# Patent

## Title
Limonene, pinene, or other terpenes and their alcohols, aldehydes and ketones, as polymer solvents for conducting polymers in coating formulations and their uses

## Abstract

A low-VOC (volatile organic compound) and/or low-toxicity coating formulation, including at least one non-halogenated organic solvent including any terpene or terpenoid, and at least one conducting polymer, electroactive polymer and/or conjugated polymer. In another embodiment, the present invention includes a low-VOC (volatile organic compound) and/or low-toxicity coating formulation, including about 0.001% wt. to about 99.9% wt. of at least one non-halogenated organic solvent including a terpene or terpenoid, about 0.01% wt. to about 90% wt. of at least one conducting polymer, and about 0.001% wt to about 90% wt. of at least one surfactant.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. §119(e) and is a continuation of U.S. patent application Ser. No. 10/714,296 filed Nov. 14, 2003, now abandoned, and is hereby incorporated by reference.


STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
FIELD OF THE INVENTION
The present invention relates to coating formulations including terpenes or terpenoids and their alcohols as organic solvents with conducting polymers, and more specifically, the use of terpenes to permit polymer incorporation into non-toxic or low-toxicity, non-VOC (Volatile Organic Carbons) or low-VOC formulations for various military, commercial, and recreational applications.
BACKGROUND OF THE INVENTION
Terpenes are natural solvents existing both in the citrus fruits and in many other plants, with extraordinary technical and chemical properties. Terpenes include any hydrocarbon of the formula C10H16 and are derivable chiefly from essential oils, resins, and other vegetable aromatic products. Many terpenes are acyclic, bicyclic, or monocyclic, and differ somewhat in physical properties. They can represent an optimal alternative to halogenated solvents in many civil and industrial applications.
Nearly all the terpenes, contained in the essential oils of many plants, are constituted by a skeleton of carbon atoms made of isoprene units regularly linked according with the head-tail position. Some components are shown in the following formulas. The main component of the essential citrus fruit oil is D-limonene, commonly called dipentene, that is a hydrocarbon insoluble in water; when the essential oils are used to flavor something, it's necessary to bring them in as a very thin suspension in the aqueous product (soft drinks, juices, etc.). Terpenes are environmental compatibility and can reduce evidently the environmental impact in many applications related to the organic solvent use.
U.S. Pat. No. 5,814,376 issued on Sep. 29, 1998 to Michael D. Cabelli teaches a gravure coating process for producing electroconductive polymer films. Coating is for use in sensors detecting analytes and the final product is heated. The above patent is limited to a ribbon-like or flat substrate application. The above uses a conductive polymer and exposing it to a dopant thereby changing its properties in situ. By changing it's properties they teach it can be used as a component in a measuring device. This patent does not teach the use of terpenes with conductive polymers for corrosion inhibition. Ideally, in the present invention, once used or applied, the polymer will not be changed, modified or doped. The polymer will continue to perform (prevent corrosion) if it remains in a constant state. While the mechanism for corrosion protection/inhibition has not been proven for conductive polymers, it is likely to be a passivation of the metal substrate or an ability to allow electron transfer between the coating and substrate to prevent localized charge buildup at a metal surface, which causes corrosion. By preventing a localized charge buildup at a metal surface or between two surfaces that have different oxidation potentials, it's likely that the conductive polymer inhibits the oxidation of metal and therefore the formation of corrosion products.
U.S. Pat. No. 5,932,643 issued on Aug. 3, 1999 to Frank J. Kenny teaches coating formulations and thermal transfer ribbons that form printed images containing conductive polymers. The formulations and ribbons include wax, polymer resins, a sensible material and optionally solvent. The above is teaching the polymer coatings for their thermal transfer properties. They teach utilizing toxic organic solvents, which have been used for conductive polymers long before this patent was issued. However, no terpenes or terpenoids are taught for use in this patent.
If paint formulations use limonene, pinene, or other terpenes (or terpenoids), as a solvent in a waterborne coating application instead of traditional high-VOC (volatile organic compound) solvents, it will provide a low-VOC coating application. There is currently no non-toxic, non-chrome, non-metallic containing coating formulation approved for military application. From the foregoing, it will be appreciated that there is a need in the art for organic terpene based solvent/conducting polymer coating compositions, which is environmentally safe for various types of military and commercial applications. The present invention is directed to overcoming one, or more, of the problem set forth above.
SUMMARY OF THE INVENTION
The present invention relates to low-VOC (volatile organic compound) and/or low-toxicity coating formulations, including at least one non-halogenated organic solvent including any terpene or terpenoid and at least one conducting polymer, electroactive polymer and/or conjugated polymer. In another embodiment, the present invention includes a low-VOC (volatile organic compound) and/or low-toxicity coating formulation, including about 0.001% wt. to about 99.9% wt. of at least one non-halogenated organic solvent including a terpene or terpenoid, about 0.01% wt. to about 90% wt. of at least one conducting or electroactive polymer, and about 0.001% wt to about 90% wt. of at least one surfactant.
The terpene or terpenoid includes at least one of dipentene (d-limonene), α-pinene, β-mircene, p-cimene, citronellolio, geraniale (citrale), nerol, beta-carotene, menthol, geraniol, farnesol, phytol, their homologs, derivative, enantiomers, isomers including constitutional isomers, stereoisomerisms, regioisomers, and geometric isomers, and any combination thereof. The conducting polymers include at least one of poly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene] (BAMPPV) and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV), polyphenylene vinylenes, polythiophenes, polypyrroles, polyanilines, polyacetates, polyacetylenes, polyacrylates, polyazene, polystyrene, poly-N-vinylcarbazole, polyvinylpyridine, polyindole, and any combination thereof. The conducting (including electroactive or conjugated) polymers are in neutral, oxidized or reduced form, in the form of a salt including an emeraldine salt, or in any basic or acidic form.
The present invention is used with a broader range of application methods, particularly, spray coating and dip coating. These methods are the most useful for industry and the military on large substrates and substrates with complex geometries (crevices or holes that are hard to access) including aircraft and vehicle components.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not to be viewed as being restrictive of the present invention, as claimed. These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended claims.


DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
The present invention relates to low-VOC (volatile organic compound) and/or low-toxicity coating formulations, including at least one non-halogenated organic solvent including any terpene or terpenoid and at least one conducting polymer, electroactive polymer and/or conjugated polymer. In another embodiment, the present invention includes a low-VOC (volatile organic compound) and/or low-toxicity coating formulation, including about 0.001% wt. to about 99.9% wt. of at least one non-halogenated organic solvent including a terpene or terpenoid, about 0.01% wt. to about 90% wt. of at least one conducting or electroactive polymer, and about 0.001% wt to about 90% wt. of at least one surfactant.
The following terpenes or terpenoids are constituted by a skeleton of carbon atoms made of isoprene unities regularly linked according with the head-tail position. The terpene or terpenoid includes at least one of dipentene (d-limonene), α-pinene, β-mircene, p-cimene, citronellolio, geraniale (citrale), nerol, beta-carotene, menthol, geraniol, farnesol, phytol, their homologs, derivative, enantiomers, isomers including constitutional isomers, stereoisomerisms, regioisomers, and geometric isomers, and any combination thereof. For example, Aldrich produces limonene in various optically active isomers and in a technical grade called “dipentene.” Terpenes also function as stand-alone solvents or as co solvents. As a solvent or co solvent, a terpene will act as a vehicle for application of polymers (conductive or nonconductive) or conjugated polymers onto substrates. Terpenes function as alternative solvents for polymers, including conductive or electroactive polymers and conjugated polymers, to replace more traditional, more toxic solvents including but not limited to xylenes, tetrahydrofuran (THF), benzene, n-methylpyrrolidinone (NMP), methylene chloride, and other organic solvents.
Conjugated polymers have a framework of alternating single and double carbon-carbon (sometimes carbon-nitrogen) bonds). Conjugated polymers are polyunsaturated compounds in which all backbone atoms are sp- or sp2-hybridized. For the purposes of the present invention, the terms conductive, electroactive, and conjugated will be interchangeably utilized throughout. The conducting polymers include at least one of poly [bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene] (BAMPPV) and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV), polyphenylene vinylenes, polythiophenes, polypyrroles, polyanilines, polyacetates, polyacetylenes, polyacrylates, polyazene, polystyrene, poly-N-vinylcarbazole, polyvinylpyridine, polyindole, and any combination thereof. The conducting (including electroactive or conjugated) polymers are in neutral, oxidized or reduced form, in the form of a salt including an emeraldine salt, or in any basic or acidic form. The terpene or terpenoid solvent and conducting polymer formulations are in the form comprising a solution, mixture, suspension, or emulsion. All terpenes, terpenoids, and polymers would ideally be non/low toxic and low VOC.
In other embodiments the coating formulations further include at least one of surfactant(s), H2O, and other organic components. Triton X100 is a surfactant utilized in embodiments of the present invention; however, any surfactant commercially available will suffice that includes the following characteristics. The definition of a surfactant or surface-active agent (Random House) is “any substance that when dissolved in water or other aqueous solution reduces the surface tension or interfacial tension between it and another fluid.” The idea of a surfactant is to have different functionalities on the same molecule. This will enable two different types of molecules to be somewhat miscible that normally would not be. The Triton X100 has a similar structure (carbon ring) to the polymer and the ether alcohol portion is similar to water (polar) so that the water and polymer may be somehow closely associated to form a suspension or solution rather than separating into two layers like oil and water.
In embodiments of the present invention, terpene and polymer solutions, mixtures, suspensions, or emulsions are added to organic coating systems. Above combinations are used to incorporate a polymer into an organic or inorganic coating or resin, including but not limited to epoxies, polyurethanes, and polyesters. In embodiments of the present invention, organic resin includes, but is not limited to polyamides, phenolics, polypropylenes, and polyethylenes. The present coating formulations can be applied to a substrate including, but not limited to spray coating, dip coating, spin-coating, flow-coating, doctor blade coating, or screen-printing. The substrates include plastic, rubber, metal, metallic and like surfaces. Embodiments of the present invention can be utilized for corrosion protection as replacements for hexavalent chrome.
The present invention will now be explained with references to the following non-limiting experiments.
Experimental Results
A series of terpene polymer solvent samples were prepared and analyzed. In the first experiment, approximately 5.6 mL of dipentene (d-limonene) (Aldrich) was added to beaker “A” with 0.0112 g of poly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene] (BAMPPV). The results had shown that BAMPPV was slightly soluble almost immediately in the dipentene. The terpene/BAMPPV mixture was stirred and warmed on low. The BAMPPV polymer was solubilized in solution after 25 minutes.
In the second experiment, approximately 5.6 mL of α-pinene (Aldrich) was added to beaker “B” with 0.0103 g of BAMPPV. The results shown that the BAMPPV polymer was not immediately soluble in the α-pinene terpene as in the first experiment utilizing dipentene. The dipentene/BAMPPV and α-pinene/BAMPPV solutions were separately allowed to stir overnight. In the first experiment, the BAMPPV was completely dissolved in the dipentene solvent. In the second experiment, the BAMPPV was almost completely dissolved in the α-pinene solvent; however, a small amount of solids were remaining. These experiments have shown that the solubility of the BAMPPV polymer in α-pinene is far greater than in xylenes and THF. Previous solutions trying to dissolve BAMPPV in xylenes and THF had shown a solubility factor not greater than 0.1%. Solutions of BAMPPV in dipentene have been made with 5% wt. polymer (order of magnitude difference) and have been applied to metal substrates for testing. Higher concentrations are possible.
In the second experiment, 1 mL of water was further added to beaker “B” containing the α-pinene/BAMPPV solution and was stirred to form a suspension. Water was added in order to form a waterborne coating. An ideal formulation would contain as much polymer as possible (referred to as high solids loading) and as little solvent as possible. Since water is nontoxic and inexpensive compared to any other solvent (environmentally friendly terpene or not), maximizing the polymer content, water content and minimizing any organic solvent and surfactant is the goal here. One possible exception to the idea of minimizing organics in a coating application would be the formation of azeotropes. If an organic solvent or surfactant (ideally environmentally benign) is a component in a waterborne formulation and it forms an azeotrope with water or any other cosolvent that would be removed from the drying process, it may help decrease drying time. Most solvent-based coatings are desirable from an application standpoint because they are fast drying compared to waterborne formulations, in general. If an azeotrope has a lower boiling point and/or faster drying time than either component individually, drying time can often be reduced. Faster dry times for military and commercial applications, decreases “downtime” or time in which a system may be inoperable. All components in the specified coating system can be balanced (ratios adjusted) to make multiple formulations for different conditions in which they may be used. For example, a coating used in a consistently humid environment may have a different water and/or solvent concentration (or any variation of any constituent) as compared to a coating that will be used in an arid environment for drying/curing time reasons. Another reason to vary constituent concentrations would be user specification of the physical properties of the coating. For example, one user may want a limited amount of conductive polymer whereas another user may want the maximum amount possible for a certain application. Weight of materials may factor into a coating formulation as well. Conductive polymers can function as coatings alone for certain applications or they may be additives within other bulk coating systems, such as epoxies, urethanes, polyesters or any bulk resin system. By limiting the weight of a conductive polymer (or weight percent) within a coating, to a minimum amount to achieve desired coating properties, the overall coating weight can be adjusted. Coating weight is of particular interest for flight applications.
In a third experiment, a 1% solution was made with 0.4338 g of BAMPPV and 42.95 g of dipentene. The solution in the third experiment was used for smaller test vial experiments. Smaller tests were done using different surfactants to evaluate their respective performance in the coating formulation. Ideally, a surfactant that can give the desired results in the smallest quantity possible is the most useful from an environmental and economic point of view, assuming it's low or non-toxic, of course.
In a fourth experiment, a vial of 9.904 g of dipentene was added to 0.1004 g of BAMPPV. The dipentene/BAMPPV solution was further diluted to 0.5% by adding 10.33 g of dipentene. A few milliliters of water were added to form a suspension. After sitting for an hour, a separation was observed. Then 2 drops of Triton-X100 (a surfactant) was added and the mixture was stirred for approximately 1 minute and an excellent suspension resulted. The composition remained in a suspension for a few days. After one week, separation was observed. Upon mixing the solution again for a few minutes, the suspension was again observed. The vial was then allowed to sit without stirring. The suspension was observed to be stable for at least 5 hours. Due to the concentrations of water and weight of Triton-X100 not being precisely measured, this experiment needed to be repeated.
In the fifth and sixth experiments, compositions including BAMPPV in dipentene were added with different surfactants to observe the surfactant performance. The surfactants were obtained from Osi Specialties (Greenwich, Conn.) including A1100 (gamma-aminopropyltriethoxysilane), A 1101 (gamma-aminopropyltriethoxysilane) technical grade, A1170 (bis-(gamma-triethoxysilypropyl)amine), and Y9669 (n-phenyl-gamma-aminopropyltrimethoxysilane). These additional surfactants were compared to the Triton-X100 (polyoxyethylene (10) isooctylcyclohexylether also known as alkylaryl polyether alcohol).
Further experiments were also performed to determine terpene use with conducting polymers. Vial 1: 44.0170 g of dipentene was added to 0.4408 g of polymer for a 1% solution. Vial 2: 16.9421 g of dipentene was added to 0.3369 g of polymer for a 2% solution. Vial 3: 16.9133 g of dipentene was added to 0.5076 g of polymer for a 2.9% solution. Vial 4: 4.9960 g of DI water was added to 4.2717 g of the 1% solution. Then 3 drops of Triton X100 (1 drop=0.0249 g) was added to the vial. After addition of 3 drops Triton X100, slight separation was noted at bottom, clearer layer on bottom (not completely clear). Vial 5: 2.0447 g of DI water was added to 4.3224 g of the 1% solution. Then 1 drop of Triton X (5 drop=0.0249 g) was added to the vial. Vial 6: 1.910 g of DI water was added to 4.2712 g of the 1% solution. Then 3 drops of Triton X (5 drop=−0.0249 g) was added to the vial. Vial 7: 1.9773 g of DI water was added to 4.3381 g of the 1% solution. Then 2 drops of Triton X (5 drop=0.0249 g) was added to the vial.
The results of the above experiments are as follows: 1% polymer/dipentene solution: 1.0005 g of polymer added to 98.9992 g of dipentene. Did not go completely into solution when stirred overnight, so heated and let stir overnight again. Vial A: 1.0245 g of water was added to 5.0468 g of limonene/polymer solution. 0.2693 g of Triton X100 was then added. Vial B: 3.0188 g of water was added to 5.0421 g of limonene/polymer solution. 0.2630 g of Triton X100 was then added. Vial C, 5.0184 g of water was added to 5.0455 g of limonene/solution. 0.2491 g of Triton X100 was then added.
Vial D: 0.2462 g of Triton X100 was added to 5.0477 g of limonene/polymer solution. 1.0349 g of water was added to the limonene and Triton X100. Vial E: 0.2845 g of Triton X was added to 5.0493 g of limonene/polymer solution. 3.0154 g of water was added to the limonene and Triton X100. Vial F: 0.2620 g of Triton X was added to 5.0233 g of limonene/polymer solution. 5.0168 g of water was added to the limonene and Triton X100. When adding water after Triton X, a precipitate formed on the bottom of the vial more often than when water was added before Triton X. But, after stirring for a while, both group ABC and group DEF started to look the same. Vials A and D look good, but some initial separation was noticed in B, C, E, and F.
Additional terpenes and conducting polymers experiments were performed with the following results. Vial G: 1.7914 g of dipentene was added to 0.0200 g of Poly(3-hexylthiophene-2,5-diyl) regiorandom. Vial H, 1.8051 g of pinene was added to 0.0200 g of Poly(3-hexylthiophene-2,5-diyl) regiorandom. Vial I: 1.8015 g of dipentene was added to 0.0207 g of MEH-PPV. Vial J: 1.8053 g of pinene was added to 0.0218 g of MEH-PPV. Vial K: 1.8004 g of dipentene was added to 0.0261 g of Poly(3-hexylthiophene-2,5-diyl) regioregular. Vial L: 1.8024 g of pinene was added to 0.0226 g of Poly(3-hexylthiophene-2,5-diyl) regioregular. H and G are fully soluble, K and L are mostly soluble, and I and J are mostly soluble. 24 hours later, all vials appear in the same condition all the previous day. The solutions from vials G through L were filtered with Whatman 0.2 micron syringe filters to remove any remaining solids. The solutions were then used in waterborne formulations. The solutions were filtered into new vials with designations 38A, 38B, 38C, 38D, 38E, and 38F corresponding to vials G, H, I, J, K and L, respectively. One drop of Triton X100 was added to each vial and the contents stirred. Visual results were as follows: 38A was in solution after about 20 seconds. 38B was in solution after about 30 seconds. 38C and 38D were in solution after about 25 seconds. 38E and 38F were in solution for a few seconds and the separation occurred. 38A, 38B, 38C and 38D stayed in solution after a total of 2 drops of Triton X100 was added. After 2 minutes, mixtures of 38B and 38D began to separate. After 2 min 30 seconds mixtures 38A and 38C began to separate. Optimum ratios and stirring conditions are being established.
Embodiments of the present films are included, but not limited to the following uses: light-emitting devices, photovoltaic cells, capacitors, super capacitors, devices for sensor protection against lasers, devices for optical switching and modulating, corrosion protection, adhesives, electromagnetic shielding (EMI), anti-biofouling, camouflage, chemical sensors. The use of terpenes or terpenoids to act as a solvent or co-solvent will permit the dispersion of a conducting polymer(s) into a solution, suspension, emulsion, or mixture. Embodiments of the present invention including conductive polymers are used to reduce or inhibit corrosion in organic coatings when applied to plastic, rubber, metal substrates, or their interfaces.
Coatings including the present invention terpene/conducting polymer formulations are used as low-VOC (volatile organic compound) and/or low-toxicity coatings for items including but not limited to aircraft, vehicles, ground equipment, structures and architectural components. Low-VOC coatings are desirable since they should exhibit low-VOC emissions into the atmosphere and reduce hazardous materials exposure to those personnel that apply, repair, or remove such coatings. The coatings of the present invention would be amenable but not limited to applications on aircraft or ship hardware in compliance with State and Federal environmental regulations.
It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.

## Claims

1. A method for passivating a metallic surface comprising:
providing a metallic surface;
selecting at least one solvent from the group of terpenes;
selecting at least one polymer from the group of poly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene] polymers;
solubilizing said at least one polymer in said at least one solvent to form a polymeric composition;
contacting the metallic surface with the polymeric composition to form a passivating region.

2. A method for making a passivating layer comprising:
providing a metallic surface;
selecting at least one solvent from the group of terpenes;
selecting at least one polymer from the group of poly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene] polymers;
solubilizing said at least one polymer in said at least one solvent to form a polymeric composition;
contacting the metallic surface with the polymeric composition to form a passivating layer on the metallic surface.

3. The method of claim 1 or claim 2 wherein said at least one solvent is selected from the group of terpenoids.

4. The method of claim 1, claim 2 or claim 3 wherein said group of poly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene] polymers is replaced by the group of poly(3-hexylthiophene-2,5-diyl) regiorandom polymers.

5. The passivating layer formed by the method of claim 2.