FORMING AND PROPERTIES OF LIGNIN-PHENOL-FORMALDEHYDE RESINS PREPARED WITH OXIDIZED HYDROLYSIS LIGNIN

The formation and properties of lignin-phenol-formaldehyde resins synthesized by substitution 10–40% of phenol with oxidized hydrolysis lignin relative to the recipe of the base phenol-formaldehyde resin were researched. Using the 13C NMR spectroscopy, it was found that the interaction of oxidized hydrolysis lignin with formaldehyde and methylolphenols occurs predominantly when the reaction mixture is maintained at 96–98 °C, and methylolation of the lignin preparation is possible only when the reaction centers of phenol are consumed. During the synthesis, the oxidized hydrolysis lignin partially neutralizes the alkali catalyst with the formation of a sodium salt. A decrease in the alkali content in the reaction mixture leads to an intensification of the polycondensation of methylolphenols and an increase in the molecular weight of phenol-formaldehyde oligomers. With an increase in the degree of substitution of phenol with oxidized hydrolysis lignin, the reactivity of lignin-phenol-formaldehyde resins increased. Using IR spectroscopy and solid-state NMR spectroscopy 13C, it was found that the cured resins synthesized by substituting 30 and 40% of phenol with oxidized hydrolysis lignin, compared with the cured base phenol-formaldehyde resin, are distinguished by a relatively dense cross-linked structure formed mainly by methylene bridges. Particleboards manufactured using resins synthesized by substituting 30 and 40% of phenol with oxidized hydrolysis lignin are distinguished by high physical and mechanical properties compared to boards based on the base phenol-formaldehyde resin and are not inferior to the properties of boards based on industrial phenol-formaldehyde resin brand SFZh-3014.