ABSTRACT
Abstract Mixed interior wood panel tannin adhesive formulations were developed in which lignin was in considerable proportion, 50%, of the wood panel binder, and in which no ‘fortification’ with synthetic resins, such as isocyanates or phenol-formaldehyde resins as used in the past, was necessary to obtain results satisfying relevant standards. A low molecular mass lignin obtained industrially by formic acid/acetic acid pulping of wheat straw was used. Environment-friendly, non-toxic polymeric materials of natural origin constitute up to 94% of the total panel binder. The wood panel itself is constituted of 99.5% natural materials, the balance 0.5% being composed of glyoxal, a non-toxic and non-volatile aldehyde, and of hexamine already accepted as a non-formaldehyde-yielding compound when in presence of very reactive chemical species such as a flavonoid tannin. Particleboards and two types of plywoods were shown to pass the relevant interior standards with such adhesive formulations. Moreover, the much cheaper non-purified organosolv lignin showed the same level of results as the more expensive purified type.
