Nanofiber manufacturing device

Abstract

The present invention relates to a nanofiber manufacturing apparatus having a plurality of electrospinning units disposed serially along the conveying direction of a long sheet, each electrospinning unit including: a conductive case; a collector attached to the case by means of an insulation member; a nozzle block disposed to face the collector and having a plurality of nozzles from which polymer solution is ejected mounted thereon; a power supply adapted to apply a high voltage to a space between the collector and the nozzle block; an auxiliary belt formed of an insulative porous endless belt located and freely rotated at a position encompassing the collector; and an auxiliary belt driver adapted to rotate the auxiliary belt to a rotating speed corresponding to the conveying speed of the long sheet, wherein the positive electrode of the power supply is connected to the collector, and the negative electrode thereof to the nozzle block and the case, and when the collector is seen from the nozzle block, the outer edge of the insulation member is located more outwardly than the outer edge of the collector, so that if it is assumed that the thickness of the insulation member is a and the distance between the outer edge of the insulation member and the outer edge of the collector is b, it is satisfied that a≧6 mm and a+b≧50 mm.

1 . A nanofiber manufacturing apparatus having a plurality of electrospinning units disposed serially along the conveying direction of a long sheet conveyed at a given conveying speed to accumulate nanofibers on the long sheet, each electrospinning unit comprising:
 a conductive case;   a collector attached to the case by means of an insulation member;   a nozzle block disposed to face the collector and having a plurality of nozzles from which polymer solution is ejected mounted thereon;   a power supply adapted to apply a high voltage to a space between the collector and the nozzle block;   an auxiliary belt formed of an insulative porous endless belt located and freely rotated at a position encompassing the collector; and   an auxiliary belt driver adapted to rotate the auxiliary belt to a rotating speed corresponding to the conveying speed of the long sheet,   wherein the positive electrode of the power supply is connected to the collector, and the negative electrode thereof to the nozzle block and the case, and when the collector is seen from the nozzle block, the outer edge of the insulation member is located more outwardly than the outer edge of the collector, so that if it is assumed that the thickness of the insulation member is a and the distance between the outer edge of the insulation member and the outer edge of the collector is b, it is satisfied that a÷6 mm and a+b≧50 mm.   
     
     
         2 . The nanofiber manufacturing apparatus according to  claim 1 , wherein the auxiliary belt driver comprises:
 a plurality of auxiliary belt rollers on which the auxiliary belt is rolled;   a driving motor for rotating at least one of the plurality of auxiliary belt rollers; and   an auxiliary belt position controller for controlling the position of one of the plurality of auxiliary belt rollers in such a manner as to be located on one side end portion thereof from the inside of the auxiliary belt to the outside of the auxiliary belt, thereby controlling the position of the auxiliary belt with respect to the width direction of the auxiliary belt roller.   
     
     
         3 . The nanofiber manufacturing apparatus according to  claim 1 , wherein the insulation member is made of polyamide, polyacetal, polycarbonate, modified poly phenylene ether, poly butylene terephalate, polyethylene terephthalate, non-crystal polyalylate, polysulfone, polyether sulfone, polyphenylene sulfide, polyether ether ketone, polyimide, polyethyl imide, fluorine resin, liquid crystal polymer, polypropylene, high density polyethylene, or polyethylene. 
     
     
         4 . The nanofiber manufacturing apparatus according to  claim 1 , further comprising:
 a conveying unit adapted to convey the long sheet; and   a main control unit adapted to control the operations of the conveying unit and the plurality of electrospinning units,   wherein when the main control unit monitors the quantity of current supplied from each power supply to each electrospinning unit and detects that a higher current than a given quantity of first set current is supplied from one or plurality of power supplies, the main control unit transmits a current supply stop signal for stopping the current supply from one or plurality of power supplies, and at the same time, transmits a conveying speed reduction signal for reducing the conveying speed of the conveying unit to allow the quantity of nanofibers per unit area accumulated on the long sheet to be in a given range.   
     
     
         5 . The nanofiber manufacturing apparatus according to  claim 4 , wherein if the main control unit detects that a lower current than a given quantity of second set current is supplied from one or a plurality of power supplies, the main control unit transmits a warning signal (for example, a warning sound or a warning indicating signal) for indicating the trouble of one or the plurality of power supplies. 
     
     
         6 . The nanofiber manufacturing apparatus according to  claim 4 , wherein if it is assumed that the number of power supplies conducting the current supply for a first period of time before the reduction of the conveying speed is n and the number of power supplies conducting the current supply for a second period of time after the reduction of the conveying speed is m, the conveying speed for the second period of time is set by m/n times to the conveying speed for the first period of time under the control of the main control unit. 
     
     
         7 . The nanofiber manufacturing apparatus according to  claim 1 , wherein each nozzle is located upwardly from the nozzle block to eject the polymer solution upwardly from the ejection hole thereof and has a nozzle front end portion having a shape of a cylinder cut along the plane crossing slantly to the axis of the cylinder, and the nozzle block has a polymer solution supply passage formed to supply the polymer solution to each nozzle and a polymer solution collection passage formed to collect the polymer solution overflowing from the ejection hole of each nozzle, so that the electrospinning of the nanofibers is conducted by the overflowing ejection of the polymer solution from the ejection hole of each nozzle and at the same time by the collection of the polymer solution overflowing from the ejection hole of each nozzle in such a manner as to allow the collected polymer solution to be reused as the material of the nanofibers. 
     
     
         8 . The nanofiber manufacturing apparatus according to  claim 7 , wherein an angle θ between the axis of the cylinder and the plane is in the range between 15° and 60°. 
     
     
         9 . The nanofiber manufacturing apparatus according to  claim 7 , wherein the polymer solution collection passage comprises:
 an accommodating portion adapted to contain the polymer solution overflowing from the ejection holes of the plurality of nozzles;   a cover portion adapted to cover the accommodating portion and having a plurality of nozzle holes communicating with the plurality of nozzles; and   a plurality of jackets each adapted to cover the outer periphery of each nozzle protruding from the nozzle hole and having a jacket base portion formed on the base portion thereof and a jacket front portion formed on the front end portion thereof, the jacket front portion being thinner than the jacket base portion.   
     
     
         10 . The nanofiber manufacturing apparatus according to  claim 7 , further comprising:
 a material tank adapted to store the polymer solution as the material of the nanofibers therein;   regeneration tanks adapted to regenerate the collected polymer solution and store the regenerated polymer solution thereinto;   an intermediate tank adapted to store the polymer solution supplied from the material tank or the regeneration tanks;   a first transfer unit adapted to transfer the polymer solution from the polymer solution collection passage of the nozzle block to the regeneration tanks;   a first transfer control unit adapted to control the transferring operation of the first transfer unit;   a second transfer unit adapted to transfer the polymer solution from the material tank and the regeneration tanks to the intermediate tank; and   a second transfer control unit adapted to control the transferring operation of the second transfer unit.   
     
     
         11 . The nanofiber manufacturing apparatus according to  claim 10 , wherein the second transfer control unit controls whether the polymer solution is transferred from any of the material tank and the regeneration tanks to the intermediate tank. 
     
     
         12 . The nanofiber manufacturing apparatus according to  claim 11 , wherein the first transfer control unit controls whether the polymer solution is transferred to any of the regeneration tanks, and if the polymer solution is transferred from the regeneration tanks to the intermediate tank, the second transfer control unit controls whether the polymer solution is transferred from any of the regeneration tanks to the intermediate tank. 
     
     
         13 . The nanofiber manufacturing apparatus according to  claim 1 , further comprising:
 an air permeability measurement unit adapted to measure the air permeability of the long sheet on which the nanofibers are accumulated; and   a conveying speed control unit adapted to control the conveying speed in accordance with the air permeability measured through the air permeability measurement unit.   
     
     
         14 . The nanofiber manufacturing apparatus according to  claim 13 , wherein the conveying speed control unit controls the conveying speed in accordance with the deviation quantity between the air permeability measured through the air permeability measurement unit and given target thickness. 
     
     
         15 . The nanofiber manufacturing apparatus according to  claim 1 , further comprising:
 a thickness measurement unit adapted to measure the thickness of the long sheet on which the nanofibers are accumulated; and   a conveying speed control unit adapted to control the conveying speed in accordance with the thickness measured through the thickness measurement unit.   
     
     
         16 . The nanofiber manufacturing apparatus according to  claim 15 , wherein the conveying speed control unit controls the conveying speed in accordance with the deviation quantity between the thickness measured through the thickness measurement unit and given target thickness. 
     
     
         17 . The nanofiber manufacturing apparatus according to  claim 1 , further comprising:
 air supply units adapted to supply environmentally conditioned air correspondingly to the plurality of electrospinning units; and   volatile organic compound (herein, referred to as VOC) treatment units adapted to burn and remove VOCs generated from the plurality of electrospinning units,   wherein each air supply unit has a dehumidifier adapted to produce dehumidified air by using a dehumidifying agent dried through the hot air produced by the combustion heat generated during the combustion of the VOCs.   
     
     
         18 . The nanofiber manufacturing apparatus according to  claim 17 , wherein the dehumidifier comprises:
 a dehumidifying agent containing portion in which the dehumidifying agent is contained;   an air introduction portion adapted to introduce air to be dehumidified thereinto;   a dehumidified air sending portion from which the dehumidified air is sent;   a hot air introduction portion for introducing the hot air produced by the combustion heat; and   a hot air exhaust portion for exhausting the hot air of the hot air introduction portion to the outside,   whereby the dehumidifier dries and regenerates the dehumidifying agent used for the dehumidification of the introduced air through the hot air introduced into the hot air introduction portion.   
     
     
         19 . The nanofiber manufacturing apparatus according to  claim 18 , wherein each air supply unit comprises:
 an air flowing passage through which the air to be dehumidified flows;   an environmentally conditioned air flowing passage through which the dehumidified air sent from the dehumidified air sending portion flows;   a hot air flowing passage formed separated from the environmentally conditioned air flowing passage and adapted to guide the hot air produced by the combustion heat to the hot air introduction portion; and   a dehumidifier driver for driving the dehumidifier in such a manner where the air introduction portion of the dehumidifier introduces the air flowing along the air flowing passage and the hot air introduction portion introduces the hot air flowing along the hot air flowing passage.