Heterophasic propylene copolymer with excellent stiffness and impact balance

The present invention is directed to a new heterophasic propylene copolymer (HECO), its manufacture and use.

Heterophasic propylene copolymers are well known in the art. Such heterophasic propylene copolymers comprise a matrix being either a propylene homopolymer or a random propylene copolymer in which an elastomeric copolymer is dispersed. Thus the polypropylene matrix contains (finely) dispersed inclusions being not part of the matrix and said inclusions contain the elastomer. The term inclusion indicates that the matrix and the inclusion form different phases within the heterophasic propylene copolymer, said inclusions are for instance visible by high resolution microscopy, like electron microscopy or scanning force microscopy. Down-gauging and light- weighing is a recurring market need, since it allows for energy and material savings. In order to provide a material equipped with these features, a high stiff material with good impact properties needs to be developed. The high stiffness combined with a high flowability enables lower wall thicknesses without loosing stability and thus enabling the manufacture of big parts. Additionally, the tool design can be kept simple for high flow materials since less gates are necessary. Furthermore, a cycle time reduction is possible since a certain stiffness needed for demoulding of the specimen is reached at shorter cooling times. However, the impact performance needs to stay on a high level. High flow materials, generally show high stiffness due to shorter polymer chains which have less stereo-defects. However, the impact performance becomes reduced due to shorter polymer chains which form less entanglements. Thus, it is a challenge to obtain a material of high flowability and stiffness and good impact performance.

Additionally one can distinguish between biaxial and triaxial impact strength. Although in multi-phase systems like heterophasic propylene copolymers (HECO) both strongly depend on the morphology, increasing both types of impact strength is rather challenging. This is due to the fact that they show an optimum at different particle sizes. Especially the impact strength at biaxial stress state (puncture energy) is improved at small finely dispersed particles. This can be achieved via a rubber of low molecular weight. However, such a rubber is detrimental to the impact strength at triaxial stress state (Charpy impact strength). Using a trimodal matrix concept leads to a propylene of excellent stiffness and to heterophasic copolymers showing an outstanding impact-stiffness balance. This good impact-stiffness balance is thought to be based on a fine dispersion of the rubber phase achieved by the high molecular weight part of the matrix. However, it is not known to apply this concept for heterophasic propylene copolymers (HECO) with high rubber amounts as they are necessary for automotive applications.

Thus, the object of the present invention is to obtain a material of high flowability and stiffness and good impact performance. In particular, it is an object of the present invention to obtain a material having a high flowability, a high stiffness, a high puncture energy and a high Charpy impact strength.

The finding of the present invention is to provide a heterophasic propylene copolymer which contains a matrix with a broad molecular weight distribution and a rather high amount of elastomer, preferably with rather low intrinsic viscosity.

Accordingly, the present application relates to a heterophasic propylene copolymer (HECO) comprising: (a) a matrix (M) being a polypropylene (PP), wherein said polypropylene (PP) comprises at least three polypropylene fractions (PPl), (PP2) and (PP3), the three polypropylene fractions (PPl), (PP2) and (PP3) differ from each other by the melt flow rate MFR ₂ (230 °C) measured according to ISO 1133, and (b) an elastomer (E) dispersed in said matrix (M), wherein the elastomer (E) is included in an amount of 20 wt.-% or more, based on the weight of the heterophasic propylene copolymer (HECO), optionally a low amount of polyethylene (PE) and optionally an inorganic filler (F).

The present invention also relates to a process for the preparation of a heterophasic propylene copolymer (HECO) as defined above, wherein the process comprises the step of blending the elastomer (E) with the matrix (M). The present invention also relates to an article comprising the heterophasic propylene copolymer (HECO) as defined above, and to uses of the heterophasic propylene copolymer (HECO) especially in an automotive application. In the following the invention is described in more detail.

The heterophasic propylene copolymer (HECO)

A heterophasic propylene copolymer (HECO) according to this invention comprises a polypropylene (PP) as a matrix (M) and dispersed therein an elastomer (E). Thus the polypropylene (PP) matrix contains (finely) dispersed inclusions being not part of the matrix (M) and said inclusions contain the elastomer (E) and may optionally further contain low amounts of crystalline polyethylene (PE). The term inclusion indicates that the matrix (M) and the inclusion form different phases within the heterophasic propylene copolymer (HECO), said inclusions are for instance visible by high resolution microscopy, like electron microscopy or scanning force microscopy.

Preferably the heterophasic propylene copolymer (HECO) according to this invention comprises as polymer components only the polypropylene (PP) and the elastomer (E). In other words the heterophasic propylene copolymer (HECO) may contain further additives but in a preferred embodiment no other polymer in an amount exceeding 8.0 wt-%, more preferably exceeding 6.0 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO). One additional polymer which may be present in such low amounts is a polyethylene (PE) being intimately mixed with the elastomer (E), i.e. the elastomer (E) and the optional polyethylene (PE) form the inclsuions in the matrix (M). Accordingly it is in particular appreciated that the instant heterophasic propylene copolymer (HECO) contains only the polypropylene (PP) (i.e. the matrix (M)) the elastomer (E) and optionally small amounts of polyethylene (PE) as the only polymer components. In one preferred aspect of the present invention, the heterophasic propylene copolymer

(HECO) is featured by a rather high melt flow rate. The melt flow rate mainly depends on the average molecular weight. This is due to the fact that long molecules render the material a lower flow tendency than short molecules. An increase in molecular weight means a decrease in the MFR- value. The melt flow rate (MFR) is measured in g/10 min of the polymer discharged through a defined die under specified temperature and pressure conditions and the measure of viscosity of the polymer which, in turn, for each type of polymer is mainly influenced by its molecular weight but also by its degree of branching. The melt flow rate measured under a load of 2.16 kg at 230 °C (ISO 1133) is denoted as MFR ₂ (230 °C). Accordingly, it is preferred that in the present invention the heterophasic propylene copolymer (HECO) has an MFR ₂ (230 °C) of equal or more than 50 g/lOmin, more preferably of equal or more than 70.0 g/10 min, still more preferably in the range of 70.0 to 200.0 g/lOmin, , like in the range of 75.0 to 180 g/lOmin.

Preferably it is desired that the heterophasic propylene copolymer (HECO) is

thermomechanically stable. Accordingly it is appreciated that the heterophasic propylene copolymer (HECO) has a melting temperature of at least 160 °C, more preferably of at least 162°C, still more preferably in the range of 163 to 170 °C.

The elastomer (E) of the heterophasic propylene copolymer (HECO) constitutes the main part of the xylene cold soluble fraction of the heterophasic propylene copolymer (HECO). Thus in good approximation the xylene cold soluble (XCS) fraction of heterophasic propylene copolymer (HECO) can be equated with the elastomer (E) content of the the heterophasic propylene copolymer (HECO). Accordingly, the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is preferably equal or higher than 20 wt.-%, more preferably in the range of 20 to 50 wt.-%, yet more preferably in the range of 25 to 40 wt.-%, like in the range of 25 to 35 wt- %., based on the heterophasic propylene copolymer (HECO).

In a further preferred embodiment the heterophasic propylene copolymer (HECO) of the instant invention is preferably featured by (i) a tensile modulus measured according to ISO 527-2 of at least 1,100 MPa, more preferably of at least 1,200 MPa, still more preferably in the range from 1,100 to 2500 MPa, like in a range of 1,200 to 2,200 MPa,

and/or

(ii) a Charpy notched impact strength measured according to ISO 179 (leA; 23 °C) of at least 3.5 kJ/m ² , more preferably of at least 4.5 kJ/m ² , still more preferably in the range from 4.0 to 10 kJ/m ² , like in the range of 4.0 to 8.0 kJ/m ² ,

and/or

(iii) a Charpy notched impact strength measured according to ISO 179 (leA; -20 °C) of at least 1.0 kJ/m ² , more preferably of at least 1.2 kJ/m ² , still more preferably in the range from 1.5 to 5.0 kJ/m ² ,

and/or

(iv) a puncture energy (+23 °C) determined in the instrumental falling weight (IFW) test according to ISO 6603-2 using injection moulded plaques of 60x60x2 mm of at least 6 J, more preferably of at least 12 J, still more preferably in the range of 8 to 28 J, like in the range of 12 to 25 J,

and/or

(v) a puncture energy (-20°C) determined in the instrumental falling weight (IFW) test according to ISO 6603-2 using injection moulded plaques of 60x60x2 mm of at least 3 J, more preferably of at least 7 J, still more preferably in the range of 5 to 18 J, like in the range of 7 to 15 J.

The values of puncture energy preferably refer to a heterophasic propylene copolymer (HECO) without filler (F).

In the following the individual components of the heterophasic propylene copolymer (HECO), i.e. the matrix (M) and the elastomer (E) will be defined in more detail.

As mentioned above, the matrix (M) is a polypropylene (PP), more preferably a random propylene copolymer (R-PP) or a propylene homopolymer (H-PP), the latter being especially preferred. Accordingly the comonomer content of the polypropylene (PP) is equal or below 1.0 wt.-%, yet more preferably not more than 0.8 wt.-%, still more preferably not more than 0.5 wt.-%. The weight percentage is based on the total weight of the polypropylene (PP).

As mentioned above the polypropylene (PP) is preferably a propylene homopolymer (H-PP).

The expression propylene homopolymer as used throughout the instant invention relates to a polypropylene that consists substantially, i.e. of equal or below than 99.5 wt.-%, of propylene units. In a preferred embodiment only propylene units in the propylene homopolymer are detectable. The comonomer content is determined by FT infrared spectroscopy, as described below in the example section.

In case the polypropylene (PP) is a random propylene copolymer (R-PP), it is appreciated that the random propylene copolymer (R-PP) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C4 to C ₁₂ α-olefins, in particular ethylene and/or C4 to Cg a-olefins, e.g. 1-butene and/or 1-hexene. Preferably the random propylene copolymer (R-PP) according to this invention comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, 1 -butene and 1 -hexene. More specifically the random propylene copolymer (R-PP) of this invention comprises - apart from propylene - units derivable from ethylene and/or 1-butene. In a preferred embodiment the random propylene copolymer (R-PP) comprises units derivable from ethylene and propylene only. Additionally it is appreciated that the random propylene copolymer (R-PP) has preferably a comonomer content in the range of more than 0.1 to 2.0 wt.-%, more preferably in the range of more than 0.1 to 1.6 wt.-%, yet more preferably in the range of 0.1 to 1.0 wt.-%. The weight percentage is based on the total weight of random propylene copolymer (R-PP). The term "random" indicates that the comonomers of the propylene copolymer (R-PP), as well as of the first random propylene copolymer (R-PP1), the second random propylene copolymer (R-PP2), and third random propylene copolymer (R-PP3), are randomly distributed within the propylene copolymers. The term random is understood according to IUPAC (Glossary of basic terms in polymer science; IUPAC recommendations 1996). As stated above the heterophasic propylene copolymer (HECO) has a rather high melt flow rate. Accordingly, the same holds true for its matrix (M), i.e. the polypropylene (PP). Thus it is preferred that polypropylene (PP) has a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 30.0 to 500.0 g/lOmin, more preferably of 40.0 to 400.0 g/10 min, still more preferably in the range of 50.0 to 300.0 g/lOmin.

Further it is appreciated that the matrix (M) of the heterophasic propylene copolymer (HECO) is featured by a moderately broad molecular weight distribution. Accordingly it is appreciated that the matrix of the heterophasic propylene copolymer (HECO), i.e. the polypropylene (PP), has a molecular weight distribution (MWD) of equal or more than 3.0, preferably equal or more than 3.5, more preferably in the range of 3.5 to 8.0, still more preferably in the range of 3.5 to 7.0, like 4.0 to 7.0.

Additionally the polypropylene (PP) can be defined by its molecular weight. Thus it is appreciated that the polypropylene (PP) has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC; ISO 16014-4:2003) of equal or less than 175 kg/mol, more preferably of equal or less than 165 kg/mo 1, yet more preferably in the range of 75 to 160 kg/mol, still more preferably in the range of 80 to 150 kg/mol.

The xylene cold soluble (XCS) content of the polypropylene (PP) is rather moderate.

Accordingly xylene cold soluble (XCS) content is preferably equal or below 4.0 wt.-%, more preferably equal or below 3.5 wt.-%, still more preferably in the range of 0.5 to 3.0 wt.-%, like in the range of 0.5 to 2.8 wt.-%. The weight percentage is based on the total weight of the polypropylene (PP). As indicated above the polypropylene (PP) comprises at least three, more preferably comprises three, yet more preferably consists of three, polypropylene fractions (PPl), (PP2), and (PP3), the three polypropylene fractions (PPl), (PP2), and (PP3) differ from each other by the melt flow rate MFR ₂ (230 °C) measured according to ISO 1133.

In a preferred embodiment, the first polypropylene fraction (PPl) has a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 of 80 to 500 g/1 Omin, more preferably 150 to 480 g/10 min, yet more preferably 200 to 450 g/1 Omin, still more preferably 250 to 450 g/1 Omin.

Furthermore, the second polypropylene fraction (PP2) preferably has a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 of 20 to 300 g/1 Omin, more preferably 50 to 250 g/10 min, yet more preferably 70 to 220 g/1 Omin, still more preferably 100 to 200 g/1 Omin.

In addition, the polypropylene fraction (PP3) has preferably a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 of 1 to 15 g/1 Omin, more preferably 2 to 15 g/1 Omin, yet more preferably 2 to 12 g/10 min, still more preferably 3 to 10 g/lOmin.

Preferably the melt flow rate MFR ₂ (230 °C) decreases from the first polypropylene fraction (PPl) to the third polypropylene fraction (PP3). Accordingly the ratio between the melt flow rate MFR ₂ (230 °C) of the first polypropylene fraction (PPl) and the third polypropylene fraction (PP3) [MFR (PPl) / MFR (PP3)] is preferably at least 10, more preferably at least 20, yet more preferably at least 30, like in the range of 30 to 60 and/or the ratio between the melt flow rate MFR ₂ (230 °C) of the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) [MFR (PP2) / MFR (PP3)] is preferably at least 5, more preferably at least 7, yet more preferably at least 10. In another preferred embodiment the melt flow rate MFR ₂ (230 °C) decreases from the first polypropylene fraction (PPl) to the second polypropylene fraction (PP2) and from the second polypropylene fraction (PP2) to the third polypropylene fraction (PP3). Accordingly the second polypropylene fraction (PP2) preferably has a lower melt flow rate MFR ₂ (230 °C) than the first polypropylene fraction (PPl) but a higher melt flow rate MFR ₂ (230 °C) than the third polypropylene fraction (PP3). Thus the third polypropylene fraction (PP3) preferably has the lowest melt flow rate MFR ₂ (230 °C) of the three polypropylenes fractions (PPl), (PP2), and (PP3), more preferably of all polymers present in the polypropylene (PP). Preferably at least one of the polypropylene fractions (PPl), (PP2), and (PP3) is a propylene homopolymer, even more preferred all polypropylene fractions (PPl), (PP2), and (PP3) are propylene homopolymers.

Thus in a preferred embodiment the matrix (M), i.e. the polypropylene (PP), of the heterophasic propylene copolymer (HECO) comprises

(a) a first polypropylene fraction (PPl) being a first propylene homopolymer (H-PP1) or a first random propylene copolymer (R-PP1),

(b) a second polypropylene fraction (PP2) being a second propylene homopolymer (H- PP2) or a second random propylene copolymer (R-PP2),

(c) a third polypropylene fraction (PP3) being a third propylene homopolymer (H-PP3) or a third random propylene copolymer (R-PP3),

with the proviso that at least one of the three fractions PPl, PP2, and PP3 is a propylene homopolymer, preferably at least the first polypropylene fraction (PPl) is a propylene homopolymer, more preferably all three fractions (PPl), (PP2), and (PP3) are propylene homopolymers.

As mentioned above, it is in particular preferred that at least the first polypropylene fraction (PPl) is a propylene homopolymer, a so called first propylene homopolymer (H-PP1). Even more preferred this first polypropylene fraction (PPl) has the highest melt flow rate MFR ₂ (230 °C) of the three polypropylenes (PPl), (PP2), and (PP3).

Still more preferred, in addition to the first polypropylene fraction (PPl) either the second polypropylene fraction (PP2) or the third polypropylene fraction (PP3) is a propylene homopolymer. In other words it is preferred that the polypropylene (PP) comprises, preferably consists of, only one polypropylene fraction being a random propylene copolymer. Accordingly either the second polypropylene fraction (PP2) is a propylene homopolymer, so called second propylene homopolymer (H-PP2), or the third polypropylene fraction (PP3) is a propylene homopolymer, so called third propylene homopolymer (H- PP3). It is especially preferred that all three polypropylene fractions (PPl), (PP2), and (PP3) are propylene homopolymers.

In the following the three polypropylene fractions (PPl), (PP2), and (PP3) will be described in more detail.

As mentioned above the polypropylene fractions (PPl), (PP2), and (PP3) can be random propylene copolymers or propylene homopolymers. In any case the comonomer content shall be rather low for each of the polypropylene fractions (PPl), (PP2), and (PP3). Accordingly the comonomer content of each of the three polypropylene fractions (PPl), (PP2), and (PP3) is not more than 1.0 wt.-%, yet more preferably not more than 0.8 wt.-%, still more preferably not more than 0.5 wt.-%. In case of the random propylene copolymer fractions (R- PP1), (R-PP2), and (R-PP3) it is appreciated that the comonomer content for each of the random propylene copolymer fractions (R-PPl), (R-PP2), and (R-PP3) is in the range of more than 0.2 to 3.0 wt.-%, more preferably in the range of more than 0.2 to 2.5 wt.-%, yet more preferably in the range of 0.2 to 2.0 wt.-%. The weight percentage is based on the weight of the respective random propylene copolymer fraction.

The (R-PPl), (R-PP2), and (R-PP3) comprise independently from each other monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C4 to C12 α-olefins, in particular ethylene and/or C4 to Cg a-olefins, e.g. 1-butene and/or 1-hexene. Preferably (R-PPl), (R-PP2), and (R-PP3) comprise independently from each other, especially consists independently from each other of, monomers copolymerizable with propylene from the group consisting of ethylene, 1-butene and 1-hexene. More specifically the (R-PPl), (R-PP2), and (R-PP3) comprise independently from each other - apart from propylene - units derivable from ethylene and/or 1-butene. In a preferred embodiment the

(R-PPl), (R-PP2), and (R-PP3) have apart from propylene the same comonomers. Thus in an especially preferred embodiment the (R-PP1), (R-PP2), and (R-PP3) comprise units derivable from ethylene and propylene only.

As stated above the first polypropylene fraction (PPl) is a random propylene copolymer fraction (R-PP1) or a propylene homopolymer fraction (H-PP1), the latter being preferred.

The xylene cold soluble (XCS) content of the first polypropylene fraction (PPl) is preferably equal or below 4.0 wt.-%, more preferably equal or below 3.5 wt.-%, still more preferably in the range of 0.8 to 4.0 wt.-%, like in the range of 0.8 to 3.0 wt.-%. The weight percentage is based on the weight of the first polypropylene fraction (PPl).

As stated above the first polypropylene fraction (PPl) is featured by a rather high melt flow rate MFR ₂ (230 °C). Accordingly it is appreciated that the melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 is equal or more than 80 g/lOmin, preferably of equal or more than 150 g/lOmin, more preferably in the range of 80 to 500 g/lOmin, still more preferably in the range of 150 to 480 g/lOmin, yet more preferably in the range of 200 to 450 g/lOmin, still more preferably in the range of 250 to 450 g/lOmin.

Alternatively or additionally the first polypropylene fraction (PPl) is defined by a low molecular weight. Thus it appreciated that the first polypropylene fraction (PPl) has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC; ISO 16014-4:2003) of equal or less than 130 kg/mol, more preferably of equal or less than 110 kg/mol, yet more preferably in the range of 72 to 110 kg/mol, still more preferably in the range of 75 to 100 kg/mol.

The second polypropylene fraction (PP2) can be either a random propylene copolymer fraction (second random propylene copolymer fraction (R-PP2)) or a propylene

homopolymer fraction (a second propylene homopolymer fraction (H-PP2)), the latter being preferred. The xylene cold soluble (XCS) content of the second polypropylene fraction (PP2) is preferably equal or below 4.0 wt.-%, more preferably equal or below 3.5 wt.-%, still more preferably in the range of 0.8 to 4.0 wt.-%, like in the range of 0.8 to 3.0 wt.-%. The weight percentage is based on the weight of the second polypropylene fraction (PP2).

As stated above the second polypropylene fraction (PP2) has a melt flow rate MFR ₂ (230 °C) being higher than the third polypropylene fraction (PP3). On the other hand the melt flow rate MFR ₂ (230 °C) of the first polypropylene fraction (PP1) can be higher or equally the same, preferably higher, as the melt flow rate MFR ₂ (230 °C) of the second polypropylene fraction (PP2). Accordingly it is appreciated that the second polypropylene fraction (PP2) has melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 20 to 300 g/lOmin, preferably in the range of 50 to 250 g/lOmin, more preferably in the range of 70 to below 220 g/lOmin, yet more preferably in the range of 100 to 200 g/lOmin. The third polypropylene fraction (PP3) can be either a random propylene copolymer fraction (third random propylene copolymer fraction (R-PP3)) or a propylene homopolymer fraction (a third propylene homopolymer fraction (H-PP3)), the latter being preferred.

The xylene cold soluble (XCS) content of the third polypropylene fraction (PP3) is preferably equal or below 4.0 wt.-%, more preferably equal or below 3.5 wt.-%, still more preferably in the range of 0.8 to 4.0 wt.-%, like in the range of 0.8 to 3.0 wt.-%. The weight percentage is based on the weight of the third polypropylene fraction (PP3).

As stated above the third polypropylene (PP3) has preferably the lowest melt flow rate MFR ₂ (230 °C) of the three polypropylene fractions (PP1), (PP2), and (PP3), more preferably the lowest melt flow rate MFR ₂ (230 °C) of the polymer fractions present in the polypropylene (PP). Accordingly it is appreciated that the third polypropylene (PP3) has melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 1.0 to 15.0 g/lOmin, preferably in the range of 2.0 to 15.0 g/lOmin, still more preferably in the range of 2.0 to 12.0 g/lOmin, such as 3 to 10 g/lOmin. Especially good results are obtainable in case the individual fractions are present in specific amounts. Accordingly it is preferred that the amount of the polypropylene fraction having a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 1.0 to 15.0 g/lOmin (preferably in the range of 2.0 to 15.0 g/lOmin, still more preferably in the range of 2.0 to 12.0 g/lOmin), preferably the amount of the third polypropylene fraction (PP3), is in the range of 10 to 30 wt.-%, more preferably in the range of 10 to 25 wt.-%, still more preferably 15 to 25 wt.-%, The values are based on the total weight of the matrix (M), preferably based on the amount of the polypropylene fractions (PPl), (PP2), and (PP3) together.

Further it is appreciated that the amount of the polypropylene fraction having a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 80.0 to 500.0 g/lOmin, preferably of the first polypropylene fraction (PPl), is in the range of 20 to 55 wt.-%, preferably in the range of 25 to 45 wt.-%, more preferably in the range of 30 to 45 wt.-%, still more preferably 35 to 45 wt.-%. The values are based on the total weight of the matrix (M), preferably based on the amount of the polypropylene fractions (PPl), (PP2), and (PP3) together.

Finally the remaining fraction of the three polypropylene fractions (PPl), (PP2), and (PP3), preferably the second polypropylene fraction (PP2) is present in the range of 20 to 55 wt.-%, preferably in the range of 25 to 55 wt.-%, more preferably 30 to 45 wt.-%, still more preferably 35 to 45 wt.-%. The values are based on the total amount of the matrix (M), i.e., the polypropylene (PP), preferably based on the amount of the polypropylene fractions (PPl), (PP2), and (PP3) together.

Accordingly in a preferred embodiment is the weight ratio [PP3/PP1] of the polypropylene fraction having a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 1.0 to 15.0 g/lOmin, preferably of the third polypropylene fraction (PP3), and the polypropylene fraction having a melt flow rate MFR ₂ (230 °C) measured according to ISO 1133 in the range of 80.0 to 500.0 g/lOmin, preferably of the first polypropylene fraction (PPl), is in the range of 10/45 to 25/30, more preferably in the range of 1/3 to 5/7. Very good results are achievable in case the polypropylene (PP) comprises

(a) 20.0 to 55.0 wt.-%, preferably 25.0 to 45.0 wt.-%, of the first polypropylene (PP1),

(b) 20.0 to 55.0 wt.-%, preferably 25.0 to 55.0 wt.-%, of the second polypropylene (PP2), and

(c) 10.0 to 30.0 wt.-%, preferably 15.0 to 25.0 wt.-%, of the third polypropylene (PP3), based on the total amount of the first polypropylene fraction (PP1), the second

polypropylene fraction (PP2), and the third polypropylene fraction (PP3). In one embodiment, the polypropylene (PP) is produced in a sequential polymerization process, preferably as described in detail below. Accordingly the three polypropylene fractions (PP1), (PP2), and (PP3) are an intimate mixture, which is not obtainable by mechanical blending. In another embodiment, the polypropylene (PP) is obtained by blending the polypropylene fractions (PP1), (PP2), and (PP3).

A further essential component of the present invention is the elastomer (E).

As mentioned above the properties of the elastomer (E) mainly influence the xylene cold soluble (XCS) of the final heterophasic propylene copolymer (HECO). In other words the properties defined below for the elastomer (E) are equally applicable for the the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO).

The elastomer can be any elastomer. However in a preferred embodiment of the present invention, the elastomer (E) is an ethylene copolymer elastomer comprising ethylene monomer units and comonomer units, wherein the comonomer is selected from C3 to C20 a- olefins, preferably propene, 14outene, 14iexene and 1-octene, or C ₅ to C20 α,ω-alkadienes, preferably 1 ,7-octadiene. In a more preferred embodiment, the comonomer is selected from propene, 14outene, 1 -hexene, and 1 - octene, the latter is especially preferred.

In one embodiment, the elastomer (E) has a melt flow rate MFR ₂ (190 °C) measured according to ISO 1133 of 10 to 80 g/lOmin. More preferably, the elastomer (E) has a melt flow rate MFR ₂ (190 °C) of 15 to 70 g/lOmin, still more preferably of 20 to 60 g/lOmin, yet more preferably 20 to 50 g/lOmin.

In a further preferred embodiment, the elastomer (E) has an intrinsic viscosity of 0.7 to 2.5 dl/g, preferably 0.8 to 2.0 dl/g, more preferably 0.8 to 1.5 dl/g. The intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135 °C).

Furthermore, the elastomer (E) has preferably a density of lower than 940 kg/m ³ , more preferably 920 kg/m ³ or lower, still more preferably in the range of 850 to 920 kg/m ³ , yet more preferably in the range 860 to 910 kg/m ³ . As mentioned above, the heterophasic propylene copolymer (HECO) may comprise additionally a polyethylene (PE), in particular a polyethylene (PE) as defined below. In such a case it is preferred that a mixture of the elastomer and the polyethlene (PE) shows a density as given in this paragraph. One important aspect of the present invention is that the amount of elastomer (E) in the heterophasic propylene copolymer (HECO) is rather high. Accordingly it is preferred that the elastomer (E) is present in the heterophasic propylene copolymer (HECO) in an amount of equal or more than 20.0 wt.-%, more preferably in an amount of equal or more 20.0 to 50.0 wt.-%, yet more preferably in an amount of 25.0 to 40.0 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO), preferably based on weight of the matrix (M), i.e. the polypropylene (PP), and the elastomer (E) together.

Thus it is preferred that the weight ratio between the matrix (M) and the elastomer (E) ([M]/[E]) is less than 4.0, more preferably 1.0 to below 4.0, yet more preferably 1.5 to 3.0.

Accordingly it is preferred that the heterophasic propylene copolymer (HECO) comprises,

(a) less than 80 wt.-%, more preferably 50.0 to 80.0 wt,-%, still more preferably 60.0 to 75.0 wt.-%, of the matrix (M), i.e. the polypropylene (PP), and

(b) equal or more than 20 wt.-%, more preferably 20.0 to 50.0 wt.-%, still more preferably 25.0 to 40.0 wt.-%, of the elastomer (E), based on the heterophasic propylene copolymer (HECO), preferably based on the total amount of the polypropylene (PP) and the elastomer (E).

Polyethylene (PE)

The heterophasic propylene copolymer (HECO) according to the present invention optionally further comprises a crystalline polyethylene (PE). The expression "crystalline" indicates that the polyethylene (PE) differs from the elastomers (E). Whereas the polyethylene (PE) is crystalline and not soluble in cold xylene, the elastomer (E) is predominantly non-crystalline and thus soluble in cold xylene. In a preferred embodiment the polyethylene (PE) a high density polyethylene (HDPE). The high density polyethylene (HDPE) used according to the invention is well known in the art and commercially available.

The high density polyethylene (HDPE) preferably has a melt flow rate MFR ₂ (190 °C) of 15 to 45 g/lOmin, preferably 20 to 40 g/lOmin, more preferably of 25 to 35 g/lOmin.

The high density polyethylene (HDPE) typically has a density of at least 940 kg/m ³ , preferably of at least 945 kg/m ³ , more preferably at least 955 kg/m ³ , still more preferably in the range of 945 to 970 kg/m ³ , yet more preferably in the range of 950 to 965 kg/m ³ .

The high density polyethylene (HDPE) may be present in an amount of up to 8 wt.-%, preferably up to 5 wt.-%, more preferably in the range of 0 to 8 wt.-%, like in the range of 1 to 8 wt.-%, yet more preferably in the range of 0 to 6 wt.-%, like in the range of 1 to 6 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO).

The polyethylene (PE), i.e. the high density polyethylene (HDPE), when present, is also dispersed in the matrix (M), i.e. in the polypropylene (PP), of the heterophasic propylene copolymer (HECO). More precisely the polyethylene (PE), i.e. the high density polyethylene (HDPE), is intimately mixed with the elastomer and thus forms together with the elastomer (E) the inclusions of the heterophasic propylene copolymer (HECO). Inorganic filler

In addition to the polymer components discussed above the heterophasic propylene copolymer (HECO) may optionally comprise an inorganic filler (F) in amounts of up to 25 wt.-%, preferably in an amount of up to 22 wt.-%, more preferably in the range of 4 to 25 wt.-%, still more preferably 5 to 20 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO). Preferably the inorganic filler (F) is a phyllosilicate, mica or wollastonite. Even more preferred the inorganic filler (F) is selected from the group consisting of mica, wollastonite, kaolinite, smectite, montmorillonite and talc. The most preferred the inorganic filler (F) is talc.

The mineral filler (F) preferably has a cutoff particle size d95 [mass percent] of equal or below 20 μηι, more preferably in the range of 2.5 to 1 Ομηι, like in the range of 2.5 to 8.0 μιη.

Typically the inorganic filler (F) has a surface area measured according to the commonly known BET method with N ₂ gas as analysis adsorptive of less than 22 m ² /g, more preferably of less than 20 m ² /g, yet more preferably of less than 18 m ² /g. Inorganic fillers (F) fulfilling these requirements are preferably anisotropic mineral fillers (F), like talc, mica and wollastonite. Further components

The instant heterophasic propylene copolymer (HECO) may comprise typical additives, like acid scavengers (AS), antioxidants (AO), nucleating agents (NA), hindered amine light stabilizers (HALS), slip agents (SA), and pigments. Preferably the amount of additives excluding the inorganic filler (F) shall not exceed 7 wt.-%, more preferably shall not exceed 5 wt.-%, like not more than 3 wt.-%, within the instant heterophasic propylene copolymer (HECO).

Thus the heterophasic propylene copolymer (HECO) preferably comprises

(a) less than 75.0 wt.-%, more preferably 50.0 to 70.0 wt,-%, still more preferably 60.0 to 65.0 wt.-%, of the matrix (M), i.e. the polypropylene (PP), and (b) equal or more than 20.0 wt.-%, more preferably 20.0 to 50.0 wt.-%, still more preferably 25.0 to 40.0 wt.-%, of the elastomer (E),

(c) up to 8 wt.-%, more preferably 0 to 8 wt.-%, like in the range of 1 to 8 wt.-%, still more preferably in the range of 0 to 6 wt.-%, of the polyethylene (PE), preferably of the high density polyethylene (HDPE),

(d) up to 25 wt.-%, more preferably 4 to 25 wt.-%, still more preferably 5 to 20 wt.-% of the inorganic filler (F), preferably talc,

based on the total weight of the heterophasic propylene copolymer (HECO). Articles made from the heterophasic propylene copolymer (HECO)

The heterophasic propylene copolymer (HECO) of the present invention is preferably used for the production of automotive articles, like moulded automotive articles, preferably automotive injection moulded articles. Even more preferred is the use for the production of car interiors and exteriors, like bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like, especially bumpers.

The current invention also provides (automotive) articles, like injection molded articles, comprising at least to 60 wt.-%, more preferably at least 70 wt.-%, yet more preferably at least 75 wt.-%, like consisting, of the inventive heterophasic propylene copolymer (HECO). Accordingly the present invention is especially directed to automotive articles, especially to car interiors and exteriors, like bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like, in particular bumpers, comprising at least to 60 wt- %, more preferably at least 70 wt.-%, yet more preferably at least 75 wt.-%, like consisting, of the inventive heterophasic propylene copolymer (HECO).

Uses according to the invention

The present invention also relates to the use of the heterophasic propylene copolymer (HECO) as described above in an automotive application. In a preferred embodiment, the heterophasic propylene copolymer (HECO) is used in a bumper. The present invention will now be described in further detail by the examples provided below. Preparation of the heterophasic propylene copolymer (HECO)

The heterophasic propylene copolymer (HECO) as defined above can be produced by a process as defined below. The heterophasic propylene copolymer (HECO) according to the present invention can be prepared by a process, comprising the step of blending the elastomer (E) with the matrix (M). The term "blending" refers according to the present invention to the action of providing a blend out of at least two different, pre-existing materials. On the other hand, the term "mixing" includes blending but also includes the in-situ formation of a blend by reacting one material in the presence of another material.

The process according to the present invention may further comprise the step of blending a polypropylene fraction selected from (PP1), (PP2) and (PP3) with a mixture containing the remaining two polypropylene fractions obtaining thereby the polypropylene (PP). In a further embodiment, the process for the preparation of the polypropylene (PP) comprises the step of (a) blending a polypropylene fraction selected from (PP1), (PP2) and (PP3) with a further different polypropylene fraction selected from (PP1), (PP2) and (PP3) and subsequently adding the remaining fraction selected from (PP1), (PP2) and (PP3), or (b) blending the polypropylene fractions (PP1), (PP2), and (PP3) with each other in one step. The individual polypropylene fractions (PP1), (PP2) and (PP3) can be produced in a conventional way, for instance in a loop reactor or in a loop/gas phase reactor system.

In another embodiment, the present invention is directed to a sequential polymerization process for producing the polypropylene (PP) according to the instant invention, said polypropylene (PP) comprises a first polypropylene fraction (PP1), a second polypropylene fraction (PP2) and a third polypropylene fraction (PP3). Said process may comprise the steps of

(al) polymerizing propylene and optionally at least one ethylene and/or C4 to C12 a-olefin in a first reactor (Rl) obtaining the first polypropylene fraction (PPl),

(bl) transferring the first polypropylene fraction (PPl) into a second reactor (R2), (cl) polymerizing in the second reactor (R2) and in the presence of said first

polypropylene fraction (PPl) propylene and optionally at least one ethylene and/or C4 to C12 a-olefin obtaining thereby the second polypropylene fraction (PP2), the first polypropylene fraction (PPl) being mixed with the second polypropylene fraction (PP2),

(dl) transferring the mixture of step (cl) into a third reactor (R3),

(el) polymerizing in the third reactor (R3) and in the presence of the mixture obtained in step (cl) propylene and optionally at least one ethylene and/or C4 to C12 a-olefin obtaining thereby the third polypropylene fraction (PP3), wherein the first polypropylene fraction (PPl), the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) are mixed with each other and form the polypropylene (PP);

or

(a2) polymerizing propylene and optionally at least one ethylene and/or C4 to C12 a-olefin in a first reactor (Rl) obtaining the first polypropylene fraction (PPl),

(b2) transferring the first polypropylene fraction (PPl) into a second reactor (R2), (c2) polymerizing in the second reactor (R2) and in the presence of said first

polypropylene fraction (PPl) propylene and optionally at least one ethylene and/or C4 to C12 α-olefin obtaining thereby the third polypropylene fraction (PP3), the first polypropylene fraction (PPl) being mixed with the third polypropylene fraction (PP3),

(d2) transferring the mixture of step (c2) into a third reactor (R3),

(e2) polymerizing in the third reactor (R3) and in the presence of the mixture obtained in step (c2) propylene and optionally at least one ethylene and/or C4 to C12 a-olefin obtaining thereby the second polypropylene fraction (PP2), wherein the first polypropylene fraction (PPl), the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) are mixed with each other and form the polypropylene (PP); polymerizing propylene and optionally at least one ethylene and/or C4 to C ₁₂ a-olefin in a first reactor (Rl) obtaining the second polypropylene fraction (PP2), transferring the second polypropylene fraction (PP2) into a second reactor (R2), polymerizing in the second reactor (R2) and in the presence of said second polypropylene fraction (PP2) propylene and optionally at least one ethylene and/or C4 to C ₁₂ a-olefin obtaining thereby the third polypropylene fraction (PP3), the second polypropylene fraction (PP2) being mixed with the third polypropylene fraction (PP3),

transferring the mixture of step (c3) into a third reactor (R3),

polymerizing in the third reactor (R3) and in the presence of the mixture obtained in step (c3) propylene and optionally at least one ethylene and/or C4 to C ₁₂ a-olefin obtaining thereby the first polypropylene fraction (PPl), wherein the first polypropylene fraction (PPl), the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) are mixed with each other and form the polypropylene (PP); polymerizing propylene and optionally at least one ethylene and/or C4 to C ₁₂ a-olefin in a first reactor (Rl) obtaining the second polypropylene fraction (PP2), transferring the second polypropylene fraction (PP2) into a second reactor (R2), polymerizing in the second reactor (R2) and in the presence of said second polypropylene fraction (PP2) propylene and optionally at least one ethylene and/or C4 to C ₁₂ α-olefin obtaining thereby the first polypropylene fraction (PPl), the second polypropylene fraction (PP2) being mixed with the first polypropylene fraction (PPl),

transferring the mixture of step (c4) into a third reactor (R3),

polymerizing in the third reactor (R3) and in the presence of the mixture obtained in step (c4) propylene and optionally at least one ethylene and/or C4 to C ₁₂ a-olefin obtaining thereby the third polypropylene fraction (PP3), wherein the first polypropylene fraction (PPl), the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) are mixed with each other and form the polypropylene (PP);

or

(a5) polymerizing propylene and optionally at least one ethylene and/or C4 to C12 a-olefin in a first reactor (Rl) obtaining the third polypropylene fraction (PP3),

(b5) transferring the third polypropylene fraction (PP3) into a second reactor (R2), (c5) polymerizing in the second reactor (R2) and in the presence of said third

polypropylene fraction (PP3) propylene and optionally at least one ethylene and/or C4 to C12 a-olefin obtaining thereby the first polypropylene fraction (PPl), the third polypropylene fraction (PP3) being mixed with the first polypropylene fraction (PPl),

(d5) transferring the mixture of step (c5) into a third reactor (R3),

(e5) polymerizing in the third reactor (R3) and in the presence of the mixture obtained in step (c5) propylene and optionally at least one ethylene and/or C4 to C12 a-olefin obtaining thereby the second polypropylene fraction (PP2), wherein the first polypropylene fraction (PPl), the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) are mixed with each other and form the polypropylene (PP);

or

(a6) polymerizing propylene and optionally at least one ethylene and/or C4 to C12 a-olefin in a first reactor (Rl) obtaining the third polypropylene fraction (PP3),

(b6) transferring the third polypropylene fraction (PP3) into a second reactor (R2), (c6) polymerizing in the second reactor (R2) and in the presence of said third

polypropylene fraction (PP3) propylene and optionally at least one ethylene and/or

C4 to C12 α-olefin obtaining thereby the second polypropylene fraction (PP2), the third polypropylene fraction (PP3) being mixed with the second polypropylene fraction (PP2),

(d6) transferring the mixture of step (c6) into a third reactor (R3),

(e6) polymerizing in the third reactor (R3) and in the presence of the mixture obtained in step (c6) propylene and optionally at least one ethylene and/or C4 to C12 a-olefin obtaining thereby the first polypropylene fraction (PP1), wherein the first polypropylene fraction (PP1), the second polypropylene fraction (PP2) and the third polypropylene fraction (PP3) are mixed with each other and form the polypropylene (PP).

Preferably between the second reactor (R2) and the third reactor (R3) , the monomers are flashed out.

For preferred embodiments of the polypropylene (PP), the first polypropylene fraction (PP1), the second polypropylene fraction (PP2), and the third polypropylene fraction (PP3), reference is made to the definitions given above.

The term "sequential polymerization process" indicates that the polypropylene is produced in at least three reactors connected in series. Accordingly the present process comprises at least a first reactor (Rl), a second reactor (R2), and a third reactor (R3). The term "polymerization reactor" shall indicate that the main polymerization takes place. Thus in case the process consists of four polymerization reactors, this definition does not exclude the option that the overall process comprises for instance a pre-polymerization step in a pre-polymerization reactor. The term "consist of is only a closing formulation in view of the main

polymerization reactors.

The first reactor (Rl) is preferably a slurry reactor (SR) and can be any continuous or simple stirred batch tank reactor or loop reactor operating in bulk or slurry. Bulk means a polymerization in a reaction medium that comprises of at least 60 % (w/w) monomer.

According to the present invention the slurry reactor (SR) is preferably a (bulk) loop reactor (LR).

The second reactor (R2), and the third reactor (R3) are preferably gas phase reactors (GPR). Such gas phase reactors (GPR) can be any mechanically mixed or fluid bed reactors.

Preferably the gas phase reactors (GPR) comprise a mechanically agitated fluid bed reactor with gas velocities of at least 0.2 m/sec. Thus it is appreciated that the gas phase reactor is a fluidized bed type reactor preferably with a mechanical stirrer.

Thus in a preferred embodiment the first reactor (Rl) is a slurry reactor (SR), like loop reactor (LR), whereas the second reactor (R2), and the third reactor (R3) are gas phase reactors (GPR). Accordingly for the instant process at least three, preferably three polymerization reactors, namely a slurry reactor (SR), like loop reactor (LR), a first gas phase reactor (GPR-1), and a second gas phase reactor (GPR-2) connected in series are used. If needed prior to the slurry reactor (SR) a pre-polymerization reactor is placed.

A preferred multistage process is a "loop-gas phase"-process, such as developed by Borealis A/S, Denmark (known as BORSTAR® technology) described e.g. in patent literature, such as in EP 0 887 379, WO 92/12182 WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 or in WO 00/68315.

A further suitable slurry-gas phase process is the Spheripol ^® process of Basell.

Preferably, in the instant process for producing the polypropylene (PP) as defined above the conditions for the first reactor (Rl), i.e. the slurry reactor (SR), like a loop reactor (LR), of step (a) may be as follows:

the temperature is within the range of 50 °C to 110 °C, preferably between 60 °C and 100 °C, more preferably between 68 and 95 °C,

the pressure is within the range of 20 bar to 80 bar, preferably between 40 bar to 70 bar,

- hydrogen can be added for controlling the molar mass in a manner known per se.

Subsequently, the reaction mixture from step (a) is transferred to the second reactor (R2), i.e. gas phase reactor (GPR-1), i.e. to step (c), whereby the conditions in step (c) are preferably as follows:

- the temperature is within the range of 50 °C to 130 °C, preferably between 60 °C and 100 °C, the pressure is within the range of 5 bar to 50 bar, preferably between 15 bar to 35 bar,

hydrogen can be added for controlling the molar mass in a manner known per se. The condition in the third reactor (R3), preferably in the second gas phase reactor (GPR-2), is similar to the second reactor (R2).

The residence time can vary in the three reactor zones. In one embodiment of the process for producing the polypropylene the residence time in bulk reactor, e.g. loop is in the range 0.1 to 2.5 hours, e.g. 0.15 to 1.5 hours and the residence time in gas phase reactor will generally be 0.2 to 6.0 hours, like 0.5 to 4.0 hours.

If desired, the polymerization may be effected in a known manner under supercritical conditions in the first reactor (Rl), i.e. in the slurry reactor (SR), like in the loop reactor (LR), and/or as a condensed mode in the gas phase reactors (GPR).

Preferably the process comprises also a prepolymerization with the catalyst system, as described in detail below, comprising a Ziegler-Natta procatalyst, an external donor and optionally a cocatalyst.

In a preferred embodiment, the prepolymerization is conducted as bulk slurry polymerization in liquid propylene, i.e. the liquid phase mainly comprises propylene, with minor amount of other reactants and optionally inert components dissolved therein.

The prepolymerization reaction is typically conducted at a temperature of 10 to 60 °C, preferably from 15 to 50 °C, and more preferably from 20 to 45 °C.

The pressure in the prepolymerization reactor is not critical but must be sufficiently high to maintain the reaction mixture in liquid phase. Thus, the pressure may be from 20 to 100 bar, for example 30 to 70 bar. The catalyst components are preferably all introduced to the prepolymenzation step.

However, where the solid catalyst component (i) and the cocatalyst (ii) can be fed separately it is possible that only a part of the cocatalyst is introduced into the prepolymerization stage and the remaining part into subsequent polymerization stages. Also in such cases it is necessary to introduce so much cocatalyst into the prepolymerization stage that a sufficient polymerization reaction is obtained therein.

It is possible to add other components also to the prepolymerization stage. Thus, hydrogen may be added into the prepolymerization stage to control the molecular weight of the prepolymer as is known in the art. Further, antistatic additive may be used to prevent the particles from adhering to each other or to the walls of the reactor.

The precise control of the prepolymerization conditions and reaction parameters is within the skill of the art.

According to the invention the polypropylene (PP) preferably is obtained by a multistage polymerization process, as described above, in the presence of a catalyst system comprising as component (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester.

The procatalyst used according to the invention is prepared by

a) reacting a spray crystallized or emulsion solidified adduct of MgCl ₂ and a C ₁ -C ₂ alcohol with T1CI ₄

b) reacting the product of stage a) with a dialkylphthalate of formula (I)

wherein R ¹ and R ² are independently at least a C ₅ alkyl under conditions where a transesterification between said Ci to C ₂ alcohol and said dialkylphthalate of formula (I) takes place to form the internal donor

c) washing the product of stage b) or

d) optionally reacting the product of step c) with additional T1CI4.

The procatalyst is produced as defined for example in the patent applications WO 87/07620, WO 92/19653, WO 92/19658 and EP 0 491 566. The content of these documents is herein included by reference. First an adduct of MgCl ₂ and a C ₁ -C ₂ alcohol of the formula MgCl ₂ *nROH, wherein R is methyl or ethyl and n is 1 to 6, is formed. Ethanol is preferably used as alcohol.

The adduct, which is first melted and then spray crystallized or emulsion solidified, is used as catalyst carrier.

In the next step the spray crystallized or emulsion solidified adduct of the formula

MgCl ₂ *nROH, wherein R is methyl or ethyl, preferably ethyl and n is 1 to 6, is contacting with T1CI4 to form a titanized carrier, followed by the steps of

• adding to said titanised carrier

(i) a dialkylphthalate of formula (I) with R ¹ and R ² being independently at least a C ₅ -alkyl, like at least a Cg-alkyl,

or preferably

(ii) a dialkylphthalate of formula (I) with R ¹ and R ² being the same and being at least a C ₅ -alkyl, like at least a Cg-alkyl,

or more preferably

(iii) a dialkylphthalate of formula (I) selected from the group consisting of propylhexylphthalate (PrHP), dioctylphthalate (DOP), di-iso- decylphthalate (DIDP), and ditridecylphthalate (DTDP), yet more preferably the dialkylphthalate of formula (I) is a dioctylphthalate (DOP), like di-iso-octylphthalate or diethylhexylphthalate, in particular diethylhexylphthalate, to form a first product,

• subjecting said first product to suitable transesterification conditions, i.e. to a

temperature above 100 °C, preferably between 100 to 150 °C, more preferably between 130 to 150 °C, such that said methanol or ethanol is transesterified with said ester groups of said dialkylphthalate of formula (I) to form preferably at least 80 mol-%, more preferably 90 mol-%, most preferably 95 mol.-%, of a dialkylphthalate of formula (II)

with R ¹ and R ² being methyl or ethyl, preferably ethyl,

the dialkylphthalat of formula (II) being the internal donor and

• recovering said transesterification product as the procatalyst composition

(component (i)).

The adduct of the formula MgCl ₂ *nROH, wherein R is methyl or ethyl and n is 1 to 6, is in a preferred embodiment melted and then the melt is preferably injected by a gas into a cooled solvent or a cooled gas, whereby the adduct is crystallized into a morphologically advantageous form, as for example described in WO 87/07620.

This crystallized adduct is preferably used as the catalyst carrier and reacted to the procatalyst useful in the present invention as described in WO 92/19658 and WO 92/19653.

As the catalyst residue is removed by extracting, an adduct of the titanised carrier and the internal donor is obtained, in which the group deriving from the ester alcohol has changed. In case sufficient titanium remains on the carrier, it will act as an active element of the procatalyst. Otherwise the titanization is repeated after the above treatment in order to ensure a sufficient titanium concentration and thus activity.

Preferably the procatalyst used according to the invention contains 2.5 wt.-% of titanium at the most, preferably 2.2% wt.-% at the most and more preferably 2.0 wt.-% at the most. Its donor content is preferably between 4 to 12 wt.-% and more preferably between 6 and 10 w -%.

More preferably the procatalyst used according to the invention has been produced by using ethanol as the alcohol and dioctylphthalate (DOP) as dialkylphthalate of formula (I), yielding diethyl phthalate (DEP) as the internal donor compound.

Still more preferably the catalyst used according to the invention is the BCF20P catalyst of Borealis (prepared according to WO 92/19653 as disclosed in WO 99/24479; especially with the use of dioctylphthalate as dialkylphthalate of formula (I) according to WO 92/19658) or the catalyst Polytrack 8502, commercially available from Grace.

For the production of the polypropylene (PP) according to the invention the catalyst system used preferably comprises in addition to the special Ziegler-Natta procatalyst an

organometallic cocatalyst as component (ii).

Accordingly it is preferred to select the cocatalyst from the group consisting of

trialkylaluminium, like triethylaluminium (TEA), dialkyl aluminium chloride and alkyl aluminium sesquichloride.

Component (iii) of the catalysts system used is an external donor represented by formula (Ilia) or (Illb). Formula (Ilia) is defined by

Si(OCH ₃ ) ₂ R ₂ ⁵ (Ilia)

wherein R ⁵ represents a branched-alkyl group having 3 to 12 carbon atoms, preferably a branched-alkyl group having 3 to 6 carbon atoms, or a cyclo-alkyl having 4 to 12 carbon atoms, preferably a cyclo-alkyl having 5 to 8 carbon atoms. It is in particular preferred that R ⁵ is selected from the group consisting of iso-propyl, iso- butyl, iso-pentyl, tert. -butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl,

methylcyclopentyl and cycloheptyl.

Formula (Illb) is defined by

Si(OCH ₂ CH ₃ ) ₃ (NR ^x R ^y ) (Illb)

wherein R ^x and R ^y can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms.

R ^x and R ^y are independently selected from the group consisting of linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, branched aliphatic hydrocarbon group having 1 to 12 carbon atoms and cyclic aliphatic hydrocarbon group having 1 to 12 carbon atoms. It is in particular preferred that R ^x and R ^y are independently selected from the group consisting of methyl, ethyl, n-propyl, n-butyl, octyl, decanyl, iso-propyl, iso-butyl, iso- pentyl, tert. -butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.

More preferably both R ^x and R ^y are the same, yet more preferably both R ^x and R ^y are an ethyl group.

More preferably the external donor of formula (Illb) is diethylaminotriethoxysilane .

More preferably the external donor is selected from the group consisting of

diethylaminotriethoxysilane [Si(OCH ₂ CH ₃ ) ₃ (N(CH ₂ CH ₃ ) ₂ )], dicyclopentyl dimethoxy silane [Si(OCH ₃ ) ₂ (cyclo-pentyl) ₂ ], diisopropyl dimethoxy silane [Si(OCH ₃ ) ₂ (CH(CH ₃ ) ₂ ) ₂ ] and mixtures thereof.

In a further embodiment, the Ziegler-Natta procatalyst can be modified by polymerising a vinyl compound in the presence of the catalyst system, comprising the special Ziegler-Natta procatalyst (component (i)), an external donor (component (iii) and optionally a cocatalyst (component (iii)), which vinyl compound has the formula:

CH ₂ =CH-CHR ³ R ⁴

wherein R ³ and R ⁴ together form a 5- or 6-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising 1 to 4 carbon atoms, and the modified catalyst is used for the preparation of the heterophasic propylene copolymer according to this invention. The polymerized vinyl compound can act as an a-nucleating agent.

Concerning the modification of catalyst reference is made to the international applications WO 99/24478, WO 99/24479 and particularly WO 00/68315, incorporated herein by reference with respect to the reaction conditions concerning the modification of the catalyst as well as with respect to the polymerization reaction.

Subsequently the obtained polypropylene (PP) is belended with the elastomer (E) and the optional additives. Typically extruders, like single screw extruders as well as twin screw extruders are used for blending. Other suitable devices include planet extruders and single screw co-kneaders. Especially preferred are twin screw extruders including high intensity mixing and kneading sections. Suitable melt temperatures for preparing the heterophasic propylene copolymer (HECO) are in the range from 170 to 300 °C, preferably in the range from 200 to 260 °C. The heterophasic propylene copolymer (HECO) recovered from the extruder is usually in the form of pellets. These pellets are then preferably further processed, e.g. by injection molding to generate articles, like the articles defined in more detail above.

In the following the present invention is further illustrated by means of examples.

E X A M P L E S

A. Measuring methods

The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined. Calculation of comonomer content of the second polypropylene fraction (PP2):

C(ff2) - w(PPl)x C{PP1)

= C(PP2)

w(PP2)

wherein

w(PPl) is the weight fraction of the first polypropylene fraction (PP1), i.e. the

product of the first reactor (Rl),

w(PP2) is the weight fraction of the second polypropylene fraction (PP2), i.e. of the polymer produced in the second reactor (R2),

C(PP1) is the comonomer content [in wt.-%] of the first polypropylene fraction

(PP1), i.e. of the product of the first reactor (Rl),

C(R2) is the comonomer content [in wt.-%] of the product obtained in the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2),

C(PP2) is the calculated comonomer content [in wt.-%] of the second polypropylene

(PP2).

Calculation of the xylene cold soluble (XCS) content of the second polypropylene fraction (PP2):

XS(R2)- w(PPl)xXS(PPl)

= XS(PP2)

w(PP2)

wherein

w(PPl) is the weight fraction of the first polypropylene fraction (PP1), i.e. the

product of the first reactor (Rl),

w(PP2) is the weight fraction of the second polypropylene fraction (PP2), i.e. of the polymer produced in the second reactor (R2),

XS(PPl) is the xylene cold soluble (XCS) content [in wt.-%] of the first

polypropylene fraction (PP1), i.e. of the product of the first reactor (Rl), XS(R2) is the xylene cold soluble (XCS) content [in wt.-%] of the product obtained in the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2),

XS(PP2) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the second polypropylene fraction (PP2).

Calculation of melt flow rate MFR ₂ (230 °C) of the second polypropylene fraction (PP2):

[log( FR (R2)) -w(PPl) log (MFR (PPl))]

MFR(PP2) = 10 w(PP2)

wherein

w(PPl) is the weight fraction of the first polypropylene fraction (PP1), i.e. the

product of the first reactor (Rl),

w(PP2) is the weight fraction of the second polypropylene fraction (PP2), i.e. of the polymer produced in the second reactor (R2),

MFR(PPl) is the melt flow rate MFR ₂ (230 °C) [in g/lOmin] of the first polypropylene fraction (PP1), i.e. of the product of the first reactor (Rl),

MFR(R2) is the melt flow rate MFR ₂ (230 °C) [in g/lOmin] of the product obtained in the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2),

MFR(PP2) is the calculated melt flow rate MFR ₂ (230 °C) [in g/lOmin] of the second polypropylene fraction (PP2).

Calculation of comonomer content of the third polypropylene fraction (PP3):

C(ff3) - w(R2)x C(R2)

= C(PP3)

w(PP3)

wherein

w(R2) is the weight fraction of the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2), w(PP3) is the weight fraction of the third polypropylene fraction (PP3), i.e. of the polymer produced in the third reactor (R3),

C(R2) is the comonomer content [in wt.-%] of the product of the second reactor

(R2), i.e. of the mixture of the first polypropylene fraction (PP1) and second polypropylene fraction (PP2), C(R3) is the comonomer content [in wt.-%] of the product obtained in the third reactor (R3), i.e. the mixture of the first polypropylene fraction (PP1), the second polypropylene fraction (PP2), and the third polypropylene fraction (PP3),

C(PP3) is the calculated comonomer content [in wt.-%] of the third polypropylene fraction (PP3).

Calculation of xylene cold soluble (XCS) content of the third polypropylene fraction (PP3):

XS(R3) - w(R2)x XS(R2)

= XS(PP3)

w(PP3)

wherein

w(R2) is the weight fraction of the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2), w(PP3) is the weight fraction of the third polypropylene fraction (PP3), i.e. of the polymer produced in the third reactor (R3),

XS(R2) is the xylene cold soluble (XCS) content [in wt.-%] of the product of the second reactor (R2), i.e. of the mixture of the first polypropylene fraction (PP1) and second polypropylene fraction (PP2),

XS(R3) is the xylene cold soluble (XCS) content [in wt.-%] of the product obtained in the third reactor (R3), i.e. the mixture of the first polypropylene fraction (PP1), the second polypropylene fraction (PP2), and the third polypropylene fraction (PP3),

XS(PP3) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the third polypropylene fraction (PP3).

Calculation of melt flow rate MFR ₂ (230 °C) of the third polypropylene fraction (PP3):

log( FR (R3)) -w(R2) log (MFR (R2))]

w(PP3)

MFR (PP3) = 10

wherein

w(R2) is the weight fraction of the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2), w(PP3) is the weight fraction of the third polypropylene fraction (PP3), i.e. of the polymer produced in the third reactor (R3), MFR(R2) is the melt flow rate MFR ₂ (230 °C) [in g/1 Omin] of the product of the second reactor (R2), i.e. of the mixture of the first polypropylene fraction (PP1) and second polypropylene fraction (PP2),

MFR(R3) is the melt flow rate MFR ₂ (230 °C) [in g/1 Omin] of the product obtained in the third reactor (R3), i.e. the mixture of the first polypropylene fraction (PP1), the second polypropylene fraction (PP2), and the third polypropylene fraction (PP3),

MFR(PP3) is the calculated melt flow rate MFR ₂ (230 °C) [in g/1 Omin] of the third polypropylene fraction (PP3).

Number average molecular weight (M _n ), weight average molecular weight (M _w ) and molecular weight distribution (MWD) are determined by Gel Permeation Chromatography (GPC) according to the following method:

The weight average molecular weight Mw and the molecular weight distribution (MWD = Mw/Mn wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) is measured by a method based on ISO 16014-1 :2003 and ISO 16014- 4:2003. A Waters Alliance GPCV 2000 instrument, equipped with refractive index detector and online viscosimeter was used with 3 x TSK-gel columns (GMHXL-HT) from TosoHaas and 1 ,2,4-trichlorobenzene (TCB, stabilized with 200 mg/L 2,6-Di tert butyl-4-methyl- phenol) as solvent at 145 °C and at a constant flow rate of 1 mL/min. 216.5 μΐ. of sample solution were injected per analysis. The column set was calibrated using relative calibration with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/mol and a set of well characterized broad polypropylene standards. All samples were prepared by dissolving 5 - 10 mg of polymer in 10 mL (at 160 °C) of stabilized TCB (same as mobile phase) and keeping for 3 hours with continuous shaking prior sampling in into the GPC instrument.

Density is measured according to ISO 1183-1 - method A (2004). Sample preparation is done by compression moulding in accordance with ISO 1872-2:2007.

MFR ₂ (230 °C) is measured according to ISO 1133 (230 °C, 2.16 kg load).

MFR ₂ (190 °C) is measured according to ISO 1133 (190 °C, 2.16 kg load). Quantification of comonomer content by FTIR spectroscopy

The comonomer content is determined by quantitative Fourier transform infrared spectroscopy (FTIR) after basic assignment calibrated via quantitative ¹³ C nuclear magnetic resonance (NMR) spectroscopy in a manner well known in the art. Thin films are pressed to a thickness of between 100-500 μιη and spectra recorded in transmission mode.

Specifically, the ethylene content of a polypropylene-co-ethylene copolymer is determined using the baseline corrected peak area of the quantitative bands found at 720-722 and 730- 733 cm ^"1 . Specifically, the butene or hexene content of a polyethylene copolymer is determined using the baseline corrected peak area of the quantitative bands found at 1377- 1379 cm ^"1 . Quantitative results are obtained based upon reference to the film thickness. The xylene cold solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25 °C according ISO 16152; first edition; 2005-07-01

Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135 °C).

Melting temperature T _m , crystallization temperature T„ is measured with Mettler TA820 differential scanning calorimetry (DSC) on 5-10 mg samples. Both crystallization and melting curves were obtained during 10 °C/min cooling and heating scans between 30 °C and 225 °C. Melting and crystallization temperatures were taken as the peaks of endotherms and exotherms.

Also the melt- and crystallization enthalpy (Hm and He) were measured by the DSC method according to ISO 11357-3.

The tensile modulus is measured at 23 °C according to ISO 527-1 (cross head speed 1 mm/min) using injection moulded specimens according to ISO 527-2(lB), produced according to EN ISO 1873-2 (dog 10 bone shape, 4 mm thickness).

Charpy notched impact strength is determined according to ISO 179 / leA at 23 °C and at - 20 °C by using injection moulded test specimens as described in EN ISO 1873-2 (80 x 10 x 4 mm).

Puncture energy is determined in the instrumental falling weight (IFW) test according to ISO 6603-2 using injection moulded plaques of 60x60x2 mm and a test speed of 4.4 m/s. Puncture energy reported results from an integral of the failure energy curve measured at +23°C and -20°C. Shrinkage is determined on centre gated, injection moulded circular disks (diameter 180 mm, thickness 3 mm, having a flow angle of 355° and a cut out of 5°). Two specimens are moulded applying two different holding pressure times (10s and 20s respectively). The melt temperature at the gate is 260°C, and the average flow front velocity in the mould 100 mm/s. Tool temperature: 40 °C, back pressure: 600 bar.

After conditioning the specimen at room temperature for 96 hours the dimensional changes radial and tangential to the flow direction are measured for both disks. The average of respective values from both disks are reported as final results.

Particle size (d50 and cutoff particle size d95 (Sedimentation)) is calculated from the particle size distribution [mass percent] as determined by gravitational liquid sedimentation according to ISO 13317-3 (Sedigraph)

BET has been measured according to ISO 9277

B. Examples

All polymers were produced in a Borstar pilot plant with a prepolymerization reactor, one slurry loop reactor and two gas phase reactors. The catalyst Polytrack 8502, commercially available from Grace (US) was used in combination with diethylaminotriethoxysilane

[Si(OCH ₂ CH3)3(N(CH ₂ CH3) ₂ )] (U donor) as external donor and triethylaluminium (TEAL) as activator and scavenger in the ratios indicated in table 1. The catalyst was modified by polymerising a vinyl compound in the presence of the catalyst system.

Table 1: Preparation of the polypropylene (PP)

* polymer produced in GPR1

** polymer produced in GPR2 Table 1 summarizes the polymer design of trimodal polypropylenes which is used in the working example. A trimodal polypropylene (PP) having the same MFR as a commercially available unimodal polypropylene polymer (HK060AE) was used.

Table 2: Compound recipes for working example and comparative example

Rest to 100 wt-% are additives, like antioxidants and pigments (e.g. Carbon black) HK060AE is a commercial product of Borealis AG, which is a polypropylene homopolymer having a MFR ₂ (230 °C/2.16 kg) of 125 g/lOmin and a density of 905 kg/m ³ .

Engage 8400 is a commercial product of Dow Elastomers, which is an ethylene- octene copolymer having a MFR ₂ (190 °C, 2.16 kg) of 30 g/lOmin and a density of 870 kg/m ³ .

HDPE is a commercial high density polypropylene (HDPE) "MG9601" of

Borealis which has a MFR (190 °C/2.16 kg) of 30 g/lOmin and a density of 960 kg/m ³

Talcum is a commercially talcum "Steamic T1CA" available from from Luzenac with a d50 of 1.8 μηι^ cutoff particle size (dg ₅ ) of 6.2 μιη and a BET of 8.0 m ² /g.

The property profiles of the resulting materials are summarized in table 3. Table 3: Property profiles of polypropylene plastomer blends

Although the working example and the comparative example show a similar melt flow rate, the working example according to the invention - based on a trimodal polypropylene - shows as significantly improved stiffness level, and a slightly improved Charpy impact strength at room temperature. More significant is the improvement of the puncture energy by using a trimodal matrix, the puncture energy of the blend with elastomer is more than tripled compared to that of the commercial reference.