Preparation And Study Of Nano - SiO 2 - Shell / Silicone Modified Core - Shell Acrylate Emulsion

With the continuous development of industry, Polyacrylate emulsion is widely used in coatings industry as one of the water-based polymer materials. The polyacrylate was sticky when it is heated, cooled variable and poor water resistance,etc. The core-shell structure of polyacrylate emulsion had two glass transition temperature and can alleviate the film-forming temperature of polyacrylate at room temperature. The combination of inorganic nanocomposites and polymer is one of the most important methods in the preparation of new functional materials, which can effectively improve the water resistance, weather resistance and low temperature performance, etc, Which can be widely used in coatings, inks, printing, etc.Firstly, in this paper, polyacrylate emulsion with soft core and hard shell structure were synthesized by core-shell emulsion technology and seed emulsion polymerization using MMA and BA as the main monomer. The influence of core-shell ratio, reaction time, temperature, the dosage of initiator, the dosage of emulsifier and ratio in the emulsion was studied. The result indicated that, the core-shell polyacrylate emulsion with good properties can be synthesized after reacting for 7 h when the hard and soft monomer ratio was 1:1 to 1:1.2 in core-shell, and the reaction temperature was 66⁷0 ℃, Using KPS and SBS redox system as the initiator, whichthe mole ratio of KPS/SBS was 2:1and the amount was 0.5% of the total amount of the monomers, the dosage in the core-shell ratio was 65:35. The adhesion and water resistance of the emulsion were improved While adding functional monomer AA,GMA, HEA to the emulsion system. The gel was 0.51%, the water absorption of the latex film was 14.8%, the viscosity was 621 mPa·s and the average particle size of109.5 nm.Secondly, on the basis of the synthesis of core-shell polyacrylate emulsion,Selecting the appropriate organic silicon monomer was used to modify polyacrylate emulsion.The experiment studied the selection and dosage of the organic silicon monomer. The results showed that choosing KH570 as organic silicon monomer with an 8%amount. The organic silicon modified polyacrylate emulsion was obtained withhigh conversion rate of 95.9%, the water absorption of the latex film was 12.01%and the average particle size of 158.6 nm.The modified emulsion has better heat resistance and mechanical strength.Thirdly, an appropriate nano-SiO₂ modified organic silicon was used to modify core-shell polyacrylate emulsion, The experiment investigated the effect of different forms of nano-SiO₂ on emulsionand the influence of the dosage of organic silicon（KH570） and nano-SiO₂ on the properties of emulsion. The results showed that: when the dosage of KH570 was 1.5%,SiO₂ nanoparticles were obtained from 2% TEOS via sol-gel process and the reaction temperature was 66-70 ℃, The stable composite modified emulsion was obtained with water absorption of the latex film was11.4%and the average particle size of 161.5 nm. The DSC curves showed that there were two glass transition temperatures（Tg） which were higher than theoretical Tg.TEM showed that modified composite emulsion particles also have obvious core-shell structure. FT-IR showed that nano-SiO₂ and silicon successfully grafted onto the polyacrylate chain. TGA curves indicated that the modified emulsion latex film had better thermal stability compared with polyacrylate emulsion.Finally, conventional emulsion, core-shell emulsion and nano-SiO₂/silicone modified polyacrylate composite emulsion and BASF emulsion were compared. The results showed that: core-shell polyacrylate emulsion had a lower water absorption than conventional emulsion and better film-forming, the nano-SiO₂/silicone modified polyacrylate composite emulsion have lower water absorption, higher solid content,smaller particle size than BASF emulsion.