SOLVENT PRETREATMENT of LIGNIN for OBTAINING of LOW VISCOSITY LIGNOPOLYOLS by OXYPROPYLATION for SYNTHESIS of POLYURETHANES

Abstract

Wheat straw lignin was pretreated by organic solvents of different polarity: ethylacetate, ethylmethylketone and ethylmethylketone/water mixture, using sequential extraction technique. The total yield of fractions was ∼ 40% (w/w). In comparison with non- treated lignin the solvent soluble fractions have lower molecular weights, lower polydispersity and average functionality indices. The low viscosity lignopolyols with lignin substituent content up to 40%, suitable for rigid polyurethane foams obtaining were produced by the oxypropylation of isolated fractions. The non-soluble in organic solvents lignin residue represent a purified natural aromatic amorphous cross-linked polymer. Therefore besides oxypropylation its application as filler of thermostable polymers with enhanced flammable resistance could be beneficial biorefinery approach.