Kin Ohmura, Osaka Chemical11.02.18
Currently, a fiber with less than one micrometer in diameter is considered to be a nanofiber. There are several production technologies used to make these nanofibers, but electrospinning and meltblown are the most standard methods. All of them are the manufacturing method for the nonwoven fabric and the nonwoven fabrics feature different thicknesses and other properties depending on how they are made. Also, the nonwoven fabric made with nanofibers is provided with the yarn used as a raw material.
With the electrospinning method, dissolved polymers in the solvent are used as the raw materials of the ingredient of the yarn. The concentration of the polymer of the ingredient is 20% and the remaining 80% evaporates along with the solvents. One hundred percent of the ingredient would become fiber by the meltblown method because all of the molten polymer would be spun. Accordingly, the meltblown method is superior in productivity and the electrospinning method is inferior to that.
As for the thinness of these fibers, the method of electrospinning can produce a thin fiber of around 50nm in diameter, the meltblown method could produce fibers that are at least around 200nm in limitation. Once the limitation of the thinness of the meltblown method is addressed—it was around 500nm in fiber diameter—it can reach 200nm thanks to technological developments. Although the meltblown method has been able to compete with electrospinning with thinness of the fiber, there is a big difference in fiber diameter distribution between both processes. Uniformity is high in the fiber diameter of the electrospinning method and the distribution map draws a sharp curve. However, the meltblown method has a big unevenness of the fiber diameter and the distribution map becomes the gentle curve. The mean fiber diameter is 600nm. In this way, there is a different between mode of the fiber diameter and the mean fiber diameter, yet the electrospinning method has a very small difference. These facts influence the pore size distribution of the nonwoven fabrics. As for the electrospinning, the pore size distribution of the nonwoven fabric is equal even though some characteristics vary between the two processes. This characteristic comes out as the difference of the sampling efficiency when the nonwoven is used for a filter.
Among the many makers of electrospinning nonwoven fabrics, the enterprises producing nanofiber nonwoven fabrics of meltblown are limited. Tapyrus, Mitsui Chemicals, Asahi Kasei, and Kuraray have all produced meltblown nanofiber nonwoven fabrics in Japan. Since the main use of the product is air or liquid filters and the equalization of the fiber diameter is required so the development of the accuracy of filtration degree should be pushed forward.
In terms of the meltblown nonwoven cloth which was recently developed by Tapyrus, most of the fiber diameter is 350nm and the mean fiber diameter is 400nm. This means the difference between each diameter is small, making the fiber highly uniform. As for the filter with this nonwoven fabric, sampling efficiency increases more than the conventional nonwoven of the same fabric basis weight per area.
With the electrospinning method, dissolved polymers in the solvent are used as the raw materials of the ingredient of the yarn. The concentration of the polymer of the ingredient is 20% and the remaining 80% evaporates along with the solvents. One hundred percent of the ingredient would become fiber by the meltblown method because all of the molten polymer would be spun. Accordingly, the meltblown method is superior in productivity and the electrospinning method is inferior to that.
As for the thinness of these fibers, the method of electrospinning can produce a thin fiber of around 50nm in diameter, the meltblown method could produce fibers that are at least around 200nm in limitation. Once the limitation of the thinness of the meltblown method is addressed—it was around 500nm in fiber diameter—it can reach 200nm thanks to technological developments. Although the meltblown method has been able to compete with electrospinning with thinness of the fiber, there is a big difference in fiber diameter distribution between both processes. Uniformity is high in the fiber diameter of the electrospinning method and the distribution map draws a sharp curve. However, the meltblown method has a big unevenness of the fiber diameter and the distribution map becomes the gentle curve. The mean fiber diameter is 600nm. In this way, there is a different between mode of the fiber diameter and the mean fiber diameter, yet the electrospinning method has a very small difference. These facts influence the pore size distribution of the nonwoven fabrics. As for the electrospinning, the pore size distribution of the nonwoven fabric is equal even though some characteristics vary between the two processes. This characteristic comes out as the difference of the sampling efficiency when the nonwoven is used for a filter.
Among the many makers of electrospinning nonwoven fabrics, the enterprises producing nanofiber nonwoven fabrics of meltblown are limited. Tapyrus, Mitsui Chemicals, Asahi Kasei, and Kuraray have all produced meltblown nanofiber nonwoven fabrics in Japan. Since the main use of the product is air or liquid filters and the equalization of the fiber diameter is required so the development of the accuracy of filtration degree should be pushed forward.
In terms of the meltblown nonwoven cloth which was recently developed by Tapyrus, most of the fiber diameter is 350nm and the mean fiber diameter is 400nm. This means the difference between each diameter is small, making the fiber highly uniform. As for the filter with this nonwoven fabric, sampling efficiency increases more than the conventional nonwoven of the same fabric basis weight per area.
