| With the enhancement of environmental awareness and the improvement of environmental protection laws,using water-borne coatings which replaced the traditional solvent-based paints has become the development trend.Compared with solvent-based coatings,water-borne coatings have poor performance in coating film denseness,water resistance,color development,and adhesion.At present,the factors that affect the performance of water-borne coatings are mainly focused on the the synthesis of emulsion types,wetting agents,dispersants,pigments and fillers and so on,but there are few studies on the effect of water phase oligomers on the properties of creep materials in emulsions.Therefore,aiming at the oligomers in acrylate polymer emulsions,the separation process of aqueous oligomers and their effects on the properties of polymer emulsions and creep materials were discussed in this paper,which is the basis for preparing polymer latex coatings with excellent properties.Two different acrylate polymer emulsions were synthesized by semicontinuous seeded emulsion polymerization.Reactive emulsifiers and anionic emulsifiers were used to reduce the influence of free small molecular emulsifiers.The results showed that the emulsion had better performance when the ratio of DS4:AR10 was 2:1 and the dosage was2% of monomer.The polymerization conditions were optimized.When the amount of initiator was 0.5% of the total amount of monomer and 30% of the initiator was added in one drink,the polymer emulsion was stable and the conversion rate was high when the residual and pre-emulsion were dripped in parallel.TEM observation showed that the synthesized latex particles had regular spherical structure.The optimum separation conditions of aqueous oligomers were determined by ultrahigh speed centrifugation at room temperature.The results show that the separation effect of water phase and particle phase is good when the rotating speed is 4000 rpm and the centrifugal time is 180 min.The molecular weight of water phase oligomer in emulsion is between 4000～4500 and its distribution coefficient is about 1.1 measured by GPC.Infrared spectrum analysis showed that the structure of aqueous oligomer was similar to that of co-polyacrylate dispersant,so it has certain dispersing ability to pigments and fillers.The effects of water phase oligomers on the particle size,water absorption,film forming temperature and viscosity of the emulsion were studied.The results showed that with the increase of AA content,the diameter of St-BA and MMA-BA polymer emulsions and the water absorption of emulsion films increased with the increase of the amount of AA in aqueous phase.In the ST-BA system,the film forming temperature shows a slight increase trend,and the viscosity of the film does not change much.In the MMA-BA system,the viscosity increases and the film-forming temperature decreases.The water-borne high gloss paint and interior wall latex paint were prepared with two different acrylic emulsions as base materials,and the effect of water phase oligomers on the properties of the coatings was studied.The results show that with the increase of oligomer content,the color difference of the coating decreases and the color developing property becomes better.In the latex coating,the oligomer has little effect on the washing resistance of the coating.The viscosity of ST-BA system coatings changes little during storage,but the viscosity of MMA-BA system coatings decreases seriously.The results show that this phenomenon is related to the distribution of AA on the surface of emulsion particles. |
