High melt strength polypropylene

Abstract

The present invention is related to a high melt strength polypropylene (HMS-PP) comprising units derivable from at least one polyunsaturated fatty acid, a process for preparing said high melt strength polypropylene (HMS-PP), as well as an article comprising said high melt strength polypropylene (HMS-PP).

Claims

1. A high melt strength polypropylene (HMS-PP), having a branching index g determined by GPC below 0.9 and comprising units derivable from: i) propylene, and ii) at least one polyunsaturated fatty acid, wherein the high melt strength polypropylene (HMS-PP) comprises 0.05 to 2.0 wt % of units derivable from at least one polyunsaturated fatty acid based on the overall weight of the high melt strength polypropylene (HMS-PP).

2. The high melt strength polypropylene (HMS-PP) according to claim 1, wherein the at least one polyunsaturated fatty acid is linoleic acid and/or -linolenic acid.

3. The high melt strength polypropylene (HMS-PP) according to claim 1, wherein the ratio x/(zw) is in the range of 0.25 to 2.0, wherein x is the intensity of the .sup.1H NMR signal (400 MHZ, 1,2-tetrachloroethane-d.sub.2) at 5.55 to 5.27 ppm, z is the intensity of the .sup.1H NMR signal (400 MHZ, 1,2-tetrachloroethane-d.sub.2) at 4.85 to 4.73 ppm and w is the intensity of the .sup.1H NMR signal (400 MHZ, 1,2-tetrachloroethane-d.sub.2) at 4.73 to 4.66 ppm.

4. The high melt strength polypropylene (HMS-PP) according to claim 1, fulfilling in-equation (I): $\begin{array}{cc}\frac{F_{30}\left(\mathrm{HMSPP}\right)-F_{200}\left(\mathrm{HMSPP}\right)}{F_{30}\left(\mathrm{HMSPP}\right)}0.15& \left(I\right)\end{array}$ wherein [F.sub.30(HMSPP)] is the F.sub.30 melt strength of the high melt strength polypropylene (HMS-PP) determined according to ISO 16790:2005 at 30 bar and [F.sub.200(HMSPP)] is the F.sub.200 melt strength of the high melt strength polypropylene (HMS-PP) determined according to ISO 16790:2005 at 200 bar.

5. The high melt strength polypropylene (HMS-PP) according to claim 1, wherein the high melt strength polypropylene (HMS-PP) has an additional F.sub.30 melt strength (AMS), determined according to ISO 16790:2005, compared to the F.sub.30 melt strength (LMS) of a linear polypropylene having the same melt flow rate MFR.sub.2, determined at 230 C. and a load of 2.16 kg according to ISO 1133, as the high melt strength polypropylene (HMS-PP), of above 2.0 cN, wherein the additional F.sub.30 melt strength (AMS) is determined according to equation (II): $\begin{array}{cc}AMS=MS\left(HMS-PP\right)-LMS,& \left(\mathrm{II}\right)\end{array}$ wherein AMS is the additional F.sub.30 melt strength (AMS), determined according to ISO 16790:2005, compared to the F.sub.30 melt strength (LMS) of a linear polypropylene having the same melt flow rate MFR.sub.2, determined at 230 C. at a load of 2.16 kg according to ISO 1133, as the high melt strength polypropylene (HMS-PP) in [cN], MS (HMS-PP) is the F.sub.30 melt strength of the high melt strength polypropylene (HMS-PP), determined according to ISO 16790:2005 in [cN], LMS is the F.sub.30 melt strength (LMS) of a linear polypropylene having the same melt flow rate MFR.sub.2, determined at 230 C. at a load of 2.16 kg according to ISO 1133, as the high melt strength polypropylene (HMS-PP) in [cN], and wherein the F.sub.30 melt strength (LMS) is determined according to equation (III): $\begin{array}{cc}LMS=17.35{\mathrm{MFR}}^{-0.994},& \left(\mathrm{III}\right)\end{array}$ wherein MFR is the melt flow rate MFR.sub.2, determined at 230 C. at a load of 2.16 kg according to ISO 1133, of the high melt strength polypropylene (HMS-PP).

6. The high melt strength polypropylene (HMS-PP) according to claim 1, having a crystallization temperature Tc determined according to DSC below 120 C.

7. A process for the preparation of a high melt strength polypropylene (HMS-PP), comprising the steps of: a) providing a linear propylene polymer (L-PP), b) blending said propylene polymer (L-PP) with a coupling agent (CA) comprising a polyunsaturated fatty acid, and c) irradiating the mixture obtained in step b) by means of electron beam irradiation, wherein the mixture obtained in step b) comprises 0.1 to 2.0 wt % of the coupling agent (CA) comprising a polyunsaturated fatty acid, based on the overall weight of the mixture obtained in step b).

8. The process according to claim 7, wherein the dosage of the electron beam radiation according to step c) is in the range of 50 to 150 kGy.

9. The process according to claim 7, wherein the coupling agent (CA) comprising a polyunsaturated fatty acid is native linseed oil.

10. A composition (C) comprising at least 10.0 wt %, based on the overall weight of the composition (C), of recycled high melt strength polypropylene (r-HMS-PP), being high melt strength polypropylene (HMS-PP) according to claim 1, which is recovered from a waste plastic material derived from post-consumer and/or industrial waste.

11. The composition (C) according to claim 10, wherein the melt flow rates MFR.sub.2, determined at 230 C. at a load of 2.16 kg according to ISO 1133, of the recycled high melt strength polypropylene (r-HMS-PP) and of the originating high melt strength polypropylene (o-HMS-PP), being the high melt strength polypropylene, the recycled high melt strength polypropylene (r-HMS-PP) is obtained from, fulfil in-equation IV: $\begin{array}{cc}\frac{{\mathrm{MFR}}_2\left(\mathrm{oHMSPP}\right)}{{\mathrm{MFR}}_2\left(\mathrm{rHMSPP}\right)}0.95& \mathrm{IV}\end{array}$ wherein MFR.sub.2 (OHMSPP) is the melt flow rate MFR.sub.2, determined at 230 C. at a load of 2.16 kg according to ISO 1133, of the originating high melt strength polypropylene (o-HMS-PP) and MFR.sub.2 (rHMSPP) is the melt flow rate MFR.sub.2, determined at 230 C. at a load of 2.16 kg according to ISO 1133, of the recycled high melt strength polypropylene (r-HMS-PP).

12. The composition (C) according to claim 10, comprising additives (AD) selected from the group consisting of flame retardants, fillers, pigments, impact modifiers, antioxidants, nucleating agent, process stabilizers, slip agents, or mixtures thereof.

13. An article comprising the high melt strength polypropylene (HMS-PP) according to claim 1 or the composition (C) according to claim 10.

Description

EXAMPLES

(1) A. Measuring Methods

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

(3) Quantification of Microstructure by NMR Spectroscopy

(4) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers. Quantitative .sup.13C{.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimized 10 mm extended temperature probehead at 125 C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory 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 optimized tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6 k) transients were acquired per spectra.

(5) 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).

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

(7) 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.

(8) 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).

(9) 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.

(10) The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:

(11) $\left[\mathrm{mmmm}\right]\%=100*\left(\mathrm{mmmm}/\mathrm{sum}\mathrm{of}\mathrm{all}\mathrm{pentads}\right)$

(12) 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.

(13) 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).

(14) 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:

(15) $P_{21e}=\left(I_{e6}+I_{e8}\right)/2$

(16) 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:

(17) $P_{12}=I_{\mathrm{CH}3}+P_{12e}$

(18) The total amount of propene was quantified as the sum of primary inserted propene and all other present regio defects:

(19) $P_{\mathrm{total}}=P_{12}+P_{21e}$

(20) The mole percent of 2.1 erythro regio defects was quantified with respect to all propene:

(21) $\left[21e\right]\mathrm{mol}\%=100*\left(P_{21e}/p_{\mathrm{total}}\right)$

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

(23) 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.

(24) 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.

(25) 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:

(26) 0$E=0.5\left(S+S+S+0.5\left(S+S\right)\right)$

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

(28) $E=0.5\left(I_H+I_G+0.5\left(I_C+I_D\right)\right)$
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.

(29) The mole percent comonomer incorporation was calculated from the mole fraction:

(30) $E\left[\mathrm{mol}\%\right]=100*\mathrm{fE}$

(31) The weight percent comonomer incorporation was calculated from the mole fraction:

(32) $E\left[\mathrm{wt}\%\right]=100*\left(\mathrm{fE}*28.06\right)/\left(\left(\mathrm{fE}*28.06\right)+\left(\left(1-\mathrm{fE}\right)*42.08\right)\right)$

(33) 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 (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.

(34) Determination of Grafted Coupling Agent Concentration (-Linolenic Acid) after Irradiation by .sup.1H-NMR

(35) 1. Soxhlett Extraction to Remove Non Grafted Coupling Agent

(36) 2.5 g of the ground sample are weighed into a soxhlett sleeve. In a round flask (250 ml) 200 ml n-hexane are placed, the sleeve is inserted into the soxhlet. Extraction of non grafted coupling agent takes place under reflux cooling over a period of 24 hours. The residue is dried overnight in the vacuum drying oven at 90 C., cooled to room temperature and used for .sup.1H NMR spectroscopy method.

(37) 2. .sup.1H NMR Spectroscopy Method

(38) Quantitative .sup.1H NMR spectra recorded in the solution-state using a BrukerAVNEO 400 NMR spectrometer operating at 400.15 MHz. All spectra were recorded using a .sup.13C optimised 10 mm selective excitation probe head at 125 C. using nitrogen gas for all pneumatics.

(39) Approximately 200 mg of material was dissolved in approximately 3 ml 1,2-tetrachloro-ethane-d.sub.2 (TCE-d.sub.2) using approximately 3 mg of Hostanox 03 (CAS 32509-66-3) as stabiliser. Standard single-pulse excitation was employed utilising a 30 degree pulse, a relaxation delay of 3 s and 10 Hz sample rotation. A total of 64 k data points were collected per FID with a dwell time of 61 s, corresponding to a spectral window of approximately ppm. 512 transients were acquired per spectra using 4 dummy scans. This setup was chosen for high sensitivity, resolution and stability with respect to unsaturated species. Quantitative .sup.1H spectra were processed applying an exponential window function with 0.3 Hz linebroadning, integrated and relevant ratios determined from the intensities of the integrals. All chemical shifts were indirectly referenced to TMS at 0.00 ppm using the signal resulting from the residual protonated solvent at 5.95 ppm {Resconi L., Cavallo L., Fait A., Piemontesi F., Chem. Rev. 2000, 100, 1253} and the intensity of the aliphatic bulk signal (I.sub.bulk) set to 100000. Characteristic signals at specific .sup.1H NMR chemical shifts corresponding to the presence of the listed structural groups were observed which are summarized in Table 1 {Resconi L., Piemontesi F., Camurati I., Sudmeijer O., Nifantef I. E., Ivschenko P. V., Kuzmina L. G., J. Am. Soc. 1998, 120, 2308-2321}:

(40) TABLE-US-00001 TABLE 1 Characteristic .sup.1H NMR signals Structural group Chemical shift .sup.1H NMR [ppm] Intensity aliphatic bulk 2.80-(0.5) y terminal vinylidene 4.73-4.66 w internal vinylidene 4.85-4.73 z vinylene 5.55-5.27 x allyl isobutenyl 5.08-4.85 v hostanox 7.00-6.81 h

(41) FIG. 1 shows a typical .sup.1H NMR spectrum of an inventive high melt strength polypropylene (HMS-PP).

(42) Ratios between intensities of specific groups were calculated compensating for influences of other groups:

(43) $\mathrm{ratio}x/z=x/\left(z-w\right)$$\mathrm{ratio}x/y=x/\left(y-\left(h/4*42\right)\right)$
Melting Temperature Tm, Crystallization Temperature Tc and Melting Enthalpy Hm

(44) The melting temperature, Tm, is determined by differential scanning calorimetry (DSC) according to ISO 11357-3 with a TA-Instruments 2920 Dual-Cell with RSC refrigeration apparatus and data station. A heating and cooling rate of 10 C./min is applied in a heat/cool/heat cycle between +23 and +210 C. The crystallization temperature (Tc) is determined from the cooling step while melting temperature (Tm) and melting enthalpy (Hm) are being determined in the second heating step.

(45) F.sub.30 and F.sub.200 Melt Strength and v.sub.30 and v.sub.200 Melt Extensibility

(46) The test described herein follows ISO 16790:2005. The strain hardening behaviour is determined by the method as described in the article Rheotens-Mastercurves and Drawability of Polymer Melts, M. H. Wagner, Polymer Engineering and Science, Vol. 36, pages 925 to 935. The strain hardening behaviour of polymers is analysed by Rheotens apparatus (product of Gdttfert, Siemensstr. 2, 74711 Buchen, Germany) in which a melt strand is elongated by drawing down with a defined acceleration.

(47) The Rheotens experiment simulates industrial spinning and extrusion processes. In principle a melt is pressed or extruded through a round die and the resulting strand is hauled off. The stress on the extrudate is recorded, as a function of melt properties and measuring parameters (especially the ratio between output and haul-off speed, practically a measure for the extension rate). For the results presented below, the materials were extruded with a lab extruder HAAKE Polylab system and a gear pump with cylindrical die (L/D=6.0/2.0 mm). For measuring F.sub.30 melt strength and v30 melt extensibility, the pressure at the extruder exit (=gear pump entry) is set to 30 bars by by-passing a part of the extruded polymer. For measuring F.sub.200 melt strength and v200 melt extensibility, the pressure at the extruder exit (=gear pump entry) is set to 200 bars by by-passing a part of the extruded polymer. The gear pump was pre-adjusted to a strand extrusion rate of 5 mm/s, and the melt temperature was set to 200 C. The spinline length between die and Rheotens wheels was 80 mm. At the beginning of the experiment, the take-up speed of the Rheotens wheels was adjusted to the velocity of the extruded polymer strand (tensile force zero): Then the experiment was started by slowly increasing the take-up speed of the Rheotens wheels until the polymer filament breaks. The acceleration of the wheels was small enough so that the tensile force was measured under quasi-steady conditions. The acceleration of the melt strand drawn down is 120 mm/sec.sup.2. The Rheotens was operated in combination with the PC program EXTENS. This is a real-time data-acquisition program, which displays and stores the measured data of tensile force and drawdown speed. The end points of the Rheotens curve (force versus pulley rotary speed), where the polymer strand ruptures, are taken as the F.sub.30 melt strength and v.sub.30 melt extensibilty values, or the F.sub.200 melt strength and v.sub.200 melt extensibilty values, respectively.

(48) The additional melt strength (AMS) is calculated according to equation (II)

(49) $\begin{array}{cc}AMS=MS\left(HMS-PP\right)-LMS,& \left(\mathrm{II}\right)\end{array}$
wherein AMS is the additional F.sub.30 melt strength (AMS) determined according to ISO 16790:2005 compared to the F.sub.30 melt strength (LMS) of a linear polypropylene having the same melt flow rate MFR.sub.2 (230 C., 2.16 kg) determined according to ISO 1133 as the high melt strength polypropylene (HMS-PP) in [cN], MS(HMS-PP) is the F.sub.30 melt strength of the high melt strength polypropylene (HMS-PP) determined according to ISO 16790:2005 in [cN], LMS is the F.sub.30 melt strength (LMS) of a linear polypropylene having the same melt flow rate MFR.sub.2 (230 C., 2.16 kg) determined according to ISO 1133 as the high melt strength polypropylene (HMS-PP) in [cN], and the F.sub.30 melt strength (LMS) of the corresponding linear polypropylene having the same melt flow rate as the high melt strength polypropylene (HMS-PP) and a polydispersity in the range of 3 to 5 is determined according to equation (III)

(50) $\begin{array}{cc}LMS=17.35{\mathrm{MFR}}^{-0.994},& \left(\mathrm{III}\right)\end{array}$
wherein MFR is the melt flow rate MFR.sub.2 (230 C., 2.16 kg) determined according to ISO 1133 of the high melt strength polypropylene (HMS-PP).

(51) Equation (III) is the fitting function of the melt flow rate MFR.sub.2 (230 C., 2.16 kg) determined according to ISO 1133 and the F.sub.30 melt strength as defined above of commercial linear propylene homopolymers tested by the Rheotens. The melt flow rates and F.sub.30 melt strength of said commercial linear propylene homopolymers from Borealis are summarized in Table 2.

(52) TABLE-US-00002 TABLE 2 F.sub.30 melt strength as a function of the melt flow rate Commercial linear PP MFR [g/10 min] F.sub.30 melt strength [cN] BA390 0.2 87 BE50 0.3 60 HA001 0.5 35 HA507 0.9 17 HB600TF 2.0 9 HC205TF 5.0 3.5 HD120MO 10.0 1.8
The Branching Index g

(53) 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 TCB 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.

(54) The necessary concentration of each elution slice is determined by a RI detector. [].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:

(55) $g_n^{}=\frac{{.Math.}_0^i{a}_i*\frac{{\left[\right]}_{\mathrm{br},i}}{{\left[\right]}_{\mathrm{lin},t}}}{.Math.a_i}$
Where a.sub.i is dW/d log M of fraction i and A.sub.i is the cumulative dW/d log M 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 a 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.
gpcBR Index:

(56) The gpcBR index is calculated by using the following formula:

(57) ${\mathrm{gpc}}_{\mathrm{BR}}=\left[\left(\frac{{\left[\right]}_{\mathrm{lin}}}{\left[\right]\left(\mathrm{bulk}\right)}\right)\right].Math.{\left[\frac{M_w\left(LS15\right)}{M_{w,\mathrm{lin}}}\right]}^{}-1$

(58) Where the Mw (LS15) is calculated from the light scattering elution area of 150 angle and [] (bulk) from the corresponded viscosity detector elution area by using the Cirrus Multi-Offline SEC-Software Version 3.2 and the following approach.

(59) $M_w\left(\mathrm{LS}15\right)=\frac{K_{LS}.Math.{\mathrm{Area}}_{LS15-d\mathrm{et}}}{\frac{dn}{dc}.Math.{\mathrm{Area}}_{\mathrm{RI}-\mathrm{de}t}}$$\left[\right]\left(\mathrm{bulk}\right)=K_{\mathrm{IV}}.Math.\frac{.Math.{\mathrm{nSp}}_i}{C}\left(\mathrm{dl}/g\right)$

(60) Where K.sub.LS is the light scattering constant of 150 angle, dn/dc is the refractive index increment as calculated from the detector constant of the RI detector, K.sub.IV is the detector constant of the viscometer, Sp.sub.i is the specific viscosity at each chromatographic slice and C is the corresponded concentration in g/dl.

(61) Shear Thinning Index SHI

(62) The characterization of polymer melts by dynamic shear measurements complies with ISO standards 6721-1 and 6721-10. The measurements were performed on an Anton Paar MCR501 stress controlled rotational rheometer, equipped with a 25 mm parallel plate geometry. Measurements were undertaken on compression moulded plates using nitrogen atmosphere and setting a strain within the linear viscoelastic regime. The oscillatory shear tests were done at 2000 applying a frequency range between 0.01 and 300 rad/s and setting a gap of 0.5 mm.

(63) In a dynamic shear experiment the probe is subjected to a homogeneous deformation at a sinusoidal varying shear strain or shear stress (strain and stress controlled mode, respectively). On a controlled strain experiment, the probe is subjected to a sinusoidal strain that can be expressed by

(64) 0$\begin{array}{cc}\left(t\right)={}_0\sin \left(t\right)& \left(1\right)\end{array}$

(65) If the applied strain is within the linear viscoelastic regime, the resulting sinusoidal stress response can be given by

(66) $\begin{array}{cc}\left(t\right)={}_0\sin \left(t+\right)& \left(2\right)\end{array}$
where .sub.0, and .sub.0 are the stress and strain amplitudes, respectively; is the angular frequency; is the phase shift (loss angle between applied strain and stress response); t is the time.

(67) Dynamic test results are typically expressed by means of several different rheological functions, namely the shear storage modulus, G, the shear loss modulus, G, the complex shear modulus, G*, the complex shear viscosity, q*, the dynamic shear viscosity, , the out-of-phase component of the complex shear viscosity, and the loss tangent, tan , which can be expressed as follows:

(68) $\begin{array}{cc}{G}^{}=\frac{{}_0}{{}_0}\cos \left[\mathrm{Pa}\right]& \left(3\right)\end{array}$$\begin{array}{cc}{G}^{}=\frac{{}_0}{{}_0}\sin \left[\mathrm{Pa}\right]& \left(4\right)\end{array}$$\begin{array}{cc}{G}^{}=G^{}+{\mathrm{iG}}^{}\left[\mathrm{Pa}\right]& \left(5\right)\end{array}$$\begin{array}{cc}{}^{*}={}^{}-i{}^{}\left[\mathrm{Pa}.Math.s\right]& \left(6\right)\end{array}$$\begin{array}{cc}{}^{}=\frac{G^{}}{}\left[\mathrm{Pa}.Math.s\right]& \left(7\right)\end{array}$$\begin{array}{cc}{}^{}=\frac{G^{},}{}\left[\mathrm{Pa}.Math.s\right]& \left(8\right)\end{array}$

(69) The determination of so-called Shear Thinning Index, which correlates with MWD and is independent of Mw, is done as described in equation 9.

(70) $\begin{array}{cc}SH{I}_{\left(x/y\right)}=\frac{\mathrm{Eta}*\mathrm{at}0.05\mathrm{rad}/s)}{\mathrm{Eta}*\mathrm{fat}285\mathrm{rad}/s}& \left(9\right)\end{array}$

(71) For example, the SHI.sub.(0.05/2285) is defined by the value of the complex viscosity, in Pa s, determined at a frequency of 0.05 rad/s, divided by the value of the complex viscosity, in Pa s, determined at a frequency of 285 rad/s.

(72) The values of storage modulus (G), loss modulus (G), complex modulus (G*) and complex viscosity (*) were obtained as a function of frequency ().

(73) Thereby, e.g. *.sub.300rad/s (eta*.sub.300rad/s) is used as abbreviation for the complex viscosity at the frequency of 285 rad/s and *.sub.0.05rad/s (eta*.sub.0.05rad/s) is used as abbreviation for the complex viscosity at the frequency of 0.05 rad/s.

(74) The loss tangent tan (delta) is defined as the ratio of the loss modulus (G) and the storage modulus (G) at a given frequency. Thereby, e.g. tan.sub.0.05 is used as abbreviation for the ratio of the loss modulus (G) and the storage modulus (G) at 0.05 rad/s and tan.sub.300 is used as abbreviation for the ratio of the loss modulus (G) and the storage modulus (G) at 300 rad/s. The elasticity balance tan.sub.0.05/tan.sub.300 is defined as the ratio of the loss tangent tan.sub.0.05 and the loss tangent tan.sub.300.

(75) The polydispersity index, PI, is defined by equation 10.

(76) $\begin{array}{cc}\mathrm{PI}=\frac{10^5}{G^{}\left({}_{\mathrm{COP}}\right)},& \left(10\right)\end{array}$${}_{\mathrm{COP}}=\mathrm{for}\left(G^{}=G^{}\right)$
where .sub.COP is the cross-over angular frequency, determined as the angular frequency for which the storage modulus, G, equals the loss modulus, G.

(77) The values are determined by means of a single point interpolation procedure, as defined by Rheoplus software. In situations for which a given G* value is not experimentally reached, the value is determined by means of an extrapolation, using the same procedure as before. In both cases (interpolation or extrapolation), the option from Rheoplus Interpolate y-values to x-values from parameter and the logarithmic interpolation type were applied.

REFERENCES

(78) [1] Rheological characterization of polyethylene fractions, Heino, E. L., Lehtinen, A., Tanner J., Seppl, J., Neste Oy, Porvoo, Finland, Theor. Appl. Rheol., Proc. Int. Congr. Rheol, 11th (1992), 1, 360-362. [2] The influence of molecular structure on some rheological properties of polyethylene, Heino, E. L., Borealis Polymers Oy, Porvoo, Finland, Annual Transactions of the Nordic Rheology Society, 1995. [3] Definition of terms relating to the non-ultimate mechanical properties of polymers, Pure & Appl. Chem., Vol. 70, No. 3, pp. 701-754, 1998.

(79) The xylene hot insoluble (XHU) fraction is determined according to EN 579. About 2.0 g of the polymer (m.sub.p) are weighted and put in a mesh of metal which is weighted, the total weight being represented by (m.sub.p+m). The polymer in the mesh is extracted in a soxhlet apparatus with boiling xylene for 5 hours. The eluent is then replaced by fresh xylene and boiling is continued for another hour. Subsequently, the mesh is dried and weighted again (mHu+m). The mass of the xylene hot insoluble (mHu) obtained by the formula mHu+mm.sub.m=mHu is put in relation to the weight of the polymer (m.sub.p) to obtain the fraction of xylene insolubles mHu/m.sub.p.

B. Examples

(80) Inventive examples IE1 to IE7 and comparative examples CE1, CE2 and CE2a were prepared as follows:

(81) As a linear precursor, the linear polypropylene homopolymer HA001 of Borealis is used, having MFR of 0.6 g/10 min (230 C., 2.16 kg/cm.sup.2; ISO 1133), a melting point of 161 C., a crystallization temperature of 116 C., having an isotacticity of 97.3% (pentad concentration by .sup.13C NMR) produced by slurry process using a Ziegler-Natta catalyst. The F30 melt strength of the stabilized powder is 35 cN.

(82) The linseed oil was purchased from Lausitzer lmhle Hoyerswerda GmbH and is cold-pressed linseed oil comprising 99 g fats, 23 g monounsaturated fatty acids, 60 g poly-unsaturated fatty acids, 15 g saturated fatty acids and 0.22 g protein per 100 mL.

(83) The propylene homopolymer fluff HA001 of Borealis was compounded into pellets on a Prism TSE 24MC under nitrogen with the linseed oil in amounts as indicated in Table 4 (examples P0 to P4). The throughput was 10 kg/h. The additives were dosed via a pre-blend or direct dosing to the extruder. The temperature setting of the extruder was between 20 C. and 240 C. The thus obtained pellets were irradiated as follows:

(84) The E Beam irradiation process was performed in three steps:

(85) Radiation of granulate with a dose of 80-110 kGy, 10 MeV at 20 C. in inert atmosphere, belt speed 50 mm/s, belt width 800 mm, bed height of irradiated sample 50 mm.

(86) Heating of the radiated granulate for 30 minutes at 60 C. in inert atmosphere.

(87) De-activating the radicals by heating 30 minutes at 100 C. in inert atmosphere

(88) The concentration of the grafted coupling agent was determined by .sup.1H NMR spectroscopy as described above. The results are summarized in Table 3.

(89) The properties of the obtained inventive and comparative polypropylenes are summarized in Table 4.

(90) Further, the following commercial polymers were used as comparative examples: CE3 is the commercial HMS-PP PF814 of LyondellBasell CE4 is the commercial HMS-PP WB140HMS of Borealis

(91) As can be gathered from Table 4, the rheological properties of the high melt strength polypropylene (HMS-PP) according to the present invention are comparable with the properties of comparative examples CE3 and CE4 being high melt strength polypropylenes prepared with a peroxide as radical source and butadiene as coupling agent. Table 4 also shows that the ratio between the F.sub.30 melt strength and the F.sub.200 melt strength is stable for the inventive examples which indicates that the inventive high melt strength polypropylene can be re-extrudated without deterioration of the rheological properties. Further, no nucleation effects occur since the crystallization temperature Tc remains on the same level compared to the linear precursor (HA001).

(92) Examples IE2, IE5, IE6, and IE7 are all based on the same linear polypropylene homopolymer HA001, to which 0.5 wt % of the same coupling agent was added and was irradiated with the same dose. Nevertheless, the properties are slightly different. This deviation is a normal behavior.

(93) A very desirable value of the F.sub.30 melt strength of the high melt strength polypropylene (HMS-PP) is close to 30 cN or more preferably at least 30 cN. The important fact is that all inventive examples achieve this goal even if there is some variation of the properties despite partly the same conditions as mentioned above.

(94) As indicated already above, the variation of properties is normal. After the step of irradiation, the high melt strength polypropylene still contains some radicals. These radicals further react when the sample of the high melt strength polypropylene is transported to the step of measurement of a particular property, e.g. MFR or melt strength. In the examples disclosed herein, care has been taken to bring the sample rather quickly to the respective measurement step. Nevertheless, one cannot guarantee achieving always the same conditions if it comes to time span, temperature, and concentration of coupling agent. Minor deviations in conditions may cause measurable differences in properties.

(95) Inventive Examples IE8 to IE13 were prepared in the same manner as inventive examples IE1 to IE7 except for the coupling agent used. Table 5 indicates the type and amount of coupling agent added and the corresponding results.

(96) Walnut oil is Walnu{umlaut over (b)}l from Aromatika BV, Netherlands, containing 9.8 wt % saturated fat.

(97) Tung oil is Allendo from Bindulin Werk, CAS Nr. 8001-20-5.

(98) Sunflower oil is Osolio from Spar containing 10 wt % saturated fat.

(99) All these three oils were purchased from a regular supermarkets in Linz, Austria.

(100) TABLE-US-00003 TABLE 3 Determination of grafted coupling agent concentration (-linolenic acid) by .sup.1H-NMR structural group aliphatic terminal internal ally bulk vinylidene vinylidene vinylene isobutenyl hostanox chemical shift .sup.1H NMR [ppm] ratio 2.80-(0.5) 4.73-4.66 4.85-4.73 5.55-5.27 5.08-4.85 7.00-6.81 ratio x/y = x/ intensity x/z = x/ (y material y w z x v h (z w) (h/4*42)) HA001 100000 0.61 0.67 0.00 0.00 49.88 0.00 0.00E+00 LSO 100000 0.00 0.00 16100.00 0.00 1.61E01 P1 100000 0.61 0.67 35.36 0.00 51.49 589.33 3.56E04 P2 100000 0.76 0.79 18.09 0.00 51.4 603.00 1.82E04 P3 100000 1.04 1.06 5.96 0.00 44.33 298.00 5.99E05 HA001 irradiated 100000 1.83 17.43 3.72 13.83 53.29 0.24 3.74E05 CE3 100000 2.79 15.95 2.98 13.75 48.16 0.23 3.00E05 P1 irradiated 100000 0.48 13.53 8.33 10.38 42.16 0.64 8.37E05 P1 irradiated 100000 0.70 14.22 8.03 10.72 47.18 0.59 8.07E05 insoluble P2 irradiated 100000 1.10 16.32 5.76 12.49 47.56 0.38 5.79E05 P2 irradiated 100000 1.00 16.39 5.48 12.22 50.49 0.36 5.51E05 insoluble P3 irradiated 100000 1.34 17.92 4.65 13.30 55.45 0.28 4.68E05 P3 irradiated 100000 1.16 17.40 4.16 12.89 44.79 0.26 4.18E05 insoluble

(101) TABLE-US-00004 TABLE 4 Properties of inventive and comparative examples SHI Cross- ETA Cross- over F.sub.200 (F.sub.30 Coupling MFR 0.05/ over point Eta Eta tand F.sub.30 melt F.sub.30 melt F.sub.200)/ Dose agent [g/10 285 point Gc PI .0.05 285 at 0.1 strength AMS strength F.sub.30 Tm Tc Example [kGy] [wt %] min] [] [rad/s] [kPa] [Pa1] [Pa s] [Pa s] rad/s [cN] [cN] [cN] [%] [ C.] [ C.] HA001 0 0 0.6 163 113 P0 0 0 2.4 161 116 P1 0 0.5 1.1 163 113 P2 0 0.25 1.1 163 115 P3 0 0.1 1.2 161 115 P4 0 0.05 1.2 161 116 IE1 80 0.5 11.3 27.5 126 20675 4.8 4257 154.9 3.3 19.0 17.4 157 113 IE2 110 0.5 2.3 53.1 37 8624 11.6 6262.4 118.0 1.6 37.4 37.1 157 112 IE3 110 0.25 3.8 40.0 92.9 11991 8.3 4223 105.5 2.1 35.1 34.7 155 114 IE4 110 0.1 7.0 33.0 163 16582 6.0 3610.4 109.5 2.7 28.0 27.5 154 114 IE5 110 0.5 3.1 46.9 74.2 11056 9.0 5043.7 107.6 1.7 36.1 30.5 34.7 4% 157 113 IE6 110 0.5 3.4 44.9 65.7 11633 8.6 5400.3 120.4 1.8 37.7 32.5 34.9 8% 157 113 IE7 110 0.5 3.6 44.4 113 12686 7.9 4467.5 100.6 1.8 35.2 30.4 34.6 2% 157 113 CE1 60 0 5.0 38.7 40 16503 6.1 7890.2 203.9 2.1 CE2 80 0 11.2 26.5 80 19916 5.0 4159.4 150.0 2.7 CE2a 110 0 5.3 36.8 90.9 13749 7.3 4469.9 121.6 2.1 CE3 nd nd 2.5 40.0 14 8500 11.8 8000 200.0 1.8 35.0 28.0 28 25% 159 125 CE4 0 nd 2.0 62.5 2 8000 12.5 10000 160.0 1.4 36.0 27.3 30 20% 160 129

(102) TABLE-US-00005 TABLE 5 Properties of inventive and comparative examples Coupling SHI ETA Crossover Crossover Eta Dose Coupling agent MFR 0.05/285 point point PI .0.05 Example [kGy] agent [wt %] [g/10 min] [] [rad/s] Gc [kPa] [Pa1] [Pa s] HA001 0 0 0.6 P0 0 0 2.4 P1 0 Linseed oil 0.5 1.1 P2 0 Linseed oil 0.25 1.1 P3 0 Linseed oil 0.1 1.2 P4 0 Linseed oil 0.05 1.2 IE3 110 Linseed oil 0.25 3.8 40.0 92.9 11991 8.3 4223 IE8 110 Walnut oil 0.25 4.3 58.7 11.1 6996.3 14.3 9313.4 IE9 110 Tung oil 0.25 1.4 75.7 3.0 3847.9 26.0 11987.0 IE10 110 Sunflower oil 0.25 7.1 83.2 2.2 3472.5 28.8 13281.0 IE11 90 Walnut oil 0.25 2.9 55.2 13.1 8277.8 12.1 9374.7 IE12 90 Tung oil 0.25 0.8 88.9 1.3 3632.5 27.5 18421.0 IE13 90 Sunflower oil 0.25 4.5 59.2 10.7 8194.8 12.2 11046.0 CE1 60 0 5.0 38.7 40 16503 6.1 7890.2 CE2 80 0 11.2 26.5 80 19916 5.0 4159.4 CE2a 110 0 5.3 36.8 90.9 13749 7.3 4469.9 CE3 nd nd 2.5 40.0 14 8500 11.8 8000 CE4 0 nd 2.0 62.5 2 8000 12.5 10000 tand F.sub.30 melt F.sub.30 F.sub.200 (F.sub.30 Eta 285 at 0.1 strength AMS melt strength F.sub.200)/F.sub.30 Tm Tc Example [Pa s] rad/s [cN] [cN] [cN] [%] [ C.] [ C.] HA001 163 113 P0 161 116 P1 163 113 P2 163 115 P3 161 115 P4 161 116 IE3 105.5 2.1 35.1 34.7 155 114 IE8 158.8 1.6 30.7 26.6 26.5 14% 158 123 IE9 158.4 1.3 35.5 23.3 31.6 11% 158 125 IE10 159.6 1.2 27.5 25.0 23.4 15% 158 123 IE11 169.8 1.8 28.0 22.0 25.5 9% nd nd IE12 207.2 1.2 35.2 14.6 34.6 2% nd nd IE13 186.5 1.6 25.5 21.6 22.5 12% nd nd CE1 203.9 2.1 CE2 150.0 2.7 CE2a 121.6 2.1 CE3 200.0 1.8 35.0 28.0 28 25% 159 125 CE4 160.0 1.4 36.0 27.3 30 20% 160 129