KR20080066273A - Process for producing olefin using prepolymerized olefin polymerization catalyst - Google Patents

Abstract

A process for polymerizing olefin by using a prepolymerized olefin polymerization catalyst is provided to realize simple olefin polymerization process while exhibiting excellent catalytic activity. A process for polymerizing olefin comprises the steps of: (a) mixing a Ziegler-Natta catalyst with propylene in the presence of an external electron donator to carry out primary prepolymerization of the Ziegler-Natta catalyst; (b) mixing the prepolymerized Ziegler-Natta catalyst obtained from step (a) with 3-methylbutene-1 to carry out secondary prepolymerization and to obtain a prepolymerized Ziegler-Natta catalyst; and (c) carrying out polymerization of olefin by using the prepolymerized Ziegler-Natta catalyst obtained from step (b).

Description

Olefin polymerization method using prepolymerized catalyst for olefin polymerization {PROCESS FOR PRODUCING OLEFIN USING PREPOLYMERIZED OLEFIN POLYMERIZATION CATALYST}

The present invention relates to an olefin polymerization method using a catalyst for olefin polymerization prepolymerized using an external electron donor.

Propylene polymers are versatile plastics that are used for a wide range of applications because of their excellent formability and mechanical strength and their low cost. However, it is intended to improve the properties such as stiffness, transparency, and high cycle injection moldability in injection molding without impairing various properties inherent in the propylene polymer according to the field of use. It is known that these properties can be improved by increasing the crystallization rate of the propylene polymer.

Many substances and the like are already known as additives for increasing the crystallization rate of propylene polymers. Commercially available products include aluminum salts of aromatic carboxylic acids, dibenzylidene sorbitol, substituted dibenzylidene sorbitol, and the like. The addition of these additives (hereinafter referred to as nucleating agent) increases the crystallinity in the process of polypropylene being cooled from the molten state to the solid state by the nucleating agent, thereby increasing the crystallinity and improving the stiffness. When crystals are formed, they are quickly formed by the nucleating agent, thereby miniaturizing the size of the crystals. As a result, light scattering can be suppressed, thereby improving performance of transparency, glossiness, and shortening of the molding cycle of the propylene polymer. However, these nucleating agents are all low molecular weight materials, and when used as nucleating agents, they are fragrant and cannot be used in food applications.In the case of disintegration or sublimation during molding, there is gas generation, mold contamination, or dispersibility in propylene polymer. Therefore, there exists a fault that a biaxial kneader is needed in order to improve dispersibility.

On the other hand, as a method of improving the defects of the current nucleating agent, a number of methods using a high melting point polymer compound as a nucleating agent have been proposed.

For example, the melting point of the polymer of 3-methylbutene-1 is much higher than that of general polypropylene (melting point of 176 ° C in pure isotactic polypropylene), which is about 310 ° C. Has been.

JP-45-32430 discloses a method of blending a 3-methylbutene-1 polymer with a propylene polymer to improve the transparency and rigidity of the propylene polymer. According to the publication, a polypropylene containing 3-methylbutene-1 polymer and 4 to 18 carbon atoms obtained by a stepwise polymerization method in which a feed monomer is sequentially converted using a catalyst system made by combining titanium trichloride and diethylaluminum chloride. The transparency of copolymers of other alpha olefins is described as being improved. However, the effect of improving transparency is insufficient, and there is no improvement effect on the propylene homopolymer. Since a low activity catalyst is used, the polymerization amount and molecular weight of 3-methylbutene-1 per 1 g of the titanium catalyst component are reduced, and the stereoregularity and control ability of the catalyst are lowered, thereby obtaining a highly crystalline 3-methylbutene-1 polymer. There is no transparency improvement effect. Productivity also requires dozens of hours to obtain the desired 3-methylbutene-1 polymer, resulting in very low productivity of the propylene polymer.

Japanese Patent Application Laid-Open No. 60-139731 also describes a propylene polymer composition containing a 3-methylbutene-1 polymer, but 3-methylbutene-1 has a small nucleating effect and does not contain a 3-methylbutene-1 polymer. The improvement in the crystallization temperature of the propylene polymer containing the 3-methylbutene-1 polymer relative to the crystallization temperature of the polymer was insufficient at about 4 ° C. Japanese Patent Laid-Open No. 62-275111 describes a method of using a titanium-containing catalyst system supported on a specific Mg-based carrier, but includes a propylene polymer composition containing 3-methylbutene-1 polymer relative to the crystallization temperature of the propylene polymer. The improvement of crystallization temperature did not show a big improvement below 10 degreeC.

Korean Patent Application No. 1989-015383 discloses a method having a high crystallization temperature by a two-step polymerization method in which a 3-methylbutene-1 content is polymerized in an amount exceeding 10 g using a specific catalyst system and then polymerized with propylene. A propylene polymer containing -methylbutene-1 polymer was obtained and found to further improve transparency. Here, 3-methylbutene-1 has a lower molecular weight due to a lower growth rate in polymerization compared to linear alpha olefins such as propylene, so that the nucleation capacity is lowered when the polymerization amount of 3-methylbutene-1 per 1g titanium catalyst component is less than 10g. Therefore, it is explained that in order for the performance of the 3-methylbutene-1 polymer as a nucleating agent to be sufficient, the amount of polymerization of 3-methylbutene-1 per 1 g of titanium catalyst component needs to exceed 10 g. However, the boiling point of 3-methylbutene-1 requires a high pressure reactor to react at a high temperature of about 20 ° C, and an excess of 3-methylbutene-1 is required to increase the polymerization amount of 3-methylbutene-1 per 1g of titanium catalyst component. This can lead to very disadvantageous costs.

In order to solve the above problems, the present invention is first prepolymerized by mixing Ziegler-Natta catalyst and propylene in the presence of an external electron donor, followed by secondary prepolymerization by mixing 3-methylbutene-1, and then olefin. It is an object of the present invention to provide an olefin polymerization method which is simple in the process of polymerization of olefins during prepolymerization and excellent in catalytic activity by adding and polymerizing olefins.

The present invention

a) first prepolymerization of the Ziegler-Natta catalyst by mixing propylene with Ziegler-Natta catalyst in the presence of an external electron donor;

b) preparing a prepolymerized Ziegler-Natta catalyst by secondary prepolymerization by mixing 3-methylbutene-1 with the prepolymerized Ziegler-Natta catalyst obtained in step a); And

c) providing an olefin polymerization method comprising the step of polymerizing olefin using the prepolymerized Ziegler-Natta catalyst of step b).

In the present invention, propylene is first mixed with Ziegler-Natta catalyst in the presence of an external electron donor to first prepolymerize the Ziegler-Natta catalyst and then 3-methylbutene-1 is mixed to the first prepolymerized Ziegler. After the second prepolymerization of the nata-based catalyst, olefins are added thereto to polymerize the olefin using the second prepolymerized Ziegler-Natta catalyst.

In the olefin polymerization method according to the present invention, since the external electron donor is first polymerized with propylene during prepolymerization, the polymerization time can be shortened, the process of polymerizing the olefin can be simplified, and the catalytic activity can be increased.

In addition, the olefin polymerization method can increase the catalytic activity by about 20 ~ 30 wt% than conventional.

In the process according to the invention, 'polymerization' does not only mean homopolymerization of olefins, but also copolymerizes two or more olefins such as olefins such as ethylene, 1-butene, 1-hexene and propylene to copolymerize the copolymer. Copolymerization process to prepare.

In the monomer injection order of the prepolymerization step, it is preferable to sequentially inject propylene and 3-methylbutene-1. The reason for this is that when a catalyst prepolymerized with only 3-methylbutene-1 is used for propylene polymerization, some of the propylene particles are broken and powder is formed and the bulk density tends to be low. In addition, when the external electron donor is injected into the first prepolymerization step, the propylene and 3-methylbutene-1 may be simultaneously acted on, thus allowing more pre-regular prepolymerization.

After the Ziegler-Natta catalyst is decomposed into uniform particles in the prepolymerization process, the olefins in the polymerization step are adsorbed onto the Ziegler-Natta catalyst surface. Such Ziegler-Natta catalysts may be used without particular limitation as long as they are generally used for olefin polymerization, but include transition metal compounds containing Group 4, Group 5 or Group 6 elements of the periodic table; And organometallic compounds comprising a Group 13 element of the periodic table.

The transition metal compound is preferably a solid titanium catalyst containing magnesium, titanium, a halogen element and an internal electron donor as the main catalyst in the Ziegler-Natta catalyst. Herein, the internal electron donor may be, for example, a diether compound, a phthalate compound, or a mixture thereof. Specifically, diisobutyl phthalate may be used.

The organometallic compound is a co-catalyst in a Ziegler-Natta catalyst, and an organoaluminum compound is preferable, for example trialkyl aluminum, dialkyl aluminum halide, alkyl aluminum dihalide, aluminum dialkyl hydride, alkyl aluminum sesquihalide And the like, and among these, one kind or a mixture of two or more kinds can be used.

Specifically, the organometallic compound may be Al (C ₂ H ₅ ) ₃ , Al (C ₂ H ₅ ) ₂ H, Al (C ₃ H ₇ ) ₃ , Al (C ₃ H ₇ ) ₂ H, Al (iC ₄ H ₉ ) ₂ H, Al (C ₈ H ₁₇ ) ₃ , Al (C ₁₂ H ₂₅ ) ₃ , Al (C ₂ H ₅ ) (C ₁₂ H ₂₅ ) ₂ , Al (iC ₄ H ₉ ) (C ₁₂ H ₂₅ ) ₂ , Al (iC ₄ H ₉ ) ₂ H, Al (iC ₄ H ₉ ) ₃ , (C ₂ H ₅ ) ₂ AlCl, (iC ₃ H ₉ ) ₂ AlCl, (C ₂ H ₅ ) ₃ Al ₂ Cl ₃ and the like.

The organometallic compound may also be a mixture of organoaluminum compounds. At this time, the organometallic compound belonging to group 13 in the periodic table can be used as the mixture, it is preferable to use a mixture of different organoaluminum compounds. For example, the mixture of the organoaluminum compounds may be a mixture of Al (C ₂ H ₅ ) ₃ and Al (iC ₄ H ₉ ) ₃ ; A mixture of Al (C ₂ H ₅ ) ₃ , Al (C ₂ H ₅ ) ₃ and Al (C ₈ H ₁₇ ) ₃ ; A mixture of Al (C ₄ H ₉ ) ₂ H and Al (C ₈ H ₁₇ ) ₃ ; A mixture of Al (iC ₄ H ₉ ) ₃ and Al (C ₈ H ₁₇ ) ₃ ; A mixture of Al (C ₂ H ₅ ) ₃ and Al (C ₁₂ H ₂₅ ) ₃ ; A mixture of Al (iC ₄ H ₉ ) ₃ and Al (C ₁₂ H ₂₅ ) ₃ ; A mixture of Al (C ₂ H ₅ ) ₃ and Al (C ₁₆ H ₃₃ ) ₃ ; A mixture of Al (C ₃ H ₇ ) ₃ and Al (C ₁₈ H ₃₇ ) ₂ (iC ₄ H ₉ ), and the like, but is not limited thereto.

In this case, the molar ratio of the organometallic compound to the transition metal compound is preferably 5 to 50.

As the external electron donor, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 5 to 30 carbon atoms and a substituted or unsubstituted carbon atom 1 It is characterized by including the organosilane compound which contains at least 1 or more functional group among the alkoxy groups of 20, and contains at least 1 or more oxygen atoms.

Specifically, examples of the external electron donor include aromatic organic silane compounds including diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane, phenylmethyldimethoxysilane, and the like; Trimethylmethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, dicy Aliphatic organic silane compounds including clohexyldimethoxysilane and the like; Or mixtures thereof.

At this time, the molar ratio of the external electron donor to the transition metal compound is preferably 1 to 10.

The olefin is preferably an alpha olefin such as ethylene, propylene, 3-methylbutene-1, 4-methylpentene-1, 1-hexene and the like.

The feed amount of propylene and 3-methylbutene-1 in steps a) and b) may be added at a rate of 0.02 to 10 g olefins / g Ziegler-Natta catalyst / hour, preferably 0.02 to 6 g olefins / g Ziegler -Can be added at a rate of Nata catalyst / hour.

In the olefin polymerization method of the present invention, preferred non-polar solvents for use in the prepolymerization step of a) and b) include alkane compounds such as hexane, normal heptane, octane, nonane, decane, cycloalkane compounds, and the like. Hexane is most preferred. These are preferably used after purification before use so as not to affect the catalytic activity.

The reaction temperature of the prepolymerization process may be applied in the range of -10 ° C to 50 ° C, and preferably, the prepolymerization process may be performed at a temperature of 0 ° C to 40 ° C. If the temperature is less than -10 ℃ it is difficult to achieve a sufficient amount of the prepolymerization reaction, the present invention is difficult to achieve the desired effect, if it exceeds 50 ℃ there is a problem that the economic effect due to the excess temperature is not preferable because .

In addition, the prepolymerization process may be carried out for a reaction time of 0.1 to 10 hours, the reaction time of 0.5 to 5 hours is more preferred.

After the olefin is bonded to the Ziegler-Natta-based catalyst through the prepolymerization step as described above, the olefin polymerization step is performed using the olefin polymerization. The polymerization reaction of the olefin in the presence of the catalyst of the present invention is conventional Ziegler-Natta. It can proceed similarly to the polymerization method of an olefin using a system catalyst. However, the olefin polymerization reaction of the present invention is preferably carried out substantially in the absence of oxygen and water. At this time, the polymerization temperature of the olefin may be carried out under a pressure of 1 to 100 atm, preferably about 2 to 50 atm, at a temperature of about 20 to 200 ℃, more preferably about 50 to 180 ℃.

Hereinafter, the present invention will be described in detail through embodiments of the present invention. However, embodiments of the present invention may be modified in various forms, the scope of the present invention should not be limited by the embodiments described below. Embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

Properties of the polymer synthesized in the following Examples were measured through the following experimental method.

(1) active

The polymerization activity (kg PP / g catalyst) of the catalyst was calculated as the weight (kg) ratio of the resulting polymer per amount of catalyst used (g catalyst).

(2) melt flow index (MFR)

The melt flow index is measured using a weight of 2.16 kg at a temperature of 230 ° C. in accordance with ASTM D1238, expressed as weight in g of polymer melted out for 10 minutes (g / 10 min).

(3) three-dimensional rule diagram

The stereoregularity (%) of the polymer is the weight ratio of the polymer that is not extracted in boiling o -xylene for 1 hour (unit:%). Detailed description of the stereoregularity measurement of the polymer is as follows.

First, 200 ml o -xylene is prepared in a flask and then filtered with a 200 mm No. 4 extraction paper. The aluminum pan was dried in an oven at 150 ° C. for 30 minutes, then cooled in a desiccator and weighed. Next, 100 ml of filtered o -xylene was collected by a pipette, transferred to an aluminum pan, and heated to 145 to 150 ° C to evaporate all o -xylene. The aluminum pan was then vacuum dried for 1 hour at a temperature of 100 ± 5 ° C. and a pressure of 13.3 kPa. After the aluminum pan was cooled in a desiccator, the above procedure was repeated twice, and the o -xylene-only blank test was completed within a weight error of 0.0002 g.

Next, after drying the polymer obtained in Example 1 (70 DEG C, 13.3 kPa, 60 minutes, vacuum drying), 2 g ± 0.0001 g of the cooled polymer sample in a desiccator was placed in a 500 ml flask, and 200 ml was placed therein. o -xylene was added. The flask was connected to nitrogen and cooling water and the flask was heated to reflux o -xylene for 1 hour. Thereafter, the flask was placed in air for 5 minutes, cooled to 100 ° C. or lower, and the flask was shaken and placed in a thermostat (25 ± 0.5 ° C.) for 30 minutes to precipitate insoluble matters. The resultant solution in which the precipitate was formed was filtered repeatedly until it was cleared with 200 mm No. 4 extraction paper. After drying at 150 ° C. for 30 minutes, 100 ml of the filtered solution was added to a pre-weighed aluminum pan after cooling in a desiccator, and the aluminum pan was heated to 145 to 150 ° C. to evaporate o -xylene. . The evaporated aluminum pan was vacuum dried for 1 hour at a temperature of 70 ± 5 ° C. and a pressure of 13.3 kP, and repeated two times of cooling in a desiccator, and weighed to an error within 0.0002 g.

The weight ratio (XS) of the part dissolved in o -xylene in the polymer was calculated by the following equation, and the weight ratio (XI = 100-XS) of the polymer not extracted in o -xylene was obtained therefrom. It was a stereogram.

[Equation]

In the above equation,

XS = o -xylene dissolved in polymer, wt%

Vbo = volume of initial o -xylene, ml (= 200 ml)

Vb1 = o -volume taken from the polymer dissolved in xylene, ml (= 100 ml)

Vb2 = volume of o -xylene taken during the blank test, ml (= 100 ml)

W2 = sum of the weight of polymer remaining in the aluminum pan after evaporating the aluminum pan and o -xylene, g

W1 = weight of aluminum pan, g

Wo = weight of initial polymer, g (= 2 g)

B = average value of the balance remaining in the aluminum pan during the ball test, g

XI (stereogram) = 100-XS (weight ratio of polymer not extracted in o -xylene)

(4) crystallization temperature

It was measured at 10 ° C / min in temperature rise rate with a DSC-1 differential scanning calorimeter manufactured by Parkin Elma.

(5) polymerization result

The result of the polymerization is accompanied by the apparent density of the polymer (g / ml), the melt index (g / 10 min), the stereoregularity (weight ratio of the polymer not extracted in o -xylene (% by weight)), and the crystallization temperature (Tc). It is summarized in Table 1 below.

Preparation Example Preparation of Catalyst

[Catalyst 1]: Preparation of Transition Metal Compound

25.25 g of magnesium compound (Mg (Cl ₂ · 77C ₂ H ₅ OH)) and 150 ml of anhydrous heptane were added to a 500 ml glass reactor at 0 ° C. in a nitrogen atmosphere, followed by stirring. Next, 100 ml of 0 ° C TiCl ₄ was added thereto, and the mixture was reacted at room temperature for 1 hour, and then 150 ml of TiCl ₄ was added dropwise, and the reaction mixture was heated to 100 ° C for 2 hours, after which the supernatant was separated, and 200 ml of TiCl _{4 was} added. Was added dropwise and reacted for 2 hours at 120 ° C. After the reaction was completed, TiCl ₄ was removed, washed 6 times with heptane at 80 ° C., and dried under vacuum at 40 ° C.

[Catalyst 2]: Preparation of Transition Metal Compound

25.25 g of magnesium compound (Mg (Cl ₂ · 77C ₂ H ₅ OH)) and 150 ml of anhydrous heptane were added to a 500 ml glass reactor under a nitrogen atmosphere at 0 ° C. and stirred, followed by a 2,2-diisobutyl-diether compound. 21.6 ml of 1,3-dimethoxypropane was added dropwise and stirred for 10 minutes, then 100 ml of 0 ° C TiCl ₄ was added and reacted at room temperature for 1 hour, and then 150 ml of TiCl _{4 was} added dropwise and heated to 100 ° C for 2 hours. After that, the supernatant was separated and 200 ml of TiCl ₄ was added dropwise and reacted for 2 hours at 120 ° C. After the reaction, the TiCl ₄ was removed, washed six times with heptane at 80 ° C., and dried under vacuum at 40 ° C. Was

[Mixed catalyst]: Preparation of a mixed catalyst of [catalyst 1] and [catalyst 2]

The prepared [catalyst 1] and [catalyst 2] were mixed at a volume ratio of 1: 1, and then stored in a vacuum. The solid titanium catalyst contained 2.1% by weight of titanium atoms.

Example 1

Step a: prepolymerization

After purging the high-pressure reactor having a capacity of 0.5 l with argon at high temperature, 2 g of the mixed catalyst of Preparation Example 1, 200 ml of hexane, 8.75 mmol of triethylaluminum, 8.75 mmol of trimethylmethoxysilane were added, and propylene was adjusted to 18 cc / min. Prepolymerization was carried out for 1 hour at ℃. Thereafter, 10 g of 3-methylbutene-1 was injected, followed by prepolymerization for 2 hours. After washing three times with hexane, the hexane slurry was used for polymerization, and the remainder was vacuum dried at room temperature for 2 hours. In the prepolymerization catalyst thus obtained, the amount of the high molecular weight monomer polymerized around the catalyst was 3 to 4 g per 1 g of the catalyst.

step b: polymerization

The autoclave reactor with a capacity of 2 L was vacuum dried for 1 hour and then purged sufficiently with nitrogen, and 4 mmol of triethylaluminum, 0.4 mmol of dicyclopentyldimethoxysilane at room temperature, and 5.0 ppm of titanium in the prepolymerized catalyst obtained above. The volume was as low as possible and then injected into the reactor. Thereafter, 3300 ppm of hydrogen was added, followed by 1.2 L of liquid propylene, and then the temperature was raised to 70 ° C. while stirring the reactor to carry out polymerization for 1 hour. After the polymerization reaction was completed, the unreacted gas was discharged, and the reaction was terminated after cooling the temperature to room temperature. The resulting polymer was collected separately and dried in a vacuum oven at 70 ° C. for at least 1 hour to obtain a white polymer. The polymerization results are summarized in Table 1 below.

Example 2

The prepolymerization catalyst of Example 1 was used for the polymerization, and when the temperature was 60 ° C. at the start of the polymerization, 200 cc / min of ethylene was injected to uniformly autoclave the ethylene copolymer in the propylene copolymer at about 2.0 wt%. Polymerization was carried out in the same manner as in Example 1 except that the polymer was pressed in and supplied to a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 1

Without the prepolymerization step, the polymerization was carried out by the polymerization method of Example 1 using 10 mg of the catalyst not subjected to prepolymerization during polymerization and dicyclopentyldimethoxysilane as an external electron donor. The polymerization experiment results are summarized in Table 1.

Comparative Example 2

Prepolymerization was performed under the same conditions except that propylene was not injected under the prepolymerization condition of Example 1. The polymerization was carried out in the same manner as in Example 1 to obtain a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 3

Except that 10g of 3-methylbutene-1 was injected under the prepolymerization conditions of Example 1, followed by prepolymerization at 20 ° C. for 2 hours, and then prepolymerization was carried out for 1 hour at 18 cc / min. Prepolymerization was carried out under the same conditions. The polymerization was carried out in the same manner as in Example 1 to obtain a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 4

Prepolymerization was carried out under the same conditions except that 3-methylbutene-1 and propylene were simultaneously injected under the prepolymerization conditions of Example 1. The polymerization was carried out in the same manner as in Example 1 to obtain a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 5

Under prepolymerization conditions of Example 1, 3-methylbutene-1 was first injected into trimethylmethoxysilane, and then prepolymerization was carried out under the same conditions except that propylene was injected. The polymerization was carried out in the same manner as in Example 1 to obtain a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 6

Without the prepolymerization step, when the temperature was 60 ° C at the start of the polymerization, 150 cc / min of ethylene was injected to uniformly use the 10 mg of the catalyst which was not prepolymerized during the polymerization and have an ethylene content of about 2.0 wt% in the propylene copolymer. A white polymer was obtained by polymerization in the same manner as in Example 1 except that the autoclave was press-fitted. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 7

The prepolymerization catalyst of Comparative Example 3 was used for polymerization, and when the temperature was 60 ° C. at the start of polymerization, 150 cc / min of ethylene was injected to uniformly autoclave the ethylene content of the propylene copolymer at about 2.0 wt%. Polymerization was carried out in the same manner as in Example 1 except that the polymer was pressed in and supplied to a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparative Example 8

The prepolymerization catalyst of Comparative Example 5 was used for the polymerization, and when the temperature was 60 ° C. at the start of the polymerization, 150 cc / min of ethylene was injected to uniformly autoclave the ethylene content of the propylene copolymer at about 2.0 wt%. Polymerization was carried out in the same manner as in Example 1 except that the polymer was pressed in and supplied to a white polymer. The polymerization experiment results are summarized in Table 1 below.

Comparing Comparative Examples 1 and 2, it can be seen that in Comparative Example 2 prepolymerized with 3-methylbutene-1 compared to Comparative Example 1 without prepolymerization, the crystallization temperature was markedly improved to about 14 ° C. This is because the melting point of the prepolymerized 3-methylbutene-1 polymer is much higher than the melting point of general propylene and thus serves as nucleating agent. However, Comparative Example 2 using a prepolymerized catalyst has a disadvantage in that activity is lower than that of Comparative Example 1 using a general catalyst.

As in Example 1, if propylene is first prepolymerized in the presence of an external electron donor and then sequentially prepolymerized with 3-methylbutene-1, it is compared with the case of Comparative Example 2 prepolymerized with 3-methylbutene-1 alone. When the crystallization temperature was maintained at a similarly high level, the activity was improved.

Comparing Example 1 with Comparative Example 3 which changed the monomer injection order during prepolymerization, the crystallization temperature slightly increased in Comparative Example 3, but the stereoregularity was significantly lowered. This is presumably due to the fact that some of the propylene polymer was broken when prepolymerized with 3-methylbutene-1 and then prepolymerized with propylene.

When propylene and 3-methylbutene-1 were simultaneously prepolymerized as in Comparative Example 4, the stereoregularity was improved than that of Comparative Example 3, but the crystallization temperature was significantly lowered when compared with Example 1 and Comparative Example 3, which were two-stage prepolymerized. This is because in the prepolymerization at the same time, since 3-methylbutene-1 is less reactive than propylene, most of the prepolymerization is propylene and thus the prepolymerization catalyst does not act as a nucleating agent.

Also, as in the case of Example 1 and Comparative Example 5, when the external electron donor is introduced in different order, the stereoregularity and the crystallization temperature are not significantly different, but the difference in activity is significant. Therefore, the external electron donor may be introduced in the propylene prepolymerization step. It can be seen that productivity can increase when.

In the case of Example 2, which is a random copolymer, prepolymerization of propylene in the presence of an external electron donor and then prepolymerization of 3-methylbutene-1 increased the crystallization temperature in comparison with that of Comparative Example 6 without prepolymerization. It can be seen that the prepolymerization method contributes to the improvement of crystallinity in the case of the copolymer as well as the homo.

In addition, as in the case of homopolymerization, the stereoregularity and the crystallization temperature were not significantly different according to the order of introducing the external electron donors as in the case of Example 2 and Comparative Example 8. It can be seen that productivity can be increased when introducing a donor.

Therefore, prepolymerization of propylene and 3-methylbutene-1 as mentioned above allows the polymerization of highly crystalline polypropylene with high crystallization temperature while maintaining high activity and stereoregularity.

The olefin polymerization method according to the present invention can shorten the prepolymerization time, simplify the prepolymerization process, and increase the catalytic activity.

Claims (17)

a) first prepolymerization of the Ziegler-Natta catalyst by mixing propylene with Ziegler-Natta catalyst in the presence of an external electron donor; b) preparing a prepolymerized Ziegler-Natta catalyst by secondary prepolymerization by mixing 3-methylbutene-1 with the prepolymerized Ziegler-Natta catalyst obtained in step a); And c) polymerizing the olefin using the prepolymerized Ziegler-Natta catalyst of step b). The method according to claim 1, wherein the Ziegler-Natta catalyst is a transition metal compound containing a Group 4, 5 or 6 elements of the periodic table; And an organometallic compound comprising a Group 13 element of the periodic table. The olefin polymerization method according to claim 2, wherein the molar ratio of the organometallic compound to the transition metal compound is 5 to 50. The method of claim 2, wherein the transition metal compound comprises a solid titanium catalyst containing magnesium, titanium, a halogen element and an internal electron donor. The method of olefin polymerization according to claim 4, wherein the internal electron donor comprises a diether compound, a phthalate compound, and a mixture thereof. The method of olefin polymerization according to claim 2, wherein the molar ratio of the external electron donor to the transition metal compound is 1 to 10. The method of claim 1, wherein the external electron donor is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted carbon atom having 6 to 30 aryl groups, a substituted or unsubstituted carbon atom having 5 to 30 cycloalkyl groups And at least one or more functional groups selected from substituted or unsubstituted alkoxy groups having 1 to 20 carbon atoms, and at least one oxygen silane compound. 8. The method of claim 7, wherein the external electron donor comprises an aromatic organic silane compound comprising diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane and phenylmethyldimethoxysilane; Trimethylmethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane and dicy Aliphatic organic silane compounds including clohexyldimethoxysilane; Or a mixture thereof. The method of olefin polymerization according to claim 2, wherein the organometallic compound comprises an organoaluminum compound. The method of claim 9, wherein the organoaluminum compound is one or a mixture of two or more selected from trialkyl aluminum, dialkyl aluminum halide, alkyl aluminum dihalide, aluminum dialkyl hydride and alkyl aluminum sesquihalide. . The method of claim 10, wherein the organoaluminum compound is Al (C ₂ H ₅ ) ₃ , Al (C ₂ H ₅ ) ₂ H, Al (C ₃ H ₇ ) ₃ , Al (C ₃ H ₇ ) ₂ H, Al ( iC ₄ H ₉ ) ₂ H, Al (C ₈ H ₁₇ ) ₃ , Al (C ₁₂ H ₂₅ ) ₃ , Al (C ₂ H ₅ ) (C ₁₂ H ₂₅ ) ₂ , Al (iC ₄ H ₉ ) (C ₁₂ H ₂₅ ) ₂ , Al (iC ₄ H ₉ ) ₂ H, Al (iC ₄ H ₉ ) ₃ , (C ₂ H ₅ ) ₂ AlCl, (iC ₃ H ₉ ) ₂ AlCl and (C ₂ H ₅ ) ₃ It is one or a mixture of two or more selected from Al ₂ Cl ₃ olefin polymerization method. The olefin polymerization method according to claim 1, wherein the olefin of step c) is an α-olefin including ethylene, propylene, 3-methylbutene-1, 4-methylpentene-1, and 1-hectene. The olefin polymerization method according to claim 1, wherein the amount of propylene injected in step a) is added at a rate of 0.02 to 10 g olefin / g Ziegler-Natta catalyst / hour. The method of claim 1, wherein the amount of 3-methylbutene-1 injected in step b) is introduced at a rate of 0.02 to 10 g olefins / g Ziegler-Natta catalyst / hour. The method of claim 1, wherein the reaction temperature of the prepolymerization process of step a) and b) is carried out in the range of -10 ℃ to 50 ℃. The method of claim 1, wherein the olefin polymerization temperature of step c) is 20 to 200 ℃ olefin polymerization method. The olefin polymerization method of claim 1, wherein the olefin polymerization pressure of step c) is 1 to 100 atmospheres.