Method of manufacturing a halogenated polyolefin

Abstract

A method of manufacturing an iodinated polyolefin. The method comprises adding a halogenating agent, polyolefin and an activator to a reactor extruder under a nitrogen atmosphere. The halogenating age

Description

[001] The present invention relates to a method of manufacturing a halogenated polyolefin, notably an iodinated polyolefin, and to halogenated polyolefin obtained by said method.

[002] The direct functionalization of unactivated C-H bonds in aliphatic hydrocarbons is a well-known concept that has led to substantial work on the transformations of the C-H bond since it holds significant importance as the building block of the majority of non-metallic materials, ranging from small molecules to long chain macromolecules. The majority of the synthetic activation strategies reported in the literature have included the utilization of bare metals or transition metal complexes and catalysts for amination, hydroxylation, azidation, alkylation, dehydrogenation, and halogenation type of reactions for low molecular weight compounds. One of the most traditional metal-free approaches for the direct conversion of aliphatic C-H bonds is the introduction of free radicals (through irradiation, radical initiators or thermal activation). This approach has sparked significant research interest in the past, leading to intensified efforts to expand its applicability to a variety of hydrocarbon molecules. While the field of C-H diversification is rapidly expanding, certain C-H transformations, such as the iodination of aliphatic alkanes, continue to present difficulties. Iodine is considered an excellent leaving group given its large size and low electronegativity. Consequently, in nucleophilic substitution reactions, iodine's ability to stabilize negative charge effectively and its weak bond with the carbon atom make it highly desirable as a leaving group. However, due to the unfavorable thermodynamics associated with the reaction of iodine itself (characterized by a large positive enthalpy of hydrogen abstraction), the direct iodination of low-molecular-weight alkanes present challenges. Currently, the majority of direct iodination methods rely on free radical mechanisms, employing highly electrophilic radicals such as perfluoroalkyl radicals (Liguori et al., A New Direct Homolytic Iodination Reaction of Alkanes by Perfluoroalkyl Iodides, The Royal Society of Chemistry, Italy, 1997), tert-butyl hypoiodite (obtained in-situ) (Org. Lett. 2003, 5 (24), 4729-4731; J. Am. Chern. Soc. 1968, 90 (3), 808-809), or a combination of hypervalent iodine, I2, and azoiodotrimethylsilane (TMSN3) (Angew. Chem. Int. Ed. 2005, 44 (36), 5851-5854). While these strategies offer operational convenience for alkane iodination, they can be challenging and impractical due to the high instability of certain generated reagents or the toxic and explosive nature of others. To overcome these limitations, Schreiner et al. (Angew. Chem. Int. Ed. 1999, 38 (18), 2786-2788) have developed a promising phase transfer single electron (SET) approach utilizing crushed NaOH and iodoform (HCI3) under mild conditions. Other publications report iodination of hydrocarbons using an N-iodoamide at 100 °C under white LED irradiation (Org. Chern. 2017, 82 (14), 7093-7100).

[003] However, while the iodination methods mentioned earlier exhibit a certain degree of diversity, they have primarily been restricted to small molecules. In contrast, other halogens or polar groups have been successfully incorporated into complex molecules and even polyolefins. Thus, improvements in methods to obtain the direct iodination of polyolefins are still of interest.

[004] Polyethylene is a low-cost commodity polymer that finds extensive use in various applications, such as food storage, packaging, and biomedical devices. However, its inert nature severely limits its interaction with polar additives, fillers, plastic blends, and materials like glass and metal. To overcome these limitations and enhance the properties of polyethylene without compromising its performance, polar functional groups have been introduced along the polymer backbone. This strategy has gained significant popularity due to its ability to greatly modify the physical properties of the final product, expanding its applicability in high-performance engineering applications. While some studies report metal-free free-radical mechanisms which have successfully translated their concepts from small molecule surrogates to polyethylene, regarding iodinated polyethylene, only a few reports have been published, relying on plasma technology where polymer films were exposed to iodine vapors for controlled durations (Surf. Coat. Technol. 2009, 203 (23), 3647-3655 ; J. Polym. Sci. Part Polym. Chem. 1987, 25 (4), 1187-1190 ; J. Polym. Sci. Part Polym. Chern. 1990, 28 (4), 923-929 ; J. Photopolym. Sci. Technol. 2005, 18 (2), 251-254 ; Polym. J. 1995, 27 (6), 575-578). It has been reported that after an exposure of 141 days, an incorporation of 0.34% iodine was achieved (Macromolecules 1990, 23 (17), 3922-3928), this shows that the reported iodination method for polyethylene can be accomplished, but it requires significantly longer reaction times.

[005] The inventors have developed an improved method for iodinating polyolefin, notably polyethylene, that is solvent-free, metal-free, and operates at low temperatures. This method also has the advantages of achieving high conversion rates and minimizing reaction time.

[006] In accordance with one aspect as defined in claim 1, the present invention provides a method of manufacturing a halogenated polyolefin comprising: - halogenating a polyolefin in a reaction chamber of an extruder-reactor, notably a reaction chamber kept under nitrogen atmosphere, by reacting the polyolefin with a halogenating agent in the presence of an activator, wherein the halogenating agent comprises iodoform (HCI3) and the activator comprises sodium hydroxide (NaOH).

[007] The dependent claims define preferred or alternative embodiments.

[008] Any feature described herein in relation to a particular aspect of the invention may be used in relation to any other aspect of the invention.

[009] As used herein, the term "consisting essentially of is intended to limit the scope of a statement or claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the invention.

[0010] Terminology used for describing particular embodiments is not intended to be limiting for the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and / or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified otherwise.

[0011] The polyolefin is preferably selected from the group consisting of: polyethylene (PE) ; notably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very-low-density polyethylene (VLDPE), ultra-low-density polyethylene (ULDPE) and medium-density polyethylene (MDPE) ; polypropylene (PP) ; polymethylpentene (PMP) ; polybutene-1 (PB-1) ; ethylene-octene copolymers ; stereo-block PP ; olefin block copolymers; propylene-butane copolymers ; polyisobutylene (PIB); poly(a-olefin)s ; ethylene propylene rubber (EPR) ; ethylene propylene diene monomer (M-class) rubber (EPDM rubber) ; and combinations thereof. Preferably the polyolefin is selected from the group consisting of: polyethylene (PE); notably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very-low-density polyethylene (VLDPE), ultra-low-density polyethylene (ULDPE) and medium-density polyethylene (MDPE); polypropylene (PP); and combinations thereof. More preferably the polyolefin is a polyethylene or a polypropylene.

[0012] As used herein, polyethylene (PE) is a thermoplastic polymer characterized by its low density. It includes: - low-density polyethylene (LDPE): a linear polymer with a density below 0.940 g / cm3, known for flexibility, - linear low-density polyethylene (LLDPE): a linear polymer with densities ranging from 0.915 to 0.925 g / cm3, offering improved tensile strength and puncture resistance compared to LDPE, - very-low-density polyethylene (VLDPE): a linear polymer with very low density, typically used in packaging and films, - ultra-low-density polyethylene (ULDPE): a variant of VLDPE with even lower density and excellent impact resistance, - medium-density polyethylene (MDPE): a linear polymer with densities ranging from 0.926 to 0.940 g / cm3, used in applications requiring moderate toughness and flexibility. Polypropylene (PP) is a versatile thermoplastic polymer known for its chemical resistance and toughness. Polymethylpentene (PMP) is a transparent thermoplastic with excellent heat resistance and low density, used where transparency and chemical resistance are crucial. Polybutene-1 (PB-1) is a linear thermoplastic polymer known for its high tensile strength and impact resistance. Ethylene-Octene copolymers combine the properties of ethylene (flexibility) and octene (rigidity), often used fortheir elasticity and impact resistance. StereoBlock PP refers to polypropylene with a block copolymer structure, offering enhanced mechanical properties compared to homopolymer PP. Olefin Block Copolymers are copolymers where different olefin monomers are arranged in alternating blocks, combining various properties of the individual monomers. Propylene-Butane Copolymers combine propylene and butane monomers, providing flexibility and low-temperature resistance. Polyisobutylene (PIB) is an elastomeric polymer with long isobutylene chains, used primarily for its sealing and insulation properties. Poly(a-Olefins) encompass a class of polymers comprising various a-Olefins, valued for their flexibility and compatibility with other materials. Ethylene Propylene Rubber (EPR) is a copolymer of ethylene and propylene, known for its elasticity and heat resistance. Ethylene propylene diene monomer (EPDM Rubber) is a terpolymer of ethylene, propylene, and a diene monomer, offering excellent resistance to heat, ozone, and UV radiation.

[0013] As used herein, Mn represents number average molecular weight and Mw represents weigh average molecular weight. The polyolefin comprises, more preferably consist essentially of, and most preferably consist of compound(s) having a Mn in the range of 5000 to 100000 g / mol, preferably in the range of 5000 to 50000 g / mol, more preferably in the range of 10000 to 40000 g / mol. The polyolefin comprises, more preferably consist essentially of, and most preferably consist of compound(s) having a Mw in the range of 10000 to 500000 g / mol, preferably in the range of 25000 to 400000 g / mol, more preferably in the range of 50000 to 300000 g / mol.

[0014] The halogenating agent comprises, more preferably consists essentially of, and most preferably consists of iodoform (HCI3).

[0015] Iodoform has several advantages over the iodizing agents generally used, such as elemental iodine or potassium iodide. Iodoform is a solid at ambient conditions and is a stable substance, easy to handle and store, unlike elemental iodine which is volatile and requires particular handling precautions. Iodoform is less toxic than other iodizing agents, which improves safety during handling and use. Moreover, in the present conditions of reaction of iodinating a polyolefin in a reaction chamber of an extruder-reactor, elemental iodine, diiodomethane and potassium iodide have proved to be unreactive.

[0016] The activator comprises, more preferably consists essentially of, and most preferably consists of sodium hydroxide (NaOH). NaOH has the advantage of being solid at ambient conditions and is a stable substance that is easy to handle and manipulate; it is also readily available. The activator may comprise potassium hydroxide (KOH) and / or lithium hydroxide (LiOH). However, care may be required when using KOH or LiOH to avoid or minimise undesired elimination reactions due to their higher basicity which could affect the specificity and efficiency of the reaction.

[0017] Preferably, the combination of the polyolefin, the halogenating agent and the activator make up at least 95 wt%, more preferably at least 98 wt% of the total materials introduced into the reaction chamber. Indeed, the materials introduced into the reaction chamber preferably consist essentially of, and preferably consist of, the polyolefin, the halogenating agent and the activator.

[0018] The halogenating agent and the activator are preferably in an undissolved state, notably a solid state, when introduced into the extruder-reactor that is to say that the halogenating agent and the activator when introduced into the extruder-reactor chamber are preferably not dissolved in water or in another solvent but may nevertheless comprise residual ambient humidity water. This facilitates handling and avoids the need to deal with the presence of solvent(s). Preferably, the halogenating agent and the activator are not dried before being introduced into the extruder-reactor or into the reaction chamber but are introduced with the presence of any inevitable residual humidity. Preferably, each of the halogenating agent and the activator when introduced into the reaction chamber comprises no more than 1 wt %, preferably no more than 0,5 wt %, more preferably no more than 0,2 wt %, even more preferably no more than 0,1 wt % of water based on the weight of the halogenating agent or the activator respectively.

[0019] The halogenating reaction is conducted in the reaction chamber of an extruderreactor, notably a screw extruder. This is a polymer reaction engineering process that combines traditionally polymer chemistry (polymerization and chemical modification) and extrusion (blending, compounding, structuring, devolatilization, and shaping) into a single process carried out in a screw extruder. The extruder reactor used to perform the halogenation reaction may be any common extruder-reactor found in the industry, for example a single screw extruder or a corotating twin-screw extruder.

[0020] Preferably the extruder is a co-rotating twin screw extruder and the screws are operated at a rotational speed ranging from 100 rpm to 300 rpm, preferably at a rotational speed ranging from 200 rpm to 300 rpm. The use of a co-rotating twin screw extruder operated at 200 rpm to 300 rpm offers several advantages related to improved mixing, throughput, and control over residence time. These benefits can enhance the efficiency and effectiveness of the extrusion process. Notably, high shearing during the reaction leads to a better mass transfer which in turn leads to better iodination fixation on the polymer backbone. When the screws are operated at a rotational speed higher than 300 rpm it has been observed formation of products comprising carbon double bonds.

[0021] The step of halogenating a polyolefin in a reaction chamber of an extruder-reactor, by reacting the polyolefin with a halogenating agent in the presence of an activator is preferably performed in a reaction chamber kept under an inert atmosphere, and preferably under a nitrogen atmosphere. While argon atmosphere or helium atmosphere may be used, nitrogen atmosphere presents several advantages. Nitrogen atmosphere enables to minimize oxidative degradation, in fact by excluding oxygen, nitrogen helps prevent oxidative degradation of the polyolefin during the halogenation process. Nitrogen atmosphere also provides an inert environment that ensures the purity of the halogenation reaction, reducing the likelihood of side reactions or impurities. Moreover, the inert atmosphere of nitrogen maintains the integrity and desired properties of the polyolefin and halogenated product, ensuring consistent quality. It is also readily available.

[0022] During halogenation the polyolefin in the reaction chamber is preferably maintained at a temperature in the range from 25°C to 150°C, preferably at a temperature in the range from 60°C to 150°C, more preferably at temperature in the range from 90°C to 120°C. This advantageous low reaction temperature contrast to the high temperatures (above 200°C, for example up to 250°C) used in traditional chlorination and bromination methods.

[0023] The polyolefin, when introduced in the extruder-reactor is preferably in an undissolved state, notably a solid state, that is to say in a state in which it is not dissolved in a solvent. The polyolefin may however comprise residual ambient humidity water, notably it is understood that before being used, the polyolefin need not be dried before being used but may be used with the presence of inevitable residual humidity. The polyolefin may comprise no more than 1 wt %, preferably no more than 0,5 wt %, more preferably no more than 0,2 wt %, even more preferably no more than 0,1 wt % of water based on the weight of the polyolefin when introduced into the extruder-reactor or when introduced into the reaction chamber. When introduced into the reaction chamber of the extruder-reactor, the polyolefin may be in a softened form, notably at a temperature greater than or equal to its vicat softening temperature.

[0024] The halogenating reaction in the reaction chamber of the extruder-reactor may be carried out in a relatively short time compared to other iodination methods. The polyolefin may be reacted with the halogenating agent in the presence of an activator in the reaction chamber of the extruder-reactor for a duration in the range of 30 min to 2h30, preferably for a duration in the range of 1h to 2h. This relatively short duration facilitates industrial use.

[0025] The halogenating agent and the activator are preferably introduced into the reaction chamber and put into contact with the polyolefin in the reaction chamber subsequent to the polyolefin having been introduced into the reaction chamber; this facilitates control of the halogenating reaction. The halogenating agent and the activator may be mixed together prior to their introduction in the reaction chamber. Alternatively, the halogenating agent and the activator may be introduced separately into the reaction chamber. If the halogenating agent and the activator are introduced separately into the reaction chamber, the halogenating agent is preferably introduced prior to the introduction of the activator. The molar ratio of the halogenating agent to the activator is preferably in the range 3:1 to 1:1, more preferably in the range 2:1 to 1:1 (total amounts introduced into the reaction chamber). If the activator is used in excess compared to the halogenating agent, such as to have for example a molar ratio of the halogenating agent to the activator of 1:3, it will generate the formation of products comprising carbon double bonds.

[0026] The molar ratio of the total quantity of polyolefin repeating unit introduced into the reaction chamber to the total quantity of the halogenating agent introduced into the reaction chamber is preferably in the range 3:1 to 1:3, more preferably in the range 2:1 to 1:1. By way of illustration, Figure 1 shows the polymeric structure of PE and PP with their corresponding repeating units. To illustrate the molar ratio between the polyolefin repeating unit and the halogenating agent introduced into the reaction chamber, if considering 1 gram of polyethylene (PE) and a desire for a 1:1 molar ratio between the molar ratio of the quantity of polyolefin repeating unit of the polyolefin introduced into the reaction chamber and the quantity of the halogenating agent introduced into the reaction chamber, the mass of halogenating agent is calculated as below: Calculation of the moles of PE repeating units: Molar mass of PE repeating unit (C2H4) = 28 g / mol Moles of PE repeating unit in 1 gram: 1 g / 28 g / mol = 0.0357 moles Calculation of the mass of HCI3 needed for 1:1 ratio: Molar mass of HCI3 = 394 g / mol Mass of HCI3 for 0.0357 moles: 0.0357 moles x 394 g / mol = 14.06 g Thus, for 1 gram of PE to be introduced into the reaction chamber and a desired 1:1 molar ratio with HCI3, 14.06 grams of HCI3 should be introduced into the reaction chamber.

[0027] The molar ratio of the total quantity of polyolefin repeating unit introduced into the reaction chamber to the total quantity of halogenating agent introduced into the reaction chamber to the total quantity of activator introduced into the reaction chamber is preferably in the range 1:2:1 to 1:1:1.

[0028] The totality of the halogenating agent and the activator may be introduced into the reaction chamber in a single step. Preferably the halogenating agent and the activator are introduced in to the reaction chamber progressively during the halogenation of the polyolefin, for example in a plurality of individual portions, for example, a first portion of halogenating agent and activator may introduced in to the reaction chamber to initiate the halogenation reaction, then the halogenating reaction is allowed to proceed during a pre-defined duration with the first portion of halogenating agent and activator, and then a second portion of halogenating agent and activator may be added to the reaction chamber to allow the halogenating reaction to proceed further. The halogenating agent and the activator may be introduced in 2,3,4 or more portions over the duration of the halogenating reaction, preferably at regular time intervals. The halogenating agent and the activator may be introduced in 4 separate, but equivalent portions each portion being introduced at 30 min intervals. The gradual addition of the halogenating agent and activator improves the reaction yield. When a fresh portion of halogenating agent and activator are added, it initiates a new reaction cycle, resulting in more efficient grafting of the halogen atom (notably iodine atom) onto the polymer backbone. When introduced in several portions into the reaction chamber, the molar ratio of the halogenating agent to the activator for each portion is preferably in the range 3:1 to 1:1, more preferably in the range 2:1 to 1:1. When the halogenating agent and the activator are introduced in separate portions, the molar ratio of the total quantity of polyolefin repeating unit to the total quantity of halogenating agent introduced is preferably in the range 3:1 to 1:3, more preferably in the range from 2:1 to 1:1, the molar ratio of the total quantity of polyolefin repeating unit introduced into the reaction chamber to the total quantity of halogenating agent introduced into the reaction chamber to the total quantity of activator introduced into the reaction chamber is preferably in the range 1:2:1 to 1:1:1.

[0029] Subsequent to the halogenation reaction, the functionalized polymer is removed from the reaction chamber; it may be used directly in a further reaction without any purification or may be purified with any suitable method. The recovered halogenated polymer may be for example purified by being dissolved in a mixture of 50 / 50 (volume / volume) of xylene / water, notably when the polyolefin is a polyethylene, and then precipitated in a large excess of methanol. The functionalized polymer may then be recovered by vacuum filtration, rinsed with methanol and dried overnight under vacuum. When the polyolefin is a polypropylene, the functionalized polymer may be initially dissolved in a mixture of 50 / 50 (volume / volume) of toluene / water. For a complete characterization of the functionalized polymer, at the end of cycle of the halogenating reaction, prior to being purified, the functionalized polymer may be recovered and kept in a sample holder for 24 hours to adjust to the atmospheric relative humidity.

[0030] The halogenated polyolefin preferably has a weight rate of halogenation ranging from 4 % and 25 %. The characterization of the halogenated polyolefin may be made by any suitable method, such as XPS, TGA and / or 1H NMR. TGA is the preferred method of analysis since it is more accurate than XPS and 1H NMR; thus, if the weight rate of halogenation is measured by TGA, XPS and 1H NMR the results from TGA should be taken as being the most accurate. XPS takes longer to perform than TGA and the accuracy of 1H NMR depend on the whole solubility of the sample in the adequate deuterated method.

[0031] The halogenated polyolefin comprises, more preferably consist essentially of, and most preferably consist of compound(s) having a number average molecular weight Mn in the range of 5000 to 100000 g / mol, preferably in the range of 5000 to 50000 g / mol, more preferably in the range of 10000 to 40000 g / mol. The halogenated polyolefin comprises, more preferably consist essentially of, and most preferably consist of compound(s) having a weight average molecular weight Mw in the range of 10000 to 500000 g / mol, preferably in the range of 25000 to 400000 g / mol, more preferably in the range of 50000 to 300000 g / mol.

[0032] Embodiments of the inventions will now be described, by way, of example only.

[0033] Example 1: Iodination reaction of polyolefin Different polyolefins were halogenated with different halogenating agent and activator with different molar ratios as disclosed in Table 1 and according to the procedure described below. The results are provided in Table 2 with the according protocols for characterization of the obtained halogenated polyolefins. Table 1 Exp P Hal Ac [X] / [Hal] / [Ac] Reaction time (hour) SS (rpm) 1 LLDPE HCI3 NaOH 1 / 2 / 1 1 100 2 LLDPE HCI3 NaOH 1 / 1 / 1 1 100 3 LLDPE HCI3 NaOH 1 / 1 / 1 0.5 100 4 LLDPE HCI3 NaOH 1 / 1 / 1 2 100 5 LLDPE HCI3 NaOH 1 / 1 / 1 2 200 6 LLDPE HCI3 NaOH 1 / 1 / 1 2 300 7 LLDPE HCI3 NaOH 2 / 1 / 1 2 100 8 LLDPE HCI3 NaOH 3 / 1 / 1 2 100 9 LLDPE HCI3 TBD 1 / 1 / 1 2 200 10 LLDPE HCI3 AIBN 1 / 1 / 1 2 200 11 LLDPE HCh DBU 1 / 1 / 1 2 200 12 LLDPE I2 NaOH 1 / 1 / 1 2 100 13 LLDPE I2 TBD 1 / 1 / 1 2 100 14 LLDPE HCCh NaOH 1 / 1 / 1 2 100 15 LLDPE HCBr3 NaOH 1 / 1 / 1 2 100 16 iPP HCI3 NaOH 1 / 1 / 1 2 200 Keys: P = polyolefin ; LLDPE = linear low-density polyethylene LLDPE (Mn=1500 g / mol, D =2.3, density=0.92 g / cm3); iPP = isotactic polypropylene (Mn=5000 g / mol, D =2.4, density=0.9 g / cm3); Hal = halogenating agent ; HCh = iodoform (M= 393.73 g / mol, p= 4.1 g / cm3) ; I2 (M= 253. 80 g / mol, p= 4.93 g / cm3); HCCI3 = (M= 119. 38 g / mol, p= 1.49 g / cm3); HCBr3 = (M= 252.73 g / mol, p=2.89 g / cm3); Ac = activator ; NaOH = sodium hydroxide (M=39.99 g / mol, p=2.13 g / cm3) ; TBD = 1,5,7-triazabicyclo[4.4.0]dec-5-ene (M= 139. 20 g / mol, p= 1.28 g / cm3) ; AIBN = azobisisobutyronitrile (M= 164.21 g / mol, p=1.1 g / cm3) ; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene (M=152.24 g / mol, p=1.01 g / cm3); [X] = molar ratio of polyolefin repeating unit; [X] / [Hal] / [Ac] = Molar ratio of polyolefin repeating unit to halogenating agent to activator; SS = Speed Screw Rate All compounds were purchased from Sigma Aldrich and used without further purification. Procedure for the iodination reaction of polyolefin for the different binder compositions: The samples were prepared using an Xplore DSM vertical microcompounder (Xplore MC 5 model), which had a capacity of 5 cm3. The microcompounder used intermeshing conical twin-screws operating at a speed of 200 rpm, accompanied by a continuous nitrogen purge. A manual floodgate was used, allowing for either extrusion or recirculation, to facilitate the reactive extrusion process. To initiate the reaction, the polyolefin (polyethylene or polypropylene (35.7 mmol)) was introduced into the extruder chamber. The chamber was preheated to a temperature of 106°C, and at every 30-minute interval, additional portions of iodoform (HCI3) and sodium hydroxide (NaOH) were added. The total quantities of iodoform and sodium hydroxide used were 14 g and 1.42 g, respectively. The reaction proceeded for a total duration of 2 hours, maintaining a consistent speed throughout. Following the completion of the reaction cycle, the polymer was recovered and placed in a sample-holder for 24 hours to allow it to adjust to the ambient relative humidity. Subsequently, the purification of the polymer was carried out by dissolving it in a mixture of 50:50 xylene / water (for polyethylene) or toluene / water (for polypropylene). The resulting solution was then precipitated into methanol. The mixture underwent vacuum filtration, and the resulting solid was rinsed with methanol before being dried overnight under vacuum prior to characterization. (The above procedure corresponds to experiment 5. Other experiments are produced similarly with the conditions and ratio indicated in Table 1). Table 2: Exp Mw (g / mol) Tm (°C) Xc (%) lode wt% XPS (accuracy 5%) TGA (accuracy 1%) 1H NMR (accuracy 5-10%) 1 11000 103.9 16.3 4 2 - 86.4 6 9 13 3 14950 82.9 8 6 4 - 78.6 6 13 5 14000 83.4 7 10 15 16 6 12000 71.0 5 23 7 13170 87.5 11 18 8 13820 89.3 9.2 13 9 No reaction 10 No reaction 11 No reaction 12 No reaction 13 No reaction 14 No reaction 15 No reaction 16 - 147.5 23 22 Keys: Mw = weigh average molecular weight; Tm = Melting Temperature; Xc = Percentage of crystallization; lode wt% = grafting content of iodine onto PE (entries 1 -15) and PP (entry 16), by weight percent; Relative Molar mass determined by Size Exclusion Chromatography (PS (Polystyrene) Standards, 50 °C, 1mL / min). In Exp 5, as detailed in Table 2, the SEC analysis of both PE and iodinated PE is depicted in Figure 2. Melting Temperature (Tm) was determined by Differential Scanning Calorimetry (10 °C / min, second scan, under nitrogen). DSC analysis was conducted using a DSC Q2000 from TA instruments under inert atmosphere (N2 / 50 ml / min). Samples (weight: around 5-7 mg) were sealed in aluminum DSC pans, placed in the DSC cell and heated from -60 to 150 °C (for polyethylene, as for polypropylene is -80 to 250°C with a heating rate of 10°C / min. Figure 3 illustrates the results of the DSC analysis for both PE and iodinated PE as outlined in Exp 5 of Table 2. Percentage of crystallization (Xc) was determined by Differential Scanning Calorimetry from AHm values (with AH°m = 293 J / g for LLDPE and 207 J / g for iPP). DSC analysis was conducted as described above. X-ray photoelectron spectroscopy (XPS) evaluated the composition of the iodinated PE with a VERSAPROBE PHI 5000 instrument from Physical Electronics. The instrument was equipped with a monochromatic Al Ka X-ray source. X-ray photoelectron spectra were collected at a takeoff angle of 45°, and the electron energy analyzer was operated in the CAE (constant analyzer energy) mode. To compensate for the built-up charge on the sample surface during measurements, a dual beam charge neutralization system consisting of an electron gun (approximately 1 eV) and an Ar ion gun (less than or equal to 10 eV) was employed. The binding energies were referenced to the C1s peak at 284.6 eV. Atomic concentration percentages were determined using CasaXPS software based on the XPS data. Figures 4A and 4B depict XPS spectra, with Figure 4A showing binding energies ranging from 282 to 288 eV, and Figure 4B highlighting energies between 617 and 625 eV, where only iodinated PE exhibits a signal, as observed in Exp 5 of Table 2. Thermoqravimetric Analyses (TGA) was performed on a TGAQ500 from TA Instruments. About 10 mg of the product was weighed. The analyses were conducted from 25 to 1000 °C following a 20°C / min heating ramp under a N2 flow of 60 mL.min’1. Figure 5 presents the TGA comparing PE and iodinated PE as outlined in Exp 5 of Table 2. The figure includes a zoom on the iodine loss, focusing on the temperature range from 150 to 500 °C. 1H-Nuclear magnetic resonance (NMR) measurements were carried out on a Bruker Advance 500 (500 MHz) spectrometer using deuterated chloroform (CDCh) as solvent at ambient temperature (298 K). Figures 6A and 6B depict 1H-NMR spectra of PE and iodinated PE, respectively, as outlined in Exp 5 of Table 2. Results As shown in Table 2, the association between iodoform as the halogenating agent and sodium hydroxide enable to provide high rate of iodinated polyolefins in less than two hours, while the association of iodoform with other type activator or the association of sodium hydroxide with other type of common halogenating agent did not provide halogenated polyolefins.

Claims

1. A method of manufacturing a halogenated polyolefin comprising:- halogenating a polyolefin in a reaction chamber of an extruder-reactor, notably a reaction chamber kept under nitrogen atmosphere, by reacting the polyolefin with a halogenating agent in the presence of an activator,wherein the halogenating agent comprises iodoform (HCI3) and the activator comprises sodium hydroxide (NaOH).

2. The method according to claim 1, wherein the halogenating agent and the activator are in a solid state when introduced into the reaction chamber.

3. The method according to claim 1 or claim 2, wherein the materials introduced into the reaction chamber consist essentially of, and preferably consists of, the polyolefin, the halogenating agent and the activator.

4. The method according to any preceding claim, wherein the halogenating agent consists essentially of, preferably consists of iodoform.

5. The method according to any preceding claim, wherein the activator consists essentially of, preferably consists of sodium hydroxide.

6. The method according to any preceding claim, wherein the polyolefin is selected from the group consisting of: polyethylene (PE), notably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very-low-density polyethylene (VLDPE), ultra-low-density polyethylene (ULDPE) and medium-density polyethylene (MDPE) ; polypropylene (PP) ; polymethylpentene (PMP) ; polybutene-1 (PB-1) ; ethyleneoctene copolymers ; stereo-block PP ; olefin block copolymers; propylene-butane copolymers; polyisobutylene (PIB); poly(a-olefin)s ; ethylene propylene rubber (EPR) ; ethylene propylene diene monomer (M-class) rubber (EPDM rubber) ; and combinations thereof.

7. The method according to claim 6, wherein the polyolefin is a polyethylene or a polypropylene, preferably a polyethylene.

8. The method according to any preceding claim, wherein the molar ratio of the total quantity of the halogenating agent introduced into the reaction chamber to the total quantity of the activator introduced into the reaction chamber is in the range 3:1 to 1:1, preferably in the range from 2:1 to 1:1.

9. The method according to any preceding claim, wherein during halogenation of the polyolefin, the polyolefin in the reaction chamber is maintained at a temperature in the range 25°C to 150°C, preferably at a temperature in the range 60°C to 150°C, more preferably at temperature in the range 90°C to 120°C.

10. The method according to any preceding claim, wherein the molar ratio of the total quantity of polyolefin repeating unit of the polyolefin introduced into the reaction chamber to the total quantity of the halogenating agent introduced into the reaction chamber is in the range from 3:1 to 1:3, preferably in the range 2:1 to 1:1.

11. The method according to any preceding claim, wherein the molar ratio of the total quantity of polyolefin repeating unit of the polyolefin introduced into the reaction chamber to the total quantity of the halogenating agent introduced into the reaction chamber to the total quantity of the activator introduced into the reaction chamber is in the range 1:2:1 to 1:1:1.

12. The method according to any preceding claim, wherein the extruder-reactor is a corotating twin screw extruder and wherein the screws are operated at a rotational speed in the range 100 rpm to 300 rpm, preferably at a rotational speed in the range 200 rpm to 300 rpm.

13. The method according to any preceding claim, wherein the polyolefin is reacted with the halogenating agent in the presence of the activator in the reaction chamber of the extruder-reactor for a duration of 30 min to 2h30, preferably for a duration of 1h to 2h.

14. The method according to any preceding claim, wherein the halogenated polyolefin has a weight rate of halogenation ranging from 4 % and 25 %.

15. Halogenated polyolefin obtained by a method of manufacturing a halogenated polyolefin in accordance with any preceding claim.

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