Method for preparing dispersant using lignin degradation products

A method for preparing dispersant using lignin degradation products, wherein preparation of the lignin degradation products in step (1) comprises the following specific sub-steps:

• 1) mixing lignin, an alkaline activator and the metal oxide catalyst by a mass ratio, suspending the mixed materials in an aqueous solution, and blending the mixture well;
• 2) letting the mixed substances to react for 0.5 to 2 h at a temperature within the range of 120-200° C. and microwave power within a range of 200-400 W;
• 3) performing suction filtration after the reaction liquid gets cool to remove solid residues and obtain the lignin degradation products;
• wherein preparation of the dispersant in step (2) specifically comprises the following sub-steps:
• 1) adding monomers to the lignin degradation products obtained in step (1), letting the mixed materials react for 30-50 min at a temperature within a range of 50-70° C., then slowly adding a cross-linking agent, stirring the substances to let a reaction proceed for 2.5-4.5 h at a temperature within the range of 80-100° C., and after the reaction ends, adding urea and isocyanate to let condensation reaction proceed for 4 h;
• 2) adjusting the pH value of the liquid obtained after the condensation reaction to 9.5-10.5, and cooling the liquid to room temperature to obtain the dispersant.