Research on the development of modified adhesives based on the phenol liquefaction products of bagasse pulp concentrate black liquor

The concentrated black liquor (HL) from bagasse pulping was liquefied with phenol under acidic conditions to produce a liquefied product (HLP). The HLP was characterized using FT-IR, SEM, and XRD techniques. A modified phenolic resin adhesive (HLPF) was subsequently synthesized via a one-step copolymerization of HLP with formaldehyde, and HLPF plywood was prepared by hot pressing. The results demonstrated that:1) Optimization of liquefaction process parameters: liquid phenol ratio of 35 %, liquefaction temperature of 110 °C, liquefaction time of 2.2 h, 15 % catalyst dosage;2) The wet bonding strength of plywood pressed by HLPF and PF resins are similar,1.34 MPa and 1.24 MPa, respectively; 3) The liquefied HLP contains new absorption peaks at 1596 cm −1 , 1463 cm −1 , and low wave number area, which has higher aromaticity and more active substituent groups, and the absorption peaks at the intermediate wave number region The absorption peaks in the middle wave number area showed curve changes, showing the formation of substituents and polymer degradation. After liquefaction, HLP was gradually degraded into residue particles; however, as the liquefaction time increased, some small molecules recondensed into macromolecules and precipitated crystalline particles; The crystalline particles were primarily the inorganic salt Na 2 SO 4 ; the absorption peaks of the HLPF resin were similar to those of the PF resin, indicating that both were structurally similar; Modified HLPF has better thermal stability. • Bagasse pulping concentrated black liquor after liquefaction treatment, can prepare modified phenolic resin. • Under the liquefaction of phenol and sulfuric acid, lignin and hemicellulose and other macromolecules in the black liquor are effectively degraded. • The prepared modified phenolic resin can be used in the production of indoor structural boards and artificial boards. • Direct liquefaction of untreated black liquor of papermaking pulping provides a new method for the resourceful conversion of waste black liquor.