DE202021004043U1 - Filter fleece for liquid separation from a gas flow - Google Patents

Abstract

Filter fleece, in particular for use in a filter element for separating liquid from a gas flow, comprising at least two different types of fibers, with at least a first type of fiber (1) consisting of coarse fibers and a second type of fiber (2) consisting of fine fibers, with fibers of the first or second Fiber type (1, 2) are oleophilic and fibers of the opposite first or second fiber type (1, 2) are oleophobic.

Description

The invention relates to a filter fleece according to claim 1 and a filter element according to claim 11.

The cleaning of gas flows, in particular the separation of the finest liquid droplets, for example in the form of mist, from gases or gas mixtures is necessary in various production processes. Here, in particular, oil, pollutant particles and aerosols are to be removed from a gas flow. Known filters and the filter fleeces they contain are usually expensive to produce and have only a very short service life.

For example EP 2 058 041 A1 discloses a multi-layer filter element having a fiberglass mat layer and a nanofiber mat layer for separating contaminants from a gas stream. The use of filter fleece layers with uniform fibers is usually associated with a high pressure loss and a short service life.

The object of the invention is therefore to provide a nonwoven filter fabric which reduces a pressure loss compared to the prior art and has a longer service life.

Main features of the invention are set out in claim 1 and claim 11. Configurations are the subject of the subclaims.

The invention relates to a filter fleece, in particular for use in a filter element for separating liquid from a gas flow, comprising at least two different fiber types, with at least a first fiber type consisting of coarse fibers and a second fiber type consisting of fine fibers, with fibers of the first or second fiber type being oleophilic and fibers of the opposite first or second fiber species are oleophobic.

Such a non-woven filter fabric enables, in particular, the separation of oil from a gas flow. The combination of two different fiber diameters, namely in the form of fine and coarse fibers, and two different fiber properties, namely an oleophilic or oleophobic surface finish of the at least two fiber types within a nonwoven filter layer, makes it easier to separate contaminants, in particular oil, from a gas flow. In particular, this reduces the pressure loss, which saves energy, increases the service life and improves the separation efficiency.

The wetting distribution of a liquid, in particular oil, in the filter fleece can be influenced by the different surface properties and fiber dimensions of the first and second fiber types and the liquid can be guided in a targeted manner. As a result, there are no islands of liquid in the filter fleece and the filter fleece has less saturation, which in turn reduces the pressure loss compared to the prior art. Due to the lower pressure difference, the service life of the filter fleece is increased.

If fibers are assigned an oleophilic or oleophobic property here, this characterizes in particular the surface quality and thus their property in relation to the surrounding media, for example a gas flow and the impurities contained therein. Also included are surfaces that are more oleophilic or oleophobic in character, without excluding smaller surface portions with other properties.

The filter fleece comprises at least two different fiber types. A type of fiber includes coarse fibers, the specification being roughly based on the average diameter of the fibers, which is at least larger than the average diameter of those fibers of the fine fiber type. One of the fiber types has a mainly oleophilic surface. The corresponding opposite type of fiber has a mainly oleophobic surface.

The coarse fibers are used in particular for strength and for draining the oil, while the fine fibers of the second type of fiber have a particularly positive effect on oil separation.

In a preferred embodiment, the second type of fiber has fine fibers with an average diameter of less than or equal to 2.5 μm, preferably 0.1 to 2 μm, particularly preferably 0.6 to 0.7 μm.

The first type of fiber preferably has coarse fibers with an average diameter greater than or equal to 3 μm, preferably from 3 to 8 μm, particularly preferably from 3.5 to 5 μm. These dimensions are particularly advantageous.

In a preferred embodiment, the mean fiber length of the first and/or second fiber type is a few millimeters, preferably <1 to 100 mm.

Preferably, the coarse fibers of the first type of fibers can be oleophilic. This oleophilic property affects the surface finish of the fibers. The fiber itself can be oleophilic or be oleophobic and have an oleophilic surface, which is achieved, for example, by a coating.

Preferably, the fine fibers of the second type of fiber may be oleophobic. This oleophobic property particularly affects the surface finish of the fibers.

In a preferred embodiment, the oleophilic fibers of the first and/or second fiber type are microglass fibers. Glass fibers and micro glass fibers are oleophilic in a gas atmosphere, or at least their surface.

Preferably, the oleophilic fibers of the first and/or second fiber type are made of borosilicate glass.

The coarse fibers of the first fiber type are preferably oleophilic or have an oleophilic surface finish.

In a preferred embodiment, the oleophobic fibers of the first or second fiber type have an oleophobic coating. This allows fibers to be used that combine the properties of different materials or fiber types. For example, glass fibers can be coated with oleophobic materials, combining fiber properties of glass fibers, such as fineness, strength, length, and diameter, with an oleophobic surface finish. In this way, in particular, oleophobic fibers with a smaller fiber diameter can be obtained. Commercially available oleophobic polymer fibers mostly have an average diameter of 5 μm and larger. In contrast, glass fibers are commercially available with an average diameter of up to 400 nm. The preferred use of glass fibers with a diameter of less than or equal to 2.5 μm and coating with an oleophobic material, so that oleophobic fibers are obtained, can result in significantly improved separation efficiency be obtained.

For this purpose, micro glass fibers are preferably coated with oleophobic materials, for example polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), C6-based fluorocarbons. A corresponding coating can in particular be applied wet-chemically or by PVD and CVD methods.

In a preferred embodiment, the oleophobic coating is only superficially applied to fibers. This means the coating does not penetrate the base fiber material.

Preferably, the oleophobic coating covers 70 to 100% of the fibers. This ensures a sufficiently oleophobic surface property against uncovered areas of a base fiber made of another material, for example glass.

Particularly preferably, the oleophobic fibers of the first or second fiber type are essentially completely coated with an oleophobic coating.

In an alternative embodiment, the oleophobic fibers are preferably made of oleophobic materials such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polyvinylidene fluoride (PVDF), fluorocarbons or polyethyleneimine.

The filter fleece preferably has a proportion of 5 to 75% oleophobic fibers, particularly preferably 10 to 35%.

In a preferred embodiment, the porosity of the filter fleece is 75 to 99%.

The filter fleece preferably has a thickness of 0.2 to 2 mm. The filter fleece thickness can be determined, for example, according to DIN EN ISO 9073-2:1997-02.

In a preferred embodiment, the air permeability of the filter fleece is 20 l/m ² s to 2500 l/m ² s. The air permeability of a filter fleece can be determined, for example, according to ISO 9237:1995-06.

The filter fleece preferably has a weight per unit area of 25 to 200 g/m ² . The basis weight can be determined according to ISO 536:2012-07.

Furthermore, the filter fleece preferably has an average pore size of 2 μm to 200 μm. Mean pore size is measurable according to ASTM F316.

Furthermore, the fineness of the filter fleece is preferably 1 to 50 μm.

The above parameters define, individually and in combination with one another, an efficient filter fleece for separating liquids from a gas flow. In combination with the size of the fibers and their surface quality, a filter fleece is obtained which has a reduced pressure loss, in particular when it is wetted with oil, improved filter efficiency and a longer service life.

The filter fleece preferably contains at least one binder. This causes the fibers connected to each other and stabilizes the filter fleece. In a preferred development, the filter fleece has one or more binders. The binder or binders are preferably selected from the group: acrylates, vinyl chlorides, latex and latex derivatives, for example butadiene latex, epoxides and/or mixtures thereof.

In a preferred embodiment, the filter fleece additionally or alternatively has at least one binding fiber. The one or more binding fibers are preferably selected from the group: polyethylene terephthalate (PET), polycaprolactone (PCL), polyvinyl acetate (PVAc), copolymer of polyethylene terephthalate or combinations thereof. Alternatively, the binding fiber is, for example, a bicomponent fiber.

In addition, the invention includes a filter element for cleaning a medium afflicted with liquid and/or solid particles, with at least one filter layer consisting of a filter fleece according to one of the preceding claims. A filter element is a component that has at least one filter fleece. In addition to the one nonwoven filter fabric, further separating means and also further nonwoven filter layers can be provided.

The filter element preferably has a plurality of filter layers. In particular, at least one of these filter layers consists of a filter fleece according to the invention. Further filter layers with the same or different composition can be provided.

In a preferred embodiment, all filter layers consist of a nonwoven filter fabric according to the invention.

The efficiency of the filter element can be increased by using several filter layers made from a filter fleece.

The filter element preferably has 2 to 25 layers, particularly preferably 2 to 15 layers, each of which consists in particular of the nonwoven filter fabric according to the invention.

• • Bereitstellung zumindest zweier unterschiedlicher Fasersorten, in Form einer ersten und einer zweiten Fasersorte, wobei die Fasern der ersten und zweiten Fasersorte jeweils aus Mikroglasfasern bestehen,
• • Oleophobisierung der ersten oder zweiten Fasersorte,
• • Suspendieren der ersten und zweiten Fasersorte in Lösungsmittel,
• • Vlieslegung mittels Nassvliesverfahren mit Lösungsmittelentfernung zur Herstellung eines Rohvlieses,
• • Trocknung des Rohvlieses.

A method for producing a filter fleece, in particular for use in a filter element for separating liquid from a gas flow, comprising at least two different types of fibers, wherein at least a first type of fiber consists of coarse fibers and a second type of fiber consists of fine fibers preferably comprises the following steps:

• • Provision of at least two different fiber types in the form of a first and a second fiber type, the fibers of the first and second fiber types each consisting of micro glass fibers,
• • oleophobic treatment of the first or second fiber type,
• • suspending the first and second type of fiber in solvent,
• • Non-woven laying using the wet non-woven process with solvent removal to produce a raw non-woven fabric,
• • Drying of the raw fleece.

By using two differently fine or coarse fiber types, based on the average fiber diameter, e.g. based on micro glass fibers and subsequent oleophobic treatment of one of the fiber types, a filter fleece with optimized separation properties and efficiency is obtained after fleece laying.

In a preferred development, the raw fleece is impregnated with at least one binder after the fleece has been laid and before drying. As a result, the fibers of the filter fleece are connected to one another and the filter fleece is stabilized.

Preferably, the solvent in which the first and second fiber grades are suspended is water.

In a preferred development, in addition to fibers of the first and second fiber type, further components are suspended in the solvent, for example chopped fibers (chopped strands) or binding fibers.

The fibers of the first or second fiber type are preferably made oleophobic by coating by means of PVD, CVD or wet-chemical deposition. PVD stands for physical vapor deposition. CVD stands for chemical vapor deposition, in particular it is a plasma process.

In the case of oleophobic treatment using wet-chemical processes, for example, fluorocarbon as the coating material, in particular a polymer modified with C6 fluorocarbon, is dispersed in water at a concentration of 20 to 30%

A non-woven filter fabric as described above, comprising at least two different fiber types, wherein at least a first fiber type consists of coarse fibers and a second fiber type consists of fine fibers, wherein fibers of the first or second fiber type are oleophilic and fibers of the opposite first or second fiber type are oleophobic, is preferably in a filter element ment used to separate liquid from a gas stream.

• 1 einen Ausschnitt aus einem Filtervlies

Further features, details and advantages of the invention result from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. It shows:

• 1 a section of a filter fleece

1 shows a section of a filter fleece with fibers of the first type of fiber 1, which are coarser than the fibers of the second type of fiber 2. The fibers of the first type of fiber are preferably oleophilic and therefore untreated. The fibers of the second fiber type 2 are more preferably coated with an olephobic coating.

Examples:

Oleophobicization:

Dry glass fibers (1st or 2nd fiber type) are made oleophobic in a wet-chemical process. A quantity of glass fibers is immersed in an acetic acid aqueous (pH 5) oleophobic solution (0.1 to 12 g/L oleophobic polymer) for 5 to 60, particularly preferably 20-30 minutes. The fibers are then separated from the liquid (suction). The oleophobic fibers are dried at 150 to 180°C.

Example compositions of filter fleeces according to the invention:

• a)
  • 5-85% 2nd fiber type (fine fibers),
  • 5-85% 1st fiber type (coarse fibers)
• b)
  • 5-85% 2nd fiber type (fine fibers) oleophobic,
  • 5-85% 1st fiber type (coarse fibers) oleophilic.
• c)
  • 5-85% 2nd fiber type (fine fibers) oleophilic,
  • 5-85% 1st fiber type (coarse fibers) oleophobic.
• d) 5-85% 2nd fiber type (fine fibers) oleophobic,
  • 5-85% 1st fiber type (coarse fibers) oleophilic,
  • 10% chopped strands
  Chopped strands: cut glass fibers - average length 4 to 12 mm, average diameter 5.5 µm
• e)
  • 70% 1st fiber type,
  • 20% 2nd fiber type oleophobic,
  • 10% chopped strand,

1. 1. Fasersorte: B39 Fasern sind Glasfasern mit einem mittleren Durchmesser 5 µm.
2. 2. Fasersorte: B06 Fasern sind Glasfasern, die einen mittleren Durchmesser 0,65 µm aufweisen.

Examples of fiber types:

1. 1. Fiber type: B39 fibers are glass fibers with an average diameter of 5 µm.
2. 2. Fiber type: B06 fibers are glass fibers with an average diameter of 0.65 µm.

• 5-85 % Faser 1 + 5-85% Faser 2 + 10% (Chopped strand oder Bindefaser) werden in Wasser (7,5-13 g/L) unter Rühren suspendiert und mittels Nassvliesverfahren zu einem fortlaufenden Filtermaterial hergestellt. Nach der Vlieslegung wird ein Bindemittel (bspw. Acrylat 1-7%) zugesetzt. Die Trocknung erfolgt in einem kontinuierlichen Prozess mit einer Temperaturrampe von 60 - 210°C für 1 Minute.

Production example:

• 5-85% fiber 1 + 5-85% fiber 2 + 10% (chopped strand or binding fiber) are suspended in water (7.5-13 g/L) with stirring and produced into a continuous filter material by means of a wet-laid process. After the fleece has been laid, a binder (e.g. 1-7% acrylate) is added. The drying takes place in a continuous process with a temperature ramp of 60 - 210°C for 1 minute.

The percentages refer to the percentage by weight of a specific type of fiber in relation to the total weight of the filter fleece.

All features that have been described for the filter fleece, the filter element, the method or the use can be transferred to the other objects of the invention.

The invention is not limited to one of the embodiments described above, but can be modified in many ways.

All of the features and advantages resulting from the claims, the description and the drawing, including structural details, spatial arrangements and method steps, can be essential to the invention both on their own and in a wide variety of combinations.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2058041 A1 [0003]

Claims (12)

Filter fleece, in particular for use in a filter element for separating liquid from a gas flow, comprising at least two different types of fibers, with at least a first type of fiber (1) consisting of coarse fibers and a second type of fiber (2) consisting of fine fibers, with fibers of the first or second Fiber type (1, 2) are oleophilic and fibers of the opposite first or second fiber type (1, 2) are oleophobic. filter fleece claim 1 , characterized in that the second type of fiber (2) has fine fibers with an average diameter of less than or equal to 2.5 µm, preferably from 0.1 to 2 µm, particularly preferably from 0.6 to 0.7 µm. Filter fleece according to one of the preceding claims, characterized in that the first type of fiber (1) has coarse fibers with an average diameter greater than or equal to 3 µm, preferably from 3 to 8 µm, particularly preferably from 3.5 to 5 µm. Filter fleece according to one of the preceding claims, characterized in that the coarse fibers of the first fiber type (1) are oleophilic. Filter fleece according to one of the preceding claims, characterized in that the fine fibers of the second fiber type (2) are oleophobic. Filter fleece according to one of the preceding claims, characterized in that the oleophilic fibers of the first and/or second fiber type (1, 2) are polymer fibres, in particular micro glass fibres. Filter fleece according to one of the preceding claims, characterized in that the oleophobic fibers of the first or second fiber type (1, 2) have an oleophobic coating. Filter fleece according to one of the preceding claims, characterized in that the porosity is 75 to 99%. Filter fleece according to one of the preceding claims, characterized in that at least one binder is contained. Filter fleece according to one of the preceding claims, characterized in that at least one binding fiber is contained. Filter element for cleaning a medium afflicted with liquid and/or solid particles, having at least one filter layer consisting of a filter fleece according to one of the preceding claims. filter element after claim 11 , characterized in that the filter element has a plurality of filter layers, each of a non-woven filter according to claim 1 exist.

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