Ethylene/Alpha-Olefin Copolymer and Method for Preparing the Same

Abstract

The present invention relates to an ethylene/alpha-olefin copolymer having a high weight average molecular weight and narrow molecular weight distribution, and at the same time, a reduced characteristic relaxation time, thereby showing excellent physical properties, and a method for preparing the same.

A resin composition having improved volume resistance and excellent light transmittance may be prepared by using such ethylene/alpha-olefin copolymer. Accordingly, the ethylene/alpha-olefin copolymer may be utilized in various uses in electrical and electronic industrial fields.

Claims

1. An ethylene/alpha-olefin copolymer satisfying the following conditions (a) to (c): (a) a characteristic relaxation time (λ) at 190° C. in shear rate conditions of 0.1 to 500 rad/s, is less than 10.0 millisecond; (b) a weight average molecular weight is from 40,000 to 150,000 g/mol; and (c) a molecular weight distribution is from 1.5 to 2.5.

2. The ethylene/alpha-olefin copolymer according to claim 1, wherein the characteristic relaxation time is from 1.0 to 9.5 millisecond.

3. The ethylene/alpha-olefin copolymer according to claim 1, wherein the weight average molecular weight is from 41,000 to 130,000 g/mol.

4. The ethylene/alpha-olefin copolymer according to claim 1, wherein the molecular weight distribution is from 1.5 to 2.4.

5. The ethylene/alpha-olefin copolymer according to claim 1, which has a density from 0.850 to 0.910 g/cc.

6. The ethylene/alpha-olefin copolymer according to claim 1, which has a melt index (190° C., 2.16 kg load conditions) from 0.1 to 50 g/10 min.

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

8. An encapsulant film comprising an ethylene/alpha-olefin copolymer satisfying the following conditions (a) to (c): (a) a characteristic relaxation time (λ) at 190° C. in shear rate conditions of 0.1 to 500 rad/s, is less than 10.0 millisecond; (b) a weight average molecular weight is from 40,000 to 150,000 g/mol; and (c) a molecular weight distribution is from 1.5 to 2.5.

9. The encapsulant film according to claim 8, further comprising one or more selected from the group consisting of a crosslinking agent, a crosslinking auxiliary agent, a silane coupling agent, an unsaturated silane compound, an amino silane compound, a light stabilizer, a UV absorbent and a thermal stabilizer.

10. A solar cell module comprising the encapsulant film of claim 8.

11. A method for preparing the ethylene/alpha-olefin copolymer of claim 1, the method comprising: (S1) a step of preparing a polymerization product of ethylene and an alpha-olefin monomer; (S2) a step of dissolving the polymerization product in an organic solvent; and (S3) a step of mixing with an alcohol of 2 to 5 carbon atoms to form the ethylene/alpha-olefin copolymer as a precipitate.

12. The method of claim 11, wherein the organic solvent is a compound of 7 to 16 carbon atoms.

13. The method of claim 11, wherein the organic solvent is one or more selected from the group consisting of heptane, octane, isooctane, toluene, xylene and cumene.

14. The method of claim 11, wherein the alcohol of 2 to 5 carbon atoms is one or more selected from the group consisting of ethanol, propan-1-ol, propan-2-ol, butan-1-ol, buta-2-ol, 2-methylpropan-2-ol, pentan-1-ol, pentan-2-ol, pentan-2-ol, pentan-3-ol, 2-methylbutan-2-ol and 3-methylbutan-2-ol.

15. The method of claim 11, wherein the step (S2) and the step (S3) are alternately repeatedly performed by twice to five times.

Description

EXAMPLES

[0105] Hereinafter, the present invention will be explained in more detail referring to embodiments. However, the embodiments are provided only for illustration, and the scope of the present invention is not limited thereto.

[0106] Preparation of Catalyst

[0107] (1) Preparation of Ligand Compound

Synthesis of N-tert-butyl-1-(1,2-dimethyl-3H-benzo[b]cyclopenta[d]thiophen-3-yl)-1,1-dimethylsilanamine

[0108] To a 100 ml schlenk flask, 4.65 g (15.88 mmol) of chloro(1,2-dimethyl-6,7-dihydro-3H-benzo[b]cyclopenta[d]thiophene-3-yl)dimethylsilane was weighed and added, and 80 ml of THF was injected thereto. At room temperature, tBuNH.sub.2 (4 eq, 6.68 ml) was injected thereto and reacted at room temperature for 3 days. After finishing the reaction, THF was removed, and the resultant reaction product was filtered with hexane. After drying solvents, 4.50 g (86%) of a yellow liquid was obtained.

[0109] .sup.1H NMR (in CDCl.sub.3, 500 MHz): δ 7.99 (d, 1H), δ 7.83 (d, 1H), δ 7.35 (dd, 1H), δ 7.24 (dd, 1H), δ 3.49 (s, 1H), δ 2.37 (s, 3H), δ 2.17 (s, 3H), δ 1.27 (s, 9H), δ 0.19 (s, 3H), δ −0.17 (s, 3H).

[0110] (2) Preparation of Transition Metal Compound

##STR00001##

[0111] To a 50 ml schlenk flask, the ligand compound (1.06 g, 3.22 mmol/1.0 eq) and 16.0 ml (0.2 M) of MTBE were put and stirred first. n-BuLi (2.64 ml, 6.60 mmol/2.05 eq, 2.5 M in THF) was added thereto at −40° C. and reacted at room temperature overnight. After that, MeMgBr (2.68 ml, 8.05 mmol/2.5 eq, 3.0 M in diethyl ether) was slowly added thereto dropwisely at −40° C., and TiCl.sub.4 (2.68 ml, 3.22 mmol/1.0 eq, 1.0 M in toluene) was put in order, followed by reacting at room temperature overnight. After that, the reaction mixture was passed through celite using hexane for filtration. After dying the solvents, 1.07 g (82%) of a brown solid was obtained.

[0112] .sup.1H-NMR (in CDCl.sub.3, 500 MHz): δ 7.99 (d, 1H), δ 7.68 (d, 1H), δ 7.40 (dd, 1H), δ 7.30 (dd, 1H), δ 3.22 (s, 1H), δ 2.67 (s, 3H), δ 2.05 (s, 3H), δ 1.54 (s, 9H), δ 0.58 (s, 3H), δ 0.57 (s, 3H), δ 0.40 (s, 3H), δ −0.45 (s, 3H).

Preparation Example 1

[0113] While injecting a hexane solvent in 5.00 kg/h and 1-butene in 1.30 kg/h, a 1.5 L continuous process reactor was pre-heated at 120° C. A triisobutylaluminum (Tibal, 60 μmol/min), the transition metal compound of [Formula 1] (0.35 μmol/min) and a dimethylanilinium tetrakis(pentafluorophenyl)borate co-catalyst (1.05 μmol/min) were injected into the reactor at the same time. Then, into the reactor, ethylene (0.87 kg/h) and a hydrogen gas (20 cc/min) were injected and copolymerization reaction was continuously carried out while maintaining a pressure of 89 bar and 150° C. for 60 minutes or more to prepare a copolymer. After drying for 12 hours or more in a vacuum oven, an ethylene/alpha-olefin copolymer was prepared.

Preparation Examples 2 to 8

[0114] Ethylene/alpha-olefin copolymers were prepared by the same method as in Preparation Example 1 except for changing polymerization conditions as shown in Table 1 below.

TABLE-US-00001 TABLE 1 Polymerization C2 Alpha-olefin Cat. Co-cat. Tibal Solvent temp. kg/h Type kg/h μmol/min μmol/min kg/h ° C. Preparation 0.87 1-C4 1.30 0.35 1.05 60 5.00 150 Example 1 Preparation 0.87 1-C4 0.90 0.15 0.45 20 5.00 140 Example 2 Preparation 0.87 1-C4 0.90 0.25 0.75 30 7.00 150 Example 3 Preparation 0.87 1-C4 1.00 0.20 0.60 30 5.00 145 Example 4 Preparation 0.87 1-C4 1.50 0.44 1.32 30 4.65 160 Example 5 Preparation 0.87 1-C8 0.48 0.48 0.43 30 5.00 160 Example 6 Preparation 0.87 1-C8 0.50 0.55 1.65 30 5.00 160 Example 7 Preparation 0.87 1-C8 1.30 0.70 2.10 60 4.00 160 Example 8

Example 1

[0115] Step (S2)

[0116] 20 g of the ethylene/alpha-olefin copolymer of Preparation Example 1 and 400 ml of heptane were mixed to prepare a composition and stirred at 80° C. until a copolymer was completed dissolved and became transparent with the naked eye.

[0117] Step (S3)

[0118] After reducing the temperature to room temperature, the transparent composition was added dropwisely to 1.4 L of isopropyl alcohol while stirring. After finishing the dropwise addition, a liquid phase portion was removed, and a precipitate solid phase was separated and dried in vacuum at 110° C. for 48 hours.

[0119] Step (S2) and step (S3) were alternately repeatedly performed four times to prepare an ethylene/alpha-olefin copolymer.

Examples 2 to 8, and Comparative Examples 1 to 8

[0120] Ethylene/alpha-olefin copolymers were prepared by the same method as in Example 1 except for changing the type of the ethylene/alpha-olefin copolymer and the number of performing step (S2) and step (S3) as in Table 2 below.

TABLE-US-00002 TABLE 2 Ethylene/alpha-olefin Number of Number of copolymer step (S2) step (S3) Example 1 Preparation Example 1 4 4 Example 2 Preparation Example 2 4 4 Example 3 Preparation Example 3 4 4 Example 4-1 Preparation Example 4 3 3 Example 4-2 Preparation Example 4 4 4 Example 5-1 Preparation Example 5 1 1 Example 5-2 Preparation Example 5 2 2 Example 5-3 Preparation Example 5 3 3 Example 5-4 Preparation Example 5 4 4 Example 6 Preparation Example 6 4 4 Example 7 Preparation Example 7 4 4 Example 8 Preparation Example 8 4 4 Comparative Example 1 Preparation Example 1 0 0 Comparative Example 2 Preparation Example 2 0 0 Comparative Example 3-1 Preparation Example 3 0 0 Comparative Example 3-2 Preparation Example 3 0 1 Comparative Example 4 Preparation Example 4 0 0 Comparative Example 5 Preparation Example 5 0 0 Comparative Example 6 Preparation Example 6 0 0 Comparative Example 7-1 Preparation Example 7 0 0 Comparative Example 7-2 Preparation Example 7 1 0 Comparative Example 8 Preparation Example 8 0 0

Experimental Example 1

[0121] With respect to the ethylene/alpha-olefin copolymers prepared in the Examples and Comparative Examples, physical properties were evaluated according to the methods below and are shown in Table 3.

[0122] (1) Characteristic Relaxation Time

[0123] A complex viscosity according to the angular speed of the copolymer was obtained at 190° C. in an angular speed range of 0.1-500 rad/s at 5% strain using ARES-G2 Rheometer of TA Co., and a characteristic relaxation time was calculated by fitting using a Carreau-Yasuda equation below.

η(γ)=η.sub.∞+(η.sub.0−η.sub.∞)[1+(λγ).sup.α].sup.(n−1)/α

[0124] η(γ): Viscosity

[0125] η.sup.∞: Infinite viscosity

[0126] η0: Zero-shear viscosity

[0127] λ: Relaxation time

[0128] γ: Shear-rate

[0129] α: Material constants

[0130] n: Shear thinning index

[0131] (2) Weight Average Molecular Weight (Mw) and Molecular Weight Distribution (MWD)

[0132] A weight average molecular weight (Mw) and a number average molecular weight (Mn) were measured using gel permeation chromatography (GPC), and the molecular weight distribution was calculated through dividing the weight average molecular weight (Mw) by a number average molecular weight (Mn). [0133] Column: PL Olexis [0134] Solvent: Trichlorobenzene (TCB) [0135] Flow rate: 1.0 mL/min [0136] Specimen concentration: 1.0 mg/mL [0137] Injection amount: 200 μL [0138] column temperature: 160° C. [0139] Detector: Agilent High Temperature RI detector [0140] Standard: Polystyrene (calibrated by cubic function)

[0141] (3) Density (g/cm.sup.3)

[0142] Measurement was conducted according to ASTM D-792.

[0143] (4) Melt Index (MI.sub.2.16, g/10 Min)

[0144] Measurement was conducted according to ASTM D-1238 (condition E, 190° C., 2.16 kg load).

TABLE-US-00003 TABLE 3 Characteristic Density Melt index relaxation time Mw (g/mol) MWD (g/cm.sup.3) (g/10 min) Example 1 4.9 73,000 2.08 0.864 4.7 Example 2 4.8 72,000 2.03 0.873 5.0 Example 3 4.3 58,000 2.02 0.875 14.3 Example 4-1 4.1 49,000 2.16 0.880 18.5 Example 4-2 3.5 50,000 2.00 0.880 17.1 Example 5-1 8.0 44,000 2.25 0.871 30.0 Example 5-2 5.3 44,000 2.19 0.871 29.5 Example 5-3 4.2 46,000 2.10 0.871 27.2 Example 5-4 3.0 46,000 2.05 0.871 25.4 Example 6 9.2 83,000 1.92 0.901 2.4 Example 7 4.4 70,000 2.02 0.902 6.0 Example 8 3.2 45,000 2.15 0.872 27.8 Comparative 53.1 69,000 2.31 0.864 5.0 Example 1 Comparative 87.1 69,000 2.30 0.873 5.5 Example 2 Comparative 25.2 56,000 2.27 0.875 15.6 Example 3-1 Comparative 24.3 56,000 2.25 0.875 15.2 Example 3-2 Comparative 16.9 48,000 2.36 0.880 20.2 Example 4 Comparative 12.1 43,000 2.37 0.871 33.8 Example 5 Comparative 190.2 79,000 2.20 0.901 2.8 Example 6 Comparative 70.0 67,000 2.29 0.902 6.4 Example 7-1 Comparative 67.2 67,000 2.27 0.902 6.2 Example 7-2 Comparative 4.8 41,000 2.54 0.872 36.5 Example 8

[0145] As summarized in the table above, it was confirmed that the Examples prepared the ethylene/alpha-olefin copolymers by performing the steps of dissolving in an organic solvent and precipitating in an alcohol according to the present invention, satisfied all the characteristic relaxation time, Mw, and MWD in the numerical ranges specified in the present invention.

[0146] Particularly, when comparing Examples 4-1 and 4-2, and Examples 5-1 to 5-4, with the increase of repeating number of the dissolving in an organic solvent and the precipitating in an alcohol, an ethylene/alpha-olefin copolymer having an even higher molecular weight and narrower MWD was prepared, and the characteristic relaxation time was gradually reduced.

[0147] Meanwhile, the Comparative Examples are cases of not performing the steps of dissolving in an organic solvent and the precipitation in an alcohol after polymerizing ethylene and an alpha-olefin monomer. It was confirmed that Comparative Examples 1 to 7-2, etc. showed markedly increased characteristic relaxation time in contrast to the Examples, and Comparative Example 8 showed wide MWD and deviated from the conditions defined in the present invention.

[0148] Particularly, it was confirmed that in Comparative Example 3-2 in which dissolving in an organic solvent was not performed and precipitation in an alcohol was directly performed, as well as in the Comparative Examples not using both the organic solvent and the alcohol, a copolymer chain was insufficiently released, precipitation in an alcohol was insufficiently performed, and a low molecular weight portion was not removed. Accordingly, the characteristic relaxation time was still long. In addition, in Comparative Example 7-2 in which dissolving in an organic solvent was performed but precipitation in an alcohol was not performed, long characteristic relaxation time was shown, because the removal of a branch-type low molecular weight portion was not achieved.

Experimental Example 2

[0149] 6 g of the ethylene/alpha-olefin copolymer was put in a 0.5 T square frame, and the front side and the rear side were covered with 3T steel plates. This was injected into a high temperature press. After continuously treating at 190° C., 25 N/cm.sup.2 (240 seconds), six times of decompressing/pressurizing degassing, and at 190° C., 151 N/cm.sup.2 for 240 seconds, the temperature was reduced by 15° C. per minute to 30° C., and in this case, the pressure was maintained to 151 N/cm.sup.2. By maintaining 30° C. and 151 N/cm.sup.2 for 300 seconds, the manufacture of a specimen was completed.

[0150] Then, with respect to the specimen thus manufactured, volume resistance and total transmittance were measured by the methods below and shown.

[0151] (1) Volume Resistance (Ω.Math.Cm)

[0152] Measurement was conducted by applying a voltage of 1000 V for 600 seconds using Agilent 4339B High-resistance meter (product of Agilent Technologies K.K.) under temperature conditions of 23±1° C. and humidity conditions of 50±3%.

[0153] (2) Light Transmittance (%)

[0154] Light transmittance at 550 nm was measured using Shimadzu UV-3600 spectrophotometer. [0155] Measurement mode: transmittance [0156] Wavelength interval: 1 nm [0157] Measurement rate: medium

TABLE-US-00004 TABLE 4 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 1 2.60 × 10.sup.16 91.1 Comparative 3.10 × 10.sup.14 91.0 Example 1

TABLE-US-00005 TABLE 5 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 2 5.20 × 10.sup.16 90.6 Comparative 2.50 × 10.sup.14 90.5 Example 2

TABLE-US-00006 TABLE 6 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 3 7.50 × 10.sup.16 90.5 Comparative 1.00 × 10.sup.14 90.4 Example 3-1 Comparative 2.10 × 10.sup.14 90.4 Example 3-2

TABLE-US-00007 TABLE 7 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 4-1 3.40 × 10.sup.16 89.3 Example 4-2 4.50 × 10.sup.16 89.5 Comparative 1.40 × 10.sup.14 89.2 Example 4

TABLE-US-00008 TABLE 8 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 5-1 8.90 × 10.sup.15 90.2 Example 5-2 2.20 × 10.sup.16 90.2 Example 5-3 3.00 × 10.sup.16 90.3 Example 5-4 4.10 × 10.sup.16 90.5 Comparative 3.20 × 10.sup.14 90.2 Example 5

TABLE-US-00009 TABLE 9 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 6 9.80 × 10.sup.16 89.0 Comparative 4.20 × 10.sup.14 88.8 Example 6

TABLE-US-00010 TABLE 10 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 7 1.60 × 10.sup.16 88.6 Comparative 4.60 × 10.sup.14 88.5 Example 7-1 Comparative 4.42 × 10.sup.14 88.5 Example 7-2

TABLE-US-00011 TABLE 11 Volume resistance (Ω .Math. cm) Light transmittance (%) Example 8 1.50 × 10.sup.16 90.4 Comparative 7.80 × 10.sup.14 90.2 Example 8

[0158] The tables above are summaries of corresponding Examples and Comparative Examples, using the same Preparation Example. As shown above, it was confirmed that all the ethylene/alpha-olefin copolymers prepared according to the present invention could accomplish excellent volume resistance and light transmittance. On the contrary, as in the Comparative Examples, if the conditions were deviated from the scope of the present invention, including deviated characteristic relaxation time or wide MWD, the volume resistance was deteriorated.

[0159] Like this, an ethylene/alpha-olefin copolymer satisfying all of the characteristic relaxation time, Mw and MWD defined in the present invention, may achieve excellent levels of volume resistance and light transmittance without using a separate additive.