WO2005118691A2

WO2005118691A2 - Separation of polyolefins from polyamides

Info

Publication number: WO2005118691A2
Application number: PCT/US2005/019821
Authority: WO
Inventors: Lloyd Ballard Mauldin; Jerry Allen Cook
Original assignee: Chemical Products Corporation
Priority date: 2004-06-04
Filing date: 2005-06-03
Publication date: 2005-12-15
Also published as: WO2005118691A3

Abstract

In the recycling of polyamides, for example Nylon 6 and Nylon 6,6, from post-consumer or post-industrial waste, a process is disclosed to separate polyamide polymers from commingled polyolefin polymer waste components, for example polypropylene, by admixing the waste with an ester solvent composition and heating the admixture to a temperature above the melting temperature of the contained polyolefins to form an ester solvent composition further containing dissolved polyamide polymer and a separate immiscible liquid polyolefin phase. The ester solvent composition preferably contains cyclic ester solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof. A process is also disclosed to decompose polyester by heating in the presence of a cyclic ester solvent to a temperature above about 215 degrees Celsius. The polyester decomposition products are useful as components of an ester solvent composition for separating polyamide polymers from polyolefin polymers or an industrial solvent.

Description

SEPARATION OF POLYOLEFINS FROM POLYAMIDES CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Application Serial No. 10/708,479 filed September 27, 2004 and U.S. Application Serial No. 10/708,693 filed June 4, 2004. BACKGROUND OF INVENTION Billions of pounds of post-consumer carpet waste are generated each year in the United States. Landfilling is not an environmentally friendly solution since carpet fibers, like many other synthetic polymers, are not biodegradable. Furthermore, the cost of disposal is increasing due to efforts to make landfills more environmentally secure and to preserve limited capacity. Environmental concerns and governmental regulations have spurred efforts to recycle as much of the non-biodegradable synthetic polymer waste stream as practicable. In a post-consumer carpet waste there are generally three predominant components: backing fiber, face fiber, and non-fibrous backing materials. Polypropylene is present in the primary and secondary backing of most carpets, generally in the form of woven ribbons or nonwoven fabric. In addition, polypropylene fiber is sometimes found as the face fiber. The most common face fibers are the polyamides, Nylon 6 and Nylon 6,6. Backing compositions generally contain binders such as SBR latex and fillers such as calcium carbonate. Commercial carpet may employ mixed polyolefin, polyvinyl chloride, or polyurethane non-fibrous

backing components. The fiber component of the overall post-consumer carpet waste stream would be expected to consist of approximately 40% Nylon 6; 40% Nylon 6,6; and 10% polypropylene. Sorting carpet pieces according to face fiber type before the pieces are shredded, further size-reduced, and separated into a fibrous component and a non- fibrous binder and dirt component, can yield segregated commingled fiber wastes composed of about 80% Nylon 6 or Nylon 6,6 and about 5% to 10% polypropylene. This amount of polypropylene polymer in polyamide degrades the physical properties of the polyamide polymer to such an extent that it is unsuitable for virtually all typical Nylon 6 or Nylon 6,6 applications. Thus, the utility of Nylon 6 and Nylon 6,6 polymers recovered from waste is, to a great extent, dependent upon the absence of polyolefin polymer contaminants. Solvents such as octane have been proposed to dissolve polypropylene bonded to polyamide fibers without altering the Polyamide fibers. The polypropylene is separated from the solvent by cooling with subsequent filtration (Tselishcheva et al.; International Polymer Science and Technology; 29, No.8, p.T/55-6; 2002). This process would appear to be unsuitable for a waste containing a substantial proportion of polyamide because of the difficulty of effectively removing polypropylene-laden solvent from a substantial mass of polyamide fibers. U.S. 5,430,068 (Subramanian) teaches a process for recovering polyamide from admixtures with foreign materials by dissolving the polyamide, at an elevated temperature substantially below the melting temperature of Polypropylene, in a solvent selected from the group consisting of a substantially anhydrous ethylene glycol, propylene glycol, and aliphatic carboxylic acid having from 2 to 6 carbon atoms, filtering, then combining the polyamide solution with an additional quantity of substantially the same solvent at a lower temperature to cause the polyamide to precipitate. The named solvents may react with components of the carpet backing such as calcium carbonate. Rapid cooling by addition of substantial quantities of cool solvent is necessitated by degradation of polyamide when held in the hot solvent. U.S. Patent 5,898,063 (Stefandl) teaches a recycling and recovery process for waste carpet employing a solvent such as ethylene glycol, propylene glycol, glycerol and various mixtures of these solvents, or, alternatively, an organic formate, hydrochloric acid, formic acid, methanol, nitric acid, glacial acetic acid, fluorinated alcohols, m-cresol, phenolic compounds, chloroform-methanol, methanol-lithium chloride, potassium thiocyanate, benzyl alcohol, butane diol 1,1, dimethyl sulfoxide, triethylene glycol, or tetraethylene glycol. Nylon 6 and Nylon 6,6 are taught to be soluble in each of solvents at various elevated temperatures. Once again, these solvents may react with components of the waste carpet backing present with the Nylon 6 and Nylon 6,6 or degrade the dissolved polyamide polymer, additionally, most present environmental, and worker health and safety hazards. U.S. Patent 6,140,463 (Stefandl) teaches recovery of a purer Nylon polymer from carpet by dissolving and precipitating the Nylon polymer at least twice utilizing the same solvents described in U.S. Patent 5,898,063 (Stefandl). U.S. Patent 5,994,417 teaches a process for recovering polymers from commingled materials by selectively dissolving the polymer in a solvent and then contacting the solution with an anti-solvent comprising a compressed fluid, near, at or above its critical pressure into which the solvent is soluble but into which the polymer is insoluble. The anti-solvent is selected from the group consisting of ethane, propane and carbon dioxide. All of these prior art approaches to the separation of Nylon 6 or Nylon 6,6 polyamide polymers from the polypropylene polymer usually found in the backing of carpets suffer from shortcomings, thus an unmet need exists for an environmentally benign, inexpensive means of purifying polyamide polymer recovered from commingled polyamide and polyolefin wastes. SUMMARY OF INVENTION This invention is directed to a process for separating the polyolefin component from the polyamide component of post-consumer or post-industrial waste containing commingled polyamide polymers and polyolefin polymers. This invention is particularly directed to a process for the recovery of polyamide polymer from commingled fibers of Nylon 6 or Nylon 6,6 and polypropylene. It is an objective of this invention to provide a means of recycling and purifying polyamide polymer from waste material containing polyolefin polymer commingled with polyamide polymer. The polyamide fiber may be the major synthetic component or it may be present in lesser amounts compared to the polyolefin. It is a further objective of this invention to provide a means for recovery of polyamide polymer from carpeting materials containing Nylon 6 or Nylon 6,6 face fibers associated with polypropylene fibers and possibly other polyolefin polymers, as well as natural fibers. A process for separation of polyamide components of commingled waste from polyolefin components is disclosed. Polyamide components are dissolved or suspended in an ester solvent composition at a temperature above the melting temperature of the polyolefin components of the commingled waste. The molten polyolefin components of the commingled waste form an immiscible phase separate from the ester solvent phase containing dissolved and suspended polyamides. The separate polyolefin phase can be easily separated from the ester solvent phase. The ester solvent composition can include, for example, a cyclic ester, for example, a carbonate ester. The ester solvent composition can also include a polyester decomposition product in a cyclic ester solvent composition produced by dissolution of a polyester polymer component in a cyclic ester solvent composition and heating to a temperature sufficient to cause decomposition of the polyester polymer. A decomposed polyester product can then be recovered that can be employed as a component in an ester solvent composition suitable for separating commingled polyamide polymers from polyolefin polymers, as well as a component in industrial solvents for other purposes such as paint and grease stripping. DETAILED DESCRIPTION Polyolefins, particularly polypropylene, have been unexpectedly found to be immiscible in ester solvent compositions containing dissolved polyamides at temperatures above the melting temperature of the polyolefin. For example, Nylon 6 or Nylon 6,6 can be dissolved from commingled polyamide polymer and polyolefin polymer waste by ester solvent compositions, at temperatures above the melting temperature of polypropylene or other polyolefins. An immiscible viscous liquid polyolefin phase floats on the ester composition containing dissolved Nylon 6 or Nylon 6,6 polyamide polymer. Thus, entrainment of Nylon-bearing solvent in the polyolefin phase is virtually eliminated and the polyolefin can be removed from the process and recovered as a substantially ester-free and polyamide-free material without substantial filtration and washing cost. The process is preferably conducted at ambient pressure, in which case the selection of ester solvent compositions is limited to those that have high boiling temperatures. Nylon 6 or Nylon 6,6 recovered by the process of the present invention may be utilized in place of or blended with virgin polyamides in any known polyamide applications including extruding the melted material to form fiber which may be dyed. An exemplary ester solvent composition is a cyclic ester, for example, a carbonate ester, such as ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof. These cyclic esters are environmentally benign and exhibit relatively low acute toxicity, as well as low chronic toxicity. In practice of the invention, commingled fibers composed of polyamide and polypropylene are separated into polyamide polymer and polypropylene polymer by admixing the fibers with an ester solvent composition. In an exemplary embodiment the ester solvent composition is a cyclic ester, preferably propylene carbonate, in sufficient quantity to suspend the fibers. The admixture is heated to a temperature above about 165 degrees Celsius at ambient pressure whereupon the polypropylene fibers melt and form an immiscible phase separate from the ester composition phase containing dissolved and suspended polyamide polymer. The polyamide polymer is not significantly degraded even upon heating to a temperature near the melting temperature of the polyamide polymer. Higher temperatures offer advantages in that more of the polyamide polymer is dissolved thus promoting the coalescence of polypropylene into a separate phase, and in that the viscosity of the molten polypropylene decreases with temperature, once again promoting the coalescence of the polypropylene into a separate phase floating on the surface of the propylene carbonate phase. Upon cooling of the solution, polyamide precipitates as small discrete particles suspended within the polypropylene carbonate phase, but the polypropylene polymer phase solidifies into a solid mass which can then be easily separated from the polyamide polymer suspended in propylene carbonate. Polyamides for which this process is suited include Nylon 6 and Nylon 6,6. Other cyclic esters, such as ethylene carbonate or butylene carbonate, can be substituted for propylene carbonate in this exemplary practice of the present invention. Copending U.S. patent application 10/708,479 (Mauldin) discloses that polyester polymer is decomposed when heated in the presence of a cyclic ester such as propylene carbonate. The cyclic ester admixed with polyester polymer decomposition products is taught to have utility as an industrial solvent. This novel solvent composition is also suitable for the practice of the present invention. The production of this solvent composition is detailed below. The process of this invention can be advantageously and quite satisfactorily practiced with any commingled waste containing both polyolefin and polyamide polymeric components. For example, this process can be practiced with any caφet as the starting material, provided only that there are significant amounts of nylon fibers present. The nylon can be either of the types found most often in caφet, Nylon 6 (poly-6-aminocaprioic acid) or Nylon 6,6 (poly-hexamethyleneadipamide). In another exemplary embodiment of the invention, the starting material is caφeting or caφet waste composed of Nylon face fibers with polyolefins only being present as components of the caφet backing. The caφet waste may be pre-sorted and the fibrous components of the caφet waste may be separated from dirt and non- fibrous components of the waste, such as non-fibrous backing components, by shredding, cutting, grinding, washing, screening, air elutriation, particle size separation techniques, and combinations thereof. This starting material is admixed with propylene carbonate and heated to a temperature of at least about 165 degrees Celsius. The commingled caφet waste may constitute between 2% and 50% by weight of the admixture. The temperature is preferably appropriately selected based on the caφeting composition and operating parameters. Substantial dissolution of Nylon 6,6 requires a higher temperature than substantial Nylon 6 dissolution. Separation of polyolefins from the polyamide polymer present in the starting material does not require dissolution of all polyamide polymer present in the admixture or even a substantial quantity of the polyamide polymer present in the admixture. However, substantial amounts of polyamide fiber hinder the formation of a separate polyolefin phase. The amount of ester solvent composition present in the admixture and degree of dissolution of polyamide polymer should be sufficient to allow molten globules of polyolefin sufficient mobility to coalesce and form a separate phase. The ester solvent composition may, for example, comprise about 98% to about 30% by weight of the admixture. Undissolved polyamide fibers can be recovered from the ester solvent composition phase along with dissolved polyamide polymer by cooling the ester solvent phase to a temperature sufficient to precipitate the dissolved polyamide polymer. The cooled ester solvent can then be separated from the polyamide polymer by, for example, electrophoresis, sedimentation, flocculation, filtration, centrifugation, or combinations thereof. In yet another exemplary embodiment of the present invention, post-consumer waste may be physically sorted to obtain a sorted caφet waste composed exclusively of caφet pieces having only Nylon 6 face fibers. In this embodiment the Nylon 6 polymer component can be separated from the polyolefin polymer component of the commingled post-consumer caφet waste by admixing the waste with an ester solvent composition. The admixture may be heated to a temperature and for a period of time sufficient to dissolve at least a portion of the Nylon 6 fibers in the ester solvent composition and to form a separate discrete molten phase. Preferably the admixture is heated to a temperature above about 190 degrees Celsius, more preferably to a temperature above about 200 degrees Celsius, and for a period of at least about 5 minutes. The discrete molten polyolefin phase can be separated from the ester solvent composition phase including dissolved Nylon 6 polymer component by, for example, skimming, decantation, filtration, centrifugation or combinations thereof. The Nylon 6 can be separated from the ester solvent composition by vaporization of the solvent composition. Alternatively, the ester solvent composition phase can be cooled to a temperature sufficient to precipitate the dissolved Nylon 6 polymer, preferably to a temperature below about 150 degrees Celsius, more preferably to a temperature below about 100 degrees Celsius. The cooling can be accomplished by simply lowering the temperature of the composition phase or by adding cool ester solvent to the phase. A miscible non-solvent can be added to the ester solvent composition phase, if desired, to change the solubility characteristics of the solvent phase and to aid in precipitation of the Nylon 6 polymer. The ester solvent composition can be separated from the precipitated Nylon 6 polymer by, for example, electrophoresis, sedimentation, flocculation, filtration, centrifugation, or combinations thereof. Similarly, post-consumer waste can be physically sorted to obtain a caφet waste composed exclusively of caφet pieces having only Nylon 6,6 face fibers. The Nylon 6,6 polymer component can be separated from the polyolefin polymer component of the caφet waste by admixing the commingled caφet waste with an ester solvent composition and heated to a temperature and for a period of time sufficient to dissolve at least a portion of the Nylon 6,6 fibers in the ester solvent composition and to form a separate discrete molten polyolefin phase. Preferably the admixture is heated to a temperature above about 215 degrees Celsius, more preferably to a temperature above about 220 degrees Celsius, and for a period of at least about 5 minutes. _^The discrete molten polyolefin phase and any undissolved matter suspended in the ester solvent composition can be separated from the ester solvent composition phase including the Nylon 6,6 polymer component by the aforementioned conventional means. The Nylon 6,6 can be separated from the ester solvent composition phase by vaporization of the solvent composition. Alternatively, the ester solvent composition phase can be cooled to a temperature sufficient to precipitate dissolved Nylon 6,6 polymer, preferably to a temperature below about 170 degrees Celsius, more preferably to a temperature below about 100 degrees Celsius. A miscible non-solvent can be added to the ester solvent composition phase, if desired, to change the solubility characteristics of the solvent phase and to aid in precipitation of the Nylon 6,6 polymer. The ester solvent composition can be separated from the precipitated Nylon 6,6 polymer by the aforementioned methods. Another exemplary practice of the present invention involves admixing commingled polyamide fibers and polypropylene fibers physically separated from post-consumer caφet waste with an ester solvent composition containing a cyclic ester, for example, propylene carbonate, ethylene carbonate, butylene carbonate or mixtures thereof, and esters produced by the decomposition of polyester, for example, poly (ethylene terephthalate), when it is heated in the presence of a cyclic ester to a temperature of about 215 degrees Celsius. The economics of the process of the present invention are improved by employing recycled polyester as a portion of the ester solvent composition. The polyamide portion, for example, Nylon 6 or Nylon 6,6, dissolved or suspended in the ester solvent composition phase can be recovered by precipitation of dissolved material upon cooling, followed by filtration and washing. Thus, the process of the present invention also allows recovery and recycling of polyester from post-consumer or post-industrial waste directly into useful industrial chemicals which can be employed as components of industrial solvents not only for separation of polyolefins from polyamides, but also for p poses such as paint and grease stripping. U.S. 4,118,187 (Sidebotham) and U.S. 4,137,393 (Sidebotham) employ solvents to selectively dissolve polyester from assortments of commingled fibers as a means of recovering unaltered polyester polymer of sufficient purity for reuse in polyester fiber production. One of the solvents named in these patents is the cyclic ester, propylene carbonate. U.S. 5,554,657 (Brownscombe) teaches the use of ethylene carbonate and propylene carbonate as solvents for polyester in the temperature range of 190 degrees to 200 degrees Celsius in an intricate process to recover polyester from a mixed polymer waste while maintaining the polyester polymer in polymer form. Cyclic esters, however, have been unexpectedly found to decompose dissolved polyester as the temperature of the solution is increased above about 215 degrees Celsius for a period of time, preferably at least about 3 minutes, more preferably at least 15 minutes, sufficient to cause decomposition of the polyester. This decomposition is evidenced by substantial reduction in the proportion of dissolved polyester that is recovered as precipitated polyester polymer upon cooling of the solution. For example, poly(ethylene terephthalate) has been observed to dissolve in l l propylene carbonate only at a temperature between about 190 and 200 degrees Celsius. No appreciable dissolution of fibers is observed below a temperature of about 180 degrees Celsius. It has been unexpectedly discovered that polyester dissolved in cyclic esters decomposes when the solution is heated above a temperature of about 215 degrees Celsius for at least 3 minutes to form a second ester solvent composition containing decomposed polyester. Upon cooling of the solution to ambient temperature, little or no precipitation of polyester polymer occurs. The polyester has been decomposed into monomeric and oligomeric units soluble in the cyclic ester solvent at ambient temperature. Thus, polyester extracted from polyester-rich waste streams by selective dissolution in a cyclic ester such as propylene carbonate or ethylene carbonate can be easily and immediately converted into a component of an industrial solvent by subjecting the polyester solution to increased temperature. Polyester can be extracted from a mixed polymer waste, such as commingled post-consumer or post-industrial polymer waste, by known techniques for dissolution in cyclic esters, solid- liquid separation may be necessary after dissolution of polyester but before decomposition of dissolved polyester depending upon the other constituents of the mixed polymer waste. The decomposed dissolved polyester composition is then cooled to a temperature below about 70 degrees Celsius upon which the composition may be separated from solid impurities by, for example, sedimentation, flocculation, filtration, centrifugation, or combinations thereof. Solid- liquid separation performed after decomposition of polyester is preferred to yield a solvent solution containing minimal suspended solids. In a further exemplary embodiment, the polyester component of commingled waste comprises polyester face fibers, such as poly(ethylene terephthalate) face fibers, from post-consumer caφet. The caφet face fibers are admixed with an initial ester solvent composition. The caφet face fibers may constitute, for example, between 2% and 50% by weight of the admixture. The admixture is heated to a temperature above about 220 degrees Celsius, preferably above about 230 degrees Celsius, for a period of at least 5 minutes, preferably at least 15 minutes, to form a second ester solvent composition. The second ester solvent composition is separated from solid polyester and impurities by, for example, electrophoresis, sedimentation, flocculation, filtration, centrifugation, or combinations thereof. The second ester solvent composition is then cooled to a temperature below about 50 degrees Celsius, preferably below about 30 degrees Celsius and more preferably to ambient temperature. The cooled second ester solvent composition is separated from precipitated solids by, for example, sedimentation, flocculation, filtration, centrifugation, or combinations thereof. An exemplary solvent for dissolution of poly(ethylene terephthalate) is propylene carbonate. Propylene carbonate is known to be useful as a component of industrial solvents. U.S. Patent Application 20030119686 (Machac, Jr.) describes the environmental and employee health and safety benefits to be realized by utilization of industrial solvents containing propylene carbonate as opposed to more volatile and toxic solvents. Employing polyester decomposition products as a significant component of industrial solvents also containing cyclic esters such as ethylene carbonate, propylene carbonate, butylene carbonate, and mixtures thereof, will reduce the cost of these solvent compositions and allow them to compete more easily with some of the traditional industrial solvents. In yet another aspect, two or more nylons, for example, Nylon 6 and Nylon 6,6, can be separated from a polyolefin, for example, from polypropylene. A commingled polymer mixture can contain Nylon 6, Nylon 6,6, polypropylene, and polyester. The commingled mixture can be admixed with a carbonate ester solvent, for example, with propylene carbonate. The solvent and mixture can be heated to between about 170°C and about 210°C. At that temperature polypropylene melts and the Nylon 6 and polyester dissolves in the propylene carbonate. The Nylon 6,6, however, remains substantially undissolved at this temperature. The solvent containing the dissolved Nylon 6 and polyester can then be separated from the remaining undissolved Nylon 6,6 and heated above about 215°C, at which temperature the polyester is decomposed. The Nylon 6 can be separated from the propylene carbonate, as described earlier. The Nylon 6,6 phase can then be admixed with a carbonate ester solvent, for example, propylene solvent, and heated to above about 220 °C. At that temperature, substantially all of the Nylon 6,6 dissolves in the propylene carbonate leaving a discrete molten polyolefin phase. Any insoluble impurities, if present, remain substantially undissolved at this temperature. The solvent containing the dissolved Nylon 6,6 can then be separated from the discrete molten polyolefin phase and any remaining insoluble impurities. The Nylon 6,6 can be separated from the propylene carbonate, as described. An advantage of the process of the present invention is the ability to separate polyamide polymers, for example, Nylon polymers, from polyolefin polymers using a safe, environmentally acceptable process to recover clean, relatively pure Nylon. The advantages also include the recovery and recycling polyester in the form of a decomposition product and its use as a significant component of industrial solvents, including ester solvent compositions suitable for separating polyamide polymers from polyolefin polymers. Further details regarding the invention are set forth in the non- limiting examples which follow. EXAMPLE 1 Propylene carbonate was added to a large heated and stirred glass laboratory vessel and heated to a temperature of 200 degrees Celsius. Fibers recovered from post-residential caφet composed of Nylon 6 face fibers and polypropylene fibers from the backing structure were slowly added to the hot propylene carbonate such that 50 grams of caφet fibers were admixed with 1000 grams of propylene carbonate. All evidence of fibers disappeared from the propylene carbonate within about 3 minutes of completion of fiber addition, and viscous globules could be observed floating in the propylene carbonate. Approximately 80% of the propylene carbonate was drained from the flask, cooled to about 80 degrees C. A particulate was filtered from the cooled propylene carbonate. The propylene carbonate was returned to the flask and reheated to 220 degrees C. whereupon an additional 50 grams of the same caφet fibers were added along with additional propylene carbonate to maintain an approximate proportion of 50 grams caφet fibers to 1000 grams of propylene carbonate. The particulate precipitate filtered from the cooled propylene carbonate was washed with methanol and dried. The above process was repeated until the volume of the viscous phase floating on the propylene carbonate phase was approximately 30% of the volume of the propylene carbonate phase, whereupon the entire contents of the flask were drained. The viscous phase cooled to form a hard mass which was identified as polypropylene. The washed and dried precipitate from the cooled propylene carbonate phase was analyzed by Differential Scanning Calorimetry and found to have the characteristics of pure crystalline Nylon 6 polyamide polymer. Multiple batches of washed and dried precipitate were collected, mixed with an equal amount of virgin Nylon 6 polymer, melted and extruded into Nylon 6 fiber that exhibited the tenacity expected of pure virgin Nylon 6 fiber. EXAMPLE 2 Poly(ethylene terephthalate) yarn was cut into approximately 3 inch lengths, weighed, and place into an Erlenmeyer flask. Propylene carbonate was added to the flask such that 25 grams of poly (ethylene terephthalate) was admixed with 100 grams of propylene carbonate. The Erlenmeyer flask was heated with gentle stirring on a hot plate. The polyethylene terephthalate) yarn was observed to be unaffected when the temperature of the admixture reached 180 degrees Celsius, but it had disappeared by the time the admixture had reached a temperature of 200 degrees Celsius. The admixture was further heated to a temperature of 220 degrees Celsius and held- at this temperature of 15 minutes. After the admixture was cooled to room temperature, it was filtered and the filtrate was weighted. Only 1.2 grams of solids were found in the admixture, thus approximately 95%> of the polyester had been decomposed into compounds soluble in the propylene carbonate at room temperature. The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

1. A method for separating the polyolefin component from the polyamide component of a post-consumer or post- industrial commingled waste containing both polyolefin and polyamide polymeric components comprising: (a) admixing the commingled waste with an ester solvent composition; (b) heating the admixture to a temperature above the melting temperature of the polyolefin component sufficient to dissolve at least a portion of the polyamide component of the commingled waste in the ester solvent composition and form a separate immiscible molten polyolefin phase; and (c) separating the ester solvent composition containing dissolved polyamide from the immiscible polyolefin phase.

2. A method for separating a polyolefin component from a polyamide component of a commingled polymer composition comprising:

(a) admixing the commingled polymer composition with an ester solvent composition comprising at least one cyclic ester, wherein the polyolefin is immiscible in the ester solvent composition;

(b) heating the admixture to a temperature above the melting temperature of the polyolefin component sufficient to dissolve at least a portion of the polyamide component of the commingled polymer composition in the ester solvent composition and to form a separate immiscible molten polyolefin phase; and

(c) separating the ester solvent composition containing dissolved polyamide from the immiscible polyolefin phase.

3. The method of claim 1 or 2 wherein in step (a) the ester solvent composition comprises about 98% to about 30%> by weight of the admixture.

4. The method of claim 1 or 2 wherein in step (a) the commingled waste is composed predominantly of Nylon 6 fibers commingled with polypropylene fibers.

5. The method of claim 1 or 2 wherein in step (a) the commingled waste is composed predominantly of Nylon 6,6 fibers commingled with polypropylene fibers. 6. The method of claim 5 wherein in step (b) the admixture is heated to a temperature above about 220 degrees Celsius to dissolve Nylon 6,

6.

7. The method of claim 1 or 2 wherein in step (a) the ester solvent composition is predominantly ethylene carbonate, propylene carbonate, butylene carbonate, or combinations thereof.

8. The method of claim 1 wherein in step (a) the ester solvent composition is predominantly propylene carbonate.

9. The method of claim 1 or 2 wherein in step (a) the ester solvent composition contains a cyclic ester and a decomposition product of polyester formed by heating the polyester in the presence of the cyclic ester to a temperature above about 215 degrees Celsius.

10. The method of claim 9 wherein the ester solvent composition contains propylene carbonate and a decomposition product of polyester formed by heating the polyester in the presence of propylene carbonate to a temperature above about 215 degrees Celsius.

11. The method of claim 8 or 9 wherein the polyester is poly (ethylene terephthalate).

12. The method of claim 1 wherein in step (b) the ester solvent composition contains dissolved polyamide polymer and suspended undissolved polyamide polymer separate from the immiscible molten polyolefin phase.

13. A method for separating the Nylon 6 polymer component from the polyolefin polymer component of commingled post-consumer caφet waste containing polyolefin and Nylon 6 polyamide fibers comprising: (a) admixing the commingled caφet waste with an ester solvent composition containing at least one cyclic ester; (b) heating the admixture to a temperature above about 190 degrees Celsius for a period of at least about 5 minutes to dissolve at least a portion of the Nylon 6 fibers in the ester solvent composition and form a separate discrete molten polyolefin phase; (c) separating the discrete molten polyolefin phase from the ester solvent composition by skimming, decantation, filtration, centrifugation, or combinations thereof; and (d) separating the ester solvent composition from dissolved Nylon 6 polymer.

14. The method of claim 13 wherein in step (a) the ester solvent composition containing at least one cyclic ester is propylene carbonate, ethylene carbonate, butylene carbonate, or mixtures thereof.

15. The method of claim 13 wherein in step (b) the admixture is heated to a temperature above about 200 degrees Celsius.

16. The method of claim 13 wherein in step (a) the commingled caφet waste constitutes between 2% and 50% by weight of the admixture.

17. The method of claim 13 wherein the post-consumer caφet waste containing polyolefin and Nylon 6 polyamide fibers contains polypropylene fibers derived from the caφet backing structure.

18. The method of claim 17 wherein the post-consumer caφet waste containing polyolefin and Nylon 6 fibers denotes the fibrous components of a pre- processed waste which process comprises physically sorting post-consumer waste to obtain a sorted caφet waste composed exclusively of caφet pieces containing only Nylon 6 face fibers, then separating the fibrous components of the sorted caφet waste from dirt and non-fibrous caφet backing components by shredding, cutting, grinding, washing, screening, air elutriation, particle size separation techniques, and combinations thereof.

19. A method for separating the Nylon 6,6 polyamide polymer component from the polyolefin polymer component of commingled post-consumer caφet waste containing polyolefin and Nylon 6,6 fibers comprising: (a) admixing the commingled caφet waste with an ester solvent composition containing at least one cyclic ester; (b) heating the admixture to a temperature above about 215 degrees Celsius for a period of at least about 5 minutes to dissolve at least a portion of the Nylon 6,6 fibers in the ester solvent composition and form a separate discrete molten polyolefin phase; (c) separating the discrete molten polyolefin phase from the ester solvent composition phase by skimming, decantation, filtration, centrifugation, or combinations thereof; and (d) separating the ester solvent composition from dissolved Nylon 6,6 polymer.

20. The method of claim 13 or 19 wherein after step (c) and before step (d) the ester solvent composition is cooled to a temperature to precipitate dissolved Nylon polymer and then in step (d) the cooled ester solvent is separated from the precipitated Nylon polymer by electrophoresis, sedimentation, flocculation, filtration, centrifugation, or combinations thereof.

21. The method of claim 19 wherein in step (a) the ester solvent composition is propylene carbonate, ethylene carbonate, butylene carbonate, or mixtures thereof.

22. The method of claim 19 wherein in step (b) the admixture is held at a temperature above about 215 degrees Celsius for a period of at least about 15 minutes.

23. The method of claim 19 wherein in step (d) the ester solvent composition is cooled to a temperature below about 100 degrees Celsius.

24. The method of claim 19 wherein the post-consumer caφet waste containing polyolefin and Nylon 6,6 polyamide fibers contains polypropylene fibers derived from the caφet backing structure.

25. The method of claim 24 wherein the post-consumer caφet waste containing polyolefin and Nylon 6,6 fibers denotes the fibrous component of a pre- processed waste which process comprises physically sorting post-consumer waste to obtain a sorted caφet waste composed exclusively of caφet pieces containing only Nylon 6,6 face fibers, separating the fibrous component of the sorted caφet waste from dirt and non-fibrous caφet backing components by shredding, cutting, grinding, washing, screening, air elutriation, particle size separation techniques, and combinations thereof.

26. The method of claim 19 wherein in step (a) the ester solvent composition is propylene carbonate.

27. The method of claim 1 wherein in step (c) the ester solvent composition containing dissolved polyamide and the immiscible polyolefin phase are cooled prior to separation to form an ester composition containing suspended polyamide and a separate solid polyolefin mass.

28. The method of claim 1 or 2, wherein the polyamide component is one or more nylons.

29. A method for separating a Nylon 6 polymer component from a polyolefin polymer component of commingled polymer composition comprising:

(a) admixing the commingled polymer composition with a carbonate ester solvent composition;

(b) heating the admixture to a temperature above about 190 degrees Celsius to dissolve at least a portion of the Nylon 6 polymer component in the carbonate ester solvent composition and form a separate discrete molten polyolefin phase; and

(c) separating the discrete molten polyolefin phase from the carbonate ester solvent composition phase.

30. The method of claim 29 wherein the admixture is heated to a temperature above about 200 degrees Celsius.

31. The method of claim 29, wherein the commingled polymer composition comprises between 2% and 50% by weight of the admixture.

32. The method of claim 29, wherein the commingled polymer composition comprises polypropylene.

33. The method of claim 29, wherein the carbonate ester solvent comprises propylene carbonate, ethylene carbonate, butylene carbonate or combinations thereof.

34. The method of claim 30, wherein the commingled polymer composition comprises caφet.

35. A method for separating a Nylon 6,6 polyamide component from a polyolefin polymer component of commingled polymer composition comprising: (a) admixing the commingled polymer composition with a carbonate ester solvent composition to form an admixture; (b) heating the admixture to a temperature above about 215 degrees

Celsius to dissolve at least a portion of the Nylon 6,6 fibers in the carbonate ester solvent composition and to form a separate discrete molten polyolefin phase; and (c) separating the discrete molten polyolefin phase from the carbonate ester solvent composition.

36. A method for separating Nylon 6 polymer and Nylon 6,6 polymer from a commingled polymer mixture also containing a polyolefin, comprising: a) admixing the commingled polymer mixture with an ester solvent composition; b) heating the admixture to a temperature between about 170°C and about 210°C for a period of time to dissolve at least a portion of the Nylon 6 polymer leaving Nylon 6,6 polymer in the commingled polymer mixture undissolved; c) separating the ester solvent composition including dissolved Nylon 6 polymer from undissolved Nylon 6,6 polymer and the polyolefin; d) separating the ester solvent composition from the dissolved Nylon 6; e) admixing the undissolved Nylon 6,6 polymer and polyolefin with an ester solvent composition; f) heating the admixture of Nylon 6,6 polymer and ester solvent composition to a temperature above about 215°C for a period of time to dissolve at least a portion of the Nylon 6,6 polymer and form a separate discrete molten polyolefin phase; g) separating the discrete molten polyolefin phase from the ester solvent composition including the dissolved Nylon 6,6 polymer; and h) separating the dissolved ester solvent composition from the dissolved Nylon 6,6.

37. The method of claim 37 wherein the commingled polymer mixture further includes polyester polymer, step (b) includes dissolving polyester polymer along with Nylon 6 polymer, and step (c) includes separating the ester solvent composition including dissolved Nylon 6 polymer and dissolved polyester polymer from the undissolved Nylon 6,6 and polyolefin and then heating the ester solvent composition including dissolved Nylon 6 and polyester polymers to a temperature above about 215°C for a period of time to decompose dissolved polyester polymer.

38. A polyolefin composition produced_by (a) admixing a commingled polymer composition comprising polyolefin and polyamide-with a carbonate ester solvent composition to form an admixture; (b) heating the admixture to a temperature above the melting temperature of the polyolefin sufficient to dissolve at least a portion of the polyamide and to form a separate immiscible molten polyolefin phase; and (c) separating the polyolefin from the dissolved polyamide and carbonate ester solvent composition.

39. A polyamide composition produced by (a) admixing a commingled polymer composition comprising polyolefin and polyamide with an ester solvent composition to form an admixture; (b) heating the admixture to a temperature above the melting temperature of the polyolefin sufficient to dissolve at least a portion of the polyamide and to form a separate immiscible molten polyolefin phase; and (c) separating the immiscible polyolefin phase from the admixture.

40. A method for decomposing the polyester component of a commingled post-consumer or post-industrial waste into monomeric and oligomeric units constituting a portion of an ester solvent composition comprising; (a) admixing the commingled waste with an initial ester solvent composition containing at least one cyclic ester; (b) heating the admixture to a temperature above about 215 degrees

Celsius for a period of at least 3 minutes to form a second ester solvent composition; (c) cooling the second ester solvent composition to a temperature below about 70 degrees Celsius; and (d) separating the second ester solvent composition from solid impurities by sedimentation, flocculation, filtration, centrifugation, or combinations thereof.

41. The method of claim 40 wherein in step (a) the initial ester solvent composition comprises about 98% to about 30%o by weight of the admixture.

42. The method of claim 40 wherein the polyester materials constitute poly(ethylene terephthalate) materials physically separated from post-consumer or post-industrial waste.

43. The method of claim 40 wherein in step (b) the admixture is held at a temperature above about 215 degrees Celsius for a period of at least 15 minutes.

44. The method of claim 40 wherein in step (a) the initial ester solvent composition is constituted principally of ethylene carbonate, propylene carbonate, butylene carbonate, or combinations thereof.

45. The method of claim 40 wherein in step (a) the initial ester solvent composition is constituted principally of propylene carbonate.

46. A method for decomposing poly(ethylene terephthalate) face fibers from post-consumer caφet into components of a liquid ester solvent composition comprising: (a) admixing the poly(ethylene terephthalate) face fibers with an initial carbonate ester solvent composition; (b) heating the admixture to a temperature above about 220 degrees

Celsius for a period of at least about 5 minutes to form a second ester solvent composition; (c) separating the second ester solvent composition from solid polyester and impurities by electrophoresis, sedimentation, flocculation, filtration, centrifugation, or combinations thereof; (d) cooling the second ester solvent composition to a temperature below about 30 degrees Celsius; and (e) separating the cooled second ester solvent composition from precipitated solids by electrophoresis, sedimentation, flocculation, filtration, centrifugation, or combinations thereof.

47. The method of claim 46 wherein in step (a) the solvent is propylene carbonate, ethylene carbonate, butylene carbonate or mixtures thereof.

48. The method of claim 46 wherein in step (a) the poly (ethylene terephthalate) face fibers constitute between 2% and 50%> by weight of the admixture.

49. A method for decomposing polyester into compounds having an appreciable solubility in cyclic esters at about 30 degrees Celsius and constituting a component of a liquid ester solvent composition comprising: (a) admixing polyester with ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof; (b) heating the admixture to a temperature above about 220 degrees Celsius for a period of at least about 5 minutes to form an ester solvent composition; (c) separating the ester solvent composition from solid polyester and impurities by sedimentation, flocculation, filtration, centrifugation, or combinations thereof; (d) cooling the ester solvent composition to a temperature below about 50 degrees Celsius; and (e) separating the cooled ester solvent composition from precipitated solids by sedimentation, flocculation, filtration, centrifugation, or combinations thereof.

50. The method of claim 49 wherein in step (a) polyester is admixed with propylene carbonate.

51. The method of claim 49 wherein in step (b) the admixture is held at a temperature above about 220 degrees Celsius for a period of more than about 15 minutes.

52. The method of claim 49 wherein in step (d) the ester solvent composition is cooled to ambient temperature.

53. The method of claim 39, 46 or 49 wherein in step (b) the admixture is heated to a temperature above about 230 degrees Celsius.

54. Chemical compositions employed as solvents containing: at least (1) a decomposition product of poly( ethylene terephthalate) polyester; and (2) one or more cyclic esters.

55. Chemical compositions employed as solvents containing as one component compounds resulting from the thermal degradation of poly(ethylene terephthalate) dissolved in ethylene carbonate, propylene carbonate, butylene carbonate, or mixtures thereof.

56. The polyamide composition of claim 39, wherein the ester solvent composition is propylene carbonate.

57. The method of claim 1, wherein the post-consumer or post- industrial commingled waste further comprises a polyester.