WO2009071323A1 - Polymère de polyéthylène de faible densité, linéaire et multimodal - Google Patents

Polymère de polyéthylène de faible densité, linéaire et multimodal Download PDF

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Publication number
WO2009071323A1
WO2009071323A1 PCT/EP2008/010358 EP2008010358W WO2009071323A1 WO 2009071323 A1 WO2009071323 A1 WO 2009071323A1 EP 2008010358 W EP2008010358 W EP 2008010358W WO 2009071323 A1 WO2009071323 A1 WO 2009071323A1
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Prior art keywords
ethylene
polymer
molecular weight
olefin
film
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PCT/EP2008/010358
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English (en)
Inventor
Marit Seim
Siw Bodil Fredriksen
Irene Helland
Jorunn Nilsen
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Borealis Technology Oy
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Publication of WO2009071323A1 publication Critical patent/WO2009071323A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/08—Copolymers of ethene
    • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
    • C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/08—Copolymers of ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2314/00—Polymer mixtures characterised by way of preparation
    • C08L2314/02—Ziegler natta catalyst

Definitions

  • This invention relates to a multimodal linear low density polymer suitable for the manufacture of films which possess excellent impact properties as well as to films and other articles made from the polymer.
  • the polymer can be used to form monolayer films or a single layer in a multilayer film, e.g. a cast film or blown film. Further the invention relates to a process for producing the polymers as well to polymers having some special improved features.
  • LLDPE linear low density polyethylene
  • a broad range of LLDPE's are now used in injection molding, rotational molding, blow molding, pipe, tubing, and wire and cable applications.
  • LLDPE has essentially a linear backbone with only short chain branches, usually about 3 to 10 carbon atoms in length.
  • the length and frequency of branching, and, consequently, the density is controlled by the type and amount of comonomer and the catalyst type used in the polymerization.
  • LLDPE resins typically incorporate 1-butene or 1-hexene as the comonomer.
  • the use of a higher molecular weight alpha-olefin comonomer produces resins with significant strength advantages relative to those of ethyl ene/1- butene copolymers.
  • the predominant higher alpha-olefin comonomers in commercial use are 1-hexene, 4-methyl-l-pentene, and 1-octene.
  • the bulk of the LLDPEs manufactured today are used in film products where the excellent physical properties and drawdown characteristics of LLDPE film makes them well suited for a broad spectrum of applications. LLDPE films are often characterized by excellent tensile strength, high ultimate elongation, good impact strength, and excellent puncture resistance.
  • WO03/066699 describes films formed from an in situ blend of two polymer components in which a metallocene catalyst is used to manufacture the polymer. The films are said to have excellent sealing properties.
  • WO2005/014680 describes further in situ multimodal LLDPE polymers which have applications in injection moulding. The polymers are again manufactured using metallocene catalysis.
  • LLDPE's are generally made using particular constrained geometry metallocene catalysts and are for use in pipe manufacture.
  • the present inventors sought new multimodal polymers and films made therefrom that possess particularly good impact properties without compromising processability. This allows, for example, the formation of strong films with lower material cost.
  • the present inventors have now prepared a new polymer with remarkably high impact strength as well as good tear resistance which also possess desirable processability.
  • Good processability means, in general, higher output with less energy needed.
  • the invention provides a multimodal linear low density polyethylene polymer having a final density of 900 to 940 kg/m 3 , and containing at least two ⁇ -olefin comonomers in addition to ethylene comprising:
  • (B) 75 to 55 wt% of a higher molecular weight component being a copolymer of ethylene and at least one ⁇ -olef ⁇ n; wherein the multimodal LLDPE has a dart drop of at least 700 g; and wherein components (A) and (B) are preferably obtainable using a Ziegler-Natta catalyst.
  • the invention provides a multimodal linear low density polyethylene polymer having a final density of 900 to 940 kg/m 3 , and containing at least one ⁇ -olefin comonomer in addition to ethylene comprising:
  • the invention provides a process for the manufacture of a multimodal LLDPE as hereinbefore described comprising: in a first stage polymerising ethylene and optionally at least one ⁇ -olefin so as to form 25 to 45 wt% of a lower molecular weight component and; transferring the product of the first stage to a second stage and in a second stage polymerising ethylene and at least one ⁇ -olefin to form 75 to 55 wt% of a higher molecular weight component; ; wherein components (A) and (B) are preferably obtainable using a Ziegler- Natta catalyst.
  • the invention provides a composition comprising a multimodal linear low density polymer as hereinbefore described.
  • the invention provides an article, preferably a film comprising a multimodal linear low density polymer as hereinbefore described.
  • the invention provides use of a film as hereinbefore described in packaging as well as an article packaged using said film.
  • a multimodal polymer having a dart drop of at least 700 g is meant that when said multimodal polymer is formulated as a film of thickness 40 ⁇ m following the protocol set out in the film blowing example below, the dart drop of the formed film when measured using ISO 7765-1, method "A" (A dart with a 38 mm diameter hemispherical head is dropped from a height of 0.66 m onto a film clamped over a hole. If the specimen fails, the weight of the dart is reduced and if it does not fail the weight is increased. At least 20 specimens are tested. The weight resulting in failure of 50% of the specimens is calculated), a value of at least 700 g is obtained.
  • This invention relates to a multimodal linear low density polyethylene having at least two components, a lower molecular weight component (A) and a higher molecular weight component (B).
  • the multimodal LLDPE polymer of the invention should have a density of
  • the MFR 2 of the multimodal LLDPE is preferably be in the range 0.001 to 10 g/lOmin, preferably 0.01 to 5 g/lOmin, e.g. 0.05-1 g/10min. Generally, MFR 2 is less than 5, especially less than 3 g/10min (ISO 1133, 190 °C/min, 2,16 kg load).
  • the MFR 5 of the multimodal LLDPE is preferably be in the range 0.05 to 10 g/10min, preferably 0.1 to 5 g/10min, e.g. 0.5-3 g/10min, especially 0.8 to 3 g/10min (ISO 1133, 190 °C/min, 5,0 kg load).
  • the MFR 2I for multimodal LLDPE should be in the range 5 to 150, preferably 10 to 100 g/10min, e.g. 15 to 70 g/10 min (ISO 1133, 190 °C/min, 21,6 kg load).
  • the FRR (MFR 21 /MFR 2 ) of the polymer of the invention may be 10 to 100.
  • the Mw of multimodal LLDPE should be in the range 100,000 to 400,000, preferably 130,000 to 300,000.
  • the Mn should be in the range 5000 to 35,000, preferably 8,000 to 25,000.
  • the Mw/Mn for multimodal LLDPE should be in the range 5 to 25, e.g. 7 to 22.
  • the multimodal LLDPE of the invention possess a low xylene soluble fraction.
  • the XS may be less than 20 wt%.
  • the multimodal LLDPE may formed from ethylene along with at least one other ⁇ -olef ⁇ n comonomer, preferably at least one C3-12 ⁇ -olefin comonomer, more preferably at least one C4-12 ⁇ -olefin comonomer, e.g. 1-butene, 1-hexene or 1- octene.
  • the HMW component can contain at least one comonomer which is the same as one employed in the LMW component but ideally both components are not polymers of ethylene and butene alone.
  • both components can be polymers of ethylene and hexene (or ethylene and octene and so on) although it will be appreciated that both components are different even if the same comonomer is used in both components.
  • the molecular weight of the two components must be different.
  • Preferred comonomer combinations include (LMW/HMW) butene/hexene, hexene/butene and hexene/hexene.
  • the multimodal LLDPE is preferably formed from ethylene along with at least two other ⁇ -olefin comonomers, preferably C3-12 ⁇ -olefin comonomers.
  • the multimodal LLDPE is a terpolymer, i.e. the polymer contains ethylene and two comonomers. It is also preferred if the HMW component contains at least one comonomer which is different from that employed in the LMW component.
  • the HMW component contains at least one comonomer which is of higher molecular weight to that employed in the LMW component.
  • the HMW component can comprise the same monomer as used in the LMW component as long as the HMW component additionally contains a comonomer different from and preferably heavier than that used in the LMW component.
  • the amount of comonomer present in the multimodal LLDPE as a whole is preferably 1 to 20 wt%, e.g. 2 to 15% wt% relative to ethylene, especially 5 to 13 wt%.
  • the 1-hexene content of the LLDPE of the invention is less than 8 mol%.
  • the butene content of the multimodal polymer of the invention is less than 5 mol%, more preferably less than 4 mol%, determined by C 13 NMR.
  • the molar ratio of these components may be in the range 5:1 to 1 :5, e.g. 3:1 to 1 :3, preferably 1 :1 to 1 :3.
  • butene is a cheaper comonomer than hexene any increase in the butene content without loss of properties is advantageous.
  • the multimodal LLDPE of the invention comprises at least a lower molecular weight component (LMW) and a higher molecular weight (HMW) component.
  • LMW lower molecular weight component
  • HMW higher molecular weight
  • a polyethylene e.g. LLDPE composition
  • multimodal a polyethylene, e.g. LLDPE composition
  • multimodal polymer includes so called “bimodal” polymer consisting of two fractions.
  • LLDPE will show two or more maxima or is typically distinctly broadened in comparison with the curves for the individual fractions.
  • the polymer fractions produced in the different reactors will each have their own molecular weight distribution and weight average molecular weight.
  • the individual curves from these fractions form typically together a broadened molecular weight distribution curve for the total resulting polymer product.
  • the LMW component has a lower molecular weight than the higher molecular weight component. Preferably there may be a difference in molecular weight of at least 1000, preferably at least 5000, especially at least 20,000 between components.
  • the multimodal LLDPE of the invention is preferably bimodal or trimodal, especially bimodal.
  • the lower molecular weight component of the multimodal LLDPE preferably has a MFR 2 of at least 50, preferably at least 100 g/10min, preferably 110 to 3000 g/10min, e.g. 110 to 500 g/lOmin, especially 150 to 400 g/lOmin.
  • the molecular weight of the low molecular weight component should preferably range from 15,000 to 50,000, e.g. 20,000 to 40,000.
  • the Mw/Mn of the LMW component is in the range 3 to 10, e.g. 5 to 8.
  • the density of the lower molecular weight component may range from 930 to 980 kg/m 3 , e.g. 940 to 970 kg/m 3 preferably 945 to 965 kg/m 3 , especially 947 to 955 kg/m 3 . It is a feature of the invention that the density of the LMW component is comparatively low for a multimodal polymer. It is preferred however if the density is 950 kg/m 3 or more.
  • the amount of LMW component is critical. In order to ensure the very high dart drop values required of the polymers of the invention, the HMW component needs to be in excess.
  • the lower molecular weight component should preferably form 25 to 45 wt%, e.g. 30 to 43% by weight, especially 32 to 42 wt%, most especially 33 to 40 wt% of the multimodal LLDPE. Ideal splits are around 35 or 36% LMW component.
  • the LMW component forms less than 41 wt% of the multimodal LLDPE, e.g. 30 to 40 wt%. Especially preferably the lower molecular weight component forms 39 wt% or less of the multimodal LLDPE.
  • the lower molecular weight component can be an ethylene homopolymer (i.e. where ethylene is the only monomer present) but is preferably an ethylene copolymer, especially where only one comonomer is present. Especially preferably it is a copolymer of ethylene and 1-butene .
  • the comonomer content in the LMW component is preferably kept as low as possible. Comonomer contents of the order of less than 3 wt% are appropriate, preferably less than 2wt% .
  • the higher molecular weight component should have a lower MFR 2 and a lower density than the lower molecular weight component.
  • the higher molecular weight component should have an MFR 2 of less than 1 g/10 min, preferably less than 0.5 g/10 min, especially less than 0.2 g/lOmin.
  • the MFR 21 of the HMW component should be in the range 0.1 to 20, preferably 1 to 10 g/10min, e.g. 2 to 8 g/10 min.
  • the higher molecular weight component should have a density of less than 915 kg/m , e.g. less than 913 kg/m , preferably less than 912 kg/m , especially less than 910 kg/m 3 . It is a feature of the invention that the HMW component possesses a very low density. It is also preferred however if the density of the HMW component is greater than 902 kg/m 3 . Ideally, the density should be in the range 902 to 912 kg/m 3 .
  • the Mw of the higher molecular weight component may range from 100,000 to 1,000,000, preferably 150,000 to 500,000.
  • the Mw/Mn of the HMW component is in the range 3 to 10, e.g. 5 to 8.
  • the higher molecular weight component forms 70 to 40 wt%, e.g. 65 to 45% by weight, more preferably 60 to 50, especially 60 to 52 wt% of the multimodal LLDPE.
  • the HMW component forms more than 59 wt% of the multimodal LLPDE, preferably more than 60 wt%, e.g. 61 wt% or more, e.g. more than 61 wt%.
  • the HMW component can form 62 wt% or more, e.g. 63 wt% or more, such as 64 wt% or more of the multimodal LLDPE.
  • the higher molecular weight component is preferably an ethylene copolymer, in particular a binary copolymer (i.e. where only one comonomer is present) or a terpolymer (with two comonomers). It is preferred if the HMW component contains at least one ⁇ -olefin which is not present in the LMW component. It is also preferred if the HMW component contains at least one comonomer of greater molecular weight than those used in the LMW component.
  • the HMW component preferably contains at least 2 ⁇ -olefin comonomers.
  • the HMW component is a binary copolymer of ethylene and hexene or a terpolymer of ethylene, butene and hexene.
  • the amount of comonomer present in the HMW component may range from 1 to 6 wt%, e.g. 2 to 5 wt%, especially 3 to 5 wt%. It should be noted that comonomer amounts in HMW component can not be measured directly (in a process where the HMW component is formed second in a multistage process), but may be calculated based on the amount of the LMW component present and of the final polymer as well as knowledge of the production split.
  • the butene content may be of the order of less than 1 mol%, e.g. 0.1 to 1 mol%, such as 0.2 to 0.8 mol% and the hexene content in the range 1 to 5 mol%.
  • the molar ratio between these two may be at least 1 :2, e.g. at least 1 :4, preferably at least 1 :6, especially at least 1 :10.
  • the LMW component is an ethylene butene copolymer and the HMW component is an ethylene hexene copolymer or ethylene butene hexene terpolymer.
  • the LMW component is an ethylene homopolymer and the HMW component is an ethylene butene octene terpolymer.
  • the invention therefore provides a multimodal linear low density polyethylene polymer having a final density of 900 to 940 kg/m 3 , and containing butene and hexene in addition to ethylene comprising: (A) 39 wt% or less of a lower molecular weight component being an ethylene butene copolymer;
  • the invention therefore provides a multimodal linear low density polyethylene polymer having a final density of 900 to 940 kg/m 3 , and containing butene and hexene in addition to ethylene comprising:
  • the invention therefore provides a multimodal linear low density polyethylene polymer having a final density of 900 to 940 kg/m 3 , and containing butene and hexene in addition to ethylene comprising:
  • the multimodal LLDPE may comprise other polymer components over and above the LMW and HMW components.
  • the polymer may contain up to 10 % by weight of a polyethylene prepolymer (obtainable from a prepolymerisation step as well known in the art).
  • the prepolymer component may be comprised in one of LMW and HMW components, preferably LMW component, as defined above.
  • the polymer of the invention can exhibit very high dart drop.
  • Dart drop F50 (ISO 7765/1) may be at least 240, e.g. at least 350 g, preferably at least 400 g, e.g. at least 50Og, more preferably at least 700 g, especially at least 800 g, most especially at least 900 g.
  • Some polymers of the invention exhibit dart drop values of over 1000 g.
  • the multimodal LLDPE polymer of the invention also exhibits excellent tear resistance.
  • tear resistance in the machine direction may be at least IN, preferably at least 1. IN, especially ay least 1.2N.
  • the tear resistance in the transverse direction may be at least ION, preferably at least 11 N, especially at least 12 N.
  • the polymer of the invention can exhibit excellent shear thinning properties.
  • the SHI 1/100 values may be 11 or more, preferably 12 or more.
  • the SHI 2.7/210 values are typically 35 or more, e.g. 40 or more.
  • Multimodal LLDPE polymers may be prepared for example by two or more stage polymerization or by the use of two or more different Ziegler Natta polymerization catalysts in a one stage polymerization. It is important, however, to ensure that the higher and lower molecular weight components are intimately mixed prior to extrusion. This is most advantageously achieved by using a multistage process.
  • the multimodal LLDPE is produced in a two-stage polymerization using the same Ziegler-Natta catalyst in both steps.
  • Two-stage polymerisation can be carried out in one reactor or e.g. in two different reactors. In the latter case, for example, two slurry reactors or two gas phase reactors could be employed.
  • the multimodal LLDPE is made using a slurry polymerization in a loop reactor followed by a gas phase polymerization in a gas phase reactor.
  • a loop reactor - gas phase reactor system is marketed by Borealis as a BORSTAR reactor system.
  • Any multimodal LLDPE of the invention is preferably formed in a two stage process comprising a first slurry loop polymerisation followed by gas phase polymerisation.
  • 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. 50-65 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.
  • polymerization may if desired be effected under supercritical conditions.
  • Slurry polymerisation may also be carried out in bulk where the reaction medium is formed from the monomer being polymerised.
  • the reaction temperature used will generally be in the range 60 to 115°C (e.g. 70 to HO 0 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 or low boiling point hydrocarbons such as propane together with monomer (e.g. ethylene).
  • the lower molecular weight polymer fraction is produced in a continuously operating loop reactor where ethylene is polymerised in the presence of comonomer(s), a Ziegler Natta polymerization catalyst with conventional cocatalysts, i.e. compounds of Group 13 metal, like Al alkyl compounds, and a chain transfer agent such as hydrogen.
  • the diluent is typically an inert aliphatic hydrocarbon, preferably isobutane or propane.
  • the C4/C2 ratio in the first stage is 200 to 600 mol/kmol.
  • the hydrogen feed may be of the order of 50 to 150 g/h.
  • the higher molecular weight component can then be formed in a gas phase reactor using the same catalyst.
  • the split between the two components is critical. Whilst higher concentrations of HMW component increase the dart drop and tear resistance, it becomes more difficult to run a process for the manufacture of the polymer when the proportion of HMW component becomes too high. It is a feature of the invention that very high dart drop values can be achieved at conventional LMW/HMW split ratios.
  • the LMW and HMW components are made in situ.
  • the HMW component is made as a second step in a multistage polymerisation it is not possible to measure its properties directly.
  • the density, MFR2 etc of the HMW component can be calculated using Kim McAuley's equations.
  • both density and MFR2 can be found using K. K. McAuley and J. F. McGregor: On-line Inference of Polymer Properties in an Industrial Polyethylene Reactor, AIChE Journal, June 1991, Vol. 37, No, 6, pages 825-835.
  • the density is calculated from McAuley's equation 37, where final density and density after the first reactor is known.
  • MFR2 is calculated from McAuley's equation 25, where final MFR2 and MFR2 after the first reactor is calculated.
  • All components of the multimodal LLDPE of the invention are preferably made using a Ziegler Natta catalyst.
  • Preferred Ziegler-Natta catalysts comprise a transition metal component and an activator.
  • the transition metal component comprises a metal of Group 4 or 5 of the Periodic System (IUPAC) as an active metal. In addition, it may contain other metals or elements, like elements of Groups 2, 13 and 17.
  • the transition metal component is a solid. More preferably, it has been supported on a support material, such as inorganic oxide carrier or magnesium halide. Examples of such catalysts are given, among others in WO
  • the transition metal component comprises a titanium halide, a magnesium alkoxy alkyl compound and an aluminium alkyl dihalide supported on an inorganic oxide carrier.
  • a catalyst of Ziegler Natta type wherein the active components are dispersed and solidified within Mg-based support by the emulsion/solidification method adapted to PE catalyst, e.g. as disclosed in WO03106510 of Borealis, e.g. according to the principles given in the claims thereof.
  • the catalyst is a non-silica supported catalyst, i.e. the active components are not supported to an external silica support.
  • the support material of the catalyst is a Mg-based support material. Examples of such preferred Ziegler-Natta catalysts are described in EP 0 810 235.
  • Multimodal (e.g. bimodal) polymers can also be made by mechanical blending of the polymer in a known manner.
  • the polyethylene composition is produced using a ZN catalysts disclosed in EP 688794.
  • a ZN catalysts disclosed in EP 688794.
  • Conventional cocatalysts, supports/carriers, electron donors etc can be used.
  • the Ziegler Natta catalyst is a Mg complex formed with BOMAG (butyl octyl magnesium) and 2-ethylhexanol.
  • BOMAG butyl octyl magnesium
  • 2-ethylhexanol 2-ethylhexanol.
  • the molar ratio of these components can be in the range EHA/Mg molar ratio 1.5 to 2.5.
  • the catalyst is ideally supported on a carrier such as silica.
  • a carrier such as silica.
  • Ethyl aluminium dichloride is the preferred Al compound and TiCl 4 the preferred titanium species.
  • a crucial aspect of the invention is the very high amount of HMW polymer present in the multimodal LLDPE.
  • To achieve such a marked split between lower and higher molecular weight components requires manipulation of the polymerisation parameters. For example, higher levels of catalyst than normal might be used, the ethylene partial pressure may be lowered in the LMW phase compared to conventional levels but elevated in the HMW phase. It may also be necessary to increase flushing from the LMW stage.
  • the multimodal polymer of the invention can be combined with other polymer components, e.g. LDPE, LLDPE components or HDPE polymers to form a composition comprising the polymer of the invention. It is also possible to combine two polymers of the invention to make a highly preferred composition. Preferably however, no other polymer components are present and the multimodal polymer of the invention is the only polymer component used in the manufacture of a film (or layer of a film).
  • the polymer can however form a composition with conventional additives such as antioxidants, UV stabilisers, acid scavengers, nucleating agents, anti-blocking agents as well as polymer processing agent (PPA).
  • PPA polymer processing agent
  • the polymer of the invention can be in the form of powder or pellets, preferably pellets.
  • Pellets are obtained by conventional extrusion, granulation or grinding techniques and are an ideal form of the polymer of the invention because they can be added directly to converting machinery. Pellets are distinguished from polymer powders where particle sizes are less than 1 mm. The use of pellets ensures that the composition of the invention is capable of being converted in a film, e.g. monolayer film, by the simple in line addition of the pellets to the converting machinery.
  • the polymers of the invention have been found to allow the formation of films having an ideal balance of properties. They have excellent mechanical properties and are readily processed. In particular, films exhibit high dart impact strengths, high tear strengths, sealability and good processability.
  • the films of the invention are preferably monolayer films or the polymer of the invention is used to form a layer within a multilayer film.
  • Any film of the invention may have a thickness of 10 to 250 ⁇ m, preferably 20 to 200 ⁇ m, e.g. 30 to 150 ⁇ m, such as e.g. 30 to 135 ⁇ m, preferably 30 to 60 ⁇ m.
  • the films of the invention can be manufactured using simple in line addition of the polymer pellets to an extruder.
  • a polymer mixture it is important that the different polymer components be intimately mixed prior to extrusion and blowing of the film as otherwise there is a risk of inhomogeneities, e.g. gels, appearing in the film.
  • it is especially preferred to thoroughly blend the components for example using a twin screw extruder, preferably a counter- rotating extruder prior to extrusion and film blowing.
  • Sufficient homogeneity can also be obtained by selecting the screw design for the film extruder such that it is designed for good mixing and homogenising.
  • the film of the invention can be blown or cast, preferably blown.
  • Blown films will typically be produced by extrusion through an annular die, blowing into a tubular film by forming a bubble which is collapsed between nip rollers after solidification. This film can then be slit, cut or converted (e.g. gusseted) as desired. Conventional film production techniques may be used in this regard.
  • the composition will be extruded at a temperature in the range 160°C to 240°C, and cooled by blowing gas (generally air) at a temperature of 10 to 50°C to provide a frost line height of 1 or 2 to 8 times the diameter of the die.
  • the blow up ratio should generally be in the range 1.5 to 4, e.g. 2 to 4, preferably 2.5 to 3.
  • the film of the invention can also be a cast film.
  • the cast film process involves the extrusion of polymers melted through a slot or flat die to form a thin, molten sheet or film. This film is "pinned" to the surface of a chill roll (typically water-cooled and chrome-plated) by a blast of air from an air knife or vacuum box. The film quenches immediately and then has its edges slit prior to winding. Because of the fast quenching step, a cast film generally has better optical properties than a blown film and can be produced at higher line speeds.
  • the films of the invention exhibit high dart impact strengths and tear strengths, especially in the machine direction. In the passages which follow, certain parameters are given based on a specific film thickness.
  • Dart drop F50 (ISO 7765/1) may be at least 240, e.g. at least 350 g, preferably at least 400 g, e.g. at least 500g, more preferably at least 700 g, especially at least 800 g, most especially at least 900 g.
  • Some polymers of the invention exhibit dart drop values of over 1000 g.
  • Elmendorf Tear resistances in the machine direction for a 40 ⁇ m film, especially a monolayer film, more especially a monolayer film consisting essentially of the multimodal polymer of the invention may be at least 1.5 N.
  • Elmendorf Tear resistances in the transverse direction for a 40 ⁇ m film prepared as described in the examples section may be at least IO N, 12N, especially at least 15N. In general as TD tear resistance improves, MD resistance decreases.
  • the tear resistance in the transverse direction may be at least 1 ON, preferably at least 11 N, especially at least 12 N.
  • the films of the invention may be laminated on to barrier layers as is known in the art.
  • barrier layers i.e. a layer which is impermeable to water and oxygen, into the film structure. This can be achieved using conventional lamination techniques.
  • Suitable barrier layers are known and include polyamide, ethylene vinyl alcohol, PET and metallised Al layers.
  • the invention provides a laminate comprising a film as hereinbefore defined laminated onto a barrier layer.
  • a barrier layer may be convenient to laminate the barrier layer onto two monolayer films as hereinbefore described thereby forming a 3 layer structure in which the barrier layer forms the middle layer.
  • the films of the invention have a wide variety of applications but are of particular interest in packaging of food and drink, consumer and industrial goods, medical devices and in heavy duty packaging. Specific applications include industrial liners, heavy duty shipping sacks, carrier bags, bread bags and freezer bags.
  • the polymers of the invention may also be used in rotomoulding, injection moulding, blow moulding, extrusion coating, wire, cable and pipe formation.
  • Density of the materials is measured according to ISO 1183-1 :2004 "Immersion method".
  • MFR2/5/21 are measured according to ISO 1133 at 190°C at loads of 2.16, 5 and
  • Impact resistance is determined on Dart-drop (g/50%).
  • Dart-drop is measured using ISO 7765-1, method "A”.
  • a dart with a 38 mm diameter hemispherical head is dropped from a height of 0.66 m onto a film clamped over a hole. If the specimen fails, the weight of the dart is reduced and if it does not fail the weight is increased. At least 20 specimens are tested. The weight resulting in failure of 50% of the specimens is calculated.
  • the films were produced as described below in the film preparation example.
  • the tear strength is measured using the ISO 6383/2 method.
  • the force required to propagate tearing across a film specimen is measured using a pendulum device.
  • the pendulum swings under gravity through an arc, tearing the specimen from a pre-cut slit.
  • the specimen is fixed on one side by the pendulum and on the other side by a stationary clamp.
  • the tear strength is the force required to tear the specimen.
  • the relative tear resistance (N/mm) is then calculated by dividing the tear resistance by the thickness of the film.
  • Molecular weights, molecular weight distribution ( Mn, Mw, MWD)
  • a Waters 150CV plus instrument, equipped with refractive index detector and online viscosimeter was used with 3 x HT6E styragel columns from Waters (styrene-divinylbenzene) and 1 ,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-Di tert butyl-4-methyl-phenol) as solvent at 140 °C and at a constant flow rate of 1 mL/min. 500 ⁇ L of sample solution were injected per analysis.
  • the column set was calibrated using universal calibration (according to ISO 16014- 2:2003) with 10 narrow MWD polystyrene (PS) standards in the range of 1.05 kg/mol to 11 600 kg/mol.
  • FTIR Fourier transform infrared spectroscopy
  • Shear thinning index (SHI) which correlates with MWD and is independent of Mw, was calculated according to Heino ("Rheological characterization of polyethylene fractions" Heino, E. L., Lehtinen, A., Tanner J., Seppala, J., Neste Oy, Porvoo, Finland, Theor. Appl. Rheol., Proc. Int. Congr. Rheol, 11th (1992), 1, 360-362, and "The influence of molecular structure on some rheological properties of polyethylene", Heino, EX., Borealis Polymers Oy, Porvoo, Finland, Annual Transactions of the Nordic Rheology Society, 1995.)
  • SHI value is obtained by calculating the complex viscosities ⁇ *(1.0 kPa) and ⁇ *(100 kPa) at a constant value of complex modulus of 1.0 kPa and 100 kPa, respectively.
  • the shear thinning index SHI(I /100) is defined as the ratio of the two viscosities ⁇ *(l kPa) and ⁇ *(100 kPa), i.e. ⁇ (l)/ ⁇ (100).
  • the Melting Temperature (Tm) and the Crystallization Temperature (Tcr) were measured with Mettler TA820 differential scanning calorimeter (DSC) on 3 ⁇ 0.5 mg samples. Both crystallization and melting curves were obtained during 10°C/min cooling and heating scans between -10 - 200°C. Melting and crystallization temperatures were taken as the peaks of endotherms and exotherms, respectively. The degree of crystallinity was calculated by comparison with heat of fusion of a perfectly crystalline polyethylene, i.e. 290 J/g.
  • BOMAG butyl octyl magnesium, 20wt% sol in toluene 1,4 mol Mg/kg of carrier
  • 2-ethylhexanol (2-EHA - 2,56 mol/kg of carrier, dried on molecular sieves) was slowly added (at least Ih addition).
  • the EHA/Mg molar ratio was 1,83. Reaction temperature was kept below 38°C. The solution was mixed for 5h minimum.
  • pentane (0,55kg/kg of carrier) was added to the reactor and mixed for 5h.
  • the temperature was kept under 40°C.
  • TiCl 4 (0,7 mol/kg of carrier) was added during at least 45 min and the reactor temperature was kept.
  • the mixture was mixed during 5h at a temperature between 40 and 50°C.
  • the polymerisation were carried out in a two stage process comprising a slurry loop polymerisation followed by a gas phase polymerisation.
  • the first stage of the polymerisations below was carried out in a 500 dm 3 loop reactor in the presence of ethylene, comonomer, propane and hydrogen in the amounts specified in table 1.
  • the temperature was 85°C
  • the catalyst was added directly to the loop reactor as well as the cocatalyst.
  • the cocatalyst (TEA) as 10 wt% solution in pentane) are further diluted with propane to have a final concentration between 1 and 2 wt%.
  • the amount of cocatalyst fed is calculated in order to maintain an Al/Ti ratio of 20 mol/mol.
  • the polymer containing active catalyst was separated from the reaction medium and transferred to a gas phase reactor operated at 20 bar pressure and 85°C where additional ethylene, hydrogen and comonomer were added and the amount are also specified in Table 1.

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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)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)

Abstract

La présente invention concerne un polymère de polyéthylène de faible densité, linéaire et multimodal ayant une densité finale de 900 à 940 kg/m3, et contenant au moins un comonomère d'α-oléfine outre l'éthylène, qui comprend : (A) moins de 41 % en poids d'un composant de masse moléculaire inférieure étant un homopolymère d'éthylène ou un copolymère d'éthylène et au moins une α-oléfine ; et (B) plus de 59 % en poids d'un composant de masse moléculaire supérieure étant un copolymère d'éthylène et au moins une α-oléfine ayant une densité dans la plage de 902 à 912 kg/m3 ; et les composants (A) et (B) pouvant être obtenus en utilisant un catalyseur de Ziegler-Natta.
PCT/EP2008/010358 2007-12-05 2008-12-05 Polymère de polyéthylène de faible densité, linéaire et multimodal WO2009071323A1 (fr)

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EP2415598A1 (fr) * 2010-08-06 2012-02-08 Borealis AG Film multicouche
WO2016083209A1 (fr) * 2014-11-26 2016-06-02 Borealis Ag Couche de film
US20160280821A1 (en) * 2013-12-13 2016-09-29 Borealis Ag Multistage process for producing polyethylene compositions
WO2016198273A1 (fr) 2015-06-10 2016-12-15 Borealis Ag Copolymère multimodal comprenant de l'éthylène et au moins deux comonomères d'alpha-oléfine, et articles finaux fabriqués à partir du copolymère
WO2016198271A1 (fr) 2015-06-10 2016-12-15 Borealis Ag Copolymère multimodal de polyéthylène
KR101907331B1 (ko) 2014-11-26 2018-10-11 보레알리스 아게 필름 층을 위한 폴리에틸렌 조성물
CN109135551A (zh) * 2018-08-09 2019-01-04 深圳市前海奇迹新材料有限公司 一种高柔韧性水性uv涂料
CN111448227A (zh) * 2017-12-26 2020-07-24 陶氏环球技术有限责任公司 包括多峰型乙烯类聚合物和低密度聚乙烯(ldpe)的组合物
CN111655744A (zh) * 2017-12-26 2020-09-11 陶氏环球技术有限责任公司 韧性改善的多峰型乙烯类聚合物组合物
EP2970644B1 (fr) 2013-03-11 2022-09-14 Chevron Phillips Chemical Company LP Nouvelles compositions de polyéthylène moyenne densité
US11555084B2 (en) 2017-12-26 2023-01-17 Dow Global Technologies Llc Multimodal ethylene-based polymer processing systems and methods
US11680120B2 (en) 2017-12-26 2023-06-20 Dow Global Technologies Llc Dual reactor solution process for the production of multimodal ethylene-based polymer
US11680119B2 (en) 2017-12-26 2023-06-20 Dow Global Technologies Llc Process for the production of multimodal ethylene-based polymers

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EP0916693A2 (fr) * 1994-07-08 1999-05-19 Union Carbide Chemicals & Plastics Technology Corporation Feuille extrudée d'un mélange de copolymères d'éthylène
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WO2012016938A1 (fr) * 2010-08-06 2012-02-09 Borealis Ag Film multicouche
CN103068574A (zh) * 2010-08-06 2013-04-24 北欧化工公司 多层膜
US10053246B2 (en) 2010-08-06 2018-08-21 Borealis Ag Multilayer film
CN103068574B (zh) * 2010-08-06 2016-06-29 北欧化工公司 多层膜
EP2415598A1 (fr) * 2010-08-06 2012-02-08 Borealis AG Film multicouche
EP2970644B1 (fr) 2013-03-11 2022-09-14 Chevron Phillips Chemical Company LP Nouvelles compositions de polyéthylène moyenne densité
US10000592B2 (en) * 2013-12-13 2018-06-19 Borealis Ag Multistage process for producing polyethylene compositions
US20160280821A1 (en) * 2013-12-13 2016-09-29 Borealis Ag Multistage process for producing polyethylene compositions
WO2016083209A1 (fr) * 2014-11-26 2016-06-02 Borealis Ag Couche de film
CN107000406A (zh) * 2014-11-26 2017-08-01 博里利斯股份公司 薄膜层
KR20170086565A (ko) * 2014-11-26 2017-07-26 보레알리스 아게 필름 층
US10494465B2 (en) 2014-11-26 2019-12-03 Borealis Ag Film layer
KR101907331B1 (ko) 2014-11-26 2018-10-11 보레알리스 아게 필름 층을 위한 폴리에틸렌 조성물
CN107000406B (zh) * 2014-11-26 2021-10-08 博里利斯股份公司 薄膜层
KR102006091B1 (ko) 2014-11-26 2019-07-31 보레알리스 아게 필름 층
WO2016198273A1 (fr) 2015-06-10 2016-12-15 Borealis Ag Copolymère multimodal comprenant de l'éthylène et au moins deux comonomères d'alpha-oléfine, et articles finaux fabriqués à partir du copolymère
US10619036B2 (en) 2015-06-10 2020-04-14 Borealis Ag Multimodal polyethylene copolymer
WO2016198271A1 (fr) 2015-06-10 2016-12-15 Borealis Ag Copolymère multimodal de polyéthylène
US11572461B2 (en) 2015-06-10 2023-02-07 Borealis Ag Multimodal copolymer of ethylene and at least two alpha-olefin comonomers and final articles made thereof
CN111448227A (zh) * 2017-12-26 2020-07-24 陶氏环球技术有限责任公司 包括多峰型乙烯类聚合物和低密度聚乙烯(ldpe)的组合物
CN111655744A (zh) * 2017-12-26 2020-09-11 陶氏环球技术有限责任公司 韧性改善的多峰型乙烯类聚合物组合物
US11555084B2 (en) 2017-12-26 2023-01-17 Dow Global Technologies Llc Multimodal ethylene-based polymer processing systems and methods
US11603452B2 (en) 2017-12-26 2023-03-14 Dow Global Technologies Llc Multimodal ethylene-based polymer compositions having improved toughness
US11680120B2 (en) 2017-12-26 2023-06-20 Dow Global Technologies Llc Dual reactor solution process for the production of multimodal ethylene-based polymer
US11680119B2 (en) 2017-12-26 2023-06-20 Dow Global Technologies Llc Process for the production of multimodal ethylene-based polymers
CN109135551A (zh) * 2018-08-09 2019-01-04 深圳市前海奇迹新材料有限公司 一种高柔韧性水性uv涂料

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