Filter For Separating Hydrophilic And Hydrophobic Fluids And Method For The Production Thereof

Abstract

The invention relates to a filter for separating hydrophilic from hydrophobic fluids, wherein the filter comprises an oleophobic polymer, consists thereof or is coated therewith, and wherein the filter exhibits hydrophilic and oleophobic properties, wherein at least some of the repetitive units of the oleophobic polymer can be traced back to a fluorine-containing monomer which is an ionic organic molecule that has an ionic group, a cross-linkable group and a fluorine-containing group. The invention further relates to a method for producing such a filter and to a method for separating hydrophilic and hydrophobic fluids by using such a filter.

Claims

1. A filter for separating hydrophilic and hydrophobic fluids, wherein the filter comprises the filter coated with an oleophobic polymer; and wherein the filter exhibits hydrophilic and oleophobic properties, and wherein at least some of the repetitive units of the oleophobic polymer are based on a monomer that contains fluorine and that is an ionic organic molecule that has an ionic group, a crosslinkable group, and a group containing fluorine.

2. The filter in accordance with claim 1, wherein the filter is a porous filter layer.

3. The filter in accordance with claim 2, wherein the porous filter layer is a coated substrate.

4. The filter in accordance with claim 1, wherein the group containing fluorine is a perfluorinated carbon group.

5. The filter in accordance with claim 1, wherein the crosslinkable group comprises a reactive double bond.

6. The filter in accordance with claim 1, wherein the ionic group is an ionically charged heterocyclic and/or in that the charge is delocalized over a plurality of atoms of the ionic group.

7. The filter in accordance with claim 1, wherein the ionic group or the monomer containing fluorine is positively charged overall.

8. The filter in accordance with claim 1, wherein a spacer is arranged between the ionic group and the group containing fluorine and/or between the ionic group and the crosslinkable group.

9. The filter in accordance with claim 1, wherein the oleophobic polymer is a copolymer; and in that at least some other portions of the repetitive units are based on a hydrophilic comonomer that has a polymerizable group and a hydrophilic group.

10. The filter in accordance with claim 9, wherein the proportion of the repetitive units of the copolymer that are based on the monomer containing fluorine is between 0.1 and 50 mol %.

11. The filter in accordance with claim 9, wherein a further proportion of the repetitive units of the copolymer is based on a crosslinking comonomer that has at least two crosslinkable groups or at least one crosslinkable group and one reactive group.

12. A method of producing the filter of claim 1, said method comprises the following steps: providing a solution of the monomer containing fluorine and optionally of the further comonomers; applying this solution to a substrate; and crosslinking the monomers to form the polymer.

13. A method of producing the filter of claim 1, said method comprises the following steps: providing a solution of the oleophobic polymer and optionally of further polymer or monomer components; applying this solution to a substrate; and removing the solvent.

14. A method of producing a filter in accordance with claim 1, said method comprises the following steps: providing a solution of the oleophobic polymer and optionally of further polymer or monomer components; precipitating or phase extruding with an antisolvent.

15. A method of separating hydrophilic and hydrophobic fluids utilizing the filter in accordance with claim 1.

16. The filter in accordance with claim 1, wherein the filter is a filter membrane.

17. The filter in accordance with claim 1, wherein the filter is a filter membrane having a filter layer, with a pore size of the filter layer being between 1 nm and 1 mm.

18. The filter in accordance with claim 1, wherein the filter is a filter membrane having a filter layer, with the pore size of the filter layer being between 10 nm and 0.5 mm.

19. The filter in accordance with claim 2, wherein the porous filter layer is a coated substrate, with the coated substrate comprising polytetrafluoroethylene, expanded polytetrafluoroethylene, polysulfone, polyether sulfone, polyethylene, polypropylene, polyester, polyurethane, polyvinylidene difluoride, polyamide, polystyrene, polyacrylonitrile, cellulose-based materials, a metal mesh, or combinations thereof.

20. The filter in accordance with claim 6, wherein the ionic group is an ionically charged heteroaromatic group.

Description

[0094] Further details and advantages of the invention result from the Figures and embodiments described in the following. There are shown in the Figures:

[0095] FIG. 1: a comparison of the behavior of uncoated substrates and substrates coated with an oleophobic polymer with respect to watery and oily phases; and

[0096] FIG. 2: an experimental design for separating a water/oil mixture using a filter in accordance with the invention.

[0097] FIG. 1 shows a textile of cotton fibers partially coated in a manner in accordance with the invention. The line divides the two halves, with the left half being uncoated and the right half being coated. Dots 1a and 1b each show sunflower oil that has been dyed red. The difference is clearly visible. In the coated region, an oil drop is formed having a contact angle considerably over 90, while the drop is absorbed in the uncoated region. At the dots 1c and 1d, dyed drops of water have been applied to both sides and are absorbed by the textile in both cases. The recipe used is described in the following Example 6.

[0098] FIG. 2 shows a commercial filter of Macherey-Nagel coated in accordance with the invention. The filter used has the specification MN 616, an area density of 85 g/m.sup.2, a thickness of 0.2 mm, and an average retention capacity of 4-12 m. The filter was first wetted by a hexadecane dyed red for 1 minute. The hexadecane remained in the filter here and did not move through the filter, as is the case with a non-coated filter. Water dyed blue was subsequently added that moved through the filter without problem. FIG. 2a here shows how water and oil are separated in the filter after the addition of water. FIG. 2b shows how all the water moves through the filter and how the oil is retained. This image was taken after 2 hours. The recipe used will be described in the following Example 1.

EXAMPLE 1

Synthesis of a Hydrophilic and Oleophobic Membrane:

[0099] The substances shown in the following table were added to a flask and stirred for 5 minutes. A filter paper (MN616, see above) was subsequently wetted by this monomer mixture with the aid of a pipette. As part of the reproduction experiments, other methods were also additionally used such as the dipping process and the spray process.

TABLE-US-00001 Quantity [mg] Substance 10 2,2-dimethoxy-2-phenylacetophenone 100 3-(1H,1H,2H,2H-perfluorooctyl)-1-vinyl imidazolium iodide 100 3,3-(hexane-1,6-diyl)bis(1-vinyl imidazolium)dibromide 125 Acetonitrile 125 Propane-1-ol 75 Water

[0100] The paper impregnated in this manner was then irradiated with the aid of a UV-LED lamp at a wavelength of approximately 365 nm for 3 minutes. The filter obtained was now slightly yellowed (iodine/triiodide) at the coated points. To examine the properties of the coating obtained more exactly, the contact angles of water and hexadecane were measured. Water here represents the hydrophilic component and hexane represents the hydrophobic component. Each value was measured 3 times and the mean value was noted.

Results:

[0101]

TABLE-US-00002 Contact angle Drop used after 5 seconds Water [~4 l] Fully immersed Hexadecane [~7 l] 123 (2.5)

[0102] The hexadecane drop remained unchanged as a drop on the filter paper for 2 minutes.

[0103] In addition, a separation of oil and water was carried out using the filter. The results are shown in Table 2.

EXAMPLE 2

[0104] The recipe described in Example 1 was also applied to a commercially available paper tissue of Tork. It was likewise irradiated with a UV-LED lamp for 3 minutes. The coating obtained was likewise yellow. In the case of this substrate, the contact angle was additionally measured using diiodomethane.

TABLE-US-00003 Contact angle Drop used after 5 seconds Water [~4 l] Fully immersed n-hexadecane [~6 l] 115 (4.5) Diiodomethane [1.5 l] 124 (1.5)

EXAMPLE 3

[0105] This example is very similar to Example 1; however, in this case, the still more hydrophilic chloride salt of the fluorinated cation was used. The same filter material and the same process materials were used as in Example 1.

TABLE-US-00004 Quantity [mg] Substance 10 2,2-dimethoxy-2-phenylacetophenone 100 3-(1H,1H,2H,2H-perfluorooctyl)-1-vinyl imidazolium chloride 100 3,3- (hexane-1,6-diyl)bis(1-vinyl imidazolium)dibromide 125 Acetonitrile 125 Propane-1-ol 75 Water

[0106] Although the chloride salt of the fluorosurfactant has the much higher solubility, the water drop on the substrate was absorbed considerably more slowly. While the water drop in Example 1 was immersed below 5 seconds, it was now only observed after approximately 15 seconds. The contact angle of water measured directly at the start was 115 (4.5).

TABLE-US-00005 Contact angle Drop used after 15 seconds Water [~4 l] Fully immersed n-hexadecane [~7 l] 115 (3) Diiodomethane [~1.5 l] 126 (1.5)

EXAMPLE 4

[0107] The same recipe as in Example 3 was used to coat a cellulose fiber. A contact angle measurement was not possible exactly due to the many fibers that formed a very inhomogeneous surface since the values fluctuated too greatly. It was, however, possible to observe that water was absorbed after a few seconds while both hexadecane and diiodomethane remained on the cellulose fabric for at least 2 minutes. The following table shows the preparation of examples in accordance with the invention for the UV hardening of oleophobic and hydrophilic coatings:

TABLE-US-00006 Quantity [mg] Example 5 6 7 8 9 10 2,2-dimethoxy-2-phenylacetophenone 20 20 20 30 20 20 3-(1H,1H,2H,2H-perfluorooctyl)-2- 200 200 100 100 100 100 ((1H,1H,2H,2H-perfluorooctyl)thio)-1-vinyl imidazolium chloride Ethylene glycol dimethacrylate 500 100 Methanol 500 500 300 300 300 300 3,3-(hexane-1,6-diyl)bis(2-((1H,1H,2H,2H- 500 perfluorooctyl)thio)-1-vinyl imidazolium) dichloride Trimethylpropane triacrylate 100 Polyethyleneimine 100 Tetraethylene glycol dimethacrylate 100 Butyl methacrylate 100

[0108] A cotton textile and a stainless steel mesh were coated with the recipe from Example 5 and were each hardened with a UV lamp for 30 minutes. FIG. 1 shows a cotton textile partially coated with the recipe used.

[0109] A cotton textile was coated with the recipe from Example 6. The textile was subsequently hardened with a UV lamp for 30 minutes. The textile obtained had hydrophilic and oleophobic properties.

[0110] The recipe prepared in Example 7 was hardened with a UV lamp for 30 minutes and exhibited a special behavior. The recipe behaved as a hydrophilic and oleophobic coating on a cotton textile; in contrast, on a glass carrier, this recipe demonstrated hydrophobic and oleophobic properties in a remarkable manner. This shows that the separating effects can be adapted to the respective surface quality and texture.

[0111] Example 8 was likewise hardened with a UV lamp for 30 minutes and subsequently applied to a textile. It likewise exhibited hydrophilic and oleophobic properties.

[0112] Example 9 was applied as a textile coating; Example 10 was hardened as a monolith both on a textile and on a glass carrier with UV for 30 minutes. These recipes exhibited hydrophilic and oleophobic properties both on glass and on the textile.

EXAMPLES 10 AND 11

[0113]

TABLE-US-00007 Quantity [mg] Example # 10 11 Azobisisobutyronitrile 20 20 (AIBN) 3-(1H,1H,2H, 300 300 2H-perfluorooctyl)- 2-((1H,1H,2H,2H- perfluorooctyl)thio)- 1-vinyl imidazolium chloride Ethylene glycol 500 500 dimethacrylate Methanol 500 500 Titanium dioxide 100 nanoparticles

[0114] A commercial polyurethane foam having a pore size distribution between 1 m and 500 m was wetted with the two recipes and was subsequently hardened in a glass vessel at 65 C. for 4 h. The membrane thus obtained that was still very flexible was hydrophilic and oleophobic and was suitable for separating water and olive oil. The foam was then washed multiple times with water and acetone. Water and oil were subsequently again successfully separated with the aid of the membrane.

EXAMPLES 12, 13, AND 14

[0115]

TABLE-US-00008 Quantity in mg Example 12 13 14 Water 100 100 100 3-(1H,1H,2H,2H- 4 4 4 perfluorooctyl)-1-vinyl imidazolium chloride 2-acrylamido-2- 4 4 methylpropane sulfonic acid sodium salt 50% in water 2,2-azobis(2- 0.15 0.15 0.15 methylpropionamidine)- dihydrochloride Sodium acrylate 1.5 2-[(3,5- 0.2 dimethylpyrazolyl) carboxyamino]ethylmethacrylate

[0116] Water and the monomers were presented first in recipes 12, 13, and 14. The solution was subsequently vigorously mixed at 75 C. for 15 minutes and the azo radical starter was added. The solution was then held at 75 C. for 1 h at full stirring speed. The obtained depositable solid was removed with the aid of a centrifuge and the textile was wetted with the supernatant. The textile was subsequently dried at 80 C. for 3 minutes and subsequently fixed at 150 C. for 1 minutes. The textiles obtained were water-permeable and oil-repelling.

EXAMPLE 15 PREPARATION OF POLYMER SOLUTIONS

[0117]

TABLE-US-00009 Quantity in mg Example # 15 16 Water 100 100 3-(1H,1H,2H,2H-perfluorooctyl)-1-vinyl 6 4 imidazolium chloride 2,2-azobis(2-methylpropionamidine)- 0.15 0.15 dihydrochloride Butyl acrylate 4

[0118] Water and the monomers were presented first in recipes 15, and 16. The solution was subsequently vigorously mixed at 75 C. for 15 minutes and the azo radical starter was added. The solution was then held at 75 C. for 1 h at full stirring speed. The stirring speed was subsequently carefully reduced and stirring was continued at a very low stirring speed for 2 h. A white solid was obtained in both experiments here. This solid exhibited a molar mass distribution of 60,000 Da to 450,000 Da.

[0119] The dried homopolymer from Example 15 was able to be dissolved at over 220 g/I in Novec HFE 7100 IPA (3M). The viscosity obtained was able to be set between 50 mPas and more than 5,000 mPas at 20 C. Both films and direct membranes or fibers can be produced in this viscosity range.

[0120] The copolymer from Example 16 was now also partially soluble in organic solvents due to the increased proportion of butylacrylate. The polymer was soluble over 20 g/I in DMAC and DMF. This solubility thus permits the integration in existing polymer membranes such as polysulfones, poly(vinylidene difluoride) or polyacrylonitrile. Through the selection of the copolymers and co-membrane polymers, a hydrophilic and oleophobic membrane can now be produced, for example, as a flat membrane or as a hollow fiber membrane.