Process to produce cellulosic-plastic composites, said composites, and articles made thereof

Abstract

A cellulosic-polyethylene composite material and a process to produce a cellulosic- polyethylene composite material comprising the step of melt blending more than 1.0 wt.% of a compatibilizer with a polyethylene resin and a cellulosic particulate component to obtain a cellulosic-polyethylene composite material, wherein the compatibilizer is a grafted resin comprising polyethylene and polypropylene, wherein the polyethylene is present at a content of at least 50.0 wt.%; has a melt index MI2 of at least 6.0 g / 10 min; has a complex viscosity at 0.1 rad / sec at 190 °C of at most 25,000 Pa.s; and has a ratio of complex viscosities at a frequency of 0.1 rad / sec to 100 rad / sec of at most 10; wherein the ratio of the melt index MI2 of the compatibilizer to the polyethylene resin is at least 6.0; and the resulting cellulosic- polyethylene composite material has a content of polypropylene of 0.20 to 3.0 wt.%.

Description

[0001] PROCESS TO PRODUCE CELLULOSIC-PLASTIC COMPOSITES, SAID COMPOSITES, AND ARTICLES MADE THEREOF

[0002] Technical Field

[0003] The present disclosure relates to cellulosic-plastic composites, such as wood plastic composites, comprising polyethylene produced with the addition of a compatibilizer such as a grafted polyethylene.

[0004] Technical background

[0005] Composite materials prepared from plastics and natural fibers are widely used as wood substitutes. These composite materials can be used in a variety of products for structural and decorative architectural applications, as well as automotive uses.

[0006] Architectural products containing these composite materials prepared from plastics and natural fibers are frequently prepared by extrusion. The architectural products containing these composite materials can be used in both residential and commercial applications.

[0007] In automotive applications, the articles made from these composite materials can be manufactured by molding, injection molding, and compression molding. Examples of articles are knobs, interior door handles, and decorative interior fascia; as well as concealed parts such as sound-deadening panels, trunk liners, tire covers, bins, and carpet backings.

[0008] A well-known problem in the formation of composite materials prepared from plastics and natural fibers is the incompatibility of the cellulosic component with the plastic. Natural fibers are hydrophilic, with many free polar hydroxyl groups on the surface. Plastics are hydrophobic. Therefore, the plastics do not readily wet the surface of the natural fiber and adhere thereto. This causes a loss of strength in the resulting composite material. The addition of coupling agents to the composite material is useful in this respect.

[0009] W02020169548 A1 discloses a process to produce a polyolefin composition comprising a blend of polyethylene and polypropylene and to said polyolefin compositions. The process comprises the steps of providing one or more polyethylenes, one or more polypropylenes, one or more epoxy functionalized polymers; and one or more grafted and / or modified polyolefins selected from acid-grafted polyolefins and / or anhydride- modified polyolefins; wherein the polyolefin is selected from polyethylene and / or polypropylene; and the modified polyolefins have an MI2 of at least 50 g / 10 min as determined according to ISO 1133:1997 and meltblending the different components to form a polyolefin composition.

[0010] US 2011 / 263,758 A1 discloses a method for recycling polymer containers contaminated with oil, for example used HDPE motor oil containers, in an energy efficient manner, that does not require a costly washing step. The commercial value of the polymers is preserved by converting the contaminated polymers into value-added products. Composites are made from discarded motor oil containers, the residual motor oil therein, cellulosic fibers, and blending agents or other additives.

[0011] CN 116 041 839 A relates to tea waste reinforced polypropylene material and a preparation method thereof. The tea waste reinforced polypropylene material is at least prepared from, by weight, 15-40 parts of tea waste, 60-85 parts of recycled polypropylene, 0-3 parts of recycled polyethylene, 0.5-1 part of anhydride and 0.5-1 part of lubricant. The waste tea biomass tea branches, tea stems and tea leaf residues are used as reinforcing materials for recycling polypropylene.

[0012] CN 103 102 679 A discloses an antistatic wood flour-nylon 6 composite material and a preparation method thereof. The antistatic wood flour-nylon 6 composite material comprises the raw materials in parts by weight: 50-70 parts of nylon 6, 30-50 parts of wood flour, 4-8 parts of a composite coupling compatilizer and 1-3 parts of a composite antistatic agent. The composite antistatic agent comprises the components in parts by weight: 10-30 parts of stearamidopropyl dimethylamine-beta-ethoxyl quaternary ammonium nitrate, 30-60 parts of dodecyl dimethyl betaine, 20-40 parts of N, N-bi(2-hydroxyl ethyl)-N-(3'-dodecyloxyl-2'- hydroxyl propyl) methyl sulfate methyl ammonium and 5-10 parts of (3- lauramidopropyl)trimethyl sulfate methyl ammonium.

[0013] CN 104 448 874 A relates to a wood-plastic composite and a making method of the woodplastic composite. The wood-plastic composite comprises, by weight, 40-62% of wood meal, 30-45% of recycled PP / PE mixed plastics, 2-6% of compatilizer, 0.5-0.8% of antioxidant, 4- 10% of fillers and 1-3% of lubricants. The wood-plastic composite can be normally produced through the recycled PP plastics and recycled PE plastics at any mixed ratio, the screening process for recycling the PP plastics and the PE plastics is omitted, and the recycling cost of raw materials is lowered.

[0014] Balasuriya P W et al. in “Morphology and Mechanical Properties of Reconstituted Wood Board Waste-Polyethylene Composites” (Composite interfaces, Vol. 10, No. 2-3, pp. 319-341 (2003) discloses the preparation of a wood-plastic composite (WPC) comprising HDPE as base resin, wood waste and a MA-g-PE as compatibilizer

[0015] The circular economy concept aims to recycle more polymers from post-consumer resins (PCR) and post-industrial resins (PIR). The post-consumer resins of polyethylene type are mainly coming from domestic or household waste. The volume of polyethylene originating from post-consumer waste is increasing. Brand owners and converters are fostering the use of more and more recycled material in their marketed articles to answer final customers’ demands to lower carbon footprint impact and energy consumption.

[0016] There is a need for a cellulosic-polyethylene composite material comprising recycled polymer material and a good balance of mechanical properties and aspect properties. There is a need for a cellulosic-polyethylene composite material comprising blends of polyethylene and polypropylene (such as in recycled material) and a good balance of mechanical properties and aspect properties.

[0017] Summary

[0018] It has now been found that one or more of the above-mentioned needs can be fulfilled by preparing a cellulosic-polyethylene composite material comprising a compatibilizer, a polyethylene resin, and a cellulosic particulate component wherein the compatibilizer is produced from a blend of polyethylene and polypropylene wherein the polyethylene is the major component (such as a recycled polyethylene material).

[0019] According to a first aspect, the invention provides for a process to produce a cellulosic- polyethylene composite material comprising the step of melt blending a compatibilizer with a polyethylene resin, a cellulosic particulate component and an optional lubricant, to obtain a cellulosic-polyethylene composite material remarkable in that the compatibilizer is provided at a content of more than 1.0 wt.% based on the total weight of the cellulosic-polyethylene composite material, wherein the compatibilizer:

[0020] - is a grafted resin comprising a blend of polyethylene and polypropylene wherein the polyethylene and / or polypropylene is grafted with a grafting agent being or comprising one or more selected from maleic anhydride, glycidyl methacrylate, methyl methacrylate, acrylic acid, butyl acrylate, vinyl acetate, diethyl maleate, acrylamide, acrylonitrile, and any mixture thereof; and wherein polyethylene is present at a content of at least 50.0 wt.% based on the total weight of the compatibilizer;

[0021] - has a melt index MI2 of at least 6.0 g / 10 min as determined according to ISO 1133- 2011 at 190 °C under a load of 2.16 kg;

[0022] - a complex viscosity at 0.1 rad / sec at 190 °C of at most 25,000 Pa.s as determined according to the method of the description; and a ratio of complex viscosity at a frequency of 0.1 rad / sec to the complex viscosity at a frequency of 100 rad / sec of at most 10 said ratio being measured at 190 °C according to the method of the description; in that, the ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin is at least 6.0; and in that the resulting cellulosic-polyethylene composite material has a content of polypropylene of from 0.20 wt.% to 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR.

[0023] Surprisingly, it was found that it is possible to enhance the balance of properties using a specific thermally treated and grafted recycled polyethylene as a compatibilizer. As shown by the examples, the addition of such a compatibilizer made from recycled material allows for improvement of the balance of mechanical properties by comparison to a known compatibilizer. Also, it was shown that the visual aspect of the cellulosic-polyethylene composite material is maintained compared to those produced from virgin compatibilizer. The use of recycled material to produce the compatibilizer has the additional advantage that it allows for incorporating more recycled plastic material in the composite. While in prior art the addition of recycling material used to damage the balance of properties by comparison to the use of similar virgin material, the incorporation of recycled material in the form of a compatibilizing agent allows to improve the balance of properties by comparison to a similar composite produced from a virgin compatibilizer.

[0024] According to the disclosure polypropylene content in the cellulosic-polyethylene composite material is brought, at least partially, by the recycled polyethylene used in the compatibilizer, but can also be brought as a further component or by the polyethylene resin when it is a recycled polyethylene as well. In an embodiment, all the polypropylene present in the cellulosic-polyethylene composite material comes from the compatibilizer.

[0025] In one or more embodiments: the polyethylene resin is provided at a content of at least 20.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the cellulosic particulate component is provided at a content ranging from 10.0 to 70.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the compatibilizer is provided at a content ranging from 1.0 to 40.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the lubricant is provided at a content ranging from 0 to 5.0 wt.% based on the total weight of the cellulosic-polyethylene composite material.

[0026] In a preferred embodiment, the process comprises preparing the compatibilizer by extruding a raw polyethylene-containing material with a grafting agent using an extruder with one or more thermal regulation devices, wherein extrusion is performed together with a thermal treatment of the polyethylene-containing material at a maximum barrel temperature Ts of at least 315 °C in one or more hot zones of the extruder and wherein the raw polyethylene-containing material has a melt index (Ml R) ranging from 0.1 to 5.0 g / 10 min as determined according to ISO 1133- 2011 at 190 °C under a load of 21.6 kg; preferably from 0.1 to 4.0 g / 10min; more preferably from 0.1 to 3.5 g / 10 min ; and even more preferably from 0.1 to 3.0 g / 10 min.

[0027] One or more of the following can be used to further define the compatibilizer and the optional lubricant

[0028] With preference, the grafting agent comprises or consists of one or more functional monomers selected from maleic anhydride, glycidyl methacrylate, methyl methacrylate, acrylic acid, butyl acrylate, vinyl acetate, diethyl maleate, acrylamide, acrylonitrile, and any mixture thereof.

[0029] With preference, the grafting agent is provided in content ranging from 1.0 to 6.0 wt.% based on the total weight of the raw polyethylene-containing material.

[0030] With preference, the raw polyethylene-containing material is a recycled material being a blend of polyethylene and polypropylene, wherein the polypropylene is present at a content ranging from 0.5 to 50.0 wt.% based on the total weight of the raw polyethylene-containing material, preferably from 0.6 to 40.0 wt.% or from 0.8 to 30.0 wt.%; more preferably from 1.0 to 25.0 wt.%, even more preferably from 1.2 to 20.0 wt.%; most preferably from 1.5 to 15.0 wt.% and even most preferably from 1.8 to 10.0 wt.% or from 2.0 to 5.0 wt.%.

[0031] In an embodiment, the process further comprises providing from 0 to 5.0 wt.% of a lubricant selected from zinc stearate, calcium stearate, magnesium stearate, ethylene bis-stearamide (EBS), polyester wax, polypropylene wax, polyethylene wax, ethylene bis-oleamide, stearyl stearate, distearyl phthalate, pentaerythritol adipate stearate, ethylene glycol distearate, pentaerythritol tetrastearate, glycerol tristearate, polyethylene glycol 400 monostearate, glycerol monooleate, glycerol distearate, and any mixture thereof.

[0032] For example, the lubricant is added at a content of at least 0.1 wt.% based on the total weight of the cellulosic-polyethylene composite material so that the process further comprises providing from 0.1 to 5.0 wt.% of a lubricant.

[0033] In such a case, the step of melt blending comprises melt blending the lubricant with the other components to obtain a cellulosic-polyethylene composite material.

[0034] In a preferred embodiment, the lubricant is or comprises polyethylene wax, and the step of melt blending comprises melt blending the polyethylene wax with the other components to obtain a cellulosic-polyethylene composite material.

[0035] With preference the polyethylene wax has a number average molecular weight (Mn) of at most 6,000 Da as determined by gel permeation chromatography; preferably at most 4,000 Da; more preferably at most 3,000 Da. In an embodiment, the process is devoid of a step of addition of a lubricant.

[0036] For example, the compatibilizer has a grafting agent content of at least 0.3 wt.% based on the total weight of the compatibilizer as determined by the titration method of the description.

[0037] For example, the compatibilizer is a grafted resin comprising a blend of polyethylene and polypropylene, wherein polypropylene is present at a content ranging from 1.0 to 50.0 wt.% based on the total weight of the compatibilizer; preferably from 0.6 to 40.0 wt.% or from 0.8 to 30.0 wt.%; more preferably from 1.0 to 25.0 wt.%, even more preferably from 1.2 to 20.0 wt.%; most preferably from 1.5 to 15.0 wt.% and even most preferably from 1.8 to 10.0 wt.%, or from 2.0 to 5.0 wt.%.

[0038] For example, the compatibilizer has a melt index MI2 ranging from 5.5 to 50.0 g / 10 min or from 6.0 to 50.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably from 6.0 to 45.0 g / 10 min or from 6.2 to 40.0 g / 10 min; preferably from 6.4 to 30.0 g / 10 min; more preferably, from 6.6 to 25.0 g / 10 min; even more preferably from 6.8 to 20.0 g / 10 min; and most preferably from 6.8 to 18.0 g / 10 min.

[0039] For example, the compatibilizer has a number average molecular weight (Mn) ranging from 8,000 to 20,000 Da as determined by size exclusion chromatography; preferably ranging from 10,000 to 18,000 Da or from 12,000 to 17,000 Da.

[0040] For example, the compatibilizer comprises the grafting agent at a content ranging from 0.3 to 4.0 wt.% based on the total weight of the compatibilizer; preferably from 0.5 to 2.5 wt.% or from 0.6 to 3.5 wt.%.

[0041] According to the disclosure, the ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin is at least 6.0. For example, it can range from 6.0 to 20.0; preferably from 6.2 to 18.0; more preferably from 6.4 to 16.0; even more preferably from 6.6 to 16.0; most preferably from 6.8 to 14.0; and even most preferably from 7.0 to 12.0.

[0042] One or more of the following can be used to further define the polyethylene resin

[0043] For example, the polyethylene resin has a melt index (MI2) ranging from 0.1 to 25.0 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg ; preferably from 0.1 to 3.0 g / 10 min.

[0044] For example, the polyethylene resin has a melt index (MI2) of at most 25.0 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg; preferably at most 20.0 g / 10 min: more preferably at most 15.0 g / 10 min; even more preferably at most 10.0 g / 10 min; most preferably at most 8.0 g / 10 min; even most preferably at most 5.0 g / 10 min; or at most 4.0 g / 10 min; or at most 3.5 g / 10 min or at most 3.0 g / 10 min. For example, the polyethylene resin has a melt index (MI2) of at least 0.1 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg; preferably at least 0.2 g / 10 min.

[0045] For example, the polyethylene resin comprises at least 10.0 wt.% based on the total weight of the polyethylene resin of recycled polyethylene resin; preferably at least 30.0 wt.%: more preferably at least 50.0 w.% and even more preferably at least 80 wt.%.

[0046] In an embodiment, the polyethylene resin is recycled polyethylene resin.

[0047] For example, the polyethylene resin has a density ranging from 0.910 to 0.970 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; with preference ranging from 0.912 to 0.965 g / cm3; more preferably from 0.915 to 0.960 g / cm3; and even more preferably from 0.917 to 0.956 g / cm3.

[0048] One or more of the following can be used to further define the cellulosic particulate component

[0049] For example, the cellulosic particulate component is selected from wood fiber, wood particles, wood chips, ground wood, wood flour, wood flakes, wood veneers, wood laminates, sawdust, paper, newspaper, cardboard, wood pulp fiber, chemical pulp, recycled paper fiber, recycled boxes, recycled box fiber, recycled newspaper, recycled newspaper fiber, recycled computer printout, recycled computer printout fiber, milling tailings, hardwood fiber, softwood fiber, newsprint, ground newsprint, magazines, ground magazines, books, ground books, ground cardboard, wheat chaff, bamboo fiber, pond sludge, cork and combinations thereof.

[0050] For example, the cellulosic particulate component is selected from wood fiber, wood particles, wood chips, ground wood, wood flour, wood flakes, wood veneers, wood laminates, sawdust, paper, wood pulp fiber, and combinations thereof.

[0051] Preferably, the cellulosic particulate component is selected from wood fiber, wood flour, and combinations thereof.

[0052] One or more of the following can be used to further define cellulosic-polyethylene composite material

[0053] With preference, the cellulosic-polyethylene composite material has a content of polypropylene of at least 0.25 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR; preferably at least 0.30 wt.% more preferably at least 0.35 wt.%.

[0054] Advantageously, the cellulosic-polyethylene composite material has a content of polypropylene of at most 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR; preferably, at most 2.5 wt.%; more preferably, at most 2.0 wt.%; even more preferably at most 1.5 wt.%, and most preferably at most 1.0 wt.%. For example, the cellulosic-polyethylene composite material has a content of polypropylene ranging from 0.20 to 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR; preferably from 0.25 to 2.5 wt.%; more preferably from 0.30 to 2.0 wt.%; even more preferably from 0.35 to 1.5 wt.%; and most preferably from 0.35 to 1 .0 wt.%.

[0055] The polypropylene is brought by the recycled material but can be add as such (i.e. as a further component to the blend) to reach a desired content in the cellulosic-polyethylene composite material.

[0056] According to a second aspect, the invention provides for a cellulosic-polyethylene composite material produced according to the process of the first aspect.

[0057] In a preferred embodiment, the cellulosic-polyethylene composite material has a melt index MI2 of at least 1.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably at least 2.0 g / 10 min; more preferably at least 3.0 g / 10 min and even more preferably at least 4.0 g / 10 min.

[0058] In a preferred embodiment, the cellulosic-polyethylene composite material has a content of polypropylene ranging from 0.20 to 3.0 wt.% based on the total weight of the cellulosic- polyethylene composite material as determined by13C NMR; preferably from 0.25 to 2.5 wt.%; more preferably from 0.30 to 2.0 wt.%; even more preferably from 0.35 to 1.5 wt.%; and most preferably from 0.35 to 1 .0 wt.%.

[0059] According to a third aspect, the invention provides for an article manufactured from the cellulosic-polyethylene composite material according to the second aspect. With preference, the article is an extruded article, an injection moulded article, or a compression moulded article.

[0060] According to a fourth aspect, the invention provides for a multi-layered article comprising at least one layer comprising the cellulosic-polyethylene composite material according to the second aspect. With preference, the article is an injection moulded article or a compression moulded article.

[0061] According to a fifth aspect, the invention provides for a process to produce an article according to the third or the fourth aspect comprising producing a cellulosic-polyethylene composite material by the process according to the first aspect and manufacturing an article from the cellulosic-polyethylene composite material, with preference manufacturing is performed by extrusion, or compression molding, or injection molding.

[0062] Detailed description It is to be understood that this disclosure is not limited to particular processes or compositions described, as such processes or compositions 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 disclosure will be limited only by the appended claims.

[0063] When describing the polymers, uses and processes of the disclosure, the terms employed are to be construed by the following definitions, unless a context dictates otherwise. For the disclosure, the following definitions are given:

[0064] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context dictates otherwise. By way of example, "a composition" means one composition or more than one composition.

[0065] 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”.

[0066] 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, 5 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 endpoints also includes the endpoint 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.

[0067] All references cited in the present specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references herein specifically referred to are incorporated by reference. Indication of a standard method to determine a parameter implies referring to the standard in force at the priority date of the application, in case the year of the standard is not indicated.

[0068] 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 disclosure. 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 disclosure 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.

[0069] Unless otherwise defined, all terms used in disclosing the disclosure, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present disclosure.

[0070] The terms “polyethylene” (PE) and “ethylene polymer” may be used synonymously. The term “polyethylene” encompasses ethylene homopolymer as well as ethylene copolymer resin which can be derived from ethylene and one or more comonomers selected from the group consisting of C3-C20 alpha-olefins, such as propylene, 1 -butene, 1 -pentene, 4-methyl-1- pentene, 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene, 1 -tetradecene, 1 -hexadecene, 1- octadecene and 1-eicosene.

[0071] The term “fluff’ refers to polyethylene material with the hard catalyst particle at the core of each grain and is defined as the polymer material after it exits the polymerization reactor (or the final polymerization reactor in the case of multiple reactors connected in series).

[0072] The terms “polyethylene resin” or “ethylene homopolymer resin” or “ethylene copolymer resin” refer to polyethylene fluff that is extruded. As used herein, the term “polyethylene” may be used as a shorthand for “polyethylene resin”.

[0073] 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 PCRs are made of recycled products from waste created by consumers. The terms “PostIndustrial Resin”, which may be abbreviated as “PIR”, is used to denote the waste components from pre-consumer resins during packaging processes. In other words, the PIRs are made of recycled products created from scrap by manufacturers.

[0074] The term “recycled polyethylene composition” or “recycled polyethylene-containing material” contrasts with the term “virgin polyethylene composition” “virgin polyethylene-containing material”, the term “virgin” is used to denote a polyethylene composition or material directly obtained from a polyethylene-containing polymerization plant. The terms “directly obtained” is meant to include that the polyethylene composition may optionally be passed through a pelletization step, or an additivation step or both.

[0075] Under normal production conditions in a production plant, it is expected that the melt index (MI2, HLMI, MI5) will be different for the fluff than for the polyethylene resin. Under normal production conditions in a production plant, it is expected that the density will be slightly different for the fluff than for the polyethylene resin (if PCR resins are considered, it is not a question of fluff or pellets but it is a question of flakes or pellets). Unless otherwise indicated, density and melt index for the polyethylene resin refer to the density and melt index as measured on the polyethylene resin as defined above.

[0076] The invention provides for a process to produce a cellulosic-polyethylene composite material comprising the step of melt blending a compatibilizer with a polyethylene resin, a cellulosic particulate component, and an optional lubricant, to obtain a cellulosic-polyethylene composite material wherein the compatibilizer is provided at a content of more than 1.0 wt.% based on the total weight of the cellulosic-polyethylene composite material, wherein the compatibilizer:

[0077] - is a grafted resin comprising a blend of polyethylene and polypropylene, wherein the polyethylene and / or polypropylene is grafted with a grafting agent being or comprising one or more selected from maleic anhydride, glycidyl methacrylate, methyl methacrylate, acrylic acid, butyl acrylate, vinyl acetate, diethyl maleate, acrylamide, acrylonitrile, and any mixture thereof; and wherein polyethylene is present at a content of at least 50.0 wt.% based on the total weight of the compatibilizer;

[0078] - has a melt index MI2 of at least 6.0 g / 10 min as determined according to ISO 1133- 2011 at 190 °C under a load of 2.16 kg;

[0079] - a complex viscosity at 0.1 rad / sec at 190 °C of at most 25,000 Pa.s as determined according to the method of the description; and a ratio of complex viscosity at a frequency of 0.1 rad / sec to the complex viscosity at a frequency of 100 rad / sec of at most 10 said ratio being measured at 190 °C according to the method of the description; and in that, the ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin is at least 6.0; and in that the resulting cellulosic-polyethylene composite material has a content of polypropylene of from 0.20 wt.% to 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR.

[0080] For example, the process of producing a cellulosic-polyethylene composite material comprises the sub-step of providing the compatibilizer, the polyethylene resin the cellulosic particulate component, and the optional lubricant wherein the polyethylene resin is provided at a content of at least 20.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; the cellulosic particulate component is provided at a content ranging from 10.0 to 70.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and the compatibilizer is provided at a content ranging from more than 1.0 wt.% to at most 40.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the lubricant is provided at a content ranging from 0 to 5.0 wt.% based on the total weight of the cellulosic-polyethylene composite material. The polyethylene resin is provided at a content of at least 20.0 wt.%; such as ranging from 20.0 to 80.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; preferably, ranging from 25.0 to 75.0 wt.%; more preferably ranging from 30.0 to 70.0 wt.%.

[0081] The cellulosic particulate component is provided at a content ranging from 10.0 wt.% to 70.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; preferably, ranging from 20.0 to 60.0 wt.%; more preferably ranging from 30.0 to 50.0 wt.%.

[0082] The compatibilizer is provided at a content of at least 1.0 wt.%, such as ranging from 1.0 wt.% to 40.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; preferably, ranging from 1.5 to 35.0 wt.%; more preferably ranging from 2.0 to 30.0 wt.%; even more preferably ranging from 2.0 to 25.0 wt.%, and most preferably ranging from 2.5 to 20.0 wt.%.

[0083] In an embodiment, a low content of the compatibilzer is provided such as a content ranging from 1.0 wt.% to 10.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; preferably, ranging from 1.5 to 8.0 wt.%; more preferably ranging from 2.0 to 6.0 wt.%; even more preferably ranging from 2.0 to 5.0 wt.%, and most preferably ranging from 2.5 to 4.0 wt.%.

[0084] The compatibilizer is provided at a content ranging from 8.0 wt.% to at most 40.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; preferably, ranging from 9.0 to 35.0 wt.%; more preferably ranging from 10.0 to 30.0 wt.%; even more preferably ranging from 11 .0 to 25.0 wt.%, and most preferably ranging from 12.0 to 20.0 wt.%.

[0085] When present, the lubricant is provided such as a content ranging from 0.1 wt.% to 5.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; preferably, ranging from 0.5 to 4.5 wt.%; more preferably ranging from 0.8 to 4.2 wt.%; even more preferably ranging from 1 .0 to 4.0 wt.%, and most preferably ranging from 1 .2 to 3.8 wt.%.

[0086] In an embodiment, the process is devoid of a step of addition of a lubricant.

[0087] In an embodiment, the process comprises the sub-step of grafting a raw polyethylenecontaining material to produce said compatibilizer. The raw polyethylene-containing material is a blend of polyethylene and polypropylene that has not yet undergone the grafting process. The raw polyethylene-containing material is a blend of polyethylene and polypropylene comprising polyethylene selected from virgin polyethylene, recycled polyethylene, and any mixture thereof; and polypropylene selected from virgin polypropylene, recycled polypropylene, and any mixture thereof. It is understood that the polyethylene and polypropylene respective content in the raw polyethylene-containing material is the same as in the compatibilizer. In an embodiment, the process comprises the sub-step of preparing the polyethylene wax by thermal treatment of a raw polyethylene-containing material.

[0088] In a preferred embodiment, the process comprises preparing the compatibilizer by extruding a raw polyethylene-containing material with a grafting agent using an extruder with one or more thermal regulation devices, wherein extrusion is performed together with thermal treatment of the polyethylene-containing material at a maximum barrel temperature Ts of at least 315 °C in one or more hot zones of the extruder and wherein the raw polyethylene-containing material has a melt index (Ml R) ranging from 0.1 to 5.0 g / 10 min as determined according to ISO 1133- 2011 at 190 °C under a load of 2.16 kg.

[0089] For example, preparing the compatibilizer comprises the following steps: a) providing a twin-screw extruder with one or more thermal regulation devices; b) providing a raw polyethylene-containing material comprising at least 50 wt.% of polyethylene based on the total weight of the polyethylene-containing material; c) providing a grafting agent in a content ranging from 0.8 to 10.0 wt.% based on the total weight of the polyethylene-containing material provided on step (b), wherein the grafting agent comprises at least one double bound per molecule; d) extruding the polyethylene-containing material and the grafting agent to obtain a compatibilizer; wherein step (d) of extruding comprises a thermal treatment of the polyethylene-containing material at a maximum barrel temperature Ts ranging from 315°C to 410 °C in one or more hot zones of the extruder wherein the thermal treatment is performed by self-heating of the material; and e) recovering a compatibilizer.

[0090] For example, to produce the compatibilizer the maximum barrel temperature Ts ranging from 315 °C to 410°C in step (d) is obtained by self-heating of the material wherein the extruder is a twin screw extruder and the one or more hot zones have a total length equal to or greater than 6 D with D being the screw diameter, wherein the extrusion is performed with mechanical specific energy greater than or equal to 0.30 kWh / kg, wherein the screw profile comprises at least one hot zone with successive kneading blocks elements over a length of at least 4 D followed by a left-handed element with D being the screw diameter, wherein the thermal regulation devices, are set to initial imposed barrel temperatures ranging between 240 and 320 °C, and are switched off when the barrel temperature in the zone spontaneously exceeds the imposed barrel temperature by at least 3 °C without the need of external heat application. The process of grafting polyethylene-containing material involves increasing the melt index of the said polyethylene-containing material to produce a compatibilizer with a melt index that is increased by a factor k of more than 2.0; preferably by a factor k of at least 3.0; preferably by a factor k of at least 5.0; preferably by a factor k of at least 6.0; preferably by a factor k of at least 8.0; preferably by a factor k of at least 10.0; preferably by a factor k of at least 15.0; preferably by a factor k of at least 20.0; preferably by a factor k of at least 40.0.

[0091] So that the ratio of the melt index of the compatibilizer (MI2 T) to the melt index of the polyethylene-containing material (MI2 R) is more than 2.0; preferably of at least 3.0, preferably by at least 5.0; preferably at least 6.0; preferably at least 8.0; preferably at least 10.0; preferably at least 15.0; preferably at least 20.0; preferably at least 40.0.

[0092] The treatment of the raw polyethylene-containing material to obtain a compatibilizer is performed by extrusion wherein step (d) of extruding comprises a thermal treatment of the polyethylene-containing material at a maximum barrel temperature Ts of at least 315 °C and at most 410°C in one or more hot zones of the extruder; preferably wherein extrusion is performed with a residence time of less than 10 min.

[0093] The extruder is a twin-screw extruder. The extruder is a twin-screw extruder provided with a screw profile that shows an aggressive design, as shown in Figure 1 , to impart high mechanical energy to the polyethylene-containing material.

[0094] As known to the person skilled in the art, thermal regulation devices can be used as heating means to impart thermal energy to the polyethylene-containing material in the extruder, in addition to the thermal energy already generated by the mixing.

[0095] Extrusion mixing varies with the type of screw and screw profile and is capable of significant generation of mechanical energy, such as shear energy and / or elongation energy. Therefore, energy is introduced into the extrusion process in terms of mechanical energy and thermal energy. Heating and / or cooling of the barrels can be achieved, for example, electrically, by steam, or by the circulation of thermally controlled liquids such as oil or water.

[0096] The extruder screw comprises a screw main body, that is composed of cylindrical elements and an axis of rotation supporting the elements. The axis of rotation extends straight from its basal end to its tip. In a state in which the extruder screw is rotatably inserted in the cylinder of the barrel, the basal end of the extruder screw is positioned on one end side of the barrel, on which the supply port is provided, and the tip of the extruder screw is positioned on the other end side of the barrel, on which the discharge port is provided.

[0097] Screw extruders have a modular system that allows different screw elements to be drawn into the central shaft to build a defined screw profile. The extruder screw may comprise one or more elements selected from conveying elements, kneading elements, right-handed (normal) screw elements, left-handed (inverse) screw elements and any combination thereof. The elements are arranged in a defined order from the basal end to the tips of the extruder screw and this order, as well as the type and number of elements involved, defines the screw profile. Extruders and screw elements are commercially available for example at Leistritz.

[0098] In an embodiment of the disclosure, the treatment of the polyethylene-containing material is handled by mechanical energy.

[0099] When high mechanical energy is requested, the extruder provided has a specific screw profile that is built to be “aggressive”, meaning that high mechanical energy will be imparted to the polyethylene-containing material. High mechanical energy will result in an increase of the temperature in the extruder as known to the person skilled in the art so that the thermal treatment is performed by self-heating of the material. Self-heating of the material is achieved from viscous dissipation in a twin-screw extruder.

[0100] In such an embodiment, the twin-screw extruder is selected to comprise one or more hot zones, preferably being filled mixing zones, wherein the total length of the one or more hot zones is equal to or greater than 6 D with D being the screw diameter.

[0101] It is understood that in case the screw profile is selected to comprise a single hot zone, then the total length of the said hot zone is equal to or greater than 6 D with D being the screw diameter. In such a case, the hot zone is also the melting zone of the twin-screw extruder.

[0102] In case, the screw profile comprises two or more hot zones, then a first hot zone comprises successive kneading blocks elements over a length of at least 4 D followed by a left-handed element with D being the screw diameter, and one or more additional hot zones placed downstream the first hot zone are filled mixing zones, each comprising kneading blocks elements over a length of at least 4 D followed by a kneading left-handed element or by a lefthanded element with D being the screw diameter. For example, the twin-screw extruder comprises two filled mixing zones wherein each of the filled mixing zones has a length equal to or greater than 4 D with D being the screw diameter. Preferably the first hot zone is or comprises the melting zone of the extruder. For example, the twin-screw extruder comprises three filled mixing zones wherein each of the filled mixing zones has a length equal to or greater than 4 D with D being the screw diameter.

[0103] Various mixing elements could be considered in the one or more hot zones but the most preferred ones do not drive any forward conveying (dispersive kneading blocks elements with disks offset by 90 degrees). Other disk offset angles could be considered (examples 30 degrees, 45 degrees, 60 degrees) but 90 degrees is preferred. The preferred minimum width of the disk is 0.3 D. Thus, preferably, the successive kneading blocks elements of at least one hot zone comprise disks with disks offset by 90 degrees and a disk width of at least 0.3 D wherein D is the screw diameter. More preferably the successive kneading blocks elements of three hot zones comprise disks with disks offset by 90 degrees and a disk width of at least 0.3 D wherein D is the screw diameter.

[0104] For example, the twin-screw extruder comprises more than two filled mixing zones wherein the total length of filled mixing zones is equal to or greater than 8 D with D being the screw diameter. For example, the twin-screw extruder comprises more than three filled mixing zones wherein the total length of filled mixing zones is equal to or greater than 9 D with D being the screw diameter

[0105] For example, the strong melting zone of the twin-screw extruder is made of successive mixing elements over a length of 4 D, with D being the screw diameter, followed by a left-handed element; preferably a full-flight left-handed element.

[0106] In a preferred embodiment, the thermal regulation devices of twin-screw extruder allow cooling the barrels and the process comprises switching off the thermal regulation devices when the barrel temperature in the zone spontaneously exceeds the imposed barrel temperature by at least 1 °C without the need for external heat application; preferably, by at least 2 °C, preferably, by at least 3 °C; more preferably by at least 5 °C; even more preferably, by at least 8 °C; and most preferably, by at least 10 °C.

[0107] Indeed, when starting extrusion, thermal regulation devices will be switched on, in particular in the melting zone to allow the material to melt. Then, when the polymer is self-heating the thermal regulation devices are switched off to allow the increase of the temperature inside the extruder.

[0108] In a preferred embodiment, step (d) of extruding the polyethylene-containing material comprises performing the extrusion with mechanical specific energy greater than or equal to 0.25 kWh / kg, preferably greater than or equal to 0.28 kWh / kg; more preferably greater than or equal to 0.30 kWh / kg; even more preferably greater than or equal to 0.35 kWh / kg; most preferably greater than or equal to 0.40 kWh / kg and even most preferably greater than or equal to 0.45 kWh / kg.

[0109] High rotation screw speeds are preferred, but the precise value of a high rotation screw speed is “extruder diameter” dependent. For example, when considering a diameter D of 18 mm twin- screw extruder, high rotational screw speed is considered to be higher than 500 rpm, preferably higher than 800 rpm. For example, when considering a diameter D = 58 mm twin-screw extruder, high rotational screw speed is considered to be higher than 250 rpm, preferably higher than 350 rpm. Non-limiting examples of suitable extruder screws with specific screw profiles are illustrated in figures 1 and 2.

[0110] In such an embodiment, step (d) is performed a maximum barrel temperature of at least 315 °C; preferably at least 320 °C; more preferably at least 330 °C; even more preferably at least 340 °C, and most preferably at a temperature of at least 350 °C, or at a temperature of at least 360 °C.

[0111] For example, step (d) of extruding the polyethylene-containing material comprises a thermal treatment at a maximum barrel temperature of at most 410 °C in at least one hot zone; preferably at a temperature of at most 405 °C; more preferably at a temperature of at most 400 °C; even more preferably at a temperature of at most 395 °C and most preferably at a temperature of at least 390 °C.

[0112] The thermal treatment of material in step (d) is preferably performed a maximum barrel temperature ranging from 315 to 410 °C; preferably, ranging from 320 °C to 405 °C; more preferably ranging from 330 °C to 405 °C; even more preferably, ranging from 340 °C to 400 °C ; most preferably at a maximum barrel temperature ranging from 360 to 400 °C and even most preferably at a maximum barrel temperature ranging from 340 to 395 °C or ranging from 350 °C to 395 °C, or at a maximum barrel temperature ranging from 320 to 390 °C. The maximum barrel temperature Ts is the highest temperature amongst the imposed or measured temperatures along the extruder.

[0113] The extrusion conditions may be adapted by the person skilled in the art to impart sufficient energy to obtain a compatibilizer with a melt index (MI2 T) in the targeted range.

[0114] Screw speed can be adapted in function of the targeted maximum barrel temperature Ts and of the capacity of the extruder. Higher screw speed allows a higher increase of the polymer temperature. For example, the screw speed ranging from 100 to 1200 rpm; preferably from 110 rpm to 1200 rpm; more preferably from 150 rpm to 1100 rpm; even more preferably from 200 rpm to 1000 rpm; most preferably from 300 rpm to 900 rpm; and even most preferably from 320 to 800 rpm or from 350 to 1200 rpm.

[0115] In an 18 mm screw diameter twin-screw extruder, the preferred screw speed is higher than 500 rpm; in a 58 mm screw diameter twin-screw extruder, the preferred screw speed is higher than 250 rpm.

[0116] For example, step (d) of extruding the polyethylene-containing material comprises performing the extrusion with a residence time of less than 10 minutes, such as ranging from 10 seconds to 10 minutes; preferably with a residence time ranging from 20 seconds to 5 minutes; more preferably with a residence time ranging from 10 to 180 seconds or from 10 to 120 seconds or from 20 to 100 seconds or from 30 to 80 seconds.

[0117] For example, the extruder comprises one or more venting parts at the end of the extruder (before the die). Such venting parts, connected to a vacuum pump, allows removing at least a part of the unreacted grafting agent.

[0118] For example, the extruder is selected to have a surface treatment. For example, one or more elements of the extruder are made of CrVNb microalloyed steel. Extruders with surface treatments are commercially available from Leistritz.

[0119] The process according to the disclosure comprises a step (c) of providing a grafting agent comprising at least one double bound per molecule. For example, the grafting agent comprises at least one vinyl group per molecule.

[0120] For example, the grafting agent comprises or consists of one or more functional monomers selected from maleic anhydride (MAH), glycidyl methacrylate (GMA), methyl methacrylate (MMA), acrylic acid (AAc), butyl acrylate (BA) vinyl acetate (VA), diethyl maleate (DEM), acrylamide (AAm), acrylonitrile (CAN), and any mixture thereof. With preference, the grafting agent is or comprises maleic anhydride (MAH).

[0121] The grafting agent is provided in a content ranging from 0.1 to 10.0 wt.% or from 0.5 to 10.0 wt.% or from 0.8 to 10.0 wt.% based on the total weight of the polyethylene-containing material; preferably, from 0.9 to 8.0 wt.%; more preferably, from 1.0 to 6.0 wt.%; even more preferably, from 1.1 to 5.5 wt.%; most preferably, from 1.2 to 5.0 wt.%; even most preferably, from 1.3 to 4.5 wt.%; or from 1 .5 to 4.0 wt.%; or from 2.0 to 5.0 wt.%.

[0122] For example, the grafting agent is provided in a content of at least 0.1 wt.% or at least 0.2 wt.% or at least 0.5 wt.% or at least 0.7 wt.% or at least 0.8 wt.% or at least 0.9 wt.% based on the total weight of the polyethylene-containing material; preferably, at least 1.0 wt.%; more preferably at least 1.1wt.%; even more preferably at least 1.2 wt.%; most preferably at least 1 .3 wt.% and even most preferably at least 1 .5 wt.% or at least 1 .8 wt.%; or at least 2.0 wt.%.

[0123] For example, the grafting agent is provided in a content of at most 10.0 wt.% or at most 8.0 wt.% based on the total weight of the polyethylene-containing material; preferably, at most 6.0 wt.%; more preferably, at most 5.5 wt.%; even more preferably at most 5.0 wt.%; most preferably at most 4.5 wt.% and even most preferably at most 4.0 wt.%.

[0124] The grafting agent is introduced in the extruder by the main hoper, for example via a specific dosing system, or via a lateral injection in the extruder; preferably, the grafting agent is introduced via the main hoper. The step of providing a grafting agent may further comprise providing one or more additives in addition to the grafting agent. For example, one or more additives such as, by way of example, antioxidants, light stabilizers, acid scavengers, flame retardants, lubricants, antistatic additives, nucleating / clarifying agents, colourants, slip agents, anti-blocking agents, processing aids, and any mixture thereof.

[0125] Although peroxides are not required, in an embodiment, the process further comprises providing one or more peroxides in addition to the grafting agent.

[0126] For example, the content of peroxide is at most 1000 ppm based on the total weight of the polyethylene-containing material; preferably at most 800 ppm; more preferably at most 500 ppm; even more preferably at most 200 ppm and most preferably at most 100 ppm.

[0127] For example, the content of peroxides ranges from 0 to 1000 ppm based on the total weight of the polyethylene-containing material; preferably from 10 to 800 ppm; more preferably from 20 to 500 ppm, even more preferably from 30 to 250 ppm, and most preferably from 50 to 100 ppm.

[0128] For example, the one or more peroxides are or comprise organic peroxides selected from the group consisting of diacetyl peroxide, cumyl-hydro-peroxide, dibenzoyl peroxide, dialkyl peroxide, 2,5-methyl-2,5-di(terbutylperoxy)-hexane, and combinations thereof.

[0129] In a preferred embodiment, the process is devoid of a step of providing one or more peroxides in addition to the grafting agent. In such an embodiment no peroxides are used so that the content of peroxide is 0 ppm.

[0130] Step (e) comprises recovering a compatibilizer that is the grafted and treated polyethylenecontaining material.

[0131] For example, the compatibilizer has a melt index (MI2 T) ranging from 5.5 to 50.0 g / 10 min or from 6.0 to 50.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably from 6.0 to 45.0 g / 10 min or from 6.2 to 40.0 g / 10 min; preferably from 6.4 to 30.0 g / 10 min; more preferably, from 6.6 to 25.0 g / 10 min; even more preferably from 6.8 to 20.0 g / 10 min; and most preferably from 6.8 to 18.0 g / 10 min.

[0132] For example, the compatibilizer has a melt index MI2 of at most 50.0 g / 10 min or at most 45.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably, at most 40.0 g / 10 min or at most 35.0 g / 10 min; more preferably, at most 30.0 g / 10 min or at most 28 g / 10 min; even more preferably, at most 25.0 g / 10 min; most preferably, at most 24.0 g / 10 min; and even most preferably, at most 20.0 g / 10 min or at most 18.0 g / 10 min. For example, the compatibilizer has a melt index MI2 of at least 5.5 g / 10 min or at least 5.8 g / 10 min; preferably, at least 6.0 g / 10 min or at least 6.2 g / 10 min; more preferably, at least 6.4 g / 10 min; even more preferably, at least 6.6 g / 10 min; most preferably, at least 6.8 g / 10 min; and even most preferably, at least 6.9 g / 10 min.

[0133] In an embodiment, the compatibilizer has a grafting agent content of at least 0.3 wt.% based on the total weight of the compatibilizer as determined by the titration method of the description.

[0134] For example, the grafting agent is present in the compatibilizer at a content ranging from 0.3 to 5.0 wt.% based on the total weight of the compatibilizer; preferably from 0.5 to 4.0 wt.%; more preferably from 0.6 to 3.5 wt.%; even more preferably from 0.8 to 2.5 wt.%; and most preferably from 1.0 to 2.2 wt.%, or from 1.2 to 3.5 wt.%, or from 1.4 to 3.0 wt.%. It is understood that the grafting agent content represents the grafted content as determined by titration and does not include the unreacted grafting agent. In other words, the grafting agent content determination is performed after purification as described in the methods. Purification can include a venting procedure performed at the end of the extruder. The compatibilizer (i.e., the grafted polyethylene) corresponds to the starting material that has been grafted and thermally treated to increase the melt index.

[0135] In particular, it was found that the compatibilizer has a ratio of complex viscosity at a frequency of 0.1 rad / sec to the complex viscosity at a frequency of 100 rad / sec of at most 20, said ratio being measured at 190 °C; preferably, of at most 18; preferably, of at most 15; preferably, of at most 12; preferably, of at most 10.0; preferably, of at most 9.0; more preferably, of at most 8.5; even more preferably, of at most 8.0; and most preferably, of at most 7.0.

[0136] In an embodiment, the compatibilizer has a complex viscosity at 0.1 rad / sec at 190 °C of at most 25,000 Pa s; preferably at most 22,000 Pa.s; preferably at most 20,000 Pa.s; preferably at most 18,000 Pa.s; more preferably at most 15,000 Pa.s; even more preferably of at most 12,000 Pa.s most preferably of at most 10,000 Pa.s; and even most preferably of at most 9,000 Pa.s; or at most 8,000 Pa.s, or at most 5,000 Pa.s, or at most 4,000 Pa.s, or at most 3,500 Pa.s, or at most 3,000 Pa.s, or at most 2,500 Pa.s, or at most 2,300 Pa.s,

[0137] In an embodiment, the compatibilizer has a complex viscosity at 0.1 rad / sec at 190 °C ranging from 200 to 25,000 Pa s; preferably from 250 to 22,000 Pa.s; preferably from 300 to 20,000 Pa.s; preferably from 350 to 18,000 Pa.s; more preferably from 380 to 15,000 Pa.s; even more preferably from 400 to 12,000 Pa.s; most preferably from 410 to 10,000 Pa.s; and even most preferably from 410 to 9,000 Pa.s; or from 400 to 8,000 Pa.s, or from 400 to 5,000 Pa.s.

[0138] With preference, the compatibilizer has an Mz / Mw of at most 7.0 as determined by size exclusion chromatography; preferably at most 6.0; preferably at most 5.0. For example, the compatibilizer has a number average molecular weight (Mn) ranging from 8,000 to 20,000 Da as determined by size exclusion chromatography; preferably ranging from 10,000 to 18,000 Da or from 12,000 to 17,000 Da.

[0139] For example, the compatibilizer further has a tan delta (G7G’) at 0.1 rad at 190 °C above 2.5; preferably of at least 3.0; more preferably of at least 5.0 and even more preferably of at least 10.0.

[0140] In one embodiment, the polyethylene-containing material further has a tan delta (G G’ measured at 0.1 rad / s at 190 °C) of at most 3.0; preferably of at most 2.6.

[0141] In one embodiment, the polyethylene-containing material further has a tan delta (G G’ measured at 0.1 rad / s at 190 °C) ranging from 0.5 to 3.0; preferably, from 0.8 to 2.6.

[0142] For example, the compatibilizer is a grafted resin comprising a blend of polyethylene and polypropylene, wherein polypropylene is present at a content ranging from 0.5 to 50.0 wt.% based on the total weight of the compatibizer, preferably from 0.8 to 40.0 wt.% or from 1 .0 to 30.0 wt.%; more preferably from 1.2 to 25.0 wt.%, even more preferably from 1.5 to 20.0 wt.%; most preferably from 2.0 to 15.0 wt.% and even most preferably from 2.5 to 10.0 wt.%.

[0143] The optional lubricant

[0144] The process further comprises providing from 0 to 5.0 wt.% of a lubricant selected from zinc stearate, calcium stearate, magnesium stearate, ethylene bis-stearamide (EBS), polyester wax, polypropylene wax, polyethylene wax, ethylene bis-oleamide, stearyl stearate, distearyl phthalate, pentaerythritol adipate stearate, ethylene glycol distearate, pentaerythritol tetrastearate, glycerol tristearate, polyethylene glycol 400 monostearate, glycerol monooleate, glycerol distearate, and any mixture thereof.

[0145] In the embodiments wherein the lubricant is present, the step of melt blending comprises melt blending the lubricant with the other components to obtain a cellulosic-polyethylene composite material.

[0146] In a preferred embodiment, the lubricant is or comprises polyethylene wax, and the step of melt blending comprises melt blending the polyethylene wax with the other components to obtain a cellulosic-polyethylene composite material.

[0147] With preference the polyethylene wax has a number average molecular weight (Mn) of at most 6,000 Da as determined by gel permeation chromatography; preferably at most 4,000 DA; more preferably at most 3,000 Da.

[0148] In one or more embodiments, the process is devoid of a step of addition of a lubricant.

[0149] The raw polyethylene-containing material The raw polyethylene-containing material used to produce the polyethylene wax can be the same or different from the one used to produce the compatibilizer. In a preferred embodiment, they are the same.

[0150] The raw polyethylene-containing material is a recycled polyethylene-containing material or a mixture of virgin and recycled polyethylene-containing materials. In some embodiments, the raw polyethylene-containing material is a recycled polyethylene-containing material. As used herein, the terms “recycled polyethylene composition” encompasses both Post-Consumer Resins (PCR) and Post-Industrial Resins (PIR).

[0151] Suitable polyethylene includes but is not limited to a homopolymer of ethylene, a copolymer of ethylene, and a higher alpha-olefin comonomer. Thus, preferably, the polyethylene in the raw polyethylene-containing material is one or more polyethylene homopolymers, one or more polyethylene copolymers, and any mixture thereof.

[0152] The term "copolymer" refers to a polymer, which is made by linking two different types of monomers in the same polymer chain. Preferred comonomers are alpha-olefins having from 3 to 20 carbon atoms or from 3 to 10 carbon atoms. More preferred comonomers are selected from the group comprising propylene, butene-1 , pentene-1 , hexene-1 , heptene-1 , octene-1 , nonene-1 , decene-1 , and any mixture thereof. Even more preferred comonomers are selected from the group comprising butene-1 , hexene-1 , octene-1 , and any mixture thereof. The most preferred comonomer is hexene-1 .

[0153] The term “homopolymer” refers to a polymer that is made by linking only one monomer in the absence of comonomers. Ethylene homopolymers are therefore essentially without any comonomer. By "essentially without" it is meant that no comonomer is intentionally added during the production of the polyethylene, but can nevertheless be present in up to 0.2 wt.%, preferably in up to 0.1 wt.% and most preferably in up to 0.05 wt.%, relative to the total weight of the polyethylene.

[0154] The raw polyethylene-containing material is selected to comprise polyethylene and polypropylene wherein polyethylene is present in at least 50 wt.% based on the total weight of the raw polyethylene-containing material. With preference, the polyethylene-containing material is selected to comprise at least 55 wt.% of polyethylene based on the total weight of the polyethylene-containing material; preferably, at least 60 wt.%.

[0155] With preference, the raw polyethylene-containing material is a recycled material being a blend of polyethylene and polypropylene, wherein the polypropylene is present at a content ranging from 1.0 to 50.0 wt.% based on the total weight of the raw polyethylene-containing material, preferably from 0.6 to 40.0 wt.% or from 0.8 to 30.0 wt.%; more preferably from 1.0 to 25.0 wt.%, even more preferably from 1.2 to 20.0 wt.%; most preferably from 1.5 to 15.0 wt.% and even most preferably from 1 .8 to 10.0 wt.% or from 2.0 to 5.0 wt.%.

[0156] In an embodiment, the raw polyethylene-containing material is a recycled polyethylenecontaining material. Recycled polyethylene-containing material may contain one or more polymers different from polyethylene and polypropylene selected from polyacrylate, polyethylene terephthalate (PET), polystyrene (PS), and polylactic acid (PLA).

[0157] In an embodiment, the raw polyethylene-containing material is a recycled polyethylenecontaining material comprising films. In such an embodiment, the raw polyethylene-containing material has a melt index (Ml R) ranging from 0.1 to 2.0 g g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg and a density ranging from 0.910 g / cm3to 0.940 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C.

[0158] In an embodiment, the raw polyethylene-containing material is a recycled polyethylenecontaining material comprising blow molded articles. In such an embodiment, the raw polyethylene-containing material has a melt index (Ml R) ranging from 0.5 to 5.0 g g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg and a density ranging from 0.940 g / cm3to 0.970 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C.

[0159] In a general embodiment (whatever the origin of the recycled material), the raw polyethylenecontaining material is a recycled polyethylene-containing material having a melt index (Ml R) ranging from 0.1 to 5.0 g g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg and a density ranging from 0.910 g / cm3to 0.970 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C.

[0160] For example, the raw polyethylene-containing material has a melt index (Ml R) of at least 0.1 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably at least 0.2 g / 10 min.

[0161] For example, the raw polyethylene-containing material has a melt index (Ml R) of at most 5.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably at most 4.5 g / 10 min; more preferably at most 4.0 g10 min; even more preferably at most 3.5 g / 10 min; most preferably at most 3.0 g / 10 min and even most preferably at most 2.8 g / 10 min.

[0162] For example, the raw polyethylene-containing material has a density of at least 0.910 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; preferably, at least 0.912 g / cm3; more preferably, at least 0.915 g / cm3. For example, the raw polyethylene-containing material has a density of at most 0.970 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; preferably, of at most 0.965 g / cm3; more preferably, of at most 0.960 g / cm3; and even more preferably at most 0.956 g / cm3.

[0163] In some embodiments, the raw polyethylene-containing material has an Mz / Mw of at least 4.0 as determined by gel permeation chromatography; preferably, ranging from 4.0 to 50.0; preferably, from 5.0 to 25.0; preferably, from 7.0 to 15.0.

[0164] In some embodiments, the polyethylene-containing material has a complex viscosity at 0.1 rad / sec at 190 °C of ranging from 20,000 to 80,000 Pa s; preferably, ranging from 22,000 to 70,000 Pa s; more preferably, ranging from 25,000 to 60,000 Pa s; and even more preferably, ranging from 30,000 to 50,000 Pa s.

[0165] In some embodiments, the polyethylene-containing material has an Mw / Mn ranging from 5.0 to 30.0 as determined by gel permeation chromatography; preferably ranging from 6.0 to 20.0; preferably ranging from 7.0 to 15.0.

[0166] In some embodiments, the polyethylene-containing material has a complex viscosity ratio above 10; preferably, a complex viscosity ratio of at least 11 ; more preferably, a complex viscosity ratio of at least 12.

[0167] The polyethylene resin

[0168] For example, the polyethylene resin can be selected from a virgin polyethylene resin, a recycled polyethylene, or a mixture of virgin and recycled polyethylene resins. In some embodiments, the polyethylene resin comprises at least 10.0 wt.% of recycled polyethylene based on the total weight of the polyethylene resin; preferably at least 30.0 wt.%: more preferably at least 50.0 w.% and even more preferably at least 80 wt.%. In an embodiment, the polyethylene resin is a recycled polyethylene resin (100 wt.% of recycled polyethylene resin).

[0169] According to the present disclosure, the polyethylene resin is selected from a high-density polyethylene resin, a medium-density polyethylene resin, a low-density polyethylene resin, a linear low-density polyethylene resin and any mixture thereof. With preference, the polyethylene resin is selected from a high-density polyethylene resin, a linear low-density polyethylene resin and any mixture thereof.

[0170] For example, the polyethylene resin has a density ranging from 0.910 to 0.970 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; preferably, ranging from 0.912 g / cm3to 0.965 g / cm3; more preferably, ranging from 0.915 g / cm3to 0.960 g / cm3; and even more preferably, ranging from 0.917 g / cm3to 0.956 g / cm3. In an embodiment, the polyethylene resin has a density of at least 0.910 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; preferably, at least preferably, at least 0.912 g / cm3; more preferably, at least 0.915 g / cm3; even more preferably of at least 0.917 g / cm3.

[0171] For example, the polyethylene resin has a density of at most 0.970 g / cm3or of at most 0.965 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; preferably, of at most 0.962 g / cm3; more preferably, of at most 0.960 g / cm3; and even more preferably, of at most 0.956 g / cm3.

[0172] For example, the cellulosic-polyethylene composite material is for blow-molding applications and the polyethylene resin is suitable for blow-molding applications.

[0173] For example, the polyethylene resin has a melt index (MI2) ranging from 0.1 to 25.0 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg; preferably from 0.1 to 3.0 g / 10 min.

[0174] For example, the polyethylene resin has a melt index (MI2) of at most 25.0 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg; preferably at most 20.0 g / 10 min: more preferably at most 15.0 g / 10 min; even more preferably at most 10.0 g / 10 min; most preferably at most 8.0 g / 10 min; even most preferably at most 5.0 g / 10 min; or at most 4.0 g / 10 min; or at most 3.5 g / 10 min or at most 3.0 g / 10 min.

[0175] For example, the polyethylene resin has a melt index (MI2) of at least 0.1 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg; preferably at least 0.2 g / 10 min.

[0176] The cellulosic particulate component

[0177] Cellulosic particulate can be any known, conventional, or commercially used cellulosic particulate that can be used in cellulosic-thermoplastic composites. Examples of suitable cellulosic particulate can be wood fiber, wood particles, wood chips, ground wood, wood flour, wood flakes, wood veneers, wood laminates, sawdust, paper, newspaper, cardboard, wood pulp fiber, chemical pulp, recycled paper fiber, recycled boxes, recycled box fiber, recycled newspaper, recycled newspaper fiber, recycled computer printout, recycled computer printout fiber, milling tailings, hardwood fiber, Softwood fiber, newsprint, ground newsprint, magazines, ground magazines, books, ground books, ground cardboard, wheat chaff, bamboo fiber, pond sludge, cork and combinations thereof.

[0178] . It will be understood by a person skilled in the art that wood pulp can be any known wood pulp material, for example, thermomechanical wood pulp, chemical thermomechanical wood pulp, and combinations thereof. For example, the cellulosic particulate component is selected from wood fiber, wood particles, wood chips, ground wood, wood flour, wood flakes, wood veneers, wood laminates, sawdust, paper, wood pulp fiber, and combinations thereof.

[0179] Preferably, the cellulosic particulate component is selected from wood fiber, wood flour, and combinations thereof.

[0180] In a preferred embodiment, the step of providing the cellulosic particulate component comprises drying the cellulosic particulate component at a temperature of at least 60°C for a time of at least 24 hours. In case some foam is observed at the die exit of the extruder, an additional drying may be performed.

[0181] The cellulosic-polyethylene composite material

[0182] In a preferred embodiment, the cellulosic-polyethylene composite material has a melt index MI2 of at least 1.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; preferably at least 2.0 g / 10 min; more preferably at least 3.0 g / 10 min and even more preferably at least 4.0 g / 10 min.

[0183] According to the disclosure, the cellulosic-polyethylene composite material comprises at least 0.20 wt.% of polypropylene. With preference, the cellulosic-polyethylene composite material has a content of polypropylene of at least 0.25 wt.% based on the total weight of the cellulosic- polyethylene composite material as determined by13C NMR; preferably at least 0.30 wt.% more preferably at least 0.35 wt.%.

[0184] Advantageously, the cellulosic-polyethylene composite material has a content of polypropylene of at most 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR; preferably, at most 2.5 wt.%; more preferably, at most 2.0 wt.%; even more preferably at most 1.5 wt.%, and most preferably at most 1.0 wt.%.

[0185] For example, the cellulosic-polyethylene composite material has a content of polypropylene ranging from 0.20 to 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR; preferably from 0.25 to 2.5 wt.%; more preferably from 0.30 to 2.0 wt.%; even more preferably from 0.35 to 1.5 wt.%; and most preferably from 0.35 to 1 .0 wt.%.

[0186] According to the disclosure, at least a part of the polypropylene comes from the compatibilizer. Additional polypropylene can come from the polyethylene resin when it is or contains a recycled polyethylene resin containing polypropylene, and / or can be added to the composite as a distinct component. 1

[0187] The disclosure also relates to an article manufactured from the cellulosic-polyethylene composite material

[0188] In a preferred embodiment, the article is an extruded article, an injection moulded article, or a compression moulded article.

[0189] In case the article is an extruded article, it preferably comprises polyethylene wax.

[0190] The article can be a multi-layered article comprising at least one layer comprising the decribed cellulosic-polyethylene composite material . With preference, the article is an injection moulded article or a compression moulded article.

[0191] The invention also provides for a process to produce an article comprising producing a cellulosic-polyethylene composite material and manufacturing an article from the cellulosic- polyethylene composite material, with preference manufacturing is performed by extrusion, or compression molding, or injection molding.

[0192] Test methods

[0193] The melt flow index MI2 of the polyethylene is determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg.

[0194] The HLMI of the polyethylene is determined according to ISO 1133-2011 at 190 °C under a load of 21.6 kg.

[0195] The Mn, Mw, Mz, Mw / Mn and Mz / Mw: The molecular weight (Mn(number average molecular weight), Mw(weight average molecular weight) and molecular weight distributions D (Mw / Mn) and D’ (Mz / Mw) were determined by size exclusion chromatography (SEC. Briefly, a GPC-IR5 from Polymer Char was used: 10 mg polyethylene sample was dissolved at 160 °C in 10 ml of trichlorobenzene for 1 hour. Injection volume: about 400 pl, 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 (2800-3000 cm-1). Calibration: narrow standards of polystyrene (PS) (commercially available). Calculation of molecular weight Mi of each fraction i of eluted polyethylene is based on the Mark-Houwink relation (log (MpE) = 0.965909 x log (Mps) - 0.28264) (cut off on the low molecular weight end at MPE = 1000).

[0196] The molecular weight averages used in establishing molecular weight / property relationships are the number average (Mn), weight average (Mw) and z average (Mz) molecular weight. These averages are defined by the following expressions and are determined from the calculated Mi:

[0197] Here Nj and Wj are the number and weight, respectively, of molecules having molecular weight Mi. The third representation in each case (farthest right) defines how one obtains these averages from SEC chromatograms, hi is the height (from baseline) of the SEC curve at the ithelution fraction and Mj is the molecular weight of species eluting at this increment.

[0198] The molecular weight distribution (MWD) is then calculated as Mw / Mn.

[0199] The comonomer content in polyethylene, the polypropylene content of other polymer content in a polyethylene-polypropylene blend are determined by13C-NMR analysis of pellets according to the method described by G.J. Ray et al. (Macromolecules, 1977, 10, (4), 773- 778).

[0200] Crystallisation temperature (Tc) and Melting temperature (Tm) are determined according to ISO 11357-3:2018 on a DSC Q2000 instrument by TA Instruments. To erase the thermal history the samples are first heated to 220 °C and kept at 220 °C for 3 minutes. Then the polymer is cooled at -20 °C / min. up to 20 °C and kept at 20 °C for 3 minutes. The crystallization temperature is determined during this cooling step. The crystallization temperature Tc corresponds to the temperature of the extremum of the spectrogram presenting the heat flux associated with the polymer as a function of the temperature during its cooling. The polymer is then melted up to 220 °C at 20 °C / min. and the melting temperature is determined during this heating step. The melting temperature corresponds to the temperature of the extremum of the spectrogram presenting the heat flux associated with the polymer as a function of the temperature during its melting.

[0201] The density was measured according to the method of standard ISO 1183-1 :2012 (immersion method) at a temperature of 23 °C. ity: The complex shear modulus G*(w) G’(w)+jG”(w) (J2=-

[0202] 1 , G’(w): storage modulus and G”(w): loss modulus) was determined using a DHR-2, a stress- controlled rheometer from TA Instruments. Frequency sweeps have been carried out in the linear domain (1 % strain) at 190°C from 100 to 0.01 rad.s-1under nitrogen flow to prevent thermal oxidative degradation. The used geometry was 25 mm diameter parallel plates with a 2 mm gap. The samples (25 mm diameter, 2 mm thickness) for these experiments were obtained beforehand using an injection press (Babyplast type). The complex viscosity ?7*(®) is calculated according to the following equation of the linear viscoelasticity:

[0203] Determination of the MA content (titration)

[0204] Few grams of the grafted product are purified in a vacuum oven at 140 °C for 24h, this step is crucial to remove all of the unreacted maleic acid by evaporation beyond the melting temperature of the polymer. This step is not needed when a venting procedure is performed at the end of the extruder.

[0205] The grafted maleic anhydride reacts with water hence forming the maleic acid form (diacid) which is optically active due to the presence of one asymmetric carbon in its molecule.

[0206] Hydrolysis of maleic anhydride to form maleic acid.

[0207] The MA content of the purified products is calculated from the acid number. 0.5 g of the grafted polymer with maleic anhydride are dissolved in xylene at 120 °C in a flask with high agitation for 30 min. Then water drops are added to the solution after lowering the temperature to c.a. 100 °C. The hot solution is then titrated immediately with ethanolic 0.05N KOH using three to four drops of 1 % thymol blue in DMF indicator, the equivalence is observed when the solution turns from clear yellow to blue. A 0.5 - 1 .0 mL excess of KOH solution is added, and the deep blue color was back -titrated to yellow end point by the addition of 0.05N isopropanolic HOI to the hot solution. The ethanolic KOH solution is previously standardized against a solution of known concentration of potassium hydrogen phthalate in water using phenolphthalein indicator.

[0208] The acid number and the maleic anhydride content were calculated as follows: 56,1 -MA acid number x 98

[0209] MA^ = 2 X 561

[0210] The grafted MA content is classified into 4 categories:

[0211] Low : 0.2 - 0.5 %

[0212] Medium : 0.5 - 0.8 % High : 0.8 - 1 %

[0213] Very high : above 1 % (1 - 1.5 %)

[0214] Ultra high : above 1.5 %

[0215] The Young Modulus, Strain at Break, Stress at Break, were determined according to ISO-527- 1 : Uniaxial tensile strength tests were performed on using a robot Zwick Kuka testing machine. To comply with ISO-527-1 standard, the testing speed was 50 mm / min to measure yield stress and elongation at break, and 1 mm / min to determine the Young’s modulus. ISO 527 type 1 B samples were tested for each formulation.

[0216] The Impact Strength was determined according to ISO 180: C-Notched Charpy impact test samples were performed on V-Notch Type 1A samples (80 x 10 x 4 mm) at ambient temperature (23 C) following ISO 180. At least ten samples were tested for each series to assure good reproducibility of the measurements.

[0217] EXAMPLES

[0218] Example 1 : Preparation of the compatibilizer

[0219] PE-g-MA7 was produced at a screw speed of 750 rpm and a throughput of 300 Kg / h with a torgue of 64 %.

[0220] The extruder was a ZSE 50MAXX pilot line (50 mm diameter twin screw extruder with L / D = 48) with three hot zones each comprising one left-handed element.

[0221] The mechanical specific energy (MSE) was 0.359 kWh / kg. 3% of maleic anhydride was introduced (pellets introduced in the hooper). The pressure at the melt pump was 33 bar. The temperature (Tmelt) measured inside the extruder, close to the die was 270°C

[0222] Polyethylene flakes (post-consumer resin - PCR-PE - flakes described as “standard noncolor sorted bottles from the yellow bag”) were used. The initial melt index of the PCR-PE - flakes ranged from 0.6 to 1.8 g / 10 min. The recycled polyethylene material used contained about 3 wt.% of polypropylene.

[0223] Example 2 Preparation of the composites

[0224] Selection of the material

[0225] Compatibilizers PE-g-MAH products:

[0226] BIND1 : Polybond 3009, a commercial grade from SI Group (previously Chemtura), characterized by (information taken in the datasheet) an MI2 of 5 g / 10 min, a grafting level between 0.8 and 1.2 wt. %, a density = 0.95 and a melting temperature = 127°C. BIND2: PE-g-MA7 grade described in example 1 , this grade being, considering its melt index value (MI2 = 6.93 g / 10 min). The grafting level was also between 0.8 and 1.2 wt. %. The complex viscosity at 0.1 rad / sec at 190 °C was 1 ,772 Pa.s. The complex viscosity at 100 rad / sec at 190 °C was 457.7 Pa.s. The ratio of complex viscosity at a frequency of 0.1 rad / sec to the complex viscosity at a frequency of 100 rad / sec was 3.87.

[0227] The wood flour used was MOD-FIBER PLAST -CB 150E (softwood), commercial products from La.So.Le company.

[0228] The polyethylene resin used was M6040 commercial grade available from TotalEnergies with a melt index of 0.9 g / 10 min at 190°C and 2.16 kg and a density of 0.934 g / cm3.

[0229] Wood plastic composite (WPC) production

[0230] Production of WPC pellets was performed using a ZSK26 twin-screw extruder (L / D = 52) with a standard screw profile (i.e. with only one left-handed element, one mixing element in front of it and mainly transport elements in the rest of the screw) and an imposed temperature profile of 190 °C in the barrel, 210°C at the filter and the die (measured temperature in the melted polymer at the die was 228 °C )

[0231] The wood flour was introduced thanks to two side-feeders. Considering the side-feeder maximum throughput, a maximum wood content of 30 wt.% in the final WPC pellets is estimated. Before introduction in the side-feeder, the wood flour was dried at 60 °C during more than 24 hours.

[0232] - WPC1 is a comparative blend of 70 wt. % M6040 with 30 wt.% wood flour (reference without compatibilizer);

[0233] - WPC2 is a comparative blend of 58 wt.% M6040, 12 wt.% Polybond 3009 and 30 wt.% wood flour;

[0234] - WPC3 is an inventive blend of 58 wt.% M6040, 12 wt.% PE-g-MA7 and 30 wt.% wood flour.

[0235] WPC1 and WPC2 were devoid of polypropylene, whereas WPC3 had a polypropylene content of 0.36 wt.%. The ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin was 5.6 in WPC2 and 7.7 in WPC3.

[0236] WPC EVALUATIONS Mechanical properties

[0237] WPC mechanical properties were evaluated in two cases:

[0238] On compressed plates. For the evaluation of the properties, samples were extracted from the plates using a Charlyrobot; On injected samples. The samples were injected in the Dr Boy injection machine in 15.008. When cutting samples, bubbles appear in the center (probably due to some remaining water in the WPG pellets).

[0239] Evaluations performed with the WPG are collected in Tables 2 and 3. Table 2 Properties on compressed plates

[0240] Table 3 Properties on injected samples

[0241] From the results, it can be seen that the balance of mechanical properties is better in WPC3, than in WPC2. Thus, is better in the composite comprising recycled material by comparison the one containing virgin material only. In particular, it can be noted that the traction modulus is better in WPC3 while at the same time, impact properties are maintained by comparison to WPC2. This is surprising because the presence of polypropylene in a PE composition is known to reduce the impact properties.

[0242] It was found that it is possible to further improve the impact properties with the selection of a compatibilizer that shows a greater ratio of the melt index MI2 of the compatibilizer to the melt index Ml20f the polyethylene resin. Also, in case a greater content of polypropylene is incorporated in the composite, maintenance of the impact properties can be obtained with the selection of a compatibilizer that shows a greater ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin. To maintain good impact properties the content of polypropylene is preferably kept to at most 3.0 wt.%.

[0243] Example 3 Tests on the visual aspect

[0244] The PE-g-MA7 grade is a PE-g-MAH grade produced starting from PCR-PE in the form of colored flakes (Figure 3a). The PE-g-MA7 grade is used in the form of gray rPE-g-MAH pellets (Figure 3b).

[0245] When used as a compatibilizer in WPC, no trace of the gray color remains. In fact, due to the color induced by the wood, the final sample could not be distinguished from the sample produced with a virgin PE-g-MAH grade. Indeed, in Figure 3 c) the sample at the right corresponds to the WPC3 and the other to the WPC2. It can be seen that the grey colour of the rPE-g-MAH does not influence the WPC sample final colour.

Claims

CLAIMS1 . A process to produce a cellulosic-polyethylene composite material comprising the step of melt blending a compatibilizer with a polyethylene resin and a cellulosic particulate component to obtain a cellulosic-polyethylene composite material, characterized in that the compatibilizer is provided at a content of more than 1.0 wt.% based on the total weight of the cellulosic-polyethylene composite material, in that the compatibilizer:- is a grafted resin comprising a blend of polyethylene and polypropylene, wherein the polyethylene and / or polypropylene is grafted with a grafting agent being or comprising one or more selected from maleic anhydride, glycidyl methacrylate, methyl methacrylate, acrylic acid, butyl acrylate, vinyl acetate, diethyl maleate, acrylamide, acrylonitrile, and any mixture thereof; and wherein polyethylene is present at a content of at least 50.0 wt.% based on the total weight of the compatibilizer;- has a melt index MI2 of at least 6.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg;- a complex viscosity at 0.1 rad / sec at 190 °C of at most 25,000 Pa.s as determined according to the method of the description; and a ratio of complex viscosity at a frequency of 0.1 rad / sec to the complex viscosity at a frequency of 100 rad / sec of at most 10 said ratio being measured at 190 °C according to the method of the description; in that, the ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin is at least 6.0; and in that the resulting cellulosic-polyethylene composite material has a content of polypropylene of from 0.20 wt.% to 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by 13C NMR.

2. The process according to claim 1 is characterized in that the polyethylene resin is provided at a content of at least 20.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the cellulosic particulate component is provided at a content ranging from 10.0 to 70.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the compatibilizer is provided at a content ranging from 1 .0 to 40.0 wt.% based on the total weight of the cellulosic-polyethylene composite material; and / or the lubricant is provided at a content ranging from 0 to 5.0 wt.% based on the total weight of the cellulosic-polyethylene composite material.

3. The process according to any one of claims 1 or 2 is characterized in that the compatibilizer has a grafting agent content of at least 0.3 wt.% based on the total weight of the compatibilizer as determined by the titration method of the description; and / or in that the compatibilizer is a grafted resin comprising a blend of polyethylene and polypropylene, wherein the polypropylene is present at a content ranging from 0.5 to 50.0 wt.% based on the total weight of the compatibilizer; preferably from 1.2 to 20.0 wt.%.

4. The process according to any one of claims 1 to 3 is characterized in that the compatibilizer has a melt index MI2 ranging from 6.2 to 40.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg; and / or in that the ratio of the melt index MI2 of the compatibilizer to the melt index MI2 of the polyethylene resin is ranging from 6.0 to 20.0.

5. The process according to any one of claims 1 to 4 is characterized in that the polyethylene resin has a melt index (MI2) ranging from 0.1 to 25.0 g / 10 min as determined according to ISO 1133-2005 at 190 °C under a load of 2.16 kg; and / or in that the cellulosic-polyethylene composite material has a content of polypropylene ranging from 0.25 to 3.0 wt.% based on the total weight of the cellulosic-polyethylene composite material as determined by13C NMR.

6. The process according to any one of claims 1 to 5 is characterized in that the polyethylene resin comprises at least 10.0 wt.% based on the total weight of the polyethylene resin of recycled polyethylene; and / or in that the polyethylene resin has a density ranging from 0.910 to 0.970 g / cm3as determined according to ISO 1183-1 :2012 at 23 °C; with preference ranging from 0.915 to 0.960 g / cm3.

7. The process according to any one of claims 1 to 6 is characterized in that it comprises preparing the compatibilizer by extruding a raw polyethylene-containing material with a grafting agent using an extruder with one or more thermal regulation devices, wherein extrusion is performed together with a thermal treatment of the polyethylene-containing material at a maximum barrel temperature Ts of at least 315 °C in one or more hot zones of the extruder and wherein the raw polyethylene-containing material has a melt index (Ml R) ranging from 0.1 to 5.0 g / 10 min as determined according to ISO 1133- 2011 at 190 °C under a load of 2.16 kg.

8. The process according to claim 7 is characterized in that the grafting agent comprises or consists of one or more functional monomers selected from maleic anhydride, glycidyl methacrylate, methyl methacrylate, acrylic acid, butyl acrylate, vinyl acetate, diethyl maleate, acrylamide, acrylonitrile, and any mixture thereof; and / or in that the grafting agent is provided in a content ranging from 1.0 to 6.0 wt.% based on the total weight of the raw polyethylene-containing material.

9. The process according to 7 or 8 is characterized in that the raw polyethylene-containing material is a recycled material being a blend of polyethylene and polypropylene, wherein polypropylene is present at a content ranging from 0.5 to 50.0 wt.% based on the total weight of the raw polyethylene-containing material, preferably from 1.0 to 25.0 wt.%; more preferably from 2.0 to 5.0 wt.%.

10. The process according to any one of claims 1 to 9 is characterized in that the cellulosic particulate component is selected from wood fiber, wood particles, wood chips, ground wood, wood flour, wood flakes, wood veneers, wood laminates, sawdust, paper, newspaper, cardboard, wood pulp fiber, chemical pulp, recycled paper fiber, recycled boxes, recycled box fiber, recycled newspaper, recycled newspaper fiber, recycled computer printout, recycled computer printout fiber, milling tailings, hardwood fiber, softwood fiber, newsprint, ground newsprint, magazines, ground magazines, books, ground books, ground cardboard, wheat chaff, bamboo fiber, pond sludge, cork and combinations thereof; preferably selected from wood fiber, wood flour, and combinations thereof.

11. The cellulosic-polyethylene composite material produced according to any one of claims 1 to 10.

12. The cellulosic-polyethylene composite material according to claim 11 characterized in that it has a melt index MI2 of at least 4.0 g / 10 min as determined according to ISO 1133-2011 at 190 °C under a load of 2.16 kg and / or in that the cellulosic-polyethylene composite material comprises polypropylene, wherein polypropylene is present at a content ranging from 0.20 to 3.0 wt.% based on the total weight of the cellulosic- polyethylene composite material.

13. Article manufactured from the cellulosic-polyethylene composite material according to claim 12.

14. A multi-layered article characterized in that it comprises at least one layer comprising the cellulosic-polyethylene composite material according to claim 12.

15. The article according to any one of claims 13 or 14 is characterized in that the article is an extruded article, or an injection moulded article, or a compression moulded article.

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