Influence of process variables on the properties of pulp and paper sheets obtained by sulphite pulping of olive tree wood

A central composition design was developed to study the influence of proces s variables (temperature, pulping time, sulphite concentration, anthraquino ne concentration and liquid/solid relation) on the properties of pulps (yie ld, holocellulose, alpha-cellulose and lignin contents, and brightness) and the paper sheets (stretch, burst index and tear index) obtained from them, in the sulphite pulping of olive tree wood. Equations that reproduce the p roperties of pulps prepared by sulphite pulping and of paper sheets obtaine d from it are reported. The proposed equations fit the experimental yield a nd the holocellulose and alpha-cellulose contents of the pulps with errors less than 5%, as well as brightness with errors less than 10%. Also, they r eproduce the lignin content of the pulps, and the stretch, burst index and tear index of the paper sheets with errors less than 15%. Obtaining pulps w ith acceptably high yield, holocellulose and alpha-cellulose contents, and also a high brightness, in addition to low lignin contents, entails operati ng at a temperature of 193 degrees C for 143 min, using a sulphite concentr ation of 19.85%, an anthraquinone concentration of 0.1% and a liquid/solid relation of 6.24. These are also the most suitable conditions for obtaining paper sheets with a high stretch, burst index and tear index.