Patent Description:
Provided herein are methods for preparing phthalonitrile coating compositions, including embodiments which address the processing challenges described above. The coating compositions is in the form of pastes, or sprays, formulations which may be readily applied to a variety of substrates. Embodiments of these formulations can be stored for extended periods of time (e.g., > <NUM> weeks) and still be cured to form high quality, void free thermosets.

A method of preparing a phthalonitrile coating composition according to claim <NUM> is provided.

Other principal features and advantages of the disclosure will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.

Illustrative embodiments of the disclosure will hereafter be described with reference to the accompanying drawings.

Provided herein are methods for preparing phthalonitrile coating compositions. The coating compositions, including phthalonitrile pastes, and phthalonitrile sprays are also encompassed.

A phthalonitrile moiety refers to a portion of a molecule, compound, the portion having the following structure:
<CHM>.

The term "crosslink" and the like refers to covalent bonds formed between cyano groups on different phthalonitrile moieties induced by heat and generally, a curing agent.

In embodiments, a method of making a phthalonitrile coating composition comprises heating a phthalonitrile precursor composition comprising a bisphthalonitrile compound to a temperature and for a period of time to form a phthalonitrile prepolymer composition comprising a bisphthalonitrile prepolymer. The phthalonitrile prepolymer composition is cooled to ambient temperature and pulverized to form particles. The particles are combined with a liquid medium to form a phthalonitrile solution. If desired, one or more additives may be added to the phthalonitrile solution. The phthalonitrile solution is mixed to form the phthalonitrile coating composition. In embodiments, the mixed phthalonitrile composition is stored for a period of time to form the phthalonitrile coating composition. In embodiments, a portion of the liquid medium is removed from the mixed phthalonitrile composition to form the phthalonitrile coating composition. By "a portion" it is meant less than all so that at least some liquid medium remains in the formed phthalonitrile coating composition. As further described below, these steps may be further leveraged to achieve various types of phthalonitrile pastes, and phthalonitrile sprays.

The phthalonitrile precursor composition comprises a bisphthalonitrile compound. A variety of types of bisphthalonitrile compounds may be used, including combinations of different types of bisphthalonitrile compounds. The bisphthalonitrile compound comprises two terminal phthalonitrile moieties which are connected via one or more linking groups such as an aromatic ether, a thioether, an imide, a sulfone, a heterocyclic ether, an aromatic ketone, a urethane, a urea, an amide, an ester, an oxamide, and combinations thereof. Such bisphthalonitrile compounds are commercially available or may be formed using known synthetic methods. The synthetic methods used to provide such bisphthalonitrile compounds generally result in different numbers of the linking group(s) being incorporated into the bisphthalonitrile compounds between the two terminal phthalonitrile moieties and a corresponding distribution of molecular weights. Thus, in the present disclosure, the phrase "bisphthalonitrile compound" may be referred to as an "oligomer" and the like. Similarly, the phrase encompasses each of the bisphthalonitrile compounds formed by such a synthetic method, each of which may have a different number of the linking group(s) and a different molecular weight. Thus, the bisphthalonitrile precursor composition may comprise each of these bisphthalonitrile compounds. The phrase "bisphthalonitrile compound" also encompasses a small molecule, a molecule which is distinguished from an oligomer by having no more than one linking group between the two terminal phthalonitrile moieties. Illustrative bisphthalonitrile compounds include those described in <CIT>; <CIT>; <CIT>; and International Pat.

In embodiments, the bisphthalonitrile compound comprises at least one aromatic ether linking group and at least one aromatic ketone linking group between the two terminal phthalonitrile moieties. Such bisphthalonitrile compounds may be formed using known synthetic methods, e.g., involving the reaction of a dihydroxyaromatic with a dihaloaromatic such as dihalobenzophenone, followed by endcapping with <NUM>-nitrophthalonitrile. An illustrative such bisphthalonitrile compound is shown in <FIG>, formed using bisphenol A as the dihydroxyaromatic and dichlorobenzophenone as the dihaloaromatic. As is shown, the average value of n is <NUM>. Such a bisphthalonitrile compound may be obtained commercially, e.g., Bis A Oligomeric Phthalonitrile Composition from the Naval Research Laboratory. However, other similar bisphthalonitrile compounds may be used, e.g., those based on other dihydroxyaromatics, including other bisphenols. Illustrative dihydroxyaromatics include bisphenol AF, resorcinol, <NUM>,<NUM>-bis(<NUM>-hydroxyphenyl)propane, <NUM>,<NUM>-bis(<NUM>-hydroxyphenyl)-<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoropropane, and the like.

Although not necessary, the phthalonitrile precursor composition may comprise a curing agent. A variety of types of curing agents may be used, provided the curing agent is capable of inducing crosslinking reactions between phthalonitrile moieties, i.e. reactions between cyano groups on phthalonitrile moieties to form covalent crosslinks. These covalent crosslinks may include polytriazine-type, polyindoline-type, phthalocyanine-type crosslinks, and combinations thereof. Combinations of different types of curing agents may be used. If a curing agent is not included, the crosslinking reactions will still occur, albeit at a slower rate.

Illustrative curing agents include amines, diamines, phenolics, acids, metals, metal salts, and combinations thereof. Regarding diamines, illustrative curing agents include <NUM>,<NUM>'-(<NUM>,<NUM>-phenylenedioxy)dianiline; <NUM>,<NUM>'-(<NUM>,<NUM>-phenylenedioxy)dianiline; bis[<NUM>-(<NUM>-aminophenoxy)phenyl]sulfone; <NUM>,<NUM>'-(<NUM>,<NUM>'- isopropylidenediphenyl- <NUM> , <NUM> '-diyldioxy)dianiline; <NUM>,<NUM>'-(<NUM> ,<NUM> -phenylenediisopropylidene)dianiline; <NUM>,<NUM>'-(<NUM>,<NUM>-phenylenediisopropylidene)dianiline; <NUM>,<NUM>'-(<NUM>,<NUM>'-biphenyl-<NUM>,<NUM>'-diyldioxy)dianiline, <NUM>,<NUM>'- methylenedianiline; <NUM>,<NUM>'-sulphonyldianiline; <NUM>,<NUM>'-methylene-bis(<NUM>-methylaniline); <NUM>,<NUM>'- methylenedianiline; <NUM>,<NUM>'-methylenedianiline; <NUM>,<NUM>'-oxydianiline; <NUM>,<NUM>'-(isopropylidene)dianiline; <NUM>,<NUM>'- (hexafluoroisopropylidene)dianiline; <NUM>,<NUM>'-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline; <NUM>,<NUM>'-diaminobenzophenone; and melamine. Regarding phenolics, hydroxy quinone is an illustrative curing agent. Regarding metals and metal salts, illustrative curing agents include copper acetylacetonate, palladium acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, and iron acetylacetonate. Other illustrative curing agents include those described in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and International Pat.

If a curing agent is included in the phthalonitrile precursor composition, the amount of the curing agent may be in a range of from <NUM> weight% to <NUM> weight%, including from <NUM> weight% to <NUM> weight%, and from <NUM> weight% to <NUM> weight% as compared to the total weight of the phthalonitrile precursor composition. When multiple curing agents are used, these weight percentages refer to the total weight of the multiple curing agents.

The phthalonitrile precursor composition may comprise one or more types of phthalonitrile additives. Phthalonitrile additives are small molecules comprising one or more phthalonitrile moieties (e.g., <NUM> such moieties). The additives are distinguished from the oligomers, prepolymers, and thermoset polymers described herein. Although the bisphthalonitrile compound of the phthalonitrile precursor composition may also be a small molecule, the bisphthalonitrile compound is a different compound, i.e., a different chemical species, from the phthalonitrile additive. Similarly, curing agents and phthalonitrile additives refer to different compounds. A variety of types of phthalonitrile additives may be used, including combinations of different types of additives. Illustrative phthalonitrile additives include those described in <CIT>.

If a phthalonitrile additive is included in the phthalonitrile precursor composition, it may be present at an amount in a range of from <NUM> mol% to <NUM> mol%, including from <NUM> mol% to <NUM> mol%, from <NUM> mol% to <NUM> mol%, and from <NUM> mol% to <NUM> mol%. The term "mol%" refers to the mole percentage of the phthalonitrile additive as compared to the total moles of the phthalonitrile additive and the bisphthalonitrile compound in the phthalonitrile precursor composition. When multiple phthalonitrile additives and/or bisphthalonitrile compounds are used, these mole percentages refer to the total moles of the multiple phthalonitrile additives and the total moles of the multiple bisphthalonitrile compounds.

In embodiments, however, phthalonitrile additives are not used and the phthalonitrile precursor composition (and the phthalonitrile coating composition) is free of any such phthalonitrile additives. This includes the phthalonitrile pastes, and phthalonitrile sprays being free of phthalonitrile additives. Such embodiments exclude the use of phthalonitrile additives comprising ether functional groups or thioether functional groups such as those disclosed in <CIT>.

Otherwise, the balance of the phthalonitrile precursor composition may be made up of the one or more types of bisphthalonitrile compounds. Thus, the bisphthalonitrile compound(s) may be present in the phthalonitrile precursor composition at an amount of at least <NUM> weight%, at least <NUM>% weight%, at least <NUM> weight%, or <NUM> weight% as compared to the total weight of the phthalonitrile precursor composition.

As noted above, the present methods comprise heating the phthalonitrile precursor composition to a temperature and for a period of time. These conditions induce crosslinking reactions between phthalonitrile moieties to form the phthalonitrile prepolymer composition comprising the bisphthalonitrile prepolymer. However, these conditions generally result in partial curing such that only a portion (less than all) of the phthalonitrile moieties are crosslinked. That is, partial curing converts a portion (less than all) of the bisphthalonitrile compound, and if present, a portion (less than all) of the phthalonitrile additive, to the bisphthalonitrile prepolymer comprising the covalent crosslinks described above. Uncrosslinked bisphthalonitrile compound, and if a phthalonitrile additive and/or curing agent were used, uncrosslinked phthalonitrile additive, and/or unreacted curing agent also remain such that the phthalonitrile prepolymer composition also comprises these components.

Conditions to achieve partial curing are different than those used to convert the phthalonitrile coating composition to a thermoset polymer, and involve lower temperatures and/or shorter times. Thus, the number of covalent crosslinks, i.e., the degree of crosslinking, achieved during partial curing is less than in the thermoset polymer. Although the conditions to achieve partial curing will depend upon the type of phthalonitrile precursor composition selected, illustrative conditions include heating at a temperature no more than <NUM> for no more than <NUM> minutes, or no more than <NUM> for no more than <NUM> minutes. Conditions further include a temperature in a range of from <NUM> to <NUM> or <NUM> to <NUM> for from <NUM> minutes to <NUM> minutes or from <NUM> minutes to <NUM> minutes.

The present methods further comprise cooling the phthalonitrile prepolymer composition to ambient temperature. "Ambient temperature" is room temperature, a temperature in a range of from <NUM> to <NUM>. The cooling may comprise quench cooling. Quench cooling refers to cooling over a short period of time, e.g., within <NUM> seconds, <NUM> seconds, or <NUM> seconds. As noted above, the method further comprises pulverizing the phthalonitrile prepolymer composition to form particles, including a powder. This may be accomplished using a mortar and pestle and may include centrifugal mixing, although other pulverizing techniques may be used.

The present methods further comprise combining the particles with a liquid medium to form the phthalonitrile solution. The liquid medium may comprise one or more solvents, e.g., organic solvents. Although a variety of types of solvents may be used, selection is generally based on the ability of the liquid medium to dissolve the bisphthalonitrile prepolymer of the phthalonitrile prepolymer composition. In embodiments, the bisphthalonitrile prepolymer has a solubility in the liquid medium in a range of from <NUM>/mL to <NUM>/mL at ambient temperature and atmospheric pressure. This includes a range of from <NUM>/mL to <NUM>/mL, and from <NUM>/mL to <NUM>/mL. The composition of the liquid medium is also guided by the desired form of the phthalonitrile coating composition, i.e., paste, or spray.

In embodiments, the liquid medium comprises a solvent having a boiling point of greater than <NUM>, greater than <NUM>, or greater than <NUM>. Solvents with relatively high boiling points are well retained under ambient conditions, improving shelf life and stability. In embodiments, the liquid medium comprises two solvents having different boiling points but which are still miscible with one another. The solvent having the lower boiling point facilitates dissolution of the bisphthalonitrile prepolymer, while the solvent having the higher boiling point resists removal under ambient conditions. One of the solvents may having a boiling point of greater than <NUM>, greater than <NUM>, or greater than <NUM> as described above, while the other solvent may have a lower boiling point. If a portion (less than all) of the liquid medium is eventually removed to form the phthalonitrile coating composition, the solvent having the lower boiling point may be removed via evaporation at ambient temperature.

Illustrative solvents include alcohols and ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, n-butyl acetate, <NUM>-phenoxyethanol, n-methylpyrrolidone. These are examples of polar organic solvents. Other illustrative solvents include nonpolar organic solvents such as toluene, xylene, and benzene.

The amount of liquid medium (as well as the relative amounts of different types of solvents, if more than one type is used) used depends on the desired form of the phthalonitrile coating composition. However, in embodiments, the amount of liquid medium in the phthalonitrile solution is at least <NUM> weight% as compared to the total weight of the solution. This includes at least <NUM> weight%, at least <NUM> weight%, at least <NUM> weight%, and in a range of from <NUM> weight% to <NUM> weight% of the liquid medium as compared to the total weight of the phthalonitrile solution. The amount of the phthalonitrile prepolymer composition in the phthalonitrile solution may be no more than <NUM> weight% as compared to the total weight of the solution. This includes no more than <NUM> weight%, no more than <NUM> weight%, no more than <NUM> weight%, no more than <NUM> weight%, and in a range of from <NUM> weight% to <NUM> weight% of the phthalonitrile prepolymer composition as compared to the total weight of the phthalonitrile solution.

If desired, one or more additives may be added to the phthalonitrile solution. For example, fillers may be used. Fillers are generally non-reactive with respect to the components of the phthalonitrile solution and may be used to tune the properties of the phthalonitrile coating composition and the thermoset polymer formed therefrom. Thus, the types of fillers used and their amounts may be selected depending upon the desired use for the phthalonitrile coating composition and the thermoset polymer. Combinations of different types of fillers may be used.

Illustrative fillers include carbon-based fillers such as carbon black (e.g., Super P), graphite, carbon fiber, and the like. Other fillers include metallic fillers such as nickel, silver, copper, gold, platinum, iridium, iron, titanium, zinc, and the like. Metallic fillers also include alloys comprising such metals such as stainless steel, nichrome, and the like. Other fillers include metal oxide fillers such as silica, fumed silica, alumina, iron oxide, and the like. Other fillers include polymeric fillers such as those composed of a polyaryletherketone (e.g., polyetheretherketone (PEEK), polyetherketoneketone (PEKK)), a polyetherimide, and the like.

The morphology of the fillers is not particularly limited. The fillers may be particulate in form and have an aspect ratio of less than <NUM> (encompassing spherical shapes, elliptical shapes, and the like) or have an aspect ratio of greater than <NUM> (encompassing elongated shapes such as wires, rods, tubes, whiskers, fibers, needles, and the like). Similarly, the dimensions of the fillers are not particularly limited. The fillers may have a nanoscale dimension in which one, two, or all three dimensions are <NUM> or less. The fillers may have a microscale dimension in which one, two, or all three dimensions are in a range of from <NUM> to <NUM>.

In embodiments, a filler is added to the phthalonitrile solution at an amount in a range of from <NUM> weight% to <NUM> weight%, including from <NUM> weight% to <NUM> weight%, and from <NUM> weight% to <NUM> weight% as compared to the total weight of the phthalonitrile solution. When multiple fillers are used, these weight percentages refer to the total weight of the multiple fillers.

Other additives which may be included in the phthalonitrile solution include dispersants, flow agents, cure promoters, surfactants, the like, and combinations thereof. Again, a variety of types of these components may be added to tune the properties of the phthalonitrile coating composition and the thermoset polymer formed therefrom. When present, they may be included in amounts described above with respect to the fillers. The phthalonitrile additives described above may also be used as additives in the phthalonitrile solution. However, as noted above, in embodiments, phthalonitrile additives are not used and the phthalonitrile solution (and the phthalonitrile coating composition) is free of any such additives.

In embodiments, if an additive is used, it is not a non-reactive plasticizer such as the acid esters, trimellitates, organophosphates, and polymer non-reactive plasticizers disclosed in <CIT>. In such embodiments, neither the phthalonitrile solution, nor the resulting phthalonitrile coating composition contains such a non-reactive plasticizer.

The present methods further comprise mixing the phthalonitrile solution. The mixing may be carried out using a variety of techniques, e.g., centrifugal mixing, shaking, hand mixing, shear mixing, etc. The mixing is generally carried out at room temperature, i.e., without the application of heat, and in ambient atmosphere. The mixing may be carried out at a speed and for a time, both selected to facilitate dissolution of the bisphthalonitrile prepolymer and homogeneous distribution of any additives, if present. Illustrative speeds include those in a range of from <NUM> rpm to <NUM> rpm, from <NUM> rpm to <NUM> rpm, and from <NUM> rpm to <NUM> rpm. Illustrative times include those in a range of from <NUM> seconds to <NUM> minutes, from <NUM> minute to <NUM> minutes, from <NUM> minute to <NUM> minutes, and from <NUM> minute to <NUM> minutes. The mixing may be carried out in one step or multiple steps. The use of multiple steps involves a first mixing at an initial speed for an initial time, followed by at least a second mixing at another speed for another time. (See Example <NUM>.

Depending upon the desired form of the phthalonitrile coating composition, the present methods may or may not comprise additional steps to form the phthalonitrile coating composition. In embodiments such as for phthalonitrile sprays, the mixed phthalonitrile solution may be used as is and may be sprayed onto a desired substrate to form a phthalonitrile coating thereon using a variety of spraying techniques (e.g., spray gun).

In other embodiments, such as for phthalonitrile pastes, the mixed phthalonitrile solution may be stored for a period of time under conditions that minimize or prevent removal of the liquid medium (e.g., by covering and using at ambient temperature). This step facilitates the dissolution of the bisphthalonitrile prepolymer. The period of time may be at least <NUM> day, at least <NUM> days, at least <NUM> days, or in a range of from <NUM> day to <NUM> days.

Phthalonitrile composite films, according to examples not according to the claimed invention, involve an additional step of applying the mixed phthalonitrile solution onto a fibrous material comprising a plurality of fibers, such as a scrim comprising glass fibers, carbon fibers, alumina fibers, ceramic fibers, or combinations thereof. The fibrous material may be woven or nonwoven. The mixed phthalonitrile solution infiltrates the fibrous material/scrim to fill void spaces between the plurality of fibers. After application of the mixed phthalonitrile solution onto the fibrous material, a portion of the liquid medium (or a component thereof) may be removed, e.g., via evaporation. The evaporation is generally carried out at room temperature, i.e., without the application of heat, and in ambient atmosphere (i.e., air). The result is a phthalonitrile composite film. The phthalonitrile composite film may also be referred to as a "prepreg. " (See Examples, below.

The phthalonitrile coating compositions, including the pastes, and sprays, are also encompassed by the present disclosure. They each comprise (or consist of) one or more types of a bisphthalonitrile prepolymer composition; a liquid medium; and optionally, one or more types of an additive. Any of the bisphthalonitrile prepolymer compositions, liquid media, and additives described herein may be used at the amounts described herein in any combination without limitation. Phthalonitrile composite films further comprise the fibrous material comprising the plurality of fibers into which the mixed phthalonitrile solution is infiltrated. Phthalonitrile pastes may be characterized by a shear viscosity of greater than <NUM> P s (<NUM>,<NUM> cps), greater than <NUM> P s (<NUM>,<NUM> cps), greater than <NUM> P s (<NUM>,<NUM> cps), or in a range of from <NUM> P s <NUM>,<NUM> to <NUM> P·s (<NUM>,<NUM> cps), all as measured at room temperature and <NUM>. Phthalonitrile sprays may be characterized by a shear viscosity of less than <NUM> P s (<NUM> cps), less than <NUM> P s (<NUM> cps), less than <NUM> P s (<NUM> cps), or in a range from <NUM> P s to <NUM> P s (<NUM> to <NUM> cps), all as measured at room temperature and <NUM>. In both cases, these shear viscosities may be measured using a Malvern viscometer with a parallel plate geometry (<NUM> plate, <NUM> gap) and a shear rate range from <NUM> to <NUM>.

The phthalonitrile coating compositions, including the pastes, and spraysmay be used in a variety of environments, including the aerospace industry, the automobile industry, the submarine industry, the electronics industry, the construction industry, and the like. Thus the phrases "aerospace industry," "automobile industry," and "submarine industry" may refer to any device, craft, machine, or components thereof used in the industries such as aircraft, an airplane, a rotocraft, a boat, a submarine, a space ship, a trajectory device, a drone, a satellite, an automobile, a bus, a locomotive, a train car, and the like.

In embodiments, a method of preparing a phthalonitrile spray comprises (a) heating a phthalonitrile precursor composition comprising a bisphthalonitrile compound to a temperature and for a period of time to form a phthalonitrile prepolymer composition comprising a bisphthalonitrile prepolymer; (b) cooling the phthalonitrile prepolymer composition to ambient temperature and pulverizing the phthalonitrile prepolymer composition to form particles; (c) combining the particles with a liquid medium to form a phthalonitrile solution; (d) optionally, adding an additive to the phthalonitrile solution; and (e) mixing the phthalonitrile solution to form a phthalonitrile coating composition, wherein the phthalonitrile coating composition is a phthalonitrile spray having a shear viscosity of less than <NUM> P s (<NUM> cps) as measured at ambient temperature and <NUM>. This includes the shear viscosity being less than <NUM> P·s (<NUM> cps), less than <NUM> P·s (<NUM> cps), or in a range from <NUM> P·s to <NUM> P·s (<NUM> to <NUM> cps), all as measured at room temperature and <NUM>. Any of the phthalonitrile precursor compositions, bisphthalonitrile compounds, liquid media, additives, etc., as described herein may be used, in various amounts and combinations as described herein.

In embodiments, a method of preparing a phthalonitrile spray comprises (a) heating a phthalonitrile precursor composition comprising a bisphthalonitrile compound to a temperature and for a period of time to form a phthalonitrile prepolymer composition comprising a bisphthalonitrile prepolymer; (b) cooling the phthalonitrile prepolymer composition to ambient temperature and pulverizing the phthalonitrile prepolymer composition to form particles; (c) combining the particles with a liquid medium to form a phthalonitrile solution; (d) optionally, adding an additive to the phthalonitrile solution; (e) mixing the phthalonitrile solution; and (f) storing the mixed phthalonitrile solution for a second period of time at ambient temperature to form a phthalonitrile coating composition, wherein the phthalonitrile coating composition is a phthalonitrile paste having a shear viscosity of greater than <NUM> P·s (<NUM>,<NUM> cps) as measured at ambient temperature and <NUM>. This includes the shear viscosity being greater than <NUM> P s (<NUM>,<NUM> cps), greater than <NUM> P s (<NUM>,<NUM> cps), or in a range of from <NUM> P s to <NUM> P·s (<NUM>,<NUM> to <NUM>,<NUM> cps), all as measured at room temperature and <NUM>. Any of the phthalonitrile precursor compositions, bisphthalonitrile compounds, liquid media, additives, etc., as described herein may be used, in various amounts and combinations as described herein.

A method of preparing a phthalonitrile composite film comprises (a) heating a phthalonitrile precursor composition comprising a bisphthalonitrile compound to a temperature and for a period of time to form a phthalonitrile prepolymer composition comprising a bisphthalonitrile prepolymer; (b) cooling the phthalonitrile prepolymer composition to ambient temperature and pulverizing the phthalonitrile prepolymer composition to form particles; (c) combining the particles with a liquid medium to form a phthalonitrile solution; (d) optionally, adding an additive to the phthalonitrile solution; (e) mixing the phthalonitrile solution; (f) applying the mixed phthalonitrile solution to a fibrous material comprising a plurality of fibers to infiltrate the mixed phthalonitrile solution into void spaces between fibers of the plurality of fibers; and (g) removing a portion of the liquid medium to form a phthalonitrile coating composition as a phthalonitrile composite film. Any of the phthalonitrile precursor compositions, bisphthalonitrile compounds, liquid media, additives, fibrous material, etc., as described herein may be used, in various amounts and combinations as described herein.

As shown in <FIG>, any of the disclosed phthalonitrile coating compositions may be applied onto a surface <NUM> of substrate <NUM> to form a coating <NUM> thereon. The phthalonitrile coating compositions are particularly useful for application onto vertical surfaces, overhead surfaces, and substrates having complex geometries and hard to reach areas. The substrate <NUM> may be a component used in any of the industries listed above and composed of any type of material, e.g., metal, glass, and the like. The application technique depends upon the form of the phthalonitrile coating composition. For example, phthalonitrile pastes may be applied by spreading, painting, brushing, wiping, etc., while phthalonitrile sprays are sprayed as described above. Phthalonitrile composite films may be applied by pressing, molding, etc. The resulting coating may have any desired thickness, e.g., in a range of from <NUM> to <NUM>. The thickness also depends upon the form of the phthalonitrile coating composition used. In any of the embodiments, a second substrate may be placed on the coating <NUM>. The coating <NUM> functions to adhere the two substrates together.

In whichever environment and for whichever application they are to be used, the phthalonitrile coating compositions (or coatings formed therefrom) are generally cured to form a thermoset polymer therefrom. Such curing involves heating for a period of time, generally, in an inert environment. The temperatures and/or times are greater than those used to achieve the partial curing described above so as to increase (e.g., maximize) the degree of crosslinking between phthalonitrile moieties. The curing may be carried out according to a curing profile involving holds at certain temperatures for certain periods of times. The curing profile may also involve use of certain heating rates to achieve the different temperatures. Various curing profiles may be used, depending upon the selected phthalonitrile coating composition and the desired properties for the thermoset polymer. An illustrative curing profile is provided in the Example, below. Another illustrative curing profile is <NUM> (<NUM> minutes), <NUM> (<NUM> minutes), <NUM> (<NUM> minutes), <NUM> (<NUM> minutes), <NUM> (<NUM> minutes). The present methods may further comprise curing to convert the phthalonitrile coating composition (or coating formed therefrom) to a thermoset polymer. The thermoset polymer may be characterized by a glass transition temperature Tg, including in a range of from <NUM> to <NUM>, including from <NUM> to <NUM>, and from <NUM> to <NUM>. The Tg may be measured using a differential scanning calorimeter. The thermoset polymer may be characterized by a degradation temperature of greater than <NUM>, greater than <NUM>, or greater than <NUM>. The degradation temperature may be measured using a thermogravimetric analyzer (e.g., TGA Q500).

The coated substrates and thermoset polymers formed using the methods described above are also encompassed by the present disclosure.

Bisphenol A oligomeric phthalonitrile composition (Bis A PEEK PN), Bisphenol AF oligomeric phthalonitrile composition (Bis AF PEEK PN), and Resorcinol n=<NUM> oligomeric phthalonitrile composition (Resorcinol PEEK PN) were purchased from the Naval Research Laboratory and used as received. Each of these compositions contains <NUM>% (by weight) of Bis [<NUM>-(<NUM>-aminophenoxy) phenyl] Sulfone curing agent. <NUM>-Methyl-<NUM>-pentanone (MIBK) and <NUM>-butanone (MEK) were purchased from Sigma Aldrich and dried prior to use. <NUM>-Phenoxyethanol was purchased from Sigma Aldrich and used as received. Ketaspire KT-<NUM> UFP was purchased from Solvay Specialty Polymers and used as received. Aerosil® R <NUM> fumed silica was provided by Evonik Resource Efficiency GmbH and was used as received.

A <NUM>" diameter crystallization dish was lined with aluminum foil. To this dish, <NUM> of the Bis A PEEK PN was poured into the crystallizing dish and spread evenly. The dish was placed in a <NUM> furnace in air and allowed to heat for <NUM> minutes. The crystallizing dish was then removed from the oven and allowed to quench cool at room temperature until it became a frangible solid (usually within <NUM> minute). The solid was then peeled off the aluminum foil and ground up using a mortar and pestle until it became a rough powder (Bis A PEEK prepolymer).

<NUM> of MIBK was added to a mixing cup along with two <NUM>" diameter glass beads followed by <NUM> Ketaspire KT-<NUM> UFP, <NUM> R972 fumed silica, and <NUM> of the B-staged Bis A PEEK prepolymer powder (Example <NUM>). This solution was mixed in a centrifugal mixer at <NUM> rpm for <NUM> minutes. The cup was then sealed using parafilm and allowed to sit for two days to allow for dissolution of the bisphthalonitrile prepolymer while minimizing/preventing loss of MIBK. The resulting solution was a viscous paste that can be buttered onto substrates using a spatula or similar tool.

A <NUM> mil thick glass scrim was taped over a silanized release film on a glass plate. <NUM> MIBK, <NUM> <NUM>-phenoxyethanol, <NUM> Ketaspire KT-<NUM> UFP, <NUM> Aerosil R972, and <NUM> Bis A PEEK prepolymer powder (Example <NUM>) was added to a mixing cup. This solution was mixed in a centrifugal mixer according to the following schedule: <NUM> seconds at <NUM> rpm, <NUM> seconds at <NUM> rpm, <NUM> seconds at <NUM> rpm, <NUM> minute wait, <NUM> seconds at <NUM> rpm, and <NUM> minutes at <NUM> rpm. The resulting solution was then filtered using a <NUM> mesh screen. This filtered solution was poured onto the glass scrim and a wooden stick was used to distribute the solution evenly. This solution was allowed to air dry in a hood. Once the top surface was dry, the sample was gently peeled up from the release film and turned over. The backside of the prepreg was allowed to air dry in the hood until it was tack-free.

<NUM> of Bis A PEEK prepolymer (Example <NUM>), <NUM> Ketaspire KT-<NUM> UFP, <NUM> MEK, <NUM> MIBK, and four <NUM>" diameter glass beads were added to a mixing cup and mixed in a centrifugal mixer at <NUM> rpm for <NUM> minutes. The resulting solution was poured into a spray cup containing a <NUM> mesh screen for filtration. The solution was then sprayed via a high-volume low pressure (HVLP) spray gun onto a metallic substrate. Passes were quick and at least <NUM> seconds was given between coats to allow for solvent flashing.

A <NUM>" diameter crystallization dish was lined with aluminum foil. To this dish, <NUM> of the Bis AF PEEK PN was poured into the crystallizing dish and spread evenly. The dish was placed in a <NUM> furnace in air and allowed to heat for <NUM> minutes. The crystallizing dish was then removed from the oven and allowed to quench cool at room temperature until it became a frangible solid (usually within <NUM> minute). The solid was then peeled off the aluminum foil and ground up using a mortar and pestle until it became a rough powder (Bis AF PEEK prepolymer).

<NUM> Bis AF PEEK prepolymer, <NUM> Ketaspire KT-<NUM> UFP, <NUM> MIBK, and three <NUM>" diameter glass beads were added to a mixing cup. This solution was mixed in a centrifugal mixer at <NUM> rpm for <NUM> minutes. The cup was then sealed using parafilm and allowed to sit for eleven days to allow for dissolution of the bisphthalonitrile prepolymer while minimizing/preventing loss of MIBK. The resulting solution was a viscous paste that can be buttered onto substrates using a spatula or similar tool.

<NUM> of Bis AF PEEK prepolymer, <NUM> MIBK, and three <NUM>" diameter glass beads were added to a mixing cup and mixed in a centrifugal mixer at <NUM> rpm for <NUM> minutes. The resulting solution was poured into a spray cup containing a <NUM> mesh screen for filtration. The solution was then sprayed via a HVLP spray gun onto a metallic substrate. The coated substrate was allowed to air dry in a fume hood overnight.

A <NUM>" diameter crystallization dish was lined with aluminum foil. To this dish, <NUM> of the Resorcinol PEEK PN was poured into the crystallizing dish and spread evenly. The dish was placed in a <NUM> furnace in air and allowed to heat for <NUM> minutes. The crystallizing dish was then removed from the oven and allowed to quench cool at room temperature until it became a frangible solid (usually within <NUM> minute). The solid was then peeled off the aluminum foil and ground up using a mortar and pestle until it became a rough powder (Resorcinol PEEK prepolymer).

<NUM> of MIBK was added to a mixing cup along with two <NUM>" diameter glass beads followed by <NUM> Ketaspire KT-<NUM> UFP, <NUM> R972 fumed silica, and <NUM> of the B-staged Resorcinol PEEK prepolymer powder (Example <NUM>). This solution was mixed in a centrifugal mixer at <NUM> rpm for two minutes followed by <NUM> rpm for two minutes. The cup was then sealed using parafilm and allowed to sit for two days to allow for dissolution of the bisphthalonitrile prepolymer while minimizing/preventing loss of MIBK. The resulting solution was a viscous paste that can be buttered onto substrates using a spatula or similar tool.

<NUM> of Resorcinol PEEK prepolymer, <NUM> MIBK, and three <NUM>" diameter glass beads were added to a mixing cup and mixed in a centrifugal mixer at <NUM> rpm for <NUM> minutes. The resulting solution was poured into a for filtration. The solution was then sprayed via a HVLP spray gun onto a metallic substrate. The coated substrate was allowed to air dry in a fume hood overnight.

Samples were cured under nitrogen in a box furnace using the following cure schedule: <NUM> (<NUM> minutes), <NUM> (<NUM> hours), <NUM> (<NUM> hours), <NUM> (<NUM> hours), <NUM> (<NUM> hours).

Pastes: Paste formulations allowed for room temperature application onto a variety of substrates while maintaining good tack. As they were too viscous to be applied with a brush, they were buttered on a variety of substrates using a spatula or similar tool. However, the high viscosity allowed for application onto vertical substrates without experiencing significant sagging prior to post cure. Moreover, the final viscosity of the pastes is adjustable by changing the total amount of solvent added. Sealed pastes maintained their viscosities in excess of <NUM> days. However, dried pastes were rejuvenated with additional solvent and a quick mix. Post curing of pastes produced void free thermosets.

Prepreg (examples not according to the claimed invention): Prepreg formulations allowed for room temperature application onto a variety of substrates. The prepreg formulations were stored at room temperature in open air for up to <NUM> days without experiencing any cracking or breaking. When stored in a sealed container, however, the mechanical flexibility of the prepreg formulations were maintained in excess of <NUM> days. Prepreg formulations are amenable to cutting into various shapes and molding into complex geometries at room temperature due to their high flexibility. Post curing of prepreg formulations produced void free thermosets.

Spray: Spray formulations allowed for room temperature application onto a variety of substrates. The spraying deposits a thin film layer onto the desired substrate, including vertical substrates without sagging. Thicknesses up to <NUM> mils were readily achieved. Sprayed substrates were maintained at room temperature in excess of seven days between spraying and post curing without issue. Post curing of spray formulations produced a void free thermoset.

The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more.

Claim 1:
A method of preparing a phthalonitrile coating composition, the method comprising:
(a) heating a phthalonitrile precursor composition comprising a bisphthalonitrile compound to a temperature of not more than <NUM> and for a period of time of not more than <NUM> minutes to form a phthalonitrile prepolymer composition comprising a bisphthalonitrile prepolymer;
(b) cooling the phthalonitrile prepolymer composition to ambient temperature and pulverizing the phthalonitrile prepolymer composition to form particles, wherein ambient temperature is a temperature in a range of from <NUM> to <NUM>;
(c) combining the particles with a liquid medium to form a phthalonitrile solution;
(d) optionally, adding an additive to the phthalonitrile solution; and
(e) mixing the phthalonitrile solution to form a phthalonitrile coating composition, wherein the phthalonitrile coating composition is in the form of a spray or paste, the spray having a shear viscosity of less than <NUM> P s (<NUM> cps) as measured at ambient temperature and <NUM> and the paste having a shear viscosity of greater than <NUM> P·s (<NUM>,<NUM> cps) as measured at ambient temperature and <NUM>, the shear viscosity being measured using a Malvern viscometer with a parallel plate geometry (<NUM> plate, <NUM> gap) and a shear rate range from <NUM> to <NUM>.