Novel fluoroelastomer and curable composition thereof

Abstract

The present invention relates to a novel fluoroelastomer and to a curable composition comprising the fluoroelastomer and at least one curing agent. The present invention also relates to a method for manufacturing a shaped article comprising curing the curable composition and to cured articles obtainable from the composition.

Description

SSPI 2024 / 025 NOVEL FLUOROELASTOMER AND CURABLE COMPOSITION THEREOF REFERENCE TO RELATED APPLICATIONS This application claims priority from European patent application Nr. 24200171.7 filed on September 13, 2024, the whole content of this application being incorporated herein by reference for all purposes. TECHNICAL FIELD

[0001] The present invention relates to a novel fluoroelastomer and to a curable composition comprising the fluoroelastomer and at least one curing agent. The present invention also relates to a method for manufacturing a shaped article comprising curing the curable composition and to cured articles obtainable from the composition. TECHNICAL BACKGROUND

[0002] Fluorinated polymers are known as specialty chemicals for diverse applications thanks to their unique properties, e.g. enhanced chemical and thermal stability, excellent electrical properties, etc.

[0003] Fluoroelastomers, in particular perfluoroelastomers, are materials exhibiting excellent heat- and chemical-resistance, which are hence generally used in the manufacture of sealing articles such as oil seals, gaskets, shaft seals and O-rings, wherein the leak-tightness, the mechanical properties and the resistance to various substances such as mineral oils, hydraulic fluids, solvents and chemical agents of diverse nature must be ensured over a wide range of working temperatures for their shelf life.

[0004] Fluoroelastomers, and in particular tetrafluoroethylene (TFE)-based fluoroelastomers, have been extensively employed in applications requiring superior resistance to extreme conditions, such as elevated temperatures and exposure to aggressive chemicals. The outstanding performance of these materials is fundamentally dependent on the curing (cross-linking) process, which is essential for converting the raw, uncured polymer into a robust elastomeric network.SSPI 2024 / 025

[0005] In their uncured state, fluoroelastomers consist of linear or branched polymer chains with limited mechanical integrity and thermal stability. Curing involves the formation of covalent cross-links between these polymer chains, resulting in a three-dimensional network structure. This cross-linked architecture imparts the elastomer with enhanced mechanical strength, elasticity, chemical resistance, and the ability to retain its properties under demanding service conditions.

[0006] Various curing chemistries have been developed for fluoroelastomers. A widely used approach relies on the incorporation of reactive functional groups—such as pendant -CN groups—into the polymer backbone. These functionalities enable cross-linking reactions in the presence of suitable curing agents, which may include peroxides, bisphenols, or other cross- linking systems. The specific chemistry and mechanism of cross-linking are selected based on the desired balance of properties and processing requirements. US20210395416 is an example of the known art in this domain.

[0007] The curing process is typically initiated by the application of heat and / or pressure to a compounded elastomer formulation containing the base polymer, curing agents, and other additives. Key parameters for evaluating and controlling the curing process include scorch time (ts2) and t90. Scorch time denotes the interval before the onset of rapid cross-linking; a shorter scorch time indicates earlier initiation of cure, which can limit the available processing window for shaping or molding the material. Parameter t90, on the other hand, represents the time required to achieve 90% of the maximum torque (as measured by rheometry), serving as an indicator of the time to optimal cure. The interplay between scorch time and t90is critical: minimizing scorch time can enhance productivity but may compromise processability, while optimizing t90 ensures complete cross-linking and optimal material performance. Fine-tuning these curing parameters, without impacting the mechanical properties of the cured material, is of significant interest to practitioners inSSPI 2024 / 025 the field, as it enables the customization of processing and end-use properties. SUMMARY OF THE INVENTION

[0008] A first object of the present invention is a fluoroelastomer [fluoroelastomer (A)] comprising recurring units derived from tetrafluoroethylene (TFE) and from 0.1 to 10.0% by moles (mol%), with respect to the total moles of recurring units of the fluoroelastomer (A), of recurring units derived from at least one perfluorovinylether of formula (I): CF2=CF-OCF2O-RF-X (I) wherein RFis a perfluoro(oxy)alkylene group having 1 to 20 carbon atoms and X is -C(O)NH2 or -CN.

[0009] A second object of the present invention is a composition comprising a fluoroelastomer (A) of the present invention and at least one curing agent (CA).

[0010] A third object of the present invention is a method for manufacturing a shaped article, comprising curing a composition of the present invention.

[0011] The present invention also relates to cured articles obtainable from the composition comprising the fluoroelastomer (A) and at least one curing agent (CA). DETAILED DESCRIPTION OF THE INVENTION

[0012] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub- ranges encompassed within that range as if each numerical value and sub- range is explicitly recited.

[0013] As used herein, the concentration of recurring units in ‘percent by mol’ (mol%) refers to the concentration relative to the total number of recurring units in the polymer, unless explicitly stated otherwise.SSPI 2024 / 025

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. Accordingly, various changes and modifications described herein will be apparent to those skilled in the art. Moreover, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

[0015] For the purpose of the present description and of the following claims: the use of parentheses around symbols or numbers identifying the formulae, for example in expressions like ‘polymer (P)’, etc., has the mere purpose of better distinguishing the symbol or number from the rest of the text and, hence, said parenthesis can also be omitted.

[0016] The expression ‘fluorinated’ or ‘fluoro-‘ is used herein to refer to compounds, polymers, monomers, etc. that are either fully or partially fluorinated, i.e. wherein all or only a part of the hydrogen atoms have been replaced by fluorine atoms. Analogously, the expression ‘perfluorinated’ or ‘perfluoro-‘ is intended to denote compounds that are fully fluorinated. In the present invention, the expression ‘(per)fluorinated’ or ‘(per)fluoro-‘ is used to refer to both partially fluorinated and perfluorinated compounds.

[0017] For the puporse of this invention, the expression ‘elastomer’ is intended to denote a polymer resin serving as a base constituent for obtaining a true elastomer.

[0018] True elastomers are defined by the ASTM, Special Technical Bulletin, No. 184 standard as materials that are capable of being stretched, at room temperature, to twice their intrinsic length and that, once they have been released after holding them under tension for five minutes, return to within 10% of their initial length in the same time.

[0019] The expression ‘fluoroelastomer’ is intended to denote a fully or partially fluorinated elastomer.

[0020] The expression ‘perfluoro(oxy)alkylene group’ is used herein to refer to both an alkylene group and an oxyalkylene group comprising at least one catenary oxygen atom, that are fully fluorinated.SSPI 2024 / 025

[0021] Within the context of the present invention, the expression ‘at least one’ is intended to denote one or more than one.

[0022] In the present invention, the expression ‘phr’ refers to ‘parts per hundred rubber’ and any amount expressed in phr is based on 100 parts by weight of an elastomer.

[0023] The present invention provides a fluoroelastomer [fluoroelastomer (A)] comprising: - recurring units derived from tetrafluoroethylene (TFE); and - from 0.1 to 10.0% by moles (mol%), with respect to the total moles of recurring units of the fluoroelastomer (A), of recurring units derived from at least one perfluorovinylether of formula (I): CF2=CF-OCF2O-RF-X (I) wherein RF is a perfluoro(oxy)alkylene group having 1 to 20 carbon atoms and X is -C(O)NH2or -CN.

[0024] RFmay be a linear or branched perfluoro(oxy)alkylene group.

[0025] RF may be a perfluoro(oxy)alkylene group having 1 to 10 carbon atoms.

[0026] Advantageously, RF is a linear perfluoro(oxy)alkylene group of formula: (CF2)n-1-(O)x-(CF2)m-1wherein x = 0 or 1; n and m are, independently of each other, positive integers; and the sum of n and m is from 3 to 12, with a proviso that m = 1, when x = 0.

[0027] RFmay be a linear perfluoro(oxy)alkylene group having 3 to 10 carbon atoms. Non-limiting examples of linear perfluoro(oxy)alkylene groups are - CF2-, -CF2CF2-, -CF2CF2CF2-, -CF2CF2-O-CF2-, -CF2-O-CF2CF2-, - CF2CF2CF2CF2-, -CF2CF2-O-CF2CF2-, -CF2CF2CF2-O-CF2-, -CF2-O- CF2CF2CF2-, -CF2CF2CF2CF2CF2-, -CF2CF2CF2-O-CF2CF2-, -CF2CF2-O- CF2CF2CF2-, -CF2-O-CF2CF2CF2CF2-, -CF2CF2CF2CF2-O-CF2-, - CF2CF2CF2CF2CF2CF2-, -CF2-O-CF2CF2CF2CF2-, -CF2CF2-O-CF2CF2CF2-, - CF2CF2CF2-O-CF2CF2-, and -CF2CF2CF2CF2-O-CF2-.

[0028] Alternatively, RF may be a branched perfluoro(oxy)alkylene group having 3 to 10 carbon atoms. Non-limiting examples of branchedSSPI 2024 / 025 perfluoro(oxy)alkylene groups are -CF(CF3)CF2-, -CF2CF(CF3)-, - CF2CF2CF(CF3)-, -CF2CF(CF3)CF2-, -CF(CF3)CF2CF2-, - CF2CF(CF3)2-, - CF(CF3)2CF2-, -CF2-O-CF(CF3)CF2-, -CF2-O-CF2CF(CF3)-, -CF(CF3)CF2-O- CF2-, -CF2CF(CF3)-O-CF2-, -CF(CF3)CF2CF2CF2-, -CF2CF(CF3)CF2CF2-, - CF2CF2CF(CF3)CF2-, -CF2CF2CF2CF(CF3)-, -CF2-O-C(CF3)2CF2-, -CF2-O- CF2C(CF3)2-, -CF2-O-CF2CF(CF3)CF2-, -CF2-O-CF(CF3)CF2CF2-, -CF2-O- CF2CF2CF(CF3)-, -CF2C(CF3)2-O-CF2-, -C(CF3)2CF2-O-CF2-, - CF2CF2CF(CF3)-O-CF2-, -CF2CF(CF3)CF2-O-CF2-, -CF(CF3)CF2CF2-O-CF2, -CF(CF3)CF2-O-CF2CF2-, -CF2CF(CF3)-O-CF2CF2-, -CF2CF2-O- CF(CF3)CF2-, and -CF2CF2-O-CF2CF(CF3)-.

[0029] When X = -C(O)NH2, the chemical compound having formula (I) can advantageously be selected from the group consisting of: CF2=CF-OCF2O-CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF2CF2-C(O)NH2,CF2=CF-OCF2O-CF2CF2CF2CF2-C(O)NH2,CF2=CF-OCF2O-CF(CF3)CF2- C(O)NH2, CF2=CF-OCF2O-CF2CF(CF3)-C(O)NH2, CF2=CF-OCF2O-CF2CF2- O-CF2-C(O)NH2, -CF2=CF-OCF2O-CF2CF2-O-CF2CF2-C(O)NH2, CF2=CF- OCF2O-CF2CF2CF2-O-CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF2CF2-O- CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF(CF3)CF2-O-CF2-C(O)NH2, CF2=CF- OCF2O-CF2CF(CF3)-O-CF2-C(O)NH2, CF2=CF-OCF2O-CF(CF3)CF2-O- CF2CF2-C(O)NH2, and CF2=CF-OCF2O-CF2CF(CF3)-O-CF2CF2-C(O)NH2.

[0030] When X = -CN, the chemical compound having formula (I) is conveniently selected from the group consisting of: CF2=CF-OCF2O-CF2CF2-CN, CF2=CF-OCF2O-CF2CF2CF2-CN,CF2=CF- OCF2O-CF2CF2CF2CF2-CN,CF2=CF-OCF2O-CF(CF3)CF2-CN, CF2=CF- OCF2O-CF2CF(CF3)-CN, CF2=CF-OCF2O-CF2CF2-O-CF2-CN, CF2=CF- OCF2O-CF2CF2-O-CF2CF2-CN, CF2=CF-OCF2O-CF2CF2CF2-O-CF2-CN, CF2=CF-OCF2O-CF2CF2CF2-O-CF2CF2-CN, CF2=CF-OCF2O-CF(CF3)CF2- O-CF2-CN, CF2=CF-OCF2O-CF2CF(CF3)-O-CF2-CN, CF2=CF-OCF2O- CF(CF3)CF2-O-CF2CF2-CN, and CF2=CF-OCF2O-CF2CF(CF3)-O-CF2CF2- CN. The compound may advantageously be selected from the groupSSPI 2024 / 025 consisting of CF2=CFOCF2OCF2CF2CN and CF2=CFOCF2OCF2CF2OCF2CN.

[0031] The fluoroelastomer (A) may further comprise recurring units derived from at least one (per)fluorinated monomer, different from tetrafluoroethylene (TFE) and perfluorovinylether of formula (I) as above defined.

[0032] In one embodiment, the (per)fluorinated monomer, different from tetrafluoroethylene (TFE) and perfluorovinylether of formula (I), is selected from the group consisting of: - C3-C8 perfluoroolefins, such as hexafluoropropylene (HFP); - C2-C6 fluoroolefins comprising at least one of Cl, Br and I, such as chlorotrifluoroethylene (CTFE); - C2-C8hydrogen-containing fluoroolefins, such as vinyl fluoride, 1,2- difluoroethylene, vinylidene fluoride (VDF), trifluoroethylene (TrFE), pentafluoropropylene, and hexafluoroisobutylene; - (per)fluoroakylethylenes of formula CH2=CH-RF0, in which RF0 is a C1-C6 (per)fluoroalkyl or a C1-C6(per)fluorooxyalkyl having one or more ether group; - (per)fluoroalkylvinylethers (PAVE) of formula CF2=CFORF1, in which RF1 is a C1-C6 (per)fluoroalkyl group such as -CF3, -C2F5 and -C3F7; - (per)fluorooxyalkylvinylethers of formula CF2=CFORF2, in which RF2is a C1-C12(per)fluorooxyalkyl having one or more ether group; - (per)fluorodioxoles of formula:wherein each of Rf3, Rf4, Rf5, and Rf6, equal to or different from each other, is a fluorine atom, a C1-C6fluoro- or per(halo)fluoroalkyl, optionally comprising one or more oxygen atom, such as -CF3, -C2F5, -C3F7, -OCF3, and - OCF2CF2OCF3;SSPI 2024 / 025 - perfluorovinylethers of formula (II) CF2=CF-[OCF2CFXII(CF2)a1]m1-O- (CF2)n1-CN, with XIIbeing F or CF3; a1 being 0, 1 or 2; m1 being 0, 1, 2, 3 or 4; and n1 being an integer from 1 to 12; - perfluorovinylethers of formula (III) CF2=CF-[OCF2CFXIII(CF2)a2]m2-O- CF2CF(CF3)-CN, with XIIIbeing F or CF3; a2 being 0, 1 or 2; and m2 being 0, 1, 2, 3 or 4; - perfluorovinylethers of formula (IV) CF2=CF-[OCF2CFXIV]m3-O-(CF2)n2- RCOX, with XIVbeing F or CF3; m3 being 0, 1, 2, 3 or 4; n2 being an integer from 1 to 12; and RCOXbeing selected from the group consisting of carboxylic groups –COOH; carboxylate groups -COOXa, with Xa being a monovalent metal or an ammonium group; carboxamide group - CONH2; and alkoxycarboxylic group -COORH, with RHbeing a (fluoro)(hydro)carbon group, preferably a C1-C3 alkyl group; and - perfluorovinylethers of formula (V) CF2=CF-(OCF2CFXV)m4-O- CF2CF(CF3)-RCOX’, with XVbeing F or CF3; m4 being 0, 1, 2, 3 or 4; and RCOX’having the meaning as defined for RCOX.

[0033] In a particular embodiment, the (per)fluorinated monomer is a (per)fluoroalkylvinylether (PAVE) of formula CF2=CFOCF3 (perfluoromethylvinylether).

[0034] In another particular embodiment, the (per)fluorooxyalkylvinylethers of formula CF2=CFORF2 are (per)fluoromethoxyvinylethers (MOVE) with RF2 being -CF2OCF2CF3(MOVE1), -CF2OCF2CF2OCF3(MOVE2) or -CF2OCF3(MOVE3).

[0035] In one embodiment, the perfluorovinylether of formula (II) is CF2=CF-O- CF2CF(CF3)-O-CF2CF2-CN [perfluoro(8-cyano-5-methyl-3,6-dioxa-1- octene)]. In the other embodiment, the perfluorovinylether of formula (III) is CF2=CF-O-CF2CF2CF2-O-CF2CF(CF3)-CN [perfluoro(9-cyano-9-methyl-3,7- dioxa-1-nonene)].

[0036] It may happen for fluoroelastomer (A) to include recurring units derived from fluorine-free monomers, which will be hereunder referred to as hydrogenated monomers. Examples of hydrogenated monomers are notably hydrogenatedSSPI 2024 / 025 α-olefins, including ethylene, propylene, 1-butene, diene monomers, styrene monomers, and other α-olefins being typically used.

[0037] Optionally, the fluoroelastomer (A) of the present invention comprises recurring units derived from a bis-olefin (OF) having general formula:wherein R1, R2, R3, R4, R5, and R6, equal to or different from each other, are independently selected from the group consisting of F, Cl, H, C1-C5 (fluoro)alkyl groups and ORB groups, RB being a branched or linear alkyl radical which can be fluorinated or chlorinated; and Z is a branched or linear C1-C18(hydro)carbon radical, optionally containing at least one oxygen atom, preferably a (per)fluoro(poly)oxyalkylene radical.

[0038] Advantageously, the bis-olefin (OF) is selected from the group consisting of those complying with formulae (OF-1), (OF-2), and (OF-3):wherein j is an integer between 2 and 10, preferably between 4 and 8, and R’1, R’2, R’3, and R’4, equal to or different from each other, are H, F or C1-C5 alkyl or C1-C5 (per)fluoroalkyl group;wherein each of A, equal to or different from each other, is F, Cl or H; each of B, equal to or different from each other, is F, Cl, H, or ORB, RB being a branched or straight chain alkyl radical which can be fluorinated or chlorinated; E is a divalent group having 2 to 10 carbon atoms, optionally fluorinated, which may be inserted with ether linkages; andSSPI 2024 / 025 wherein E, A and B have the same meaning as above defined; R’5, R’6, and R’7, equal to or different from each other, are H, F, C1-C5 alkyl group or C1- C5(per)fluoroalkyl group.

[0039] In a particular embodiment, the bis-olefin (OF) is (OF-2), wherein E is a - (CF2)m- group, with m being an integer of from 3 to 5. Preferably, the bis olefin of (OF-2) type is F2C=CF-O-(CF2)5-O-CF=CF2.

[0040] For embodiments wherein the fluoroelastomer (A) comprises recurring units derived from a bis-olefin (OF), as detailed above, the amount of the bis-olefin (OF) is generally of at least 0.04 mol%, preferably at least 0.05 mol%, and / or at most 0.25 mol%, preferably at most 0.20 mol%, with respect to the total moles of recurring units of the fluoroelastomer (A).

[0041] Exemplary fluoroelastomers (A) of the present invention are those having recurring units derived from the following monomers: - tetrafluoroethylene (TFE); - perfluorovinylether of formula (I); - (per)fluoroalkylvinylethers (PAVE); - optionally perfluorovinylether(s) of formula (II) and / or (III); and - optionally bis-olefin (OF).

[0042] In one embodiment, a fluoroelastomer (A) of the present invention comprises recurring units derived from the following monomers: - from 20.0 to 70.0 mol% of TFE; - from 0.1 to 10.0 mol% of perfluorovinylether of formula (I); - from 20.0 to 78.0 mol% of PAVE; - from 0 to 10.0 mol% of perfluorovinylether(s) of formula (II) and / or (III); and - from 0 to 0.25 mol% of bis-olefin (OF), the mol% being based on the total moles of recurring units of the fluoroelastomer (A).

[0043] In a particular embodiment, the fluoroelastomer (A) comprises recurring units derived from TFE, from 0.1 to 10.0 mol% of perfluorovinylether of formula (I),SSPI 2024 / 025 and perfluoromethylvinylether, the mol% being based on the total moles of recurring units of the fluoroelastomer (A).

[0044] In a more particular embodiment, the perfluorovinylether of formula (I) is CF2=CF-OCF2O-CF2CF2-CN (7-CNMOVE).

[0045] In another more particular embodiment, the perfluorovinylether of formula (I) is CF2=CF-OCF2O-CF2CF2-O-CF2-CN (8-O-CNMOVE).

[0046] End chains, defects or minor amounts of monomer impurities leading to recurring units different from those above mentioned, typically less than 0.1 mol% with respect to the total moles of recurring units, can be still present in the exemplary preferred fluoroelastomers (A), without this affecting properties of the material.

[0047] In the present invention, a perfluorovinylether of formula (I) may be prepared by a process comprising a step of reacting a hydrogenated diol compound with a carbonyl fluoride: CF2=CF-OCF2O-RF-X (I) wherein RFis a perfluoro(oxy)alkylene group having 1 to 20 carbon atoms; and X is -C(O)NH2or -CN.

[0048] Particularly, the carbonyl fluoride is selected from the group consisting of carbonyl (di)fluoride [C(O)F2], carbonyl fluoride bromide [C(O)FBr] and carbonyl fluoride chloride [C(O)FCl].

[0049] In the present invention, the hydrogenated diol compound may be linear or branched. The hydrogenated diol compound can be symmetric or asymmetric. Advantageously, the hydrogenated diol compound has 2 to 18 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 8 carbon atoms.

[0050] Exemplary hydrogenated diol compounds are diethylene glycol, dipropylene glycol, ethylene glycol, 1,2-propanediol, propane-2,2-diol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5- pentanediol, 1,6-hexanediol, 2-methyl-2-propyl-1,3-propanediol, 3-methyl- 1,3-propanediol, and 1,10-decanediol.SSPI 2024 / 025

[0051] Preferably, the hydrogenated diol compound is selected from the group consisting of diethylene glycol, 1,3-propanediol, and 1,5-pentanediol.

[0052] In one embodiment, the process for manufacturing a perfluorovinylether of formula (I) comprises the steps of: (a) reacting a hydrogenated diol compound with a carbonyl fluoride to obtain a fluoroformate compound; (b) reacting the fluoroformate compound with fluorine (F2) to obtain a perfluoroformate compound; (c) reacting the perfluoroformate compound with an olefinic compound to obtain a perfluorohalogen ether; (d) converting the perfluorohalogen ether to an ester compound; (e) reacting the ester compound with ammonia to obtain an amide compound; and (f) removing chlorine (Cl2) from the amide compound.

[0053] Advantageously, the conversion from a fluoroformate compound to a perfluoroformate compound, i.e. step (b) of the process is implemented in the presence of at least one (per)haloolefin comprising at least one carbon- carbon double bond and having at least one fluorine or chlorine atom on either one of carbon atoms of said double bond, optionally additionally comprising at least one heteroatom different from F and Cl, in particular oxygen (O).

[0054] Particularly, the olefinic compound in step (c) is represented by a formula of CAF=CA’F, wherein A and A’, equal to or different from each other, are H, Cl or Br, with a proviso that both A and A’ are not H.

[0055] In general, fluoroelastomers (A) are amorphous having a low degree of crystallinity (less than 20% by volume of crystalline phase) and a glass transition temperature (Tg) below room temperature. The fluoroelastomer (A) of the present invention has advantageously a Tg below 10°C, preferably below 5°C and more preferably below 0°C.

[0056] Another object of the present invention is a composition comprising a fluoroelastomer (A) as above defined and at least one curing agent (CA).SSPI 2024 / 025

[0057] The expression ‘curing’ is intended to denote a chemical process employed in polymer chemistry that brings about the toughening or hardening of a polymer by cross-linking polymer chains, resulting in a three-dimensional (3D) polymeric network, where the degree of crosslinking determines the rigidity and durability of the resulting polymeric network. Curing can be induced by heat, radiation, electron beams, chemical additives referred to as curing agents, etc.

[0058] The expression ‘curing agent (CA)’ is intended to denote an agent able to promote the cross-linking of a fluoroelastomer (A) through reaction with the cure sites of monomers within the fluoroelastomer (A).

[0059] The choice of the curing agent (CA) is not particularly limited and one skilled in the art may select the most suitable curing agent (CA) depending on the nature of the cure sites of the fluoroelastomer (A).

[0060] The curing agent (CA) may be a compound possessing catalytic activity towards activation of -C(O)NH2 and / or -CN groups of the fluoroelastomer (A), where the curing agent (CA) is referred to as a catalytic curing agent (CAcat).

[0061] In one embodiment, a catalytic curing agent (CAcat) is selected from the group consisting of: - an organic compound generating ammonia upon heating, for instance, under conditions such as those encountered during curing / post-cure; and - an organotin compound, such as notably allyl-, propargyl-, triphenyl-, and allenyl-tin compounds, preferably tetraalkyl or tetraaryl tin compounds.

[0062] Particularly, a catalytic curing agent (CAcat) is an organic compound generating ammonia upon heating, selected from the group consisting of: - (thio)ureas of formula (U) and salts thereofwherein E is O or S; and each of Ru, equal to or different from each other, is selected from the group consisting of H and C1-C6 hydrocarbon groups, particularly C1-C6alkyl groups;SSPI 2024 / 025 - cyclic addition products of ammonia or primary amine and aldehyde; - (thio)carbamates of formula (C)wherein E is O or S; Rb is a C1-C36 hydrocarbon group; and Rc is H or a C1- C6alkyl group; and - ammonium salts of organic and inorganic acids selected from the group consisting of ammonium carboxylates, optionally fluorinated; ammonium sulfonates, optionally fluorinated; ammonium phosphates, phosphonates or sulfonates, optionally fluorinated; and ammonium salts of sulfuric acid, carbonic acid, nitric acid and phosphoric acid.

[0063] More particularly, a catalytic curing agent (CAcat) is an organic compound generating ammonia upon heating, selected from the group consisting of: - (thio)ureas of formula (U-1)wherein E’ is O or S; - cyclic aldehyde adduct trimers of formulawherein each of Ra, equal to or different from each other, is selected from the group consisting of H and C1-C6 hydrocarbon groups, particularly C1-C6 alkyl groups; - hexamethylene tetramine of formula:SSPI 2024 / 025 - carbamates of formula (C-1):wherein R’dis a C1-C36hydrocarbon group, optionally substituted with a benzyl group.

[0064] The curing agents (CAcat) which have been found particularly useful in the composition of the present invention are the following: - (CAcat-1) urea of formula;- (CAcat-2) acetaldehyde ammonia trimer of formula;- (CAcat-3) hexamethylene tetramine; and - (CAcat-4) benzyl carbamate of formula.

[0065] Notably, (CAcat-1) urea is the preferred option in view of cost, availability and reactivity.

[0066] The curing agent (CA) may be a compound possessing a plurality of groups having reactivity towards -C(O)NH2and / or -CN groups of the fluoroelastomer (A), where the curing agent (CA) is referred to as a functional curing agent (CAfunc).

[0067] In one embodiment, a functional curing agent (CAfunc) is selected from the group consisting of: - (CAfunc-1) bis-amino(thio)phenol compounds [aminophenol (AP)] of formula:SSPI 2024 / 025wherein A is a bond, -SO2-, -O-, -C(O)-, or a C1-C10 (fluoro)alkyl; each of E, equal to or different from each other, is O or S; and the amino (NH2-) and -EH groups are interchangeably in ortho, meta or para positions with respect to the group A; - (CAfunc-2) aromatic tetramine compounds [amine (TA)] of formula:wherein A’ is a bond, -SO2-, -O-, -C(O)-, or a C1-C10 (fluoro)alkyl group; each of RN, equal to or different from each other, is a hydrogen atom or a C1-C12hydrocarbon group; and the amino groups are interchangeably in ortho, meta, or para positions with respect to the group A’; - (CAfunc-3) bis-amidoxime / amidine / amidrazone compounds of formula:wherein Ra1is OH or H; Ra2is H or NH2; and E is a C1-C18divalent group, optionally fluorinated; - (CAfunc-4) bis-imidoylamidine compounds of formulawherein Ebis a C1-C18 divalent group, optionally fluorinated, and Rbis a C1- C12 group, optionally fluorinated.

[0068] In a particular embodiment, A in (CAfunc-1) is a C1-C10perfluoroalkyl, e.g. - C(CF3)2-.SSPI 2024 / 025

[0069] In another particular embodiment, A’ in (CAfunc-2) is a C1-C10 perfluoroalkyl, e.g. -C(CF3)2-.

[0070] Among (CAfunc-3) as above defined, mention can be notably made of: (CAfunc-3-A) fluorinated bis-amidoxime compounds of formula:wherein Rfis a divalent fluorinated alkylidene group, preferably -(CF2)n-, with n being an integer of from 1 to 10, or Rf is a (per)fluorooxyalkylene group, preferably a group selected from -(CFX)p(OCF2CFX)n(OCFX)m-O-(CFX)p- with X being F or CF3; n and m being zero or positive integers, with a proviso that n+m is from 1 to 100;

[0071] (CAfunc-3-B) aromatic bis-amidoxime compounds of formula:wherein Jais a bond, -SO2-, -O-, -C(O)-, or C1-C10 (fluoro)alkyl group;

[0072] (CAfunc-3-C) fluorinated bis-amidrazone compounds of formula:wherein Rf1 is a divalent fluorinated alkylidene group, preferably -(CF2)n-, with n being an integer of from 1 to 10; or Rf1 is a (per)fluorooxyalkylene group, preferably a group selected from -(CFX)p(OCF2CFX)n(OCFX)m-O- (CFX)p- with X being F or CF3; n and m being zero or positive integers, with a proviso that n+m is from 1 to 100;

[0073] (CAfunc-3-D) aromatic bis-amidrazone compounds of formula:SSPI 2024 / 025 wherein Jcis a bond, -SO2-, -O-, -C(O)-, or a C1-C10 (fluoro)alkyl group.

[0074] The curing agent (CA) may be a chemical compound comprising a cation and an anion of formula Anq-Qpn+, wherein m, n, p and q are positive integers; m*p = n*q; Qn+is a cation; and Aq-is an anion of the formula:wherein R is, independently each other, H, halogen, alkyl, aryl, aralkyl, or cycloalkyl, which may be halogenated, fluorinated, or perfluorinated; two or more of R and R' groups may together form a ring; R is, independently each other, may contain one or more heteroatom(s); and R' can be the identical to R, with the proviso that R' is not a halogen. This kind of the curing agent (CA) is referred to as a cross-linking curing agent (CAcross).

[0075] In a particular embodiment, each R is F such that the central carbon of the anion is bonded to two perfluoromethyl groups.

[0076] In another particular embodiment, R’ is selected from the group consisting of H, phenyl, methoxyphenyl tolyl, phenoxy, fluorophenyl, trifluoromethylphenyl, and CF3.

[0077] Preferably, each R is F and R’ is an aromatic ring, either substituted or unsubstituted. More preferably, R’ is an aromatic ring substituted with one or more C1-C3alkyl. Even more preferably, R’ is an aromatic ring substituted with one, two or three -CF3groups.

[0078] The choice of the cation Qn+is not particularly limited. Metal ions can be used, though the cation is preferably selected from ammonium, phosphonium and organo onium ions, more preferably an organo onium ion.

[0079] Preferred organo onium ions are mono-, bi-, tri- and tetra-alkyl ammonium ions, and mono-, bi-, tri- and tetra-alkyl phosphonium ions, more preferably tetra-alkyl ammonium and tetra-alkyl phosphonium, most preferably tetra- butyl ammonium and tetra-butyl phosphonium

[0080] More particularly, the anion can be substituted or unsubstituted. Non- limitative examples of the anion include tetra-alkyl ammonium 2-phenyl-SSPI 2024 / 025 1,1,1,3,3,3-hexafluoroisopropanolate, tetra-alkyl ammonium 1,1,1,3,3,3- hexafluoroisopropanolate, tetra-butyl phosphonium 2-phenyl-1,1,1,3,3,3- hexafluoroisopropanolate, tetra-butyl phosphonium 1,1,1,3,3,3- hexafluoroisopropanolate, tetra-butyl phosphonium 2-methoxyphenyl- 1,1,1,3,3,3-hexafluoroisopropanolate, and tetra-butyl phosphonium 2-p-tolyl- 1,1,1,3,3,3-hexafluoroisopropanolate.

[0081] Advantageously, a cross-linking curing agent (CAcross) is tetra-butyl phosphonium 2-p-tolyl-1,1,1,3,3,3-hexafluoroisopropanolate.

[0082] The cross-linking curing agent (CAcross) may be introduced into the composition of the present invention in a conventional manner. The cross- linking curing agent (CAcross) may be introduced per se or its anion and cation may be separately introduced in combination with other anion(s) or cation(s), e.g. a sodium salt of the anion and a chloride salt of the cation. It is also possible to use the cross-linking curing agent (CAcross) supported on an inert carrier, e.g. SiO2 carrier.

[0083] One or more curing agent (CA) can be selected from the group consisting of a catalytic curing agent (CAcat); a functional curing agent (CAfunc); and a cross-linking curing agent (CAcross), and can be used in the composition of the present invention.

[0084] The curing agent (CA) is preferably a functional curing agent (CAfunc) as described above, more preferably (CAfunc-1), i.e. bis-amino(thio)phenol compound [aminophenol (AP)].

[0085] The aminophenol (AP) can be selected from the group consisting of 4,4’- [2,2,2-trifluoro-1-(trifluoromethyl)-ethylidene] bis(2-aminophenol); 4,4’- sulfonyl bis(2-aminophenol); 3,3’-diaminobenzidine, and 3,3’,4,4’- tetraaminobenzophenone.

[0086] Particularly preferred aminophenol (AP) is 4,4’-[2,2,2-trifluoro-1- (trifluoromethyl)-ethylidene] bis(2-aminophenol), also known as bis- aminophenol AF, having formula:SSPI 2024 / 025

[0087] In the present invention, the composition comprising a fluoroelastomer (A) and at least one curing agent (CA) may further comprise ingredients which are commonly used for curing fluoroelastomers.

[0088] Particularly, the composition may further comprise: - one or more than one metallic basic compound, generally selected from the group consisting of oxides or hydroxides of divalent metals, e.g. Mg, Zn, Ca and Pb, and metal salts of a weak acid, for instance Ba, Na, K, Pb, Ca stearates, benzoates, carbonates, oxalates or phosphites; - one or more than one acid acceptor which is not a metallic basic compound, generally selected from nitrogen-containing organic compounds, such as 1,8- bis(dimethylamino)naphthalene, octadecylamine, etc.; and - other conventional additives, such as reinforcing fillers, thickeners, pigments, antioxidants, stabilizers, processing aids, etc.

[0089] Another object of the present invention is a process for manufacturing a shaped article, comprising curing the composition of the present invention.

[0090] The composition can be processed by conventional methods, e.g. injection molding, extrusion molding, compression molding, calendaring, extrusion, etc. to produce the desired shaped article, which is advantageously subject to curing during the process and / or in a subsequent step (post-treatment or post-cure), advantageously transforming the composition which is uncured and relatively soft, into a finished article made of the cured fluoroelastomer composition which is non-tacky, strong, insoluble, chemically and thermally resistant.

[0091] The present invention also pertains to shaped articles obtainable from the composition as above detailed. Said shaped articles are generally obtained by molding, advantageously injection molding or compression molding, and curing the composition as above detailed.SSPI 2024 / 025

[0092] The shaped articles of the present invention may be used in various fields, for instance semiconductor applications, oil & gas applications, chemical processing industry, wearable smart devices, and healthcare applications, such as medical equipment.

[0093] The shaped articles may be sealing articles, including O (square)-rings, packings, gaskets, diaphragms, shaft seals, valve stem seals, piston rings, crankshaft seals, cam shaft seals, and oil seals, or piping and tubings, in particular sealing parts or other elements in semiconductor manufacturing devices.

[0094] Should the disclosure of any of the patents, patent applications, and publications that are incorporated herein by reference conflict with the present description to the extent that it might render a term unclear, the present description shall take precedence.

[0095] The present invention will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not limitative of the scope of the invention.

[0096] EXAMPLES

[0097] Raw Materials

[0098] 1,4-diiodoperfluorobutane (chain transfer agent): synthesized within Syensqo;

[0099] ammonium persulfate (APS) (initiator): commercially available from Titolchimica;

[0100] bis-aminophenol AF (BOAP) (curing agent): commercially available from Apollo Scientific;

[0101] carbon black (N 990 MT) (reinforcing filler): commercially available from Cancarb Ltd.

[0102] Measurement Methods

[0103] Rheology

[0104] Mooney viscosity ML (1+10) at 121°C was measured with a Mooney viscometer according to ASTM method D1646 and was recorded in Mooney units (MU).SSPI 2024 / 025

[0105] Compression set

[0106] Compression set (CS) values were measured on O-rings (#214 class) according to ASTM D395B at 200°C and 300°C. The CS values in Table 1 below are the average of determinations made on 4 specimens, respectively.

[0107] Mechanical properties

[0108] TS (tensile strength in MPa), M100(modulus in MPa at an elongation of 100%) and EB (elongation at break in %) were determined according to the ASTM D412C Standard, after post-cure.

[0109] Cure behavior

[0110] Cure behavior was characterized by MDR at 170°C, by determining the following properties: - ML: minimum torque (lb x in); - MH: maximum torque (lb x in); - tS2: scorch time, time for two units rise from ML (sec); - t50: time to reach 50% of curing (sec); and - t90: time to reach 90% of curing (sec).

[0111] Synthesis of CF2=CF-OCF2O-CF2CF2-CN (7-CNMOVE)

[0112] CF2=CF-OCF2O-CF2CF2-CN (7-CNMOVE) was prepared according to the following procedure. Into a 1,000 ml stainless steel reactor equipped with mechanical stirrer, gas inlet, gas outlet, and a thermocouple to check internal temperature, 200 ml of CH3CN was loaded and kept at -20°C by using a thermocriostatic bath. Under vigorous stirring, a flow constituted by 6.0 Nl / h (normal liters per hour) of COF2, was fed into the reactor through a first inlet pipe; 10 g / h of 1,3-propanediol was fed into the reactor by a syringe pump through a second inlet pipe.

[0113] After 24 hours of feeding, the flows were interrupted and most of the CH3CN and HF formed as by-products were removed in vacuum at 30°C. Subsequently, the temperature of the reactor was increased up to 120°C collecting all the product in a cold trap, where about 50 g of NaF was addedSSPI 2024 / 025 to remove residual traces of HF. After filtering, 479 g of fluoroformate FC(O)O-CH2CH2CH2-OC(O)F were recovered.

[0114] In the same reactor equipped with a condenser kept at 0°C and a cold trap kept at -78°C with dry ice, 350 g of 1,2,3,4-tetrachloro-hexafluorobutene was loaded and kept at 40°C by a thermocriostatic bath. Under vigorous stirring, a flow constituted by 6.0 Nl / h of F2diluted in 18 Nl / h of He was fed into the reactor through a first inlet pipe, while 6.2 g / h of the FC(O)O-CH2CH2CH2- OC(O)F was fed to the reactor by a syringe pump through a second inlet pipe.

[0115] After 16 hours of feeding, the flows were interrupted; the reactor temperature was lowered to -30°C; and the content of the trap at -78°C was reloaded into the reactor. Feeding 6.0 Nl / h of F2 diluted by 18 Nl / h of He from the first inlet pipe, while a flow constituted by 0.3 Nl / h of perfluoromethylvinylether diluted in 1.5 Nl / h of He was fed from the second inlet pipe.

[0116] After a few hours, the F2 conversion, evaluated via GC analysis, fell to zero confirming that all hydrogen atoms were converted into fluorine atoms.

[0117] The resulting organic phase contained FC(O)O-CF2CF2CF2-OC(O)F.

[0118] Using the same reactor, the organic phase containing FC(O)O-CF2CF2CF2- OC(O)F was loaded and kept at -50°C by a thermocriostatic bath. Under vigorous stirring, a flow constituted by 3.5 Nl / h of F2diluted in 9 Nl / h of He was fed into the reactor through a first inlet pipe, while 17.4 g / h of 1,2- dichlorodifluoro ethylene was fed into the reactor by a syringe pump through a second inlet pipe.

[0119] After 12 hours of feeding, the crude mixture was distilled to recover 38 g of FC(O)O-CF2CF2CF2-OCF2OCFClCF2Cl.

[0120] The product thus obtained was kept at 0°C in a perfluoroalkoxy alkane (PFA) bottle and then 30g of CH3OH was added under vigorous stirring to the bottle. The cooling was stopped once the temperature became room temperature, and the mixture was then transferred into a separating funnel, while adding water to separate the fluorinated phase. The lower phase was recovered and was dried over Na2SO4, obtaining the desired methyl esterSSPI 2024 / 025

[0121] A three-necked round bottom flask equipped with temperature probe, magnetic stirring and dropping funnel was charged, at room temperature, with CH3OH (700g) and the ester CH3OC(O)-CF2CF2-OCF2OCFClCF2Cl obtained from the previous step (250g; 96%).180g of a 4N ammonia solution in methanol was added dropwise for one hour at room temperature and the mixture was maintained under stirring for one additional hour. When the reaction was complete, methanol was removed by evaporation at 50°C under vacuum, isolating 219 g of NH2C(O)-CF2CF2OCF2OCFClCF2Cl (1,2- dichloro-perfluoroethoxy-difluoromethoxy tetrafluoro propanamide).

[0122] A three necked round bottom flask equipped with temperature probe, condenser and dropping funnel was charged with 355g of acetonitrile, zinc (55g) and zinc chloride (13.5g). The reaction mixture was warmed up to 80°C and 190g of NH2C(O)-CF2CF2OCF2OCFClCF2Cl was added dropwise for 4 hours. The mixture was maintained at 80°C for one additional hour after which the reaction was considered complete. Then the reaction crude was cooled at room temperature allowing zinc chloride to precipitate overnight. The day after, the liquid phase was separated from the precipitated crystals in grey color and further purified by centrifugation (30 min; 4,000 rpm). The resulting solution was analyzed by 19F-NMR confirming the formation of trifluoro-vinyloxy difluoromethoxy tetrafluoro propenamide.

[0123] A five necked jacketed 1L glass reactor equipped with temperature probe, condenser, dropping funnel, N2 inlet and PTFE impeller, was charged with 515 g of trifluoro-vinyloxy difluoromethoxy tetrafluoro propenamide in acetonitrile solution (24%). The impeller was set to 300 rpm, the solution cooled down at -18°C under N2 atmosphere and then 135g of trifluoroacetic anhydride (TFAA) was added dropwise maintaining the internal temperature at -18 / -20°C. Once the addition of TFAA was complete, 102g of pyridine was added dropwise for 50 min observing that the solution became yellow. After 30 min at -20°C, the reaction was complete and the impeller was stopped, obtaining a biphasic crude mixture. The lower phase, containing the desired product, was separated and collected as a clear colorless liquid. The upperSSPI 2024 / 025 solution was washed twice with 180g of chilled water recovering further product in a lower organic phase. Once all the organic phases were collected together, they were further washed with 50g of chilled water in a separating funnel and the resulting organic phase was dehydrated with anhydrous Na2SO4 and filtrated on 0.2 μm PTFE membrane. The resulting colorless liquid was purified through distillation obtaining 70g of pure CF2=CF2OCF2OCF2CF2CN (tetrafluoro-vinyloxy difluoromethoxy tetrafluoro propane nitrile, 7-CNMOVE).

[0124] Synthesis of CF2=CF-OCF2O-CF2CF2OCF2-CN (8-O-CNMOVE)

[0125] CF2=CF-OCF2O-CF2CF2OCF2-CN (8-O-CNMOVE) was prepared following the same procedure described for the preparation of 7-CNMOVE except that diethylene glycol was used as a starting diol instead of 1,3-propanediol.

[0126] Preparative Example 1

[0127] A surfactant system was prepared by mixing 0.27 g of 30% (v / v) aqueous solution of NH4OH; 10.53 g of demineralized water; 2.7 g of hexafluoro- propyleneoxide oligomer containing a carboxyl group of formula: C3F7O(CF(CF3)CF2O)nCF(CF3)COOH (n being an integer of from 4 to 6; and average molecular weight 1300); and 40.5 g of 40% (w / w) aqueous solution of cyclic C6O4 of formula:.

[0128] In a 5.0 L reactor equipped with a mechanical stirrer operating at 630 rpm, 3.0 L of demineralized water and 54.0 g of the surfactant system, previously prepared, were introduced. Subsequently, 2.5 g of 1,4-diiodoperfluorobutane (C4F8I2) and 16.6 g of 7-CNMOVE were introduced. The reactor was then heated and maintained at a set-point temperature of 80°C, where a mixture of 36.0 mol% of tetrafluoroethylene (TFE) and 64.0 mol% of perfluoromethylvinylether (PMVE) was then added until the pressure reached 21.0 bar (2.1 MPa).1.5 g of ammonium persulfate (APS) was subsequently introduced, while maintaining the pressure at set-point of 21.0SSPI 2024 / 025 bar by continuous feeding of a gaseous mixture of 60.0 mol% of TFE and 40.0 mol% of PMVE (up to a total amount of 1,250 g), to which 32.4 g of 7- CNMOVE was added stepwise in 20 portions. Each portion was made with 5% of increase in conversion starting from the beginning of the polymerization. Also, 0.75 g of APS was introduced at 50% conversion of the gaseous mixture.

[0129] The reactor was then cooled and vented. The latex was recovered, and coagulated with nitric acid. The polymer as obtained was separated from the aqueous phase, washed with demineralized water and dried in a convection oven at 120°C for 16 hours. The fluoroelastomer (I) was characterized by NMR: 64.6 mol% of TFE; 34.7 mol% of PMVE, and 0.7 mol% of 7-CNMOVE. Mooney viscosity at 121°C was 91 MU

[0130] Preparative Example 2

[0131] In a 5.0 L reactor equipped with a mechanical stirrer operating at 630 rpm, 3.0 L of demineralized water and 43 g of the same surfactant system (as described in the Preparative Example 1) were introduced. Subsequently, 2.5 g of C4F8I2and 16.2 g of 8-O-CNMOVE were introduced, and the reactor was heated and maintained at a set-point temperature of 80°C. A mixture of 36.0 mol% of TFE and 64.0 mol% of PMVE was then added until the pressure became 21.0 bar (2.1 MPa).1.2 g of APS were then introduced, while maintaining the pressure at set-point of 21 bar by continuous feeding of a gaseous mixture of 60.0 mol% of TFE and 40.0 mol% of PMVE (up to a total amount of 1,000 g), to which 32.3 g of 8-O-CNMOVE was added stepwise in 20 portions. Each portion was made with 5% of increase in conversion starting from the beginning of the polymerization. Also, 0.6 g of APS was introduced at 50% conversion of the gaseous mixture.

[0132] The reactor was then cooled and vented. The latex was recovered, and coagulated with nitric acid. The polymer as obtained was separated from the aqueous phase, washed with demineralized water and dried in a convection oven at 120°C for 16 hours. The fluoroelastomer (II) as obtained wasSSPI 2024 / 025 characterized by NMR: 64.6 mol% of TFE; 34.3 mol% of PMVE, and 1.1 mol% of 8-O-CNMOVE. Mooney viscosity at 121°C was 20 MU.

[0133] Preparative Example 3

[0134] Preparative Example 1 was repeated except for the initial addition of 22.6 g of 7-CNMOVE before heating the reactor, and the stepwise addition of 46.0 g of 7-CNMOVE in 20 portions. Each portion was made with 5% of increase in conversion starting from the beginning of the polymerization.

[0135] The fluoroelastomer (III) as obtained was characterized by NMR: 59.4 mol% of TFE, 39.6 mol% of PMVE, and 1.0 mol% of 7-CNMOVE. Mooney viscosity at 121°C was 44 MU.

[0136] Comparative Preparative Example 1

[0137] A surfactant system was prepared by mixing 0.65 g of 30% (v / v) aqueous solution of NH4OH; 25.16 g of demineralized water; 6.45 g of hexafluoro- propyleneoxide oligomer containing a carboxyl group of formula: C3F7O(CF(CF3)CF2O)nCF(CF3)COOH (n being an integer of from 4 to 6; and average molecular weight 1300); and 96.74 g of 40% (w / w) aqueous solution of cyclic C6O4of formula:.

[0138] In a 10.0 L reactor equipped with a mechanical stirrer operating at 545 rpm, 7.2 L of demineralized water and 129.0 g of the surfactant system, previously prepared, were introduced. Subsequently, 6.2 g of 1,4- diiodoperfluorobutane (C4F8I2) and 44.2 g of 8-CNVE were introduced. The reactor was then heated and maintained at a set-point temperature of 80°C, where a mixture of 34.5 mol% of tetrafluoroethylene (TFE) and 65.5 mol% of perfluoromethylvinylether (PMVE) was then added until the pressure reached 21.0 bar (2.1 MPa).3.6 g of ammonium persulfate (APS) was subsequently introduced, while maintaining the pressure at set-point of 21.0 bar by continuous feeding of a gaseous mixture of 57.5 mol% of TFE and 42.5 mol% of PMVE (up to a total amount of 3,000 g), to which 89.3 g of 8-SSPI 2024 / 025 CNVE was added stepwise in 20 portions. Each portion was made with 5% of increase in conversion starting from the beginning of the polymerization. Also, 1.8 g of APS was introduced at 50% conversion of the gaseous mixture.

[0139] The reactor was then cooled and vented. The latex was recovered, and coagulated with nitric acid. The polymer as obtained was separated from the aqueous phase, washed with demineralized water and dried in a convection oven at 120°C for 16 hours.

[0140] The fluoroelastomer (IV) was characterized by NMR: 62.4 mol% of TFE; 36.8 mol% of PMVE, and 0.8 mol% of 8-CNVE. Mooney viscosity at 121°C was 62 MU.

[0141] Compounding and curing

[0142] The fluoroelastomer (I) from Preparative Example 1 in an amount of 100 phr was compounded together with 20 phr of carbon black (N 990 MT) and 0.70 phr of BOAP in a two-rolls open mill, corresponding to Ex.1. Subsequently, Ex.2 and Ex.3 and Comparative Ex.1 were prepared in the same manner, i.e. using 100 phr of fluoroelastomer (II) from Preparative Example 2, fluoroelastomer (III) from Preparative Example 3 and fluoroelastomer (IV) from Comp. Preparative Example 1 respectively, 20 phr of the same carbon black and 0.70 phr of BOAP.

[0143] Plaques were cured in a pressed mold for 25 min at 170°C and subsequently post-treated in an air circulating oven for (8+16)h at 290°C.

[0144] The mechanical properties were determined on specimens punched out from the plaques, according to the ASTM D412C, after post-cure.

[0145] Cure behaviors, mechanical properties and compression set values of Ex.1, Ex.2, Ex.3 and Comp. Ex.1 are indicated in Table 1. Table 1 Ex.1 Ex.2 Ex.3 Comp. Ex. 1Cure behaviors ML (lb x in) 1.6 0.3 0.6 1.2 MH (lb x in) 14.0 10.9 13.6 12.3SSPI 2024 / 025 ts2(sec) 487 169 406 557 t50(sec) 776 212 598 900 t90(sec) 1036 374 930 1262 Mechanical properties TS (MPa) 20.9 13.3 14.7 17.7 M100 (MPa) 6.5 3.7 4.0 4.0 EB (%) 201 189 198 230 Compression Set after 70 hours at 200°C & 300°C 200°C (%) 18 22 15 22 300°C (%) 26 35 26 30

[0146] Fluoroelastomers (I) to (III) exhibit a faster onset of curing than fluoroelastomer (IV) and an overall good balance of mechanical properties.

Claims

SSPI 2024 / 025 Claims Claim 1. A fluoroelastomer [fluoroelastomer (A)] comprising: - recurring units derived from tetrafluoroethylene (TFE); and - from 0.1 to 10.0% by moles (mol%), with respect to the total moles of recurring units of the fluoroelastomer (A), of recurring units derived from at least one perfluorovinylether of formula (I): CF2=CF-OCF2O-RF-X (I) wherein RFis a perfluoro(oxy)alkylene group having 1 to 20 carbon atoms and X is -C(O)NH2 or -CN. Claim 2. Fluoroelastomer (A) according to claim 1, wherein RFis a linear or branched perfluoro(oxy)alkylene group. Claim 3. Fluoroelastomer (A) according to claim 1 or 2, wherein RFis a perfluoro(oxy)alkylene group having 1 to 10 carbon atoms. Claim 4. Fluoroelastomer (A) according to any one of claims 1 to 3, wherein the perfluorovinylether of formula (I) is selected from the group consisting of CF2=CF-OCF2O-CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF2CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF(CF3)CF2- C(O)NH2, CF2=CF-OCF2O-CF2CF(CF3)-C(O)NH2, CF2=CF-OCF2O-CF2CF2-O- CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF2CF2-O-CF2-C(O)NH2, CF2=CF-OCF2O- CF2CF2CF2-O-CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF(CF3)CF2-O-CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF(CF3)-O-CF2-C(O)NH2, CF2=CF-OCF2O-CF(CF3)CF2-O- CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF(CF3)-O-CF2CF2-C(O)NH2, CF2=CF- OCF2O-CF2CF2-O-CF2CF2-C(O)NH2, CF2=CF-OCF2O-CF2CF2-CN, CF2=CF- OCF2O-CF2CF2CF2-CN,CF2=CF-OCF2O-CF2CF2CF2CF2-CN,CF2=CF-OCF2O- CF(CF3)CF2-CN, CF2=CF-OCF2O-CF2CF(CF3)-CN, CF2=CF-OCF2O-CF2CF2-O- CF2-CN, CF2=CF-OCF2O-CF2CF2CF2-O-CF2-CN, CF2=CF-OCF2O-CF2CF2CF2- O-CF2CF2-CN, CF2=CF-OCF2O-CF(CF3)CF2-O-CF2-CN, CF2=CF-OCF2O-SSPI 2024 / 025 OCF2O-CF2CF(CF3)-O-CF2CF2-CN, and CF2=CF-OCF2O-CF2CF2-O-CF2CF2- CN. Claim 5. Fluoroelastomer (A) according to any one of claims 1 to 4, further comprising recurring units derived from at least one (per)fluorinated monomer, different from tetrafluoroethylene (TFE) and perfluorovinylether of formula (I). Claim 6. Fluoroelastomer (A) according to claim 5, wherein the (per)fluorinated monomer is selected from the group consisting of: - C3-C8perfluoroolefins, such as hexafluoropropylene (HFP); - C2-C6fluoroolefins comprising at least one of Cl, Br and I, such as chlorotrifluoroethylene (CTFE); - C2-C8 hydrogen-containing fluoroolefins, such as vinyl fluoride, 1,2- difluoroethylene, vinylidene fluoride (VDF), trifluoroethylene (TrFE), pentafluoropropylene, and hexafluoroisobutylene; - (per)fluoroakylethylenes of formula CH2=CH-RF0, in which RF0is a C1-C6(per)fluoroalkyl or a C1-C6 (per)fluorooxyalkyl having one or more ether group; - (per)fluoroalkylvinylethers (PAVE) of formula CF2=CFORF1, in which RF1 is a C1-C6(per)fluoroalkyl group, such as –CF3, -C2F5, and –C3F7; - (per)fluorooxyalkylvinylethers of formula CF2=CFORF2, in which RF2is a C1- C12 (per)fluorooxyalkyl having one or more ether group; - (per)fluorodioxoles of formula:wherein each of Rf3, Rf4, Rf5, and Rf6, equal to or different from each other, is a fluorine atom, a C1-C6 fluoro- or per(halo)fluoroalkyl, optionally comprisingSSPI 2024 / 025 one or more oxygen atom, such as -CF3, -C2F5, -C3F7, -OCF3, and - OCF2CF2OCF3; - perfluorovinylethers of formula (II) CF2=CF-[OCF2CFXII(CF2)a1]m1-O-(CF2)n1- CN, with XIIbeing F or CF3; a1 being 0, 1 or 2; m1 being 0, 1, 2, 3 or 4; and n1 being an integer from 1 to 12; - perfluorovinylethers of formula (III) CF2=CF-[OCF2CFXIII(CF2)a2]m2-O- CF2CF(CF3)-CN, with XIIIbeing F or CF3; a2 being 0, 1 or 2; and m2 being 0, 1, 2, 3 or 4; - perfluorovinylethers of formula (IV) CF2=CF-[OCF2CFXIV]m3-O-(CF2)n2-RCOX, with XIVbeing F or CF3; m3 being 0, 1, 2, 3 or 4; n2 being an integer from 1 to 12; and RCOX being selected from the group consisting of carboxylic groups –COOH; carboxylate groups -COOXa, with Xabeing a monovalent metal or an ammonium group; carboxamide group -CONH2; and alkoxycarboxylic group -COORH, with RH being a (fluoro)(hydro)carbon group, preferably a C1-C3alkyl group; and - perfluorovinylethers of formula (V) CF2=CF-(OCF2CFXV)m4-O-CF2CF(CF3)- RCOX’, with XVbeing F or CF3; m4 being 0, 1, 2, 3 or 4; and RCOX’ having the meaning as defined for RCOX. Claim 7. Fluoroelastomer (A) according to claim 6, wherein the (per)fluorinated monomer is a (per)fluoroalkylvinylether (PAVE) of formula CF2=CFOCF3 (perfluoromethylvinylether). Claim 8. Fluoroelastomer (A) according to any one of claims 1 to 7, further comprising recurring units derived from a bis-olefin (OF) having formula:wherein R1, R2, R3, R4, R5, and R6, equal to or different from each other, are independently selected from the group consisting of F, Cl, H, C1-C5(fluoro)alkylSSPI 2024 / 025 groups and ORB groups, RB being a branched or linear alkyl radical which can be fluorinated or chlorinated; and Z is a branched or linear C1-C18 (hydro)carbon radical, optionally containing at least one oxygen atom, preferably a (per)fluoro(poly)oxyalkylene radical. Claim 9. A composition comprising fluoroelastomer (A) of any one of claims 1 to 8 and at least one curing agent (CA). Claim 10. The composition according to claim 9, wherein the curing agent (CA) is selected among compounds possessing catalytic activity towards activation of -C(O)NH2 and / or -CN groups of the fluoroelastomer (A), and wherein the curing agent (CA) is referred to as a catalytic curing agent (CAcat) selected from the group consisting of: - an organic compound generating ammonia upon heating; and - an organotin compound. Claim 11. The composition according to claim 10, wherein the catalytic curing agent (CAcat) is an organic compound generating ammonia upon heating, selected from the group consisting of: - (thio)ureas of formula (U) and salts thereofwherein E is O or S and each of Ru, equal to or different from each other, is selected from the group consisting of H and C1-C6hydrocarbon groups, particularly C1-C6 alkyl groups; - cyclic addition products of ammonia or primary amine and aldehyde; - (thio)carbamates of formula (C)SSPI 2024 / 025wherein E is O or S; Rbis a C1-C36hydrocarbon group; and Rcis H or a C1-C6alkyl group; and - ammonium salts of organic and inorganic acids selected from the group consisting of ammonium carboxylates, optionally fluorinated; ammonium sulfonates, optionally fluorinated; ammonium phosphates, phosphonates or sulfonates, optionally fluorinated; and ammonium salts of sulfuric acid, carbonic acid, nitric acid and phosphoric acid. Claim 12. The composition according to claim 11, wherein the catalytic curing agent (CAcat) is an organic compound generating ammonia upon heating, selected from the group consisting of - (thio)ureas of formula (U-1)wherein E’ is O or S; - cyclic aldehyde adduct trimers of formulawherein each of Ra, equal to or different from each other, is selected from the group consisting of H and C1-C6 hydrocarbon groups, particularly C1-C6 alkyl groups; - hexamethylene tetramine of formula; andSSPI 2024 / 025 - carbamates of formulawherein R’dis a C1-C36hydrocarbon group, optionally substituted with a benzyl group. Claim 13. The composition according to claim 9, wherein the curing agent (CA) is selected among compounds possessing a plurality of groups having reactivity towards -C(O)NH2 and / or -CN groups of the fluoroelastomer (A), and wherein the agent (CA) is referred to as a functional curing agent (CAfunc) selected from the group consisting of: - (CAfunc-1) bis-amino(thio)phenol compounds [aminophenol (AP)] of formula:wherein A is a bond, -SO2-, -O-, -C(O)-, or a C1-C10(fluoro)alkyl group; each of E, equal to or different from each other, is O or S; and the amino (-NH2) and –EH groups are interchangeably in ortho, meta or para positions with respect to the group A; - (CAfunc-2) aromatic tetramine compounds [amine (TA)] of formula:wherein A’ is a bond, -SO2-, -O-, C(O)-, or a C1-C10 (fluoro)alkyl group; each of RN, equal to or different from each other, is a hydrogen atom or a C1-C12hydrocarbon group; and the amino groups are interchangeably in ortho, meta, or para positions with respect to the group A’; - (CAfunc-3) bis-amidoxime / amidine / amidrazone compounds of formula:SSPI 2024 / 025wherein Ra1is OH or H; Ra2is H or NH2; and E is a C1-C18 divalent group, optionally fluorinated; - (CAfunc-4) bis-imidoylamidine compounds of formulawherein Ebis a C1-C18 divalent group, optionally fluorinated, and Rbis a C1-C12 group, optionally fluorinated. Claim 14. A method for manufacturing a shaped article, comprising curing a composition of any one of claims 9 to 13. Claim 15. Cured articles obtainable from the composition of any one of claims 9 to 13, said cured articles being sealing articles, including O (square)-rings, packings, gaskets, diaphragms, shaft seals, valve stem seals, piston rings, crankshaft seals, cam shaft seals, oil seals, piping and tubings.

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