MULTIMODAL POLYETHYLENE THIN FILM

Abstract

The present invention relates to a reactor system for a multimodal polyethylene polymerization process, comprising; (a) a first reactor; (b) a hydrogen removal unit arranged between the first reactor and a second reactor comprising at least one vessel connected with a depressurization equipment, preferably selected from vacuum pump, compressor, blower, ejector or a combination, thereof, the depressurization equipment allowing to adjust an operating pressure to a pressure in a range of 100-200 kPa (abs); (c) the second reactor; and. (d) a third reactor and the use of a film thereof.

Claims

1. A reactor system for a multimodal polyethylene polymerization process, comprising; (a) a first reactor; (b) a hydrogen removal unit arranged between the first reactor and a second reactor comprising at least one vessel connected with a depressurization equipment, preferably selected from vacuum pump, compressor, blower, ejector or a combination thereof, the depressurization equipment allowing to adjust an operating pressure to a pressure in a range of 100-200 kPa (abs); (c) the second reactor; and (d) a third reactor.

2. The reactor system according to claim 1, wherein the depressurization equipment allows to adjust the operating pressure in the hydrogen removal unit to a pressure in the range of 103-145 kPa (abs), preferably 104-130 kPa (abs), most preferably 105 to 115 kPa (abs).

3. The reactor system according to claim 1, wherein the hydrogen removal unit further contains a stripping column for the separation of hydrogen and a liquid diluent.

4. A process for producing a multimodal polyethylene composition in the reactor system according to claim 1, comprising; (a) polymerizing ethylene in an inert hydrocarbon medium in the 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 having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol or medium molecular weight polyethylene having a weight average molecular weight (Mw) of more than 90,000 to 150,000 g/mol wherein the low molecular weight polyethylene, respectively the medium molecular weight polyethylene, has a density at least 0.965 g/cm3, and the low molecular weight polyethylene has MI.sub.2 in the range from 10 to 1,000 g/10 min and the medium molecular weight polyethylene has MI.sub.2 in the range from 0.1 to 10 g/10 min; (b) removing in the 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; (c) polymerizing ethylene and optionally C.sub.4 to C.sub.12 -olefin comonomer in the 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 having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or a first ultra high molecular weight polyethylene in the form of a homopolymer or a copolymer having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol and transferring a resultant mixture to the third reactor; and (d) polymerizing ethylene, and optionally C.sub.4 to C.sub.12 -olefin comonomer in the 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 having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or a second ultra high molecular weight polyethylene in the form of a homopolymer or copolymer having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol.

5. The process according to claim 4, wherein the removing 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.

6. The process according to claim 4, wherein the operation pressure in the hydrogen removal unit is in the range of 103-145 kPa(abs), more preferably 104-130 kPa (abs), and most preferred 105 to 115 kPa (abs).

7. A multimodal polyethylene composition obtainable by a process according to claim 4, comprising; (A) 30 to 65 parts by weight, preferably 40 to 65 parts by weight, preferably 43 to 52 parts by weight, most preferred 44 to 50 parts by weight, of the low molecular weight polyethylene, the low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol and having a MI.sub.2 from 500 to 1,000 g/10 min according to ASTM D 1238; (B) 8 to 30 party by weight, 8 to 20 parts by weight, preferably 10 to 18 parts by weight, most preferred 10 to 15 parts by weight, of the first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or the first ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol; and (C) 30 to 50 parts by weight, preferably 37 to 47 parts 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 1,000,000 g/mol or the second ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mole, 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/cm.sup.3, and wherein the molecular weight distribution of the multimodal polyethylene composition is from 13 to 60, preferably 20 to 28, preferably from 24 to 28, measured by gel permeation chromatography.

8. The multimodal polyethylene composition according to claim 7, wherein the MI.sub.2 is from 600 to 800 g/10 min.

9. The multimodal polyethylene composition according to claim 7, wherein the molecular weight distribution is from 23 to 28, preferably from 24 to 26, and more preferably from 25 to 26 measured by gel permeation chromatography.

10. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a weight average molecular weight from 80,000 to 1,300,000 g/mol, preferably 150,000 to 400,000 g/mol, preferably from 200,000 to 350,000 g/mol, measured by Gel Permeation Chromatography.

11. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a number average molecular weight from 5,000 to 30,000 g/mol, 5,000 to 15,000 g/mol, preferably 7,000 to 12,000 g/mol, measured by Gel Permeation Chromatography.

12. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a Z average molecular weight from 900,000 to 6,000,000 g/mol, 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.

13. The polyethylene composition according to claim 7 wherein the multimodal polyethylene composition has a density from 0.950 to 0.962 g/cm.sup.3, preferably from 0.953 to 0.959 g/cm.sup.3, according to ASTM D 1505 and/or a melt flow index MI.sub.5 from 0.01 to 50 g/10 min, and/or MI.sub.2 from 0.03 to 0.15 g/10 min preferably from 0.03 to 0.10 g/10 min.

14. The polyethylene composition according to claim 13, wherein the MI.sub.5 is from 0.01 to 1 g/10 min.

15. Film comprising the multimodal polyethylene composition according to claim 7, wherein the film has a thickness from 4 to 40 m, preferably from 4 to 30 m, and most preferably 4 to 20 m.

Description

EXPERIMENTAL AND EXAMPLES

Composition Related Examples

[0098] The medium or high density polyethylene preparation was carried out in three reactors in series. Ethylene, hydrogen, hexane, catalyst and TEA (triethyl aluminum) co-catalyst were fed into a first reactor in the amounts shown in Table 1. A high activity Ziegler-Natta catalyst was used. The catalyst preparation is for example described in Hungarian patent application 0800771R. The polymerization in first reactor was carried out to make a low molecular weight polyethylene. All of polymerized slurry polymer from first reactor was then transferred to a hydrogen removal unit to remove unreacted gas and some of hexane from polymer. The operating pressure in the hydrogen removal unit was be varied in a range of 100 to 115 kPa where residual hydrogen was removed more than 98% by weight but not more than 99.8% by weight from hexane before transferring to a second polymerization reactor. Some fresh hexane, ethylene and/or comonomer were fed into second reactor to produce first high molecular weight polyethylene (HMW1). All of polymerized polymer from second reactor was fed into the third reactor which produce second high molecular weight polyethylene (HMW2). Ethylene, comonomer, hexane and/or hydrogen were fed into the third reactor.

Comparative Example 1 (CE1)

[0099] A homopolymer was produced in first reactor to obtain a low molecular weight portion before transferring such polymer to hydrogen removal unit. Reactant mixture was introduced into the hydrogen removal unit to separate the unreacted mixture from the polymer. Residual hydrogen was removed 97.6% by weight when hydrogen removal unit was operated at pressure of 150 kPa. The low molecular weight polymer was then transferred to the second reactor to produce a first high molecular weight polymer. Final, produced polymer from second reactor was transferred to the third reactor to create a second high molecular weight polymer. In third, a copolymerization was carried out by feeding 1-butene as a comonomer.

Example 1 (E1)

[0100] Example 1 was carried out in the same manner as Comparative Example 1 except that the hydrogen removal unit was operated at pressure of 115 kPa. The residual of hydrogen from first reactor was removed 98.0% by weight. Characteristic properties of these multimodal polymers are shown in Table 2. As it can be seen, an improvement of stiffness-impact balance was observed when the percentage of removed hydrogen residual increased compared with the properties of Comparative Example 1.

Example 2 (E2)

[0101] Example 2 was carried out in the same manner as Comparative Example 1 except that the hydrogen removal unit was operated at pressure of 105 kPa. The residual hydrogen from the first reactor was removed to an extend of 99.1% by weight. The operational of hydrogen removal unit under this pressure leads to an expansion of a polymer properties range. As seen in Table 2, a final melt flow rate of E2 was lower than a final melt flow rate of CE1 resulted in an improvement of Charpy impact while still maintained the flexural modulus.

Comparative Example 2 (CE2)

[0102] Comparative Example 2 was carried out in the same manner as Comparative Example 1 except that the hydrogen removal unit was operated at pressure of 102 kPa. The residual of hydrogen from first reactor was removed to an extend of 99.9% by weight. The operational of hydrogen removal unit under this pressure leads to an expansion of a polymer properties range. As seen in Table 2, the final melt flow rate and a density of CE2 were quite similar to a final melt flow rate and a density of E2. A decay of Charpy impact was showed in CE2 compared to E2.

Comparative Example 3 (CE3)

[0103] A homopolymer was produced in a first reactor to obtain a low molecular weight portion before transferring the polymer to a hydrogen removal unit. Reactant mixture was introduced into the hydrogen removal unit to separate the unreacted mixture from the polymer. Hydrogen residual was removed to an extend of 97.9% by weight when hydrogen removal unit was operated at pressure of 150 kPa. The low molecular weight polymer was then transferred to a second reactor to produce a first high molecular weight polymer. In the second reactor, a copolymerization was carried out by feeding 1-butene as a comonomer. Finally, in-situ bimodal copolymer from second reactor was transferred to a third reactor to create a second high molecular weight copolymer portion. Characteristic properties of this multimodal polymers is shown in Table 2. A significant improvement in Charpy impact at room temperature could be obtained by decreasing a density of final polymer when co-polymer was produced in both the second and the third reactor.

Example 3 (E3)

[0104] Example 3 was carried out in the same manner as Comparative Example 3 except that the hydrogen removal unit was operated at pressure of 105 kPa. The residual of hydrogen from first reactor was removed to an extend of 98.8% by weight. The polymer obtained by this process operation had a melt flow rate of 0.195 g/10 min (5 kg loading) lower than such value obtained from CE3. As seen in Table 2, it revealed an improvement of stiffness-impact balance when the percentage of removed hydrogen residual increases compared with the properties of Comparative Example 3.

Comparative Example 4 (CE4)

[0105] A homopolymer was produced in first reactor to obtain a low molecular weight portion before transferring such polymer to hydrogen removal unit. Reactant mixture was introduced into the hydrogen removal unit to separate the unreacted mixture from the polymer. Residual hydrogen was removed 97.6% by weight when hydrogen removal unit was operated at pressure of 150 kPa (abs). The low molecular weight polymer was then transferred to the second reactor to produce a first high molecular weight polymer. Final, produced polymer from second reactor was transferred to the third reactor to create a second high molecular weight polymer. In third, a copolymerization was carried out by feeding 1-butene as a comonomer. As seen in Table 2 and 3, the final melt flow rate of CE4 were quite similar to a final melt flow rate of E5. A decay of charpy impact and flexural modulus were showed in CE4 compared to E5, even it showed lower density of E5.

Example 5 (E5)

[0106] Example 5 was carried out in the same manner as Comparative Example 4 except that the hydrogen removal unit was operated at pressure of 115 kPa (abs). The residual of hydrogen from first reactor was removed to an extend of 98.5% by weight. The polymer obtained by this process operation had a melt flow rate of 48 g/10 min (5 kg loading) lower than such value obtained from CE3. As seen in Table 2, it revealed an improvement of stiffness-impact balance when the percentage of removed hydrogen residual increases compared with the properties of Comparative Example 4.

Example 6 (E6)

[0107] Example 6 was carried out in the same manner as Example 4 except that the comonomer feeding in the third ultra high molecular weight polyethylene. The polymer produced by this process leads to an excellent improvement of Charpy impact strength while still maintained the flexural modulus. As shown in table 2, the inventive example 6 with IV of 23 dl/g show the high impact strength (one notched impact without break) and flexural modulus as compared to comparative samples, however, the melt flow index is unmeasurable due to high viscosity and high Mw.

TABLE-US-00001 TABLE 1 CE1 E1 E2 CE2 CE3 E3 E4 CE4 E5 E6 W.sub.A, % 55 55 55 55 45 45 30 50 50 30 W.sub.B, % 20 20 20 20 25 25 30 10 10 30 W.sub.C, % 25 25 25 25 30 30 40 40 40 40 First reactor Polymerization type Homo Homo Homo Homo Homo Homo Homo Homo Homo Homo Temperature, C. 80 80 80 80 80 80 80 80 80 80 Total pressure, kPa 800 800 800 800 800 800 800 800 800 800 Ethylene, g 1,100.72 1,100.70 1,100.86 1,100.74 900.30 900.30 540.50 725.21 725.57 485.70 Hydrogen, g 1.62 1.62 1.55 1.55 2.97 2.99 1.34 1.13 1.13 1.23 Hydrogen removal unit Pressure, kPa (abs) 150 115 105 102 150 105 105 150 115 105 Hydrogen remove, % 97.6 98.0 99.1 99.9 97.9 98.8 98.9 97.7 98.5 98.3 Second reactor Polymerization type Homo Homo Homo Homo Copo Copo Homo Copo Copo Homo Temperature, C. 70 70 70 70 70 70 70 80 80 70 Total pressure, kPa 250 250 250 250 250 250 400 300 300 400 Ethylene, g 400.52 400.81 400.35 400.06 500.17 500.31 540.36 145.35 145.21 485.78 Hydrogen, g 0 0 0 0 0 0 0 0 0 0 1-butene, g 0 0 0 0 18.84 18.91 0 8 8 0 Third reactor Polymerization type Copo Copo Copo Copo Copo Copo Homo Copo Copo Copo Temperature, C. 70 70 70 70 70 70 80 80 80 70 Total pressure, kPa 400 400 400 400 400 400 600 600 600 600 Ethylene, g 500.74 500.11 500.30 500.63 600.02 601.19 720.60 580.53 580.46 647.54 Hydrogen, g 0 0.001 0.001 0.001 0 0.001 0 0.59 1.37 0 1-butene, g 35.05 30.01 30.03 30.04 60.01 60.04 0 27 27 20.60 W.sub.Ameans percent by weight of Polymer in the first reactor W.sub.Bmeans percent by weight of Polymer in the second reactor W.sub.Cmeans percent by weight of Polymer in the third reactor

TABLE-US-00002 TABLE 2 CE1 E1 E2 CE2 CE3 Powder MI.sub.5, 0.474 0.372 0.240 0.242 0.275 g/10 min MI.sub.21, 13.83 10.80 7.38 7.23 6.40 g/10 min Density, 0.9565 0.9578 0.9555 0.9567 0.9441 g/cm.sup.3 IV, dl/g Mw 276,413 244,279 291,295 319,487 252,160 Mn 8,877 8,724 8,843 8,472 8,016 Mz 2,788,607 2,370,678 3,401,041 4,135,007 1,638,224 PDI 31 28 33 38 31 Pellet MI.sub.5, 0.436 0.410 0.232 0.199 0.298 g/10 min MI.sub.21, 14.46 11.68 7.876 6.696 7.485 g/10 min Density, 0.9577 0.9574 0.9568 0.9566 0.9442 g/cm.sup.3 IV, dl/g 2.97 3.03 3.52 3.64 3.12 % Crystallinity, % 64.70 67.24 64.78 66.16 57.49 Charpy, 23.5 29.9 35.3 30.5 47.9 23 C., kJ/m.sup.2 Flexural 1,130 1,210. 1,123 1,123 727 modulus, MPa E3 E4 CE4 E5 E6 Powder MI.sub.5, 0.200 54.80 48.07 NA g/10 min MI.sub.21, 4.81 0.145 641 653 NA g/10 min Density, 0.9438 0.9534 0.9606 0.9590 0.9409 g/cm.sup.3 IV, dl/g 9.00 1.07 1.06 23 Mw 306,468 868,813 77,334 91,752 1,269,336 Mn 7,637 24,107 5,400 6,035 23,450 Mz 2,643,953 5,112,060 667,276 1,027,956 5,262,195 PDI 40 36 14 15 54.13 Pellet MI.sub.5, 0.195 60.62 55.47 g/10 min MI.sub.21, 4.604 713.1 752.2 g/10 min Density, 0.9440 0.9608 0.9594 g/cm.sup.3 IV, dl/g 3.37 9.00 1.0 1.1 23 % Crystallinity, % 54.05 68.23 69.52 65.64 58.20 Charpy, 50.9 84.4 1.5 1.8 85.41 23 C., kJ/m.sup.2 Flexural 785 1,109 1,147 1,196 890 modulus, MPa

Film Related Examples

[0108] 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.

[0109] The inventive example E7 was produced follow the inventive process to make the multimodal polyethylene composition as shown in table 3. 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.

[0110] The inventive example E8 is the multimodal polyethylene composition produced by inventive process and having polymer as shown in table 5 in the range of claims with MI.sub.2 of 0.114 g/10 min 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-US-00003 TABLE 3 Process condition of inventive example 7, E7 and E8 and comparative example 6, CE7 Condition Unit CE7 E7 E8 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

[0111] 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 4. 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-US-00004 TABLE 4 Experiment and conditions for film preparation Experiment 1 Experiment 2 Experiment 3 Blown film parameter (Ex. 1) (Ex. 2) (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

[0112] The comparative example 4 (CE5) is the commercial resin EL-Lene H5604F produced by SCG Chemicals., Co. Ltd. with MI.sub.2 of 0.03 g/10 min and density of 0.9567 g/cm.sup.3. It is the bimodal polyethylene produced in slurry cascade process.

[0113] The comparative example 5 (CE6) is the blend of CE4 with commercial resin LLDPE, Dow Butene 1211, with MI.sub.2 of 1.0 g/10 min and density of 0.9180 g/cm.sup.3. It is the practical way in film production to get better film strength in particular dart drop impact and tear strength.

[0114] The comparative example 6 (CE7) is the multimodal polyethylene composition produced by the inventive process and having the composition and molecular weight distribution out of the specific range of composition for thin film.

[0115] The films were further evaluated for processability and mechanical properties in both machine direction, MD and transverse direction, TD as shown in table 5.

TABLE-US-00005 TABLE 5 Properties of polyethylene compositions and film thereof Properties CE5 CE6 CE7 E7 E8 Resin MI.sub.2, g/10 min 0.03 0.065 0.08 0.08 0.114 MI.sub.2 of LMW NA NA 624 715 722 Density, g/cm.sup.3 0.957 0.952 0.955 0.957 0.957 Density of HMW1, NA NA 0.921 0.924 0.921 g/cm.sup.3 Density of HMW2, NA NA 0.946 0.947 0.947 g/cm.sup.3 Mn (g/mol) 7,788 8,298 9,579 9,027 8856 Mw (g/mol) 240,764 276,362 284,257 232,875 228,400 Mz (g/mol) 1,817,918 1,956,827 1,666,188 1,403,576 1,346,144 PDI 30.9 33.3 29.7 25.8 25.7 Melt strength at 0.28 0.25 0.22 0.26 NA break, N Draw down ratio at 10.5 12.2 12.8 12.5 NA break Film Ex. 1 Ex. 2 Ex. 3 Ex1 Ex1 Ex. 1 Ex. 2 Ex1 Output, kg/hr 16.0 NA 12.8 19.1 20.3 19.7 19.9 20.3 Film thickness, 12 5 5 12 12 12 5 12 micron Screw speed, rpm 85 85 60 85 85 85 85 85 Nip roll take up 80 150 95 80 80 80 150 80 speed, rpm Blow up ratio, 4:1 4:1 4:1 4:1 4:1 4:1 4:1 4:1 BUR Bubble Stability Good Bubble Good Good Good Good Good Good Break Dart drop impact, g 105 113 140 124 159 108 124 Tensile Strength at 722 889 428 537 895 1068 537 Break (MD), kg/cm.sup.2 Tensile Stregnth at 501 574 320 537 745 499 537 Break (TD), kg/cm.sup.2 Elongation at 266 52 161 226 417 192 226 Break (MD), % Elongation at 510 388 390 488 605 365 488 Break (TD), % Tear Strength 4.14 8.4 7.8 5.5 6.6 2.3 5.5 (MD), g Tear Strength 50 14 49 26 60 27 26 (TD), g Puncture Energy, 26 39 21 29 31 46 29 N-cm/u

[0116] The inventive example 7 shows superior properties of 12 micron film prepared by the same conditions compared to comparative examples, CE5, CE6 and CE7. The inventive E8 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.

[0117] Further experiment to make a thin film at 5 micron was performed in Experiment 2. The Inventive example E7 and E8 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 CE5 however bubble break was suddenly found. It was possible to make the 5 micron film with CE5 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 example1 E7 and E8 has higher draw down at break compared to comparative example CE5.

[0118] Moreover the properties of the 5 micron film made by inventive example E7 in Experiment 2 are also equivalent to 12 micron film made by CE5 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 CE6.

[0119] These results support that the inventive multimodal polyethylene composition provide better balance of mechanical strength with high output for thin film preparation.

[0120] The features disclosed in the foregoing description and in the claims may, both separately and in any combination, be material for realizing the invention in diverse forms thereof.