Patent Description:
Recent demand for plastics in the automotive industry is towards weight reduction with preservation of the mechanical property profile, particularly stiffness and toughness, and surface appearance. One approach to prepare polypropylene compositions featuring a reduced density is the application of compositions containing inorganic fillers or glass fibres. However, the density reduction by using inorganic filler filled or glass fibre reinforced polypropylene compounds is limited. Therefore, a possible next step to support further weight reduction is foaming during the injection-moulding conversion step which can be applied for non-visible and visible automotive parts. Foamed parts have the advantage of reduced density but the disadvantage of poor surface and mechanical properties. Thus, the majority of foamed parts are not used for visible interior / exterior applications due to inhomogeneous surface appearance and/or poor toughness/stiffness balance. For example, <CIT> refers to a polypropylene composition (C), comprising a) a first heterophasic propylene copolymer (HECO1) having a comonomer content of the xylene soluble fraction (XCS) equal or above <NUM> mol-%, said first heterophasic propylene copolymer comprising i) a first matrix being a first propylene polymer (M1) and ii) a first elastomeric propylene copolymer (E1) being dispersed in said first matrix, b) a second heterophasic propylene copolymer (HECO2) having a comonomer content of the xylene soluble fraction (XCS) below <NUM> mol-%, said second heterophasic propylene copolymer comprising iii) a second matrix being a second propylene polymer (M2) and iv) a second elastomeric propylene copolymer (E1) being dispersed in said second matrix, c) an inorganic filler (F), d) optionally a high density polyethylene (HDPE), and e) optionally a plastomer (PL) being a copolymer of ethylene and a C4 to C8 α-olefin. <CIT> refers to a mineral-filled polypropylene composition and <CIT> refers to a fiber reinforced composition.

Accordingly, there is a need in the art for a foamable polypropylene composition proving an excellent mechanical property profile in terms of toughness/stiffness balance accompanied by an excellent surface appearance in foamed parts.

Therefore, it is an object of the present invention to provide a foamable polypropylene composition providing a good balance of mechanical properties in terms of toughness/stiffness balance and excellent surface appearance in foamed parts.

The finding of the present invention is that composition comprising a heterophasic polypropylene and at least one foaming agent (FA) selected from chemical and physical foaming agents is highly suitable for the preparation of foamed parts showing a good balance of mechanical properties in terms of toughness/stiffness balance and excellent surface appearance in foamed parts.

Accordingly, the present invention is directed to a foamable polypropylene composition (C), comprising.

based on the overall polypropylene composition (C).

According to one embodiment of the present invention, the heterophasic propylene copolymer (HECO1) has i) a comonomer content of the xylene cold soluble (XCS) ≤ <NUM> mol. -%, preferably ≤ <NUM> mol-%, more preferably ≤ <NUM> mol. -%, and most preferably ≤ <NUM> mol. -%, e.g. between <NUM> and <NUM> mol. -%, preferably between <NUM> and <NUM> mol. -%, more preferably between <NUM> and <NUM> mol. -%, and most preferably between <NUM> and <NUM> mol. -%, and/or ii) an intrinsic viscosity (IV) of the xylene cold soluble (XCS) fraction > <NUM> dl/g.

According to another embodiment of the present invention, further comprising a heterophasic propylene copolymer (HECO2) comprising i) a matrix (M2) being a propylene polymer (PP2) and ii) an elastomeric propylene copolymer (E2) being dispersed in said matrix.

According to still another embodiment of the present invention, the heterophasic propylene copolymer (HECO2) has i) a melt flow rate MFR<NUM> (<NUM>, <NUM>) measured according to ISO <NUM> in the range from <NUM> to <NUM>/<NUM>, and/or ii) a xylene cold soluble (XCS) fraction in the range of <NUM> to <NUM> wt. -%, and/or iii) a comonomer content of the xylene cold soluble (XCS) fraction in the range from <NUM> to <NUM> mol-%, and/or iv) an intrinsic viscosity (IV) of the xylene cold soluble (XCS) fraction < <NUM> dl/g.

According to one embodiment of the present invention, the foamable polypropylene composition further comprises a high density polyethylene (HDPE) and/or a plastomer (PL) being a copolymer of ethylene and a C<NUM> to C<NUM> α-olefin.

According to another embodiment of the present invention, the matrix (M1) of the heterophasic propylene copolymer (HECO1) and/or the matrix (M2) of the heterophasic propylene copolymer (HECO2) has/have a melt flow rate MFR<NUM> (<NUM>, <NUM>) measured according to ISO <NUM> in the range from <NUM> to <NUM>/<NUM>.

According to still another embodiment of the present invention, the propylene homopolymer (H-PP), preferably a semicrystalline propylene homopolymer (H-PP), has i) a melt flow rate MFR<NUM> (<NUM>) determined according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, and/or ii) a melting temperature Tm in the range from <NUM> to <NUM>.

According to one embodiment of the present invention, the foaming agent (FA) is a chemical foaming agent, preferably a bicarbonate or a mixture of citric acid and bicarbonate.

According to another embodiment of the present invention, the foamable polypropylene composition (C) has before foaming.

According to still another embodiment of the present invention, the foamable polypropylene composition (C) has after foaming on plaques of <NUM> thickness.

The present invention is also directed to the use of the foamable polypropylene composition (C) as defined herein for the production of a foamed part.

The present invention is further directed to a foamed part, preferably foamed automotive part, comprising the foamable polypropylene composition (C) as defined herein.

In the following, the present invention is described in more detail.

The inventive foamable polypropylene composition (C) comprises a heterophasic propylene copolymer (HECO1) comprising a matrix (M1) being a propylene polymer (PP1) and an elastomeric propylene copolymer (E1) being dispersed in said matrix. Thus the matrix (M1) contains (finely) dispersed inclusions being not part of the matrix (M1) and said inclusions contain the elastomeric propylene copolymer (E1). The term inclusion indicates that the matrix (M1) and the inclusion form different phases as defined below.

Further, the inventive foamable polypropylene composition comprises at least one foaming agent (FA) selected from chemical and physical foaming agents.

It is appreciated that the foamable polypropylene composition optionally comprises a propylene homopolymer (H-PP) and/or an inorganic filler (F).

Accordingly, it is preferred that the foamable polypropylene composition (C) comprises.

It is appreciated that the amounts for the components i) to iv) in the polypropylene composition (C) are selected in the given ranges, so that they add up to <NUM> wt.

For example, the foamable polypropylene composition (C) comprises,.

It is appreciated that the amounts for the components i) to iii) in the polypropylene composition (C) are selected in the given ranges, so that they add up to <NUM> wt.

That is to say, in this embodiment, the foamable polypropylene composition (C) is preferably free of the inorganic filler (F).

Alternatively, the foamable polypropylene composition (C) comprises the inorganic filler (F). In this embodiment, the foamable polypropylene composition (C) preferably comprises.

Preferably, the foamable polypropylene composition (C) is obtained by melt blending the first heterophasic propylene copolymer (HECO1) comprising a matrix (M1) being the propylene polymer (PP1) and a dispersed phase being the elastomeric propylene copolymer (E1), the optional propylene homopolymer (H-PP), the optional inorganic filler (F), and the foaming agent (FA).

According to one embodiment of the present invention, the foamable polypropylene composition (C) further comprises a heterophasic propylene copolymer (HECO2) which is different from the heterophasic propylene copolymer (HECO1).

Said heterophasic propylene copolymer (HECO2) comprises a matrix (M2) being a propylene polymer (PP2) and an elastomeric propylene copolymer (E2) being dispersed in said matrix. Thus the matrix (M2) contains (finely) dispersed inclusions being not part of the matrix (M2) and said inclusions contain the elastomeric propylene copolymer (E2).

Therefore, in case the foamable polypropylene composition (C) comprises the heterophasic propylene copolymer (HECO2), the foamable polypropylene composition (C) comprises a heterophasic system comprising a matrix (M) formed by the propylene polymer (PP1) and the propylene polymer (PP2), and the first elastomeric propylene copolymer (E1) and the second elastomeric propylene copolymer (E2) are dispersed in said matrix (M). Thus the matrix (M) contains (finely) dispersed inclusions being not part of the matrix (M) and said inclusions contain the elastomeric propylene copolymer (E1) and the elastomeric propylene copolymer (E2).

If the foamable polypropylene composition (C) comprises the heterophasic propylene copolymer (HECO2), the foamable polypropylene composition (C) preferably further comprises a high density polyethylene (HDPE) and/or a plastomer (PL) being a copolymer of ethylene and a C<NUM> to C<NUM> α-olefin, more preferably a high density polyethylene (HDPE) and a plastomer (PL) being a copolymer of ethylene and a C<NUM> to C<NUM> α-olefin.

Preferably, the foamable polypropylene composition (C) contains the propylene polymer (PP1) and the propylene polymer (PP2) forming the matrix (M) in a ratio of <NUM>:<NUM> to <NUM>:<NUM> and the elastomeric propylene copolymer (E1) and the elastomeric propylene copolymer (E2) in a ratio of <NUM>:<NUM> to <NUM>:<NUM>.

Preferably, the foamable polypropylene composition (C) is obtained by melt blending the first heterophasic propylene copolymer (HECO1) comprising a matrix (M1) being the propylene polymer (PP1) and a dispersed phase being the elastomeric propylene copolymer (E1), the second heterophasic propylene copolymer (HECO2) comprising a matrix (M2) being the propylene polymer (PP2) and a dispersed phase being the elastomeric propylene copolymer (E2), the optional inorganic filler (F), the at least one foaming agent (FA), optionally the high density polyethylene (HDPE) and optionally the plastomer (PL). Melt blending of said first heterophasic propylene copolymer (HECO1) and said second heterophasic propylene copolymer (HECO2) results in a heterophasic system wherein the propylene polymer (PP1) and the propylene polymer (PP2) form the matrix (M) and the elastomeric propylene copolymer (E1) and the elastomeric propylene copolymer (E2) form the dispersed phase.

Preferably, the foamable polypropylene composition (C) according to this invention comprises as polymer components only the heterophasic propylene copolymer (HECO1), the optional propylene homopolymer (H-PP), the optional heterophasic propylene copolymer (HECO2), the optional high density polyethylene (HDPE) and the optional plastomer (PL). In other words, the foamable polypropylene composition (C) may contain further additives but no other polymer in an amount exceeding <NUM> wt. -%, more preferably exceeding <NUM> wt. -%, like exceeding <NUM> wt. -%, based on the total foamable polypropylene composition (C). One additional polymer which may be present in such low amounts is a polyethylene which is a reaction by-product obtained by the preparation of the polypropylene composition (C). Accordingly, it is in particular appreciated that the instant polypropylene composition (C) contains only the heterophasic propylene copolymer (HECO1), the optional propylene homopolymer (H-PP), the optional heterophasic propylene copolymer (HECO2), the optional high density polyethylene (HDPE), the optional plastomer (PL) and optionally polyethylene in amounts as mentioned in this paragraph.

The foamable polypropylene composition (C) of the present invention may include additives (AD).

Accordingly, it is preferred that the polypropylene composition (C) further comprises <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of additives (AD), based on the overall weight of the foamable polypropylene composition (C). The additives (AD) are described in more detail below.

It is preferred that the foamable polypropylene composition (C) has before foaming a moderate melt flow rate. Thus, it is preferred that the melt flow rate MFR<NUM> (<NUM>, <NUM>) determined according to ISO <NUM> of the polypropylene composition (C) is in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>, like in the range of <NUM> to <NUM>/<NUM>.

Further, it is preferred that the foamable polypropylene composition (C) before foaming is featured by a rather high flexural modulus determined on compact (non-foamed) injection-moulded specimen. Accordingly, it is preferred that the foamable polypropylene composition (C) has a flexural modulus according to ISO <NUM> on plaques of <NUM> thickness of at least <NUM> MPa, like in the range of <NUM> to <NUM> MPa.

Additionally or alternatively to the previous paragraph, it is preferred that the foamable polypropylene composition (C) before foaming has a Charpy Impact Strength (NIS+<NUM>) measured according to ISO <NUM>-1eA:<NUM> at +<NUM> of at least <NUM> kJ/m<NUM>, like in the range of <NUM> to <NUM> kJ/m<NUM>.

Additionally or alternatively to the previous paragraph, it is preferred that the foamable polypropylene composition (C) before foaming has a puncture energy measured according to ISO <NUM>-<NUM> (on 60x60x2 mm<NUM> specimens) at +<NUM> of at least <NUM> J, like in the range of <NUM> to <NUM> J.

Thus, it is preferred that the foamable polypropylene composition (C) before foaming has.

For example, the foamable polypropylene composition (C) before foaming has.

It is preferred that the foamable polypropylene composition (C) has after foaming on plaques of <NUM> thickness a flexural modulus according to ISO <NUM> of at least <NUM> MPa, like in the range of <NUM> to <NUM> MPa.

Additionally or alternatively, the foamable polypropylene composition (C) has after foaming on plaques of <NUM> thickness a puncture energy measured according to ISO <NUM>-<NUM> (on 60x60x2 mm<NUM> specimens) at +<NUM> of at least <NUM> J, like in the range of <NUM> to <NUM> J.

Preferably, the foamable polypropylene composition (C) has after foaming on plaques of <NUM> thickness a flexural modulus according to ISO <NUM> of at least <NUM> MPa, like in the range of <NUM> to <NUM> MPa, and a puncture energy measured according to ISO <NUM>-<NUM> (on 60x60x2 mm<NUM> specimens) at +<NUM> of at least <NUM> J, like in the range of <NUM> to <NUM> J.

In the following, the single components of the foamable polypropylene composition (C) are described in more detail.

The inventive polypropylene composition (C) comprises a heterophasic propylene copolymer (HECO1).

The heterophasic propylene copolymer (HECO1) according to this invention comprises a matrix (M1) being the propylene polymer (PP1) and dispersed therein an elastomeric propylene copolymer being the elastomeric propylene copolymer (E1). Thus the matrix (M1) contains (finely) dispersed inclusions being not part of the matrix (M1) and said inclusions contain the elastomeric propylene copolymer (E1). The term inclusion indicates that the matrix (M1) and the inclusion form different phases within the heterophasic propylene copolymer (HECO1). The presence of second phases or the so called inclusions are for instance visible by high resolution microscopy, like electron microscopy or atomic force microscopy, or they can be detected by dynamic mechanical thermal analysis (DMTA). Specifically, in DMTA the presence of a multiphase structure can be identified by the presence of at least two distinct glass transition temperatures.

Accordingly, the heterophasic propylene copolymer (HECO1) according to this invention preferably comprises.

Preferably the weight ratio between the propylene polymer (PP1) and the elastomeric propylene copolymer (E1) [PP1/E1] of the heterophasic propylene copolymer (HECO1) is in the range of <NUM>/<NUM> to <NUM>/<NUM>, more preferably in the range of <NUM>/<NUM> to <NUM>/<NUM>, yet more preferably in the range of <NUM>/<NUM> to <NUM>/<NUM>, like in the range of <NUM>/<NUM> to <NUM>/<NUM>.

Preferably, the heterophasic propylene copolymer (HECO1) according to this invention comprises as polymer components only the propylene polymer (PP1) and the elastomeric propylene copolymer (E1). In other words, the heterophasic propylene copolymer (HECO1) may contain further additives but no other polymer in an amount exceeding <NUM> wt. -%, more preferably exceeding <NUM> wt. -%, like exceeding <NUM> wt. -%, based on the total heterophasic propylene copolymer (HECO1). One additional polymer which may be present in such low amounts is a polyethylene which is a reaction by-product obtained by the preparation of the heterophasic propylene copolymer (HECO1). Accordingly, it is in particular appreciated that the instant heterophasic propylene copolymer (HECO1) contains only the propylene polymer (PP1), the elastomeric propylene copolymer (E1) and optionally polyethylene in amounts as mentioned in this paragraph.

The heterophasic propylene copolymer (HECO1) applied according to this invention is featured by a rather low melt flow rate. Accordingly, the heterophasic propylene copolymer (HECO1) has a melt flow rate MFR<NUM> (<NUM>) in the range of <NUM> to <NUM>/<NUM>, preferably in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>.

Preferably, it is desired that the heterophasic propylene copolymer (HECO1) is thermo mechanically stable. Accordingly, it is appreciated that the heterophasic propylene copolymer (HECO1) has a melting temperature of at least <NUM>, more preferably in the range of <NUM> to <NUM>, still more preferably in the range of <NUM> to <NUM>.

The heterophasic propylene copolymer (HECO1) comprises apart from propylene also comonomers. Preferably the heterophasic propylene copolymer (HECO1) comprises apart from propylene ethylene and/or C<NUM> to C<NUM> α-olefins. Accordingly, the term "propylene copolymer" according to this invention is understood as a polypropylene comprising, preferably consisting of, units derivable from.

Thus, the heterophasic propylene copolymer (HECO1), i.e. propylene polymer (PP1) as well as the elastomeric propylene copolymer (E1), can comprise monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C<NUM> to C<NUM> α-olefins, in particular ethylene and/or C<NUM> to C<NUM> α-olefins, e.g. <NUM>-butene and/or <NUM>-hexene. Preferably, the heterophasic propylene copolymer (HECO1) according to this invention comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, <NUM>-butene and <NUM>-hexene. More specifically, the heterophasic propylene copolymer (HECO1) of this invention comprises - apart from propylene - units derivable from ethylene and/or <NUM>-butene. In a preferred embodiment, the heterophasic propylene copolymer (HECO1) according to this invention comprises units derivable from ethylene and propylene only. Still more preferably the propylene polymer (PP1) as well as the elastomeric propylene copolymer (E1) of the heterophasic propylene copolymer (HECO1) contain the same comonomers, like ethylene.

Additionally, it is appreciated that the heterophasic propylene copolymer (HECO1) preferably has a rather low total comonomer content, preferably ethylene content. Thus, it is preferred that the comonomer content of the heterophasic propylene copolymer (HECO1) is in the range from <NUM> to <NUM> mol-%, preferably in the range from <NUM> to 35mol-%, more preferably in the range from <NUM> to <NUM> mol-%.

The xylene cold soluble (XCS) fraction measured according to according ISO <NUM> (<NUM>) of the heterophasic propylene copolymer (HECO1) is in the range of <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, still more preferably in the range from <NUM> to <NUM> wt.

Further it is appreciated that the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO1) is specified by its intrinsic viscosity. A low intrinsic viscosity (IV) value reflects a low weight average molecular weight. For the present invention it is appreciated that the xylene cold soluble fraction (XCS) of the heterophasic propylene copolymer (HECO1) has an intrinsic viscosity (IV) measured according to ISO <NUM>/<NUM> (at <NUM> in decalin) > <NUM> dl/g. More preferably, the xylene cold soluble fraction (XCS) of the heterophasic propylene copolymer (HECO1) has an intrinsic viscosity (IV) in the range of > <NUM> to <NUM> dl/g, preferably in the range of <NUM> to <NUM> dl/g, more preferably in the range of <NUM> to <NUM> dl/g.

Additionally, it is preferred that the comonomer content, i.e. ethylene content, of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO1) is ≤ <NUM> mol-%, preferably ≤ <NUM> mol-%, more preferably ≤ <NUM> mol. -%, and most preferably ≤ <NUM> mol. For example, the heterophasic propylene copolymer (HECO1) has a comonomer content of the xylene cold soluble (XCS) fraction between <NUM> and <NUM> mol. -%, preferably between <NUM> and <NUM> mol. -%, more preferably between <NUM> and <NUM> mol. -%, and most preferably between <NUM> and <NUM> mol. The comonomers present in the xylene cold soluble (XCS) fraction are those defined above for the propylene polymer (M1) and the elastomeric propylene copolymer (E1), respectively. In one preferred embodiment the comonomer is ethylene only.

The heterophasic propylene copolymer (HECO1) can be further defined by its individual components, i.e. the propylene polymer (PP1) and the elastomeric propylene copolymer (E1).

The propylene polymer (PP1) can be a propylene copolymer or a propylene homopolymer, the latter being preferred.

In case the propylene polymer (PP1) is a propylene copolymer, the propylene polymer (PP1) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C<NUM> to C<NUM> α-olefins, in particular ethylene and/or C<NUM> to C<NUM> α-olefins, e.g. <NUM>-butene and/or <NUM>-hexene. Preferably the propylene polymer (PP1) according to this invention comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, <NUM>-butene and <NUM>-hexene. More specifically the propylene polymer (PP1) of this invention comprises - apart from propylene - units derivable from ethylene and/or <NUM>-butene. In a preferred embodiment the propylene polymer (PP1) comprises units derivable from ethylene and propylene only.

The propylene polymer (PP1) according to this invention has a melt flow rate MFR<NUM> (<NUM>/<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>.

As mentioned above the heterophasic propylene copolymer (HECO1) is featured by a low comonomer content. Accordingly, the comonomer content of the propylene polymer (PP1) is in the range of <NUM> to <NUM> mol-%, yet more preferably in the range of <NUM> to <NUM> mol-%, still more preferably in the range of <NUM> to <NUM> mol-%. It is especially preferred that the propylene polymer (PP1) is a propylene homopolymer.

The propylene polymer (PP1) preferably comprises at least two polymer fractions, like two or three polymer fractions, all of them are propylene homopolymers. Even more preferred the propylene polymer (PP1) comprises, preferably consists of, a first propylene homopolymer fraction (H-PP1a) and a second propylene homopolymer fraction (H-PP1b).

Preferably, the first propylene homopolymer fraction (H-PP1a) and the second propylene homopolymer fraction (H-PP1b) differ in melt flow rate.

Accordingly, one of the propylene homopolymer fractions (H-PP1a) and (H-PP1b) of the propylene polymer (PP1) is the low melt flow rate MFR<NUM> (<NUM> / <NUM>) fraction and the other fraction is the high melt flow rate MFR<NUM> (<NUM> / <NUM>) fraction, wherein further the low flow fraction and the high flow fraction fulfil in equation (I), more preferably in equation (Ia), still more preferably in equation (Ib), <MAT> <MAT> <MAT> wherein MFR (high) is the melt flow rate MFR<NUM> (<NUM> / <NUM>) [g/<NUM>] of the propylene homopolymer fraction with the higher melt flow rate MFR<NUM> (<NUM> / <NUM>) and MFR (low) is the melt flow rate MFR<NUM> (<NUM> / <NUM>) [g/<NUM>] of the propylene homopolymer fraction with the lower melt flow rate MFR<NUM> (<NUM> / <NUM>).

Preferably, the first propylene copolymer fraction (H-PP1a) is the random copolymer fraction with the higher melt flow rate MFR<NUM> (<NUM> / <NUM>) and the second propylene copolymer fraction (H-PP1b) is the random copolymer fraction with the lower melt flow rate MFR<NUM> (<NUM> / <NUM>).

Accordingly, it is preferred that the first propylene homopolymer fraction (H-PP1a) has a melt flow rate MFR<NUM> (<NUM> / <NUM>) in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM> and/or that the second propylene homopolymer fraction (H-PP1b) has a melt flow rate MFR<NUM> (<NUM> / <NUM>) in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>.

Further, the weight ratio between the first propylene homopolymer fraction (H-PP1a) and second propylene homopolymer fraction (H-PP1b) preferably is <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>, still more preferably <NUM>:<NUM> to <NUM>:<NUM>.

The heterophasic propylene copolymer (HECO1) preferably comprises <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of the propylene polymer (PP1), based on the total weight of the heterophasic propylene copolymer (HECO1).

Additionally, the heterophasic propylene copolymer (HECO1) preferably comprises <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of the elastomeric propylene copolymer (E1), based on the total weight of the heterophasic propylene copolymer (HECO1).

Thus, it is appreciated that the heterophasic propylene copolymer (HECO1) preferably comprises, more preferably consists of, <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of the propylene polymer (PP1) and <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of the elastomeric propylene copolymer (E1), based on the total weight of the heterophasic propylene copolymer (HECO1).

Accordingly, a further component of the heterophasic propylene copolymer (HECO1) is the elastomeric propylene copolymer (E1) dispersed in the matrix (M1) being the propylene polymer (PP1). Concerning the comonomers used in the elastomeric propylene copolymer (E1) it is referred to the information provided for the first heterophasic propylene copolymer (HECO1). Accordingly, the elastomeric propylene copolymer (E1) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C<NUM> to C<NUM> α-olefins, in particular ethylene and/or C<NUM> to C<NUM> α-olefins, e.g. <NUM>-butene and/or <NUM>-hexene.

Preferably, the elastomeric propylene copolymer (E1) comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, <NUM>-butene and <NUM>-hexene. More specifically, the elastomeric propylene copolymer (E1) comprises - apart from propylene - units derivable from ethylene and/or <NUM>-butene. Thus, in an especially preferred embodiment the elastomeric propylene copolymer (E1) comprises units derivable from ethylene and propylene only.

The comonomer content of the elastomeric propylene copolymer (E1) preferably is in the range of <NUM> to <NUM> mol-%, more preferably in the range of <NUM> to <NUM> mol-%, still more preferably in the range of <NUM> to <NUM> mol-%.

The heterophasic propylene copolymer (HECO1) as defined in the instant invention may contain up to <NUM> wt. -% additives, like nucleating agents and antioxidants, as well as slip agents and antiblocking agents. Preferably the additive content (without α-nucleating agents) is below <NUM> wt. -%, like below <NUM> wt.

According to a preferred embodiment of the present invention, the heterophasic propylene copolymer (HECO1) contains an α-nucleating agent.

According to this invention the alpha nucleating agent is not an additive (AD).

The alpha-nucleating agent is preferably selected from the group consisting of.

Preferably the alpha-nucleating agent comprised in the composition of the invention is vinylcycloalkane polymer and/or vinylalkane polymer, more preferably vinylcycloalkane polymer, like vinylcyclohexane (VCH) polymer. Vinyl cyclohexane (VCH) polymer is particularly preferred as α-nucleating agent. It is appreciated that the amount of vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, more preferably of vinylcyclohexane (VCH) polymer, in the composition is not more than <NUM> ppm, preferably not more than <NUM> ppm, more preferably not more than <NUM> ppm, like in the range of <NUM> to <NUM> ppm, preferably in the range of <NUM> to <NUM> ppm, more preferably in the range of <NUM> to <NUM> ppm. Furthermore, it is appreciated that the vinylcycloalkane polymer and/or vinylalkane polymer is introduced into the composition by the BNT technology. With regard to the BNT-technology reference is made to the international applications <CIT>, <CIT> and particularly <CIT>. According to this technology a catalyst system, preferably a Ziegler-Natta procatalyst, can be modified by polymerizing a vinyl compound in the presence of the catalyst system, comprising in particular the special Ziegler-Natta procatalyst, an external donor and a cocatalyst, which vinyl compound has the formula:.

wherein R<NUM> and R<NUM> together form a <NUM>- or <NUM>-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising <NUM> to <NUM> carbon atoms, and the modified catalyst is preferably used for the preparation of the heterophasic composition (HECO) present in the modified polypropylene composition (mPP). The polymerized vinyl compound acts as an alpha-nucleating agent. The weight ratio of vinyl compound to solid catalyst component in the modification step of the catalyst is preferably of up to <NUM> (<NUM>:<NUM>), more preferably up to <NUM> (<NUM>:<NUM>), like in the range of <NUM> (<NUM>:<NUM>) to <NUM> (<NUM>:<NUM>).

Such nucleating agents are commercially available and are described, for example, in "<NPL>).

The heterophasic propylene copolymer (HECO1) can be produced by blending the propylene polymer (PP1) and the elastomeric propylene copolymer (E1). However, it is preferred that the heterophasic propylene copolymer (HECO1) is produced in a sequential step process, using reactors in serial configuration and operating at different reaction conditions. As a consequence, each fraction prepared in a specific reactor may have its own molecular weight distribution and/or comonomer content distribution.

Accordingly, it is preferred that the heterophasic propylene copolymer (HECO1) is produced in a sequential polymerization process comprising the steps of.

Of course, in the first reactor (R1) the second polypropylene fraction can be produced and in the second reactor (R2) the first polypropylene fraction can be obtained. The same holds true for the elastomeric propylene copolymer phase.

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

The term "sequential polymerization process" indicates that the heterophasic propylene copolymer (HECO1) is produced in at least two, like three or four reactors connected in series. Accordingly, the present process comprises at least a first reactor (R1) and a second reactor (R2), more preferably a first reactor (R1), a second reactor (R2), a third reactor (R3) and a fourth reactor (R4). 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 (R1) 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 <NUM> % (w/w) monomer. According to the present invention the slurry reactor (SR) is preferably a (bulk) loop reactor (LR).

The second reactor (R2) can be a slurry reactor, like a loop reactor, as the first reactor or alternatively a gas phase reactor (GPR).

The third reactor (R3) and the fourth reactor (R4) 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 <NUM>/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 (R1) is a slurry reactor (SR), like a loop reactor (LR), whereas the second reactor (R2), the third reactor (R3) and the fourth reactor (R4) are gas phase reactors (GPR). Accordingly for the instant process at least four, preferably four polymerization reactors, namely a slurry reactor (SR), like a loop reactor (LR), a first gas phase reactor (GPR-<NUM>), a second gas phase reactor (GPR-<NUM>) and a third gas phase reactor (GPR-<NUM>) connected in series are used. If needed prior to the slurry reactor (SR) a pre-polymerization reactor is placed.

In another preferred embodiment the first reactor (R1) and second reactor (R2) are slurry reactors (SR), like a loop reactors (LR), whereas the third reactor (R3) and the fourth reactor (R4) are gas phase reactors (GPR). Accordingly for the instant process at least three, preferably three polymerization reactors, namely two slurry reactors (SR), like two loop reactors (LR), and two gas phase reactors (GPR-<NUM>) and (GPR-<NUM>) connected in series are used. If needed prior to the first 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 <CIT>, <CIT> <CIT>, <CIT>, <CIT>, <CIT> or in <CIT>.

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

Preferably, in the instant process for producing the heterophasic propylene copolymer (HECO1) as defined above the conditions for the first reactor (R1), i.e. the slurry reactor (SR), like a loop reactor (LR), of step (a) may be as follows:.

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

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 <NUM> to <NUM> hours, e.g. <NUM> to <NUM> hours and the residence time in gas phase reactor will generally be <NUM> to <NUM> hours, like <NUM> to <NUM> hours.

Subsequently, the reaction mixture from step (c) is transferred into the third reactor (R3), i.e. gas phase reactor (GPR-<NUM>) and, optionally, into a fourth reactor (R4), i.e. gas phase reactor (GPR-<NUM>). The conditions and residence times in reactors (R3) and/or (R4) are preferably identical with the conditions and residence times in reactor (R2) as outlined in the previous paragraphs.

If desired, the polymerization may be effected in a known manner under supercritical conditions in the first reactor (R1), 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 <NUM> to <NUM>, preferably from <NUM> to <NUM>, and more preferably from <NUM> to <NUM>.

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 <NUM> to <NUM> bar, for example <NUM> to <NUM> bar.

The catalyst components are preferably all introduced to the prepolymerization 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 heterophasic propylene copolymer (HECO1) 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 for preparing the heterophasic composition (HECO1) is prepared by.

The procatalyst is produced as defined for example in the <CIT>, <CIT>, <CIT> and <CIT>. The content of these documents is herein included by reference.

First an adduct of MgCl<NUM> and a C<NUM>-C<NUM> alcohol of the formula MgCl<NUM>*nROH, wherein R is methyl or ethyl and n is <NUM> to <NUM>, 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<NUM>*nROH, wherein R is methyl or ethyl, preferably ethyl and n is <NUM> to <NUM>, is contacting with TiCl<NUM> to form a titanized carrier, followed by the steps of.

The adduct of the formula MgCl<NUM>*nROH, wherein R is methyl or ethyl and n is <NUM> to <NUM>, 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 <CIT>.

This crystallized adduct is preferably used as the catalyst carrier and reacted to the procatalyst useful in the present invention as described in <CIT> and <CIT>.

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 <NUM> wt. -% of titanium at the most, preferably <NUM>% wt. -% at the most and more preferably <NUM> wt. -% at the most. Its donor content is preferably between <NUM> to <NUM> wt. -% and more preferably between <NUM> and <NUM> wt.

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 catalyst as described in the example section; especially with the use of dioctylphthalate as dialkylphthalate of formula (I).

For the production of the heterophasic composition (HECO1) 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 trialkylaluminum, like triethylaluminum (TEA), dialkyl aluminum chloride and alkyl aluminum sesquichloride.

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

wherein R<NUM> represents a branched-alkyl group having <NUM> to <NUM> carbon atoms, preferably a branched-alkyl group having <NUM> to <NUM> carbon atoms, or a cyclo-alkyl having <NUM> to <NUM> carbon atoms, preferably a cyclo-alkyl having <NUM> to <NUM> carbon atoms.

It is in particular preferred that R<NUM> is selected from the group consisting of iso-propyl, iso-butyl, iso-pentyl, tert. -butyl, tert. -amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.

Si(OCH<NUM>CH<NUM>)<NUM>(NRxRy)     (IIIb).

wherein Rx and Ry can be the same or different a represent a hydrocarbon group having <NUM> to <NUM> carbon atoms.

Rx and Ry are independently selected from the group consisting of linear aliphatic hydrocarbon group having <NUM> to <NUM> carbon atoms, branched aliphatic hydrocarbon group having <NUM> to <NUM> carbon atoms and cyclic aliphatic hydrocarbon group having <NUM> to <NUM> carbon atoms. It is in particular preferred that Rx and Ry 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 Rx and Ry are the same, yet more preferably both Rx and Ry are an ethyl group.

More preferably the external donor is of formula (IIIa), like dicyclopentyl dimethoxy silane [Si(OCH<NUM>)<NUM>(cyclo-pentyl)<NUM>], diisopropyl dimethoxy silane [Si(OCH<NUM>)<NUM>(CH(CH<NUM>)<NUM>)<NUM>].

Most preferably the external donor is dicyclopentyl dimethoxy silane [Si(OCH<NUM>)<NUM>(cyclopentyl)<NUM>] (donor D).

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:.

wherein R<NUM> and R<NUM> together form a <NUM>- or <NUM>-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising <NUM> to <NUM> carbon atoms, and the modified catalyst is used for the preparation of the heterophasic composition (HECO) according to this invention. The polymerized vinyl compound can act as an α-nucleating agent.

Concerning the modification of catalyst reference is made to the international applications <CIT>, <CIT> and particularly <CIT>, 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.

It is appreciated that foamable polypropylene composition (C) optionally comprises a propylene homopolymer (H-PP).

The expression propylene homopolymer used in the instant invention relates to a polypropylene that consists substantially, i.e. of at least <NUM> wt. -%, based on the total weight of the polypropylene, preferably of at least <NUM> wt. -%, more preferably of at least <NUM> wt. -%, of propylene units. In one embodiment of the present invention, only propylene units in the propylene homopolymer are detectable.

The propylene homopolymer (H-PP) is preferably a semicrystalline propylene homopolymer (H-PP).

The propylene homopolymer (H-PP), preferably the semicrystalline propylene homopolymer (H-PP), has preferably a melting temperature Tm in the range of <NUM> to <NUM>, like in the range of <NUM> to <NUM>.

Additionally or alternatively, it is preferred that the propylene homopolymer (H-PP), preferably the semicrystalline propylene homopolymer (H-PP), has a melt flow rate MFR<NUM> (<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>, yet more preferably in the range of <NUM> to <NUM>/<NUM>, still yet more preferably in the range of <NUM> to <NUM>/<NUM>, like in the range of <NUM> to <NUM>/<NUM>.

For example, the semicrystalline propylene homopolymer (H-PP), has a melting temperature Tm in the range of <NUM> to <NUM>, like in the range of <NUM> to <NUM> or a melt flow rate MFR<NUM> (<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>, yet more preferably in the range of <NUM> to <NUM>/<NUM>, still yet more preferably in the range of <NUM> to <NUM>/<NUM>, like in the range of <NUM> to <NUM>/<NUM>.

Preferably, the semicrystalline propylene homopolymer (H-PP), has a melting temperature Tm in the range of <NUM> to <NUM>, like in the range of <NUM> to <NUM> and a melt flow rate MFR<NUM> (<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>, yet more preferably in the range of <NUM> to <NUM>/<NUM>, still yet more preferably in the range of <NUM> to <NUM>/<NUM>, like in the range of <NUM> to <NUM>/<NUM>.

Such a propylene homopolymer (H-PP), preferably semicrystalline propylene homopolymer (H-PP), is known in the art. For instance the semicrystalline propylene homopolymer (H-PP) can be the commercial product HJ120UB of Borealis AG.

An optional component of the foamable polypropylene composition (C) according to this invention is the presence of an inorganic filler (F).

Preferably the inorganic filler (F) is a mineral filler. It is appreciated that the inorganic filler (F) is preferably a phyllosilicate, mica, wollastonite or carbon black. Even more preferred the inorganic filler (F) is selected from the group consisting of mica, wollastonite, kaolinite, smectite, montmorillonite, talc and carbon black.

The most preferred inorganic fillers (F) are talc and/or carbon black. It is especially preferred that the inorganic filler (F) is talc.

In one embodiment, the inorganic filler (F) is talc and carbon black.

It is appreciated that the filler (F) has median particle size (D<NUM>) in the range of <NUM> to <NUM> and a top cut particle size (D<NUM>) in the range of <NUM> to <NUM>, preferably a median particle size (D<NUM>) in the range of <NUM> to <NUM> and top cut particle size (D<NUM>) in the range of <NUM> to <NUM>, more preferably a median particle size (D<NUM>) in the range of <NUM> to <NUM> and top cut particle size (D<NUM>) of <NUM> to <NUM>.

According to this invention the filler (F) does not belong to the class of alpha nucleating agents and additives (AD).

The inorganic filler (F) is state of the art and a commercially available product.

It is one requirement of the present invention that the foamable polypropylene composition (C) according to this invention comprises at least one foaming agent (FA) being selected from chemical and physical foaming agents.

The term "foaming agent" refers to an agent which is capable of producing a cellular structure in a polypropylene composition during foaming.

It is appreciated that the expression "at least one" foaming agent (FA) means that the foaming agent (FA) comprises, preferably consists of, one or more kinds of foaming agent(s).

Accordingly, it should be noted that the at least one foaming agent (FA) may comprise one kind of foaming agent (FA). Alternatively, the at least one foaming agent (FA) may comprise a mixture of two or more kinds of foaming agents. For example, the at least one foaming agent (FA) may comprise a mixture of two or three kinds of foaming agents, like two kinds of foaming agents.

In one embodiment of the present invention, the at least one foaming agent (FA) comprises, preferably consists of, two kinds of foaming agents.

Chemical foaming agents include e.g. azodicarbonamide, diazoaminobenzene, azo-bis-isobutyro-nitrile and analogs thereof, citric acid, ammonium carbonate, bicarbonates such as sodium hydrogen carbonate (or sodium bicarbonate) and the like. Physical foaming agents include e.g. nitrogen, carbon dioxide and other inert gases.

Preferably, the at least one foaming agent (FA) is/are (a) chemical foaming agent(s). More preferably, the at least one foaming agent (FA) comprises, preferably consists of, two kinds of chemical foaming agents.

For example, the at least one foaming agent (FA) is a mixture of citric acid and bicarbonate, such as sodium hydrogen carbonate (or sodium bicarbonate).

Alternatively, the at least one foaming agent (FA) is a bicarbonate, preferably sodium hydrogen carbonate (or sodium bicarbonate).

The heterophasic propylene copolymer (HECO2) according to this invention comprises a matrix (M2) being the propylene polymer (PP2) and dispersed therein an elastomeric propylene copolymer being the elastomeric propylene copolymer (E2). Thus the matrix (M2) contains (finely) dispersed inclusions being not part of the matrix (M2) and said inclusions contain the elastomeric propylene copolymer (E2). Regarding the term "inclusions", reference is made to the definition provided above.

Accordingly, the heterophasic propylene copolymer (HECO2) according to this invention preferably comprises.

Preferably the weight ratio between the propylene polymer (PP2) and the elastomeric propylene copolymer (E2) [PP2/E2] of the heterophasic propylene copolymer (HECO2) is in the range of <NUM>/<NUM> to <NUM>/<NUM>, more preferably in the range of <NUM>/<NUM> to <NUM>/<NUM>, yet more preferably in the range of <NUM>/<NUM> to <NUM>/<NUM>, like in the range of <NUM>/<NUM> to <NUM>/<NUM>.

Preferably, the heterophasic propylene copolymer (HECO2) according to this invention comprises as polymer components only the propylene polymer (PP2) and the elastomeric propylene copolymer (E2). In other words, the heterophasic propylene copolymer (HECO2) may contain further additives but no other polymer in an amount exceeding <NUM> wt. -%, more preferably exceeding <NUM> wt. -%, like exceeding <NUM> wt. -%, based on the total heterophasic propylene copolymer (HECO2). One additional polymer which may be present in such low amounts is a polyethylene which is a reaction by-product obtained by the preparation of the heterophasic propylene copolymer (HECO2). Accordingly, it is in particular appreciated that the instant heterophasic propylene copolymer (HECO2) contains only the propylene polymer (PP2), the elastomeric propylene copolymer (E2) and optionally polyethylene in amounts as mentioned in this paragraph.

The heterophasic propylene copolymer (HECO2) applied according to this invention is featured by a rather high melt flow rate. Accordingly, the heterophasic propylene copolymer (HECO2) has a melt flow rate MFR<NUM> (<NUM>) in the range of <NUM> to <NUM>/<NUM>, preferably in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>.

Preferably, it is desired that the heterophasic propylene copolymer (HECO2) is thermo mechanically stable. Accordingly, it is appreciated that the heterophasic propylene copolymer (HECO2) has a melting temperature of at least <NUM>, more preferably in the range of <NUM> to <NUM>, still more preferably in the range of <NUM> to <NUM>.

The heterophasic propylene copolymer (HECO2) comprises apart from propylene also comonomers. Preferably the heterophasic propylene copolymer (HECO2) comprises apart from propylene ethylene and/or C<NUM> to C<NUM> α-olefins. Accordingly, the term "propylene copolymer" according to this invention is understood as a polypropylene comprising, preferably consisting of, units derivable from.

Thus, the heterophasic propylene copolymer (HECO2), i.e. the propylene polymer (PP2) as well as the elastomeric propylene copolymer (E2), can comprise monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C<NUM> to C<NUM> α-olefins, in particular ethylene and/or C<NUM> to C<NUM> α-olefins, e.g. <NUM>-butene and/or <NUM>-hexene. Preferably, the heterophasic propylene copolymer (HECO2) according to this invention comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, <NUM>-butene and <NUM>-hexene. More specifically, the heterophasic propylene copolymer (HECO2) of this invention comprises - apart from propylene - units derivable from ethylene and/or <NUM>-butene. In a preferred embodiment, the heterophasic propylene copolymer (HECO2) according to this invention comprises units derivable from ethylene and propylene only. Still more preferably the propylene polymer (PP2) as well as the elastomeric propylene copolymer (E2) of the heterophasic propylene copolymer (HECO2) contain the same comonomers, like ethylene.

Additionally, it is appreciated that the heterophasic propylene copolymer (HECO2) preferably has a rather low total comonomer content, preferably ethylene content. Thus, it is preferred that the comonomer content of the heterophasic propylene copolymer (HECO2) is in the range from <NUM> to <NUM> mol-%, preferably in the range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-%.

The xylene cold soluble (XCS) fraction measured according to according ISO <NUM> (<NUM>) of the heterophasic propylene copolymer (HECO2) is in the range of <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, still more preferably in the range from <NUM> to <NUM> wt.

Further it is appreciated that the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO2) is specified by its intrinsic viscosity. A low intrinsic viscosity (IV) value reflects a low weight average molecular weight. For the present invention it is appreciated that the xylene cold soluble fraction (XCS) of the heterophasic propylene copolymer (HECO2) has an intrinsic viscosity (IV) measured according to ISO <NUM>/<NUM> (at <NUM> in decalin) of < <NUM> dl/g, preferably in the range of <NUM> to <NUM> dl/g, more preferably in the range of <NUM> to <NUM> dl/g, and most preferably in the range of <NUM> to <NUM> dl/g.

Additionally, it is preferred that the comonomer content, i.e. ethylene content, of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO2) is from <NUM> to <NUM> mol-%. The comonomers present in the xylene cold soluble (XCS) fraction are those defined above for the propylene polymer (PP2) and the elastomeric propylene copolymer (E2), respectively. In one preferred embodiment the comonomer is ethylene only.

The heterophasic propylene copolymer (HECO2) can be further defined by its individual components, i.e. the propylene polymer (PP2) and the elastomeric propylene copolymer (E2).

The propylene polymer (PP2) can be a propylene copolymer or a propylene homopolymer, the latter being preferred.

In case the propylene polymer (PP2) is a propylene copolymer, the propylene polymer (PP2) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C<NUM> to C<NUM> α-olefins, in particular ethylene and/or C<NUM> to C<NUM> α-olefins, e.g. <NUM>-butene and/or <NUM>-hexene. Preferably the propylene polymer (PP2) according to this invention comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, <NUM>-butene and <NUM>-hexene. More specifically the propylene polymer (PP2) of this invention comprises - apart from propylene - units derivable from ethylene and/or <NUM>-butene. In a preferred embodiment the propylene polymer (PP2) comprises units derivable from ethylene and propylene only.

The propylene polymer (PP2) according to this invention has a melt flow rate MFR<NUM> (<NUM>/<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM>.

As mentioned above the heterophasic propylene copolymer (HECO2) is featured by a low comonomer content. Accordingly, the comonomer content of the propylene polymer (PP2) is in the range of <NUM> to <NUM> mol-%, yet more preferably in the range of <NUM> to <NUM> mol-%, still more preferably in the range of <NUM> to <NUM> mol-%. It is especially preferred that the propylene polymer (PP2) is a propylene homopolymer.

The heterophasic propylene copolymer (HECO2) preferably comprises <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of the propylene polymer (PP2), based on the total weight of the heterophasic propylene copolymer (HECO2).

Additionally, the heterophasic propylene copolymer (HECO2) preferably comprises <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -% of the elastomeric propylene copolymer (E2), based on the total weight of the heterophasic propylene copolymer (HECO2).

Thus, it is appreciated that the heterophasic propylene copolymer (HECO2) preferably comprises, more preferably consists of, <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of the propylene polymer (PP2) and <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of the elastomeric propylene copolymer (E2), based on the total weight of the heterophasic propylene copolymer (HECO2).

Accordingly, a further component of the heterophasic propylene copolymer (HECO2) is the elastomeric propylene copolymer (E2) dispersed in the matrix (M2) being the propylene polymer (PP2). Concerning the comonomers used in the elastomeric propylene copolymer (E2) it is referred to the information provided for the heterophasic propylene copolymer (HECO2). Accordingly, the elastomeric propylene copolymer (E2) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C<NUM> to C<NUM> α-olefins, in particular ethylene and/or C<NUM> to C<NUM> α-olefins, e.g. <NUM>-butene and/or <NUM>-hexene. Preferably, the elastomeric propylene copolymer (E2) comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, <NUM>-butene and <NUM>-hexene. More specifically, the elastomeric propylene copolymer (E2) comprises - apart from propylene - units derivable from ethylene and/or <NUM>-butene. Thus, in an especially preferred embodiment the elastomeric propylene copolymer (E2) comprises units derivable from ethylene and propylene only.

The comonomer content of the elastomeric propylene copolymer (E2) preferably is in the range of <NUM> to <NUM> mol-%, more preferably in the range of <NUM> to <NUM> mol-%, still more preferably in the range of <NUM> to <NUM> mol-%.

The heterophasic propylene copolymer (HECO2) as defined in the instant invention may contain up to <NUM> wt. -% additives, like nucleating agents and antioxidants, as well as slip agents and antiblocking agents. Preferably the additive content (without α-nucleating agents) is below <NUM> wt. -%, like below <NUM> wt.

According to a preferred embodiment of the present invention, the heterophasic propylene copolymer (HECO2) contains an α-nucleating agent.

wherein R<NUM> and R<NUM> together form a <NUM>- or <NUM>-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising <NUM> to <NUM> carbon atoms, and the modified catalyst is preferably used for the preparation of the heterophasic compostion (HECO) present in the modified polypropylene composition (mPP). The polymerized vinyl compound acts as an alpha-nucleating agent. The weight ratio of vinyl compound to solid catalyst component in the modification step of the catalyst is preferably of up to <NUM> (<NUM>:<NUM>), more preferably up to <NUM> (<NUM>:<NUM>), like in the range of <NUM> (<NUM>:<NUM>) to <NUM> (<NUM>:<NUM>).

The heterophasic propylene copolymer (HECO2) can be produced by blending the propylene polymer (PP2) and the elastomeric propylene copolymer (E2). However, it is preferred that the heterophasic propylene copolymer (HECO2) is produced in a sequential step process, using reactors in serial configuration and operating at different reaction conditions. As a consequence, each fraction prepared in a specific reactor may have its own molecular weight distribution and/or comonomer content distribution.

The heterophasic propylene copolymer (HECO2) according to this invention is preferably produced in a sequential polymerization process, i.e. in a multistage process, known in the art, wherein the propylene polymer (PP2) is produced at least in one slurry reactor, preferably in a slurry reactor and optionally in a subsequent gas phase reactor, and subsequently the elastomeric propylene copolymer (E2) is produced at least in one, i.e. one or two, gas phase reactor(s).

Accordingly it is preferred that the heterophasic propylene copolymer (HECO2) is produced in a sequential polymerization process comprising the steps of.

The term "sequential polymerization process" indicates that the heterophasic propylene copolymer (HECO2) is produced in at least two, like three or four reactors connected in series. Accordingly, the present process comprises at least a first reactor (R1) and a second reactor (R2), more preferably a first reactor (R1), a second reactor (R2), and a third reactor (R3). Regarding the term "polymerization reactor", reference is made to the definition provided above.

The first reactor (R1) 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 <NUM> % (w/w) monomer.

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

The third reactor (R3) is preferably a gas phase reactor (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 <NUM>/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 (R1) is a slurry reactor (SR), like a 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 a loop reactor (LR), a first gas phase reactor (GPR-<NUM>) and a second gas phase reactor (GPR-<NUM>) connected in series are used. If needed prior to the slurry reactor (SR) a pre-polymerization reactor is placed.

In another preferred embodiment the first reactor (R1) and second reactor (R2) are slurry reactors (SR), like a loop reactors (LR), whereas the third reactor (R3) is a gas phase reactors (GPR). Accordingly for the instant process at least three, preferably three polymerization reactors, namely two slurry reactors (SR), like two loop reactors (LR), and a gas phase reactor (GPR-<NUM>) connected in series are used. If needed prior to the first slurry reactor (SR) a pre-polymerization reactor is placed.

Preferably, in the instant process for producing the heterophasic propylene copolymer (HECO2) as defined above the conditions for the first reactor (R1), i.e. the slurry reactor (SR), like a loop reactor (LR), of step (a) may be as follows:.

The condition in the third reactor (R3), preferably in the second gas phase reactor (GPR-<NUM>) is similar to the second reactor (R2).

According to the invention the heterophasic propylene copolymer (HECO2) 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.

Regarding the preferred catalyst system, reference is made to the catalyst defined above with regard to the heterophasic propylene copolymer (HECO1).

According to another preferred embodiment, the Ziegler-Natta catalyst for the preparation of the heterophasic propylene copolymer (HECO2) comprises a high-yield Ziegler-Natta type catalyst including an internal donor component, which can be used at high polymerization temperatures of <NUM> or more. Such high-yield Ziegler-Natta catalyst can comprise a succinate, a diether, a phthalate etc., or mixtures therefrom as internal donor (ID) and are for example commercially available from LyondellBasell under the Avant ZN trade name. Examples of the Avant ZN series are Avant ZN <NUM> and Avant ZN <NUM>. Avant ZN <NUM> is a Ziegler-Natta catalyst with <NUM> wt% titanium and a diether compound as internal electron donor, which is commercially available from LyondellBasell. Avant ZN <NUM> is a Ziegler-Natta catalyst with <NUM> wt % titanium and a succinate compound as internal electron donor, which is commercially available from LyondellBaselll. A further example of the Avant ZN series is the catalyst ZN180M of LyondellBasell.

In a further embodiment, the Ziegler-Natta procatalyst for the production of the second heterophasic propylene copolymer (HECO2) can also be modified by polymerizing a vinyl compound in the presence of the catalyst system as described above.

According to a preferred embodiment of the present invention, the foamable polypropylene composition (C) further comprises a plastomer (PL) being a copolymer of ethylene and a C<NUM> to C<NUM> α-olefin.

The plastomer (PL) can be any elastomeric polyolefin with the proviso that it chemically differs from the elastomeric propylene copolymers (E1) and (E2) as defined herein. More preferably the plastomer (PL) is a very low density polyolefin, still more preferably a very low density polyolefin polymerized using single site catalysis, preferably metallocene catalysis. Typically, the plastomer (PL) is an ethylene copolymer.

The plastomer (PL) has a density below <NUM>/cm<NUM>. More preferably, the density of the plastomer (PL) is equal or below <NUM>/cm<NUM>, still more preferably in the range of <NUM> to <NUM>/cm<NUM>.

Preferably, the plastomer (PL) has a melt flow rate MFR<NUM> (<NUM>, <NUM>) of less than <NUM>/<NUM>, more preferably from <NUM> to <NUM>/<NUM>, still more preferably from <NUM> to <NUM>/<NUM>, like a range from <NUM> to <NUM>/<NUM>.

Preferably, the plastomer (PL) comprises units derived from ethylene and a C4 to C20 α-olefin.

The plastomer (PL) comprises, preferably consists of, units derivable from (i) ethylene and (ii) at least another C4 to C20 α-olefin, like C4 to C10 α-olefin, more preferably units derivable from (i) ethylene and (ii) at least another α-olefin selected form the group consisting of <NUM>-butene, <NUM>-pentene, <NUM>-hexene, <NUM>-heptene and <NUM>-octene. It is especially preferred that the plastomer (PL) comprises at least units derivable from (i) ethylene and (ii) <NUM>-butene or <NUM>-octene. It is especially preferred that the plastomer (PL) is a copolymer of ethylene and <NUM>-octene.

In an especially preferred embodiment, the plastomer (PL) consists of units derivable from ethylene and <NUM>-octene.

The comonomer content, like the C4 to C20 α-olefin content, of the plastomer (PL) is in the range of <NUM> to <NUM> mol-%, more preferably in the range of <NUM> to <NUM> mol-%, still more preferably in the range of <NUM> to <NUM> mol-%, like in the range of <NUM> to <NUM> mol-%.

In one preferred embodiment the plastomer (PL) is prepared with at least one metallocene catalyst. The plastomer (PL) may also be prepared with more than one metallocene catalyst or may be a blend of multiple elastomers prepared with different metallocene catalysts. In some embodiments, the plastomer (PL) is a substantially linear ethylene polymer (SLEP). SLEPs and other metallocene catalysed plastomers (PL) are known in the art, for example, <CIT>. These resins are also commercially available, for example, as Queo™ plastomers available from Borealis, ENGAGE™ plastomer resins available from Dow Chemical Co. or EXACT™ polymers from Exxon or TAFMER™ polymers from Mitsui.

According to a preferred embodiment of the present invention, the foamable polypropylene composition (C) further comprises a high density polyethylene (HDPE).

The expression "high density polyethylene" used in the instant invention relates to a polyethylene obtained in the presence of a Ziegler-Natta or metallocene catalyst that consists substantially, i.e. of more than <NUM> mol-%, still more preferably of at least <NUM> mol-%, of ethylene units. In a preferred embodiment only ethylene units in the high density polyethylene (HDPE) are detectable.

The high density polyethylene (HDPE) has a density of at least <NUM>/cm<NUM>. More preferably, the high density polyethylene (HDPE) has a density in the range of <NUM> to <NUM>/cm<NUM>, still more preferably in the range of <NUM> to <NUM>/cm<NUM>, like in the range of <NUM> to <NUM>/cm<NUM>.

It is especially preferred that the high density polyethylene (HDPE) has a weight average molecular weight Mw in the range of <NUM> to <NUM>/mol, preferably in the range of <NUM> to <NUM>/mol, still more preferably in the range of <NUM> to <NUM>/mol.

Further it is preferred that the high density polyethylene (HDPE) has a rather broad molecular weight distribution (Mw/Mn). Accordingly, it is preferred that the molecular weight distribution (Mw/Mn) of the high density polyethylene (HDPE) is in the range of <NUM> to <NUM>, more preferably in the range of <NUM>. 5to <NUM>, like in the range of <NUM> to <NUM>.

Additionally, it is preferred that the high density polyethylene (HDPE) has a rather low melt flow rate. Accordingly, the melt flow rate MFR (<NUM>, <NUM>) measured according to ISO <NUM> of the high density polyethylene (HDPE) is preferably in the range of <NUM> to <NUM>/<NUM>, more preferably in the range of <NUM> to <NUM>/<NUM>, still more preferably in the range of <NUM> to <NUM>/<NUM> at <NUM>.

Preferably, the high density polyethylene (HDPE) according to the present invention is a high density polyethylene known in the art. In particular, it is preferred that the high density polyethylene (HDPE) is the commercial ethylene homopolymer MB7541 of Borealis AG.

In addition to the components set out above, the foamable polypropylene composition (C) of the invention may further include additives (AD). Typical additives are acid scavengers, antioxidants, colorants, light stabilisers, plasticizers, slip agents, anti-scratch agents, dispersing agents, processing aids, lubricants, pigments, and the like. As indicated above, the nucleating agent (NU) and the inorganic filler (F) are not regarded as additives (AD).

Such additives are commercially available and for example described in "<NPL>).

Furthermore, the term "additives (AD)" according to the present invention also includes carrier materials, in particular polymeric carrier materials.

Preferably the foamable polypropylene composition (C) of the invention does not comprise (a) further polymer (s) different to the heterophasic propylene copolymer (HECO1), the optional heterophasic propylene copolymer (HECO2), the optional propylene homopolymer (H-PP), the optional plastomer (PL) and the optional high density polyethylene (HDPE), in an amount exceeding <NUM> wt. -%, preferably in an amount exceeding <NUM> wt. -%, more preferably in an amount exceeding <NUM> wt. -%, based on the weight of the polypropylene composition (C). Any polymer being a carrier material for additives (AD) is not calculated to the amount of polymeric compounds as indicated in the present invention, but to the amount of the respective additive.

The polymeric carrier material of the additives (AD) is a carrier polymer to ensure a uniform distribution in the foamable polypropylene composition (C) of the invention. The polymeric carrier material is not limited to a particular polymer. The polymeric carrier material may be ethylene homopolymer, ethylene copolymer obtained from ethylene and α-olefin comonomer such as C<NUM> to C<NUM> α-olefin comonomer, propylene homopolymer and/or propylene copolymer obtained from propylene and α-olefin comonomer such as ethylene and/or C<NUM> to C<NUM> α-olefin comonomer.

The foamable polypropylene composition (C) of the present invention is preferably used for the production of foamed parts, more preferably of foamed automotive parts. Even more preferred is the use for the production of foamed automotive parts, especially of car interiors and exteriors, like bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like.

The current invention also provides foamed parts, more preferably of foamed automotive parts, comprising, preferably comprising at least <NUM> wt. -%, more preferably at least <NUM> wt. -%, yet more preferably at least <NUM> wt. -%, like consisting of, the inventive composition. Accordingly, the present invention is especially directed to parts for automotives, especially to car interiors and exteriors, like bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like, comprising, preferably comprising at least <NUM> wt. -%, more preferably at least <NUM> wt. -%, yet more preferably at least <NUM> wt. -%, like consisting of, the inventive composition.

The present invention is also directed to the use of the inventive foamable polypropylene composition (C) for the production of a foamed part as described in the previous paragraphs.

The present invention will now be described in further detail by the examples provided below.

Calculation of comonomer content of the first elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of comonomer content of the second elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the fourth reactor (R3), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of the xylene cold soluble (XCS) content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third and fourth reactor (R3+R4), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of the xylene cold soluble (XCS) content of the first elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of the xylene cold soluble (XCS) content of the second elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the fourth reactor (R4): <MAT> wherein.

Calculation of melt flow rate MFR<NUM> (<NUM>) of the second propylene polymer fraction, i.e. the polymer fraction produced in the second reactor (R2), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of the intrinsic viscosity of the xylene soluble fraction of the first elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of the intrinsic viscosity of the xylene soluble fraction of the second elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the fourth reactor (R4), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of comonomer content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third and fourth reactor (R3+R4), of the heterophasic propylene copolymer (HECO1): <MAT> wherein.

Calculation of comonomer content of the elastomeric copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO2): <MAT> wherein.

Calculation of the xylene cold soluble (XCS) content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO2): <MAT> wherein.

Calculation of melt flow rate MFR<NUM> (<NUM>) of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO2): <MAT> wherein.

Calculation of comonomer content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the heterophasic propylene copolymer (HECO2): <MAT> wherein.

MFR<NUM> (<NUM>) is measured according to ISO <NUM> (<NUM>, <NUM> load).

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers. Quantitative <NUM>C{<NUM>H} NMR spectra were recorded in the solution-state using a Bruker Advance III <NUM> NMR spectrometer operating at <NUM> and <NUM> for <NUM>H and <NUM>C respectively. All spectra were recorded using a <NUM>C optimised <NUM> extended temperature probehead at <NUM> using nitrogen gas for all pneumatics. Approximately <NUM> of material was dissolved in <NUM> of <NUM>,<NUM>-tetrachloroethane-d<NUM> (TCE-d<NUM>) along with chromium-(III)-acetylacetonate (Cr(acac)<NUM>) resulting in a <NUM> solution of relaxation agent in solvent (<NPL>). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least <NUM> hour. Upon insertion into the magnet the tube was spun at <NUM>. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, <NUM> recycle delay and a bi-level WALTZ16 decoupling scheme (<NPL>; <NPL>). A total of <NUM> (<NUM>) transients were acquired per spectra. Quantitative <NUM>C{<NUM>H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at <NUM> ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed <NPL>).

For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at <NUM> ppm.

Characteristic signals corresponding to regio defects (<NPL>; <NPL>; <NPL>) or comonomer were observed.

The tacticity distribution was quantified through integration of the methyl region between <NUM>-<NUM> ppm correcting for any sites not related to the stereo sequences of interest (<NPL>; <NPL>).

Specifically the influence of regio defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio defect and comonomer integrals from the specific integral regions of the stereo sequences.

The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:<MAT>.

The presence of <NUM>,<NUM> erythro regio defects was indicated by the presence of the two methyl sites at <NUM> and <NUM> ppm and confirmed by other characteristic sites.

Characteristic signals corresponding to other types of regio defects were not observed (<NPL>).

The amount of <NUM>,<NUM> erythro regio defects was quantified using the average integral of the two characteristic methyl sites at <NUM> and <NUM> ppm: <MAT>.

The total amount of propene was quantified as the sum of primary inserted propene and all other present regio defects: <MAT>.

The mole percent of <NUM>,<NUM> erythro regio defects was quantified with respect to all propene: <MAT>.

For copolymers characteristic signals corresponding to the incorporation of ethylene were observed (<NPL>).

With regio defects also observed (<NPL>; <NPL>; <NPL>) correction for the influence of such defects on the comonomer content was required.

The weight percent comonomer incorporation was calculated from the mole fraction:<MAT>.

The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

Quantitative <NUM>C{<NUM>H} NMR spectra recorded in the molten-state using a Bruker Avance III <NUM> NMR spectrometer operating at <NUM> and <NUM> for <NUM>H and <NUM>C respectively. All spectra were recorded using a <NUM>C optimised <NUM> magic-angle spinning (MAS) probehead at <NUM> using nitrogen gas for all pneumatics. Approximately <NUM> of material was packed into a <NUM> outer diameter zirconia MAS rotor and spun at <NUM>. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification (<NPL>. ; <NPL>; <NPL>)). Standard single-pulse excitation was employed utilising the transient NOE at short recycle delays of <NUM> (<NPL>. ) and the RS-HEPT decoupling scheme (<NPL>. A total of <NUM> (<NUM>) transients were acquired per spectrum. This setup was chosen due its high sensitivity towards low comonomer contents.

Quantitative <NUM>C{<NUM>H} NMR spectra were processed, integrated and quantitative properties determined using custom spectral analysis automation programs. All chemical shifts are internally referenced to the bulk methylene signal (δ+) at <NUM> ppm (<NPL>.

Characteristic signals corresponding to the incorporation of <NUM>-octene were observed (<NPL>. ; <NPL>; <NPL>) and all comonomer contents calculated with respect to all other monomers present in the polymer. Characteristic signals resulting from isolated <NUM>-octene incorporation i.e. EEOEE comonomer sequences, were observed. Isolated <NUM>-octene incorporation was quantified using the integral of the signal at <NUM> ppm. This integral is assigned to the unresolved signals corresponding to both *B6 and *βB6B6 sites of isolated (EEOEE) and isolated double non-consecutive (EEOEOEE) <NUM>-octene sequences respectively. To compensate for the influence of the two *βB6B6 sites the integral of the ββB6B6 site at <NUM> ppm is used: <MAT>.

Characteristic signals resulting from consecutive <NUM>-octene incorporation, i.e. EEOOEE comonomer sequences, were also observed. Such consecutive <NUM>-octene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the ααB6B6 sites accounting for the number of reporting sites per comonomer: <MAT>.

Characteristic signals resulting from isolated non-consecutive <NUM>-octene incorporation, i.e. EEOEOEE comonomer sequences, were also observed. Such isolated non-consecutive <NUM>-octene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the ββB6B6 sites accounting for the number of reporting sites per comonomer: <MAT>.

Characteristic signals resulting from isolated triple-consecutive <NUM>-octene incorporation, i.e. EEOOOEE comonomer sequences, were also observed. Such isolated triple-consecutive <NUM>-octene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the ααγB6B6B6 sites accounting for the number of reporting sites per comonomer: <MAT>.

With no other signals indicative of other comonomer sequences observed the total <NUM>-octene comonomer content was calculated based solely on the amount of isolated (EEOEE), isolated double-consecutive (EEOOEE), isolated non-consecutive (EEOEOEE) and isolated triple-consecutive (EEOOOEE) <NUM>-octene comonomer sequences: <MAT>.

Characteristic signals resulting from saturated end-groups were observed. Such saturated end-groups were quantified using the average integral of the two resolved signals at <NUM> and <NUM> ppm. The <NUM> ppm integral is assigned to the unresolved signals corresponding to both 2B6 and <NUM> sites of <NUM>-octene and the saturated chain end respectively. The <NUM> ppm integral is assigned to the unresolved signals corresponding to both 3B6 and <NUM> sites of <NUM>-octene and the saturated chain end respectively. To compensate for the influence of the 2B6 and 3B6 <NUM>-octene sites the total <NUM>-octene content is used: <MAT>.

The ethylene comonomer content was quantified using the integral of the bulk methylene (bulk) signals at <NUM> ppm. This integral included the γ and 4B6 sites from <NUM>-octene as well as the δ+ sites. The total ethylene comonomer content was calculated based on the bulk integral and compensating for the observed <NUM>-octene sequences and end-groups: <MAT>.

It should be noted that compensation of the bulk integral for the presence of isolated tripleincorporation (EEOOOEE) <NUM>-octene sequences is not required as the number of under and over accounted ethylene units is equal.

The total mole fraction of <NUM>-octene in the polymer was then calculated as: <MAT>.

The total comonomer incorporation of <NUM>-octene in mol percent was calculated from the mole fraction in the standard manner: <MAT>.

The mole percent ethyelene incorporation was calculated from the formula: <MAT>.

Characteristic signals corresponding to the incorporation of <NUM>-butene were observed (<NPL>) and all comonomer contents calculated with respect to all other monomers present in the polymer.

Characteristic signals resulting from isolated <NUM>-butene incorporation i.e. EEBEE comonomer sequences, were observed. Isolated <NUM>-butene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the *B2 sites, accounting for the number of reporting sites per comonomer: <MAT>.

Characteristic signals resulting from double consecutive <NUM>-butene incorporation i.e. EEBBEE comonomer sequences were observed. Consecutive double <NUM>-butene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the aaB2B2 sites accounting for the number of reporting sites per comonomer: <MAT>.

Characteristic signals resulting from non consecutive <NUM>-butene incorporation i.e. EEBEBEE comonomer sequences were also observed. Non-consecutive <NUM>-butene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the ββB2B2 sites accounting for the number of reporting sites per comonomer: <MAT>.

Due to the overlap of the *B2 and *βB2B2 sites of isolated (EEBEE) and non-consecutivly incorporated (EEBEBEE) <NUM>-butene respectively the total amount of isolated <NUM>-butene incorporation is corrected based on the amount of non-consecutive <NUM>-butene present: <MAT>.

Characteristic signals resulting from triple consecutive <NUM>-butene incorporation i.e. EEBBBEE comonomer sequences were observed. Consecutive triple <NUM>-butene incorporation was quantified using the integral of the signal at <NUM> ppm assigned to the ααγB2B2B2 sites accounting for the number of reporting sites per comonomer: <MAT>.

With no other signals indicative of other comonomer sequences, i.e. butene chain initiation, observed the total <NUM>-butene comonomer content was calculated based solely on the amount of isolated (EEBEE), double consecutive (EEBBEE), non-consecutive (EEBEBEE) and triple consecutive (EEBBBEE) <NUM>-butene comonomer sequences: <MAT>.

Characteristic signals resulting from saturated end-groups were observed. The content of such saturated end-groups was quantified using the average of the integral of the signals at <NUM> and <NUM> ppm assigned to the <NUM> and <NUM> sites respectively: <MAT>.

The relative content of ethylene was quantified using the integral of the bulk methylene (δ+) signals at <NUM> ppm: <MAT>.

The total ethylene comonomer content was calculated based the bulk methylene signals and accounting for ethylene units present in other observed comonomer sequences or end-groups: <MAT>.

The total comonomer incorporation of <NUM>-butene in mole percent was calculated from the mole fraction in the usual manner: <MAT>.

Molecular weight averages (Mw, Mn), and the molecular weight distribution (MWD), i.e. the Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight), were determined by Gel Permeation.

Chromatography (GPC) according to ISO <NUM>-<NUM>:<NUM> and ASTM D <NUM>-<NUM>. A PolymerChar GPC instrument, equipped with infrared (IR) detector was used with <NUM> x Olexis and 1x Olexis Guard columns from Polymer Laboratories and <NUM>,<NUM>,<NUM>-trichlorobenzene (TCB, stabilized with <NUM>/L <NUM>,<NUM>-Di tert butyl-<NUM>-methyl-phenol) as solvent at <NUM> and at a constant flow rate of <NUM>/min. <NUM>µL of sample solution were injected per analysis. The column set was calibrated using universal calibration (according to ISO <NUM>-<NUM>:<NUM>) with at least <NUM> narrow MWD polystyrene (PS) standards in the range of <NUM>,<NUM>/mol to <NUM><NUM>/mol. Mark Houwink constants for PS, PE and PP used are as described per ASTM D <NUM>-<NUM>. All samples were prepared by dissolving <NUM> - <NUM> of polymer in <NUM> (at <NUM>) of stabilized TCB (same as mobile phase) for <NUM> hours for PP or <NUM> hours for PE at max. <NUM> under continuous gentle shaking in the autosampler of the GPC instrument.

DSC analysis: melting temperature (Tm), crystallization temperature (Tc): measured with a TA Instrument Q2000 differential scanning calorimeter (DSC) on <NUM> to <NUM> samples. DSC run according to ISO <NUM> / part <NUM> / method C2 in a heat / cool / heat cycle with a scan rate of <NUM>/min in the temperature range of - <NUM> to +<NUM>. Crystallization temperature was determined from the cooling step, while melting temperature was determined from the heating scan.

Intrinsic viscosity is measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>).

The xylene solubles (XCS, wt. -%): Content of xylene cold solubles (XCS) is determined at <NUM> according ISO <NUM>; first edition; <NUM>-<NUM>-<NUM>. The part which remains insoluble is the xylene cold insoluble (XCI) fraction.

Flexural Modulus: The flexural modulus was determined in <NUM>-point-bending according to ISO <NUM> on 80x10x4 or <NUM> or <NUM> test bars as indicated injection molded at <NUM> in line with EN ISO <NUM>-<NUM>. In case of non-foamed specimen 80x10x4 mm the test speed for modulus determination was <NUM>/s, while for specimen with dimensions of 80x10x3 or <NUM> the test speed was <NUM>/s.

Charpy notched impact test: The charpy notched impact strength (Charpy NIS) was measured according to ISO <NUM>2C / DIN <NUM> at +<NUM>, using injection molded bar test specimens of 80x10x4 mm prepared in accordance with ISO <NUM>-<NUM>:<NUM>.

Puncture energy and energy to maximum force were determined on plaques with dimensions 100x148x2 or <NUM> during instrumented falling weight impact testing according to ISO <NUM>-<NUM>. The test was performed at room temperature with a lubricated tip striker with a diameter of <NUM> and impact velocity of <NUM>/s. The deformation mechanism was classified according to ISO <NUM>-<NUM>: <NUM> - Chapter <NUM>: Calculations.

Mean square error (MSE) is a values which gives information about the surface homogeneity. The value was calculated according to a method described in detail in <CIT>, which is incorporated herein in its entirety. An optical measurement system, as described by <NPL> or <NPL>) was used for characterizing the surface quality.

The basic principle of the measurement system is to illuminate the plates with a defined light source (LED) in a closed environment and to record an image with a CCD-camera system.

The specimen is floodlit from one side and the upwards reflected portion of the light is deflected via two mirrors to a CCD-sensor. The created grey value image is analyzed in lines. From the recorded deviations of grey values the mean square error average (MSEaverage) or mean square error maximum (MSEmax) values are calculated allowing a quantification of surface quality/homogeneity, i.e. the higher the MSE value the more pronounced is the surface defect.

The MSEaverage values were collected on compact injection-moulded plaques 440x148x2. <NUM> produced with grain K50. The plaques were injection-moulded with filling times of <NUM> sec.

In case of foamed injection moulded plates a qualitative surface evaluation was done by collecting images from the surface of A5 plaques.

First, <NUM> mol of MgCl2 x <NUM> EtOH was suspended under inert conditions in <NUM> of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of -<NUM> and <NUM> of cold TiCl4 was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to <NUM>. At this temperature, <NUM> mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to <NUM> during <NUM> minutes and the slurry was allowed to stand for <NUM> minutes. Then, another <NUM> of TiCl4 was added and the temperature was kept at <NUM> for <NUM> minutes. After this, the catalyst was filtered from the liquid and washed six times with <NUM> heptane at <NUM>. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described in general e.g. in patent publications <CIT>, <CIT> and <CIT>.

The catalyst was further modified (VCH modification of the catalyst). <NUM> of mineral oil (Paraffinum Liquidum PL68) was added to a <NUM> stainless steel reactor followed by <NUM> of triethyl aluminum (TEAL) and <NUM> of dicyclopentyl dimethoxy silane (donor D) under inert conditions at room temperature. After <NUM> minutes <NUM> of the catalyst prepared above (Ti content <NUM> wt. -%) was added and after additionally <NUM> minutes <NUM> of vinylcyclohexane (VCH) was added. The temperature was increased to +<NUM> during <NUM> minutes and was kept there for <NUM> hours. Finally, the temperature was decreased to +<NUM> and the concentration of unreacted VCH in the oil/catalyst mixture was analysed and was found to be <NUM> ppm weight.

The catalyst for the preparation of HECO2 is the commercial catalyst ZN180M by Lyondell Basell used along with dicyclopentyl dimethoxy silane (donor D) as donor.

The aluminum to donor ratio, the aluminum to titanium ratio and the polymerization conditions are indicated in table <NUM>.

A Borstar PP pilot plant comprised of a stirred-tank prepolymerization reactor, a liquid-bulk loop reactor, and one, two or three gas phase reactors (GPR1 to GPR3) were used for the main polymerization. The resulting polymer powders were compounded in a co-rotating twin-screw extruder Coperion ZSK <NUM> at <NUM> with <NUM> wt. -% of Irganox B225 (<NUM>:<NUM>-blend of Irganox <NUM> (Pentaerythrityl-tetrakis(<NUM>-(<NUM>',<NUM>'-di-tert. butyl-<NUM>-hydroxytoluyl)-propionate and tris (<NUM>,<NUM>-di-t-<NUM> butylphenyl) phosphate) phosphite) of BASF AG, Germany) and <NUM> wt. -% calcium stearate.

Inventive examples IE1, IE2 and IE4 and comparative examples CE1, CE2 and CE3 and E4 HECO1, HECO2, HECO3, H-PP, PL, HDPE and inorganic filler were melt blended in a co-rotating twin screw extruder in amounts as indicated in Table <NUM>. The polymer melt mixture was discharged and pelletized.

Injection-moulding foaming was performed on an Engel E380 machine using <NUM> wt. - %, based on the total weight of the composition, chemical blowing agent masterbatch POLYTHLENE EE25C manufactured by EIWA CHEMICAL IND. , LTD, which comprises the foaming agent sodium hydrogen carbonate dispersed in a polyethylene matrix. The materials were foamed using core back technology from <NUM> starting thickness to <NUM> end thickness.

The inventive example IE1 shows that the addition of more than <NUM> wt. -% of HECO1 to a polyproyplene homopolymer helped to achieve puncture energy and energy to max force at high level on foamed parts which is not the case for the corresponding comparative example CE1. The same result was observed for the compositions IE2 and E4 further filled with inorganic filler.

Claim 1:
Foamable polypropylene composition (C) comprising
a) a heterophasic propylene copolymer (HECO1) having a melt flow rate MFR<NUM> (<NUM>, <NUM>) measured according to ISO <NUM> in the range from <NUM> to <NUM>/<NUM> and a xylene cold soluble (XCS) fraction determined at <NUM> according ISO <NUM> in the range of <NUM> to <NUM> wt.-% , said heterophasic propylene copolymer (HECO1) comprising
i) a matrix (M1) being a propylene polymer (PP1) and
ii) an elastomeric propylene copolymer (E1) being dispersed in said matrix,
b) a propylene homopolymer (H-PP),
c) optionally an inorganic filler (F), wherein the inorganic filler (F) is talc and/or carbon black, and
d) at least one foaming agent (FA) selected from chemical and physical foaming agents, whereby the composition (C) comprises:
i) <NUM> to <NUM> wt.-% of the heterophasic propylene copolymer (HECO1),
ii) <NUM> to <NUM> wt.-% of the propylene homopolymer (H-PP),
iii) <NUM> to <NUM> wt.-% of the inorganic filler (F), and
iv) <NUM> to <NUM> wt.-% of the foaming agent (FA),
based on the overall polypropylene composition (C).