WO2000047636A2

WO2000047636A2 - A MULTI-STAGE PROCESS FOR THE PREPARATION OF A HIGHLY STEREOREGULAR AND MELT PROCESSABLE α-OLEFIN POLYMER PRODUCT

Info

Publication number: WO2000047636A2
Application number: PCT/FI2000/000096
Authority: WO
Inventors: Thomas Garoff; Pauli Leskinen
Original assignee: Borealis AS; Borealis Technology Oy
Current assignee: Borealis AS; Borealis Technology Oy
Priority date: 1999-02-12
Filing date: 2000-02-11
Publication date: 2000-08-17
Anticipated expiration: 2001-08-12
Also published as: FI990284A0; WO2000047636A3; AU2551900A

Abstract

The invention relates to a process for the preparation of a highly stereoregular and melt processable α-olefin polymer product. The product is obtained by (i) producing a low melt flow rate polymerization product by contacting an α-olefin under polymerization conditions with a first high activity polymerization catalyst system comprising a transition metal compound, a first organometal compound and a stereoregulating external electron donor, and little or no hydrogen termination agent; (ii) producing in one or more steps a high melt flow rate polymerization product by contacting an α-olefin under polymerization conditions with a second high activity polymerization catalyst system comprising a transition metal compound, a second organometal compound and a stereoregulating external electron donor, and a hydrogen termination agent; and (iii) integrating or combining the low and high melt flow rate polymerization products. A surprisingly good yield of the high melt flow rate polymerization product is achieved if the second organometal compound contains, on an atom basis, more halogen per metal than the first organometal compound.

Description

A multi-stage process for the preparation of a highly stereoregular and melt processable α-olefin polymer product

The invention relates to a process for the preparation of a highly stereoregular and melt processable α-olefϊn polymer product, comprising: (i) producing a low melt flow rate polymerization product by contacting an α-olefϊn under polymerization conditions with a first high activity polymerization catalyst system comprising a transition metal compound, a first organometal compound and a stereoregulating external electron donor, and little or no hydrogen termination agent; (ii) producing in one or more stages a high melt flow rate polymerization product by contacting an α-olefin under polymerization conditions with a second high activity polymerization catalyst system comprising a transition metal compound, a second organometal compound and a stereoregulating external electron donor, and a hydrogen termination agent; and (iii) integrating or combining the low and high melt flow rate polymerization products.

The above mentioned symbols (i) to (iii) do not necessary represent separate steps, but can also represent measures, which are carried out partly simultaneously or have been integrated in any convenient way.

The word "comprising" means that the subsequently listed subject matter must be included, but that further subject matter may also be included. It is open. See Grubb, P.W., Patents in Chemistry and Biotechnology, Clarendon Press, Oxford, 1986, p. 220.

By melt flow rate (MFR) is meant the mass of a polymer extruded through a standard cylindrical die at standard temperature in a laboratory rheometer carrying a standard piston and load. Thus MFR is a measure of the melt viscosity of a polymer and hence of its molar mass (≡ molecular weight). The lower the MFR, the higher is the molar mass. It is frequently used for characterizing polyolefins, e.g. polypropene, where the standard conditions MFR_mi are: temperature 230 °C, die dimensions 9.00 mm in length and 2.095 mm in diameter, load of the piston 2.16 kg (mi=2), 5.0 kg (mi=5), 10.0 kg (mi=10) or 21.6 kg (mi= 21). See Alger, M.S.M., Polymer Science Dictionary, Elsevier 1990, p. 257. The standard generally used is ISO 1133, ASTM D 1238, DIN 53735 and BS 2782:7:720A.

By α-olefin monomer is in this connection meant an α-olefin which is capable of polymerization by the insertion (Ziegler-Natta) mechanism. An α-olefin is a compound having the structure CH₂ = CHR, wherein R is a linear or cyclic alkyl group. Typical α-olefin monomers of the invention are propene (R = -CH₃), butene-1 (R = -CH₂CH₃), 4-methylρentene-l (R = CH₂CH(CH₃)₂), hexene-1 (R = -(CH₂)₃CH₃) and octene-1 (R = -(CH₂)₅CH₃). By an α-olefm polymer is meant an α-olefϊn homopolymer or copolymer. As monomers to be copolymerized can, in addition to α-olefin monomers of the above mentioned type, also be used ethene. By transition metal compound is in this connection meant a transition metal compound which is capable of contributing to the polymerization ability of said polymerization catalyst system. The transition metal compound is the basis of the Ziegler-Natta system's so called "catalyst" or "procatalyst". By first organometal compound is in this connection meant an organometal compound which is capable of contributing to the polymerization ability of said polymerization catalyst system. The organometal compound is also called the "cocatalyst" of the Ziegler-Natta system.

By second organometal compound is in this connection meant either a "cocatalyst" or any organometal compound which fulfills the above mentioned definition and does not act as a drastic catalyst poison. Thus, the skilled person understands what is meant by the above-mentioned terms.

The presence of a stereoregulating electron donor in a high activity α-olefϊn polymerization catalyst produces a stereospecific polymer. Such a polymer usually has high isotacticity, i.e. a high portion of α-olefϊn units in the macromolecular chain having the same configuration with respect to a common direction along the chain. With propene polymers, the xylene soluble fraction XS is a measure of the isotacticity of the polymer. Isotactic macromolecules are associated and crystallized whereby their solubility is lower. Therefore, the lower the XS of an α-olefϊn polymer, the higher its isotacticity.

The preparation of highly stereoregular and melt processable polymers of α-olefms, such as propene, in many phases or steps, is e.g. known from JP patent application 91048 and FI patent application 961722.

According to the examples of the latter document, propylene is in a first step polymerized in the presence of an MgCl₂/TiC /Et₃Al/D (D= stereoregulating external electron donor) type catalyst system and no or a small amount of hydrogen as molar mass reducing agent into a stereoregular propylene polymer having low MFR, and in a second step polymerized in the presence of the same catalyst system and a large amount of hydrogen teπnination agent to a propylene polymer having high MFR. The result is a stereoregular propene polymer product having a broad molar mass distribution in the form of a low MFR (high molar mass) fraction and a high MFR (low molar mass) fraction.

It is assumed that the overall high stereoregularity and the presence of a polymer fraction of low MFR gives good strength and rigidity as well as low creep to the polymer product. The presence of a polymer fraction of high MFR, on the other hand, gives good melt processability and flexibility to the polymer product.

When using a multi-phase or -stage process of the above mentioned type for the preparation of α-olefin polymer products, preparation of the polymer fraction having a high MFR presented the following problems.

In order to obtain a polymer fraction of high MFR, very large amounts of hydrogen were needed. On the other hand, the very large amounts of hydrogen lowered the activity of the catalyst, leading to small yields of high MFR fraction. This problem occured due to the presence of stereoregulating external electron donor and is thus e.g. common in processes where a high MFR fraction is prepared in a low MFR polymer fraction giving a product having an MFR combination on a desired level.

The above mentioned problem relating to the production of the high MFR fraction of the α-olefϊn polymer product has now been solved principally in the following new way.

As was initially mentioned, the present invention relates to an improved polymerization process for the polymerization of a highly stereoregular and melt processable α-olefin polymer product. In the process, a low and a high melt flow rate polymerization product are produced by contacting an α-olefin with, respectively, a first high activity polymerization catalyst system comprising a first organometal compound, and little or no hydrogen teπnination reagent, and a second high activity polymerization catalyst system comprising a second organometal compound, and more hydrogen termination reagent, and integrating or combining the polymerization products. In the former contacting, a low MFR polymer fraction is produced and in the latter contacting, a high MFR polymer fraction is produced.

Now, it has been realized that the above mentioned problem can be solved, if in the process, the second organometal compound contains, on an atom basis, more halogen per metal than the first organometal compound. By using a more halogenated organometal compound in the high MFR polymerization stage, a sufficient amount of the high MFR polymer fraction is produced and the high MFR polymer fraction has a high stereoregularity.

The improvements obtained by using a more halogenated organometal compound when producing the high MFR polymer fraction are undisputable and verified by several examples.

According to a non-limiting model of the catalyst system, the stereoregulating external donor takes part in an equiUbrium between a catalyst-bound state where it exclusively produces isotactic polymer and a catalyst-unbound state where it, among others, allows molecular weight regulating termination by hydrogen. A more halogenated organoaluminium compound is believed to coordinate more strongly to the donor and displace the equilibrium in favour of the catalyst-unbound state, thereby giving polymer of a higher MFR (lower molar mass). The former state is only little disturbed, thus giving a high enough isotacticity/stereoregularity.

The product of the claimed process is a mixture of said low MFR polymerization product and said high MFR product. The products can e.g. be combined by mechanical mixing in a melt processor. Preferably they are integrated by (ii) producing the high MFR polymerization product in the presence of (i) the low MFR polymerization product. By low MFR polymerization product is e.g. meant the whole reaction mixture resulting from the low MFR polymerization or just a part thereof. Preferably, the high MFR polymerization is carried out in the presence of both the low MFR polymer and its catalyst system, i.e. the first high activity polymerization catalyst system.

Most preferably, the second high activity polymerization catalyst system does not have a separate transition metal compound of its own, but it comprises a mixture and/or reaction product of the first high activity polymerization catalyst system and said second organometal compound.

Advantageously, said second organometal compound is added to the first high activity polymerization catalyst system before (ii) producing the high melt flow rate polymerization product, preferably between (i) producing the low melt flow rate polymerization product and (ii) producing the high melt flow rate polymerization product. This is easily accomplished e.g. by adding the second organometal compound to the high MFR polymerization reactor or preferably, to the pipeline connecting the low and high MFR polymerization reactors, such as the loop and gas phase reactors, respectively. However, if step (ii) comprises more than one substep (gas phase reactor), the second organometal compound can be added after the first substep (gas phase reactor).

When using two successive steps, the latter step of producing high MFR polymer is especially improved by employing therein a more halogenated organometal compound. When using a slurry reactor in the former step and at least one gas phase reactor in the latter step, the donor of the former step is believed to concentrate on the solid catalyst surface before or in conjunction with the latter step. This means still more catalyst-bound donor and less an amount of high MFR polymer. By employing the present invention and adding a more halogenated organometal compound to the high MFR phase, still larger amounts of donor are liberated from the catalyst and still more high MFR polymer is produced.

According to an embodiment of the invention, the first organometallic compound is a conventional so called cocatalyst, preferably a first organoaluminium compound. More preferably, the first organoaluminium compound has the formula (1)

R_3m-_nAl_mX_n (1)

wherein R is a C C₁₂ alkyl, X is a halogen, m is 1 or 2 and n is an integer such that 0< n <3 m-1. Advantageously, the first organoaluminium compound having the formula (1) is a tri-Cι-C₁₂ alkyl aluminium, most preferably triethyl aliuriinium TEA.

According to an embodiment of the invention, the second organometal compound is a second organo umi-nium compound. Typically, it is selected among more halogenated so called olefin polymerization cocatalysts. See above. Preferably, the second organoaluminium compound has the formula (2)

wherein R' is a C C₁₂ alkyl, X' is a halogen, m' is 1 or 2 and n' is such an integer that n'/m' > n/m, wherein n and m are the same as in formula (1), and n' < 3m'. Advantageously, the second organoaluminium compound which has the formula (2) is selected from C₁-C -al-kylaluminium dihalides such as ethylaluminium dichloride, di-Cι-C -alkylalu-ninium halides such as dielhylaluminium chloride and C C - altylalu-r-tinium sesquihahdes such as ethylaluminium sesquichloride, as well as mixtures thereof. The most preferable second organoaluminium compounds which have the formula (2) are emylaluniinium dichloride EADC and diethylaluminium chloride DEAC. It should be born in mind that the above mentioned first and second organometal compounds are not selected independently, but always so that the second organometal compound has more halogen per metal than the first one. Typical first organometal compound/second organometal compound pairs of the invention are trialkyl alum--nium/dialkyl aluminium halide, trialkyl alu-r----nium/alkyl aluminium sesquihalide, trialkyl alumi-mum/alkyl aluminium dihalide, dialkyl aluminium halide/alkyl uminium sesquihalide, dialkyl ahuninium halide/alkyl aluminium dihalide, alkyl aluminium sesquihalide/alkyl aluminium dichloride. Preferable first organometal compound/second organometal compound pairs of the invention are triethyl aluminium diethyl aluminium chloride, triethyl aluπiinium ethyl aluminium sesquichloride, triethyl aluminium ethyl alu--ninium dichloride, diethyl aluminium chloride/ethyl aluminium sesquichloride, diethyl aluminium chloride/ethyl aluminium dichloride and ethyl aluminium sesquichloride/ethyl aluminium dichloride. The most preferable first organometal compound second organometal compound pair is triethyl aluminium/ethyl aluminium dichloride.

The organometal compounds are selected according to their assumed ability to interact with the stereoregulating external electron donor(s) of the catalyst system(s). Therefore, the selection of a suitable stereoregulating external electron donor is also a very important part of the invention. Usually, the organometal compounds of the invention are selected among the conventional less and more halogenated cocatalysts used in the art. Consequently, the stereoregulating external electron donor(s) is(are) also usually selected among the corresponding conventional electron donors of the art.

The stereoregulating external donor(s) is(are) preferably selected from hydro- carboxy silane compounds and hydrocarboxy alkane compounds. More preferably, the stereoregulating external donor is selected from hydrocarbyloxy silane compounds which have the formula (3)

R^" _n..Si(OR^'")₄-_n" (3)

wherein R and R are, independently, a Cι-C₁₂-hydrocarbyl, and n" is an integer 1-3.

More specific examples of useful hydrocarboxy silane compounds are tricyclo- pentylmethoxy silane, tricyclopentylethoxy silane, triphenylmethoxy silane, tri- phenylethoxy silane, diphenyldimethoxy silane, diphenyldiethoxy silane, dicyclo- pentyldimethoxy silane, dicyclopentyldiethoxy silane, methylphenyldimethoxy silane, methylphenyldiethoxy silane, ethylphenyldimethoxysilane, ethylphenyldi- ethoxysilane, cyclopentyltrimethoxy silane, phenyltrimethoxy silane, cyclopentyltri- ethoxy silane and phenyltriethoxy silane.

Still more preferably, the hydrocarbyloxy silane compound having the formula (3) is a di-C -C₁₂-hydrocarbyl-di-C₁-C₃-alkoxy silane or a C -C₁₂-hydrocarbyl-Cι-C₃- alkyl-di-Cι-C₃-alkoxy silane, and most preferably it is dicyclopentyl dimethoxy silane.

Assumingly, the second organometal compound interfers with the donor equilibrium by coordinating more strongly with the stereoregulating electron donor. See above. As a consequence, hydrogen termination is facilitated. Although even small amounts of the second organometal compound will shift the equilibrium in the direction of producing more high MFR material, it is important to establish the amount of used second organometal compound with respect to the amount of used donor. When using an organoaluminium compound as the second organometal compound, the amounts thereof expressed as aluminium Al₂ and of the stereoregulating external electron donor D preferably are such that the molar feed ratio Al₂/D is from about 0.1 to about 30, more preferably from about 0.4 to about 15.

When aiming at a high amount of high MFR polymer fraction (step (ii) with one gas phase reactor) having high isotacticity/stereoregularity, the amount of the second organometal compound must be functional, but not so high as to remove essentially all of the stereoregulating electron donor, because then, isotactic polymer is not produced. In that case, when using an organoaluminium compound as the second organometal compound, the optimal feed ratio Al₂/D is from about 0.5 to about 1.5, preferably from about 0.6 to about 1.4.

The amounts of the other reagents and/or components are defined more closely below in connection with the transition metal compound used in the claimed process.

As was stated above, the invention relates to a process for the preparation of a highly stereoregular and melt processable α-olefm polymer product, comprising: (i) producing a low melt flow rate polymerization product by contacting an α-olefϊn under polymerization conditions with a first high activity polymerization catalyst system and little or no hydrogen termination agent; (ii) producing a high melt flow rate polymerization product by contacting an α-olefm under polymerization conditions with a second high activity polymerization catalyst system and a hydrogen termination agent; and (iii) integrating or combining the low and high melt flow rate polymerization products.

Preferably, the low melt flow rate polymerization product is produced by contacting propene as the α-olefϊn. According to one embodiment of the invention, the low melt flow rate polymerization product is produced by contacting propene as the C₃-Cio-α-olefϊn and ethene as a comonomer. The ethene comonomer improves the properties of some propene polymer grades. Then, usually, more than or equal to 90% by weight of propene is used as as the α-olefϊn and less than or equal to 10% by weight of ethene is used as the comonomer.

If there is only one step (ii), the ethylene content used in that step is preferably below 10%. If, on the other hand, there are several substeps (ii), ethylene is preferably added in an amount giving an ethylene content in the (ii) part of the product of from 20 to 50%.

In the field of Ziegler-Natta catalysis, the use of an organometal compound is fundamental. The compound is generally called a cocatalyst. The use of a stereoregulating electron donor is also common. It is generally called an external electron donor. The present invention is based on the interaction between the external donor and two different organometal compounds. Thus, the type of said third catalyst component, namely the transition metal component, is not critical, as long as it is capable of high activity polymerization. See the initial discussion on the meaning and role of the components.

In the claimed process, one or more highly active and stereospecific catalyst systems are preferred. Advantageously, the first high activity polymerization catalyst system is the reaction product of a supported intermediate containing magnesium, titanium, halogen and optionally an internal donor, with the first organometal compound and the stereoregulating external electron donor. Said reaction product is preferably obtained by contacting magnesium chloride or a complex thereof, titanium tetrachloride and an internal electron donor into a solid intermediate and contacting the solid intermediate with the first organometal compound and the stereoregulating external electron donor.

In order to act as support for the titanium tetrachloride and the internal electron donor in the solid intermediate, the magnesium chloride must be in a chemically active form. This means that the magnesium chloride must have lower crystallinity and higher specific surface area than conventional commercial magnesium chloride. Magnesium chloride may be activated mechanically. In such a process, it is dry- comilled together with the internal electron donor. Then, the comilled product is heat-treated with an excess of titanium tetrachloride, followed by repeated washings with titanium tetrachloride and/or hydrocarbons to give the solid intermediate. Typically, such a solid intermediate exhibits a high specific surface area (50-300 m /g) and contain from 0.5 to 3% by weight of titanium.

Preferably, the magnesium chloride is activated chemically. This can be accomplished by contacting a complex of magnesium chloride, the titanium tetrachloride and the internal electron donor, whereby the complex is converted to activated magnesium chloride supporting the titanium tetrachloride and the internal electron donor.

According to one preferred embodiment of the invention, said complex of magnesium chloride is a solid adduct of magnesium chloride and an alcohol having the formula (1)

MgCl₂-nR""OH (1)

wherein n is 1-6, preferably 2-4 and R"" is a Ci-Cio-alkyl, preferably a Cι-C₃-alkyl. n is preferably 2-4. Most preferably, the solid adduct of magnesium chloride and an alcohol having the formula (1) is a complex of the formula MgCl₂-3C₂H₅OH.

The solid adduct of magnesium chloride and alcohol having the formula (1) is conveniently prepared by heating and melting the magnesium chloride and the alcohol together, dispersing or spraying the melt into small droplets and solidifying the droplets by contact with a cooled medium. The dispersion of the melt into small droplets may typically take place by pouring the melt into hot silicon oil under stirring, thereby foπning a hot dispersion of molten droplets in silicon oil. Then, the solidification is brought about by pouring the hot dispersion into cold hydrocarbon.

Preferably, however, the melt of magnesium chloride and alcohol is sprayed by means of pressurized inert gas through a die into a space containing cold inert gas, whereby the small droplets are formed and solidified almost instantly. This process is also called spray crystallization.

Finally, said solid magnesium dichloride/alcohol adduct which has been obtained in powder form is contacted with the titanium tetrachloride and the internal electron donor. The titanium tetrachloride both removes the alcohol thereby exposing coordination sites on the magnesium chloride and coordinates to part of the formed coordination sites. The internal electron donor coordinates to another part of the coordination sites. There may be chemical reactions between the alcohol and the internal electron donor. Anyway, the result is a solid intermediate comprising magnesium chloride supporting the titanium tetrachloride and the internal electron donor or its reaction product.

The internal electron donor used for preparing the solid intermediate is any organic compound which contains an electron donating atom such as N, P, O and S, gives catalytic activity and enables stereospecific polymerization. The art of Ziegler-Natta catalysis knows a multitude of suitable electron donors for this purpose. Preferably, the internal electron donor is a C C₁ alkyl ester of a carboxylic acid. Typical such esters are Ci-Ci-t-alkyl esters of aliphatic dicarboxylic acids such as maleic acid, malonic acid and cyclohexanedicarboxylic acid, Cι-C₁ -alkyl esters of aromatic monocarboxylic acids such as substituted and unsubstituted benzoic acids, and Cι-Ci₄-alkyl esters of aromatic dicarboxylic acids, such as phthalic acid.

According to a preferred embodiment of the invention, the internal electron donor is a C₄-C1₄ alkyl ester of an aromatic carboxylic acid. More preferably, the internal electron donor is a di-C₄-Ci₄-alkyl ester of a dicarboxylic acid. Most preferably, the internal electron donor is a di-C₄-Ci₄-a--kyl ester of an aromatic dicarboxylic acid, such as a di-C₄-Ci₄-alkyl phthalate.

Preferably, the above mentioned solid intermediate is produced by contacting said solid adduct of magnesium dichloride and a CrC₃-alcohol as the magnesium chloride complex and a C₄-C₁₄-alkyl ester of a carboxylic acid as the internal electron donor, whereby said complex, said titanium tetrachloride and said ester most preferably are being contacted at an elevated temperature to produce said solid intermedi- ate in the form of a transesterification product. Thereby, said adduct, said titanium tetrachloride and said ester are contacted at 110-200 °C, preferably at 120-150 °C at which temperature the transesterification takes place.

When preparing the above mentioned solid intermediate, the used amounts of magnesium chloride or a complex thereof and titanium tetrachloride are such that in said catalyst system, the molar ratio Mg/Ti is preferably between about 1 and about 200, most preferably between about 5 and about 50. The used amount of said internal donor (ID) is preferably such that in said intermediate, the molar ratio ID/Ti is between about 0.1 and about 10, most preferably between about 0.3 and about 3. When the solid intermediate is contacted with the first organometal compound and the stereoregulating external electron donor to give said first high activity polymerization catalyst system, the contacting can take place in one, two or more steps.

According to one embodiment of the invention, said solid intermediate is contacted first with one out of two portions containing the first organoaluminium compound, and then with the other.

As is common with polymerization catalyst systems of this kind, the catalyst system can alternatively be coated with a small amount of polymer before using it in the actual polymerization. This is called prepolymerization. In a prepolymerization, said solid intermediate is typically contacted with the stereoregulating external donor and the first organoaluminium compound, as well as a small portion of olefin (not necessary the same one as in the main polymerization step or steps), under polymerization conditions, in order to obtain particles of the first high activity polymerization catalyst system which are coated with a polyolefin. Such a prepolymerized catalyst system is easy to handle and has a desirable morphology.

In the first high activity polymerization catalyst system used in the claimed process, the used amounts of the first organoaluminium compound expressed as aluminium Ali and said titanium tetrachloride of said solid intermediate, expressed as titanium Ti, are preferably such that the molar feed ratio Ali/Ti leading to the first high activity polymerization catalyst system is from about 1 to about 1000, more preferably from about 50 to about 500, most preferably from about 100 to about 300.

Correspondingly, the used amounts of the first organoaluminium compound expressed as aluminium Ali and the stereoregulating external electron donor D are preferably such that the molar feed ratio AljJD leading to the first high activity polymerization catalyst system is from about 0.1 to about 100, most preferably from about 2 to about 20. The used amounts of the stereoregulating external electron donor D and said titanium tetrachloride expressed as titanium Ti are preferably such that the molar feed ratio D/Ti leading to the first high activity polymerization catalyst system is from about 2 to about 100, more preferably from about 10 to about 50.

The low MFR polymerization product is preferably produced (see step or measure (i) above) under conditions which give polypropene having a MFR selected from MFR₂ values larger than or equal to 0.01 g/10 min and smaller than 50 g/10 min. More preferably, the low MFR polymerization product is produced under conditions which give polypropene having a MFR selected from MFR₂ values larger than or equal to 0.05 g/10 min and smaller than or equal to 20 g/10 min.

The invention also covers embodiments outside the examples. Equipped with the basic information provided by this document, the parameters, reactants, etc. can be optimized to produce high MFR polymer having a low XS value. Thus, (i) the low melt flow rate polymerization product is preferably produced under conditions which give polypropene having an isotacticity, expressed as XS (xylene soluble fraction), selected from XS values smaller than or equal to 8.0% by weight, more preferably XS values smaller than or equal to 4.0% by weight.

The steps or measures of the process can be carried out in any convenient apparatus, having one or more reactors. The process can be a batch or continuous process. Preferably, the process is carried out in two or more reactors, which are connected in series.

According to one embodiment of the invention, the low MFR product is (i) produced in a bulk reactor, preferably in a loop bulk reactor. The low MFR polymerization product is preferably produced under bulk polymerization conditions selected from:

- a temperature selected from temperatures which are higher than or equal to 40 °C and lower than or equal to 120 °C, preferably temperatures which are higher than or equal to 60 °C and lower than or equal to 90 °C,

- a pressure selected from pressures which are higher than or equal to 20 bar and lower than or equal to 80 bar, preferably pressures which are higher than or equal to 30 bar and lower than or equal to 60 bar,

- a hydrogen to propene molar feed ratio selected from molar ratios which are lower than or equal to 2- 10^" , preferably lower than or equal to 4- 10^" .

The process according to the invention comprises the production of a high MFR polymerization product. See step or measure (ii) above (with one substep). The high MFR product is preferably produced by contacting propene as said α-olefin monomer. The high MFR propene polymer product is conveniently produced under conditions which give polypropene having a melt flow rate selected from MFR values larger than 20 g/10 min and smaller than or equal to 2000 g/10 min. Preferably, the conditions are such that a propene polymer is obtained having a melt flow rate selected from MFR₂ values larger than or equal to 65 g/10 min and smaller than or equal to 1500 g/10 min, most preferably larger than or equal to 80 g/10 min and smaller than or equal to 1200 g/10 min.

When step (ii) contains more than one substep (two or more gas phase reactors) for producing heterophasic polymer, the amount of product produced in the additional substeps influences one the MFR of the final product.

The high melt flow rate polymerization product is preferably produced in a gas phase reactor GPR. Advantageously, the high MFR polymerization product is produced under gas phase polymerization conditions selected from:

- a temperature selected from temperatures which are higher than or equal to 50 °C and lower than or equal to 130 °C, preferably temperatures which are higher than or equal to 70 °C and lower than or equal to 100 °C,

- a pressure selected from pressures which are higher than or equal to 10 bar and lower than or equal to 60 bar, preferably pressures which are higher than or equal to

20 bar and lower than or equal to 40 bar,

- a hydrogen to propene molar concentration ratio selected from molar ratios which are higher than or equal to 0.001 and lower than or equal to 0.20, preferably higher than or equal to 0.005 and lower than or equal to 0.15.

As was mentioned above, (i) the production of the low melt flow rate polymerization product and (ii) the production of the high melt flow rate polymerization product are preferably carried out in successive, preferably two polymerization reactors. It was also mentioned that step (ii) can comprise more than one substep, which is performed in gas phase reactors.

Further, the process is carried out under polymerization conditions which produce (i) low melt flow rate polymerization product and (ii) high melt flow polymerization product in a mass ratio selected from ratios larger than or equal to 20:80 and smaller than or equal to 70:30.

When selecting the parameters of the present process, they are preferably selected so as to give a highly stereoregular and melt processable propene polymer product having a melt flow rate selected from MFR₂ values larger than or equal to 1.0 g/10 min and smaller than or equal to 200 g/10 min, more preferably larger than or equal to 5.0 g/10 min and smaller than or equal to 50 g/10 min, most preferably smaller than or equal to 30 g/10 min.

As was stated in connection with the aims of the invention, a more halogenated second organometal compound can also be used to produce high MFR polymer having a high isotacticity, i.e. a low XS value. This was accomplished by optimizing the molar ratio between the second metalorganic compound and the stereoregulating external electron donor. In examples 1 to 12 and 14 of the invention where the Al₂ was fed into the pipe line between the bulk and first gas phase reactors, the optimal ratio Al₂/D was between about 0.5 and about 1.5, preferably between about 0.6 and about 1.4. In case of example 13 where Al₂ was fed after the first gas phase reactor, the amount of Al₂ is preferably higher, amounting to an Al₂/D ratio of about 5 to 15, preferably about 8 to about 12.

Preferably, the process is carried out under conditions which give a highly stereoregular and melt processable propene polymer product having an isotacticity, expressed as XS (xylene soluble fraction), selected from XS values smaller than or equal to 10% by weight, more preferably smaller than or equal to 6% by weight for one gas phase step systems. In more than one gas phase step systems, the XS values preferably exceed 10 w-%.

Examples

Preparation of catalyst system

A transesterified transition metal catalyst component prepared according to EP 279818 and EP 491566, herewith included by reference, was used when broad MWD material was produced. The catalyst was preactivated with a low amount of TEA (Al Ti molar ratio = 2).

The preactivated transition metal catalyst component was treated by prepolymerization. The prepolymerization reactor was operated at 25 °C and 40...50 bar pressure. The residence time was 8-10 minutes. Hydrogen feed to prepolymerization was 0.05-1 g/h. Catalyst, cocatalyst, donor, and EADC feeds and molar ratios are shown in Table 1. Table 1

Catalyst, TEA, D-donor and EADC feeds:

Polymerization

After prepolymerization, the treated catalyst was used in a loop-gas phase reactor polymerization. The loop reactor was operated mainly at 80 °C and the residence time in the reactor was 45 min.

The operation conditions in the loop reactor were as follows:

Temperature 80 °C (70 °C when EADC precontact was tested in

PP-r)

Pressure 42...50 bar Hydrogen feed 0.05...4 g/h Propene feed 52...85 kg/h Slurry density -430 kg/m³ Solids concentration -30 Production rate -10 kg/h Mileage 15...60 kg/h The operation conditions in the gas phase reactor (GPR) were as follows:

Temperature 85 °C

Total pressure 29 bar

Propene feed -50 kg (+ 70...75 kg from the loop reactor)

Propene concentration 65...80 mol-%

Hydrogen feed 400...1000 g/h

Hydrogen concentration 10...12 mol-%

Fluidization velocity 0.25...0.3 m/s

Bed level 100...200% (2.5...4 kPa)

Production rate 8...18 kg/h

Residence time 2...3.5 h

A summary of the comparative and working examples (where EADC has been used) is shown in Table 2. Analysis are from a powder sample.

In Table 3, process parameters and results for Examples 13 and 14 and comparative Example 3 are shown. These examples were carried out in a laboratory scale reactor system comprising a loop reactor (step (i)) and two gas phase reactors ((iia) and (iib)). Total Al/Ti ratio (mole/mole) was 250 and Al/D ratio (mole/mole) was 10. DEAC was used instead of EADC. Catalyst was the same as in examples 1-12.

The xylene soluble fraction (XS) and amorphous fraction (AM) were measured and calculated as follows:

2.0 g of polymer are dissolved in 250 ml p-xylene at 135 °C under agitation. After 30 ± 2 minutes the solution is allowed to cool for 15 minutes at ambient temperature and then allowed to settle for 30 minutes at 25 ± 0.5 °C. The solution is filtered with filter paper into two 100 ml flasks.

The solution from the first 100 ml vessel is evaporated in nitrogen flow and the residue is dried under vacuum at 90 °C until constant weight is reached.

XS% = (100 x iiii X vo) / (mo x v,)

mo = initial polymer amount (g) mi = weight of residue (g) vo = initial volume (ml) vi = volume of analyzed sample ( ml)

The solution from the second 100 ml flask is treated with 200 ml of acetone under vigorous stirring. The precipitate is filtered and dried in a vacuum oven at 90 °C. 20

Claims

1. A process for the preparation of a highly stereoregular and melt processable α-olefin polymer product, comprising: (i) producing a low melt flow rate polymerization product by contacting an α-olefϊn under polymerization conditions with a first high activity polymerization catalyst system comprising a transition metal compound, a first organometal compound and a stereoregulating external electron donor, and little or no hydrogen termination agent; (ii) producing in one or more stages a high melt flow rate polymerization product by contacting an α-olefin under polymerization conditions with a second high activity polymerization catalyst system comprising a transition metal compound, a second organometal compound and a stereoregulating external electron donor, and a hydrogen termination agent; and (iii) integrating or combining the low and high melt flow rate polymerization products, characterized in that the second organometal compound contains, on an atom basis, more halogen per metal than the first organometal compound.

2. A process according to claim 1, characterized in that it comprises (iii) integrating the low and high melt flow rate polymerization products by (ii) producing the high melt flow rate polymerization product in the presence of the product of (i) the low melt flow polymerization.

3. A process according to claim 1 or 2, characterized in that the second high activity polymerization catalyst system comprises a mixture and/or reaction product of the first high activity polymerization catalyst system and said second organometal compound.

4. A process according to claim 3, characterized in that said second organometal compound is added to the first high activity polymerization catalyst system before (ii) producing the high melt flow rate polymerization product, preferably between (i) producing the low melt flow rate polymerization product and (ii) producing the high melt flow rate polymerization product.

5. A process according to any preceding claim, characterized in that (i) the production of the low melt flow rate polymerization product and (ii) the production of the high melt flow rate polymerization product are carried out in successive, preferably at least two successive polymerization reactors.

6. A process according to any preceding claim, characterized in that the first organometal compound is a first organoaluminium compound, preferably an organoalum-nium compound having the formula (1) 17

AM% = (100 x m₂ x v₀) / (π-o x Vi) m_o = initial polymer amount (g) m₂ = weight of precipitate (g) v₀ = initial volume (ml)

Vi = volume of analyzed sample (ml)

Table 2

The results of the comparative and working examples.

As it its known the broadening of the molar mass distribution of high MFR products has been very difficult. In comparative example 2 the aim was to use a loop/gas split of 40/60 with MFR₂ = 1 in loop and MFR₂ = 20 in the final product. Without EADC feed to the gas phase reactor, however the highest MFR₂ in the final product was only 3 in spite of a very high hydrogen feed and a long residence time in the GPR and in spite of a very short residence time in the loop reactor. See the data in table 2 above. 18

From working example 1 an EADC feed to the GPR was started. At first, EADC was fed into the bed of GPR but it was soon realized that the best feeding place is direct feed line between the loop reactor and the GPR where EADC can react with the donor in liquid phase and its dispersion over the polymer is good. In the beginning, the amount of EADC was quite high to ensure the effect of the reaction. Immediately very high MFR in the GPR was achieved. In the beginning, the XS on the final product was also on the very high level. Because the target was to get stiff material with low XS, EADC/D-donor molar ratio was started to optimize and EADC/D-donor molar ratio was gradually decreased to a value of about 0.6 mol/mol.

0.6 mol/mol was too low an amount for EADC and the hydrogen sensitivity in the GPR started to decrease. EADC/D-donor molar ratio was increased to the value 1.3 which is the optimum to get good hydrogen sensitivity in GPR and to reach a low XS value of the product.

In example 13 and 14 the effect of DEAC on hydrogen sensitivity in 2^nd GPR (in the "rubber phase") was evaluated when producing propylene/ethylene heterophasic copolymer. Heterophasic copolymerizations were carried out in three stages: the first stage homopolymerization in bulk phase and the second stage homopolymerization in gas phase and the third stage propylene/ethylene copolymerization in gas phase. The temperature was 70-80 °C. In example 13, where the DEAC was added after the 1^st GPR the DEAC/donor molar ratio was 10, and in Example 14, where the DEAC was added into the pipe line between the bulk phase and first gas phase reactor, the DEAC/donor molar ratio was 1.5.

Claims

19

Table 3

The analytical results of PP-b copolymers

From the table it can be noticed that in Example 13 the IV value decreased to 2.9 dl/g, and in case of Example 14 to 2.8 dl/g from the IV value 3.3 dl/g of the comparative Example 3, where no DEAC was added.

Rθm-n lmXn (1) wherein R is a Cι-C₁ alkyl, X is a halogen, m is 1 or 2 and n is an integer such that 0 ≤ n < 3m- 1, most preferably a tri-CrCι alkyl aluminium like triethyl aluminium.

7. A process according to any preceding claim, characterized in that said second organometal compound is a second organo uminium compound, preferably an organoaluminium compound having the formula (2)

R'_3m'-_n'Al_m'X'_n' (2)

wherein R' is a Cι-Cι₂ alkyl, X' is a halogen, m' is 1 or 2 and n' is such an integer that n'/m' > n/m, wherein n and m are the same as in formula (1), and n' < 3m', more preferably ethylaluminium dichloride, diethylaluminium chloride, ethyl- uminium sesquichloride, or a mixture thereof, most preferably ethylaluminium dichloride.

8. A process according to any preceding claim, characterized in that the stereoregulating external donor is selected from hydrocarbyl hydrocarbyloxy silane compounds and hydrocarbyloxy alkane compounds and preferably is a hydrocarbyl hydrocarbyloxy silane compound which has the formula (3)

wherein R and R are, independently, a CrC₁₂-hydrocarbyl, and n" is an integer 1- 3, more preferably a di-C₄-Cι₂-hydrocarbyl-di-Cι-C₃-alkoxy silane like dicyclo- pentyl dimethoxy silane.

9. A process according to claim 7 or 8, characterized in that the used amounts of said second organoaluminium compound expressed as aluminium Al₂ and the stereoregulating external electron donor D are such that the molar feed ratio Al₂/D is from about 0.1 to about 30, preferably from about 0.4 to about 10, most preferably from about 0.6 to about 1.4.

10. A process according to any preceding claim, characterized in that (i) the low melt flow rate polymerization product is produced by contacting propene as the α-olefin.

11. A process according to any preceding claim, characterized in that the first high activity polymerization catalyst system is the reaction product of an intermediate containing magnesium, titanium, halogen and optionally an internal donor, with the first organometal compound and the stereoregulating external electron donor.

12. A process according to claim 11, characterized in that the first high activity polymerization catalyst system has been prepared by contacting magnesium dichloride or a complex thereof, titanium tetrachloride and an internal electron donor into a solid intermediate and contacting the solid intermediate with the first organometal compound and the stereoregulating external electron donor.

13. A process according to claim 12, characterized in that said solid intermediate is contacted first with one out of two portions containing the first organoaluminium compound, and then with the other.

14. A process according to claim 12 or 13, characterized in that said solid intermediate is contacted with the stereoregulating external donor and the first organoaluminium compound, as well as a small portion of an olefin under polymerization conditions, in order to obtain particles of the first high activity polymerization catalyst system which are coated with polyolefin.

15. A process according to any of claims 12-14, characterized in that the used amounts of the first organoaluminium compound expressed as aluminium Ali and said titanium tetrachloride of said solid intermediate expressed as titanium Ti are such that the molar feed ratio Ali/Ti leading to the first high activity polymerization catalyst system is from about 1 to about 1000, preferably from about 50 to about 500, most preferably about 100 to about 300.

16. A process according to any of claims 11-15, characterized in that the used amoimts of the first org-moaluminium compound expressed as aluminium Al_! and the stereoregulating external electron donor D are such that the molar feed ratio Ali/D leading to the first high activity polymerization catalyst system is from about 0.1 to about 100, preferably from about 2 to about 20.

17. A process according to any of claims 12-16, characterized in that the used amounts of the stereoregulating external electron donor D and said titanium tetrachloride expressed as titanium Ti are such that the molar feed ratio D/Ti leading to the first high activity polymerization catalyst system is from about 1 to about 100, preferably from about 10 to about 50.

18. A process according to any of claims 10-17, characterized in that (i) the low melt flow rate polymerization product is produced under conditions which give polypropene having a melt flow rate selected from MFR₂ values larger than or equal to 0.01 g/10 min and smaller than 50 g/10 min, preferably larger than or equal to 0.05 g/10 min and smaller than 20 g/10 min.

19. A process according to any of claims 10-18, characterized in that (i) the low melt flow rate polymerization product is produced under conditions which give polypropene having an isotacticity, expressed as XS (xylene soluble fraction), selected from XS values smaller than or equal to about 8.0% by weight, preferably smaller than or equal to about 4.0% by weight.

20. A process according to any preceding claim, characterized in that (i) the low melt flow rate polymerization product is produced in a bulk reactor, preferably in a loop bulk reactor.

21. A process according to claim 20, characterized in that (i) the low melt flow rate polymerization product is produced under bulk polymerization conditions selected from:

- a hydrogen to propene molar feed ratio selected from molar ratios which are lower than or equal to 2-10^" , preferably lower than or equal to 4-10^" .

22. A process according to any preceding claim, characterized in that (ii) the high melt flow rate polymerization product is produced by contacting propene as the α-olefin.

23. A process according to claim 22, characterized in that (ii) the high melt flow rate polymerization product is produced under conditions which give a melt flow rate selected from MFR₂ values larger than 20 g/10 min and smaller than or equal to 2000 g/10 min, preferably larger than or equal to 65 g/10 min and smaller than or equal to 1500 g/10 min, most preferably larger than or equal to 80 g/10 min and smaller than or equal to 1200 g/10 min.

24. A process according to any preceding claim, characterized in that (ii) the high melt flow rate polymerization product is produced in a gas phase reactor.

25. A process according to claim 24, characterized in that (ii) the high melt flow rate polymerization product is produced under gas phase polymerization conditions selected from:

20 bar and lower than or equal to 40 bar,

- a hydrogen to propene molar concentration ratio selected from molar ratios which are higher than or equal to 0.001 and lower than or equal to 0.2, preferably higher than or equal to 0.005 and lower than or equal to 0.15.

26. A process according to any preceding claim, characterized in that (ii) the production of high melt flow rate polymerization product is carried out in several, preferably three, most preferably two substeps.

27. A process according to claim 26, characterized in that in the first substep, the amount of ethylene is from 0 to 10%, based on the combined weight of the α-olefin and the ethylene.

28. A process according to claim 26 or 27, characterized in that in the second or other subsequent substeps, the amount of ethylene is over 10%, preferably from about 20% to about 50%, based on the combined weight of the α-olefin and the ethylene.

29. A process according to any preceding claim, characterized in that one of the low and high melt flow rate products, or both, are produced by copolymerizing said α-olefin with another α-olefin or ethene.

30. A process according to any of claims 10-29, characterized in that it is carried out under conditions which give a highly stereoregular and melt processable propene polymer product having a melt flow rate selected from MFR₂ values larger than or equal to 1.0 g/10 min and smaller than or equal to 200 g/10 min, preferably larger than or equal to 5.0 g/10 min and smaller than or equal to 50 g/10 min.

31. A process according to any of claims 10-25, characterized in that it is carried out under conditions which give a highly stereoregular and melt processable propene polymer product having an isotacticity, expressed as XS (xylene soluble fraction), selected from XS values smaller than or equal to 10% by weight, preferably smaller than or equal to 6% by weight, for processes having one substep in step (ii).