COMPOSITION CONTAINING RECYCLED MATERIALS FOR PIPES

Abstract

Composition comprising a heterophasic propylene copolymer with low melt flow rate and rather low amount of xylene cold solubles and a recycled polymer composition being rich in polypropylene.

Claims

1. A composition comprising a recycled polymer composition (RPC) and a heterophasic propylene copolymer (HECO), said composition is obtained by blending, wherein (a) the recycled polymer composition (RPC) comprises at least 80 wt.-%, based on the weight of the recycled polymer composition (RPC), of a recycled polypropylene, and (b) the heterophasic propylene copolymer (HECO) has (b1) a xylene cold soluble (XCS) fraction determined at 25° C. according to ISO 16152 in the range of 5.0 to 18 and (b2) a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of 0.05 to 1.5 g/10 min, wherein further (a) the weight ratio between the heterophasic propylene copolymer (HECO) and the recycled polymer composition (RPC) [(HECO)/(RPC)] is in the range of 1.1 to 7.0, and (b) the percentage by weight of the heterophasic propylene copolymer (HECO) together with the recycled polymer composition (RPC) [(HECO)+(RPC)], based on the weight of the composition, is at least 85 wt-%.

2. The composition according to claim 1 having a tensile modulus measured according to ISO 527-2 in the range of 1100 to 1600 MPa and/or a content of limonene as determined using solid phase microextraction (HS-SPME-GC-MS) of from 0.5 to 40 mg/kg.

3. The composition according to claim 1 consisting of the recycled polymer composition (RPC), the heterophasic propylene copolymer (HECO) and optional additives (AD), wherein preferably (a) the percentage by weight of the heterophasic propylene copolymer (HECO) together with the recycled polymer composition (RPC) [(HECO)+(RPC)], based on the weight of the composition, is at least 90 wt.-%, and (b) the remaining part up to 100 wt-%, based on the weight of the composition, are additives (AD).

4. The composition according to claim 1, wherein the composition has a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of 0.05 to 2.0 g/10 min and preferably the recycled polymer composition (RPC) has a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 of at least 8.0 g/10 min.

5. The composition according to claim 1, wherein the recycled polymer composition (RPC) has (a) a content of limonene determined by using solid phase microextraction (HS-SPME-GC-MS) of from 5 to 100 mg/kg; and/or (b) a total fatty acid content determined by using solid phase microextraction (HS-SPME-GC-MS) of from 20 to 100 mg/kg.

6. The composition according to claim 1, wherein the recycled polymer composition (RPC) additionally comprises minor amounts of recycled polyethylene, recycled polystyrene, recycled polyamide and inorganic compounds selected from the group consisting of talc, chalk and mixtures thereof, with the proviso that the amounts are as follows: (a) not more than 15.0 wt.-%, based on the weight of the recycled polymer composition (RPC), of recycled polyethylene; (b) not more than 8.00 wt.-%, based on the weight of the recycled polymer composition (RPC), of recycled polystyrene; (c) not more than 1.50 wt.-%, based on the weight of the recycled polymer composition (RPC), of recycled polyamide; and (d) not more than 2.50 wt.-% based on the weight of the recycled polymer composition (RPC), of inorganic components selected from the group consisting of talc, Chalk, and mixtures thereof.

7. The composition according to claim 1, wherein the heterophasic propylene copolymer (HECO) contains only propylene and ethylene derived units, wherein further (a) the heterophasic propylene copolymer (HECO) has an ethylene content determined by .sup.13C-NMR spectroscopy in the range of 3.0 to 8.0 wt.-%, and/or (b) the ethylene content of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) determined by .sup.13C-NMR spectroscopy is in the range 30 of to 36 wt.-%.

8. The composition according to claim 1, wherein the intrinsic viscosity determined according to DIN ISO 1628/1 (in decalin at 135° C.) of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is in the range of 2.9 to 4.5 dl/g, preferably in the range of 3.2 to 3.8 dl/g.

9. The composition according to claim 1, wherein the heterophasic propylene copolymer (HECO) comprises a semicrystalline propylene homopolymer (PPH) as matrix in which a propylene-ethylene rubber as elastomeric propylene copolymer (EPC) is dispersed, wherein the semicrystalline propylene homopolymer (PPH) preferably has a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of 0.05 to 1.5 g/10 min.

10. The composition according to claim 9, wherein the semicrystalline polypropylene (PPH) comprises two semicrystalline propylene homopolymer fractions (PPH1) and (PPH2), wherein (a) the percentage by weight of the two semicrystalline propylene homopolymer fractions (PPH1) and (PPH2) together ((PPH1)+(PPH2)), based on the weight of the semicrystalline propylene homopolymer (PPH), is at least 90 wt.-%; and (b) weight ratio between the two semicrystalline propylene homopolymer fractions (PPH1) and (PPH2) ((PPH1)/(PPH2)) is in the range of 0.8 to 1.4; wherein further (c) the semicrystalline propylene homopolymer fraction (PPM) has a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of 0.01 to 1.0 g/10 min; and (d) the semicrystalline propylene homopolymer (PPH) has a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 in the range of 0.05 to 2.0 g/10 min.

11. The composition according to claim 1, wherein the heterophasic propylene copolymer (HECO) is alpha-nucleated.

12. A process for producing a composition according to claim 1, wherein the heterophasic propylene copolymer (HECO), the recycled polymer composition (RPC) and the optional additives (AD) are mixed, obtaining thereby the composition.

13. A pipe comprising at least 90 wt.-%, based on the weight of the pipe, of a composition according to claim 1.

14.-16. (canceled)

17. The composition according to claim 1, wherein the recycled polymer composition (RPC) has a melt flow rate MFR.sub.2 (230° C./2.16 kg) measured according to ISO 1133 of at least 8.0 g/10 min.

18. The composition according to claim 10, wherein the melt flow rate MFR2 ratio of the semicrystalline propylene homopolymer (PPH) to the semicrystalline propylene homopolymer fraction (PPM) (MFR2 (PPH)/MFR2(PPH1)) is at least 3.

Description

EXAMPLES

Measuring Methods

[0269] 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. Melt flow rate MFR.sub.2 (230° C./2.16 kg) was determined according to ISO 1133 at a load of 2.16 kg at 230° C.

Quantification of Microstructure by NMR Spectroscopy

[0270] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers. Quantitative .sup.13C{.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 10 mm extended temperature probehead at 125° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6 k) transients were acquired per spectra. 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).

[0271] For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

[0272] 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.

[0273] 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., Macromolecules 30 (1997) 6251).

[0274] 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.

[0275] 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)

[0276] 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.

[0277] 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).

[0278] 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

[0279] 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

[0280] 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

[0281] 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)

[0282] For copolymers characteristic signals corresponding to the incorporation of ethylene were observed (Cheng, H. N., Macromolecules 17 (1984), 1950).

[0283] 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.

[0284] 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.

[0285] 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+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

[0286] Through the use of this set of sites the corresponding integral equation becomes:

E=0.5(I.sub.H+I.sub.G+0.5(I.sub.C+I.sub.D))

using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified.

[0287] The mole percent comonomer incorporation was calculated from the mole fraction:

E[mol %]=100*fE

[0288] The weight percent comonomer incorporation was calculated from the mole fraction:

E[wt %]=100*(fE*28.06)/((fF*28.06)+((1−fE)*42.08))

[0289] 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.

Limonene Quantification was Carried Out Using Solid Phase Microextraction (HS-SPME-GC-MS) by Standard Addition.

[0290] 50 mg ground samples were weighed into 20 mL headspace vials and after the addition of limonene in different concentrations and a glass-coated magnetic stir bar, the vial was closed with a magnetic cap lined with silicone/PTFE. Micro capillaries (10 pL) were used to add diluted limonene standards of known concentrations to the sample. Addition of 0, 2, 20 and 100 ng equals 0 mg/kg, 0.1 mg/kg, 1 mg/kg and 5 mg/kg limonene, in addition standard amounts of 6.6 mg/kg, 11 mg/kg and 16.5 mg/kg limonene were used in combination with some of the samples tested in this application. For quantification, ion-93 acquired in SIM mode was used. Enrichment of the volatile fraction was carried out by headspace solid phase microextraction with a 2 cm stable flex 50/30 pm DVB/Carboxen/PDMS fibre at 60° C. for 20 minutes. Desorption was carried out directly in the heated injection port of a GCMS system at 270° C.

GCMS Parameters:

Column: 30 m HP 5 MS 0.25*0.25

[0291] Injector: Splitless with 0.75 mm SPME Liner, 270° C.
Temperature program: −10° C. (1 min)
Carrier gas: Helium 5.0, 31 cm/s linear velocity, constant flow
MS: Single quadrupole, direct interface, 280° C. interface temperature
Acquisition: SIM scan mode
Scan parameter: 20-300 amu
SIM Parameter: m/Z 93, 100 ms dwell time

Total Free Fatty Acid Content

[0292] Fatty acid quantification was carried out using headspace solid phase micro-extraction (HS-SPME-GC-MS) by standard addition.

[0293] 50 mg ground samples were weighed in 20 mL headspace vial and after the addition of limonene in different concentrations and a glass coated magnetic stir bar the vial was closed with a magnetic cap lined with silicone/PTFE. 10 μL Micro-capillaries were used to add diluted free fatty acid mix (acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid and octanoic acid) standards of known concentrations to the sample at three different levels. Addition of 0, 50, 100 and 500 ng equals 0 mg/kg, 1 mg/kg, 2 mg/kg and 10 mg/kg of each individual acid. For quantification ion 60 acquired in SIM mode was used for all acids except propanoic acid, here ion 74 was used.

GCMS Parameter:

[0294] Column: 20 m ZB Wax plus 0.25*0.25
Injector: Split 5:1 with glass lined split liner, 250° C.
Temperature program: 40° C. (1 min) @6° C./min to 120° C., @15° C. to 245° C. (5 min)
Carrier: Helium 5.0, 40 cm/s linear velocity, constant flow
MS: Single quadrupole, direct interface, 220° C. inter face temperature
Acquisition: SIM scan mode
Scan parameter: 46-250 amu 6.6 scans/s
SIM Parameter: m/z 60.74, 6.6 scans/s

FTIR-Spectroscopy

[0295] Determination of the components and their amount in the recycled polymer composition is accomplished by FTIR-spectroscopy:
Resolution: 2 cm.sup.−1
Layer thickness of compression molded specimen: ca. 100 μm
Apodisation: strong
Method: transmission
Polypropylene: 1167 cm.sup.−1
Polystyrene: 1601.5 cm.sup.−1
Polyamide: 3300 cm.sup.−1
Talc: 3676 cm.sup.−1
Chalk: 1797 cm.sup.−1
Rest to 100 wt.-% is polyethylene

[0296] Charpy notched impact strength was determined according to ISO 179 1eA at 23° C. using 80×10×4 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

[0297] Tensile Modulus was determined according to ISO 527-2 (cross head speed=50 mm/min; 23° C.) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

[0298] Density of the polymer was determined according to ISO 1183-1:2004 method A on compression moulded specimen prepared according to EN ISO 1872-2 (February 2007) and is given in g/cm.sup.3.

[0299] Xylene cold solubles (XCS) content was determined at 25° C. according ISO 16152; first edition; 2005 Jul. 1.

[0300] Intrinsic viscosity (IV) was determined according to DIN ISO 1628/1, October 1999 (in decalin at 135° C.).

[0301] Heat deflection temperature (HDT) was determined according to ISO 75 A with a load of 1.8 MPa using 80×10×4 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

[0302] The oxidation induction time (OIT) at 200° C. was determined with a TA Instrument Q20 according to ISO11357-6. Calibration of the instrument was performed with Indium and Tin, according to ISO 11357-1. Each polymer sample (cylindrical geometry with a diameter of 5 mm and thickness of 0.5±0.05 mm) was placed in an open aluminium crucible, heated from 25° C. to 200° C. at a rate of 20° C. min.sup.−1 in nitrogen with a gas flow rate of 50 mL min.sup.−1, and allowed to rest for 5 min before the atmosphere was switched to oxygen, also at a flow rate of 50 mL min.sup.−1. The samples were maintained at constant temperature, and the exothermal heat associated with oxidation was recorded. The oxidation induction time was the time interval between the initiation of oxygen flow and the onset of the oxidative reaction.

Pipe Pressure Test

[0303] Pressure test performance was measured according to ISO 1167. In this test, a specimen is exposed to constant circumferential (hoop) stress of 2.5 MPa at elevated temperature of 95° C. in water-in-water. The time in hours to failure is recorded. The tests were performed on pipes produced on conventional pipe extrusion equipment, the pipes having a diameter of 110 mm and a wall thickness of 4 mm.

[0304] FNCT (full notch creep test) is determined according ISO 16770. The test specimens are compression moulded plates (thickness 10 mm). The test specimens are stressed in an aqueous solution at 80° C. and 4 MPa. For each sample 3 specimens are tested. The average value of the three measurements are used to report the time in hours.

Falling Weight Impact Testing at −10° C.

[0305] For practical testing of the impact resistance, the pipes were subjected to external blows by the staircase method according to EN 1411. In this test, a series of pipes were conditioned at −10° C. and subjected to a hammer with a falling from different heights. As a result, H.sub.50 [=mm] indicates the height, at which 50% of the pipes fail.

Conditioning Temperature: −10° C.; Conditioning Period: 60 min; Conditioning: in air;
Striker: d25; Weight: 10 kg.

[0306] Ring stiffness tests have been performed according to ISO 9969 at +23° C. on pipes having a diameter of 110 mm and a wall thickness of 4 mm.

EXAMPLES

[0307] A number of blends were produced with DIPOLEN PP, a polypropylene-rich recycled plastic material (from Mtm Plastics GmbH, material according to the February 2014 specification) as the recycled polymer composition (RCP). In each of the blends 15 to 40 wt.-% of a heterophasic propylene copolymer (HECO) as compatibilizer was added.

[0308] The compositions were prepared via melt blending on a co-rotating twin screw extruder. The polymer melt mixture was discharged and pelletized.

[0309] In the following the used components are specified in more detail:

Recycled Polymer Composition (RCP): DIPOLEN PP

[0310]

TABLE-US-00001 TABLE 1 Composition of Dipolen PP Dipolen PP [wt.-%].sup.1 polypropylene 93 polyethylene 4.5 Polystyrene 1.0 Polyamide 0.2 Talc, chalk 1.3 .sup.1The concentration of the components has been measured by IR spectroscopy;

TABLE-US-00002 TABLE 2 Limonene content in DIPOLEN PP Sample Limonen [mg/kg] HS-SPME-GC-MS.sup.1 Dipolen PP 20.6 ± 1.7 .sup.1Headspace Soldiphase Microextraction. Material available from mtm plastics GmbH, according to 2018 specification.

TABLE-US-00003 TABLE 3 Total fatty acid content in Dipolen PP Sample Limonen [mg/kg] HS-SPME-GC-MS.sup.1 Dipolen PP 35.7 mg/kg .sup.1The concentration of acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, octanoic acid, nonanoic acid and decanoic acid in each sample was added together to give a total fatty acid concentration value.

Heterophasic Propylene Copolymer (HECO)

Preparation of the Catalyst

[0311] First, 0.1 mol of MgCl.sub.2×3 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of −15° C. and 300 ml of cold TiCl.sub.4 was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20° C. At this temperature, 0.02 mol of diethylhexylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135° C. during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCl.sub.4 was added and the temperature was kept at 135° C. for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80° C. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described in general e.g. in patent publications EP 491 566, EP 591 224 and EP 586 390.

[0312] For the preparation of the HECO as indicated below triethylaluminium (TEAL), dicyclopentyldimethoxysilane (D-donor), catalyst as produced above and vinyl cyclohexane (VCH) were added into oil, like mineral oil, e.g. Technol 68 (kinematic viscosity at 40° C. 62-74 cSt), in amounts so that TEAL/Ti was 125 mol/mol, TEAL/D donor was 5 mol/mol, and weight ratio of VCH/solid catalyst was 1:1. The mixture was heated to 60-65° C. and allowed to react until the content of the unreacted vinylcyclohexane in the reaction mixture was ˜150 ppm. Catalyst concentration in the final oil-catalyst slurry was 10-20 wt-%.

TABLE-US-00004 TABLE 4 Polymerization conditions for heterophasic propylene copolymer (HECO) Unit HECO Loop Temperature [° C.] 85 Pressure [kPa] 5500 H.sub.2/C.sub.3 ratio [mol/kmol] 0.08 MFR.sub.2 [g/10 min] 0.05 C2 [wt.-%] 0 Split [wt.-%] 46 GPR 1 Temperature [° C.] 90 Pressure [kPa] 2500 H.sub.2/C.sub.3 ratio [mol/kmol] 214 MFR.sub.2 [g/10 min] 0.30 XCS [wt.-%] 1.5 C2 [wt.-%] 0 Split [wt.-%] 40 GPR 2 Temperature [° C.] 80 Pressure [kPa] 2000 H.sub.2/C.sub.2 ratio [mol/kmol] 20 C.sub.2/C.sub.3 ratio [mol/kmol] 550 MFR.sub.2 [g/10 min] 0.25 XCS [wt.-%] 11 C2 of XCS [wt.-%] 33 IV of XCS [dl/g] 3.5 C2 total [wt.-%] 5.1 Split [wt.-%] 14 C2 ethylene IV intrinsic viscosity XCS xylene cold soluble fraction H.sub.2/C.sub.3 ratio hydrogen/propylene ratio C.sub.2/C.sub.3 ratio ethylene/propylene ratio Loop Loop reactor ½ GPR ½ gas phase reactor

[0313] The heterophasic propylene copolymer (HECO) has been melt mixed with 0.1 wt.-% Irgafos 168, 0.15 wt.-% Irganox 1010 and 0.2 wt.-% Irganox PS802.

TABLE-US-00005 TABLE 5 Properties of the compositions CE1 IE1 IE2 IE3 DIPOLEN PP [wt.-%] 100 15 25 40 HECO [wt.-%] — 85 75 60 MFR.sub.2 [g/10 min] 13 0.6 0.75 1.2 Tensile modulus [MPa] 1280 1530 1446 1400 Charpy notched impact [kJ/m.sup.2] 5.2 34.5 19.9 10.9 [23° C.] HDT [° C.] — 55.4 54 53 OIT [min] <3 54 33 21

[0314] Pipes were produced as follows:

[0315] The compositions of table 5 were extruded into solid wall pipes in the following way:

External diameter: 110 mm
Wall thickness: 4 mm
Extruder was a single screw extruder of Kraus Maffei 36D with screw diameter of 45 mm
Temperatur profile: Barrel zones: 220/220/215/210/210° C.;
120 kg/hr; line speed 1.56 m/min

TABLE-US-00006 TABLE 6 Properties of the pipes IE1 IE2 IE3 Pipe pressure test 95° C.; 2.5 MPa [hrs] 1960 1900 900 Ring stiffness [kN/m.sup.2] 8.9 7.8 7.5 Falling weight staircase [mm] 2610 2480 2180