Patents by Inventor Lawrence R. Sita

Lawrence R. Sita has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 9546230
    Abstract: The present invention provides a method of producing a polyolefin composition comprising contacting a binuclear metallocene pre-catalyst and a co-catalyst, adding a excess of a metal alkyl, then adding a first olefin monomer. The method allows for the production of polyolefins with a highly stereoregular stereochemical microstructure through living coordination polymerization in which rapid reversible chain transfer between a racemic mixture of a chiral active transition metal propagating center and multiple equivalents of inert main group metal alkyl is competitive with chain-growth propagation at the active center.
    Type: Grant
    Filed: January 13, 2014
    Date of Patent: January 17, 2017
    Assignee: University of Maryland, College Park
    Inventor: Lawrence R. Sita
  • Patent number: 9416069
    Abstract: Disclosed is a method of producing a polyolefin composition comprising contacting a metallocene pre-catalyst, a co-catalyst, a primary surrogate, and a secondary surrogate; adding a first olefin monomer; and polymerizing the first monomer for a time sufficient to form the polyolefin. Also disclosed is a method of producing a block polyolefin composition comprising contacting a metallocene pre-catalyst, a co-catalyst, a primary surrogate, and a secondary surrogate; 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. The method allows for the production of polyolefins of low molecular weights and narrow molecular weight distributions.
    Type: Grant
    Filed: January 4, 2011
    Date of Patent: August 16, 2016
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Jia Wei
  • Patent number: 9175103
    Abstract: Disclosed is a method of producing a polyolefin composition comprising contacting a metal alkyl and a first olefin monomer, then adding a first co-catalyst, a second co-catalyst, a pre-catalyst, and a second olefin monomer. The method allows for the production of a series of copolymers with tunable incorporation ratios of the first olefin monomer. The method also allows for the production of polyolefins of low molecular weights and narrow molecular weight distributions.
    Type: Grant
    Filed: June 10, 2011
    Date of Patent: November 3, 2015
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Jia Wei, Wei Zhang
  • Publication number: 20140221586
    Abstract: The present invention provides a method of producing a polyolefin composition comprising contacting a binuclear metallocene pre-catalyst and a co-catalyst, adding a excess of a metal alkyl, then adding a first olefin monomer. The method allows for the production of polyolefins with a highly stereoregular stereochemical micrsostructure through living coordination polymerization in which rapid reversible chain transfer between a racemic mixture of a chiral active transition metal propagating center and multiple equivalents of inert main group metal alkyl is competitive with chain-growth propagation at the active center.
    Type: Application
    Filed: January 13, 2014
    Publication date: August 7, 2014
    Applicant: University of Maryland, College Park
    Inventor: Lawrence R. SITA
  • Publication number: 20140073752
    Abstract: Disclosed is a method of producing a polyolefin composition comprising contacting a metal alkyl and a first olefin monomer, then adding a first co-catalyst, a second co-catalyst, a pre-catalyst, and a second olefin monomer. The method allows for the production of a series of copolymers with tunable incorporation ratios of the first olefin monomer. The method also allows for the production of polyolefins of low molecular weights and narrow molecular weight distributions.
    Type: Application
    Filed: June 10, 2011
    Publication date: March 13, 2014
    Applicant: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Jia Wei, Wei Zhang
  • Patent number: 8513366
    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.
    Type: Grant
    Filed: March 17, 2006
    Date of Patent: August 20, 2013
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Matthew B. Harney, Yonghui Zhang
  • Publication number: 20130109900
    Abstract: Disclosed is a method of producing a polyolefin composition comprising contacting a metallocene pre-catalyst, a co-catalyst, a primary surrogate, and a secondary surrogate; adding a first olefin monomer; and polymerizing the first monomer for a time sufficient to form the polyolefin. Also disclosed is a method of producing a block polyolefin composition comprising contacting a metallocene pre-catalyst, a co-catalyst, a primary surrogate, and a secondary surrogate; 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 foam said block polyolefin composition. The method allows for the production of polyolefins of low molecular weights and narrow molecular weight distributions.
    Type: Application
    Filed: January 4, 2011
    Publication date: May 2, 2013
    Applicant: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Jia Wei
  • Patent number: 8188200
    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.
    Type: Grant
    Filed: November 10, 2008
    Date of Patent: May 29, 2012
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Wei Zhang
  • Publication number: 20110028654
    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.
    Type: Application
    Filed: November 10, 2008
    Publication date: February 3, 2011
    Applicant: University of Maryland, college Park Office of Technology Commercialization
    Inventors: Lawrence R. Sita, Wei Zhang
  • Patent number: 7868088
    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.
    Type: Grant
    Filed: March 17, 2006
    Date of Patent: January 11, 2011
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Matthew B. Harney, Yonghui Zhang
  • Publication number: 20090220786
    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.
    Type: Application
    Filed: March 17, 2006
    Publication date: September 3, 2009
    Inventors: Lawrence R. Sita, Matthew B. Harney, Yonghui Zhang
  • Publication number: 20090209703
    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.
    Type: Application
    Filed: March 17, 2006
    Publication date: August 20, 2009
    Applicant: UNIVERSITY OF MARYLAND, COLLEGE PARK
    Inventors: Lawrence R. Sita, Matthew B. Harney, Yonghui Zhang
  • Patent number: 7541412
    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.
    Type: Grant
    Filed: January 29, 2007
    Date of Patent: June 2, 2009
    Assignee: University of Maryland, College Park
    Inventor: Lawrence R. Sita
  • Patent number: 7183364
    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.
    Type: Grant
    Filed: December 22, 2003
    Date of Patent: February 27, 2007
    Assignee: University of Maryland, College Park
    Inventor: Lawrence R. Sita
  • Patent number: 7053157
    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.
    Type: Grant
    Filed: July 19, 2002
    Date of Patent: May 30, 2006
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R Sita, Richard J Keaton, Kumudini C Jayaratne
  • Patent number: 7041759
    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: wherein the groups M and R1–R4 are defined herein. The group R4 includes a solid-support.
    Type: Grant
    Filed: November 20, 2003
    Date of Patent: May 9, 2006
    Assignee: The University of Maryland, College Park
    Inventors: Lawrence R. Sita, Yonghui Zhang
  • Publication number: 20040198930
    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.
    Type: Application
    Filed: January 20, 2004
    Publication date: October 7, 2004
    Inventors: Lawrence R. Sita, Richard J. Keaton, Kumudini C. Jayaratne
  • Publication number: 20040186253
    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.
    Type: Application
    Filed: December 22, 2003
    Publication date: September 23, 2004
    Applicant: University of Maryland, College Park
    Inventor: Lawrence R. Sita
  • Publication number: 20040110632
    Abstract: An olefin polymerization pre-catalyst, an activated catalyst and a process for preparing the catalysts are described herein.
    Type: Application
    Filed: November 20, 2003
    Publication date: June 10, 2004
    Applicant: The University of Maryland, College Park
    Inventors: Lawrence R. Sita, Yonghui Zhang
  • Patent number: 6579998
    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, R1, R2, R3, R4 and R5 are defined herein.
    Type: Grant
    Filed: May 7, 2001
    Date of Patent: June 17, 2003
    Assignee: University of Maryland, College Park
    Inventors: Lawrence R. Sita, Kumudini C. Jayaratne