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 gains 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 were 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> refers to a nucleating composition comprising (a) a first nucleating agent, which comprises a cyclic dicarboxylate salt compound; and (b) a second nucleating agent, which comprises talc.

<CIT> refers to a polypropylene composition comprising (A) <NUM> to <NUM> wt% based on the total weight of the final polypropylene composition of a heterophasic polypropylene (HECO) comprising <NUM> to <NUM> wt% of dispersed phase based on the total weight of the HECO with the dispersed phase having a comonomer content of <NUM> to <NUM> wt% and the HECO having a melt flow rate MFRPP in the range of <NUM> to <NUM>/<NUM> and being prepared in the presence of a Ziegler Natta catalyst (ZN-C), (B) <NUM> to <NUM> wt% of one or more elastomers based on the total weight of the final polypropylene composition, (C) <NUM> to <NUM> wt% of at least one filler based on the total weight of the final polypropylene composition, wherein the polypropylene composition fulfils inequation (<NUM>) <MAT> with the dispersed phase being measured as xylene cold soluble (XCS) fraction at <NUM> according to ISO <NUM>, the comonomer content of the dispersed phase being measured with NMR, the MFRComp and the MFRPP being measured at <NUM> and at a load of <NUM> according to ISO <NUM> and the fogging being measured gravimetrically according to ISO <NUM>, method B.

<CIT> refers to a polypropylene composition (PC) comprising one or more polypropylenes (P), <NUM> to <NUM> wt. % based on the total weight of the polypropylene composition (PC) of one or more additives (A), whereby each of the additives (A) has a melting temperature determined by DSC of <NUM> or more; and the polypropylene composition (PC) is free from additives having a melting temperature determined by DSC below <NUM>.

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. It is also desired that the polypropylene compositions result in foamed parts having low volatile content.

The finding of the present invention is that a polypropylene composition having excellent foamability in combination with a fine cellular structure, a low volatile content and good balance of mechanical properties of the foamed parts can be obtained with a specific combination of a polypropylene homopolymer and polypropylene copolymer.

Therefore the present invention is directed to a polypropylene composition comprising.

According to one embodiment of the present invention, the composition comprises, preferably consists of, a) at most <NUM> wt. -%, based on the total weight of the composition, of the polypropylene homopolymer (HPP), b) from <NUM> to <NUM> wt. -%, based on the total weight of the composition, of a polypropylene copolymer (CPP), and c) from <NUM> to <NUM> wt. -%, based on the total weight of the composition, of at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilisers, acid scavengers, nucleating agents, foaming agents, antioxidants and mixtures thereof.

According to another embodiment of the present invention, the polyproyplene composition has a) a melt flow rate MFR<NUM> (<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>; and/or b) a content of volatile organic compounds no greater than <NUM>µg/g composition in pellet form; and/or c) a glass transition temperature Tg (measured with DMTA according to ISO <NUM>-<NUM>) of -<NUM> or above, preferably -<NUM> or above.

According to yet another embodiment of the present invention, the nucleating agent selected from <NUM>,<NUM>-cyclohexane dicarboxylic acid, hydroxybis(<NUM>,<NUM>,<NUM>,<NUM>-tetra-tert. butyl-<NUM>-hydroxy-<NUM>-dibenzo(d,g)(<NUM>,<NUM>,<NUM>)dioxaphosphocin <NUM>-oxidato)aluminium and mixtures thereof.

According to one embodiment of the present invention, the polypropylene homopolymer (HPP) has been polymerized in the presence of a Ziegler-Natta catalyst or a single-site catalyst.

According to another embodiment of the present invention, the polypropylene copolymer (CPP) has been polymerized in the presence of a Ziegler-Natta catalyst or a single-site catalyst.

According to yet another embodiment of the present invention, the polypropylene homopolymer (HPP) has i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, ii) a content of <NUM>,<NUM> erythro regiodefects as determined from <NUM>C-NMR spectroscopy in the range from <NUM> to <NUM> mol. -%, iii) an isotactic triad fraction (mm) determined from <NUM>C-NMR spectroscopy of at least <NUM> %, and iv) a xylene cold soluble fraction (XCS) determined at <NUM> according ISO <NUM> of equal or below <NUM> wt.

According to one embodiment of the present invention, the polypropylene homopolymer (HPP) has i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, and/or ii) a content of <NUM>,<NUM> erythro regiodefects as determined from <NUM>C-NMR spectroscopy of ≤ <NUM> mol. -%, and/or iii) an isotactic triad fraction (mm) determined from <NUM>C-NMR spectroscopy in the range from <NUM> to <NUM> %, and/or iv) a molecular weight distribution Mw/Mn measured according to ISO <NUM> in the range of ≥ <NUM>, and/or v) a xylene cold soluble fraction (XCS) determined at <NUM> according to ISO <NUM> in the range from <NUM> to <NUM> wt.

According to another embodiment of the present invention, the polypropylene copolymer (CPP) is a random copolymer of propylene with ethylene and/or C4 to C8 alpha-olefins, preferably propylene with ethylene or C4 or C6 alpha-olefins, most preferably ethylene or C6 alpha-olefins.

According to yet another embodiment of the present invention, the polypropylene copolymer (CPP) has i) a comonomer content in the range from <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene copolymer (CPP); and/or ii) a melt flow rate MFR<NUM> (<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, preferably in the range from <NUM> to <NUM>/<NUM>.

According to another aspect of the present invention, an injection molded article comprising the polypropylene composition as defined herein is provided.

According to one embodiment, the article has i) a flexural modulus measured according to ISO <NUM> of at least <NUM><NUM> MPa, preferably at least <NUM><NUM> Mpa; and/or ii) a puncture energy measured according to ISO <NUM>-<NUM> of at least <NUM> J, preferably at least <NUM> J.

According to a further aspect of the present invention, a foamed article, preferably foamed injection molded article, comprising the polypropylene composition as defined herein is provided.

According to a still further aspect, the use of a polypropylene composition as defined herein for reducing the stiffness reduction factor of a foamed injection molded article by at least <NUM> as determined by the difference of the flexural modulus measured according to ISO <NUM> of the non-foamed and foamed injection molded article is provided.

In the following the invention is defined in more detail.

The polypropylene (PP) composition according to this invention comprises.

In a preferred embodiment, the polypropylene composition according to this invention does not comprise (a) further polymer(s) different to the polymer present in the polypropylene (PP) composition, i.e. different to the polypropylene homopolymer (HPP) and the polypropylene copolymer (CPP). Typically, if an additional polymer is present, such a polymer is a carrier polymer for additives and thus does not contribute to the improved properties of the claimed polypropylene composition.

Accordingly in one embodiment the polypropylene composition consists of the polypropylene homopolymer (HPP), the polypropylene copolymer (CPP), the optional filler (F) and the at least one additive, which might contain in low amounts of polymeric carrier material. However, this polymeric carrier material is not more than <NUM> wt. -%, preferably not more than <NUM> wt. -%, based on the total weight of the polypropylene composition, present in said polypropylene composition.

In one embodiment, it is thus preferred that the polypropylene composition consists of.

Preferably, the polypropylene composition comprises, more preferably consists of,.

wherein the composition comprises from <NUM> to <NUM> wt. -%, based on the total weight of the composition, of one or more nucleating agents.

In one embodiment, the polypropylene composition comprises, preferably consists of,.

For example, the polypropylene composition comprises, preferably consists of,.

Alternatively, the polypropylene composition comprises, preferably consists of,.

Preferably the polypropylene composition has a melt flow rate MFR<NUM> (<NUM>, <NUM>) measured according to ISO <NUM> in the range from <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>, like in the range from <NUM> to <NUM>/<NUM>.

Additionally or alternatively, the polypropylene composition has a content of volatile organic compounds no greater than <NUM>µg/g composition in pellet form, preferably no greater than <NUM>µg/g composition in pellet form and most preferably no greater than <NUM>µg/g composition in pellet form.

Additionally or alternatively, the polypropylene composition has a glass transition temperature Tg (measured with DMTA according to ISO <NUM>-<NUM>) of -<NUM> or above, preferably -<NUM> or above and most preferably in the range from -<NUM> to +<NUM>.

In a preferred embodiment, the polypropylene composition has.

For example, the polypropylene composition has.

It is preferred that the polypropylene composition has a bimodal molecular structure.

It is appreciated that the polypropylene composition imparts an advantageous stiffness reduction factor to foamed injection molded articles. Preferably, the polypropylene composition imparts a stiffness reduction factor to a foamed injection molded article of ≤ <NUM>, more preferably ≤ <NUM> and most preferably ≤ <NUM>, such as in the range from <NUM> to <NUM>, as determined by the difference of the flexural modulus measured according to ISO <NUM> of the non-foamed and foamed injection molded article.

Thus, it is preferred that the stiffness reduction factor of a foamed injection molded article is reduced by at least <NUM> as determined by the difference of the flexural modulus measured according to ISO <NUM> of the non-foamed and foamed injection molded article and compared to an article prepared from a polypropylene composition comprising a polypropylene homopolymer as polymer material only.

The polypropylene composition according to the invention may be compounded and pelletized using any of the variety of compounding and blending machines and methods well known and commonly used in the resin compounding art.

For blending the individual components of the instant polypropylene composition a conventional compounding or blending apparatus, e.g. a Banbury mixer, a <NUM>-roll rubber mill, Buss-co-kneader or a twin screw extruder may be used. The polypropylene compositions recovered from the extruder/mixer are usually in the form of pellets. These pellets are then preferably further processed, e.g. by injection molding to generate articles and products of the inventive composition.

In the following, the individual components of the polypropylene composition are described in more detail.

The polypropylene composition must comprise a polypropylene homopolymer (HPP) in amounts of at most <NUM> wt. -%, e.g. from <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene composition. Preferably, the polypropylene composition comprises the polypropylene homopolymer (HPP) in amounts of at most <NUM> wt. -%, e.g. from <NUM> to <NUM> wt. -%, like in the range of <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene composition.

It is preferred that the polypropylene homopolymer (HPP) has a melt flow rate MFR<NUM> (<NUM>, <NUM>) measured according to ISO <NUM> in the range from <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>.

The polypropylene homopolymer (HPP) can be unimodal or multimodal, like bimodal. However, it is preferred that polypropylene homopolymer (HPP) is unimodal.

The expression "unimodal" as used herein refers to the modality of the polymer, i.e. the form of its molecular weight distribution curve, which is the graph of the molecular weight fraction as a function of its molecular weight.

When the polypropylene homopolymer (HPP) is unimodal with respect to the molecular weight distribution, it may be prepared in a single stage process e.g. as slurry or gas phase process in a slurry or gas phase reactor. Preferably, the unimodal polypropylene homopolymer (HPP) is polymerized in a slurry polymerization. Alternatively, the unimodal polypropylene homopolymer (HPP) may be produced in a multistage process using at each stage process conditions which result in similar polymer properties.

The term "polypropylene homopolymer (HPP)" used in the present invention relates to a polypropylene that consists substantially, i.e. of more than <NUM> wt. -% of, preferably of more than <NUM> wt. -%, even more preferably of more than <NUM> wt. -%, still more preferably of at least <NUM> wt. -%, of propylene units. In a preferred embodiment, only propylene units in the polypropylene homopolymer (HPP) are detectable.

It is appreciated that the polypropylene homopolymer (HPP) is a homopolymer being polymerized in the presence of a Ziegler-Natta catalyst or a single-site catalyst.

In one embodiment, the polypropylene homopolymer (HPP) has been polymerized in the presence of a single-site catalyst.

In this case, the polypropylene homopolymer (HPP) preferably has a xylene cold soluble (XCS) content of equal or below <NUM> wt. -%, based on the total weight of the polypropylene homopolymer (HPP). For example, the polypropylene homopolymer(HPP) has a xylene cold soluble (XCS) content in the range from <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene homopolymer (HPP).

It is further preferred that the polypropylene homopolymer (HPP) has a relatively high melting temperature Tm. More precisely, it is preferred that the polypropylene homopolymer (HPP) has a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>. For example, the polypropylene homopolymer (HPP) has a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM>.

The relatively high melting temperature Tm indicates that the polypropylene homopolymer (HPP) has a rather low content of regiodefects. It is preferred that the polypropylene homopolymer (HPP) has a content of <NUM>,<NUM> erythro regiodefects as determined from <NUM>C-NMR spectroscopy in the range from <NUM> to <NUM> mol. More preferably, the polypropylene homopolymer (HPP) has <NUM>,<NUM> erythro regiodefects in the range from <NUM> to <NUM> mol. -% and most preferably in the range from <NUM> to <NUM> mol. -%, determined by <NUM>C-NMR spectroscopy.

Additionally or alternatively, the polypropylene homopolymer (HPP) has an isotactic triad fraction (mm) determined from <NUM>C-NMR spectroscopy of at least <NUM> %. For example, the polypropylene homopolymer (HPP) has an isotactic triad fraction (mm) determined from <NUM>C- NMR spectroscopy of at least <NUM> %, more preferably of at least <NUM> %, like in the range from <NUM> to <NUM> %.

It is thus preferred that the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) which has been polymerized in the presence of a single-site catalyst, has.

For example, the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) which has been polymerized in the presence of a single-site catalyst, has.

Alternatively, the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) which has been polymerized in the presence of a single-site catalyst, has.

It is further preferred that the polypropylene homopolymer (HPP) has a weight average molecular weight (Mw) 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, and/or a number average molecular weight (Mn) of <NUM> to <NUM>/mol, more preferably <NUM> to <NUM>/mol, determined by GPC according to ISO <NUM>.

It is preferred that the polypropylene homopolymer (HPP) has a molecular weight distribution Mw/Mn measured according to ISO <NUM> of ≤ <NUM>, preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, and most preferably in the range from <NUM> to <NUM>.

Thus, in one embodiment the polypropylene homopolymer (HPP).

For example, the polypropylene homopolymer (HPP).

Alternatively, the polypropylene homopolymer (HPP).

The polypropylene homopolymer (HPP) is preferably produced by a single- or multistage process polymerization of propylene such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or combinations thereof. The polypropylene homopolymer (HPP) can be made either in loop reactors or in a combination of loop and gas phase reactor. Those processes are well known to one skilled in the art.

In one embodiment, the polypropylene homopolymer (HPP) is polymerized in the presence of a single-site catalyst.

It is preferred that the catalyst system includes a catalyst component according to formula (I)
<CHM>
wherein.

The catalyst system of the invention can be used in non-supported form or in solid form.

The catalyst system of the invention may be used as a homogeneous catalyst system or heterogeneous catalyst system.

The catalyst system of the invention in solid form, preferably in solid particulate form can be either supported on an external carrier material, like silica or alumina, or, in a particularly preferred embodiment, is free from an external carrier, however still being in solid form. For example, the solid catalyst system is obtainable by a process in which.

Particular complexes of the invention include:.

The catalysts have been described inter alia in <CIT> which is incorporated by reference herewith. A particularly preferred catalyst is catalyst number <NUM> of <CIT>. The preparation of the metallocenes has been described in <CIT> which is incorporated by reference herewith. The complex preparation of the particular preferred catalyst has been described as E2 in <CIT>.

For the avoidance of doubt, any narrower definition of a substituent offered above can be combined with any other broad or narrowed definition of any other substituent.

Throughout the disclosure above, where a narrower definition of a substituent is presented, that narrower definition is deemed disclosed in conjunction with all broader and narrower definitions of other substituents in the application.

The ligands required to form the complexes and hence catalysts/catalyst system of the invention can be synthesised by any process and the skilled organic chemist would be able to devise various synthetic protocols for the manufacture of the necessary ligand materials. For Example <CIT> discloses the necessary chemistry. Synthetic protocols can also generally be found in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. The examples section also provides the skilled person with sufficient direction.

As stated above a cocatalyst is not always required. However, when used, the cocatalyst system comprises a boron containing cocatalyst as well as an aluminoxane cocatalyst.

The aluminoxane cocatalyst can be one of formula (II):
<CHM>
where n is usually from <NUM> to <NUM> and R has the meaning below.

Aluminoxanes are formed on partial hydrolysis of organoaluminum compounds, for example those of the formula AlR<NUM>, AlR<NUM>Y and Al<NUM>R<NUM>Y<NUM> where R can be, for example, C<NUM>-C<NUM> alkyl, preferably C<NUM>-C<NUM> alkyl, or C<NUM>-C<NUM>-cycloalkyl, C<NUM>-C<NUM>-arylalkyl or alkylaryl and/or phenyl or naphthyl, and where Y can be hydrogen, halogen, preferably chlorine or bromine, or C<NUM>-C<NUM> alkoxy, preferably methoxy or ethoxy. The resulting oxygen-containing aluminoxanes are not in general pure compounds but mixtures of oligomers of the formula (II).

The preferred aluminoxane is methylaluminoxane (MAO). Since the aluminoxanes used according to the invention as cocatalysts are not, owing to their mode of preparation, pure compounds, the molarity of aluminoxane solutions hereinafter is based on their aluminium content.

According to the present invention the aluminoxane cocatalyst is used in combination with a boron containing cocatalyst, i.e. when a cocatalyst system or a cocatalyst is present, which is usually not required.

Boron based cocatalysts of interest include those of formula (III).

wherein Y independently is the same or can be different and is a hydrogen atom, an alkyl group of from <NUM> to about <NUM> carbon atoms, an aryl group of from <NUM> to about <NUM> carbon atoms, alkylaryl, arylalkyl, haloalkyl or haloaryl each having from <NUM> to <NUM> carbon atoms in the alkyl radical and from <NUM>-<NUM> carbon atoms in the aryl radical or fluorine, chlorine, bromine or iodine. Preferred examples for Y are methyl, propyl, isopropyl, isobutyl or trifluoromethyl, unsaturated groups such as aryl or haloaryl like phenyl, tolyl, benzyl groups, p-fluorophenyl, <NUM>,<NUM>- difluorophenyl, pentachlorophenyl, pentafluorophenyl, <NUM>,<NUM>,<NUM>-trifluorophenyl and <NUM>,<NUM>-di(trifluoromethyl)phenyl. Preferred options are trifluoroborane, triphenylborane, tris(<NUM>-fluorophenyl)borane, tris(<NUM>,<NUM>-difluorophenyl)borane, tris(<NUM>-fluoromethylphenyl)borane, tris(<NUM>,<NUM>,<NUM>-trifluorophenyl)borane, tris(penta-fluorophenyl)borane, tris(tolyl)borane, tris(<NUM>,<NUM>-dimethyl-phenyl)borane, tris(<NUM>,<NUM>-difluorophenyl)borane and/or tris (<NUM>,<NUM>,<NUM>-trifluorophenyl)borane.

Particular preference is given to tris(pentafluorophenyl)borane.

Borates can be used, i.e. compounds containing a borate <NUM>+ ion. Such ionic cocatalysts preferably contain a non-coordinating anion such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amine or aniline derivatives such as methylammonium, anilinium, dimethylammonium, diethylammonium, N- methylanilinium, diphenylammonium, N,N-dimethylanilinium, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridinium, p-bromo-N,N- dimethylanilinium or p-nitro-N,N-dimethylanilinium.

Preferred ionic compounds which can be used according to the present invention include:.

Preference is given to triphenylcarbeniumtetrakis(pentafluorophenyl) borate,.

Suitable amounts of cocatalyst will be well known to the skilled man.

The molar ratio of boron to the metal ion of the metallocene may be in the range <NUM>:<NUM> to <NUM>:<NUM> mol/mol, preferably <NUM>:<NUM> to <NUM>:<NUM>, especially <NUM>:<NUM> to <NUM>:<NUM> mol/mol.

The molar ratio of Al in the aluminoxane to the metal ion of the metallocene may be in the range <NUM>:<NUM> to <NUM>: <NUM> mol/mol, preferably <NUM>:<NUM> to <NUM>: <NUM>, and more preferably <NUM>:<NUM> to <NUM>:<NUM> mol/mol.

The catalyst of the invention can be used in supported or unsupported form. The particulate support material used is preferably an organic or inorganic material, such as silica, alumina or zirconia or a mixed oxide such as silica-alumina, in particular silica, alumina or silica-alumina. The use of a silica support is preferred. The skilled man is aware of the procedures required to support a metallocene catalyst.

Especially preferably the support is a porous material so that the complex may be loaded into the pores of the support, e.g. using a process analogous to those described in <CIT>, <CIT> and <CIT>. The particle size is not critical but is preferably in the range <NUM> to <NUM>, more preferably <NUM> to <NUM>. The use of these supports is routine in the art.

In an alternative embodiment, no support is used at all. Such a catalyst system can be prepared in solution, for example in an aromatic solvent like toluene, by contacting the metallocene (as a solid or as a solution) with the cocatalyst, for example methylaluminoxane previously dissolved in an aromatic solvent, or can be prepared by sequentially adding the dissolved catalyst components to the polymerization medium.

In one particularly preferred embodiment, no external carrier is used but the catalyst is still presented in solid particulate form. Thus, no external support material, such as inert organic or inorganic carrier, for example silica as described above is employed.

In order to provide the catalyst of the invention in solid form but without using an external carrier, it is preferred if a liquid/liquid emulsion system is used. The process involves forming dispersing catalyst components (i) and (ii) in a solvent, and solidifying said dispersed droplets to form solid particles.

In particular, the method involves preparing a solution of one or more catalyst components; dispersing said solution in an solvent to form an emulsion in which said one or more catalyst components are present in the droplets of the dispersed phase; immobilising the catalyst components in the dispersed droplets, in the absence of an external particulate porous support, to form solid particles comprising the said catalyst, and optionally recovering said particles.

This process enables the manufacture of active catalyst particles with improved morphology, e.g. with a predetermined spherical shape, surface properties and particle size and without using any added external porous support material, such as an inorganic oxide, e.g. silica. By the term "preparing a solution of one or more catalyst components" is meant that the catalyst forming compounds may be combined in one solution which is dispersed to the immiscible solvent, or, alternatively, at least two separate catalyst solutions for each part of the catalyst forming compounds may be prepared, which are then dispersed successively to the solvent. In a preferred method for forming the catalyst at least two separate solutions for each or part of said catalyst may be prepared, which are then dispersed successively to the immiscible solvent.

More preferably, a solution of the complex comprising the transition metal compound and the cocatalyst is combined with the solvent to form an emulsion wherein that inert solvent forms the continuous liquid phase and the solution comprising the catalyst components forms the dispersed phase (discontinuous phase) in the form of dispersed droplets. The droplets are then solidified to form solid catalyst particles, and the solid particles are separated from the liquid and optionally washed and/or dried. The solvent forming the continuous phase may be immiscible to the catalyst solution at least at the conditions (e. temperatures) used during the dispersing step.

The term "immiscible with the catalyst solution" means that the solvent (continuous phase) is fully immiscible or partly immiscible i.e. not fully miscible with the dispersed phase solution.

Preferably, said solvent is inert in relation to the compounds of the catalyst system to be produced. Full disclosure of the necessary process can be found in <CIT>.

The inert solvent must be chemically inert at least at the conditions (e.g. temperature) used during the dispersing step. Preferably, the solvent of said continuous phase does not contain dissolved therein any significant amounts of catalyst forming compounds. Thus, the solid particles of the catalyst are formed in the droplets from the compounds which originate from the dispersed phase (i.e. are provided to the emulsion in a solution dispersed into the continuous phase).

The terms "immobilisation" and "solidification" are used herein interchangeably for the same purpose, i.e. for forming free flowing solid catalyst particles in the absence of an external porous particulate carrier, such as silica. The solidification happens thus within the droplets. Said step can be effected in various ways as disclosed in said <CIT>. Preferably solidification is caused by an external stimulus to the emulsion system such as a temperature change to cause the solidification. Thus in said step the catalyst component(s) remain "fixed" within the formed solid particles. It is also possible that one or more of the catalyst components may take part in the solidification/immobilisation reaction.

Accordingly, solid, compositionally uniform particles having a predetermined particle size range can be obtained.

Furthermore, the particle size of the catalyst particles of the invention can be controlled by the size of the droplets in the solution, and spherical particles with a uniform particle size distribution can be obtained.

The process is also industrially advantageous, since it enables the preparation of the solid particles to be carried out as a one-pot procedure. Continuous or semicontinuous processes are also possible for producing the catalyst.

In the polymerization process according to the present invention fresh catalyst is preferably only introduced into the first reactor or, if present, into the prepolymerization reactor or vessel, i.e. no fresh catalyst is introduced into the second reactor or any further reactor being present upstream of the first reactor or upstream of the prepolymerization vessel. Fresh catalyst denotes the virgin catalyst species or the virgin catalyst species subjected to a prepolymerization.

Alternatively, the polypropylene homopolymer (HPP) has been polymerized in the presence of a Ziegler-Natta catalyst.

In this case, the polypropylene homopolymer (HPP) preferably has a xylene cold soluble (XCS) content in the range from <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene homopolymer (HPP).

It is further preferred that the polypropylene homopolymer (HPP) has a relatively high melting temperature Tm. For example, the polypropylene homopolymer (HPP) has a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM>.

The relatively high melting temperature Tm indicates that the polypropylene homopolymer (HPP) has a rather low content of regiodefects. It is preferred that the polypropylene homopolymer (HPP) has a content of <NUM>,<NUM> erythro regiodefects as determined from <NUM>C-NMR spectroscopy of ≤ <NUM> mol. -%, preferably of <NUM> mol. As well-known in the art, polypropylenes having such an amount of <NUM>,<NUM>-erythro regiodefects are preferably produced with a Ziegler-Natta catalyst.

Additionally or alternatively, the polypropylene homopolymer (HPP) has an isotactic triad fraction (mm) determined from <NUM>C-NMR spectroscopy in the range from <NUM> to <NUM> %.

It is preferred that the polypropylene homopolymer (HPP) has a weight average molecular weight (Mw) 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, and/or a number average molecular weight (Mn) of <NUM> to <NUM>/mol, more preferably <NUM> to <NUM>/mol, determined by GPC according to ISO <NUM>.

It is preferred that the polypropylene homopolymer (HPP) has a molecular weight distribution Mw/Mn measured according to ISO <NUM> of ≥ <NUM>, preferably in the range from <NUM> to <NUM>, and most preferably in the range from <NUM> to <NUM>.

Additionally or alternatively, the polypropylene homopolymer (HPP) has a density in the range from <NUM> to <NUM>/cm<NUM>.

Thus, in one embodiment the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP), which has been polymerized in the presence of a Ziegler-Natta catalyst, has.

For example, the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP), which has been polymerized in the presence of a Ziegler-Natta catalyst, has.

Alternatively, the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP), which has been polymerized in the presence of a Ziegler-Natta catalyst, has.

This polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) which has been polymerized in the presence of a Ziegler-Natta catalyst, is preferably produced by a single- or multistage process polymerization of propylene such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or combinations thereof. The polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) which has been polymerized in the presence of a Ziegler-Natta catalyst, can be made either in loop reactors or in a combination of loop and gas phase reactor. Those processes are well known to one skilled in the art.

It is appreciated that the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) which has been polymerized in the presence of a Ziegler-Natta catalyst, is preferably polymerized in the presence of a Ziegler-Natta catalyst, which are known to those skilled in the art.

It is a further requirement of the present invention that the polypropylene composition comprises a polypropylene copolymer (CPP) in an amount from <NUM> to <NUM> wt. -%, based on the total weight of the composition. The presence of the polypropylene copolymer (CPP) has the advantageous effect that it triggers the formation of finer cellular structures in foamed-injection molded plates in comparison to plates based on polypropylene homopolymers only.

Preferably, the polypropylene composition comprises the polypropylene copolymer (CPP) 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.

It is appreciated that the term "polypropylene copolymer (CPP)" encompasses propylene random copolymers, heterophasic propylene copolymers (HECO) and mixtures thereof.

As known for the skilled person, random propylene copolymer is different from heterophasic polypropylene which is a propylene copolymer comprising a propylene homo or random copolymer matrix component (<NUM>) and an elastomeric copolymer component (<NUM>) of propylene with one or more of ethylene and C<NUM>-C<NUM> alpha-olefin copolymers, wherein the elastomeric (amorphous) copolymer component (<NUM>) is dispersed in said propylene homo or random copolymer matrix polymer (<NUM>).

The term "random propylene copolymer" denotes a copolymer of propylene monomer units and comonomer units, in which the comonomer units are randomly distributed in the polymeric chain. Thus, a random copolymer is different from a heterophasic copolymer comprising a matrix phase and an elastomeric phase dispersed therein, as described in detail below. Accordingly, the random propylene copolymer (RCPP) does not contain an elastomeric polymer phase dispersed therein, i.e. is monophasic and has just one glass transition temperature. However, the random propylene copolymer (RCPP) can be the matrix phase of a heterophasic propylene copolymer (HECO). 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 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.

Preferably, the polypropylene copolymer (CPP) is a propylene random copolymer (RCPP).

Thus, the polypropylene copolymer (CPP) preferably comprises, preferably consists of, units derived from.

Accordingly, the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), may comprise units derived from propylene, ethylene and optionally at least another C4 to C8 alpha-olefin.

Alternatively, the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), comprises units derived from propylene, and C4 or C6 alpha-olefins. Preferably, the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), comprises units derived from propylene, and C6 alpha-olefin.

Preferably, the units derivable from propylene constitute the main part of the propylene copolymer (CPP), i.e. at least <NUM> wt. -%, more preferably of at least <NUM> wt. -%, still more preferably of <NUM> to <NUM> wt. -%, yet more preferably of <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP). Accordingly, the amount of units derived from ethylene and/or C4 to C8 alpha-olefins, i.e. other than propylene, in the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP) is in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, based on the total weight of the polypropylene copolymer (CPP), preferably the random propylene copolymer (RC-PP1).

Additionally, it is preferred that the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP) has a melting temperature Tm of at least <NUM>, preferably in the range of <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>, like in the range of <NUM> to <NUM>.

Concerning the melt flow rate MFR<NUM> (<NUM>), it is appreciated that the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP) preferably has a melt flow rate MFR<NUM> (<NUM>) measured according to ISO <NUM> in the range of <NUM> to <NUM>/<NUM>, preferably in the range from <NUM> to <NUM>/<NUM>.

It is preferred that the polypropylene copolymer (CPP) has been polymerized in the presence of a Ziegler-Natta catalyst or a single-site catalyst.

As regards the Ziegler-Natta catalyst, the single-site catalyst and preferred embodiments thereof, it is referred to the statements provided above when discussing the polypropylene homopolymer (HPP) in more detail.

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

Preferably, the polypropylene composition comprises the 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 filler (F).

Preferably, the filler (F) is a mineral filler (F).

If present, the filler (F) is selected from talcum, mica, wollastonite, glass fibers, carbon fibers and mixtures thereof
In general, the filler (F) may have a 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 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 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>.

It is required that the polypropylene composition comprises at least one additive in an amount ranging from <NUM> to <NUM> wt. -%, based on the total weight of the composition. The at least one additive is selected from the group consisting of colorants, pigments such as carbon black, stabilisers, acid scavengers, foaming agents, antioxidants and mixtures thereof.

It is to be noted that the term "at least one" additive in the meaning of the present invention means that the additive comprises one or more additives(s). In one embodiment, the additive is thus one additive. Alternatively, the additive comprises two or more, such as two or three, additives.

Preferably, the additive comprises two or more, such as two or three, additives.

The term "additive" covers also additives which are provided as a masterbatch containing the polymeric carrier material as discussed above.

It is appreciated that the polypropylene composition comprises a nucleating agent. Thus, the polypropylene composition comprises a nucleating agent and one or more further additives selected from colorants, pigments such as carbon black, stabilisers, acid scavengers, foaming agents, antioxidants and mixtures thereof.

For example, the polypropylene composition contains preferably a nucleating agent, more preferably an α-nucleating agent. Even more preferred the polypropylene composition according to the present invention is free of β-nucleating agents. Accordingly, the nucleating agent is preferably selected from the group consisting of.

Preferably, the α-nucleating agent is a nucleating agent selected from <NUM>,<NUM>-cyclohexane dicarboxylic acid, hydroxybis(<NUM>,<NUM>,<NUM>,<NUM>-tetra-tert. butyl-<NUM>-hydroxy-<NUM>-dibenzo(d,g)(<NUM>,<NUM>,<NUM>)dioxaphosphocin <NUM>-oxidato)aluminium and mixtures thereof. For example, commercially available α-nucleating agents, which can be used for the composition of the invention are, for example, Irgaclear XT <NUM> from Ciba Speciality Chemicals, Hyperform HPN-<NUM> and Hyperform HPN-20E from Milliken & Company and/or ADK STAB NA-<NUM> nucleating agent.

The polypropylene composition comprises from <NUM> to <NUM> wt. -%, based on the total weight of the composition, of the nucleating agent. Preferably, the polypropylene composition comprises from <NUM> to <NUM> wt. -%, based on the total weight of the composition, of a nucleating agent based on hydroxybis(<NUM>,<NUM>,<NUM>,<NUM>-tetra-tert. butyl-<NUM>-hydroxy-<NUM>-dibenzo(d,g)(<NUM>,<NUM>,<NUM>)dioxaphosphocin <NUM>-oxidato)aluminium.

Additionally or alternatively, the polypropylene composition comprises (a) foaming agent(s).

Throughout the present invention, the term "foaming agent" refers to an agent which is capable of producing a cellular structure in a polypropylene composition during foaming. Suitable foaming agents comprise e.g. bicarbonates, preferably bicarbonates and polyolefin carrier. Such foaming agents are commercially available, from e.g. EIWA CHEMICAL IND.

The polyproyplene composition of the present invention comprises the foaming agent preferably in an amount of less than <NUM> wt. -%, more preferably from <NUM> wt. -% to <NUM> wt. -% and most preferably from <NUM> wt. -% to <NUM> wt. -%, based on the total weight of the polypropylene composition. In a preferred embodiment, the polyproyplene composition of the present invention comprises the foaming agent in an amount of between <NUM> wt. -% and <NUM> wt. -%, based on the total weight of the polypropylene composition.

Generally, such additives are commercially available and are described, for example, in "Plastic Additives Handbook", 5th edition, <NUM> of Hans Zweifel.

In one preferred embodiment, the polypropylene composition comprises (a) nucleating agent(s) and (a) foaming agent(s) and optionally at least one additive selected from colorants, pigments such as carbon black, stabilisers, acid scavengers, antioxidants and mixtures thereof.

Preferably, the polypropylene composition comprises (a) nucleating agent(s) and (a) foaming agent(s) and at least one additive selected from colorants, pigments such as carbon black, stabilisers, acid scavengers, antioxidants and mixtures thereof.

The present polyproypylene composition can be used for the production of articles such as molded articles, preferably injection molded articles. Furthermore, the present polyproypylene 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 invention refers to a foamed article, preferably foamed injection molded article comprising the polypropylene composition as defined herein.

As already described above, the polypropylene composition, as defined herein, advantageously reduces the stiffness reduction factor of a foamed injection molded article.

Thus, the present invention refers in another aspect to the use of the polypropylene composition for reducing the stiffness reduction factor of a foamed injection molded article by at least <NUM> as determined by the difference of the flexural modulus measured according to ISO <NUM> of the non-foamed and foamed injection molded article. It is appreciated that the stiffness reduction factor is reduced compared to a foamed injection molded article being prepared from a polypropylene composition comprising the polypropylene homopolymer (HPP) only, i.e. the polypropylene composition is free of the polypropylene copolymer (CPP).

With regard to the polypropylene composition and preferred embodiments thereof, it is referred to the statements provided above when discussing the composition in more detail.

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

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>.

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

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 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.

Flexural Modulus was determined in <NUM>-point-bending according to ISO <NUM> on injection molded specimens of <NUM> x <NUM> x <NUM> prepared in accordance with ISO <NUM>-<NUM>:<NUM>.

Glass transition temperature Tg and storage modulus G' were determined by dynamic mechanical analysis (DMTA) according to ISO <NUM>-<NUM>. The measurements were done in torsion mode on compression moulded samples (40x10x1 mm3) between -<NUM> and +<NUM> with a heating rate of <NUM>/min and a frequency of <NUM>. While the Tg was determined from the curve of the loss angle (tan(δ)), the storage modulus (G') curve was used to determine the temperature for a G' of <NUM> MPa representing a measure for the heat deflection resistance.

Puncture energy and Energy to max Force were determined on plaques with dimensions 148x148x2 mm during instrumented falling weight impact testing according to ISO <NUM>-<NUM>. The test was performed at room temperature with a lubricated tup with a diameter of <NUM> and impact velocity of <NUM>/s.

Number average molecular weight (Mn) and weight average molecular weight (Mw) 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>-methylphenol) 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.

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.

Cell structure of the foamed parts was determined by light microscopy from a cross-section of the foamed injection-molded plate.

Volatile organic content (VOC) is measured according to VDA <NUM>, October <NUM>.

Total carbon emission was determined according to VDA <NUM>:<NUM> from pellets.

The metallocene (rac-anti-dimethylsilandiyl(<NUM>-methyl-<NUM>-phenyl-<NUM>-methoxy-<NUM>-tert-butylindenyl)(<NUM>-methyl-<NUM>-(<NUM>-tert-butylphenyl)indenyl)zirconium dichloride) has been synthesized as described in <CIT>. The metallocene containing catalyst was prepared using said metallocene and a catalyst system of MAO and trityl tetrakis(pentafluorophenyl)borate according to Catalyst <NUM> of <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 random propylene/<NUM>-hexene copolymer was produced in a multistage process with a prepolymerization reactor followed by one slurry loop reactor and one gas phase reactor. As catalyst the metallocene containing catalyst prepared as described above was used. The polymerization process conditions, the properties of the propylene polymer fractions and of the random propylene/<NUM>-hexene copolymers (C3C6-<NUM>) are shown in table <NUM>.

The polypropylene compositions were prepared by mixing in a co-rotating twin-screw extruder ZSK18 from Coperion with a typical screw configuration and a melt temperature in the range of <NUM>-<NUM>. The melt strands were solidified in a water bath followed by strand pelletization.

The mechanical characteristics of the inventive examples IE1, IE2 and IE3 and of comparative examples CE1 and CE2 are indicated in table <NUM> below.

Claim 1:
Polypropylene composition comprising
a) at most <NUM> wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP),
b) from <NUM> to <NUM> wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP),
c) from <NUM> to <NUM> wt.-%, based on the total weight of the composition, of a filler (F) which is selected from talcum, mica, wollastonite, glass fibers, carbon fibers and mixtures thereof, and
d) from <NUM> to <NUM> wt.-%, based on the total weight of the composition, of at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilisers, acid scavengers, foaming agents, antioxidants and mixtures thereof, and
wherein the composition comprises from <NUM> to <NUM> wt.-%, based on the total weight of the composition, of one or more nucleating agents,
wherein the sum of the amount of the polypropylene homopolymer (HPP), the polypropylene copolymer (CPP), the filler (F) and the at least one additive in the polypropylene composition is <NUM> wt.-%.