KR20070115001A - Method for producing polyolefin having high stiffness - Google Patents

Abstract

A method for preparing polyolefin is provided to produce polyolefin having high stiffness in a continuous polymerization reactor with high polymerization activity by using a pre-polymerization catalyst obtained from a Ziegler-Natta catalyst. A method for preparing polyolefin includes a step of polymerizing or copolymerizing olefins in a multi-stage continuous polymerization reactor in the presence of a catalyst system consisting of (a) a pre-polymerization catalyst, (b) an organometallic compound of a group 1 or 3 metal on the periodic table, and (c) an external electron donor. The pre-polymerization catalyst is obtained by reacting olefin monomers in the presence of a Ziegler-Natta based solid complex titanium catalyst, at least two aluminum compounds comprising alkylaluminum and halogenated aluminum, and an electron donor to polymerize a high-molecular-weight monomer on the surface of the catalyst.

Description

Polyolefin manufacturing method with high rigidity {METHOD FOR PRODUCING POLYOLEFIN HAVING HIGH STIFFNESS}

The present invention relates to a method for producing a polyolefin having high rigidity with high polymerization activity in a continuous polymerization process, more specifically, prepolymerization catalyst, organometallic compound of Group I or Group III metal of the periodic table and external electrons In the presence of a catalyst system consisting of a donor, the present invention relates to a method for producing an olefin, characterized in that the olefin is polymerized or copolymerized in a multistage continuous polymerization reactor.

Although many olefin polymerization catalysts and polymerization processes have been reported so far, in order to give a greater commercial meaning to the catalysts invented, the properties of the polymers obtained by using the invention catalysts are improved to increase productivity or to improve product quality. Efforts and demands to improve the activity and stereoregularity of the catalysts themselves continue.

Many olefin polymerization catalysts and catalyst production processes based on titanium, including magnesium, have been reported, and there are many known methods for preparing a catalyst using a solution of a magnesium compound to control the particle shape and size of the catalyst. There is a method of obtaining a magnesium solution by reacting a magnesium compound with an electron donor such as alcohol, amine, ether, ester, carboxylic acid, etc. in the presence of a hydrocarbon solvent. In the case of using alcohol, U.S. Patent Nos. 4,330,649, 5,106,807, and Japan Reference is made to published patent publication no. 58-83006. And US Patent Nos. 4,315,874, 4,399,054 and 4,071,674 report a method for preparing magnesium solutions.

U.S. Patent Nos. 4,347,158, 4,422,957, 4,425,257, 4,618,661, and 4,680,381 propose a method of preparing a catalyst after pulverizing a Lewis acid compound such as aluminum chloride to magnesium chloride as a support. However, although the catalytic activity is complemented in the above patents, there are disadvantages in that the shape of the catalyst, such as the shape, size, size distribution of the catalyst irregularities, and stereoregularity should be complemented.

Regarding the shape of the catalyst, in the preparation of a titanium-based polymerization catalyst supported on a magnesium compound, a mixed solvent of alcohol and a cyclic ether is used to dissolve the magnesium halide compound, and then a titanium halide compound such as TiCl ₄ is reacted. It is known that the shape of the catalyst particles can be controlled, but there is a disadvantage in that the yield of the catalyst is low. In order to overcome this, the magnesium halide compound is dissolved using a mixed solvent of alcohol and cyclic ether, and reacted with a metal compound. Has been proposed to control the production yield and shape of catalysts by first reacting with metal halide compounds at relatively low temperatures to produce particles with controlled particle shape and further reacting with metal halide compounds secondly. .

However, there is a continuing need for development of an effective new catalyst production method and polyolefin production method that can further improve catalytic activity and stereoregularity and improve physical properties of the polymer to be produced.

An object of the present invention is to provide a method for polymerizing and copolymerizing a polyolefin having high rigidity with high polymerization activity in a continuous polymerization reactor by using a prepolymer catalyst obtained by applying a commonly used Ziegler-Natta catalyst.

The polyolefin production method of the present invention is a surface of the catalyst by reacting an olefin monomer at low temperature and low pressure in the presence of a Ziegler-Natta-based solid complex titanium catalyst, two or more aluminum compounds and alkyl donors including alkylaluminum and aluminum halides. Multistage continuous polymerization reactor in the presence of a catalyst system comprising a prepolymerization catalyst (a) obtained by polymerizing a high molecular weight monomer in an organic solvent, an organometallic compound (b) and an external electron donor (c) of a Group I or Group III metal of the periodic table. It is characterized in that the olefin is polymerized or copolymerized.

The prepolymerization catalyst (a) used in the present invention is obtained by prepolymerizing a Ziegler-Natta-based solid complex titanium catalyst through the following prepolymerization process.

The prepolymerization process comprises (1) a solid complex titanium catalyst; (2) at least two aluminum compounds containing alkylaluminum and aluminum halides; And (3) reacting the olefin monomer at a temperature of −50 to 50 ° C. in the presence of an electron donor to polymerize a high molecular weight monomer on the surface of the catalyst.

As the solid complex titanium catalyst used in the preparation of the prepolymerization catalyst used in the present invention, any conventional solid titanium catalyst for olefin polymerization may be used, which may be prepared by various methods. As the most common method, various methods are known in which a magnesium compound is brought into contact with a titanium compound containing at least one halogen and, if necessary, the product is treated with an electron donor. Some of these methods are described in JP 2,230,672, 2,504,036, 2,553,104 and 2,605,922 and JP 51-28189, 51-136625 and 52-87486. have.

In addition, as a solid titanium catalyst used in the preparation of the prepolymerization catalyst of the present invention, U.S. Patent Nos. 4,482,687, 4,277,372, 3,642,746, 3,642,772, 4,158,642, 4,148,756, 4,477,639, and Conventional Ziegler-Natta catalysts described in 4,518,706, 4,946,816, 4,866,022, 5,013,702, 5,124,297, 4,330,649, European Patent 131,832, JP-A-63-54004 and the like can be used.

In a preferred embodiment, the process for preparing the solid complex titanium catalyst 1 consists of the following four steps:

(i) dissolving the magnesium halide compound in a mixed solvent of a cyclic ether and at least one alcohol compound, (ii) reacting the magnesium compound solution with the metal halide compound first at a relatively low temperature to obtain particles, and then secondly Reacting the titanium compound with a titanium compound to prepare a carrier, (iii) reacting the carrier with the titanium compound and an electron donor to support titanium, and (iv) washing the prepared catalyst under a high temperature hydrocarbon solvent.

When the prepolymerization process is a liquid prepolymerization, an inert solvent such as hexane, heptane or kerosene may be used as the reaction medium, but the olefin itself may serve as a reaction medium, and the solid complex titanium catalyst (1 The concentration of c) is preferably from about 0.01 to about 500 mmol, more preferably from about 1 to about 50 mmol of titanium atoms per 1 L of solvent.

The aluminum compound (2) is at least one selected from alkylalkyl compounds such as trialkylaluminum such as triethylaluminum and tributylaluminum, trialkenylaluminum such as triisoprenylaluminum and ethylaluminum sesquiethoxide And at least one aluminum compound selected from aluminum halides such as ethylaluminum sesquichloride, ethylaluminum dichloride, propylaluminum dichloride and butylaluminum dibromide. The use ratio of the aluminum compound is preferably about 1 to 100 mol per mole of titanium atoms in the catalyst (1), and more preferably about 2 to 20 mol, and more preferably less than 1 mol, the addition effect is less than 100 mol There is a problem that the catalyst is excessively reduced.

The electron donor (3) is preferably at least one selected from an organosilicon compound having an alkoxy group, that is, an alkoxysilane compound, and these types include diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane, and phenyl. Aromatic silanes such as methyldimethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane, t-butyltrimethoxysilane, cyclohexyl Methyldimethoxysilane, dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, vinyltriethoxysilane, octyltriethoxysilane, iso Aliphatic silanes such as decyltriethoxysilane, and mixtures thereof, and especially branched alkyldialkoxysilanes such as diisobutyldimethoxysilane and dicyclopentyldimethoxysil among the aforementioned silane compounds. The cycloalkyl dialkoxysilane is preferred as.

In particular, the organosilicon compound, at least three or more organosilicon compounds having a melt index (MFR) of the homopolymer polymerized using the respective organosilicon compounds under the same polymerization conditions are respectively less than 5, more than 5 to 20, 20 It is preferable to mix and use.

The use ratio of the electron donor (3) is preferably about 0.001 to 5 mol, more preferably about 0.1 to 1.0 mol per mole of titanium atoms in the solid complex titanium catalyst (1).

It is preferable to use at least one selected from ethylene, propylene, 1-butene, 1-hexene, and 1-octene as the olefin monomer used in the preparation of the prepolymerization catalyst.

In the prepolymerization catalyst, the weight of the polymer prepolymerized on the catalyst surface is preferably 1 to 100 g, especially 20 to 70 g, per g catalyst.

The prepolymerization catalyst prepared as above is preferably used for the polymerization of olefins such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, vinylcycloalkane or cycloalkene. In particular, this prepolymerization catalyst is suitable for the polymerization of α-olefins having three or more carbon atoms, copolymerization of these mutually, copolymerization thereof with less than 20 mol% of ethylene, and polyunsaturated compounds such as conjugated or nonconjugated dienes. Advantageously applied to their copolymerization.

As the organometallic compound (b) used as a cocatalyst in the polyolefin production method of the present invention, an organoaluminum compound is preferable, and specifically, trialkylaluminum such as triethylaluminum and tributylaluminum, and triisoprenylaluminum Alkenylaluminum, partially alkoxylated alkylaluminum, for example dialkylaluminum alkoxides such as diethylaluminum ethoxide and dibutylaluminum butoxide, ethylaluminum sesquiethoxide and butylaluminum sesquiethock Alkyl aluminum sesquialkoxides such as seeds and alkyl aluminum dihalides such as ethyl aluminum dichloride, propyl aluminum dichloride and butyl aluminum dibromide, partially halogenated aluminum, such as diethyl aluminum hydride or dibutyl aluminum hydride Aluminum hydride and di It is preferred to select among partially alkoxylated and halogenated alkylaluminums such as dialkylaluminum hydrides such as butylaluminum hydride, ethylaluminum ethoxychloride, butylaluminum butoxychloride and ethylaluminum ethoxybromide.

As the external electron donor (c) used in the present invention, an external electron donor material commonly used for olefin polymerization may be used. The external electron donor is mainly used to optimize the activity and stereoregularity of the catalyst in the polymerization of the olefin. Used. Examples of external electron donors usable in the present invention include organic acids, organic acid anhydrides, organic acid esters, alcohols, ethers, aldehydes, ketones, silanes, amines, amine oxides, amides, diols, oxygen such as phosphate esters, silicon, nitrogen, sulfur, And organic compounds containing phosphorus atoms and mixtures thereof.

Particularly preferred external electron donors are organosilicon compounds having an alkoxy group, i.e., alkoxysilane compounds, and their kinds include aromatic silanes such as diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane and phenylmethyldimethoxysilane. , Isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane, t-butyltrimethoxysilane, cyclohexylmethyldimethoxysilane, dicyclopentyldimeth Aliphatic silanes such as methoxysilane, dicyclohexyldimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, vinyltriethoxysilane, and mixtures thereof, and particularly the silane compounds described above. Among these, branched alkyl dialkoxysilanes such as diisobutyldimethoxysilane and dicycloalkyl dialkoxysilanes such as dicyclopentyldimethoxysilane are effective. The compounds may be used alone or in combination of two or more thereof.

Continuous polymerization or copolymerization in the multistage reactor of olefins in the presence of the catalyst system of the present invention proceeds in the same manner as the polymerization of olefins using a conventional Ziegler-type catalyst. In particular, it is carried out substantially in the absence of oxygen and water. In the case of a liquid phase slurry reactor in a multi-stage reactor, it is preferably performed at a temperature of about 20 to 200 ° C., more preferably at a temperature of about 50 to 180 ° C. and a pressure of atmospheric pressure to 100 atm, and preferably at a pressure of about 2 to 50 atm. Can be. And it is essential to operate the polymerization temperature below the polymer sintering temperature in the gas phase fluidized bed reactor. In order to prevent mass formation, the catalyst of the present invention is preferably used at 30 ° C to 110 ° C, and more preferably at 75 to 95 ° C. The operating pressure of the fluidized bed reactor is preferably operated to 1000psi, more preferably 150 ~ 300psi. Even in this range, it is preferable to operate at high pressure because the heat capacity per unit volume is high.

The present invention can be understood in more detail by the following examples, the following examples are only examples for illustrating the present invention and are not intended to limit the protection scope of the present invention.

[ Example  And Comparative example ]

Example  One

[ Of the prepolymerization catalyst (a)  Produce]

Step 1: Prepare Magnesium Compound Solution

MgCl in 500L reactor with mechanical stirrer replaced by nitrogen atmosphere₂ 15 kg, toluene 225 kg, tetrahydrofuran 17 kg, butanol 31 kg was added, and stirred at 70 rpm, the temperature was raised to 110 ℃ and maintained for 3 hours to obtain a uniform solution.

Step 2: Solid Carrier  Produce

Cool the temperature of the solution obtained in step 1 to 17 ℃ and TiCl ₄ After adding 32 kg, the temperature of the reactor was increased to 60 ° C. over 1 hour, and when the reactor reached 60 ° C., 13 kg of TiCl ₄ was added thereto for 40 minutes to react for 30 minutes. After the reaction, the mixture was allowed to stand for 30 minutes to settle the carrier, and the upper solution was removed. 90 kg of toluene was added to the slurry remaining in the reactor, and washed three times by stirring, standing, and removing the supernatant.

Step 3: Solid Complex  Titanium catalyst manufacturers

Toluene 80 kg, TiCl ₄ at a stirring speed of 60 rpm to the carrier prepared in step 2 After adding 90 kg, the temperature of the reactor was raised to 110 ° C. for 1 hour and aged for 1 hour. After standing for 15 minutes, the precipitate was settled and the supernatant was separated. Here again 87 kg of toluene and TiCl ₄ 52 kg and 4.2 kg of diisobutyl phthalate were added thereto. The temperature of the reactor was raised to 120 ° C., and the reaction was maintained for 1 hour. After the reaction, the mixture was allowed to stand for 30 minutes to separate the supernatant, and 80 kg of toluene and 76 kg of TiCl ₄ were injected again, followed by reaction at 100 ° C. for 30 minutes. After the reaction was allowed to stand for 30 minutes, the supernatant was separated, and 65 kg of hexane was added thereto, followed by stirring while maintaining the temperature of the reactor at 60 ° C. for 30 minutes. The stirring was stopped and the supernatant was separated after standing for 30 minutes. Hexane was added to the remaining catalyst slurry layer and washed six times in the same manner to prepare a final solid complex titanium catalyst. Ti content of the prepared catalyst was 2.8% by weight.

Step 4: Prepolymerization

     The high-pressure reactor with a capacity of 150 L was washed with hexane, and then, 360 g of the catalyst obtained in step 3, 33 kg of hexane, 730 mmol of diethylaluminum chloride, 730 mmol of diethylaluminum chloride and 80 mmol of cyclohexylmethyldimethoxysilane were added to the reactor maintained at 5 ° C. After the addition and stirring for 30 minutes, the polymerization was carried out for 6.3 hours while controlling the polymerization temperature not to exceed 15 ° C while flowing 0.4 kg / h with propylene. In the prepolymerization catalyst thus obtained, the amount of polymer polymerized around the catalyst was 7 g per 1 g of catalyst.

[Continuous Multistage Polymerization Reaction]

Propylene homopolymerization was carried out in a continuous multistage polymerization reactor system for performance evaluation of the prepared prepolymerization catalyst. The polymerization reaction system used consists of two liquid phase slurry reactors and one gas phase fluidized bed reactor. Each reactor was purged with nitrogen to remove moisture and oxygen in the reactor, and two liquid phase reactors injected 36 kg of liquid propylene, and one gas phase reactor injected about 40 kg of seed powder. The large cycle operation of the entire reactor system was carried out for 4 hours. Then, the cyclohexyl methyldimethoxysilane was continuously injected into the triethylaluminum and the external electron donor into the first stage liquid slurry reactor, and after 1 hour, the prepolymerized catalyst prepared above was continued at a rate of 1 g / hr based on the solid complex titanium catalyst. Injection was carried out to carry out the polymerization reaction. The powder produced at the rate of 15 kg / h was weighed every hour through the plant's drying system. Xylene solubles, flexural modulus (FM) and Izod impact strength of the powder were analyzed. The results are shown in Table 1.

Example  2

In step 4 of preparing the prepolymerization catalyst (a) of Example 1, a prepolymerization catalyst was prepared using 1500 mmol of triethylaluminum instead of 730 mmol of triethylaluminum, and polymerization was carried out under the same conditions as in Example 1. The results are shown in Table 1.

Example  3

In step 4 of preparing the prepolymerization catalyst (a) of Example 1, a prepolymerization catalyst was prepared using 1500 mmol of triethylaluminum and 1500 mmol of diethylaluminum chloride, and polymerization was carried out under the same conditions as in Example 1. The results are shown in Table 1.

Example  4

In the continuous multistage polymerization reaction step of Example 1, a gas phase fluidized bed reactor was added to the fourth reactor, where a copolymerization reaction was made to produce an impact copolymer. The results are shown in Table 1.

Example  5

In the continuous multi-stage polymerization step of Example 2, a gas phase fluidized bed reactor was added to the fourth reactor, where a copolymerization reaction was made to produce an impact copolymer. The results are shown in Table 1.

Example  6

In the continuous multistage polymerization step of Example 3, a gas phase fluidized bed reactor was added to the fourth reactor, where a copolymerization reaction was made to produce an impact copolymer. The results are shown in Table 1.

Comparative example  One

In step 4 of the prepolymerization catalyst (a) of Example 2, a prepolymerization catalyst was prepared using only 730 mmol of triethylaluminum as an aluminum compound without using a silane compound, and polymerization was performed on the catalyst obtained under the same conditions as in Example 1. Was carried out. The results are summarized in Table 1.

Comparative example  2

In step 4 of the prepolymerization catalyst (a) of Example 2, a prepolymerization catalyst was prepared using only 730 mmol of triisobutylaluminum as an aluminum compound without using a silane compound, and the catalyst obtained under the same conditions as in Example 1. The polymerization was carried out. The results are summarized in Table 1.

Comparative example  3

In the continuous multistage polymerization reaction step of Comparative Example 1, a gas phase fluidized bed reactor was added to the fourth reactor, where a copolymerization reaction was conducted to produce an impact copolymer. The results are shown in Table 1.

TABLE 1

Polymerization result

Polymerization Activity (kgPP / gCat) Xylene Melt (%) Flexural Modulus (kg / ㎠) Izod impact strength at 23 ℃ (kgcm / cm) Example 1 13 1.8 19,200 3.0 Example 2 12 1.9 19,100 2.9 Example 3 13 1.9 19,000 3.1 Example 4 16 1.7 12,500 7.5 Example 5 17 1.9 12,500 7.3 Example 6 15 1.7 12,700 7.4 Comparative Example 1 11 2.1 18,100 2.9 Comparative Example 2 8 2.0 18,200 2.8 Comparative Example 3 14 2.1 12,000 7

* Flexural modulus measurement is ASTM D790

* Izod impact strength measurement is in accordance with ASTM D256.

Example  7

[ Of the prepolymerization catalyst (a)  Produce]

Step 1: Prepare Magnesium Compound Solution

MgCl ₂ in a 500L reactor equipped with a mechanical stirrer replaced with a nitrogen atmosphere 15 kg, toluene 225 kg, tetrahydrofuran 17 kg, butanol 31 kg was added, and stirred at 70 rpm, the temperature was raised to 110 ℃ and maintained for 3 hours to obtain a uniform solution.

Step 2: Solid Carrier  Produce

Cool the temperature of the solution obtained in step 1 to 17 ℃ and TiCl ₄ After adding 32 kg, the temperature of the reactor was increased to 60 ° C. over 1 hour, and when the reactor reached 60 ° C., 13 kg of TiCl ₄ was added thereto for 40 minutes to react for 30 minutes. After the reaction, the mixture was allowed to stand for 30 minutes to settle the carrier, and the upper solution was removed. 90 kg of toluene was added to the slurry remaining in the reactor, and washed three times by stirring, standing, and removing the supernatant.

Step 3: Solid Complex  Titanium catalyst manufacturers

Toluene 80 kg, TiCl ₄ at a stirring speed of 60 rpm to the carrier prepared in step 2 After adding 90 kg, the temperature of the reactor was raised to 110 ° C. for 1 hour and aged for 1 hour. After standing for 15 minutes, the precipitate was settled and the supernatant was separated. Here again 87 kg of toluene and TiCl ₄ 52 kg and 4.2 kg of diisobutyl phthalate were added thereto. The temperature of the reactor was raised to 120 ° C., and the reaction was maintained for 1 hour. After the reaction, the mixture was allowed to stand for 30 minutes to separate the supernatant, and 80 kg of toluene and 76 kg of TiCl ₄ were injected again, followed by reaction at 100 ° C. for 30 minutes. After the reaction was allowed to stand for 30 minutes, the supernatant was separated, and 65 Kg of hexane was added thereto, followed by stirring while maintaining the temperature of the reactor at 60 ° C. for 30 minutes. The stirring was stopped and the supernatant was separated after standing for 30 minutes. Hexane was added to the remaining catalyst slurry layer and washed six times in the same manner to prepare a final solid complex titanium catalyst. Ti content of the prepared catalyst was 2.8% by weight.

Step 4: Prepolymerization

     The high-pressure reactor with a capacity of 150 L was washed with hexane, and then 360 g of the catalyst obtained in step 3, 33 kg of hexane, 730 mmol of diethylaluminum chloride, 730 mmol of diethylaluminum chloride, dicyclopentyldimethoxysilane and cyclohexyl were added to the reactor maintained at 5 ° C. Methyldimethoxysilane and vinyltriethoxysilane were added in the order of 30 mmol, respectively, stirred for 30 minutes, and then polymerized for 6.3 hours while controlling the polymerization temperature not to exceed 15 ° C while flowing 0.4 kg / h with propylene. In the prepolymerization catalyst thus obtained, the amount of polymer polymerized around the catalyst was 7 g per 1 g of catalyst.

[Continuous Multistage Polymerization Reaction]

Propylene homopolymerization was carried out in a continuous multistage polymerization reactor system for performance evaluation of the prepared prepolymerization catalyst. The polymerization reaction system used consists of two liquid phase slurry reactors and two gas phase fluidized bed reactors. Each reactor was purged with nitrogen to remove moisture and oxygen in the reactor, and two liquid phase reactors injected 36 kg of liquid propylene, and one gas phase reactor injected about 40 kg of seed powder. The large cycle operation of the entire reactor system was carried out for 4 hours. Into the first stage liquid slurry reactor, triethylaluminum and the external electron donor were continuously injected with the same electron donor as used in the previous prepolymerization step, and after 1 hour, the prepolymerized catalyst prepared above was 1 g based on the solid complex titanium catalyst. The polymerization was continued by injecting at a rate of / hr. In the fourth gas phase reactor, a copolymerization reaction was performed to produce an impact copolymer. The powder produced was weighed every hour through the plant's drying system. Xylene solubles, flexural modulus (FM) and Izod impact strength of the powder were analyzed. The results are shown in Table 2.

Example  8

In step 4 of the preparation of the prepolymerization catalyst (a) of Example 7, a prepolymerization catalyst was prepared using 50 mmol of dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, and vinyltriethoxysilane, respectively. The polymerization was carried out under the same conditions as in 7. The results are shown in Table 2.

Example  9

In step 4 of preparing the prepolymerization catalyst (a) of Example 7, a prepolymerization catalyst was prepared using 30 mmol of octyltriethoxysilane instead of vinyltriethoxysilane, and polymerization was carried out under the same conditions as in Example 7. . The results are shown in Table 2.

Example  10

In step 4 of preparing the prepolymerization catalyst (a) of Example 7, a prepolymerization catalyst was prepared using 30 mmol of isodecyltriethoxysilane instead of vinyltriethoxysilane, and polymerization was carried out under the same conditions as in Example 7. It was. The results are shown in Table 2.

Comparative example  4

In step 4 of preparing the prepolymerization catalyst (a) of Example 7, a prepolymerization catalyst was prepared without using a silane compound, and polymerization was carried out under the same conditions as in Example 7. The results are shown in Table 2.

Comparative example  5

In step 4 of preparing the prepolymerization catalyst (a) of Example 7, a prepolymerization catalyst was prepared using only 80 mmol of cyclohexylmethyldimethoxysilane instead of the three silane compounds, and polymerization was performed under the same conditions as in Example 7. Was carried out. The results are shown in Table 2.

Comparative example  6

In step 4 during the preparation of the prepolymerization catalyst (a) of Example 7, a prepolymerization catalyst was prepared using only 150 mmol of cyclohexylmethyldimethoxysilane instead of the three silane compounds, and polymerized under the same conditions as in Example 7. Was carried out. The results are shown in Table 2.

TABLE 2

Polymerization result

Polymerization Activity (kgPP / gCat) Xylene Melt (%) Flexural Modulus (kg / ㎠) Izod impact strength at 23 ℃ (kgcm / cm) Example 7 16 1.7 12,800 7.5 Example 8 14 1.5 13,000 7.2 Example 9 17 1.7 12,700 7.5 Example 10 15 1.6 12,800 7.5 Comparative Example 4 14 2.4 11,800 7 Comparative Example 5 16 1.7 12,500 7.5 Comparative Example 6 12 1.5 12,700 7.5

* Flexural modulus measurement is in accordance with ASTM D790.

* Izod impact strength is measured according to ASTM D256.

According to the olefin production method of the present invention, the content of xylene melt is low, the rigidity and polymerization activity is higher, thereby increasing the productivity of the multi-stage continuous polymerization process.

Claims (7)

Prepolymerization catalyst obtained by polymerizing a high molecular weight monomer on the surface of a catalyst by reacting a Ziegler-Natta-based solid complex titanium catalyst with an olefin monomer in the presence of at least two aluminum compounds containing alkylaluminum and aluminum halides and electron donors ( a), a polyolefin production method for polymerizing or copolymerizing olefins in a multistage continuous polymerization reactor in the presence of a catalyst system consisting of an organometallic compound (b) and an external electron donor (c) of a Group I or Group III metal of the periodic table. The method of claim 1, wherein the aluminum compound is at least one selected from triethylaluminum, tributylaluminium, triisoprenyl aluminum and ethyl aluminum sesquiethoxide and ethyl aluminum sesquichloride, ethyl aluminum dichloride, A method for producing a polyolefin, characterized in that at least one aluminum compound selected from propyl aluminum dichloride and butyl aluminum dibromide. The polyolefin production method according to claim 1 or 2, wherein the aluminum compound is used in an amount of 1 to 100 mol per mol of titanium atoms in the solid complex titanium catalyst. The method of claim 1 or 2, wherein the electron donor is at least one organosilicon compound having an alkoxy group. 5. The organosilicon compound of claim 4, wherein the organosilicon compound has a melt index (MFR) of less than 5, more than 5 to 20, and more than 20 of the homopolymer polymerized using each organosilicon compound under the same polymerization conditions. A method for producing a polyolefin, characterized by using a mixture of more than one species. The polyolefin production method according to claim 1 or 2, wherein the organometallic compound (b) is an organoaluminum compound. The polyolefin production method according to claim 1 or 2, wherein the external electron donor (c) is an alkoxysilane compound.