| Polyacrylate emulsion is widely used in water-based inks because of its low cost, environment-friendly, good transparency after film formation,excellent weatherability, and good adhesion. Water as solvent of water-based inks will slow down the drying and filming process. In the process of using water-based inks, a certain amount of ethanol is often added into inks to improve the drying rate in the industry, hence, excellent ethanol resistance stability is often needed for the emulsion. Generally, Problems of the high value of gel ratio in the polymerization and the poor storage stability appeared because polyacrylate emulsion is a thermodynamically unstable system. The emulsion was prepared in the early stage, which's basic performance have been approved by clients, but the gel ratio is still high in the polymerization, the ethanol resistance stability of emulsion and yellow water-based inks need to be improved. This paper focuses on the factors that affect the polymerization stability of the emulsion, achieve the purpose of decreasing the gel ratio of the emulsion to below 1%, meantime,to seek valid ways to improve the ethanol resistance stability of emulsion and yellow water-based inks without affecting the basic properties of emulsions. The main work of this paper is as follows.(1) The effects of polymerization process, emulsifier, polymer monomer and initiator on the gel ratio were investigated to found out the vast majority of gel were formatted at the polymerization of core monomers. It was found out that reducing the amount of bottoming initiator could reduce the gel ratio effectively. The gel ratio of emulsion is less than 1% when the dosage of initiator is 0.05%, And a small amount of dodecyl mercaptan was added in polymerization could also significantly reduce the gel ratiao of the emulsion.(2) The emulsion was prepared shows good ethanol resistance stability in the oven with 50 °C that the emulsion could stable for more than a mouth. However, the emulsion with grinding resin was flocculated in 1 hour at 50 °C after adding an amount of ethanol. The main reason caused flocculation is the poor solubility of the grinding resin under the mixed solvent of ethanol and water. It can improve the ethanol stability of the emulsion by replacing the grinding resin with good dissolving performance.Adding protective colloid to improve the ethanol resistance stability of the emulsion is also an effective way. It was found that diacetone acrylamide(DAAM) and functional monomer acrylic acid had effect on ethanol resistance stability of yellow water-based inks which were formulated by emulsion and permanent yellow G. Replacing the DAAM with N-hydroxyethyl acrylamide (HEAA), acrylic acid (AA) with MAA,the yellow water-based ink prepared by new crosslinking system emulsion could stable from 1 hour to 4 months at room temperature.(3) The wet friction performance of the emulsion is related to the film forming condition. The high value of the wet friction and crosslinking degree due to long film formation time and high film forming temperature.The main factors affecting the emulsion film formation is pH regulator in the short film forming time at 60 °C, ammonia will volatilize rapidly in the process of film formation because of low boiling point, which will lead to crosslink quickly. The better water resistance of latex film, the higher the number of wet friction. |
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