EP2131941A1

EP2131941A1 - Layer for use in a hepa filter element

Info

Publication number: EP2131941A1
Application number: EP07866229A
Authority: EP
Inventors: Klaus Veeser; Armin Greiner; Harald Von Schischka; Jürgen Adolph; Toan-Hieu Giang
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 2007-03-07
Filing date: 2007-12-03
Publication date: 2009-12-16
Also published as: DE102007011365B4; CN101622047B; CN101622047A; AU2007348647B2; AU2007348647A1; US20100101199A1; WO2008107006A1; DE102007011365A1; US8709139B2

Abstract

A layer for use in a HEPA filter element solves the problem of disclosing a filter element which satisfies HEPA requirements. Said layer comprises a first support layer (1) for stabilization which contains polypropylene fibers, and a second deposition layer (2) which contains polypropylene fibers, wherein the polypropylene fibers of the deposition layer (2) are at least partially electrostatically charged, and wherein the support layer (1) and the deposition layer (2) are constructed as nonwoven material which is at least partially free of glass fiber. The layer according to the invention can be easily pleated while having excellent filter efficiency.

Description

Location for use in a HEPA filter element

description

Technical area

The invention relates to a layer for use in a HEPA filter element.

State of the art

Filter elements that meet HEPA requirements are already known from the prior art. HEPA filter elements may be designed as particulate filters that serve to filter over 99.9% of all particles larger than 0.1 to 0.3 μm from the air.

These particles may include viruses, respirable dusts, mite eggs and excrements, pollen, smoke particles, asbestos, bacteria, various toxic dusts and aerosols.

HEPA filter elements are used, inter alia, in the medical field, in particular in operating rooms, intensive care units and laboratories. Furthermore, uses in clean rooms and in nuclear technology are known.

BESTATIGUNGSKOPIE The European standard for the classification of a HEPA filter element is the DIN EN 1822 with the filter classes H10 to H14 (HEPA). It is known that particles with a size of 0.1 to 0.3 microns are the hardest to separate. The particle size of the most difficult-to-separate particles under certain conditions is classified as "most penetrating particle size", which is why HEPA filter elements are classified according to their effectiveness in terms of particle size by means of a test aerosol so-called DEHS (di-2-ethylhexyl sebacate).

Although known from the prior art filter elements often show good to very good filter efficiency, but are made of materials that can be hazardous to human health. For example, HEPA filter elements are known, which have considerable glass fibers. Glass fibers can leak out of the position from which the filter element is made and damage the human organism.

Furthermore, the known layers for HEPA filter elements are not readily plissiable, since glass fibers are subjected to mechanical stress during pleating processes and break easily. The pleated filter elements are less elastic and prone to breakage. The fractures form holes or perforations, which adversely affect the filter efficiency. Such a filter can no longer meet HEPA requirements because unwanted particles can pass through the resulting damaged areas.

Presentation of the invention

The invention is therefore based on the object to provide a layer for use in a HEPA filter element, which is easily plissiable at high filter efficiency. According to the invention the above object is achieved by a layer having the features of claim 1. Thereafter, the layer comprises a first polypropylene fiber-containing carrier layer for stabilization and a second polypropylene fibers containing Abscheideschicht, wherein the polypropylene fibers of the Abscheideschicht are at least partially electrostatically charged and wherein the carrier layer and the Abscheideschicht are designed as at least partially glass fiber-free nonwovens.

According to the invention it has been recognized that the use of nonwoven fabrics of polypropylene fibers allows the formation of a very elastic and plissierfähigen layer with suitable porosity. Furthermore, it has been recognized that reducing or eliminating glass fibers increases the elasticity of the ply and avoids damage. Breakages due to excessive brittleness of the situation are avoided according to the invention. Finally, it has been recognized that nonwovens of polypropylene fibers can be thermally bonded to one another without any problems in such a way that pleating of the interconnected support layer and deposition layer is possible with virtually no displacement of the layers relative to each other. Consequently, the object mentioned above is achieved.

Against this background, it is concretely conceivable that neither the support layer nor the deposition layer have glass fibers, namely that the support layer and the deposition layer are formed free of glass fibers. By this specific embodiment, a layer can be generated, which contains no human endangering materials.

The backing layer could have a basis weight of 70 to 200 g / m ² . The choice of this basis weight allows sufficient stabilization of the layer to pleat it. Furthermore, the choice of this basis weight allows the order of a very thin and highly porous Deposition layer, which itself has only a low rigidity and makes no contribution to the overall rigidity of the situation.

The polypropylene fibers of the carrier layer could be electrostatically charged. This specific embodiment allows the use of the carrier layer as a pre-separator or prefilter.

The deposition layer could have a basis weight of 10 to 80 g / m ² . This range has surprisingly been found to be particularly suitable to meet HEPA requirements. The porosity can be adjusted depending on the fineness of the fibers. The finer the fibers used, the lower the basis weight can be chosen to meet the requirements of each filter class.

Against this background, it is conceivable that the deposition layer comprises nanofibers made of polyamide, polyacrylonitrile or polycarbonate. Furthermore, it is conceivable that a layer of nanofibers of the mentioned materials is applied to the deposition layer. Nanofibers allow the deposition of very fine particles and can significantly increase the filtration efficiency of the layer described here.

The layer may have a third layer containing polypropylene fibers having a basis weight of 8 g / m ² and includes the separating layer sandwiched together with the carrier layer. This concrete embodiment is suitable for the production of the situation in a melt-blown process. The third layer also provides a protective layer for the anti-abrasion and electrical discharge coating layer. The third layer allows air to pass without significant resistance, making it particularly suitable as a substrate for depositing the deposition layer through a melt-blown process. They go through the melt-blown process coated polypropylene fibers of the deposition layer with the third layer a cohesive composite in which they stick to the fibers of the third layer.

Against this background, the polypropylene fibers of the carrier layer could contain core-sheath fibers with a sheath of metallocene polypropylene and a core of pure polypropylene. This specific embodiment allows melting of the shell, wherein the core is not affected in its polymer structure. As a result of the melting of the jacket, the individual core-sheath fibers can combine with one another and with the polypropylene fibers of the deposition layer. In concrete terms, it is conceivable that the carrier layer is prefabricated with the Abscheideschicht and the third layer is connected by ultrasonic welding.

The polypropylene fibers of the deposition layer could be formed as melt-blown fibers having an average diameter of 1 to 2 μm. This specific embodiment allows the creation of a nonwoven fabric with very small pores. Due to the fine porosity very fine particles can be deposited so that the layer meets HEPA requirements.

The polypropylene fibers of the third layer could be selectively thermally bonded together. Concretely, the polypropylene fibers of the third layer could be bonded to each other by a point seal method, whereby individual punctiform regions of the polypropylene fibers are melted and their polymer structure is changed so that they are brittle, but the fused areas of different polypropylene fibers are only fused together at points before, so that the third layer as a planar structure in its entirety is movable and deformable without breaking. The carrier layer, the deposition layer and the third layer could be thermally bonded together by ultrasound-welded or laser-welded regions such that the layer is pleatable. The ultrasonically welded or laser welded areas could be in the form of line patterns or dot patterns. This ensures that there are unwelded areas between the welded areas which are non-destructively bendable or foldable. The welded areas are often brittle due to the thermal impact. Against this background, it is concretely conceivable that the welded regions connect all three layers to one another by melting the polypropylene fibers in the respective layers and melting them together to form a composite which penetrates the layers.

The layer could have a basis weight of 160 g / m ² , a thickness of 0.92 mm and an air permeability of 315 dm ³ / m ² s at a pressure difference of 200 Pa, the pressure difference between upstream and downstream side of the situation prevails. Surprisingly, it has been found that a layer with this thickness and this weight per unit area shows the said air permeability at said pressure difference. Such a location is particularly suitable for use in room air purifiers, since the room air purifier can work with a low electrical power consumption. In that regard, a gentle and cost-effective operation of a room air cleaner is possible.

The situation could cause a pressure drop from upstream side to downstream side of at most 100 Pa at a flow velocity of a gaseous medium to be filtered of 15 cm / s. Such a situation is particularly suitable for use in devices that suck air from a first room to a second room. The low pressure drop of Upstream to downstream allows gentle operation of the suction unit, as this must do little work to suck a filter to be filtered gaseous medium through the layer. Against this background, it is conceivable that the pressure drop is less than 40 Pa at a flow velocity of 5 cm / s and less than 80 Pa at a flow velocity of 10 cm / s. A layer which exhibits these properties is particularly suitable for use in electrically operated filter arrangements, in particular in room air cleaners.

The location could have a filter efficiency of at least 85% at one

Flow velocity of a gaseous medium of at most 8 cm / s have. In concrete terms, it is conceivable that the test aerosol DEHS according to the European standard DIN EN 1822 is used as the gaseous medium. When this test aerosol hits the upstream side of the sheet at 8 cm / s, at least 85% of the hardest-to-be-separated particles are separated. These particles, which are the most difficult to separate, have a certain particle size, namely the MPPS ("most penetrating particle size") A layer which exhibits these properties is suitable for use in a HEPA filter element because it meets the requirements of filters of the filter class H 10 is enough.

A filter element could comprise a bellows, wherein the bellows is made of a pleated layer, and wherein the bellows is inserted in a filter door. Such a filter element is suitable as a module for a room air cleaner, since the filter element can be used together with the filter door in an existing arrangement. If the bellows is made of a layer described here, the filter element is designed as a HEPA filter element. The filter door could have a perforated bottom, which is associated with an at least partially encircling frame which surrounds the bellows. This concrete embodiment of the bellows can be glued into the frame, which cracks and gaps in the frame area can be avoided. The perforations in the bottom ensure that the medium to be filtered penetrates through the perforations and passes through the pleated position of the bellows. A flow past the medium to be filtered by splitting or scribing between the bellows and the frame is prevented by sticking the bellows.

There are now various possibilities for embodying and developing the teaching of the present invention in an advantageous manner. For this purpose, on the one hand to refer to the subordinate claims and on the other hand to the following explanation of a preferred embodiment of the invention with reference to the drawings.

In conjunction with the explanation of the preferred embodiment of the invention with reference to the drawing, generally preferred embodiments and developments of the teaching are explained.

Brief description of the drawing

In the drawing show

1 is a schematic view of a layer which has three layers,

2 is a sectional view of a bellows, which is made of a pleated layer according to FIG. 1,

3 is a plan view of the bellows of FIG. 2, 4 is a plan view of the filter door, in which the bellows is inserted as shown in FIG. 3,

5 is a diagram which shows the pressure drop between inflow side and outflow side of a layer as a function of the

Flow velocity shows, and

Fig. 6 is a diagram showing the penetration of the particles to be deposited as a function of the flow velocity in a double logarithmic representation.

Embodiment of the invention

1 shows a layer for use in a filter element comprising a carrier layer 1 containing first polypropylene fibers for stabilization and a separator layer 2 containing a second polypropylene fibers. The polypropylene fibers of the deposition layer 2 are at least partially electrostatically charged. The carrier layer 1 can also be electrostatically charged and serve as a pre-separator or prefilter. The carrier layer 1 and the deposition layer 2 are designed as glass fiber-free nonwovens.

The carrier layer 1 has a basis weight of 110 g / m ² and is made of polypropylene fibers. The polypropylene fibers of the carrier layer 1 are configured as core-sheath fibers with a sheath of metallocene polypropylene and a core of pure polypropylene.

The deposition layer has a basis weight of 36 g / m ² and is made of polypropylene fibers. The polypropylene fibers are configured as electret microfibers. The polypropylene fibers of the deposition layer 2 were applied to the third layer 3 by a melt-blown process, which has a basis weight of 14 g / m ² . The third layer 3 is also made of polypropylene fibers and acts to protect a substrate on which the polypropylene fibers of the deposition layer 2 are applied during a melt-blown process.

The third layer 3 comprises polypropylene fibers which are selectively thermally bonded together by a "point seal" method The third layer 3 and the backing layer 1 sandwich the deposition layer 2 therebetween.

In the concrete embodiment mentioned above, the carrier layer 1, the deposition layer 2 and the third layer 3 exclusively contain polypropylene fibers and are completely free of glass fibers. Therefore, the situation described here is almost completely incinerable and easy to dispose of.

The situation described in the specific embodiment has a basis weight of 160 g / m ² and a thickness of 0.92 mm. At a pressure difference of 200 Pa, which is established between upstream side and downstream side of the layer, the layer shows an air permeability of 315 dm ³ / m ² s.

The following table shows flow velocities, pressure drops, efficiencies for the respective MPPS, penetration and particle sizes MPPS. These measurement results were determined by measurements in accordance with DIN EN 1822 at the position described in the specific embodiment.

table

Fig. 5 shows the pressure drop from the upstream side to the downstream side of the layer as a function of the flow velocity. It can be clearly seen from FIG. 5 that, with an inflow velocity of 15 cm / sec, the pressure drop is at most 110 Pa. In that regard, the situation according to the invention shows excellent permeability to a medium to be filtered, whereby electric motors of suction units can be operated inexpensively and gently. In Fig. 5 a regression line is drawn, which was determined from the measurements. It can be seen from Fig. 5 clearly shows a linear dependence of the pressure drop from the flow velocity at least up to a flow velocity of 15 cm / s.

Fig. 6 shows the penetration of the hardest to be separated particles as a function of the flow velocity. The table is taken at a flow velocity of 1, 3 cm / sec, a diameter of the hardest to be separated particles of 0.071 microns. These show a penetration of 1, 2%. That is, 98.8% of the most difficult to be separated at the flow velocity of 1, 3 cm / sec particles are deposited by the inventive layer. At a flow velocity of 5.3 cm / sec 89.5% of the hardest to be deposited particles are deposited. In that regard, the layer according to the invention shows filter properties which make it suitable for use in H EPA filter elements. Fig. 2 shows a bellows 4, which is made of a layer of the type described here. The location is pleated and has 70 double folds.

Fig. 3 shows the bellows 4 in a plan view. The bellows 4 are associated with strip-shaped elements 5, which are connected to the pleat backs. The strip-shaped elements 5 space the fold backs and thus the folds. As a result, a gluing or connecting the wrinkles is prevented in particular when flowing through.

Fig. 4 shows a filter door 6, in which the bellows 4 is glued in Fig. 3. The filter door 6 surrounds the bellows 4 with a frame 7, wherein between the frame 7 and the bellows 4 adhesive is introduced to prevent the formation of slots or gaps.

The filter door 6 has a bottom 8, here by a partial

Breakthrough of the bellows 4 is exposed. The bottom 8 has perforations 9, through which the medium to be filtered can flow. The filter door 6 further has locking lugs 10, which can be locked with a recording of a room air purifier. As a result, the filter door 6 can be used together with the bellows 4 as a module.

The layer described here or the filter element described here can serve as an air filter to filter microorganisms from contaminated air. Here, the position or the filter element shows a particularly favorable ratio of filter efficiency and pressure drop.

The situation described here and the filter element described here show no release of microfibers from the position to the ambient air. In this respect, the position and the filter element can be used in areas where allergy sufferers move. The use of hydrophobic fibers, namely polypropylene fibers, prevents the growth of bacteria, fungi and similar pollutants on the surface of the sheet or filter element. Furthermore, the situation is fully incinerable.

Due to the properties described here, the layer is particularly suitable for use in air filter elements for room air purifiers or for air filter elements in hospitals.

With regard to further advantageous embodiments and developments of the teaching of the invention reference is made on the one hand to the general part of the description and on the other hand to the appended claims.

Finally, it should be emphasized that the previously purely arbitrarily chosen embodiment is only for the purpose of discussing the teaching of the invention, but this does not limit this embodiment.

Claims

claims

A sheet for use in a HEPA filter element, comprising a first polypropylene support layer (1) for stabilization and a second polypropylene fiber-containing release layer (2), the polypropylene fibers of the deposition layer (2) being at least partially electrostatically charged, and wherein the support layer ( 1) and the deposition layer (2) are configured as at least partially glass fiber-free nonwovens.

2. Layer according to claim 1, characterized in that the carrier layer (1) has a basis weight of 70 to 200 g / m ² .

3. Layer according to claim 1 or 2, characterized in that the polypropylene fibers of the carrier layer (1) are charged electrostatically.

4. Layer according to one of claims 1 to 3, characterized in that the deposition layer (2) has a basis weight of 10 to 80 g / m ² .

5. Layer according to one of claims 1 to 4, characterized by a third polypropylene fibers containing layer (3) which has a basis weight of at least 8 g / m ² and, together with the carrier layer (1), the deposition layer (2) sandwiches.

6. Layer according to one of claims 1 to 5, characterized in that the polypropylene fibers of the carrier layer (1) core-sheath fibers with a shell of metallocene polypropylene and a core of pure polypropylene.

7. Layer according to one of claims 1 to 6, characterized in that the polypropylene fibers of the Abscheideschicht (2) are formed as melt-blown fibers having an average diameter of 1 to 2 microns.

8. Layer according to one of claims 1 to 7, characterized in that the polypropylene fibers of the third layer (3) are selectively thermally connected to each other.

9. Layer according to one of claims 5 to 8, characterized in that the carrier layer (1), the Abscheideschicht (2) and the third layer (3) exclusively contain polypropylene fibers.

10. Layer according to one of claims 5 to 9, characterized in that the carrier layer (1), the Abscheideschicht (2) and the third layer (3) by ultrasonically welded or laser welded areas are thermally connected to each other such that the position is plissable.

11. A layer according to any one of claims 1 to 10, characterized by a basis weight of 160 g / m ² , a thickness of 0.92 mm and an air permeability of 315 dm ³ / m ² s at a pressure difference of 200 Pa, the between upstream side and downstream side of the situation prevails.

12. A layer according to any one of claims 1 to 11, characterized by a pressure drop from inflow side to downstream side of at most 100 Pa at a flow velocity of a gaseous medium to be filtered of 15 cm / s.

13. The layer according to one of claims 1 to 12, characterized by a filter efficiency of at least 85% at a flow velocity of a gaseous medium of at most 8 cm / s.

14. Filter element comprising a bellows (4), wherein the bellows (4) is made of a pleated layer according to one of the preceding claims, and wherein the bellows (4) in a filter door (6) is inserted.

15. Filter element according to claim 14, characterized in that the filter door (6) has a perforated bottom (8), which is associated with an at least partially encircling frame (7) which surrounds the bellows (4).