Role of surfactant in pesticide microcapsule suspension

2021-07-26 15:19:21

Anionic surfactants such as alkyl naphthalene sulfonate, lignin sulfonate, alkyl thiosuccinate, polyoxyvinyl alkyl aryl sulfonate, etc; Nonionic surfactants such as polyoxyvinyl alkyl ether, polyoxyvinyl alkyl phenyl ether, polyoxyvinyl styryl phenyl ether, polyoxyvinyl alkyl ester, low substituted hydroxypropyl cellulose, hydroxymethyl starch sodium, microcrystalline cellulose, cross-linked polyvinylpyrrolidone, cross-linked carboxymethyl fiber sodium, effervescent disintegrating agent, etc, Two or more surfactants can be used. The actual production of crystal seeds, such as 20% bensulfuron methyl effervescent tablets, 20% pyrazosulfuron methyl effervescent tablets, 5% imidacloprid effervescent tablets, 18% dichloroquinic acid. Bensulfuron methyl effervescent tablets, 25% bensulfuron methyl effervescent tablets, 25% bensulfuron methyl effervescent tablets, etc.

Microcapsule suspension refers to a small spherical suspension with a particle size of several microns ~ tens of microns, in which the effective component (core material) is wrapped in the capsule wall material. It is mainly composed of active ingredients, oil-soluble monomers, organic solvents, surfactants, water-soluble monomers, water, etc. There are two kinds of processing methods: one is physical mechanical method, the other is chemical synthesis method.

The interfacial polymerization in chemical synthesis has the following advantages: 1) the particle size and wall thickness are easy to control; 2) This method is commonly used in industrial production because of the large choice of synthetic polymer capsule wall materials. The operation steps of the interfacial polymerization method are as follows: firstly, the oil phase (uniform mixture of oil-soluble monomer and active ingredient) is dispersed in the water phase (aqueous solution containing water-soluble monomer), so that the polymerization reaction between the water phase and the oil phase occurs at the interface, and a film is formed around the oil phase to make a micro rubber capsule. The technical difficulty is to select appropriate capsule materials and surfactants in order to control the release of active ingredients.

If organophosphorus pesticide is made into Hui capsule, it has the following advantages: 1) reduce toxicity and reduce the odor of pesticide; 2) Stabilize the original drug; 3) Reduce drug damage; 4) The cost is equivalent to that of emulsion preparation; 5) Prolong the efficacy and other characteristics. Main varieties: 20% chlorpyrifos microcapsule, 20% diyanong microcapsule, 16% phoxim microcapsule, etc.

The function of surfactant in pesticide microcapsule suspension is to control the release rate of technical drug, improve the utilization rate of pesticide and prolong its validity period, so as to reduce the quantity and frequency of pesticide application and improve the pressure of pesticide on the environment. The surfactants used to prepare Che capsule suspension are polymethylene polyphenyl isocyanate, diethylenetriamine, sodium lignosulfonate and 1,6_ Hexamethylene diamine, polyethylene glycol, carboxymethyl cellulose, Tween-80, etc.