POLYPROPYLENE-POLYETHYLENE COMPOSITION WITH IMPROVED FLOWABILITY

Abstract

The invention is related to a composition of polypropylene and polyethylene, which contains specific compatibilizer and flow enhancer. Furthermore the present invention is also related to articles comprising the said composition and the use of said articles in packaging application.

Claims

1. A polymer composition comprising a) 10 to 50 wt % of a polymer blend (A) comprising 30 to 70 wt % of polypropylene (A1) and 70 to 30 wt % of polyethylene (A2), b) 47 to 90 wt % of a polypropylene (B) having a melt flow rate MFR2 (230 C.) measured according to ISO 1133 of not lower than 50 g/10 min, and c) 3 to 25 wt % of a Compatibilizer (C) being a heterophasic polyolefin composition comprising 55 to 90 wt % of a matrix (C1) being a polypropylene and 45 to 10 wt % of an elastomer (C2) being a copolymer of ethylene and propylene or C4 to C10 alpha olefin with a glass transition temperature Tg measured according to ISO 6721-7 of below 25 C. and an intrinsic viscosity measured according to DIN ISO 1628/1 at 135 C. of at least 3.0 dl/g, wherein the polymer composition has a melt flow rate MFR2 (230 C.) measured according to ISO 1133 of higher than 25 g/10 min.

2. The polymer composition according to claim 1, wherein the heat deflection temperature (HDT) measured according to ISO 75B of said polymer composition is at least 5 C. higher than the HDT of the polymer blend (A).

3. The polymer composition according to claim 1, wherein said polymer composition has (i) a Charpy Notched Impact Strength measured according to ISO 179-1eA at 23 C. of at least 15% higher than the polymer blend (A), and at the same time (ii) a Tensile Modulus measured according to ISO527-2 of at least 20% higher than the polymer blend (A).

4. The polymer composition according to claim 1, wherein the polymer blend (A) is a recycled material, which is recovered from waste plastic material derived from at least one of post-consumer or post-industrial waste.

5. The polymer composition according to claim 1, wherein the polypropylene (A1) has a melt flow rate MFR2 (230 C.) measured according to ISO 1133 of 0.1 to 30.0 g/10 min.

6. The polymer composition according to claim 1, wherein the polypropylene (B) is a heterophasic polyolefin composition having a xylene cold soluble (XCS) content measured according to ISO 6427 in the range of 7.0 to 25.0 wt %.

7. The polymer composition according to claim 1, wherein the intrinsic viscosity (IV) measured according to ISO 1268-1 (decalin) of the xylene cold soluble (XCS) fraction of the polypropylene (B) being a heterophasic polyolefin composition is below 3.5 dl/g.

8. The polymer composition according to claim 1, wherein the melt flow rate MFR2 (230 C.) measured according to ISO 1133 of the xylene cold insoluble (XCI) fraction of the polypropylene (B) being a heterophasic polyolefin composition is in the range of 100.0 to 1500.0 g/10 min.

9. The polymer composition according to claim 1, wherein the polypropylene (B) has at least one of: (i) a total propylene content of 85.0 to 96.0 wt %, or (ii) a propylene content in the xylene cold soluble (XCS) fraction of 45.0 to 75.0 wt %.

10. The polymer composition according to claim 1, wherein the Compatibilizer (C) is selected from the group consisting of (i) an in-reactor blend obtained by a sequential polymerization process in at least two reactors, whereby first the matrix (C1) is produced and secondly a elastomer (C2) being a copolymer of ethylene and propylene is produced in the presence of the matrix (C1) and (ii) a mechanical blend of a matrix (C1) and a elastomer (C2) being a copolymer of ethylene and C4 to C10 alpha olefin.

11. The polymer composition according to claim 1, wherein the matrix (C1) is selected from the group consisting of isotactic polypropylene homopolymer, predominantly isotactic polypropylene homopolymer, random copolymers of propylene with ethylene, C4 to C8 alpha-olefins, and combinations thereof, wherein the total comonomer content ranges from 0.05 to 10.0 wt %, whereby the polypropylenes have a density of from 0.895 to 0.920 g/cm.sup.3 measured according to ISO 1183.

12. The polymer composition according to claim 1, wherein the polymer composition may further comprise inorganic or organic reinforcements.

13. An article comprising a polymer composition according to claim 1.

14. A process comprising forming packaging articles from the polymer composition according to claim 1.

Description

EXAMPLES

1. Measuring Methods

[0110] MFR was measured according to ISO 1133 at a load of 2.16 kg, at 230 C. for the pure PP components and all compositions.

[0111] Charpy Notched impact strength was determined according to ISO 179 1eA at 23 C. using 80104 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

[0112] 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).

[0113] Heat Deflection Temperature (HDT) was determined according to ISO 75 B with a load of 0.45 MPa using 80104 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

[0114] Xylene cold solubles (XCS) content was determined at 25 C. according ISO 16152; first edition; 2005-07-01.

[0115] Intrinsic viscosity (IV) was measured according to DIN ISO 1628/1, October 1999 (in decalin at 135 C.).

[0116] Glass transition temperature Tg and storage modulus G were determined by dynamic mechanical analysis (DMTA) according to ISO 6721-7. The measurements were done in torsion mode on compression moulded samples (40101 mm3) between 100 C. and +150 C. with a heating rate of 2 C./min and a frequency of 1 Hz. While the Tg was determined from the curve of the loss angle (tan()), the storage modulus (G) curve was used to determine the temperature for a G of 40 MPa representing a measure for the heat deflection resistance.

[0117] Melting temperature (Tm) and crystallization temperature (Tc) were measured with Mettler TA820 differential scanning calorimetry (DSC) on 5 to 10 mg samples. DSC is run according to ISO 11357-3:1999 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 (Hc) are determined from the cooling step, while melting temperature and heat of fusion (Hf) are determined from the second heating step.

[0118] Comonomer content, especially ethylene content is measured with Fourier transform infrared spectroscopy (FTIR) calibrated with .sup.13C-NMR. When measuring the ethylene content in polypropylene, a thin film of the sample (thickness about 250 m) was prepared by hot-pressing. The area of absorption peaks 720 and 733 cm.sup.1 for propylene-ethylene-copolymers was measured with Perkin Elmer FTIR 1600 spectrometer.

[0119] Polyethylene content of the recyclate was determined using the DSC technique described above for determining the Melting temperature (Tm) and crystallization temperature (Tc).

[0120] For the recyclate the polyethylene content was calculated from the PE melting enthalpy in DSC (Hm(PE)) associated to the lower melting point for the composition (Tm(PE)) in the range of 110 to 130 C. For the determination of the present invention for fully crystalline PE a melting enthalpy of 298 J/g and an average degree of crystallinity of 50% was assumed.

2. Examples

Materials Used

Polymer Blend (A)

[0121] Dipolen S is a recycled polymer mixture comprising polyethylene and polypropylene obtained from mtm plastics GmbH, Niedergebra, Germany and has a polyethylene content of 40 wt % determined by DSC analysis. The melting points determined by DSC were 162 C. (PP) and 128 C. (PE).

Polypropylene (B)

[0122] PP1: Polypropylene (PP1) is a heterophasic polypropylene copolymer BJ998MO which is commercially available from Borealis AG.

[0123] PP2: Polypropylene (PP2) is a heterophasic polypropylene copolymer BJ400HP which is commercially available from Borealis AG.

[0124] PP3: Polypropylene (PP3) is a heterophasic polypropylene copolymer BJ368MO which is commercially available from Borealis AG.

[0125] Characterization of PP1 to PP3 is summarized in Table 1

TABLE-US-00001 TABLE 1 characterization of PP1 to PP3 PP 1 PP 2 PP 3 MFR [g/10 min] 100.0 100.0 70.0 MFR of XCI [g/10 min] 350 160 160 XCS [wt %] 22.0 13.0 20.0 C2 total [wt %] 10.0 6.5 9.5 C2 in XCS [wt %] 35 54 38 IV of XCS [dl/g] 3.4 2.0 2.2

Compatibilizer (C)

Heterophasic Copolymer HECO-1:

[0126] HECO-1 was produced in a Borstar PP pilot plant with a prepolymerization reactor, one slurry loop reactor and one gas phase reactors.

[0127] The catalyst used for preparing HECO-1 has been produced as follows: First, 0.1 mol of MgCl.sub.23 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 dioctylphthalate (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. (Ti-content: 1.9 wt % and Mg-content: 22.0 wt %) Catalyst and its preparation concept is described in general e.g. in patent publications EP491566, EP591224 and EP586390. The catalyst was used in combination with dicyclopentyldimethoxysilane [Si(OCH.sub.3).sub.2(cyclo-pentyl).sub.2] as external donor (ED) and triethylaluminium (TEAL) as activator and scavenger in the ratios indicated in table 2. The catalyst was modified by polymerizing a vinyl compound in the presence of the catalyst system. The respective process is described in EP 1 028 984 and EP 1 183 307. The specific reaction parameters can be seen in Table 2.

TABLE-US-00002 TABLE 2 Preparation of heterophasic copolymer HECO-1 HECO-1 Prepolymerization temperature [ C.] 30 pressure [kPa] 5400 TEAL/ED [mol/mol] 6 residence time [h] 0.3 Loop H.sub.2 amount [mol %] 3.89 Temperature [ C.] 85 Pressure [barg] 51.5 MFR.sub.2 [g/10 min] 88 Split [wt %] 73 2. Gas phase H.sub.2 amount [mol %] 0.00009 C.sub.2/C.sub.3 [mol/kmol] 378 Temperature [ C.] 85 Pressure [barg] 25 Split [wt %] 27 Product MFR.sub.2 [g/10 min] 10.9 XCS [wt %] 24.5 IV of XCS [dl/g] 6.3 C2 of XCS [wt %] 20.8 Tg of XCS [ C.] 32

[0128] The polymer compositions of polymer blend (A), polypropylene (B) and Compatibilizer (C) were prepared on a Coperion ZSK 25 co-rotating twin-screw extruder equipped with a mixing screw configuration with an L/D ratio of 25. A melt temperature of 200-220 C. was used during mixing, solidifying the melt strands in a water bath followed by strand pelletization.

[0129] For the reason of good comparison, CE5 is shown here being BH345MO commercially available from Borealis AG with a recognized good combination of very high stiffness, good flow properties and good impact strength. It has a MFR of 45 g/10 min and a density of 0.905 g/cm.sup.3. The amounts of the different components and the mechanical properties of the inventive examples and comparative examples can be seen in Table 3.

TABLE-US-00003 TABLE 3 Composition and mechanical properties of IE 1 to IE5 and CE1 to CE5 (A) PP (B) (C) MFR NIS NIS Tens. Mod. Tens Mod. HDT B HDT Ex [wt %] type [wt %] type [wt %] type [g/10 min] [kJ/m.sup.2] [ %] [MPa] [ %] [ C.] [ C.] CE1 100 Dipolen S 7 5.00 820 71 CE2 30 Dipolen S 70 PP1 46 8.2 64 1220 49 88 17 CE3 50 Dipolen S 50 PP1 30 9.0 80 1124 37 80 9 CE4 70 Dipolen S 30 PP1 18 8.3 66 1078 32 75 4 IE1 30 Dipolen S 65 PP1 5 HECO-1 44 10.1 102 1205 47 86 15 IE2 30 Dipolen S 60 PP1 10 HECO-1 38 10.6 112 1186 45 86 15 IE3 30 Dipolen S 55 PP1 15 HECO-1 32 11.5 130 1167 42 85 14 IE4 30 Dipolen S 60 PP2 10 HECO-1 41 6.4 28 1319 60 85 14 IE5 30 Dipolen S 60 PP3 10 HECO-1 34 9.5 90 1266 54 90 19 CE5 100 BH345MO 45 5 1400 85 (A) Polymer blend (A) (C) Compatibilizer (C) MFR MFR 230 C./2.16 kg NIS Charpy NIS 23 C.