(19)
(11)EP 3 510 053 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.07.2020 Bulletin 2020/31

(21)Application number: 17767780.4

(22)Date of filing:  08.09.2017
(51)International Patent Classification (IPC): 
C08F 2/00(2006.01)
C08F 2/01(2006.01)
C08F 2/18(2006.01)
C08L 23/04(2006.01)
B01J 19/00(2006.01)
C08F 2/12(2006.01)
C08J 5/18(2006.01)
C08L 23/06(2006.01)
(86)International application number:
PCT/EP2017/072571
(87)International publication number:
WO 2018/046656 (15.03.2018 Gazette  2018/11)

(54)

MULTIMODAL POLYETHYLENE COMPOSITION AND A FILM COMPRISING THE SAME

MULTIMODALE POLYETHYLENDÜNNSCHICHT

FILM MINCE DE POLYÉTHYLÈNE MULTIMODAL


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 12.09.2016 EP 16188329

(43)Date of publication of application:
17.07.2019 Bulletin 2019/29

(73)Proprietors:
  • Thai Polyethylene Co., Ltd.
    10800 Bangkok (TH)
  • SCG Chemicals Co., Ltd.
    Bangkok 10800 (TH)

(72)Inventors:
  • MATTAYAN, Arunsri
    Bangkok 10800 (TH)
  • TRAISILANUN, Saranya
    Bangkok 10800 (TH)
  • CHEEVASRIRUNGRUANG, Watcharee
    Bangkok 10800 (TH)
  • KLOMKAMOL, Warachad
    Bangkok 10800 (TH)

(74)Representative: Erbacher, Martin 
Boehmert & Boehmert Anwaltspartnerschaft mbB Pettenkoferstrasse 22
80336 München
80336 München (DE)


(56)References cited: : 
WO-A1-2008/049551
US-B1- 6 713 561
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates to Multimodal polyethylene composition for producing film.

    [0002] The demand of polyethylene resins is increasingly being used in a variety of applications. As required high performance of polyethylene for a relatively new plastic. In order for balancing processability and physical properties of ethylene copolymers, the development in multimodal composition has been investigated.

    [0003] A variety of films, which may be applied as the single layer or to the core or the surface of the multi-layer films, are known in the art. Likewise, a variety of polymer compositions, in particular polyethylene compositions, for producing such films are described.

    [0004] WO 2008/049551 A1 discloses a multimodal polyethylene molding composition for producing pipes having improved mechanical properties.

    [0005] US 6,713,561 discloses a polyethylene molding compound and addresses ESCR/stiffness relation and swelling rate and further proposes a method for producing the same.

    [0006] WO 2013/144324 A1 discloses a polymer composition comprising a homopolymer, a first copolymer and a second copolymer of specific MFR5, density and molecular weight distribution. The polymer composition is prepared in a process involving a slurry loop reactor and two gas phase reactors.

    [0007] WO 2006/092378 A1 discloses a film prepared from a polymer composition having a specific MFR5 and density and comprising three constituents, namely a homopolymer and two different copolymers.

    [0008] US 2015/0051364 A1 is related to a multimodal polyethylene copolymer comprising at least three components and having a specific density and MFR21. At least one of the three components is a copolymer.

    [0009] US 2010/0016526 A1 is related to a thin film which may be produced from bimodal HDPE polymer having specific density. The composition is prepared by a two stage cascade polymerization with series using a mixed catalyst system.

    [0010] However, in light of the above prior art, there is still a need to provide multimodal polyethylene compositions for preparing films and films prepared by using multimodal polyethylene compositions overcoming drawbacks of the prior art, in particular high density polyethylene compositions for blown film with improved properties regarding high output, good bubble stability, high mechanical strength and high toughness at film thicknesses from 4 to 40 micron or, preferably, less.

    [0011] Therefore, it is the further object of the present invention to provide multimodal polyethylene compositions for preparing films and films prepared this way overcoming drawbacks of the prior art, in particular overcoming the drawbacks mentioned above.

    [0012] A multimodal polyethylene composition comprising;
    1. (A) 43 to 52 percent by weight, most preferred 44 to 50 percent by weight, of the low molecular weight polyethylene which is a homopolymer having a density of ≥ 0.965 g/cm3, the low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol and having a MI2 from 600 to 800 g/10 min according to ASTM D 1238;
    2. (B) 8 to 20 percent by weight, preferably 10 to 18 percent by weight, most preferred 10 to 15 percent by weight, of the first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000g/mol or the first ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000g/mol; and
    3. (C) 30 to 50 percent by weight, preferably 37 to 47 percent by weight, most preferred 39 to 45 parts by weight, of the second high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000g/mol or the second ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000g/mol, wherein
    the density of the first high molecular weight polyethylene or the first ultra high molecular weight polyethylene and the second high molecular weight polyethylene or the second ultra high molecular weight polyethylene are in the range from 0.920 to 0.950 g/cm3, and
    wherein the molecular weight distribution of the multimodal polyethylene composition is from 23 to 28, preferably from 24 to 28, measured by gel permeation chromatography.

    [0013] In a preferred embodiment, the MI2 is from 600 to 800 g/10 min.

    [0014] In a preferred embodiment, the multimodal polyethylene composition has a weight average molecular weight from 150,000 to 400,000 g/mol, preferably from 200,000 to 350,000 g/mol, measured by Gel Permeation Chromatography.

    [0015] Furthermore, it is preferred, that the multimodal polyethylene composition has a number average molecular weight from 5,000 to 15,000 g/mol, preferably from 7,000 to 12,000 g/mol, measured by Gel Permeation Chromatography.

    [0016] Preferably, the multimodal polyethylene composition has a Z average molecular weight from 1,000,000 to 3,000,000 g/mol, preferably from 1,000,000 to 2,500,000 g/mol, measured by Gel Permeation Chromatography.

    [0017] Preferably, the multimodal polyethylene composition has a density from 0.950 to 0.962 g/cm3, preferably from 0.953 to 0.959 g/cm3, according to ASTM D 1505 and/or MI2 from 0.03 to 0.15 g/10 min preferably from 0.03 to 0.12 g/10 min.

    [0018] Finally, the object is achieved by a film comprising the inventive multimodal polyethylene composition, wherein the film has a thickness of 4 to 40 µm, preferably 4 to 30 µm, and most preferably 4 to 20 µm.

    [0019] In preferred embodiments "parts by weight" is "percent by weight".

    [0020] Regarding the inventive film, it is preferred that the film substantially comprises the inventive multimodal polyethylene composition, which means that the film does comprise further constituents only in amounts which do not affect the film properties regarding output, bubble stability, mechanical strength, toughness and the like. Most preferred the film is consisting of the inventive multimodal polyethylene composition. In addition, it was found that by using the inventive multimodal polyethylene composition a blown film can be prepared with high output, good bubble stability, high mechanical strength and high toughness which is superior over the prior arts, in particular at a film thickness from 5 to 12 micron.

    [0021] The object is further achieved by, a process for producing a multimodal polyethylene composition comprising;
    1. (a) polymerizing ethylene in an inert hydrocarbon medium in a first reactor in the presence of a catalyst system, selected from Ziegler-Natta catalyst or metallocene, and hydrogen in an amount of 0.1-95% by mol with respect to the total gas present in the vapor phase in the first reactor to obtain a low molecular weight polyethylene or medium molecular weight polyethylene;
    2. (b) removing in a hydrogen removal unit 98.0 to 99.8% by weight of the hydrogen comprised in a slurry mixture obtained from the first reactor at a pressure in the range of 103-145 kPa (abs) and transferring the obtained residual mixture to the second reactor;
    3. (c) polymerizing ethylene and optionally C4 to C12 α-olefin comonomer in a second reactor in the presence of a catalyst system, selected from Ziegler-Natta catalyst or metallocene, and in the presence of hydrogen in an amount obtained in step (b) to obtain a first high molecular weight polyethylene or a first ultra high molecular weight polyethylene in the form of a homopolymer or a copolymer and transferring a resultant mixture to the third reactor; and
    4. (d) polymerizing ethylene, and optionally C4 to C12 α-olefin comonomer in a third reactor in the presence of a catalyst system, selected from Ziegler-Natta catalyst or metallocene, and hydrogen, wherein the amount of hydrogen in the third reactor is in a range of 0.1-70% by mol, preferably 0.1-60% by mol with respect to the total gas present in the vapor phase in the third reactor or optionally substantial absence of hydrogen to obtain a second high molecular weight polyethylene or a second ultra high molecular weight polyethylene in the form of a homopolymer or copolymer.


    [0022] Preferably, the removing in the hydrogen removal unit is removing of 98.0-99.8% by weight of the hydrogen, more preferable 98.0-99.5% by weight, and most preferred 98.0 to 99.1 % by weight.

    [0023] The catalyst for use in the process is selected from a Ziegler-Natta catalyst, a single site catalyst including metallocene-bases catalyst and non- metallocene-bases catalyst or chromium based might be used, preferably conventional Ziegler-Natta catalyst or single site catalyst. The catalyst is typically used together with cocatalysts which are well known in the art.

    [0024] Innert hydrocarbon is preferably aliphatic hydrocarbon including hexane, isohexane, heptane, isobutane. Preferably, hexane (most preferred n-hexane) is used. Coordination catalyst, ethylene, hydrogen and optionally α-olefin comonomer are polymerized in the first reactor. The entire product obtained from the first reactor is then transferred to the hydrogen removal unit to remove 98.0 to 99.8% by weight of hydrogen, unreacted gas and some volatiles before being fed to the second reactor to continue the polymerization. The polyethylene obtained from the second reactor is a bimodal polyethylene which is the combination of the product obtained from the first reactor and that of the second reactor. This bimodal polyethylene is then fed to the third reactor to continue the polymerization. The final multimodal (trimodal) polyethylene obtained from the third reactor is the mixture of the polymers from the first, the second and the third reactor.

    [0025] The polymerization in the first, the second and the third reactor is conducted under different process conditions. These can be the variation and concentration of ethylene and hydrogen in the vapor phase, temperature or amount of comonomer being fed to each reactor. Appropriate conditions for obtaining a respective homo- or copolymer of desired properties, in particularly of desired molecular weight, are well known in the art. The person skilled in the art is enabled on basis of his general knowledge to choose the respective conditions on this basis. As a result, the polyethylene obtained in each reactor has a different molecular weight. Appropriate conditions for obtaining a respective homo- or copolymer of desired properties, in particularly of desired molecular weight, are well known in the art. Preferably, low molecular weight polyethylene is produced in the first reactor, while ultra high and/or high molecular weight polyethylene are produced in the second and third reactor, respectively.

    [0026] The term first reactor refers to the stage where the low molecular weight polyethylene (LMW) or the medium molecular weight polyethylene (MMW) is produced. The term second reactor refers to the stage where the first high or ultra high molecular weight polyethylene (HMW1) is produced. The term third reactor refers to the stage where the second high or ultra high molecular weight polyethylene (HMW2) is produced.

    [0027] The low molecular weight polyethylene polymer polymerized in the first reactor has a the weight average molecular weight (Mw) of 20,000-90,000 g/mol.

    [0028] The medium molecular weight polyethylene polymer polymerized in the first reactor has a number average molecular weight (Mn) of 9,000 to 12,000 g/mol and a weight average molecular weight (Mw) of more than 90,000 to 150,000 g/mol.

    [0029] The first high or ultra high molecular weight polyethylene polymer polymerized in the second reactor has a weight average molecular weight (Mw) of more than 150,000 to 5,000,000 g/mol.

    [0030] The second high or ultra high molecular weight polyethylene polymer polymerized in the third reactor has a weight average molecular weight (Mw) of more than 150,000 to 5,000,000 g/mol.

    [0031] The LMW or MMW is produced in the first reactor in the absence of comonomer in order to obtain a homopolymer.

    [0032] In this process, ethylene is polymerized in the first reactor in the absence of comonomer in order to obtain high density LMW or MMW polyethylene having density ≥0.965 g/cm3 and MI2 in the range of 10-1000 g/10min for LMW and 0.1 to 10 g/10 min for MMW. In order to obtain the target density and MI in the first reactor, the polymerization conditions are controlled and adjusted. The temperature in the first reactor ranges from 65-90°C, preferably 68-85°C. Hydrogen is fed to the first reactor so as to control the molecular weight of the polyethylene. The molar ratio of hydrogen to ethylene in the vapor phase can be varied depending up on the target MI. However, the preferred molar ratio ranges from 0.5-8.0, more preferably 3.0-6.0. The first reactor is operated at pressure between 250 and 900 kPa, preferably 400-850 kPa. An amount of hydrogen present in the vapor phase of the first reactor is in the range of 20-95% by mole, preferably 50-90% by mol.

    [0033] Before being fed to the second reactor, the slurry obtained from the first reactor containing LMW or MMW polyethylene preferably in hexane is transferred to a hydrogen removal unit which may have a flash drum connected with depressurization equipment preferably including one or the combination of vacuum pump, compressor, blower and ejector where the pressure in the flash drum is reduced so that volatile, unreacted gas, and hydrogen are removed from the slurry stream. The operating pressure of the hydrogen removal unit typically ranges from 103-145 kPa (abs), preferably 104-130 kPa (abs) in which 98.0 to 99.8% by weight of hydrogen can be removed, preferably 98.0 to 99.5% by weight.

    [0034] The polymerization conditions of the second reactor are notably different from that of the first reactor. The temperature in the second reactor ranges from 70-90°C, preferably 70-80°C. The molar ratio of hydrogen to ethylene is not controlled in this reactor since hydrogen is not fed into the second reactor. Hydrogen in the second reactor is the hydrogen left over from the first reactor that remains in slurry stream after being flashed at the hydrogen removal unit. Polymerization pressure in the second reactor ranges from 100-3000 kPa, preferably 150-900 kPa, more preferably 150-400 kPa and is controlled by the addition of inert gas such as nitrogen.

    [0035] Hydrogen removal is the comparison result of the amount of the hydrogen present in the slurry mixture before and after passing through the hydrogen removal unit. The calculation of hydrogen removal is performed according to the measurement of gas composition in the first and the second reactor by gas chromatography.

    [0036] After the substantial amount of hydrogen is removed to achieve the inventive concentration, slurry from the hydrogen removal unit is transferred to the second reactor to continue the polymerization. In this reactor, ethylene can be polymerized with or without α-olefin comonomer to form HMW1 polyethylene in the presence of the LMW or MMW polyethylene obtained from the first reactor. The α-olefin comomer that is useful for the copolymerization includes C4-12, preferably 1-butene and/or 1-hexene, more preferably 1-butene.

    [0037] After the polymerization in the second reactor, the slurry obtained is transferred to the third reactor to continue the polymerization.

    [0038] The HMW2 is produced in the third reactor by copolymerizing ethylene with optionally α-olefin comonomer at the presence of LMW and HWM1 obtained from the first and second reactor. The α-olefin comonomer that is useful for the copolymerization include C4-12, preferably 1-butene and/or 1-hexene, more preferably 1-butene.

    [0039] In order to obtain the target density and the target MI in the third reactor, the polymerization conditions are controlled and adjusted. However, the polymerization conditions of the third reactor are notably different from the first and second reactor. The temperature in the third reactor ranges from 68-90°C preferably 68-80°C. Hydrogen is fed to the third reactor so as to control the molecular weight of polyethylene. The molar ratio of hydrogen to ethylene can be varied depending up on the target MI. However, the preferred molar ratio ranges from 0.01-2.0. Polymerization pressure in the third reactor ranges from 150-900 kPa, preferably 150-400 kPa, and is controlled by the addition of inert gas such as nitrogen.

    [0040] The final (free-flow) multimodal polyethylene composition is obtained by separating hexane from the slurry discharged from the third reactor.

    [0041] The resultant polyethylene powder may then be mixed with antioxidants and optionally additives before being extruded and granulated into pellets.

    [0042] The pellets was then blown into a film using the conventional tubular blow film process with different thickness and further evaluated for the film properties.

    Definition and Measurement Methods



    [0043] MI2: Melt flow index (MFR) of polyethylene was measured according to ASTM D 1238 and indicated in g/10 min that determines the flowability of polymer under testing condition at 190°C with load 2.16 kg.

    [0044] Density: Density of polyethylene was measured by observing the level to which a pellet sinks in a liquid column gradient tube, in comparison with standards of known density. This method is determination of the solid plastic after annealing at 120 °C follow ASTM D 1505.

    [0045] Molecular weight and Polydispersity index (PDI): The weight average molecular weight (Mw), the number average molecular weight (Mn) and the Z average molecular weight (MZ) in g/mol were analysed by gel permeation chromatography (GPC). Polydispersity index was calculated by Mw/Mn.

    [0046] Around 8 mg of sample was dissolved in 8 ml of 1,2,4-trichlorobenzene at 160°C for 90 min. Then the sample solution, 200 µl, was injected into the high temperature GPC with IR5, an infared detector (Polymer Char, Spain) with flow rate of 0.5 ml/min at 145°C in column zone and 160°C in detector zone. The data was processed by GPC One® software, Polymer Char, Spain. Film bubble stability : It was determined during the blown film process, the axial oscillation of the film bubble was observed during increasing the nip roll take up speed and continue more than 30 minute. Good bubble stability is defined when film is not oscillating and bubble is not break.

    [0047] Output : The film was blown following the blown film conditions. Then the film was collected for a minute and weight. The output of film from unit of g/min is then calculated and reported in the unit of kg/hr.

    [0048] Dart drop impact: This test method follow method A of ASTM D1709 that covers the determination of the energy that cause plastic film to fail under specified conditions of free-falling dart impact. This energy is expressed in terms of the weight of the falling from a specified height, 0.66 ± 0.01 m, which result in 50% failure of specimens tested.

    [0049] Puncture resistance: This testing is in-housed method that a specimen is clamped without tension between circular plates of a ring clamp attachment in UTM. A force is exerted against the center of the unsupported portion of the test specimen by a solid steel rod attached to the load indicator until rupture of specimen occurs. The maximum force recorded is the value of puncture resistance

    [0050] Tensile strength of film: The test methods cover the determination of tensile properties of film (less than 1.0 mm. in thickness) followed ASTM D882. The testing employs a constant rate of grip separation, 500 mm/min.

    [0051] Tear strength : This test method covers the determination of the average force to propagate tearing through a specified length of plastic film using an Elmendorf-type tearing tester followed ASTM D 1922

    [0052] Melt strength and Draw down ratio (DP) : They are determined using GOEFFERT Rheotens. The melt extrudate is performed by single screw extruder with 2mm die diameter at melt temperature 190oC.the extrudate pass through Rheotens haul-off with controlled the ramp speed. The haul-off force is record. The force(N) is collect as a function of draw ratio(DD). Melt strength and draw down ratio is define as the force at break and draw down ratio at break respectively.

    Examples



    [0053] To prepare an inventive film from the above compositions, it was found that a sub-range of multimodal polyethylene compositions which might be obtained using the inventive reactor system are particularly preferred. In detail, the compositions suitable to form the inventive film are as follows and have the following properties. The following comparative examples refer to the film related compositions.

    [0054] The inventive example E1 was produced follow the disclosed process to make the multimodal polyethylene composition as shown in table 1. The specific multimodal polyethylene compositions enhance superior properties of film in particular the ability to make thin film. The thin film is represented the low thickness of the film such as 5 micron. It could be also refer to the ability to down-gauge the film thickness with equivalent properties to conventional film thickness.

    [0055] The inventive example E2 is the multimodal polyethylene composition produced by the disclosed process and having polymer as shown in table 3 in the range of claims with MI2 of 0.114 g/10min and density of 0.9570 g/cm3.It shows good processing in film production and higher output rate with maintaining properties in particular dart drop impact and puncture resistance at 12 micron film thickness.
    Table 1: Process condition of inventive example 1, El, inventive example 2, E2 and comparative example 3, CE3
    ConditionUnitCE3E1E2
    1st Reactor  
    Split ratio % 49-50 45-47 45-47
    Temperature (°C) 81-85 81-85 81-85
    Pressure kPa 700-750 650-700 580-620
    Hydrogen flow rate NL/h 246 226 248
    2nd Reactor  
    Split ratio % 6-8 10-12 10-12
    Temperature (°C) 70-75 70-75 70-75
    Pressure kPa 150-300 150-300 150-300
    Hydrogen flow rate NL/h 0 0 0
    Co-monomer kg/h 0.031 0.010 0.0135
    Comonomer/Ethylene Feed - 0.018 0.0033 0.0046
    H2 removal   99.0 98.9 99.4
    Comonomer type - 1-Butene 1-Butene 1-Butene
    3rd Reactor  
    Split ratio % 42-43 42-43 42-43
    Temperature (°C) 70-75 70-75 70-75
    Pressure kPa 150-300 150-300 150-300
    Hydrogen flow rate NL/h 12.85 13.02 17.28
    Co-monomer kg/h 0.052 0.0152 0.0099
    Comonomer/Ethylene Feed - 0.0048 0.0013 0.0009
    Comonomer type - 1-Butene 1-Butene 1-Butene


    [0056] The comparative example 1 (CE1) is the commercial resin EL-Lene™ H5604F with MI2 of 0.03 g/10min and density of 0.9567 g/cm3. It is the bimodal polyethylene produced in slurry cascade process.

    [0057] The comparative example 2 (CE2) is the blend of CE1 with commercial resin LLDPE, Dow™ Butene 1211, with MI2 of 1.0 g/10min and density of 0.9180 g/cm3. It is the practical way in film production to get better film strength in particular dart drop impact and tear strength.

    [0058] The comparative example 3 (CE3) is the multimodal polyethylene composition produced by the disclosed process and having the composition and molecular weight distribution out of the specific range of composition for thin film.

    [0059] From the molding composition so prepared, a film was produced in the following way. The films having different thickness and output were prepared on the internal blown film machine comprising a single screw extruder connecting with tubular blow film apparatus. The temperature setting from extruder to the die is from 175 to 205 °C. The screw speed and nip roll take up speed to prepare different film thickness in each experiment is defined in table 2. The film was produced at a blow-up ratio of 4:1 and a neck height of 30 cm with bubble diameter of 23 cm and film lay flat of 39 cm.
    Table 2 : Experiment and conditions for film preparation
    Blown film parameterExperiment 1 (Ex.1)Experiment 2 (Ex.2)Experiment 3 (Ex.3)
    Film thickness 12 5 5
    Screw speed (rpm) 85 85 60
    Nip roll take up speed (rpm) 80 150 95
    BUR 4:1 4:1 4:1
    Neck height (cm) 30 30 30


    [0060] The films were further evaluated for processability and mechanical properties in both machine direction, MD and transverse direction, TD as shown in table 3.
    Table 3: Properties of polyethylene compositions and film thereof
    PropertiesCE1CE2CE3E1E2
    Resin 
    MI2, g/10min 0.03 0.065 0.08 0.08 0.114
    MI2 of LMW NA NA 624 715 722
    Density, g/cm3 0.9567 0.9521 0.9548 0.9566 0.9570
    Density of HMW1, g/cm3 NA NA 0.9212 0.9237 0.9213
    Density of HMW2, g/cm3 NA NA 0.9464 0.9465 0.9472
    Mn (g/mol) 7,788 8,298 9,579 9,027 8856
    Mw (g/mol) 240,764 276,362 284,257 232,875 228400
    Mz (g/mol) 1,817,918 1,956,827 1,666,188 1,403,576 1346144
    PDI 30.9 33.3 29.7 25.8 25.7
    Melt strength at break, N 0.28 0.25 0.22 0.26 NA
    Draw down ratio at break 10.5 12.2 12.8 12.5 NA
    Film 
     CE1 (Ex.1)CE1 (Ex.2)CE1 (Ex.3)CE2 (Ex1)CE3 (Ex1)E1 (Ex.1)E1 (Ex.2)E2 (Ex1)
    Output, kg/hr 16.0 NA 12.8 19.1 18.8 19.7 19.9 20.3
    Film thickness, micron 12 5 5 12 12 12 5 12
    Screw speed, rpm 85 85 60 85 85 85 85 85
    Nip roll take up speed, rpm 80 150 95 80 80 80 150 80
    Blow up ratio, BUR 4:1 4:1 4:1 4:1 4:1 4:1 4:1 4:1
    Bubble Stability Good Bubble Break Good Good Good Good Good Good
    Dart drop impact, g 105 - 113 140 130 159 108 124
    Tensile Strength at Break (MD), kg/cm2 722 - 889 428 826 895 1068 537
    Tensile Stregnth at Break (TD), kg/cm2 501 - 574 320 484 745 499 537
    Elongation at Break (MD), % 266 - 52 161 226 417 192 226
    Elongation at Break (TD), % 510 - 388 390 554 605 365 488
    Tear Strength (MD), g 4.14 - 8.4 7.8 4.74 6.6 2.3 5.5
    Tear Strength (TD), g 50 - 14 49 47 60 27 26
    Puncture Energy, N-cm/u 26 - 39 21 31 31 46 29


    [0061] The inventive example 1 and 2, E1 shows superior properties of 12 micron film prepared by the same conditions compared to comparative examples, CE1, CE2 and CE3. E2 shows maintain film property and higher output with good bubble stability. In particular dart drop impact strength, tensile strength of film in both directions and puncture resistance. Also the film is produced with higher output.

    [0062] Further experiment to make a thin film at 5 micron was performed in Experiment 2. The Inventive example E1 show better draw ability at higher output which can be easily drawn into 5 micron film with good bubble stability and good mechanical strength. The same experiment was applied to the comparative example CE1 however bubble break was suddenly found. It was possible to make the 5 micron film with CE1 only in the case of lowering output by reducing screw speed and nip roll take up speed as done in Experiment 3. This is also related to draw down at break measured by rheoten. The inventive example 1 E1 has higher draw down at break compared to comparative example CE1.

    [0063] Moreover the properties of the 5 micron film made by inventive example E1 in Experiment 2 are also equivalent to 12 micron film made by CE1 with Experiment 1 in particular dart drop impact strength, tensile strength at break and puncture resistance. This also indicated the ability to downgauge the film thickness without sacrifice of mechanical properties. It was also possible to obtain good mechanical properties without use of LLDPE as compared to comparative example CE2.

    [0064] These results support that the inventive multimodal polyethylene composition provide better balance of mechanical strength with high output for thin film preparation.


    Claims

    1. A multimodal polyethylene composition comprising;

    (A) 43 to 52 percent by weight, most preferred 44 to 50 percent by weight, of the low molecular weight polyethylene which is a homopolymer having a density of ≥ 0.965 g/cm3, the low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol and having a MI2 from 600 to 800 g/10 min according to ASTM D 1238;

    (B) 8 to 20 percent by weight, preferably 10 to 18 percent by weight, most preferred 10 to 15 percent by weight, of the first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000g/mol or the first ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000g/mol; and

    (C) 30 to 50 percent by weight, preferably 37 to 47 percent by weight, most preferred 39 to 45 parts by weight, of the second high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000g/mol or the second ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000g/mol, wherein

    the density of the first high molecular weight polyethylene or the first ultra high molecular weight polyethylene and the second high molecular weight polyethylene or the second ultra high molecular weight polyethylene are in the range from 0.920 to 0.950 g/cm3, and
    wherein the molecular weight distribution of the multimodal polyethylene composition is from 23 to 28, preferably from 24 to 28, measured by gel permeation chromatography.
     
    2. The multimodal polyethylene composition according to claim 1, wherein the molecular weight distribution is from 24 to 26, more preferably 25 to 26.
     
    3. The multimodal polyethylene composition according to any of the claims 1 to 2, wherein the multimodal polyethylene composition has a weight average molecular weight from 150,000 to 400,000 g/mol, preferably from 200,000 to 350,000 g/mol, measured by Gel Permeation Chromatography.
     
    4. The multimodal polyethylene composition according to any of the claims 1 to 3, wherein the multimodal polyethylene composition has a number average molecular weight from 5,000 to 15,000 g/mol, preferably 7,000 to 12,000 g/mol, measured by Gel Permeation Chromatography.
     
    5. The multimodal polyethylene composition according to any of the claims 1 to 4, wherein the multimodal polyethylene composition has a Z average molecular weight from 1,000,000 to 3,000,000 g/mol, preferably from 1,000,000 to 2,500,000 g/mol, measured by Gel Permeation Chromatography.
     
    6. The polyethylene composition according to any of the claims 1 to 5 wherein the multimodal polyethylene composition has a density from 0.950 to 0.962 g/cm3, preferably from 0.953 to 0.959 g/cm3, according to ASTM D 1505 and/or MI2 from 0.03 to 0.15 g/10 min preferably from 0.03 to 0.12 g/10 min.
     
    7. Film comprising the multimodal polyethylene composition according to any of the claims 1 to 6, wherein the film has a thickness from 4 to 40 µm, preferably from 4 to 30 µm, and most preferably 4 to 20 µm.
     


    Ansprüche

    1. Multimodale Polyethylenzusammensetzung umfassend:

    (A) 43 bis 52 Gewichtsprozent, am meisten bevorzugt 44 bis 50 Gewichtsprozent, Polyethylen mit niedrigem Molekulargewicht, das ein Homopolymer mit einer Dichte von ≥ 0,965 g/cm3 ist, wobei das Polyethylen mit niedrigem Molekulargewicht ein Gewichtsmittel des Molekulargewichts (Mw) von 20.000 bis 90.000 g/mol und einen MI2 von 600 bis 800 g/10 min gemäß ASTM D 1238 hat;

    (B) 8 bis 20 Gewichtsprozent, vorzugsweise 10 bis 18 Gewichtsprozent, am meisten bevorzugt 10 bis 15 Gewichtsprozent, erstes Polyethylen mit hohem Molekulargewicht mit einem Gewichtsmittel des Molekulargewichts (Mw) von mehr als 150.000 bis 1.000.000 g/mol oder erstes Polyethylen mit ultrahohem Molekulargewicht mit einem Gewichtsmittel des Molekulargewichts (Mw) von mehr als 1.000.000 bis 5.000.000 g/mol; und

    (C) 30 bis 50 Gewichtsprozent, vorzugsweise 37 bis 47 Gewichtsprozent, am meisten bevorzugt 39 bis 45 Gewichtsprozent, zweites Polyethylen mit hohem Molekulargewicht mit einem Gewichtsmittel des Molekulargewichts (Mw) von mehr als 150.000 bis 1.000.000 g/mol oder zweites Polyethylen mit ultrahohem Molekulargewicht mit einem Gewichtsmittel des Molekulargewichts (Mw) von mehr als 1.000.000 bis 5.000.000 g/mol, wobei

    die Dichte des ersten Polyethylens mit hohem Molekulargewicht oder des ersten Polyethylens mit ultrahohem Molekulargewicht und das zweite Polyethylen mit hohem Molekulargewicht oder das zweite Polyethylen mit ultrahohem Molekulargewicht in dem Bereich von 0,920 bis 0,950 g/cm3 ist, und
    wobei die Molekulargewichtsverteilung der multimodalen Polyethylenzusammensetzung von 23 bis 28, vorzugsweise 24 bis 28 ist, gemessen mittels Gelpermeationschromatographie.
     
    2. Multimodale Polyethylenzusammensetzung nach Anspruch 1, wobei die Molekulargewichtsverteilung von 24 bis 26 ist, vorzugsweise von 25 bis 26.
     
    3. Multimodale Polyethylenzusammensetzung nach einem der Ansprüche 1 bis 2, wobei die multimodale Polyethylenzusammensetzung ein Gewichtsmittel des Molekulargewichts von 150.000 bis 400.00 g/mol, vorzugsweise von 200.000 bis 350.000 g/mol, gemessen durch Gelpermeationschromatographie hat.
     
    4. Multimodale Polyethylenzusammensetzung nach einem der Ansprüche 1 bis 3, wobei die multimodale Polyethylenzusammensetzung ein Zahlenmittel des Molekulargewichts von 5.000 bis 15.000 g/mol, vorzugsweise 7.000 bis 1.000 g/mol, gemessen mittels Gelpermeationschromatographie, hat.
     
    5. Multimodale Polyethylenzusammensetzung nach einem der Ansprüche 1 bis 4, wobei die multimodale Polyethylenzusammensetzung ein Z-Mittel des Molekulargewichts von 1.000.000 bis 3.000.000 g/mol, vorzugsweise 1.000.000 bis 2.500.000 g/mol, gemessen mittels Gelpermeationschromatographie, hat.
     
    6. Polyethylenzusammensetzung nach einem der Ansprüche 1 bis 5, wobei die multimodale Polyethylenzusammensetzung eine Dichte von 0,950 bis 0,962 g/cm3, vorzugsweise von 0,953 bis 0,959 g/cm3, gemäß ASTM D 1505 und/oder MI2 von 0,03 bis 0,15 g/10 min, vorzugsweise von 0,03 bis 0,12 g/10 min hat.
     
    7. Film umfassend die multimodale Polyethylenzusammensetzung nach einem der Ansprüche 1 bis 6, wobei der Film eine Dicke von 4 bis 40 µm, vorzugsweise von 4 bis 30 µm, und am meisten bevorzugt 4 bis 20 µm hat.
     


    Revendications

    1. Composition de polyéthylène multimodal comprenant ;

    (A) 43 à 52 % en poids, plus préférablement 44 à 50 % en poids, du polyéthylène de faible poids moléculaire qui est un homopolymère ayant une densité supérieure ou égale à 0,965 g/cm3, le polyéthylène de faible poids moléculaire ayant un poids moléculaire moyen en poids (Mp) de 20.000 à 90.000 g/mol et ayant un MI2 allant de 600 à 800 g/10 minutes selon la norme D 1238 de l'ASTM ;

    (B) 8 à 20 % en poids, préférablement 10 à 18 % en poids, plus préférablement 10 à 15 % en poids du premier polyéthylène de poids moléculaire élevé ayant un poids moléculaire moyen en poids (Mp) supérieur à 150.000 à 1.000.000 g/mole ou du premier polyéthylène de poids moléculaire ultra élevé ayant un poids moléculaire moyen en poids (Mp) de plus de 1.000.000 à 5.000.000 g/mole ; et

    (C) 30 à 50 pour cent en poids, préférablement 37 à 47 pour cent en poids, plus préférablement 39 à 45 parties en poids du deuxième polyéthylène de poids moléculaire élevé ayant un poids moléculaire moyen en poids (Mp) de plus de 150.000 à 1.000.000 g/mole ou du deuxième polyéthylène de poids moléculaire ultra élevé ayant un poids moléculaire moyen en poids (Mp) de plus de 1.000.000 à 5.000.000 g/mole, dans laquelle

    la densité du premier polyéthylène de poids moléculaire élevé ou du premier polyéthylène de poids moléculaire ultra élevé et celle du deuxième polyéthylène de poids moléculaire élevé ou du deuxième polyéthylène de poids moléculaire ultra élevé sont comprises entre 0,920 et 0,950 g/cm3, et
    dans laquelle la distribution du poids moléculaire de la composition de polyéthylène multimodal est de 23 à 28, préférablement de 24 à 28, mesurée par chromatographie par perméation sur gel.
     
    2. Composition de polyéthylène multimodal selon la revendication 1, dans laquelle la distribution du poids moléculaire est de 24 à 26, plus préférablement de 25 à 26.
     
    3. Composition de polyéthylène multimodal selon l'une quelconque des revendications 1 à 2, la composition de polyéthylène multimodal ayant un poids moléculaire moyen en poids allant de 150.000 à 400.000 g/mole, préférablement de 200.000 à 350.000 g/mole, mesuré par chromatographie par perméation sur gel.
     
    4. Composition de polyéthylène multimodal selon l'une quelconque des revendications 1 à 3, la composition de polyéthylène multimodal ayant un poids moléculaire moyen en nombre allant de 5.000 à 15.000 g/mol, préférablement de 7.000 à 12.000 g/mol, mesuré par chromatographie par perméation sur gel.
     
    5. Composition de polyéthylène multimodal selon l'une des revendications 1 à 4, la composition de polyéthylène multimodal ayant un poids moléculaire moyen Z allant de 1.000.000 à 3.000.000 g/mole, préférablement allant de 1.000.000 à 2.500.000 g/mole, mesuré par chromatographie par perméation sur gel.
     
    6. Composition de polyéthylène selon l'une quelconque des revendications 1 à 5, la composition de polyéthylène multimodal ayant une densité de 0,950 à 0,962 g/cm3, préférablement allant de 0,953 à 0.959 g/cm3, selon la norme D 1505 de l'ASTM et/ou un MI2 allant de 0,03 à 0,15 g/10 minutes, préférablement allant de 0,03 à 0,12 g/10 minutes.
     
    7. Film comprenant la composition de polyéthylène multimodal selon l'une quelconque des revendications 1 à 6, le film ayant une épaisseur de 4 à 40 µm, préférablement de 4 à 30 µm et plus préférablement encore de 4 à 20 µm.
     






    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description