WO2014016347A1

WO2014016347A1 - Nanofiltration membrane with a layer of polymer and oxide particles

Info

Publication number: WO2014016347A1
Application number: PCT/EP2013/065637
Authority: WO
Inventors: Martin Mechelhoff; Thomas FRÜH; Christopher Kohl; Udo Schmidt; Georg KUNZENDORF
Original assignee: Lanxess Deutschland Gmbh
Priority date: 2012-07-25
Filing date: 2013-07-24
Publication date: 2014-01-30

Abstract

The invention relates to a nanofiltration membrane with a porous support membrane, the surface of the support membrane being coated with rubber-like polymer particles, produced by emulsion polymerisation and having an average particle diameter of less than 70 nm, preferably between 30 and 60 nm, particularly preferably between 40 and 50 nm and having at least one nanoparticulate oxide from the series Fe₂O3, Fe3O4, Fe(OOH), ΤiΟ2 and SiO2. The rubber-like polymer particles are obtained from monomers which contain at least one conjugated diene as a functional group.

Description

NANOFILTRATION MEMBRANE WITH A LAYER OF POLYMER AND

oxide particles

The invention relates to a nanofiltration membrane, a process for the preparation of this membrane and their use.

In the chemical industry, food industry, beverage industry, electronics industry and in the pharmaceutical industry, membranes are used for the separation of solid-liquid mixtures and liquids. In terms of environmental technology, these are also used in the purification of wastewater and the production of drinking water.

Various membrane separation processes are known from the prior art. These include microfiltration, ultrafiltration and nanofiltration, as well as reverse osmosis. These methods are to be assigned to the mechanical separation processes. The separation mechanisms are caused by different membrane structures. They separate by means of membrane pores whose diameters are smaller than those of the particles to be separated.

Another important mechanism in the separation with nanofiltration and reverse osmosis membranes are, in addition to steric effects, the electrostatic interaction of ions in solution or partially dissociated hydrocarbons with corresponding charged groups on the surface of a membrane in aqueous solution. This interaction allows a separation of two substances with a similar particle radius, but different charge or valency. Likewise, separation may occur with membranes having correspondingly small pores, e.g. for nanofiltration or reverse osmosis, based on the different diffusion tendency in the permeation through the membrane of the substances present in a solution.

Known processes for the treatment of liquids under pressure are microfiltration, ultrafiltration and nanofiltration. The pore sizes of the nano-, ultra- and microfiltration membranes are about 0.001 μm to 10.0 μm. For the characterization of membranes, the retention R with respect to a substance is usually used.

R = wfFeed - wfPermeaf) x 100 [%]

w (feed) where w denotes the mass fraction of any substance. The retention describes the percentage of a separated substance in the permeate (in Latin "permeare"), based on the concentration in the feed, and depends not only on the temperature but also on the transmembrane pressure or flow and the concentration of the starting solution. "

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The retentate (Latin "retenere" = retain) contains the increased compared to the feed concentration of the substance to be separated.

This demonstrates the difficulty in assessing the separation properties of a membrane. A rough classification of the membranes is often given by the molecular cut-off (cut-off) along with the flow. This separation limit is equivalent to the molecular weight for which the membrane has a retention of at least 90% and can be very different, especially in the field of nanofiltration depending on the molecular structure of the substances to be separated. The cut-off of nanofiltration membranes is usually <1500 g / mol. Ultrafiltration membranes usually have a cut-off of <about 150 000 g / mol.

In addition to ceramic membranes which have a long service life due to their stability against organic compounds, acids or alkalis, it is above all membranes based on organic polymers which are used for separations at the molecular level, in particular for the purification of liquids. In particular, in the extraction of drinking water from seawater, river water or even wastewater by reverse osmosis and in product processing increasingly ultra and nanofiltration or reverse osmosis membranes are used.

In order to reduce the investment and operating costs of a membrane system, the highest possible flow is sought while at the same time at least equivalent retention of the membrane. This can e.g. be achieved by a hydrophilization of the membrane material. Methods for

Hydrophilization, in addition to the corresponding chemical modification of the actual polymer material, also includes the addition of hydrophilic additives which are incorporated as uniformly as possible into the polymer matrix during membrane production.

CJ. Kurth et al, JDA Journal, Third Quarter 2010, 26-31, Membrane Systems, therefore describe the use of zeolite nanoparticles in thin-film nanocomposite membranes (TFNs)

Increase in the flow of Brackish Water Reverse Osmosis Membrane (BWRO) or Seawater Reverse Osmosis Membrane (SWRO) (Seawater = Brackish water).

EMV Hoek et al, Desalination 283 (2011) 89-99 describe the modification of ultrafiltration membranes with inorganic particles, in particular Cu, Ag, and zeolites, for the preparation of mixed-matrix membranes. In particular, the use of zeolites has been reported to improve flow. Chan Hyun Lee et al, Journal of Membrane Science, 392-393 (2012). 157-166 describe the use of hydrophilic SiC nanoparticles in poly (arylene ether sulfone) copolymer membranes, which did not lead to a significant improvement of the flow, but to an increased salt retention. Other membranes comprising a support membrane and a release active polymer coating with inorganic and organic particles for use as a separation membrane in batteries are known from US 2010/206804. CN 101824118 A discloses release-active polymer coatings. Further composite membranes are known from EP 1254697 and EP 071 1199 Bl. A disadvantage of these membranes is further that there is no sufficient stability of the membranes under extreme pH values and that a satisfactory flow can not be achieved.

The use of ZnO nanoparticles in mixed-matrix polyethersulfone (PES) membranes is described by S. Balta et al., Journal of Membrane Science 389 (2012) 155-161.

In addition, one major problem with all known membrane synthesis methods is to control the adjustment of the pore size and the pore shape of the separation-active layer exactly and uniformly and thus to achieve a very narrow pore size distribution.

Polymeric membranes of a wide variety of polymers are available at relatively low cost for wide pH ranges and many applications, but are mostly not resistant to organic solvents as well as very high and / or very low pHs. Also, a permanent temperature resistance at over 80 ° C is rarely given. While there are many approaches to improve these properties on polymer membranes, one of the above is often one of the above.

Requirements not met. In addition, most polymers are plastically deformable at higher temperatures. This causes compaction of the entire membrane when operated under pressure at higher temperatures. The compaction leads to complete compression of the pore structure of a membrane and thus to a large increase in the filtration resistance. The flow drop is thus induced. Another disadvantage of the usual

Polymeric materials is the poor resistance to organic solvents or oils and the plasticizing effect of the oils on the polymers. As a result, the separation capacity of the membranes is impaired.

Membrane technology plays an important role in the purification of liquid mixtures. In particular, in the extraction of drinking water from seawater by means of reverse osmosis and in product processing increasingly ultra and nanofiltration or reverse osmosis membranes are used.

In membrane processes dilute solutions are usually concentrated and separated organic solvents, water or salt solutions. Here are either recyclables or _Λ

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Pollutants obtained in more concentrated and possibly lower-salt solutions, which can be cost-effective subsequent storage, transport, disposal and processing. In particular, in wastewater treatment, it is the goal of the membrane treatment to recover the largest part of the volume as permeate in a not or only slightly loaded form. The concentrated retentate can with less effort with respect to still existing

Reclaimed recyclables or disposed of in this concentrated form, for example by incineration, cheaper.

The field of membrane processes involves very different processes. Accordingly, different membranes and their technical designs are available. Technically relevant membrane separation processes are predominantly operated as crossflow filtrations. High shear stresses due to high flow velocities and special module constructions are designed to minimize membrane contamination and reduce concentration polarization.

Commercially available nanofiltration membranes are composite membranes prepared by interfacial condensation, such as described in US 5,049,167. However, these known membranes can be prepared only very expensive and only in compliance with costly safety measures, since as starting materials z. As carcinogenic diamines and highly reactive acrylic chlorides are used. Such membranes can be configured in many ways, for example as flat film modules, cassette modules, spiral wound modules or hollow fiber modules.

Furthermore, commercial filtration membranes can usually be used only at process temperatures up to about 80 ° C.

It is therefore an object of the present invention to provide a high-performance nanofiltration membrane which has high thermal stability, good stability in organic and inorganic solvents and at high and low pH values, and also good

Separation properties based on a suitable surface modification and increased flow of water has. Another object of the invention is also to provide a method by which it is possible to produce defined pore sizes for the respective membranes. It is known in the art that polymer particles on a porous substrate having a broader pore size distribution can be deposited to obtain a composite membrane having a narrower pore size distribution. The voids between the particles form pores with which separation from a liquid can be performed. The composite membranes obtained in this way can be used, for example, as ultrafiltration and micro-membranes. filtration membranes are used. To achieve the object, therefore, a nanofiltration membrane of the aforementioned type is provided, wherein the surface of the support membrane produced by emulsion rubbery polymer particles having a mean particle diameter <70 nm, preferably between 30 to 65 nm, more preferably between 40 to 50 nm and with nanoparticles at least an oxide selected from Fe ₂ O ₃ , FesO i, Fe (OOH), TiO ₂ , and SiO ₂ , and both rubbery polymer particles and oxide nanoparticles form the release active layer and the rubbery polymers are prepared from monomers; which contain as functional group at least one conjugated diene. It is here to distinguish between the filtration property of a membrane, characterized for example by the cut-off, and the structure of the filtration membrane.

Separation, separation properties, separation behavior are used as synonyms. The separation effect is with the help of 0. g. Cut-off defined.

Due to their size, the rubbery ones prepared by emulsion polymerization and to be used in the release active layer besides the oxide nanoparticles

Polymer particles also nanoparticles.

The use of emulsion polymerized rubbery polymer particles having an average particle diameter <70 nm, preferably between 30 to 65 nm, more preferably between 40 and 50 nm, offers numerous advantages over other polymer particles, since the chemical and physical properties of the rubbery polymer particles, such as

Particle size, particle morphology, swelling behavior, hardness, dimensional stability, and surface energy can be adjusted. This is done on the one hand by the manufacturing process, in particular by the polymerization process, as well as by the selection of suitable base monomers and on the other hand by the selection of suitable functional groups whose concentration and settlement area in the polymer particles can be selectively adjusted or tailored within wide limits.

The release-active layer is thus the rubber-like polymer particles produced by emulsion polymerization with a mean particle diameter <70 nm, preferably between 30 to 65 nm, more preferably between 40 to 50 nm, layer also referred to as polymer layer, the nanofiltration membrane according to the invention, which moreover at least one Contains oxide in the form of nanoparticles.

Emulsion polymerization is understood to mean, in particular, a process which is known per se, in which water is usually used as the reaction medium, in which the monomers used are in the presence or absence of emulsifiers and free-radical-forming substances with formation _r

Polymerization of mostly aqueous polymer latexes (see, for example, Römpp Lexikon der Chemie, Volume 2, 10th Edition 1997; PA Lovell, MS El-Aasser, Emulsion Polymerization and Emulsion Polymers, John Wiley & Sons, ISBN: 0 471 96746 7; H. Gerrens, Fortschr. Hochpolym. Forsch. 1, 234 (1959)). In contrast to the suspension or dispersion polymerization, the emulsion polymerization generally gives finer particles which allow a smaller gusset diameter and thus smaller pore sizes in the separation-active layer. Particles of size less than 500 nm are generally not accessible by suspension or dispersion polymerization and therefore these particles are generally unsuitable for the purposes of the present invention. Surprisingly, it has now been found that the flow through nanofiltration membranes can be considerably increased if the surface of the supporting membrane of a nanofiltration membrane is coated with rubbery polymer particles having an average particle diameter of <70 nm and with nanoparticles of at least one oxide produced by emulsion polymerization and both rubber-like polymer particles and oxide particles. Nanoparticles form the separation-active layer.

The choice of monomers sets the glass transition temperature and the glass transition width of the rubbery polymer particles. The determination of the glass transition temperature (Tg) and the width of the glass transition (ATg) of the rubbery polymer particles is carried out by differential scanning calorimetry (DSC), preferably as described below. For this purpose, two cooling / heating cycles are carried out for the determination of Tg and ATg. Tg and ATg are determined in the second heating cycle. For the determinations, approximately 10-12 mg of the selected polymer particle is placed in a Perkin-Elmer DSC sample container (standard aluminum pan). The first DSC cycle is carried out by first cooling the sample to -100 ° C with liquid nitrogen and then heating to + 150 ° C at a rate of 20K / min. The second DSC cycle is started by immediately cooling the sample as soon as a sample temperature of + 150 ° C is reached. In the second heating cycle, the sample is again heated to + 150 ° C as in the first cycle. The heating rate in the second cycle is again 20K / min. Tg and ATg are determined graphically on the DSC curve of the second heating process. For this purpose, three straight lines are applied to the DSC curve. The 1st straight line is applied to the curve part of the DSC curve below Tg, the 2nd straight line to the curve branch with inflection point passing through Tg and the 3rd straight line to the curve branch of the DSC curve above Tg. In this way, three straight lines with two intersections are obtained. Both intersections are each characterized by a characteristic temperature. The glass transition temperature Tg is obtained as the mean value of these two temperatures and the width of the glass transition ATg is obtained from the difference between the two temperatures. Preferably, the rubbery polymer particles have a glass transition temperature (Tg) of -85 ° C to 150 ° C, preferably -75 ° C to 110 ° C, more preferably -70 ° C to 90 ° C on.

The width of the glass transition is preferably greater than 5 ° C., more preferably greater than 10 ° C., in the case of the rubbery polymer particles used according to the invention. Rubbery polymer particles according to the invention are prepared from monomers which contain at least one conjugated diene as the functional group.

According to the invention, preference is given to using monomers or monomer combinations selected from the series consisting of 1,3-butadiene, isoprene, 2-chlorobutadiene and 2,3-dichlorobutadiene.

Particular preference is given to monomers or monomer combinations of the series 1,3-butadiene, isoprene, chloroprene and 2,3-dichlorobutadiene.

According to the invention (meth) denotes both the respective acrylic compound and the respective methacrylic compound.

According to the invention, from 1 to 80% by weight, preferably from 1 to 60% by weight, more preferably from 1 to 40% by weight, even more preferably from 1 to 30% by weight, of the stated monomers are used for the preparation of the rubbery polymer particles.

In addition to the monomers having at least one conjugated diene functionality, other monomers from the series vinyl acetate, styrene or derivatives thereof, acrylonitrile, tetrafluoroethylene, vinylidene fluoride, hexafluoropropene, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (for the preparation of the rubbery polymer particles meth) acrylate, glycidyl (meth) acrylate, acrylic acid, methacrylic acid, diacetoneacrylamide, double bond-containing hydroxy, epoxy, carboxy or keto compounds.

Particular preference is given to monomers or monomer combinations of the series acrylonitrile, styrene, α-methylstyrene, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,

Hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, acrylic acid, methacrylic acid, diacetoneacrylamide, tetrafluoroethylene, vinylidene fluoride and hexafluoropropene.

The rubbery polymer particles may be crosslinked or uncrosslinked. The rubbery polymer particles may in particular be those based on homopolymers or random copolymers. The terms homopolymers and random copolymers are known to the person skilled in the art and are explained, for example, by Vollmert, Polymer Chemistry, Springer 1973. The following may be used in particular as the polymer base of the rubbery, crosslinked or uncrosslinked rubbery polymer particles containing functional groups:

BR: polybutadiene, ABR:

IR: polyisoprene,

SBR: styrene-butadiene random copolymers having styrene contents of 1-60, preferably 5-50 wt%, FKM: fluororubber,

ACM: acrylate rubber,

NBR: polybutadiene-acrylonitrile copolymers having acrylonitrile contents of 5-60, preferably 10-60, weight percent,

CR: polychloroprene EAM: ethylene / acrylate copolymers,

EVM: ethylene / vinyl acetate copolymers.

Further preferred rubbery polymer particles are thermoplastic and those based on methacrylates, in particular methyl methacrylate, styrene, alpha-methylstyrene and acrylonitrile.

The rubbery polymer particles preferably have an approximately spherical geometry.

The rubbery polymer particles used according to the invention have an average particle diameter of less than 70 nm, preferably between 30 and 65 nm, particularly preferably between 40 and 50 nm.

The average particle diameter is determined by ultracentrifugation with the aqueous latex of the rubbery polymer particles from the emulsion polymerization. The method gives a mean value for the particle diameter taking into account any agglomerates. (HG Müller (1996) Colloid Polymer Science 267: 1113-1116 and W. Scholtan, H. Lange (1972) Kolloid-Z and Z. Polymere 250: 782). Ultracentrifugation has the advantage of characterizing the total particle size distribution and calculating various means such as number average and weight average from the distribution curve. The average diameter data used according to the invention relate to the weight average. Diameter data such as dio, d ₅ o and dgo can be used. These data mean that 10, 50 or 80% by weight of the particles have a diameter which is smaller than the corresponding numerical value in% by weight. The diameter determination by means of dynamic light scattering is carried out on the latex. Common are lasers operating at 633 nm (red) and 532 nm (green). Dynamic light scattering gives an average of the particle size distribution curve. The average diameter data used according to the invention relate to this mean value. The rubbery polymer particles are prepared by emulsion polymerization, wherein the particle size is adjusted in a wide diameter range by varying the starting materials and emulsifier concentration, initiator concentration, liquor ratio of organic to aqueous phase, ratio of hydrophilic to hydrophobic monomers, amount of crosslinking monomer, polymerization temperature, etc. After polymerization, the latices are treated by vacuum distillation or by stripping with superheated steam to separate volatile components, especially unreacted monomers.

Further processing of the rubbery polymer particles thus prepared, in particular by coagulation processes, can be dispensed with. The rubber-like emulsion polymerization prepared according to the invention

Polymer particles are at least partially crosslinked in a preferred embodiment.

The crosslinking of the rubbery polymer particles prepared by emulsion polymerization is preferably carried out by the addition of polyfunctional monomers in the polymerization, more preferably by the addition of compounds having at least two, preferably 2 to 4 copolymerizable C = C double bonds, in particular by adding at least one compound of the series Diisopropenylbenzol , Divinylbenzene, divinyl ether, divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N, N'-m-phenylene maleimide, 2,4-tolylene bis (maleimide), triallyl trimellitate, glycidyl methacrylate, acrylates and methacrylates of polyvalent, preferably 2- to 4-valent C 2 to C 10 alcohols, in particular ethylene glycol, 1,2-propanediol, butanediol, hexanediol, polyethylene glycol having 2 to 20, preferably 2 to 8 oxyethylene units, neopentyl glycol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sorbitol and also unsaturated polyesters from aliphatic di- and polyol and maleic acid, fumaric acid, and / or itaconic acid.

Crosslinking of the rubbery polymer particles may be achieved directly during emulsion polymerization, such as by copolymerization with crosslinking multifunctional compounds or by subsequent crosslinking as described below. Direct crosslinking during emulsion polymerization is preferred. Preferred multifunctional comonomers are compounds having at least two, preferably 2 to 4, copolymerizable C =C double bonds, in particular Diisopropenylbenzene, divinylbenzene, divinyl ether, divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N, N'-m-phenylene maleimide, 2,4-tolylene bis (maleimide) and / or triallyl trimellitate. In addition, the acrylates and methacrylates of aliphatic amines, epoxides and polyhydric, preferably 2- to 4-valent C 2 to C 10 alcohols, such as ethylene glycol, 1,2-propanediol, butanediol, hexanediol, polyethylene glycol having from 2 to 20, preferably 2 to 8 oxyethylene units, neopentyl glycol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sorbitol with unsaturated polyesters of aliphatic di- and polyols and maleic acid, fumaric acid, and / or itaconic acid.

The crosslinking during the emulsion polymerization can also be carried out by continuing the polymerization up to high conversions or in the monomer feed process by polymerization with high internal conversions. Another possibility is to carry out the emulsion polymerization in the absence of regulators.

For the crosslinking of the uncrosslinked or slightly crosslinked rubbery polymer particles following the emulsion polymerization, it is best to use the latices obtained in the emulsion polymerization.

Suitable crosslinking chemicals in this case are organic peroxides, in particular dicumyl peroxide, t-butylcumyl peroxide, bis (t-butyl-peroxy-isopropyl) benzene, di-t-butyl peroxide, 2,5-ditmethylhexane-2,5-dihydroperoxide, 2,5-dimethylhexine-3,2,5-dihydroperoxide, dibenzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, t-butyl perbenzoate and organic azo compounds, in particular azo-bis-isobutyronitrile and azo-bis-cyclohexanenitrile and di- and Polymercaptoverbindungen, in particular dimercaptoethane, 1,6-dimercaptohexane, 1,3,5-trimercaptotriazine and mercapto-terminated polysulfide rubbers, in particular mercapto-terminated reaction products of bis-chloroethyl formal with sodium polysulfide.

The optimum temperature for carrying out the postcrosslinking is naturally dependent on the reactivity of the crosslinker and can be carried out at temperatures from room temperature - about 23 ° C - to about 180 ° C optionally under elevated pressure (see Houben- Weyl, Methods of the organic Chemistry, 4th Edition, Volume 14/2, page 848). Particularly preferred crosslinking agents are peroxides.

The crosslinking of rubbers containing C =C double bonds to give rubbery polymer particles to be used according to the invention can also be described in dispersion or emulsion with simultaneous, partial or even complete hydrogenation of the C =C double bond by hydrazine as described in US Pat. No. 5,302,696 or US Pat. No. 5,442,009 or other hydrogenating agents, for example Organometallhydridkomplexe done. Within the scope of the present invention the degree of crosslinking is defined by the swelling index [dimensionless] and the gel content [wt%].

Before, during or after postcrosslinking, an agglomeration of particles may possibly be carried out. The rubber-like polymer particles which are at least partially crosslinked in a preferred embodiment according to the invention therefore have insoluble fractions (gel content) in toluene at 23 ° C. of at least about 50% by weight, preferably at least about 80% by weight, particularly preferably 90% by weight. more preferably at least about 98% by weight. The insoluble in toluene content is determined in toluene at 23 ° C. Here, 250 mg of the rubbery polymer particles are swollen in 25 ml of toluene for 24 hours with shaking at 23 ° C.

After centrifugation at 20,000 rpm, the insoluble fraction is separated and dried. The gel content results from the quotient of the dried residue and the weight and is given in percent by weight.

The rubber-like polymer particles which are at least partially crosslinked in a preferred embodiment therefore also have a swelling index of less than about 80, more preferably less than 60, even more preferably less than 40, in toluene at 23 ° C. In particular, the swelling indices of the rubbery polymer particles (Qi) are between 1 and 20, more preferably between 1 and 10. The swelling index is calculated from the weight of the solvent-containing rubbery polymer particles swollen in toluene at 23 ° C for 24 hours (after centrifugation at 20,000 rpm) and calculated on the weight of the dry rubbery polymer particles:

Qi = wet weight of the polymer particles / dry weight of the rubbery polymer particles.

To determine the swelling index, 250 mg of the rubbery polymer particles are allowed to swell in 25 ml of toluene with shaking for 24 hours. The gel is centrifuged off and weighed and then dried at 70 ° C to constant weight and weighed again.

According to the invention, the release-active layer preferably consists of at least one monolayer of the rubber-like polymer particles to be produced by emulsion polymerization and of at least one oxide likewise in the form of nanoparticles, ie at least one oxide whose particle size is typically in the range from 1 to 100 nanometers.

Nanoparticulate oxides preferred according to the invention are those of the elements Al, Si, Ca, Fe, Mn, Cr, Ti, V, Zn, Zr, Sn. "

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Particular preference is given to using nanoparticulate oxides of the elements Fe, Al, Zn, Ti, Zr or Si. Very particular preference is given to Fe ₂ O ₃ , Fe (OOH), Al ₂ O ₃ , ZnO, TIO ₂ , ZrO ₂ or SIO ₂ . Even more preferred is S1O _second

The nanoparticulate oxides are randomly distributed in the separating active layer. The content of nanoparticulate oxides in the separation-active layer is preferably 0.1 to 75% by weight, more preferably 0.5 to 60% by weight, most preferably 1 to 50% by weight.

The application / incorporation of the nanoparticulate oxides on the support membrane or in the separation-active layer is preferably carried out by the mixing of oxides with the suspension of the rubbery polymer particles and the subsequent application of the mixture as a layer on a porous support membrane.

ZnO, Al ₂ O ₃ and ZrO ₂ nanoparticles which are suitable according to the invention are obtainable, for example, from Sigma-Aldrich (St. Louis, MO). Nanoparticles of S1O ₂ are available as Aerosil® 380 from Evonik Industries AG, Dusseldorf. Nanoparticulate, Ti0 ₂ is available from Kronos Titan (Leverkusen).

Preferably, the supporting membrane of the nanofluid membrane consists of an inorganic or organic material.

Moreover, it is advantageous that the porous support membrane is chemically and / or mechanically stable. It should be pH-stable and also in organic solvents, such as aldehydes, ketones, monohydric and polyhydric alcohols, benzene derivatives, halogenated hydrocarbons, ethers, esters, carboxylic acids, cyclic hydrocarbons, amines, amides, lactams, lactones, sulfoxides, Alkanes, alkenes.

Preferably, a support membrane is selected which is chemically stable in the following solvents: acetone, toluene, benzene, water, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, N-ethylpyrrolidone, pyridine, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentane , Hexane, heptane, octane, nonane, decane, methyl ethyl ketone, diethyl ether, dichloromethane, tetrachloroethane, carbon tetrachloride, methyl tert-butyl ether,

Chlorobenzene, dichlorobenzene, trichlorobenzene, nitrobenzene, ethyl acetate, cyclohexane.

It has been found that the nanofluid membrane according to the invention is stable, in particular also in the pH range of 10 to 16 and / or in the pH range of 2 to 4.

For the application of the nanofluid membrane according to the invention, it is also useful that the support membrane consists of a material which is thermally stable both at room temperature and in typical application process temperatures. A temperature stability of 50 to 200 ° C, preferably between 70 and 150 ° C and 80 to 120 ° C is also conceivable. As an inorganic, permeable supporting membrane preferably micro-glass fiber fleeces, metal fleeces, dense glass fiber fabric or metal fabric, but also ceramic or carbon fiber nonwovens or fabrics are used. The skilled person will appreciate that all other known, preferably flexible, provided with open pores or openings in the appropriate size materials can be used as support membranes. Also ceramic

Composite materials can be used, in particular inorganic support materials of an oxide selected from Al ₂ O ₃ , titanium oxide, zirconium oxide or silicon oxide. Also preferably, the inorganic support membrane comprises a material selected from ceramic, SiC, S1 ₃ N ₄ , carbon, glass, metal or semimetal. Further, organic polymer materials having sufficient chemical and thermal resistance can be used as the supporting membrane, particularly polyimide, polytetrafluoroethylene, polyvinylidene fluoride, polyetherimide, polyetherketone, polyetheretherketone, polyethersulfone, polysulfone, polybenzimidazole, polyamide.

Preferably, the porous support membranes have a pore size of less than 500 nm. With particular preference, they have a pore size of less than 100 nm and very particularly preferably less than 50 nm.

The pore size of the porous support membrane is particularly preferably smaller than the mean particle diameter of the polymer particles or of the nanoparticulate oxides.

Preferably, the thickness of the support membrane 20 to 200 μιη, more preferably from 40 to 150 μηι, most preferably from 50 to 140 μιη. Preferably, the rubbery polymer particles prepared by emulsion polymerization are at least partially functionalized by the addition of polyfunctional monomers in the polymerization. Preference is given to the polyfunctional monomers from the group of compounds having at least two, preferably 2 to 4, copolymerizable C =C double bonds, in particular diisopropenylbenzene, divinylbenzene, divinyl ether, divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1, 2-polybutadiene, N, N ' -m-phenylene-maleimide, 2,4-toluylenebis (maleimide), triallyl trimellitate, acrylates and methacrylates of aliphatic amines, epoxides and polyhydric, preferably 2- to 4-valent C 2 to C 10 -alcohols, in particular ethylene glycol, 1,2-propanediol , Butanediol, hexanediol, polyethylene glycol having 2 to 20, preferably 2 to 8 oxyethylene units, neopentyl glycol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sorbitol and unsaturated polyesters of aliphatic di- and

Polyols and maleic acid, fumaric acid, and / or itaconic acid.

The separation-active layer of the nanofiltration membrane according to the invention preferably has at least one monolayer of the mixture of nanoparticulate oxides and polymer particles having the average particle diameter <70 nm, preferably between 30 and 65 nm, particularly preferably between 40 and 50 nm. _Λ

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A preferred embodiment of the nanofluid membrane according to the invention has a separation-active layer with a thickness of from 0.1 to 20 μm, with several layers of the polymer particles lying on top of one another.

Preferably, the thickness of the separation-active layer is at most as thick as the support membrane. Another invention is the production process of the nanofiltration membrane according to the invention, wherein a dispersion (latex) of rubbery polymer particles prepared by emulsion polymerization is applied to the support membrane together with at least one nanoparticulate oxide and a polymer layer (release active layer) is formed on the support membrane. It has been found that the dispersion of rubbery polymer particles prepared by emulsion polymerization is largely monodisperse, i. H. According to the method of dynamic light scattering, 95.4% of the polymer particles are in a size class with a deviation of ± 7 nm.

The nanoparticulate oxides are preferably incorporated by addition and mixing in the polymer suspension.

Preferably, the process is carried out continuously.

The aqueous dispersion preferably comprises rubbery polymer particles having a mean particle diameter <70 nm, preferably between 30 and 65 nm, particularly preferably between 40 and 50 nm, the dry rubber content after the polymerization being at least 20%, preferably at least 25%, more preferably at least

30%, based on the total volume of the polymer.

The concentration of latices to a dry rubber content of not more than 65% based on the total volume of the polymer is conceivable for the production of the membrane as well as a dilution of up to 1%. The dry rubber content is determined as follows: The dry rubber content is determined with a halogen moisture meter, such as the Mettler Toledo Halogen Moisture Analyzer HG63. Here, a latex is dried at a temperature of 140 ° C and weighed continuously. The measurement is considered complete when the weight loss is less than 1 mg / 50 sec. The dry rubber content after the polymerization is preferably at most 65%, based on the total volume of the polymer. Preferably, the latex with the rubbery polymer particles is applied to the support membrane by means of a nozzle.

In a subsequent step, the nanofiltration membrane formed in this way is dried. In a preferred embodiment, the nanofiltration membrane formed in this way can additionally be crosslinked, whereby the rubber-like polymer particles with one another and / or with the

Supporting membrane to be connected. Usually, chemical (covalent and / or ionic) as well as physical types of crosslinking are induced by electromagnetic (e.g., UV), thermal, and / or radioactive radiation. All conventional crosslinking aids can be used. This further reduces the pore size and modifies the filtration properties.

Another invention is the use of rubbery polymer particles prepared by emulsion polymerization with average particle diameters <70 nm, preferably between 30 to 65 nm, more preferably between 40 to 50 nm together with at least one nanoparticulate oxide for producing a nanofiltration membrane. Likewise one

Invention is the use of the nanofiltration membrane for the food industry, for the chemical industry and for the biochemical industry. This list is not limiting.

Another invention is the use of a nanofiltration membrane comprising at least one porous support membrane, which with, prepared by emulsion polymerization rubbery polymer particles having an average particle diameter smaller than 70 nm and with

Nanoparticles at least one oxide of the elements Al, Si, Ca, Fe, Mn, Cr, Ti, V, Zn, Zr, Sn is coated for the filtration of water and wastewater and for the purification of drinking water. Another invention is the use of the nanofiltration membrane according to claim 1 for the filtration of water and wastewater and for the purification of drinking water. The invention will be explained below with reference to at least one example, which, however, is in no way limiting. EXAMPLES

Preparation of polymer particles

The following starting materials were used for the preparation of the rubbery polymer particles. In Table 1, formulation ingredients are based on 100 parts by weight of the monomer mixture.

Monomers i) butadiene (99%, destabilized) of Lanxess Deutschland GmbH

2) Acrylonitrile (99% stabilized with hydroquinone monomethyl ether), the Merck KGaA 3) styrene (98%) of KMF Laboratory Chemistry GmbH

4) trimethylolpropane trimethacrylate (96%) from Aldrich; Product number: 24684-0;

(Abbreviation: TMPTMA)

Hydroxyethyl methacrylate (97% of Arcos, abbreviation: HEMA) emulsifiers

⁶⁾ Disproportionated rosin acid (abbreviated as HS) - calculated as the free acid starting from the amount of Dresinate® 835 used (Abieta® DR 835A from Arizona Chemical BV /

CAS No. 28161-39-9)

The Dresinate® 835 batch used was characterized by the solids content and by the emulsifier components present as the sodium salt, as the free acid and as the neutral.

The solids content was determined according to the procedure described by Maron, S. H .; Madow, B.P .; Borneman, E. "The effective equivalent of certain rosin acids and soaps" Rubber Age, April 1952, 71-72.

The mean value of three aliquots of the Dresinate® 835 batch used was found to be 71% by weight solids.

The emulsifier components present as the sodium salt and as the free acid were determined by titration according to the method described by Maron, S.H., Ulevitch, I.N., Eider, M.E., Fatty and Rosin Acids, Soaps, and Their

Mixtures, Analytical Chemistry, Vol. 21, 6, 691-695. - 17 -

To determine (in an example) 1.213 g Dresinate® 835 (71%) was dissolved in a mixture of 200 g of distilled water and 200 g of distilled isopropanol, treated with an excess of sodium hydroxide solution (5 ml 0.5 N NaOH) and with 0.5 N hydrochloric acid back titrated. The titration course was followed by potentiometric pH measurement. The evaluation of the titration curve was carried out as described in Analytical Chemistry, Vol. 21, 6, 691-695.

Three aliquots of the Dresinate® 835 batch used were averaged:

Total emulsifier content: 2.70 mmol / g dry mass

Na salt: 2.42 mmol / g dry mass

Free acid: 0.28 mmol / g dry mass

With the aid of the molar masses for the sodium salt of disproportionated abietic acid (324 g / mol) and the molar mass for the free disproportionated abietic acid (302 g / mol), the proportions by weight of Na salt, free acid and unperfected portions of the Dresinate® used were 835 batch calculated:

Sodium salt of disproportionated rosin acid: 78.4% by weight

Free disproportionated rosin acid: 8.5% by weight

Unrecorded proportions (neutral body) 13.1% by weight In the following formulations, the amounts of Dresinate® 835 used in the polymerizations were converted into free acid (abbreviated as HS) and as parts by weight based on 100 parts by weight of monomers specified. In this conversion, the neutral body was not considered.

To reconstruct the conversion of the amounts of disproportionated abietic acid (HS) indicated in Table 1 on the basis of the amounts of Dresinate 835® used, the following Table 1 is added:

Table 1:

Weighing in at Dresinate® 835 Calculated amount of disproportionate

Abietic acid (without neutral substance)

[g dry matter] [g dry matter]

0.25 0.20

0.5 0.41

1.0 0.82

1.5 1.22

2.0 1.63

2.5 2.04

3.0 2.45

3.5 2.86

4.0 3.26 Weighing in at Dresinate® 835 Calculated amount of disproportionate

Abietic acid (without neutral substance)

[g dry matter] [g dry matter]

4.5 3.67

4.75 3.87

5.0 4.08

Partially hydrogenated tallow fatty acid - abbreviated as FS (Edenor HTiCT N from Cognis Oleo Chemicals, CAS No. 61790-37-2). The Gesamtemulgatorgehalt and the average molecular weight of Edenor ^® HTiCT used N-batch were titrimetrically determined using the following methods: Maron, SH, Ulevitch, IN, Elder, ME "Fatty and Rosin Acids, soaps, and Their Mixtures, Analytical Chemistry, Vol 21, 6, 691-695; Maron, SH; Madow, BP; Borneman, E. "The effective equivalent of certain rosin acids and soaps" Rubber Age (1952), 71 71-2) The titration (in one example, 1.5 g Edenor® HTiCT N in a mixture of 200 g distilled water and 200 g of distilled isopropanol, treated with an excess of 15 ml of NaOH (0.5 mol / 1) and titrated back with 0.5 M hydrochloric acid.

Here, was obtained as a mean of three aliquots of the Edenor ^® used HTiCT N-Charge:

Total emulsifier content: 3.673 mmol / g dry mass

Molecular Weight (Free Acid): 274.8 mg / mmol In the following formulations, the amounts of partially hydrogenated tallow fatty acid used (as commercially available) were reported as "Free Acid = FS".

The calculation of the carried out for setting the specified in the tables degrees of neutralization based on the titrimetrically determined contents of the various constituents of the Dresinate® used 835- and Edenor ^® HTiCT N-batches. The neutralization grades were adjusted with potassium hydroxide.

Tert-Dodecyl Mercaptan Regulator from Chevron Phillips Chemical Company LP (Sulfole 120 / CAS

No. 90501-34-1) The preparation of the rubbery polymer particles was carried out by emulsion polymerization in a 20 1 autoclave with stirrer. For the polymerization runs, 4.3 kg of monomers were used with 0.34 g of 4-methoxyphenol (Arcos Organics, Item No. 126001000, 99%, CAS No. 150-76-5). The total emulsifier and total amounts of water given in the table (minus the amounts of water required for the preparation of the aqueous premix and p-menthane hydroperoxide solutions) were initially introduced together with the emulsifiers and the necessary amounts of potassium hydroxide in the autoclave.

After temperature control of the reaction mixture to 15 ° C in the listed polymerization batches each 50% freshly prepared aqueous Premix solutions (4%) were added to the autoclave. These premix solutions consisted of:

0.284 g of ethylenediaminetetraacetic acid (Fluka, article number 03620),

0.238 g of iron (II) sulfate * 7 H ₂ O (Riedel de Haen, item number: 12354) (without

Calculated water of crystallization)

0.576 g Rongalit C ^®, Na formaldehyde sulfoxylate 2-hydrate (Merck-Schuchardt,

Item 8.06455 or BASF Tl / T 5952 e October 1996) (without

Calculated water of crystallization) as well

0.874 g trisodium phosphate * 12 H ₂ O (Acros, article number 206520010) (without

Calculated water of crystallization).

For the activation of the polymerizations are listed (80-47-7 Trigonox ^® NT 50 from Akzo-Degussa CAS-No.) Of the styrene-containing Type 5 and g for the acrylonitrile-type 1.7g p-menthane hydroperoxide used, which in 200 ml the emulsifier solution prepared in the reactor were emulsified.

When reaching 30% conversion, the remaining 50% of the premix solution was added.

The temperature control during the polymerization was carried out by adjusting the coolant quantity and the coolant temperature in the temperature ranges indicated in the tables.

Upon reaching a polymerization conversion of more than 85% (usually: 90% to 100%), the polymerization was stopped by adding an aqueous solution of 2.35 g of diethylhydroxylamine (DEHA, Aldrich, Article No. 03620). Removal of volatiles

To remove volatiles from the latex, the latex was subjected to steam distillation at atmospheric pressure.

The polymer particles thus prepared are used for a nanofiltration membrane according to the invention.

Table 2 shows the recipe of the rubbery polymer particles produced; the following indexes are used:

¹⁾ butadiene (unstabilized)

²⁾ Acrylonitrile (99% stabilized with hydroquinone monomethyl ether), Merck KGaA

³⁾ Styrene (stabilized with 100 to 150 ppm of 4-tert-butylpyrocatechol)

⁴⁾ trimethylolpropane trimethacrylate (96% from Aldrich)

⁵⁾ hydroxyethyl methacrylate (97% from Arcos)

⁶⁾ Amount calculated from the amount of Dresinate 835 calculated

disproportionated rosin acid (abbreviated as HS)

⁷⁾ Edenor ^® HTiCT N from Oleo Chemicals (abbreviated as FS / CAS-No. 61790-37-2)

⁸⁾ tert-dodecylmercaptan (Sulfol® 120 from Chevron Phillips)

The properties of the particles produced are shown in Table 3.

Table 2:

Table 3:

Production of the nanofiltration membrane according to the invention

The support membrane used was an ultrafiltration membrane made of polysulphone which was placed in isopropanol for 30 minutes in a solution of 20% by weight of polyethylene glycol at 400 g / mol prior to processing. This membrane was coated by means of a spiral doctor with an aqueous dispersion.

For Type 1, the dispersion consisted solely of rubbery polymer particles as described above. For type 2 - 5, the mixture of the rubber-like polymer particles consisted by above preparation together with nanoscale particles of type SiC Bindzil ^® cc301 and Levasil ^® 200/30 [Akzo Nobel Chemicals Holding GmbH, Aachen, (Bindzil ^® cc301 CAS No. 141029-67. 7631-86-9)] in a concentration of 5 and 10 -6) (Levasil ^® 200/30 CAS-No.%., based on the solids content of the polymer dispersion urpsrünglichen. The support membrane was coated at a rate of 20 mm / sec. The wet film thickness of the dispersion layer results from the type of spiral doctor blade with about 6.7 μιη, resulting in a dry film thickness of the separating active layer of about 1.9 μιη results. The drying was carried out at about 60 ° C under atmospheric pressure for 30 minutes.

Determination of filtration properties

The filtration properties of the nanofiltration membranes according to the invention were measured with a solution of 2000 ppm MgSÜ ₄ in water. This feed solution was applied to the membrane in cross flow under a feed pressure of 5 bar at 20 ° C. and a flow rate of 4 l / min. The salt concentration remaining in the permeate was determined by the conductivity of the solution and related to the concentration in the feed in order to obtain the retention of the membrane.

Filtration properties of the nanofiltration membranes of the invention

The values measured in the filtration tests are shown in Table 4:

Conc

Type Additive flux / l / m ² h retention /%

Wt.%)

1 - - 4.0 14.3

2 Bindzil ^® cc301 5 25,9 23,6

3 Bindzil ^® cc301 10 30.2 30.4

Levasil ^®

4 5 22,6 21,4

200/30

Levasil ^®

5 10 38.0 27.8

200/30 It can be clearly seen that the flow of the membrane increases as a result of the addition of the SiCV particles. At the same time, there was also an increase in the backlog for MgSÜ ₄ .

Claims

claims

1. Nanoiiltration membrane with a porous support membrane, characterized in that the surface of the support membrane produced by emulsion polymerization rubbery polymer particles having an average particle diameter smaller than 70 nm and with nanoparticles at least one oxide selected from the series Fe ₂ 0 ₃ ,

Fe ₃ O ₁ , Fe (OOH), TIO ₂ and SIO ₂ , and both rubbery polymer particles and oxide nanoparticles form the release active layer and the rubbery polymer particles have been prepared from monomers containing at least one conjugated diene as the functional group.

2. Nanoiiltration membrane according to claim 1, characterized in that as monomers for the preparation of the rubbery polymer particles monomers from the series butadiene, isoprene, 2-chlorobutadiene and 2,3-dichlorobutadiene, vinyl acetate, styrene or derivatives thereof, 2-vinylpyridine and 4-vinylpyridine, Acrylonitrile, acrylamides, methacrylamides, tetrafluoroethylene, vinylidene fluoride, hexafluoropropene, double bond-containing hydroxy, epoxy, amino, carboxy, phosphorus or keto compounds.

3. Nanoiiltration membrane according to claim 2, characterized in that the rubbery polymer particles consist of more than 60% by weight of the monomers.

4. Nanoiiltration membrane according to claim 1, characterized in that the supporting membrane consists of an inorganic or organic material.

5. Nanoiiltration membrane according to claim 4, characterized in that the pore size of the supporting membrane is less than 500 nm, preferably less than 100 nm and particularly preferably less than 50 nm.

6. Nanoiiltration membrane according to claim 5, characterized in that the pore size of the support membrane is smaller than the average particle diameter of the rubbery polymer particles.

7. Nanoiiltration membrane according to claim 6, characterized in that the thickness of the support membrane 5 to 100 μηι, preferably 20 to 80 μιη and most preferably of 30 μιη Μ8 60 μιη.

8. Nanoiiltration membrane according to claims 1 to 7, characterized in that the rubbery polymer particles have a glass transition temperature (Tg) of -85 ° C to 150 °

C, preferably - 75 ° C to 110 ° C, more preferably -70 ° C to 90 ° C, have.

9. nanofiltration membrane according to spoke 8, characterized in that the rubbery polymer particles produced by emulsion polymerization are at least partially crosslinked.

10. nanofiltration membrane according to spoke 9, characterized in that the rubbery polymer particles produced by emulsion polymerization are at least partially functionalized by the addition of polyfunctional monomers in the polymerization.

11. nanofiltration membrane according to spoke 10, characterized in that the polyfunctional monomers are selected from the group consisting of: compounds having at least two, preferably 2 to 4 copolymerisable C = C-

Double bonds such as diisopropenylbenzene, divinylbenzene, divinyl ether, divinylsulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N, N'-m-phenylene maleimide, 2,4-tolylene bis (maleimide), triallyl trimellitate, acrylates and methacrylates of aliphatic amines, Epoxides and polyhydric, preferably 2- to 4-valent C 2 to C 10 alcohols, such as ethylene glycol, 1,2-propanediol, butanediol,

Hexanediol, polyethylene glycol having 2 to 20, preferably 2 to 8 oxyethylene units, neopentyl glycol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sorbitol and unsaturated polyesters of aliphatic diols and polyols and maleic acid, fumaric acid, and / or itaconic acid.

12. nanofiltration membrane according to spoke 11, characterized in that the rubbery polymer particles have an approximately spherical geometry.

13. nanofiltration membrane according to spoke 12, characterized in that the rubbery polymer particles in toluene at 23 ° C insoluble fractions of at least about 70% by weight, preferably at least about 80% by weight, more preferably 90% by weight, more preferably at least about 98% by weight.

14. Nanofiltration membrane according to spoke 1, characterized in that the content of nanoparticulate oxides in the separation-active layer is 0.1-60 wt .-%.

15. A process for producing a nanofiltration membrane according to one or more of claims 1 to 14 with a porous support membrane according to any one of the preceding claims, characterized in that a dispersion of

Emulsion polymerization prepared rubbery polymer particles applied to the support membrane and a polymer layer is formed on the support membrane.

16. Use of a nanofiltration membrane comprising at least one porous support membrane, which with, produced by emulsion polymerization rubbery Polymer particles having an average particle diameter smaller than 70 nm and with nanoparticles of at least one oxide of the elements Al, Si, Ca, Fe, Mn, Cr, Ti, V, Zn, Zr, Sn coated for the filtration of water and wastewater and for purification of drinking water.

17. Use of the Nanoiiltrationsmembran according to one of claims 1 to 14 for the food industry, the chemical industry or biochemical industry.