Study On Synthesis And Application Of Dispersant Of Naphthalene Sulfonate Formaldehyde Condensate

In recent years,with the increase of national attention to environmental protection,higher requirements are put forward to the pesticide industry,which also stimulates the enthusiasm of the pesticide industry to develop environmental protection water suspension concentrate（SC）.Dispersant is one of the essential additives in the processing of pesticide suspension concentrate.The dispersant of naphthalene sulfonate formaldehyde condensate occupies the main position in pesticide additives because of its advantages such as acid resistance,alkali resistance,hard water resistance,no penetration and foaming.Naphthalene sulfonic formaldehyde condensation（NNO）dispersants with different polymerization degrees（n≈2,3,4,5）were synthesized from concentrated sulfuric acid,industrial naphthalene and formaldehyde by four steps of sulfonation,hydrolysis,condensation and neutralization.The influences of different factors in the process of sulfonation,hydrolysis and condensation on the total acidity of the reaction system,the sulfonation rate of the product,the dispersion force,the average degree of polymerization and the content of Na₂SO₄were explored through orthogonal experiment and optimization experiment of orthogonal experiment.The optimal synthesis conditions were determined:the molar ratio of naphthalene to concentrated sulfuric acid was 1:1.5 and concentrated sulfuric acid was added within 40min and sulfonated at 155℃for 3h;15g of water was added within 20min and hydrolyzed at130℃for 35min;the molar ratio of naphthalene and formaldehyde was 1:1.05;formaldehyde was added within 45min,condensed at 105℃for 7h,and 25g of water was added in the reaction.The structure correctness of the synthesized product was confirmed by IR and NMR.The structure-activity relationship between the surface properties and thermodynamic parameters of naphthalene sulfonate formaldehyde condensate（NNO）with different degree of polymerization was studied.The results showed that with the increase of the average degree of polymerization,γ_CMC,CMC,Γ_Max,ΔG_micandΔG_adsgradually decreased,while A_CMCand p C₂₀gradually increased.When the polymerization degree of dispersant was n≈5,CMC=5.2mmol/L andγ_CMC=48.90m N/m.The synthetic product was used as wetting dispersant in 5.7%emamectin benzoate SC,and the best formula was determined by screening the dosage of wetting dispersant and thickening agent.When the amount of wetting dispersant（n≈5）was4%,the suspension rate and the absolute value of zeta potential were the highest,and the viscosity was the lowest.It was found that the higher the degree of polymerization,the greater the saturated adsorption amount of the product on the surface of the particles,the higher the suspension rate of SC,the smaller the viscosity,the faster the structure recovery,and the higher the recovery rate of the structure.When the degree of polymerization（n≈4,5）was obtained,the suspension rate of the prepared emamectin benzoate SC was more than 90%,and the absolute value of zeta potential was more than 40Mv,which met the performance requirements of suspension agents.At the same time,the stability of the SC prepared by using the polymerization degree（n≈4,5）as the wetting dispersant is better than that of the imported dispersant MD-425.