FIELD OF THE INVENTION

The present invention relates to a process for preparing a porous fluoropolymer film.

TECHNICAL BACKGROUND

Fluorinated polymers such as polyvinylidene fluoride (PVDF) and copolymers derived from it have a large number of uses, in particular in which they are deposited in the form of a film on a substrate.

Thus, it is known to manufacture electroactive copolymers based on vinylidene fluoride (VDF) and trifluoroethylene (TrFE), which may optionally contain a third monomer such as chlorotrifluoroethylene (CTFE) or 1, 1 -chlorofluoroethylene (CFE). Other copolymers, based on VDF and hexafluoropropene (HFP), have utility for the protection, planarization or passivation of substrates or electronic devices.

The deposition of such fluoropolymers in film form can be carried out from a formulation called "ink", formed by mixing fluoropolymer, and optionally additives, in a vehicle composition.

However, in certain applications, in particular in the field of electronics, batteries or filtration or separation membranes, it is necessary for the fluoropolymer films to be porous.

Thus, different processes have been developed for manufacturing porous fluoropolymer films.

For example, the article by Tamano-Machiavello et al.,

Hydrophobic / Hydrophilic P (VDF-TrFE) / PHEA Polymer Blend Membranes, Journal of Polymer Science, Part B: Polymer Physics, vol. 54, p.672-679, describes a process for obtaining mixed hydrophobic / hydrophilic membranes. In

a first step, a porous membrane of a P copolymer (VDF-TrFE) is prepared. For this, the copolymer is mixed with polyethylene oxide (POE) as sacrificial blowing agent and the mixture is dissolved in N, N-dimethylformamide (DMF), a solvent for the fluorinated copolymer. The solution is deposited on a support at a temperature of 70 ° C. and then cooled to room temperature. The POE is then removed from the membrane by immersing it in water, which creates cavities or pores in place of the sacrificial POE which goes into solution in water. The membrane should then be rinsed with water to remove all the POE. This process is a long, multi-step process that uses a toxic solvent, DMF. In addition, the

This article also generally mentions processes for manufacturing porous membranes using immersion / rinsing, phase separation induced by temperature changes (TIPS, for Temperature-Induced Phase Separation) and penetration steps. water from humidified air in a freshly deposited film (VIPS for Vapor-Induced Phase Separation). All of these processes are multi-step or complex and difficult to implement or rely on the undesirable use of water.

There is therefore a real need to provide a process for preparing a porous fluoropolymer film that is easier to implement, does not require immersion of the film in water or the use of pore-forming polymers, which can contaminate the film. final membrane, nor temperature changes.

SUMMARY OF THE INVENTION

The invention relates firstly to a process for preparing a porous film of a fluoropolymer, comprising the following steps:

- providing an ink comprising the fluoropolymer and a vehicle comprising a solvent for the fluoropolymer and a non-solvent for the fluoropolymer, said solvent for the fluoropolymer and said non-solvent for the fluoropolymer being miscible with one another;

- the deposition of ink on a substrate;

- evaporation of the vehicle comprising the solvent and the non-solvent. In this process:

the non-solvent is selected from the group consisting of benzyl alcohol, benzaldehyde, or a mixture thereof; and,

the solvent has a saturated vapor pressure at 20 ° C. greater than that of the non-solvent, preferably greater by at least 20 Pa.

In embodiments, the fluoropolymer is a polymer comprising units derived from vinylidene fluoride as well as units derived from at least one other monomer of formula CXiX2 = CX3X4, in which each group Xi, X2, X3 and X4 is independently selected from H, Cl, F, Br, I and alkyl groups comprising from 1 to 3 carbon atoms, which are optionally partially or fully halogenated; and preferably the fluoropolymer comprises units derived from vinylidene fluoride and at least one monomer chosen from trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, 1, 1 -chlorofluoroethylene, hexafluoropropene, 3,3,3- trifluoropropene, 1, 3,3,3-tetrafluoropropene,

2.3.3.3-tetrafluoropropene, 1 -chloro-3,3,3-trifluoropropene and 2-chloro-3.3.3-trifluoropropene; and more preferably the fluoropolymer is chosen from poly (vinylidene-co-hexafluoropropene fluoride), poly (vinylidene-co-trifluoroethylene fluoride), poly (vinylidene-ter-trifluoroethylene-ter-chlorotrifluoroethylene fluoride) and poly (vinylidene-fer-trifluoroethylene-ter-1, 1 -chlorofluoroethylene).

In embodiments, the solvent is selected from the group consisting of ketones, esters, especially cyclic esters, dimethylsulfoxide, phosphoric esters such as triethyl phosphate, carbonates, ethers such as tetrahydrofuran, and a mixture. thereof, preferably the solvent being selected from the group consisting of ethyl acetate, methyl ethyl ketone, gamma-butyrolactone, triethyl phosphate, cyclopentanone, propylene glycol monomethyl ether acetate and a mixture of these.

In embodiments, the solvent is gamma-butyrolactone and the non-solvent is benzyl alcohol, or the solvent is ethyl acetate and the non-solvent is benzyl alcohol, or the solvent is benzyl alcohol, or the solvent is ethyl acetate. methyl ethyl ketone and the non-solvent is benzyl alcohol.

In some embodiments, the vehicle comprises a proportion by weight of non-solvent of the fluoropolymer, in percentage, within the range going from (the limit of solubility - 60%) to the limit of solubility, more preferably in the range going from (the solubility limit - 60%) to (the solubility limit - 10%), even more preferably in the range from (the solubility limit - 50%) to (the solubility limit - 20%); and / or the vehicle comprises a proportion by mass of solvent for the fluoropolymer, in percentage, within the range going from (100 - the solubility limit) to (100 - (the solubility limit - 60%)), more preferably in the range going from (100 - (the solubility limit - 10%)) to (100 - (the solubility limit - 60%)), even more preferably in the range going from (100 - (the solubility limit - 20%)) to (100 - (the solubility limit - 50%)); relative to the total weight of the mixture of solvent and non-solvent for the fluoropolymer; the solubility limit being expressed as a percentage by mass.

In some embodiments, the evaporation of the vehicle comprising the solvent and the non-solvent is carried out at a temperature less than or equal to 60 ° C, preferably less than or equal to 50 ° C.

In some embodiments, the deposition is carried out by coating by centrifugation, by spraying or atomization, by coating in particular with a bar or a film puller, by coating with a slit head, by immersion, by roller printing, by printing. in screen printing, by flexography printing, by lithography printing or by inkjet printing.

In embodiments, the ink does not include a sacrificial polymer.

In embodiments, the temperature applied during evaporation of the vehicle comprising the solvent and the non-solvent is essentially constant or varies by less than 20 ° C, preferably less than 10 ° C.

In embodiments, the method is a method for making a filtration or separation membrane, or a battery membrane.

The present invention also relates to a porous film capable of being obtained by the above process, said film having a pore volume estimated by the Barret Joyner Halenda method ranging from 0.020 cm 3 / g to 0.05 cm 3 / g, preferably ranging from 0.025 cm 3 / g to 0.05 cm 3 / g.

The present invention also relates to a porous film capable of being obtained by the above process, said film having a BET specific surface area greater than or equal to 2 m 2 / g, preferably greater than or equal to 3 m 2 / g.

The present invention makes it possible to meet the need expressed above.

It more particularly provides a process for the preparation of a porous film of a fluoropolymer which is simple, easily implemented and which does not necessarily require, during the formation of the film, the application of changes in temperature.

temperature or temperatures other than room temperature or a fixed temperature close to room temperature. In addition, the process according to the invention does not require the use of other sacrificial polymers, in particular hydrophilic, difficult to remove and capable of affecting the purity of the films, nor the immersion of the film in non-solvents and more particularly of water can leave traces of moisture or ionic impurities in the final porous films.

This is accomplished through the use of an ink whose liquid vehicle comprises a solvent for the fluoropolymer and a non-solvent for the fluoropolymer, said solvent and said non-solvent for the fluoropolymer being miscible with each other, the deposition conditions. of the film being adjusted so as to obtain porosity in the film from this ink.

Without wishing to be bound by theory, the inventors believe that the presence of non-solvent could cause local precipitation of the fluoropolymer at the time of "drying" (that is to say during the evaporation of the ink vehicle. deposited on a substrate), ultimately leading to the formation of pores.

According to certain particular embodiments, the invention can be implemented using inks the vehicle of which has a favorable ecotoxicological profile.

BRIEF DESCRIPTION OF THE FIGURES

[Fig. 1] represents a scanning electron microscope image of the film obtained by the method described in Example 1.

[Fig. 2] represents a scanning electron microscope image of the film obtained by the method described in Example 1.

[Fig. 3] represents a scanning electron microscope image of the film obtained by the method described in Example 1.

[Fig. 4A] shows a scanning electron microscope image of a film obtained by the method described in Example 2, for an evaporation carried out at room temperature.

[Fig. 4B] shows a scanning electron microscope image of a film obtained by the method described in Example 2, for an evaporation carried out at 30 ° C.

[Fig. 4C] shows a scanning electron microscope image of a film obtained by the method described in Example 2, for an evaporation carried out at 40 ° C.

[Fig. 4D] shows a scanning electron microscope image of a film obtained by the method described in Example 2, for an evaporation carried out at 50 ° C.

[Fig. 4E] shows a scanning electron microscope image of a film obtained by the method described in Example 2, for an evaporation carried out at 60 ° C.

The white horizontal bar at the bottom right of each shot represents a length of 10 µm.

[Fig. 5A] shows an optical microscope image of film obtained by the method described in Example 2, for an evaporation carried out at room temperature.

[Fig. 5B] shows an optical microscope image of film obtained by the method described in Example 2, for an evaporation carried out at 30 ° C.

[Fig. 5C] represents an optical microscope image of film obtained by the method described in Example 2, for an evaporation carried out at 40 ° C.

[Fig. 5D] represents an optical microscope image of film obtained by the method described in Example 2, for an evaporation carried out at 50 ° C.

[Fig. 5E] represents an optical microscope image of film obtained by the method described in Example 2, for an evaporation carried out at 60 ° C.

The white horizontal bar at the bottom right of each shot represents a length of 100 µm.

[Fig. 6] schematically represents a neural network which can be used for the implementation of the invention, in certain embodiments.

[Fig. 7] schematically shows a computer system that can be used to implement the invention, in certain embodiments.

DETAILED DESCRIPTION

The invention is now described in more detail and in a nonlimiting manner in the description which follows.

Unless otherwise indicated, all percentages relating to amounts are percentages by weight.

In the present application, the expression “a fluoropolymer” should be understood to mean “one or more fluoropolymers”. It is the same with all other species. Thus, for example, the expression "a non-solvent" should be understood to mean "one or more non-solvents".

Ink

The method according to the invention uses an ink comprising a fluoropolymer and a vehicle.

The fluoropolymer is preferably a carbon chain polymer which comprises structural units (or units, or repeating units, or units) comprising at least one fluorine atom.

Preferably, the fluoropolymer comprises units derived from (that is to say which are obtained by polymerization of) vinylidene fluoride (VDF) monomers.

In some embodiments, the fluoropolymer is a PVDF homopolymer.

However, it is preferred that the fluoropolymer is a copolymer (in the broad sense), that is to say that it comprises units derived from at least one monomer other than VDF.

A single X monomer can be used, or several different X monomers, depending on the case.

In some embodiments, the X monomer can be of the formula CXiX2 = CX3X4, in which each group Xi, X2, X3 and X4 is independently selected from H, Cl, F, Br, I and C1 - alkyl groups. C3 (preferably in C1 -C2), which are optionally partially or totally halogenated - this monomer X being different from VDF (that is to say that if X1 and X2 represent H, at least one of X3 and X4 does not represent F; and if X1 and X2 represent F, at least one of X3 and X4 does not represent H).

In certain embodiments, each X1, X2, X3 and X4 group independently represents an H, F, Cl, I or Br atom, or a methyl group optionally comprising one or more substituents selected from F, Cl, I and Br.

In some embodiments, each group X1, X2, X3 and X4 independently represents an H, F, Cl, I or Br atom.

In some embodiments, only one of X1, X2, X3 and X4 represents a Cl or I or Br atom, and the others of the groups X1, X2, X3 and X4 independently represent: an H or F atom or an alkyl group in C1 -C3 optionally comprising one or more fluorine substituents; preferably, an H or F atom or a C1 -C2 alkyl group optionally comprising one or more fluorine substituents; and of

more preferably, an H or F atom or a methyl group optionally comprising one or more fluorine substituents.

Examples of X monomers are: vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropene (HFP), trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1, 3,3,3-tetrafluoropropene (in cis or preferably trans form), hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes and in particular 1, 1, 3, 3,3-pentafluoropropene or 1, 2, 3,3,3-pentafluoropropene, perfluoroalkylvinylethers and in particular those of general formula Rf-0-CF = CF2, Rf being an alkyl group, preferably from C1 to C4 (examples preferred being perfluoropropylvinylether or PPVE and perfluoromethylvinylether or PMVE).

In some embodiments, monomer X has a chlorine or bromine atom. It can in particular be chosen from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Chlorofluoroethylene can denote either 1 -chloro-1 -fluoroethylene or 1 -chloro-2-fluoroethylene. The 1 -chloro-1 -fluoroethylene (CFE) isomer is preferred. The chlorotrifluoropropene is preferably 1 -chloro-3,3,3-trifluoropropene (in cis or trans form, preferably trans) or 2-chloro-3,3,3-trifluoropropene.

In certain preferred embodiments, the fluoropolymer comprises units derived from VDF and HFP, or else is a polymer P (VDF-HFP) consisting of units derived from VDF and HFP.

The molar proportion of repeating units derived from the HFP is preferably from 2 to 50%, in particular from 5 to 40%.

In some preferred embodiments, the fluoropolymer comprises units derived from VDF and CFE, or CTFE, or TFE, or TrFE. The molar proportion of repeat units derived from monomers other than VDF is preferably less than 50%, more preferably less than 40%.

In certain preferred embodiments, the fluoropolymer comprises units derived from VDF and TrFE, or else is a polymer P (VDF-TrFE) consisting of units derived from VDF and TrFE.

In certain preferred embodiments, the fluoropolymer comprises units derived from VDF, TrFE and another monomer X as defined above, other than VDF and TrFE, or else is a polymer P (VDF-T rFE-X) consisting of units derived from VDF, T rFE and another monomer X as defined above, other than VDF and TrFE. In this case, preferably, the other monomer X is chosen from TFE, HFP, trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1, 3,3,3-tetrafluoropropene (in the oois or preferably trans form), bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Particularly preferred are CTFE or CFE.

When units derived from VDF and T rFE are present, the proportion of units derived from TrFE is preferably from 5 to 95 mol.% Relative to the sum of units derived from VDF and T rFE, and in particular: from 5 at 10 mol.%; or from 10 to 15 mol.%; or from 15 to 20 mol.%; or from 20 to 25 mol.%; or from 25 to 30 mol.%; or from 30 to 35 mol.%; or from 35 to 40 mol.%; or from 40 to 45 mol.%; or from 45 to 50 mol.%; or from 50 to 55 mol.%; or from 55 to 60 mol.%; or from 60 to 65 mol.%; or from 65 to 70 mol.%; or from 70 to 75 mol.%; or from 75 to 80 mol.%; or from 80 to 85 mol.%; or from 85 to 90 mol.%; or from 90 to 95 mol.%. A range of 15 to 55 mol.% Is particularly preferred.

When units derived from another X monomer, in addition to VDF and TrFE, are present (the X monomer being in particular CTFE or CFE), the proportion of units derived from this other X monomer in the fluoropolymer (for example relative to all the units) may vary, for example, from 0.5 to 1 mol%; or from 1 to 2 mol.%; or from 2 to 3 mol.%; or from 3 to 4 mol.%; or from 4 to 5 mol.%; or from 5 to 6 mol.%; or from 6 to 7 mol.%; or from 7 to 8 mol.%; or from 8 to 9 mol.%; or from 9 to 10 mol.%; or from 10 to 12 mol.%; or from 12 to 15 mol.%; or from 15 to 20 mol.%; or from 20 to 25 mol.%; or from 25 to 30 mol.%; or from 30 to 40 mol.%; or from 40 to 50 mol.%. Ranges from 1 to 20 mol.%, And preferably from 2 to 15 mol.%, Are particularly suitable.

The molar composition of the units in fluoropolymers can be determined by various means such as infrared spectroscopy or RAMAN spectroscopy. Conventional methods of elemental analysis for the elements carbon, fluorine and chlorine or bromine or iodine, such as X-ray fluorescence spectroscopy, make it possible to calculate the mass composition of the polymers, from which the molar composition is deduced.

Multi-core NMR techniques can also be used, in particular proton (1 H) and fluorine (19F), by analysis of a solution of the polymer in an appropriate deuterated solvent.

It is finally possible to combine elemental analysis, for example for heteroatoms such as chlorine or bromine or iodine, and NMR analysis. Thus, the content of units obtained from CTFE, in a P terpolymer (VDF-TrFE-CTFE) for example, can be determined by measuring the chlorine content by elemental analysis.

The viscosity of the fluoropolymer is preferably from 0.1 to 100 kPo (kiloPoise) by performing a measurement at 230 ° C and at 100 s -1 of shear rate (according to ASTM D4440)

The fluoropolymer is preferably random and linear.

The fluoropolymer can be homogeneous or heterogeneous. A homogeneous polymer has a uniform chain structure, the statistical distribution of the units resulting from the different monomers hardly varying between the chains. In a heterogeneous polymer, the chains exhibit a distribution in units resulting from the various monomers of multimodal or spread type. A heterogeneous polymer therefore comprises chains richer in a given unit and chains poorer in this unit.

The ink vehicle comprises a fluoropolymer solvent and a fluoropolymer non-solvent. The fluoropolymer solvent and the fluoropolymer non-solvent are miscible with each other.

The term “vehicle comprising a / the solvent for the fluoropolymer and a / the non-solvent for the fluoropolymer” means the association in particular of a solvent for the fluoropolymer with a non-solvent for the fluoropolymer. This vehicle is preferably homogeneous at the molecular level.

By “solvent for the fluoropolymer” is meant a liquid in which the fluoropolymer is capable of dissolving. By “dissolution of the fluoropolymer in a solvent” is meant the formation of a true solution, that is to say single-phase or homogeneous at the molecular level.

By “non-solvent of the fluoropolymer” is meant a liquid in which the fluoropolymer is not capable of completely dissolving (or in which the fluoropolymer is not completely soluble). The addition of the polymer in a non-solvent does not make it possible to obtain a true, single-phase or homogeneous solution at the molecular level.

The solubility of the fluoropolymer in a given liquid can be determined for example by adding an amount of fluoropolymer of 5% w / w to said liquid at room temperature (eg 25 ° C), stirring, if necessary with moderate heating to a temperature of 60 ° C or less (for example at a temperature of 60 ° C), for example for 60 minutes, then allowing to cool to room temperature (for example 25 ° C) and observing visually, at this temperature, after for example 60 minutes whether or not solid polymer remains in suspension.

The term “miscible” is understood to mean capable of mixing to form, in the absence of the polymer, a homogeneous mixture at the molecular level and preferably transparent, without any trace of liquid / liquid phase separation.

The use of a vehicle in which the solvent and the non-solvent are miscible allows easier handling of the ink and facilitates the preparation of the porous film.

The solvents and non-solvents which can be used in the present invention can be, in general, any vehicle that is liquid at room temperature, and can in particular be chosen from alcohols, ethers, halogenated vehicles, alkanes, cycloalkanes, aromatic vehicles, ketones, aldehydes, esters, including cyclic esters, carbonates, phosphates, furans, amides and sulfoxides, as well as combinations thereof.

As the solvent for the fluoropolymer, any liquid vehicle capable of dissolving the fluoropolymer can be used. Preferably, the solvent is chosen from the group consisting of ketones, esters, in particular cyclic esters, dimethylsulfoxide, phosphoric esters such as triethyl phosphate, carbonates, ethers such as tetrahydrofuran, and a mixture of these. this. Highly volatile solvents are particularly preferred, in particular methyl ethyl ketone or ethyl acetate. The latter also has the advantage of having a favorable ecotoxicological profile. Low volatile solvents can also be used, in particular gamma-butyrolactone, triethyl phosphate, cyclopentanone, propylene glycol monomethyl ether acetate.

Particularly preferably, the non-solvent is benzyl alcohol, benzaldehyde, or a mixture thereof. These non-solvents offer the advantage of both being low volatility and having a favorable ecotoxicological profile (so-called “green” non-solvents).

Particularly advantageously, the non-solvent is not water and, more preferably, does not include water.

Examples of combinations of solvent and of non-solvent for the fluoropolymer which can be used in the invention are: ethyl acetate / benzyl alcohol; ethyl acetate / benzaldehyde; gamma-butyrolactone / benzyl alcohol; gamma-butyrolactone / benzaldehyde; triethyl phosphate / benzyl alcohol; triethyl phosphate / benzaldehyde; cyclopentanone / benzyl alcohol;

cyclopentanone / benzaldehyde; propylene glycol acetate / benzyl alcohol monomethyl ether; propylene glycol / benzaldehyde monomethyl ether acetate; methyl ethyl ketone / benzyl alcohol; methyl ethyl ketone / benzaldehyde. Particularly preferably, the solvent is gamma-butyrolactone and the non-solvent is benzyl alcohol, or the solvent is ethyl acetate and the non-solvent is benzyl alcohol, or the solvent is methyl ethyl ketone and the non-solvent is benzyl alcohol.

Advantageously, the solvent can have a lower boiling point than that of the non-solvent. This can make it possible to accelerate the precipitation of the fluoropolymer during the evaporation of the ink vehicle and to use inks comprising a lower proportion of non-solvent of the fluoropolymer. Preferably, the solvent has a boiling point at least 10 ° C lower than that of the non-solvent, more preferably at least 20 ° C lower, more preferably at least 30 ° C lower.

Advantageously, the solvent can have a saturated vapor pressure at 20 ° C. greater than that of the non-solvent. This can make it possible to accelerate the precipitation of the fluoropolymer during the evaporation of the ink vehicle and to use inks comprising a lower proportion of non-solvent of the fluoropolymer. Preferably, the solvent has a saturated vapor pressure at 20 ° C greater by at least 20 Pa than that of the non-solvent, more preferably greater by at least 50 Pa, more preferably greater by at least 100 Pa .

For a mixture comprising a given solvent and a non-solvent for the fluoropolymer, it is possible to determine a “solubility limit” (or dissolution limit) of the fluoropolymer in this mixture, at a certain temperature and at a certain concentration in polymer; within the meaning of the invention, this “solubility limit” corresponds to the mass proportion of non-solvent (relative to the total of the mixture of solvent and non-solvent) from which the fluoropolymer precipitates in a macroscopically visible manner (ie (i.e. visible to the naked eye) in the mixture. This solubility limit can be defined by determining the solubility of the fluoropolymer in mixtures with increasing proportions by mass of non-solvent,

Preferably, the ink comprises a proportion by weight of non-solvent for the fluoropolymer, in percentage, in the range going from (the solubility limit - 60%) to the solubility limit, more preferably in the range going from ( the solubility limit - 60%) to (the solubility limit

- 10%), even more preferably in the range going from (the solubility limit - 60%) to (the solubility limit - 20%), even more preferably in the range going from (the solubility limit - 50%) at (the solubility limit - 20%), relative to the total weight of the mixture of solvent and non-solvent for the fluoropolymer, the solubility limit being expressed as a percentage by mass and as defined in the previous paragraph.

The use of a non-solvent in a proportion by weight below the solubility limit, or even significantly below the solubility limit, can allow easier preparation of the ink and can improve the stability of the ink in the ink. the weather.

In embodiments, the ink comprises a proportion by weight of non-solvent of the fluoropolymer, in percentage, ranging from (the solubility limit - 60%) to (the solubility limit -50%), or in the range from (the solubility limit - 50%) to (the solubility limit - 40%), or in the range from (the solubility limit - 40%) to (the solubility limit - 30% ), or in the range from (the solubility limit - 30%) to (the solubility limit - 20%), or in the range from (the solubility limit - 20%) to (the solubility limit - 15%), or in the range from (the solubility limit - 15%) to (the solubility limit - 10%), or in the range from (the solubility limit - 10%) to (the solubility limit - 10%) solubility - 8%),or in the range from (the solubility limit - 8%) to the solubility limit, relative to the total weight of the mixture of solvent and non-solvent of the fluoropolymer, the solubility limit being expressed as a percentage by mass.

Preferably, the ink comprises a proportion by weight of solvent for the fluoropolymer, in percentage, within the range going from (100

- the solubility limit) to (100 - (the solubility limit - 60%)), more preferably in the range going from (100 - (the solubility limit -10%)) to (100 - (the solubility limit) - 60%)), even more preferably in the range going from (100 - (the solubility limit - 20%)) to (100 - (the solubility limit - 50%)), relative to the total weight of the mixture of solvent and non-solvent for the fluoropolymer, the solubility limit being expressed as a percentage by mass.

In embodiments, the ink comprises a proportion by weight of the fluoropolymer solvent, in percent, ranging from (100 - (the limit of solubility - 50%)) to (100 - (the limit of solubility - 60%)), or in the range from (100 - (the solubility limit - 40%)) to (100 - (the solubility limit - 50%)), or in the range from (100 - ( the solubility limit - 30%)) to (100 - (the solubility limit - 40%)), or in the range from (100 - (the solubility limit - 20%)) to (100 - (the limit solubility - 30%)), or in the range from (100 - (the solubility limit - 15%)) to (100 - (the solubility limit - 20%)), or in the range from (100 - (the solubility limit - 10%)) to (100 - (the solubility limit - 15%)),or in the range from (100 - (the solubility limit - 8%)) to (100 - (the solubility limit - 10%)), or in the range from (100 - the solubility limit) to ( 100 - (the solubility limit - 8%)), relative to the total weight of the mixture of solvent and non-solvent of the fluoropolymer, the solubility limit being expressed as a percentage by mass.

In other embodiments, the ink comprises 0.1 to 5%, or 5 to 10%, or 10 to 20%, or 20 to 30%, or 30 to 40%, or 40 to 50%, or 50 to 60%, or 60 to 70%, or 70% to 80%, or 80 to 90%, or 90 to 95%, or 95 to 99.9%, by weight of fluoropolymer solvent, relative to the total weight of liquid vehicle.

In embodiments, the ink comprises 0.1 to 5%, or 5 to 10%, or 10 to 20%, or 20 to 30%, or 30 to 40%, or 40 to 50%, or 50 to 60%, or 60 to 70%, or 70% to 80%, or 80 to 90%, or 90 to 95%, or 95 to 99.9%, by weight of fluoropolymer non-solvent, based on the total weight of liquid vehicle.

The ink may contain 0.1 to 60%, preferably 0.5 to 30%, more preferably 1 to 25%, more preferably 3 to 20% by weight of polymer, relative to the total weight ink. The polymer can consist of the above fluoropolymer, or can include said fluoropolymer and one or more additional polymers. The ink preferably comprises from 0.1 to 60%, more preferably from 0.5 to 30%, more preferably from 1 to 25%, even more preferably from 3 to 20%, by weight of the fluoropolymer, relative to to the total ink weight.

Advantageously, the ink does not include a sacrificial polymer. By “sacrificial polymer” (or “porogenic polymer”) is meant a polymer intended to be removed to form the porous film, the elimination of this polymer from the film creating pores in the film. Such a polymer is therefore present in the ink used to form the film but is not substantially present in the final porous film.

The ink may optionally comprise one or more additives, in particular chosen from agents modifying rheology, agents modifying the resistance to aging, agents modifying adhesion,

pigments or dyes, fillers (including nanofillers). The ink may also contain one or more additives which have been used for the synthesis of the polymer or polymers.

However, particularly preferably, the ink does not include rheology modifiers (also called “rheological additives”), in particular silica particles, calcium carbonate particles, and / or crosslinked polymer particles. . Preferably, the ink does not include agents for modifying surface or interfacial tension, such as surfactants.

In certain embodiments in which it is desired to crosslink the polymers after deposition of the composition, the ink comprises at least one additive to aid crosslinking preferably chosen from free radical initiators, photoinitiators, co-agents such as bifunctional or polyfunctional molecules in terms of reactive double bonds, basic crosslinking agents such as di-amines, and combinations thereof.

In other embodiments, no crosslinking aid additive, such as a photoinitiator or a crosslinking agent, is present in the ink.

The total content of additives is preferably less than 20% by weight, more preferably less than 10% by weight, relative to the total of polymers and additives.

The ink preferably has a non-volatile solids content of 0.1 to 60%, preferably 0.5 to 30%, more preferably 1 to 25%, more preferably 3 to 20% by weight .

Ink deposit

The ink described above is deposited on a substrate. The substrate may be a surface of a metal, coated or not with an oxide or nitride layer of said metal or of another metal, of a plastic material, of wood, of paper, of concrete, of mortar. or grout, of glass, of plaster, of woven or non-woven fabric, of leather, etc. Preferably, the substrate is a surface of glass, or of silicon, coated or not with silicon nitride or oxides of silicon, or quartz, or a polymer material (in particular polyethylene terephthalate or polyethylene naphthalate), or a metal other than silicon, or a mixed surface made up of several different materials, coated or not with passivating layers of oxides or nitrides metallic.

Applying the ink can include spreading by discrete or continuous means. The deposition can be carried out in particular by coating by centrifugation (“spin-coating”), by spraying or atomization (“spray coating”), by coating in particular with a bar or a film puller (“bar coating”), by coating with a slot-die coating, by immersion (“dip coating”), by roller printing (“roll-to-roll printing”), by screen-printing, by flexography printing, lithography printing or ink-jet printing.

Preferably, the ink is deposited on the substrate at a temperature less than or equal to 60 ° C, more preferably less than or equal to 50 ° C, even more preferably less than or equal to 40 ° C, for example at ambient temperature (between 15 and 30 ° C).

Filmification

The vehicle comprising the solvent and the non-solvent of the fluoropolymer is evaporated after the deposition. The fluoropolymer layer (which may also optionally include one or more polymers and / or additives) then solidifies to form a porous film.

In order to obtain a porous film, and not a continuous film (that is to say non-porous), a temperature less than or equal to an “evaporation limit temperature” is applied during the evaporation step of the. ink vehicle (also referred to as the "drying" step in the present description). This evaporation limit temperature depends on the vehicle of the ink, in particular on the solvent and the non-solvent of the fluoropolymer and on their proportions, and on the duration of the evaporation when the latter is less than a few hours.

Preferably, the temperature at which the evaporation of the ink vehicle is carried out is less than or equal to 60 ° C, more preferably less than or equal to 55 ° C, even more preferably less than or equal to 50 ° C. For example, the evaporation of the ink vehicle is carried out at a temperature ranging from 0 to 60 ° C, more preferably from 5 to 55 ° C, even more preferably at room temperature (from 15 to 30 ° C). In some embodiments, the temperature is 0 to 5 ° C, or 5 to 10 ° C, or 10 to 15 ° C, or 15 to 20 ° C, or 20 to 25 ° C, or 25 at 30 ° C, or 30 to 35 ° C, or 35 to 40 ° C, or 40 to 45 ° C, or 45 to 50 ° C, or 50 to 55 ° C, or 55 to 60 ° C, or 60 to 65 ° C, or 65 to 70 ° C.

The duration of the evaporation can be, for example, from 1 minute to 48 hours, preferably from 5 minutes to 24 hours, more preferably from 10 minutes to 15 hours. During this period, the temperature can remain constant, or else vary, as long as it remains less than or equal to the evaporation limit temperature. For example, the temperature can vary within the ranges mentioned above.

Advantageously, the temperature applied during the step of evaporating the ink vehicle exhibits a variation during the step, the amplitude of which is less than or equal to 50 ° C, preferably less than or equal to 40 ° C, more preferably less than or equal to 30 ° C, even more preferably less than or equal to 20 ° C, even more preferably less than or equal to 10 ° C. In some embodiments, the applied temperature remains constant or substantially constant during the evaporation of the ink vehicle. The porosity of the film can be adjusted by varying the temperature during the evaporation step.

Preferably, the environment in which the evaporation of the vehicle is carried out has a relative humidity less than or equal to 10%, more preferably less than or equal to 5%, more preferably less than or equal to 3%, more preferably equal to at 0%.

Advantageously, the method according to the invention does not include a step of immersing the fluoropolymer film in a liquid to create pores in said film, in particular no step of immersing the film in water or in a watery liquid.

The fluoropolymer layer thus formed (after evaporation) may in particular have a thickness of 50 nm to 150 μm, preferably from 200 nm to 120 μm, and more preferably from 500 nm to 100 μm.

In some embodiments, a crosslinking step can be performed by subjecting the layer to radiation, such as X, gamma, UV radiation or by thermal activation.

The porous film preferably has pores having an average diameter of 0.1 to 10 µm, more preferably 0.2 to 5 µm, more preferably 0.3 to 4 µm. The average pore diameter can be measured by scanning electron microscopy.

Obtaining a porous film can be determined by observing the film with an optical and / or electron microscope (for example with a scanning electron microscope) and / or by observing the appearance of the film with the naked eye: a porous film having a white appearance, as opposed to the translucent or transparent appearance of a non-porous film.

Applications

The porous fluoropolymer film can be used as an electroactive layer and / or as a dielectric layer in an electronic device, and in particular when the fluoropolymer is a P (VDF-TrFE) or P (VDF-TrFE-CFE) copolymer. ) or P (VDF-T rFE-CTFE) as described above and the pores are filled with another liquid or solid substance, such as for example an insulating oil, an electroactive polymer, or insulating non-electroactive, so that the composite layer obtained exhibits dielectric properties.

When the porous film of the invention is used as a deposition on a substrate, one or more additional layers can be deposited on the substrate provided with the fluoropolymer film, for example one or more layers of polymers, of semiconductor materials, or of metals, in a manner known per se.

By electronic device is meant either a single electronic component, or a set of electronic components, capable of fulfilling one or more functions in an electrical or electronic circuit.

According to certain variations, the electronic device is more particularly an optoelectronic device, that is to say capable of emitting, detecting or controlling electromagnetic radiation.

Examples of electronic devices, or where appropriate optoelectronic, concerned by the present invention are ferroelectric memories, transistors (in particular field effect), chips, batteries, electrodes, photovoltaic cells, light-emitting diodes (LEDs ), organic light-emitting diodes (OLEDs), sensors, actuators, transformers, haptic devices, microelectromechanical systems (MEMS) and detectors.

Electronic and optoelectronic devices are used and integrated in many devices, equipment or electronic sub-assemblies and in many objects and applications such as televisions, computers, mobile phones, rigid or flexible screens, layered photovoltaic modules thin, light sources, energy sensors and converters, medical devices, floors and walls, roofs and ceilings, etc.

In all cases, the electronic device may in particular comprise a substrate and electronic elements supported thereon, which may comprise layers of conductive material, of material.

semiconductor and others. The electronic elements are preferably on a single side of the substrate but in some embodiments they can be on both sides of the substrate. The porous layer according to the invention can be an integral part of the electronic components, cover all or part of the electronic elements, and all or part of the substrate.

The porous film can also be used, in an electronic device, such as an ultrasonic detector or transmitter, as ultrasonic wave absorbing layers.

It can also be used as, or for the manufacture of, a separator membrane in a battery, for example in a lithium-based battery.

The porous fluoropolymer film can also be used as, or for the manufacture of, a filtration or microfiltration membrane, or separation membrane, such as a separation membrane in a liquid-liquid separation device, liquid-gas, liquid-solid, gas-gas or solid-solid.

Ink preparation

The ink can be prepared by dispersing the fluoropolymer, in solid form, (and optionally the other polymers) in the vehicle comprising the solvent and the non-solvent of the fluoropolymer, and preferably by mixing.

The temperature applied during preparation is preferably 0 to 100 ° C, more preferably 10 to 75 ° C, more preferably 15 to 60 ° C, and most preferably 20 to 30 ° C. In some embodiments, the preparation is carried out at room temperature. Advantageously, the preparation is carried out with moderate stirring.

The vehicle comprising the solvent and the non-solvent for the fluoropolymer can be prepared by mixing the solvent for the fluoropolymer with the non-solvent for the fluoropolymer. This mixture can be prepared before, during or after the incorporation of the fluoropolymer (and / or of the possible other polymers), that is to say that the fluoropolymer can be dispersed in the solvent and the non-solvent already mixed. , or the fluoropolymer, the solvent and the non-solvent can be added at the same time, or the fluoropolymer can be added in the solvent or in the non-solvent, the non-solvent or the solvent being added afterwards.

When additives must be added to form the ink according to the invention, they can be added before, during or after the dispersion of the polymers in the liquid vehicle.

The solvent and the non-solvent for the fluoropolymer can be a known solvent or non-solvent for the fluoropolymer. Alternatively, it is possible to evaluate the solubility of the fluoropolymer in a given liquid vehicle, so as to determine whether this vehicle is a solvent or a non-solvent for the fluoropolymer, for example in the manner described above.

According to other embodiments, the solubility of the fluoropolymer in a given liquid vehicle can be determined by a computer implemented method. This method is based on a function configured to associate a probability of solubility of the fluoropolymer with solubility parameters of a vehicle composition, for example determined by learning.

Function determined by learning

Preferably, the above function is determined by a computer implemented method.

The determination of this function may be based on training a training data set and then training the function based on the training data set.

The training data set includes, for several respective vehicle compositions:

- a plurality of solubility parameters of the vehicle composition;

- in association with information on the solubility of the fluoropolymer in the vehicle composition in question.

By “association” is meant here that there is a link between the data in question, for each vehicle composition. Thus, solubility parameters and solubility information can be stored in a relational database. For example, the solubility parameters and the information on the solubility can be entered in respective fields of the same database.

The information on the solubility of the fluoropolymer is preferably a binary information of yes / no type, that is to say soluble or insoluble. It can thus for example be coded in the form of a 0 or a 1. This information can be determined if necessary by an experimental test for each vehicle composition of the training data set, for example by adding a certain amount of fluoropolymer to the vehicle composition, stirring, if necessary by heating moderately. (for example at a temperature less than or equal to 60 ° C, or less than or equal to 50 ° C, or less than or equal to 40 ° C) but preferably at room temperature, and by visually observing after for example 15 or 60 minutes whether or not solid polymer remains in suspension.

The solubility parameters of the vehicle composition may in particular be two in number, or preferably three in number.

It is in particular preferred to choose the solubility parameters from the Hansen solubility parameters.

The Hansen solubility parameters are as follows:

- 5d: dispersive component (energy linked to the forces of dispersion between the molecules of the composition);

- dr: polar component (energy linked to intermolecular dipolar forces between the molecules of the composition); and

- 5h: hydrogen component (energy linked to hydrogen bonds between the molecules of the composition).

Preferably, all of the Hansen solubility parameters are provided at the same reference temperature, for example 25 ° C.

The solubility parameters used in the training data set can thus be 5d and d R ; or ôd and ôh; or d R and ôh; or particularly preferably ôd, d R and ôh.

The Hansen solubility parameters can be given in MPa 1/2 or in any other unit (for example in (cal / cm 3 ) 1/2 ).

The solubility parameters can be determined by experimental tests combined with theoretical considerations (semi-empirical methods). So for example, Hoy determined the components ôd, d R and ôh in a semi-empirical way using (Handbook of Solubility Parameters, and Other Cohesion Parameters, 1983 edition, page 59):

1. The experimental evaluation of the Hildebrand solubility parameter expressed as ôt (Hildebrand solubility parameter) = (ôd 2 + ô P 2 + ôh 2 ) 1/2 (enthalpy of vaporization measurements and use of equations of state ).

2. The estimate of ôh from an aggregation number obtained from an equation resulting from the regression of the molar volume as a function of the Tb / Tc ratio (boiling temperature, crystallization temperature), of the molecular mass and density.

3. The calculation of the parameter d R by a method of contribution of groups to the molar attraction.

4. The deduction of the parameter 5d, by difference, from the expression of the Hildebrand solubility parameter (point 1).

Preferably, the solubility parameters are taken from one or more pre-existing reference tables. By “reference table” is meant a compilation of data relating to the cohesive energy (which ultimately translates into the solubility parameters) of various vehicle compositions, these data being derived from experimental or semi-empirical work carried out. according to the same methodology, and preferably with the same equipment and by the same team.

In some embodiments, all of the solubility parameters of the training data set come from a single reference table. In other embodiments, the solubility parameters of the training data set are taken from two or more different reference tables. It has surprisingly been observed that the use of data originating from at least two different reference tables leads to the determination of a reliable function. Using at least two different lookup tables can be advantageous in that it can minimize the risk of bias or error in the training data. It is thus possible to integrate into the training data set a first set of solubility parameters for a given vehicle composition, from a first reference table, and a second set of solubility parameters for the same given vehicle composition, from a second reference table. It is also possible to proceed in this way for several given vehicle compositions or for all vehicle compositions.

By way of example, the solubility parameters can be taken from a reference table contained in the CRC Handbook of Solubility Parameters and Other Cohesion Parameters, by Allan FM Barton, 2 nd edition (1991), and for example from Table 2 of Chapter 7 and / or Table 5 of Chapter 8 of this book.

The vehicle compositions of the training data set can be pure substances and / or mixtures of substances. The term "pure substance" is used as opposed to "mixture of substances". A pure substance thus preferably has a mass purity greater than or equal to 98%, or to 99%, or to 99.5%, or

at 99.9%. It is understood that a pure substance within the meaning of the present application may contain small amounts of impurities.

When mixtures of substances are considered, the solubility parameters can be determined by experimental or semi-empirical tests, or preferably be calculated as a linear combination from the solubility parameters of the pure substances in the mixture. In such a linear combination, the weighting coefficients applied preferably correspond to the volume proportions of each of the substances.

The training data set can be divided into a training data set and a test data set. Learning can then be implemented by performing sequences of a training phase (on the training data set) and a test phase (on the test data set), and until the test phase gives a positive result (that is, until the test phase meets a validation criterion). Alternatively, the training data set can be entirely constituted by the training data set, and no test phase is performed, or else the test phase is performed on additional data.

It is also possible to provide for the training data set to be successively divided N times in a different manner into a training data set and a test data set. Each time, the training phase and test phase sequences are carried out as described above. This results in N different models. The model with the best statistical validation (lowest error) is chosen as the final model for the function.

This method is particularly suitable when the training dataset is small, because it offers efficient use of a limited amount of data.

The learning can be carried out by machine learning, according to any technique known to those skilled in the art.

The learning can in particular be based on a neural network model.

The neural network can be binary response (perceptron network) or gradual response, giving a probability for example in the form of any value between 0 and 1 (sigmoid neural network for example).

The neural network has an input layer, one or more intermediate layers, or hidden layers, and an output layer.

The input layer contains part of the training data. It feeds a single intermediate or hidden layer, or else a succession of intermediate or hidden layers, which itself feeds the output layer.

Each intermediate layer performs a digital operation using data from the previous layer, with the digital operation involving varying parameters. The result of the digital operation feeds into the next layer.

The output layer also performs a digital operation on the basis of data from the previous layer, the digital operation involving variable parameters. The result of the numerical operation provides an estimate of the probability of solubility.

An error function is then calculated from this solubility probability estimate and the corresponding solubility information in the training data set. The variable parameters of the intermediate layer (s) and of the output layer are optimized so as to minimize the error function. The network can, in certain cases, feed back with the results of calculations (outputs) becoming inputs for neurons of the layer considered or of the preceding layers. Preferably, a network without feedback is used.

By way of example, and with reference to figure 6, the solubility parameters 1, 2, 3 can be supplied as input to three neurons 4, 5, 6 of a single intermediate layer, which themselves feed a output layer 7.

Each of the intermediate neurons 4, 5, 6 calculates a numerical function from the solubility parameters 1, 2, 3. The numerical function can for example comprise a linear or affine combination of the solubility parameters 1, 2, 3, the coefficients ( weight) of the linear or affine combination corresponding to variable parameters as described above; the numerical function can also comprise the application of another mathematical function to such a linear or affine combination, by way of example the application of a hyperbolic tangent function.

The output layer 7 calculates a digital function from the values ​​coming from the intermediate neurons 4, 5, 6.

In certain embodiments, a threshold can be associated with each intermediate neuron 4, 5, 6. Each intermediate neuron 4, 5, 6 is therefore activated or not with respect to the output layer 7, that is to say. that is to say feeds the output layer 7 or not, depending on whether the value of the calculated digital function fulfills a condition defined with respect to the threshold or not. The threshold, like the weights, represents a variable parameter as described above.

The digital function of the output layer 7 can for example comprise a linear or affine combination of the values ​​originating from the intermediate neurons 4, 5, 6, the coefficients of the linear or affine combination corresponding to variable parameters as described above; the digital function can also comprise the application of another mathematical function to such a linear or affine combination, by way of example the application of a hyperbolic tangent function or any other exponential function or combination of exponential functions.

When the neural network has a binary response, the value resulting from the digital function of the output layer 7 is compared with a predetermined threshold, to give a response of yes / no type, which can for example be coded in the form of 'a 0 or a 1.

When the neural network has a gradual response, the value resulting from the digital function of the output layer 7 is for example any value between 0 and 1, indicating a probability of solubility of the fluoropolymer in the vehicle composition.

In either case, the value resulting from the numerical function of the output layer 7 is compared to the information on the solubility of the polymer (for example encoded as a 0 or a 1) and an error function is calculated.

The above steps are repeated a number of times, both by varying the variable parameters (weight, threshold) of intermediate neurons 4, 5, 6 and of the output layer 7, and by varying the resulting data. of the training data set, so as to minimize the error function.

At the end of the process, a function configured to associate a probability of solubility of the fluoropolymer with a vehicle composition is obtained. This function is determined according to the values ​​of the variable parameters (weight, threshold) optimized by the previous process.

Selection of substances or mixtures of substances

The function configured to associate a probability of solubility of a fluoropolymer with a vehicle composition can be used in a computer-implemented method to select the fluoropolymer solvent and / or the fluoropolymer non-solvent and / or the proportions of solvent and non-solvent for the fluoropolymer in the vehicle comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer.

Thus, in general, the function can be used to obtain a probability of fluoropolymer solubility for a vehicle composition to be tested, which is not in the training data set.

This function is then applied to the solubility parameters of the vehicle composition to be tested.

The probability of solubility obtained by applying the function represents an estimate of the ability of the fluoropolymer to be dissolved in the vehicle composition. This estimate can be obtained either in binary form (yes / no answer), or in the form of any probability (for example any value from 0 to 1). In this second case, the probability is compared to a threshold value in order to define whether the fluoropolymer is considered soluble or insoluble in the vehicle composition.

Depending on the result of the test, the composition of the vehicle to be tested may or may not be retained.

In some embodiments, the function is applied successively to a plurality of vehicle compositions to be tested, so as to select one or more of these compositions.

The test vehicle compositions can be pure substances or mixtures of substances.

When it comes to pure substances, the solubility parameters to which the function is applied can be determined by experimental or semi-empirical tests, as exemplified above, or preferably be taken from one or more reference tables. pre-existing ones, as described above.

In the case of mixtures, the solubility parameters to which the function is applied can be determined by experimental or semi-empirical tests or preferably be calculated as a linear combination from the solubility parameters of the pure substances in mixture. . In such a linear combination, the weighting coefficients applied preferably correspond to the volume proportions of each of the solvents.

The selection function and / or method described above can be used to select a solvent for the fluoropolymer; a solvent is then retained if the fluoropolymer is considered soluble therein.

The function and / or the selection method described above can also be used to select a non-solvent for the fluoropolymer; a non-solvent is then retained if the fluoropolymer is considered insoluble therein.

The selection function and / or method described above can also be applied to select the proportions of solvent for the fluoropolymer and non-solvent for the fluoropolymer in the vehicle used for the preparation of the ink.

In this case, the vehicle composition to be tested, at the solubility parameters of which the function is applied, is a mixture comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer.

In preferred embodiments, the function is applied successively to a plurality of test vehicle compositions all consisting of a mixture comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer, the proportion of solvent for the fluoropolymer and / or a non-solvent for the fluoropolymer varying in the different compositions to be tested, so as to select one or more of these compositions.

A carrier composition (consisting of a mixture comprising the fluoropolymer solvent and the fluoropolymer nonsolvent) can then be selected if the fluoropolymer is believed to be soluble therein.

When the function is applied successively to a plurality of mixtures comprising an increasing proportion of non-solvent of the fluoropolymer, the method can make it possible to determine a range of proportions of non-solvent of the fluoropolymer in which the limit of solubility is estimated to lie. .

Thus, the solvent of the fluoropolymer and / or the non-solvent of the fluoropolymer and / or the proportions of solvent and of non-solvent in the vehicle comprising the solvent of the fluoropolymer and the non-solvent of the fluoropolymer can be chosen according to a selection process implemented by computer and comprising:

a) providing a function configured to associate a probability of solubility of the fluoropolymer with solubility parameters of a vehicle composition, for example a function determined by learning as described above;

b) providing solubility parameters associated with at least one vehicle composition (this vehicle composition being a mixture in the case of selecting the proportions of solvent and non-solvent);

c) applying the function provided in step a) to the solubility parameters provided in step b), so as to obtain a probability of fluoropolymer solubility associated with each respective vehicle composition;

d) as the case may be:

- the selection of a composition as a solvent for the fluoropolymer, in which the fluoropolymer is considered soluble, or

- the selection of a composition as a non-solvent for the fluoropolymer, in which the fluoropolymer is considered insoluble, or

- the selection of a vehicle composition as a mixture comprising the solvent of the fluoropolymer and the non-solvent of the fluoropolymer, in which the mass proportion of non-solvent is estimated to be less than the solubility limit, and preferably is estimated to be within one of the ranges mentioned above, relative to the solubility limit, according to a predetermined test.

Such a method allows efficient, reliable, easy and rapid selection because it does not necessarily require carrying out multiple dissolution experiments.

The selected vehicle composition can then be used to make an ink by dispersing the fluoropolymer in said vehicle composition.

Computer system

When it comes to a computer-implemented method, it is understood that all the steps or almost all the steps of the method are executed by a computer or a set of computers. The steps can be performed fully automatically, or partially automatically. In some embodiments, the initiation of certain steps can be performed in response to an interaction with a user. The degree of automation envisaged can be predefined and / or defined by the user.

By way of example, the distribution of the training data set between a training data set and a test data set can be decided by the user, or it can be determined automatically.

The learning is carried out automatically, according to any learning technique known to those skilled in the art. In particular, the error function is preferably automated according to any variant known to those skilled in the art.

Referring to Fig. 7, an example of a system that can be used to perform the computer-implemented methods described above, via a computer program, is provided. In this example, the system is a computer, for example a workstation.

The computer thus comprises a processor unit 1010 connected to a computer bus 1000, and a random access memory 1070 (RAM) also connected to the computer bus 1000. The computer further comprises a graphics processor unit 1 1 10 which is associated with a video random access memory 1100 connected to the computer bus. A mass memory device controller 1020 manages access to a mass memory device, such as a hard disk 1030. Mass memory devices 1040 adapted to tangibly represent computer program instructions and them. data includes all forms of non-volatile memories, including, for example, semiconductor memory devices such as EPROM, EEPROM and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical discs, and CD-ROM discs. These can also be supplemented by or incorporated into specific ASICs (application-specific integrated circuits). A network adapter 1050 manages access to a network 1060. The computer may also include a haptic device 1090 such as a cursor control device, keyboard, or the like. A cursor control device is used to allow the user to selectively position a cursor at any location of the display 1080. In addition, the cursor control device allows the user to select various commands and signals. input control. The cursor control device includes signal generating devices for control signals input to the system. Typically it can be a mouse, the mouse button being used to generate the signals. The computer system may also include a touch screen and / or a touch pad.

The computer program can comprise instructions executable by a computer, the instructions comprising means for causing the above system to implement the method. The program can be recorded on any data medium, including system memory. The program may for example be implemented in digital electronic circuits, or in computer hardware, firmware or software, or combinations thereof. The program may be implemented as an apparatus, for example a product tangibly represented in a machine readable memory device for execution by a programmable processor. Process steps can be performed by a programmable processor executing an instruction program to perform process functions by processing input data and generating outputs. The processor can thus be programmable and be coupled to receive data and instructions from, and to transmit data and instructions to, a memory device, at least one input device and at least one output device. The program can be implemented in a high level procedural or object oriented programming language, or in a machine or assembly language. The language can be compiled or interpreted. The program can be a full installer or an updater.

EXAMPLES

The following examples illustrate the invention without limiting it.

Example 1

Solubility estimation model

A training data set was formed from the following table:

[Table 1 d

In this table, the Hansen solubility parameters are given in MPa 1/2 . Notations (2) or (5) indicate that these Hansen solubility parameters come either from Table 2 in Chapter 7 or from Table 5 in Chapter 8 of the CRC Handbook of Solubility Parameters and Other Cohesion Parameters, by Allan FM Barton, 2 nd edition (1991).

The information relating to the solubility was obtained experimentally with a P copolymer (VDF-TrFE) comprising 80% of VDF units and 20% of TrFE units (in molar proportions).

The JMP 13.0.0 software from the SAS company was used to provide a neural network as shown schematically in FIG. 6.

20 rows of the table were used for training the model and 6 for validation. The success rate obtained is 100%.

The “KFold” validation method was used. This method, as explained by the software manual, divides the data into K subgroups. Successively, each of the K subgroups is used to validate the fit or model created with the remainder of the data not included in the K subgroup, which makes it possible to obtain K different models. The model with the best statistical validation (lowest error) is chosen as the final model.

From this modeling the following prediction model was obtained.

Functions of the three neurons of the middle (hidden) layer:

- H1 = tan h (0.5 x (0.288078 x bd + 0.029058 xd R + 0.092642 x bu - 4.79788));

- H2 = tan h (0.5 x (0.131723 x bd - 0.16692 xd R - 0.03299 x bu - 0.05098));

- H3 = tan h (0.5 x (0.399484 x bd - 0.11103x d R - 0.05299 x bu - 4.13038)).

In the above, the Hansen solubility parameters are expressed in MPa 1/2 .

Function of the output neuron: S = exp (201, 3275 x H1 + 192.4403 x H2 - 156.203 x H3 - 82.431 1).

The probability of non-solubility (or non-dissolution) is S / (1 + S) and the probability of solubility is 1 - probability of non-solubility.

The model thus obtained can be applied to any new vehicle composition not present in the previous training table.

Selecting a vehicle for ink

The model described above is used to evaluate the probabilities of dissolution (or of solubility) of a copolymer P (VDF-TrFE) comprising 80% of VDF units and 20% of TrFE units (in molar proportions) (copolymer "FC-20") in different mixtures of benzyl alcohol and gamma-butyrolactone. As stated above, gamma-butyrolactone is a solvent for FC-20 and benzyl alcohol is a non-solvent for FC-20 copolymer.

These dissolution probabilities are given in the table below (the first two columns of the table represent the mass proportion of the substance in the mixture evaluated).

[Table 2]

The solubility limit (switching from a non-precipitating to precipitating mixture) is between a proportion of about 58% and a proportion of about 68% by weight of benzyl alcohol. Thus, any mixture comprising a solvent-based liquid vehicle composed of less than 58% by weight of benzyl alcohol and of more than 42% by weight of gamma-butyrolactone, relative to the total sum of the weights of benzyl alcohol and of gamma-butyrolactone, could potentially be used as an ink vehicle for the manufacture of porous films.

Preparation of a polymer film

An ink containing 8.34% by weight (relative to the total weight of the ink) of FC-20 copolymer in a mixture of 17.1% by weight of benzyl alcohol and 82.9% by weight of gamma-butyrolactone is prepared as follows. The FC-20 copolymer is dissolved in the gamma-butyrolactone / benzyl alcohol mixture by gradually adding, with stirring, the copolymer powder to the mixture, in a stirred vessel. To speed up dissolution, the mixture can be heated during dissolution to a temperature below 70 ° C.

The ink thus obtained is deposited at room temperature on a glass plate using an applicator bar (“bar-coater”) of the Dr. Blade type (scraper not coming into contact with the glass). The deposit is left to dry (that is to say left to evaporate) at room temperature overnight under a ventilated hood. A brittle white film with a homogeneous appearance is thus obtained. Typical film thickness is 80 µm.

The images of the film obtained using a scanning electron microscope are shown in Figures 1, 2 and 3.

Example 2

An ink containing 8.3% by weight (relative to the total weight of the ink) of FC-20 copolymer in a mixture of 17.1% by weight of benzyl alcohol and 82.9% by weight of gamma-butyrolactone is prepared.

Five deposits are then made with this ink on a glass plate using an applicator bar ("bar-coater") of the Dr. Blade type then the five deposits are left to dry overnight under a ventilated hood, each at a different temperature: the ambient temperature; 30 ° C; 40 ° C; 50 ° C; or 60 ° C. Films with a thickness of 10 to 50 µm are obtained.

The films thus prepared are observed under a scanning electron microscope (FIGS. 4A, 4B, 4C, 4D and 4E) and under an optical microscope (FIGS. 5A, 5B, 5C, 5D and 5E).

It is noted that the application of a drying temperature of 50 ° C, 40 ° C, 30 ° C or equal to the ambient temperature makes it possible to obtain a porous white film while the application of a temperature of drying at 60 ° C results in a translucent non-porous film.

Example 3

The films of Example 2, dried at different temperatures, were analyzed by porosimetry. An ASAP 2020 Micromeritics device was used for these purposes. Between 140 and 270 mg of film is introduced into a measuring cell and the degassing is carried out at room temperature for 16 hours under a vacuum of less than 2 microns of mercury (Hg). The nitrogen adsorption-desorption isotherms are then measured at a temperature of 77 K (c. -196 ° C). The BET (Brunauer Emmett Teller) specific surface area is calculated by the apparatus at values ​​of the R / R0 ratio between 0.06 and 0.2. The pore volume in the meso and macro porous region is estimated by the BJH method (Barret Joyner Halenda).

The table below summarizes the results obtained:

It appears from these results that the lower the drying temperature, the higher the specific surface and the pore volume. The sample, dried at 60 ° C, could not be analyzed because of its heterogeneous appearance.

CLAIMS

Process for preparing a porous film of a fluoropolymer, comprising the following steps:

- providing an ink comprising the fluoropolymer and a vehicle comprising a solvent for the fluoropolymer and a non-solvent for the fluoropolymer, said solvent for the fluoropolymer and said non-solvent for the fluoropolymer being miscible with one another; depositing the ink on a substrate;

- evaporation of the vehicle comprising the solvent and the non-solvent;

in which :

the non-solvent is selected from the group consisting of benzyl alcohol, benzaldehyde, or a mixture thereof; and, the solvent has a saturated vapor pressure at 20 ° C higher than that of the non-solvent, preferably at least 20 Pa higher.

Process according to Claim 1, in which the fluoropolymer is a polymer comprising units derived from vinylidene fluoride as well as units derived from at least one other monomer of formula CXiX2 = CX3X4, in which each group Xi, X2, X3 and X4 is independently selected from H, Cl, F, Br, I and alkyl groups comprising from 1 to 3 carbon atoms, which are optionally partially or fully halogenated; and preferably the fluoropolymer comprises units derived from vinylidene fluoride and from at least one monomer chosen from trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, 1, 1 - chlorofluoroethylene, hexafluoropropene, 3,3,3- trifluoropropene, 1, 3,3,3-tetrafluoropropene, 2, 3,3,3-tetrafluoropropene, 1 -chloro-3,3,3-trifluoropropene and 2-chloro-3,3, 3-trifluoropropene; and more preferably the fluoropolymer is chosen from poly (vinylidene fluoride-co-hexafluoropropene), poly (vinylidene-co-trifluoroethylene fluoride), poly (vinylidene fluoride-ter-).

trifluoroethylene-ter-chlorotrifluoroethylene) and poly (vinylidene-iron-trifluoroethylene-iron-1, 1 -chlorofluoroethylene fluoride).

Process according to one of Claims 1 and 2, in which the solvent is chosen from the group consisting of ketones, esters, in particular cyclic esters, dimethylsulfoxide, phosphoric esters such as triethyl phosphate, carbonates and ethers such as as tetrahydrofuran, and a mixture of these, preferably the solvent being chosen from the group consisting of ethyl acetate, methyl ethyl ketone, gamma-butyrolactone, triethyl phosphate, cyclopentanone, propylene glycol monomethyl ether acetate and a mixture thereof.

Process according to one of claims 1 to 3, wherein the solvent is gamma-butyrolactone and the non-solvent is benzyl alcohol, or the solvent is ethyl acetate and the non-solvent is alcohol benzyl, or the solvent is methyl ethyl ketone and the non-solvent is benzyl alcohol.

Process according to one of claims 1 to 4, in which the vehicle comprises a proportion by mass of non-solvent for the fluoropolymer, in percentage, within the range going from (the solubility limit - 60%) to the solubility limit , more preferably in the range from (the solubility limit

- 60%) to (the solubility limit - 10%), even more preferably in the range from (the solubility limit

- 50%) to (the solubility limit - 20%); and / or the vehicle comprises a proportion by mass of solvent for the fluoropolymer, in percentage, within the range going from (100 - the solubility limit) to (100 - (the solubility limit - 60%)), more preferably in the range going from (100 - (the solubility limit - 10%)) to (100 - (the solubility limit - 60%)), even more preferably in the range going from (100 - (the solubility limit - 20 %)) to (100 - (the solubility limit - 50%)); relative to the total weight of the mixture of solvent and non-solvent for the fluoropolymer; the solubility limit being expressed as a percentage by mass.

6. Method according to one of claims 1 to 5, wherein the evaporation of the vehicle comprising the solvent and the non-solvent is carried out at a temperature less than or equal to 60 ° C, preferably less than or equal to 50 ° C. .

7. Method according to one of claims 1 to 6, wherein the solvent has a boiling point lower than that of the non-solvent, preferably at least 10 ° C lower.

8. Method according to one of claims 1 to 7, wherein the deposition is carried out by coating by centrifugation, by spraying or atomization, by coating in particular with a bar or a film puller, by coating with a slotted head, by immersion, roller printing, screen printing, flexography printing, lithography printing or inkjet printing.

9. Method according to one of claims 1 to 8, wherein the ink does not include a sacrificial polymer.

10. Method according to one of claims 1 to 9, wherein the temperature applied during the evaporation of the vehicle comprising the solvent and the non-solvent is essentially constant or varies by less than 20 ° C, preferably less than 10 ° C.

11. Method according to one of claims 1 to 10, for the manufacture of a filtration or separation membrane, or a battery membrane.

12. Porous film obtainable by the method according to any one of claims 1 to 10, said film having a pore volume estimated by the Barret Joyner Halenda method ranging from 0.020 cm 3 / g to 0.05 cm 3 / g, preferably ranging from 0.025 cm 3 / g to 0.05 cm 3 / g.

13. Porous film obtainable by the process according to any one of claims 1 to 10, said film having a BET specific surface area greater than or equal to 2, preferably greater than or equal to 3.