Lignin from waste black liquors ‐ II: different lignins in phenol formaldehyde resin

Lignin precipitated from different black liquors wasted from the cooking of rice straw, bagasse and cotton stalks, to produce pulp and paper, can replace phenol by up to 40 per cent in phenol formaldehyde resin. The properties of the resin produced from bagasse lignin formaldehyde are nearly the same as when the resin IS produced from phenol formaldehyde. Replacement of phenol by lignin in phenol formaldehyde resin has an economical effect and reduces the pollution caused by draining black liquor into rivers and streams. The properties of the resin produced from rice straw lignin are lower than resin from bagasse and cotton stalk lignin. The effect of increasing the content of lignin in the resin on the resin properties was studied. The effect of polymerization time and temperature on the resin properties is also clarified. The molecular structure of the lignins used plays an important role on the properties of the phenol lignin formaldehyde produced.