The present invention provides a process for the preparation of a multimodal polyethylene comprising: (i) polymerising ethylene and optionally an α-olefin comonomer in a first polymerisation stage to produce a first ethylene polymer; and (ii) polymerising ethylene and optionally an α-olefin comonomer, in the presence of said first ethylene polymer, in a second polymerisation stage, wherein the first and second polymerisation stages are carried out in the presence of an unsupported metallocene catalyst and each polymerisation stage produces at least 5% wt of the multimodal polyethylene, and the multimodal polyethylene has a multimodal molecular weight distribution, a molecular weight of at least 50,000 g/mol and a bulk density of at least 250 g/dm.sup.3, and wherein a solution of the unsupported metallocene catalyst in a solvent is employed. The present invention also provides a multimodal polyethylene, a process for preparing a pipe comprising preparing a multimodal polyethylene and extruding the multimodal recycle polyethylene to produce a pipe, and a pipe obtained by such a process.

Processes for reducing shutdown time of a sub-system/ reactor component in an LDPE process. The process includes closing one or more pairs of upstream lock-out valves, each pair of upstream lock-out valves being located in an inlet stream upstream of the reactor component and configured to cease fluid flow into the reactor component through said inlet stream when said pair of upstream lock-out valves is closed; closing one or more pairs of downstream lock-out valves, each pair of downstream lock-out valves being located in an outlet stream downstream of the reactor component and configured to cease fluid flow out of the reactor component through said outlet stream when said pair of downstream lock-out valves is closed; depressurizing the reactor component; introducing purge gas comprising N.sub.2 into the reactor component at and withdrawing the purge gas from the reactor component.

Processes for reducing shutdown time of a sub-system/ reactor component in an LDPE process. The process includes closing one or more pairs of upstream lock-out valves, each pair of upstream lock-out valves being located in an inlet stream upstream of the reactor component and configured to cease fluid flow into the reactor component through said inlet stream when said pair of upstream lock-out valves is closed; closing one or more pairs of downstream lock-out valves, each pair of downstream lock-out valves being located in an outlet stream downstream of the reactor component and configured to cease fluid flow out of the reactor component through said outlet stream when said pair of downstream lock-out valves is closed; depressurizing the reactor component; introducing purge gas comprising N.sub.2 into the reactor component at and withdrawing the purge gas from the reactor component.

A hinged component comprises a polyethylene composition having a density of from 0.940 to 0.965 g/cm.sup.3, a melt index of less than 30 g/10 min, a molecular weight distribution M.sub.w/M.sub.n of less than 5.0 and a unimodal profile in a gel permeation chromatograph.

A hinged component comprises a polyethylene composition having a density of from 0.940 to 0.965 g/cm.sup.3, a melt index of less than 30 g/10 min, a molecular weight distribution M.sub.w/M.sub.n of less than 5.0 and a unimodal profile in a gel permeation chromatograph.

The present invention discloses a homogeneous, single site catalyst of formula (I) and a process for preparation thereof using a ligand. The present invention further discloses a process for preparation of linear polyethylene of high molecular weight and degree of crystallinity by using the homogeneous, single site catalyst of formula I.

##STR00001##

The present invention discloses a homogeneous, single site catalyst of formula (I) and a process for preparation thereof using a ligand. The present invention further discloses a process for preparation of linear polyethylene of high molecular weight and degree of crystallinity by using the homogeneous, single site catalyst of formula I.

##STR00001##

An organometallic complex, a catalyst composition employing the same, and a method for preparing polyolefin are provided. The organometallic compound has a structure represented by Formula (I)

##STR00001##

, wherein M is Ti, Zr, or Hf; X is —O—, or —NR.sup.6—; R.sup.1 and R.sup.2 are independently hydrogen, C.sub.1-6 alkyl group, C.sub.6-12 aryl group, or R.sup.1 and R.sup.2 are combined with the carbon atoms, to which they are attached, to form an C.sub.6-12 aryl moiety; R.sup.3, R.sup.4 and R.sup.5 are independently fluoride, chloride, bromide, C.sub.1-6 alkyl group, C.sub.6-12 aryl group, C.sub.3-6 hetero aryl group, C.sub.7-13 aryl alkyl group or C.sub.7-12 alkyl aryl group; and R.sup.6 is hydrogen, C.sub.6-12 aryl group or C.sub.7-12 alkyl aryl group.

An organometallic complex, a catalyst composition employing the same, and a method for preparing polyolefin are provided. The organometallic compound has a structure represented by Formula (I)

##STR00001##

, wherein M is Ti, Zr, or Hf; X is —O—, or —NR.sup.6—; R.sup.1 and R.sup.2 are independently hydrogen, C.sub.1-6 alkyl group, C.sub.6-12 aryl group, or R.sup.1 and R.sup.2 are combined with the carbon atoms, to which they are attached, to form an C.sub.6-12 aryl moiety; R.sup.3, R.sup.4 and R.sup.5 are independently fluoride, chloride, bromide, C.sub.1-6 alkyl group, C.sub.6-12 aryl group, C.sub.3-6 hetero aryl group, C.sub.7-13 aryl alkyl group or C.sub.7-12 alkyl aryl group; and R.sup.6 is hydrogen, C.sub.6-12 aryl group or C.sub.7-12 alkyl aryl group.

The present invention relates to a cable jacket composition comprising a multimodal olefin copolymer, said copolymer having density of 0.935-0.960 g/cm.sup.3 and MFR.sub.2 of 2.2-10.0 g/10 min and said composition having ESCR of at least 2000 hours and a cable shrinkage of 0.70% or lower. The invention further relates to the process for preparing said composition and its use as outer jacket layer for a cable, preferably a communication cable, most preferably a fiber optic cable.