Research Of High Solid Content Styrene Butadiene Latex

In recent years,high solid content latex has an important application value in coating,paper coating,foaming materials and other aspects.With the increase of market demand,the related preparation research is also developing rapidly,and the effect is remarkable(such as polyacrylate and other latex,which can make its solid content close to 70%).In contrast,there are some difficulties in the preparation of high solid SBL,such as its small particle size,high viscosity,poor stability and other factors,which bring challenges to the concentration technology.At present,foreign research is relatively advanced.In the application aspect: the Kaneka company of Japan has applied for the preparation patent of high solid SBL,the German company Bayer and the Korea company Kumho Tire have also industrialized the preparation technology of high solid content SBL.In China,the preparation of large-size SBR latex and the research of one-step polymerization of high solid content SBR latex are also in progress,but there are no related products available.In this paper,the two-step process is used to synthesize large-size SBL,and then concentrate the large-size SBR latex to prepare high solid content SBL.Through the study of large-size latex polymerization technology and stable control technology of latex concentration process,SBL with various properties meeting the requirements and solid content more than 50% was developed.First of all,in the study of polymerization process of base latex,the basic latex synthesized by high temperature polymerization and low temperature oxidation-reduction polymerization were compared.The reaction rate of latex prepared by high temperature polymerization is obviously faster than that of low temperature polymerization.The gel content of latex prepared by high temperature polymerization reached 89 times that of low temperature polymerization,and the increase of gel content was helpful to the stability of latex system.The viscosity of high temperature polymerized latex was 25.13mpa·s,and that of low temperature polymerized latex was 12.37mpa·s.The temperature and amount of emulsifier in the process of high temperature polymerization were studied.Considering the solid content,particle size and interval distribution of the latex,the best performance was obtained when the amount of emulsifier was kept at 4.0~4.5phr and the polymerization temperature was controlled at 60?.Secondly,in the study of large-size latex polymerization technology,the influence of agglomeration method on latex particle size and other properties was mainly studied: the influence of different agglomerators on latex particle size and stability,the change of latex particle distribution,viscosity and surface tension after agglomeration,the relationship between pH and latex stability,and the influence of stirring rate and temperature on latex agglomeration were studied.The results show the particle size of the latex can be increased to225.5nm by laser particle size analyzer,and the mechanical stability is strong when choosing the agglomerator of maleic acid,the dosage is 0.5% of the quality of latex.The viscosity of latex decreased obviously after agglomeration.When the surface tension of latex drops,the tension should be controlled above 40 mN/m to avoid flocculation and demulsification.The pH value of the latex is acidic after agglomeration,and the latex is easy to flocculate.It is the best to adjust the pH to about 9.The stirring rate should be controlled at 200r/min during agglomeration.High temperature is not conducive to the reaction,and the agglomerate of SBL is suitable for normal temperature.On this basis,the concentration technology of the latex after agglomeration was studied,and the effect of three concentration methods on SBL was compared.The centrifugal concentration method and the paste concentration method could increase the solid content of latex to some extent,but the concentration degree was limited,so it was not suitable for the concentration of SBL.In the evaporation concentration method,when the concentration temperature is between 55? and 58?,and the amount of potassium oleate is between 0.09%and 0.12%,the stability effect is good and the amount of foaming is small.Finally,the solid content of concentrated SBL was 57.2%.In the experiment,the self-made high solid content SBR latex was compared with the same type of domestic high solid SBR latex and the high solid SBR latex imported from Germany.The physical properties of self-made latex are better than those of domestic latex,but there is a certain gap compared with German latex.