In-situ Preparation Of Polyisoprene And Ethylene-propylene Rubber Particles By Gas-phase Polymerization

Gas phase polymerization process is a kind of process with low energy comsumption, short process flow, which is commonly used in manufacturing of polyolefins, such as polyethylene and polypropylene nowadays. Polyolefins particles can be obtained directly. Compared with solvent polymerization, gas phase polymerization has the advantages of no solvent using, no complex and long condensation or separation processes, high safety in operation, low investment and manufacturing cost, less pollution. It is the developing direction of polyolefins industry.Unlike manufacturing synthetic resins, gas phase polymerization has many difficulties in producing rubbers. The main reason is that rubbers are very sticky, and rubber particles are very easy to agglomerate at the beginning of polymerization. This will lead to poor fluidity of particles, prohibiting the dispersion of reaction heat, even bringing to explosive polymerization.In this work, exploratory research was carried out on in-situ preparation of polyisoprene and ethylene-propylene rubber particles by gas phase polymerization. A new universal method of preventing agglomeration of rubber particles was proposed. This new method is to support both the selected catalyst systems and nano-SiO2 on micron-size carrier silica. During polymerization process, nano-SiO2 always stays on the outside of the particle and forms a barrier layer, which is effective for preventing agglomeration of polymer particles.For the in-situ preparation of polyisoprene rubber particles, Nd(OiPr)3/MAO//BuCl was selected as the catalyst system. Morphology of products’ particles, polyisoprene microstructure, molecular weight and molecular weight distribution, and polymerization activities were characterized. The cis-1,4 contents were 89～93%, weight average molecular weights were 30～59×104, and molecular weight distributions were 1.90～3.11, polymerization activities were 31 176kgPIP/(molNd-h), It was found that with the increase of nano-SiO2, the polymer agglomeration decreases as well as polymerization activities, molecular weight and molecular weight distribution increase; the content of cis-l,4-unit tends to decrease, but the change is insignificant. The temperature and pressure affect polymerization activity considerably. With the increase of temperature and pressure, both of polymerization activities and the molecular weight of polyisoprene decrease. The microstructure of polyisoprene does not change significantly.For the in-situ preparation of ethylene-propylene rubber particle by gas phase polymerization, rac-[Et(Ind)2]ZrCl2/MAO was selected as the catalyst system. Morphology of ethylene-propylene rubber particles, microstructure, molecular weight and molecular weight distribution, and polymerization activities were characterized. Ethylene units in copolymer were 80～83mol%, weight average molecular weights were 6～8×104, and molecular weight distributions were 2～3, and polymerization activities were 190-330kg/(molZr·h), Similarly, importing nano-SiO2 can effectively prevent the agglomeration of ethylene-propylene rubber particles. Polymerization activity decreased slightly, whereas, microstructure only slightly changed when nano-SiO2 was introduced. It was also found that with the increase of temperature, polymerization activities increase greatly while both the molecular weight and molecular weight distribution tend to decrease, the content of ethylene units in polymers decrease.In summary, non-sticky polyisoprene rubber particles and ethylene-propylene rubber particles were in-situ prepared successfully in gas phase polymerization by this method, and the common key problem of rubber particles’ agglomeration was solved.