KR20180040405A - Process for preparing polypropylene - Google Patents

Abstract

The present invention relates to a production method of polypropylene, and more specifically, to a production method of polypropylene which uses a metallocene supported catalyst prepared by specifying the order of carrying a promoter and a catalyst precursor on a carrier, and particularly the carrying condition of the promoter. According to the production method of the present invention, polypropylene with a low molecular weight can be produced without preliminary polymerization as in conventional methods by increasing the molecular weight reduction according to the addition of hydrogen.

Description

PROCESS FOR PREPARING POLYPROPYLENE [0002]

The present invention relates to a method for producing polypropylene using a metallocene supported catalyst which is suitable for producing a low molecular weight polypropylene with a large decrease in molecular weight due to the introduction of hydrogen.

Unlike the heterogeneous Ziegler-Natta catalyst, the homogeneous metallocene catalyst has the advantage of controlling the microstructure of the polymer produced by the metallocene catalyst. However, the synthesis of the metallocene catalyst is difficult, and the Tm of the Ziegler-Natta catalyst is low, which is a necessity to overcome.

On the other hand, the ansa-metallocene compound is an organometallic compound containing two ligands connected to each other by a bridge group. The bridge group prevents the rotation of the ligand, Activity and structure are determined.

Such metallocene compounds are used as catalysts for the production of olefinic homopolymers or copolymers. In particular, it is known that metallocene compounds containing cyclopentadienyl-fluorenyl ligands can produce high molecular weight polyethylene, thereby controlling the microstructure of polypropylene. It is also known that a metallocene compound containing an indenyl ligand can produce a polyolefin having excellent activity and improved stereoregularity.

In addition, the metallocene catalyst for producing polypropylene is subjected to a carrying process in order to be applied to bulk polymerization. When the carrying process is difficult and the loading is not performed well, problems such as fouling occur in the process.

Generally, the metallocene supported catalyst undergoes a pre-polymerization process before the polymerization in order to avoid process problems. In such a case, it is difficult to produce a low molecular weight polypropylene and the process is complicated.

It is an object of the present invention to provide a method of producing a low molecular weight polypropylene without pre-polymerization before the polymerization by using a supported metallocene catalyst produced by a supported method, .

The present invention comprises a step of polymerizing a propylene monomer while introducing a hydrogen gas in a batch form before polymerization so as to be 100 to 2,000 (mol.ppm) under a metallocene supported catalyst,

The metallocene supported catalyst may contain,

a) supporting an alkylaluminoxane-based co-catalyst on a carrier; And

b) adding a catalyst precursor solution containing the metallocene compound of formula (1) and a solvent to the product carrying the alkylaluminoxane co-catalyst, and reacting the mixture to react the metallocene compound with the carrier on which the alkylaluminoxane- , The method comprising the steps of:

Wherein the step a) is carried out by slowly injecting an alkylaluminoxane-based co-catalyst into a carrier and stirring at a temperature of 100 ° C to 150 ° C for 2 hours to 12 hours,

A process for the preparation of polypropylene is provided:

[Chemical Formula 1]

In Formula 1,

M ¹ is a Group 4 transition metal;

X is the same or different halogen;

A is a bridge group connecting an indenyl group as an element of Group 14;

R ¹ is alkyl, alkenyl, alkylaryl, arylalkyl or aryl of 1 to 20 carbon atoms;

R ² is hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl;

R ³ , R ^{3 '} , R ⁴ , R ^4' , R ⁵ , R ^{5 '} , R ⁶ , R ^6' , R ⁷ , R ^{7 '} , R ⁸ and R ^8' Hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl;

n is an integer of 1 to 20;

Wherein R ¹ and R ² are each alkyl having 1 to 4 carbon atoms; R ³ and R ^{3 '} are each alkyl, alkenyl, or arylalkyl having 1 to 20 carbon atoms; R ⁴ and R ^{4 '} are each aryl or alkylaryl of 1 to 20 carbon atoms; n is an integer from 1 to 6, M is zirconium, X is Cl, and A may be carbon, Si, or germanium.

The step a) is preferably carried out by slowly introducing an alkylaluminoxane-based co-catalyst into the carrier at room temperature and stirring at a temperature of 120 ° C to 150 ° C for 2 hours to 5 hours.

After the step a), it is preferable to perform the step of removing the upper layer solution from the reaction solution and washing the remaining reaction product with the solvent at least twice.

The step b) may be carried out at a temperature of 50 ° C to 90 ° C for 4 hours to 6 hours.

Further, after the step b), the step of removing the upper layer solution from the reaction solution and decanting the remaining reaction product using the solvent may be repeated at least twice.

The carrier may include at least one member selected from the group consisting of silica, silica-alumina, and silica-magnesia.

The alkylaluminoxane-based co-catalyst may be at least one member selected from the group consisting of methyl aluminoxane, ethyl aluminoxane, propyl aluminoxane, and butyl aluminoxane.

The step of polymerizing the propylene monomer may include slurry polymerization, bulk polymerization, or gas phase polymerization in which the reaction is carried out at a temperature of 25 to 500 ° C and a pressure of 1 to 100 kgf / cm ² for 10 minutes to 24 hours

The metallocene supported catalyst may have a catalytic activity of 10 kg / gCat · hr or more, which represents the produced weight of the polymer obtained per unit weight of the catalyst per unit time.

The polypropylene according to the present invention may have an MFR of 2 to 1,000.

According to the present invention, the metallocene supported catalyst is prepared by specifying the order of carrying the promoter and the catalyst precursor on the carrier and the supporting condition of the co-catalyst, and then adjusting the amount of hydrogen supplied during the polymerization of the propylene monomer, The decrease in the molecular weight can be increased with the introduction of hydrogen without preliminary polymerization. Therefore, the present invention has the effect of easily producing not only polypropylene having a molecular weight of 200,000 or more but also polypropylene having a low molecular weight of less than 200,000.

1 shows the results of GPC analysis of homopolypropylene produced according to Examples 1 to 3 of the present invention.
Fig. 2 shows the results of GPC analysis of homopolypropylene prepared according to Comparative Examples 1 to 3. Fig.

Hereinafter, a method for producing homopolypropylene according to one preferred embodiment of the present invention and homopolypropylene produced therefrom will be described in more detail.

In the present invention, the terms first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

Moreover, the terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprising," "comprising," or "having ", and the like are intended to specify the presence of stated features, But do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

According to an embodiment of the present invention, there is provided a process for producing a polypropylene resin, which comprises polymerizing a propylene monomer while introducing hydrogen gas in a batch form before polymerization so as to have a molar ratio of 100 to 2,000 (mol.ppm) The Rosen-supported catalyst comprises: a) supporting an alkylaluminoxane-based co-catalyst on a carrier; And b) adding a catalyst precursor solution containing the metallocene compound of formula (1) and a solvent to the product carrying the alkylaluminoxane co-catalyst, and reacting the resultant to react the metallocene compound Wherein the step a) is carried out by slowly introducing an alkylaluminoxane-based cocatalyst into the carrier and stirring the mixture at a temperature of 100 ° C to 150 ° C for 2 hours to 12 hours, A process for the production of polypropylene is provided:

[Chemical Formula 1]

In Formula 1,

M ¹ is a Group 4 transition metal;

X is the same or different halogen;

A is a bridge group connecting an indenyl group as an element of Group 14;

R ¹ is alkyl, alkenyl, alkylaryl, arylalkyl or aryl of 1 to 20 carbon atoms;

R ² is hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl;

R ³ , R ^{3 '} , R ⁴ , R ^4' , R ⁵ , R ^{5 '} , R ⁶ , R ^6' , R ⁷ , R ^{7 '} , R ⁸ and R ^8' Hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl.

The present invention is characterized in that a metallocene supported catalyst is used to increase the molecular weight reduction due to the introduction of hydrogen when polyolefins, preferably polypropylene, are produced.

Therefore, the present invention can easily produce polypropylene having a molecular weight of less than 200,000 as well as polypropylene having a molecular weight of 200,000 or more. That is, in the present invention, the low molecular weight polypropylene includes polypropylene having Mw of less than 200,000, preferably Mw of 50,000 to 150,000, and high molecular weight polypropylene of polypropylene having Mw of 200,000 or more, preferably Mw of 200000 to 400000 .

The metallocene supported catalyst is prepared by reacting a silica support with a cocatalyst, removing the solvent from the upper layer after precipitation, washing with a solvent, and adding a catalyst precursor

At this time, the supporting method of the present invention is characterized in that a high temperature ( ≥ 100 ° C) is applied and the reaction time is further reduced when a cocatalyst is carried on a carrier unlike the conventional method. Therefore, the metallocene supported catalyst prepared by the method of the present invention can increase the supporting ratio of the catalyst by a simple method without changing the amount of raw material, time and temperature, and can prevent gelation of the catalyst And the catalytic activity is excellent. In addition, the present invention can produce a polyolefin having a low molecular weight in a desired range by increasing the decrease in the molecular weight of the polymer by controlling the amount of hydrogen input without the need of a separate pre-polymerization in the polymerization process.

In this method of the present invention, the step a) is a step for supporting the cocatalyst on the carrier.

By specifying the reaction temperature in the step a), the effect of increasing the hydrogen reactivity of the final supported catalyst can be exhibited. Preferably, the step a) is carried out by slowly introducing the alkylaluminoxane-based cocatalyst into the carrier at room temperature and stirring at a temperature of 100 ° C to 150 ° C for 2 to 12 hours. In the step a), it is more preferable that the supporting rate is further increased by slowly injecting the alkylaluminoxane-based co-catalyst into the carrier at room temperature and carrying out the carrying reaction while stirring at 120 to 150 ° C for 2 to 5 hours .

When the reaction temperature is lower than 100 ° C, there is a problem that the supporting ratio of the promoter is low. When the temperature is higher than 150 ° C, the catalyst is deformed

If the reaction time is less than 2 hours, there is a problem that the supporting rate of the co-catalyst is also lowered. If the reaction time is more than 12 hours, the reaction time becomes too long, which is inefficient and the toll ratio may be added according to the increase of the process time.

In addition, it is preferable that the alkylaluminoxane-based promoter is slowly injected at room temperature when the carrier is injected.

After the step a), the decantation process may be further performed before the metallocene compound of step b) described later is supported on the carrier. Preferably, after the step a), the step of removing the upper layer solution from the reaction solution and decanting the remaining reaction product using a solvent may be repeated at least twice. More preferably, the decantation process may be repeated twice.

The decantation process may use a cannula to decant the solvent, and the solvent may be the same as that used in the polymerization reaction.

Meanwhile, in the step b), the metallocene compound of formula (1) is supported on the support carrying the cocatalyst.

Specifically, a catalyst precursor solution containing the compound of Formula 1 is introduced into the reaction product of the support and the alkylaluminoxane-based co-catalyst. The introduction conditions of the catalyst precursor are not particularly limited, but may be carried out at a temperature of 10 to 30 캜.

In the step b), the reaction is preferably carried out at a temperature of 50 to 90 degrees for 4 to 6 hours. When the reaction temperature is lower than 50 deg. C, the supporting ratio of the catalyst precursor is lowered. When the temperature is higher than 90 deg. C, decomposition due to the stability of the catalyst precursor may occur. If the reaction time is less than 4 hours, there is also a problem that the supporting rate is lowered. If the reaction time is longer than 6 hours, the stability of the catalyst precursor may become a problem.

Further, the metallocene compound of formula (1) is supported on the support carrying the cocatalyst through step (b), the upper layer solution is removed from the reaction solution as in step (a), and the remaining reaction product is treated with di And repeating the process of decanting at least two or more times. The method may further comprise washing the reaction product with a solvent at least twice.

And, in the production of the supported catalyst, it is possible to proceed under a solvent, and the amount thereof to be used is not limited. Examples of the solvent include pentane, hexane, heptane, nonane, decane, toluene, benzene, dichloromethane, chlorobenzene, and the like.

Meanwhile, the metallocene supported catalyst of the present invention may be prepared by the above-mentioned method, and the catalyst may be one in which the alkylaluminoxane co-catalyst and the metallocene compound represented by the following formula (1) are sequentially carried on the carrier.

[Chemical Formula 1]

In Formula 1,

M ¹ is a Group 4 transition metal;

X is the same or different halogen;

A is a bridge group connecting an indenyl group as an element of Group 14;

R ¹ is alkyl, alkenyl, alkylaryl, arylalkyl or aryl of 1 to 20 carbon atoms;

R ² is hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl;

R ³ , R ^{3 '} , R ⁴ , R ^4' , R ⁵ , R ^{5 '} , R ⁶ , R ^6' , R ⁷ , R ^{7 '} , R ⁸ and R ^8' Hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl.

Preferably, R ¹ and R ² in the general formula (1) are each alkyl having 1 to 4 carbon atoms; R ³ and R ^{3 '} are each alkyl, alkenyl, or arylalkyl having 1 to 20 carbon atoms; R ⁴ and R ^{4 '} are each aryl or alkylaryl of 1 to 20 carbon atoms; n is an integer from 1 to 6, M is zirconium, X is Cl, and A may be carbon, Si, or germanium.

The metallocene compound of formula (1) contains two indenyl groups as ligands. In particular, since the bridge group connecting the ligands is substituted with a functional group, the activity as a catalyst can be maximized. Accordingly, when the compound of Formula 1 is supported on its own or on a carrier and used as a catalyst in the production of polyolefins, a polyolefin having desired physical properties can be more easily produced.

At this time, the carrier may be any one generally used in the technical field to which the present invention belongs, so that it is not particularly limited, but one or more carriers selected from the group consisting of silica, silica-alumina and silica-magnesia may be used. On the other hand, when supported on a support such as silica, since the silica carrier and the functional group of the metallocene compound are chemically bonded and carried, there is almost no catalyst liberated from the surface of the support in the olefin polymerization process and the polyolefin is produced by slurry or gas phase polymerization There is no fouling of the polymer wall or the polymer particles.

In addition, since the polyolefin produced in the presence of the catalyst containing such a silica carrier is excellent in the particle shape and the apparent density of the polymer, the supported catalyst of the present invention can be produced by a conventional slurry polymerization or bulk polymerization or gas phase polymerization process, Can be used suitably.

Accordingly, in the present invention, a carrier which is dried at a high temperature and has a siloxane group having high reactivity on the surface can be used. Specifically, silica, silica was dried at high temperature - can be used are alumina and the like, which are typically _{Na 2 O, K 2 CO 3} , BaSO 4, Mg (NO 3) an oxide of _2, such as carbonate, sulfate, nitrate component .

The alkylaluminoxane-based co-catalyst used in the present invention may be represented by the following formula (2).

(2)

In Formula 2,

M ² is a Group 13 metal element;

R ⁵ are the same or different and are each an alkyl, alkenyl, alkylaryl, arylalkyl or aryl having 1 to 20 carbon atoms;

m may be an integer of 2 or more.

The alkylaluminoxane-based promoter is preferably a compound wherein R ⁵ in the general formula (2) is methyl, ethyl, propyl, isopropyl, isopropenyl, n- butyl (n-butyl), sec- butyl (sec -butyl), tert- butyl (tert -butyl), pentyl (pentyl), hexyl (hexyl), octyl (octyl), decyl (decyl), dodecyl (dodecyl) Tridecyl, tetradecyl, pentadecyl, hexadecyl, octadecyl, eikosyl, dokosyl, tetrakosyl, cyclododecyl, cyclohexyl, Cyclohexyl, cyclooctyl, phenyl, tolyl, or ethylphenyl; M ² may be aluminum.

In Formula 2, m may be an integer of 2 or more, or an integer of 2 to 500, preferably 6 or more, or an integer of 6 to 300, more preferably 10 or more, or an integer of 10 to 100.

The alkylaluminoxane co-catalyst may include a metal element capable of forming a bond through interaction with a functional group introduced into a bridge group of the metallocene compound of Formula 1. The promoter compound of Formula 2 may exist in a linear, circular or network form. Examples of the promoter compound include at least one of methyl aluminoxane, ethyl aluminoxane, propyl aluminoxane and butyl aluminoxane. have.

In the catalyst of the present invention, the metallocene compound of Formula 1 may be supported in an amount of 40 to 240 μmol, preferably 80 to 160 μmol, based on 1 g of silica per weight of carrier. The alkylaluminoxane-based co-catalyst may be supported in an amount of 8 to 25 mmol, preferably 10 to 20 mmol, based on 1 g of silica per weight of carrier, for example. The boron-based promoter may be supported in an amount of 50 to 300 μmol, preferably 64 to 240 μmol, per 1 weight of carrier, for example, 1 g of silica. In the catalyst for olefin polymerization according to the present invention, the molar ratio of the boron-based promoter to the metallocene compound may be 0.1 to 3.0, preferably 0.2 to 2.0, more preferably 0.3 to 1.4, 0.5 to 1.2.

In the method for preparing the supported metallocene catalyst of the present invention, the reaction can proceed under an inert atmosphere.

The catalyst of the present invention has an improved catalytic activity over that of the catalyst prepared by the conventional method, and even if the loading condition of the metallocene compound changes, that is, the reaction temperature, the reaction time, the type of silica and the loading amount of the metallocene compound There is an advantage that a supported catalyst capable of producing polypropylene having improved activity can be produced. In particular, when the supported catalyst of the present invention is used, low molecular weight polypropylene in a desired range can be easily obtained only by controlling the amount of hydrogen supplied, without the need of pre-polymerization before the polymerization.

On the other hand, the step of polymerizing the propylene monomer for producing the polypropylene may be carried out by slurry polymerization, bulk polymerization or the like which is carried out at a temperature of 25 to 500 ° C and a pressure of 1 to 100 kgf / cm ² for 10 minutes to 24 hours Gas phase polymerization. At this time, the polymerization reaction temperature is preferably 25 to 200, more preferably 50 to 100. The polymerization reaction pressure is preferably 1 to 70 kgf / cm ² , more preferably 5 to 50 kgf / cm ² . The polymerization reaction time is preferably 10 minutes to 5 hours.

Further, in the present invention, the step of polymerizing the propylene monomer may be carried out by introducing hydrogen gas in a pre-polymerization batch form so as to have a molar ratio of 100 to 2,000 (mol.ppm) under a supported metallocene catalyst prepared by the above- And polymerizing the propylene monomer.

When the amount of hydrogen is less than 100 (mol.ppm), MI of the produced polymer is too low. When the amount of hydrogen is more than 2000 (mol.ppm), the MI is too high and analysis error occurs.

In the polymerization reaction, the supported catalyst may be used in a state of being dissolved or diluted in a solvent such as pentane, hexane, heptane, nonane, decane, toluene, benzene, dichloromethane, chlorobenzene and the like. At this time, by treating the solvent with a small amount of alkylaluminum or the like, a small amount of water or air that can adversely affect the catalyst can be removed in advance.

As described above, the catalyst of the present invention has a catalyst activity more than 2 times higher than that of the existing catalyst when calculated by the ratio of the weight (kg) of the polymer produced per unit weight (g) .

According to another embodiment of the present invention, polypropylene having a molecular weight of less than 200,000 as well as polypropylene having a molecular weight of 200,000 or more can be provided.

Preferably, the polypropylene may have an MFR of from 2 to 2000.

Preferably, the polypropylene produced according to the present invention may be a homopolypropylene having a weight average molecular weight (Mw) of 50,000 to 400,000, depending on the amount of hydrogen charged. The homopolypropylene may be homopolypropylene having a low molecular weight of 50000 to 150000 and may include a high molecular weight homopolypropylene having a Mw of 200,000 to 400,000.

The polyolefin thus produced may have a molecular weight distribution (Mw / Mn) of 2.4 or less or 2.4 to 3.0. The polypropylene may have a melt index (MI) of 2 to 1000 (g / 10 min).

The activity of the metallocene-supported catalyst for olefin polymerization according to the present invention, when calculated by the ratio of the weight (kg) of the produced polymer per unit weight (g) of the catalyst unit used based on the unit time (h) 10 kg / gCat · hr or more.

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited thereto.

[ Example  One]

Supported catalyst preparation

Under the Ar condition, methylaluminoxane (MAO) (23.2 mL, 10 mmole) was slowly added to the silica gel (3 g) and stirred at 120 캜 for 4 hours. After termination of the reaction, the mixture was allowed to cool to room temperature and allowed to stand for 15 minutes and decant through a cannula. Then, toluene (25 mL) was added to the reaction product, stirred for 1 minute, allowed to stand for 20 minutes, and the solvent was decanted using a cannula, and the same procedure was repeated once more. The catalyst precursor (50 mu mol) was dissolved in toluene (20 mL), the mixture prepared above was transferred using a cannula and washed with toluene (5 mL). After stirring at 55 ° C for 5 hours, the reaction mixture was cooled to room temperature and allowed to stand for 15 minutes, and the solvent was decanted using a cannula. Toluene (25 mL) was added, stirred for 1 minute, left for 10 minutes, and the solvent was removed using a cannula twice. Hexane (25 mL) was added thereto, stirred for 1 minute, allowed to stand for 20 minutes, and the solvent was decanted using a cannula. The hexane (20 mL) containing the atmer (0.09 g) was added thereto and washed with hexane And the mixture was stirred for 10 minutes, decanted as in the previous case, and dried under vacuum overnight. Followed by further vacuum drying at 45 DEG C for 2 hours to obtain a supported catalyst.

Homopolypropylene manufacture

First, a 2L stainless steel reactor was vacuum-dried at 65, cooled, 1.5 mmol of triethylaluminum was added at room temperature, hydrogen was added, and 770 g of propylene was added sequentially. After stirring for 10 minutes, the supported catalyst prepared above was introduced into the reactor under nitrogen pressure. Then, the temperature of the reactor was increased to 70 within 5 minutes, and then bulk polymerization was conducted for 1 hour to prepare homopolypropylene.

After the completion of the reaction, unreacted propylene was vented. At this time, the amounts of hydrogen and supported catalysts are shown in Table 1.

[ Example  2 to 3]

Homopolypropylene was prepared using the same supported catalyst and polymerization method as in Example 1, except that the amounts of hydrogen and supported catalyst were changed as shown in Table 1.

[ Comparative Example  One]

Supported catalyst preparation

Silica gel (3 g) was placed under Ar in a 250 mL Schlenk flask and MAO (23 mL, 30 mmol) was slowly added at room temperature and stirred at 95 ° C for 18 hours. After completion of the reaction, the reaction mixture was allowed to cool to room temperature and allowed to stand for 15 minutes, and the solvent was decanted using a cannula. Then, toluene (25 mL) was added to the reaction product, stirred for 1 minute, left to stand for 20 minutes, and the solvent was decanted using a cannula. The catalyst precursor (50 mu mol) was dissolved in toluene (20 mL), transferred to the flask using a cannula, and washed with toluene (5 mL). After stirring at 55 ° C for 5 hours, the reaction mixture was cooled to room temperature and allowed to stand for 15 minutes, and the solvent was decanted using a cannula. Toluene (25 mL) was added, stirred for 1 minute, left for 10 minutes, and the solvent was removed using a cannula twice. Hexane (25 mL) was added thereto, stirred for 1 minute, allowed to stand for 20 minutes, and the solvent was decanted using a cannula. The hexane (20 mL) containing the atmer (0.09 g) was added thereto and washed with hexane And the mixture was stirred for 10 minutes, decanted as in the previous case, and dried under vacuum overnight. Followed by further vacuum drying at 45 DEG C for 4 hours to obtain a supported catalyst.

Homopolypropylene manufacture

First, a 2L stainless steel reactor was vacuum-dried at 65, cooled, 1.5 mmol of triethylaluminum was added at room temperature, hydrogen was added, and 770 g of propylene was added sequentially. After stirring for 10 minutes, the supported catalyst prepared above was introduced into the reactor under nitrogen pressure. Then, the temperature of the reactor was increased to 70 within 5 minutes, and then bulk polymerization was conducted for 1 hour to prepare homopolypropylene.

 After the completion of the reaction, unreacted propylene was vented. At this time, the amounts of hydrogen and supported catalysts are shown in Table 1.

[ Comparative Example  2 to 3]

Homopolypropylene was prepared using the same supported catalyst and polymerization method as in Comparative Example 1, except that the amounts of hydrogen and supported catalyst were changed as shown in Table 1.

[ Experimental Example ]

The catalyst activity, MFR (melt flow rate) and Mw were measured for Examples 1 to 3 and Comparative Examples 1 to 3 in a normal manner, and the results are shown in Table 1 below.

≪ Measurement method of physical properties of polymer &

Catalyst activity: Calculated as the ratio of the weight of polymer produced per kg of supported catalyst mass (kg PP) based on unit time (h).

The results of GPC analysis of the homopolypropylene prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Figs. 1 and 2, respectively.

Amount of catalyst
(mg) H2 Activity MFR Mw (mol.ppm) (kg / g.hr) Comparative Example 1 30 331 9.8 5.6 368,515 Comparative Example 2 30 827 11.7 8.9 295,584 Comparative Example 3 25 1160 10.7 21.3 219,768 Example 1 30 331 10.8 3.7 456,180 Example 2 25 827 14.7 10.6 204,764 Example 3 25 1160 10.3 - 117,540

The results of Table 1 and FIGS. 1 and 2 indicate that by using the supported metallocene supported catalyst by controlling the reaction temperature of the cocatalyst, it is possible to increase the molecular weight reduction of the polypropylene according to the hydrogen input amount have. Therefore, the present invention can easily produce a polypropylene having a high molecular weight of 200,000 or more and a polypropylene having a low molecular weight of 200,000 or less.

On the other hand, in Comparative Examples 1 to 3, it was not possible to produce polypropylene having a low molecular weight of less than 200,000 by using a supported metallocene catalyst in which a promoter was supported at a low temperature on a carrier and a metallocene compound was supported thereon .

Accordingly, the present invention can produce a polypropylene having a low molecular weight by a simple method according to hydrogen charging conditions while maximizing the polymerization activity as compared with the prior art.

Claims (11)

Polymerizing the propylene monomer while introducing hydrogen gas in a batch form before the polymerization so as to have a molar ratio of 100 to 2,000 (mol.ppm) under a metallocene supported catalyst,
The metallocene supported catalyst may contain,
a) supporting an alkylaluminoxane-based co-catalyst on a carrier; And
b) adding a catalyst precursor solution containing the metallocene compound of formula (1) and a solvent to the product carrying the alkylaluminoxane co-catalyst, and reacting the mixture to react the metallocene compound with the carrier on which the alkylaluminoxane- , The method comprising the steps of:
Wherein the step a) is carried out by slowly injecting an alkylaluminoxane-based co-catalyst into a carrier and stirring at a temperature of 100 ° C to 150 ° C for 2 hours to 12 hours,
Production method of polypropylene:
[Chemical Formula 1]

In Formula 1,
M ¹ is a Group 4 transition metal;
X is the same or different halogen;
A is a bridge group connecting an indenyl group as an element of Group 14;
R ¹ is alkyl, alkenyl, alkylaryl, arylalkyl or aryl of 1 to 20 carbon atoms;
R ² is hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl;
R ³ , R ^{3 '} , R ⁴ , R ^4' , R ⁵ , R ^{5 '} , R ⁶ , R ^6' , R ⁷ , R ^{7 '} , R ⁸ and R ^8' Hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl, alkylaryl, arylalkyl or aryl.
The method according to claim 1,
Wherein R ¹ and R ² are each alkyl having 1 to 4 carbon atoms; R ³ and R ^{3 '} are each alkyl, alkenyl, or arylalkyl having 1 to 20 carbon atoms; R ⁴ and R ^{4 '} are each aryl or alkylaryl of 1 to 20 carbon atoms; n is an integer of 1 to 6, M is zirconium, X is Cl, A is carbon, Si or germanium
A process for producing polypropylene.
The method according to claim 1,
Wherein the step a) is carried out by slowly introducing alkyl aluminoxane-based co-catalyst into the carrier at room temperature and stirring at 120 to 150 ° C for 2 to 5 hours.
The method according to claim 1,
Further comprising, after the step a), removing the upper layer solution from the reaction solution and decanting the remaining reaction product using a solvent at least twice or more.
The method according to claim 1,
Wherein the step (b) is carried out at a temperature of 50 ° C to 90 ° C for 4 hours to 6 hours.
The method according to claim 1,
Removing the upper layer solution from the reaction solution after the step b), and washing the remaining reaction product with a solvent at least twice.
The method according to claim 1,
Wherein the carrier comprises at least one member selected from the group consisting of silica, silica-alumina and silica-magnesia.
The method according to claim 1,
Wherein the alkylaluminoxane-based co-catalyst is at least one selected from the group consisting of methyl aluminoxane, ethyl aluminoxane, propyl aluminoxane, and butyl aluminoxane.
The method according to claim 1,
Wherein the step of polymerizing the propylene monomer comprises:
Bulk polymerization or vapor phase polymerization in which the reaction is carried out at a temperature of 25 to 500 DEG C and a pressure of 1 to 100 kgf / cm < ² > for 10 minutes to 24 hours
A process for producing polypropylene.
The method according to claim 1,
Wherein the metallocene supported catalyst has a catalytic activity of not less than 10 kg / gCat 占 나타내는 r which represents the produced weight of the polymer obtained per unit weight of the catalyst per unit time.
The method according to claim 1,
A process for producing polypropylene having an MFR of 2 to 1000.

Images