Patent Description:
Ziegler-Natta ("ZN") catalysts are widely used to polymerize ethylene and propylene monomers into polyolefin polymers. ZN catalysts can be exemplified by the magnesium/titanium catalyst system described in <CIT> and <CIT>, and the pre-activation procedure using a mixture of organometallic compounds as described in <CIT>. The catalysts are typically dry powders such as the commercially available UCAT™ A Catalyst available from Univation Technologies, LLC, Houston, TX. Other ZN catalysts are formed by spray drying and used in slurry form. Such a catalyst, for example contains titanium, magnesium, and an electron donor, and optionally, and aluminum halide. The catalyst is then introduced into a hydrocarbon medium such as mineral oil to provide the slurry form. Such a spray dried slurry catalyst is described in <CIT>and<CIT>.

For ZN catalysts stored and/or transported to polymerization units as powders, catalyst activity may suffer when stored and/or transported for longer period of times or when stored and/or transported at elevated temperatures such as those temperatures typical of tropical or arid regions. Thus, catalyst activity, reduction of production rates, varying comonomer and hydrogen responses, and polymer properties can be affected due to aging of the catalyst. "Aging" is typically described as catalyst deactivation or loss of catalyst activity. For example, the degree of aging is typically ascertained by measuring the activity or productivity of a given catalyst batch over an extended period.

Various methods and systems for testing catalyst systems have been developed. For instance,<NPL>; <NPL>; <NPL>; and <NPL>, generally, discuss methods of using high-throughput screening methods and devices in the development and evaluation of catalyst systems. Various test methods are also discussed in <CIT>, <CIT>, and <CIT>, <CIT>, and <CIT>. Other background references include <CIT>, <CIT>, <CIT>, and <CIT>.

<CIT> discloses a process for the storage of olefin polymerisation catalyst components comprises storing solid Ziegler-Natta catalyst components containing mainly Ti, Mg, a halogen and an electron donor under CO2 or an inert gas containing CO2. <CIT> discloses a process for preparing a storage-stable catalytic complex for stereospecific α-olefin polymerization, by preactivation with a preactivator shortly after catalyst complex preparation. <CIT> discloses for improving the storage stability of a Ziegler catalyst composed of a titanium-containing solid ingredient and an organoluminum compound, by first subjecting the catalytic composition to a pre-polymerization treatment and then to a contacting treatment with carbon dioxide and/or carbon monoxide.

However, there remains a need to reduce the loss of catalyst activity in polymerization processes that employ ZN catalysts, especially those ZN catalysts that are reduced with aluminum alkyl compounds that are stored and/or transported as dry powders.

The invention provides for a process for reducing the loss of catalyst activity of a Ziegler-Natta catalyst as described in the attached claims.

The invention also provides for a process comprising: storing and/or transporting a reduced ZN catalyst for at least <NUM> days at a temperature of <NUM> or less; contacting the reduced ZN catalyst with one or more one or more olefin monomers under polymerizable conditions; and recovering the polyolefin polymers as described in the attached claims.

Other embodiments of the invention are described and claimed herein and are apparent by the following disclosure.

Processes for reducing the loss of catalyst activity are provided. In a class of embodiments, the catalyst may have a fresh catalyst activity and aged, stored and/or transported at a controlled temperature to provide an aged catalyst system having an aged catalyst activity that is at least <NUM>% of the fresh catalyst activity. As used herein, "fresh catalyst activity" refers to the catalyst activity of the catalyst system when it is fed to the polymerization system soon (before the catalyst substantially changes) after the catalyst is manufactured.

As used herein, "catalyst aging" refers to the phenomenon wherein the responses of the catalyst change over a period of time during which the catalyst is stored and/or transported after manufacture. These changes in catalyst responses are reflected in the fact that the catalyst will have different response(s) when compared to producing a polymer at the same conditions with a catalyst made by the same recipe but one which has been stored and/or transported under different conditions and for a different period of time.

As used herein, "aged catalyst activity" refers to the catalyst activity of a catalyst when it is fed to the polymerization system after the catalyst has been stored and/or transported for a period of at least <NUM> days, preferably at least <NUM> days, more preferably at least <NUM> days, and even more preferably at least <NUM> days. The aged catalyst activity is at least <NUM>% of the fresh catalyst activity, preferably greater than <NUM>% of the fresh catalyst activity, and even more preferably greater than <NUM>% of the fresh catalyst activity.

As used herein, "at a controlled temperature" refers to maintaining the temperature within given range taking into account the temperature at times may exceed either end of the range so long as the nature of the chemical or composition that is being controlled at a given temperature or temperature range is not materially altered or effected. The controlled temperature is <NUM> or less; such as <NUM> or less, <NUM> or less; <NUM> or less; or <NUM> or less. The controlled temperature also can be a temperature that is maintained within <NUM> (+/- of a given temperature); alternatively, within <NUM> (+/- of a given temperature); alternatively, within <NUM> (+/- of a given temperature); alternatively, within <NUM> (+/- of a given temperature); and alternatively, within <NUM> (+/- of a given temperature).

A process for polymerizing polyolefin polymers is also disclosed herein, the process comprising: a) preparing a Ziegler-Natta (ZN) catalyst by contacting the ZN catalyst with at least one aluminum alkyl compound to produce a reduced ZN catalyst; b) optionally, drying the reduced ZN catalyst; c) storing and/or transporting the reduced ZN catalyst for at least <NUM> days at a temperature of <NUM> or less; d) polymerizing one or more olefin monomers under polymerizable conditions with the reduced ZN catalyst; and e) recovering the polyolefin polymers. As used herein, "polymerizable conditions" refer those conditions including a skilled artisan's selection of temperature, pressure, reactant concentrations, optional solvent/diluents, reactant mixing/addition parameters, and other conditions within at least one polymerization reactor that are conducive to the reaction of one or more olefin monomers when contacted with an activated olefin polymerization catalyst to produce the desired polyolefin polymer.

The terms "catalyst" and "catalyst system" are intended to be used interchangeably and refer to any one or more polymerization catalysts, activators, co-catalysts, supports/carriers, or combinations thereof. The catalyst, for example, may include any Ziegler-Natta (ZN) transition metal catalyst, such as those catalysts disclosed in <NPL>); or in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT> and <CIT>. Other examples of ZN catalysts are discussed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT> and <CIT>. In general, ZN catalysts include transition metal compounds from Groups <NUM> to <NUM>, or Groups <NUM> to <NUM>, or Groups <NUM> to <NUM> of the Periodic Table of Elements. As used herein, all reference to the Periodic Table of the Elements and groups thereof is to the <NPL>), unless reference is made to the Previous IUPAC form denoted with Roman numerals (also appearing in the same), or unless otherwise noted. Examples of such catalysts include those comprising Group <NUM>, <NUM> or <NUM> transition metal oxides, alkoxides and halides, or oxides, alkoxides and halide compounds of titanium, zirconium or vanadium; optionally in combination with a magnesium compound, internal and/or external electron donors (alcohols, ethers, siloxanes, etc.), aluminum or boron alkyl and alkyl halides, and inorganic oxide supports.

ZN catalysts may be represented by the formula: MRx, where M is a metal from Groups <NUM> to <NUM>, preferably Groups <NUM> to <NUM>, more preferably Group <NUM>, most preferably titanium; R is a halogen or a hydrocarbyloxy group; and x is the valence of the metal M. Non-limiting examples of R include alkoxy, phenoxy, bromide, chloride and fluoride.

In a class of embodiments, the ZN catalysts may include at least one titanium compound having the formula Ti(OR)aXb, wherein R is selected from the group consisting of a C<NUM> to C<NUM> aliphatic or aromatic, substituted or unsubstituted, hydrocarbyl group; X is selected from the group consisting of Cl, Br, I, and combinations thereof; a is selected from the group consisting of <NUM>, <NUM> and <NUM>; b is selected from the group <NUM>, <NUM>, <NUM>, and <NUM>; and a + b = <NUM> or <NUM>. As used herein, "hydrocarbyl" refers to a moiety comprising hydrogen and carbon atoms.

Non-limiting examples where M is titanium include TiCl<NUM>, TiCl<NUM>, TiBr<NUM>, Ti(OCH<NUM>)Cl<NUM>, Ti(OC<NUM>H<NUM>). <NUM>Cl, Ti(OC<NUM> H<NUM>)Cl<NUM>, Ti(OC<NUM>H<NUM>)<NUM>Cl, Ti(OC<NUM>H<NUM>)<NUM>Cl<NUM>, Ti(OC<NUM>H<NUM>)<NUM>Br<NUM>, Ti(OC<NUM>H<NUM>)Cl<NUM>, Ti(OCOCH<NUM>)Cl<NUM>, Ti(OCOC<NUM>H<NUM>)Cl<NUM>, TiCl<NUM>/3AlCl<NUM>, Ti(OC<NUM> H<NUM>)Cl<NUM>, and combinations thereof.

In a class of embodiments, the ZN catalysts may include at least one magnesium compound. The at least one magnesium compound may have the formula MgX<NUM>, wherein X is selected from the group consisting of Cl, Br, I, and combinations thereof. The at least one magnesium compound may be selected from the group consisting of: MgCl<NUM>, MgBr<NUM> and MgI<NUM>. ZN catalysts based on magnesium/titanium electron-donor complexes that are useful in the invention are described in, for example, <CIT> and <CIT>. ZN catalysts derived from Mg/Ti/Cl/THF are also contemplated, which are well known to those of ordinary skill in the art.

Still other suitable ZN catalysts are disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT> and <CIT> and published <CIT> A2 and <CIT>.

The catalyst system may further be contacted with a co-catalyst also known as an activator or modifier, for example, at least one alkyl aluminum compound. Suitable co-catalysts may be represented by the formula M<NUM> M<NUM>v X<NUM>c R<NUM>b-c, wherein M<NUM> is a metal from Group <NUM> to <NUM> and <NUM> to <NUM> of the Periodic Table of Elements; M<NUM> is a metal of Group <NUM> of the Periodic Table of Elements; v is a number from <NUM> to <NUM>; each X<NUM> is any halogen; c is a number from <NUM> to <NUM>; each R<NUM> is a monovalent hydrocarbon radical or hydrogen; b is a number from <NUM> to <NUM>; and wherein b minus c is at least <NUM>.

Non-limiting examples of co-catalysts include methyllithium, butyllithium, dihexylmercury, butylmagnesium, diethylcadmium, benzylpotassium, diethylzinc, tri-n-butylaluminum, diisobutyl ethylboron, diethylcadmium, di-n-butylzinc and tri-n-amylboron, and, in particular, the aluminum alkyl compounds, such as tri-hexyl-aluminum, triethylaluminum, trimethylaluminum, and triisobutylaluminum. Other co-catalysts include mono-organohalides and hydrides of Group <NUM> metals, and mono- or di-organohalides and hydrides of Group <NUM> and <NUM> metals. Non-limiting examples of these co-catalysts include di-isobutylaluminum bromide, isobutylboron dichloride, methyl magnesium chloride, ethylberyllium chloride, ethylcalcium bromide, di-isobutylaluminum hydride, methylcadmium hydride, diethylboron hydride, hexylberyllium hydride, dipropylboron hydride, octylmagnesium hydride, butylzinc hydride, dichloroboron hydride, di-bromo-aluminum hydride and bromocadmium hydride. Additional co-catalysts may be found in <CIT> and <CIT>.

In a class of embodiments, the aluminum alkyl compound may be selected from the group consisting of at least one of tri-n-hexyl aluminum, triethyl aluminum, diethyl aluminum chloride, trimethyl aluminum, dimethyl aluminum chloride, methyl aluminum dichloride triisobutyl aluminum, tri-n-butyl aluminum, diisobutyl aluminum chloride, isobutyl aluminum dichloride, (C<NUM>H<NUM>)AlCl<NUM>, (C<NUM>H<NUM>O)AlCl<NUM>, (C<NUM>H<NUM>)AlCl<NUM>, (C<NUM>H<NUM>O)AlCl<NUM>, (C<NUM>H<NUM>O)AlCl<NUM>, and combinations thereof.

The catalyst system may optionally be supported. The terms "support" or "carrier" are used interchangeably herein and refer to any support material, including inorganic or organic support materials. The term "supported" as used herein refers to one or more compounds that are deposited on, contacted with, vaporized with, bonded to, or incorporated within, adsorbed or absorbed in, or on, a support or carrier. In some embodiments, the support material can be a porous or semi-porous support material. In other embodiments, the support material can be a non-porous support material.

Non-limiting examples of support materials include inorganic oxides and inorganic chlorides, and in particular such materials as talc, clay, silica, alumina, magnesia, zirconia, iron oxides, boria, calcium oxide, zinc oxide, barium oxide, thoria, aluminum phosphate gel, and polymers such as polyvinylchloride and substituted polystyrene, functionalized or crosslinked organic supports such as polystyrene divinyl benzene polyolefins or polymeric compounds, and mixtures thereof, and graphite, in any of its various forms. Non-limiting examples of inorganic support materials include inorganic oxides and inorganic chlorides.

Commercial supports include the ES70 and ES757 family of silicas available from PQ Corporation, Malvern, Pennsylvania. Other commercial supports include Sylopol™ Silica Supports including <NUM> silica and <NUM> silica available from Grace Catalyst Technologies, Columbia, Maryland.

Examples of supporting a catalyst system are described in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>; and <CIT>; <CIT>; <CIT>; and <CIT>.

In a class of embodiments, one general example of preparing a ZN catalyst includes the following: dissolve TiCl<NUM> in a heterocyclic solvent such as tetrahydrofuran (THF) or oxolane, reduce the compound to TiCl<NUM> using Mg or other suitable reduction agent, add MgCl<NUM>, and remove the solvent. The MgTiCl<NUM> (ethyl acetate)<NUM> derivative is particularly preferred.

The ZN catalyst is prepared by providing a precursor composition of the ZN catalyst comprising at least one titanium compound; contacting the at least one titanium compound in the precursor composition with at least one aluminum alkyl compound in a hydrocarbon solvent, such as an alkane (e.g., pentane or isopentane) or aliphatic mineral oil, where the aluminum alkyl compound converts the at least one titanium compound in the precursor composition into a modified state of the ZN catalyst; and removing at least a portion of the aluminum alkyl compound in the hydrocarbon solvent not consumed in converting the at least one titanium compound into the modified state. The hydrocarbon solvent may also be selected from the group consisting of at least one of isopentane, hexane, heptane, toluene, xylene, naptha, and combinations thereof.

Optionally, the hydrocarbon solvent may be removed from the modified precursor composition of the ZN catalyst. In a class of embodiments, a schematic is provided below of the synthesis of a ZN catalyst followed by a reduction of the ZN catalyst with at least one alkyl aluminum compound. The reduction process may include taking the precursor ZN catalyst in a hydrocarbon solvent, such as, for example, an alkane (e.g., pentane or isopentane), contacting the precursor with one or more alkyl aluminum compounds, such as TMA, TEAL, TIBA, DEAC, TMAC and/or TNHAL, and drying the ZN catalyst.

Contacting of the at least one titanium compound in the precursor composition with the aluminum alkyl compound includes providing a molar ratio of the aluminum alkyl compound to the at least one titanium compound in a range from <NUM>:<NUM> to <NUM>:<NUM> or in a range from <NUM>:<NUM> to <NUM>:<NUM>.

In an embodiment, precipitating the at least one magnesium compound with the at least one titanium compound on the carrier material includes: dissolving the at least one magnesium compound and the at least one titanium compound in a molar ratio of <NUM>:<NUM> to <NUM>:<NUM> (mole the at least one magnesium compound : mole at least one titanium compound) in tetrahydrofuran to form a magnesium compound/titanium compound solution; mixing the carrier material in the magnesium compound/titanium compound solution; and removing the tetrahydrofuran to form the precursor composition of the ZN catalyst.

The processes of the invention can be used in a polymerization process comprising: a) preparing a Ziegler-Natta (ZN) catalyst by contacting the ZN catalyst with at least one aluminum alkyl compound to produce a reduced ZN catalyst; b) optionally, drying the reduced ZN catalyst; c) storing and/or transporting the reduced ZN catalyst for at least <NUM> days at a temperature of <NUM> or less; d) polymerizing one or more olefin monomers under polymerizable conditions with the reduced ZN catalyst; and e) recovering the polyolefin polymers. Such a process is directed at preserving the catalyst activity or reducing the loss of catalyst of the ZN catalysts.

In particular, ZN catalyst may be activated by different methods and chemistries. One example includes forming a Ti/MG/donor complex on MgCl<NUM>, silica, or other support. Then, the co-catalyst may be added to the polymerization reactor directly or to the catalyst feed system. In other examples, ZN catalysts are made by depositing a Ti/Mg/THF complex onto dehydrated silica that also has an aluminum alkyl compound added to the silica to remove residual hydroxyl groups. Its activity may then be adjusted for the production of various polymer products with varying levels of aluminum alkyl compound(s) such as for making linear low density polyethylene (LLDPE) requiring higher levels of aluminum alkyl compounds. Such ZN catalysts appear to be more susceptible to aging effects due to temperature and time.

In an embodiment, the reduced ZN catalyst has substantially the same catalyst activity during the storing and/or transporting. Various methods have been suggested for measuring catalyst activity. For instance,<NPL>; <NPL>; <NPL>; and <NPL>. Various test methods are also discussed in <CIT>, <CIT>, and <CIT>; <CIT>; and <CIT>. A particularly useful method is known as the "accelerated aging method" disclosed in <CIT>, beginning on page <NUM>. It is the method that is applied unless otherwise stated.

As used herein, "substantially" refers to having the essential elements to produce the same or similar result. In other embodiments, "substantially" refers to within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, within <NUM>% of a first and second reference point or value, or within <NUM>% of a first and second reference point or value.

In another class of embodiments, the reduced ZN catalyst may comprise a T<NUM> catalyst activity at the beginning of the storing and/or transporting and a T<NUM> catalyst activity at the end of the storing and/or transporting, and wherein the T<NUM> catalyst activity is within <NUM>% of the T<NUM> catalyst activity, preferably within <NUM>% such as within <NUM>%, within <NUM>%, within <NUM>%, or within <NUM>% of the T<NUM> catalyst activity. As used herein, "storing" refers to a period that runs from the end of catalyst production to the beginning of transporting the catalyst to the polymerization unit facility. Storing may also include, in the aggregate with the aforementioned, "additional storing" that spans the interim period where a catalyst has arrived at a polymerization unit facility but awaits being introduced into the polymerization reactor or catalyst feeder. As used herein, "transporting" refers to a period that runs from the end of storing, including any additional storing, to arriving at the polymerization unit facility, including any intermediate stops or detours of various durations.

The storing and/or transporting of the reduced ZN catalyst is for at least <NUM> days, such as at least <NUM> days, at least <NUM> days, at least <NUM> days, at least <NUM> days, at least <NUM> days, at least <NUM> days, or at least <NUM> days.

The storing and/or transporting of the reduced ZN catalyst is at a temperature of <NUM> or less, such as <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less.

The catalysts are typically placed, stored, and/or transported in portable containers or vessels for storage or shipment between the catalyst production facilities and the polymerization unit facilities. The portable containers or vessels may be moved locally within a plant site or may be shipped by truck, plane, or ship to other plant locations around the world. The portable vessels may be cylinders, drums, DOT approved containers, or any other suitable portable vessel. In order to control the aging of the catalyst, the container or vessel may be held at controlled temperatures as described herein. In one embodiment, the container or vessel is held at a controlled temperature by placing the container or vessel in a controlled temperature environment, such as a refrigerated truck or shipping vessel. Alternatively, the portable vessel may be provided with any other suitable method of maintaining the interior of the portable vessel at a controlled temperature. For example, the container or vessel may have an interior or exterior cooling element or means to maintain the controlled temperature.

The catalysts may be used to polymerize one more olefin monomers to make polymers in any desired polymerization process. For instance, suitable polymerization processes may include high pressure, solution, slurry, super-critical, and/or gas phase processes. For the sake of brevity and illustration purposes only, embodiments of the present invention will be further described below with regard to the polymerization of ethylene monomer to make polyethylene using a gas phase, fluidized bed polymerization process.

In very general terms, a gas phase, fluidized bed polymerization process for producing polyethylene polymers and other types of polyolefin polymers is conducted by passing a gaseous stream containing ethylene and optionally, one or more comonomers continuously through a fluidized bed reactor under reactive conditions and in the presence of one or more catalysts at a velocity sufficient to maintain the bed of solid particles in a suspended condition. A continuous cycle is employed where the cycling gas stream, otherwise known as a recycle stream or fluidizing medium, is heated in the reactor by the heat of polymerization. The hot gaseous stream, also containing unreacted gaseous (co)monomer, is continuously withdrawn from the reactor, compressed, cooled and recycled into the reactor. Product is withdrawn from the reactor and make-up (co)monomer is added to the system, e.g., into the recycle stream or reactor, to replace the polymerized monomer.

An industrial-scale reactor that may be utilized is capable of producing greater than <NUM> of polymer per hour (Kg/hr) to about <NUM>,<NUM>/hr or higher of polymer. The reactor may be capable of producing greater than <NUM>/hr, or greater than <NUM>/hr, or greater than <NUM>,<NUM>/hr, or greater than <NUM>,<NUM>/hr, or greater than <NUM>,<NUM>/h, or greater than <NUM>,<NUM>/hr, or greater than <NUM>,<NUM>/hr. Such reactors, for example, can have an inner diameter of at least about <NUM> inches in the region where the fluid bed resides, and is generally greater than about <NUM> feet on the industrial-scale, and can exceed <NUM>, <NUM>, <NUM>, or <NUM> feet.

The conditions for polymerizations vary depending upon the monomers, catalysts and equipment availability. The specific conditions are known or can be readily determined by those skilled in the art. For example, the temperatures can range from about -<NUM> to about <NUM>, often about <NUM> to about <NUM>. Pressures can be within the range of about <NUM> bar to about <NUM> bar, such as about <NUM> bar to about <NUM> bar. Additional details of the polymerization process and reaction conditions can be found in <CIT>.

The gas phase process can be operated in a condensed mode, where an inert or induced condensable/condensing agent/fluid is introduced to the process to increase the cooling capacity of the reactor system. These inert condensable fluids are referred to as induced condensing agents or ICA's. Condensed mode processes are further described in <CIT> and <CIT>.

Additional processing details are more fully described in, for example, <CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT><CIT>and<CIT>.

The term "polyethylene" refers to a polymer having at least <NUM> wt% ethylene-derived units, preferably at least <NUM> wt% ethylene-derived units, more preferably at least <NUM> wt% ethylene-derived units, or <NUM> wt% ethylene-derived units, or <NUM> wt% ethylene-derived units, or <NUM> wt% ethylene-derived units. The polyethylene can thus be a homopolymer or a copolymer, including a terpolymer, having one or more other monomeric units. A polyethylene described herein can, for example, include at least one or more other olefin(s) and/or comonomer(s). Suitable comonomers include α-olefins, such as C<NUM>-C<NUM> α-olefins or C<NUM>-C<NUM> α-olefins. The α-olefin comonomer can be linear or branched, and two or more comonomers can be used, if desired. Examples of suitable comonomers include linear C<NUM>-C<NUM> α-olefins, and α-olefins having one or more C<NUM>-C<NUM> alkyl branches, or an aryl group. Specific examples include propylene; <NUM>-methyl-<NUM>-butene; <NUM>,<NUM>-dimethyl-<NUM>-butene; <NUM>-pentene; <NUM>-pentene with one or more methyl, ethyl or propyl substituents; <NUM>-hexene with one or more methyl, ethyl or propyl substituents; <NUM>-heptene with one or more methyl, ethyl or propyl substituents; <NUM>-octene with one or more methyl, ethyl or propyl substituents; <NUM>-nonene with one or more methyl, ethyl or propyl substituents; ethyl, methyl or dimethyl-substituted <NUM>-decene; <NUM>-dodecene; and styrene. It should be appreciated that the list of comonomers above is merely exemplary, and is not intended to be limiting. Preferred comonomers include propylene, <NUM>-butene, <NUM>-pentene, <NUM>-methyl-<NUM>-pentene, <NUM>-hexene, <NUM>-octene and styrene.

In a class of embodiments, the one or more olefin monomers may comprise C<NUM>-C<NUM> olefin monomers. In another class of embodiments, the one or more olefin monomers may comprise ethylene and a C<NUM>-C<NUM> α-olefin monomer.

Other useful comonomers include conjugated and non-conjugated dienes, which can be included in minor amounts in terpolymer compositions. Non-conjugated dienes useful as co-monomers preferably are straight chain, hydrocarbon diolefins or cycloalkenyl-substituted alkenes, having <NUM> to <NUM> carbon atoms. Suitable non-conjugated dienes include, for example: (a) straight chain acyclic dienes, such as <NUM>,<NUM>-hexadiene and <NUM>,<NUM>-octadiene; (b) branched chain acyclic dienes, such as <NUM>-methyl-<NUM>,<NUM>-hexadiene; <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-octadiene; and <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-octadiene; (c) single ring alicyclic dienes, such as <NUM>,<NUM>-cyclohexadiene; <NUM>,<NUM>-cyclo-octadiene and <NUM>,<NUM>-cyclododecadiene; (d) multi-ring alicyclic fused and bridged ring dienes, such as tetrahydroindene; norbornadiene; methyl-tetrahydroindene; dicyclopentadiene (DCPD); bicyclo-(<NUM>. <NUM>)-hepta-<NUM>,<NUM>-diene; alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes, such as <NUM>-methylene-<NUM>-norbornene (MNB), <NUM>-propenyl-<NUM>-norbornene, <NUM>-isopropylidene-<NUM>-norbomene, <NUM>-(<NUM>-cyclopentenyl)-<NUM>-norbornene, <NUM>-cyclohexylidene-<NUM>-norbornene, and <NUM>-vinyl-<NUM>-norbornene (VNB); and (e) cycloalkenyl-substituted alkenes, such as vinyl cyclohexene, allyl cyclohexene, vinyl cyclooctene, <NUM>-vinyl cyclohexene, allyl cyclodecene, and vinyl cyclododecene. Of the non-conjugated dienes typically used, the preferred dienes are dicyclopentadiene, <NUM>,<NUM>-hexadiene, <NUM>-methylene-<NUM>-norbornene, <NUM>-ethylidene-<NUM>-norbornene, and tetracyclo-(δ-<NUM>,<NUM>)-<NUM>,<NUM>-dodecene. Particularly preferred diolefins are <NUM>-ethylidene-<NUM>-norbornene (ENB), <NUM>,<NUM>-hexadiene, dicyclopentadiene (DCPD), norbornadiene, and <NUM>-vinyl-<NUM>-norbornene (VNB).

The ZN catalysts may be employed in polymerization processes to produce a variety of polymers to be fabricated along or with other polymers and/or materials in a variety of end-use applications. Such end-uses applications include, without limitation, films (e.g., blown and cast, optionally, oriented MD and/or TD), film-based products, film cells, film membranes, wrap films, diaper components, diaper backsheets, housewrap, personal care containers, pouches, stand-up pouches, liners, geo membranes, greenhouse films, bags, packaging, wire and cable coating compositions, articles formed by molding techniques, e.g., injection or blow molding, extrusion coating, foaming, casting, and combinations thereof.

It is to be understood that while the invention has been described in conjunction with the specific embodiments thereof, the foregoing description is intended to illustrate and not limit the scope of the invention. Other aspects, advantages and modifications will be apparent to those skilled in the art to which the invention pertains.

Therefore, the following examples are put forth so as to provide those skilled in the art with a complete disclosure and description and are not intended to limit the scope of that which the inventors regard as their invention.

A catalyst aging study was conducted using a Ziegler-Natta (ZN) catalyst sold under the trade name UCAT™ A Catalyst available from Univation Technologies, LLC, Houston, TX. The ZN catalyst was reduced by contacting it with at least one aluminum alkyl compound to produce a reduced ZN catalyst.

Heat aged samples were stored at the temperatures and times listed in Table <NUM> in a bomb with a pressure gauge in an oven under nitrogen conditions. The bomb was periodically checked to insure that the nitrogen conditions were being maintained. Catalyst activity as determined by a thirty minute slurry homopolymerization at <NUM>, <NUM> psi C<NUM>, and sufficient H<NUM> to yield <NUM> MI resin (I<NUM> or simply I<NUM> for shorthand according to ASTM D1238, condition E (<NUM>/<NUM>)).

Table <NUM> below shows the amount of aluminum alkyl reduction with the aging condition, i.e., temperature, along with the catalyst activity change or loss.

As shown in Table <NUM>, the highly reduced ZN catalysts lose activity over time when exposed to temperatures greater than ambient. In particular, the catalyst activity loss is at ~<NUM>% within one year. In contrast, lightly reduced ZN catalyst (<NUM> TNHAL/THF) shows no sign of activity loss after half a year at <NUM>.

Claim 1:
A process for reducing the loss of catalyst activity of a Ziegler-Natta catalyst, the process comprising:
a) preparing a Ziegler-Natta (ZN) catalyst by providing a precursor composition of the ZN catalyst comprising at least one titanium compound;
contacting the at least one titanium compound in the precursor composition with at least one aluminum alkyl compound in a hydrocarbon solvent, wherein the aluminum alkyl compound converts the at least one titanium compound in the precursor composition into a modified state of the ZN catalyst; and,
removing at least a portion of the aluminium alkyl compound in the hydrocarbon solvent not consumed in converting the at least one titanium compound into the modified state to produce a reduced ZN catalyst;
b) optionally, drying the reduced ZN catalyst; and
c) storing and/or transporting the reduced ZN catalyst for at least <NUM> days at a temperature of <NUM> or less;
wherein the reduced ZN catalyst has a fresh catalyst activity and an aged catalyst activity, wherein the fresh catalyst activity is the catalyst activity of the catalyst when the catalyst is fed to a polymerization system soon after the catalyst is manufactured and before the catalyst substantially changes, and the aged catalyst activity is the catalyst activity of the catalyst when it is fed to the polymerization system after the catalyst has been stored and/or transported; and,
the aged catalyst activity is at least <NUM>% of the fresh catalyst activity; and,
wherein the contacting of the at least one titanium compound in the precursor composition with the aluminum alkyl compound includes providing a molar ratio of the aluminum alkyl compound to the titanium compound in a range from <NUM>:<NUM> to <NUM>:<NUM>.