Synthesis And Properties Of Organosilicon/Acrylate Soap-free Emulsion Polymerization

Acrylic emulsion commonly used as coatings and adhesives, the conventional preparation process should be added to the small molecular emulsifier, they will migrate to the film surface in the film, then educe water resistance and mechanical properties of the film. Based on the traditional process of emulsion polymerization, some new methods for preparing emulsions, such as micro emulsion polymerization, miniemulsion polymerization, emulsion polymerization, directional radiation emulsion polymerization, core-shell emulsion polymerization, soap-free emulsion polymerization were developed, directly according to the required performance products, the appropriate aggregation method is selected. Acrylic emulsion posses strong adhesion, but the hardness, water resistance, weather resistance of latex films needs to be improved. Therefore, appropriate methods should be used to optimize the performance of acrylate emulsion. This paper first describes polymerization process and polymerization mechanism of soap-free emulsion, core-shell emulsion silicon-containing, preparation method and application progress of acrylate emulsion, and then describes in detail the soap-free core-shell acrylate emulsion and preparation of silicone modified acrylate emulsion preparation and research.In the second chapter, by soap-free emulsion polymerization and core-shell emulsion polymerization method,2-acrylamide-2-methyl propane sulfonic acid (AMPS) as a polymerizable emulsifier; methyl methacrylat and butyl acrylate as a nuclear reactive monomer methyl methacrylate; acrylate methacrylate as shell reactive monomer, using potassium persulfate water soluble thermal decomposition initiator to prepare acrylate emulsion. The process of polymerization process specific to the polymerizable emulsifier AMPS was added into the reaction system in all, using semi-continuous monomer dropping successively dropping nuclear layer and shell monomer. The effects of reaction temperature, the ratio of soft/hard monomer, seed monomer feeding time and dosage, shell monomer feeding time, initiator, reactive emulsifier and monomer polymerization stability and properties of emulsion influence. The optimum preparation process formula is determined by experiment. Experiments show that:the reaction time is3.5hours, the reaction temperature is80℃, soft and hard monomer BA:MMA the best proportion is15:6; seed monomer feeding time is30minutes, the dosage of monomer dosage of1/4, the latex particle diameter minimum; shell polymerization stage, initiator and monomer adding synchronization polymerization, thermal fluctuations are small, stable polymerization process was formed, determine the initiator content is0.8wt%; the functional monomer MAA is added in the shell, Normal core-shell particles was prepared, determine the amount of MAA monomer is3%～4%.In the third chapter, silicone KH570monomer used to modify acrylate emulsion was prepared by the optimum formula of the previous chapter. Effects of the influences of adding method and amount on the emulsion polymerization and emulsion stability of membrane, and the use of TG, TEM, PCS were used to characterize the structure and morphology of silicone acrylic polymer. Experiments show that, in the monomer drop after10minutes before instillation of organosilicon monomer KH570, the stability of emulsion was the best, the monomer conversion rate is higher; the addition of KH570is6wt%, acrylate latex film pencil hardness, water resistance, stain resistance were improved,10%of down absorptivity of latex film was descended, the pencil hardness increase from HB to4H, and the contact angle to water increased by14°. Through the TG test shows that the decomposition temperature than pure acrylic polymers thermal silicone acrylic polymers thermal decomposition temperature increased by20℃, said that the thermal stability of silicone acrylate polymer is improved. Through the infrared characterization, silicon acrylic polymer IR spectra with Si-O-Si key features of the absorption peak at1065cm-1, illustrate the silicone grafted onto the acrylic latex particles. TEM display silicone-acrylate latex particles with multi-layer core-shell structure, organosilicon polymer coated in core-shell structure acrylate latex particles in the outer layer, uniform particle size distribution. PCS test showed that the average particle size of241nm silicone acrylate emulsion, showed a single distribution.