Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/0007—Electro-spinning
  • D01D5/0015—Electro-spinning characterised by the initial state of the material
  • D01D5/003—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/10—Other agents for modifying properties

Definitions

• the present invention relates to a process for the production of polymer fibers, in particular of nano- and mesofibers, in which a colloidal dispersion of at least one essentially water-insoluble polymer is electrospun in an aqueous medium, and also fibers obtainable by this process.
• a polymer melt or a polymer solution is usually exposed to a high electric field at an edge serving as an electrode, for example, by passing the polymer melt or polymer solution under low pressure through an electric field in an electric field Due to the resulting electrostatic charging of the polymer melt or polymer solution, a material flow directed towards the counterelectrode, which solidifies on the way to the counterelectrode, is formed with this method , so-called nonwovens or ensembles of ordered fibers.
• DE-A1-101 33 393 discloses a process for the production of hollow fibers with an inner diameter of 1 to 100 nm, in which a solution of a water-insoluble polymer - for example a poly-L-lactide solution in dichloromethane or a polyamide 46- Solution in pyridine - electrospun.
• a solution of a water-insoluble polymer - for example a poly-L-lactide solution in dichloromethane or a polyamide 46- Solution in pyridine - electrospun.
• a similar method is also known from WO-A1-01 / 09414 and DE-A1-103 55 665.
• DE-A1-10 2004 009 887 relates to a process for producing fibers with a diameter of ⁇ 50 ⁇ m by electrostatic spinning or spraying a melt of at least one thermoplastic polymer.
• the electrospinning of polymer melts allows only fibers with diameters greater than 1 ⁇ m to be produced.
• nano and / or mesofibers are required with a diameter of less than 1 micron, which can be produced by the known electrospinning process only by using polymer solutions.
• WO 2004/080681 A1 relates to devices and methods for the electrostatic processing of polymer formulations.
• the polymer formulations may be solutions, dispersions, suspensions, emulsions, mixtures thereof or polymer melts.
• electrospinning is mentioned, among others.
• no concrete polymer formulations which are suitable for electrospinning are mentioned.
• WO 2004/048644 A2 discloses the electrosynthesis of nanofibers and nano-composite films.
• solutions also encompasses heterogeneous mixtures such as suspensions or dispersions, inter alia, fibers from electrically conductive polymers can be prepared according to WO 2004/048644 A2, which according to WO 2004/048644 A2 are preferably obtained from the corresponding monomers Get solutions.
• Nano- and mesofibers by electrospinning of colloidal dispersions "of 24 February 2005 with the German application DE 10 2005 008 926.7 relates to
• the object of the present invention is to provide a process optimized for electrospinning of aqueous polymer dispersions which is optimized with respect to DE 10 2005 008 926.7, with which polymer fibers having optimized structural and / or mechanical properties can be obtained.
• the object is achieved by the provision of a method in which a colloidal dispersion of at least one essentially water-insoluble polymer is electrospun in an aqueous medium.
• the process according to the invention is then characterized in that the colloidal dispersion contains at least one nonionic surfactant.
• fibers with a high water resistance can be obtained, which are characterized by a good mechanical stability. It is possible with the inventive method to produce nano- and mesofibers with a diameter of less than 1 .mu.m from aqueous dispersions, so that the use of non-aqueous toxic, combustible, irritating, explosive and / or corrosive solvents can be avoided. Since the fibers produced by the process according to the invention are composed of essentially water-insoluble polymers, a subsequent process step for water stabilization of the fibers is not required.
• a colloidal dispersion of at least one substantially water-insoluble polymer is electrospun in an aqueous medium.
• substantially water-insoluble polymers are, for the purposes of the present invention, in particular polymers having a solubility in water of less than 0.1% by weight.
• a dispersion in the sense of the present invention in accordance with textbook knowledge, denotes a mixture of at least two immiscible phases, one of the at least two phases being liquid.
• dispersions are subdivided into aerosols, emulsions and suspensions, the second or further phase being gaseous in the case of aerosols, solid in the case of emulsions and solid in the case of suspensions.
• Suspensions are preferably used in the process according to the invention.
• the colloidal polymer dispersions preferably used according to the invention are also referred to in the technical language as latex.
• the colloidal polymer dispersions according to the invention can be prepared by all processes known to the skilled person for this purpose, particularly good results being obtained by electrospinning of latexes produced by emulsion polymerization of suitable monomers.
• the latex obtained by emulsion polymerization is used directly in the process of the invention without further workup.
• the aqueous medium in which the substantially water-insoluble polymer is present is generally water.
• the aqueous medium may contain other additives in addition to water, eg. B. additives used in the emulsion polymerization of suitable monomers to produce a latex. Suitable additives are known in the art.
• the colloidal dispersion used for electrospinning contains at least one nonionic surfactant.
• any surfactants known to the person skilled in the art can be used in the process according to the invention.
• nonionic surfactants provides steric stabilization of the colloidal dispersion. Thereby, the mechanical stability of the fibers obtained by the method according to the invention can be improved. Furthermore, it was found that the use of nonionic surfactants can improve the formation of fibers by electrospinning versus spraying the colloidal polymer dispersion. Furthermore, it has been found that by the presence of nonionic surfactants, a decrease in the viscosity of the colloidal dispersion can be achieved, whereby the production of thinner and more compact fibers than without addition of nonionic surfactants is possible. Furthermore, an increase in the conductivity of the dispersions and a decrease in the surface tension can be detected.
• Suitable nonionic surfactants are known in the art and z. B. selected from the group consisting of (oligo) oxyalkylene groups containing surfactants, carbohydrate-containing surfactants and amine oxides.
• (oligo) oxyalkylene - (OR 1 ) n - it is to be understood that the (ON-go) oxyalkylene group-containing surfactants may have one or more oxyalkylene groups
• R 1 an alkylene group, preferably an alkylene group having 2 to 4 carbon atoms, and n is at least 1, preferably 3 to 30. In this case, n is usually an average of the number of oxalkylene groups. If n is greater than 1, the radicals R 1 in the n oxyalkylene be the same or different.
• Suitable (oligo) oxyalkylene-containing surfactants are, for. B. selected from the group consisting of (oligo) oxyethylene groups (polyethylene glycol groups) containing surfactants, (oligo) oxypropylene groups containing surfactants, (oligo) oxybutylene groups containing surfactants and surfactants containing two or more different oxyalkylene groups, eg. Example, (oligo) oxyethylene groups and (oligo) oxypropyl len phenomenon, in random order or in the form of blocks (Blockcopolymeri- sat), z. B. block copolymers based on propylene oxide and ethylene oxide.
• the (oligo) oxyalkylene-containing surfactants are preferably selected from the group consisting of fatty alcohol alkoxylates, alkoxylated triglycerides and alkylalkylene glycol ethers alkylated on both sides.
• Suitable alkoxylates or alkoxylated compounds are, for. Ethoxylates, propoxylates, butoxylates or random or block copolymers (or oligomers) composed of two or more different alkoxylates, e.g. As ethoxylates and propoxylates.
• Suitable carbohydrate-containing surfactants are, for. B. selected from the group consisting of alkylpolyglycosides, sucrose esters, Sorbinanestern (sorbitan), z. As polyoxyethylene sorbitan trioleate, and fatty acid N-methylglucamiden (fatty acid glucamides).
• the nonionic surfactants suitable according to the invention may contain either (oligo) oxyalkylene groups or carbohydrate groups or both (oligo) oxyalkylene groups and carbohydrate groups.
• Suitable amine oxides are, in particular, alkyldimethylamine oxides.
• nonionic surfactants are known to the person skilled in the art and are commercially available or can be prepared by processes known to the person skilled in the art.
• the nonionic surfactants used according to the invention may in principle be present in amounts in the colloidal dispersions which do not lead to coagulation. The optimum amounts are dependent, inter alia, on the surfactant used and the application temperature.
• the at least one nonionic surfactant is preferably present in the colloidal dispersions in an amount of from 0.5 to 10% by weight, particularly preferably from 0.3 to 5% by weight, based on the total weight of the essentially water-insoluble polymer used. It has been found that particularly good process results - both in terms of the formation of polymer fibers and in terms of quality, z.
• the polymer fibers - are obtained when 0.3 to 1 wt .-%, preferably 0.5 to 1 wt .-%, based on the total weight of the dispersion, of the nonionic surfactant, z. B. a block copolymer based on various alkylene oxides, eg. B. based on propylene oxide and ethylene oxide.
• the at least one nonionic surfactant contained in the colloidal dispersions according to the process according to the invention can either be prepared during the preparation of the colloidal dispersions, in particular a polymer latex which is prepared by emulsion polymerization, or subsequently after the preparation of the colloidal dispersions, for.
• a polymer latex which is prepared by emulsion polymerization
• the at least one nonionic surfactant is added subsequently to the final colloidal dispersion prior to the start of the electrospinning process.
• Buna N® polybutadiene; Polytetrafluoroethylene; modified and unmodified celluloses, homo- and copolymers of ⁇ -olefins and copolymers composed of two or more of the above-mentioned polymer-forming monomer units existing selected group of water-insoluble polymer. All the abovementioned polymers can be used in the latices to be used according to the invention individually or in any combination with one another and in any desired mixing ratio.
• aromatic vinyl compounds such as styrenes, alpha-methylstyrenes; Vinylacetates, vinyl ethers, butadienes, isoprenes, methacrylates, acrylamide, vinylsulfonic acid, vinylsulfonic acid esters, vinyl esters, vinyl alcohol, acrylonitrile, vinyl sulfones and / or vinyl halides, good results are achieved.
• the substantially water-insoluble polymers are selected from homo- or copolymers based essentially on aromatic vinyl compounds such as styrenes, alpha-methylstyrenes, acrylates, eg. As methyl or butyl acrylates, and / or methacrylates.
• All of the aforementioned polymers can be used uncrosslinked or crosslinked, provided that their solubility in water is less than 0.1% by weight.
• substantially water-insoluble polymers are commercially available or can be prepared according to processes known to those skilled in the art.
• substantially water-insoluble polymers are used, which are prepared by emulsion polymerization, suitable by emulsion polymerization available polymers are mentioned above.
• the polymer latex obtained in the emulsion polymerization can be used directly in the electrospinning process according to the invention as a colloidal dispersion, preferably after addition of the nonionic surfactant.
• the average weight-average particle diameter of the at least one essentially water-insoluble polymer generally being from 1 nm to 2.5 ⁇ m, preferably from 10 nm to 1.2 ⁇ m, particularly preferably from 15 nm to 1 ⁇ m is.
• the average weight-average particle diameter of emulsion-produced latex particles which are used in a preferred embodiment in the method according to the invention is generally from 30 nm to 2.5 microns, preferably from 50 nm to 1, 2 microns (determined according to W. Scholtan and H. Lange in Kolloid Z. and Polymers 250 (1972), pp. 782-796 by means of ultracentrifuge).
• colloidal polymer suspensions, in particular latexes in which the polymer particles have a weight-average particle diameter of 50 nm to 500 nm, in particular very particularly preferably 50 nm to 250 nm.
• the colloidal suspension preferably used according to the invention may have particles with monomodal particle size distribution of the polymer particles or with bimodal or polymodal particle size distribution.
• mono-, bi- and polymodal particle size distribution are known to the person skilled in the art.
• the latex particles can be arranged in any manner known to the person skilled in the art. For example, only particles with gradient structure, core-shell structure, salami structure, multi-core structure, multi-layer structure and raspberry morphology may be mentioned.
• latex also means the mixture of two or more latices.
• the preparation of the mixture can be carried out by any known method, e.g. by mixing two latices at any time prior to spinning.
• the colloidal dispersion in addition to the at least one water-insoluble polymer and the at least one nonionic surfactant, additionally contains at least one water-soluble polymer, a polymer having a solubility in water of at least 0 being water-soluble for the purposes of the present invention, 1 wt .-% is understood.
• the at least one water-soluble polymer which is preferably additionally present in the colloidal dispersions can serve as a template polymer.
• the fiber formation from the colloidal polymer dispersion is further favored over spraying (electrospraying).
• the template polymer serves as a kind of "glue" for the essentially water-insoluble polymers of the colloidal dispersion.
• the water-soluble polymer in a preferred embodiment of the method according to the invention for. B. removed by washing / extraction with water.
• water-insoluble polymer fibers in particular nano- and microfibers, are obtained, without disintegration of the polymer fibers.
• the water-soluble polymer may be a homopolymer, copolymer, block polymer, graft copolymer, star polymer, hyperbranched polymer, dendrimer, or a mixture of two or more of the foregoing types of polymers. According to the findings of the present invention, the addition of at least one water-soluble polymer not only accelerates / promotes fiber formation. Rather, the quality of the resulting fibers is significantly improved.
• water-soluble polymers known to those skilled in the art may be added to the colloidal dispersion of at least one substantially water-insoluble polymer in an aqueous medium, in particular with polyvinyl alcohol; Polyalkylene oxides, eg.
• polyethylene oxides Poly-N-vinylpyrrolidone; hydroxymethylcelluloses; hydroxyethylcelluloses; hydroxypropyl; Carboxymethylcelluloses; maleic; alginates; collagens; Combinations composed of two or more of the monomeric units constituting the above-mentioned polymers, copolymers composed of two or more monomer units constituting the aforementioned polymers, graft copolymers composed of two or more of the monomeric units constituting the aforementioned polymers, star polymers composed of two or more of them above-mentioned polymer-forming monomer units, highly branched polymers composed of two or more of the above-mentioned polymer-forming monomer units and dendrimers composed of two or more of the above-mentioned polymer-forming monomer units selected group of selected water-soluble polymers particularly good results.
• the water-soluble polymer is selected from polyvinyl alcohol, polyethylene oxides and poly-N-vinyl
• water-soluble polymers are commercially available or can be prepared according to processes known to those skilled in the art.
• the solids content of the colloidal dispersion to be used according to the invention-based on the total weight of the dispersion- is preferably from 5 to 60% by weight, particularly preferably from 10 to 50% by weight and very particularly preferably from 10 to 40% by weight. %.
• the colloidal dispersion to be used in the process according to the invention comprises at least one substantially water-insoluble polymer, at least one nonionic surfactant and optionally at least one water-soluble polymer in an aqueous medium, based on the total weight of the dispersion, from 0 to 25 wt .-%, particularly preferably 0.5 to 20 wt .-% and most preferably 1 to 15 wt .-%, of at least one water-soluble polymer.
• the colloidal dispersions used according to the invention comprise, in each case based on the total amount of the colloidal dispersion,
• % By weight of at least one substantially water-insoluble polymer, ii) from 0.1 to 10% by weight, preferably from 0.3 to 5% by weight, particularly preferably from 0.3 to 1
• % By weight of at least one nonionic surfactant iii) 0 to 25% by weight, preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight of at least one water-soluble polymer, and iv) 5 to 94, 9 wt .-%, preferably 10 to 89.2 wt .-%, particularly preferably 15 to 88.5 wt .-% water.
• the weight ratio of substantially water-insoluble polymer to the water-soluble polymer preferably present in the colloidal dispersion depends on the polymers used.
• the substantially water-insoluble polymer and the preferably used water-soluble polymer can be used in a weight ratio of 10: 1 to 1:10, preferably 9: 1 to 1: 9, particularly preferably 8: 2 to 2: 8.
• the colloidal dispersion to be used in accordance with the invention can be electrospun in any manner known to the person skilled in the art, for example by extrusion of the dispersion, preferably of the latex, under low pressure through a cannula connected to one pole of a voltage source to a counter electrode arranged at a distance from the cannula outlet.
• the distance between the cannula and the counterelectrode acting as collector and the voltage between the electrodes is set such that between the electrodes an electric field of preferably 0.5 to 2 kV / cm, particularly preferably 0.75 to 1.5 kV / cm and most preferably 0.8 to 1 kV / cm forms.
• the stability and compactness of the fibers produced by the process according to the invention can be further improved if the fibers - preferably after removal of the water-soluble polymer - heated to a temperature above the glass transition temperature or the melting point of the polymer or polymer mixture used become.
• the temperature is dependent on the glass transition temperature or the melting point of at least one water-insoluble polymer and is z. B. 5 to 50 0 C, preferably 10 to 40 0 C, particularly preferably 15 to 30 0 C above the glass transition temperature or the melting point of the respective at least one water-insoluble polymer.
• a period of z. B. 5 to 90 min. Preferably 10 to 60 min., Preferably in a low oxygen or oxygen-free atmosphere, eg. B. under nitrogen or under argon heated.
• the fibers produced it may be expedient to subsequently chemically bond them together or, for example. through a chemical intermediary to network with each other.
• a fiber layer formed by the fibers can be further improved, in particular with regard to water and temperature resistance.
• Another object of the present invention are fibers, in particular nano- and mesofibers, which are obtainable by the method according to the invention.
• the fibers according to the invention are distinguished by the fact that, owing to the addition according to the invention of the at least one nonionic surfactant, they have optimized structural and / or mechanical properties compared to fibers which are produced without addition of the nonionic surfactant, in particular with regard to uniformity, compactness and Stability.
• the diameter of the fibers according to the invention is preferably 10 nm to 50 ⁇ m, particularly preferably 50 nm to 2 ⁇ m and very particularly preferably 100 nm to 1 ⁇ m.
• the length of the fibers depends on the purpose and is usually 50 microns to several kilometers.
• the fiber produced by the above-mentioned method of the present invention may be coated with, for example, a substance selected from the group consisting of inorganic compounds, polymers and metals, and then the water-insoluble polymer contained therein, for example, thermally, chemically, biologically, radiation-induced, photochemically Plasma, ultrasound or extraction with a solvent, be degraded.
• a substance selected from the group consisting of inorganic compounds, polymers and metals and then the water-insoluble polymer contained therein, for example, thermally, chemically, biologically, radiation-induced, photochemically Plasma, ultrasound or extraction with a solvent, be degraded.
• the materials suitable for coating and the methods suitable for dissolving the fiber-internal material are described, for example, in DE-A1-101 33 393.
• the present invention relates to colloidal dispersions of at least one substantially water-insoluble polymer in an aqueous medium, which additionally comprises at least 0.5% by weight of a water-soluble polymer having a solubility in water of at least 0.1% by weight and at least one nonionic Containing surfactant.
• the colloidal dispersions according to the invention based in each case on the total weight of the dispersion, contain i) 5 to 60% by weight, preferably 10 to 50% by weight, more preferably 10 to 40
• % By weight of at least one substantially water-insoluble polymer, ii) from 0.1 to 10% by weight, preferably from 0.3 to 5% by weight, particularly preferably from 0.3 to 1% by weight of at least one nonionic surfactant iii ) 0 to 25 wt .-%, preferably 0.5 to 20 wt .-%, particularly preferably 1 to 15
• Wt .-% of at least one water-soluble polymer and iv) 5 to 94.9 wt .-%, preferably 10 to 89.2 wt .-%, particularly preferably 15 to 88.5 wt .-% water.
• Suitable substantially water-insoluble polymers, aqueous media, water-soluble polymers and nonionic surfactants and suitable amounts of these components in the colloidal dispersions are mentioned above.
• the colloidal dispersions according to the invention are preferably used in the process according to the invention.
• the present invention relates to the use of nonionic surfactants in a process for producing polymer fibers by an electrospinning process.
• FIG. 1 shows a schematic representation of a device suitable for carrying out the electrospinning method according to the invention
• Example 2 is a scanning electron micrograph of the fibers obtained according to Example 2 before and after water treatment
• suitable for carrying out the method according to the invention for electrospinning comprises a syringe 3 provided at its tip with a capillary nozzle 2 connected to one pole of a voltage source 1 for receiving the colloidal dispersion 4 according to the invention.
• a square counterelectrode 5 connected to the other pole of the voltage source 1 is arranged at a distance of about 20 cm, which acts as a collector for the fibers formed.
• a voltage between 18 kV and 35 kV is set at the electrodes 2, 5 and the colloidal dispersion 4 is discharged through the capillary nozzle 2 of the syringe 3 at a low pressure. Due to the electrostatic charging of the essentially water-insoluble polymers in the colloidal dispersion due to the strong electric field of 0.9 to 2 kV / cm, a material flow directed towards the counterelectrode 5 occurs, forming fiber 6 on the way to the counter electrode 5 solidified, as a result of which fibers 7 with diameters in the micrometer and nanometer range are deposited on the counter electrode 5.
• a colloidal dispersion of at least one essentially water-insoluble polymer and at least one nonionic surfactant is electrospun in an aqueous medium using the aforementioned device.
• the determination of the solids content in the dispersion is determined gravimetrically by means of a Mettler Toledo HR73 Halogen Moisture Analyzer by approximately 1 ml of sample is heated within 2 minutes at 200 0 C and the sample dried to constant weight, and then weighed.
• the average particle size is the weight average value d 50 , determined by means of an analytical ultracentrifuge (according to W. Scholtan and H. Lange in Kolloid-Z and Polymers 250 (1972), pp. 782-796).
• the size, i. the diameter and length of the fibers is determined by evaluation of electron micrographs.
• the polymer latex used in the following examples contains polystyrene in an amount of. 40 wt .-%, based on the total weight of the polymer latex.
• the mean particle size (weight average, d 50 ) is 100 nm (Example 1, 2) or 200 nm (Example 3).
• the preparation of polymer latices containing polystyrene having the abovementioned particle sizes is carried out by customary methods known to the person skilled in the art. In this case, usually a polymer latex is obtained with a polystyrene content of> 30 wt .-%, which is then diluted with water to the desired concentration.
• water-soluble polymer is poly is used (vinyl alcohol) (PVA I) having a weight average molecular weight (Mw) of 195000 g / mol, which is hydrolyzed to 98% (MOWIOL ® 56-98 from Kuraray Specialties Europe KSE GmbH), or PO - ly (vinyl alcohol) (PVA II) with a weight average molecular weight (Mw) of 145000 g / mol, which is 99% hydrolyzed (MOWIOL ® 28 - 99 from Kuraray Specialties Europe KSE).
• nonionic surfactant is a block copolymer based on propylene oxide and ethylene oxide (Basensol ® of BASF AG).
• the preparation of the electrospinning according to Example 2 used colloidal dispersions is carried out by mixing a polystyrene-containing latex with water, wherein the above-mentioned polymer latex containing polystyrene in an amount of. 40 wt .-%, based on the total weight of the polymer latex, is obtained.
• the solids content of the dispersion to be spun is 18% by weight.
• To the polymer latex is added the above-mentioned polyvinyl alcohol in aqueous solution (10% strength by weight), so that the colloidal dispersion to be spun contains about 4.5% by weight PVA II and the weight ratio of polystyrene to polyvinyl alcohol (PVA II ) in the mixture is 80:20.
• the nonionic surfactant is added to this mixture, the amount of nonionic surfactant in the colloidal dispersion to be spun being about 0.5% by weight.
• Table 1 summarizes the colloidal dispersions to be spun:
• PS polystyrene having an average particle size of 100 nm (in water about 40 wt .-% strength) 3) based on the total weight of the dispersion 4) aqueous solution 5) addition amount of water added 6) Basensol ®: block copolymer based on propylene oxide and ethylene oxide from BASF AG
• colloidal dispersions I and I V prepared according to item 1 are electrospun in the apparatus shown in FIG.
• the dispersion is thereby conveyed at a temperature of 15 to 16 0 C by a syringe 3 with a provided at the top capillary nozzle 2 with an inner diameter of 0.3 mm with a sample feed of 0.7 ml / h, wherein the distance between the electrodes 2, 5 is 200 mm and a voltage of 30 kV is applied between the electrodes.
• the resulting fibers are treated with water for 17 hours at room temperature to remove the water-soluble polymer.
• FIG. 2 shows the scanning electron micrographs of the fibers produced from the colloidal dispersions I (left) and IV (right).
• the upper images each show the fibers obtained before treatment with water, and the lower figures show the corresponding fibers after treatment with water.
• FIG. 2 shows the scanning electron micrographs of the fibers produced from the colloidal dispersions I (left) and IV (right).
• the upper images each show the fibers obtained before treatment with water, and the lower figures show the corresponding fibers after treatment with water.
• I fibers by electrospinning the dispersion I
• I V fibers by electrospinning the dispersion I V.
• nonionic surfactant gives more uniform polymer fibers than without the addition of surfactant, which do not dissolve in water in individual polystyrene particles.
• colloidal dispersion is used, which is based on a 40 wt .-% polystyrene latex.
• the weight-average particle size of the polystyrene particles (d 50 ) is 200 nm.
• the dispersion contains 4.5% by weight, based on the total amount of dispersion, of polyvinyl alcohol PVA II, the weight ratio of polystyrene to PVA II being 85:15, and 0 , 8 wt .-%, based on the total amount of the dispersion, of the nonionic surfactant.
• PS polystyrene having an average particle size of 200 nm (in water 40 wt .-% ig) 2) based on the total weight of the dispersion 3) aqueous solution 4)
• Basensol ® block copolymer based on propylene oxide and ethylene oxide from BASF AG
• the electrospinning is carried out in the apparatus shown in Figure 1, under the following conditions: Inner diameter of the capillary nozzle: 0.3 mm
• the resulting fibers are treated with water for 17 hours at room temperature to remove the water-soluble polymer.
• a portion of the fibers obtained after the electrospinning is heated before treatment with water at temperatures of 1 10 0 C and 130 0 C in each case for 15, 30 and 60 minutes.
• the other part of the resulting fibers is heated after treatment with water under the appropriate conditions.
• FIGS. 3 and 4 show scanning electron micrographs of the respective fibers in comparison to unheated fibers. Photographs of fibers that were not treated with water prior to heating are shown on the left, and images of fibers treated with water before heating are shown on the right. 3 shows photographs of fibers are shown, which were heated at 1 10 0 C, and in Figure 4 photographs of fibers are shown, which were heated at 130 0 C. Further, in Figure 3, for comparison, a fiber is shown (before and after water treatment) which has not been heated.
• the invention is not limited to one of the above-described embodiments, but can be modified in many ways. It can be seen, however, that the present invention relates to a process for the production of polymer fibers, in particular of
• Nanofibers and mesofibres after the electrospinning process, in which a colloidal dispersion at least one substantially water-insoluble polymer (and at least one nonionic surfactant) optionally further comprising at least one water-soluble polymer in an aqueous medium is electrospun. Furthermore, the present invention relates to fibers obtainable by this process.

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• 2007
  • 2007-08-20 JP JP2009525045A patent/JP2010501738A/ja not_active Ceased
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