Development Of Preparation Technology Of Uniform Large-sized Polystyrene Resin Beads

With the development of biological engineering and separation engineering,biological macromolecules separation and medical chromatographic separationtechnology are in urgent need of large size resin beads which have a specific particle size(0.4-1.0 mm)and narrow size distribution.The current preparation of the product with the qualified particle size distribution is to sieve the microsphere prepared by suspension polymerization,which wastes a lot of raw materials.Therefore,it is urgent to develop an available preparation process of large size resin beads,greatly improving the utilization of raw materials.In this thesis,we tried to combine the theory of jet vibration,the theory of surface activity and the theory of polymerization to analyze the factors that affect the uniformity of droplet formation and the sphericity and monodispersity of the particles during the polymerization,hoping to develop a continuous preparation process of uniform large size resin beads.Specific research work is as follows:1.The needle-type jet dispersion technology developed by ourselves was employed to investigate the effects of jet orifice diameter,fluid velocity,vibration frequency and fluid properties on the droplet size and uniformity.The results showed that when the liquid velocity satisfies the condition of smooth flow and the frequency satisfies the Schneider empirical formula,uniform droplets with controlled particle size and distribution standard deviation of less than 3%can be obtained.The state of flow,the disturbance frequency,the fluid surface energy and kinetic energy were the main factors affecting the droplet size after analyzing 145 groups of experimental data liquids with four different liquids,water,ethanol,styrene and styrene pre-polymer.Four quasi-numbers(?)were used to characterize thesefactors and a uniform particle droplet size predictive control model was established.The droplet size predicted by this model was less than 3%relative to the actual particle size,which confirmed that this model is very effective in controlling the formation of uniform droplet and predicting droplet diameter.2.In order to make the monodisperse monomer droplets into uniform spherical resin beads,the interaction between droplet and interface was analyzed based on the theory of surface activity.Combined with experimental results,it can be concluded that as long as the surface tension of aqueous solution is less than 16mN/m,styrene droplets will be spherical under the surface of the water,and then become spherical particles after polymerization.3.On the basis of theory of free radical polymerization,pre-polymerizing the monomer was proposed to reduce the loss of monomer dissolved in solution and coalescence during polymerization,hoping to obtain monodisperse large size spherical resin beads by in situ polymerization of uniform monomer droplets.The effects of pre-polymerization temperature,polymerization temperature and initiator concentration on product yield and resin particle size were investigated.It was found that uniform pre-polymer droplets can be used to prepare monodisperse polymer spheres and when the viscosity of pre-polystyrene droplets is 28 cP,the yield of large-sized spherical resin beads is more than 98%,the standard deviation is less than 3%,which indicated that the pre-polymerization can be used in the preparation of the uniform large-size resin beads.4.The law of volume variation during the polymerization of the pre-polystyrene was investigated experimentally and the particle size variation model was developed to predict and control the particle size of uniform large-sized resin beads.The operating conditions for the preparation of polystyrene resin beads with a particle size of 1.00 mm were predicted and polystyrene microspheres with a particle size of 1.00 mm and the standard deviation of particle size of 1.87%were successfully prepared.With the technology of jet vibration for producing uniform droplets and in-situ polymerization of droplets,the predictive control model of uniform droplets and the particle size variation model of droplet polymerization process established in this thesis can help to prepare uniform specific sized resin beads.A new technology of continuous preparation of uniform large-sized resin beads has been developed.