The Synthesis Of Lignin Based Epoxy Resin

The content of lignin is lower than that of cellulose in botanic field, it is natural organic macromolecule and covers 15% to 36% of the botanic body. It is three-dimensional network macromolecule with C-C bond and ether bond and its basic structure unit is phenyl propane structure unit, so lignin macromolecule structure is very complicate. It can be the same energy materials and chemical materials as petroleum because of its phenyl characteristic, aliphatic characteristic in side-chain and a variety of functional groups. Lignin is the by-product in papermaking industry, its valid utilization can decrease environmental pollution and it is good to treat pulping waste liquor. On the other hand, it can develop and utilize regenerative resources, solving resources waste problem.It's studied that lignin synthesizes lignin based epoxy resin, developing new method of utilization lignin.Firstly, lignin is purified by the method of Lunquist liquid-liquid and cresol-sulfuric, the result shows that the yield of the latter is higher than that of the former, and the ash is almost the same. The chemical modification of lignin and 1,2-epoxy propane in the presence of alkali metal hydroxide and organic solvent and the catalyst, the reaction should be carried out at temperature above the glass transition temperature of lignin. The lignin derivatives and epichlorohydrin are reacted, the reaction temperature is equal to the room temperature. By means of centrifugation and purification, terminally the color of the lignin based epoxy resin is red-brown. During synthesis of epoxy resin, we change the ratio of material and the reaction time, and we measure the epoxy equivalent, discover the epoxy equivalent of lignin-based epoxy resin higher than the commercial epoxy resin bi-phenyl A. The epoxy resin has no value without curing, and it must cure to its end use. The curing reagent of this study is trithylenetetraamine, the stoichiometric amount of the curing reagent is amine equivalent /epoxy equivalent is 1. The mechanical properties of cured lignin based epoxy resin are tested, and the result shows the tensile strength, the tensile stretch are higher than that of bi-phenyl A. young's modulus increases with the content of lignin increases.The adhesive is prepared with lignin based epoxy resin, the curing reagent and filler-calcium carbonate. The best application are the pressure is 15 kg/cm2, the dosage is 270 g/cm (double size ), hot pressing time is 7~8min, the temperature is 150 . The bond quality can reach the GB requirement, meeting the grade oneplywood production.