FR3148427A1 - Process for producing a fluoropolymer - Google Patents

Abstract

The present invention relates to a process for producing a fluoropolymer in the presence of a surfactant comprising a disulfide bond.

Description

Process for producing a fluoropolymer Technical field of the invention

The present invention relates to a method for producing a fluoropolymer. In particular, the present invention relates to a method for producing a fluoropolymer in the presence of a surfactant comprising a disulfide bond.

Technological background of the invention

Fluoropolymers exhibit excellent mechanical and thermal properties, in addition to their exceptional chemical inertness. They are used in high-performance applications such as lithium-ion batteries, coatings, or water treatment. Fluoropolymers are notably prepared by aqueous free-radical emulsion or suspension polymerization. Among the fluorinated polymers, vinylidene fluoride is of particular importance in new energy applications. Since vinylidene fluoride is a gas or a supercritical fluid depending on the polymerization process, the polymerization mechanism can be more complex than most emulsion polymerization processes. However, the overall polymerization mechanism follows the standard emulsion polymerization process and the recipe includes water, vinylidene fluoride, a surfactant, a water-soluble initiator, and some additives (chain transfer agent, buffer, antifouling agent). Polymerization takes place in a high-pressure reactor, where vinylidene fluoride is initially present in both the gas and aqueous phases, and in the PVDF particles during polymerization.

To achieve a stable dispersion of PVDF particles and good polymeric properties, a suitable surfactant must be used. Thus, different types of surfactants/stabilization techniques have been used industrially and/or described in the literature for the emulsion polymerization of vinylidene fluoride, such as molecular fluorinated surfactants, non-fluorinated molecular surfactants or “surfactant-free” techniques. One of the important points is to find a surfactant that will limit the formation of coagulum during the polymerization process.

There is thus still a need for efficient fluoropolymer production processes that overcome the above-mentioned drawbacks.

According to a first aspect, the present invention relates to a process for producing a fluorinated polymer P1 characterized in that step a) of polymerization of a fluorinated monomer M1 is carried out in the presence of a cyclic surfactant S1 with 5, 6 or 7 links of formula (I)

in which n is an integer from 3 to 5; R ^a and R ^b are, independently of each other and independently for each unit n, selected from the group consisting of H, F, C ₁ -C _{2 0} alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₁ -C _{2 0} fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₂₀ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₂₀ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; ; and a polymeric hydrocarbon chain; or the unit [CR ^a R ^b ] forms a carbonyl group C=O or thiocarbonyl group C=S. In the monomer M2 of formula (I), R ^a and R ^b are the substituents of the carbon atom C of the unit [CR ^a R ^b ].

Surprisingly, by means of the present process it is possible to produce fluorinated polymers, in particular poly(vinylidene fluoride), with good yield and avoiding the formation of coagulum. This is made possible by the use as surfactant of a disulfide compound of formula (I).

According to a preferred embodiment, in said surfactant S1 of formula (I), at least one of the substituents R ^a or R ^b of at least one unit n comprises a functional group -CO ₂ H.

According to a preferred embodiment, said surfactant S1 is in the form of a solution, preferably aqueous, the concentration of which is less than 5 g/l.

According to a preferred embodiment, step a) is carried out at a temperature above 40°C and a pressure of 10 to 120 bara.

According to a preferred embodiment, said fluorinated monomer M1 is selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene

According to a preferred embodiment, step a) is carried out in the presence of a monomer M3 different from the monomer M1 and selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, 2-trifluoromethyl-3,3,3-trifluoro-1-propene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, acrylate amyl, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, hydroxyethylhexyl acrylate, hydroxyethylhexyl methacrylate, acryloyloxy propylsuccinate and combinations thereof.

According to a preferred embodiment, said monomer M1 is vinylidene fluoride.

According to a preferred embodiment, in said surfactant S1 at least one of the substituents R ^a or R ^b in at least one of the units n is of formula (III) –[C(R ⁵ )(R ⁶ )] _m -C(R ⁷ )(R ⁸ )-CO ₂ H with m being an integer between 1 and 8; R ⁵ , R ⁶ and R ⁷ are independently of one another H, F, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type, C ₁ -C ₅ fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₆ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₁₂ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; R ⁸ is selected from the group consisting of H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the acid, amine, hydroxyl or ketone type.

According to a preferred embodiment, said surfactant S1 is of formula (I)

in which R ⁵ , R ⁶ and R ⁷ are independently of each other H, C ₁ -C ₅ alkyl, C ₁ -C ₅ fluoroalkyl; R ⁸ is selected from the group consisting of H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type; m is an integer between 1 and 6.

According to a particular embodiment, said surfactant S1 is lipoic acid.

According to a preferred embodiment, the fluorinated polymer P1 is obtained in the form of a latex and the particle size of said fluorinated polymer is from 10 nm to 800 nm.

According to a preferred embodiment, said fluorinated polymer P1 has a solid content of between 10% and 55%.

Detailed description of the invention

According to a first aspect of the present invention, a method for producing a fluoropolymerP1 is provided. Said method comprises a step a) of polymerization of a fluorinated monomerM1. Said step a) is carried out in the presence of a surfactant.S1. Step a) is preferably also carried out in the presence of an initiator.

Monomer M1

A fluorinated vinyl monomer is understood to mean a monomer comprising a C=C double bond and comprising at least one fluorine atom.

According to one embodiment, said monomer M1 is selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or ₅ , the monomer of formula R ¹ _CH ... in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, 2-trifluoromethyl-3,3,3-trifluoro-1-propene.

Preferably, said monomer M1 is selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4.

More preferably, said monomer M1 is selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene.

In particular, said monomer M1 is vinylidene fluoride.

Surfactant S1

Preferably, said surfactant S1 is a compound comprising a disulfide bond. More preferably, said surfactant S1 is a 5-, 6- or 7-membered cyclic compound comprising a disulfide bond.

According to a preferred embodiment, said surfactantS1 is a 5-, 6- or 7-membered cyclic compound of formula (I)

in which n is an integer from 3 to 5; R ^a and R ^b are, independently of each other and independently for each unit n, selected from the group consisting of H, F, C ₁ -C _{2 0} alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₁ -C _{2 0} fluoroalkyl substituted or not by one or more functional groups of the acid, amine, hydroxyl or ketone type; C ₃ -C ₂₀ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₂₀ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; or the unit [CR ^a R ^b ] forms a carbonyl C=O or thiocarbonyl C=S group.

The term carboxylic acid refers to a CO ₂ H functional group or a salt thereof. The term amine refers to a -NR'R'' functional group in which R' and R'' are independently H or C ₁ -C ₅ alkyl. The term hydroxyl refers to an -OH functional group. The term ketone refers to a -C(O)-R' functional group with R' being C ₁ -C ₅ alkyl. The term aldehyde refers to a -C(O)H functional group. The term amide refers to a -C(O)-NR'R'' functional group in which R' and R'' are independently H or C ₁ -C ₅ alkyl. The term cyano refers to a -CN functional group. The term ester refers to a functional group -C(O)-OR' or -OC(O)-R' with R' being C ₁ -C ₅ alkyl. The term thioester refers to a functional group -C(S)-OR' or -OC(S)-R' with R' being C ₁ -C ₅ alkyl. The term sulfonic acid refers to a functional group -SO ₃ H or a salt thereof. The term phosphoric acid refers to a functional group -P(O)(OH) ₂ or a salt thereof. When these substituents are arranged on a cycloalkyl or aryl, they are preferably located in the meta or para position. The expression polymeric hydrocarbon chain refers to a polymer comprising monomeric units derived from a vinyl group optionally substituted by one or more functional groups of the carboxylic acid, halogen, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and on which one of the substituents R ^a or R ^b of the monomer M2 of formula or one of the substituents R ⁵ , R ⁶ , R ⁷ or R ⁸ is grafted. For example, the polymeric hydrocarbon chain may be a polyethylene, polypropylene, poly(acrylic acid), poly(methyl methacrylate), poly(methyl acrylic acid), poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(trifluoroethylene), poly(chlorotrifluoroethylene), polystyrene, polybutadiene. Preferably, the polymeric hydrocarbon chain is preferably a polymer comprising monomeric units M1 , M3 or a mixture of the two. Preferably, at least one of the substituents R ^a or R ^b of at least one unit n comprises a functional group -CO ₂ H.

More preferably, said surfactantS1 is a 5-, 6- or 7-membered cyclic compound of formula (I)

in which n is an integer from 3 to 5; R ^a and R ^b are, independently of each other and independently for each unit n, selected from the group consisting of H, F, C ₃ -C _{2 0} alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C _{2 0} fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₁₀ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₁₂ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; and at least one of the substituents R ^a or R ^b of at least one unit n comprises a functional group -CO ₂ H.

In particular, said surfactantS1 is a 5 or 6 membered cyclic compound of formula (I)

in which n is 3 or 4; R ^a and R ^b are, independently of each other and independently for each n unit, selected from the group consisting of H, F, C ₃ -C ₈ alkyl substituted or not by one or more functional groups of carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; and at least one of the substituents R ^a or R ^b of at least one n unit comprises a functional group -CO ₂ H.

According to a preferred embodiment, in said surfactant S1 , at least one of the substituents R ^a or R ^b in at least one of the units n is of formula (III) –[C(R ⁵ )(R ⁶ )] _m -C(R ⁷ )(R ⁸ )-CO ₂ H with m being an integer between 1 and 8; R ⁵ , R ⁶ and R ⁷ are independently of each other H, F, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type, C ₁ -C ₅ fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₆ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₁₂ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; R ⁸ is selected from the group consisting of H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the acid, amine, hydroxyl or ketone type. Preferably, at least one of the substituents R ^a or R ^b in at least one of the n units is of formula (III) –[C(R ⁵ )(R ⁶ )] _m -C(R ⁷ )(R ⁸ )-CO ₂ H with m being an integer between 1 and 6; R ⁵ , R ⁶ and R ⁷ are independently of each other H, F, C ₁ -C ₃ alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type, C ₁ -C ₃ fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₄ -C ₆ cycloalkyl substituted or not by one or more functional groups of carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₁₀ aryl substituted or not by one or more functional groups of carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; R ⁸ is selected from the group consisting of H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type. In particular, at least one of the substituents R ^a or R ^b in at least one of the n units is of formula (III) –[C(R ⁵ )(R ⁶ )] _m -C(R ⁷ )(R ⁸ )-CO ₂ H with m being an integer between 1 and 6; R ⁵ , R ⁶ and R ⁷ are independently of each other H or F; R ⁸ is selected from the group consisting of H and C ₁ -C ₅ alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type. More particularly, at least one of the substituents R ^a or R ^b in at least one of the n units is of formula (III) –[C(R ⁵ )(R ⁶ )] _m -C(R ⁷ )(R ⁸ )-CO ₂ H with m being an integer between 3 and 6; R ⁵ , R ⁶ and R ⁷ are H; R ⁸ is selected from the group consisting of H and C ₁ -C ₅ alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type.

According to a preferred embodiment, in said copolymer, said surfactantS1 is a five-membered cyclic compound (n = 3) of formula (I). Advantageously, said surfactantS1 is of formula (I) below

in which R ⁵ and R ⁶ are independently of each other H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₁ -C ₅ fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₆ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₁₂ aryl substituted or not by one or more functional groups of carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; R ⁸ is selected from the group consisting of H and C ₁ -C ₅ alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type; m is an integer between 1 and 6.

Preferably, said surfactantS1 is of formula (I) below

in which R⁵and R⁶are independently of each other H, C₁-C₃alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type, C₁-C₃ fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; R⁸is selected from the group consisting of H and C₁-C₈alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type; m is an integer between 1 and 6, preferably m is an integer from 3 to 6.

More preferably, said surfactantS1 is of formula (I) below

in which R ⁵ and R ⁶ are independently of each other H, C ₁ -C ₃ alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; R ⁸ is selected from the group consisting of H and C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the acid, amine, hydroxyl or ketone type; m is an integer between 1 and 6, preferably m is an integer from 3 to 6.

In particular, said surfactantS1 is of formula (I) below

in which R ⁵ and R ⁶ are H; R ⁸ is selected from the group consisting of H and C ₁ -C ₅ alkyl substituted or not by one or more functional groups of acid, amine, hydroxyl or ketone type; m is an integer between 1 and 6, preferably m is an integer from 3 to 6.

More particularly, said surfactantS1 is lipoic acid of formula (I) below

in which R ⁵ , R ⁶ and R ⁸ are H; m = 4.

Preferably, said surfactant S1 is present in a concentration of less than 5 g/l, advantageously less than 4.5 g/l, preferably less than 4.0 g/l.

Monomer M3

According to a particular embodiment, said step a) of the present method can be carried out in the presence of a monomer M3 . Said monomer M3 is copolymerizable with said monomer M1 to form copolymers comprising monomeric units derived from monomer M1 and monomeric units derived from monomer M3 .

According to a preferred embodiment, said monomer M3 is different from monomer M1 and is selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, 2-trifluoromethyl-3,3,3-trifluoro-1-propene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, hydroxyethylhexyl acrylate, hydroxyethylhexyl methacrylate, acryloyloxy propylsuccinate and combinations thereof.

According to a preferred embodiment, said monomer M1 is vinylidene fluoride, said monomer M3 selected from the group consisting of vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, 2-trifluoromethyl-3,3,3-trifluoro-1-propene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, acrylate hexyl, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, hydroxyethylhexyl acrylate, hydroxyethylhexyl methacrylate, acryloyloxy propylsuccinate and combinations thereof.

According to a particular embodiment, said monomer M1 is vinylidene fluoride, said monomer M3 selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, hydroxyethylhexyl acrylate, hydroxyethylhexyl methacrylate, acryloyloxy propylsuccinate and combinations thereof.

Initiator

Step a) of the present process is carried out in the presence of an initiator.

The initiator may be one or a combination of several initiators known in the art to be useful in the emulsion polymerization of halogenated monomers. Suitable non-limiting classes of initiators include persulfate salts, peroxides, and redox systems. Examples of persulfate salts are sodium persulfate, potassium persulfate, or ammonium persulfate. The amount of persulfate salt added to the reaction mixture based on the total weight of monomer added to the reaction mixture is typically about 0.005 to about 1.0 wt. %. Organic peroxides that are useful include dialkyl peroxides, alkyl hydroperoxides, peroxyesters, and peroxydicarbonates. A suitable example of a dialkyl peroxide is di-tert-butyl peroxide. Examples of suitable peroxy esters include tert-amyl peroxypivalate, tert-butyl peroxypivalate and succinic acid peroxide. Examples of suitable peroxydicarbonate initiators include di-n-propyl peroxydicarbonate and diisopropyl peroxydicarbonate, which are typically added to the reaction mixture in an amount based on the total weight of monomer added to the reaction mixture of about 0.5 to about 2.5 wt. %.

The initiator may comprise a redox system. By "redox system" is meant a system comprising an oxidizing agent, a reducing agent, and optionally a promoter acting as an electron transfer medium. The promoter is a component that, in different oxidation states, is capable of reacting with both the oxidizing agent and the reducing agent, thereby accelerating the overall reaction. Oxidizing agents include, for example, persulfate salts; peroxides, such as hydrogen peroxide; hydroperoxides, such as tert-butyl hydroperoxide and cumene hydroperoxide; and oxidizing metal salts such as, for example, ferric sulfate and potassium permanganate. Examples of reducing agents include sodium formaldehyde sulfoxylate; sodium or potassium sulfite, bisulfite, or metabisulfite; ascorbic acid; oxalic acid; and reduced metal salts. Typical promoters include transition metal salts such as ferrous sulfate. In redox systems, the oxidizing agent and reducing agent are typically used in an amount of about 0.01 to about 0.5 weight percent based on the total weight of monomer added to the reaction mixture. The promoter, if used, is typically used in an amount of about 0.005 to about 0.025 weight percent based on the total weight of monomer added to the reaction mixture.

Production process

Preferably, said process is an emulsion process carried out in aqueous phase.

Step a) of the present process is preferably carried out at a temperature above 40°C, preferably at a temperature between 40°C and 120°C, more preferably at a temperature between 40°C and 110°C, in particular at a temperature between 40°C and 100°C.

Step a) of the present process is preferably carried out at a pressure of 10 to 120 bara, advantageously at a pressure of 15 bara to 110 bara, preferably at a pressure of 20 bara to 100 bara.

A paraffin antifoulant is optionally used in the polymerization. Any long-chain saturated hydrocarbon wax or oil may be used. The oil or wax is added to the reactor prior to formation of the fluoropolymer, in an amount sufficient to minimize adhesion of polymers to the reactor components. This amount is generally proportional to the interior surface area of the reactor and may vary from about 1 to about 40 mg/cm2 of interior surface area of the reactor. If a paraffin wax or hydrocarbon oil is used as the antifoulant, the amount used is generally about 5 mg/cm2 of interior surface area of the reactor.

The polymerization reaction mixture may optionally contain a buffering agent to maintain a controlled pH during the polymerization reaction. The pH is typically controlled in the range of 3 to 8. The buffering agent may be added at the beginning, at various points, or throughout the polymerization. Suitable exemplary buffering agents are phosphate buffers and acetate buffers, which are well known to those skilled in the art.

Molecular weight regulators, also known as chain transfer agents, may optionally be used to adjust the molecular weight profile of the product. They may be added in a single portion at the beginning of the reaction, incrementally, or continuously throughout the reaction. The amount of molecular weight regulator added to the polymerization reaction is typically from about 0.05 to about 5 wt. %, more typically from about 0.1 to about 2 wt. % based on the total weight of monomer added to the reaction mixture. Oxygenated compounds such as alcohols, carbonates, ketones, esters, and ethers may serve as molecular weight regulators. Examples of suitable oxygenated compounds include isopropyl alcohol, acetone, ethyl acetate, and diethyl carbonate. Other classes of molecular weight regulators include halogenated compounds such as chlorocarbons, hydrochlorocarbons, hydrofluorocarbons, chlorofluorocarbons, and hydrochlorofluorocarbons. Particular examples of halogenated molecular weight regulators include 1-fluoroethane, trichlorofluoromethane, and 1,1-dichloro-2,2,2-trifluoroethane. Certain hydrocarbons can be used as molecular weight regulators, such as hydrocarbons that contain two to five carbon atoms, with ethane and propane being particular examples.

In addition to surfactant S1 , one or more other surfactants S2 may be added. For example, said surfactant S2 comprises a polyethylene glycol segment and a polypropylene glycol segment. Preferably, said surfactant S2 has an HLB value of 1 to 20, in particular an HLB value of 1 to 5 or 10 to 15. In particular, said surfactant S2 comprising a polyethylene glycol segment and a polypropylene glycol segment, has an HLB value of 1 to 5 and a weight average molecular weight of 2500 to 10000 g.mol-1. Alternatively, said surfactant S2 comprising a polyethylene glycol segment and a polypropylene glycol segment, has an HLB value of 10 to 15 and a weight average molecular weight of 500 to 2500 g.mol-1.

Preferably, said surfactant S1 is added continuously during step a). The term continuous encompasses the addition of said surfactant S1 by multiple additions throughout the production process. Alternatively, said surfactant S1 is added batchwise. The term batchwise encompasses the addition of said surfactant S1 once at the beginning of the process or during the process in a single addition. The addition of said surfactant S1 may be prior to, simultaneous with or subsequent to that of the initiator. It is preferable to add at least a portion of said monomer M1 in the initial charge of the reactor, i.e. before the initiation of the polymerization reaction.

Fluorinated polymer P1

Said fluorinated polymerP1 obtained according to the present process comprises monomeric units derived from the monomerM1. Said fluorinated polymerP1may be a homopolymer derived from the monomerM1or a copolymer derived from the monomerM1and monomerM3.

As mentioned above, said monomerM1is preferably vinylidene fluoride. Thus, said fluorinated polymerP1 may preferably be a homopolymer of vinylidene fluoride.

According to another embodiment, the polymer P 1 is a copolymer of vinylidene fluoride with at least one comonomer compatible with vinylidene fluoride, such as any of the monomers M3 , other than vinylidene fluoride.

Generally, the polymer P 1 preferably contains at least 50 mol% vinylidene fluoride, advantageously at least 60 mol% vinylidene fluoride, preferably at least 70 mol% vinylidene fluoride. The comonomer M3 may be present in a content of 1 to 50%, advantageously 2 to 30% by weight relative to the weight of said polymer P 1 .

According to a preferred embodiment, the polymer P 1 is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a mass content of hexafluoropropylene monomer units of 2 to 30%, advantageously of 2 to 25%, preferably of 2 to 20%, preferably of 4 to 15% by weight relative to the weight of said polymer P 1 . According to another embodiment, the polymer P 1 is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a mass content of hexafluoropropylene monomer units of 10 to 30%, advantageously of 10 to 25% by weight relative to the weight of said polymer P 1 .

According to one embodiment, the polymer P 1 is a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE).

According to one embodiment, the polymer P 1 is a copolymer of vinylidene fluoride and chlorotrifluoroethylene (CTFE).

According to one embodiment, the polymer P 1 is a VDF-TFE-HFP terpolymer. According to one embodiment, the polymer P 1 is a VDF-TrFE-TFE terpolymer (TrFE being trifluoroethylene). In these terpolymers, the mass content of VDF is at least 10%, the comonomers being present in variable proportions.

According to a particular embodiment, the polymer P 1 comprises monomeric units carrying at least one of the following functions: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic. The function is introduced by a chemical reaction which may be grafting, or a copolymerization of the vinylidene fluoride (VDF) monomer with a monomer carrying at least one of said functional groups and a vinyl function capable of copolymerizing with vinylidene fluoride, according to techniques well known to those skilled in the art. Examples of monomers carrying an acid function and copolymerizable with vinylidene fluoride are listed among the monomer M3 . The content of functional groups in said polymer P 1 is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

Thus, said polymer P 1 may be, for example, a copolymer of vinylidene fluoride and a monomer M 3 selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate. Preferably, the content of monomer M 3 in said polymer P 1 is from 0.01% to 5 mol%. In this embodiment, at least 40% of the units resulting from the monomer M 3 are distributed between two vinylidene fluoride units.

The polymer P 1 preferably has a high molecular weight. By high molecular weight, as used herein, is meant a polymer P 1 having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to ASTM D-3835 measured at 232°C and 100 sec-1.

According to one embodiment, the polymer P 1 bearing functional groups can be crosslinked either by self-condensation of its functional groups or by reaction with a catalyst and/or a crosslinking agent, such as melamine resins, epoxy resins and the like, as well as known low molecular weight crosslinking agents such as di- or higher polyisocyanates, polyaziridines, polycarbodiimides, polyoxazolines, dialdehydes such as glyoxal, acetoacetates, malonates, acetals, di- and trifunctional thiols and acrylates, cycloaliphatic epoxy molecules, organosilanes such as epoxysilanes and amino silanes, carbamates, diamines and triamines, inorganic chelating agents such as certain zinc and zirconium salts, titaniums, glycourils and other aminoplasts. In some cases, functional groups from other polymerization ingredients, such as surfactants, initiators, seed particles, may be involved in the crosslinking reaction. When two or more functional groups are involved in the crosslinking process, the complementary reactive group pairs are, for example, hydroxyl-isocyanate, acid-epoxy, amine-epoxy, hydroxyl-melamine, acetoacetate-acid. The acrylate and/or methacrylate monomers not containing functional groups capable of entering into crosslinking reactions after polymerization should preferably represent 70% or more by weight of the total monomer mixture, and more preferably, should be greater than 90% by weight. According to one embodiment, the polymer P1 comprises a crosslinking agent selected from the group consisting of isocyanates, diamines, adipic acid, dihydrazides and combinations thereof.

According to a preferred embodiment, said fluorinated polymer P1 is obtained in the form of a latex and the particle size of said fluorinated polymer P1 is from 10 nm to 800 nm. The particle size is determined by laser granulometry. A particle size analyzer of the Malvern INSITEC System type is used for the measurement. This is carried out in a dry process by laser diffraction on a powder with a focal length of 100 mm.

According to a preferred embodiment, said fluorinated polymer P1 has a solid content of between 10% and 55%, preferably between 10% and 50%, in particular between 10 and 40%.

Use

Said fluorinated polymer P1 as obtained by the present process can be used in various applications. Thus, said fluorinated polymer P1 can be used as a binder for an electrode (cathode or anode) or as a coating for a separator.

Said fluorinated polymer P1 according to the present invention can be used as a binder for an electrode. Thus, according to another aspect, the present invention provides an electrode composition comprising said fluorinated polymer P1 according to the present invention, an active material and optionally a conductive agent.

In a preferred embodiment, the electrode composition has the following mass composition:

a. 50% to 99.9% active material, preferably 50% to 99%,

b. 25% to 0% conductive agent, preferably 25% to 0.5%,

c. 25% to 0.05% of said fluorinated polymer P1 according to the invention, preferably 25% to 0.5%,

d. 0% to 5% of at least one additive selected from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and a flow aid;

the sum of all these percentages being 100%.

The conductive agents in the electrode are composed of one or more materials that can enhance the conductivity. Some examples include carbon blacks such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor-grown carbon fiber; metal powders such as SUS powder, and aluminum powder.

Active materials in electrode compositions are materials that are capable of storing and releasing lithium ions.

In a preferred embodiment, said electrode is a negative electrode. In particular, for a negative electrode, said active material is selected from the group consisting of a lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy and Li ₄ TiO ₁₂ . The shape of the negative electrode active material is not particularly limited but is preferably particulate.

In another preferred embodiment, said electrode is a positive electrode. Preferably, for a positive electrode, said active material is selected from the group consisting of LiCoO ₂ , Li(Ni, Co, AI)O ₂ , Li(1+ x), NiaMnbCoc (x represents a real number of 0 or more, a = 0.8, 0.6, 0.5, or 1/3, b = 0.1, 0.2, 0.3, or 1/3, c = 0.1, 0.2, or 1/3), LiNiO ₂ , LiMn ₂ O ₄ , LiCoMnO ₄ , Li ₃ NiMn ₃ O ₃ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Li ₃ V ₂ (PO ₄ ) ₃ , a Li Mn spinel substituted by a different element having a composition represented by Li1+xMn2-x-yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between 0 and 2, lithium titanate LixTiOy – x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni. The shape of the positive electrode active material is not particularly limited but is preferably particulate. In addition, the surface of each of the materials described above can be coated. The coating material is not particularly limited as long as it has lithium ion conductivity and contains a material capable of being maintained as a coating layer on the surface of the active material. Examples of the coating material include LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , and Li ₃ PO ₄ .

Said electrode composition can be deposited on at least one face of a current collector to form said electrode. This deposition can be carried out in the presence of an organic solvent, water, a mixture of both or by a solvent-free process. Said organic solvent can be selected from the group consisting of n-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), triethylphosphite (TEP), acetone, cyclopentanone, tetrahydrofuran, methyl ethylketone (MEK), methyl isobutyl ketone (MiBK), ethyl acetate (EA), butyl acetate (BA), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), gamma-butyrolactone and N-butylpyrrolidone; and mixtures thereof.

According to another aspect of the present invention, a Li-ion battery is provided. Preferably, the Li-ion battery comprises a positive electrode, a negative electrode and a separator, at least one electrode being an electrode according to the present invention.

According to another aspect of the present invention, said fluorinated polymer P1 according to the present invention can be used as a coating in a separator arranged between two electrodes. Said separator according to the present invention comprises a coating comprising, preferably consisting of, said fluorinated polymer P1 according to the present invention, optionally arranged on one or both faces of a porous support. In this case, the coating is used to coat the support of a separator, on at least one face, in the form of a monolayer or multilayers. There is no particular limitation in the choice of the support which is coated with the coating of the invention, as long as it is a porous substrate having pores. When it comprises several layers, the coating as described in the present invention is arranged on the external face of the support, that is to say on the face which will first be in contact with the electrolytic composition used in the battery. Advantageously, the application of the coating to the support is done by aqueous means or by solvent means. The porous substrate may be in the form of a membrane or a fibrous fabric. When the porous substrate is fibrous, it may be a nonwoven web forming a porous web, such as a web obtained by direct spinning or melt blowing (of the "spunbond" or "melt blown" type) or electro-spinning. Examples of porous substrates useful in the invention as a support include, but are not limited to: polyolefins, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, poly(phenylene oxide), poly(phenylene sulfide), polyethylene naphthalene or mixtures thereof. However, other heat-resistant engineering plastics may be used without particular limitation. Nonwoven materials made of natural and synthetic materials may also be used as the substrate of the separator. The porous substrate generally has a thickness of 1 to 50 µm, and are typically membranes obtained by extrusion and stretching (wet or dry process) or cast nonwovens. The porous substrate preferably has a porosity of between 5% and 95%. The average pore size (diameter) is preferably between 0.001 and 50 µm, more preferably between 0.01 and 10 µm. The support may also be aluminum or aluminum coated with a polymer layer.

In addition to said composition, the separator coating may contain inorganic particles that serve to form micropores in the coating (the interstices between inorganic particles). The addition of inorganic particles may also contribute to heat resistance or improve wettability. In one embodiment, said coating comprises from 50 to 99 weight percent inorganic particles, based on the weight of the coating. These inorganic particles must be electrochemically stable (not subject to oxidation and/or reduction in the range of voltages used). In addition, the powdered inorganic materials preferably have high ionic conductivity. Low density materials are preferred over higher density materials because the weight of the produced battery can be reduced. The dielectric constant is preferably equal to or greater than 5. According to one embodiment, said inorganic particles are selected from the group consisting of: BaTiO3, Pb(Zr,Ti)O3, Pb 1-x LaxZryO3 (0<x<1, 0<y<1), PBMg3Nb2/3)3,PbTiO3, hafnia (HfO (HfO2), SrTiO 3, SnO2, CeO2, MgO, NiO, CaO, ZnO, Y2O3, bohemite (y-AlO(OH)), Al2O3, TiO2, SiC, ZrO2, boron silicate, BaSO4, nano-clays, or mixtures thereof. The separator coating may optionally comprise from 0 to 15% by weight based on the polymer, and preferably 0.1 to 10% by weight of additives, selected from thickeners, agents pH adjustment agents, anti-sedimentation agents, surfactants, wetting agents, fillers, anti-foaming agents and fugitive or non-fugitive adhesion promoters. The fillers mentioned here in the additives are different from the inorganic particles mentioned above.

According to another aspect of the present invention, a Li-ion battery is provided. Preferably, the Li-ion battery comprises a positive electrode, a negative electrode and said separator according to the present invention.

According to another aspect of the present invention, said fluorinated polymer P1 can be used in the preparation of a conductive polymer, a solid electrolyte for fuel cells, a hydrophilic coating, a hydrophobic coating or a UV-absorbing coating.

Examples

A 4-liter high-pressure reactor was filled with 1450 mL of water and then flushed with nitrogen. After that, it was heated to 83°C and then filled with 88 bars of vinylidene fluoride. The pressure was kept constant during the reaction using a vinylidene fluoride feed. The reaction was initiated by the injection of potassium persulfate (0.1 g/L). A lipoic acid solution was administered in the form of successive additions of 3 mL of said solution. Once the reaction was complete, the reactor was cooled and opened. The product was isolated as a stable latex with little or no coagulum. Examples Lipoic acid concentration (g/l) Duration (min) Solid content (%) Particle size (nm) Coagulum 1 2 120 17.8 292 No 2 3 120 15.9 251 No 3 2 144 19.7 402 No

Claims (12)

Process for producing a fluorinated polymer P1, characterized in that step a) of polymerization of a fluorinated monomer M1 is carried out in the presence of a cyclic surfactant S1 with 5, 6 or 7 links of formula (I)

in which n is an integer from 3 to 5; R ^a and R ^b are, independently of each other and independently for each unit n, selected from the group consisting of H, F, C ₁ -C _{2 0} alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₁ -C _{2 0} fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₂₀ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₂₀ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; and a polymeric hydrocarbon chain; or the unit [CR ^a R ^b ] forms a carbonyl C=O or thiocarbonyl C=S group. Process according to the preceding claim, characterized in that, in said surfactant S1 of formula (I), at least one of the substituents R ^a or R ^b of at least one unit n comprises a functional group -CO ₂ H. Method according to the preceding claim, characterized in that said surfactant S1 is in the form of a solution, preferably aqueous, the concentration of which is less than 5 g/l. Method according to any one of the preceding claims, characterized in that step a) is carried out at a temperature above 40°C and a pressure of 10 to 120 bara. A process according to any one of the claims, characterized in that said fluorinated monomer M1 is selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene Process according to any one of the preceding claims, characterized in that step a) is carried out in the presence of a monomer M3 different from the monomer M1 and selected from the group consisting of vinylidene fluoride, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole), the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H, the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5, the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4, the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4, perfluorobutyl ethylene, trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, 2-trifluoromethyl-3,3,3-trifluoro-1-propene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, hydroxyethylhexyl acrylate, hydroxyethylhexyl methacrylate, acryloyloxy propylsuccinate and combinations thereof. Process according to any one of the preceding claims, characterized in that said monomer M1 is vinylidene fluoride. Process according to any one of the preceding claims, characterized in that in said surfactant S1 at least one of the substituents R ^a or R ^b in at least one of the units n is of formula (III) –[C(R ⁵ )(R ⁶ )] _m -C(R ⁷ )(R ⁸ )-CO ₂ H with m being an integer between 1 and 8; R ⁵ , R ⁶ and R ⁷ are independently of each other H, F, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type, C ₁ -C ₅ fluoroalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₃ -C ₆ cycloalkyl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; C ₆ -C ₁₂ aryl substituted or not by one or more functional groups of the carboxylic acid, amine, hydroxyl, ketone, aldehyde, amide, cyano, ester, thioester, sulfonic acid, phosphoric acid type; R ⁸ is selected from the group consisting of H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the acid, amine, hydroxyl or ketone type. Process according to any one of the preceding claims, characterized in that said surfactant S1 is of formula (I)

wherein R ⁵ , R ⁶ and R ⁷ are independently of each other H, C ₁ -C ₅ alkyl, C ₃ -C ₆ cycloalkyl, C ₆ -C ₁₂ aryl or C ₁ -C ₅ fluoroalkyl; R ⁸ is selected from the group consisting of H, C ₁ -C ₅ alkyl substituted or not by one or more functional groups of the acid, amine, hydroxyl or ketone type. Method according to any one of the preceding claims, characterized in that said surfactant S1 is lipoic acid. Process according to any one of the preceding claims, characterized in that said fluorinated polymer P1 is obtained in the form of a latex and the particle size of said fluorinated polymer P1 is from 10 nm to 800 nm. Method according to any one of the preceding claims, characterized in that said fluorinated polymer P1 has a solids content of between 10% and 55%.