Lignin utilization from black liquor as raw material lignin resorsinol formaldehyde adhesives (LRF)

Black liquor is the result of pulp processing which contains several chemical compounds such as lignin, carbohydrate degradation products, resins and fatty acids. The main objective of the study was to determine the amount of lignin content contained in black liquor from the kraft process and its potential as a raw material for adhesives. Several research results state that the lignin contained in black liquor can be used as an adhesive. Lignin was isolated from black liquor by means of repeated deposition (reprepitation). The lignin obtained was then tested by FTIR, then the lignin was used as an adhesive with the addition of resorcinol and formaldehyde with an applicative composition of lignin resorcinol formaldehyde adhesive on a resin with a mole ratio of lignin (L) : resorcinol (R) : formaldehyde (F) = 1: 0.5 : 2; 1 : 0.3 : 2; with an additive content of 1.5% of the solid resin. Then tested for specific gravity, pH, content of non-volatile solids, viscosity, and gelatination. The results of the study were in the form of black liquor, dark brown to blackish in color with the form of a slightly viscous concentrated liquid. In testing with a pH meter, it showed that the initial pH of the black liquor was 12, this indicates that the waste pulp in the form of leachate is alkaline. Indicators on pH and specific gravity alone do not meet PF adhesive standards. The shape, appearance, viscosity (thickness), residual evaporation and gelatinization period are in accordance with PF adhesive standards. The results obtained from the ratio of different moles of resorcinol do not differ much from the test results, but it can be seen from the data that the specific gravity of the LRF adhesive (1:0,5:2) is closer to the standard for PF adhesive, although the distance between the two values is not much different. Overall this adhesive has the potential and needs further research for its application.