Method for producing a solution consisting of a polymer containing recurrent azole units, solutions produced according to said method and use of the same

1. A method of preparing a solution of a polymer comprising recurring azole units, which comprises dissolving a sufficiently dried polymer comprising recurring azole units of the formula

wherein the radicals Ar, Ar 1 and Ar 2 are tetravalent, divalent or trivalent aromatic or heteroaromatic groups and the radicals X, which are identical within a repeating unit, are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a group having 1–20 carbon atoms,

in N,N-dimethylacetamide having a sufficiently low water content at a temperature of 250° C. or less under an inert gas atmosphere, wherein a sufficiently dried polymer comprising recurring awls units of the formula (1) or (2) of which 90% by weight based on the total weight of the polymer comprising recurring azole units has a particle size of less than 1 mm is used.

2. The method as claimed in claim 1 , wherein X, which are identical within a repeating unit, are each an oxygen atom, a sulfur atom or an amino group bearing a hydrogen atom, a branched or unbranched alkyl, alkoxy group or an aryl group.

3. The method as claimed in claim 1 , wherein the polymer comprising recurring azole units is firstly milled and then dried before dissolution in N,N-dimethylacetamide.

4. The method as claimed in claim 1 , wherein the polymer comprising recurring azole units is dissolved at a temperature in the range from 160° C. to 250° C.

5. The method as claimed in claim 3 , wherein the polymer comprising recurring azole units is dissolved at a temperature in the range from 180° C. to 220° C.

6. The method as claimed in claim 4 , wherein a dried polymer comprising recurring azole units of the formula (1) or (2) which has a water content of less than 3% by weight based on the total weight of the polymer comprising recurring azole units is used.

7. The method as claimed in claim 5 , wherein a dried polymer comprising recurring azole units of the formula (1) or (2) which has a water content of less than 3% by weight based on the total weight of the polymer comprising recurring azole units is used.

8. The method as claimed in claim 1 , wherein said N,N-dimethylacetamide has a water content of less than 0.4% by weight based on the total weight of the N,N-dimethylacetamide.

9. The method as claimed in claim 7 , wherein said N,N-dimethylacetamide has a water content of less than 0.4% by weight based on the total weight of the N,N-dimethylacetamide.

10. The method as claimed in claim 1 , wherein the polymer comprising recurring azole units is dissolved over a period of less than 10 hours.

11. The method as claimed in claim 1 , wherein a polymer comprising recurring benzimidazole units of the formula (3):

wherein n is an integer greater than or equal to 10, is used.

12. A solution of a polymer comprising recurring azole units obtained by the method as claimed in claim 1 , wherein, in head-space analysis of the solution of a polymer comprising recurring azole units at 50° C., the height of the peaks of dimethylamine and/or trimethylamine is less than 10% of the height of the DMAc peak.

13. A solution of a polymer comprising recurring azole units obtained by the method as claimed in claim 1 , wherein the solution of a polymer comprising recurring azole units contains less than 3% by weight, based on the total weight of the polymer comprising recurring azole units, of material which can be separated off by filtration through a filter having a pore opening of 4 pm at 100° C.

14. The solution as claimed in claim 13 , wherein, in head-space analysis of the solution of a polymer comprising recurring azole units at 50° C., the height of the peaks of dimethylamine and/or trimethylamine is less than 10% of the height of the DMAc peak.

15. The solution as claimed in claim 14 which contains 25% by weight or less) based on its total weight, of polymer comprising recurring azole units.