Viscose Pulp Origin and the Traceability a Buyer Can Demand
Buyers verify viscose pulp origin using stable isotope profiling alongside physically segregated chain of custody documentation from pulp mill to yarn.
Acid Sulfite
Acidic Delignification
Extraction of lignin from wood chips using a sulfurous acid and bisulfite solution represents a primary method for producing high-purity dissolving pulp. This acid sulfite process operates at a low pH, typically between one and two, which facilitates the hydrolytic degradation of hemicelluloses. Mill operators monitor this step to ensure the removal of non-cellulosic elements before further chemical purification.
Process Control
Regular monitoring of temperature and cooking duration prevents the excessive degradation of the cellulose chains themselves. If the temperature exceeds one hundred and forty degrees Celsius prematurely, the acid sulfite reaction can degrade the alpha cellulose content. Automated titration systems track the concentration of free sulfur dioxide throughout the digestion cycle to maintain the target acidity.
This control is necessary to prevent the condensation of lignin, which renders the wood chips difficult to bleach and reduces the brightness of the finished pulp.
Fibre Property
The resulting pulp exhibits high reactivity suitable for viscose. High solubility of the remaining hemicellulose fractions during subsequent steps ensures a pure starting material.
Yield Comparison
Industrial evaluations demonstrate that this method yields less residual hemicellulose than alternative alkaline digestion processes. While the prehydrolysis kraft process offers higher strength, the acid sulfite route excels in providing a pulp that reacts more readily with subsequent esterification agents. The trade-off between chemical recovery cost and product reactivity defines the commercial viability of this extraction route.