Lawrence R Sita

US Patent:

7041759, May 9, 2006

Filed:

Nov 20, 2003

Appl. No.:

10/716604

Inventors:

Lawrence R. Sita - Silver Spring MD, US
Yonghui Zhang - College Park MD, US

Assignee:

The University of Maryland, College Park - College Park MD

International Classification:

C08F 4/52
C08F 4/76

US Classification:

526172, 526161, 526134, 526133, 526127, 526130, 526904, 526943, 526348, 502103

Abstract:

An olefin polymerization pre-catalyst, an activated catalyst and a process for preparing the catalysts are described herein. The pre-catalyst has the formula:.

US Patent:

7053157, May 30, 2006

Filed:

Jul 19, 2002

Appl. No.:

10/484210

Inventors:

Lawrence R Sita - Silver Spring MD, US
Richard J Keaton - Greenbelt MD, US
Kumudini C Jayaratne - Bartelsville OK, US

Assignee:

University of Maryland, College Park - College Park MD

International Classification:

C08F 4/64
C08F 4/642
C08F 4/643

US Classification:

526 86, 526 78, 526 79, 526 83, 526 87, 526113, 526114, 526118, 526119, 526161, 526172

Abstract:

The present invention relates to a method of producing multimodal polyolefins using at least one or more activated metallocene catalysts. The activated metallocene catalysts are used in combination in a single-process method. The method allows for the production of multimodal polyolefins of tunable composition, molecular weight and polydispersity.

US Patent:

7183364, Feb 27, 2007

Filed:

Dec 22, 2003

Appl. No.:

10/740826

Inventors:

Lawrence R. Sita - Silver Spring MD, US

Assignee:

University of Maryland, College Park - College Park MD

International Classification:

C08F 4/52
C08F 4/76
C08F 4/44

US Classification:

526172, 526161, 526348, 526336, 526339, 5263482, 5263486, 526351, 526352, 5263485, 5263483

Abstract:

Disclosed is a method of producing a polyolefin composition comprising contacting a metallocene pre-catalyst with a substoichiometric amount of a co-catalyst; adding a first olefin monomer; and polymerizing the first monomer for a time sufficient to form the polyolefin. The method allows for the use of a minimum amount of activating co-catalyst, and allows for the production of stereoregular and non-stereoregular polyolefins. The use of configurationally stable metallocene pre-catalysts allows for the production of monomodal isotactic polyolefins having narrow polydispersity. The use of configurationally unstable metallocene pre-catalysts allows for the production of monomodal atactic polyolefins having narrow polydispersity. The method of the present invention optionally further comprises contacting the polyolefin with a second amount of said co-catalyst; adding a second olefin monomer; polymerizing said second olefin monomer to form a block-polyolefin composition. Also disclosed are monomodal diblock copolymer compositions made according to the present invention.

US Patent:

7541412, Jun 2, 2009

Filed:

Jan 29, 2007

Appl. No.:

11/698975

Inventors:

Lawrence R. Sita - Silver Spring MD, US

Assignee:

University of Maryland, College Park - College Park MD

International Classification:

C08F 4/68
C08F 2/04

US Classification:

5261692, 526161, 526172, 526943, 526941, 526134, 5263482, 5263483, 5263485, 5263486, 526348, 526336, 526339, 5263402, 5263403, 526 79, 526 87

Abstract:

Disclosed is a method of producing a polyolefin composition comprising contacting a metallocene pre-catalyst with a substoichiometric amount of a co-catalyst; adding a first olefin monomer; and polymerizing the first monomer for a time sufficient to form the polyolefin. The method allows for the use of a minimum amount of activating co-catalyst, and allows for the production of stereoregular and non-stereoregular polyolefins. The use of configurationally stable metallocene pre-catalysts allows for the production of monomodal isotactic polyolefins having narrow polydispersity. The use of configurationally unstable metallocene pre-catalysts allows for the production of monomodal atactic polyolefins having narrow polydispersity. The method of the present invention optionally further comprises contacting the polyolefin with a second amount of said co-catalyst; adding a second olefin monomer; polymerizing said second olefin monomer to form a block-polyolefin composition. Also disclosed are monomodal diblock copolymer compositions made according to the present invention.

US Patent:

7868088, Jan 11, 2011

Filed:

Mar 17, 2006

Appl. No.:

11/886536

Inventors:

Lawrence R. Sita - Silver Spring MD, US
Matthew B. Harney - Fairfax VA, US
Yonghui Zhang - Old Saybrook CT, US

Assignee:

University of Maryland, College Park - College Park MD

International Classification:

C08L 53/00

US Classification:

525 89

Abstract:

Methods for modulated degenerative transfer living polymerization and isotactic-atactic stereoblock and stereogradient poly(olefins) thereby Abstract A method of producing a multiblock, stereoblock polyolefin having substantially uniform microstructure is disclosed. The method includes contacting a Ziegler-Natta pre-catalyst with a co-catalyst and an olefin to polymerize the olefin and form a first stereoblock, adding a methyl donator that changes the stereoregularity of the polymerization, and polymerizing the olefin to form a second stereoblock. The methods of the present invention allow for the production of poly(olefin)s having predictable degrees of incorporation of stereoerrors of a known type. The methods allows for the production of a variety of poly(olefin) microstructures, ranging from stereoblock to stereogradient poly(olefin)s and poly(olefin)s having fully isotactic to fully atactic microstructures.

US Patent:

8188200, May 29, 2012

Filed:

Nov 10, 2008

Appl. No.:

12/742055

Inventors:

Lawrence R. Sita - Silver Spring MD, US
Wei Zhang - Gaithersburg MD, US

Assignee:

University of Maryland, College Park - College Park MD

International Classification:

C08F 4/642
C08F 4/643
C08F 4/6592
C08F 293/00

US Classification:

526161, 526 79, 526 87, 526133, 526160, 526336, 526339, 526348, 526943, 502103, 502114, 502128, 502152, 525245, 525247

Abstract:

Disclosed is a method of producing a polyolefin composition comprising contacting a metallocene pre-catalyst, co-catalyst, and a stoichiometric excess of a metal alkyl; adding a first olefin monomer; and polymerizing the first monomer for a time sufficient to form the polyolefin. The method allows for the use of minimum amounts of activating co-catalyst and metallocene pre-catalyst. Also disclosed is a method of producing a block polyolefin composition comprising contacting a metallocene pre-catalyst, a co-catalyst, and a stoichiometric excess of a metal alkyl; adding a first olefin monomer; polymerizing the first monomer for a time sufficient to form the polyolefin; adding a second monomer; and polymerizing the second olefin monomer for a time sufficient to form said block polyolefin composition. Also disclosed are amorphous atactic polymer and copolymer compositions made according to the present invention.

US Patent:

8513366, Aug 20, 2013

Filed:

Mar 17, 2006

Appl. No.:

11/886535

Inventors:

Lawrence R. Sita - Silver Spring MD, US
Matthew B. Harney - Fairfax VA, US
Yonghui Zhang - Old Saybrook CT, US

Assignee:

University of Maryland, College Park - College Park MD

International Classification:

C08F 2/00
C08F 4/72
C08F 210/00
C08F 110/06

US Classification:

526 86, 526170, 526348, 526351

Abstract:

Methods for modulated degenerative transfer living polymerization and isotactic-atactic stereoblock and stereogradient poly(olefins) thereby Abstract A method of producing a multiblock, stereoblock polyolefin having substantially uniform microstructure is disclosed. The method includes contacting a Ziegler-Natta pre-catalyst with a co-catalyst and an olefin to polymerize the olefin and form a first stereoblock, adding a methyl donator that changes the stereoregularity of the polymerization, and polymerizing the olefin to form a second stereoblock. The methods of the present invention allow for the production of poly(olefin)s having predictable degrees of incorporation of stereoerrors of a known type. The methods allows for the production of a variety of poly(olefin) microstructures, ranging from stereoblock to stereogradient poly(olefin)s and poly(olefin)s having fully isotactic to fully atactic microstructures.

US Patent:

20020045536, Apr 18, 2002

Filed:

May 7, 2001

Appl. No.:

09/849244

Inventors:

Lawrence Sita - Silver Spring MD, US
Kumudini Jayaratne - College Park MD, US

International Classification:

B01J031/00

US Classification:

502/104000, 502/102000, 502/103000, 502/117000, 502/150000

Abstract:

An olefin polymerization pre-catalyst and a method for preparing an activated olefin polymerization catalyst composition from the pre-catalyst are disclosed: wherein M, R, R, R, Rand Rare defined herein.