Electrospinning is a technology that produces a supermicro fiber having a diameter ranging from several tens to several hundreds of nanometers. Electrospinning is regarded as being the most advantageous in terms of industrialization because its principle and equipment is simpler and its application is easier compared to other nanofiber production methods. When an electric force is applied to a polymer solution dissolved in a melt or a solvent, electric charges are induced on a liquid surface of a polymer solution formed at the tip of a spinning nozzle or spinneret by a surface tension and a mutual repulsive force between the induced electric charges is produced in an opposite direction to that of the surface tension. When a threshold voltage exceeding the surface tension of the pedant droplet of the polymer solution is applied, a charged jet of the polymer solution formed by an electric repulsive force escapes from the tip of the spinning nozzle. The ejected jet develops a whipping motion in which the jet is ripped into thin strips so as to be fiberized and the solvent evaporates while flying in the air, thereby forming a nonwoven web in which supermicro fibers are laminated on a collector. Thus formed electrospun web can have breathability due to its numerous microporous structures, but have the characteristics of flexibility, ultra thinness, and ultra lightweightness as consisting of fiber assemblies having a diameter of a nanometer unit.
Since the fibers prepared by such an electrospinning technology can be potentially used in a wide range of applications, including filtrations, optical fibers, protective textures, drug delivery systems, tissue engineering frameworks, and gas separation membranes, their intensive scientific research is in progress.
In addition, thus prepared fibers have a diameter ranging from several micrometers to several nanometers depending on the preparation conditions, a very large surface area per unit mass, and flexibility. This suggests a possibility that the electrospun fibers will be used as adsorption agents. The characteristics of a number of voids formed between fibers and great dispersion of the fibers to an external stress suggest a possibility that the electrospun fibers will be used as efficient adsorption membranes, as their fluidity will be excellent and their structure will not be destroyed due to the flow.
Korean Patent Laid-Open Publication No. 2003-0077384 discloses an electro-brown spinning process of preparing a nanofiber web, in which a polymer solution is discharged through a spinning nozzle applied with a high voltage while compressed air is sprayed through a lower end of the spinning nozzle so that spun fibers are collected in the form of a web on a collector disposed below the spinning nozzle and grounded to the earth. However, this conventional method entails a problem in that the fiber discharged by the compressed air with high pressure and speed collide with and rebound from the surface of the collector, thereby contaminating the nozzle. In addition, there is involved a problem in that in case of spinning the polymer solution, the fibers are highly likely to be embrittled due to recovery of a solvent, and the amount of the polymer solution discharged is reduced as much as the amount of the solvent recycled, thereby reducing the production amount of the fibers.
In particular, the fiber preparation technology using a general electrospinning method according to the prior art has a limitation in that micro fibers with a diameter of 100 nm or less are not uniformly collected, and thus encounter a drawback in that its application range is significantly limited.