Acid hydrolytic treatment of cotton linters

The use of cotton linters pulps in blends with different pulps, e.g. recycled paper pulps, is limited by their poor papermaking properties. Cotton linters, with their particular chemical and supramolecular characteristics are difficult to hydrate by refining. The low interfiber cohesion of linter fibers is due to the poor development of external fibrillation and fiber conformability with refining. Considering that cutting of the cellulose chain increases the number of exposed hydrophilic groups, a controlled. acid catalysed hydrolytic degradation was proposed as a low cost alternative to increase fiber hydrophilicity. Behaviour of the hydrolysed samples (with hydrochloric acid) during refining in PFI mills is analysed at two values of the polymerization degree (DP), 2000-3000 and 1000-1500, versus regard to the sample without treatment. The conclusion is that the more aggressive the acid hydrolysis, the more unfavourable tendencies in mechanical properties occur. Some of the refining energy consumption was reduced by the acid treatment but, for the same consumption, hydrolysed pulps show lower mechanical properties values. The acid treatment causes a decrease in the fiber's intrinsic strength and during the mechanical treatment the fiber length is reduced, which leads to lower tear levels.