The influence of alkaline pre-hydrolysis on hemicelluloses removal and the impact of the treatment on soda pulp quality were investigated. The pre-hydrolysis conditions were selected as NaOH-5 and 7.5% based on the oven dry weight of the sample, time-30, 60 and 90 minutes, and temperature-60 and 90 °C. Each treated sample was divided into two portions: one-third was used for chemical analysis and the other two-thirds for soda pulping. The influence of the pre-hydrolysis conditions was determined by measuring the cellulose and lignin content and the removal of hemicelluloses. The lignin and cellulose content increased under the intense treatment conditions and the hemicellulose removal was higher at higher dosages of NaOH, temperatures and times, varying between 4.55% and 8.31%. The treated sample was subjected to soda pulping during 20 minutes pulping time, at 175 °C temperature and 16% sodium hydroxide (based on dry weight). Then, the pulping yield, kappa number and strength properties of the unbleached pulp were determined by corresponding Tappi standard test methods. The pulping yield and kappa number ranged from 41 to 46.6% and from 41.6 to 61.85, respectively. The highest values of tensile strength, tear strength and burst strength indices were determined as 75.35 Nm/g, 17.9 mN.m 2 /g and 3.31 kPa.m 2 /g, respectively.

Alkaline peroxide mechanical pulping of paulownia wood harvested from exotic tree plantations in northern Iran was investigated. The fiber length, width, and cell wall thickness of this wood were measured as 0.82 mm, 40.3 μm, and 7.1 μm, respectively. The chemical composition including cellulose, lignin, and extractives soluble in ethanol-acetone, 1% NaOH, hot and cold water was determined as 49.5%, 25%, 12.1%, 26.9%, 11.4%, and 8.1% respectively. The ash content of this wood was 0.45%. Pre-washed chips were chemically treated at 70°C for 120 minutes with different combinations of three dosages (1.5, 3, and 4.5%) of hydrogen peroxide and three dosages (1.5, 3, and 4.5%) of sodium hydroxide prior to defibration. Other chemicals including DTPA, sodium silicate, and MgSO4 were constant at 0.5%, 3%, and 0.5%, respectively. The results showed that using a 1.5% hydrogen peroxide and 4.5% sodium hydroxide charge, the brightness of APMP pulp reached 68.7% ISO and higher chemical dosages did not improve the brightness; however, to produce APMP pulp with higher strength, a sodium hydroxide charge of 4.5% was needed. The tensile strength, tear strength, burst strength indices, and bulk density of the APMP pulp produced from 1.5% hydrogen peroxide and 4.5% sodium hydroxide were measured as 15.5Nm/g, 6.54mN.m2/g, 0.56kPa.m2/g, and 3.47cm3/g, respectively. The resulting pulp was bulky and is suitable for use in the middle layer of boxboard to provide the desired stiffness with a lower basis weight.