|
Title
Development of green adhesives for fibreboard manufacturing using tannins and lignin from pulp mill residues
Authors
FREDERIQUE BERTAUD SANDRA TAPIN-LINGUA ANTONIO PIZZI PAOLA NAVARRETE and MICHEL PETIT-CONIL
Published
Volume 46 Issue 7-8 September-October
Keywords
lignin, tannin, pulping liquor, bark, adhesives, phenol, particleboard, panel, green chemical, wood, residues,
sustainability, formaldehyde
Abstract
In order to reduce formaldehyde emissions from wood panels and to develop green adhesives, natural phenolic
polymers of tannins and lignin have been investigated as substitutes of petrol-based chemicals used in wood panels.
The potential of several wood barks, obtained from pulp mills as industrial wastes, has been evaluated for tannin
extraction and further for their adhesive properties. Aqueous extractions were carried on wood barks of five different
tree species on a laboratory scale – Aleppo pine barks led to the highest yield (15%) compared to spruce, Douglas fir,
maritime pine and eucalyptus. Urea and sulfite used as water-additives favoured the extraction of condensed tannins,
especially for spruce and Douglas fir barks. Eucalyptus barks presented the lowest tannins contents. Pyr-GC/MS of the
bark extracts showed that Douglas fir and Aleppo pine tannins were mainly constituted of phenol and catechol tannins.
The adhesive potential of these tannins was also established. Cooking liquors from pulp mills are very rich in lignin.
Lignin was isolated by acidification/precipitation of black liquors. The abilities of softwood and hardwood kraft liquors
under several extraction conditions were compared. After glyoxylation, these lignins presented interesting adhesive
properties. Furthermore, novel formulations of [tannin/hexamine + glyoxylated lignin] were tested for wood
particleboard manufacturing. The internal bond strength of a panel manufactured with 60% tannin/40% lignin satisfied
the value required by the European standard.
Link
|
