FIELD OF THE INVENTION

[0001] The present disclosure relates to a process for the preparation of isotactic porous propylene polymers. The said porous propylene polymers are particularly useful to prepare heterophasic copolymers comprising said isotactic porous propylene polymer as a polymer matrix within which a low cristallinity ethylene containing copolymer can be included.

BACKGROUND OF THE INVENTION

[0002] The preparation of heterophasic copolymers via the sequential polymerization, sometimes referred to as the "in situ blending of polymers", is often preferred. According to this technique, a relatively high crystalline propylene polymer is prepared in a first polymerization reactor and then transferred to a successive polymerization reactor, wherein a low cristallinity elastomeric component (for instance, a propylene-ethylene copolymer) is formed.

[0003] In this kind of process, where each reactor can work at different polymerization conditions, in terms of catalyst, pressure, temperature, amounts of comonomer(s) and molecular weight regulator(s), the tailoring of the process conditions allows to produce a wide range of heterophasic propylene copolymers, as well as different concentrations of semicrystalline component and low cristallinity elastomeric component. Processes of this type are described for example in EP 640649 and WO2010/146074 where the catalyst system is formed by precontacting, before the first polymerization step, a solid catalyst component of the Ziegler-Natta type in which a phthalate or a mixture of 1,3-diether and succinate are used as internal donor, a trialkyl- aluminum cocatalyst and an alkylalkoxysilane as external electron donor to improve stereospecificity. In both cases, the precontacting temperature is set preferably in the range 0-30°C. In EP640649 the precontacting temperature is 0°C while in WO2010/146074 a temperature of 25°C is used.

[0004] When the sequential polymerization process is directed to the preparation of heterophasic copolymers with a relevant amount of low cristallinity elastomeric polymer the porosity of the relatively high cristallinity polymer matrix plays an important role. [0005] As a general rule, the higher is the porosity of the polymer matrix produced in the first step the higher is the amount of elastomeric component that can be incorporated, within said matrix, in the second polymerization step.

[0006] On the other hand, if the porosity of the matrix is poor, the presence of an excessive amount of elastomeric polymer fraction on the surface of the particles considerably increases the tackiness of said particles giving raise to agglomeration phenomena which in turn can cause reactor walls sheeting, plugging or even clogging.

[0007] An important macroscopic measurement of the polymer porosity is given by the polymer bulk density. The bulk density or apparent density is the mass per unit of volume of a material, including voids inherent in the material of interest. In case of polymer particles of regular morphology, relatively low values of bulk density indicate a relatively high porosity of the polymer powder. Thus, at least for certain applications it would be desired to produce in the first polymerization step a propylene polymer endowed with both higher porosity (lower bulk density) and high cristallinity.

[0008] In WO2008/015113 it is described that it is possible to modulate the porosity of the polymer matrix produced in the first polymerization step by careful selection of catalyst precontact and polymerization step. In particular, it is recommended contacting the Z/N catalyst component (including a donor selected from the group consisting of, among others, phthalates, succinates and ethers) with an alkyl-Al compound, an external donor compound, optionally in the presence of propylene, at a temperature from 5°C to 30°C and a weight ratio propylene/(catalytic component) ranging from 0 to 2.0 in order to prepare a high cristallinity polymer matrix having a value of bulk density lower than 0.40 g/cm . In fact, the teaching is that the bulk density of the semi-crystalline matrix may be decreased by setting the pre-contact temperature in the higher end of the range 5-30°C. This teaching, also followed in WO2010/146074, would demonstrate an improvement in polymer porosity with respect to the 0°C pre-contact temperature of EP640649. However, the working examples of the cited reference do not explore the whole range of precontact temperatures but limit the treatment in the range 15-25°C. By comparison of examples 1 and 2 it is possible to see that the increase of precontact temperature involves a decrease of polymer bulk density (therefore higher porosity) but also a decrease of catalyst stereo specificity proved by the higher amount of xylene soluble matter. It is therefore clear for the skilled in the art that the 30°C highest limit for the pre-contact temperature has its technical basis on the necessary compromise between high porosity and high cristallinity. In fact, the comparative runs carried out by the applicant confirm that by precontacting at 30°C a ZN catalyst component containing phthalates, an aluminum alkyl and an alkoxysilane, the decrease in stereospecificity is even more pronounced.

[0009] In view of the above, it has been very surprising to discover that with a specific catalyst containing both diethers and succinates as internal donors, higher precontact temperatures can be used without substantially observing decrease of stereospecificity.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of the present disclosure a process for the preparation of a porous propylene (co)polymer having a porosity higher than 0.33 cm /g carried out in the presence of a catalyst system comprising (a) a solid catalyst component comprising a magnesium halide, a titanium compound having at least a Ti-halogen bond and at least two electron donor compounds one of which being present in an amount from 50 to 90% by mol with respect to the total amount of donors and selected from succinates and the other being selected from 1,3 diethers, (b) an aluminum alkyl and optionally (c) an external electron donor compound, and comprising the following steps

(i) contacting the catalyst components (a), (b) and optionally (c) for a period of time ranging from 1 to 60 minutes, at a temperature ranging from 35 to 55°C; optionally,

(ii) pre-polymerizing with one or more olefins of formula CH ₂ =CHR, where R is H or a

Q-Cio hydrocarbon group, up to forming amounts of polymer from about 0.1 up to about 1000 g per gram of solid catalyst component (a); and

(iii) polymerizing propylene in the optional presence of minor amounts of ethylene and/or

C4-Q0 alpha olefins producing said porous propylene (co)polymer.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferably, the succinate present in the solid catalyst component (a) is selected from succinates of formula (I) below

(I)

in which the radicals Ri and R ₂ , equal to, or different from, each other are a Ci-C ₂ o linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms; and the radicals R ₃ and R ₄ equal to, or different from, each other, are Ci-C ₂ o alkyl, C ₃ -C ₂₀ cycloalkyl, C ₅ -C ₂ o aryl, arylalkyl or alkylaryl group with the proviso that at least one of them is a branched alkyl; said compounds being, with respect to the two asymmetric carbon atoms identified in the structure of formula (I), stereoisomers of the type (S,R) or (R,S).

[0012] Ri and R ₂ are preferably Ci-Cg alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl groups. Particularly preferred are the compounds in which Ri and R ₂ are selected from primary alkyls and in particular branched primary alkyls. Examples of suitable Ri and R ₂ groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Particularly preferred are ethyl, isobutyl, and neopentyl.

[0013] Particularly preferred are the compounds in which the R ₃ and/or R ₄ radicals are secondary alkyls like isopropyl, sec -butyl, 2-pentyl, 3-pentyl or cycloalkyls like cyclohexyl, cyclopentyl, cyclohexylmethyl.

[0014] Examples of the above-mentioned compounds are the (S,R) (S,R) forms pure or in mixture, optionally in racemic form, of diethyl 2,3-bis(trimethylsilyl)succinate, diethyl 2,3-bis(2-ethylbutyl)succinate, diethyl 2,3-dibenzylsuccinate, diethyl 2,3- diisopropylsuccinate, diisobutyl 2,3-diisopropylsuccinate, diethyl 2,3- bis (cyclohexylmethyl) succinate, diethyl 2,3-diisobutylsuccinate, diethyl 2,3- dineopentylsuccinate, diethyl 2,3-dicyclopentylsuccinate, diethyl 2,3- dicyclohexylsuccinate.

[0015] Among the 1,3-diethers mentioned above, particularly preferred are the compounds of formula (II)

(Π)

where R ¹ and R ¹¹ are the same or different and are hydrogen or linear or branched C C^ hydrocarbon groups which can also form one or more cyclic structures; R ^EI groups, equal or different from each other, are hydrogen or C C^ hydrocarbon groups; groups equal or different from each other, have the same meaning of R ^EI except that they cannot be hydrogen; each of R ¹ to R ^w groups can contain heteroatoms selected from halogens, N, O, S and Si.

[0016] Preferably, R ^IV is a 1-6 carbon atom alkyl radical and more particularly a methyl while the R ¹¹¹ radicals are preferably hydrogen. Moreover, when R ¹ is methyl, ethyl, propyl, or isopropyl, R ¹¹ can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, isopentyl, 2-ethylhexyl, cyclopentyl, cyclohexyl, methylcyclohexyl, phenyl or benzyl; when R ¹ is hydrogen, R ⁿ can be ethyl, butyl, sec-butyl, tert-butyl, 2-ethylhexyl, cyclohexylethyl, diphenylmethyl, p-chlorophenyl, 1-naphthyl, 1-decahydronaphthyl; R ¹ and R ¹¹ can also be the same and can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, neopentyl, phenyl, benzyl, cyclohexyl, cyclopentyl.

[0017] Specific examples of ethers that can be advantageously used include: 2-(2- ethylhexyl) 1 ,3-dimethoxypropane, 2-isopropyl- 1 ,3-dimethoxypropane, 2-butyl- 1,3- dimethoxypropane, 2-sec-butyl- 1 ,3-dimethoxypropane, 2-cyclohexyl- 1 ,3- dimethoxypropane, 2-phenyl- 1 ,3-dimethoxypropane, 2-tert-butyl- 1 ,3-dimethoxypropane, 2-cumyl- 1 ,3-dimethoxypropane, 2-(2-phenylethyl)- 1 ,3-dimethoxypropane, 2- (2- cyclohexylethyl)- 1 ,3-dimethoxypropane, 2- (p-chlorophenyl)- 1 ,3-dimethoxypropane, 2- (diphenylmethyl)- 1 ,3-dimethoxypropane, 2( 1 -naphthyl)- 1 ,3-dimethoxypropane, 2(p- fluorophenyl)- 1 ,3-dimethoxypropane, 2( 1 -decahydronaphthyl)- 1 ,3-dimethoxypropane, 2(p-tert-butylphenyl)- 1 ,3-dimethoxypropane, 2,2-dicyclohexyl- 1 ,3-dimethoxypropane, 2,2-diethyl- 1 ,3-dimethoxypropane, 2,2-dipropyl- 1 ,3-dimethoxypropane, 2,2-dibutyl- 1,3- dimethoxypropane, 2,2-diethyl- 1 ,3-diethoxypropane, 2,2-dicyclopentyl- 1,3- dimethoxypropane, 2,2-dipropyl-l,3-diethoxypropane, 2,2-dibutyl-l,3-diethoxypropane, 2- methyl-2-ethyl- 1 ,3-dimethoxypropane, 2-methyl-2-propyl- 1 ,3-dimethoxypropane, 2- methyl-2-benzyl- 1 ,3-dimethoxypropane, 2-methyl-2-phenyl- 1 ,3-dimethoxypropane, 2- methyl-2-cyclohexyl- 1 ,3-dimethoxypropane, 2-methyl-2-methylcyclohexyl- 1 ,3- dimethoxypropane, 2,2-bis(p-chlorophenyl)- 1 ,3-dimethoxypropane, 2,2-bis(2- phenylethyl)- 1 ,3-dimethoxypropane, 2,2-bis(2-cyclohexylethyl)- 1 ,3-dimethoxypropane, 2- methyl-2-isobutyl- 1 ,3-dimethoxypropane, 2-methyl-2- (2-ethylhexyl)- 1 ,3- dimethoxypropane, 2,2-bis(2-ethylhexyl)- 1 ,3-dimethoxypropane,2,2-bis(p-methylphenyl)- 1 ,3-dimethoxypropane, 2-methyl-2-isopropyl- 1 ,3-dimethoxypropane, 2,2-diisobutyl- 1 ,3- dimethoxypropane, 2,2-diphenyl- 1 ,3-dimethoxypropane, 2,2-dibenzyl- 1 ,3- dimethoxypropane, 2-isopropyl-2-cyclopentyl- 1 ,3-dimethoxypropane, 2,2- bis(cyclohexylmethyl)- 1 ,3-dimethoxypropane, 2,2-diisobutyl- 1 ,3-diethoxypropane, 2,2- diisobutyl- 1 ,3-dibutoxypropane, 2-isobutyl-2-isopropyl- 1 ,3-dimetoxypropane, 2,2-di-sec- butyl- 1 ,3-dimetoxypropane, 2,2-di-tert-butyl- 1 ,3-dimethoxypropane, 2,2-dineopentyl- 1 ,3- dimethoxypropane, 2-iso-propyl-2-isopentyl- 1 ,3-dimethoxypropane, 2-phenyl-2-benzyl- 1 ,3-dimetoxypropane, 2-cyclohexyl-2-cyclohexylmethyl- 1 ,3-dimethoxypropane.

Furthermore, particularly preferred are the 1,3-diethers of formula (III)

(III)

8] where the radicals R ^w have the same meaning explained above and the radicals R ^EI and R ^v radicals, equal or different to each other, are selected from the group consisting of hydrogen; halogens, preferably CI and F; C C ₂ o alkyl radicals, linear or branched; C ₃ - C ₂ o cycloalkyl, C6-C ₂₀ aryl, C ₇ -C ₂₀ alkylaryl and C ₇ -C ₂₀ arylalkyl radicals and two or more of the R ^v radicals can be bonded to each other to form condensed cyclic structures, saturated or unsaturated, optionally substituted with R radicals selected from the group consisting of halogens, preferably CI and F; Q-C ₂ o alkyl radicals, linear or branched; C ₃ - C ₂₀ cycloalkyl, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ alkaryl and C ₇ -C ₂₀ aralkyl radicals; said radicals R ^v and R ^VI optionally containing one or more heteroatoms as substitutes for carbon or hydrogen atoms, or both.

[0019] Preferably, in the 1,3-diethers of formulae (II) and (III) all the R ^EI radicals are hydrogen, and all the R ^w radicals are methyl. Moreover, are particularly preferred the 1,3- diethers of formula (III) in which two or more of the R ^v radicals are bonded to each other to form one or more condensed cyclic structures, preferably benzenic, optionally substituted by R ^VI radicals. Specially preferred are the compounds of formula (IV):

(IV)

[0020] where the R radicals equal or different are hydrogen; halogens, preferably CI and F; C1-C20 alkyl radicals, linear or branched; C ₃ -C2o cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C ₇ -C ₂₀ aralkyl radicals, optionally containing one or more heteroatoms selected from the group consisting of N, 0, S, P, Si and halogens, in particular CI and F, as substitutes for carbon or hydrogen atoms, or both; the radicals R ¹¹¹ and R ^w are as defined above for formula (III).

Specific examples of compounds comprised in formulae (III) and (IV) are:

1 , 1 -bis(methoxymethyl)-cyclopentadiene;

l,l-bis(methoxymethyl)-2,3,4,5-tetramethylcyclopentadiene;

l,l-bis(methoxymethyl)-2,3,4,5-tetraphenylcyclopentadiene; , 1 -bis (methoxymethyl -2,3,4,5-tetrafluorocyclopentadiene;

, 1 -bis (methoxymethyl -3,4-dicyclopentylcyclopentadiene;

, 1— bis(methoxymethy )indene; l,l-bis(methoxymethyl)-2,3-dimethylindene; , 1 -bis (methoxymethyl -4,5,6,7-tetrahydroindene;

, 1 -bis (methoxymethyl -2,3,6,7-tetrafluoroindene;

, 1 -bis (methoxymethyl -4,7-dimethylindene;

, 1 -bis (methoxymethyl -3,6-dimethylindene;

, 1 -bis (methoxymethyl -4-phenylindene;

, 1 -bis (methoxymethyl -4-phenyl-2-methylindene ;

, 1 -bis (methoxymethyl -4-cyclohexylindene;

, 1 -bis (methoxymethyl -7-(3,3,3-trifluoropropyl)indene;

, 1 -bis (methoxymethyl -7-trimethyisilylindene;

, 1 -bis (methoxymethyl -7 -trifluoromethylindene ;

, 1 -bis (methoxymethyl -4,7-dimethyl-4,5,6,7-tetrahydroindene;

, 1 -bis (methoxymethyl -7 -methylindene ;

, 1 -bis (methoxymethyl -7-cyclopenthylindene;

, 1 -bis (methoxymethyl -7-isopropylindene;

, 1 -bis (methoxymethyl -7-cyclohexylindene;

, 1 -bis (methoxymethyl - 7 - tert-butylindene ;

, 1 -bis (methoxymethyl -7-tert-butyl-2-methylindene;

, 1 -bis (methoxymethyl -7-phenylindene;

, 1 -bis (methoxymethyl -2-phenylindene;

, 1 -bis (methoxymethyl - 1 H-benz [e] indene ;

, 1 -bis (methoxymethyl - lH-2-methylbenz[e]indene;

,9-bis(methoxymethyl fluorene;

,9-bis(methoxymethyl -2,3,6,7-tetramethylfluorene;

,9-bis(methoxymethyl -2,3,4,5, 6,7-hexafluorofluorene;

,9-bis(methoxymethyl -2,3-benzofluorene;

,9-bis(methoxymethy )-2,3,6,7-dibenzofluorene;

,9-bis(methoxymethyl 2.7- diisopropylfluorene;

,9-bis(methoxymethyl 1.8- dichlorofluorene; 9,9-bis(methoxymethyl)-2,7-dicyclopentylfluorene;

9,9-bis(methoxymethyl)- 1 ,8-difluorofluorene;

9,9-bis(methoxymethyl)- 1 ,2,3,4-tetrahydrofluorene;

9,9-bis(methoxymethyl)-l, 2,3,4,5,6,7, 8-octahydrofluorene;

9,9-bis(methoxymethyl)-4-tert-butylfluorene.

[0021] As explained above, the catalyst component (a) comprises, in addition to the above electron donors, a titanium compound having at least a Ti-halogen bond and a Mg halide. The magnesium halide is preferably MgCl ₂ in active form which is widely known from the patent literature as a support for Ziegler-Natta catalysts. Patents USP 4,298,718 and USP 4,495,338 were the first to describe the use of these compounds in Ziegler-Natta catalysis. It is known from these patents that the magnesium dihalides in active form used as support or co-support in components of catalysts for the polymerization of olefins are characterized by X-ray spectra in which the most intense diffraction line that appears in the spectrum of the non-active halide is diminished in intensity and is replaced by a halo whose maximum intensity is displaced towards lower angles relative to that of the more intense line.

[0022] The preferred titanium compounds used in the catalyst component of the present invention are TiCl ₄ and TiCl ₃ ; furthermore, also Ti-haloalcoholates of formula Ti(OR) _n _ yX _y can be used, where n is the valence of titanium, y is a number between 1 and n-1, X is halogen and R is a hydrocarbon radical having from 1 to 10 carbon atoms.

[0023] Preferably, the catalyst component (a) has an average particle size higher than 50 μιη, preferably higher than 60 and more preferably ranging from 70 to 100 μιη. Preferably the porosity determined by mercury method of the solid catalyst component due to pore with radius equal to or less than 1 μιη is at least 0.35 cm /g, more preferably higher than

0.40 and especially ranging from 0.45 cm 3 /g to 0.6 cm 3 /g.

[0024] As explained the succinate is present in amount ranging from 50 to 90% by weight with respect to the total amount of donors. Preferably it ranges from 60 to 85%by weight and more preferably from 65 to 80%by weight. The 1,3-diether preferably constitutes the remaining amount with respect to the total amount of donors.

[0025] The alkyl-Al compound (b) is preferably chosen among the trialkyl aluminum compounds such as for example triethylaluminum, tri-n-hexylaluminum, tri-n- octylaluminum. It is also possible to use mixtures of trialkylaluminum's with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides such as AlEt ₂ Cl and Al ₂ Et ₃ Cl ₃ .

[0026] Preferred external electron-donor compounds (c) include silicon compounds, ethers, esters such as ethyl 4-ethoxybenzoate, amines, heterocyclic compounds and particularly 2,2,6,6-tetramethyl piperidine, ketones and the 1,3-diethers. Another class of preferred external donor compounds is that of silicon compounds of formula R _a ⁵ R _b ⁶ Si(OR ⁷ ) _c , where a and b are integer from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R ⁵ , R ⁶ , and R ⁷ , are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. Particularly preferred are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl-t- butyldimethoxysilane, dicyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-t- butyldimethoxysilane and l,l,l,trifluoropropyl-2-ethylpiperidinyl-dimethoxysilane and l,l,l,trifluoropropyl-metil-dimethoxysilane. The external electron donor compound is used in such an amount to give a molar ratio between the organo-aluminum compound and said electron donor compound of from 5 to 500, preferably from 7 to 400 and more preferably from 10 to 200.

[0027] Preferably, the contact of step (i) is carried out at a temperature ranging from 40 to 50°C. The time of the treatment preferably ranges from 3 to 40 minutes.

[0028] The above catalyst components (a), (b) and optionally (c) are fed to a pre- contacting vessel, in amounts such that the weight ratio (b)/(a) is in the range of 2-15 and preferably in the range 5-10.

[0029] In the process of the present disclosure the compound (c) is preferably present and used in amounts to give a molar ratio between the organo-aluminum compound (b) and said electron donor compound of from 1 to 250, preferably from 3 to 150 and more preferably from 5 to 100. The precontact vessel can be either a stirred tank or a loop reactor in which the catalyst forming components are preferably contacted, under stirring, with a liquid inert hydrocarbon solvent such as, e.g., propane, n-hexane or n-heptane. Preferably, in the pre-contacting step propylene is absent.

[0030] The pre-contacted catalyst can then be fed to the prepolymerization reactor where step (ii) can take place. Preferably, the prepolymerization step (ii) is present. [0031] The prepolymerization step can be carried out in a first reactor selected from a loop reactor or a continuously stirred tank reactor or in a sequence of two loop reactors. The prepolymerization can be carried out either in gas-phase or in liquid-phase. Preferably it is carried out in liquid-phase. The liquid medium comprises liquid alpha-olefin monomer(s), optionally with the addition of an inert hydrocarbon solvent. Said hydrocarbon solvent can be either aromatic, such as toluene, or aliphatic, such as propane, hexane, heptane, isobutane, cyclohexane and 2,2,4-trimethylpentane. The amount of hydrocarbon solvent, if any, is lower than 40% by weight with respect to the total amount of alpha-olefins, preferably lower than 20% by weight. Preferably, step (ii) is carried out in the presence of inert hydrocarbons particularly propane.

[0032] The average residence time in this reactor generally ranges from 20 to 150 minutes, preferably from 30 to 80 minutes. The temperature is comprised between 10°C and 50°C, preferably between 20°C and 40°C. Adopting these conditions allows to obtain a pre-polymerization degree in the preferred range from 60 to 800g per gram of solid catalyst component, preferably from 150 to 500 g per gram of solid catalyst component. Preferably, step (ii) is further characterized by a low concentration of solid in the slurry, typically in the range from 50 g to 300 g of solid per liter of slurry.

[0033] The pre-polymerization step is preferably carried out in the absence of any molecular weight regulator, such as hydrogen. Alternatively, in some cases hydrogen can be fed to the prepolymerization reactor, thus tailoring the intrinsic viscosity of the prepolymer obtained from step b) in a range between 0.2 and 6.0 dl/g.

[0034] A polymeric slurry containing the pre-polymer/catalyst system is discharged from the pre-polymerization reactor and is continuously fed to the polymerization step (iii).

[0035] The polymerization step (iii) of the present disclosure is preferably carried out in gas-phase reactors, preferably in a sequence of two or more fluidized bed reactors.

[0036] In the fluidized bed reactor of step iii) propylene is polymerized to give the semi- crystalline matrix. A gaseous mixture comprising propylene, optional comonomer, hydrogen as molecular weight regulator, and an inert gas is fed to the gas-phase reactor. Limited amounts of olefin comonomers may be also fed to step iii). Preferably, the total amount of comonomers incorporated in the semi-crystalline matrix is less than 10% by weight, preferably less than 5% by weight. The preferred comonomers are ethylene, 1- butene, 1-hexene and 1-octene. The Melt Flow Rate value according to ISO 1133 (230°C, 2.16 Kg) can vary within a wide range going from 0.01 to 300 g/lOmin and particularly from 0.1 to 250 g/lOmin. The porosity of the polymer coming from step (iii) preferably ranges from 0.33 to 0.60 cm /g, more preferably from 0.35 to 0.60 and especially from

0.40 to 0.55 cm 3 /g. The polymer bulk density ranges from 0.30 to 0.37 g/cm 3. The amount of insoluble fraction in xylene at 25°C of the porous polymer produced with the process of the invention is preferably higher than 97% and more preferably ranging from 97.5 to 99%wt when it is propylene homopolymer. In case of preparation in step iii) of small amounts of comonomers the cristallinty of the polymer becomes lower and the amount of xylene soluble fraction increases.

[0037] The operating temperature is selected between 50 and 120°C, preferably between 60 and 85°C, while the operating pressure is between 1.0 and 3.0 MPa, preferably between 1.4 and 2.5 MPa.

[0038] The hydrogen/propylene molar ratio is generally comprised between 0.0002 and 0.7, the propylene monomer being comprised from 10% to 100% by volume, preferably from 30 to 70% by volume, based on the total volume of the gases present in the reactor. The remaining portion of the feeding mixture is comprised of inert gases and one or more a-olefin comonomers, if any. Inert gases useful to dissipate the heat generated by the polymerization reaction are conveniently selected from nitrogen or preferably saturated light hydrocarbons, the most preferred one being propane.

[0039] Inert gases can also be used for adjusting the production split in the overall polymerization process, i.e. in the sequence of serially connected gas-phase reactors.

[0040] In case of preparation of heterophasic copolymers, the polymer produced in the polymerization step iii) preferably represents from 15 to 90% by weight, more commonly from 20 to 60% by weight, of the heterophasic copolymer produced in the overall process. In this type of processes, the polymer is transferred to a successive polymerization step iv). The polymer powder is generally passed through a solid/gas separation step, in order to prevent the gaseous mixture discharged by the first reactor from entering the gas-phase reactor of step iv). The gaseous mixture is separated and recycled back to the first polymerization reactor, while the polymer particles are fed to the polymerization step iv). [0041] Step iv) is carried out in one or more gas-phase reactors, preferably fluidized bed reactors, to prepare one or more olefin copolymers partially soluble in xylene at ambient temperature in a percentage higher than 15% by weight, preferably from 40 to 95% by weight. Said copolymers may be selected from:

copolymers of ethylene/propylene, ethylene/ 1-butene, ethylene/ 1-hexene;

copolymers of propylene/ 1-butene, propylene/l-hexene;

terpolymers of ethylene, propylene and a-olefin C ₄ -C ₁₂ .

[0042] Preferably, copolymers of ethylene with propylene and/or 1-butene are prepared in step iv) according to the present disclosure.

[0043] According to a preferred embodiment of the disclosure, the polymerization step iv) is carried out in a single fluidized bed reactor, wherein a copolymer of ethylene with propylene and/or 1-butene is prepared, said copolymer containing from 10 to 80% by weight of ethylene.

[0044] According to an alternative preferred embodiment of the disclosure, the polymerization step iv) comprises a sequence of two fluidized bed reactors, so that two distinct ethylene copolymers with a different ethylene/comonomer composition can be prepared.

[0045] When different ethylene concentrations are established in the polymerization reactors of step iv), the process herein disclosed allows to incorporate a more amorphous elastomeric component with a less amorphous elastomeric component, simultaneously providing an efficient dispersion of said two elastomeric components into the crystalline matrix produced in the first polymerization step iii).

[0046] The polymer produced in (iv) is preferably an ethylene copolymer containing from 15 to 75% wt of a C3-C ₁₀ alpha olefin, optionally containing minor proportions of a diene, being for at least 60% soluble in xylene at room temperature. Preferably, the alpha olefin is selected from propylene or butene-1 and its content ranges preferably from 20 to 70%wt.

[0047] The final polymer composition obtained through the process of the invention preferably comprises 30-90 parts by weight, preferably 40-80 parts by weight of (A) a propylene polymer optionally containing minor amounts of ethylene and/or C4-Q0 alpha olefins being insoluble in xylene at 25°C and 10-70 preferably 20-60 parts by weight of (B) an ethylene copolymer soluble in xylene preferably containing from 20 to 70% of C ₃ - Cio alpha olefin. The said propylene polymer compositions having a ratio between the intrinsic viscosities of the polymer produced in (iii) and that of the polymer produced in (iv) in tetrahydronaphthalene at 135 °C of the portion soluble in xylene and of the portion insoluble in xylene at room temperature of from 0.3 to 5.

[0048] The total ethylene content is higher than 9%, preferably higher than 10 % and more preferably ranging from 10 to 50% by weight.

[0049] The value of the intrinsic viscosity of the xylene soluble fraction determined on the reactor grade polymer composition ranges from 0.5 dl/g to 6.0 dl/g.

[0050] The compositions obtained according to the process of the present disclosure can be obtained as reactor grade with a Melt Flow Rate value according to ISO 1133 (230°C, 2.16 Kg) ranging from 0.01 to 100 g/lOmin, preferably from 0.1 to 70 and more preferably from 0.2 to 60. If desired they can be visbroken according to known technique in order to reach the final MFR value suited for the selected application. The chemical degradation of the polymer (visbreaking) is carried out in the presence of free radical initiators, such as peroxides. Examples of radical initiators that can be used for this purpose are 2,5- dimethyl-2,5-di(tert-butylperoxide)-hexane and dicumyl- peroxide. The degradation treatment is carried out by using the appropriate quantities of free radical initiators, and preferably takes place in an inert atmosphere, such as nitrogen. Methods, apparatus, and operating conditions known in the art can be used to carry out this process.

[0051] Depending on the operative conditions selected in the above defined steps from i) to iv), the heterophasic propylene copolymers obtained by means of the present disclosure can be used in a wide range of applications due to the high versatility of the claimed process. Main advantages are achieved in the following fields:

[0052] - roofing/geomembranes/bitumen in view of the optimal balance of fluidity, softness, weldability;

[0053] - automotive in view of the optimal balance of stiffness, impact resistance, shrinkage, fluidity;

- injection molding in view of the optimal balance of fluidity, impact resistance, stiffness and transparency. EXAMPLES

[0054] The following examples are given in order to better illustrate the disclosure without limiting it in any manner.

[0055] Characterization

The data of the propylene polymer materials were obtained according to the following methods:

Xylene- soluble fraction

2.5 g of polymer and 250 mL of o-xylene are introduced in a glass flask equipped with a refrigerator and a magnetical stirrer. The temperature is raised in 30 minutes up to the boiling pint of the solvent. The so obtained solution is then kept under reflux and stirring for further 30 minutes. The closed flask is then kept for 30 minutes in a thermostatic water bath at 25°C for 30 minutes. The solid thus obtained is filtered on quick filtering paper and the filtered liquid is divided into two 100 ml aliquots. One 100 ml aliquot of the filtered liquid is poured in a previously weighed aluminum container, which is heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container is then kept on an oven at 80°C under vacuum until constant weight is obtained. The residue is weighed to determine the percentage of xylene-soluble polymer.

Comonomer content of the final polymer

By IR spectroscopy.

Molar ratio of feed gasses

Determined by gas-chromatography

Melt flow rate (MFR)

Determined according to ISO 1133 (230°C, 2.16 Kg)

Porosity and surface area with mercury:

The measure is carried out using a "Porosimeter 2000 series" by Carlo Erba.

The porosity is determined by absorption of mercury under pressure. For this determination use is made of a calibrated dilatometer (diameter 3 mm) CD ₃ (Carlo Erba) connected to a reservoir of mercury and to a high-vacuum pump (1- 10 ^" mbar). A weighed amount of sample is placed in the dilatometer. The apparatus is then placed under high vacuum (<0.1 mm Hg) and is maintained in these conditions for 20 minutes. The dilatometer is then connected to the mercury reservoir and the mercury is allowed to flow slowly into it until it reaches the level marked on the dilatometer at a height of 10 cm. The valve that connects the dilatometer to the vacuum pump is closed and then the mercury pressure is gradually increased with nitrogen up to 140 kg/cm . Under the effect of the pressure, the mercury enters the pores and the level goes down according to the porosity of the material.

The porosity (cm /g), due to pores up to Ιμιη for catalysts (ΙΟμιη for polymers), the pore distribution curve, and the average pore size are directly calculated from the integral pore distribution curve which is function of the volume reduction of the mercury and applied pressure values (all these data are provided and elaborated by the porosimeter associated computer which is equipped with a "MILESTONE 200/2.04" program by C. Erba).

Poured Bulk Density [g/cm ]: measured according to DIN-53194

[0056] General procedure for the preparation of MgCl ₂ »(EtOH) _m adducts.

An initial amount of micro spheroidal MgCl ₂ -2.8C ₂ HsOH was prepared according to the method described in Example 2 of USP 4,399,054 but operating at 3,000 rpm instead of 10,000. The so obtained adduct having an average particle size of 87 μιη was then subject to thermal dealcoholation at increasing temperatures from 30 to 130°C operating in nitrogen current until the molar alcohol content per mol of Mg is 1.16.

[0057] Preparation of solid catalyst component - general procedure.

Into a 1000 mL four- necked round flask, purged with nitrogen, 500 mL of TiCl ₄ were introduced at 0°C. While stirring, 30 grams of the micro spheroidal MgCli l.ieCiHsOH adduct (prepared as described above) were added. The temperature was raised to 120°C and kept at this value for 60 minutes. During the temperature increase, an amount of diethyl 2,3-diisopropylsuccinate was added such as to have a Mg/succinate molar ratio of 11. After the mentioned 60 minutes, the stirring was stopped, the liquid siphoned off and the treatment with TiCl ₄ was repeated at 100°C for 1 hour in the presence of an amount of 9,9-bis(methoxymethyl)fluorene such as to have a Mg/donor molar ratio of 7. After that time the stirring was stopped, the liquid siphoned off and the treatment with TiCl ₄ was repeated at 100°C for 30 min. After sedimentation and siphoning at 75°C the solid was washed six times with anhydrous hexane (6 x 100 ml) at 60 °C.

EXAMPLES 1-3 and COMPARATIVE EXAMPLE 1

[0058] General polymerization conditions

The polymerization is carried out in continuous by means of a process setup comprising: - 1.5 liter vessel for the pre-contact of the catalyst components;

- a loop prepolymerization reactor having a volume of 80 liters;

- a sequence of two serially connected fluidised bed reactors, each having a volume of 1.5 m ³ .

Example 1

[0059] Precontacting - Step i)

A Ziegler-Natta catalyst system was used as the polymerization catalyst, comprising:

- a solid catalyst component prepared with the procedure described above;

triethylaluminium (TEAL) as the cocatalyst ;

dicyclopentyldimethoxysilane (DCPMS) as the external donor.

The above solid catalyst components is fed to the pre-contacting vessel, the weight ratio TEAL/solid catalyst was 4, the weight ratio TEAL/DCPMS was 4

The above components were pre-contacted at a temperature of 40°C for 9 minutes.

[0060] Prepolymerization - Step ii)

The catalyst system withdrawn from the pre-contacting vessel was continuously fed to the prepolymerization loop reactor together with a liquid stream of propylene and propane. The prepolymerization in the loop reactor was operated with a weight ratio C3¾/C ₃ H ₆ of 1.5, at the temperature reported in Table 1.

[0061] Polymerization - Step iii)

A polypropylene slurry was continuously discharged from the loop reactor and fed to the first fluidized bed reactor where propylene was polymerized using H ₂ as the molecular weight regulator and in the presence of propane as inert diluent. Ethylene as comonomer was fed to this reactor. The polymerization was carried out at a temperature of 80°C and at a pressure of 2.0 MPa.

The composition of the gas phase in the fluidized bed reactor is specified in Table 1, as well as some properties of the obtained semi-crystalline matrix. It can be seen from Table 1 that the polypropylene resin had a poured bulk density of 0.360 g/cm and a porosity of

0.360 cm ³ /g.

EXAMPLE 2

[0062] Precontacting - Step i)

Carried out as described in example 1 with the difference that the precontacting temperature was 50°C.

[0063] Prepolymerization - Step ii)

Carried out as described in example 1

[0064] Polymerization - Step III)

Carried out as described in example 1 with minor adjustment in the gas-phase composition.

[0065] It can be seen from Table 1 that the polypropylene resin had a poured bulk density

0.340 g/cm 3 and a porosity of 0.443 cm 3 /g. The fraction soluble in xylene amounted to

7.5% by weight.

EXAMPLE 3

[0066] Precontacting - Step i)

Carried out as described in example 2 with the difference that the TEAL/solid catalyst weight ratio was 8.

[0067] Prepolymerization - Step ii)

Carried out as described in example 1.

[0068] Polymerization - Step III)

Carried out as described in example 1.

The polypropylene resin had a poured bulk density of 0.333 g/cm and a porosity of 0.498 cm /g. The fraction soluble in xylene amounted to 7.5% by weight.

[0069] Polymerization - Step iv)

The obtained semi-crystalline polymer was continuously discharged from the first reactor, separated from propylene and propane by means of a gas/solid separator, and then introduced into a second fluidized bed reactor where an ethylene/propylene copolymer is prepared according to the operative conditions shown in Table 2. The rubbery copolymer obtained in step iv) is characterized by an amount of soluble polymer in xylene of 52.4% by weight having an intrinsic viscosity of 2.45 dl/g. The Melt index "L" of the final polymer composition is 3.54 dg/min and its total weight amount of ethylene is 15%.

COMPARATIVE EXAMPLE 1

[0070] Precontacting - Step i)

Carried out as described in example 1 with the difference that the precontacting temperature was 30°C.

[0071] Prepolymerization - Step ii)

Carried out as described in example 1

[0072] Polymerization - Step III)

Carried out as described in example 1

It can be seen from Table 1 that the polypropylene resin had a poured bulk density of

0.375 g/cm 3 and a porosity of 0.324 cm 3 /g. The fraction soluble in xylene amounted to 7.9% by weight.

EXAMPLE 4

[0073] A series of three runs each of which comprising catalyst precontact and propylene polymerization were carried out in an autoclave equipped with a precontacting pot. The equipment of the precontacting pot was a jacketed reactor of 250 milliliter that under mechanical stirring was charged with 75 mL of hexane, 0.76 grams of TEAL, 0.16 grams of cycloexylmethyldimetoxy silane and 0.025 grams of solid catalyst prepared as described above at the temperature and for the time reported in Table 3. Under propylene atmosphere the hexane slurry, 1.25 NL of hydrogen and 1.2 Kg of propylene were transferred to a 4 liter steel autoclave equipped with a stirrer, pressure gauge and thermometer. The system was heated to 70°C over 10 minutes under stirring, and maintained under these conditions for 120 min. At the end of the polymerization, the polymer was recovered by removing any unreacted monomers and was dried under vacuum. Precontact conditions and polymerization results are reported in table 3.

COMPARATIVE EXAMPLE 2

[0074] A series of two runs comprising catalyst precontact and propylene polymerization were carried out as described in Example 4 with the only difference that 0.025 grams of solid catalyst prepared as described in Ex. 1 of WO2008/015113 were used. At the end of the polymerization, the polymer was recovered by removing any unreacted monomers and was dried under vacuum. Precontact conditions and polymerization results are reported in table 3.

[0075] TABLE 1

[0076] TABLE 2 - Polymerization Step IV) [0077] Table 3