Sheet material and filter element with hydrophobic separating layer, use thereof and process for production of same

Abstract

The present invention relates to a sheet material and filter element, where the sheet material and the filter element have a hydrophobic separating layer, and also to use thereof and to a process for production of same.

Claims

1. A sheet material with at least one of the following layer A and at least one of the following layer B: A: a hydrophobic porous membrane; and B: a hydrophobically modified fibrous separating layer, wherein the at least one hydrophobic porous membrane A and the at least one hydrophobically modified fibrous separating layer B are in contact with one another without any fixed connection to one another.

2. The sheet material as claimed in claim 1, wherein the at least one hydrophobically modified fibrous separating layer B has a hydrophobic modification with a fluorine-containing compound, with a silicon-containing compound and/or with an aliphatic hydrocarbon.

3. The sheet material as claimed in claim 1, wherein the at least one hydrophobically modified fibrous separating layer B is a nonwoven-fabric drainage layer.

4. The sheet material as claimed in claim 1, wherein the at least one hydrophobically modified fibrous separating layer B consists of polyester fibers, polyimide fibers and/or polyolefin fibers with hydrophobic modification.

5. The sheet material as claimed in claim 1, which consists of gamma-sterilizable materials.

6. A process for the production of the sheet material as claimed in claim 1, comprising: (1) provision of the at least one hydrophobic porous membrane A; (2) provision of the at least one hydrophobically modified fibrous separating layer B; (3) arrangement of the at least one hydrophobic porous membrane A and of the at least one hydrophobic fibrous separating layer B to give the sheet material such that the at least one hydrophobic porous membrane A and the at least one hydrophobically modified fibrous separating layer B are in contact with one another without any fixed connection to one another.

7. A filter element comprising: the sheet material of claim 1 and at least one anchoring element, wherein the edge regions of the at least one hydrophobic porous membrane A have been embedded in fluid-tight manner into the anchoring element.

8. The filter element as claimed in claim 7, which is an air filter.

9. A process for the production of the filter element of claim 7, comprising: (I) provision of the sheet material of claim 1; (II) provision of the at least one anchoring element; (III) fluid-tight embedding of the edge regions of the at least one hydrophobic porous membrane A into the at least one anchoring element.

Description

EXAMPLE

(1) Various filter units of the present invention and of the prior art (pleated candle filters with two end caps and filter housing, and specifically a filter capsule whose structure is shown in FIG. 1) were studied in the experiments described below.

(2) Method for Measurement of Average Air Flow Rate

(3) The measurement is made on the filter capsule. A pressure regulator at the ingoing end/upstream end is used to set a predetermined pressure difference Δp (between ingoing and outgoing end of the filter capsule housing). An air flow rate meter (attached on the outflow side or at the outgoing end of the housing) is used to determine the air flow rate (average air flow rate, average value of 3 measurements).

(4) Conditions for Water Intrusion Test (WIT)

(5) Water is charged to the upstream end of the filter housing. A pressure of 1.5 bar is then applied to the system and stabilized for 10 min. Intrusion of the water into the first layer of the membrane takes place during the test time of 10 min. The pressure drop is measured. The WIT value, as measure of water intrusion, is calculated from the pressure drop, the known test time, and the measured volume of water required to compensate the pressure drop. The measurement device used for the test is a Sartocheck 4 from Sartorius Stedim Biotech GmbH.

(6) The hydrophobically modified membrane used was a membrane as described in DE 10 2011 121 018 A1 (hydrophobic PESU, average pore size 0.2 μm, thickness 120 μm).

(7) The candle filters of the invention that were studied were installed as capsules with installed height 9 and had the layer sequence BAB (PP/PE nonwoven core-and-sheath fabric*//hydrophobically modified membrane//PP/PE nonwoven core-and-sheath fabric*). “*” here means that the PP/PE nonwoven core-and-sheath fabric comprised a hydrophobic modification obtained as follows. The filter area was 0.182 m.sup.2.

(8) For the hydrophobic modification procedure, a roll of fiber material was unwound and passed at room temperature through an impregnation bath comprising a mixture of 20% of NUVA 3049 fl. (Archroma GmbH) and 80% of water (impregnation time 1 min). The wetted web was then passed through a drying oven (110° C., convection 3 min) in order to remove the solvent, and wound up when dry.

(9) Candle filters having the same structure but having separating layers without hydrophobic impregnation were used as comparative example.

(10) AFR before WIT was first determined as described above. Each of the capsules was then subjected as described above to a WIT, and AFR was again determined immediately thereafter. In another series of tests, each of the capsules was subjected to a WIT and allowed to stand for one hour (25° C., 1013 hPa), and AFR was again determined. FIGS. 2 to 4 show the results.

(11) FIG. 1 is a diagram of the experimental setup of example 1 (water intrusion test with compressed air), where A indicates a measurement device (Sartocheck 4 from Sartorius Stedim Biotech GmbH) and C indicates a setup with pleated candle filter with two end caps and filter housing B.

(12) FIG. 2 shows the AFR, based on 1 m.sup.2 of filter area, for comparative capsules (in each case on the left) and capsules of the invention (in each case on the right) before a WIT. Within the bounds of accuracy of measurement, no difference in AFR between the different types of capsule (with and without hydrophobic impregnation) is observed.

(13) FIG. 3 shows AFR, based on 1 m.sup.2 of filter area, for comparative capsules (in each case on the left) and capsules of the invention (in each case on the right) immediately after a WIT. The AFR reduction due to WIT is much greater for the comparative capsules than for the capsules of the invention.

(14) FIG. 4 shows AFR, based on 1 m.sup.2 of filter area, for comparative capsules (in each case on the left) and capsules of the invention (in each case on the right) one hour after a WIT. It can clearly be seen that one hour after the WIT the capsules of the invention exhibit significantly higher AFR than conventional capsules of the prior art.

(15) The present invention provides sheet materials which can be used to produce improved filter units. Because a hydrophobic fibrous separating layer is used, high air flow rate through the sheet material is obtained, even after contact with water under pressure, for example in the context of a WIT.