Coating composition comprising fluoropolymer and fluorinated liquids suitable for electronic communication articles

Abstract

The coating composition is described as comprising a fluoropolymer; a fluorinated solvent; and a fluorinated alcohol. In some embodiments, the coating composition further comprises a compound having one or more alkoxysilyl groups and / or a compound having one or more amino groups. When these compounds are crosslinked compounds, the fluoropolymer generally contains cure sites. The coating composition may further comprise fillers such as silica, glass fibers, (e.g., crystalline) fluoropolymer particles, and combinations thereof. Methods of coating substrates and articles (such as electronic and telecommunications articles) are also described.

Description

Summary of the Invention

[0001] In one embodiment, a coating composition is described comprising a fluoropolymer, a fluorinated solvent, and a fluorinated alcohol. In some embodiments, the fluoropolymer is soluble in the fluorinated solvent. The fluoropolymer may comprise at least 80, 85, or 90 wt.% of polymeric units selected from tetrafluoroethylene (TFE) and one or more unsaturated perfluorinated alkyl ethers of a perfluorinated monomer. In some embodiments, the fluoropolymer is insoluble in the fluorinated alcohol. The fluorinated alcohol is generally present in an amount not exceeding 10 wt.% of the sum of the fluorinated solvent and the fluorinated alcohol. The fluorinated solvent may be a partially fluorinated ether, such as 3-ethoxyperfluorinated 2-methylhexane or 3-methoxyperfluorinated 4-methylpentane. In some embodiments, the coating composition further comprises compounds having one or more alkoxysilyl groups and / or compounds having one or more amino groups. When these compounds are crosslinking compounds, the fluoropolymer generally comprises a cure site. In some embodiments, the coating composition further comprises silica, glass fiber, or a combination thereof. In some embodiments, the coating composition further comprises (e.g., crystalline) fluoropolymer particles.

[0002] It also describes methods for coating substrates and articles (especially electronic and telecommunications articles). Simple Explanation of the Diagram

[0003] [Figure 1] depicts the viscosity change over time for a composition containing various fluorinated alcohols. Implementation

[0004] This document describes a coating composition comprising a fluoropolymer, a fluorinated solvent, and a fluorinated alcohol. Fluoroplastics

[0005] The fluoropolymer comprises a fluoropolymer that is predominantly or solely derived from perfluorinated comonomers, including tetrafluoroethylene (TFE) and one or more unsaturated (e.g., alkenyl, vinyl) perfluorinated alkyl ethers. As used herein, "predominantly" means that at least 80, 85, or 90% by weight of the fluoropolymer polymerizing units are derived from such perfluorinated comonomers, such as tetrafluoroethylene (TFE), and one or more unsaturated perfluorinated alkyl ethers, based on the total weight of the fluoropolymer. In some embodiments, the fluoropolymer comprises at least 81, 82, 83, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, or 97% 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 TFE-derived polymerizing units. In some embodiments, the maximum amount derived from TFE polymerizing units is no more than 60% by weight or 55% by weight.

[0006] In some advantageous embodiments, one or more unsaturated perfluorinated alkyl ether systems are selected from the following general formulas: Rf-O-(CF2)n-CF=CF2, where n is 1 (allyl ether) or 0 (vinyl ether), and Rf represents a perfluoroalkyl residue, which may be inserted with an oxygen atom once or more. Rf may contain up to 10 carbon atoms, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. Rf preferably contains up to 8 carbon atoms, more preferably up to 6 carbon atoms, and most preferably 3 or 4 carbon atoms. In one embodiment, Rf has 3 carbon atoms. In another embodiment, Rf has 1 carbon atom. Rf may be straight-chain or branched, and may or may not contain cyclic units. Specific examples of Rf include residues having one or more ether functionalities, 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, Other specific examples of Rf include residues that do not contain ether functionality, and include, but are not limited to, -C4F9; -C3F7, -C2F5, -CF3, wherein the C4 and C3 residues may be branched or straight, but are preferably straight.

[0007] Unsaturated perfluorinated alkyl groups may contain allyl or vinyl groups. Both have C-C double bonds. Perfluorinated vinyl groups are CF2=CF-; perfluorinated allyl groups are CF2=CFCF2-.

[0008] Suitable examples of perfluorinated alkyl vinyl ethers (PAVE) and perfluorinated alkyl allyl ethers (PAAE) include, but are not limited to, perfluorinated (methyl vinyl) ether (PMVE), perfluorinated (ethyl vinyl) ether (PEVE), perfluorinated (n-propyl vinyl) ether (PPVE-1), perfluorinated-2-propoxypropyl vinyl ether (PPVE-2), perfluorinated-3-methoxy-n-propyl vinyl ether, perfluorinated-2-methoxy-ethyl vinyl ether, CF2=CF-O-CF2-O-C2F5, CF2=CF-O-CF2-O-C3F7, CF3-(CF2)2-O-CF(CF3)-CF2-O-CF(CF3)-CF2-O-CF=CF2, and their allyl ether homologues. Specific examples of allyl ethers include CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-(CF3)3-O-CF3.

[0009] Further examples include, but are not limited to, vinyl ethers as described in European Patent EP 1,997,795.

[0010] In some embodiments, (e.g., amorphous) fluoropolymers comprise at least one allyl ether polymeric unit, such as alkyl vinyl ethers CF2=CFCF2OCF2CF2CF3. Such fluoropolymer systems are described in WO 2019 / 161153; these are incorporated herein by reference.

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

[0012] In some embodiments, one or more unsaturated perfluorinated alkyl ethers comprise unsaturated cyclic perfluorinated alkyl ethers, such as 2,2-bis(trifluoromethyl-4,5-difluoro-1,3-dioxane). In other embodiments, the fluoropolymer is substantially free of unsaturated cyclic perfluorinated alkyl ethers, such as 2,2-bis(trifluoromethyl-4,5-difluoro-1,3-dioxane. "Substantially free" means in amounts of zero or sufficiently low that such fluoropolymers have substantially the same properties.

[0013] Fluoropolymers generally comprise polymeric units derived from one or more unsaturated perfluorinated alkyl ethers (PAVE) (e.g., PMVE, PAAE, or combinations thereof), in an amount of at least 10, 15, 20, 25, 30, 45, or 50% by weight of the total monomeric units of the fluoropolymer. When the amount of polymeric units derived from one or more unsaturated perfluorinated alkyl ethers is less than 30 wt.%, amorphous fluoropolymers generally comprise other comonomers, such as HFP, to reduce crystallinity. In some embodiments, the fluoropolymer comprises no more than 50, 45, 40, or 35% by weight of polymeric units derived from one or more unsaturated perfluorinated alkyl ethers (PMVE, PAAE, or combinations thereof) of the total monomeric units of the fluoropolymer. The molar ratio of units derived from TFE to those derived from the aforementioned perfluorinated alkyl ethers may be, for example, from 1:1 to 5:1. In some embodiments, the molar ratio is in the range of 1.5:1 to 3:1.

[0014] In some embodiments, one or more unsaturated perfluorinated alkyl ethers comprise unsaturated cyclic perfluorinated alkyl ethers, such as 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxane. The amorphous fluoropolymers primarily comprise or comprise only (e.g., repeatedly) the following: polymeric units derived from two or more perfluorinated comonomers, including tetrafluoroethylene (TFE) and one or more unsaturated cyclic perfluorinated alkyl ethers, such as 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxane, are commercially available as "TEFLON™ AF", "CYTOP™", and "HYFLON™".

[0015] Fluoropolymers containing sufficient amounts of polymer units of one or more unsaturated perfluorinated alkyl ethers are generally amorphous fluoropolymers. As used herein, amorphous fluoropolymers are materials that are essentially non-crystalline or do not possess a distinct melting point (peak value), as determined by differential scanning calorimetry according to DIN EN ISO 11357-3:2013-04 under a nitrogen flow and a heating rate of 10 °C / min. Generally, amorphous fluoropolymers have glass transition temperatures (Tg) of less than 26 °C, less than 20 °C, or less than 0 °C, and for example, from -40 °C to 20 °C, or from -50 °C to 15 °C, or from -55 °C to 10 °C. Fluoropolymers generally have a Mooney viscosity (ML 1+10, at 121 °C) of about 2 to about 150, for example, from about 10 to 100, or from 20 to 70. For amorphous polymers containing cyclic perfluorinated alkyl ether units, the glass transition temperature is generally 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 / 5kg) is between 0.1 and 1000 g / 10 min.

[0016] The fluorine content of fluoropolymers is generally at least 60, 65, 66, 67, 68, 69, or 70 wt.%, and generally not greater than 76, 75, 74, or 73 wt.%. The fluorine content can be achieved by appropriately selecting the comonomers and their amounts.

[0017] These highly fluorinated amorphous fluoropolymers generally do not dissolve to at least 1 wt.% in hydrogen-containing organic liquids at room temperature and standard pressure (for example, they are insoluble in any of methyl ethyl ketone (“MEK”), tetrahydrofuran (“THF”), ethyl acetate, or N-methylpyrrolidone (“NMP”).

[0018] Fluoropolymers may contain partially fluorinated or non-fluorinated comonomers and combinations thereof, although this is not preferred. Typical partially fluorinated comonomers include, but are not limited to, 1,1-difluoroethylene (difluoroethylene, VDF) and vinyl fluoride (VF), or trifluorochloroethylene, or trichlorofluoroethylene. Examples of non-fluorinated comonomers include, but are not limited to, ethylene and propylene. The amount of units derived from these comonomers, based on the total weight of the fluoropolymer, ranges from 0 to 8% by weight. In some embodiments, the concentration of this comonomer, based on the total weight of the fluoropolymer, is not greater than 7, 6, 5, 4, 3, 2, or 1% by weight.

[0019] In a preferred embodiment, the curable fluoropolymer-based perfluoroelastomer comprises (only) repeating units derived from the perfluorinated comonomer, but may, if desired, contain units derived from the curing site monomer and the modifying monomer. The curing site monomer and the modifying monomer may be partially fluorinated, non-fluorinated, or perfluorinated, and preferably perfluorinated. The perfluoroelastomer may contain 69 to 73, 74, or 75% by weight of fluorine (based on the total amount of the perfluoroelastomer). The fluorine content can be achieved by appropriately selecting the comonomer and its amount.

[0020] Fluoropolymers can be prepared by methods known in the art, such as total polymerization, suspension polymerization, solution polymerization, or aqueous emulsion polymerization. Various emulsifiers can be used as described in the art, including, for example, 3H-perfluoro-3-[(3-methoxy-propoxy)propionic acid. For example, the polymerization process can be carried out by free radical polymerization of the monomer alone or as a solution, emulsion, or dispersion in an organic solvent or water. Seeded polymerization may or may not be used. Curable fluoroelastomers that can be used also include commercially available fluoroelastomers, particularly perfluoroelastomers.

[0021] Fluoroelastomers can have a single-peak, bi-peak, or multi-peak weight distribution. Fluoropolymers may or may not have a core-shell structure. Core-shell polymers are polymers in which the composition of the comonomer, or the ratio of the comonomers, or the reaction rate is changed to produce a shell with different compositions when polymerization is nearing completion (generally after at least 50 mol% of the comonomer has been consumed). solidification sites

[0022] In some embodiments, the fluoropolymer comprises a curable fluoropolymer containing one or more curing sites. The curing site is a functional group that reacts in the presence of a curing agent or curing system to crosslink the polymer. The curing site is generally introduced by copolymerizing curing site monomers that already contain functional comonomers of the curing site or its precursors. One indicator of crosslinking is that the dried and cured coating composition is insoluble in the fluorinated solvent of the coating.

[0023] Curing sites can be introduced into polymers using curing site monomers (i.e., functional monomers described below), functional chain transfer agents, and starter molecules. Fluoroelastomers may contain curing sites that are reactive to more than one class of curing agents.

[0024] Curable fluoroelastomers may also contain curing sites as side groups in the main chain or at the terminal positions. Curing sites within the fluoropolymer main chain can be introduced by using suitable curing site monomers. Curing site monomer systems contain one or more functional monomers that can act as curing sites, or contain precursors that can be converted into curing sites.

[0025] In some embodiments, the curing site contains iodine or bromine atoms.

[0026] Iodine-containing chain transfer agents can be used to introduce iodine-containing curing site end groups during polymerization. Iodine-containing chain transfer agents will be described in more detail below. Iodine end groups can be introduced using a halogenated redox system as described below.

[0027] Besides iodine-containing curing sites, other curing sites may also exist, such as Br-containing curing sites or curing sites containing one or more nitrile groups. Br-containing curing sites can be introduced by monomers containing Br-containing curing sites.

[0028] Examples of comonomers in the cured portion include, for example: (a) Bromo- or iodine-(per)fluoroalkyl-(per)fluorovinyl ethers, including, for example, those having the following formula: ZRf-O-CX=CX2 Each X may be the same or different and represents H or F, Z represents Br or I, and Rf represents a C1-C12 (per)fluoroalkyl group optionally containing chlorine 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, where Z represents Br or I; and (b) Bromo- or iodoperfluoroolefins, such as those having the following formula: Z'-(Rf)r-CX=CX2 Each X independently represents H or F, Z' series Br or I, Rf series optionally contains a chlorine atom in a C1-C12 perfluoroalkyl group, and r series 0 or 1; and (c) Nonfluorinated bromine and iodo-olefins, such as bromoethylene, iodoethylene, 4-bromo-1-butene, and 4-iodo-1-butene.

[0029] Specific examples include, but are not limited to, compounds according to (b), wherein X is a series of H, such as an X-series H, and Rf is a C1 to C3 perfluoroalkyl compound. Specific examples include: bromo- or iodo-trifluoroethylene, 4-bromo-perfluorobutene-1, 4-iodo-perfluorobutene-1, or bromo- or iodo-fluoroolefins, such as 1-iodo-2,2-difluoroethylene, 1-bromo-2,2-difluoroethylene, 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.

[0030] In some embodiments, the curing site comprises a chlorine atom. Such curing site monomers include those having the general formula: CX1X2=CY1Y2, wherein X1 and X2 are independently H and F; Y1 is H, F, or Cl; and Y2 is Cl, a fluoroalkyl group (RF) having at least one Cl substituent, a fluoroether group (ORF) having at least one Cl substituent, or -CF2-ORF. The fluoroalkyl group (RF) is generally partially or fully fluorinated C1-C5 alkyl groups. Examples of curing site monomers having a chlorine atom include CF2=CFCl, CF2=CF-CF2Cl, CF2=CF-O-(CF2)n-Cl, n=1 to 4; CH2=CHCl, CH2=CCl2.

[0031] Generally, the amount of iodine, bromine, or chlorine, or combinations thereof, in a fluoropolymer relative to the total weight of the fluoropolymer is between 0.001% by weight and 5% by weight, preferably between 0.01% by weight and 2.5% by weight, or between 0.1% by weight and 1% by weight, or between 0.2% by weight and 0.6% by weight. In one embodiment, the curable fluoropolymer contains, by weight of the fluoropolymer, between 0.001% by weight and 5% by weight, preferably between 0.01% by weight and 2.5% by weight, or between 0.1% by weight and 1% by weight, more preferably between 0.2% by weight and 0.6% by weight.

[0032] In other embodiments, halogenated chain transfer agents may be used to provide terminal curing sites. Chain transfer agents are compounds capable of reacting with propagating polymer chains and terminating chain propagation. Examples of chain transfer agents described for the production of fluoroelastomers include those having the formula RIx, where R is an x-valent fluoroalkyl or fluoropyranyl group having 1 to 12 carbon atoms, which may be inserted via one or more ether oxygen atoms and may also contain chlorine and / or bromine atoms. R may be Rf, and Rf may be an x-valent (per)fluoroalkyl or (per)fluoropyranyl group, which may be inserted via one or more ether oxygen atoms. Examples include α-ω diiodoalkanes, α-ω diiodofluoroalkanes, and α-ω diiodoperfluoroalkanes, which may contain one or more ether oxygen atoms in the chain. "α-ω (alpha-omega)" indicates the terminal position of the iodine atom in the molecule. Such compounds may 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. Other examples include fluorinated diiodoether compounds of the following formula: Rf-CF(I)-(CX2)n-(CX2CXR)mOR"f-Ok-(CXR'CX2)p-(CX2)q-CF(I)-R'f where X is independently selected from F, H, and Cl; Rf and R'f are independently selected from F and monovalent perfluoroalkanes having 1 to 3 carbon atoms; R is F, or partially fluorinated or perfluorinated alkanes containing 1 to 3 carbon atoms; R"f is a divalent fluorinated alkyl group having 1 to 5 carbons or a divalent fluorinated alkyl ether having 1 to 8 carbons and at least one ether bond; k is 0 or 1; and n, m, and p are independently selected from integers from 0 to 5, where n plus m is at least 1, and p plus q is at least 1.

[0033] Fluoropolymers may or may not contain units derived from at least one modifying monomer. The modifying monomer can introduce branched sites into the polymer structure. Generally, the modifying monomer is a diene, diene ether, or polyether. Diolefins and diene (poly)ethers can be perfluorinated, partially fluorinated, or non-fluorinated. Preferably, they are perfluorinated. Suitable perfluorinated diene ethers include those represented by the following general formulas: CF2=CF-(CF2)nO-(Rf)-O-(CF2)m-CF=CF2, where n and m are independently 1 or 0, and Rf represents a perfluorinated straight-chain or branched, cyclic or acyclic aliphatic or aromatic hydrocarbon residue, which may be inserted through one or more oxygen atoms and contains up to 30 carbon atoms. Particularly suitable perfluorinated diene ethers are divinyl ethers represented by the following formula: CF2 = CF - O - (CF2)nO - CF = CF2, where n is an integer between 1 and 10, preferably 2 to 6. For example, n can be 1, 2, 3, 4, 5, 6, or 7. More preferably, n represents a non-even integer, such as 1, 3, 5, or 7.

[0034] Further specific examples include diene ethers according to the following general formula CF2 = CF - (CF2)nO - (CF2)pO - (CF2)m - CF = CF2 where n and m are independently 1 or 0, and p is an integer from 1 to 10 or from 2 to 6. For example, n can be chosen to represent 1, 2, 3, 4, 5, 6, or 7, preferably 1, 3, 5, or 7.

[0035] A more suitable perfluorinated diene ether can be represented by the following formula: CF2=CF-(CF2)pO-(RafO)n(RbfO)m-(CF2)q-CF=CF2, where Raf and Rbf are different straight-chain or branched perfluoroalkyl groups with 1 to 10 carbon atoms, particularly 2 to 6 carbon atoms, and may or may not be inserted with one or more oxygen atoms. Raf and / or Rbf may also be perfluorinated phenyl or substituted phenyl; n is an integer between 1 and 10, and m is an integer between 0 and 10, preferably m is 0. In addition, p and q are independently 1 or 0.

[0036] In another embodiment, the perfluorinated diene ether can be represented by the formula just described, wherein m, n, and p are zero, and q are 1 to 4.

[0037] The modified monomers can be prepared by methods known in the art and are commercially available from sources such as Anles Ltd., St. Petersburg, Russia.

[0038] Preferably, no or only a small amount (e.g., ethylene-based unsaturated) modifying monomers are used. The typical amount, based on the total weight of the fluoropolymer, includes 0 to 5% by weight, or 0 to 1.4% by weight. For example, the modifier may be present in an amount from about 0.1% to about 1.2% by weight, or from about 0.3% to about 0.8% by weight, based on the total weight of the fluoropolymer. Combinations of modifiers may also be used. Furthermore, in general embodiments, the fluoropolymer composition comprises no more than 8, 7, 6, 5, 4, 3, 2, 1, or 0.1 wt% of polymeric units containing (e.g., (meth)acrylate) esters.

[0039] Fluoropolymers having halogen curing sites (iodine, bromine, and chlorine) can be advantageous for UV curing, as described in WO2021 / 091864, which is incorporated herein by reference. For thermosetting or electron beam curing, fluoropolymers having nitrile curing sites can be used alternatively. Furthermore, including curing sites (such as nitrile sites) can improve the adhesion of fluoropolymer compositions to substrates (e.g., copper), even in the absence of crosslinking agents.

[0040] When a combination of fluoropolymers with different curing sites is used, the composition can be characterized as dual-cured, containing different curing sites that are reactive to different curing systems.

[0041] In some embodiments, the fluoropolymer contains a nitrile-containing curing site and corresponding amidine, amidine salt, amide, amide / amide, and ammonium salt. Fluoropolymers having nitrile-containing curing sites are known, such as those described in U.S. Patent Nos. 6,720,360 and 7,019,082.

[0042] The nitrile-containing curing sites may be reactive to other curing systems, such as, but not limited to, bisphenol curing systems, peroxide curing systems, and trioxide curing systems. Curing systems, and particularly amine curing systems. Examples of monomers containing nitrile curing sites correspond to the following formula: CF2 = CF - CF2 - O - Rf - CN; CF2 = CFO(CF2)rCN; CF2=CFO[CF2CF(CF3)O]p(CF2)vOCF(CF3)CN; CF2=CF[OCF2CF(CF3)]kO(CF2)uCN; where r represents an integer from 2 to 12; p represents an integer from 0 to 4; k represents 1 or 2; v represents an integer from 0 to 6; u represents an integer from 1 to 6; and Rf is a perfluoroalkyl or divalent perfluoroether group. Specific examples of nitrile-containing fluorinated monomers include, but are not limited to, perfluoro(8-cyano-5-methyl-3,6-dioxo-1-octene), CF2=CFO(CF2)5CN, and CF2=CFO(CF2)3OCF(CF3)CN.

[0043] In some embodiments, the amount of the comonomer containing the nitrile curing site is generally at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5% by weight, and generally not more than 10% by weight; the above is based on the total weight of the fluoropolymer.

[0044] The composition may include a curable fluoropolymer and a second fluoropolymer lacking curing sites (e.g., halogens or nitriles). The amount of the fluoropolymer lacking curing sites is generally less than 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 wt.% of the total fluoropolymer. In this embodiment, the composition generally has a sufficient amount of fluoropolymer with curing sites to achieve adequate adhesion and / or crosslinking. Fluorinated solvents

[0045] The fluoropolymer (coating solution) composition contains at least one fluorinated solvent. In general embodiments, the fluoropolymer is soluble in the fluorinated solvent. In other embodiments, the fluoropolymer is dispersed in the solvent. The solvent is generally present in an amount of at least 25% by weight of the total 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 greater, based on the total weight of the coating solution composition.

[0046] The fluoropolymer (coating solution) composition generally contains 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% by weight of fluoropolymer, based on the total weight of the coating solution composition. In some embodiments, the fluoropolymer coating solution composition contains at least 2, 3, 4, or 5% by weight of fluoropolymer. In some embodiments, the fluoropolymer coating solution composition contains at least 6, 7, 8, 9, or 10% by weight of fluoropolymer. Based on the total weight of the coating solution composition, the fluoropolymer coating solution composition generally contains no more than 50, 45, 40, 35, 30, 25, or 20% by weight of fluoropolymer.

[0047] In general embodiments, one or more of the fluoropolymers in the composition are soluble in a fluorinated solvent. One or more of the fluoropolymers in the composition are soluble in a fluorinated solvent, such as HFE-7300, at a concentration of at least 10 wt.% solids. In some embodiments, one or more of the fluoropolymers in the composition are soluble in a fluorinated solvent, such as HFE-7300, at a concentration of at least 15, 20, 25, 30, 35, 40, 45, or 50 wt.% solids. In other embodiments, the fluoropolymers are dispersed in the fluorinated solvent at such concentrations, but are insoluble in the fluorinated solvent.

[0048] The optimal amounts of solvent and fluoropolymer can vary depending on the end application. For example, to provide a thin coating, a very diluted solution of fluoropolymer in a solvent is desirable, for example, the amount of fluoropolymer can be from 0.01% to 5% by weight. Furthermore, for spray coating applications, a low-viscosity coating composition may be preferable to a high-viscosity solution. The concentration of fluoropolymer in the solution affects the viscosity and can be adjusted accordingly. An advantage of this disclosure is that solutions with high concentrations of fluoropolymer can also be prepared, yet still provide a low-viscosity, transparent liquid composition.

[0049] In some embodiments, the fluoropolymer coating solution composition may be a liquid. The liquid may have a viscosity of, for example, 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 may have a viscosity of, for example, from 2,000 to 100,000 mPas at room temperature (20°C + / - 2°C).

[0050] The solvent is a liquid under ambient conditions and generally has a boiling point greater than 50°C. Preferably, the solvent has a boiling point below 200°C, allowing it to 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.

[0051] The solvents are partially or fully fluorinated. Therefore, the solvents are non-aqueous. Various 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.

[0052] 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 generally greater than 0 and may be at least 10, 20, 30, 40, 50, 60, 70, or 80.

[0053] As used in this paper, GWP is a relative value of the global warming potential of a compound based on its structure. The GWP of a compound, as defined by the Intergovernmental Panel on Climate Change (IPCC) in 1990 and updated in subsequent reports, is calculated as the warming effect caused by the release of 1 kg of the compound relative to the warming effect caused by the release of 1 kg of CO2 over a specified integration time horizon (ITH). The F series represents the radiative forcing per unit mass of compound (the change in the flux of radiation penetrating the atmosphere due to the IR absorption of this compound), the Co series represents the atmospheric concentration of the compound at the initial time, the τ series represents the atmospheric lifetime of the compound, the t series represents time, and the x series represents the compound of interest.

[0054] 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. More preferably, it comprises non-fluorinated alkyl groups and perfluorinated alkyl groups, and more preferably, the perfluorinated alkyl groups are branched.

[0055] In one embodiment, the partially fluorinated ether or polyether solvent corresponds to the following formula: In Rf-OR, Rf is a perfluorinated or partially fluorinated alkyl or (poly)ether group, and R is a nonfluorinated or partially fluorinated alkyl group. Generally, Rf can have 1 to 12 carbon atoms. Rf can be a primary, secondary, or tertiary fluorinated or perfluorinated alkyl residue. This means that when Rf is a primary alkyl residue, the carbon atom bonded to the ether atom contains two fluorine atoms and is bonded to another carbon atom of the fluorinated or perfluorinated alkyl chain. In this case, Rf corresponds to Rf 1-CF2-, and the polyether can be described by the general formula: Rf 1-CF2-OR.

[0056] When Rf is a secondary alkyl residue, the carbon atom bonded to the ether atom is also bonded to a fluorine atom and two carbon atoms of part and / or perfluorinated alkyl chains, and Rf corresponds to (Rf 2Rf 3)CF-. Polyethers correspond to (Rf 2Rf 3)CF-OR.

[0057] When Rf is a tertiary alkyl residue, the carbon atom bonded to the ether atom is also bonded to three carbon atoms of three partially fluorinated and / or perfluorinated alkyl chains, and Rf corresponds to (Rf 4Rf 5Rf 6)-C-. Polyethers correspond to (Rf 4Rf 5Rf 6)-C-OR. Rf 1; Rf 2; Rf 3; Rf 4; Rf 5; Rf 6 correspond to the definition of Rf and are perfluorinated or partially fluorinated alkyl groups, which may be inserted once or more via an ether oxygen. They may be linear, branched, or cyclic. Combinations of polyethers may also be used, as well as combinations of primary, secondary, and / or tertiary alkyl residues.

[0058] Examples of solvents containing partially fluorinated alkyl groups include C3F7OCHFCF3 (CAS No. 3330-15-2).

[0059] An example of a solvent containing perfluorinated (poly)ethers in Rf is C3F7OCF(CF3)CF2OCHFCF3 (CAS No. 3330-14-1).

[0060] In some embodiments, the fluorinated ether solvent corresponds to the following formula: CpF2p+1-O-CqH2q+1, where q is an integer from 1 to 5, such as 1, 2, 3, 4, or 5, and p is an integer from 5 to 11, such as 5, 6, 7, 8, 9, 10, or 11. Preferably, CpF2p+1 has branches. Preferably, CpF2p+1 has branches, and q is 1, 2, or 3.

[0061] 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-dodecano-2-(trifluoromethyl)hexane. These solvents are available, for example, under the trade name NOVEC from 3M Company, St. Paul, MN.

[0062] Fluorinated (e.g., ethers and polyethers) solvents can be used alone or in combination with other solvents that may be fluorinated or non-fluorinated. When non-fluorinated solvents are combined with fluorinated solvents, the concentration of non-fluorinated solvent relative to the total amount of solvent is generally less than 30, 25, 20, 15, 10, or 5 wt% . Representative non-fluorinated solvents include ketones, such as acetone, MEK, methyl isobutyl ketone, methyl pentyl 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 δ-valerolactone and γ-valerolactone.

[0063] As described in WO2021 / 091864, coating compositions comprising fluoropolymers, fluorinated solvents, and curing agents are "stable," meaning they remain homogeneous when stored in a sealed container at room temperature for at least 24 hours. In some embodiments, the coating composition remains stable for one week or longer. "Homogeneous" means that the coating composition, immediately after shaking, does not exhibit visible separation of precipitates or visible stratification when placed in a 100 ml glass container and allowed to stand at room temperature for at least 4 hours. However, the industry will find advantages in coating compositions with improved stability. In some embodiments, coating compositions further comprising fluorinated alcohols described herein are stable for 48, 72, or 96 hours or longer. In some embodiments, coating compositions further comprising fluorinated alcohols described herein are stable for 100, 200, 300, 400, 500, or 600 hours or longer. [Fluorinated alcohols]

[0064] Fluorinated alcohols contain a single hydroxyl group or more than one hydroxyl group. In some embodiments, fluorinated alcohols contain linear, branched, or cyclic (per)fluoroalkyl or (per)fluoropyranyl groups. In some embodiments, linear (per)fluoroalkyl alcohols provide a greater improvement in stability compared to branched (per)fluoroalkyl alcohols. In some embodiments, the (per)fluoroalkyl or (per)fluoropyranyl group may be interrupted with heteroatoms (e.g., O, N, S) as appropriate.

[0065] In some embodiments, fluorinated alcohols have the following formula: Rf-(CH2)nOH)p, wherein Rf is a (per)fluoroalkyl or (per)fluoroalkyl group. The number of CH2 groups can be 0, 1, or greater than 1. In some embodiments, n is 1. Alcohols generally contain a single -OH group (i.e., p-1). However, low molecular weight diols and polyols may also be suitable (i.e., p-2 or 3).

[0066] In general embodiments, Rf is a perfluorinated C1 to C4 alkyl or C2 to C4 alkyl group, i.e., perfluoromethyl, perfluoroethyl, perfluoroethylene, perfluoropropyl, perfluoropropylene, perfluorobutyl, or perfluorobutene. Representative fluorinated alcohols include, for example, CF3CH2OH, C2F5CH2OH, n-C3F7CH2OH, (CF3)2CFCH2OH, (CF3)2CFCF2CH2OH, CF3OCF2CF2CH2OH, HCF2CF2CH2OH, H(CF2)4CH2OH, n-C3F7CH2CH2OH, and (CF2CH2OH)2.

[0067] In some embodiments, the fluorinated alcohol generally also has a boiling point below 200°C, making it easily removable. In some embodiments, the fluorinated alcohol has a boiling point below 190, 180, 170, 160, 150, 140, 130, 120, 110, or 100°C. In some embodiments, the fluorinated alcohol has a boiling point of at least 50, 55, 60, 65, or 70°C. The boiling point of the fluorinated alcohol may differ from that of the fluorinated solvent by at least 5 or 10 degrees to facilitate the separation of the fluorinated alcohol from the fluorinated solvent when the solvent is removed from the coating composition.

[0068] In some embodiments, at a fluoropolymer concentration of 10 wt%, the fluoropolymer system is insoluble in fluorinated alcohols.

[0069] As demonstrated in upcoming examples, fluorinated alcohols have been found to significantly improve the shelf-life stability of coating compositions. These improvements are accompanied by the maintenance of other physical properties (such as Dk and Df) of the dried and, where applicable, cured coating compositions. Alkoxysilane & Amine Compounds

[0070] In some embodiments, fluorinated alcohols improve the stability of coating compositions comprising compounds having one or more alkoxysilanes. Without intending to be bound by theory, it is hypothesized that fluorinated alcohols may reduce the hydrolysis of alkoxysilanes to Si-OH.

[0071] In some embodiments, fluorinated alcohols improve the stability of coating compositions comprising compounds having one or more amine groups. Without being bound by theory, it is hypothesized that fluorinated alcohols can act as weak acids to prevent premature curing of amines at their reactive curing sites.

[0072] Amines can be aliphatic or aromatic. Amine compounds can be used to provide a crosslinked fluoropolymer layer by curing fluoropolymers with (e.g., nitrile) curing sites using an amine curing agent (e.g., heat). Amine compounds can also be used in combination with vinyl unsaturated compounds to provide a crosslinked fluoropolymer layer by curing fluoropolymers with halogen curing sites using (e.g., radiation).

[0073] In some embodiments, the compound may be characterized as a crosslinked compound comprising at least two amino groups, at least two alkoxysilyl groups, or at least one amine and at least one alkoxysilyl group.

[0074] In some embodiments, compounds containing one or more alkoxysilyl groups and / or one or more amino groups may be fluorinated. Such compounds may be fluorinated curing agents, such as those described in 83602 US002; these are incorporated herein by reference. In some embodiments, the fluorinated curing agent may be soluble in a fluorinated solvent.

[0075] In some embodiments, the curing agent is a non-fluorinated curing agent, such as that described in WO2021 / 091864, which is incorporated herein by reference.

[0076] Combinations of fluorinated and non-fluorinated curing agents can also be used.

[0077] In some embodiments, the amine may be characterized as an amino-substituted organosilicon ester or ester equivalent having at least one, preferably two or three ester or ester equivalent groups on a silicon atom. Ester equivalents are known to those skilled in the art and include compounds such as silane amines (RNR'Si), silane alkanoates (RC(O)OSi), Si-O-Si, SiN(R)-Si, SiSR, and RCONR'Si compounds, which may be thermally and / or catalytically substituted with 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 may not be H. These ester equivalents can also be cyclic, such as ethylene glycol, ethanolamine, ethylenediamine (e.g., N-[3-(trimethoxysilyl)propyl]ethylenediamine), and their acetamine derivatives.

[0078] Another example of such cyclic compounds is...

[0079] In this cyclic example, R' is as defined in the preceding sentence, except that it may not be aryl. It is well known that 3-aminopropylalkoxysilanes cyclize upon heating, and such RNHSi compounds can be used in this invention. Preferably, the amino-substituted organosilicon ester or ester equivalent has an ester group such as a methoxy group, which readily volatilizes as methanol. The amino-substituted organosilicon must have at least one ester equivalent; for example, it may be a trialkoxysilane.

[0080] For example, amino-substituted organosilanes can have the following formula: (Z2N-L-SiX'X"X'''), where Z is a hydrogen, alkyl, or substituted aryl or alkyl group (including amine-substituted alkyl); and L is a divalent straight-chain C1-12 alkyl group, or may contain C3-8 cycloalkyl, 3- to 8-membered heterocycloalkyl, C2-12 enyl, C4-8 cycloenyl, 3- to 8-membered heterocycloenyl or heteroaryl unit; and each of X', X" and X''' is a C1-18 alkyl, halogen, C1-8 alkoxy, C1-8 alkylcarbonyloxy, or amino group, provided that at least one of X', X" and X''' is a labile group. Furthermore, any two or all of X', X" and X''' may be covalently linked. The amino group may be an alkylamino group.

[0081] L may be a divalent aromatic group or may be inserted with one or more divalent aromatic groups or heteroatom groups. The aromatic group may include heteroaromatic groups. The heteroatom is preferably nitrogen, sulfur, or oxygen. L may optionally be substituted with C1-4 alkyl, C2-4 alkenyl, C2-4 alkynyl, C1-4 alkoxy, amino, C3-6 cycloalkyl, 3 to 6-membered heterocycloalkyl, monocyclic aryl, 5 to 6-membered heteroaryl, C1-4 alkylcarbonyloxy, C1-4 alkyloxycarbonyl, C1-4 alkylcarbonyl, formyl, C1-4 alkylcarbonylamino, or C1-4 aminocarbonyl. L may further optionally be inserted via -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-trimethoxysilylpropyl)n-methylamine, 3-(2-aminoethyl)aminopropyltrimethoxysilane (SILQUEST A-1120), SILQUEST A-1130, (aminoethylaminomethyl)phenethyltrimethoxysilane, (aminoethylaminomethyl)phenethyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (SILQUEST A-1110), and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (SILQUEST A-1110). A-2120), bis-(γ-triethoxysilylpropyl)amine (SILQUEST A-1170), N-(2-aminoethyl)-3-aminopropyltributoxysilane, 6-(aminohexylaminopropyl)trimethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyltriethoxysilane, p-(2-aminoethyl)phenyltrimethoxysilane, 3-aminopropyltris(methoxyethoxyethoxy)silane, 3-aminopropylmethyldiethoxy-silane, oligomeric amine silanes (such as DYNASYLAN) 1146), 3-(N-methylamino)propyltrimethoxysilane, 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: Bis-silylurea [RO)3Si(CH2)NR]2C=O is another example of an organosilicon ester or ester equivalent that has been substituted with an amino group.

[0083] In some embodiments, the curing agent comprises a blocked amine group and an alkoxysilyl group. This blocked amine curing agent can be characterized by the following general formula: (R4O)3-Si-(CH2)mN=C(R1)(R2) where R1 and R2 are independently selected from straight-chain or branched alkyl groups containing 1 to 6 carbon atoms, as previously described. R1 is independently selected from straight-chain or branched alkyl groups containing 1 to 6 carbon atoms, m is an integer from 1 to 4, and each R4 is independently a C1 or C2 alkyl group.

[0084] An illustrative curing agent system comprising blocked amino and alkoxysilane groups is shown below: N-(1,3-dimethylbutylene)aminopropyltriethoxysilane.

[0085] This curing agent is available from Gelest and from 3M ("3M™ Dynamer™ Rubber Curative RC5125"). An additional example of a blocked amine electron donor precursor.

[0086] In some embodiments, the amine curing agent comprises an aziridinyl group and an alkoxysilane group. Such compounds are known, for example, by way of US 3,243,429; these are incorporated herein by reference. Aziridinyl alkoxysilane compounds may have the following general structure: Wherein R” refers to hydrogen or C1-C4 alkyl (e.g., methyl); X refers to a bond, a divalent atom, or a divalent bonded group; n refers to 0, 1, or 2; m refers to 1, 2, or 3; and the sum or n+m refers to 3.

[0087] A representative compound is 3-(2-methylaziridinyl)ethylcarboxypropyltriethoxysilane.

[0088] In some embodiments, the vinyl unsaturated curing agent comprises at least one vinyl unsaturated group and at least one alkoxysilyl group. Suitable curing agents include, for example, (meth)acrylic alkoxysilanes, such as 3-(methacrylic alkoxy)propyltrimethoxysilane, 3-(methacrylic alkoxy)propylmethyldimethoxysilane, 3-(acrylic alkoxypropyl)methyldimethoxysilane, 3-(methacrylic alkoxy)propyldimethylmethoxysilane, and 3-(acrylic alkoxypropyl)dimethylmethoxysilane. In some embodiments, the amount of (meth)acrylic alkoxysilane is at least 2, 3, 4, or 5 wt.% to obtain a highly crosslinked fluoropolymer. Suitable alkenylalkoxysilanes include vinyldimethylethoxysilane, vinylmethyldiethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriphenoxysilane, vinyltri-tert-butoxysilane, vinyltriisobutoxysilane, vinyltriisopropoxysilane, vinyltri(2-methoxyethoxy)silane, and allyltriethoxysilane.

[0089] In some embodiments, ethylene-based unsaturated curing agents may have the following general formula. X1-L1-SiRm(OR1)3-m; wherein X1 is an vinyl unsaturated group, such as (meth)acrylyl or vinyl; L1 is an organic divalent bonded group having 1 to 12 carbon atoms; R is independently a C1-C4 alkyl group, and most generally methyl or ethyl; R1 is independently H or C1-C4 alkyl group, and most generally methyl or ethyl; and m is in the range of 0 to 2.

[0090] In general embodiments, L1 is an alkyl group. In some embodiments, L1 is an alkyl group having 1, 2, or 3 carbon atoms. In other embodiments, L1 comprises or is composed of aromatic groups such as phenyl or (e.g., C1-C4) alkylphenyl groups.

[0091] In some embodiments, such alkoxysilanes may be characterized as "non-functional" and have the following chemical formula: R2Si(OR1)m wherein R1 is independently alkyl as previously described; R2 is independently hydrogen, alkyl, aryl, alkylaryl, or OR1; and m is in the range of 1 to 3, and is generally 2 or 3 as previously described.

[0092] Suitable alkoxysilanes of the formula R2Si(OR1)m 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.

[0093] Preferably, the alkyl group(s) of the alkoxysilane comprises 1 to 6, more preferably 1 to 4 carbon atoms. The preferred alkoxysilanes used herein are selected from the group consisting of tetramethoxysilanes, tetraethoxysilanes, methyltriethoxysilanes, dimethyldiethoxysilanes, and any mixtures thereof. The preferred alkoxysilanes used herein include tetraethoxysilane (TEOS). Alkoxysilanes lacking organic functional groups used in methods of manufacturing coating compositions may be partially hydrolyzed, such as in the case of partially hydrolyzed tetramethoxysilane (TMOS), which may be purchased from Mitsuibishi Chemical Company under the trademark "MS-51".

[0094] When present, the amount of the nonfunctional alkoxysilane compound (e.g., TESO) is generally 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 solvents in the coating composition). In some embodiments, the amount of the nonfunctional alkoxysilane compound is no more than 5, 4.5, 4, 3.5, or 3% by weight solids.

[0095] A variety of other nonfluorinated and fluorinated amine compounds, both with and without alkoxysilyl groups, are described in the literature, including, for example, amidine, bis(aminophenol), and bis(aminothiophenol).

[0096] The compound containing one or more alkoxysilyl groups and / or one or more amino groups is generally present in an amount of at least 0.5, 1, 1.5, or 2 wt.% of the total weight of the fluoropolymer. The maximum amount of the fluorinated curing agent is generally no more than 10, 9, 8, 7, 6, or 5 wt.% of the total weight of the fluoropolymer.

[0097] When manufacturing the coating composition, compounds comprising one or more alkoxysilyl groups and / or one or more amino groups may be included in the coating composition. Alternatively, the coating composition (as manufactured) may be provided in the absence of such compounds. These compounds may be added subsequently before applying the coating composition to the substrate. Crystalline fluoropolymers

[0098] In some embodiments, the composition further comprises a crystalline fluoropolymer.

[0099] Crystalline fluoropolymers can exist as particles. Alternatively, crystalline fluoropolymers can exist as a second phase, which can be formed by sintering crystalline fluoropolymer particles at or above the melting temperature of the crystalline fluoropolymer particles, or by melting and extruding fluoropolymer compositions.

[0100] In some embodiments, fluoropolymer particles may be characterized as "agglomerates" (e.g., latex particles), meaning weak associations between primary particles (such as particles held together by charge or polarity). During the preparation of the coating solution, agglomerates generally physically break down into smaller entities (such as primary particles). In other embodiments, fluoropolymer particles may be characterized as "aggregates," meaning strongly bonded or fused particles, such as covalently bonded or thermally bonded particles prepared by processes such as sintering, arcing, flame hydrolysis, or plasma. During the preparation of the coating solution, aggregates generally do not break down into smaller entities (such as primary particles). "Primary particle size" refers to the average diameter of a single (non-agglomerated, non-cohesive) particle.

[0101] In one embodiment, this coating composition is prepared by blending a latex containing (e.g., crystalline) fluoropolymer particles with a latex containing amorphous fluoropolymer particles.

[0102] The latex can be combined by any suitable means, such as by vortex mixing for 1 to 2 minutes. The method further includes agglomerating the mixture of latex particles. Agglomeration 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 salt may be undesirable. The method further includes optionally washing the agglomerated mixture of amorphous fluoropolymer particles and crystalline fluoropolymer particles. The washing step can substantially remove emulsifiers or other surfactants from the mixture and can help obtain a well-mixed blend of substantially non-agglomerated dry particles. In some embodiments, the surfactant level in the resulting dry particle mixture can be, for example, less than 0.1% by weight, less than 0.05% by weight, or less than 0.01% by weight. The method further includes drying the agglomerated latex mixture. The agglomerated latex mixture can be dried by any suitable means, such as air drying or oven drying. In one embodiment, the agglomerated latex mixture can be dried at 100°C for 1 to 2 hours.

[0103] In some embodiments, the dried coagulated latex mixture may be dissolved in a solvent suitable for dissolving amorphous fluoropolymer particles to form a stable coating composition containing a homogeneous dispersion of crystalline fluoropolymer particles in a solution of amorphous fluoropolymer. In other embodiments, the dried coagulated latex mixture may be heat-treated.

[0104] The coating solution can be used to provide a coating on a substrate by applying a layer of coating composition to the surface of the substrate and drying the coating composition (i.e., removing the fluorinated solvent by evaporation). In some embodiments, the method further includes heating the coated substrate to a temperature above the melting temperature of the fluoropolymer particles to sinter the polymer particles.

[0105] In some embodiments, the method further comprises rubbing (e.g., buffing, polishing) the dried layer to form an amorphous fluoropolymer adhesive layer containing (e.g., crystalline) micron and optionally submicron fluoropolymer particles. Various rubbing techniques can be employed at the time of coating formation or later when the coated article is used or about to be used. Simply rubbing or buffing the coating a few times with cheesecloth or other suitable fabric, non-fabric, 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 employed. Rubbing can also reduce the haze of the cured coating.

[0106] A thin, continuous or nearly continuous fluoropolymer surface layer is formed on the coating surface by crystalline fluoropolymer particles, which is disposed on the underlying coating containing amorphous fluoropolymers. In a preferred embodiment, the thin crystalline fluoropolymer layer is relatively uniformly spread over the underlying coating, and it appears thinner and more uniform than if the fluoropolymer particles had only undergone fibrillation (e.g., due to orientation or other stretching).

[0107] The average roughness (Ra) of a surface is the arithmetic mean of the absolute values ​​of the surface height deviations measured from the mean plane. Fluoropolymer layers or films have low average roughness. In some embodiments, Ra is at least 40 or 50 nm and up to 100 nm before friction. In some embodiments, the surface is smoothed by at least 10, 20, 30, 40, 50, or 60% after friction. In some embodiments, Ra is less than 35, 30, 25, or 20 nm after friction.

[0108] When a thin coating is prepared from micron-sized fluoropolymer particles, the average roughness may be greater. In some embodiments, the average roughness is in the micron range. However, when the thickness of the coating or fluoropolymer film is greater than (e.g., crystalline) the particle size of the fluoropolymer particles, the surface of the fluoropolymer coating or film may have a low average roughness as previously described.

[0109] The advantage of the coating composition described herein is that it can be used to prepare coatings of varying thicknesses, both high and low. In some embodiments, the dried and cured coating has a thickness of 0.1 micrometers to 10 mils. In some embodiments, the dried and cured coating thickness is at least 0.2, 0.3, 0.4, 0.5, or 0.6 micrometers. In some embodiments, the dried and cured coating thickness is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 micrometers, and up to 100, 150, or 200 micrometers.

[0110] Various crystalline fluoropolymer particles, including mixtures of different crystalline fluoropolymer particles, can be used. Crystalline fluoropolymer particles generally have high crystallinity and therefore a distinct melting point (maximum peak value), as determined by differential scanning calorimetry according to DIN EN ISO 11357-3:2013-04 under a nitrogen flow and a heating rate of 10°C / min. Therefore, fluoropolymer particles are generally thermoplastic.

[0111] For example, crystalline fluoropolymers (e.g., particles) may include fluoropolymer particles having a Tm of at least 100, 110, 120, or 130°C. In some embodiments, crystalline fluoropolymers (e.g., particles) may include fluoropolymer particles having a Tm of no more than 350, 340, 330, 320, 310, or 300°C.

[0112] Crystalline fluoropolymers (e.g., particles) generally have a fluorine content greater than about 50 percent by weight. Furthermore, fluoropolymers (e.g., particles) may include fluoropolymers having a fluorine content between about 50 and about 76 percent by weight, between about 60 and about 76 percent by weight, or between about 65 and about 76 percent by weight.

[0113] Representative crystalline fluoropolymers include, for example, perfluorinated fluoropolymers such as 3M™ Dyneon™ PTFE dispersions TF 5032Z, TF 5033Z, TF 5035Z, TF 5050Z, TF 5135GZ, and TF 5070GZ; and 3M™ Dyneon™ Fluorothermoplastic Dispersions PFA 6900GZ, PFA 6910GZ, FEP 6300GZ, THV 221, THV 340Z, and THV 800. Other suitable fluoropolymer particles are available from suppliers such as Asahi Glass, Solvay Solexis, and Daikin Industries, and are familiar to those skilled in the art.

[0114] Commercially available aqueous dispersions typically contain up to 5 to 10 wt.% nonionic and / or ionic surfactants. These surfactants are substantially removed by washing away the aggregated mixture. Residual surfactant concentrations of less than 1, 0.05, or 0.01 wt.% may be present. Using "polymerized" aqueous fluoropolymer latexes is generally more convenient because they do not contain such high levels of nonionic / ionic surfactants.

[0115] As previously mentioned, crystalline fluoropolymers have melting points that can be determined by DSC. Crystallinity depends on the choice and concentration of the polymerizing monomers in the fluoropolymer. For example, PTFE homopolymers (containing 100% TFE units) have a melting point (Tm) higher than 340°C. Adding comonomers (such as unsaturated (per)fluorinated alkyl ethers) lowers the Tm. For example, when a fluoropolymer contains about 3 to 5 wt.% of such comonomer units, the Tm is about 310°C. As another example, when a fluoropolymer contains about 15 to 20 wt.% HFP polymerizing units, the Tm is about 260 to 270°C. As yet another example, when a fluoropolymer contains 30 wt.% of (per)fluorinated alkyl ethers (e.g., PMVE) or other polymerizing units of (various) comonomers that reduce crystallinity, the fluoropolymer no longer has a melting point detectable by DSC and is therefore characterized as amorphous.

[0116] In some embodiments, the crystalline fluoropolymer (e.g., particles) contains at least 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or about 100 wt.% of TFE polymeric units. The crystalline fluoropolymer (e.g., particles) generally has a larger amount of TFE polymeric units than crosslinked fluoropolymers. More generally, the crystalline fluoropolymer particles contain at least 85, 90, 95, or about 100 wt.% of TFE polymeric units. Furthermore, the crystalline fluoropolymer (e.g., particles) generally contains a lower concentration of unsaturated (per)fluorinated alkyl ethers (e.g., PMVE) than amorphous fluoropolymers. In general embodiments, the crystalline fluoropolymer (e.g., particles) contains less than 30, 25, 20, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, or 5 wt.% of (per)fluorinated alkyl ether (e.g., PMVE) polymeric units.

[0117] In some embodiments, the crystalline fluoropolymer is a copolymer formed from monomers comprising tetrafluoroethylene (“TFE”), hexafluoropropylene (“HFP”), and difluoroethylene (“VDF”, “VF2”). The monomer structures of these constituent components are shown below: TFE:CF2=CF2 (1) VDF:CH2=CF2(2) HFP:CF2=CF-CF3 (3)

[0118] In some embodiments, the crystalline fluoropolymer is composed of at least two constituent monomers (HFP and VDF), and in some embodiments it is composed of all three constituent monomers in different amounts.

[0119] Tm depends on the amounts of TFE, HFP, and VDF. For example, a fluoropolymer containing approximately 45 wt.% TFE polymeric units, approximately 18 wt.% HFP polymeric units, and approximately 37 wt.% VDF polymeric units has a Tm of approximately 120°C. As another example, a fluoropolymer containing approximately 76 wt.% TFE polymeric units, approximately 11 wt.% HFP polymeric units, and approximately 13 wt.% VDF polymeric units has a Tm of approximately 240°C. By increasing the number of HFP / VDF polymeric units while decreasing the number of TFE polymeric units, the fluoropolymer becomes amorphous. For an overview of crystalline and amorphous fluoropolymers, see: Ullmann's Encyclopedia of Industrial Chemistry (7th Edition, 2013 Wiley-VCH Verlag. 10. 1002 / 14356007.a11 393 pub 2) Chapter: Fluoropolymers, Organic.

[0120] In some embodiments, the crystalline fluoropolymer contains very few or no VDF polymeric units. The amount of VDF polymeric units is no more than 5, 4, 3, 2, or 1 wt.% of the total crystalline fluoropolymer.

[0121] In some embodiments, the crystalline fluoropolymer comprises HFP polymerization units. The amount of HFP polymerization units may be at least 1, 2, 3, 4, or 5 wt.% of the total crystalline fluoropolymer. In some embodiments, the amount of HFP polymerization units is not greater than 15, 14, 13, 12, 11, or 10 wt.% of the total crystalline fluoropolymer.

[0122] In some embodiments, the fluoropolymer of the composition described herein contains little or no vinyl difluoroethylene (VDF) (i.e., CH2=CF2) or VDF coupled to hexafluoropropylene (HFP) polymeric units. The VDF polymeric units may undergo dehydrofluorination (i.e., HF elimination reaction) as described in US2006 / 0147723. This reaction is limited by the number of polymeric VDF groups coupled to HFP groups contained in the fluoropolymer.

[0123] Crystalline fluoropolymers (e.g., particles) and amorphous fluoropolymers (e.g., particles) can be combined in various ratios. For example, based on the total weight percentage of solids (i.e., excluding solvents), the coating composition contains about 5 to about 95 weight percent of crystalline fluoropolymers (e.g., particles) and about 95 to about 5 weight percent of amorphous fluoropolymers. In some embodiments, the coating composition contains about 10 to about 75 weight percent of crystalline fluoropolymers (e.g., particles) and about 90 to about 25 weight percent of amorphous polymers.

[0124] In some embodiments, the coating composition or fluoropolymer film contains at least 5, 10, or 15 weight percent, ranging from about 50, 55, 60, 65, 70, 75, or 80 weight percent of crystalline fluoropolymer (e.g., particles) and about 20, 30, 40, or 50 to about 90 weight percent of amorphous fluoropolymer. In some embodiments, the coating composition contains about 10 to about 30 weight percent of crystalline fluoropolymer particles and about 90 to about 70 weight percent of amorphous fluoropolymer.

[0125] In some embodiments, the fluoropolymer composition comprises fluoropolymer particles having a particle size greater than 1 micrometer. In general embodiments, the fluoropolymer particles have an average particle size not greater than 75, 70, 65, 60, 55, 50, 45, 35, 30, 30, 25, 20, 15, 10, or 5 micrometers. In some embodiments, the particle size of the fluoropolymer particles is smaller than the thickness of the fluoropolymer coating or fluoropolymer film. The average particle size is generally reported by the supplier. The particle size of the fluoropolymer particles in the fluoropolymer coating or fluoropolymer film can be determined by microscopy.

[0126] In some embodiments, the fluoropolymer particles comprise a mixture of particles, including fluoropolymer particles having a particle size greater than 1 micrometer and fluoropolymer particles having a particle size of 1 micrometer or less. In some embodiments, the submicron fluoropolymer particle size range may be about 50 to about 1000 nm, or about 50 to about 400 nm, or about 50 to about 200 nm.

[0127] The weight ratio of fluoropolymer particles with a diameter greater than 1 micrometer to fluoropolymer particles with a diameter of 1 micrometer or smaller generally ranges from 1:1 to 10:1. In some embodiments, the weight ratio of the larger to the smaller fluoropolymer particles is at least 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1.

[0128] Crystalline fluoropolymers (e.g., particles) are insoluble in fluorinated solvents. Crystalline fluoropolymers (e.g., particles) are also insoluble in non-fluorinated organic solvents, such as methyl ethyl ketone (“MEK”), tetrahydrofuran (“THF”), ethyl acetate, or N-methylpyrrolidone (“NMP”). additive

[0129] Compositions containing curable fluoroelastomers may further contain additives as known in the art. Examples include acid acceptors. These 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, lead hydrogen phosphate, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, hydrotalcite, etc. Organic acceptors include epoxy resins, sodium stearate, and magnesium oxalate. Particularly suitable acid acceptors include magnesium oxide and zinc oxide. Blends of acid acceptors may also be used. The amount of acid acceptor usually depends on the nature of the acid acceptor used. Generally, the amount of acid acceptor used is between 0.5 and 5 parts per 100 parts of fluoropolymer.

[0130] Fluoropolymer compositions may further contain additives such as stabilizers, surfactants, ultraviolet ("UV") absorbers, antioxidants, plasticizers, lubricants, fillers, and processing aids, which are generally used in the processing or compounding of fluoropolymers, provided that they are sufficiently stable for the intended use conditions. Specific examples of additives include carbon particles, such as carbon black, graphite, and soot. Other additives include, but are not limited to, pigments, such as iron oxide and titanium dioxide. Other additives include, but are not limited to, clay, silicon dioxide, barium sulfate, silica, glass fiber, or other additives known in the art.

[0131] In some embodiments, the fluoropolymer composition comprises silica, glass fiber, thermally conductive particles, or a combination thereof. Any amount of silica and / or glass fiber and / or thermally conductive particles may be present. In some embodiments, the amount of silica and / or glass fiber is at least 0.05, 0.1, 0.2, or 0.3 wt.% of the total solids of the composition. In some embodiments, the amount of silica and / or glass fiber is not greater than 5, 4, 3, 2, or 1 wt.% of the total solids of the composition. Low concentrations of silica can be used to thicken the coating composition. Furthermore, low concentrations of glass fiber can be used to improve the strength of the fluoropolymer film. In other embodiments, the amount of glass fiber may be at least 5, 10, 15, 20, 25, 35, 40, 45, or 50 wt.% of the total solids of the composition. The amount of glass fiber is generally not greater than 55, 50, 45, 40, 35, 25, 20, 15, or 10 wt.%. In some embodiments, the glass fibers have an average length of at least 100, 150, 200, 250, 300, 350, 400, 450, or 500 micrometers. In some embodiments, the glass fibers have an average length of at least 1, 2, or 3 mm and generally no greater than 5 or 10 mm. In some embodiments, the glass fibers have an average diameter of at least 1, 2, 3, 4, or 5 micrometers and generally no greater than 10, 15, 30, or 25 micrometers. The glass fibers may have an aspect ratio of at least 3:1, 5:1, 10:1, or 15:1.

[0132] In some embodiments, the fluoropolymer composition does not contain inorganic oxide particles (e.g., silica). In other embodiments, the fluoropolymer composition includes inorganic oxide particles (e.g., silica and / or thermally conductive). In some embodiments, the amount of inorganic oxide particles (e.g., silica and / or thermally conductive) is at least 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 wt.% of the total solids of the composition. In some embodiments, the amount of inorganic oxide particles (e.g., silica and / or thermally conductive) is no more than 90, 85, 80%, 75, 70, or 65 wt.% of the total solids of the composition. Various combinations of silica and thermally conductive particles may be used. In some embodiments, the total amount of inorganic oxide particles (e.g., silica and thermally conductive) or the amount of specific types of silica particles (e.g., fused silica, fuming silica, glass bulbs, etc.) or thermally conductive particles (e.g., boron nitride, silicon carbide, alumina, aluminum trihydrate) is no greater than 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 wt.% of the total solids of the composition. Higher concentrations of inorganic oxide particles (e.g., silica) can be advantageous for further reducing dielectric properties. Therefore, compositions including inorganic oxide particles (e.g., silica) can have lower dielectric properties than cross-linked fluoropolymers alone.

[0133] In some embodiments, the inorganic oxide particles (e.g., silica) and / or glass fibers have a dielectric constant of no greater than 7, 6.5, 6, 5.5, 5, 4.5, or 4 at 1 GHz. In some embodiments, the inorganic oxide particles (e.g., silica) and / or glass fibers have a loss factor of no greater than 0.005, 0.004, 0.003, 0.002, or 0.0015 at 1 GHz.

[0134] In some embodiments, the composition comprises inorganic oxide particles or glass fibers primarily consisting of silica. In some embodiments, the amount of silica is generally at least 50, 60, 70, 75, 80, 85, or 90 wt.% of the inorganic oxide particles or glass fibers. In some embodiments, the amount of silica is generally at least 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or greater (e.g., at least 99.5, 99.6, or 99.7) wt.% silica. Higher silica concentrations generally result in lower dielectric constants. In some embodiments, the silica particles (e.g., molten) may further comprise low concentrations of other metal / metal oxides, such as Al₂O₃, Fe₂O₅, TiO₂, K₂O, CaO, MgO, and Na₂O. In some embodiments, the total amount of such metal / metal oxides (e.g., Al₂O₃, CaO, and MgO) is independently no greater than 30, 25, 20, 15, or 10 wt.%. In some embodiments, the inorganic oxide particles or glass fibers may contain B₂O₃. The amount of B₂O₃ may range up to 25 wt.% of the inorganic oxide particles or glass fibers. In other embodiments, (e.g., fuming) silica particles may further contain low concentrations of additional metal / metal oxides such as Cr, Cu, Li, Mg, Ni, P, and Zr. In some embodiments, the total amount of such metals or metal oxides is no greater than 5, 4, 3, 2, or 1 wt.%. In some embodiments, silica may be described as quartz. The amount of non-silica metals or metal oxides can be determined by inductively coupled plasma mass spectrometry. (e.g., silica) inorganic oxide particles are generally dissolved in hydrofluoric acid and distilled at low temperature to H₂SiF₆.

[0135] In some embodiments, inorganic particles may be characterized as "aggregates," meaning weak associations between primary particles (such as particles held together by charge or polarity). During the preparation of the coating solution, aggregates generally physically break down into smaller entities (such as primary particles). In other embodiments, inorganic particles may be characterized as "aggregates," meaning strongly bonded or molten particles, such as covalently bonded or thermally bonded particles prepared by processes such as sintering, arcing, flame hydrolysis, or plasma. During the preparation of the coating solution, aggregates generally do not break down into smaller entities (such as primary particles). "Primary particle size" refers to the average diameter of a single (non-aggregated, non-cohesive) particle.

[0136] (For example, silica) particles can have various shapes, such as spherical, elliptical, straight-chain, or branched. Molten and fuming silica aggregates are more often branched. The size of the aggregate is usually at least 10 times the size of the primary particles in the discrete fraction.

[0137] In other embodiments, the particles (e.g., silica) may be characterized as glass bubbles. The glass bubbles may be prepared from soda lime borosilicate glass. In this embodiment, the glass may contain approximately 70 percent silica (silicon dioxide), 15 percent alkali (sodium oxide), and 9 percent lime (calcium oxide), and smaller amounts of various other compounds.

[0138] In some embodiments, the inorganic oxide particles may be characterized as (e.g., silica) nanoparticles having an average or median particle size of less than 1 micrometer. In some embodiments, the average or median particle size of the (e.g., silica) inorganic oxide particles is 500 or 750 nm. In other embodiments, the average particle size of the (e.g., silica) inorganic oxide particles may be at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 micrometers. In some embodiments, the median particle size is not greater than 30, 25, 20, 15, or 10 micrometers. In some embodiments, the composition contains very little or no (e.g., colloidal silica) nanoparticles having a particle size of 100 nanometers or smaller. The concentration of nanoparticles (e.g., colloidal silica) is generally less than (10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt.%). Inorganic oxides (e.g., silica particles) may contain a normal particle size distribution with a single peak or a particle distribution with two or more peaks.

[0139] In some embodiments, no more than 1 wt.% of inorganic oxide particles (e.g., silica) have a particle size greater than or equal to 3 or 4 micrometers. In some embodiments, no more than 1 wt.% of inorganic oxide particles (e.g., silica) have a particle size greater than or equal to 5 or 10 micrometers. In other embodiments, no more than 5, 4, 3, 2, or 1 wt.% of particles have a particle size greater than 45 micrometers. In some embodiments, no more than 1 wt.% of particles have a particle size in the range of 75 to 150 micrometers.

[0140] In some embodiments, the average or median particle size refers to the "primary particle size," which is the average or median particle size of discrete, non-aggregated, non-cohesive particles. For example, the particle size of colloidal silica or glass bubbles is generally the average or median particle size. In a preferred embodiment, the average or median particle size refers to the average or median diameter of the aggregate. The particle size of inorganic particles can be measured using a transmission electron microscope. The particle size of fluoropolymer coating solutions can be measured using dynamic light scattering.

[0141] In some embodiments, (e.g., silica) inorganic particles have a specific gravity in the range of 2.18 to 2.20 g / cc.

[0142] Aggregate particles, such as those in the case of fuming and molten (e.g., silica) particles, may have a lower surface area than primary particles of the same size. In some embodiments, (e.g., silica) particles have a BET surface area in the range of about 50 to 500 m² / g. In some embodiments, the BET surface area is less than 450, 400, 350, 300, 250, 200, 150, or 100 m² / g.

[0143] In some embodiments, inorganic nanoparticles may be characterized as colloidal silica. It should be understood that unmodified colloidal silica nanoparticles typically contain hydroxyl or silanol functional groups on the nanoparticle surface and are generally characterized as hydrophilic.

[0144] In some embodiments, inorganic particles (e.g., silica aggregates) and especially colloidal silica nanoparticles are surface-treated with hydrophobic surface-treatment agents. Common hydrophobic surface-treatment agents include compounds such as alkoxysilanes (e.g., octadecyltriethoxysilane), silazanes, or siloxanes. Various hydrophobic fuming silicas are commercially available from AEROSIL™, Evonik, and various other suppliers. Representative hydrophobic fuming silicas include AEROSIL™ grades R 972, R 805, RX 300, and NX 90 S.

[0145] In some embodiments, (e.g., silica aggregates), the inorganic particles are surface-treated with fluorinated alkoxysilane compounds. These compounds generally contain perfluoroalkyl or perfluoropolyether groups. The perfluoroalkyl or perfluoropolyether groups generally have no more than 4, 5, 6, 7, or 8 carbon atoms. The alkoxysilane can be bonded to the alkoxysilane using various divalent linking groups, including alkylene groups, carbamates, and -SO2N(Me)-. Some representative fluorinated alkoxysilanes are described in US5274159 and WO2011 / 043973; these are incorporated herein by reference. Other fluorinated alkoxysilanes are commercially available.

[0146] In some embodiments, the fluoropolymer composition includes thermally conductive particles. In some embodiments, the thermally conductive inorganic particles are preferably non-conductive materials. Suitable non-conductive, thermally conductive materials include ceramics, such as metal oxides, hydroxides, oxyhydroxides, silicates, borides, carbides, and nitrides. Suitable ceramic fillers include, for example, silicon oxide, zinc oxide, alumina trihydrate (ATH) (also known as hydrated alumina, alumina, and aluminum trihydroxide), aluminum nitride, boron nitride, silicon carbide, and beryllium oxide. Other thermally conductive fillers include carbon-based materials, such as graphite, and metals, such as aluminum and copper. Combinations of different thermally conductive materials can be used. Such materials are non-conductive, i.e., have an electronic band gap greater than 0 eV, and in some embodiments, at least 1, 2, 3, 4, or 5 eV. In some embodiments, such materials have an electronic band gap not greater than 15 or 20 eV. In this embodiment, the composition may optionally further comprise low concentrations of thermally conductive particles having an electronic band gap of less than 0 eV or greater than 20 eV.

[0147] In an advantageous embodiment, the thermally conductive particles comprise a material having a bulk thermal conductivity > 10 W / m*K. The thermal conductivity of some representative inorganic materials is illustrated in the table below.

[0148] thermal conductive materials

[0149] In some embodiments, the thermally conductive particles comprise (multiple) materials having an overall thermal conductivity of at least 15 or 20 W / m*K. In other embodiments, the thermally conductive particles comprise (multiple) materials having an overall thermal conductivity of at least 25 or 30 W / m*K. In still other embodiments, the thermally conductive particles comprise (multiple) materials having an overall thermal conductivity of at least 50, 75, or 100 W / m*K. In still other embodiments, the thermally conductive particles comprise (multiple) materials having an overall thermal conductivity of at least 150 W / m*K. In general embodiments, the thermally conductive particles comprise (multiple) materials having an overall thermal conductivity of no more than about 350 or 300 W / m*K.

[0150] Thermally conductive particles can be obtained in various shapes, such as spherical and needle-like, and can be irregular or plate-like. In some embodiments, the thermally conductive particles are crystals, generally having a geometric shape. For example, hexagonal boron nitride crystals are commercially available from Momentive. Furthermore, alumina trihydrate is described as a hexagonal plate. Combinations of particles with different shapes can be used. Thermally conductive particles typically have an aspect ratio of less than 100:1, 75:1, or 50:1. In some embodiments, thermally conductive particles have an aspect ratio of less than 3:1, 2.5:1, 2:1, or 1.5:1. In some embodiments, substantially symmetrical (e.g., spherical, hemispherical) particles can be used.

[0151] Boron nitride particles can be purchased from 3M through the retailer "3MTM Boron Nitride Cooling Fillers".

[0152] In some embodiments, the boron nitride particles have a total density of at least 0.05, 0.01, 0.15, or 0.03 g / cm³, and up to about 0.60, 0.70, or 0.80 g / cm³. The surface area of ​​the boron nitride particles may be <25, <20, <10, <5, or <3 m² / g. The surface area is generally at least 1 or 2 m² / g.

[0153] In some embodiments, the particle size d (0.1) of the boron nitride (e.g., plate) particles is in the range of about 0.5 to 5 micrometers. In some embodiments, the particle size d (0.9) of the boron nitride (e.g., plate) particles is at least 5, and ranges up to 20, 25, 30, 35, 40, 45, or 50 micrometers.

[0154] In some embodiments, the coating composition comprises additives having hydroxyl or alkoxy groups, such as the aforementioned metal oxides (e.g., silica) and / or alkoxysilane compounds lacking amine groups. method

[0155] Fluoropolymer compositions can be prepared by mixing a polymer, (multiple) curing agents, optional additives, and a fluorinated solvent. In some embodiments, the fluoropolymer is first dissolved in a fluorinated solvent, followed by the addition of other additives, including (multiple) curing agents and electron donor compounds.

[0156] Fluoropolymers and fluorinated curing agents can be combined in conventional rubber processing equipment to provide solid mixtures, i.e., solid polymers containing additional components, also referred to in the art as "compounds". Typical equipment includes rubber mills, internal mixers (such as Banbury mixers), and mixing extruders. During mixing, the components and additives are uniformly distributed throughout the resulting fluorinated polymer "compound" or polymer sheet. The compound is then preferably crushed, for example by cutting it into smaller pieces, and then dissolved in a solvent.

[0157] The fluoropolymer coating solution compositions provided herein are suitable for coating substrates. The fluoropolymer coating solution compositions can be formulated to have different viscosities, depending on the solvent and fluoropolymer content and the presence of optional additives. The fluoropolymer coating solution compositions generally contain or are solutions of fluoropolymers and can be in liquid or paste form. Preferably, the compositions are liquids, and more preferably they are solutions containing one or more fluoropolymers as described herein dissolved in solvents as described herein.

[0158] The fluoropolymer compositions provided herein are suitable for coating substrates and can be adjusted (by solvent content) to allow for viscosity applied by various coating methods, including but not limited to spraying or printing (e.g., but not limited to ink printing, 3D printing, screen printing), painting, dipping, roller coating, bar coating, dip coating, and solvent casting.

[0159] Coated substrates and articles can be prepared by applying a fluoropolymer composition to the substrate and removing the solvent. Curing can occur during or after solvent removal. The solvent can be reduced or completely removed, for example, by evaporation, drying, or by boiling. After solvent removal, the composition can be characterized as "dried".

[0160] The method for manufacturing the crosslinked fluoropolymers described herein involves curing the fluoropolymer with photochemical radiation (e.g., UV or electron beam). The fluoropolymer composition, substrate, or both are transmissive to the curing radiation system. In some embodiments, a combination of UV curing and thermal (e.g., post-)curing is used. The curing system is performed at an effective temperature and effective time to produce the cured fluoroelastomer. Optimal conditions can be tested by examining the mechanical and physical properties of the fluoroelastomer. Curing can be performed in an oven under pressure or without pressure. Post-curing cycles can be applied at elevated temperatures and / or pressures to ensure complete curing. Curing conditions depend on the curing system used.

[0161] In some embodiments, the thermosetting of the fluoropolymer may optionally be performed at a lower temperature. Post-curing at a lower temperature is suitable for coating heat-sensitive substrates. In some embodiments, post-curing occurs at a temperature ranging from 100, 110, 120, 130, 135, or 140°C to a maximum of 170°C for a period of 5 to 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 an advantageous embodiment, after curing, the fluoropolymer is sufficiently crosslinked such that at least 80, 85, 90, 95, or 100 wt.% or more of the fluoropolymer cannot be dissolved in a fluorinated solvent (e.g., 3-ethoxyperfluorinated 2-methylhexane) at a weight ratio of 5 grams of fluoropolymer to 95 wt% of the fluorinated solvent (at 25°C for 12 hours).

[0162] The composition can be used to impregnate, print (e.g., screen print) onto, or coat (e.g., by spraying, painting, dip coating, roller coating, bar coating, solvent casting, paste coating) a substrate. The substrate can be organic, inorganic, or a combination thereof. Suitable substrates can include any solid surface and can include substrates selected from: glass, plastics (e.g., polycarbonate), composites, metals (stainless steel, aluminum, carbon steel), metal alloys, wood, paper, etc. If the composition contains pigments (e.g., titanium dioxide, or black fillers such as graphite or soot), the coating can be colored; if the pigments or black fillers are absent, the coating can be colorless.

[0163] Before coating, the surface of the substrate can be pretreated with adhesives and primers. For example, applying an adhesive or primer can improve the adhesion of the coating to the metal surface. Examples include commercially available primers or adhesives, such as those from the brand name CHEMLOK.

[0164] Articles containing coatings derived from the compositions provided herein include, but are not limited to, impregnated textiles, such as protective clothing. Another example of impregnated textiles is glass curtains impregnated with fluoropolymer compositions described herein (e.g., silica-containing). Textiles may include fabrics or non-fabricated materials. Other articles include those exposed to corrosive environments, such as seals and seal and valve assemblies used in chemical processes, such as, but not limited to, chemical reactors, molds, chemical processing equipment (e.g., for etching), or valves, pumps, and pipes (particularly for corrosive substances or hydrocarbon fuels or solvents); gas turbines, electrodes, fuel transport, containers, and systems for transporting acids and alkalis; batteries, fuel cells, electrolytic cells, and articles used for etching.

[0165] The coating composition described herein has the advantage of being able to be used to prepare coatings or fluoropolymer sheets of varying thicknesses. In some embodiments, the dried and cured fluoropolymer has a thickness of 0.1 micrometers 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 micrometers. In some embodiments, the dried and cured fluoropolymer has a thickness of at least 1, 2, 3, 4, 5, or 6 micrometers.

[0166] In general 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, 2.10, 2.05, 2.00, 1.95, or 1.90. In some embodiments, the dielectric constant is at least 1.90, 1.95, or 2.00. The dried and cured (i.e., cross-linked) components have 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, or 0.0003. In some embodiments, the dielectric loss is at least 0.00022, 0.00023, 0.00024, or 0.00025.

[0167] The dried and cured coating exhibits good adhesion to metals such as copper. For example, in some embodiments, the T-peel strength to copper foil is at least 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6 N / mm, and at most at least 1 N / mm (i.e., 10 N / cm), 1.5 N / mm, 2 N / mm, or 2.5 N / mm or greater, as determined by the test methods described in the examples.

[0168] In some embodiments, the dried and cured coating has good hydrophobic and oleophobic properties, as described in the black permanent marker resistance test in PCT application PCT / US2019 / 036460, in which the marker fluid forms beads and is easily removed with a tissue or cloth.

[0169] In some embodiments, the dried and cured coating exhibits good hydrophobic and oleophobic properties, as determined by contact angle measurements (as determined according to the test methods described in the examples). In some embodiments, the static, advancing, and / or receding contact angles with water may be at least 100, 105, 110, 115, 120, or 125 degrees, and generally not greater than 130 degrees. In some embodiments, the advancing and / or receding contact angles with hexadecane may be at least 60, 65, 70, or 75 degrees.

[0170] In some embodiments, the dried and cured coating (e.g., film) exhibits low water absorption, such as less than 0.5, 0.4, 0.3, 0.2, or 0.1, as determined by the moisture absorption test method described in the examples.

[0171] In some embodiments, the composition exhibits a low coefficient of thermal expansion, such as less than 150, 100, 50, 40, 30, 20, or 10, as determined by the test methods described in the examples. For some insulating applications, the coefficient of thermal expansion is less important and can range up to 175, 200, or 225. Electronic telecommunications items

[0172] The fluoropolymer compositions described herein are suitable for electronic and telecommunications articles, as described in the previously cited WO2021 / 091864. As used herein, "electronic" means a device that uses the electromagnetic spectrum (e.g., electrons, photons); and "telecommunications" means the transmission of symbols, signals, messages, text, writing, images, and sounds, or information of any nature, by means of wires, radio, optics, or other electromagnetic systems.

[0173] Perfluoropolymers can have substantially lower dielectric constants and dielectric loss properties than polyimides, which is particularly important for fifth-generation cellular network ("5G") products. For example, the cross-linked fluoropolymer compositions described herein can have dielectric constants (Dk) 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, 2.10, 2.05, 2.00, or 1.95. In some embodiments, the dielectric constant is at least 2.02, 2.03, 2.04, or 2.05. Furthermore, the cross-linked fluoropolymer compositions described herein may have low dielectric losses, 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, or 0.0003. In some embodiments, the dielectric loss is at least 0.00022, 0.00023, 0.00024, or 0.00025. Dielectric properties (e.g., constant or loss) can be determined according to the test methods described in the examples. Generally, the dielectric constant and dielectric loss increase as the number of non-fluorine atoms decreases (e.g., the number of carbon-hydrogen and / or carbon-oxygen bonds increases).

[0174] In one embodiment, the electronic telecommunications article is an integrated circuit, or in other words, a silicon wafer or microchip, that is, a microelectronic circuit array formed by fabricating various electrical and electronic components (resistors, capacitors, transistors, etc.) on a semiconductor material (silicon) wafer. Various integrated circuit designs have been described in the literature.

[0175] In some embodiments, particularly when a thin fluoropolymer film needs to be applied to a substrate, the method includes applying a coating solution (e.g., spin coating) to the substrate. The coating solution comprises a fluorinated solvent and a fluoropolymer. The method generally includes removing the fluorinated solvent (e.g., by evaporation). In this embodiment, the substrate in contact with the solvent, or its coated surface (e.g., SiO2), is substantially insoluble in the fluorinated solvent of the coating solution. Furthermore, the method generally includes recovering, or in other words, reusing, the fluorinated solvent of the coating solution.

[0176] In some embodiments, the fluoropolymer may be characterized as a patterned fluoropolymer layer. The patterned fluoropolymer layer may be formed by any suitable additive or subtractive process known in the art.

[0177] Patterned fluoropolymer layers can be used to fabricate other layers, such as circuits with patterned electrode materials. Suitable electrode materials and deposition methods are known in the art. Such electrode materials include, for example, inorganic or organic materials, or composites of both. Exemplary electrode materials include: further dispersions or pastes of polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), or doped conjugated polymers, graphite, or metal particles (such as Au, Ag, Cu, Al, Ni, or mixtures thereof), as well as sputtered or evaporated metals (such as Cu, Cr, Pt / Pd, Ag, Au, Mg, Ca, Li, or mixtures thereof), or metal oxides (such as indium tin oxide (ITO), F-doped ITO, GZO (gallium-doped zinc oxide), or AZO (aluminium-doped zinc oxide)). Organometallic precursors can also be used and deposited from the liquid phase.

[0178] In another embodiment, a fluoropolymer (e.g., photoresist) layer may be disposed on a metal (e.g., copper) substrate during the manufacture of a printed circuit board (PCB). A printed circuit board (or PCB) is used to mechanically support and electrically connect electronic components using conductive paths, conductive rails, or signal traces etched from a metal sheet (e.g., copper) laminated on a non-conductive substrate. Such boards are generally made of insulating materials, such as glass fiber reinforced (glass fiber) epoxy resin or paper-reinforced phenolic resin. The electrical pathways are generally made of negative photoresist, as previously described. Therefore, in this embodiment, a cross-linked fluoropolymer is disposed on the surface of the (e.g., copper) metal substrate. Uncross-linked portions of the fluoropolymer are removed to form conductive (e.g., copper) pathways. The cross-linked fluoropolymer (e.g., photoresist) remains, disposed between the conductive (e.g., copper) pathways of the printed circuit board. Solder is used to mount components onto these board surfaces. In some embodiments, the printed circuit board further includes integrated circuitry. Printed circuit board assemblies are used in virtually every electronic item, including computers, computer printers, televisions, and mobile phones.

[0179] In another embodiment, the cross-linked fluoropolymer film described herein can be used as an insulating layer, passivation layer, and / or protective layer in the manufacture of integrated circuits.

[0180] In one embodiment, a thin fluoropolymer film (e.g., generally having a thickness of less than 50, 40, or 30 nm) may be disposed on a passivation layer (e.g., SiO2) disposed on an electrode patterned silicon wafer.

[0181] In another embodiment, a thicker fluoropolymer film (e.g., typically having a thickness of at least 100, 200, 300, 400, or 500 nm) may be disposed on an electrode-patterned silicon wafer. In this embodiment, the fluoropolymer layer may function as both a passivation layer and an insulating layer. Passivation uses a thin coating to provide electrical stability by isolating the transistor surface from the electrical and chemical conditions of the environment.

[0182] In another embodiment, the cross-linked fluoropolymer film described herein can be used as a substrate for an antenna. The transmitter's antenna emits (e.g., at a high frequency) energy into space, while the receiver's antenna captures this energy and converts it into electrical energy.

[0183] Patterned electrodes for an antenna can also be formed by photolithography. Screen printing, flexographic printing, and inkjet printing can also be used to form electrode patterns as known in the art. Various antenna designs for (e.g., mobile) computing devices (smartphones, tablets, laptops, desktop computers) have been described in the literature.

[0184] The low-dielectric fluoropolymer films and coatings described herein can also be used as insulation and protective layers for transmitter antennas in cellular towers and other (e.g., outdoor) and indoor structures.

[0185] In another embodiment, the low-dielectric fluoropolymer composition described herein can also be used in optical fiber cables. The low-dielectric fluoropolymer composition described herein can be used as a cladding layer, coating, outer sheath, or a combination thereof.

[0186] In other embodiments, the low-dielectric fluoropolymer films and coatings described herein can also be used in flexible cables and as an insulating film on electromagnetic wires. For example, in a laptop, the cable connecting the main logic board to the display (which bends every time the laptop is turned on or off) can be a low-dielectric fluoropolymer composition with copper conductors as described herein.

[0187] Fluoropolymer films and coatings are generally not sealing components of equipment used in wafer and chip manufacturing.

[0188] Those skilled in the art will understand that the low-dielectric fluoropolymer compositions described herein can be used in a variety of electronic and telecommunications articles, particularly as a substitute for polyimide, and that such applications are not limited to the specific articles described herein.

[0189] As used herein, the term "partially fluorinated alkyl" means an alkyl group in which some, but not all, of the hydrogen atoms bonded to the carbon chain have been replaced by fluorine. For example, the F2HC- or FH2C- groups are partially fluorinated methyl groups. The term "partially fluorinated alkyl" also covers alkyl groups in which at least one hydrogen atom has been replaced by fluorine, and the remaining hydrogen atoms have been partially or completely replaced by other atoms (e.g., other halogen atoms, such as chlorine, iodine, and / or bromine). For example, residues of the formula F2ClC- or FHClC- are also partially fluorinated alkyl residues.

[0190] "Partially fluorinated ether" refers to an ether containing at least one partially fluorinated group, or an ether containing one or more perfluorinated 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. The term "partially fluorinated alkyl" also covers ether groups in which at least one hydrogen atom has been replaced by fluorine, and the remaining hydrogen atoms have been partially or completely replaced by other atoms (e.g., other halogen atoms, such as chlorine, iodine, and / or bromine). For example, ethers of the formula F2ClC-O-CF3 or FHClC-O-CF3 are also partially fluorinated ethers.

[0191] The terms "perfluorinated alkyl" or "perfluoro alkyl" are used herein to describe alkyl groups in which all hydrogen atoms bonded to the alkyl chain have been replaced by fluorine atoms. For example, F3C- represents perfluoromethyl.

[0192] "Perfluorinated ether" is an ether in which all hydrogen atoms have been replaced by fluorine atoms. An example of a perfluorinated ether is F3C-O-CF3.

[0193] The following examples are provided to further illustrate this disclosure, but are not intended to limit this disclosure to the specific examples and embodiments provided. Example

[0194] Unless otherwise stated, all parts, percentages, ratios, etc., in the examples and the remainder of this specification are by weight. Unless otherwise indicated, all other reagents are obtained from or available from precision chemical suppliers such as Sigma-Aldrich Company, St. Louis, Missouri, or can be synthesized by known methods. Table 1 (below) lists the materials used in the examples and their sources.

[0195] Table 1. List of Materials Test methods Viscosity test method

[0196] All solution viscosities were measured using a Brinell viscometer at room temperature according to standard procedures, and the results are expressed in cP (centipoise). Dk / Df testing method at 25GHz

[0197] All measurements of the separated dielectric resonators were performed near 25 GHz according to standard IEC 61189-2-721. Thin materials or films were inserted between two fixed dielectric resonators. The resonant frequency and quality factor of the cylinders are affected by the presence of the sample, allowing direct calculation of the complex dielectric constant (dielectric constant and dielectric loss). The geometry of the separated dielectric resonator fixture used in our measurements was designed by QWED in Warsaw, Poland. This 25 GHz resonator operates in TE01d mode, which has only an azimuthal electric field component, ensuring the electric field remains continuous at the dielectric interface. The dielectric component in the sample plane was measured using the separated dielectric resonator. Critically coupled loop coupling was used in all of these dielectric resonator measurements. This 25 GHz split post resonator measurement system was combined with a Keysight VNA (vector network analyzer, PNA 8364C, 10 MHz-50 GHz). Calculations were performed using QWED's commercial Split Post Resonator Software to provide a powerful tool for determining the complex electric permittivity of each sample at 25 GHz. Example Preparation of coating solution and test film

[0198] The coating solution was prepared by adding filler and then crosslinking agent (10% solution in HFE-7300) to the PFE solution in HFE-7300 at a designed wt.% based on the weight of PFE, and then thoroughly mixing by vortexing at 2500 rpm for about 2 minutes.

[0199] The test film was prepared by coating the coating solution onto release paper to a thickness of 10 to 20 micrometers and then curing it in an oven at 180°C for 2 hours. Stability study of formulations in the presence of crosslinking agents

[0200] The representative viscosities of PFE131 solution (5 wt.% in HFE-7300) and 4 wt.% NH[C3H6Si(OEt)3]2 crosslinking agent were measured over time (in hours (hr) under rolling (R) or stationary (S) conditions. The results are summarized in Table 2.

[0201] Rf-OH effect on formulation stability

[0202] In the search for stabilizers, different approaches focus on the reactive modification of the amine and silyl groups in the formation of amine-silane crosslinking agents. One approach is to add alcohols to reduce the hydrolysis rate of the alkyl groups, thereby enhancing shelf-life stability. Compatibility of stabilizer with HFE-7300

[0203] It has been found that adding hydrocarbon alcohols (e.g., methanol) to a nitrile-functionalized perfluoroelastomer (CN-PFE) solution in HFE causes CN-PFE to precipitate from the HFE solvent, and the fluorinated alcohol exhibits better compatibility and solubility in the CN-PFE / HFE solution, as shown in Table 3. The wt.% amount of alcohol is related to the total weight of the fluoropolymer solution.

[0204] Stabilizer effect on the stability of coating formulations during storage

[0205] Further studies on alcohols in CN-PFE with amino-silane crosslinking agents, and the stability results of representative formulations are recorded and summarized in Table 4.

[0206] Rf-OH stabilizer effect on Dk / Df

[0207] After demonstrating that stability during storage was enhanced by the addition of fluorinated alcohol stabilizers, the effects of the stabilizers on potential Dk and Df were examined, and the results are summarized in Table 5.

[0208]

[0209] All references, patents, and patent applications cited in the foregoing patent applications are incorporated herein by reference in their entirety. In the event of any inconsistency or conflict between the incorporated references and this application, the information provided above shall prevail. The foregoing is intended to enable those skilled in the art to implement the disclosed embodiments and should not be construed as limiting the scope of the invention, which is defined by the scope of the patent applications and all their equivalents.

Claims

1. A coating composition comprising a fluoropolymer, wherein the fluoropolymer further comprises a nitrile or halogen curing site; a crosslinking compound comprising at least two amino groups, at least two alkoxysilyl groups, or at least one amino group and at least one alkoxysilyl group; a partially fluorinated ether solvent; and a fluorinated alcohol having the following formula: Rf-(CH2)nOH)p, wherein Rf is a C1 to C4 perfluoroalkyl group or an oxygen-interrupted perfluoroalkyl group; n is 1 or 2; and p is 1 or 2.

2. The coating composition of claim 1, wherein the fluoropolymer is soluble in the fluorinated ether solvent.

3. The coating composition of claim 1, wherein the fluoropolymer is insoluble in the fluorinated alcohol.

4. The coating composition of claim 1, wherein the fluorinated alcohol is present in an amount not exceeding 10 wt.% of the total of the fluorinated ether solvent and the fluorinated alcohol.

5. The coating composition of claim 1, wherein the fluorinated alcohol comprises a single hydroxyl group.

6. The coating composition of claim 1, wherein the fluorinated alcohol comprises a straight-chain (per)fluoroalkyl or (per)fluoroalkyl group.

7. The coating composition of claim 1, wherein the fluorinated alcohol has a boiling point of not more than 160°C.

8. The coating composition of claim 1, wherein the portion of the fluorinated ether solvent has the following formula: CpF2p+1-O-CqH2q+1 where q is an integer from 1 to 5 and p is an integer from 5 to 11.

9. The coating composition of claim 8, wherein the CpF2p+1- unit is branched.

10. The coating composition of claim 1, wherein the portion of the fluorinated ether solvent has a GWP of less than 1000.

11. The coating composition of claim 1, wherein the fluorinated ether solvent is 3-ethoxyperfluorinated 2-methylhexane or 3-methoxyperfluorinated 4-methylpentane.

12. The coating composition of claim 1, wherein the crosslinking compound comprises at least one amino group and at least one alkoxysilyl group.

13. The coating composition of claim 1, wherein the crosslinking compound is non-fluorinated.

14. The coating composition of claim 1, wherein the coating composition further comprises an additive having hydroxyl or alkoxy groups.

15. The coating composition of claim 14, wherein the additive comprises a metal oxide or an alkoxysilane compound lacking an amino group.

16. The coating composition of claim 15, wherein the metal oxide comprises silica, including fuming silica, fused silica, glass bubble, or a combination thereof.

17. The coating composition of claim 16, wherein the silica is present in an amount of at least 10 wt.% based on the total amount of the crosslinked fluoropolymer layer.

18. The coating composition of claim 1, wherein the fluoropolymer comprises at least 80% by weight of polymeric units of perfluorinated monomers.

19. The coating composition of claim 18, wherein the perfluorinated monosystem is selected from tetrafluoroethylene (TFE) and one or more unsaturated perfluorinated alkyl ethers.

20. The coating composition of claim 1, wherein the fluoropolymer comprises 40 to 60% by weight of TFE polymeric units based on the total weight of the fluoropolymer.

21. The coating composition of claim 19, wherein the unsaturated perfluorinated alkyl ether of the fluoropolymer has the general formula Rf-O-(CF2)n-CF=CF2, wherein n is 1 or 0, and Rf is a perfluorinated alkyl or perfluorinated ether group.

22. The coating composition of claim 1, wherein the fluoropolymer further comprises polymeric units of HFP.

23. The coating composition of claim 1, wherein the composition further comprises fluoropolymer particles, thermally conductive fillers, or a combination thereof.

24. The coating composition of claim 1, wherein once the portion of the fluorinated ether solvent and fluorinated alcohol is removed, the composition has i) a dielectric constant (Dk) less than 2.50; ii) a dielectric loss less than 0.004; or a combination thereof.

25. A method of manufacturing a coated substrate, comprising: providing a coating composition as claimed in claim 1; applying the coating composition to the substrate; and removing a portion of the fluorinated ether solvent and fluorinated alcohol to form a fluoropolymer layer.

26. The method of claim 25, further comprising crosslinking the fluoropolymer by exposure to heat, photochemical radiation, or a combination thereof.

27. The method of claim 25, wherein the crosslinked fluoropolymer is insoluble in the partially fluorinated ether solvent.

28. The method of claim 25, wherein the substrate is metal.

29. The method of claim 26, wherein the substrate is a component of an electronic communication article.

30. The method of claim 25, wherein the fluoropolymer layer is a substrate, a patterned layer, an insulating layer, a passivation layer, a covering layer, a protective layer, or a combination thereof.

31. The method of claim 29, wherein the article is an integrated circuit, a printed circuit board, or an antenna.

32. An electronic communication article comprising a fluoropolymer layer comprising a coating composition as claimed in claims 1 to 24.

33. The electronic communication article as claimed in claim 32, wherein the fluorinated ether solvent and fluorinated alcohol have been removed.

34. The electronic communication article of claim 32, wherein the fluoropolymer layer is a substrate, a patterned layer, an insulating layer, a passivation layer, a covering layer, a protective layer, or a combination thereof.

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