Study On Preparation Process Of Solvent Chlorinated EVA

Ethylene chloride-vinyl acetate copolymer（CEVA）is an important resin in preparing composite ink binder for printing.At present,the industrial preparation of CEVA by chloroform solvent method has problems such as difficult to control the viscosity of the product and less selection of EVA raw materials.Therefore,in this study,various EVA raw materials were selected,and the preparation process of CEVA by chloroform solvent method was optimized and systematically studied by using aerobic degradation technology.The CEVA products were characterized,and the frost resistances of which were discussed.The work of this thesis has important practical significance and application value.Firstly,the effects of oxygenation time and chlorine content on the viscosity of CEVA were investigated using EVAs with 28%VA and different MI values as raw material.The results showed that the influence of oxygenation time on CEVA viscosity was linearly decreased,and the mathematical model was obtained as y=-1.07x+448;the influence of chlorine content on CEVA viscosity showed a power-law decreasing relationship,and a mathematical model was obtained:y=1488.91e^-0.11x+282.43.At the same time,a methodology for viscosity control of CEVA by aerobic degradation technology was established.Subsequently,EVA with different VA contents was used as raw material to study the influence of VA content on CEVA viscosity.The results show that the viscosity of CEVA is negatively correlated with the VA content at the same chlorine content.When the chlorine content was 15%,the VA content had the greatest impact on the CEVA viscosity.When the VA content increased from 19%to 28%,the CEVA viscosity decreased by 53.5%,from 1150 m Pa·s to 535 m Pa·s.Then,the influence of MI value and VA content on the chlorination reaction was studied.It was found that the MI value and VA content had little effect on the chlorine utilization rate of chlorination reaction.Under the same VA content of raw materials,when the actual chlorine content of chlorinated products was about 47%,as the MI value increased from 5.8 g/10 min to 158 g/10 min,which was about 27.2 times increase,the chlorine utilization rate increased only by 6.9%,from 79.46%to 86.36%;When the actual chlorine content of chlorinated products was between 45%and 48%,as the VA content increased from 19%to 40%,which was more than doubled,the chlorine utilization rate increased only by 7.93%,from 81.3%to 89.23%.The effect on chlorine utilization rate was as follows:VA content>chlorine content>MI value.The results of a series of characterization experiments such as thermogravimetric analysis,differential scanning calorimetry,gelpermeation chromatography,and Fourier transform infrared spectrum showed that VA content had little effect on the thermal stability of CEVA,and had no effect on the crystallinity and solubility of CEVA.The molecular weight distribution of CEVA was slightly wider than that of EVA.The smaller the MI value was,the easier the chain rupture of EVA occurred in the chlorination reaction.The ethylene part in molecular chain structure is more prone to chlorination than vinyl acetate part.Moreover,the removal of HCl will form C=C double bond on the CEVA molecular chain.Finally,the effects of CEVA addition,chlorine content and VA content on the frost resistant performance of CEVA were discussed through low-temperature freezing test.The results show that CEVA content,chlorine content and VA content have an optimal value to improve the frost resistance of CPP composite ink.When the addition of CEVA was 16.5%of CPP,the chlorine content was 20%,and the VA content was 19%,the frost resistant performance of CEVA was the best.The above research results provide the methodological basis and certain theoretical guidance for regulating product viscosity,improving reaction raw material scheme,optimizing product parameters,and thus improving product quality in CEVA industrial production.In conclusion,the work of this thesis has important practical significance and application value.