Process for the stereospecific polymerization of isoprene

摘要

Stereospecific polyisoprene is produced by polymerizing isoprene under substantially anhydrous conditions in an inert hydrocarbon solvent in the presence of (a) titanium tetrachloride, tetrabromide or tetraiodide and (b) a hydride or halohydride of a Group II or III metal (Mendeleeeff) or a complex of such a hydride or halohydride with an ether, tetrahydrofuran or a tertiary amine; or an aminoalane or halo-amino-alane having the general formula R1R11NAlHX where X is a hydrogen or halogen atom or a secondary amino radical (-NR1R11) wherein the nitrogen atom may be bonded to alkyl, aryl, alkyl-aryl or cycloalkyl radicals or may form part of a heterocyclic ring. The preferred Group II and III metals of the hydride or halohydride are aluminium, magnesium, zinc and cadmium, advantageously aluminium. With low Al/Ti ratios a polyisoprene with a predominantly trans-1,4 structure is obtained, while with high Al/Ti ratios a predominantly cis-1,4 structure is obtained. In the examples isoprene is polymerized using titanium tetrachloride and one of the following:-(1) AlH.(Cl2).O(C2H5)2; (2) AlH.I2.O(C2H5)2; (3) AlH3.O(C2H5)2; (4) AlH3.N(CH3)3; (5) AlH2.Cl.N(C2H5)3; (6) -AlH.(Cl)2.N(CH3)3; (7) (CH3)2NAlH2; (8) CH3)2NAlHBr; (9) (C6H5)2NAlHCl; (10 (C6H5)2NAlH2; (11)