| The development of pesticide formulation towards water-based, granulation, high efficiency and low toxicity depends on high performace pesticide adjuvants such as dispersant. Compared to the dispersants coming from petrochemical industry, lignin-based dispersants derived from bioresource show large advantages. As a by-product of paper pulping and biofuel industry, it shows double benefits to the environment and resources by enching the ultilization and improving the value of technical lignin. However, technical lignin come from different plants and process appear different compositions and structure which result in different surface activity and application performace of lignin-based dispersants. So, it can make therotical guidance for choosing an appropriate way to develop high performance lignin-based pesticide dispersant by studying the reaction activity of different resouces of technical lignin in different chemical modification and the effect of structure features to the dispersion performace in pesticide formulation.Enzymatic hydrolysis lignin(EHL), pine alkali lignin(PAL) and wheat straw alkali lignin(WAL) were used as the raw material for sulfomethylation and carboxymethylation. The changes of molecule structure with which the effect to the dispersion performance in 40% Myclobutanil wettable powder(WP) and 80% Dimethomorph water dispersible granule(WG) were studied. The result showed that, PAL appeared the highest reactivity in sulfomthylation followed by EHL and the reactivity of WAL in sulfomethylation was poor. The reactivity of sulfomethylation was mainly related with the content of phenolic hydroxyl group. In different dosage of sulfonating agent, the sulfomethylation products of three kinds of lignin showed nearly dispersion ability in 40% Myclobutanil WP due to the comparatively strong hydrophility of the pesticide. While used as the dispersant of a strong hydrophobility pesticide named Dimethomorph, all the three kinds of lignin exhibited the best dispersion performace at a low sulfonating dosage after sulfomethylation. However, dispersion performance differed with the the variation of sulfonation degree which was due to the different carboxyl groups in the three different sources of lignin. Particularly speaking, the hydrophility of PAL was changed mainly by the introduced sulfonic group due to a low carboxyl group. At low sulfonation degree, the hydrophobility of SPAL was strong which resulted in the best dispersion performance to Dimethomorph. On the other side, the hydrophility of WAL was easily changed due to a higher carboxyl group which resulted in a bigger variation in the dispersion of Dimethomorph.During the carboxymethylation, the reactivity of PAL and WAL were similar high and the reactivity of EHL was poor. The carboxymethylation reaction activity was influenced by phenolic hydroxyl content and molecular weight. The dispersion performance of the three kind of carboxymethylated lignin in these two pesticides had nearly the same trend. The dispersion ability was mostly increased as the carboxyl group content increased. However, while exceeded some content, it also changed the hydrophibility of the dispersant and lowered the absorpted amount which resulted in the decrease of the suspensibility. Of the three varieties carboxymethylated lignin, CMPAL with an approparite hydrophobic and hydrophililic blance exhibited best dispersion ability to the Dimethomorph, followed by CMWAL which was due to a too high carboxyl group content. The performance of CMEHL was really poor due to the lower solubility and less effective dispersant ingredient resulted from the low carboxymethylation reactivity and large molecule weight.In summary, dispersants prepared from different sources of lignin were strongly adsorpted onto the weak hydrophobic pesticide such as Myclobutanil though with a different sulfonation degree. In this situation, sulfonation or sulfomethylation is an appropriate modification for technical lignin. The adsorpted amount of dispersant onto the strong hydrophobic pesticide such as Dimethomorph were easily changed with the variation of the hydrophility of sulfonated lignin derived from different sources then resulted in the obvious change of the dispersion performance. All the three kinds of sulfonated lignin from different sources exhibited better dispersion performance at a low sulfonation agent dosage. Compared with sulfomethylation, carboxymethylation had a mild influence to the hydrophility of the lignin dispersant. So the dispersion performance of CMWAL and CMPAL showed comparatively little change with the increased of carboxyl group and even increased with the increase of carboxyl group.Epichlorohydrin was used to increase the molecule weight of two different lignosulfonate(one is an ultrafiltrated sulfonated lignin named TDMN, the other is a sulfite pulping spent liquor called SXMN) by consendation. Result showed that Mw increased with the increase of the epichlorohydrin. After consendation, the dispersion performance of TDMN in Dimethomorph was largely improved due to a low Mw of the raw TDMN. The performance of SXMN was not obviously changed by the consendation due to a comparatively high Mw of the raw SXMN.To prepare pesticide dispersant from enzymatic hydrolysis residue(EHR), sulfomethylation, graft sulfonation, carboxymethylation and high temperature sulfomethylation were studied. The result showed that some dispersant used in 40% Myclobutanil WP could be prepared by sulfomethylation and carboxymethylation, which the performace was similar to Borresperse NA. A high performance dispersant used in 80% Dimethomorph WG was prepared by high temperature sulfomethylation, of which the suspensibility exceeded the native commercial lignosulfonate named SXMN and nearly closed to the Kinsperse126 manufacutred by Borregard.The high temperature sulfomethylation modified with EHR was further studied. The results showed that the sulfonation degree obviously increased with the increased sodium sulfite anhydrous dosage. With the sulfonating agent at a comparatively low dosage(12%), formaldehyde content had little effect on the sulfonation degree and Mw. The reaction temperature had significant influence on the sulfonation degree and molecular weight, and the higher the temperature was, the more serious damage to the lignin structure which resulted in the decrease of the molecular weight. The addition of anthraquinone had little effect on the remaining residue, sulfonation degree and molecular weigh. |
PDF Full Text Request