Ethylene/alpha-olefin copolymers having excellent processability

Abstract

The present invention relates to an ethylene/alpha-olefin copolymer having excellent processability. The ethylene/alpha-olefin copolymer according to the present invention has low complex viscosity at high shear rate and has excellent processability, and thus it could be applied to the processing of a large diameter pipe, a complex pipe or the like.

Claims

1. An ethylene/alpha-olefin copolymer in which: the density (g/cm.sup.3) is 0.930 to 0.950; MFR.sub.5 (g/10 min, measured at 190? C. in accordance with ASTM 1238) is 0.1 to 5; the melt flow rate ratio (MFR.sub.21.6/MFR.sub.5, measured at 190? C. in accordance with ASTM 1238) is 10 to 200; and when a graph of complex viscosity (?*[Pa.Math.s]) versus frequency (?[rad/s]) is fitted to the power law of the following Equation 1, a C.sub.1 value is 250,000 to 400,000 and a C.sub.2 value is ?0.7 to ?0.5, and when fitted to the cross model of the following Equation 2, a C.sub.1 value is 1,500,000 to 2,500,000, a C.sub.2 value is 3 to 10, a C.sub.3 value is 0.2 to 0.3, x is frequency, and y is complex viscosity: $\begin{array}{cc}y=c_1{x}^{c_2}& \left[\mathrm{Equation}1\right]\\ y=\frac{c_1}{1+{\left(c_{2}x\right)}^{\left(1-c_3\right)}}.& \left[\mathrm{Equation}2\right]\end{array}$

2. The ethylene/alpha-olefin copolymer according to claim 1 wherein when x in Equation 2 is 800, the value of y is 3,000 to 5,000.

3. The ethylene/alpha-olefin copolymer according to claim 2 wherein the value of y is 4,000 to 4,900.

4. The ethylene/alpha-olefin copolymer according to claim 1 wherein when x in Equation 2 is 1,200, the value of y is 3,000 to 3,800.

5. The ethylene/alpha-olefin copolymer according to claim 4 wherein the value of y is 3,000 to 3,700.

6. The ethylene/alpha-olefin copolymer according to claim 1 wherein the C.sub.2 value in Equation 2 is 5 to 8.

7. The ethylene/alpha-olefin copolymer according to claim 1 wherein the ethylene/alpha olefin copolymer has a weight average molecular weight (g/mol) of 10,000 to 400,000, and a molecular weight distribution (Mw/Mn, PDI) of 5 to 30.

8. The ethylene/alpha-olefin copolymer according to claim 1 wherein the alpha-olefin is one or more selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene.

9. The ethylene/alpha-olefin copolymer according to claim 1 wherein the ethylene/alpha-olefin copolymer is prepared by polymerizing ethylene and alpha-olefin in the presence of one or more of the first metallocene compounds represented by the following Chemical Formula 1; and one ore more of the second metallocene compounds selected among the compounds represented by the following Chemical Formulae 3 to 5: ##STR00024## in Chemical Formula 1, A is hydrogen, halogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkylaryl, C.sub.7-C.sub.20 arylalkyl, C.sub.1-C.sub.20 alkoxy, C.sub.2-C.sub.20 alkoxyalkyl, C.sub.3-C.sub.20 heterocycloalkyl, or C.sub.5-C.sub.20 heteroaryl; D is O, S, N(R), or Si(R)(R), wherein R and R are the same as or different from each other, and each independently hydrogen, halogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkenyl, or C.sub.6-C.sub.20 aryl; L is C.sub.1-C.sub.10 linear or branched alkylene; B is carbon, silicon, or germanium; Q is hydrogen, halogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkylaryl, or C.sub.7-C.sub.20 arylalkyl; M is a Group 4 transition metal; X.sup.1 and X.sup.2 are the same as or different from each other, and each independently halogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.6-C.sub.20 aryl, nitro, amido, C.sub.1-C.sub.20 alkylsilyl, C.sub.1-C.sub.20 alkoxy, or C.sub.1-C.sub.20 sulfonate; C.sup.1 and C.sup.2 are the same as or different from each other, and each independently represented by any one of the following Chemical Formula 2a, Chemical Formula 2b or Chemical Formula 2c, provided that both of C.sup.1 and C.sup.2 are not represented by the following Chemical Formula 2c: ##STR00025## in Chemical Formulae 2a, 2b and 2c, R.sub.1 to R.sub.17 and R.sub.1 to R.sub.9 are the same as or different from each other, and each independently hydrogen, halogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.1-C.sub.20 alkylsilyl, C.sub.1-C.sub.20 silylalkyl, C.sub.1-C.sub.20 alkoxysilyl, C.sub.1-C.sub.20 alkoxy, C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkylaryl, or C.sub.7-C.sub.20 arylalkyl, wherein two or more adjacent groups among R.sub.10 to R.sub.17 may be connected together to form substituted or unsubstituted aliphatic or aromatic ring;
(Cp.sup.1R.sup.a).sub.n(Cp.sup.2R.sup.b)M.sup.1Z.sup.1.sub.3-n[Chemical Formula 3] in Chemical Formula 3, M.sup.1 is a Group 4 transition metal; Cp.sup.1 and Cp.sup.2 are the same as or different from each other, and each independently any one selected from the group consisting of cyclopentadienyl, indenyl, 4,5,6,7-tetrahydro-1-indenyl, and fluorenyl radical, each of which may be substituted by hydrocarbon having 1 to 20 carbon atoms; R.sup.a and R.sup.b are the same as or different from each other, and each independently hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.10 alkoxy, C.sub.2-C.sub.20 alkoxyalkyl, C.sub.6-C.sub.20 aryl, C.sub.6-C.sub.10 aryloxy, C.sub.2-C.sub.20 alkenyl, C.sub.7-C.sub.40 alkylaryl, C.sub.7-C.sub.40 arylalkyl, C.sub.8-C.sub.40 arylalkenyl, or C.sub.2-C.sub.10 alkynyl; Z.sup.1 is halogen atom, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.10 alkenyl, C.sub.7-C.sub.40 alkylaryl, C.sub.7-C.sub.40 arylalkyl, C.sub.6-C.sub.20 aryl, substituted or unsubstituted C.sub.1-C.sub.20 alkylidene, substituted or unsubstituted amino, C.sub.2-C.sub.20 alkylalkoxy, or C.sub.7-C.sub.40 arylalkoxy; and n is 1 or 0;
(Cp.sup.3R.sup.c).sub.mB.sup.1(Cp.sup.4R.sup.d)M.sup.2Z.sup.2.sub.3-m[Chemical Formula 4] in Chemical Formula 4, M.sup.2 is a Group 4 transition metal; Cp.sup.3 and Cp.sup.4 are the same as or different from each other, and each independently any one selected from the group consisting of cyclopentadienyl, indenyl, 4,5,6,7-tetrahydro-1-indenyl and fluorenyl radical, each of which may be substituted by hydrocarbon having 1 to 20 carbon atoms; R.sup.c and R.sup.d are same as or different from each other, and each independently hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.10 alkoxy, C.sub.2-C.sub.20 alkoxyalkyl, C.sub.6-C.sub.20 aryl, C.sub.6-C.sub.10 aryloxy, C.sub.2-C.sub.20 alkenyl, C.sub.7-C.sub.40 alkylaryl, C.sub.7-C.sub.40 arylalkyl, C.sub.8-C.sub.40 arylalkenyl, or C.sub.2-C.sub.10 alkynyl; Z.sup.2 is halogen atom, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.10 alkenyl, C.sub.7-C.sub.40 alkylaryl, C.sub.7-C.sub.40 arylalkyl, C.sub.6-C.sub.20 aryl, substituted or unsubstituted C.sub.1-C.sub.20 alkylidene, substituted or unsubstituted amino group, C.sub.2-C.sub.20 alkylalkoxy, or C.sub.7-C.sub.40 arylalkoxy; B.sup.1 is one or more selected from the radicals containing carbon, germanium, silicon, phosphorous or nitrogen atom, which crosslink Cp.sup.3R.sup.c ring to Cp.sup.4R.sup.d ring, or crosslink one Cp.sup.4R.sup.d ring to M.sup.2, or combinations thereof, and m is 1 or 0;
(Cp.sup.5R.sup.e)B.sup.2(J)M.sup.3Z.sup.3.sub.2[Chemical Formula 5] in Chemical Formula 5, M.sup.3 is a Group 4 transition metal; Cp.sup.5 is any one selected from the group consisting of cyclopentadienyl, indenyl, 4,5,6,7-tetrahydro-1-indenyl and fluorenyl radical, each of which may be substituted by hydrocarbon having 1 to 20 carbon atoms; R.sup.e is hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.10 alkoxy, C.sub.2-C.sub.20 alkoxyalkyl, C.sub.6-C.sub.20 aryl, C.sub.6-C.sub.10 aryloxy, C.sub.2-C.sub.20 alkenyl, C.sub.7-C.sub.40 alkylaryl, C.sub.7-C.sub.40 arylalkyl, C.sub.8-C.sub.40 arylalkenyl, or C.sub.2-C.sub.10 alkynyl; Z.sup.3 is halogen atom, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.10 alkenyl, C.sub.7-C.sub.40 alkylaryl, C.sub.7-C.sub.40 arylalkyl, C.sub.6-C.sub.20 aryl, substituted or unsubstituted C.sub.1-C.sub.20 alkylidene, substituted or unsubstituted amino, C.sub.2-C.sub.20 alkylalkoxy, or C.sub.7-C.sub.40 arylalkoxy; B.sup.2 is one or more selected from the radicals containing carbon, germanium, silicon, phosphorous or nitrogen atom, which crosslink Cp.sup.5R.sup.e ring to J, or combinations thereof; and J is any one selected from the group consisting of NR.sup.f, O, PR.sup.f and S, wherein R.sup.f is C.sub.1-C.sub.20 alkyl, aryl, substituted alkyl or substituted aryl.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows GPO curve of a copolymer prepared in a comparative example and an example of the present invention.

(2) FIG. 2 shows the results obtained by fitting a graph of complex viscosity versus frequency in accordance with a comparative example and an example of the present invention to a power law and a cross model.

(3) FIG. 3 shows the results obtained by fitting a graph of complex viscosity versus frequency in accordance with a comparative example and an example of the present invention to a cross model.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) Hereinafter, preferred examples are provided for better understanding of the invention. However, these examples are for illustrative purposes only and the invention is not ion are not intended to be limited by these examples.

First Metallocene Compound

Preparation Example 1

(5) ##STR00022##

(6) 1-1) Preparation of Ligand Compound

(7) 2 g of fluorene was dissolved in 5 mL of MTBE and 100 mL of hexane, and 5.5 mL of 2.5 M n-BuLi hexane solution was added dropwise in a dry ice/acetone bath and stirred overnight at room temperature. 3.6 g of (6-(tert-butoxy)hexyl)dichloro(methyl)silane was dissolved in 50 mL of hexane, and fluorene-Li slurry was transferred under a dry ice/acetone bath for 30 minutes and stirred overnight at room temperature. At the same time, 5,8-dimethyl-5,10-dihydroindeno[1,2-b]indole (12 mmol, 2.8 g) was also dissolved in THF (60 mL), and 2.5 M n-BuLi hexane solution (5.5 mL) was added dropwise in a dry ice/acetone bath and stirred overnight at room temperature. The reaction solution of fluorene and (6-(tert-butoxy)hexyl)dichloro(methyl)silane was subjected to NMR sampling to confirm the completion of reaction. Thereafter, the 5,8-dimethyl-5,10-dihydroindeno[1,2-b]indole-Li solution was transferred under a dry ice/acetone bath and stirred overnight at room temperature. After reaction, the reaction mixture was extracted with ether/water and the remaining moisture in the organic layer was removed with MgSO.sub.4 to give the ligand compound (Mw 597.90, 12 mmol). It could be confirmed by .sup.1H-NMR that two isomers were produced.

(8) .sup.1H NMR (500 MHz, d.sub.6-benzene): ?0.30??0.18 (3H, d), 0.40 (2H, m), 0.65?1.45 (8H, m), 1.12 (9H, d), 2.36?2.40 (3H, d), 3.17 (2H, m), 3.41?3.43 (3H, d), 4.17?4.21 (1H, d), 4.34?4.38 (1H, d), 6.90?7.80 (15H, m)

(9) 1-2) Preparation of Metallocene Compound

(10) 7.2 g (12 mmol) of the ligand compound synthesized in 1-1 above was dissolved in 50 mL of diethylether, and 11.5 mL of 2.5 M n-BuLi hexane solution was added dropwise in a dry ice/acetone bath and stirred overnight at room temperature. The mixture was dried under vacuum to give sticky oil having a brown color. This oil was dissolved in toluene to give a slurry. ZrCl.sub.4(THF).sub.2 was prepared, and 50 mL of toluene was added thereto to prepare a slurry. 50 mL of toluene slurry of ZrCl.sub.4(THF).sub.2 was transferred in a dry ice/acetone bath. As the mixture was stirred overnight at room temperature, the color was changed to violet. The reaction solution was filtered to remove LiCl. The filtrate was dried under vacuum to remove toluene, hexane was added thereto, and the mixture was sonicated for 1 hour. The slurry was filtered to give the metallocene compound (6 g, Mw 758.02, 7.92 mmol, Yield 66 mol %) having a dark violet color as a filtered solid. Two isomers were observed through .sup.1H-NMR.

(11) .sup.1H NMR (500 MHz, CDCl.sub.3): 1.19 (9H, d), 1.71 (3H, d), 1.50?1.70 (4H, m), 1.79 (2H, m), 1.98?2.19 (4H, m), 2.58 (3H, s), 3.38 (2H, m), 3.91 (3H, d), 6.66?7.88 (15H, m)

Preparation Example 2

(12) ##STR00023##

(13) 2-1) Preparation of Ligand Compound

(14) To a 250 mL flask was introduced 2.63 g (12 mmol) of 5-methyl-5,10-dihydroindeno[1,2-b]indole, which was then dissolved in 50 mL of THF. Then, 6 mL of 2.5 M n-BuLi hexane solution was added dropwise in a dry ice/acetone bath and stirred overnight at room temperature. In another 250 mL flask, 1.62 g (6 mmol) of (6-(tert-butoxy)hexyl)dichloro(methyl)silane was prepared by dissolving it in 100 mL of hexane, which was then slowly added dropwise to a lithiated solution of 5-methyl-5,10-dihydroindeno[1,2-b]indole under a dry ice/acetone bath and stirred overnight at room temperature. After reaction, the mixture was extracted with ether/water. The organic layer was treated with MgSO.sub.4 to remove the remaining moisture and then dried under vacuum to give 3.82 g (6 mmol) of the ligand compound which was confirmed by .sup.1H-NMR.

(15) .sup.1H NMR (500 MHz, CDCl.sub.3): ?0.33 (3H, m), 0.86?1.53 (10H, m), 1.16 (9H, d), 3.18 (2H, m), 4.07 (3H, d), 4.12 (3H, d), 4.17 (1H, d), 4.25 (1H, d), 6.95?7.92 (16H, m)

(16) 2-2) Preparation of Metallocene Compound

(17) 3.82 g (6 mmol) of the ligand compound synthesized in 2-1 above was dissolved in 100 mL of toluene and 5 mL of MTBE, and then 5.6 mL (14 mmol) of 2.5 M n-BuLi hexane solution was added dropwise in a dry ice/acetone bath and stirred overnight at room temperature. In another flask, 2.26 g (6 mmol) of ZrCl.sub.4(THF).sub.2 was prepared as a slurry by adding 100 mL of toluene. ZrCl.sub.4(THF).sub.2 as a toluene slurry was transferred to the litiated ligand in a dry ice/acetone bath. The mixture was stirred overnight at room temperature, and the color was changed to violet. The reaction solution was filtered to remove LiCl. The filtrate thus obtained was dried under vacuum, hexane was added thereto, and the mixture was sonicated. The slurry was filtered to give the metallocene compound (3.40 g, Yield 71.1 mol %) having a dark violet color as a filtered solid.

(18) .sup.1H NMR (500 MHz, CDCl.sub.3): 1.74 (3H, d), 0.85?2.33 (10H, m), 1.29 (9H, d), 3.87 (3H, s), 3.92 (3H, s), 3.36 (2H, m), 6.48?8.10 (16H, m)

Second Metallocene Compound

Preparation Example 3: Preparation of [tBu-O(CH2)6C5H4]2ZrCl2]

(19) t-Butyl-O(CH.sub.2).sub.6Cl was prepared using 6-chlorohexanol according to the method described in Tetrahedron Lett. 2951 (1988), and then reacted with NaCp to give t-Butyl-O(CH.sub.2).sub.6C.sub.5H.sub.5(Yield 60%, b.p. 80? C./0.1 mmHg).

(20) Also, t-Butyl-O(CH.sub.2).sub.6C.sub.5H.sub.5 was dissolved in THF at ?78? C., n-BuLi was slowly added thereto, and the mixture was warmed to room temperature and then reacted for 8 hours. Again at a temperature of ?78? C., thus prepared lithium salt solution was slowly added up to a suspension solution of ZrCl.sub.4(THF).sub.2 (1.70 g, 4.50 mmol)/THF (30 mL) and the mixture was further reacted at room temperature for 6 hours.

(21) All volatile substances were dried under vacuum and hexane solvent was added to the resulting oily liquid substance, which was then filtered. The filtrate was dried under vacuum, and hexane was added to induce a precipitate at a low temperature (?20? C.). The resulting precipitate was filtered at a low temperature to give [tBu-O(CH.sub.2).sub.6C.sub.5H.sub.4].sub.2ZrCl.sub.2 compound (Yield 92%) as a white solid.

(22) .sup.1H NMR (300 MHz, CDCl.sub.3): 6.28 (t, J=2.6 Hz, 2H), 6.19 (t, J=2.6 Hz, 2H), 3.31 (t, 6.6 Hz, 2H), 2.62 (t, J=8 Hz), 1.7-1.3 (m, 8H), 1.17 (s, 9H)

(23) .sup.13C NMR (CDCl.sub.3): 135.09, 116.66, 112.28, 72.42, 61.52, 30.66, 30.61, 30.14, 29.18, 27.58, 26.00

Hybrid Supported Catalyst

Examples 1 and 2

(24) 3.0 kg of toluene solution was added to a 20 L sus autoclave reactor and the reactor temperature was maintained at 40? C. 500 g of silica (SP2212 produced by Grace Davison) was added to the reactor, and silica was sufficiently dispersed. Then, 2.78 kg of 10 wt % methyl aluminoxane(MAO)/toluene solution was added to the reactor. Then, the reaction temperature was raised up to 80? C. and the mixture was stirred at 200 rpm for 15 hours or more. The reactor temperature was again lowered to 40? C., and then 300 g of 7.5 wt % Catalyst Preparation Example 2/toluene solution was added to the reactor and stirred at 200 rpm for 1 hour. 250 g of 8.8 wt % Catalyst Preparation Example 1/toluene solution was added to the reactor and stirred at 200 rpm for 1 hour. Catalyst Preparation Example 3 (20 g) was dissolved in toluene and added to the reactor, and the mixture was stirred at 200 rpm for 2 hours. 70 g of cocatalyst (anilinium tetrakis(pentafluorophenyl)borate) was diluted in 70 g of tolune and added to the reactor, and then stirred at 200 rpm for 15 hours or more. After lowering the reactor temperature to room temperature, the stirring was stopped. Then, settling was performed for 30 minutes and the reaction solution was subjected to decantation. Toluene slurry was transferred to a filter dryer and filtered. 3.0 kg of toluene was added to the reactor and stirred for 10 minutes. Then, stirring was stopped and filtering was performed. 3.0 kg of hexane was added to the reactor and stirred for 10 minutes. Then, stirring was stopped and filtering was performed. The filtrate was dried at 50? C. under reduced pressure for 4 hours to produce a 500 g-SiO.sub.2-supported catalyst.

(25) [Ethylene/1-Butene Copolymer]

(26) The respective hybrid supported metallocene catalysts prepared in Examples 1 and 2 were subjected to bimodal operation with two reactors by using a hexane slurry stirred tank process polymerization machine to produce an olefin polymer. As a comonomer, 1-butene was used.

(27) The polymerization conditions using the respective hybrid supported metallocene catalysts prepared in Examples 1 and 2 are summarized in Table 1 below.

(28) TABLE-US-00001 TABLE 1 Catalyst used Example 1 Example 2 R1 ethylene supply amount (kg/hr) 7.0 7.0 R1 pressure (kg/cm.sup.2) 7.5 7.2 R1 temperature (? C.) 84.4 85.0 R1 hydrogen injection amount (g/hr) 3.10 2.44 R2 ethylene supply amount (kg/hr) 6.0 6.0 R2 pressure (kg/cm.sup.2) 4.7 4.8 R2 temperature(? C.) 75.2 73.0 R2 1-butene injection amount (g/hr) 18.0 18.0 Catalytic activity (kg PE/g SiO.sub.2) 6.1 7.8

Comparative Examples 1 to 3

(29) For comparison with the polymers produced using the hybrid supported metallocene catalysts from Examples 1 and 2, the following copolymers having similar density were used as Comparative Examples.

Comparative Example 1

(30) Hostalene 4731B available from LyondellBasell Industries

Comparative Example 2

(31) XRT-70 available from Total Refining & Chemicals

Comparative Example 3

(32) XP9020 available from Daelim Industrial Co., Ltd.

(33) [Evaluation of Physical Properties of Copolymer]

(34) The physical properties of the copolymers prepared in Examples and Comparative Examples were evaluated by the following methods.

(35) 1) Density: ASTM1505

(36) 2) Melt Flow Rate (MFR, 5 kg/21.6 kg): measured at a temperature of 190? C., ASTM1238

(37) 3) MFRR (MFR.sub.21.6/MFR.sub.5): the ratio where MFR.sub.21.6 melt index (MI, load: 21.6 kg) is divided by MFR.sub.5 (MI, load: 5 kg).

(38) 4) Mn, Mw, MWD, GPC curve: samples were melted and pre-treated in 1,2,4-trichlorobenzene containing BHT 0.0125% using PL-SP260 at 160? C. for 10 hours. The number average molecular weight and the weight average molecular weight were measured at a temperature of 160? C. using PL-GPC220. The molecular weight distribution was indicated by the ratio of the weight average molecular weight and number average molecular weight.

(39) 5) Graph of the complex viscosity versus frequency, fitting the power law and cross model: the complex viscosity was measured with ARES (Advanced Rheometric Expansion System) (TA Instruments). The samples were set using parallel plates with 25.0 mm diameter at 190? C. so that the gap between plates becomes 2.0 mm. Measurements were conducted in dynamic strain frequency sweep mode and in the frequency range of 0.05 rad/s to 500 rad/s at a strain rate of 5%. 10 points for each decade, a total of 41 points, were measured. The power law and cross model fitting was carried out by using a TA Orchestrator software which is a measurement program.

(40) First, among the above results, the results relating to the physical properties of the copolymers are shown in Table 2 below. Also, GPC curve of the respective copolymers is shown in FIG. 1.

(41) TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Unit Example 1 Example 2 Example 3 Example 1 Example 2 Density g/cm.sup.3 0.947 0.947 0.941 0.9432 0.9448 MFR.sub.5 g/10 min 0.45 0.75 0.42 0.31 0.23 MFR.sub.21.6 g/10 min 12.4 18.6 9.6 10.1 7.5 MFRR.sub.21.6/5 28 25 22 33 33 Mn 13,100 14,400 14,100 12,500 11,100 Mw 197,000 189,000 181,000 219,000 239,000 MWD 15.10 13.08 12.83 17.52 21.54

(42) Next, a graph of the complex viscosity versus frequency of the copolymer prepared in Example 2, and the results obtained by fitting the graph to power law and cross model are shown in FIG. 2.

(43) As shown in FIG. 2, it could be confirmed that the graph of the complex viscosity versus frequency of the copolymer prepared in Example 2, and the results obtained by fitting the graph to the power law and cross model were very similar, and that both power law and cross model were suitable models to evaluate quantitatively the flow properties of the copolymers according to the present invention.

(44) The copolymers prepared in Examples and Comparative Examples were fitted to the power law and cross model, and the values of variables thus obtained are shown in Table 3 below. In addition, based on the resulting values of variables, the values of complex viscosity at the frequencies of 800 rad/s and 1,200 rad/s in the cross model are shown in Table 3 below.

(45) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 1 Example 2 Power Law C.sub.1 214950 187270 205150 360090 337500 C.sub.2 ?0.5111 ?0.4978 ?0.4446 ?0.6141 ?0.6277 Cross Model C.sub.1 645230 590910 376790 1978500 1958600 C.sub.2 1.81966 2.22020 0.33886 6.57477 7.09718 C.sub.3 0.33584 0.36301 0.25547 0.29941 0.28975 Processing 800 rad/s 5075.7 4988.3 5727.0 4879.7 4222.2 area 1200 rad/s 3884.6 3860.3 4251.5 3675.2 3160.6

(46) If the polyethylene copolymers were applied to the large-diameter pipe or the composite pipe, they received a strong pressure and thus, it could be evaluated that the lower the complex viscosity at high frequency range, the higher the processability. Accordingly, it was possible to predict that the lower the complex viscosity value at 800 rad/s and 1200 rad/s which were in the range of high frequencies in the cross model, the actual processability was excellent.

(47) Thus, as shown in Table 3, it could be confirmed that the complex viscosity values of Examples compared to Comparative Examples was low at frequencies of 800 rad/s and 1,200 rad/s. Accordingly, the polyethylene copolymer according to the present invention had excellent processability at high shear rate and thus it could be preferably applied to the processing of a large diameter pipe or a complex pipe.