Compound comprising fluoroelastomers and curing agents, fluoroelastomer article, and curing process

Abstract

This document provides curable fluoroelastomer blends comprising a fluoroelastomer and a curing agent. The curing agent comprises an aminocarboxylic acid and an amidine-containing molecule, or a salt thereof as a reaction product between the aminocarboxylic acid and the amidine-containing molecule. Further provided are articles comprising such curable fluoroelastomer blends or products of curing such fluoroelastomer blends; methods for curing such blends; and methods for manufacturing such articles.

Description

Technical Field

[0001] This article describes curing agents for compounding (also known as curable components) and specifically includes compounding containing perfluoroelastomers, as well as articles cured from such compounding. Prior Technology

[0002] This specification references several patents, patent applications, and publications to provide a more comprehensive description of the technological advancements involved in this invention. The full disclosures of each of these patents, patent applications, and publications are incorporated herein by reference.

[0003] Elastomer blends containing fluoroelastomers have achieved remarkable commercial success due to their suitability for use in harsh environments, particularly those exposed to high temperatures, corrosive chemicals, and plasma. For example, these blends are used in seals in wafer fabrication equipment, aircraft engines, oil well drilling rigs, and as sealing elements in industrial equipment operating under high temperatures and corrosive chemicals.

[0004] The properties of cured elastomer blends are primarily due to the stability and inertness of the comonomers that constitute the major portion of the polymer backbone of such blends. These monomers include tetrafluoroethylene and perfluoro(alkyl vinyl) ethers. To fully exploit the elastomer properties, the elastomer blends are typically crosslinked (i.e., vulcanized or cured). For this purpose, a small portion of the curing site monomer is copolymerized with another monomer (whether fluorinated or perfluorinated). During crosslinking, this curing site monomer reacts with a curing agent to form a crosslinked elastomer entity in the form of an article.

[0005] US2017 / 0088693A describes fluoroelastomer curing agents and cured fluoroelastomers, wherein the curing agent is selected from 1,3-diiminoisoindoline or derivatives thereof. Cured fluoroelastomers formed from such curing agents can be used as seals and gaskets in high-temperature and reactive plasma environments because such curing agents create more efficient crosslinking that is both thermally and chemically stable.

[0006] 1,3-Diiminoisoindoline and its derivatives are excellent curing agents, providing cured fluoroelastomers with higher thermal stability and compound stability during processing, such as milling, extrusion, and storage stability. However, when using such curing agents, the open time ("scorch" or "scorch time") at the curing temperature may not be long enough. A longer scorch time contributes to better processability in the manufacturing process. Therefore, it is desirable to develop curing agents with longer scorch times, which can form cured fluoroelastomers with higher thermal stability.

[0007] U.S. Patent No. 4,676,922 describes phthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, or mixtures thereof as anti-scorching agents for sulfur and N-cyclohexyl-2-benzothiazole sulfenamide (an accelerator). U.S. Patent No. 8,318,850 describes various curing agents, such as bis(aminophenol), aryltetramine, and compounds that generate ammonia, such as urea, guanidine, and amidine. U.S. Patent No. 5,565,512 describes ammonium salts of organic or inorganic acids as curing agents in mixtures. U.S. Patent No. 6,281,296 describes components capable of generating ammonia as curing agents for nitrile-containing fluoroelastomers. However, when the curing agent is 1,3-diiminoisoindoline or a derivative thereof, these methods are insufficient to provide cured fluoroelastomers with higher thermal stability.

[0008] Therefore, there remains a need for curing agents for these blends, which provide cured fluoroelastomers with superior performance at higher temperatures and longer coking times during processing. Furthermore, there remains a need for articles produced from these blends, as well as methods for manufacturing these blends and articles. Summary of the Invention

[0009] This document provides a compound comprising one or more fluoroelastomers, the fluoroelastomers comprising copolymer units of: one or more unsaturated fluorinated olefins; a second different unsaturated olefin comonomer selected from the group consisting of fluorinated vinyl ethers, fluorinated olefins, olefins, and mixtures of two or more of these; and one or more curing site monomers selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers. The compound further comprises a curing agent comprising an aminocarboxylic acid and a molecule containing an amidine moiety, or an aminocarboxylic acid salt containing an amidine moiety. Further provided are articles comprising the compound; articles comprising a product cured with the compound; and methods of manufacturing the compound and the articles. Implementation

[0010] [Abbreviations]

[0011] As used herein, the following abbreviations have the definitions set forth below.

[0012] "h", "hr", and "hrs" refer to hours.

[0013] "%" refers to percentage.

[0014] "mole%" or "mol%" refers to mole percentage.

[0015] "wt%" refers to weight percentage.

[0016] [[ID=2​​​​​​​​​​​​​​​​​​​​​​​​​​​​​As used herein, the terms "about" and "at or about," when used to modify a quantity or value, refer to an approximate value that is greater than or less than the exact quantity or value set forth in the claims or described herein. The exact value of an approximation is determined by an appropriate approximation that would be recognized as an exact value by one skilled in the art. As used herein, the term expresses the idea that similar values ​​not precisely listed in the claims or described herein can produce results or effects equivalent to those set forth in the claims or described herein, which those skilled in the art acknowledge can acceptablely be caused by such similar values.

[0024] As used herein, the term "article" means an unfinished or finished article, thing, or object, or an element or feature of an unfinished or finished article, thing, or object. As used herein, when the article is unfinished, the term "article" can mean any article, thing, object, element, device, etc., having a form, shape, or construction that can undergo further processing to become a finished article. When the article is unfinished, the term "preform" can mean that form, shape, or construction, or any part thereof, that can undergo further processing to become finished. This further processing may include one or more chemical processes, such as curing, or one or more physical processes, such as finishing, sanding, or otherwise shaping.

[0025] As used herein, when an article is finished, it is an article, thing, object, element, device, etc., which is in a form, shape, or structure suitable for a particular use / purpose and requires no further processing of the whole article or a part thereof.

[0026] An article may include one or more elements or sub-components that are partially completed and await further processing or assembly with other elements / sub-components that will together constitute the finished article. Furthermore, as used herein, the term "article" may refer to a system or structure of an article.

[0027] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof mean non-exclusive inclusion. For example, a process, method, article of manufacture, or apparatus that includes a list of elements is not limited to the elements listed, but may include other elements not expressly listed or inherent to the process.

[0028] The connecting phrase "consisting essentially of" limits the scope of the patent application to the specified materials or steps without materially affecting the fundamental and novel features of the claimed invention. "A claim that 'consisting essentially of' falls between a closed claim stated as 'consisting of' and a fully open claim written as 'comprising.'" When an invention or part thereof is described using open-ended terms such as "comprising," it should be understood that, unless otherwise specified in specific circumstances, the description also includes a description of the invention using the terms "consisting of" and "essentially of."

[0029] Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive "or" rather than an exclusive "or". For example, condition A or B can be satisfied by any of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0030] As used herein, the term "copolymer" refers to a polymer comprising copolymeric units obtained by copolymerizing two or more comonomers. In this respect, a copolymer may be described herein by reference to its constituent comonomers or the amount of those comonomers, such as "a copolymer comprising ethylene and 15% by weight of acrylic acid" or a similar description. Such a description may be considered informal because it does not refer to the comonomers as comonomeric units; because it does not include the conventional nomenclature of copolymers, such as the International Union of Pure and Applied Chemistry (IUPAC) nomenclature; because it does not use terminology that defines the product by method; or for other reasons. However, as used herein, a description of a copolymer by reference to its constituent comonomers or the amount of those comonomers means that the copolymer contains comonomers of the specified comonomers (in the specified amount when specified). For the constituent comonomers of a copolymer, the terms "unit," "repeating unit," and "residue" are synonyms and used interchangeably herein. As a conclusion, the copolymer is not the product of a reaction mixture containing a given amount of a given comonomer, unless explicitly stated otherwise.

[0031] As used herein, the term "fluorinated olefin" refers to a straight-chain, branched, or cyclic hydrocarbon structure containing at least one carbon-carbon double bond and further containing at least one fluorine atom.

[0032] As used herein, the term "alkyl" refers to a straight-chain, branched, or cyclic hydrocarbon structure and combinations thereof. The term "alkyl" does not include unsaturated portions, such as vinyl or aryl structures. Examples of straight-chain alkyl groups include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, and hexyl. Branched alkyl groups include, for example, but not limited to, secondary and tertiary butyl and isopropyl. Examples of cyclic hydrocarbon groups include, but are not limited to, cyclopropyl, cyclopentyl, cyclohexyl, cyclobutyl, and cyclooctyl.

[0033] As used herein, the term "fluorinated olefin" refers to a straight-chain, branched, or cyclic carbon structure containing at least one carbon-carbon double bond and at least one fluorine atom.

[0034] As used herein, the term "alkoxy" refers to an alkyl group attached to an oxygen atom by a single bond. Other bonds of the oxygen atom are attached to a carbon atom. Examples include, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, cyclopropoxy, and cyclohexyloxy.

[0035] As used herein, the term "compound" refers to a curable composition, such as a mixture of chemical entities containing at least a fluoroelastomer and a curing agent. This mixture of chemical entities has not yet been cured and has not undergone processing conditions that would cause the mixture of chemical entities to cure.

[0036] As used herein, the term "fluorine-", when placed as a prefix before the name of a chemical entity, refers to a chemical entity having at least one fluorine atom, including but not limited to: fluoroelastomers, perfluoroelastomers, fluorovinyl groups, and perfluorovinyl ethers. As used herein, the prefix "perfluorine-" refers to a fully fluorinated molecule or portion, wherein every position that could be occupied by a hydrogen atom is occupied by a fluorine atom. The prefix "fluorine-", when placed before the name of a chemical entity, explicitly includes fully fluorinated chemical entities. Therefore, the prefix "fluorine-" refers to a fluorinated molecule or group, a fully fluorinated molecule or group, or a combination of a fluorinated molecule or group and a fully fluorinated molecule or group.

[0037] As used herein, the term "aromatic" refers to a chemical entity comprising at least one unsaturated atomic ring, which is stabilized by the interactions of the bonds forming that ring. Typical examples of such chemical entities are benzene and naphthalene.

[0038] As used herein, the term "phenyl" refers to a chemical entity of the formula -C6H5, which is derived from benzene by removing a hydrogen atom. The carbon atom lacking this hydrogen atom is used to form a bond with another chemical entity.

[0039] As used herein, the terms "cured" and the related terms derived from the intransitive verb "to cure" refer to covalent crosslinking. For example, when a fluoroelastomer compound is exposed to conditions (i.e., curing conditions) that cause sufficient crosslinking between the fluoroelastomer molecules and the curing agent (if present), the fluoroelastomer compound is cured such that the resulting entity cannot be further processed, molded, or extruded into a different form, shape, structure, or configuration. Once an entity containing a fluoroelastomer compound has been cured by exposure to curing conditions, the covalent crosslinking is irreversible, and the entity cannot be recured to present a substantially different form or structure. The resulting entity can be an article as defined above.

[0040] The related terms "cured" and the derived automatic word "to cure" also include different degrees of processing of a mixture, such that the resulting entity may exhibit a range of physical properties due to varying degrees of curing. For example, within the meaning of the term "cured" as set forth herein, a mixture may be initially cured to obtain an unprocessable form, shape, etc. Cured mixtures may subsequently undergo additional curing conditions that provide further curing. Such additional curing conditions may be referred to herein as "curing" or "post-curing." In other words, the terms "cured" and the derived automatic word "to cure" refer to the initial curing process that produces the first cured entity, and also to any subsequent curing process that produces a subsequently cured entity that may have different material or physical properties than the first cured entity.

[0041] [Scope and preferred variants]

[0042] Unless otherwise expressly stated, any ranges set forth herein explicitly include their endpoints. Specifying a quantity, concentration, or other value or parameter as a range specifically discloses all possible ranges formed by any possible upper and lower limits, whether or not such upper and lower limit pairs are explicitly disclosed herein. The mixtures, methods, and articles described herein are not limited to the specific values ​​disclosed when ranges are defined in the specification.

[0043] The disclosure of any variations of the methods, mixtures, and articles described herein, with respect to materials, chemical entities, methods, steps, values, and / or ranges (whether or not determined to be preferred), is particularly intended to include any possible combinations of materials, methods, steps, values, ranges, etc. Any combination described herein is a preferred variation of the methods, mixtures, and articles described herein.

[0044] [Mixture]

[0045] This document provides formulations containing specific curing agents. More specifically, such formulations comprise:

[0046] A. Fluoroelastomers comprising the following copolymer units:

[0047] (1) One or more fluorinated olefins;

[0048] (2) One or more olefin comonomers different from (1), selected from the group consisting of fluorovinyl ethers, olefins, and mixtures thereof; and

[0049] (3) One or more monomers selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers; and

[0050] B. A curing agent comprising amide carboxylic acid and a molecule containing an amidine moiety, or an amide carboxylic acid salt containing an amidine moiety.

[0051] [A) Fluoroelastic

[0052] The fluoroelastomer A described herein, suitable for use in blends, may be fluorinated or perfluorinated and comprises at least three comonomer units: A(1) one or more fluorinated olefins; A(2) one or more olefin comonomers other than the fluorinated olefin A(1), selected from the group consisting of fluoroalkyl vinyl ethers, fluoroalkoxy vinyl ethers, olefins, and mixtures of two or more of these; and A(3) one or more curing site monomers selected from the group consisting of nitrile fluorinated olefins and nitrile fluorinated vinyl ethers.

[0053] The preferred fluoroelastomer A comprises at least three comonomer units: A(1) one or more fluorinated olefins in about 25 to 74.9 moles; A(2) one or more olefin comonomers different from fluorinated olefin A(1) in about 25 to 74.9 moles, selected from the group consisting of fluorovinyl ethers, olefins, and mixtures of two or more of these; and A(3) one or more curing site monomers in about 0.1 to 10 moles, selected from the group consisting of nitrile fluorinated olefins and nitrile fluorinated vinyl ethers. The mole percentage of the comonomer repeating units of each of A(1), A(2), and A(3) is based on the total number of moles of the comonomer repeating units in fluoroelastomer A, and the sum of the mole percentage of the comonomer repeating units of comonomers A(1), A(2), and A(3) and the mole percentage of the comonomer repeating units of any other comonomer that may be present in fluoroelastomer A is 100 mol.

[0054] As a result of the use of different initiators or chain transfer agents during polymerization, the fluoroelastomer A suitable for use in the blends described herein can contain a wide variety of end groups. Non-limiting examples of suitable end groups include sulfonates, sulfonic acids, carboxylic esters, carboxylic acids, carboxylamines, difluoromethyls, trifluorovinyls, and perfluorinated alkyl groups. Fluoroelastomer A with two different end groups is also suitable. Carboxylic acids are preferred end groups.

[0055] Such mixtures may contain two or more fluoroelastomers A that are different from each other in any respect, including but not limited to different comonomers (1), (2) or (3); one or more additional comonomers; the same comonomers (1), (2) and (3) and the same additional comonomers (if present) but with different compositional ranges; different end groups; different synthetic methods; or different molecular weights.

[0056] [A)(1) Fluorinated olefins]

[0057] Suitable fluorinated olefins A (1) include, but are not limited to, monomers containing at least one alkene-unsaturated carbon-carbon bond and at least one fluorine atom, preferably at least two fluorine atoms. More preferably, fluorinated olefin A (1) is a perfluorinated monomer. Examples of suitable fluorinated olefins include, for example, tetrafluoroethylene; 1,1-difluoroethylene; 1,1,2-trifluoroethylene; 1-fluoroethylene; chlorotrifluoroethylene; 1-fluoropropene; 1,1-difluoropropene; 1,1,3-trifluoropropene; 1,2,3,3,3-pentafluoropropene; 1,1,3,3,3-pentafluoropropene; hexafluoropropene; and combinations of two or more of these. Even more preferred fluorinated olefins include tetrafluoroethylene, 1,1-difluoroethylene, and hexafluoropropene. The concentration of fluorinated olefin A (1) can be in the range of about 25.0 to about 74.9 moles of the total monomer units in the fluoroelastomer A. Based on the preferred range of other comonomers of fluoroelastomer A as described below, and based on the principle that the total mole percentage of comonomers of fluoroelastomer A is 100 mol%, the preferred and better ranges of fluorinated olefin A (1) are derived by means of the difference.

[0058] [A)(2) Olefin comonomers]

[0059] The suitable olefin comonomer A(2), which is different from the fluorinated olefin A(1), is selected from the group consisting of: fluorovinyl ethers, olefins, and combinations of two or more of the above.

[0060] Examples of suitable fluorovinyl ethers include, for example, perfluoro(alkylvinyl) ethers, perfluoro(alkoxyvinyl) ethers, fluoro(alkylvinyl) ethers, fluoro(alkoxyvinyl) ethers, and combinations of two or more of these. Suitable fluorovinyl ether monomers include, for example, those shown in formulas (I) to (V):

[0061] CF2=CFO(Rf' O)n(Rf" O)mRf (I)

[0062] The Rf series consists of straight-chain or branched perfluoroalkyl groups having 1 to 6 carbon atoms, while the Rf' and Rf' series consist of different straight-chain or branched perfluoroalkyl groups having 2 to 6 carbon atoms. Furthermore, the m and n series are independently chosen integers such that 0 m 10 and 0 n 10.

[0063] Additional examples of suitable fluorovinyl ether monomers include those having the composition of formula (II):

[0064] CF2=CFO(CF2CFXO)nRf (II)

[0065] Wherein the X series is F or CF3, the n series is an integer equal to 0, 1, 2, 3, 4 or 5, and the Rf series is a straight-chain or branched perfluoroalkyl group having 1 to 6 carbon atoms. Preferably, n is equal to 0 or 1, and Rf contains 1 to 3 carbon atoms. Examples of such fluorovinyl ether monomers include perfluoro(methyl vinyl) ethers and perfluoro(propyl vinyl) ethers.

[0066] Other fluorovinyl ether monomers suitable for the preparation of fluoroelastomer (A) include compounds having formulas (III), (IV), and (V):

[0067] CF2=CFO[(CF2)mCF2CFZ]nRf (III)

[0068] The Rf series consists of straight-chain or branched perfluoroalkyl groups with 1 to 6 carbon atoms; the m series consists of integers equal to 0 or 1; the n series consists of integers equal to 0, 1, 2, 3, 4, or 5; and the Z series consists of F or CF3.

[0069] CF2=CFO[(CF2=CFCF3O)n(CF2CF2CF2O)m(CF2)p]CxF2x+1 (IV)

[0070] Where m and n are independently chosen integers, such that 0 m 10 and 0 n 10; p is an integer equal to 0, 1, 2, or 3; and x is an integer equal to 0, 1, 2, 3, 4, or 5. Specific embodiments of this class include compounds in which n = 0 or n = 1; independently, m = 0 or m = 1; and x = 1.

[0071] Other suitable fluorovinyl ether monomers include those having the following formula:

[0072] CF2=CFOCF2CF(CF3)O(CF2O)mCnF2n+1 (V),

[0073] Where n is an integer equal to 0, 1, 2, 3, 4 or 5; m is an integer equal to 0, 1, 2 or 3; and preferably, n=1.

[0074] Examples of preferred fluorovinyl ether monomers include perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluoroethyl vinyl ether, and combinations of two or more of these. Examples of preferred perfluoro(alkoxyvinyl) ethers include perfluoromethoxyvinyl ether, perfluoropropoxyvinyl ether, and perfluoroethoxyvinyl ether, and combinations of two or more of these. Examples of preferred olefins include ethylene, propylene, 1-butene, 2-butene, and combinations of two or more of these.

[0075] Suitable fluoroelastomer A may include at least one fluorovinyl ether, at least one fluorinated olefin, and at least one olefin copolymer residue.

[0076] The concentration of olefin comonomer A (2) in fluoroelastomer A is based on the total mole number of comonomer units in fluoroelastomer A in the range of 25 to 74.9 mole percent, preferably 30 to 65 mole percent, and even more preferably 45 to 55 mole percent.

[0077] [A)(3) Solidified site monomer]

[0078] Fluoroelastomer A further comprises one or more copolymer units of a curing site monomer (3), the amount of which is based on the total mole number of the copolymer monomer units in fluoroelastomer A, typically from 0.1 to 10 mole percent, preferably between 0.3 and 1.5 mole percent. Although more than one type of curing site monomer may be present, a curing site monomer containing at least one nitrile substituent is preferred. Preferred curing site monomers include, but are not limited to, nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers. Useful nitrile-containing curing site monomers include those having formulas (VI) to (X):

[0079] CF2=CF-O(CF2)nCN (VI),

[0080] Where n is an integer, such that 2 n 12, and preferably 2 n 6;

[0081] CF2=CF-O[CF2-CFCF3-O]n-CF2-CFCF3CN (VII),

[0082] Where n is an integer equal to 0, 1, 2, 3, or 4; and preferably n is equal to 0, 1, or 2.

[0083] CF2=CF-[OCF2CFCF3]xO-(CF2)nCN (VIII),

[0084] Where x equals 1 or 2, and n is an integer equal to 0, 1, 2, 3, or 4; and

[0085] CF2=CF-O-(CF2)nO-CF(CF3)CN (IX).

[0086] Where n is an integer equal to 2, 3 or 4.

[0087] Preferably, monomers having formula (VII) are used as curing site monomers. More preferably, curing site monomers include perfluorinated polyethers having nitrile and trifluorovinyl ether groups. Particularly preferred curing site monomer systems are perfluorinated (8-cyano-5-methyl-3,6-dioxa-1-octene) (8-CNVE), represented by formula (X):

[0088] CF2=CFOCF2CF(CF3)OCF2CF2CN (X).

[0089] [B) Curing agent

[0090] The mixtures described herein further comprise a curing agent comprising an aminocarboxylic acid and a molecule containing an amidine moiety. Alternatively, the curing agent comprises an aminocarboxylic acid salt of a molecule containing an amidine moiety. Any amidine-containing molecule and any combination of two or more amidine-containing molecules are suitable for use in the curing agents described herein. Some suitable amidine-containing molecules are described in U.S. Patent No. 9,908,992 to Fox et al. and U.S. Patent No. 7,521,510 to Aufdermarsh et al. Preferred amidine-containing molecules are selected from the group consisting of molecules having formulas (XI), (XII), and (XIII):

[0091]

[0092]

[0093]

[0094] Each of R1, R2, R3, and R4 is selected from the group consisting of: H, halogen atom, C1 to C4 alkyl, wherein the alkyl group is straight-chain, branched, or cyclic; at least two of R1, R2, R3, and R4 can form a ring having a saturated or unsaturated hydrocarbon entity, such that the phenyl group is substituted as desired into a bicyclic or tricyclic group, such as naphthyl or phenanthryl, anthracene, perhydronaphthyl, 1,2,3,4-tetrahydronaphthyl ("tetralinyl"), perhydrophenanthryl, or perhydroanthrene; OR'; and aryl; R' is selected from the group consisting of: H; C1 to C4 alkyl, wherein the alkyl group is straight-chain, branched, or cyclic; and phenyl or substituted phenyl. When R' is a substituted phenyl group, it can be substituted by one or more of R1, R2, R3 and R4 as defined above, provided that R1, R2, R3 and R4 do not further form a ring when they are present as substituents of the substituted phenyl group.

[0095] Non-limiting examples of curing agents having formula (XI) include isoindoline, substituted isoindoline, isoindoline derivatives, and combinations of two or more of these. Suitable isoindoline is described in detail in U.S. Patent No. 5,691,272 to Matsumoto et al. Preferred isoindolines include, but are not limited to, 1,3-diiminoisoindoline, 5,6-dichloro-1,3-diiminoisoindoline, 4,5,6,7-tetrachloro-1,3-diiminoisoindoline, 5,6-difluoro-1,3-diiminoisoindoline, 4,5,6,7-tetrafluoro-1,3-diiminoisoindoline, 4,7-dihydroxy-1,3-diiminoisoindoline, 5,6-dimethyl-1,3-diiminoisoindoline, 5,6-dicyano-1,3-diiminoisoindoline, 5,6-bisphenoxy-1,3-diiminoisoindoline, and 5,6-bis-o-tolyloxy-1,3-diiminoisoindoline. More preferably, it is a combination of 1,3-diiminoisoindoline and two or more curing agents containing 1,3-diiminoisoindoline.

[0096] Non-limiting examples of curing agents having formula (XII) include benzalamide, substituted benzalamide, benzalamide derivatives, or combinations of two or more of these. Suitable amidines are described in U.S. Patent No. 7,514,506 to Mansfield et al. Preferred benzalamides include, but are not limited to, benzalamide, 2-methylbenzalamide, 3-methylbenzalamide, 4-methylbenzalamide, 2-phenylbenzalamide, 3-phenylbenzalamide, 4-phenylbenzalamide, 2-methoxybenzalamide, 3-methoxybenzalamide, 4-methoxybenzalamide, 2-chlorobenzalamide, 3-chlorobenzalamide, 4-chlorobenzalamide, and 2-fluorobenzalamide. Formamidinium, 3-fluorobenzamidinium, 4-fluorobenzamidinium, 2-trifluoromethylbenzamidinium, 3-trifluoromethylbenzamidinium, 4-trifluoromethylbenzamidinium, 2-cyanobenzamidinium, 4-cyanobenzamidinium, 2-hydroxybenzamidinium, 4-hydroxybenzamidinium, α-naphthylbenzamidinium, β-naphthylbenzamidinium, N-methylbenzamidinium, N-phenylbenzamidinium, N-tolylbenzamidinium. More preferably, benzamidinium, N-phenylbenzamidinium, and combinations of two or more curing agents containing benzamidinium or N-phenylbenzamidinium.

[0097] Non-limiting examples of curing agents having formula (XIII) include guanidine, substituted guanidine, guanidine derivatives, or combinations of two or more of these. Suitable guanidines are described in U.S. Patent No. 6,638,999 to Bish et al. Examples of preferred guanidines and guanidine derivatives include, but are not limited to, N,N”-diphenylguanidine; N-phenyl-N'-methylguanidine; N-(2-methylphenyl)-N'-phenylguanidine; N-(3-methylphenyl)-N”-phenylguanidine; N-(4-methylphenyl)-N”-phenylguanidine; N-(2-chlorophenyl)-N”-phenylguanidine; N-(3-chlorophenyl)-N”-phenylguanidine; N-(4-chlorophenyl)-N”-phenylguanidine; N-(2-fluorophenyl)-N”-phenylguanidine; N-(3-fluorophenyl)-N”-phenylguanidine; N-(4-fluorophenyl)-N”-phenylguanidine; N-(4-trifluoromethylphenyl)-N”-phenylguanidine; N-(2-trifluoromethylphenyl)-N”-phenylguanidine; N,N'-(di-2-methylphenyl)guanidine; N-2-naphthyl-N'-phenylguanidine; and N-(4-methylphenyl)-N”-phenylguanidine. More preferably, it is a combination of N,N”-diphenylguanidine and two or more curing agents containing N,N”-diphenylguanidine.

[0098] Curing agent B further comprises a amide carboxylic acid. Any amide carboxylic acid and any combination of two or more amide carboxylic acids are suitable for use in curing agent B. Suitable amide carboxylic acids have the following formula (XIV):

[0099]

[0100] X=CO,-CH(R")CO,-CH(R")CH(R")CO,-C(R")=C(R")CO

[0101] R"=H or Me

[0102] Preferred amide carboxylic acids include oxalic acid (X=C(O)), malonic acid (X=CH2C(O)), 3-methylmalonic acid (X=CH(CH3)C(O), R and S isomers), and combinations of two or more of these acids or their amidine salts. Alternatively, the curing agent comprises one or more salts of an amide carboxylic acid with an amidine of structure (XI, XII, or XIII).

[0103] Without being bound by theory, it is believed that amide carboxylic acid forms a complex with amidine and delays the curing chemistry at processing temperatures. Further hypothesizing that amide carboxylic acid participates in the high-temperature curing process as a secondary curing agent, thereby generating a more stable crosslinked network, this dual system contributes to processability by reducing charring through increased processing time and improving the properties of cured mixtures and products.

[0104] Curing agents can be synthesized by combining amide carboxylic acids with one or more amidine-containing molecules. The acid-base reaction that occurs when the amide carboxylic acid comes into contact with one or more amidine moieties is instantaneous.

[0105] In practice, during the blending process to produce the mixture, the amide carboxylic acid and the amidine-containing molecule can be added to the fluoroelastomer A solvent-free. Alternatively, the salt can be pre-formed, for example, by reacting the amide carboxylic acid with the amidine-containing molecule in solution to form an amide carboxylate salt, and then added to the fluoroelastomer A during the blending process to produce the mixture. Suitable solvents include common organic solvents, with acetone being preferred. The salt is separated as a substantially solvent-free solid before being added to the blend to produce the mixture.

[0106] The amidine-containing molecules and amide carboxylic acids can be combined in molar ratios ranging from 2 moles of amidine-containing molecules to 1 mole of amide carboxylic acid (2:1) to 1:2, or from 2:1 to 1:3, to form curing agent B. Preferably, the amide carboxylic acid and amidine-containing molecules are combined in equal molar amounts, i.e., a molar ratio of 1:1.

[0107] Based on the total amount of fluoroelastomer A, the concentration of curing agent B in the fluoroelastomer blend ranges from about 0.1 to about 10 phr, preferably from 0.1 to 5 phr, and more preferably from about 0.3 to about 2 phr. An excess of curing agent B can be used relative to the amount required to react with all curing sites present in fluoroelastomer A.

[0108] [additive]

[0109] The blends described herein may contain one or more additives. Suitable additives and amounts are described in detail in the above-cited U.S. Patent No. 9,908,992. Preferred additives, including but not limited to fillers, stabilizers, plasticizers, lubricants, and processing aids, typically used in blending, may be incorporated into the blends described herein, provided that they have sufficient stability to the intended use conditions. In particular, low-temperature performance may be enhanced by incorporating perfluoropolyethers.

[0110] In short, fillers can be used in elastomers as a means of balancing the modulus, tensile strength, elongation, hardness, abrasion resistance, electrical conductivity, and processability of such blends. Carbon black is the most commonly used. The blends described herein may contain one or more grades of carbon black.

[0111] Examples of suitable carbon blacks include MT carbon black (medium-grained thermal cracking carbon black) specified as N-991, N-990, N-908, and N-907, as well as large-grained furnace black. MT carbon black is preferred.

[0112] One or more non-carbon black fillers may be present in the mixtures described herein. Examples of suitable non-carbon black fillers are silica, such as anhydrous silica, acid silica, fumed silica, or precipitated silica. Surface-treated silica is also suitable. Such silica is available from Degussa AG (Degussa Aktiengesellschaft, Frankfurt, Germany) under the trademark Aerosil™. Particularly useful types are Aerosil™ 200 silica and Aerosil™ 972 silica. Other suitable silica includes Reolosil™ silica, such as Reolosil™ QS13, Reolosil™ QS102, and Reolosil™ QS30, available from Tokuyama KK (Tokyo, Japan).

[0113] Additional suitable types of non-carbon black fillers include, for example, mineral fillers (such as BaSO4, Al2O3, and TiO2), polymer micropowders, and fluorine additives. Polymer micropowders are typically partially crystalline polymers. Micropowders comprise finely separated, easily dispersible fluoropolymers that are solid at the highest temperatures used in the manufacture and curing of the blends described herein. "Solid" means a fluoropolymer with a crystallization melt temperature higher than the processing temperature of the blends described herein.

[0114] Polymer micropowders that can be used in these blends include, but are not limited to, polymer micropowders based on a group of polymers known as tetrafluoroethylene (TFE) polymers. This group includes polytetrafluoroethylene (PTFE) and copolymers of TFE with at least one copolymerizable modifying monomer in a small concentration of about 1 mole percent or less, such that the polymer micropowder does not melt or soften during processing of the fluoroelastomer (A) containing the polymer micropowder. The modifying monomer can be, for example, hexafluoropropylene (HFP), perfluoro(propyl vinyl) ether (PPVE), perfluorobutylethylene, trichlorofluoroethylene, or another monomer with a side group introduced into the polymer molecule.

[0115] Tetrafluoroethylene polymers used as additives in fluoroelastomer blends comprise copolymers of TFE having sufficient concentrations of copolymer units of one or more monomers to lower the melting point below that of PTFE. Such copolymers generally have melt viscosities in the range of 0.5–60 x 10³ Pa·s, but viscosities outside this range are also known. Perfluoroolefins and perfluoro(alkyl vinyl) ethers are preferred comonomers. Hexafluoropropylene and perfluoro(propyl vinyl) ethers are preferred. Examples of TFE copolymers include TFE / hexafluoropropylene copolymers and TFE / perfluoro(propyl vinyl) ether copolymers, provided they meet the limitations on melt temperature relative to the processing temperature of the perfluoroelastomer. If the particle size is acceptable, these copolymers can be used as is, as a powder separated from the polymerization medium, or they can be ground from larger raw materials to a suitable particle size.

[0116] The mixtures described herein may further include polymer-reinforcing fillers. Polymer-reinforcing fillers include thermoplastic polymers and thermosetting polymers. Polymer-reinforcing fillers may or may not be crosslinkable with any curing site of the fluoroelastomer A. Non-limiting examples of polymer-reinforcing fillers are those having at least one crosslinkable group selected from the group consisting of at least one end of the main chain or side chain: cyano (-CN), carboxyl (-COOH), alkoxycarbonyl (-COOR9, where R9 is a monovalent organic group), and an acid halide group (-COX1, where X1 is a halogen atom) capable of crosslinking with the fluoroelastomer A.

[0117] The fluoropolymer may contain monomer units independently selected from the group consisting of vinylidene fluoride (VDF), tetrafluoroethylene, and hexafluoropropylene, as well as at least one additional monomer, such as tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl ether), chlorotrifluoroethylene, trifluoroethylene, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutylene, fluoroethylene, and iodine-containing fluorinated vinyl ethers, ethylene, propylene, alkyl vinyl ethers, and combinations thereof.

[0118] Examples of suitable polymer-reinforced fillers include, but are not limited to, thermoplastic fluoropolymers.

[0119] Typically, the amount of each individual filler can be based on the amount of fluoroelastomer in the blend, ranging from 0.01 phr, preferably 1 phr to 200 phr. Also typically, when the blend contains more than one filler, the total amount of all fillers is less than or equal to 200 phr. More specifically, when the blend contains one or more polymer fillers, the amount of the one or more fillers is based on the total number of parts of fluoroelastomer A, ranging from about 0.01 to about 200 parts, and preferably at least about 1 to about 50 parts. When the blend contains one or more carbon black fillers, the amount is based on 100 parts of fluoroelastomer A, ranging from about 0.01 to about 70 phr of carbon black, preferably from about 0.01 to about 50 phr, more preferably from about 1 to about 50 phr, and even more preferably from about 10 to about 50 phr, or from about 20 to about 40 phr, or from about 25 to about 35 phr of carbon black. The amount of one or more non-carbon black fillers in the mixture is based on 100 parts of fluoroelastomer A, preferably in the range of about 1 to about 100 phr, more preferably from about 1 to about 30 phr.

[0120] [Methods for producing mixtures]

[0121] The fluoroelastomer blends described herein can be prepared by mixing fluoroelastomer A, one or more curing agents B, and desired components (such as fillers and other additives) in a conventional rubber compounding process, such as a two-roll rubber mill, a mixer (e.g., a Banbury mixer), or an extruder, until homogeneous. During these compounding processes, care should be taken to maintain the temperature of the blend at or below its curing temperature.

[0122] [Products]

[0123] Further provided are uncured articles comprising one or more of the mixtures described herein, and cured articles obtained by curing the uncured articles. The cured articles comprise one or more products of the cured mixtures described herein. Suitable and preferred mixtures for use in the cured and uncured articles are as described above with respect to the mixtures themselves.

[0124] Uncured products are made from compound by conventional molding methods such as extrusion, calendering, and molding. During these molding processes, care should be taken to keep the temperature of the compound at or below its curing temperature.

[0125] [Compound Curing and Products]

[0126] The mixtures and uncured articles described herein can be cured by applying sufficient heat or pressure to allow curing agent B to form crosslinks with the monomers at the curing sites. When compression molding is used as the curing process, a post-curing cycle is preferably followed by a compression curing cycle, during which the compression-cured mixture is heated for several hours at a temperature typically higher than the molding temperature.

[0127] Some preferred methods for curing the mixtures and articles described herein include curing the mixture containing fluoroelastomer A with at least one curing agent. Preferred compositions for the mixtures and uncured articles used in this method are as described above.

[0128] The vulcanization (curing) of the compound is typically carried out under heat. The rate of vulcanization increases with increasing temperature. For an ideal curing agent, the vulcanization rate is fast at high curing temperatures and slow in low-temperature pre-vulcanization processes such as mixing and extrusion.

[0129] In rubber technology, charring refers to the premature vulcanization of a compound before final curing or crosslinking can be completed. The problem with faster-curing compounds is lower charring time or "charring safety." Charring time is typically reported as the time it takes for a compound to reach a given viscosity increment at typical mixing and extrusion temperatures (usually at or below 121°C). T3, T10, and T18 are the times, in minutes, for a compound to increase its viscosity by 3, 10, and 18 units, respectively, at the Mooney viscosity at the test temperature (typically 121°C). The longer the time before the viscosity reaches the predetermined increment, the better the charring safety of the compound. The viscosity component of the charring time determination is typically measured by a viscometer, such as a Mooney viscometer, and reported in Mooney units. Generally, for blends considered safe for coking, when tested at 121°C, the time T10 for the blend viscosity to increase by 10 Mooney units is greater than 10 minutes, preferably greater than 20 minutes, or even better, greater than 30 minutes.

[0130] Typically, curing behavior is measured at one or more fixed intervals using a rheometer, such as a dynamic modulus rheometer (MDR). The curing behavior of rubber compounds is usually measured at vulcanization, curing, or crosslinking temperatures. Typically, this temperature ranges from 150°C to 210°C. This curing behavior is characterized by an increase in viscosity at this temperature. A greater increase in viscosity indicates better vulcanization. Sufficient time is required before a significant increase in viscosity for the mold to be loaded; this is another measure to obtain better processability or charring safety. Ts2 is the time it takes for the viscosity to increase by two torque units (measured in dN·m). The longer the time, the better the charring safety of the compound. Preferably, Ts2 is greater than 30 seconds, more preferably greater than 1 minute.

[0131] When cured and post-cured as needed, the articles described herein exhibit suitable thermal stability and chemical resistance for applications requiring exposure to harsh conditions, such as those used in semiconductor wafer fabrication.

[0132] Advantageous properties of cured products include suitable ranges in hardness, tensile strength, and compressive strength.

[0133] The chemical structure of elastomers gives them an inherent hardness that can be measured using a Shore hardness tester. Stiffer rubbers typically have a higher tensile modulus (see below), making them more resilient. They are also more resistant to extrusion, a process used to manufacture stock materials for custom manufacturing.

[0134] The compressive deformation of a material is the permanent deformation remaining after the force applied to the material is removed. Lower values ​​of compressive deformation, i.e., smaller deformation, are beneficial for sealing applications.

[0135] Tensile strength is the amount of force required to tear a rubber specimen until it breaks. Tensile strength is also called ultimate tensile strength and is reported in megapascals (MPa) or pounds per square inch (psi) according to ASTM D412. Tensile strength is a critical factor for designers and buyers because it indicates the point of failure caused by the stretching of the rubber. Higher tensile strength is advantageous for sealing applications.

[0136] Tensile modulus is the stress or force required to produce strain or elongation in a rubber sample. Tensile modulus and tensile strength are two different properties. A moderate tensile modulus is beneficial for sealing applications. The sealing material must deform sufficiently to conform to the equipment to be sealed.

[0137] The cured products described herein can be used as O-rings, seals, and gaskets in high-temperature environments, in various chemical environments, such as high-temperature automotive applications, and in semiconductor manufacturing equipment.

[0138] Some notable embodiments of the cured and uncured mixtures, articles, and methods described herein include one or more of the following features:

[0139] ˙Fluorinated olefin A(1) is selected from the group consisting of: tetrafluoroethylene; hexafluoropropylene; 1,1-difluoroethylene; 1,1,2-trifluoroethylene; 1-fluoroethylene; and combinations of two or more of these;

[0140] ˙Fluorinated olefin comonomer A(2) is selected from the group consisting of: perfluoro(methyl vinyl) ethers, perfluoro(propyl vinyl) ethers, and combinations thereof;

[0141] Curing agent B is a amide carboxylate containing amidine molecules;

[0142] Curing agent B is selected from 1,3-diiminoisoindoline or 5,6-dichloro-1,3-diiminoisoindoline, diphenylguanidine or oxamine salt of benzamide;

[0143] The mixture contains at least one filler; and

[0144] The at least one filler is selected from the group consisting of: polymer-reinforced fillers, polymer powders, mineral powders, carbon black, stabilizers, plasticizers, lubricants, processing aids, and combinations of two or more of the above.

[0145] The following examples are provided to further describe the invention in detail. These examples, illustrating preferred embodiments of the invention as currently considered, are intended to be illustrative and not limiting.

[0146] [Example]

[0147] In the table below, embodiments of the present invention are indicated by "E" and comparative embodiments are indicated by "C".

[0148] [Preparation of curing agent]

[0149] [1,3-Diiminoisoindoline tunabarate (B1)]

[0150] 1,3-Diiminoisoindoline (6.0 g, 41.33 mmol) and acetone (50 mL) were added to a 100 mL two-necked round-bottom flask under a nitrogen atmosphere. The mixture was stirred at room temperature for 15 minutes, and oxalic acid (3.68 g, 41.33 mmol) was slowly added in small portions with vigorous stirring, maintaining the temperature at approximately 25 °C. The mixture was stirred at room temperature (RT) for 12 h. The resulting slurry was filtered and washed with acetone (2 x 3 mL). The filtered solid was then dried under vacuum at 70 °C to obtain 1,3-diiminoisoindoline onyxate (9.4 g, 40.10 mmol) as a grayish-white solid.

[0151] [1,3-Diiminoisoindolineonium acetate (B2)]

[0152] Following the procedure described above for the synthesis of 1,3-diiminoisoindoline oxaloacetate, a mixture of 1,3-diiminoisoindoline (6.0 g, 41.33 mmol) and acetic acid (2.48 g, 41.33 mmol) was stirred in acetone, then filtered and dried to obtain 1,3-diiminoisoindoline oxaloacetate (8.33 g, 39.8 mmol) as a grayish-white solid.

[0153] [1,3-Diiminoisoindolineonium oxalate (B3)]

[0154] Following the procedure described above for the synthesis of 1,3-diiminoisoindoline oxalate, a mixture of 1,3-diiminoisoindoline (6.0 g, 41.33 mmol) and oxalic acid (1.87 mmol, 2.06 mmol) was stirred in acetone, then filtered and dried to obtain 1,3-diiminoisoindoline oxalate (7.60 g) as a grayish-white solid.

[0155] [Diphenylguanidine oxaloacetate (B4)]

[0156] Following the procedure described above for the synthesis of 1,3-diiminoisoindoline oxalamide, a mixture of diphenylguanidine (4.97 g, 28.4 mmol) and oxalamide (3.68 g, 28.4 mmol) was stirred in acetone, then filtered and dried to obtain diphenylguanidine oxalamide (8.36 g, 27.8 mmol) as a white solid.

[0157] [Benzamidine oxaloacetate (B5)]

[0158] Following the procedure described above for the synthesis of 1,3-diiminoisoindoline oxalamide, a mixture of benzamide (4.96 g, 41.33 mmol) and oxalamide (3.68 g, 41.33 mmol) was stirred in acetone, then filtered and dried to obtain benzamide oxalamide (8.33 g, 39.8 mmol) as a white solid.

[0159] [Material]

[0160] Perfluoroelastomers having monomers of the formula TFE / PMVE / cyano curing sites, as described in U.S. Patent No. 6,638,999 to C. Bish et al. or U.S. Patent No. 9,908,992 to P. Fox et al.

[0161] 1,3-Diiminoisoindoline: Obtained from MilliporeSigma (formerly known as Sigma-Aldrich) of St. Louis, Missouri.

[0162] Oxalic acid: Obtained from Millibor Sigma

[0163] MT carbon black or N-990 (CB): Obtained from Cancarb Limited, Medisinghart, Alberta, Canada.

[0164] [Testing Method]

[0165] Coking or pre-sulfurization characteristics of the mixture

[0166] This feature is based on ASTM D1646 (2019) and uses a Mooney viscometer (Alpha Technology Mooney mv2000) to measure viscosity increases. Mooney coking was performed by running a Small Rotor at 121°C for 30 minutes.

[0167]

[0168] Curing properties were measured using a Monsanto Dynamic Modulus Rheometer (MDR 2000) under the following conditions: ASTM D5289 (2019).

[0169] Temperature: as listed in the table.

[0170] Dynamic mode frequency: 1.66Hz

[0171] Vibration amplitude: 0.5

[0172] Test duration: 20 minutes

[0173] Record the following curing parameters:

[0174] MH: Maximum torque level, in dN.m

[0175] ML: Minimum torque level, in dN.m

[0176] ts2: Increased to more than ML 2 units per minute

[0177] TC90: 90% of maximum torque per minute

[0178] The test specimens are prepared from elastomers compounded with appropriate additives, as described in the formulations listed in the following examples. Compounding is performed on a rubber mill. The milled composition is formed into sheets, and the samples are extruded through a die to form disc-shaped test specimens for Mooney and MDR measurements.

[0179] O-rings are made by preforming sheet metal. The preforms are then molded and post-cured.

[0180] Tensile properties

[0181] Unless otherwise specified, stress / strain properties are measured on a K214 O-ring. Physical property measurements are obtained according to the methods described in ASTM D412 (2016) and D1414 (2015). Record the following parameters:

[0182] M100, modulus at 100% elongation, in MPa.

[0183] TB, tensile strength at break, in MPa.

[0184] EB, Elongation at Break, in percentage (%)

[0185] The compressive deformation of O-ring samples was determined according to ASTM D395B(2019) and D1414.

[0186] Table 1 shows the formulations of the examples and comparative examples.

[0187]

[0188] Table 2 describes the results of Mooney coking, MDR, tensile and compressive deformation data for various formulations.

[0189]

[0190]

[0191] The use of compositions B-1, B-4, and B-5 significantly reduces coking, thus making the machining of parts easier. Parts produced in this way also exhibit comparable or better tensile and compressive deformation.

[0192] While certain preferred embodiments of the invention have been described and specifically illustrated above, they are not intended to limit the invention to such embodiments. Various modifications may be made without departing from the scope and spirit of the invention as set forth in the following claims.

Claims

1. A compound comprising: (A) one or more fluoroelastomers comprising copolymer units of: (1) one or more fluorinated olefins; (2) one or more olefin comonomers, which are different from the one or more fluorinated olefins (1) and selected from the group consisting of fluorinated vinyl ethers, olefins, and combinations of two or more fluorinated vinyl ethers or olefins; and (3) one or more curing site monomers selected from the group consisting of nitrile fluorinated olefins and nitrile fluorinated vinyl ethers; and (B) a curing agent comprising amide carboxylic acid and an amidine molecule, or an amidine molecule-containing amide carboxylic acid salt.

2. The compound as claimed in claim 1, comprising 0.1 to 10 phr of the curing agent B based on the total weight of the one or more fluoroelastomers A.

3. The mixture as described in claim 1, wherein, The amidine-containing molecule is selected from the group consisting of molecules having the structural formula (XI), (XII), or (XIII): wherein each of R1, R2, R3, and R4 is selected from the group consisting of: H, halogen atoms, C1 to C4 alkyl groups, wherein the alkyl group is straight-chain, branched, or cyclic; at least two of R1, R2, R3, and R4 are capable of forming a ring having a saturated or unsaturated hydrocarbon; OR'; and an aryl group; and R' is selected from the group consisting of: C1 to C4 alkyl groups, wherein the alkyl group is straight-chain, branched, or cyclic; and substituted or unsubstituted phenyl groups.

4. The mixture as described in claim 3, wherein, The molecular system having formula (XI) is selected from the group consisting of 1,3-diiminoisoindoline, benzalkonium chloride and diphenylguanidine.

5. The mixture as described in claim 1, wherein, The curing agent contains a nitrocarboxylic acid having formula (XIV) or a carboxylate of a nitrocarboxylic acid having formula (XIV): X=CO,-CH(R”)CO,-CH(R”)CH(R”)CO,-C(R”)=C(R”)COR”=H or Me.

6. The mixture as described in claim 5, wherein, The acetocarboxylic acid is oxamic acid, and the acetocarboxylic acid salt is oxamic acid salt.

7. The mixture as described in claim 1, wherein, The fluorinated olefins are selected from the group consisting of tetrafluoroethylene, 1,1-difluoroethylene and mixtures thereof.

8. The mixture as described in claim 1, wherein, The fluorovinyl ether is selected from the group consisting of perfluoro(methyl vinyl) ethers and perfluoro(propyl vinyl) ethers.

9. The compound as described in claim 1, further comprising at least one filler.

10. The mixture as described in claim 9, wherein, The filler is selected from the group consisting of polymer-reinforcing fillers, polymer powders, mineral powders, carbon black, stabilizers, plasticizers, lubricants, processing aids, and combinations thereof.

11. The mixture as described in claim 1, wherein, When the mixture is heated at 121°C for 10 minutes, the viscosity of the mixture increases by less than 10 Mooney units.

12. The mixture as described in claim 1, wherein, When heated at 199°C for 30 seconds, the viscosity of the mixture increased by less than 2 N-dm.

13. A fluoroelastomer article comprising a compound as described in claim 1 or a product of a compound cured as described in claim 1.

14. The fluoroelastomer article as described in claim 13 is in the form of a gasket, seal, tubing, sheet, washer or O-ring.

15. The fluoroelastomer article as described in claim 13, wherein, According to method ASTM D395B, the compression set measured after 70 hours of compression at 25% in air at 204°C is less than 15%.

16. A curing method comprising the following steps: A fluoroelastomer is cured with at least one curing agent comprising amide carboxylic acid and an amidine molecule, or an amide carboxylic acid salt containing an amidine molecule.

17. The curing method as described in claim 16, comprising a amide carboxylic acid having formula (XIV) or a carboxylate of a amide carboxylic acid having formula (XIV): X=CO,-CH(R”)CO,-CH(R”)CH(R”)CO,-C(R”)=C(R”)COR”=H or Me.

18. The curing method as described in claim 17, wherein, The acetocarboxylic acid is oxamic acid, and the acetocarboxylic acid salt is oxamic acid salt.

19. The curing method as described in claim 16, wherein, The amidine-containing molecule is selected from the group consisting of molecules having the structural formula (XI), (XII), or (XIII): wherein each of R1, R2, R3, and R4 is selected from the group consisting of: H, halogen atoms, C1 to C4 alkyl groups, wherein the alkyl group is straight-chain, branched, or cyclic; at least two of R1, R2, R3, and R4 are capable of forming a ring having a saturated or unsaturated hydrocarbon; OR'; and an aryl group; and R' is selected from the group consisting of: C1 to C4 alkyl groups, wherein the alkyl group is straight-chain, branched, or cyclic; and substituted or unsubstituted phenyl groups.

20. The curing method as described in claim 19, wherein, The amidine-containing molecule is selected from the group consisting of 1,3-diiminoisoindoline, benzamide, and diphenylguanidine.

21. A mixture, which is the product of the method as described in claim 16, wherein, When the product is heated at 121°C for 10 minutes, the viscosity of the mixture increases by less than 10 Mooney units.

22. A mixture, which is the product of the method as described in claim 16, wherein, When heated at 199°C for 30 seconds, the viscosity of the mixture increased by less than 2 N-dm.

23. A fluoroelastomer article, which is the product of the method described in claim 16.

24. The fluoroelastomer articles as described in claim 23 are gaskets, seals, tubing, sheets, washers or O-rings.

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