Thermoplastic rubbers and process for preparing same

Claim 1

Process for preparing thermoplastic rubbers which are copolymers of propylene with ethylene containing from 25% to 50% by weight of polymerized ethylene and the balance polymerized propylene, said copolymers showing on X-rays examination in the unoriented state a polypropylene-type and/or a polyethylene-type crystallinity, the polypropylene crystallinity content ranging from 3 to 50% and the polyethylene-type crystallinity being less than 20%, said copolymers being further characterized in that in the infrared spectrum thereof the value of the R ratio between the absorption intensity of the band at 11.88 microns and that of the absorption at 12.16 microns is from 2 to 6, the R ratio being less than 4 when the polymerized propylene content of the polymers is lower than 70% by weight, comprised between 3 and 6 when the polymerized propylene content ranges from 70 to 80% by weight, characterized in that mixtures of propylene and ethylene are polymerized in the presence of a catalyst consisting of the product obtained by reacting (A) a catalyst-forming component which is an addition and/or substitution reaction product of an electron-donor compound (or Lewis base) with an Al-trialkyl compound, or the addition reaction product of an electron-donor compound with an Al-alkyl compound containing two or more aluminum atoms bound to each other through an oxygen or nitrogen atom, with (B) a catalyst-forming component obtained by contacting an addition compound of a halogenated compound of di-, tri-, or tetravalent titanium and an electron-donor compound with a carrier comprising an anhydrous active magnesium dihalide, said component (A) being characterized in that it is prepared by reacting 1.0 mole of Al-alkyl compound with 0.1 to 1.0 mole of a Lewis base which is an ester of an oxygenated organic or inorganic acid, a polyamine compound, or, when catalyst-forming component (B) is prepared starting from a complex of a halogenated titanium compound with a polyamine, any Lewis base other than said esters of oxygenated organic or inorganic acids and polyamine compounds, and catalyst-forming component (B) being characterized in that, in its X-rays powder spectrum, a halo appears in place of the most intense diffraction line characteristic of the X-rays powder spectrum of the normal, non-active magnesium dihalide, in that the amount of Ti compound contained therein, expressed as Ti metal, is less than 0.3 g-atoms per mole of the total amount of the electron-donor used in preparing the catalyst, and in that the molar ratio between said Ti compound and the Al-alkyl compound is from 0.001 to 0.1.