Appeal No. 1998-3157
Application No. 08/466,797
catalyst system is prepared by a process which
comprises the following steps:
a) spray-drying an aqueous slurry at 8-10
weight % of ammonium dawsonite, the spray-drying
being conducting with a spray-dryer including a
rotating disk, the dawsonite being synthesized
through the reaction of aluminum sulfate and
ammonium bicarbonate at a pH from 7.5 to 7.7,
wherein the ammonium dawsonite is filtered only
between the reaction and the spray-drying, the
entrance temperature in the spray-dryer being
from 350 to 450°C and the exit temperature being
from 130 to 150°C, the feed flowrate of the
ammonium dawsonite slurry being from 3.0 to 4.0
kg/minute, and the disk speed being from 10000 to
14000 rpm, and calcining the product from the
spray-dryer at 600-700°C for 4 to 6 hours so as
to obtain a spherical gamma-aluminum of pore
volume from 1.0 to 2.0 ml/g and surface area from
150 to 250 m2/g while the residual sulfate content
is between 10 and 20 weight %;
b) impregnating the aluminum from a) with a
titanium halide solution in a hydrocarbon solvent
at 80-140°C during one hour or more so that the
final titanium content incorporated is from 0.5
to 1.0 weight %, thus making a catalyst
composition; and
c) contacting the catalyst composition from
b) with an alkyl aluminum co-catalyst so as to
provide an Al/Ti ratio from 15/1 to 60/1;
to form a spherical polyethylene of ultrahigh
molecular weight having an internal attrition angle of
from 30 to 40°.
THE REFERENCES
Pistor 3,627,684 Dec. 14, 1971
McKenzie 4,465,782 Aug. 14, 1984
Green et al. (Green) 4,628,040 Dec. 09, 1986
Lo et al. (Lo) 4,876,321 Oct. 24, 1989
Hang et al. (Hang) 4,983,693 Jan. 08, 1991
Martin et al. (Martin) 5,142,077 Aug. 25, 1992
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