High-molecular-weight lignin pesticide dispersant with high carboxyl group content and preparing method thereof

The invention discloses a high-molecular-weight lignin pesticide dispersant with high carboxyl group content and a preparing method thereof. The preparing method includes the steps that after lignin and catechol are mixed evenly, concentrated sulfuric acid is added, and after reactions, the product is cooled to the room temperature, purified and dried to obtain phenolated lignin; the phenolated lignin and alkenyl succinic anhydride are placed in a reactor, and organic solvent and a sodium hydroxide solid are added and stirred; the temperature is raised to 80 DEG C-95 DEG C to conduct reactions, and carboxylation lignin is obtained after filtering, washing and drying; the carboxylation lignin is added into water to form a water solution under the stirring condition, the pH value is adjusted to 10-12, epoxy chloropropane is added to conduct a polycondensation reaction, and the pH value of a reaction solution is adjusted to 6-7 to obtain the lignin pesticide dispersant. The weight-average molecular weight of the obtained dispersant is larger than 15000, and the carboxyl group content is 3.2-4.0 mmol/g. The high-molecular-weight lignin pesticide dispersant is suitable for various kinds of pesticide wettable powder and water dispersible granules and has excellent dispersibility, stability, wettability and heat storing performance.