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• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F290/00—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups
  • C08F290/02—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups on to polymers modified by introduction of unsaturated end groups
  • C08F290/04—Polymers provided for in subclasses C08C or C08F
  • C08F290/042—Polymers of hydrocarbons as defined in group C08F10/00
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F110/02—Ethene
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F210/04—Monomers containing three or four carbon atoms
  • C08F210/08—Butenes
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
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  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
  • C08F4/44—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
  • C08F4/60—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
  • C08F4/62—Refractory metals or compounds thereof
  • C08F4/64—Titanium, zirconium, hafnium or compounds thereof
  • C08F4/659—Component covered by group C08F4/64 containing a transition metal-carbon bond
  • C08F4/65908—Component covered by group C08F4/64 containing a transition metal-carbon bond in combination with an ionising compound other than alumoxane, e.g. (C6F5)4B-X+
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
  • C08F4/44—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
  • C08F4/60—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
  • C08F4/62—Refractory metals or compounds thereof
  • C08F4/64—Titanium, zirconium, hafnium or compounds thereof
  • C08F4/659—Component covered by group C08F4/64 containing a transition metal-carbon bond
  • C08F4/6592—Component covered by group C08F4/64 containing a transition metal-carbon bond containing at least one cyclopentadienyl ring, condensed or not, e.g. an indenyl or a fluorenyl ring
  • C08F4/65922—Component covered by group C08F4/64 containing a transition metal-carbon bond containing at least one cyclopentadienyl ring, condensed or not, e.g. an indenyl or a fluorenyl ring containing at least two cyclopentadienyl rings, fused or not
  • C08F4/65927—Component covered by group C08F4/64 containing a transition metal-carbon bond containing at least one cyclopentadienyl ring, condensed or not, e.g. an indenyl or a fluorenyl ring containing at least two cyclopentadienyl rings, fused or not two cyclopentadienyl rings being mutually bridged
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F10/02—Ethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
  • C08F2500/09—Long chain branches
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
  • C08F2500/12—Melt flow index or melt flow ratio
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2314/00—Polymer mixtures characterised by way of preparation
  • C08L2314/06—Metallocene or single site catalysts
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S526/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S526/943—Polymerization with metallocene catalysts

Definitions

• This invention relates to the field of long chain branched polymers and a process to make them.
• This invention relates to novel polyolefin polymers, processes for producing such polymers, and applications for such polymers.
• the commercial significance of polyolefin polymers is enhanced by the variety of forms they may take which often exhibit different physical properties. These different properties make polyolefin polymers useful in many different end use applications.
• the structural features of polyolefins that are considered most significant are molecular weight, which is related to polymer chain length, the type and tacticity of side- chain branches, and the distribution of side-chain branches along the main polymer chains. Over the years, considerable attention has been given to the molecular architecture of polyolefins. Polyolefins can be commercially produced using any one of a number of processes.
• LPEs linear polyethylenes
• LPEs low density polyethylenes
• LPEs are traditionally produced by addition polymerization of ethylene, or by the copolymerization of ethylene and an alpha-olefin comonomer, in a variety of processes using coordination catalysts.
• LDPEs are traditionally produced by free-radical polymerization of ethylene in high temperature and high pressure reactors using peroxide initiators. These two broad categories of polyethylenes have significant structural and physical differences. The most important difference between LPEs and LDPEs is the nature of the side-chain branching. LDPEs are highly side-chain branched having dendritic (tree-like) long chain side branches attached to the main polymer chains.
• Dendritic side-chain branching gives certain advantages, particularly processing advantages, to the polymer melts.
• processing advantages are balanced by disadvantages inherent with LDPEs relating to mechanical properties of the solid polymers such as lower stiffness, hardness, low tear resistance, low environmental stress crack resistance (ESCR) and, low tensile strength. These properties relative to LPEs with equivalent density and melt index properties.
• LPEs without long chain side branches have good mechanical properties such as good stiffness, hardness, tensile strength characteristics, tear resistance, and ESCR; however, from a processing standpoint, LPEs have the disadvantages of a tendency to melt fracture and low shear sensitivity resulting in high melt viscosity, low melt strength and higher processing costs.
• dienes are simultaneously incorporated into propagating chains, thereby creating a covalent bridge between two linear molecules.
• the resulting structure in the vicinity of the bridge is typically shaped like the letter "H".
• the resultant side-chain branches can be long and are usually paired rather than isolated.
• the complexity of the branching approaches that of dendritic branching ultimately causing the polymer to lose its linear mechanical characteristics.
• polymers produced with dienes have encountered resistance to approval by regulatory authorities for food contact applications.
• United Kingdom Patent 901,148 demonstrates the production of branched polyethylene by treating molten polyethylene with oxygen. One method of doing this is by forcing air into the molten polyethylene during melt extrusion. This method of production results in non-linear long chain branches.
• United States Patent 4,586,995 discloses the irradiation of molten polyethylene in the absence of oxygen to produce Y branches having two to fifty carbon chains per ten thousand carbon atoms in the main polymer chain.
• United Kingdom Patent 1,379,853 discloses the introduction of branches into polyethylene during the degradation of high density polyethylene in the presence of an organic peroxide.
• Japanese Kokai 59-59,760 discusses the production of long chain branched polyethylene by heating polyethylene containing a terminal vinyl group at 180° - 360°C under vacuum conditions or an inert atmosphere for five minutes to six hours.
• the polymer produced has long chain branches with a frequency of 3.5 branches per molecule. These branches are non ⁇ linear.
• a third type of process for producing branching in linear polyethylene is the use of a polymerization cocatalyst which contains a long chain branched polymeric group.
• U.S. Patent 4,500,648 and divisionals thereof disclose high density polyethylene production with branches prepared by polymerization of ethylene in the presence of a coordination catalyst containing an organoaluminum compound having a branched polymeric hydrocarbyl group as one of its substituents.
• the polymers produced by this method contain non-linear long chain branches.
• a method for the preparation of LLDPE using only ethylene is described in European Application Number 87108556.9 EPA 250,999.
• the method used is the oligomerization of ethylene using nickel based catalysts followed by copolymerization of the olefin mixture with ethylene through use of a chromium catalyst system.
• the objective of this application is to utilize a process for preparing higher olefins to prepare a mixture of olefins which is then copolymerized to yield the LLDPE structure.
• the LLDPE prepared in this method consists of polyethylene with a distribution of side-chains having 14 to 200 carbon atoms.
• One deficiency of this application is that it utilizes very low activity catalysts to form the oligomers and the subsequent copolymers.
• this application does not recognize the importance of utilizing even longer side-chains than those described in the application.
• EP 91301811.5 presents the polymerization of ethylene using Nickel complexes to give LLDPE containing long-chain branching.
• JP Hl-251748 presents the copolymerization of ethylene and hexene using Nickel based polymerization catalysts. Using the catalyst systems described in the application, ethylene copolymers containing short and long chain branches are produced.
• Nickel based catalyst systems 1) the low catalyst activities (30 g polymer/mmol catalyst in 1 hr) ; and 2) molecular weight distribution is proportional to molecular weight, therefore high molecular weights are accompanied by broad molecular weight distributions. This method does not produce higher Mw with narrow Mw/Mn.
• linear long chain side branches This invention relates to novel polymers and processes for making polymers incorporating linear long chain side branches.
• linear is herein defined to include side chains that have some side chain branching but are not dendritic.
• the linear long chain branches are comprised of sidechains being at least 250 carbons long, which have molecular weights at least as great as the critical molecular weight for entanglement (M c ) of the polymer.
• M c critical molecular weight for entanglement
• the linear long chain branches occur.at a frequency of less than 5.0 branches per 1000 carbon atoms in the main polymer chains.
• the linear long chain branched polymers are produced by incorporating a macromolecule during metallocene-catalyzed solution polymerization processes (solvent or bulk process at low, medium or high pressure) .
• the long chain branched polymers possess the processability characteristics of conventional long chain branched polymer melts and the mechanical characteristics of conventional solid linear polymers.
• Polymers produced in accordance with this invention are useful for fabrication into a wide variety of articles by injection molding, extrusion coating and molding, blown film, cast film, thermoforming and rotational molding.
• a vinyl unsaturated molecule can be considered a large alpha- olefin.
• Linear copolymers are produced by additional polymerization of two or more vinyl terminated monomers ranging in size from two to thirty carbon atoms.
• copolymers are produced in which vinyl terminated polymers, also called macromonomers or macromers, are incorporated into the addition polymerization reaction along with the monomers.
• the vinyl terminated polymers responsible for the unique characteristics of polymers produced in accordance with the present invention are molecules having molecular weights greater than the critical molecular weight for entanglement (M c ) ⁇ f; the polymer into which the vinyl terminated polymers are incorporated.
• the M c for polyethylene is 3,800.
• the vinyl terminated polymers of this invention are 250 or more carbon atoms long, preferably 350 to 3500, even more preferably 300 to 3000, or have a Mw of greater than 6000. Further, the vinyl terminated polymers of this invention are incorporated into the growing polymer at an average frequency of no more than 5 long side chains per 1000 carbon atoms along the main chain, preferably the average frequency is 0.2 to 3 long side chains per 1000 carbon atoms, more preferably 0.9 to 2 long side chains per carbon atoms. Using traditional coordination catalyst processes, these vinyl terminated polymers do not incorporate into growing polymer chains.
• the vinyl terminated polymers of this invention which eventually become side chains can be homopolymers or copolymers of one or more C2 to C 30 olefin, preferably alpha olefins, even more preferably homo or copolymers of ethylene, propylene, l-butene, l-pentene, 1-hexene, 1-octene and 4-methylpentene-l. Cyclic olefins are also useful monomers in the practice of this invention.
• the main chain can also be a homopolymer or copolymer of one or more C 2 to C 30 olefins, preferably alpha olefins, even more preferably homo or copolymers of ethylene, propylene, butene-1, pentene-1, hexene-1, octene-1 and 4-methyl-pentene-l.
• Copolymer is herein defined to include polymers of 2 to 4 different monomers and block copolymers of any of the above olefins or alpha olefins.
• the vinyl terminated polymers useful in this invention can be prepared using a variety of metallocene catalysts and process conditions.
• catalyst and process conditions depends upon the desired polymer composition and molecular weights.
• High vinyl termination content is necessarily preferred.
• Conditions which favor their formation are high temperatures, no comonomer, no transfer agents like hydrogen, and a non-solution process or a dispersion using an alkane diluent.
• the metallocene should be active at relatively high temperatures.
• the selected metallocene may also be thermally activated to yield the beta-hydrogen eliminated product; vinyl ends. Thus one could prepare materials at low temperature then increase the temperature to get the beta-hydride eliminated product.
• the steric requirements of the metallocene will affect the degree to which copolymerization occurs.
• Metallocenes which possess steric hindrance will yield vinyl terminated polymers which are relatively free of branches when compared to metallocenes which do not possess this hindrance.
• Another method producing vinyl termination involves production of polymer with an ethylene "cap” or end with the needed vinyl group. This could be accomplished by bet,._.nning polymerization at a low temperature, for example, below zero degrees Celsius, and raising the reaction temperature at the "end” of the reaction, for example, to above ten degrees Celsius, and simultaneously adding ethylene so that the ethylene preferentially polymerizes to form an end "cap” or block.
• a block copolymer of ethylene and a C 3 to C 30 alpha olefin would also present the necessary vinyl termination.
• the vinyl terminated polymers can be optimally copoly erized using metallocenes which are sterically unhindered.
• the polymerization system should be a single-phase, or if two-phase, the vinyl terminated polymers must be sufficiently mobile to permit their copolymerization.
• the preferred process for their copolymerization is a solution process.
• the process solvent and temperature preferred are those in which the vinyl terminated polymer is soluble or substantially swollen.
• the present invention preferably utilizes catalyst system comprising a metallocene catalyst with cocatalyst activators of an alumoxane or a "non- coordinating" anion.
• the metallocene catalyst is an activated cyclopentadienyl group 4 transition metal compound.
• the metallocene catalysts employed in this invention are organometallic coordination compounds which are cyclopentadienyl derivatives of group 4 metals of the periodic table of the elements and include mono-, di- and tri- cyclopentadienyls and their derivatives. Particularly desirable are the metallocenes of the group 4 metals: titanium, zirconium and hafnium.
• the cyclopentadienyl metallocenes of this invention can be activated with either an alumoxane or a "non-coordinating" anion-type activator. In general at least one metallocene compound is employed in formation of the catalyst system.
• Metallocenes employed in accordance with this invention contain at least one cyclopentadienyl ring and preferably comprise titanium, zirconium, or hafnium, most preferably hafnium, or zirconium for bis- cyclopentadienyl compounds and titanium for mono- cyclopentadienyl compounds.
• the cyclopentadienyl ring can be substituted or unsubstituted or contain one or more substituents e.g. from 1 to 5 substituents such as for example, hydrocarbyl substituent e.g. up to five C ⁇ to C2 0 hydrocarbyl substituents or other substituents e.g. for example, a trialkyl cyclic substituent.
• a metallocene may contain 1, 2 or 3 cyclopentadienyl rings, however, two rings are preferred for use with hafnium or zirconium. One ring is preferred for use with titanium.
• the catalyst system used in this invention can be described as comprising cyclopentadienyl transition metal catalyst having at least one delocalized pi- bonded moiety and an activating cocatalyst.
• the catalyst system used in this invention can also be described as comprising a cyclopentadienyl transition metal catalyst of a transition metal compound containing a single cyclopentadienyl group and a heteroatom containing group each bonded to the transition metal, said cyclopentadienyl group and heteroatom containing groups optionally bridged through a divalent moiety and an activating cocatalyst.
• the macromonomer in another embodiment of the present invention can be polymerized in a gas phase process. This may be achieved by pre-polymerizing the macromonomer by one of many methods known in the art.
• the method for supporting a catalyst known in U.S. Patent Application 885,170 filed 5-18-92, incorporated by reference, discloses how to place a catalyst on a support.
• This supported catalyst can then be combined with the macromonomer under appropriate polymerization conditions to pre-polymerize the macromonomer with the supported catalyst.
• This combination can then be introduced into a gas phase polymerization reactor to produce long chain branched polymers in this invention.
• This macromonomer may also be pre-polymerized with other traditional gas phase supported catalysts and similarly introduced into the gas phase polymerization reactor.
• the pre- polymerization process is normally a slow, controlled process to initiate controlled polymer fracture or support fracture thus, one of ordinary skill in the art would be sure to maintain appropriate reaction conditions such as temperatures from 40°C to 140°C in a suitable solvent with the introduction of ethylene, or suitable comonomers to form the macromonomers in a controlled amount.
• the process of this invention is practiced with that class of ionic catalysts referred to, disclosed, and described in European Patent Applications EP 0 277 003 Al and EP 0 277 004 Al, and PCT Application WO 92/00333, and U.S. Patents 5,055,438 and 5,096,867, which are herein incorporated by reference.
• the ionic catalysts used in this invention can be represented by one of the following general formulae (all references to groups being the new group notation of the Periodic Table of the Elements as described by Chemical and Engineering News, 63(5), 27, 1985): 1. [ ⁇ [(A-Cp)MX 1 ] + ⁇ d ] ⁇ [B'] d" ⁇
• (A-Cp) is either (Cp) (Cp*) or Cp-A'-Cp*;
• Cp and Cp* are the same or different cyclopentadienyl rings substituted with from zero to five substituent groups S, each substituent group S being, independently, a radical group which is a hydrocarbyl, substituted- hydrocarbyl, halocarbyl, substituted-halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyl- substituted organometalloid, disubstituted boron, disubstituted Group 15 element, substituted Group 16 element or halogen radicals, or Cp and Cp* are cyclopentadienyl rings in which any two adjacent S groups are joined forming a C4 to C20 ring to give a saturated or unsaturated polycyclic cyclopentadienyl ligand;
• a 1 is a bridging group, which group may serve to restrict rotation of the Cp and Cp* rings or (C 5 H 5 _ y _ x S x x) and JS « ( z - ⁇ _y) groups;
• (C5H5_y_ x S x ) is a cyclopentadienyl ring substituted with from zero to five S radicals;
• x is from 1 to 5 denoting the degree of substitution;
• M is titanium, zirconium, or hafnium
• Xi is a hydride radical, hydrocarbyl radical, substituted-hydrocarbyl radical, hydrocarbyl- substituted organometalloid radical or halocarbyl- substituted organometalloid radical which radical may optionally be covalently bonded to both or either M and L or all or any M, S, or S 1 ;
• J is an element from Group 15 of the Periodic Table of Elements with a coordination number of 3 or an element from Group 16 with a coordination number of 2
• S is a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, hydrocarbyl-substituted organometalloid, or halocarbyl- substituted organometalloid
• z is the coordination number of the element J
• y is 0 or 1;
• L is an olefin, diolefin or aryne ligand, or a neutral Lewis base; L* can also be a second transition metal compound of the same type such that the two metal center M and M* are bridged by Xj , and X' ⁇ , wherein M* has the same meaning as M and X* ⁇ has the same meaning as Xi where such dimeric compounds which are precursors to the cationic portion of the catalyst are represented by the formula:
• w is an integer from 0 to 3;
• B is a chemically stable, non-nucleophilic anionic complex having a molecular diameter about or greater than 4 angstroms or an anionic Lewis-acid activator resulting from the reaction of a Lewis-acid activator with the precursor to the cationic portion of the catalyst system described in formulae 1-4.
• B' is a Lewis-acid activator
• X ⁇ can also be an alkyl group donated by the Lewis-acid activator
• d is an integer representing the charge of B.
• the improved catalysts are preferably prepared by combining at least two components.
• the first component is a cyclopentadienyl derivative of a Group 4 metal compound containing at least one ligand which will combine with the second component or at least a portion thereof such as a cation portion thereof.
• the second component is an ion-exchange compound comprising a cation which will irreversibly react with at least one ligand contained in said Group 4 metal compound (first component) and a non-coordinating anion which is either a single coordination complex comprising a plurality of lipophilic radicals covalently coordinated to and shielding a central formally charge-bearing metal or metalloid atom or an anion comprising a plurality of boron atoms such as polyhedral boranes, carboranes and metallacarboranes.
• suitable anions for the second component may be any stable and bulky anionic complex having the following molecular attributes: 1) the anion should have a molecular diameter greater than 4 A; 2) the anion should form stable ammonium salts; 3) the negative charge on the anion should be delocalized over the framework of the anion or be localized within the core of the anion; 4) the anion should be a relatively poor nucleophile; and 5) the anion should not be a powerful reducing to oxidizing agent.
• Anions meeting these criteria such as polynuclear boranes, carboranes, metallacarboranes, polyoxoanions and anionic coordination complexes are well described in the chemical literature.
• the cation portion of the second component may comprise Bronsted acids such as protons or protonated Lewis bases or may comprise reducible Lewis acids such as ferricinum, tropylium, triphenylcarbenium or silver cations.
• the second component is a Lewis-acid complex which will react with at least one ligand of the first component, thereby forming an ionic species described in formulae 1-4 with the ligand abstracted from the first component now bound to the second component.
• Alumoxanes and especially methylalumoxane the product formed from the reaction of trimethylaluminum in an aliphatic or aromatic hydrocarbon with stoichiometric quantities of water, are particularly preferred Lewis-acid second components.
• the second component reacts with one of the ligands of the first component, thereby generating an ion pair consisting of a Group 4 metal cation and the aforementioned anion, which anion is compatible with and "non-coordinating" toward the Group 4 metal cation formed from the first component.
• the anion of the second compound must be capable of stabilizing the Group 4 metal cation's ability to function as a catalyst and must be sufficiently labile to permit displacement by an olefin, diolefin or an acetylenically unsaturated monomer during polymerization.
• the catalysts of this invention may be supported.
• the Group 4 metal compounds i.e., titanium, zirconium, and hafnium metallocene compounds, useful as first compounds in the preparation of the improved catalyst of this invention are cyclopentadienyl derivatives of titanium, zirconium and hafnium.
• useful titanocenes, zirconocenes, and hafnocenes may be represented by the following general formulae:
• (JS'.- l -y) wherein: (A-Cp) is either (Cp) (Cp*) or Cp-A'-Cp*; Cp and Cp* are the same or different cyclopentadienyl rings substituted with from zero to five substituent groups S, each substituent group S being, independently, a radical group which is a hydrocarbyl, substituted- hydrocarbyl, halocarbyl, substituted-halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyl- substituted organometalloid, disubstituted boron, disubstituted Group 15 elements, substituted Group 16 elements or halogen radicals, or Cp and Cp* are cyclopentadienyl rings in which any two adjacent S groups are joined forming a C4 to C20 ring to give a saturated or unsaturated polycyclic cyclopentadienyl ligand;
• R is a substituent on one of the cyclopentadienyl radicals which is also bonded to the metal atom;
• A' is a bridging group, which group may serve to restrict rotation of the Cp and Cp* rings or (C 5 H5_ y _ x S x ) and JS' (z-x-y) groups; y is 0 or 1; ' (C5H5_y_ x S x ) is a cyclopentadienyl ring substituted with from zero to five S radicals; x is from 1 to 5 denoting the degree of substitution;
• J is an element from Group 15 of the Periodic Table of Elements with a coordination number of 3 or an element from Group 16 with a coordination number of 2
• S is a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, hydrocarbyl-substituted organometalloid, or halocarbyl- substituted organometalloid
• z is the coordination number of the element J
• L is an olefin, diolefin or aryne ligand, or a neutral Lewis base;
• L 1 can also be a second transition metal compound of the same type such that the two metal centers M and M* are bridged by Xi and X' ⁇ , wherein M* has the same meaning as M and X•i has the same meaning as Xi where such dimeric compounds which are precursors to the cationic portion of the catalyst are represented by formula 4;
• w is an integer from 0 to 3; and Xl and X2 are, independently, hydride radicals, hydrocarbyl radicals, substituted hydrocarbyl radicals, halocarbyl radicals, substituted halocarbyl radicals, and hydrocarbyl- and halocarbyl-substituted organometalloid radicals, disubstituted Group 15 element radicals, or substituted Group 16 element radicals; or XI and X2 are joined and bound to the metal atom.to form a metallacycle ring containing from about 3 to about 20 carbon atoms; or X ⁇ and X2 together can be an olefin, diolefin or aryne ligand; or when Lewis-acid activators are used, Xi and X2 can also be joined to form a anionic chelating ligand or can independently be any mono-valent anionic ligand including halides.
• Table 1 depicts representative constituent moieties for the metallocene components of formulae 6- 9. The list is for illustrative purposes only and should not be construed to be limiting in any way. A number of final components may be formed by permuting all possible combinations of the constituent moieties with each other.
• Illustrative compounds of the formula 6 type are: bis(cyclopentadienyl)hafnium dimethyl, ethylenebis(tetrahydroindenyl)zirconium dihidryde, bis(pentamethyl)zirconium ethylidene, dimethylsilyl(l- fluorenyl) (cyclopentadienyl)titanium dichloride and the like.
• Illustrative compounds of the formula 7 type are: bis(cyclopentadienyl) (1,3-butadiene(zirconium) , bis(cyclopentadienyl) (2,3-dimethyl-1,3-butadiene) zirconium, bis(pentamethylcyclopentadienyl) (benzene) zirconium, bis(pentamethylcyclopentadienyl) titanium ethylene and the like.
• Illustrative compounds of the formula 8 type are: (pentamethylcyclopentadienyl) (tetramethylcyclopentadienylmethylene) zirconium hydride, (pentamethylcyclopentadienyl) (tetramethylcyclopentadienyl)-
• Illustrative compounds of the formula 9 type are: dimethylsilyl(tetramethylcyclopentadienyl) (t-butylamido)zirconium dichloride, ethylene(methylcyclopentadienyl) (phenylamido)titanium dimethyl, methylphenylsilyl(indenyl) (phenyphosphido)hafnium dihydride and (pentamethylcyclopentadienyl) (di-t- butylamido)hafnium dimethoxide.
• the above compounds and those permuted from Table 1 include the neutral Lewis base ligand (L 1 ).
• the conditions under which complexes containing neutral Lewis base ligands such as ether or those which form dimeric compounds is determined by the steric bulk of the ligands about the metal center.
• the t-butyl group in M ⁇ 2Si( e4C5) (N-t-Bu)ZrCl has greater steric requirements that the phenyl group in Me2Si(M ⁇ 4C5) (NPh)ZrCl2Et2 ⁇ thereby not permitting ether coordination in the former compound in its solid state.
• Ionic catalysts can be prepared by reacting a transition metal compound with some neutral Lewis acids, such as B(CgFg) 3 or an alumoxane, which upon reaction with the hydrolyzable ligand (X) of the transition metal compound forms an anion, such as ([B(CsF5) 3 (X) ] "" ) , which stabilizes the cationic transition metal species generated by the reaction.
• Ionic catalysts can be, and preferably are, prepared with activator components which are ionic compounds or compositions.
• Compounds useful as an activator component in the preparation of the ionic catalyst systems used in the process of this invention comprise a cation, which is preferably a Bronsted acid capable of donating a proton, and a compatible non-coordinating anion which anion is relatively large (bulky) , capable of stabilizing the active catalyst species (the Group 4 _- cation) which is formed when the two compounds are combined and said anion will be sufficiently labile to be displaced by olefinic diolefinic and acetylenically unsaturated substrates or other neutral Lewis bases such as ethers, nitriles and the like.
• Two classes of compatible non-coordinating anions have been disclosed in copending U.S. Patent Application Nos.
• 133,052 and 133,480 1) anionic coordination complexes comprising a plurality of lipophilic radicals covalently coordinated to and shielding a central charge-bearing metal or metalloid core, and 2) anions comprising a plurality of boron atoms such as carboranes, metallacarboranes and boranes.
• activator compounds containing single anionic coordination complexes which are useful in this invention may be represented by the following general formula:
• [L"-H] is a Bronsted acid
• M 1 is a metal or metalloid
• Q l to Q n are, independently, bridged or unbridged hydride radicals, dialkylamido radicals, alkoxide and aryloxide radicals, hydrocarbyl and substituted- hydrocarbyl radicals, halocarbyl and substituted- halocarbyl radicals and hydrocarbyl and halocarbyl- substituted organometalloid radicals and any one, but not more than one, of Qi to Q n may be a halide radical; m is an integer representing the formal valence charge of M; and n is the total number of ligands q. As indicated above, any metal or metalloid capable of forming an anionic complex which is stable in water may be used or contained in the anion of the second compound.
• Suitable metals include, but are not limited to, aluminum, gold, platinum and the like.
• Suitable metalloids include, but are not limited to, boron, phosphorus, silicon and the like.
• Compounds containing anions which comprise coordination complexes containing a single metal or metalloid atom are, of course, well known and many, particularly such compounds containing a single boron atom in the anion portion, are available commercially. In light of this, salts containing anions comprising a coordination complex containing a single boron atom are preferred.
• the preferred activator compounds comprising boron may be represented by the following general formula: 11. [L"-H] + [BAr ⁇ 2X3X4] "" wherein:
• B is a boron in a valence state of 3;
• Ari and Ar2 are the same or different aromatic or substituted-aro atic hydrocarbon radicals containing from about 6 to about 20 carbon atoms and may be linked to each other through a stable bridging group; and X 3 and X 4 are, independently, hydride radicals, hydrocarbyl and i-ubstituted-hydrocarbyl radicals, halocarbyl and substituted-halocarbyl radicals, hydrocarbyl- and halocarbyl-substituted organometalloid radicals, disubstituted Group 15 element radicals, substituted Group 16 element radicals and halide radicals, with the proviso that X 3 and X4 will not be halide at the same time.
• Ar ⁇ and Ar2 may, independently, be any aromatic or substituted-aromatic hydrocarbon radical.
• Suitable aromatic radicals include, but are not limited to, phenyl, naphthyl and anthracenyl radicals.
• Suitable substituents on the substituted-aromatic hydrocarbon radicals include, but are not necessarily limited to, hydrocarbyl radicals, organometalloid radicals, alkoxy and aryloxy radicals, alkylamido radicals, fluorocarbyl and fluorohydrocarbyl radicals and the like such as those useful as X 3 and X 4 .
• the substituent may be ortho, meta or para, relative to the carbon atoms bonded to the boron atom.
• each may be the same or a different aromatic or substituted- aromatic radical as are Ar ⁇ and Ar2, or the same may be a straight or branched alkyl, alkenyl or alkynyl radical, a cyclic hydrocarbon radical or an alkyl- substituted cyclic hydrocarbon radical.
• X 3 and X4 may also, independently be alkoxy or dialkylamido radicals wherein the alkyl portion of said alkoxy and dialkylamido radicals, hydrocarbyl radicals and organometalloid radicals and the like.
• Ar ⁇ and Ar2 could be linked to either X 3 or X4.
• X 3 and X4 may also be linked to each other through a suitable bridging group.
• the most preferred activator compounds comprising boron may be represented by the following general formula: 12. [L"-H] + [B(C 6 F 5 ) 3 Q]- wherein:
• F is fluorine
• C is carbon and B, L 1 , and Q are defined hereinabove.
• Polymeric Q substituents on the most preferred anion offer the advantage of providing a highly soluble ion- exchange activator component and final ionic catalyst.
• Soluble catalysts and/or precursors are often preferred over insoluble waxes, oils, phases, or solids because they can be diluted to a desired concentration and can be transferred easily using simple equipment in commercial processes.
• Activator components based on anions which contain a plurality of boron atoms may be represented by the following general formulae:
• [L"-H] is either H+ or a Bronsted acid derived from the protonation of a neutral Lewis base
• X, X', X", XQ , X ⁇ and XQ are, independently, hydride radicals, halide radicals, hydrocarbyl radicals, substituted-hydrocarbyl radicals, halocarbyl radicals, substituted-halocarbyl radicals, or hydrocarbyl- or halocarbyl-substituted organometalloid radicals;
• a trisubstituted ammonium salt of a borane or carborane anion satisfying the general formula: wherein: ax is either 0 or 1; ex is either 1 or 2 ; ax + ex 2; and bx is an integer ranging from about 10 to 12;
• a trisubstituted ammonium salt of a metallaborane or metallacarborane anion satisfying the following general formula: 17. [[[(CH) a2 (BH) mz (H) bz ] cz -] 2 M nz+ ] dz - wherein: az is an integer from 0 to 2; bz is an integer from 0 to 2; cz is either 2 or 3; mz is an integer from about 9 to 11; az + bz + cz 4; and nz and dz are, respectively, 2 and 2 or 3 and 1.
• Illustrative, but not limiting, examples of second components which can be used in preparing catalyst systems utilized in the process of this invention wherein the anion of the second component contains a plurality of boron atoms are mono-, di-, trialkylammonium and phosphonium and dialkylarylammonium and -phosphonium salts such as bis[tri(n-butyl)ammonium] dodecaborate, bis[tri(n- butyl)ammonium]decachlorodecaborate, tri(n- butyl)ammonium dodecachlorododecaborate, tri(n- butyl)ammonium 1-carbadecaborate, tri(n-butyl)ammonium 1-carbaundecaborate, tri(n-butyl)ammonium 1- carbadodecaborate, tri(n-butyl)ammonium 1- trimethylsilyl-1-carbadecaborate, tri(n-butyl)
• An alumoxane is generally a mixture of both the linear and cyclic compounds.
• R 3 , R 4 , R 5 and R 6 are, independently a Ci- ⁇ alkyl radical, for example, methyl, ethyl, propyl, butyl or pentyl and "p" is an integer from 1 to about 50. Most preferably, R 3 , R 4 , R 5 and R 6 are, each methyl and "p" is a least 4.
• R ° groups may be halide.
• M' and M are as described previously and Q' is a partially or fully fluorinated hydrocarbyl.
• alumoxanes can be prepared by various procedures.
• a trialkyl aluminum may be reacted with water, in the form of a moist inert organic solvent; or the trialkyl aluminum may be contacted with a hydrated salt, such as hydrated copper sulfate suspended in an inert organic solvent, to yield an alumoxane.
• a hydrated salt such as hydrated copper sulfate suspended in an inert organic solvent
• Suitable alumoxanes which may be utilized in the catalyst systems of this invention are those prepared by the hydrolysis of a trialkylaluminu , such as trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, dimethylaluminum chloride, diisobutylaluminum chloride, diethylaluminum chloride and the like.
• a trialkylaluminu such as trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, dimethylaluminum chloride, diisobutylaluminum chloride, diethylaluminum chloride and the like.
• the most preferred alumoxane for use is methylalumoxane (MAO) .
• Methylalumoxanes having an average degree of oligomerization of from 4 to 25 (“p" 4 to 25) , with
• an alumoxane is not a discrete material.
• a typical alumoxane will contain free trisubstituted or trialkyl aluminum, bound trisubstituted or trialkyl aluminum, and alumoxane molecules of varying degree of oligomerization.
• Those methylalumoxanes most preferred contain lower levels of trimethylaluminum. Lower levels of trimethylaluminum can be achieved by reaction of the trimethylaluminum with a Lewis base or by vacuum distillation of the trimethyl aluminum or any other means known in the art.
• some alumoxane molecules are in the anionic form as represented by equations 1- 3, and thus for our purposes, are considered "non- coordinating" anions.
• the activator compositions most preferred for forming the ionic catalyst used in this process are those containing a tetrapentafluorophenyl boron anion; two or more tripentafluorophenyl boron anion groups covalently bond to a central atomic molecular or polymeric complex or particle; tripentafluorophenyl boron; or methylalumoxane.
• Other examples of activator specific compositions which may be used to form an anionic catalyst useful in this invention are identified and more fully described in European Patent Application Nos. 0 277 003 and 0 277 004 and WO 92/00333 which are hereby incorporated by reference.
• This invention relates to a process to produce long chain branched polymers, to catalysts used to produce long chain branched polymers and to the polymers themselves.
• This invention relates to a method for producing polymers with substantially linear long chain branching comprising contacting, under polymerization conditions, a vinyl terminated polymer (macromonomer) with a chain length of 250 or more carbons, with one or more olefin monomers and a metallocene catalyst system comprising a mono, di, or tri cyclopentadienyl transition metal catalyst cocatalized with a non-coordinating anion or an alumoxane or a Lewis acid activator.
• This invention also contemplates a process for producing a branched polymer comprising: contacting in the presence of a polymerization catalyst system,
• a macromonomer at least 250 carbons long comprising one or more C2-C 30 olefinic monomer units said macromonomer having chain end vinyl unsaturation
• a polymerizable olefinic monomer or monomer mixture under conditions to (co)polymerize the monomers and incorporate the macromonomer into the growing (co)polymer chain via the chain end unsaturation, said catalyst system comprising mono-, di-, or tri- cyclopentadienyl transition metal catalyst cocatalized with a non-coordinating anion, an aluminium alkyl, or an alumoxane.
• the reaction is maintained at 70°C, more preferably 70 to 100 ⁇ C, even more preferably at 90°C.
• the weight ratio of macromonomer to olefin monomer present is between about 1:1 to about 1:5, preferably about 1:1.5 to about 1:3, more preferably about 1:2.
• the branched polymers of this invention are comprised of a family of polyolefins and olefin copolymers which are copolymerizable by metallocene polymerization.
• Long chain branched polymers of this type are made by copolymerization of vinyl terminated polymers with the desired ethylenically unsaturated monomer or monomers.
• the family of polyolefins includes low to high density polyethylene or ethylene- alpha-olefin copolymers as well as polypropylene and polypropylene copolymers.
• the vinyl terminated polymers useful in this invention include high density polyethylene and polyethylene copolymers. Production of these polymers gives control over the side-chain molecular weight and composition.
• the branched polymers of this invention can be a low-density polyethylene with a high-density polyethylene branch. They are also not limited to side-chains consisting of the same polymer composition as the backbone. Likewise it is noted that the macromonomers can comprise homopolymers or copolymers of olefins, particularly of C 2 to C 30 alpha olefins. specifically a copolymer or polymer with more than 250 carbons that has vinyl termination can be used.
• the metallocene catalysts disclosed in this invention can produce vinyl- terminated homopolymers and copolymers. However, another method the produce vinyl termination is to produce a polymer with an ethylene "cap" or end with the needed vinyl group.
• the main chain and the sidechains may be the same of different olefin homo or copolymers.
• main and side chains of ethylene are preferred.
• the ability to prepare long-chain branched olefins in which the side-chain compositions are significantly different from the backbone adds a unique dimension to the polymers of this invention
• the branched polymers of this invention typically have a weight average molecular weight at or above 50,000, preferably 50,000 to 1,000,000 and a Mw/Mn of 6 or less.
• the vinyl terminated polymers (macromers) that become the side chains in the branched polymers of this invention are typically more than 200 carbons long, preferably 250 to 3500, even more preferably 300 to 3000 carbons long. Further these side chains insert into the main chain at an average of up to 5 side chains per 1000 main chain carbons, although it is statistically possible for a particular main chain to have no side chains.
• a narrow composition distribution of the side chains may be obtained.
• a narrow composition distribution means that among the individual polymer main chains the number of side chains are roughly similar. For example, three main chains with 2, 3, and 2 side chains respectively have a very narrow composition distribution, while three main chains with 3, 9, and 20 sides chains, respectively, have a broad composition distribution.
• the main chain is a copolymer made using a titanium containing monocyclopentadienyl metallocene catalyst, it will have a narrow composition distribution and higher comonomer incorporation than traditional coordination catalysts.
• the vinyl terminated macromonomer can be produced in one step of a continuous or series process which then proceeds to copolymerize the macromonomer with one or more alpha olefins. It is also comtemplated that the macromonomer can be produced separately by one process and then polymerized later in a separate similar or different process.
• a large group of metallocene catalysts may be selected from to produce both the vinyl terminated polymers (macromers) and the branched polymers of this invention.
• the choice of catalyst system is influenced by the characteristics desired in the final product. For example, a noncoordinating anion activation system rather than MAO could be found to be preferable to avoid isomerization problems, or the metallocene catalyst Cp2ZrM ⁇ 2 (bis cyclopentadienyl zirconium dimethyl) with (pfp) 3 B (perflourotriphenyl boron) as the cocatalyst activator could be chosen because of this system's high activity at higher temperatures such as 90°C and above.
• this catalyst system gives high levels of vinyl ends during polymerization in hexane and few or no vinyl ends when polymerized in toluene.
• the resulting vinyl terminated polymers are branched. This branching can be eliminated if a sterically hindered catalyst like (MesCp)2 rM ⁇ 2 (bis pentamethylcyclopentadienyl zirconium dimethyl) is used.
• This catalyst system sterically inhibits the copolymerization of vinyl terminated polymers.
• the vinyl terminated macromonomers of this invention can be branched. However the level of this branching does not approach a dendritic structure. These macromers and those that have little or no side chain branching or are substantially linear will be referred to as linear.
• the catalyst choices for copolymerization of vinyl terminated polymers with other monomers are also large and include catalyst systems containing bridged and unbridged bis cyclopentadienyl transition metal compounds as well as monocyclopentadienyl transition metal compounds.
• Monocyclopentadienyl transition metal catalysts are preferred as they polymerize large "monomers" well.
• monocyclopentadienyl (Mono Cp) transition metal catalysts, particularly titanium incorporate more monomer than coordination catalysts.
• a Mono Cp Ti catalyst to make lower density products over the Tris(perfluorophenyl)Boron activated systems utilized in example 1 and 2 to make high density material.
• Molten polyethylene is highly viscous.
• the viscosity is a function of weight-average molecular weight (M w ) ; molecular weight distribution (M w /M n ) , also called the index of polydispersity; and the shear rate exerted on the polymer.
• M w weight-average molecular weight
• M w /M n molecular weight distribution
• the molecular weight values are in part related to branching of the polymer.
• Molten polyethylene is classified as a pseudoplastic fluid, which means that its viscosity decreases with increasing shear rate.
• the relationship between viscosity and shear rate depends upon the molecular weight distribution and degree of long chain branching of the polymer. Polymers having a broad molecular weight distribution tend to have lower viscosity values at conditions of high shear rates than polymers having a narrow molecular weight distribution while having equivalent viscosities at conditions of low shear rates.
• viscosity as a function of shear rate is also dependent upon the degree of long chain branching of a polymer which affects molecular weight distribution.
• a polymer with long chain branching will have higher viscosity values at low shear rates and lower viscosity values at high shear rates compared to an unbranched polymer with equivalent molecular weight.
• Lower viscosity at high shear rates means the long chain branched polymer can be extruded at lower temperatures and at a higher rate which results in less energy consumption.
• the inventors have found that the positive viscosity processing characteristics of a polymer at both ends of the shear rate range may be achieved by polymers in accordance with the present invention.
• the predictable solid polymer mechanical properties achievable by polymers in accordance with the present invention are good impact and tear resistance, good environmental stress crack resistance (ESCR) values, good tensile properties, good modulus/density balance, good reblock/density balance, and good clarity, relative to linear polyethylenes without long chain branching.
• This unique balance of favorable polymer melt processability and solid polymer mechanical characteristics is achieved through the creation of remote long chain branching at a frequency and length great enough to impart processability characteristics of LDPEs but at a low enough frequency so as not to destroy the superior solid polymer physical characteristics of LPEs.
• this balance is achieved by the introduction of some linear long chain branches having a average molecular weight greater than the critical molecular weight for entanglement (M c ) of the polymer with a linear long chain branching frequency less than 5.0 branches per 1,000 carbon atoms of the main polymer chains.
• M c critical molecular weight for entanglement
• These polymers may be produced over a wide range of molecular weight distributions (M w /M n ) (index of polydispersity) of 2.0 to 10.
• the frequency of long chain branching is less than 5 branches per 1,000 carbon atoms of the main polymer chains (preferably an average frequency of 0.2 to 3 chains per 1000 C, atom, even more preferably an average frequency of 0.9 to 2 chains per 1000 C, even more preferably an average frequency of 1 to 2 chains per 1000 C) with a preferred molecular weight distribution range of about 2 to about 6, more preferably 2 to 4.
• compositions can be branched. This may occur when a branched polymer is blended with another polymer or when the branched polymer is part of a reactor blend.
• branched polymer is present at least 5 weight percent, even more preferably at least 10 weight percent, even more preferably at least 40 to 70 weight percent.
• the viscosity characteristics of polymers of the present invention are not the only processing advantages.
• Another advantage of polymers having linear long chain branching in accordance with the present invention are the superior elastic characteristics of the polymer melt.
• Molten polyethylene exhibits elastic properties over a wide temperature range. After molten polyethylene passes through the die of an extruder under pressure, the strand of polyethylene increases in diameter or thickness. This is known as extrudate swell. At low shear rates, extrudate swell increases as molecular weight and long chain branching increase. In other words, extrudates typically swell as molecular weight distribution broadens.
• Polymers produced in accordance with the present invention exhibit increased extrudate swell.
• the significance of this increased extrudate swell is that is a reflection of what is known as the elastic nature of the polymer.
• the elastic nature of the polymer is very important in certain polymer melt extrusion processes such as the manufacture of tubular film, chill roll casting and extrusion coating in which an extruded web of film is produced which is stretched in the direction of flow. Such extrusion processes can only be carried out with materials that are able to sustain a tensile stress on the melt. In other words, it is important that the polymer melt be somewhat elastic. There should be a balance between the elasticity of the polymer melt and the viscosity in blow molding operation.
• the balance between elasticity and viscosity of the polymer melt affects polymer parison integrity. If the balance of properties is in favor of viscosity over elasticity, the polymer melt will not have good stability and tend to sag during certain extrusion processes. There is a strong correlation between extrudate swell ratios and parison integrity.
• the introduction of long chain branching in accordance with the present invention results in polymer melts having swell ratios indicative of good elastic properties for extrusion processes.
• the presence of a small amount of long chain branching in a linear molecule increases elasticity of the polymer melt by introducing very long relaxation times in the relaxation spectrum of the melt.
• Long chain branching in accordance with the present invention has another important advantage of changing the elongational characteristics of polymer melts.
• the presence of long chain branching increases the value of the longational viscosity and introduces a maximum elongation viscosity as a function of strain rate.
• the polymers produced in accordance with the present invention have still another advantage of having a reduced tendency to melt fracture at high shear rates. Smooth extrudates of polymer melts may be obtained easily at low shear rates.
• the critical shear rate of a polymer is related to the degree of entanglement of the polymer. The greater the degree of entanglement of the polymer, the lower the critical shear rate. Since the polymers produced in accordance with the present invention, due to the linear long chain branching, have less entanglement than linear polymers, the critical shear rate of these polymers will be increased. The result is that polymers made in accordance with the present invention have a reduced tendency to melt fracture at high shear rates than conventional linear polymers.
• the polymers of the present invention also enjoy the good solid polymer mechanical properties associated with short chain branching distributions of single site catalyst polymerizations.
• the polymers produced in accordance with the present invention may have high molecular weights with narrow molecular weight distributions. These narrow distributions result in products having lower extractables caused by amorphous waxes, better clarity due to the absence of large light refracting crystals, and superior impact resistant due to increased number of tie molecules binding crystal regions together.
• the frequency of chain branching is determined by 13C NMR spectrometry for homopolymers and by measuring the viscous energy of activation of copolymers with a parallel plate oscillating shear melt rheometer.
• GPC gel permeation chromatography
• LALLS low angle light scattering
• Sample A is an ethylene-hexene copolymer made in a gas phase process with a metallocene catalyst which is known to have no long chain branches.
• RI refractive index detector
• LALLS detection method By comparing the molecular weight values calculated by the standard refractive index detector (RI) and the LALLS detection method, one sees that there is no significant difference in the values suggesting there are no hidden branches. Comparing the RI and LALLS values for sample B, an increase of 5,000 in molecular weight is seen by the LALLS detection method. With sample C, a 25,000 molecular weight increase is detected. The higher molecular weight of samples B and C as determined with the LALLS detector are evidence of long chain branching.
• Hi ⁇ h viscous energy of activation (Ea) .
• Polymer viscous energy of activation can be determined with parallel plate shear melt rheometry. Melt viscosity-temperature dependence is determined by performing shear rate superposition. The resulting shift factors are fitted to an Arrhenius equation; the product is the viscous energy of activation.
• HDPE represents narrow MWD, linear homopolymers in the 5-50 MI range.
• LLDPE represents narrow MWD, linear ethylene-butene copolymers with comonomer content "12% and MI in the 1-2 dg/min range.
• HMW-HDPE represents narrow MWD, linear ethylene homopolymers with Mw's greater than 200k (i.e., MI ⁇ 0.2 dg/min).
• LDPE represents long-chain branched, ethylene homopolymers produced in a free-radical process.
• the LPE w/ LCB represents some of the branched polymers of this invention.
• melt viscosities can be measured vs. shear rate with a capillary rheometer.
• the position of the LDPE samples reflects the known fact that LDPEs are more "shear thinning" than linear polyethylenes, i.e., their viscosities decrease more rapidly as shear rate increases than do the viscosities of linear polyethylenes.
• the position of the LPE w/ LCB is clear evidence that this NMWD linear homopolymer contains long-chain branching.
• the branched polymers of this invention have a viscosity measured at 340sec- 1/190°C of 0.75(0.0115 x Mw - 325).
• melt strength can be determined with a Rheotens Instrument which consists of a capillary rheometer equipped with an accelerating wheel take-off station.
• the melt tensile force in the capillary rheometer extrudate is measured as a function of the instantaneous wheel velocity.
• the branched polymers of this invention will exhibit a melt tensile force of 1.3((7.68 x 10 ⁇ 5 ) x (Mw of the polymer) - 4.32) .
• the unusually high tensile force observed with the LDPE is attributed to its long-chain branching.
• Evidence of the maximum frequency of the long-chain branches in a linear polymer can be determined with carbon-13 NMR if the polymer contains no short-chain branches, due to the comonomer, which are larger than 3 carbons in length.
• the carbon atom in the polymer's backbone to which a branch, which is larger than 3 carbons in length, is attached produces a signal in the C13-NMR spectrum at 38 ppm, which is distinguishable from all other carbons in the qualifying test sample and therefore a measure of the maximum number of long- chain branch points.
• the density of the polymer was 0.953 g/cm , with a weight- average molecular weight (M w ) of 29,000 with a level of vinyl that was not detected by NMR, and an index of polydispersity (M w /M n ) of 3.28.
• the polymer had a chain branching frequency of 0.48 branches per 1,000 carbon atoms of the main polymer chains by 13 C NMR analysis.
• EXAMPLE 2 Polymerization with Macromer A
• a one liter solution polymerization autoclave reactor was charged with 400ml toluene, 25g of macromer A produced in example 1 (linear ethylene homopolymer having a weight-average molecular weight (M w ) of 29,000 with very low levels, i.e. not detected, of vinyl unsaturations per 1,000 carbon atoms) and 100 psig ethylene, and 0.24 millimoles of bis (cyclopentadiene) dimethyl zirconium tris (pentafluorophenyl) boron catalyst (in toluene) with an initial reactor temperature of 45°C. The solution temperature was raised to 102"C and reacted for 0.33 hours.
• M w weight-average molecular weight
• the polymerization yielded 57.0 g of polymer after drying in a vacuum oven for 24 hours until odor-free.
• the dried polymer consisted of irregularly-shaped particles ranging in size from less than 0.1 mm to greater than 1.0 cm.
• the density of the polymer was 0.953 g/cm 3 , with a weight-average molecular weight (M w ) of 82,500 and an index of polydispersity (M w /M n ) of 5.3
• the polymer had a long chain branching frequency of 2 long chain branches per 1,000 main chain carbon atoms by 13 C NMR analysis.
• a one liter autoclave solution polymerization reactor was charged with 400 ml of hexane, 20 psig ethylene, and 60 mg of bis (cyclopentadiene) dimethyl zirconium catalyst and 60 mg of tris (pentafluoronyl) boron catalyst activator. The mixture was reacted at 90°C for 0.7 hours. The polymerization yielded 26g of polymer after drying in a vacuum oven for 24 hours until odor-free. The weight-average molecular weight (M w ) of the polymer was 21,000 and the index of polydispersity (M w /M n ) was 8.2. The polymer had a chain branching frequency of 1.22 branches per 1,000 main chain carbon atoms of the main polymer chains by 13 C NMR analysis.
• a one liter autoclave solution polymerization reactor was charged with 400ml of toluene, 25g macromer B produced in example 3(linear ethylene homopolymer having a weight-average molecular weight (M w ) of 21,000 and 1.0 vinyl unsaturations per 1,000 carbon atoms) and 50 psig ethylene, and 0.24 milimoles bis (cyclopentadiene) dimethyl zirconium tris (pentafluorophenyl) boron catalyst (in toluene) .
• the mixture was reacted at 60°C (42° exotherm)for 0.28 hours.
• the polymerization yielded 78.8g of polymer after drying in a vacuum oven for 24 hours until odor- free.
• the weight-average molecular weight (M w ) was 32,000 and index of polydispersity or MWD, (M w /M n ) was 3.0.
• the polymer had a linear long chain branching frequency of 0.48 branches per 1,000 carbon atoms of the main polymer chains by 13 C NMR analysis.

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