Polyethylene and Its Chlorinated Polyethylene

Abstract

There are provided a polyethylene capable of improving tensile strength while maintaining excellent processability and Mooney viscosity characteristics when preparing a chlorinated polyethylene compound by implementing a molecular structure having a low content of low molecular weight and a high content of high molecular weight, and a chlorinated polyethylene prepared using the same.

Claims

1. A polyethylene having a density of 0.945 g/cm.sup.3 or more when measured in accordance with ASTM D-1505, wherein a fraction of an area representing a high molecular weight content of log Mw>6.0 is 4 to 12%, a fraction of an area representing a medium molecular weight content of 4.5<log Mw<5.0 is 35 to 50%, and a fraction of an area representing a low molecular weight content of log Mw<4.0 is 10% or less, relative to a total area of a molecular weight distribution curve drawn with a log value of weight average molecular weight as the x axis and a molecular weight distribution with respect to the log value as the y axis using gel permeation chromatography, and an entanglement molecular weight (M.sub.e) of the following Equation 1 is 27,000 to 52,000 g/mol:
M.sub.e=(ρRT)/G.sub.N.sup.0  [Equation 1] wherein Equation 1, ρ is a density (kg/m.sup.3) of polyethylene measured in accordance with ASTM D-1505×0.8, R is a gas constant of polyethylene of 8.314 Pa.Math.m.sup.3/mol.Math.K, T is an absolute temperature of the measured temperature, and G.sub.N.sup.0 is a plateau modulus of polyethylene, which is a storage modulus when a loss modulus has a minimum value in a region where the storage modulus is greater than the loss modulus, wherein the storage modulus and loss modulus are measured while changing an angular frequency to 0.05 to 500 rad/s under conditions of 190° C. and 0.5% strain using a rotary rheometer.

2. The polyethylene of claim 1, wherein the density of the polyethylene is 0.945 to 0.955 g/cm.sup.3 when measured in accordance with ASTM D-1505.

3. The polyethylene of claim 1, wherein a fraction of an area representing an ultra-high molecular weight content of 6.5<log Mw relative to a total area of a molecular weight distribution curve is 0.1 to 3% in the molecular weight distribution curve drawn using gel permeation chromatography.

4. The polyethylene of claim 1, wherein a fraction of an area representing an ultra-low molecular weight content of log Mw<3.5 is 2% or less, and a fraction of an area representing a low molecular weight content of 3.5≤log Mw<4.0 is 7% or less in the molecular weight distribution curve.

5. The polyethylene of claim 1, wherein the polyethylene has a melt index of 0.5 to 3 g/10 min when measured at a temperature of 190° C. under a load of 5 kg in accordance with ASTM D 1238.

6. The polyethylene of claim 1, wherein the polyethylene has a melt flow rate ratio obtained by dividing MFR.sub.21.6 measured at 190° C. under a load of 21.6 kg in accordance with ASTM D 1238 by MFR.sub.5.0 measured at 190° C. under a load of 5.0 kg in accordance with ASTM D 1238 of 10 to 20.

7. The polyethylene of claim 1, wherein the polyethylene has a weight average molecular weight of 150,000 to 300,000 g/mol.

8. The polyethylene of claim 1, wherein the polyethylene has a molecular weight distribution of 5 to 15.

9. The polyethylene of claim 1, wherein the polyethylene has an MDR torque of 7 to 12 Nm when measured at 180° C. for 10 min using a moving die rheometer.

10. The polyethylene of claim 1, wherein the polyethylene is an ethylene homopolymer.

11. A chlorinated polyethylene prepared by reacting the polyethylene of claim 1 with chlorine, and has a Mooney viscosity of 70 to 80 when measured at 121° C.

12. A chlorinated polyethylene compound comprising the chlorinated polyethylene of claim 11.

13. the polyethylene of claim 1, wherein the density of the polyethylene is 0.945 to 0.955 g/cm.sup.3.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0197] The present invention will be described in more detail with the following examples. However, these examples are for illustrative purposes only, and the invention is not intended to be limited by these examples.

<Preparation of First Transition Metal Compound>

Synthesis Example 1: Preparation of [tert-Bu-O—(CH.SUB.2.).SUB.6.-C.SUB.5.H.SUB.4.].SUB.2.ZrCl.SUB.2

[0198] tert-Butyl-O—(CH.sub.2).sub.6—Cl was prepared by the method shown in Tetrahedron Lett. 2951 (1988) using 6-chlorohexanol, and reacted with NaCp to obtain tert-Butyl-O—(CH.sub.2).sub.6—C.sub.5H.sub.5 (yield 60%, b.p. 80° C./0.1 mmHg).

[0199] In addition, tert-Butyl-O—(CH.sub.2).sub.6—C.sub.5H5 was dissolved in THF at −78° C., and normal butyllithium (n-BuLi) was slowly added thereto. Thereafter, it was heated to room temperature and reacted for 8 hours. The lithium salt solution synthesized as described above was slowly added to a suspension solution of ZrCl.sub.4(THF).sub.2 (1.70 g, 4.50 mmol)/THF (30 mL) at −78° C., and further reacted for about 6 hours at room temperature.

[0200] All volatiles were dried in vacuum and the resulting oily liquid material was filtered by adding a hexane solvent. The filtered solution was dried in vacuum, and hexane was added to obtain a precipitate at a low temperature (−20° C.). The obtained precipitate was filtered at a low temperature to obtain [tert-Bu-O—(CH.sub.2).sub.6—C.sub.5H.sub.4].sub.2ZrCl.sub.2 in the form of a white solid (yield 92%).

[0201] .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).

[0202] .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.

[0203] <Preparation of Second Transition Metal Compound>

Synthesis Example 2

[0204] Step 1: Preparation of Ligand Compound 4-(3,5-di-tert-butylphenyl)-2-isopropyl-1H-indene (1.39 g, 4 mmol) was added in a 50 ml schlenk flask as a Cp unit, and THF (13 ml) was add thereto, followed by cooling to −20° C. or less. After the cooled mixed solution was stirred for 5 minutes, NBL (1.7 ml, 2.5M in hexane) was added and reacted for overnight to prepare lithiated Cp. When the NBL was added, the mixed solution turned reddish brown.

[0205] Dichloro(tert-butoxy)hexyl)methylsilane (1.14 g) was added in another 100 mL schlenk flask, and THF (13 ml) was add thereto. After cooling the schlenk flask to −20° C. or less, the lithiated Cp prepared above was added dropwise to react. When the reaction was completed, the solvent in the resulting reactant was removed by distillation under vacuum reduced pressure, and the resulting salt was filtered off using hexane (Hex). After t-BuNH.sub.2 (1.7 ml) was added to the resulting reactant to react, the resulting precipitate was filtered off using hexane, and a ligand compound of 1-(6-(tert-butoxy)hexyl)-N-(tert-butyl)-1-(4-(3,5-di-tert-butylphenyl)-2-isopropyl-1H-inden-1-yl)-1-methylsilanamine was obtained (yellow oil, 2.41 g, yield 97% (molar basis)).

[0206] NMR (400 MHz, C6D6), 7.70-7.68 (m, 1H), 7.60-7.47 (m, 4H), 7.34-7.19 (m, 2H), 7.07 (s, 0.5H), 6.89 (s, 0.5H), 3.36-3.21 (m, 4H), 3.12 (s, 1H), 2.52-2.44 (m, 0.5H), 2.00-1.92 (m, 0.5H), 1.72-1.39 (m, 8H), 1.39 (s, 9H), 1.31 (s, 9H), 1.23 (s, 3H) 1.19 (s, 3H), 1.13 (s, 9H) 0.98 (s, 9H) 0.32 (s, 1H), 0.25 (s, 0.5H), 0.20 (s, 1H), 0.12 (s, 0.5H)

[0207] Step 2: Preparation of Transition Metal Compound

[0208] The ligand compound of 1-(6-(tert-butoxy)hexyl)-N-(tert-butyl)-1-(4-(3,5-di-tert-butylphenyl)-2-isopropyl-1H-inden-1-yl)-1-methylsilanamine (2.4 g, 3.9 mmol) prepared in step 1 was added in a 100 ml schlenk flask, and toluene (13 ml) was add thereto, followed by cooling to −20° C. or less. After sufficiently cooling by stirring for 5 minutes, NBL (5.1 ml, 2.5 M in hexane) was added to the resulting mixed solution to perform lithiation. It was confirmed that the color of the mixed solution turned brown after lithiation. When the lithiation was completed, the resulting reaction solution was cooled to 0° C. After NMB (13 ml, 3 M in ether) was added thereto, the temperature was immediately lowered to −20° C., and TiCl.sub.4 (3.9 ml, 1 M in toluene) was added. Smoke was generated at the time of addition and the reaction solution immediately turned brown. After the addition, o/n stirring was performed, and then the salt was removed through a filter to obtain a transition metal compound (2a) (brown oil, 2.16 g, yield 80% (molar basis)).

##STR00008##

[0209] NMR (400 MHz, C6D6), 7.79-7.76 (m, 2H), 7.64-7.47 (m, 5H), 3.35-3.21 (m, 2H), 2.76-2.49 (s, 2H), 1.99-1.91 (m, 4H), 1.70-1.60 (m, 4H), 1.53 (s, 9H), 1.51-1.44 (m, 4H), 1.36 (s, 9H), 1.30 (s, 9H), 1.20 (s, 6H), 1.13 (s, 9H), 0.59 (s, 3H), 0.12 (s, 3H)

[0210] <Preparation of Hybrid Supported Catalyst>

Synthesis Example 3

[0211] (1) Preparation of Support

[0212] Silica (SYLOPOL948™, manufactured by Grace Davison) was dehydrated and dried at a temperature of 600° C. for 12 hours under vacuum.

[0213] (2) Preparation of Hybrid Supported Catalyst

[0214] 10 g of the silica dried in step (1) was introduced to a glass reactor, and 100 mL of toluene was additionally added and stirred. After sufficient dispersion of the silica, 60.6 mL of 10 wt % methylaluminoxane (MAO)/toluene solution was added thereto. Thereafter, the temperature was raised to 80° C. and the mixture was slowly reacted while stirring at 200 rpm for 16 hours. After lowering the temperature to 40° C. again, the reaction solution was washed with a sufficient amount of toluene to remove unreacted aluminum-based compounds, and the remaining toluene was removed under reduced pressure. 100 mL of toluene was added thereto again, to which 0.24 mmol of the first transition metal compound prepared in Synthesis Example 1 dissolved in toluene was added together and reacted for 1 hour. After completion of the reaction, 0.12 mmol of the second transition metal compound prepared in Synthesis Example 2 dissolved in toluene was added and further reacted for 2 hours while stirring. After completion of the reaction, stirring was stopped and the toluene layer was separated and removed. Then, the remaining toluene was removed under reduced pressure at 40° C. to prepare a hybrid supported catalyst.

Synthesis Example 4

[0215] A hybrid supported catalyst was prepared in the same manner as in Synthesis Example 3, except that the amount of the second transition metal compound was changed to 0.06 mmol (molar ratio of first transition metal compound: second transition metal compound=4:1).

[0216] <Preparation of Polyethylene>

Example 1

[0217] An ethylene homopolymerization reaction was performed using the hybrid supported catalyst prepared in Synthesis Example 3 under the following conditions.

[0218] First, 30 kg/hr of hexane, 10 kg/hr of ethylene, 1 g/hr of hydrogen and 130 cc/hr of triethylaluminum (TEAL) were introduced to a 0.2 m.sup.3 single-CSTR reactor, and then the hybrid supported catalyst prepared in Synthesis Example 3 was injected thereto at 0.2 kg/hr. At this time, the reactor was maintained at a temperature of 82° C. and a pressure of 7.0 kg/cm′ to 7.5 kg/cm.sup.2, and the polymerization was performed for about 4 hours. Thereafter, the polymerization product was made into final polyethylene through a solvent removal plant and a dryer.

Example 2

[0219] Polyethylene was prepared in the same manner as in Example 1, except that the hydrogen was introduced at 1.5 g/hr.

Example 3

[0220] Polyethylene was prepared in the same manner as in Example 1, except that the hydrogen was introduced at 0.5 g/hr.

Comparative Example 1

[0221] High-density polyethylene (CE2080™, manufactured by LG Chem.) prepared using a Ziegler-Natta catalyst was used.

Comparative Example 2

[0222] High-density polyethylene (SC200™, manufactured by LG Chem.) prepared using a metallocene catalyst was used.

Comparative Example 3

[0223] High-density polyethylene (SC100E™, manufactured by LG Chem.) prepared using a metallocene catalyst was used.

Comparative Example 4

[0224] High-density polyethylene (CE6040X™, manufactured by LG Chem.) prepared using a Ziegler-Natta catalyst was used.

Comparative Example 5

[0225] Polyethylene was prepared in the same manner as in Example 1, except that the hydrogen was not introduced during polymerization.

Comparative Example 6

[0226] Polyethylene was prepared in the same manner as in Example 1, except that the hybrid supported catalyst prepared in Synthesis Example 4 was used.

Comparative Example 7

[0227] Commercially available polyethylene (5000CP™, manufactured by Lotte Chemical) was used.

Experimental Example 1

[0228] GPC analysis was performed on the polyethylene prepared in Examples and Comparative Examples in the following manner, and the content of each molecular weight distribution, that is, a fraction was calculated. The results are shown in Table 1 below.

[0229] Fraction (%): GPC analysis was performed, and the fraction was calculated as an area (%) occupied by log Mw section relative to a total area in the resulting molecular weight distribution curve. The sum of the fraction is 100±1, which may not be exactly 100.

[0230] The GPC analysis was specifically performed under the following conditions.

[0231] Waters PL-GPC220 was used as the gel permeation chromatography (GPC) instrument, and a Polymer Laboratories PLgel MIX-B 300 mm length column was used. An evaluation temperature was 160° C., and 1,2,4-trichlorobenzene was used for a solvent at a flow rate of 1 mL/min. Each polyethylene sample was pretreated by dissolving in 1,2,4-trichlorobenzene containing 0.0125% of BHT for 10 hours using a GPC analyzer (PL-GP220), and the sample with a concentration of 10 mg/10 mL was supplied in an amount of 200 μL. Mw and Mn were obtained using a calibration curve formed using a polystyrene standard. 9 kinds of the polystyrene standard were used with the molecular weight of 2000 g/mol, 10000 g/mol, 30000 g/mol, 70000 g/mol, 200000 g/mol, 700000 g/mol, 2000000 g/mol, 4000000 g/mol, and 10000000 g/mol.

TABLE-US-00001 TABLE 1 Fraction (%) Less 3.5 or 4.0 or More than 5.0 or More than More than More than more~less more~4.5 4.5~less more~6.0 6.0~6.5 6.5~7.0 than Log Mw 3.5 than 4.0 or less than 5.0 or less or less or less 7.0 Ex. 1 0.54 3.78 19.85 41.58 29.79 3.41 1.05 0 Ex. 2 0.80 3.93 18.74 42.72 29.63 3.20 0.98 0 Ex. 3 0.51 3.63 20.24 41.19 29.81 3.53 1.09 0 Comp. Ex. 1 2.64 8.89 22.89 29.03 31.99 3.94 0.62 0 Comp. Ex. 2 2.22 8.53 24.15 28.17 34.64 2.27 0.02 0 Comp. Ex. 3 0.00 2.12 14.47 37.98 42.85 2.51 0.07 0 Comp. Ex. 4 0.57 4.30 16.22 34.09 42.47 2.35 0 0 Comp. Ex. 5 0.38 2.94 21.85 40.81 28.42 3.74 1.86 0 Comp. Ex. 6 0.51 4.27 22.49 41.21 28.25 2.74 0.53 0 Comp. Ex. 7 0.73 5.12 17.45 30.62 43.69 2.35 0.04 0

Experimental Example 2

[0232] The physical properties of the polyethylene prepared in Examples and Comparative Examples were measured in the following manner, and the results are shown in Table 2.

[0233] (1) Weight average molecular weight (Mw, g/mol) and molecular weight distribution (PDI, polydispersity index): GPC analysis was performed in the same manner as in Experimental Example 1, and the molecular weight distribution (PDI) was calculated by measuring a weight average molecular weight (Mw) and a number average molecular weight (Mn), and then obtaining a ratio of Mw/Mn.

[0234] (2) MI.sub.5.0 and MFRR.sub.21.6/5: Melt Index (MI.sub.5.0) of the polyethylene prepared in Examples and Comparative Examples was measured in accordance with ASTM D1238 (Condition E, 190° C., 5.0 kg load). In addition, the melt flow rate ratio (MFRR.sub.21.6/5) was calculated by dividing MFR.sub.21.6 by MFR.sub.5, and the MFR.sub.21.6 was measured in accordance with ASTM D 1238 at 190° C. under a load of 21.6 kg and the MFR.sub.5 was measured in accordance with ASTM D 1238 at 190° C. under a load of 5 kg.

[0235] (3) Density (g/cm.sup.3): Density (g/cm.sup.3) was measured in accordance with ASTM D-1505.

[0236] (4) MDR torque (M.sub.H−M.sub.L): MDR torque of each polyethylene sample was measured with Alpha Technologies Production MDR (Moving Die Rheometer) in order to evaluate the degree of cross-linking of polyethylene.

[0237] Specifically, a sample sheet was prepared at 140° C. for 10 min after mixing 100 g of each polyethylene sample prepared in Examples and Comparative Examples, 0.4 g of a phenolic antioxidant (AO), and 1.2 g of a cross-linking agent (DCP, dicumyl peroxide) at 80° C. Then, a M.sub.H value and a M.sub.L value of the sample sheet were measured at 180° C. for 10 min with MDR (Moving die rheometer). The MDR torque (M.sub.H−M.sub.L) was calculated by subtracting the M.sub.L value from the M.sub.H value. Herein, the M.sub.H is a maximum vulcanizing torque measured at full cure, and the M.sub.L is a minimum vulcanizing torque stored.

[0238] (5) Entanglement molecular weight (Me): The entanglement molecular weight (Me) was calculated from a storage modulus and a loss modulus measured with a rotational rheometer.

[0239] Specifically, a storage modulus and a loss modulus of each polyethylene sample according to Examples and Comparative Examples were measured with a rotational rheometer. Then, a plateau modulus)(G.sub.N.sup.0 was obtained from them and the entanglement molecular weight was calculated according to the following Equation 1.

M.sub.e=(ρRT)/G.sub.N.sup.0  [Equation 1]

[0240] in Equation 1,

[0241] ρ is a density (kg/m.sup.3) of polyethylene measured in accordance with ASTM D-1505×0.8,

[0242] R is a gas constant of polyethylene (8.314 Pa.Math.m.sup.3/mol.Math.K),

[0243] T is an absolute temperature (K) of the measured temperature, and

[0244] G.sub.N.sup.0 is a plateau modulus of polyethylene, which is a storage modulus when a loss modulus has a minimum value in a region where the storage modulus is greater than the loss modulus, wherein the storage modulus and loss modulus are measured while changing an angular frequency to 0.05 to 500 rad/s under conditions of 190° C. and 0.5% strain using a rotary rheometer.

TABLE-US-00002 TABLE 2 MDR torque Mw MI.sub.5.0 Density (M.sub.H − M.sub.L) Me (g/mol) PDI (g/10 min) MFRR.sub.21.6/5 (g/cm.sup.3) (Nm) (g/mol) Ex. 1 216,000 5.7 1.25 10.6 0.948 11.7 41,300 Ex. 2 196,000 6.1 2.41 10.3 0.950 11.5 49,500 Ex. 3 233,000 5.6 1.0 10.9 0.947 11.8 34,800 Comp. Ex. 1 177,000 9.1 1.30 15.2 0.958 5.6 13,800 Comp. Ex. 2 168,000 5.0 0.8 16.0 0.955 7.7 10,300 Comp. Ex. 3 171,000 4.5 0.8 11.0 0.950 9.0 21,500 Comp. Ex. 4 174,000 4.8 1.0 11.2 0.952 6.3 15,400 Comp. Ex. 5 264,000 5.1 0.49 11.2 0.945 12.1 25,100 Comp. Ex. 6 182,000 6.0 3.0 14.2 0.953 10.7 52,600 Comp. Ex. 7 175,000 5.2 1.2 12.3 0.952 9.5 31,700

Experimental Example 3

[0245] Chlorinated polyethylene was prepared using the polyethylene prepared in one of the above Examples and Comparative Examples, and physical properties of the prepared chlorinated polyethylene were evaluated by the following method. The results are shown in Table 3.

[0246] (1) Preparation of Chlorinated Polyethylene

[0247] 5,000 L of water and 550 kg of polyethylene prepared in one of Examples and Comparative Examples were added to a reactor, followed by sodium polymethacrylate as a dispersant, oxypropylene and oxyethylene copolyether as an emulsifier, and benzoyl peroxite as a catalyst. Then, chlorination was carried out by injecting gaseous chlorine at a final temperature of 132° C. for 3 hours. The chlorinated reactant was neutralized with NaOH or Na.sub.2CO.sub.3 for 4 hours, washed again with running water for 4 hours, and finally dried at 120° C. to prepare a chlorinated polyethylene in a powder form.

[0248] (2) Mooney viscosity (MV): Wrap a rotor in a Mooney viscometer with a CPE sample and close a die. After preheating to 121° C. for 1 min, the rotor was rotated for 4 min to measure MV (Mooney viscosity, 121° C., ML1+4).

TABLE-US-00003 TABLE 3 MV Ex. 1 73 Ex. 2 71 Ex. 3 76 Comp. Ex. 1 72 Comp. Ex. 2 72 Comp. Ex. 3 85 Comp. Ex. 4 87 Comp. Ex. 5 86 Comp. Ex. 6 64 Comp. Ex. 7 83

Experimental Example 4

[0249] A CPE compound was prepared using the polyethylene prepared in one of the above Examples and Comparative Examples in Experimental Example 3, and physical properties were evaluated.

[0250] (1) Preparation of CPE Compound

[0251] 40 wt % of the chlorinated polyethylene prepared using the polyethylene prepared in one of Examples and Comparative Examples in Experimental Example 3, 15 wt % of a plasticizer, 2 wt % of a cross-linking agent, and a residual amount of inorganic additives of talc and carbon black were compounded and processed to prepare a CPE compound specimen.

[0252] (2) MV (Mooney viscosity) of CPE compound: Wrap a rotor in a Mooney viscometer with a CPE compound sample and close a die. After preheating to 100° C. for 1 min, the rotor was rotated for 4 min to measure MV (Mooney viscosity, 100° C., ML1+4). The results are shown in Table 4.

[0253] (3) Tensile strength (MPa) of CPE compound: After cross-linking the CPE compound specimen prepared above at 160° C. for 10 minutes, the tensile strength (MPa) of the CPE compound was measured under a condition of 500 mm/min according to ASTM D-412. The results are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Tensile strength MV (MPa) Ex. 1 54 13.9 Ex. 2 53 13.7 Ex. 3 55 14.0 Comp. Ex. 1 53 11.9 Comp. Ex. 2 53 12.5 Comp. Ex. 3 60 12.5 Comp. Ex. 4 60 12.6 Comp. Ex. 5 61 14.2 Comp. Ex. 6 42 9.8 Comp. Ex. 7 59 13.1

[0254] Referring to the results of the experiments, the CPE compounds prepared using the polyethylene of Examples 1 to 3 had improved tensile strength while maintaining excellent Mooney viscosity characteristics compared to Comparative Examples.