KR100242208B1 - Metallocene catalysts and process for preparing polypropylene - Google Patents

Abstract

The present invention relates to a method for producing a polypropylene capable of controlling the properties and molecular weight distribution by sequentially adding a metallocene catalyst and a Ziegler-Natta catalyst.

The present invention is to sequentially add a metallocene catalyst and a Ziegler-Natta catalyst in the production of polypropylene having various molecular weights, molecular weight distribution, melting point by polymerization, and as a co-catalyst of the Ziegler-Natta catalyst of the general formula R _n 1 or a mixture thereof selected from organoaluminum compounds or aluminoxanes represented by AlY _3-n (wherein R is a hydrocarbon having 1-20 carbon atoms, Y is halogen and 0 ≦ _n ≦ ₃ ) It is characterized by using aluminoxane as a cocatalyst of the metallocene catalyst.

Polypropylene produced by the present invention has a variety of properties and molecular weight distribution, can be molded and used in a variety of products such as plates, films, containers, fibers.

Description

Method for producing polypropylene having various distributions by sequential addition of metallocene catalyst and Ziegler-Natta catalyst

The present invention relates to a method for producing a polypropylene capable of controlling the properties and molecular weight distribution by sequentially adding a metallocene catalyst and a Ziegler-Natta catalyst, and more specifically, a Ziegler-Natta catalyst and a metallocene catalyst In use, the present invention relates to a method for producing polypropylene having different properties and molecular weight distribution by varying the order of administration during polymerization, the polymerization time of each catalyst, and the use of a promoter.

The Ziegler-Natta catalyst system refers to a catalyst system composed of a combination of a main catalyst composed mainly of transition metal compounds, a cocatalyst composed of an organic metal compound, and an electron donor. This catalyst has been developed in the direction of improving polymerization activity and stereoregularity until now, and the properties and molecular weight distribution of the resulting polypropylene are determined when its components and production methods are determined. Therefore, in order to change the properties and molecular weight distribution of the polypropylene, it should be accompanied by a change in the constituents and a polymerization method in the preparation of the catalyst.

Metallocene catalysts are a type of organometallic compound and are known as homogeneous catalysts. Metallocene catalysts generally exhibit interactivity and have a single polymerization activity so that the M _w / M _n value of the polymer is as narrow as about 2 and the co-unit distribution of the copolymer is uniform. In particular, it is known to enable the polymerization or copolymerization of cycloolefins such as cyclopentene and norborene. Metallocene catalysts exhibit various changes in the stereospecificity, molecular weight, catalytic activity, etc. of the polymer depending on the structure of the ligand in olefin polymerization. The metallocene catalyst is largely composed of four parts of a central metal, π ligand, bridge structure, and σ ligand. The polymerization mechanism of olefin is affected by the structural change of the metallocene catalyst and the electronic and steric effect by the change of the core metal and ligand, and thus the activity of the catalyst, molecular weight and stereospecificity of the polymerized polymer are changed. .

The molecular weight and molecular weight distribution of the polymer are important factors in determining the physical, mechanical and rheological properties of the polymer. Molecular weight has a great influence on the mechanical properties of the polymer, while molecular weight distribution is the center of polymer design because it controls the melt processability as a factor controlling the rheological properties of the polymer. In general, when the molecular weight of the polyolefin is large, it is known that the toughness, rigidity, stress cracking resistance due to the environment is increased, but processing is difficult due to the high melt viscosity. The molecular weight distribution requires different properties depending on the type of polymer to be produced. In general, the polymer having a narrow molecular weight distribution has a poor flow rate in the processing process because the melt viscosity decreases less with the shear rate than the polymer having a wide molecular weight distribution. Therefore, narrower molecular weight distribution is required for fiber extrusion and thin sheet injection, and wider molecular weight distribution is required for general injection and extrusion. Therefore, in order to satisfy various processing conditions while maintaining the physical properties of the polymer, it is necessary to control the molecular weight distribution. In particular, by having a molecular weight distribution in the form of bimodal distribution it is possible to increase the mechanical strength to the high molecular weight portion and to control the processability to the low molecular weight portion.

Various methods are used to control the molecular weight distribution of the polymer.

Firstly, a multistage reactor is used. This method is a method that polymerizes a polymer while sequentially passing through reactors having various polymerization conditions, thereby synthesizing a polymer having a wide molecular weight distribution, which is widely applied in various processes. However, this method has to go through several reactors, so there are problems in efficiency and economics. The second method is to blend polymers of various molecular weights after polymerization. This method also requires an additional cost after the polymerization, and may have a compatibility problem due to a difference in melt viscosity between blending polymers. The third method is to produce polypropylene having desired properties and molecular weight distribution from the polymerization stage by manipulating the catalyst in a single reactor.

Metallocene catalyst can change various stereoregularity, melting point, crystallinity, etc. of the polymer finally produced by the change of structure and polymerization conditions. Accordingly, by using various types of metallocene catalysts mixed with Ziegler-Natta catalysts, it is expected that a product having desired properties such as molecular weight distribution and stereoregularity can be produced.

When processing requires an atactic polypropylene moiety, it is possible to control the stereoregularity of the final polymer produced by polymerizing polypropylene using a mixed catalyst system in which a catalyst producing a polymer having no stereoregularity is mixed. When various molecular weight distributions are required, it is thought that the molecular weight distribution can be controlled by mixing a metallocene catalyst and a Ziegler-Natta catalyst which produce polymers of different molecular weights. On the other hand, the difficulty in processing due to the narrow molecular weight distribution of the metallocene catalyst and the improved adaptability to the process of the metallocene catalyst are expected to be improved by mixing with the Ziegler-Natta catalyst.

The methods reported in the existing literature for the control of molecular weight distribution are intended to form crops of multiple metals using several metals in the synthesis of catalysts, and each Gag is intended to improve molecular weight distribution by manipulating the active site of catalytic metal components. . However, in such a method, the production process and the catalyst component of the catalyst are complicated, so that it is difficult to find reproducibility as well as analysis of the catalyst.

Recently, various mixed catalyst systems using metallocene catalysts have been attempted in order to supplement the disadvantages of metallocene catalysts and to prepare catalyst systems capable of controlling molecular weight distribution. US Patent No. 4,975, 403, US Pok. US Patent 4,701,432, US Patent 5,183,867, European Patent 436328, Japanese Patent Laid-Open No. 5-255435, etc., a method of simultaneously introducing a Ziegler-Natta active site and a metallocene catalyst from the step of preparing the catalyst, European Patent 585512A1 The following describes a method of introducing a metallocene catalyst to a Ziegler-Natta catalyst through a ligand exchange reaction. However, these methods have difficulty in securing the reproducibility as well as analyzing the catalyst because a new catalyst has to be prepared. Japanese Patent Application Laid-open No. Hei 4-85306 discloses a method for reforming a Ziegler-Natta catalyst to a metallocene catalyst, but it is not easy to control molecular weight distribution and properties. U.S. Patent 5,395,810, U.S. Patent 5,242,876, Japanese Patent Application Laid-Open No. 5-255431, European Patent 536104A1, European Patent 436399A2, Korean Patent Publication No. 94-23934, etc. The polymerization of olefins is presented. However, in these patents, only the polymerization by a mixed catalyst of two catalysts is presented, and no specific reference is made to the selection of polymerization conditions or the selection of organometallic compounds for the control of molecular weight distribution and properties.

The present invention is to solve the problems of the prior art, in the use of Ziegler-Natta and metallocene catalyst to produce a polypropylene having the desired properties and molecular weight distribution, the two catalysts are added sequentially, and the cocatalyst By using an organoaluminum compound or aluminoxane as appropriate, and controlling the properties and molecular weight distribution of the final polypropylene to be polymerized by changing the polymerization time of the catalyst and the like and thereby improving the processability and physical properties The purpose is to provide.

In the present invention, a metallocene catalyst and a Ziegler-Natta catalyst are sequentially added, and an organoaluminum compound or aluminoxane or a mixture thereof is suitably used as a promoter, and polymerization time, external electron donor administration, etc. are controlled. do.

Hereinafter, a method for preparing a polypropylene whose molecular weight distribution and properties can be controlled by the sequential addition of the Ziegler-Natta catalyst and the metallocene catalyst according to the present invention will be described in detail.

In the present invention, the term "polymerization" may be used to include not only homopolymerization but also copolymerization, and the term "polymer" may be used to mean not only homopolymer but also copolymer.

As used herein, the term "polypropylene" refers to a block or irregular copolymer of propylene homopolymers or other α-olefins having 2 to 18 carbon atoms. Examples of other α-olefins include ethylene, 1-butene, 1-pentene, 1-hexene and 1-octene. The amount of α-olefin copolymerized with propylene is up to 0-50 mol% per mole propylene.

In the present invention, "sequential addition" refers to a time or sequence in which a single or mixed catalyst of Ziegler-Natta catalyst and metallocene catalyst is combined in a single reactor or in one or more series connected polymerization reactors or in one or more parallel connected polymerization reactors. In the case of reactors connected in parallel, this means that there is a spatial difference in the addition of the catalyst. Examples of sequential additions include, but are not limited to, a method in which the synthesis of polypropylene by addition of at least one Ziegler-Natta catalyst is performed before or after the synthesis of polypropylene by addition of at least one metallocene catalyst. And how to do it.

The Ziegler-Natta catalyst system is characterized in that it is formed of a [A] transition metal compound, an [A] organoaluminum compound as a cocatalyst, and an optionally [C] electron donor.

The catalyst component [A] is of the general formula MR ⁺ _x , wherein M is a metal, R is halogen or hydrocarbyloxy and x is the oxidation number of the metal. Preferably M is a group IV B or V B or VI of the periodic table. A metal belonging to group B , more preferably a metal of group IV B of the Periodic Table, even more preferably titanium, R is preferably chlorine or bromine or alkoxy or phenoxy and more preferably chlorine or e. Oxy, and more preferably, chlorine.), And a mixture of transition metal compounds may be used, in which case the number of transition metal compounds is not limited.

The transition metal compound may or may not be supported. If supported, a chemically inert solid is used which does not cause a chemical reaction with a Ziegler-Natta catalyst or a metallocene catalyst.

Cocatalyst component [B] is an organoaluminum compound represented by the general formula R _n AlY _3-n , wherein R is a hydrocarbon having 1-20 carbon atoms, Y is halogen, and 0 ≦ _n ≦ ₃ , or Aluminoxane or mixtures thereof. Specific examples of the aluminoxane include general formula (I) and general formula (II).

A compound represented by the above may be exemplified, and in addition, it may be a ladder structure, a lattice structure, an oxobridged cluster structure, or the like. In such aluminoxane, R is a hydrocarbon such as methyl group, ethyl group, propyl group, butyl group, etc., m is 2 or more, preferably an integer of 5-40.

Said promoter component] B] is not added at the time of preparation of a catalyst, but is added at the time of superposition | polymerization.

The subcatalyst component [C] can be classified into an internal electron donor present in the catalyst as an electron donor and an external electron donor administered together with a promoter during polymerization. The internal electron donor may be added during the preparation of the catalyst to exemplify the phthalate-based compound, and specifically, to diisobutyl phthalate, dinormalbutyphthalate, dioctyl phthalate, or a mixture thereof.

The external electron donor is specifically represented by the following structural formula (III)

(Wherein R ¹ , R ³ is an alkoxy group or arylalkyl group such as methoxy, ethoxy, butoxy, R ² is an alkyl group such as methyl, ethyl, butyl or an alkoxy group such as methoxy, ethoxy, butoxy or arylalkyl) , R ⁴ is an aromatic group such as phenyl, atracenyl, naphthalenyl or a cycloaliphatic group such as cyclopentyl, cyclohexyl, cyclooctyl, and X is carbon, silicon or the like. This is mainly used. The external electron donor is used in an amount of 0.001-50 mol%, preferably 0.01-20 mol%, more preferably 0.02-10 mol%, per mole of promoter. If the content is less than 0.001 mol%, the problem of improvement of stereoregularity does not occur, and if it is used at an extremely high amount of 50 mol%, it no longer affects stereoregularity.

On the other hand, the metallocene catalyst system is characterized in that it is formed of [D] transition metal compound, [E] organoaluminum compound and optionally [F] water as a promoter.

The catalyst component [D] is a transition metal compound, specifically a compound containing a transition metal selected from the group consisting of titanium, zirconium and hafnium of Group IV B of the periodic table, preferably a group having a conjugated? Formula (IV) as transition metal compound

(Wherein R ¹ , R ³ is a cycloalkadienyl group or an aryl group, R ³ , R ⁴ is a cycloalkadienyl group, an anil group, an indenyl group, a fluorel group, aralalkyl, alkoxy or a halogen atom or hydrogen, and M is Transition metal, X may be a lower alkyl group, alkenyl group, chiral group and Si, S, N, O, P, etc.) or an ionizing ionic compound represented by the following formula (V)

(Where, [C ^+] is the cation is, [A ^-]. Is an anion) is used.

In the formula (IV), the cycloalkadienyl group includes a cyclopentadienyl group, methylcyclopentadienyl group, ethylcyclopentadienyl group, t-butylcyclopentadienyl group, dimethylcyclopentadienyl group, pentamethylcyclopentadienyl group, and phenyl Ligands such as cyclopentadienyl groups, indenyl groups, tetrahydroindenyl groups, fluorenyl groups or substituted ligands can be exemplified.

Examples of the aryl group include a phenyl group and a tolyl group. Examples of the aryl group include a benzyl group and a neophil group. Examples of the alkoxy group include a methoxy group, propoxy group, isopropoxy group and butoxy group. Can be. Fluorine, chlorine, etc. can be illustrated as a halogen atom, A methyl group, an ethyl group, a propyl group, isopropyl group, a butyl group, an ethylene group, a dimethyl silicone group etc. can be illustrated as a lower alkyl group and an alkenyl group.

In addition to the anion in the formula (V) is _{[B (C 6 F 5)} 4] - and the like can be given ^{_{-, [B (C 6 H}} 5) 4].

However, each component is not limited to this example.

The transition metal compound may or may not be supported. In the case of the supporting metal compound, a chemically inert solid which does not cause a chemical reaction with a Ziegler-Natta catalyst or a metallocene catalyst should be used.

The cocatalyst component [E] is an organoaluminum compound, which has the same structure as the catalyst component [B] in the Ziegler-Natta catalyst, and is also administered during the polymerization of propylene. Catalyst component [F] is water, and this water is water contained in the compound or salt used when preparing the catalyst component (E) or the water which melt | dissolved in the polymerization solvent.

In the present invention, polypropylene is prepared by a method of polymerization by sequentially adding a single or a mixture of a Ziegler-Natta catalyst and a metallocene catalyst. When the catalysts are added sequentially, the properties of polypropylene change as the polymerization time of each catalyst changes. As the polymerization time by the metallocene catalyst increases, the catalytic activity increases, but the stereoregularity and molecular weight of the polypropylene decreases. The longer the polymerization time by the Ziegler-Natta catalyst, the lower the activity, but the stereoregularity and molecular weight increase.

In preparing the polypropylene by the above method, the polymerization reaction can be carried out in a gas phase, a liquid phase, or a solution phase. When performing a polymerization reaction in a liquid phase, a hydrocarbon solvent may be used and olefin itself may be used as a solvent. Hydrocarbons used as solvents include butane, isobutane, pentane, hexane, heptane, octane, nonane, decane dodecane, hexadecane, octadecane and other aliphatic hydrocarbons, cyclopentane, methylcyclopentane, cyclohexane, cyclooctane, etc. And alicyclic hydrocarbons, aromatic hydrocarbons such as benzene, toluene and xylene, and petroleum such as gasoline, kerosene and diesel. The external electron donor may or may not be added, and the stereoregularity increases when the external electron donor is added.

In addition, the molecular weight and molecular weight distribution of the polypropylene can be controlled by adding or not adding hydrogen during the polymerization of the polypropylene. When hydrogen is added, the molecular weight decreases, whereas the value of the molecular weight distribution is reduced. Becomes high.

On the other hand, polymerization temperature is -50-350 degreeC normally, Preferably it is the range of 0-310 degreeC. If it is below -50 ° C, the polymerization activity is not good, and if it exceeds 350 ° C, the stereoregularity is poor, which is not good. The polymerization pressure is usually at atmospheric pressure-250 kg / cm 2, preferably atmospheric pressure-200 kg / cm 2 and if it exceeds 250 kg / cm 2, it is not preferable from an industrial and economical point of view. The polymerization reaction can be carried out by any of batch, semicontinuous and continuous methods.

In addition, during the polypropylene polymerization, heat stabilizers, light stabilizers, flame retardants, carbon blacks, pigments, antioxidants, and the like, which are commonly added, may be added. Furthermore, polypropylene having a variety of properties and molecular weight distribution according to the present invention can be mixed with low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene, polybutene, EP (ethylene / propylene) rubber and the like.

Hereinafter, although an Example demonstrates this invention, this invention is not limited by these Examples.

In the following examples, thermal properties, regularity, molecular weight, molecular weight distribution, etc. were measured by the following method.

(1) thermal properties

Thermal properties such as melting point (Tm), temperature crystallization temperature (Ce), and glass transition temperature (Tg) of the polymer were investigated by differential scanning calorimetry (DSC), and the instrument was DSC7 from Perkin Elmer. The sample was weighed to 5.5 ± 9.5 mg and placed in an aluminum pan, and then subjected to the first irradiation at a temperature rising rate of 20 ° C./min from 50 ° C. to 200 ° C. under a 1.2 kg / cm 2 nitrogen stream, and then to 20 ° C. to 50 ° C. T _mc was measured while cooling at a rate of / min. T _m and heat of fusion (Δ11 _m ) were measured while performing secondary irradiation at a temperature increase rate of 20 ° C./min to 50 ° C.-200 ° C. The temperature and the heat of fusion were corrected by the standard method using high purity indium. The Tg of polypropylene was irradiated while rapidly cooling to -60 ° C at a rate of 100 ° C / min after the first temperature increase, and then again at a rate of 20 ° C / min. The crystallinity of polypropylene was calculated by dividing the heat of fusion of each polymer by 188 J / g, the standard heat of fusion.

(2) I.I: Isotacticity Index

Stereoregularity of polypropylene was performed with an isotacticity index (I. I.), an amount insoluble in boiling heptane. The polymer was previously treated with a heat stabilizer to prevent degradation during analysis. A certain amount of completely dried polymer was quantitatively placed in a timing filter and extracted with heptane in a Soklet type extraction apparatus. The extraction time was calibrated to 5 hours. After extraction, the remaining polymer was collected and dried in vacuo at 80 ° C. After quantitative determination, the weight was measured. Without lead, lead is the weight ratio of the polymer and the original polymer. I was obtained.

(3) Molecular weight and molecular weight distribution

The molecular weight and molecular weight distribution of the polymer were determined using gel permeation chromatography (GPC). GPC used PL-210 GPC of Polymer Laboratory Co., Ltd. and was measured by RI detector using 1,2,4-trichlorobenzene as a solvent at 160 ° C. The calibration curve obtained from polystyrene with narrow molecular weight distribution was corrected again with a standard polyethylene sample to obtain a molecular weight calibration curve. Using this, the number average molecular weight (M _n ), weight average molecular weight (M _w ) and molecular weight distribution (M _w / M _n ) and the like.

Production Example

* Ziegler-Natta catalyst manufacture

Under a nitrogen atmosphere, a certain amount of toluene and 100 zirconia beads 3 mm in diameter were added to a 200 ml stainless steel container. Miso dichloride, titanium tetrachloride, and diisobutyl phthalate and dioctyl phthalate were added to the internal electron donor, followed by ball-milling at room temperature for 72 hours. The Ziegler-Natta catalyst thus formed was washed five times with toluene and then dispersed in a certain amount of toluene. The catalyst thus prepared was named MgCl ₂ -Ti catalyst. The content of Ti in the supported catalyst was 1.10 wt%.

* Preparation of Metallocene Catalyst

Aldrich's rac-ethylenebis (indenyl) zirconium (4) dichloride catalyst, ie rac-Et (Ind) ₂ ZrCl ₂ (EIZ) catalyst, was used.

Example 1

The polymerization of propylene was carried out at atmospheric pressure using a vitreous reactor. The reactor was decompressed to a vacuum of 3 torr or less and charged with nitrogen of high purity five times. After adjusting the temperature of the reactor to 40 ° C. constantly, 200 ml of toluene as a solvent was quantified by a syringe while nitrogen was blown to prevent backflow of air. When the temperature is kept constant, the gas unit (propylene) is flowed into the solvent until it is saturated while checking with a flow controller. Then, EIZ catalyst and Ziegler-Natta, which are metallocene catalysts having polymerization conditions and metal contents as shown in Table 1 below, MgCl ₂ -Ti catalyst was added sequentially and aluminoxane was added as a cocatalyst to polymerize propylene. First, EIZ catalyst was added and 10 minutes later, MgCl ₂ -Ti catalyst was added to polymerize. After the polymerization was carried out for one time with one catalyst, another catalyst was added, and the polymerization was performed for the remaining time, and the total polymerization time was 1 hour. The polymerization was terminated by injecting 10 ml of ethanol. The reaction product was stirred for about 24 hours in about 5% by weight HCl- methanol and then again for 24 hours in clean methanol. The filter paper was then filtered and vacuum dried at about 80 ° C. for at least 24 hours to obtain the final polymerized product. The overall activity value of the catalyst was determined in kgpolymer / (mol metal.mol-monomer.h) from the weight of the final product.

Physical property measurement results are shown in Table 1 below.

Comparative Example 1

The Ziegler-Natta catalyst or the metallocene catalyst was carried out in the same manner as in Example 1 except that each was used alone according to the polymerization conditions shown in Table 1 below. When using a Ziegler-Natta catalyst or a metallocene catalyst alone, only the same aluminoxane as in Example 1 was used as a promoter. Physical property measurement results are shown in Table 1 below.

As a result, Example 1 had two melting points compared to Comparative Example 1, and the catalytic activity was about the middle value of the Ziegler-Natta catalyst and the metallocene catalyst.

Example 2

Next, the Ziegler-Natta catalyst and the metallocene catalyst having the same contents as in Table 2 were administered in the order shown in Table 2, and triethylaluminum was polymerized when polymerizing with the Ziegler-Natta catalyst, and aluminoxane was polymerized with the metallocene catalyst. It carried out similarly to Example 1 except having superposed | polymerized using it as a promoter. The total polymerization time was similarly 1 hour, and the results of the physical properties are shown in Table 2 below.

Comparative Example 2

The same process as in Example 2 was carried out except that the Ziegler-Natta catalyst and the metallocene catalyst were sequentially added to each other without polymerization. In case of polymerization alone using Ziegler-Natta catalyst, polymerization was carried out using triethylaluminum as cocatalyst and aluminoxane as cocatalyst in polymerization using metallocene catalyst alone. 2 is shown.

Example 2 had two melting points compared to Comparative Example 2, and the catalytic activity was about the middle value of each of the Ziegler-Natta and metallocene catalysts. The molecular weight also showed a moderate value, but the molecular weight distribution was increased in each case. Polypropylene was controlled according to the change of polymerization time by each catalyst. The longer the polymerization time by the metallocene catalyst, the lower the stereoregularity and molecular weight of the polypropylene and the longer the polymerization time by the Ziegler-Natta catalyst. Stereoregularity and molecular weight increased.

Example 3

As in Example 2, the polymerization was carried out using triethylaluminum as a co-catalyst when polymerizing with a Ziegler-Natta catalyst and aluminoxane as a co-catalyst when polymerizing with a metallocene catalyst. The donor cyclohexyldimethoxymethylsilane was administered by 0.2 times the amount of triethylaluminum. The total polymerization time was similarly 1 hour, and the results of the physical properties are shown in Table 3 below.

Comparative Example 3

Except for polymerization using only Ziegler-Natta catalyst alone, it was carried out in the same manner as in Example 3, the physical properties are shown in Table 3 below.

As a result of the experiment, when the external electron donor was added as in Example 3, it was found that the stereoregularity was increased as compared with Example 2 which was not added.

Example 4

The hydrogen was carried out in the same manner as in Example 2 except that a predetermined ratio of hydrogen and gas units were mixed in a mixing chamber so that the partial pressure of hydrogen was 0.27 atm. In the case of the polymerization with hydrogen, the concentration of the monomer dissolved in the solvent was calculated by converting the partial pressure of ethylene, and the measurement results of the physical properties are shown in Table 4 below.

[Comparative Example 4]

A Ziegler-Natta catalyst or a metallocene catalyst was added in the same manner as in Example 4 except that the polymerization was carried out using a single catalyst instead of polymerization. The results of the measurement of the physical properties are shown in Table 4 below.

In the case of Example 4 in which hydrogen was added, the molecular weight was lower than that in Example 2 in which hydrogen was not added, and the value of the molecular weight distribution was higher than in the case where no hydrogen was added.

As in the present invention, a Ziegler-Natta catalyst and a metallocene catalyst are sequentially added and polymerized using an organoaluminum compound or aluminoxane as a cocatalyst. The produced polypropylene has various properties and molecular weight distribution.

In addition, in the present invention, the stereoregularity may be increased by adding an external electron donor, or the molecular weight may be reduced by adding hydrogen, and the stereoregularity and molecular weight may be controlled by controlling the polymerization time by the catalyst.

Polypropylene according to the present invention can be molded and used in a variety of products such as plates, films, containers, fibers.

Claims (4)

In the production of polypropylene having various molecular weights, molecular weight distribution, melting point and stereoregularity by polymerization, the polymerization temperature and atmospheric pressure are 0-310 ° C using aluminoxane as a metallocene catalyst and cocatalyst having the following structure: After polymerization for 10% to 80% of the normal polymerization time under a polymerization pressure of ˜250 kg / cm ₂ , MR ⁺ x supported on MgCl ₂ , where M is a metal, R is halogen or hydrocarbyloxy, x Ziegler-Natta catalysts and cocatalysts, which are transition metal compounds represented by the oxidation number of a metal, are represented by the general formula R _n AlY _3-n (where R is a hydrocarbon having 1 to 20 carbon atoms, and Y is halogen , 0 ≦ n ≦ 3) or a mixture of organoaluminum compounds or aluminoxanes, or a mixture thereof, and polymerize for 20% to 90% of the polymerization time under the same conditions, thereby having various molecular distributions. Pro Process for preparing alkylene. (Wherein R ¹ , R ² is a cycloalkydienyl group or an aryl group, R ³ , R ⁴ is a cycloalkadienyl group, an aryl group, indenyl group, fluorel group, aralalkyl, alkoxy or a halogen atom or hydrogen, M is a transition metal, X is a lower alkyl group, an alkenyl group, a chiral group and Si, S, N, O, P, etc.) The method of claim 1, wherein an external electron donor is added during polymerization to increase stereoregularity. The method for producing polypropylene according to claim 1, wherein the molecular weight is reduced by adding hydrogen during polymerization and the value of the molecular weight distribution is increased. The polypropelin prepared according to claim 1 is a homopolymer of propylene or an irregular copolymer of α-olefin and propylene having 2 to 18 carbon atoms or a block copolymer of α-olefin and propylene having 2 to 18 carbon atoms. Method for producing a polypropylene, characterized in that.