Laboratory scale test sheets prepared from pine wood (Pinus sylvestris L.) pulps

Ingredients

Pine wood (Pinus sylvestris L.), alkaline sulphate solution, demineralised water

Preparation Steps

Original Recipe Text

Cellulosic pine pulps were prepared using the sulphate method. Pine wood (Pinus sylvestris L.) was suspended in an alkaline sulphate solution where the amount of active alkali added was 20–38% (to dry weight wood) and the liquid to wood ratio (v:w) was 4. The pulping was conducted in a 15 dm3 PD-114 stainless laboratory digester with a maximal digestion temperature of 172 °C (p. 3). The material was washed with demineralised water and incubated overnight to remove residual alkali soluble fractions. Solids were disintegrated for 3 min in a JAC SHPD28D propeller pulp disintegrator. Fibres were screened using a 0.2 mm gap screen. The pulps were refined to 30°SR in a JAC PFID12X PFI mill. Finally, sheets were formed in a Rapid-Koethen class apparatus with a specified base weight of 80 g/m² (p. 3).

Evidence

"The pulps with a broad spectrum of lignin content were prepared from wood raw material in order to compare changes in tensile properties of papers with differential chemical compositions under various paper-ageing conditions. ... The manufactured sheets of paper were stored in air conditioned conditions until being used in further experiments."

Remarks

The study examined the impact of lignin content (Kappa numbers 19–90) and relative humidity (0% vs 59%) on paper durability at 90 °C over 90 days. It was found that papers produced at a neutral pH do not suffer significantly higher degradation rates due to lignin, which contradicts historical assumptions about lignin's negative impact (p. 3, 6). The results indicate that increased relative humidity contributes to a 40–68% reduction in strength properties, whereas dry aging only causes 5–22% (p. 6). The study specifically isolated the role of humidity from acidity by maintaining neutral conditions (p. 2).