EP1203035A1 - Ameliorations relatives a des polymeres - Google Patents

Ameliorations relatives a des polymeres

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Publication number
EP1203035A1
EP1203035A1 EP00949766A EP00949766A EP1203035A1 EP 1203035 A1 EP1203035 A1 EP 1203035A1 EP 00949766 A EP00949766 A EP 00949766A EP 00949766 A EP00949766 A EP 00949766A EP 1203035 A1 EP1203035 A1 EP 1203035A1
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EP
European Patent Office
Prior art keywords
molecular weight
weight fraction
polymer
catalyst
polymer chain
Prior art date
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EP00949766A
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German (de)
English (en)
Inventor
Arild Follestad
Espen Ommundsen
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Borealis Technology Oy
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Borealis Technology Oy
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Publication of EP1203035A1 publication Critical patent/EP1203035A1/fr
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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
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/04—Monomers containing three or four carbon atoms
    • C08F110/06—Propene
    • 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
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/02—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
    • 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
    • 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
    • C08F4/65912—Component covered by group C08F4/64 containing a transition metal-carbon bond in combination with an organoaluminium compound
    • 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
    • C08F4/65916—Component covered by group C08F4/64 containing a transition metal-carbon bond supported on a carrier, e.g. silica, MgCl2, polymer

Definitions

  • the present invention relates to a process for the preparation of olefin polymers (including homopolymers and copoly ⁇ ners) , and to novel polymers obtainable thereby. More particularly the invention relates to a process and products wherein polymer chain defects (i.e. irregularities in the otherwise regular structure of a polymer, such as side chains or crystallinity disrupting monomer units) are introduced in a controlled manner across the molecular weight distribution of the polymer.
  • polymer chain defects i.e. irregularities in the otherwise regular structure of a polymer, such as side chains or crystallinity disrupting monomer units
  • the molecular weight distribution of polymers affects their properties, in particular their mechanical strength and processing properties. Mechanical strength is to a large extent determined by higher molecular weight fractions, whereas extrudability is determined by lower molecular weight fractions.
  • polyolefins having improved mechanical and processing properties may be obtained if the molecular weight distribution is tailored to the end use of the polymer.
  • polymers having a broad, or multi-modal, molecular weight distribution are desirable.
  • Polymers having a multi-modal molecular weight distribution consist of two or more polymer components and are generally characterised by a broad molecular weight distribution; such polymers exhibit excellent processability.
  • the mechanical properties of polymer products may be further manipulated by the inclusion of polymer chain defects, for example by incorporation of -olefin comonomers to vary the nature and relative content of short chain branches present as side chains. Depending on the nature of such a comonomer, its inclusion may result in an increase or, less commonly, a decrease in the degree of branching on the main polymer backbone.
  • polymer chain defects amongst individual polymer components is important in determining polymer properties.
  • the ability to control such distribution over the molecular weight distribution of a polymer is therefore particularly desirable, as in particular is the ability to produce multi -modal, e.g. bi -modal, molecular weight distribution copolymers in which polymer chain defects such as comonomer molecules are selectively incorporated in one part of the molecular weight distribution.
  • Polymers having a multi-modal, e.g. bi-modal, molecular weight distribution in which such defects, in particular increased relative content of side chains resulting from comonomer inclusion, are concentrated in a higher molecular weight fraction are especially desirable.
  • Such polymers exhibit good impact resistance, tear strength and environmental stress crack resistance.
  • a polymer chain defect such as a comonomer in a higher molecular weight fraction of a polymer may stimulate formation or enhance the effect of "tie molecules" which are able to participate in more than one crystal lamella. This is believed to contribute to the improved mechanical properties, especially the improved environmental stress crack resistance, of such polymers.
  • polystyrene resins can be produced in a single reactor using either catalyst mixtures or multi-site catalysts, e.g. two or more metallocene complex catalysts.
  • catalyst mixtures or multi-site catalysts e.g. two or more metallocene complex catalysts.
  • WO 95/04761 describes the use of a combination of three metallocene complexes to produce a polymer product having a controlled molecular weight distribution.
  • a catalyst system provides for little control over levels of incorporation of polymer chain defects such as comonomer molecules.
  • the lower molecular weight polymer molecules contain a relatively higher proportion of comonomer than the higher molecular weight polymer molecules.
  • this is generally limited to incorporation of comonomer in a lower molecular weight component; by way of example the majority of the ethylene copolymers exemplified in EP-A-0676418 contain a higher proportion of copolymer in the lower molecular weight fraction, and in only one product does the comonomer level of the higher molecular weight fraction exceed that of the lower molecular weight fraction (by a factor of 2:1) .
  • prior art products tend to exhibit a relatively poor balance of impact and stiffness and low environmental stress crack resistance.
  • the present invention is based on the finding that a catalyst system comprising a support material coimpregnated with at least two metallocenes and any necessary or desired cocatalyst (s) (i.e. a system in which all the catalyst and cocatalyst materials are simultaneously applied to the support material during preparation of the system) may be used in a single reaction stage to prepare new and useful olefin homopolymers and copolymers with highly advantageous properties.
  • s cocatalyst
  • a process for the preparation of an olefin polymer wherein olefin polymerisation is effected under essentially constant conditions in a single reactor in the presence of a catalyst system comprising a support material coimpregnated with at least two metallocene olefin polymerisation catalysts having different propensities for incorporation of polymer chain defects.
  • the metallocenes used in catalyst systems according to the invention are preferably selected to produce an olefin polymers in which the polymer chain defect content of a higher molecular weight fraction of the polymer is at least 3, preferably at least 5, e.g. at least 10, times that of a lower molecular weight fraction.
  • the level of polymer chain defect incorporation in a (or the) lower molecular weight fraction of such a polymer may advantageously be zero or substantially zero, in which case this fraction may essentially constitute a homopolymer, e.g. an ethylene homopolymer.
  • the catalyst is one capable of producing a copolymer in which short chain branching derived from comonomer incorporation is mainly, e.g.
  • the invention provides an olefin copolymer obtainable by the process in accordance with the invention, and products (e.g. containers, fibres, films, sheets, tubes, etc.) fabricated therefrom.
  • a polyolefin having essentially complete particle to particle homogeneity and comprising at least a higher molecular weight fraction and a lower molecular weight fraction, wherein the polymer chain defect content of said higher molecular weight fraction is at least 3 times that of said lower molecular weight fraction.
  • Preferred metallocenes for use in catalyst systems in accordance with the invention are those having catalytic sites capable of producing polymer components having a weight average molecular weight in the range
  • catalyst systems are those including a first metallocene capable of producing a relatively lower weight average molecular weightMw (higher melt flow rate) polymer (e.g. having a weight average molecular weight in the range 1,000 to 1,000,000, preferably 2,000 to 500,000) with a lower level of polymer chain defect incorporation, and a second metallocene capable of producing a relatively higher weight average molecular weight (lower melt flow rate) polymer (e.g. having a weight average molecular weight in the range 10,000 to 10,000,000, preferably 50,000 to 1,000,000) with a higher level of polymer chain defect incorporation.
  • a first metallocene capable of producing a relatively lower weight average molecular weightMw (higher melt flow rate) polymer (e.g. having a weight average molecular weight in the range 1,000 to 1,000,000, preferably 2,000 to 500,000) with a lower level of polymer chain defect incorporation
  • a second metallocene capable of producing a relatively higher weight average molecular weight (lower melt flow
  • Typical levels of polymer chain defect incorporation in a lower molecular weight component of the polymer are in the range 0 to 50, e.g. 0 to 25.
  • Typical levels of polymer chain defect incorporation in a higher molecular weight component of the polymer will be in the range from 0.1 to about 333, e.g. 5 to 100.
  • polymer chain defect level As used herein, the terms “polymer chain defect level”, “level of polymer chain defect incorporation” and “polymer chain defect content” are used interchangeably and are intended to define the average polymer chain defect content of any given polymer component or fraction over its entire molecular weight range.
  • levels of polymer chain defects such as comonomers are expressed as the short chain branching frequency, i.e. the number of short chain branches per thousand carbon atoms . This may be illustrated in the case of a homopolymer of propylene, in which a single monomeric unit comprises two backbone carbon atoms and one branching methyl group, so that there is Vb branch per total carbon atom content . This corresponds to a short chain branching frequency of 1000/3.
  • a comonomer to be incorporated may include non-branched or linear comonomers such as ethylene.
  • Comonomers which serve to reduce the degree of branching may act as crystallinity-disrupting units which result in a decrease in the crystallinity of the polymer material.
  • the comonomer level is determined by the average number of non-branched (or linear) units per thousand carbon atoms.
  • the process of the invention may be employed in both the homopolymerisation and copolymerisation of olefins.
  • homopolymerisation e.g. of ethylene
  • metallocenes the other metallocene catalysing formation of a backbone chain with long chain branches derived from the in si tu- generated comonomer.
  • long chain branches may advantageously each contain at least 10 monomer units and may advantageously be essentially homopoiymeric .
  • At least 50% by weight of the copolymer product preferably derives from a C 2 - ⁇ o -olefin monomer, more particularly from a C 2 _ 4 ⁇ - olefin monomer, preferably ethylene or propylene.
  • the other comonomer (s) may be any monomers capable of copolymerisation with the olefin monomer, preferably mono or polyunsaturated C 2 _ 20 compounds, in particular monoenes or dienes, especially C 2 _ 10 ⁇ -olefins such as ethene, propene, but-1-ene, pent-1-ene, hex-1-ene, oct- 1-ene or mixtures thereof, and may include in si tu- generated comonomers as discussed above. Bulky comonomers, e.g. styrene or norbornene may also be used.
  • the process is particularly effective for the preparation of copolymers of ethene with one or more copolymerisable monomers, e.g. C 3 _ 20 mono and dienes, more preferably C 3 _ 10 ⁇ -olefin monomers, and for the preparation of copolymers of propene with one or more copolymerisable monomers, e.g. C 4-20 mono and dienes, more preferably C
  • C Copolymers of propene with one or more copolymerisable monomers, e.g. C 4-20 mono and dienes, more preferably C
  • C Co- 10 ⁇ -olefin monomers or ethylene.
  • the process of the invention is particularly useful for the polymerisation of ethylene and hex-1-ene.
  • the polymer product has ethylene as the major monomer, i.e.
  • Catalyst systems containing metallocenes which respectively have stereospecific and non-stereospecific sites may also be used in accordance with the invention to produce polymers containing fractions with different crystallinities , for example polypropylenes containing isotactic and atactic fractions.
  • Metallocenes useful in accordance with the invention include cyclopentadienyl -containing organometallic compounds, preferably comprising a group 4, 5 or 6 metal, especially a group 4 metal.
  • the metallocene capable of producing the lower molecular weight fraction will preferably comprise a group 4 metal .
  • Metallocenes are an example of complexes in which a metal is complexed by ⁇ -ligands, i.e. complexes in which metals are complexed by the extended ⁇ -orbital system of organic ligands.
  • metal : ⁇ - ligand complexes may be used where the metal is complexed by one, two or more ⁇ -ligands.
  • twin ⁇ -ligand metallocenes and single ⁇ -ligand "half metallocenes" e.g. those developed by Dow
  • the term metallocene as used herein is used to refer to all such catalytically active complexes containing one or more ⁇ - ligands.
  • the metal in such complexes is preferably a group 4, 5, 6, 7 or 8 metal or a lanthanide or actinide, especially a group 4, 5 or 6 metal, particularly Zr, Hf , Ti or Cr.
  • the ⁇ -ligand preferably comprises a cyclopentadienyl ring, optionally with a ring carbon replaced by a heteroatom (e.g. N, B, S or P) , optionally substituted by pendant or fused ring substituents and optionally linked by a bridge (e.g.
  • a 1 to 4 atom bridge such as (CH 2 ) 2 , C(CH 3 ) 2 or Si(CH 3 ) 2 ) to a further optionally substituted homo or heterocyclic cyclopentadienyl ring.
  • the ring substituents may for example be halo atoms or alkyl groups optionally with carbons replaced by heteroatoms such as O, N and Si, especially Si and O and optionally substituted by mono or polycyclic groups such as phenyl or naphthyl groups. Examples of such homo or heterocyclic cyclopentadienyl ligands are well known from the scientific and patent literature, e.g.
  • ⁇ -bonding ligand may for example be of formula I
  • Cp is an unsubstituted, mono-substituted or polysubstituted homo or heterocyclic cyclopentadienyl, indenyl, tetrahydroindenyl , fluorenyl, benzindenyl, cyclopenta [1] phenanthrenyl , azulenyl, or octahydrofluorenyl ligand;
  • m is zero or an integer having a value of 1, 2, 3, 4 or 5; and where present each Y which may be the same or different is a substituent attached to the cyclopentadienyl ring moiety of Cp and selected from halogen atoms, and alkyl, alkenyl, aryl, aralkyl , alkoxy, alkylthio, alkylamino, (alkyl) 2 P, alkylsilyloxy, alkylgermyloxy, acyl , acyloxy and amido groups or
  • the rings fused to the homo or hetero cyclopentadienyl rings may themselves be optionally substituted e.g. by halogen atoms or groups containing 1 to 10 carbon atoms.
  • Suitable ⁇ -bonding ligands include the following: cyclopentadienyl, indenyl, fluorenyl, pentamethyl- cyclopentadienyl , methyl-cyclopentadienyl , 1,3 -dimethyl -cyclopentadienyl, i-propyl -cyclopentadienyl , 1,3- di-i-propyl-cyclopentadienyl , n-butyl-cyclopentadienyl , 1 , 3 -di -n-butyl -cyclopentadienyl , t-butyl - cyclopentadienyl, 1, 3-di-t-butyl-cyclopentadienyl, trimethylsilyl -cyclopentadienyl , 1, 3-di-trimethylsilyl- cyclopentadienyl, benzyl -cyclopentadien
  • the catalyst complex used according to the invention may include other ligands; typically these may be halide, hydride, alkyl, aryl , alkoxy, aryloxy, amide, carbamide or other two electron donor groups .
  • the catalyst composition comprises two ⁇ -ligand catalysts, preferably a combination of unbridged and bridged bis- ⁇ -liganded complexes of group 4, 5 or 6 metals, e.g. where the unbridged ⁇ -ligand complex is a metallocene with two homo or heterocyclopentadienyl ligands which are optionally ring substituted by fused or pendant substituent groups and the bridged ⁇ -ligand complex comprises two ⁇ -liganding groups joined by a 1 to 4 atom chain.
  • a metallocene combination would thus be (i) an unbridged biscyclopentadienyl Ti, Zr or Hf compound and (ii) a bridged bis-indenyl Ti, Zr or Hf compound, e.g. substituted Cp 2 ZrCl 2 in combination with optionally substituted CH 2 CH 2 (Ind) 2 ZrCl 2 or Si (CH 3 ) 2 (Ind) 2 ZrCl 2 .
  • An alternative combination would be a dimethylsilylbis (fluorenyl) Ti , Zr or Hf complex (e.g. optionally substituted SiMe, (fluorenyl) ZrCl 2 ) and a substituted biscyclopentadienyl Ti, Zr or Hf complex.
  • the different types of catalyst sites in the catalyst material used in the process of the invention may be present in substantially equal numbers (i.e. a mole ratio of 1:1, or 1:1:1, etc. for two or three catalyst -type systems) .
  • one catalyst type may be predominant with other catalyst types being present at a relative mol. % of for example 1 to 100% (100% representing a 1:1 mole ratio), preferably 5 to 80%, especially 10 to 70%.
  • the catalyst system may include one or more cocatalysts or catalyst activators and in this regard any appropriate cocatalyst or activator may be used.
  • cocatalysts and catalyst activators suitable for use in the invention include aluminium trialkyls (e.g. triethylaluminium) , aluminoxanes such as methylaluminoxane, cationic activators such as boron containing compounds, transition metal compounds (e.g. halogenide compounds), magnesium compounds, group 3 organometallic compounds, e.g. aluminium or boron based compounds.
  • Such materials may be solids, liquids or may be in solution in a liquid phase of the catalyst material which may be a solution, a solid, a dispersion, a suspension, a slurry, etc.
  • aluminoxanes include C 1-10 alkyl aluminoxanes, in particular methyl aluminoxane and aluminoxanes in which the alkyl groups comprise isobutyl groups optionally together with methyl groups.
  • Such aluminoxanes may be used as the sole cocatalyst or alternatively may be used together with other cocatalysts.
  • other cation complex forming catalyst activators may be used. In this regard mention may be made of the silver and boron compounds known in the art.
  • activators should react with the ⁇ -liganded complex to yield an organometallic cation and a non-coordinating anion (see for example the discussion on non-coordinating anions J " in EP-A-617052 (Asahi)).
  • Aluminoxane cocatalysts are described by Hoechst in WO 94/28034. These are cyclic oligomers of cage-like structure having up to 40, preferably 3 to 20, f/Al(R")0> repeat units (where R" is hydrogen, C 1-10 alkyl (preferably methyl and/or isobutyl) or C 6 _ 18 aryl or mixtures thereof) .
  • the support material of the catalyst system may be an inorganic or organic carrier material, preferably a solid particulate material which is preferably porous.
  • catalyst support materials may be used in this regard, e.g. porous inorganic or organic materials, for example oxides such as silica, alumina, silica- alumina, silica with Ti , zirconia, etc, non-oxides such as magnesium halides, e.g. MgCl 2 , aluminium phosphate, zeolites etc, and polymers such as polystyrene, polymethacrylate, polystyrene-divinylbenzene and polyolefins such as polyethylene and polypropylene.
  • an inorganic support material this will preferably be treated, e.g. thermally or chemically to remove surface hydroxyl .
  • the ratio between the different metallocenes be substantially uniform within carrier particles, i.e. it is preferred that the ratio be the same on the surface as it is at different depths within the particles and that the ratio be substantially uniform between the particles.
  • the polymerisation may be effected using conventional procedures, e.g. as a slurry, gas phase, solution or high pressure polymerisation.
  • Slurry polymerisation includes polymerisation at slightly supercritical conditions. Mixed gas phase and slurry reactors are preferred.
  • Slurry polymerisation (e.g. bulk polymerisation) is preferably effected, e.g. in a tank reactor or more preferably a loop reactor.
  • a major monomer is propylene this may also function as a solvent/diluent as well as a reagent.
  • a non- polymerizable organic compound e.g. a C 3-10 alkane, for example propane or isobutane, may be used as a diluent. Where this is done, the volatile non-reacted or non- reactive materials will desirably be recovered and reused .
  • the reactor used in the process of the invention may conveniently be any of the conventionally used polymerisation reactors, e.g. reactors for solution polymerisation, slurry tank or slurry loop polymerisation or gas phase polymerisation, etc.
  • the reaction temperature will generally be in the range 60 to 110°C (e.g. 85-110°C)
  • the reactor pressure will generally be in the range 5 to 80 bar (e.g. 25-65 bar)
  • the residence time will generally be in the range 0.3 to 5 hours (e.g. 0.5 to 2 hours)
  • the diluent used will generally be an aliphatic hydrocarbon having a boiling point in the range -70 to +100°C.
  • polymerisation may if desired be effected under supercritical conditions, especially in loop reactors .
  • the reaction temperature used will generally be in the range 60 to 115°C (e.g. 70 to 110°C)
  • the reactor pressure will generally be in the range 10 to 25 bar
  • the residence time will generally be 1 to 8 hours.
  • the gas used will commonly be a non-reactive gas such as nitrogen together with monomer (e.g. ethylene or propylene) .
  • reaction temperature used will generally be in the range 130 to 270°C
  • reactor pressure will generally be in the range 20 to 400 bar
  • residence time will generally be in the range 0.1 to 1 hour.
  • the solvent used will commonly be a hydrocarbon with a boiling point in the range 80-200°C.
  • the catalyst material is introduced into the reactor used in the process of the invention as a single material containing all the components of the catalyst material, and may be a solution, a solid, a dispersion, a suspension or a slurry, etc.
  • the quantity of catalyst used will depend upon the nature of the catalyst, the reactor types and conditions and the properties desired for the polymer product. Conventional catalyst quantities, such as described in the publications referred to herein, may be used.
  • hydrogen may be used to further control the molecular weight of the olefin copolymer produced in the reactor. Molecular weight control may be effected through control of the hydrogen concentration or, alternatively, through control of the hydrogen consumption during the polymerisation process. In such cases, it is preferable to use a catalyst system which is responsive to hydrogen. Control over the molecular weight of the polymer can be readily achieved by monitoring the hydrogen and monomer consumption, i.e. for hydrogen the difference between hydrogen input and hydrogen output and for monomer the difference between monomer input and output. The ratio of hydrogen consumption to monomer consumption can be correlated well with polymer molecular weight and the product molecular weight can accordingly be adjusted to the desired level using this correlation and by appropriate adjustment of the hydrogen and monomer feed rate levels.
  • the process of the invention may optionally comprise further stages in addition to that of polymerisation, e.g. drying steps; blending of the polymer product with one or more further materials, e.g. further polymers, antioxidants, radiation (e.g. UV- light) stabilizers, antistatic agents, fillers, plasticisers, carbon black, colours, etc.; granulation, extrusion and pelletization; etc.
  • further materials e.g. further polymers, antioxidants, radiation (e.g. UV- light) stabilizers, antistatic agents, fillers, plasticisers, carbon black, colours, etc.
  • granulation, extrusion and pelletization etc.
  • the final polymer products of the process of the invention preferably have a melt flow rate of 0.1 to 500, a weight average molecular weight of 30,000 to 500,000 and a melting point of 70-165°C (e.g. 70-136°C for copolymers of ethylene and 120 to 165°C for copolymers of propylene) .
  • Such polymers may be formulated together with conventional additives, e.g. antioxidants , UV- stabilizers, colours, fillers, plasticisers, etc. and may be used for fibre or film extrusion, for raffia, for pipes, for cable or wire applications or for moulding, e.g. injection moulding, blow moulding, rotational moulding, etc., using conventional moulding and extrusion equipment.
  • the products of the invention have improved molecular weight and polymer chain defect distributions.
  • the process of the invention may be used with particular advantage to tailor the distribution of molecular weights in the higher molecular weight fraction of the overall polymer and this may be done in such a way as to include comonomer (which may provide side chains and as a result increased strength) primarily in the high molecular weight fraction.
  • comonomer may incorporate more into the longer rather than the shorter polymer chains as compared, for example, with the product obtained using a Ziegler or Phillips type catalyst in a similar process, so improving the mechanical properties of the polymer product.
  • the process of the invention allows the user to tailor the placement of comonomer into a high molecular weight fraction of a polymer and also to tailor the molecular weight profile of such a higher molecular weight fraction of a polymer.
  • the polymers produced using the catalysts or processes according to the invention have a number of beneficial properties relative to polymers produced using conventional techniques. For example, where a comonomer such as but-1-ene or hex-1-ene is used, this incorporates primarily into the longer rather than the shorter polymer chains so improving the mechanical and processing properties of the polymer product.
  • the polymer products have a high degree of particle to particle homogeneity.
  • the homogeneity of a polymer is often a matter of particular concern to end users since inhomogeneity may give rise to phenomena known as fish eyes, gels or white spots. This is particularly important for films but is also important for wires, cables, blow moulded products, injection moulded products, rotational moulded products, pipes and fibres.
  • Techniques suitable for isolating individual fractions of a sample of the copolymer include temperature rising elution fractionation. Differential scanning calorimetry, preferably using a stepwise isothermal segregation technique, may be used to measure comonomer content (see J.A. Parker, D.C. Bassett, R.H. Olley & P. Jaaskelainen, Polymer 35 [1994] , 4140) . There are several methods known in the art for determining the molecular weight distribution of a particular polymer sample; typically it may be determined by gel permeation chromatography . The contents of all of the documents referred to above are hereby incorporated herein by reference.
  • Figure 1 shows differential scanning calorimetry curves for polymers produced using conventional single site catalyst systems
  • Figures 2-5 and 7 show differential scanning calorimetry curves for polymers in accordance with the invention produced using dual site catalyst systems and corresponding differential scanning calorimetry curves for polymers produced using conventional single site catalyst systems;
  • Figure 6 shows a gel permeation chromatography curve for a polymer produced in accordance with the invention and corresponding gel permeation chromatography curves for polymers produced using conventional single site catalyst systems.
  • Figure 8 shows gel permeation chromatography curves for ethylene homopolymers produced in accordance with the invention.
  • Cp* pentamethyl-substituted cyclopentadienyl ligand, (CH 3 ) 5 Cp;
  • Mw weight average molecular weight
  • MWD molecular weight distribution
  • TREF temperature rising elution fractionation
  • a catalyst solution was prepared by mixing the following chemicals :
  • a catalyst solution was prepared by mixing the following chemicals :
  • a catalyst solution was prepared by mixing the following chemicals :
  • a catalyst solution was prepared by mixing the following chemicals :
  • a catalyst solution was prepared by mixing the following chemicals : - 0 . 0244 g Cp* 2 ZrCl 2
  • Figure 1 shows melting curves for the polymers produced using catalysts (A) and (D) .
  • the same height of curve at different melting temperatures is indicative of a greater proportion of the polymer at the lower melting temperature than at the higher. This is due to the difference in crystallinity and hence lower specific melting enthalpy at lower melting temperatures.
  • the height of the curves in Figure 1 therefore indicates the relative concentration of the polymer at each melting temperature. This means that the product produced using catalyst (A) has lower crystallinity than that produced using catalyst (D) , and the cross-over point is about 65 °C. Both of these polymers were found to exhibit a degree of fouling in the reactor.
  • Figures 2 and 3 show melting curves for the polymer produced using the dual site catalyst (E) and for the polymers produced using the corresponding single site catalysts, (B) and (D) .
  • the dual site catalyst did not exhibit fouling. This is considered surprising given that the low crystallinity polymer components each have melting temperatures lower than the polymerisation temperature.
  • the dual site DSC curves correspond to a product having low crystallinity components and correspond well with the melting curves for those products produced from the individual catalyst components. T " he shift of the main peak may be explained by co-crystallisation.
  • Figures 4 and 5 show melting curves for the polymer produced using the dual site catalyst (C) and for the polymers produced using the corresponding single site catalysts, (A) and (B) .
  • the dual site catalyst did not exhibit fouling.
  • comonomer content may be determined according to the equation:
  • Y -0.8714. t + 113.67 where Y is comonomer content (branches per 1000 C atoms) and t is the melting temperature.
  • the low crystallinity/high comonomer/high Mw tail profile confirms that a product comprising a mixture of low and high molecular weight, homo and copolymers, may be produced in accordance with the invention in a single reaction stage.
  • the catalyst was produced analogously to supported catalyst (D) except that zirconium was used in place of hafnium and the relative amounts were adjusted to produce a supported catalyst product comprising
  • a dually impregnated carrier was prepared as above using a catalyst solution prepared by mixing 0.044 g (nBuCp) 2 ZrCl 2 , 0.0269 g Et (1- Ind) 2 HfCl 2 , 1.2 ml MAO solution (30 wt% MAO in toluene from Albemarle SA) , and 0.4 ml toluene .
  • the supported catalyst product comprised 0.011 mmol (nBuCp) 2 ZrCl 2 /g carrier; 0.0531 mmol
  • the polymer made with catalyst (F) with a high hexene concentration during polymerisation shows a typical single component co-polymer DSC melting behaviour.
  • the polymers made with catalyst (G) each contain two components of different crystallinity. This is most obvious on the product made with a high hexene concentration where a clear shoulder in the high crystallinity area is seen. The total curve is also shifted towards higher melting temperatures. This may be due to the high comonomer response from the Hf sites which consume most of the added comonomer, thereby causing a lower incorporation of comonomer in the polymer produced by the Zr sites. For the product made with a low hexene concentration, a disturbance on both sides of the peak can be detected, indicating at least two components.
  • the product made with catalyst (G) with a high hexene concentration during polymerisation has a higher Mw and Molecular weight distribution than that made with catalyst (F) .
  • This, together with an increase in melting temperature, and maintained melting enthalpy, is explained by the presence of two polymer fractions, one with a lower Mw and comonomer content than the other.
  • [g 1 is the ratio of measured viscosity to the theoretical viscosity of linear polymer with the same molecular weight]
  • Figure 8 shows the MWD of the samples from GPC measurements, the abscissa showing log (MW) and the ordinate showing dW.MW/d(MW) where W is the mass or mass fraction of polymer.
  • Example 6 Catalyst preparations
  • the catalyst was prepared analogously to supported catalyst (F) to give a supported catalyst product comprising 0.0314 g rac-dimethylsilyl bis (indenyl) - zirconium chloride.
  • the catalyst was prepared analogously to supported catalyst (F) to give a supported catalyst product comprising 0.0384 g dimethylsilyl bis (9 -fluorenyl ) - zirconium chloride.
  • a dually impregnated carrier was prepared analogously to supported catalyst (G) to give a supported catalyst comprising 90 mol% (0.0283 g) of rac-dimethylsilyl bis (indenyl) zirconium chloride and 10 mol% (0.0038 g) of dimethylsilyl bis (9-fluorenyl) zirconium chloride.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)

Abstract

L'invention concerne des homopolymères et des copolymères d'oléfines, comprenant de nouveaux produits ayant une homogénéité de particule à particule sensiblement complète et possédant des défauts de chaîne polymère introduits de manière contrôlée à travers leur répartition de poids moléculaire. Ces homopolymères et ces copolymères d'oléfines sont préparés par le biais d'un procédé comprenant la polymérisation dans des conditions sensiblement constantes, dans un réacteur unique, en présence d'un système catalyseur comportant un matériau de support co-imprégné au moyen d'au moins deux catalyseurs métallocènes de polymérisation d'oléfines ayant des propensions différentes d'incorporation de défauts de chaîne polymère.
EP00949766A 1999-07-29 2000-07-31 Ameliorations relatives a des polymeres Withdrawn EP1203035A1 (fr)

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GB9917851 1999-07-29
GBGB9917851.9A GB9917851D0 (en) 1999-07-29 1999-07-29 Process
PCT/GB2000/002970 WO2001009200A1 (fr) 1999-07-29 2000-07-31 Ameliorations relatives a des polymeres

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