Fluoropolymer composition containing a curing agent having ethylenic unsaturation and electron donating groups, and substrates coated therewith

Abstract

A method for making crosslinked fluoropolymers is described. The method includes applying a composition to a substrate, the composition including a fluoropolymer, a fluorinated solvent, and one or more curing agents including ethylenically unsaturated groups and electron donating groups or precursors thereof. The method further includes removing the solvent and curing the fluoropolymer with actinic (e.g., ultraviolet "UV") radiation. Also described are compositions including a fluoropolymer dissolved in a fluorinated solvent and one or more curing agents including ethylenically unsaturated groups and electron donating groups or precursors thereof, and articles including the crosslinked fluoropolymer.

Description

Summary of the Invention

[0001] In one embodiment, a method for making a crosslinked fluoropolymer is described. The method includes applying a composition to a substrate, the composition including a fluoropolymer, a fluorinated solvent, and one or more curing agents including ethylenically unsaturated groups and electron donating groups or precursors thereof. The method further includes removing the solvent and curing the fluoropolymer with actinic (e.g., ultraviolet "UV") radiation.

[0002] In another embodiment, a composition is described that includes a fluoropolymer dissolved in a fluorinated solvent and one or more curing agents that include ethylenically unsaturated groups and electron donating groups or precursors thereof.

[0003] In each of these embodiments, the fluoropolymer comprises a sufficient amount (e.g., at least 90% by weight) of polymerized units derived from perfluorinated monomers such that the fluoropolymer is soluble in a fluorinated solvent. The fluoropolymer further comprises cure sites selected from iodine, bromine, and chlorine.

[0004] Also described are articles such as sheets or coated substrates comprising the crosslinked fluoropolymer compositions described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Described herein are compositions comprising fluoropolymers dissolved in fluorinated solvents, articles such as films and coated substrates, and methods of making the crosslinker fluoropolymers.

[0006] The fluoropolymers described herein are copolymers that contain polymerized units (e.g., repeating units) that are derived primarily or exclusively from two or more perfluorinated comonomers. Copolymers refer to polymeric materials that result from the simultaneous polymerization of two or more monomers. In some embodiments, the comonomers include tetrafluoroethene (TFE) and one or more unsaturated perfluoro (e.g., alkenyl, vinyl) alkyl ethers.

[0007] In some preferred embodiments, the one or more unsaturated perfluoroalkyl ethers have the general formula: R f -O-(CF2) n -CF=CF2 [wherein n is 1 (allyl ether) or 0 (vinyl ether); R f R represents a perfluoroalkyl residue optionally interrupted by one or more oxygen atoms. f may contain up to 10 carbon atoms, for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. f contains 8 or less, more preferably 6 or less carbon atoms and most preferably 3 or 4 carbon atoms. f has 3 carbon atoms. In another embodiment, R f has one carbon atom. f R may be linear or branched and may or may not contain cyclic units. f Illustrative examples of include residues having one or more ether functional groups, including, but not limited to: -(CF2)-O-C3F7, -(CF2)2-O-C2F5, -(CF2) r3 -O-CF3, -(CF2-O)-C3F7, -(CF2-O)2-C2F5, -(CF2-O)3-CF3, -(CF2CF2-O)-C3F7, -(CF2CF2-O)2-C2F5, -(CF2CF2-O)3-CF3

[0008] R f Other specific examples include residues that do not contain an ether functionality, including, but are not limited to, -CF, -C,F, -CF, where the C and C residues may be branched or linear, but are preferably linear.

[0009] Specific examples of suitable perfluoroalkyl vinyl ethers (PAVEs) and perfluoroalkyl allyl ethers (PAAEs) include perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), perfluoro(n-propyl vinyl) ether (PPVE-1), perfluoro-2-propoxypropyl vinyl ether (PPVE-2), perfluoro-3-methoxy-n-propyl vinyl ether, perfluoro-2-methoxy-ethyl vinyl ether, CF2=CF-O-CF2-O-CF2F 5、 CF2=CF-O-CF2-O-C3F7, [ka] and their allyl ether homologues. Specific examples of allyl ethers include CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C3F7, CF2=CF-CF2-O-(CF3)3-O-CF3.

[0010] Further examples include, but are not limited to, the vinyl ethers described in European Patent Application No. 1,997,795(B1).

[0011] Such perfluorinated ethers are commercially available, for example from Anles Ltd. (St. Petersburg, Russia) and other companies, or can be prepared according to the methods described in U.S. Pat. No. 4,349,650 (Krespan) or European Patent No. 1,997,795, or modifications thereof known to those skilled in the art.

[0012] In some embodiments, the one or more unsaturated perfluoroalkyl ethers include unsaturated cyclic perfluoroalkyl ethers such as 2,2-bistrifluoromethyl-4,5-difluoro-1,3 dioxole. In other embodiments, the fluoropolymer is substantially free of unsaturated cyclic perfluoroalkyl ethers such as 2,2-bistrifluoromethyl-4,5-difluoro-1,3 dioxole. By substantially free, we mean that the amount is zero or sufficiently low, and such fluoropolymer properties are approximately the same.

[0013] In some preferred embodiments, the fluoropolymer is derived primarily or exclusively from a perfluorinated comonomer comprising tetrafluoroethene (TFE) and one or more of the above unsaturated perfluoroalkyl ethers. As used herein, "predominantly" means that at least 90% by weight of the polymerized units of the fluoropolymer are derived from such perfluorinated comonomers, such as tetrafluoroethene (TFE) and one or more unsaturated perfluoroalkyl ethers, based on the total weight of the fluoropolymer. In some embodiments, the fluoropolymer comprises at least 91, 92, 93, 94, 95, 96, or 97% by weight or more of such perfluorinated comonomers, based on the total weight of the fluoropolymer. The fluoropolymer may contain at least 40, 45, or 50% by weight of polymerized units derived from TFE. In some embodiments, the maximum amount of polymerized units derived from TFE is 60% by weight or less.

[0014] The fluoropolymer typically comprises polymerized units derived from one or more of unsaturated perfluoroalkyl ethers (PAVEs) (e.g., PMVE, PAAE, or combinations thereof) in an amount of at least 10, 15, 20, 25, 30, 45, or 50% by weight based on the total polymerized monomer units of the fluoropolymer. In some embodiments, the fluoropolymer comprises polymerized units derived from one or more of unsaturated perfluoroalkyl ethers (PMVEs, PAAEs, or combinations thereof) in an amount of 50, 45, 40, or 35% by weight or less based on the total polymerized monomer units of the fluoropolymer. The molar ratio of units derived from TFE to units derived from the above-mentioned fully fluorinated alkyl ethers can be, for example, 1:1 to 5:1. In some embodiments, the molar ratio is in the range of 1.5:1 to 3:1.

[0015] Although the fluoropolymer may be thermoplastic, in a preferred embodiment, the fluoropolymer is amorphous. As used herein, an amorphous fluoropolymer is a material that is essentially free of crystallinity or has no significant melting point (peak maximum) as determined by differential scanning calorimetry according to DIN EN ISO 11357-3:2013-04 under nitrogen flow and a heating rate of 10°C / min. Typically, an amorphous fluoropolymer has a glass transition temperature (Tg) of less than 26°C, less than 20°C, or less than 0°C, for example, from -40°C to 20°C, or from -50°C to 15°C, or from -55°C to 10°C. The fluoropolymer may typically have a Mooney viscosity (ML1+10 at 121°C) of about 2 to about 150, for example, from 10 to 100, or from 20 to 70. For amorphous polymers containing cyclic perfluorinated alkyl ether units, the glass transition temperature is typically at least 70° C., 80° C., or 90° C. and can range up to 220° C., 250° C., 270° C., or 290° C. The MFI (297° C. / 5 kg) is 0.1 to 1000 g / 10 min.

[0016] In other embodiments, the fluoropolymer may have a melt point below 150°C or 100°C.

[0017] The fluoropolymer is preferably a curable fluoropolymer containing one or more cure sites. A cure site is a functional group that reacts in the presence of a curing agent or curing system to crosslink the polymer. A cure site is typically introduced by copolymerizing a cure site monomer, which is a functional comonomer that already contains a cure site or its precursor. One indication of crosslinking is that the dried and cured coating composition was not soluble in the fluorinated solvent of the coating.

[0018] Cure sites can be introduced into the polymer by using cure site monomers, i.e., functional monomers, functional chain transfer agents, and starter molecules as described below. Fluoroelastomers may contain cure sites that are reactive to more than one class of curatives.

[0019] Curable fluoroelastomers may also contain cure sites in the backbone as pendant groups or at terminal positions. Cure sites within the fluoropolymer backbone can be introduced by using suitable cure site monomers. Cure site monomers are monomers that contain one or more functional groups that can act as cure sites or precursors that can be converted to cure sites.

[0020] In some embodiments, the cure site comprises an iodine atom or a bromine atom.

[0021] Iodine-containing cure site end groups can be introduced by using iodine-containing chain transfer agents in the polymerization, which are described in more detail below. To introduce iodine end groups, halogenated redox systems, as described below, can be used.

[0022] In addition to the iodine curesites, other curesites may also be present, such as Br-containing curesites or curesites containing one or more nitrile groups. The Br-containing curesites may be introduced by a Br-containing curesite monomer.

[0023] Examples of cure site comonomers include, for example: (a) Bromo- or iodo-(per)fluoroalkyl-(per)fluorovinyl ethers, including, for example, those having the formula: ZRf-O-CX=CX2 [wherein each X may be the same or different and represents H or F, Z is Br or I, and Rf is C1-C12 (per)fluoroalkylene, optionally containing chlorine atoms and / or ether oxygen atoms]. Suitable examples include ZCF2-O-CF=CF2, ZCF2CF2-O-CF=CF2, ZCF2CF2CF2-O-CF=CF2, CF3CFZCF2-O-CF=CF2, or ZCF2CF2-O-CF2CF2CF2-O-CF=CF2 [wherein Z represents Br or I], (b) Bromo- or iodo-perfluoroolefins, such as those having the formula: Z'-(Rf) r -CX=CX2 wherein each X independently represents H or F, Z′ is Br or I, and Rf is a C1-C 12 perfluoroalkylene, and r is 0 or 1; and (c) Non-fluorinated bromo- and iodo-olefins, such as vinyl bromide, vinyl iodide, 4-bromo-1-butene, and 4-iodo-1-butene.

[0024] Specific examples include, but are not limited to, compounds according to (b) where X is H, such as compounds where X is H and Rf is C1-C3 perfluoroalkylene. Particular examples include bromo- or iodo-trifluoroethene, 4-bromo-perfluorobutene-1, 4-iodo-perfluorobutene-1, or bromo- or iodo-fluoroolefins such as 1-iodo,2,2-difluoroethene, 1-bromo-2,2-difluoroethene, 4-iodo-3,3,4,4,-tetrafluorobutene-1, and 4-bromo-3,3,4,4-tetrafluorobutene-1, 6-iodo-3,3,4,4,5,5,6,6-octafluorohexene-1.

[0025] In some embodiments, the cure site comprises a chlorine atom. Such cure site monomers have the general formula: CX1X2=CY1Y2, where X1, X2 are independently H and F, Y1 is H, F, or Cl, and Y2 is Cl, a fluoroalkyl group having at least one Cl substituent (R F ), a fluoroether group having at least one Cl substituent (OR F ), or -CF2-OR F Fluoroalkyl groups (R F ) is typically a partially or fully fluorinated C1-C5 alkyl group. Examples of cure site monomers having chlorine atoms include CF2=CFCl, CF2=CF-CF2Cl, CF2=CF-O-(CF2) n -Cl[n=1-4], CH2=CHCl, and CH2=CCl2.

[0026] Typically, the amount of iodine or bromine or chlorine or combinations thereof in the fluoropolymer is 0.001-5 wt%, preferably 0.01-2.5 wt%, or 0.1-1 wt%, or 0.2-0.6 wt%, based on the total weight of the fluoropolymer. In one embodiment, the curable fluoropolymer contains 0.001-5 wt%, preferably 0.01-2.5 wt%, or 0.1-1 wt%, more preferably 0.2-0.6 wt% iodine based on the total weight of the fluoropolymer.

[0027] The composition may optionally further comprise a second fluoropolymer that does not have halogen cure sites. The amount of fluoropolymer that does not have halogen cure sites is typically less than 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 weight percent of all fluoropolymers. Thus, the composition has a sufficient amount of fluoropolymer that has halogen cure sites so that adequate crosslinking is achieved.

[0028] In one embodiment, the composition further comprises a second fluoropolymer derived primarily or exclusively from two or more perfluorinated comonomers including tetrafluoroethene (TFE) and one or more unsaturated cyclic perfluoroalkyl ethers, such as 2,2-bistrifluoromethyl-4,5-difluoro-1,3 dioxole. Such fluoropolymers are commercially available as "TEFLON™ AF", "CYTOP™", and "HYFLON™".

[0029] In some embodiments, the second fluoropolymer contains a nitrile-containing cure site. When a combination of fluoropolymers with different cure sites is utilized, the composition can be characterized as dual cure, containing different cure sites that are reactive to different cure systems.

[0030] Fluoropolymers having nitrile-containing cure sites are known, such as those described in US Pat. No. 6,720,360.

[0031] The nitrile-containing cure site may be reactive towards other cure systems, such as, but not limited to, bisphenol cure systems, peroxide cure systems, triazine cure systems, and especially amine cure systems. Examples of nitrile-containing cure site monomers have the following formula: CF2=CF-CF2-O-Rf-CN, CF2 = CFO(CF2) r C.N.; CF2 = CFO[CF2CF(CF3)O] p (CF2) v OCF(CF3)CN; CF2=CF[OCF2CF(CF3)] k O(CF2) u C.N., [wherein r is an integer of 2 to 12, p is an integer of 0 to 4, k is 1 or 2, v is an integer of 0 to 6, u is an integer of 1 to 6, and Rf is a perfluoroalkylene or divalent perfluoroether group. Specific examples of nitrile-containing fluorinated monomers include, but are not limited to, perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene), CF2=CFO(CF2)5CN, and CF2=CFO(CF2)3OCF(CF3)CN.

[0032] In some embodiments, the amount of nitrile-containing cure site comonomer is typically at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 wt. % based on the total weight of the fluoropolymer, and typically no more than 10 wt. %. Suitable curing agents for nitrile cure sites are known in the art and include, but are not limited to, amidines, amidoximes, and others described in WO 2008 / 094758 A1, which is incorporated herein by reference.

[0033] In other embodiments, the composition is substantially free of fluoropolymers having nitrile-containing cure sites.

[0034] In other embodiments, halogenated chain transfer agents can be utilized to provide terminal cure sites. Chain transfer agents are compounds capable of reacting with a growing polymer chain and terminating the chain growth. Examples of chain transfer agents that have been reported for the production of fluoroelastomers include those of the formula RI x where R is an x-valent fluoroalkyl or fluoroalkylene group having 1 to 12 carbon atoms, which may be interrupted by one or more ether oxygens, and may contain chlorine and / or bromine atoms. R may be Rf, which may be an x-valent (per)fluoroalkyl or (per)fluoroalkylene group, which may be interrupted one or more times by ether oxygens. Examples include α-ω diiodoalkanes, α-ω diiodofluoroalkanes, and α-ω diiodoperfluoroalkanes, which may contain one or more catenary ether oxygens. "α-ω" indicates that the iodine atoms are at the terminal positions of the molecule. Such compounds can be represented by the general formula XRY, where X and Y are I, and R is as described above. Specific examples include diiodomethane, α-ω (or 1,4-) diiodobutane, α-ω (or 1,3-) diiodopropane, α-ω (or 1,5-) diiodopentane, α-ω (or 1,6-) diiodohexane, and 1,2-diiodoperfluoroethane. [ka] wherein X is independently selected from F, H, and Cl; f and R' f is independently selected from F and a monovalent perfluoroalkane having 1 to 3 carbons, R is F or a partially or fully fluorinated alkane containing 1 to 3 carbons, and R'' fis a divalent fluoroalkylene having 1 to 5 carbons or a divalent fluorinated alkylene ether having 1 to 8 carbons and at least one ether bond, k is 0 or 1, n, m, and p are independently selected from integers from 0 to 5, n+m is at least 1, and p+q is at least 1.

[0035] The fluoropolymer may or may not contain units derived from at least one modifying monomer. The modifying monomer can introduce branching sites into the polymer structure. Typically, the modifying monomer is a bisolefin, a bisolefin ether or a polyether. The bisolefin and bisolefin (poly)ether may be fully fluorinated, partially fluorinated or non-fluorinated. Preferably, they are fully fluorinated. Suitable fully fluorinated bisolefin ethers include those represented by the following general formula: CF2=CF-(CF2) n -O-(Rf)-O-(CF2) m -CF=CF2 [wherein n and m are, independently of one another, either 1 or 0, and Rf represents a perfluorinated, linear or branched, cyclic or acyclic, aliphatic or aromatic hydrocarbon residue containing up to 30 carbon atoms, optionally interrupted by one or more oxygen atoms]. A particularly suitable perfluorinated bisolefin ether is a di-vinyl ether of the formula: CF2=CF-O-(CF2) n -O-CF=CF2 [wherein n is an integer of 1 to 10, preferably 2 to 6, for example, n can be 1, 2, 3, 4, 5, 6, or 7]. More preferably, n represents an odd number, for example, 1, 3, 5, or 7.

[0036] Further specific examples include bis-olefin ethers conforming to the general formula: CF2=CF-(CF2) n -O-(CF2) p-O-(CF2) m -CF=CF2 [wherein n and m are independently either 1 or 0, and p is an integer from 1 to 10 or from 2 to 6.] For example, n may be selected to represent 1, 2, 3, 4, 5, 6, or 7, preferably 1, 3, 5, or 7.

[0037] Further suitable perfluorinated bisolefin ethers can be represented by the formula: [ka] [In the formula, R af and R bf are different linear or branched perfluoroalkylene groups of 1 to 10 carbon atoms, in particular 2 to 6 carbon atoms, which may or may not be interrupted by one or more oxygen atoms. af and / or R bf may also be a perfluorinated phenyl or substituted phenyl group, n is an integer from 1 to 10, m is an integer from 0 to 10, and preferably m is 0. Furthermore, p and q are independently 1 or 0.

[0038] In another embodiment, the perfluorinated bisolefin ether can be represented by the formula immediately above, where m, n, and p are zero, and q is 1-4.

[0039] The modifying monomers can be prepared by methods known in the art and are commercially available, for example, from Anles Ltd. (St. Petersburg, Russia).

[0040] Preferably, no modifier is used or only a small amount is used. Typical amounts include 0-5 wt.%, or 0-1.4 wt.%, based on the total weight of the fluoropolymer. The modifier can be present, for example, in an amount of about 0.1 wt.% to about 1.2 wt.%, or about 0.3 wt.% to about 0.8 wt.%, based on the total weight of the fluoropolymer. A combination of modifiers can also be used.

[0041] The fluoropolymer may contain partially fluorinated or non-fluorinated comonomers and combinations thereof, but are not preferred. Typical partially fluorinated comonomers include, but are not limited to, 1,1-difluoroethene (vinylidene fluoride, VDF) and vinyl fluoride (VF) or trifluorochloroethene or trichlorofluoroethene. Examples of non-fluorinated comonomers include, but are not limited to, ethene and propene. The amount of units derived from these comonomers includes 0-8 wt.%, based on the total weight of the fluoropolymer. In some embodiments, the concentration of such comonomers is less than or equal to 7, 6, 5, 4, 3, 2, or 1%, based on the total weight of the fluoropolymer.

[0042] In a preferred embodiment, the curable fluoropolymer is a perfluoroelastomer that contains only repeat units derived (exclusively) from perfluorinated comonomers, but may contain units derived from cure site monomers and, if necessary, modifying monomers. The cure site monomers and modifying monomers may be partially fluorinated, non-fluorinated, or fully fluorinated, preferably fully fluorinated. The perfluoroelastomer may contain 69 to 73, 74, or 75% by weight fluorine (based on the total amount of perfluoroelastomer). The fluorine content can be achieved by appropriate selection of comonomers and their amounts.

[0043] Such highly fluorinated amorphous fluoropolymers are typically soluble in hydrogen-containing organic liquids only to the extent of at least 1% by weight at room temperature and standard pressure (e.g., in neither methyl ethyl ketone ("MEK"), tetrahydrofuran ("THF"), ethyl acetate, nor N-methyl pyrrolidinone ("NMP").

[0044] Fluoropolymers can be prepared by methods known in the art, such as bulk, suspension, solution, or aqueous emulsion polymerization. For example, the polymerization process can be carried out by free radical polymerization of monomer alone or as a solution, emulsion, or dispersion in organic solvent or water. Seed polymerization may or may not be used. Curable fluoroelastomers that can be used also include commercially available fluoroelastomers, especially perfluoroelastomers.

[0045] Fluoropolymers can have a monomodal or bimodal or multimodal weight distribution. Fluoropolymers can have a core-shell structure or not. Core-shell polymers are polymers in which the composition of the comonomers, or the ratio of the comonomers, or the reaction rate is changed toward the end of the polymerization, typically after at least 50 mol% of the comonomers have been consumed, to form a shell of a different composition.

[0046] The fluoropolymer composition described herein contains one or more ethylenically unsaturated curing agents. The ethylenically unsaturated curing agent is typically present in an amount of at least 1, 1.5, or 2 weight percent based on the total weight of the fluoropolymer. For compositions with a lower amount of crosslinking, the ethylenically unsaturated curing agent can be present in a lower amount, such as at least 0.005, 0.1, 0.2, 0.3, or 0.5 weight percent. The maximum amount of the ethylenically unsaturated curing agent is typically not more than 10, 9, 8, 7, 6, or 5 weight percent based on the total weight of the fluoropolymer.

[0047] The ethylenically unsaturated groups of the curing agent are typically (meth)acryl, including (meth)acrylates RCH=CHCOO- and (meth)acrylamide RCH=CHCONH-, where R is hydrogen or methyl, alkenyl, including vinyl (CH=CH-), or alkynyl.

[0048] Useful multi(meth)acrylate curing agents include: (a) di(meth)acrylic-containing monomers, for example, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol monoacrylate monomethacrylate, ethylene glycol diacrylate, alkoxylated aliphatic diacrylates, alkoxylated cyclohexanedimethanol diacrylate, alkoxylated hexanediol diacrylate, alkoxylated neopentyl glycol diacrylate, caprolactone-modified neopentyl glycol hydroxypivalate diacrylate, caprolactone-modified neopentyl glycol Hydroxypivalate diacrylate, cyclohexane dimethanol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, hydroxypivalaldehyde modified trimethylolpropane diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, propoxylated neopentyl glycol diacrylate, tetraethylene glycol diacrylate, tricyclodecane dimethanol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, etc. (b) tri(meth)acrylic-containing monomers, such as glycerol triacrylate, trimethylolpropane triacrylate, ethoxylated triacrylates (e.g., ethoxylated trimethylolpropane triacrylate), propoxylated triacrylates (e.g., propoxylated glyceryl triacrylate, propoxylated trimethylolpropane triacrylate), trimethylolpropane triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, etc. (c) Higher functional (meth)acrylic-containing monomers, such as ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, pentaerythritol triacrylate, ethoxylated pentaerythritol tetraacrylate, and caprolactone modified dipentaerythritol hexaacrylate.

[0049] In some embodiments, the ethylenically unsaturated curing agent comprises at least 2 or 3 ethylenically unsaturated groups. The maximum number of ethylenically unsaturated groups is typically 3, 4, 5, or 6. In this embodiment, the ethylenically unsaturated groups are preferably alkenyl groups. Thus, in some embodiments, the composition, the composition is substantially free of (meth)acrylate groups.

[0050] The ethylenically unsaturated curing agent may be linear, branched, or may contain cyclic groups. The ethylenically unsaturated curing agent may be aliphatic or aromatic. Examples of useful ethylenically unsaturated curing agents include triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, tri(methylallyl)isocyanurate, tris(diallylamine)-s-triazine, triallyl-phosphite, (N,N')-diallyl acrylamide, hexaallyl phosphoramide, (N,N,N,N)-tetraalkyl tetraphthalamide, (N,N,N',N-tetraallyl malonamide, trivinyl isocyanurate, N,N'-m-phenylene bismaleimide, diallyl-phthalate, and tri(5-norbornene-2-methylene) cyanurate. In some embodiments, the ethylenically unsaturated curing agent is heterocyclic, such as in the case of triallyl isocyanurate (TAIC).

[0051] In some embodiments, the ethylenically unsaturated curing agent comprises a silicone-containing moiety, such as a silane or siloxane. When the curing agent comprises a silicone-containing moiety, the curing agent can also promote adhesion of the fluoropolymer to the substrate.

[0052] Suitable ethylenically unsaturated curing agents that contain a silicone-containing moiety include, for example, diallyldimethylsilane and 1,3-divinyltetramethyldisiloxane.

[0053] In some embodiments, the ethylenically unsaturated curing agent comprises at least one ethylenically unsaturated group and at least one alkoxysilane group.Suitable curing agents include, for example, (meth)acryloylalkoxysilane, such as 3-(methacryloxy)propyltrimethoxysilane, 3-(methacryloxy)propylmethyldimethoxysilane, 3-(acryloyloxypropyl)methyldimethoxysilane, 3-(methacryloyloxy)propyldimethylmethoxysilane, and 3-(acryloyloxypropyl)dimethylmethoxysilane.In some embodiments, the amount of (meth)acryloylalkoxysilane is at least 2, 3, 4, or 5 wt % to achieve a highly crosslinked fluoropolymer.

[0054] Suitable alkenylalkoxysilanes include vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, vinylmethyldiethoxysilane, vinyltriacetoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriphenoxysilane, vinyltri-t-butoxysilane, vinyltris-isobutoxysilane, vinyltriisopropenoxysilane, vinyltris(2-methoxyethoxy)silane, and allyltriethoxysilane.

[0055] In some embodiments, the ethylenically unsaturated curing agent has the general formula: X 1 -L 1 -SiR m (OR 1 ) 3-m [In the formula, X 1 is an ethylenically unsaturated group such as (meth)acrylic or vinyl, L 1 is an organic divalent linking group having 1 to 12 carbon atoms, R is independently C1-C4 alkyl, most typically methyl or ethyl; R 1is independently H or C1-C4 alkyl, most typically methyl or ethyl; m may range from 0 to 2.

[0056] In an exemplary embodiment, L 1 is an alkylene group. In some embodiments, L 1 is an alkylene group having 1, 2, or 3 carbon atoms. 1 comprises or consists of an aromatic group such as phenyl or (eg, C1-C4) alkylphenyl.

[0057] The composition may include a single ethylenically unsaturated curing agent or a combination of ethylenically unsaturated curing agents as described immediately above.

[0058] The compositions described herein further comprise an electron donating group or a precursor thereof. The electron donating group may be present on the same compound, such as in the case of an aminoalkene or a vinylaniline, or the electron donating group may be present as a separate compound.

[0059] The fluoropolymer and / or curing agent contain chromophores, i.e., atoms or groups that absorb light at a particular frequency. In some embodiments, the fluoropolymer and / or curing agent may not have sufficient absorbance independently, but in combination with each other, they have sufficient absorbance.

[0060] In some embodiments, the fluoropolymer, curing agent, or combination thereof has an absorbance of at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 at wavelengths ranging from 190 nm to 400 nm. In some embodiments, such absorbance is at wavelengths of at least 200 nm, 210 nm, 220 nm, 230 nm, or 240 nm. In some embodiments, such absorbance is at wavelengths of 350, 340, 330, 320, 310 nm, or 290 nm or less. In other embodiments, the fluoropolymer, curing agent, or combination thereof has an absorbance of at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 at wavelengths ranging from 150 nm to 200 nm.

[0061] Without intending to be bound by theory, it is speculated that upon exposure to actinic (e.g., UV) radiation of suitable wavelength and intensity, halogen atoms in the cure sites of the fluoropolymer are excited and ionized. The ionized halogen atoms react with electron donating groups rendering protonated cure sites in place of the former halogen atoms. Such protonated cure sites covalently bond with ethylenically unsaturated groups of the curing agent.

[0062] The compound containing the electron donating group is typically an amine or a precursor thereof, although other electron donating groups can be utilized. Suitable amines include primary amines, secondary amines, tertiary amines, and combinations thereof. The amines may be aliphatic or aromatic.

[0063] Exemplary amine compounds include diaminohexane, N,N,N',N'-tetramethyl-1,4-diaminobutane (TMDAB); N,N-dimethylaniline; triethylenetetramine; and diethylenetriamine. In some embodiments, the amine groups are separated by alkylene groups having at least 3, 4, 5, or 6 (e.g., carbon) atoms. Typically, the number of (e.g., carbon) atoms is 12 or less. If the amine compound has insufficient chain length, it may be a less effective electron donor group. The alkylene group may optionally include a substituent such as a siloxane, provided that the compound is an electron donor or a precursor thereof.

[0064] In some embodiments, the electron donor compound may be characterized as an electron donor precursor, meaning that the compound is not an electron donor when it is first combined with the fluoropolymer, however, the precursor compound decomposes or otherwise reacts to form the (e.g., amine) electron donor before or during cure.

[0065] Electron donor precursors include nitrogen-containing nucleophilic compounds such as heterocyclic secondary amines; guanidine; compounds that decompose in situ at temperatures between 40° C. and 330° C. to produce guanidine; compounds that decompose in situ at temperatures between 40° C. and 330° C. to produce primary or secondary amines; compounds of the formula R1-NH-R2, where R1 is H-, C1-C 10 an aliphatic hydrocarbon group or an aryl group having a hydrogen atom at the α-position, and R2 is a C1-C 10 an aliphatic hydrocarbon group, an aryl group having a hydrogen atom at the α-position, -CONHR3, -NHCO2R3, or -OH', where R3 is a C1-C 10 aliphatic hydrocarbon groups; and substituted amidines of the formula HN=CRNRR, where R, R, R are independently H-, alkyl or aryl groups, and at least one of R, R and Re is not H.

[0066] As used herein, "heterocyclic secondary amine" refers to an aromatic or aliphatic cyclic compound having at least one secondary amine nitrogen contained within the ring. Such compounds include, for example, pyrrole, imidazole, pyrazole, 3-pyrroline, and pyrrolidine.

[0067] Guanidines are compounds derived from guanidine, i.e., compounds containing the -NHCNHNH- group, such as, but not limited to, diphenylguanidine, diphenylguanidine acetate, aminobutylguanidine, biguanidine, isopentylguanidine, di-σ-tolylguanidine, o-tolylbiguanide, and triphenylguanidine.

[0068] Other compounds that decompose in situ at temperatures between 40° C. and 330° C. to produce either primary or secondary amines include, but are not limited to, di- or poly-substituted ureas (e.g., 1,3-dimethylurea); N-alkyl or -dialkyl carbamates (e.g., N-(tert-butyloxycarbonyl)propylamine); di- or poly-substituted thioureas (e.g., 1,3-dimethyl-thiourea); aldehyde-amine condensation products (e.g., 1,3,5-trimethylhexahydro-1,3,5-triazine); N,N'-dialkylphthalamide derivatives (e.g., N,N'-dimethylphthalamide); and amino acids.

[0069] When a thermally activated electron donor precursor compound is utilized as described immediately above, the composition is typically heated before and / or during curing.

[0070] Another type of amine electron donor is represented by the formula: [ka] and [ka] Bis(aminophenols) and bis(aminothiophenols) of the formula [ka] where A is SO2, O, CO, alkyl having 1 to 6 carbon atoms, perfluoroalkyl having 1 to 10 carbon atoms, or a carbon-carbon bond connecting two aromatic rings. The amino and hydroxyl groups in the above formula are interchangeably located in meta and para positions relative to the A group.

[0071] In some embodiments, the amine electron donor compound is an aziridine compound. In some embodiments, the aziridine compound comprises at least two aziridine groups. The aziridine compound may comprise 3, 4, 5, 6, or more than 6 aziridine groups. The aziridine compound has the following structure: [ka] wherein R is a core moiety having a valence of Y; L is a bond, a divalent atom, or a divalent linking group; R1, R2, R3, and R4 are independently hydrogen or C1-C4 alkyl (e.g., methyl); Y is typically 2, 3 or more.

[0072] In some embodiments, R is -SO2-. In some embodiments, R is a residue of a multi(meth)acrylate compound. In some embodiments, L is a C1-C4 alkylene optionally substituted with one or more (e.g., adjacent or pendant) oxygen atoms, thereby forming an ether or ester bond. In an exemplary embodiment, R1 is methyl and R2, R3, and R4 are hydrogen.

[0073] Representative aziridine compounds include trimethylolpropane tri-[β-(N-aziridinyl)-propionate, 2,2-bishydroxymethylbutanol tris[3-(1-aziridine)propionate]; 1-(aziridin-2-yl)-2-oxabut-3-ene; and 4-(aziridin-2-yl)-but-1-ene; and 5-(aziridin-2-yl)-pent-1-ene.

[0074] In some embodiments, polyaziridine compounds can be prepared by reacting divinyl sulfone with alkylene (e.g., ethylene)imines, as described in U.S. Patent No. 3,235,544 (Christena). A representative compound is di(2-propyleneiminoethyl)sulfone, shown below: [ka]

[0075] The polyaziridine compounds described above contain at least two aziridine groups at the time the compounds are added to the coating composition. In other embodiments, the polyaziridine compounds do not contain two aziridine groups at the time the compounds are added to the composition, and further form polyaziridines in-situ. For example, a compound containing a single aziridine group and a single (meth)acrylate group can form a dimer or oligomerize by reaction of the (meth)acrylate groups, thereby forming a polyazirdine (i.e., diaziridine) compound.

[0076] In some embodiments, the composition comprises an electron donor compound that comprises at least one (e.g., primary, secondary, tertiary) amine group and at least one organosilane (e.g., alkoxysilane) group. Such compounds can improve the bond that independently crosslinks the fluoroelastomers described herein, thereby providing a second fluoropolymer crosslinking mechanism. By using an ethylenically unsaturated curing agent in combination with an amino-substituted organosilane, lower concentrations of the curing agent and electron donor compound can be utilized to provide a highly crosslinked fluoropolymer.

[0077] In some embodiments, the amines may be characterized as amino-substituted organosilane esters or ester equivalents having at least one, preferably two or three, ester or ester equivalent groups on the silicon atom. Ester equivalents are well known to those skilled in the art and include compounds such as silane amides (RNR'Si), silane alkanoates (RC(O)OSi), Si-O-Si, SiN(R)-Si, SiSR and RCONR'Si compounds that are thermally and / or catalytically replaceable by R''OH. R and R' are independently selected and may include hydrogen, alkyl, arylalkyl, alkenyl, alkynyl, cycloalkyl, and substituted analogs such as alkoxyalkyl, aminoalkyl, and alkylaminoalkyl. R'' may be the same as R and R', except that it is not H. These ester equivalents may also be cyclic compounds, such as those derived from ethylene glycol, ethanolamine, ethylenediamine (e.g., N-[3-(trimethoxysilyl)propyl]ethylenediamine), and their amides.

[0078] Examples of such cyclic compounds of alternative ester equivalents include: [ka]

[0079] In this example of a cyclic compound, R' is as defined above, but may not be aryl. 3-aminopropylalkoxysilanes are known to cyclize upon heating, and these RNHSi compounds would be useful in the present invention. Preferably, the amino-substituted organosilane ester or ester equivalent has an ester group, such as methoxy, which is easily volatilized as methanol. The amino-substituted organosilane must have at least one ester equivalent, and may be, for example, a trialkoxysilane.

[0080] For example, amino-substituted organosilanes can be represented by the formula (Z2N-L-SiX'X''X''') [wherein, Z is hydrogen, alkyl, or substituted aryl or alkyl, such as amino-substituted alkyl; L may be a divalent linear C1-12 alkylene, or may comprise a C3-8 cycloalkylene, a 3-8 membered heterocycloalkylene, a C2-12 alkenylene, a C4-8 cycloalkenylene, a 3-8 membered heterocycloalkenylene, or a heteroarylene unit; each of X', X'' and X''' is a C1-18 alkyl, halogen, C1-8 alkoxy, C1-8 alkylcarbonyloxy, or amino group, with the proviso that at least one of X', X'', and X''' is a labile group. Additionally, any two or all of X', X'' and X''' may be linked via a covalent bond. The amino group may be an alkylamino group.

[0081] L may be divalent aromatic or may be interrupted by one or more divalent aromatic or heteroatom groups. The aromatic group may include a heterocyclic aromatic group. The heteroatom is preferably nitrogen, sulfur or oxygen. L is optionally substituted with C1-4 alkyl, C2-4 alkenyl, C2-4 alkynyl, C1-4 alkoxy, amino, C3-6 cycloalkyl, 3-6 membered heterocycloalkyl, monocyclic aryl, 5-6 membered heteroaryl, C1-4 alkylcarbonyloxy, C1-4 alkyloxycarbonyl, C1-4 alkylcarbonyl, formyl, C1-4 alkylcarbonylamino or C1-4 aminocarbonyl. L is further optionally interrupted by -O-, -S-, -N(Rc)-, -N(Rc)-C(O)-, -N(Rc)-C(O)-O-, -OC(O)-N(Rc)-, -N(Rc)-C(O)-N(Rd)-, -OC(O)-, -C(O)-O-, or -OC(O)-O-. Each of Rc and Rd is independently hydrogen, alkyl, alkenyl, alkynyl, alkoxyalkyl, aminoalkyl (primary, secondary, or tertiary), or haloalkyl.

[0082] Examples of amino-substituted organosilanes include 3-aminopropyltrimethoxysilane (SILQUEST A-1110), 3-aminopropyltriethoxysilane (SILQUEST A-1100), bis(3-trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)amine, bis(3-trimethoxysilylpropy)n-methylamine, 3-(2-aminoethyl)aminopropyltrimethoxysilane (SILQUEST A-1120), SILQUEST A-1130, (aminoethylaminomethyl)phenethyltrimethoxysilane, (aminoethylaminomethyl)phenethyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (SILQUEST A-2120), bis-(γ-triethoxysilylpropyl)amine (SILQUEST A-2120), and the like. A-1170), N-(2-aminoethyl)-3-aminopropyl tributoxysilane, 6-(aminohexylaminopropyl)trimethoxysilane, 4-aminobutyl trimethoxysilane, 4-aminobutyl triethoxysilane, p-(2-aminoethyl)phenyl trimethoxysilane, 3-aminopropyl tris(methoxyethoxyethoxy)silane, 3-aminopropyl methyl diethoxysilane, oligomeric aminosilanes such as DYNASYLAN 1146, 3-(N-methylamino)propyl trimethoxysilane , N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropyldimethylethoxysilane, and the following cyclic compounds. [ka] [ka] [ka] [ka]

[0083] Bis-silyl urea, [RO)3Si(CH2)NR]2C=O, is another example of an amino-substituted organosilane ester or ester equivalent.

[0084] In some embodiments, the curing agent may include an amino group with latent functionality. One example of such a curing agent is a blocked amine group such as: R 3 -N=C(R 1 )(R 2 ) [In the formula, R 1 and R 2 are independently selected from linear or branched alkyl groups containing 1 to 6 carbon atoms. In an exemplary embodiment, R is methyl and R 2 R is a linear or branched alkyl group containing at least 2, 3, 4, 5, or 6 carbon atoms. 3 is typically an organic group (e.g., having a molecular weight of less than 500, 450, 400, 350, 300, or 250 g / mole).

[0085] The blocked amines can be activated by water adsorbed on the surface of the substrate being coated or by moisture provided by humidity. Deblocking begins in minutes and is generally complete within a few hours (e.g., 2 hours). During deblocking, -N=C(R 1 )(R 2 ) groups can be converted to -NH2 and then reacted with (e.g., nitrile cure sites) of the fluoropolymer.

[0086] In some embodiments, the curing agent comprises a blocked amine group and an alkoxysilane group. Such blocked amine curing agents have the following general formula: (R 4 O)3-Si-(CH2) m -N=C(R1)(R2) [In the formula, R 1 and R 2 is, as previously described, independently selected from linear or branched alkyl groups containing 1 to 6 carbon atoms.

[0087] R 1 is independently selected from linear or branched alkyl groups containing 1 to 6 carbon atoms, m is an integer from 1 to 4, and each R 4 are independently a C1 or C2 alkyl group.

[0088] One exemplary curing agent containing blocked amine and alkoxysilane groups is N-(1,3-dimethylbutylidene)aminopropyl-triethoxysilane, shown below: [ka]

[0089] Such curing agents are available from Gelest and from 3M as "3M™ Dynamer™ Rubber Curative RC5125." Blocked amines are additional examples of electron donor precursors.

[0090] In some embodiments, the amine curing agent comprises an aziridine group and an alkoxysilane group. Such compounds are known, for example, from U.S. Pat. No. 3,243,429, which is incorporated herein by reference. Aziridine alkoxysilane compounds have the general structure: [ka] [In the formula, R″ is hydrogen or C1-C4 alkyl (e.g., methyl), X is a bond, a divalent atom, or a divalent linking group; n is 0, 1, or 2; m is 1, 2, or 3; The sum or n+m is 3.

[0091] One representative compound is 3-(2-methylaziridinyl)ethylcarboxylpropyltriethoxysilane.

[0092] A variety of other suitable aziridine crosslinkers are known and are described in WO 2014 / 075246, published May 22, 2014, and in "NEW GENERATION OF MULTIFUNCTIONAL CROSSLINKERS" (see https: / / www.pstc.org / files / public / Milker00.pdf), which are incorporated herein by reference.

[0093] The composition may include a single (eg, amine) electron donor compound, or a combination of amine electron donor compounds may be present.

[0094] The amount of (e.g., amine) electron donor compound is typically at least 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, or 0.5% by weight solids (i.e., excluding solvent of the coating composition). In some embodiments, the amount of (e.g., amine) electron donor compound is no more than 5, 4.5, 4, 3.5, or 3% by weight solids.

[0095] In some embodiments, the fluoropolymer composition further comprises an alkoxysilane compound that does not have an amine functionality. In some embodiments, such an alkoxysilane has the formula: R 2 Si(OR 1 ) m [In the formula, R 1 are independently alkyl as defined above; R 2 are independently hydrogen, alkyl, aryl, alkaryl, or OR 1 and m ranges from 1 to 3, and as noted above, is typically 2 or 3.

[0096] formula R 2 Si(OR 1 ) m Suitable alkoxysilanes include, but are not limited to, tetra-, tri-, or dialkoxysilanes, and any combination or mixture thereof. Representative alkoxysilanes include propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane.

[0097] Preferably, the alkyl group of the alkoxysilane contains 1 to 6, more preferably 1 to 4 carbon atoms. Preferred alkoxysilanes for use herein are selected from the group consisting of tetramethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and any mixtures thereof. Preferred alkoxysilanes for use herein include tetraethoxysilane (TEOS). Alkoxysilanes without organofunctional groups utilized in the method of making the coating composition may be partially hydrolyzed, such as in the case of partially hydrolyzed tetramethoxysilane (TMOS) available under the trade designation "MS-51" from Mitsuibishi Chemical Company.

[0098] When present, the amount of alkoxysilane compound without (amine / electron donor) functionality (e.g., TESO) is typically at least 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, or 0.5 wt.% solids (i.e., excluding solvent of the coating composition). In some embodiments, the amount of alkoxysilane compound without functional groups is no more than 5, 4.5, 4, 3.5, or 3 wt.% solids.

[0099] In an exemplary embodiment, the composition described herein comprises a cure system comprising an ethylenically unsaturated compound in combination with an electron donor compound, such as an amine, in the absence of an organic peroxide. The organic peroxide is an electron acceptor and therefore competes with the ionized halogen atom, thereby reducing crosslinking of the fluoropolymer. In some embodiments, the composition is also substantially free of other electron acceptors that reduce crosslinking.

[0100] The fluoropolymer (coating solution) composition comprises at least one solvent. The solvent is capable of dissolving the fluoropolymer. The solvent is typically present in an amount of at least about 25% by weight based on the total weight of the coating solution composition. In some embodiments, the solvent is present in an amount of at least 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95%, or more based on the total weight of the coating solution composition.

[0101] The fluoropolymer (coating solution) composition typically comprises at least 0.01, 0.02, 0.03, 0.03, 0.04, 0.04, 0.05, 0.06, 0.7, 0.8, 0.9, or 1 weight percent fluoropolymer based on the weight of the total coating solution composition. In some embodiments, the fluoropolymer coating solution composition comprises at least 2, 3, 4, or 5 weight percent fluoropolymer. In some embodiments, the fluoropolymer coating solution composition comprises at least 6, 7, 8, 9, or 10 weight percent fluoropolymer. The fluoropolymer coating solution composition typically comprises no more than 50, 45, 40, 35, 30, 25, or 20 weight percent fluoropolymer based on the weight of the total coating solution composition.

[0102] The optimal amount of solvent and fluoropolymer may vary depending on the end application. For example, a very dilute fluoropolymer solution in the solvent may be desired, for example, 0.01% to 5% by weight of fluoropolymer, to provide a thin coating. Also, for spray coating applications, a low viscosity composition may be preferred over a high viscosity solution. The concentration of fluoropolymer in the solution affects the viscosity and may be adjusted accordingly. An advantage of the present disclosure is that solutions can also be prepared that contain high concentrations of fluoropolymer, yet still result in a low viscosity clear liquid composition.

[0103] In some embodiments, the fluoropolymer coating solution composition can be a liquid. The liquid can have, for example, a viscosity of less than 2,000 mPas at room temperature (20° C.+ / -2° C.). In other embodiments, the fluoropolymer coating solution composition is a paste. The paste can have, for example, a viscosity of 2,000 to 100,000 mPas at room temperature (20° C.+ / -2° C.).

[0104] The solvent is liquid at ambient conditions and typically has a boiling point above 50° C. Preferably, the solvent has a boiling point below 200° C. so that it can be easily removed. In some embodiments, the solvent has a boiling point below 190, 180, 170, 160, 150, 140, 130, 120, 110, or 100° C.

[0105] The solvent is partially or fully fluorinated. A variety of partially or fully fluorinated solvents are known, including perfluorocarbons (PFCs), hydrochlorofluorocarbons (HCFCs), perfluoropolyethers (PFPEs), and hydrofluorocarbons (HFCs), as well as fluorinated ketones and fluorinated alkylamines.

[0106] In some embodiments, the solvent has a Global Warming Potential (GWP, 100 year ITH) of less than 1000, 900, 800, 700, 600, 500, 400, 300, 200, or 100. The GWP is typically greater than 0, and may be at least 10, 20, 30, 40, 50, 60, 70, or 80.

[0107] As used herein, GWP is a relative measure of the global warming potential of a compound based on the structure of the compound.The GWP of a compound, defined by the Intergovernmental Panel on Climate Change (IPCC) in 1990 and revised in subsequent reports, is calculated as the warming caused by 1 kilogram of compound emission relative to the warming caused by 1 kilogram of CO2 emission over a specific integration time horizon (ITH).

number

[0108] In some embodiments, the solvent comprises a partially fluorinated ether or a partially fluorinated polyether. The partially fluorinated ether or polyether may be linear, cyclic, or branched. Preferably, it is branched. Preferably, the partially fluorinated ether or polyether comprises a non-fluorinated alkyl group and a fully fluorinated alkyl group, more preferably, the fully fluorinated alkyl group is branched.

[0109] In one embodiment, the partially fluorinated ether or polyether solvent has the formula: Rf-OR where Rf is a perfluorinated or partially fluorinated alkyl or (poly)ether group and R is a non-fluorinated or partially fluorinated alkyl group. Typically, Rf may have 1 to 12 carbon atoms. Rf may be a primary, secondary or tertiary fluorinated or perfluorinated alkyl residue. This means that when Rf is a primary alkyl residue, the carbon atom linked to the ether atom contains two fluorine atoms and is bonded to another carbon atom of the fluorinated or perfluorinated alkyl chain. In that case, Rf is R f 1 This polyether corresponds to the general formula: f 1 It can be represented as -CF2-OR.

[0110] When Rf is a secondary alkyl residue, the carbon atom linked to the ether atom is also linked to one fluorine atom and two carbon atoms of a partially and / or fully fluorinated alkyl chain, and Rf is (R f 2 R f 3 This polyether corresponds to (R f 2 Rf 3 ) CF-OR.

[0111] When Rf is a tertiary alkyl residue, the carbon atom linked to the ether atom is also linked to three carbon atoms of a partially and / or fully fluorinated alkyl chain, and Rf is (R f 4 R f 5 R f 6 )-C-. This polyether corresponds to (R f 4 R f 5 R f 6 )-C-OR. R f 1 , R f 2 , R f 3 , R f 4 , R f 5 , R f 6 corresponds to the definition of Rf and is a perfluorinated or partially fluorinated alkyl group, optionally interrupted by one or more ether oxygens. They may be linear or branched or cyclic. Also, combinations of polyethers may be used, as may combinations of primary, secondary and / or tertiary alkyl residues.

[0112] An example of a solvent containing a partially fluorinated alkyl group is C3F7OCHFCF3 (CAS number 3330-15-2).

[0113] An example of a solvent where Rf comprises a perfluorinated (poly)ether is C3F7OCF(CF3)CF2OCHFCF3 (CAS number 3330-14-1).

[0114] In some embodiments, the partially fluorinated ether solvent has the formula: CpF2p+1-O-CqH2q+1 [wherein q is an integer from 1 to 5, for example, 1, 2, 3, 4, or 5, and p is an integer from 5 to 11, for example, 5, 6, 7, 8, 9, 10, or 11]. p F 2p+1 is branched. Preferably, C p F 2p+1 is branched and q is 1, 2 or 3.

[0115] Representative solvents include, for example, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane and 3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-(trifluoromethyl)hexane. Such solvents are commercially available, for example, under the trade name NOVEC from 3M Company (St. Paul, Minn.).

[0116] Fluorinated (e.g., ether and polyether) solvents may be used alone or in combination with other solvents, which may be fluorochemical solvents or non-fluorochemical solvents. When non-fluorochemical solvents are combined with fluorinated solvents, the concentration of non-fluorochemical solvents is typically less than 30, 25, 20, 15, 10, or 5% by weight based on the total amount of solvent. Representative non-fluorochemical solvents include ketones such as acetone, MEK, methyl isobutyl ketone, methyl amyl ketone, and NMP; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, and methyltetrahydrofurfuryl ether; esters such as methyl acetate, ethyl acetate, and butyl acetate; and cyclic esters such as delta-valerolactone and gamma-valerolactone.

[0117] In some embodiments, the composition further comprises crystalline fluoropolymer particles.

[0118] In one embodiment, such coating compositions are prepared by blending a latex containing crystalline fluoropolymer particles with a latex containing amorphous fluoropolymer particles. The fluoropolymer particles typically have a small average particle size, e.g., less than 400 nm, but can be larger, especially if the applied coating is rubbed after curing. For example, the fluoropolymer particle size range can be about 50 to about 1000 nm, or about 50 to about 400 nm, or about 50 to about 200 nm.

[0119] The latexes can be combined by any suitable manner, such as vortex mixing for 1-2 minutes. The method further includes coagulating the mixture of latex particles. Coagulation can be carried out, for example, by cooling (e.g., freezing) the blended latex or by adding a suitable salt (e.g., magnesium chloride). Cooling is particularly desirable for coatings used in semiconductor manufacturing and other applications where the introduction of salts may be undesirable. The method optionally further includes washing the coagulated mixture of amorphous and crystalline fluoropolymer particles. The washing step can substantially remove emulsifiers or other surfactants from the mixture and can aid in obtaining a well-mixed blend of substantially non-agglomerated dry particles. In some embodiments, the surfactant level of the resulting dry particle mixture can be, for example, less than 0.1 wt%, less than 0.05 wt%, or less than 0.01 wt%. The method further includes drying the coagulated latex mixture. The coagulated latex mixture can be dried by any suitable means, such as air drying or oven drying. In one embodiment, the coagulated latex mixture can be dried at 100° C. for 1 to 2 hours.

[0120] The dried coagulated latex mixture can be dissolved in a solvent suitable for dissolving the amorphous fluoropolymer particles to form a stable coating composition containing a homogeneous dispersion of crystalline fluoropolymer particles in a solution of amorphous fluoropolymer.

[0121] The coating solution can be utilized to provide a coating on a substrate by applying a layer of the coating composition to the surface of the substrate and drying the coating composition (i.e., removing the fluorinated solvent by evaporation).

[0122] In some embodiments, the method further comprises scrubbing (eg, buffing, polishing) the dried layer, thereby forming an amorphous fluoropolymer binder layer containing crystalline submicron fluoropolymer particles.

[0123] The submicron crystalline fluoropolymer particles at the coating surface form a thin continuous or nearly continuous fluoropolymer surface layer disposed on the underlying coating of amorphous fluoropolymer. In a preferred embodiment, the thin crystalline fluoropolymer layer is smeared relatively uniformly on the underlying coating and appears thinner and more uniform than if the fluoropolymer particles were simply subjected to fibrillation (e.g., by orientation or other stretching).

[0124] The average roughness (Ra) of a surface is the arithmetic mean of the absolute value of the surface height deviation measured from the mean plane. In some embodiments, Ra is at least 40 or 50 nm and up to 100 nm before rubbing. In some embodiments, the surface after rubbing is at least 10, 20, 30, 40, 50, or 60% smoother. In some embodiments, Ra is less than 35, 30, 25, or 20 nm after rubbing.

[0125] Various rubbing techniques can be used when forming the coating or when the coated article is or will be used thereafter. Simply wiping or buffing the coating several times using cheesecloth or other suitable woven, nonwoven, or knitted fabric is often sufficient to form the desired thin layer. Those skilled in the art will understand that many other rubbing techniques can be used. Rubbing can also reduce the haze of the cured coating.

[0126] Various crystalline fluoropolymer particles can be used, including mixtures of different crystalline fluoropolymer particles.Crystalline fluoropolymer particles typically have a high degree of crystallinity and therefore a significant melting point (peak maximum) as determined by differential scanning calorimetry according to DIN EN ISO 11357-3:2013-04 under nitrogen flow and a heating rate of 10 ° C. / min.

[0127] For example, the crystalline fluoropolymer particles may include particles of a fluoropolymer having a Tm of at least 100, 110, 120, or 130° C. In some embodiments, the crystalline fluoropolymer particles may include particles of a fluoropolymer having a Tm of 350, 340, 330, 320, 310, or 300° C. or less.

[0128] The crystalline fluoropolymer particles typically have a fluorine content of greater than about 50 weight percent, and may include particles of fluoropolymers having a fluorine content of about 50 to about 76 weight percent, about 60 to about 76 weight percent, or about 65 to about 76 weight percent.

[0129] Representative crystalline fluoropolymers include, for example, 3M™ Dyneon™ PTFE Dispersions TF5032Z, TF5033Z, TF5035Z, TF5050Z, TF5135GZ, and TF5070GZ; and perfluorinated fluoropolymers such as 3M™ Dyneon™ Fluorothermoplastic Dispersions PFA6900GZ, PFA6910GZ, FEP6300GZ, and THV340Z.

[0130] Other suitable fluoropolymer particles are available from suppliers such as Asahi Glass, Solvay Solexis, and Daikin Industries, and will be known to those skilled in the art.

[0131] Commercially available aqueous dispersions usually contain non-ionic and / or ionic surfactants at concentrations up to 5-10% by weight. These surfactants are substantially removed by washing the coagulated blend. Residual surfactant concentrations of less than 1, 0.05, or 0.01% by weight may be present. It is often more convenient to use "as-polymerized" aqueous fluoropolymer latexes since they do not contain as high a content of non-ionic / ionic surfactants.

[0132] As mentioned above, crystalline fluoropolymers have a melting point that can be determined by DSC. The degree of crystallinity depends on the choice and concentration of polymerized monomers of the fluoropolymer. For example, PTFE homopolymer (containing 100% TFE units) has a melting point (Tm) above 340°C. The addition of comonomers such as unsaturated (per)fluoroalkyl ethers reduces the Tm. For example, when the fluoropolymer contains about 3-5% by weight of polymerized units of such comonomers, the Tm is about 310°C. As yet another example, when the fluoropolymer contains about 15-20% by weight of polymerized units of HFP, the Tm is about 260-270°C. As yet another example, when the fluoropolymer contains 30% by weight of polymerized units of (per)fluoroalkyl ethers (e.g., PMVE) or other comonomers that reduce the degree of crystallinity, the fluoropolymer no longer has a melting point detectable via DSC and is therefore characterized as being amorphous.

[0133] In some embodiments, crystalline fluoropolymer particles contain at least 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or about 100% by weight of polymerized units of TFE.In addition, crystalline fluoropolymer particles typically contain a lower concentration of unsaturated (per)fluoroalkyl ether (e.g., PMVE) than amorphous fluoropolymers.In typical embodiments, crystalline fluoropolymer particles contain less than 30, 25, 20, 15, 10, or 5% by weight of polymerized units of (per)fluoroalkyl ether (e.g., PMVE).

[0134] In some embodiments, the crystalline fluoropolymer is a copolymer formed from constituent monomers known as tetrafluoroethylene ("TFE"), hexafluoropropylene ("HFP"), and vinylidene fluoride ("VDF", "VF2"). The monomer structures of these constituents are shown below. TFE:CF2=CF2(1) VDF:CH2=CF2(2) HFP:CF2=CF-CF3(3)

[0135] In some embodiments, the crystalline fluoropolymer is composed of at least two constituent monomers (HFP and VDF), and in some embodiments, all three constituent monomers, in various molar amounts.

[0136] Tm depends on the amount of TFE, HFP, and VDF. For example, a fluoropolymer containing about 45% by weight of TFE polymerized units, about 18% by weight of HFP polymerized units, and about 37% by weight of VDF polymerized units has a Tm of about 120°C. As yet another example, a fluoropolymer containing about 76% by weight of TFE polymerized units, about 11% by weight of HFP polymerized units, and about 13% by weight of VDF polymerized units has a Tm of about 240°C. By increasing the amount of HFP / VDF polymerized units, while decreasing the amount of TFE polymerized units, the fluoropolymer becomes amorphous. A summary of crystalline and amorphous fluoropolymers is described in Ullmann's Encyclopedia of Industrial Chemistry (7th edition, 2013 Wiley-VCH Verlag.10.1002 / 14356007.a11 393 pub 2) Chapter: Fluoropolymers, Organic.

[0137] The crystalline fluoropolymer particles and the amorphous fluoropolymer particles can be combined in various ratios. For example, the coating composition contains about 5 to about 95 weight percent of the crystalline fluoropolymer particles and about 95 to about 5 weight percent of the amorphous fluoropolymer, based on the total weight percent of solids (i.e., excluding solvent). In some embodiments, the coating composition contains about 10 to about 75 weight percent of the crystalline fluoropolymer particles and about 90 to about 25 weight percent of the amorphous fluoropolymer.

[0138] In some embodiments, the coating composition contains from about 10 to about 50 weight percent crystalline fluoropolymer particles and from about 90 to about 50 weight percent amorphous fluoropolymer. In some embodiments, the coating composition contains from about 10 to about 30 weight percent crystalline fluoropolymer particles and from about 90 to about 70 weight percent amorphous fluoropolymer.

[0139] The composition containing the curable fluoroelastomer may further contain additives known in the art. Examples include acid acceptors. Such acid acceptors can be inorganic acid acceptors or blends of inorganic and organic acid acceptors. Examples of inorganic acceptors include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide, dibasic lead phosphate, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, hydrotalcite, and the like. Organic acceptors include epoxy, sodium stearate, and magnesium oxalate. Particularly suitable acid acceptors include magnesium oxide and zinc oxide. Blends of acid acceptors can be used as well. The amount of acid acceptor generally depends on the nature of the acid acceptor used. Typically, the amount of acid acceptor used is 0.5 to 5 parts per 100 parts of fluorinated polymer.

[0140] The fluoropolymer composition may contain additional additives typically utilized in the processing and compounding of fluoropolymers, such as stabilizers, surfactants, ultraviolet ("UV") absorbers, antioxidants, plasticizers, lubricants, fillers, and processing aids, provided that they have sufficient stability under the intended conditions of use. Specific examples of additives include carbon particles such as carbon black, graphite, and soot. Additional additives include, but are not limited to, pigments, such as iron oxide, titanium dioxide. Other additives include, but are not limited to, clay, silicon dioxide, barium sulfate, silica, glass fiber, or other additives known and used in the art.

[0141] The fluoropolymer composition can be prepared by mixing a polymer, a curing agent including at least one ethylenically unsaturated curing agent, at least one compound having an electron donating group, optional additives, and a fluorinated solvent. In some embodiments, the fluoropolymer is first dissolved in a fluorinated solvent, and the curing agent and other additives including the electron donor compound are then added.

[0142] The coating compositions described herein that include fluorinated solvents are "stable," meaning that the coating composition remains homogeneous when stored in a sealed container at room temperature for at least 24 hours. In some embodiments, the coating composition is stable for one week or more. "Homogeneous" refers to a coating composition that does not show a visibly separated precipitate or a visibly separated layer when freshly shaken, placed in a 100 mL glass container, and allowed to stand at room temperature for at least 4 hours.

[0143] In some embodiments, the fluoropolymer is first combined with other solid ingredients, in particular with the electron donor (e.g., amine) compound and ethylenically unsaturated curing agent described herein. The fluoropolymer and amine compound can be combined in conventional rubber processing equipment to provide a solid mixture, i.e., a solid polymer containing additional ingredients, also referred to in the art as a "compound". Typical equipment includes rubber mills, internal mixers such as Banbury mixers, and mixing extruders. During mixing, the components and additives are uniformly dispersed throughout the resulting fluorinated polymer "compound" or polymer sheet. The compound is then preferably comminuted, for example by cutting into smaller pieces, and then dissolved in a solvent.

[0144] The fluoropolymer coating solution composition described herein is suitable for coating a substrate. The fluoropolymer coating solution composition can be formulated to have various viscosities depending on the content of solvent and fluoropolymer and the presence or absence of optional additives. The fluoropolymer coating solution composition typically contains or is a solution of fluoropolymer, and can be in the form of a liquid or paste. Although the composition may contain dispersed or suspended materials, these materials are preferably additives and are not fluoropolymers of the type described herein. Preferably, the composition is a liquid, more preferably a solution containing one or more fluoropolymers described herein dissolved in a solvent described herein.

[0145] The fluoropolymer compositions described herein are suitable for coating substrates and can be adjusted in viscosity (by solvent content) to make them applicable by various coating methods, including but not limited to spray coating or printing (e.g., but not limited to, ink printing, 3D printing, screen printing), painting, impregnation, roller coating, bar coating, dip coating, and solvent casting.

[0146] Coated substrates and articles can be prepared by applying the fluoropolymer composition to a substrate and removing the solvent. Curing can occur upon, during, or after removal of the solvent. The solvent can be reduced or completely removed, for example, by evaporation, drying, or by allowing the solvent to evaporate. After removal of the solvent, the composition can be characterized as "dry."

[0147] The method of making crosslinked fluoropolymers described herein includes curing the fluoropolymer with actinic radiation (e.g., UV or electron beam). The fluoropolymer composition, the substrate, or both are transparent to the curing radiation. In some embodiments, a combination of UV curing and thermal (e.g., post) curing is utilized. The curing is carried out at an effective temperature and for an effective time to form a cured fluoroelastomer. Optimization of conditions can be tested by examining the fluoroelastomer for its mechanical and physical properties. Curing can be carried out in an oven with or without pressure. A post-cure cycle at elevated temperature and / or pressure may be applied to ensure complete completion of the curing process. The curing conditions depend on the cure system used.

[0148] In some embodiments, the composition is cured by UV curing. The fluoropolymer of the composition described herein contains little or no vinylidene fluoride (VDF) (i.e., CH2=CF2) or polymerized units of VDF bonded to hexafluoropropylene (HFP). The polymerized units of VDF can undergo dehydrofluorination (i.e., HF elimination reaction) as described in US Patent Application Publication No. 2006 / 0147723. The reaction is limited by the number of polymerized VDF groups bonded to the HFP groups contained in the fluoropolymer. The double bonds generated as a result of dehydrofluorination can then react (via Michael addition) with aminoalkoxysilanes, thereby grafting fluorinated pendant alkoxysilane groups onto the fluoropolymer backbone. When irradiated with UV light, such pendent groups can undergo free radical copolymerization with multifunctional (meth)acrylate compounds.

[0149] However, since the fluoropolymer of the composition described herein contains little or no polymerized units of VDF (i.e., CH2=CF2) attached to HFP groups, the fluoropolymer is not affected by the reaction scheme described immediately above. As the following examples show, amine compounds alone can initiate UV curing in the absence of free radical photoinitiators. The inclusion of free radical photoinitiators typically does not increase the crosslinking of the fluoropolymer. This result suggests that the fluoropolymer is not crosslinked via a free radical mechanism.

[0150] The composition may optionally further comprise a photoinitiator, although a conventional free radical initiator is not required, hi other embodiments, the composition is substantially free of free radical initiators, including such free radical photoinitiators.

[0151] In some embodiments, the UV radiation may have sufficient intensity at wavelengths of at least 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, or 240 nm. In some embodiments, the UV radiation may have sufficient intensity at wavelengths of 350 nm, 340 nm, 330 nm, 320 nm, 310 nm, or 290 nm or less. In some embodiments, the (e.g., UV) actinic radiation has sufficient intensity at wavelengths in the range of 270-290 nm such that in the presence of an (e.g., amine) electron donor, wavelength-induced single electron transfer reactions can occur between C-C1 bonds or C-Br bonds. In some embodiments, the UV radiation has sufficient intensity at wavelengths in the range of less than 240 nm (150-200 nm) such that in the presence of an (e.g., amine) electron donor, wavelength-induced single electron transfer reactions can occur between C-C1 bonds or C-Br bonds.

[0152] UV light sources can be of various types. Low intensity sources such as black lights provide typically 0.1 or 0.5 mW / cm 2 (milliwatts per square centimeter) to 10mW / cm 2 (measured by, for example, a UVIMAP UM 365 LS dosimeter (Electronic Instrumentation & Technology, Inc., Sterling, VA) approved by the United States National Institute of Standards and Technology). High intensity sources are generally in the range of 10, 15, or 20 mW / cm 2 Ultra-high intensity, up to 450mW / cm 2 In some embodiments, the high intensity light source provides an intensity in the range of up to 500, 600, 700, 800, 900, or 1000 mW / cm. 2The UV light for polymerizing the ethylenically unsaturated monomers can be provided by a variety of sources, such as light emitting diodes (LEDs), fluorescent black lights, arc lamps such as xenon-arc lamps and medium and low pressure mercury lamps (including germicidal lamps), microwave-powered lamps, lasers, or combinations thereof. The composition can also be polymerized with higher intensity light sources available from FusionUVSystemsInc. Lamps emitting ultraviolet or blue light are typically preferred. UV exposure times for polymerization and curing can vary depending on the intensity of the light source used. For example, full cure with a low intensity light source can be achieved with exposure times ranging from about 30 to 300 seconds, while full cure with a high intensity light source can be achieved with shorter exposure times ranging from about 5 to 20 seconds. Partial cure with a high intensity light source can typically be achieved with exposure times ranging from about 2 seconds to about 5 or 10 seconds. In some embodiments, post-cure can be carried out at temperatures of 170°C to 250°C for 0.1 to 24 hours.

[0153] In some embodiments, the post-cure of the fluoropolymer may be optionally carried out at lower temperatures. Lower temperature post-curing is suitable for coating heat-sensitive substrates. In some embodiments, the post-cure is carried out at temperatures ranging from 100, 110, 120, 130, 135, or 140°C up to 170°C for 5-10 minutes to 24 hours. In some embodiments, the temperature is no greater than 169, 168, 167, 166, 165, 164, 163, 162, 161, or 160°C. In some embodiments, the temperature is no greater than 135, 130, 125, or 120°C. In preferred embodiments, after curing, the fluoropolymer is sufficiently crosslinked such that at least 80, 85, 90, 95, or more than 100 wt. % cannot be dissolved (at 25° C. within 12 hours) in a fluorinated solvent (e.g., 3-ethoxyperfluoro2-methylhexane) at a weight ratio of 5 grams of fluoropolymer in 95 wt. % of the fluorinated solvent.

[0154] The composition can be used to impregnate a substrate, print (e.g., screen print) onto a substrate, or coat a substrate, such as, but not limited to, spray coating, paint dip coating, roller coating, bar coating, solvent casting, paste coating, etc. The substrate can be organic, inorganic, or a combination thereof. Suitable substrates can include any solid surface, including substrates selected from glass, plastics (e.g., polycarbonate), composites, metals (stainless steel, aluminum, carbon steel), alloys, wood, paper, among others. The coating can be colored, if the composition contains a pigment, e.g., titanium dioxide or a black filler such as graphite or soot, or colorless, if no pigment or black filler is present.

[0155] Bonding agents and primers may be used to pretreat the surface of the substrate before coating. For example, the adhesion of the coating to the metal surface can be improved by applying an adhesive or primer. Examples include commercially available primers or adhesives, such as those available under the trade name CHEMLOK. Articles containing a coating of the composition described herein include, but are not limited to, impregnated fabrics, such as protective clothing. Fabrics can include woven or nonwoven fabrics. Other articles include articles exposed to corrosive environments, such as seals and sealing parts and valves used in chemical processing, including but not limited to chemical reactors, molds, parts or linings of chemical processing equipment, such as for etching, or especially corrosive materials or hydrocarbon fuels or solvents; combustion engines, electrodes, fuel delivery, acid and base containers and delivery systems for acids and bases, valves, pumps and tubing for electric cells, fuel cells, electrolytic cells, and articles used in or for etching.

[0156] An advantage of the coating compositions described herein is that they can be used to prepare thick or thin coatings or fluoropolymer sheets. In some embodiments, the dried and cured fluoropolymer has a thickness of 0.1 microns to 1 or 2 mils. In some embodiments, the dried and cured fluoropolymer has a thickness of at least 0.2, 0.3, 0.4, 0.5, or 0.6 microns. In some embodiments, the dried and cured fluoropolymer has a thickness of at least 1, 2, 3, 4, 5, or 6 microns.

[0157] In typical embodiments, the dried and cured (i.e., crosslinked) composition has a low dielectric constant (Dk), typically less than 2.75, 2.70, 2.65, 2.60, 2.55, 2.50, 2.45, 2.40, 2.35, 2.30, 2.25, 2.20, 2.15, 2.20, 2.15. In some embodiments, the dielectric constant is at least 2.02, 2.03, 2.04, 2.05. The dried and cured (i.e., crosslinked) composition has a low dielectric loss, typically less than 0.01, 0.009, 0.008, 0.007, 0.006, 0.005, 0.004, 0.003, 0.002, 0.001, 0.0009, 0.0008, 0.0007, 0.0006, 0.0005, 0.0004, 0.0003. In some embodiments, the dielectric loss is at least 0.00022, 0.00023, 0.00024, 0.00025.

[0158] The dried and cured coatings may exhibit good adhesion to a variety of substrates (e.g., glass, polycarbonate) as evidenced by the coating exhibiting a score of 2, and preferably 3 or 4, according to the Scalding Water Test described in the Examples. In preferred embodiments, the dried and cured coatings are durable as evidenced by the coating exhibiting a score of 2, and preferably 3 or 4, according to the Abrasion Test described in International Application PCT / US2019 / 036460, which is incorporated herein by reference. In some embodiments, the coatings are durable according to the Abrasion Test after being subjected to the Scalding Water Test.

[0159] In some embodiments, the dried and cured coating has good hydrophobic and oleophobic properties according to the black oil marker resistance test, i.e., marker fluid beads, described in previously cited International Application No. PCT / US2019 / 036460 and can be easily removed with a paper towel or cloth.

[0160] In some embodiments, the dried and cured coating has good hydrophobicity and oleophobicity as determined by contact angle measurements (as determined according to the test methods described in the Examples). In some embodiments, the advancing and / or receding contact angles with water may be at least 100, 105, 110, 115, 120, 125, or 130 degrees. In some embodiments, the advancing and / or receding contact angles with hexadecane may be at least 60, 65, 70, or 75 degrees. In some embodiments, the coating exhibits such contact angles after being subjected to a boiling water test or after being subjected to a boiling water test and an abrasion test (as determined according to the test methods described in previously cited International Application PCT / US2019 / 036460).

[0161] In some embodiments, the dried and cured coatings exhibit good corrosion resistance (i.e., do not corrode) according to the Acid / Base Corrosion Test described in previously cited International Application No. PCT / US2019 / 036460.

[0162] As used herein, the term "partially fluorinated alkyl" refers to an alkyl group in which some, but not all, hydrogens attached to the carbon chain are replaced with fluorine. For example, F2HC- or FH2C- groups are partially fluorinated methyl groups. Alkyl groups in which the remaining hydrogen atoms are partially or completely replaced with other atoms, such as other halogen atoms, such as chlorine, iodine and / or bromine, are also encompassed by the term "partially fluorinated alkyl" as long as at least one hydrogen is replaced with fluorine. For example, residues of the formula F2ClC- or FHClC- are also partially fluorinated alkyl residues.

[0163] A "partially fluorinated ether" is an ether that contains at least one partially fluorinated group, or an ether that contains one or more fully fluorinated groups and at least one non-fluorinated group or at least one partially fluorinated group. For example, F2HC-O-CH3, F3C-O-CH3, F2HC-O-CFH2, and F2HC-O-CF3 are examples of partially fluorinated ethers. Ether groups in which the remaining hydrogen atoms are partially or completely replaced with other atoms, such as other halogen atoms such as chlorine, iodine, and / or bromine, are also encompassed by the term "partially fluorinated alkyl" as long as at least one hydrogen is replaced with fluorine. For example, ethers of the formula F2ClC-O-CF3 or FHClC-O-CF3 are also partially fluorinated ethers.

[0164] The terms "perfluorinated alkyl" or "perfluoro alkyl" are used herein to refer to an alkyl group in which all of the hydrogen atoms attached to the alkyl chain have been replaced with fluorine atoms. For example, F3C- represents a perfluoromethyl group.

[0165] A "perfluorinated ether" is an ether in which all hydrogen atoms have been replaced with fluorine atoms. An example of a perfluorinated ether is F3C-O-CF3. The present invention includes the following aspects. (1) A method for making a crosslinked fluoropolymer, comprising the steps of: i) applying a composition to a substrate, said composition comprising: a fluorinated solvent and a fluoropolymer comprising a sufficient amount of polymerized units derived from perfluorinated monomers such that the fluoropolymer is soluble in the fluorinated solvent, the fluoropolymer comprising cure sites selected from iodine, bromine, and chlorine; one or more curing agents comprising ethylenically unsaturated groups and electron donating groups or precursors thereof; ii) removing the solvent; and iii) curing said fluoropolymer with actinic radiation. (2) The method of claim 1, wherein the actinic radiation comprises ultraviolet radiation. (3) The method according to item 1 or 2, wherein the fluoropolymer has less than 5, 4, 3, 2, or 1 weight percent polymerized units of VDF. (4) The method according to any one of items 1 to 3, wherein the composition does not contain an organic peroxide. (5) The method according to any one of items 1 to 4, wherein the fluoropolymer comprises at least 90% by weight of polymerized units derived from perfluorinated monomers. (6) The method according to any one of items 1 to 5, wherein the perfluorinated monomer is selected from tetrafluoroethene (TFE) and one or more unsaturated perfluoroalkyl ethers. (7) The unsaturated perfluoroalkyl ether of the fluoropolymer has the general formula Rf -O-(CF 2 ) n -CF=CF 2 [In the formula, n is 1 or 0, and R f is a perfluoroalkyl group or a perfluoroether group. (8) The method according to any one of items 1 to 7, wherein the curing agent containing an electron-donating group is an amine compound. (9) The method according to item 8, wherein the amine compound is a primary amine, a secondary amine, or a tertiary amine. 10. The method of claim 8, wherein the amine compound is an aminoorganosilane ester compound or an ester equivalent. (11) The method according to any one of items 1 to 10, wherein the curing agent contains at least two ethylenically unsaturated groups. (12) The method according to any one of items 1 to 11, wherein the curing agent contains at least one ethylenically unsaturated group and at least one alkoxysilane group. (13) The method according to any one of items 1 to 12, wherein the ethylenically unsaturated group is selected from (meth)acrylic or alkenyl. (14) The method according to any one of items 1 to 13, wherein the curing agent is linear, branched, or contains a cyclic group. (15) The method according to any one of items 1 to 14, wherein the composition further comprises one or more alkoxysilane compounds having no amine group. (16) The method according to any one of items 1 to 15, wherein the fluoropolymer contains 40 to 60% by weight of polymerized units of TFE, based on the total weight of the fluoropolymer. (17) The method according to any one of items 1 to 16, wherein the fluoropolymer comprises 0 to 5 wt. % of polymerized units derived from non-fluorinated or partially fluorinated monomers. (18) The method according to any one of items 1 to 17, wherein the composition comprises 0.01 to 25 wt.% of the fluoropolymer, based on the weight of the fluoropolymer and the fluorinated solvent. (19) The method according to any one of items 1 to 18, wherein the fluorinated solvent is a partially fluorinated ether. (20) The fluorinated solvent has the formula: C p F 2p+1 -OC q H 2q+1 [In the formula, q is an integer of 1 to 5, and p is an integer of 5 to 11.] (21)C above p F 2p+1 21. The method according to claim 20, wherein the -unit is branched. (22) The method according to any one of items 1 to 21, wherein the fluorinated solvent has a GWP of less than 1000. (23) The method according to any one of items 1 to 22, wherein the composition further comprises a second fluoropolymer. 24. The method of claim 23, wherein the second fluoropolymer does not have cure sites selected from iodine, bromine, and chlorine. (25) The method according to item 23 or 24, wherein the second fluoropolymer is insoluble in the fluorinated solvent. 26. The method of claim 25, wherein the second fluoropolymer comprises crystalline fluoropolymer particles. (27) The method according to any one of items 1 to 26, wherein the substrate is a release liner, an organic substrate, or an inorganic substrate. (28) A composition comprising a fluorinated solvent and a fluoropolymer, The fluoropolymer is contains a sufficient amount of polymerized units derived from perfluorinated monomers so as to be soluble in said fluorinated solvent; and comprising cure sites selected from iodine, bromine, and chlorine; The composition comprises one or more curing agents comprising an ethylenically unsaturated group and an electron donating group or a precursor thereof. (29) The composition according to item 28, wherein the fluoropolymer, the fluorinated solvent, the ethylenically unsaturated curing agent, and / or the compound containing an electron donating group or a precursor thereof are further characterized according to any one of items 2 to 26. (30) An article comprising a crosslinked fluoropolymer composition, the crosslinked fluoropolymer composition comprising at least 90% by weight, based on the total weight of the fluoropolymer, of polymerized units derived from a perfluorinated monomer, the fluoropolymer being crosslinked with an ethylenically unsaturated group, an alkoxysilane group, or a combination thereof, the crosslinked fluoropolymer composition comprising a compound comprising an electron donating group or a residue thereof. 31. The article of claim 30, wherein a portion of the fluoropolymer comprises one or more cure sites selected from iodine, bromine, chlorine, or combinations thereof. (32) The article according to item 30 or 31, wherein 95 to 100% of the crosslinked fluoropolymer is not dissolved in 3-ethoxyperfluoro2-methylhexane solvent at a concentration of 5 g of crosslinked fluoropolymer per 95 g of solvent at 25°C within 12 hours. (33) The article according to any one of items 30 to 32, wherein the article is a sheet of the crosslinked fluoropolymer composition. (34) The article according to any one of items 30 to 33, wherein the article further comprises a substrate, and the crosslinked fluoropolymer is disposed on a surface of the substrate. (35) The article according to any one of items 30 to 34, wherein the fluoropolymer, the fluorinated solvent, the ethylenically unsaturated curing agent, the compound containing an electron donating group or a precursor thereof, and / or the substrate are further characterized according to any one of items 2 to 26.

[0166] The following examples are provided to further illustrate the present disclosure, without intending to limit the disclosure to the specific examples and embodiments described. EXAMPLES

[0167] Unless otherwise stated or readily apparent from the context, all parts, percentages, ratios, etc. in the examples and elsewhere in the specification are by weight. [Table 1]

[0168] Preparation of fluorinated ether dienes As described in US Patent No. 5,384,374, a fluorinated ether diol (HO-CH2-CF2-O-(CF2CF2)CF2-CH2-OH (0.16 mol)) with an average molecular weight of 1500 and an average hydroxyl functionality of 1.8 was reacted with sodium methoxide (0.34 mol) and then with allyl bromide (40 g, 0.36 mol) in a 250 mL three-neck flask with a condenser at 60° C. overnight. After the reaction, the reaction mixture was washed with water and the pale yellow liquid was dried over CaCl2 before rotavapor to remove any residual allyl bromide.

[0169] General Procedure - Preparation of Perfluoroelastomer PFE Coating Solution with Multifunctional Alkene / Aminosilane Ester Photocrosslinker: Perfluoroelastomer PFE 40, 60, or 90 solutions were prepared by cutting PFE 40, 60, 90 gums separately into small pieces and adding them to HFE solvent (HFE-7300 or HFE-7500) to make 10 wt% PFE in HFE solution (10 g PFE and 90 g HFE). The container was sealed with PTFE tape and paraffin film. The solution was subjected to vigorous shaking overnight (about 12 hours) to ensure complete homogenization.

[0170] All aminosilanes, initiators were dissolved or dispersed in HFE to form 1 wt% or 5 wt% solutions or suspensions (e.g., 0.5 g TAIC was added to 9.5 g HFE to form a 5 wt% suspension in a vial). To the PFE solution was added the amine (e.g., aminosilane), alkene, and optionally a photoinitiator. For example, a sample (5% TAIC, 1% APES, 2% TMOS) was prepared by adding 0.3157 g TAIC suspension (5 wt% in HFE), 0.0606 g APES suspension (5 wt% in HFE), and 0.1224 g TMOS solution (5 wt% in 7500) to 3 g PFE40 solution (10 wt% in PFE40). Many silanes form suspensions rather than solutions in HFE. Such suspensions were homogenized using a vortex shaker at 1000 rpm for 10 seconds to form a well-dispersed slurry before being added to the PFE-HFE solution, and the percentages in the formula (e.g., 5%, 3%, 1%) were mass fractions based on the solid content of PFE (e.g., PFE40+5%APES+2%1173 means: PFE40 / APES solids=95:5 and PFE40 / 1173 solids=98:2).

[0171] General Procedure - Preparation of Perfluoroelastomer PFE Coating Solution with Fluorinated Alkene / Aminosilane Ester Photocrosslinker: In a similar manner as above, perfluoroelastomer PFE 40, 60, or 90 solutions were prepared by cutting PFE 40, 60, 90 gums separately into small pieces and placing them in HFE solvent to obtain a 10 wt% solution of PFE in HFE in a glass jar. The glass jar was sealed with Teflon tape and paraffin film. The solution was subjected to vigorous shaking overnight (about 12 hours) until completely homogenous. Most of the alkene was dissolved or dispersed in the HFE to form a 1 wt% or 5 wt% solution or suspension. In cases where there was rapid phase separation between the alkene and HFE solution, and where the alkene sample was solid at room temperature and did not completely disperse in the HFE7500, the alkene was dissolved in methanol or methoxypropanol instead. These alkenes include 4,4'-bis((1,2,2-trifluorovinyl)oxy)-1,1'-biphenyl (dissolved in methanol), chloro-1,2-phenylenediacrylate (dissolved in methanol), perchloro-1,2-phenylenediacrylate (dissolved in methoxypropanol), 2,4,6-tribromobenzene-1,3,5-triyl triacrylate (dissolved in methoxypropanol). In addition to the alkenes, all silanes and photoinitiators were dissolved or dispersed in HFE to form 1% or 5% by weight solutions or suspensions. To the PFE was added the alkene or polyfunctional alkene, and other chemicals including silanes and initiators as indicated in the table.

[0172] Table 2. Crosslinking yield of cured fluoropolymers For crosslinking yield studies, samples were prepared by depositing 3 g of solution onto PET film. The coated film was dried for 2 hours at ambient temperature and 20 minutes at 50°C. After the samples were completely dried, the PET film samples were placed on a wood or stainless steel board and cured under a single 500 watt H bulb or 500 watt D bulb UV lamp at a speed of 30 feet per minute (as indicated in the table) in 5 to 10 runs. After UV curing, many samples were also heat cured in an oven at 120°C for 5 minutes (as indicated in the table). Some of the same samples were also subjected to heat cure conditions without UV curing.

[0173] The UV-cured samples (1-2 mil thick) were peeled from the PET film, weighed, and then dissolved in HFE in a vial. The mass ratio of cured PFE sample / HFE solvent was 5 / 95. The vial was subjected to vigorous shaking overnight (approximately 12 hours) after which any observations were recorded, as described in the table below. The precipitated samples in the HFE solution (i.e., crosslinked PFE) were collected, dried, and weighed. In some cases, the gel (i.e., less crosslinked PFE) was collected, dried, and weighed. [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10]

[0174] Preparation of dispersed crystalline fluoropolymer particles coated with PFE40: Perfluoroelastomer latex PFE-1 was mixed with crystalline fluoropolymer latex PFA, PTFE, or THV, respectively, in the weight ratios listed in Table 11. The solutions were vortex mixed for 1-2 minutes. The well-mixed solutions were then frozen at a temperature of -20°C for 4 hours, then removed and thawed in warm water. After thawing, the precipitate was filtered and washed with deionized (DI) water. The resulting solids were dried in an oven at 100°C for 1-2 hours. The dried coagulated solids were mixed with HFE to form a 10 wt% solution in HFE. TAIC and APS were also added to the HFE compositions as shown in Table 11. Each composition was placed in a shaker for 3-4 hours to obtain a stable, well-dispersed homogenous composition.

[0175] Samples were prepared by depositing 3 g of the solution onto a PET film. The coated film was dried for 2 hours at ambient temperature and 20 minutes at 50°C. After the samples were completely dried, the PET film samples were placed on a wood or stainless steel board and cured under a single 500 watt H bulb at a speed of 30 feet per minute in 5 to 10 runs (as indicated in the table). After UV curing, some samples were also heat cured in an oven at 120°C for 5 minutes (as indicated in Table 11).

[0176] The UV-cured samples (1-2 mil thick) were peeled off from the PET film, weighed, and then dissolved in HFE in a vial. The mass ratio of cured PFE sample / HFE solvent was 5 / 95. After subjecting the vial to vigorous shaking overnight (approximately 12 hours), any observations were recorded, as described in the table below. The precipitated sample in the HFE solution (i.e., crosslinked PFE) was collected, dried, and weighed. [Table 11]

Claims

1. 1. A method for making a crosslinked fluoropolymer comprising the steps of: i) applying a composition to a substrate, said composition comprising: a fluorinated solvent and a fluoropolymer comprising at least 90% by weight of polymerized units derived from fully fluorinated monomers such that the fluoropolymer is soluble in the fluorinated solvent and includes cure sites selected from iodine, bromine, and chlorine; one or more curing agents comprising an ethylenically unsaturated group and an electron donating group that is an amino group or a precursor thereof, said electron donating group may be on the same curing agent having said ethylenically unsaturated group or on a different curing agent; The composition is free of organic peroxides; and ii) removing the solvent; and and iii) curing said fluoropolymer with actinic radiation.

2. The method of claim 1 , wherein the actinic radiation comprises ultraviolet radiation.

3. The method of claim 1 , wherein the fluoropolymer has less than 5% by weight of polymerized units of VDF.

4. 2. The method of claim 1, wherein the perfluorinated monomer is selected from tetrafluoroethene (TFE) and one or more unsaturated perfluoroalkyl ethers.

5. The unsaturated perfluoroalkyl ether of the fluoropolymer has the general formula R ｆ -O-(CF ２ ) ｎ -CF=CF ２ [In the formula, n is 1 or 0, and R ｆ is a perfluoroalkyl group or a perfluoroether group.

6. The method of claim 1 , wherein the curing agent containing electron donating groups is an amine compound.

7. The method of claim 6, wherein the amine compound is an aminoorganosilane ester compound or an ester equivalent.

8. The method of claim 1 , wherein the curing agent comprises at least two ethylenically unsaturated groups, or at least one ethylenically unsaturated group and at least one alkoxysilane group.

9. The method of claim 1 , wherein the fluoropolymer comprises 0 to 5 weight percent polymerized units derived from non-fluorinated or partially fluorinated monomers.

10. The fluorinated solvent has the formula: C ｐ F ２ｐ＋１ -O-C ｑ H ２ｑ＋１ [In the formula, q is an integer from 1 to 5, and p is an integer from 5 to 11.] The method of claim 1 , wherein the fluorinated ether is a partially fluorinated ether having the formula:

11. The method of any one of claims 1 to 10, wherein the composition further comprises a second fluoropolymer that is insoluble in the fluorinated solvent.

12. The method of claim 11 , wherein the second fluoropolymer comprises crystalline fluoropolymer particles.

13. A composition comprising a fluorinated solvent and a fluoropolymer, The fluoropolymer is comprises at least 90% by weight of polymerized units derived from perfluorinated monomers such that the polymer is soluble in the fluorinated solvent; and comprising cure sites selected from iodine, bromine, and chlorine; The composition comprises one or more curing agents comprising an ethylenically unsaturated group and an electron donating group that is an amino group or a precursor thereof, the electron donating group may be on the same curing agent having the ethylenically unsaturated group or may be on a different curing agent; The composition is free of organic peroxides.

14. An article comprising a crosslinked fluoropolymer composition, said crosslinked fluoropolymer composition comprising at least 90 wt. % of polymerized units derived from a perfluorinated monomer, based on a total weight of said fluoropolymer; the fluoropolymer is crosslinked with ethylenically unsaturated groups, alkoxysilane groups, or a combination thereof; The crosslinked fluoropolymer composition comprises a compound that includes an electron donating group that is an amino group or a residue thereof; The composition is free of organic peroxides; An article, wherein a portion of the fluoropolymer comprises one or more cure sites selected from iodine, bromine, chlorine, or combinations thereof.

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