Polypropylene And Method For Preparing The Same

Abstract

The present invention provides a homopolypropylene having high strength and a low content of low molecular weights together with excellent processability, and a preparation method thereof.

Claims

1. A homopolypropylene satisfying the following conditions: i) a melt index of 200 to 2000 g/10 min as measured at 230 C. under a load of 2.16 kg according to ASTM D12384, ii) a molecular weight distribution of 3.3 or less, iii) a residual stress ratio of 0.05% or less, and iv) a content of xylene solubles of 1.0 wt % or less.

2. The homopolypropylene of claim 1, wherein the homopolypropylene has a molecular weight distribution of 2.5 to 3.3.

3. The homopolypropylene of claim 1, wherein the homopolypropylene has a residual stress ratio of 0.02 to 0.03%.

4. The homopolypropylene of claim 1, wherein the homopolypropylene has a content of xylene solubles of 0.6 to 0.7 wt %.

5. The homopolypropylene of claim 1, wherein the homopolypropylene has a melting point of 150 to 155 C.

6. A preparation method of the homopolypropylene of claim 1, comprising adding 700 to 2500 ppm of hydrogen, in the presence of a catalyst composition including a compound of the following Chemical Formula 1 to polymerize a propylene monomer: ##STR00006## wherein A is carbon, silicon, or germanium, X.sub.1 and X.sub.2 are independently a halogen, R.sub.1 and R.sub.5 are independently a C.sub.6-20 aryl substituted with a C.sub.1-20 alkyl, R.sub.2 to R.sub.4 and R.sub.6 to R.sub.8 are independently hydrogen, a halogen, a C.sub.1-20 alkyl, a C.sub.2-20 alkenyl, a C.sub.1-20 alkylsilyl, a C.sub.1-20 silylalkyl, a C.sub.1-20 alkoxysilyl, a C.sub.1-20 ether, a C.sub.1-20 silyl ether, a C.sub.1-20 alkoxy, a C.sub.6-20 aryl, a C.sub.7-20 alkylaryl, or a C.sub.7-20 arylalkyl, and R.sub.9 and R.sub.10 are identical to each other and are a C.sub.2-20 alkyl.

7. The preparation method of claim 6, wherein A is silicon.

8. The preparation method of claim 6, wherein R.sub.1 and R.sub.5 are independently a phenyl group substituted with a C.sub.3-6 branched alkyl group.

9. The preparation method of claim 6, wherein R.sub.9 and R.sub.10 are identical to each other and are a C.sub.24 linear alkyl group.

10. The preparation method of claim 6, wherein R.sub.9 and R.sub.10 are ethyl, respectively.

11. The preparation method of claim 6, wherein the compound of Chemical Formula 1 is represented by the following Chemical Formula 1a: ##STR00007##

12. The preparation method of claim 6, wherein the compound of Chemical Formula 1 is supported by a carrier.

13. The preparation method of claim 6, wherein the catalyst composition further includes one or more of a compound represented by the following Chemical Formula 2, a compound represented by the following Chemical Formula 3, and a compound represented by the following Chemical Formula 4:
[Chemical Formula 2]
[Al(R.sub.11)-O].sub.m.sup. wherein each R.sub.11 is identical to or different from each other and is independently a halogen, a C.sub.1-20 hydrocarbon, or a C.sub.1-20 hydrocarbon substituted with a halogen, and m is an integer of 2 or more;
[Chemical Formula 3]
J(R.sub.12).sub.3 wherein each R.sub.12 is identical to or different from each other and is independently a halogen, a C.sub.1-20 hydrocarbon, or a C.sub.1-20 hydrocarbon substituted with a halogen, and J is aluminum or boron; and
[Chemical Formula 4]
[E-H].sup.+[ZQ.sub.4].sup.or [E].sup.+[ZQ.sub.4].sup. wherein E is a neutral or cationic Lewis base, H is a hydrogen atom, Z is a Group 13 element, and each Q is identical to or different from each other and is independently a C.sub.6-20 aryl group or a C.sub.1-20 alkyl group in which one or more hydrogen atoms are unsubstituted or substituted with a halogen, a C.sub.1-20 hydrocarbon, an alkoxy, or a phenoxy.

14. A non-woven fabric for washing, comprising the homopolypropylene of claim 1.

Description

Preparation Example 1

[0100] Step 1) Preparation of (diethylsilane-diyl)-bis(2-methyl-4-(4-tert-butyl-phenyl)indenyl)silane

[0101] 2-methyl-4-tert-butyl-phenylindene (20.0 g) was dissolved in a toluene/THF solution at a volume ratio=10/1 (220 mL), an n-butyllithium solution (2.5 M, a hexane solvent, 22.2 g) was slowly added dropwise thereto, and stirring was performed at room temperature for a day. To the resulted mixed solution, diethyldichlorosilane (6.2 g) was slowly added dropwise at 78 C., stirred for about 10 minutes, and further stirred at room temperature for a day. Thereafter, water was added to separate an organic layer, and the solvent was distilled off under reduced pressure to obtain (diethylsilane-diyl)-bis(2-methyl-4-(4-tert-butyl-phenyl)indenyl)silane.

Step 2) Preparation of [(diethylsilane-diyl)-bis(2-methyl-4-(4-tert-butyl-phenyl)indenyl)]zirconium dichloride

[0102] (Diethylsilane-diyl)-bis(2-methyl-4-(4-tert-butyl-phenyl)indenyl)silane prepared in step 1 was dissolved in a toluene/THF solution at a volume ratio=5/1 (120 mL), an n-butyllithium solution (2.5 M, a hexane solvent, 22.2 g) was slowly added dropwise at 78 C., and stirring was performed at room temperature for a day. To the resulted reactant solution, a solution prepared by diluting zirconium chloride (8.9 g) in toluene (20 mL) was slowly added dropwise at 78 C., and stirred at room temperature for a day. From the resulted reactant solution, a solvent was removed under reduced pressure, dichloromethane was added, filtering was performed, and the filtrate was removed by distillation under reduced pressure. Recrystallization was performed using toluene and hexane to obtain high-purity rac-[(diethylsilane-diyl)-bis(2-methyl-4-(4-tert-butyl-phenyl)indenyl)]zirconium dichloride (10.1 g, a yield of 34%, a weight ratio of rac:meso=20:1).

##STR00004##

Step 3) Preparation of Supported Catalyst

[0103] To a 3 L reactor, 100 g of silica and 10 wt % of a methylaluminoxane solution (670 g, solvent: toluene) were added, and reacted at 90 C. for 24 hours. After the reaction was completed and precipitation was finished, an upper layer solution was removed, and a remaining reaction product was washed twice with toluene. As an ansa-metallocene compound prepared in step 2, 5.8 g of rac-[(diethylsilane-diyl)-bis(2-methyl-4-(4-tert-butyl-phenyl)indenyl)]zirconium dichloride was diluted with 500 ml of toluene, added to the reactor, and reacted at 70 C. for 5 hours. After the reaction was completed and precipitation was finished, an upper layer solution was removed, a remaining reaction product was washed with toluene, washed again with hexane, and dried in vacuo, thereby obtaining 150 g of a silica-supported metallocene catalyst in a solid particle form.

Preparation Example 2

[0104] A silica-supported metallocene catalyst was prepared in the same manner as in step 3 of Preparation Example 1, except that diethylsilandiyl(2-ethyl-4-(4-tert-butyl-phenyl)-indenyl) (2-methyl-4-(4-tert-butyl-phenyl)indenyl)zirconium dichloride was used, instead of the transition metal compound prepared in step 2 of Preparation Example 1.

Preparation Example 3

[0105] A silica-supported metallocene catalyst was prepared in the same manner as in step 3 of Preparation Example 1, except that dimethylsilanediyl bis(2-methylindenyl)zirconium dichloride) was used, instead of the transition metal compound prepared in step 2 of Preparation Example 1.

Preparation Example 4

[0106] A silica-supported metallocene catalyst was prepared in the same manner as in step 3 of Preparation Example 1, except that dimethylsilanediyl bis(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride was used, instead of the transition metal compound prepared in step 2 of Preparation Example 1.

Preparation Example 5

[0107] A silica-supported metallocene catalyst was prepared in the same manner as in step 3 of Preparation Example 1, except that compound (I) of the following structure was used, instead of the transition metal compound prepared in step 2 of Preparation Example 1.

##STR00005##

Example 1

[0108] Bulk-slurry polymerization of propylene was carried out using continuous two loop reactors, in the presence of the silica-supported metallocene catalyst prepared in Preparation Example 1.

[0109] Here, triethylaluminum (TEAL) and hydrogen gas were added using a pump, respectively, at the content described in the following Table 1, and for bulk-slurry polymerization, the supported catalyst prepared according to Preparation Example 1 was used in a mud catalyst form mixed with oil and greases to be a content of 30 wt %. The temperature of the reactor was 70 C., and operation was performed so that an hourly output was about 40 kg.

[0110] The specific reaction conditions for the polymerization process of Example 1 are as shown in the following Table 1, and by the polymerization process, a homopolypropylene was prepared.

Examples 2 to 5

[0111] A homopolypropylene was prepared in the same manner as in Example 1, except under the conditions described in Table 1.

Comparative Example 1

[0112] As a Z/N homopolypropylene, commercially available H7910 (manufactured by LG Chem.) was used.

Comparative Examples 2 to 4

[0113] A homopolypropylene was prepared in the same manner as in Example 1, except under the conditions described in Table 1.

Comparative Example 5

[0114] A homopolypropylene was prepared in the same manner as in Example 1, except that 500 ppm of hydrogen was added.

Comparative Example 6

[0115] A homopolypropylene was prepared in the same manner as in Example 1, except that 3000 ppm of hydrogen was added.

Comparative Example 7

[0116] A homopolypropylene was prepared in the same manner as in Example 1, except that the silica-supported metallocene catalyst prepared in Preparation Example 5 was used, and the conditions described in Table 1 were used.

TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 4 5 1 2 3 4 5 6 7 Catalyst Prep- Prep- Prep- Prep- Prep- Z/N Prep- Prep- Prep- Prep- Prep- Prep- aration aration aration aration aration catalyst aration aration aration aration aration aration Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 1 ple 1 ple 1 ple 1 ple 2 ple 3 ple 4 ple 1 ple 1 ple 5 Amount of 30 30 30 30 30 30 30 30 30 30 30 30 catalyst (wt %) Pressure 35 35 35 35 35 35 35 35 35 35 35 (kg/cm.sup.2) Added 40 40 40 40 40 40 40 40 40 40 40 amount of propylene (kg/h) Added 50 50 50 50 50 50 50 50 50 50 50 amount of TEAL (ppm) Polymerization 70 70 70 70 70 70 70 70 70 70 70 temperature ( C.) Added 700 1500 1750 2000 2500 550 290 1400 500 3000 1500 amount of hydrogen (ppm)

Experimental Example 1

[0117] For the homopolypropylenes prepared in the examples and the comparative examples, evaluation of physical properties was performed by the following methods. The results are shown in the following Table 2.

[0118] (1) Melt index (MI, g/10 min): measured at 230 C. under a load of 2.16 kg according to ASTM D1238, and represented as a weight (g) of a polymer which was melted out for 10 minutes.

[0119] (2) Xylene solubles (wt %): xylene was added to each sample of homopolypropylenes, and pretreated by heating at 135 C. for 1 hour and cooling for 30 minutes. Xylene was flowed at a flow rate of 1 mL/min for 4 hours in OmniSec equipment (FIPA from Viscotek), and when base lines of RI (refractive index), DP (pressure across middle of bridge), and IP (inlet pressure through bridge top to bottom) were stabilized, a concentration of the pretreated sample and an injection amount were recorded and measurement was performed, and then a peak area was calculated.

[0120] (3) Melting Point (Tm, C.)

[0121] The temperature of the homopolypropylene to be measured was increased to 200 C., maintained at that temperature for 5 minutes, decreased to 30 C., and then increased again, and a peak of a differential scanning calorimeter (DSC, manufactured by TA Instruments) curve was determined as a melting point. Here, a temperature increase rate and a temperature decrease rate were 10 C./min, and as the melting point, a result measured at a second temperature increase section was used.

[0122] (4) Molecular weight distribution (MWD, polydispersity index) of polymer: a molecular weight (Mw/Mn) was determined as a ratio of Mw/Mn after measuring Mw and Mn using gel permeation chromatography (GPC). Specifically, a Waters PL-GPC220 instrument using a PLgel Mixed-B column of a 300 mm length from Polymer Laboratories was used for measurement. Here, the evaluation temperature was 160 C., 1,2,4-trichlorobenzene was used as a solvent, and a flow rate was 1 mL/min. A sample was prepared at a concentration of 10 mg/10 mL, and supplied in an amount of 200 L. A calibrated curve formed using a polystyrene standard was used to derive Mw and Mn values. As the molecular weight (g/mol) of the polystyrene standard, nine types of 2000/10,000/30,000/70,000/200,000/700,000/2,000,000/4,000,000/10,000,000 were used.

[0123] (5) Measurement of Residual Stress Ratio

[0124] Each sample was taken from the homopolypropylenes according to the examples and the comparative examples, a strain at 200% were applied to each sample at 235 C., and a change in residual stress for 10 minutes was measured.

[0125] For the measurement of residual stress, a Discovery Hybrid Rheometer (DHR) from TA Instruments was used, and a sample was sufficiently loaded between upper and lower plates having a diameter of 25 mm, dissolved at 235 C., a gap was fixed at 1 mm, and measurement was performed.

[0126] Based on the data of the measured residual stress, a ratio of the residual stress (RS%) was calculated according to the following Equation 1, and the results are shown in the following Table 2:

[Equation 1]

Residual stress ratio (Y)=(RS.sub.1/RS.sub.0)*100

wherein RS.sub.0 is residual stress at 0.02 seconds (t.sub.0) after applying a strain at 200% to a sample at 235 C., and RS.sub.1 is residual stress at 1.00 second (t.sub.1) after applying a strain at 200% to a sample at 235 C.

TABLE-US-00002 TABLE 2 Example Comparative Example 1 2 3 4 5 1 2 3 4 5 6 7 MI 220 450 800 1100 1500 950 200 210 220 140 2400 480 (g/10 min) Xylene 0.6 0.6 0.6 0.7 0.7 2.2 0.6 1.5 0.6 0.6 0.8 0.7 solubles (wt %) Tm 154 154 154 154 154 162 152 155 153 154 155 154 ( C.) MWD 3.0 3.1 3.1 3.2 3.3 4.1 3.1 4.7 4.0 3.0 3.4 3.4 Residual 0.03 0.03 0.02 0.03 0.02 0.15 0.3 0.4 0.20 0.04 0.02 0.08 stress ratio (%)

[0127] As a result of experiments, the homopolypropylenes of Examples 1 to 5 prepared by the preparation method according to the present invention had a low content of xylene solubles and a low residual stress ratio, together with narrow MWD and MI in a range of 200 to 2000 g/10 min, and the MI was increased with an increase of an added amount of hydrogen. In addition, the homopolypropylenes of Examples 1 to 5 represented significantly decreased xylene solubles and residual stress ratio, and had a significantly narrow molecular weight distribution, as compared with the homopolypropylene of Comparative Example 1 prepared using a Ziegler-Natta catalyst.

[0128] In addition, in Comparative Examples 2 to 4 using the compound having a different structure as a catalytic active material, due to a difference in hydrogen reactivity depending on a difference in a catalyst structure, added amounts of hydrogen required for preparation of a polymer having equivalent MI were different from each other, however the molecular weight distribution was increased and the residual stress ratio was greatly increased, as compared with Example 1 having an equivalent MI. In addition, in Comparative Example 7 using the compound having an identical ligand structure but containing a tether group of alkoxyalkyl as a bridge group connecting two ligands, high MWD and residual stress ratio were represented. Deteriorated processability was confirmed therefrom.

[0129] In addition, when an identical catalyst was used but the condition of the added amount of hydrogen was not satisfied, the melt index was excessively low or high as in Comparative Examples 5 and 6, thereby confirming deteriorated processability.

Experimental Example 2

[0130] <Manufacture of non-woven fabric>

[0131] A melt blowing process was performed using resin compositions including homopolypropylene according to the examples and the comparative examples, thereby manufacturing spunbond non-woven fabric.

[0132] Specifically, a 25 mm twin-screw extruder was used to manufacture a master batch including homopolypropylenes according to the examples and the comparative examples, and 2000 ppm of Irganox 1010 and 2000 ppm of Irgafos 168 as an antioxidant, which was then pelletized. Subsequently, the master batch pellets were extruded into an extra fine fiber web by a process similar to that described in a reference [Report No. 4364 of the Naval Research Laboratories, published May 25, 1954 entitled Manufacture of Superfine Organic Fibers by Wente, V. A., Boone, C. D., and Fluharty, E. L.], except that a 31 mm Brabender conical twin screw extruder was used to supply the melted master batch composition to a melt pump (65 rpm), and then to a melt blowing die of a width of 25 cm having an outlet (10 outlets/cm) having an outlet diameter of 381 m.

[0133] The melting temperature was 235 C., the screw speed was 120 rpm, the die was maintained at 235 C. primary air temperature and pressure were 300 C. and 60 kPa (8.7 psi), respectively, a polymer treatment speed was 5.44 kg/h, and a distance of collector/die was 15.2 cm.

[0134] <Evaluation of physical properties of non-woven fabric>

[0135] For each spunbond non-woven fabric manufactured using the homopolypropylenes according to the examples and the comparative examples, evaluation of physical properties was performed as follows, and the results are shown in the following Table 3.

[0136] (1) Weight of non-woven fabric (gsm)

[0137] A weight of the manufactured non-woven fabric was measured, and a weight of the non-woven fabric per unit area was calculated.

[0138] (2) Processability of non-woven fabric

[0139] It was confirmed whether a single yarn of fiber occurred when manufacturing the non-woven fabric, and the processability of the non-woven fabric was evaluated according to the following criteria.

[0140] <Evaluation criteria>

[0141] Good: an occurrence rate of a single yarn of fiber was 10% or less, that is, a time during which fiber was not produced due to occurrence of a single yarn was 2.4 hours or less, based on 24 hours to produce fiber.

[0142] Poor: an occurrence rate of a single yarn of fiber was more than 10%, that is, a time during which fiber was not produced due to occurrence of a single yarn was more than 2.4 hours, based on 24 hours to produce fiber.

[0143] (3) Strength of non-woven fabric

[0144] Strength (N/5 cm) in a machine direction (MD) and strength in a cross direction (CD) were measured by a cut-strip method of a width of 5 cm, according to a method of ASTM (American Society for Testing and Materials) D 5035:2011 (2015).

[0145] (4) Roughness of non-woven fabric

[0146] The roughness of the non-woven fabric was measured by a blind panel evaluation of 10 people, and evaluated by the following criteria:

[0147] <Evaluation criteria>

[0148] : determined to be excellent when 7 or more people evaluated the non-woven fabric tactility as being rough

[0149] o: determined to be good when 4 to 6 people evaluated the non-woven fabric tactility as being rough

[0150] : determined to be normal when 2 or 3 people evaluated the non-woven fabric tactility as being rough

[0151] : determined to be poor when one or fewer persons evaluated the non-woven fabric tactility as being rough

TABLE-US-00003 TABLE 3 Example Comparative Example 1 2 3 4 5 1 2 3 4 5 6 7 Weight 37 38 36 37 36 40 41 40 39 38 39 38 of non- woven fabric (gsm) Pro- Good Good Good Good Good Poor Poor Poor Poor Poor Good Poor cessability Strength 22/15 20/13 17/12 15/11 14/11 10/8 11/8 11/6 11/8 24/15 12/9 16/10 (MD/CD, N/5 cm) Roughness

[0152] According to an embodiment of the present invention, the non-woven fabric manufactured using the homopolypropylenes of Examples 1 to 5 in which MI, MWD, xylene solubles, and residual stress ratios were all optimized, represented high strength and roughness, together with excellent processability.

[0153] Moreover, it was found that from the high roughness property of the homopolypropylenes according to Examples 1 to 5, the non-woven fabric for washing requiring a high roughness property may be manufactured, with only primary processing without blending with an additive.

[0154] Meanwhile, in Comparative Example 1 in which the homopolypropylene was prepared using a Ziegler-Natta catalyst, processability was poor, and strength and roughness properties were greatly deteriorated, as compared with Examples 1 to 5. In particular, it was found that in order to manufacture a non-woven fabric for washing using the homopolypropylene prepared according to Comparative Example 1, due to the low roughness property, blending with an additive for increasing the roughness property and a secondary processing are essential.

[0155] In addition, in Comparative Examples 2 to 4 in which compounds having different structures were used as a catalytic active material, due to a higher residual stress ratio than that of Example 1 having an identical MI, poor processability was represented, and as a result, web formation was poor, whereby strength deterioration occurred.

[0156] In addition, in Comparative Example 5 in which an identical catalyst was used, but the added amount of hydrogen was out of the range of the added amount condition of hydrogen and was excessively low, the MI value was lowered to less than 200 g/10 min, thereby representing poor processability. However, in Comparative Example 6 in which the added amount of hydrogen was excessively high, due to an MI of more than 2000 g/10 min, a lowered roughness property was represented, and also due to high MWD of more than 3.3 and increased xylene solubles, the strength property was also lowered as compared with the examples.

[0157] In addition, in Comparative Example 7 having an identical ligand structure, but using a compound containing a tether group of alkoxyalkyl as a bridge group connecting two ligands, the prepared homopolypropylene had high MWD and residual stress, thereby representing poor processability. From the results, it was confirmed that for implementing homopolypropylene satisfying the requirements of physical properties according to the present invention, the transition metal compound having the structure of Chemical Formula 1 is preferred.