DE102013213318A1 - Asymmetric porous membranes of aldehyde-crosslinked thermoplastic silicone elastomer - Google Patents

Abstract

The invention relates to an asymmetrically porous membrane M made of at least two amino NH groups per molecule thermoplastic silicone elastomer S1, which is crosslinked by means of aldehyde; two processes for the preparation of the aldehyde-crosslinked asymmetrically porous membrane M, wherein in a first step, a solution of thermoplastic silicone elastomer S1, which has at least two amino NH groups per molecule, and solvent L is prepared, in a second step, the solution in a mold is brought in a third step, the solution brought into contact with a precipitating medium F is brought into contact, wherein a membrane is formed, in a fourth step solvent L and precipitation medium F are removed from the membrane and in a fifth step the Membrane is subjected to crosslinking, wherein the covalently crosslinked membrane M is formed, wherein in the first method in the first step and the second method in the fifth step, an aldehyde-containing aldehyde reagent AR is added; and the use of the membrane M for the separation of mixtures.

Description

The invention relates to a process for producing porous membranes having an asymmetric pore structure of a thermoplastic silicone elastomer, which are crosslinked by means of aldehyde, and to their use.

The separation of mixtures with membranes is usually more energy efficient than conventional separation methods, such. As fractional distillation or chemical adsorption. The search for new membranes with a longer lifetime, improved selectivities, better mechanical properties, a higher flow rate and lower costs are highly regarded aspects of current membrane research.

Asymmetrically constructed porous membranes for the separation of different mixtures of substances are known in the literature. So describes US 3,133,137 the preparation and use of asymmetrically constructed cellulose acetate membranes prepared after the phase inversion process. The process is also referred to as the LoebSourirajan process. Thus prepared membranes have a porous substructure and a selective layer. The thin cover layer is responsible for the separation performance, while the porous substructure leads to a mechanical stability of the membranes. This type of membranes is used in plants for reverse osmosis for drinking water or ultrapure water production from sea or brackish water use.

The use of silicones as membrane material is also state of the art. Silicones are rubber-like polymers with a low glass transition point (Tg <-50 ° C) and a high proportion of free volume in the polymer structure. In GB 1536432 describes the preparation of membranes based on silicones. Described applications include both pervaporation and the separation of gases. Very thin silicone membranes, which would actually be necessary for optimum membrane performance, are not manageable due to the insufficient mechanical properties. In order to obtain the necessary mechanical stability of the silicones, the described membranes are always composite systems with a partially very complicated and complex, multilayer structure. The separation-selective silicone layer is always by methods such. As spraying or solution application, applied to a porous carrier substrate.

The use of OrganopolysiloxanCopolymeren as membranes is state of the art. For example, in US 2004/254325 describe the preparation and use of thermoplastically processable organopolysiloxane / polyurea copolymers. In addition, in JP 6277438 Also claimed silicone-polyimide copolymers as a material for the production of compact membranes. The applications listed there are aimed at the separation of gases.

Also in the literature are porous membranes of silicone carbonate ( JP 59225703 ) as well as silicone-polyimide copolymers ( JP 2008/86903 ) known. In both copolymers, however, the mechanical strength and the selectivity for a technical use are not sufficient.

In principle, only such polymers are suitable for the production of porous membranes which have sufficient mechanical strength and sufficient flexibility.

In WO 2010020584 describes membranes with an asymmetric pore structure of silicone copolymers, which are produced by a phase inversion process and which are characterized by high gas permeability. However, in membranes made of this material, it proves to be disadvantageous that an undesirable so-called "cold flow" occurs, whereby the porous membranes under continuous load can change their membrane structure. To prevent this, the membranes can be crosslinked after the formation of the porous structure. The crosslinking of membranes can be effected by the addition of crosslinkers and, if appropriate, catalysts or initiators. A disadvantage of this process is that the crosslinking agents must be added during membrane production and thus influence the production process or adversely affect the membrane properties. In many cases, special polymers must be elaborately prepared so that they carry reactive groups to the crosslinker. For free-radical crosslinking or crosslinking by means of hydrosilylation, the polymers must be modified, for example, with vinyl groups.

Another crosslinking mechanism that is already known in the field of purely organic polymers is the so-called N-methylol crosslinking. In this case, by copolymerization with suitable Produces monomeric polymers which carry N-methylolamide groups. These are known to bind covalently to alcoholic groups even at lower temperatures in the absence of water at elevated temperature or in the presence of acidic catalysts. Likewise, they can react with each other and thus cause a crosslinking of the polymer. In both cases, covalent ether bonds are formed, which are known to be very strong and are only broken again under extreme physical or chemical stress. This effect makes itself for example EP 0143175 A exploiting, which generates by free radical emulsion polymerization polymer dispersions, which are nachvernetzbar via the methylol mechanism.

Also amine-containing silicones can be cross-linked via the methylol mechanism, as in DE 10 2008 054 679 A1 is described.

It was the object to provide crosslinked membranes with an asymmetric pore structure, which have the positive properties of the membranes of silicone copolymers, and which have an increased stability. It should be possible to use common thermoplastic silicone elastomers which need not be modified with specific crosslinkable groups. In addition, it should be possible to carry out the crosslinking gently after the membrane production.

The invention relates to an asymmetrically porous membrane M made of at least two amino NH groups per molecule thermoplastic silicone elastomer S1, which is crosslinked by means of aldehyde.

The invention also provides a first process for preparing the aldehyde-crosslinked asymmetrically porous membrane M, in which
in a first step, a solution of thermoplastic silicone elastomer S1 which has at least two amino-NH groups per molecule, an aldehyde-containing aldehyde reagent AR and solvent L is prepared,
in a second step, the solution is brought into a mold,
in a third step, the solution brought into contact with a precipitating medium F is brought into contact, forming a membrane,
in a fourth step, solvent L and precipitation medium F are removed from the membrane and
in a fifth step, the membrane is subjected to crosslinking, wherein the covalently crosslinked membrane M is formed.

The invention also provides a second process for the preparation of the aldehyde-crosslinked asymmetrically porous membrane M, in which
in a first step, a solution of thermoplastic silicone elastomer S1, which has at least two amino NH groups per molecule, and solvent L is prepared,
in a second step, the solution is brought into a mold,
in a third step, the solution brought into contact with a precipitating medium F is brought into contact, forming a membrane,
in a fourth step, solvent L and precipitation medium F are removed from the membrane and
in a fifth step, in the resulting membrane, an aldehyde-containing aldehyde reagent AR is introduced and the membrane is then crosslinked, wherein the covalently crosslinked membrane M is formed.

Optionally, the solution of the thermoplastic silicone elastomer S1 still contains fillers FS and / or additives Z.

Thermoplastic elastomers are usually not covalently postcrosslinked but crosslink purely through physical interactions. As shown in Examples 2 to 6, the post-crosslinking leads to significantly improved membrane properties compared to non-covalently crosslinked membranes.

The crosslinked membranes M are also distinguished by the fact that their shrinkage in moisture atmosphere compared to uncrosslinked membranes is significantly reduced.

As thermoplastic silicone elastomers S1, silicone copolymers are preferably used. Examples of such silicone copolymers include the groups of the silicone carbonate, silicone imide, silicone imidazole, silicone urethane, silicone amide, silicone polysulfone, silicone polyether sulfone, silicone polyurea, and the like polyoxalyldiamine silicone copolymers.

wobei das Strukturelement E ausgewählt wird aus den allgemeinen Formeln (Ia–f)

wobei das Strukturelement F ausgewählt wird aus den allgemeinen Formeln (IIa–f)

wobei
R³ substituierte oder unsubstituierte Kohlenwasserstoffreste bedeuten, die durch Sauerstoff- oder Stickstoffatome unterbrochen sein können,
R^H Wasserstoff, oder die Bedeutung von R³ hat,
X einen Alkylen-Rest mit 1 bis 20 Kohlenstoffatomen, in dem einander nicht benachbarte Methyleneinheiten durch Gruppen -O- ersetzt sein können, oder einen Arylenrest mit 6 bis 22 Kohlenstoffatomen,
Y einen zweiwertigen, gegebenenfalls durch Fluor oder Chlor substituierten Kohlenwasserstoffrest mit 1 bis 20 Kohlenstoffatomen,
D einen gegebenenfalls durch Fluor, Chlor, C₁-C₆-Alkyl- oder C₁-C₆-Alkylester substituierten Alkylenrest mit 1 bis 700 Kohlenstoffatomen, in dem einander nicht benachbarte Methyleneinheiten durch Gruppen -O-, -COO-, -OCO-, oder -OCOO-, ersetzt sein können, oder Arylenrest mit 6 bis 22 Kohlenstoffatomen,
B, B' eine reaktive oder nicht reaktive Endgruppe, welche kovalent an das Polymer gebunden ist,
m eine ganze Zahl von 1 bis 4000,
n eine ganze Zahl von 1 bis 4000,
g eine ganze Zahl von mindestens 1,
h eine ganze Zahl von 0 bis 40,
i eine ganze Zahl von 0 bis 30 und
j eine ganze Zahl größer 0 bedeuten. Particularly preferred is the use of organopolysiloxane / polyurea / polyurethane / polyamide or polyoxalyldiamine copolymers of the general formula (I)

wherein the structural element E is selected from the general formulas (Ia-f)

wherein the structural element F is selected from the general formulas (IIa-f)

in which
R ^{3 is} substituted or unsubstituted hydrocarbon radicals which may be interrupted by oxygen or nitrogen atoms,
R ^{H is} hydrogen, or has the meaning of R ³ ,
X is an alkylene radical having 1 to 20 carbon atoms, in which non-adjacent methylene units may be replaced by groups -O-, or an arylene radical having 6 to 22 carbon atoms,
Y is a divalent, optionally substituted by fluorine or chlorine hydrocarbon radical having 1 to 20 carbon atoms,
D is an optionally substituted by fluorine, chlorine, C ₁ -C ₆ alkyl or C ₁ -C ₆ alkyl substituted alkylene radical having 1 to 700 carbon atoms, in which non-adjacent methylene units by groups -O-, -COO-, -OCO - or -OCOO-, may be replaced, or arylene radical having 6 to 22 carbon atoms,
B, B 'is a reactive or non-reactive end group which is covalently bonded to the polymer,
m is an integer from 1 to 4000,
n is an integer from 1 to 4000,
g is an integer of at least 1,
h is an integer from 0 to 40,
i is an integer from 0 to 30 and
j is an integer greater than 0.

The radicals R ³ are monovalent or divalent hydrocarbon radicals having 1 to 18 carbon atoms which are optionally substituted by halogen atoms, amino groups, ether groups, ester groups, epoxy groups, mercapto groups, cyano groups or (poly) glycol radicals, the latter being selected from oxyethylene and / or or oxypropylene units, more preferably alkyl radicals having 1 to 12 carbon atoms, in particular the methyl radical.

Examples of radicals R ³ are alkyl radicals, such as the methyl, ethyl, n-propyl, iso-propyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl , n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl; Hexyl radicals, such as the n-hexyl radical; Heptyl radicals, such as the n-heptyl radical; Octyl radicals, such as the n-octyl radical and iso-octyl radicals, such as the 2,2,4-trimethylpentyl radical; Nonyl radicals, such as the n-nonyl radical; Decyl radicals, such as the n-decyl radical; Dodecyl radicals, such as the n-dodecyl radical; Octadecyl radicals, such as the n-octadecyl radical; Cycloalkyl radicals such as the cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl radicals; Aryl radicals, such as the phenyl, naphthyl, anthryl and phenanthryl radicals; Alkaryl radicals, such as o-, m-, p-tolyl radicals; Xylyl radicals and ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical, the α- and the β-phenylethyl radical.

Examples of substituted radicals R ³ are methoxyethyl, ethoxyethyl and the ethoxyethoxyethyl or chloropropyl and Trifluorpropylrest.

Examples of divalent radicals R ³ are the ethylene radical, Polyisobutylendiylreste and propanediylterminierte polypropylene glycol.

The radical R ^H is preferably hydrogen or the radicals indicated above for R ³ .

Preferably, radical Y is optionally substituted by halogen atoms, such as fluorine or chlorine, substituted hydrocarbon radicals having 3 to 13 carbon atoms, more preferably a hydrocarbon radical having 3 to 13 carbon atoms, in particular the 1,6-hexamethylene radical, the 1,4-cyclohexylene radical , the methylenebis (4-cyclohexylene) radical, the 3-methylene-3,5,5-trimethylcyclohexylene radical, the phenylene and the naphthylene radical, the m-tetramethylxylylene radical and the methylene-bis (4-phenylene) radical ,

Examples of divalent hydrocarbon radicals Y are alkylene radicals, such as the methylene, ethylene, n-propylene, iso-propylene, n-butylene, iso-butylene, tert-butylene, n-pentylene, iso-pentylene -, neo-pentylene, tert-pentylene, hexylene, such as the n-hexylene, heptylene, such as the n-heptylene, octylene, such as the n-octylene and iso-octylene, such as the 2,2,4-trimethylpentylene, Nonylene radicals, such as the n-nonylene radical, decylene radicals, such as the n-decylene radical, dodecylene radicals, such as the n-dodecylene radical; Cycloalkylene radicals, such as cyclopentylene, cyclohexylene, cycloheptylene radicals, and methylcyclohexylene radicals, such as the methylene-bis (4-cyclohexylene) and the 3-methylene-3,5,5-trimethylcyclohexylene radical; Arylene radicals, such as the phenylene and the naphthylene radical; Alkarylene radicals, such as o-, m-, p-tolylene radicals, xylylene radicals, such as the m-tetramethylxylylene radical, and ethylphenylene radicals; Aralkylenreste, such as the benzylene radical, the α- and the β-phenylethylene radical and the methylene-bis (4-phenylene) radical.

Preferably, radical X is alkylene radicals having 1 to 20 carbon atoms, which may be interrupted by oxygen atoms, particularly preferably alkylene radicals having 1 to 10 carbon atoms, which may be interrupted by oxygen atoms, particularly preferably n-propylene, isobutylene, 2-oxabutylene and methylene radicals.

Examples of radicals X are the examples given for radical Y and optionally substituted alkylene radicals in which the carbon chain may be interrupted by oxygen atoms, such as. B. 2-Oxabutylenrest.

The radical B is preferably a hydrogen atom, a radical OCN-Y-NH-CO-, a radical H ₂ NY-NH-CO-, a radical R ³ ₃ Si (O-SiR ³ ₂ ) _n - or a radical R ³ ₃ Si (O-SiR ³ ₂ ) _n -XE-.

The radical B 'is preferably the radicals indicated for B.

The radicals D are preferably divalent polyether radicals and alkylene radicals, particularly preferably divalent polypropylene glycol radicals and also alkylene radicals having at least 2 and at most 20 carbon atoms, such as ethylene, 2-methylpentylene and butylene radical, in particular polypropylene glycol radicals having 2 to 600 carbon atoms and the ethylene and 2-methylpentylene.

n is preferably a number of at least 3, in particular at least 10 and preferably at most 800, in particular at most 400.

m is preferably the ranges specified for n.

Preferably, g is a number of at most 100, more preferably from 10 to 60.

H is preferably a number of at most 10, particularly preferably 0 or 1, in particular 0.

j is preferably a number of at most 400, particularly preferably 1 to 100, in particular 1 to 20.

I preferably has a number of at most 10, particularly preferably 0 or 1, in particular 0.

For example, E = Ia, R ^H = H, Y = 75 mol% of m-tetramethylxylylene and 25 mol% of methylenebis (4-cyclohexylene), R ³ = CH ₃ , X = n-propylene, D = 2-methylpentylene , B, B '= H ₂ NY-NH-CO-, n = 14, g = 9, h = 1, i = 0, j = 10.

The aldehyde reagents AR used in the process contain aldehydes. The aldehyde reagents AR can be gases, liquids or solids.

The aldehyde present in the aldehyde reagents AR preferably has the general formula (III) O = CH-R ⁴ (III) on, where
R ^{4 is} a hydrogen atom, a hydrocarbon radical having 1 to 20 C atoms, wherein the carbon chain interrupted by non-adjacent - (CO) -, -O-, -S- or -NR ⁵ groups and substituted with -CN or -halogen can be;
R ^{5 is} a hydrocarbon radical having 1 to 20 C atoms.

The aldehyde reagents AR used according to the invention may be gases, liquids or solids.

If the aldehyde reagents AR are gaseous, they are preferably pure gases, such as formaldehyde gas, or mixed with inert gases, such as argon or nitrogen. If a gas mixture AR is used, it preferably contains more than 5% by weight of aldehyde mixed with an inert gas. The gas mixture AR preferably contains 0 to 0.01% by weight of oxygen and particularly preferably no oxygen.

If the aldehyde reagents AR used are solids, they are preferably used as the solution. Preferred solvents are liquids which dissolve 1 to 50% by weight of aldehyde reagent at 20 ° C. and 1013 hPa, and which are compatible with the process conditions. Examples of particularly preferred solvents for preparing the aldehyde solutions AR are water, alcohols, such as isopropanol or methanol, ethers, such as THF, polar aprotic solvents, such as N, N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone. Aqueous stabilizers Al can be added as stabilizer alcohols, such as methanol. Particularly preferred aqueous aldehyde solutions AR are formalin solutions which preferably contain 10 to 50% by weight of formaldehyde, 3 to 20% by weight of methanol and 30 to 87% by weight of water.

R ⁴ is preferably a hydrogen atom or alkyl or aryl radicals having in each case 1 to 10 C atoms. The aldehyde reagent AR is particularly preferably formaldehyde, paraformaldehyde or glyoxal, if appropriate in a mixture with inert gas or a solvent.

The thermoplastic silicone elastomer S1 has at least two amino NH groups per molecule. In a primary NH ₂ group formally two amino NH groups are included, therefore, one primary amino group per polymer is sufficient for the crosslinking. In a secondary amino group, only one amino NH group is included, therefore at least two secondary amino groups per polymer are required for crosslinking. Preferably, the silicone thermoplastic elastomer S1 has at least three amino NH groups per molecule. Preferably, the silicone thermoplastic elastomer S1 has amino groups selected from primary and secondary amino groups. Secondary amino groups are z. B. amides, as they occur in urea units. The aldehyde reagent AR is preferably used in an amount such that the molar ratio of aldehyde groups in AR to primary or secondary amino groups of the thermoplastic silicone elastomer S1 is between 0.01 and 10, more preferably between 0.1 and 8, in particular between 0.5 and 5th

The solution of the thermoplastic silicone elastomer S1 prepared in the first step may contain as additive A at least one filler FS. Non-reinforcing fillers FS with a BET surface area of up to 50 m ² / g are, for example, quartz, diatomaceous earth, calcium silicate, zirconium silicate, zeolites, metal oxide powders such as aluminum, titanium, iron or zinc oxides or their mixed oxides, barium sulfate, Calcium carbonate, gypsum, silicon nitride, silicon carbide, boron nitride, glass and plastic powder. A list of others Fillers in particulate form can be found in EP 1940940 , Reinforcing fillers, ie fillers having a BET surface area of at least 50 m ² / g, in particular 100 to 400 m ² / g are, for example, fumed silica, precipitated silica, aluminum hydroxide, carbon black, such as furnace and acetylene black and mixed silicon-aluminum oxides large BET surface area.

The fillers FS mentioned can be rendered hydrophobic, for example by treatment with organosilanes, organosilazanes or siloxanes or by etherification of hydroxyl groups to alkoxy groups. It can be a type of filler FS, it can also be a mixture of at least two fillers FS are used.

Preferably, the solution prepared in the first step contains at least 3, more preferably at least 5, in particular at least 10 and at most 40 parts by weight of filler FS per 100 parts by weight of thermoplastic silicone elastomer S1.

The solution or suspension prepared in the first step may optionally contain 0 to 150 parts by weight, more preferably 0.0001 to 80 parts by weight of additives, as further constituent Z per 100 parts by weight of thermoplastic silicone elastomer S1. These additives may be, for example, resinous polyorganosiloxanes, adhesion promoters, pigments, dyes, plasticizers, organic polymers, heat stabilizers, inhibitors, fungicides or bactericides, such as methylisothiazolones or benzisothiazolones, crosslinking aids, leveling agents, surface-active substances, adhesion promoters, light stabilizers such as UV absorbers and / or radical scavengers, Be thixotropic agent.

The thermoplastic silicone elastomers S1 are suitable for the simple and cost-effective production of asymmetrically constructed membranes M with the aid of the phase inversion process. The urea groups of the thermoplastic silicone elastomers S1 bring about a physical crosslinking of the membranes M via hydrogen bonds after the phase inversion and thus fix the asymmetric structure. However, physical crosslinking is not sufficient to achieve high stability and resilience.

A high mechanical stability of the membranes M, u. a. compared to the pressure of the substance mixture to be separated, however, M is absolutely necessary for technical use of the membranes. The mechanical stability is significantly improved by the covalent crosslinking of the membranes. In particular, when using membranes in reverse osmosis, ultra-, nano-, microfiltration and gas separation and pervaporation plants membranes are needed that can withstand very high mechanical loads.

The flexibility remains despite the covalent crosslinking. Possible collapse of the porous structures after the phase inversion process, even at higher temperatures, is not observed.

The amide moieties of the silicone thermoplastic elastomers S1 affect the diffusion and solubility of the molecules to be separated, which in most cases results in an improvement in the selectivity of the membranes M over pure silicones. The membranes M have a significantly higher flow rate and a significantly improved stability over membranes of the prior art.

Although the selectivities of the silicones known in the literature in some cases seem sufficient for the separation of gas mixtures, the achievable gas flows of these membranes are too low, which strongly adversely affects their overall performance and thus also hampers the technical use.

Furthermore, the pore structure of the membranes M can be easily varied over a wide range. This also membrane applications, such. B. microfiltration or H ₂ O-vapor / H ₂ O-liquid separation realize that were not achievable with the previously made membranes of silicone copolymers.

Similarly, compared to most commercial membranes, hydrophobic media are also easy to separate. The crosslinked, porous membranes M thus have a significantly improved property profile with regard to very important membrane properties compared to pure silicone or other silicone copolymer membranes.

The membranes M are further characterized by having excellent storage stability. This means that the membranes M have no significant changes in the separation performance after a storage time of 4 months.

Characteristic of membranes produced by the phase inversion process, also referred to as the Loeb-Sourirajan process, is their asymmetric structure with a thin release-selective layer and a porous substructure providing mechanical stability. Such membranes are particularly preferred.

In the first step of both processes for the preparation of the membranes M, the thermoplastic silicone elastomer S1 is dissolved in an organic or inorganic solvent L or mixtures thereof.

Preferred organic solvents L are hydrocarbons, halogenated hydrocarbons, ethers, alcohols, aldehydes, ketones, acids, anhydrides, esters, N-containing solvents and S-containing solvents.

Examples of common hydrocarbons are pentane, hexane, dimethylbutane, heptane, hex-1-ene, hexa-1,5-diene, cyclohexane, turpentine, benzene, isopropylbenzene, xylene, toluene, naphthalene, and tetrahydronaphthalene. Examples of common halogenated hydrocarbons are fluoroform, perfluoroheptane, methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, pentyl chloride, bromoform, 1,2-dibromoethane, methylene iodide, fluorobenzene, chlorobenzene and 1,2- dichlorobenzene. Examples of common ethers are diethyl ether, butyl ethyl ether, anisole, diphenyl ether, ethylene oxide, tetrahydrofuran, furan and 1,4-dioxane. Examples of common alcohols are methanol, ethanol, propanol, butanol, octanol, cyclohexanol, benzyl alcohol, ethylene glycol, ethylene glycol monomethyl ether, propylene glycol, butyl glycol, glycerol, phenol and m-cresol. Examples of common aldehydes are acetaldehyde and butyraldehyde. Examples of common ketones are acetone, diisobutyl ketone, butan-2-one, cyclohexanone and acetophenone. Common examples of acids are formic acid and acetic acid. Common examples of anhydrides are acetic anhydride and maleic anhydride. Common examples of esters are acetic acid methyl ester, ethyl acetate, butyl acetate, phenyl acetate, glycerol triacetate, diethyl oxalate, dioctyl sebacate, methyl benzoate, dibutyl phthalate and tricresyl phosphate. Common examples of nitrogen-containing solvents are nitromethane, nitrobenzene, butyronitrile, acetonitrile, benzonitrile, malononitrile, hexylamine, aminoethanol, N, N-diethylaminoethanol, aniline, pyridine, N, N-dimethylaniline, N, N-dimethylformamide, N-methylpiperazine, N- Methyl 2-pyrrolidone, N-ethyl-2-pyrrolidone and 3-hydroxypropionitrile. Common examples of sulfur-containing solvents L are carbon disulfide, methanethiol, dimethyl sulfone, dimethyl sulfoxide and thiophene.

Common examples of inorganic solvents are water, ammonia, hydrazine, sulfur dioxide, silicon tetrachloride and titanium tetrachloride.

In a preferred embodiment of the invention, the thermoplastic silicone elastomer S1 is dissolved in solvent mixtures L. Common examples of binary solvent mixtures L are isopropanol-N-methylpiperazine, isopropanol-aminoethanol, isopropanol-N, N-diethylaminoethanol, isopropanol-dimethylformamide, isopropanol-tetrahydrofuran, isopropanol-N-methyl-2-pyrrolidone, isopropanol-N-ethyl-2 -pyrrolidone and isopropanol-dimethyl sulfoxide. Preference is given to mixing ratios of 5: 1 to 1: 5, more preferably is the range of 4: 1 to 1: 4 and most preferably the range 3: 1 to 1: 3.

In a further preferred embodiment of the invention, the thermoplastic silicone elastomer S1 is dissolved in tertiary solvent mixtures L. Common examples of tertiary solvent mixtures are isopropanol-N-methylpiperazine-aminoethanol, isopropanol-N-methylpiperazine-dimethylformamide, isopropanol-N-methylpiperazine-tetrahydrofuran, isopropanol-N-methylpiperazine-dimethylsulfoxide, isopropanol-aminoethanol-dimetylformamide, isopropanol-N-methylpiperazine N, N-diethylaminoethanol, isopropanol-dimethylformamide-N, N-diethylaminoethanol, isopropanol-aminoethanol-tetrahydrofuran, isopropanol-aminoethanol-dimethylsulfoxide and isopropanol-dimethylformamide-dimethylsulfoxide. Preferred mixing ratios are 3: 1: 1, 2: 1: 1, 1: 1: 1, 1: 2: 2 and 1: 2: 3.

Preferred solvents L for the thermoplastic silicone elastomer S1 dissolve in the precipitation medium F at 20 ° C and 1 bar to at least 20 wt .-%, in particular at least 50 wt .-%.

Suitable solvent pairs L are water-isopropanol, water-tetrahydrofuran, water-dimethylformamide, water-N-methylpiperazine, water-dimethyl sulfoxide, water-aminoethanol, water-N, N-diethylaminoethanol, THF-dimethylformamide, isopropanol-dimethylformamide, THF-N- Methyl-2-pyrrolidone, isopropanol-N-methyl-2-pyrrolidone and the described binary and tertiary solvent mixtures L.

In one embodiment of the invention, the thermoplastic silicone elastomer S1 is initially charged, then the solvent or solvent mixture L is added.

In a particularly preferred embodiment, the thermoplastic silicone elastomer S1 is initially charged, mixed with N-methyl-2-pyrrolidone and then completely dissolved with isopropanol.

The concentration of silicone elastomer S1 is preferably in a range of 5 to 60% by weight based on the weight of the solution of the silicone thermoplastic elastomer S1. In a preferred embodiment of the invention, the concentration of silicone elastomer S1 is 10 to 40% by weight. In a particularly preferred embodiment of the invention, the concentration of silicone elastomer S1 is in a range of 12 to 33% by weight.

The solutions of the thermoplastic silicone elastomer S1 are preferably prepared by conventional methods, e.g. As stirring, shaking or mixing, more preferably by shaking in the solvent L or solvent mixture L.

By heating the solutions, the solution process can sometimes be considerably accelerated. Preference is given to temperatures of 10 to 160 ° C. Further preferred is the temperature range of 22 to 40 ° C. Particularly preferred is the preparation of the solution of thermoplastic silicone elastomer S1 at room temperature.

The solutions are mixed until a homogeneous solution is obtained, in which the thermoplastic silicone elastomer S1 is completely dissolved. The time for this dissolution process is z. B. between 5 min and 48 h. In a preferred embodiment of the invention, the dissolution process lasts between 1 h and 24 h, more preferably between 2 h and 8 h.

In one embodiment of the invention further additives Z are added to the thermoplastic silicone elastomer S1. Typical additives Z are inorganic salts and polymers soluble in the precipitation medium F. Common inorganic salts are LiF, NaF, KF, LiCl, NaCl, KCl, MgCl ₂ , CaCl ₂ , ZnCl ₂ and CdCl ₂ . In a preferred embodiment of the invention are added as additives Z water-soluble polymers of the polymer solution. Common water-soluble polymers are poly (ethylene glycols), poly (propylene glycols), poly (propylene ethylene glycols), poly (vinyl pyrrolidones), poly (vinyl alcohols), silicone-alkylene oxide copolymers and sulfonated polystyrenes. A large part of the additives Z dissolves in the precipitation medium F in the phase inversion and is no longer contained in the membrane M. Residues of the additives Z, which still remain in the membrane M after production, can make the membrane M more hydrophilic overall.

In this case, mixtures of different additives Z can also be incorporated into the solution of the thermoplastic silicone elastomer S1. Thus, in a particularly preferred embodiment of the invention, 2% by weight of LiCl and 3% by weight of poly (vinyl pyrrolidone) are added to the polymer solution. As a result of the additives Z, the membrane M becomes significantly more porous after the phase inversion process.

The concentration of the additives Z in the solution of the thermoplastic silicone elastomer S1 is between 0.01% by weight and up to 50% by weight. In a preferred embodiment of the invention, the concentration is 0.1% by weight to 15% by weight. In a particularly preferred embodiment of the invention, the concentration of the additives Z is 1 to 5 wt .-%.

In the first method, the aldehyde reagent AR is added in the first step to the prepared solution of the thermoplastic silicone elastomer S1.

The aldehyde reagent AR may be added as a solution, solid or gaseous. It is preferably added as a solution or solid.

In the second step, the described solution of the thermoplastic silicone elastomer S1 is brought into a mold, preferably a film or a fiber. For this, the solutions of the thermoplastic silicone elastomer S1 are preferably applied to a substrate or spun. The solutions applied to substrates are preferably further processed into flat membranes, while the spun solutions are preferably processed into hollow fiber membranes.

In a preferred embodiment of the invention, the solutions of the thermoplastic silicone elastomer S1 are applied to a substrate by means of a doctor blade application.

It has proven to be particularly advantageous to filter the solution before the doctor blade application with conventional filter cartridges. In this step, large particles are removed, which in the Membrane production can lead to defects. The pore width of the filter is preferably 0.2 .mu.m to 100 .mu.m. Preferred pore sizes are 0.2 μm to 50 μm. Particularly preferred pore sizes are from 0.2 to 10 microns.

It has also proven to be particularly advantageous to degas the solutions of the thermoplastic silicone elastomer S1 prior to the application of the doctor blade.

The height of the polymer film is significantly influenced by the gap height of the doctor blade used. The gap height of the doctor blade is preferably at least 1 μm, particularly preferably at least 20 μm, in particular at least 50 μm and preferably at most 2000 μm, particularly preferably at most 500 μm, in particular at most 300 μm. In order to avoid bleeding of the polymer film after the doctor blade application, the doctor height should not be set too high.

The width of the squeegee job is basically not limited. Typical widths are in the range of 5 cm to 2 m. In a preferred embodiment of the invention, the doctor blade width is at least 10 cm and at most 1 m, in particular at most 50 cm.

Another way to make the wet polymer film is by meniscus coating a suitable substrate with the solutions of the silicone thermoplastic elastomer S1. Other ways to make the polymer films include all conventional methods, for. Casting, spraying, screen printing, gravure printing and spin on disk. The film thickness is adjusted by the viscosity of the solution and by the film-forming speed.

The speed of the job must always be chosen so that the solution can still wet the substrate, so that during the film production no flow disturbances. Typical speeds are preferably at least 1 cm / s, more preferably at least 1.5 cm / s, in particular at least 2.5 cm / s and preferably at most 1 m / s, more preferably at most 0.5 m / s, in particular at most 10 cm / s.

In a preferred embodiment of the invention, the order takes place at temperatures above 20 ° C. In a particularly preferred embodiment of the invention, the application takes place in a temperature range of 25 to 50 ° C.

There are basically several ways to set the temperature. Both the prepared solutions and the substrates used can be adjusted to the temperature. In some cases it may be advantageous to heat both the solutions of the thermoplastic silicone elastomer S1 and the substrate to the desired temperature.

In a preferred embodiment of the invention, the solution is heated to 40 ° C to 60 ° C and applied to the tempered to 20 ° C to 25 ° C substrate. The temperatures should be chosen so that the crosslinking reaction is not or only delayed takes place.

As substrates for the polymer films described, basically all flat surfaces are suitable. Metals, polymers, fabrics, polymer-coated fabrics and glasses are particularly suitable as the substrate material. Suitable metals consist of titanium, iron, copper, aluminum and their alloys.

As substrates, it is possible to use all polymers which can be processed into films or nonwovens. Examples of such polymers are cellulose, polyamides, polyimides, polyetherimides, polycarbonates, polybenzimidazoles, polyethersulfones, polyesters, polysulfones, polytetrafluoroethylenes, polyurethanes, polyvinyl chlorides, polyether glycols, polyethylene terephthalate (PET), polyaryl ether ketones, polyacrylonitrile, polymethyl methacrylates, polyphenylene oxides, polycarbonates, polyethylenes, polypropylenes and their possible copolymers. As glass substrates, all common glasses can be used. Examples are z. As quartz glass, leaded glass, float glass or soda-lime glass.

The materials described can be present as plates, films, nets, woven and nonwoven, as well as nonwovens. In the manufacture of the membranes on woven or non-woven nets and on nonwovens, the spacer is already connected to the membrane.

In a preferred embodiment of Invention, the film is applied to a PET film with a layer thickness of 100 microns to 50 microns. In a likewise preferred embodiment of the invention, the film is produced on a glass plate with a layer thickness of 0.5 to 1.5 mm. In a further preferred embodiment, the film is produced on a PTFE-coated fabric.

In a particularly preferred embodiment of the invention, the film is applied to nonwovens, so that forms a membrane-nonwoven composite material after the precipitation process, which in the subsequent production of the membrane modules time savings and low production costs are achieved. The preferred preparation of the porous membranes on the nonwovens is divided into the application of the still wet polymer film on the nonwoven with subsequent phase inversion with the precipitation medium F in the third step.

Particularly preferred are nonwoven fabrics which have no defects on the surface, such. As holes or perpendicular fibers have.

The porous membrane can be applied both to non-woven and woven nonwovens.

In a preferred embodiment of the invention, the porous membrane is applied to a nonwoven web. Preferred materials for the nonwoven fabrics used are cellulose, polyester, polyethylenes, polypropylenes, polyethylene / polypropylene copolymers or polyethylene terephthalates.

In a particularly preferred embodiment of the invention, the porous membrane is applied to a nonwoven polyester nonwoven.

In a further preferred embodiment of the invention, the porous membrane is applied to a glass fiber fleece, carbon fiber or aramid fiber fleece.

The layer thickness of the substrates for the porous membrane depends on the technical conditions of the coating system and is preferably at least 10 .mu.m, more preferably at least 50 .mu.m, in particular at least 100 .mu.m and preferably at most 2 mm, more preferably at most 600 .mu.m, in particular at most 400 .mu.m ,

The substrates used for the preparation of the membranes can be treated on the surface with additional substances. To call here would u. a. Flow control agents, surface-active substances, adhesion promoters, light stabilizers such as UV absorbers and / or radical scavengers. In a preferred embodiment of the invention, the films are additionally treated with ozone or UV light. To produce the respectively desired property profiles of the membranes, such additives are preferred.

In a further preferred embodiment of the invention, the thermoplastic silicone elastomer S1 is processed in the second step by spinning into hollow fibers.

The outer diameter of the fiber is preferably at least 10 μm, particularly preferably at least 100 μm, in particular at least 200 μm, more preferably at least 300 μm and preferably at most 5 mm, particularly preferably at most 3 mm, in particular at most 2 mm.

The maximum inner diameter of the hollow fiber is limited by the maximum outer diameter and is preferably at least 8 μm, more preferably at least 80 μm, in particular at least 180 μm, better at least 280 μm and preferably at most 4.5 mm, particularly preferably at most 1.9 mm, in particular at most 900 μm.

In order to prevent the collapse of the inner channels during the hollow fiber manufacturing process, another medium can be injected in this channel.

The medium is either gas or liquids.

Examples of typical gaseous media are air, compressed air, nitrogen, oxygen or carbon dioxide.

Examples of typical liquid media are water or organic solvents. Preferred organic solvents are hydrocarbons, halogenated hydrocarbons, ethers, alcohols, aldehydes, ketones, acids, anhydrides, esters, N-containing solvents and S-containing solvents.

Due to the suitable selection of the precipitation medium F and of the medium applied inside the hollow fiber, the phase inversion can take place only from outside, only from the inside or from both sides at the same time. Thus, in the hollow fiber membrane, the separation-selective layer can be formed on the outside, inside or in the hollow fiber wall. In a preferred embodiment of the invention, water is used as the precipitation medium F and toluene is injected inside the hollow fiber.

Another way to prevent the collapse of the hollow fibers is the use of non-woven tubes. In this case, as with the substrate-bound membranes, the polymer solution is applied to the outside or on the inside of the tube.

In the production of the hollow fibers, a second polymer layer may also be co-spun.

Particularly preferred is spinning at elevated temperatures. Thus, the speed for the production of the hollow fibers can be increased. Typical temperatures are above 20 ° C. Spinning is particularly preferred at temperatures of from 20 ° C to 150 ° C. In a particularly preferred embodiment of the invention, the hollow fibers are prepared at 25 to 55 ° C. The temperatures should be chosen so that the crosslinking reaction is not or only delayed takes place.

For the production of the membranes, the films or hollow fibers can be pre-dried for a defined time before being immersed in the precipitation bath.

The predrying can take place at ambient conditions. In some cases, it may be advantageous to pre-dry at defined environmental conditions, i. H. Temperature and relative humidity. The temperature is preferably at least 0 ° C, more preferably at least 10 ° C, in particular at least 25 ° C and preferably at most 150 ° C, particularly preferably at most 75 ° C. If variant 1 of the process is used, and the aldehyde reagent AR has already been added, it must be ensured during the predrying that the crosslinking process does not yet begin.

The length of the pre-drying time depends on the environmental conditions. Typically, the predrying time is longer than 5 seconds.

In a preferred embodiment of the invention, the predrying time is 7 seconds to 10 minutes.

In a particularly preferred embodiment of the invention, the predrying time is 10 to 30 seconds.

In a likewise preferred embodiment of the invention, the predrying time is 30 seconds to 1 minute.

In the third step, the solutions brought into shape, in particular the polymer films or hollow fibers are brought into contact with a precipitation medium F, in particular dipped in a precipitation bath filled with precipitation medium F. The third step represents a phase inversion process.

The precipitation medium F is a liquid in which the thermoplastic silicone elastomer S1 is preferably at most 2% by weight soluble at 20 ° C. In a preferred embodiment of the invention, the solvent L or solvent mixture L used for the preparation of the solution in the first step dissolves in the precipitation medium F at the pressure and temperature prevailing in the third step to at least 10% by weight, in particular at least 30% by weight.

The most common precipitation medium F is water, especially deionized water. For the preparation of the membranes M water is also the preferred precipitation medium F. Further preferred precipitation media F are alcohols, eg. As methanol, ethanol, isopropanol and long-chain alcohols, or N-containing solvents such. For example acetonitrile. In addition, however, the solvents and solvent mixtures which are described for the preparation of the polymer solution are basically suitable as precipitation medium F. However, it is always important to ensure that the thermoplastic silicone elastomer S1 does not dissolve completely in the precipitation medium F.

The temperature of the precipitation medium F can have a great influence on the structure of the membrane M. The temperature of the precipitation medium F for the preparation of the uncrosslinked membranes M is between the melting temperature and the boiling temperature of the precipitation medium F used. The temperature is preferably in a range of 0 ° C to 80 ° C. More preferably, the temperature is in a range of 10 ° C to 60 ° C. The temperatures should be chosen so that the crosslinking reaction is not or only delayed takes place.

In addition, the precipitation medium F may also contain additives that influence the precipitation of the thermoplastic silicone elastomer S1 in the precipitation bath. Typical additives of the precipitation medium F are inorganic salts and polymers soluble in the precipitation medium F. Common inorganic salts are LiF, NaF, KF, LiCl, NaCl, KCl, MgCl ₂ , CaCl ₂ , ZnCl ₂ and CdCl ₂ . In a preferred embodiment of the invention, water-soluble polymers are added to the precipitation medium F. Common water-soluble polymers are poly (ethylene glycols), poly (propylene glycols), poly (propylene ethylene glycols), poly (vinyl pyrrolidones), poly (vinyl alcohols), silicone-alkylene oxide copolymers and sulfonated polystyrenes. The precipitation medium F may also contain the customary in solutions additives and additives. Examples include flow control agents, surface-active substances, adhesion promoters, light stabilizers such as UV absorbers and / or radical scavengers.

Most of the additives are no longer contained in the membrane after production. Additives remaining in the membrane M after preparation may make the membrane M more hydrophilic.

In this case, mixtures of different additives in the precipitation medium F can be incorporated with. Thus, in a particularly preferred embodiment of the invention, 0.3 to 0.8% by weight of dodecyl sulfate and 0.3 to 0.8% by weight of LiF are added to the precipitation bath.

The concentration of the additives in the precipitation medium F is preferably at least 0.01 wt .-%, particularly preferably at least 0.1 wt .-%, in particular at least 1 wt .-% and preferably at most 30 wt .-%, particularly preferably at most 15 Wt .-%, in particular at most 5 wt .-%.

To generate the respective desired property profiles of the membranes M, such additives are preferred.

The speed with which the solution brought into shape, in particular the polymer film or the hollow fiber dips into the precipitation medium F, must in principle be chosen so that the solvent exchange necessary for membrane production can take place. Typical immersion speeds are preferably at least 1 cm / s, more preferably at least 2 cm / s, in particular at least 5 cm / s, more preferably at least 10 cm / s and preferably at most 1 m / s, particularly preferably at most 50 cm / s, in particular at most 30 cm / s.

The speed is preferably adjusted so that the uncrosslinked membranes M are produced continuously. In such a method, the production of the wet shaped solution is preferably at the same rate as immersion in the inversion bath. The time between the preparation of the solution brought into the mold and the immersion in the precipitation medium F is adjusted so that the solution brought into the form passes through the possibly necessary time for predrying.

The angle at which the shaped solution is immersed in the precipitation medium F must always be chosen so that the solvent exchange is not blocked. Typical angles are preferably at least 1 °, particularly preferably at least 10 °, in particular at least 15 ° and preferably at most 90 °, particularly preferably at most 70 °, in particular at most 45 °. Hollow fibers are preferably immersed in the precipitation medium F at an angle of 85 ° to 90 °.

The preparation of the hollow fibers can be done with or without an air gap between the nozzle and precipitation bath.

The time length of the aging of the shaped solution in the precipitation medium F must always be selected so that there is sufficient time until the solvent exchange has taken place. Typical times are preferably at least 10 s, more preferably at least 30 s, in particular at least 1 min and preferably at most 20 h, particularly preferably at most 60 min, in particular at most 30 min.

In the fourth step, residues of solvent L and / or precipitation medium F are removed from the uncrosslinked membrane, which is preferably done by evaporation.

In the fifth step, the covalently uncrosslinked membrane consisting of thermoplastic silicone elastomer S1 is subjected to crosslinking. The temporal sequence is arbitrary, both steps can be performed sequentially or simultaneously. The removal of residues of solvent L and / or precipitation medium F is preferably carried out first in the fourth step, followed by crosslinking of the thermoplastic silicone elastomer S1 in the fifth step.

In the first method, the membrane is crosslinked in the fifth step. The crosslinking takes place by increasing the temperature. The crosslinking is preferably carried out at temperatures of 40 ° C to 250 ° C, more preferably at 60 ° C to 200 ° C, in particular at 80 ° C to 150 ° C.

In the second method, the aldehyde reagent AR is introduced into the membrane in the fifth step, for example by immersion, spraying or by gassing of the membrane. Subsequently, the crosslinking reaction by a temperature increase to 40 ° C to 250 ° C, more preferably accelerated to 60 ° C to 200 ° C, in particular to 80 ° C to 150 ° C.

Preferably, in the fifth step of the second process, the membrane is immersed in a bath containing an aldehyde reagent AR, or the membrane is stored in a formaldehyde gas-containing atmosphere. A bath preferably contains an aqueous solution with 10 to 50 wt .-% aldehyde, which is optionally stabilized with alcohol. Particularly preferred is an aqueous solution with 10 to 50 wt .-% of formaldehyde or glyoxal, which is optionally stabilized with alcohol, preferably methanol. Immersion in the bath may be carried out in an inert gas atmosphere, such as under argon or nitrogen purge, or even in the presence of oxygen, for example in air. The formaldehyde gas-containing atmosphere preferably consists of more than 5 wt .-% formaldehyde in an inert gas, such as argon or nitrogen, and preferably contains 0 wt .-% to 0.01 wt .-% oxygen and more preferably no oxygen.

The necessary duration of treatment of the membrane with aldehyde reagents AR is determined by the rate of diffusion of the aldehyde reagent into the membrane and can not be stated as a whole. The optimum duration can be determined experimentally depending on the temperature, the concentration of the aldehyde in the bath or the atmosphere and the material composition and the membrane thickness.

When the membrane is immersed in a bath containing an aldehyde reagent AR, the duration is preferably 5 minutes to 24 hours, more preferably 10 minutes to 12 hours.

If the membrane is stored in a formaldehyde gas-containing atmosphere, the duration is preferably 5 seconds to 24 hours, more preferably 10 seconds to 18 hours, particularly preferably 20 seconds to 1 hour.

In both variants, it may also be advantageous to add a catalyst for the crosslinking reaction. In principle, all Lewis and Bronsted acids are suitable as catalyst. These can be added directly to the thermoplastic silicone elastomer S1 or to a solution of the thermoplastic silicone elastomer S1 or applied as a separate component.

The crosslinked membranes M are characterized in that the degree of crosslinking> 50% is preferably> 70%. The degree of crosslinking is defined as the proportion of polymer which no longer dissolves in organic solvents which normally dissolve the silicone thermoplastic elastomers S1. Examples of such solvents are THF or iso-propanol. One method for determining the degree of crosslinking is to extract the membrane in isopropanol at 82 ° C. (1.013 bar (abs.)) For 1 h, followed by gravimetric determination of the insoluble polymer fraction.

By crosslinking the membranes of thermoplastic silicone elastomer S1, crosslinking units of the general formula N-CHR ⁴ -N are obtained between the N atoms of the thermoplastic silicone elastomers S1.

A typical method for modifying or functionalizing the cross-linked membranes M is the treatment of the membranes M with high or low pressure plasma or with corona discharges.

By the removal of the membranes M into a plasma, the membranes z. B. subsequently sterilized, cleaned or etched with masks.

Also preferred is the modification of the membrane surface properties. Depending on the plasma process used, the surface can be rendered hydrophobic or hydrophilized.

The membranes M, in particular flat and hollow fiber membranes M produced according to the above-described phase inversion process and crosslinking have a layer thickness of preferably at least 0.1 .mu.m, more preferably at least 1 .mu.m, in particular at least 10 .mu.m, more preferably at least 50 .mu.m and preferably at most 2000 μm, more preferably at most 1000 μm, in particular at most 500 μm, better at most 250 μm.

The membranes M have a porous structure after production. Depending on the choice of production parameters, the free volume is at least 5% by volume and at most up to 99% by volume, based on the volume of the crosslinked silicone elastomer S1. Preference is given to membranes M having a free volume of at least 20% by volume, more preferably at least 30% by volume, in particular at least 35% by volume and preferably at most 90% by volume, particularly preferably at most 80% by volume, in particular at most 75% by volume.

The membranes M basically have an anisotropic structure. A more compact cover layer is followed by an increasingly porous polymer skeleton. The polymer backbone is covalently crosslinked.

The selective cover layer may be closed, d. H. there are no pores> 1000 Å, which is useful as a gas separation membrane, with a pore size smaller than 100 Å, as a nanofiltration membrane M, with a pore size smaller than 20 Å, as a reverse osmosis membrane M, with a pore size smaller than 10 Å , or as membrane M is necessary for pervaporation.

With closed, separation-selective layers, the thickness is preferably at least 10 nm, particularly preferably at least 100 nm, in particular at least 200 nm and preferably at most 200 μm, particularly preferably at most 100 μm, in particular at most 20 μm.

Any existing defects that could affect the separation efficiency of the membranes M negative, can be closed by a so-called top coat. Preferred polymers have a high gas permeability. Particularly preferred polymers are polydimethylsiloxanes. Another way to close off defects on the surface is by a thermal treatment of the surfaces. The polymer on the surface melts and thus closes the imperfections.

Another object of the invention is the use of porous cross-linked membranes M for the separation of mixtures. Typical compositions of the mixtures to be separated include solid-solid, liquid-liquid, gas-gaseous, solid-liquid, solid-gaseous, and liquid-gas mixtures. Tertiary mixtures can also be separated with the membranes M.

Preferably, with the membranes M gaseous-gas, liquid-solid and liquid-liquid mixtures are separated. The separation is preferably carried out in a one-step process or in so-called. Hybrid processes, d. H. two or more consecutive separation steps. For example, liquid-liquid substance mixtures are first purified by distillation and subsequently separated further with the aid of the porous membranes M.

The membranes M can be used in all membrane processes. Typical membrane processes are z. Reverse osmosis, gas separation, pervaporation, resin infusion in the manufacture of composites, nanofiltration, ultrafiltration and microfiltration.

The membranes M are produced by selecting the appropriate production parameters in such a way that the pore structure necessary for the respective application is produced.

In a preferred embodiment of the invention, membranes M are obtained with a closed, selective layer, i. H. the pore sizes are preferably in a range of 1-10 Å, which are particularly suitable for the separation of gas mixtures. Due to the anisotropic structure of the membranes M, the flow and thus the performance compared to compact, non-porous silicone membranes can be significantly increased. For the separation of the gas mixtures thus clearly small amounts of energy are necessary. The membranes M can be produced significantly faster and cheaper, which is absolutely necessary for the technical use of such membranes M.

The covalent crosslinking increases the mechanical stability. In addition, the stability to solvents or gases that can dissolve the membrane is increased and thus prevents the membrane from being damaged or destroyed in the separation process.

Gaseous-gaseous mixtures that can be separated with the membranes M, z. O ₂ / N ₂ , air, H ₂ / N ₂ , H ₂ O vapor / air, H ₂ / CO ₃ , H ₂ / CO ₂ , CO / CO ₂ , N ₂ / CO ₂ , O ₂ / CO ₂ , H ₂ / CH ₄ , CH ₄ / CO ₂ , CH ₄ / H ₂ S, CH ₄ / C _n H _{2n + 2} , CH ₄ / H ₂ O, gaseous organic compounds / air or gaseous organic compounds / N ₂ .

For the separation of volatile, organic impurities, engl. so-called volatile organic compounds (abbr. VOC), in wastewater membranes M also have favorable release properties. The membranes M are used in so-called pervaporation plants. Typical impurities that can be separated with the membranes M from the wastewater, z. As benzene, acetone, isopropanol, ethanol, methanol, xylenes, toluene, vinyl chloride, hexane, anilines, butanol, acetaldehyde, ethylene glycol, DMF, DMAC, methyl ethyl ketones and methyl isobutyl ketone.

In a further preferred embodiment of the invention, the membrane M has pores in a range of 1 nm to 100 nm. These structures are suitable for the production of ultrafiltration membranes. Typical applications of ultrafiltration membranes M are the purification of electrodeposition paint in the automotive industry, protein purification in the food industry, e.g. As in the production of cheese or clarification of fruit juices, cleaning of oil-water emulsions, eg. As for the cooling and lubricating of workpieces, and the industrial water purification of waste water with particulate impurities, eg. B. latex residues in the wastewater.

In a further preferred embodiment of the invention, the membrane M has pores in a range of 100 nm to 10 microns. These membranes M are particularly preferred for use in microfiltration systems.

Typical applications of the microfiltration membranes M are z. As the removal of bacteria or viruses from water, the sterile filtration of pharmaceutical products, the sterilization of wine and beer and the production of particle-free ultrapure water for the electrical industry.

In a further preferred embodiment of the invention, the porous membranes M are coated with an additional polymer on the surface.

The additional polymer coating is preferably a compact film.

The thickness of the additional layer depends on the intended application of the end membrane. The thicknesses of the coatings are in a range of preferably at least 10 nm, particularly preferably at least 50 nm, in particular at least 100 nm and preferably at most 500 μm, more preferably at most 50 μm, in particular at most 10 μm.

Suitable materials for the coating are all polymers processable into films. Examples of typical polymers are cellulose acetate, polyamides, polyamides, polyetherimides, polycarbonates, polybenzimidazoles, polyethersulfones, polyesters, polysulfones, polytetrafluoroethylenes, polyurethanes, silicones, polydimethylsilicones, polymethylphenylsilicones, polymethyloctylsilicones, polymethylalkylsilicones, polymethylarylsilicone, polyvinylchlorides, polyvinyl alcohols, polyether glycols, polyethylene terephthalate (PET), Polyaryletherketones, polyacrylonitrile, polymethylmethacrylates, polyphenylene oxides, polycarbonates, polyethylenes, polypropylenes and their possible copolymers.

The polymers can be applied to the membranes M by conventional methods. Examples of common coating methods are lamination, spraying, knife coating or gluing. The membrane M must have a surface structure which makes it possible that compact and tightly closed films can be applied. This can be adjusted inter alia by the pore structure of the membrane M. In a preferred embodiment of the invention, the additional coating is applied to membranes M having pores in a range of 10 nm-5 μm. In a particularly preferred embodiment of the invention, the additional coating is applied to membranes M having pores in a range of 100 nm-1 μm.

The high permeability and good film formation on the surface of the membranes M membranes can be achieved with better overall performance. In this case, both the membrane flow as also the selectivity of the membranes M can be further improved. The covalent crosslinking increases the stability of the membrane.

Another application of the membranes M is the barrier effect against liquid water with simultaneous water vapor permeability. The membranes M can z. B. in garments, such. As jackets are incorporated.

Further examples of applications of the membranes M can be found inter alia in Membrane Technology and Applications, Second Edition, RW Baker, NY, Wiley, 2004 ,

The crosslinking of the membranes M significantly improves the mechanical properties of the films. Thus, it is known in membranes of the prior art that pressure fluctuations of the feed streams can lead to a rupture of the membranes and thus to failure of the membranes. Especially thin membranes are very vulnerable in this regard. Thus, compact silicone membranes with comparable throughputs as the membranes M layer thicknesses of about 1 .mu.m to 10 .mu.m. These films are mechanically so unstable that they can only by complicated methods, eg. B. by the application of a thin compact silicone film on a still water surface, even processed. The construction of complicated multilayer composite membranes is absolutely necessary. In addition, lamination poses a risk of detaching the silicone layer from the substrate.

In such auxiliary structures can be dispensed with in the membranes M, since the membranes next to the compact and thin selective layer have a porous, crosslinked substructure, which gives the membranes M sufficient mechanical stability. The membranes M are easy to process and can be further processed without an additional porous carrier structure. If found to be favorable for specific separation applications, the membranes M can also be applied to porous structures. This can be done either directly on the carrier, d. H. the polymer film is applied to the substrate and so immersed in the precipitation medium F, or the membrane M is prepared and laminated in a further step on the support structure. As adhesives z. As silicone, acrylate, epoxy, poly (urethane) or poly (olefin) based adhesives are used. Optionally, adhesion promoters such. As silanes are used to improve the adhesion of the membranes M on the support structures on.

The composite material can also be produced by thermally welding the membrane M to the support structure.

The membranes M can easily be installed in membrane modules. Basically, the construction of hollow fiber modules, spiral wound winding modules, plate modules, cross-flow modules or dead-end modules, depending on the shape of the membrane M as a flat or hollow fiber membrane, possible. The membranes M can be easily integrated into the processes of the currently common methods and with the components that are required in addition to the membrane for the construction of the modules.

All the above symbols of the above formulas each have their meanings independently of each other. In all formulas, the silicon atom is tetravalent.

In the following examples, unless otherwise indicated, all amounts and percentages are by weight, all pressures are 1.013 bar (abs.) And all temperatures are 20 ° C.

Description of the starting compounds used:
Paraformaldeyhd, formalin solution (37 wt% formaldehyde, 12 wt% methanol, 51 wt% water) and glyoxal solution (40 wt% in water) were purchased from Sigma-Aldrich, Germany.

In the following examples the solubility of the polymer portion of the produced membranes is determined as follows ("solubility test"):
The membrane piece is dried at 100 ° C, weighed and extracted for one hour at 82 ° C and 1.013 bar (abs.) In iso-propanol. Non-crosslinked membranes completely dissolve under these conditions. After one hour, the membrane is again dried at 100 ° C and then weighed.

Preparation of asymmetrically porous membranes from a squeegee solution

A doctor blade applicator (Coatmaster 509 MC-I, Erichson) is used to prepare a membrane from a doctoring solution. As Filmziehrahmen is a chambered doctor blade with a film width of 11 cm and a Gap height of 300 microns used. The glass plate used as a substrate is fixed by means of a vacuum suction plate. The glass plate is wiped with a cleanroom cloth soaked in ethanol prior to the knife application. This will remove any particulate contamination.

Subsequently, the Filmziehrahmen is filled with the solution and pulled with a constant film drawing speed of 25 mm / s over the glass plate.

Thereafter, the still liquid wet film is dipped into the water-filled inversion tank. The solvent exchange and the uniform precipitation of the polymer can be observed optically by the turbidity of the film. The time for the phase inversion is about 1 min.

The membrane is removed from the pool after a total of 25 minutes and dried in air. The membrane can be easily detached from the substrate.

Example 1 Production of a Non-Crosslinked, Asymmetric, Porous Silicone Membrane (Not According to the Invention)

4.2 g of an organopolysiloxane-polyurea copolymer (SLM TPSE 100, Wacker Chemie AG) are added with stirring to 12.9 g of isopropanol. Subsequently, 12.9 g of NMP (N-methyl-pyrrolidone) are added to the mixture and the entire mixture is dissolved for 16 h at room temperature.

This gives a colorless, viscous solution having a solids content of 14 wt .-%, which is hereinafter referred to as squeegee solution.

From this squeegee solution an asymmetric membrane is prepared according to the procedure described above. An approximately 67 μm thick, opaque membrane is obtained. In the scanning electron microscope, the anisotropic structure of the membrane is clearly visible. The compact cover layer is followed by an open-pore and porous substructure. The total porosity of the membrane thus produced is 80% by volume.

The degree of crosslinking according to the solubility test described above is 0% by weight.

Example 2: Crosslinking of a membrane by insertion into formalin solution

A membrane from Example 1 is placed in a membrane in an aqueous methanol-stabilized formalin solution (37% by weight of formaldehyde, 12% by weight of methanol, 51% by weight of water) for 18 hours. Subsequently, the membrane is annealed at 120 ° C for 15 min. The degree of crosslinking of the membrane according to the solubility test described above was 91%.

Example 3: Crosslinking of a membrane by placing in glyoxal solution

A membrane from Example 1 is placed in an aqueous glyoxal solution (40% by weight of glyoxal) for 18 h. Subsequently, the membrane is annealed at 120 ° C for 60 min. The degree of crosslinking of the membrane according to the solubility test described above was 71%.

Example 4: Crosslinking with gaseous formaldehyde

A 10 cm × 10 cm membrane piece from Example 1 is treated with a continuous stream of gaseous formaldehyde and N ₂ , heated to 110 ° C. in a sealed chamber. The gas stream of formaldehyde and N ₂ is generated by heating paraformaldehyde to 125 ° C and passing an N ₂ stream at 1 L / min. The condensation of formaldehyde in the supply pipes to the chamber is prevented by tempering the pipes to 140 ° C. After different gassing times, the degree of crosslinking is determined according to the solubility test described above: attempt Fumigation time [min] Degree of crosslinking [%] #1 15 98.1 # 2 70 99.6

After the solubility test, the membrane is still present as an opaque membrane, which also confirms the structure fixation by the crosslinking.

Example 5: Mechanical Investigations of the Membranes of Examples 1 and 4

The tensile tests are after EN ISO 527-3 carried out. For the investigation of the mechanical properties, 5 rectangular test pieces (6 cm × 1 cm) are punched out of the produced membranes. The test pieces thus produced are pulled apart at a speed of 0.5 cm / s. The modulus of elasticity is determined from the determined stress-strain curves. Modulus of elasticity [N / mm ⁵ ] example 1 21.98 Example 4, # 1 23.4

The crosslinked membrane of Example 4 shows a significantly increased modulus of elasticity compared to the uncrosslinked membrane from Example 1. Thus, the crosslinked membranes are much more stable and resilient than the uncrosslinked membranes.

EXAMPLE 6 Testing of the Thermal Stability and Shrinkage of Membranes from Example 1 and Example 4

It is a 7.5 cm x 7.8 cm large membrane piece of Example 1 and a 7.5 cm x 7.8 cm large membrane piece of Example 4 (# 1) at 80 ° C in water and the shrinkage of the two Materials determined in the after 24 h, the dimensions of the membrane pieces were redetermined. Time [h] Example 1 Shrink [%] Example 2 Shrink [%] 0 0.0 0.0 24 10.2 0.0

The crosslinked membrane of Example 4 shows a much lower shrinkage than the uncrosslinked membrane of Example 1.

It is clear from the examples given that the cross-linked membranes achieve better property profiles than the non-cross-linked membranes.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 3,133,137 [0003]
• GB 1536432 [0004]
• US 2004/254325 [0005]
• JP 6277438 [0005]
• JP 59225703 [0006]
• JP 2008/86903 [0006]
• WO 2010020584 [0008]
• EP 0143175A [0009]
• DE 102008054679 A1 [0010]
• EP 1940940 [0046]

Cited non-patent literature

• Membrane Technology and Applications, Second Edition, RW Baker, New York, Wiley, 2004 [0170]
• EN ISO 527-3 [0191]

Claims (11)

Asymmetrically porous membrane M of thermoplastic silicone elastomer S1 having at least two amino-NH groups per molecule, which is crosslinked by means of aldehyde. A process for preparing the aldehyde cross-linked asymmetric porous membrane M of claim 1, comprising the steps of preparing a solution of thermoplastic silicone elastomer S1 having at least two amino NH groups per molecule, aldehyde-containing aldehyde reagent AR and solvent L, in a second step, the solution is brought into a mold, in a third step, the solution brought into contact with a precipitating medium F is brought into contact, forming a membrane, in a fourth step, solvent L and precipitation medium F are removed from the membrane and in a fifth step, the membrane is subjected to crosslinking, wherein the covalently crosslinked membrane M is formed. A process for the preparation of the aldehyde cross-linked asymmetric porous membrane M according to claim 1, wherein in a first step, a solution of thermoplastic silicone elastomer S1, which has at least two amino NH groups per molecule, and solvent L is prepared, in a second step the Solution is brought into a mold in a third step, the solution brought into contact with a precipitating medium F is brought into contact, forming a membrane, in a fourth step, solvent L and precipitation medium F are removed from the membrane and in a fifth step, in the resulting membrane, an aldehyde-containing aldehyde reagent AR is introduced and the membrane is then crosslinked, wherein the covalently crosslinked membrane M is formed. Membrane M according to Claim 1 or Process according to Claim 2 or 3, in which the thermoplastic silicone elastomer S1 is organopolysiloxane / polyurea / polyurethane / polyamide or polyoxalyldiamine copolymers of the general formula (I)

wherein the structural element E is selected from the general formulas (Ia-f)

wherein the structural element F is selected from the general formulas (IIa-f)

and wherein R ^{3 represents} substituted or unsubstituted hydrocarbon radicals which may be interrupted by oxygen or nitrogen atoms, R ^{H is} hydrogen, or the meaning of R ³ , X is an alkylene radical having 1 to 20 carbon atoms in which non-adjacent methylene units Y is a divalent, optionally substituted by fluorine or chlorine, hydrocarbon radical having 1 to 20 carbon atoms, D is optionally substituted by fluorine, chlorine, C ₁ -C ₆ -alkyl- or C ₁ -C ₆ -alkyl substituted alkylene radical having 1 to 700 carbon atoms, in which non-adjacent methylene units may be replaced by groups -O-, -COO-, -OCO-, or -OCOO-, or arylene radical having 6 to 22 carbon atoms, B, B 'is a reactive or non-reactive end group which is covalently bound to the polymer, m is an integer from 1 to 4000, n is an integer from 1 to 4000, g is an integer of at least 1, h is an integer of 0 to 40, i is an integer of 0 to 30, and j is an integer greater than 0. Membrane M according to Claim 1 or 4 or Process according to Claims 2 to 4, in which the aldehyde has the general formula (III) O = CH-R ⁴ (III) wherein R ^{4 is} a hydrogen atom, a hydrocarbon radical having 1 to 20 C atoms, wherein the carbon chain interrupted by non-adjacent - (CO) -, -O-, -S- or -NR ⁵ groups and with -CN or -halogen may be substituted; R ^{5 is} a hydrocarbon radical having 1 to 20 C atoms. Membrane M according to claim 1, 4 or 5 or process according to claim 2 to 5, wherein the thermoplastic silicone elastomer S1 has amino groups selected from primary and secondary amino groups and aldehyde reagent AR is used in an amount such that the molar ratio of aldehyde groups in AR to primary or secondary amino groups of the thermoplastic silicone elastomer S1 is between 0.01 and 10. A method according to claim 2 to 6, wherein the thermoplastic silicone elastomer S1 is at most 2% by weight soluble at 20 ° C in the precipitation medium F. The method of claim 2 to 7, wherein the crosslinking takes place by raising the temperature to at least 60 ° C. The method of claim 2 to 8, wherein a flat membrane is produced. The method of claim 2 to 8, wherein a hollow fiber membrane is produced. Use of the membrane M according to claim 1 or 4 to 6 or method according to claim 2 to 10 for the separation of mixtures.