POLYPROPYLENE-ULTRAHIGH-MOLECULAR-WEIGHT-POLYETHYLENE COMPOSITIONS

Abstract

PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition having: —a melting temperature Tm in the range of 125 to 150° C. (DSC, ISO 11357, Part 3), —an MFR2 of 0.15 to 0.60 g/10min (2.16 kg, 230° C., IS01133), —units derived from 1-hexene in an amount of at least 1.80 wt.-%, and—a XS according to IS116152 of less than 5.0 wt.-% all weight percentages with respect to the total PP/UHMW-PE composition.

Claims

1: PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition having: a melting temperature Tm in the range of 125 to 150° C. (DSC, ISO 11357, Part 3), an MFR.sub.2 of 0.15 to 0.60 g/10 min (2.16 kg, 230° C., ISO1133), units derived from 1-hexene in an amount of at least 1.80 wt. %, and a XS according to ISO16152 of less than 5.0 wt. % all weight percentages with respect to the total PP/UHMW-PE composition.

2: The PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition of claim 1, having units derived from ethylene in an amount of 0.5 to 15 wt. % with respect to the total PP/UHMW-PE composition.

3: Pipe comprising a PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition), the PP/UHMW-PE having a melting temperature Tm in the range of 125 to 150° C. (DSC, ISO 11357, Part 3), an MFR2 of 0.15 to 0.60 q/10 min (2.16 kg, 230° C., ISO1133), units derived from 1-hexene in an amount of at least 1.80 wt. %, and a XS according to ISO16152 of less than 5.0 wt. % all weight percentages with respect to the total PP/UHMW-PE composition.

4: Process for the preparation of the PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition according to claim 1, comprising the steps of; (a) introducing a stream of propylene and 1-hexene to a first reactor, so that the molar ratio of the feed rate of 1-hexene to the feed rate of propylene is from 2.0 to 4.0 mol/kmol; further introducing a stream of catalyst system to the first reactor, whereby the catalyst system includes; (i) a catalyst having the following structure: ##STR00004## wherein, M is zirconium or hafnium; each X independently is a sigma—donor ligand; L is a bridge of formula -(ER.sup.10.sub.2).sub.y-; y is 1 or 2; E is C or Si; each R.sup.10 is independently a C.sub.1-C.sub.20-hydrocarbyl group, tri(C.sub.1-C.sub.20 alkyl)silyl group, C.sub.6-C.sub.20 aryl group, C.sub.7-C.sub.20 arylalkyl group or C.sub.7-C.sub.20 alkylaryl group; R.sup.1 are each independently the same or are different from each other and are a CH.sub.2-R.sup.11 group, with R.sup.11 being H or linear or branched C.sub.1-C.sub.6 alkyl group, C.sub.3-C.sub.8 cycloalkyl group, C.sub.6-C.sub.10 aryl group; R.sup.3, R.sup.4 and R.sup.5 are each independently the same or different from each other and are H or a linear or branched C.sub.1-C.sub.6 alkyl group, C.sub.7-C.sub.20 arylalkyl group, C.sub.7-C.sub.20 alkylaryl group, or C.sub.6-C.sub.20 aryl group with the proviso that if there are four or more R.sup.3, R.sup.4 and R.sup.5 groups different from H present in total, one or more of R.sup.3, R.sup.4 and R.sup.5 is other than tert butyl; R.sup.7 and R.sup.8 are each independently the same or different from each other and are H, a CH.sub.2-R.sup.12 group, with R.sup.12 being H or linear or branched C.sub.1-C.sub.6 alkyl group, SiR.sup.13.sub.3, GeR.sup.13.sub.3, OR.sup.13, SR.sup.13, NR.sup.13.sub.2, wherein R.sup.13 is a linear or branched C.sub.1-C.sub.6 alkyl group, C.sub.7-C.sub.20 alkylaryl group and C.sub.7-C.sub.20 arylalkyl group or C.sub.6-C.sub.20 aryl group, R.sup.9 are each independently the same or different from each other and are H or a linear or branched C.sub.1-C.sub.6 alkyl group; and R.sup.2 and R.sup.6 all are H; and (ii) a cocatalyst system comprising a boron containing cocatalyst and an aluminoxane cocatalyst: (iii) polymerizing propylene and 1-hexene in the presence of the catalyst system in the first reactor to produce a first intermediate; withdrawing a product stream comprising the first intermediate from the first reactor; transferring the stream comprising the first intermediate to a second reactor and further polymerizing propylene in the second reactor in the presence of the first intermediate by feeding further propylene, 1-hexene and hydrogen into the second reactor such that the molar ratio of the concentration of hydrogen to the concentration of propylene is in the range of 0.1 to 0.8 mol/kmol; and further the molar ratio of the concentration of 1-hexene to the concentration of propylene is in the range of 4.0 to 6.0 mol/kmol thus yielding a second intermediate and withdrawing a stream comprising the second intermediate from the second reactor (b) transferring at least a part of the stream comprising the second intermediate to a third reactor and further polymerizing ethylene in the presence of the second intermediate by introducing ethylene into the third reactor to yield the PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition, whereby the molar ratio of the concentration of hydrogen to the concentration of ethylene is less than 500 mol/1.0×10.sup.6 mol.

5: Process according to claim 4, comprising comprises feeding no fresh catalyst system to the second nor the third reactor.

6: Process according to claim 4, whereby the first intermediate has: a melting temperature Tm in the range of 145 to 155° C. (DSC, ISO 11357, Part 3), and/or an MFR2 of 0.20 to 0.55 g/10 min (2.16 kg, 230° C., ISO1133), and/or units derived from 1-hexene in an amount of at least 0.5 wt. %, and/or units derived from 1-hexene in an amount of less than 2.5 wt. %, and/or a XS measured according to ISO16152 of less than 11.0 wt. %, and/or a XS measured according to ISO16152 of more than 7.5 wt. %.

7: Process according to claim 4, whereby the second intermediate has; an MFR2 of 0.25 to 0.55 g/10 min (2.16 kg, 230° C., ISO1133), and/or units derived from 1-hexene in an amount of at least 2.0 wt. %.

8: Process according to claim 4, whereby the amount of the first intermediate in the second intermediate is from 41 to 49% by weight.

9: Process according to claim 4, whereby the amount of the second intermediate in the PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition is from 85 to 99.5% by weight.

10: Process according to claim 4, whereby the ratio of the MFR2(second intermediate)/MFR2(final PP/UHMW-PE composition) is 1.25 to 2.00.

11: Process according to claim 4, whereby the first reactor is a loop reactor and/or the second reactor is a gas phase reactor and/or the third reactor is a gas phase reactor.

12: Process according to claim 4, whereby a prepolymerization precedes the first polymerization stage taking place in the first reactor.

13: The PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition of claim 1.

14. (canceled)

15: Process of dispersing an UHMW-PE composition having a weight average molecular weight Mw of above 1.5×10.sup.6 q/mol by providing a polypropylene composition having: a melting temperature Tm in the range of 125 to 150° C. (DSC, ISO 11357, Part 3), units derived from 1-hexene in an amount of at least 1.80 wt. %.

16: The pipe according to claim 3, wherein the PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) composition includes units derived from ethylene in an amount of 0.5 to 15 wt. % with respect to the total PP/UHMW-PE composition.

Description

DETAILED DESCRIPTION

[0128] In the following several particularly preferred embodiments are described.

[0129] In a first embodiment the PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) has [0130] a melting temperature Tm in the range of 137 to 142° C. (DSC, ISO 11357, part 3), [0131] an MFR.sub.2 of 0.15 to 0.60 g/10 min (2.16 kg, 230° C., ISO1133), [0132] units derived from 1-hexene in an amount of 2.3 to 3.0 wt.-%, [0133] a XS according to ISO16152 of less than 2.5 wt.-%; and [0134] units derived from ethylene in an amount of 4.0 to 8.0 wt.-% with respect to the total PP/UHMW-PE composition.

[0135] The MFR.sub.2 of 0.15 to 0.60 g/10 min (2.16 kg, 230° C., ISO1133) of the first embodiment is preferably 0.15 to 0.30 g/10 min.

[0136] The XS according to ISO16152 of the first embodiment is less than 2.0 wt.-%.

[0137] In a second embodiment the PP/UHMW-PE (Polypropylene-Ultrahigh-Molecular-Weight-Polyethylene) has [0138] a melting temperature Tm in the range of 137 to 143° C. (DSC, ISO 11357, part 3), [0139] an MFR.sub.2 of 0.15 to 0.60 g/10 min (2.16 kg, 230° C., ISO1133), [0140] units derived from 1-hexene in an amount of 2.3 to 3.0 wt.-%, [0141] a XS according to ISO16152 of less than 2.5 wt.-%; and [0142] units derived from ethylene in an amount of 8.0 to 12 wt.-% with respect to the total PP/UHMW-PE composition.

[0143] The MFR.sub.2 of 0.15 to 0.60 g/10 min (2.16 kg, 230° C., ISO1133) of the second embodiment is preferably 0.15 to 0.30 g/10 min.

[0144] The melting temperature Tm of the second embodiment is preferably in the range of 139 to 143° C. (DSC, ISO 11357, part 3).

Experimental Part

Measurement Methods:

Al and Zr Determination (ICP-Method)

[0145] The elementary analysis of a catalyst was performed by taking a solid sample of mass, M, cooling over dry ice. Samples were diluted up to a known volume, V, by dissolving in nitric acid (HNO.sub.3, 65%, 5% of V) and freshly deionised (DI) water (5% of V). The solution was then added to hydrofluoric acid (HF, 40%, 3% of V), diluted with DI water up to the final volume, V, and left to stabilise for two hours.

[0146] The analysis was run at room temperature using a Thermo Elemental iCAP 6300 Inductively Coupled Plasma—Optical Emmision Spectrometer (ICP-OES) which was calibrated using a blank (a solution of 5% HNO.sub.3, 3% HF in DI water), and 6 standards of 0.5 ppm, 1 ppm, 10 ppm, 50 ppm, 100 ppm and 300 ppm of Al, with 0.5 ppm, 1 ppm, 5 ppm, 20 ppm, 50 ppm and 100 ppm of Hf and Zr in solutions of 5% HNO3, 3% HF in DI water.

[0147] Immediately before analysis the calibration is ‘resloped’ using the blank and 100 ppm Al, 50 ppm Hf, Zr standard, a quality control sample (20 ppm Al, 5 ppm Hf, Zr in a solution of 5% HNO3, 3% HF in DI water) is run to confirm the reslope. The QC sample is also run after every 5th sample and at the end of a scheduled analysis set.

[0148] The content of hafnium was monitored using the 282.022 nm and 339.980 nm lines and the content for zirconium using 339.198 nm line. The content of aluminium was monitored via the 167.079 nm line, when Al concentration in ICP sample was between 0-10 ppm (calibrated only to 100 ppm) and via the 396.152 nm line for Al concentrations above 10 ppm.

[0149] The reported values are an average of three successive aliquots taken from the same sample and are related back to the original catalyst by inputting the original mass of sample and the dilution volume into the software.

[0150] In the case of analysing the elemental composition of prepolymerized catalysts, the polymeric portion is digested by ashing in such a way that the elements can be freely dissolved by the acids. The total content is calculated to correspond to the weight % for the prepolymerized catalyst.

[0151] GPC: Molecular weight averages, molecular weight distribution, and polydispersity index (M.sub.n, M.sub.w, M.sub.w/M.sub.n)

[0152] Molecular weight averages (Mw, Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI=Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) were determined by Gel Permeation Chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99.

[0153] A PolymerChar GPC instrument, equipped with infrared (IR) detector was used with 3×Olexis and 1x 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

Quantification of Copolymer Microstructure by NMR Spectroscopy Comonomer Determination by NMR Spectroscopy (C2)

[0154] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was further 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-(I)-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.

[0155] 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).

[0156] 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.

[0157] 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.

[0158] 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(Sββ+Sβy+Sβδ+0.5(Sαβ+Sαy))

[0159] 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))

[0160] 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.

[0161] The mole percent comonomer incorporation was calculated from the mole fraction:

E[mol %]=100*fE

[0162] The weight percent comonomer incorporation was calculated from the mole fraction:

E[wt %]=100*(fE*28.06)/((fE*28.06)+((I−fE)*42.08))

[0163] 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.

Comonomer Determination: Hexene Content—.SUP.13.C NMR Spectroscopy

[0164] Quantitative .sup.13C{.sup.1H} NMR spectra recorded in the molten-state using a Bruker Avance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 7 mm magic-angle spinning (MAS) probehead at 180° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification.(Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382., Parkinson, M., Klimke, K., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2007; 208:2128., Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373). Standard single-pulse excitation was employed utilising the NOE at short recycle delays of 3s (Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382., Pollard, M., Klimke, K., Graf, R., Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004; 37:813.). and the RS-HEPT decoupling scheme (Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239., Griffin, J. M., Tripon, C., Samoson, A., Filip, C., and Brown, S. P., Mag. Res. in Chem. 2007 45, S1, S198). A total of 16384 (16k) transients were acquired per spectra.

[0165] Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

[0166] Characteristic signals corresponding to the incorporation of 1-hexene were observed and the comonomer content quantified in the following way.

[0167] The amount of 1-hexene incorporated in PHP isolated sequences was quantified using the integral of the αB4 sites at 44.2 ppm accounting for the number of reporting sites per comonomer:

H=IαB4/2

[0168] The amount of 1-hexene incorporated in PHHP double consecutive sequences was quantified using the integral of the ααB4 site at 41.7 ppm accounting for the number of reporting sites per comonomer:

HH=2*IααB4

[0169] When double consecutive incorporation was observed the amount of 1-hexene incorporated in PHP isolated sequences needed to be compensated due to the overlap of the signals αB4 and αB4B4 at 44.4 ppm:

H=(IaB4−2*IααB4)/2

[0170] The total 1-hexene content was calculated based on the sum of isolated and consecutively incorporated 1-hexene:

Htotal=H+HH

[0171] When no sites indicative of consecutive incorporation observed the total 1-hexeen comonomer content was calculated solely on this quantity:

Htotal=H

[0172] Characteristic signals indicative of regio 2,1-erythro defects were observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

[0173] The presence of 2,1-erythro regio defects was indicated by the presence of the Pa$ (21e8) and Pay (21e6) methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic signals.

[0174] The total amount of secondary (2,1-erythro) inserted propene was quantified based on the αα21e9 methylene site at 42.4 ppm:

P21=Iαα21e9

[0175] The total amount of primary (1,2) inserted propene was quantified based on the main Sαα methylene sites at 46.7 ppm and compensating for the relative amount of 2,1-erythro, αB4 and ααB4B4 methylene unit of propene not accounted for (note H and HH count number of hexene monomers per sequence not the number of sequences):

P12=I.sub.sαα+2*P21+H+HH/2

[0176] The total amount of propene was quantified as the sum of primary (1,2) and secondary (2,1-erythro) inserted propene:

Ptotal=P12+P21=I.sub.sαα+3*Iαα21e9+(IαB4−2*IααB4)/2+IααB4

This simplifies to:

Ptotal=I.sub.sαα+3*Iαα21e9+0.5*IαB4

[0177] The total mole fraction of 1-hexene in the polymer was then calculated as:

fH=Htotal/(Htotal+Ptotal)

[0178] The full integral equation for the mole fraction of 1-hexene in the polymer was:

fH=(((IαB4−2*IααB4)/2)+(2*IααB4))/((I.sub.sαα+3*Iαα21e9+0.5*IαB4)+((IαB4−2*IααB4)/2)+(2*IααB4)) [0179] This simplifies to:

fH=(IαB4/2+IααB4)/(I.sub.sαα+3*Iαα21e9+IαB4+IααB4)

[0180] The total comonomer incorporation of 1-hexene in mole percent was calculated from the mole fraction in the usual manner:

H[mol %]=100*fH

[0181] The total comonomer incorporation of 1-hexene in weight percent was calculated from the mole fraction in the standard manner:

H[wt %]=100*(fH*84.16)/((fH*84.16)+((1−fH)*42.08))

Melt Flow Rate (MFR)

[0182] The melt flow rate (MFR) or melt index (MI) is measured according to ISO 1133. Where different loads can be used, the load is normally indicated as the subscript, for instance, MFR.sub.2 which indicates 2.16 kg load. The temperature is selected according to ISO 1133 for the specific polymer, for instance, 230° C. for polypropylene. Thus, for polypropylene MFR.sub.2 is measured at 230° C. temperature and under 2.16 kg load.

[0183] DSC Analysis, Melting Temperature (Tm) and Crystallization Temperature (Tc): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is 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 +225° C.

[0184] Crystallization temperature and heat of crystallization (Hc) are determined from the cooling step, while melting temperature and heat of fusion (Hf) are determined from the second heating step.

Xylene Solubles (XS)

[0185] The xylene soluble (XS) fraction as defined and described in the present invention is determined in line with ISO 16152 as follows: 2.0 g of the polymer were dissolved in 250 ml p-xylene at 135° C. under agitation. After 30 minutes, the solution was allowed to cool for 15 minutes at ambient temperature and then allowed to settle for 30 minutes at 25+/−0.5 0C. The solution was filtered with filter paper into two 100 ml flasks. The solution from the first 100 ml vessel was evaporated in nitrogen flow and the residue dried under vacuum at 90° C. until constant weight is reached. The xylene soluble fraction (percent) can then be determined as follows:

XS%=(100.m.Vo)/(mo.v); mo=initial polymer amount (g); m=weight of residue (g); Vo=initial volume (ml); v=volume of analysed sample(ml).

Catalyst Activity

[0186] The catalyst activity was calculated on the basis of following formula:

Catalyst Activity=(production rate of the polymer (kg/h))/(feed rate of the catalyst g/h) x average residence time of the polymer in the reactor (h))

Productivity

[0187] Overall productivity was calculated as

[00001]$\mathrm{Catalyst}\mathrm{Productivity}\left(\mathrm{kg}-\frac{\mathrm{PP}}{g}\right)=\frac{\mathrm{production}\mathrm{rate}\mathrm{of}\mathrm{the}\mathrm{polymer}\left(\frac{\mathrm{kg}}{h}\right)}{\mathrm{feed}\mathrm{rate}\mathrm{of}\mathrm{the}\mathrm{catayst}\left(\frac{g}{h}\right)}$

[0188] For both the catalyst activity and the productivity the catalyst loading is either the grams of prepolymerized catalyst or the grams of metallocene present in that amount of prepolymerized catalyst.

[0189] The composition of the catalysts (before the off-line prepolymerization step) has been determined by ICP as described above. The metallocene content of the prepolymerized catalysts has been calculated from the ICP data as follows:

[00002]$\begin{array}{cc}\frac{A1}{Zr}\left(\mathrm{mol}/\mathrm{mol}\right)=\frac{\mathrm{Al}\left(\mathrm{wt}\%,\mathrm{ICP}\right)/26,90}{\mathrm{Zr}\left(\mathrm{wt}\%,\mathrm{ICP}\right)/91,22}& \mathrm{Equation}1\end{array}$$\begin{array}{cc}\mathrm{Zr}\left(\mathrm{mol}\%\right)=\frac{100}{\frac{\mathrm{Al}}{\mathrm{Zr}}\left(\mathrm{mol}/\mathrm{mol}\right)+1}& \mathrm{Equation}2\end{array}$$\begin{array}{cc}\mathrm{MC}\left(\mathrm{wt}\%,\mathrm{unprepol},\mathrm{cal}\right)=\frac{100\times \left(\mathrm{Zr},\mathrm{mol}\%\times \mathrm{MwMC}\right)}{\mathrm{Zr}.\mathrm{mol}\%\times \mathrm{MwMC}-\left(100-\mathrm{Zr}.\mathrm{mol}\%\right)\times \mathrm{MwMAO}}& \mathrm{Equation}3\end{array}$$\begin{array}{cc}\mathrm{MC}\left(\mathrm{wt}\%,\mathrm{prepolymerized}\mathrm{cat}\right)=\frac{\mathrm{MC}\left(\mathrm{wt}\%.\mathrm{unprepolymerized}\mathrm{cal}\right)}{\mathrm{DP}+1}& \mathrm{Equation}4\end{array}$

EXAMPLES

[0190] Examples were carried out in pilot scale. A three reactor process set up was used, whereby the first reactor was a loop reactor and the second and third reactors were gas phase reactors.

[0191] The catalyst abbreviated “SSC” used in the inventive examples was prepared as described in detail in WO 2015/011135 A1 (metallocene complex MC1 with methylaluminoxane (MAO) and borate (cocatalyst system) resulting in Catalyst 3 described in WO 2015/011135 A1) with the proviso that the surfactant was 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol. The metallocene complex (MC1 in WO 2015/011135 A1) was prepared as described in WO 2013/007650 A1 (metallocene E2 in WO 2013/007650 A1).”

[0192] Comparative examples used a two reactor system. For comparative example 1 15 wt.-% of a LLDPE material produced with a single site catalyst was introduced in the pelletization.

TABLE-US-00001 TABLE 1 Examples Comp. Comp. Working Working Working Example Example 1 Example 2 Example 1 Example 2 Example 3 Product PPr PPr PPr PPr PPr name (hexene) (hexene) (hexene) (hexene) (hexene) Catalyst SSC SSC SSC SSC SSC Prepolymer isaton reactor Temp. (° C.) 20 20 20 20 20 Press. (kPa) 4771 4765 4755 4763 4769 Catalyst system 3.7 3.9 3.8 3.7 3.5 feed (g/h) C3 feed (kg/h) 62 62 62 62 62 H2 (g/h) 0.10 0.10 0.10 0.10 0.10 1. Reactor. loop Temp. (° C.) 75.0 75.0 75.0 75.0 75.0 Press. (kPa) 4531.5 4527.0 4536.0 4536.7 4539.6 C3 feed (kg/h) 164.7 164.5 164.4 164.7 164.7 C6 feed (kg/h) 1.1 1.1 1.1 1.1 1.1 H2 feed (g/h) 0.2 0.2 0.2 0.2 0.2 Feed H2/C3 0.0 0.0 0.0 0.0 0.0 ratio (mol/kmol) Feed C6/C3 3.3 3.3 3.3 3.3 3.3 ratio (mol/kmol) Production 34.4 36.8 37.3 37.4 35.9 rate (kg/h) Solid 32.6 33.3 33.2 34.0 31.6 Concentration (wt.-%) 1 and 2 reactor 46.7 42.2 45.7 42.3 43.6 Polymer Split (wt.-%) Catalyst 9.7 10.1 10.3 10.7 10.8 productivity after B2 (kg/g) Catalyst activity 24.2 24.8 25.1 26.6 26.2 in B2 (kg/g h) MFR2 (g/10 min) 0.48 0.58 0.36 0.34 0.47 Total C6 (wt.-%) 1.3 1.2 1.4 1.2 1.3 Tm (° C.) 148.4 149.4 150.4 151.4 152.4 XS (%) 6.2 7.2 8.2 9.2 10.2 Fines (%) 5.03 6.03 7.03 8.03 9.03 APS (mm) 6.4 7.4 8.4 9.4 10.4 Bulk Density (kg/m3) 465 466 467 468 469 2. Reactor. GPR Temp. (° C.) 80.0 80.0 80.0 80.0 80.1 Press. (kPa) 2400.0 2398.9 2400.0 2400.0 2399.9 C3 feed (kg/h) 210.4 207.7 207.1 207.3 208.9 H2 feed (g/h) 0.3 0.3 0.6 0.9 1.8 C6 feed (g/h) 2.0 2.3 2.2 2.9 3.2 H2/C3 0.4 0.4 0.4 0.3 0.5 concentration ratio (mol/kmol) C6/C3 4.9 5.2 5.2 5.1 4.9 concentration ratio (mol/kmol) Polymer residence 2.0 2.0 2.0 2.0 2.0 time (h) Bed level (cm) 140.0 139.9 140.0 140.0 140.4 1 and 2 reactor 53.3 57.8 54.3 57.7 56.4 Polymer Split (wt.-%) MFR2 (g/10 min) 0.3 0.3 0.3 0.4 0.5 C6 (wt.-%) 2.3 2.6 2.6 2.8 2.8 3. Reactor. GPR Temp. (° C.) 75.0 75.0 75.0 Press. (kPa) 2499.6 2500.4 2498.9 Bed level (cm) 100.1 100.1 100.0 C3 feed (kg/h) 0.0 0.0 0.0 H2 feed (g/h) 0.0 0.0 0.0 C2 feed (kg/h) 50.0 50.0 50.0 H2/C2 0.0 0.0 0.0 concentration ratio (mol/kmol) Polymer Split 7.0 10.0 10.0 (wt.-%) (3.sup.rd reactor product vs. total) MFR2 (g/10 min) 0.2 0.2 0.3 XS (%) 1.7 2.0 1.5 Catalyst 19.6 20.0 22.9 24.1 23.2 productivity (kg PP/g cat) Final product Tcr (° C.) 105.4 102.4 102.7 101.6 101.6 Tm (° C.) 138.4 137.9 138.5 140.4 140.4 Pellet MFR2 0.3 0.3 0.18 0.17 0.20 (g/10 min) Total C6 (wt.-%) 2.4 2.5 2.5 2.6 2.6 Total C2 (wt.-%) 6 10.2 10 XS (%) 0.57 0.58 1.6 2.1 2 Bulk Density (kg/m3) 508 501 513 510 506 APS (mm) 1.32 1.35 1.56 1.41 1.48