PROCESSES FOR REDUCING THE FOULING OF SURFACES

Abstract

Process for reducing the fouling of a surface O, wherein an aqueous solution S of at least one polymer P comprising styrene and at least one ester E of (meth)acrylic acid and polyethylene oxide in a molar ratio of 0.05:1 to 50:1 is applied to said surface O.

Claims

1. A process for reducing fouling of a surface O, the process comprising: applying an aqueous solution S comprising at least one polymer P comprising styrene and at least one ester E of (meth)acrylic acid and polyethylene oxide in a molar ratio of 0.05:1 to 50:1 to said surface O, wherein said aqueous solution S comprises at least 50% by weight of water.

2. The process according to claim 1, wherein said surface O is a membrane M.

3. The process according to claim 1, wherein said at least one ester E has an average molar mass Mn of 300 to 10000 g/mol.

4. The process according to claim 1, wherein said at least one ester E has an average molar mass Mn of 800 to 3000 g/mol.

5. The process according to claim 1, wherein said polymer P has an average molar mass Mn of 5000 to 100,000 g/mol.

6. The process according to claim 1, wherein said polymer P is a statistical copolymer.

7. The process according to claim 1, wherein said aqueous solution S comprises 0.001 to 1% by weight of said at least one polymer P.

8. The process according to claim 1, wherein said at least one polymer P has been obtained in a solution polymerization.

9. The process according to claim 8, wherein said at least one polymer P has been obtained in a solution polymerization in a solvent comprising at least 50% by weight based on the solvent of at least one alcohol.

10. The process according to claim 1, wherein said at least one polymer P is applied to said surface O in intervals of 1 day to 24 months.

11. The process according to claim 2, wherein said membrane M is a RO, FO, NF, UF or MF membrane.

12. The process according to claim 1, wherein said process is used in treating industrial or municipal waste water, sea water, brackish water, fluvial water, surface water or drinking water, desalination of sea or brackish water, dialysis, plasmolysis or processing of food and beverages.

13. A polymer, comprising: styrene and at least one ester E of (meth)acrylic acid and polyethylene oxide in a molar ratio of 0.3:1 to 15:1, wherein said at least one ester E of (meth)acrylic acid and polyethylene oxide has an average molar mass Mn of 1500 to 10000 g/mol.

14. The polymer according to claim 13, wherein said polymer comprises styrene and said at least one ester E in a molar ratio of 0.5:1 to 2:1.

15. The polymer according to claim 13, wherein said polymer P has an average molar mass Mn of 5000 to 100,000 g/mol.

16. The polymer according to claim 13, wherein said polymer is obtained by a solution polymerization of styrene and said at least one ester E.

17. A polymer, comprising: styrene and at least one ester E of (meth)acrylic acid and polyethylene oxide in a molar ratio of 0.05:1 to 50:1, wherein said at least one ester E has an average molar mass Mn of 300 to 10000 g/mol and wherein said polymer P has been obtained by a solution polymerization.

18. The polymer according to claim 17, wherein said polymer is obtained by a solution polymerization in a solvent comprising at least 50% by weight based on the solvent of at least one alcohol.

19. A process for making the polymer according to claim 13, the process comprising: polymerizing styrene and said at least one ester E via a solution polymerization.

20. The process according to claim 19, wherein said solution polymerization is carried out in a solvent comprising at least 50% by weight based on the solvent of at least one alcohol.

21. A process for reducing fouling of a membrane, the process comprising: applying the polymer according to claim 13 to the membrane.

22. A membrane, comprising: on a surface of the membrane, a layer of at least one polymer P comprising styrene and at least one ester E of (meth)acrylic acid and polyethylene oxide in a molar ratio of 0.05:1 to 50:1.

23. The membrane according to claim 22, wherein said layer of at least one polymer P is a self-assembled monolayer.

Description

[0217] FIG. 1 shows Tapping-mode AFM material contrast images of the identical spot on a Nadir UP150 membrane before (A) and after (B) adsorptive coating with polymer X3. The coating procedure was carried out on flat sheet PES Nadir UP150 analogous to example 17.4.

[0218] Topography and phase shift images shown in FIG. 1 were measured using a MFP-3D Atomic Force Microscope (AFM). Images clearly show that a thin layer of a polymer was adsorbed to the porous membrane surface. The layer seems homogeneous, yet thin, as individual pores of the membrane could still be discerned.

Colloidal Probe AFM

[0219] Force measurements with the AFM were performed by the colloidal probe technique, where the sharp tip was replaced by a micrometer sized colloidal sphere to improve force sensitivity in nanomechanical measurements and allow for a quantitative analysis of the interaction force, as described in Butt et al., Surface Science Reports, 2005, 59, 1-152. By choosing an appropriate chemical modification of the colloidal probe specific interaction forces, could be measured.

[0220] Colloidal Probe measurements were performed on a MFP-3D AFM software version IGOR 6.11. For measurement colloidal probes made of 1) polystyrene, radius 3.3 m (Polybead Microspheres), 2) silica, radius 3.2 m (Silica Microspheres), 3) amino functionalized, radius 3.1 m (Polybead Amino Microspheres) were used. The probes were glued to tip-less cantilevers (HQ:CSC38 type A from Fa MikroMasch, k=0.09 N/m) using a 2K epoxy from UHU (UHU plus 300). The probes were dried and hardened for 24 h at room temperature. Force distance curves were performed at ramp speeds of 1 Hz in relative trigger mode (max load 5 nN) and a dwell time of Os. Nadir UP150 membrane samples were immersed for two hours in respective aqueous solutions prior to colloidal probe measurements. In the case of coated membranes, the samples were stored in a 0.1 wt % solution of X3 polymer in water for two hours. Samples were rinsed thoroughly with water to remove excess polymer prior to colloidal probe measurements.

[0221] Force-Distance Curves of an OH functionalized, a NH2 functionalized and polystyrene colloidal probes (3.2 m, 3.1 m and 3.3 m diameter respectively) were recorded in 1 mM NaCl solution at pH=7.3 on approach against a blank Nadir UP150 membrane and a Nadir UP150 coated with polymer X3. The partially negatively charged PES membrane surface attracts the amino functionalized probe on approach, as is evident in the observed snap-in (negative or attractive interaction force) at a distance of a few nanometers to the surface. On the other hand, no attractive interaction is observed in the case of the OH terminated, as well as the polystyrene probe. Upon coating with X3 polymer a steric penalty is added and all probes independent of their chemistry or partial surface charge experience a repulsive force upon approach, which is more pronounced for the hydrophilic probes than hydrophobic ones.

[0222] Besides an introduction of steric repulsion on approach, the Sty:PEGMA coating also reduces the adhesiveness.

[0223] The cumulative distribution function for adhesion of a NH2 functionalized and a polystyrene colloidal probe were recorded in 1 mM NaCl solution at pH=7.3 against a blank Nadir UP150 membrane and a Nadir UP150 membrane coated with polymer X3.

[0224] The cumulative distribution function for adhesion of a NH2 functionalized colloidal probe, representing a hydrophilic moiety, on a blank Nadir UP150 membrane is very broad ranging from a few nN/m to 4.5 mN/m, with a variable slope. d100.1 mN/m, d500.6 mN/m and d903 mN/m. This curve is dramatically shifted towards lower adhesion reaching 100% already at 0.1 mN/m once the Sty:PEGMA coating is applied.

[0225] This implies that both the modes of interaction, which is indicative of a uniform functionalization of the Nadir UP150 membrane, as well as the magnitude of interaction or adhesiveness, are dramatically reduced. The polystyrene probe which serves as an example of a hydrophobic moiety adheres less strongly to the native Nadir UP150 membrane but still sticks (100% reached at 0.5 mN/m). Further, after coating the Nadir UP150 membrane with polymer X3 adhesion of hydrophobic moieties of the polystyrene probe is strongly reduced (100% reached at <0.1 mN/m).