Method for the thermal stabilisation of fibres and said type of stabilised fibres

Abstract

The invention relates to a method for the production of thermally stabilised melt spun fibres, in which polyacrylonitrile (PAN) fibres or PAN fibre precursors produced by melt spinning are treated in an aqueous alkaline solution which comprises in addition a solvent for PAN. Likewise, the invention relates to fibres which are producible according to this method.

1 - 15 . (canceled) 
     
     
         16 . A method of thermally stabilising melt spun acrylic fibres in which an acrylic fibre produced by melt spinning or a fibre precursor, which involves pre-stabilising the acrylic fibre produced by melt spinning or the fibre precursor with a mixture comprising a solvent for polyacrylonitrile and an aqueous alkaline solution. 
     
     
         17 . The method according to  claim 16 , wherein the mixture comprises from 0.1 to 60% by volume of the solvent and from 40 to 99.9% by volume of the aqueous alkaline solution. 
     
     
         18 . The method according to  claim 16 , wherein the solvent is selected from the group consisting of dimethylsulphoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene carbonate, propylene carbonate, aqueous sodium rhodanide solutions, and mixtures thereof. 
     
     
         19 . The method according to  claim 16 , wherein the pre-stabilisation is effected in a modification bath comprising the mixture at a temperature of 20 to 80° C., within a dwell time of 5 s to 2 min. 
     
     
         20 . The method according to  claim 16 , wherein the aqueous alkaline solution comprises from 3 to 15 mol/l of at least one alkaline earth- or alkali salt. 
     
     
         21 . The method according to  claim 16 , wherein the proportions of solvent and aqueous alkaline solution in the mixture are adjusted as a function of the titre. 
     
     
         22 . The method according to  claim 16 , wherein an oxidative stabilisation and carbonisation under inert gas, at temperatures of 800 to 1,700° C. follows the pre-stabilisation. 
     
     
         23 . The method according to  claim 22 , wherein the oxidative stabilisation is effected at a temperature of 200 to 350° C. in an oxygen- or air-containing atmosphere. 
     
     
         24 . The method according to  claim 16 , wherein the fibre precursor is produced by a method in which
 i. a copolymerisation of 95 to 80% by mol of acrylonitrile with at least one comonomer selected from
 a) 5 to 20% by mol of at least one alkoxyalkyl acrylate of the general formula I 
   
       
         
           
           
               
               
           
         
          with 
          R=C n H 2n+1  and n=1-8 and m=1-8,
 b) 0 to 10% by mol of at least one alkylacrylate of the general formula II 
 
       
       
         
           
           
               
               
           
         
          with 
          R=C n H 2n+1  and n=1-18,
 c) 0 to 10% by mol of at least one vinyl ester of the general formula III 
 
       
       
         
           
           
               
               
           
         
          with 
          R=C n H 2n+1  and n=1-18, 
         is implemented in the presence of at least one initiator and 
         ii. the copolymer is spun with an extruder with at least one nozzle at the extruder outlet to form mono- or multifilaments. 
       
     
     
         25 . The method according to  claim 24 , wherein the copolymer has a melt viscosity which is constant or decreases with increasing temperature up to 240° C. 
     
     
         26 . The method according to  claim 24 , wherein 8 to 12% by mol of the comonomer in a) and/or 1 to 5% by mol of the comonomer in b) and/or 1 to 5% by mol of the comonomer in c) are present. 
     
     
         27 . The method according to  claim 24 , wherein the copolymerisation is effected by precipitation polymerisation, emulsion polymerisation and/or polymerisation in a solvent. 
     
     
         28 . The method according to  claim 27 , wherein the solvent is selected from the group consisting of dimethylsulphoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene carbonate, propylene carbonate, aqueous sodium rhodanide solution and mixtures thereof. 
     
     
         29 . A melt spun fibre stabilised thermally according to the method of  claim 16 . 
     
     
         30 . The melt spun fibre according to  claim 29 , which is further processed to form a carbon fibre by an oxidative stabilisation and carbonisation under inert gas, at a temperature of 800 to 1,700° C.