Ethylene/alpha-olefin copolymer having excellent environmental stress crack resistance

Abstract

Provided is an ethylene/alpha-olefin copolymer having excellent environmental stress crack resistance.

Claims

1. An ethylene/alpha-olefin copolymer, wherein a weight average molecular weight is 50,000 g/mol to 250,000 g/mol, a molecular weight distribution (Mw/Mn) is 4 to 20, a density is 0.950 g/cm.sup.3 to 0.965 g/cm.sup.3, a melt flow rate ratio (MFR.sub.5/MFR.sub.2.16) as measured at 190 C. according to ASTM 1238 is 3 to 10, and environmental stress crack resistance as measured according to ASTM D1693-B is 150 hours to 350 hours.

2. The ethylene/alpha-olefin copolymer of claim 1, wherein the weight average molecular weight is 180,000 g/mol to 220,000 g/mol.

3. The ethylene/alpha-olefin copolymer of claim 1, wherein the molecular weight distribution (Mw/Mn) is 10 to 15.

4. The ethylene/alpha-olefin copolymer of claim 1, wherein the melt flow rate ratio is 5 to 8.

5. The ethylene/alpha-olefin copolymer of claim 1, wherein the environmental stress crack resistance is 200 hours to 400 hours.

6. The ethylene/alpha-olefin copolymer of claim 1, wherein crack resistance is 100 hours or more, the crack resistance is a time at which a water pressure begins to decrease, when the water pressure of 5 bar is applied to the inside of a cap obtained by injection-molding of the ethylene/alpha-olefin copolymer while the cap is immersed in a bath containing a 5% igepal solution, wherein the cap is a 28 mm cap according to PET standard PCO 1881.

7. The ethylene/alpha-olefin copolymer of claim 1, wherein the alpha-olefin is one or more selected from the group consisting of 1-propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1 -pentene, 1-octene, 1-decene, 1-docene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, and mixtures thereof.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereinafter, preferred examples will be provided for better understanding of the present invention. However, the following examples are provided only for understanding the present invention more easily, but the content of the present invention is not limited thereby.

Preparation Example

(2) ##STR00003##

(3) Into a well-dried 250 mL Schlenk flask, 11.6 mL (100 mmol) of indene was introduced and diluted in 80 mL of THF, followed by stirring. 48 mL of a 2.5M nBuLi hexane solution was slowly added thereto, and 3 hours later, 18.3 g (95 mmol) of 6-chloro hexyl tert-butyl ether was added and reacted for about 12 hours. It was observed that the reaction mixture turned into a light pink suspension as the reaction progressed. After the reaction was completed, 100 mL of water was added to the mixture, followed by extraction with 100 mL of ether three times or more. The collected organic layer was dried over MgSO.sub.4, followed by solvent removal by vacuum filtration and additional vacuum distillation at 100 C., 20 mmHg, thereby obtaining a pure tether-indene ligand with a yield of 90%.

(4) .sup.1H NMR (500 MHz, CDCl.sub.3): 1.22 (9H, s), 1.62 (2H, m), 1.77 (2H, m), 2.58 (2H, m), 3.36 (2H, s), 3.42 (2H, m), 6.28 (1H, s), 7.19 (1H, m), 7.24 (1H, m), 7.40 (1H, m), 7.48 (1H, m)

(5) 10 mmol of the obtained ligand was dissolved in 45 mL of ether, and then, 5 mL (1.25 equivalents) of a nBuLi hexane solution was added thereto. 6 hours later, 20 g (0.95 equivalents) of an nBuCpZrCl.sub.3 toluene solution (0.273 g/mmol) was slowly added thereto at 78 C., and the temperature was raised, and then the solution was additionally stirred for a day. The reaction mixture was passed through a filter to obtain a filtrate, which was concentrated, extracted with 100 mL of hexane, and concentrated again to obtain the title compound with a yield of 90% or more.

(6) .sup.1H NMR (500 MHz, CDCl.sub.3): 0.93 (3H, t), 1.15 (9H, s), 1.241.55 (10H, m), 1.581.64 (2H, m), 3.34 (2H, m), 5.77 (0.5H, s), 5.82 (1H, m), 6.02 (0.5H, s), 6.40 (1H, s), 6.62 (1H, s), 7.26 (2H, m), 7.42 (2H, m)

Example 1

Step 1) Preparation of Supported Catalyst

(7) Into a glass reactor, 49.7 mL of a 10 wt % methylaluminoxane (MAO)/toluene solution was introduced, 9.1 g of silica (product name: Grace 952, particle size: 30 m, surface area: 300 m.sup.2/g, pore volume: 1.6 mL/g, pore diameter: 20 nm) was introduced at 40 C., and then the solution was stirred at 200 rpm for 16 hours while raising the temperature of the reactor to 60 C. Thereafter, the temperature was lowered again to 40 C., 441 mg of the metallocene compound of Preparation Example was dissolved in toluene in a solution state and introduced, followed by stirring for 2 hours. Next, 730 mg of N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate was dissolved in 20 mL of toluene and introduced in a solution state, followed by stirring at 40 C. for 2 hours. After the reaction was completed, stirring was stopped, a toluene layer was separated and removed, and then remaining toluene was removed under reduced pressure at 40 C., thereby preparing a single metallocene supported catalyst.

Step 2) Preparation of Ethylene/1-Butene Copolymer

(8) Polymerization was performed using the supported catalyst prepared above and a hexane slurry stirred tank process. Polymerization conditions included 10 kg/hr of ethylene, a pressure of 7 kg/cm.sup.2, a temperature of 82 C., 3 g/hr of hydrogen, and 7 cc/min of 1-butene.

Example 2

(9) An ethylene/1-butene copolymer was prepared in the same manner as in Example 1, except that a polymerization condition of 3.5 g/hr of hydrogen was used in step 2 of Example 1.

Example 3

(10) An ethylene/1-butene copolymer was prepared in the same manner as in Example 1, except that a polymerization condition of 3.6 g/hr of hydrogen was used in step 2 of Example 1.

Example 4

(11) An ethylene/1-butene copolymer was prepared in the same manner as in Example 1, except that a polymerization condition of 3.7 g/hr of hydrogen was used in step 2 of Example 1.

Example 5

(12) An ethylene/1-butene copolymer was prepared in the same manner as in Example 1, except that a polymerization condition of 3.3 g/hr of hydrogen was used in step 2 of Example 1.

Comparative Examples 1 to 4

(13) The following compounds were used as Comparative Examples. Comparative Example 1: CAP602 (INEOS) Comparative Example 2: CAP508 (INEOS) Comparative Example 3: Lutene H ME1000 (LG Chem) Comparative Example 4: Lumicene M5220 (Total)

Experimental Example

(14) Physical properties of the copolymers of Examples and Comparative Examples were evaluated by the following methods. 1) Density: ASTM D1505. 2) Melt Index (MFR, 5 kg/2.16 kg): measurement temperature of 190 C., ASTM 1238. 3) MFRR(MFR.sub.5/MFR.sub.2.16): a ratio obtained by dividing MFR.sub.5 melt index (MI, 5 kg of load) by MFR.sub.2.16 (MI, 2.16 kg of load). 4) Mn, Mw, and MWD: samples were pretreated by dissolving in 1,2,4-trichlorobenzene containing 0.0125% BHT using PL-SP260 at 160 C., 10 hours, and a number average molecular weight and a weight average molecular weight thereof were measured at a measurement temperature of 160 C. using PL-GPC220. A molecular weight distribution was represented by a ratio of the weight average molecular weight and the number average molecular weight. 5) Environmental stress crack resistance (ESCR): The time until F50 (50% destruction) was measured using a 10% Igepal CO-630 Solution under a temperature condition of 50 C. according to ASTM D1693-B. 6) Crack Resistance: a cap (28 mm cap according to PET standard PCO 1881) was manufactured using the ethylene/alpha-olefin copolymer and an Angel injection molding machine of 120 ton screw 30 standard under conditions of a processing temperature of 240 C., an injection speed of 78 mm/s, and a holding pressure of 650 bar. While the molded cap was immersed in a bath containing a 5% igepal solution, a water pressure of 5 bar was applied to the inside of the cap, and the time at which the water pressure begins to decrease was measured.

(15) The results are shown in the following Table 1.

(16) TABLE-US-00001 TABLE 1 Weight average Molecular MFRR(MFR.sub.5/ molecular weight Crack Density MFR.sub.2.16 MFR.sub.2.16) weight distribution ESCR Resistance Unit g/cm3 g/10 min g/mol Time Time Ex. 1 0.952 0.22 6.7 200k 10.6 350 110 Ex. 2 0.952 0.45 7.2 170k 12.3 220 100 Ex. 3 0.953 0.52 6.9 168k 12.2 190 105 Ex. 4 0.953 0.56 6.9 165k 12.6 185 105 Ex. 5 0.951 0.33 6.6 180k 9.8 255 115 Comparative 0.952 0.78 3.4 140k 9.8 180 95 Ex. 1 Comparative 0.952 1.74 3.4 105k 8.8 130 40 Ex. 2 Comparative 0.953 0.84 3.9 155k 13.4 50 35 Ex. 3 Comparative 0.952 2.00 3.5 85k 4.3 20 12 Ex. 4