Polybutadienes neodymium catalyst

Andreussi P, Lauretti E, Miani B (1994) Europrene Neods Improved cis- 1,4-Polybutadiene by Neodymium Catalysts, Stepol, Milano, Italy, Jun 6-10... 

Polybutadiene obtained by rare earth metal compounds has very high cis-1,4 content, and the polymerization is quasi-living. Therefore, we investigated in detail the modification of polybutadiene by neodymium catalyst with tin compound. 

In. he industrial processes for the production of polybutadiene with Ti, Co, or Ni catalysts it can be controlled to only a very small extent. In comparison with the commercially available polybutadienes, SE-BR (SE stands for Seltene Erden, which means rare earths) has a broader molecular- weight distribution, which can be altered, however, by varying the ratio of Lewis acid to neodymium. Table II shows that an increase of this ratio from 0.8 to 2.0 increases the molecular weight distribution from 7 (which is close to that of Ni-BR) to 27. 

For reasons of space diolefin polymerization has not been included in this Chapter. Some information and pertinent references are summarized here. 1,3-E>ienes can be polymerized by lithium alkyls or by Ziegler-Natta type catalysts, containing titanium or cobalt, nickel, and neodymium. Industrially important products are 1,4-cis-polybutadiene (>2 Mt/a) and 1,4-cis-polyisoprene (>1 Mt/a). They are... 

Medium-c/5 lithium-polybutadiene was first developed by Firestone Tire and Rubber Company in 1955 [86]. Solution polymerization using anionic catalysts is usually based on butyllithium. Alkyllithium initiation does not have the high stereospecificity of the coordination catalysts based on titanium, cobalt, nickel, or neodymium compounds. Polymerization in aliphatic hydrocarbon solvents such as hexane or cyclohexane yields a polymer of about 40 % cis, 50 % trans structure with 10 % 1,2-addition. However, there is no need for higher cis content because a completely amorphous structure is desired for mbber applications the glass transition temperature is determined by the vinyl content. The vinyl content of the polybutadiene can be increased up to 90 % by addition of small amounts of polar substances such as ethers. 

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