KR100242209B1 - Method of manufacturing polypropylene - Google Patents

Abstract

The present invention relates to a method for producing a polypropylene capable of controlling properties and molecular weight distribution using a co-support catalyst of Ziegler-Natta and metallocene.

The present invention uses a co-supported catalyst in which a Ziegler-Natta catalyst and a metallocene catalyst are mixed in preparing a polypropylene having various molecular weight distribution and stereoregularity by polymerization, and a general formula R _n AlY ₃ as a cocatalyst. using one or a mixture of organoaluminum compounds represented by _-n (wherein R is a hydrocarbon having 1-20 carbon atoms, Y is halogen and 0≤n≤3) or aluminoxane. It features.

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 using co-supported catalyst composition of Ziegler-Natta and metallocene for olefin polymerization

The present invention relates to a method for producing polypropylene using a co-support catalyst of Ziegler-Natta and metallocene, and more particularly, using a co-support catalyst of Ziegler-Natta catalyst and metallocene, and a cocatalyst. The present invention relates to a method for producing a polypropylene capable of controlling properties and molecular weight distribution by a polymerization method using an organoaluminum compound.

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 polymer has a narrow Mw / Mn value of about 2 as well as uniform copolymer distribution of the copolymer. 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 to improve molecular weight distribution by manipulating the active site of each catalytic metal component. . 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. In US Patent 4,975,403, US Patent 4,530,914, Korean Patent Publication No. 89-5155, etc., a method of polymerizing olefins by mixing heterogeneous metallocene catalysts has been proposed. US Patent 5,395,810, US Patent 5,242,876, Japanese Patent Laid-Open No. 5-255431, European Patent 536104A1, European Patent 436399A2, and Korean Traditional Publication No. 94-23934 are used for a mixed catalyst of a Ziegler-Natta catalyst and a metallocene catalyst. The polymerization of olefins is shown. 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, using a Ziegler-Natta and metallocene co-support catalyst in order to produce a polypropylene having the desired properties and molecular weight distribution, the organic aluminum compound or aluminoxane as a promoter The purpose of the present invention is to provide a method of more easily controlling the properties and molecular weight distribution of the final polypropylene to be polymerized.

Another object of the present invention is to provide a polypropylene having improved workability and physical properties for each application through a co-catalyst of Ziegler-Natta and metallocene.

The present invention uses a co-supported catalyst in which a Ziegler-Natta catalyst and a metallocene catalyst are mixed in preparing a polypropylene having various molecular weight distribution and stereoregularity by polymerization, and a general formula R _n AlY ₃ as a cocatalyst. using one or a mixture of organoaluminum compounds or aluminoxanes represented by _-n , where R is a hydrocarbon having 1-20 carbon atoms, Y is halogen, and 0 ≦ n ≦ 3 It is done.

Hereinafter, a method for preparing a polypropylene whose molecular weight distribution and properties can be controlled by a mixed catalyst 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 "polymer" may also 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, the "co-catalyst" means a co-support of at least one Ziegler-Natta catalyst and at least one metallocene catalyst. The composition ratio of the metallocene catalyst to the Ziegler-Natta catalyst in the co-support catalyst is up to 0.01-99.9% by weight.

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 M ₁ R ⁺ _x where M is a metal, R is a halogen or hydrocarbyloxy and x is the oxidation number of the metal. Preferably M is a group IV B or V B of the periodic table. Or a metal belonging to group VI 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 ethoxy, even 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. As a support, a chemically inert solid which does not cause a chemical reaction with a Ziegler-Natta catalyst or a metallocene catalyst is used.

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 catalyst [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 the seed catalyst 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 such as methoxy, ethoxy, butoxy or allylalkyl group, R ² is an alkyl group such as methyl, ethyl, butyl or an alkoxy group such as methoxy, ethoxy, butoxy or arylalkyl) R4 is an aromatic compound such as phenyl, atracenyl, naphthalenyl, or a cycloaliphatic group such as cyclopentyl, cyclohexyl, cyclooctyl, and X is carbon, silicon, etc. 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.

Meanwhile, 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 support is a chemically inert solid that does not cause chemical reactions with Ziegler-Natta catalysts or metallocene catalysts.

The catalyst 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.

When the polypropylene is prepared by polymerizing propylene by the above method, the polymerization reaction may be performed in gas phase, liquid phase, or 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, petroleum such as gasoline, kerosene and diesel, and the like, and may or may not be added with an external electron donor.

The polymerization temperature is usually in the range of -50 to 350 ° C, preferably 0 to 310 ° C. 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 (T _mc ) 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 ± 0.5mg and placed in an aluminum pan, and then irradiated at a temperature rising rate of 20 ° C./min from 50 ° C. to 200 ° C. under a nitrogen stream of 1.2 kg / cm 2 and then 20 ° C. to 200 ° C. to 50 ° C. Tmc was measured while cooling at a rate of / min. Tm and heat of fusion (Δ11m) 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 the completely dried polymer was quantitatively placed in a timing filter and extracted with heptane in a Soxhlet type extraction apparatus. The extraction time was fixed at 5 hours, and the remaining polymer was collected after extraction, dried in vacuo at 80 ° C, quantitatively weighed and weighed. The I.I was calculated as the weight ratio of the polymer remaining without melting and the originally put polymer.

(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, now 3 mm, were added to a 200 ml stainless steel vessel. 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 co-support catalyst for Ziegler-Natta and metallocene catalysts

The Ziegler-Natta catalyst and toluene prepared above were placed in a nitrogen-substituted reactor, and then a metallocene catalyst was used for a predetermined time at a predetermined temperature. Toluene solution in which the Et (Ind) ₂ ZrCl ₂ (EIZ) catalyst was dissolved was added. After the reaction, the mixture was washed five times with toluene. The catalyst thus prepared was named MgCl ₂ -Ti-M catalyst. The analysis results of the prepared catalysts are shown in Table 1. The amount of the co-supported EIZ catalyst was supported while changing with respect to the amount of Ti supported.

As a result, the content of Ti in the prepared MgCl ₂ -Ti-M catalyst decreased and the content of Zr increased as the amount of EIZ increased.

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 unit) is flowed in a solvent until it is saturated while checking with a flow controller, and then a promoter, 9.89 × 10 ^-3 moles of cyclohexyldimethoxymethylsilane, MgCl _2- 1.24 x 10 ^-5 mol of Ti-M catalysts were sequentially added to initiate a polymerization reaction. As cocatalyst, triethylaluminum (TEA) or aluminoxane (MAO) or a mixture of triethylaluminum and aluminoxane was used, respectively. The reaction time was fixed at 1 hour and 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 activity of the catalyst was determined in units of kg polymer / (mol metal. Mol-monomer. H) from the weight of the final product.

Physical property measurement results are shown in Table 2 below.

Comparative Example 1

For comparison, the polymerization process was carried in the same manner as in example 1, polymerization of propylene with MgCl ₂ -Ti-M catalyst instead of MgCl ₂ -Ti catalyst, exhibited a physical property measurement results are shown in Table 2 below.

In the results of Table 2, Example 1 compared to Comparative Example 1, the activity, melting point was reduced, but the molecular weight distribution was increased, the stereoregularity was compared in the case of a large amount of metallocene catalyst (3.4 or more) Higher than yes.

TABLE 1

TABLE 2

As in the present invention, a co-supported catalyst of a Ziegler-Natta catalyst and a metallocene catalyst is used, and polymerization is carried out using an organoaluminum compound or aluminoxane as a cocatalyst. The produced polypropylene has various properties and molecular weight distribution. It can be molded into various products such as film, container, and fiber.

Claims (3)

In the preparation of polypropylene having various molecular weight distribution and stereoregularity by polymerization, a metallocene compound having the following structure and M1R + x (where M is a metal and R is halogen or hydrocarbyloxy and x is a metal) Co-supporting the transition metal compound represented by the oxidation number MgCl ₂ at the same time to prepare a polymerization catalyst, and the catalyst and the co _- catalyst as a general formula R _n AlY _3-n (where R is a hydrocarbon having 1 to 20 carbon atoms And Y is halogen and 0 ≦ n ≦ 3), and a polymerization pressure of 0˜310 ° C. polymerization temperature and atmospheric pressure of 250 kg / cm 2 by adding one or a mixture thereof selected from organoaluminum compounds or aluminoxanes. Process for producing polypropylene with various molecular distributions under (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 the content of the central metal M ₁ of the Ziegler-Natta catalyst in the co-supported catalyst is 0.5 to 2.0% by weight and the composition ratio of the metallocene catalyst to the Ziegler-Natta catalyst is 0.01 to 99.9% by weight. Method for producing polypropylene. The process for producing polypropylene according to claim 1, wherein the polypropylene is a homopolymer of propylene or an irregular copolymer or a block copolymer of olefins having 2 to 18 carbon atoms and propylene.