Research On Preparation, Characterization And Application Of High Boiling Solvent Lignin

Lignin is the third abundant organic substance in nature. Presently, most industrial lignin products were produced from the black liquid of pulp and paper industry. Only small amount of them were used to prepare lignin sulfonate, and others were burned as fuel. For efficacious application of biomass resources, the high boiling solvent method was developed to produce high boiling solvent lignin (HBSL). In order to obtain the optimum technology for HBSL extraction, orthogonal experiments were carried out on peanut shell, bamboo, and masson pine. The effects of some factors on the extraction of HBSL were studied, such as reaction temperature, mass ratio of solid to liquid, concentration of solvent and reaction time. This research will lay a foundation for industrial application of lignin resources.Compared with traditional lignin products, more functional groups were well preserved in HBSL. The general hydroxyl value, ash content, residual polysaccharide content, and element composition of HBSL were investigated by traditional chemical methods. The C9formula of HBSL was then calculated by these basic data of chemical groups. The structure characteristics of HBSL were analyzed by FT-IR, UV and NMR spectrum. The similarities and the differences in structure and functional groups between enzymatic hydrolysis lignin and HBSL were also discussed.The optimum conditions were acquired by degrading HBSL with solid super acid as a catalyst. The aromatic substance was confirmed by GC-MS analysis in the degradation products of HBSL, which indicated that HBSL contained polyhydroxybenzene or polybenzene compound. The research on the degradation of lignin provided a reference for the potential application of HBSL in replacing petrochemical materials in the future.Moreover, as a natural polymer, lignin was renewable and biodegradable. With the increasingly serious problems of environmental pollution and the crisis of oil resources, more and more attention has been paid to the use of renewable and degradable natural polymer. Due to the defects of traditional lignin, the purification and modification are usually necessary before using lignosulfate or alkali lignin effectively. However, HBSL can be used in various fields without the process of purification or modification because of its high chemical activity and purity. HBSL has successfully been used in modifing rubber, epoxy resin and polyurethane. Results show that it can not only reduce the consumption of petrochemical materials, but also improve some properties of the polymers.Rubber is one of most important polymer materials and the application of HBSL in rubber industry is of great significance. The compatibility of HBSL derivatives with different rubbers were investigated, including chloroprene rubber (CR), nitrile butadiene rubber (NBR) and ethylene propylene diene methylene (EPDM). The epoxidized HBSL could be used as a curing agent in CR and the amount of it was an important factor affecting the properties of CR. The anti-aging, solvent resistance and the mechanical properties of CR were improved with increasing amount of epoxidized HBSL. The tensile strength of NBR was improved when the hydromethyl modified HBSL was added by coprecipitating HBSL with NBR. The breaking elongation and the anti-aging property of EPDM were also improved when the composite material of HBSL/nano-silica was added.Epoxy resin has been used as dope, adhesive or engineering material in many fields. In the process of making the lignin based epoxy resin, biphenol-A (BPA) was replaced by HBSL entirely or partly, which may not only minimize the potential pollution of BPA but also reduce the cost effectively. HBSL could be used directly in epoxy resin preparation without further modification. The solvent resistance and the thermal endurance properties of the modified epoxy resin were improved considerably.Polyurethane was a macromolecule elastomer developed rapidly in recent years. Since HBSL had abundant aliphatic and phenolic hydroxyl groups which could substitute polyol to react with the isocyanate, HBSL was used in polyurethane synthesis in this article. The rigidity, tensile strength and solvent resistance of polyurethane were improved by adding appropriate amount of HBSL. The best performance of polyurethane could be achieved when the lignin dosage was about15%. The masson pine HBSL modified polyurethane had favorable solvent resistance and tensile strength; while the peanut shell HBSL modified polyurethane performed well in breaking elongation test.