The invention relates to a method for improving the colour index of
cellulose esters especially consisting of cellulose acetate. According to
the inventive method, a delignified eucalyptus pulp is subjected to a
preliminary treatment in order to remove pigments or chromophoric
substances, and the process-modified eucalyptus pulp obtained is
converted into cellulose esters in a conventional manner. The inventive
method is characterized in that a delignified eucalyptus pulp having a
cellulose content of more than approximately 80 wt. % and a pentosan
content of more than approximately 1 wt. % is extracted by means of a
solvent which dissolves oligomer pentosans but not the pulp of the
delignified eucalyptus pulp, especially at a temperature of up to
approximately 200 .degree. C. and a pressure of up to approximately 30
bar. The inventive method leads to an improvement in the colour index of
cellulose esters or the fibres and filaments produced therefrom, in an
economical and technically simple manner.
