HK1175735B - Composite silicone membranes with high separating action - Google Patents

Description

Composite polysiloxane membrane with high separation effect

Technical Field

Polysiloxane membranes are suitable for a variety of separation methods. One advantage of polysiloxane membranes is in particular that they are resistant to a wide variety of organic solvents and can therefore be used widely without problems with solvent-based membrane processes such as organophilic nanofiltration or gas separation. Solvent-based nanofiltration is a pressure-driven separation process based on membranes, which separate molecules dissolved in organic solvents at the molecular level. At present, solvent-resistant films are used in the food industry, petrochemical industry, chemical industry, and in the pharmaceutical industry for the preparation of pharmaceutically active ingredients.

Furthermore, polysiloxane membranes are used for Gas Separation (GS). Conventional gas separation processes are nitrogen separation from air, hydrogen recovery, air drying, processes for dissolving hydrocarbons and removing volatile organic components. Polysiloxane membranes generally have significantly higher permeability, but generally lower selectivity, than other polymers used in gas separation processes. Various applications in the field of gas separation are described in detail in the following literature sources: ind, eng, chem, res, vol.41, No.6, 2002.

Background

One example of a suitable solvent-based nanofiltration for polysiloxane membranes is hexane recovery in the production of vegetable oils. Significant energy savings can be achieved by using the membrane in hexane recovery.

The first step in oil production is oil extraction. During the extraction process, the oil raw material is mixed with hexane. This gives a hexane solution of the oil, which is also known as oil-water mixture (miscella). The dissolved oil contains up to more than 95% triacylglycerides and, as minor components, phospholipids, Free Fatty Acids (FFA), pigments, sterols, hydrocarbons, proteins and their breakdown products.

The oil-water mixture contained 70-75% hexane. The oil and hexane may be separated by multi-stage separation, such as by distillation. This requires a relatively high energy consumption for evaporating the hexane. In contrast, if the membrane is used to separate at least a substantial portion of the hexane, considerable energy savings can be achieved.

Problems that may arise in the use of silicone membranes are inadequate long-term stability in hexane-containing systems and undesirable build-up of substances on the membrane surface.

The use of silicone composite membranes (also known as composite silicone membranes) is well known in the vegetable oil industry. Studies that have been performed in this field are described, for example, in the following documents: litt. lipid98(1996), pp.10-14, JAOCS79(2002) pp.937-942. The relationship between membrane surface hydrophobicity in a solution of an oil-water mixture of soybean oil and aggregation of components on the membrane surface has been described in the following documents: InColoiddesandsurfaces, A: Physichemistry engineering artifacts 204(2002) 31-41.

Another example of a solvent-based nanofiltration application for which polysiloxane membranes are suitable in principle is, for example, the mixture of hydroformylation (hydro-formation) reactions: elements, Degussa-science Newsletter,18, (2007)30-35, EP-A1-1931472; from the metathesized reaction mixture: RecoveryofEnlargedOcefined metals catalysis by nanofilaltivation and Eco-Friendlysolvent, A.Kerani, T.Renouard, C.Fischmeister, C.Bruneau, M.Rabille-Baudry, ChemSusChem2008,1,927, EP 1817097; from the mixture of suzuki coupling reactions: solvent-resistant nanofiltractionatof Enlarged (NHC) Pd (allyl) ClComplexesForCross-coupling reactions, DirkSchoeps, VolodymySashuk, KatrinEbert, HerbertPulenio, Organometallics2009,28,3922; or from a telomerization reaction mixture: a homogeneous catalyst was isolated in US20090032465a 1.

Extensive research on various solvent-based nanofiltration processes (organic solvent nanofiltration, OSN) is given by the following literature: chem.Soc.Rev.,2008,37, 365-. It is also demonstrated that the silicone membranes of the prior art retain up to 90% of the triglycerides on the membrane from the hexane solution. Wherein the triglyceride is characterized by a molar mass of 900g/mol (+ -10%).

One manufacturer of commercially available silicone membranes is GMTMembrantechnikGmbH (germany). The silicone separating layer of their membranes is prepared, for example, using the method described in German patent 19507584. In this process, the silicone coating is additionally crosslinked by radiation. This is said to reduce swelling of the separation layer in solvent-containing systems. However, the membrane swells significantly in hydrophobic media such as low molecular weight n-paraffins and loses significantly performance and retention capacity. Furthermore, the membrane is very hydrophobic, which leads to a significant aggregation of hydrophobic components on the membrane surface, for example in oil-water mixtures, or during concentration of pharmaceutically active ingredients, or in concentration of homogeneous catalyst systems, or in concentration of dyes.

In patent applications US20070007195, EP1741481 and EP0979851, membranes for the preparation of the separating layer by curing silicone acrylates are described. In this process, silicone acrylates modified only at the chain ends are used. It also gives an indication of the preparation process, where all processes share the fact that solvents which have to be distilled off are also used during the preparation. This is disadvantageous because solvent vapor must be removed.

Furthermore, such membranes were found not to have a better selectivity than DE19507584 or other membranes of the prior art. Generally, a sufficient selectivity in industrial separation tasks is only counted when significantly more than 95% of the component to be retained is retained on the membrane. All of the currently known membranes based on polysiloxanes or polysiloxane acrylates do not have such sufficient retention properties for the application in question.

Disclosure of Invention

Against this background, it is an object of the present invention to provide films based on polysiloxanes which make it possible to separate at least 95% of components having a molecular weight of less than 800g/mol from organic solvents having a molar mass of <200g/mol, preferably <150g/mol, particularly preferably <120 g/mol. Examples of such solvents are tetrahydrofuran, hexane, heptane, isopropanol, toluene, dichloromethane, acetone and ethyl acetate.

It is also an object of the present invention to reduce the tendency of the silicone films known to date to swell to a high degree, in particular in, for example, aliphatic solvents, such as hexane and heptane, by suitable crosslinking.

Successful reduction of swelling in the above solvents is manifested as a long retention of the separating properties. Under otherwise identical conditions, the membranes according to the prior art, for example from the solvent toluene to the solvent hexane, which is strongly swelling, exhibit a double size exclusion range (polystyrene with a retention of 90% of the corresponding molecular weight MWCO). This also applies specifically to the films prepared in EP1741481, although it is shown herein that a reduced tendency to swell has occurred. The examples disclosed in EP1741481 show a change in the retention properties, which confirms that swelling has definitely occurred. Simple considerations in this context for the effect shown, i.e. non-swelling, are not sufficient.

It is also an object of the present invention to reduce the extreme hydrophobicity and increase the hydrophilicity of the currently known polysiloxane membranes by incorporating hydrophilic components into the membrane polymer.

Surprisingly, it has been found that silicone composite membranes having one or more separation membrane layers have particularly advantageous properties for the stated purposes.

Thus, if at least one separating film layer is prepared by curing the side chain-modified polysiloxane acrylates of the general formula I, the object of the invention is achieved by a polysiloxane composite film having one or more separating film layers.

Wherein:

a is from 25 to 500, preferably from 25 to 300, in particular from 30 to 200,

b is from 1 to 25, preferably from 1 to 15, in particular from 1 to 8,

c is 0 to 20, preferably 0 to 10, in particular 0,

R¹independently of one another, identical or different alkyl or aryl radicals having 1 to 30 carbon atoms, which optionally have ether and/or ester and/or epoxy and/or alcohol functional groups, preferably identical or different alkyl or aryl radicals having 1 to 30 carbon atoms, in particular methyl or phenyl,

R²independently of one another, identical or different from one another: r¹、R³And R⁴，

R³Identical or different organic radicals having one or more acrylate groups, preferably substituents of the formula II or III,

d-0-12, e-0 or 1, f-0-12, g-0-2, h-1-3,

wherein: g + h is 3, and g + h is 3,

R⁶independently of one another, identical or different, alkyl or aryl having 1 to 30 carbon atoms, or H.

R⁷The same or different divalent hydrocarbon groups, preferably-CR⁶ ₂-, in particular-CH₂-，

R⁴The polyether radicals of the formula IV are preferably identical or different

-(CH₂)_i-O-(CH₂CH₂O)_j-(CH₂CH(CH₃)O)_k-(CH₂CHR⁸O)_l-R⁹

Formula IV

i is 0 to 12, preferably 3 to 7, in particular 3,

j＝0-50，k＝0-50，l＝0-50，

R⁸alkyl or aryl, identical or different, having from 2 to 30 carbon atoms, preferably ethyl and phenyl,

R⁹alkyl or aryl, or H or alkanoyl, having 2 to 30 carbon atoms, which are identical or different, preferably methyl, H or acetyl.

The invention also relates to a composite film produced by curing the silicone acrylate of formula I, said composite film consisting of a plurality of different silicone acrylate layers.

Furthermore, it has been found that particularly advantageous classes of silicone films can be prepared if mixtures of different silicone acrylates are cured. By selecting the mixture, the cut-off, the degree of crosslinking and the nature of the hydrophilicity can be set efficiently and directly (steplessly) in previously unknown ranges.

Thus, the invention also relates to a polysiloxane membrane having one or more separation membrane layers which are prepared by curing a mixture of different polysiloxane acrylates.

Particularly advantageously, the mixture of different silicone acrylates comprises at least the following components:

a) one or more silicone acrylates having an average silicon content of > 29% by weight, preferably one or more silicone acrylates of the formula I having an average silicon content of > 29% by weight, in particular one or more silicone acrylates of the formula I in which b ═ c ═ 0 having an average silicon content of > 29% by weight,

wherein, for component a:

a is from 25 to 500, preferably from 25 to 300, in particular from 30 to 200,

b is 0 to 15, preferably 0 to 8, in particular 0,

c is 0 to 20, preferably 0 to 10, in particular 0,

with the proviso that when b is 0, R²＝R³，

b) One or more silicone acrylates having a silicon content of < 27.5% by weight, preferably one or more silicone acrylates of the formula I having a silicon content of < 27.5% by weight, in particular one or more silicone acrylates of the formula I wherein c >3 having a silicon content of < 27.5% by weight,

wherein, for component b:

a is 1 to 24, preferably 5 to 20, particularly preferably 10 to 20, and in particular 10, 11, 12, 13, 14, 15, 16 or 17, in particular

b is 0 to 25, preferably 3 to 10, particularly preferably 3, 4, 5, 6, 7 or 8,

c is 0 to 20, preferably 0 to 10, particularly preferably 0 or 1, 2, 3 or 4,

provided that when b is 0, R²＝R³。

Preferably, components a) and b) are present in the mixture in a mass ratio of 10:1 to 1:10, in particular in a mass ratio of 2:8 to 8: 2.

The structural formula is a polymer having a molecular weight distribution, and thus the values a, b, c, j, k, and l are average values and may not be integers.

The different monomer units (siloxane chains or polyoxyalkylene chains) of the components shown in the formulae can be composed of blocks, can be composed of any desired number of blocks and any desired sequence, or can have a statistical distribution. The numerical values used in the formulae are to be understood as statistical means.

The silicon content of the silicone acrylate is influenced by the degree of organic modification. The more organic ligands are bound to the siloxane backbone, the lower the silicon content. It has been found that when a silicone composite film has a separating layer prepared by curing a mixture of different silicone acrylates, a silicone composite film with advantageous properties is obtained. In this case, curing is carried out using one or more relatively highly modified silicone acrylates having a Si content of < 27.5% by weight (component b) in admixture with one or more relatively lowly modified silicone acrylates having a Si content of > 29% by weight (component a).

The properties of the films obtained using the silicone acrylate mixtures according to the invention have the advantageous properties shown below.

Particularly advantageous properties are obtained if silicone acrylates modified only at the chain ends (known as α, ω -modified silicone acrylates) are used as component a). Furthermore, advantageous properties are exhibited if side-chain-modified silicone acrylates are used as component b).

In addition to the silicone acrylates described, it is advantageous to add various other substances to the mixture, such as fillers, stabilizers, colorants or organic acrylates. This list should not be construed as comprehensive.

The invention relates to novel composite membranes having at least one separating layer which is produced from a special silicone acrylate or a silicone acrylate mixture.

For the preparation of the composite membranes of the invention, suitable materials as substrates are generally solvent-resistant porous three-dimensional structures which can be used as support materials, such as nonwovens, or microfiltration or ultrafiltration membranes, or separators, such as battery separators, for example(trademarks of Evonik Degussa GmbH) or

In principle, all structures which provide filtration and/or phase separation which can be modified from the specific silicone acrylates of the present invention to form composite membranes are suitable.

The invention also relates to composite films obtained by curing the polysiloxane acrylates of the invention of formula I using photoinitiators, by means of electromagnetic radiation at a wavelength below 800nm and/or by means of electron beams. In particular, the curing is carried out by UV radiation at a wavelength below 400 nm.

The invention also relates to composite membranes comprising cured silicone acrylates of formula I having ultrafiltration membranes as support membranes.

In particular, the use of different silicone acrylate mixtures makes it possible to set the properties of the film in a targeted manner. By setting a defined mixing ratio, the membrane can be tailored to specific requirements and to solve specific separation problems. Evonikkgoldschmidt gmbh provides a variety of commercially available silicone acrylates suitable for preparing the films of the present invention.

The conventional product of EvonikkGoldschmidtGmbH isRC902、RC715。RC902 andRC715 is a linear polymer modified only at the chain ends.RC902 has a silicon content of for example 34 wt%,the RC715 has a silicon content of, for example, 32 wt.%, these being relatively low-modified products. Side chain modified siloxanes with a silicon content of, for example, 24% by weight are also available. The content of organic components/groups is relatively higher than the silicon oxide main chain ratio. For exampleRC902 andRC715 corresponds to the linear chain end modified polymer of component a) when different polysiloxane acrylate mixtures are used, while the side chain modified polymer corresponds to component b).

The polysiloxane composite membranes described above are prepared by coating a porous support material, for example based on microfiltration or ultrafiltration membranes or membranes. As support materials that can be used in this case, in principle all known macroporous (macrogrous) materials: K. V.Peinemann and S.Nunes, Membrane technology inter chemical industry, Wiley-VCHVerlag GmbH, 2006. As porous support material, particularly suitable are membranes selected from the following materials: polyacrylonitrile (PAN), Polyimide (PI), Polyetheretherketone (PEEK), polyvinylidene fluoride (PVDF), Polyamide (PA), polyamide-imide (PAI), Polyethersulfone (PES), Polybenzimidazole (PBI), Sulfonated Polyetherketone (SPEEK), Polyethylene (PE), polypropylene (PP), and inorganic porous materials and/or ceramic or polymeric ceramic membranes prepared using alumina, titania, zirconia, silica and/or titanium nitrite, and mixtures and/or modifications or composites of the various support membrane materials.

The polysiloxane composite membranes described above are suitable for separation tasks in organic solvents. According to embodiments, they are capable of separating or retaining dissolved molecules having a molecular weight of less than 2000g/mol, preferably molecules having a molecular weight of less than 1000g/mol, and particularly preferably molecules having a molecular weight of less than 500g/mol, with a retention of at least 90% by weight, preferably > 95% by weight, more preferably > 98% by weight, and in particular > 99% by weight.

In a particularly preferred embodiment of the invention, at least 95% of the components having a molecular weight of less than 800g/mol, preferably a molecular weight of <200g/mol, particularly preferably <150g/mol and in particular <120g/mol, can be separated from the components having different molecular weights dissolved in the organic solvent by means of the membrane according to the invention. Examples of such solvents that can be trapped are tetrahydrofuran, hexane, heptane, isopropanol, toluene, dichloromethane, acetone, ethyl acetate, preferably hexane or heptane.

In principle, the dissolved molecules can be all molecules which are soluble in the respective solvent. The invention therefore also relates to the use of the polysiloxane composite membranes according to the invention, for example, for separating homogeneous catalyst systems from reaction mixtures, for separating triglycerides from solvents such as hexane, heptane, ethanol or acetone, for separating oligomers from monomer solutions, or for separating (pharmaceutically) active ingredients or precursors thereof from reaction mixtures or solutions.

The invention also relates to the use of said polysiloxane-acrylate composite membranes for trapping or separating homogeneous catalyst systems from reaction mixtures, for separating triglycerides from solvents having a molecular weight of less than 200g/mol, for separating oligomers from monomer solutions, or for separating (pharmaceutically) active ingredients or precursors thereof from reaction mixtures or solutions.

Preferred solvents for use in the process are hydrocarbons of 1 to 8 carbon atoms, preferably hexane or heptane, isomers or mixtures thereof, or CO₂。

The composite membranes according to the invention are particularly suitable for purifying substances, since, for example, molecular weight fractions below a set range can be separated from a solution in a targeted manner at set separation parameters such as temperature, pressure and solvent. Under customary system conditions, for example 30 °, 30bar pressure (TMP transmembrane pressure), fractions having a molecular weight of less than 1000g/mol, preferably less than 600g/mol and in particular less than 300g/mol can be separated from the n-heptane solution in this way.

Starting from a mixture of side-chain-modified and chain-end α, ω -modified silicone acrylates, the membrane separation efficiency can be set in a targeted manner (with a wide range) for different solvent systems (see also fig. 1 or fig. 2 in this case).

The invention also relates to a method for producing composite films, wherein a support film is coated with at least one silicone acrylate of the formula I and/or a mixture of a plurality of silicone acrylates and is subsequently cured at room temperature by means of electromagnetic radiation and/or electron beam radiation.

The silicone acrylate or, if appropriate, the silicone acrylate mixture is added, optionally with a common solvent, to conventionally used roller systems, for example for the application of anti-stick coatings for support materials, for example for labeling applications, it being particularly advantageous not to use further solvents for this purpose. A photoinitiator was previously added to the silicone acrylate. The silicone acrylate is added to the film material in an amount of 0.3-2 μm in layer thickness by means of a roller system and cured by a free radical mechanism by means of UV radiation or electron beam radiation. No other thermal energy is required. The silicone acrylate cured immediately after passing through the reaction chamber. In the reaction chamber, the radical domains are quenched by oxygen, and therefore, it is necessary to inert the reaction chamber with nitrogen.

Drawings

Figure 1 shows the polystyrene cut-off for different molecular weights and solvent flux for polysiloxane acrylate membranes of different compositions.

Figure 2 shows the polystyrene retention and solvent flux over time for the membranes of the invention (30% b) and 70% a)) and the prior art membrane (100% a)).

Detailed description of the preferred embodiments

Examples

The present invention will be described in the following examples to illustrate the invention, but is not intended to limit the invention, its scope of application arising from the entirety of the specification and claims, to the embodiments described in the examples. If ranges, general formulae or compound classes are mentioned below, these should not only include the corresponding ranges or compound classes explicitly described, but also include all sub-ranges and sub-classes of compounds which can be obtained by excluding individual values (ranges) or compounds. In the context of this specification, if a document is cited, the entire contents of the document should be incorporated into the disclosure of the present invention. If compounds such as organically modified silicone acrylates are described in the context of the present invention as comprising a plurality of different monomer units, these units can be present in these compounds in a random distribution (random oligomer) or in a regular manner (block oligomer). The expression of the number of units in such compounds is to be understood as being the statistical average averaged over all corresponding compounds.

Preparation of the film

The TEGO silicone acrylate from Evonik Goldschmidt GmbH was used for coating according to commercially available ultrafiltration membranes composed of acrylonitrile, available from GMT, Rheinfelde or GE-Osmonics, Vista, USA, as distributed by Desalogics, Ratzeburg. The layers were applied using a smooth roll coating apparatus with a 5 roll mill. The coating is carried out at a coating weight of 0.6 to 1.5g/m 2. The coating is crosslinked with UV or the like in an inert nitrogen atmosphere. To this end, a suitable photoinitiator, for example a hydroxyketone, is added to the silicone acrylate in an amount of 1/100 based on the mass of silicon. In this way, composite membranes with different mixtures and sequence of components a) and b) corresponding to the polysiloxane acrylates are produced on the basis of the ultrafiltration membranes. The following coatings with different mass contents of component a) and component b) were prepared in each case, based on the total amount of silicone acrylate:

90% by weight of a) and 10% by weight of b);

80% by weight of a) and 20% by weight of b), and also 3% by weight, based on the total amount of silicone acrylate, of a further inorganic filler;

70% by weight of a) and 30% by weight of b), and 3% by weight, based on the total amount of silicone acrylate, of a further inorganic filler and no inorganic filler and

100% by weight of b).

The components a) and b) of formula 1 used in the examples have the following structures:

component a) a ═ 83, b ═ 0, c ═ 0, R¹＝CH₃，

R²＝(CH₂)₃-O-CH₂-C(C₂H₅)(CH₂O-C(O)-CH＝CH₂)₂

Si content 34.2% by weight

Component b) a ═ 13, b ═ 5, c ═ 0, R¹＝R²＝CH₃

R³A substituent of formula II

Si content 23.8% by weight

The components are prepared using a prior art process as described in DE3920294C 1.

Silica is used as the inorganic filler.

As a comparative prior art membrane, only a membrane based on the components a) was investigatedRC 902.

The properties of the membranes produced are determined in the so-called molecular weight cut-off (MWCO) method in n-heptane. For example, the MWCO process is described in the following documents: journal of membrane science291(2007) 120-. The method is based on measuring the retention (MWCO curve) of different styrene oligomers with their molecular weight.

By using the MWCO method, the degree to which dissolved species having a defined molecular weight can be separated can be estimated. In fig. 1 and 2, the molar mass (Mw) of the dissolved substance (polystyrene in this case) is plotted against the retention (wt.%, converted from mass concentration) on the membrane investigated in each case.

The stability of the separation layer was determined by determining the MWCO curve and the membrane permeability over time in n-heptane.

The membranes were tested by cross-flow filtration. The working temperature was 30 ℃ and the transmembrane pressure (TMP) was 30 bar. In long-term experiments, a pressure of 10bar was used. The membrane was adjusted using pure solvent until a steady state flow was reached. The pure solvent was then replaced by a mixture of solvent and oligomeric styrene indicator. After the steady state flow was again reached, samples of permeate and feed streams were taken and the styrene oligomer content was determined by a method similar to the MWCO method.

Fig. 1 and 2 show the results of retention performance for polystyrene with different molecular weights, and solvent flux for silicone acrylate membranes of different compositions. The permeate liquid was n-heptane.

The results in table 1 demonstrate that the properties of the separation membrane layer can be set specifically by mixtures of various tegoroc products in order to set a membrane with an excellent separation efficiency, but a lower flux, as a membrane with a high flux, but a lower separation efficiency. In this way, by mixing various silicone acrylates, various properties of the film can be set specifically for the application.

From the MWCO curves it can be found that the membrane with the highest content of component a) of 90% has the lowest relative rejection and the highest permeate flux. On the other hand, membranes consisting of 100% of component b) virtually no longer have a permeation flux for n-heptane and have a very high rejection. The results for the mixture of 20/80 and 30/70 with and without filler show that its properties can be effectively and directly set.

A comparative experiment of a film according to the invention with 30% b) and 70% a) was carried out with a polysiloxane film according to the prior art (100% a)) as described above in n-heptane. After a constant run of the membrane in hexane at 10bar and 30 ℃ for a further 11 days, the MWCO test was carried out again.

The results in fig. 2 show that the membranes according to the invention have a separation limit that is significantly biased towards lower molecular weights.

The shift from the separation curve of the prior art membrane to a higher molecular weight, and the increase in permeate flux, indicate that the membrane is unstable in heptane. The membrane according to the invention showed no relevant changes in permeation flux performance and separation properties as a function of run time, which confirms the stability of the membrane in heptane.

Claims (13)

1. Composite membrane for separating dissolved molecules with a molecular weight below 1000g/mol from a solvent selected from hydrocarbons with 1-8 carbon atoms, comprising a separation membrane layer and a support membrane, said composite membrane having one or more separation membrane layers, characterized in that at least one separation membrane layer is prepared by curing a mixture of different silicone acrylates, said mixture of different silicone acrylates comprising at least the following components:

a) one or more silicone acrylates having an average silicon content of greater than 29% by weight of formula I:

wherein, for component a):

a＝25-500，

b＝0-15，

c＝0-20，

provided that when b is 0, R²＝R³，

b) One or more silicone acrylates having an average silicon content of less than 27.5% by weight of formula I,

wherein, for component b):

a＝1-24，

b＝3-10，

c＝0-20，

in the general formula I, R¹Independently of one another, identical or different, alkyl or aryl having 1 to 30 carbon atoms, which optionally have ether and/or ester and/or epoxy and/or alcohol functional groups,

R²independently of one another, identical or different from one another: r¹、R³Or R⁴，

R³Independently of one another, identical or different organic radicals having one or more acrylate groups,

R⁴polyether groups which may be identical or different, and

the filler is filled in the inner cavity of the shell,

wherein the filler is silica.

2. The composite film according to claim 1, wherein a group represented by the general formula II or III is used as the substituent R³，

d-0-12, e-0 or 1, f-0-12, g-0-2, h-1-3,

wherein: g + h is 3, and g + h is 3,

R⁶independently of one another, identical or different, alkyl or aryl having 1 to 30 carbon atoms, or H,

R⁷the same or different divalent hydrocarbon radicals-CR⁶ ₂-。

3. Composite film according to claim 1, characterised in that it is composed of a plurality of different layers of silicone acrylate.

4. Composite film according to claim 1, characterized in that two different silicone acrylates are used, wherein a chain-end α, ω -modified silicone acrylate is used as component a) and a side-chain modified silicone acrylate of formula I is used as component b).

5. Composite membrane according to claim 1, characterized in that the mass ratio of the components a) and b) present in the mixture is between 10:1 and 1: 10.

6. Composite film according to claim 1, characterized in that the silicone acrylate is cured with a photoinitiator by means of electromagnetic radiation having a wavelength below 800nm and/or by means of an electron beam.

7. The composite membrane according to claim 1, characterized in that the support membrane is a solvent-resistant porous three-dimensional support structure selected from the group consisting of a non-woven fabric or a microfiltration membrane or an ultrafiltration membrane or a membrane.

8. The composite membrane of claim 1, wherein the support membrane is prepared from a porous support material selected from the group consisting of: polyacrylonitrile, polyimide, polyetheretherketone, polyvinylidene fluoride, polyamide-imide, polyethersulfone, polybenzimidazole, sulfonated polyetherketone, polyethylene, polypropylene, and inorganic porous materials and/or ceramic or polymeric ceramic membranes prepared using alumina, titania, zirconia, silica and/or titanium nitrite, as well as mixtures, modifications or composites of the various support membrane materials.

9. Use of a composite membrane according to any of claims 1-8 in the rejection of dissolved molecules having a molecular weight below 1000g/mol with a rejection of at least 90 wt%.

10. Use according to claim 9 for the entrapment or separation of a homogeneous catalyst system from a reaction mixture, separation of triglycerides from solvents with molecular weights below 200g/mol, separation of oligomers from a monomer solution, or separation of active ingredients or precursors thereof from a reaction mixture or solution.

11. Use according to claim 10, characterized in that hydrocarbons of 1 to 8 carbon atoms or mixtures thereof are used as solvent.

12. Use according to claim 9, characterized in that the molecular weight fraction having a molecular weight below 1000g/mol is separated from an n-heptane solution at 30 ℃ and a pressure of 30 bar.

13. Method for producing a composite film according to any of claims 1 to 8, characterized in that a support film is coated with at least one silicone acrylate of the formula I and/or a mixture of a plurality of silicone acrylates and subsequently cured at room temperature by means of electromagnetic radiation and/or electron beam radiation.