Propylene copolymer composition with improved long-term mechanical properties

Abstract

Propylene-ethylene random copolymers with improved long-term mechanical properties, especially improved impact strength retention, their manufacture as well as their use, e.g. for the production of moulded articles, particularly injection moulded articles, such as thin-walled plastic containers for packaging.

Claims

1. Propylene-ethylene random copolymers having: (i) a melt flow rate MFR.sub.2 (according to ISO 1133, 230 C., 2.16 kg) in the range of 30 to 70 g/10 min, (ii) a total ethylene comonomer content of 2.0 to 5.0 mol % (iii) a content of the orthorhombic gamma-crystal phase 100.K of 20% to less than 40% as determined by wide-angle X-ray diffraction (WAXS) on a 60602 mm.sup.3 injection moulded test specimens as described in the experimental part, and comprising a) a blend of a-1) 1.0 to 10.0 wt %, based on the total weight of the propylene-ethylene random copolymer, of a masterbatch comprising a propylene homopolymer as carrier polymer and 10 to 2000 ppm, based on the masterbatch, of a polymeric -nucleating agent (pNA), and a-2) 0.02 to 1.0 wt %, based on the total weight of the propylene-ethylene random copolymer, of a soluble -nucleating agent (sNA).

2. Propylene-ethylene copolymers according to claim 1, wherein the copolymers are comprised by two propylene copolymer fractions: b) a first propylene copolymer fraction (PP-COPO-1) and c) a second propylene copolymer fraction (PP-COPO-2) having an ethylene comonomer content of at most 6.5 mol %, said first propylene copolymer fraction (PP-COPO-1) having a higher MFR.sub.2 and/or a lower ethylene comonomer content than said second propylene copolymer fraction (PP-COPO-2).

3. Propylene-ethylene copolymers according to claim 2, wherein the propylene copolymer fraction (PP-COPO-2) has an ethylene comonomer content of at least 2.0 mol % and most 6.5 mol % and the first propylene copolymer fraction (PP-COPO-1) has an ethylene comonomer content in the range of 0.5 mol % to at most 5.0 mol %, whereby the first propylene copolymer fraction (PP-COPO-1) has an ethylene comonomer content below that of the second propylene copolymer fraction (PP-COPO-2).

4. Propylene-ethylene copolymers according to claim 2, wherein the propylene copolymer fraction (PP-COPO-1) has a melt flow rate MFR.sub.2 (230 C.) in the range of in the range of 20.0 to 120 g/10 min and the second propylene copolymer fraction (PP-COPO-2) has a melt flow rate MFR.sub.2 (230 C.) in the range of 20.0 to 120 g/10 min, whereby the MFR.sub.2 of the second propylene copolymer fraction (PP-COPO-2) is lower than the MFR.sub.2 of the first propylene copolymer fraction (PP-COPO-1).

5. Propylene-ethylene copolymers according to claim 2, wherein the second propylene copolymer fraction (PP-COPO-2) has an ethylene comonomer content which is higher than the ethylene comonomer content of the first propylene copolymer fraction (PP-COPO-1) and has an MFR.sub.2 which is lower than the MFR.sub.2 of the first propylene copolymer fraction (PP-COPO-1).

6. Propylene-ethylene copolymers according to claim 1, wherein the polymeric -nucleating agent in the masterbatch is a polymerized vinyl compound of formula (I): ##STR00002## wherein R.sub.1 and R.sub.2 together form a 5 or 6 membered saturated or unsaturated or aromatic ring or they stand independently for a lower alkyl comprising 1 to 4 carbon atoms.

7. Propylene-ethylene copolymers according to claim 1, wherein the masterbatch comprising a propylene homopolymer and the polymeric -nucleating agent is obtained in a sequential polymerization process, comprising a prepolymerization step in which a vinyl compound according to claim 6 is first polymerized with a catalyst system, comprising a Ziegler-Natta catalyst component, a cocatalyst and optional external donor, the reaction mixture of the polymer of the vinyl compound and the catalyst system is then introduced in a first polymerization reactor (R1) where a first propylene homopolymer fraction is produced, followed by a second polymerization reactor (R2), wherein the second propylene homopolymer fraction is produced in the presence of the first propylene homopolymer fraction.

8. Propylene-ethylene copolymers according to claim 1, wherein the soluble -nucleating agent is selected from the group consisting of sorbitol derivatives, nonitol derivatives, benzene-trisamides, and mixtures thereof.

9. Propylene-ethylene copolymers according to claim 1, wherein the propylene-ethylene copolymers have been polymerized in the presence of: a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic compound; b) optionally a co-catalyst (Co), and c) optionally an external donor (ED).

10. Propylene-ethylene copolymers according to claim 9, wherein: a) the internal donor (ID) is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives and/or mixtures thereof; b) the molar-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is 5 to 45.

11. Propylene-ethylene copolymers according to claim 1, wherein the propylene-ethylene copolymers are produced in a polymerization process comprising at least one reactor (R1) or at least two reactors (R1) and (R2), whereby in the first reactor (R1) a first propylene copolymer fraction (PP-COPO-1) is produced and subsequently transferred into the second reactor (R2), in the second reactor (R2) a second propylene copolymer fraction (PP-COPO-2) is produced in the presence of the first propylene copolymer fraction (PP-COPO-1).

12. Moulded articles, comprising a propylene-ethylene copolymer according to claim 1.

13. Thin wall packaging claim 1, made by injection moulding, comprising a propylene-ethylene copolymer according to claim 1.

14. Moulded articles according to claim 12, wherein a tensile modulus (measured according to ISO 527) measured after 96 hours of storage at +231 C. and 50% relative humidity (standard conditions) of at least 1000 MPa and tensile modulus (measured according to ISO 527) measured after 1344 hours of storage under standard conditions of at least 1100 MPa and, simultaneously by a puncture energy (measured according to ISO 6603-2; 60602 mm.sup.3 specimens) measured after 96 hours of storage under standard conditions of at least 19 J, and measured after 1344 hours of storage under standard conditions of at least 19 J.

Description

EXPERIMENTAL PART

A) Measuring Methods

(1) 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.

(2) Calculation of comonomer content of the second propylene copolymer fraction (PP-COPO-2):

(3) $\begin{array}{cc}\frac{C\left(\mathrm{PP}\right)-w\left(\mathrm{PP}1\right)C\left(\mathrm{PP}1\right)}{w\left(\mathrm{PP}2\right)}=C\left(\mathrm{PP}2\right)& \left(I\right)\end{array}$
wherein w(PP1) is the weight fraction [in wt %] of the first propylene copolymer fraction (PP-COPO-1), w(PP2) is the weight fraction [in wt %] of second propylene copolymer fraction (PP-COPO-2, C(PP1) is the comonomer content [in mol %] of the first propylene copolymer fraction (PP-COPO-1), C(PP) is the comonomer content [in mol %] of the propylene-ethylene copolymer, C(PP2) is the calculated comonomer content [in mol %] of the second propylene copolymer fraction (PP-COPO-2).

(4) Calculation of melt flow rate MFR.sub.2 (230 C.) of the second propylene copolymer fraction (PP-COPO-2):

(5) $\begin{array}{cc}\mathrm{MFR}\left(\mathrm{PP}2\right)={10}^{\left[\frac{\log \left(\mathrm{MFR}\left(\mathrm{PP}\right)\right)-w\left(\mathrm{PP}1\right)\log \left(\mathrm{MFR}\left(\mathrm{PP}1\right)\right)}{w\left(\mathrm{PP}2\right)}\right]}& \left(\mathrm{III}\right)\end{array}$
wherein w(PP1) is the weight fraction [in wt %] of the first propylene copolymer fraction (PP-COPO-1), w(PP2) is the weight fraction [in wt %] of second propylene copolymer fraction (PP-COPO-2), MFR(PP1) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the first propylene copolymer fraction (PP-COPO-1), MFR(PP) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the propylene-ethylene copolymer, MFR(PP2) is the calculated melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the second propylene copolymer fraction (PP2-COPO-2).

(6) MFR.sub.2 (230 C.) is measured according to ISO 1133 (230 C., 2.16 kg load).

(7) Quantification of Microstructure by NMR Spectroscopy

(8) 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 of 1,2-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 (6 k) transients were acquired per spectra.

(9) 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).

(10) With characteristic signals corresponding to 2,1 erythro regio defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

(11) 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.

(12) 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:
E=0.5(S+S+S+0.5(S+S))

(13) Through the use of this set of sites the corresponding integral equation becomes:
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.

(14) The mole percent comonomer incorporation was calculated from the mole fraction:
E[mol %]=100*fE

(15) The weight percent comonomer incorporation was calculated from the mole fraction:
E[wt %]=100*(fE*28.06)/((fE*28.06)+((1fE)*42.08))

(16) 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. The relative content of isolated to block ethylene incorporation was calculated from the triad sequence distribution using the following relationship (equation (I)):

(17) $\begin{array}{cc}I\left(E\right)=\frac{f\mathrm{PEP}}{\left(f\mathrm{EEE}+f\mathrm{PEE}+f\mathrm{PEP}\right)}100& \left(I\right)\end{array}$
wherein
I(E) is the relative content of isolated to block ethylene sequences [in %];
fPEP is the mol fraction of propylene/ethylene/propylene sequences (PEP) in the sample;
fPEE is the mol fraction of propylene/ethylene/ethylene sequences (PEE) and of ethylene/ethylene/propylene sequences (EEP) in the sample;
fEEE is the mol fraction of ethylene/ethylene/ethylene sequences (EEE) in the sample
The Xylene Solubles (XCS, wt %):

(18) Content of xylene cold solubles (XCS) is determined at 25 C. according ISO 16152; first edition; 2005-07-01

(19) Tensile Test:

(20) The tensile modulus was measured at 23 C. according to ISO 527-1 (cross head speed 1 mm/min) using injection moulded specimens moulded at 180 C. or 200 C. according to ISO 527-2(1B), produced according to EN ISO 1873-2 (dog 10 bone shape, 4 mm thickness).

(21) The tensile modulus for the examples was measured after 96 h and 1344 hours of storage.

(22) Puncture energy was determined in the instrumental falling weight (IFW) test according to ISO 6603-2 using injection moulded plaques of 60602 mm.sup.3 and a test speed of 2.2 m/s. Puncture energy reported results from an integral of the failure energy curve measured at +23 C.

(23) The puncture energy for the examples was measured after 96 h and 1344 hours of storage

(24) Wide-Angle X-Ray Scattering (WAXS)

(25) Samples prepared for WAXS were prepared in the same way as for the puncture energy measurement.

(26) The determination of crystallinity and of polymorphic composition was performed in reflection geometry using a Bruker D8 Discover with GADDS x-ray diffractometer operating with the following settings: x-ray generator: 30 kV and 20 mA; .sub.1=6 & .sub.2=13; sample-detector distance: 20 cm; beam size (collimator): 500 m; and duration/scan: 300 seconds. 3 measurements have been performed on each sample. Intensity vs. 2 curves between 2=10 and 2=32.5 were obtained by integrating the 2-dimensional spectra. The quantification of intensity vs. 2 curves were then performed as follows:

(27) Intensity vs. 2 curve was acquired with the same measurement settings on an amorphous iPP sample, which was prepared by solvent extraction. An amorphous halo was obtained by smoothing the intensity vs. 2 curve. The amorphous halo has been subtracted from each intensity vs. 2 curve obtained on actual samples and this results in the crystalline curve.

(28) The crystallinity index X.sub.c is defined with the area under the crystalline curve and the original curve using the method proposed by Challa et al. (Makromol. Chem. vol. 56 (1962), pages 169-178) as:

(29) $X_c=\frac{\mathrm{Area}\mathrm{under}\mathrm{crystalline}\mathrm{curve}}{\mathrm{Area}\mathrm{under}\mathrm{original}\mathrm{spectrum}}100.$

(30) In a two-phase crystalline system (containing - and -modifications), the amount of -modification within the crystalline phase B was calculated using the method proposed by Turner-Jones et al. (Makromol. Chem. Vol. 75 (1964), pages 134-158) as:

(31) $B=\frac{I^{}\left(300\right)}{I^{}\left(110\right)+I^{}\left(040\right)+I^{}\left(130\right)+I^{}\left(300\right)},$
where, I.sup.(300) is the intensity of (300) peak, I.sup. (110) is the intensity of (110) peak, I.sup.(040) is the intensity of (040) peak and I.sup.(130) is the intensity of (130) peak obtained after subtracting the amorphous halo.

(32) In a two-phase crystalline system (containing - and -modifications), the amount of -modification within the crystalline phase G (=K) was calculated using the method developed by Pae (J. Polym. Sci., Part A2, vol. 6 (1968), pages 657-663) as:

(33) $G=\frac{I^{}\left(117\right)}{I^{}\left(130\right)+I^{}\left(117\right)},$
where, I.sup.(130) is the intensity of (130) peak and I.sup.(117) is the intensity of (117) peak obtained after subtracting a base line joining the base of these peaks.

B) Examples

(34) Catalyst for Inventive Examples:

(35) Used Chemicals:

(36) 20% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), provided by Chemtura 2-ethylhexanol, provided by Amphochem

(37) 3-Butoxy-2-propanol(DOWANGL PnB), provided by Dow

(38) bis(2-ethylhexyl)citraconate, provided by SynphaBase

(39) TiCl.sub.4, provided by Millenium Chemicals

(40) Toluene, provided by Aspokem

(41) Viscoplex 1-254, provided by Evonik

(42) Heptane, provided by Chevron

(43) Preparation of a Mg Complex

(44) First a magnesium alkoxide solution was prepared by adding, with stirring (70 rpm), into 1 1 kg of a 20 wt-% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), a mixture of 4.7 kg of 2-ethylhexanol and 1.2 kg of butoxypropanol in a 20 l stainless steel reactor. During the addition the reactor contents were maintained below 45 C. After addition was completed, mixing (70 rpm) of the reaction mixture was continued at 60 C. for 30 minutes. After cooling to room temperature 2.3 kg g of the donor bis(2-ethylhexyl)citraconate was added to the Mg-alkoxide solution keeping temperature below 25 C. Mixing was continued for 15 minutes under stirring (70 rpm)

(45) Preparation of Solid Catalyst Component

(46) 20.3 kg of TiCl.sub.4 and 1.1 kg of toluene were added into a 20 l stainless steel reactor. Under 350 rpm mixing and keeping the temperature at 0 C., 14.5 kg of the Mg complex prepared in example 1 was added during 1.5 hours. 1.7 l of Viscoplex 1-254 and 7.5 kg of heptane were added and after 1 hour mixing at 0 C. the temperature of the formed emulsion was raised to 90 C. within 1 hour. After 30 minutes mixing was stopped catalyst droplets were solidified and the formed catalyst particles were allowed to settle. After settling (1 hour), the supernatant liquid was siphoned away.

(47) Then the catalyst particles were washed with 45 kg of toluene at 90 C. for 20 minutes followed by two heptane washes (30 kg, 15 min). During the first heptane wash the temperature was decreased to 50 C. and during the second wash to room temperature.

(48) The solid catalyst component was used along with triethyl-aluminium (TEAL) as co-catalyst and dicyclo pentyl dimethoxy silane (D-donor) as donor.

Comparative Example 1 (CE1)

(49) The catalyst used in the polymerization processes of the comparative example (CE1) was the catalyst of the example section of WO 2010009827 A1 (see pages 30 and 31) along with triethyl-aluminium (TEAL) as co-catalyst and dicyclo pentyl dimethoxy silane (D-donor) as donor.

Comparative Example 2 (CE2)

(50) The catalyst used in the polymerization processes of the comparative example (CE2) was prepared as described now:

(51) First, 0.1 mol of MgCl.sub.23 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of 15 C. and 300 ml of cold TiCl.sub.4 was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20 C. At this temperature, 0.02 mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135 C. during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCl.sub.4 was added and the temperature was kept at 135 C. for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80 C. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described in general e.g. in patent publications EP491566, EP591224 and EP586390.

(52) The catalyst was used along with triethyl-aluminium (TEAL) as co-catalyst and cyclohexylmethyl dimethoxy silane (C-donor) as donor.

(53) The polymerization was done in a Borstar pilot plant with a prepolymerization reactor, a loop reactor and a gas phase reactor (1.sup.st GPR) for IE1 and CE1 and for CE2 a Spheripol pilot plant with a prepolymerization reactor and two loop reactors were used.

(54) The polymerization conditions are indicated in table 1.

(55) TABLE-US-00001 TABLE 1 Preparation of the Examples IE1 CE1 CE2 TEAL [g/tC3] 180 150 160 Donor [g/tC3] 50 50 40 Prepolymerization Temperature [ C.] 33 30 28 Residence time [h] 0.33 0.3 0.08 Loop (PP-COPO-1) Temperature [ C.] 70 70 68 Residence time [h] 0.5 0.7 0.47 C2/C3 [mol/kmol] 8.1 6.7 7.5 H2/C3 [mol/kmol] 5.5 11.5 15.8 MFR [g/10 min] 43 48 50 C2 [mol %] 4.0 3.7 5.3 XCS [wt %] 7 4.7 8.4 split [%] 55 55 50 1st GPR/2.sup.nd Loop (PP-COPO-2) Temperature [ C.] 86 85 68 Residence time [h] 2.1 1.74 0.47 C2/C3 [mol/kmol] 22.1 30 7.5 H2/C3 [mol/kmol] 56.9 139 15.8 MFR [g/10 min] 38 47 50 C2 [mol %] 5.2 5.2 5.3 XCS [wt %] 8 6.4 8.4 split [%] 45 45 50

(56) All polymer powders were compounded in a co-rotating twin-screw extruder Coperion ZSK 57 at 220 C. with 0.2 wt.-% of Irganox B225 (1:1-blend of Irganox 1010 (Pentaerythrityl-tetrakis(3-(3,5-di-tert.butyl-4-hydroxytoluyl)-propionate and tris (2,4-di-t-butylphenyl) phosphate) phosphite) of BASF AG, Germany) and 0.05 wt.-% calcium stearate and the below described nucleating agents.

(57) The material of the inventive example IE1 as well as the materials of comparative examples CE1 and CE2 were nucleated with a) 2 wt % of a masterbatch of a propylene homopolymer having an MFR.sub.2 of 20 g/10 min and 200 ppm of vinylcycloalkane polymer (pVCH), based on the total weight of the propylene-ethylene copolymers and

(58) b) 0.2 wt % of the sorbitol M3988, commercially available from Milled, based on the total weight of the propylene-ethylene copolymers.

(59) Preparation of the Propylene Homopolymer (i.e. of the Masterbatch):

(60) A catalyst prepared as described above for the Inventive Examples was modified with vinylcyclohexane (VCH).

(61) 41 liters of mineral oil (Paraffinum Liquidum PL68) were added to the prepolymerization reactor of a Borstar pilot plant followed by 1.79 kg of triethyl aluminium (TEAL) and 0.79 kg of dicyclopentyl dimethoxy silane (donor D) under inert conditions at room temperature. Afterwards 5.5 kg of the catalyst prepared as described above for the inventive Examples was added, followed by 5.55 kg of vinylcyclohexane (VCH).

(62) Propylene homopolymer was prepared in the Borstar pilot plant comprising the Prepolymerization reactor (CSTR), one loop reactor and one gas phase reactor.

(63) TABLE-US-00002 TABLE 2 preparation of masterbatch propylene homopolymer TEAL/Ti [mol/mol] 90 TEAL/Donor [mol/mol] 5 Prepolymerization B1 Temperature [ C.] 30 B1 Pressure [barg] 55 B1 Residence time [h] 0.38 Loop B2 Temperature [ C.] 80 B2 Pressure [barg] 55 B2 Residence time [h] 0.6 B2 H2/C3 ratio [mol/kmol] 0.36 B2 Split [%] 50 B2 MFR2 [g/10 min] 10 GPR1 B3 Temperature [ C.] 80 B3 Pressure [barg] 30 B3 Residence time [h] 2.0 B3 H2/C3 ratio [mol/kmol] 159.6 B3 split [%] 50 B3 MFR2 [g/10 min] 19.5 Final product MFR.sub.2 [g/10 min] 20

(64) The polymer was stabilized by melt mixing a co-rotating twin-screw extruder at 200-230 C. with 0.2 wt.-% of Irganox B225 (1:1-blend of Irganox 1010 (Pentaerythrityl-tetrakis(3-(3,5-di-tert.butyl-4-hydroxytoluyl)-propionate and tris (2,4-di-t-butylphenyl) phosphate) phosphite) of BASF AG, Germany) and 0.1 wt.-% calcium stearate.

(65) As Comparative Example 3 (CE3), Inventive Example 4 (IE4) of WO 2014187687 was added.

(66) The polymers according to this patent application were produced with the same catalyst and the same process as IE1 of the instant invention.

(67) The polymers differ in the C2 total amount and in the C2 amount of the second propylene fraction (PP-COPO-2).

(68) The polymers of WO 2014187687 were nucleated only with 2 wt % of a masterbatch of a propylene homopolymer having an MFR.sub.2 of 20 g/10 min and 200 ppm of vinylcycloalkane polymer (pVCH) (prepared as described above), based on the total weight of the propylene-ethylene copolymers. No soluble alpha nucleating agent was added.

(69) The properties of the nucleated copolymers are shown in Table 2:

(70) TABLE-US-00003 TABLE 2 properties of nucleated copolymers Example IE1 CE1 CE2 CE3 MFR.sub.2 (230 C., 2.16 kg) [g/10 min] 45 45 45 40 C2 total (NMR) [mol %] 4.8 5.5 5.5 5.2 100.K/WAXS [%] 34 42 40 n.m. Tensile modulus after 96 h [MPa] 1089 1122 1089 1048 Tensile modulus after 1344 h [MPa] 1202 1224 1250 n.m Puncture energy after 96 h [J] 22.2 18.7 18.7 3.1 Puncture energy after 1344 h [J] 21.6 10.1 13.8 n.m n-PEP.sup.1) [%] 66.3 72.1 64.9 65.3 EEE [mol %] 0.47 0.42 0.53 0.61 EEP [mol %] 1.16 1.11 1.52 1.38 PEP [mol %] 3.21 3.95 3.79 3.75 PPP [mol %] 87.88 86.28 86.5 85.88 EPP [mol %] 7.20 8.02 7.37 8.10 EPE [mol %] 0.08 0.21 0.28 0.28 ${}^{1)}I\left(e\right)=\frac{\mathrm{fPEP}}{\left(\mathrm{fEEE}+\mathrm{fPEE}+\mathrm{fPEP}\right)}100\left(I\right)$

(71) From Table 1 it can be seen that the inventive propylene-ethylene copolymer has clearly higher puncture energy after 96 h than the polymer of CE4.

(72) From FIG. 1 the changes in tensile modulus and puncture energy from measurement after 96 h to measurement of 1344 h can be seen. The polymer of IE1 clearly performs best, i.e. high level of impact strength retention compared to the polymers of CE1 and CE2.

(73) From FIG. 2 it can be seen that the polymer of IE1 has a clearly slower trend of puncture energy decrease than the polymers of the comparative examples CE1 and CE2.