FIELD OF THE INVENTION

[0001] The present disclosure relates to a process for the preparation of catalyst components for the (co)polymerization of olefins, in particular propylene, comprising Mg, Bi, Ti and halogen elements and optionally at least an electron donor compound.

BACKGROUND OF THE INVENTION

[0002] Catalyst components for the polymerization of olefins, such as ethylene and propylene, are widely known in the art and such catalyst may be of the Ziegler- Natta category type. The first catalyst of this type widely used in the industry was based on the use of solid T1CI ₃ obtained by reduction of T1CI ₄ with aluminum alkyls. The activity and stereospecificity of the catalysts were not so high so that the polymer had to be subjected to a deashing treatment to remove the catalyst residues and to a washing step for removing the atactic polymer (polypropylene) produced. Ziegler-Natta catalysts used industrially comprise a solid catalyst component, constituted by a magnesium dihalide on which are supported a titanium compound and optionally an internal electron donor compound, used in combination with an Al-alkyl compound.

[0003] The use of magnesium chloride based supports led to increases in catalyst activities and to the development of various techniques for the production of magnesium chloride based support and deriving catalysts. In both ethylene and propylene polymerization, the catalyst activity is particularly important.

[0004] When the Ziegler-Natta catalysts ("ZN catalysts") are to be used for propylene polymerization, they contain an internal donor. Moreover, ZN catalysts are often used together with an external donor (for example an alkoxysilane) which helps in obtaining higher isotacticity. One class of internal donors is constituted by the esters of phthalic acid, diisobutylphthalate being the most used. The phthalates are generally used as internal donors in combination with alkylalkoxysilanes as external donor. This catalyst system is capable of giving good performances in terms of activity, and propylene polymers with high isotacticity and xylene insolubility. It is however of general interest the possibility of increasing the intrinsic capability of the solid catalyst components, particularly of those based on donors different from phthalates, to produce stereoregular polymers. In fact, an intrinsically more stereospecific catalyst component would allow the use of a smaller amount of stereoregulating internal and/or external donor to reach the target of polymer xylene insolubility and this, in turn, would be translated into the possibility of obtaining a higher plant productivity.

[0005] Based on this, it would be very convenient to find a way of improving the stereo specificity of a solid catalyst component, and in particular, it would be convenient that this method be of wide applicability.

[0006] Performance improvement of ZN catalysts can be obtained by introducing additional substances into the final ZN catalysts or into its magnesium chloride based support. Due to the fact such substances may modifiy the catalyst structure and/or its performances they are also called "modifiers".

[0007] US4,237,254 discloses a catalyst preparation in which a magnesium hydroxychloride compound is converted into magnesium chloride based support by reacting it with halogenating agents such as benzoylchloride. Then the support is comilled with a benzoate as internal donor and treated with TiCl ₄ . In some cases, the support is treated with an additional halogenating agent which can include inorganic compounds like B1CI ₃ before the contact with the internal donor. Due to the fact that the comparison runs are not back-to-back, the document does not clarify whether the use of the additional chlorinating agents helps in terms of stereo specificity in connection with the use of benzoates as internal donors. An attempt made by the applicant demonstrated however that when the use of B1CI ₃ in the catalyst is associated to the presence of benzoates as internal donors, there is no improvement in activity/stereospecificity. Therefore, the B1CI ₃ does not seem to act as an effective modifier under the conditions used in US4,237,254. [0008] Introduction of catalyst modifiers in the support or its Mg compound based precursor may not be efficient if the support or precursor is produced in a large scale and then converted into several types of catalysts differing for specific recipes or further ingredients. As a consequence, for certain types of catalysts, the presence of the modifier in the support may be unnecessary or even undesired. On the other hand, using a large scale plant only to produce small quantity of modified support or precursor would also be inefficient.

[0009] Furthermore, if the production of the support or its Mg compound based precursor is a continuous process, the change of product campaign can lead to a significant loss of time and material. In addition, depending on the manufacturing recipe, certain supports or precursor may not be suited to include modifiers without changing their chemical structure and related properties.

[0010] It would therefore be useful to have a versatile process to produce modified ZN catalysts allowing the introduction of the modifier in a dedicated way so as not to impact other catalyst preparation routes based on the same starting supports or precursors.

[0011] The applicant has now surprisingly found a new process for the preparation of a solid catalyst component showing improvement in activity and/or stereospecificity when polymerizing olefins such as ethylene or propylene.

[0012] Furthermore, the process is very effective and versatile, allowing obtaining a ZN modified solid catalyst component starting from an unmodified catalyst precursor.

SUMMARY OF THE INVENTION

[0013] It is therefore an object of the present disclosure a process for the preparation of a solid catalyst component for the (co)polymerization of CH ₂ =CHR olefins, in which R is hydrogen or hydrocarbyl radical with 1-12 carbon atoms, comprising a Ti compound, a Bi compound and optionally an electron donor on a Mg chloride based support, said process comprising one or more steps (a) carried out at a temperature ranging from 0 to 150°C in which a Mg based compound of formula (MgCl _m X ₂ -m)'nLB, in which m ranges from 0 to 2, n ranges from 0 to 6, X is, independently R ¹ , OR ¹ , -OCOR ¹ or 0-C(0)-OR ¹ group, in which R ¹ is a C1-C20 hydrocarbon group, and LB is a Lewis base, is reacted with a liquid medium comprising a Ti compound, having at least a Ti-Cl bond, in an amount such that the Ti/Mg molar ratio is greater than 3; said process being characterized by the fact that in at least one of said steps (a) a Bi compound is dissolved or dispersed in said liquid medium comprising the titanium compound.

DETAILED DESCRIPTION OF THE INVENTION

[0014] In a particular embodiment the bismuth compound is dissolved or dispersed in a liquid medium comprising a titanium compound of formula T^OR ¹ ^- yCl _y , where q is the valence of titanium and y is a number between 1 and q and R ¹ is a Ci-C2o hydrocarbon group.

[0015] Among them, particularly preferred are titanium polyhalogenated compounds such as titanium tetrahalides or halogenalcoholates. Preferred specific titanium compounds are TiCl ₄ and Ti(OEt)Cl _3.

[0016] The liquid medium comprising the Ti compound can be a mixture of the Ti compound in another liquid diluent. Preferred diluents are hydrocarbons, optionally chlorinated, that are liquid at room temperature. In a very preferred embodiment the liquid medium consists of the liquid titanium compound.

[0017] The magnesium based compound used as a starting compound in the first of the one or more steps (a) is preferably selected among adducts of formula where n is a number between 0.1 and 6, and R ¹ is a hydrocarbon radical having 1-18 carbon atoms. Preferably, n ranges from 1 to 5 and more preferably from 1.5 to 4.5.

[0018] The adduct can be suitably prepared by mixing alcohol and magnesium chloride, operating under stirring conditions at the melting temperature of the adduct (100-130°C). Then, the adduct is mixed with an inert hydrocarbon immiscible with the adduct thereby creating an emulsion which is quickly quenched causing the solidification of the adduct in the form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in US 4,399,054 and US 4,469,648.

[0019] Another useable method for the spherulization is the spray cooling described for example in US 5,100,849 and US 4,829,034. Adducts having the desired final alcohol content can be obtained by directly using the selected amount of alcohol during the adduct preparation.

[0020] The above mentioned adduct can be directly reacted with Ti compound or it can be previously subjected to thermal controlled dealcoholation (80-130°C) so as to obtain an adduct in which the number of moles of alcohol is lowered and its porosity increased. When the dealcoholation is carried out, it generally brings the number of moles of alcohol per mole of Mg to less than 3, preferably between 0.1 and 2.5.

[0021] The reaction between the Mg based compound, in particular the MgCl ₂ - alcohol adduct and the Ti compound can be carried out by suspending the Mg based compound in large excess of cold TiCl ₄ (generally 0°C); the mixture is heated up to a temperature ranging from 60-140°C and kept at this temperature for 0.1-4 hours, preferably 0.5-2 hours. After that time, stirring is discontinued and after the settlement of the solid particles the liquid phase is removed.

[0022] This reaction step (a) can be carried out one or more times under identical or different conditions. For example, the temperature and duration of treatment can be changed. In a preferred embodiment, the number of steps (a) is comprised between 1 and 3.

[0023] If used, the electron donor compound can be added in the desired ratios during one or more of the reaction steps (a) between the Mg based compound and the liquid Ti compound.

[0024] Preferably the electron donor compound is added at least during the first step (a) of reaction between the Mg based compound and the Ti compound. In some cases such a treatment can be repeated one or two additional times.

[0025] In another embodiment, the electron donor compound, as described in

WO2004/106388, can be added as a fresh reactant to the solid intermediate catalyst component obtained by the above described reaction between the adduct and the Ti compound.

[0026] In a particular embodiment, the reaction step (a) is carried out by a continuous feeding of liquid Ti compound, preferably TiCl ₄ , in an apparatus and under conditions that are described in WO02/48208. Under this embodiment the Mg based compound is fed batchwise while a continuous stream of liquid Ti compound with the desired temperature profile is fed and a liquid phase containing dissolved reaction product is continuously withdrawn. Under these basic conditions the Bi compound and, optionally, the electron donor can be added at any time during the feeding of the Ti compound.

[0027] As mentioned above, in one or more of the reaction steps (a), the liquid medium comprising the titanium compound also comprises a dissolved or dispersed Bi compound.

[0028] The Bi compounds preferably do not have Bi-carbon bonds. In particular the Bi compounds can be selected from Bi halides, Bi carbonate, Bi acetate, Bi nitrate, Bi oxide, Bi sulphate, Bi sulfide. Compounds in which Bi has the valence +3 are preferred. Among Bi halides, preferred are Bi trichloride and Bi tribromide. The most preferred Bi compound is B1CI ₃ .

[0029] The amount of bismuth compound dispersed or solubilized in the titanium compound ranges from 0.005 to 0.1 mole per mole of Mg, preferably from 0.010 to 0.040.

[0030] Although the Bi compound can be added to the reaction system already including the Mg based compound in the liquid medium comprising the Ti compound, it constitutes a preferred embodiment the preparation of a liquid mixture comprising dissolving or dispersing the Bi compound in the liquid medium comprising the Ti compound and then reacting said mixture with the Mg based compound. The reaction conditions described for the reaction step (a) above apply here as well.

[0031] The Bi compound can be used in any of the one or more reaction steps (a) which comprises the process of the present disclosure. Preferably however, it is used in only one of the steps (a).

[0032] At the end of the last step (a) the solid catalyst component is preferably subjected to washings with hydrocarbon solvents until chloride ions are no longer detectable with the conventional techniques.

[0033] The process for the preparation of a solid catalyst component for the

(co)polymerization according to the present disclosure allows obtaining a catalyst component having preferably a content of Bi ranging from 0.5 to 40%, more preferably from 0.5 to 35, and even more preferably from 0.5 to 20 or especially from 1 to 20%wt with respect to the total amount of solid catalyst component.

[0034] The particles of solid catalyst component have substantially spherical morphology and average diameter ranging between 5 and 150 μιη, preferably from 20 to 100 μιη and more preferably from 30 to 90 μιη. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than 1.5 and preferably lower than 1.3.

[0035] In general the amount of Mg preferably ranges from 8 to 30% more preferably from 10 to 25%wt with respect to the total weight of solid catalyst component.

[0036] The amount of Ti can range from 0.5 to 5% and more preferably from 0.7 to 3%wt with respect to the total weight of solid catalyst component.

[0037] It has been observed that the amount of Ti decreases as the amount of Bi increases. As a result, and this is a particular aspect of the present disclosure, the Mg/Ti molar ratio of the disclosed catalyst is greater than the corresponding ratio of the catalyst not containing Bi.

[0038] When used, the internal electron donor is selected from the group consisting of ethers, amines, silanes, carbamates, ketones, esters of aliphatic acids, alkyl and aryl esters of optionally substituted aromatic polycarboxylic acids, diol derivatives chosen among monoesters monocarbamates and monoesters monocarbonates or mixtures thereof.

[0039] When the internal donor is selected from alkyl and aryl esters of optionally substituted aromatic polycarboxylic acids preferred donors are the esters of phthalic acids. Preferred esters of aliphatic acids are selected from malonic, glutaric, maleic and succinic acids. Specific examples of such esters are n-butylphthalate, di- isobutylphthalate, and di-n-octylphthalate. [0040] Preferably, the ethers can be selected from the 1,3 diethers of the formula (I):

wherein R, R ¹ , R ⁿ , R ^m , R ^w and R ^v are equal to or different from each other, and are hydrogen or hydrocarbon radicals having from 1 to 18 carbon atoms; and R ^VI and R ^vn are equal to or different from each other, and have the same meaning of R-R ^v except that R ^VI and R ^vn cannot be hydrogen; one or more of the R-R ^vn groups can be linked to form a cycle. The 1,3-diethers in which R ^VI and R ^vn are selected from CrC ₄ alkyl radicals are particularly preferred.

[0041] It is also possible to use mixtures of the above mentioned donors. Specific mixtures are those constituted by esters of succinic acids and 1,3 diethers as disclosed in WO2011/061134.

[0042] When it is desired to increase the capability of the catalyst to distribute an olefin co-monomer within a polymer chain, such as in case of production of ethylene/a-olefin copolymers, it is preferred to choose the electron donor among monofunctional donors, chosen among ethers and CrC ₄ alkyl esters of aliphatic mono carboxylic acids. Preferred ethers are the C ₂ -C ₂₀ aliphatic ethers and in particular, cyclic ethers preferably having 3-5 carbon atoms cyclic ethers such as tetrahydrofurane, dioxane. Preferred esters are ethylacetate and methyl formiate. Among them tetrahydrofurane and ethylacetate are the most preferred.

[0043] In general, the final amount of electron donor compound in the solid catalyst component may range from 0.5 to 40 wt by weight preferably in the range from 1 to 35 wt with respect to the toal weight of the solid catalyst component.

[0044] It has been observed that also the Mg/donor molar ratio is influenced by the presence of Bi and it is generally greater than the corresponding ratio for catalysts not containing Bi. In case the donor belongs to alkyl and aryl esters of optionally substituted aromatic polycarboxylic acids, in particular phthalates, the Mg/Ti molar ratio is equal to, or greater than, 13, preferably in the range 14-40, and more preferably from 15 to 40. Correspondingly, the Mg/donor molar ratio is greater than 16, more preferably higher than 17, and usually ranging from 18 to 50.

In case the donor belongs to diethers of formula (I) the Mg/Ti molar ratio is greater than 6, preferably higher than 7, while the Mg/donor molar ratio ranges typically from 9 to 20 and preferably from 10 to 20.

[0045] The solid catalyst component obtained according to the present disclosure preferably shows a surface area (by B.E.T. method) generally between 20 and 500 m 2 /g and preferably between 50 and 400 m 2 /g, and a total porosity (by B.E.T. method) greater than 0.2 cm 3 /g, preferably between 0.3 and 0.6 cm 3 /g. The porosity (Hg method) due to pores with radius up to 10.000 A, generally ranges from 0.3 to 1.5 cm 3 /g, preferably from 0.45 to 1 cm 3 /g.

The solid catalyst component has preferably an average particle size ranging from 5 to 120 μιη and more preferably from 10 to 100 μιη.

[0046] The solid catalyst component prepared according to the process of the present disclosure is converted into catalyst for the polymerization of olefins by reacting it with organoaluminum compounds according to known methods.

[0047] The organoaluminum compound is preferably chosen from the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt ₂ Cl and Al ₂ Et ₃ Cl ₃ , possibly in mixture with the above cited trialkylaluminums.

[0048] The Al/Ti ratio is greater than 1 and is generally comprised between 50 and

2000, preferably between 50 and 500.

[0049] Optionally, an external electron-donor compound can be used. It is prefereably selected from silicon compounds, ethers, esters, amines, heterocyclic compounds and 2,2,6,6-tetramethylpiperidine and ketones. Another class of preferred external donor compounds is that of silicon compounds of formula (R6) _a (R7) _b Si(ORg) _c , where a and b are integers from 0 to 2, c is an integer from 1 to 4 and the sum of (a+b+c) is 4; R ₆ , R ₇ , and R ₈ , are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. Particularly preferred are the silicon compounds in which a is 1, b is 1, and c is 2, at least one of R ₆ and R ₇ is selected from branched alkyl, cycloalkyl or aryl groups with 3-10 carbon atoms optionally containing heteroatoms, and R ₈ is a Q-Qo alkyl group, in particular methyl. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane (C donor), diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane (D donor), diisopropyldimethoxysilane, (2- ethylpiperidinyl)t-butyldimethoxysilane, (2-ethylpiperidinyl)thexyldimethoxysilane, (3,3,3-trifluoro-n-propyl)(2-ethylpiperidinyl)dimethoxysilan e, methyl(3,3,3-trifluoro-n- propyl)dimethoxysilane. Moreover, the silicon compounds in which a is 0 and c is 3, R ₇ is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R ₈ is methyl are also preferred. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and thexyltrimethoxysilane.

[0050] The external electron donor compound is used in such an amount to give a molar ratio between the organoaluminum compound and said external electron donor compound of from 0.1 to 500, preferably from 1 to 300, and more preferably from 3 to 100.

[0051] The catalyst prepared according to the present disclosure can be used in a process for the (co)polymerization of CH ₂ =CHR olefins, in which R is hydrogen or a hydrocarbyl radical with 1-12 carbon atoms.

[0052] The polymerization process can be carried out according to available techniques, for example slurry polymerization using as diluent an inert hydrocarbon solvent, or bulk polymerization using the liquid monomer (for example propylene) as a reaction medium. Moreover, it is possible to carry out the polymerization process in gas-phase operating in one or more fluidized or mechanically agitated bed reactors.

[0053] The polymerization is carried out at a temperature of from 20 to 120°C, preferably from 40 to 80°C. When the polymerization is carried out in gas-phase the operating pressure may range between 0.5 and 5 MPa, preferably between 1 and 4 MPa. In the bulk polymerization the operating pressure may range between 1 and 8 MPa, preferably between 1.5 and 5 MPa.

[0054] The process of the present disclosure incorporates the Bi compound into the solid catalyst component without the need of including the Bi compound into the Mg based compound used as a support precursor. Accordingly, the Mg based compound can be used also in catalyst preparation recipes which do not involve the use of Bi compounds. The Bi containing catalyst prepared according to the present disclosure shows, in propylene homopolymerization, an increased activity/stereospecificity balance particularly due to increased stereospecificity compared with catalysts prepared under the same conditions but not including bismuth atoms. This may mean that given level of polymer stereoregularity (expressed as percentage of xylene insoluble matter) can be obtained with a lower amount of internal donor with respect to the same catalyst not including bismuth atoms. A more efficient incorporation of donor in the catalyst allows in turn the use of a lower amount of donor in the catalyst preparation process and a reduced generation of by-products in the reaction between Ti compound, Mg compound and internal donor.

[0055] In the polymerization conditions indicated in the experimental section, the catalyst component obtained with the process of the present disclosure is able to produce polypropylene with an isotacticity, expressed in terms of xylene insolubility, of at least 98% preferably higher than 98.5 and more preferably higher than 99%.

[0056] The following examples are given in order to better illustrate the disclosure without limiting it.

EXAMPLES

CHARACTERIZATIONS

Determination of Mg, Ti

[0057] The determination of Mg and Ti content in the solid catalyst component has been carried out via inductively coupled plasma emission spectroscopy on "LC.P Spectrometer ARL Accuris". [0058] The sample was prepared by analytically weighting, in a "Fluxy" platinum crucible, 0.1 to 0.3 grams of catalyst and 2 grams of lithium metaborate/tetraborate 1/1 mixture. After addition of some drops of KI solution, the crucible was inserted in a "Claisse Fluxy" apparatus for the complete burning. The residue was collected with a 5% v/v HN0 ₃ solution and then analyzed via ICP at the following wavelengths: Magnesium, 279.08 nm; Titanium, 368.52 nm.

Determination of Bi

[0059] The determination of Bi content in the solid catalyst component has been carried out via inductively coupled plasma emission spectroscopy on "LC.P Spectrometer ARL Accuris".

[0060] The sample was prepared by analytically weighting in a 200 cm ³ volumetric flask 0.1 to 0.3 grams of catalyst. After slow addition of both ca. 10 milliliters of 65% v/v HNO ₃ solution and ca. 50 cm of distilled water, the sample underwent a digestion for 4÷6 hours. Then the volumetric flask was diluted to the mark with deionized water. The resulting solution was directly analyzed via ICP at the following wavelength: Bismuth, 223.06 nm.

Determination of internal donor content

[0061] The determination of the content of internal donor in the solid catalytic compound was done through gas chromatography. The solid component was dissolved in acetone, an internal standard was added, and a sample of the organic phase was analyzed in a gas chromatograph, to determine the amount of donor present at the starting catalyst compound.

Determination of X.I.

[0062] 2.5 g of polymer and 250 ml of o-xylene were placed in a round-bottomed flask provided with a cooler and a reflux condenser and kept under nitrogen. The obtained mixture was heated to 135°C and was kept under stirring for about 60 minutes. The final solution was allowed to cool to 25°C under continuous stirring, and the insoluble polymer was then filtered. The filtrate was then evaporated in a nitrogen flow at 140°C to reach a constant weight. The content of said xylene- soluble fraction is expressed as a percentage of the original 2.5 grams and then, by difference, the X.I. %.

Melt flow rate (MIL)

[0063] The melt flow rate MIL of the polymer was determined according to ISO

1133 (230°C, 2.16 Kg).

Procedure for the preparation of the Mg based compound I (spherical adduct)

[0064] Micro spheroidal MgCL pCiHsOH adduct was prepared according to the method described in Example 2 of WO98/44009. The solid spherical particles obtained, containing 57 wt% of ethanol, underwent a dealcoholation step under warm nitrogen flow until the level of ethanol reached 50 wt%.

Procedure for the preparation of the Mg based compound II (spherical adduct)

[0065] Micro spheroidal MgCli pCiHsOH adduct was prepared according to the method described in Example 2 of WO98/44009, with the difference that B1CI ₃ in a powder form and in the amount indicated in Table 1 was added in the step of molten MgCl ₂ -EtOH adduct preparation. The solid spherical particles obtained, containing 57 wt% of ethanol, underwent a dealcoholation step under warm nitrogen flow until the level of ethanol reached 50 wt%.

Procedure for the preparation of the Mg based compound III

[0066] The synthesis of the precursor was performed as described in Example 1 of

US 4,220,554. The so obtained support has the following composition: Mg, 20.2 wt.%; CI, 29.8 wt.%; EtOH groups 41.5 wt.%.

Procedure for the preparation of the phthalate-based solid catalyst component

[0067] Into a 500 ml round bottom flask, equipped with mechanical stirrer, cooler and thermometer, 300 ml of T1CI ₄ were introduced at room temperature under nitrogen atmosphere. After cooling to 0°C, while stirring, B1CI ₃ in a powder form and in the amount indicated in Table 1, diisobutylphthalate (DIBP) in the amount indicated in Table 1, and 15.0 g of the Mg based compound I, II or III (prepared as described above) were sequentially added into the flask. The amount of fed internal donor was such to meet a Mg/donor molar ratio indicated in Table 1. The temperature was raised to 100°C and maintained for 1 hour (first step (a)). Thereafter, stirring was stopped, the solid product was allowed to settle, and the supernatant liquid was siphoned off at 100°C. After the supernatant was removed, additional fresh TiCl ₄ was added at room temperature together with, if used, diisobutylphthalate in the amount indicated in Table 1 to reach the initial liquid volume again. The mixture was then heated at 120°C and kept at this temperature for 30 minutes (second step (a)). Stirring was stopped again, the solid was allowed to settle and the supernatant liquid was siphoned off at 100°C. After the supernatant was removed, additional fresh TiCl ₄ was added at room temperature to reach the initial liquid volume again. The mixture was then heated at 120°C and kept at this temperature for 15 minutes (third step (a)). Stirring was stopped again, the solid was allowed to settle and the supernatant liquid was siphoned off at 100°C. The solid was washed with anhydrous heptane four times in temperature gradient down to 90°C and one time at 25°C. The obtained solid was then dried under vacuum and analyzed.

Procedure for the preparation of the glutarate-based solid catalyst component

[0068] The preparation of the glutarate-based solid catalyst component was the same as the phthalate-based solid catalyst component with the difference that diethyl, 3,3-dipropylglutarate was used instead of diisobutylphthalate and the temperature of the first step (a) was 120 °C instead of 100 °C.

[0069] Mg based compound, amount of glutarate, amount of BiCl ₃ and

Mg/glutarate molar ratio are reported in Table 2.

General procedure for the polymerization of propylene

[0070] A 4-liter steel autoclave equipped with a stirrer, pressure gauge, thermometer, catalyst feeding system, monomer feeding lines and thermostating jacket, was purged with nitrogen flow at 70°C for one hour. A suspension containing 75 ml of anhydrous hexane, 0.76 g of AlEt ₃ (6.66 mmol), 0.33 mmol of external donor and 0.006 to 0.010 g of solid catalyst component, previously precontacted for 5 minutes, was charged. Either dicyclopentyldimethoxysilane, D donor, or cyclohexylmethyldimethoxysilane, C donor, were used as external donor as specified in Tables 1 and 2. ] The autoclave was closed and the desired amount of hydrogen was added

(in particular, 2 NL in D donor tests, 1.5 NL in C donor tests). Then, under stirring, 1.2 kg of liquid propylene was fed. The temperature was raised to 70°C in about 10 minutes and the polymerization was carried out at this temperature for 2 hours. At the end of the polymerization, the non-reacted propylene was removed; the polymer was recovered and dried at 70°C under vacuum for 3 hours. Then the polymer was weighed and characterized.

The polymerization results for the phthalate-based solid catalyst component are reported in Table 1, while the results for the glutarate-based solid catalyst component are reported in Table 2.

Table 1: Propylene polymerization using phthalate-based solid catalyst components

Aliquot of DIBP in the first step (a) + Aliquot of DIBP in the second step (a) = 100

Table 2: Propylene polymerization using glutarate-based solid catalyst components

Aliquot of Glu in the first step (a) + Aliquot of Glu in the second step (a) = 100