Composition for depolymerizing resins and methods of accomplishing the same

Abstract

Disclosed herein is a fluid composition for depolymerizing a polymer comprising 5 to 90 volume percent of carbon dioxide in supercritical fluid form; 5 to 90 volume percent of superheated water; and 5 to 90 volume percent of an alcohol; where the alcohol is in either its superheated state or supercritical fluid; where all volume percents are based on a total volume of the fluid composition; where the fluid composition is at a temperature greater than 150°C, a pressure greater than 500 psi for a time period greater than 30 minutes.

Description

COMPOSITION FOR DEPOLYMERIZING RESINS AND METHODS OFACCOMPLISHING THE SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application 63 / 541,045 filed on September 28, 2023, the entire contents of which is incorporated herein in its entirety.BACKGROUND

[0002] This disclosure relates to a composition for depolymerizing resins and methods of accomplishing the same. In another embodiment, this disclosure relates to a composition for separating reinforcement fillers, or any other inorganic material from resins in which they are embedded.

[0003] Polymeric resins are used to manufacture a wide variety of commercial products. For example, they are used in food packaging, exterior body panels of automobiles and computers, marine watercraft and boat hulls, fiberglass line pipe and down hole tubulars, exterior skins for radar evading aircraft, textiles, helmets, automobile tires, composites that are used in sports equipment and windmill airfoils, and the like. When these commercial products are discarded, they are transported to a landfill, where they take a large amount of time to depolymerize. Polymeric resins are a large contributor to landfills, where they remain for long periods of time. In addition, commercial products that include polymeric resins often contaminate bodies of water such as oceans and lakes, where it difficult to collect and recycle them.

[0004] The recycling of polymeric resins and their composites first requires the various items found in a landfill to be segregated according to the type of resin used and then subjected to recycle and or decomposition. Both of these processes are labor intensive and expensive.

[0005] One manner of decomposing discarded polymeric resins is via thermal degradation. This involves heating the polymeric resin above its thermal decomposition temperature in an oxygen containing atmosphere to form carbon dioxide and a variety of other carbon containing byproducts. The carbon dioxide obtained from such a process is often released to the atmosphere, which is undesirable. Alternatively, it may be captured and sequestered, which add to the cost of such a recycling program. There are not very manyavailable commercial products that can use this carbon dioxide to make the recycling of resins a successful commercial venture.

[0006] One particularly large class of resins, and their composites, are thermoset based where their crosslinking prevents them from melting. Thus, their only option for recycling would involve cutting, shredding, or grinding the material and incorporate it as a filler. Another option is to decompose and pyrolyze the resin to retrieve the reinforcement, other inorganics or metallics for recycle, but this process is energy intensive and often detrimentally affects quality of the remining reinforcement, inorganic, or metallic materials.

[0007] It is therefore desirable to develop a solution for recycling polymeric resins including thermoset resins that depolymerizes these resins to produce liquified product for reuse in new materials and facilitates their separation from any other reinforcement, inorganics, metallics, or fillers that can also be reused in other materials. This, in turn, reduces environmental pollution, can be broadly applied to a variety of different resins at one time, and that facilitates the reuse of the recycled products.SUMMARY

[0008] Disclosed herein is a fluid composition for depolymerizing a polymer comprising 5 to 90 volume percent of carbon dioxide in supercritical fluid form; 5 to 90 volume percent of superheated water; and 5 to 90 volume percent of an alcohol; where the alcohol is in either its superheated state or supercritical fluid; where all volume percents are based on a total volume of the fluid composition; where the fluid composition is at a temperature greater than 150°C, a pressure greater than 500 psi for a time period greater than 30 minutes.

[0009] Disclosed herein too is a method of separating a filler from a polymeric composite comprising contacting the polymeric composite with a fluid composition at a temperature greater than 300°C, a pressure greater than 500 psi for a time period greater than 30 minutes; wherein the fluid composition comprises superheated water, superheated or supercritical alcohol and a supercritical gas; depressurizing the fluid composition at a rate of greater than 100 psi per second; fragmenting the polymeric composite into polymeric resin particles; liquifying the polymeric resin particles; and delaminating the fdler from the polymeric resin particles.

[0010] Disclosed herein too is a composition comprising aromatic and aliphatic species derived from the decomposition of a polymeric composite; where the aromatic species have the structures (1) and (2):where for structure (1), each Rhis independently a C1-20 hydrocarbyl group such as a C1-20 alkyl, a substituted C1-20 alkyl, a Ce-io aryl, or substituted Ce-io aryl, and n is 0 to 5; where for structure (2), Raand Rbare each independently a C1-20 alkoxy or C1-20 alkyl, and p and q are each independently integers of 0 to 4, such that when p or q is less than 4, the valence of each carbon of the ring is fdled by hydrogen; where Xais a bridging group connecting two hydroxy-substituted aromatic groups, where the bridging group and the hydroxy substituent of each Ci> arylene group are disposed ortho, meta, or para to each other on the Ci> arylene group; where Xais a single bond, -O-, -S-, -S(O)-, -S(O)2-, -C(O)-, or a Ci- 18 organic group, which is cyclic or acyclic, aromatic or non-aromatic, and can further comprise halogens, oxygen, nitrogen, sulfur, silicon, or phosphorous heteroatoms; and where the aliphatic species has the structure (3)(3); where in structure (3), Ri, R2, and R3 can be the same or different and can independently be a hydrogen; a saturated or unsaturated hydrocarbyl, having between 1 and 20 carbon atoms, where the hydrocarbyl unit can be linear, branched or cyclic and may be substituted or unsubstituted.BRIEF DESCRIPTION OF THE FIGURES

[0011] FIG. 1 depicts the reaction between bisphenol A diglycidyl ether and a polyetheramine (Jeffamine D230);

[0012] FIG. 2 is a schematic depiction of potential species that are generated upon depolymerization and solubilization of an amine-cured crosslinked epoxy;

[0013] FIG. 3 A is a depiction of the nomenclature used to define the different experimental samples; it also shows the different fluid compositions that are used to liquify polymers;

[0014] FIG. 3B-1 and 3B-2 are depictions of two different NMR spectra that show different aromatic and aliphatic species obtained from the decomposition of an epoxy polymer used in a composite;

[0015] FIG. 4 includes Table 5 that shows the molar ratios of aromatic to aliphatic species using NMR;

[0016] FIG. 5 is another depiction of the nomenclature used to define the different experimental samples; it also shows the different fluid compositions that are used to liquify polymers; superheated ethylene glycol (EG) or superheated glycerol may be used in addition to supercritical carbon dioxide and superheated water to facilitate liquification of an epoxy polymer in a composite; and

[0017] FIG. 6 is bar graph that shows the percentage of soluble species obtained when superheated ethylene glycol (EG) or superheated glycerol are respectively used in addition to supercritical carbon dioxide and superheated water to facilitate liquification of an epoxy polymer in a composite.DETAILED DESCRIPTIONDefinitions

[0018] The polymeric resins defined herein are described as being either in pure form or in composite form. Polymeric resins in their pure form generally contain the polymer in amounts of greater than 93 weight percent (wt%), preferably greater than 96 wt%, based on total weight of a commercial product. In addition, the polymeric resins described herein can either be thermoplastic where they may be able to be remelted and formed into other shapes, or thermoset form where melting is not possible. They may contain small amounts of additives such as antioxidants, antiozonants, mold release agents, thermal stabilizers, dyes and colorants, impact modifiers, gelling agents, or the like, or a combination thereof. The additives are uniformly dispersed throughout the volume of the polymer (i.e., the polymer in its pure form may be considered to be homogeneous) and the properties are isotropic. Examples of a polymeric resin in its pure form include Ziploc® bags, Saran wrap, soft drink containers, milk containers, automotive outer body panels, plastic furniture, computer housing(s), or the like.

[0019] The polymeric resins in composite form generally contain fillers in amounts of 7 to 90 wt%, based on a total weight of the polymeric composite. The fillers may be in particulate form or in fibrous form. Fillers in particulate form include glass beads, graphite particles, graphite oxide particles, carbon black, fumed silica or titania, or the like. Fillers in their fibrous form can include polymeric fibers, carbon fibers, or inorganic fibers. The inorganic fibers may include glass fibers, ceramic fibers, carbon nanotubes, or the like. Examples of polymeric resins in composite form include wind turbine airfoils, tennis rackets, automotive frames, or the like. The fibers may be chopped fibers or continuous fibers. Polymeric resins in their composite form may generally be heterogeneous and their properties may or may not be isotropic.

[0020] Another class of polymers includes polymer alloys and blends where two or more chemically distinct polymers are blended to create miscible blends or immiscible blends to produce polymeric materials with distinct properties.

[0021] It is to be noted, that there may be some overlap in the definitions of pure polymers and polymers contained in composites. There may be some overlap between the amounts of polymers contained in the pure polymer form and the polymers present in composite form.

[0022] Disclosed herein is a fluid composition for depolymerizing polymeric resins into a liquid or solid form (i.e., the lower molecular weight species that may undergo polymerization to produce a new polymeric resin) without subjecting the polymeric resin to thermal degradation, to mechanical abrasion, or a combination thereof. The fluid composition comprises a gas, that at sufficient pressure and temperature, becomes a supercritical fluid together with superheated water. In another embodiment, the fluid composition can comprise a gas, that at sufficient pressure and temperature, becomes a supercritical fluid, and is combined with an organic solvent that can also be in a liquid state or supercritical fluid state and combined with superheated water.

[0023] The gas (used in the supercritical fluid state), the superheated water either alone or in combination with the organic solvent (used in the superheated and / or supercritical fluid state) have a different chemical composition from each other. The gas referred to herein is a gas at room temperature. The organic solvent is typically a liquid at room temperature. The terms “supercritical gas” and “supercritical organic solvent” are both used to describe fluids that are in their respective supercritical states but are different from each other in terms of their respective chemical compositions.

[0024] In an embodiment, the fluid composition may also be used to separate composites into their constituent components. For example, a composite that comprises fillers and a polymeric matrix may be separated into a portion that is rich in fillers (e.g., particulate fillers, fibrous fillers, and the like) and a portion that is polymer-rich (where the polymer is derived from the matrix). The portion that is polymer-rich may be liquified and undergoes depolymerization to form an oligomer-rich stream. The term oligomer is inclusive of monomers, dimers, trimers, tetramers, and the like, having a number average molecular weight of 200 to 5000 grams per mole. In the case of fibrous filler obtained from a composite, the recovered fibers have a substantially similar aspect ratio as the original fibers used in the composite.

[0025] Disclosed herein too is a method of treating a polymeric resin (either in its pure form or as part of a composite) with the fluid composition to depolymerize the polymeric resin into a plurality of lower molecular weight species (oligomers) that may be reused to form a polymeric resin. When a composite is treated with the fluid composition, the polymeric resin (either in polymeric form or in the form of a lower molecular weight species) is also separated from the fillers. The method comprises permitting the fluid composition to impregnate the polymeric resin (either in its pure form or as part of a composite) under pressure, rapidly depressurizing the solvated polymeric resin causing it to undergo fragmentation and liquification in the fluid composition. During the process of fragmentation and / or liquification, bond cleavage results in the depolymerization of the polymer matrix to produce the oligomer-rich solution from which various low molecular weight species can be isolated and recycled for further use.

[0026] In an embodiment, none of the ingredients of the fluid composition undergo a reaction with the oligomers obtained during fragmentation and / or liquification. In another embodiment, one or more ingredients of the fluid composition may undergo a reaction with the oligomers obtained during fragmentation and / or liquification.

[0027] As noted above, the fluid composition comprises superheated water (also referred to herein as a first superheated fluid), a superheated organic solvent (also referred to herein as a second superheated fluid) or supercritical organic solvent (also referred to herein as a first supercritical fluid) and a supercritical gas (a gas in its supercritical state) (also referred to herein as a second supercritical fluid).

[0028] A superheated fluid is a liquid that is heated to a temperature higher than its boiling point measured at atmospheric pressure. A supercritical fluid (SCF) is a material thatcan be either liquid or gas, used in a state above the critical temperature and critical pressure where gases and liquids can coexist. The supercritical fluid has no surface tension as there is no liquid / gas phase boundary. The “gas” that is used as the second supercritical fluid (in the fluid composition used to treat the polymeric resin) is typically one that is in gaseous form at room temperature and pressure. Examples of such gases include oxygen, nitrogen, carbon dioxide, gaseous hydrocarbons, nitrous oxide, nitric oxide, nitrogen dioxide, ammonia, sulfur dioxide, ozone, halogens, dichlorodifluoromethane, or the like, or a combination thereof. Examples of gaseous hydrocarbons are methane, ethane, propane, butane, ethylene, propylene, butylene, or the like, or a combination thereof. Examples of halogens are fluorine, bromine, chlorine, or a combination thereof. In a preferred embodiment, the supercritical gas comprises carbon dioxide.

[0029] The superheated water is preferably distilled water having a purity of 99 mole percent (mole%) or greater.

[0030] The organic solvent that may be used in its superheated or supercritical state in the fluid composition includes polar aprotic solvents, polar protic solvents, non-polar solvents, or combinations thereof. The solvents are typically liquids at room temperature and atmospheric pressure. The solvent has a Hildebrand solubility parameter between 15 and 40 (MPa)1 / 2, preferably 18 to 30 (MPa)1 / 2and more preferably 22 to 28 (MPa)1 / 2. The superheated or supercritical solvent is typically a liquid at room temperature and room pressure. The Hildebrand solubility parameter is defined as the square root of the cohesive energy density given by the following equation:5 = (E / V)1 / 2, where E is the energy of vaporization, V = Volume and 5 is the Hildebrand solubility parameter. This value is generally reported in MPa1 / 2. Some examples of solvents that may be used in superheated form or in supercritical form fluid composition are listed in the non-limiting Table 1 below. Combinations of solvents from Table 1 may be used. Combinations of water with solvents from Table 1 may also be used in the fluid composition.Table 1Water has a Hildebrand solubility parameter of 48 (MPa)1 / 2.

[0031] Examples of liquid polar aprotic solvents such as, propylene carbonate, ethylene carbonate, butyrolactone, acetonitrile, benzonitrile, nitromethane, nitrobenzene, sulfolane, dimethylformamide, N-methylpyrrolidone, or the like, or a combination thereof. Polar protic solvents include alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, or the like, or combinations thereof), diols (e.g., ethylene glycol, 1,4-butanediol, propylene- 1,3 -diol, beta propylene glycol, or the like, or a combination thereof), triols (e.g., glycerol), acetic acid, formic acid, or a combination thereof. Non-polar solvents include benzene, toluene, methylene chloride, carbon tetrachloride, hexane, diethyl ether, tetrahydrofuran, or the like, or a combination thereof. Co- solvents comprising a polar solvent with a non-polar solvent may also be utilized to modify the solvating power (the ability to penetrate and solubilize the polymeric composition) of the fluid composition.

[0032] It is generally desirable to use polar solvents to treat polar polymers and nonpolar solvents to treat non-polar polymers, though combinations of these fluids may be used to treat either polar or non-polar polymers. Conversely, a polar fluid may be used to treat a non-polar polymer that contains a polar dispersed polymeric phase or alternatively, a nonpolar fluid may be used to treat a polar polymer that has dispersed in it a non-polar dispersed polymeric phase.

[0033] Exemplary organic solvents for use in the fluid composition include alcohols. An exemplary alcohol is ethanol. It is to be noted that the gas or the organic solvent used in the fluid composition may be varied in type or quantity in order to change the solvating power of the fluid composition.

[0034] In an embodiment, the fluid composition used to fragment, liquify and depolymerize the polymeric resins may comprise two or more superheated fluids and one or more supercritical fluids. In another embodiment, the fluid composition used to fragment, liquify and depolymerize the polymeric resins may comprise two or more supercritical fluids and one or more superheated fluids.

[0035] In an embodiment, each ingredient (the gas, water and the organic solvent) may be present in the fluid composition in an amount of 5 to 90 volume percent, preferably 20 to 70 volume percent and preferably 25 to 40 volume percent, based on a total volume of the fluid composition. It is to be noted that while the volume of the water and the organic solvent are measured at room temperature, the volume of the gas is determined under supercritical conditions (i.e., when it is in both a liquid and gaseous state) or alternatively, when it is in liquid form.

[0036] In a preferred embodiment, when the polymeric resin (present in pure form or in composite form) is a polar polymer (e.g., a poly epoxide, a polyamide, a polycarbonate, or the like) the fluid composition generally comprises carbon dioxide in supercritical fluid form in an amount of 25 to 40 volume percent, preferably 28 to 35 volume percent; superheated water in an amount of 25 to 40 volume percent, preferably 27 to 35 volume percent; and an alcohol in either its superheated state or supercritical fluid state in an amount of 25 to 40 volume percent, preferably 27 to 35 volume percent, based on a total volume of the fluid composition.

[0037] In an embodiment, treatment of polymeric resin is conducted with the superheated water and the superheated or supercritical alcohol being present in a volume ratio of 45:55 to 55:45 (in the reactor where the impregnation of the polymeric resin takes place). The remaining portion of the fluid composition comprises the supercritical carbon dioxide.

[0038] In an embodiment, the fluid composition may contain a variety of different additives. These additives include additives that facilitate impregnation of the polymeric resin by the components present in the fluid composition such as surfactants and salts. Other additives can include catalysts that facilitate depolymerization of the polymeric resin.

[0039] The addition of salts may be advantageous. The salts may be inorganic salts or salts that include organic and inorganic ions. Common salt-forming cations include ammonium (NH4+), calcium (Ca2+), iron (Fe2+and Fe3+), magnesium (Mg2+), potassium (K+), pyridinium (CsH5NH+), quaternary ammonium (NR4+), and sodium (Na+). The anions may be inorganic or organic. Common salt- forming anions (parent acids in parentheses where available) include carbonates (CO32‘) (carbonic acid), chlorides (Cl-) (hydrochloric acid), cyanides (CN-) (hydrocyanic acid), fluorides (F-) (hydrofluoric acid), nitrates (NO3 ") (nitric acid), nitrites (NO2 ") (nitrous acid), phosphates (PO4a”) (phosphoric acid), sulfates (SO42”) (sulfuric acid), all anions of carboxylic acid (including formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid and andarachidic acid) such as, for example, acetates (CFFCOO-) (acetic acid), citrates (HOC(COO-)(CH2COO“)2) (citric acid), oxalates, and stearates. Combinations of salts may be used.

[0040] In an embodiment, the catalyst is formed from a metal selected from the group consisting of zirconium, titanium, hafnium, vanadium, niobium, tantalum, scandium, yttrium, iron, cobalt, nickel, chromium, molybdenum, manganese, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. The ligands for the selected metal catalysts can comprise, halides, alkoxides, acetates or other carboxylates, Inflates, tosylates, or a combination thereof. Alternatively, the metal catalysts may be multi-metallic clusters have oxo ligands and combinations of halides, alkoxides, acetates or other carboxylates, triflates, tosylates, or a combination thereof.

[0041] Polymeric resins (in pure form or in composite form) that can be treated with the fluid composition include thermoplastic polymers, thermosetting polymers (crosslinked polymers), blends of thermoplastic polymers, blends of thermosetting polymers, and blends of thermoplastic polymers with thermosetting polymers. The polymeric resin can be a homopolymer, a copolymer, a block copolymer, an alternating copolymer, a random copolymer, a random blocky copolymer, a graft copolymer, a star block copolymer, an ionomer, a dendrimer, or a combination comprising at least one of the aforementioned polymers. The polymer may be a biodegradable polymer, an electrolyte, or a combination thereof.

[0042] Examples of thermoplastic polymers that can be used in the polymeric material include polyacetals, polyacrylics, polycarbonates, polyalkyds, polystyrenes, polyolefins, polyesters, polyamides, polyaramides, polyamideimides, polyarylates, polyurethanes, epoxy polymers, phenolics, silicones, polyarylsulfones, polyethersulfones, polyphenylene sulfides, polysulfones, polyimides, polyetherimides, polytetrafluoroethylenes, poly etherketones, polyether ether ketones, polyether ketone ketones, polybenzoxazoles, polyoxadiazoles, polybenzothiazinophenothiazines, polybenzothiazoles, polypyrazinoquinoxalines, polypyromellitimides, polyguinoxalines, polybenzimidazoles, polyoxindoles, polyoxoisoindolines, polydioxoisoindolines, polytriazines, polypyridazines, polypiperazines, polypyridines, polypiperidines, polytriazoles, polypyrazoles, polycarboranes, polyoxabicyclononanes, poly dibenzofurans, polyphthalides, poly anhydrides, poly(vinyl ethers), poly(vinyl thioethers), poly(vinyl alcohols), poly(vinyl ketones), poly(vinyl halides), poly(vinyl nitriles), poly(vinyl esters), polysulfonates, polysulfides, polythioesters, polysulfones, polysulfonamides, polyureas, polyphosphazenes, polysilazanes, polypropylenes, polyethylenes, poly(ethylene terephthalates), poly(vinylidene fluorides), polysiloxanes, or the like, or a combination thereof.

[0043] Examples of thermosetting polymers include epoxy polymers, unsaturated polyester polymers, polyimide polymers, bismaleimide polymers, bismaleimide triazine polymers, cyanate ester polymers, vinyl polymers, benzoxazine polymers, benzocyclobutene polymers, acrylics, alkyds, phenol-formaldehyde polymers, novolacs, resoles, melamineformaldehyde polymers, urea-formaldehyde polymers, hydroxymethylfurans, isocyanates, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, unsaturated polyesterimides, or the like, or a combination thereof.

[0044] Examples of blends of thermoplastic polymers include acrylonitrile-butadiene- styrene / polyamide blends, polycarbonate / acrylonitrile-butadiene-styrene blends, acrylonitrile butadiene styrene / poly(vinyl chloride) blends, polyphenylene ether / poly styrene blends, polyphenylene ether / polyamide blends, polysulfone / acrylonitrile-butadiene-styrene blends, polycarbonate / thermoplastic urethane blends, polycarbonate / polyethylene terephthalate blends, polycarbonate / polybutylene terephthalate blends, thermoplastic elastomer alloys, polyamide elastomers, polyester elastomers, polyethylene terephthalate / polybutylene terephthalate blends, polyacetal elastomers, styrene-maleic anhydride / acrylonitrile-butadiene- styrene, poly ether ether ketone / poly ethersulfone blends, poly ether etherketone / poly etherimide poly ethylene / poly amide blends, poly ethylene / poly acetal blends, or the like.

[0045] Examples of biodegradable polymers include polylactic acid (PLA) polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly-caprolactone (PCL), copolymers of poly lactic -glycolic acid and poly-caprolactone (PCL-PLGA copolymer), polyhydroxy alkanoates, polyhydroxy-butyrate-valerate (PHBV), polyorthoester (POE), polyethylene oxide-butylene terephthalate (PEO-PBTP), poly-D,L-lactic acid-p-dioxanonc- poly ethylene glycol block copolymer (PLA-DX-PEG), or the like, or a combination thereof.

[0046] Examples of polyelectrolytes are poly(styrene sulfonic acid), polyacrylic acid, pectin, carrageenan, alginates, carboxymethylcellulose, polyvinylpyrrolidone, or the like, or a combination thereof.

[0047] In an embodiment, the polymeric resin that is treated with the fluid composition is preferably a thermosetting polymer. An exemplary polymeric resin that is treated with the fluid composition to delaminate it from the filler is a polyepoxide.

[0048] Polymeric composites contain particulate or fibrous fillers. The fibrous fillers may be glass fibers, carbon fibers, ceramic fibers, metal fibers, or a combination thereof. The fibers may be continuous or chopped. The fibrous fillers may be present in the composite in the form of woven and non-woven plies. The fibrous fillers may be present in amounts greater than 40 wt%, preferably greater than 50 wt%, based on a total weight of the polymeric composite.

[0049] In an embodiment, in one method of using the fluid composition, a polymeric resin (in pure or in composite form) is first treated with one or more superheated fluid(s) (a first superheated fluid and / or a second superheated fluid) and / or a supercritical fluid (a first supercritical fluid) in a reactor that is capable being effectively pressurized and heated to a desired temperature. The superheated fluid(s) or a combination of a superheated fluid with a supercritical fluid is charged to the reactor in their respective states.

[0050] In an embodiment, the first superheated fluid is superheated water, while the second superheated fluid is a superheated solvent. In an embodiment, the superheated solvent is superheated ethanol. The first supercritical fluid is supercritical ethanol. Treating the polymeric resin with supercritical ethanol during the treatment with the superheated water and / or superheated ethanol is optional.

[0051] In short, a superheated fluid is charged to the reactor in its superheated state and a supercritical fluid is charged to the device in its supercritical state. The polymer is fedto the device simultaneously with the superheated fluid(s) or the combination of the superheated fluid with the supercritical fluid and is mixed in the presence of the fluid. The polymer may be fed to the device in the form of a melt (e.g., at a temperature above its glass transition temperature or above its melting point), a solid (e.g., a powder, pellets, a briquette, a composite), a suspension, or in a solution. When fed to the device in the form of a suspension or in the form of a solution, the fluid for forming the suspension or the solution can be chemically the same or different from the supercritical fluid or the superheated fluid.

[0052] The superheated fluid(s) or the combination of the superheated fluid(s) with the supercritical fluid penetrates the polymeric resin (in pure or composite form) and swells it. The swollen polymer may then be treated with one or more supercritical fluids (a second supercritical fluid). In an embodiment, the second supercritical fluid is supercritical carbon dioxide.

[0053] It is to be noted that the polymeric resin may be treated sequentially with the first superheated fluid, the second superheated fluid and the first or second supercritical fluids. In other words, each fluid may be introduced into the reactor sequentially until all fluids are present in the reactor simultaneously to impregnate the polymeric resin. In another embodiment, the polymeric resin may be treated with all of the fluids (all of the superheated and supercritical fluids) simultaneously from the start of the impregnation process.

[0054] The swollen polymer is treated for a period of 30 minutes to 5 days, preferably 60 minutes to 4 days, and more preferably 2 hours to 3 days. The extended period of time, for which the polymeric resin is exposed to the superheated and / or supercritical fluids permits the uptake of a large volume of the superheated and / or supercritical fluid. This uptake of a large volume of fluid leads to rupture (termed fragmentation) when the pressure is removed. This fragmentation is observed in both thermoplastic and thermosetting resins but is more pronounced in the thermosetting resins because the pronounced expansion that occurs within the polymer upon depressurization. When the deformation of the polymer occurs more rapidly than the rate of chain relaxation, fragmentation occurs.

[0055] In an embodiment, the temperature of the reactor during the uptake of superheated fluids and / or supercritical fluids (by the polymeric resin) is greater than 150°C, preferably greater than 200°C, preferably greater than 225°C, preferably greater than 240°C, preferably greater than 270°C, and preferably greater than 300°C. The temperature of the reactor is generally less than the critical point of water, which is around 370°C. The pressure of the reactor during the uptake of superheated fluids and / or supercritical fluids is greaterthan 500 pounds per square inch (psi), preferably greater than 1000 psi, preferably greater than 1500 psi, preferably greater than 2000 psi, preferably greater than 4500 psi, preferably greater than 5000 psi, preferably greater than 6000 psi, preferably greater than 7000 psi, and more preferably greater than 8000 psi, preferably greater than 10,000 psi. The pressure in the reactor may be as high as 25,000 psi. This exposure of the polymeric resin to the fluid composition at an elevated pressure and temperature for an extended period to time of 30 minutes to 5 days is referred to as a pressure soak time or period.

[0056] The polymeric resin is subjected to only one cycle of increased pressure and temperature in the reactor during which the polymer is impregnated with the superheated and / or supercritical fluids. In other words, after depressurization, the polymer is not treated to another cycle of increased pressure and temperature in the reactor. The effects of depressurization are detailed below. In an embodiment, the volume of the polymeric resin during pressurization increases by over 100%, preferably over 200%, and more preferably over 300%, based on an initial volume of the polymeric resin.

[0057] The swollen polymer is subjected to rapid depressurization to produce fragmentation of the polymeric resin. During the rapid depressurization, polymeric resins present in composites are delaminated and separated from fillers present in the polymeric composite. The fragmentation of the polymeric resin produces polymeric particles that have a higher surface area than that of the original polymeric resin (prior to being treated with the superheated and / or supercritical fluids). This increase in surface area facilitates dissolution of the fragmented particles in the superheated and / or supercritical fluids to produce liquification of the polymer. During the liquification, bond cleavage takes place in the liquified polymer producing depolymerization of the polymer. In an embodiment, the hydrolysis of the fragmented polymer results in the depolymerization of the polymer to produce an oligomerrich phase in the fluid composition. The term “oligomer” is inclusive of monomers, dimers, trimers, tetramers, pentamers, and so on having a number average molecular weight of 200 to 5000 grams per mole.

[0058] The depressurization rate depends on the overall minimum size dimension of the material being depolymerized and liquified. In order for fragmentation to occur, the rate of depressurization should exceed the rate of diffusion of the fluid composition being used for depolymerization. Under these conditions, the fluid composition cannot escape the material, and the material is then subjected to excessive hydrostatic tension that will cause the material to fragment thereby dramatically enhancing the surface area for faster depolymerization ofthe material upon further treatment of the fluid composition. For materials with minimum dimensions of 0.125 inches thick, minimum depressurization rates of 1000 psi / second are useful and preferably rates of 5000 psi / second to 50000 psi / second are preferred. Higher depressurization rates will always produce finer fragments until a saturation point is obtained for a particular material to be depolymerized and fluid composition being used. For materials with minimum thickness greater than 0.125 inches and on the order of 1 inch thick, slower depressurizations rates can be used and a minimum range of 100 psi / second but a preferred range of 1000 psi / second to 5000 psi / second may be sufficient. For materials with material thicknesses greater than 1 inch, minimum depressurization rates in the range of 10 psi / second may be sufficient for fragmentation.

[0059] In an embodiment, the depressurization step begins with a release in pressure from the reactor after treatment with the fluid composition and may be conducted rapidly at a rate of 5000 psi per second (psi / second) to 50,000 psi / second, 10,000 to 40,000 psi / minute, 20,000 to 35,000 psi / minute till ambient conditions are reached. Alternatively, the depressurization may be conducted slowly after treatment with the fluid composition at a rate of 100 psi / second to less than 5000 psi / second, 200 psi / second to 3000 psi / second, 300 to 1000 psi / second till ambient conditions are reached.

[0060] In an embodiment, during depressurization gases that escape from the reactor may be collected and condensed to collect the products of depolymerization along with other volatiles (carbon dioxide and ethanol). These products of depolymerization may be subjected to further purification and segregation and be used for future polymerization or for other purposes.

[0061] In the case of a pure polymer, the oligomer-rich phase may be subjected to further treatment (such as distillation, centrifugation, filtration, washing, and the like) to isolate the oligomers. A library of different oligomers may be obtained from the depolymerization of the pure polymer in this manner. The polymers and oligomers derived from this process are never in the form of a foam.

[0062] In the case of a polymeric composite, the liquification will produce a polymer- rich phase along with an oligomer-rich phase and a filler-rich phase. By increasing the time of liquification a larger portion of the polymer-rich phase will gradually undergo conversion to the oligomer-rich phase. In other words, with the passage of time (during liquification), the polymer-rich phase will decrease relative to the oligomer-rich phase. The polymer-rich phase and / or the oligomer-rich phase is separated from the filler-rich phase by techniquessuch as centrifugation, filtration, or the like. The fillers may be segregated from the fillerrich phase by centrifugation and reused in a composite, while the polymers and oligomers are separated from the polymer-rich phase by techniques such as distillation, filtration, liquid chromatography, or the like.

[0063] One of the novel compositions obtained from this process is a combination of the fluid composition with both polymers and oligomers derived from depolymerization of the polymeric resin. In certain glass filled composites, the glass fibers are present in an amount of 25 to 50 wt%, based on a total weight of the composite.

[0064] In an embodiment, a composition obtained from the process may contain a mixture of aromatic species and aliphatic species. The mixture of aromatic species may include those having the structures (1), (2) and (3) shown below.; where for structure (1), each Rhis independently a C1-20 hydrocarbyl group such as a C1-20 alkyl, a substituted C1-20 alkyl, a Ce-io aryl, or substituted Ce-io aryl, and n is 0 to 5. The substituted C1-20 alkyl or substituted Ce-io aryls may include P, O, S, N or halogen substitution.

[0065] In a preferred embodiment, for structure (1), Rhis a Ci to C3 alkyl, while n may be 1 or 2.In another preferred embodiment, moiety of structure 1 may have the structure 1A shown below.(1A),where R5, Re and R7 may each independently be a substituted or unsubstituted Ci to C20 alkyl or a Ci to C20 cycloalkyl. The substitution may include P, O, S, N atoms.

[0066] For structure (2), Raand Rbare each independently a C1-20 alkoxy or C1-20 alkyl, and p and q are each independently integers of 0 to 4, such that when p or q is less than 4, the valence of each carbon of the ring is filled by hydrogen. In an aspect, p and q is each 0, or p and q is each 1, and Raand Rbare each a C1-3 alkyl group, preferably methyl, disposed meta to the hydroxy group on each arylene group. Xais a bridging group connecting the two hydroxy-substituted aromatic groups, where the bridging group and the hydroxy substituent of each Ct> arylene group are disposed ortho, meta, or para (preferably para) to each other on the Ct> arylene group, for example, a single bond, -O-, -S-, -S(O)-, -S(O)2-, -C(O)-, or a C1-18 organic group, which can be cyclic or acyclic, aromatic or non-aromatic, and can further comprise heteroatoms such as halogens, oxygen, nitrogen, sulfur, silicon, or phosphorous.For example, Xacan be a substituted or unsubstituted C3-18 cycloalkylidene; a C1-25 alkylidene of the formula -C(Rc)(Rd) - wherein Rcand Rdare each independently hydrogen, C1-12 alkyl, C1-12 cycloalkyl, C7-12 arylalkyl, C1-12 heteroalkyl, or cyclic C7-12 heteroarylalkyl; or a group of the formula -C(=Re)- wherein Reis a divalent C1-12 hydrocarbon group.

[0067] In a preferred embodiment, for structure (2) Xais a Ci to Cis organic group, preferably a Ci to Ce organic group, which can be cyclic or acyclic, aromatic or non- aromatic; and Raand Rbare each independently a Ci to C20 alkyl, and p and q are each independently integers of 0 to 4, such that when p or q is less than 4, the valence of each carbon of the ring is filled by hydrogen.

[0068] In yet another embodiment, structure (2) may reduce to structure (2A):(2A), where R7, Rs and R9 can be the same or different and can independently be a hydrocarbyl group having 1 to 20 carbon atoms, where the hydrocarbyl unit can be linear, branched, cyclic, or any combination thereof. Moreover, the hydrocarbyl fragment may be saturated or unsaturated and may include one or more of the following hetero atoms: N, O, S, and / or P.

[0069] For structure (3), Ri, R2, and R3 can be the same or different and can independently be a hydrogen; a saturated or unsaturated hydrocarbyl, having between 1 and 20 carbon atoms, where the hydrocarbyl unit can be linear, branched or cyclic and may be substituted or unsubstituted. Substitution may occur with N, O, S, and / or P.

[0070] In an embodiment, when a polymeric composite that comprises a polymer having aryl groups (e.g., epoxies, phenolics, aromatic polyesters, or the like) is subjected to pressurization and depressurization in the presence of supercritical and / or superheated fluids, a mixture that comprises aromatic and aliphatic species may be obtained. The aromatic species and aliphatic species may be monomers, dimers, trimers or oligomers and may be reacted to undergo polymerization. In other words, at least one or more of the aromatic and / or aliphatic species derived from the cleavage of polymers may be capable of being polymerized.

[0071] The molar ratios of aromatic species to aliphatic species can vary from 0.05:1.10 to 0.15:1.00. In other words, the molar ratio of aromatic to aliphatic species expressed as a percentage (of the sum of aromatic and aliphatic species) can vary from about 3% to about 20%, preferably about 5% to about 15%, and more preferably 6 to 10%, based on the total moles of aromatic and aliphatic species derived from the liquefaction of the polymers in the polymeric composite.

[0072] The fillers obtained from the filler-rich phase may be washed using the same fluids contained in the fluid composition.

[0073] In an embodiment, vapors from the reactor may be collected during the depressurization and any valuable byproducts (such as, for example, monomers and other volatiles) recovered for further use.

[0074] As noted above, the fillers recovered from a composite do not suffer any substantial change in physical properties or chemical properties from those used initially. The aspect ratio (length divided by diameter) of the recovered fibers is substantially the same as that of the initial fibers. The lack of mechanical abrasion or thermal degradation during the recovery process prevents reduction in fiber quality, dimensions or thermomechanical properties. The fibers recovered in this process can be reused to produce another component.

[0075] The process of recovering fillers and of depolymerizing the polymer may be a batch process, a semi-continuous process or a continuous process.

[0076] This method of treating the polymeric resin (in pure form or in composite form) is particularly effective for recycling crosslinked polymers. This method of recyclingpolymeric composites is useful for recycling wind turbine airfoils (epoxy based resin and glass), aerospace components (carbon fiber and epoxy based), automotive components (epoxy based and carbon or glass) as well as marine components (vinyl ester resin glass fiber based).

[0077] In an exemplary embodiment, composites containing glass fibers and epoxies (a crosslinked polymer) may be recycled using the aforementioned method. The epoxycontaining composite may be first treated with superheated water (the first superheated fluid) and optionally with superheated ethanol (the second superheated fluid) or with supercritical ethanol (the first supercritical fluid). It is then treated with supercritical carbon dioxide. This treatment (with 3 fluids - superheated water, superheated ethanol or supercritical ethanol, and supercritical carbon dioxide) occurs at a pressure of 500 to 9000 psi, preferably 3000 to 8500 psi, preferably 4500 to 8000 psi and a temperature of greater than 240°C, preferably greater than or equal to 245°C for a time period of 24 to 120 hours, preferably 48 to 80 hours. As noted above, this treatment at an elevated temperature and pressure for a period of time is sometimes referred to as the pressure soak time or period.

[0078] The fluid composition in the reactor comprises water and ethanol in a 45:55 to 55:45 volume ratio. The supercritical carbon dioxide constitutes the remainder of the fluid composition in the reactor. The combination of water, ethanol and carbon dioxide facilitates an efficient liquification of the polymeric resin (the epoxy) present in the composite. The liquified product comprises water, ethanol, carbon dioxide, a polymer-rich phase and an oligomer-rich phase. The oligomer-rich phase can be extracted from the reactor and repeatedly washed to obtain the oligomers. The fibers may also be extracted from the reactor and repeatedly washed to obtain glass fibers that may be used to produce another composite. The oligomers may also be repolymerized and used to produce another composite. The composites produced in this manner may be used to produce another wind turbine airfoil.

[0079] The fluid composition and the method of using it to depolymerize it is exemplified by the following non-limiting examples.EXAMPLEExample 1

[0080] This example is conducted to demonstrate the extraction of fibers and the depolymerization of an epoxy polymer from a composite. It exemplifies the methodology detailed above for separating the fibers from an epoxy containing composite using the fluidcomposition detailed herein. Epoxy based thermosets are not soluble in common solvents, do not melt, and generally cannot be reprocessed.

[0081] In this example, the epoxy containing composite is treated with 3 different fluid compositions. The first fluid composition comprises supercritical carbon dioxide and super critical ethanol. The second fluid composition comprises supercritical carbon dioxide and superheated water. The third fluid composition comprises supercritical carbon dioxide, supercritical ethanol and superheated water. In the third fluid composition, the volume ratio of water to ethanol is 50:50. All epoxy containing composites were saturated with the respective fluid composition for 3 days (72 hours) at 245°C. Table 2 below shows the respective fluid compositions along with the pressure of the supercritical carbon dioxide. The pressure of the supercritical carbon dioxide (shown in the Table 2 below) is the pressure of the respective fluid composition that the epoxy containing composite was subjected to.

[0082] The epoxy-containing composite was first treated with superheated water (the first superheated fluid) and then with supercritical ethanol (the first supercritical fluid). Following the impregnation of the epoxy-containing composite with the superheated water and supercritical ethanol, it is treated with supercritical carbon dioxide (the second supercritical fluid) at different pressures (shown in the Table 2), a temperature of 245°C for a time period of 72 hours.

[0083] From the Table 2 it may be seen that the fiber cleaning efficiency improves with pressure. For example, it may be seen that when the composite is treated with water, ethanol and carbon dioxide the cleaning efficiency improves at pressures of 6000 to 8000 psi compared with the cleaning efficiency below 1000 psi. Similarly, it may be seen that at 6000 psi, the best cleaning efficiency is obtained when all three fluids (superheated water, supercritical ethanol and supercritical carbon dioxide) are used in the fluid composition versus those compositions that have only two fluids (supercritical carbon dioxide and superheated water or supercritical carbon dioxide and supercritical ethanol). This reveals that there is a synergy between the carbon dioxide, the ethanol and water that functions to clean the fibers very efficiently.

[0084] Cleaning efficiency is measured using ASTM D3171-22 “Standard Test Methods for Constituent Content of Composite Materials” This is a bum out test using a furnace to ascertain mass loss of the fiber. A higher “cleaning efficiency” is a recovered fiber batch that has very little mass loss after treatment in the furnace. Eittle or no polymeric matrix remaining.Table 2Key: scCCh = supercritical carbon dioxide; shbbO = superheated water; scEtOH = supercritical ethanolExample 2

[0085] This example was conducted to determine the different oligomeric products that are formed from the depolymerization of the polyepoxide in the epoxy-containing composite. As noted above, liquefication of crosslinked thermosets, and thermoset composites results in the formation of low molecular weight polymers and oligomers with a range of molecular weights between 200 and 5,000 g / mol.

[0086] FIG. 1 depicts the reaction between bisphenol A diglycidyl ether (commonly abbreviated BADGE or DGEBA) and JEFFAMINE D230. JEFFAMINE D230 is a polyetheramine - a difunctional, primary amine with an average molecular weight of about 230 g / mol. The primary amine groups are located on secondary carbon atoms at the end of the aliphatic polyether chain.

[0087] FIG. 2 is a schematic diagram that shows the potential moieties that may be formed as a result of the fragmentation of epoxy network.

[0088] The oligomer and polymers can be either linear, or branched, or a combination of both linear and branched mixtures. The chemical functionality present on the oligomer and polymer fragments is a combination of aliphatic and aromatic alcohols, including phenolic residues. Also present on the oligomer are primary and secondary amines, again a combination of aliphatic and aromatic from the liquefication of amine cured epoxy resins. The ratio of aliphatic to aromatic content is readily quantified by proton nuclear magneticresonance (’ H NMR) spectroscopy and can vary between 5:95 to 95:5 mole percent. The ratio of alcohols; aliphatic, aromatic and phenolic can be identified by using phosphorus labeling and31P NMR, as described by Meng et al. in Nature Protocol 2019 (NATURE PROTOCOLS |VOL 14 [SEPTEMBER 2019 | 2627-2647 https: / / doi.org / 10.1038 / s41596- 019-0191-1). Similarly, the amine content and ratio of primary and secondary amines can similarly be determined by an adaptation of the procedure of Meng et al.

[0089] The amino-alcohol oligomeric and polymeric liquefied products were found to be soluble in a range of organic solvents, tetrahydrofuran, toluene, anisole, diethyl ether, chloroform, dichloromethane and acetone.

[0090] The depolymerization process of amine cured epoxy thermosets produces oligomeric products that are amino-alcohol functionalized. Various thermosets that are encountered for this process involve:1) an aromatic epoxide cured with an aliphatic amine.2) an aromatic epoxide cured with an aromatic amine.3) an aliphatic epoxide cured with an aliphatic amine.4) an aliphatic epoxide cured with an aromatic amine.5) various combinations of 1 through 4 above.

[0091] Amine cured epoxy thermosets, and amine cured epoxy thermoset composites, can have a range of aromatic and aliphatic content. The amino-alcohol oligomer produced by the depolymerization results in compositions having ranges of mole percentages of aromatic to aliphatic content as shown in the Tables 3 and 4 below.Table 3More preferably compositions ranges of the aromatic to aliphatic content in the amino-alcohol oligomers would be as shown below in Table 4.Table 4Example 3

[0092] In this example was conducted to evaluate some of the different potentially commercially valuable species that are produced when the fragmentation of an epoxy network occurs under the conditions detailed above.

[0093] For this example, some of the species seen in the FIG. 2 were quantified using phosphorus NMR. A mixture of liquified resin sample was subjected to a phosphitylation reaction following which phosphorus NMR was conducted. The nomenclature adopted for the samples seen in the Table 5 is shown in the FIG. 3A. From the FIG. 3A, it may be seen that samples liquified in a mixture of supercritical carbon dioxide and superheated water are labelled A, while those liquified in a mixture of supercritical carbon dioxide, superheated water and supercritical ethanol are labelled B. FIG. 3B includes graphs of representative phosphorus NMR of the phosphitylation reaction mixture of liquified resin samples that was conducted in a mixture of supercritical carbon dioxide, superheated waster and supercritical alcohol. Peaks a, b and c in both the spectra represent aliphatic amino- alcohols, while peaks d and e in the spectra represent aromatic hydroxyl species.

[0094] The results of several liquified mixtures are shown in the FIG. 4. FIG. 4 contains a table (Table 5) that details the ratio of aromatic to aliphatic component ratios determined by phosphorus-31 NMR spectroscopy. From the Table 5 in FIG. 4 it may be seen that the molar ratio of aromatic to aliphatic species can vary from 0.05 : 1.10 to 0.15 : 1.00. In other words, the molar ratio of aromatic to aliphatic species expressed as a percentage (of the sum of aromatic and aliphatic species) can vary from about 4% to about 15%, preferably about 5% to about 12%. At least a portion of the aromatic species, the aliphatic species, or a combination thereof are polymerizable.

[0095] From the Table 5 in FIG. 4, it may be seen that the liquified mixtures contain the following aromatic and aliphatic species. These are shown in the Table 6.Table 6where in Table 6, for structure (1), each Rhis independently a C 1-20 hydrocarbyl group such as a C1-20 alkyl, a substituted C1-20 alkyl, a Ce-io aryl, or substituted C6-10 aryl, and n is 0 to 5. The substituted C1-20 alkyl or substituted C6-10 aryls may include P, O, S, N or halogen substitution.

[0096] In Table 6, for structure (2), Raand Rbare each independently a C1-20 alkoxy or Ci -20 alkyl, and p and q are each independently integers of 0 to 4, such that when p or q is less than 4, the valence of each carbon of the ring is filled by hydrogen. In an aspect, p and q is each 0, or p and q is each 1, and Raand Rbare each a C1-3 alkyl group, preferably methyl, disposed meta to the hydroxy group on each arylene group. Xais a bridging group connecting the two hydroxy-substituted aromatic groups, where the bridging group and the hydroxy substituent of each C>, arylene group are disposed ortho, meta, or para (preferably para) to each other on the C7, arylene group, for example, a single bond, -O-, -S-, -S(O)-, - S(O)2-, -C(O)-, or a Ci-is organic group, which can be cyclic or acyclic, aromatic or nonaromatic, and can further comprise heteroatoms such as halogens, oxygen, nitrogen, sulfur, silicon, or phosphorous. For example, Xacan be a substituted or unsubstituted C3-18 cycloalkylidene; a C1-25 alkylidene of the formula -C(Rc)(Rd) - wherein Rcand Rdare each independently hydrogen, Ci-12 alkyl, C1-12 cycloalkyl, C7-12 arylalkyl, C1-12 heteroalkyl, or cyclic C7-12 heteroarylalkyl; or a group of the formula -C(=Re)- wherein Reis a divalent Ci-12 hydrocarbon group.

[0097] In Table 6, in structure (3), Ri, R2, and R3 can be the same or different and can independently be a hydrogen; a saturated or unsaturated hydrocarbyl, having between 1 and 20 carbon atoms, where the hydrocarbyl unit can be linear, branched or cyclic and may be substituted or unsubstituted. Substitution may occur with N, O, S, P, a halogen, or a combination thereof.Example 4

[0098] This example is conducted to demonstrate the use of ethylene glycol (EtOH) and / or glycerol as potential solvents for the liquification of polymers and polymeric composites. FIG. 5 depicts the nomenclature adopted for determining sample compositions.Three different fluid compositions were used for liquification of the polymeric composite samples. The polymeric composite comprised an epoxy thermoset and glass fibers. The first fluid composition (Bl) included supercritical carbon dioxide and superheated water. The second fluid composition (B8) included supercritical carbon dioxide, superheated water and superheated ethylene glycol (EG). The superheated water and superheated ethanol were used in a volume ratio of 1 : 1. The third fluid composition (B5) included supercritical carbon dioxide, superheated water and glycerol. The water and glycerol was used in a 1:1 volume ratio. Each sample was pressurized to 3000 pounds per square inch (psi) for a period of 72 hours. Samples with the letter “c” next to them were subjected to rapid depressurization after 24 hours followed by slow depressurization after 48 hours. The temperate during pressurization was 225°C.

[0099] The result of this exposure to pressure and the fluid composition produced the liquefaction results as seen in the FIG. 5. From the bar chart seen in FIG. 5, it may be seen that as the temperature of pressurization is increased, a larger fraction of the polymeric composite is liquified (i.e., it is converted to a soluble mixture of reactants).

[0100] At temperatures of 220°C or greater it may be seen that a substantial portion of the polymeric composite is converted into a soluble liquid that can be subjected to further fractionation and used for other reactions downstream. In summary, this method of liquification may be used to recover a large amount of polymeric resin from a polymeric article or a polymeric composite.

[0101] While the invention has been described with reference to some embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A fluid composition for depolymerizing a polymer comprising:5 to 90 volume percent of carbon dioxide in supercritical fluid form;5 to 90 volume percent of superheated water; and5 to 90 volume percent of an alcohol; where the alcohol is in either its superheated state or supercritical fluid; where all volume percents are based on a total volume of the fluid composition; where the fluid composition is at a temperature greater than 150°C, a pressure greater than 500 psi for a time period greater than 30 minutes.

2. The fluid composition for Claim 1, where the carbon dioxide is present in an amount of 25 to 40 volume percent, the water is present in an amount of 25 to 40 volume percent and the alcohol is present in an amount of 25 to 40 volume percent, based on a total volume of the fluid composition.

3. The fluid composition of any one of the foregoing claims, where the carbon dioxide is present in an amount of 28 to 35 volume percent; the superheated water is present in an amount of 27 to 35 volume percent; and the alcohol is present in an amount of 27 to 35 volume percent.

4. The fluid composition of any one of the foregoing claims, where the alcohol is ethanol.

5. The fluid composition of any one of the foregoing claims, where a volume ratio of superheated water to the superheated or supercritical alcohol is 45:55 to 55:45.

6. The fluid composition of any one of the foregoing claims, where the fluid composition is at a pressure of 3000 to 25,000 psi and at a temperature of greater than 270°C.

7. The fluid composition of any one of the foregoing claims, where the fluid composition is at a pressure of 4000 to 10,000 psi and at a temperature of greater than 245°C.

8. The fluid composition of any one of the foregoing claims, further comprising a polymer-rich phase, an oligomer rich-phase and a filler-rich phase.

9. The fluid composition of any one of the foregoing claims, further comprising an oligomer having a number average molecular weight of 200 to 5000 grams per mole.

10. The fluid composition of any one of the foregoing claims, where the time period is 24 to 120 hours.

11. The fluid composition of any one of the foregoing claims, where the oligomer comprises aliphatic and aromatic alcohols derived from a liquefied amine cured epoxy resin.

12. The fluid composition of any one of the foregoing claims, where the oligomer further comprises primary and secondary amines derived from a liquefied amine cured epoxy resin.

13. The fluid composition of any one of the foregoing claims, where the oligomer further comprises one or more of an aromatic epoxide cured with an aliphatic amine, an aromatic epoxide cured with an aromatic amine, an aliphatic epoxide cured with an aliphatic amine and an aliphatic epoxide cured with an aromatic amine.

14. A method of separating a filler from a polymeric composite comprising: contacting the polymeric composite with a fluid composition at a temperature greater than 300°C, a pressure greater than 500 psi for a time period greater than 30 minutes; wherein the fluid composition comprises superheated water, superheated or supercritical alcohol and a supercritical gas; depressurizing the fluid composition at a rate of greater than 100 psi per second; liquifying the polymeric resin particles; and delaminating the filler from the polymeric resin particles.

15. The method of Claim 14, further comprising fragmenting the polymeric composite into polymeric resin particles.

16. The method of any one of the foregoing claims, further comprising hydrolytically cleaving bonds in the polymer particles to depolymerize the polymer.

17. The method of any one of the foregoing claims, wherein the fluid composition is at a temperature greater than 300°C, a pressure greater than 500 psi for a time period greater than 30 minutes.

18. The method of any one of the foregoing claims, wherein the fluid composition is at a pressure of 4500 to 10,000 psi and at a temperature of greater than 245°C.

19. The method of any one of the foregoing claims, where the polymeric composite comprises a polyepoxide and glass fibers.

20. The method of any one of the foregoing claims, where the polymeric composite is contacted with the superheated water prior to contacting the polymeric composite with the superheated or supercritical ethanol.

21. The method of any one of the foregoing claims, where the polymeric composite is contacted with the superheated or supercritical ethanol prior to contacting it with the supercritical gas.

22. The method of any one of the foregoing claims, where the polymeric composite is simultaneously contacted with superheated water, superheated or supercritical alcohol and a supercritical gas.

23. The method of any one of the foregoing claims, where the alcohol is ethanol and where the supercritical gas is supercritical carbon dioxide.

24. The method of any one of the foregoing claims, where the depressurization rate is less than 5000 psi / second.

25. The method of any one of the foregoing claims, where the depressurization rate is less than 1000 psi / second.

26. The method of any one of the foregoing claims, where the depressurization rate is 5000 psi / second to 50,000 psi / second.

27. The method of any one of the foregoing claims, further comprising condensing volatiles that are discharged during the depressurization.

28. A composition comprising: aromatic and aliphatic species derived from the decomposition of a polymeric composite; where the aromatic species have the structures (1) and (2):; where for structure (1), each Rhis independently a C1-20 hydrocarbyl group such as a C1-20 alkyl, a substituted C1-20 alkyl, a Ce-io aryl, or substituted Ce-io aryl, and n is 0 to 5; where for structure (2), Raand Rbare each independently a C1-20 alkoxy or C1-20 alkyl, and p and q are each independently integers of 0 to 4, such that when p or q is less than 4, the valence of each carbon of the ring is fdled by hydrogen; where Xais a bridging group connecting two hydroxy-substituted aromatic groups, where the bridging group and the hydroxy substituent of each Ce arylene group are disposed ortho, meta, or para to each other on the Ce arylene group; where Xais a single bond, -O-, -S-, -S(O)-, -S(O)2-, -C(O)-, or a Ci- 18 organic group, which is cyclic or acyclic, aromatic or non-aromatic, and can further comprise halogens, oxygen, nitrogen, sulfur, silicon, or phosphorous heteroatoms; and where the aliphatic species has the structure (3)where in structure (3), Ri, R2, and R3 can be the same or different and can independently be a hydrogen; a saturated or unsaturated hydrocarbyl, having between 1 and 20 carbon atoms, where the hydrocarbyl unit can be linear, branched or cyclic and may be substituted or unsubstituted.

29. The composition of Claim 28, wherein a molar ratio of aromatic to aliphatic species expressed as a percentage is about 3% to about 20%, based on the total moles of aromatic and aliphatic species derived from the liquefaction of the polymers in the polymeric composite.

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