METHOD FOR THE PREPARATION OF OLEFIN POLYMERISATION CATALYST SUPPORT AND AN OLEFIN POLYMERISATION CATALYST
The present invention relates to a catalyst support, to a preparation process thereof, to a Ziegler-Natta catalyst, as well as to the use of the catalyst for polymerising olefins.
BACKGROUND ART
Ziegler-Natta (ZN) polyolefin catalysts are well known in the field of polymers. Generally, they comprise (a) at least a catalyst component formed from a transition metal compound of Group 4 to 6 of the Periodic Table (IUPAC, Nomenclature of Inorganic Chemistry, 1989) , a metal compound of Group 1 to 3 of the Periodic Table (IUPAC) , and, optionally, a compound of group 13 of the Periodic Table (IUPAC) and/or an internal donor compound. ZN catalyst may also comprise (b) further catalyst component (s) , such as a cocatalyst and/or an external donor.
Various methods have been developed for preparing ZN catalysts . In one method the catalyst components are impregnated on a particulate support material, such as silica, to obtain a solid ZN catalyst system. For example in WO 01 55230 of Borealis a solution of a chlorine-containing compound, e.g. ethylaluminium dichloride, and a magnesium hydrocarbyloxy compound is first prepared and the obtained solution is impregnated together with a transition metal compound into a porous support .
Solid ZN catalysts, wherein no external support, such as silica, is used, are also known in the field. US 4 496 660 of Dow discloses a catalyst support formed by reacting in an inert diluent (A) the reaction product of (1) an
organomagnesium component, (2) an oxygen- and/or nitrogen- containing compound, optionally dissolved or dispersed to a halide containing compound of a transition metal; and (B) a transition metal-free halide source. In the examples the compound (1) is combined with the compound (2) and a halogen- free aluminium compound and then a transition metal compound is added. The obtained solids are then reacted with the compound (B) . EP 591 922 of Mitsui discloses a titanium catalyst prepared by contacting (A) a solution of a halogencontaining magnesium compound, an alcohol having at least 6 carbon atoms and a hydrocarbon solvent, with an organoaluminum compound to form a solid complex which is treated with (B) a tetravalent titanium compound.
WO 99 55741 of Fina describes a process for preparing a Ziegler-Natta catalyst by (i) mixing in a hydrocarbon solvent a dialkyl magnesium compound with a chlorinating agent to precipitate a magnesium dichloride derivative. The chlorinating agent is obtainable from the reaction between an alcohol ROH and an alkyl aluminium chloride. The precipitate is washed or reacted to remove unwanted reducing species and the obtained magnesium dichloride derivative is titanated. WO 99 58584 of Borealis describes a further method for preparing a ZN catalyst, wherein a Mg compound is first reacted with an alcohol and the obtained complex is added to a solution of chlorine containing aluminium compound to form a solid reaction product. The obtained slurry is used as such in the next step and to this slurry titanium tetrachloride is added. EP 197 166 of Dow describes a catalyst solution, wherein (A) an organomagnesium compound, (B) an organic OH-containing compound, (C) a reducing halide source of Al or B and (D) a transition metal compound are added in the order (A) , (B) , (C) and (D) ; or (A) , (B) , (D) and (C) , and the obtained
reaction solution is used as such for the polymerisation. Again no washing steps between the additions are made and no separation of the final reaction product from the reaction media is effected.
Accordingly, although much development work has been done in the field of Ziegler-Natta catalysts, there remains a continuing search for alternative or improved methods of producing ZN catalysts with desirable properties, such as morphology .
SUMMARY OF THE INVENTION
The present invention provides a further process for preparing a solid catalyst support, and a ZN catalyst component based on said support, with an unexpected effect. A further solid catalyst support and a further ZN catalyst component with improved properties are also provided.
A further aspect of the invention is to provide an olefin polymerisation process using the ZN catalyst prepared according to the preparation process of the invention.
DESCRIPTION OF THE INVENTION
It has been found that when a solid reaction product is formed from a magnesium hydrocarbyloxy compound and a halogen-containing compound of an element of Group 13 or 14 of the Periodic Table (IUPAC, Nomenclature of Inorganic Chemistry, 1989, used also below) , and the obtained solid product is recovered from the reaction mixture, a solid catalyst precursor, herein referred as a catalyst support material, with i.a. markedly improved morphology can be obtained. The support material of the invention can then be treated with further catalytically active compound(s), such
as with one or more transition metal compounds, to obtain a catalyst component for olefin polymerisation.
According to the general method of the invention a particulate catalyst support to be used as a polymerisation catalyst component is prepared first by (a) contacting a solution of a magnesium hydrocarbyloxy compound (compound
(1)) with (b) a solution of a halogen-containing compound of an element of Group 13 or 14 of the Periodic Table (IUPAC)
(compound (2)) to obtain a solid particulate reaction product. Then the obtained reaction product is recovered from the reaction mixture by separating the solid product from the liquid reaction medium and/or by washing the product before it is used as a support material .
There are, however, some problems relating to the particle size of the precipitated MgCl2 support. Thus, it has been found that a very small particle size is normally produced with the general method described above. The classical methods, such as use of slow precipitation in diluted solutions or use of low temperature to slow down the reactions have only a limited effect on the particle size (PS) of the precipitated MgCl2. In practice, it has been difficult to bring up the PS of the precipitated MgCl2 over 10 μm.
In some previous studies it has been found that a suitable morphology and also a suitable narrow particle size distribution (PSD) can be created to a precipitated MgCl2 support (carrier) material if a Mg-alcoholate is added into a solution of Et-AlCl2 (EADC) . The precipitated MgCl2 support has to be washed at least one time with a suitable hydrocarbon solution. When this support material is reacted
with TiCl4 after wash, then a catalyst is achieved with a narrow PSD and a good morphology. This catalyst, when used in polymerisation of ethene has given a PE material with a narrow PSD and a low portion of fines. However, there still remains the problem with particle size of support and thus of the catalyst and finally of the produced polymer.
It has now been surprisingly found that the particle size of the precipitated MgCl2 carrier (support) material can be adjusted by changing the precipitation temperature. According to the invention it has been found that, if a higher (elevated) temperature is used in the precipitation reaction, then PS of the carrier will become bigger. As a higher temperature it is meant a temperature at least 30 °C. The effect of using higher temperature is very surprising, because normally an opposite behaviour is seen in precipitation reactions.
Due to the beneficial properties of the support material of the invention, the good morphology is maintained during the treatment step of the support with further catalytically active compounds, whereby also the resulting final catalyst component has an excellent morphology. The obtained catalyst has in addition to a narrow particle size distribution (PSD) also a desired average particle size (PS) , which is bigger than if said higher temperature were not used during the precipitation step.
Furthermore, the final catalyst of the invention exhibits high catalytic activity and the polymer product produced therewith has i.a. a decreased amount of fines (i.e. particles with size < 100 μm) , i.e. below 15 %, preferably
below 10 % of fines. Even fines content below 6 % can be obtained.
The process for preparing the catalyst carrier (support) and further the catalyst are illustrated in Figures 1 and 2.
Figure 1 illustrates the carrier synthesis. Figure 2 illustrates the catalyst synthesis.
By using said higher temperature, i.e. temperature of at least 30 °C, and having as an upper limit 70 °C, in the precipitation reaction, i.e. in the step, where the Mg- alcoholate is added to the EADC solution, an average PS of the carrier will be at least 20 μm, preferably over 30 μm, and more preferably in the range of 20 to 70 μm, most preferably in the range 30 to 60 μm. The catalyst, which is formed after Ti-treatment of this carrier material, also gets this larger PS. The larger PS of the catalyst leads, due to the replica phenomena, also to a larger PS of the polymer particle. This is an important advantage, especially, when this catalyst is used in a gas phase polymerization process.
In a preferred embodiment of the invention the solution of the compound (s) (1) is added to the solution of compound (s) (2) to cause the solidification (precipitation) of the solid reaction product. A slowly addition under mixing is preferred. By slowly addition it is meant herein that the solution (1) is added gradually, e.g. dropwise or other similar means, to cause a uniform solidification reaction as known in the art .
It has been found that in order to achieve the beneficial properties of the support material, the obtained solid reaction product should be recovered from the reaction mixture of solution (1) and (2) before the use as a support. The recovery step can be effected in various ways including the separation of the liquid reaction medium from the solid reaction product, e.g. by filtration, decantation or suction, and/or washing the solid product with a wash solution e.g. in a manner known in the art, before it is used as a support material . Thus the possible washing step can be carried out after the solids are separated from the liquid medium or, alternatively, without any separation of the solids from the reaction mixture (or the liquid reaction medium is removed only partially) , by adding the wash solution directly to the reaction mixture. The recovery step of the invention covers also the dilution of the reaction mixture and the use of the diluted support slurry in the next step for preparing the catalyst component .
It is evident for a skilled person that the washing efficiency can be varied within the scope of the invention depending on the desired washing effect and can be controlled e.g. by the number of the washing steps, the temperature, the solvent (s) used for washing, the amount of the wash solution and the washing time. The wash temperature can be e.g. 0 to 100 °C, suitably 20 to 100 °C, e.g. 40 to 80 °C, such as 55 70 °C. Thus the duration of a washing (e.g. the mixing time of the slurry in a wash solution) depends on the desired effect and can be chosen accordingly. The washing effect depends on the separation efficiency of the solid material from the solution.
Further treatment steps of the solid reaction product may also be possible after the combination of solutions (1) and (2) (i.e. after the precipitation reaction) before or during the recovery step of the invention. Such treatment includes e.g. a heating step of the reaction mixture after the solidification at an elevated temperature, e.g. up to 100 °C, such as 40 to 80 °C, suitably 50 to 75 °C, for a suitable period of time, such as from 5 minutes to 24 hours, e.g. 10 to 120 minutes, such as 20 to 60 minutes, before the recovery step.
In a preferable embodiment, the molar ratio of the element of Group 13 or 14 of the Periodic Table to magnesium in the catalyst support material of the invention is at least 0.3 (≥ 0.3) . Preferably the molar ratio of said element of Group 13 or 14 of the Periodic Table to magnesium is at least 0.4 ( 0.4), or preferably at least 0.5 (≥ 0.5), or at least of 0.6 (≥ 0.6) . Said ratios result in a catalyst with very good morphology and reduced amount of fines content of the produced polymer product . In a further embodiment of the invention said molar ratio may be even at least 0.7 (≥ 0.7) or 0.80 (≥ 0.80), such as 0.85 (≥ 0.85), depending on the properties desired for the catalyst. In principle, the upper limit of said ratio range is not limited, but may be e.g. 1.1. In one preferred embodiment said upper limit of said molar ratio is 0.99. The above-said molar ratio can be determined in a known manner, e.g. using flame atomic absorption method with e.g. a nitrous oxide/acetylene flame.
Accordingly, the recovery step already improves i.a. the morphology of the catalyst and the produced polymer compared to the prior art practices, wherein the reaction product has not been recovered (i.e. the reaction mixture is used as such
or the solids are separated from the reaction media and used without any washing step) . And said preferable molar ratio of the support material can provide further advantages, such as a preferred morphology with e.g. desirable yields of the catalyst component. However, as is described above, the problems relating to the particle size of the catalyst support and thus of the catalyst can be solved by using a higher temperature during the precipitation reaction of compounds (1) and (2) .
It is generally known that the said molar ratio of the obtained catalyst support can depend on the used starting material, the used preparation method of the support material, reaction conditions and any treatment steps of the reaction product after the combination of the solutions (1) and (2) , and can be chosen accordingly to achieve the desired ratio.
Preferably, the molar ratio of the element of compound (2) to magnesium in the support material is adjusted to a desired range by means of the recovery step of the invention, i.e. by separating the solids from the liquid reaction medium and/or by washing the solids as described above. Particularly, the obtained solid reaction product is washed with a wash solution, and the washing procedure can be repeated, if needed, until the desired ratio is obtained. The ratio can be monitored between the washings, if needed, e.g. by analysing the support samples in a conventional manner the relevant contents of the reaction product or the reaction medium, e.g. the mol-% of Mg and the mol-% of the element from Group 13 or 14 of the Periodic Table in the formed carrier material.
Suitably, a moderate washing is effected to achieve the molar ratio of the invention. Thus the washing treatment of the invention provides convenient means for adjusting the ratio of the support elements to the preferred level (generally, the more thorough washing the lower ratio is obtained) .
The said molar ratio of the support material of the invention is believed to give a beneficial loading of the active species in the final catalyst component .
After the recovery step of the invention, the solid reaction product can be used as a support material for further catalytically active compounds, such as one or more transition metal compound (s) to form a final polymerisation catalyst component, such as the ZN catalyst component of the invention. The term particulate/solid support material means herein an intermediate, i.e. catalyst precursor, that is treated with further catalyst forming compounds as defined below to obtain the final catalyst component. Preferably, the solid support of the invention is first formed in the absence of the catalyst forming transition metal compound, and after the formation thereof treated with said transition metal compound.
Accordingly, in the method of the invention for preparing a Ziegler-Natta catalyst component, the catalyst support of the invention, prepared according to the present method, is suspended in an organic solvent and treated at least with one transition metal compound. The treatment step is preferably effected in a manner known in the art .
Generally, in the final solid catalyst particles, the molar ratio of Mg:Ti can be e.g. between 10:1 to 1:10, preferably
less than 6:1, such as between less than 6:1 and 1:1. The molar ratio of Ti:Al can be e.g. between 10:1 to 1:2, e.g. 5:1 to 1:1. The ratios can be determined in a manner known in the art .
The final catalyst component, e.g. the ZN catalyst component, thus obtained may be combined with further catalyst component (s) conventionally used in the art, such as a cocatalyst (e.g. aluminium alkyl compounds) and/or an external donor compound selected from silanes and (internal) electron donors as defined below. Said further catalyst component (s) can be combined with the present catalyst component during the preparation method of the present catalyst component, or during the actual polymerisation step by adding the catalyst component of the invention and the further component (s) separately into a reactor.
The invention thus provides a controllable method to obtain active catalyst particles with i.a. the desirable loading of the active species and highly preferable morphology, e.g. in addition to a a narrow particle size distribution also a bigger particle size. Further, as described above a markedly reduced fines content in the polymer is achieved. The catalyst support and the final catalyst prepared thereof are also novel with improved properties and thus form part of the invention.
According to the invention, when a higher precipitation temperature, i.e. preferably a temperature in the range of 30°C to 70°C, is used the average size of the catalyst particles of the invention is bigger, i.e. it may vary between 20 to 500 μm, preferably between 20 to 200 μm, more preferably between 30 to 100 μm. The most preferred average
particle size of the catalyst of the invention is between 30
70 μm. However, it should be noted that the most desired particle size of the catalyst depends on the polymerisation process wherein the catalyst is used. Higher catalyst particles are especially preferred in the gas phase polymerization of the ethylene.
In a still further embodiment of the invention the catalyst component (s) can be prepolymerised before the actual polymerisation step.
Starting Compounds for the Support Material
The basic idea of the invention lies in the specific post treatment step of a reaction product formed from the Mg and the Group 13 or 14 compound, which brings the advantages of the invention. Thus the starting material for the catalyst support of the invention can be chosen from one or more magnesium compound (s), provided that at least one Mg compound contains hydrocarbyloxy, and from one or more halogencontaining compound (s) of an element of Group 13 or 14 of the Periodic Table, which are usable for forming a ZN catalyst and which can be brought in a solution and, when contacted together in suitable conditions, form a reaction product which solidifies in said reaction media. Such compounds, the solutions thereof, as well as the reaction conditions to obtain the solid reaction product thereof, are within the skills of a person working in the field of Ziegler-Natta chemistry.
Accordingly, the catalyst support of the invention comprises a reaction product formed at least from:
1) Compound (1) : magnesium hydrocarbyloxy compound of a general formula (I) :
Mg(0R1)2.n(R1)nχx (I), wherein each Rx is independently a Cι_2o hydrocarbyl group, e.g. a C2-ι5 group, preferably a C3_10 group, such as a C4-10 group, suitably a C4_ιo group e.g. an alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl , aryl, arylalkyl, or alkylaryl, wherein alkyl used as alone or as part of another option can be linear or branched and aryl is preferably of 5-12 carbon ring atoms, suitably phenyl or naphthyl ; e.g. each Rx is independently an ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl; each X is independently a halogen, preferably chlorine; 0 ≤ n < 2 and n may or may not be an integer; 0 ≤ x < 2 and may or may not be an integer; and the sum of (2-n) , n and x is 2. In a preferred embodiment of the invention, a magnesium hydrocarbyloxy compound of formula Mg (ORx) 2-n (Ri) nX (I)/ wherein each Rx and X are independently as defined above; x is 0 and 0 ≤ n < 2 , is used, which may be commercially available or, preferably, is a reaction mixture of a magnesium alkyl compound of formula Mg(Rx)2 (III), wherein each Ri independently is as defined above, with an alcohol RχOH, wherein Ri is as defined above; and
2) Compound (2) : A halogen-containing compound of an element of Group 13 or 14 of Periodic Table (IUPAC) , which is preferably a compound of Group 13, such as a halogencontaining aluminium or boron compound. Halogen is e.g. chlorine, bromine or iodine, preferably chlorine. In one preferred embodiment said compound is of formula (II) :
wherein each R
x is independently as defined above in formula (I) , and particularly in case of formula (II) an alkyl of up to 6 , such as up to 4 , carbon atoms ; and each X is independently a halogen, such as chlorine; 0 ≤ x < 3 and x may or may not be an integer; e.g. dialkyl aluminium chloride, such as dimethyl aluminium chloride, diethyl aluminium chloride, diisobutyl aluminium chloride, or alkyl aluminium dichloride, such as ethyl aluminium dichloride (EADC) or methyl aluminium dichloride;
The molar ratio of the element of compound (2) to Mg used may be between 0.5:1 and 2:1, preferably 0.8:1 to 1.2:1, such as 1:1.
Optionally, the present support material comprises further catalytically active compounds, e.g. those useful in a ZN catalyst, such as one or more (internal) electron donors, e.g. those known in the art for (co) polymerising propylene and higher olefins, including organic compounds containing oxygen, nitrogen, sulphur and/or phosphorus, such as organic acids, organic acid anhydrides, organic acid esters, alcohols, ethers, aldehydes, ketones, amines, amine oxides, amides, thiols, various phosphorus acid esters and amides, and the like, added as such or formed in situ, and such compound (s) may be added into one of the solutions of (1) and (2) before the combination of the solutions, or into the reaction media of compounds (1) and (2) . Preferably, the support consists of the reaction product of compound (1) , optionally prepared from compound (III) and RχOH as defined above, and of compound (2) .
Alternatively, said at least one (internal) electron donor or further compound (s) can be added after the formation of the
support product, e.g. when treating the obtained support with the transition metal compound.
Solutions of the Starting Compounds
The term solution is understood herein broadly to include solutions prepared from (a) one or more of the support forming compounds in liquid form (liquid at the room temperature or a melt prepared at a higher temperature) , and/or (b) from an organic solvent (s) .
The solutions are suitably formed using an organic solvent that dissolves the compounds. Preferred solvents include inert hydrocarbons, e.g. linear or branched aliphatic, alicyclic or aromatic C5-2o hydrocarbons, preferably C6-ι hydrocarbons, wherein the ring systems may contain hydrocarbon, e.g. Cι-6 alkyl substituents, such as cyclohexane, hexane, heptane, octane or toluene, or any mixtures thereof. E.g. linear or branched alkanes, e.g. hexane, heptane or octane, may be used.
Wash Solution
As the wash solution, e.g. any organic solvent or mixtures thereof known in the art can be used. Preferable solvents include hydrocarbons as defined above, e.g. pentane, hexane or heptane, particularly heptane.
The Catalyst Component for the Polymerisation of Olefins
The invention further provides a catalyst component, comprising the catalyst support of the invention treated with one or more further catalytically active compound (s), such as one or more transition metal compound(s), e.g. those conventionally used in the ZN catalysts, metallocenes,
metallocene type complexes, chromium compounds etc., or any mixtures thereof, and/or a cocatalyst .
Preferably a Ziegler-Natta catalyst component is provided, wherein said support is treated at least with:
3) One transition metal compound of Group 4 to 10, preferably of Group 4 to 6, more preferably of Group 4, of the Periodic Table (IUPAC) . The transition metal compound is suitably a Ti compound. Particularly, a tetravalent Ti compound can be used. Examples of such compounds are: TiX4 (IV) , wherein each X is independently defined as above in formula (I), such as Cl ; and
wherein each X and Ri are as defined above in formula (I) p is 0, 1, 2 or 3 ;
Preferably, titanium tetrachloride is used.
In the method of the invention for preparing a catalyst component, the solid catalyst support of the invention, preferably as prepared by the present method, is treated with a further catalytically active compound (s) as defined above. Preferably a Ziegler-Natta catalyst component is prepared by suspending the particulate support of the invention in an organic solvent as defined above and treating the support at least with one transition metal compound as defined above. The treatment step is preferably effected in a manner known in the field of ZN chemistry. The molar ratio of the transition metal to be added is preferably 2 to 0.3, e.g. 1.5 to 0.4, such as 1 to 0.5 to one mol Mg present in the support material .
In case of a ZN catalyst, the optional addition of an (internal) electron donor can be effected, as said above, during the formation of the support or, alternatively after the formation of the support product, e.g. together with the transition metal compound.
Embodiments
The solution of. the magnesium hydrocarbyloxy compound is preferably a solution of a magnesium alkoxy compound which may be a commercially available magnesium alkoxy compound or be prepared from a magnesium alkyl compound and an alcohol .
Accordingly, in a preferred embodiment for preparing the catalyst support and a supported polymerisation catalyst, suitably a ZN catalyst component, of the invention: A solution (1) containing a magnesium hydrocarbyloxy compound of formula Mg (ORx) 2-n ( ι)nXχ (D , wherein Rx and X are as defined above; x is 0 and 0 ≤ n < 2 , is prepared first: by contacting, in a hydrocarbon solvent (e.g. heptane), a compound of formula Mg(Rx)2 (III), wherein Rx is as defined above under formula (I), e.g. each Rx is independently methyl , ethyl , propyl , butyl , pentyl , hexyl , heptyl or octyl , e.g. di(n-butyl) magnesium, n-butyl sec-butyl magnesium, butyl ethyl magnesium or butyl octyl magnesium, preferably butyl octyl magnesium (BOMAG) ; with an alcohol of formula RxOH, wherein Rx is as defined above under formula (I) , suitably a cycloalkyl, cycloalkylalkyl, aryl, alkylaryl, arylalkyl or alkyl, each containing from 2 to 15, preferably from 3 to 10 carbon atoms. Preferably Rx is a C3.X5 cycloalkyl or branched or unbranched C3.X5 alkyl, preferably a C4-xo cycloalkyl or a branched or unbranched C4-10 alkyl, such as cyclopentanol, 2- methyl-2-propanol, 2-ethyl-l-butanol, 2 -methyl-1-pentanol , 2-
ethyl-pentanol, 2-ethyl-l-hexanol, n-heptanol, n-octanol and decanol, preferably 2-ethyl-l-hexanol. The alcohols which are usable to transform the magnesium hydrocarbyl to a magnesium hydrocarbyloxy complex soluble in a hydrocarbon solvent, are known in the art or can be readily determined by a skilled person. Said contact is effected in a temperature between 0 and 100 °C, preferably at 10 to 40 °C, e.g. at 20 to 30 °C . The reaction can be completed by heating the system at 50 to 100 °C for 10 to 100 min. Preferably the alcohol is added to the Mg solution. The molar ratio of Mg dihydrocarbyl to RxOH (Mg:RxOH) is preferably from 1:1 to 1:4, more preferably 1:1 to 1:3.5, e.g. 1:1.5 to 1:3.5, especially 1:1.8 to 1:3.1.
The solution (2) of the halogen-containing compound is prepared by dissolving in a hydrocarbon solvent as defined above (e.g. toluene) a compound of formula
wherein each Rx is independently as defined above, preferably an alkyl of up to 6, such as up to 4, carbon atoms; and each X is independently a halogen, such as chlorine; and x may of may not be an integer 0 ≤ x < 3; e.g. dimethyl aluminium chloride, diethyl aluminium chloride, diisobutyl aluminium chloride, ethyl aluminium dichloride and methyl aluminium dichloride, preferably ethyl aluminium dichloride (EADC) . Such solutions may also be commercially available, whereby they may be further diluted, if desired, with a solvent as defined above.
The prepared reaction mixture (1), i.e. Mg-hydrocarbyloxy- containing solution (1) , is then added slowly to the obtained Al solution (2) .
According to the invention the addition is done at a temperature between 30 and 70 °C, preferably at 30 to 60 °C and may be effected under stirring.
After the addition the formed slurry may be heated to e.g. 20 to 100 °C, such as 40 to 80 °C, suitably 50 to 70 °C, for a suitable period of time, such as from 5 minutes to 24 hours, e.g. 10 to 120 minutes, such as 30 to 60 minutes.
In case of EADC, the molar ratio of Al:Mg used may be of 0.5:1 to 2:1, preferably 0.7:1 to 1.5:1, or 0.8:1 to 1.2:1, such as 0.9:1 to 1.1:1, suitably 1:1. If another Al compound is used in place of EADC, then the Al compound is used in an amount that results in a halogen content which corresponds to the halogen content obtained with EADC at the above given ratios .
The formed reaction product is washed with hydrocarbon solvent, such as heptane until a molar ratio of Al:Mg of ≥ 0.3, e.g. of > 0.4 suitably of ≥ 0.6, preferably 0.4 ≤ Al:Mg < 1.1, such as 0.6 < Al:Mg < 0.99, or e.g. 0.7 < Al:Mg < 0.99 is achieved. In one further embodiment also a ratio of ≥ 0.80, e.g. > 0.85, such as 0.85 < Al.Mg < (0.99 to 1, e.g 0.99) may be used. The washing step can be carried out in a temperature between 0 to 100 °C, suitably 20 to 100 °C, e.g. 40 to 80 °C, such as 55 -70 °C.
The solid catalyst support obtained can then be used for the preparation of the catalyst component . Preferably, the support is slurried in a fresh hydrocarbon solvent as defined above (e.g. heptane) and to the slurry titanium tetrachloride
is added slowly e.g. in a manner known in the art, at the temperature of 0 to 100 °C, preferably at 10 to 50 °C. The components are allowed to react with each other e.g. at 20 to 100 °C, e.g. 50 to 80 °C, for 10 to 120 minutes, such as 30 to 60 minutes. Titanium tetrachloride is added to the support material e.g. in a molar ratio of 2 to 0.3 mol Ti, preferably 1 to 0.5 mol Ti, to one mol of Mg in the support.
The supported catalyst particles may then be washed and dried in a conventional manner.
Preferably, the washing is carried out with heptane at elevated temperature to achieve the support material of the invention. Preferably, the molar ratio of the element of compound (2) (e.g. Al) :Mg of the support material is adjusted with the washing step to the level of the invention.
This embodiment provides a convenient alternative for moderate washing of the product to achieve said ratios in higher levels, e.g. between 0.6 and 0.99, such as 0.70 to 0.85, with, again, e.g. an excellent morphology of the obtained catalyst and the resulting polymer product.
Polymerisation Process
As mentioned above the catalyst particles of the invention can be used as such or together with a separate cocatalyst and/or an electron donor, as a Ziegler-Natta catalyst for the (co) polymerisation of an olefin in a manner known in the art. It is also possible to combine said catalyst with one or more other ZN and/or non-ZN catalysts.
The olefin to be polymerised using the catalyst system of the invention can be any olefin polymerisable in a coordination
polymerisation including an alpha-olefin alone or a mixture of one or more comonomers . Preferable olefins are alpha- olefins, e.g. ethylene or propene, or a mixture of ethylene or propene with one or more alpha-olefin (s) . Preferable comonomers are C2-C12 olefins, preferably C4-C10 olefins, such as 1-butene, isobutene, 1-pentene, 1-hexene, 4-methyl-l- pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, as well as diene, such as butadiene, 1, 7-octadiene and 1, 4-hexadiene, or cyclic olefins, such as norbornene, and any mixtures thereof.
The present catalyst is particularly preferred for the polymerisation of polyethylene and any copolymers thereof. It may also suitably be used to produce e.g. polypropylene homopolymers and any copolymers thereof .
Polymerisation may be effected in one or more, e.g. one, two or three polymerisation reactors, using conventional polymerisation techniques, in particular gas phase, solution phase, slurry or bulk polymerisation. Polymerisation can be a batch or continuous polymerisation process. Generally a combination of slurry (or bulk) and at least one gas phase reactor is preferred, particularly with gas phase operation coming last .
For slurry reactors, the reaction temperature will generally be in the range of 40 to 110 °C (e.g. 60 - 110 °C) , the reactor pressure will generally be in the range 10 to 80 bar, and the residence time will generally be in the range 0.3 to 5 hours (e.g. 0.5 to 2 hours). For ethylene full scale polymerizing process typical temperatures are between 70 and 105 °C and pressure is usually between 40 and 70 bar. The diluent used will generally be an aliphatic hydrocarbon having a boiling point in the range —70 to +100 °C. In such
reactors, polymerisation may, if desired, be effected under supercritical conditions.
For gas phase reactors, the reaction temperature used will generally be in the range 60 to 115 °C (e.g. 70 to 110 °C) , the reactor pressure will generally be in the range 10 to 30 bar, and the residence time will generally be 1 to 8 hours.
The catalyst of the invention is especially suitable for polymerizing ethylene.
Generally the quantity of catalyst used will depend upon the nature of the catalyst, the reactor types and conditions and the properties desired for the polymer product. Conventional catalyst quantities, such as described in the publications referred herein, may be used.
With the method of the invention a catalyst system with a high bulk density and a good morphology is obtained and the catalyst exhibits a high catalytic activity. According to the so-called replica effect the bulk density and the morphology correlates with product bulk density and product morphology. Thus the catalyst leads to a polymer which also has advantageous properties, e.g. low fines level.
EXAMPLES
The following examples are provided by way of illustration of the invention. All the used starting materials and solvents are commercially available or can be prepared according or analogously to methods described in the literature, e.g.: (C4H9) x.5Mg(C8HX7) o.s n 20 wt-% heptane solution: supplied by Crompton, Germany (BOMAG) ; EtAlCl2 in 18.5 wt-% toluene solution: Crompton, Germany (EADC) ; triethylaluminium in 20
wt-% heptane solution (TEA-20) : Crompton, Germany; TiCl4 : Aldrich, Germany.
It is referred also to Figures 1 and 2, which illustrate the synthesis .
Examples 1 to 6 were done on laboratory scale. Examples 7 and 8 were prepared in a 90 1 reactor. Examples 9 and 10 were made in a 20 1 reactor.
Examples 1 to 6 (Examples 1 —3 comparative examples)
Preparation of the Mg-alcoholate
The Mg-alcoholate was prepared in a larger batch. The same Mg-alcoholate complex was then used in all the precipitation tests. About 24 kg of the Mg-alcoholate complex was produced. The Mg-alcoholate complex synthesis was started by adding 16,0 kg (472 g Mg, 19,42 mol Mg) of 20 % heptane solution of (C4H9)x,5 g(C8HX7)o,5 (BOMAG, 2,95 % Mg) into a reactor at room temperature. To this solution 4,921 kg (37,79 mol) of 2-ethyl-hexanol (EHA) was added slowly at room temperature. The Mg/EHA molar ratio in this mixture was 1:1,945. The temperature was held at about room temperature and the reactants were allowed to react with each other for 108 min. 3,757 kg (52,1 mol) of n-pentane was added at room temperature to reduce viscosity and the Mg-alcoholate complex was allowed to stabilise for 120 min at 20 - 30 °C. After this the Mg-alcoholate solution is allowed to temperate back to room temperature. Analyses showed that the Mg-alcoholate complex had a concentration of 2,4 % Mg.
Preparation of the carrier material
13, 7 g of a 20 w-% pentane solution of EADC or 11,9 g of a 25 w-% toluene solution of EADC together with 5 ml of toluene was added into a glass reactor. The temperature was then adjusted to a temperature between -10 °C and +60 °C. At this temperature 23,5 g of the Mg-complex (Mg w-% 2,23) was added. The addition took 30 min. After this the temperature was increased to 60 °C and the reactants were allowed to react with each other for 30 min. Mixing speed was 460 rpm. The Al/Mg molar ratio in the reaction mixture was 1:1. After reaction, the liquid was siphoned off and the carrier washed one time with 40 ml of heptane for 20 min at 60 °C. The wash solution was then siphoned off.
Preparation of the catalysts
A new carrier-heptane slurry was created by adding 20 ml of heptane to the reactor. To this slurry 1,18 ml of TiCl4 was added. The Ti/Mg molar ratio was 0,5/1. The temperature was increased to 60 °C and the reactants were allowed to react with each other for 30 min. After reaction the liquid was drawn off, and the catalyst was washed two times with 40 ml portions of heptane at 60 °C for 20 min. Finally 35 ml of the wash heptane was siphoned off, and the remaining heptane catalyst slurry was studied in respect of its chemical composition and physical appearance.
Characterisation of the catalysts
The compositions of the catalysts were measured in respect of their Mg, Al , Ti, and Cl content. The average PS of the catalysts was measured by Coulter counting.
Homo-polymerisation of ethene
A 3 1 autoclave reactor was used. 1800 ml (1.127 kg, 15.6 mol) of pentane was introduced into the reactor as reaction medium. After adding the polymerisation medium the temperature of the reactor was adjusted to 90 °C. The co- catalyst and the catalyst were fed into the reactor by means of two feed vessels that were connected in line to the reactor lid. About 5 - 10 mg of the studied catalyst in an appropriate slurry volume was added into the upper feed vessel together with 10 ml (6.3 g, 87 mmol) of pentane. A 10 wt-% heptane solution of tri-ethyl-aluminium (TEA) was used as co-catalyst. The co-catalyst was added to the lower feed vessel. An Al/Ti molar ratio of 15 was used in the homo- polymerisations (about 0.5 ml TEA). The co-catalyst was first let into the reactor and the catalyst was after that introduced by pressurising the upper feed vessel to 7 bar with N2 and then letting the over pressure push in the catalyst in to the reactor. The manoeuvre was done three times. One additional 500 ml feed vessel was connected in series between the lid of the reactor and the ethene monomer feed line. 17.5 bar of H2 pressure was added to this feed vessel (390 mmol) . The polymerisation was started by opening the monomer feed line and thereby introducing both the H2 together with the ethene monomer. A total pressure of 13.7 bar was maintained by the ethene feed trough out the polymerisation. The polymerisation was carried out for 1 h at 90 °C. The polymerisation was stopped by venting off the monomer and the pentane .
Characterisation of the polymers
The polymers were characterised in respect of their MFR- values, bulk density (BD) and their particle size (PS) . The results of examples 1 6 are listed in Table 1.
Examples 8 (Comparative) and 9
All steps in the catalyst synthesis were carried out in the 90 1 reactor.
Synthesis was made with Mg:Al:Ti ratios of 1:1:0,5
17,5 kg (2940 g EADC, 23,2 mol EADC) of a 16,8 % pentane solution of ethyl -aluminium-di-chloride (EADC) was added to the 90 1 reactor in inert conditions at 20 °C. Mixing rate was 350 rpm. Pressure was adjusted to 0,5 bar of over pressure, after which the vessel was closed and the pressure allowed to increase with temperature to avoid boiling of pentane. Temperature was set to 20 °C in Example 8 and to +50 °C in Example 9.
25,1 kg (559,73 g Mg, 23,0 mol Mg) of a 2,23 % Mg hydrocarbon solution of Mg-di-2-ethyle-hexanolate (Mg(0R)2) was added slowly during 45 - 145 min into the reactor. The Al/Mg molar ratio was 1. Temperature was kept at the desired temperature, i.e. 20 °C or +50 °C. Mixing rate was 350 rpm. After the addition of the Mg (OR) 2 solution temperature was increased to 60 °C, after which the reactants were allowed to react with each other. Temperature increase and reaction time took about 90 min. Mixing rate was kept as before between 350 rpm.
After the reaction was completed the carrier was allowed to settle for 60 min and then the supernatant was siphoned off.
27 kg (270 mol) of heptane (C7) was added. The heptane was preheated to 20 °C. The carrier material was washed for 10 min at 20 °C. After this the carrier was allowed to settle for 60 min and the wash heptane was siphoned off.
A new heptane slurry was prepared by adding 30 kg (299 mol) of heptane together with 2,18 kg (11,5 mol) of TiCl at 20 °C. The Ti/Mg molar ratio was 0,5. After this, the temperature was increased to 60 °C and the components were allowed to react with each other for 60 - 90 min at the appropriate temperature. After the reaction, the catalyst was allowed to settle for 40 min and the reaction solution was siphoned off.
The created catalyst was washed two times following the wash procedures of the carrier material . The catalyst was not dried but left in a slurry that later on was changed to a mineral oil slurry. 5 kg of Technol Oil 68 was added when making the oil slurry of the catalyst. About 10 kg of product, containing the oil, remaining hydrocarbons and the catalyst was achieved in this type of a catalyst synthesis.
Changes during the test series
Temperature was changed in the precipitation step. Temperatures 20 °C and +50 °C were studied.
Characterisation of the catalysts and the polymers
The catalysts were characterised and test polymerised in the same way as described in Examples 1 to 6. The results of examples 7 and 8 are listed in Table 2.
Examples 9 and 10 (Comparative examples)
Examples 9 and 10 were prepared in a 20 1 reactor
4,76 1 (4,34 kg, 5,82 mol) of a Etylaluminium dichloride (EADC) solution in toluene was added into a 20 1 reactor in inert conditions at room temperature. The concentration of the EADC solution was 17 w-% (3,61 w-% Al) , and its density was 0,9124 g/ml . The temperature was then adjusted to 10 °C or to +10 °C and stirring to 300 rpm.
8,24 1 (6,23 kg, 5,82 mol) of magnesium-di-2-ethyl-hexanol (Mg(OR)2) was added during 40 min to the reactor. Temperature was kept as close as possible to 10 °C or to +10 °C trough out the addition of the Mg-alcoholate.
After addition, temperature was increased to 60 °C and the reactants were allowed to react with each other in this temperature for 30 min. After this temperature was decreased down to 20 °C. The whole solution slurry (13 1) was shifted over to a settling vessel that was equipped with a watch glass that was stretching along the whole side of the vessel so that the progress of the settling could be followed in detail. The precipitate was allowed to settle for 2 h to a volume of 7 1. After this 6 1 of the clear solution was siphoned off. The remaining 7 1 of precipitate slurry was shifted back to the 20 1 reactor.
The settling vessel was flushed twice with 3 1 portions of heptane that was passed over into the 20 1 reactor so that after the additions the total volume of liquids in the 20 1 reactor was again 13 1. The precipitate (carrier) was now
washed for 20 min at room temperature after which it was shifted back to the settling vessel. Again, the Mg-carrier was allowed to settle for 2 h to a volume of 7 1 after which 6 1 of the wash solution was siphoned off. The remaining 7 1 of carrier slurry was shifted back into the 20 1 reactor.
A slurry sample of the carrier solution was taken and the Mg content was measured. Based on the measured amount of Mg the amount of TiCl4 was calculated. Mg/Ti molar ratio was set to be 2.
TiCl4 was added together with 6 1 of heptane. Temperature was increased to 75 °C and the reactants were allowed to react with each other for 45 min. After this the solution was once again shifted over to the settling vessel and allowed to settle until a precipitate volume of 7 1 was reached. The clear solution was then siphoned off. After siphoning, the catalyst slurry was shifted over to the 20 1 reactor.
The catalyst was now washed twice with heptane . The heptane wash was carried out by adding 6 1 of heptane in 3 1 portions trough the settling vessel in order to insure full shift over of the catalyst into the 20 1 reactor. The catalyst was then washed for 10 20 min at room temperature. After washing the catalyst slurry was shifted over to the settling vessel where the catalyst was allowed to settle until it had reached a volume of 7 1. After siphoning off of the clear solution the catalyst was shifted back into the 20 1 reactor.
Characterisation of the catalysts and the polymers
The composition of the catalysts were measured and all the catalysts were test polymerised in the same way as described in Examples 1 to 6. The results from examples 9 and 10 are listed in Table 3.
In the following Tables 1 - 3 Tprec indicates the precipitation temperature/°C in step (i) , Mg/Ti, Al/Ti and Cl/Ti refer to the chemical composition of the catalyst and PS/μm refers to the average particle size of the catalyst (measured by Coulter method) . Activity refers to the activity with a 1 h polymerisation. As polymer properties are disclosed bulk density, BD/kg/m3 (ASTM D 1895) , Melt Flow Rate, MFR2/kg 10 min (IS01133, 2,16 kg load, 190 °C) , the average particle size APS/mm (Coulter) , molecular weight, Mw/g/mol and molecular weight distribution as Mw/Mn, MWD (GPC) .
TABLE 1: Examples 1 to 6. Examples 1 and 2 are comparative examples. Carrier and catalyst prepared on laboratory scale.
Table 2. Examples 7 and 8. Example 7 is comparative example Carrier and catalyst prepared in the 90 1 reactor.
Table 3. Examples 9 and 10 are comparative examples Carrier and catalyst prepared in the 20 1 reactor.