Styrene-acrylic emulsion polymerization is generally used sub-temperature control, monomer drop phase control reaction temperature 78 ~ 85 ° C between the polymerization temperature below 78 ° C, the reaction rate slowed down significantly, the monomer can not drop very Fast polymerization, resulting in local monomer concentration in the system is too large, can easily lead to burst poly-red kettle, the operation more difficult. When the polymerization temperature is higher than 85 ° C, the emulsifier can not adsorb to the surface of the latex particles rapidly and maintain the stability of the latex particles. At the same time, the polymer particles become soft and sticky due to the increase of the polymerization rate. While the possibility of cohesion increases, is not conducive to the stability of the emulsion system, so easy to produce coarse particles within the emulsion. Determination of temperature depends mainly on the decomposition temperature of the initiator, potassium peroxide half-life should be the same level with the reaction. In addition, the temperature is too high, the emulsifier point of emulsion is lower than the emulsion polymerization temperature, emulsifier precipitation from the solution, loss of emulsification, polymerization can not be normal, resulting in increased slag, so the emulsion polymerization temperature and emulsifier cloud point Close to. Considering the above factors, the polymerization temperature is 75 ~ 85 ° C and the reaction time is 2 h. The effect of holding time on the polymer properties is obvious. But the molecular weight of the polymer becomes larger and the molecular weight distribution becomes narrow. The retention time is short, the monomer conversion is low, the molecular weight of the resin is small, and the physical and mechanical properties of the coating are decreased.
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