Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymerizing in two or more physically distinct zones
Reexamination Certificate
2000-01-27
2001-10-16
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymerizing in two or more physically distinct zones
C526S082000, C526S090000, C526S161000, C526S169000, C526S169100, C526S172000, C526S901000, C526S905000
Reexamination Certificate
active
06303710
ABSTRACT:
FIELD OF THE INVENTION
Olefin polymerizations using late transition metal catalysts can be controlled using hydrogen to regulate the polymerization rate, and the effect on polymerization rate is reversible when the hydrogen is removed.
TECHNICAL BACKGROUND
Polymerizations of olefins using late transition metal catalysts, that is metals of Groups 6 through 10 (new IUPAC notation) such as Fe, Co, Ni, and Pd have been of interest lately, see for instance World Patent Applications 96/23010, 98/03559, 98/30610, 98/30609, 98/47934, 98/47933, 98/40420 and 98/40374, and U. S. Pat. No. 5,714,556. Catalysts such these are of great interest because besides making known commercial polymers such as high and low density polyethylenes, they are also capable of making polyolefins with new structures.
It is known that hydrogen can be used to lower by chain transfer the molecular weight of polymers produced with many of these catalysts, see World Patent Applications 99/61492 and 99/62963. However, in many instances a relatively large amount of hydrogen is required to get a desired lowering of polyolefin molecular weight.
It is also known that initial (at the start of a polymerization) olefin polymerization rates with these catalysts may be very high resulting in a tendency to overheat the polymerization in its initial stages. This often is undesirable, since it may adversely affect the morphology and/or structure of the polyolefin formed, and/or may reduce the overall productivity of the polymerization catalyst. It may also be desirable to slow the polymerization temporarily when changing polymerization conditions such as pressure and/or temperature, so as to avoid making “transition” material. Therefore a method for controlling olefin polymerization rates with these catalysts without significantly affecting later polymerization and/or the overall catalyst productivity is desired.
SUMMARY OF THE INVENTION
The invention concerns an improved process for the polymerization of olefins using as part of a polymerization catalyst a coordination compound containing a transition metal of Group 6 through Group 10, wherein the improvement comprises, carry out said polymerization in two or more stages at least one of which stages is a slow polymerization stage and one of which stages is a fast polymerization stage, and wherein:
in a slow polymerization stage at least 0.1 mole percent of hydrogen, based on the amount of monomer (olefin) present, is present in said polymerization;
in a fast polymerization stage a level of hydrogen is present that is no more than 0.8 of a level of hydrogen present in said slow polymerization stage;
and provided that at least 5 percent by weight of a polymer produced in said process is produced in said fast polymerization stage, and at least 2 percent by weight of a polymer produced in said process is produced in said slow polymerization stage.
REFERENCES:
patent: 5714556 (1998-02-01), Johnson et al.
patent: 197 07 236 A1 (1998-08-01), None
patent: 0 009 160 A1 (1980-04-01), None
patent: 522635 A1 (1993-01-01), None
patent: 570051 A1 (1993-11-01), None
patent: 0 580 930 A1 (1993-11-01), None
patent: 0 570 051 A1 (1993-11-01), None
patent: 580930 A1 (1994-02-01), None
patent: 0 874 005 A1 (1998-10-01), None
patent: 1 434 264 (1976-05-01), None
patent: WO 96/23010 (1996-08-01), None
patent: WO 98/03559 (1998-01-01), None
patent: WO 98/30610 (1998-07-01), None
patent: WO 98/30609 (1998-07-01), None
patent: WO 98/40420 (1998-09-01), None
patent: WO 98/40374 (1998-09-01), None
patent: WO 98/47934 (1998-10-01), None
patent: WO 98/47933 (1998-10-01), None
patent: WO 99/61492 (1999-12-01), None
patent: WO 99/62963 (1999-12-01), None
Copy of International Search Report (PCT/US00/02095) dated May 30, 2000.
E. I. Du Pont de Nemours and Company
Rabago R.
Wu David W.
LandOfFree
Control of olefin polymerization using hydrogen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control of olefin polymerization using hydrogen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control of olefin polymerization using hydrogen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2553217