Process for the preparation of polyether polyols

Abstract

Process for the preparation of a polyether polyol containing at most 20 ppm of sodium and/or potassium, which process comprises the steps of: (a) reacting an initiator having at least two active hydrogen atoms with at least one alkylene oxide in the presence of a catalyst comprising an alkali metal hydroxide; (b) neutralising the polyether polyol reaction product obtained in step (a) by contacting this reaction product with an acid having a pKa of less than 5 and water, wherein the acid and water are added in such amount that after addition: the water content is 2% by weight or less on the basis of the total weight of polyether polyol present and the molar ratio of acid to alkali metal hydroxide is in the range of from 0.3 to 1.0; (c) optionally reducing the water content in the reaction mixture to less than 2% by weight, based on total weight of polyether polyol; (d) removing the salt crystals from the polyether polyol and recovering the neutralised polyether polyol containing at most 20 ppm of sodium and/or potassium.

1 . Process for the preparation of a polyether polyol containing at most 20 ppm of sodium and/or potassium, which process comprises the steps of 
 (a) reacting an initiator having at least two active hydrogen atoms with at least one alkylene oxide in the presence of a catalyst comprising an alkali metal hydroxide;    (b) neutralising the polyether polyol reaction product obtained in step (a) by contacting this reaction product with an acid having a pKa of less than 5 and water, wherein the acid and water are added in such amount that after addition: 
 the water content is 2% by weight or less on the basis of the total weight of polyether polyol present and  
 the molar ratio of acid to alkali metal hydroxide is in the range of from 0.3 to 1.0;  
   (c) optionally reducing the water content in the reaction mixture to less than 2% by weight, based on total weight of polyether polyol;    (d) removing the salt crystals from the polyether polyol and recovering the neutralised polyether polyol containing at most 20 ppm of sodium and/or potassium.    
     
     
         2 . Process as claimed in  claim 1 , wherein the polyether polyol has a molecular weight of 2500 or less.  
     
     
         3 . Process as claimed in  claim 1  or  2 , wherein in step (b) an aqueous acid solution is used which comprises at least 50% by weight of acid having a pKa of less than 5.  
     
     
         4 . Process as claimed in any one of the preceding claims, wherein the acid is phosphoric acid.  
     
     
         5 . Process as claimed in any one of the preceding claims, wherein step (c) is applied.  
     
     
         6 . Process as claimed in  claim 5 , wherein in step (c) the water content is reduced to 0.2% by weight or less based on total weight of polyether polyol.  
     
     
         7 . Process as claimed in any one of the preceding claims, wherein in step (d) the salt crystals present in the polyether polyol are removed by filtration.