Multimodal polyethylene container

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 thereof as a container.

Claims

1. A process for producing a multimodal polyethylene composition in a reactor system comprising: (a1) a first reactor having a catalyst system selected from Ziegler-Natta catalyst or metallocene; (b1) a hydrogen removal unit arranged between the first reactor and a second reactor, said hydrogen removal unit comprising at least one vessel connected with depressurization equipment selected from a vacuum pump, a compressor, a blower, an ejector or a combination thereof, the depressurization equipment configured to adjust an operating pressure to a pressure in a range of 103-145 kPa (abs); (c1) the second reactor; and (d1) a third reactor, the process comprising: (a2) polymerizing ethylene in an inert hydrocarbon medium in the first reactor in the presence of the catalyst system and hydrogen in an amount of 0.1-95% by mole 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 MI2 in the range from 10 to 1,000 g/10 min and the medium molecular weight polyethylene has MI2 in the range from 0.1 to 10 g/10 min; (b2) 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; (c2) polymerizing ethylene and optionally C.sub.4-12 α-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 (b2) 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 (d2) polymerizing ethylene, and optionally C.sub.4-12 α-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, 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 homopolymer or copolymer having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol.

2. The process according to claim 1, wherein the pressure in the hydrogen removal unit is in the range of 105 to 115 kPa (abs).

3. The process according to claim 1, wherein the hydrogen removal unit further comprises a stripping column for the separation of the hydrogen in the slurry mixture from a liquid diluent.

4. The process of claim 1, wherein the amount of hydrogen in the third reactor is in a range of 0.1-60% by mol.

5. The process according to claim 1, wherein the removing is removing of 98.0-99.5% by weight of the hydrogen.

6. The process according to claim 5, wherein the pressure in the hydrogen removal unit is in the range of 105 to 115 kPa (abs).

7. A multimodal polyethylene composition comprising: (A) 30 to 65 parts by weight of a low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol; (B) 10 to 40 parts by weight of 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 having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol; and (C) 10 to 50 parts by weight of 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 having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol, wherein the multimodal polyethylene composition has a FNCT at 80° C., 3.5 MPa with the environment of 2% solution of 4-nonylphenyl-polyethylene glycol from 10 to 270 hours, and wherein (A), (B), and (C) each have a different weight average molecular weight.

8. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a swelling ratio at shear rate 1400 1/sec determined at temperature of 190° C. in a circular length 0.25 mm orifice die 2 mm diameter and entrance angle by 45° of at least 170%.

9. The multimodal polyethylene composition according to claim 7, wherein the FNCT at 80° C., 3.5 MPa with the environment of 2% solution of 4-nonylphenyl-polyethylene glycol is from 12 to 250 hours.

10. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a weight average molecular weight from 150,000 to 500,000 g/mol, measured by Gel Permeation Chromatography.

11. The multimodal polyethylene composition according to claim 10, wherein the weight average molecular weight is from 200,000 to 400,000 g/mol.

12. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a number average molecular weight from 8,000 to 25,000 g/mol, measured by Gel Permeation Chromatography.

13. The multimodal polyethylene composition according to claim 7, wherein the multimodal polyethylene composition has a Z average molecular weight from 1,000,000 to 5,000,000 g/mol, measured by Gel Permeation Chromatography.

14. The multimodal polyethylene composition according to claim 7 wherein the multimodal polyethylene composition has a density from 0.940 to 0.966 g/cm.sup.3, according to ASTM D 1505 and/or MI.sub.5 from 0.01 to 7 g/10 min, and/or MI.sub.21 from 0.2 to 130 g/10 min.

15. A container comprising the multimodal polyethylene composition according to claim 7.

16. The container according to claim 15, obtained by blow molding, sheet forming or thermoforming.

17. The container according to claim 15, wherein the container has a volumetric capacity of 0.25 L to 40 L.

18. The container according to claim 15, wherein the container has a volumetric capacity of 40 L to 500 L.

19. The container according to claim 15, wherein the container has a volumetric capacity of 500 L to 2,000 L.

20. A multimodal polyethylene composition comprising: (A) 40 to 65 parts by weight of a low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol; (B) 10 to 40 parts by weight of 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 having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol; and (C) 10 to 50 parts by weight of 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 having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol, wherein the multimodal polyethylene composition has a swelling ratio at shear rate 1400 1/sec determined at temperature of 190° C. in a circular length 0.25 mm orifice die 2 mm diameter and entrance angle by 45° of at least 170%, and has a FNCT at 80° C., 3.5 MPa with the environment of 2% solution of 4-nonylphenyl-polyethylene glycol from 10 to 270 hours, and wherein (A), (B), and (C) each have a different weight average molecular weight.

Description

EXPERIMENTAL AND EXAMPLES

Composition Related Examples

(1) 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 amount shown in table 1. A commercial available Ziegler-Natta catalyst was used. The catalyst preparation is for example described in Hungary patent application 08 00771r. The polymerization in first reactor was carried out to make a low molecular weight polyethylene or medium 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 (abs) 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)

(2) 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.

Example 1 (E1)

(3) 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 (abs). 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)

(4) 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 (abs). 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 strength while still maintained the flexural modulus.

Comparative Example 2 (CE2)

(5) 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 (abs). 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 strength was showed in CE2 compared to E2.

Comparative Example 3 (CE3)

(6) 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 (abs). The low molecular weight polymer was then transferred to a second reactor to produce an ultra 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 high molecular weight copolymer portion. Characteristic properties of this multimodal polymers is shown in Table 2. A significant improvement in Charpy impact strength 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)

(7) 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 (abs). 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.

Example 4 (E4)

(8) A homopolymer was produced in the first reactor to obtain a medium molecular weight portion before transferring such polymer to hydrogen removal unit. The hydrogen removal unit was operated at pressure of 105 kPa (abs) to separate the unreacted mixture from the polymer. The residual of hydrogen from first reactor was removed to an extend of 98.9% by weight. The medium molecular weight polymer was then transferred to the second reactor to produce a first ultra high molecular weight polymer. Finally, produced polymer from second reactor was transferred to the third reactor to create a second ultra high molecular weight polymer. The second and third reactors are operated under hydrogen depleted polyethylene polymerization. The processable in-situ ultra high molecular weight polyethylene is produced by this process operation leads to an excellent improvement of Charpy impact strength while still maintained the flexural modulus. The conventional UHMWPE with very high IV was known that it was unable to measured MI21. The inventive example E4 with IV of 9 dl/g show good melt flow ability beyond the known art.

Comparative Example 4 (CE4)

(9) 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)

(10) 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)

(11) 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.

(12) 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.A means percent by weight of Polymer in the first reactor W.sub.B means percent by weight of Polymer in the second reactor W.sub.C means percent by weight of Polymer in the third reactor

(13) 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.sup.a, 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.sup.a, 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

Composition Related Examples

(14) To prepare an inventive container from the above inventive composition, it was surprisingly found that the sub-range of the multimodal polyethylene composition which might be obtained using the inventive reactor system is particularly preferred. In detail, it was found that the composition is suitable to form the inventive container are as follows and have the following properties. The following examples and comparative examples refer to the container related composition.

(15) Polyethylene compositions for small, medium and large containers are included in the examples.

(16) Small Container Applications

(17) Polyethylene composition for Jerrycan and bottle applications are included in the examples for small containers. The process conditions and polymer properties are shown in table 3. The inventive examples E7, E8 and E9 were compared with comparative examples CE5, CE6 and CE7 for Jerrycans. The inventive example E10 and E11 was compared with comparative examples CE8 for bottles. The physical and mechanical properties are shown in Table 4.

(18) The inventive example E7, E8, E9, E10 and E11 were produced with the inventive process for making multimodal polyethylene composition. The 1-Butene is applied for copolymerization of inventive example E7, E8, E10 and E11 while 1-hexene is used in the inventive example E9.

(19) The comparative example CE5 was commercial resin Marlex® HXM50100 using chromium catalyst in Chevron Phillips Loop Slurry PE Process.

(20) The comparative example CE6 is the multimodal polyethylene composition produced by the inventive process and having the composition out of the specific range of composition for containers.

(21) The comparative example CE7 and CE8 were multimodal polyethylene composition selected from US 2006/0074194 A1 and WO2004/056921 A1, respectively.

(22) TABLE-US-00003 TABLE 3 Process condition and polymer properties of inventive example E7, E8, E9, E10 and E11 and comparative example, CE5, CE6, CE7 and CE8. Comparative Inventive Inventive Comparative example 5 Example 7 Inventive Example 9 example 6 (CE5) (E7) examples (E8) (E9) (CE6) Polymerization condition 1.sup.st Reactors Split ratio (%) N/A 47-48 50-52 50-52 50-52 Temperature N/A 81-85 81-85 81-85 81-85 (° C.) Pressure (kPa) N/A 500-600 600-700 600-700 700-800 Hydrogen N/A 98 139 85 164 (L/hr) 2nd Reactors Split ratio (%) N/A 20-21 17-18 12-14 6-8 Temperature N/A 70-75 70-75 70-75 70-75 (° C.) Pressure (kPa) N/A 150-300 150-300 150-300 150-300 Comonomer/ N/A 0.001 0.003 0.001 0.004 C2H4 H2 removal (%) N/A 98.96 98.97 98.97 98.91 3rd Reactors Split ratio (%) N/A 31-32 29-31 37-38 40-42 Temperature N/A 70-75 70-75 70-75 70-75 (° C.) Pressure (kPa) N/A 150-300 150-300 150-300 150-300 Hydrogen (L/hr) N/A 34 11 6 1 Comonomer/ N/A 0.013 0.010 0.130 0.009 C2H4 feed Polymer Properties Mw 213,927 287,680 289,586 344,356 N/A Mn 18,152 14,134 13,654 11,505 N/A Mw/Mn 11.79 20.41 21.21 29.93 N/A Mz 1,879,128 1,881,789 1,870,039 2,829,938 N/A Comonomer 1-Hexene 1-Butene 1-Butene 1-Hexene 1-Butene type Comonomer 0.28 0.45 0.42 0.47 N/A content (% mole) Comparative Comparative Inventive Inventive example 7 example 8 Example 10 Example 11 (CE7) (CE8) (E10) (E11) Polymerization condition 1.sup.st Reactors Split ratio (%) 45 46 44-46 47-49 Temperature N/A N/A 81-85 81-85 (° C.) Pressure (kPa) N/A N/A 500-600 450-500 Hydrogen N/A N/A 135 82 (L/hr) 2nd Reactors Split ratio (%) 29 32 17-18 12-14 Temperature N/A N/A 70-75 65-70 (° C.) Pressure (kPa) N/A N/A 150-300 140-250 Comonomer/ N/A N/A 0.003 0.001 C2H4 H2 removal (%) N/A N/A 98.97 98.62 3rd Reactors Split ratio (%) 26 22 37-39 37-41 Temperature N/A N/A 70-75 75-80 (° C.) Pressure (kPa) N/A N/A 150-300 150-300 Hydrogen (L/hr) N/A N/A 37 54 Comonomer/ N/A N/A 0.002 0.016 C2H4 feed Polymer Properties Mw N/A N/A 231,117 217,462 Mn N/A N/A 11,044 10,492 Mw/Mn N/A N/A 20.93 20.73 Mz N/A N/A 1,872,020 1,877,827 Comonomer 1-Butene 1-Butene 1-Butene 1-Butene type Comonomer N/A N/A 0.47 0.39 content (% mole)

(23) TABLE-US-00004 TABLE 4 Polymer Properties of Inventive example, E7, E8, E9, E10 and E11 comparative example, CE5, CE6, CE7 and CE8. CE5 E7 E8 E9 CE6 CE7 CE8 E10 E11 Physical properties MI.sub.5 0.263 0.307 0.286 0.222 0.236 0.400 0.950 1.15 1.61 (g/10 min) MI.sub.21 7.44 7.02 7.47 7.45 7.51 N/A N/A 22.18 31.15 (g/10 min) Density 0.9520 0.9536 0.9553 0.9552 0.9546 0.9540 0.9570 0.9557 0.9579 (g/cm.sup.3) Mechanical properties Charpy.sup.b 23.4 23.6 23.8 30.9 22.83 16 12.3 11.8 8.33 Impact 23° C. (kJ/m.sup.2) Flexural 931 1,006 1,037 1,010 949 N/A N/A 1,124 1,143 modulus (MPa) FNCT.sup.a 10 42 57 39 N/A N/A 10 18 15 (80° C., 3.5 MPa, hr) Processing properties Swell ratio 295% 214% 206% 209% 125% 135% 142% 233% 237% at γ = 1400 s.sup.−1 Elongational 1.17 1 1 1.10 1 N/A N/A 1 1 hardening (eh) at rate 1 1/sec Elongational 1.09 1 1 1.08 1 N/A N/A 1 1 hardening (eh) at rate 5 1/sec Tan(delta) 0.512 0.435 0.433 0.452 0.364 N/A N/A 0.550 0.575 at 600 rad/s

(24) The polyethylene produced with Chromium catalyst was generally known for high melt strength and swell ratio contributed by the long chain branch while the mechanical properties are acceptable for container applications. The mechanical properties of inventions (E7, E8 and E9) including flexural modulus, charpy impact strength as well as FNCT.sup.a are more superior over the prior art, CE5. Additionally, when 1-hexene was used as comonomer in the 2.sup.nd and 3.sup.rd reactor component, the inventive example E9 shows good melt strength as determined by the elongation hardening rate. The good balance of processing and mechanical properties was contributed from the ultrahigh molecular weight portions in the inventive multimodal polyethylene compositions. The high elasticity of multimodal polyethylene composition was also detected in the inventive samples as determined by tan delta, which ensure the good processing behavior of the multimodal polyethylene composition.

(25) The significant difference was found when the ultrahigh molecular weight composition in the 2.sup.nd reactor is higher than 10 wt %. This was obviously seen when comparing the results of inventive examples (E7, E8 and E9) with comparative example (CE6) produced using the inventive process. The mechanical balance of flexural modulus, Charpy impact of CE6 is accordance well with the advantage of the inventive process however the swell ratio is dramatically lower than the invention when the composition is out of the claim range. Similarly, the multimodal polyethylene composition contributes the excellent swell ratio and charpy impact resistance than the prior art CE7.

(26) Similar experimental results were obtained from the highest MI.sub.5 range sample which applicable for the bottle size applications. The E10 and E11 show higher FNCT.sup.a than CE8. Additionally, the swell ratio results shown that E10 and E11 have a more superior processing property of blow molding application than CE8.

(27) These evidence supports that the specific range of multimodal polyethylene composition plays an important role and provides a good balance of mechanical strength with the good processing properties in parallel for small blow molding containers.

(28) Medium and Large Container Applications

(29) Polyethylene composition for fuel tank and intermediate bulk container (IBC) applications are included in the examples for medium and large containers. The process conditions and polymer properties are shown in table 5. The inventive examples E12, E13 and E14 were compared with comparative examples CE9, CE10 and CE11. The physical and mechanical properties are shown in Table 6.

(30) The inventive example E12, E13 and E14 were produced with the inventive process for making multimodal polyethylene composition. The 1-butene comonomer is applied for copolymerization of inventive example E12 and E13 while 1-hexene is used in the inventive example E14.

(31) The comparative example CE9 and CE10 were commercial resin using chromium catalyst in Chevron Phillips Loop Slurry PE Process. The CE9 and CE10 are Novatec® HB111R and Titanex® HM4560UA, respectively.

(32) The comparative example CE11 was multimodal polyethylene composition selected from U.S. Pat. No. 8,802,768 B2.

(33) TABLE-US-00005 TABLE 5 Process condition of Inventive example, E12, E13, E14 and comparative example, CE9, CE10, and CE11. Comparative Comparative Inventive Inventive Inventive Comparative example 9 example 10 Example Example Example example 11 (CE9) (CE10) 12 (E12) 13 (E13) 14 (E14) (CE11) Polymerization condition 1.sup.st Reactors Split ratio (%) N/A N/A 47-49 48-50 50-52 50 Temperature (° C.) N/A N/A 81-85 81-85 81-85 N/A Pressure (kPa) N/A N/A 500-550 550-600 600-700 N/A Hydrogen (L/hr) N/A N/A 150 158 85 N/A 2nd Reactors Split ratio (%) N/A N/A 19-21 19-21 12-14 27 Temperature (° C.) N/A N/A 70-75 70-75 70-75 N/A Pressure (kPa) N/A N/A 150-300 150-300 150-300 N/A Comonomer/C2H4 N/A N/A 0.002 0.002 0.001 N/A H2 removal (%) N/A N/A 99.02 99.08 98.97 N/A 3rd Reactors Split ratio (%) N/A N/A 30-32 30-32 37-38 23 Temperatur (° C.) N/A N/A 70-75 70-75 70-75 N/A Pressure (kPa) N/A N/A 150-300 150-300 150-300 N/A Hydrogen (L/hr) N/A N/A 8 11 6 N/A Comonomer/C.sub.2H.sub.4 N/A N/A 0.06 0.05 0.13 N/A feed Polymer structure Mw 278,486 251,179 279,068 254,592 344,356 N/A Mn 16,086 12,552 13,429 11,770 11,505 N/A Mw/Mn 17.31 20.02 20.78 21.63 29.93 N/A Mz 2,957,950 2,506,738 1,536,565 1,509,257 2,829,938 N/A Co-monomer type 1-Hexene 1-Hexene 1-Butene 1-Butene 1-Hexene 1-Butene Comonomer 0.47 0.39 0.74 0.63 0.47 N/A content (% mole)

(34) TABLE-US-00006 TABLE 6 Polymer properties of Inventive example E12, E13, E14 and comparative example CE9, CE10, and CE11. Comparative Comparative Inventive Inventive Inventive Comparative example 9 example 10 Example Example Example example 11 (CE9) (CE10) 12 (E12) 13 (E13) 14 (E14) (CE11) Physical properties MI.sub.5 (g/10 min) 0.194 0.302 0.256 0.258 0.222 N/A MI.sub.21 (g/10 min) 6.03 7.11 6.02 5.58 7.45 4.40 Density (g/cm.sup.3) 0.9477 0.9499 0.9484 0.9516 0.9552 0.948 Mechanical properties Charpy impact.sup.b 28.9 22.1 30.6 24.9 30.9 N/A resistance 23° C. (kJ/m.sup.2) Charpy impact.sup.b 12.3 8.8 12.4 12.9 18.9 N/A resistance −40° C. (kJ/m.sup.2) Flexural modulus 835 847 866 914 1,010 N/A (MPa) FNCT.sup.a N/A 28 227 140 189 N/A (80° C., 3.5 MPa, hr) FNCT.sup.b, water (hr) 70 N/A >700 N/A N/A N/A Processing properties Swell ratio at 285% 290% 193% 189% 209% 163% γ = 1400 s.sup.−1 Elongational 1.16 1.01 1 1 1.10 N/A hardening value (eh) at rate 1 1/sec Elongational 1.11 1.05 1 1 1.08 N/A hardening value (eh) at rate 5 1/sec Tan(delta) at 600 rad/s 0.532 0.485 0.407 0.411 0.407 N/A

(35) The inventions for medium and large container show the similar tendency of the results to those of small containers. Focusing on FNCT, both method FNCT.sup.a and FNCT.sup.b on the example CE9, CE10 compared with E12, E13 and E14; the testing results emphasized that all the samples produced with the inventive process for making multimodal polyethylene composition have the FNCT.sup.a,b properties remarkably beyond the prior arts (CE9, CE10) with 1-butene or 1-hexene is applied as the comonomer in copolymerization of the 2.sup.nd and 3.sup.rd reactor components as shown in the table 6.

(36) For the swell ratio testing results, the inventive multimodal polyethylene composition examples has the swell ratio higher than that of as comparative example CE11 significantly, however the mechanical properties in the patent application U.S. Pat. No. 8,802,768 B2 cannot be compared with the inventive testing results because of different testing methods.

(37) The good balance of processing and mechanical properties was contributed from the ultrahigh molecular weight portions in the inventive multimodal polyethylene compositions.

(38) The evidence supports that the specific range of multimodal polyethylene composition plays an important role to the swell ratio and provides a good balance of mechanical strength with processing properties for medium and large blow molding containers.

(39) 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.