Methods to improve the stability of polymer solutions

Abstract

The invention relates to a method for improving the stability of a polymer solution, which includes a step involving the incorporation of a solvent preparation with at least one polymer to form a polymer solution. This solvent preparation consists of a mixture containing at least one molecule with at least one sulfoxide functional group; and at least one molecule with at least one amide functional group, in which the nitrogen atom of the amide functional group bears a hydrogen atom. The polymer solution contains less than 1% by mass of polyethersulfone. The solvent preparation contains between 30% and 65% by mass of the molecule containing the sulfoxide functional group and between 35% and 70% by mass of the molecule containing the amide functional group, in which the nitrogen atom of the amide functional group bears a hydrogen atom, by mass of the solvent preparation. The polymers described above include at least one of the polysulfones, polyethersulfones and polyphenylsulfones; and in which the resulting polymer solution remains stable after storage at 0°C for at least one week.

Description

COMPOSITION OF SOLVENT(S) COMPRISING A MIXTURE OF A MOLECULE HAVING A SULFOXIDE FUNCTION AND OF A MOLECULE HAVING AN AMIDE FUNCTION FIELD OF THE INVENTION

[0001] The invention relates to a composition of solvent(s) and its use for stabilizing polymeric solutions, said polymeric solutions being usable in particular for the manufacture of films, membranes, artificial leathers, polymeric suede, polymeric fibers, coatings, electronic circuits, batteries, in particular lithium-ion (Li-ion), or for the protection of electrical cables by sheathing. The invention also relates to a solution of polymer(s) and to a filtration membrane obtained from the solution of polymer(s). TECHNICAL BACKGROUND

[0002] Polymer films or hollow polymer fibers can be used in various applications, such as the coating of textiles, in particular artificial leathers, suede of shoes or personal protective equipment; batteries, in particular Li-ion batteries; membranes, in particular for water treatment or dialysis; protection of electrical cables by sheathing; electronic circuits.

[0003] Among the polymers which can be used in these applications, mention may be made of polyurethanes (PU), polysulfones (PSU), polyvinylidene fluorides (PVDF), polyethersulfones (PES), polyphenylsulfones (PPSU), cellulose acetate, polyamide- imides (PAI) or polyimides (PI), this list not being exhaustive.

[0004] The manufacturing processes for these polymer films or fibers include many steps, among which we can mention: - synthesis of the polymer in a solvent medium, - dissolution of the polymer in a solvent in the case where the polymer resulting from the synthesis is introduced in solid form (for example in extruded form or beads) in order to obtain a polymer solution, - production of a film by a process of coating the polymeric solution followed by drying (heat treatment: dry process) to evaporate the solvent, this step can also be substituted by a step of: - production of a film or a hollow fiber by a process of impregnation on a support or spinning of the polymeric solution followed by quenching in a third solvent (water for example) making it possible to precipitate the polymer and to make migrate the solvent from the polymeric solution to the third solvent (coagulation: wet process).

[0005] The method may further include: - possibly recycling the solvent, - possibly sending the aqueous solutions generated to wastewater treatment plants.

[0006] Currently, the solvents commonly used for the manufacture of these films or hollow polymer fibers are polar aprotic solvents, such as NMP (N-methyl-pyrrolidone), DMF (dimethylformamide) and DMAc (dimethylacetamide). These solvents nevertheless have many toxicological drawbacks because they are classified as CMR (carcinogenic-mutagenic-reprotoxic) and toxic.

[0007] There is therefore an interest in replacing these solvents with solvents having a better toxicological profile.

[0008] Alternatives to these toxic solvents have been proposed.

[0009] Document WO 2005 / 090447 proposes replacing NMP with N-ethyl-2-pyrrolidone (NEP). NEP is now classified as reprotoxic by the European Union.

[0010] In document WO 2008 / 012231, it is proposed to replace NMP with 1,5-dimethylpyrrolidone (DMP). Reprotoxicity studies indicated that DMP is suspected of being reprotoxic in the same way as NMP.

[0011] More recently, document WO 2013 / 107822 proposes partially or totally replacing toxic solvents, such as NMP, DMF or DMACs with a solvent chosen from N-butylpyrrolidone, N-isobutylpyrrolidone, N-t-butylpyrrolidone, N-n-pentylpyrrolidone, N-(methyl-substituted butyl)pyrrolidone, N-propyl- or N-butyl pyrrolidone whose core is methyl-substituted or N-(methoxypropyl)pyrrolidone.

[0012] It has also been proposed to use dimethyl sulfoxide (DMSO) as a solvent for the manufacture of films or hollow polymer fibers.

[0013] The use of DMSO and 2-pyrrolidone alone pose problems of stability of the polymer solutions, which makes an industrial process very difficult, if not impossible, to implement without significant adaptation of the process. DMSO or 2-pyrrolidone make it possible to dissolve polymers such as polyurethanes or polysulfones by heating these solutions to approximately 50° C. for several hours, but the polymer solutions obtained gel, or even solidify, quickly after returning to working temperatures. of the order of 0 to 20°C.

[0014] To date, there are no compositions of solvents, not classified as CMR, allowing both to dissolve polymers and to obtain stable polymeric solutions, in particular at low temperature (temperature of the order of 0°C per example), over a period that can range from a few days to several weeks (3 weeks for example). In fact, to obtain an industrial solution, the polymer solutions must be stable and not gel for a few hours, or even a few weeks, thus making it possible to overcome the vagaries of industrial production (unit stoppage, problem of heating workshops , etc.), and the problem of storage, and this at temperatures which can reach 0°C for example.

[0015] Document JP126681 1 proposes a hollow fiber membrane obtained by mixing a polyethersulfone, DMSO, 2-pyrrolidone and a polyethylene glycol with an average molecular weight of 200 (PEG 200). This document teaches that 2-pyrrolidone makes it possible to increase the permeability of the hollow fiber membrane as well as the mechanical strength. 2-Pyrrolidone, like Poly Ethylene Glycol (PEG) or Poly Vinyl Pyrrolidone (PVP), is therefore used to improve the permeation of the membrane. It is known that the addition of pore-forming agents makes it possible to modify the structure of the pores of the membranes and thus the permeation. We can cite for example the article Desalination 207 (2007), 324-339 "Synthesis, characterization and performance of asymmetric polyethersulfone (PES) ultrafiltration membranes with polyethylene glycol of different molecular weights as additives" as well as the article Physics and Chemistry of the Earth 67-69 (2014), 125 -131 "Preparation of antifouling polyvinylpyrrolidone modified polyethersulfone ultrafiltration membrane for water purification". Document JP126681 1 in no way mentions the problem of the stability of polymer solutions and it does not describe the composition of solvent(s) according to the present invention. SUMMARY OF THE INVENTION

[0016] The invention relates firstly to a composition of solvent(s) comprising a mixture of at least one molecule having at least one sulfoxide function and at least one molecule having at least one amide function where the nitrogen atom bears a hydrogen atom (-NH-C(O)-), said composition being substantially free of polyethersulfones. By "substantially free of polyethersulfones", it is meant that said composition may contain one or more polyethersulfones, in an amount of less than 1% by weight, preferably less than 0.5% by weight, relative to the total weight of the composition.

[0017] According to a particular embodiment, the composition of solvent(s) according to the invention is substantially free of polymers. By “substantially free of polymers”, it is meant that said composition of solvent(s) may contain one or more polymers, in an amount of less than 1% by weight, preferably less than 0.5% by weight, relative to the total weight of composition.

[0018] According to a preferred embodiment, the molecule bearing the amide function is cyclic. Preferably, the molecule bearing an amide function is 2-pyrrolidone. Preferably, the molecule bearing an amide function is not epsilon-caprolactam

[0019] According to a preferred embodiment, the molecule bearing a sulfoxide function is dimethyl sulfoxide.

[0020] According to one embodiment, the composition of solvent(s) according to the invention comprises dimethyl sulphoxide and 2-pyrrolidone.

[0021] According to one embodiment, the composition of solvent(s) according to the invention comprises: - from 21 to 75% by weight, preferably from 25 to 70% by weight, more preferably from 30 to 65% by weight of the molecule carrying a sulfoxide function, - from 25 to 80% by weight, preferably from 30 to 75% by weight, more preferably from 35 to 70% by weight of the molecule carrying an amide function where the nitrogen atom carries a hydrogen atom, relative to the total weight of the composition.

[0022] According to one embodiment, the composition according to the invention further comprises at least one other co-solvent, preferably chosen from water, ketones, amines, alcohols, ethers, esters, sulfones, aromatics, acetals or from N-butylpyrrolidone, N-isobutylpyrrolidone, N-t-butylpyrrolidone, N-n-pentylpyrrolidone, N-(methyl-substituted butyl)pyrrolidone, N-propyl- or N-butyl pyrrolidone whose ring is methyl-substituted or N-(methoxypropyl)pyrrolidone, dipropylene glycol dimethyl ether (DPGDME), polyglyme, ethyl diglyme, 1,3-dioxolane, methyl-5(dimethylamino)-2-methyl- 5-oxopentoate.

[0023] The invention also relates to the use of the composition of solvent(s) according to the invention for improving the stability of polymer solutions.

[0024] Preferably, the polymer solutions are polymer solutions having sulfone or urethane functions.

[0025] Preferably, the polymer solution is a polysulfone or polyethersulfone or polyphenylsulfone solution, preferably a polysulfone solution.

[0026] The invention also relates to a solution of polymer(s), said solution comprising a composition of solvent(s) comprising a mixture of at least one molecule having at least one sulphoxide function and of at least one molecule having at least one function amide wherein the nitrogen atom bears a hydrogen atom (-NH-C(O)-), said polymer solution being substantially free of polyethersulfones. By "substantially free of polyethersulfones", it is meant that said solution of polymer(s) may contain one or more polyethersulfones, in an amount of less than 1% by weight, preferably less than 0.5% by weight, relative to the total weight of said solution.

[0027] Preferably, the polymer of the solution of polymer(s) has sulphone or urethane functions.

[0028] According to a preferred embodiment, the polymer solution comprises a composition of solvent(s) as defined in the present invention.

[0029] According to one embodiment, the polymer solution comprises: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polymers, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the polymer solution.

[0030] A subject of the invention is also a filtration membrane obtained from the solution of polymers according to the invention.

[0031] The invention also relates to an artificial leather obtained from the solution of polymers according to the invention.

[0032] The invention also relates to the use of the polymer solution according to the invention, for the manufacture of films, artificial leathers, polymeric suede, polymeric fibers, coatings, membranes, batteries, electronic circuits , or for the protection of electric cables.

[0033] The composition of solvent(s) according to the present invention makes it possible to stabilize polymer solutions, and this over a wide temperature range, in particular at low temperatures. The present invention makes it possible to provide a single composition of solvent(s) having a universal character and making it possible to stabilize very varied polymers, namely polyurethanes, polyethersulfones and polysulfones as well.

[0034] The polymer solutions according to the present invention are stable, at room temperature and / or at low temperature, and over a period of up to several weeks.

[0035] The solvent(s) used are not or only slightly toxic. In particular, the solvent(s) used are not CMR classified. DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0036] The invention is now described in more detail and without limitation in the description which follows.

[0037] The present invention provides a composition of solvent(s) comprising a mixture of at least one molecule having at least one sulfoxide function and of at least one molecule having at least one amide function where the nitrogen atom carries an atom of hydrogen (-NH-C(O)-), said composition being substantially free of polyethersulfones, preferably completely free of polyethersulfones. The two molecules (the one carrying the sulfoxide function and the one carrying the amide function) are distinct from each other.

[0038] The molecule carrying the sulfoxide function can for example comprise from 2 to 24 carbon atoms, preferably from 2 to 12 carbon atoms, more preferably from 2 to 6 carbon atoms.

[0039] The molecule carrying the amide function can for example comprise from 2 to 24 carbon atoms, preferably from 2 to 12 carbon atoms, more preferably from 2 to 6 carbon atoms, more preferably from 2 to 5, in a completely most preferred 2, 3 or 4 carbon atoms.

[0040] Preferably, the molecule(s) having at least one sulfoxide function have a single sulfoxide function.

[0041] Preferably, the molecule(s) having at least one amide function have a single amide function.

[0042] According to one embodiment of the invention, the composition of solvent(s) consists essentially, and preferably exclusively, of molecules carrying a sulfoxide function and molecules carrying an amide function where the nitrogen atom carries an atom of hydrogen (-NH-C(O)-).

[0043] According to one embodiment, the composition of solvent(s) according to the invention is substantially free of polymers, preferably completely free of polymers, in particular of polymers of the polyethersulfone type.

[0044] By “polymers”, within the meaning of the present invention, is meant any molecule having at least two identical units (monomers) connected by a covalent bond. The polymer according to the present invention can be of natural or synthetic origin, which can be obtained by polymerization, polycondensation or polyaddition.

[0045] Preferably, the molecule having at least one amide function is cyclic, in particular the amide function is a cyclic amide function. More preferably, the molecule having at least one amide function is 2-pyrrolidone.

[0046] Preferably, the molecule carrying a sulfoxide function is dimethyl sulfoxide (DMSO).

[0047] According to a particular embodiment, the composition of solvent(s) comprises DMSO and 2-pyrrolidone. According to one embodiment, the composition of solvent(s) according to the invention consists essentially, and preferably exclusively, of DMSO and 2-pyrrolidone.

[0048] Preferably, the composition of solvent(s) according to the invention comprises: - from 21 to 75% by weight, preferably from 25 to 70% by weight, more preferably from 30 to 65% by weight of molecule(s) carrying a sulfoxide function, - from 25 to 79% by weight, preferably from 30 to 75% by weight, more preferably from 35 to 70% by weight of molecule(s) carrying an amide function where the nitrogen atom carries an atom of hydrogen, relative to the total weight of the composition of solvent(s).

[0049] According to one embodiment, the composition of solvent(s) consists essentially, and preferably exclusively, of: - from 21 to 75% by weight, preferably from 25 to 70% by weight, more preferably from 30 to 65% by weight of molecule(s) carrying a sulfoxide function, - from 25 to 79% by weight, preferably from 30 to 75% by weight, more preferably from 35 to 70% by weight of molecule(s) carrying an amide function where the nitrogen atom carries an atom of hydrogen, relative to the total weight of the composition of solvent(s).

[0050] According to one embodiment, the mass ratio between the molecule(s) bearing at least one sulfoxide function and the molecule(s) bearing at least one amide function ranges from 90 / 10 to 10 / 90, preferably from 80 / 20 to 20 / 80, more preferably from 70 / 30 to 30 / 70, more preferably from 60 / 40 to 40 / 60.

[0051] According to one embodiment, the composition of solvent(s) comprises approximately 50% by weight of DMSO and approximately 50% by weight of 2-pyrrolidone, relative to the total weight of the composition of solvent(s).

[0052] According to one embodiment, the composition of solvent(s) also comprises at least one other solvent, different from the two molecules described above. Mention may be made, without limitation, as an example of other solvents: - the water ; - ketones, such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, hexanone, cyclohexanone, ethylamine ketone, isophorone, trimethylcyclohexanone, gamma-butyrolactone, diacetone alcohol; - amines, such as monoethanolamine (MEoA), diethanolamine (DEoA), propanolamine (PoA), butyl- / ' so-propanol-amine (BiPoA), the / ' so-propanolamine (iPoA), 2-[2-(3-amino-propoxy)ethoxy]ethanol, N-2- hydroxyethyldiethylenetriamine, (3-methoxy)-propylamine (MoPA), 3-isopropoxypropylamine (IPOPA) , monoethylamine, diethylamine, diethylaminopropylamine (DEAPA), triethylamine (TEA), acetonitrile; - alcohols, such as ethanol, methanol, propanol, isopropanol, glycerol, diacetone alcohol, butanol, methylisobutylcarbinol, hexylene glycol, benzyl alcohol; - ethers, such as tetrahydrofuran (THF), methyl furan, methyl tetrahydrofuran, tetrahydropyran, glycoldialkyl ether; - esters, such as dibasic esters, dimethylglutarate, dimethylsuccinate, dimethyladipate, butylacetate, ethylacetate, diethylcarbonate, dimethylcarbonate, propylene carbonate, ethylmethylcarbonate, glycerolcarbonate, dimethyl-2-methylglutarate, dimethyl-2-methyladipate, dimethyl-2-methylsuccinate, N-butylpropionate, Benzyl acetate, ethylethoxypropionate; - sulfones, such as dimethylsulfone, sulfolane; - aromatics, such as toluene, xylene; - acetals, such as methylal, ethylal, butylal, dioxolane, TOU (tetraoxaundecane); - Type E or P glycol ethers, such as dipropylene glycol dimethyl ether (DPGDME), dipropylene glycol methyl ether.

[0053] As examples of other solvents, mention may also be made of the following solvents: N-butylpyrrolidone, N-isobutylpyrrolidone, N-t-butylpyrrolidone, N-n-pentylpyrrolidone, N-(methyl-substituted butyl)pyrrolidone, N-propyl- or N -butyl pyrrolidone, the ring of which is methyl-substituted or N-(methoxypropyl)pyrrolidone, polyglyme, ethyl diglyme, 1,3-dioxolane, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate.

[0054] According to one embodiment, the composition of solvent(s) also comprises at least one blowing agent, such as a PEG or PVP.

[0055] The present invention also proposes the use of the composition of solvent(s) according to the invention to improve the stability of polymer solutions.

[0056] The solutions of polymers or polymeric solutions are obtained by dissolving or dispersing the polymers in the composition of solvent(s) according to the invention.

[0057] The polymer solutions or polymer solutions can be chosen from polyurethane solutions, polysulfone solutions, polyphenylsulfone solutions, polyethersulfone solutions, polyvinylidene fluoride (PVDF) solutions, cellulose acetate, polyamide- imides (PAI) or polyimides (PI).

[0058] Preferably, the polymer solutions are polymer solutions having sulfone or urethane functions. Preferably, the polymer solutions are chosen from polyurethane solutions, polyphenylsulfone solutions, polyethersulfone solutions, and polysulfone solutions, more preferably from polysulfone and polyurethane solutions, in particular from polysulfone solutions .

[0059] By “polysulfone”, within the meaning of the present invention, is meant a polymer having at least two units (n>2) of formula:

[0060] By “polyethersulfone”, within the meaning of the present invention, is meant a polymer having at least two units (n>2) of formula:

[0061] By “polyphenylsulfone”, within the meaning of the present invention, is meant a polymer having at least two units (n>2) of formula:

[0062] Within the meaning of the present invention, a polyethersulfone is not a polysulfone.

[0063] The compositions of solvent(s) according to the present invention effectively make it possible to improve the stability of the polymer solutions at ambient temperature (temperature ranging from 20° C. to 30° C., preferably approximately 25° C.) or at low temperature (temperature ranging from from -10° C. to +10° C., preferably about 0° C.), preferably the stability is improved both at room temperature and at low temperature.

[0064] The compositions of solvent(s) according to the present invention make it possible to improve the storage stability of the polymer solutions, in particular for a storage period which can vary from a few hours to several weeks.

[0065] Improving the stability of solutions can be characterized by obtaining a liquid solution, unlike a solid or a gel. The improvement can also be characterized by a transparent or very slightly colored appearance, as opposed to a cloudy appearance. Improved stability can be evaluated immediately after preparation of the solutions or after a prolonged period, for example ranging from 1 day to 3 weeks.

[0066] The present invention also provides a solution of polymers, said solution comprising a composition of solvent(s) comprising a mixture of at least one molecule having at least one sulfoxide function and at least one molecule having at least one amide function where the the nitrogen atom carries a hydrogen atom (-NH-C(O)-), said solution being substantially free of polyethersulfones. The two molecules (the one carrying the sulfoxide function and the one carrying the amide function) are distinct from each other.

[0067] Preferably, the solution of polymers according to the invention is completely free of polyethersulfones.

[0068] Preferably, the solution of polymers according to the invention is a solution of polymer having sulfone or urethane functions, it being understood that said solution is substantially, in particular totally free, of polyethersulfones.

[0069] The solution of polymers according to the invention can comprise a polysulfone and / or a polyurethane and / or a polyphenylsulfone.

[0070] According to a preferred embodiment, the polymer solution according to the invention is a polysulfone solution.

[0071] According to one embodiment of the invention, the composition of solvent(s) of the polymer solution according to the invention essentially consists of molecules carrying a sulfoxide function and molecules carrying an amide function where the nitrogen atom bears a hydrogen atom (-NH-C(O)-).

[0072] Preferably, the molecule bearing an amide function is cyclic, in particular the amide function can be a cyclic amide function. More preferably, the molecule bearing the amide function is 2-pyrrolidone.

[0073] Preferably, the molecule carrying a sulfoxide function is dimethyl sulfoxide (DMSO).

[0074] According to a particular embodiment, the composition of solvent(s) of the polymer solution comprises DMSO and 2-pyrrolidone. According to one embodiment, the composition of solvent(s) of the solution of polymers according to the invention consists essentially, and preferably exclusively, of DMSO and 2-pyrrolidone.

[0075] According to one embodiment, the composition of solvent(s) of the polymer solution comprises: - from 21 to 75% by weight, preferably from 25 to 70% by weight, more preferably from 30 to 65% by weight of the molecule carrying a sulfoxide function, - from 25 to 79% by weight, preferably from 30 to 75% by weight, more preferably from 35 to 70% by weight of the molecule carrying an amide function where the nitrogen atom carries a hydrogen atom, relative to the total weight of the composition of solvent(s).

[0076] According to one embodiment, the composition of solvent(s) of the polymer solution consists essentially, and preferably exclusively, of: - from 21 to 75% by weight, preferably from 25 to 70% by weight, more preferably from 30 to 65% by weight of the molecule carrying a sulfoxide function, - from 25 to 79% by weight, preferably from 30 to 75% by weight, more preferably from 35 to 70% by weight of the molecule carrying an amide function where the nitrogen atom carries a hydrogen atom, relative to the total weight of the composition of solvent(s).

[0077] According to one embodiment of the invention, the polymer solution comprises: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polymers, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the solution.

[0078] According to one embodiment of the invention, the polymer solution essentially consists of: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polymers, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the solution.

[0079] According to one embodiment of the invention, the polysulfone solution comprises: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polysulfone, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the solution.

[0080] According to one embodiment of the invention, the polysulfone solution essentially consists of: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polysulfone, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the solution.

[0081] According to one embodiment of the invention, the polyurethane solution comprises: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polyurethane, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the solution.

[0082] According to one embodiment of the invention, the polyurethane solution essentially consists of: - from 5 to 50% by weight, preferably from 8 to 35% by weight of polyurethane, and - from 50 to 95% by weight, preferably from 65 to 92% by weight of the composition of solvent(s), relative to the total weight of the solution.

[0083] The invention also relates to a filtration membrane obtained from the solution of polymers according to the invention.

[0084] Preferably, the filtration membrane is a hollow fiber membrane which can be used in a non-limiting manner for the treatment of water or for dialysis.

[0085] Preferably, the membrane according to the invention is obtained from the polysulfone solution according to the invention.

[0086] The filtration membrane according to the invention can be obtained according to a process well known to those skilled in the art.

[0087] According to one embodiment of the invention, the filtration membrane is obtained by a method comprising: - supply of a polymer, preferably a polysulfone, - dissolution of the polymer in the composition of solvent(s) according to the invention comprising a mixture of at least one molecule having a sulfoxide function and at least one molecule having at least one amide function where the nitrogen atom bears a hydrogen atom (-NH-C(O)-) in order to obtain the solution of polymers, preferably of polysulfone, according to the invention - production of a hollow fiber by a process of spinning the polymer solution followed by quenching in a third solvent (water for example) making it possible to precipitate the polymer and to cause the solvent to migrate from the polymer solution to the third solvent ( coagulation: wet process), - possibly recycling the solvent, - possibly sending the aqueous solutions generated to wastewater treatment plants.

[0088] The invention also relates to an artificial leather obtained from the solution of polymers according to the invention.

[0089] Preferably, the artificial leather is obtained from the polyurethane solution according to the invention.

[0090] The artificial leather according to the invention can be obtained according to a process well known to those skilled in the art.

[0091] According to one embodiment of the invention, the artificial leather is obtained by a process comprising: - synthesis of the polymer, preferably a polyurethane, in a solvent medium in order to obtain a polymer in solid form or in the form of a resin containing the polymer and solvent, - dissolution of the polymer in solid or resin form in the composition of solvent(s) according to the invention comprising a mixture of at least one molecule having a sulfoxide function and of a molecule having at least one amide function where the atom of nitrogen carries a hydrogen atom (-NH-C(O)-) in order to obtain the solution of polymers, preferably of polyurethane, according to the invention - production of a film by a process of coating the polymeric solution followed by drying (heat treatment: dry process) to evaporate the solvent,

[0092] This step can also be substituted by a step of: - production of a film by a process of impregnation on a support of the polymeric solution followed by soaking in a third solvent (water for example) making it possible to precipitate the polymer and to make the solvent migrate from the polymeric solution towards the third solvent (coagulation: wet process), - possibly recycling the solvent, - possibly sending the aqueous solutions generated to wastewater treatment plants.

[0093] The invention also relates to the use of the polymer solution according to the invention, for the manufacture of articles such as films, artificial leathers, polymeric suede, polymeric fibers, coatings, membranes, batteries, electronic circuits, or for the protection of electric cables. EXAMPLES

[0094] Different polymer solutions were prepared and their stability was evaluated.

[0095] The polymers used are the following: - Polyurethane (PU): Desmoderm® KB2H available from Bayer, - Polyethersulfone (PES): PES® E3010 available from BASF, - Polysulfone PSU: Solvay Udel® P-3500.

[0096] The following solvent(s) compositions were prepared: - DMSO = 100%, - 2-pyrrolidone = 100%, - DMSO / 2-pyrrolidone = mass ratio 50 / 50, obtained by mixing 45g of DMSO and 45g of 2-pyrrolidone, - DMSO / 2-pyrrolidone = mass ratio 20 / 80, obtained by mixing 18g of DMSO and 72g of 2-pyrrolidone.

[0097] The polymer solutions were then prepared by adding the polymer to each solvent composition. They have the following proportions: PU solution = 12.5% ​​by weight of PU and 87.5% by weight of the composition of solvent(s), obtained by adding 12.86g of PU and 90g of composition of solvent(s), PES solution = 15% by weight of PES and 85% by weight of the composition of solvent(s), obtained by adding 15.88g of PES and 90g of composition of solvent(s), PSU solution=10% by weight of PSU and 90% by weight of the composition of solvent(s), obtained by adding 10g of PSU and 90g of composition of solvent(s).

[0098] The PES and PU polymer solutions are stirred and heated in a water bath at 50° C. until complete dissolution. A stability observation at 0° C. is then carried out for 1 day.

[0099] The PSU solutions are stirred and heated in a water bath at 70° C. until complete dissolution. An observation of stability at low temperature (0° C.) is then carried out for 3 weeks.

[0100] The results are presented in the tables below. Table 1: Evaluation of the solubility at 50°C, dissolution time and appearance after returning to room temperature (25°C) of the solutions of polyethersulfones ESP Composition Solubility at Dissolution Time of Aspect after returning to solvent(s) 50°C Ambient temperature Yes - liquid Very clear liquid Clear DMSO 5h slightly orange-yellow Yes - liquid 2-pyrrolidone clear 24h Yellow yellow clear liquid Yes - liquid DMSO / 2-pyrrolidone transparent 8h Yellow transparent liquid 50 / 50 YELLOW Table 2: Evaluation of the stability of polyethersulfone solutions at low temperature (0°C) after 1 day of storage

[0101] The composition of solvent(s) according to the invention makes it possible to improve the stability at low temperature of polymer solutions comprising a polyethersulfone while maintaining a satisfactory appearance after returning to room temperature. Table 3: Evaluation of the solubility at 50°C, dissolution time and appearance after returning to room temperature (25°C) of the solutions of polyurethane COULD Composition Solubility at Dissolution Time of Aspect after returning to solvent(s) 50°C Ambient temperature YES - liquid DMSO transparent 7h Yellow yellow transparent fluid YES - liquid Viscous transparent 2-pyrrolidone transparent 10h colorless colorless YES - liquid DMSO / 2-pyrrolidone Transparent transparent fluid 12h 50 / 50 colorless colorless Table 4: Evaluation of the stability of polyurethane solutions at low temperature (0°C) after 1 day of storage

[0102] The composition of solvent(s) according to the invention makes it possible to improve the stability at low temperature of polymeric solutions comprising a polyurethane and to obtain an improved appearance after returning to room temperature. Table 5: Evaluation of the solubility at 50°C, dissolution time and appearance after returning to room temperature (25°C) of the polysulfone solutions PSU Composition Solubility at Time of Aspect after return to dissolution of solvent(s) 50°C Ambient temperature YES - Liquid Gel in Liquid White Background DMSO 10h cloudy white colorless supernatant YES - liquid 2-pyrrolidone clear 20h Clear colorless clear liquid YES - liquid DMSO / 2-pyrroli transparent 15h20 Colorless transparent liquid done 50 / 50 colorless Yes - liquid DMSO / 2-pyrroli transparent 6:30 p.m. Colorless transparent liquid done 20 / 80 colorless Table 6: Evaluation of the stability of polysulfone solutions at low temperature (0°C) after 1, 2 and 3 weeks of storage Table 6 shows that the polysulfone solution according to the invention is more stable than a polysulfone solution in DMSO alone or in 2-pyrrolidone alone. In particular, polysulfone solutions comprising a composition of solvent(s) comprising DMSO and 2-pyrrolidone in a 50 / 50 ratio give excellent results in terms of stability at low temperature and this over a period of up to at 3 weeks.

Claims

DEMANDS 1. Composition of solvent(s) comprising a mixture of at least one molecule having at least one sulfoxide function and at least one molecule having at least one amide function where the nitrogen atom bears a hydrogen atom (-NH-C(O)-), said composition being substantially free of polyethersulfones.

2. Composition according to claim 1, wherein the molecule bearing the amide function is cyclic.

3. Composition according to claim 1 or 2, wherein the molecule bearing a sulfoxide function is dimethyl sulfoxide.

4. Composition according to any one of claims 1 to 3, wherein the molecule bearing an amide function is 2-pyrrolidone.

5. Composition according to any one of claims 1 to 4, comprising dimethyl sulfoxide and 2-pyrrolidone.

6. Composition according to any one of claims 1 to 5, comprising: - from 21 to 75% by weight, preferably from 25 to 70% by weight, preferably even more from 30 to 65% by weight of the molecule bearing a sulfoxide function, - 25 to 80% by weight, preferably 30 to 75% by weight, preferably again 35 to 70% by weight of the molecule bearing an amide function where the nitrogen atom carries a hydrogen atom, relative to the total weight of the composition.

7. Use of the composition according to any one of claims 1 to 6, to improve the stability of polymer solutions, preferably polymers having sulfone or urethane functions.

8. Use according to claim 7, wherein the polymer solution is a solution of polysulfone or polyethersulfone or polyphenylsulfone, preferably a solution of polysulfone.

9. Polymer solution(s), said solution comprising a solvent composition(s) comprising a mixture of at least one molecule having at least one sulfoxide function and at least one molecule having at least one amide function where the nitrogen atom bears a hydrogen atom (-NH-C(O)-), said polymer solution being substantially free of polyethersulfones.

10. Polymer solution according to claim 9, wherein the polymer has sulfone or urethane functions.

11. Polymer solution according to claim 9 or 10, wherein the composition of solvent(s) is as defined in any one of claims 2 to 6.

12. Polymer solution according to any one of claims 9 to 11, comprising - 5 to 50% by weight, preferably 8 to 35% by weight of polymers, and - 50 to 95% by weight, preferably 65 to 92% by weight of the solvent composition(s), relative to the total weight of the polymer solution.

13. Filtration membrane obtained from the polymer solution according to any one of claims 9 to 12.

14. Artificial leather obtained from the polymer solution according to any one of claims 9 to 12.

15. Use of the polymer solution according to any one of claims 9 to 12, for the manufacture of films, artificial leathers, polymer suede, fibers polymers, coatings, membranes, batteries, electronic circuits, or for the protection of electrical cables.