Commercial lignosulfonates from different sulfite processes as partial phenol replacement in PF resole resins

Abstract

Four commercial spruce lignosulfonates representing the most common acidic, neutral, and alkaline sulfite pulping processes and varying significantly in molecular weight characteristics were tested as partial (40 wt %) phenol substitute materials for the manufacture of lignosulfonate‐phenol‐formaldehyde (LPF) resole resins. Similar as recently reported for technical lignins from nonsulfite pulping processes (kraft, soda, organosolv), all lignosulfonates of this study effectuated a faster viscosity gain during resole cooking compared to the lignin‐free reference resin (1000 mPa s after 120 min vs. 250 min to reach 1000 mPa s). Sodium lignosulfonate featuring the lowest weight average molecular weight (Mw 5780 g mol−1) and dispersity (Ð 6.1) turned out to be superior to the other lignosulfonates with regard to curing rate (B‐time; 3:37 min vs. 6:41–9:08 min) and tensile shear strength development under hot pressing (120 °C; TS,max = 5.64 N mm−2 after 8 min) for beech veneer strips glued together with the respective LPF resins. Calcium and magnesium lignosulfonates are less suited with regard to phenol replacement due to the poor performance of the respective LPF adhesives in terms of tensile shear strength (TS,max = 3.29–3.49 N mm−2 after 12 min) most likely caused by considerable amounts of side products formed in the course of formose‐type reactions. Phenolation of the two promising lignosulfonates, that is, sodium and ammonium lignosulfonate, did neither considerably increase the rate of PF network formation during resin cooking and curing nor improve tensile strength development during hot pressing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45893.

Effect of spent sulfite liquor on urea–formaldehyde resin performance

“…This may have been promoted by changes in the polymerization kinetics and, as the molar mass of LS (≥180 g mol −1 ) is higher than that of UF monomers (urea up to trimethylolurea—60–150 g mol −1 ), the polymer may have grown faster and achieved the intended viscosity in shorter times. This effect has been reported in previous works, where an accelerated increase of viscosity was observed . When comparing both modified resins, the one with TSSL had a shorter condensation time (40 min).…”

Characterization of Wood-based Industrial Biorefinery Lignosulfonates and Supercritical Water Hydrolysis Lignin

“…S-LS lignin showed lower mass change and higher residual mass than A-LS and SCWH. This can be attributed to the higher decomposition degree of S-LS caused by the more severe pulping process [59,60], and partially to the existence of inorganic impurities [39], as indicated in the results of the elemental analysis. The DTG curves demonstrate the maximum temperatures at which weight loss occurred in the lignin polymers.…”

Hydroxymethylation of technical lignins from South American sources with potential use in phenolic resins

“…Lignin utilization as replacement of phenol in resol or novolac phenol‐formaldehyde (PF) is an attractive alternative due to its high availability, abundance, less toxicity, and cost. Different composite materials based on resols PF adhesives using unmodified and chemically modified lignins have been obtained including strand boards, plywoods, and laminates . It was reported that replacements greater than 50% of P by unmodified lignin produce a negative impact on the performance of wood composites .…”