Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
1998-07-07
2003-05-20
Gonzalez, Porfirio Nazario (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C534S015000, C502S103000, C502S117000, C526S160000, C526S943000, C526S127000, C526S352000, C556S054000, C556S058000, C556S043000, C556S001000
Reexamination Certificate
active
06566544
ABSTRACT:
TECHNICAL FIELD
This invention relates to novel catalysts, catalyst systems, methods of production of olefin polymers, and elastomeric olefin polymers, particularly crystalline and amorphous block polymers by use of the novel catalysts of the invention. A principal area of interest is the preparation and use of novel cyclopentadienyl or indenyl metallocene catalysts to produce elastomeric stereoblock polymers, and methods of control of catalyzed polymeric reactions to produce polymers having properties ranging from crystalline thermoplastics to thermoplastic elastomers to amorphous gum elastomers.
BACKGROUND ART
Crystalline, amorphous, and elastic polypropylenes are known. Crystalline polypropylenes are generally regarded as comprising of predominantly isotactic or syndiotactic structures and amorphous polypropylene is regarded as comprising predominantly of an atactic structure. U.S. Pat. Nos. 3,112,300 and 3,112,301 both of Natta, et. al. describe isotactic and prevailingly isotactic polypropylene.
U.S. Pat. No. 3,175,199 to Natta et al. describes an elastomeric polypropylene which can be fractioned out of a polymer mixture containing prevailingly isotactic and atactic polypropylenes. When separated from the polymer mixture, a fraction of this polymer showed elastomeric properties which were attributed to a stereoblock structure comprising alternating blocks of isotactic and atactic stereosequences.
Previously, the catalysts used to produce stereoblock amorphous crystalline polypropylenes consisted of heterogeneous catalysts comprising titanium or vanadium halides on a support (Natta and Crespi 1965; German Patent DD 300,293 of Arnold et al.), or tetralkyl zirconium or titanium on a metal oxide support U.S. Pat. No. 4,335,225 of Collette (du Pont). These heterogeneous catalysts do not consist of single sites, but of multiple sites and thus produce a mixture of polymeric materials which can be fractionated by extraction into suitable solvents. The various fractions typically have different molecular weights and molecular weight distributions and vary in their physical properties.
Metallocene catalysts are capable of polymerizing alpha olefins to atactic, isotactic, or syndiotactic structures. In particular, rigid bridged indenyl metallocenes represented by the general structure A and B are known in the art where M=Ti, Zr, and Hf:
As disclosed by Ewen (“Mechanisms of Stereochemical Control in Propylene Polymerizations with Soluble Group 4B Metallocene/Methylalumoxane Catalysts” J. Am. Chem. Soc. 1984, 106, 6355-6364), stereorigid catalysts of racemic geometry A produce isotactic polypropylene whereas stereorigid catalysts of meso geometry B produce atactic polypropylene.
A metallocene catalyst was disclosed which yields elastomeric polypropylene (Chien, Llinas et al. 1991; Cheng, Babu et al. 1992; Llinas, Dong et al. 1992). This catalyst had rather low activity (3.5×10
5
gm polymer/mol Ti.hr) and yielded polypropylenes with molecular weights less than M
w
=200,000. This polymer was more homogeneous in its composition, and was completely soluble in diethyl ether. Polypropylenes produced with this catalyst had melting points below 70° C., with elongations up to 1300% and tensile strength of 1750 psi.
Accordingly, there is a need for more active catalyst systems, the structure of which can be controlled in the reaction system during polymerization to produce a selected ratio of atactic/isotactic stereosequences, resulting in high molecular weight polymers with narrow molecular weight distributions having preselected properties, including thermoplastic elastomeric properties.
THE INVENTION
DISCLOSURE OF INVENTION
OBJECTS AND ADVANTAGES
It is an object and advantage of this invention to provide a new class of metallocene catalysts, and methods of polymerization employing the catalysts to produce a wide range of alpha olefin polymers, including isotactic-atactic stereoblock polymers having a broad range of structures, including isotactic stereosequences of varying lengths to provide a preselected range of properties, including highly elastomeric thermoplastic properties.
It is another object and advantage of this invention to provide stereoblock alpha olefin polymers with preselected properties by control of catalyst substituents and process conditions.
It is another object and advantage of this invention to provide processes for preparation of a wide variety of stereoblock polymers through control of the catalyst geometry.
It is another object and advantage of this invention to provide a novel class of polymer systems, including stereoblock polymers having preselected properties.
It is another object and advantage of this invention to provide a novel class of high molecular weight atactic polypropylenes.
Still other objects and advantages of the invention will be evident from the Descriptions, Drawings, and Claims of this application.
SUMMARY
This invention is directed to novel metallocene-complex catalysts the structure and activity of which can be controlled to produce a wide range of olefin polymers and co-polymers, and preferably for the production of stereoblock poly alpha-olefins comprising a wide range of preselected amorphous and crystalline segments for precise control of the physical properties thereof, principally elastomeric thermoplastic properties. More specifically, this invention is directed to novel metallocene catalysts and catalyst systems for producing stereoblock polypropylene comprising alternating isotactic and atactic diastereosequences, which result in a wide range of elastomeric properties. The amount and number of crystalline sections, the isotactic pentad content, the number and length of intermediate atactic chains and overall molecular weight are all controllable by the electronic and steric nature of the catalysts and the process conditions. The novel catalysts provided by the present invention are ligand-bearing non-rigid metallocenes the geometry of which can change on a time scale that is slower than the rate of olefin insertion, but faster than the average time to construct (polymerize) a single polymer chain, in order to obtain a stereoblock structure in the produced polyolefins. The symmetry of the catalyst structure is such that upon isomerization the catalyst symmetry alternates between a chiral and an achiral geometry. This geometry alternation can be controlled by selecting ligand type and structure, and through control of polymerization conditions to precisely control the physical properties of the resulting polymers.
This invention includes a novel process for tailoring the block size distribution and resulting properties of the polymer such as the tacticity, molecular weight, molecular weight distribution, melt flow rate, melting point, crystallite aspect ratio, tensile set and tensile strength by varying the structure of the catalyst and the conditions of the polymerization reaction.
In a preferred embodiment the catalysts and methods of this invention produce a novel class of elastomeric polymers comprising units derived from propylene, which have a high molecular weight and a narrow molecular weight distribution, which are homogeneous in their composition. By homogeneous in composition, we mean that if the polymer can be fractionated by whatever solvent or solvent system(s), all the polymer fractions have similar molecular weight distributions M
w
/M
n
, typically less than 7, preferably less than 5, and most preferred less than 4.
The thermoplastic elastomeric polypropylenes of this invention exhibit elongations to break from 20% to 5000%, typically between 100% and 3000% with tensile sets between 5% and 300%, typically between 10% and 200%, and preferably between 10% and 70%. Tensile strengths for these polypropylenes range from 100 psi to 6000 psi, typically between 400 psi and 5000 psi. The crystallinity of the polymers range from amorphous materials with no melt, to crystalline thermoplastic with melting points of about 165° C. Preferably he melting points range from about 500 to about 165° C.
The catalyst s
Coates Geoffrey W.
Hauptman Elisabeth
Waymouth Robert M.
Dulin, Esq. Jacques M.
Gonzalez Porfirio Nazario
Innovation Law Group, Ltd.
The Board of Trustees of the Leland Stanford Jr. University
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