Non-stretched polypropylene-based film

Abstract

The polypropylene copolymer according to the present invention has a low melting point and also is excellent in the low temperature heat sealing effect, transparency and strength, and the film prepared therefrom can be effectively used as a sealing layer of the non-stretched polypropylene-based film.

Claims

1. A non-stretched polypropylene-based film comprising a propylene-ethylene-1-butene terpolymer which has a melting point (Tm) of 125 to 135 C., a molecular weight distribution (Mw/Mn, PDI) of 2.3 to 3.5, and a xylene soluble (Xs) content of 2.0 wt or less, wherein the terpolymer has a crystallization temperature (Tc) of 75 to 87 C., wherein the terpolymer has MFR.sub.2,16(g/10 min, measured at 230 C. according to ASTM1238) of 5 to 7, and wherein, when heat-sealed at 134 C. and 0.2 MPa for 1 second, a sealing strength of the terpolymer is 300 to 500 g/15mm.

2. The non-stretched polypropylene-based film according to claim 1, which comprises a sealing layer comprising the terpolytner.

3. The non-stretched polypropylene-based film according to claim 2, which further comprises a polypropylene-based core layer and a skin layer which are sequentially formed on the sealing layer.

4. The non-stretched polypropylene-based film according to claim 1, wherein the terpolytner is prepared by copolymerizing propylene, ethylene and 1-butene in the presence of a catalyst comprising a metallocene compound represented by the following Chemical Formula 1: ##STR00005## in Chemical Formula 1, X is halogen which is the same as or different from each other, R.sub.1 is C.sub.6-20 aryl substituted by C.sub.1-20 alkyl, R.sub.2, R.sub.3 and R.sub.4 are 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 ether, C.sub.1-C.sub.20 silylehter, 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, A is carbon, silicon, or germanium R.sub.5 is C.sub.1-20 alkyl substituted by C.sub.1-20 alkoxy, and R.sub.6 is hydrogen, C.sub.1-C.sub.20 alkyl, or C.sub.2-C.sub.20 alkenyl.

5. The non-stretched polypropylene-based film according to claim 4, wherein X is chloro.

6. The non-stretched polypropylene-based film according to claim 4, wherein R.sub.1 is phenyl substituted by tert-butyl.

7. The non-stretched polypropylene-based film according to claim 4, wherein R.sub.2, R.sub.3 and R.sub.4 are hydrogen.

8. The non-stretched polypropylene-based film according to claim 4 wherein A is silicon.

9. The non-stretched polypropylene-based film according to claim 4, wherein R.sub.5 is 6-tert-butoxy-hexyl, and R.sub.6 is methyl.

10. The non-stretched polypropylene-based film according to claim 4, wherein the compound is a compound represented by the following Chemical Formula: ##STR00006##

11. The non-stretched polypropylene-based film according to claim 2 wherein the sealing layer further comprises a propylene-based elastomer.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

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

PREPARATION EXAMPLE 1

(2) ##STR00004##

Step 1) Preparation of (6-t-butoxyhexyl)(methyl-bis(2-methyl-4-tert-butyl-phenylindenyl)silane

(3) 2-methyl-4-tert-butylphenylindene (20.0 g, 76 mmol) was dissolved in toluene/THF=10/1 solution (230 mL) to which n-butyllithium solution (2.5 M, hexane solvent, 22 g) was slowly added dropwise at 0 C., and then stirred at room temperature for a day. Thereafter, (6-t-butoxyhexyl)dichloromethane silane/1.27g) was slowly added dropwise to the mixed solution at 78 C. stirred for about 10 minutes and then stirred at room temperature for a day.

(4) Thereafter, the organic layer was separated by adding water, and the solvent was distilled under reduced pressure to obtain (6-t-butoxyhexyl)(methyl)-bis(2-methyl-4-tert-butyl-phenylindenyl)silane.

(5) .sup.1H NMR (500 MHz, CDCl.sub.3, 7.26 ppm): 0.20-0.03 (3H, m), 1.26 (9H, s), 0.50-1.20 (4H, m), 1.20-1.31 (11H, m), 1.40-1.62 (20H, m), 2.19-2.23 (6H, m), 3.30-3.34 (2H, m), 3.73-3.83 (2H, m), 6.89-6.91 (2H, m), 7.19-7.61 (14H, m)

Step 2) Preparation of [(6-t-butoxyhexylmethylsilane-diyl)-bis(2-methyl-4-tert-butylphenylindenyl)]zirconium dichloride

(6) (6-t-butoxyhexyl)(methyl)-bis(2-methyl-4-tert-butyl-phenylindenyl)silane prepared in the step 1 was dissolved in toluene/THF 5/1 solution (95 mL) to which n-butyl lithium solution (2.5 M, hexane solvent, 22 g) was slowly added dropwise at 78 C. and then stirred at room temperature for a day. To the reaction solution, bis(N,N-diphenyl-1,3-propanediamido)dichlorozirconium bis(tetrahydrofuran) [Zr(C.sub.5H.sub.6NCH.sub.2CH.sub.2NC.sub.5H.sub.6)Cl.sub.2(C.sub.4H.sub.8O).sub.2] was dissolved in toluene (229 mL) and then slowly added dropwise at 78 C., followed by stirring at room temperature for a day. After cooling the reaction solution at 78 C., HCl ether solution (1 M, 183 mL) was slowly added dropwise and then stirred at 0 C. for 1 hour. Thereafter, the mixture was filtered and dried under vacuum to which hexane was added and then stirred to precipitate a crystal. The precipitated crystal was filtered and dried under vacuum to obtain [(6-t-butoxyhexylmethylsilane-diyl)-bis(2-methyl-4-tert-butylphenylindenyl)]zirconium dichloride (20.5 g, of 61%).

(7) .sup.1H NMR (500 MHz, CDCl.sub.3, 7.26 ppm): 1.20 (9H, s), 1.27 (3H, s), 1.34 (18H, s), 1.20-1.90 (10H, m), 2.25 (3H, s), 2.26 (3H, s), 3.38 (2H, t), 7.00 (2H, s), 7.09-7.13 (2H, m), 7.38 (2H, d), 7.45 (4H, d), 7.58 (4H, d), 7.59 (2H, d), 7.65 (2H, d)

Step 3) Preparation of a Supported Catalyst

(8) 3 g of silica was pre-weighed into a shrink flask to which 52 mmol of methylaluminoxane (MAO) was added and then reacted at 90 C. for 24 hours. After precipitation, the upper layer was removed and washed two times with toluene. 180 mol of ansa-metallocene compound [(6-t-butoxyhexylmethylsilane-diyl)-bis(2-methyl-4-tert-butylphenylindenyl)]zirconium dichloride synthesized above was dissolved in toluene and then reacted at 70 C. for 5 hours. After completion of the reaction, the upper layer solution was removed and the residual reaction product was washed with toluene and again washed with hexane and then dried under vacuum to obtain 5 g of silica-supported metallocene catalyst in the form of a solid particle.

EXAMPLE 1

(9) Step 1

(10) The polypropylene polymer was prepared by using the metallocene supported catalyst prepared in Preparation Example 1, by the following method.

(11) First, a 2 L stainless steel reactor was dried under vacuum at 65 C. and then cooled, to which 1.5 mmol of triethylaluminum was added at room temperature, 0.37 L of hydrogen was added, and 1.5 L of propylene were added, sequentially. Then, after stirring for 10 minutes, the metallocene supported catalyst prepared in Preparation Example 1 was added to the reactor under nitrogen pressure. Then, the reactor temperature was raised up to 70 C. within 5 minutes, followed by polymerization for 1 hour. After completion of the reaction, unreacted propylene was vented.

(12) Step 2

(13) In order to minimize the deformation and damage of the resin at a high temperature, 500-1000 ppm of calcium stearate (neutralizing agent), 500-1000 ppm of Irganox 1010 (primary antioxidant), 1000-1500 ppm of Irganox 168 (secondary antioxidant), 1000-1500 ppm of Erucamide (slip agent) and SiO.sub.2 (anti-blocking agent) as additives were added based on the amount of the polypropylene polymer powder sample prepared in the step 1, and strands were drawn at 5-15 kg/h at 180-220 C. Then, the prepared strands were pelletized by a pelletizer at 500-900 rpm to prepare a pellet.

EXAMPLE 2

(14) C3 elastomer (VM3020FL) was mixed to the polymer prepared in the step 1 of Example 1, and the pellet was prepared by the following method.

(15) Specifically, in order to minimize the deformation and damage of the resin at a high temperature, 500-1000 ppm of calcium stearate (neutralizing agent), 500-1000 ppm of Irganox 1010 (primary antioxidant), 1000-1500 ppm of Irganox 168 (secondary antioxidant), 1000-1500 ppm of Erucamide(slip agent) and 1000-1500 ppm of SiO.sub.2(anti-blocking agent) as additives were added based on the amount of the polypropylene polymer powder sample prepared in the step 1 of Example 1, and then mixed with 5 wt % of C3 elastomer (VM3020FL) having the characteristics of low-temperature crystallization region in order to improve the heat-sealability of the resin. Strands were drawn at 5-15 kg/h at 180-220 C. Then, the prepared strands were pelletized by a pelletizer at 500-900 rpm to prepare a pellet

COMPARATIVE EXAMPLE 1

(16) WINTECT product (available from JPP Corporation) was used as Comparative Example 1.

COMPARATIVE EXAMPLE 2

(17) T3450L (available from LG Chem Ltd.) was used as Comparative Example 2.

EXPERIMENTAL EXAMPLE

(18) The physical properties of the respective copolymers prepared in Examples and Comparative Examples were measured by the following method.

(19) (1) Melting point (Tm) of the polymer: The melting point of the polymer was measured using Differential Scanning Calorimeter (DSC, device name: DSC 2920, manufacturer: TA instrument). Specifically, the polymer was heated up to 220 C. and then maintained at the same temperature for 5 minutes. After cooling to 20 C., the temperature was again increased. At this time, the increasing speed and the lowering speed of the temperature was adjusted to 10 C./min, respectively.

(20) (2) Crystallization temperature (Tc) of the polymer: the crystallization temperature was set from a DSC curve that appears while reducing the temperature under the same conditions as the melting point.

(21) (3) Melt Index (MI): measured at 230 C. under a load of 2.16 kg in accordance with ASTM D1238, and expressed as weight (g) of the polymer obtained by melting for 10 minutes.

(22) (4) Sealing strength: measured in accordance with ASTM F1921. Specifically, after preparing two films with a width of 15 mm, the films were sealed at 128-140 C. and 0.2 MPa for 1 second, and then the force required for peeling out the two films were measured. At this time, the sealing strength was measured by a value where the measured force was divided by the width of the polymer.

(23) (5) Tensile strength and elongation: the film test sample that measured the thickness was fixed to UTM equipment (ZWICK Roell Inc.), to fill the cross-sectional area. MD and TD directions of the test sample were measured at a speed of 200 mm/min, respectively. The tensile strength (kg/cm.sup.2) was confirmed by dividing the elongation (%), the yield load (Kgf) and load at break(kg) of the respective samples by the cross-sectional area (cm.sup.2)

(24) (6) Xylene soluble: Xylene was added to the sample, heated at 135 C. for 1 hour, and then cooled for 30 minutes, followed by pre-treatment. Xylene was flowed at a rate of 1 mL/min for 4 hours with OminiSec (Viscotek Corporation, FIPA) equipment. When the base line of RI, DP and IP was stabilized, the concentration and the injection amount of the pre-treated samples were filled and measured, thereby calculating the peak area.

(25) The results are shown in Tables 1 and 2 below.

(26) TABLE-US-00001 TABLE 1 Xylene Tm Tc MI soluble Sealing strength (g/15 mm) ( C.) ( C.) (g/10 min) (wt %) 128 C. 131 C. 134 C. 137 C. 140 C. Comparative 123.9 87.7 6.6 1.1 49 74 99 242 x.sup.1) Example 1 Comparative 128.3 82.1 7.6 10.2 102 256 496 x x Example 2 Example 1 125.4 84.6 5.8 0.9 59 122 321 x x Example 2 125.1 85.3 6.2 1.0 85 170 420 x x .sup.1)Not peeled when measured up to 500 g/15 mm

(27) TABLE-US-00002 TABLE 2 MD TD Tensile Tensile Tensile Tensile Strength Strength Elonga- Strength Strength Elonga- @ Yield @ Break tion @Yield @ Break tion (kg/cm.sup.2) (kg/cm.sup.2) (%) (kg/cm.sup.2) (kg/cm.sup.2) (%) Comparative 203 370 487 157 370 >700 Example 1 Comparative 197 543 494 164 394 >700 Example 2 Example 1 203 444 481 156 429 >700 Example 2 188 281 372 154 385 >700