Electrospinning of polyamide nanofibers

Abstract

The invention relates to a process for the preparation of polyamide nanofibers by electrospinning, wherein the process is a multi-nozzle electrospinning process with the use of a multi-nozzle device or a nozzle-free electrospinning with the use of nozzle free device, comprising steps wherein a high voltage is applied, a polymer solution comprising a polymer and a solvent is fed to the multi-nozzle device or the nozzle free device and transformed under the influence of the high voltage into charged jet streams the jet streams are deposited on a substrate or taken up by a collector, and the polymer in the jet streams solidifies thereby forming nanofibres, and wherein the polymer comprises a semi-crystalline polyamide having a C/N ratio of at most 5.5 and a weight average molecular weight (Mw) of at most 35,000. The invention also relates polyamide nanofibers made by the electrospinning process, as well as to products made thereof and use thereof.

1 . Process for the preparation of polyamide nanofibers by electrospinning, wherein the process is a multi-nozzle electrospinning process with the use of a multi-nozzle device or a nozzle-free electrospinning with the use of nozzle free device, comprising steps wherein
 a high voltage is applied   a polymer solution comprising a polymer and a solvent is fed to the multi-nozzle device or the nozzle free device and transformed under the influence of the high voltage into charged jet streams   the jet streams are deposited on a substrate or taken up by a collector and   the polymer in the jet streams solidifies thereby forming nanofibres and wherein the polymer comprises a semi-crystalline polyamide having a C/N ratio of at most 5.5 and a weight average molecular weight (Mw) of at most 35,000.   
     
     
         2 . Process according to  claim 1 , wherein the process is a multi-nozzle electrospinning process comprises steps wherein
 the high voltage is applied between a spinneret and a collector, or between a separate electrode and a collector, the spinneret comprising a series of spinning nozzles,   a stream of a polymer solution comprising a polymer and a solvent is fed to the spinneret, and   the polymeric solution exits from the spinneret through the spinning nozzles and transforms under the influence of the high voltage into charged jet streams.   
     
     
         3 . Process according to  claim 1 , wherein the process is a nozzle-free electrospinning process. 
     
     
         4 . Process according to  claim 1 , wherein the C/N ratio is in the range of 2-5, and/or the polyamide is a homopolyamide of polyamide 46, polyamide 26, polyamide 4, polyamide 36, 
     
     
         5 . Process according to  claim 1 , wherein the polyamide is present in an amount of at least 50 wt. % relative to the polymer, and the polyamide has an Mw in the range of 2,000-30,000. 
     
     
         6 . Process according to  claim 1 , wherein the polymer comprises a second polyamide having a C/N ratio of more than 5.5 and/or an Mw of at more than 35,000, and/or a water soluble polymer. 
     
     
         7 . Process according to  claim 1 , wherein the solution comprises an additive. 
     
     
         8 . Process according to  claim 1 , wherein the solvent comprises either (I) water, a water soluble salt, and either methanol, ethanol, glycol and/or glycerin, or (II) formic acid and/or acetic acid, and at least one liquid selected from the group consisting of water, methanol, ethanol, glycol, glycerin, and methyl formate. 
     
     
         9 . Process according to  claim 1 , comprising one or more of the following steps: a washing step, a drying step, a curing step, and/or a post condensation step. 
     
     
         10 . Nanofibres or nano-web consisting of a polymer composition comprising a polyamide having a C/N ratio of at most 5.5 and an Mw of at most 35,000. 
     
     
         11 . Nanofibres or nano-web consisting of a polymer composition comprising a polyamide having a C/N ratio of less than 5 and a Tm of at least 300° C. 
     
     
         12 . Nanofibres or nano-web consisting of a polymer composition comprising a polyamide having a C/N ratio of more than 5.5 and an Mw of at most 35,000 and a linear or branched polyamide having an Mw of more than 35,000. 
     
     
         13 . Use of nanofibres or a nano-web according to  claim 10 , or a micro-porous membrane made thereof, for the use of any one of the following applications: molecular separations and filtration, like gas/gas filtration, hot gas filtration, particle filtration, liquid filtration such as micro filtration, ultra filtration, nano filtration, reverse osmosis; waste water purification, oil and fuel filtration electrochemical applications, including electro-dialysis, electro-deionization, batteries and fuel cells; controlled release applications including pharmaceutical and nutraceutical components; pertraction, pervaporation and contactor applications; immobilization of enzymes, and humidifiers, drug delivery; (industrial) wipes, surgical gowns and drapes, wound dressing, tissue engineering, protective clothing, catalyst supports, and coatings. 
     
     
         14 . Separation process wherein nanofibres or a nanoweb according to  claim 10 .