EP4263628A1

EP4263628A1 - Macromonomer, method for obtaining same and copolymer containing same

Info

Publication number: EP4263628A1
Application number: EP21851610.2A
Authority: EP
Inventors: Cédrick FAVERO; Olivier Braun; Emmanuelle READ; Thierry LEBLANC; Johann Kieffer
Original assignee: SNF Group
Current assignee: SNF Group
Priority date: 2020-12-17
Filing date: 2021-12-13
Publication date: 2023-10-25
Also published as: AR124350A1; WO2022129768A1; US20240132644A1; CA3202439A1; FR3118041B1; CN116615475A; FR3118041A1

Abstract

The present invention relates to an LCST macromonomer, obtained by reaction between an LCST telomer and a compound containing a carbon-carbon double bond. The invention also relates to an LCST copolymer, obtained by reaction between the LCST macromonomer and a water-soluble monomer.

Description

MACROMONOMER, METHOD FOR OBTAINING IT AND THE COPOLYMER

CONTAINER

Field of invention

The invention relates to the field of LCST macromonomers, a process for obtaining said macromonomer and the copolymers comprising said macromonomers.

Prior state of the art

Water-soluble polymers with a thickening effect are used in many fields such as cosmetics, detergents, printing inks, dispersion paints, textiles, civil engineering, construction, but also in enhanced oil and gas recovery.

There are many different chemistries, known to those skilled in the art, of polymers which can be used as thickeners. An important class of polymers is called thermosensitive. These polymers have pendent or chain-end groups that have an LCST (lower critical demixing temperature). These LCST groups correspond to groups whose solubility in water for a given concentration is modified beyond a certain temperature and according to salinity.

In addition, during its use it must be ensured that the aqueous solution comprising the polymer does not comprise gel particles. Indeed, even small, these gel particles whose dimensions are of the order of a micrometer can strongly affect the thickening performance during use.

The object of the present invention is therefore to provide heat-sensitive copolymers, that is to say copolymers obtained by polymerization of one or more macromonomers with LCST.

Furthermore, the invention aims to provide such copolymers whose effect as a thickening agent is at least equal to that of the polymers of the prior art and which, during their uses, are free of gel particles. Disclosure of Invention

The macromonomer at LCST

The invention relates to a novel LCST macromonomer of formula (I):

Formula (I) in which,

- Ri, R2 and R3 independently are a hydrogen atom, a methyl group, C(=O)-YRs, CH ₂ C(=O)-YR ₅ , C(=O)-OM ⁺ , OR CH ₂ C (=O)-OM ⁺ ;

- Y is NR's or O;

- R5, R' 5 independently are a hydrogen atom or a carbon radical, saturated or unsaturated, optionally aromatic, linear, branched or cyclic, comprising 1 to 30 carbon atoms, comprising from 0 to 4 heteroatoms chosen from the group comprising O, N, and S;

- R4 is CH ₂ , C(=O), CÔH4-C(CH3) ₂ -NH-C(=O)- WHERE CÔFL is a disubstituted benzene ring, C(=O)O-CH ₂ -CH(OH) -CH ₂ , OR CH ₂ -O-CH ₂ -CH(OH)-CH ₂ ;

- M ⁺ is an alkali metal cation, an alkaline earth metal cation, or an ammonium; the symbol M ⁺ includes the case where the metal cation carries two positive charges, when it is an alkaline earth metal cation;

- X is chosen from the groups of formula Z-Rs-S in which Z is O, NH, or OC(=O), OC(=O)-CH(NH ₂ ) and Rs is a C _n H _2n group with n integer between 1 and 30, preferably between 1 and 18;

- monomer A is of formula (II):

Formula (II) - the monomer B is of formula (III):

Formula (III) in which,

- RÔ, RÔ' and R7 independently are a carbon radical, saturated or unsaturated, optionally aromatic, linear, branched or cyclic, comprising 1 to 30 carbon atoms, comprising from 0 to 4 heteroatoms chosen from the group comprising O, N, and S,

- the monomer C is at least one anionic monomer and/or at least one cationic monomer and/or at least one nonionic monomer,

- u, v and w are the molar proportions of the monomers, such that u + v + w = 100% mol, and

• u is between 50 and 99 mol%, preferably between 60 and 98 mol%, more preferably between 70 and 95 mol% relative to all of the molar proportions of the monomers A, B, and C,

• v is between 1 and 20 mol%, preferably between 1 and 15 mol%, more preferably between 2 and 10 mol% relative to all of the molar proportions of the monomers A, B, and C,

• w is between 0 and 30 mol%, preferably between 1 and 25 mol%, more preferably between 3 and 20 mol% relative to all of the molar proportions of the monomers A, B, and C.

Concerning the formula (I) of the LCST macromonomer described above, and repeated in the remainder of this text, when R4 is CÔH4-C(CH3)2-NH-C(=O)-, the benzene ring CÔFL is preferably substituted in the para position.

The semi-developed formula (II) of the monomer A described above, and repeated in the rest of this text, is as follows: -CH2-CH[C(=O)-NRÔR'6]-.

The semi-developed formula (III) of the monomer B described above, and repeated in the remainder of this text, is as follows: -CH2-CH[C(=O)-NHR7]-. In the present text, the term “% mol” represents the molar percentage of the chemical species considered, also denoted “% molar” or “mol%”.

The macromonomer can have an alternating, block or random monomer distribution. Preferably, the distribution of the monomers is statistical.

Preferably, the macromonomer is of formula (I) in which:

- Ri, R2 and R3 independently are a hydrogen atom, or a methyl group,

- R4 is CH2, C(=O), CÔH4-C(CH3)2-NH-C(=O)- WHERE CÔLL is a disubstituted benzene ring, C(=O)O-CH ₂ -CH(OH)- CH ₂ , OR CH ₂ -O-CH ₂ -CH(OH)-CH ₂ ;

- X is of formula Z-Rg-S in which Z is an O or NH and Rg is a Cnthn group with an integer of between 1 and 30;

- Monomer C is at least one anionic monomer;

- RÔ and RÔ' independently are a carbon radical, saturated or unsaturated comprising between 2 and 10 carbons;

- R7 is a carbon radical, saturated or unsaturated, linear or branched comprising between 3 and 10 carbon atoms.

Preferably, the monomer C is at least one anionic monomer chosen from acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-acrylamido acid 2-methylpropane sulfonic, vinylsulfonic acid, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid, styrenesulfonic acid; and the water-soluble salts of these monomers such as their alkali metal, alkaline earth metal, or ammonium salts.

Preferably, the macromonomer is of formula (I) in which:

- Ri, R2 and R3 independently are a hydrogen atom, a methyl group;

- R4 is CH2, C(=O), CÔH4-C(CH3)2-NH-C(=O)- WHERE CÔLL is a disubstituted benzene ring, C(=O)O-CH ₂ -CH(OH)- CH ₂ , CH ₂ -O-CH ₂ -CH(OH)-CH ₂ ;

- X has the formula Z-Rg-S in which Z is an O, NH and Rg is a C _n H2n group with n being an integer between 1 and 18;

- monomer C is 2-acrylamido-2-methylpropane sulphonic acid and/or its alkali metal, alkaline-earth metal or ammonium salt;

- RÔ and RÔ’ are the -CH2-CH3 group;

- R7 is the -C(CH3)3 group. According to the general knowledge of those skilled in the art, the LCST groups correspond to groups whose solubility in water for a given concentration is modified beyond a certain temperature and as a function of salinity. These are groups exhibiting a transition temperature by heating defining their lack of affinity with the solvent medium. The lack of affinity with the solvent results in an opacification or a loss of transparency.

The minimum transition temperature is called “LCST” (lower critical solution temperature). For each group concentration at LCST, a heating transition temperature is observed. It is greater than the LCST which is the minimum point of the curve. Below this temperature the macromonomer is soluble in water, above this temperature the macromonomer loses its solubility in water.

Usually, the measurement of the LCST can be done visually: the temperature at which the lack of affinity with the solvent appears, i.e. the cloud point, is determined. The cloud point corresponds to the opacification of the solution or loss of transparency.

The LCST can also be determined according to the type of phase transition, for example by DSC (differential scanning calorimetry, from the English acronym “Differential Scanning Calorimetry”), by a measurement of transmittance or by a measurement of viscosity.

A person skilled in the art knows the different techniques for determining the LCST, and knows how to choose the technique best suited to his situation.

Preferably, the LCST is determined by determining the cloud point by transmittance according to the following protocol.

The transition temperature is measured for a compound at LCST for a solution having a mass concentration in deionized water of 1% by weight of said compound. The cloud point corresponds to the temperature at which the solution has a transmittance equal to 85% of light rays having a wavelength between 400 and 800 nm.

In other words, the temperature at which the solution has a transmittance equal to 85% corresponds to the minimum transition temperature LCST of the compound, in this case from the macromonomer to LCST. In general, a transparent composition has a maximum transmittance value of light, whatever the wavelength between 400 nm and 800 nm, through a sample 1 cm thick, at least 85%, preferably at least 90%. This is why the cloud point corresponds to a transmittance of 85%.

According to the invention, the LCST macromonomer has a molecular weight preferentially comprised between 500 g/mol and 50000 g/mol, more preferentially comprised between 1000 g/mol and 25000 g/mol, even more preferentially comprised between 5000 g/mol and 10000 g /mol. Molecular weight is defined as number average molecular weight.

The preparation of the macromonomer at LCST

According to another aspect, the invention also relates to the preparation of the LCST macromonomer as described above.

In general, the LCST macromonomer is obtained by synthesizing an LCST telomere with a functional end, then by grafting onto it an ethylenic group.

Preparation of the macromonomer at LCST as described above includes:

- the preparation of at least one LCST telomere from at least one monomer A of formula (II), at least one monomer B of formula (III), at least one monomer C and from one telogen agent,

- the preparation of a macromonomer by reaction between the LCST telomere obtained and a compound containing a carbon-carbon double bond, the carbon-carbon double bond still being present in the LCST macromonomer obtained after said reaction.

According to the invention, in a first step the telomeres are synthesized by telomerization using a telogenic agent. Telomerization favors the synthesis of low molecular weight LCST oligomers (called telomeres).

For the purpose of simplifying this text, the "monomers A, B, and C" refer both to the monomers whose telomerization leads to the telomere at LCST, and to the constituent monomers of the telomere and of the macromonomer obtained by polymerization of the telomere with a compound containing a carbon-carbon double bond. It will however be understood that within the telomere and the macromonomer, the monomers A, B, and C are no longer capable of reacting by polymerization, since they have already polymerized with each other, and are therefore linked between them. Within the telomere and macromonomer, monomers A, B, and C can also be referred to as "motifs" or "monomer units".

“Telomerization” means oligomerization or polymerization by chain reaction, carried out in the presence of an excess of transfer agent, and such that the terminal groups are fragments of the transfer agent. The oligomer or the polymer obtained is called “telomere”.

According to the invention, the telogenic agent is chosen from the compounds of formula Z'-Rg-SH in which Z' is OH, NH2, HO-C(=O)-CH(NH2) or C(=O)-OH , Rg is a C _n H2n group with n integer between 1 and 30.

Preferably, the telogenic agent is chosen from the compounds of formula Z'-Rs-SH in which Z' is OH or NH2 and Rg is a C _n H2n group with n being an integer between 1 and 30.

Preferably, the telogenic agent is chosen from the compounds of formula Z'-Rio-SH in which Z' is OH or NH2 and Rio is a C _n H2n group with an integer of between 1 and 18.

According to the invention, the LCST telomere is of formula (IV):

Formula (IV) in which,

- X is chosen from the groups of formula Z'-Rs-S in which Z' is OH, NH2, HO- C(=O)-CH(NH2) OR C(=O)-OH, and Rg is a group C _n H2n with n integer between 1 and 30,

- monomer A is of formula (II):

Formula (II) - the monomer B is of formula (III):

Formula (III) in which,

Preferably, the macromonomer is of formula (I) in which the monomer C is an anionic monomer.

According to a preferred embodiment, the telomere is of formula (IV) in which:

- X has the formula Z'-Rg-S in which Z' is OH or NH2 and Rg is a C _n H2n group with n being an integer between 1 and 30, - the monomer C comprises at least one anionic monomer chosen from acrylic acid; methacrylic acid; itaconic acid; crotonic acid; maleic acid; fumaric acid, 2-acrylamido 2-methylpropanesulfonic acid, vinylsulfonic acid, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid, styrenesulfonic acid; and the water-soluble salts of these monomers such as their alkali metal, alkaline-earth metal or ammonium salts,

- RÔ and RÔ' independently are a carbon radical, saturated or unsaturated comprising between 2 and 10 carbon atoms,

- R? is a carbon radical, saturated or unsaturated, linear or branched comprising between 3 and 10 carbon atoms.

According to another preferred embodiment, the telomere is of formula (V):

Formula (V) in which,

- the distribution of the three monomers is statistical,

- monomer C is 2-acrylamido 2-methylpropane sulphonic acid and/or its alkali metal, alkaline earth metal or ammonium salt,

- u, v and w are the molar proportions of the three monomers such that u + v + w = 100% mol, and

• u is between 50 and 99 mol%, preferably between 60 and 98 mol%, more preferably between 70 and 95 mol% relative to all of the molar proportions of the three monomers,

• v is between 1 and 20 mol%, preferably between 1 and 15 mol%, more preferably between 2 and 10 mol% relative to all of the molar proportions of the three monomers,

• w is between 0 and 30 mol%, preferably between 1 and 25 mol%, more preferably between 3 and 20 mol% relative to all of the molar proportions of the three monomers. According to the invention, in a second step, once the LCST telomeres have been formed, a vinyl double bond is introduced at the end of the chain so that the said LCST telomeres serve as LCST macromonomers which can in turn be polymerized.

According to the invention, the end of the chain is functionalized via a compound containing a carbon-carbon double bond. This compound containing a carbon-carbon double bond is preferably chosen from acryloyl chloride, acrylic acid, methacryloyl chloride, methacrylic acid, maleic anhydride, methacrylic anhydride, unsaturated aliphatic isocyanates, allyl chloride, allyl bromide, glycidyl acrylate, and glycidyl methacrylate, T allyl glycidyl ether, methallyl glycidyl ether. More preferably the compound containing a carbon-carbon double bond comprises acryloyl chloride.

The reactions that can be implemented for this functionalization are alkylation, esterification, amidation, transesterification or transamidation.

The thermosensitive copolymer

Another aspect of the invention relates to a heat-sensitive copolymer comprising:

- 95% mol to 99.99999% mol of at least one water-soluble monomer and,

- 10' ⁵ % mol to 5% mol of at least one LCST macromonomer of formula (I) as described above.

The heat-sensitive copolymer comprises at least one water-soluble monomer and at least one macromonomer of formula (I). In other words, the thermosensitive copolymer is a copolymer of at least one of each of these two types of monomers.

The heat-sensitive copolymer is obtained by polymerization of said at least one water-soluble monomer and at least one LCST macromonomer of formula (I), in the molar proportions mentioned above.

By “polymer comprising at least one monomer”, is meant a polymer obtained from several molecules of at least one monomer. Thus, a polymer of a monomer corresponds to a polymer obtained from several repeating units of molecules of a monomer. In the present text, the term “water-soluble” designates a compound (in particular a monomer) forming an aqueous solution without insoluble particles when it is added under stirring for 4 hours at 25° C. at a concentration of 20 gL ¹ in water. deionized.

Preferably, the copolymer comprises between 1×10′ ⁵ and 5 mol% of LCST macromonomer of formula (I), preferably between 1×10′ ⁴ and 2 mol% relative to the total number of monomers of the copolymer.

Typically, the water-soluble monomer can be selected from the group comprising nonionic monomers, anionic monomers, cationic monomers, and mixtures of nonionic monomers and anionic monomers.

The water-soluble monomer can be a non-ionic monomer which can in particular be chosen from the group comprising water-soluble vinyl monomers, and particularly acrylamide; N-isopropylacrylamide; N,N-dimethylacrylamide; N-vinylformamide; Tacryloyl morpholine; N,N-diethyl acrylamide; N-tert-butyl acrylamide; N-vinylpyrrolidone; N-vinyl caprolactam; and diacetone acrylamide. Advantageously, the nonionic monomer is acrylamide.

According to a particular embodiment, the copolymer comprises between 0 and 99.99999 mol% of nonionic monomer(s).

The water-soluble monomer can also be an anionic monomer. The anionic monomer(s) that can be used in the context of the invention can be chosen from a wide group. These monomers can have acrylic, vinyl, maleic, fumaric, malonic, itaconic, allylic functions and contain a carboxylate, phosphonate, phosphate, sulphate, sulphonate group, or another group with an anionic charge.

The anionic monomer can be in the acid form or else in the form of an alkaline-earth metal or alkali metal salt. Examples of suitable monomers include acrylic acid; methacrylic acid; itaconic acid; crotonic acid; maleic acid; fumaric acid; monomers of strong acid type having, for example, a function of the sulphonic acid or phosphonic acid type, such as 2-acrylamido-2-methylpropane sulphonic acid, vinyl sulphonic acid, vinyl phosphonic acid, allyl sulphonic acid, allyl phosphonic acid , styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid; and the water-soluble salts of these monomers such as their salts of alkali metals, alkaline earth metals, or ammonium. Advantageously, the anionic monomer is 2-acrylamido-2-methylpropane sulphonic acid or acrylic acid.

According to a particular embodiment, the copolymer comprises between 0 and 99.9999 mol% of anionic monomer(s).

The water-soluble monomer can optionally be a cationic monomer of the acrylamide, acrylic, vinyl, allylic or maleic type possessing an amine or quaternary ammonium function. Mention may be made, in particular and without limitation, of dimethylaminoethyl acrylate (ADAME), and dimethylaminoethyl methacrylate (MADAME) quaternized or salified, dimethyldiallylammonium chloride (DADMAC), acrylamido propyltrimethyl ammonium chloride (APT AC) and methacrylamido propyltrimethyl ammonium chloride (MAPTAC). Preferably, the cationic monomer is dimethylaminoethyl methacrylate (MADAME).

According to a particular embodiment, the heat-sensitive copolymer comprises between 0 and 99.99999 mol% of cationic monomer(s),

The polymer according to the invention can be branched. In a manner known per se, a branched polymer is a polymer which has branches, groups or ramifications on the main chain, arranged globally in a plane. The branching can preferably be carried out during (or optionally after) the polymerization, in the presence of a branching/crosslinking agent and optionally of a transfer agent. The transfer agent is preferably chosen from ethylene bisacrylamide (MBA), ethylene glycol di-acrylate, polyethylene glycol dimethacrylate, diacrylamide, cyanomethylacrylate, vinyloxyethylacrylate or methacrylate, triallylamine, tetraallylammonium chloride, formaldehyde, glyoxal, compounds of the glycidyl ether type such as ethylene glycol diglycidyl ether, or epoxies or any other means well known to those skilled in the art allowing crosslinking.

In general, the heat-sensitive copolymer does not require any particular polymerization technique for its preparation. Indeed, it can be obtained according to all the polymerization techniques well known to those skilled in the art. This may in particular involve the use of free radicals, such as for example polymerization by free radicals by means of UV, azo, redox or thermal initiators as well as controlled radical polymerization known as RAFT (reversible chain transfer by addition). -fragmentation, from English “Reversible-Addition Fragmentation chain Transfer”), NMP (polymerization in the presence of nitroxides, from English “Nitroxide Mediated Polymerization”) or ATRP (radical polymerization by transfer of atoms, from English "Atom Transfer Radical Polymerization."

In general, the heat-sensitive copolymer does not require the development of a particular polymerization process for its preparation. Indeed, it can be obtained according to all the polymerization processes well known to those skilled in the art.

It can in particular be a question of polymerization in solution; gel polymerization; precipitation polymerization; emulsion polymerization (aqueous or reverse); suspension polymerization; or micellar polymerization.

The thermosensitive copolymer can be in liquid, gel or solid form when its preparation includes a drying step such as “spray drying” (drying by spraying), drum drying, microwave drying or even fluidized bed drying. .

Advantageously, the heat-sensitive copolymer has a molecular weight of between 100,000 and 25,000,000 g/mol, preferably between 250,000 and 20,000,000 g/mol, and even more preferably between 500,000 and 15,000,000 g/mol.

The LCST groups of the heat-sensitive copolymer have a transition temperature by heating of 0 to 140° C. for a mass concentration in deionized water of 1% by weight of said LCST groups.

The thermosensitive copolymer has, for a given mass concentration in aqueous solution and beyond a given critical temperature, viscosification properties, also called viscosifying properties or thermoviscosifying properties.

These properties of viscosification by heating observed beyond the transition temperature of the LCST chains are due to the association of the chains, which have become insoluble, with each other, in order to limit the exposure to water of the LCST units. These viscosifying properties are observed beyond the transition temperature and when the polymer concentration in solution is sufficient to allow intermolecular interactions between LCST groups carried by chains of different copolymers. The minimum necessary concentration, called “critical aggregation concentration or Critical Aggregation Concentration in English (acronym CAC)”, is evaluated by rheology measurements. It corresponds to the concentration from which the viscosity of an aqueous solution of heat-sensitive copolymer becomes greater than the viscosity of a solution of the equivalent polymer not comprising any LCST groups.

Another aspect of the invention relates to the use of these heat-sensitive (co)polymers. More specifically, the invention relates to the use of these (co)polymers in the oil and gas industry, hydraulic fracturing, paper, water treatment, construction, mining , cosmetics, textiles, detergents or civil engineering. Preferably, the (co)polymers are used in the field of the exploitation of oil and/or gas wells such as enhanced oil and gas recovery, conformance, acid treatments or hydraulic fracturing. More specifically, the invention also relates to a method for operating an oil and/or gas well, in particular for enhanced oil and/or gas recovery, conformance, acid treatments or hydraulic fracturing, including at least the following steps:

- preparation of an aqueous solution comprising at least one heat-sensitive (co)polymer previously described,

- injection of the aqueous solution into the oil and/or gas well.

Another aspect of the invention relates to a method for drilling wells in an underground formation comprising a step of evacuating the drilling cuttings by means of a drilling fluid comprising at least one heat-sensitive (co)polymer previously described.

The preparation of heat-sensitive polymers is part of a general principle of improving the performance of products and more particularly of improving the thickening power. Reducing the quantity of product required for the application therefore implicitly contributes to the reduction of greenhouse gas emissions such as CO2.

The invention and the resulting advantages will emerge better from the following examples given in order to illustrate the invention and not in a limiting manner. Description of figures

The figures below illustrate, in a non-limiting manner, the advantages and characteristics of the invention:

[Fig. 1] is a graph which represents the viscosity as a function of the temperature for a solution of polymer PI at pH=1 and pH=8.

[Fig. 2] is a graph which represents the viscosity as a function of the temperature for a solution of polymer P2.

Examples of embodiments of the invention

1/ Synthesis of the Tl telomere

To make a telomere called T1, the following process is performed.

In a jacketed reactor:

- We charge deionized water (410g), and 2-acrylamido-2-methylpropane sulfonic acid (ATBS, 48.3g, or 0.21 mol), tert-butyl acrylamide (TBA, 6.7g, or 0.05 mol) and diethylacrylamide (DEA, 114g, i.e. 0.89 mol).

- The mixture is stirred.

- The pH of the mixture is adjusted between 4.0 and 5.0 using a 40% NaOH solution by weight in water.

- The mixture obtained is heated to 50°C.

- Deoxygenate with a nitrogen sparge for 40 minutes.

- Add aminoethanethiol HCl (2.5g).

- 2,2'-azobis(2-methylpropionamidine) dihydrochloride (0.22g) is added to initiate telomerization.

- After stabilization of the temperature, the mixture is stirred for 2 hours and then cooled to 25°C.

The telomere obtained is of formula (VI):

Formula (VI)

In which u=85% mol, v=5% mol and w=10% mol, relative to the total number of moles of the three monomers. 2/ Synthesis of macromonomer Ml

To make a macromonomer called M1, the following process is performed.

In a jacketed reactor:

- 400g of telomer T1 solution at 23% by weight in water are loaded.

- The solution is stirred. - The pH is adjusted to 7.5 using a solution of NaOH 40% by weight in water.

- Cool to 5°C.

- Using a burette, add 1.5g of acryloyl chloride drop by drop.

- The pH is continuously adjusted between 7 and 9 using a 40% NaOH solution by weight in water. - The temperature is maintained at 5°C throughout the reaction.

- The mixture is stirred for 2 hours after the end of the reaction while continuing to check the pH.

A concentrated viscous solution containing 25% by weight of macromonomer M1 of formula (VII) is obtained.

Formula (VII)

Of course, u, v, and w remain unchanged, and are therefore such that u=85 mol%, v=5 mol% and w=10 mol%, relative to the total number of moles of the three monomers.

3/ Synthesis of the heat-sensitive copolymer in PI solution

The thermosensitive copolymer is prepared by radical polymerization.

In a 1 liter adiabatic reactor:

- 189 g of solution of dimethylaminoethyl methacrylate (MADAME) at 100% by weight in water, 290 g of solution of macromonomer M1 at 25% by weight in water and 20 g of water are charged.

- The solution is stirred.

- Deoxygenate with a nitrogen sparge for 30 minutes.

- The polymerization is initiated at low temperature with an oxidizing-reducing couple Mohr's salt - sodium persulfate and does not exceed 30°C.

- A polymer PI is obtained.

4/ PI polymer viscosity test

An aqueous solution of polymer PI at 1% by weight is prepared in deionized water at pH=8 adjusted with the aid of a solution of NaOH at 40% by weight in water, and a solution of polymer PI whose pH was lowered to 1 using a concentrated acid solution.

The viscosity of the 2 solutions is measured with a rheometer (cone-plane module 6 cm, angle 2°) with shearing at 10 s ¹ according to a temperature ramp ranging from 5 to 80° C. We thus obtain the graph of figure 1. On this graph, we observe that the aqueous solution has an increase in viscosity V (cps) with the temperature T (°C), until reaching a maximum threshold around 80°C of about 900 centipoise (cps) for the solution at pH = 1 and about 650 cps for the solution at pH = 8.

The presence of gel particles is assessed by passing the copolymer solution through a 200 µm filter and observing the number of gel points on the filter.

For the aqueous solution of polymer PI, we note the absence of gel particles.

5/ Synthesis of a P2 polymer in solution

The copolymer is prepared by radical polymerization.

In a 1 liter adiabatic reactor:

- 78 g of acrylamide (AM) solution at 50% by weight in water, 109 g of 2-acrylamido-2-methylpropane sulfonic acid (ATBS) at 50%, 237.6 g of macromonomer M1 solution are charged 25% by weight in water and 574 g of water. Transfer agent is added.

- The solution is stirred.

- Deoxygenate with a nitrogen sparge for 30 minutes.

- Polymerization is initiated at low temperature with an oxidizing-reducing peroxide - sodium metabisulphite couple and does not exceed 30°C.

- A polymer P2 is obtained.

6/ P2 polymer viscosity test

An aqueous solution of polymer P2 at 4% by weight in a brine comprising 60 g/l of NaCl is prepared.

The viscosity of the solution is measured with a rheometer (cone-plane module 6cm, angle 2°) with a shear at 7s ¹ according to a temperature ramp ranging from 20 to 80°C. We thus obtain the graph of figure 2.

On this graph, it is observed that the aqueous solution exhibits an increase in viscosity V (cps) with the temperature T(°C), until reaching a maximum threshold around 45°C of about 17,000 cps. Above this threshold, the viscosity decreases. By resuming the protocol previously described, we note the absence of gel particles for the aqueous solution of polymer P2.

Thus, these examples show that the copolymer of the invention has a significant and satisfactory thickening power for use as a thickening agent, and also has the advantage of being free of gel particles during its use.

Claims

1. LCST macromonomer of formula (I):

Formula (I) in which,

- Y is NR's or O;

- R4 is CH ₂ , C(=O), CÔH4-C(CH3) ₂ -NH-C(=O)- WHERE CÔF is a disubstituted benzene ring, C(=O)O-CH ₂ -CH(OH) -CH ₂ , OR CH ₂ -O-CH ₂ -CH(OH)-CH ₂ ;

- M ⁺ is an alkali metal cation, an alkaline earth metal cation, or an ammonium;

- X is chosen from the groups of formula Z-Rs-S in which Z is O, NH, OC(=O), O-C(=O)-CH(NH ₂ ) and Rs is a C _n H _2n group with n integer between 1 and 30,

- monomer A is of formula (II):

Formula (II)

- the monomer B is of formula (III):

[Chem. 3]

Formula (III) in which,

- RÔ, Rô' and R7 independently are a carbon radical, saturated or unsaturated, optionally aromatic, linear, branched or cyclic, comprising 1 to 30 carbon atoms, comprising from 0 to 4 heteroatoms chosen from the group comprising O, N, and S;

- the monomer C is at least one anionic monomer and/or at least one cationic monomer and/or at least one nonionic monomer;

- u, v and w are the molar proportions of the monomers such that u + v + w = 100% mol, and

• u is between 50 and 99 mol%, preferably between 60 and 98 mol%, more preferably between 70 and 95 mol% relative to all of the molar proportions of the monomers A, B, and C.

2. Macromonomer according to claim 1, in which:

- R1, R2 and R3 independently are a hydrogen atom, or a methyl group;

- R4 is CH2, C(=O), CÔH4-C(CH3)2-NH-C(=O)- WHERE CÔFU is a disubstituted benzene ring, C(=O)O-CH ₂ -CH(OH)- CH ₂ , OR CH ₂ -O-CH ₂ -CH(OH)-CH ₂ ;

- X is of formula Z-Rg-S in which Z is O or NH and Rg is a Cnfhn group with an integer of between 1 and 30;

- RÔ and RÔ' independently are a carbon radical, saturated or unsaturated comprising between 2 and 10 carbon atoms;

3. Macromonomer according to one of the preceding claims, in which monomer C is an anionic monomer.

4. Macromonomer according to one of the preceding claims, in which the monomer C comprises at least one anionic monomer chosen from acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-acrylamido 2-methylpropane sulfonic acid, vinylsulfonic acid, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid, styrenesulfonic acid; and the water-soluble salts of these monomers such as their alkali metal, alkaline earth metal, or ammonium salts.

5. Macromonomer according to one of the preceding claims, in which:

- R1, R2 and R3 independently are a hydrogen atom, or a methyl group;

- R4 is CH2, C(=O), CÔH4-C(CH3)2-NH-C(=O)- WHERE CÔIH is a disubstituted benzene ring, C(=O)O-CH ₂ -CH(OH)- CH ₂ , OR CH ₂ -O-CH ₂ -CH(OH)-CH ₂ ;

- X is of formula Z-Rg-S in which Z is an O or NH and Rg is a Cnfhn group with an integer of between 1 and 18;

- RÔ and RÔ’ are the -CH2-CH3 group;

- R7 is the -C(CH3)3 group.

6. Macromonomer according to one of the preceding claims, in which the monomer C is 2-acrylamido-2-methylpropane sulphonic acid and/or its alkali metal, alkaline-earth metal or ammonium salt.

7. Method for preparing at least one LCST macromonomer according to one of the preceding claims comprising:

8. Method of preparation according to claim 7, in which the telogenic agent is chosen from the compounds of formula Z'-Rs-SH in which Z' is OH, NH2, HO-C(=O)-CH-(NH2 ) OR C(=O)-OH, and Rg is a C _n H2n group with n being an integer between 1 and 30.

9. Method of preparation according to one of claims 7 to 8, in which the telogenic agent is chosen from the compounds of formula Z'-Rs-SH in which Z' is OH or NH2 and g is a C _n H2n group. with n integer between 1 and 30.

10. Method of preparation according to one of claims 7 to 9, in which the telogenic agent is chosen from the compounds of formula Z'-Rio-SH in which Z' is OH or NH2 and Rio is a group C _n H2n with n integer between 1 and 18.

11. Method of preparation according to one of claims 7 to 10, in which the compound containing a carbon-carbon double bond is chosen from acryloyl chloride, acrylic acid, methacryloyl chloride, methacrylic acid, maleic anhydride, methacrylic anhydride, unsaturated aliphatic isocyanates, allyl chloride, allyl bromide, glycidyl acrylate, and glycidyl methacrylate, allyl glycidyl ether, and metallyl glycidyl ether .

12. Thermosensitive copolymer, comprising:

- 95% mol to 99.99999% mol of at least one water-soluble monomer, and

- 10′ ⁵ mol% to 5 mol% of at least one LCST macromonomer according to one of claims 1 to 6.

13. Heat-sensitive copolymer according to claim 12, in which the water-soluble monomer is chosen from nonionic monomers, anionic monomers and/or cationic monomers.

14. Heat-sensitive copolymer according to claim 12, in which the water-soluble monomer is a non-ionic monomer chosen from the group comprising water-soluble vinyl monomers, preferably acrylamide; N-isopropylacrylamide; the N,N-dimethylacrylamide; N-vinylformamide; acryloyl morpholine; N,N-diethyl acrylamide; N-tert-butyl acrylamide; N-vinylpyrrolidone; N-vinyl caprolactam; and diacetone acrylamide.

15. Thermosensitive copolymer according to claim 12, in which the water-soluble monomer is an anionic monomer chosen from the group comprising acrylic acid; methacrylic acid; itaconic acid; crotonic acid; maleic acid; fumaric acid; monomers of strong acid type preferably having a function of sulphonic acid or phosphonic acid type, such as 2-acryl amido 2-methylpropane sulphonic acid, vinyl sulphonic acid, vinyl phosphonic acid, allyl sulphonic acid, allylphosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid; and the water-soluble salts of these monomers such as their alkali metal, alkaline earth metal, or ammonium salts.

16. Heat-sensitive copolymer according to claim 12, in which the water-soluble monomer is a cationic monomer chosen from the group comprising quaternized or salified dimethylaminoethyl acrylate (ADAME) and dimethylaminoethyl methacrylate (MADAME), dimethyldiallylammonium chloride (DADMAC) , acrylamido propyltrimethyl ammonium chloride (APT AC) and methacrylamido propyltrimethyl ammonium chloride (MAPTAC).