Fluoroelastomer Compounds

Abstract

Fluoroelastomer compounds containing certain types of carbon black, and cured articles formed from the compounds, which exhibit many useful properties in cured fluoroelastomer articles.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to fluoroelastomer compounds containing certain types of carbon black and cured articles formed therefrom. [Background technology]

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 384,691, filed November 22, 2022, the disclosure of which is expressly incorporated herein by reference in its entirety.

[0003] Fluoroelastomer (FKM or FPM) articles are characterized by their resistance to high temperatures, acids and alkalis, oils, and chemicals. The properties of FKM articles arise primarily from the stability and inertness of the copolymerized monomers that make up the majority of the polymeric backbone of these compounds. Such monomers include tetrafluoroethylene (TFE) and vinylidene fluoride (VDF). To fully develop their elastomeric properties, elastomeric compounds are typically crosslinked, i.e., vulcanized or cured. For this purpose, a small percentage of cure site monomers, optionally copolymerized with the monomers, are used. By crosslinking, the cure site monomers react with the curing agent to form a crosslinked elastomeric body in the form of an article.

[0004] Mechanical properties such as low compression set are also required for fluoroelastomer articles for use in various industries. The mechanical properties of cured elastomer compounds are usually adjusted by incorporating additives. Carbon black is used as an additive to improve mechanical properties. U.S. Pat. No. 10,472,494, the entirety of which is incorporated herein by reference, discloses a fluoroelastomer compound containing a specific type of curing agent and carbon black having an average particle size of at least about 100 nm to about 500 nm.

[0005] The final properties of the finished product can also vary depending on the type of curing agent selected, so it is important to select an appropriate curing agent that allows for good processing and achieves good mechanical properties. Summary of the Invention [Means for solving the problem]

[0006] Fluoroelastomer compounds containing certain types of carbon black exhibit many useful properties in cured fluoroelastomer articles.

[0007] The present invention provides (A) a fluoroelastomer having a hydrogen content of at least 0.75% by weight; (B) a curing agent comprising an organic peroxide and a multifunctional coagent; (C) one or more carbon blacks, wherein at least one of the carbon blacks has a molecular weight of 20 to 40 m 2 / g of a statistical thickness specific surface area; The present invention relates to a compound comprising:

[0008] The present invention further relates to articles manufactured using the compounds disclosed above. DETAILED DESCRIPTION OF THE INVENTION

[0009] (abbreviation) The claims and the description herein should be interpreted using the abbreviations and definitions set forth below. "h" and "hrs" refer to hours. "%" refers to the term percent. "Mol %" refers to mole percent. "wt%" refers to weight percent. "°C" refers to degrees Celsius. "Parts" refers to parts by weight. "phr" refers to parts per hundred parts of fluoroelastomer (rubber); those skilled in the art use and recognize this measurement term. For example, 3 parts of a component per 100 parts of fluoroelastomer would be written as 3 phr. In these compounds, processes, and articles described herein, phr is based on 100 parts fluoroelastomer. "g" stands for gram.

[0010] (definition) As used herein, the article "a" refers to one as well as more than one and does not necessarily restrict its referent noun to the grammatical category of singular.

[0011] As used herein, the terms "about" and "exactly or approximately," when used to modify an amount or value, refer to an approximation of an amount or value that is greater than or less than the exact amount or value recited in a claim or the present specification. The exact value of an approximation is determined by what a person skilled in the art would recognize as an appropriate approximation to the exact value. As used herein, terms conveying similar values ​​that are not exactly recited in a claim or the present specification can produce results or effects equivalent to those recited in the claim or the present specification, and therefore, a person skilled in the art would recognize that they are acceptable results of similar values.

[0012] As used herein, the term "article" refers to an unfinished or finished item, thing, object, or element or feature of an unfinished or finished item, thing, or object. As used herein, if the article is unfinished, the term "article" can refer to any item, thing, object, element, device, etc. having a form, shape, configuration that can undergo further processing to become a finished product. When the article is unfinished, the term "preform" can refer to the form, shape, configuration of which any portion can undergo further processing to become a finished product. As used herein, if the article is finished, the term "article" refers to the article, thing, object, element, device, etc. in a form, shape, configuration that is suitable for a particular use / purpose without further processing in whole or in part.

[0013] An article may include one or more elements or subassemblies that are either partially completed and awaiting further processing, or are in assembly with other elements / subassemblies that together would comprise a completed article. Additionally, as used herein, the term "article" may refer to a system or configuration of articles.

[0014] As used herein, the terms "include," "including," "includes," "including," "having," "having," or any other variation thereof, refer to a non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not limited to only the listed elements and may include other elements not expressly listed or inherent. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive or, not an exclusive, inclusive or. For example, 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 A and B are both true (or present). As used herein, the terms "include," "including," "including," "having," "consisting essentially of," and "consisting of," or any other variation thereof, may refer to either a non-exclusive or an exclusive inclusion.

[0015] When these terms refer to a more exclusive inclusion, they limit the scope of the claim to those recited materials or steps that materially affect the novel element of the invention being described.

[0016] When these terms refer to an entirely exclusive inclusion, they exclude any element, step, or ingredient not expressly recited in the claim. As used herein, terms describing molecules or polymers follow the terminology in the IUPAC Compendium of Chemical Terminology_version 2.15 (International Union of Pure and Applied Chemistry), dated September 7, 2009.

[0017] As used herein, the prefix "fluoro," when placed as a prefix before a chemical name, indicates that at least one hydrogen atom of the chemical has been replaced with a fluorine atom.

[0018] As used herein, the term "fluorinated olefin" refers to a linear, branched, or cyclic fluorinated hydrocarbon structure containing at least one unsaturated double bond.

[0019] As used herein, the term "alkyl" refers to linear, branched, or cyclic hydrocarbon structures and combinations thereof. Alkyl does not include aromatic structures. Examples of linear alkyl groups include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups. Examples of branched alkyl groups include, for example, s- and t-butyl, and isopropyl groups. Examples of cyclic hydrocarbon groups include cyclopropyl, cyclopentyl, cyclohexyl, cyclobutyl, and cyclooctyl groups.

[0020] As used herein, the term "alkoxy" or "alkoxyl" refers to an alkyl group connected to an oxygen atom by a single bond. The other bond to the oxygen atom is connected to a carbon atom. Examples include methoxy, ethoxy, propoxy, isopropoxy, cyclopropyloxy, and cyclohexyloxy.

[0021] As used herein, the term "another curing agent different from curing agent B" refers to a curing agent that does not have the same chemical structure as curing agent B.

[0022] As used herein, the term "compound" refers to a composition that is curable, i.e., a curable composition and a mixture of chemicals that includes at least a fluoroelastomer and a curing agent, which mixture of chemicals has not been cured or subjected to processing conditions that would cause the mixture of chemicals to undergo curing.

[0023] As used herein, the term "cured" refers to a resultant material that includes a fluoroelastomer and that has been exposed to those conditions (i.e., cure conditions) that cause the fluoroelastomer molecules to form sufficient crosslinks between them so that the resultant material assumes a form, shape, configuration, or structure that cannot be reprocessed, molded, or extruded into a different one. That is, once the resultant material that includes a fluoroelastomer has been cured by exposure to cure conditions, the material cannot be recured to assume a substantially different form, shape, configuration, or structure.

[0024] As used herein, the terms "curing" and "cured" refer to the processing of a compound (also referred to herein as a curable composition) that results in a material that assumes a form or shape or configuration or structure that cannot be reprocessed, molded, or extruded into something different. Such processing is referred to as a "curing process / treatment" that requires exposure of the compound to specific conditions (such conditions are referred to as curing conditions) to initiate the curing process.

[0025] The material resulting from the curing process is a "cured" material, i.e., an article as defined herein above. For clarity, curing results in the compound taking on the form, shape, configuration, or structure of an article. Cured articles of the compounds described herein include, but are not limited to, O-rings, seals, and gaskets.

[0026] The terms "curing" and "cured" also expressly include varying degrees of processing of a compound such that the resulting material assumes a form or shape or configuration or structure that cannot be reprocessed, molded, or extruded into something different and may exhibit particular physical properties as a result of curing.

[0027] In essence, these compounds may be initially cured to reach a non-reprocessable form, shape, etc., which is referred to herein as "curing." The cured compound may then be subjected to additional curing conditions, which provide additional subsequent cure. Such additional curing conditions may be variously referred to herein as either "curing" or "post-curing." That is, the terms "curing" and "cured" refer to the initial curing process that results in an initially cured, resulting material, and also specifically refer to any subsequent curing process that results in a subsequently cured, resulting material that may or may not have different material or physical properties than that of the initially cured, resulting material.

[0028] (Scope and Preferred Variants) Any range described herein expressly includes its endpoints unless otherwise specified. The description of an amount, concentration, or other value or parameter as a range specifically discloses all possible ranges formed from any possible range upper limit and any possible range lower limit, regardless of whether such range upper and lower limit pairs are expressly disclosed herein. The compounds, processes, and articles described herein are not limited to the specific values ​​disclosed in defining ranges in this description.

[0029] The disclosure herein of any variations on the materials, chemicals, methods, steps, values ​​and / or ranges, etc. of the processes, compounds and articles described herein is specifically intended to include—whether identified as preferred or non-preferred—any possible combination of materials, methods, steps, values, ranges, etc. For purposes of providing accurate and sufficient support for the claims, any disclosed combination is a preferred variation of the processes, compounds and articles described herein.

[0030] Compound A) Fluoroelastomer Fluoroelastomers (FKM) are typically copolymers containing 25 to 75 weight percent copolymerized units of a first fluoromonomer, which may be vinylidene fluoride (VDF) or tetrafluoroethylene (TFE), based on the total weight of the fluoroelastomer. The remaining units in the fluoroelastomer are composed of one or more additional copolymerized monomers different from the first monomer, selected from the group consisting of fluoromonomers, hydrocarbon olefins, and mixtures thereof. Examples of such copolymerized monomers include perfluoromethyl vinyl ether (PMVE), ethylene (E), propylene (P), and hexafluoropropylene (HFP). The hydrogen content of the fluoroelastomer (FKM) is at least 0.75 weight percent, based on the total weight of the fluorocarbon elastomer.

[0031] The fluoroelastomer may optionally contain units of one or more cure site monomers. When present, copolymerized cure site monomers typically amount to 0.05 to 7 wt. % based on the total weight of the fluoroelastomer. Examples of suitable cure site monomers include i) bromine-, iodine-, or chlorine-containing fluorinated olefins or fluorinated vinyl ethers; ii) nitrile-group-containing fluorinated olefins or fluorinated vinyl ethers; and iii) non-conjugated dienes. The fluoroelastomer may contain diiodoperfluoroalkane compounds I (CF2), which provide cure sites attached to the thermal carbon of the fluoroelastomer. n The polymerization can be carried out in the presence of an iodide- or bromine-containing chain transfer agent such as I (wherein n is 3 to 7).

[0032] Preferred TFE-based fluoroelastomer copolymers include FE / PMVE / E, TFE / P, and TFE / P / VDF. Preferred VDF-based fluorocarbon elastomeric copolymers include VDF / HFP, VDF / HFP / TFE, and VDF / PMVE / TFE. Any of these elastomeric copolymers may further contain cure site monomer units and cure sites formed by iodine- or bromine-containing chain transfer agents.

[0033] Fluoroelastomers (FKM) typically have glass transition temperatures below 25° C., exhibit little or no crystallinity at room temperature, and exhibit little or no melting temperature.

[0034] (B) Hardener The fluoroelastomers used in the compounds of the present invention are capable of undergoing a crosslinking reaction with a curing agent.

[0035] The curing agent is an organic peroxide / multifunctional coagent system. Useful organic peroxides are those that generate free radicals at the curing temperature. Dialkyl peroxides or bis(dialkyl peroxides) that decompose at temperatures above 50°C are particularly preferred. In many cases, it is preferred to use di-tert-butyl peroxide, which has a tertiary carbon atom attached to the peroxy oxygen. 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane are the most useful of this type of peroxide. Other peroxides can be selected from compounds such as dicumyl peroxide, dibenzoyl peroxide, tert-butyl perbenzoate, and di[1,3-dimethyl-3-(t-butylperoxy)butyl]carbonate. When present in the curable compositions of the present invention, 1 to 5 phr of peroxide is generally used.

[0036] The polyfunctional coagent used with the organic peroxide is a polyunsaturated compound that can cooperate with the peroxide to provide a useful cure. These coagents can be added in amounts of 0.1 to 10 phr, preferably 2 to 5 phr. The coagent can be one or more of the following compounds: triallyl cyanurate; triallyl isocyanurate (TAIC); polytriallyl isocyanurate, tri(methallyl)isocyanurate; tris(methallyl)isocyanate (TMAIC); tris(diallylamine)-s-triazine; triallyl phosphite; N,N-diallylacrylamide; hexaallyl phosphoramide; N,N,N',N'-tetraalkyltetraphthalamide; N,N,N',N'-tetraallylmalonamide; trivinyl isocyanurate; 2,4,6-trivinylmethyltrisiloxane; and tri(5-norbornene-2-methylene)cyanurate. Triallyl isocyanurate (TAIC) and tri(methallyl) isocyanate (TMAIC) are particularly useful.

[0037] (C) Carbon black The compounds of the present invention contain one or more carbon blacks. One of the carbon blacks of the present invention is 20 to 40 m 2 / g, or 25-35m 2 / g 2 The statistical thickness specific surface area (STSA) is the external surface area accessible to the rubber, and the total surface area (NSA measurement) is the total surface area including micropores. STSA can be measured according to ASTM D6556-07.

[0038] In addition, the iodine adsorption number is greater than 60 g / kg, and ideally at least 145 g / kg. Iodide adsorption can be measured according to ASTM D1510.

[0039] Furthermore, the carbon black of the present invention has a particle size of at least 50 cm 3 / 100g DBP absorption or at least 74cm 3The nitrogen adsorption specific surface area can be measured in accordance with ASTM D2414B.

[0040] Additionally, the pH of the carbon black is at least 7, alternatively at least 9.

[0041] The pH can be measured according to ASTM D1512.

[0042] This type of carbon black has undetectable PAHs (polycyclic aromatic hydrocarbons), with a detection limit of 5 ppb.

[0043] The carbon black of the present invention may be amorphous.

[0044] An example of a carbon black having the above disclosed properties is CarbonNeat 90, available from CarbonNeat, 16930 West Catawba Ave., Suite 102, Cornelius, NC 28031.

[0045] The concentration of carbon black (C) in the compound ranges from 1 to 100 phr, or from 5 to 60 phr.

[0046] More than one type of carbon black can be used, and if more than one type of carbon black is used, at least one of the carbon blacks must be a carbon black described above.

[0047] When such specific carbon blacks are used, the compositions exhibit good mechanical properties and excellent compression set.

[0048] Other ingredients The compounds described herein may further include a metal sulfide, such as those disclosed in U.S. Patent Application Publication No. 2017 / 0022347A. Examples of such metal sulfides include calcium sulfide, magnesium sulfide, manganese sulfide, iron sulfide, and copper sulfide. The concentration of the metal sulfide is typically about 0.1 to 20 phr, preferably 1 to 20 phr, and more preferably 5 to 20 phr.

[0049] Additives typically utilized in compounding, such as stabilizers, plasticizers, lubricants, fillers, and processing aids, can be incorporated into the compounds described herein, provided they are sufficiently stable under the intended conditions of use. In particular, the incorporation of perfluoropolyethers can enhance low temperature performance.

[0050] In addition to or in combination with carbon black, non-carbon black fillers may be present in the compounds described herein. Examples of non-carbon black fillers that may be used include anhydrous silicas, such as acidic silica or fumed silica. Such silicas are available from Degussa Aktiengesellschaft (Frankfurt, Germany) under the Aerosil® trademark. A particularly useful type is Aerosil® 200 silica. Other suitable silicas include Reolosil® silicas, such as Reolosil® QS13, Reolosil® QS102, and Reolosil® QS30, available from Tokuyama Corporation (Tokyo). The amount of silica ranges from 1 to 25 phr, but is preferably 1 to 7 phr or less.

[0051] Additional types of fillers include fine powders or fluoroadditives. Fine powders are usually partially crystalline polymers. Fine powders include finely divided, easily dispersed plastic fluoropolymers that are solid at the highest temperatures used in the manufacture and curing of the compounds described herein. The term "solid" refers to plastic fluoropolymers that have a crystalline melting temperature higher than the processing temperature of the compounds described herein.

[0052] Fine powders that can be used in these compounds include, but are not limited to, those primarily from the group of polymers known as tetrafluoroethylene (TFE) polymers. This group includes polytetrafluoroethylene (PTFE) and copolymers of TFE with a low concentration of at least one copolymerizable modifying monomer, about 1 mole percent or less, so that the fine powder does not melt or soften during processing of the fluoroelastomer A containing the fine powder. The modifying monomer can be, for example, hexafluoropropylene (HFP), perfluoro(propyl vinyl) ether (PPVE), perfluorobutylethylene, chlorotrifluoroethylene, or another monomer that introduces a side group into the polymer molecule.

[0053] Tetrafluoroethylene polymers used as additives in these compounds include copolymers of TFE having copolymerized units of one or more monomers in a sufficient concentration to lower the melting point below that of PTFE. Such copolymers typically have a viscosity of 0.5 to 60 x 10 3They have melt viscosities in the Pa·s range, although viscosities outside this range are known. Perfluoroolefins and perfluoro(alkyl vinyl) ethers are preferred comonomers. Hexafluoropropylene and perfluoro(propyl vinyl) ether are most preferred. Examples of TFE copolymers include TFE / hexafluoropropylene copolymers and TFE / perfluoro(propyl vinyl) ether copolymers, provided that the melt temperature constraints relative to the processing temperature of the fluoroelastomer are met. These copolymers may be utilized in powder form, as isolated from the polymerization medium if the particle size is acceptable, or they may be milled to the appropriate particle size from larger size starting materials.

[0054] The amount of non-carbon black filler in these compounds ranges from about 0.01 to 50 phr, alternatively from 0.1 to 20 phr, alternatively from at least about 1 to 5 phr.

[0055] Compound preparation process and cured article The compounds described herein can be prepared by mixing the fluoroelastomer (A), curative (B), carbon black (C), and optional ingredients until homogeneous using a rubber compounding procedure such as a two-roll rubber mill, internal mixer, or extruder. These compounds can be cured by applying sufficient heat and / or pressure to cause the curative B to crosslink with the cure sites, or a dual cure system can be used. When cured using compression molding, a press cure cycle is preferably followed by a post-cure cycle to achieve the optimum cure state, during which the press-cured compound is heated at elevated temperatures above 200°C for several hours.

[0056] The compounds described herein cure into the articles described herein and exhibit thermal stability and chemical resistance suitable for the applications in which they are used. These articles are useful as seals and gaskets for high temperature situations and in a variety of chemical environments, in seals for high temperature automotive applications, and as O-rings.

[0057] The compounds of the present invention are useful for the manufacture of gaskets, tubing, seals, and other molded parts. Such articles are typically produced by molding a compounded blend of the curable composition with various additives under pressure, curing the part, and then subjecting it to a post-cure cycle. The cured compositions have excellent mechanical properties as well as excellent thermal stability and chemical resistance. [Example]

[0058] Curing properties Unless otherwise stated, cure properties were measured using a Montech D-RPA3000 under the following conditions (ISO6502): Moving die frequency: 1.66Hz Hertz vibration amplitude: ±0.5° [degrees] Temperature: 160℃ Sample weight: 6 to 10 g Duration: 45 minutes The following cure parameters were recorded: MH: Maximum torque level, in dN.m ML: Minimum torque level, in dN.m ts2: Minutes until 2.26dNm rise from ML tc90: Maximum torque up to 90% of the physical characteristics

[0059] physical properties Compression set was carried out on stranded pipes according to ISO 815.

[0060] raw material Fluoroelastomer A: Tecnoflon® PL855 is a peroxide cured grade containing vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and perfluoroalkyl vinyl ether (PAVE) with a fluorine content of 64% and is available from Solvay. Fluoroelastomer B: Viton™ GBL-200S is a peroxide cured grade containing hexafluoropropylene (HFP), vinylidene fluoride (VDF), and tetrafluoroethylene (TFE), with a fluorine content of 68%, available from Chemours. Carbon Black A: Neat 90, STSA 28-30, available from CarbonNeat, 16930 West Catawba Ave., Suite 102, Cornelius, NC 28031 Carbon Black B: Thermax N990, STSA 6-9, available from Cancarb Limited. Hardener: Luperox® 101 XL45, available from (Arkema), is a hardener package containing 2,5-dimethyl 2,5-di-(tert-butylperoxy)hexane and inorganic carriers (CaCO3) and (SiO2). Auxiliary Agent A TAIC:HTAIC DLC®-A 72%, available from Harwick Standard Distribution Corporation, Akron, Ohio, USA. Auxiliary Agent B: TMAIC, DIAK8, available from Vanderbilt Chemicals, LLC.

[0061] Examples 1 to 8 The compounds disclosed in Tables 1 and 2 were prepared.

[0062] [Table 1]

[0063] [Table 2]

[0064] These ingredients were compounded in a conventional manner using an internal mixer and / or a two-roll rubber mill to prepare curable compositions (Examples 1-8) containing the ingredients shown in Table 1 or Table 2. Properties are also shown in Tables 1 and 2.

[0065] The compression set of the composition containing carbon black A is improved compared to the composition containing carbon black B.

[0066] Formulations using typical commercial carbon blacks such as Thermax N990 and cured with TMAIC coagent exhibit a very poor state of cure as indicated by high compression set.

[0067] Compositions using TMAIC coagent and Neat90 carbon black exhibit compression set values ​​similar to those obtained with Thermax N990 and TAIC coagents known to be used in the market.

Claims

1. (A) at least one fluoroelastomer having a hydrogen content of 0.75 wt. % or greater; (B) at least one curing agent comprising an organic peroxide and a multifunctional coagent; (C) one or more carbon blacks, wherein at least one of the carbon blacks has a viscosity of 20 to 40 m / s. ２ / g of a statistical thickness-specific surface area; Compound containing.

2. 10. The compound of claim 1, wherein the carbon black has an iodide adsorption of at least 60 g / kg as measured according to ASTM D1510.

3. 4. The compound of claim 1 or 3, wherein the carbon black comprises two or more types of carbon black.

4. 4. The compound of claim 3, wherein the fluoroelastomer further comprises at least one cure site monomer.

5. The compound of any one of claims 1 to 4, further comprising at least one component selected from the group consisting of fine powders, stabilizers, plasticizers, lubricants, processing aids, and mixtures thereof.

6. An article made by curing the composition of any one of claims 1 to 5.

7. 7. The article of claim 6 in the form of a molded article selected from a gasket, a tube, a seal, a diaphragm, a sheet, or an O-ring.

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