MXPA00003829A - Process for the production of heterophasic polymer compositions, and compositions thus obtained - Google Patents

Abstract

Process for the preparation of heterophasic polyolefin compositions comprising;i) a stage where a) the polymerization of the propylene to form a crystalline propylene or ethylene polymer, and b) the copolymerization of the ethylene with a C3-C10&agr;-olefin take place to form an elastomeric copolymer;said stage being carried out in the presence of a Ziegler-Nattacatalyst;ii) a treatment stage where the polymer obtained in polymerization stage (i) is made to contact with:a) a compound capable of deactivating the catalist present in said stage i);and b) a catalyst (2) obtained by containing (I) a compound containing a transition metal M, and at least one ligand coordinated with the metal M by a&pgr;bond, and (II) a cocatalyst;iii) a copolymerization stage where the ethylene and a C3-C10&agr;-olefin are polymerized in the presence of a polymer treated as in stage (ii), and said catalyst (2).

Description

PROCEDURE FOR THE PRODUCTION OF HETEROFASIC POLYMERIC COMPOSITIONS, AND COMPOSITIONS OBTAINED IN THIS MANNER This invention relates to a process for the preparation of a thermoplastic elastomeric polyolefin composition through the polymerization of olefins CH2 = CHR, wherein R is selected from H and an alkyl radical having from 1 to 8 carbon atoms. More precisely, this invention relates to a process for the sequential polymerization of olefins developed in the presence of catalysts belonging to different classes in the various stages. In addition, this invention relates to polymer compositions obtainable by said polymerization process. Sequential polymerization processes for the preparation of heterophasic polyolefin compositions with thermoplastic and elastomeric properties are already known. One such method for the production of the compositions mentioned above is described, by way of example, in the patent application EP-A-400333. Said compositions, which contain a crystalline polyolefin fraction and an elastomeric polyolefin fraction, are produced by polymerization in the presence of the Ziegler-Natta catalyst. Processes for the sequential polymerization of olefins developed in at least 2 stages of polymerization are also known, wherein the first polymerization is presented with a Ziegler-Natta catalyst, and the second polymerization initiated after deactivation of the Ziegler-Natta catalyst. , it is presented with a metallocene catalyst. A process of those mentioned is described, by way of example, in International Patent Application WO 96/11218. The process described leads to the production of a polymer composition comprising a crystalline polyolefin fraction and an elastomeric polyolefin fraction. It is also known, from the patent application EP-A-763553, a process in which, by sequential polymerization, a heterophasic and elastomeric thermoplastic composition is produced which contains an elastomeric fraction produced with Ziegler-Natta catalyst and an elastomeric fraction produced with metallocene catalysts. The process described in said patent application provides for at least three steps, wherein the metallocene catalyst operating in the presence of the Ziegler-Natta catalyst is added during the last step. A multistage sequential polymerization process has been discovered wherein two different fractions of elastomeric polymers can be produced in separate and subsequent steps; with said method, in fact, the second fraction occurs in the total absence of the catalyst that produces the first elastomeric fraction. In this way, it is possible to obtain heterophasic polyolefin compositions containing, in addition to the crystalline polyolefin fraction, two different elastomeric polyolefin fractions, one produced only with Ziegler-Natta catalysts, and the other only with catalysts containing a p-bond, such as the metallocene catalysts. Furthermore, thanks to the process of the present invention, the heterophasic composition does not have the undesired effects inevitably present when deactivation of the Ziegler-Natta catalyst step is not carried out. Therefore, this invention provides a process for the preparation of a heterophasic polyolefin composition comprising: i) a step where the polymerization of propylene to form a crystalline propylene polymer is carried out in any order; less 80% by weight, insoluble in xylene at room temperature or propylene with ethylene and / or a C -C 0 α-olefin, to form a crystalline propylene copolymer containing more than 85% by weight of propylene, or polymerization of ethylene to form an ethylene or ethylene homopolymer with a C3-C2-α-olefin to form an ethylene copolymer containing up to 20 mole% of the C3-C2 α-olefin, and b ) the copolymerization of ethylene and a C3-C10 α-olefin, and optionally a diene, to form an elastomeric copolymer partially soluble in xylene at room temperature, containing up to 70% by weight of ethylene in the fraction soluble in xylene at room temperature environment; said stage developed in the presence of a Ziegler-Natta catalyst (1) obtained by contacting the following components: a catalyst component containing a titanium compound and an electron donor compound, both supported on Mg chloride; an organometallic compound, and optionally an electron donor compound; ii) a treatment step wherein the polymer obtained in the polymerization step (i) is made to contact, in any given sequence, with: a) a compound capable of deactivating the catalyst present in said step (i); and b) a catalyst (2) obtained by contacting (I) a compound containing a transition metal M and at least one ligand coordinated with the metal M via a p-bond, and (II) at least one cocatalyst , chosen from alumoxanes for example; iii) a copolymerization step wherein the ethylene and a C3-C10 α-olefin are polymerized in the presence of a polymer treated as indicated in (ii), and said catalyst (2). For the purposes of the present patent application, the term at room temperature means a temperature of about 25 ° C. The solubility in xylene is determined according to the method indicated below.

The amount of ethylene fed during the copolymerization step (ii) is such that the weight percentage of ethylene with respect to the total monomers in the copolymer produced in this manner preferably varies between 30 and 80%, most preferably between 50 and 75. %. A preferred method of the present invention is where 20 to 45% by weight of the polymer matrix (1) is produced in step (i). A particularly preferred method of the present invention is where in step (i) (b) an elastomeric copolymer is produced, whose xylene-soluble fraction contains up to 40% by weight of ethylene. Furthermore, the preferred method of the present invention is where in step (i) (b) the copolymer fraction insoluble in xylene at room temperature is from 1 to 15% by weight with respect to the total polymer produced in step (i). ). The polymers produced in step (i) of the process of the present invention are prepared in two or more polymerization phases, using, from the known Ziegler-Natta catalyst mentioned above, those which are extremely stereospecific. Examples of said catalysts are described in the European patent EP 45 977, and the patents of E.U.A. Nos. 4,339,054; 4,472,524 and 4,473,660. The solid catalyst components used in these catalysts comprise, as electron donor compounds, those chosen from ethers, ketones, lactones, compounds which contain N, P, and / or S atoms, and mono- and mono-ester acids. dicarboxylic Particularly suitable are the italic acid esters, such as diisobutyl-, dioctyl-, diphenyl phthalate, and benzylbutyl phthalate. Other suitable electron donors in particular are the 1,3-diethers of the formula wherein R1 and R ", which are the same or different from each other, are alkyl, cycloalkyl or aryl radicals with 1 to 18 carbon atoms, Rm or R? v, equal or different from each other, are alkyl radicals of 1 to 4 atoms of carbon or 1,3-diethers, where the carbon atom in position 2 has a cyclic or polycyclic structure containing 5, 6 or 7 carbon atoms, and two or three unsaturations. Ethers with such a structure are described in patent applications European Published EP-A-361493, and 728769. Representative examples of said compounds are: 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2- cyclopentyl-1,3-dimethoxypropane, 2-isopropyl-2-isoamyl-1,3-dimethoxypropane and 9,9-bis (methoxymethyl) fluorene The preparation of the catalyst components mentioned above is carried out in various methods. , an adduct MgCI2 nROH (particularly in the form of spherical particles) where n generally varies from 1 to 3, and ROH is ethanol, butanol, sobutanol, and is caused to react with an excess of T 1 C 4 containing the electron donor compound. The reaction temperature generally varies from 80 to 130 ° C. Subsequently, the solid is isolated and reacted once more with TiCU, optionally, in the presence of an electron donor compound, and subsequently seped and washed with a hydrocarbon until all the chlorine ions disappear. The titanium compound, expressed as Ti, in the solid catalyst component is generally present in a percentage ranging from 0.5 to 10% by weight; the amount of electron donor compound that remains fixed in the solid component (internal donor) generally ranges from 5 to 20 mole% with respect to magnesium dihalide. The titanium compounds which can be used for the preparation of the solid catalyst components are the halides and the halogen alcoholates. The preferred compound is titanium tetrachloride. The method for the preparation of the solid catalyst component mentioned above leads to the formation of magnesium chloride in its active form. In addition, there are other reactions already known in the literature that lead to the formation of magnesium chloride in active form, starting from magnesium compounds other than halides, such as magnesium carboxylates. The active form of the magnesium chloride of the solid catalyst components can be recognized by the fact that in the X-ray spectrum of the solid catalyst component the higher intensity reflection appearing in the non-activated magnesium chloride spectrum (with an area of surface area less than 3 m2 / g) is no longer present, although instead there is a halogen with the maximum intensity displaced with respect to the position of the higher intensity reflection of the non-activated magnesium chloride, or due to the fact that the higher intensity reflection has an average height width of at least 30% greater than the higher intensity reflection that appears / in the non-activated magnesium chloride spectrum. The most active forms are those where halogen appears in the X-ray spectrum of the component. The Al-alkyl compounds which can be used as cocatalysts comprise Al-trialcalis, such as Al-triethyl, Al-triisobutyl, Al-tributyl, and Al-linear or cyclic alkyls containing 2 or more Al atoms linked together by atoms of O or N or by groups S04 and S03. The Al-alkyl compound is generally used in such quantities that it causes the Al / Ti ratio to vary from 1 to 100. The catalyst can make previous contact with small amounts of olefin (prepolymerization), keeping the catalyst in suspension in a hydrocarbon solvent , and developing the polymerization at a temperature that varies from room temperature to 60 ° C, thus producing an amount of polymer equal to 0.5-3 times the weight of the catalyst. The electron donor compounds that can be used as external donors (ie, added to the Al-alkyl compounds) include the aromatic ester acids, such as alkylbenzoates, and in particular, the silicon compounds containing at least one S-bond. -OR (where R is a hydrocarbon radical), 2,2,6,6-tetramethylpiperidine and 2,6-diisopropylpiperidine. Examples of silicon compounds are (tert-butyl) 2Si (OCH3) 2, (cyclohexyl) 2Si (OCH3) 2, (cyclohexyl) (meth1) Si (OCH3) 2, (cyclopentyl) 2Si (OCH2 ) 2, and (phenol) 2Si (OCH3) 2. The 1,3 diethers having the formulas described above can also be used in a useful manner. The external donor can be omitted if the internal donor is one of the mentioned dietors. The Ziegler-Natta catalysts are particularly suitable for the process of the present invention with a narrow particle size distribution. Examples of said Ziegler-Natta catalysts and the polymerization processes that can be used are described in published European patent application EP-A-395083. The treatment step (ii) is preferably carried out by first executing step (a) and subsequently step (b). In the case where phase (b) is carried out first, and then phase (a), it is better to deactivate the Ziegler-Natta catalyst (1) using water. Compounds suitable for use in step (ii) (a) may be chosen, for example, from compounds having the general formula 5 Ry.iXH, where R is hydrogen or a hydrocarbon group of 1 to 10 carbon atoms, X is chosen from atoms O, N or S and y is the valence of X. Non-limiting examples of said compounds are alcohols, thiols, mono- and di-alkylamine, NH3, water and H2S. The preferred compounds are those where X is an O atom, and the one that is particularly preferred among these is water. Other examples of compounds that can be used as deactivators are CO, COS, CS2, C02, 02, as well as the acetylene or fused compounds. / The molar ratio between the deactivating compound and the transition metal compound to be deactivated must be such as to ensure the actual deactivation of the catalyst used in step (i). The value of said ratio is preferably greater than 50, most preferably greater than 150, in particular greater than 250. The catalyst (2) which is used in steps (ii) and (iii) is obtained by contacting an compound (I) containing at least one ligand L, having a mono- or polycyclic structure containing conjugated p-electrons, coordinated with the metal M. The metal M is generally chosen from groups IVB, VB and VIB of the Periodic table of the elements, preferably of Ti, Zr, V and Hf.

Said compounds (I) and the compounds used as cocatalysts, such as methylalumoxanes, are already known in the art. The compounds (I) can generally be represented by the formula. CpxMayBz where Cp is a cyclopentadienyl ring that can be part of a polycyclic structure, such as indenyl or fluorenyl; x is 1, 2, or 3; M is the transition metal mentioned above. A and B, the same or different, are chosen from hydrogen, halogens and alkyl groups, optionally containing heterogeneous atoms such as O, N and S; y and z are zero or integers greater than zero, as long as the sum of x, y, z corresponds to the oxidation number of M. Preferably, at least one of the cyclopentadienyl Cp rings bears at least one substituent, such as alkyl radicals and aryl, in particular an alkyl substituent, such as C1-C5 alkyl radicals. In addition, the cyclopentadienyl rings may be connected to one another in the form of bivalent groups, for example alkylene (polymethylene) or dialkylsilane groups. Specific examples are zirconium dichloride bis (cyclopentadienyl) derivatives having various cyclopentadienyl substituted rings. Some of said components are described, for example, in the aforementioned international patent application WO 96/11218. Examples of compounds (I) that can be used for the purpose of the present invention are: (Me5Cp) MMe3, (Me5Cp) M (OMe) 3, (Me5Cp) MCl3, CpMCI3, CpMME3, (MeCp) MME3, (Me3Cp) MME3 , (Me4Cp) MCI3, CpMBu3, (Me5Cp) 2MCI2, (lnd) MBenz3, (H4lnd) MBenz3, (Cp) 2MCI2, (Me3S¡Cp) 2MCl2, (Cp) 2MMe2, (Cp) 2MEt2, (Cp) 2MPh2) (Cp) 2M (OMe) 2, (Cp) 2M (OMe) 2CI, (MeCp) 2MCI2, (Me5Cp) 2MMe2, (Me5Cp) 2MMeCI, (Cp) (Me5Cp) MCI2, (1-MeFlu) 2MCI2, (BuCp ) 2MCI2, (Me3Cp) 2MCI2, (Me4Cp) 2MCl2, (Me4Cp) 2M (OMe) 2, (Me3Cp) 2MCI2, (Me5Cp) 2M (OH) CI, (Me5Cp) 2M (OH) 2, (Me5Cp) 2M ( Ph) 2, (Me5Cp) 2M (Me) CI, (EtMe 4Cp) 2MCl 2, [(Ph) Me 4 Cp] 2MCI 2, (Et 5Cp) 2MCl 2, (Me 5Cp) 2M (Ph) CI, (lnd) 2MCI 2, (lnd) 2MME 2, (H4lnd) 2MCl2, (H4lnd) 2MME2, [(Me3Si) 2Cp] 2MCI2, (Me4Cp) (Me5Cp) MCl2, C2H4 (lnd) 2MCl2, C2H4 (lnd) 2MME2, C2H4 (H4lnd) 2MCI2l C2H4 (H4lnd) 2MME2, Me2Si (Me4Cp) 2MCl2, Me2Si (Me4Cp) 2MME2, Me2SiCp2MCI2, Me2SiCp2MME2, Me2Si (Me4Cp) 2M (OMe) Me, Me2Si (Flu) 2MCI2, Me2Si (2-Et-5-iPrCp) 2MCI2, Me2Si (H4lnd) 2MCI2, Me2Si (H4Flu) 2MCl2, Me2SiCH2 (lnd) 2MCI2, Me2Si (2- Melnd) 2MCI2, Me2Si (2-Me-5-Et-Cp) 2MCI2, Me2Si (2-Me-5-Me-Cp) 2MCI2, Me2Si (2-Me-4,5-benzoindenyl) 2MCl2, Me2Si (4, 5-benzoindenyl) 2MCl2, Me2Si (Etlnd) 2MCI2, Me2Si (2-iPr-lnd) 2MCI2, Me2Si (2-tert-butyl-lnd) 2MCI2, Me2Si (3-tert-butyl-5-Me-Cp) 2MCl2, Me2Si (3 -tert-butyl-5-Me-Cp) 2MMe2, C2H4 (2-Me-4,5-benzolnd) 2MCI2, Me2C (Flu) CpMCI2, Ph2Si (lnd) 2MCI2, Ph (Me) Si (lnd) 2MCI2, C2H4 (H4lnd) M (NMe2) OMe, isopropylidene- (3-tert-butyl-Cp) (Flu) MCI2, Me2C (Me4Cp) (MeCp) MCl2, Me2Si (lnd) 2MCI2 , Me2Si (Me4Cp) 2M (OEt) CI, C2H4 (lnd) 2M (NMe2) 2, C2H4 (Me4Cp) 2MCI2, C2Me2 (lnd) 2MCI2, Me2Si (3-Me-lnd) 2MCI2, C2H4 (2-Me-lnd) 2MCI2, C2H4 (3-Me-lnd) 2MCI2, C2H4 (4,7-dmethyl-lnd) 2MCl2, C2H4 (5,6-dimethyl-lnd) 2MCI2, C2H4 (3,4,7-trimethyl-lnd) 2MCI2, C2H4 (2-methyl-H4lnd) 2MCI2, C2H4 (4,7-dimethyl-H4lnd) 2MCl2, C2H4 (2,4,7-trimethyl-H4lnd) 2MCI2, Me2Si (4I7-dmethyl-lnd) 2MCI2, Me2Si (5,6-dimethyl-lnd) 2MCI2, and Me2Si (2,4,7-tr Methyl-H4-lnd) 2MCI2. The symbols in the formulas mentioned above have the following meanings: Me = methyl, Et = ethyl, Pr = isopropyl, Bu = Butyl, Ph = Phenyl, Cp = cyclopentadienyl, lnd = indenyl, H4lnd = 4,5,6,7-tetrahydroindenyl, Benz = benzyl, Flu = fluorenyl, M = Ti, Zr, or Hf.

Zr. The alumoxanes forming the cocatalyst (II) comprise the linear oligomeric compounds of the formula: R- (AI (R) -0) n-AIR2 or cyclic compounds of the formula R- (AI (R) -0-) m Where n it varies from for example, 1 to 40, m from 3 to 40, and R is an alkyl group preferably containing from 1 to 8 carbon atoms. A specific example of such compounds is methylalumoxane. As an alternative to the alumoxanes, compounds capable of forming a metallocene alkyl cation can be used as cocatalysts. Examples of said compounds are the compounds of formula Y + Z ", where Y + is a Br0nsted acid capable of donating a proton and reacting irreversibly with a substituent A or B of the metallocene compound, and Z" is a compatible anion which does not coordinate , and is capable of stabilizing the active catalyst that originates from the reaction of the compounds, is sufficiently labile that it can be moved by an olefinic substrate. Preferably, the anion Z "comprises one or more boron ions, most preferably it is an anion of the formula BAr4", where the substituents of Ar, the same or different, are alkyl radicals, such as phenyl, pentafluorophenyl, bis (trifluoromethyl) phenyl. Particularly preferred is tetrakis-pentafuorophenyl-borate. In addition, compounds of the formula BAr3 can suitably be used, where B is boron, and the Ar substituents, the same or different, have the meaning mentioned above. The deactivation treatment of step (ii), wherein the polymer of step (i) is made to have contact with the deactivating agents mentioned above, can be carried out in various ways, in particular by keeping the polymer in suspension in a liquid medium. (chosen, for example, from hydrocarbon solvents and olefin monomers), or in a gas medium (such as nitrogen, gaseous hydrocarbons or olefin monomers), said liquid or gaseous medium contains deactivating agents. The contact time varies, for example, from 1 minute to several hours. Humidified hexane is an example of a solvent that contains a deactivant. At the end of the treatment (a) the solvent is removed and the polymer is subjected to treatment (b). The treatment (b) is preferably carried out using a solution of the transition metal compound (I) the hydrocarbon solvent containing the cocatalyst (II) in dispersed form, an alumoxane, such as polymethylalumoxane (MAO), tetraisobutylalumoxane. or tetra (2,4,4-trimetrilpentyl) -alumoxane, and optionally an Alkyl compound, such as triisobityl-aluminum Al-triethyl. The molar ratio between the cocatalyst (II) and the transition metal compound (I) is also greater than two, preferably from 5 to 1000. The treatment (b) can also be developed by suspending the treatment polymer (a) in a solvent of hydrocarbon containing catalyst (2), generally operated at temperatures ranging from 0 to 100 ° C, preferably from 10 to 60 ° C. Alternatively, the polymer obtained from the treatment (a) can be made to have contact with a minimum amount of hydrocarbon solvent containing the catalyst (2), but sufficient to maintain the catalyst (2) in solution. The amount of the transition metal compound (I) contained in the product obtained in step (ii) can vary considerably, since it depends on the type of compound (I) used and the relative amount of polymer that is desired to be produced in the various stages. In general, said amount ranges from 1 O7 to 5 O "3 g of metal M / g of polymer produced in step (ii) preferably from 5 10" 7 to 5 10"4, most preferably 1 0" 6 to 1 0-4. The polymerization step (iii), as well as the preceding steps, can be carried out in a liquid or gaseous phase, operating in one or more reactors, following polymerization methods known in the art.

During step (iii) it is also possible to feed into the polymerization reactor an aluminum compound selected from aluminum trialkyls where the alkyl groups have from 1 to 12 carbon atoms, and linear or cyclic alumoxanes containing from 1 to 50 repeating units of the formula - (R4) AIO-, wherein R4 is an alkyl group of 1 to 12 carbon atoms, or an aryl or cycloalkyl group of 6 to 10 carbon atoms carbon. In general, the trialkylaluminum compound is added in the polymerization reactor when the treatment (b) in step (ii) is carried out in the absence of an Al-alkyl compound. The C4-C10 α-olefins fed to the process of the present invention comprise linear and branched α-olefins. Said α-olefins are preferably chosen from 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1 -pentene. The preferred α-olefin is 1-butene. Examples of dienes that can be used in the process of the present invention are: 1,4-butadiene, 1,4-hexadiene, 2-methyl-1,4-pentene, 1,5-cyclooctadiene, 1,4-cycloheptadiene, norbornadiene and ethylidene -norborneno. As indicated above, this invention also relates to polymer compositions obtainable from the process of the present invention. In particular, it is an object of this invention to have heterophasic polymer compositions that exhibit a particular balance of softness, impact resistance and flexibility. 2) from 16 to 55%, preferably from 16 to 50%, of a fraction partially soluble in xylene at room temperature, made of ethylene copolymers with a C3-C10 α-olefin; said fraction comprises an elastomeric copolymer of ethylene with a C3-C10 α-olefin, and optionally minor amounts of a diene, soluble in xylene at room temperature, and from 1 to 15%, with respect to the sum of said fractions (1 ) and (2), of a crystalline copolymer of ethylene with a C3-C10 α-olefin insoluble in xylene at room temperature; said elastomeric copolymer contains up to 40% ethylene; 3) from 15 to 60, preferably from 20 to 60%, of an elastomeric copolymer selected from copolymers of ethylene with a C3-Cio α-olefin containing from 30 to 80%, preferably from 50 to 75%, of ethylene, said copolymer has a ratio of PMp / PMn less than 7. Said polymer compositions have a ratio between the amount of said fraction soluble in xylene at room temperature of copolymer fraction (2) and the amount of polymer fraction (1) equal or less than 1.5. A preferred example of the composition of the present invention are those compositions wherein the amount of ethylene in the xylene-soluble fraction at room temperature of the copolymer fraction (2) is less than 38% by weight. The fraction polymer (1) is preferably a copolymer of propylene with an ethylene or a C4-C10 α-olefin, or mixtures thereof.

The crystalline ethylene polymer is, for example, an HDPE or an LLDPE. The C4-C10 α-olefins that can be used for the preparation of the polymer compositions of this invention comprise linear and branched α-olefins. Said α-olefins are preferably chosen from 1-butane, 1-pentane, 1-hexene, 1-octene, and 4-methyl-1 -pentene. The a-olefin that is particularly preferred is 1-butene. Examples of dienes that can be used in the process of the present invention are: 1,4-butadiene, 1,4-hexadiene, 2-methyl-1,4-pentene, 1,5-cyclooctadiene, 1,4-cycloheptadiene, and ethyliden-norbomeno. Preferably, the diene which is optionally present in the fraction copolymer (2) varies in amount from 0.5 to 10% by weight with respect to the weight of the copolymer fraction (2). The intrinsic viscosity of the elastomeric copolymer of fraction (2) preferably ranges from 1.5 to 4.5 dl / g. The elastomeric copolymer (3) is preferably chosen from copolymers of ethylene with propylene or 1-butene, preferably containing from 30 to 80%, most preferably from 50 to 75% by weight of ethylene. Typically, the elastomeric copolymer (3) has intrinsic viscosity values greater than 1.5 dl / g, in particular greater than 2 dl / g, for example from 2.2 to 6 dl / g. The compositions of the present invention have melt flow rate (MFR) values that vary greatly depending on the type of process to which it is subjected. The highest values of MFR can be obtained using known techniques, that is, directly in polymerization by means of molecular weight regulators (particularly hydrogen), or by following polymer formation, by means of a chemical viscosity separation with free radical initiators . By way of example, the MFR of the composition of the present invention, determined with the method described below, can vary from 0.1 to 100 g / 10 min. The compositions of the present invention may also contain various additives commonly used in thermoplastic polymer compositions, such as stabilizers, antioxidant agents, anticorrosive agents, anti-UV agents, carbon black, pigments, plasticizing agents, slip agents, etc. The compositions of the present invention are useful particularly for the preparation of extrusion or injection products, in particular for the preparation of sheets and films, both single-layer and multi-layer, wherein at least one of the layers contains the compositions of the present invention. The following examples are given to illustrate, but not limit the present invention. Tests have been developed on the polymer and films of the present invention to evaluate their characteristics and properties; The 1 methodology that is used in the development of such tests is described below. Solubility: determined as a percentage of soluble residue in xylene at 25 ° C as follows. A solution of the sample in xylene is prepared at a concentration of 1% by weight, keeping the sample in xylene under stirring conditions for one hour at 135 ° C.

After stirring the solution it is left to cool to 95 ° C, after which it is poured into a bath kept at 25 ° C and left for 20 minutes without stirring, and for an additional 10 minutes after stirring, it concludes. The solution is then filtered and acetone is added to a portion of the filtrate to obtain the precipitation of the dissolved polymer. The polymer obtained in this way is recovered, washed, dried and finally weighed to determine the percentage soluble in xylene. Intrinsic viscosity (I.V.): is determined in tetrahydronaphthalin at 135 ° C. Melt flow rate (MFR): in accordance with ASTM-D 1238, condition L. Elasticity modulus: ASTM D-790. Hardness (Shore D): ASTM D-2240. Impact resistance (ZOD): ASTM D-256. Brightness: the f is measured. action of the luminous flux reflected by the surface of the film used for the test. The light beam has a fixed angle of incidence. The following simplified Fresnel equation, suitable for non-metals, is used: F = 1/2 [sin2 (go) / sin2 (i + r)] + [tg2 (i + r)] l / lo where F is the fraction of luminous flux, I is the emergent flow, so is the incidence flow, i is the angle of incidence, r is the refraction angle, and sin r is (sin i) / n, where n is the refractive index. The apparatus used is a Zehnetner ZGM 1020 photometer for a reading of an angle of incidence of 45 60 °. The brightness value is given as the average value of three readings. Fluorescence: the variation of brightness of a specimen produced by injection molding is determined using an automatic injection procedure. The operating conditions are: melting temperature 220 ° C, molding temperature 40 ° C, and back pressure of 10 bar. The dimensions of the specimens are 175x74x3 mm. The specimen prepared in this way is placed in an oven at 80 ° C for 3 days. The brightness of the sample is measured at the end of this period. Energy: biaxial impact resistance is measured using a hammer for impact. The apparatus used for the impact test is a CEAST 6758/000 model n. 2. The specimen having measures of 175x74x3 mm and prepared by injection is struck with a hammer of 5.3 kg falling from a height of 30 cm.

EXAMPLES FROM 1 TO 5 AND COMPARATIVE EXAMPLE 1C General operating conditions / »\ During the polymerization, the gas phase is continuously analyzed by gas chromatography to determine the content of ethylene, propylene, hydrogen and propane. The gases mentioned above are fed in such a way that during the course of the polymerization their concentration in the gas phase remains constant. Step (i) (a) 10 Propylene is pre-polymerized in liquid propanol in a reactor with an internal temperature of 20 to 25 ° C in the presence of the catalyst and cocatalyst, ie, Al-triethyl (TEAL), and the appropriate amounts of dicyclopentyl dimethoxysilane (DCPMS) an electron donor in liquid propane. The catalyst, which contains titanium diisobutyl phthalate as the electron donor, has been prepared according to the procedure of Example 3 described in the patent application EP-A-395083. Step (i) (b) The prepolymer of the preceding step is discharged into a second reactor having a temperature of 60 ° C. Subsequently, hydrogen, propane, propylene and ethylene are fed in desired ratios and amounts to obtain the composition in a gas phase.

During the aforementioned polymerization process, the gas phase composition is kept constant by feeding a mixture of propylene, ethylene, propane and hydrogen using instruments that regulate and / or measure the flow of the monomers. Step (ii), step (a) In an apparatus the polymer obtained in step (i) is made to make contact for 5 to 30 minutes with a flow of humidified propane. Stage (ii), phase (b) The polymer discharged from the apparatus after phase (a) is transported to a second apparatus with a nitrogen and propane atmosphere, where it is made to have contact with liquid propanol, where meso-ethylene-bis (4,7-dimethyl-1-indenyl) zirconium dichloride (mEBDMIZrCb), the methylalumoxane (MAO) cocatalyst, and triisobutylaluminum are dispersed in the catalyst. (IT BAL). Previously the catalyst and aluminum compounds mentioned above have been dispersed in liquid propanol in an apparatus operating at 20 ° C. The polymer is allowed to make contact with the metallocene catalyst for approximately 15 minutes at a temperature of 40 ° C. Later the propane is eliminated by instantaneous vaporization. Step (iii) The copolymerization is carried out in a reactor operating at 45 ° C where ethylene, propylene, propane and hydrogen are added to the previously obtained polymer. The copolymerization is carried out operating at a pressure of 12 to 15 bars for three to six hours. At the end of the polymerization the polymer particles are subjected to a steam treatment, dried at 60 ° C and subsequently stabilized. The operating conditions and the amounts of catalysts and cocatalysts used in the composition, as well as the properties of the polymer blends are indicated respectively in the following tables. Example 5 refers to a heterophasic polymer composition that has been produced in accordance with the process of the present invention, perd * whose properties are not optimal, because it has a composition different from what is considered normal. The fluorescence test shows that the specimen of Example 4 displays very low, fluorescence, the specimen of Example 1 (~ shows low fluorescence, while the specimen of Comparative Example 1 its fluorescence is very obvious.

Stage (i) fa) TABLE 2 Stage (i) (a) TABLE 3 Stage (i) (b) 1) Weight fraction determined with respect to the composition obtained in steps (i) (a) and (b) TABLE 4 Stage (ii) and (iii) 1) The water is fed in molar excess 2) Percentage of ethylene in the copolymer produced in step (iii) 3) Intrinsic viscosity of the xylene-soluble fraction of the copolymer produced in step (iii) TABLE 5 1) NB = no rupture of the specimen TABLE 6

Claims (8)

1. - A process for the preparation of a heterophasic polyolefin composition comprising: i) a step where the polymerization of propylene to form a crystalline propylene polymer with at least 80% by weight is carried out in any order; insoluble in xylene at room temperature, or propylene with ethylene and / or a C4-C10 α-olefin to form a crystalline propylene copolymer containing more than 85% by weight of propylene, with the polymerization of ethylene to form a homopolymer of ethylene or ethylene with a C3-C-? 2 α-olefin, to form an ethylene copolymer containing up to 20% by mol of the C3-C-α2 α-olefin, and b) the copolymerization of ethylene and a C3-C10 α-olefin, and optionally a diene, to form an elastomeric copolymer partially soluble in xylene at room temperature, containing up to 70% by weight of ethylene in the fraction soluble in xylene at room temperature; said step is carried out in the presence of a Ziegler-Natta catalyst (1) obtained by causing the following components to make contact: a catalytic component containing a titanium compound and an electron-donor compound, both supported on MG chloride; an organometallic compound, and optionally an electron donor compound; ii) a treatment stage where the polymer obtained in the polymerization stage deactivating the catalyst present in step (i); and b) a catalyst (2) obtained by contacting (I) a compound containing a transition metal M, and at least one ligand coordinated to the metal M via a p-bond, and (II) at least one cocatalyst selected from the alumoxanes for example; iii) a copolymerization step wherein the ethylene and a C3-C10 α-olefin are polymerized in the presence of a treated polymer treated as indicated in step (ii), and said catalyst (2).

2. The process according to claim 1, further characterized in that in the copolymerization step (ii) the molar ratio between ethylene and the total amount of monomers fed ranges from 0.5 to 0.7.

3. The process according to claims 1 and 2, further characterized in that the fractions of the elastomeric copolymer (1) (b) soluble in xylene contain up to 40% by weight of ethylene.

4. The process according to claims 1 to 3, further characterized in that the C3-C10 α-olefin is propylene or 1-butene. 5. The polymer compositions obtainable from the process of claims 1 to

5.

6. The polymer compositions according to claim 5, which comprise (weight percentage): 1) of 10 to 45%, preferably 15 to 40% of a crystalline polymer fraction selected from environment greater than 80%, preferably greater than 90%, a copolymer of propylene with ethylene or a C4-C10 α-olefin, or mixtures of said comonomers; said copolymers contain more than 85% propylene, and have an insolubility in xylene at room temperature greater than 80%, or a homopolymer or copolymer of ethylene with a C3-C12 α-olefin; said copolymer contains up to 20 mole% of the C3-C12 α-olefin; 2) from 16 to 55%, preferably from 16 to 50%, of a fraction partially soluble in xylene at room temperature, made of copolymers of ethylene with a C3-C10 α-olefin; said fraction comprises an elastomeric copolymer of ethylene with a C3-C10 α-olefin, and optionally minor amounts of a diene, soluble in xylene at room temperature, and from 1 to 15%, with respect to the sum of said fractions (1 ) and (2), of a crystalline copolymer of ethylene with a C3-C10 α-olefin insoluble in xylene at room temperature; said elastomeric copolymer contains up to 40% ethylene; 3) from 15 to 60, preferably from 20 to 60%, of an elastomeric copolymer selected from copolymers of ethylene with a C3-C10 α-olefin with a molar ethylene content ranging between 30 and 75%, said copolymer having a weight average molecular weight ratio / number average molecular weight less than 4; said polymer compositions have a ratio between the amount of said fraction soluble in xylene at room temperature of copolymer fraction (2) and the amount of polymer fraction (1) equal to or less than 1.5.

7. - The compositions according to claim 6, further characterized in that the elastomeric copolymer (3) has intrinsic viscosity values greater than 1.5 dl / g.

8. Articles that can be obtained with the compositions according to claims 6 and 7.