Production of foam webs from high-temperature-resistant polysulfones or polyether sulfones

Abstract

The invention relates to a process for producing foam webs by foam extrusion of a mixture of a polysulfone or polyether sulfone and a volatile blowing agent, where the blowing agent is water or a mixture of water with an inert gas or organic liquid, e.g. an alcohol or a ketone.

1 . A process for producing a foam sheet having a thickness of more than 0.5 cm, said process comprising mixing thermoplastic polymers selected from polysulfone or polyether sulfone or mixtures thereof and from 1 to 10% by weight, based on the thermoplastic polymers, of a volatile blowing agent, at above 300° C. under pressure, and extruding the mixture into the open atmosphere using a slot die, wherein the blowing agent is a mixture of water with up to 200 parts by weight, based on 100 parts by weight of water, of an alkanol or of an aliphatic ketone.  
   
   
       2 . The process of  claim 1 , wherein the blowing agent is a mixture of water with up to 100 parts by weight, based on 100 parts by weight of water, of an alkanol or of an aliphatic ketone with a boiling point between 50 and 100° C.  
   
   
       3 . (canceled)  
   
   
       4 . The process of  claim 1 , wherein acetone is used as ancillary blowing agent.  
   
   
       5 . The process of  claim 1 , wherein the foam sheet has a thickness of from 0.5 to 8 cm and a density of from 30 to 100 g/l.  
   
   
       6 . The process of  claim 1 , wherein the foam sheet has a thickness of from 1 to 8 cm and a density of from 43 to 63 g/l.