Electrospun silicone elastomer nonwoven fabric

Abstract

The invention relates to an electrospinning solution containing (i) at least one organic solvent; (ii) an addition-crosslinking silicone elastomer composition containing (A) at least one organopolysiloxane compound which has groups comprising aliphatic carbon-carbon multiple bonds; (B) at least one organopolysiloxane compound with Si-bonded hydrogen atoms; or, in place of (A) and (B), or in addition to (A) and (B), (C) at least one organopolysiloxane compound which has SiC-bonded groups with aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms with the proviso that none of the components (A), (B), and (C) has a viscosity of more than 800,000 mPa∙s, measured at 25 °C and a shearing rate of 0.1 s-1; (D) at least one hydrosilylation catalyst; and (E) no silicon-containing fillers or at least one silicon-containing filler; and (iii) at least one polysiloxane which has a viscosity of more than 5,000,000 mPa∙s, measured at 25 °C and a shearing rate of 0.1 s-1, and which differs from (A), (B), (C), and (E).

Description

[0001] Electrospun silicone elastomer fleece

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

[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 hold 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 (PEI) 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. The silicone is then located in the core of the electrospun fiber.For example, CN101498057 describes the coaxial electrospinning of a silicone rubber (core) together with PVP as a water-soluble polymer (sheath). The silicone is dissolved in dichloromethane, PVP in ethanol. To obtain silicone fibers, the sheath polymer is removed with water in a subsequent step. US2014322512 (corresponding to WO2014143866) describes a needle-free electrospinning process for producing silicone-PLGA core-sheath fibers, in which a flowable silicone elastomer is used. The disadvantage is that, in order to obtain pure silicone fibers, the accompanying polymer must be removed in a step subsequent to the electrospinning process. This typically takes place in an aqueous washing step.

[0009] The task is therefore to provide silicone compositions that can be used in the electrospinning process without accompanying polymers and thus no longer exhibit the above-mentioned disadvantages of the state of the art.

[0010] Completely unexpectedly, it was found that the present electrospinning solution according to the invention solves this problem. It is suitable for use in an electrospinning process for producing a nanofiber nonwoven fabric consisting entirely of silicone. The at least one organopolysiloxane (iii) contained according to the invention, which has a sufficient molecular weight and thus a viscosity greater than 5,000,000 mPa-s (measured at 25 °C and a shear rate of 0.1 s -1) is crucial, as this component assumes the template effect, resulting in the formation of fibers. The organopolysiloxane (iii) can optionally also contain suitable functional groups to be incorporated into the silicone elastomer network. By adding the organopolysiloxane (iii) to the electrospinning solution, pure silicone fibers are obtained, thus making a subsequent washing step obsolete. The present invention therefore relates to an electrospinning solution containing

[0011] (i) at least one organic solvent, and

[0012] (ii) an addition-curing silicone elastomer composition containing

[0013] (A) at least one organopolysiloxane compound having radicals with aliphatic carbon-carbon multiple bonds,

[0014] (B) at least one organopolysiloxane compound with Si-bonded hydrogen atoms, or instead of (A) and (B) or in addition to (A) and

[0015] (B)

[0016] (C) at least one organopolysiloxane compound which has Si-C-bonded radicals with aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms, with the proviso that none of the components (A), (B) and (C) has a viscosity greater than 800,000 mPa-s, measured at 25°C and a shear rate of 0.1 s- 1 ,

[0017] (D) at least one hydrosilylation catalyst,

[0018] (E) no or at least one silicon-containing filler, and

[0019] (iii) at least one polysiloxane with a viscosity greater than 5,000,000 mPa-s measured at 25°C and a shear rate of 0.1 s -1 , and which is different from (A) , (B) , (C) and (E).

[0020] 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 explicitly understand this type of disclosure to mean that every combination of different levels of preference is explicitly disclosed and explicitly desired.

[0021] Organic solvent (i)

[0022] A single or a mixture of shifting organic solvents can be used as the solvent. Suitable organic solvents include hydrocarbons, halogenated hydrocarbons, ethers, alcohols, aldehydes, ketones, acids, anhydrides, esters, N-containing solvents, S-containing solvents, and organosilicon solvents.

[0023] Examples of common hydrocarbons are pentane, hexane, dimethylbutane, heptane, hex-1-ene, hexa-1,5-diene, cyclohexane, turpentine, benzene, isopropylbenzene, xylene, toluene, white spirit, naphthalene, and terahydronaphthalene. Examples of common halogenated hydrocarbons are fluoroform, perfluoroheptane, methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, tetrachloroethene, trichloroethene, 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, triethylene glycol, 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, glycerin, phenol, and m-cresol.Examples of common aldehydes are acetaldehyde and butyralaldehyde. 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 methyl acetate, ethyl acetate, butyl acetate, phenyl acetate, glycerol tricarboxylic acid ester, diethyl oxalate, dioctyl sebacate, methyl benzoate, dibutyl phthalate, DBE® (DuPont de Nemours), and tricresyl phosphorus ester. 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 and 3-hydroxypropionitrile.Common examples of sulfur-containing solvents are carbon disulfide, methanethiol, dimethyl sulfone, dimethyl sulfoxide, and thiophene. Common examples of organosilicon solvents are volatile, linear, or cyclic siloxanes with a maximum of five silicon atoms, particularly hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, hexamethylcyclotrisiloxane, and octamethylcyclotetrasiloxane.

[0024] The electrospinning solution according to the invention preferably contains 30 to 98 wt.%, particularly preferably 50-95 wt.% solvent

[0025] (i) •

[0026] Addition-curing silicone elastomer composition (ii)

[0027] The compounds (A) and (B) or (C) used in the addition-crosslinking silicone elastomer composition (ii) 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.

[0028] Component (A)

[0029] 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.

[0030] 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)

[0031] R 4 aR 5 bS i 0 ( 4-ab ) / 2 ( D inserted , where

[0032] R 4 independently of one another, identically or differently, an organic or inorganic radical free from aliphatic carbon-carbon multiple bonds,

[0033] 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 to ff -carbon to ff 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.

[0034] 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.

[0035] 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 is the phenyl radical.

[0036] 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.

[0037] 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)-

[0038] 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, -

[0039] (CH2) or (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 .

[0040] Examples for R 4Divalent radicals which are Si-bonded 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-, -C(CF3)2-, - (CH2)O-C6H4-(CH2)O-, - (CH2)O-C6H4-C6H4-(CH2)O-, - (CH2O)p, (CH2CH2O)O, - (CH2)O-OX-C6H4-SO2-C6H4-OX-(CH2)O-, where x is 0 or 1, and Ph, o and p have the meaning given above. The radical R is preferably 4a 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.

[0041] For rest R 5 from formula (I) can be any group that is accessible to an addition reaction (hydrosilylation) with a SiH-functional compound.

[0042] 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 .

[0043] Preferably, the residue R 5alkenyl 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 preferably used.

[0044] The molecular weight of component (A) can vary within wide limits, approximately between 10 2 and 10 6 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 5g / 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 5 have 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.

[0045] 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 .

[0046] Component (B)

[0047] As organosilicon compounds (B) it is possible to use all hydrogen-functional organosilicon compounds which have previously been used in addition-crosslinkable compositions.

[0048] As organopolysiloxanes (B) which have Si-bonded hydrogen atoms, preferably linear, cyclic or branched organopolysiloxanes comprising units of the general formula (III) R 4 cHdSiO (4-cd) / 2 (III) is used, where

[0049] 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.

[0050] 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).

[0051] The molecular weight of component (B) can also vary within wide limits, approximately between 10 2 and 10 6 g / mol. For example, component (B) may be a relatively low-molecular 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.

[0052] The structure of the molecules forming component (B) is also not fixed; in particular, the structure of a higher molecular weight, i.e., oligomeric or polymeric SiH-containing siloxane can be linear, cyclic, branched, or even resinous or 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 4 has the meaning given above. Branched and network-like polysiloxanes additionally contain trifunctional and / or tetrafunctional units, where those of the formula R 4 SiO3 / 2, HS1O3 / 2 and S1O4 / 2 are preferred, where R 4 has the meaning given above .

[0053] Of course, mixtures of different siloxanes that meet the criteria of component (B) can also be used. In particular, the molecules forming component (B) may also contain aliphatically unsaturated groups in addition to the obligatory SiH groups. Particularly preferred is the use of low molecular weight SiH-functional compounds such as tetrakis (dimethylsiloxy) silane and tetramethylcyclotetrasiloxane, as well as higher molecular weight, SiH-containing siloxanes, such as poly (hydrogenmethyl) siloxane and poly (dimethylhydrogenmethyl) siloxane with 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 some of the methyl groups are replaced by 3,3,3-trifluoropropyl or phenyl groups.

[0054] 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.

[0055] Components (A) and (B) used according to the invention are commercially available products or can be prepared by conventional processes. 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).

[0056] Component (C)

[0057] If siloxanes (C) are used, they are preferably those consisting of units of the general formulas (IV), (V) and (VI)

[0058] R 4 fSiO4 / 2 (IV)

[0059] R 4 g R 5 SiO3-g / 2 (V)

[0060] R 4 hHSiO3-h / 2 (VI) where

[0061] 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.

[0062] Examples of organopolysiloxanes (C) are those made of SiO4 / 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 4 2SiO units, as well as linear organopolysiloxanes consisting essentially of R4 2R 5 SiOi / 2- , R 4 2SiO- and R 4 HSiO units with R 4 and R 5 equal to the meaning given above. 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 -1 .

[0063] Organopolysiloxanes (C) are commercially available or can be prepared using conventional methods.

[0064] The addition-crosslinking silicone elastomer composition (11) according to the invention usually contains 30-95 wt.%, preferably 30-80 wt.% and particularly preferably 35-70 wt.% of (A), based on the total mass of the addition-crosslinking silicone elastomer composition (11).

[0065] The addition-crosslinking silicone elastomer composition (II) 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.

[0066] If the addition-crosslinking silicone elastomer composition (11) according to the invention contains component (C), usually 30-95 wt.%, preferably 30-80 wt.%, particularly preferably 40-70 wt.% of (C) are contained in the formulation, based on the total mass of the addition-crosslinking silicone elastomer composition (11).

[0067] Component (D)

[0068] 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).

[0069] The concentration of component (D) in the addition-curing silicone elastomer composition (11) is sufficient to catalyze the hydrosilylation reaction of components (A) and (B) when exposed to generate the heat required in the process described herein. 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 cure rate may be slow 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.

[0070] 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.

[0071] Component (E)

[0072] 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 m 2 / g are particularly preferred. The silica fillers mentioned may be hydrophilic or hydrophobicized using known methods.

[0073] Surface-treated silicas (E) are preferably used. The surface treatment is achieved by methods known in the art for hydrophobizing fine-particle fillers.

[0074] 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 (II) 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.

[0075] 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)

[0076] R 3 sio l / 2 M-unit (VII),

[0077] R 2 si0 2 / 2 D-unit (VIII),

[0078] RSi0 3 / 2 T-unit (IX),

[0079] Si°4 / 2Q unit (X) in which

[0080] 1 2

[0081] 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.

[0082] 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.

[0083] 2

[0084] R are identical or independently different monovalent hydrocarbon radicals (alkyl, aryl, aralkyl). 2

[0085] 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.

[0086] 2

[0087] R preferably has 1 to 6 carbon atoms. Methyl and phenyl are particularly preferred.

[0088] The preferred R radicals are methyl, ethyl, phenyl, and vinyl. 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).

[0089] 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.

[0090] Preferably, at most 1 wt.%, in particular at most 0.5 wt.% of the radicals R are OH.

[0091] 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 .

[0092] 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.

[0093] In the addition-crosslinking silicone composition (ii) according to the invention, the component (E) is preferably used as a single or likewise preferably as a mixture of several finely divided fillers.

[0094] The addition-crosslinking silicone elastomer composition (II) according to the invention preferably contains 0 to 45 wt.% (E), particularly preferably 0-35 wt.% (E). The addition-crosslinking silicone compositions according to the invention can optionally contain all further additives known to the person skilled in the art for addition-crosslinkable compositions. These additives can be, for example, rheological additives, inhibitors, light stabilizers, flame-retardants, dispersing aids, heat stabilizers, etc.

[0095] For the sake of clarity, the amounts used of each individual component of the silicone composition (ii) are chosen so that they always add up to 100% by weight.

[0096] Component (iii)

[0097] Component (iii) is a polysiloxane different from (A), (B), (C) and (E) with a viscosity greater than 5,000,000 mPa-s measured at 25°C and a shear rate of 0.1 s -1 .

[0098] The polysiloxane in component (iii) is predominantly linear with no or only a few branches, and the content of T and Q units does not exceed a maximum of 500 ppm. Such polysiloxanes have long been known to those skilled in the art. For example, the T unit is described above by the general formula (IX) and the Q unit by the general formula (X).

[0099] The polysiloxane of component (iii) is preferably an organopolysiloxane composed of units of the general formula (XI)

[0100] RfmRfnS 10 ( 4-mn ) / 2 (XI) where

[0101] R 7independently of one another, identical or different, an organic or inorganic radical free from aliphatic carbon-carbon multiple bonds,

[0102] R 8 independently of one another, identically or differently, denote a monovalent, substituted or unsubstituted, Si-C-bonded hydrocarbon radical having at least one aliphatic carbon to ff -carbon to ff multiple bond, m denotes 0, 1, 2 or 3, and n denotes 0, 1 or 2, with the proviso that the sum m + n is less than or equal to 3.

[0103] At R 7 is preferably alkyl or aryl, particularly preferably methyl or phenyl.

[0104] At R 8is, if present, preferably a vinyl group. The vinyl group can be terminal or in the polysiloxane chain. Preference is given to a predominantly linear polysiloxane (iii). Particular preference is given to a predominantly linear polysiloxane (iii) which contains vinyl groups both terminally (as M vi -unit) as well as in the polysiloxane chain (as D vi -unit).

[0105] The polysiloxane (iii) can also be completely free of R 8 be.

[0106] Component (iii) has a vinyl group content of 0 to 20 mol%. A vinyl group content of 0 to 2 mol% is preferred. One (iii) or a mixture of two or more (iii) components can be used.

[0107] The electrospinning solution according to the invention preferably contains 1 to 40 wt.% (iii), particularly preferably 1-25 wt.% (iii).

[0108] For the sake of clarity, it should be noted that the amounts used of components (i), (ii) and (iii) of the electrospinning solution according to the invention are selected such that they always add up to 100% by weight.

[0109] A further subject of the present invention is therefore a process for producing nonwovens in which, in the first step, all components are mixed in such a way that the electrospinning solution according to the invention is in the form of a solution and, in a second step, a nonwoven made of fibers made of pure silicone elastomers is produced from this solution by means of electrospinning.

[0110] In a third step, the fibers can be cured, either thermally or by electromagnetic irradiation.

[0111] Depending on the design, the first step (preparation of the electrospinning solution) can be carried out at a later time or immediately before the second step (electrospinning).

[0112] The preparation of the electrospinning solution in the first step can be carried out in one or more individual steps. Components (i), (ii), and (iii) can be mixed in any order and combination. Thus, components (ii) and (iii) can be partially or completely dissolved in (i) simultaneously or separately, and the two pre-solutions can then be mixed to form a single solution.

[0113] However, individual components of the silicone elastomer composition (ii) can also be mixed separately with (iii) or (i). In particular, this includes two-component silicones, in which components (A), (B), and (D) are often not present together. For the electrospinning solution, this can mean, for example, that components (A), (D), and parts of (E) are mixed with (iii) and (i) in one or more steps, and separately, components (B) and parts of (E) are mixed with (iii) and (i) in one or more steps.

[0114] If the silicone composition (ii) contains component (E), i.e., a filler, it may be advantageous to first disperse this in at least one component from (ii) or in (iii). This is preferably done in at least one component from (ii). This dispersion step is preferably carried out using a high-speed mixer (= dissolver), wherein a scraper can additionally preferably be used to achieve uniform distribution of the fillers. A planetary dissolver with a scraper is preferably used. Dissolver disks with any arrangement and number of teeth can be used.

[0115] Mixing tools of any kind, such as magnetic stirrers, KPG stirrers, centrifugal mixers, planetary mixers or high-speed mixers, are suitable for dissolving any components from (ii) or (iii) in the solvent (i).

[0116] The second step, the electrospinning process from solution, is known in the art and is described in detail in WO2014114501, for example. The third step, the crosslinking of the fibers, is preferably carried out thermally, preferably at 30 ° C to 250 ° C, more preferably at least 50 ° C, in particular at least 100 ° C, preferably at 120-210 ° C. Thermal curing is carried out, for example, by means of a heatable collector, by means of infrared radiation with a wavelength of 780 nm to 1 mm or an oven. If UV-switchable hydrosilylation catalysts (D) are used, crosslinking is carried out by irradiation with light with a wavelength of 230-400 nm, preferably for at least 1 second, more preferably at least 5 seconds and preferably at most 500 seconds, more preferably at most 240 seconds. If IR-switchable hydrosilylation catalysts (D) are used, this is done analogously, but with infrared radiation of wavelength 780 nm to 1 mm.

[0117] 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.

[0118] Crosslinking with photoinitiators can be carried out under protective gas such as N2 or Ar or under air.

[0119] 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 1 minute, in order to cure them.

[0120] Crosslinking is particularly preferably carried out under UV radiation, particularly at 254 nm.

[0121] The present invention further relates to the crosslinked nonwovens according to the invention produced by the process according to the invention. 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, in filters, and in membranes.

[0122] 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.

[0123] Furthermore, the nonwovens according to the invention can also preferably be used in wound plasters.

[0124] The nonwovens according to the invention can also be used as a bacteriophobic and / or antimicrobial coating.

[0125] The nonwovens according to the invention are also preferred for use in packaging materials, particularly for food packaging. The nonwovens according to the invention are also suitable for coating containers for storing liquids, allowing the containers to be completely emptied.

[0126] 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.

[0127] The nonwovens according to the invention can particularly preferably also be used 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.

[0128] 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.

[0129] The nonwovens according to the invention can also be used as a carrier or support layer for other membranes.

[0130] Examples

[0131] The following examples describe the basic feasibility of the present invention, without, however, limiting it to the contents disclosed therein.

[0132] 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. Starting materials

[0133] Vinyl polymer used (ill):

[0134] Dimethyl vinyl silyloxy-terminated dimethyl siloxane-methylvinyl-siloxane copolymer, with 0.1 mol% vinyl groups and a viscosity of 30,000,000 mPas at 25°C and a shear rate of 0.1 s -1 . The molecular weight M w (Mass average molecular weight, determined by GPC) is 600,000 g / mol.

[0135] Addition-curing silicone elastomer compositions used ( 11 ):

[0136] As silicone composition 1, a UV-curing silicone rubber composition was prepared according to Example 6 in US2018208797A (corresponding to WO 2017 / 089496 A1).

[0137] As silicone composition 2, a thermally crosslinking silicone composition according to Example 6 in US2018208797A corresponding to WO2017 / 089496 A1 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 US2009088524 A (corresponding to EP2050768B1) (Catalyst 6).

[0138] The two-component, thermally curing silicone elastomer LUMISIL® LR 7601 / 60 available from Wacker Chemie AG was used as silicone composition 3.

[0139] Solvents used (i) :

[0140] - n-butyl acetate (n-butyl acetate)

[0141] - Chloroform

[0142] Viscosity measurement: Viscosity measurements were performed on an air-bearing MCR 302 rheometer from Anton Paar at 25 °C. A cone-plate system (25 mm, 2 °) with a gap of 105 pm was used. Excess material was removed (trimmed) with a spatula at a gap distance of 115 pm. The cone was then moved to a gap distance of 105 pm so that the gap was completely filled. Before each measurement, a "pre-shear" is performed, during which the shear history is erased through sample preparation, application, and trimming. The pre-shear is carried out for 60 seconds at a shear rate of 0.1 s. -1 , followed by a rest period of 300 seconds. The shear viscosity is determined using a step profile in which the sample is subjected to a constant shear rate of 0.1 s -1 and 1 s -1for 100 seconds each. A measurement is recorded every 10 seconds, resulting in 10 measurement points per shear rate. The average of these 10 measurement points determines the shear viscosity at the respective shear rate.

[0143] From examples

[0144] Example 1 - Preparation of Solution 1

[0145] 30 g of silicone composition 1 were dissolved in 60 g of n-butyl acetate. Subsequently, 10 g of the vinyl polymer were added and dissolved.

[0146] Example 2 - Preparation of Solution 2

[0147] 30 g of silicone composition 2 were dissolved in 60 g of n-butyl acetate. Subsequently, 10 g of the vinyl polymer were added and dissolved.

[0148] Example 3 - Preparation of Solution 3

[0149] 30 g of the A component of the elastomer LUMIS IL® LR 7601 / 60 A were dissolved in 60 g of n-butyl acetate. Subsequently, 10 g of the vinyl polymer were added and dissolved. Separately, 30 g of the B component of the elastomer LUMIS IL® LR 7601 / 60 B were dissolved in 60 g of n-butyl acetate, followed by 10 g of the vinyl polymer and dissolved. Both components were combined in a 1:1 ratio and immediately used as the electrospinning solution.

[0150] Example 4 - Preparation of Solution 4 30 g of silicone composition 2 were dissolved in 62 g of n-butyl acetate. Then, 8.0 g of the vinyl polymer were added and dissolved.

[0151] Example 5 - Preparation of Solution 5 30 g of silicone composition 2 were dissolved in 55 g of n-butyl acetate. Subsequently, 15 g of the vinyl polymer were added and dissolved.

[0152] Example 6 - Preparation of Solution 6

[0153] 20 g of silicone composition 2 were dissolved in 76 g of chloroform. Subsequently, 4.0 g of the vinyl polymer were added and dissolved.

[0154] Example 7 (not according to the invention) - Preparation of solution 7 30 g of silicone composition 2 were dissolved in 70 g of n-butyl acetate.

[0155] Electrospinning:

[0156] The electrospinning process was carried out analogously to W02014114501. For this purpose, the corresponding solutions 1 to 7 were spun on an electrospinning system under the following conditions: Voltage: 22.5 kV DC

[0157] Distance between cannula and electrode: 40 cm

[0158] Cannula diameter: 1 mm Flow rate: 5 mL / h

[0159] 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. If silicone composition 2 or 3 (solutions 2 to 7) was used, the sample was cured in an oven at 150 °C for 20 minutes. If silicone composition 1 (solution 1) was used, the sample was irradiated with a mercury vapor lamp for 10 minutes.

[0160] In the case of electrospinning of the inventive solutions 1 to 6, a nonwoven fabric composed of sub-micron fibers was obtained. The diameter of the resulting fibers was determined by SEM.

[0161] In the case of electrospinning of solution 7 (not according to the invention) no fibers were obtained.

[0162] Table 1 shows an overview of the composition of the examples and the result of electrospinning.

[0163] Table 1

[0164] Ex = Examples

[0165] * not according to the invention

Claims

Patent claims 1. Electrospinning solution containing (i) at least one organic solvent, and (ii) an addition-curing silicone elastomer composition containing (A) at least one organopolysiloxane compound having radicals with aliphatic carbon-carbon multiple bonds, (B) at least one organopolysiloxane compound with Si-bonded hydrogen atoms, or instead of (A) and (B) or in addition to (A) and (B) (C) at least one organopolysiloxane compound which has Si-C-bonded radicals with aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms, with the proviso that none of the components (A), (B) and (C) has a viscosity greater than 800,000 mPa-s, measured at 25°C and a shear rate of 0.1 s- 1 , (D) at least one hydrosilylation catalyst, (E) no or at least one silicon-containing filler, and (iii) at least one polysiloxane with a viscosity greater than 5,000,000 mPa-s measured at 25°C and a shear rate of 0.1 s -1 , and which is different from (A) , (B) , (C) and (E).

2. Electrospinning solution according to claim 1, characterized in that the content of organic solvent (i) is 30-98 wt%.

3. Electrospinning solution according to claim 1, characterized in that the content of organic solvent (i) is 50 - 95 wt.%.

4. Electrospinning solution according to one of claims 1 to 3, characterized in that the content of polysiloxane (iii) is 1 - 40 wt.%.

5. A process for producing nonwovens in which, in the first step, all components according to one of claims 1 to 4 are mixed so that the electrospinning solution according to the invention is in the form of a solution, and in a second step, a nonwoven made of fibers of pure silicone elastomer composition is produced from this solution by means of electrospinning.

6. A process for producing nonwovens according to claim 5, characterized in that the fibers are cured in a third step.

7. A process for producing nonwovens according to claims 5 and 6, characterized in that the curing takes place thermally or by electromagnetic irradiation.

8. Cured nonwoven fabric produced by the process according to one of claims 6 or 7.

9. Use of the nonwoven fabric according to claim 8 as a coating for three-dimensional structures, in wound plasters, in packaging materials, in filters and membranes.

10. Use of the nonwoven fabric according to claim 8 in filters and membranes.

Images