Study Of Novel Synthesis Methods Of The Modifying Poly （Vinyl Chloride-co-vinyl Acetate） And In-situ Copolymer/nano-SiO₂Composite Resin

This paper described systematically a novel synthesis method of Poly (vinyl chloride-co-vinyl acetate)(PVVA) copolymer by suspension radical copolymerization. The functionalization of the copolymer and its modification by the incorporation of nano-SiO2particles were also studied. In order to enhancing the property of PVVA copolymer, a simple synthesis technique which was clean and available in the industrial production was developed to introduce carboxyl group into PVVA copolymer, and then PVVA emulsion and paste resin were prepared by hybrid micro-suspension polymerization technique. When nano-SiO2particles were dispersed into PVVA copolymer resin by in-situ suspension copolymerization, the processing properties and the inherent qualities of PVVA production were improved significantly.1. Poly (vinyl chloride-co-vinyl acetate) copolymer was prepared by suspension polymerization. The effect of VAc monomer to the properties of PVVA copolymer was investigated and discussed in this paper. The influence factors and control methods of the chain segment uniformity of PVVA copolymer, the average molecular weight and particle characteristics of PVVA were explored. Several key problems which restricted the improvement of PVVA product quality in industrial production were solved. Especially, the chain segment uniformity of copolymer was enhanced by controlling the variation range of saturated vapor pressure in the polymerization.2. PVVA/SiO2nanocomposite was prepared by radical suspension polymerization of the monomers in the presence of fumed nano-SiO2pre-modified with y-methylacryloxypropl trimethoxy silane. Through CPA and Mercury injection measurement, morphology comparison (SEM), it can be concluded that the grain porosity and specific surface area of nanocomposite resin could be enhanced due to the incorporation of suitable amount of nano-SiO2to PVVA. The relation between grain characteristics and plasticizing process rheology properties of PVVA/nano-SiO2composite resin was studied by torque rheometer. From the plasticizing curve, it can be seen that the melting time of the mixture sample was shortened, and the melting temperature was lowered. The processing charactristic was correlated with the porosity degree of the composite resin.3. To achieve the carboxyl-functionalization of the Poly (vinyl chloride-co-vinyl acetate) copolymer, a novel preparation technique was developed based on the traditional method. Maleic anhydride (MAH) was esterified by ethanol (EtOH) to obtain mono-ethyl maleate (MEM). The influence of reaction conditions, such as temperature and reaction time, on the yield rate of MEM was studied in order to attain a higher yield rate of MEM. PVVA containing carboxyl group was synthesized by reacting esterified MAH with vinyl chloride and vinyl acetate in terms of aqueous suspension polymerization method. FT-IR spectra showed that carboxyl group was successfully introduced into the PVVA molecular structure through this method. The addition of MEM resulted in the acid value of copolymer increasing obviously. Meanwhile, the coating adhesive force of Poly (vinyl chloride-co-vinyl acetate-co-maleic anhydride) resin was also improved.4. Nano-SiO2particles were incorporated into Poly (vinyl chloride-co-vinyl acetate-co-maleic anhydride)(PVVM) resin by in-situ copolymerization. Morphology observation showed that the nano-SiO2were well dispersed by nanometer scale in the copolymer matrix of the nanocomposite films, while nano-SiO2tend to agglomerate in the composites films prepared by solution blending PVVM/nano-SiO2composite. The in-situ PVVM/nano-SiO2composite resin showed a better heat resistance and mechanical properties than that obtained from solution blending. Solution viscosity and adhesive ability of the nanocomposite can be significantly enhanced by incorporation of nano-SiO2through in-situ polymerization. The enhancement is related to better dispersion of nano-SiO2particles in polymer matrix. Therefore the modification effect of the nanocomposite resin was more excellent.5. PVVA copolymer latex was prepared by Hybrid Micro-suspension Polymerization technique and the control method of the latex particle size was analyzed systematically. The research results showed the mixing of SDS/CA-SA saponification system and oily monomer could produce solubilizing micellar phase and increase PVVA latex particle size effectively. When the composite seed emulsion was added, the particle size of PVVA latex synthesized would display a bimodal distribution. The influence of spray and drying process of PVVA latex on secondary particle of PVVA resin and Brookfield paste viscosity of PVVA plastisol was also explored. Through paste viscosity measurement and grain morphology comparison, it can be concluded that the secondary particle of PVVA resin play an important role in paste viscosity control. The grain which have regular form and gathered with incompact primary particles would have lower paste viscosity. The secondary particle characteristic of PVVA could be obtained by adjusting spray and drying conditions, such as outlet and inlet dry temperature.