Process for producing electret and production apparatus

Abstract

A process for manufacturing an electret article, comprising passing melt-extruded thermoplastic resin fibers through a mist space substantially formed from droplets of a polar liquid, and then collecting the fibers, wherein the thermoplastic resin fibers contain electrical-chargeability enhancing agents, and the average diameter of the droplets is less than 20 μm, is disclosed. Further, an apparatus for manufacturing an electric article, comprising (1) a means for melt-extruding a thermoplastic resin containing electrical-chargeability enhancing agents to form thermoplastic resin fibers; (2) a means for spraying droplets consisting essentially of a polar liquid to a space downstream of a direction of said thermoplastic resin extruded from said means for melt-extruding a thermoplastic resin, to thereby form a mist space, the average diameter of said droplets being less than 20 μm; and (3) a means for collecting said thermoplastic resin fibers which have been passed through said mist space, is also disclosed.

1 . A process for manufacturing an electret article, comprising passing melt-extruded thermoplastic resin fibers through a mist space substantially formed from droplets of a polar liquid, and then collecting the fibers, wherein said thermoplastic resin fibers contain electrical-chargeability enhancing agents, and the average diameter of said droplets is less than 20 μm.  
   
   
       2 . The process according to  claim 1 , wherein the thermoplastic resin fibers are not subjected to a drying step after passing through said mist space.  
   
   
       3 . The process according to  claim 1 , wherein a resin-droplet percentage of the formula:  
       (Wp/Wf)×100  
     wherein Wp denotes the amount of said droplets forming said mist space and sprayed to a unit volume thereof within a certain period of time, and Wf denotes the amount of said melt-extruded thermoplastic resin passed through said mist space within a certain period of time is 500 or more.  
   
   
       4 . The process according to  claim 1 , wherein a heated gas is blown onto said melt-extruded thermoplastic resin fibers.  
   
   
       5 . The process according to  claim 1 , wherein a volume specific resistivity of said thermoplastic resin is 10 14  ∩·cm or higher.  
   
   
       6 . The process according to  claim 5 , wherein a volume specific resistivity of said thermoplastic resin is 10 16  Ω·cm or higher.  
   
   
       7 . The process according to  claim 1 , wherein said polar liquid is water.  
   
   
       8 . The process according to  claim 1 , wherein said electrical-chargeability enhancing agent is at least one compound selected from a group consisting of a hindered amine compound, a metallic salt of a fatty acid, a metallic oxide, and an unsaturated carboxylic acid-modified high-molecular compound.  
   
   
       9 . The process according to  claim 1 , wherein the average diameter of said droplets is 15 μm or less.  
   
   
       10 . An apparatus for manufacturing an electric article, comprising (1) a means for melt-extruding a thermoplastic resin containing electrical-chargeability enhancing agents to form thermoplastic resin fibers; (2) a means for spraying droplets consisting essentially of a polar liquid to a space downstream of a direction of said thermoplastic resin extruded from said means for melt-extruding a thermoplastic resin, to thereby form a mist space, the average diameter of said droplets being less than 20 μm; and (3) a means for collecting said thermoplastic resin fibers which have been passed through said mist space.