SISTEMAS DE CATALIZADOR ZIEGLER-NATTA MODIFICADOS DURANTE SU OBTENCION

SISTEMAS DE CATALIZADOR DEL TIPO ZIEGLER NATTA QUE CONTIENEN COMO COMPONENTES: A) UN COMPONENTE SOLIDO QUE CONTIENE TITANIO Y QUE SE OBTIENE MEDIANTE REACCION DE UNA COMPOSICION DE TITANIO CON UNA COMPOSICION DE MAGNESIO, UN HALOGENO, UN OXIDO INORGANICO COMO VEHICULO, UN ALCANOL C SUB,1} C SUB,8} Y UN ESTER DE ACIDO ORGANICO COMO COMPOSICION DE DONADOR DE ELECTRONES, ASI COMO COCATALIZADOR, B) UNA COMPOSICION DE ALUMINIO, Y C) OPCIONALMENTE OTRA COMPOSICION DE DONADOR DE ELECTRONES. LA REACCION DE LOS COMPONENTES INDIVIDUALES QUE SIRVE PARA LA FABRICACION DE LOS COMPONENTES SOLIDOS Y CON CONTENIDO DE TITANIO A) SE REALIZA EN PRESENCIA DE UN HIDROCARBURO AROMATICO EN CALIDAD DE DISOLVENTE. Ziegler-Natta-type catalyst system contains (a) a solid component containing titanium (Ti), obtained by reacting a Ti compound with a compound of magnesium (Mg), a halogen, an inorganic oxide as carrier, a 1-8 carbon (C) alkanol and a carboxylic ester as electron donor; and, as co-catalyst, (b) an aluminium (Al) compound and (c) optionally another electron donor compound as active constituents. In the preparation of (a), the individual components are reacted in the presence of an aromatic hydrocarbon as solvent. Also claimed are: (i) a method of producing the catalyst system; (ii) propylene polymers prepared using this catalyst system; and (iii) films, fibres and mouldings made from these polymers. Preferably component (a) is prepared in a 7-12 C alkylbenzene, especially ethylbenzene. The inorganic oxide has a pH of 1-6.5 and average particle diameter of 5-200 mu m and contains 5-30 volume-% pores or ducts with an average diameter of 1-20 mu m. It preferably is spray dried and especially consists of silica gel. The Al compound (b) is a tri-(1-8 C alkyl)-Al compound. Component (c) is an organo-silicon compound of formula R nSi(OR )4-n (I); R = 1-20 C alkyl, 5-7-membered cycloalkyl (optionally mono-substituted by 1-10 C alkyl) or 6-20 C aryl or arylalkyl; R = 1-20 C alkyl; n = 1, 2 or 3.