Classifications

• • 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
  • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers

Definitions

• This invention relates to the polymerization of ethylene in a solution
• polymerization process which utilizes at least two different types of polymerization reactors, namely at least one stirred reactor and at least one tubular reactor.
• CSTR continuously stirred tank reactor
• the polymerization of ethylene is highly exothermic. Accordingly, it is common practice to use ambient or chilled reactor feeds to maximize reactor productivity for a given reaction temperature.
• CSTR Clefin-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-styrene-
• the present invention is generally useful for preparing ethylene homopolymers or copolymers.
• the present invention provides a process for the preparation of polyethylene having a density of from 0.890 to 0.970 g/cc comprising the polymerization of ethylene and a comonomer in at least two polymerization reactors, wherein said process comprises:
• said additional tempered ethylene is added at a temperature of between 100° C and said final discharge temperature.
• reaction configuration described herein is suitable for the preparation of ethylene-copolymer plastomers (i.e. copolymers having a very low density, such as ethylene-octene copolymers having a density of from 0.850 to 0.900); thermoplastic ethylene copolymers (i.e. copolymers having a density of from about 0.900 to 0.955 g/cc) and even ethylene homopolymers.
• ethylene-copolymer plastomers i.e. copolymers having a very low density, such as ethylene-octene copolymers having a density of from 0.850 to 0.900
• thermoplastic ethylene copolymers i.e. copolymers having a density of from about 0.900 to 0.955 g/cc
• even ethylene homopolymers even ethylene homopolymers.
• the present invention is especially suitable for the preparation of thermoplastic ethylene copolymers having a density of from about 0.900 to 0.930 g/cc.
• the comonomer used to prepare these copolymers has a lower reactivity ratio than ethylene - i.e. the ethylene is preferentially consumed in the CSTR, leaving a polymer solution with residual monomer that is comonomer rich.
• the present invention provides a process for the preparation of polyethylene having a density of from 0.900 to 0.930 g/cc comprising the polymerization of ethylene in at least two polymerization reactors, wherein said process comprises:
• CSTR continuously stirred tank reactor
• said tempered ethylene is added at a temperature of between 100° C and said final discharge temperature.
• this lower rate of polymerization may be obtained by not adding any additional catalyst to the tubular reactor - i.e. the residual catalyst from the CSTR(s) catalyzes the reaction in the tubular reactor.
• the present invention provides a process for the preparation of polyethylene having a density of from 0.900 to 0.930 g/cc comprising the polymerization of ethylene in at least two polymerization reactors, wherein said process comprises:
• CSTR continuously stirred tank reactor
• Any catalyst system that is capable of providing ethylene polymers under solution conditions may be employed.
• catalyst system includes at least one "transition metal catalyst” (also referred to herein as a “catalyst compound”) and may also include a cocatalyst or activator.
• catalyst compound includes any compound that, once appropriately activated, is capable of catalyzing the polymerization or
• the catalyst compound comprises at least one Group 3 to Group 5 metal atom (preferably a Group 4 to 12 transition metal, most preferably a Group 4 metal such as titanium, zirconium or hafnium) or lanthanide or actinide atom.
• Zeroegler Natta polymerization catalysts may also be employed. These catalysts typically comprise a group 4 or group 5 metal - especially titanium or vanadium - in combination with hydrocarbyl aluminum activator of the general formula:
• R a1 is a hydrocarbyl group having from 1 to 10 carbon atoms
• OR b1 is an alkoxy or aryloxy group where OR b1 is a hydrocarbyl fragment having from 1 to 10 carbon atoms and being bonded to oxygen
• hydrocarbyl aluminum activator in widespread use include trimethyl aluminum, trimethyl aluminum and tributyl aluminum.
• Preferred Ziegler Natta catalysts contain at least one of titanium or vanadium.
• exemplary titanium compounds include titanium halides (especially titanium chlorides, of which TiCI 4 is preferred); titanium alkyls; titanium alkoxides (which may be prepared by reacting a titanium alkyl with an alcohol) and "mixed ligand" compounds (i.e.
• vanadium compounds which contain more than one of the above described halide, alkyl and alkoxide ligands).
• exemplary vanadium compounds may also contain halide, alkyl or alkoxide ligands.
• vanadium oxy trichloride (“VOCI 3 ”) is known as a Ziegler Natta catalyst component and is suitable for use in the present invention.
• conventional Ziegler Natta catalysts may also incorporate additional components such as an electron donor (for example an amine or an ether) and/or a magnesium
• a halide source (which is typically a chloride such as tertiary butyl chloride) is typically used when a magnesium alkyl compound is employed.
• Such components may be added to the other catalyst components prior to introduction to the reactor or may be directly added to the reactor.
• the Ziegler Natta catalyst contains a titanium
• catalyst compound in the process of this invention instead of (or in addition to) a Ziegler Natta catalyst.
• catalyst compounds typically comprise a metal atom, at least one "functional" ligand and at least one leaving group. Further details follow.
• the phrase “leaving group” generally refers to one or more chemical moieties bound to the metal center of the catalyst compound that can be abstracted from the catalyst compound, thus producing a species active towards olefin polymerization or oligomerization.
• the "new" numbering scheme for the Periodic Table Groups are used as in the CRC HANDBOOK OF CHEMISTRY AND PHYSICS (David R. Lide ed., CRC Press 81 st ed. 2000).
• hydrocarbyl includes aliphatic, cyclic, olefinic, acetylenic and aromatic radicals (i.e. hydrocarbon radicals) comprising hydrogen and carbon that are deficient by one hydrogen.
• hydrocarbon radicals i.e. hydrocarbon radicals
• a “hydrocarbylene” is deficient by two hydrogens.
• an "alkyl” includes linear, branched and cyclic paraffin radicals that are deficient by one hydrogen.
• a -CH 3 group (“methyl)
• a CH3CH2- group (“ethyl”) are examples of alkyls.
• alkenyl includes linear, branched and cyclic olefin radicals that are deficient by one hydrogen; alkynyl radicals include linear, branched and cyclic acetylene radicals deficient by one hydrogen radical.
• aryl groups includes phenyl, naphthyl, pyridyl and other radicals whose molecules have the ring structure characteristic of benzene,
• a C 6 H 5 " aromatic structure is an "phenyl”
• a C 6 H 4 2" aromatic structure is an "phenylene”.
• An "arylalkyl” group is an alkyl group having an aryl group pendant there from, examples of which include benzyl, phenethyl, tolylmethyl and the like;
• an "alkylaryl” is an aryl group having one or more alkyl groups pendant there from, examples of which include tolyl, xylyl, mesityl, cumyl and the like.
• an "alkylene” includes linear, branched and cyclic hydrocarbon radicals deficient by two hydrogens.
• -CH 2 - methylene
• --CH 2 CH 2 - ethylene
• Other groups deficient by two hydrogen radicals include “arylene” and "alkenylene”.
• heteroatom includes any atom other than carbon and hydrogen that can be bound to carbon.
• a “heteroatom-containing group” is a hydrocarbon radical that contains a heteroatom and may contain one or more of the same or different heteroatoms.
• a heteroatom-containing group is a hydrocarbyl group containing from 1 to 3 atoms selected from the group consisting of boron, aluminum, silicon, germanium, nitrogen, phosphorous, oxygen and sulfur.
• Non- limiting examples of heteroatom-containing groups include radicals of imines, amines, oxides, phosphines, ethers, ketones, oxoazolines heterocyclics, oxazolines, thioethers, and the like.
• heterocyclic refers to ring systems having a carbon backbone that comprise from 1 to 3 atoms selected from the group consisting of boron, aluminum, silicon, germanium, nitrogen, phosphorous, oxygen and sulfur, unless the heteroatom (non-carbon atom) is described.
• alkylcarboxylate As used herein, an “alkylcarboxylate”, “arylcarboxylate”, and
• alkylarylcarboxylate is an alkyl, aryl, and alkylaryl, respectively, that possesses a carboxyl group in any position. Examples include CeHsChfeCiOJO “ , CH3C(0)0 " , etc.
• non-interfering means that the ligand (or cation) being referred to does not interfere with olefin polymerization (i.e. that it does not reduce the activity of olefin polymerization by more than 50% in comparison to a polymerization conducted in the absence of the ligand or cation).
• substituted means that the group following that term possesses at least one moiety in place of one or more hydrogens in any position, the moieties selected from such groups as halogen radicals (esp., CI, F, Br), hydroxyl groups, carbonyl groups, carboxyl groups, amine groups, phosphine groups, alkoxy groups, phenyl groups, naphthyl groups, Ci to Ci 0 alkyl groups, C 2 to Cio alkenyl groups, and combinations thereof.
• halogen radicals esp., CI, F, Br
• hydroxyl groups esp., carbonyl groups, carboxyl groups, amine groups, phosphine groups, alkoxy groups, phenyl groups, naphthyl groups, Ci to Ci 0 alkyl groups, C 2 to Cio alkenyl groups, and combinations thereof.
• substituted alkyls and aryls includes, but are not limited to, acyl radicals, alkylamino radicals, alkoxy radicals, aryloxy radicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonyl radicals,
• aryloxycarbonyl radicals carbomoyl radicals, alkyl- and dialkyl-carbamoyl radicals, acyloxy radicals, acylamino radicals, arylamino radicals, and combinations thereof.
• lines used to represent associations between a metal atom ("M”, Group 3 to Group 15 atoms) and a ligand or ligand atom (e.g. cyclopentadienyl, nitrogen, oxygen, halogen ions, alkyl, etc.), as well as the phrases “associated with”, “bonded to” and “bonding”, are not limited to representing a certain type of chemical bond, as these lines and phrases are meant to represent a "chemical bond”; a
• chemical bond defined as an attractive force between atoms that is strong enough to permit the combined aggregate to function as a unit, or "compound”.
• any transition metal catalyst compound which is activated by an aluminum alkyl or methyl aluminoxane (MAO), or an "ionic activator" discussed in Part
• Preferred catalyst compounds are group 4 metal complexes (especially titanium or zirconium) which contain one cyclopentadienyl ligand ("homocyclopentadienyl complexes") or two cyclopentadienyl ligands ("biscyclopentadienyl complexes").
• the bulky ligands are generally represented by one or more open, acyclic, or fused ring(s) or ring system(s) or a combination thereof.
• the ring(s) or ring system(s) of these bulky ligands are typically composed of atoms selected from Groups 13 to 16 atoms of the Periodic Table of Elements.
• the atoms are selected from the group consisting of carbon, nitrogen, oxygen, silicon, sulfur, phosphorous, germanium, boron and aluminum or a combination thereof.
• the ring(s) or ring system(s) are composed of carbon atoms such as but not limited to those
• the metal atom is preferably selected from Groups 3 through 5 and the lanthanide or actinide series of the Periodic Table of Elements.
• the metal is a transition metal from Groups 4 through 12, more preferably Groups 4, 5 and 6, and most preferably the transition metal is from Group 4.
• catalyst compounds are represented by the formula:
• M is a metal atom from the Periodic Table of the Elements and may be a Group 3 to 12 metal or from the lanthanide or actinide series of the Periodic Table of
• M is a Group 4, 5 or 6 transition metal, more preferably M is zirconium, hafnium or titanium.
• the bulky ligands, L A and L B are open, acyclic or fused ring(s) or ring system(s) and are any ancillary ligand system, including unsubstituted or substituted, cyclopentadienyl ligands or cyclopentadienyl-type ligands, heteroatom substituted and/or heteroatom containing cyclopentadienyl-type ligands.
• Non-limiting examples of bulky ligands include cyclopentadienyl ligands, cyclopentaphenanthreneyl ligands, indenyl ligands, benzindenyl ligands, fluorenyl ligands, octahydrofluorenyl ligands, cyclooctatetraendiyl ligands, cyclopentacyclododecene ligands, azenyl ligands, azulene ligands, pentalene ligands, phosphoyl ligands, phosphinimine, pyrrolyl ligands, pyrozolyl ligands, carbazolyl ligands, borabenzene ligands and the like, including hydrogenated versions thereof, for example tetrahydroindenyl ligands.
• cyclopentadienyl ligands include cyclopenta
• L A and L B may be any other ligand structure capable of .eta.-bonding to M, preferably .eta. 3 -bonding to M and most preferably .eta. 5 -bonding.
• L A and L B may comprise one or more heteroatoms, for example, nitrogen, silicon, boron, germanium, sulfur and phosphorous, in combination with carbon atoms to form an open, acyclic, or preferably a fused, ring or ring system, for example, a hetero-cyclopentadienyl ancillary ligand.
• L A and L B bulky ligands include but are not limited to bulky amides, phosphides, alkoxides, aryloxides, phosphinimides, imides, carbolides, borollides, porphyrins, phthalocyanines, corrins and other
• each L A and L B may be the same or different type of bulky ligand that is bonded to M. In one embodiment of formula (I) only one of either L A or L B is present.
• each L A and L B may be unsubstituted or substituted with a combination of substituent groups R.
• substituent groups R include one or more from the group selected from hydrogen, or linear, branched alkyl radicals, or alkenyl radicals, alkynyl radicals, cycloalkyl radicals or aryl radicals, acyl radicals, aroyl radicals, alkoxy radicals, aryloxy radicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonyl radicals, aryloxycarbonyl radicals, carbomoyi radicals, alkyl- or dialkyl- carbamoyl radicals, acyloxy radicals, acylamino radicals, aroylamino radicals, straight, branched or cyclic, alkylene radicals, or combination thereof.
• substituent groups R have up to 50 non-hydrogen atoms, preferably from 1 to 30 carbon that can also be substituted with halogens or heteroatoms or the like.
• alkyl substituents R include methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl or phenyl groups and the like, including all their isomers, for example tertiary butyl, isopropyl, and the like.
• hydrocarbyl radicals include fluoromethyl, fluroethyl, difluroethyl, iodopropyl, bromohexyl, chlorobenzyl and hydrocarbyl substituted organometalloid radicals including trimethylsilyl,
• Non-hydrogen substituents R include the atoms carbon, silicon, boron, aluminum, nitrogen, phosphorous, oxygen, tin, sulfur, germanium and the like, including olefins such as but not limited to olefinically unsaturated substituents including vinyl-terminated ligands, for example but-3-enyl, prop-2-enyl, hex-5-enyl and the like.
• At least two R groups are joined to form a ring structure having from 3 to 30 atoms selected from carbon, nitrogen, oxygen, phosphorous, silicon, germanium, aluminum, boron or a combination thereof.
• a substituent group R group such as 1-butanyl may form a carbon sigma bond to the metal M.
• ligands may be bonded to the metal M, such as at least one leaving group
• the term "leaving group” is any ligand that can be abstracted from a bulky ligand catalyst compound to form a bulky ligand catalyst species capable of polymerizing one or more olefin(s).
• Q is a monoanionic labile ligand having a sigma-bond to M.
• n is 0, 1 or 2 such that formula (I) above represents a neutral bulky ligand catalyst compound.
• Non-limiting examples of Q ligands include weak bases such as amines, phosphines, ethers, carboxylates, dienes, hydrocarbyl radicals having from 1 to 20 carbon atoms, hydrides or halogens and the like or a combination thereof. In another embodiment, two or more Q's form a part of a fused ring or ring system.
• Other examples of Q ligands include those substituents for R as described above and including cyclobutyl, cyclohexyl, heptyl, tolyl, trifluromethyl, tetramethylene,
• the catalyst compound is represented by the following formula:
• L A AL B MQn (II) These compounds represented by formula (II) are known as bridged, ligand catalyst compounds.
• L A , L B , M, Q and n are as defined above.
• Non-limiting examples of bridging group A include bridging groups containing at least one Group 13 to 16 atom, often referred to as a divalent moiety such as but not limited to at least one of a carbon, oxygen, nitrogen, silicon, aluminum, boron, germanium and tin atom or a combination thereof.
• bridging group A contains a carbon, silicon or germanium atom, most preferably A contains at least one silicon atom or at least one carbon atom.
• the bridging group A may also contain substituent groups R as defined above including halogens and iron.
• Non-limiting examples of bridging group A may be represented by R' 2 C, R' 2 Si, R' 2 Si R' 2 Si, R' 2 Ge, R'P, where R' is independently, a radical group which is hydride, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyl-substituted
• the bridged, ligand catalyst compounds of formula (II) have two or more bridging groups A.
• the catalyst compounds are those where the R substituents on the bulky ligands L A and L B of formulas (I) and (II) are substituted with the same or different number of substituents on each of the bulky ligands.
• the bulky ligands L A and L B of formulas (I) and (II) are different from each other.
• catalyst compounds useful in the invention include bridged heteroatom, mono-bulky ligand compounds. More specifically, these highly preferred catalysts are group 4 metal (especially titanium) complexes
• bridging groups are dialkyl silyls - especially dimethyl silyl.
• the amine portion of the ligand preferably has an alkyl substituent on the nitrogen atom (especially tertiary butyl) with the remaining nitrogen bands bonding to the transition metal (preferably titanium) and the silicon atome of the preferred dimethyl silyl bridging group.
• the cyclopentadienyl ligand is pi-bonded to the transition metal and covalently bonded to the bridging group.
• the cyclopentadienyl group is preferably substituted, especially tetra methyl cyclopentadienyl.
• Preferred catalyst compounds include dimethylsilyltetramnethyl
• the catalyst compound is represented by the formula:
• M is a Group 3 to 16 metal atom or a metal selected from the Group of actinides and lanthanides of the Periodic Table of Elements, preferably M is a Group 4 to 12 transition metal, and more preferably M is a Group 4, 5 or 6 transition metal, and most preferably M is a Group 4 transition metal in any oxidation state, especially titanium;
• L c is a substituted or unsubstituted bulky ligand bonded to M; J is bonded to M; A is bonded to M and J; J is a heteroatom ancillary ligand; and A is a bridging group;
• Q is a univalent anionic ligand; and n is the integer 0, 1 or 2.
• L c , A and J may form a fused ring system.
• L c of formula (III) is as defined above for L A in formula (I) and A, M and Q of formula (III) are as defined above in formula (I).
• J is a heteroatom containing ligand in which J is an element with a coordination number of three from Group 15 or an element with a coordination number of two from Group 6 of the Periodic Table of Elements.
• J contains a nitrogen, phosphorus, oxygen or sulfur atom with nitrogen being most preferred.
• catalyst compound is a complex of a metal, preferably a transition metal, a bulky ligand, preferably a substituted or unsubstituted pi-bonded ligand, and one or more heteroallyl moieties, such as those described in U.S. Patent 5,527,752.
• the catalyst compounds are represented by the formula:
• M is a Group 3 to 16 metal, preferably a Group 4 to 12 transition metal, and most preferably a Group 4, 5 or 6 transition metal;
• L D is a bulky ligand that is bonded to M; each Q is independently bonded to M and Q 2 (YZ) forms a unicharged polydentate ligand;
• a or Q is a univalent anionic ligand also bonded to M;
• X is a univalent anionic group when n is 2 or X is a divalent anionic group when n is 1 ; n is 1 or 2.
• L and M are as defined above for formula (I).
• Q is as defined above for formula (I), preferably Q is selected from the group consisting of -0-, -NR--, -CR 2 - and --S-.
• Y is either C or S.
• Z is selected from the group consisting of -OR, - NR 2 , --CR 3 , -SR, --S1R3, -PR 2 , -H, and substituted or unsubstituted aryl groups, with the proviso that when Q is --NR-- then Z is selected from one of the group consisting of -OR, -NR 2 , --SR, --SiR 3 , "PR 2 and --H;
• R is selected from a group containing carbon, silicon, nitrogen, oxygen, and/or phosphorus, preferably where R is a hydrocarbon group containing from 1 to 20 carbon atoms, most preferably an alkyl, cycloalkyl, or an aryl group;
• n is an integer from 1 to 4, preferably 1 or 2;
• X is a univalent anionic group when n is 2 or X is a divalent anionic group when n is 1 ; preferably X is a carbamate, carboxylate, or other heteroallyl mo
• the catalyst compounds are heterocyclic ligand complexes where the bulky ligands, the ring(s) or ring system(s), include one or more heteroatoms or a combination thereof.
• heteroatoms include a Group 13 to 16 element, preferably nitrogen, boron, sulfur, oxygen, aluminum, silicon, phosphorous and tin. Examples of these bulky ligand catalyst compounds are described in U.S. Patent 5,637,660.
• the catalyst compounds are represented by the formula:
• M is a metal selected from Group 3 to 13 or lanthanide and actinide series of the Periodic Table of Elements; Q is bonded to M and each Q is a monovalent, bivalent, or trivalent anion; X and Y are bonded to M; one or more of X and Y are heteroatoms, preferably both X and Y are heteroatoms; Y is contained in a heterocyclic ring J, where J comprises from 2 to 50 non-hydrogen atoms, preferably 2 to 30 carbon atoms; Z is bonded to X, where Z comprises 1 to 50 non-hydrogen atoms, preferably 1 to 50 carbon atoms, preferably Z is a cyclic group containing 3 to 50 atoms, preferably 3 to 30 carbon atoms; t is 0 or 1 ; when t is 1 , A is a bridging group joined to at least one of X, Y or J, preferably X and J; q is 1 or 2; n is an integer from 1 to 4 depending
• the catalyst compounds include complexes of Ni 2+ and Pd 2+ described in U.S. Patent 5,852,145. These complexes can be either dialkyl ether adducts, or alkylated reaction products of the described dihalide complexes that can be activated to a cationic state by the activators or cocatalysts are described below. Also included as catalyst compounds are those diimine based ligands of Group 8 to 10 metal compounds.
• Suitable catalyst compounds are those Group 5 and 6 metal imido complexes described in U.S. Patent 5,851 ,945, which is incorporated herein by reference.
• bulky ligand catalyst compounds include bridged bis(arylamido) Group 4 compounds, bridged bis(amido) catalyst compounds and catalysts having bis(hydroxy aromatic nitrogen ligands).
• the catalyst compounds of the invention described above include their structural or optical or enantiomeric isomers (meso and racemic isomers) and mixtures thereof.
• Highly preferred catalyst compounds are group IV metal compounds which contain at least one cyclopentadienyl ligand.
• Aluminoxanes especially methyl aluminoxane, are well known cocatalyst for organometallic catalyst compounds. Methyl aluminoxane, and near variants thereof (which typically contain small levels of higher alkyl groups) are commercially available products. Although the exact structure of these aluminoxanes is still somewhat uncertain, it is generally agreed that they are oligomeric species that contain repeating units of the general formula:
• R is (predominantly) methyl
• ionic activators also referred to herein as activator compounds
• organometallic catalyst compounds as described in USP 5,198,401 (HIatky and Turner) and US 5,132,380 (Stevens and Neithamer).
• these activators comprise a cation and a substantially non-coordinating anion.
• boron activators initially cause the abstraction of one or more of the activatable ligands in a manner which ionizes the catalyst into a cation, then provides a bulky, labile, non-coordinating anion which stabilizes the catalyst in a cationic form.
• the boron activator/phosphinimine catalyst may also form a non-ionic coordination complex which is catalytically active for olefin polymerization.
• the boron activator is described as being four coordinate - i.e. there must be four ligands bonded to the boron atom.
• Preferred boron activators are described in (i) - (ii) below:
• each R 9 is independently selected from the group consisting of a hydrogen atom and a Ci -4 alkyl radical;
• R 7 is a pentafluorophenyl radical.
• preferred boron activators may be described as salts of tetra(perfluorophenyl) boron. More specifically, the preferred activators are anilinium, carbonium, oxonium, phosphonium and sulfonium salts of tetra(perfluorophenyl) boron, with anilinium and trityl (or "triphenyl methylium”) salts being especially preferred.
• Exemplary ionic activators include:
• triphenylmethylium tetrakispentafluorophenyl borate triphenylmethylium tetrakispentafluorophenyl borate
• ionic activators which are suitable for the process of this invention are N,N- dimethylaniliniumtetrakispentafluorophenyl borate, and triphenylmethylium tetrakispentafluorophenyl borate (also known as "trityl borate").
• boron activator in an equimolar amount with respect to the transition metal of the catalyst (i.e. boron/titanium ratio of 1/1 , when the catalyst is an organotitanium complex) through mole ratios of from 0.3/1 to 10.0/1 may be used.
• Solution processes for the copolymerization of ethylene and an alpha olefin having from 3 to 12 carbon atoms are well known in the art. These processes are conducted in the presence of an inert hydrocarbon solvent typically a C 5- i 2 hydrocarbon which may be unsubstituted or substituted by a C-M alkyl group, such as pentane, methyl pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated naphtha.
• an inert hydrocarbon solvent typically a C 5- i 2 hydrocarbon which may be unsubstituted or substituted by a C-M alkyl group, such as pentane, methyl pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated naphtha.
• a solution polymerization process may use one, two (or more) polymerization reactors.
• the process of this invention must use at least one CSTR and one tubular reactor.
• the polymerization temperature in at least one CSTR is from about 80° C to about 280° C (preferably from about 120° C to 220° C) and the tubular reactor is operated at a slightly higher temperature.
• Cold feed i.e. chilled solvent and/or monomer
• the polymerization enthalpy heats the reactor.
• the polymerization solution which exits in the reactor may be more than 100° C hotter than the reactor feed temperature.
• Agitation efficiency in the CSTR may be determined by measuring the reactor temperature at several different points. The largest temperature difference (i.e. between the hottest and coldest temperature measurements) is described as the internal temperature gradient for the polymerization reactor.
• a very well mixed CSTR has a maximum internal temperature gradient of less than 10° C.
• a particularly preferred agitator system is described in copending and commonly assigned U.S. Pat. No. 6,024,483.
• Preferred pressures are from about 500 psi to 8,000 psi.
• the most preferred reaction process is a "medium pressure process", which means that the pressure in each reactor is preferably less than about 6,000 psi (about 41 ,000 kiloPascals or kPa), and most preferably from about 1 ,500 psi to 3,000 psi (about 10,000-21 ,000 kPa).
• each CSTR it is preferable to add catalyst to each of the CSTR(s) in order to maintain a high reactor rate.
• the catalyst used in each CSTR may be the same or different but it is generally preferable to use the same type of catalyst in each CSTR. It is preferred that at least 60 weight % of the ethylene fed to the CSTR(s) is polymerized to polyethylene in the CSTR(s) , with at least 70% ethylene conversion being highly preferred.
• the process of this invention requires a tubular reactor that is connected to the discharge of the at least on CSTR. (For clarity, if two CSTR's are used in series, then the tubular reactor receives the discharge from the second CSTR).
• tubular reactor is meant to convey its conventional meaning - namely a simple tube.
• the tubular reactor of this invention will have a length/diameter (L/D) ratio of at least 0/1.
• the tubular reactor is not agitated.
• the tubular reactor is operated adiabatically. Thus, as polymerization progresses, the remaining
• the temperature increase along the length of the tubular reactor is greater than 3° C (i.e. that the discharge temperature from the tubular reactor is at least 3° C greater than the discharge temperature from the CSTR that feeds the tubular reactor).
• the tubular reactor used in this invention has a feed port for additional ethylene and solvent.
• the feed is "tempered” - i.e. the temperature of the additional ethylene and/or solvent is heated to above ambient (preferably to about 100° C) but the temperature is below the discharge temperature of the tubular reactor.
• the ethylene is tempered to between 100 and 200° C. It is most preferred to add the ethylene with solvent.
• the amount of solvent (expressed as a weight ratio, based on ethylene) is preferably from 20/1 to 0.1/1 , especially from 10/1 to 1/1
• the tubular reactor may also have feed ports for additional catalyst, cocatalyst, comonomer and/or telomerization agent (such as hydrogen).
• additional catalyst such as hydrogen
• cocatalyst such as cocatalyst
• comonomer such as hydrogen
• telomerization agent such as hydrogen
• the total volume of the tubular reactor is preferably at least 10 volume % of the volume of the at least one CSTR, especially from 30% to 200% (for clarity, if the volume of the CSTR is 1000 litres, then the volume of the tubular reactor is at least 00 litres and is preferably from 300 to 2000 litres).
• the total amount of ethylene added to the tubular reactor is preferably from 1 to 50 weight % of the total ethylene added to the CSTR(s). For example, if one CSTR is being operated with an ethylene flow rate of 1000 kg/hr, then the ethylene flow to the tubular reactor would be from 10 to 500 kg/hr. Similarly, if two CSTR(s) were being operated with an ethylene flow of 1000 kg/hr to the first and 500 kg/hr to the second, then the flow of ethylene to the tubular reactor would be from 15 to 750 kg/hr.
• Suitable monomers for copolymerization with ethylene include C3-12 alpha olefins which are unsubstituted or substituted by up to two d-6 alkyl radicals.
• Illustrative non- limiting examples of such alpha-olefins are one or more of propylene, 1-butene, 1- pentene, 1-hexene, 1-octene and 1-decene. Octene-1 is highly preferred.
• the monomers are dissolved/dispersed in the solvent either prior to being fed to the first CSTR (or for gaseous monomers the monomer may be fed to the reactor so that it will dissolve in the reaction mixture).
• the solvent and monomers Prior to mixing, are generally purified to remove potential catalyst poisons such as water, oxygen or other polar impurities.
• the feedstock purification follows standard practices in the art, e.g. molecular sieves, alumina beds and oxygen removal catalysts are used for the purification of monomers.
• the solvent itself as well e.g. methyl pentane, cyclohexane, hexane or toluene
• the catalyst components may be premixed in the solvent for the reaction or fed as separate streams to each reactor.
• catalyst is only added to the CSTR(s) - i.e. not added to the tubular reactor.
• the discharge from the CSTR (or final CSTR if more than one is used in series) must be directed to a tubular reactor.
• premixing may be desirable to provide a reaction time for the catalyst components prior to entering the first CSTR.
• Such an "in line mixing” technique is described in the patent literature (most notably U.S. Pat. No. 5,589,555, issued Dec. 31 , 1996 to DuPont Canada Inc.).
• the residence time in each reactor will depend on the design and the capacity of the reactor. Generally the reactors should be operated under conditions to achieve a thorough mixing of the reactants. As previously noted, the polymerization reactors are arranged in series (i.e. with the solution from the at least one CSTR being transferred to the tubular reactor).
• the first part of the examples illustrates the copolymerization of ethylene and octene-1 to prepare the resins used in this invention.
• Density is determined using the displacement method according to ASTM D792.
• This example illustrates the continuous flow, solution copolymerization of ethylene at a medium pressure using a single pilot scale reactor system and a Ziegler Natta catalyst.
• the first reactor was a continuously stirred tank reactor ("CSTR") with a volume of 24 liters.
• the second reactor for experiments 2-4 was a tubular reactor having a volume of 82% of the CSTR volume (19.7 liters). Monomers, solvent and catalyst were fed into the reactor as indicated in Table 1.
• the solvent used in these experiments was methyl pentane.
• a Ziegler Natta catalyst consisting of titanium tetrachloride (TiCI 4 ), butyl ethyl magnesium (BEM) and tertiary butyl chloride (TBC), with an aluminum activator consisting of triethyl aluminum (TEAL or EtsAI) and diethyl aluminum ethoxide (DEAO or Et 2 AIOEt) was used.
• the BEM and TEAL were provided “premixed" (20/1 Mg/AI mole ratio).
• All catalyst components were mixed in the methyl pentane solvent.
• the mixing order was BEM/TEAL and TBC; followed by TiCI 4 ; followed by DEAO.
• the catalyst was pumped into the reactor together with the methyl pentane solvent.
• the catalyst flow rate had an aim point expressed as parts per million TiCI 4 by weight, as shown in the table and was adjusted to maintain total ethylene conversions above 80%.
• the effective volume of this tube is about 10% of the volume of the CSTR.
• Table 1 shows a "tubular reactor volume” of 10% - even though this volume is simply the volume of the discharge tube.
• the product produced in this reactor establishes a “baseline” for melt index, density and stress exponent.
• a second comparative experiment was conducted using essentially the same catalyst and CSTR as the first comparative experiment.
• a tubular reactor having a volume of 19.7 liters (about 82% of the volume of the CSTR) was connected to the discharge of the CSTR.
• No additional ethylene or catalyst was added to the tubular reactor.
• Further polymerization took place in the tubular reactor, as evidenced by a temperature increase of 14.5° C, corresponding to an estimated additional 14.3 kg/hr of copolymer formation.
• the estimation of 14.3 kg of polymer produced was made using the known enthalpy of reaction for this polymerization, combined with a heat and mass balance, using techniques that are well known to those skilled in the art).
• the polymer produced in this experiment contained a substantial amount of low molecular weight copolymer/low density copolymer (i.e. "waxy copolymer” containing a large amount of comonomer). This is illustrated by the change in hexane extractable level from 0.66 to 0.76 wt%.
• Comparative experiment 3 was conducted using the same CSTR and tubular reactor of comparative experiment 2, but additional ethylene was added to the tubular reactor.
• the temperature of the ethylene added to the tubular reactor was similar to the temperature of the ethylene added to the CSTR (about 41 0 C)
• Ethylene copolymer was prepared in essentially the same manner as
• a homopolymerization was conducted using the above described Ziegler/Natta catalyst.
• a tubular reactor having a volume of 82% of the CSTR was employed and a temperature rise of 24.8° C was observed across the length of the tubular reactor.
• the ethylene feed into the tubular reactor was tempered to 126° C.
• the homopolymer had a density of 0.965 g/cc, an Ml (or l 2 ) of 9.3 g/10 minutes and a hexane extractable level of 0.18%
• This example illustrates the use of a three reactor configuration (two CSTRs and a tubular reactor) and the use of a single site catalyst.
• the single site catalyst system includes a titanium catalyst component (namely cycopentadienyl) (tritertary butyl phosphinimine) titanium dichloride; methylalummoxane (or MAO); a hindered phenol (2,6 diterterary butyl, 6 ethyl phenol) and tetrakis
• a titanium catalyst component namely cycopentadienyl
• tritertary butyl phosphinimine titanium dichloride
• methylalummoxane (or MAO) methylalummoxane
• a hindered phenol 2,6 diterterary butyl, 6 ethyl phenol
• the first CSTR flows into the second CSTR which flows into the tubular reactor (i.e. the three reactors are connected in series).
• the first CSTR has a volume that is 54% of the volume of the second CSTR.
• the second CSTR used in this example was the same CSTR used in Examples 1 and 2.
• the tubular reactor had a volume of 82% of the volume of the second CSTR.
• a multi reactor process for the polymerization of ethylene is provided.
• the use of a tubular reactor in this process allows for higher catalyst efficiencies and lower energy consumption.
• the polyethylene that is produced by this process is useful for the production of a wide variety of products including extruded films and molded goods.

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