Lignin polyisocyanates

Epoxy Resins. The use of lignin in organic polyisocyanate-liquid aromatic epoxide binders has also been evaluated (73), According to the authors, the lignin served only as a diluent, although fairly high levels of substitution ( 35%) by lignin were achieved. 

The use of lignin, essentially as a diluent (extender), has also been investigated (75). In this case, di- or polyisocyanates were reacted with ethylene or propylene carbonates in a solution containing lignin. These mixed ethylene and propylene carbonate-containing organic polyisocyanates were suitable as particleboard adhesives. 

Various types of lignin-derived polyurethane products and their precursors appeared to satisfy these constraints. This paper summarizes experimental efforts aimed at developing lignin-derived polyol, polyisocyanate, and polyurethane products. 

Li.gru.n-VeAd.ved Potyi ocqanaXeA Efforts to increase the incorporation of lignin into polyurethane products have concentrated on transforming polymeric lignins into polyisocyanates useful for reacting with polyols. Two alternative reaction pathways have been explored with the three lignin-like model compounds shown in Figure 3. These models were vanillic acid or a derivative thereof (Model Type A) a derivative of tetralin di-carboxylic anhydride (Model Type B) and a derivative of a styrene-maleic anhydride copolymer (Model Type C). 

Attempts to increase the lignin content in polyurethane products via either increased lignin contents of the polyols, or via the formulation of lignin-derived polyisocyanates, have so far largely failed. This is primarily attributed to lignin s limited solubility characteristics. 

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