Cationization Of Styrene Maleic Anhydride Copolymer And Preparation Of Cationic Aqueous Pigment Dispersions

In order to prepare a cationic pigment dispersion with high stability, two kinds of cationic polymer (SMG) were synthesized by grafting styrene maleic anhydride copolymer (SMA). One was water soluble, the other was unsoluble. The water soluble polymer was used directly as a kind of polymeric dispersants, and the pigment microcapsules were prepared with the unsoluble polymer. The two dispersion systems were investigated by DLS techniques. The result shows that the dispersion of microcapsules is more stable.In the process of grafting SMA, glycidyl triethyl ammonium (GTA) was synthesized first. The effects of solvents on translation rate and epoxy value were investigated. The result indicated that the reaction speed was higher, however, the epoxy groups were lower in the polar solvents than in the non polar solvents. GTA with lower epoxy value was obtained in methanol or ethanol, while GTA with higher epoxy value was obtained in N,N-dimethylformamide (DMF). Study on the grafting of SMA with GTA shew that water-soluble SMG was obtained by GTA with lower epoxy value, and unsoluble SMG was obtained by GTA with higher epoxy value. The GTA with high epoxy value acted as a cross-linking agent.The dispersibility of water-soluble SMG was compared with SDS (sodium dodecylsulfate), and the effects of shattering methods (milling or ultrasonic) was studied too. The results indicated that water-soluble SMG was a good dispersant, and milling methods was suitable for polymeric dispersants.To obtain more stable cationic pigment dispersion, a SMA-coated pigment was crosslinked by GTA with higher epoxy value. The effects of quantity of GTA, reaction temperature and reaction time on zeta potential were investigated. The cationic microcapsules were obtained when m(GTA):m(pigment)=3:1, at 80℃for 3-4 hours. The Zeta potential of the water-based dispersion was above +30mV in the condition of pH=7.0. The microcapsules were examined by observing from transmission electron microscope (TEM), testing of diameter distribution of particles and dispersion stabilization. It is shown that the microcapsules have not been destroyed during being modified, and the particle size distribution is concentrated, and the dispersion stabilization becomes much better.The two kinds of dispersing systems were investigated. It indicates that compared with the direct dispersing system, the microcapsule dispersing systerm was more stable.