COMPATIBILIZATION OF RECYCLED POLYETHYLENE-POLYPROPYLENE BLENDS

Abstract

The present invention is directed to a polyethylene-polypropylene composition comprising a blend (A) being a recycled material, said blend comprising polypropylene and polyethylene, and a compatibilizer (B) being a C.sub.2C.sub.3C.sub.4 terpolymer. Further, the present invention is directed to an article comprising said polyethylene-polypropylene composition and a process for preparing said polyethylene-polypropylene composition. The present invention is also directed to the use of a compatibilizer (B) being a C.sub.2C.sub.3C.sub.4 terpolymer for improving the impact-stiffness balance and the morphology of the blend (A).

Claims

1. A polyethylene-polypropylene composition, obtainable by blending: a) 85.0 to 99.0 wt. %, based on the overall weight of the polyethylene-polypropylene composition, of a blend (A) comprising i) polypropylene, and ii) polyethylene, wherein the weight ratio of polypropylene to polyethylene is in the range of 3:7 to 7:3, and wherein blend (A) is a recycled material, which is recovered from a waste plastic material derived from post-consumer and/or industrial waste; and b) 1.0 to 15.0 wt. %, based on the overall weight of the polyethylene-polypropylene composition, of a compatibilizer (B) being a C.sub.2C.sub.3C.sub.4 terpolymer having a density determined according to ISO 1183 equal or below 880 kg/m.sup.3.

2. The polyethylene-polypropylene composition according to claim 1, wherein the C.sub.2C.sub.3C.sub.4 terpolymer has a melt flow rate MFR.sub.2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 2.0 to 40.0 g/10 min.

3. The polyethylene-polypropylene composition according to claim 1, wherein the weight ratio between the blend (A) and the compatibilizer (B) is in the range of 99:1 to 5:1.

4. The polyethylene-polypropylene composition according to claim 1, wherein the C.sub.2C.sub.3C.sub.4 terpolymer has: i) an ethylene content in the range of 2.0 to 15.0 wt. %, and/or ii) a 1-butene content in the range of 5.0 to 30.0 wt. %, based on the overall weight of the C.sub.2C.sub.3C.sub.4 terpolymer.

5. The polyethylene-polypropylene composition according to claim 1, wherein the C.sub.2C.sub.3C.sub.4 terpolymer has a melting temperature Tm determined according to ISO 11357-below 180° C. in the range of 150 to 165° C.

6. The polyethylene-polypropylene composition according to claim 1, wherein the C.sub.2C.sub.3C.sub.4 terpolymer has a glass transition temperature Tg-below −5° C. in the range of −25 to −12° C.

7. The polyethylene-polypropylene composition according to claim 1, wherein blend (A) has a content of limonene as determined by using solid phase microextraction (HS-SPME-GC-MS) of (i) from 1 ppm to 100 ppm or (ii) from 0.10 ppm to less than 1 ppm.

8. The polyethylene-polypropylene composition according to claim 1, wherein blend (A) has a relative amount of units derived from ethylene of greater than 20 wt. %, based on the overall weight of blend (A).

9. The polyethylene-polypropylene composition according to claim 1, wherein blend (A) contains: i) up to 6.0 wt. % polystyrene, and/or ii) up to 3 wt. % talc, and/or iii) up to 5.0 wt. % polyamide, and/or iv) up to 3 wt. % chalk, based on the overall weight of blend (A).

10. The polyethylene-polypropylene composition according to claim 1, having a melt flow rate MFR.sub.2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 0.1 to 50.0 g/10 min.

11. The polyethylene-polypropylene composition according to claim 1, having a Charpy notched impact strength determined according to ISO 179/1eA at 23° C. of at least 6.0 kJ/m.sup.2.

12. The polyethylene-polypropylene composition according to claim 1, having a tensile modulus determined according to ISO 527-2 of at least 600 MPa.

13. An article, comprising the polyethylene-polypropylene composition according to claim 1.

14. A process for preparing the polyethylene-polypropylene composition according to claim 1, comprising the steps of: a) providing the blend (A) in an amount of 85.0 to 99.0 wt. %, based on the overall weight of the polyethylene-polypropylene composition, b) providing the compatibilizer (B) in an amount of 1.0 to 15.0 wt. %, based on the overall weight of the polyethylene-polypropylene composition, c) melting and mixing the blend of blend (A) and the compatibilizer (B), optionally in the presence of 0 to 1.0 wt. % of a stabilizer or a mixture of stabilizers, and d) optionally pelletizing.

15. (canceled)

Description

EXPERIMENTAL SECTION

[0130] The following Examples are included to demonstrate certain aspects and embodiments of the invention as described in the claims. It should be appreciated by those of skill in the art, however, that the following description is illustrative only and should not be taken in any way as a restriction of the invention.

Test Methods

[0131] The tensile modulus (TM) was measured according to ISO 527-2 (cross head speed=1 mm/min for determination of the modulus, thereafter switching to 50 mm/min until break at 23° C.) using injection moulded specimens as described in EN ISO 5247-2 (dog bone shape, 4 mm thickness). The measurement was done after 96 h conditioning time of the specimen.

[0132] The impact strength was determined as Charpy Notched Impact Strength (NIS) according to ISO 179-1eA at+23° C. on injection moulded specimens of 80×10×4 mm prepared according to EN ISO 1873-2. According to this standard samples are tested after 96 hours.

Comonomer Content poly(propylene-co-ethylene-co-butene)

[0133] Quantitative .sup.13C{.sup.1H} NMR spectra recorded in the molten-state using a Bruker Advance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 7 mm magic-angle spinning (MAS) probe head at 180° C. using nitrogen gas for all pneumatics.

[0134] Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4.5 kHz. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification {1, 2, 6} Standard single-pulse excitation was employed utilising the NOE at short recycle delays {3, 1} and the RS-HEPT decoupling scheme {4, 5}. A total of 1024 (1 k) transients were acquired per spectra.

[0135] Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

[0136] Characteristic signals corresponding to regio defects were not observed {11}. The amount of propene was quantified based on the main Sαα methylene sites at 44.1 ppm:

Ptotal=I.sub.Sαα

[0137] Characteristic signals corresponding to the incorporation of 1-butene were observed and the comonomer content quantified in the following way. The amount isolated 1-butene incorporated in PPBPP sequences was quantified using the integral of the αB2 sites at 44.1 ppm accounting for the number of reporting sites per comonomer:

B=I.sub.αB2/2

[0138] The amount consecutively incorporated 1-butene in PPBBPP sequences was quantified using the integral of the ααB2 site at 40.5 ppm accounting for the number of reporting sites per comonomer:

BB=2*L.sub.ααB2

[0139] The total 1-butene content was calculated based on the sum of isolated and consecutively incorporated 1-butene:

Btotal=B+BB

[0140] The total mole fraction of 1-butene in the polymer was then calculated as: fB=(Btotal/(Etotal+Ptotal+Btotal))

[0141] Characteristic signals corresponding to the incorporation of ethylene were observed and the comonomer content quantified in the following way. The amount isolated ethylene incorporated in PPEPP sequences was quantified using the integral of the Sαγ sites at 37.9 ppm accounting for the number of reporting sites per comonomer:

E=I.sub.Sαγ/2

[0142] With no sites indicative of consecutive incorporation observed the total ethylene comonomer content was calculated solely on this quantity:

Etotal=E

[0143] The total mole fraction of ethylene in the polymer was then calculated as:

fE=(Etotal/(Etotal+Ptotal+Btotal))

[0144] The mole percent comonomer incorporation was calculated from the mole fractions:

B [mol %]=100*fB

E [mol %]=100*fE

[0145] The weight percent comonomer incorporation was calculated from the mole fractions:

B [wt %]=100*(fB*56.11)/((fE*28.05)+(fB*56.11)+((1−(fE+fB))*42.08))

E [wt %]=100*(fE*28.05)/((fE*28.05)+(fB*56.11)+((1−(fE+fB))*42.08))

BIBLIOGRAPHIC REFERENCES

[0146] 1) Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382. [0147] 2) Parkinson, M., Klimke, K., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2007; 208:2128. [0148] 3) Pollard, M., Klimke, K., Graf, R., Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004; 37:813. [0149] 4) Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239. [0150] 5) Griffin, J. M., Tripon, C., Samoson, A., Filip, C., and Brown, S. P., Mag. Res. in Chem. 2007 45, S1, S198. [0151] 6) Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373. [0152] 7) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443. [0153] 8) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromolecules 30 (1997) 6251. [0154] 9) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225. [0155] 10) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128. [0156] 11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

[0157] Ratio of units derived from C2 and C3: The ethylene content of blend (A) was determined by quantitative Fourier transform infrared spectroscopy (FTIR) calibrated to results obtained from quantitative .sup.13C NMR spectroscopy.

[0158] Thin films were pressed to a thickness of between 300 to 500 μm at 190° C. and spectra recorded in transmission mode. Relevant instrument settings include a spectral window of 5000 to 400 wave-numbers (cm.sup.−1), a resolution of 2.0 cm.sup.−1 and 8 scans.

[0159] Quantitative .sup.13C{.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Avance 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-d2 (TCE-d2) 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. Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. 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) and the ethylene fraction calculated as the fraction of ethylene in the blend with respect to all monomer in the polymer: fE=(E/(P+E) The ethylene 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. The mole percent of ethylene was calculated from the mole fraction: E [mol %]=100*fE. The weight percent comonomer incorporation was calculated from the mole fraction: E [wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

iPP, PE, PS, PA and PE Content:

[0160] Calibration standards were prepared by blending iPP and HDPE to create a calibration curve. The thickness of the films of the calibration standards were 300 μm. For the quantification of the iPP, PS and PA 6 content in the samples quantitative IR spectra were recorded in the solid-state using a Bruker Vertex 70 FTIR spectrometer. Spectra were recorded on 25×25 mm square films of 50-100 μm thickness prepared by compression moulding at 190° C. and 4-6 mPa. Standard transmission FTIR spectroscopy was employed using a spectral range of 4000-400 cm.sup.−1, an aperture of 6 mm, a spectral resolution of 2 cm.sup.−1, 16 background scans, 16 spectrum scans, an interferogram zero filling factor of 32 and Norton Beer strong anodization.

[0161] The absorption of the band at 1167 cm.sup.−1 in iPP is measured and the iPP content is quantified according to a calibration curve (absorption/thickness in cm versus iPP content in weight %).

[0162] The absorption of the band at 1601 cm.sup.−1 (PS) and 3300 cm.sup.−1 (PA6) are measured and the PS and PA6 content quantified according to the calibration curve (absorption/thickness in cm versus PS and PA content in wt %). The PE content is obtained by subtracting iPP, PS and PA6 from 100. The analysis is performed as double determination.

[0163] Talc and chalk content: measured by Thermogravimetric Analysis (TGA); experiments were performed with a Perkin Elmer TGA 8000. Approximately 10-20 mg of material was placed in a platinum pan. The temperature was equilibrated at 50° C. for 10 minutes, and afterwards raised to 950° C. under nitrogen at a heating rate of 20° C./min. The weight loss between ca. 550° C. and 700° C. (WCO.sub.2) was assigned to CO.sub.2 evolving from CaCO.sub.3, and therefore the chalk content was evaluated as:

Chalk content=100/44×WCO.sub.2

Afterwards the temperature was lowered to 300° C. at a cooling rate of 20° C./min. Then the gas was switched to oxygen, and the temperature was raised again to 900° C. The weight loss in this step was assigned to carbon black (Wcb). Knowing the content of carbon black and chalk, the ash content excluding chalk and carbon black was calculated as:

Ash content=(Ash residue)−56/44×WCO.sub.2−Wcb

[0164] Where Ash residue is the weight % measured at 900° C. in the first step conducted under nitrogen. The ash content is estimated to be the same as the talc content for the investigated recyclates.

[0165] MFR: melt flow rates were measured with a load of 2.16 kg (MFR.sub.2) at 230° C. or 190° C. as indicated. The melt flow rate is that quantity of polymer in grams which the test apparatus standardized to ISO 1133 extrudes within 10 minutes at a temperature of 230° C. (or 190° C.) under a load of 2.16 kg.

[0166] The melting temperature was determined by means of DSC in accordance with ISO 11357.

[0167] The glass transition temperature Tg is determined by dynamic mechanical analysis according to ISO 6721-7. The measurements are done in torsion mode on compression moulded samples (40×10×1 mm.sup.3) between −100° C. and +150° C. with a heating rate of 2° C./min and a frequency of 1 Hz.

[0168] The density was determined according to ISO 1183.

Limonene Content in DIPOLEN

[0169] Measurement

[0170] Limonene quantification was carried out using solid phase microextraction (HS-SPME-GC-MS) by standard addition.

[0171] 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.

[0172] GCMS Parameters:

[0173] Column: 30 m HP 5 MS 0.25*0.25

[0174] Injector: Splitless with 0.75 mm SPME Liner, 270° C.

[0175] Temperature program: −10° C. (1 min)

[0176] Carrier gas: Helium 5.0, 31 cm/s linear velocity, constant flow

[0177] MS: Single quadrupole, direct interface, 280° C. interface temperature

[0178] Acquisition: SIM scan mode

[0179] Scan parameter: 20-300 amu

[0180] SIM Parameter: m/Z 93, 100 ms dwell time

TABLE-US-00001 TABLE 1 Limonene content in DIPOLEN (Blend (A)) Limonene [mg/kg] Sample HS-SPME-GC-MS.sup.[1] Dipolen S 31.5 ± 2.6 .sup.[1]Headspace Soldiphase Microextraction. Materials available from mtm plastics GmbH, according to 2018 specifications.

Total Free Fatty Acid Content

[0181] Fatty acid quantification was carried out using headspace solid phase micro-extraction (HS-SPME-GC-MS) by standard addition.

[0182] 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.

[0183] GCMS Parameter:

[0184] Column: 20 m ZB Wax plus 0.25*0.25

[0185] Injector: Split 5:1 with glass lined split liner, 250° C.

[0186] Temperature program: 40° C. (1 min) @6° C./min to 120° C., @15° C. to 245° C. (5 min)

[0187] Carrier: Helium 5.0, 40 cm/s linear velocity, constant flow

[0188] MS: Single quadrupole, direct interface, 220° C. inter face temperature

[0189] Acquisition: SIM scan mode

[0190] Scan parameter: 46-250 amu 6.6 scans/s

[0191] SIM Parameter: m/z 60.74, 6.6 scans/s

TABLE-US-00002 TABLE 2 Total fatty acid content in Dipolen (Blend (A)) Total fatty acid Sample concentration [mg/kg].sup.[1] Dipolen S 70.6 .sup.[1]The 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 totally fatty acid concentration value.

Experiments

[0192] A number of blends were produced with DIPOLEN S as blend (A), a polyethylene-polypropylene blend from Mtm Plastics GmbH, materials according to the August 2018 specifications.

[0193] In each of the blends 5 to 10 wt.-% of a reactor-derived compatibilizer (B) was added. As compatibilizer (B) the following commercially available terpolymers were used:

TABLE-US-00003 TABLE 3 Properties of the compatibilizers (B) B1 B2 Compatibilizer Tafmer PN 0040 Tafmer PN 20300 MFR [g/10 min] 4.0 30.0 Tm [° C.] 160 160 Tg [° C.] −16 −26 Density [kg/m.sup.3] 868 868 C2 [wt.-%] 4.7 19.9 C4 [wt.-%] 8.9 7.1

[0194] The compositions were prepared via melt blending on a co-rotating twin screw extruder with 0.3 wt.-% Irganox B225F (AO) as stabilizer. The polymer melt mixture was discharged and pelletized. For testing the mechanical properties, specimens were produced and tested according to ISO 179 with 1eA notched specimens to measure the Charpy notched impact strength (NIS) and according to ISO 527-1/2 with 1A specimens to measure the tensile properties at room temperature. The results are summarized in Table 4.

TABLE-US-00004 TABLE 4 Composition and properties of the inventive and comparative examples CE1 IE1 IE2 IE3 IE4 A [wt.-%] 99.7 94.7 89.7 94.7 89.7 B1 [wt.-%] — 5 10 — — B2 [wt.-%] — — — 5 10 AO [wt.-%] 0.3 0.3 0.3 0.3 0.3 NIS [kJ/m.sup.2] 5.7 6.8 8.9 6.4 8.2 TM [MPa] 850 736 640 755 641

[0195] As can be gathered from Table 4, the compositions according to the inventive examples have a higher impact strength than the reference which contains no compatibilizer while the tensile modulus remains on a high level.