FIELD OF INVENTION

The present invention relates to a method for the treatment of polyolefin compositions. More in particular the methods described herein may be used to increase the melt flow index of a polyolefin composition and/or to at least partially remove an odour from a polyolefin composition.

BACKGROUND OF THE INVENTION

Sometimes there is the need to treat or to modify some properties of an existing polyolefin composition and this preferably without having to blend in other polyolefin and/or additives. Properties that might need to be modified are, for example, the melt flow index, the odour, level of impurities to name a few. Especially methods for increasing the melt flow index of an existing polymer composition are of interest, as it would allow making a certain polyolefin composition with a high melt flow index more suitable to be used in injection moulding.

Typically, polypropylene compositions with a MFI below 20 g/10 min are generally considered to be difficult to be used in injection moulding. There is a demand for methods to treat these polypropylene compositions to significantly increase the melt flow index (e.g. MFI), preferably to an MFI of at least 30 g/10 min, preferably at least 40 g/10 min.

Typically, polyethylene compositions with a MI2 below 1.0 g/10 min are generally considered to be difficult to be used in injection moulding. There is a demand for methods to treat these polypropylene compositions to significantly increase the melt flow index (e.g. MI2), preferably to an MI2 of at least 3.0 g/10 min, preferably at least 4.0 g/10 min.

Typically PCR (post-consumer recycled) polyolefins compositions have low melt index values, typically close to MI2 of 0.2 g/10 min for PCR polyethylene and close to MFI of 10 g/10 min for PCR polypropylene, which makes them rather unsuitable for injection moulding and hence, limits the applications of recycled polyolefins. A method that could increase the melt flow index of recycled polyolefins would create a significant added value to the recycled polyethylene composition as it expands the application field of such polyolefin compositions. Such methods may also contribute to the plastic waste problem, as more plastics can be turned into a useful polyolefin composition after recycling. The method may also be used to implement the “Cradle- to-Cradle ” philosophy in the field of polyolefins.

Another aspect of interest in the field of recycled polyolefins might be the odour of recycled polyolefins. There is a demand for methods of treatment of polyolefins that at least partially remove the odour of recycled polyolefin compositions. Preferably, the method of treatment of a polyolefin composition does not cause decolouration of the polyolefin composition. Preferably, the method of treatment of a polyolefin composition does not cause yellowing of the polyolefin composition.

Preferably, said method of treatment of a polyolefin composition can be carried out by performing a single extrusion of said polyolefin composition.

An increase of the melt index of PCR polyethylene (typically from 0.2 g/10 min. to 4 g/10 min.) is not evident at all as, during a standard extrusion process, the melt index generally decreases. The situation is slightly different in polypropylene as methods for increasing the melt flow index of polypropylene exist. However these methods involve blending peroxides into the polypropylene and extruding said blend. However, such methods result in polypropylene with peroxide contaminants and residues, whereas there is a rising demand for “clean” polyolefins. If high peroxide content must be avoided, e.g. to avoid too much peroxide residuals, the melt index increase of polypropylene in a standard extrusion process is limited. Similar or if polyethylene is present as in a polypropylene composition, which may be very frequent in PCR polypropylene, then such polyethylene will contribute to a melt index decrease during a standard pelletization, hence, the melt index increase of said polypropylene in a standard extrusion process is limited. Hence, there is a demand for alternative -clean- methods and/or methods providing a higher increase in melt flow index.

Preferably, the method of treatment of a polyolefin composition should have a low safety risk, especially in terms of fire risk. Preferably, the increase in melt flow index does not negatively impact the mechanical properties.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method for treating polyolefin compositions. It has now surprisingly been found that the above objectives can be attained either individually or in any combination by a process as disclosed herein.

In a first aspect, the present invention relates to the use of ultrasound to improve the melt index of a polyolefin composition. More specifically, the invention provides a method for treating a polyolefin composition, the polyolefin composition comprising polyethylene (PE) and/or polypropylene (PP). The method comprises the steps of: a) melting said polyolefin composition, thereby creating a molten polyolefin flow at an initial temperature (T) and a flow rate (Q); and, b) applying ultrasound (US) at a power (Pus) to said molten polyolefin flow.

Most preferably, in step b) inequality (I) is fulfilled: 1.3 3.6 * c _rr — 4.0 * c _RE > 0 (I).

Herein:

P _us is the power of the applied ultrasound expressed in Watt;

Q is the flow rate of the molten polyolefin flow, expressed in kg/h;

T is the initial temperature of the molten polyolefin, expressed in °C prior to the applied ultrasound;

XPP is the weight fraction of polypropylene (PP) expressed in wt% in the polyolefin composition, based on the total combined weight of PP and PE present in the polyolefin composition; and,

XPE is the weight fraction of polyethylene (PE) expressed in wt% in the polyolefin composition, based on the total combined weight of PP and PE present in the polyolefin composition.

In some preferred embodiments, the polyolefin composition comprises a physical blend mixture of polyethylene and polypropylene, whereby inequality (II) is fulfilled: 3.6 * c _rr — 4.0 * c _RE > b (II) wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80.

In some preferred embodiments, the polyolefin is polyethylene (XPE = 100 wt%), whereby inequality (III) is fulfilled: 1.3 400 + b (III) wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80.

In some preferred embodiments, the polyolefin is polypropylene (crr = 100 wt%), whereby inequality (IV) is fulfilled: l- ³ * ¾ ^{£ +} 7 ^’ > 360 + jff (IV) wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80.

In some preferred embodiments, wherein T is at least 220°C, preferably at least 270°C. In some preferred embodiments, the ultrasound power normalized by the polymer quantity (i.e. , the introduced ultrasound power divided by the polymer throughput) is applied to the polyolefin composition in amount of at least 300.0 kJ/kg, preferably of at least 500.0 kJ/kg.

In some preferred embodiments, the polyolefin composition comprises at least 50.0% by weight, preferably at least 80.0% by weight polyolefin, compared to the total weight of the polyolefin composition. For example, the polyolefin composition may comprise additives or contaminants, which result in a polyolefin composition comprising less than 100% polyolefin.

In some preferred embodiments, the polyolefin composition comprises at least 50.0% by weight, preferably at least 80.0% by weight polyethylene, compared to the total weight of the polyolefin composition.

In some preferred embodiments, the polyolefin composition comprises at least 40.0% by weight, preferably at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least 80.0% by weight polyethylene, compared to the total weight of the polyolefin composition.

In some preferred embodiments, the polyolefin composition comprises at least 40.0% by weight, preferably at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least 80.0% by weight polypropylene, compared to the total weight of the polyolefin composition.

In some preferred embodiments, the polyolefin composition comprises at least 40.0% by weight, preferably at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least 80.0% by weight, preferably at least 90.0% by weight, preferably at least 95.0% by weight, preferably at least 99.0% by weight polyethylene and polypropylene combined, compared to the total weight of the polyolefin composition.

In some preferred embodiments, XPE > 50 wt% and the initial melt flow index is an HLMI of at least 0.01 g/10 min.

In some preferred embodiments, XPE > 50 wt% and/or XPP > 40 wt%; preferably XPE > 50 wt% or XPP > 50 wt%.

In some preferred embodiments, the method steps a) and b) are continuous.

In some preferred embodiments, the polyolefin composition is a recycled polyolefin composition.

In some preferred embodiments, the ultrasound in step b) is applied inside an extruder. In some preferred embodiments, wherein the ultrasound in step b) is applied in the metering zone, core, die, or nozzle, of an extruder, preferably in the die or core.

In some preferred embodiments, treating a polyolefin composition involves increasing the melt flow index of said polyolefin composition, preferably at least by a factor k of 2, preferably at least by a factor k of 5, preferably at least by a factor k of 7. The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

In Figure 1 , the obtained k values (melt flow ratio) of the experiments of Table 1 , i.e. polyethylene compositions, are plotted in function of their Q.

In Figure 2, the obtained k values (melt flow ratio) of the experiments of Table 1, 2 and 3, i.e. polyethylene compositions, polypropylene compositions, and mixed polyethylene/polypropylene compositions, are plotted in function of their Q.

Figure 3 depicts the mount of the ultrasonic sonotrode over the die of the extruder as used in the examples.

Figure 4 shows the absence of a colour change when performing the inventive method.

DETAILED DESCRIPTION OF THE INVENTION

Before the present method used in the invention is described, it is to be understood that this invention is not limited to particular methods described, as such methods may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

When describing the methods of the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a composition" means one composition or more than one composition.

The terms "comprising", "comprises" and "comprised of as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising", "comprises" and "comprised of" also include the term “consisting of”. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims and statements, any of the embodiments can be used in any combination.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention.

Preferred statements (features) and embodiments of the methods of this invention are set herein below. Each statement and embodiment of the invention so defined may be combined with any other statement and/or embodiments unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features or statements indicated as being preferred or advantageous. Hereto, the present invention is in particular captured by any one or any combination of one or more of the below numbered statements 1 to 46 and/or embodiments with any other statement(s) and/or embodiment(s).

1. A method for treating a polyolefin composition, the polyolefin composition comprising polyethylene (PE) and/or polypropylene (PP), the method comprising the steps of: a) melting said polyolefin composition, thereby creating a molten polyolefin flow at an initial temperature (T) and a flow rate (Q); and, b) applying ultrasound (US) at a power (Pus) to said molten polyolefin flow; whereby in step b) inequality (I) is fulfilled:

1.3 * ^ + T - 3.6 * c _Rr - 4.0 * c _R£ > 0 (I) wherein,

P _us is the power of the applied ultrasound expressed in Watt;

Q is the flow rate of the molten polyolefin flow, expressed in kg/h;

T is the initial temperature of the molten polyolefin, expressed in °C prior to the applied ultrasound;

XPP is the weight fraction of polypropylene (PP) expressed in wt% in the polyolefin composition, based on the total combined weight of PP and PE present in the polyolefin composition; and,

XPE is the weight fraction of polyethylene (PE) expressed in wt% in the polyolefin composition, based on the total combined weight of PP and PE present in the polyolefin composition. The method according to statement 1, wherein treating a polyolefin composition involves increasing the melt flow index of said polyolefin composition, preferably at least by a factor k of 2, preferably at least by a factor k of 3, preferably at least by a factor k of 4, preferably at least by a factor k of 5, preferably at least by a factor k of 6, preferably at least by a factor k of 7, preferably at least by a factor k of 8. The method according to statement 1 or statement 2, wherein the polyolefin composition is a recycled polyolefin composition. The method according to any one of statements 1 to 3, whereby in step b) inequality (II) is fulfilled: 3.6 * c _rr — 4.0 * c _RE > b (II) wherein b is 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80. The method according to any one of statements 1 to 4, wherein the polyolefin is polyethylene, whereby in step b) inequality (III) is fulfilled:

1.3 400 + 0 (HI) wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80. The method according to any one of statements 1 to 5, wherein the polyolefin is polypropylene, whereby in step b) inequality (IV) is fulfilled:

1.3 360 + 0 (IV) wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80. 7. The method according to any one of statements 1 to 6, wherein the polyolefin composition comprises a physical blend mixture of polyethylene and polypropylene, whereby in step b) inequality (II) is fulfilled: 3.6 * c _rr — 4.0 * c _RE > b (II) wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80.

8. The method according to any one of statements 1 to 7, wherein the polyolefin composition comprises at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least 80.0% by weight, preferably at least 90.0% by weight, preferably at least 95.0% by weight, for example at least 98.0% by weight, for example at least 99.0% by weight, of polyolefin (polyethylene and polypropylene), compared to the total weight of the polyolefin composition.

9. The method according to any one of statements 1 to 8, wherein X _PE is at least 10.0% by weight, preferably at least 20.0% by weight, preferably at least 30.0% by weight, preferably at least 40.0% by weight, preferably at least 50.0% by weight, preferably at least 60.0% by weight, polyethylene, compared to the combined weight of polyethylene and polypropylene in the polyolefin composition.

10. The method according to any one of statements 1 to 9, wherein X _PE is at most 95.0% by weight, preferably at most 90.0% by weight, preferably at most 80.0% by weight, preferably at most 75.0% by weight, preferably at most 70.0% by weight, preferably at most 65.0% by weight, polyethylene, compared to the combined weight of polyethylene and polypropylene in the polyolefin composition.

11. The method according to any one of statements 1 to 10, wherein X _PE is at least 10.0% by weight to at most 95.0% by weight, preferably at least 20.0% by weight to at most 90.0% by weight, preferably at least 30.0% by weight to at most 80.0% by weight, preferably at least 40.0% by weight to at most 75.0% by weight, preferably at least 50.0% by weight to at most 70.0% by weight, preferably at least 60.0% by weight to at most 65.0% by weight, polyethylene, compared to the combined weight of polyethylene and polypropylene in the polyolefin composition.

12. The method according to any one of statements 1 to 11, wherein the polyolefin composition comprises at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least 80.0% by weight, preferably at least 90.0% by weight, preferably at least 95.0% by weight, for example at least 98.0% by weight, for example at least 99.0% by weight, polyethylene, compared to the total weight of the polyolefin composition. 13. The method according to any one of statements 1 to 12, wherein the polyolefin composition comprises at least 40.0% by weight, preferably at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least 80.0% by weight, preferably at least 90.0% by weight, preferably at least 95.0% by weight, for example at least 98.0% by weight, for example at least 99.0% by weight, polypropylene, compared to the total weight of the polyolefin composition.

14. The method according to any one of statements 1 to 13, wherein T is at least 200°C, preferably at least 220°C, preferably at least 240°C, preferably at least 250°C, preferably at least 260°C, preferably at least 270°C.

15. The method according to any one of statements 1 to 14, wherein T is at most 340°C, preferably at most 330°C, preferably at most 320°C, preferably at most 310°C, preferably at most 300°C, preferably at most 290°C, preferably at most 280°C.

16. The method according to any one of statements 1 to 15, wherein T is at least 200°C to at most 340°C, preferably at least 220°C to at most 330°C, preferably at least 240°C to at most 320°C, preferably at least 250°C to at most 310°C, preferably at least 260°C to at most 300°C, preferably at least 265°C to at most 290°C, preferably at least 270°C to at most 280°C.

17. The method according to any one of statements 1 to 16, wherein the initial melt flow index is an HLMI when XPE > 50 wt% of at least 0.01 g/10 min, preferably at least 0.05 g/10 min, preferably at least 0.10 g/10 min, preferably at least 0.50 g/10 min, preferably at least 1.00 g/10 min; determined according to ISO 1133:1997, procedure A, conditions G (190°C, 21.6kg).

18. The method according to any one of statements 1 to 17, wherein the initial melt flow index is an HLMI when XPE > 50 wt% of at most 1000.0 g/10 min, preferably at most 500.0 g/10 min, preferably at most 100.0 g/10 min, preferably at most 75.0 g/10 min, preferably at most 50.0 g/10 min, preferably at most 25.0 g/10 min, determined according to ISO 1133:1997, procedure A, conditions G (190°C, 21.6kg).

19. The method according to any one of statements 1 to 18, wherein the initial melt flow index is an HLMI when XPE > 50 wt% of at least 0.01 g/10 min to at most 500.0 g/10 min, preferably at least 0.05 g/10 min at most 100.0 g/10 min, preferably at least 0.10 g/10 min at most 75.0 g/10 min, preferably at least 0.50 g/10 min at most 50.0 g/10 min, preferably at least 1.00 g/10 min at most 25.0 g/10 min; determined according to ISO 1133:1997, procedure A, conditions G (190°C, 21.6kg).

20. The method according to any one of statements 1 to 19, wherein the initial melt flow index is an MI2 when XPE > 50 wt%, of at least 0.01 g/10 min, preferably at least 0.05 g/10 min, preferably at least 0.10 g/10 min; determined according to ISO 1133:1997, procedure A, conditions D (190°C, 2.16kg). The method according to any one of statements 1 to 20, wherein the initial melt flow index is an MI2 when X _PE > 50 wt% of at most 250 g/10 min, preferably at most 200 g/10 min, preferably at most 100 g/10 min, preferably at most 50 g/10 min, preferably at most 25 g/10 min; determined according to ISO 1133:1997, procedure A, conditions D (190°C, 2.16kg). The method according to any one of statements 1 to 21, wherein the initial melt flow index is an MI2 when X _PE > 50 wt% of at least 0.01 g/10 min to at most 250.00 g/10 min, preferably at least 0.05 g/10 min to at most 200.00 g/10 min, preferably at least 0.10 g/10 min to at most 100.00 g/10 min, preferably at least 0.50g/10 min to at most 50.00 g/10 min, preferably at least 1.00 g/10 min to at most 25.00 g/10 min; determined according to ISO 1133:1997, procedure A, conditions D (190°C, 2.16kg). The method according to any one of statements 1 to 22, wherein the initial melt flow index is an MFI when X _PP ³ 50 wt% of at least 0.01 g/10 min, preferably at least 0.05 g/10 min, preferably at least 0.10 g/10 min, preferably at least 0.50 g/10 min, preferably at least 1.00 g/10 min; determined according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16kg). The method according to any one of statements 1 to 23, wherein the initial melt flow index is an MFI when X _PP ³ 50 wt% of at most 250.00 g/10 min, preferably at most 200.00 g/10 min, preferably at most 100.00 g/10 min, preferably at most 50.00 g/10 min, preferably at most 25.00 g/10 min; determined according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16kg). The method according to any one of statements 1 to 24, wherein the initial melt flow index is an MFI when X _PP ³ 50 wt% of at least 0.01 g/10 min to at most 250.00 g/10 min, preferably at least 0.05 g/10 min to at most 200.00 g/10 min, preferably at least 0.10 g/10 min to at most 100.00 g/10 min, preferably at least 0.50 g/10 min to at most 50.00 g/10 min, preferably at least 1.00 g/10 min to at most 25.00 g/10 min; determined according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16kg). The method according to any one of statements 1 to 25, wherein the target melt flow index is an MI2 when X _PE > 50 wt% of at least 1.0 g/10 min, preferably at least 2.0 g/10 min, preferably at least 3.0 g/10 min, preferably at least 4.0 g/10 min; determined according to ISO 1133:1997, procedure A, conditions D (190°C, 2.16kg). The method according to any one of statements 1 to 26, wherein the target melt flow index is an MFI when X _PP ³ 50 wt% of at least 1.5 g/10 min, preferably at least 1.8 g/10 min, preferably at least 5.0 g/10 min, preferably at least 10.0 g/10 min, preferably at least 15.0 g/10 min, preferably at least 20.0 g/10 min, preferably at least 25.0 g/10 min, preferably at least 30.0 g/10 min; determined according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16kg). The method according to any one of statements 1 to 27, wherein the ultrasound power normalized by the polymer quantity is applied to the polyolefin composition in amount, in terms of Pus/Q (i.e., the introduced ultrasound power divided by the polymer throughput), of at least 50 kJ/kg, preferably at least 10.0 kJ/kg, preferably at least 25.0 kJ/kg, preferably at least 50.0 kJ/kg, preferably at least 75.0 kJ/kg, preferably at least 100.0 kJ/kg, preferably at least 150.0 kJ/kg, preferably at least 300.0 kJ/kg, preferably at least 400.0 kJ/kg, preferably at least 500.0 kJ/kg. The method according to any one of statements 1 to 28, wherein the ultrasound power, normalized by the polymer quantity is applied to the polyolefin composition in amount, in terms of Pus/Q, of at most 1000.0 kJ/kg, preferably at most 750.0 kJ/kg. The method according to any one of statements 1 to 29, wherein the ultrasound power, normalized by the polymer quantity Pus/Q, is at least 10.0 kJ/kg to at most 1000.0 kJ/kg, preferably at least 25.0 kJ/kg to at most 750.0 kJ/kg, preferably at least 50.0 kJ/kg to at most 500.0 kJ/kg, preferably at least 75.0 kJ/kg to at most 250.0 kJ/kg, preferably at least 100.0 kJ/kg to at most 200.0 kJ/kg, preferably at least 125.0 kJ/kg to at most 175.0 kJ/kg, preferably at least 150.0 kJ/kg to at most 175.0 kJ/kg. The method according to any one of statements 1 to 30, wherein the method steps a) and b) are continuous. The method according to any one of statements 1 to 31 , wherein the method step a) involves melting the polyolefin composition in an extruder. The method according to any one of statements 1 to 32, wherein the ultrasound in step b) is applied inside an extruder. The method according to any one of statements 1 to 33, wherein ultrasound in step b) is applied in the core, the metering zone, core, die, or nozzle, of an extruder, preferably in the die or core. The method according to any one of statements 1 to 34, wherein during step a) and/or step b) a devolatilisation step is performed, or more preferably wherein after step b) a devolatilisation step is performed. The method according to any one of statements 1 to 35, wherein after step a) and/or step b) the molten polyolefin is contacted with water, whereafter a devolatilisation step is performed. The method according to any one of statements 1 to 36, wherein the none of the L* a*b* parameters of the polyolefin composition after the method is performed differ more than 20%, preferably more than 15%, preferably more than 10%, preferably more than 5%, preferably more than 1%, of the L* a*b* parameters of the polyolefin composition before the method is performed. 38. The method according to any one of statements 1 to 37, wherein the odour is improved as measured through the short chain content (volatiles) by a thermodesorption analysis (TDA) coupled with a chromatography analysis.

39. The method according to any one of statements 1 to 38, wherein the frequency of the ultrasound is at least 16kHz, preferably at least 20 kHz, preferably at least 25 kHz, preferably at least 30 kHz, preferably at least 33 kHz.

40. The method according to any one of statements 1 to 39, wherein the frequency of the ultrasound is at most 1 GHz, preferably at most 1MHz, preferably at most 2000 kHz, preferably at most 500 kHz, preferably at most 100 kHz, preferably at most 40 kHz.

41. The method according to any one of statements 1 to 40, wherein the frequency of the ultrasound is at least 16 kHz to at most 1GHz, preferably at least 18 kHz to at most 1 MHz, preferably at least 20 kHz to at most 2000 kHz, preferably at least 25 kHz to at most 500 kHz, preferably at least 30 kHz to at most 100 kHz, preferably at least 33 kHz to at most 40 kHz.

42. The method according to any one of statements 1 to 41, wherein in step b), the ultrasound is constant, preferably Pus(t) = constant.

43. The method according to any one of statements 1 to 42, wherein in step b), the ultrasound per polyolefin flow is constant, preferably Pus/Q (t) = constant.

44. The method according to any one of statements 1 to 43, comprising the following step: c) cooling and/or contacting the molten polyolefin flow after step b) with a liquid coolant, preferably with water.

45. The method according to any one of statements 1 to 44, wherein the temperature of the liquid coolant in step c) is at most 50°C, preferably at most 40°C, preferably at most 30°C, preferably at most 25°C preferably at most 20°C.

46. The method according to any one of statements 1 to 45, wherein the method is a continuous method.

The present invention provides a method for treating a polyolefin composition, the polyolefin composition comprising polyethylene (PE) and/or polypropylene (PP), the method comprising the steps of: a) melting said polyolefin composition, thereby creating a molten polyolefin flow at an initial temperature (T) and a flow rate (Q); and, b) applying ultrasound (US) at a power (Pus) to said molten polyolefin flow.

More preferably, the method fulfils in step b) inequality (I):

1.3 * ^ + T - 3.6 * c _Rr - 4.0 * c _R£ > 0 (I) wherein,

P _us is the power of the applied ultrasound expressed in Watt; Q is the flow rate of the molten polyolefin flow, expressed in kg/h;

T is the initial temperature of the molten polyolefin, expressed in °C prior to the applied ultrasound;

XPP is the weight fraction of polypropylene (PP) expressed in wt% in the polyolefin composition, based on the total combined weight of PP and PE present in the polyolefin composition; and,

XPE is the weight fraction of polyethylene (PE) expressed in wt% in the polyolefin composition, based on the total combined weight of PP and PE present in the polyolefin composition.

In particular, the sum of the numeric value of XPP the numeric value of XPE is 100. Since the weight fractions of PE and PP are expressed based on the total combined weight of PP and PE, and not based on the total combined weight of the polyolefin composition, the sum of the numeric value of XPP the numeric value of XPE will still be 100 if additives (for example talc) or contaminants are present.

As used herein, the parameter Q is calculated as: 1.3 * + r — 3.6 * c _RR — 4.0 * c _RE .

According to the present invention, Q > b, wherein b is 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80.

When no polyethylene is present in the polyolefin composition, the parameter Q is calculated as: 1.3 * ^ + T - 360. When no polypropylene is present in the polyolefin composition, the parameter Q is calculated as: 1.3 + T — 400.

As used herein the term “melt flow index” is a measure of the ease of flow of the melt of a thermoplastic polymer. It is defined as the mass of polymer, in grams, flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures. Herein, three different melt flow indexes may be used, i.e. :

- when X _PE > 50 wt%: MI2 according to ISO 1133:1997, procedure A, conditions D, using 2.16kg at 190°;

- when X _PE > 50 wt%; HLMI according to ISO 1133:1997, procedure A, conditions G, using 21.6kg at 190°C; and,

- when X _PP ³ 50 wt%; MFI according to ISO 1133:1997, procedure A, conditions M, using 2.16kg at 190°.

Hence for X _PE > 50 wt% both MI2 and HLMI can be used, preferably MI2 or HLMI is used so that the result falls in the range on 0.1 g/10 min to 100 g/10min. Preferably, in case whereby MI2 < 0.1 g/10 min, HLMI should be used as melt flow index herein.

As used herein, the factor k is defined as the ratio of the melt flow index of the polyolefin composition obtained after the inventive method has been carried out over the melt flow index of the polyolefin composition subjected apart from step b), the same process steps of inventive step, i.e. same Q, same T, same XPP and same XPE but Pus = 0 W; wherein the melt flow index in both the numerator and denominator of this ratio may be MI2; or, wherein the melt flow index in both the numerator and denominator of this ratio may be HLMI; or wherein the melt flow index in both the numerator and denominator of this ratio may be MFI. Preferably, the ratio k is defined by the MI2 or HLMI when XPE > 50 wt%, and the ratio k is defined by the MFI when XPP ³ 50 wt%.

In some embodiments, the factor k is at least 2.0, preferably at least 3.0, preferably 4.0, preferably at least 5.0, preferably at least 6.0, preferably 7.0, preferably at least 8.0.

In some embodiments, treating a polyolefin composition involves increasing the melt flow index MI2 of said polyolefin composition, preferably at least by a factor k of 2, preferably at least by a factor k of 3, preferably at least by a factor k of 4, preferably at least by a factor k of 5, preferably at least by a factor k of 6, preferably at least by a factor k of 7, preferably at least by a factor k of 8.

In some embodiments, treating a polyolefin composition involves increasing the melt flow index HLMI of said polyolefin composition, preferably at least by a factor k of 2, preferably at least by a factor k of 3, preferably at least by a factor k of 4, preferably at least by a factor k of 5, preferably at least by a factor k of 6, preferably at least by a factor k of 7, preferably at least by a factor k of 8.

In some embodiments, treating a polyolefin composition involves increasing the melt flow index MFI of said polyolefin composition, preferably at least by a factor k of 2, preferably at least by a factor k of 3, preferably at least by a factor k of 4, preferably at least by a factor k of 5, preferably at least by a factor k of 6, preferably at least by a factor k of 7, preferably at least by a factor k of 8.

Such method allows treatment of a polyolefin composition to obtain an increase in melt flow index and/or the removal of at least part of the volatile components and/or odour of the polyolefin composition. Preferably, the colour of the polyolefin does not change by carrying out the method. Preferably, little smoke and/or fumes are formed during the method. To determine XPP and XPE, first the weight fraction of polyethylene and weight fraction polypropylene in the polyolefin composition may be determined, preferably by ¹³ C NMR. The sum of these two weight fractions is equated to exactly 100 (, where after the relative fractions XPP and X _PE can be calculated by a rule of three. Hence, the sum of XPP and XPE is always 100 wt%, even if there are other polymers, fillers, or impurities in the polyolefin compositions, which is other the case when dealing with PCR products.

In some embodiments, the initial temperature (T) of the molten polyolefin is measured, prior to applying ultrasound. In some embodiments, the initial temperature is measured right before the ultrasound is applied. For continuous methods, the initial temperature may be measured between 1 mm to 10 mm, preferably between 2 mm and 8 mm, preferably between 4 and 6 mm, upstream from the point where the ultrasound waves cross the molten flow for the first time.

The description of extruders (laboratory equipment or industrial extruders) is often performed providing, amongst other information, the diameter of the screw (D). In some embodiments, for example for continuous methods, the temperature may be measured at a distance corresponding to a value from 0 to 2 * D before the ultrasound sonotrode, preferably corresponding to a value from 0 to D before the ultrasound sonotrode.

In some embodiments, the molten polyolefin flow is routed through a flow chamber, and in said flow chamber ultrasound is applied. In some embodiments, the ultrasound is produced by an ultrasonic sonotrode. Preferably, the ultrasound is produced by an ultrasonic sonotrode comprising a flow chamber for accommodating at least part of the molten polyolefin flow. In embodiments where a flow chamber is used, the initial temperature (T) may be measured between 1 mm to 10 mm, preferably between 2 mm and 8 mm, preferably between 4 and 6 mm before the entrance of the flow chamber.

As used herein, the term “sonotrode” refers to a tool that creates ultrasonic vibrational energy and applies this vibrational energy to the molten polyolefin flow. In some embodiments, multiple sonotrodes or ultrasound devices may be placed in series, Pus then being the sum of the individual Pus for each sonotrode or ultrasound device.

In some embodiments, the sonotrode comprises at least one piezoelectric transducer, preferably a stack of piezoelectric transducers; attached to a first end of a tapering metal rod. Preferably, the second end of the tapering metal rod is placed inside the flow chamber, when present. Preferably, an alternating current at the frequency of the desired ultrasound is applied to the one or more piezoelectric transducer(s). As used herein, the term “polyolefin” may be any olefin homo-polymer or any co-polymer of an olefin and one or more comonomers. The olefin can for example be ethylene, propylene, 1- butene, 1-pentene, 1 -hexene, 4-methyl-1-pentene or 1-octene, but also cycloolefins such as for example cyclopentene, cyclohexene, cyclooctene or norbornene. Most preferred polyolefins for use in the present invention are olefin homo-polymers and co-polymers of an olefin and one or more comonomers, wherein said olefin and said one or more comonomer is different, and wherein said olefin is ethylene or propylene. The term "comonomer" refers to olefin comonomers which are suitable for being polymerized with olefin monomers, preferably ethylene or propylene monomers. Comonomers may comprise but are not limited to aliphatic C2-C20 alpha-olefins. Examples of suitable aliphatic C2-C20 alpha-olefins include ethylene, propylene, 1 -butene, 4-methyl-1-pentene, 1 -hexene, 1-octene, 1-decene, 1-dodecene, 1- tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. In some embodiments, the comonomer is vinyl acetate.

Preferably, the polyolefin is selected from polyethylene and polypropylene homo- and co polymers. More preferably the polyolefin is polyethylene. Alternatively, the polyolefin is polypropylene. Melt index conditions are only described for polyethylene and polypropylene. For other polymers, the precise conditions must be adapted as explained, for example, in the ISO 1133:1997 standard (above mentioned).

Suitable polyethylene includes but is not limited to homo-polymer of ethylene, co-polymer of ethylene and a higher alpha-olefin comonomer. Suitable polypropylene includes but is not limited to homo-polymer of propylene, co-polymer of propylene and ethylene as comonomer or a higher alpha-olefin comonomer. The term "co-polymer" refers to a polymer, which is made by linking two different types of monomer in the same polymer chain. The term “homo-polymer” refers to a polymer which is made by linking only one monomer (ethylene for PE, propylene for PP) in the absence of comonomers. In some embodiments, the preferred comonomer for polyethylene is 1-hexene. In some embodiments, the comonomer for polypropylene is ethylene or 1 -butene, preferably ethylene.

In some embodiments, the polyolefin composition is a recycled polyolefin composition. As used herein, the terms “recycled polyolefin composition” encompasses both Post-Consumer Resins (PCR) and Post-Industrial Resins (PIR).

The terms “Post-Consumer Resin”, which may be abbreviated as “PCR”, is used to denote the components of domestic waste, household waste or end of life vehicle waste. In other words, the PCR are made of recycled products from waste created by consumers. The terms “Post-Industrial Resin”, which may be abbreviated as “PI R”, is used to denote the waste components from pre-consumer resins during packaging processes. In other words, the PIR are made of recycled products created from scrap by manufacturers.

The term “recycled polyolefin composition” contrasts to the term “virgin polyolefin composition”, the terms “virgin polyolefin composition” are used to denote a polyolefin composition directly obtained from a polyolefin polymerization plant. The terms “directly obtained” is meant to include that the polyolefin composition may optionally be passed through a pelletization step or an additivation step or both.

In some embodiments, XPE is 100 wt% (i.e. the polyolefin composition is essentially free from polypropylene), whereby in step b) inequality (III) is fulfilled:

1.3 400 + b (III) wherein b is preferably 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80; and, wherein preferably all the polyolefin is polyethylene.

In some embodiments, XPP is 100 wt% (i.e. the polyolefin composition is essentially free from polyethylene), whereby in step b) inequality (IV) is fulfilled:

1.3 360 + b (IV) wherein b is preferably 0, preferably 10, preferably 20, preferably 30, preferably 40, preferably 50, preferably 60, preferably 70, preferably 80; and, wherein preferably all the polyolefin is polypropylene.

In some embodiments, the polyolefin composition comprises at least 50.0% by weight, preferably at least 60.0% by weight, preferably at least 70.0% by weight, preferably at least

80.0% by weight, preferably at least 90.0% by weight, preferably at least 95.0% by weight, polyolefin (i.e. the total sum of polyethylene and/or polypropylene), compared to the total weight of the polyolefin composition. This allows the polyolefin composition to comprise impurities, such as other polymers, fillers, and/or additives. This is typical for a recycled polyolefin composition.

In some embodiments, T is at least 200°C to at most 340°C, preferably at least 220°C to at most 330°C, preferably at least 240°C to at most 320°C, preferably at least 250°C to at most 310°C, preferably at least 260°C to at most 300°C, preferably at least 265°C to at most 290°C, preferably at least 270°C to at most 280°C. At higher temperatures fire hazards may occur, especially in the presence of oxygen gas or air.

In some embodiments, ultrasound may be used in step a) to melt the polyolefin. In some embodiments, the target melt flow index is a MI2 when XPE > 50 wt% of at least 1.0 g/10 min, preferably at least 2.0 g/10 min, preferably at least 3.0 g/10 min, preferably at least 4.0 g/10 min; determined according to ISO 1133:1997, procedure A, conditions D (190°C, 2.16kg); or an MFI when XPP ³ 50 wt% of at least 1.5 g/10 min, preferably at least 1.8 g/10 min, preferably at least 5.0 g/10 min, preferably at least 10.0 g/10 min, preferably at least 15.0 g/10 min, preferably at least 20.0 g/10 min, preferably at least 25.0 g/10 min, preferably at least 30.0 g/10 min; determined according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16kg). As used herein, the term “target melt flow index” is the desired melt flow index of the polyolefin composition after the method is performed. Preferably, the target melt flow index allows for easy injection moulding of the polyolefin composition.

In some embodiments, ultrasound is applied to the polyolefin composition in amount, in terms of Pus/Q, of at least 10.0 kJ/kg to at most 1000.0 kJ/kg, preferably at least 25.0 kJ/kg to at most 750.0 kJ/kg, preferably at least 50.0 kJ/kg to at most 500.0 kJ/kg, preferably at least 75.0 kJ/kg to at most 250.0 kJ/kg, preferably at least 100.0 kJ/kg to at most 200.0 kJ/kg, preferably at least 125.0 kJ/kg to at most 175.0 kJ/kg, preferably at least 150.0 kJ/kg to at most 175.0 kJ/kg. At higher values of Pus/Q, the polyolefin may degrade too much resulting in inferior properties. To avoid degradation a sequence of several sonotrodes, optionally separated by temperature control systems, may be used, spearing the allied ultrasound over a longer period of time.

Pus is determined by the ultrasound equipment: it is typically indicated on the equipment. Q is determined by the extruder conditions: it is typically indicated on the control table. Alternatively, Q could be experimentally determined by a measure of the weight of polymer extruded in a specific lapse of time

In some embodiments, the frequency of the ultrasound is at least 16 kHz to at most 1GHz, preferably at least 18 kHz to at most 1 MHz, preferably at least 20 kHz to at most 2000 kHz, preferably at least 25 kHz to at most 500 kHz, preferably at least 30 kHz to at most 100 kHz, preferably at least 33 kHz to at most 40 kHz. Especially below 20 kHz, noise pollution may occur.

In some embodiments, the method steps a) and b) are continuous, i.e. uninterrupted. Preferably, the molten polyolefin flow created in step a) has a constant flow rate in function of time. Preferably, the power P _us in step b) is constant in function of time. Preferably, the power P _us in step b) is constant in function of time over a time period At, whereby At is preferably at least 1 min. Preferably, the power Pus/Q (t) in step b) is constant in function of time. Preferably, the power Pus/Q (t) in step b) is constant in function of time over a time period At, whereby At is preferably at least 1 min. In some embodiments, an existing extruder may be used in the inventive method, said extruder being modified to include an ultrasound device (or a series of several ultrasound devices) in its flow path and/or wherein a flow chamber containing an ultrasound device (or a series of ultrasound devices) is added to the nozzle or in the die of the extruder.

In some embodiments, an extruder may be used wherein the ultrasound device (or a series of ultrasound devices) is applied in the core of the extruder, preferably along the screw of the extruder, more preferably in the metering zone. In some embodiments, water may be added inside the extruder to be contacted with the molten polyolefin composition, and that in an amount and temperature avoiding solidification of the molten polyolefin; after the polyolefin composition has been contacted with the water, a devolatilisation step may be performed. Contacting the molten polyolefin with water may remove impurities from the polyolefin composition, and the devolatilisation step may at least partially remove the impurities from the extruder together with the water vapour.

In some embodiments, more than one ultrasound treatment could be applied, for example, one treatment in the core of the extruder and another one just after the die at the exit of the extruder. In some embodiments, a series of ultrasound sonotrodes could be considered. This latter case is especially interesting in industrial cases considering a high throughput Q. In such cases, introduction of the required ultrasound power could be performed via multiple ultrasound devices put in series. In such cases Pus in formula (I) is considered as the sum of the individual Pus values in series.

The following examples serve to merely illustrate the invention and should not be construed as limiting its scope in any way. While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes and modifications without departing from the scope of the invention.

EXAMPLES

Melt flow index

- The melt index is herein referred to as “MFI” when the melt index is measured at 230°C with a load of 2.16 kg and using a normal die (length = 8 mm; diameter = 2.095 mm). In general, such conditions may be used when polypropylene is considered, or a PCR polypropylene.

- The melt index is herein referred to as “MI2” when the melt index is measured at 190°C with a load of 2.16 kg and using a normal die (length = 8 mm; diameter = 2.095 mm). In general, such conditions may be used when a polyethylene is considered, or a PCR polyethylene. - The melt index is herein referred to as “HLMI” when the melt index is measured at 190°C with a load of 21.6 kg and using a normal die (length = 8 mm; diameter = 2.095 mm). In general, such conditions may be used when polyethylene is considered or a PCR polyethylene.

Many polyethylenes or PCR polyethylenes may thus be characterized both by MI2 and HLMI values. When very viscous polyethylenes are considered, only HLMI values are usually provided.

Determination of XPP and XPE

The values XPP and XPE are determined by ¹³ C NMR analysis according to the state of the art of ¹³ C NMR analysis of ethylene and/or propylene based polyolefins.

The ¹³ C NMR analysis was performed under conditions such that the signal intensity in the spectrum is directly proportional to the total number of contributing carbon atoms in the sample. Such conditions are well known to the skilled person and include for example sufficient relaxation time etc. In practice, the intensity of a signal is obtained from its integral, i.e. the corresponding area. The data were acquired using proton decoupling, several hundred even thousands scans per spectrum, at a temperature of 130°C. The sample was prepared by dissolving a sufficient amount of polyolefin composition in 1,2,4-trichlorobenzene (TCB 99 % spectroscopic grade) at 130°C and occasional agitation to homogenize the sample, followed by the addition of hexadeuterobenzene (C6D6, spectroscopic grade) and a minor amount of hexamethyldisiloxane (HMDS, 99.5+ %), with HMDS serving as internal standard. To give an example, about 200 to 600 mg of polyolefin composition were dissolved in 2.0 ml of TCB, followed by addition of 0.5 ml of Obϋb and 2 to 3 drops of HMDS. The chemical shifts are referenced to the signal of the internal standard HMDS, which is assigned a value of 2.03 ppm.

NMR ¹³ C observed signals are assigned according to the monomer involved and corresponding literature. The following non-exhaustive literature references can be used: G.J. Ray et al. in Macromolecules, vol 10, n°4, 1977, p. 773-778 and Y. D Zhang et al in Polymer Journal, vol 35, n°7, 2003, p. 551-559.

The values XPP and XPE relative to the total weight of the polyolefin composition can be determined from the appropriate peaks area combination, a well-known method to the skilled person.

Optionally, eee an PPP

XPE ~ d eee+ ppp XPP ~ eee+ ppp wherein, eee is the NMR signal associated with a repeating unit of three consecutive ethylene units in a polyolefin backbone; and ppp is the NMR signal associated with a repeating unit of three consecutive polypropylene units in a polyolefin backbone.

Ultrasound

An ultrasonic sonotrode was provided by Aktive Arc Ultrasonics and placed over the die of a Leistritz ZSE 18 HPe extruder as illustrated by FIG. 3. The ultrasonic sonotrode comprises a flow chamber wherein molten polymer is provided from the die of the extruder. The screw diameter of the Leistritz ZSE 18 HPe extruder is 18 mm.

Ultrasound acoustic waves are generated by the ultrasonic sonotrode at a fixed frequency of 35 kHz, and are direct to the flow chamber. The output power of the ultrasonic sonotrode can be set (via a setting in terms of percentage of the full power). The initial temperature can be set by the settings of the extruder and for these experiments, a temperature probe is at the juncture of the die and the flow chamber, measuring the temperature of the molten polyolefin flow before the molten polyolefin flow interacts with the ultrasound waves in the flow chamber. After the molten polyolefin leaves, i.e. the extrudate, the exit of the flow chamber the molten polyolefin is exposed to the atmosphere at a temperature of 21 °C and it is fed into a first water bath at 15°C and a length of 160 cm. The distance between the exit of the flow chamber and entrance of the first water bath is 7.0 cm. In a few cases, after leaving the first water bath, the extrudate is fed into second water bath at 15°C and a length of 160 cm, before being fed into a granulator to yield granules of treated polyolefin on which the measurements were performed from determining the MI2, HLMI and/or MFI. The second water bath optional; it may be used in cases of significant heating of the polymer.

Examples and comparative examples were generated by extrusions, varying the values of T, Q, PUS, on different polyolefin compositions in the set up as described above. During every experiment, Pus was switched to 0 to determine the melt flow index (MI2 or HLMI) with no ultrasound applied. The flow Q was indicated on (and recorded from) the Leistritz control panel. Pus was indicated on (and recorded from) the Leistritz control panel. No antioxidants were added during the additional pelletization/ultrasound treatments.

Determination of the volatiles content by thermal desorption analysis (TDA) coupled with gas chromatography (GC)

The polymer sample (40 to 60 mg) is introduced in a ATD/GC equipment (:Automatic Thermal Desorber) with FID (flame ionization detector) detection for the quantitative analysis. In this analysis, a thermal desorption process is imposed to the polymer sample during 15 minutes at 150°C in an oven. Volatile organic compounds are extracted from the sample by an imposed helium flux and are captured in an adsorbant cartridge TENAX cooled at -30°C.

In a second process, volatile compounds are injected in a chromatographic separation column via a rapid heating process of the cartridge at 230°C. The analytes are separated onto the column before being detected by FID.

Results: The compounds are identified based on their retention times in comparison with previously determined retention times of n-paraffins, in the same experimental conditions. The quantification of the components is performed using an external calibration curve (linear) established using 1 -hexene as reference.

Chromatographic analysis conditions:

Capillary column: type: HP-5 Length: 60m

Internal diameter: 0.32mm Phase type: 5% Ph-Me-siloxane Phase thickness: 1 pm

Detector type: F.I.D

Temperature: 280°C

Air flow: 450 ml/min

Hydrogen flow: 40 ml/min

Flow make up: 30ml/min (constant)

GC oven programmation: Isothermal temperature 1: 45°C Isotherm time 1 : 15 minutes Heating rate: 5°C/min Isothermal temperature 2: 280°C

Isothermal time 2: 25 min. or 5 min. for the calibration line

ATD conditions

Thermo desorption equipment: TurboMatrix ATD from Perkin Elmer Oven temperature: 150°C Desorption time: 15 minutes.

Trap temperature: Low temperature: -30°C (trapping mode)

High temperature: 230°C (desorption mode) Desorption time of the trap: 10 minutes Trap heating rate: 99 °C/s Temperature of the transfer line: 250°C Valve block temperature: 200°C Carrier gas pressure: 12.5 psi Inlet split flow: 37 ml/min Outlet split flow: 16.5ml/min Desorption flow: 20 ml/min Considered mode: MS Purge time: 1 minute

Run time: 79 minutes (32 minutes for the calibration line)

Linear viscoelastic measurements

The determination of dynamical viscosity was made by using a Rheometric Scientific ARES rheometer. This method has been extensively described in the literature devoted to polymer rheology (see e.g. W. W. Graessley, Chapter 3 in Physical Properties of Polymers, 2nd Edition, ACS Professional Reference Book, Washington D.C., 1993). The measurements are performed on a Rheometric Scientific ARES rheometer between two 25 mm diameter plates; the gap between the plates is between 1 and 2 mm, and is thoroughly adapted according to the suitable thickness of the polymer sample once this latter has been inserted between the plates and warmed up to 190, 210 or 230°C. The gap value is then recorded to be taken into account by the calculation software. The sample is then temperature-conditioned for a period of 5 minutes before the measurement is started. The measurement was performed at 190°C, 210°C, and 230°C. After temperature conditioning, the measurement starts by applying an oscillatory strain g*(w,ΐ)=c _M .b ^iwΐ , with a given amplitude YM and a given frequency w to the bottom plate via a precision motor, whereas the top plate is kept fixed. The amplitude YM of this shear strain has been chosen in the linear zone of viscoelasticity of the polymer and is kept constant through the whole requirement experiment. The circular frequency (w in rad/s) varies from 0.05-0.1 rad/s to 250-500 rad/s, typically 0.1 to 250 rad/s, and the shear strain is typically 10 %.

The oscillating shear strain is translated inside the material into an oscillating shear stress a*(o,t), which in-phase and out-of-phase components are recorded as functions of the frequency [omega], and used for the calculation of the complex modulus G*(co) as well as complex viscosity h*(w) of the polymer: Cross-over points G _c (modulus where G’=G”) and co _c (frequency w where G’=G”) were also determined.

The activation energy is determined using the “time-temperature superposition principle” approach as described in the following reference: H. Mavridis and R.N. Shroff, Polymer Engineering and Science 32, 1778 (1992). When only one activation energy E _act is reported, it corresponds to:

With E _H and Ev respectively the horizontal and vertical activation energy determined following the approach described in the above reference.

Molecular mass measurements

The molecular weight (M _n (number average molecular weight), M _w (weight average molecular weight) and z-average M _z ) and molecular weight distributions M _w /M _n and M _z /M _w were determined by size exclusion chromatography (SEC) and in particular by gel permeation chromatography (GPC).

Detailed procedure for polyethylene:

10 mg polyethylene sample was dissolved at 160°C in 10 ml of trichlorobenzene for 1 hour.

A GPC-IR5 from Polymer Char was used with the following conditions:

Injection volume of the above “PE in solution” sample: about 400mI automatic sample preparation and injection temperature: 160°C; Column temperature: 145°C;

Detector temperature: 160°C; Two Shodex AT-806MS (Showa Denko) and one Styragel HT6E (Waters) columns were used with a flow rate of 1 ml/min;

Detector: Infrared detector (2800-3000cnr ¹ );

Calibration was performed with narrow standards of polystyrene (PS) (commercially available).

Calculation of molecular weight M, of each fraction i of eluted polyethylene is based on the Mark-Houwink relation (log10(Mp _E ) = 0.965909 x log10(Mps) - 0.28264) (cut off on the low molecular weight end at M _PE = 1000).

The molecular weight averages used in establishing molecular weight/property relationships are the number average (M _n ), weight average (M _w ) and z average (Mz) molecular weight. These averages are defined by the following expressions and are determined form the calculated M,:

Here N, and W are the number and weight, respectively, of molecules having molecular weight M,. The third representation in each case (farthest right) defines how one obtains these averages from SEC chromatograms h, is the height (from baseline) of the SEC curve at the ith elution fraction and M, is the molecular weight of species eluting at this increment.

The procedure for polypropylene is equivalent except for the calculation of molecular weight M, of each fraction i of eluted polypropylene which is based on the “polypropylene” Mark- Houwink relation (logio(Mpp) = logio(Mps) - 0.25323) (cut off on the low molecular weight end at Mpp ⁼ 1000).

When PE and PP are both present in the sample, the considered procedure is selected based on the main component.

Flexural modulus

Flexural modulus was measured according to ISO 178.

Notched Izod impact

Notched Izod impact strength was measured according to ISO 180.

Polyolefin compositions

The following polyolefin compositions are used in the examples of Table 1, 2 and 3:

PE1 = Polyethylene HDPE 5502 (LOT: H112E00640) commercialised by Total. The reported density according to ISO 1183:2004 is 0.954 g/cm ³ ; the reported MI2 according to ISO 1133/D: 1997 (190°C, 2.16 kg) is 0.25 g/10 min; the reported HLMI according to ISO 1133/G:1997 (190°C, 21.6 kg) is 22 g/10 min. The polyethylene was produced using a chromium based catalyst.

PE2 = rHDPE VEOLIA, i.e. a recycled PE from Veolia. It had a grey green colour and a strong detergent smell. The density was 0.959 g/cm ³ , initial MI2 of 0.29 g/10min and HLMI of 32.8 g/10min.

PE3 = TGS PLUS 003GR194, a recycled PE grade containing 6 % of PP and characterized by a melt index MI2 = 0.29 g/10 min. and a density of 0.9591 g/cm ³ . DSC analysis using the following thermal history:

Equilibrate at 25°C

- Heat at 10°C/min. from 25°C to 220°C Isotherm at 220°C during 3 minutes

- Cool at -10°C/min. from 220°C to 0°C Isotherm at 0°C during 3 minutes

- Heat at 10°C/min. from 25°C to 220°C

Doing so, the crystallization temperature is 120.0°C and the melting temperature (second heating process) is 130.5°C; the associated melting enthalpy is 179.1 J/g.

GPC-HT analysis: M _n = 13900 dalton M _w = 116000 dalton M _z = 548000 dalton

PP1 = PP regranulate 500S commercialised by Vogt. The reported density according to EN ISO 55990 is 0.92 g/cm ³ , the reported MFI according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16 kg) is 11.5 g/10 min. PP1 is a recycled grade containing 10 wt % of polyethylene.

PP2 = homopolymer polypropylene PPH 7060 commercialised by Total. The reported density according to ISO 1183:2004 is 0.905 g/cm ³ ; the reported MFI according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16 kg) is 12 g/10 min.

MIX 1 = Mix PO PO920H Schwartz, is a recycled flux comprising 60 % by weight PE and 40 % PP by weight, compared to the total weight of the polyethylene and polypropylene combined. MIX 1 has a reported MFI of 3.72 g/10 min according to ISO 1133:1997, procedure A, conditions M (230°C, 2.16 kg).

Table 1 - Treatment of polyethylene

Table 2 - Treatment of polypropylene

Table 3 - Treatment of a polyethylene - polypropylene mixture

Example colour change: Figure 4 shows the absence of colour change after the inventive method. The experiments started with virgin PP2.

Volatile reduction as measured by TDA/GC: Volatile measurements performed with PP-1 samples. Using the ultrasound, the amount of compound “< nC12” is significantly reduced.

Example mechanical properties

PP2 (homopolymer polypropylene PPH 7060) was extruded at low and high screw speed, with and without ultrasound. Results are shown in Table 4 below.

Table 4: Properties of PP2 after extrusion in different conditions, with or without the use of ultrasound a shift of the whole distribution of masses towards lower values is observed when using the ultrasound during pelletization.

Comparing the samples of table 4 with each other in terms of mechanical properties, it can be observed that flexural modulus and Izod are all very close to each other, despite a significant change of the melt index.