The influence of properties in cellulose pulps on the reactivity in viscose manufacturing

This paper describes properties in cellulose pulps to adress the increased quality demands on pulps for viscose production. Several grades of cellulose pulps were selected to investigate their chemical reactivity based on pulping process, original wood type and intrinsic viscosity. In total, six sulfite pulps and four sulfate pulps were chosen, of which all but one sulfate pulp were of dissolving grade. The physical and chemical properties of the pulps were tested. The influence of these properties on xanthation and viscose manufacturing as well as their correlation to each of the three selection criteria was investigated by the use of multivariate data analyses. Two methods to describe cellulose reactivity were used: a laboratory scale viscose test method for cellulose reactivity (Fock) and a filter clogging test for viscose dope. It was shown that all pulps chosen in this investigation formed groups according to all three selection criteria using principal component analysis. The analysis shows that sulfite pulps, from both wood types, are strongly correlated to the variables Fock reactivity, pore size and concentration of extractives. Sulfate pulps, however, are separated into two groups, hardwood and softwood. Hardwood sulfate pulps are strongly described by the variables permeability, content of hemicelluloses and filter clogging value. Softwood sulfate pulps, on the other hand, are described by variables such as alpha cellulose content, R10 and R18. Partial least square regression showed that Fock reactivity is influenced by the following cellulose pulp properties, in order of importance: absorption rate with caustic, pore area, permeability and pore diameter. The main property affecting the filter clogging value of the viscose dope is pulp permeability, followed by pore diameter, content of hemicelluloses, R18 and pore area.