Process for the manufacture of a capacitor film

Abstract

Process for producing of a capacitor film comprising the steps of (a) polymerizing propylene in the presence of a catalyst comprising a solid catalyst system obtaining a polypropylene, (b) subjecting said polypropylene to a film forming process obtaining a capacitor film, wherein during the polymerization step (a) said catalyst comprising the solid catalyst system fragments into nanosized catalyst fragments being distributed in said polypropylene, said solid catalyst system comprises a transition metal, a metal which is selected from one of the groups 1 to 3 of the periodic table (IUPAC), and an internal electron donor.

Claims

1. Process for producing a capacitor film comprising the steps of: (a) polymerizing propylene and optionally ethylene and/or at least one C.sub.4 to C10 -olefin in the presence of a catalyst comprising a solid catalyst system (SCS) to obtain a polypropylene (PP), (b) subjecting said polypropylene (PP) to a film forming process to obtain a capacitor film, wherein said polypropylene (PP) is the only polymer in the capacitor film, wherein during the polymerization step (a) said catalyst comprising the solid catalyst system (SCS) fragments into nanosized catalyst fragments (F) being distributed in said polypropylene (PP), said solid catalyst system (SCS) comprises: (i) a compound of a transition metal of the periodic table (IUPAC), (ii) a compound of a metal selected from one of the groups 1 to 3 of the periodic table (IUPAC), and (iii) an electron donor (E), and wherein the polypropylene is not subjected to a washing step and wherein the solid catalyst system (SCS) is obtained by: (a) preparing a solution of a complex (C) of a metal which is selected from one of the groups 1 to 3 of the periodic table (IUPAC) and an electron donor (E), said complex (C) is obtained by reacting a compound (CM) of said metal with said electron donor (E) or a precursor (EP) thereof in an organic solvent, (b) mixing said solution of complex (C) with a liquid transition metal compound (CT), (c) obtaining thereby an emulsion of a continuous phase and an dispersed phase, said dispersed phase is in form of droplets and comprises the complex (C) and the transition metal compound (CT), and (d) solidifying the droplets of the dispersed phase obtaining thereby the solid catalyst system (SCS).

2. Process according to claim 1, wherein the polypropylene (PP): (a) has <2,1> erythro regiodefects of equal or below 0.4 mol.-% determined by .sup.13C-NMR spectroscopy, and/or (b) has a breakdown voltage at 100 C. of at least 350 AC/m measured on a biaxially oriented polypropylene (BOPP) film made from said polypropylene (PP) at a draw ratio in machine direction and in transverse direction of 4.59.5, and/or (c) fulfils the equation $\frac{\left(P75-P110\right)}{P75}1006.0;$ wherein P75 is the permittivity measured at 50 Hz and 75 C., P110 is the permittivity measured at 50 Hz and 110 C.; and/or (d) fulfils the equation $\frac{\left(P75-P120\right)}{P75}10012.0;$ wherein P75 is the permittivity measured at 50 Hz and 75 C., P120 is the permittivity measured at 50 Hz and 120 C.; and/or (e) fulfils the equation $\frac{\left(D75-D110\right)}{D75}100-10.0,$ wherein D75 is the dissipation (tan delta) measured at 50 Hz and 75 C, D110 is the dissipation (tan delta) measured at 50 Hz and 110 C.; and/or (f) fulfils the equation $\frac{\left(D75-D120\right)}{D75}10010.0,$ wherein D75 is the dissipation (tan delta) measured at 50 Hz and 75 C.; D120 is the dissipation (tan delta) measured at 50 Hz and 120 C.

3. Process according to claim 1, wherein the solid catalyst system (SCS) (a) has a specific surface area measured according to ASTM D 3663 of less than 20 m.sup.2/g, and/or (b) comprises catalytically inactive solid material, wherein said material optionally has (b1) a specific surface area below 500 m.sup.2/g, and/or (b2) a mean particle size (d50) below 200 nm.

4. Process according to claim 1, wherein the polypropylene (PP) is: (i) a propylene homopolymer, or (ii) a random propylene copolymer with a comonomer content of equal or below 1.0 wt. %, the comonomers are ethylene and/or at least one C.sub.4 to C.sub.10 -olefin.

5. Process according to claim 1, wherein the film forming process is a drawing process in which the polypropylene (PP) is drawn in machine direction and in transverse direction, wherein the draw ratio in both directions is at least 4.0.

6. Process according to claim 1, wherein: (a) a surfactant is used to form and/or stabilize the emulsion, and/or (b) the temperature during formation of the emulsion is equal or below 60 C.

7. Process according to claim 1, wherein after film forming the obtained capacitor film is metalized.

Description

EXAMPLES

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) Quantification of Microstructure by NMR Spectroscopy

(3) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the isotacticity, regio-regularity and comonomer content of the polymers.

(4) 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 probe head at 125 C. using nitrogen gas for all pneumatics.

(5) 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 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 8192 (8k) transients were acquired per spectra

(6) 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.

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

(8) 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.

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

(10) 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.

(11) 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).

(12) 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.

(13) 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)

(14) 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.

(15) 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).

(16) 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

(17) 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

(18) 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

(19) 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

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

(21) 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.

(22) 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 {.sup.1H} 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.

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

(24) 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)+((1fE)*42.08))

(25) 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.

(26) 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

(27) 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

(28) where PEE and EPP represents the sum of the reversible sequences PEE/EEP and EPP/PPE respectively.

(29) 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)
Molecular Weight Averages, Molecular Weight Distribution, Branching Index (Mn, Mw, MWD, g) determined by SEC/VISC-LS

(30) 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. A PL 220 (Polymer Laboratories) GPC equipped with a refractive index (RI), an online four capillary bridge viscometer (PL-BV 400-HT), and a dual light scattering detector (PL-LS 15/90 light scattering detector) with a 15 and 90 angle was used. 3 Olexis and 1 Olexis Guard columns from Polymer Laboratories as stationary phase and 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-Di tert butyl-4-methyl-phenol) as mobile phase at 160 C. and at a constant flow rate of 1 mL/min was applied. 200 L of sample solution were injected per analysis. The corresponding detector constants as well as the inter detector delay volumes were determined with a narrow PS standard (MWD=1.01) with a molar mass of 132900 g/mol and a viscosity of 0.4789 dl/g. The corresponding dn/dc for the used PS standard in TCB is 0.053 cm.sup.3/g.

(31) The molar mass at each elution slice was determined by light scattering using a combination of two angels 15 and 90. All data processing and calculation was performed using the Cirrus Multi-Offline SEC-Software Version 3.2 (Polymer Laboratories a Varian inc. Company). The molecular weight was calculated using the option in the Cirrus software use combination of LS angles in the field sample calculation options subfield slice MW data from.

(32) The data processing is described in details in G. Saunders, P. A. G: Cormack, S. Graham; D. C. Sherrington, Macromolecules, 2005, 38, 6418-6422. Therein the Mw, at each slice is determined by the 90 angle by the following equation:

(33) ${\mathrm{Mw}}_i=\frac{K_{\mathrm{LS}}*{R\left(\right)}^{90}}{\frac{dn}{dc}*R*P\left(\right)}$

(34) The Rayleigh ratio R().sup.90 of the 90 angle is measured by the LS detector and R is the response of the RI-detector. The particle scatter function P() is determined by the usage of both angles (15 and 90) as described by C. Jackson and H. G. Barth (C. Jackson and H. G. Barth, Molecular Weight Sensitive Detectors in Handbook of Size Exclusion Chromatography and related techniques, C.-S. Wu, 2.sup.nd ed., Marcel Dekker, New York, 2004, p. 103). For the low and high molecular region in which less signal of the LS detector or RI detector respectively was achieved a linear fit was used to correlate the elution volume to the corresponding molecular weight.

(35) The dn/dc used in the equation is calculated from the detector constant of the RI detector, the concentration c of the sample and the area of the detector response of the analysed sample. The relative amount of branching is determined using the g-index of the branched polymer sample. The long chain branching (LCB) index is defined as g=[].sub.br/[].sub.lin. It is well known if the g value increases the branching content decreases. [] is the intrinsic viscosity at 160 C. in trichlorobenzene of the polymer sample at a certain molecular weight and is measured by an online viscosity and a concentration detector. The intrinsic viscosities were measured as described in the handbook of the Cirrus Multi-Offline SEC-Software Version 3.2 with use of the Solomon-Gatesman equation.

(36) The necessary concentration of each elution slice is determined by a RI detector.

(37) [].sub.lin is the intrinsic viscosity of a linear sample and [].sub.br the viscosity of a branched sample of the same molecular weight and chemical composition. The number average of g.sub.n and the weight average g.sub.w are defined as:

(38) 0$g_n^{}=\frac{\underset{0}{\overset{i}{.Math.}}{a}_i*\frac{{\left[\right]}_{\mathrm{br},i}}{{\left[\right]}_{\mathrm{lin},i}}}{.Math.a_i}$$g_w^{}=\frac{\underset{0}{\overset{i}{.Math.}}{A}_i*\frac{{\left[\right]}_{\mathrm{br},i}}{{\left[\right]}_{\mathrm{lin},i}}}{\underset{0}{\overset{i}{.Math.}}{A}_i*{\left(\frac{{\left[\right]}_{\mathrm{br},i}}{{\left[\right]}_{\mathrm{lin},i}}\right)}^2}$
where a.sub.i is dW/dlogM of fraction i and A.sub.i is the cumulative dW/dlogM of the polymer up to fraction i. The [].sub.lin of the linear reference (linear isotactic PP) over the molecular weight was measured with an online viscosity detector. Following K and values were obtained (K=30.68*10.sup.3 and =0.681) from the linear reference in the molecular weight range of log M=4.5-6.1. The [].sub.lin per slice molecular weight for the g calculations was calculated by following relationship [].sub.lin,i=K*M.sub.i.sup.. [].sub.br,i was measured for each particular sample by online viscosity and concentration detector.

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

(40) Xylene Cold Soluble Fraction (XCS wt %)

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

(42) Melting temperature (T.sub.m) and heat of fusion (H.sub.f), crystallization temperature (T.sub.c) and heat of crystallization (H.sub.c): measured with Mettler TA820 differential scanning calorimetry (DSC) on 5 to 10 mg samples. DSC is run according to ISO 3146/part 3/method C2 in a heat/cool/heat cycle with a scan rate of 10 C./min in the temperature range of +23 to +210 C. Crystallization temperature and heat of crystallization (H.sub.c) are determined from the cooling step, while melting temperature and heat of fusion (H.sub.f) are determined from the second heating step

(43) Tensile modulus in machine direction was determined according to ISO 527-3 at 23 C. on the biaxially oriented films. Testing was performed at a cross head speed of 1 mm/min.

(44) Electrical breakdown strength (EB63%) The electrical breakdown strength was measured according to IEC 60243-2 (1998). The obtained raw data was evaluated according to IEC 60727, part 1 & 2

(45) The method (IEC 60243-2) describes a way to measure the electrical breakdown strength for insulation materials on compression moulded plaques. The electrical breakdown strength is determined within a high voltage cabinet using metal rods as electrodes as described in IEC 60243-2. The voltage is raised over the film/plaque at 2 kV/s until a breakdown occurs.

Definition

(46)
Eb:E.sub.b=U.sub.b/d

(47) The electrical field strength (U.sub.b, [kV]) in the test sample at which breakdown occurs. In homogeneous plaques and films the electrical electric breakdown strength (E.sub.b,[kV/mm]) can be calculated by dividing U.sub.b by the thickness of the plaque/film (d, [mm]) The unit of E.sub.b is kV/mm. For each BOPP film, 10 individual breakdown measurements are performed. To characterize a material via its breakdown strength a parameter describing an average breakdown strength must be derived from the 10 individually obtained results. This parameter is often referred to as Eb63% parameter. To obtain this parameter a statistical evaluation as described in IEC 60727, part 1 & 2 was carried out which is briefly outlined here: The 10 individual breakdown results (E.sub.b, kV/mm) per BOPP film are evaluated using a Weibull plot, wherein the 63 percentile (scale parameter of the Weibull distribution) is used to characterize the material's breakdown strength (Eb63%). The -parameter is the slope of the linear regression curve through these 10 points. The -parameter is the shape parameter of the Weibull distribution.

(48) Electrical conductivity was calculated as the inverse of the electrical resistance as determined in accordance to ASTM D257.

(49) Porosity: BET with N.sub.2 gas, ASTM 4641, apparatus Micromeritics Tristar 3000; sample preparation: at a temperature of 50 C., 6 hours in vacuum.

(50) Surface area: BET with N.sub.2 gas ASTM D 3663, apparatus Micromeritics Tristar 3000: sample preparation at a temperature of 50 C., 6 hours in vacuum.

(51) Ash content: Ash content is measured according to ISO 3451-1 (1997)

(52) Mean particle size (d50) is given in nm and measured with Coulter Counter LS200 at room temperature with n-heptane as medium, particle sizes below 100 nm by transmission electron microscopy.

(53) Particle size (d10) is given in nm and measured with Coulter Counter LS200 at room temperature with n-heptane as medium.

(54) Particle size (d90) is given in nm and measured with Coulter Counter LS200 at room temperature with n-heptane as medium.

(55) SPAN is defined as follows:

(56) $\frac{d90\left[m\right]-d10\left[m\right]}{d50\left[m\right]}$
ICP Method

(57) The elemental 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 further diluted with DI water up to the final volume, V, and left to stabilize for two hours. 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), and standards of 0.5 ppm, 1 ppm, 10 ppm, 50 ppm, 100 ppm and 300 ppm of Al, Mg and Ti in solutions of 5% HNO.sub.3.

(58) Immediately before analysis the calibration is resloped using the blank and 100 ppm standard, a quality control sample (20 ppm Al, Mg and Ti in a solution of 5% HNO.sub.3, 3% HF in DI water) is run to confirm the reslope. The QC sample is also run after every 5.sup.th sample and at the end of a scheduled analysis set.

(59) The content of Mg was monitored using the 285.213 nm line and the content for Ti using 336.121 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.

(60) 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.

(61) Dielectric Analysis (DEA) is measured on a DEA 2070 of TA-Instruments with a gold coated sputter. The measurement was conducted at a ramp of 3 C./min to 130 C. at 50 Hz and a constant spring force (F) of 100 N.

(62) The dielectric analysis measures the two fundamental electrical characteristics of material, i.e. capacitance and conductance, as functions of time, temperature and frequency. The capacitance of a material is the ability to store electric charge and the conductance of a material is the ability to conduct electric charge. Capacitance and conductance are important properties. Dissipation is not dependent on thickness, nor on orientation degree of the film. The properties determined by dielectric analysis are:

(63) e=permittivity

(64) e=loss factor

(65) tan =dissipation factor (e/e)

(66) =ionic conductivity [1/cm]

(67) The conductance is proportional to the permittivity and the ionic conductivity is derived from the loss factor. Permittivity and loss factor both provide valuable information about molecular motion. The permittivity determines the alignment of dipoles and the loss factor corresponds to the energy required to align dipoles and move ions. The permittivity is low for polymers at low temperature because the dipoles can't move to align themselves with the electric field. Ionic conduction is not significant until the polymer turns fluid, i.e. above the glass transition temperature (T.sub.g) and the melting temperature (T.sub.m).

(68) Above the glass transition temperature the loss factor is used to calculate the bulk ionic conductivity, using the equation:
=ee.sub.10
=ionic conductivity
=angular frequency (2f)
f=frequency (Hz)
e.sub.10=absolute permittivity of free space (8.851012 F/m)

B. Examples

(69) Catalyst PreparationIE1

(70) Solid Catalyst system used in the present invention was prepared according to example 8 of WO2004/029112, except that diethylaluminium chloride was used as an aluminium compound instead of triethyl aluminium. Catalyst contained 3.4 wt.-% of Ti, 12.8 wt.-% of Mg and 53 wt-% of Cl.

(71) PolymerisationIE1

(72) Polymer was produced in prepolymerisation reactor of 50 m.sup.3, one slurry loop reactor of 150 m.sup.3 and one gas phase reactor with the process parameters according to Table 1. The solid catalyst system was as described in Catalyst preparationIE1. As co-catalyst triethylaluminium (TEA) was used and as external donor dicyclopentyldimethoxysilane was used. Polymerisation data is enclosed in Table 1.

(73) TABLE-US-00001 TABLE 1 Preparation Parameter Unit IE1 Prepolymerisation Temperature [ C.] 30 Pressure [kPa] 5300 Al/donor ratio [mol/mol] 5 Residence time [h] 0.31 Catalyst feed [g/h] 4.9 Loop Temperature [ C.] 80 Pressure [kPa] 5400 Residence time [h] 0.8 H2/C3 ratio [mol/kmol] 0.1 MFR2 [g/10 min] 0.5 XCS [wt %] 2.8 GPR 1 Temperature [ C.] 80 Pressure [kPa] 2300 Residence time [h] 1.1 H2/C3 ratio [mol/kmol] 54 XCS/pellet [wt %] 1.5 MFR.sub.2/pellet [g/10 min] 3.4 Split loop/GPR [wt %] 40/60

Comparative ExampleCE1

(74) CE1 is commercially available very high purity Borclean HB311BF propylene homopolymer grade of Borealis AG for dielectric applications, which has MFR.sub.2 (230 C.) of 2.2 g/10 min, T.sub.in (DSC, ISO 3146) of 161 to 165 C., very low ash content 10-20 ppm (measured by ISO 3451-1) and has been produced by a TiCl.sub.3 based Ziegler-Natta catalyst. The commercial product has been further purified after the polymerization to reduce the catalyst residues.

(75) Film Preparation (for Polymers IE1 and CE1)

(76) Films of 7.0 m were prepared by extrusion at a temperature of 215 to 240 C. and pressure of 40 bar. After cooling the machine direction orientation at a temperature of 140 C. was performed, followed by traverse direction orientation at a temperature of 160 C. Orientation ratios of 4.59.5 were chosen.

(77) Polymer properties of IE1 and CE1 are disclosed in Table 2, and measured film properties in Table 3.

(78) TABLE-US-00002 TABLE 2 Polymer Properties CE 1 IE 1 MFR.sub.2 [g/10 min] 2.3 3.4 Tm [ C.] 161 161 Tc [ C.] 112 111 Mw [g/mol] 227000 218000 MWD [] 4.0 3.9 <2,1> e [mol-%] 0 0 Tensile modulus [MPa] 1788 1774 Ash content [ppm] <20 60 Washed [] yes no <2,1> e 2,1 erythro regio defects

(79) TABLE-US-00003 TABLE 3 Film properties CE 1 IE 1 Thickness [m] 7.0 7.0 Electrical property Amount of weak points [200 V/m-#/m.sup.2] 0.04 0 [250 V/m-#/m.sup.2] 0.07 0.09 [300 V/m-#/m.sup.2] 0.27 0.13 [350 V/m-#/m.sup.2] 0.6 0.32 [400 V/m-#/m.sup.2] n.a. 0.6 FS [VDC/m] 740 675

(80) Field strength at break down 100 C., resistance, Tan at 80 C. and resistance and electrical conductivity have values generally accepted for polypropylene in capacitor films.

(81) Catalyst PreparationIE2

(82) Solid Catalyst system as described in Catalyst preparationIE1 is used.

(83) PolymerisationIE2

(84) The polymer was produced on bench scale in a 5 liter reactor in a two step procedure with the process parameters outlined in Table 4

(85) a) Bulk Polymerisation

(86) The catalyst was mixed with half of the amount of TEAL and external donor (Do) (dicyclopentyldimethoxysilane). The second half of TEAL and donor was added to the reactor. After 10 minutes of contact between the catalyst, TEAL and donor the mixture was injected to the reactor. Hydrogen was added, followed by 1.4 kg of propylene and the temperature was increased to 80 C. during 18 minutes. After 30 minutes not reacted propylene was flashed out and the polymer was collected and MFR was analysed.

(87) b) Bulk+Gas Polymerisation

(88) The bulk step in this test was done as described in a). After having flashed out not reacted propylene after the bulk step the reaction was continued in the gas phase by feeding 6 mol of hydrogen and required amount of propylene to reach the pressure 20 bar. The pressure was maintained at 20 bar by feeding propylene according to consumption. When the targeted split, as indicated by propylene consumption, was reached the reaction was stopped by flashing out not reacted propylene. The polymer was collected and analysed and tested. Polymerisation data is disclosed in Table 4.

(89) TABLE-US-00004 TABLE 4 Preparation Parameter Unit IE2 Catalyst [mg] 42.3 Al/Ti [mol/mol] 100 TEA [L] 410 Al/Do [mol/mol] 10 Do [L] 60 Bulk Temperature [ C.] 80 C. Residence time [h] 0.5 Yield [g] 390 H2 [mmol] 6 MFR [g/10 min] 0.7 GPR Temperature [ C.] 80 C. Pressure [kPa] 2000 Residence time [h] 0.8 Yield [g] 809 Split bulk/GPR [wt.-%] 52/48

Comparative ExampleCE2

(90) CE2 is commercially available very high purity Borclean HC318BF propylene homopolymer grade of Borealis AG for dielectric applications, which has MFR.sub.2 (230 C.) of 3.2 g/10 min, T.sub.m (DSC, ISO 3146) of 161 C., ash content below 20 ppm (measured by ISO 3451-1) and has been produced by a TiCl.sub.3 based Ziegler-Natta catalyst. The commercial product has been further purified after the polymerization to reduce the catalyst residues. Polymer properties of polymers of IE2 and CE2 are disclosed in Table 5.

(91) TABLE-US-00005 TABLE 5 Properties of the polymer CE 2 IE 2 MFR.sub.2 [g/10 min] 3.2 3.1 Tm [ C.] 161 161.5 Tc [ C.] nm 116.5 XCS [wt.-%] nm 1.6 Ash [ppm] <20 220 Washed yes no nmnot measured
Film Preparation for Polymers of IE2 and CE2

(92) Films of 24-29 m were prepared by extrusion (Brabender Extrusiograph, screw 4:1 and mixer, torque 55 Nm, and 60 rpm) at temperature of 230 to 235 C. and pressure 400 bar.

(93) After cooling and drying the granules (2h at 70 C.) orientation was performed using Brckner Karo IV stretcher. Machine direction orientation was followed by traverse direction orientation at orientation ratio 55 at a temperature of 160 C.

(94) DEA (permittivity e, loss factor e and Tan Delta) measurements were made using the films as prepared above.

(95) In Table 6 results of permittivity e (P), loss factor e (L) and Tan Delta (D) values at 50 Hz and at temperatures about 75, 110 C. and 120 C. (P75, P110, P120, L75, L110, L120, D75, D110 and D120 respectively) are given.

(96) Curves based on the results are disclosed on FIGS. 1 and 2.

(97) The ratios I-IV are calculated based on measured results:

(98) $\begin{array}{cc}\frac{\left(P75-P110\right)}{P75}1006.0;& I\end{array}$
wherein
P75 is the permittivity measured at 50 Hz and 75 C.,
P110 is the permittivity measured at 50 Hz and 110 C.;

(99) $\begin{array}{cc}\frac{\left(P75-P120\right)}{P75}10012.0;& \mathrm{II}\end{array}$
wherein
P75 is the permittivity measured at 50 Hz and 75 C.,
P120 is the permittivity measured at 50 Hz and 120 C.;

(100) $\begin{array}{cc}\frac{\left(D75-D110\right)}{D75}100-10.0& \mathrm{III}\end{array}$
wherein
D75 is the dissipation (tan delta) measured at 50 Hz and 75 C.,
D110 is the dissipation (tan delta) measured at 50 Hz and 110 C.;

(101) $\begin{array}{cc}\frac{\left(D75-D120\right)}{D75}10010.0& \mathrm{IV}\end{array}$
wherein
D75 is the dissipation (tan delta) measured at 50 Hz and 75 C.;
D120 is the dissipation (tan delta) measured at 50 Hz and 120 C.

(102) TABLE-US-00006 TABLE 6 Permittivity, Loss factor and Tan Delta measurements at 50 Hz and temperatures about 75, 110 and 120 C. IE2 CE2 P75 2.526* 2.366# P110 2.435** 2.173## P120 2.381*** 2.053### L75 0.003737* 0.00978# L110 0.003359** 0.01329## L120 0.002755*** 0.01173### D75 0.00148* 0.004134# D110 0.001379** 0.006115## D120 0.001157*** 0.005716### I 3.57 8.16 II 5.56 13.23 III 7.43 47.92 IV 21.82 38.27 Accurate measurement temperatures/ C. *74.21 **108.89 ***119.31 #74.8 ##109.48 ###119.9

(103) As can be taken from the measuring results of table 6 and the FIGS. 1 and 2, the permittivity and dissipation of the inventive example is less effected by the temperature than the comparative example.