobic layer 28, a very extensive agglomeration of the liquid contaminant 20 occurs despite prolonged use. Accordingly, only very few small liquid droplets enter the space between the first hydrophobic layer 24 and the second more hydrophobic layer 28, so that they can be reliably separated by the separation stage 22 despite the aging of the filter insert 10.

[0080] Reference symbol

[0081] 10 filter inserts

[0082] 12 particle filter stage

[0083] 14 solid impurities 16 fluid

[0084] 18 Coalescing stage

[0085] 20 liquid contaminants

[0086] 22 separation stage

[0087] 24 first more hydrophobic layer 26 more hydrophilic layer

[0088] 28 second more hydrophobic layer

Claims

Claims 1. A filter insert (10) for a fluid filter device, comprising: i) at least one particle filter stage (12) for separating solid contaminants (14) from the fluid (16) to be filtered, comprising at least one filter medium, ii) at least one coalescer stage (18) different from the particle filter stage (12) for agglomerating liquid contaminants (20) dispersed in the fluid (16) to be filtered, and iii) at least one separation stage (22) spaced apart from the coalescer stage (18) for separating agglomerated liquid contaminants (20) from the fluid (16) to be filtered, comprising at least one first more hydrophobic layer (24), wherein the first more hydrophobic layer (24) has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°, wherein the at least one coalescer stage (18) comprises: 11.1) a more hydrophilic layer (26), wherein the more hydrophilic layer (26) has a contact angle for water measured by the Washburn method of 90.0° or less, and 11.2) a second more hydrophobic layer (28) contacting the more hydrophilic layer (26) and / or bonded to the more hydrophilic layer (26), wherein the second more hydrophobic layer (28) has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 90.2°.

2. Filter insert (10) according to claim 1, wherein the liquid contaminants (20) comprise water or consist of water.

3. Filter insert (10) according to one of claims 1 or 2, wherein the separation stage (22) is spaced from the coalescing stage (18) by 2 mm or more.

4. Filter insert (10) according to one of claims 1 to 3, wherein the first more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 92.0°.

5. Filter insert (10) according to one of claims 1 to 4, wherein the more hydrophilic layer has a contact angle for water measured by the Washburn method of 89.0° or less.

6. Filter insert (10) according to one of claims 1 to 5, wherein the second more hydrophobic layer has a contact angle for water measured according to the drop contour method according to DIN EN ISO 19403:2020 of more than 92.0°.

7. Filter insert (10) according to one of claims 1 to 6, wherein the surface of the first more hydrophobic layer (24) is at least partially formed by a first more hydrophobic material, wherein the first more hydrophobic material has a contact angle for water of more than 90.2°, and / or wherein the surface of the more hydrophilic layer (26) is at least partially formed by a more hydrophilic material, wherein the more hydrophilic material has a contact angle for water of 90.0° or less, and / or wherein the surface of the second more hydrophobic layer (28) is at least partially formed by a second more hydrophobic material, wherein the second more hydrophobic material has a contact angle for water of more than 90.0°.

8. Filter insert (10) according to one of claims 1 to 7, wherein the contact angle measured for water between the more hydrophilic layer and the second more hydrophobic layer differs by 5° or more.

9. Filter insert (10) according to one of claims 1 to 8, wherein the first more hydrophobic layer (24) is designed as a sieve-shaped or grid-shaped layer, and / or wherein the second more hydrophobic layer (28) is designed as a sieve-shaped or grid-shaped layer.

10. Filter insert (10) according to one of claims 1 to 9, wherein the more hydrophilic layer (26) is a textile fabric.

11. Filter insert (10) according to one of claims 1 to 10, wherein the more hydrophilic layer (26) and the second more hydrophobic layer (28) are at least partially connected to one another.

12. Filter insert (10) according to one of claims 7 to 11, wherein the second more hydrophobic layer (28) is formed by coating a partial layer of the more hydrophilic layer (26) with the second more hydrophobic material.

13. A fluid filter device for filtering a fluid (16), comprising: i) a filter housing, and ii) a filter insert (10) arranged in the filter housing according to one of claims 1 to 12.

14. A method for filtering a fluid (16) with a fluid filter device according to claim 13, comprising the method steps: a) separating solid contaminants (14) from the fluid (16) to be filtered with the particle filter stage (12) of the filter insert (10), b) agglomerating liquid contaminants dispersed in the fluid (16) to be filtered with the coalescing stage (18) to obtain agglomerated liquid contaminants (20) in the fluid (16) to be filtered, and c) separating the agglomerated liquid contaminants (20) from the fluid (16) to be filtered with the separation stage (22) to obtain a filtered fluid (16).

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