Methylolation Lignin

The addition of phenol-formaldehyde precondensate to lignin or methylolated lignin has been known as a way to introduce phenolic reactivity into lignin, and this is usually applied to the preparation of lignin-based... 

Although the lignins do not perform adequately as full binders, they can be used as extenders. Now the resin supplies the benzylalcohol functionality and the lignins (and wood chips) need only supply alcohol groups to make ether linkages. The results for data on methylolated lignins are expressed in Table II as indices. The index is obtained by dividing the... 

In order to evaluate the method, the three lignins were methylolated, formulated with R-PF resin and waferboards made. The boards were tested for dry MOR, MOE, wet MOR and IB, but only the last term was the pa rameter chosen for quality determinations by the authors. Limited number of testing results are given in Table III. The data are not corrected for board density. The pass level for Canadian requirements is IB = 0.345 MPa, so all of the boards prepared passed, even those containing binder with 50% of the PF resin replaced with methylolated lignin. 

Exploded wood and Kraft methylolated lignins make poor quality binders at 2% loading, but should give better binders at 12%, which is not economical. The bark material is only marginally better. 

IB = internal bond strength F = suffix used to indicate methylolated sample WtpF = weight of PF resin in a lOOg board WtML = weight of methylolated lignin in a lOOg board Rf = total aliphatic OH index Ra = total alcohol index... 

Blending of Lignin-Phenolic Resin System. The methylolated lignin was blended with the phenolic resins at a solid weight ratio of 75/25 and at room temperature. The mixture was mechanically stirred for 15 minutes. The gel time, pH, and solids content were determined for each resin system. 

CH20/Phenol Ratio Methylolated Lignin/Phenolic Resin Ratio Viscosity pH Gel Time... 

Peng and Riedl (1994) investigated the chemorheology of phenol formaldehyde resins filled with unmodified and methylolated lignin fillers. They found that both fillers reduced the reaction rate and that the chemorheology profile of filled systems is better represented by the WLF model than by the Arrenhius model. 

---