Preparation Of Polyisoprene Particles By Supported Rare-earth Catalyst In Gas Phase

At present, solution polymerization is mainly used for polymerization of isoprene. Compared with solution polymerization, gas phase polymerization has many advantages such as none solvent, low energy consumption, simple process, low cost, less pollution which make it significant. In this paper, polyisoprene particles of good morphology were prepared by using supported catalyst in gas phase polymerization by introducing ultra-fine powder in different ways.Nd(OiPr)3/MAO/t-BuCl was selected for gas phase / solution polymerization of isoprene. The catalyst system was immobilized on micron-size support (SiO2) to prepare supported catalyst. Then nano-particles were introduced and the supported catalyst was coated with nano-particles, so the anti-sticking supported catalyst was prepared. It was supposed that the nano-particles could be adsorbed on the surface of polymer, forming a barrier layer. Polyisoprene particles can be obtained by the anti-sticking supported catalyst in gas phase polymerization using NaCl as dispersing agent. Polymerization temperature, polymerization pressure, the amount of Nd and nano-particles loaded, different types of nano-particles and support were investigated. The polymerization activities was as high as 1.6×105 g·mol-1·h-1, and the Mw can reach to 90×104.The cis-1,4 contents can reach to 94%.By immobilizing rare-earth catalyst system Nd(naph)3/Al(i-Bu)3/Al2Et2Cl3 on support, the supported catalyst was synthesized for polymerization of isoprene in gas phase. During the polymerization, additional inorganic particles were directly introduced as dispersing agent. The inorganic particles are effective for preventing agglomeration of polymer particles. Thus polymer particles of good morphology could be obtained. Three kinds of dispersing agents with different diameter(30nm,1.5μm,10μm) have been employed.The amount of inorganic particles was different when the polymer varied from agglomeration to particles. Inorganic particles whose diameter were 1.5μm were the most effective, because polyisorene particles with good morphology could be obtained when relatively less amount was used. The activity varied slightly near 1.5×106 g·mol-1·h-1 and the content of cis-1,4 can reach to 96.2%.The Mw was in the range of 50×104～70×104. Two methods for particle growth were found. When nano-particles (Nano2) were used as dispersing agent, the particle morphology went through three processes:bulk, irregular particles, spherical particles. While polymer using micro-particles went through two processes:bulk, spherical particles.In summary, polyisoprene particles of good morphology can be obtained with supported Nd catalyst in gas phase polymerization by introducing inorganic particles In two ways.