Foamable polypropylene composition

Abstract

The present invention relates to a polypropylene composition, an injection molded article comprising the polypropylene composition, a foamed article comprising the polypropylene composition and the use of the polypropylene composition for reducing the stiffness reduction factor of the foamed injection molded article by at least 200, the stiffness reduction factor is determined by the difference in flexural modulus of the unfoamed and foamed injection molded article measured according to ISO 178.

Description

[0001] This application is a divisional application of the patent application with application number 201980060904.4 filed on October 2, 2019 and invention name “Foamable Polypropylene Composition”. Technical Field

[0002] The present invention relates to a polypropylene composition, an injection-molded article comprising the polypropylene composition, a foamed article comprising the polypropylene composition and use of the polypropylene composition for reducing the stiffness reduction factor of a foamed injection-molded article by at least 200, the stiffness reduction factor being determined by the difference in flexural modulus measured according to ISO 178 between the unfoamed and foamed injection-molded article. Background Art

[0003] Polypropylene is used in many applications and is the material of choice in many areas, such as automotive applications, because it can be tailored to the specific purpose required. However, recent demand in the plastics industry is trending towards weight reduction. The foaming of polymer compounds via injection molding (FIM) technology has gained widespread attention in science and industry due to its ability to produce low-density parts with high geometric accuracy and improved dimensional stability. Using this technology, products with a porous core and solid skin can be molded in a single operation. Basically, FIM involves the use of an inert gas, which is dispersed in the polymer melt, or by pre-blending the resin with a chemical blowing (or foaming) agent that releases an inert gas when heated. The bubbles then expand in the melt, filling the mold and creating an internal porous structure. In injection molding of thermoplastic materials containing a blowing agent, the mixture is maintained under sufficient back pressure to confine the gas and prevent premature expansion. Depending on the weight requirement, a specific amount of material is added and the melt is injected into the mold. Unless a sufficiently high equilibrium pressure is applied, the trapped gas expands as soon as the melt / gas mixture enters the empty mold. Achieving a uniform, high-cell density microcellular structure in FIM—critical for achieving better mechanical properties and excellent emissions in foamed plastics—is challenging and can be controlled through process conditions. The effects of varying process conditions such as blowing agent content, mold temperature, melt temperature, injection pressure, and back pressure to produce high-quality bubbles with low skin thickness, small cell size, and a narrow cell size distribution are well known. However, the effects of polymer design on foam structure and emissions have been little studied to date.

[0004] As a result, there remains a need for polypropylene compositions having excellent foamability. Furthermore, it is desirable that these polypropylene compositions result in foamed parts having a fine porous structure while maintaining a good balance of mechanical properties. It is also desirable that polypropylene compositions result in foamed parts having a low volatile content. Summary of the Invention

[0005] The finding of the present invention is that with a specific combination of polypropylene homopolymer and polypropylene copolymer it is possible to obtain polypropylene compositions having excellent foamability combined with a fine cellular structure of the foamed part, a low volatile content and well-balanced mechanical properties.

[0006] Therefore, the present invention relates to a polypropylene composition comprising

[0007] a) 65 to 85 wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP),

[0008] b) 10 to 35 wt. % of a polypropylene copolymer (CPP), based on the total weight of the composition,

[0009] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0010] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive being selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof,

[0011] The total amount of the polypropylene homopolymer (HPP), the polypropylene copolymer (CPP), the filler (F) and the at least one additive in the polypropylene composition is 100.0 wt%.

[0012] According to one embodiment of the present invention, the composition comprises, preferably consists of, a) 65 to 75 wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP), b) 25 to 35 wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP), and c) 2.5 to 5 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, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants and mixtures thereof.

[0013] According to another embodiment of the present invention, the polypropylene composition has a) a melt flow rate MFR2 (230°C) measured according to ISO 1133 in the range of 15.0 to 80.0 g / 10 min; and / or b) a content of volatile organic compounds of not more than 150 μg / g of the composition in pellet form; and / or c) a glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of -10°C or more, preferably -5°C or more.

[0014] According to yet another embodiment of the present invention, the composition comprises 0.1 to 0.5 wt. % of one or more nucleating agents, preferably a nucleating agent selected from 1,2-cyclohexanedicarboxylic acid, bis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1,3,2)dioxaphosphocine 6-oxide)hydroxyaluminum, and mixtures thereof, based on the total weight of the composition.

[0015] According to one embodiment of the present invention the polypropylene homopolymer (HPP) is polymerized in the presence of a Ziegler-Natta catalyst or a single site catalyst.

[0016] According to another embodiment of the present invention the polypropylene copolymer (CPP) is polymerized in the presence of a Ziegler-Natta catalyst or a single site catalyst.

[0017] 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 of 150 to 160°C, ii) an amount of 13 2,1-erythro regio-defect content determined by C-NMR spectroscopy, iii) at least 97.5% of the 13 iv) a xylene cold soluble fraction (XCS) determined at 23° C. according to ISO 16152 equal to or lower than 1.5% by weight.

[0018] 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 of 162 to 170°C, and / or ii) ≤ 0.10 mol% of 13 iii) a content of 2,1-erythro regio defects determined by C-NMR spectroscopy, and / or iii) a content of 2,1-erythro regio defects in the range of 95.0 to 98.0% by 13 iv) a molecular weight distribution Mw / Mn measured in accordance with ISO 16014 in the range of ≥ 4.0, and / or v) a xylene cold soluble fraction (XCS) determined at 23° C. in accordance with ISO 16152 in the range of 1.5 to 3.5 wt.-%.

[0019] 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 α-olefins, preferably propylene with ethylene or C4 or C6 α-olefins, most preferably ethylene or C6 α-olefins.

[0020] According to yet another embodiment of the present invention, the polypropylene copolymer (CPP) has i) a comonomer content in the range of 2.0 to 6.0 wt.-%, preferably in the range of 2.0 to 4.0 wt.-%, based on the total weight of the polypropylene copolymer (CPP); and / or ii) a melt flow rate MFR2 (230°C) measured according to ISO 1133 in the range of 0.1 to 10.0 g / 10 min, preferably in the range of 0.7 to 8.0 g / 10 min.

[0021] According to another aspect of the present invention there is provided an injection moulded article comprising the polypropylene composition as defined herein.

[0022] According to one embodiment, the article has i) a flexural modulus measured according to ISO 178 of at least 1000 MPa, preferably at least 1300 MPa; and / or ii) a puncture energy measured according to ISO 6603-2 of at least 3.5 J, preferably at least 4.5 J.

[0023] According to a further aspect of the present invention there is provided a foamed article, preferably a foamed injection moulded article, comprising the polypropylene composition as defined herein.

[0024] According to a yet further aspect, there is provided the use of the polypropylene composition as defined herein for reducing the stiffness reduction factor of a foamed injection molded article by at least 200, the stiffness reduction factor being determined by the difference in flexural modulus measured according to ISO 178 of the unfoamed and foamed injection molded article. DETAILED DESCRIPTION

[0025] The present invention is defined in more detail hereinafter.

[0026] Polypropylene composition

[0027] The polypropylene (PP) composition according to the present invention comprises

[0028] a) 65 to 85 wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP),

[0029] b) 10 to 35 wt. % of a polypropylene copolymer (CPP), based on the total weight of the composition,

[0030] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0031] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive being selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof,

[0032] The total amount of the polypropylene homopolymer (HPP), the polypropylene copolymer (CPP), the filler (F) and the at least one additive in the polypropylene composition is 100.0 wt%.

[0033] In a preferred embodiment the polypropylene composition according to the present invention does not comprise (a) further polymers different from the polymers present in the polypropylene (pp) composition, i.e. different from the polypropylene homopolymer (HPP) and the polypropylene copolymer (CPP). Typically, if an additional polymer is present, this polymer is a carrier polymer for additives and thus does not contribute to the improved properties of the claimed polypropylene composition.

[0034] According to one embodiment, the polypropylene composition consists of a polypropylene homopolymer (HPP), a polypropylene copolymer (CPP), optionally a filler (F) and at least one additive, the polypropylene composition may contain a small amount of polymeric carrier material, however, the polymeric carrier material is present in the polypropylene composition in an amount of not more than 2.0 wt.-%, preferably not more than 1.6 wt.-%, based on the total weight of the polypropylene composition.

[0035] In one embodiment, it is therefore preferred that the polypropylene composition consists of

[0036] a) 65 to 85 wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP),

[0037] b) 10 to 35 wt. % of a polypropylene copolymer (CPP), based on the total weight of the composition,

[0038] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0039] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive being selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof,

[0040] The total amount of the polypropylene homopolymer (HPP), the polypropylene copolymer (CPP), the filler (F) and the at least one additive in the polypropylene composition is 100.0 wt%.

[0041] Preferably, the polypropylene composition comprises, preferably consists of,

[0042] a) 65 to 75 wt. % of a polypropylene homopolymer (HPP), based on the total weight of the composition,

[0043] b) 25 to 35 wt. % of a polypropylene copolymer (CPP), based on the total weight of the composition, and

[0044] c) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0045] In one embodiment, the polypropylene composition comprises, preferably consists of,

[0046] a) 65 to 85 wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP), the polypropylene homopolymer (HPP) being polymerized in the presence of a single-site catalyst,

[0047] b) 10 to 35 wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP), the polypropylene copolymer (CPP) being polymerized in the presence of a single-site catalyst or a Ziegler-Natta catalyst,

[0048] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0049] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0050] For example, the polypropylene composition comprises, preferably consists of,

[0051] a) 65 to 85 wt. % of a polypropylene homopolymer (HPP), based on the total weight of the composition, the polypropylene homopolymer (HPP) having

[0052] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 150 to 160° C.,

[0053] ii) in the range of 0.50 to 1.00 mol% of 13 The content of 2,1-erythro regiodefects was determined by C-NMR spectroscopy.

[0054] iii) At least 97.5% of 13 isotactic triad fraction (mm) determined by C-NMR spectroscopy, and

[0055] iv) a xylene cold soluble fraction (XCS), determined at 23° C. according to ISO 16152, equal to or lower than 1.5% by weight,

[0056] b) 10 to 35 wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP), the polypropylene copolymer (CPP) being polymerized in the presence of a Ziegler-Natta catalyst,

[0057] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0058] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0059] Optionally, the polypropylene composition comprises, preferably consists of,

[0060] a) 65 to 85 wt. % of a polypropylene homopolymer (HPP), based on the total weight of the composition, the polypropylene homopolymer (HPP) having

[0061] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 150 to 160° C.,

[0062] ii) in the range of 0.50 to 1.00 mol% of 13 The content of 2,1-erythro regiodefects was determined by C-NMR spectroscopy.

[0063] iii) At least 97.5% of 13 isotactic triad fraction (mm) determined by C-NMR spectroscopy, and

[0064] iv) a xylene cold soluble fraction (XCS), determined at 23° C. according to ISO 16152, equal to or lower than 1.5% by weight,

[0065] b) 10 to 35 wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP), the polypropylene copolymer (CPP) being polymerized in the presence of a single-site catalyst,

[0066] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0067] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0068] In one embodiment, the polypropylene composition comprises, preferably consists of,

[0069] a) 65 to 85 wt.-%, based on the total weight of the composition, of a polypropylene homopolymer (HPP), the polypropylene homopolymer (HPP) being polymerized in the presence of a Ziegler-Natta catalyst,

[0070] b) 10 to 35 wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP), the polypropylene copolymer (CPP) being polymerized in the presence of a Ziegler-Natta catalyst,

[0071] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0072] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0073] For example, the polypropylene composition comprises, preferably consists of,

[0074] a) 65 to 75 wt. % of a polypropylene homopolymer (HPP), based on the total weight of the composition, the polypropylene homopolymer (HPP) having

[0075] i) a melting temperature, Tm, measured by differential scanning calorimetry (DSC), in the range of 162 to 170°C, and

[0076] / or

[0077] ii) ≤ 0.10 mol% of 13 The content of 2,1-erythro regio defects as determined by C-NMR spectroscopy, and / or

[0078] iii) in the range of 95.0 to 98.0% by 13 isotactic triad fraction (mm) as determined by C-NMR spectroscopy, and / or

[0079] iv) a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range ≥ 4.0, and / or

[0080] v) a xylene cold soluble fraction (XCS), determined at 23° C. according to ISO 16152, in the range of 1.5 to 3.5% by weight,

[0081] b) 10 to 35 wt.-%, based on the total weight of the composition, of a polypropylene copolymer (CPP), the polypropylene copolymer (CPP) being polymerized in the presence of a Ziegler-Natta catalyst,

[0082] c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and

[0083] d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, the at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0084] Preferably, the polypropylene composition has a melt flow rate MFR2 (230°C, 2.16 kg) measured according to ISO 1133 in the range of 15.0 to 80.0 g / 10 min, more preferably in the range of 15.0 to 60 g / 10 min, like in the range of 15.0 to 40.0 g / 10 min.

[0085] Additionally or alternatively, the polypropylene composition has a content of volatile organic compounds of not more than 150 μg / g of the composition in granular form, preferably not more than 100 μg / g of the composition in granular form and most preferably not more than 30 μg / g of the composition in granular form.

[0086] Additionally or alternatively, the polypropylene composition has a glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of -10°C or more, preferably -5°C or more and most preferably in the range of -5 to +10°C.

[0087] In a preferred embodiment, the polypropylene composition has

[0088] a) a melt flow rate MFR2 (230°C, 2.16 kg) measured according to ISO 1133 in the range of 15.0 to 80.0 g / 10 min, more preferably in the range of 15.0 to 60 g / 10 min, such as in the range of 15.0 to 40.0 g / 10 min, and / or

[0089] b) a volatile organic compound content of no more than 150 μg / g of the composition in granular form, preferably no more than 100 μg / g of the composition in granular form and most preferably no more than 30 μg / g of the composition in granular form, and / or

[0090] c) a glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of -10°C or higher, preferably -5°C or higher and most preferably in the range of -5 to +10°C.

[0091] For example, a polypropylene composition having

[0092] a) a melt flow rate MFR2 (230°C, 2.16 kg) measured according to ISO 1133 in the range of 15.0 to 80.0 g / 10 min, more preferably in the range of 15.0 to 60 g / 10 min, such as in the range of 15.0 to 40.0 g / 10 min, or

[0093] b) a volatile organic compound content of no more than 150 μg / g of the composition in granular form, preferably no more than 100 μg / g of the composition in granular form and most preferably no more than 30 μg / g of the composition in granular form, or

[0094] c) a glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of -10°C or higher, preferably -5°C or higher and most preferably in the range of -5 to +10°C.

[0095] For example, a polypropylene composition having

[0096] a) a melt flow rate MFR2 (230°C, 2.16 kg) measured according to ISO 1133 in the range of 15.0 to 80.0 g / 10 min, more preferably in the range of 15.0 to 60 g / 10 min, such as in the range of 15.0 to 40.0 g / 10 min, and

[0097] b) a volatile organic compound content of no more than 150 μg / g of the composition in granular form, preferably no more than 100 μg / g of the composition in granular form and most preferably no more than 30 μg / g of the composition in granular form, and

[0098] c) a glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of -10°C or higher, preferably -5°C or higher and most preferably in the range of -5 to +10°C.

[0099] Preferably, the polypropylene composition has a bimodal molecular structure.

[0100] It will be appreciated that the polypropylene composition imparts a favorable stiffness reduction factor to the foamed injection molded article. Preferably, the polypropylene composition imparts a stiffness reduction factor of ≤600, more preferably ≤550 and most preferably ≤500, such as in the range of 200 to 500, to the foamed injection molded article, as determined by the difference in flexural modulus measured by ISO 178 of the unfoamed and foamed injection molded articles.

[0101] Thus, it is preferred that the stiffness reduction factor of the foamed injection moulded article, as determined by the difference in flexural modulus measured according to ISO 178 of the unfoamed and foamed injection moulded article and compared to an article made from a polypropylene composition comprising the polypropylene composition as the only polymer material, is reduced by at least 200.

[0102] The polypropylene composition according to the present invention may be compounded and pelletized using any of a variety of compounding and blending machines and methods well known and commonly used in the resin compounding art.

[0103] In order to blend each component of polypropylene composition of the present invention, conventional compounding or blending device can be used, for example Banbury mixer, two-roll rubber mill, Buchwell blending kneader or twin screw extruder.The polypropylene composition reclaimed from forcing machine / mixing machine is normally in particle form.Preferably further process these particles then, for example, by injection molding to produce goods and the product of composition of the present invention.

[0104] In the following, the individual components of the polypropylene composition are described in more detail.

[0105] Polypropylene homopolymer (HPP)

[0106] The polypropylene composition must comprise 65 to 85 wt.-% of polypropylene homopolymer (HPP), based on the total weight of the polypropylene composition. Preferably, the polypropylene composition comprises 65 to 75 wt.-%, such as in an amount within the range of 65 to 70 wt.-%, based on the total weight of the polypropylene composition.

[0107] It is preferred that the polypropylene homopolymer (HPP) has a melt flow rate MFR2 (230°C, 2.16 kg) measured according to ISO 1133 in the range of 15.0 to 100.0 g / 10 min, more preferably in the range of 25.0 to 90.0 g / 10 min.

[0108] The polypropylene homopolymer (HPP) can be unimodal or multimodal, like bimodal. However, it is preferred that the polypropylene homopolymer (HPP) is unimodal.

[0109] As used herein, the expression "unimodal" refers to the mode of a polymer, ie the morphology of its molecular weight distribution curve, which is a plot of the molecular weight fraction as a function of its molecular weight.

[0110] When the polypropylene homopolymer (HPP) is unimodal with respect to the molecular weight distribution, it can be produced using a single-stage process (e.g., a slurry or gas phase process in a slurry or gas phase reactor). Preferably, slurry polymerization is used to polymerize the unimodal polypropylene homopolymer (HPP). Alternatively, a multi-stage process is used to produce the unimodal polypropylene homopolymer (HPP), using process conditions that result in similar polymer properties in each stage.

[0111] The term "polypropylene homopolymer (HPP)" as used in the present invention relates to a polypropylene which consists essentially, i.e. consists of more than 98.0 wt.-%, preferably more than 99.0 wt.-%, even more preferably more than 99.5 wt.-%, still more preferably at least 99.8 wt.-% of propylene units. In a preferred embodiment, only propylene units are detectable in the polypropylene homopolymer (HPP).

[0112] It is to be understood that a polypropylene homopolymer (HPP) is a homopolymer polymerized in the presence of a Ziegler-Natta catalyst or a single site catalyst.

[0113] In one embodiment the polypropylene homopolymer (HPP) is polymerized in the presence of a single site catalyst.

[0114] In this case, the polypropylene homopolymer (HPP) preferably has a xylene cold soluble (XCS) content of equal to or below 1.5 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 of 0.1 to 1.5 wt.-%, preferably in the range of 0.1 to 0.4 wt.-%, based on the total weight of the polypropylene homopolymer (HPP).

[0115] It is further preferred that the polypropylene homopolymer (HPP) has a higher melting temperature T m More precisely, it is preferred that the polypropylene homopolymer (HPP) has a melting temperature T measured by differential scanning calorimetry (DSC) in the range of 150 to 160°C. m For example, the polypropylene homopolymer (HPP) has a melting temperature T measured by differential scanning calorimetry (DSC) in the range of 152 to 158°C, preferably in the range of 152 to 156°C. m .

[0116] Higher melting temperature T m It is indicated that the polypropylene homopolymer (HPP) has a lower regio defect content. Preferably, the polypropylene homopolymer (HPP) has a regio defect content in the range of 0.50 to 1.00 mol%. 13 More preferably, the polypropylene homopolymer (HPP) has a content of 2,1-erythro regio defects in the range of 0.55 to 0.80 mol % and most preferably in the range of 0.60 to 0.80 mol %. 13 2,1-erythro regiodefects determined by C-NMR spectroscopy.

[0117] Additionally or alternatively, the polypropylene homopolymer (HPP) has at least 97.5% 13 For example, polypropylene homopolymer (HPP) has at least 98.5%, more preferably at least 99.0%, such as in the range of 99.0 to 99.5%, of isotactic triad fraction (mm) determined by C-NMR spectroscopy. 13 Isotactic triad fraction (mm) determined by C-NMR spectroscopy.

[0118] It is therefore preferred that the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) polymerized in the presence of a single-site catalyst has

[0119] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 150 to 160°C, preferably in the range of 152 to 158°C and most preferably in the range of 152 to 156°C, and / or

[0120] ii) in the range of 0.50 to 1.00 mol %, preferably in the range of 0.55 to 0.80 mol % and most preferably in the range of 0.60 to 0.80 mol % of 13 The content of 2,1-erythro regio defects as determined by C-NMR spectroscopy, and / or

[0121] iii) at least 97.5%, preferably at least 98.5%, more preferably at least 99.0%, such as in the range of 99.0 to 99.5% of 13 isotactic triad fraction (mm) as determined by C-NMR spectroscopy, and / or

[0122] iv) a xylene cold soluble fraction (XCS), determined according to ISO 16152 at 23°C, equal to or lower than 1.5 wt.-%, preferably in the range of 0.1 to 1.5 wt.-% and most preferably in the range of 0.1 to 1.4 wt.-%.

[0123] For example, polypropylene homopolymer (HPP), i.e. polypropylene homopolymer (HPP) polymerized in the presence of a single-site catalyst, has

[0124] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 150 to 160°C, preferably in the range of 152 to 158°C and most preferably in the range of 152 to 156°C, or

[0125] ii) in the range of 0.50 to 1.00 mol %, preferably in the range of 0.55 to 0.80 mol % and most preferably in the range of 0.60 to 0.80 mol % of 13 The content of 2,1-erythro regiodefects determined by C-NMR spectroscopy, or

[0126] iii) at least 97.5%, preferably at least 98.5%, more preferably at least 99.0%, such as in the range of 99.0 to 99.5% of 13 Isotactic triad fraction (mm) as determined by C-NMR spectroscopy, or

[0127] iv) a xylene cold soluble fraction (XCS), determined according to ISO 16152 at 23°C, equal to or lower than 1.5 wt.-%, preferably in the range of 0.1 to 1.5 wt.-% and most preferably in the range of 0.1 to 1.4 wt.-%.

[0128] Alternatively, the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) polymerized in the presence of a single-site catalyst, has

[0129] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 150 to 160°C, preferably in the range of 152 to 158°C and most preferably in the range of 152 to 156°C, and

[0130] ii) in the range of 0.50 to 1.00 mol %, preferably in the range of 0.55 to 0.80 mol % and most preferably in the range of 0.60 to 0.80 mol % of 13 The content of 2,1-erythro regiodefects determined by C-NMR spectroscopy, and

[0131] iii) at least 97.5%, preferably at least 98.5%, more preferably at least 99.0%, such as in the range of 99.0 to 99.5% of 13 isotactic triad fraction (mm) determined by C-NMR spectroscopy, and

[0132] iv) a xylene cold soluble fraction (XCS), determined according to ISO 16152 at 23°C, equal to or lower than 1.5 wt.-%, preferably in the range of 0.1 to 1.5 wt.-% and most preferably in the range of 0.1 to 1.4 wt.-%.

[0133] It is further preferred that the polypropylene homopolymer (HPP) has a weight average molecular weight (Mw) in the range of 80 to 500 kg / mol, preferably in the range of 100 to 400 kg / mol, more preferably in the range of 120 to 350 kg / mol, and / or a number average molecular weight (Mn) of 20 to 200 kg / mol, more preferably 50 to 150 kg / mol (determined by GPC according to ISO 16014).

[0134] It is preferred that the polypropylene homopolymer (HPP) has a molecular weight distribution Mw / Mn measured according to ISO 16014 of ≤ 4.0, preferably in the range of 1.5 to 4.0, more preferably in the range of 2.0 to 4.0 and most preferably in the range of 2.5 to 4.0.

[0135] Thus, in one embodiment, the polypropylene homopolymer (HPP)

[0136] i) is unimodal, and / or

[0137] ii) having a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range of ≤ 4.0, preferably in the range of 2.0 to 4.0 and more preferably in the range of 2.5 to 4.0.

[0138] For example, polypropylene homopolymer (HPP)

[0139] i) is unimodal, or

[0140] ii) having a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range of ≤ 4.0, preferably in the range of 2.0 to 4.0 and more preferably in the range of 2.5 to 4.0.

[0141] Alternatively, polypropylene homopolymer (HPP)

[0142] i) is unimodal, and

[0143] ii) having a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range of ≤ 4.0, preferably in the range of 2.0 to 4.0 and more preferably in the range of 2.5 to 4.0.

[0144] Polypropylene homopolymer (HPP) is preferably produced by a single-stage or multi-stage polymerization of propylene (such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or a combination thereof). Polypropylene homopolymer (HPP) can be produced in a loop reactor or a combination of a loop and a gas phase reactor. These methods are well known to a person skilled in the art.

[0145] In one embodiment the polypropylene homopolymer (HPP) is polymerized in the presence of a single site catalyst.

[0146] Preferably, the catalyst system comprises a catalyst component according to formula (I)

[0147]

[0148] in

[0149] M is zirconium or hafnium;

[0150] Each X is independently a σ-donor ligand;

[0151] L is the formula -(ER 10 2) y -'s bridge;

[0152] y is 1 or 2;

[0153] E is C or Si;

[0154] Each R10 C1 to C 20 -hydrocarbyl group, tri(C1 to C 20 Alkyl) silanyl group, C6 to C 20 Aryl group, C7 to C 20 Aralkyl group or C7 to C 20 an alkaryl group, or L is an alkylene group such as methylene or ethylene;

[0155] R 1 are independently the same or different from each other and are CH2-R 11 Group, R 11 is H or a linear or branched C1 to C6 alkyl group, a C3 to C8 cycloalkyl group, a C6 to C 10 aryl groups;

[0156] R 3 、R 4 and R 5 are independently the same or different from each other and are H or a linear or branched C1 to C6 alkyl group, a C7 to C 20 Aralkyl groups, C7 to C 20 Alkaryl group or C6 to C 20 Aryl groups, provided there are a total of four or more R 3 、R 4 and R 5 Group, R 3 、R 4 and R 5 One or more of is not tert-butyl;

[0157] R 7 and R 8 are independently the same or different from each other and are H, CH2-R 12 Group, R 12 is H or a linear or branched C1 to C6 alkyl group, SiR 13 3.GeR 13 3. OR 13 SR 13 NR 13 2,

[0158] in

[0159] R 13 is a linear or branched C1 to C6 alkyl group, a C7 to C 20 Alkaryl groups and C7 to C 20 Aralkyl group or C6 to C 20 Aryl group.

[0160] The catalyst system may also include

[0161] (ii) a cocatalyst system comprising a boron-containing cocatalyst and an aluminoxane cocatalyst;

[0162] It should be emphasized that, in some cases, the use of such a co-catalyst may not be necessary. The catalyst system of the present invention can be used in an unsupported form or a solid form. The catalyst system of the present invention can be used as a homogeneous catalyst system or a heterogeneous catalyst system.

[0163] The catalyst system of the present invention in solid form, preferably in the form of solid particles, can be supported on an external support material, such as silica or alumina, or, in a particularly preferred embodiment, without an external support, while still being in solid form. For example, the solid catalyst system can be obtained by the following process, wherein

[0164] (a) forming a liquid / liquid emulsion system comprising a solution of catalyst components (i) and (ii), the catalyst components (i) and (ii) being dispersed in a solvent to form dispersed droplets; and

[0165] (b) forming solid particles by solidifying the dispersed droplets.

[0166] Specific complexes of the present invention include:

[0167] Racemic-trans-dimethylsilylene[2-methyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0168] Racemic-trans-dimethylsilylene[2-isobutyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0169] Racemic-trans-dimethylsilylene[2-neopentyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0170] Racemic-trans-dimethylsilylene[2-benzyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0171] Racemic-trans-dimethylsilylene[2-cyclohexylmethyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0172] Racemic-trans-dimethylsilylene[2-methyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacene-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0173] Racemic-trans-dimethylsilylene[2-isobutyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0174] Racemic-trans-dimethylsilylene[2-neopentyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacene-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

[0175] Racemic-trans-dimethylsilylene[2-benzyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl, and

[0176] Racemic-trans-dimethylsilylene[2-cyclohexylmethyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacene-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl.

[0177] The catalyst is described in particular in WO 2015 / 011135, which is incorporated herein by reference. A particularly preferred catalyst is catalyst No. 3 of WO 2015 / 011135. The preparation of metallocenes is described in WO 2013 / 007650, which is incorporated herein by reference. The complex preparation of a particularly preferred catalyst is described as E2 in WO 2013 / 007650.

[0178] For the avoidance of doubt, any narrow definition of a substituent provided above may be combined with any other broad or narrow definition of any other substituent.

[0179] Throughout the above disclosure, where a narrow definition of a substituent is given, that narrow definition is considered disclosed together with all broad and narrow definitions of other substituents in this application.

[0180] The ligands required to form the complex and thus the catalyst / catalyst system of the present invention can be synthesized by any method, and experienced organic chemists can devise various synthetic schemes to produce the necessary ligand materials. For example, WO2007 / 116034 discloses the necessary chemical substances. Synthetic schemes can also be found in WO2002 / 02576, WO2011 / 135004, WO2012 / 084961, WO2012 / 001052, WO2011 / 076780 and WO2015 / 158790. The Examples section also provides sufficient guidance for the skilled artisan.

[0181] As mentioned above, a cocatalyst is not always necessary. However, when used, cocatalysts include boron-containing cocatalysts and aluminoxane cocatalysts.

[0182] The aluminoxane cocatalyst may be one of formula (II):

[0183]

[0184] wherein n is generally 6 to 20 and R has the following meanings.

[0185] Aluminoxanes are formed by partial hydrolysis of organoaluminum compounds such as those of the formula AlR3, AlR2Y, and Al2R3Y3, wherein R can be, for example, C1 to C 10 Alkyl (preferably C1 to C5 alkyl) or C3 to C 10 Cycloalkyl, C7 to C 12 - aralkyl or alkaryl and / or phenyl or naphthyl, and wherein Y can be hydrogen, halogen (preferably chlorine or bromine) or C1 to C 10 The alkoxy group is preferably a methoxy group or an ethoxy group. The oxygen-containing aluminoxane obtained is usually not a pure compound but a mixture of oligomers of formula (II).

[0186] The preferred aluminoxane is methylaluminoxane (MAO).Since the aluminoxanes used according to the invention as cocatalysts are not pure compounds due to the way they are prepared, the molar concentrations of the aluminoxane solutions hereinafter are based on their aluminum content.

[0187] According to the present invention, the aluminoxane cocatalyst is used in combination with a boron-containing cocatalyst, ie, when a cocatalyst system or cocatalyst is present, the aluminoxane cocatalyst is generally not necessary.

[0188] Boron-based cocatalysts of interest include those of formula (III)

[0189] BY3(III)

[0190] wherein Y is independently the same or different and is a hydrogen atom, an alkyl group containing 1 to about 20 carbon atoms, an aryl group containing 6 to about 15 carbon atoms, an alkaryl group, an aralkyl group, a haloalkyl group or a haloaryl group, each of which has 1 to 10 carbon atoms in the alkyl group and 6 to 20 carbon atoms in the aryl group or each of which has fluorine, chlorine, bromine or iodine. Preferred examples of Y are methyl, propyl, isopropyl, isobutyl or trifluoromethyl, unsaturated groups such as aryl or haloaryl groups, for example, phenyl, tolyl, a benzyl group, p-fluorophenyl, 3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl, 3,4,5-trifluorophenyl and 3,5-bis(trifluoromethyl)phenyl. Preferred options are trifluoroborane, triphenylborane, tri(4-fluorophenyl)borane, tri(3,5-difluorophenyl)borane, tri(4-fluoromethylphenyl)borane, tri(2,4,6-trifluorophenyl)borane, tri(pentafluorophenyl)borane, tri(tolyl)borane, tri(3,5-dimethyl-phenyl)borane, tri(3,5-difluorophenyl)borane and / or tri(3,4,5-trifluorophenyl)borane.

[0191] Tris(pentafluorophenyl)borane is particularly preferred.

[0192] Borates, i.e. compounds containing borate ions, can be used. Such ionic promoters preferably contain non-coordinating anions, such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amines or aniline derivatives, such as methylammonium, aniline, dimethylammonium, diethylammonium, N-methylaniline, diphenylammonium, N,N-dimethylaniline, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridinium, p-bromo-N,N-dimethylaniline or p-nitro-N,N-dimethylaniline.

[0193] Preferred ionic compounds that can be used according to the present invention include:

[0194] triethylammonium tetra(phenyl)borate,

[0195] Tributylammonium tetra(phenyl)borate,

[0196] trimethylammonium tetra(tolyl)borate,

[0197] Tributylammonium tetra(tolyl)borate,

[0198] Tributylammonium tetrakis(pentafluorophenyl)borate,

[0199] Tripropylammonium tetrakis(dimethylphenyl)borate,

[0200] Tributylammonium tetrakis(trifluoromethylphenyl)borate,

[0201] Tributylammonium tetrakis(4-fluorophenyl)borate,

[0202] N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate,

[0203] N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate,

[0204] N,N-dimethylanilinium tetra(phenyl)borate,

[0205] N,N-diethylanilinium tetra(phenyl)borate,

[0206] N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,

[0207] N,N-di(propyl)ammonium tetrakis(pentafluorophenyl)borate,

[0208] Di(cyclohexyl)ammonium tetrakis(pentafluorophenyl)borate,

[0209] triphenylphosphonium tetrakis(phenyl)borate,

[0210] triethylphosphonium tetrakis(phenyl)borate,

[0211] Diphenylphosphonium tetrakis(phenyl)borate,

[0212] tri(methylphenyl)phosphonium tetra(phenyl)borate,

[0213] tris(dimethylphenyl)phosphonium tetra(phenyl)borate,

[0214] triphenylcarbeniumtetrakis(pentafluorophenyl)borate,

[0215] or ferroceniumtetrakis(pentafluorophenyl)borate.

[0216] Preferably, triphenylcarbonium tetrakis(pentafluorophenyl)borate,

[0217] N,N-dimethylcyclohexyl ammonium tetrakis(pentafluorophenyl)acid, or

[0218] N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

[0219] The appropriate amount of co-catalyst to use is known to the skilled person.

[0220] The molar ratio of boron to the metal ion in the metallocene may be in the range of 0.5:1 to 10:1 mol / mol, preferably 1:1 to 10:1 mol / mol, in particular 1:1 to 5:1 mol / mol.

[0221] The molar ratio of Al in the aluminoxane to the metal ion in the metallocene may be in the range of 1:1 to 2000:1 mol / mol, preferably 10:1 to 1000:1 mol / mol, and more preferably 50:1 to 500:1 mol / mol.

[0222] The catalyst of the present 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 zirconium oxide 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 person is aware of the steps required to support the metallocene catalyst.

[0223] Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support, for example using methods similar to those described in WO94 / 14856 (Mobil), WO95 / 12622 (Borealis) and WO2006 / 097497. The particle size is not critical, but is preferably in the range of 5 to 200 μm, more preferably 20 to 80 μm. The use of such supports is conventional in the art.

[0224] In an alternative embodiment, no support is used at all. Such catalysts can be prepared in solution (e.g., in an aromatic solvent such as toluene) by contacting the metallocene (as a solid or as a solution) with a cocatalyst (e.g., methylaluminoxane predissolved in an aromatic solvent), or can be prepared by sequentially adding the dissolved catalyst components to the polymerization medium.

[0225] In a particularly preferred embodiment, no external support is used, but the catalyst is still present in solid particulate form. Thus, no external support material, such as an inert organic or inorganic support, for example the above-mentioned silica, is employed.

[0226] In order to provide the catalyst of the present invention in solid form without the use of an external carrier, it is preferred to use a liquid / liquid emulsion system. This method involves forming a dispersion of catalyst components (i) and (ii) in a solvent and solidifying the dispersed droplets to form solid particles.

[0227] In particular, the method involves preparing a solution of one or more catalyst components; dispersing the solution in a solvent to form an emulsion, wherein the one or more catalyst components are present in droplets of the dispersed phase; immobilizing the catalyst components in the dispersed droplets in the absence of an external particulate porous support to form solid particles comprising the catalyst, and optionally recovering the particles.

[0228] The method enables the production of active catalyst particles having an improved morphology (e.g., having a predetermined spherical shape, surface properties, and particle size) without the use of any added external porous support material, such as an inorganic oxide, for example, silica. The term "preparing a solution of one or more catalyst components" means that the catalyst-forming compounds may be combined in one solution, which is dispersed in an immiscible solvent, or alternatively, for each portion of the catalyst-forming compounds, at least two separate catalyst solutions are prepared, which are then dispersed sequentially in the solvent.

[0229] In a preferred method of forming the catalyst, at least two separate solutions are prepared for each or a portion of the catalyst and then dispersed sequentially in immiscible solvents.

[0230] More preferably, the solution comprising the complex of the transition metal compound and the cocatalyst is combined with a solvent to form an emulsion, wherein the inert solvent forms a continuous liquid phase, and the solution comprising the catalyst components forms a 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 with the catalyst solution at least under the conditions (e.g., temperature) used during the dispersion step.

[0231] The term "immiscible with the catalyst solution" means that the solvent (continuous phase) is completely immiscible or partially immiscible with the dispersed phase solution, ie, not completely miscible.

[0232] Preferably, the solvent is inert with respect to the compounds of the catalyst system to be produced.A full disclosure of the necessary process can be found in WO 03 / 051934.

[0233] The inert solvent must be chemically inert at least under the conditions (e.g., temperature) used during the dispersion step. Preferably, the solvent of the continuous phase does not contain any significant amount of the catalyst-forming compound dissolved therein. Thus, solid particles of catalyst are formed in the droplets from compounds originating from the dispersed phase (i.e., provided to the emulsion, in solution dispersed into the continuous phase).

[0234] The terms "immobilisation" and "curing" are used interchangeably herein for the same purpose (i.e., in the absence of an external porous particle support such as silica, for forming free-flowing solid catalyst particles). Curing thus occurs within the droplets. This step can be implemented in various ways as disclosed in WO 03 / 051934. Preferably, curing is caused by an external stimulus to the emulsion system, such as a temperature change to cause curing. Thus, in this step, the catalyst components remain "fixed" within the formed solid particles. It is also possible that one or more catalyst components may participate in the curing / immobilization reaction.

[0235] Therefore, compositionally uniform particles of a solid having a predetermined particle size range can be obtained.

[0236] Furthermore, the particle size of the catalyst particles of the present 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.

[0237] The process is also industrially advantageous because it enables the preparation of solid particles in a one-pot process. Continuous or semi-continuous processes can also be used to produce the catalyst.

[0238] In the polymerization process according to the present invention, fresh catalyst is preferably introduced only 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 present upstream of the first reactor or upstream of the prepolymerization vessel. Fresh catalyst means the original catalyst species or the original catalyst species that has undergone prepolymerization.

[0239] Optionally, the polypropylene homopolymer (HPP) is polymerized in the presence of a Ziegler-Natta catalyst.

[0240] In this case the polypropylene homopolymer (HPP) preferably has a xylene cold soluble (XCS) content in the range of 1.5 to 3.5 wt.-%, preferably in the range of 1.5 to 3.0 wt.-%, based on the total weight of the polypropylene homopolymer (HPP).

[0241] It is further preferred that the polypropylene homopolymer (HPP) has a higher melting temperature T m For example, the polypropylene homopolymer (HPP) has a melting temperature T measured by differential scanning calorimetry (DSC) in the range of 162 to 170° C., preferably in the range of 162 to 168° C. m .

[0242] Higher melting temperature T m=Indicates that the polypropylene homopolymer (HPP) has a rather low regio defect content. Preferably, the polypropylene homopolymer (HPP) has ≤ 0.10 mol%, preferably 0.0 mol% of 13 The content of 2,1-erythro regio defects is determined by C-NMR spectroscopy. As is well known in the art, polypropylene having such an amount of 2,1-erythro regio defects is preferably produced with a Ziegler-Natta catalyst.

[0243] Additionally or alternatively, the polypropylene homopolymer (HPP) has a content in the range of 95.0 to 98.0% of 13 Isotactic triad fraction (mm) determined by C-NMR spectroscopy.

[0244] Preferably, the polypropylene homopolymer (HPP) has a weight average molecular weight (Mw) in the range of 80 to 500 kg / mol, preferably in the range of 100 to 400 kg / mol, more preferably in the range of 120 to 350 kg / mol, and / or a number average molecular weight (Mn) of 20 to 200 kg / mol, more preferably 50 to 150 kg / mol (determined by GPC according to ISO 16014).

[0245] It is preferred that the polypropylene homopolymer (HPP) has a molecular weight distribution Mw / Mn measured according to ISO 16014 of > 4.0, preferably in the range of 4.0 to 8.0 and most preferably in the range of 4.0 to 7.0.

[0246] Additionally or alternatively, polypropylene homopolymer (HPP) has a viscosity in the range of 0.900 to 0.910 g / cm 3 density within the range of .

[0247] Thus, in one embodiment the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) polymerized in the presence of a Ziegler-Natta catalyst, has

[0248] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 162 to 170°C, preferably in the range of 162 to 168°C, and / or

[0249] ii) ≤ 0.10 mol% of 13 The content of 2,1-erythro regio defects as determined by C-NMR spectroscopy, and / or

[0250] iii) in the range of 95.0 to 98.0% by 13 isotactic triad fraction (mm) as determined by C-NMR spectroscopy, and / or

[0251] iv) a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range of ≥ 4.0, preferably in the range of 4.0 to 8.0 and most preferably in the range of 4.0 to 7.0, and / or

[0252] v) a xylene cold soluble fraction (XCS) determined according to ISO 16152 at 23° C. in the range of 1.5 to 3.5 wt.-%, preferably in the range of 1.5 to 3.0 wt.-%.

[0253] For example, polypropylene homopolymer (HPP), i.e. polypropylene homopolymer (HPP) polymerized in the presence of a Ziegler-Natta catalyst, has

[0254] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 162 to 170°C, preferably in the range of 162 to 168°C, or

[0255] ii) ≤ 0.10 mol% of 13 The content of 2,1-erythro regiodefects determined by C-NMR spectroscopy, or

[0256] iii) in the range of 95.0 to 98.0% by 13 Isotactic triad fraction (mm) as determined by C-NMR spectroscopy, or

[0257] iv) a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range of ≥ 4.0, preferably in the range of 4.0 to 8.0 and most preferably in the range of 4.0 to 7.0, or

[0258] v) a xylene cold soluble fraction (XCS) determined according to ISO 16152 at 23° C. in the range of 1.5 to 3.5 wt.-%, preferably in the range of 1.5 to 3.0 wt.-%.

[0259] Alternatively, the polypropylene homopolymer (HPP), i.e. a polypropylene homopolymer (HPP) polymerized in the presence of a Ziegler-Natta catalyst, has

[0260] i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 162 to 170°C, preferably in the range of 162 to 168°C, and

[0261] ii) ≤ 0.10 mol% of 13 The content of 2,1-erythro regiodefects determined by C-NMR spectroscopy, and

[0262] iii) in the range of 95.0 to 98.0% by 13 isotactic triad fraction (mm) determined by C-NMR spectroscopy, and

[0263] iv) a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range of ≥ 4.0, preferably in the range of 4.0 to 8.0 and most preferably in the range of 4.0 to 7.0, and / or

[0264] v) a xylene cold soluble fraction (XCS) determined according to ISO 16152 at 23° C. in the range of 1.5 to 3.5 wt.-%, preferably in the range of 1.5 to 3.0 wt.-%.

[0265] Polypropylene homopolymer (HPP), i.e., polypropylene homopolymer (HPP) polymerized in the presence of a Ziegler-Natta catalyst, is preferably produced by a single-stage or multi-stage polymerization of propylene, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization, or a combination thereof. Polypropylene homopolymer (HPP), i.e., polypropylene homopolymer (HPP) polymerized in the presence of a Ziegler-Natta catalyst, can be produced in a loop reactor or in a combination of a loop and a gas phase reactor. These methods are well known to one skilled in the art.

[0266] It is to be understood that the polypropylene homopolymer (HPP), i.e. the polypropylene homopolymer (HPP) polymerized in the presence of a Ziegler-Natta catalyst, is preferably polymerized in the presence of a Ziegler-Natta catalyst known to a person skilled in the art.

[0267] Polypropylene copolymer (CPP)

[0268] A further requirement of the present invention is that the polypropylene composition comprises a polypropylene copolymer (CPP) in an amount of 10 to 35 wt.%, based on the total weight of the composition. The polypropylene copolymer (CPP) has the advantageous effect of inducing the formation of a finer cellular structure in the foamed injection-molded sheet compared to sheets based on polypropylene homopolymer alone.

[0269] Preferably, the polypropylene composition comprises the polypropylene copolymer (CPP) in an amount of 25 to 35 wt.-%, like in the range of 27.5 to 32.5 wt.-%, based on the total weight of the polypropylene composition.

[0270] It is to be understood that the term "polypropylene copolymer (CPP)" comprises propylene random copolymers, heterophasic propylene copolymers (HECO) and mixtures thereof.

[0271] As known to the skilled person, random propylene copolymers are distinguished from heterophasic polypropylenes which are propylene copolymers comprising a propylene homopolymer or random copolymer matrix component (1) and an elastomeric copolymer component (2) of propylene with one or more copolymers of ethylene and C4 to C8 α-olefins, wherein the elastomeric (amorphous) copolymer component (2) is dispersed in the propylene homopolymer or random copolymer matrix polymer (1).

[0272] The term "random propylene copolymer" refers to a copolymer of propylene monomer units and comonomer units, wherein the comonomer units are randomly distributed in the polymer chain. Therefore, random copolymers are different from heterophasic copolymers comprising a matrix phase and an elastomeric phase dispersed therein, as described in detail below. Therefore, random propylene copolymers (RCPP) do not comprise an elastomeric polymer phase dispersed therein, that is, are single-phase and have only one glass transition temperature. However, random propylene copolymers (RCPP) can be the matrix phase of heterophasic propylene copolymers (HECO). The presence of a second phase or so-called inclusions is, for example, visible by high-resolution microscopy (such as electron microscopy or atomic force microscopy) or by dynamic mechanical thermal analysis (DMTA). Specifically, in DMTA, the presence of a heterophasic structure can be identified by the presence of at least two different glass transition temperatures.

[0273] Preferably, the polypropylene copolymer (CPP) is a propylene random copolymer (RCPP).

[0274] Thus, the polypropylene copolymer (CPP) preferably comprises, preferably consists of, units derived from

[0275] (i) propylene, and

[0276] (ii) ethylene and / or C4 to C8 alpha-olefins, preferably propylene with ethylene or C4 to C6 alpha-olefins, most preferably ethylene or C6 alpha-olefins.

[0277] Thus, the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), may comprise units derivable from propylene, ethylene and optionally at least one further C4 to C8 alpha-olefin.

[0278] Alternatively, the polypropylene copolymer (CPP), preferably a random propylene copolymer (RCPP), comprises units derived from propylene and C4 or C6 alpha-olefins.Preferably, the polypropylene copolymer (CPP), preferably a random propylene copolymer (RCPP), comprises units derived from propylene and C6 alpha-olefins.

[0279] Preferably, units derived from propylene constitute the major part of the propylene copolymer (CPP), i.e. at least 90.0 wt.-%, more preferably at least 94.0 wt.-%, still more preferably from 94.0 to 98.0 wt.-%, yet more preferably from 96.0 to 98.0 wt.-%, based on the total weight of the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP). Thus, the amount of units derived from ethylene and / or C4 to C8 α-olefins (i.e. other than propylene) in the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), is in the range of 2.0 to 6.0 wt.-%, more preferably in the range of 2.0 to 4.0 wt.-%, based on the total weight of the polypropylene copolymer (CPP), preferably the random propylene copolymer (RC-PP1).

[0280] Additionally, it is preferred that the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), has a melting temperature T of at least 130°C, preferably in the range of 130 to 170°C, more preferably in the range of 135 to 158°C, such as in the range of 135 to 158°C. m .

[0281] Concerning the melt flow rate MFR2 (230°C), it is to be appreciated that the polypropylene copolymer (CPP), preferably the random propylene copolymer (RCPP), preferably has a melt flow rate MFR2 (230°C) measured according to ISO 1133 in the range of 0.1 to 10.0 g / 10 min, preferably in the range of 0.7 to 8.0 g / 10 min.

[0282] Preferably, the polypropylene copolymer (CPP) is polymerized in the presence of a Ziegler-Natta catalyst or a single site catalyst.

[0283] With regard to the Ziegler-Natta catalysts, single-site catalysts and preferred embodiments thereof, reference is made to the statements provided above when discussing the polypropylene homopolymer (HPP) in more detail.

[0284] Filler (F)

[0285] Additionally the polypropylene composition according to this invention may comprise filler (F) in an amount of 0 to 30.0 wt.-%, based on the total weight of the polypropylene composition.

[0286] Preferably, the polypropylene composition comprises filler (F) in an amount in the range of 2 to 20 wt.-%, like in the range of 3 to 15 wt.-%, based on the total weight of the polypropylene composition.

[0287] In a particular embodiment the polypropylene composition is free of filler (F).

[0288] Preferably, the filler (F) is a mineral filler (F).

[0289] If present, filler (F) is preferably selected from talc, mica, wollastonite, glass fibers, carbon fibers and mixtures thereof.

[0290] Typically, the filler (F) may have a particle size d in the range of 5 to 30 μm, preferably in the range of 5 to 25 μm, more preferably in the range of 5 to 20 μm. 50 .

[0291] The preferred filler (F) is talc. Preferably, a filler having a particle size d in the range of 0.1 to 10 μm, preferably in the range of 0.2 to 6.0 μm, more preferably in the range of 0.3 to 4.0 μm is used. 50 as filler (F). Most preferably, talc is used as the only filler (F). Still more preferably, the talc used has a top cut particle size of 0.8 to 50 μm, preferably 1.0 to 25 μm and most preferably 1.2 to 20 μm (95% of the particles are below this size according to ISO 787-7).

[0292] At least one additive

[0293] It is desired that the polypropylene composition comprises at least one additive in an amount ranging from 2.5 to 5 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, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

[0294] It should be noted that the term "at least one" additive in the context of the present invention means that the additive comprises one or more additives. In one embodiment, the additive is therefore one additive. Alternatively, the additive comprises two or more (such as two or three) additives.

[0295] Preferably, the additive includes two or more (such as two or three) additives.

[0296] The term "additive" also includes additives provided as a masterbatch comprising the polymeric carrier materials discussed above.

[0297] It will be appreciated that the polypropylene composition preferably comprises a nucleating agent. Thus, it is preferred that the polypropylene composition comprises a nucleating agent and one or more further additives selected from colorants, pigments such as carbon black, stabilizers, acid scavengers, blowing agents, antioxidants and mixtures thereof.

[0298] For example, the polypropylene composition preferably comprises a nucleating agent, more preferably an α-nucleating agent. Even more preferred polypropylene compositions according to the present invention do not contain a β-nucleating agent. Thus, the nucleating agent is preferably selected from the group consisting of

[0299] (i) salts of monocarboxylic and polycarboxylic acids, for example sodium benzoate or aluminum tert-butylbenzoate, and

[0300] (ii) dibenzylidenesorbitol (e.g. 1,3:2,4-dibenzylidenesorbitol) and C1 to C8-alkyl-substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g. 1,3:2,4-di(methylbenzylidene)sorbitol) or substituted nonitol derivatives, such as 1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, and

[0301] (iii) salts of phosphoric acid diesters, for example sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate or aluminium-hydroxy-bis[2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate] (also known as 2,2'-methylene-bis(4,6-di-t-butylphenylphosphate) basic aluminium), and

[0302] (iv) vinylcycloalkane polymers and vinylalkane polymers, and

[0303] (v) mixtures thereof.

[0304] Preferably, the α-nucleating agent is selected from 1,2-cyclohexanedicarboxylic acid, bis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1,3,2)dioxaphosphocin 6-oxidato)aluminum and mixtures thereof. For example, commercially available α-nucleating agents that can be used in the compositions of the present invention are nucleating agents such as Irgaclear XT 386 from Ciba Speciality Chemicals, Hyperform HPN-68L and Hyperform HPN-20E from Milliken & Company, and / or ADK STAB NA-21 nucleating agent.

[0305] In one embodiment, the polypropylene composition comprises 0.1 to 0.5 wt% of a nucleating agent, based on the total weight of the composition. Preferably, the polypropylene composition comprises 0.1 to 0.5 wt% of a nucleating agent based on bis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1,3,2)dioxaphosphoctane 6-oxide)hydroxyaluminum, based on the total weight of the composition.

[0306] Additionally or alternatively, the polypropylene composition comprises a blowing agent.

[0307] Throughout the present invention, the term "blowing agent" refers to an agent capable of generating a porous structure in a polypropylene composition during foaming. Suitable blowing agents include, for example, bicarbonate salts, preferably bicarbonate salts and a polyolefin carrier. Such blowing agents are commercially available, for example, from EIWA CHEMICAL IND. CO., LTD.

[0308] The polypropylene composition of the present invention comprises a blowing agent in an amount of preferably less than 10 wt.-%, more preferably from 1 wt.-% to 7 wt.-%, and most preferably from 1.5 wt.-% to 3 wt.-%, based on the total weight of the polypropylene composition. In a preferred embodiment, the polypropylene composition of the present invention comprises a blowing agent in an amount of between 2 wt.-% and 3 wt.-%, based on the total weight of the polypropylene composition.

[0309] Typically, such additives are commercially available and are described, for example, in “Plastic Additives Handbook” by Hans Zweifel, 5th edition, 2001 .

[0310] In a preferred embodiment, the polypropylene composition comprises a nucleating agent and a blowing agent and optionally at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, antioxidants and mixtures thereof.

[0311] Preferably, the polypropylene composition comprises a nucleating agent and a blowing agent and optionally at least one additive selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, antioxidants and mixtures thereof.

[0312] Products and uses

[0313] The polypropylene composition of the present invention can be used for producing articles, such as molded articles, preferably injection molded articles. In addition, the polypropylene composition of the present invention can be used for producing foamed articles, such as foamed injection molded articles. Even more preferably, for producing the purposes of automotive products (particularly automotive interior products and exterior products, such as instrument brackets, front modules, front walls, structural supports, bumpers, side trims, auxiliary pedals, body panels, spoilers, instrument panels, interior trims, etc.). Preferably, the article is an automotive interior product.

[0314] Therefore, another aspect of the present invention relates to an injection moulded article comprising the polypropylene composition as defined herein.

[0315] Preferably, the article has

[0316] i) a flexural modulus measured according to ISO 178 of at least 1000 MPa, preferably at least 1300 MPa; and / or

[0317] ii) a puncture energy measured according to ISO 6603-2 of at least 3.5 J, preferably at least 4.5 J.

[0318] Preferably, the article has

[0319] i) a flexural modulus measured according to ISO 178 of at least 1000 MPa, preferably at least 1300 MPa; or

[0320] ii) a puncture energy measured according to ISO 6603-2 of at least 3.5 J, preferably at least 4.5 J.

[0321] Optionally, the article has

[0322] i) a flexural modulus measured according to ISO 178 of at least 1000 MPa, preferably at least 1300 MPa; and

[0323] ii) a puncture energy measured according to ISO 6603-2 of at least 3.5 J, preferably at least 4.5 J.

[0324] In a further invention the present invention relates to a foamed article, preferably a foamed injection moulded article, comprising the polypropylene composition as defined herein.

[0325] As already described above, the polypropylene composition as defined herein advantageously reduces the stiffness reduction factor of foamed injection molded articles.

[0326] Therefore, the present invention further relates to the use of a polypropylene composition for reducing the stiffness reduction factor of a foamed injection molded article by at least 200, as determined by the difference in flexural modulus of the unfoamed and foamed injection molded article measured according to ISO 178. It is to be understood that the stiffness reduction factor is reduced compared to a foamed injection molded article produced from a polypropylene composition comprising only a polypropylene homopolymer (HPP), i.e. the polypropylene composition does not contain a polypropylene copolymer (CPP).

[0327] Concerning the polypropylene composition and preferred embodiments thereof, reference is made to the statements provided above when discussing the composition in more detail.

[0328] The present invention will now be described in further detail by way of the embodiments provided below.

[0329] Example

[0330] 1. Definition / Measurement Method

[0331] Unless otherwise defined, the following definitions of terms and determination methods apply to the above general description of the invention as well as the following examples.

[0332] MFR2 (230°C) is measured according to ISO 1133 (230°C, 2.16 kg load).

[0333] Xylene cold solubles (XCS, wt. %) are determined according to ISO 16152; 1st edition; 2005-07-01 at 25°C.

[0334] The intrinsic viscosity is measured according to DIN ISO 1628 / 1, October 1999 (in decalin at 135° C.).

[0335] Quantification of microstructure by NMR spectroscopy

[0336] The comonomer content of the polymers was quantified using quantitative nuclear magnetic resonance (NMR) spectroscopy. 1 H and 13 Quantitative measurements were recorded in solution on a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz, respectively. 13 C{ 1 H}NMR spectroscopy. 13All spectra were recorded at 125°C using a C-optimized 10mm extended temperature probe, with nitrogen used for all pneumatics. Approximately 200mg of material was dissolved in 3ml of 1,2-tetrachloroethane-d2 (TCE-d2) along with chromium (III) acetylacetonate (Cr(acac)3) to obtain a 65mM solution of the relaxant in the solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5(2009), 475). To ensure a homogeneous solution, the NMR tube was further heated in a rotary oven for at least 1 hour after initial sample preparation in a heating block. After insertion of the magnet, the tube was rotated at 10Hz. This setting was chosen primarily to obtain high resolution and was quantitatively required for accurately quantifying ethylene content. Standard single-pulse excitation without NOE was used with an optimized tip angle, a 1 s recycle delay, and a two-stage WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6k) transients were acquired for each spectrum.

[0337] Quantification was performed using a proprietary computer program 13 C{ 1 H} NMR spectra are processed, integrated, and relevant quantitative properties are determined from the integrals. All chemical shifts are indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This method allows for comparable references even when this structural unit is not present. Characteristic signals corresponding to ethylene incorporation are observed (Cheng, HN, Macromolecules 17 (1984), 1950).

[0338] In cases where characteristic signals corresponding to 2,1-erythro regio defects are observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100(4), 1253, Cheng, HN, Macromolecules 1984, 17, 1950, and WJ. Wang and S. Zhu, Macromolecules 2000, 33, 1157), it is necessary to correct for the influence of the regio defects on the determined properties. Characteristic signals corresponding to other types of regio defects are not observed.

[0339] The method of Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157) was used to 13 C{ 1 The comonomer fraction is quantified by integrating multiple signals across the entire spectral region of the H spectrum. This method was chosen for its robustness and ability to account for the presence of regio defects when necessary. The integration region was slightly adjusted to improve applicability across the full range of comonomer contents encountered.

[0340] For systems where only isolated ethylene is observed in PPEPP sequences, the method of Wang et al. was modified to reduce the influence of non-zero integrals at sites known to be absent. This approach reduces the overestimation of ethylene content in such systems and is achieved by reducing the number of sites used to determine absolute ethylene content to:

[0341] E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

[0342] By using this set of sites, the corresponding integral equation becomes:

[0343] E=0.5(I H +I G +0.5(I C +I D ))

[0344] The same symbols are used as in the article by Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157). No modifications are made to the equations for absolute propylene content.

[0345] Calculate the mole percentage of comonomer incorporation from the mole fraction:

[0346] E [mol %] = 100 * fE

[0347] Calculate the weight percent of comonomer incorporation from the mole fraction:

[0348] E[weight%]=100*(fE*28.06) / ((fE*28.06)+((1-fE)*42.08))

[0349] The triad-level comonomer sequence distribution was determined using the analytical method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robustness, and the integration region was slightly adjusted to improve applicability to a wider range of comonomer contents.

[0350] Flexural modulus was determined in 3-point bending according to ISO 178 on injection molded specimens 80 x 10 x 4 mm prepared according to ISO 294-1:1996.

[0351] The glass transition temperature (Tg) and storage modulus (G') were determined by dynamic mechanical analysis (DMTA) according to ISO 6721-7. Measurements were performed in torsional mode on compression-molded samples (40 x 10 x 1 mm3) at a heating rate of 2°C / min and a frequency of 1 Hz between -100°C and +150°C. While Tg was determined from the loss angle (tan(δ)) curve, the storage modulus (G') curve was used to determine the temperature at which G', representing 40 MPa, represents a measure of heat distortion resistance.

[0352] The puncture energy and the energy to maximum force are determined in an instrumented drop-weight impact test according to ISO 6603-2 on panels with dimensions of 148×148×2 mm. The test is carried out at room temperature with a lubricated hammer with a diameter of 20 mm and an impact velocity of 10 mm / s.

[0353] Number average molecular weight (M n ) and weight average molecular weight (M w) were determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99. A PolymerChar GPC instrument equipped with an infrared (IR) detector was used at 160° C. and a constant flow rate of 1 mL / min, using 3× Olexis and 1× Olexis guard columns from Polymer Laboratories and 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol) as the solvent. The column set was calibrated using a universal calibration (according to ISO 16014-2:2003) with at least 15 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11,500 kg / mol. The Mark Houwink constants for the PS, PE, and PP used were those described in accordance with ASTM D 6474-99. All samples were prepared by dissolving 5.0 to 9.0 mg of polymer in 8 mL (at 160°C) of stabilized TCB (same as mobile phase) in the autofeeder of the GPC instrument at up to 160°C with continuous gentle shaking for 2.5 hours for PP and 3 hours for PE.

[0354] Particle size d 50 and top cut d 95 Calculated according to ISO 13317-3 (Sedigraph) from the particle size distribution [mass percent] determined by gravitational liquid sedimentation.

[0355] DSC analysis, melting temperature (Tm) and crystallization temperature (Tc):

[0356] Measurements were performed on 5 to 7 mg samples using a TA Instrument Q2000 Differential Scanning Calorimeter (DSC). The DSC was operated according to ISO 11357 / Part 3 / Method C2 using a heating / cooling / heating cycle over a temperature range of -30 to +225°C at a scan rate of 10°C / min. The crystallization temperature and the heat of crystallization (Hc) were determined from the cooling step, while the melting temperature and the heat of fusion (Hf) were determined from the second heating step.

[0357] The cell structure of the foamed parts was determined by optical microscopy from cross sections of the foamed, injection-molded plaques.

[0358] The volatile organic compound content (VOC) was measured according to VDA 278, October 2011.

[0359] The total carbon emissions were determined from the pellets according to VDA 277:1995.

[0360] 2. Examples

[0361] Synthesis of Metallocene:

[0362] The metallocene (rac-trans-dimethylsilylene(2-methyl-4-phenyl-5-methoxy-6-tert-butylindenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride) was synthesized as described in WO 2013 / 007650. The metallocene-containing catalyst was prepared using a catalyst system of the metallocene and MAO and trityl tetrakis(pentafluorophenyl)borate according to catalyst 3 of WO 2015 / 11135, with the proviso that the surfactant was 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol.

[0363] Table 1. Polymerization process conditions and properties of polypropylene homopolymer HPP1

[0364] B1 prepolymerization reactor Temperature (℃) 20 Pressure (kPa) 5238 B2 loop reactor Temperature (℃) 70 Pressure (kPa) 5292 H2 / C3 ratio (mol / kmol) 0.42 Polymer split ratio (weight %) 49.0 MFR2(g / 10min) 91.0 XCS (%) 1.4 B3 gas phase reactor Temperature (℃) 80 Pressure (kPa) 2406 H2 / C3 ratio (mol / kmol) 3.2 Polymer split ratio (weight %) 51.0 MFR2(g / 10min) 71.0 XCS (%) 1.3

[0365] The random propylene / 1-hexene copolymer was produced in a multistage process using a prepolymerization reactor to which a slurry loop reactor and a gas phase reactor were connected. As catalyst, a metallocene-containing catalyst prepared as described above was used. The properties of the polymerization conditions, propylene polymer fraction and the random propylene / 1-hexene copolymer (C3C6-1) are shown in Table 2.

[0366] Table 2: Polymerization process conditions and properties of polypropylene homopolymer CPP1

[0367]

[0368]

[0369] The polypropylene composition was prepared by compounding in a co-rotating twin-screw extruder ZSK18 from Coperion with a typical screw configuration and a melt temperature in the range of 200 to 220° C. The molten strands were solidified in a water bath and then pelletized.

[0370] Table 3: Overview of the compositions used in the inventive examples and comparative examples CE1, CE2, IE1, IE2 and IE3

[0371] IE1 IE2 IE3 CE1 CE2 HPP1 [weight%] 66.5 66.5 96.5 HPP2 [weight%] 66.5 96.5 CPP1 [weight%] 30 CPP2 [weight%] 30 30 additive [weight%] 3.5 3.5 3.5 3.5 3.5

[0372] HPP1 is a polyol from Borealis AG with a melt flow rate MFR2 of about 71 g / 10 min.

[0373] (230 ° C) isomeric unimodal polypropylene homopolymer, and is as shown in Table 1

[0374] Prepared in the presence of the single-active site catalyst listed.

[0375] HPP2 is a polymer from Borealis AG with a melt flow rate MFR2 of about 75 g / 10 min.

[0376] The commercially available unimodal polypropylene homopolymer HJ120UB has a Tm of 164°C (230°C), a density of 0.905 g / cm3 and is produced in the presence of a Ziegler-Natta catalyst.

[0377] CPP1 is a polyol from Borealis AG having a melt flow rate MFR2 of 1.4 g / 10 min.

[0378] (230°C), 5 wt% C6 content propylene-hexene random copolymer, and was prepared in the presence of the single-site catalyst listed in Table 2.

[0379] CPP2 is a commercially available propylene-ethylene random copolymer from Borealis AG having a C2 content of 3.1 wt%, an MFR2 (230° C.) of 1.9 g / 10 min.

[0380] RB206MO contains about 0.10% of an ADK STAB NA-21 nucleating agent based on bis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1,3,2)dioxaphosphocine 6-oxide)hydroxyaluminum and is prepared in the presence of a Ziegler-Natta catalyst.

[0381] Additives included 1.5 wt% carbon black, 0.2 wt% of

[0382] The present invention comprises a nucleating agent Hyperform HPN-20E, 0.15 wt % of an antioxidant Irganox B215FF from BASF AG, Germany, 0.15 wt % of calcium stearate and 1.5 wt % of a carrier material.

[0383] The mechanical characteristics of inventive examples IE1, IE2 and IE3 and comparative examples CE1 and CE2 are shown in Table 4 below.

[0384] Table 4: Characteristics of the prepared polypropylene (PP) compositions

[0385]

[0386] As can be seen from Table 4, the polypropylene compositions offer excellent foamability and mechanical properties. By using the compositions of the examples of the present invention, it is possible to obtain foamed injection-molded sheets with a fine porous structure while maintaining a good balance of mechanical properties. In addition to the fine porous structure and maintained mechanical properties, the unfoamed and foamed compositions of the present invention exhibit low volatile organic compound content. IE1 is a blend of CPP1 and HPP1 from CE2. Blending CPP1 with HPP1 triggers the formation of fine pores and a uniform pore structure in the foamed part, which is not the case when HPP1 is used alone. The same effect is observed when CPP2 is added to the propylene homopolymer. It can be seen that the foamed part exhibits a lower flexural modulus than the unfoamed part. This reduction is measured by the stiffness reduction factor, which has the lowest values in IE1, IE2, and IE3. A comparison of the properties of the foamed parts in the examples reveals that the examples of the present invention have higher puncture energy (IE1, IE2) and higher stiffness (IE3) than the foamed comparative examples (CE1, CE2).

Claims

1. A polypropylene composition comprising a) 65 to 85 wt. % of a polypropylene homopolymer (HPP), based on the total weight of the composition, b) 10 to 35 wt. % of a polypropylene copolymer (CPP), based on the total weight of the composition, c) 0 to 30 wt. % of a filler (F), based on the total weight of the composition, and d) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof, The total amount of the polypropylene homopolymer (HPP), the polypropylene copolymer (CPP), the filler (F) and the at least one additive in the polypropylene composition is 100.0 wt%.

2. The polypropylene composition according to claim 1, wherein the composition comprises, preferably consists of, a) 65 to 75 wt.-%, based on the total weight of the composition, of the polypropylene homopolymer (HPP), b) 25 to 35 wt.% of said polypropylene copolymer (CPP), based on the total weight of said composition, and c) 2.5 to 5 wt. % of at least one additive, based on the total weight of the composition, selected from the group consisting of colorants, pigments such as carbon black, stabilizers, acid scavengers, nucleating agents, blowing agents, antioxidants, and mixtures thereof.

3. The polypropylene composition according to claim 1 or 2, wherein the polypropylene composition has a) a melt flow rate MFR2 (230°C) measured according to ISO 1133 in the range of 15.0 to 80.0 g / 10 min; and / or b) a volatile organic compound content of no more than 150 μg / g of the composition in granular form; and / or c) a glass transition temperature Tg of -10°C or higher, preferably -5°C or higher (measured with DMTA according to ISO 6721-7).

4. The polypropylene composition according to any one of claims 1 to 3, wherein the composition comprises 0.1 to 0.5 wt.-%, based on the total weight of the composition, of one or more nucleating agents, preferably a nucleating agent selected from 1,2-cyclohexanedicarboxylic acid, bis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1,3,2)dioxaphosphocine 6-oxide)hydroxyaluminum and mixtures thereof.

5. The polypropylene composition according to anyone of claims 1 to 4, wherein the polypropylene homopolymer (HPP) is polymerized in the presence of a Ziegler-Natta catalyst or a single-site catalyst.

6. The polypropylene composition according to anyone of claims 1 to 5, wherein the polypropylene copolymer (CPP) is polymerized in the presence of a Ziegler-Natta catalyst or a single site catalyst.

7. The polypropylene composition according to any one of claims 1 to 6, wherein the polypropylene homopolymer (HPP) has i) a melting temperature Tm measured by differential scanning calorimetry (DSC) in the range of 150 to 160° C., ii) in the range of 0.50 to 1.00 mol% of 13 The content of 2,1-erythro regiodefects was determined by C-NMR spectroscopy. iii) At least 97.5% of 13 isotactic triad fraction (mm) determined by C-NMR spectroscopy, and iv) a xylene cold soluble fraction (XCS), determined according to ISO 16152 at 23°C, equal to or lower than 1.5 wt%.

8. The polypropylene composition according to any one of claims 1 to 6, wherein the polypropylene homopolymer (HPP) has i) a melting temperature, Tm, measured by differential scanning calorimetry (DSC) in the range of 162 to 170°C, and / or ii) ≤ 0.10 mol% of 13 The content of 2,1-erythro regio defects as determined by C-NMR spectroscopy, and / or iii) in the range of 95.0 to 98.0% by 13 isotactic triad fraction (mm) as determined by C-NMR spectroscopy, and / or iv) a molecular weight distribution Mw / Mn measured according to ISO 16014 in the range ≥ 4.0, and / or v) a xylene cold soluble fraction (XCS), determined according to ISO 16152 at 23° C., in the range of 1.5 to 3.5 wt.-%.

9. The polypropylene composition according to any one of claims 1 to 8, wherein the polypropylene copolymer (CPP) is a random copolymer of propylene with ethylene and / or C4 to C8 α-olefins, preferably propylene with ethylene or C4 or C6 α-olefins, most preferably ethylene or C6 α-olefins.

10. The polypropylene composition according to any one of claims 1 to 9, wherein the polypropylene copolymer (CPP) has i) a comonomer content in the range of 2.0 to 6.0 wt.-%, preferably in the range of 2.0 to 4.0 wt.-%, based on the total weight of the polypropylene copolymer (CPP); and / or ii) a melt flow rate MFR2 (230° C.) measured according to ISO 1133 in the range of 0.1 to 10.0 g / 10 min, preferably in the range of 0.7 to 8.0 g / 10 min.

11. An injection molded article comprising the polypropylene composition according to any one of claims 1 to 10.

12. The injection molded article according to claim 11, wherein the article has iii) a flexural modulus measured according to ISO 178 of at least 1000 MPa, preferably at least 1300 MPa; and / or iv) a puncture energy measured according to ISO 6603-2 of at least 3.5 J, preferably at least 4.5 J.

13. A foamed article, preferably a foamed injection-molded article, comprising the polypropylene composition according to any one of claims 1 to 10.

14. Use of the polypropylene composition according to any one of claims 1 to 10 for reducing the stiffness reduction factor of a foamed injection molded article by at least 200, the stiffness reduction factor being determined by the difference in flexural modulus measured according to ISO 178 of the unfoamed and foamed injection molded article.

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