Patent Description:
Polypropylene is used in many applications and is for instance the material of choice in many fields such as automotive applications because they can be tailored to specific purposes needed. However, the recent demand in plastic industry is towards weight reduction. Foaming of polymer compounds via injection-molding (FIM) technology is gaining wide interest both scientifically and industrially due to its capability to produce low-density parts with high geometrical accuracy and improved dimensional stability. With this technique, a product with a cellular core and solid skin can be molded in a single operation. Basically, FIM includes the use of an inert gas that is to be dispersed in the polymer melt or by pre-blending a resin with a chemical blowing (or foaming) agent which under heat releases inert gas. The gas bubbles then expand within the melt, filling the mould and creating the internal cellular structure. In injection molding of thermoplastics containing a blowing agent the mixture is held under sufficient back pressure to retain the gas and prevent premature expansion. Depending on the weight requirements, a specific amount of material is dosed and the melt is injected into the mold. The entrapped gas expands as soon as the melt/gas mixture enters the empty mould unless a sufficiently high enough counter pressure is applied. Achieving uniform and high-cell-density microstructure, which is critical for obtaining superior mechanical properties and excellent emissions in foamed plastics is challenging in FIM and can be controlled by process conditions. The influence of process conditions such as blowing agent content, mould temperature, melt temperature, injection pressure, and back pressure may be varied in order to produce high quality foam in terms of low skin thickness, small cell sizes, and narrow cell size distribution is well known. However, the influence of polymer design on the foamed structure and emissions has been rarely investigated so far.

<CIT> discloses a polypropylene composition that provides an excellent balance between mechanical properties, optical behaviour and low amounts of extractable substances combined with good retortability. <CIT> discloses polymeric compositions comprising a propylene-dominated copolymer component in intimate mixture with a soft thermoplastic blend component.

As a result, polypropylene compositions with excellent foamability are still desired. Furthermore, it is desired that these polypropylene compositions result in foamed parts having a fine cellular structure and at the same time keep good balance of mechanical properties.

The finding of the present invention is that a polypropylene composition having excellent foamability in combination with a good balance of mechanical properties of the foamed parts can be obtained with a combination of a specific heterophasic propylene copolymer and specific copolymer of propylene.

The present invention is directed to a polypropylene composition (C) comprising:.

The present invention is further directed to an injection molded article comprising the polypropylene composition (C).

The present invention is also directed to a foamed article, preferably foamed injection molded article, comprising the polypropylene composition (C).

The invention is finally also directed to the use of a copolymer (CP), preferably a random copolymer, of propylene and at least one comonomer selected from the group of C<NUM>-C<NUM> alpha- olefins that has been synthesized in the presence of a single-site catalyst in a composition comprising a heterophasic propylene copolymer for increasing the Charpy Notched Impact Strength and/or elongation at break of the composition without significantly reducing either the tensile or flexural modulus.

In the following, the invention is defined in more detail.

A propylene homopolymer is a polymer that essentially consists of propylene monomer units. Due to impurities especially during commercial polymerization processes, a propylene homopolymer can comprise up to <NUM> mol% comonomer units, preferably up to <NUM> mol% comonomer units and most preferably up to <NUM> mol% comonomer units.

A propylene random copolymer is a copolymer of propylene monomer units and comonomer units, preferably selected from ethylene and C4-C12 alpha-olefins, in which the comonomer units are distributed randomly over the polymeric chain. The propylene random copolymer can comprise comonomer units from one or more comonomers different in their amounts of carbon atoms. In the following amounts are given in % by weight (wt. -%) unless it is stated otherwise.

A heterophasic polypropylene is a propylene-based copolymer with a crystalline matrix phase, which can be a propylene homopolymer or a random copolymer of propylene and at least one alpha-olefin comonomer, and an elastomeric phase dispersed therein. In case of a random heterophasic propylene copolymer, said crystalline matrix phase is a random copolymer of propylene and at least one alpha-olefin comonomer.

The elastomeric phase can be a propylene copolymer with a high amount of comonomer that is not randomly distributed in the polymer chain but is distributed in a comonomer-rich block structure and a propylene-rich block structure. A heterophasic polypropylene usually differentiates from a monophasic propylene copolymer in that it shows two distinct glass transition temperatures Tg which are attributed to the matrix phase and the elastomeric phase.

The polypropylene composition (C) of the present invention comprises several essential components, including the heterophasic propylene copolymer (HECO) and the copolymer (CP), preferably random copolymer, of propylene. Accordingly, the propylene composition (C) comprises:.

In a preferred embodiment, the polypropylene composition (C) of the present invention comprises.

The polypropylene composition (C) of the present invention can comprise further components, in addition to the essential components as defined above. However, it is preferred that the individual contents of the heterophasic propylene copolymer (HECO), the copolymer (CP), preferably random copolymer, of propylene, and the optional filler (F) add up to at least <NUM> wt. -%, more preferably to at least <NUM> wt. -%, based on the total weight of the polypropylene composition (C).

Typical further polymeric components could be, for example, additives, the selection of which would be well-known to the skilled practitioner, and masterbatch polypropylenes, used to introduce the additives to the polypropylene composition (C).

Typically additives would be selected from antioxidants, anti-slip agents, nucleating agents, anti-scratch agents, anti-scorch agents, metal deactivators, UV-stabilisers, acid scavengers, lubricants, antistatic agents, pigments and the like, as well as combinations thereof. These additives are well known in the polymer industry and their use will be familiar to the skilled practitioner. Any additives which are present may be added as an isolated raw material or in a mixture with a carrier polymer, i.e. in a so-called master batch.

In one embodiment the polypropylene composition (C) of the present invention comprises:.

The content of heterophasic propylene copolymer (HECO) within the polypropylene composition (C) is from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, most preferably from <NUM> to <NUM> wt.

The content of copolymer (CP), preferably random copolymer, of propylene within the polypropylene composition (C) is from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, most preferably from <NUM> to <NUM> wt.

It is therefore preferred that the polypropylene composition (C) comprises:.

It is further preferred that the polypropylene composition (C) comprises:.

Preparing and further processing the polypropylene composition (C) includes mixing the individual components of the polypropylene composition (C), for instance by use of a conventional compounding or blending apparatus, e.g. a Banbury mixer, a <NUM>-roll rubber mill, Buss-co- kneader or a twin screw extruder. A typical extruding temperature is in the range of <NUM> to <NUM>, or more preferably in the range of <NUM> to <NUM>.

The polypropylene composition (C) of the present invention has a melt flow rate MFR<NUM> measured according to ISO <NUM> at <NUM> and <NUM> of from <NUM> to <NUM>/<NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>/<NUM>.

The polypropylene composition (C) of the present invention has a Charpy Notched Impact Strength NIS measured according to ISO <NUM>-1eA at <NUM> of greater than or equal to <NUM> kJ/m<NUM>, preferably of greater than or equal to <NUM> kJ/m<NUM>, more preferably of greater than or equal to <NUM> kJ/m<NUM>, most preferably of greater than or equal to <NUM> kJ/m<NUM>.

The polypropylene composition (C) of the present invention preferably has a tensile modulus measured according to ISO <NUM>-<NUM>,-<NUM> in the range from <NUM> to <NUM> MPa, more preferably in the range from <NUM> to <NUM> MPa, most preferably in the range from <NUM> to <NUM> MPa.

The polypropylene composition (C) of the present invention preferably has a flexural modulus measured according to ISO <NUM> in the range of <NUM> to <NUM> MPa, more preferably in the range from <NUM> to <NUM> MPa, most preferably in the range from <NUM> to <NUM> MPa.

The polypropylene composition (C) of the present invention preferably has a melting temperature (Tm) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>.

The polypropylene composition (C) of the present invention preferably has a crystallization temperature (Tc) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>.

The polypropylene composition (C) of the present invention preferably has a puncture energy measured according to ISO <NUM>-<NUM> at <NUM> in the range from <NUM> to <NUM> J, more preferably from <NUM> to <NUM> J, most preferably in the range from <NUM> to <NUM> J.

The polypropylene composition (C) of the present invention preferably has a puncture energy measured according to ISO <NUM>-<NUM> at -<NUM> in the range from <NUM> to <NUM> J, more preferably from <NUM> to <NUM> J, most preferably in the range from <NUM> to <NUM> J.

The polypropylene composition (C) of the present invention preferably has an elongation at break measured according to ISO <NUM> in the range from <NUM> to <NUM>%, more preferably from <NUM> to <NUM>%, most preferably in the range from <NUM> to <NUM>%.

The polypropylene composition (C) of the present invention preferably has a shrinkage in flow measured according to EN DIN ISO <NUM>-4of less than <NUM>%, more preferably of less than <NUM>%, most preferably of less than <NUM>%.

The polypropylene composition (C) of the present invention preferably has a shrinkage cross flow measured according to EN DIN ISO <NUM>-<NUM> of less than <NUM>%, more preferably of less than <NUM>%, most preferably of less than <NUM>%.

The heterophasic propylene copolymer (HECO) of the present invention preferably has a content of ethylene as determined from <NUM>C-NMR spectroscopy in the range from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, most preferably in the range from <NUM> to <NUM> wt.

The heterophasic propylene copolymer (HECO) of the present invention preferably has a melt flow rate MFR<NUM> measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, more preferably from <NUM> to <NUM>/<NUM>, most preferably in the range from <NUM> to <NUM>/<NUM>.

The heterophasic propylene copolymer (HECO) of the present invention preferably has a xylene cold soluble fraction (XCS) determined at <NUM> according to ISO <NUM> in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, most preferably in the range from <NUM> to <NUM> wt. -%, like in the range from <NUM> to <NUM> wt.

The heterophasic propylene copolymer (HECO) of the present invention preferably has an intrinsic viscosity (iV) of the xylene cold soluble fraction measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>) in the range from <NUM> to <NUM> dl/g, more preferably in the range from <NUM> to <NUM> dl/g, most preferably in the range from <NUM> to <NUM> dl/g, like in the range from <NUM> to <NUM> dl/g.

The heterophasic propylene copolymer (HECO) of the present invention preferably has a Charpy Notched Impact Strength NIS measured according to ISO <NUM>-<NUM> eA at <NUM> in the range of <NUM> to <NUM> kJ/m<NUM>, more preferably from <NUM> to <NUM> kJ/m<NUM>, most preferably in the range from <NUM> to <NUM> kJ/m<NUM>.

The heterophasic propylene copolymer (HECO) of the present invention preferably has a flexural modulus measured according to ISO <NUM> in the range of <NUM> to <NUM> MPa, more preferably from <NUM> to <NUM> MPa, most preferably in the range from <NUM> to <NUM> MPa.

According to a preferred embodiment, the heterophasic propylene copolymer (HECO) of the present invention has been polymerized using a heterogeneous Ziegler-Natta type catalyst system and/or has been polymerized in a multi-stage polymerization plant.

The copolymer (CP), preferably random copolymer, of the present invention is a copolymer of propylene and at least one comnomer selected from the group of C<NUM>-C<NUM> alpha olefins that has been synthesized in the presence of a single-site catalyst, preferably either a copolymer of propylene and <NUM>-butene or a copolymer of propylene and <NUM>-hexene that has been synthesized in the presence of a single-site catalyst.

The copolymer (CP), preferably random copolymer, of the present invention has a melt flow rate MFR<NUM> measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, more preferably from <NUM> to <NUM>/<NUM>, yet more preferably from <NUM> to <NUM>/<NUM>, most preferably from <NUM> to <NUM>/<NUM>.

The copolymer (CP), preferably random copolymer, of the present invention has a xylene cold soluble fraction (XCS) determined at <NUM> according to ISO <NUM> in the range from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, yet more preferably from <NUM> to <NUM> wt. -%, most preferably in the range from <NUM> to <NUM> wt.

The copolymer (CP), preferably random copolymer, of the present invention preferably has a melting temperature (Tm) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>.

The copolymer (CP), preferably random copolymer, of the present invention has a comonomer content of from <NUM> to <NUM> mol. -%, more preferably from <NUM> to <NUM> mol. -%, yet more preferably from <NUM> to <NUM> mol. -%, most preferably in the range from <NUM> to <NUM> mol.

According to one preferred embodiment, the copolymer (CP) of the present invention is a random copolymer of propylene and <NUM>-hexene, comprising.

wherein the copolymer (CP) has an overall <NUM>-hexene content in the range of <NUM> to <NUM> mol. -%, and wherein the copolymer (CP) has a xylene soluble content (XCS) in the range of <NUM> to <NUM> wt.

According to another preferred embodiment, the copolymer (CP) of the present invention is a random copolymer of propylene and <NUM>-butene, comprising.

wherein the copolymer (CP) has an MFR of <NUM> to <NUM>/<NUM> and a <NUM>-butene content of <NUM> to <NUM> mol. -%, and wherein copolymers (CP-A) and (CP-B) are different.

The copolymer (CP) is preferably a random copolymer of propylene, in particular obtainable, preferably obtained, by a process as defined in detail below.

The process for the preparation of a random copolymer (CP) of propylene present in the polypropylene composition (C) as defined above is a sequential polymerization process comprising at least two reactors connected in series, wherein said process comprises the steps of.

in the first reactor (R-<NUM>) and second reactor (R-<NUM>) the polymerization takes place in the presence of a solid catalyst system (SCS), said solid catalyst system (SCS) comprises.

Concerning the definition of the random copolymer (CP), the first random propylene copolymer (A) and the second random propylene copolymer (B) it is referred to the definitions given above.

The solid catalyst system (SCS) is defined in more detail below.

The term "sequential polymerization process" indicates that the random copolymer (CP) is produced in at least two reactors connected in series. More precisely the term "sequential polymerization process" indicates in the present application that the polymer of the first reactor (R-<NUM>) is directly conveyed with unreacted comonomers to the second reactor (R-<NUM>). Accordingly the decisive aspect of the present process is the preparation of the random copolymer (CP) in two different reactors, wherein the reaction material of the first reactor (R-<NUM>) is directly conveyed to the second reactor (R-<NUM>). Thus the present process comprises at least a first reactor (R-<NUM>) and a second reactor (R-<NUM>). In one specific embodiment the instant process consists of two polymerization reactors (R-<NUM>) and (R-<NUM>). The term "polymerization reactor" shall indicate that the main polymerization takes place there. Thus in case the process consists of two 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 "consists of" is only a closing formulation in view of the main polymerization reactors.

The first reactor (R-<NUM>) is a slurry reactor (SR) and can be any continuous or simple stirred batch tank reactor or loop reactor operating in slurry. According to the present invention the slurry reactor (SR) is preferably a loop reactor (LR).

The second reactor (R-<NUM>) and any subsequent reactor are gas phase reactors (GPR). Such gas phase reactors (GPR) can be any mechanically mixed or fluid bed reactors. Preferably the gas phase reactor(s) (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 (GPR) is a fluidized bed type reactor preferably with a mechanical stirrer.

The condition (temperature, pressure, reaction time, monomer feed) in each reactor is dependent on the desired product which is in the knowledge of a person skilled in the art. As already indicated above, the first reactor (R-<NUM>) is a slurry reactor (SR), like a loop reactor (LR), whereas the second reactor (R-<NUM>) is a gas phase reactor (GPR-<NUM>). The subsequent reactors - if present - are also gas phase reactors (GPR).

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> or in <CIT>.

Multimodal polymers can be produced according to several processes which are described, e.g. in <CIT>, <CIT>, and <CIT>. The contents of these documents are included herein by reference.

Preferably, in the instant process for producing the random copolymer (CP) as defined above the conditions for the first reactor (R-<NUM>), 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 (R-<NUM>), i.e. gas phase reactor (GPR-<NUM>), i.e. to step (D), whereby the conditions in step (D) are preferably as follows:.

The residence time can vary in both reactor zones.

In one embodiment of the process for producing the random copolymer (CP) the residence time in the slurry reactor (SR), e.g. loop (LR) is in the range <NUM> to <NUM> hours, e.g. <NUM> to <NUM> hours and the residence time in the gas phase reactor (GPR) will generally be <NUM> to <NUM> hours, like <NUM> to <NUM> hours.

If desired, the polymerization may be effected in a known manner under supercritical conditions in the first reactor (R-<NUM>), i.e. in the slurry reactor (SR), like in the loop reactor (LR).

The conditions in the other gas phase reactors (GPR), if present, are similar to the second reactor (R-<NUM>).

The present process may also encompass a pre-polymerization prior to the polymerization in the first reactor (R-<NUM>). The pre-polymerization can be conducted in the first reactor (R-<NUM>), however it is preferred that the pre-polymerization takes place in a separate reactor, so called pre-polymerization reactor.

The random copolymer (CP) according to the present invention is prepared in the presence of a solid catalyst system (SCS) comprising a transition metal compound.

In a preferred embodiment the transition metal compound has the formula (I).

Suitably, in each X as -CH<NUM>-Y, each Y is independently selected from C6-C20-aryl, NR"<NUM>, -SiR"<NUM> or - OSiR"<NUM>. Most preferably, X as -CH<NUM>-Y is benzyl. Each X other than -CH<NUM>-Y is independently halogen, C1-C20-alkyl, C1-C20-alkoxy, C6- C20-aryl, C7-C20-arylalkenyl or -NR"<NUM> as defined above, e.g. - N(C1-C20-alkyl)<NUM>.

Preferably, each X is halogen, methyl, phenyl or -CH<NUM>-Y, and each Y is independently as defined above.

Cp is preferably cyclopentadienyl, indenyl or fluorenyl, optionally substituted as defined above. Ideally Cp is cyclopentadienyl or indenyl.

In a suitable subgroup of the compounds of formula (I), each Cp independently bears <NUM>, <NUM>, <NUM> or <NUM> substituents as defined above, preferably <NUM>, <NUM> or <NUM>, such as <NUM> or <NUM> substituents, which are preferably selected from C1-C20-alkyl, C6- C20-aryl, C7-C20-aryialkyl (wherein the aryl ring alone or as a part of a further moiety may further be substituted as indicated above), -OSiR"<NUM>, wherein R" is as indicated above, preferably C1-C20-alkyl.

R, is preferably a methylene, ethylene or a silyl bridge, whereby the silyl can be substituted as defined above, e.g. a (dimethyl)Si=, (methylphenyl)Si=, (methylccylcohexyl)silyl= or (trimethylsilylmethyl)Si=; n is <NUM> or <NUM>. Preferably, R" is other than hydrogen.

A specific subgroup includes the well known metallocenes of Zr and Hf with two eta5-ligands which are bridged with cyclopentadienyl ligands optionally- substituted with e.g. siloxy, or alkyl (e.g. C1-<NUM>-alkyl) as defined above, or with two bridged indenyl ligands optionally substituted in any of the ring moieties with e.g. siloxy or alkyl as defined above, e.g. at <NUM>-, <NUM>-, <NUM>- and/or <NUM>-positions. Preferred bridges are ethylene or -SiMe<NUM>.

The preparation of the metallocenes can be carried out according or analogously to the methods known from the literature and is within skills of a person skilled in the field. Thus for the preparation see e.g. <CIT>, examples of compounds wherein the metal atom bears a -NR"<NUM> ligand see i. in <CIT> and <CIT>. For the preparation see also e.g. in <CIT>. <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

The complexes of the invention are preferably asymmetrical. That means simply that the two indenyl ligands forming the metallocene are different, that is, each indenyl ligand bears a set of substituents that are either chemically different, or located in different positions with respect to the other indenyl ligand. More precisely, they are chiral, racemic bridged bisindenyl metallocenes. Whilst the complexes of the invention may be in their syn configuration ideally, they are in their anti configuration. For the purpose of this invention, racemic-anti means that the two indenyl ligands are oriented in opposite directions with respect to the cyclopentadienyl-metal-cyclopentadienyl plane, while racemic-syn means that the two indenyl ligands are oriented in the same direction with respect to the cyclopentadienyl-metal-cyclopentadienyl plane.

Preferred complexes of the invention are of formula (II') or (II)
<CHM>
wherein.

Particularly preferred compounds of the invention include:.

The most preferred metallocene complex (procatalyst) is rac-anti-dimethylsilandiyl(<NUM>-methyl-<NUM>-phenyl-<NUM>-methoxy-<NUM>-tert-butyl-indenyl)(<NUM>-methyl-<NUM>-(<NUM>-tert-butylphenyl)indenyl)zirconium dichloride.

Besides the metallocene complex (procatalyst), the metallocene catalyst comprises additionally a cocatalyst as defined in <CIT>. Accordingly the preferred cocatalyst is methylaluminoxane (MAO) and/or a borate, preferably trityl tetrakis(pentafluorophenyl)borate.

It is especially preferred that the metallocene catalyst is unsupported, i.e. no external carrier is used. Regarding the preparation of such a metallocene complex again reference is made to <CIT>.

In addition, the polypropylene composition according to the present invention may comprise a mineral filler (F) in amounts from <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene composition.

Preferably, the polypropylene composition comprises the mineral filler (F) in amounts from <NUM> to <NUM> wt. -%, like in the range of <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene composition.

In one specific embodiment, the polypropylene composition is free of a mineral filler (F).

If present, the mineral filler (F) is preferably selected from mica, wollastonite, kaolinite, smectite, montmorillonite, talc and mixtures thereof.

In general, the mineral filler (F) may have a median particle size d<NUM> in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>.

A preferred filler (F) is talc. Preferably talc having a median particle size d<NUM> in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM> is used as filler (F). Most preferably, talc is used as the sole mineral filler (F). Still more preferably, the talc used has a top-cut particle size (<NUM>% of particles below that size, according to ISO <NUM>-<NUM>) of <NUM> to <NUM>, preferably from <NUM> to <NUM> and most preferably from <NUM> to <NUM>.

The present polypropylene composition (C) can be used in the production of articles such as molded articles, preferably injection molded articles. Furthermore, the present polypropylene composition can be used for the production of foamed articles such as foamed injection molded articles. Even more preferred is the use for the production of automotive articles, especially of automotive interior articles and exterior articles, like instrumental carriers, front end module, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like. Preferably, the article is an automotive interior article.

The present invention thus refers in another aspect to an injection molded article comprising the polypropylene composition as defined herein.

In a further aspect the present invetion refers to a foamed article, preferably foamed injection molded article comprising the polypropylene composition as defined herein.

It is preferred that the foamed article has.

It is especially preferred that the foamed article as described herein has a flexural modulus measured according to ISO <NUM> that is in the range of <NUM> to <NUM> MPa lower than the flexural modulus of an unfoamed injection-molded article measured according to ISO <NUM>.

The present invention is further directed to the use of a copolymer (CP), preferably a random copolymer, of propylene and at least one comonomer selected from the group of C<NUM>-C<NUM> alpha-olefins that has been synthesized in the presence of a single-site catalyst in a composition comprising a heterophasic propylene copolymer for increasing the Charpy Notched Impact Strength and/or elongation at break of the composition without degrading either the tensile or flexural modulus.

All preferred embodiments as described for the polypropylene composition (C), heterophaisc propylene copolymer (HECO) and copolymer (CP), preferably a random copolymer, of propylene may also be applied to the present articles and uses as described.

The present invention will now be illustrated by the examples provided below. The experimental data and examples shown below are understood by the skilled practitioner to be illustrative and do not further delimit the invention.

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

The xylene cold solubles (XCS, wt. -%) were determined at <NUM> according to ISO <NUM>; first edition; <NUM>-<NUM>-<NUM>.

Quantification of microstructure by NMR spectroscopy - Ethylene content in HECO Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content 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 WALTZ <NUM> 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>).

With characteristic signals corresponding to <NUM>,<NUM> erythro regio defects observed (as described in <NPL>, in <NPL>, and in <NPL>) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

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. Standard single-pulse excitation was employed utilising the NOE at short recycle delays of <NUM> (<NPL>. and the RS-HEPT decoupling scheme (<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. All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at <NUM> ppm.

Characteristic signals corresponding to the incorporation of <NUM>-hexene were observed and the comonomer content quantified in the following way.

The amount of <NUM>-hexene incorporated in PHP isolated sequences was quantified using the integral of the αB4 sites at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

The amount of <NUM>-hexene incorporated in PHHP double consecutive sequences was quantified using the integral of the ααB4 site at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

When double consecutive incorporation was observed the amount of <NUM>-hexene incorporated in PHP isolated sequences needed to be compensated due to the overlap of the signals αB4 and αB4B4 at <NUM> ppm: <MAT>.

The total <NUM>-hexene content was calculated based on the sum of isolated and consecutively incorporated <NUM>-hexene: <MAT>.

When no sites indicative of consecutive incorporation observed the total <NUM>-hexeen comonomer content was calculated solely on this quantity: <MAT>.

Characteristic signals indicative of regio <NUM>,<NUM>-erythro defects were observed (<NPL>).

The presence of <NUM>,<NUM>-erythro regio defects was indicated by the presence of the Pαβ (21e8) and Pαγ (21e6) methyl sites at <NUM> and <NUM> ppm and confirmed by other characteristic signals.

The total amount of secondary (<NUM>,<NUM>-erythro) inserted propene was quantified based on the αα21e9 methylene site at <NUM> ppm: <MAT>.

The total amount of primary (<NUM>,<NUM>) inserted propene was quantified based on the main Sαα methylene sites at <NUM> ppm and compensating for the relative amount of <NUM>,<NUM>-erythro, αB4 and ααB4B4 methylene unit of propene not accounted for (note H and HH count number of hexene monomers per sequence not the number of sequences): <MAT>.

The total amount of propene was quantified as the sum of primary (<NUM>,<NUM>) and secondary (<NUM>,<NUM>-erythro) inserted propene: <MAT>.

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

The full integral equation for the mole fraction of <NUM>-hexene in the polymer was: <MAT>.

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

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

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) probe head 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 {klimke06, parkinson07, castignolles09} Standard single-pulse excitation was employed utilising the NOE at short recycle delays {klimke06, pollard04} and the RS-HEPT decoupling scheme. {fillip05, griffin07} A total of <NUM> (<NUM>) transients were acquired per spectra using a <NUM> recycle delay.

Quantitative <NUM>C{<NUM>H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at <NUM> ppm {randall89}.

Basic comonomer content method spectral analysis method:
Characteristic signals corresponding to the incorporation of <NUM>-butene were observed {randall89} and the comonomer content quantified in the following way.

The amount of <NUM>-butene incorporated in PPBPP isolated sequences was quantified using the integral of the αB2 sites at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

The amount of <NUM>-butene incorporated in PPBBPP double consecutively sequences was quantified using the integral of the ααB2B2 site at <NUM> ppm accounting for the number of reporting sites per comonomer: <MAT>.

When double consecutive incorporation was observed the amount of <NUM>-butene incorporated in PPBPP isolated sequences needed to be compensated due to the overlap of the signals αB2 and αB2B2 at <NUM> ppm: <MAT>.

The total <NUM>-butene content was calculated based on the sum of isolated and consecutively incorporated <NUM>-butene: <MAT>.

The amount of propene was quantified based on the main Sαα methylene sites at <NUM> ppm and compensating for the relative amount of αB2 and αB2B2 methylene unit of propene not accounted for (note B and BB count number of butene monomers per sequence not the number of sequences): <MAT>.

The full integral equation for the mole fraction of <NUM>-butene in the polymer was: <MAT>.

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

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

Tensile Modulus and elongation at break were determined according to ISO <NUM>-<NUM> (cross head speed = <NUM>/min; test speed <NUM>/min at <NUM>) using dog-bone shape specimens machined from the injection molded or foam injection molded plaques as specified below.

Flexural Modulus was determined in <NUM>-point-bending according to ISO <NUM> on injection molded specimens of <NUM> x <NUM> x <NUM> resp. <NUM><NUM> machined from the injection molded or foam injection molded plaques as specified below.

Charpy Notched Impact Strength was determined according to ISO <NUM>-<NUM> eA at <NUM> on injection molded specimens of <NUM> x <NUM> x <NUM> resp. <NUM><NUM> machined from the injection molded or foam injection molded plaques as specified below.

Puncture energy and Energy to max Force were determined on plaques with dimensions <NUM> x <NUM> x <NUM> resp. <NUM><NUM> machined from the injection molded or foam injection molded plaques as specified below using an instrumented falling weight impact testing according to ISO <NUM>-<NUM>. The test was performed at room temperature with a lubricated tip with a diameter of <NUM> and impact velocity of <NUM>/s.

Particle size d<NUM> and top cut d<NUM> were calculated from the particle size distribution [mass percent] as determined by gravitational liquid sedimentation according to ISO <NUM>-<NUM> (Sedigraph).

DSC analysis, melting temperature (Tm) and crystallization temperature (Tc): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on <NUM> to <NUM> samples. DSC is 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 and heat of crystallization (Hc) are determined from the cooling step, while melting temperature and heat of fusion (Hf) are determined from the second heating step.

The shrinkage in flow and cross flow direction was determined according to EN DIN ISO <NUM>-<NUM> on injection molded plaques of 60x60x2 mm<NUM>. The plates had been molded on an Engel emotion <NUM>/<NUM> with a melt temperature of <NUM> and all other paramerers following ISO <NUM>-<NUM>. Shrinkage in flow and cross flow direction relative to the original mold dimension was determied after <NUM> hours at <NUM>.

The catalyst used in the inventive examples is prepared as described in detail in <CIT> (metallocene complex MC1 with methylaluminoxane (MAO) and borate resulting in Catalyst <NUM> described in <CIT>) with the proviso that the surfactant is <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoro-<NUM>-(<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptafluoropropoxy)-<NUM>-propanol. The metallocene complex (MC1 in <CIT>) is prepared as described in <CIT> (metallocene E2 in <CIT>).

The Polypropylene compositions (P) were prepared in a Borstar PP pilot unit with sequential process comprising a loop reactor and a gas phase reactor. The reaction conditions are summarized in Table <NUM>. Table <NUM> describes the recipes for compounding the comparative and inventive examples, whilst Tables <NUM> and <NUM> contain the properties of the comparative and inventive examples.

Injection-moulding of the presented compositions was performed on an Engel E380 machine. Firstly non-foamed injection moulded plaques with dimensions of 400x200x2 mm were prepared using conventional injection-moulding technology as described in the literature [<NPL>]. In a second step foaming injection-moulding was performed using the chemical blowing agent masterbatch POLYTHLENE EE25C manufactured by EIWA CHEMICAL IND. The materials were foamed using core back technology from <NUM> starting thickness to <NUM> end thickness. Foamed injection-moulded plates with dimensions of 400x200x3 mm were produced. Specimen for further characterization were prepared from the non-foamed and foamed plaques.

Claim 1:
A polypropylene composition (C) comprising:
i) from <NUM> to <NUM> wt.-%, based on the total weight of the composition, of a heterophasic propylene copolymer (HECO),
ii) from <NUM> to <NUM> wt.-%, based on the total weight of the composition, of a copolymer (CP) of propylene and at least one comonomer selected from the group of C<NUM>-C<NUM> alpha-olefins that has been synthesized in the presence of a single-site catalyst, wherein the copolymer (CP) has a comonomer content of from <NUM> to <NUM> mol.-%, a melt flow rate MFR<NUM> measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, and a xylene cold soluble fraction (XCS) determined at <NUM> according to ISO <NUM> in the range from <NUM> to <NUM> wt.-%,
wherein the polypropylene composition (C) has a melt flow rate MFR<NUM> measured according to ISO <NUM> at <NUM> and <NUM> of from <NUM> to <NUM>/<NUM>,
and wherein the polypropylene composition (C) has a Charpy Notched Impact Strength NIS measured according to ISO <NUM>-1eA at <NUM> of greater than or equal to <NUM> kJ/m<NUM>.