Synthesis of styrene ion exchange resin(3)
In addition to conventional ion exchange resins, micron fine-grained ion exchange resins are also developing rapidly. This kind of resin is mainly used for chromatographic separation. Therefore, a sufficiently small particle size (100~400 mesh) and a relatively narrow particle size distribution are key technical indicators.
Suspension polymerization can prepare spheres with diameters ranging from 0.01 to 5mm. The preparation of fine particle resin requires rapid stirring and suspension stabilizer with strong dispersion performance. If polyvinyl alcohol with alcoholysis degree of 77% and intrinsic viscosity of 0.99 is used for suspension polymerization at 80 ℃ at the rotating speed of 740r/min, 7~38 μ M. However, when the degree of alcoholysis is 98% and the degree of polymerization is 1500, only millimeter sized pellets can be obtained. Under the same conditions, the diameter of styrene divinylbenzene suspension copolymer microspheres is related to the hydrophilic lipophilic equilibrium value HLB of the dispersant. In order to obtain microspheres with narrow distribution, it is not necessary to achieve satisfactory results only by adjusting hub value.
When the microspheres are prepared by suspension method, it is easy to appear that the adhesion and particle size distribution of the microspheres are wide. Using polyvinyl alcohol sodium dodecylbenzene sulfonate (DBS) mixed dispersant, or using 1% polyvinyl alcohol or 1%dbs Na as dispersant, and adding a certain amount of PVA or DBS Na in the polymerization process can effectively prevent the adhesion of styrene diethylene copolymer microspheres, and the particle size distribution of the microspheres is relatively narrow.
Smaller size (4~10 μ m) Microspheres should be prepared by dispersion polymerization or seed polymerization. The former is to make the monomer, initiator, surfactant and medium miscible into a homogeneous system, and the final microspheres are obtained from the polymer primary nuclei precipitated after polymerization. The latter starts from lotion polymerization, and the seed polymer of lotion polymerization is repeatedly swelled and polymerized with monomer, and finally the micron sized microspheres with very narrow distribution are obtained.
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