Fluoroelastomer compounds

Abstract

The present invention relates to fluoroelastomer compounds comprising specific types of carbon black, and articles cured from these compounds. These particular types of carbon black improve both tensile strength and elongation at break when added to fluoroelastomer compounds.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 384,684, filed on November 22, 2022, the disclosure of which is hereby incorporated herein by reference in its entirety. Technical field

[0003] The present invention relates to fluorocarbon elastomer blends comprising a specific type of carbon black and a curing agent, and articles cured from these blends. Background art

[0004] Elastomer blends containing fluorocarbon elastomers have achieved remarkable commercial success due to their use in harsh environments, particularly during exposure to high temperatures and corrosive chemicals. For example, these blends are used in the hot sections of aircraft engines, seals in oil well drilling equipment, and as sealing elements in industrial equipment operating at high temperatures.

[0005] The properties of cured elastomer blends are mainly due to the stability and inertness of the comonomers that make up the main part of the polymer backbone of these blends. Such monomers include tetrafluoroethylene and perfluoro(alkyl vinyl) ethers. To fully develop elastomeric properties, elastomer blends are typically cross - linked (i.e., vulcanized or cured). For this purpose, a small percentage of cure - site monomers are copolymerized with the monomers (whether fluorinated or perfluorinated). Upon cross - linking, the cure - site monomers react with a curing agent to form a cross - linked elastomeric entity in the form of an article.

[0006] Cure - site monomers containing at least one nitrile group can be used, such as perfluoro - 8 - cyano - 5 - methyl - 3,6 - dioxaoct - 1 - ene, and compositions containing such cure - site monomers are described in U.S. Patent No. 7,999,049, columns 10 to 16.

[0007] Fluorocarbon elastomer blends containing amidines are disclosed in U.S. Patent No. 10,472,494, which is hereby incorporated herein by reference in its entirety.

[0008] The mechanical properties of cured elastomer blends are typically adjusted by incorporating many types of additives. Both tensile strength and elongation at break are highly desired properties for cured elastomer blends, but it is difficult to obtain a combination of high tensile strength and high elongation at break. Summary of the invention

[0009] When added to fluorocarbon elastomer blends, a specific type of carbon black improves both tensile strength and elongation at break.

[0010] The present invention relates to a blend comprising:

[0011] (A) A fluoroelastomer comprising copolymer units of the following items:

[0012] (1) One or more unsaturated fluorinated olefins;

[0013] (2) One or more unsaturated fluorinated olefin comonomers, which are different from (1) and are selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures thereof; and

[0014] (3) One or more curing site monomers selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluoro vinyl ethers;

[0015] (B) At least one curing agent; and

[0016] (C) One or more carbon blacks, at least one of which has a statistical thickness surface area between 20 and 40 m 2 / g.

[0017] The present invention further relates to an article comprising a cured compound, the cured compound comprising, before curing:

[0018] (A) A fluoroelastomer comprising copolymer units of the following items:

[0019] (1) One or more unsaturated fluorinated olefins,

[0020] (2) One or more unsaturated fluorinated olefin comonomers, which are different from (1) and are selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures thereof; and

[0021] (3) One or more curing site monomers selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluoro vinyl ethers;

[0022] (B) At least one curing agent; and

[0023] (C) One or more carbon blacks, at least one of which has a statistical thickness surface area between 20 and 40 m 2 / g. Detailed Description

[0024] Abbreviations

[0025] The claims and the specification herein are explained using the abbreviations and definitions listed below.

[0026] "h", "hrs" mean hour.

[0027] "%" means the term "percent".

[0028] "mol%" means mole percent.

[0029] "wt%" means weight percent.

[0030] "°C" means degree Celsius.

[0031] "parts" means parts by weight.

[0032] "phr" means parts per hundred parts of fluoroelastomer (rubber); this measurement term is used and recognized by those skilled in the art. For example, 3 parts of a component per 100 parts of fluoroelastomer is written as 3 phr. In the blends, methods, and articles described herein, phr is based on 100 parts of fluoroelastomer.

[0033] "g" means gram.

[0034] "Ph" means phenyl ring.

[0035] Definitions

[0036] As used herein, the article "a" means one and more than one and does not necessarily limit the noun it refers to to the singular grammatical category.

[0037] As used herein, when used to modify a quantity or value, the terms "about" and "at or about" mean a quantity or value that is an approximation greater than or less than the exact quantity or exact value recited in the claims or described herein. The exact value of the approximation is determined based on what those skilled in the art would recognize as a suitable approximation of that exact value. As used herein, this term indicates that similar values not precisely recited in the claims or not precisely described herein can result in the same results or effects as those values recited in the claims or described herein, for which results and effects those skilled in the art would recognize as acceptably caused by these similar values.

[0038] As used herein, the term "article" refers to an unfinished or finished item, thing, object, or an element or feature of an unfinished or finished item, thing, or object. As used herein, when the article is unfinished, the term "article" may refer to any item, thing, object, element, device, etc. having a form, shape, or configuration that can undergo further processing to become a finished article. When the article is unfinished, the term "preform" may refer to that form, shape, or configuration, any part of which can undergo further processing to become finished. As used herein, when the article is finished, the term "article" refers to an item, thing, object, element, device, etc. in a form, shape, or configuration suitable for a particular use / purpose without further processing of the entire entity or a part thereof.

[0039] An article may include one or more components or sub-components that are partially finished and awaiting further processing or assembly with other components / sub-components that will together constitute the finished article. Further, as used herein, the term "article" may refer to a system or configuration of articles.

[0040] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", or any other variations thereof refer to non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not limited to the listed elements, but may include other elements not expressly listed or inherent thereto. Further, unless expressly stated to the contrary, "or" refers to inclusive "or" rather than exclusive "or". For example, the condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present). As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "consisting essentially of", and "consisting of", or any other variations thereof may refer to non-exclusive inclusion or exclusive inclusion.

[0041] When these terms refer to more exclusive inclusion, these terms limit the scope of the claim to those materials or steps that substantially affect the novel elements of the invention.

[0042] When these terms refer to complete and exclusive inclusion, these terms exclude any element, step, or component not expressly recited in the claim. As used herein, terms describing a molecule or polymer follow the terms in the IUPAC Compendium of Chemical Terminology, version 2.15 (International Union of Pure and Applied Chemistry) of September 7, 2009.

[0043] As used herein, the term "unsaturated fluorinated olefin" refers to a straight-chain, branched-chain, or cyclic hydrocarbon structure that contains at least one unsaturated double bond and contains at least one fluorine atom.

[0044] As used herein, the term "alkyl" refers to straight-chain, branched-chain, or cyclic hydrocarbon structures and combinations thereof. Alkyl does not include aromatic structures. Examples of straight-chain alkyls include methyl, ethyl, propyl, butyl, pentyl, and hexyl. Branched-chain alkyls include, for example, sec-butyl and tert-butyl, as well as isopropyl. Examples of cyclic hydrocarbon groups include cyclopropyl, cyclopentyl, cyclohexyl, cyclobutyl, and cyclooctyl.

[0045] As used herein, the term "alkoxy" or "alkoxyl" refers to an alkyl group attached to an oxygen atom by a single bond. The other bond of the oxygen atom is connected to a carbon atom. Examples include methoxy, ethoxy, propoxy, isopropoxy, cyclopropoxy, and cyclohexyloxy.

[0046] As used herein, the term "blend" refers to a composition that is capable of being cured (i.e., a curable composition), and refers to a mixture of chemical entities that includes at least a fluoroelastomer and a curing agent. The mixture of chemical entities has not been cured or has not been subjected to processing conditions that would cause the mixture of chemical entities to cure to undergo curing.

[0047] As used herein, the prefix term "fluoro-" when placed as a prefix before a chemical entity name refers to a chemical entity having at least one fluorine atom, as exemplified by the following names: fluoroelastomer, perfluoroelastomer, fluoro vinyl, and perfluoro vinyl ether. The prefix "fluoro-" when placed as a prefix before a chemical entity name expressly includes "perfluoro-" chemical entities. Thus, the prefix "fluoro-" when before a chemical entity name denotes both "fluoro-" entities and "perfluoro-" entities.

[0048] As used herein, the term "cured" refers to the resulting entity that contains a fluoroelastomer and has been exposed to those conditions (i.e., curing conditions) that cause sufficient cross-linking to form among the fluoroelastomer molecules themselves, such that the resulting entity assumes a form or shape or configuration or structure that cannot be reprocessed, molded, or extruded into a different form or shape or configuration or structure. That is, once the resulting entity containing the fluoroelastomer has been exposed to curing conditions and thereby cured, the entity cannot be recured to assume a substantially different form or shape or configuration or structure.

[0049] As used herein, the terms "curing" and "cured" refer to the processing of a blend (also referred to herein as a curable composition) that results in an entity having a form, shape, configuration, or structure that cannot be reprocessed, molded, or extruded into a different form, shape, configuration, or structure. Such processing refers to the "curing process", which requires the blend to be exposed to certain conditions to initiate the curing process, such conditions being referred to as curing conditions.

[0050] The entity resulting from the curing process is a "cured" entity, i.e., an article as defined above. It is to be understood that curing results in a blend having the form, shape, configuration, or structure of an article. Cured articles of the blends described herein include, but are not limited to, O-rings, seals, and gaskets.

[0051] The terms "curing" and "cured" also expressly include different degrees of processing of the blend such that the resulting entity has a form, shape, configuration, or structure that cannot be reprocessed, molded, or extruded into a different form, shape, configuration, or structure and the resulting entity as a result of curing may exhibit certain physical properties.

[0052] In this regard, these blends can initially be cured to achieve a non-reprocessable form, shape, etc., which has been referred to herein as "cured". The cured blend can further be subjected to additional curing conditions that provide additional subsequent curing. Such additional curing conditions may be variously referred to herein as "curing" or "post-curing". That is, the terms "curing" and "cured" refer both to the initial curing process that results in the resulting entity of the first cure and also expressly to any subsequent curing process that results in a resulting entity of a subsequent cure that may or may not have different materials or physical properties from those of the resulting entity of the first cure.

[0053] Ranges and Preferred Variants

[0054] Unless otherwise expressly stated, any range set forth herein expressly includes its endpoints. A quantity, concentration, or other value or parameter set forth as a range specifically discloses all possible ranges formed by any possible upper range limit and any possible lower range limit, regardless of whether such pairs of upper and lower range limits are expressly disclosed herein. The blends, methods, and articles described herein are not limited to the specific values disclosed when defining ranges in the specification.

[0055] The disclosure herein of any variations of the methods, blends, and articles described herein, in terms of materials, chemical entities, methods, steps, values, and / or ranges, etc. (whether or not determined to be preferred), is specifically intended to include any possible combinations of materials, methods, steps, values, ranges, etc. For the purpose of providing detailed, accurate, and sufficient support for the claims, any disclosed combination is a preferred variation of the methods, blends, and articles described herein.

[0056] Blend

[0057] A) Fluoroelastomer

[0058] The fluoroelastomers described herein can be fluorinated or perfluorinated and contain at least the following three comonomer units: (1) one or more unsaturated fluorinated olefins; (2) one or more unsaturated fluorinated olefin comonomers that are different from the unsaturated fluorinated olefin (1) and are selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures thereof; and (3) one or more cure site monomers selected from the group consisting of nitrile-containing fluorinated olefins, nitrile-containing fluoro vinyl ethers, or mixtures thereof, wherein the mole percentage of each of (1), (2), and (3) is based on the total mole percentage of (1), (2), and (3) in the fluoroelastomer.

[0059] Alternatively, the fluoroelastomer can be fluorinated or perfluorinated and contain at least the following three comonomer units: (1) about 25 to 74.9 mole percent of one or more unsaturated fluorinated olefins; (2) about 25 to 74.9 mole percent of one or more unsaturated fluorinated olefin comonomers that are different from the unsaturated fluorinated olefin (1) and are selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures of at least two of fluoro vinyl ethers, unsaturated fluorinated olefins, and unsaturated olefins; and (3) about 0.1 to 10 mole percent of one or more cure site monomers selected from the group consisting of nitrile-containing fluorinated olefins, nitrile-containing fluoro vinyl ethers, or mixtures thereof, wherein the mole percentage of each of (1), (2), and (3) is based on the total mole percentage of (1), (2), and (3) in the fluoroelastomer.

[0060] Due to the use of different initiators or chain transfer agents during polymerization, the fluoroelastomers described herein can contain any of a variety of end groups. Non-limiting examples of end groups include sulfonate esters, sulfonic acids, carboxylic acid esters, carboxylic acids, carboxamides, difluoromethyl, trifluorovinyl, or perfluorinated alkyl groups.

[0061] (1) Unsaturated fluorinated olefin

[0062] Unsaturated fluorinated olefin (1) includes unsaturated monomers containing at least one fluorine atom, alternatively at least two fluorine atoms, and alternatively perfluorinated monomers. Examples of unsaturated fluorinated olefins include tetrafluoroethylene (C2F4), hexafluoropropylene, 1,1-difluoroethylene; 1,1,2-trifluoroethylene; 1-fluoroethylene; and combinations thereof. The concentration of unsaturated fluorinated olefin (1) can range from 25 to 74.9 mole percent of the total moles of monomer units in the fluoroelastomer.

[0063] (2) Unsaturated fluorinated olefin comonomer

[0064] The unsaturated fluorinated olefin comonomer (2) different from the unsaturated fluorinated olefin (1) is selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures thereof.

[0065] Examples of fluoro vinyl ethers for preparing fluoroelastomers include perfluoro(alkyl vinyl) ethers (PAVE), perfluoro(alkoxy vinyl) ethers, fluoro(alkyl vinyl) ethers, fluoro(alkoxy vinyl) ethers, and mixtures thereof. Suitable perfluorinated (alkyl vinyl) ethers that can be used to prepare the blends described herein include those represented by formulas (II) to (VI):

[0066] CF2=CFO(R f′ O) n (R f″ O) m R f (II)

[0067] wherein R f′ and R f″ are different straight-chain or branched perfluoroalkylene groups having 2-6 carbon atoms, m and n are independently 0-10, and R f is a perfluoroalkyl group having 1-6 carbon atoms.

[0068] Additional examples of perfluoro(alkyl vinyl) ethers include compositions having formula (III):

[0069] CF2=CFO(CF2CFXO) n R f (III),

[0070] wherein X is F or CF3, n is 0-5, and R f is a perfluoroalkyl group having 1-6 carbon atoms. Alternatively, n is 0 or 1, and R f contains 1-3 carbon atoms. Examples of such perfluorinated (alkyl vinyl) ethers include perfluoro(methyl vinyl) ether and perfluoro(propyl vinyl) ether.

[0071] Other perfluoro(alkyl vinyl) ether monomers useful for preparing fluorine elastomers include monomers having the formulas (IV), (V), and (VI):

[0072] CF2=CFO[(CF2) m CF2CFZO] n R f (IV),

[0073] wherein R f is a perfluoroalkyl group having 1 to 6 carbon atoms, m = 0 or 1, n = 0 - 5, and Z = F or CF3;

[0074] CF2=CFO[(CF2CFCF3O) n (CF2CF2CF2O) m (CF2) p C x F 2x+1 (V),

[0075] wherein m and n = 1 - 10, p = 0 - 3, and x = 1 - 5. Specific examples of this type include monomers wherein n = 0 - 1, m = 0 - 1, and x = 1, and

[0076] CF2=CFOCF2CF(CF3)O(CF2O) m C n F 2n+1 (VI),

[0077] wherein n = 1 - 5, m = 1 - 3, and wherein, alternatively, n = 1.

[0078] Examples of perfluoro(alkyl vinyl) ethers include perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluoroethyl vinyl ether. Examples of perfluoro(alkoxy vinyl) ethers include perfluoromethoxy vinyl ether, perfluoropropoxy vinyl ether, and perfluoroethoxy vinyl ether.

[0079] Examples of unsaturated fluorinated olefins include tetrafluoroethylene (C2F4); hexafluoropropene; 1,1 - difluoroethylene; 1,1,2 - trifluoroethylene; 1 - fluoroethylene; 1 - fluoropropene; 1,1 - difluoropropene; 1,1,3 - trifluoropropene; 1,1,3,3,3 - pentafluoropropene; and combinations thereof. Examples of unsaturated olefins include ethylene, propylene, 1 - butene, 2 - butene, and combinations thereof. Mixtures of fluoro vinyl ethers, unsaturated fluorinated olefins, and unsaturated olefins can also be used.

[0080] The concentration of the unsaturated fluorinated olefin comonomer in the fluoroelastomer ranges from 25 to 74.9 mole percent, alternatively from 30 to 65 mole percent, alternatively from 45 to 55 mole percent, based on the total mole percent of the monomer units in the fluoroelastomer.

[0081] (3) Curing site monomer

[0082] The fluoroelastomer (A) further comprises copolymerized units of one or more curing site monomers containing at least one nitrile substituent. Alternatively, the curing site monomer is selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers (3). The amount of such curing site monomers is generally from 0.1 to 10 mole percent, alternatively between 0.3 and 1.5 mole percent, based on the total mole percent of the polymerizable monomer units used to prepare the fluoroelastomer. Although there may be more than one type of curing site monomer, the curing site monomer contains at least one nitrile substituent. Useful nitrile-containing curing site monomers include those having the formulas (VII)-(XI):

[0083] CF2=CF-O(CF2) n -CN(VII)

[0084] where n = 2-12, alternatively 2-6;

[0085] CF2=CF-O[CF2-CFCF3-O] n -CF2-CFCF3-CN(VIII),

[0086] where n = 0-4, alternatively 0-2;

[0087] CF2=CF-[OCF2CFCF3] x -O-(CF2) n -CN(IX),

[0088] where x = 1-2, and n = 1-4; and

[0089] CF2=CF-O-(CF2) n -O-CF(CF3)CN(X),

[0090] where n = 2-4.

[0091] The monomer having the formula (IX) is used as the curing site monomer. In particular, the curing site monomer includes a perfluorinated polyether having a nitrile group and a trifluorovinyl ether group. Alternatively, the curing site monomer is perfluoro(8-cyano-5-methyl-3,6-dioxaoct-1-ene) (8-CNVE) and is represented by the formula (XI):

[0092] CF2=CFOCF2CF(CF3)OCF2CF2CN(XI)

[0093] B) Curing agent

[0094] The blend contains at least one curing agent (B). Any curing agent can be used as long as it can react with the above-mentioned curing sites.

[0095] A suitable curing agent (B) is a compound that decomposes to produce ammonia at a temperature between 40 °C and 330 °C, alternatively between 90 °C and 220 °C. It is also referred to as an ammonia-producing compound. Examples of such ammonia-producing compounds include dicyandiamide, aldehyde-ammonia condensation products (including acetaldehyde ammonia); and other compounds such as hexamethylenetetramine; carbamates, such as tert-butyl carbamate, benzyl carbamate, and HCF2CF2CH(CH3)OCONH2; ureas; urea hydrochlorides; thioureas; amides, such as phthalimide; metal ammonia complexes, such as tetraamine copper(II) hydrate; ammonia-Lewis acid adducts; formamides, such as oxamic acid; biurets; unsubstituted amidines, such as formamidine, formamidine hydrochloride, and formamidine acetate.

[0096] Another suitable curing agent (B) is a compound that produces nitrogen-containing heterocyclic cross-links. Examples of such compounds include triazines, benzimidazoles, benzoxazoles, triazoles, amidines, and hydrazides.

[0097] Other examples of the types of curing agents (B) that can be used in the blends described herein include organotin curing agents or amino-containing benzene curing agents. Non-limiting examples of organotin curing agents include, but are not limited to, allyltin, propargyl-triphenyltin, and allenyltin curing agents. Specific examples of organotin curing agents include tetraalkyltin, tetraaryl tin, and tetraphenyltin curing agents.

[0098] Examples of amino-containing benzene curing agents include bis(aminophenol) and bis(aminobenzenethiol) having the formulas (XII) and (XIII)

[0099]

[0100] and tetraamines having the formula (XIV)

[0101]

[0102] Wherein A is SO2, O, CO, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, or a carbon-carbon bond connecting two aromatic rings. The amino and hydroxyl groups in the above formulas XII and XIII are interchangeable at the meta and para positions relative to the group A. Specific examples of the bis(aminophenol) and bis(aminobenzenethiol) curing agents include 2,2-bis[3-amino-4-hydroxyphenyl]hexafluoropropane (diaminodiphenol AF); 4,4′-sulfonylbis(2-aminophenol); 3,3′-diaminobenzidine; and 3,3′,4,4′-tetraaminobenzophenone, among which 3,3′-diaminobenzidine is preferred.

[0103] The amount of curing agent employed will necessarily depend on the desired degree of crosslinking in the final product and the type and concentration of the reactive moieties in the blend described herein. An example of the level of the curing agent should be about 0.1 to 7 parts of the compound per 100 parts of the perfluoroelastomer, preferably about 1 to 5 parts of the compound per 100 parts of the perfluoroelastomer.

[0104] C) Carbon black

[0105] The blend of the present invention comprises one or more carbon blacks (C). The carbon black of the present invention has a statistical thickness surface area (STSA) measured by ASTM D6556-07 between 20 and 40 m 2 / g. The STSA is the outer surface area accessible to the rubber, while the total surface measurement (NSA measurement) is the total surface area including micropores. The STSA of the carbon black used in the formulation of the present invention may alternatively be between 25 and 35 m 2 / g.

[0106] In addition to the STSA, the iodine adsorption rate is higher than 60 g / kg and desirably higher than 145 g / kg. The iodide absorption rate can be measured according to ASTM D1510.

[0107] Furthermore, the carbon black of the present invention has a DBP absorption rate of a nitrogen surface area higher than 50 cm 3 / 100 g and alternatively 74 cm 3 / 100 g. The nitrogen surface area can be measured according to ASTM D2414B.

[0108] In addition, the pH of the carbon black is higher than 7 and alternatively higher than 9.

[0109] The pH can be measured according to ASTM D1512.

[0110] This type of carbon black has undetectable PAH (polycyclic aromatic hydrocarbons) with a detection limit of 5 ppb. The carbon black of the present invention can be amorphous.

[0111] The inventors of the present invention have found that when such specific carbon blacks are used in fluoroelastomer blends, the tensile strength increases without a decrease in the elongation at break.

[0112] An example of a carbon black having the properties disclosed above is Carbon Neat 90 available from CarbonNeat Corporation.

[0113] The concentration of carbon black (C) in these blends ranges from 1 to 100 phr, alternatively 5 to 100 phr.

[0114] Two or more carbon blacks can be used. When two or more carbon blacks are used, at least one carbon black needs to be the above-mentioned carbon black.

[0115] Other components

[0116] The blends described herein can additionally contain non-perfluoroelastomers capable of crosslinking independently with the curing sites of any fluoroelastomer (A). Examples of non-perfluoroelastomers are those having at least one crosslinkable group selected from the group consisting of: cyano (-CN), carboxyl (-COOH), alkoxycarbonyl (-COOR9, where R9 is a monovalent organic group), and acyl halide (-COX1, where X1 is a halogen atom) capable of undergoing a crosslinking reaction with the fluoroelastomer (A).

[0117] Examples of non-perfluoroelastomers include, but are not limited to, fluorine-containing but not perfluorinated rubbers; thermoplastic fluororubbers; and rubber compositions containing fluororubbers.

[0118] The fluororubber can contain monomer units independently selected from the group consisting of vinylidene fluoride (VDF), tetrafluoroethylene, and hexafluoropropylene, and at least one additional monomer such as tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl ether), chlorotrifluoroethylene, trifluoroethylene, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, vinyl fluoride, and iodine-containing fluorinated vinyl ethers, ethylene, propylene, alkyl vinyl ethers, and combinations thereof.

[0119] Additives typically used in compounding such as stabilizers, plasticizers, lubricants, fillers, and processing aids can be incorporated into the blends described herein provided they have sufficient stability for the intended use conditions. In particular, low-temperature performance can be enhanced by incorporating perfluoropolyethers.

[0120] In addition to or in combination with carbon black, non-carbon black fillers may be present in the blends described herein. Examples of non-carbon black fillers that may be used include anhydrous silica, such as acidic silica or fumed silica. Such silica is available from Degussa Aktiengesellschaft (Frankfurt, Germany) under the trademark. A particularly useful type is 200 silica. Other suitable silicas include those available from Tokuyama KK (Tokyo, Japan), such as silica, e.g., QS13, QS102, and QS30. The amount of silica ranges from 1 to 25 phr, alternatively not exceeding 1 to 7 phr.

[0121] Additional types of fillers include micronized or fluorine additives. Micronized materials are generally partially crystalline polymers. Micronized materials include finely divided, readily dispersible plastic fluoropolymers that are solid at the highest temperatures used in the manufacture and curing of the blends described herein. The term "solid" refers to a plastic fluoropolymer having a crystalline melting temperature above the processing temperature of the blends described herein.

[0122] Micronized materials that may be used in these blends include, but are not limited to, micronized materials based on polymers of the group known as tetrafluoroethylene (TFE) polymers. This group includes polytetrafluoroethylene (PTFE) and copolymers of TFE with a small concentration of at least one copolymerizable modifying monomer of about 1 mole percent or less such that the micronized material does not melt or soften during the processing of the fluoroelastomer A containing the micronized material. The modifying monomer may be, for example, hexafluoropropylene (HFP), perfluoro(propyl vinyl) ether (PPVE), perfluorobutylethylene, chlorotrifluoroethylene, or another monomer that introduces a side group into the polymer molecule.

[0123] TFE copolymers used as additives in these blends include copolymers of TFE having a sufficient concentration of copolymer units of one or more monomers to reduce the melting point to below that of PTFE. Such copolymers generally have a melting point in the range of 0.5 - 60×10 3The melt viscosity is within the range of Pa·s, but viscosities outside this range are also known. Perfluoroolefins and perfluoro(alkyl vinyl) ethers are preferred comonomers. Hexafluoropropene and perfluoro(propyl vinyl) ether are most preferred. Examples of TFE copolymers include TFE / hexafluoropropene copolymers and TFE / perfluoro(propyl vinyl) ether copolymers, provided that they meet the restrictions on the melting temperature relative to the processing temperature of the perfluoroelastomer. If the particle size is acceptable, then these copolymers can be used in the form of a powder separated from the polymerization medium, or they can be ground to a suitable particle size starting from a larger size feedstock.

[0124] The amount of non-carbon black filler in these blends ranges from about 0.01 to 33 phr and alternatively at least about 1 to 5 phr.

[0125] Methods for preparing blends and cured articles

[0126] The blends described herein can be prepared by using rubber compounding procedures such as a two-roll rubber mill, a Banbury mixer (e.g., a Banbury mixer), or by mixing the fluoroelastomer (A), one or more curing agents (B), carbon black (C), and optional components in an extruder until homogeneous. These blends can be cured by applying heat and / or pressure sufficient to cause the curing agent (B) to form crosslinks with one or more cure site monomers, or a dual-cure system can also be used. When compression molding is used for curing, a pressure curing cycle is followed by a post-curing cycle, during which the pressure-cured blend is heated at a high temperature above 300 °C for several hours.

[0127] When cured, the blends described herein become the articles described herein and exhibit suitable thermal stability and chemical resistance for the applications in which these articles are used. In particular, articles cured from these blends show a combination of high tensile strength and high elongation at break. These articles are useful as seals and gaskets for high-temperature environments, in a wide range of chemical environments, in seals for high-temperature automotive applications, and as O-rings.

[0128] Examples

[0129] Materials

[0130] Fluoroelastomer (FE): Comprising 48.8 wt.% of tetrafluoroethylene (TFE) units, 49.0 wt.% of perfluoro(methyl vinyl) ether (PMVE) units, and 2.2 wt.% of perfluoro(8-cyano-5-methyl-3,6-dioxaoct-1-ene) (8-CNVE) units. The fluoroelastomer can be prepared by the method disclosed in U.S. Patent No. 5,789,489, columns 10 to 11.

[0131] Perfluoro(methyl vinyl ether): Available from Chemours.

[0132] 8-CNVE: Perfluoro(8-cyano-5-methyl-3,6-dioxaoct-1-ene), which can be prepared by the method disclosed in U.S. Patent No. 5,637,748.

[0133] Curing agent (CA-1): Dicyandiamide available from Sigma aldrich.

[0134] Carbon black 1 (CB-1): N908 medium thermal carbon black, with STSA of 6 - 9, available from Cancarb Limited, Alberta, Canada.

[0135] Carbon black 2 (CB-2): Neat90, available from CarbonNeat, Room 102, 16930 West Catawba Avenue, Cornelius, NC 28031, STSA: 28 - 30

[0136] The materials shown in Table 1 were used to prepare Example 1 (E1), Example 2 (E2) and Comparative Example 1 (CE1) by compounding these components on a two-roll rubber mill. The milled compound was formed into sheets, and sample dies were punched into one or more O-rings (AS214) or one or more dumbbell (Dogbone) shapes to form test samples. Elongation at break and tensile strength were measured according to ASTM D1414.

[0137] Table 1

[0138]

[0139]

Claims

1. A blend, comprising: (A) A fluoroelastomer comprising copolymer units of: (1) One or more unsaturated fluorinated olefins; (2) One or more unsaturated fluorinated olefin comonomers different from (1) and selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures thereof; and (3) One or more curing site monomers selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluoro vinyl ethers; (B) At least one curing agent; and (C) One or more carbon blacks, at least one of which has a statistical thickness surface area between 20 and 40 m 2 / g.

2. The admixture according to claim 1, wherein, The curing agent comprises a compound that decomposes to produce ammonia at a temperature between 40 °C and 330 °C.

3. The admixture according to claim 1, wherein, The curing agent comprises a compound that produces nitrogen-containing heterocyclic crosslinking bonds.

4. The admixture according to any one of claims 1 to 3, wherein, The carbon black has an iodine absorption rate of at least 60 g / kg.

5. The admixture according to any one of claims 1 to 4, wherein, The carbon black comprises two or more types of carbon black.

6. The admixture according to any one of claims 1 to 5, wherein, The unsaturated fluorinated olefin is selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and mixtures thereof.

7. The admixture according to any one of claims 1 to 6, wherein, The unsaturated fluorinated olefin comonomer is selected from the group consisting of perfluoro(methyl vinyl) ether, hexafluoropropylene, perfluoro(propyl vinyl) ether, and mixtures thereof.

8. The admixture according to any one of claims 1 to 7, wherein The curing agent is selected from the group consisting of amidinium amidine HCl, N′,N″-diamino amidine; phenyloxoamino amidine, 3-(5-phenyl-4H-1,2,4-triazolyl) amidine, 1H-pyrrolyl amidine, benzimidazolyl amidine, aminothioxo amidine; amidinyl thiourea, dicyandiamide, aminocarbonylmethyl amidine HCl, N-amino amidine bicarbonate, N″-1H-pyrazolyl-N′-tert-butoxycarbonyl amidine, 2-pyridyl amidine HCl, sulfinic amidine; and mixtures thereof.

9. The blend according to any one of claims 1 to 8, further comprising at least one filler selected from the group consisting of non-perfluorinated fluoroelastomers, fine powders, stabilizers, plasticizers, lubricants, processing aids, and mixtures thereof.

10. An article comprising a cured blend, the cured blend comprising, before curing: (A) A fluoroelastomer comprising copolymer units of: (1) One or more unsaturated fluorinated olefins, (2) One or more unsaturated fluorinated olefin comonomers different from (1) and selected from the group consisting of fluoro vinyl ethers, unsaturated fluorinated olefins, unsaturated olefins, and mixtures thereof; and (3) One or more curing site monomers selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluoro vinyl ethers; (B) At least one curing agent; and (C) one or more carbon blacks, at least one of which has a statistical thickness surface area between 20 and 40 m 2 / g.

11. The article according to claim 10, wherein the article is in the form of a gasket, tube, seal, and O-ring.

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