Method and expansion device for preparing expanded microspheres

Abstract

The present invention relates to a method of preparing expanded thermoplastic microspheres, comprising charging thermally expandable microspheres into an expansion device comprising rotating feeding means enveloped by a hollow body, and one or more scrapers. The invention further relates to an expansion device for expanding thermoplastic microspheres.

1 - 17 . (canceled)  
   
   
       18 . An expansion device for preparing expanded thermoplastic microspheres comprising rotatable feeding means enveloped by a hollow body, and one or more scrapers positioned between the outer radius of the feeding means and the inner surface of the hollow body.  
   
   
       19 . An expansion device according to  claim 18 , wherein said one or more wscrapers are mounted on the feeding means and extend radially beyond the outer radius of the feeding means towards the inner surface of the hollow body.  
   
   
       20 . An expansion device according to  claim 18 , wherein said one or more scrapers, alone, or in combination, effect a scraping of from about 20 to about 95% of the longitudinal length of the inner surface of the hollow body.  
   
   
       21 . An expansion device according to  claim 18 , wherein one or two scrapers effects a scraping of from about 70 to about 100% of the longitudinal length of the inner surface of the hollow body and 2 to 4 scrapers effect a scraping of from about 10 to about 40% of the longitudinal length of the inner surface of the hollow body.  
   
   
       22 . An expansion device according to  claim 18 , wherein said one or more scrapers are mounted on the feeding means starting at the inlet side of the expansion device and extending therefrom.  
   
   
       23 . An expansion device according to  claim 18 , wherein said one or more scrapers, or a surface layer of said one or more scrapers, are/is made of a fluoroplastic material.  
   
   
       24 . An expansion device according to  claim 18 , wherein the hollow body is provided with one or more heaters.  
   
   
       25 . An expansion device according to  claim 18 , wherein the feeding means is provided with one or more heaters.  
   
   
       26 . An expansion device according to  claim 18 , wherein the feeding means is in the form of a screw.  
   
   
       27 . An expansion device according to  claim 18 , wherein the feeding means is in the form of one or more paddles protruding from a central core.