Electrostatic spray apparatus and method of electrostatic spray

Abstract

An electrostatic spray apparatus configured such that multiple spinning units, each having multiple nozzles arranged two-dimensionally to electrostatically spray a polymer solution and a first collector disposed so as to be opposed to the multiple nozzles via an insulating sheet, are installed on collecting sections for holding a moving collecting sheet, and such that an air stream is formed orthogonal to the spray direction from the nozzles to the first collector and toward the collecting sheet inside the spinning unit.

1 . An electrostatic spray apparatus comprising:
 multiple spinning units each having multiple nozzles arranged two-dimensionally to electrostatically spray a polymer solution containing a polymeric substance and formed into a liquid using a solvent and a first collector disposed so as to be opposed to said multiple nozzles via an insulating sheet, the polarity of the voltage applied to said first collector being different from that of the voltage applied to said nozzles or said first collector being grounded to the ground potential,   a first power supply for applying a predetermined high voltage to said nozzles, and   a collecting section provided with said spinning units and movably holding a collecting sheet, wherein   said spinning unit is provided with air stream forming means flowing in a direction substantially orthogonal to the spray direction from said nozzles to said first collector for forming an air stream toward said collecting sheet.   
     
     
         2 . The electrostatic spray apparatus according to  claim 1 , wherein
 said air stream forming means has an air intake port formed at a position opposed to the installation face of said spinning unit that is installed on said collecting section, and a conductive member to which a power supply having the same polarity as that of the voltage applied to said nozzles is connected is provided at said air intake port,   second collectors having conductivity are disposed behind said collecting sheet in said collecting sections, and the polarity of the voltage applied to said second collector is different from that of the voltage applied to the conductive member at said air intake port or said second collector is grounded to the ground potential, and   said collecting sheet is fed along the faces of said second collectors.   
     
     
         3 . The electrostatic spray apparatus according to  claim 1 , wherein said spinning unit has a conductive plate made of a conductive metal and integrally molded with said nozzles, said polymer solution is stored in the concave section formed in said conductive plate, and said polymer solution is supplied to said nozzles. 
     
     
         4 . The electrostatic spray apparatus according to  claim 1 , wherein said spinning unit comprises:
 said first collector disposed so as to be opposed to said nozzles,   said insulating sheet disposed between said nozzles and said first collector, and   said air intake port formed on the face opposed to said installation face installed on said collecting section to generate an air stream toward said collecting section in a direction substantially orthogonal to the spray direction of said polymeric substance.   
     
     
         5 . The electrostatic spray apparatus according to  claim 1 , further comprising:
 a feed roller around which said collecting sheet is wound in a roll state, and   a take-up roller for taking up said collecting sheet that is fed from said feed roller and moved inside said collecting section and on which said polymeric substance is laminated.   
     
     
         6 . The electrostatic spray apparatus according to  claim 2 , wherein said multiple spinning units are each installed on said collecting section having said collecting sheet disposed in a direction substantially orthogonal to the direction of said air stream, and said second collector of said collecting section attracts said polymeric substance electrostatically sprayed so that said polymeric substance is laminated on said collecting sheet thereby to form a polymeric web. 
     
     
         7 . The electrostatic spray apparatus according to  claim 1 , wherein the pressure inside said collecting sections is set to a negative pressure that is lower than the ambient air pressure. 
     
     
         8 . The electrostatic spray apparatus according to  claim 1 , wherein said collecting sections are each provided with a recovery unit into which the air inside said spinning units flows to recover the solvent contained in said polymer solution. 
     
     
         9 . The electrostatic spray apparatus according to  claim 1 , wherein said multiple spinning units are disposed continuously in the movement direction of said collecting sheet. 
     
     
         10 . The electrostatic spray apparatus according to  claim 1 , wherein the height of said nozzle is 5 mm or more, and the inside diameter of the spray port at the tip of said nozzle is in the range of 0.1 to 1.0 mm. 
     
     
         11 . The electrostatic spray apparatus according to  claim 1 , wherein said spinning units installed on said collecting sections are configured so as to be removable. 
     
     
         12 . A method of electrostatic spray comprising the steps of:
 feeding a polymer solution containing a polymeric substance and formed into a liquid using a solvent to multiple nozzles arranged two-dimensionally,   applying a high voltage to said nozzles to electrostatically spray said polymer solution from said nozzles,   generating an air stream flowing in a direction substantially orthogonal to the direction of electrostatic spray in each of spinning units having said nozzles, and   applying said air stream to said polymeric substance electrostatically sprayed and charged so that said polymeric substance is laminated on a collecting sheet disposed substantially orthogonal to the direction of said air stream.   
     
     
         13 . The method of electrostatic spray according to  claim 12 , having the step of laminating said polymeric substance on said collecting sheet by moving said polymeric substance electrostatically sprayed and charged in a direction orthogonal to the spray direction from said nozzles by the Coulomb forces. 
     
     
         14 . The method of electrostatic spray according to  claim 12 , having the operation of always detecting the holding amount of said polymer solution and maintaining the level of said polymer solution constant in the step of supplying said polymer solution containing said polymeric substance and formed into a liquid using a solvent to said multiple nozzles. 
     
     
         15 . The method of electrostatic spray according to  claim 12 , wherein the polarity of the voltage applied to said first collector disposed so as to be opposed to said nozzles is different from that of the voltage applied to said nozzles or said first collector is grounded to the ground potential to generate attraction forces to attract charged liquid droplets separated from said nozzles, electrostatically sprayed and formed into minute charged particles. 
     
     
         16 . The method of electrostatic spray according to  claim 12 , wherein the polarity of the voltage applied to said second collector disposed along the side of said collecting sheet opposite to the side on which said polymeric substance is laminated is different from that of the voltage applied to said nozzles or said second collector is grounded to the ground potential to generate attraction forces to attract minute charged particles electrostatically sprayed from said nozzles. 
     
     
         17 . The method of electrostatic spray according to  claim 12 , having the step of recovering said solvent contained in said polymer solution from said air streams in said spinning units. 
     
     
         18 . The method of electrostatic spray according to  claim 12 , having the step of laminating said polymeric substance on the same collecting sheet by independently operating said multiple spinning units having said nozzles. 
     
     
         19 . The method of electrostatic spray according to  claim 18 , having the step of controlling the operation states of said multiple spinning units depending on the specifications of a polymeric web to be produced. 
     
     
         20 . The method of electrostatic spray according to  claim 18 , having the step of laminating a different polymeric substance on said collecting sheet in at least one of said multiple spinning units.