Patent Application
20240209217
In one embodiment, an electronic telecommunication article is described comprising a layer of fluoropolymer composition comprising an uncrosslinked fluoropolymer comprising at least 80, 85, or 90% by weight of polymerized units perfluorinated monomers including one or more unsaturated perfluorinated alkyl ethers. In typical embodiments, the uncrosslinked fluoropolymer comprises at least 10, 20, or 30 wt. % of one or more unsaturated perfluorinated alkyl ethers. The uncrosslinked fluoropolymer may be characterized as amorphous. The uncrosslinked fluoropolymer is soluble in fluorinated solvent.
In another embodiment, a method of making a coated substrate is described comprising providing a fluoropolymer composition comprising a fluoropolymer comprising at least 80, 85, or 90% by weight of polymerized units of perfluorinated monomers including one or more unsaturated perfluorinated alkyl ethers; and applying the fluoropolymer composition to a substate.
In one embodied method, the fluoropolymer composition further comprises a fluorinated solvent; and the method further comprises removing the fluorinated solvent after applying the fluoropolymer composition to the substrate. The fluorinated solvent may be a partially fluorinated ether such as 3-ethoxy perfluorinated 2-methyl hexane, or 3-methoxy perfluorinated 4-methyl.
In another embodiment, a coated article is described comprising a (e.g. copper) substrate and a fluoropolymer composition comprising an uncrosslinked fluoropolymer comprising at least 80, 85, or 90% by weight of polymerized units perfluorinated monomers including one or more unsaturated perfluorinated alkyl ethers; The fluoropolymer compositions described herein may optionally further comprise crystalline fluoropolymer, silica, glass or quartz fibre, thermally conductive filler or a combination thereof. The crystalline fluoropolymer may be present as particles ranging in size from submicron to greater than 1 micron.
Also described are fluoropolymer compositions and coating solutions comprising such fluoropolymer compositions dissolved in a fluorinated solvent.
Presently described are certain fluoropolymer compositions (e.g. films and coatings) for use in electronic telecommunication articles. As used herein, electronic refers to devices using the electromagnetic spectrum (e.g. electons, photons); whereas telecommunication is the transmission of signs, signals, messages, words, writings, images and sounds or information of any nature by wire, radio, optical or other electromagnetic systems.
Polyimide materials are used extensively in the electronic telecommunications industry. The structure of poly-oxydiphenylene-pyromellitimide, “Kapton” is as follows:
Polyimide films exhibited good insulating properties with dielectric constants values in the range of 2.78-3.48 and dielectric loss between 0.01 and 0.03 at 1 Hz at room temperature.
Perfluoropolyners can have substantially lower dielectric constants and dielectric loss properties than polyimides which is particularly important for fifth generation cellular network technology (“5G”) articles. For example, fluoropolymer compositions described herein can have a dielectric constant (Dk) of 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, 2.05. Further, the fluoropolymer compositions described herein can have a low dielectric loss, typically less than 0.01, 0.009, 0.008, 0.007, 0.006, 0.005, 0.004, 0.003, 0.002, 0.001, 0.0009, 0.0008, 0.0007, 0.0006, 0.0005, 0.0004, 0.0003. In some embodiments, the dielectric loss is at least 0.00022, 0.00023, 0.00024, 0.00025. The dielectric properties (e.g. constant and loss) can be determined according to the test method described in the examples. As the number of non-fluorine atoms increases (e.g. number of carbon-hydrogen and/or carbon-oxygen bonds increases) the dielectric constant and dielectric loss also typically increases.
However, perfluoropolymers have not been used in place of polyimides is various electronic telecommunications articles are least in part by the lack of perfluoropolymer materials that can be bond to certain substrates such as copper, especially at lower temperatures. Hence, the perfluoropolymer compositions described are suitable for use in place of polyimides in various electronic telecommunication articles.
In one embodiment, the electronic telecommunication article is an integrated circuit or in other words a silicon chip or microchip, i.e. a microscopic electronic circuit array formed by the fabrication of various electrical and electronic components (resistors, capacitors, transistors, and so on) on a semiconductor material (silicon) wafer. Various integrated circuit designs have been described in the literature.
In some embodiments, particularly when it is desirable to apply a thin fluoropolymer film to the substrate, the method comprises applying a coating solution (e.g. spin coating) to a substrate. The coating solution comprises a fluorinated solvent and a fluoropolymer. The method typically comprises removing the fluorinated solvent (e.g. by evaporation). In this embodiment, the substrate or (e.g. SiO2) coated surface thereof that comes in contact with the solvent is substantially insoluble in the fluorinated solvent of the coating solution. Further, the method typically comprises recycling, or in other words reusing, the fluorinated solvent of the coating solution.
In some embodiments, the fluoropolymer may be characterized are a patterned fluoropolymer layer. A patterned fluoropolymer may be formed by any suitable additive or subtractive method known in the art. With reference to
The patterned fluoropolymer layer can be used to fabricate other layers such as a circuit of 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 the two. Exemplary electrode materials include polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene) (PEDOT) or doped conjugated polymers, further dispersions or pastes of graphite or particles of metal such as Au, Ag, Cu, Al, Ni or their mixtures as well as sputter-coated or evaporated metals such as Cu, Cr, Pt/Pd, Ag, Au, Mg, Ca, Li or mixtures 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 may also be used and deposited from a liquid phase.
In another embodiment, a (e.g. patterned) fluoropolymer layer can be disposed upon a metal (e.g. copper) substrate in the manufacture of a printed circuit board (PCB). An illustrative perspective view of a printed circuit board is depicted in
In another embodiment, a fluoropolymer layer or in other word fluoropolymer film as described herein can be utilized as an insulating layer, passivation layer, and/or protective layer in the manufacture of integrated circuits.
With reference to
With reference to
In another embodiment, the fluoropolymer film described herein can be utilized as a substrate for antennas. The antenna of the transmitter emits (e.g. high frequency) energy into space while the antenna of the receiver catches this and converts it into electricity.
The patterned electrodes of an antenna can also be formed from photolithography. Screen printing, flexography, and ink jet printing can also be utilized to form the electrode pattern as known in the art. Various antenna designs for (e.g. mobile) computing devices (smart phone, tablet, laptop, desktop) have been described in the literature. One representative split ring monopole antenna is depicted in
The low dielectric fluoropolymer films and coatings described herein can also be utilized as insulating and protective layers of transmitter antennas of cell towers and other (e.g. outdoor) structures. There are two major types of antennas used in cell towers.
In another embodiment, the low dielectric fluoropolymer compositions described herein may also be utilized in fiber optic cable. With reference to
In other embodiments, the low dielectric fluoropolymer films and coatings described herein can also be utilized for flexible cables and as an insulating film on magnet wire. For example, in a laptop computer, the cable that connects the main logic board to the display (which must flex every time the laptop is opened or closed) may be a low dielectric fluoropolymer composition as described herein with copper conductors.
The electronic telecommunication article is typically not a sealing component of equipment used in wafer and chip production.
One of ordinary skill in the art appreciates that the low dielectric fluoropolymer compositions described herein can be utilized in various electronic telecommunication articles, particularly in place of polyimide, and such utility is not limited to the specific articles described herein.
The uncrosslinked fluoropolymer comprises a fluoropolymer are derived predominantly or exclusively from perfluorinated comonomers including tetrafluoroethene (TFE) and one or more of the unsaturated (e.g. alkenyl, vinyl) perfluorinated alkyl ethers. “Predominantly” as used herein means at least 80, 85, or 90% by weight based on the total weight of the fluoropolymer, of the polymerized units of the fluoropolymer are derived from such perfluorinated comonomers such as tetrafluoroethene (TFE) and one or more unsaturated perfluorinated alkyl ethers. 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% by weight or greater of such perfluorinated comonomers, based on the total weight of the fluoropolymer. The fluoropolymers may contain at least 40, 45, or 50% by weight of polymerized units derived from TFE. In some embodiments, the maximum amount of polymerized units derived from TFE is no greater than 60% or 55% by weight.
In some favored embodiments, the one or more unsaturated perfluorinated alkyl ethers are selected from the general formula:
wherein n is 1 (allyl ether) or 0 (vinyl ether) and Rf represents a perfluoroalkyl residue which may be interrupted once or more than once by an oxygen atom. Rf may contain up to 10 carbon atoms, e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. Preferably Rf contains up to 8, 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 linear or branched, and it may contain or not contain a cyclic unit. Specific examples of Rf include residues with one or more ether functions 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 for Rf include residues that do not contain an ether function and include but are not limited to —C4F9; —C3F7, —C2F5, —CF3, wherein the C4 and C3 residues may be branched or linear, but preferably are linear.
The unsaturated perfluorinated alkyl either may comprise allyl or vinyl groups. Both have C═C double bonds. Whereas a perfluorinated vinyl group is CF2═CF—; a perfluorinated allyl group is CF2═CFCF2—.
Specific examples of suitable perfluorinated alkyl vinyl ethers (PAVE's) and perfluorinated alkyl allyl ethers (PAAE's) include but are not limited to perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE), perfluoro (n-propyl vinyl) ether (PPVE-1), perfluoro-2-propoxypropylvinyl ether (PPVE-2), perfluoro-3-methoxy-n-propylvinyl ether, perfluoro-2-methoxy-ethylvinyl 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, CF2═CF—CF2—O—(CF3)3—O—CF3. Further examples include but are not limited to the vinyl ether described in European patent application EP 1,997,795 B1.
In some embodiments, the (e.g. amorphous) fluoropolymer comprises polymerized units of at least one allyl ether, such as alkyl vinyl ether is CF2═CFCF2OCF2CF2CF3. Such fluoropolymers are described in WO 2019/161153; incorporated herein by reference.
Perfluorinated alkyl ethers as described above are commercially available, for example from Anles Ltd., St. Petersburg, Russia and other companies or may be prepared according to methods described in U.S. Pat. No. 4,349,650 (Krespan) or EP 1,997,795, or by modifications thereof as known to a skilled person.
The fluoropolymer typically comprises polymerized units derived from one or more of the unsaturated perfluorinated alkyl ethers (PAVE) (e.g. PMVE, PAAE or a combination thereof), in an amount of at least 10, 15, 20, 25, 30, 45, or 50% by weight, based on the total polymerized monomer units of the fluoropolymer. When the amount of polymerized units derived from one or more of the unsaturated perfluorinated alkyl ethers is less than 30 wt. %, the amorphous fluoropolymer typically comprises other comonomers such as HFP to reduce the crystallinity. In some embodiments, the fluoropolymer comprises no greater than 50, 45, 40, or 35% by weight of polymerized units derived from one or more of the unsaturated perfluorinated alkyl ethers (PMVE, PAAE or a combination thereof), based on the total polymerized monomer units of the fluoropolymer. The molar ratio of units derived from TFE to the perfluorinated alkyl ethers described above may be, for example, from 1:1 to 5:1. In some embodiments, the molar ratio ranges from 1.5:1 to 3:1.
In some embodiments, the one or more unsaturated perfluorinated alkyl ethers comprises unsaturated cyclic perfluorinated alkyl ethers, such as 2,2-bistrifluoromethyl-4,5-difluoro-1,3 dioxole. Amorphous fluoropolymer that comprise predominantly, or exclusively comprise, (e.g. repeating) polymerized units derived from two or more perfluorinated comonomers including tetrafluoroethene (TFE) and one or more unsaturated cyclic perfluorinated alkyl ethers, such as 2,2-bistrifluoromethyl-4,5-difluoro-1,3 dioxole are commercially available as “TEFLON™ AF”, “CYTOP™”, and “HYFLON™”.
Fluoropolymers comprising a sufficient amount of polymerized units of one or more of the unsaturated perfluorinated alkyl ethers are typically amorphous fluoropolymers. As used herein, amorphous fluoropolymers are materials that contain essentially no crystallinity or possess no significant melting point (peak maximum) as determined by differential scanning calorimetry in accordance with DIN EN ISO 11357-3:2013-04 under nitrogen flow and a heating rate of 10° C./min. Typically, amorphous fluoropolymers have a glass transition temperature (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 −50° C. to 15° C., or −55° C. to 10° C. The fluoropolymers may typically have a Mooney viscosity (ML 1+10 at 121° C.) of from about 2 to about 150, for example from 10 to 100, or from 20 to 70. For amorphous polymers containing cyclic perfluorinated alky ether units, the glass transition temperature is typically at least 70° C., 80° C., or 90° C., and may range up to 220° C., 250° C., 270° C., or 290° C. The MFI (297° C./5 kg) is between 0.1-1000 g/10 min.
The fluorine content of the fluoropolymer is typically at least 60, 65, 66, 67, 68, 69, or 70 wt. % of the fluoropolymer and typically no greater than 76, 75, 74, or 73 wt. %. The fluorine content may be achieved by selecting the comonomers and their amounts accordingly.
Such highly-fluorinated amorphous fluoropolymers typically do not dissolve to the extent of at least 1 wt. %, at room temperature and standard pressure, in a hydrogen-containing organic liquid (e.g., it does not dissolve in any of methyl ethyl ketone (“MEK”), tetrahydrofuran (“THF”), ethyl acetate or N-methyl pyrrolidinone (“NMP”)).
Amorphous and crystalline fluoropolymers can be prepared by methods known in the art, such as bulk, suspension, solution or aqueous emulsion polymerization. (See for example EP 1,155,055; U.S. Pat. No. 5,463,021; WO 2015/088784 and WO 2015/134435) Various emulsifiers can be used as described in the art, including for example 3H-perfluoro-3-[(3-methoxy-propoxy)propanoic acid. For example, the polymerization process can be carried out by free radical polymerization of the monomers alone or as solutions, emulsions, or dispersions in an organic solvent or water. Seeded polymerizations may or may not be used. Curable fluoroelastomers that can be used also include commercially available fluoroelastomers, in particular perfluoroelastomers.
The fluoropolymers may have a monomodal or bi-modal or multi-modal weight distribution. The fluoropolymers may or may not have a core-shell structure. Core-shell polymers are polymers where towards the end of the polymerization, typically after at least 50% by mole of the comonomers are consumed, the comonomer composition or the ratio of the comonomers or the reaction speed is altered to create a shell of different composition.
The fluoropolymer layer comprises uncrosslinked (e.g. amorphous) fluoropolymer. The uncrosslinked fluoropolymer of the coated substrate or article is soluble in fluroinated solvent. The fluroinated solvent will subsequently be described in greater detail. In some embodiments, the fluorinated solvent is solvent is a partially fluorinated ether such as 3-ethoxy perfluorinated 2-methyl hexane, or 3-methoxy perfluorinated 4-methyl. By soluble it is meant that at least 10, 15, 20, 25, or 30 wt. % of the uncrosslinked fluoropolymer is soluble in fluorinated solvent.
The fluoropolymer layer comprises uncrosslinked (e.g. amorphous) fluoropolymer. An uncrosslinked fluoropolymer lacks crosslinks of a chemical curing agent that renders the fluoropolymer insoluble in fluorinated solvent. Thus, the fluoropolymer compositions described herein lacks chemical curing agents and/or the fluoropolymer(s) thereof lack cure sites that reacts with such chemical curing agent. It is appreciated that a chemical curing agent in the absence of a fluoropolymer with cure sites does not result in crosslinks of a chemical curing agent. It is also appreciated that a fluoropolymer with cure sites in the absence of a chemical curing agent does not result in crosslinks of a chemical curing agent. Thus, the fluoropolymer(s) may optionally contain one or more cure sites in the absence of a chemical curing agent. Alternatively, the fluoropolymer composition may optionally contain chemical curing agent in the absence of fluoropolymer with cure sites.
In typical embodiments, the fluropolymer composion lacks chemical curing agents, described in WO 2021/091864 incorporated herein by reference. Thus, the fluoropolymer lacks chemical curing agents such as a peroxides, amines, ethylenically unsaturated compounds; and amino organosilane ester compounds or ester equivalent. The fluoropolymer composition also lacks one or more compounds comprising an electron donor group (such as an amine) in combination with an ethylenically unsaturated group.
In typical embodiments, the fluoropolymer(s) of the fluoropolymer composition also lacks cure sites such as iodine, bromine, chlorine, nitrile as well as amidines, amidine salts, imidate, amides and ammonium salts. However, fluoropolymers comprising such cure sites are commercially available. Thus, some of the exemplified composition comprise such cure sites, even though such cure sites are not reacted with a chemical curing agent to chemically crosslink the fluoropolymers. Further, the inclusion of cure sites, such as nitrile, can improve adhesion of the fluoropolymer composition to a substrate.
Cure sites are functional groups that react in the presence of a curing agent or a curing system to cross-link the polymers. The cure sites are typically introduced by copolymerizing cure-site monomers, which are functional comonomers already containing the cure sites or precursors thereof. One indication of crosslinking is that the dried and cured coating composition was not soluble in the fluorinated solvent of the coating.
The cure sites may be introduced into the polymer by using cure site monomers, i.e. functional monomers, functional chain-transfer agents and starter molecules as further described in WO 2021/091864. The fluoroelastomers may contain cure sites that are reactive to more than one class of curing agents.
The fluoroelastomers contain cure sites in the backbone, as pendent groups, or cure sites at a terminal position. Cure sites within the fluoropolymer backbone can be introduced by using a suitable cure-site monomer. Cure site monomers are monomers containing one or more functional groups that can act as cure sites or contain a precursor that can be converted into a cure site.
In some embodiments, the fluoropolymer comprises halogen cure sites, i.e. cure sites comprising iodine, bromine or chlorine. When present, the amount of iodine or bromine or chlorine or their combination in the fluoropolymer is between 0.001 and 5%, preferably between 0.01 and 2.5%, or 0.1 to 1% or 0.2 to 0.6% by weight with respect to the total weight of the fluoropolymer. In one embodiment the curable fluoropolymers contain between 0.001 and 5%, preferably between 0.01 and 2.5%, or 0.1 to 1%, more preferably between 0.2 to 0.6% by weight of iodine based on the total weight of the fluoropolymer.
In some embodiments, the fluoropolymer contains nitrile-containing cure sites as well as corresponding amidines, amidine salts, imidate, amides and ammonium salts. Fluoropolymers with nitrile-containing cure sites are known, such as described in U.S. Pat. Nos. 6,720,360 and 7,019,082. When present, the amount of nitrile-containing cure site comonomer is typically at least 0.5, 1, 1.5, 2, 2.5, 3. 3.5, 4, 4.5 or 5% by weight and typically no greater than 10% by weight; based on the total weight of the fluoropolymer.
The fluoropolymers may or may not contain units derived from at least one modifying monomer. The modifying monomers may introduce branching sites into the polymer architecture. Typically, the modifying monomers are bisolefins, bisolefinic ethers or polyethers. The bisolefins and bisolefinic (poly)ethers may be perfluorinated, partially fluorinated or non-fluorinated. Preferably they are perfluorinated. Suitable perfluorinated bisolefinic ethers include those represented by the general formula:
wherein n and m are independent from each other either 1 or 0 and wherein Rf represents a perfluorinated linear or branched, cyclic or acyclic aliphatic or aromatic hydrocarbon residue that may be interrupted by one or more oxygen atoms and comprising up to 30 carbon atoms. A particular suitable perfluorinated bisolefinic ether is a di-vinylether represented by the formula:
wherein n is an integer between 1 and 10, preferably 2 to 6, e.g. n may be 1, 2, 3, 4, 5, 6 or 7. More preferably, n represents an uneven integer, for example 1, 3, 5 or 7.
Further specific examples include bisolefinic ethers according the general formula
wherein n and m are independently either 1 or 0 and p is an integer from 1 to 10 or 2 to 6. For example, n may be selected to represent 1, 2, 3, 4, 5, 6 or 7, preferably, 1, 3, 5 or 7.
Further suitable perfluorinated bisolefinic ethers can be represented by the formula
wherein Raf and Rbf are different linear or branched perfluoroalkylene groups of 1-10 carbon atoms, in particular, 2 to 6 carbon atoms, and which may or may not be interrupted by one or more oxygen atoms. Raf and/or Rbf may also be perfluorinated phenyl or substituted phenyl groups; n is an integer between 1 and 10 and m is an integer between 0 and 10, preferably m is 0. Further, p and q are independently 1 or 0.
In another embodiment, the perfluorinated bisolefinic ethers can be represented by the formula just described wherein m, n, and p are zero and q is 1-4.
Modifying monomers can be prepared by methods known in the art and are commercially available, for example, from Anles Ltd., St. Petersburg, Russia.
Preferably, (e.g. ethylenically unsaturated) modifying monomers are not used or only used in low amounts. Typical amounts include from 0 to 5%, or from 0 to 1.4% by weight based on the total weight of the fluoropolymer. Modifiers may be present, for example, in amounts from about 0.1% to about 1.2% or from about 0.3% to about 0.8% by weight based on the total weight of fluoropolymer. Combinations of modifiers may also be used. Further, in typical embodiments, the fluoropolymer composition comprises no greater than 8, 7, 6, 5, 4, 3, 2, 1 or 0.1 wt.-% of polymerized units bearing (e.g. (meth)acrylate) ester-containing moieties.
The 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-difluoroethene (vinylidenefluoride, VDF) and vinyl fluoride (VF) or trifluorochloroethene or trichlorofluoroethene. Examples of non-fluorinated comonomers include but are not limited to ethene and propene. In typical embodiments, the fluoropolymer composition comprises no greater than 8, 7, 6, 5, 4, 3, 2, 1 or 0.1 wt.-% of polymerized units derived from non-fluorinated or partially fluorinated monomers based on the total weight of the fluoropolymer.
In one embodiment, the uncrosslinked (e.g. amorphous) fluoropolymer is a coagulated latex. Coagulation may be carried out, for example, by chilling (e.g., freezing) the blended latexes or by adding a suitable salt (e.g., magnesium chloride) or inorganic acid. Chilling is especially desirable for coatings that will be used in semiconductor manufacturing and other applications where the introduction of salts may be undesirable. The method further comprising optionally washing the coagulated fluoropolymer particles. The washing step may substantially remove emulsifiers or other surfactants from the mixture and can assist in obtaining a well-mixed blend of substantially unagglomerated dry particles. In some embodiments, the surfactant level of the resulting dry particle mixture may, for example, be less than 0.1% by weight, less than 0.05% by weight or less than 0.01% by weight. The method further comprises drying the coagulated latex mixture. The coagulated latex mixture can be dried by any suitable means such as air drying or oven drying. In one embodiment, the coagulated latex mixture can be dried at 100° C. for 1-2 hours. Fluoropolymer particles that are derived from coagulating a latex are submicron in size. 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.
In some embodiments, the dried coagulated latex can be dissolved in a fluorinated solvent suitable for dissolving the (e.g. amorphous) fluoropolymer particles to form a stable coating composition.
In some embodiments, the fluoropolymer composition lacks crystalline fluorpolymers. However, the fluoropolymer composition of the fluoropolymer layer may optionally further comprise crystalline fluoropolymer provided the presence thereof does not detract from the solubility of the (e.g. amorphous) fluoropolymer in fluorinated solvent. The crystalline fluoropolymer may be present as particles.
When a coating solution of (e.g. amorphous) fluoropolymer that is soluble in the fluorinated solvent of the coating solution and insoluble crystalline fluoropolymer particles are applied to a substrate and dried, the amorphous fluoropolymer remains soluble in the same fluorinated solvent provided that the dried coating has not been subjected to heat such that the amorphous and crystalline fluoropolymer co-crystalline with each other.
A variety of crystalline fluoropolymer (e.g. particles) may be employed including mixtures of different crystalline fluoropolymer (e.g. particles). The crystalline fluoropolymer particles typically have high crystallinity and therefore a significant melting point (peak maximum) as determined by differential scanning calorimetry in accordance with DIN EN ISO 11357-3:2013-04 under nitrogen flow and a heating rate of 10° C./min. Thus, the crystalline fluoropolymer (e.g. particles) are typically thermoplastic.
For example, the crystalline fluoropolymer (e.g. particles) may include fluoropolymers having a Tm of at least 100, 110, 120, or 130° C. In some embodiments, the crystalline fluoropolymer (e.g. particles) may include fluoropolymers having a Tm no greater than 350, 340, 330, 320, 310 or 300° C.
The crystalline fluoropolymer (e.g. particles) typically have a fluorine content greater than about 50 weight percent. Also, the fluoropolymer (e.g. particles) may include fluoropolymers having a fluorine content between about 50 and about 76 weight percent, between about 60 and about 76 weight percent, or between about 65 and about 76 weight percent.
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™ Dyneonr™ Fluorothermoplastic Dispersions PFA 6900GZ, PFA 6910GZ, FEP 6300GZ, THV 221, THV 340Z, and THV 800. Other suitable fluoropolymer (e.g. particles) are available from suppliers such as Asahi Glass, Solvay Solexis, and Daikin Industries and will be familiar to those skilled in the art.
Commercial aqueous dispersion usually contain non-ionic and/or ionic surfactants at concentration up to 5 to 10 wt. %. These surfactants are substantially removed by washing the coagulated blends. A residual surfactant concentration of less than 1, 0.05, or 0.01 wt. % may be present. Quite often it is more convenient to use the “as polymerized” aqueous fluoropolymer-latexes as they do not contain such higher contents of non-ionic/ionic surfactants.
As previously described, the crystalline fluoropolymers have a melt point that can be determined by DSC. Crystallinity depends on the selection and concentration of polymerized monomers of the fluoropolymer. For example, PTFE homopolymers (containing 100% TFE-units) have a melting point (Tm) above 340° C. The addition of comonomers, such as the unsaturated (per)fluorinated alkyl ethers, reduces the Tm. For example, when the fluoropolymer contains about 3-5 wt. % of polymerized units of such comonomer, the Tm is about 310° C. As yet another example, when the fluoropolymer contains about 15-20 wt. % of polymerized units of HFP, the Tm is about 260-270° C. As yet another example, when the fluoropolymer contains 30 wt. % of polymerized units of (per)fluorinated alkyl ethers (e.g. PMVE) or other comonomer(s) that reduce the crystallinity the fluoropolymer no longer has a detectable melting point via DSC, and thus is characterized as being amorphous.
In some embodiments, the crystalline fluoropolymer (e.g. particles) contain at least 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or about 100 wt. % of polymerized units of TFE. The crystalline fluoropolymer (e.g. particles) typically have a greater amount of polymerized units of TFE than the first amorphous fluoropolymer. More typically the crystalline fluoropolymer (e.g. particles) contain at least 70, 75, 85, 90, 95 or about 100 wt. % of polymerized units of TFE. Further, the crystalline fluoropolymer (e.g. particles) typically comprise a lower concentration of unsaturated (per)fluorinated alkyl ethers (e.g. PMVE) than the amorphous flurorpolymer. In typical embodiments, the crystalline fluoropolymer (e.g. particles) contain less than 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, or 5 wt. % of polymerized units of (per)fluorinated alkyl ethers.
In some embodiments, the crystalline fluoropolymers are copolymers formed from the constituent monomers known as tetrafluoroethylene (“TFE”), hexafluoropropylene (“HFP”), and vinylidene fluoride (“VDF,” “VF2,”). The monomer structures for these constituents are shown below:
In some embodiments, the crystalline fluoropolymer consists of at least two of the constituent monomers (HFP and VDF), and in some embodiments all three of the constituents monomers in varying amounts.
The Tm depends on the amounts of TFE, HFP, and VDF. For example, a fluoropolymer comprising about 45 wt. % of polymerized units of TFE, about 18 wt. % of polymerized units of HFP, and about 37 wt. % of polymerized units of VDF has a Tm of about 120° C. As yet another example, a fluoropolymer comprising about 76 wt. % of polymerized units of TFE, about 11 wt. % of polymerized units of HFP, and about 13 wt. % of polymerized units of VDF has a Tm of about 240° C. By increasing the polymerized units of HFP/VDF, while reducing the polymerized units of TFE, the fluoropolymer becomes amorphous. An overview of crystalline and amorphous Fluoropolymers is described by Ullmann's Encyclopedia of Industrial Chemistry (7th Edition, 2013 Wiley-VCH Verlag. 10. 1002/14356007.a11 393 pub 2) Chapter: Fluoropolymers, Organic.
In some embodiments, the crystalline fluoropolymers comprise little or no polymerized units of VDF. The amount of polymerized units of VDF is no greater than 5, 4, 3, 2, or 1 wt. % of the total crystalline fluoropolymer.
In some embodiments, the crystalline fluoropolymers comprises polymerized units of HFP. The amount of polymerized units of HFP can be at least 1, 2, 3, 4, 5 wt. % of the total crystalline fluoropolymer. In some embodiments, the amount of polymerized units of HFP is no greater than 15, 14, 13, 12, 11, or 10 wt. % of the total crystalline fluoropolymer.
In some embodiments, the crystalline fluoropolymers of the compositions described here comprise little or no polymerized units of vinylidene fluoride (VDF) (i.e. CH2═CF2) or VDF coupled to hexafluoropropylene (HFP). Polymerized units of VDF can undergo dehydrofluorination (i.e. an HF elimination reaction) as described in US2006/0147723. The reaction is limited by the number of polymerized VDF groups coupled to an HFP group contained in the fluoropolymer.
When present, the coating composition or fluoropolymer layer contains at least 5, 10 or 15 weight percent ranging up to about 50, 55, 60, 65, 70, 75, or 80 weight percent crystalline fluoropolymer (e.g. particles) and about 20, 30, 40, or 50 to about 90 or 95 weight percent (e.g. amorphous) uncrosslinked fluoropolymer. In some embodiments, the coating composition contains about 10 to about 30 weight percent crystalline fluoropolymer (e.g. particles) and about 90 to about 70 weight percent (e.g. amorphous) uncrosslinked fluoropolymer.
In some embodiments, the fluoropolymer particles may be characterized as an “agglomerate” (e.g. of latex particles), meaning a weak association between primary particles such as particles held together by charge or polarity. Agglomerates are typically physically broken down into smaller entities such as primary particles during preparation of the coating solution. In other embodiments, the fluoropolymer particles may be characterized as an “aggregate”, meaning strongly bonded or fused particles, such as covalently bonded particles or thermally bonded particles prepared by processes such as sintering, electric arc, flame hydrolysis, or plasma. Aggregates are typically not broken down into smaller entities such as primary particles during preparation of the coating solution. “Primary particle size” refers to the mean diameter of a single (non-aggregate, non-agglomerate) particle.
In some embodiments, fluoropolymer composition comprises fluoropolymer particles having a particle size of greater than 1 micron. In typical embodiments, the fluoropolymer particles have an average particle size of no greater than 75, 70, 65, 60, 55, 50, 45, 35, 30, 30, 25, 20, 15, 10, or 5 microns. In some embodiments, the particle size of the fluoropolymer particles is less than the thickness of the fluoropolymer coating or fluoropolymer film layer. The average particle size is typically reported by the supplier. The particle size of the fluoropolymer particles of the fluoropolymer coating or fluoropolymer film layer can be determined by microscopy.
In some embodiments, the fluoropolymer particles comprise a mixture of particles including fluoropolymer particles having a particle size of greater than 1 micron and fluoropolymer particles having a particle size of 1 micron 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.
The weight ratio of fluoropolymer particles having a particle size greater than 1 micron to fluoropolymer particles having a particle size of 1 micron or less typically ranges from 1:1 to 10:1. In some embodiments, the weight ratio of larger to smaller fluoropolymer particles is at least 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1.
The crystalline fluoropolymer (e.g. particles) are insoluble in fluorinated solvent. The crystalline fluoropolymer (e.g. particles) are also insoluble in non-fluorinated organic solvent such as methyl ethyl ketone (“MEK”), tetrahydrofuran (“THF”), ethyl acetate or N-methyl pyrrolidinone (“NMP”). By insoluble it is meant that less than 1, 0.5, 0.1, 0.01, or 0.001 wt % of the fluoropolymer is soluble in fluorinated solvent.
The fluoropolymer coating compositions comprise at least one fluorinated solvent. The solvent is capable of dissolving the amorphous fluoropolymer. The crystalline fluoropolymer (e.g. particles) are insoluble in the fluorinated solvent. The amorphous fluoropolymer of the fluoropolymer composition of the coated substrate or article remains soluble in the fluorinated solvent.
The fluoropolymer coating compositions may be prepared by mixing the fluoropolymers, optional additives and the fluorinated solvent. In some embodiments, the amorphous fluoropolymer is first dissolved in the fluorinated solvent and the crystalline fluoropolymer particles and other additives added thereafter.
The fluorinated solvent is typically present in an amount of at least 25% by weight based on the total weight of the coating 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 composition.
The fluoropolymer coating composition typically comprises at least 0.01, 0.02, 0.03, 0.03, 0.04, 0.04, 0.05, 0.06, 0.7, 0.8. 0.9 or 1% by weight of fluoropolymer, based on the weight of the total coating composition. In some embodiments, the fluoropolymer coating composition comprises at least 2, 3, 4, or 5% by weight of fluoropolymer. In some embodiments, the fluoropolymer coating composition comprises at least 6, 7, 8, 9 or 10% by weight of fluoropolymer. The fluoropolymer coating composition typically comprises no greater than 50, 45, 40, 35, 30, 25, or 20% by weight of fluoropolymer, based on the weight of the total coating composition. Thus, the coating composition can contain various concentrations of (e.g. amorphous) fluoropolymer that is soluble in fluorinated solvent.
Optimum amounts of solvent and fluoropolymers may depend on the final application and may vary. For example, to provide thin coatings, very dilute solutions of fluoropolymer in the solvent may be desired, for example amounts of from 0.01% by weight to 5% by weight of fluoropolymer. Also for application by spray coating composition of low viscosity may be preferred over solutions with high viscosity. The concentration of fluoropolymer in the solution affects the viscosity and may be adjusted accordingly. An advantage of the present disclosure is that also solutions with high concentrations of fluoropolymer can be prepared that still provide clear liquid composition of low viscosity.
In some embodiments, the fluoropolymer coating compositions may be liquids. The liquids may have, for example, a viscosity of less than 2,000 mPas at room temperature (20° C.+/−2° C.). In other embodiments, the fluoropolymer coating solution compositions are pastes. The pastes may have, for example, a viscosity of from 2,000 to 100.000 mPas at room temperature (20° C.+/−2° C.).
The solvent is a liquid at ambient conditions and typically has a boiling point of greater than 50° C. Preferably, the solvent has a boiling point below 200° C. so that it can be easily removed. In some embodiments, the solvent has a boiling point below 190, 180, 170, 160, 150, 140, 130, 120, 110, or 100° C.
The solvent is partially fluorinated or perfluorinated. Thus, the solvent is non-aqueous. Various partially fluorinated or perfluorinated solvents are known including perfluorocarbons (PFCs), hydrochlorofluorocarbons (HCFCs), perfluoropolyethers (PFPEs), and hydrofluorocarbons (HFCs), as well as fluorinated ketones and fluorinated alkyl amines.
In some embodiments, the solvent has a global warming potential (GWP, 100 year ITH) of less than 1000, 900, 800, 700, 600, 500, 400, 300, 200 or 100. The GWP is typically greater than 0 and may be at least 10, 20, 30, 40, 50, 60, 70, or 80.
As used herein, GWP is a relative measure of the global warming potential of a compound based on the structure of the compound. The GWP of a compound, as defined by the Intergovernmental Panel on Climate Change (IPCC) in 1990 and updated in subsequent reports, is calculated as the warming due to the release of 1 kilogram of a compound relative to the warming due to the release of 1 kilogram of CO2 over a specified integration time horizon (ITH).
where F is the radiative forcing per unit mass of a compound (the change in the flux of radiation through the atmosphere due to the IR absorbance of that compound), Co is the atmospheric concentration of a compound at initial time, τ is the atmospheric lifetime of a compound, t is time, and x is the compound of interest.
In some embodiments, the solvent comprises a partially fluorinated ether or a partially fluorinated polyether. The partially fluorinated ether or polyether may be linear, cyclic or branched. Preferably, it is branched. Preferably it comprises a non-fluorinated alkyl group and a perfluorinated alkyl group and more preferably, the perfluorinated alkyl group is branched.
In one embodiment, the partially fluorinated ether or polyether solvent corresponds to the formula:
wherein Rf is a perfluorinated or partially fluorinated alkyl or (poly)ether group and R is a non-fluorinated or partially fluorinated alkyl group. Typically, Rf may have from 1 to 12 carbon atoms. Rf may be a primary, secondary or tertiary fluorinated or perfluorinated alkyl residue. This means, when Rf is a primary alkyl residue the carbon atom linked to the ether atoms contains two fluorine atoms and is bonded to another carbon atom of the fluorinated or perfluorinated alkyl chain. In such case Rf would correspond to Rf1—CF2— and the polyether can be described by the general formula: Rf1—CF2—O—R.
When Rf is a secondary alkyl residue, the carbon atom linked to the ether atom is also linked to one fluorine atoms and to two carbon atoms of partially and/or perfluorinated alkyl chains and Rf corresponds to (Rf2Rf3)CF—. The polyether would correspond to (Rf2Rf3)CF—O—R.
When Rf is a tertiary alkyl residue the carbon atom linked to the ether atom is also linked to three carbon atoms of three partially and/or perfluorinated alkyl chains and Rf corresponds to (Rf4Rf5Rf6)—C—. The polyether then corresponds to (Rf4Rf5Rf6)—C—OR. Rf1; Rf2; Rf3; Rf4; Rf5; Rf6 correspond to the definition of Rf and are a perfluorinated or partially fluorinated alkyl group that may be interrupted once or more than once by an ether oxygen. They may be linear or branched or cyclic. Also a combination of polyethers may be used and also a combination of primary, secondary and/or tertiary alkyl residues may be used.
An example of a solvent comprising a partially fluorinated alkyl group includes C3F7OCHFCF3 (CAS No. 3330-15-2).
An example of a solvent wherein Rf comprises a perfluorinated (poly)ether is C3F7OCF(CF3)CF2OCHFCF3 (CAS No. 3330-14-1).
In some embodiments, the partially fluorinated ether solvent corresponds to the formula:
wherein q is an integer from 1 to and 5, for example 1, 2, 3, 4 or 5, and p is an integer from 5 to 11, for example 5, 6, 7, 8, 9, 10 or 11. Preferably, CpF2p+1 is branched. Preferably, CpF2p+1 is branched and q is 1, 2 or 3.
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-dodecafluroro-2-(trifluoromethyl)hexane. Such solvents are commercially available, for example, under the trade designation NOVEC from 3M Company, St. Paul, MN.
The fluorinated (e.g. ethers and polyethers) solvents may be used alone or in combination with other solvents, which may be fluorochemical solvents or non-fluorochemical solvents. When a non-fluorochemical solvent is combined with a fluorinated solvent, the concentration non-fluorochemical solvent is typically less than 30, 25, 20, 15, 10 or 5 wt-% with respect to the total amount of solvent. Representative non-fluorochemical solvents include ketones such as acetone, MEK, methyl isobutyl ketone, methyl amyl ketone and NMP; ethers such as tetrahydrofuran, 2-methyl tetrahydrofuran and methyl tetrahydrofurfuryl ether; esters such as methyl acetate, ethyl acetate and butyl acetate; cyclic esters such as delta-valerolactone and gamma-valerolactone.
The coating composition described herein including fluorinated solvent is “stable, meaning that the coating composition remains homogeneous when stored for at least 24 hours at room temperature in a sealed container. In some embodiments, the coating composition is stable for one week or more. “Homogeneous” refers to a coating composition that does not exhibit a visibly separate precipitate or visibly separate layer when freshly shaken, placed in a 100 ml glass container and allowed to stand at room temperature for at least 4 hours.
Compositions containing curable fluoroelastomers may further contain additives as known in the art. Examples include acid acceptors. Such acid acceptors can be inorganic or blends of inorganic and organic acid acceptors. Examples of inorganic acceptors include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide, dibasic lead phosphate, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, hydrotalcite, etc. Organic acceptors include epoxies, sodium stearate, and magnesium oxalate. Particularly suitable acid acceptors include magnesium oxide and zinc oxide. Blends of acid acceptors may be used as well. The amount of acid acceptor will generally depend on the nature of the acid acceptor used. Typically, the amount of acid acceptor used is between 0.5 and 5 parts per 100 parts of fluorinated polymer.
The fluoropolymer composition may contain further additives, such as stabilizers, surfactants, ultraviolet (“UV”) absorbers, antioxidants, plasticizers, lubricants, fillers, and processing aids typically utilized in fluoropolymer processing or compounding, provided they have adequate stability for the intended service conditions. A particular example of additives includes carbon particles, like carbon black, graphite, soot. Further additives include but are not limited to pigments, for example iron oxides, titanium dioxides. Other additives include but are not limited to clay, silicon dioxide, barium sulphate, silica, glass fibers, or other additives known and used in the art.
In some embodiments, the fluoropolymer composition comprises silica, glass fibers, thermally conductive particles, or a combination thereof Δny amount of silica and/or glass fibers and/or thermally conductive particles may be present. In some embodiments, the amount of silica and/or glass fibers is at least 0.05, 0.1, 0.2, 0.3 wt. % of the total solids of the composition. In some embodiments, the amount of silica and/or glass fibers is no greater than 5, 4, 3, 2, or 1 wt. % of the total solids of the composition. Small concentrations of silica can be utilized to thicken the coating composition. Further, small concentrations of glass fibers can be used to improve the strength of the fluoropolymer film. In other embodiments, the amount of glass fibers can 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 fibers is typically no greater than 55, 50, 45, 40, 35, 25, 20, 15, or 10 wt. %. In some embodiments, the glass fibers have a mean length of at least 100, 150, 200, 250, 300, 350, 400, 450, 500 microns. In some embodiments, the glass fibers have a mean length of at least 1, 2, or 3 mm and typically no greater than 5 or 10 mm. In some embodiments, the glass fibers have a mean diameter of at least 1, 2, 3, 4, or 5 microns and typically no greater than 10, 15, 30, or 25 microns. The glass fibers can have aspect ratio of at least 3:1, 5:1, 10:1, or 15:1.
In some embodiments, the fluoropolymer composition is free of (e.g. silica) inorganic oxide particles. In other embodiments, the fluoropolymer composition comprises (e.g. silica and/or thermally conductive) inorganic oxide particles. In some embodiments, the amount of (e.g. silica and/or thermally conductive) inorganic oxide particles 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 (e.g. silica and/or thermally conductive) inorganic oxide particles is no greater than 90, 85, 80, 75, 70, or 65 wt. % of the total solids of the composition. Various combinations of silica and thermally conductive particles can be utilized. In some embodiments, the total amount of (e.g. silica and thermally conductive) inorganic oxide particles or the amount of a specific type of silica particle (e.g. fused silica, fumed silica, glass bubbles, etc.) or thermally conductive particle (e.g. boron nitride, silicon carbide, aluminum oxide, 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 (e.g. silica) inorganic oxide particles can be favorable to further reducing the dielectric properties. Thus, the compositions including (e.g. silica) inorganic oxide particles can have even lower dielectric properties than the fluoropolymer composition alone.
In some embodiments, the (e.g. silica) inorganic oxide particles and/or glass fibers have a dielectric contant at 1 GHz of no greater than 7, 6.5, 6, 5.5, 5, 4.5, or 4. In some embodiments, the (e.g. silica) inorganic oxide particles and/or glass fibers have a dissipation factor at 1 GHz of no greater than 0.005, 004, 0.003, 0.002, or 0.0015.
In some embodiments, the composition comprises inorganic oxide particles or glass fibers that comprise predominantly silica. In some embodiments, the amount of silica is typically 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 typically 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 typically have lower dielectric constants. In some embodiments, (e.g. fused) silica particle can further comprise small concentration of other metals/meta oxides such as Al2O3, Fe2O5, TiO2, K2O, CaO, MgO and Na2O. In some embodiments, the total amount of such metals/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 comprise B2O3 The amount of B2O3 can range up to 25 wt. % of the inorganic oxide particles or glass fibers. In other embodiments, (e.g. fumed) silica particle can further comprise small concentration of additional metals/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 5, 4, 3, 2, or 1 wt. %. In some embodiments, the silica may be described as quartz. The amount of non-silica metals or metal oxides can be determined by uses of inductively coupled plasma mass spectrometry. The (e.g. silica) inorganic oxides particles are typically dissolved in hydrofluroic acid and distilled as H2SiF6 at low temperatures.
In some embodiments, the inorganic particles may be characterized as an “agglomerate”, meaning a weak association between primary particles such as particles held together by charge or polarity. Agglomerate are typically physically broken down into smaller entities such as primary particles during preparation of the coating solution. In other embodiments, the inorganic particles may be characterized as an “aggregate”, meaning strongly bonded or fused particles, such as covalently bonded particles or thermally bonded particles prepared by processes such as sintering, electric arc, flame hydrolysis, or plasma. Aggregates are typically no broken down into smaller entities such as primary particles during preparation of the coating solution. “Primary particle size” refers to the mean diameter of a single (non-aggregate, non-agglomerate) particle.
The (e.g. silica) particles may have various shapes such as spherical, ellipsoid, linear or branched. Fused and fumed silica aggregates are more commonly branched. The aggregate size is commonly at least 10× the primary particle size of discrete part.
In other embodiments, the (e.g. silica) particles may be characterized as glass bubbles. The glass bubble may be prepared from soda lime borosilicate glass. In this embodiment, the glass may contain about 70 percent silica (silicon dioxide), 15 percent soda (sodium oxide), and 9 percent lime (calcium oxide), with much smaller amounts of various other compounds.
In some embodiments, the inorganic oxide particles may be characterized as (e.g. silica) nanoparticles, having a mean or median particles size less than 1 micron. In some embodiments, the mean or median particle size of the (e.g. silica) inorganic oxide particles is at 500 or 750 nm. In other embodiments, the mean 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 microns. In some embodiments, the mean particle size in no greater than 30, 25, 20, 15, or 10 microns. In some embodiments, the composition comprises little or no (e.g. colloidal silica) nanoparticles having a particle of 100 nanometers or less. The concentration of (e.g. colloidal silica) nanoparticles is typically less than (10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt. %) The inorganic oxide (e.g. silica particle) may comprise a normal distribution of particle sizes having a single peak or a distribution of particles having two or more peaks.
In some embodiments, no greater than 1 wt. % of the (e.g. silica) inorganic oxide particles have a particle size greater than or equal to 3 or 4 microns. In some embodiments, no greater than 1 wt. % of the (e.g. silica) inorganic oxide particles have a particle size greater than or equal to 5 or 10 microns. In other embodiments, no greater than 5, 4, 3, 2, or 1 wt. % of the particles have a particle size greater than 45 microns. In some embodiments, no greater than 1 wt. % of the particles have a particle size ranging from 75 to 150 microns.
In some embodiments, the mean or median particle size refers to the “primary particle size” referring to the mean or median diameter of discrete a non-aggregated, non-agglomerated particles. For example, the particle size of colloidal silica or glass bubbles is typically the mean or median particle size of In preferred embodiments, the mean or median particle size refers to the mean or median diameter of the aggregates. The particle size of the inorganic particles can be measured using transmission electron microscopy. The particle size of the fluoropolymer coating solution can be measured using dynamic light scattering.
In some embodiments, the (e.g. silica) inorganic particles have a specific gravity ranging from 2.18 to 2.20 g/cc.
Aggregated particles, such as in the case of fumed and fused (e.g. silica) particles, can have a lower surface area than primary particles of the same size. In some embodiments, the (e.g. silica) particle have a BET surface area ranging from 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 In some embodiments, the inorganic nanoparticles may be characterized as colloidal silica. It is appreciated that unmodified colloidal silica nanoparticles commonly comprise hydroxyl or silanol functional groups on the nanoparticle surface and are typically characterized as hydrophilic.
In some embodiments, (e.g. silica aggregate) inorganic particles and especially colloidal silica nanoparticles are surface treated with a hydrophobic surface treatment. Common hydrophobic surface treatments include compounds such as alkoxylsilanes (e.g. octadecytriethoxysilane), silazane, or siloxanes. Various hydrophobic fumed silicas are commercially available from AEROSIL™, Evonik, and various other suppliers. Representative hydrophobic fumed silica include AEROSIL™ grades R 972, R 805, RX 300, and NX 90 S.
In some embodiments, (e.g. silica aggregate) inorganic particles are surface treated with a fluorinated alkoxysilane silane compound. Such compounds typically comprise a perfluoroalkyl or perfluoropolyether group. The perfluoroalkyl or perfluoropolyether group typically has no greater than 4, 5, 6, 7, 8 carbon atoms. The alkoxysilane group can be bonded to the alkoxy silane group with various divalent linking groups including alkylene, urethane, and —SO2N(Me)-. Some representative fluorinated alkoxy silanes are described in U.S. Pat. No. 5,274,159 and WO 2011/043973; incorporated herein by reference. Other fluorinated alkoxy silanes are commercially available.
In some embodiments, the fluoropolymer composition comprises thermally conductive particles.
In some embodiments, the thermally conductive inorganic particles are preferably an electrically non-conductive material. Suitable electrically non-conductive, thermally conductive materials include ceramics such as metal oxides, hydroxides, oxyhydroxides, silicates, borides, carbides, and nitrides. Suitable ceramic fillers include, e.g., silicon oxide, zinc oxide, alumina trihydrate (ATH) (also known as hydrated alumina, aluminum oxide, and aluminum trihydroxide), aluminum nitride, boron nitride, silicon carbide, and beryllium oxide. Other thermally conducting fillers include carbon-based materials such as graphite and metals such as aluminum and copper. Combinations of different thermally conductive materials may be utilized. Such materials are not electrically 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 no greater than 15 or 20 eV. In this embodiment, the composition may optionally further comprise a small concentration of thermally conductive particles having an electronic band gap of less than 0 eV or greater than 20 eV.
In favored embodiments, 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 set forth in the following table.
In some embodiments, the thermally conductive particles comprise material(s) having a bulk thermal conductivity of at least 15 or 20 W/m*K. In other embodiments, the thermally conductive particles comprise material(s) having a bulk thermal conductivity of at least 25 or 30 W/m*K. In yet other embodiments, the thermally conductive particles comprise material(s) having a bulk thermal conductivity of at least 50, 75 or 100 W/m*K. In yet other embodiments, the thermally conductive particles comprise material(s) having a bulk thermal conductivity of at least 150 W/m*K. In typical embodiments, the thermally conductive particles comprise material(s) having a bulk thermal conductivity of no greater than about 350 or 300 W/m*K.
Thermally conductive particles are available in numerous shapes, e.g. spheres and acicular shapes that may be irregular or plate-like. In some embodiments, the thermally conductive particles are crystals, typically have a geometric shape. For example, boron nitride hexagonal crystals are commercially available from Momentive. Further, alumina trihydrate is described as a hexagonal platelet. Combinations of particles with different shapes may be utilized. The thermally conductive particles generally have an aspect ratio less than 100:1, 75:1, or 50:1. In some embodiment, the thermally conductive particles have an aspect ratio less than 3:1, 2.5:1, 2:1, or 1.5:1. In some embodiments, generally symmetrical (e.g., spherical, semi-spherical) particles may be employed.
Boron nitride particles are commercially available from 3M as “3M™ Boron Nitride Cooling Fillers”.
In some embodiments, the boron nitride particles has a bulk density of at least 0.05, 0.01, 0.15, 0.03 g/cm3 ranging up to about 0.60, 0.70, or 0.80 g/cm3. The surface area of the boron nitride particle can be <25, <20, <10, <5, or <3 m2/g. The surface area is typically at least 1 or 2 m2/g.
In some embodiments, the particle size, d(0.1), of the boron nitride (e.g. platelet) particles ranges from about 0.5 to 5 microns. In some embodiments, the particle size, d(0.9), of the boron nitride (e.g. platelet) particles is at least 5 ranging up to 20, 25, 30, 35, 40, 45, or 50 microns.
In some embodiments, a method of making a coated substrate is described comprising providing a fluoropolymer composition comprising an (e.g. amorphous) fluoropolymer; and applying the fluoropolymer composition to a substate. The fluoropolymer composition may comprise optional crystalline fluoropolymer (e.g. particles) and other additives as previously described.
In some embodiments, the fluoropolymer composition further comprises a fluorinated solvent; and the method further comprises removing the fluorinated solvent after applying the fluoropolymer composition to the substrate.
The fluoropolymer coating compositions described herein may be adjusted (by the solvent content) to a viscosity to allow application by different coating methods, including, but not limited to spray coating or printing (for example but not limited to ink-printing, 3D-printing, screen printing), painting, impregnating, roller coating, bar coating, dip coating and solvent casting.
The solvent may be reduced or completely removed, for example for evaporation, drying or by boiling it off After removal of the solvent the composition may be characterized as “dried”. The coated substrate may be dried at or above the boiling point of the fluorinated solvent. The amorphous fluoropolymer is soluble in the fluorinated solvent of the coating solution; wherein the crystalline fluoropolymer (e.g. particles) are not soluble in the fluorinated solvent of the coating solution.
In some embodiments, the method further comprises heating the substrate comprising the fluoropolymer composition to a temperature above the melt temperature of the fluoropolymer particles to sinter the fluoropolymer particles.
In other embodiments, the method comprises thermally extruding the fluoropolymer composition onto a substrate. The fluoropolymer can be combined with option materials in conventional rubber processing equipment to provide a solid mixture, i.e. a solid polymer containing additional ingredients, also referred to in the art as a “compound”. Typical equipment includes rubber mills, internal mixers, such as Banbury mixers, and mixing extruders. During mixing the components and additives are distributed uniformly throughout the resulting fluorinated polymer “compound” or polymer sheets. The compound is then preferably comminuted, for example by cutting it into smaller pieces and is then dissolved in the solvent.
In yet another embodiment, the method comprises laminating a fluoropolymer film to the substrate with heat and pressure. The fluoropolymer film can be heated laminated at temperatures ranging from 120° C. to 350° C. In some embodiments, the fluoropolymer film can be heat laminated at a temperature less than 325 or 300°. In some embodiments, the fluoropolymer film can he heat laminated at a temperature no greater than 290, 280, 270, 260, 250, 240, 230, 220, 210, or 200° C. Lower temperatures are amenable to bonding heat sensitive substrate and reducing manufacturing energy costs.
When the method involves heating, the composition lacks crystalline fluropolymer (e.g. particles) or the temperature is insufficient for co-crystallization of the amorphous fluoropolymer with the crystalline fluoropolymer (e.g. particles). The lack of co-crystallization may be evident by the composition having a normalized crystallinity of 100% or less than 100% as described in cofiled 83758US002.
The compositions may be used for impregnating substrates, printing on substrates (for example screen printing), or coating substrates, for example but not limited to spray coating, painting dip coating, roller coating, bar coating, solvent casting, paste coating. The substrate may be organic, inorganic, or a combination thereof. Suitable substrates may include any solid surface and may include substrate selected from glass, plastics (e.g. polycarbonate), composites, metals (stainless steel, aluminum, carbon steel), metal alloys, wood, paper among others. The coating may be colored in case the compositions contains pigments, for example titanium dioxides or black fillers like graphite or soot, or it may be colorless in case pigments or black fillers are absent.
Bonding agents and primers may be used to pretreat the surface of the substrate before coating. For example, bonding of the coating to metal surfaces may be improved by applying a bonding agent or primer. Examples include commercial primers or bonding agents, for example those commercially available under the trade designation CHEMLOK.
The fluoropolymer can exhibit good adhesion to various substrates (e.g. glass, polycarbonate, and metals, such as copper. In some embodiment, the substrate has an average peak to valley heigh surface roughness (i.e. Rz) of about 1 to 1.5 microns. In other embodiments, the substrate has an Rz of greater than 1.5, 2. 2.5, or 3 microns. In some embodiment, the substrate has an Rz) of no greater than 5, 4, 3, 2 or 1.5 microns. For example, in some embodiments, the T-peel to copper foil is at least 5, 6, 7, 8, 9 or 10 N/cm ranging up to 15, 20, 25 30, or 35 N/cm or greater as determined by the test method described in the examples.
In some embodiments, the fluoropolymer composition dried has hydrophobic and oleiphobic properties, as determined by Contact Angle Measurements (as determined according to the test method described in the examples). In some embodiments, the static, advancing and/or receding contact angle with water can be at least 100, 105, 110, 115, 120, 125 and typically no greater than 130 degrees. In some embodiments, the advancing and/or receding contact angle with hexadecane can be at least 60, 65, 70, or 75 degrees.
As used herein the term “partially fluorinated alkyl” means an alkyl group of which some but not all hydrogens bonded to the carbon chain have been replaced by fluorine. For example, an F2HC—, or an FH2C— group is a partially fluorinated methyl group. Alkyl groups where the remaining hydrogen atoms have been partially or completely replaced by other atoms, for example other halogen atoms like chlorine, iodine and/or bromine are also encompassed by the term “partially fluorinated alkyl” as long as at least one hydrogen has been replaced by a fluorine. For example, residues of the formula F2ClC— or FHClC— are also partially fluorinated alkyl residues.
A “partially fluorinated ether” is an ether containing at least one partially fluorinated group, or an ether that contains one or more perfluorinated groups and at least one non-fluorinated 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. Ethers groups where the remaining hydrogen atoms have been partially or completely replaced by other atoms, for example other halogen atoms like chlorine, iodine and/or bromine are also encompassed by the term “partially fluorinated alkyl” as long as at least one hydrogen has been replaced by a fluorine. For example, ethers of the formula F2ClC—O—CF3 or FHClC—O—CF3 are also partially fluorinated ethers.
The term “perfluorinated alkyl” or “perfluoro alkyl” is used herein to describe an alkyl group where all hydrogen atoms bonded to the alkyl chain have been replaced by fluorine atoms. For example, F3C— represents a perfluoromethyl group.
A “perfluorinated ether” is an ether of which all hydrogen atoms have been replaced by fluorine atoms. An example of a perfluorinated ether is F3C—O—CF3.
The following examples are provided to further illustrate the present disclosure without any intention to limit the disclosure to the specific examples and embodiments provided.
Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. Unless otherwise indicated, all other reagents were obtained, or are available from fine chemical vendors such as Sigma-Aldrich Company, St. Louis, Missouri, or may be synthesized by known methods. Table 1 (below) lists materials used in the examples and their sources.
All split-post dielectric resonator measurements were performed in accordance with the standard IEC 61189-2-721 near a frequency of 25 GHz. Each thin material or film was inserted between two fixed dielectric resonators. The resonance frequency and quality factor of the posts are influenced by the presence of the specimen, and this enables the direct computation of complex permittivity (dielectric constant and dielectric loss). The geometry of the split dielectric resonator fixture used in our measurements was designed by the Company QWED in Warsaw Poland. This 25 GHz resonator operates with the TE01d mode which has only an azimuthal electric field component so that the electric field remains continuous on the dielectric interfaces. The split post dielectric resonator measures the permittivity component in the plane of the specimen. Loop coupling (critically coupled) was used in each of these dielectric resonator measurements. This 25 GHz Split Post Resonator measurement system was combined with Keysight VNA (Vector Network Analyzer Model PNA 8364C 10 MHz-50 GHz). Computations were performed with the commercial analysis Split Post Resonator Software of QWED to provide a powerful measurement tool for the determination of complex electric permittivity of each specimen at 25 GHz.
T-peel measurements were conducted using an INSTRON electromechanical universal testing machine using ASTM D1876 standard method for “Peel Resistance of Adhesives,” more commonly known as the ‘T-peel” test. Peel data was generated using an INSTRON Model 1125 Universal Testing Instrument (Norwood, MA) equipped with a Sintech Tester 20 (MTS Systems Corporation, Eden Prairie, MN). Samples were prepared as follows.
Perfluoropolymer films/sheets were obtained by heat-pressing the corresponding coagulated or co-coagulated fluoropolymers sandwiched between two PTFE release sheets. The films were pressed at various temperatures (according to the tables below) between heated platens of a Wabash Hydraulic press and then immediately transferred to a cold press. After cooling to room temperature by a “cold pressing”, the resulting sample sheets were peeled off from the PTFE sheets. The resulting films were cut into coupons and subsequently laminated with two Cu foil coupons to obtain sandwich structures (with the perfluoropolymer composite films in the middle). Then the laminated samples were heated at 200-250° C. for 30 minutes between heated platens of a Wabash Hydraulic press and immediately transferred to a cold press. After cooling to room temperature by a “cold pressing”, the resulting sample was subjected to the T-peel measurement test method. The laminated samples were pressed and cut into strips with 1.0-1.5 centimeters (cm) width for T-peel measurement.
Perfluoropolymer coating solutions of Table 5 were individually coated on a copper substrate and the resulting coated substrates were dried at room temperature and then subsequently heated at 80-165° C. for 10-30 minutes. The coated copper samples were either laminated against an uncoated copper coupon or a coated copper coupon for heat lamination for bonding at temperatures (as described in Table 5, below). Then the laminated samples were heated at 200° C. for 30 minutes between heated platens of a Wabash Hydraulic press and immediately transferred to a cold press. After cooling to room temperature by a “cold pressing”, the resulting sample was subjected to the T-peel measurement test method. The laminated samples were pressed and cut into strips with 1 cm width for T-peel measurement.
Sample material (10 wt. %, according to Table 6) was coated onto a glass substrate and then dried at 120° C. for 5 minutes. Then the coated glass substrate was subjected to heating for 10 minutes at 150° C., 200° C., or 300° C. individually. The sample was then peeled off of the glass slide and the film was submerged in HFE-7500 and sealed in a glass vial. The glass vial was well sealed with PTFE tape and paraffin film. The vial was then subject to shaking overnight at room temperature to determine if the film dissolved. Solubility results are recorded in Table 6.
PFE was dissolved/dispersed in HFE-7300 by cutting the fluoropolymer materials into small pieces and placing them into separated glass jars and to each of the glass jars was added HFE-7300 solvent. The containers were well sealed with PTFE tape and paraffin film. The solution was subject to vigorous shaking overnight (˜12 hours) to become completely homogenous to obtain PFE in HFE-7300 solutions.
The above prepared solutions were coated on a copper foil substrate with a No. 24 Meyer rod or simply poured the solutions onto the liner to obtain thicker coating samples, and the resulting coatings on copper foil were normally dried at room temperature overnight or cured 120-165° C. for 20-105 minutes. The coated copper substrates were available for adhesion to copper and Dk/Df measurements (Table 5).
The coagulated perfluoropolymer powders or gums were pressed into films/sheets by a heat laminator. Each of the coagulated fluoropolymer powders or gums was placed between two PTFE release sheets and were heat-pressed for 30 minutes (according to Tables 2, 3, and 4 based on the melting points of perfluoroplastic resins) between heated platens of a Wabash Hydraulic press and subsequently quenched with a cold press. After cooling to room temperature by a “cold pressing”, the resulting sample was available to use.
The resulting sheets/films were used for Dk/Df, CTE measurements and for bonding to Cu substrate. Some coagulated polymers may also contain inorganic fillers. They were obtained by coagulating polymers in the presence of inorganic fillers.
Examples 1-19 are also soluble in HFE-7500.
All cited references, patents, and patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/053241 | 4/6/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63184276 | May 2021 | US |
