FOAMED POLYPROPYLENE COMPOSITION

Abstract

The present invention is directed to a polypropylene composition (C) a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 15 to 40 g/ 10 min, the use of said polypropylene composition (C) for the production of a foamed article and a foamed article comprising said polypropylene composition (C).

Claims

1-15. (canceled)

16. A polypropylene composition (C) having a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 15 to 40 g/10 min, comprising a) a first heterophasic propylene copolymer (HECO1) having a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 50 to 200 g/10 min, said first heterophasic propylene copolymer comprising i) a first matrix being a first propylene polymer (M1) and ii) a first elastomeric propylene copolymer (E1) dispersed in said first matrix, b) a second heterophasic propylene copolymer (HECO2) having a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 3 to <50 g/10 min, said second heterophasic propylene copolymer comprising iii) a second matrix, which is a second propylene polymer (M2) and iv) a second elastomeric propylene copolymer (E2) dispersed in said second matrix, c) a high density polyethylene (HDPE) having a melt flow rate MFR.sub.2 (190° C.) determined according to ISO 1133 in the range of 2 to 15 g/10 min, d) a plastomer (PL), which is a copolymer of ethylene and a C.sub.4 to C.sub.8 α-olefin and having a melt flow rate MFR.sub.2 (190° C.) determined according to ISO 1133 in the range of 10 to 70 g/10 min, e) an inorganic filler (F), f) a foaming agent (FA) comprising citric acid in combination with a bicarbonate, and g) optionally, a nucleating agent.

17. The polypropylene composition (C) according to claim 16, wherein the composition comprises a) 35.0 to 55.0 wt.-% of the first heterophasic propylene copolymer (HECO1), b) ≥20.0 wt.-% of the second heterophasic propylene copolymer (HECO2), c) 2.0 to 10.0 wt.-% of the high density polyethylene (HDPE), d) 5.0 to 15.0 wt.-% of the plastomer (PL) being a copolymer of ethylene and a C.sub.4 to C.sub.8 α-olefin, e) 1.0 to 20.0 wt.-% of the inorganic filler (F), and f) 1.0 to 10.0 wt.-% of the foaming agent, based on the overall polypropylene composition (C).

18. The polypropylene composition (C) according to claim 16, wherein i) the matrix of the first heterophasic propylene copolymer (HECO1) being the first propylene polymer (M1) has a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 50 to 200 g/10 min, and ii) the matrix of the second heterophasic propylene copolymer (HECO2) being the second propylene polymer (M2) has a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 50 to 200 g/10 min.

19. The polypropylene composition (C) according to claim 16, wherein the first heterophasic propylene copolymer (HECO1) has i) a xylene soluble fraction (XCS) in the range of 15.0 to 35.0 wt.-%, and/or ii) a xylene soluble fraction (XCS) whose intrinsic viscosity (IV) is <3.5 dl/g at 135° C., and/or iii) a xylene soluble fraction (XCS) whose ethylene content is from 30.0 to 40.0 wt.-%, based on the total weight of the xylene soluble fraction (XCS).

20. The polypropylene composition (C) according to claim 16, wherein the second heterophasic propylene copolymer (HECO2) has i) a xylene soluble fraction (XCS) in the range of 10.0 to 35.0 wt.-%, and/or ii) a xylene soluble fraction (XCS) whose intrinsic viscosity (IV) is <4.0 dl/g at 135° C., and/or iii) a xylene soluble fraction (XCS) whose ethylene content is 35.0 to 50.0 wt.-%, based on the total weight of the xylene soluble fraction (XCS).

21. The polypropylene composition (C) according to claim 16, wherein the first propylene polymer (M1) and/or the second propylene polymer (M2) are propylene homopolymers.

22. The polypropylene composition (C) according to claim 16, wherein the first elastomeric propylene copolymer (E1) and/or the second elastomeric propylene copolymer (E2) are copolymers of propylene and ethylene.

23. The polypropylene composition (C) according to claim 16, wherein the plastomer (PL) i) is a copolymer of ethylene and 1-octene, and/or ii) has a density of below 0.900 g/cm.sup.3.

24. The polypropylene composition (C) claim 16, wherein the inorganic filler (F) is talc and/or wollastonite.

25. The polypropylene composition (C) according to claim 16, wherein the bicarbonate is selected from the group consisting of sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, ammonium bicarbonate, and mixtures thereof.

26. The polypropylene composition (C) according to claim 25, wherein the bicarbonate is sodium bicarbonate.

27. The polypropylene composition (C) according to claim 16, wherein said polypropylene composition (C) is a foamable polypropylene composition.

28. A foamed article comprising the polypropylene composition (C) according to claim 16.

29. The foamed article according to claim 28, wherein said foamed article is an automotive article.

Description

EXAMPLES

1. Measuring Methods

[0330] The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined. Calculation of comonomer content of the elastomeric copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the first heterophasic propylene copolymer (HECO1):

[00001]$\begin{array}{cc}\frac{C\left(PP\right)-w\left(PP12\right)xC\left(PP12\right)}{w\left(PP3\right)}=C\left(PP3\right)& \left(I\right)\end{array}$

[0331] wherein [0332] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fraction, i.e. the polymer produced in the first and second reactor (R1+R2), [0333] w(PP3) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3), [0334] C(PP12) is the comonomer content [in mol-%] of the first and second propylene polymer fraction, i.e. the polymer produced in the first and second reactor (R1+R2), [0335] C(PP) is the comonomer content [in mol-%] of the first propylene polymer fraction, the second propylene polymer fraction and the elastomeric propylene copolymer fraction, i.e. polymer produced in the first, second and third reactor (R1+R2+R3), [0336] C(PP3) is the calculated comonomer content [in mol-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3).

[0337] Calculation of the xylene cold soluble (XCS) content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the first heterophasic propylene copolymer (HECO1):

[00002]$\begin{array}{cc}\frac{XS\left(\mathrm{HECO}\right)-w\left(PP12\right)xXS\left(PP12\right)}{w\left(E\right)}=XS\left(E\right)& \left(\mathrm{II}\right)\end{array}$

[0338] wherein [0339] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fraction, i.e. the polymer produced in the first and second reactor (R1+R2), [0340] w(E) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3) [0341] XS(PP12) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second propylene polymer fraction, i.e. the polymer produced in the first and second reactor (R1+R2), [0342] XS(HECO) is the xylene cold soluble (XCS) content [in wt.-%] of the first propylene polymer fraction, the second propylene polymer fraction and the elastomeric propylene copolymer fraction, i.e. polymer produced in the first, second reactor and third reactor (R1+R2+R3), [0343] XS(E) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the second and third reactor (R2+3).

[0344] Calculation of melt flow rate MFR.sub.2 (230° C.) of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the first heterophasic propylene copolymer (HECO1):

[00003]$\begin{array}{cc}\mathrm{MFR}\left(PP3\right)=10\left[\frac{\log \left(\mathrm{MFR}\left(\mathrm{PP}\right)\right)-w\left(PP12\right)x\log \left(\mathrm{MFR}\left(PP12\right)\right)}{w\left(PP3\right)}\right]& \left(\mathrm{III}\right)\end{array}$

[0345] wherein [0346] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0347] w(PP3) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3), [0348] MFR(PP12) is the melt flow rate MFR.sub.2 (230° C.) [in g/10 min] of the first and second propylene fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0349] MFR(PP) is the melt flow rate MFR.sub.2 (230° C.) [in g/10 min] of the first and second propylene polymer fractions and the elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0350] MFR(PP3) is the calculated melt flow rate MFR.sub.2 (230° C.) [in g/10 min] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3).

[0351] Calculation of comonomer content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the first heterophasic propylene copolymer (HECO1):

[00004]$\begin{array}{cc}\frac{C\left(\mathrm{HECO}\right)-w\left(PP\right)xC\left(PP\right)}{w\left(E\right)}=C\left(E\right)& \left(\mathrm{IV}\right)\end{array}$

[0352] wherein [0353] w(PP) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0354] w(E) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer, i.e. of the polymer produced in the third reactor (R3), [0355] C(PP) is the comonomer content [in mol -%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0356] C(HECO) is the comonomer content [in mol -%] of the propylene copolymer, i.e. is the comonomer content [in mol -%] of the polymer obtained after polymerization in the third reactor (R3), [0357] C(E) is the calculated comonomer content [in mol -%] of the elastomeric propylene copolymer fraction, i.e. of the polymer produced in the third reactor (R3).

[0358] Calculation of comonomer content of the first elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the second heterophasic propylene copolymer (HECO2):

[00005]$\begin{array}{cc}\frac{C\left(PP\right)-w\left(PP12\right)xC\left(PP12\right)}{w\left(PP3\right)}=C\left(PP3\right)& \left(V\right)\end{array}$

[0359] wherein [0360] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0361] w(PP3) is the weight fraction [in wt.-%] of the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3), [0362] C(PP12) is the comonomer content [in mol-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0363] C(PP) is the comonomer content [in mol-%] of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0364] C(PP2) is the calculated comonomer content [in mol-%] of the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3).

[0365] Calculation of comonomer content of the second elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the fourth reactor (R3), of the second heterophasic propylene copolymer (HECO2):

[00006]$\begin{array}{cc}\frac{C\left(PP\right)-w\left(PP123\right)xC\left(PP123\right)}{w\left(PP4\right)}=C\left(PP4\right)& \left(\mathrm{VI}\right)\end{array}$

[0366] wherein [0367] w(PP123) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0368] w(PP4) is the weight fraction [in wt.-%] of second elastomeric propylene copolymer fraction, i.e. the polymer produced in the fourth reactor (R4), [0369] C(PP123) is the comonomer content [in mol-%] of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0370] C(PP) is the comonomer content [in mol-%] of the first and second propylene polymer fractions and the first and second elastomeric propylene copolymer fractions, i.e. the polymer produced in the first, second, third and fourth reactor (R1+R2+R3+4), [0371] C(PP4) is the calculated comonomer content [in mol-%] of the second elastomeric propylene copolymer fraction, i.e. the polymer produced in the fourth reactor (R4).

[0372] Calculation of the xylene cold soluble (XCS) content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third and fourth reactor (R3+R4), of the second heterophasic propylene copolymer (HECO2):

[00007]$\begin{array}{cc}\frac{XS\left(\mathrm{HECO}\right)-w\left(PP12\right)xXS\left(PP12\right)}{w\left(E\right)}=XS\left(E\right)& \left(\mathrm{VII}\right)\end{array}$

[0373] wherein [0374] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0375] w(E) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third and fourth reactor (R3+R4) [0376] XS(PP12) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0377] XS(HECO) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second propylene polymer fractions and the elastomeric propylene copolymer fraction, i.e. polymer produced in the first, second, third and fourth (R1+R2+R3 +R4), [0378] XS(E) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third and fourth reactor (R3+R4).

[0379] Calculation of the xylene cold soluble (XCS) content of the first elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the second heterophasic propylene copolymer (HECO2):

[00008]$\begin{array}{cc}\frac{XS\left(PP\right)-w\left(PP12\right)xXS\left(PP12\right)}{w\left(PP3\right)}=XS\left(PP3\right)& \left(\mathrm{VIII}\right)\end{array}$

[0380] wherein [0381] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0382] w(PP3) is the weight fraction [in wt.-%] of the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3) [0383] XS(PP12) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second elastomeric propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0384] XS(PP) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second propylene polymer fraction and the first elastomeric propylene copolymer fraction, i.e. polymer produced in the first, second and third reactor (R1+R2+R3), [0385] XS(PP3) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3).

[0386] Calculation of the xylene cold soluble (XCS) content of the second elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the fourth reactor (R4):

[00009]$\begin{array}{cc}\frac{XS\left(PP\right)-w\left(PP123\right)xXS\left(PP123\right)}{w\left(PP4\right)}=XS\left(PP4\right)& \left(\mathrm{IX}\right)\end{array}$

[0387] wherein [0388] w(PP123) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0389] w(PP4) is the weight fraction [in wt.-%] of the second propylene copolymer fraction, i.e. the polymer produced in the fourth reactor (R4) [0390] XS(PP123) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0391] XS(PP) is the xylene cold soluble (XCS) content [in wt.-%] of the first and second propylene polymer fractions and the first and second elastomeric propylene copolymer fractions, i.e. polymer produced in the first, second, third and fourth reactor (R1+R2+R3+R4), [0392] XS(PP4) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the second elastomeric propylene copolymer fraction, i.e. the polymer produced in the fourth reactor (R4).

[0393] Calculation of melt flow rate MFR.sub.2 (230° C.) of the second propylene polymer fraction, i.e. the polymer fraction produced in the second reactor (R2), of the second heterophasic propylene copolymer (HECO2):

[00010]$\begin{array}{cc}\mathrm{MFR}\left(\mathrm{PP}2\right)=10\left[\frac{\log \left(\mathrm{MFR}\left(PP\right)\right)-w\left(PP1\right)x\log \left(\mathrm{MFR}\left(PP1\right)\right)}{w\left(PP2\right)}\right]& \left(X\right)\end{array}$

[0394] wherein [0395] w(PP1) is the weight fraction [in wt.-%] of the first propylene polymer fraction, i.e. the polymer produced in the first reactor (R1), [0396] w(PP2) is the weight fraction [in wt.-%] of the first second propylene polymer fraction, i.e. the polymer produced in the second reactor (R2), [0397] MFR(PP1) is the melt flow rate MFR.sub.2 (230° C.) [in g/10 min] of the first propylene polymer fraction, i.e. the polymer produced in the first reactor (R1), [0398] MFR(PP) is the melt flow rate MFR.sub.2 (230° C.) [in g/10 min] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0399] MFR(PP2) is the calculated melt flow rate MFR.sub.2 (230° C.) [in g/10 min] of the first propylene polymer fraction, i.e. the polymer produced in the second reactor (R2).

[0400] Calculation of the intrinsic viscosity of the xylene soluble fraction of the first elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third reactor (R3), of the second heterophasic propylene copolymer (HECO2):

[00011]$\begin{array}{cc}\frac{\mathrm{IV}\left(\mathrm{PP}\right)-XCS\left(PP12\right)\mathrm{xIV}\left(\mathrm{PP}12\right)}{XCS\left(PP3\right)}=\mathrm{IV}\left(\mathrm{PP}3\right)& \left(\mathrm{XI}\right)\end{array}$

[0401] wherein [0402] XCS(PP12) is the xylene soluble fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0403] XCS(PP3) is the xylene soluble fraction [in wt.-%] of the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3), [0404] IV(PP12) is the intrinsic viscosity [in dl/g] of the xylene soluble fraction of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0405] IV(PP) is the intrinsic viscosity [in dl/g] of the xylene soluble fraction of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. polymer produced in the first, second and third reactor (R1+R2+R3), [0406] IV(PP3) is the calculated intrinsic viscosity [in dl/g] of the xylene soluble fraction of the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the third reactor (R3).

[0407] Calculation of the intrinsic viscosity of the xylene soluble fraction of the second elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the fourth reactor (R4), of the second heterophasic propylene copolymer (HECO2):

[00012]$\begin{array}{cc}\frac{\mathrm{IV}\left(\mathrm{PP}\right)-XCS\left(PP123\right)x\mathrm{IV}\left(\mathrm{PP}123\right)}{XCS\left(PP4\right)}=\mathrm{IV}\left(\mathrm{PP}4\right)& \left(\mathrm{XII}\right)\end{array}$

[0408] wherein [0409] XCS(PP123) is the xylene soluble fraction [in wt.-%] of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0410] XCS(PP4) is the xylene soluble fraction [in wt.-%] of second elastomeric propylene copolymer fraction, i.e. the polymer produced in the fourth reactor (R4), [0411] IV(PP123) is the intrinsic viscosity [in dl/g] of the xylene soluble fraction of the first and second propylene polymer fractions and the first elastomeric propylene copolymer fraction, i.e. the polymer produced in the first, second and third reactor (R1+R2+R3), [0412] IV(PP) is the intrinsic viscosity [in dl/g] of the xylene soluble fraction of the first and second propylene polymer fractions and the first and second elastomeric propylene copolymer fractions, i.e. polymer produced in the first, second, third and fourth reactor (R1+R2+R3+R4), [0413] IV(PP4) is the calculated intrinsic viscosity [in dl/g] of the xylene soluble fraction of the second elastomeric propylene copolymer fraction, i.e. the polymer produced in the fourth reactor (R4).

[0414] Calculation of comonomer content of the elastomeric propylene copolymer fraction, i.e. the polymer fraction produced in the third and fourth reactor (R3+R4), of the second heterophasic propylene copolymer (HECO2):

[00013]$\begin{array}{cc}\frac{C\left(\mathrm{HECO}\right)-w\left(PP12\right)xC\left(PP12\right)}{w\left(E\right)}=C\left(E\right)& \left(\mathrm{XIII}\right)\end{array}$

[0415] wherein [0416] w(PP12) is the weight fraction [in wt.-%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0417] w(E) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third and fourth reactor (R3+R4) [0418] C(PP12) is the comonomer content [in mol -%] of the first and second propylene polymer fractions, i.e. the polymer produced in the first and second reactor (R1+R2), [0419] C(HECO) is the comonomer content [in mol -%] of the first and second propylene polymer fractions and the elastomeric propylene copolymer, i.e. polymer produced in the first, second, third and fourth (R1+R2+R3+R4), [0420] C(E) is the calculated comonomer content [in mol -%] of the elastomeric propylene copolymer fraction, i.e. the polymer produced in the third and fourth reactor (R3+R4).

[0421] MFR.sub.2 (230° C.) is measured according to ISO 1133 (230° C., 2.16 kg load).

[0422] MFR.sub.2 (190° C.) is measured according to ISO 1133 (190° C., 2.16 kg load).

[0423] Quantification of Microstructure by NMR Spectroscopy

[0424] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers. Quantitative .sup.13C {.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 10 mm extended temperature probehead at 125° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). 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 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. 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, 1 s recycle delay and a bi-level 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 per spectra. Quantitative .sup.13C {.sup.1H} 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 30.00 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 Cheng, H. N., Macromolecules 17 (1984), 1950).

[0425] For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

[0426] Characteristic signals corresponding to regio defects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) or comonomer were observed.

[0427] The tacticity distribution was quantified through integration of the methyl region between 23.6-19.7 ppm correcting for any sites not related to the stereo sequences of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromoleucles 30 (1997) 6251).

[0428] Specifically the influence of regio defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio defect and comonomer integrals from the specific integral regions of the stereo sequences. The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:

[0429] [mmmm]%=100 * (mmmm/sum of all pentads)

[0430] The presence of 2,1 erythro regio defects was indicated by the presence of the two methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic sites.

[0431] Characteristic signals corresponding to other types of regio defects were not observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

[0432] The amount of 2,1 erythro regio defects was quantified using the average integral of the two characteristic methyl sites at 17.7 and 17.2 ppm:

[0433] P.sub.21e=(I.sub.e6+I.sub.e8)/2

[0434] The amount of 1,2 primary inserted propene was quantified based on the methyl region with correction undertaken for sites included in this region not related to primary insertion and for primary insertion sites excluded from this region:

[0435] P.sub.12=I.sub.CH3+P.sub.12e

[0436] The total amount of propene was quantified as the sum of primary inserted propene and all other present regio defects:

[0437] P.sub.total=P.sub.12+P.sub.21e

[0438] The mole percent of 2,1 erythro regio defects was quantified with respect to all propene:

[0439] [21e] mol %=100* (P.sub.21e/P.sub.total)

[0440] For copolymers characteristic signals corresponding to the incorporation of ethylene were observed (Cheng, H. N., Macromolecules 17 (1984), 1950).

[0441] With regio defects also observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) correction for the influence of such defects on the comonomer content was required.

[0442] The comonomer fraction was quantified using the method of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157) through integration of multiple signals across the whole spectral region in the .sup.13C {.sup.1H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

[0443] For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et. al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

[0444] E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

[0445] Through the use of this set of sites the corresponding integral equation becomes:

[0446] E=0.5(I.sub.H+I.sub.G+0.5(I.sub.C+I.sub.D)) using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified.

[0447] The mole percent comonomer incorporation was calculated from the mole fraction:

[0448] E[mol %]=100*fE

[0449] The weight percent comonomer incorporation was calculated from the mole fraction:

[0450] E [wt %]=100* (fE * 28.06)/((fE * 28.06)+((1-fE)*42.08))

[0451] The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

[0452] Number Average Molecular Weight (M.sub.n), Weight Average Molecular Weight (M.sub.w) and Molecular Weight Distribution (MWD)

[0453] Molecular weight averages (Mw, Mn), and the molecular weight distribution (MWD), i.e. the Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight), were determined by Gel Permeation

[0454] Chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99. A PolymerChar GPC instrument, equipped with infrared (IR) detector was used with 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-methyl-phenol) as solvent at 160° C. and at a constant flow rate of 1 mL/min 200 μL. of sample solution were injected per analysis. The column set was calibrated using 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. Mark Houwink constants for PS, PE and PP used are as described per ASTM D 6474-99. All samples were prepared by dissolving 5.0-9.0 mg of polymer in 8 mL (at 160° C.) of stabilized TCB (same as mobile phase) for 2.5 hours for PP or 3 hours for PE at max. 160° C. under continuous gentle shaking in the autosampler of the GPC instrument. DSC analysis, melting temperature (Tm). crystallization temperature (Tc): measured with a TA Instrument Q2000 differential scanning calorimeter (DSC) on 5 to 7 mg samples. DSC run according to ISO 11357/part 3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min in the temperature range of −30 to +230° C. Crystallization temperature was determined from the cooling step, while melting temperature was determined from the heating scan.

[0455] Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.).

[0456] Density is measured according to ISO 1183-187. Sample preparation is done by compression moulding in accordance with ISO 1872-2:2007.

[0457] The xylene solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25° C. according ISO 16152; first edition; 2005-07-01. The part which remains insoluble is the xylene cold insoluble (XCI) fraction.

[0458] Flexural Modulus: The flexural modulus was determined in 3-point-bending according to ISO 178 on 80×10×4 mm.sup.3 test bars injection molded at 23° C. in line with EN ISO 1873-2.

[0459] Charpy notched impact test: The charpy notched impact strength (Charpy NIS) was measured according to ISO 179 2C/DIN 53453 at 23° C. and −20° C., using injection molded bar test specimens of 80×10×4 mm prepared in accordance with ISO 294-1:1996

[0460] Shrinkage in flow and shrinkage cross flow were determined on film gate injection moulded plaques: One is a sector (radius 300 mm and opening angle of)20° and the other one a stripe (340×65 mm). The two specimens are injection moulded at the same time in different thicknesses and back pressures (2 mm and 300, 400, 500 bars; 2.8 mm and 300, 400, 500 bars; 3.5 mm and 300, 400, 500 bars). The melt temperature is 240° C. and the temperature of the tool 25° C. Average flow front velocity is 3.0±0.2 mm/s for the 2 mm tool, 3.5±0.2 mm/s for the 2.8 mm tool and.0±0.2 mm/s for the 3.5 mm tool.

[0461] After the injection moulding process the shrinkage of the specimens is measured at 23° C. and 50% humidity. The measurement intervals are 1, 4, 24, 48 and 96 hours after the injection moulding. To determine the shrinkage 83 and 71 measurement points (generated by eroded dots on the tool surface) of the sector and the stripe, respectively, are recorded with a robot. Both, in flow and cross flow shrinkage of the 2.8 mm thick plates exposed to a back pressure of 400 bars at 96 hours after the injection moulding process are reported as final results.

[0462] Surface Appearance of Compact and Foamed Parts

[0463] The tendency to show flow marks was examined with a method as described below. This method is described in detail in WO 2010/149529, which is incorporated herein in its entirety.

[0464] An optical measurement system, as described by Sybille Frank et al. in PPS 25 Intern. Conf. Polym. Proc. Soc 2009 or Proceedings of the SPIE, Volume 6831, pp 68130T-68130T-8 (2008) was used for characterizing the surface quality.

[0465] This method consists of two aspects:

[0466] 1. Image Recording:

[0467] The basic principle of the measurement system is to illuminate the plates with a defined light source (LED) in a closed environment and to record an image with a CCD-camera system.

[0468] A schematic setup is given in FIG. 1.

[0469] 2. Image Analysis:

[0470] The specimen is floodlit from one side and the upwards reflected portion of the light is deflected via two mirrors to a CCD-sensor. The such created grey value image is analyzed in lines. From the recorded deviations of grey values the mean square error average (MSEaverage) or mean square error maximum (MSEmax) values are calculated allowing a quantification of surface quality/homogeneity, i.e. the higher the MSE value the more pronounced is the surface defect. MSEaverage and MSEmax values are not comparable. Generally, for one and the same material, the tendency to flow marks increases when the injection speed is increased.

[0471] The MSEaverage values were collected on compact injection-moulded plaques 440×148×2.8 mm produced with grain G1. The plaques were injection-moulded with different filling times of 1.5, 3 and 6 sec respectively.

[0472] Further Conditions:

[0473] Melt temperature: 240° C.

[0474] Mould temperature 30° C.

[0475] Dynamic pressure: 10 bar hydraulic

[0476] The MSEmax values were collected on compact injection-moulded plaques 210×148×2 mm produced with a one-point gating system and a grain marked here as G2, which differs from G1. The plaques were injection-moulded with filling time of 1.5 s.

[0477] The foamed parts were prepared by adding the corresponding foaming agent (see table 1 below) during the conversion step.

[0478] Cell structure of the foamed parts was determined by light microscopy and computer tomography from a cross-section of the foamed injection-moulded plate. The computer tomography scans were performed at a laboratory system Nanotom 180 NF (GE Phoenix|x-ray, Wunstorf, Germany). Since a matrix detector (Hamamatsu 2300×2300 pixels) was used, the system works in cone beam geometry. The Voxel edge length was set to 5 μm and 1700 projection images were collected. To reduce noise and motion artefacts, 6 images at each angular position were read out with the first image to be skipped and the other 5 images to be averaged and saved to disc.

[0479] Maximum force at break was determined on plaques with dimensions 148×148×2 mm during instrumented falling weight impact testing according to ISO 6603-2. The test was performed at room temperature with a lubricated tup with a diameter of 20 mm and impact velocity of 10 mm/s. The maximum force at break was determined as the maximum peak at the force-deformation curve collected during the test.

[0480] Compression test was performed on 10×10×2 mm plaques at room temperature according to ISO 604: 2002. The tests were carried out on a Zwick Z010U machine with a test speed of 0,87 mm/min at room temperature. The compressive stress was determined at 1 mm deformation. Thus, the compressive stress is defined as the force at break at 1 mm deformation divided by the specimen area at the beginning of the experiment.

[0481] Total carbon emission was determined according to VDA 277:1995 from pellets. The Total Volatiles value is the total emission of organic carbon, determined according to the method in VDA 277. This value represents the amount of organic compounds which are emitted by a test sample which compounds can be found in the interior of a car.

[0482] Total emission was determined according to 15012219-4 (Daimler AG standard) in a 1 m.sup.3 emission test chamber VCE 2000 (Votsch Industrietechnik GmbH, Bahlingen) fitted with a FID type MD 123 I/VE (Testa GmbH, Munich).

[0483] Odour was determined according to VDA 270:1992 according to variant 3 from pellets with a panel of 7 people.

2. EXAMPLES

[0484] The following inventive example IE1 as well as comparative examples CE1, CE2 and CE3 and the reference were prepared by melt blending the components set out in table 1 (without the foaming agent) on a co-rotating twin screw extruder. The polymer melt mixture was discharged and pelletized. Subsequently, compacted and foamed injection-moulded plaques 210×148×2 mm were produced with a one-point gating system. The plaques were injection-moulded with a filling time of 0.8 s. The foaming agent was added for IE1 and CE1, CE2 and CE3 during the conversion step.

TABLE-US-00001 TABLE 1 Overview of the composition for inventive example IE and comparative examples C1, CE2 and CE3 as well as the compacted reference IE CE1 CE2 CE3 Reference foamed foamed foamed foamed compacted HECO1 [wt.-%] 38 38 38 38 38 HECO2 [wt.-%] 26.5 26.5 26.5 26.5 26.5 PL [wt.-%] 8 8 8 8 8 HDPE [wt.-%] 5 5 5 5 5 Talc [wt.-%] 14.5 14.5 14.5 14.5 14.5 FA1 [wt.-%] 2 FA2 [wt.-%] 2 FA3 [wt.-%] 2 FA4 [wt.-%] 2 NA [wt.-%] 0.1 0.1 0.1 0.1 0.1 Additives [wt.-%] 7.9 7.9 7.9 7.9 7.9 HECO1 is the commercial heterophasic propylene copolymer BJ998MO of Borealis. HECO2 is the commercial heterophasic propylene copolymer EG066AI of Borealis. PL is the commercial ethylene-octene copolymer Queo8230 of Borealis having a density of 0.880 g/cm.sup.3, a melt flow rate MFR.sub.2 (190° C.) of 30.0 g/10 min and an 1-octene content of 7.5 mol-%. HDPE is the commercial high density polyethylene BorPure ™ MB7541 of Borealis. Talc is the commercial Talc Jetfine 3CA of Luzenac. FA1 is the commercial foaming agent EE25C of Eiwa. FA2 is the commercial foaming agent Hydrocerol ITP825 of Clariant. FA3 is the commercial foaming agent Tracel IM4215 of Tramaco. FA4 is the commercial foaming agent Tracel PO4135F of Tramaco. NA is the commercial nucleating agent NA-21 of Adeka Corporation. Additives is a masterbatch of typical additives such as antioxidants, carbon black, hindered amine light stabilizers, slipping agents, etc.

[0485] The properties of the comparative and inventive examples collected on 2 mm compact and chemically injection-moulded foamed plates are set out in table 2 below.

TABLE-US-00002 TABLE 2 Properties of comparative and inventive examples collected on 2 mm compact and chemically injection-moulded foamed plates. IE CE1 CE2 CE3 Reference foamed foamed foamed foamed compacted Total carbon emission [μgC/g] 88 88 96 83 94 Odour (7 persons) Average 3.6 4.8 5.6 4.2 3.8 median 4 5 6 5 4 MFR.sub.2, 230° C. [g/10 min] 29.97 Filler content [wt.-%] 14.5  MSE, 1.5 s 11.6 Total emission μg/m.sup.3 22100 38400 21200 according to toluene ISO12219-4 equivalent Appearance foamed 2 2 3 4 1 part (1-excelllent, 5- bad) Skin thickness foam [μm] 200 300 300 300 — Cell diameter foam [μm] 133 120 120 250 —

[0486] The cell structure of the inventive and comparative examples is also shown in FIG. 1 below.

[0487] The total carbon emissions of the foamed plates were best for CE3, however the odour which is very decisive for interior applications was best for IE, i.e. when using a foaming agent (FA) comprising citric acid in combination with a bicarbonate. Furthermore, IE and CE1 gave the finest foam. The surface of the foamed parts was investigated giving school marks from 1 (excellent surface) to 5 (bad surface) on the grained surface. IE1 and CE1 showed the best results. Altogether, the inventive example IE showed the best combination of surface appearance and mechanical properties as well as sufficient odour and emission properties.