FR3168221A1 - Process for functionalizing polyolefins by reactive extrusion - Google Patents

Abstract

Method for Functionalizing Polyolefins by Reactive Extrusion The invention relates to a method for preparing at least one functionalized polyolefin (I) by reactive extrusion, under inert or non-inert conditions. The invention also relates to a polyolefin functionalized with oxime groups (I-A), as well as a polyolefin functionalized with carbonyl groups (I-B) obtained according to the method of the invention. Figure for abstract: Fig. 1

Description

Process for functionalizing polyolefins by reactive extrusion

Background of the invention

The invention relates to a process for functionalizing polyolefins by reactive extrusion via the introduction of oxime or carbonyl groups.

Object and summary of the invention

Currently, plastic pollution is constantly increasing and has therefore become a major problem. Indeed, this source of pollution has particularly harmful effects on waterways, seas and oceans, and on marine animals.

Approximately one-third of the plastics produced are polyolefins. This plastic waste is generally made from polymers designed to be resistant, both mechanically and chemically. Their recycling and recovery are therefore difficult.

Nowadays, plastic waste is often either landfilled, incinerated, or mechanically recycled. Landfilling carries the risk of dispersing lighter plastics due to wind. Incineration has the disadvantage of releasing toxic products, including greenhouse gases. For example, HCl is released when PVC is burned. It is therefore necessary to find alternatives for closed-loop recycling of plastic waste or to "upcycle" it, that is, to transform it into smaller, more valuable molecules.

Currently, plastic recycling is primarily mechanical: the polymer is extruded for reuse. The drawback of this process is that the polymer degrades with repeated extrusions, leading to a decrease in its mechanical properties. Consequently, the polymer can no longer be reused after a certain number of extrusions. Furthermore, contaminated plastics are very difficult to recycle in this way.

Another solution currently being researched is the chemical or enzymatic degradation of polymers.

Regarding the enzymatic degradation of polymers, one notable example is the enzymatic degradation of PET (Nature, vol. 580 (2020), 216-219). This method, using enzymes, allows for the depolymerization of at least 90% of PET into monomers within 10 hours. These monomers can then be reused, for example, to synthesize new PET. While this solution appears effective, it is only applicable to PET, and not to polyolefins, which contain only hydrocarbon chains that are less reactive than the ester groups of PET.

Regarding chemical degradation, a widely studied pathway is the introduction of polar groups, and in particular ester groups, via prior oxidation of the parent polymer introducing carbonyl or hydroxyl groups, followed by a Baeyer-Villiger reaction. However, the preliminary step is not well controlled because it is not selective.

Another method was reported by Conk et al. (Science, 377, 1561-1566, 2022), which describes the production of propylene by partial dehydrogenation of polyethylene and tandem ethanolyse-isomerization. This method is particularly interesting because it yields highly valuable products. However, this method requires the use of expensive catalysts: iridium or platinum-zinc complexes for polyethylene dehydrogenation, and a second-generation Hoveyda-Grubbs metathesis catalyst and [PdP(t-Bu)3(µ-Br)]2 for isomerization. Furthermore, high heating and pressure are required.

The Applicant therefore sought an easy-to-implement alternative method for recycling and valorizing polyolefins. Initially, the Applicant focused particularly on functionalizing these polyolefins with oxime groups, with the aim of utilizing the specific reactivity of these oxime groups to valorize the polyolefins. Indeed, as explained in the document by Rykaczewski et al. (Nature Synthesis, 2022, vol. 1, 24-36), oxime groups exhibit such reactivity towards transition metals and photocatalysis that they constitute reagents of choice for the synthesis of nitrogen heterocycles, amino alcohols, and amines, among others.

In order to introduce oxime groups into polyolefins, the Applicant sought a method that was easy to implement and efficient. Advantageously, the method should be reproducible. Advantageously, the method should be usable with various polyolefins, and in particular different grades of polyethylene, polypropylene, and/or ethylene-propylene copolymer, possibly hydroxylated at the terminal position.

The photochemical transformation allowing the introduction of an oxime group onto an alkane has been studied, notably for the synthesis of caprolactam, a precursor of Nylon-6. For example, the Toray process (US 3,090,739) involves the preparation of cyclohexanone oxime by photochemically introducing oxime units into cyclohexane using NOCl and HCl under UV light (mercury vapor lamp). The cyclohexanone oxime is then transformed into caprolactam under acidic conditions. This process has the drawback of using corrosive NOCl and HCl. To overcome this problem, the use of less corrosive alternative reagents has been investigated. In particular, it has been reported, notably in the document Wysocki et al. (ChemPhotoChem, 2018, 2, 22-26), the photochemical transformation of cyclohexane into cyclohexanone oxime using tert-butyl nitrite (t-BuONO) and UV irradiation.

Furthermore, the Applicant described in patent application PCT/FR2024/050991 the introduction of oxime groups into polyolefins, followed by a post-functionalization reaction. The oxime group is advantageously introduced under irradiation using a nitrosating agent. Subsequently, the oxime groups present on the functionalized polyolefin can be reacted with other oxime groups to obtain a wide variety of compounds. This method has the advantage of being simple to implement and versatile.

Other methods for functionalizing polyolefins with various functional groups, including oximes, carbonyls, and amides, have been described in Baur et al. (Angew. Chem. Int. Ed. 2023, 62, e202310990), Lu et al. (Angew. Chem. Int. Ed. 2024, e202410849), and Shi et al. (J. Am. Chem. Soc. 2023, 145, 21527–21537). The processes involved are complex and/or require multiple steps and/or expensive reagents and/or catalysts. Therefore, these processes are difficult to scale up to an industrial level.

The Applicant continued its research, seeking to develop new methods for functionalizing polyolefins to enhance their value. These methods should be simple and efficient to implement, preferably scalable to industrial production, and capable of yielding a wide variety of compounds. It was in this context that the Applicant became interested in reactive extrusion. To date, the Applicant is unaware of any documents describing the introduction of functionalities into polyolefins by reactive extrusion. The Applicant therefore undertook a research project to identify and develop a method for functionalizing polyolefins using reactive extrusion.

More particularly, the invention relates to the preparation of at least one functionalized polyolefin (I) comprising, preferably consisting of, the following steps:
1) have at least one polyolefin of formula II:
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0, and
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder.

This preparation process has the advantage of being simple to implement and does not require the use of corrosive or toxic reagents. The functionalized polyolefin thus obtained does not require a purification step. Furthermore, the process according to the invention makes it possible to obtain a polyolefin functionalized with oxime groups or with carbonyl groups, depending on the operating conditions chosen.

The preparation process according to the invention has one or more of the following characteristics:
- at least one nitrosation agent III is chosen from:
(III-A), (III-B), (III-C), and their mixtures,
with :
- R4 and R5 being identical or different and independently representing a group chosen from (C1-C6)alkyl, N[(C1-C6)alkyl] ₃ , CO[(C1-C6)alkyl], SO ₂ Ph, CO-Ph-CF ₃ ,
- or R4 and R5 together forming a (C5-C10) cycloalkylene group possibly substituted by one or more (C1-C6) linear or branched alkyl groups, or a -SO ₂ -Ph-C(CH ₃ ) ₂ - group, or a -CO-Ph-CO- group,
- R6 representing a phthalimide group or a linear or branched (C1-C6)alkyl group, and
- R7 representing an aromatic or heteroaromatic group possibly perfluorinated;
- at least one nitrosating agent is chosen from:
(III-1), (III-2),
(III-3), (III-4), (III-5), (III-6), (III-7), (III-8), (III-9), and their mixtures;
- the molar ratio of nitrosating agent(s) III / repeat units of polyolefin(s) II ranges from 0.01 to 2, preferably from 0.1 to 0.5;
- at least one polyolefin II is chosen from polyethylene, polypropylene possibly hydroxylated in the terminal position, an ethylene-propylene copolymer possibly hydroxylated in the terminal position, and mixtures thereof;
- in step 2), the temperature within the extruder is greater than or equal to the melting temperature of at least one polyolefin II, and less than the degradation temperature of at least one nitrosating agent III;
- step 2) is carried out under inert conditions, in order to obtain at least one polyolefin functionalized with IA oxime groups;
- the process further includes a step 3) subsequent to step 2), said step 3) consisting of reacting the oxime groups present in at least one polyolefin functionalized with IA oxime groups;
- step 3) includes the reaction of at least one acid chloride with the oxime groups of at least one polyolefin functionalized with IA oxime groups;
- step 3) includes a Beckmann rearrangement;
- step 3) includes an acid hydrolysis reaction, subsequent to the Beckmann rearrangement;
- step 3) includes the reduction of oxime groups of at least one polyolefin functionalized with IA oxime groups;
- step 3) includes the reaction of at least one isocyanate with the oxime groups of at least one polyolefin functionalized with IA oxime groups;
- step 3) includes a polymer chain grafting reaction, such as polyethylene glycol or polycaprolactone chains;
- step 3) includes an acid hydrolysis reaction of at least one polyolefin functionalized with oxime groups IA, in order to obtain at least one polyolefin functionalized with carbonyl groups IB;
- step 2) is carried out in the presence of air, in order to obtain at least one polyolefin functionalized with carbonyl groups IB;
- the process includes a step 4), subsequent to step 2) and subsequent to step 3) when the latter is carried out, consisting of reacting the carbonyl groups present in at least one functionalized polyolefin with carbonyl groups IB;
- step 4) includes a Baeyer-Villiger reaction; and
- step 4) includes a Baeyer-Villiger reaction followed by a methanolysis reaction.

The invention further relates to a polyolefin functionalized with oxime groups obtained according to the process of the invention, as well as a polyolefin functionalized with carbonyl groups obtained according to the process of the invention. The functionalized polyolefins obtained according to the processes of the invention have the advantage of being pure or nearly pure and requiring little or no purification, and/or of being obtainable in various physical forms (filaments, granules, etc.), and/or of being directly moldable.

Other features and advantages of the present invention will become apparent from the description given below, with reference to the attached drawings which illustrate an example of its embodiment without any limiting character.

FIG. 1 There FIG. 1 is the ^1H NMR spectrum of carbonyl functionalized HDPE IB-1.

FIG. 2 There FIG. 2 is the ^1H NMR spectrum of carbonyl functionalized HDPE IA-1.

FIG. 3 There FIG. 3 is the ^1H NMR spectrum of the functionalized ester HDPE IC-1.

Detailed description of the invention

The invention relates to a reactive extrusion process for preparing at least one functionalized polyolefin I from at least one polyolefin II. More specifically, the process preferably comprises the following steps:
1) have at least one polyolefin II with the following formula:
[Chem. 1]
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0.
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder.

In the context of the invention, "at least one polyolefin II" means exactly one polyolefin II or a mixture of several different polyolefins, each of formula II. In what follows, and unless otherwise specified, reference is made to "the polyolefin" instead of "the at least one polyolefin" for the sake of simplicity, but it is understood that one or more polyolefins II may be used without departing from the scope of the invention.

According to a preferred embodiment, the polyolefin of formula II is such that R1 represents _CH3 , R2 represents H, _CH3 or OH, n represents an integer from 0 to 100000, and m represents an integer from 0 to 100000, it being understood that n and m are not both equal to 0. In other words, according to this embodiment, polyolefin II is either a homopolymer of ethylene or propylene, optionally hydroxylated at the terminal position, or a copolymer of ethylene and/or propylene, optionally hydroxylated at the terminal position.

According to a first embodiment, polyolefin II is a homopolymer. In other words, according to this embodiment, polyolefin II is either polyethylene (i.e. n=0 and m≠0), or polypropylene or polybutylene or polyhexylene possibly hydroxylated in the terminal position (i.e. m=0 and n≠0, and R1 represents Me, Et or Bu respectively).

According to this first embodiment, the polyethylene can be low-density polyethylene or high-density polyethylene.

In the context of the invention, "low-density polyethylene" or LDPE is produced by radical polymerization at high pressures (typically from 500 atm to 3000 atm) and high temperatures (typically from 200 °C to 300 °C) (see Aggarwal et al., Chem. Rev. 1957, 57, 4, 665-742, and Jubinville et al., Sustain. Mater. Technol. 25, 2020, e00188). This type of polymerization generates numerous branches, both long and short. These are due to inter- and intramolecular chain transfers, respectively, during polymerization. The density of LDPE ranges from 0.915 to 0.933 ^g.cm³ .

Within the framework of the invention, the density of the different polymers can be determined according to the ISO 1183-3:1999 standard.

In the context of the invention, "high-density polyethylene" or HDPE can be synthesized at lower pressures (typically from 1 atm to 300 atm), for example in the presence of a Ziegler-Natta metal catalyst (see Aggarwal et al., Chem. Rev. 1957, 57, 4, 665-742, and Jubinville et al., Sustain. Mater. Technol. 25, 2020, e00188). This process yields a linear polyethylene with little or no branching. The density of HDPE ranges from 0.93 to 0.97 g/ ^cm³ .

High-density polyethylene (HDPE) and low-density polyethylene (LDPE) differ in their degree of branching and their level of crystallinity. High-density polyethylene is more crystalline than low-density polyethylene.

According to this first embodiment, the polypropylene is preferably an isotactic polypropylene, that is to say that the distribution of the R1 substituents is uniform along the main chain of the polymer.

According to a second embodiment, polyolefin II is a copolymer. In other words, the polyolefin is such that n ≠ 0 and m ≠ 0. The copolymer can be a block or statistical copolymer.

Preferably according to this embodiment, polyolefin II is either a copolymer of ethylene and propylene, possibly hydroxylated, or a linear low-density polyethylene (LLDPE).

In the context of the invention, a "linear low-density polyethylene" or LLDPE is a copolymer of ethylene with an olefin selected from propylene, butylene, pentylene, hexylene, and octylene. Such a polymer can be obtained by the Ziegler-Natta method (see Aggarwal et al., Chem. Rev. 1957, 57, 4, 665-742, and Jubinville et al., Sustain. Mater. Technol. 25, 2020, e00188). The density of LLDPE ranges from 0.92 to 0.94 ^g.cm³ .

According to an advantageous embodiment of the invention, the degree of crystallinity (mass or volume) of polyolefin II ranges from 40% to 95%, preferably from 40% to 80%. The degree of crystallinity is a measure of the proportion of crystalline material in the sample studied. Within the scope of the invention, the degree of crystallinity can, for example, be determined by differential scanning calorimetry (DSC) by the ratio between the enthalpy of fusion measured for the sample under consideration and the enthalpy of fusion of a 100% crystalline sample.

According to an advantageous embodiment of the invention, the melting temperature of polyolefin II ranges from 120 °C to 140 °C. Within the scope of the invention, the melting temperature of polyolefin II can be measured by thermogravimetric analysis (TGA) or by differential scanning calorimetry (DSC). In the context of the invention, the melting temperature corresponds to the temperature measured at the maximum peak of the thermal phenomenon corresponding to melting.

The second step of the process according to the invention consists of reacting at least one polyolefin II with at least one nitrosating agent III in order to obtain at least one functionalized polyolefin I.

In the context of this invention, "functionalized polyolefin" or "functionalized polyolefin with functional groups" refers to a polyolefin comprising at least one functional group. When the functionalized polyolefin comprises several functional groups, these may be distributed regularly or statistically throughout the polyolefin. These functional groups may be integrated into a polymer chain (i.e., the functional groups are integrated into the polymer chain (on the main chain and/or on the branched chain(s) if present)), and/or be pendant (i.e., the functional groups are substituents). In one particular embodiment, the distribution of the functional groups may be directed by the prior introduction of functional groups that guide the selectivity during the functional group incorporation reaction.

By "functional group" we mean an organic group or fragment other than alkyl. Examples of functional groups include: =N-OH (oxime), -C(O)-alkyl, -C(O)O-alkyl, -C(O)-alkylene-OC(O)-alkyl, -C(O)OH, -C(O)-alkylene-OH, -COOH, -NH-C(O)-alkyl, -N(H)-OH, and _NH2 .

For the purposes of this invention, alkyl means a hydrocarbon chain -( _CH2 ) _n - _CH3 with n representing an integer greater than or equal to 0. Typically, n represents an integer from 0 to 18, preferably from 0 to 12, unless otherwise specified.

The term "alkylene" means a divalent alkyl group –( _CH₂ ) _n , where n is an integer greater than or equal to 0, preferably an integer from 0 to 18, and even better an integer from 0 to 12, unless otherwise specified.

Preferably, nitrosating agent III has the following formula:

[Chem. 2]
(III),

with R3 representing a group comprising an N, O or S atom bonded to the NO group.

Preferably, nitrosating agent III is of formula III-a, III-b or III-c as described below.

Nitrosating agent III-a has the following formula:

[Chem. 3]
(III-a)

with R4 and R5 being identical or different and independently representing a group chosen from (C1-C6)alkyl, N[(C1-C6)alkyl] ₃ , CO[(C1-C6)alkyl], SO ₂ Ph, CO-Ph-CF ₃ , or R4 and R5 together forming a (C5-C10) cycloalkylene group optionally substituted by one or more linear or branched (C1-C6) alkyl groups, or a -SO ₂ -Ph-C(CH ₃ ) ₂ - group, or a -CO-Ph-CO- group; preferably R4 and R5 being identical or different and independently representing a group chosen from (C1-C6)alkyl, N( _CH3 ) ₃ , CO[(C1-C6)alkyl], _SO2Ph , CO-Ph- _CF3 , or R4 and R5 together forming a (C5-C6) cycloalkylene group optionally substituted by one or more linear or branched (C1-C6) alkyl groups, or a _-SO2 -Ph-C( _CH3 ) _2- group, or a -CO-Ph-CO- group.

Nitrosating agent III-b has the following formula:

[Chem. 4]
(III-b)

with R6 representing a phthalimide group or a linear or branched (C1-C6)alkyl group, preferably R6 representing a linear or branched (C1-C6)alkyl group.

The nitrosating agent III-c has the following formula:

[Chem. 5]
(III-c)

with R7 representing an aromatic or heteroaromatic group possibly perfluorinated, preferably R7 representing an aromatic or heteroaromatic group perfluorinated, more preferably R7 representing a heteroaromatic group perfluorinated.

Preferably, at least one nitrosating agent III is chosen from:

[Chem. 6]
(III-1),

[Chem. 7]
(III-2),

[Chem. 8]
(III-3),

[Chem. 9]
(III-4),

[Chem. 10]
(III-5),

[Chem. 11]
(III-6),

[Chem. 12]
(III-7),

[Chem. 13]
(III-8), and

[Chem. 14]
(III-9),

and their mixtures.

According to a preferred embodiment, only one nitrosating agent is used.

According to a preferred embodiment, nitrosating agent III is tert-butylnitrite III-9.

Preferably, the molar ratio of nitrosating agent III to repeat units of polyolefin II ranges from 0.01 to 2, preferably from 0.1 to 0.5.

The term "repeat unit" or "repeat unit" of a polymer refers to the smallest constituent unit whose repetition describes the polymer. In the case of a copolymer, this unit is made up of several distinct repeat units.

Within the framework of the invention, the number of moles of repeating units of a polymer is estimated using the method detailed in Fazekas et al., Science 375, 545-550 (2022): the number of moles of repeating units of a polymer (homopolymer or copolymer) is calculated by the ratio between the mass of polymer involved and the molar mass of the repeating unit (if homopolymer) or repeating units (if copolymer). For the specific case of polyolefins functionalized with oxime groups, it is assumed, for the purpose of determining the number of moles of repeating units, that all repeating units are functionalized with oxime groups: the number of moles of repeating units of a polyolefin functionalized with oxime groups is then equal to the ratio between the mass of polyolefin functionalized with oxime groups and the molar mass of the repeating units including an oxime group.

In the context of the invention, the reaction of at least one polyolefin II with the nitrosating agent III is carried out in an extruder. Various types of extruders can be used in the context of the invention, and in particular single-screw extruders, twin-screw extruders (coaxial twin-screw, conical twin-screw, co-rotating or counter-rotating twin-screw (with or without meshing), or parallel twin-screw), and triple-screw extruders, for example. The extruder length and rotational speed can be adjusted by those skilled in the art.

Preferably, the temperature within the extruder is greater than or equal to the melting temperature of at least one polyolefin II. Preferably, the temperature within the extruder is lower than the degradation temperature of at least one nitrosating agent III. In a particularly preferred embodiment, the temperature within the extruder is greater than or equal to the melting temperature of at least one polyolefin II, and lower than the degradation temperature of at least one nitrosating agent III. Preferably, the temperature within the extruder is uniform or substantially uniform (i.e., identical or substantially identical at every point in the extruder), although it is conceivable to use an extruder having zones with distinct temperatures without departing from the scope of the invention.

Preferably, the pressure inside the extruder is approximately 1 atm.

Preferably, the reaction of at least one polyolefin II with nitrosating agent III (step 2) is carried out without a solvent. Preferably, the reaction of at least one polyolefin II with nitrosating agent III (step 2) is carried out without a catalyst. Preferably, step 2) is carried out only in the presence of at least one polyolefin and at least one nitrosating agent.

Preferably, at least one polyolefin II is introduced at the beginning of the extruder. Preferably, at least one polyolefin II is introduced into the extruder before at least one nitrosating agent III, meaning that at least one nitrosating agent III is added to the at least one polyolefin present in the extruder. Preferably, at least one nitrosating agent III is introduced when at least one polyolefin II is in a molten state, meaning that at least one polyolefin II is placed in a zone of the extruder that is at a temperature greater than or equal to its melting point for a time sufficient to allow it to melt, and then at least one nitrosating agent III is added to the at least one polyolefin II. According to a first embodiment, at least one nitrosating agent III is added continuously to the at least one polyolefin II. Alternatively, according to another embodiment, at least one nitrosating agent III is added sequentially, according to a duration and sequence of addition that can be developed by a person skilled in the art.

Step 2) of the reaction of at least one polyolefin II with at least one nitrosating agent III in the extruder can be carried out under inert conditions or under non-inert conditions (i.e. in the presence of air). The products obtained are then different.

In the context of the invention, a reaction carried out under "inert" conditions means that it is performed in the absence of _O2 , typically under an atmosphere of _N2 or Ar, and preferably under anhydrous conditions. To achieve this, a continuous flow of _N2 or Ar within the extruder can be implemented.

According to a first embodiment, the reaction of at least one polyolefin II with at least one nitrosating agent III in the extruder (step 2) is carried out under inert conditions. According to this embodiment, at least one polyolefin functionalized with oxime groups I-A is then obtained at the end of step 2). In other words, step 2) allows the at least one polyolefin II to be functionalized with oxime groups.

In the context of this invention, "oxyme-functionalized polyolefin" or "nitrosylated polyolefin" means a polyolefin comprising at least one oxime group or substituent. When the oxime-functionalized polyolefin comprises several oxime groups or substituents, these groups or substituents may be distributed regularly or statistically throughout the oxime-functionalized polyolefin. In one particular embodiment, the distribution of the oxime groups may be guided by the prior introduction of functional groups that direct the selectivity during the oxime incorporation reaction.

By "oxime group", we mean a =N-OH group.

Within the framework of the invention, "functionalizing a polyolefin with oxime groups", "introducing oxime groups onto a polyolefin" and "nitrosylating a polyolefin" are synonymous, and refer to the introduction of oxime group(s) (=N-OH) onto the polyolefin, onto the main chain and/or onto the branched chain(s) if present.

In other words, according to this first embodiment, the process according to the invention comprises the following steps:
1) have at least one polyolefin of formula (II):
[Chem. 15]
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0, and
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder under inert conditions in order to obtain at least one polyolefin functionalized with oxime groups IA.

According to this first embodiment, the process may further include a step 3) subsequent to step 2), said step 3) comprising, and preferably consisting of, reacting the oxime groups present in at least one polyolefin functionalized with IA oxime groups. According to this embodiment, the process then preferably comprises the following steps:
1) have at least one polyolefin of formula (II):
[Chem. 16]
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0,
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder under inert conditions to obtain at least one polyolefin functionalized with oxime groups IA, and
3) react the oxime groups present in at least one polyolefin functionalized with IA oxime groups.

Advantageously, in step 3, all oxime groups in the polyolefin functionalized with present I-A oxime groups react. However, it is possible to react only some of them (for example, by introducing limiting reagents), or even to react some of the oxime groups in a first reaction and a second part (or more) in a second reaction (or more), without departing from the scope of the invention.

Various reactions can be considered in step 3): reduction, Beckmann rearrangement, hydrolysis, addition of isocyanate or acid chloride, grafting of PEG or PCL chains, etc. These reactions can be carried out in an extruder or in a reactor. If these reactions are carried out in an extruder, it can be the one used in step 2), or a different extruder. (The reagents needed for step 3 are then added to at least one polyolefin functionalized with I-A oxime groups present in the extruder used in step 2), or another extruder.

Step 3) may include one or more reactions of the oxime groups present in at least one polyolefin functionalized with I-A oxime groups, or even subsequent reactions to one or more reactions of said oxime groups.

According to a first embodiment, step 3) preferably comprises a reaction of an acid chloride with the oxime groups of the polyolefin functionalized with I-A oxime groups. Preferably, this reaction is carried out in a basic medium, for example in the presence of triethylamine, N,N-diisopropylethylamine, or 1,4-diazabicyclo[2.2.2.]octane. Preferably, this reaction is carried out at a temperature that allows the solubilization of the polyolefin functionalized with II oxime groups, that is, a temperature generally ranging from 20°C to 70°C, preferably from 40°C to 60°C. Preferably, this reaction is carried out in a reactor.

According to this embodiment, this step advantageously includes a step of contacting the polyolefin functionalized with oxime groups I-A with an acid chloride of the following formula IV:

[Chem. 17]
(IV)

with R8 representing a (C1-C6)alkyl group, a (C1-C6)alkene group, an aromatic group possibly substituted by one or more (C1-C6)alkyl or (C1-C6)perfluoroalkyl groups.

By "alkene" we mean an alkyl group containing at least one C=C double bond.

Preferably, R8 represents Ph, p-CF ₃ -Ph, a vinyl group (CH=CH ₂ ).

Preferably, the molar ratio of repeat units of polyolefin functionalized with I-A oxime groups / IV acid chloride ranges from 1/0.9 to 1/1.3, preferably from 1/1 to 1/1.2, and even better is 1/1.1.

Advantageously, in this reaction, the polyolefin functionalized with I-A oxime groups is dissolved in at least one solvent, possibly by heating to facilitate the solubilization of the polyolefin functionalized with I-A oxime groups. Then the IV acid chloride and the base are added.

According to a second embodiment, step 3) preferably comprises a Beckmann rearrangement reaction. The Beckmann rearrangement is known to allow the transformation of oxime group(s) into amide group(s). This reaction thus yields a polyolefin functionalized with amide groups. In this embodiment, the amide functions are incorporated into the polymer chain; that is, the polymer chain is interrupted by amide functions.

This Beckmann rearrangement reaction is advantageously carried out in an acidic medium. This Beckmann rearrangement reaction, and the operating conditions that can be used, are well known to those skilled in the art (see, for example, New J. Chem., 2020, 44, 18530-18572) and will not be detailed here. Preferably, this reaction is carried out in a reactor.

It is then possible to carry out a hydrolysis reaction of the amide groups. The amide groups are then transformed into carboxylic acid groups (COOH). The hydrolysis reaction of amide groups is usually carried out in an acidic medium. This reaction thus makes it possible to obtain carboxylic acids of varying chain lengths.

According to a third embodiment, step 3) preferably comprises a reduction reaction of oxime groups to hydroxylamine groups. This reaction then yields a polyolefin functionalized with hydroxylamine groups.

The reducing agents and operating conditions that can be used to reduce oxime groups to hydroxylamine groups are known in the prior art. _NaBH3CN is an example of a reducing agent. Preferably, this reaction is carried out in a reactor.

According to a fourth embodiment, step 3) preferably comprises a reduction reaction of oxime groups to amine groups. This reaction then yields a polyolefin functionalized with amine groups.

The reducing agents and operating conditions that can be used to reduce oxime groups to amine groups are known in the prior art. _LiAlH4 is an example of a reducing agent. Preferably, this reaction is carried out in a reactor.

According to a fifth embodiment, step 3) preferably comprises a reaction of an isocyanate with the oxime groups of the polyolefin functionalized with I-A oxime groups. Preferably, this reaction is carried out by heating the reaction mixture to a temperature enabling the solubilization of the polyolefin functionalized with I-A oxime groups, i.e. for example at a temperature ranging from 50 °C to 110 °C.

According to this embodiment, this step advantageously includes a step of contacting the polyolefin functionalized with I-A oxime groups with an isocyanate of formula V:

[Chem. 18]
(V)

with R9 and R10 being identical or different and independently representing (C1-C6) alkyl, (C6-C10) aryl, or an NCO isocyanate group; or R9 and R10 together represent a (C5-C8) cycloalkylene group.

Preferably, the molar ratio of polyolefin functionalized with oxime groups I-A / isocyanate V ranges from 1/0.8 to 1/1.2, preferably from 1/0.9 to 1/1.1, and even better is 1/1.

Preferably, this reaction is carried out in a reactor.

According to a sixth embodiment, step 3) comprises, or even consists of, a PEG (polyethylene glycol) chain grafting reaction. In this embodiment, this step advantageously includes a step of contacting the polyolefin functionalized with I-A oxime groups with at least one polyethylene glycol derivative comprising at least one reactive function capable of reacting under the reaction conditions with at least one oxime function of the polyolefin functionalized with I-A oxime groups. In the context of the invention, a polyethylene glycol "derivative" is a polyethylene glycol onto which one or more substituents or functional groups have been introduced. In the context of the invention, the reactive function of the polyethylene glycol derivative is not a hydroxyl (OH) group present on the polyethylene glycol, but another functional group capable of reacting under the reaction conditions with at least one oxime function of the polyolefin functionalized with I-A oxime groups. According to a preferred embodiment, this step involves contacting the polyolefin functionalized with I-A oxime groups with a polyethylene glycol derivative comprising at least one reactive function capable of reacting under the reaction conditions with at least one oxime function of the polyolefin functionalized with I-A oxime groups. Such a polyethylene glycol derivative comprising at least one reactive function may, for example, be polyethylene glycol acid chloride or a polyethylene glycol comprising at least one carboxylic acid function. Advantageously, the reactive function(s) of the polyethylene glycol derivative are terminal, i.e., at the end of the chain.

Preferably, this reaction is carried out in the presence of a solvent. Preferably, this reaction is carried out by heating the reaction mixture to a temperature that allows the solubilization of the polyolefin functionalized with I-A oxime groups, i.e., for example, to a temperature ranging from 50 °C to 110 °C. Preferably, this reaction is carried out in a reactor.

Advantageously, polyethylene glycol or its derivative is introduced in excess. According to this embodiment, the molar ratio of reactive functions of the polyethylene glycol derivative to oxime functions of the polyolefin functionalized with I-A oxime groups ranges from 1.1:1 to 10:1, and is preferably 10:1. In the context of the invention, the number of moles of reactive functions of the polyethylene glycol derivative is determined as detailed in Hövelmann et al., Macromolecules 2017, 50, 4169-4179. In the context of the invention, the number of moles of oxime functions of the polyolefin functionalized with II oxime groups is determined by the following formula:

[Math. 1]
,

with :
- n _{oximes IA} representing the number of oxime functions in the polyolefin functionalized with oxime groups IA,
- m _IA representing the mass of polyolefin functionalized with oxime groups IA,
- P representing the percentage of oxime functionalization of the polyolefin functionalized with IA oxime groups,
- M _{unit IA} representing the molar mass _of the oxime-free repeat unit(s) of the polyolefin functionalized with IA oxime groups (28.05 g/mol if _CH2CH2 ).

According to a seventh embodiment, step 3) comprises, or even consists of, a PCL (polycaprolactone) chain grafting reaction. In this embodiment, this step advantageously includes a step of contacting the polyolefin functionalized with I-A oxime groups with ε-caprolactam. This reaction advantageously takes place in the presence of a catalyst capable of catalyzing the ring-opening polymerization of ε-caprolactam, such as stannous octanoate, for example.

Preferably, this reaction is carried out in the presence of a solvent. Preferably, this reaction is carried out by heating the reaction mixture, for example to a temperature ranging from 50 °C to 190 °C, and typically from 100 °C to 170 °C, or even from 120 °C to 150 °C. Preferably, this reaction is carried out in a reactor.

According to an eighth embodiment, step 3) includes, or even consists of, a hydrolysis reaction, in order to convert the oxime groups into =O, and thus obtain at least one polyolefin functionalized with carbonyl groups I-B.

Typically, the hydrolysis reaction is carried out by adding water, possibly mixed with a water-miscible solvent such as acetone, formaldehyde, or 2,2,2-trifluoroacetophenone, in an acidic or basic medium. Preferably, this reaction is performed in a reactor.

For the purposes of this invention, a "carbonyl-functionalized polyolefin" is defined as a polyolefin comprising at least one carbonyl group or substituent. When the carbonyl-functionalized polyolefin comprises several carbonyl groups or substituents, these groups or substituents may be distributed regularly or statistically throughout the carbonyl-functionalized polyolefin. These functional groups may be integrated into the main chain and/or onto the branched chain(s) if present. In a particular embodiment, the distribution of the carbonyl groups may be directed by the prior introduction of functional groups that guide the selectivity during the oxime group incorporation reaction.

By "carbonyl group" we mean a -C(O)- group.

According to this eighth embodiment, the process may further include a step 4) subsequent to step 3), said step 4) preferably comprising reacting the carbonyl groups present in at least one polyolefin functionalized with carbonyl groups IB. According to this embodiment, the process then preferably comprises the following steps:
1) have at least one polyolefin of formula (II):
[Chem. 19]
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0,
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder under inert conditions in order to obtain at least one polyolefin functionalized with oxime groups IA,
3) hydrolyze the oxime groups present in at least one polyolefin functionalized with oxime groups IA, in order to obtain at least one polyolefin functionalized with carbonyl groups IB, and
4) react the carbonyl groups present in at least one polyolefin functionalized with carbonyl groups IB.

Advantageously, in step 3, all oxime groups in the polyolefin functionalized with present I-A oxime groups react. However, it is possible to react only some of them (for example, by introducing limiting reagents), or even to react some of the oxime groups in a first reaction and a second part (or more) in a second reaction (or more), without departing from the scope of the invention.

According to a second embodiment, the reaction of at least one polyolefin II with at least one nitrosating agent III in the extruder (step 2) of the process according to the invention is carried out under non-inert conditions, i.e., in the presence of oxygen and/or under non-anhydrous conditions, and typically in the presence of air. According to this embodiment, at least one polyolefin functionalized with carbonyl groups I-B is then obtained at the end of step 2). In other words, step 2 allows the at least one polyolefin II to be functionalized with carbonyl groups.

Within the framework of the invention, "functionalizing a polyolefin with carbonyl groups" and "introducing carbonyl groups onto a polyolefin" are synonymous, and refer to the introduction of carbonyl group(s) onto the polyolefin, onto the main chain and/or onto the branched chain(s) if present.

In other words, according to this second embodiment, the process according to the invention comprises the following steps:
1) have at least one polyolefin of formula (II):
[Chem. 20]
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0, and
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder under non-inert conditions in order to obtain at least one polyolefin functionalized with carbonyl groups IB.

According to this second embodiment, the process may further include a step 4) subsequent to step 2), said step 4) preferably comprising reacting the carbonyl groups present in at least one polyolefin functionalized with carbonyl groups IB. According to this embodiment, the process then preferably comprises the following steps:
1) have at least one polyolefin of formula (II):
[Chem. 21]
(II)
with :
- R1 representing a methyl, ethyl or n-butyl group,
- R2 representing H, _CH3 or OH,
- n representing an integer ranging from 0 to 100000,
- m representing an integer ranging from 0 to 100000, and
- n + m ≠ 0,
2) react at least one polyolefin II with at least one nitrosating agent III in an extruder under non-inert conditions to obtain at least one polyolefin functionalized with carbonyl groups IB, and
4) react the carbonyl groups present in at least one polyolefin functionalized with carbonyl groups IB.

Advantageously, in step 4, all carbonyl groups in the polyolefin functionalized with present I-B carbonyl groups react. However, it is possible to react only some of them (for example, by introducing limiting reagents), or even to react some of the carbonyl groups in a first reaction and a second part (or more) in a second reaction (or more), without departing from the scope of the invention.

Step 4) may include one or more reactions of the carbonyl groups present in at least one polyolefin functionalized with I-B carbonyl groups. Step 4) may include one or more reactions of the carbonyl groups present in at least one polyolefin functionalized with I-B carbonyl groups, or even reactions subsequent to one or more reactions of said carbonyl groups.

Various reactions involving the reaction of the carbonyl functions of at least one polyolefin functionalized with I-B carbonyl groups (obtained directly under non-inert conditions at the end of step 2), or obtained at the end of step 3) by acid hydrolysis of at least one oxime I-A functionalized polyolefin obtained in step 2) under inert conditions) can be considered in step 4), and in particular a Baeyer-Villiger reaction (also known as Baeyer-Villiger oxidation).

According to a first embodiment, step 4) preferably comprises a Baeyer-Villiger oxidation reaction. This reaction then yields a polyolefin functionalized with I-C ester groups.

According to this embodiment, step 4) includes a step of contacting the polyolefin functionalized with carbonyl groups I-B with a peracid, such as hydrogen peroxide, 3-chloroperbenzoic acid, peroxyacetic acid, or peroxytrifluoroacetic acid.

Preferably, this reaction is carried out in the presence of a solvent. Preferably, this reaction is carried out by heating the reaction mixture, for example to a temperature ranging from 50 °C to 190 °C, and typically from 70 °C to 110 °C.

Following the Baeyer-Villiger reaction, at least one polyolefin functionalized with I-C ester groups can undergo a methanolysis reaction. Advantageously, in this embodiment, the at least one polyolefin functionalized with I-C ester groups is then contacted with methanol. Preferably, the methanol is introduced in excess. Preferably, this reaction is carried out in the presence of a solvent. Preferably, this reaction is carried out in an acidic medium: the reaction is then carried out in the presence of an acid, such as para-toluenesulfonic acid, for example.

According to a particular embodiment, step 2) includes, prior to a possible step 3) and/or 4), the purification of the functionalized polyolefin I obtained (polyolefin functionalized with oxime groups I-A or polyolefin functionalized with carbonyl groups I-B). This purification step can, for example, be carried out by precipitation of the functionalized polyolefin I. The precipitation can be followed by centrifugation(s) and/or filtration(s). It is clear that this purification step is optional, and that those skilled in the art can determine whether it is beneficial.

According to a first embodiment, steps 2) and 3) and/or 4) of the process according to the invention are carried out sequentially: the polyolefin functionalized with I-A oxime groups (obtained in step 2)) and/or the polyolefin functionalized with I-B carbonyl groups (obtained in step 2) or 3)) is isolated (after a possible purification step) and then engaged in step 3) or 4).

According to a second embodiment, steps 2) and 3) and/or 4 of the method according to the invention are carried out successively in the same extruder: the polyolefin functionalized with oxime groups I-A (obtained in step 2)) and/or the polyolefin functionalized with carbonyl groups I-B (obtained in step 2) or 3)) is not isolated (therefore no purification step) and is engaged in step 3) or 4) by adding the reagents into the extruder to carry out the reaction of step 3) or 4).

The process according to the invention makes it easy to obtain polyolefins (or molecules of smaller molecular weight) comprising a wide variety of functional groups. It is also possible to use the known reactivity of oximes or carbonyls to obtain functional groups other than those described above without departing from the scope of the invention.

The invention also relates to the polyolefin functionalized with I-A oxime groups obtained in accordance with the process according to the invention detailed above.

The invention also relates to the polyolefin functionalized with carbonyl groups I-B obtained according to the process according to the invention detailed above (under non-inert conditions at the end of step 2), or via the formation of at least one oxime functionalized polyolefin I-A under inert conditions, followed by hydrolysis in acidic medium).

Examples

Example 1: Functionalization of HDPE under ambient air

Example 1.1: Carbonyl functionalized polyolefin I-B-1

A functionalization reaction by reactive extrusion under ambient air was carried out, as detailed below.

This reaction was carried out using a Brabender MetaStation 4 equipped with a Plastograph Type 50 mixer. The metering mixer was heated to 150 °C. The screw speed was set to 50 rpm, and HDPE II-1 (1 eq., _Mn = 15715 g/mol, Δ = 16.42; 30 g, 1.07 mol, marketed by Sigma Aldrich under reference 54799, and having a melt index of 2.2 g/10 min at 190 °C and 2.16 kg) was added sequentially to the metering mixer for 5 minutes. The screw speed was then increased to 100 rpm. Tert -butyl nitrite III-9 (0.1 eq., 12.8 mL, 0.107 mol) was then added via syringe to the mixing zone for 5 minutes. The mixture was then extruded for a residence time of 2 hours at 150 °C, with continuous monitoring of the viscosity change. The screw speed was then reduced to 0 rpm before opening the metering mixer. The resulting functionalized polymer, IB-1, was collected with a spatula and cooled to room temperature (28 g, 93% conversion).

The polymer functionalized with carbonyl groups IB-1 was analyzed by ¹ H NMR:

¹ H NMR (600 MHz, C ₂ D ₂ Cl ₄ , 110 °C) δ 2.46-2.43 (m), 1.85-1.72 (m), 1.50-1.29 (m), 1.01-0.94 (m).

The ^1H NMR spectrum obtained is shown in FIG. 1 .

The percentage of functionalization of the carbonyl-functionalized polymer IB-1 was determined by integrating characteristic signals from the ^1H NMR spectrum. Given the composition of polymer IB-1, the peaks between 0.8 and 2.0 ppm were integrated, totaling 400 protons. The protons present in the alpha and alpha' positions of the incorporated carbonyl group, appearing between 2.43 and 2.46 ppm, were used to determine the molar percentage of carbonyl groups per repeating unit. Analysis of the resulting functionalized polymer IB-1 shows that it is a carbonyl-functionalized HDPE incorporating 0.6 mol% ketone groups.

The polymer functionalized with carbonyl groups obtained I-B-1 was also analyzed by infrared spectroscopy.

IR (sec, ATR, cm ^-1 ) 2914, 2846, 1554, 1471, 1461, 1367, 1262, 1100, 1026, 803, 730, 719.

The carbonyl-functionalized polymer I-B-1 was characterized by size-exclusion chromatography, or gel permeation chromatography (140 °C, 1,3,5-trichlorobenzene). Size-exclusion chromatography or gel permeation chromatography (GPC) was performed using an Agilent PL-GPC120 (high temperature) instrument with refractive index detection, using polystyrene-in-trichlorobenzene (TCB) standard solutions with BHT at 140 °C. The instrument was equipped with a Plgel guard column and two 5 µm Plgel mixed-c columns. The results were compared with HDPE II-1 used as a reagent. The results are shown in Table 1 below.

The degree of crystallinity was determined by differential scanning calorimetry (DSC), using the ratio between the enthalpy of fusion measured for the sample and the enthalpy of fusion of a 100% crystalline sample. This revealed that the degree of crystallinity of the HDPE II-1 used as a reagent is 63%, and that of the polyolefin functionalized with I-B-1 carbonyl groups is 57%.

Example 1.2: Carbonyl functionalized polyolefin I-B-2

Another functionalization reaction by reactive extrusion under ambient air was carried out, as detailed below.

This reaction was carried out using a Thermo Scientific Minilab II HAAKE Rheomex CTW5. The dosing mixer was heated to 150 °C. The screw speed was set to 50 rpm. HDPE II-1 (M _{_n} = 15715 g/mol, Δ = 16.42; 4 g, 142.86 mmol, marketed by Sigma Aldrich under reference 54799, and having a melt index of 2.2 g/10 min at 190 °C and 2.16 kg) was added sequentially to the dosing mixer for 5 minutes. The screw speed was then increased to 100 rpm. Then, tert -butyl nitrite (1.7 mL, 14.286 mmol) was added via syringe to the mixing zone over 5 minutes, and the mixture was extruded for a residence time of 2 hours at 150 °C, with continuous monitoring of the viscosity change. The screw speed was then reduced to 0 rpm before opening the metering mixer. The modified HDPE was then directly injected into a Mould Tensile Bar 557-2289 mold using a Thermo Scientific HAAKE MiniJET PRO device. Six test specimens of carbonyl functionalized polyolefin IB-2 were thus obtained (3.86 g, 96% conversion).

The polymer functionalized with carbonyl groups IB-2 was analyzed by ¹ H NMR:

¹ H NMR (600 MHz, C ₂ D ₂ Cl ₄ , 110 °C) δ 2.46-2.43 (m), 1.85-1.75 (m), 1.50-1.29 (m), 1.01-0.94 (m).

The percentage of functionalization of the carbonyl-functionalized polymer IB-2 was determined by integrating characteristic signals from the ^1H NMR spectrum. Given the composition of the IB-2 polymer, the peaks between 0.8 and 2.0 ppm were integrated, totaling 400 protons. The protons present in the alpha and alpha' positions of the incorporated carbonyl group, appearing between 2.43 and 2.46 ppm, were used to determine the molar percentage of carbonyl groups per repeating unit. Analysis of the resulting IB-2 functionalized polymer shows that it is a carbonyl-functionalized HDPE incorporating 0.05 mol% ketone groups.

The polymer functionalized with carbonyl functions obtained I-B-2 was also analyzed by infrared spectroscopy.

IR (sec, ATR, cm ^-1 ) 3376, 2914, 2847, 2360, 2342, 1674, 1593, 1463, 1376, 1268, 1051, 972, 718, 445.

Example 2: Functionalization of HDPE under inert conditions

Example 2.1: Functionalized oxime I-A-1 polyolefin

A functionalization reaction by reactive extrusion under an inert atmosphere was carried out, as detailed below.

This reaction was carried out using Thermo Scientific Minilab II HAAKE Rheomex CTW5 equipment. The dosing mixer was heated to 150 °C. The screw speed was set to 50 rpm. The system was purged with nitrogen for 5 minutes. HDPE II-1 (1 eq., Mn = 15715 g/mol, Δ = 16.42; 2.2 g, 78.6 mmol, marketed by Sigma Aldrich under reference 54799, and having a melt index of 2.2 g/10 min at 190 °C and 2.16 kg) was added sequentially to the dosing mixer for 5 minutes. The screw speed was then increased to 100 rpm. Then, tert-butyl nitrite III-9 (0.1 eq., 0.95 mL, 7.86 mmol) was added via syringe to the mixing zone over 5 minutes, and the mixture was extruded for a residence time of 2 hours at 150 °C, with continuous monitoring of the viscosity change. The entire procedure was carried out under a nitrogen flow. The screw speed was then reduced to 0 rpm before opening the metering mixer. The functionalized HDPE I-A-1 was then recovered using a spatula and cooled to room temperature (2.18 g, 99% conversion). NMR analysis showed that it is an HDPE functionalized with oxime groups.

The polymer functionalized with IA-1 oxime groups was analyzed by ^1H NMR:

¹ H NMR (600 MHz, C ₂ D ₂ Cl ₄ , 110 °C) δ 2.46-2.14 (m), 1.85-1.75 (m), 1.50-1.29 (m), 1.01-0.94 (m).

The ^1H NMR spectrum obtained is shown in FIG. 2 .

The percentage of oxime functionalities incorporated into the IA-1 polymer was then determined by integrating the signals from the ^1H NMR spectrum. Given the polymer composition, the peaks between 0.8 and 2.0 ppm were integrated, totaling 400 protons. The protons present in the alpha and alpha' positions of the incorporated oxime function appear between 2.1 and 2.5 ppm and are used to determine the molar percentage of oxime function per repeat unit. It was thus determined that the IA-1 oxime-functionalized HDPE contains 0.25 molar oxime functions.

The polymer functionalized with oxime functions obtained I-A-1 was also analyzed by infrared spectroscopy.

IR (sec, ATR, cm ^-1 ) 3376, 2914, 2847, 2360, 2342, 1674, 1593, 1463, 1376, 1268, 1051, 972, 718, 445.

The oxime-functionalized polymer I-A-1 was characterized by size-exclusion chromatography, or gel permeation chromatography (140 °C, 1,3,5-trichlorobenzene). Size-exclusion chromatography or gel permeation chromatography (GPC) was performed using an Agilent PL-GPC120 (high temperature) instrument with refractive index detection, using polystyrene-in-trichlorobenzene (TCB) standard solutions with BHT at 140 °C. The instrument was equipped with a Plgel guard column and two 5 µm Plgel mixed-c columns. The results were compared with HDPE II-1 used as a reagent. The results are shown in Table 2 below.

Example 2.2: I-A-2 oxime functionalized polyolefin

Another functionalization reaction by reactive extrusion under an inert atmosphere was carried out, as detailed below.

This reaction was carried out using a Thermo Scientific Minilab II HAAKE Rheomex CTW5. The dosing mixer was heated to 150 °C. The screw speed was set to 50 rpm. The system was purged with nitrogen for 5 minutes. HDPE II-1 (M _{_n} = 15715 g/mol, Δ = 16.42; 3.12 g, 111.4 mmol, marketed by Sigma Aldrich under reference 54799, and having a melt index of 2.2 g/10 min at 190 °C and 2.16 kg) was added sequentially to the dosing mixer for 5 minutes. The screw speed was then increased to 100 rpm. Then, tert -butyl nitrite (1.5 mL, 11.14 mmol) was added via syringe to the mixing zone over a period of 5 minutes, and the mixture was extruded for a residence time of 2 hours at 150 °C, with continuous monitoring of the viscosity change. The entire procedure was carried out under a nitrogen flow. The screw speed was then reduced to 0 rpm before opening the metering mixer. The modified HDPE was then directly injected using a Thermo Scientific HAAKE MiniJET PRO device into a Mould Tensile Bar 557-2289 mold. Six test specimens of oxime IA-2 functionalized polyolefin were thus obtained (2.98 g, 96% conversion).

The polymer functionalized with IA-2 oxime groups was analyzed by ^1H NMR:

¹ H NMR (600 MHz, C ₂ D ₂ Cl ₄ , 110 °C) δ 2.46-2.14 (m), 1.85-1.75 (m), 1.50-1.29 (m), 1.01-0.94 (m).

The percentage of oxime functionalities incorporated into the IA-2 polymer was then determined by integrating the signals from the ^1H NMR spectrum. Given the polymer composition, the peaks between 0.8 and 2.0 ppm were integrated, totaling 400 protons. The protons present in the alpha and alpha' positions of the incorporated oxime function appear between 2.1 and 2.5 ppm and are used to determine the molar percentage of oxime function per repeat unit. It was thus determined that the IA-2 oxime-functionalized HDPE contains 0.1 molar oxime functions.

The polymer functionalized with oxime functions obtained I-A-2 was also analyzed by infrared spectroscopy.

IR (sec, ATR, cm ^-1 ) 3376, 2914, 2847, 2360, 2342, 1674, 1593, 1463, 1376, 1268, 1051, 972, 718, 445.

Polymers functionalized with I-A-1 and I-A-2 oxime groups can then be engaged in various reactions involving the oxime functions, as described in PCT/FR2024/050991 application.

Example 3: Baeyer-Villiger reaction on carbonyl functionalized HDPE I-B-1

A Baeyer-Villiger oxidation was then carried out on the HDPE functionalized with I-B-1 carbonyl groups, as detailed below.

HDPE functionalized with I-B-1 carbonyl groups, at an incorporation rate of 0.6 mol% (250 mg, 5.95 mmol), and 3-chloroperbenzoic acid (10.3 g, 59.5 mmol) were introduced into a round-bottom, two-necked flask equipped with a magnetic stirrer and a condenser. The flask was then placed under vacuum. Three successive cycles of vacuum and argon purging were then performed. Under argon, chlorobenzene (50 mL) was added. The reaction flask was then heated to 100 °C for 30 minutes to obtain a homogeneous mixture. The reaction mixture was then maintained at 80 °C. The reaction was allowed to proceed under stirring for 24 hours before the mixture was cooled to room temperature. The homogeneous solution was then precipitated dropwise in excess methanol (100 mL) with stirring. The mixture was then transferred to two Falcon tubes to recover the polymer by centrifugation (three cycles). The recovered polymer was placed under high vacuum (< 1 mbar) overnight before being characterized (245 mg, 98% conversion).

The IC-1 ester functionalized HDPE obtained was characterized by ^1H NMR:

¹ H NMR (600 MHz, C ₂ D ₂ Cl ₄ , 110 °C) δ (ppm) δ 4.17-4.15 (m), 2.45-2.43 (m), 2.39-2.36 (m), 1.74-1.71 (m), 1.51-1.29 (m), 1.02-0.97 (m).

The ^1H NMR spectrum obtained is shown in FIG. 3 .

The functionalized I-C-1 ester HDPE obtained was also analyzed by infrared spectroscopy.

IR (sec, ATR, cm ^-1 ) 2914, 2847, 2630, 2342, 1674, 1593, 1463, 1376, 1268, 1051, 972, 718, 445.

The I-C-1 ester-functionalized HDPE was characterized by size-exclusion chromatography, or gel permeation chromatography (140 °C, 1,3,5-trichlorobenzene). Size-exclusion chromatography, or gel permeation chromatography (GPC), was performed using an Agilent PL-GPC120 (high temperature) instrument with refractive index detection, using polystyrene-in-trichlorobenzene (TCB) standard solutions with BHT at 140 °C. The instrument was equipped with a Plgel guard column and two 5 µm Plgel mixed-c columns. The results were compared with HDPE II-1 and with HDPE functionalized with carbonyl groups I-B-1, used as a reagent. The results are shown in Table 3 below.

Example 4: Methanolyse reaction of functionalized HDPE ester I-C-1

The functionalized HDPE ester I-C-1 was then engaged in a methanolysis reaction, as detailed below.

This reaction was carried out in a sealed tube. Functionalized HDPE ester I-Cl (26 mg, 0.45 mmol) and para -toluenesulfonic acid (0.13 mL, 0.9 mmol) were placed in the tube with a magnetic stirrer. Three successive cycles of vacuum and argon purging were then performed. Anhydrous methanol (3 mL) and toluene (8 mL) were then added under an argon flow. The reaction mixture was heated at 160 °C for 5 days and then cooled to room temperature. The homogeneous solution was then precipitated in excess methanol (10 mL). After 2 hours of stirring, the reaction medium was transferred into two Falcon-type tubes and the polymer mixture (HDPE functionalized Me ester IC-2 and HDPE functionalized hydroxyketone VI) was recovered by centrifugation (three cycles) before being placed under high vacuum (< 1 mbar) overnight, before being characterized (24 mg, 92% conversion).

The IC-2 + VI polymer mixture was analyzed by ¹ H NMR:

¹ H NMR (600 MHz, C ₂ D ₂ Cl ₄ , 110 °C) δ (ppm) δ 4.18-4.16 (m), 3.87-3.81 (m), 3.75 (s), 3.45-3.47 (m), 3.43 (s), 2.45-2.43 (m), 2.39-2.36 (m), 2.13-2.08 (m), 1.74-1.70 (m), 1.50-1.25 (m), 1.02-0.97 (m).

Analysis of the ^1H NMR spectrum determined that the molar ratio of hydroxyketone VI functionalized HDPE to Me ester IC-2 functionalized HDPE is 1/3, taking into account the characteristic peaks of each of these products.

The I-C-2 + VI polymer mixture was also analyzed by infrared spectroscopy:

IR (sec, ATR, cm ^-1 ) 3376, 2914, 2847, 2630, 2342, 1674, 1593, 1463, 1376, 1268, 1051, 972, 718, 445.

The I-C-2 + VI polymer mixture was characterized by size-exclusion chromatography, or gel permeation chromatography (140 °C, 1,3,5-trichlorobenzene). Size-exclusion chromatography, or gel permeation chromatography (GPC), was performed using an Agilent PL-GPC120 (high temperature) instrument with refractive index detection, using polystyrene-in-trichlorobenzene (TCB) standard solutions with BHT at 140 °C. The instrument was equipped with a Plgel guard column and two 5 µm Plgel mixed-c columns. The results were compared with HDPE II-1, HDPE functionalized with I-B-1 carbonyl groups, and I-C-1 ester functionalized HDPE used as a reagent. The results are shown in Table 4 below.

Example 5: Mechanical tests and contact angle measurements

A study of the impact of incorporating oxime or carbonyl groups by reactive extrusion on the mechanical properties of HDPE was carried out. Three extrusion reactions were performed for this purpose, with direct shaping of the specimens using an injector at the outlet (Haake MiniJet PRO).

An extrusion of HDPE II-1, carbonyl functionalized polyolefin I-B-2 and oxime functionalized polyolefin I-A-2, as detailed above, was carried out first.

The test specimens were produced by injection molding using a Thermo Scientific HAAKE MiniJet Pro device in an ISO527-2-1BA tensile bar mold. The injector temperature was 160°C, and the mold temperature was 90°C. An injection pressure of 600 bar was used, with an injection time of 1 minute. The specimens were cured for 48 hours before tensile testing.

Tensile strength measurements were performed using a Qtest/25 Elite Controller device at a tensile speed of 10 mm/min. Five tensile strength measurements were taken on specimens from the same reaction to verify the accuracy of the measurements. The data reported in Table 5 below are the average of these five measurements.

These mechanical tests confirm that the incorporation of carbonyl groups by reactive extrusion has little or no impact on the material's mechanical properties. However, it should be noted that a slight reduction in mechanical properties is observed when oxime groups are incorporated.

Contact angle measurements were also performed on these three materials and are presented in Table 6. The contact angles were determined using a Kruss DSA100 contact angle measurement system at room temperature. For this purpose, a 2-microliter water droplet was placed on the samples. A charge-coupled device (CCD) camera was used to capture images of the water droplets for contact angle determination. Five successive contact angle measurements were taken on each sample to confirm the accuracy of the measurements.

Contact angles were determined using a Kruss DSA100 contact angle measurement system at room temperature. A 2-microliter water droplet was placed on the samples. A charge-coupled device (CCD) camera was used to capture images of the water droplets for contact angle determination. Five successive contact angle measurements were taken on each sample to confirm the accuracy of the measurements.

A decrease in contact angles after reactive extrusion reaction is observed, indicating that the incorporation of oxime or ketone functions reduces the hydrophobicity of HDPE.

Claims (21)

A process for preparing at least one functionalized polyolefin (I) comprising the following steps:
1) have at least one polyolefin of formula (II):
(II)
with :

• R1 representing a methyl, ethyl or n-butyl group,
• R2 representing H, _CH3 or OH,
• n representing an integer ranging from 0 to 100000,
• m representing an integer ranging from 0 to 100000, and
• n + m ≠ 0, and

2) react at least one polyolefin (II) with at least one nitrosating agent (III) in an extruder. A method according to claim 1, wherein at least one nitrosating agent (III) is selected from:
(III-A),(III-B),(III-C), and their mixtures,
with :

• R4 and R5 being identical or different and independently representing a group chosen from (C1-C6)alkyl, N[(C1-C6)alkyl] ₃ , CO[(C1-C6)alkyl], SO ₂ Ph, CO-Ph-CF ₃ ,
• or R4 and R5 together forming a (C5-C10) cycloalkylene group possibly substituted by one or more (C1-C6) linear or branched alkyl groups, or a _-SO2 -Ph-C( _CH3 ) _2- group, or a -CO-Ph-CO- group,
• R6 representing a phthalimide group or a linear or branched (C1-C6)alkyl group, and
• R7 representing an aromatic or heteroaromatic group possibly perfluorinated.

A method according to claim 1 or 2, wherein at least one nitrosating agent is selected from:
(III-1), (III-2),
(III-3), (III-4), (III-5), (III-6), (III-7), (III-8), (III-9), and their mixtures. A process according to any one of the preceding claims, wherein the molar ratio of nitrosating agent(s) (III) / repeating units of polyolefin(s) (II) ranges from 0.01 to 2, preferably from 0.1 to 0.5. A method according to any one of the preceding claims wherein at least one polyolefin (II) is selected from polyethylene, polypropylene optionally hydroxylated in the terminal position, an ethylene-propylene copolymer optionally hydroxylated in the terminal position, and mixtures thereof. A method according to any one of the preceding claims, wherein, in step 2), the temperature within the extruder is greater than or equal to the melting temperature of at least one polyolefin (II), and less than the degradation temperature of at least one nitrosating agent (III). A process according to any one of the preceding claims, wherein step 2) is carried out under inert conditions, in order to obtain at least one polyolefin functionalized with oxime groups (I-A). A method according to the preceding claim further comprising a step 3) subsequent to step 2), said step 3) consisting of reacting the oxime groups present in at least one polyolefin functionalized with oxime groups (I-A). A method according to the preceding claim, wherein step 3) comprises the reaction of at least one acid chloride with the oxime groups of at least one polyolefin functionalized with oxime groups (I-A). A method according to claim 8, wherein step 3) comprises a Beckmann rearrangement. A process according to the preceding claim, wherein step 3) comprises an acid hydrolysis reaction, subsequent to the Beckmann rearrangement. A process according to claim 8, wherein step 3) comprises reducing the oxime groups of at least one polyolefin functionalized with oxime groups (I-A). A process according to claim 8, wherein step 3) comprises the reaction of at least one isocyanate with the oxime groups of at least one polyolefin functionalized with oxime groups (I-A). A process according to claim 8, wherein step 3) comprises a polymer chain grafting reaction, such as polyethylene glycol or polycaprolactone chains. A process according to claim 8, wherein step 3) comprises an acid hydrolysis reaction of at least one polyolefin functionalized with oxime groups (I-A), in order to obtain at least one polyolefin functionalized with carbonyl groups (I-B). A process according to any one of claims 1 to 6, wherein step 2) is carried out in the presence of air, in order to obtain at least one polyolefin functionalized with carbonyl groups (I-B). A process according to claim 15 or 16, comprising a step 4), subsequent to step 2) and subsequent to step 3) when the latter is carried out, consisting of reacting the carbonyl groups present in at least one polyolefin functionalized with carbonyl groups (I-B). A process according to the preceding claim, wherein step 4) comprises a Baeyer-Villiger reaction. A process according to the preceding claim, wherein the Baeyer-Villiger reaction is followed by methanolysis. Polyolefin functionalized with oxime groups (I-A) obtained according to the process according to claim 7. Polyolefin functionalized with carbonyl groups (I-B) obtained according to the process according to claim 15 or 16.