Synthetic Polyisoprenes and a Process for Their Preparation

Assignee Michelin Recherche et Technique S.A. (Granges-Paccot, CH) 

A synthetic method for preparing polyisoprene having a cis-, A linkage of 99.0% or greater using diethylaluminium chloride with the rare earth salt neodymium tris(bis (2-ethylhexyl)phosphate) is described. Reproducible Mooney viscosities of 85 and higher were also observed. 

A 250-ml reaction vessel was used as the polymerization reactor. Each polymerization reaction was carried out either under static conditions in a freezer, where the container was placed in a bath of glycol, or dynamically, by subjecting the container to agitation in a tank of glycol. Isoprene monomer having a purity of 99.2% was used. All polymerizations were conducted in 10-g containers and cyclohexane at 15°C with a solvent/monomer mass ratio of 9. In a typical polymerization the neodymium catalyst/diethyl aluminium chloride base varied from 150 to 500 pmol per 100 g of isoprene. 

At the end of polymerization the mixture was treated with an additional 100 ml of cyclohexane solvent to fluidify the medium, 1 ml of 1M acetylacetone in cyclohexane added to stop the reaction, and A-l,3-dimethylbutyl-A -phenyl-p-phenylenediamine (0.02 g) added as an antioxidant. Polyisoprene was then extracted by steam stripping for 30 minutes in the presence of calcium tamolate. Each extraction was then dried for approximately 18 hours in an oven at 50°C under 200 mmHg vacuum for 72 hours. Reaction scoping results are provided in Table 1. 

TABLE 1. Dynamic reaction scoping resnlts for the polymerization of isoprene nsing a solvent/molar ratio of 9 with the rare catalyst neodyminm tris(his(2-ethylhexyl)-phosphate) diethylalnmininm chloride. 

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Title Synthetic Polyisoprenes and a Process for Their Preparation... 

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