Patent Application
20230114045
The present invention relates to upgrading of PE recycling streams using virgin high-density polyethylenes (HDPE) to give jacketing materials that have acceptable ESCR (Environmental Stress Crack Resistance) and/or strain hardening performance.
Polyolefins, in particular polyethylene and polypropylene are increasingly consumed in large amounts in a wide range of applications, including packaging for food and other goods, fibres, automotive components, and a great variety of manufactured articles.
Polyethylene based materials are a particular problem as these materials are extensively used in packaging. Taking into account the huge amount of waste collected compared to the amount of waste recycled back into the stream, there is still a great potential for intelligent reuse of plastic waste streams and for mechanical recycling of plastic wastes.
Generally, recycled quantities of polyethylene on the market are mixtures of both polypropylene (PP) and polyethylene (PE), this is especially true for post-consumer waste streams. Moreover, commercial recyclates from post-consumer waste sources are conventionally cross contaminated with non-polyolefin materials, such as polyethylene terephthalate, polyamide, polystyrene or non polymeric substances like wood, paper, glass or aluminium. These cross-contaminations drastically limit final applications or recycling streams such that no profitable final uses remain.
In addition, recycled polyolefin materials normally have properties, which are much worse than those of the virgin materials, unless the amount of recycled polyolefin added to the final compound is extremely low. For example, such materials often have limited impact strength and poor mechanical properties (such as e.g. brittleness) and thus, they do not fulfil customer requirements. For several applications, e.g. jacketing materials (for cables), containers, automotive components or household articles. This normally excludes the application of recycled materials for high quality parts, and means that they are only used in low-cost, non-demanding applications, such as e.g. in construction or in furniture. In order to improve the mechanical properties of these recycled materials, generally relatively large amounts of compatibilizing/coupling agents and elastomeric polymers are added. These materials are generally virgin materials, which are produced from oil.
U.S. Pat. No. 8,981,007 B2 relates to non-crosslinked polyethylene compositions for use in the jacketing of power cables. Generally crosslinked polyethylene is used for power cables, due to its excellent heat resistance, chemical resistance and electrical properties. However, since crosslinked polyethylene resin is a thermoset resin, it is not recyclable. There is, therefore, a demand for an eco-friendly non-crosslinked type thermoplastic polyethylene resin, which is also heat resistant and hence suitable for use in power cables.
EP 2417194 B1 also relates to uncrosslinked polyethylene compositions for use in power cables. The compositions disclosed herein are polymer blends comprising MDPE and HDPE and one or more additive(s) selected from a flame retardant, an oxidation stabilizer, a UV stabilizer, a heat stabilizer and a process aid.
DE-102011108823-A1 relates to a composite for electrical isolation of electrical cables. The composite comprises a plastic, a material having a heat conductivity of less than 1 W/(mk) and a displacement material (C). In certain embodiments, the displacement material can be a recycled material.
EP 1676283 B1 relates to medium/high voltage electrical energy transport or distribution cables comprising at least one transmissive element and at least one coating layer, said coating layer being made from a coating material comprising at least one recycled polyethylene (obtained from a waste material) with a density not higher than 0.940 g/cm3 and at least a second polyethylene material having a density higher than 0.940 g/cm3. The coating material in some of the examples of EP 1676283 B1 showed improved values with respect to stress cracking resistance with respect to those obtained from recycled polyethylene alone. However, these values were considerably less than those obtained with the virgin material, DFDG-6059@ Black.
EP 2 417 194 B1 relates to power cables comprising an non crosslinked polyethylene composition comprising 100 parts by weight of a polymer comprising 60 to 95 wt % of a linear medium density polyethylene resin comprising an alpha-olefin having 4 or more carbon atoms as a comonomer and having a melt index of 0.6-2.2 g/10 min (at 190° C. under a load of 5 kg), a differential scanning calorimetry (DSC) enthalpy of 130-190 joule/g and a molecular weight distribution of 2-30; and 5 to 40 wt % of a high-density polyethylene resin having a melt index of 0.1-0.35 g/10 min (at 190° C. under a load of 5 kg), a DSC enthalpy of 190-250 joule/g and a molecular weight distribution of 3-30; 0.1 to 10 parts by weight of one or more additive(s) selected from a flame retardant, an oxidation stabilizer, a UV stabilizer, a heat stabilizer and a process aid, based on 100 parts by weight of the polymer. None of the resins is recycled material.
Another particular problem in recycled polyethylene materials is that variations in ESCR (Environmental Stress Crack Resistance) properties can also be observed in recycled polyethylene blends depending on the waste origin. Thus, there is need for addressing these limitations in a flexible way. For jacketing applications generally an ESCR (Bell test failure time) of greater than 1000 hours is desirable.
Thus, there remains a need in the art to provide recycled polyethylene solutions for wire and cable applications, especially for jacketing materials, that have acceptable and constant ESCR (Environmental Stress Crack Resistance) performance (e.g. tensile properties), with Bell test failure time >1000 hours and good strain hardening (SH) performance with a strain hardening (SH) modulus of at least 15.0 MPa with other properties which are similar to blends of virgin polyethylene marketed for the purpose of cable jacketing. It is also desirable to maximize the loading of recycled polyethylene material.
The present invention provides compositions with acceptable ESCR and strain hardening performance, while maintaining other properties similar to the blend of virgin polyethylene marketed for the purpose of cable jacketing. The present invention is also concerned with maximising the loading of recycled material (with loadings of up to 85% recycled material) in the composition and with the use of a combination of specific blends of virgin polyethylene to improve the ESCR properties and or strain hardening properties of a mixed-plastic-polyethylene primary recycling blend (A).
In a first aspect the present invention relates to a mixed-plastic-polyethylene composition comprising
with the total amounts of C2 units and continuous C3 units based on the total weight amount of monomer units in the composition and measured according to quantitative 13C{1H} NMR measurement,
and wherein the composition has
In a second aspect the present invention relates to a mixed-plastic-polyethylene composition having
obtainable by blending and extruding components comprising
Further, the present invention relates to an article, comprising the mixed-plastic-polyethylene composition as described above or below, preferably wherein the article is a cable comprising at least one layer comprising the mixed-plastic-polyethylene composition as described above or below, more preferably wherein the article is a cable comprising a jacketing layer comprising the mixed-plastic-polyethylene composition as described above or below.
Still further, the present invention relates to a process for preparing the mixed-plastic-polyethylene composition as defined above or below, comprising the steps of:
Finally, the present invention relates to the use of a mixed-plastic-polyethylene composition as defined above or below for producing a cable layer, preferably a cable jacketing layer, having an ESCR (Bell test failure time) of more than 1000 hours and/or a strain hardening modulus (SH modulus) of from 15.0 to 30.0 MPa.
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.
For the purposes of the present description and of the subsequent claims, the term “recycled waste” is used to indicate a material recovered from post-consumer waste, as opposed to virgin polymers and/or materials. 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.
The term “virgin” denotes the newly produced materials and/or objects prior to their first use, which have not already been recycled. The term “recycled material” such as used herein denotes materials reprocessed from “recycled waste”.
The term “natural” in the context of the present invention means that the components are of natural colour. This means that no pigments (including carbon black) are included in the components of the mixed-plastic-polyethylene composition of the present invention.
A blend denotes a mixture of two or more components, wherein one of the components is polymeric. In general, the blend can be prepared by mixing the two or more components. Suitable mixing procedures are known in the art. The term secondary blend (B) refers to a blend comprising at least 90 wt.-% of a reactor made high density polyethylene material. Said high density polyethylene material preferably does not contain carbon black or any other pigments. This high density polyethylene material is a virgin material which has not already been recycled.
For the purposes of the present description and of the subsequent claims, the term “mixed-plastic-polyethylene” indicates a polymer material including predominantly units derived from ethylene apart from other polymeric ingredients of arbitrary nature. Such polymeric ingredients may for example originate from monomer units derived from alpha olefins such as propylene, butylene, octene, and the like, styrene derivatives such as vinylstyrene, substituted and unsubstituted acrylates, substituted and unsubstituted methacrylates.
Said polymeric materials can be identified in the mixed-plastic polyethylene composition by means of quantitative 13C{1H} NMR measurements as described herein. In the quantitative 13C{1H} NMR measurement used herein and described below in the measurement methods different units in the polymeric chain can be distinguished and quantified. These units are ethylene units (C2 units), units having 3, 4 and 6 carbons and units having 7 carbon atoms.
Thereby, the units having 3 carbon atoms (C3 units) can be distinguished in the NMR spectrum as isolated C3 units (isolated C3 units) and as continuous C3 units (continuous C3 units) which indicate that the polymeric material contains a propylene based polymer. These continuous C3 units can also be identified as iPP units. The continuous C3 units thereby can be distinctively attributed to the mixed-plastic-polyethylene primary recycling blend (A) as the secondary blend (B) of virgin high-density polyethylene (HDPE) in the mixed-plastic-polyethylene composition according to the present invention usually does not include any propylene based polymeric components.
The units having 3, 4, 6 and 7 carbon atoms describe units in the NMR spectrum which are derived from two carbon atoms in the main chain of the polymer and a short side chain or branch of 1 carbon atom (isolated C3 unit), 2 carbon atoms (C4 units), 4 carbon atoms (C6 units) or 5 carbon atoms (C7 units).
The units having 3, 4 and 6 carbon atoms (isolated C3, C4 and C6 units) can derive either from incorporated comomoners (propylene, 1-butene and 1-hexene comonomers) or from short chain branches formed by radical polymerization.
The units having 7 carbon atoms (C7 units) can be distinctively attributed to the mixed-plastic-polyethylene primary recycling blend (A) as they cannot derive from any comonomers. 1-heptene monomers are not used in copolymerization. Instead, the C7 units represent presence of LDPE distinct for the recyclate. It has been found that in LDPE resins the amount of C7 units is always in a distinct range. Thus, the amount of C7 units measured by quantitative 13C{1H} NMR measurements can be used to calculate the amount of LDPE in a polyethylene composition.
Thus, the amounts of continuous C3 units, isolated C3 units, C4 units, C6 units and C7 units are measured by quantitative 13C{1H} NMR measurements as described below, whereas the LDPE content is calculated from the amount of C7 units as described below.
The total amount of ethylene units (C2 units) is attributed to units in the polymer chain, which do not have short side chains of 1-5 carbon atoms, in addition to the units attributed to the LDPE (i.e. units which have longer side chains branches of 6 or more carbon atoms).
A mixed-plastic-polyethylene primary blend (A) denotes the starting primary blend containing the mixed plastic-polyethylene as described above. Conventionally further components such as fillers, including organic and inorganic fillers for example talc, chalk, carbon black, and further pigments such as TiO2 as well as paper and cellulose may be present. In a specific and preferred embodiment the waste stream is a consumer waste stream, such a waste stream may originate from conventional collecting systems such as those implemented in the European Union. Post-consumer waste material is characterized by a limonene content of from 2 to 500 mg/kg (as determined using solid phase microextraction (HS-SPME-GC-MS) by standard addition).
Mixed-plastic-polyethylene primary blend(s) (A) as used herein are commercially available. One suitable recyclate is e.g. available from Ecoplast Kunststoffrecycling GmbH under the brand name NAV 102.
Within the meaning of this invention the term “jacketing materials” refers to materials used in cable jacketing/cable coating applications for electrical/telephone/telecommunications cables. These materials are required to show good ESCR properties, such as a Bell test failure time of >1000 hours, preferably >2000 hours.
If not indicated otherwise “%” refers to weight-%.
Natural Mixed-Plastic-Polyethylene Primary Recycling Blend (A)
The mixed-plastic-polyethylene composition according to the present invention comprises a mixed-plastic-polyethylene primary recycling blend (A). It is the essence of the present invention that this primary recycling blend is obtained from a post-consumer waste stream and/or a post-industrial waste stream, preferably from a post-consumer waste stream.
According to the present invention the mixed-plastic-polyethylene primary recycling blend (A) is generally a blend, wherein at least 90 wt.-%, preferably at least 95 wt.-%, more preferably 100 wt.-% of the mixed-plastic-polyethylene primary blend originates from post-consumer waste, such as from conventional collecting systems (curb-side collection), such as those implemented in the European Union, and/or post-industrial waste, preferably from post-consumer waste.
Said post-consumer waste can be identified by its limonene content. It is preferred that the post-consumer waste has a limonene content of from 2 to 500 mg/kg.
The mixed-plastic-polyethylene primary recycling blend (A) preferably comprises
The total amounts of C2 units and continuous C3 units thereby are based on the total weight amount of monomer units in the mixed-plastic-polyethylene primary recycling blend (A) and are measured according to quantitative 13C{1H} NMR measurement.
In addition to C2 units and continuous C3 units the mixed-plastic-polyethylene primary recycling blend (A) can further comprise units having 3, 4, 6 or 7 or more carbon atoms so that the mixed-plastic-polyethylene primary recycling blend (A) overall can comprise ethylene units and a mix of units having 3, 4, 6 and 7 or more carbon atoms.
The mixed-plastic-polyethylene primary recycling blend (A) preferably comprises one or more in any combination, preferably all of:
The total amounts of C2 units, continuous C3 units, isolated C3 units, C4 units, C6 units, C7 units and LDPE content thereby are based on the total weight amount of monomer units in the mixed-plastic-polyethylene primary recycling blend (A) and are measured or calculated according to quantitative 13C{1H} NMR measurement.
Preferably, the total amount of units, which can be attributed to comonomers (i.e. isolated C3 units, C4 units and C6 units), in the mixed-plastic-polyethylene primary recycling blend (A) is from 4.00 wt % to 20.00 wt %, more preferably from 4.50 wt % to 17.50 wt %, still more preferably from 4.75 wt % to 15.00 wt % and most preferably from 5.00 wt % to 12.50 wt %, and is measured according to quantitative 13C {1H} NMR measurement.
Additionally, the mixed-plastic-polyethylene primary recycling blend (A) preferably shows non-linear viscoelastic behaviour as shown in the below defined Large Oscillatory Shear (LAOS) measurement:
The mixed-plastic-polyethylene primary recycling blend (A) preferably has a Large Amplitude Oscillatory Shear Non Linear Factor at a strain of 1000%, LAOSNLF (1000%), of from 2.200 to 10.000, more preferably from 2.400 to 8.500, still more preferably from 2.600 to 7.000 and most preferably from 2.800 to 5.000.
It is preferred that the mixed-plastic-polyethylene primary recycling blend (A) has
The mixed-plastic-polyethylene primary recycling blend (A) preferably does not comprise carbon black. It is further preferred that the mixed-plastic-polyethylene primary recycling blend (A) does not comprise any pigments other than carbon black.
The mixed-plastic-polyethylene primary recycling blend (A) preferably is a natural mixed-plastic-polyethylene primary recycling blend (A).
The mixed-plastic-polyethylene primary recycling blend (A) may also include:
all percentages with respect to the mixed-plastic-polyethylene primary recycling blend (A).
The mixed-plastic-polyethylene primary recycling blend (A) preferably has one or more, more preferably all, of the following properties in any combination:
It is preferred that the mixed-plastic-polyethylene primary recycling blend (A) has a comparatively low gel content, especially in comparison to other mixed-plastic-polyethylene primary recycling blends.
The mixed-plastic-polyethylene primary recycling blend (A) preferably has a gel content for gels with a size of from above 600 μm to 1000 μm of not more than 1000 gels/m2, more preferably not more than 850 gels/m2. The lower limit of the gel content for gels with a size of from above 600 μm to 1000 μm is usually 100 gels/m2, preferably 150 gels/m2.
Still further, the mixed-plastic polyethylene composition preferably has a gel content for gels with a size of from above 1000 μm of not more than 200 gels/m2, more preferably not more than 150 gels/m2. The lower limit of the gel content for gels with a size of from above 1000 μm is usually 10 gels/m2, preferably 25 gels/m2.
Generally, recycled materials perform less well in functional tests such as the ESCR (Bell test failure time), SH modulus and Shore D tests than virgin materials or blends comprising virgin materials.
The mixed-plastic-polyethylene primary recycling blend (A) is preferably present in the composition of the present invention in an amount of from 10 to 85 wt %, more preferably 10 to 70 wt %, still more preferably from 15 to 65 wt %, even more preferably from 20 to 55 wt % and most preferably from 25 to 50 wt %, based on the overall weight of the composition.
Secondary Blend (B) of Virgin High-Density Polyethylene (HDPE)
The mixed-plastic-polyethylene composition of the invention comprises a secondary blend (B) of virgin high-density polyethylene (HDPE).
The secondary blend (B) preferably has:
The secondary blend (B) can comprise carbon black or other pigments in an amount of of not more than 5 wt %, preferably not more than 3 wt %.
The presence of carbon black has an influence on the density of the secondary blend (B). A secondary blend (B) comprising carbon black preferably has a density of from 950 to 970 kg/m3, more preferably from 953 to 965 kg/m3.
In a preferred embodiment the secondary blend (B) does not comprise carbon black. It is further preferred that the secondary blend (B) does not comprise any pigments other than carbon black. In said embodiment the secondary blend (B) of virgin high-density polyethylene (HDPE) is preferably a natural secondary blend (B) of virgin high-density polyethylene (HDPE).
The secondary blend (B) of virgin high-density polyethylene (HDPE) preferably has a density of from 940 to 960 kg/m3, preferably from 943 to 955 kg/m3.
The secondary blend (B) includes as polymeric component a copolymer of ethylene and one or more comonomer units selected from alpha-olefins having from 3 to 6 carbon atoms. It is preferred that the polymeric component is a copolymer of ethylene and 1-butene or a copolymer of ethylene and 1-hexene.
Apart from the polymeric component the secondary blend (B) can further comprise additives in an amount of 10 wt % or below, more preferably 9 wt % or below, more preferably 7 wt % or below of the secondary blend (B). Suitable additives are usual additives for utilization with polyolefins, such as stabilizers (e.g. antioxidant agents), metal scavengers and/or UV-stabilizers, antistatic agents and utilization agents (such as processing aid agents).
The secondary blend (B) preferably has one or more, more preferably all of the following properties in any combination:
Generally, recycled materials perform less well in functional tests such as the ESCR (Bell test failure time), SH modulus and Shore D tests than virgin materials or blends comprising virgin materials.
The secondary blend (B) is preferably present in the composition of the present invention in an amount of from 15 to 90 wt %, more preferably from 30 to 90 wt %, still more preferably from 35 to 85 wt %, even more preferably from 45 to 80 wt % and most preferably from 50 to 75 wt %, based on the overall weight of the composition.
Tertiary Blend (C) of Virgin High-Density Polyethylene (HDPE)
In one specific embodiment the mixed-plastic-polyethylene composition of the invention additionally comprises a tertiary blend (C) of virgin high-density polyethylene (HDPE).
The tertiary blend (C) preferably has:
The tertiary blend (C) can comprise carbon black or other pigments in an amount of of not more than 5 wt %, preferably not more than 3 wt %.
The presence of carbon black has an influence on the density of the tertiary blend (C). A tertiary blend (C) comprising carbon black preferably has a density of from 955 to 970 kg/m3, preferably from 958 to 965 kg/m3.
In a preferred embodiment the tertiary blend (C) does not comprise carbon black. It is further preferred that the tertiary blend (C) does not comprise any pigments other than carbon black.
In said embodiment the tertiary blend (C) of virgin high-density polyethylene (HDPE) is preferably a natural tertiary blend (C) of virgin high-density polyethylene (HDPE).
The natural tertiary blend (C) of virgin high-density polyethylene (HDPE) preferably has a density of from 945 to 960 kg/m3, preferably from 947 to 955 kg/m3.
The tertiary blend (C) includes as polymeric component a copolymer of ethylene and one or more comonomer units selected from alpha-olefins having from 3 to 6 carbon atoms. It is preferred that the polymeric component is a copolymer of ethylene and 1-butene or a copolymer of ethylene and 1-hexene.
Apart from the polymeric component the tertiary blend (C) can further comprise additives in an amount of 10 wt % or below, more preferably 9 wt % or below, more preferably 7 wt % or below of the tertiary blend (C). Suitable additives are usual additives for utilization with polyolefins, such as stabilizers (e.g. antioxidant agents), metal scavengers and/or UV-stabilizers, antistatic agents and utilization agents (such as processing aid agents).
It is preferred that the tertiary blend (C) consists of said polymeric component and the optional additives.
The tertiary blend (C) preferably has one or more, more preferably all of the following properties in any combination:
The tensile properties of tensile modulus, tensile stress at break and tensile strain at break are thereby measured according to ISO 527-2 (cross head speed=1 mm/min; test speed 50 mm/min at 23° C.) using compression moulded specimens as described in ISO 17855-2 (dog bone shape, 4 mm thickness).
It is preferred that the tertiary blend (C) is a bimodal HDPE resin blend which is suitable for pipe applications. It is especially preferred that the tertiary blend is a HDPE resin suitable for PE100 pipes, i.e. pipes withstanding a hoop stress of 10.0 MPa (MRS10.0).
If present, the tertiary blend of virgin high-density polyethylene (HDPE) is preferably present in the composition of the present invention in an amount of from 1 to 20 wt %, more preferably from 2 to 18 wt %, still more preferably from 3 to 17 wt %, even more preferably from 4 to 16 wt % and most preferably from 5 to 15 wt %, based on the overall weight of the composition.
Mixed-Plastic-Polyethylene Composition
The present invention seeks to provide a mixed-plastic-polyethylene composition comprising a mixed-plastic-polyethylene primary recycling blend (A) with improved ESCR, impact strength and SH modulus compared to the mixed-plastic-polyethylene primary recycling blend (A), to levels which are suitable for jacketing applications.
The mixed-plastic-polyethylene composition as described herein is especially suitable for wire and cable applications, such as jacketing applications.
In a first aspect the present invention relates to a mixed-plastic-polyethylene composition comprising
with the total amounts of C2 units and continuous C3 units being based on the total weight amount of monomer units in the composition and measured according to quantitative 13C{1H}NMR measurement,
and wherein the composition has
In said aspect the mixed-plastic-polyethylene composition is preferably obtainable by blending and extruding components comprising
In one embodiment the mixed-plastic-polyethylene composition only comprises, preferably consists of the mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE) as polymeric components.
In another embodiment the mixed-plastic polyethylene composition comprises, preferably consists of the mixed-plastic-polyethylene primary recycling blend (A), the secondary blend (B) of virgin high-density polyethylene (HDPE) and a tertiary blend (C) of virgin high-density polyethylene (HDPE) as polymeric components.
In said embodiment the mixed-plastic polyethylene composition has a melt flow rate (ISO 1133, 2.16 kg, 190° C.) of from 0.1 to 1.0 g/10 min and being obtainable by blending and extruding components comprising
In a second aspect the present invention relates to a mixed-plastic-polyethylene composition having
In one embodiment the mixed-plastic polyethylene composition of said aspect has a melt flow rate (ISO 1133, 2.16 kg, 190° C.) of from 0.1 to 1.0 g/10 min and being obtainable by blending and extruding components comprising
In one embodiment the mixed-plastic-polyethylene composition of said aspect only comprises, preferably consists of the mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE) as polymeric components.
In another embodiment the mixed-plastic polyethylene composition of said aspect comprises, preferably consists of the mixed-plastic-polyethylene primary recycling blend (A), the secondary blend (B) of virgin high-density polyethylene (HDPE) and a tertiary blend (C) of virgin high-density polyethylene (HDPE) as polymeric components.
The following properties apply to all aspects of the mixed-plastic polyethylene composition: The mixed-plastic-polyethylene composition comprises
Further, the mixed-plastic-polyethylene composition preferably comprises one or more in any combination of, more preferably all of:
The total amounts of C2 units, continuous C3 units, isolated C3 units, C4 units, C6 units, C7 units and LDPE content thereby are based on the total weight amount of monomer units in the composition and are measured or calculated according to quantitative 13C{1H} NMR measurement.
Preferably, the total amounts of units, which can be attributed to comonomers (i.e. isolated C3 units, C4 units and C6 units), in the mixed-plastic-polyethylene composition is from 1.00 wt % to 8.00 wt %, more preferably from 2.00 wt % to 7.00 wt %, still more preferably from 3.00 wt % to 6.00 wt %, and is measured according to quantitative 13C{1H} NMR measurement. The mixed-plastic polyethylene composition according to the present invention has a
Additionally, the mixed-plastic polyethylene composition preferably shows non-linear viscoelastic behaviour as shown in the below defined Large Oscillatory Shear (LAOS) measurement:
The mixed-plastic polyethylene composition preferably has a Large Amplitude Oscillatory Shear Non Linear Factor at a strain of 1000%, LAOSNLF (1000%), of from 1.900 to 4.000, more preferably from 2.000 to 3.500, still more preferably from 2.100 to 3.000 and most preferably from 2.125 to 2.850.
The mixed-plastic polyethylene composition preferably has an impact strength at 23° C. (ISO 179-1 eA) of from 10 to 27 kJ/m2, preferably from 12 to 26 kJ/m2.
Preferably, the impact strength at 23° C. (ISO 179-1 eA) of the composition is higher than that of the secondary blend. It is preferred that the impact strength at 23° C. (ISO 179-1 eA) of the composition is at least 105%, more preferably at least 110% of the impact strength of the secondary blend (B).
Further, the mixed-plastic polyethylene composition preferably has an impact strength at 0° C. (according to ISO 179-1 eA) of from 5.0 to 12.0 kJ/m2, more preferably from 6.0 to 10.0 kJ/m2.
The mixed-plastic polyethylene composition preferably has a strain hardening modulus (SH modulus) of from 15.0 to 30.0 MPa, more preferably from 16.0 to 26.0 MPa and most preferably from 17.0 to 25.0 MPa. Preferably, the SH modulus of the mixed polyethylene composition is at least 60%, more preferably at least 65% of the SH modulus of the secondary blend (B).
Further, the mixed-plastic polyethylene composition preferably has an ESCR (Bell test failure time) of more than 1000 hours, preferably more than 1250 hours and still more preferably more than 1500 hours and most preferably more than 1800 hours. In some embodiments the mixed-plastic polyethylene composition can have an ESCR (Bell test failure time) of more than 2000 hours or even more than 5000 hours The upper limit of the ESCR can be as high as 15000 hours, usually up to 10000 hours.
It is preferred that the mixed-plastic polyethylene composition preferably has
It is further preferred that that the mixed-plastic polyethylene composition preferably has
The mixed-plastic polyethylene composition preferably has one or more, preferably all of the following rheological properties, in any combination:
Further, the mixed-plastic polyethylene composition preferably has one or more, preferably all of the following melt flow rate properties, in any combination:
Still further, the mixed-plastic polyethylene composition preferably has one or more, preferably all of the following tensile properties, in any combination:
After ageing of the 5A test specimens at 110° C. for 14 days the mixed-plastic polyethylene composition preferably has one or more, preferably all of the following tensile properties, in any combination:
Further, the mixed-plastic polyethylene composition preferably has a tear resistance of from 10.0 to 25.0 N/mm, more preferably of from 12.5 to 22.5 N/mm and most preferably of from 15.0 to 20.0 N/mm.
It is further preferred that the mixed-plastic polyethylene composition has a pressure deformation of not more than 15%, more preferably not more than 13%. The lower limit is usually at least 0%, meaning that no pressure deformation can be detected, preferably at least 1%.
Still further, the mixed-plastic polyethylene composition preferably has a water content of preferably not more than 250 ppm more preferably not more than 248 ppm. The lower limit is usually at least 25 ppm, preferably at least 50 ppm.
It is further preferred that the mixed-plastic polyethylene composition has a gel content for gels with a size of from above 600 μm to 1000 μm of from 25 to 250 gels/m2, more preferably from 35 to 225 gels/m2.
Still further, the mixed-plastic polyethylene composition preferably has a gel content for gels with a size of from above 1000 μm of not more than 35 gels/m2, more preferably not more than 30 gels/m2. The lower limit is usually at least 0, meaning that no gels of said size can be detected, preferably at least 1.0.
The composition can have further components apart from the mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE), and the optional tertiary blend (C) of virgin high-density polyethylene (HDPE), such as further polymeric components or additives in amounts of not more than 15 wt %, based on the total weight of the composition.
Suitable additives are usual additives for utilization with polyolefins, such as stabilizers, (e.g. antioxidant agents), metal scavengers and/or UV stabilizers, antistatic agents, and utilization agents. The additives can be present in the composition in an amount of 10 wt % or below, more preferably 9 wt % or below, more preferably 7 wt % or below.
Carbon black or other pigments are not enclosed in the definition of additives.
The composition can comprise carbon black or pigments in an amount of not more than 5 wt %, preferably not more than 3 wt %.
It is thereby preferred that the composition does not contain carbon black. It is further preferred that the composition does not contain any pigments other than carbon black. In said embodiment the mixed-plastic-polyethylene composition is preferably a natural mixed-plastic-polyethylene composition.
It is, however, preferred that the composition consists of the mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE), the optional tertiary blend (C) of virgin high-density polyethylene (HDPE) and optional additives.
The presence of carbon black has an influence on the density of the composition. A composition comprising carbon black preferably has a density of from 935 to 955 kg/m3, preferably from 937 to 953 kg/m3.
A composition free from carbon black preferably has a density of from 930 to 950 kg/m3, preferably from 932 to 948 kg/m3.
In one embodiment the mixed-plastic polyethylene composition comprises, more preferably consists of mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE), but does not comprise, i.e. is free of the tertiary secondary blend (C) of virgin high-density polyethylene (HDPE).
In said embodiment, the mixed-plastic polyethylene composition preferably has the following properties:
The mixed-plastic polyethylene composition preferably has one or more, preferably all of the following melt flow rate properties, in any combination:
In one embodiment mixed-plastic polyethylene composition preferably has one or more, preferably all of the following melt flow rate properties, in any combination:
Further, the mixed-plastic polyethylene composition preferably has one or more, preferably all of the following rheological properties, in any combination:
Still further, the mixed-plastic polyethylene composition preferably has a strain hardening modulus (SH modulus) of from 15.0 to 27.0 MPa, more preferably from 16.0 to 26.0 MPa and most preferably from 17.0 to 25.0 MPa. Preferably, the SH modulus of the mixed polyethylene composition is at least 60%, more preferably at least 65% of the SH modulus of the secondary blend (B).
All other properties of the mixed-plastic polyethylene composition preferably are in the range as disclosed above.
The weight ratio of the mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE) is preferably in the range of from 10:90 to 85:15, more preferably from 10:90 to 70:30, still more preferably from 15:85 to 65:35, even more preferably from 20:80 to 60:40, and most preferably from 25:75 to 50:50.
The mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE) are generally defined as described above or below.
One positive aspect of the present invention of said embodiment is that rather high amounts of mixed-plastic-polyethylene primary recycling blend (A) can be used in the composition which still shows acceptable properties especially in regard of ESCR but also regarding strain hardening and Shore D hardness.
In another embodiment the mixed-plastic polyethylene composition comprises, more preferably consists of mixed-plastic-polyethylene primary recycling blend (A), the secondary blend (B) of virgin high-density polyethylene (HDPE) and the tertiary secondary blend (C) of virgin high-density polyethylene (HDPE).
In said embodiment, the mixed-plastic polyethylene composition preferably has the following properties:
The mixed-plastic polyethylene composition preferably has one or more, preferably all of the following melt flow rate properties, in any combination:
In one embodiment the mixed-plastic polyethylene composition preferably has one or more, preferably all of the following melt flow rate properties, in any combination:
Further, the mixed-plastic polyethylene composition preferably has one or more, preferably all of the following rheological properties, in any combination:
Still further, the mixed-plastic polyethylene composition preferably has a strain hardening modulus (SH modulus) of from 18.0 to 30.0 MPa, more preferably from 20.0 to 28.0 MPa and most preferably from 21.0 to 27.0 MPa. Preferably, the SH modulus of the mixed polyethylene composition is at least 70%, more preferably at least 75% of the SH modulus of the secondary blend (B).
All other properties of the mixed-plastic polyethylene composition preferably are in the range as disclosed above.
The weight ratio of the mixed-plastic-polyethylene primary recycling blend (A) and the combined blend of the secondary blend (B) of virgin high-density polyethylene (HDPE) and the tertiary blend (C) of virgin high-density polyethylene (HDPE) is preferably in the range of from 10:90 to 83:17, more preferably 10:90 to 70:30, still more preferably from 15:85 to 65:35, even more preferably from 20:80 to 60:40, and most preferably from 25:75 to 50:50.
The mixed-plastic-polyethylene primary recycling blend (A), the secondary blend (B) of virgin high-density polyethylene (HDPE) and the tertiary blend (C) of virgin high-density polyethylene (HDPE) are generally defined as described above or below.
One positive aspect of the present invention of said embodiment is that rather high amounts of mixed-plastic-polyethylene primary recycling blend (A) can be used in the composition which still shows acceptable properties especially in regard of strain hardening but also regarding ESCR and Shore D hardness.
It has been found that the addition of the tertiary blend (C) of virgin high-density polyethylene (HDPE) to the composition in small amounts thereby especially improves the strain hardening behavior and the tensile properties without sacrificing the impact properties.
Article
The present application is further directed to an article comprising the mixed-plastic-polyethylene composition as described above.
In a preferred embodiment, the article is used in jacketing applications i.e. for a cable jacket. Preferably the article is a cable comprising at least one layer which comprises the mixed-plastic-polyethylene composition as described above.
Preferably, the cable comprising a layer such as a jacketing layer, which comprises the mixed-plastic-polyethylene composition as described above, has a cable shrinkage of not more than 2.0%, more preferably not more than 1.8%. The lower limit is usually at least 0.300, preferably at least 0.5%.
Further, the cable comprising a layer such as a jacketing layer, which comprises the mixed-plastic-polyethylene composition as described above, preferably has the following tensile properties:
The cable comprising a layer such as a jacketing layer, which comprises the mixed-plastic-polyethylene composition comprising, more preferably consisting of the mixed-plastic-polyethylene primary recycling blend (A) and the secondary blend (B) of virgin high-density polyethylene (HDPE), but does not comprise, i.e. is free of the tertiary secondary blend (C) of virgin high-density polyethylene (HDPE) as described above, preferably has the following tensile properties:
The cable comprising a layer such as a jacketing layer, which comprises the mixed-plastic-polyethylene composition comprising, more preferably consisting of the mixed-plastic-polyethylene primary recycling blend (A), the secondary blend (B) of virgin high-density polyethylene (HDPE) and the tertiary secondary blend (C) of virgin high-density polyethylene (HDPE) as described above, preferably has the following tensile properties:
All preferred aspects and embodiments as described above shall also hold for the article.
Process
The present invention also relates to a process for preparing the mixed-plastic-polyethylene composition as defined above or below. The process according to the present invention results in an improvement in the mechanical properties of the mixed-plastic-polyethylene primary recycling blend (A).
The process according to the present invention comprises the steps of:
In one embodiment the process of the invention as described above comprises the steps of:
All preferred aspects, definitions and embodiments as described above shall also hold for the process.
Use
The present invention relates to the use of a mixed-plastic-polyethylene composition as defined above or below for producing a cable layer, preferably a cable jacketing layer, having an ESCR (Bell test failure time) of more than 1000 hours, preferably more than 1250 hours and still more preferably more than 1500 hours and most preferably more than 1800 hours. In some embodiments the cable layer, preferably the cable jacketing layer, can have an ESCR (Bell test failure time) of more than 2000 hours or even more than 5000 hours. The upper limit of the ESCR can be as high as 15000 hours, usually up to 10000 hours.
It is preferred that the cable layer, preferably the cable jacketing layer, has a strain hardening modulus (SH modulus) of from 15.0 to 30.0 MPa, more preferably from 16.0 to 26.0 MPa and most preferably from 17.0 to 25.0 MPa.
All preferred aspects, definitions and embodiments as described above shall also hold for the use.
1. Test Methods
a) Melt Flow Rate
Melt flow rates were measured with a load of 2.16 kg (MFR2), 5.0 kg (MFR5) or 21.6 kg (MFR21) at 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 or 190° C. under a load of 2.16 kg, 5.0 kg or 21.6 kg.
b) Density
Density is measured according to ISO 1183-187. Sample preparation is done by compression moulding in accordance with ISO 17855-2.
c) Comonomer Content
Quantification of C2, iPP (Continuous C3), LDPE and Polyethylene Short Chain Branches in Polyethylene Based Recylates
Quantitative 13C{1H} NMR spectra were recorded in the solution-state using a Bruker AvanceIII 400 MHz 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 {singh09}. 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 {zhou07,busico07}. A total of 6144 (6 k) transients were acquired per spectra.
Quantitative 13C{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. Characteristic signals corresponding to polyethylene with different short chain branches (B1, B2, B4, B5, B6plus) and polypropylene were observed {randall89, brandolini00}.
Characteristic signals corresponding to the presence of polyethylene containing isolated B1 branches (starB1 33.3 ppm), isolated B2 branches (starB2 39.8 ppm), isolated B4 branches (twoB4 23.4 ppm), isolated B5 branches (threeB5 32.8 ppm), all branches longer than 4 carbons (starB4plus 38.3 ppm) and the third carbon from a saturated aliphatic chain end (3 s 32.2 ppm) were observed. The intensity of the combined ethylene backbone methine carbons (ddg) containing the polyethylene backbone carbons (dd 30.0 ppm), γ-carbons (g 29.6 ppm) the 4 s and the threeB4 carbon (to be compensated for later on) is taken between 30.9 ppm and 29.3 ppm excluding the Too from polypropylene. The amount of C2 related carbons was quantified using all mentioned signals according to the following equation:
fC
C2total=(Iddg −ItwoB4)+(IstarB1*6)+(IstarB2*7)+(ItwoB4*9)+I(threeB5*10)+((IstarB4plus−ItwoB4−IthreeB5)*7)+(I3s*3)
Characteristic signals corresponding to the presence of polypropylene (iPP, continuous C3)) were observed at 46.7 ppm, 29.0 ppm and 22.0 ppm. The amount of PP related carbons was quantified using the integral of Sαα at 46.6 ppm:
fC
PP
=Isαα*3
The weight percent of the C2 fraction and the polypropylene can be quantified according following equations:
wtC2fraction=fCC2total*100/(fCC2total+fCPP)
wtPP=fCPP*100/(fCC2total+fCPP)
Characteristic signals corresponding to various short chain branches were observed and their weight percentages quantified as the related branch would be an alpha-olefin, starting by quantifying the weight fraction of each:
fwtC2=fCC2total−((IstarB1*3)−(IstarB2*4)−(ItwoB4*6)−(IthreeB5*7)
fwtC3(isolated C3)=IstarB1*3
fwtC4=IstarB2*4
fwtC6=ItwoB4*6
fwtC7=IthreeB5*7
Normalisation of all weight fractions leads to the amount of weight percent for all related branches:
fsumwt % total=fwtC2+fwtC3+fwtC4+fwtC6+fwtC7+fCPP
wtC2total=fwtC2*100/fsumwt % total
wtC3total=fwtC3*100/fsumwt % total
wtC4total=fwtC4*100/fsumwt % total
wtC6total=fwtC6*100/fsumwt % total
wtC7total=fwtC7*100/fsumwt % total
The content of LDPE can be estimated assuming the B5 branch, which only arises from ethylene being polymerised under high pressure process, being almost constant in LDPE. We found the average amount of B5 if quantified as C7 at 1.46 wt %. With this assumption it is possible to estimate the LDPE content within certain ranges (approximately between 20 wt % and 80 wt %), which are depending on the SNR ratio of the three B5 signal:
wt % LDPE=wtC7total*100/1.46
d) Impact Strength
The impact strength is determined as Charpy Notched Impact Strength according to ISO 179-1 eA at +23° C. and at 0° C. on compression moulded specimens of 80×10×4 mm prepared according to ISO 17855-2.
e) Tensile Testing of 5A Specimen and that after Ageing of 5A Specimen at 110° C., 14 Days (336 h)
For tensile testing, dog bone specimens of 5A are prepared according to ISO 527-2/5A by die cutting from compression moulded plaques of 2 mm′ thickness. If ageing is needed, the 5A specimens are kept at 110° C. in a cell oven for 14 days (336 hours). All specimens are conditioned for at least 16 hours at 23° C. and 50% relative humidity before testing. Tensile properties are measured according to ISO 527-1/2 at 23° C. and 50% relative humidity with Alwetron R24, 1 kN load cell. Tensile testing speed is 50 mm/min, grip distance is 50 mm and gauge length is 20 mm.
f) Rheological Measurements
Dynamic Shear Measurements (Frequency Sweep Measurements)
The characterisation of melt of polymer composition or polymer as given above or below in the context 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 190° C. applying a frequency range between 0.01 and 600 rad/s and setting a gap of 1.3 mm.
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
γ(t)=γ0 sin(ωt) (1)
If the applied strain is within the linear viscoelastic regime, the resulting sinusoidal stress response can be given by
σ(t)=σ0 sin(ωt+δ) (2)
where
σ0 and γ0 are the stress and strain amplitudes, respectively
ω is the angular frequency
δ is the phase shift (loss angle between applied strain and stress response)
t is the time
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, η*, the dynamic shear viscosity, η′, the out-of-phase component of the complex shear viscosity η″ and the loss tangent, tan δ which can be expressed as follows:
The determination of so-called Shear Thinning Index, which correlates with MWD and is independent of Mw, is done as described in equation 9.
For example, the SHI(2.7/210) is defined by the value of the complex viscosity, in Pa s, determined for a value of G* equal to 2.7 kPa, divided by the value of the complex viscosity, in Pa s, determined for a value of G* equal to 210 kPa.
The values of storage modulus (G′), loss modulus (G″), complex modulus (G*) and complex viscosity (η*) were obtained as a function of frequency (ω).
Thereby, e.g. η*300 rad/s (eta*300 rad/s) is used as abbreviation for the complex viscosity at the frequency of 300 rad/s and η*0.05 rad/s (eta*0.05 rad/s) is used as abbreviation for the complex viscosity at the frequency of 0.05 rad/s.
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. tan0.05 is used as abbreviation for the ratio of the loss modulus (G″) and the storage modulus (G′) at 0.05 rad/s and tan300 is used as abbreviation for the ratio of the loss modulus (G″) and the storage modulus (G′) at 300 rad/s.
The elasticity balance tan0.05/tan300 is defined as the ratio of the loss tangent tan0.05 and the loss tangent tan300.
Besides the above mentioned rheological functions one can also determine other rheological parameters such as the so-called elasticity index EI(x). The elasticity index EI(x) is the value of the storage modulus (G′) determined for a value of the loss modulus (G″) of x kPa and can be described by equation 10.
EI(x)=G′ for (G″=x kPa)[Pa] (10)
For example, the EI(5 kPa) is the defined by the value of the storage modulus (G′), determined for a value of G″ equal to 5 kPa.
The polydispersity index, PI, is defined by equation 11.
where ω>COP is the cross-over angular frequency, determined as the angular frequency for which the storage modulus, G′, equals the loss modulus, G″.
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.
g) Large Amplitude Oscillatory Shear (LAOS)
The investigation of the non-linear viscoelastic behaviour under shear flow was done resorting to Large Amplitude Oscillatory Shear. The method requires the application of a sinusoidal strain amplitude, γ0, imposed at a given angular frequency, ω, for a given time, t. Provided that the applied sinusoidal strain is high enough, a non-linear response is generated. The stress, σ, is in this case a function of the applied strain amplitude, time and the angular frequency. Under these conditions, the non-linear stress response is still a periodic function; however, it can no longer be expressed by a single harmonic sinusoid. The stress resulting from linear viscoelastic response [1-3] can be expressed by a Fourier series, which includes higher harmonics contributions:
σ(t,ω,γ0)=γ0·Σn[G′n(ω,γ0)·sin(nωt)+G″n(ω,γ0)·cos(nωt)]
with σ=stress response
The non-linear viscoelastic response was analysed applying Large Amplitude Oscillatory Shear (LAOS). Time sweep measurements were undertaken on an RPA 2000 rheometer from Alpha Technologies coupled with a standard biconical die. During the course of the measurement the test chamber is sealed and a pressure of about 6 MPa is applied. The LAOS test is done applying a temperature of 190° C., an angular frequency of 0.628 rad/s and a strain of 1000% (LAOSNLF (1000%)). In order to ensure that steady state conditions are reached, the non-linear response is only determined after at least 20 cycles per measurement are completed. The Large Amplitude Oscillatory Shear Non-Linear Factor (LAOSNLF) is defined by:
with G′1=first order elastic Fourier coefficient
h) ESCR (Bell Test, h)
By the term ESCR (environmental stress cracking resistance) is meant the resistance of the polymer to crack formation under the action of mechanical stress and a reagent in the form of a surfactant. The ESCR is determined in accordance with IEC 60811-406, method B. The reagent employed is 10 weight % Igepal CO 630 in water. The materials were prepared according to instructions for HDPE as follows: The materials were pressed at 165° C. to a thickness of 1.75-2.00 mm. The notch was 0.30-0.40 mm deep.
i) Shore D Hardness
Two different Shore D hardness measurements were conducted:
Firstly, Shore D hardness is determined according to ISO 868 on moulded specimen with a thickness of 4 mm. The shore hardness is determined after 1 sec, 3 sec or 15 sec after the pressure foot is in firm contact with the test specimen. The sample is compression moulded according to ISO 17855-2 and milled into specimens of 80×10×4 mm.
Secondly, Shore D hardness is determined according to ASTM D2240-03. The same samples as for the Shore D hardness according to ISO 868 were used.
j) Strain Hardening (SH) Modulus
The strain hardening test is a modified tensile test performed at 80° C. on a specially prepared thin sample. The Strain Hardening Modulus (MPa), <Gp>, is calculated from True Strain-True Stress curves; by using the slope of the curve in the region of True Strain, λ, is between 8 and 12.
The true strain, λ, is calculated from the length, l (mm), and the gauge length, l0 (mm), as shown by Equation 1.
where Δl is the increase in the specimen length between the gauge marks, (mm). The true stress, σtrue (MPa), is calculated according to formula 2, assuming conservation of volume between the gauge marks:
σtrue=σnλ (2)
where σn is the engineering stress.
The Neo-Hookean constitutive model (Equation 3) is used to fit the true strain-true stress data from which <Gp> (MPa) for 8<λ<12 is calculated.
where C is a mathematical parameter of the constitutive model describing the yield stress extrapolated to λ=0.
Initially five specimens are measured. If the variation coefficient of <Gp> is greater than 2.5%, then two extra specimens are measured. In case straining of the test bar takes place in the clamps the test result is discarded.
The PE granules of materials were compression molded in sheets of 0.30 mm thickness according to the press parameters as provided in ISO 17855-2.
After compression molding of the sheets, the sheets were annealed to remove any orientation or thermal history and maintain isotropic sheets. Annealing of the sheets was performed for 1 h in an oven at a temperature of (120±2) ° C. followed by slowly cooling down to room temperature by switching off the temperature chamber. During this operation free movement of the sheets was allowed.
Next, the test pieces were punched from the pressed sheets. The specimen geometry of the modified ISO 37:1994 Type 3 (FIG. 3) was used.
The sample has a large clamping area to prevent grip slip, dimensions given in Table 1.
The punching procedure is carried out in such a way that no deformation, crazes or other irregularities are present in the test pieces.
The thickness of the samples was measured at three points of the parallel area of the specimen; the lowest measured value of the thickness of these measurements was used for data treatment.
k) Water Content
The water content was determined as described in ISO15512:2019 Method A—Extraction with anhydrous methanol. There the test portion is extracted with anhydrous methanol and the extracted water is determined by a coulometric Karl Fischer Titrator.
l) Cable Extrusion
The cable extrusion is done on a Nokia-Maillefer cable line. The extruder has five temperature zones with temperatures of 170/175/180/190/190° C. and the extruder head has three zones with temperatures of 210/210/210° C. The extruder screw is a barrier screw of the design Elise. The die is a semi-tube on type with 5.9 mm diameter and the outer diameter of the cable is 5 mm. The compound is extruded on a 3 mm in diameter, solid aluminum conductor to investigate the extrusion properties. Line speed is 75 m/min. The pressure at the screen and the current consumption of the extruder is recorded for each material.
m) Pressure Deformation
Pressure test is conducted according to EN 60811-508. An extruded cable sample is placed in an air oven at a 115° C. and subjected to a constant load applied by means of a special indentation device (with a rectangular indentation 0.7 mm wide knife) for 6 hours. The percentage of indentation is measured afterwards using a digital gauge.
n) Tensile Testing of Cable
Tensile testing of cable is conducted according to EN60811-501. At least 24 hours later after cable extrusion, the conductor is removed and the cable is cut into specimens of 15 cm's long. The specimens are conditioned for at least 16 hours at 23° C. and 50% relative humidity before testing.
Tensile properties are measured at 23° C. and 50% relative humidity with Zwick Z005, 500N load cell. Tensile testing speed is 25 mm/min, grip distance is 50 mm and gauge length is 20 mm.
o) Cable Shrinkage
The shrinkage of the composition is determined with the cable samples obtained from the cable extrusion. The cables are conditioned in the constant room at least 24 hours before the cutting of the samples. The conditions in the constant room are 23±2° C. and 50±5% humidity. Samples are cut to 400 mm at least 2 m away from the cable ends. They are further conditioned in the constant room for 24 hours after which they are place in an oven on a talcum bed at 100° C. for 24 hours. After removal of the sample from the oven they are allowed to cool down to room temperature and then measured. The shrinkage is calculated according to formula below:
[(LBefore−LAfter)/LBefore]×100%, wherein L is length.
p) Tear Resistance
Tear resistance is measured on compression moulded plaques of 1 mm thickness according to BS 6469 section 99.1. A test piece with a cut is used to measure the tear force by means of a tensile testing machine. The tear resistance is calculated by dividing the maximum force needed to tear the specimen by its thickness.
q) Ash Content
Thermogravimetric Analysis (TGA) experiments were performed with a Perkin Elmer TGA 8000. Approximately 10-20 mg of materials were placed in a platinum pan. The temperature was equilibrated at 50° C. for 10 minutes, and afterwards raised to 950° C. under nitrogen at 20° C./min. The ash content was evaluated as the weight % at 850° C.
r) Amount of Limonene
This method allows nature of a raw mixed-plastic-polyethylene primary recycling blend to be determined.
Limonene quantification was carried out using solid phase microextraction (HS-SPME-GC-MS) by standard addition.
20 mg cryomilled 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. Limonene was added to the samples to obtain concentration levels of 1 mg/kg, 2 mg/kg, 3 mg/kg and 4 mg/kg limonene. 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:
Column: 30 m HP 5 MS 0.25*0.25
Injector: Splitless with 0.75 mm SPME Liner, 270° C.
Temperature program: −10° C. (1 min)
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
s) Gel Content
The gel count was measured with a gel counting apparatus consisting of a measuring extruder, ME 25/5200 V1, 25*25 D, with five temperature conditioning zones adjusted to a temperature profile of 170/180/190/190/190° C.), an adapter and a slit die (with an opening of 0.5*150 mm). Attached to this were a chill roll unit (with a diameter of 13 cm with a temperature set of 50° C.), a line camera (CCD 4096 pixel for dynamic digital processing of grey tone images) and a winding unit.
For the gel count content measurements the materials were extruded at a screw speed of 30 rounds per minute, a drawing speed of 3-3.5 m/min and a chill roll temperature of 50° C. to make thin cast films with a thickness of 70 μm and a width of approximately 110 mm.
The resolution of the camera is 25 μm×25 μm on the film.
The camera works in transmission mode with a constant grey value (auto. set. margin level=170). The system is able to decide between 256 grey values from black=0 to white=256.
For detecting gels, a sensitivity level dark of 25% is used.
For each material the average number of gel dots on a film surface area of 10 m2 was inspected by the line camera. The line camera was set to differentiate the gel dot size according to the following:
Gel size (the size of the longest dimension of a gel)
600 μm to 999 μm
above 1000 μm
2. Materials
HE6063 is a natural bimodal high density polyethylene jacketing compound for energy and communication cables (available from Borealis AG).
HE3493-LS-H is a natural bimodal high density polyethylene compound for pipes (available from Borealis AG).
Additive package: The additive package consists of 27.3 wt % of pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)-propionate (CAS No. 6683-19-8), 9.1 wt % of tris (2,4-di-t-butylphenyl) phosphite (CAS No. 31570-04-4), 9.1 wt % of calcium stearate (CAS No. 1592-23-0) and 54.5 wt % of poly((6-((1,1,3,3-tetramethylbutyl)amino)-1,3,5-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4-piperidyl)imino)-1,6-hexanediyl ((2,2,6,6-tetramethyl-4-piperidyl)imino)) (CAS No. 71878-19-8).
NAV 102 is a mixed-plastic-low density polyethylene (LDPE) primary recycling blend available from Ecoplast Kunststoffrecycling GmbH. Samples of NAV 102 (NAV 102-1 with the Lot No 190206-I, NAV-102-2 with the Lot No 190611-II and NAV 102-5 with the Lot No 200312-I) differing as to melt flow rate and also rheology were tested, the properties of these samples are shown in table A.
In the following examples also two additional samples of NAV-102 (NAV 102-3 with the Lot No 190612-I and NAV 102-4 with the Lot No 190611-I) were used. The properties of these samples were not measured but should be similar to those of NAV 102-1, NAV 102-2 and NAV 102-5.
3. Experiments
CE1 (comparative example 1) are 100% reactor-made 1TE6063 pellets.
CE2 (comparative example 2) is 100% compounded 1TE6063 (blank extrusion of CE1).
In inventive example 1 (IE1), 25 wt % HE6063 was melt mixed with 75 wt % NAV 102-2.
In inventive example 2 (IE2) 50 wt % HE6063 was melt mixed with 50 wt % NAV 102-2.
In inventive example 3 (IE3) 60 wt % HE6063 was melt mixed with 40 wt % NAV 102-2.
In inventive example 4 (IE4) 75 wt % HE6063 was melt mixed with 25 wt % NAV 102-2.
In inventive example 5 (IE5), 25 wt % HE6063 was melt mixed with 75 wt % NAV 102-3.
In inventive example 6 (IE6) 50 wt % HE6063 was melt mixed with 50 wt % NAV 102-3.
In inventive example 7 (IE7) 75 wt % HE6063 was melt mixed with 25 wt % NAV 102-3.
In inventive example 8 (IE8) 50 wt % HE6063 was melt mixed with 50 wt % NAV 102-4.
In inventive example 9 (IE9) 50 wt % HE6063 was melt mixed with 50 wt % NAV 102-1.
In inventive example 10 (IE10) 75 wt % HE6063 was melt mixed with 25 wt % NAV 102-1.
In inventive example 11 (IE11) 49.7 wt % HE6063 was melt mixed with 50 wt % NAV 102-5 and 0.3 wt % additive package.
In inventive example 12 (IE12) 49.7 wt % HE6063 was melt mixed with 50 wt % NAV 102-5 and 0.3 wt % additive package.
In inventive example 13 (IE13) 50 wt % HE6063 was melt mixed with 40 wt % NAV 102-1 and 10 wt % HE3493-LS-H.
In inventive example 14 (IE14) 50 wt % HE6063 was melt mixed with 40 wt % NAV 102-2 and 10 wt % HE3493-LS-H.
In inventive example 15 (IE15) 40 wt % HE6063 was melt mixed with 50 wt % NAV 102-2 and 10 wt % HE3493-LS-H.
In inventive example 16 (IE16) 40 wt % HE6063 was melt mixed with 50 wt % NAV 102-3 and 10 wt % HE3493-LS-H.
In inventive example 17 (IE17) 40 wt % HE6063 was melt mixed with 50 wt % NAV 102-4 and 10 wt % HE3493-LS-H.
In inventive example 18 (IE18) 39.7 wt % HE6063 was melt mixed with 50 wt % NAV 102-5, 10 wt % HE3493-LS-H and 0.3 wt % additive package.
In inventive example 19 (IE19) 39.7 wt % HE6063 was melt mixed with 50 wt % NAV 102-5, 10 wt % HE3493-LS-H and 0.3 wt % additive package.
The compositions of examples CE1, CE2, IE1-IE10 and IE13-IE17 were prepared via melt blending on a co-rotating twin screw extruder (Coperion ZSK32 Megacompounder, L/D=48) at 150° C. in the first barrel after the feeding zone and 220-230° C. in all the following barrels, a screw speed of 120 rpm and a throughput rate of about 15-25 kg/h. The compositions of examples IE11, IE12, IE18 and IE19 were prepared via melt blending on a Berstoff ZE110 extruder at 200° C. in the first two barrels after the feeding zone and 230° C. in all the following barrels, a screw speed of 420 rpm for IE11, 280-300 rpm for IE12, IE18 and IE19 and a throughput rate of about 1.8 to 2.0 ton/h. The polymer melt mixtures were discharged and pelletized. Mechanical properties were tested as described above. Thereby, the final MFR of the compounds is influenced by the compounding condition, e.g, the screw speed.
The properties of the compositions and cables made from these compositions are shown below in Table B for the compositions of examples CE1-CE2, IE1-IE4 and IE8, in Table C for the compositions of examples CE1-CE2 and IE5, IE6, IE7, IE9, IE10, IE11 and IE12 and in Table D for the compositions of examples CE1-CE2 and IE13, IE14, IE15, IE16, IE17, IE18 and IE19.
For examples IE3, IE4, IE10, IE11, IE12, IE18 and IE19 the values for the LDPE content have been calculated according to the content of NAV 102 and the LDPE content of the used batch of NAV 102. For all other examples, where listed, the values for the LDPE content has been measured as described in the test method section.
The examples according to the invention show an improved balance of properties especially in regard of ESCR, SH index and Shore D hardness while maintaining good tensile properties and impact properties. Additionally, the example according to the invention show a surprisingly low gel content due to the use of NAV 102 recycling blends, which themselves have a low gel content indicating a high purity. It is believed that especially the surprisingly high ESCR values result from said high purity indicated in the low gel contents. The > in the ESCR data means that the measurement is still running.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19218162.6 | Dec 2019 | EP | regional |
| 19218176.6 | Dec 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/085509 | 12/10/2020 | WO |
