Hydrophobic properties conferred to Kraft pulp by a laccase-catalysed treatment with lauryl gallate

• Hydrophobicity was conferred to Kraft pulp by a laccase-lauryl gallate treatment.
• Adsorption of phenolic compounds was responsible for pulp hydrophobicity.
• Laccase oxidation of lauryl gallate induced formation of oligomers.
• Chemical nature and morphology of oligomers play key-role in hydrophobic properties.

Hydrophobic properties were conferred to a high-lignin-content Kraft pulp by a laccase-catalysed treatment in the presence of lauryl gallate (LG). The treatment resulted in a two-fold increase in contact angle and conferred water absorption resistance to the pulp. Kappa number was increased, indicating that some phenolic compounds were incorporated in the pulp. A control treatment with LG alone did not affect water absorption, demonstrating that laccase was essential to attain these new properties. The loss of hydrophobicity after an acetone Soxhlet extraction highlighted that adsorbed acetone-soluble compounds played a key role in the properties. GC-FID and HPSEC-UV analysis of the acetone extract indicated the formation of dodecanol and different phenolic oligomers. SEM images showed the treatment-induced changes in the fibre network. Additional experiments with various reaction times and reactant concentrations highlighted the role of LG oxidation products in the introduction of absorption resistance.