Polypropylene composition with low shrinkage at wide application temperature range

Abstract

The present application relates to a polypropylene composition having a melt flow rate MFR.2 (230° C.) measured according to ISO 1133 in the range of 5 to 50 g/10 min, to a composition comprising the polypropylene composition and one or more additive(s) in an amount of up to 4 wt.-%, based on the total weight of the composition, to a process for the preparation of the polypropylene composition and an article comprising the polypropylene composition as well as the use of the polypropylene composition for decreasing the brittle-to-ductile transition temperature.

Claims

1. A polypropylene composition having a melt flow rate MFR.sub.2 (230° C.) measured according to ISO 1133 in the range of 5 to 50 g/10 min, the polypropylene composition comprising: (a) 55 to 75 wt. %, based on the total weight of the polypropylene composition, of a crystalline fraction (CF) as determined in the CRYSTEX QC method, the crystalline fraction (CF) having i) a melting temperature (Tm) measured by differential scanning calorimetry (DSC) between 147° C. and 162° C., and ii) an ethylene content of 1 wt. %, based on the total weight of the crystalline fraction (CF); and (b) 25 to 45 wt. %, based on the total weight of the polypropylene composition, of a soluble fraction (SF) as determined in a CRYSTEX QC method, the soluble fraction (SF) having i) an intrinsic viscosity (IV) in the range of 1.0 to 2.0 dl/g, and ii) an ethylene content in the range of 18 to 30 wt. %, based on the total weight of the soluble fraction (SF), wherein said polypropylene composition has a ratio of intrinsic viscosity of the soluble fraction (IV(SF)) to intrinsic viscosity of the crystalline fraction (IV(CF)) [(IV(SF))/(IV(CF))] in the range from 0.8 to 1.1, and wherein the polypropylene composition is polymerized in the presence of a single-site catalyst consisting of racemic anti-dimethylsilanediyl[2-methyl-4-(4-tert-butylphenyl)-inden-1-yl] [2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butyl-inden-1-yl]zirconium dichloride and methylaluminoxane (MAO) as cocatalyst.

2. The polypropylene composition according to claim 1, wherein the polypropylene composition comprises a polypropylene homopolymer matrix (M) and an ethylene-propylene copolymer (EPC) dispersed in the polypropylene homopolymer matrix (M).

3. The polypropylene composition according to claim 1, wherein the polypropylene composition comprises 60 to 72 wt. %, based on the total weight of the polypropylene composition, of the crystalline fraction (CF), and 28 to 40 wt. %, based on the total weight of the polypropylene composition, of the soluble fraction (SF).

4. The polypropylene composition according to claim 1, wherein the polypropylene composition has: i) an ethylene content in the range of 4.0 to 15.0 wt. %, based on the total weight of the polypropylene composition, and/or ii) a melt flow rate MFR.sub.2 (230° C.) measured according to ISO 1133 in the range of 8 to 40 g/10 min.

5. The polypropylene composition according to claim 1, wherein the polypropylene composition has: i) a melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) between 147° C. and 162° C., and/or ii) a crystallization temperature (T.sub.c) measured by differential scanning calorimetry (DSC) between 105° C. and 135° C.

6. The polypropylene composition according to claim 1, wherein the polypropylene composition has been produced in a multi-stage process.

7. The polypropylene composition according to claim 1, wherein the crystalline fraction (CF) has: i) a melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) between 148° C. and 156° C., and/or ii) an ethylene content in the range from 0.1 to 0.8 wt. %, based on the total weight of the crystalline fraction, and/or iii) an intrinsic viscosity (IV) in the range of 0.9 to 2.2 dl/g, and/or iv) an isotacticity determined as pentad regularity from 13C-NMR spectroscopy of at least 98%, and/or v) a content of <2,1>erythro regiodefects as determined from 13C-NMR spectroscopy of equal or less than 0.2 mol.-%.

8. The polypropylene composition according to claim 1, wherein the soluble fraction (SF) has: an intrinsic viscosity (IV) in the range of 1.1 to 1.9 dl/g.

9. The polypropylene composition according to claim 1, wherein the relative content of isolated to block ethylene sequences (I(E)): i) of the polypropylene composition is at most 30%, and/or ii) of the xylene cold soluble fraction (XCS) is at least 30%, wherein the I(E) content is defined by equation (I) $\begin{array}{cc}I\left(E\right)=\frac{\mathrm{fPEP}}{\left(\mathrm{fEEE}+\mathrm{fEEP}+\mathrm{fPEP}\right)}\times 100& \left(I\right)\end{array}$ 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; fEEP is the mol fraction of ethylene/ethylene/propylene sequences (EEP) and of propylene/ethylene/ethylene sequences (PEE) in the sample; fEEE is the mol fraction of ethylene/ethylene/ethylene sequences (EEE) in the sample wherein all sequence concentrations being based on a statistical triad analysis of .sup.13C-NMR data.

10. A process for the preparation of a polypropylene composition according to claim 1, wherein a polypropylene homopolymer matrix (M) is prepared in a first stage and an ethylene-propylene copolymer (EPC) is prepared in a second stage in the presence of the polypropylene homopolymer matrix (M).

11. A composition comprising the polypropylene composition according to claim 1 and one or more additive(s) in an amount of up to 4 wt.-%, based on the total weight of the composition.

12. An article comprising the polypropylene composition according to claim 1.

13. The process according to claim 10, wherein the polymer composition has a brittle-to-ductile transition temperature (BDTT) as measured in an instrumented Charpy notched impact strength test in line with ISO 179 1 eA in the range from −10 to +5° C.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1a relates to Schematic diagram of the CRYSTEX QC instrument,

(2) FIG. 1b relates to the elution of the polypropylene composition sample and obtained soluble and crystalline fractions in the TREF column (column filled with inert material e.g. glass beads) (see Del Hierro, P.; Ortin, A.; Monrabal, B.; ‘Soluble Fraction Analysis in polypropylene, The Column Advanstar Publications, February 2014. Pages 18-23).

(3) FIG. 2 shows the brittle-to-ductile transition temperatures (BDTT) of the inventive example IE as well as the comparative example CE.

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

Examples

1. Definitions/Measuring Methods

(5) 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. Melting temperature T.sub.m, crystallization temperature T.sub.c, is measured with Mettler TA820 differential scanning calorimetry (DSC) according to ISO 11357-1 on 5-10 mg samples. Both crystallization and melting curves were obtained during 10° C./min cooling and heating scans between 30° C. and 225° C. Melting and crystallization temperatures were taken as the peaks of endotherms and exotherms.

(6) Also the melt- and crystallization enthalpy (Hm and He) were measured by the DSC method according to ISO 11357-1.

(7) MFR.sub.2 (230° C.) was measured according to ISO 1133 (230° C., 2.16 kg load).

(8) MFR.sub.2 (190° C.) was measured according to ISO 1133 (190° C., 2.16 kg load).

(9) The glass transition temperature Tg was determined by dynamic mechanical analysis according to ISO 6721-7. The measurements were done in torsion mode on compression moulded samples (40×10×1 mm.sup.3) between −100° C. and +150° C. with a heating rate of 2° C./min and a frequency of 1 Hz.

(10) The xylene cold solubles (XCS, wt.-%) were determined at 25° C. according to ISO 16152; first edition; 2005-07-01.

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

(12) Quantification of Microstructure by NMR Spectroscopy

(13) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the stereo-regularity (tacticity), regio-regularity and comonomer content 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.

(14) For polypropylene homopolymers approximately 200 mg of material was dissolved in 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2). 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 needed for tacticity distribution quantification (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). Standard single-pulse excitation was employed utilising the NOE and bi-level WALTZ 16 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, 11289). A total of 8192 (8k) transients were acquired per spectra

(15) For ethylene-propylene copolymers 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, 11289). A total of 6144 (6k) transients were acquired per spectra.

(16) Quantitative .sup.13C {.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. For ethylene-propylene copolymers 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.

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

(18) 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.

(19) 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).

(20) 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.

(21) The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:
[mmmm]%=100*(mmmm/sum of all pentads)

(22) 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.

(23) 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).

(24) 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:
P.sub.21e=(I.sub.e6+I.sub.e8)/2

(25) 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:
P.sub.12=I.sub.CH3+P.sub.12e

(26) The total amount of propene was quantified as the sum of primary inserted propene and all other present regio defects:
P.sub.total=P.sub.12+P.sub.21e

(27) The mole percent of 2,1 erythro regio defects was quantified with respect to all propene:
[21e]mol %=100*(P.sub.21e/P.sub.total)

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

(29) 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.

(30) The mole fraction of ethylene in the polymer 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 of a .sup.13C {H} spectra acquired using defined conditions. This method was chosen for its accuracy, robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability to a wider range of comonomer contents.

(31) The mole percent comonomer incorporation in the polymer was calculated from the mole fraction according to:
E [mol %]=100*fE

(32) The weight percent comonomer incorporation in the polymer was calculated from the mole fraction according to:
E [wt %]=100*(fE*28.05)/((fE*28.05)+((1−fE)*42.08))

(33) The comonomer sequence distribution at the triad level was determined using the method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150) through integration of multiple signals across the whole spectral region of a .sup.13C{.sup.1H} spectra acquired using defined conditions. This method was chosen for its robust nature. Integral regions were slightly adjusted to increase applicability to a wider range of comonomer contents.

(34) The mole percent of a given comonomer triad sequence in the polymer was calculated from the mole fraction determined by the method of Kakugo et at. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150) according to:
XXX [mol %]=100*fXXX

(35) The mole fraction comonomer incorporation in the polymer, as determined from the comonomer sequence distribution at the triad level, were calculated from the triad distribution using known necessary relationships (Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201):
fXEX=fEEE+fPEE+fPEP
fXPX=fPPP+fEPP+fEPE
where PEE and EPP represents the sum of the reversible sequences PEE/EEP and EPP/PPE respectively.

(36) The randomness of the comonomer distribution was quantified as the relative amount of isolated ethylene sequences as compared to all incorporated ethylene. The randomness was calculated from the triad sequence distribution using the relationship:
R(E) [%]=100*(fPEP/fXEX)
Crystalline and Soluble Fractions and their Respective Properties

(37) The crystalline (CF) and soluble fractions (SF) of the polypropylene compositions as well as the comonomer content and intrinsic viscosities of the respective fractions were analyzed by the CRYSTEX QC, Polymer Char (Valencia, Spain).

(38) A schematic representation of the CRYSTEX QC instrument is shown in FIG. 1a. The crystalline and amorphous fractions were separated through temperature cycles of dissolution at 160° C., crystallization at 40° C. and re-dissolution in a 1,2,4-trichlorobenzene (1,2,4-TCB) at 160° C. as shown in FIG. 1b. Quantification of SF and CF and determination of ethylene content (C2) were achieved by means of an infrared detector (IR4) and an online 2-capillary viscometer was used for determination of the intrinsic viscosity (IV).

(39) The IR4 detector was a multiple wavelength detector detecting IR absorbance at two different bands (CH3 and CH2) for the determination of the concentration and the Ethylene content in Ethylene-Propylene copolymers. IR4 detector was calibrated with series of EP copolymers with known Ethylene content in the range of 2 wt.-% to 69 wt.-% (determined by 13C-NMR).

(40) The amount of Soluble Fraction (SF) and Crystalline Fraction (CF) were correlated through the XS calibration to the “Xylene Cold Soluble” (XCS) quantity and respectively Xylene Cold Insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration was achieved by testing various EP copolymers with XS content in the range of 2-31 wt.-%.

(41) Intrinsic viscosity (IV) of the parent EP copolymer and its soluble and crystalline fractions were determined with a use of an online 2-capillary viscometer and were correlated to corresponding IV's determined by standard method in decalin according to ISO 1628. Calibration was achieved with various EP PP copolymers with IV=2-4 dL/g.

(42) A sample of the polyproyplene composition to be analyzed was weighed out in concentrations of 10 mg/ml to 20 mg/ml. After automated filling of the vial with 1,2,4-TCB containing 250 mg/l 2,6-tert-butyl-4-methylphenol (BHT) as antioxidant, the sample was dissolved at 160° C. until complete dissolution is achieved, usually for 60 min, with constant stirring of 800 rpm.

(43) As shown in a FIGS. 1a and b, a defined volume of the sample solution was injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline part is taking place. This process was repeated two times. During the first injection, the whole sample was measured at high temperature, determining the IV[dl/g] and the C2[wt.-%] of the polypropylene composition. During the second injection, the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle were measured (wt.-% SF, wt.-% C2, IV).

(44) Shrinkage (SH) was determined by injection moulding of the resin with an injection moulding machine into a mould having a cavity to form a plate of 60×60×2 mm.sup.3 in line with ISO 1873. After cooling at room temperature for 96 hours, the length and the width of the plate were determined to calculate the longitudinal (in flow) and the transversal (across flow) shrinkage in percent.

(45) Flexural Modulus was determined in 3-point-bending according to ISO 178 on 80×10×4 mm.sup.3 test bars injection moulded at 23° C. in line with EN ISO 1873-2.

(46) Brittle-to-ductile transition temperature (BDTT) was measured based on the a(cN) values as determined from Charpy instrumented impact strength according to ISO 179-2:2000 on V-notched specimen with a geometry of 80×10×4 mm.sup.3 as required in ISO 179-1eA. The a(cN) values were determined in intervals of 3° C. from −40° C. to +41° C. with an impact velocity of 1.5 m/s and plotted over temperature, calculating the BDTT as the average value of the step increase. For a detailed description of the determination of the BDTT reference is made to Grein, C. et al, Impact Modified Isotactic Polypropylene with Controlled Rubber Intrinsic Viscosities: Some New Aspects About Morphology and Fracture, J Appl Polymer Sci, 87 (2003), 1702-1712.

(47) The coefficient of linear thermal expansion (CLTE) was determined in accordance with ISO 11359-2: 1999 on 10 mm long pieces cut from the same injection molded specimens as used for the flexural modulus determination. The measurement was performed in a temperature range from +23 to +80° C. and from −30 to +80° C., respectively, at a heating rate of 5° C./min.

(48) DSC analysis, melting temperature (T.sub.m), crystallization temperature (To), heat of fusion (Hm) and heat of crystallization (He): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is running 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 +225° C. Crystallization temperature (T.sub.c) and heat of crystallization (H.sub.e) are determined from the cooling step, while melting temperature (T.sub.m) and heat of fusion (H.sub.m) are determined from the second heating step.

(49) Number average molecular weight (M) and weight average molecular weight (Mw) were determined by Gel Permeation 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.

2. Examples

(50) All the chemicals and chemical reactions were handled under an inert gas atmosphere using Schlenk and glovebox techniques, with oven-dried glassware, syringes, needles or cannulas.

(51) MAO was purchased from Albermarle and used as a 30 wt-% solution in toluene. Perfluoroalkylethyl acrylate ester mixture (CAS number 65605-70-1) was purchased from the Cytonix corporation, dried over activated molecular sieves (2 times) and degassed by argon bubbling prior to use.

(52) Hexadecafluoro-1,3-dimethylcyclohexane (PFC) (CAS number 335-27-3) was obtained from commercial sources and dried over activated molecular sieves (2 times) and degassed by argon bubbling prior to use.

(53) Triethylaluminum was purchased from Aldrich and used as a 1 M solution in n-hexane. Hydrogen is provided by Air Liquide and purified before use. Propylene is provided by Borealis and purified before use.

(54) Complex:

(55) As metallocene complex was used the racemic anti-dimethylsilanediyl[2-methyl-4-(4-tert-butylphenyl)-inden-1-yl] [2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butyl-inden-1-yl]zirconium dichloride (MC 1) according to the following formula

(56) ##STR00011##

(57) Synthesis of racemic anti-dimethylsilanediyl[2-methyl-4-(4-tert-butylphenyl)-inden-1-yl] [2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butyl-inden-1-yl]zirconium dichloride can be found in WO2013/007650.

(58) Catalyst Preparation:

(59) Inside the glovebox, 54 μL of dry and degassed mixture of perfluoroalkylethyl acrylate ester (used as surfactant) were mixed with 2 mL of MAO in a septum bottle and left to react overnight. The following day, 44.50 mg of metallocene MC1 (0.051 mmol, 1 equivalent) were dissolved with 4 mL of the MAO solution in another septum bottle and left to stir inside the glovebox.

(60) After 60 minutes, 1 mL of the surfactant solution and the 4 mL of the MAO-metallocene solution were successively added into a 50 mL emulsification glass reactor containing 40 mL of PFC at −10° C. and equipped with an overhead stirrer (stirring speed=600 rpm). Total amount of MAO is 5 mL (450 equivalents). A red emulsion formed immediately and stirred during 15 minutes at −10° C./600 rpm. Then the emulsion was transferred via a 2/4 teflon tube to 100 mL of hot PFC at 90° C., and stirred at 600 rpm until the transfer is completed, then the speed was reduced to 300 rpm. After 15 minutes stirring, the oil bath was removed and the stirrer turned off. The catalyst was left to settle up on top of the PFC and after 35 minutes the solvent was siphoned off. The remaining catalyst was dried during 2 hours at 50° C. over an argon flow. 1.0 g of a red solid catalyst was obtained.

(61) Pre-Activation Procedure:

(62) The catalyst as prepared above (MC1-Cat) was pre-polymerised according to the following procedure Off-line pre-polymerisation experiments were done in a 125 mL pressure reactor equipped with gas-feeding lines and an overhead stirrer. Dry and degassed perfluoro-1,3-dimethylcyclohexane (PFC)(15 ml) and the desired amount of the catalyst MC1-Cat (604.6 mg) to be pre-polymerised were loaded into the reactor inside a glove box and the reactor was sealed. The reactor was then taken out from the glove box and placed inside a water cooled bath kept at 25° C. The overhead stirrer and the feeding lines were then connected. The experiment was started by opening the propylene feed into the reactor and setting the stirrer speed at 450 rpm. The propylene feed was left open and the monomer consumption was compensated by keeping the total pressure in the reactor constant (about 5 barg). The experiment was continued for the polymerisation time (17.5 min) sufficient to provide the desired degree of polymerisation (DP). The reactor was then taken back inside the glove box before opening and the content was poured into a glass vessel. PFC was evaporated until a constant weight was obtained to yield 2.90 g of the pre-polymerised catalyst. The degree of polymerisation (DP) was determined gravimetrically and/or by analysis of the ash and/or aluminium content of the catalyst. Pre-polymerization degree is 3.8 g(PP)/g(cat). Prepolymerised MC 1-Cat is marked as PMC1-Cat.

(63) The catalyst used and its composition is listed in table 1:

(64) TABLE-US-00001 TABLE 1 used catalyst Catalyst DP MC1 type g/g wt.-% PMC1-Cat 3.8 0.65
Polymerisation

(65) The polypropylene composition has been prepared by means of a 3-step polymerization (bulk homopolymerisation+gas phase (GP 1) homopolymerisation+gas phase (GP2) C.sub.2/C.sub.3 copolymerisation) in a 20-L reactor, as described below.

(66) Step1: Bulk Propylene Homopolymerization

(67) A stirred autoclave (double helix stirrer) with a volume of 21.2 dm.sup.3 containing 0.2 bar-g propylene, was filled with additional 3.97 kg propylene plus the amount of H.sub.2 indicated in table 2. After adding 0.73 mmol triethylaluminium (Aldrich, 1 molar solution in n-hexane) using a stream of 250 g propylene, the solution was stirred at 20° C. and 250 rpm for 20 min. Then the catalyst was injected as described in the following. The solid, pre-polymerized catalyst (type as listed in the tables) was loaded into a 5-mL stainless steel vial inside the glovebox, the vial was attached to the autoclave, then a second 5-mL vial containing 4 ml n-hexane and pressurized with 10 bars of N.sub.2 was added on top, the valve between the two vials was opened and the solid catalyst was contacted with hexane under N.sub.2 pressure for 2 s, then flushed into the reactor with 250 g propylene. Stirring speed was increased to 250 rpm and pre-polymerisation was run for 10 min at 20° C. At the end of the prepolymerization step, the stirring speed was increased to 350 rpm and the polymerisation temperature increased to 80° C. When the internal reactor temperature reached 71° C., the amount of H.sub.2 indicated in table 2 was added with a defined flow via thermal mass flow controller. The reactor temperature was held constant throughout the polymerization. The polymerization time was measured starting when the temperature was 2° C. below the set polymerization temperature.

(68) Step 2: Gas Phase: Propylene Homopolymerization (GP1)

(69) After the bulk step was finished, the stirrer speed was adjusted to 50 rpm and the reactor pressure was reduced to 0.5 bar below the set pressure by venting. Then the stirrer speed was set to 250 rpm, the reactor temperature to 80° C. and the amount of H.sub.2 indicated in table 2 was dosed via MFC. Then the reactor P and T were held constant by propylene feed via MFC until the target split had been reached.

(70) Step 3: Gas Phase: Ethylene/Propylene Copolymerization (GP2)

(71) When the GP1 had been finished, the stirrer speed was reduced to 50 rpm. The reactor pressure was lowered to 0.3 barg by venting, the temperature and control device was set to 70° C. Then the reactor was filled with 200 g propylene at a flow of 70 g/min and flushed again to 0.3 barg.

(72) Afterwards the stirrer speed was adjusted to 250 rpm. Then the reactor was filled with the chosen C.sub.3/C.sub.2 monomer ratio (transition feed, see table 2). The speed of the reactor filling during the transition was limited by the max. flow of the gas flow controllers. When the reactor temperature reached 69° C. and the reactor pressure reached the set value, the composition of the fed C.sub.3/C.sub.2 mixture was changed to the target copolymer composition and temperature and pressure were held constant until the amount of C.sub.3/C.sub.2 gas mixture required to reach the target rubber split had been consumed.

(73) The reaction was stopped by setting the stirrer speed to 20 rpm, cooling the reactor to 30° C. and flashing the volatile components.

(74) After flushing the reactor twice with N.sub.2 and one vacuum/N.sub.2 cycle, the product was taken out and dried overnight in a fume hood. 100 g of the polymer was additivated with 0.2 wt.-% ionol and 0.1 wt.-% PEPQ (dissolved in acetone) and then dried overnight in a hood plus 2 hours in a vacuum drying oven at 60° C. Table 2 summarizes the relevant polymerization parameters.

(75) TABLE-US-00002 TABLE 2 Polymerisation parameters of the inventive example (IE) IE catalyst PMC1-Cat Prepolymerisation res. time min 10 H.sub.2 Nl 0 Bulk polymerisation Total H.sub.2 Nl 2 res. time min 40 GP1 (homopolymerisation H.sub.2 Nl 2 res. tune min 40 GP2 (copolymerisation) H.sub.2 Nl 0 res. tune min 90 C.sub.2/C.sub.3 ratio transition wt/wt 0.56 GP2 C.sub.3 feed g 215 GP2 C.sub.2 feed g 53 GP2 C.sub.2/C.sub.3 ratio wt/wt 0.25

(76) The comparative example was polymerized in a Borstar PP pilot plant with a prepolymerisation reactor, one loop and three gas phase reactors using the commercial catalyst Avant ZN104 of LyondellBasell with Triethylaluminium (TEAL) as co-catalyst and Dicyclopentyldimethoxysilane (donor D) as external donor. Table 3 summarizes the relevant polymerization parameters.

(77) TABLE-US-00003 TABLE 3 Polymerisation parameters of the comparative example (CE) Co/ED ratio mol/mol 18 Co/TC ratio mol/mol 220 Prepolymerization Residence time h 0.1 Temperature ° C. 30 Loop Reactor (LR) Split wt.-% 32.5 Temperature ° C. 70 Pressure kPa 5355 H2/C3 mol/kmol 14 MFR g/10 min 35 1st Gas Phase Reactor (GPR1) Split wt.-% 34.5 Temperature ° C. 78 Pressure kPa 2214 H2/C3 mol/kmol 78 MFR2 g/10 min 35 2nd Gas Phase Reactor (GPR2) Split wt.-% 21 Temperature ° C. 71 Pressure [kPa 2202 H2/C2 ratio mol/kmol 219 C2/C3 ratio mol/kmol 715 C2 mol % 12 MFR g/10 min 12 XCS wt % 19 3rd Gas Phase Reactor (GPR3) Temperature ° C. 83 Pressure kPa 1383 C2/C3 ratio mol/kmol 747 H2/C2 ratio mol/kmol 203 MFR g/10 min 13 split wt % 12

(78) The resulting polymer powders were compounded in a co-rotating twin-screw extruder Prism TSE16 (for IE) resp. Coperion ZSK 57 (for CE) 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-5 butylphenyl) phosphate) phosphite) of BASF AG, Germany) and 0.05 wt.-% calcium stearate. The characteristics of the inventive example IE and of the comparative example CE are indicated in tables 4a and 4b below.

(79) TABLE-US-00004 TABLE 4a General polymer characteristics IE CE MFR g/10 min 14 12 Catalyst SSC ZN Tm ° C. 149 163 Hm J/g 68 73 Tc ° C. 113 113 SF wt.-% 32.4 32.5 C2(total) wt-% 6.5 15.8 C2(SF) wt.-% 21.0 37.2 C2(CF) wt.-% 0.5 6.2 IV(total) dl/g 1.7 1.8 IV(SF) dl/g 1.7 2.2 IV(CF) dl/g 1.7 1.6 IV(SF)/IV(CF) n.a. 1.0 1.3 G′ MPa 367 410 Tg1 ° C. 0 2 Tg2 ° C. −38 −54 SH-in flow % 0.89 0.97 SH-across flow % 1.03 1.21 Flexural modulus MPa 611 671 BDTT Charpy NIS ° C. −2 12 CLTE(−30-80° C.) μm/m/° C. 111 110

(80) TABLE-US-00005 TABLE 4b Polymer characteristics determined by NMR IE CE C2 total (NMR) wt.-% 6.5 15.8 EEE mol % 1.87 8.77 EEP mol % 4.33 8.55 PEP mol % 3.52 4.76 I(E) % 36 22 C2 XCS (NMR) wt.-% 20.7 52.6 EEE mol % 4.07 18.34 FTP mol % 12.37 29.75 PEP mol % 11.58 18.28 I(E) % 41 28 B(E) % 15 28 XCS wt.-% 32.5 30.4 IV(XCS) dl/g 1.7 2.1

(81) From tables 4a and 4b, it can be gathered that the inventive example has an improved shrinkage, even if compared to a polypropylene composition that has been prepared in the presence of a Ziegler-Natta catalyst.

(82) In FIG. 2, the brittle-to-ductile transition temperatures (BDTT) are shown for the inventive example IE as well as for the comparative example CE. It can be gathered that the inventive example IE has a lower brittle-to-ductile transition temperatures (BDTT) than the comparative example CE and thus a broader application temperature range.