| abstract |
A process for producing ultrahigh molecular weight polyethylene having an intrinsic viscosity of 10 - 30 dℓ/g at 135°C in decalin comprises at least the following two polymerization reaction stages: (a) a first reaction stage in which ethylene is polymerized using a catalyst comprising a solid component containing at least Mg, Ti and/or Va and an organometallic compound and in the absence of hydrogen or its presence at a lower concentration to produce 70 - 99.5 weight parts of polyethylene having an intrinsic viscosity of 12 - 32 df/g at 135°C in decalin; and (b) a second reaction stage in which a fresh feed of ethylene is polymerized in the presence of hydrogen at higher concentration to produce 30 - 0.5 weight parts of polyethylene having an intrinsic viscosity of 0.1 - 5 df/g at 135°C in decalin. Such UHMW polyethylene has improved moldability characteristics. |