WO2011076553A1

WO2011076553A1 - Impact-resistant polyolefin compositions

Info

Publication number: WO2011076553A1
Application number: PCT/EP2010/069017
Authority: WO
Inventors: Katsuharu Tagashira; Hiroshi Takenouchi; Akihiro Otsubo
Original assignee: Basell Poliolefine Italia S.R.L.; Sunallomer Ltd.
Priority date: 2009-12-21
Filing date: 2010-12-07
Publication date: 2011-06-30
Also published as: JP5843781B2; JP2013515086A

Abstract

A polyolefϊn compositions comprising, all percentages being by weight: A) from 50 to 85% of a polypropylene component having a solubility in xylene at room temperature lower than 20% by weight; B) from 3 to 20% of a copolymer of ethylene with C₄-C₁₀ α-olefin(s) having a solubility in xylene at room temperature greater than 50% by weight; C) from 10 to 35% of a copolymer component consisting of one or more copolymer(s) of ethylene with propylene, said copolymer component having an ethylene content equal to or higher than 60% by weight and a solubility in xylene at room temperature greater than 50% by weight; wherein the amounts of A), B) and C) are referred to the total weight of A) + B) + C) and the weight ratio B₂/C₂ of the content B₂ of ethylene in B) to the content C₂ of ethylene in C) is of 1.4 or less.

Description

"IMPACT-RESISTANT POLYOLEFIN COMPOSITIONS"

The present invention relates to an impact resistant thermoplastic polyolefin composition. In particular, the present invention relates to a composition containing a propylene polymer component and two or more copolymers of ethylene with C3-C10 a-olefins.

It is known in the art of thermoplastic polymer compositions to combine propylene polymers, generally homopolymers or copolymers with minor amounts of comonomers, with elastomeric ethylene copolymers, to achieve a useful balance of rigidity (high flexural modulus) and impact resistance. For certain applications it is also desirable to achieve low values of thermal shrinkage. In fact, said property imparts a high dimensional stability to the final articles obtained from the said compositions.

In particular, in WO03/076511 and WO2005/121240 polyolefin compositions with low values of thermal shrinkage and good mechanical properties are described, comprising a propylene polymer component, a copolymer of ethylene with one or more C4-C10 a-olefins, other elastomeric or plastomeric polyolefms and mineral fillers. As shown in the examples of the said documents, by using the therein disclosed technical solutions, flexural modulus values significantly higher than 1000 MPa are obtained only by adding around 20% by weight of mineral fillers. Moreover, the melt flow rate (MFR) of the compositions with high values of flexural modulus is relatively low.

It has now been found that by selecting specific propylene polymers and ethylene/a-olefm(s) copolymers, in combination with other features relating to the composition and the proportions of the various components, it is possible to obtain a desirable balance of mechanical properties (in particular flexural modulus and Izod impact strength), combined with a low gloss, a good rheology in the molten state and low values of thermal shrinkage. Due to its mechanical and physical properties, the polyolefin composition of the present invention finds application above all in the automotive field, in particular in the preparation of door trims.

Thus the present invention relates to a composition comprising, all percentages being by weight:

A) from 50 to 85%, preferably from 60 to 80%>, of a polypropylene component comprising a propylene homopolymer or a propylene copolymer with another a- olefin or combinations thereof, said polypropylene component containing at least 85% by weight of propylene and having a MFRL value equal to or higher than 110 g/10 min., preferably equal to or higher than 120 g/10 min., the upper limit being preferably of 2500 g/10 min., and a solubility in xylene at room temperature lower than 20% by weight;

B) from 3 to 20%, preferably from 3 to 15%, of a copolymer of ethylene and one or more C4-C10 a-olefm(s), containing 15-35%) by weight of C4-C10 a-olefm(s) and having a solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being preferably from 2.5 to 4 dl/g;

C) from 10 to 35%, preferably from 10 to 25%, of a copolymer component consisting of one or more copolymer(s) of ethylene with propylene, optionally containing 0.5 to 5% by weight of a diene, said copolymer component having an ethylene content equal to or higher than 60% by weight and a solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being preferably from 2 to 4 dl/g;

wherein the amounts of A), B) and C) are referred to the total weight of A) + B) + C) and the weight ratio B₂/C₂ of the content B₂ of ethylene in B) to the content C₂ of ethylene in C) is of 1.4 or less, preferably of 1.3 or less, more preferably of 1.2 or less, the lower limit being preferably of 0.8.

From the above definitions it is evident that the term "copolymer" includes polymers containing more than one kind of comonomers.

Optionally, the composition of the present invention can comprise a mineral filler D).

However, it is not necessary to add large amounts of fillers. To the contrary it is preferred to add such fillers in very low amounts, namely 0.3 to 5 parts by weight of mineral filler D), with respect to 100 parts by weight of A) + B) + C).

The composition of the present invention can also optionally comprise a nucleating agent E), in preferred amounts of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of A) + B) + C) and optionally D).

The composition of the present invention has preferably a MFR value of 20 g/10 min. or higher, or even of 25 g/10 min. or higher, for example in the range from 20 to 60 g/10 min., in particular from 25 to 60 g/10 min.

Thus the composition of the present invention can be easily converted into various kinds of finished or semi-finished articles, in particular by using injection-molding techniques, due to its relatively high values of MFR, associated with the said high balance of properties.

The MFRL value of component A) can result from mixing various propylene homoplymers and/or copolymers with different MFRL values. In such a case the MFRL value for A) can be easily determined, on the basis of the amounts and MFRL values of the single polymers, by means of the known correlation between the MFR of a polyolefm composition and the MFR of the separate components, which, for instance, in the case of two polymer components A¹ and A², can be expressed as follows: In MFR^A =

+ W_A ²)] x In MFR¹ + [W_A ²/(W_A ¹ + W_A ²)] x In MFR²

wherein WA¹ and WA² represent the weight of components A¹) and A²) respectively, while MFR^A represent the calculated value of MFR for A) and MFR¹ and MFR² represent the MFR of components A¹) and A²) respectively.

The MFRL value of a single polymer can therefore be even lower than lOOg/10 min.

Thus the definition of MFRL value of component A) includes also the said calculated value. The amount of fraction (XI) insoluble in xylene at room temperature of component B) preferably satisfies the following equation:

(XI) < 1.14 x B₂ - 34

where B₂ is the amount of ethylene in component B), expressed as percent by weight with respect to the weight of B).

The amount of component (A) which is soluble in xylene at room temperature is, as previously said, equal to or lower than 20%, preferably equal to or lower than 10%> by weight. Typically component (A) is selected from (i) a propylene homopolymer having a preferred solubility in xylene at room temperature lower than 10% by weight, more preferably lower than 5%, and even more preferably lower than 3%, or (ii) a copolymer of propylene with at least one a-olefm of formula H₂CH=CHR, where R is H or a C₂-8 linear or branched alkyl, or a combination of (i) and (ii).

Preferably the copolymer of propylene (ii) contains at least 90% propylene, and has a preferred solubility in xylene at room temperature of lower than 15% by weight, more preferably lower than 10%, and even more preferably lower than 8%. Said α-olefm is preferably ethylene, butene-1, pentene-1, 4-methylpentene-l, hexene-1, octene-1 or any combinations thereof, and even more preferably the copolymer of propylene (ii) is a copolymer of propylene and ethylene.

As previously said, the components (B) and (C) are partially soluble in xylene at room temperature. The content of fraction of component (B) or (C) which is soluble in xylene at room temperature is preferably of about 50-95%) by weight, more preferably 55-95%) by weight.

The C4-C10 a-olefms in component (B) are generally selected from olefins of formula H₂CH=CHR, where R is a C₂-8 linear or branched alkyl. Illustrative C4-C10 α-olefms for component (B) include 1-butene, 1-pentene, 1-hexene, 4- methyl-l-pentene and 1-octene, with 1-butene being particularly preferred.

The composition of the present invention can be prepared by melt-blending components (A), (B), (C) and optionally (D) and/or (E).

The composition of the present invention can also be prepared by subjecting to melt-blending with the other polyolefm components, and optionally with the component (D) and/or (E), a masterbatch composition (I) comprising, all percentages being by weight:

A¹) from 60 to 85% of a polypropylene component comprising a propylene homopolymer or a propylene copolymer with another α-olefm or combinations thereof, said polypropylene component containing at least 85% by weight of propylene, and having a MFRL value equal to or higher than 20 g/10 min. and a solubility in xylene at room temperature lower than 20% by weight; B¹) from 15 to 40% of a copolymer of ethylene and one or more C4-C10 a-olefm(s), containing 15-35%) by weight of C4-C10 a-olefm(s) and having a solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being from 2.5 to 4 dl/g.

Kinds of preferred polymers, kinds and amounts of comonomers and amounts of fraction soluble in xylene at room temperature for the masterbatch component (A¹) are the same as described above for component (A).

Kinds and amounts of comonomers and amounts of fraction soluble in xylene at room temperature for the masterbatch component (B¹) are the same as described above for component (B).

Preferably the masterbatch composition (I) has a value of melting enthalpy AHm of the DSC melting peak detectable at a temperature between 100 and 130°C of 1 J/g or more.

In general, the components (A), (B) and (C) can be prepared separately by using known polymerization processes.

The said masterbatch composition (I) can advantageously be prepared by a sequential polymerization, comprising at least two sequential steps, wherein components (A¹) and (B¹) are prepared in separate subsequent steps, operating in each step, except the first step, in the presence of the polymer formed and the catalyst used in the preceding step. The catalyst is added only in the first step, however its activity is such that it is still active for all the subsequent steps. The polymerization, which can be continuous or batch, is carried out following known techniques and operating in liquid phase, in the presence or not of inert diluent, or in gas phase, or by mixed liquid-gas techniques.

Reaction time, pressure and temperature relative to the polymerization steps are not critical, however it is best if the temperature is from 50 to 100 °C. The pressure can be atmospheric or higher.

The regulation of the molecular weight is carried out by using known regulators, hydrogen in particular.

The said polymerizations are preferably carried out in the presence of stereospecific Ziegler- Natta catalysts.

The said catalysts are known in the art.

Conventional molecular weight regulators known in the art, such as chain transfer agents (e.g. hydrogen or ZnEt₂), may be used.

Preferred examples of Ziegler-Natta catalysts are the supported catalyst systems comprising a trialkylaluminium compound, optionally an electron donor, and a solid catalyst component comprising a halide or halogen-alcoholate of Ti and optionally an electron-donor compound supported on anhydrous magnesium chloride. Catalysts having the above-mentioned characteristics and polymerization processes employing such catalysts are well known in the patent literature; particularly advantageous are the catalysts and polymerization processes described in USP 4,399,054 and EP-A-45 977. Other examples can be found in USP 4,472,524.

The catalysts can be pre-contacted with small amounts of olefins (prepolymerization).

Mineral fillers (D) optionally present in the composition of the present invention include talc, CaC0₃, silica, mica wollastonite (CaSi0₃), clays, diatomaceaous earth, titanium oxide and zeolites. Talc is preferred. Typically the mineral filler is in particle form having an average diameter ranging form 0.1 to 5 micrometers.

Useful nucleating agents (E) include, for example, metal salts of carboxylic acids, dibenzylsorbitol derivatives, alkali metal salts of phosphate and the like.

Specific examples of the nucleating agents include sodium benzoate, aluminum adipate, aluminum p-t-butylbenzoate, 1,3,2,4-dibenzylidenesorbitol, l,3,2,4-bis(p-methyl- benzylidene)sorbitol, 1 ,3,2,4-bis(p-ethylbenzylidene)sorbitol, 1 ,3-p-chlorobenzylidene-2,4-p- methylbenzylidene)sorbitol, sodium bis(4-t-butylphenyl) phosphate, sodium bis(4-t- methylphenyl) phosphate, potassium bis(4,6-di-t-butylphenyl) phosphate, sodium 2,2'- methylene-bis(4,6-di-t-butylphenyl) phosphate, sodium 2,2'-ethylidene-bis(4,6-di-t- butylphenyl) phosphate.

The composition of the present invention can also contain additives commonly employed in the art, such as antioxidants, light stabilizers, heat stabilizers and colorants.

As previously said, the composition of the present invention can be prepared by melt-blending the components (A), (B), (C) and optionally (D) and/or (E) or by melt-blending the matsterbatch composition (I) with the other polyolefm components, and optionally with the component (D) and/or (E). Any mixing apparatus equipped with mixing elements and known in the art can be used, such as an internal mixer or extruder. For example one can use a Banbury mixer or single- screw Buss extruder or twin-screw Maris or Werner type extruder.

The present invention also provides final articles, in particular door trims, made of the said polyolefm composition.

The practice and advantages of the present invention are disclosed below in the following examples. These Examples are illustrative only, and are not intended to limit the scope of the invention in any manner whatsoever.

The following analytical methods are used to characterize the polymer compositions.

Melt Flow Rate (MFR : ASTM-D 1238, condition L (i.e. 230°C with 2.16 kg load).

[η] intrinsic viscosity: determined in tetrahydronaphtalene at 135°C.

Ethylene and butene content: I.R. Spectroscopy.

Flexural Modulus: ISO 178.

Tensile strength at break: ISO 527.

Elongation at break: ISO 527.

Notched IZOD impact test: ISO 180/1A

Gloss

10 rectangular specimens (55x60x1 mm) for each polymer to be tested are prepared by injection molding using an injection press Battenfeld BA500CD operated under the following conditions:

Screw speed: 120 rpm

Back pressure: lO bar

Mould temperature: 40°C

Melt temperature: 260°C

Injection time: 3 sec

First holding time: 5 sec

Second holding time 5 sec Cooling time (after second holding): 10 sec

The value of the injection pressure should be sufficient to completely fill the mould in the above mentioned indicated time span.

By a glossmeter the fraction of luminous flow reflected by the examined specimens surface is measured, under an incident angle of 60°. The value reported in Table III corresponds to the mean gloss value over 10 specimens for each tested polymer.

The glossmeter used is a photometer Zehntner model ZGM 1020 or 1022 set with an incident angle of 60°. The measurement principle is given in the Norm ASTM D2457. The apparatus calibration is done with a sample having a known gloss value.

Xylene soluble and isoluble fractions

2.5 g of polymer and 250 cm³ of 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 point of the solvent. The so obtained clear solution is then kept under reflux and stirring for further 30 minutes. The closed flask is then kept for 30 minutes in a bath of ice and water and in thermostatic water bath at 25 °C for 30 minutes as well. The so formed solid is filtered on quick filtering paper. 100 cm³ 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 in an oven at 80 °C under vacuum until constant weight is obtained. The weight percentage of polymer soluble in xylene at room temperature is then calculated.

The percent by weight of polymer insoluble in xylene at room temperature is considered the crystallisable portion of the polymer. This value also corresponds substantially to the isotacticity index determined by extraction with boiling n-heptane, which by definition constitutes the isotacticity index of polypropylene.

Longitudinal and transversal thermal shrinkage

A plaque of 100 x 200 x 2.5 mm is moulded in an injection moulding machine

"SANDRETTO serie 7 190" (where 190 stands for 190 tons of clamping force).

The injection conditions are:

melt temperature = 250°C;

mould temperature = 40°C;

injection time = 8 seconds;

holding time = 22 seconds;

screw diameter = 55 mm.

The plaque is measured 48 hours after moulding, through callipers, and the shrinkage is given by:

200 - read value

Longitudinal shrinkage x 100

200

100 - read value

Transversal shrinkage x 100

100

wherein 200 is the length (in mm) of the plaque along the flow direction, measured immediately after moulding;

100 is the length (in mm) of the plaque crosswise the flow direction, measured immediately after moulding;

the read_value is the plaque length in the relevant direction.

Determination of melting peaks and melting enthalpy (AHm) by differential scanning calorimetry (DSC)

The instrument used is a PerkinElmer Diamond DSC. The polymer sample is heated to 230°C at a rate of 10°C/min and kept at 230°C for 5 minutes in nitrogen stream and it is thereafter cooled at a rate of 10°C/min to 20°C, thereby kept at this temperature for 5 min to crystallise the sample. Then, the sample is again fused at a temperature rise rate of 10°C/min up to 230°C. The melting scan is recorded, a thermogram is obtained, and, from this, the temperature and fusion enthalpy value corresponding to the most intense peak between 100 and 130°C are read.

Preparation of the masterbatch composition (I)

Three masterbatch compositions are prepared. The solid catalyst component used in polymerization is a highly stereospecific Ziegler-Natta catalyst component supported on magnesium chloride, prepared according to the Example 5, lines 48-55 of the European Patent EP728769. Triethylaluminium (TEAL) is used as co-catalyst and dicyclopentyldimethoxysilane (DCPMS) as external donor.

The solid catalyst component is contacted at 12° C for 24 minutes with TEAL and DCPMS. The weight ratio between TEAL and the solid catalyst component and the weight ratio between TEAL and DCPMS are of 20 and 10 respectively.

The catalyst system is then subjected to prepolymerization by maintaining it in suspension in liquid propylene at 20° C for about 5 minutes before introducing it into the first polymerization reactor.

POLYMERIZATION

The polymerisation run is conducted in continuous in a series of two reactors equipped with devices to transfer the product from one reactor to the one immediately next to it. The first reactor is a liquid phase reactor, and the second reactor is a fluid bed gas phase reactor. Component (A¹) is prepared in the first reactor, while component (B¹) is prepared in the second reactor, respectively.

Component (A¹) is a propylene homopolymer, while component (B¹) is an ethylene/butene-1 copolymer.

Temperature and pressure are maintained constant throughout the course of the reaction. Hydrogen is used as molecular weight regulator.

The gas phase (propylene, ethylene, butene and hydrogen) is continuously analysed via gas- chromatography.

Polymerization conditions, molar ratio of the reactants and composition of the copolymers obtained are shown in Table I.

The polymer particles exiting the second reactor are subjected to a steam treatment to remove the reactive monomers and volatile substances, and then dried.

Then the polymer particles are introduced in a rotating drum, where they are mixed with 0.05% by weight of paraffin oil ROL/OB 30 (having a density of 0.842 kg/1 at 20 °C according to ASTM D 1298 and flowing point of -10 °C according to ASTM D 97), 0.15% by weight of Irganox® B 215 (made of about 34% Irganox® 1010 and 66% Irgafos® 168) and 0.04% by weight of DHT-4A (hydrotalcite).

The said Irganox 1010 is 2,2-bis[3-[,5-bis(l,l-dimethylethyl)-4-hydroxyphenyl)-l- oxopropoxy]methyl]-l,3-propanediyl-3,5-bis(l,l-dimethylethyl)-4-hydroxybenzene- propanoate, while Irgafos 168 is tris(2,4-di-tert.-butylphenyl)phosphite.

Then, the polymer particles are extruded under nitrogen in a screw extruder with a melt temperature of 200-250 °C.

The characteristics relating to the polymer compositions, reported in Table II, are obtained from measurements carried out on the so extruded polymer.

Table I

Masterbatch 1 2 3

1° Reactor (component (A¹))

Temperature (° C) 70 70 70

Amount produced (wt%) 76.7 77.6 66.6

MFR L (g/10 min.) 44 68 113

Xylene soluble (wt%) 1.8 1.9 2.1

2° Reactor (component (B¹))

Temperature (° C) 85 85 85

Pressure (MPa) 2 2 2

Amount produced (wt%) 23.3 22.4 33.4

C4/(C2+C4) mol 0.44 0.48 0.46

C4 in (B¹) (wt%) 26 29.5 27.7

Xylene soluble in (B¹) (wt%) 58.4 55.6 64.5 l.V. of xylene soluble of (B¹) (dl/g) 3.2 3.3 2.4

AHm (100-135°C peak) (J/g) 2.8 2.1 3.5

Notes: C2 = ethylene; C4 = butene; l.V. = Intrinsic Viscosity

Table II

Masterbatch 1 2 3

MFR L (g/10 min) 13.0 16.1 21.0

Xylene soluble (wt%) 15 14 22.9

Ethylene content (wt%) 17.2 15.8 24

Butene content (wt%) 6.1 6.6 9.3 Examples 1 to 3

The masterbatch compositions 1 to 3 prepared as described above, are mechanically mixed with the other components by extrusion under the previously described conditions. The proportions of the polyolefm components used in these examples are reported in Table III, together with the amounts of components A), B) and C) of the final composition, obtained by aggregating the contributions of said polyolefm components, and with the calculated value of MFR L of A), based on the previously reported correlation of MFR logarithms.

The following polyolefm components are used.

PP-1 : Propylene homopolymer having a MFRL value of 2000 g/10 min. and solubility in xylene at room temperature of 2.3% by weight;

PP-2: Propylene homopolymer having a MFRL value of 2 g/10 min. and solubility in xylene at room temperature of 2.2% by weight;

Heco: Polyolefm composition (heterophasic blend) comprising 47.4% by weight of propylene homopolymer having a MFRL value of 100 g/10 min. and solubility in xylene at room temperature of 3.5% by weight, 46.9% by weight of ethylene/propylene copolymer containing 70% by weight of ethylene and having a solubility in xylene at room temperature of 66% by weight and an intrinsic viscosity of the xylene soluble fraction of 2.5 dl/g, and 5.7% by weight of ethylene/propylene copolymer containing 34% by weight of ethylene and having a solubility in xylene at room temperature of 90% by weight and an intrinsic viscosity of the xylene soluble fraction of 2.6 dl/g.

The two ethylene/propylene copolymers of the said Heco component together constitute the component C) of the composition of the present invention (final composition). Thus the ethylene content of C) is 66.2 % by weight, the solubility in xylene at room temperature of C) is of 69% by weight and the intrinsic viscosity of the xylene soluble fraction is of about 2.5 dl/g.

In addition to the said polyolefm components, also talc and a nucleating agent, corresponding respectively to components D) and E), are added.

The talc D) used is Neotalc UN105 manufactured by Neotalc industries, Ltd. The amount of D) in the compositions of all the examples is 1 part by weight with respect to 100 parts by weight of A) + B) + C).

Sodium-2,2'-methylene-bis(4,6-di-t-butylphenyl)-phosphate (trade name NA11, manufactured by Asahi Denka K. K.) is used as nucleating agent E). The amount of E) in the compositions of all the examples is 0.2 parts by weight with respect to 100 parts by weight of A) + B) + C) + D).

The properties of the so obtained final compositions are reported in Table III.

Table III

EXAMPLE 1 2 3

Masterbatch composition No. 1 2 3

Amount of Masterbatch composition (wt%) 37 39 32

PP-1 (wt%) 26 20 20

PP-2 (wt%) - 4 11

Heco (wt%) 37 37 37

A) (wt%) 71.9 71.8 69.8

B) (wt%) 8.6 8.7 10.7

C) (wt%) 19.5 19.5 19.5

MFR L of A) (g/10 min) 200 167 128

Final composition - properties

MFR L (g/10 min) 37.6 26.3 22.9

Flexural modulus (MPa) 1276 1253 1233

Tensile strength at break (MPa) 21.1 21.3 21.3

Elongation at break (%) 4.1 7.3 9.3

IZOD resilience at 23° C (KJ/m²) 4.7 7.4 4.6

IZOD resilience at 10° C (KJ/m²) 3.9 5.4 4.0

Longitudinal shrinkage (%) 1.19 1.21 1.01

Transversal shrinkage (%) 1.30 1.34 1.19

Gloss (%) 22.5 25.2 29.7

Claims

1. A polyolefm compositions comprising, all percentages being by weight:

A) from 50 to 85% of a polypropylene component comprising a propylene homopolymer or a propylene copolymer with another α-olefm or combinations thereof, said polypropylene component containing at least 85% by weight of propylene and having a MFRL value equal to or higher than 100 g/10 min. and a solubility in xylene at room temperature lower than 20% by weight;

B) from 3 to 20%> of a copolymer of ethylene and one or more C₄-C₁₀ a-olefm(s), containing 15-35%) by weight of C₄-C₁₀ a-olefm(s) and having a solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being preferably from 2.5 to 4 dl/g;

C) from 10 to 35% of a copolymer component consisting of one or more copolymer(s) of ethylene with propylene, optionally containing 0.5 to 5% by weight of a diene, said copolymer component having an ethylene content equal to or higher than 60% by weight and a solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being preferably from 2 to 4 dl/g;

wherein the amounts of A), B) and C) are referred to the total weight of A) + B) + C) and the weight ratio B₂/C₂ of the content B₂ of ethylene in B) to the content C₂ of ethylene in C) is of 1.4 or less, the lower limit being preferably of 0.8.

2. The polyolefm composition of claim 1, further comprising 0.3 to 5 parts by weight of mineral filler D), preferably talc, with respect to 100 parts by weight of A) + B) + C).

3. The polyolefm composition of claim 1, further comprising 0.01 to 0.5 parts by weight of a nucleating agent E) with respect to 100 parts by weight of A) + B) + C) and optionally

D) .

4. The polyolefm composition of claim 1, having a MFRL value equal to or higher than 10 g/10 min., preferably equal to or higher than 15 g/10 min., more preferably equal to or higher than 20 g/10 min.

5. The polyolefm composition of claim 1, wherein the amount of fraction (XI) insoluble in xylene at room temperature of component B) satisfies the following equation:

(XI) < 1.14 x B₂ - 34

6. A composition comprising, all percentages being by weight:

A¹) from 60 to 85% of a polypropylene component comprising a propylene homopolymer or a propylene copolymer with another α-olefm or combinations thereof, said polypropylene component containing at least 85% by weight of propylene, and having a MFRL value equal to or higher than 20 g/10 min. and a solubility in xylene at room temperature lower than 20% by weight;

B¹) from 15 to 40% of a copolymer of ethylene and one or more C4-C10 a-olefm(s), containing 15-35%) by weight of C4-C10 a-olefm(s) and having a solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being preferably from 2.5 to 4 dl/g.

7. The composition of claim 5, having a MFRL value equal to or higher than 2 g/10 min.

8. The composition of claim 5, having a AHm of the DSC melting peak detectable at a temperature between 100 and 130°C of 1 J/g or more.

9. The composition of claims 5 to 7, obtainable by polymerization in the presence of a MgCl₂ supported Ziegler-Natta catalyst.

10 A process for preparing the polyolefm composition of claim 1 by subjecting to melt- blending with the other polyolefm components a masterbatch composition comprising, all percentages being by weight:

B¹) from 15 to 40% of a copolymer of ethylene and one or more C4-C10 a-olefm(s), containing 15-35%) by weight of C4-C10 a-olefm(s) and having solubility in xylene at room temperature greater than 50% by weight, the intrinsic viscosity of the xylene soluble fraction being from 2.5 to 4 dl/g.

11. Manufactured articles comprising the polyolefm composition of claim 1.

12. The manufactured articles of claim 9 in form of door trims.