It was found that, for a dissolving pulp, an enzymatic pre-treatment with an endoglucanase prior to viscose preparation did not change the correlation between the gamma number of the viscose dope and the carbon disulphide charge. Thus, the pulp stoichiometry, or reactivity, was not changed by an endoglucanase pre-treatment. It has nevertheless previously been found that the pulp reactivity, measured either by Fock's test or as the filter clogging value (Kw), increased for the same type of enzyme pre-treatment. Thus, the pulp reactivity seems to be influenced by the analysis method employed.

The original objective of this study was to reduce the consumption of carbon disulphide in the preparation of high-viscosity viscose by pre-treating two softwood pulps with enzymes prior to the viscose stages. Reactivity can, however, be measured in different ways and the methods used in this study are Fock´s test of the pulp and the gamma number of the viscose solution prior to regeneration. It was found that whilst the reactivity of a pulp that had been subjected to enzyme pretreatment increased according to Fock´s test, it did not increase when the gamma number obtained in a standardized viscose preparation process was used. This unexpected difference that was discovered between the two reactivity tests made it difficult to analyze the impact of the enzyme stage on reactivity; the underlying reasons for the different reactivity results obtained were therefore investigated first. The conclusion that may be drawn from this investigation is that Fock´s test measures the extent to which carbon disulphide reacts with a pulp sample during a standardized test whereas the gamma number measures the resulting degree of xanthate substitution on the cellulose backbone. These two reactivity tests are thus not totally correlated. It was concluded that the gamma number was the more relevant of the two tests since it reflects the dissolution ability of a pulp in the viscose preparation, which is a very basic property of viscose. A higher gamma number also means that the coagulation time in the spinning process is prolonged; this is beneficial as it can be used to increase the tenacity of the viscose fibres. Measuring the reactivity according to Fock´s test, on the contrary, provides more dubious results as the test has no undisputed correlation to the viscose preparation process.

Large amounts of carbon disulphide are consumed in the conventional production of viscose. Until a novel, eco-friendly, wood-based process for the production of cellulose textile fibres has been developed and implemented, it is important to try to find ways to improve the conventional viscose process, e.g. in terms of reducing the carbon disulphide requirement of the process. The aim of this thesis was to reduce the amount of carbon disulphide consumed in the preparation of high-viscosity viscose by pre-treating pulps with enzymes. It also aimed at investigating and linking the different measurements of reactivity, i.e. gamma number, Fock reactivity and Kw, and determining the sensitivity of the gamma number to the hemicellulose content of pulp. Reactivity was measured as Fock reactivity and gamma number. The gamma number of viscose solutions remained unchanged when an enzyme stage was used prior to the viscose process. The gamma number analysis was found to be selective not only to cellulose but also to the hemicellulosic material. It was verified that both cellulose and hemicellulose molecules in the pulp material were substituted in the viscose preparation stages, showing that the gamma number of the pulp is due to both substituted cellulose and substituted hemicelluloses. The mechanisms responsible for the Fock reactivity, or the filter-clogging value (Kw) on the one hand and the gamma number on the other, are probably not the same. It was speculated that the analysis method employed in Fock´s test and the filter-clogging value measure the results on a fibre level, whereas the gamma number measures changes mainly on a molecular level. This could explain the difference in the levels of reactivity found in this study.