| Water-based ink has been developed quickly in recent years as it meets the requirements of no VOCs with the help of water-soluble dispersant. Water-soluble acrylic-styrene resin is just the kind of resin, which has hydrophilic and hydrophobicfunctions, with high acid value, average molecular weight Mn between 3,000 to6,000 and narrow molecular weight distribution.In the research acrylic-styrene resin was synthesized through semi-batch solution polymerization process, adopting a-methyl styrene(AMS) as one of the comonomers. It was found that the addition of AMS decreased the molecular weight of resin, which also improved the structure of the resin. The amount of addition had an optimal range which was determined by a series of research.The molecular weight and molecular weight distribution index(PDI) of resin were the main structure factors affecting the dispersion ability of the acrylic-styrene resin, which were sensitive to the polymerization conditions, such as changes of temperature, type of initiators, molecular regulator, solvent. The molecular weight of resin went down as the temperature increased, but it does nothing to PDI. A proper initiator TBPO was choosed which has a proper half time corresponding to the polymerization temperature in the semi-batch process. Increasing the amount of initiator, the molecular weight and PDI went down. The effect of solvent amount acted in the same way. A novel molecular weight adjuster was applied into the process, which controlled PDI of resin effectively without side effects.The kinetics of the semi-batch polymerization was studied. Changes of the initiator concentration, conversion and monomer concentration for total monomers during the polymerization process were also investigated. The reactive ratios of monomers were evaluated using Q-e equation. The result showed AMS had more alternate trend than St in polymerization with AA, which provided theory base for the study. Through calculation, pre-adding some initiator provided more evenconcentration in the process. Also pre-added some amount of monomers, the change of monomer concentration became slighter and the acid values changed less during the process. The effect of solvent focused in the early stage of polymerization, more amount lower concentration of monomer and lower molecular weight of resin. The kinetics chain lengths during the process were evaluated, the trend of which was proved by the results of GPC.The coating properties of the aqueous liquid of resin after amination were studied. The viscosity of liquid increased with the amount of styrene in the resin, but the flaws of film decreased. The type of acrylate affected the viscosity as well, softer acrylate was higher viscosity would be, and the fluidity of liquids acted in the same way.Finally the resins prepared by different processes were used in water-based ink. The properties of ink were investigated and compared. Too much AMS in the resin caused troubles in dispersing and flaws in the film, for the molecular weight of resin was too low to wet pigments. The dryness property of harder resin was better than softer one. The resin prepared under high-pressure couldn't achieve suitable grinding particle size as its molecular weight was too low. All these showed that there was some relationship between the resin and the ink. Comparing the resin with J678 which was used widely in water-based ink, the grinding particle size was a little lower than J678, the other properties were closing. It meant that the resin prepared could be used as a dispersant in water-based ink.
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