Polymerization process

Details Polymerization process Polymerization process

1998-12-17

2001-01-16

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S106000, C526S348000, C526S348500, C526S348600

Reexamination Certificate

active

06174981

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to the polymerization and copolymerization of a mono-1-olefin monomer, such as ethylene, with a higher alpha-olefin comonomer.
Supported chromium catalysts long have been a dominant factor in the production of high density olefin polymers, such a polyethylene. As originally commercialized, these catalyst systems were used in solution polymerization processes. However, it became evident early, that a more economical route to many commercial grades of olefin polymers was a slurry process, that is, a polymerization process carried out at a temperature low enough that the resulting polymer is largely insoluble in the diluent.
It is well known that mono-1-olefins, such as ethylene, can be polymerized with catalyst systems employing vanadium, chromium or other metals impregnated on a support, such as alumina, silica, aluminum phosphate, titania, zirconium, magnesium and other reactor metals. Initially, such catalyst systems primarily were used to form homopolymers of ethylene. It soon developed, however, comonomers such as propylene, 1-butene, 1-hexene or other higher mono-1-olefins were copolymerized with ethylene to provide resins tailored to specific end uses.
One important application for ethylene polymers is the production of pipe. Polyethylene pipe typically is formed from an extrusion process, through a die. Of course, the resultant pipe must be tough and strong enough for appropriate commercial uses. In addition to having excellent physical properties after pipe extrusion, commercially desirable polyethylene pipe resins are those that can be processed at high extrusion rates and still retain these advantageous physical properties in the extruded pipe. In the alternative, a commercially desirable polyethylene resin is one that, at a constant high load melt index (HLMI), exhibits a much lower head pressure on the machine die in order to extend the life of the extrusion equipment. Unfortunately, improvement of one property, such as HLMI, in order to increase extrusion rates can be detrimental to another property, such as toughness, ESCR or polymer density. Additionally, a higher MI can cause pipe properties, such as environmental stress crack resistance (ESCR) and impact strength, to decrease.
SUMMARY OF THE INVENTION
Therefore, it is an object of this invention to provide an improved olefin polymerization process.
It is another object of this invention to provide a process to produce copolymers of ethylene and mono-1-olefins that can be extruded at an increased rate.
It is still another object of this invention to provide a process to produce copolymers of ethylene and mono-1-olefins that can be extruded at a lower head pressure on the machine die.
In accordance with this invention, herein is provided a polymerization process comprising contacting under slurry polymerization conditions at a temperature less than about 200° F. (about 93° C.) in an isobutane diluent:
a) ethylene monomer;
b) at least one mono-1-olefin comonomer having from about three to about eight carbon atoms per molecule;
c) a catalyst system comprising chromium supported on a silica-titania support, where in said support comprises from about 1 to about 10 weight percent titania, based on the weight on the support, and wherein said catalyst system has been activated at a temperature of less than about 1100° F. (about 593° C.) and not subsequently reduced;
d) a cocatalyst which is a trialkylboron compound; and
e) recovering an ethylene/mono-1-olefin copolymer.
In accordance with another embodiment of this invention, a copolymer comprising ethylene and a mono-1-olefin having from about 3 to about 8 carbon atoms carbon atoms per molecule is provided, wherein said copolymer has a high load melt index (HLMI) within a range of about 1.5 to about 12 g/10 minutes, a density within a range of about 0.94 to 0.95 g/cc, a weight average molecular weight (M
w
) greater than about 250,000, a molecular weight distribution (M
w
/M
n
) greater than about 30, an eta (0) greater than about 20×10
6
, a ratio of eta (0.1)/eta (100) of greater than about 50, and a relaxation time tau of greater than about 4 seconds.


REFERENCES:
patent: 4188471 (1980-02-01), Nasser, Jr. et al.
patent: 4246139 (1981-01-01), Witt
patent: 4312967 (1982-01-01), Norwood et al.
patent: 4517345 (1985-05-01), Eve et al.
patent: 4820785 (1989-04-01), McDaniel et al.
patent: 4981831 (1991-01-01), Knudsen et al.
patent: 5115068 (1992-05-01), Bailey et al.
patent: 5208309 (1993-05-01), McDaniel et al.
patent: 5274056 (1993-12-01), McDaniel et al.
patent: 5399539 (1995-03-01), Reagan et al.
patent: 5599887 (1997-02-01), Badley et al.

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