Patent Application
20230279204
The present invention relates to upgraded recycled blends comprising predominantly polyethylene and polypropylene.
The use of recycled materials, which are derived from a wide variety of sources is a must in the field of polyolefins. However, the recycling streams available all suffer from limited mechanical properties not allowing commercially attractive end uses. Various expensive booster polymers have been suggested for upgrading recycling streams rendering the recycling as such uneconomical. For this reason, there is at the moment very limited market for recycled blends; any upgrading component needs to be as cheap as thinkable. In blends comprising predominantly polyethylene and polypropylene, it is relatively easy to achieve higher impact strength through the addition of elastomers acting as compatibilizers like conventional ethylene-propylene rubbers or EPDM. WO 2015/169690 A1 suggests the incorporation of heterophasic ethylene-propylene copolymers (HECOs) comprising ethylene-octene-copolymers, which are commercially available, i.a. from Borealis Plastomers (NL) under the tradename Queo®, from DOW Chemical Corp (USA) under the tradename Engage®, or from ENI SpA (IT). However, the use of arbitrary heterophasic ethylene-propylene copolymers (HECOs) not necessarily yields good results, particularly with respect to stiffness. It was commonly believed that the limited stiffness could only be overcome by using plastomers having block copolymer nature such as provided by Dow Chemical as Dow Infuse OBC or Intune OBC plastomers. For example, INTUNE™ polypropylene-based OBCs (PP-OBCs) have been designed as compatibilizers rather than elastomers. They contain propylene-rich blocks compatible with polypropylene and ethylene-rich blocks compatible with polyethylene. It is readily understandable that the block copolymer introduces the options of having certain domains of higher stiffness and thereby overall increased stiffness. However, plastomers with block copolymer natures, which is easily detectable by NMR and further reflected by melting temperature, have the disadvantage of being relatively expensive. Apart from the use of OBC materials it is further known to incorporate random heterophasic copolymers (RAHECO) including a propylene ethylene random copolymer matrix and an ethylene propylene rubber as dispersed phase. However, the amount of RAHECOs required are frequently rather high. In addition to that, numerous final uses do not require excessive impact performance. The trash problem involving polymers understandably requires compatibilizers which allow repurposing the polymers in very high amounts in final products.
There was a deeply felt need of having a clever compatibilizer allowing the provision of upgraded polypropylene-polyethylene blends with a sufficiently high stiffness and moderately high impact strength at relatively low amounts of compatibilizer.
The present invention insofar provides a polyethylene-polypropylene composition having a melt flow rate of 5.0 to 12.0 g/10 min obtainable by blending
The present invention further provides an article comprising, preferably consisting of the polyethylene-polypropylene composition according to present invention.
The present invention is also concerned with a process for providing a polyethylene-polypropylene composition according to the present invention as defined above, whereby the process comprises the steps of:
In a further aspect, the present invention provides
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although, any methods and materials similar or equivalent to those described herein can be used in practice for testing of the present invention, the preferred materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. Unless clearly indicated otherwise, use of the terms “a,” “an,” and the like refers to one or more.
A plastomer is a copolymer composed of units derived from ethylene and 1-butene, ethylene and 1-hexene or ethylene and 1-octene. Plastomer indicates the copolymer has rubber like properties.
“Upgrading” means improving one or more properties such as Charpy notched impact and/or stiffness such as reflected by the tensile modulus.
For the purpose of the present invention
“improving the impact—stiffness balance” shall mean that the Charpy notched impact strength (1eA) (non-instrumented, ISO 179-1 at +23° C.) is at least 14 kJ/m2 and simultaneously the tensile modulus in MPa (ISO 527-2) is at least 850 to 1000 MPa.
For the purposes of the present description, the term “recycled waste” or “recycled material” is used to indicate a material recovered from both post-consumer waste and industrial waste, as opposed to virgin polymers. Post-consumer waste refers to objects having completed at least a first use cycle (or life cycle), i.e. having already served their first purpose; while industrial waste refers to manufacturing scrap, which does not normally reach a consumer. The term “virgin” denotes the newly produced materials and/or objects prior to their first use, which have not already been recycled. Virgin materials and recycled materials easily can be differentiated based on absence or presence of contaminants such as limonene and/or fatty acids and/or paper and/or wood. Polypropylene-polyethylene blends also can be differentiated with respect to their origin by presence of polystyrene and/or polyamide. Residual content denotes a content above the detection limit. Many different kinds of polyethylene or polypropylene can be present in “recycled material”. The ratio polypropylene (A-1) versus polyethylene plus polyethylene copolymer (A-2) is determined experimentally by using isotactic polypropylene (iPP) and high density polyethylene (HDPE) for calibration. A polymer blend is a mixture of two or more polymeric components. In general, the blend can be prepared by mixing the two or more polymeric components. A “compatibilizer” is a substance in polymer chemistry, which is added to a blend of polymers with limited miscibility in order to increase their stability. “Polypropylene-polyethylene blend” refers to a composition containing both polypropylene and polyethylene including also polypropylene copolymers as well as polyethylene copolymers. As a direct determination of the polypropylene content and polyethylene content is not possible, the weight ratio polypropylene (A-1) to polyethylene (A-2) of 19:1 to 7:3 denotes the equivalent ratio as determined from calibration by iPP and HDPE and determination by IR spectroscopy. Stabilizers are selected from the group of antioxidants and/or light stabilizers.
Compatibilizer (B)
The compatibilizer (B) according to the present invention is a plastomer selected from C2C4 plastomers, C2C6 plastomers, C2C8 plastomers and mixtures thereof, whereby the plastomer has
Such compatibilizers (and also the preferred compatibilizers as described below) are commercially available. The melting point excludes the presence of blocky character. The compatibilizer (B) according to the present invention preferably has a DSC melting point of equal or below 73° C., more preferably below 60° C. (IS011357). In a further aspect, the compatibilizer (B) according to the present invention preferably has a density of equal or lower than 875 kg/m3 (IS01183). C2C8 plastomers are particularly preferred.
When compatibilizer (B) is used without component (C) as described below, the impact strength will be increased when compared with blend (A). It should be understood that use of compatibilizer (B) in an amount of more 23 wt. % or more is possible but not really desirable since the aim is to dump blend (A) in an amount as high as possible in the resulting composition. Moreover, there is no need for having excessively high impact strength values.
Random Polypropylene Copolymer (C)
The random polypropylene copolymer (C) according to the present invention has an MFR2 (IS01133, 2.16 kg load at 230° C.) of equal or below 1.0 g/10 min. Most preferably the random polypropylene copolymer (C) according to the present invention has an MFR2 (IS01133. 2.16 kg load at 230° C.) of 0.1 to 0.5 g/10 min. The low melt flow rate ensures that sufficient polymer chains of rather long length are introduced. The rather low melt flow rate of the random polypropylene copolymer (C) contributes to impact and stiffness. The random polypropylene copolymer (C) according to the present invention preferably is a propylene ethylene copolymer, i.e. the copolymer is only composed of units derived from propylene and ethylene. Random polypropylene copolymer (C) according to the present invention are commercially available.
The random polyproyplene according to the present invention preferably has a tensile modulus of at least 950 MPa (ISO 527-2).
In yet a further aspect the random polypropylene according to the present invention preferably has an ethylene content of 3.0 to 6.0 wt.-%.
It is preferred that the random polypropylene according to the present invention having an ethylene content of 3.0 to 6.0 wt.-% is only composed of units derived from propylene and ethylene.
Most preferably the random polypropylene according to the present invention has an ethylene content of 3.0 to 6.0 wt.-%, is only composed of units derived from propylene and ethylene and has a tensile modulus of at least 950 MPa (ISO 527-2).
Polypropylene-Polyethylene Blend (A)
The polypropylene-polyethylene blend (A) according to present invention preferably has one or more of the following properties
The polypropylene-polyethylene blend (A) according to the present invention comprises
It should be understood that polypropylene-polyethylene blend (A) may vary broadly in composition, i.e. may include polypropylene homopolymers, polypropylene copolymers, polyethylene homopolymers, and polyethylene copolymers. As a direct determination of the polypropylene content and polyethylene content is not possible, the weight ratio polypropylene (A-1) to polyethylene (A-2) of 19:1 to 7:3 is the equivalent ratio as determined from calibration by iPP and HDPE.
Conventionally the polypropylene-polyethylene blend (A) according to the present invention may have one or more of the following:
It is preferred that components a) to d) as described herein add up to 100 wt.-%.
The present invention is particularly concerned with a polyethylene-polypropylene composition having a melt flow rate of 5.0 to 12.0 g/10 min obtainable by blending
Experimental Section
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 skilled 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
To establish different calibration curves different standards, iPP and HDPE and iPP, PS and PA6 were blended. For the quantification of the content of the foreign polymers, IR spectra were recorded in the solid-state using a Bruker Vertex 70 FTIR spectrometer. Films were prepared with a compression-molding device at 190° C. with 4-6 MPa clamping force. The thickness of the films for the calibration standards for iPP and HDPE was 300 μm and for the quantification of the iPP, PS and PA 6 50-100 μm film thickness was used. Standard transmission FTIR spectroscopy is employed using a spectral range of 4000-400 cm-1, an aperture of 6 mm, a spectral resolution of 2 cm-1, 16 background scans, 16 spectrum scans, an interferogram zero filling factor of 32 and Norton Beer strong apodization.
The absorption of the band at 1167 cm-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 %).
The absorption of the band at 1601 cm-1 (PS) and 3300 cm-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 content of polyethylene and ethylene containing copolymers is obtained by subtracting (iPP+PS+PA6) from 100, taking into account the content of non-polymeric impurities as determined in the methods below. The analysis is performed as a double determination.
b) Tensile Modulus and Tensile Strain at Break
were measured according to ISO 527-2 (test speed=traverse/cross head speed: for tensile modulus evaluation: 1 mm/min (0.05-0.25% measured extensometer), when 0.25% reached, then 50 mm/min until break at 23° C. using injection molded specimens 1B prepared as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness). The measurement was done after 96 h conditioning time at 23° C. of the specimen.
c) The Impact Strength
was determined as Charpy Notched Impact Strength according to ISO 179-1 eA at +23° C., at 0° C., and at −20° C. on injection molded specimens of 80×10×4 mm3 prepared according to EN ISO 1873-2. The measurement was done after 96 h conditioning time at 23° C. of the specimen.
e) Comonomer Content
Poly(Propylene-Co-Ethylene)—Ethylene Content—IR Spectroscopy Quantitative infrared (IR) spectroscopy was used to quantify the ethylene content of the poly(ethylene-co-propene) copolymers through calibration to a primary method. Calibration was facilitated through the use of a set of in-house non-commercial calibration standards of known ethylene contents determined by quantitative 13C solution-state nuclear magnetic resonance (NMR) spectroscopy. The calibration procedure was undertaken in the conventional manner well documented in the literature. The calibration set consisted of 38 calibration standards with ethylene contents ranging 0.2-75.0 wt. % produced at either pilot or full scale under a variety of conditions. The calibration set was selected to reflect the typical variety of copolymers encountered by the final quantitative IR spectroscopy method. Quantitative IR spectra were recorded in the solid-state using a Bruker Vertex 70 FTIR spectrometer. Spectra were recorded on 25 x25 mm square films of 300 μm thickness prepared by compression moulding at 180-210° C. and 4-6 MPa. For samples with very high ethylene contents (>50 mol %) 100 μm thick films were used. Standard transmission FTIR spectroscopy was employed using a spectral range of 5000-500 cm−1, an aperture of 6 mm, a spectral resolution of 2 cm−1, 16 background scans, 16 spectrum scans, an interferogram zero filling factor of 64 and Blackmann-Harris 3-term apodisation. Quantitative analysis was undertaken using the total area of the CH2 rocking deformations at 730 and 720 cm−1 (AQ) corresponding to (CH2)>2 structural units (integration method G, limits 762 and 694 cm−1). The quantitative band was normalised to the area of the CH band at 4323 cm−1 (AR) corresponding to CH structural units (integration method G, limits 4650, 4007 cm−1). The ethylene content in units of weight percent was then predicted from the normalised absorption (AQ/AR) using a quadratic calibration curve. The calibration curve having previously been constructed by ordinary least squares (OLS) regression of the normalised absorptions and primary comonomer contents measured on the calibration set.
Poly(Propylene-Co-Ethylene)—Ethylene Content—13C NMR Spectroscopy
Quantitative 13C{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 1H and 13C respectively. All spectra were recorded using a 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-d2 (TCE-d2) along with chromium (III) acetylacetonate (Cr(acac)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 optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., et al. J. Mag. Reson. 187 (2007) 225, and in Busico, V., et al, Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6k) transients were acquired per spectra. Quantitative 13C{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 comonomer fraction calculated as the fraction of ethylene in the polymer with respect to all monomer in the polymer: fE=(E/(P+E) 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 13C{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. For systems with very low ethylene content where only isolated ethylene in PPEPP sequences were observed the method of Wang et. al. was modified reducing the influence of integration of sites that are no longer 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)) Through the use of this set of sites the corresponding integral equation becomes E=0.5(IH+IG+0.5(Ic+ID)) 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. The mole percent comonomer incorporation 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)).
f) Talc and Chalk Content
TGA according to the following procedure:
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. (WCO2) was assigned to CO2 evolving from CaCO3, and therefore the chalk content was evaluated as:
Chalk content=100/44×WCO2
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×WCO2−Wcb
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.
g) MFR
Melt flow rates were measured with a load of 2.16 kg (MFR2) at 230° C. (for polypropylene) and at 190° C. (for polyethylene). 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. respectively 190° C. under a load of 2.16 kg.
h) Melting Temperature
Melting temperature was measured using DSC according to ISO 11357-3 using a temperature gradient of 10° C./min.
i) Amount of Metals
was determined by x ray fluorescence (XRF)
j) Amount of Paper, Wood
Paper and wood were determined by conventional laboratory methods including milling, floatation, microscopy and Thermogravimetric Analysis (TGA).
k) Limonene Measurement
Limonene quantification was carried out using solid phase microextraction (HS-SPME-GC-MS) by standard addition.
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 μm 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:
l) Total Free Fatty Acid Content
Fatty acid quantification was carried out using headspace solid phase micro-extraction (HS-SPME-GC-MS) by standard addition.
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 pL 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:
Experiments
A conventional random polypropylene copolymer (propylene ethylene copolymer) having a melt flow rate of 0.25 g/10 min (ISO 1133, 230° C., 2.16 kg), tensile modulus of 1006 MPa (ISO 527-2), a Charpy Impact strength of 13 kJ/m2 (ISO 179-1) and an ethylene content of 4.5 wt.-% as commercially available was used as component (C). A C2C8 plastomer (Queo 6201 as commercially available from Borealis) having a melt flow rate of 1.0 g/10 min (ISO 1133, 190° C., 2.16 kg), melting temperature of 49° C., and tensile modulus of 4 MPa was used as component (B).
For blend (A) an experimental grade originating from household trash having a melt flow rate of 13.2 g/10 min was used.
Table 1 shows the properties of the polypropylene/polyethylene blends (A) as used for the evaluation.
The compositions were compounded in a co-rotating twin-screw extruder Coperion ZSK 47 at 220° C. with 0.15 wt.-% antioxidant (Irganox B215FF from BASF AG, Germany; this is a 1:2-mixture of Pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)-propionate, CAS-no. 6683-19-8, and Tris (2,4-di-t-butylphenyl) phosphite, CAS-no. 31570-04-4)..
| Number | Date | Country | Kind |
|---|---|---|---|
| 20188512.6 | Jul 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/071257 | 7/29/2021 | WO |
