JP2817799B2 - Method for producing large symmetric polymer particles - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing large-sized polyolefin particles having a large bulk density. More specifically, the present invention relates to a method for producing symmetric polyolefin particles having a large particle size with a high yield using a metallocene catalyst.

In summarizing the present invention, a large symmetric polyolefin particle having a high bulk density is used to form a precipitated complex of an organoaluminum compound and a metallocene catalyst at a temperature lower than the polymerization temperature of the olefin monomer. By prepolymerization, and then polymerizing the olefin monomer under polymerization conditions.

The polyolefin obtained from the polymerization reactor is generally in the form of a powder having a broad particle size distribution. These polyolefin powders have poor pourability and have large amounts of undesired fine powders which make handling and processing difficult. Therefore, before processing, these polyolefins must generally be formed as large particles or pellets.

In order to obtain a large particle polyolefin, a pelletizing step is required. This pelletization step increases the price of the material. Therefore, it is extremely desirable to obtain large-sized polyolefin particles that can be used in place of pellets in the polymerization step.

In particular, large-sized polyolefin particles having a particle size in the range of about 300 to 800 μm and a narrow particle size distribution have many advantages in various applications including, for example, ease of handling.

Large particle size polymer particles have been produced by well known polymerization methods such as those disclosed in U.S. Patent No. 4,694,035, in which seeded polymerization produces large particle size polymer particles.

U.S. Pat.No. 3,687,919 discloses that some of the monomers are pre-polymerized with turbulent agitation, the pre-polymerized monomers are mixed with a large amount of added monomer, and the resulting mixture is gradually mixed with gentle agitation. Discloses a method for producing spherical particles of an ethylene monomer having a particle size distribution controlled by a two-stage polymerization method. The amount of prepolymerized monomer and the speed of agitation during prepolymerization are said to serve as controlling factors for the particle size distribution of the final product.

Other catalysts for producing polyolefins, called metallocene catalysts, have many advantages over other types of polyolefin polymerization catalysts. The advantages of using metallocene catalysts include, for example, high productivity and the ability to modulate or change the properties of many polymers by changing or changing the type of metallocene used.

The use of metallocene catalysts in the polymerization of olefins is well known in the art. German Patent Specification No. 2,608,863,
Disclosed is a catalyst system for the polymerization of ethylene, consisting of bis (cyclopentadienyl) titanium dialkyl, aluminum trialkyl and water. Similarly, German Patent Specification 2,608,933 describes a compound of the formula (cyclopentadienyl) _n ZrY _{4-n where} Y is R, CH ₂ AlR ₂ , CH ₂ CH ₂ AlR ₂ or CH ₂ CH (Al
R ₂ ), wherein R is alkyl or metalloalkyl;
And z is an integer from 1-4, and discloses a zirconium metallocene of

Metallocene catalysts are known to be useful in copolymerizing ethylene with other alpha-olefins.
U.S. Pat. No. 4,542,199 to Kaminsky et al. Describes a compound of the formula (cyclopentadienyl) ₂ MeRHal where R is a halogen, a cyclopentadienyl group, or a C ₁ -C ₆ alkyl group; Disclosed is a catalyst system comprising a catalyst of a transition metal, especially zirconium, and Hal is a halogen, especially chlorine. Catalyst system wherein Al in _{2 OR 4 (Al (R)} -O) when _n and / or cyclic molecules _{(Al (R) -O) n} + 2 above equation for a linear molecule, n represents 4- Alumoxane, which is a number of 20 and R is a methyl or ethyl residue. A similar catalyst system is disclosed in U.S. Patent No. 4,404,344.

Particularly useful metallocene catalysts for the polymerization of propylene and higher alpha-olefins are described in EP 0185
No. 918. This publication discloses a zirconium metallocene catalyst containing a bridge between two cyclopentadienyl rings. The bridge is described as being a linear hydrocarbon having 1-4 carbon atoms or a cyclic hydrocarbon having 3-6 carbon atoms.

Other metallocene catalysts are disclosed in U.S. Ser. No. 09,075.
Nos. 034,472, 095,755, No. (TBD), and (TBD) (Attorney Docket Number B-26817 / COS-567 and B-26
818 / COS-563), all of which are the inventors' inventions and are assigned to the same assignee. Application No. 096,075 discloses a catalyst system consisting of a sterically rigid hafnium metallocene catalyst in combination with an aluminum compound. Application No. 034,472 describes a method of altering the melting point and molecular weight of a polyolefin by altering the crosslinking and other substituents on the metallocene catalyst. Application No. 095,755 discloses at least two different chirality (chira)
A method for producing a polyolefin having a broad molecular weight distribution using the stereorigid metallocene catalyst and the aluminum compound of l) is described. The application numbers No. (Undecided) and No. (Undecided) dated July 15, 1988 (Attorney Docket Nos. B-26817 / COS-567 and B-26818 / COS-563) are two Disclosed are catalysts and methods for making syndiotactic polypropylene using syndiospecific metallocenes in which the bridged cyclopentadienyl groups are substantially different with respect to steric hindrance and electrical effects. Catalyst "in _{(CpR n) (CpR 'm} ) MeQ k above formula, R' in general formula R is described by, including bridge between the two cyclopentadienyl rings substituted with virtually different ways You.

Polymerization processes for prepolymerizing the catalyst prior to introducing the catalyst into the reaction zone are described in U.S. Patent Application Nos. 009,712 and 095,755.
No.

Prior to the present invention, it was unknown how to use metallocene catalysts to produce large bulk symmetric polyolefin particles having a high bulk density. The above metallocene catalyst systems generally produce polymer products in the form of very small particles.

Using a metallocene catalyst, homogeneous (slurry) polymerization, such as using toluene as a solvent, has a low bulk density (0.1%).
-0.2 g / ml) and fluff having a less dense polymer morphology (f
luff) -like particles. The fluff or powder obtained from slurry polymerization is difficult to handle. This same problem occurs in low temperature (about 50 ° C. and lower for propylene) liquid (bulk) polymerizations.

Hot bulk polymerization using a metallocene catalyst and no prepolymerization results in fluffy small particles with a closed morphology. These small fluffy particles are compressed together into jagged pieces and then aggregate to give high bulk density particles. These particles have a high bulk density,
They are not desirable because they are not uniform and difficult to handle.

High bulk density increases the solids content obtained in the reactor,
Important during the fluffing operation prior to extrusion and pelletization. Low bulk density polymers are difficult to handle, and the particle mixture itself is in the air, and it is actually dangerous if sparks come into contact with the particles.

OBJECTS OF THE INVENTION It is an object of the present invention to provide polyolefin particles of large particle size and a polymerization process for their production.

A more specific object of the present invention is to provide large symmetric polyolefin particles having a relatively narrow molecular weight distribution.

It is a further object of the present invention to provide free flowing large particle symmetric polyolefin fluffy particles having a high bulk density.

Still another object of the present invention is to provide a method for producing symmetric polyolefin particles having a high bulk density and a large particle size with a high yield using a metallocene catalyst.

SUMMARY OF THE INVENTION According to the present invention, a method has been found for producing symmetric polyolefin particles of large particle size with high bulk density using a metallocene catalyst. This method pre-contacts the alumoxane with the metallocene, thereby forming an active complex,
The active complex is precipitated with a hydrocarbon which is a non-solvent of the complex, and the complex is prepolymerized by contacting the complex with the olefin monomer at a temperature lower than its polymerization temperature, and then the olefin monomer is polymerized under polymerization conditions. Polymerized to produce symmetric polyolefin particles of large particle size.

DETAILED DESCRIPTION OF THE INVENTION The process of the present invention produces large symmetric polyolefin particles having a high bulk density. The process according to the invention requires that the complex be prepolymerized by contacting an active catalyst precipitated at a temperature significantly below the polymerization temperature of the olefin monomer with the olefin monomer, and then converting the olefin monomer under polymerization conditions. By polymerization, symmetric polyolefin particles having a large particle size can be obtained.

The active complex is formed by pre-contacting the alumoxane with the metallocene catalyst. After the complex is formed, it is precipitated with a hydrocarbon, which is generally the non-solvent for the complex. In order to produce large particle symmetric polyolefins, it is necessary to prepolymerize the precipitated active catalyst at a low temperature, whatever the method used, before polymerizing the olefin under the polymerization conditions. is important.

While the present invention is generally useful for producing large sized polymer particles of any olefin, alpha-olefins are preferred in terms of availability, reactivity and crystallinity of the final polymer. Although the present invention is particularly useful for the polymerization of olefins having 3 to 5 carbon atoms, propylene is most preferred for its availability and industrial use.

The hydrocarbons used to precipitate the active complex are non-aromatic (alicyclic or aliphatic). An important requirement for the hydrocarbon to precipitate the complex is simply that the active complex be insoluble therein. This "non-solvent" hydrocarbon is preferably 3 to 12 carbon atoms, depending on availability, volatility and ease of handling.
More preferably, it has from 3 to 7 carbon atoms.

In a preferred embodiment of the invention, the "non-solvent" hydrocarbon and monomer are the same, and the most preferred monomer "non-solvent" is propylene. The use of the monomer as the non-solvent is advantageous because the solvent recovery step is reduced and the prepolymerization time is shortened. Even when the monomers are simultaneously "precipitating hydrocarbons", the precipitation must be carried out below the polymerization temperature of the monomers.

The prepolymerization of the catalyst according to the invention must be carried out below the polymerization temperature of the olefin monomers, otherwise large, uniform polyolefin particles having a high bulk density and large particle sizes cannot generally be obtained. This, together with other factors, generally results in larger particles at lower temperatures (longer prepolymerization times, slower agitation speeds, and higher catalyst efficiency also affect particle size). Preferably, the temperature is significantly lower than the polymerization temperature of the olefin monomer.

If the prepolymerization is completed within a reasonable time, any lower temperature can be used for this prepolymerization. When propylene is used as the olefin monomer, the prepolymerization temperature is generally 70 ° C or lower, preferably 35 to 40 ° C or lower. The use of propylene is most preferred because ambient temperature is convenient.

The prepolymerization of the present invention is performed in two stages to better control the final particle size. In the first prepolymerization stage, the precipitated complex is contacted with the olefin monomer at a temperature below the polymerization temperature of the monomer. The temperature is maintained at this temperature for a time sufficient for the complex to prepolymerize. This time is generally from 0 to 10 minutes, preferably from 1 to 6 minutes, with about 5 minutes being most preferred. In the second pre-polymerization stage, the complex and the monomer are heated at a constant rate, and the pre-polymerization of the complex is continued until the final polymerization temperature is reached. At this temperature the polymerization takes place and the reaction is terminated. The first pre-polymerization step is performed at the above temperature, and the second pre-polymerization step is heating the reaction mixture to the polymerization temperature as quickly as possible in order to avoid the formation of a large amount of polymer below the final polymerization temperature. It is preferable to be performed in between. This step is preferably performed while the complex and monomer are heated at a rate not less than 5 ° C per minute, more preferably at a rate not less than 10 ° C per minute.

The final polymerization temperature depends on the particular olefin monomer used. In the case of propylene, this temperature is below about 80 ° -85 ° C, and preferably between 50 ° -80 ° C,
C is most preferred. Thus, if propylene is the monomer used in the preferred process of the present invention, the initial prepolymerization temperature is about 25 ° C, the heating rate is no less than 10 ° C per minute, and the final polymerization temperature is about 70 ° C. ° C.

The bulk density of the resulting uniform polyolefin particles of large particle size is generally 0.3 to 0.45 g / ml, and can be as high as 0.5 g / ml.

The method of the present invention preferably has a majority particle of about 300 to 8
Between 00 μm, more preferably about 90% of the particles are larger than 100 μm, yielding polyolefin particles having a particle size between 500 and 2,000 μm. The method of the present invention has about 95% of the particles
It is also possible for more than 400 μm, and in some cases 99% of the particles to yield particles larger than 400 μm.

The process of the present invention can be carried out in any type of polymerization reactor provided large symmetric polyolefin particles are produced. Examples of suitable reactors are batch reactors, loop type reactors, and the like.

The metallocene catalyst used according to the invention is of the formula R ″ (C ₅ R ′ _m ) ₂ MeQp where (C ₅ R ′ _m ) is cyclopentadienyl or substituted cyclopentadienyl; Hydrogen or a hydrocarbon group having 1-20 carbon atoms, and each R 'may be the same or different; R "is an alkylene group having 1-4 carbon atoms, a silicon hydrocarbon group, a germanium hydrocarbon group. , An alkyl phosphine or an alkyl amine,
R ″ acts to bridge the two (C ₅ R ′ _m ) rings;
Is a hydrocarbon group having 1-20 carbon atoms or halogen; Me is a metal of Group 4b of the Periodic Table of the Elements (ie, Ti, Z
r and Hf); m is an integer from 0-4; and p is 0
Which is an integer of -3.

In a preferred embodiment of the present invention, zirconium is most preferred as Me among titanium, zirconium and hafnium.

R 'may be hydrogen or a hydrocarbon group. Hydrocarbon groups useful as R 'include alkyl, alkenyl, aryl, alkylaryl or arylalkyl residues. More specifically, representative hydrocarbon residues are methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, phenyl, methylene, ethylene, propylene, and other Includes similar groups. In a preferred embodiment,
R 'is (C ₅ (R' is selected to _{be) 4)} is an indenyl radical (Ind) or hydrogenated indenyl group (IndH _4).

R ″ is two (C) to make the catalyst three-dimensionally rigid.
₅ (R ') ₄ ) A stable component that bridges the ring. R "can be organic or inorganic and can include groups pendent from the moiety that acts as a bridge. Examples of R" are 1
Includes alkylene groups having -4 carbon atoms, silicon hydrocarbon groups, germanium hydrocarbon groups, alkyl phosphines, alkyl amines, boron, nitrogen, sulfur, phosphorus, aluminum and other groups containing these elements. Suitable R "components are methylene (-CH ₂ -), ethylene (-C ₂ H ₄ -), a cycloalkyl silicon such as alkyl silicon and especially cyclopropyl silicon.

Similarly, Q may be any of the hydrocarbon groups presented for R 'above, but preferably Q is halogen, and most preferably Q is chlorine. Also in a preferred embodiment, p
Is 2.

In the polymerization of propylene or higher alpha-olefins, the metallocene catalyst must be chiral, that is, not superimposable on a mirror image, or prochiral, to produce a useful polymer product. There must be. However, the catalyst need not be chiral or sterically rigid for the polymerization of ethylene or predominantly ethylene-based copolymers.

In a more preferred embodiment of the present invention, the metallocene catalyst must be syndiospecific or isospecific. Syndiospecific metallocenes are disclosed in U.S. Patent Application Nos. (Pending) and No. (pending) dated July 15, 1988 (Attorney Docket Nos. B-26817 / COS-567 and B-26818 / COS-5).
63), which should be referred to with reference to the disclosure. Syndiospecific metallocenes have cyclopentadienyl groups that are not substantially identical. These metallocenes, when made from monomers having at least 3 carbon atoms, such as propylene, produce polyolefins with high syndiotactic index. Syndiotactic polyolefins, such as polypropylene, have been found to have a lower heat of crystallization than the corresponding isotactic polymer. Furthermore, if there is the same mole fraction of steric defects in the polymer chain, the syndiotactic polymer has a higher melting point than the isotactic polymer.

The use of metallocene catalysts generally results in polyolefins having a molecular weight distribution between about 2 and 10, preferably between 2 and 3. However, if two metallocene catalysts are used, as in the above-cited US Patent Application No. 095,755, a polyolefin having a broad molecular weight distribution will result.

The catalyst can be made by any method known in the art. However, the impure catalyst usually produces a low molecular weight, amorphous polymer, so the catalyst complex needs to be "clean". In general, the preparation of catalytic complexes consists of the formation and isolation of Cp or substituted Cp ligands, followed by the formation of the complex by reaction with a metal halide. As described above with respect to metallocene catalysts for the production of polyolefins, the catalyst of the present invention comprises an aluminum promoter,
It is particularly useful if it is preferably used in combination with alumoxane, alkylaluminum or a mixture thereof. Howard Turner, further described as inventor
Exxon Chemical Patents
According to the teaching of European Patent Specification 226,463, issued June 24, 1987, assigned to Co., Ltd., a complex between a metallocene catalyst as described herein and an excess of an aluminum cocatalyst is formed. You can release. Alumoxanes useful in combination with the catalysts of the present invention have the general formula (R)
-Al-O-) and in linear form R (R-Al-
—O) _n —AlR _{2 wherein} R is an alkyl group having 1 to 5 carbon atoms,
And n is an integer from 1 to about 20. Most preferably, R is a methyl group. Alumoxane can be produced by various methods known in the art. Preferably they can be prepared by contacting a trialkylaluminum such as trimethylaluminum with water in a suitable solvent such as benzene. Another preferred method involves the preparation of alumoxane in the presence of hydrated copper sulfate as described in US Patent No. 44,404,344, to which reference is made. The method consists in treating a dilute solution of triethylaluminum in toluene with copper sulfate. The preparation of other aluminum promoters useful in the present invention can be prepared by methods well known to those skilled in the art.

The metallocene catalysts used in the present invention are prepared by methods well known to those skilled in the art and include these methods in the above-mentioned pending applications.

The following examples are set forth to illustrate the invention and are not intended to limit the reasonable scope of the invention.

EXAMPLES In these examples, three different polymerization methods are utilized. These methods, referred to as A, B and C, are described below.

Method A (Bulk polymerization without in-situ prepolymerization) A fully baked-out 2 to 4 stainless steel zipperclave was used as a reaction vessel and purged with dry nitrogen. Three quarters (usually about 900 ml) of the total amount of liquid propylene used in the test was added to the reaction vessel. The stirrer was set at 1200 rpm and the reaction was warmed to the desired polymerization temperature. The metallocene was dissolved in a bottle containing 10 to 20 ml of toluene. The alumoxane was dissolved in a bottle containing 10 ml of toluene. Insert the contents of both bottles into a dry, degassed stainless steel cylinder (canula
te) and left in a bomb (pre-contacted) for a period of time to form the active catalyst complex. The catalyst was charged into the reactor by rapidly inhaling and discharging liquid propylene through the bomb. The polymerization was terminated by venting the monomer.

Method B (Slurry Polymerization Without In Situ Prepolymerization) This method is similar to Method A, except that a fixed volume of toluene is first tubed into the reactor in a nitrogen atmosphere.

Method C (Bulk Polymerization with In-situ Prepolymerization) The pre-contacted catalyst solution (metallocene and alumoxane in toluene) was tubed into the reactor at room temperature under a nitrogen atmosphere. Propylene was added at 30 ° C., and the catalyst was left for a certain period of time for prepolymerization. The contents of the reactor were then heated to the polymerization temperature within 5 minutes (second prepolymerization stage) and then polymerized. The polymerization was then terminated by rapidly venting the monomer.

 The results of the polymerization are shown in the following table.

As shown in Table I, polymerization experiment 1 was a low temperature bulk polymerization, polymerization experiment 2-5 was a slurry polymerization, and polymerization experiment 6 was a low temperature bulk polymerization with a prepolymerization step. All of these experiments produced small polymer particles of low density similar to those of FIG. 1 (photograph of the particles generated by Experiment No. 1).

Polymerization experiment 7 was a low-temperature bulk polymerization using a large amount of metallocene without a prepolymerization step, and polymerization experiment 8-11 was a bulk polymerization at a high temperature without a prepolymerization step. These experiments resulted in irregular, agglomerated particles of the polymer having a high bulk density.

Runs 12-20 were bulk polymerizations at elevated temperatures with prepolymerization. These experiments resulted in large, symmetric particles of polymer having a high bulk density.

The above table shows that bulk polymerization of propylene at 70 ° C and 80 ° C results in high activity and high bulk density, and control of particle size and particle shape under these conditions is achieved by pre-polymerization of the catalyst. It shows that it can be obtained.

 The table below shows the particle size distribution for experiments 15 and 19.

Table II estimates that greater than 95% by weight of the polypropylene particles produced by Experiment No. 15 is greater than 355 μm, and estimates the median particle size of the particles produced in this experiment.
648 μm.

Table III shows that about 99% by weight of the polypropylene particles produced according to Run No. 19 are greater than 355 μm and the median particle size of the particles produced in this experiment is estimated to be 799 μm.

 The main features and aspects of the present invention are as follows.

1. (a) pre-polymerizing the precipitated active complex of alumoxane and metallocene catalyst by contacting the precipitated active complex with the olefin monomer at a temperature significantly lower than the polymerization temperature of the olefin monomer, provided that the metallocene catalyst is The formula R ″ (C ₅ R ′ _m ) ₂ MeQp wherein (C ₅ R ′ _m ) is cyclopentadienyl or substituted cyclopentadienyl; R ′ is hydrogen or 1-20 carbon atoms. And each R 'may be the same or different; R "is an alkylene group having 1-4 carbon atoms, a silicon hydrocarbon group, a germanium hydrocarbon group, an alkylphosphine or an alkylamine. ,
R ″ acts to bridge the two (C ₅ R ′ _m ) rings;
Is a hydrocarbon group having 1-20 carbon atoms or halogen; Me is a metal of Group 4b of the Periodic Table of the Elements; m is 0-4
And p is an integer of 0-3; (b) further prepolymerizing the complex by heating it to the polymerization temperature as quickly as possible; and (c) Polymerizing the olefin monomer under polymerization conditions, comprising the steps of:

2. The process of claim 1 wherein the precipitated active complex is prepared by pre-contacting the alumoxane with the metallocene catalyst and then precipitating the active complex with a hydrocarbon that is a non-solvent for the active complex.

3. The process of claim 1 wherein said olefin monomer is selected from alpha-olefins having 3 to 5 carbon atoms.

4. The olefin monomer is propylene, and the step (a)
Starting at about 40 ° C. or less, and wherein step (b) is performed at a temperature of about 85 ° C. or less.

5. The method of claim 2 wherein said metallocene catalyst is selected from the class consisting of syndiospecific and isospecific metallocenes.

6. The method according to 1 above, wherein the heating in the step (b) is performed at a rate not less than 5 ° C. per minute.

7. The method according to the above item 6, wherein the metallocene catalyst is a zirconocene catalyst.

8. The method according to 1 above, wherein the alumoxane is methylalumoxane.

9. Large symmetric polyolefin particles produced by the method described in 1 above.

10. (a) alumoxane and forming an active complex by precontacting the metallocene catalyst, provided that the metallocene catalyst is represented by the following formula _{R "(C 5 R 'm} ) in the above ₂ MeQp formula (C ₅ R' _m ) is cyclopentadienyl or substituted cyclopentadienyl; R 'is hydrogen or a hydrocarbon group having 1-20 carbon atoms, and each R' may be the same or different; "Is an alkylene group having 1-4 carbon atoms, a silicon hydrocarbon group, a germanium hydrocarbon group, an alkylphosphine or an alkylamine,
R ″ acts to bridge the two (C ₅ R ′ _m ) rings;
Is a hydrocarbon group having 1-20 carbon atoms or halogen; Me is a metal of Group 4b of the Periodic Table of the Elements; m is 0-4
And p is an integer of 0-3; (b) precipitating the active complex with a hydrocarbon that is a non-solvent for the complex; (c) Pre-polymerizing by contacting the active complex with the olefin monomer at a temperature significantly lower than the polymerization temperature of the olefin monomer; (d) further pre-polymerizing by heating the complex to the polymerization temperature as quickly as possible And (e) polymerizing the olefin monomer under polymerization conditions.

11. The temperature which is significantly lower than the polymerization temperature of step (c) is 1
The process of claim 10 wherein the complex and the olefin monomer are heated to the polymerization temperature of the olefin monomer at a rate of at least 5 ° C. per minute.

12. The method according to 10 above, wherein the hydrocarbon in step (b) and the olefin monomer in (c) are the same and step (b) is performed at a temperature significantly lower than the polymerization temperature of the olefin monomer.
The method described in.

13. The olefin monomer is propylene, step (c) is initiated below about 40 ° C, and step (e) is performed at about 80 ° C.
13. The method according to the above 12, wherein the method is performed at a temperature of not more than ° C.

14. The method of claim 13 wherein said metallocene catalyst is selected from the class consisting of syndiospecific and isospecific metallocenes.

15. The above 10 wherein the metallocene catalyst is a zirconocene catalyst.
The method described in.

16. The above 10 wherein the alumoxane is methylalumoxane
The method described in.

[Brief description of the drawings]

The micrographs of FIGS. 1 to 8 were all taken at 50 × magnification. These micrographs are all polypropylene particles obtained from a polymerization process (bulk polymerization) using a metallocene catalyst in the absence of a catalyst solvent. FIGS. 1 to 3 show, without the prepolymerization to be carried out,
It is a microscope picture which shows the particle structure of the polypropylene particle obtained by bulk polymerization at the polymerization temperature. 4 to 8 are photomicrographs showing the particle structure of the polypropylene particles obtained by performing the low-temperature prepolymerization to be carried out.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08F 4/60-4/70

Claims (4)

(57) [Claims] (A) preliminarily polymerizing an active complex in which alumoxane and a metallocene catalyst are precipitated by contacting the precipitated active complex with the olefin monomer at a temperature significantly lower than the polymerization temperature of the olefin monomer; The metallocene catalyst is of the formula R ″ (C ₅ R ′ _m ) ₂ MeQp where (C ₅ R ′ _m ) is cyclopentadienyl or substituted cyclopentadienyl; R ′ is hydrogen or 1-20 A hydrocarbon group having carbon atoms, and each R 'may be the same or different; R "is an alkylene group, silicon hydrocarbon group, germanium hydrocarbon group, alkylphosphine or alkyl having 1-4 carbon atoms. An amine,
R ″ acts to bridge the two (C ₅ R ′ _m ) rings;
Is a hydrocarbon group having 1-20 carbon atoms or halogen; Me is a metal of Group 4b of the Periodic Table of the Elements; m is 0-4
And p is an integer of 0-3; (b) further prepolymerizing the complex by heating it to the polymerization temperature as quickly as possible; and (c) Polymerizing the olefin monomer under polymerization conditions, comprising the steps of: 2. The method according to claim 1, wherein the heating in step (b) is performed at a rate not less than 5 ° C. per minute. (A) forming an active complex by pre-contacting an alumoxane with a metallocene catalyst, provided that the metallocene catalyst has the following formula: R ″ (C ₅ R ′ _m ) ₂ MeQp ₅ R _'m) is cyclopentadienyl or substituted cyclopentadienyl; R' is a hydrocarbon group having a hydrogen or a 1-20 carbon atoms, and each R 'be the same or different Often; R "is an alkylene group having 1-4 carbon atoms, a silicon hydrocarbon group, a germanium hydrocarbon group, an alkylphosphine or an alkylamine;
R ″ acts to bridge the two (C ₅ R ′ _m ) rings;
Is a hydrocarbon group having 1-20 carbon atoms or halogen; Me is a metal of Group 4b of the Periodic Table of the Elements; m is 0-4
And p is an integer of 0-3; (b) precipitating the active complex with a hydrocarbon that is a non-solvent for the complex; (c) Pre-polymerizing by contacting the active complex with the olefin monomer at a temperature significantly lower than the polymerization temperature of the olefin monomer; (d) further pre-polymerizing by heating the complex to the polymerization temperature as quickly as possible And (e) polymerizing the olefin monomer under polymerization conditions. 4. The method according to claim 3, wherein the heating in step (d) is performed at a rate not less than 5 ° C. per minute.