EP3600634A1

EP3600634A1 - Filter for separating hydrophilic and hydrophobic fluids and method for the production thereof

Info

Publication number: EP3600634A1
Application number: EP18727213.3A
Authority: EP
Inventors: Benjamin Naier; Herwig Schottenberger; Rania Bakry; Gabriel PARTL
Original assignee: Universitaet Innsbruck
Current assignee: Hwk Kronbichler GmbH
Priority date: 2017-05-18
Filing date: 2018-05-17
Publication date: 2020-02-05
Also published as: WO2018211025A1; EP3403715A1; US20200139305A1

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.

Description

Filter for the separation of hydrophilic and hydrophobic fluids and process for its preparation

The invention relates to a filter for separating hydrophilic and hydrophobic fluids, wherein the filter comprises, consists of, or is coated with an oleophobic polymer, and wherein the filter exhibits hydrophilic and oleophobic properties. The invention further relates to a method for producing such a filter.

Currently, hydrophilic and hydrophobic fluids such as water and oil are usually separated from each other industrially mostly by means of water separators. Such apparatuses are usually large, expensive and not very mobile.

Filter membranes with hydrophilic and oleophobic coatings are also known from the prior art, with which also a separation of water and oil can take place. However, there are often problems with the technical solutions.

US 3,567,500 describes the use of hydrophilic and oleophobic materials based on fluoroamido-amino polymers. According to the state of knowledge However, the inventors of the present patent application could not enforce these approaches probably due to high production costs.

US 2015/136712 A1 discloses a composition comprising a hydrophilic and oleophobic co-polymer of an uncharged fluoro (meth) acrylate and a non-fluorinated betaine as co-monomers. Furthermore, membranes are described which have a coating of such a polymer in order to separate water and oil from each other. The linear fluorine chains can be mixed or applied directly with a membrane solution and thus come as a retrofit existing filters in question. However, the long-chain fluoroacrylates are limited in their solubility and the reaction requires the use of often expensive and toxic fluorine solvents. The synthesis of these polymers also requires the use of environmentally harmful surfactants. Another disadvantage is that when using fluoroacrylates, the separation performance depends very much on the chain length of the perfluoroalkyl groups. Due to legal regulations, only perfluoroalkyl chain lengths of at most C ₆ F ₁₃ may now be used in Europe and the USA, oil removal with these known polymers and co-polymers being possible only to a reduced extent at these fluorine side chain lengths.

US 9,186,631 B2 discloses a hydrophilic membrane with a contact angle for water below 5 ° and a contact angle for oil of over 90 ° C. This membrane consists of a polyethylene diacrylate, 1 / - /, 1 / - /, 2 / - /, 2 / - / - heptadecafluorodecyl polyhedral oligomeric silsesquioxane (F-POSS) and 2-hydroxy-2-methylpropiophenone. The membrane is mechanically stable due to the crosslinker and the technical characteristics are satisfactory. However, again, a perfluoroalkyl chain length of CsFi _{7 is} used and the applications are therefore limited due to the aforementioned legal regulations. In addition, polyhedral oligomeric siloxanes represent a very expensive class of substances. Another disadvantage is that the Membrane does not contain any ionic structural components, that is to say also no charge, and is therefore susceptible to microbial growth.

US 2014/0048478 A1 describes a coating for a membrane which contains hydrophilic ethylene glycol segments and oleophobic vinylidene fluoride segments and, by combining these segments, has a contact angle for water of 0 to 60 ° and a contact angle for oil of 40 ° to 100 °. A disadvantage of this technology is that the different membrane segments are often not intermixable with each other or only to a limited extent. In addition, no charged monomers or polymers can be used. This causes the membranes to be susceptible to possible contamination. Also, a cross-linked structure can be achieved with these membranes only in a very complex manner.

WO 2015/075446 A2 discloses the use of a dip-coating method for filters, in which alternately charged non-fluorine-containing polymers and fluorine-containing surfactants are applied. A disadvantage here is to observe that the fluorosurfactants adhere to one another only because of electrostatic interactions. Therefore, the coating is easily washable and is only durable for a short time. There is also the risk that fluorosurfactants are released into the environment.

US 2005/02871 11 A1 discloses the use of cationic fluorosurfactants in polymeric systems and their applications in various fields. However, to date, hydrophilic and oleophobic membranes with charged fluorosurfactants have been thought to require a mobile fluorine group. In this connection, for example, "Recent advances in oil-repellent surfaces", International Materials Reviews, 61: 2, 101-126, 2016, "Surface and solid-state properties of a fluorinated polyelectrolyte-surfactant complex", Langmuir, 1999, 15, 4867-4874, as well as "Nano-structured materials with low surface energies formed by polyelectrolytes and fluorinated amphiphiles (PEFA)", Polym. Int., 2000, 49, 636-644). The object of the invention is to provide a hydrophilic and oleophobic filter which is simple and inexpensive to produce and exhibits excellent separation properties of hydrophilic fluids.

Against this background, the invention relates to filters having hydrophilic and at the same time oleophobic properties which comprise, consist of or are coated with an oleophobic polymer. According to the present invention, at least a part of the repeating units of the oleophobic polymer is based on a fluorine-containing monomer which is an ionic organic molecule that has an ionic group and a crosslinkable group and a fluorine-containing group in a covalent bond. Because of the simultaneous hydrophilic and oleophobic properties, the filter according to the invention can be used, for example, in the separation of aqueous and oily phases of an emulsion. The aqueous phase may pass through the filter while the oily phase is retained. Furthermore, the filter according to the invention can also be used in the separation of gases or in the separation of gases and liquids with different polarities.

The filter can be a fluid-permeable and preferably layer-shaped body, for example a filter membrane, or a fluid-permeable and preferably encapsulated bed. The filter may comprise a substrate such as a membrane which is at least partially coated with a coating comprising or consisting of the oleophobic polymer. Examples of suitable substrates include textile materials such as nonwovens or webs of organic or inorganic fibers (eg silk, cotton, lyocell, polyamide or the like), paper, metal nets (eg of stainless steel or bronze), plastic membranes or porous metal or ceramic bodies such as glass frits. Organic fibers include, for example, polyolefin fibers. Porous metal or ceramic bodies include, for example, sintered bodies. Examples of suitable coatable materials for plastic membranes include polyurethanes, PVDF (polyvinylidene difluoride), PTFE (polytetrafluoroethylene), expanded PTFE, PSF (polysulfone), polyethersulfone, PAN (polyacrylonitrile), polypropylene, polyethylene, polyamide, polystyrene, polyethylene, metal nets, cellulose-based materials, and combinations it.

According to the invention, the filter comprises the oleophobic, partially fluorinated and ion-containing polymer, is made entirely of this or at least partially coated with this. For example, a granular material of a bed, the fibers of a nonwoven, embroidered fibers or a plastic membrane can be made of the described polymer. Furthermore, granular materials of a bed or each of the above-mentioned filter bodies may be at least partially coated with the described oleophobic, partially fluorinated and ion-containing polymer.

If the filter is a porous body such as a porous membrane, for example, the average pore size to achieve optimum separation between aqueous and oily phases may be between 0.001 and 1000 μιτι and preferably between 0.01 and 500 μιτι.

In one embodiment, the fluorine-containing group is a perfluorocarbon group. The perfluorinated hydrocarbon group is to be understood as meaning a hydrocarbon group in which all hydrogen atoms have been replaced by fluorine atoms. In one embodiment, the fluorine-containing functional group is a group of the type - (CF ₂ ) _n -F, where n is between 1 and 20 and is preferably 5, 6 or 7. The chain length of 5 to 7 is particularly advantageous because the oleophobic properties are already very pronounced in this chain length, but at the same time there is still a good environmental compatibility. Particularly preferred is the use of a perfluorohexyl group having the structural formula - (CF ₂ ) 6-F. Alternatively, fluoro ethers are also conceivable as fluorine-containing groups. These are preferably of the type (CF ₂ ) _n -O- (CF ₂ ) m, where n and m independently of one another can be between 1 and 6. Alternatively, fluorinated benzene derivatives are also conceivable, it being possible for 2 to 5 fluorine atoms or trifluoromethyl groups to be bonded to the aromatic.

In one embodiment, the crosslinkable group comprises a reactive double bond. Preference is given to a C = C double bond such as in particular a substituted or unsubstituted vinyl group. Also suitable in one embodiment are allyl groups, (meth) acrylate groups or (meth) acrylamide groups.

In one embodiment, the crosslinkable group comprises an isocyanate, an anhydride, an amine, an acid group, an azide, a diazonium salt or a hydroxyl group.

The crosslinkable group is reacted in the oleophobic polymer of the filter according to the invention and forms part of the covalent bond between adjacent repeat units. An unsubstituted vinyl group of the fluorine-containing monomer has in the polymer, for example, the incorporated partial structure of a divalent ethylene group.

In one embodiment, the ionic group is an ionic heterocyclic and especially heteroaromatic group.

In one embodiment, the charge is delocalized over several atoms of the ionic group.

In one embodiment, the ionic group or fluorine-containing monomer is positively charged overall. For example, it may be provided that the ionic group or the fluorine-containing monomer as a whole are simply positively charged.

In one embodiment, the ionic group is an ionic heterocyclic and especially heteroaromatic group at least one ring-forming nitrogen atom which assumes a positive charge by additional substitution. Examples include N, N-disubstituted imidazolium group, NN-disubstituted benzimidazolium group, N-substituted vinylpyridinium group or quaternary ammonium compound. Particularly preferred are N-alkylated groups such as N, N-dialkylated imidazolium groups.

The substituent on the nitrogen atom may be, for example, the crosslinkable or fluorinated group which is bonded directly or indirectly, i.e. by means of an intermediate, preferably aliphatic, spacer to the nitrogen atom.

In one embodiment, the ionic group is located between the crosslinkable and the fluorine-containing group. Preferably, the structure of the fluorine-containing monomer is such that the crosslinkable and fluorine-containing groups are located radially from the ionic group and preferably the ionic heterocycle.

In one embodiment, a spacer is arranged between the ionic and the fluorine-containing group and / or between the ionic and the crosslinkable group. The fluorine-containing or crosslinkable group in this embodiment is thus covalently bound to the ionic group by means of an intermediate spacer. Suitable spacers include uncharged and unfluorinated organyl groups. Preferred examples preferably include linear alkylene groups of 1 to 10, and preferably 1 to 5, more preferably 1, 2 or 3 carbon atoms. Especially preferred is ethylene.

In one embodiment, the spacer comprises an ether bridge (-O-) or thioether bridge (-S-). For example, the fluorine-containing group can be bonded to the spacer via an ether bridge. The spacer can be bonded to the ionic group via a thioether bridge, for example. In one embodiment, the fluorine-containing monomer has between 8 and 50, and preferably between 10 and 30, heavy atoms. In the present case, a heavy atom is understood to mean all atoms except hydrogen.

In one embodiment, the molar mass of the fluorine-containing monomer is between 100 and 3500 g / mol, preferably between 130 and 1000 g / mol.

In one embodiment, the fluorine-containing monomer is an ionic liquid.

In one embodiment, the fluorine-containing monomer comprises exactly one ionic, fluorine-containing, and crosslinkable group.

In one embodiment, the fluorine-containing monomer may also have a plurality of ionic groups and / or a plurality of fluorine-containing groups and / or crosslinkable groups. The fluorine-containing monomer preferably comprises at least two identical or different centers, each of which comprises a charged and preferably also a fluorine-containing group. The centers may be linked by a linker, which preferably connects the ionic groups of the two centers. The linkers may be such groups as described above as spacers.

In one embodiment, the functionalized monomer has an organosulfanyl group, which is preferably additionally substituted and represents an anionic group.

Suitable fluorine-containing cationic monomers include, for example, the compounds shown below:

Other suitable fluorine-containing monomers include the following molecules: Again, other suitable fluorine-containing anionic monomers include the following molecules:

In the formulas given above, Y represents a crosslinkable group as defined above, R _{f represents} a fluorine-containing group as defined above, and R represents a hydrogen or a C 1-6 alkane.

Preparation of these monomers can be carried out, for example, as described in Parti et al., "3- (1H, 1H, 2H, 2H-perfluorooctyl) -1-vinyl-4-imidazolines-2-thiones", lUCrData (2017) 2, x170648 described, done.

In one embodiment, the oleophobic polymer is a co-polymer and at least another portion of the repeat units is based on a hydrophilic co-monomer. The hydrophilic co-monomer has a polymerizable group and an ionic or uncharged hydrophilic group. These co-monomers can increase the hydrophilicity of the co-polymer. Charged such co-monomers can also improve the anti-fouling properties.

The additional co-monomer preferably has no fluorine-containing groups. This is preferable from an ecological point of view and, in the given embodiment, facilitates the coordination between hydrophilic and oleophobic properties of the coating. Examples of hydrophilic co-monomers include charged or uncharged (meth) acrylate or (meth) acrylamide monomers or

(Meth) Acrylamidmonomerderivate. Suitable examples of uncharged hydrophilic monomers include those having ethylene glycol or hydroxyl groups as side chains. Other examples include betainic monomers.

By using a hydrophilic co-monomer hydrophilic and oleophobic properties of the polymer and thus filter can be matched against each other. The oleophobic properties of the polymer or filter are generally due to the fluorine-containing groups of the fluorine-containing monomer. The higher the content of the fluorine-containing monomers in one of the present embodiments, the more oleophobic but also more hydrophobic the polymer is normally. The higher the content of the hydrophilic co-monomer in the present embodiment, the more hydrophilic the coating becomes. However, if the proportion of hydrophilic co-monomers becomes too large, the simultaneous oleophobic character is lost.

In one embodiment, the proportion of repeating units of the co-polymer based on the fluorine-containing monomer is between 0.1 and 50 mol%, preferably between 0.5 and 15 mol%, and more preferably between 1 and 10 mol .-%. In these areas, a sufficient, technically usable oleophobia is achieved and at the same time a too high fluorine concentration is avoided, which is desirable for economic and environmental reasons.

In one embodiment, the hydrophilic group is a polar or ionic group, for example, an acidic anion. Suitable examples include sulfonates or phosphonates.

In addition to the fluorinated monomer and preferably the hydrophilic co-monomer, the co-polymer may also be based on other co-monomers, for example unfunctionalized co-monomers with only one crosslinkable but no otherwise functionalized group, strongly oleophobic monomers having a crosslinkable and fluorine-containing functional group, but no charged functional group or crosslinking comonomer. Cross-linking co-monomers may have at least two crosslinkable but no otherwise functionalized groups. Instead of a crosslinkable group, a reactive group may also be present in order to be able to produce a preferably covalent bond to the surface of the substrate

Examples of potentially suitable additional comonomers include uncharged fluorine-containing monomers due to fluorine-containing (meth) acrylate monomers and (meth) acrylamide monomers, respectively. These co-monomers can increase the oleophobicity of the co-polymer. Preference may also be given to polymers, oligomers and prepolymers as co-constituents. These may be due to vinylidene difluoride, tetrafluoroethylene, vinyl fluoride, chlorotrifluoroethylene, ethylene-tetrafluoroethylene, perfluoro (ethylene-propylene) and perfluoroalkoxy compounds, as well as combinations of these as monomers.

Further examples of potentially suitable additional co-monomers include reactive and latent monomers, respectively, which are due to reactive or latent (meth) acrylate monomers, (meth) acrylamide monomers, allyl or vinyl monomers. These monomers can increase the adhesion of the polymer to various substrates. Co-monomers which comprise an isocyanate group, a blocked isocyanate group, a polymerizable trialkoxysilyl group, a polymerizable epoxy functionality or a plurality of double bonds may be preferred.

Further examples of potentially suitable additional co-monomers include hydrophobic monomers which are based on hydrophobic (meth) acrylate monomers or

(Meth) acrylamide monomers go back. Preferably, these monomers contain a branched or unbranched alkyl group. Further examples of potentially suitable additional co-monomers include (meth) acrylic acid and (meth) acrylic acid derivatives, including acrylic acid, methacrylic acid, 3-sulfopropyl acrylate, hydroxyethyl (meth) acrylate,

Lauryl (meth) acrylate, octadecyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, (poly) ethylene glycol (meth) acrylate.

Further examples of suitable additional monomers include (meth) acrylamide and (meth) acrylamide derivatives, including 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 2-acrylamido-2-methylpropanesulfonate, N, N-dimethylaminoethylacrylamide (DMAEAA), N, N- Dimethylaminopropylacrylamide (DMAPAA), trimethylammoniumethyl (meth) acrylate chloride, N-hydroxyethylacrylamide (HEAA), dimethylacrylamide (DMAA), N-isopropylacrylamide (NIPAM), diethylacrylamide (DEAA) and N-tert-butylacrylamide (t-BAA). In addition, urethane acrylate, epoxy acrylate and derivatives of the epoxy acrylate can be used.

Examples of suitable crosslinkable comonomers include methylene methyl bis (meth) acrylate, ethylenebis ethyl (meth) acrylate, bisglycidyl methacrylate, urethane dimethacrylate, hexanediol dimethacrylate,

Tetraethylene glycol dimethacrylate, (poly) ethylene glycol di (meth) acrylate, glycerol di (meth) acrylate, glycerol tri (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, dipentaerythritol hexaacrylate, dipentaerythritol penta- / hexaacrylate and

Trimethylolpropane ethoxylate triacrylate.

Further examples of potentially suitable additional co-monomers include uncharged fluoro (meth) acrylates. Examples include \ H, \ H, 2H, 2H-perfluorooctyl (meth) acrylate, pentafluoropropyl (meth) acrylate, and generally branched and unbranched 1H, 1H, 2H, 2H-perfluoroalkyl methacrylates, and 1- (1H, 1H, 2 / - /, 2 / - / - perfluorooctyl) -3-vinyl-1,3-dihydro-2H-imidazole-2-thione.

Further examples of potentially suitable additional comonomers include uncharged reactive monomers. Examples include glycidyl (meth) acrylate, trimethylvinylsilane, trimethoxyvinylsilane, triethoxyvinylsilane, triacetoxy (vinyl) silane, Tris (trimethylsiloxy) (vinyl) silane, 3- (trimethoxysilyl) propylnethacrylate, 3- (trimethoxysilyl) propyl acrylate, 3-isopropenyl-a, a-dimethylbenzyl isocyanate, 2-isocyanatoethyl (meth) acrylate, 2- [3,5-dimethylpyrazole) carboxyamino] ethyl (meth) acrylate, 1,1-bis (bisacryloyloxymethyl) ethyl isocyanate, and 2-methyl-2- (2-isocyanatoethoxy) ethyl ester. In one embodiment, the above isocyanates are protected from reaction with a blocking agent. Heat or catalyzers can be used to remove the blocking agents. As a result, the durability, the adhesion and the washing stability can be significantly improved in the production. Examples of preferred blocking agents include 2-butanone oxime, 3,5-dimethylpyrazole, ε-caprolactam, di-tert-butylamine and tert-butylbenzamine.

In one embodiment, it is provided that at least a portion of the additional monomers have a charge and preferably salts of 2-acrylamido-2-methylpropanesulfonic acid, salts of sulfopropyl (meth) acrylic acid, salts of (meth) acrylic acid, salts of [2- (methacryloyloxy ) ethyl] trimethylammonium compounds such as [2- (methacryloyloxy) ethyl] trimethylammonium chloride, (vinylbenzyl) benzyltrimethylammonium compounds, [3- (methacrylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxide betaine, diallyldi-methylammonium compounds, salts of maleic acid , Maleic acid esters and combinations thereof.

In one embodiment, it is contemplated that at least a portion of the additional monomers have additional functionality that can interact with a substrate, and preferably vinyl silanes, (meth) acryl silanes, glycidyl (meth) acrylate, isocyanates, blocked isocyanates, blocked and unblocked 3-isopropenyl-a, a-dimethylbenzyl isocyanate, and combinations of these.

In one embodiment, it is provided that at least some of the additional monomers have an additional functionality which is neutral and preferably styrene, urethane (meth) acrylates, ester (meth) acrylates, polyethylene (meth) acrylates, linear and branched alkyl (meth) acrylates and fluoro (meth) acrylates or combinations thereof.

As an alternative or supplement to cross-linking co-monomers, it may also be provided that at least some of the fluorine-containing monomers and / or the hydrophilic co-monomers have at least two crosslinkable groups.

The proportion of the repolymer units of the co-polymer, which are based on monomers or co-monomers having at least two crosslinkable groups, can in one embodiment be between 0.1 and 2 mol%.

To a certain extent, a higher degree of crosslinking can improve the resistance of the polymer and, when used as a coating, its adhesion to a substrate.

Cross-linking may also allow the creation of systems that are recyclable. It can be provided that the monomers having at least two crosslinkable groups comprise two different types of crosslinkable groups, one of these groups containing a physically or chemically cleavable bond, for example by temperature or hydrolysis.

The crosslinkable groups of the co-monomers may be formed as described in connection with the crosslinkable groups of the fluorine-containing monomers.

The co-polymer is preferably a random co-polymer with randomly distributed repeat units.

The filter also includes counterions corresponding to the ionic groups of the fluorinated and optionally hydrophilic monomers, which are, for example, halide anions or alkali metal cations can act. Examples of suitable anionic counterions include chloride, bromide, iodide, aryl sulfonate, alkyl sulfonate, perfluoroalkyl sulfonate, alkyl sulfate, sulfate, aryl phosphonate, alkyl phosphonate, monoalkyl phosphate, dialkyl phosphate, (di) hydrogen phosphate, phosphate, hexafluorophosphate, tetrafluoroborate, bicarbonate, carbonate, carbamate, alkyl carbonate, trifluoromethanesulfonate, Bis (trifluoromethylsulfonyl) imide, nonafiat, carboxylate, camphorsulfonate, vinylphosphonate, and combinations of these.

In addition to the oleophobic and hydrophilic properties for the separation of aqueous and oily phases, a further advantage of the filters according to the invention is that the ionic groups of the polymer inhibit the formation of a filter-blocking biofilm.

Due to the hydrophilic properties, it is also possible to wash the filter with water at any time.

In one embodiment, the filter or the polymer portion or the polymer coating of the filter additionally comprise micro- or nanoparticles in addition to the oleophobic polymer. These can serve to improve the scratch resistance and / or the hydrophobic and oleophobic properties of a coating resulting from the composition. Conductive particles can also be used, for example, to reduce the electrostatic charge or to dissipate frictional heat. Examples of suitable nanoparticles include silica particles, titania particles, alumina particles, zinc oxide particles, zirconia particles, silver particles, cellulose particles, carbon nanotubes, graphene, carbon particles, polytetrafluoroethylene (PTFE) particles, polyethylene particles , Polypropylene particles and combinations thereof.

In one embodiment, a filter according to the invention is used for the separation of hydrophilic and oleophobic components. The presence of pores is essential for the separation performance. The pore size is preferably at 0.001 μηη to 1000 μητι, preferably at 0.005 μηη to 500 μηη and more preferably at 0.01 to 250 μηη. The pores of a filter according to the invention may be distributed continuously or discontinuously.

A filter according to the invention is characterized in one embodiment by the fact that contact angles for water are less than 70 °, preferably less than 40 ° and particularly preferably less than 10 °. Preferably, the water may pass through the porous structure of the filter. The contact angle for hexadecane or diiodomethane can be above 50 °, preferably above 70 ° and particularly preferably above 90 °. Preferably, hydrophobic components do not pass through the porous structure.

Against the background mentioned above, the invention further relates to a method for producing a filter according to the invention comprising the step of providing a solution of the fluorine-containing monomer and optionally the other comonomers, with the step of applying this solution to a substrate, and with the step of Crosslinking of the monomers to form the polymer.

As a substrate, for example, the finished filter (for example, a finished flow, a finished PTFE membrane or a finished textile) are used. It is also conceivable that serve as a substrate starting materials for the production of the filter (for example, the fibers for the production of the web) or textile (the textile fibers or yarns).

Suitable methods of crosslinking include thermal processes, radiation, chemical curing or combinations thereof. For this purpose, UV-initiators, thermal radical initiators and / or chemical radical initiators such as peroxodisulfate salts are optionally added to the solution. There are also possible controlled free radical reactions and reversible deactivating radical polymerizations. These include atom-transfer-radical polymerization (ATPR), reversible deactivation polymerization, nitroxide mediated polymerization (NMP), reversible addition-fragmentation chain transfer (RAFT) or iodine transfer polymerization (ITP). In addition, direct radiation-curing processes, such as e-beam curing and polymerizations by means of gamma radiation are conceivable.

The ionic fluoromonomers are particularly flexible in the production of membranes for the separation of oil and water from a technical point of view.

In one application, the ionic fluoromonomers are brought to a porous surface with possible co-monomers in dissolved form, in solvents, in gaseous form, as ionic liquids or as eutectic, where they are directly cured.

In one embodiment, porogenic pores are produced in a polymer or co-polymer according to the invention, which results in the polymer or co-polymer matrix being able to be used directly as a membrane and no substrate being required.

In one application, the ionic fluoromonomers are polymerized with possible co-monomers or co-polymers in a liquid, preferably water. As a result, a polymer dispersion or copolymer dispersion is obtained. The polymer particles thus obtained in the dispersion have a particle size distribution of 30 nm to 500 μm, preferably between 50 nm and 50 μm, and particularly preferably between 90 nm and 500 nm.

In one embodiment, a described polymer or copolymer can be obtained as a solid. This solid can then be redissolved, thereby obtaining a membrane. The solvent can serve here as a porogen or can be used additional porogens. The preferred viscosity of the polymer solutions or co-polymer solutions for these applications is between 50 mPas and 10,000 mPas, preferably between 100 mPas and 5,000 mPas and particularly preferably between 200 mPas and 1,000 mPas at 20 ° C. The solvent content of the solution in the process according to the invention may generally be between 0 and 99% by weight, preferably between 50 and 99% by weight and more preferably between 70 and 99% by weight. The monomer content of the solution may be, for example, between 0.5 and 99% by weight, preferably 5 to 70% by weight, particularly preferably 10 to 40% by weight.

Furthermore, the invention relates to a method for producing a filter according to the invention, which comprises a step of providing a solution of the oleophobic polymer and optionally further polymeric or monomeric components, a step of applying this solution to a substrate and the step of chemical or physical curing of the Polymer solution, preferably a removal of the solvent comprises. The application of the solution can be carried out in the context of this method, for example by spray application or a dipping process.

A chemical hardening of the solution of the already crosslinked polymer can be carried out, for example, by an additional cross-linking of the polymer chains. For this purpose, the procedures and additives described above with the alternative method are conceivable.

Physical hardening can take place, for example, by simple drying.

In this process according to the invention, too, the solvent content of the solution may generally be for example between 0 and 99% by weight, preferably between 50 and 99% by weight and more preferably between 70 and 99% by weight. The polymer content of the solution may for example be between 0.5 and 99% by weight, preferably 5 to 70% by weight and more preferably 10 to 40% by weight. For a spray application or a dipping method, a viscosity of 1 mPas to 1, 000 mPas, in particular 2 mPas to 500 mPas and further, in particular 3 mPas to 200 mPas at 20 ° C is preferred.

The invention thus encompasses spraying methods as well as a direct coating by direct polymerization on a wide variety of substrates.

The invention further relates to a process for producing a filter according to the invention, which comprises the step of providing a solution of the oleophobic polymer and optionally further polymeric or monomeric constituents, and the step of precipitation or phase extrusion with an antisolvent. Thus, a fiber or membrane can be produced directly from a polymer solution or co-polymer solution by means of an antisolvent. The polymer solution preferably has a viscosity of from 200 mPas to 50,000 mPas, preferably from 500 mPas to 30,000 mPas and particularly preferably from 1,000 mPas to 10,000 mPas at 20 ° C.

In one embodiment, the solvent of both processes according to the invention may be water or a mixture of at least 30% by volume and preferably at least 50% by volume of water. In general, polar solvents such as water, ethanol or DMF may be suitable, from an ecological and economic point of view water or a solvent with the highest possible water content is to be preferred. The monomers used in the present invention may all be soluble in sufficient concentrations in pure water.

It can thus be stated that in one embodiment the invention comprises the co-polymerization of the fluorine-containing monomer with at least one hydrophilic co-monomer on a permeable substrate.

Generally, preferred methods of membrane fabrication include thermally-induced phase separation, non-solvent-induced phase separation, evaporation induced phase separation, vapor phase induced

Phase separation, coating of an existing porous structure, by polymerization and combinations of these methods.

Finally, the invention relates to a process for the separation of hydrophilic and hydrophobic fluids using a filter according to the invention. Filters according to the invention can generally be used for the separation of aqueous and oily phases. Exemplary applications include water treatment to the collection of spilled oil after oil spills. A removal of fluorine-containing surfactants from wastewater streams can be achieved with filters according to the invention.

In summary, it can be stated that the use of charged (ionic) fluoromonomers and fluoropolymers formed therefrom yields countless advantages over the prior art.

First, the charge of the monomers allows a much better solubility in polar solvents. Therefore, the use of only water or alcohols as a solvent is conceivable. This significantly minimizes the emission of volatile organic compounds (VOCs) and leads to much greener processes. The charged fluoromonomers and fluoropolymers themselves are salts which have a non-measurable vapor pressure and thus no intrinsic liquid.

Another advantage is that charged fluorine groups have a significantly better anti-fouling behavior than uncharged fluorine groups. Bacterial growth is one of the biggest problems in membrane technology. This can be handled more efficiently by the present invention.

Fluorosurfactant molecules are arranged in hydrophilic and fluorophilic segments. In addition, due to the ionic structure, the fluoro side chains are in a typical alkanes zig-zag arrangement and not in one for fluoride side chains usually typical helical arrangement in front. In addition, the molecules arrange themselves into hydrophilic and oleophobic segments. This can lead to better crystallinity of the fluorine side chains. In simple terms, this means that owing to the ionic structure of the fluoro groups, the oleophobicity of the systems can be increased. These effects allow the use of shorter fluoro chains with consistently high oleophobic properties.

Further details and advantages of the invention will become apparent from the figures and embodiments described below. In the figures show:

Figure 1: a comparison of the behavior of uncoated and coated with an oleophobic polymer substrates to aqueous and oily phases; and

2 shows a test setup for the separation of a water / oil mixture with a filter according to the invention.

Figure 1 shows a partially coated in accordance with the invention textile of cotton fibers. The line separates the two halves, with the left half uncoated and the right half coated. The points 1 a and 1 b show each sunflower oil, which was dyed red. The difference is clear. In the coated area, an oil drop forms with a contact angle significantly above 90 °, while in the uncoated area of the drops is absorbed. At points 1 c and 1 d, colored water drops are applied to both sides, which are absorbed by the textile in both cases. The recipe used is described in Example 6 below.

FIG. 2 shows a commercially available filter according to the invention coated by Macherey-Nagel. The filter used has the specification MN 616, a basis weight of 85g / m ² , a thickness of 0.2 mm and an average retention of 4-12 μιτι. First, the filter was wetted with a red colored hexadecane for 1 minute. The hexadecane stayed in the filter back and did not pass through the filter, as is the case with an uncoated filter. Subsequently, blue-colored water was added which easily passed through the filter. FIG. 2a shows how water and oil separate after the addition of water in the filter. Figure 2b shows how all water passes through the filter and the oil remains. This picture was taken after 2 hours. The recipe used is described in Example 1 below.

Example 1 :

Synthesis of a hydrophilic and oleophobic membrane:

The fabrics depicted in the following table were placed in a flask and stirred for 5 minutes. Subsequently, a filter paper (MN616, see above) was wetted with this monomer mixture using a pipette. In the course of reproduction experiments, other methods such as the dipping method and the spray method were also used successfully.

The impregnated paper was then irradiated with a UV LED lamp at a wavelength of about 365nm for 3 minutes. The filter obtained was now slightly yellowed at the coated sites (iodine / triiodide). In order to study more closely the properties of the obtained coating, the contact angles of water and hexadecane were measured. Water is the hydrophilic component and hexane represents the hydrophobic component. Each value was measured 3 times and the average recorded.

Results:

The hexadecane drop remained unchanged for 2 minutes as drops on the filter paper.

In addition, a separation of oil and water was made with the filter. The results are shown in FIG.

Example 2

The formulation described in Example 1 was also applied to a commercially available paper towel from Tork. This was also irradiated with a UV LED lamp for 3 minutes. The resulting coating was also yellow. In the case of this substrate, the contact angle was additionally measured with diiodomethane.

Example 3

This example is very similar to Example 1, but in this case the more hydrophilic chloride salt of the fluorinated cation was used. The same filter material and process parameters were used as in Example 1. Amount of [mg] substance

10 2,2-dimethoxy-2-phenylacetophenone

100 3- (1H, 1H, 2H, 2H-perfluorooctyl) -1-vinylimidazolium chloride

100 3,3 '- (hexane-1,6-diyl) bis (1-vinylimidazolium) dibromide

125 acetonitrile

125 propan-1-ol

75 water

Although the chloride salt of the fluorosurfactant has the significantly higher water solubility, the water droplet on the substrate was absorbed much slower. If the water drop in Example 1 was still submerged under 5 seconds, this was only observed after approx. 15 seconds. The contact angle of water measured at the beginning was 1 15 ° (± 4.5).

Example 4

The same formulation as in Example 3 was used to coat a cellulose fiber. Due to the many fibers that formed a very inhomogeneous surface, contact angle measurement was not exactly possible because the values fluctuated too much. However, it could be observed that water was absorbed after a few seconds while both hexadecane and diiodomethane remained on the cellulosic tissue for at least 2 minutes.

The following table shows the preparation of examples according to the invention for the UV curing of oleophobic and hydrophilic coatings: Amount in 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- ((1H, 1H, 2H, 2H-perfluorooctyl) thio) -1-vinylimidazolium chloride 200 200 100 100 100 100

Ethylene glycol dimethacrylate 500 100

Methanol 500 500 300 300 300 300

3,3 '- (hexane-1,6-diyl) bis (2 - ((1H, 1H, 2H, 2H-perfluorooctyl) thio) -1-vinylimidazole) dichloro 500

T methylpropane acrylate 100

Polyethyleneimine 100

Tetraethylene glycol dimethacrylate 100

Butyl methacrylate 100

A cotton fabric and a stainless steel mesh were coated with the formulation of Example 5 and cured for 30 minutes each with a UV lamp. Figure 1 shows a partially coated cotton textile with the recipe used.

With the formulation of Example 6, a cotton textile was coated. Subsequently, the textile was cured for 30 minutes with a UV lamp. The resulting textile had hydrophilic and oleophobic properties.

The formulation prepared in Example 7 was cured for 30 minutes with a UV lamp and showed a special behavior. On a cotton textile, the formulation behaved as a hydrophilic and oleophobic coating, on a glass carrier, however, this formulation showed in a remarkable way hydrophobic and oleophobic properties. This shows that the separation effects can be adapted to the respective surface texture and texture. Example 8 was also cured with a UV lamp for 30 minutes and then applied to a textile. This also showed hydrophilic and oleophobic properties.

Example 9 was applied as a textile coating. Example 10 was UV cured for both a textile and a glass support as a monolith for 30 minutes. These formulations showed hydrophilic and oleophobic properties both on glass and on the textile.

Examples 10 and 11

A commercial polyurethane foam with a pore size distribution between 1 μιτι and 500 μιτι was wetted with the two formulations and then cured in a glass jar for 4h at 65 ° C. The resulting, still very flexible membrane was hydrophilic and oleophobic and was suitable for the separation of water and olive oil. Thereafter, the foam was washed more often with water and acetone. Subsequently, water and oil were again successfully separated by means of the membrane. Example 12, 13 and 14

For formulations 12, 13 and 14, water and the monomers were initially charged. The solution was then stirred vigorously at 75 ° C. for 15 minutes and the azo radical initiator was added. Thereafter, the solution was kept at 75 ° C at full stirring speed for 1 h. Using a centrifuge, the resulting settling solid was removed and the fabric wetted with the supernatant. Subsequently, the textile was dried at 80 ° C for 3 minutes and then fixed at 150 ° C for 2 minutes. The resulting textiles were water permeable and oil repellent.

Example 15 Preparation of Polymer Solutions

For formulations 15 and 16, water and the monomers were initially charged. Subsequently, the solution was vigorously stirred at 75 ° C for 15 minutes and the azo radical initiator added. Thereafter, the solution was kept at 75 ° C at full stirring speed for 1 h. The stirring speed was then carefully reduced and stirring was continued for 2 hours at a very low stirring speed. A white solid was obtained in both experiments. This solid showed a molecular weight distribution of 60,000 Da to 450,000 Da.

The dried homopolymer from example 15 could be dissolved in excess of 220 g / l in Novec HFE 7100 IPA (3M). The viscosity obtained could be adjusted between 50 mPas and over 5,000 mPas at 20 ° C. Both films and direct membranes or fibers can be produced in this viscosity range.

The co-polymer of Example 16 was now partially soluble in organic solvents due to the increased proportion of butyl acrylate. In DMAC and DMF, the polymer was soluble above 20 g / L. This solubility thus allows incorporation into existing polymer membranes such as polysulfones, poly (vinylidene difluoride) or polyacrylonitrile. By choosing the co-polymers and co-membrane polymers, a hydrophilic and oleophobic membrane can now be produced, for example, as a flat membrane or hollow-fiber membrane.

Claims

claims

1 . A filter for separating hydrophilic from hydrophobic fluids, the filter comprising, consisting of, or coated with an oleophobic polymer, and wherein the filter exhibits hydrophilic and oleophobic properties characterized in that at least a portion of the repeat units of the oleophobic polymer is based on a fluorine-containing monomer which is an ionic organic molecule having an ionic group, a crosslinkable group and a fluorine-containing group.

2. Filter according to claim 1, characterized in that it is the filter is a porous filter layer and preferably filter membrane, wherein the pore size of the filter layer is preferably between 1 nm and 1 mm and more preferably between 10 nm and 0.5 mm.

3. Filter according to claim 2, characterized in that the filter layer is a coated substrate, wherein the substrate is preferably made of polytetrafluoroethylene, expanded polytetrafluoroethylene, polysulfone, polyethersulfone, polyethylene, polypropylene, polyesters, polyurethanes, polyvinylidene difluoride, polyamide, Polystyrene, polyacrylonitile, cellulose-based materials, a metal net or combinations thereof.

4. Filter according to one of the preceding claims, characterized in that it is the fluorine-containing group is a perfluorinated carbon group.

5. Filter according to one of the preceding claims, characterized in that the crosslinkable group comprises a reactive double bond.

6. Filter according to one of the preceding claims, characterized in that it is the ionic group is an ionically charged heterocyclic and in particular heteroaromatic group and / or that the charge is delocalized over several atoms of the ionic group.

7. Filter according to one of the preceding claims, characterized in that the ionic group or the fluorine-containing monomer are positively charged in total.

8. Filter according to one of the preceding claims, characterized in that a spacer is arranged between the ionic and the fluorine-containing group and / or between the ionic and the crosslinkable group.

9. Filter according to one of the preceding claims, characterized in that it is a co-polymer in the oleophobic polymer and at least one further part of the repetitive units to a hydrophilic co-polymer. Monomer having a polymerizable group and a hydrophilic group.

10. Filter according to claim 9, characterized in that the proportion of repetitive units of the co-polymer, which are based on the fluorine-containing monomer, between 0.1 and 50 mol .-%, preferably between 0.5 and 15 mol. -%, and more preferably between 1 and 5 mol .-%.

1 1. Filter according to claims 9 or 10, characterized in that a further part of the repeating units of the co-polymer is based on a crosslinking co-monomer which has at least two crosslinkable groups or at least one crosslinkable and one reactive group.

12. A method for producing a filter according to one of the preceding claims, characterized in that it comprises the following steps:

Providing a solution of the fluorine-containing monomer and optionally the other comonomers;

Application of this solution to a substrate; and

Crosslinking of the monomers to form the polymer.

13. A method for producing a filter according to any one of claims 1 to 1 1, characterized in that it comprises the following steps:

Providing a solution of the oleophobic polymer and optionally other polymeric or monomeric components; Application of this solution to a substrate; and

Remove the solvent.

14. A method for producing a filter according to any one of claims 1 to 1 1, characterized in that it comprises the following steps:

Providing a solution of the oleophobic polymer and optionally other polymeric or monomeric components;

Precipitation or phase extrusion with an antisolvent.

15. A process for the separation of hydrophilic and hydrophobic fluids using a filter according to one of claims 1 to 11.