Electrospinning dispersion and method for producing an electrospun silicone elastomer nonwoven fabric

Abstract

The present invention relates to a silicone elastomer-based electrospinning solution and the use thereof for producing nonwoven fabrics by way of an improved electrospinning method.

Description

[0001] Electrospin dispersion and process for producing electrospun silicone elastomer nonwoven

[0002] The present invention relates to a silicone elastomer-based electrospinning solution and its use for producing nonwovens by means of an improved electrospinning process.

[0003] State of the art

[0004] Electrospinning is a state-of-the-art process for producing nonwovens with controllable fiber diameters ranging from a few micrometers to a few nanometers. A polymer melt, solution, or dispersion is spun into a sub-micrometer-thin fiber in a strong electric field (approx. 10-50 kV) between a spinneret (capillary) and the collector, and the fiber nonwoven is deposited on a substrate. The throughput of the method can be achieved by simply numbering up the nozzles. Details of the electrospinning process are described, for example, in A. Greiner et al. Angew. Chem. 2007, 119, 5770-5805. This also provides numerous examples of polymer classes that have already been used in the electrospinning process. Typically, thermoplastics are used for electrospinning as a melt or dissolved in a suitable solvent.

[0005] Electrospun nonwovens are used, for example, for filtration, for example in respiratory masks for occupational and infection protection, as well as in air purification devices, in which the contaminated air is sucked into a container through an air inlet opening by a fan and passed through a series of filters. Fiber nonwovens with fiber diameters of a few micrometers to a few nanometers are particularly suitable for use as filter media, as they are characterized by low pressure drop and high filtration efficiency of the filter medium. The filter effect is based, among other things, on the large specific surface area of ​​the nanofibers, while the lower pressure drop and thus breathing resistance is due to the high porosity of the corresponding fiber nonwoven. The use of electrets is also known to increase the filtration efficiency of air and respiratory filters.These are dielectric objects that have a permanent charge. This property increases the ability of the filter medium to attract and retain particles such as dust, dirt and fibers that are present in the air. Typically, fluorinated polymers, ideally PTFE, are used for this purpose because they have a particularly high tendency to absorb and store negative charges (negative end of the tribological series). Electrospinning is suitable for producing nanofibers with electret properties because the electric field used applies charges directly to the fleece. US 8801998B (corresponding to EP2557206B1), for example, describes an electret for filter applications made of electrospun PU fibers equipped with PTFE nanoparticles.

[0006] Autoclavable or sterilizable filter media require the filter medium to be stable against temperature or ionizing radiation.

[0007] Accordingly, standard plastics such as polyester or polypropylene cannot be used for this purpose; instead, special, high-melting thermoplastics such as polyimide (PI) or polyetherimide (PET) are required. The resulting limited melting and solubility behavior of these thermoplastics makes their use in spinning processes complex. In contrast, silicone elastomers are temperature- or UV-crosslinkable systems. Before crosslinking, the base components are typically soluble in most aprotic solvents and, due to their mostly thinning properties, pumpable and thus easy to process. After the crosslinking step, silicone elastomers are characterized by high mechanical flexibility and stability against the effects of temperature and radiation.In addition, silicones, which are found at the negative end of the triboelectric series, are characterized by a particularly high electron affinity at the material surface and can therefore function well as electrets.

[0008] The electrospinning of silicones is also known in the art and is typically carried out from an organic solvent. In order to impart the necessary viscoelasticity to the spinning solution so that homogeneous fibers are formed during electrospinning, it is state of the art to add higher molecular weight, hydrophilic polymers to the spinning solution as thickeners. For example, according to CN109868559 a crosslinkable silicone composition (made of polymethylhydrogensiloxane, (DVi) 4 and JUPtCle) is successfully electrospun from ethanol in the presence of polyvinylpyrrolidone (PVP). Alternatively, silicones are suitable for coaxial electrospinning processes, where they are electrospun together with immiscible, usually hydrophilic polymers without prior mixing, so that core-shell fibers are obtained. The outer sheath polymer serves as a template for the formation of fibers.

[0009] The disadvantage of such spinning solutions, especially when it comes to

[0010] When it comes to electrospinning on an industrial scale, the high costs for the user in terms of occupational safety and environmental protection are important. Since organic solvents often have a low flash point, explosion protection must be considered.

[0011] Although non-flammable organic solvents such as chloroform or solvents with a high flash point such as DMF can be added to the spinning solutions, these must be viewed with particular scrutiny from the point of view of health and environmental protection.

[0012] Water-insoluble polymers can also be electrospun in the form of aqueous dispersions, as is adequately described in the prior art, for example in US2011148004A (= corresponding to EP2222902A2) and US2008261043 A (= corresponding to EP1856312A1) for dispersed polymers (latices). Typically, the water-insoluble polymer particles are stabilized using an emulsifier. In addition, a water-soluble polymer acting as a thickener, known as a template polymer, is used. This helps promote fiber formation from the colloidal polymer dispersion (electrospinning) compared to electrospraying.

[0013] The spinning of silicone dispersions by electrospinning is described in US2011165811A (=corresponding to W02010025381A2), wherein the electrospinning of dispersed pre-crosslinked silicone elastomer particles in the presence of polyethylene oxide (=PEO) as a thickener is described. The pre-crosslinked silicone elastomer particles are cured by condensation crosslinking during or after electrospinning. Fibers with spherical defects that are attributable to the pre-crosslinked particles in the dispersion have been reported. The disadvantages of condensation crosslinking of silicone elastomers are, in particular, the lower reaction rate compared to addition crosslinking or radical crosslinking, as well as the incomplete reaction, so that a residual silanol content in the cured material is unavoidable. Such polar OH groups can, however, have a negative effect on the electret properties of the spun material.In addition, the condensation crosslinking of silicones is accompanied by shrinkage, and the byproducts formed in stoichiometric amounts (such as water) can lead to undesirable porosity in the fibers. The fiber diameters disclosed in the example are 1 to 5 pm, so no nanofibers are obtained with this system. Furthermore, since no washing step is disclosed, it can be assumed that these are not pure silicone fibers.

[0014] One problem with electrospinning from aqueous dispersion is the drying of the fiber web. When the water is removed, for example, by thermal drying or drying at reduced pressure, the resulting capillary curvature pressure leads to compaction of the web structure and thus to a loss of porosity. This can lead to poorer application properties of such webs, for example, an increased pressure drop when used as a filter medium.

[0015] The object is therefore to provide aqueous silicone dispersions in order to use them in an improved electrospinning process to produce silicone nanofibers so that the above-mentioned disadvantages of the prior art no longer occur.

[0016] Completely unexpectedly, it was found that the present electrospinning dispersion according to the invention together with the present improved process according to the invention solve this problem and thus allow the production of a nanofiber nonwoven in an electrospinning process which consists entirely of silicone.

[0017] The present invention therefore relates to a

[0018] Electrospinning dispersion containing

[0019] (X ) Water

[0020] (Y) at least one emulsifier and / or at least one hydrophilic polymer

[0021] (Z) at least one silicone elastomer composition which is selected from addition-crosslinking or radically crosslinking silicone elastomer compositions, wherein the sum of the amounts of (Y) and (Z) used in the electrospinning dispersion is 4 to 50 wt.%.

[0022] In order to limit the number of pages describing the present invention, only the preferred embodiments of the individual features are listed below. However, the skilled reader should understand this type of disclosure to mean that any combination of different preference levels is explicitly disclosed and explicitly desired.

[0023] The electrospin dispersion according to the invention

[0024] For the sake of clarity, it is hereby defined that the electrospin dispersion according to the invention can be either a silicone emulsion or a silicone suspension. Processes for their preparation have long been known to the person skilled in the art from the prior art. Typically, preparation is carried out by simply stirring all components and, if appropriate, subsequent homogenization using jet dispersers, rotor-stator homogenizers, colloid mills, or high-pressure homogenizers. The known methods are also suitable for preparing the electrospin dispersion according to the invention.

[0025] The sum of the amounts of (Y) and (Z) used in the electrospinning dispersion is preferably 8 to 35 wt.%.

[0026] In the electrospinning dispersion according to the invention, the ratio of (Z) to (Y) is usually between 0.25 and 10.0, preferably between 0.5 and 8.0.

[0027] In a preferred embodiment, (Y) contains at least one hydrophilic polymer. In the electrospinning dispersion according to the invention, the ratio of (Z) to (Y) is between 0.25 and 4.0, preferably 0.5 to 3.0, particularly preferably 0.8 to 2.5.

[0028] The electrospinning dispersion according to the invention usually contains 50 to 96 wt.%, preferably 60 to 92 wt.% water (X).

[0029] The components (Z) and (Y) and any further optional components (W) are used in such amounts that, together with the water (X), they always add up to 100% by weight.

[0030] The electrospinning dispersion according to the invention exhibits a monomodal particle size distribution in its discontinuous phase for D50 = 100 to 1000 nm; preferably for D50 = 150 to 800 nm, and particularly preferably for D50 = 150 to 500 nm.

[0031] The method for measuring the particle size distribution is described below. Component (X)

[0032] Water is used as component (X). To avoid potential problems caused by salt deposits during the subsequent spinning process, demineralized water is preferred.

[0033] Component (Y)

[0034] As component (Y) at least one emulsifier and / or at least one hydrophilic polymer is used.

[0035] To clarify: the component (Y) can therefore be:

[0036] - a single emulsifier (Y)

[0037] - a mixture of at least two emulsifiers (Y)

[0038] - a single hydrophilic polymer (Y)

[0039] - a mixture of at least two hydrophilic polymers (Y)

[0040] - Combinations of these embodiments.

[0041] The electrospinning dispersion according to the invention preferably contains 0.4 to 40 wt.%, particularly preferably 4 to 20 wt.% (Y).

[0042] Hydrophilic polymer (Y)

[0043] The hydrophilic polymer may be a homopolymer, copolymer, block polymer, graft copolymer, star polymer, highly branched polymer, dendrimer or a mixture of two or more of the aforementioned polymer types. Suitable water-soluble polymers (Y) are, for example, polyvinyl alcohol, polyvinylformamide, polyvinylamine, polycarboxylic acid (polyacrylic acid, polymethacrylic acid), polyacrylamide, polyitaconic acid, poly (2-hydroxyethyl acrylate), poly (N-isopropylacrylamide), polysulfonic acid (e.g. poly (2-acrylamido-2-methyl-l-propanesulfonic acid), polymethacrylamide, polyalkylene oxides (e.g. polyethylene oxides); poly-N-vinylpyrrolidone; hydroxymethylcelluloses; hydroxyethylcelluloses; hydroxypropylcelluloses; carboxymethylcelluloses; polylactic acids; alginates; collagens; gelatin, poly (ethyleneimine), polystyrenesulfonic acid.Copolymers, block polymers, graft copolymers, star polymers, highly branched polymers or dendrimers are also possible, which are constructed from a combination of two or more of the above-mentioned polymer-forming monomer units.

[0044] In a preferred embodiment of the present invention, the water-soluble polymer is selected from the group consisting of polyvinyl alcohol, polyethylene oxides, poly-N-vinylpyrrolidone, and polyvinyl formamide. Polyvinyl alcohol is particularly preferred.

[0045] Polyvinyl alcohols used as component (Y) can be partially saponified or fully saponified polyvinyl alcohols, for example with a degree of hydrolysis of 80 to 100 mol%, in particular partially saponified polyvinyl alcohols with a degree of hydrolysis of 80 to 95 mol%, preferably 85 to 92 mol%. The polyvinyl alcohols have a Höppler viscosity in 4% aqueous solution of preferably 1 to 130 mPas (Höppler method at 20 °C, DIN 53015). Partially saponified, hydrophobically modified polyvinyl alcohols are also preferred, in particular with a degree of hydrolysis of 80 to 95 mol% and a Höppler viscosity in 4% aqueous solution of preferably 1 to 130 mPas.Examples of these are partially saponified copolymers of vinyl acetate with hydrophobic comonomers such as isopropenyl acetate, vinyl pivalate, vinyl ethyl hexanoate, vinyl esters of saturated alpha-branched monocarboxylic acids having 5 or 9 to 11 C atoms, dialkyl maleates and dialkyl fumarates such as diisopropyl maleate and diisopropyl fumarate, vinyl chloride, vinyl alkyl ethers such as vinyl butyl ether, and olefins such as ethene and decene. The proportion of hydrophobic units is preferably 0.1 to 10% by weight, based on the total weight of the partially saponified polyvinyl alcohol. Mixtures of the polyvinyl alcohols mentioned can also be used.

[0046] Most preferred are polyvinyl alcohols with a degree of hydrolysis of 85 to 94 mol% and a Höppler viscosity, in 4% aqueous solution, of 3 to 48 mPas (Höppler method at 20 ° C, DIN 53015).

[0047] Emulsifier (Y)

[0048] For the sake of clarity, the term emulsifier refers to surface-active substances (also known as surfactants) that are typically used as dispersing agents, regardless of whether the electrospin dispersion in question is actually an emulsion or a suspension.

[0049] As emulsifier (Y) for producing the electrospin dispersions according to the invention, all anionic, non-ionic, cationic or amphoteric emulsifiers known to date in the prior art can be used, both individually and as mixtures of at least two emulsifiers, with which aqueous dispersions, in particular aqueous emulsions of organopolysiloxanes, are produced.

[0050] Examples of anionic emulsifiers (Y) are:

[0051] 1. Alkyl sulfates, particularly those with a chain length of 8 to 18 C atoms, alkyl and alkaryl ether sulfates with 8 to 18 C atoms in the hydrophobic radical and 1 to 40 ethylene oxide (EO) or propylene oxide (PO) units. 2. Sulfonates, particularly alkylsulfonates with 8 to 18 C atoms, alkylarylsulfonates with 8 to 18 C atoms, taurides, esters and half-esters of sulfosuccinic acid with monohydric alcohols or alkylphenols with 4 to 15 C atoms; these alcohols or alkylphenols can optionally also be ethoxylated with 1 to 40 EO units.

[0052] 3. Alkali and ammonium salts of carboxylic acids with 8 to 20 C atoms in the alkyl, aryl, alkaryl or aralkyl radical.

[0053] 4. Partial phosphoric acid esters and their alkali and ammonium salts, in particular alkyl and alkaryl phosphates with 8 to 20 C atoms in the organic radical, alkyl ether or alkaryl ether phosphates with 8 to 20 C atoms in the alkyl or alkaryl radical and 1 to 40 EO units.

[0054] Examples of non-ionic emulsifiers (Y) are:

[0055] 6. Alkyl polyglycol ethers, preferably those with 3 to 40 EO units and alkyl radicals of 8 to 20 C atoms.

[0056] 7. Alkylaryl polyglycol ethers, preferably those having 5 to 40 EO units and 8 to 20 C atoms in the alkyl and aryl radicals.

[0057] 8. Ethylene oxide / propylene oxide (EO / PO) block copolymers, preferably those with 8 to 40 EO or PO units.

[0058] 9. Addition products of alkylamines with alkyl radicals from 8 to

[0059] 22 C atoms with ethylene oxide or propylene oxide.

[0060] 10. Fatty acids with 6 to 24 carbon atoms. 11. Alkyl polyglycosides of the general formula R -O-Z o , wherein

[0061] R is a linear or branched, saturated or unsaturated alkyl radical having an average of 8 - 24 C atoms and Z oan oligoglycoside residue with on average o = 1 - 10 hexose or pentose units or mixtures thereof.

[0062] 12. Natural substances and their derivatives, such as lecithin, lanolin, saponins, cellulose; cellulose alkyl ethers and carboxyalkyl celluloses, whose alkyl groups each contain up to 4 carbon atoms.

[0063] 13. Linear organo(poly)siloxanes containing polar groups, in particular the elements O, N, C, S, P, Si, in particular those containing alkoxy groups with up to 24 C atoms and / or up to 40 E0 and / or PO groups.

[0064] Examples of cationic emulsifiers (Y) are:

[0065] 14. Salts of primary, secondary and tertiary fatty amines with 8 to 24 C atoms with acetic acid, sulfuric acid, hydrochloric acid and phosphoric acids.

[0066] 15. Quaternary alkyl and alkylbenzeneammonium salts, especially those whose alkyl groups have 6 to 24 C atoms, especially the halides, sulfates, phosphates and acetates.

[0067] 16. Alkylpyridinium, alkylimidazolinium and alkyloxazolinium salts, in particular those whose alkyl chain has up to 18 C atoms, especially the halides, sulfates, phosphates and acetates.

[0068] The following are particularly suitable as amphoteric emulsifiers (Y): 17. Long-chain substituted amino acids, such as N-alkyl-di-(aminoethyl-)glycine or N-alkyl-2-aminopropionic acid salts.

[0069] 18. Betaines, such as N- (3-acylamidopropyl)-N, N-dimethylammonium salts with a CQ-C]_ g-acyl radical and alkyl-imidazolium betaines or quaternized alkyl or substituted alkyl derivatives of

[0070] N, N-Dimethyl-Glycine .

[0071] Preferred emulsifiers (Y) for the preparation of electrospin dispersions according to the invention are selected from the group of non-ionic emulsifiers, in particular from the alkyl polyglycol ethers listed above under 6.

[0072] Component (Y) may consist of one of the above-mentioned emulsifiers (Y) or of a mixture of two or more of the above-mentioned emulsifiers (Y); it may be used in pure form or as solutions of one or more emulsifiers (Y) in water or organic solvents.

[0073] Siliconelastomer composition (Z)

[0074] The silicone elastomer composition used according to the invention is selected from addition-crosslinking or radically crosslinking silicone elastomer compositions.

[0075] The electrospinning dispersion according to the invention preferably contains

[0076] 0.8 to 45 wt.%, particularly preferably 5.0 to 23 wt.% (Z).

[0077] Addition-curing silicone elastomer composition (Z)

[0078] The compounds (A) and (B) or (C) used in the addition-crosslinking silicone elastomer composition (Z) according to the invention are known to be chosen so that crosslinking is possible. For example, compound (A) has at least two aliphatically unsaturated radicals and (B) at least three Si-bonded hydrogen atoms, or compound (A) has at least three aliphatically unsaturated radicals and siloxane (B) has at least two Si-bonded hydrogen atoms, or instead of compound (A) and (B) siloxane (C) is used, which has aliphatically unsaturated radicals and Si-bonded hydrogen atoms in the abovementioned ratios. Mixtures of (A) and (B) and (C) with the abovementioned ratios of aliphatically unsaturated radicals and Si-bonded hydrogen atoms are also possible.

[0079] Component (A)

[0080] The silicone compositions according to the invention preferably contain as component (A) at least one aliphatically unsaturated organosilicon compound, it being possible to use all aliphatically unsaturated organosilicon compounds previously used in addition-crosslinking compositions, such as, for example, silicone block copolymers with urea segments, silicone block copolymers with amide segments and / or imide segments and / or ester-amide segments and / or polystyrene segments and / or silarylene segments and / or carborane segments and silicone graft copolymers with ether groups.

[0081] As organosilicon compounds (A) which have Si-C-bonded radicals with aliphatic carbon-carbon multiple bonds, preferably linear or branched organopolysiloxanes comprising units of the general formula (I)

[0082] R 4 aR 5 bS i 0 ( 4-ab ) / 2 ( D inserted , where R4 independently of one another, identical or different, an organic or inorganic radical free from aliphatic carbon-carbon multiple bonds,

[0083] R 5 independently of one another, identically or differently, denote a monovalent, substituted or unsubstituted, Si-C-bonded hydrocarbon radical having at least one aliphatic carbon-carbon multiple bond, a is 0, 1, 2 or 3, and b is 0, 1 or 2, with the proviso that the sum a + b is less than or equal to 3 and at least 2 radicals R 5 per molecule.

[0084] For rest R 4 They can be monovalent or polyvalent radicals, with the polyvalent radicals, such as bivalent, trivalent and tetravalent radicals, then linking several, such as two, three or four, siloxy units of the formula (I) to one another.

[0085] More examples for R 4are the monovalent radicals -F, -CI, - Br, -OR 6 , -CN, -SCN, -NCO and Si-C-bonded, substituted or unsubstituted hydrocarbon radicals, which may be interrupted by oxygen atoms or the group -C(O)-, as well as divalent radicals bonded to Si on both sides according to formula (I). If radical R 4 are Si-C-bonded, substituted hydrocarbon radicals, preferred substituents are halogen atoms, phosphorus-containing radicals, cyano radicals, -OR 6 , -NR 6 -, - NR 6 2, -NR 6 -C (0) -NR 6 2, — C(O)— NR 6 2, -C(O)R 6 , -C(O)OR 6 , -SO2-Ph and - CeFs. Where R 6 independently of one another, identically or differently, denote a hydrogen atom or a monovalent hydrocarbon radical having 1 to 20 carbon atoms and Ph equals the phenyl radical.

[0086] Examples of residues R 4are alkyl radicals, such as the methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl radical, 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, and octadecyl radicals, such as the n-octadecyl radical, cycloalkyl radicals, such as 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 β-phenylethyl radicals.

[0087] Examples of substituted radicals R 4are haloalkyl radicals, such as the 3, 3, 3-trifluoro-n-propyl radical, the 2, 2, 2, 2', 2', 2'-hexafluoroisopropyl radical, the heptafluoroisopropyl radical, haloaryl radicals, such as the o-, m- and p-chlorophenyl radical, - (CH2)- N (R 6 ) C (0) NR 6 2, - (CH2) nC (0) NR 6 2, - (CH2) O -C (0) R 6 , - (CH2) O -C (0) OR 6 , - (CH2) oC (0) NR 6 2, - (CH2) -C (0) - (CH2) P C (O) CH3, - (CH2) -O-CO-R 6 , - (CH2) - NR 6 - (CH2) P -NR 6 2, - (CH2) oO- (CH2) P CH (0H) CH20H, - (CH2) o (OCH2CH2) P 0R 6 , - (CH2) o-SO2-Ph and - (CH2) o-O-C6F5, where R 6 and Ph has the meaning given above and o and p are identical or different integers between 0 and 10 .

[0088] Examples for R 4Divalent radicals bonded to Si on both sides according to formula (I) are those which differ from the radicals R 4 mentioned monovalent examples by an additional bond occurring through substitution of a hydrogen atom, examples of such radicals are - (CH2)-, -CH(CH3)-, -C(CH3)2-, -CH (CH3) -CH2-, -C6H4-, -CH (Ph) -CH2- , ix is ​​0 or 1, and Ph, o and p have the meaning given above.

[0089] Preferably, the residue R 4 a monovalent, Si-C-bonded, optionally substituted hydrocarbon radical having 1 to 18 carbon atoms and free of aliphatic carbon-carbon multiple bonds, particularly preferably a monovalent, Si-C-bonded hydrocarbon radical having 1 to 6 carbon atoms and free of aliphatic carbon-carbon multiple bonds, in particular the methyl or phenyl radical.

[0090] For rest R5 from formula (I) can be any group that is accessible to an addition reaction (hydrosilylation) with a SiH-functional compound.

[0091] If Rest R 5 are Si-C-bonded, substituted hydrocarbon radicals, the substituents are halogen atoms, cyano radicals and -OR 6 preferred, where R 6 has the meaning given above .

[0092] Preferably, the residue R 5 alkenyl and alkynyl groups having 2 to 16 carbon atoms, such as vinyl, allyl, methallyl, 1-propenyl, 5-hexenyl, ethynyl, butadienyl, hexadienyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, vinylcyclohexylethyl, divinylcyclohexylethyl, norbornenyl, vinylphenyl, and styryl radicals, with vinyl, allyl, and hexenyl radicals being particularly preferred. The molecular weight of component (A) can vary within wide limits, approximately between 10 2 and 106 g / mol. For example, component (A) can be a relatively low molecular weight alkenyl-functional oligosiloxane, such as 1,2-divinyltetramethyldisiloxane, but also a high-polymer polydimethylsiloxane having chain-based or terminal Si-bonded vinyl groups, e.g. with a molecular weight of 10 5 g / mol (number average determined by NMR). The structure of the molecules forming component (A) is also not fixed; in particular, the structure of a higher molecular weight, i.e., oligomeric or polymeric siloxane can be linear, cyclic, branched, or resinous, network-like. Linear and cyclic polysiloxanes are preferably composed of units of the formula R 4 3SiOi / 2, R 5 R 4 2SiOi / 2, R 5 R 4 SiOi / 2 and R 4 2SiO2 / 2, where R 4 and R 5have the meaning given above. Branched and network-like polysiloxanes additionally contain trifunctional and / or tetrafunctional units, where those of the formulas R 4 SiO3 / 2, R 5 SiO3 / 2 and SiO4 / 2 are preferred. Of course, mixtures of different siloxanes that meet the criteria of component (A) can also be used.

[0093] Particularly preferred as component (A) is the use of vinyl-functional, essentially linear polydiorganosiloxanes having a viscosity of 0.1 to 800,000 mPa-s, particularly preferably 0.1 to 200,000 mPa-s, in each case at 25°C, measured according to DIN EN ISO 3219: 1994 and DIN 53019 by means of a calibrated rheometer with a cone-plate system, cone CP50-2 with an opening angle of 2° and a shear rate of 0.1 s~ 4 .

[0094] Component (B)

[0095] As organosilicon compounds (B) it is possible to use all hydrogen-functional organosilicon compounds which have previously been used in addition-crosslinkable compositions.

[0096] As organopolysiloxanes (B) which have Si-bonded hydrogen atoms, preferably linear, cyclic or branched organopolysiloxanes comprising units of the general formula (III)

[0097] R 4 cH d SiO(4-cd) / 2 (III) is used, where

[0098] R 4 has the meaning given above, c is 0, 1, 2 or 3 and d is 0, 1 or 2, with the proviso that the sum of c + d is less than or equal to 3 and at least two Si-bonded hydrogen atoms are present per molecule.

[0099] The organopolysiloxane (B) used according to the invention preferably contains Si-bonded hydrogen in the range from 0.04 to 1.7 percent by weight, based on the total weight of the organopolysiloxane (B).

[0100] The molecular weight of component (B) can also vary within wide limits, approximately between 10 2 and 10 6 g / mol. Thus, component (B) can, for example, be a relatively low molecular weight SiH-functional oligosiloxane, such as tetramethyldisiloxane, but also a high-polymer polydimethylsiloxane containing chain- or terminal SiH groups, or a silicone resin containing SiH groups. The structure of the molecules forming component (B) is also not specified; in particular, the structure of a higher molecular weight, i.e. oligomeric or polymeric SiH-containing siloxane can be linear, cyclic, branched, or resinous, network-like. Linear and cyclic polysiloxanes (B) are preferably composed of units of the formula R 4 3SiOi / 2 , HR 4 2SiOi / 2 , HR 4 SiO2 / 2 and R 4 2SiO2 / 2 , where R 4has the meaning given above. Branched and network-like polysiloxanes additionally contain trifunctional and / or tetrafunctional units, where those of the formulas R 4 SiO3 / 2 , HS1O3 / 2 and S1O4 / 2 are preferred, where R 4 has the meaning given above .

[0101] Of course, mixtures of different siloxanes that satisfy the criteria of component (B) can also be used. In particular, the molecules forming component (B) can, in addition to the obligatory SiH groups, optionally also contain aliphatically unsaturated groups. Particular preference is given to using low molecular weight SiH-functional compounds such as tetrakis(dimethylsiloxy)silane and tetramethylcyclotetrasiloxane, and higher molecular weight, SiH-containing siloxanes such as poly(hydrogenmethyl)siloxane and poly(dimethylhydrogenmethyl)siloxane having a viscosity at 25°C of 10 to 20. 000 mPa - s , measured according to DIN EN ISO 3219 : 1994 and DIN 53019 using a calibrated rheometer with a cone-plate system, cone CP50-2 with an opening angle of 2 ° and a shear rate of 0 .1 s~ 4, or analogous SiH-containing compounds in which part of the methyl groups is replaced by 3,3,3-trifluoropropyl or phenyl groups.

[0102] Component (B) is preferably present in the crosslinkable silicone compositions according to the invention in an amount such that the molar ratio of SiH groups to aliphatically unsaturated groups from (A) is from 0.1 to 20, particularly preferably between 0.3 and 2.0.

[0103] The components (A) and (B) used according to the invention are commercially available products or can be produced by conventional processes.

[0104] Instead of components (A) and (B), the silicone compositions according to the invention can contain organopolysiloxanes (C) that simultaneously contain aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms. The silicone compositions according to the invention can also contain all three components (A), (B), and (C).

[0105] Component (C)

[0106] If siloxanes (C) are used, they are preferably those consisting of units of the general formulas (IV), (V) and (VI)

[0107] R 4 fSiO4 / 2 (IV)

[0108] R 4 g R 5 SiO3-g / 2 (V)

[0109] R 4 hHSiO3-h / 2 (VI) where

[0110] R 4 and R 5 have the meaning given above, f is 0, 1, 2 or 3, g is 0, 1 or 2 and h is 0, 1 or 2, with the proviso that at least two radicals R 5 and at least two Si-bonded hydrogen atoms are present. Examples of organopolysiloxanes (C) are those of S1O4 / 2, R 4 3SiOi / 2-, R 4 2R 5 SiOi / 2 and R 4 2HSiOi / 2 units, so-called MQ resins, whereby these resins additionally contain R 4 SiO3 / 2 and R 42SiO units, as well as linear organopolysiloxanes consisting essentially of R 4 2R 5 SiOi / 2- , R 4 2SiO- and R 4 HSiO units with R 4 and R 5 equal to the meaning given above.

[0111] The organopolysiloxanes (C) preferably have an average viscosity of 0.01 to 800,000 Pa-s, particularly preferably 0.1 to 200,000 Pa-s, each at 25°C, measured according to DIN EN ISO 3219: 1994 and DIN 53019 using a calibrated rheometer with a cone-plate system, cone CP50-2 with an opening angle of 2° and a shear rate of 0.1 s~ 4 .

[0112] Organopolysiloxanes (C) are commercially available or can be prepared using conventional methods.

[0113] The addition-crosslinking silicone elastomer composition (Z) according to the invention usually contains 30-95 wt.%, preferably 30-80 wt.% and particularly preferably 35-70 wt.% (A), based on the total mass of the addition-crosslinking silicone elastomer composition (Z).

[0114] The addition-crosslinking silicone elastomer composition (Z) according to the invention usually contains 0.1-60 wt.%, preferably 0.5-50 wt.% and particularly preferably 1-40 wt.% (B), based on the total mass of the addition-crosslinking silicone elastomer composition.

[0115] If the addition-crosslinking silicone elastomer composition (Z) according to the invention contains component (C), usually 30-95% by weight, preferably 30-80% by weight, particularly preferably 40-70% by weight of (C) are contained in the formulation, based on the total mass of the addition-crosslinking silicone elastomer composition (Z).

[0116] Component (D)

[0117] All catalysts known in the art can be used as the hydrosilylation catalyst (D). Component (D) can be a platinum group metal, for example platinum, rhodium, ruthenium, palladium, osmium or iridium, an organometallic compound or a combination thereof. Examples of component (D) are compounds such as hexachloroplatinic(IV) acid, platinum dichloride, platinum acetylacetonate and complexes of the said compounds encapsulated in a matrix or a core-shell-like structure. Low molecular weight platinum complexes of the organopolysiloxanes include 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes with platinum. Further examples are platinum phosphite complexes, platinum phosphine complexes or alkylplatinum complexes. These compounds can be encapsulated in a resin matrix.Suitable hydrosilylation catalysts (D) are also those which can be activated by electromagnetic radiation (UV, UV-VIS, IR). Such catalysts have also been known from the prior art for a long time. Examples include (r|-diolef in)(<5-aryl)-platinum complexes (e.g. described in US 6046250 corresponding to EP0561919B1), Pt(II)-ß-diketonate complexes (e.g. described in CA2014996A corresponding to EP0398701B1) and (r|. 5-Cyclopentadienyl) tri(<5-alkyl) platinum(IV) complexes (e.g. described in US 6376569 corresponding to EP0561893B1) and MeCpPtMe3 as well as the complexes derived therefrom by substitution of the groups on the platinum (e.g. described in US 6127446 corresponding to EP1803728B1). The concentration of component (D) in the addition-curing silicone elastomer composition (Z) is sufficient to catalyze the hydrosilylation reaction of components (A) and (B) upon exposure to generate the heat required in the process described here. The amount of component (D) can be between 0.1 and 1000 parts per million (ppm), 0.5 and 100 ppm or 1 and 50 ppm of the platinum group metal, depending on the total weight of the components. The hardening rate may be low if the platinum group metal content is below 1 ppm.The use of more than 100 ppm of the platinum group metal is uneconomical or may reduce the stability of the adhesive formulation.

[0118] The Karstedt catalyst (platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex) is preferred for 2K systems. Platinum phosphite complexes are preferred for IK systems, as disclosed, for example, in US2009088524A, corresponding to EP2050768 A.

[0119] Component (E)

[0120] As component (E), fillers such as fumed or precipitated silica, or resinous, i.e., three-dimensionally cross-linked polyorganosiloxanes other than (A), (B), and (C) can be used. Reinforcing fillers such as fumed or precipitated silica with BET surface areas between 50 m 2 / g and 400 m 2 / g, where pyrogenic and precipitated silicas with BET surface areas of between 100 m 2 / g and 300 m2 / g are particularly preferred. The silica fillers mentioned may be hydrophilic in nature or hydrophobized by known methods. Surface-treated silicas (E) are preferably used. The surface treatment is achieved by the methods known in the art for hydrophobizing finely divided fillers.

[0121] Preferred fillers (E) have a carbon content of at least 0.01 to a maximum of 20 wt.%, preferably between 0.1 and 10 wt.%, particularly preferably between 0.5 and 5 wt.%, as a result of a surface treatment. Particularly preferred are crosslinkable, addition-crosslinking silicone elastomer compositions (Z) characterized in that the filler (E) is a surface-treated silica containing 0.01 to 2 wt.% of Si-bonded, aliphatically unsaturated groups. These are, for example, Si-bonded vinyl groups.

[0122] The three-dimensionally crosslinked polyorganosiloxanes, which are also preferred as component (E), and which are different from (A), (B) and (C), are so-called organosiloxane resins which are composed of units of the general formulas (VII), (VIII), (IX) and (X)

[0123] R 3 sio l / 2 M-unit (VII),

[0124] R 2 si0 2 / 2 D-unit (VIII),

[0125] R SiO 3 / 2 T-Unit (IX) ,

[0126] SiO4 / 2Q unit (X) in which

[0127] 1 2

[0128] R is selected from R , R , OH and OR 2 , and with the proviso that at least 20 mol% of the units are selected from units of the general formulas (IX) and (X) , and at most 2 wt.% of the radicals R are OH.

[0129] At R 1are identical or independently different monovalent organofunctional hydrocarbon radicals, unsaturated hydrocarbon radicals or a hydrogen radical, where the radical R 1 is bonded to the silicon atom via a carbon atom, or the hydrogen radical is bonded directly to the silicon atom. R is preferably 1 is an alkenyl group or the hydrogen radical. R is particularly preferably 1 the vinyl group. 2

[0130] R are identical or independently different monovalent hydrocarbon radicals (alkyl, aryl, aralkyl).

[0131] 2

[0132] Examples of unsubstituted radicals R are alkyl radicals such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl, hexyl radicals such as n-hexyl, heptyl radicals such as n-heptyl, octyl radicals such as n-octyl and iso-octyl radicals such as 2,2,4-trimethylpentyl, nonyl radicals such as n-nonyl, decyl radicals such as n-decyl; Alkenyl radicals, such as vinyl, allyl, n-5-hexenyl, 4-vinylcyclohexyl and 3-norbornenyl radicals; cycloalkyl radicals, such as cyclopentyl, cyclohexyl, 4-ethylcyclohexyl, cycloheptyl radicals, norbornyl radicals and methylcyclohexyl radicals; aryl radicals, such as phenyl, biphenylyl and naphthyl radicals; alkaryl radicals, such as o-, m-, p-tolyl radicals and ethylphenyl radicals; aralkyl radicals, such as benzyl, alpha- and ß-phenylethyl radicals.Examples of substituted hydrocarbon radicals as R radicals are halogenated hydrocarbons such as the chloromethyl, 3-chloropropyl, 3-bromopropyl, 3,3,3-trifluoropropyl and 5,5,5,4,4,3,3-heptafluorpentyl radicals as well as the chlorophenyl, dichlorophenyl and trifluorotolyl radicals.

[0133] 2

[0134] R preferably has 1 to 6 carbon atoms. Methyl and phenyl are particularly preferred.

[0135] The preferred radicals R are methyl, ethyl, phenyl and vinyl.

[0136] These organosiloxane resins (E) preferably contain at least 30 mol%, in particular at least 40 mol% and preferably at most 80 mol%, in particular at most 70 mol%, of units of the general formulas (IX) and (X).

[0137] These organosiloxane resins (E) are preferably MQ silicone resins (MQ) containing at least 80 mol% units, preferably at least 95 mol%, in particular at least 97 mol% units of the general formulas (VII) and (X). The average ratio of the units of the general formulas (VII) to (X) is preferably at least 0.25, in particular at least 0.5, and preferably 2, particularly preferably at most, in particular at most 1.5.

[0138] Preferably, at most 1 wt.%, in particular at most 0.5 wt.% of the radicals R are OH.

[0139] Preferably at least 0.01 mol%, particularly preferably at least 0.05 mol%, and preferably at most 8 mol%, in particular at most 5 mol% of the radicals R are an R 1. The average molecular weight Mn of the organosiloxane resins (E) is preferably at least 200 g / mol, in particular at least 1000 g / mol and preferably at most 100,000 g / mol, in particular at most 20,000 g / mol.

[0140] In the addition-crosslinking silicone composition (Z) according to the invention, the component (E) is preferably used as a single or likewise preferably as a mixture of several finely divided fillers.

[0141] The addition-crosslinking silicone elastomer composition (Z) according to the invention preferably contains 0 to 45 wt.% (E), particularly preferably 0-35 wt.% (E).

[0142] The addition-curing silicone compositions according to the invention may optionally contain any other additives known to the person skilled in the art for addition-curing compositions. These additives may be, for example, rheological additives, inhibitors, light stabilizers, flame-retardants, dispersing aids, heat stabilizers, etc.

[0143] For the sake of clarity, it should be noted that the amounts used for each individual component of the silicone elastomer composition (Z) are selected such that they always add up to 100% by weight.

[0144] Radically crosslinking silicone elastomer composition (Z)

[0145] Radically crosslinking silicone elastomer compositions have long been known to the person skilled in the art from the prior art. Peroxide-crosslinking silicone elastomer compositions are preferred: in the simplest case, these contain at least one organopolysiloxane with at least two crosslinkable groups per molecule, such as methyl or vinyl groups, and at least one suitable organic peroxide as a catalyst. Examples of suitable organic peroxides are acyl peroxides, such as dibenzoyl peroxide, bis-(4-chlorobenzoyl) peroxide, bis-(2,4-dichlorobenzoyl) peroxide and bis-(4-methylbenzoyl) peroxide; alkyl peroxides and aryl peroxides, such as di-tert. -butylperoxy)-2,5-dime thy 1-hexane, dicumyl peroxide and 1,3-bis-(tert.-butylperoxy-isopropyl)-benzene; perketals such as 1,1-bis-(tert.-butylperoxy)-3,3,5-trimethylcyclohexane; peresters such as diacetyl peroxydicarbonate, tert.-butyl perbenzoate, tert.-butylperoxyisopropylcarbonate, tert. -butylperoxyisononanoate, dicyclohexylperoxydicarbonate, and 2,5-dimethylhexane-2,5-diperbenzoate. One type of organic peroxide or a mixture of at least two different types of organic peroxides can be used.

[0146] In a further preferred embodiment, the radically crosslinking silicone elastomer composition (Z) according to the invention contains at least one aliphatically unsaturated organosilicon compound (A) and a photoinitiator.

[0147] In a preferred embodiment, the radically crosslinking silicone elastomer composition (Z) additionally contains at least one mercaptoalkyl-functional polydiorganosiloxane (M) of the general formula (XI):

[0148] R 7 R 8 R 9 SiO- [SiR 10 R 11 -O] y - [ SiR 12 R 13 -O] z -SiR 7 R8 R 9 (XI ) where R 12 is selected from Mercaptomethyl, Mercaptoethyl , Mercaptopropyl ,

[0149] R 10 , R 11 , R 8 , R 9 and R 13 are independently selected from C1-C2 O-hydrocarbon radicals (alkyl+aryl), and

[0150] R 7 , is selected either from mercaptomethyl, mercaptoethyl, mercaptopropyl or from a C1-C2 O-hydrocarbon radical (alkyl+aryl), and y = 1 - 200 and z = 1 - 20.

[0151] Alternatively to (A) or (M) or in addition to (A) and (M), at least one mixed functionalized mercaptoalkyl-functional polydiorganosiloxane (N) can also be used with the general formula (XII)

[0152] R 14 R 8 R 9 SiO- [SiR 10 R 11 -O] y - [SiR 15 R 13 -O] z -SiR 14 R 8 R 9(XII) where R 14 and R 15 are selected from the group comprising -sulfur-free alkenyl and alkynyl groups having 2 to 16 carbon atoms and -mercaptomethyl, mercaptoethyl and mercaptopropyl, where R 8 , R 9 , R 10 , R 11 , R 13 , y and z have the meaning given above, with the proviso that when R 14 is a sulfur-containing group, R 15 must be a sulfur-free group or if R 14 is a sulfur-free group, R 15 must be a sulfur-containing group.

[0153] The radically crosslinking silicone elastomer composition (Z) may also contain the above-mentioned components (E).

[0154] Other optional components (W)

[0155] The electrospinning dispersions according to the invention can optionally contain further ingredients. Examples of such components are salts, pH regulators, foam inhibitors, thickeners and / or protective colloids, preservatives, disinfectants, wetting agents, corrosion inhibitors, dyes, fragrances or mixtures thereof. If salts are added specifically, they serve as conductive salts in order to ensure or improve the electrospinnability of the electrospinning dispersion. Such conductive salts are suitable for the defined adjustment of the electrical conductivity and have long been known in the electrochemical industry. In particular, these conductive salts can be inorganic, organic salts or mixtures thereof. Thermally labile salts such as pyridinium formate and ammonium formate are preferably used as conductive salts.If components (W) are used, they are preferably first added to one of the components (X) or (Y), particularly preferably to the water (X).

[0156] The present invention further provides a process for producing nonwovens, in which, in a first step, the electrospinning dispersion according to the invention is prepared by mixing all components according to the invention, in a second step, a nonwoven fabric made of fibers is produced from this electrospinning dispersion by means of electrospinning, wherein the crosslinking of the silicone composition (Z) is initiated or not initiated thermally or by means of electromagnetic radiation, in a third step, the crosslinking of the silicone composition (Z) is completely cured thermally or by means of electromagnetic radiation, in a fourth step, at least once, the washing out of

[0157] (Y) from the fleece with at least one protic polar solvent (i), in a fifth step the solvent exchange of (i) is carried out by washing the fleece at least once with at least one organic solvent (ii), wherein the organic solvent (ii) is characterized in that its surface tension is lower than that of the protic polar solvent (i).

[0158] Second step:

[0159] The fibers of the fleece produced in this way preferably have a diameter of less than 1 pm.

[0160] Fourth step:

[0161] This step serves to remove component (Y). To ensure its complete removal, this step can be repeated one or more times. The protic polar solvent (i) used for this purpose can also be a mixture (i) of at least two (i) components, which contains 30 to 100 wt.% water. Preferably, (i) contains 50 to 100 wt.%, particularly preferably 85 to 100 wt.% water. Other components of (i) can be alcohols such as methanol, ethanol, and isopropanol, or surface-active substances such as surfactants or emulsifiers.

[0162] The fourth step is preferably carried out using ultrasound treatment.

[0163] Fifth step:

[0164] This step serves to exchange the protic polar solvent (i) for the organic solvent (ii). To ensure its complete removal, this step can be repeated one or more times. If the solvent exchange is carried out by repeating this step two or more times, it is preferable that an organic solvent (II) with the same or lower surface tension as in the previous exchange step is used in each subsequent exchange step.

[0165] Suitable organic solvents (11) are alcohols such as methanol, ethanol, n-propanol, isopropanol, n-amyl alcohol, i-amyl alcohol; ethers such as dioxane, tetrahydrofuran, diethyl ether, diisopropyl ether, diethylene glycol dimethyl ether; chlorinated hydrocarbons such as dichloromethane, trichloromethane, tetrachloromethane, 1, 2-dichloroethane, trichloroethylene; hydrocarbons such as pentane, n-hexane, hexane isomer mixtures, heptane, octane, white spirit, petroleum ether, benzene, toluene, xylenes; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, methyl isobutyl ketone (MIBK); esters such as ethyl acetate, butyl acetate, propyl propionate, ethyl butyrate, ethyl isobutyrate; Carbon disulfide and nitrobenzene, or mixtures of these solvents.

[0166] (ii) may also be a mixture of at least two organic solvents (11).

[0167] (ii) may also be a mixture of (i) and (ii), with the proviso that (ii) is homogeneously miscible, ie soluble in (i) and the proportion of (ii) is so high that the surface tension of the mixture of (i) and (ii) is lower than the surface tension of the pure component (i).

[0168] This fifth step preferably takes place at a temperature between 0 and 100°C.

[0169] Sixth step:

[0170] In a further particularly preferred embodiment, the sixth step is thermal drying of the washed nonwoven at 20 to 200 °C.

[0171] This sixth step preferably takes place at a reduced pressure of 0.001 to 800 mbar. The possible start of crosslinking in the second step and the complete curing in the third step of the silicone composition (Z) preferably takes place thermally, preferably at 20 ° C to 250 ° C, preferably at least 50 ° C, in particular at least 100 ° C, preferably at 120-210 ° C. The thermal curing takes place, for example, by means of a heatable collector, by means of infrared radiation with a wavelength of 780 nm to 1 mm or by means of an oven.

[0172] If crosslinking is carried out by irradiation, this is carried out with light of wavelength 230-450 nm, preferably for at least 1 second, particularly preferably for at least 5 seconds and preferably for at most 500 seconds, particularly preferably for at most 240 seconds.

[0173] If the fibers are cross-linked using photoinitiators, the irradiation with light preferably lasts at least 1 second, particularly preferably at least 5 seconds and preferably at most 500 seconds, particularly preferably at most 240 seconds.

[0174] Crosslinking with photoinitiators can be carried out under protective gas such as N2 or Ar or under air.

[0175] After irradiation with light, the irradiated fibers are optionally thermally post-treated and then heated preferably for a maximum of 1 hour, particularly preferably for a maximum of 10 minutes, in particular for a maximum of 5 minutes, in order to cure them.

[0176] Particularly preferably, crosslinking is carried out with light of wavelength 230-450 nm, in particular at 254 to 450 nm.

[0177] It is known to those skilled in the art that the reaction underlying the crosslinking of the silicone composition (Z) can take place at least partially during the electrospinning process. This can be brought about in particular by heating the ambient air or irradiating it with IR or UV radiation during electrospinning. However, a staggered crosslinking of the silicone composition is also conceivable, so that the third step is carried out separately from the second step and subsequently.

[0178] A further subject of the present invention are the crosslinked nonwovens according to the invention produced by the process according to the invention.

[0179] The present invention further relates to the use of the crosslinked nonwovens according to the invention as a coating for three-dimensional structures, in wound dressings, in packaging materials, and also in filters and membranes.

[0180] The nonwovens according to the invention are suitable as a coating for three-dimensional structures in order to modify their surface properties with regard to, for example, sound or thermal insulation or shock absorption. The breathability achievable with the coating can represent a desirable additional property. Housings, building materials, or textiles are preferably coated or laminated with the nonwovens according to the invention.

[0181] Furthermore, the nonwovens according to the invention can also preferably be used in wound plasters.

[0182] The nonwovens according to the invention can also be used as a bacteriophobic and / or antimicrobial coating.

[0183] Also preferred is the use of the inventive

[0184] Nonwovens in packaging materials, particularly in food packaging. The nonwovens according to the invention are also suitable for coating containers for storing liquids, allowing the containers to be completely emptied.

[0185] The nonwovens according to the invention can also be used particularly preferably in clothing, such as jackets, gloves, hats, or shoes, or as roofing membranes. The nonwovens according to the invention are water-repellent and breathable.

[0186] The nonwovens according to the invention can also be used particularly preferably as filter media, e.g., for air filters or for separating particles from gas or liquid streams. The nonwovens according to the invention can also be used, in particular, as filter media in respiratory masks, e.g., in FFP3 and FFP2 masks.

[0187] The nonwovens according to the invention can also be used as membranes for separating mixtures, such as in reverse osmosis, gas separation, pervaporation, nanofiltration, ultrafiltration or microfiltration. Solid-solid, gas-gas, solid-gas or liquid-gas, in particular liquid-liquid, solid-gas and liquid-solid mixtures, can be separated. If the nonwovens according to the invention are used as membranes, they can be incorporated into common modules, such as hollow fiber modules, spiral wound modules, plate modules, cross-flow modules or dead-end modules.

[0188] The nonwovens according to the invention can also be used as a carrier or support layer for other membranes.

[0189] Examples The following examples describe the basic feasibility of the present invention, without, however, limiting it to the contents disclosed therein.

[0190] In the following examples, all parts and percentages are by weight unless otherwise stated. Unless otherwise stated, the following examples are carried out at ambient atmospheric pressure, i.e., approximately 1000 hPa, and at room temperature, i.e., approximately 25 °C or a temperature that occurs when the reactants combine at room temperature without additional heating or cooling.

[0191] Mixing method

[0192] The silicone composition was mixed in a laboratory mixer from VMA-Getzmann GmbH with a toothed dissolver disc (diameter 40 mm).

[0193] Starting materials

[0194] Component (Y):

[0195] A polyvinyl alcohol with a Höppler viscosity (Höppler method at 20 ° C, DIN 53015) of 5 mPa - s and a degree of saponification of 88 % was used.

[0196] Hydrophobic silica HDK® H30 : fumed silica with dimethylsiloxy groups, BET surface area: 250 m2 / g, tamped density: 40 g / ml (available from WACKER Chemie AG).

[0197] Component ( Z )

[0198] As silicone composition 1, a UV-addition-crosslinking silicone rubber composition according to Example 6 from US2018208797A (=corresponding to WO2017089496A1) was prepared. As silicone composition 2, a thermally addition-crosslinking silicone composition according to Example 6 from US2018208797A (=corresponding to WO2017089496A1) was prepared, wherein instead of the UV-activatable platinum catalyst mentioned, a thermally activatable platinum complex with phosphite ligands suitable for one-component systems was selected, as described in US2009088524A (=corresponding to EP2050768B1) (Catalyst 6).

[0199] The two-component, thermally addition-curing silicone elastomer LUMIS IL® LR 7601 / 60 consisting of an A and a B component available from Wacker Chemie AG was used as silicone composition 3A and 3B.

[0200] Method for determining particle size distribution

[0201] "The particle size measurement of the dispersion according to the invention was carried out using a Malvern Mastersizer 2000 (Malvern Instruments GmbH, D-Herrenberg; measuring principle: Fraunhofer diffraction according to ISO 13320). The parameters used for the measurement were a spherical model with a refractive index of the continuous phase of 1.33, a refractive index of the disperse phase of 1.39, and an absorption of 0.01. The measured value is D (50), the median value of the volume distribution."

[0202] Examples of implementation

[0203] Example 1 - Preparation of electrospinning dispersion 1 (according to the invention)

[0204] 34.5 g of a 20% by weight aqueous solution of (Y) were initially introduced into a double-walled, water-cooled vessel. 10 g of the silicone composition 2 were added in portions and dispersed using the Ultra-Turrax T50 for a total of 7 minutes at 5000 rpm. The mixture was then diluted with 37.9 g of demineralized water by adding it in portions and dispersing it further at 5000 rpm for a total of 13 minutes. A smooth, white dispersion containing 12% by weight of silicone composition, 8% polyvinyl alcohol and 80% by weight of water was obtained. The particle size distribution is monomodal with a D50 value of 295 nm.

[0205] Example 2 - Preparation of electrospinning dispersion 2 (according to the invention)

[0206] The preparation was carried out analogously to Example 1, with the only difference being that silicone composition 1 was used. The particle size distribution is monomodal with a D50 value of 300 nm.

[0207] Example 3 - Preparation of electrospinning dispersion 3A and 3B (according to the invention)

[0208] Dispersion 3A: 34.5 g of a 20 wt. % aqueous solution of (Y) were initially introduced into a double-walled, water-cooled vessel. 10 g of the silicone composition 3A were added in portions and dispersed using the Ultra-Turrax T50 for a total of 7 minutes at 5000 rpm. The mixture was then diluted with 37.9 g of demineralized water by adding it in portions and dispersing further at 5000 rpm for a total of 13 minutes. A smooth, white dispersion containing 12 wt. % silicone composition, 8 wt. % polyvinyl alcohol and 80% water was obtained. The particle size distribution is monomodal with a D50 value of 295 nm.

[0209] Dispersion 3B: was prepared analogously to Dispersion 3A, with the only difference being that silicone composition 3B was used. The particle size distribution is monomodal with a D50 value of 295 nm. Example 4: Preparation of Electrospinning Dispersion 4 (according to the invention)

[0210] The preparation was carried out analogously to Example 1, with the only difference being that 1 g of the emulsifier iso-tridecyl alcohol polyglycol ether Genapol® X-080 (CAS No. 9043-30-5, available from Sigma Aldrich) was additionally added to the polyvinyl alcohol solution. A smooth, white dispersion containing 12% silicone composition, 8% polyvinyl alcohol, 1 g of emulsifier, and 79% water was obtained. The particle size distribution is monomodal with a D50 value of 350 nm.

[0211] Electrospinning:

[0212] The electrospinning process was carried out analogously to W02014114501. Electrospin dispersions 1, 2, 4, and 5 are single-component crosslinking and were spun within 24 hours of preparation. To produce the two-component system consisting of the two electrospin dispersions 3A and 3B, they were mixed in a ratio of 1:1 for 5 minutes and then spun immediately.

[0213] The conditions of the electrospinning system were as follows: Voltage: 22.5 kV DC Distance between cannula and electrode: 40 cm Diameter of cannula: 1 mm Flow rate: 5 mL / h

[0214] Aluminum foil was used as the substrate. The electrode was either static or rotated by an electric motor. After the electrospinning process was completed, the sample containing the deposited silicone material and the aluminum foil was photochemically treated using UV radiation or thermally. In the case that silicone composition 2 or 3 (dispersion 1, 3 and 4) was used, the fibers were cured in an oven at 150°C for 20 minutes. In the case that silicone composition 1 or 4 (dispersion 2 and 5) was used, the sample was irradiated for 2 minutes with a mercury vapor lamp (1.5 J / cm 2 ) irradiated.

[0215] Examples according to the invention

[0216] Washing step & solvent exchange

[0217] In order to remove the polyvinyl alcohol and thus obtain a fleece consisting only of silicone, the deposited material was peeled off the aluminum foil, placed in demineralized water (25 °C) and touched with the ultrasonic finger (UP400S, equipped with a sonotrode model S3 with a diameter of 3 mm, maximum amplitude 210 pm; max. sound power density 460 W / cm 2 The sample was treated with ultrasonic waves (available from Hielscher Ultrasonics GmbH) at 50% amplitude power three times for 5 minutes. Between washes, the water was replaced without allowing the fleece to dry out, and the sample was treated with ultrasound two more times. After this wash step, the sample was washed seven times with deionized water (75 °C). The wet fleece was placed in an aluminum dish (20 cm diameter) and washed five times with isopropanol, then five times with acetone, and finally five times with n-hexane.

[0218] Drying

[0219] The sample was dried at 25 °C until constant mass.

[0220] Comparative examples (not according to the invention)

[0221] The same electrospinning dispersion as in Examples 1 to 4 was used.

[0222] Electrospinning was also carried out analogously as described above.

[0223] Washing step & drying In order to remove the polyvinyl alcohol and thus obtain a fleece consisting only of silicone, the deposited material was peeled off the aluminum foil, placed in demineralized water (25 ° C) and touched with the ultrasonic finger (UP400S, equipped with a sonotrode model S3 with a diameter of 3 mm, maximum amplitude 210 pm; max. sound power density 460 W / cm 2The sample was treated three times for 5 minutes using a 50% amplitude ultrasonic generator (available from Hielscher Ultrasonics GmbH). Between runs, the water was replaced without allowing the fleece to dry out, and the sample was treated with ultrasound two more times. After this washing step, the sample was washed seven times with deionized water (75 °C). The sample was dried at 25 °C and atmospheric pressure until constant mass was reached.

[0224] Result comparison:

[0225] The resulting nonwoven fabric was examined by scanning electron microscopy (SEM). It was found that in the nonwovens produced by the process not according to the invention, the structure of the nonwoven fabric collapsed and its porosity decreased. In contrast, nonwovens produced by the process according to the invention, i.e., in which a solvent exchange was carried out between washing and drying, exhibited an open-pore nonwoven structure.

Claims

Patent claims 1. Electrospinning dispersion containing (X) Water (Y) at least one emulsifier and / or at least one hydrophilic polymer (Z) at least one silicone elastomer composition which is selected from addition-crosslinking or radically crosslinking silicone elastomer compositions, wherein the sum of the amounts of (Y) and (Z) used in the electrospinning dispersion is 4 to 50 wt.%.

2. Electrospinning dispersion according to claim 1, characterized in that the hydrophilic polymer (Y) is selected from the group containing polyvinyl alcohol, polyethylene oxides, poly-N-vinylpyrrolidone, polyvinylformamide.

3. Electrospinning dispersion according to claim 1 or 2, characterized in that the emulsifier (Y) is selected from the group of non-ionic emulsifiers.

4. Electrospinning dispersion according to one of claims 1 to 3, characterized in that the ratio of (Z) to (Y) is between 0.25 and 10.

5. Electrospinning dispersion according to one of claims 1 to 3, characterized in that (Y) is at least one hydrophilic polymer and the ratio of (Z) to (Y) is between 0.25 and 4.

0.

6. Electrospinning dispersion according to one of claims 1 to 5, characterized in that the monomodal particle size distribution of its discontinuous phase is for D50 = 100 to 1000 nm, preferably 150 to 800 nm.

7. A process for producing nonwovens in which, in a first step, the electrospinning dispersion according to one of claims 1 to 6 is prepared by mixing all components, in a second step, a nonwoven fabric of fibers is produced from this electrospinning dispersion by means of electrospinning, wherein the crosslinking of the silicone composition (Z) is initiated or not initiated thermally or by means of electromagnetic radiation, in a third step, the crosslinking of the silicone composition (Z) is completely cured thermally or by means of electromagnetic radiation, in a fourth step, (Y) is washed out of the nonwoven fabric at least once with at least one protic polar solvent (i), in a fifth step, the solvent exchange of (i) is carried out by washing the nonwoven fabric at least once with at least one organic solvent (11),wherein the organic solvent ( 11 ) is characterized in that its surface tension is lower than that of the protic polar solvent ( i ) ., 8 . A process for producing nonwovens according to claim 7 , characterized in that , in a sixth step , the nonwoven is thermally dried at 20 to 200 ° C.

9. A process for producing nonwovens according to claim 8, characterized in that the sixth step is carried out at a reduced pressure of 0.001 to 800 mbar.

10. A process for producing nonwovens according to any one of claims 7 to 9, characterized in that the fifth step takes place at a temperature between 0 and 100°C.

11. A process for producing nonwovens according to any one of claims 7 to 10, characterized in that step 5 is repeated at least once and in each subsequent exchange step an organic solvent (ii) with the same or lower surface tension is used than in the previous exchange step.

12. Cross-linked nonwoven fabric produced by the process according to any one of claims 8 to 11.

13. Use of the nonwoven fabric according to claim 12 as a coating for three-dimensional structures, in wound plasters, in packaging materials.

14. Use of the nonwoven fabric according to claim 12 in filters and membranes.

Images