Method and apparatus for atomising liquid media

Abstract

There is disclosed apparatus for atomising liquid media comprising an ultrasonic gas atomisation nozzle ( 11 ) having a gas flow path ( 12 ) from a plenum chamber ( 17 ) which flow path is straight and is provided with a plurality of resonance cavities ( 31 ).

1 . A method for making a polymer powder comprising: 
 melt-extruding a polymer material; and    impinging a high velocity gas stream on to the molten extrudate.    
   
   
       2 . A method according to  claim 1 , in which the high velocity gas stream is supersonic.  
   
   
       3 . A method according to  claim 2 , in which the high velocity gas stream is at Mach  2 .  
   
   
       4 . A method according to  claim 1 , in which the gas does not adversely react on or with the atomised polymer.  
   
   
       5 . A method according to  claim 1 , in which the gas is nitrogen.  
   
   
       6 . A method according to  claim 1 , in which the extrudate comprises a film.  
   
   
       7 . A method according to  claim 1 , in which the extrudate comprises filaments.  
   
   
       8 . A method according to  claim 7 , in which the filaments emerge as a sheet or ribbon from a line or spinnerettes.  
   
   
       9 . A method according to  claim 1 , in which a film or sheet or ribbon-like extrudate is impinged on both faces by a gas stream.  
   
   
       10 . Apparatus for making polymer powder comprising a die from which polymer is extruded and nozzle means impinging a high velocity gas stream on the extrudate from the die.  
   
   
       11 . Apparatus according to  claim 10 , in which the die comprises a slit for extruding a film.  
   
   
       12 . Apparatus according to  claim 10 , in which the die comprises a line of spinnerettes for extruding a sheet or ribbon of filaments.  
   
   
       13 . Apparatus according to  claim 10 , in which the nozzle means comprise a slit-form nozzle either side of the die directed towards the issuing extrudate.  
   
   
       14 . Apparatus according to  claim 10 , in which the nozzle means impinge the gas stream at an angle to the issuing extrudate so as to have a component of velocity in the direction of flow of the extrudate.  
   
   
       15 . Apparatus according to  claim 14 , in which the nozzle means form a V-shaped gas stream with an included angle between 30° and 90°.  
   
   
       16 . Apparatus according to  claim 10 , in which the die comprises a heater arrangement.