Polietileno produzido pela homopolimerização de etileno ou copolimerização de etileno com alfa-olefinas na presença de um catalisador

• Main Authors: VIDAR ALMQUIST, ARILD FOLLESTAD, TORE DRENG, ESPEN OMMUNDSEN
• Format: Patent
• Language: Portuguese
• Published: 14.11.2000
• Edition: 7
• Subjects: CHEMISTRY; COMPOSITIONS BASED THEREON; MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVINGCARBON-TO-CARBON UNSATURATED BONDS; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP

"POLIETILENO PRODUZIDO PELA HOMOPOLIMERIZAçãO DE ETILENO OU COPOLIMERIZAçãO DE ETILENO COM ALFA-OLEFINAS NA PRESENçA DE UM CATALISADOR". Um polietileno produzido pela homopolimerização de etileno ou copolimerização de etileno com -olefinas, na presença de um catalisador, caracterizado pelo fato de que a fração de polímeros de baixo peso molecular tendo PM <5000 g/mol é menor do que 12% em peso do polímero produzido e de que o polietileno produzido tem uma resistência em fusão medida expressa por um valor de desvio (OH) satisfazendo a expressão HO > K~ 1.0,05~ + K~ 2~, em que K~ 1~ é 9,10^ -5^ e K~ 2~ é 0,4. A particulate, modified chromium oxide catalyst for the polymerisation of ethylene or ethylene with alpha-olefins, comprising: a) a chromium-oxide catalyst, b) a transition metal compound, and c) a catalyst activator. A method for the preparation of the catalyst comprises the steps of: a) subjecting a chromium oxide catalyst precursor, which comprises a chromium oxide compound combined with an inorganic support, to a temperature in the range of from 400 to 950° C. under oxidising conditions, and b) impregnating the obtained chromium catalyst with a catalyst activator and with a transition metal compound which comprises at least one cyclopentadienylic ring bonded to said transition metal and at least ligand selected from the group comprising alkoxy, amido and hydrocarbyl radicals, halogen and hybride bonded to said transition metal, which cyclopentadienylic ring may contain hetero atoms, be unsubstituted or substituted, be bonded to said transition metal through a bridge, and optionally annealed to other substituted or unsubstituted ring structures, and if two cyclopentadienyl rings are present they may be bonded to each other through a bridge, and c) subjecting the thus obtained particulate catalyst to drying conditions. This catalyst is suitable for producing polyethylenes under conditions of continuous feeding of all reactants.