EP4630462A1 - Composition (c) for manufacturing aqueous dispersion comprising particles of a fluorinated polymer (f) - Google Patents

Abstract

Composition (C) for manufacturing aqueous dispersion comprising particles of a fluorinated polymer (F) The invention relates to a composition (C) suitable for manufacturing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising recurring units derived from at least one fluorinated monomer. The invention also relates to a method for preparing the composition (C) and to a process for manufacturing aqueous dispersion comprising particles of fluorinated polymers (F) using said composition (C) and to a latex obtained via such process.

Description

Composition (C) for manufacturing aqueous dispersion comprising particles of a fluorinated polymer (F)

Reference to related applications

This application claims priority from European patent application EP22211429.0 filed on December 5, 2022, the whole content of this application being incorporated herein by reference for all purposes.

Technical Field

The invention relates to a composition (C) suitable for manufacturing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising recurring units derived from at least one fluorinated monomer.

The invention also relates to a method for preparing the composition (C) and to a process for manufacturing aqueous dispersion comprising particles of fluorinated polymers (F) using said composition (C) and to a latex obtained via such process.

Background Art

Known preparation methods of fluorinated polymers are aqueous polymerization involving fluorinated surfactants. Just for the sake of example, such methods are described in W02018/189091 and WO2018/189092 from Solvay Specialty Polymers Italy S.p.A..

EPl 888655 Al a method for making a fluoropolymer comprising an aqueous emulsion polymerization process carried out in the presence of an oligomer that comprises one or more ionic groups, has a partially fluorinated backbone, and a number average molecular weight of not more than 2000 g/mol. Examples of the oligomers disclosed in EPl 888655 Al are:

CF₃(VDF)j-CH₂-COOH

CF₃-(TFE)p(VDF)q-CF₂-COOH

H-(TFE)p-(VDF)q-OSO₃H

H-(TFE)p-(VDF)q-CF₂-COOH wherein each of j, p and q represents the average number of repeating units derived from the respective monomer and are not zero; typically each of p and q are between 1 and 10 and j is between 2 and 20. The oligomers therefore consist of repeating units of the -CF₂- and/or -CH₂- type. US2008015319A1 discloses a process comprising polymerizing tetrafluoroethylene in an aqueous emulsion in the presence of a surfactant having the general formula (I):

Rf-O-L-CO₂- (I) wherein Rf is selected from a partially fluorinated alkyl group, a perfluorinated alkyl group, a partially fluorinated alkyl group interrupted by one or more oxygen atoms, and a perfluorinated alkyl group interrupted by one or more oxygen atoms, wherein Rf has from 1 to 10 carbon atoms; and L is an alkylene group having the general formula (CX₂)n wherein each X is independently selected from Rf, fluorine, and hydrogen and n is selected from 1 to 5, with the proviso that the surfactant contains at least one unit selected from a -CH₂- unit and a -CHF- unit. L may be selected from the following:

-(CF₂)g- wherein g is 1, 2, 3, 4, 5 or 6;

-CFH-(CF₂)h- wherein h is 0, 1, 2, 3, 4 or 5;

-CF₂-CFH-(CF₂)d- wherein d is 0, 1, 2, 3 or 4;

-CH₂-(CF₂)h- wherein h is 1, 2, 3 or 4;

-(CH₂)C- wherein c is 1. The surfactants disclosed in US2008015319A1 do not contain adjacent CHF units.

As well known, the use of certain fluorinated surfactants may be restricted for environmental reasons because there are not biodegradable in an acceptable lapses of time or conditions ranges.

Therefore there is a continued demand for new surfactants, suitable for preparing fluorinated polymers through aqueous polymerization processes in the presence or in the absence of nucleating agents, having improved biodegradability features.

Non-fluorinated surfactants such as alkyl phosphates, alkyl sulfonates, alkyl sulfates, or alkyl carboxylates are generally not appropriate to be used in aqueous free radical polymerization of fluorinated or partially fluorinated monomers since they bear H atoms likely to be abstracted during polymerization process by free radical species. These transfer reactions lead to fluorinated free-radical and fluorinated polymers having low molecular weights and thus having impaired properties.

Therefore there is a demand for new surfactants, suitable for preparing fluorinated polymers through aqueous free radical polymerization processes in the presence or in the absence of nucleating agents, with only limited transfer reactions and ensuring good stabilization of the aqueous dispersion of the resulting fluorinated polymers.

It has been surprisingly found that the composition (C) according to the invention comprising compound(s) of formula (I) was suitable to carry out the manufacture of aqueous dispersion comprising particles of fluorinated polymers through aqueous free radical polymerization processes with high reaction rate. Moreover, the composition (C) according to the invention comprising compound(s) of formula (I) allows preparing stable latexes comprising particles of fluorinated polymers.

Description of invention

Therefore, the invention relates to a composition (C) comprising at least one compound of formula (I):

(I) H-(CHF-CHF)_n-(CF=CH)_m-CHF-P, wherein : n is an integer greater than 0; m is an integer equal to or greater than 0,

2 < n+m < 100,

0 < m/n < 0.5, and

-P represents -C00-M, -CH2-O-M, -SO3-M or -PO3-M , wherein M is H, or an alkali metal, or an ammonium group N(R)4, wherein R, equal or different at each occurrence, is a hydrogen atom or a Ci-Ce hydrocarbon group preferably an alkyl group; with the proviso that when n+m=3, then n 0.

Generally 2 < n+m < 100 and 0 < m/n < 0.5; often 5 < n+m < 100 and 0 < m/n < 0.3; sometimes 10 < n+m < 100 and 0 < m/n < 0.2.

In some embodiments, 2 < n+m < 25 and 0 < m/n < 0.5; often 5 < n+m < 25 and 0 < m/n < 0.3; sometimes 10 < n+m < 25 and 0 < m/n < 0.2. In some instances 2 < n+m < 100 and 0 < m/n < 0.5; often 5 < n+m < 100 and 0 < m/n < 0.3; sometimes 10 < n+m < 100 and 0 < m/n < 0.2.

In some embodiments, 2 < n+m < 25 and 0 < m/n < 0.5; often 5 < n+m < 25 and 0 < m/n < 0.3; sometimes 10 < n+m < 25 and 0 < m/n < 0.2.

Composition (C) may consist of one compound of formula (I). Alternatively, composition (C) may comprise more than one compound of formula (I). In such a case each compound complying with formula (I) may differ from the other compounds in one or more of the value of n, the value of m or the nature of-P. Typically, when composition (C) comprises more than one compound of formula (I), each compound complying with formula (I) differs from the other compounds in the value of n, the value of m or both. In such a case, composition (C) may be defined as a mixture comprising more than one compound of formula

(I). Such a mixture may be represented by formula (I’):

(I’) H-(CHF-CHF)v-(CF=CH)^-CHF-P wherein v is the average of the value of n of all the compounds in the mixture and p is the average of the value of n of all the compounds in the mixture. For the sake of clarity, v and p can be fractional numbers.

In formula (I) and (F) -P represents -COO-M, -CH2-O-M, -SO3-M or -PO3-M , wherein M is H, or an alkali metal, or an ammonium group N(R)4, wherein R, equal or different at each occurrence, is a hydrogen atom or a Ci-Ce hydrocarbon group preferably an alkyl group.

Advantageously, M is an ammonium group, more preferably NFU group. Preferably, -P represents -COO-M and more preferably-P represents -COO-NH4. Accordingly, in such preferred embodiments the composition (C) according to the invention comprises at least one compound of formula (III) or (III’): with m, n, v and p as previously described.

A method for preparing the composition (C) comprising at least one compound of formula (I) is described hereafter. The method comprises the free radical addition of CHF=CHF to I-CHF-CO2-R’ to obtain an intermediate compound of formula I-(CHF-CHF)_r-CHF-CO2-R’, wherein R’ is a Ci-Ce hydrocarbon group, preferably a Ci-Ce alkyl group, and 2< r <100 which is then subject to reduction and saponification.

The first step of the process comprises the preparation of an intermediate composition (C’) comprising at least one compound of formula (II);

(II) I-(CHF-CHF)O-CHF-CO₂-R’ via a free radical addition pathway involving 1,2-difluoroethylene and a iodofluoro alkanoate. In the method according to the invention, 1,2- difluoroethylene of formula CHF=CHF, can be cis isomer, trans isomer, or a mixture thereof.

This free radical addition pathway is known by the person of ordinary skill in the art as telomerization. IUPAC Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"), compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997), online version (2019-) created by S. J. Chalk, ISBN 0-9678550-9-8 (https://doi.org/10.1351/goldbook) gives the following definition of telomerization : “the formation of an addition oligomer, having uniform end groups X' ... X" , by a chain reaction in which a chain transfer limits the length of the polymer (“telomere”) produced. An example is the polymerization of styrene in bromotrichloromethane solution (X - CCI3, X" = Br), where CI3C⁰ radicals are formed in the initiation step to produce ChCfCIBCHPhJnBr, with n greater than 1 and often less than ca. 10:”

In the example above, Br-CCh is called telogen, styrene is the taxogen and C13C[CH2CHPh]_nBr is the telomer.

In the present invention, the iodofluoro alkanoates I-CHF-CO2-R’ and I-(CHF- CHF)_P-CHF-CO2-R’ (with l< p< 10) are the telogens while 1.2-difluoroethylene CHF=CHF is the taxogen.

In the present invention, the initiation step corresponds to the generation of radical species through the decomposition of the free radical initiator, leading to the formation of °CHF-CO2-R’ radical, according to the schemes below where the free radical initiator is dibenzoylperoxide (BPO): Ph ’ + I— CHF-CQ— R' - ► Ph-I + CHFCCfe— R'

Then the propagation step i.e. the addition of CHF=CHF to °CHF-CO₂-R’ radical and the chain transfer to provide compounds of formula I-(CHF-CHF)_n+i- CHF-COO-R’ can be illustrated as follows: CO2— R'

Therefore, another object of the present invention relates to a method for manufacturing a composition (C’) comprising at least one compound of formula (II):

(II) I-(CHF-CHF)O-CHF-CO₂-R’, wherein : o is an integer,

2 < o < 25, and

R’ is a Ci-Ce hydrocarbon group, preferably a Ci-Ce alkyl group, comprising the steps of:

- (a) providing a reaction mixture (RM) under inert atmosphere comprising 1,2- difluoroethylene of formula CHF=CHF, an iodofluoro alkanoate of formula I- CHF-CO2-R’ wherein R¹ is as previously defined and a free radical initiator (FRI) solubilized in a liquid medium (LM);

- (b) generating radical species through the decomposition of the free radical initiator (FRI), leading to the formation of ^OCHF-CO₂-R’ radical, to the addition a number p of CHF=CHF molecules and to the formation of the composition (C”) comprising at least one compound of formula (II”):

(IF) I-(CHF-CHF)_P-CHF-CO₂-R’ wherein 1 < p< 10;

- (c) isolating the compounds of formula (IF) I-(CHF-CHF)p-CHF-CO₂-R’ from the reaction mixture (RM) and then providing a reaction mixture (RM’) under inert atmosphere comprising isolated compounds of formula (IT) I-(CHF-CHF)_P- CHF-CO2-R’, CHF=CHF and a free radical initiator (FRT) solubilized in a liquid medium (LM’);

- (d) generating radical species through the decomposition of the free radical initiator (FRT) in (RM’), leading to the formation of ^O(CHF-CHF)_P-CHF-CO2-R’ radical, to the addition of a number q of CHF=CHF molecules and to the formation of the composition (C’) comprising at least one compound of formula (II):

(II) I-(CHF-CHF)o-CHF-COO-R’ wherein 1< q<l 5 and o=p+q.

The addition of CHF=CHF molecules to the radical species °CHF-CO2-R’ and ^O(CHF-CHF)_P-CHF-CO2-R’ is referred to as “telomerization”.

Generally step (a) is performed at low temperature i.e. at a temperature where the free radical initiator (FRI) does not substantially decompose. Just for the sake of example, it can be at a temperature where the initiator’s half-life ti/2, defined as the time required for half of the initial initiator to decompose at a given temperature, is more than 100 hours.

Inert atmosphere is generally nitrogen or argon atmosphere.

The liquid medium (LM) of step (a) is generally a solvent or mixture of solvents which gives no or poor chain transfer reactions with the radical species in presence. 1,2-difluoroethylene, the iodofluoro alkanoate of formula LCHF-CO2- R’ and the free radical initiator are soluble in the liquid medium (LM). Suitable liquid medium (LM) can be selected from the list consisting of nitriles, ethers, both linear and cyclic, esters, fluorinated solvents and mixtures thereof. Among nitriles mention may be made of benzonitrile, isobutyronitrile, n- butyronitrile, acetonitrile and propionitrile. Among ethers mention may be made of dimethyl ether, diethyl ether, tetrahydrofiiran and dioxane. Suitable esters are for instance methyl formate, ethyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl butyrate and ethyl butyrate. Suitable fluorinated solvents are for examples Galden® Perfluoropoly ethers (PFPE), such as those of the product line Galden®SV available from Solvay Specialty Polymers Italy and fluorinated alkanes such as perfluorohexane. Good results were obtained with acetonitrile as liquid medium (LM).

The 1,2-difluoroethylene which is used in the method according to the invention, can be cis isomer, trans isomer, or a mixture thereof. Good results were obtained with trans isomer. In step (b), free radical species can be generated by a number of compounds, called free radical initiators.

I-CHF-CO2-R’ can be prepared from bromide or chloride analog, Br-CHF-CCh- R’ or CI-CHF-CO2-R’, according to reaction pathway described in Journal American Chemical Society, 2001, vol.123, no. 30, pages 7207-7219 or in Journal of Chemical Society, Perkin Trans.1, 1996, 1741-47.

Good results were obtained with R’ being ethyl group.

In step (b), radical species are generated through the decomposition of the free radical initiator (FRI) triggered by any way known by the person skilled in the art.

The choice of the free radical initiator is not particularly limited. Free radical initiator (FRI) can be selected from the list consisting of dialkyl peroxides such as di-t-butyl peroxide (DTBD), diacyl peroxides such as dibenzoyl peroxide (BPO), hydroperoxides such as t-butyl hydroperoxide, t-amyl hydroperoxide and cumyl hydroperoxide, peroxidicarbonates, peresters such as t-butyl perbenzoate, azonitrile compounds such as azobisisobutyronitrile (AIBN), In some embodiments, the free radical initiator (FRI) is diacyl peroxide of general formula RIC(O)OOC(O)R2, wherein Ri and R2 represent alkyl and/or aryl groups. Good results were obtained with dibenzoyl peroxide (BPO).

Generally, radical species are generated through the thermal decomposition of the free radical initiator (FRI) obtained by increasing the temperature. Generally, the temperature is increased and maintained up to a temperature wherein the decomposition rate of the initiator is controlled i.e. in a temperature range where the initiator’s half-life ti/2 is such that 10 minutes < ti/2 < 10 hours; preferably 0.5 hour < ti/2 < 2 hours.

Generally, the temperature is maintained during a time t such as ti/2 < t < 20 ti/2; preferably such as 5 ti/2 < t < 20 ti/2, more preferably such as 10 ti/2 < t < 20 ti/2. Good results were obtained using dibenzoylperoxide (BPO) at a temperature of 90°C for a duration ranging from 10 hours to 20 hours,

In some other embodiments, radical species are generated through the decomposition of the free radical initiator (FRI) triggered by light e.g. by UV irradiation.

In step (c) the compounds of formula (IT) I-(CHF-CHF)_P-CHF-CO2-R’ can be isolated from the reaction mixture (RM) by well-known techniques.

As an example, compounds of formula (IT) I-(CHF-CHF)_P-CHF-CO2-R’ can be isolated by removal of the monomer CHF=CHF and by further distillation of the solvent. Compounds of formula (IP) I-(CHF-CHF)_P-CHF-CO2-R’ can also be purified by any technique such as chromatography.

In some embodiments, compounds of formula (IP) I-(CHF-CHF)_P-CHF-CO2-R’ are isolated by removal of the remaining monomer CHF=CHF. For example, remaining monomer can be removed by bleeding the pressure and opening the reaction vessel.

In step (c), providing a reaction mixture (RM’) is generally performed in the same conditions as those described for providing a reaction mixture (RM) in step (a).

When compounds of formula (IP) I-(CHF-CHF)_P-CHF-CO2-R’ are isolated by removal of the monomer CHF=CHF, for example by bleeding the pressure and opening the reaction vessel, the liquid medium (LM’) is the liquid medium (LM) which remains at the end of step (a).

In some other embodiments, the liquid medium (LM’) is the liquid medium (LM) or part of the liquid medium (LM) which remains from step (a) to which is added an additional amount of liquid medium. Generally an additional amount of the same liquid medium is added at this stage. It may be a nitrile such as benzonitrile, isobutyronitrile, n-butyronitrile, acetonitrile and propionitrile, an ether both linear such as dimethyl ether, diethyl ether and cyclic such as tetrahydrofiiran and dioxane, an ester such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl butyrate and ethyl butyrate, a fluorinated solvent or a mixture thereof.

Still in some other embodiments, when compounds of formula (II‘) I-(CHF- CHF)_P-CHF-CO2-R’ are isolated by removal of the monomer CHF=CHF and substantially complete or complete removal of the liquid medium (LM), the liquid medium (LM’) is selected from the list consisting of nitriles, ethers, esters, fluorinated solvents and mixtures thereof. Examples of suitable liquid mediums are: benzonitrile, isobutyronitrile, n-butyronitrile, acetonitrile and propionitrile, dimethyl ether, diethyl ether, tetrahydrofiiran and dioxane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl butyrate and ethyl butyrate. Suitable fluorinated solvents are for examples Galden® Perfluoropolyethers (PFPE), such as those of the product line Galden®SV available from Solvay Specialty Polymers Italy and fluorinated alkanes such as perfluorohexane. Good results were obtained with acetonitrile as liquid medium (LM’). Generally, the free radical initiator (FRF) is selected from the same list as above described for the free radical initiator (FRI).

In some embodiments the free radical initiator (FRF) is the same as the free radical initiator (FRI).

Good results were obtained with (FRI) and (FRI) being dibenzoylperoxide (BPO).

In step (d), the generation of radical species through the decomposition of the free radical initiator in (RM’), leading to the formation of ^O(CHF-CHF)_P-CHF- CO2-R’ radical, to addition of q CHF=CHF and to the formation of the composition (C’) comprising at least one compound of formula (II) I-(CHF- CHF)O-CHF-CO2-R’, wherein 1< q< 15 and o=p+q, by telomerization can be performed as described for step (b).

The person of ordinary skill in the art is able to manufacture a composition (C’”) comprising at least one compound of formula (II”): (II”) I-(CHF-CHF)r-CHF-CO₂-R’ wherein 2< r <100, by iterating the steps (c) and (d) detailed above as many times as required to reach the desired value of r. For this purpose, it is common practice to adapt the reaction conditions such as the composition of the liquid medium.

Compounds of formula (II”) I-(CHF-CHF)r-CHF-CO2-R’ can be isolated from the reaction mixture at the end of the process using techniques known to the person skilled in the art of organic chemistry.

For instance, compounds of formula (IF) can be isolated by removal of the monomer CHF=CHF and by further distillation of the solvent. Compounds of formula (II”) can also be purified by known techniques, such as chromatography. Thus starting from the intermediate composition (C’), comprising at least one compound of formula (II) I-(CHF-CHF)_o-CHF-COO-R’, composition (C’”), comprising at least one compound of formula (II”) I-(CHF-CHF)_r-CHF-CO2-R’, can be obtained by iterating the steps (c) and (d) as many time as required. Similarly to composition (C), any of compositions (C’), (C”) and (C’”) may consist of one single compound of formula (II), (IF) or (III”) respectively. Alternatively, compositions (C’), (C”) and (C’”) may comprise more than one compound of formula (II), (IF) or (III”) respectively, differing the one from the other in the number of (CHF-CHF) units, that is in the value of o, p and r. Composition (C) according to the invention can be obtained by well-known methods as described below. In particular, composition (C) can be obtained by treating composition (C’”) with a reducing agent and in a subsequent step with a base.

Compounds of formula (If”) I-(CHF-CHF)_r-CHF-CO2-R’ in composition (C’”) can be reduced using any well-known reducing composition. A suitable reducing composition is Zn(0)/ ZnCh and diluted HC1, as described in Organic Chemistry, D.S. Kemp, F. Vellacio, 1980 Worth Publishers 1980 Chapter 34. The reaction may proceed according to the following scheme:

Zn/ZnCl

During this reaction, some dehydrofluorination reaction may occur thus leading to the presence of some unsaturation within the backbone in the final product as represented on the scheme above.

In a further step of the process, saponification reaction can be performed to transform the ester to the corresponding carboxylic acid salt using a treatment with a base. The product of the saponification reaction is a composition (C) in which in the at least one compound of formula (I) -P is -C00-M with M being an alkali metal cation.

The carboxylic acid salt can be further transformed to the corresponding carboxylic acid using a treatment with an acid. Recovery of the carboxylic acid from the ester is, for example, described in Tetrahedron, 1994, vol.50, n°33, pages 9847-9864.

From carboxylic acid of formula H-(CHF-CHF)n-(CF=CH)_m-CHF-CO2H, the preparation of any compound of formula (I) H-(CHF-CHF)n-(CF=CH)_m-CHF-P, wherein -P represents -C00-M, -CH2-O-M, -SO3-M or -PO3-M , wherein M is H, or an alkali metal, or an ammonium group N(R)4, wherein R, equal or different at each occurrence, is a hydrogen atom or a Ci-Ce hydrocarbon group is well known by the person of ordinary skill in the art.

For example, an ammonium salt can be obtained by treatment with aqueous NH3 of the carboxylic acid. An average molecular weight of the compounds of formulae (I) H-(CHF-CHF)_n- (CF=CH)_m-CHF-P, (II) I-(CHF-CHF)o-CHF-COO-R’, (II‘) I-(CHF-CHF)_P-CHF- CO2-R’, (II”) I-(CHF-CHF)_r-CHF-CO2-R’ comprised respectively in compositions (C), (C’), (C”) and (C’”) can be easily determined by the person of ordinary skill in the art, for example by ^JH and/or ¹⁹F NMR.

It has been found, that composition (C) according to the invention is well suited to be used in process for manufacturing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising recurring units derived from one fluorinated monomer (Ml), said process comprising free radical polymerization in aqueous medium of at least one fluorinated monomer (Ml). By fluorinated monomer (Ml) is meant an ethylenically unsaturated monomer comprising at least one fluorine atom. The choice of this fluorinated monomer is not particularly limited, any fluorinated monomer can be used.

Without being bonded to any theory, it appears that on one hand F atom on a carbon of polar group P of compound of formula (I) H-(CHF-CHF)_n-(CF=CH)_m- CHF-P according to the invention, tends to limit the transfer reactions during the free radical polymerization of fluorinated monomers and, on the other hand that the -CHF- moieties of compound of formula (I) H-(CHF-CHF)_n-(CF=CH)_m- CHF-P allow composition (C) stabilizing the aqueous dispersion of the fluorinated polymer (F).

One or more compound of formula (I) H-(CHF-CHF)n-(CF=CH)_m-CHF-P as defined above may be added to the aqueous free radical polymerization medium of the process of the invention in a total amount ranging advantageously from 0.0005% to 5% by weight based on the weight of the aqueous polymerization medium.

Therefore, another object of the invention relates to a process for manufacturing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising recurring units derived from at least one fluorinated monomer (Ml), said process comprising free radical polymerization in aqueous medium of at least one fluorinated monomer (Ml) in the presence of the composition (C) as previously defined.

In some embodiments, the fluorinated polymer (F) comprises recurring units derived from at least one fluorinated monomer (Ml) which is a C2-C3 hydrofluoroolefm (HFO) which is an unsaturated monomer composed of hydrogen, fluorine and carbon atoms. The C2-C3 hydrofluoroolefm (HFO) is generally selected from the group consisting of vinylidene fluoride (VDF), fluoroethylene, cis- 1 ,2-difluoroethylene, trans- 1 ,2-difluoroethylene, trifluoroethylene (TrFE), 2,3,3,3-tetrafluoropropylene, cis-1,3,3,3- tetrafluoropropy 1 ene, trans- 1 , 3 , 3 , 3 -tetrafluoropropyl ene, ci s- 1 , 2, 3 , 3 - tetrafluoropropylene, trans-l,2,3,3-tetrafluoropropylene, 1, 1,3,3- tetrafluoropropylene, 1 , 1 ,2, 3 -tetrafluoropropylene, cis- 1 ,2, 3 , 3 , 3 - pentafluoropropyl ene, trans- 1 , 2, 3 , 3 , 3 -pentafluoropropyl ene, 1, 1,3, 3,3- pentafluoropropylene, 1 , 1 ,2,3 ,3 -pentafluoropropylene, 3 ,3 ,3 -trifluoropropylene, 2,3,3 -trifluoropropyl ene, ci s- 1 , 3 , 3 -trifluoropropyl ene, trans- 1,3,3- trifluoropropylene, cis- 1 ,2,3-trifluoropropylene, trans- 1 ,2,3-trifluoropropylene,

1.1.3-trifluoropropylene, 1,1,2-trifluoropropylene and mixtures thereof. Preferably, the C2-C3 hydrofluoroolefm (HFO) is vinylidene fluoride (VDF), or

2.3.3.3-tetrafluoropropylene, preferably it is vinylidene fluoride (VDF). In some embodiments, the fluorinated polymer (F) consists essentially of recurring units derived from vinylidene fluoride (VDF).

In some other embodiments, the fluorinated polymer (F) comprises recurring units derived from at least one fluorinated monomer (Ml) which is tetrafluoroethylene (TFE).

In some embodiments, the fluorinated polymer (F) consists essentially of recurring units derived from tetrafluoroethylene (TFE).

In some other embodiments, the fluorinated polymer (F) further comprises recurring units derived from at least one additional fluorinated monomer (M2), wherein (M2) is different from (Ml), and thus is obtained by free radical polymerization in aqueous medium of (Ml) and said at least one additional fluorinated monomer (M2).

By additional fluorinated monomer (M2) is meant an ethylenically unsaturated monomer comprising at least one fluorine atom. The choice of this additional fluorinated monomers is not particularly limited, any fluorinated monomer can be used.

The additional fluorinated monomer (M2) may further comprise one or more other halogen atoms (Cl, Br, I) and may be partially or fully halogenated. Non-limiting examples of additional fluorinated monomers (M2) include: C2-C8 perfluoroolefms such as tetrafluoroethylene (TFE) or hexafluor opropyl ene (HFP); C2-C8 hydrogenated fluoroolefins such as vinyl fluoride, 1,2- difluoroethylene and trifluoroethylene (TrFE), hexafluoroisobutene (HFIB), perfluoroalkylethylenes of formula CH2=CH-Rfo, wherein Rfo is a Ci-Ce perfluoroalkyl group; chloro- and/or bromo- and/or iodo-C2-Ce fluoroolefins such as chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE); perfluoroalkylvinylethers (PAVE) of formula CF2=CF-O-Rfi, wherein Rfl is a Ci-Ce perfluorinated alkyl group e.g. CF3, C2F5, C3F7; partially fluorinated alkylvinylethers of formula CF2=CF-O-Rf2, wherein Rf₂ is a Ci-Ce partially fluorinated alkyl group; perfluoroalkoxyalkylvinylethers (PAAVEs) of formula CF2=CF-O-XQ, wherein Xo is a C1-C12 perfluorinated alkoxyalkyl group; partially fluorinated alkoxyalkylvinylethers of formula CF2=CF-O-XI, wherein Xi is a C1-C12 partially fluorinated alkoxyalkyl group; partially fluorinated fluoroalkoxy alkyl vinyl ethers of formula CF2=CF-O- X2, wherein X2 is a C1-C12 alkoxyalkyl group; hydrofluoroalkylvinylethers complying with formula CH2=CF-O-Y in which Y is a Ci-Ce fluoro- or perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7; fluorodioxoles, preferably perfluorodioxoles;

(per)fluoro-methoxy-vinylethers (MOVE, hereinafter) having formula: CFZ=CZ-O-CF₂-O-Rf₃ wherein Rf3 is selected among Ci-Ce (per)fluoroalkyls , linear or branched; C5-C6 cyclic (per)fluoroalkyls; and C2-C6 (per)fluorooxyalkyls, linear or branched, comprising from 1 to 3 catenary oxygen atoms, and Z = F, H; preferably Z is F and Rf₃ is -CF2CF3 (M0VE1); -CF2CF2OCF3 (M0VE2); or -CF₃ (M0VE3); sulfonyl fluoride fluoroolefins of formula: CF2=CF(CF2)_rSO2F wherein r is an integer between 0 and 10, preferably between 1 and 6, more preferably p is equal to 2 or 3; sulfonyl fluoride fluorovinyl- or fluoroallylethers of formula: CF2=CF- (CF2)_tO-(CF2)_sSO₂F wherein t is 0 or 1 and s is an integer between 1 and 10, preferably between 1 and 6, more preferably between 2 and 4, even more preferably s equals 2; sulfonyl fluoride fluoroalkoxy vinylethers of formula: CF2=CF-(OCF2CF(R_Fi))w-O-CF2(CF(R_F2))ySO2F wherein w is an integer between 0 and 2, RFI and RF2, equal or different from each other, are independently F, Cl or a Ci-Cio fluoroalkyl group, optionally substituted with one or more ether oxygens, y is an integer between 0 and 6; preferably w is 1, RFI is -CF3, y is 1 and RF2 is F; sulfonyl fluoride aromatic fluoroolefms of formula CF2=CF-Ar-SO2F wherein Ar is a C5-C15 aromatic or heteroaromatic substituent.

In some preferred embodiments, the fluorinated polymer (F) further comprises recurring units derived from at least one fluorinated monomer (M2) selected from the group consisting of cis-l,2-difluoroethylene, trans- 1,2-difluoroethylene, trifluoroethylene (TrFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), chlorofluoroethylene (CFE), chlorotrifluoroethylene (CTFE), perfluoroalkylvinylethers (PAVE) of formula CF2=CF-O-Rfi, wherein Rfi is a Ci-Ce perfluorinated alkyl group and sulfonyl fluoride fluorovinylethers of formula: CF2=CF-(CF2)tO-(CF2)_sSO2F wherein t=0 and s is an integer between 2 and 4, even more preferably s equals 2.

The perfluoroalkylvinylether (PAVE) is preferably selected from the group consisting of perfluoromethylvinylether (PMVE) of formula CF2=CF-O-CF3, perfluoroethylvinylether (PEVE) of formula CF2=CF-O-CF2-CF3 and perfluoropropylvinylether (PPVE) of formula CF2=CF-O-CF2-CF2-CF3. Also mixtures of different PAVEs can be used herein.

The sulfonyl fluoride fluorovinylether is preferably CF2=CF-O-(CF2)2SO2F (FSVE).

In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of, recurring units derived from:

- VDF and TFE;

- VDF, TFE and CTFE;

- VDF, TFE and PAVE;

-VDF, TFE and HFP;

-VDF, TFE, HFP and PAVE;

- VDF and TrFE;

-VDF, TrFE and CFE;

- VDF, TrFE and CTFE;

-VDF, TrFE and HFP;

- VDF and CFE;

- VDF and CTFE;

-VDF and HFP; -VDF, HFP and PAVE; or

-VDF, HFP and CTFE.

In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of (in mol %, with respect to the total moles of recurring units) :

- from 5% to 95% by mole of recurring units derived from vinylidene fluoride (VDF); and

- from 5% to 95% by mole of recurring units derived from at least one additional fluorinated monomer (M2).

In some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of

- from 15% to 35% by mole of recurring units derived from vinylidene fluoride (VDF); and

- from 65% to 85% by mole of recurring units derived from at least one additional fluorinated monomer (M2).

Still in some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of

- from 50% to 90% by mole of recurring units derived from vinylidene fluoride (VDF); and

- from 10% to 50% by mole of recurring units derived from at least one additional fluorinated monomer (M2).

In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of

- from 50% to 80% by moles of recurring units derived from vinylidene fluoride (VDF);

- from 15% to 30% by moles of recurring units derived from hexafluoropropylene (HFP); and

- from 5% to 20% by moles of recurring units derived from tetrafluoroethylene (TFE).

Good results were obtained with a fluorinated polymer (F) consisting of

- 58% by moles of recurring units derived from vinylidene fluoride (VDF);

- 23% by moles of recurring units derived from hexafluoropropylene (HFP); and

- 19% by moles of recurring units derived from tetrafluoroethylene (TFE).

In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of, recurring units derived from:

- TFE and PAVE; - TFE and PPVE;

- TFE and HFP;

- TFE, TrFE and HFP;

- TFE and FSVE.

In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of (in mol %, with respect to the total moles of recurring units) :

- from 55.0% to 99.5% by mole of recurring units derived from tetrafluoroethylene (TFE); and

- from 0.5% to 45% by mole of recurring units derived from at least one additional fluorinated monomer (M2).

Advantageously, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of :

- from 55.0% to 99.0% by mole of recurring units derived from tetrafluoroethylene (TFE); and

- from 45.0% to 1.0% by mole of recurring units derived from FSVE.

Still in some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of:

- from 95% to 99.5% by mole of recurring units derived from tetrafluoroethylene (TFE); and

- from 0.5% to 5% by mole of recurring units derived from at least one additional fluorinated monomer (M2).

In some embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of :

- from 85% to 99.5% by mole of recurring units derived from tetrafluoroethylene (TFE); and

- from 0.5% to 15% by mole of recurring units derived from at least one perfluoroalkylvinylether (PAVE).

Good results were obtained with a fluorinated polymer (F) consisting of:

- 99% by moles of recurring units derived from tetrafluoroethylene (TFE);

- 1% by moles of recurring units derived from perfluoropropylvinylether (PPVE). Optionally, fluorinated polymer (F) of the present invention also comprises recurring units derived from a bis-olefin [bis-olefin (OF)] having general formula: wherein Ri, R2, R3, R4, Rs and Rs, equal or different from each other, are H or C1-C5 alkyl; Z is a linear or branched Ci-Cis hydrocarbon radical (including alkylene or cycloalkylene radical), optionally containing oxygen atoms, preferably at least partially fluorinated, or a (per)fluoropolyoxyalkylene radical, e.g. as described in EP 661304 A.

The bis-olefin (OF) is preferably selected from the group consisting of those complying with formulae (OF-1), (OF-2) and (OF-3) : (OF-1) wherein j is an integer between 2 and 10, preferably between 4 and 8, and Ri, R2, R3, R4, equal or different from each other, are H, F or C 1-5 alkyl or (per)fluoroalkyl group;

(OF-2) wherein each of A, equal or different from each other and at each occurrence, is independently selected from F, Cl, and H; each of B, equal or different from each other and at each occurrence, is independently selected from F, Cl, H and ORB, wherein RB is a branched or straight chain alkyl radical which can be partially, substantially or completely fluorinated or chlorinated; E is a divalent group having 2 to 10 carbon atom, optionally fluorinated, which may be inserted with ether linkages; preferably E is a -(CF2)_m- group, with m being an integer from 3 to 6; a preferred bis-olefin of (OF-2) type is F2C=CF-O-(CF2)s-O-CF=CF2. (OF-3) wherein E, A and B have the same meaning as above defined; Rs, s, R7, equal or different from each other, are H, F or C 1-5 alkyl or (per)fluoroalkyl group. Good results were obtained with bis-olefin of (OF-1) type of formula H₂C=CH- (CF₂)₆-CH=CH₂.

In some other embodiments, the fluorinated polymer (F) comprises, preferably consists essentially of, and more preferably consists of, the following monomers composition (in mol %, with respect to the total moles of recurring units) :

(i) vinylidene fluoride (VDF) 35-85 %, hexafluoropropene (HFP) 10-45 %, tetrafluoroethylene (TFE) 0-30 %, (per)fluoroalkylvinylethers (PAVE) 0-15 %; bis-olefin (OF): 0-5 %;

(ii) vinylidene fluoride (VDF) 50-80 %, (per)fluoroalkylvinylethers (PAVE) 5 50 %, tetrafluoroethylene (TFE) 0-20 %, bis-olefin (OF): 0-5 %;

(iii) vinylidene fluoride (VDF) 20-30 %, C2-C8 non-fluorinated olefins (01) 10 30 %, hexafluoropropene (HFP) and/or (per)fluoroalkylvinylethers (PAVE) 18- 27 %, tetrafluoroethylene (TFE) 10-30 %; bis-olefin (OF): 0-5 %;

(iv) tetrafluoroethylene (TFE) 45-65 %, C2-C8 non-fluorinated olefins (01) 20 55 %, vinylidene fluoride (VDF) 5-30 %; bis-olefin (OF): 0-5 %;

(v) tetrafluoroethylene (TFE) 33-75 %, (per)fluoroalkylvinylethers (PAVE) 15 45 %, vinylidene fluoride (VDF) 5-30 %, hexafluoropropene HFP 0-30 %; bis- olefin (OF): 0-5 %;

(vi) vinylidene fluoride (VDF) 35-85 %, (per)fluoro-methoxy- vinylethers (MOVE) 5-40 %, (per)fluoroalkylvinylethers (PAVE) 0-30 %, tetrafluoroethylene (TFE) 0-40 %, hexafluoropropene (HFP) 0-30 %; bis-olefin (OF): 0-5 %;

Optionally, the fluorinated polymer (F) of the present invention also comprises iodine and/or bromine cure sites.

These iodine and/or bromine cure sites might be comprised as pending groups bound to the backbone of the fluorinated polymer (F) chain or might be comprised as terminal groups of said polymer chain.

According to a first embodiment, the iodine and/or bromine cure sites are comprised as pending groups bound to the backbone of the fluorinated polymer (F) chain; the fluorinated polymer (F) according to this embodiment typically comprises recurring units derived from brominated and/or iodinated cure-site comonomers selected from:

- bromo and/or iodo alpha-olefins containing from 2 to 10 carbon atoms such as bromotrifluoroethylene or bromotetrafluorobutene described, for example, in US 4035565 (DU PONT ) 12/07/1977 or other compounds bromo and/or iodo alphaolefins disclosed in US 4694045 (DU PONT ) 15/09/1987 ;

- iodo and/or bromo fluoroalkyl vinyl ethers (as notably described in patents US 454662 , US 4564662 (MINNESOTA MINING ) 14/01/1986 and EP 199138 A (DAIKIN IND LTD ) 29/10/1986 ).

According to a second embodiment, the iodine and/or bromine cure sites (preferably iodine cure sites) are comprised as terminal groups of the fluorinated polymer (F) chain; the fluorinated polymer according to this embodiment is generally obtained by addition to the polymerization medium during fluorinated polymer (F) manufacture of at least one of:

- iodinated and/or brominated chain-transfer agent(s); suitable chain-transfer agents are typically those of formula Rfi(I)x(Br)y, in which Rfi is a (per)fluoroalkyl or a (per)fluorochloroalkyl containing from 1 to 8 carbon atoms, while x and y are integers between 0 and 2, with 1 < x+y < 2 (see, for example, patents US 4243770 (DAIKIN IND LTD ) 6/01/1981 and US 4943622 (NIPPON MEKTRON KK ) 24/07/1990 ); and

- alkali metal or alkaline-earth metal iodides and/or bromides, such as described notably in patent US 5173553 (AUSIMONT SRL) 22/12/1992 .

Advantageously, for ensuring acceptable reactivity it is generally understood that the content of iodine and/or bromine in the fluorinated polymer (F) should be of at least 0.05 % wt, preferably of at least 0.06 % weight, with respect to the total weight of fluorinated polymer (F).

On the other side, amounts of iodine and/or bromine not exceeding preferably 7 % wt, more specifically not exceeding 5 % wt, or even not exceeding 4 % wt, with respect to the total weight of fluorinated polymer (F), are those generally selected for avoiding side reactions and/or detrimental effects on thermal stability.

Generally, the amount of iodine in the fluorinated polymer (F) ranges from 0.05 % wt to 7 % wt, preferably from 0.10 % wt to 4.0 % wt with respect to the total weight of fluorinated polymer (F).

In some preferred embodiments, iodinated chain-transfer agent are those of formula I-(CF2)k-I, in which k is an integer between 2 and 10.

Good results were obtained with I-(CF2)4-I as the iodinated chain-transfer agent. In some embodiments, the fluorinated polymer (F) of the present invention comprises recurring units derived from a bis-olefin [bis-olefin (OF)] as previously described and iodine atoms as end groups. In some embodiments, the fluorinated polymer (F) is obtained using bis-olefin of (OF-1) type H2C=CH-(CF2)e-CH=CH2 and I-(CF2)4-I as the iodinated chaintransfer agent.

In some embodiments, the process comprising free radical polymerization in aqueous medium of at least one fluorinated monomer (Ml) in the presence of the composition (C) according to the invention is performed in the presence of at least one non-fimctional perfluoropolyether (PFPE).

Any non-fimctional perfluoropolyether composed of sequences of perfluorooxyalkylene units can be advantageously utilized. Generally suitable perfluoropolyethers have neutral end groups and an average molecular weight ranging from 300 to 3000. Suitable non-fimctional perfluoropolyethers are, for example, responding to the formulae: i) R_gO(CF(CF3)-CF2O)q(CFO(CF3))r(CF2O)sRg’ with a random distribution of the perfluoro-oxyalkylene units; or ii) Rg”O(CF2CF2O)q(CFO(CF3))r(CF2O)_sR_g’” where R_g and R_g’, respectively R_g” and R_g’”, like or different from each other are -CF3, -C2F5, -C3F7 and q, r , s, respectively q’, r’ , s’, have such values as to meet the above said conditions regarding the average molecular weight.

Good results were obtained using Galden® D02 available from Solvay of formula CF3O(CF2-CF(CF3)O)_o(CF2O)_pCF3 wherein o/p = 20, having average molecular weight of 450.

In some embodiments, the process comprising free radical polymerization in aqueous medium of at least one fluorinated monomer (Ml) in the presence of the composition (C) according to the invention is performed in the presence of at least one nucleating agent. By nucleating agent is meant any agent suitable to promote latex particle formation and to allow for obtaining a fluorinated polymer having smaller primary particle size than that in the case of polymerization in the absence of said nucleating agent. Nucleating agents are well known by the person skilled in the art. Just for the sake of example nucleating agents include perfluoropolyether (PFPE) acid or salts thereof and nonionic surfactants such as nonionic hydrocarbon surfactants. Good results were obtained with hexafluoropropylene oxide oligomers bearing carboxylic acid group responding to formula C3F7O[CF(CF3)CF2O]tCF(CF3)COOH wherein t is such that the average molecular weight Mw of said oligomers ranges from lOOODa to 1500Da, preferably from 1 lOODa to 1400Da, as nucleating agent. Depending on the chemical nature of nucleating agent, it is generally used in an amount equal or less than lOOOppm; preferably equal or less than 500ppm; more preferably equal or less than lOOppm; sometimes equal or less that lOppm based on the aqueous medium. Good results were obtained with hexafluoropropylene oxide oligomers bearing carboxylic acid group in an amount equal or less than lOOppm based on the aqueous medium.

In some embodiments, the fluorinated polymer (F), is obtained using Galden® D02 available from Solvay and hexafluoropropylene oxide oligomers bearing carboxylic acid group responding to formula C3F7O[CF(CF3)CF2O]tCF(CF3)COOH, as previously defined, as nucleating agent.

The free radical polymerization in aqueous medium is typically carried out at a pressure comprised between 9 bar and 40 bar, preferably between 11 bar and 25 bar.

The polymerization temperature generally depends on, inter alia, the nature of the radical initiator used to initiate the free radical polymerization. The aqueous free radical polymerization is typically carried out at a temperature comprised between 50°C and 135°C, preferably between 55°C and 130°C.

While the choice of the radical initiator is not particularly limited, it is understood that, being the reaction conducted in an aqueous medium, water- soluble radical initiators are preferred for initiating and/or accelerating the polymerization. Nevertheless also initiators which are non-soluble in water or which have a poor solubility, can still be used in the present invention.

Both organic and inorganic radical initiators can be used in the process of the present invention. Suitable inorganic radical initiators include, but are not limited to, persulfates such as sodium, potassium and ammonium persulfates and hydrogen peroxide.

Also, organic radical initiators may be used and include, but are not limited to: acetylcyclohexanesulfonyl peroxide; diacetylperoxydicarbonate; dialkylperoxy dicarbonates such as diethylperoxy dicarbonate, dicyclohexylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate; tert butylperoxyneodecanoate; 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile; tert butylperpivalate; dioctanoylperoxide; dilauroyl-peroxide; 2,2'-azobis (2,4 dimethylvaleronitrile); tert-butylazo-2-cyanobutane; dibenzoylperoxide (BPO); tert-butyl-per-2ethylhexanoate; tert-butylpermaleate; 2,2'- azobis(isobutyronitrile); bis(tert-butylperoxy)cyclohexane; tert-butyl- peroxyisopropylcarbonate; tert-butylperacetate; 2,2'-bis (tert-butylperoxy)butane; dicumyl peroxide; di-tert-amyl peroxide; di-tert-butyl peroxide (DTBP); p- methane hydroperoxide; pinane hydroperoxide; cumene hydroperoxide; and tertbutyl hydroperoxide.

Other suitable radical initiators notably include halogenated free radical initiators such as chlorocarbon based and fluorocarbon based acyl peroxides such as trichloroacetyl peroxide, bis(perfluoro-2-propoxy propionyl) peroxide, [CF3CF2CF2OCF(CF3)COO]2, perfluoropropionyl peroxides, (CF₃CF2CF₂COO)2, (CF₃CF₂COO)2, {(CF3CF2CF2) [CF(CF3)CF₂O]mCF(CF3) COO}2 where m= 0-8, [ClCF2(CF2)_nCOO]2, and [HCF2(CF2)_nCOO]2 where n= 0-8; perfluoroalkyl azo compounds such as perfluoroazoisopropane, [(CF₃)₂CFN=]₂, R*N=NR*, where R* is a linear or branched perfluorocarbon group having 1-8 carbons; stable or hindered perfluoroalkane radicals such as hexafluoropropylene trimer radical, [(CF3)2CF]2(CF2CF2)C* radical and perfluoroalkanes.

Redox systems, comprising at least two components forming a redox couple, such as oxalate-permanganate, dimethylaniline-benzoyl peroxide, diethylanilinebenzoyl peroxide, L-ascorbic acid-hydrogen peroxide (H2O2), L-ascorbic acid- iodine (I2), and diphenylamine-benzoyl peroxide may also be used as radical initiators in the present invention.

Among inorganic radical initiators particularly preferred are inorganic persulfates and in particular, potassium and/or ammonium persulfate. Good results were obtained with ammonium persulfate (APS).

Among organic radical initiators, peroxides having a self-accelerating decomposition temperature (SADT) higher than 50°C are particularly preferred, such as for instance: di-tert-butyl peroxide (DTBP), diterbutylperoxyisopropylcarbonate, terbutyl(2-ethyl-hexyl)peroxycarbonate, terbutylperoxy-3 ,5,5 -trimethylhexanoate.

One or more radical initiators as defined above may be added to the aqueous polymerization medium of the process of the invention in a total amount ranging advantageously from 0.001% to 20% by weight based on the weight of the aqueous polymerization medium.

Typically a small amount of initiator is introduced in the reactor at the beginning of the polymerization process, in order to get it started, and subsequently an additional amount of initiator is added continuously or stepwise to the reactor until the polymerization reaction is complete. In some embodiments, the aqueous dispersion comprising particles of a fluorinated polymer (F) comprising recurring units derived from at least one fluorinated monomer (Ml), obtained by the process according to the invention is in the form of an aqueous latex therefore obtained by aqueous emulsion polymerization.

Therefore, the invention also pertains to an aqueous latex obtainable by the process according to the invention as previously described.

It also pertains to an aqueous latex comprising particles of at least one fluorinated polymer (F) as previously described and at least one compound of formula (I):

(I) H-(CHF-CHF)n-(CF=CH)_m-CHF-P, wherein : n is an integer greater than 0;

- m is an integer equal to or greater than 0,

2 < n+m < 100,

0 < m/n < 0.5, and

P represents -C00-M, -CH2-O-M, -SO3-M or -PO3-M , wherein M is H, or an alkali metal, or an ammonium group N(R)4, wherein R, equal or different at each occurrence, is a hydrogen atom or a Ci-Ce hydrocarbon group preferably an alkyl group; with the proviso that when n+m=3, then n 0.

Generally, the aqueous latex obtained by the process according to the invention comprises from 10% to 30% by weight of fluorinated polymer (F) as previously described with regard to the total weight of the aqueous latex.

Generally, the aqueous latex obtained by the process according to the invention comprises the fluorinated polymer (F) in the form of primary particles having an average primary particle size from 50 to 400 nm as measured according to ISO 22412 (2017).

By “average primary particle size” is meant the average size of primary particles of fluorinated polymer (F) obtainable by aqueous emulsion polymerization. For the purpose of the present invention, “primary particles” of fluorinated polymer (F) are to be intended distinguishable from agglomerates of primary particles. Aqueous latexes comprising primary particles of fluorinated polymer (F) are advantageously obtainable by the process according to the present invention comprising aqueous emulsion polymerization. Agglomerates of primary particles of fluorinated polymer (F) are typically obtainable by recovery and conditioning steps of fluorinated polymer (F) manufacture such as concentration and/or coagulation of aqueous fluorinated polymer (F) latexes and subsequent drying and homogenization thereby providing fluorinated polymer (F) powders.

As previously explained, fluorinated polymer (F) of the present invention comprises in some embodiments iodine and/or bromine cure sites, generally, in an amount ranging from 0.05 % wt to 7 % wt, preferably from 0.10 % wt to 4.0 % wt with respect to the total weight of fluorinated polymer (F). Such iodine containing fluorinated polymer (F) may be cured in the presence of at least one peroxide (P) which is able to generate radicals at relatively low temperature with suitable kinetics.

Therefore, another object of the invention is the use of the aqueous latex obtained by the process according to the invention in coating applications e.g. as dielectric coatings for capacitors or transistors.

Besides, another object of the invention is the use of the aqueous latex obtained by the process according to the invention in sealing or gasket applications e.g. for automotive.

Still, another object of the invention is the use of the aqueous latex obtained by the process according to the invention in piping, fitting, containment vessel, reactor or gas scrubber applications.

EXAMPLES

Preparation of ICHFCOOEt

Ethyl bromo fluoroacetate (0.24 mol, 1 eq) was added, in 1 h, to a stirred solution of anhydrous sodium iodide (0.29 mol 1.2eq) in dry acetone (240 cm3) at room temperature. When the addition was complete the reaction mixture was stirred at RT overnight. The suspension was diluted with diethyl ether (150 cm3) and filtered with a 0.45pm PTFE membrane and the residual solid was rewashed with 2 x 25 cm³ of diethyl ether. The filtered solution was evaporated under vacuum and the residual red oil was dissolved in 150 cm³ of diethyl ether and washed with 150 cm³ of semi- saturated aq. Na2S20s. The organic phase was separated and washed again with demi-water, then it was separated and dried over Na2SO4.

The organic phase was distilled under reduced pressure to give 50g of pure ethyl fluoroiodoacetate as confirmed by ^XH and ¹⁹F NMR.

Ethyl fluoroiodoacetate (90%). Oil, 63-70°C at 11/14 Torr.

1-Telomerization of CHF=CHF Step 1. Benzoyl peroxide (BPO, 1.76 g = 7.26 mmoles) was placed in a 300 mL stainless steel reactor equipped with inlet and outlet valves, a pressure transducer, a heating sock equipped with a temperature control and a magnetic stirrer. The reactor was cooled to -78°C (ethanol/CCh bath) and evacuated to remove the presence of O2 and humidity. The reactor was kept at -78°C under vacuum. A solution, composed of ICHFCChEt (8.23 g = 25.5 mmoles) and anhydrous CH3CN (120 mL), was prepared and placed in a glass container equipped with a PTFE tube. The homogeneous solution was cooled to 0°C and N2 was gently bubbled for about 20 min in order to remove O2. The degassed solution was therefore siphoned in the steel reactor. Then, the steel reactor, still under vacuum, was cooled to -196°C (liquid N2) and 27,8 g = 434 mmoles of CHF=CHF were fed. The reactor was warmed to room temperature, fitted with the heating sock and heated to 90°C with 600 rpm stirring for 15 hours. The addition product I-(CHF-CHF)_x-CHF-CO2Et , with 1< x <5 was formed. The reactor was then cooled to 30°C and unreacted CHF=CHF was bled off until P = 1 atm.

Step 2. The reactor was opened and 138 mL of a brown, homogeneous mixture was poured in an Erlenmeyer flask, cooled to 0°C and degassed with N2 for 20 min. BPO (1,65 g = 6,84 mmoles) was then added to the reactor. The reactor was cooled to -78°C, evacuated and left under vacuum. The degassed brown mixture comprising the addition product I-(CHF-CHF)_x-CHF-CO2Et was siphoned in the steel reactor. The steel reactor was then cooled to -196°C and CHF=CHF (22,4 g = 250 mmoles) was fed. The steel reactor was warmed first to room temperature, fitted with the heating sock and heated to 90°C with 600 rpm stirring for 15hrs. Once the reaction was over the steel reactor was cooled to 30°C, the excess CHF=CHF was bled off and 144 mL of a homogeneous, brown crude product was discharged.

The crude reaction product was treated overnight with active charcoal at 25°C. The active charcoal was then separated either by filtration upon a PTFE membrane or by centrifuging at 4000 rpm for 20 min at 20°C. The reactionproduct was then washed quickly at 0°C with a 3% w/v NaHCOs solution to eliminate benzoic acid arising from the BPO thermal decomposition. The washed mixture was then evaporated under vacuum at 65°C and 5 mbar residual pressure obtaining 30,44 g of a brownish, powdery a-iodo-co-ester vinylene fluoride oligomer solid corresponding to a yield of 56 mol % based on moles of CHF=CHF introduced. The average molecular weight was determined by 'H-NMR and ¹⁹F-NMR to be 121 Ig/mol corresponding to formula: I-(CHF-CHF)i55-CHF-CO2-C2H5 that is a composition comprising more than one compound of formula (II”) with an average number of (CHF CHF) units of 15.5.

2-Reduction of I-(CHF-CHF)I₅.5-CHF-CO2-C2H₅

30,44 g (25,14 mmol) of I-(CHF-CHF)i55-CHF-CO2-C2H5 were dissolved in 3100 mL of EtOH at 60°C obtaining a homogeneous light orange solution, which was placed in a glass reactor equipped with a magnetic stirrer, a cooling column connected to a bubbler, a thermocouple, a temperature reader, and solid dispenser. The solution was heated at 78°C with stirring = 900 rpm and Zn° powder (85%; 148 mmol = 11.4 g), ZnCb (173 mmol = 23.57 g) were added in small portions with the solid dispenser for a total addition time of 20 minutes. The suspension was stirred at 78°C for 60 minutes and 2.52 ml of 35% w/v HC1 were added with a dropping funnel.

The suspension was stirred at 900 rpm and at 78°C for 15 hrs. The resulting suspension was cooled to 30°C and then filtered to remove the excess of Zn°. The filtered Zn° was washed in 300 mL of acetone in order to collect by extraction any reduced products which came out of the EtOH solution at 30°C. The solution was cooled to room temperature and 2000 mL of water were added in order to wash ZnCb and ZnF away. The turbid EtOH/acetone/H2O solution was stripped with a rotary evaporator at 60°C and 165 mm Hg to distill away most of the EtOH and acetone and precipitate the desired reduced Oligomer from H2O. The H2O heterogeneous phase was filtered upon a PTFE membrane with a pore size = 5 pm. The solid was dried under a N2 stream obtaining 26.5g (99 mol%) of a light yellow/orange, powdery a-fluoromethyl-co-ester vinylene fluoride oligomer solid.

The average molecular weight was determined by ’H-NMR and ¹⁹F-NMR to be 1066g/mol corresponding to formula: H-(CHF-CHF)i4.5-(CF=CH)i-CHF-CO2- C₂H₅.

3-Saponification of H-(CHF-CHF)I₄.5-(CF=CH)I-CHF-CO2-C2H₅

26.5 g (24.86 mmol) of H-(CHF-CHF)I_{4 5}-(CF=CH)I-CHF-CO2-C₂H₅ were dissolved in 1663 mL of DMSO at 25°C obtaining an homogeneous solution. The solution was placed in a glass reactor equipped with a magnetic stirrer, a cooling column, a thermocouple, a temperature reader and a dropping funnel. The DMSO solution was heated to 40°C and a solution of 10.43g (124.4 mmol) NaHCOs in 700 mL of water was added within 45 min while stirring at 900 rpm. Then the reaction mixture was further heated to 65°C for 3hours. The glass reactor was cooled to 30°C and acidified by adding 30 mL of HC1 (35% w/v) to pH = 1. The saponified oligomers precipitated from solution and 1 volume of water was added. The precipitated oligomers were isolated by filtration upon a PTFE membrane with a pore size of 5 pm. The filtered oligomers were washed with water, filtered upon a PTFE membrane with a pore size of 5 pm. The recovered oligomers were dried in a N2 stream at 25°C obtaining 20,7 g of a brown, powdery a-fluoromethyl-co-carboxylic acid vinylene fluoride oligomer solid.

The average molecular weight was determined by ’H-NMR and ¹⁹F-NMR to be 976g/mol corresponding to formula: H-(CHF-CHF)i3-(CF=CH)i 5-CHF-CO2H 4-Preparation of ammonium salt of H-(CHF-CHF)i3-(CF=CH)i.5-CHF- CO2H

20,7 g (21,4 mmol) of H-(CHF-CHF)I₃-(CF=CH)I ₅-CHF-CO₂H were dissolved at 20°C in 210 mL of CH3CN and placed in a glass reactor equipped with a magnetic stirrer, a cooling column, a thermocouple, a temperature reader, and a dropping funnel.

143 ml of NH4OH (30% v/v; 2.5 moles) were added at a rate of 5 moles/h at 20°C under vigorous stirring and the reaction medium was further stirred for 90 min. Then the crude mixture was evaporated employing the rotary evaporator (60°C, 15 mm Hg residual P). Water was removed by adding small aliquots of CH3CN from time to time, and evaporating in the rotary evaporator to dryness. 20.7g (99%) of a product corresponding to formula: H-(CHF-CHF)i3- (CF=CH)i 5-CHF-CO2-NH4, hereinafter referred to as COMPOSITION Cl, were obtained. The average molecular weight was determined by ’H-NMR and ¹⁹F- NMR to be 993g/mol.

Polymerization materials

- H-(CHF-CHF)13-(CF=CH)15-CHF-CO₂-NH₄ (COMPOSITION Cl) was prepared as above described.

- 1,4-diiodoperfluorobutane (C4F8I2) as transfer agent was introduced in the polymerization reactor in the form of a 33wt % solution in Galden®D02.

- ammonium persulfate (APS) as initiator was introduced in the polymerization reactor in the form of a 2wt % or a 5wt % solution in demineralized water.

Example 1: Terpolymer VDF: 58% HFP: 23% TFE: 19% by moles nominal In an AISI 316 steel vertical autoclave, equipped with baffles and stirrer working at 850 rpm, were introduced 1.35 1 of demineralized water with 80 ppm of H- (CHF-CHF)i3-(CF=CH)i.5-CHF-CO2-NH4. Then the temperature was raised up to the reaction temperature of 80°C and when the later was reached, HFP (hexafluoropropene) was introduced to generate a pressure variation of 9 absolute bars. Next, a gas mixture of VDF: 58 %, HFP: 23% and TFE: 19% by mole was added via a compressor, until reaching a pressure of 22 abs bars. Then, 2 ml of iodine chain transfer agent C4F8I2 solution at 33% by volume in Galden®D02 and 20 ml of a solution of 2wt. % of ammonium persulfate (APS) in demineralized water were fed.

The polymerization pressure was maintained constant by feeding the above mentioned gas mixture.

When 250 g of gas mixture were reached, the feeding of the mixture was interrupted, the reactor cooled down to room temperature and degassed to remove unreacted monomers.

The resulting latex was discharged, degassed and post treated by coagulation. The recovered polymer was washed with demineralized water and dried at 90°C for 24 hours.

Characterization of the recovered polymer is reported in table 1.

Example 2: Perfluoroalkoxyalkane (PEA) TFE: 99% PPVE: 1% by moles nominal

The same procedure as in example 1 was followed, but feeding with pure TFE monomer and introducing by a metering 10 ml of perfluoropropyl vinyl ether (PPVE) before the feeding of ammonium persulfate solution.

Characterization of the recovered polymer is reported in table 1.

Comparative Example 1: Terpolymer VDF: 70% TFE: 11% HPF: 19% by moles nominal

In an AISI 316 steel vertical autoclave, equipped with baffles and stirrer working at 650 rpm, were introduced 3.3 1 of demineralized water.

Then the temperature was raised up to the reaction temperature of 80°C and when the later was reached, HFP was introduced to generate a pressure variation of 9 absolute bars. Next, a gas mixture of VDF: 70 %, HFP: 19% and TFE: 11% by mole was added via a compressor, until reaching a pressure of 22 abs bars. Then, 3 ml of iodine chain transfer agent C4F8I2 solution at 33% by volume in Galden®D02 and 30 ml of a solution of 5wt. % of ammonium persulfate (APS) in demineralized water were fed. The polymerization pressure was maintained constant by feeding the above mentioned gas mixture.

When 500 g of gas mixture were reached, the feeding of the mixture was interrupted, the reactor cooled down to room temperature and degassed to remove unreacted monomers.

The resulting latex was discharged, degassed and post treated by coagulation. The recovered polymer was washed with demineralized water and dried at 90°C for 24 hours.

Characterization of the recovered polymer is reported in table 1.

Comparative Example 2: Perfluoroalkoxyalkane (PEA) TEE: 99% PPVE: 1% by moles nominal

The same procedure as in example 2 was followed, but performing the reaction in an AISI 316 steel vertical autoclave, equipped with baffles and stirrer working at 650 rpm, introducing 3.3 1 of demineralized, then introducing 12 ml of perfluoropropyl vinyl ether (PPVE) before the feeding of ammonium persulfate solution, and finally introducing 7 ml of perfluoropropyl vinyl ether (PPVE) every 100 grams of fed pure TFE.

When 500 g of gas mixture were reached, the feeding of the mixture was interrupted, the reactor cooled down to room temperature and degassed to remove unreacted monomers.

Characterization of the recovered polymer is reported in table 1.

Coagulation procedure

250 ml of latex were poured using a dropping funnel in 3 liters of a of 2g/L water solution of A1₂(SO₄)3 under stirring. The latex was poured within 10 minutes making the water slightly opaque. After few minutes nucleation occurred and bigger particles were generated. Water started becoming transparent and the particles size increased till the water turned to completely transparent. Then the water was removed by filtration and the resulting flaky polymer was washed by stirring it in another volume of water for 10 minutes. The polymer was filtered and washed 5 more times before being dried in an oven at 90°C overnight. Table 1 : Polymer characterization

* Particle average diameter was measured by Dynamic Light Scattering (DLS) specifically based on Photon Correlation Spectroscopy according to ISO 22412 (2017) ** Monomer composition was determined by ¹⁹F-NMR

*** Differential Scanning Calorimetry (DSC)

**** Average molecular weights Mn (number) and Mw (weight) were measured by gel permeation chromatography (GPC).

It can be seen from the results compiled in Table 1 that very low amount of H- (CHF-CHF)i3-(CF=CH)i.5-CHF-CO2-NH4 according to the invention is suitable to prepare an aqueous dispersion of particles of a fluorinated polymer, comprising recurring units derived from VDF such as VDF-HFP-TFE copolymers, having features such as composition, glass transition and high molecular weight similar to those obtained for fluorinated polymers synthesized without surfactant. Results compiled in Table 1 also show that very low amount of H-(CHF-CHF)i3-(CF=CH)i 5-CHF-CO2-NH4 according to the invention is suitable to prepare an aqueous dispersion of particles of a fluorinated polymer, comprising recurring units derived from TFE such as TFE-PPVE copolymers while no latex is formed, when the polymerization is run without surfactant. Moreover, it appears that performing the polymerization of VDF/HFP/TFE mixtures or of TFE/PPVE mixtures, in the presence of the composition (C) according to the invention, allows preparing fluorinated polymer latexes comprising particles of very small particle average diameter.

Finally, it appears that performing the polymerization of VDF/HFP/TFE mixtures or of TFE/PPVE mixtures, in the presence of the composition (C)according to the invention, unexpectedly reduces the polymerization time to reach complete conversion, when compared to performing the polymerization without any surfactant.

Claims

C L A I M S A composition (C) comprising at least one compound of formula (I):

(I) H-(CHF-CHF)n-(CF=CH)_m-CHF-P, wherein :

- n is an integer greater than 0; m is an integer equal to or greater than 0,

2 < n+m < 100,

0 < m/n < 0.5, and

-P represents -COO-M, -CH2-O-M, -SO3-M or -PO3-M , wherein M is H, or an alkali metal, or an ammonium group N(R)4, wherein R, equal or different at each occurrence, is a hydrogen atom or a Ci-Ce hydrocarbon group, preferably a Ci-Cealkyl group; with the proviso that when n+m=3, then n 0. Composition (C) according to claim 1 which consist of one compound of formula (I). Composition (C) according to claim 1 which comprises more than one compound of formula (I) wherein each compound of formula (I) in the composition differs from the other compounds in the value of n, the value of m or both. Composition (C) according to any one of claims 1 to 3, wherein -P represents -COO-H or -COO-NH4. A method for manufacturing a composition (C’) comprising at least one compound of formula (II):

(II) I-(CHF-CHF)O-CHF-CO₂-R’, wherein : o is an integer,

2 < o < 25, and

- R’is a Ci-Ce hydrocarbon group, preferably a Ci-Ce alkyl group, comprising the steps of:

(a) providing a reaction mixture (RM) under inert atmosphere comprising 1,2-difluoroethylene of formula CHF=CHF, a iodofluoro alkanoate of formula I-CHF-CO2-R’ and a free radical initiator (FRI), solubilized in a liquid medium (LM);

(b) generating radical species through the decomposition of the free radical initiator (FRI), leading to the formation of “CHF-CCh-R’ radical, to the addition of a number p of CHF=CHF molecules and to the formation of the composition (C”) comprising at least one compound of formula (IP) I-(CHF-CHF)_P-CHF-CO2-R’, wherein l< p< 10;

(c) isolating compounds of formula (II‘) I-(CHF-CHF)_P-CHF-CO2- R’ from the reaction mixture (RM) and then providing a reaction mixture (RM’) under inert atmosphere comprising isolated compounds of formula (II”) I-(CHF-CHF)_P-CHF-CO2-R’, CHF=CHF and a free radical initiator (FRF), solubilized in a liquid medium (LM’);

(d) generating radical species through the decomposition of the free radical initiator (FRI’) in (RM’), leading to the formation of °(CHF-CHF)_P-CHF-CO2-R’ radical, to the addition of a number q of CHF=CHF molecules and to the formation of the composition (C’) comprising at least one compound of formula (II) I-(CHF- CHF)O-CHF-CO2-R’, wherein 1< q< 15 and o=p+q,. A method for manufacturing composition (C) of any one of claims 1 to 4 said method comprising obtaining a composition (C’”) comprising at least one compound of formula (II”):

(II”) I-(CHF-CHF)_r-CHF-CO₂-R’ wherein 2< r <100, by performing the method of claim 5 and iterating steps (c) and (d) as many times as required to reach the desired value of r. The method of claim 6 further comprising the step of treating composition (C’”) with a reducing agent and in a subsequent step with a base. A process for manufacturing an aqueous dispersion comprising particles of a fluorinated polymer (F) comprising recurring units derived from at least one fluorinated monomer (Ml), said process comprising free radical polymerization in aqueous medium of at least one fluorinated monomer (Ml) in the presence of the composition (C) according to claim 1 or 2. The process according to claim 8, wherein the at least one fluorinated monomer (Ml) is a C2-C3 hydrofluoroolefm (HFO) selected from the group consisting of vinylidene fluoride (VDF), fluoroethylene, cis- 1,2- difluoroethylene, trans- 1,2-difluoroethylene, trifluoroethylene (TrFE),

2.3.3.3 -tetrafluoropropylene, ci s- 1 , 3 , 3 , 3 -tetrafluoropropylene, trans-

1.3.3.3 -tetrafluoropropyl ene, cis-1,2,3,3 -tetrafluoropropyl ene, trans-

1.2.3.3 -tetrafluoropropylene, 1 , 1 ,3 ,3 -tetrafluoropropylene, 1 , 1 ,2,3- tetrafluoropropylene, cis-l,2,3,3,3-pentafluoropropylene, trans-

1.2.3.3.3 -pentafluoropropyl ene, 1,1, 3, 3, 3 -pentafluoropropyl ene,

1.1.2.3.3-pentafhioropropylene, 3,3,3-trifluoropropylene, 2,3,3- trifluoropropylene, cis- 1,3, 3 -trifluoropropyl ene, trans-1,3,3- trifluoropropylene, cis-l,2,3-trifluoropropylene, trans-1,2,3- trifluoropropylene, 1 , 1 ,3 -trifluoropropylene, 1 , 1 ,2-trifluoropropylene and mixtures thereof. The process according to claim 9, wherein the C2-C3 hydrofluoroolefm (HFO) is vinylidene fluoride. The process according to claim 8, wherein the at least one fluorinated monomer (Ml) is tetrafluoroethylene (TFE). The process according to any one of claims 8 to 11, wherein the fluorinated polymer (F) further comprises recurring units derived from at least one additional fluorinated monomer (M2), wherein (M2) is different from (Ml). 13. The process according to any one of claims 8 to 12, wherein the composition (C) comprises at least one compound of formula (III)

(III) H-(CHF-CHF)_n-(CF=CH)_m-CHF-COO-NH₄, wherein n is an integer greater than 0; m is an integer equal to or greater than 0, - 2 < n+m < 100, and

- 0 < m/n < 0.5; with the proviso that when n+m=3, then n 0.

14. The process according to any one of claims 8 to 13, wherein the fluorinated polymer (F) contains iodine.

15. The process according to any one of claims 8 to 14, wherein the aqueous dispersion comprising particles of a fluorinated polymer (F) is an aqueous latex.

16. An aqueous latex obtainable by the process according to anyone of claims 7 to 14.

17. An aqueous latex comprising particles of at least one fluorinated polymer (F) and at least one compound of formula (I):

(I) H-(CHF-CHF)n-(CF=CH)_m-CHF-P, wherein : n is an integer greater than 0; m is an integer equal to or greater than 0,

2 < n+m < 100,

0 < m/n < 0.5, and

-P represents -C00-M, -CH2-O-M, -SO3-M or -PO3-M , wherein M is H, or an alkali metal, or an ammonium group N(R)₄, wherein R, equal or different at each occurrence, is a hydrogen atom or a Ci-Ce hydrocarbon group, preferably a Ci-Cealkyl group; with the proviso that when n+m=3, then n 0. 18. The aqueous latex according to claim 16 or 17 wherein the fluorinated polymer (F) is in the form of primary particles having an average primary particle size from 50 to 400 nm as measured according to ISO 22412. 19. Use of the aqueous latex according to any one of claims 16 to 18 in coating, sealing, gasket, piping, pipe fitting, containment vessel, reactor or gas scrubber applications.