Patent TW-200504093-A (TW)
Title: Polymer composition and process to manufacture high molecular weight-high density polyethylene and film therefrom
Inventor: MICHIE WILLIAM J JR
IPC: B29C48/395
Filed: 2004-04-19
Abstract: The present invention includes a multimodal polyethylene composition has (1) a density of at least 0.940 g/cm<SP>3</SP> as measured by ASTM Method D-1505; (2) a melt flow index (I5) of from 0.2 to 1.5 g/10 min (as measured by ASTM D-1238, measured at 190 DEG C and 5 kilograms); (3) a melt flow index ratio (I21/I5) of from 20 to 50; (4) a molecular weight distribution, Mw/Mn, of from 20 to 40; (5) a bubble stability measured on specified equipment according to specified conditions for a film of 6 X 10<SP>-6</SP> m thickness of at least 1.22 m/s line speed, at least 45 kg/hr (0.013 kg/sec) output rate, or at least 0.5 lb/hr/rpm (0.0000011 kg/s/rps) specific output rate or a combination thereof; the composition comprising; and (6) a dart impact on 12.5 micron (1.25 X 10<SP>-5</SP> m) film of at least 300 g; measured according to ASTM 1709, Method A; (A) a high molecular weight fraction which; (a) is present in an amount of from 30 to 70 weight percent (based on the total weight of the composition); (b) has a density of at least 0.860 g/cm<SP>3</SP> as measured by ASTM D-1505; (c) has a melt flow index (I21) of from 0.01 to 50 g/10 min (as measured by ASTM D-1238, measured at 190 DEG C and 21.6 kilograms); and (d) a melt flow index ratio (I21/I5) of from 6 to 12; and (B) a low molecular weight fraction which; (a) is present in an amount of from 30 to 70 weight percent (based on the total weight of the composition); (b) has a density of at least 0.900 g/cm<SP>3</SP> as measured by ASTM D-1505; (c) has a melt flow index (I2) of from 0.5 to 3000 g/10 min (as measured by ASTM D-1238, measured at 190 DEG C and 2.16 kilograms); (d) a melt flow index ratio (I21/I5) of from 5 to 15; and (e) is prepared using a mole ratio of alpha olefin to ethylene of less than or equal to 0.001:1. The invention also includes a process for producing a multimodal ethylene polymer, which process comprises the following steps: (1) contacting in a first gas phase fluidized bed reactor under polymerization conditions and at a temperature of from 70 DEG C to 110 DEG C, a supported titanium magnesium catalyst precursor, cocatalyst, and a gaseous composition, the gaseous composition having; (i) a mole ratio of alpha-olefin to ethylene of from 0.01:1 to 0.8:1; and optionally (ii) a mole ratio of hydrogen to ethylene of from 0.001:1 to 0.3:1, to produce a high molecular weight polymer(HMW); and (2) transferring the HMW polymer from step 1 to a second gas phase fluidized bed reactor under polymerization conditions and at a temperature of from 70 DEG C to 110 DEG C, with a gaseous composition having; (i) a mole ratio of alpha-olefin to ethylene of from 0.0005:1 to 0.01:1; and (ii) a mole ratio of hydrogen (if present) to ethylene of from 0.01:1 to 3:1 to form a polymer blend product; and (3) melting the polymer blend product in an extruder having a mixer vent wherein; (ii) the mixture vent has an oxygen concentration of from 0.05 to 6 volume percent oxygen in nitrogen; and (ii) the extrusion temperature is sufficient to melt the polymer and achieve tailoring in the presence of oxygen; and (4) passing the molten polymer blend through one or more active screens, wherein in the case of two or more active screens, the screens are positioned in series, each active screen having a micron retention size of from 2 to 70, at a mass flux of 1.0 to 20 kg/s/m<SP>2</SP>) to form a screened molten polymer blend. The composition is preparable by the process and is preferably prepared by the process. The resin exhibits improved extrusion processing at high commercial line speeds, while exhibiting an excellent balance of bubble stability, dart drop, and FAR.