HIGH PH TREATMENT OF PULP IN A BLEACH SEQUENCE TO PRODUCE PULP HAVING LOW D.P. AND LOW COPPER NUMBER FOR USE IN LYOCELL MANUFACTURE

摘要

A high pH and a low pH process for reducing the degree of polymerization of apulp having a hemicellulose content of at least 7%. The high pH is greaterthan 8, and thelow pH process is 2 to 8. The high pH process reduces the degree ofpolymerizationwithout substantially increasing the copper number. The low pH processrequires asubsequent treatment with alkali to reduce the copper number of the pulp toless than 2.The process can be practiced in pulp mills with a bleaching sequence havingone or moreE or D stages. At the end of the bleach sequence, a pulp having a degree ofpolymerization of 200 to 1100, a copper number of less than 2, and ahemicellulosecontent of at least 7% is provided. The pulp can be used to make lyocellfibers.