Methods for recycling polyamide compositions

Abstract

A method for recycling a polyamide composition includes pretreating a polyamide composition comprising a polyamide to produce a polyamide oligomer composition comprising a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition. The method can also include exposing the polyamide oligomer composition to ammonolysis to produce a polyamide precursor composition comprising a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 452,774, filed on 17 March 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] (Field of Invention) This disclosure relates to a method for recycling thermoplastic polymers. The method includes a pretreatment step for obtaining a low molecular weight oligomer intermediate product from a nylon-containing feed. [Background technology]

[0003] Reducing the amount of scrap material generated from plastics after consumer and / or industrial use, which ultimately ends up in landfills, is becoming increasingly important. In most cases, consumer goods made from plastic components are disposed of in landfills or incinerators after their useful life has ended. Efforts are being made to develop several technologies to break down materials into their constituent components for reuse / recycling. In-kind recycling and take-back programs are beginning to emerge. However, circularity does not currently exist. The thermoplastic materials industry has a significant gap in achieving circularity and requires a consistent approach. There is still a need in the plastic recycling industry to devise practical methods for recycling polyamides such as nylon 6, nylon 66, nylon 56, nylon 46, nylon 610, or nylon 612. [Overview of the Initiative]

[0004] Various aspects of the present invention provide a method for recycling polyamide compositions. The method includes pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer composition containing a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition. The method also includes exposing the polyamide oligomer composition to ammonolisis to produce a polyamide precursor composition containing a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition.

[0005] Various aspects of the present invention provide a method for recycling polyamide compositions. The method comprises pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer composition containing a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes enzymatic treatment, subcritical water treatment, microwave treatment, or a combination thereof. The method also comprises exposing the polyamide oligomer composition to ammonolisis to produce a polyamide precursor composition containing a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition.

[0006] Various aspects of the present invention provide methods for recycling polyamide compositions. The method includes separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide starting composition having 5% by weight or less of non-polyamide components. The method also includes mechanically treating the polyamide starting composition to produce a polyamide composition in which the polyamide composition contains 5% by weight or less of non-polyamide components. The method also includes pre-treating a polyamide composition containing polyamide to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes hot water treatment, subcritical water treatment, supercritical water treatment, microwave treatment, enzymatic treatment, solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof. The method also includes exposing the polyamide oligomer composition to ammonolisis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition.

[0007] Various aspects of the present invention provide polyamides formed from polyamide precursor compositions for methods of recycling polyamide compositions.

[0008] Various aspects of the present invention provide a method for recycling polyamide compositions. The method involves pre-treating a polyamide composition containing polyamides to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamides in the polyamide composition, wherein the pre-treatment includes enzymatic treatment.

[0009] Various aspects of the present invention provide a method for recycling polyamide compositions. The method includes separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide starting composition having 5% by weight or less of non-polyamide components. The method also includes mechanically treating the polyamide starting composition to produce a polyamide composition in which the polyamide composition has 5% by weight or less of non-polyamide components. The method also includes pre-treating a polyamide composition containing polyamide to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes enzymatic treatment.

[0010] Various aspects of the present invention provide polyamides formed from polyamide oligomer compositions for methods of recycling polyamide compositions.

[0011] Various embodiments of the method of the present disclosure may have advantages over other methods for recycling polyamide compositions. For example, in various embodiments, the method generates tar-like or high-molecular-weight side products at lower concentrations and is more selective for the generation of low-molecular-weight oligomeric intermediates than other methods for recycling polyamide compositions, resulting in easier processing and higher yields. In various embodiments, the pretreatment step of the present disclosure may be more selective for generating low-molecular-weight oligomeric intermediates than other methods for recycling polyamide compositions. In various embodiments, the method of the present disclosure solves the problem of pyrolysis product formation (e.g., tar and high-molecular-weight side products) during polyamide recycling via ammonolysis by incorporating a pretreatment step of the disclosure that pre-decomposes the polyamide into a polyamide oligomer composition before ammonolysis, thereby providing easier processing and increased yields. In various embodiments, the methods of the present disclosure involve milder ammonialysis (e.g., having lower temperatures, lower pressures, lower corrosion conditions, or a combination thereof) than other methods for recycling polyamide compositions, thereby reducing the generation of undesirable by-products.

[0012] In various embodiments, the disclosed enzymatic treatment may be more specific (selective) to the formation of polyamide oligomers than currently available chemical or thermal decomposition methods. For example, the disclosed enzymatic treatment can produce crude products with lower concentrations of tar or high molecular weight byproducts compared to other polyamide composition recycling methods, for example, chemical or thermal decomposition steps operated at high temperature or high pressure.

[0013] The drawings generally illustrate various aspects of the present invention as examples, not limitations. [Brief explanation of the drawing]

[0014] [Figure 1] This is a simplified block flow diagram illustrating an aspect of the disclosed method. [Figure 2]This is a simplified block flow diagram illustrating an aspect of the disclosed method. [Figure 3] This is a simplified block flow diagram illustrating an aspect of the disclosed method. [Figure 4] This is a simplified block flow diagram illustrating an aspect of the disclosed method. [Modes for carrying out the invention]

[0015] Herein, we refer in detail to specific aspects of the subject matter to be disclosed. The subject matter to be disclosed is described in conjunction with the enumerated claims, but it will be understood that the exemplary subject matter is not intended to limit the claims to the subject matter to be disclosed.

[0016] Throughout this document, please understand that values ​​expressed in range form should be interpreted flexibly to include not only the numerical values ​​explicitly listed as limits to the range, but also all individual numerical values ​​or subranges contained within that range, as if each numerical value and subrange were explicitly listed. For example, the range "approximately 0.1% to approximately 5%" or "approximately 0.1% to approximately 5%" should be interpreted to include not only approximately 0.1% to approximately 5%, but also individual values ​​(e.g., 1%, 2%, 3%, and 4%) and subranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, and 3.3% to 4.4%) within the indicated range. The notation "approximately X to Y" has the same meaning as "approximately X to approximately Y" unless otherwise specified. Similarly, the notation "approximately X, Y, or approximately Z" has the same meaning as "approximately X, approximately Y, or approximately Z" unless otherwise specified.

[0017] As used in this document, the terms "a", "an", or "the" are used to include one or more than one, unless the context clearly dictates otherwise. The term "or" is used to refer to a non-exclusive "or" unless otherwise indicated. The recitation of "at least one of A and B" or "at least one of A or B" has the same meaning as A, B, or A and B. In addition, it should be understood that the phraseology or terminology employed in the present specification and not otherwise defined is for the purpose of description only and is not intended to be limiting. Any use of section headings is intended to aid the reading of the document and should not be construed as limiting. Information associated with a section heading may occur within or outside that particular section.

[0018] In the methods described in the present specification, acts may be performed in the specific order listed herein. Alternatively, in any of the aspects disclosed herein, the specific acts may be performed in any order without departing from the principles of the present invention, unless a temporal or operational order is explicitly recited. Further, the specified acts may be performed concurrently, unless explicitly detailed in the language of the claims to be performed separately, or the language of the claims requires otherwise. For example, a claimed act of performing X and a claimed act of performing Y may be carried out simultaneously in a single operation, and the resulting process is included within the literal scope of the claimed process.

[0019] As used in the present specification, the term "about" can allow for variability in a value or range, for example, within 10%, within 5%, or within 1% of the stated value or the limits of the stated range, and includes the exact stated value or range.

[0020] As used herein, the term "substantially" refers to the majority or nearly all, such as at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%. As used herein, the term "substantially free" can mean that the amount of the material present is absent or present in a negligible amount such that it does not affect the material properties of the composition comprising the material, such that about 0 wt% to about 5 wt% of the composition is the material, or about 0 wt% to about 1 wt%, or about 5 wt% or less, or about 4.5 wt%, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, less than 0.01, equal to or more than those, or about 0.001 wt% or less, or about 0 wt%.

[0021] As used herein, the term "polymer" refers to a molecule having at least one repeating unit, and may include copolymers.

[0022] As used herein, the terms "polyamide" and "nylon" are interchangeable and define a class of thermoplastic polymers. Examples of polyamides or nylons include polyamide 46, polyamide 56, polyamide 66, polyamide 7, polyamide 610, polyamide 12, polyamide 612, polyamide 1212, and the like. A method of recycling a polyamide composition.

[0023] Various aspects of the present invention provide methods of recycling a polyamide composition. The method includes pretreating a polyamide composition comprising a polyamide to produce a polyamide oligomer composition comprising polyamide oligomers having a lower molecular weight than the polyamide in the polyamide composition. The method can also include exposing the polyamide oligomer composition to ammonolysis to produce a polyamide precursor composition comprising polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition.

[0024] Polyamide compositions can be homogeneous compositions. Homogeneous compositions can include solids of uniform size, semi-solid slurries, slurry solutions, homogenized liquid solutions of dissolved polymers, or combinations thereof. Polyamide compositions can be particulate compositions. The particles can have any preferred shape, such as round particles, irregular particles, strips, or combinations thereof. The particles may be less than 100 mm, less than 50 mm, less than 5 mm, or less than 1 mm. 50 The particles may have a specific size. This method may include mechanically treating a polyamide starting composition to form a polyamide composition. The polyamide starting composition may have the same composition as the polyamide composition. The mechanical treatment may include size reduction, cutting, grinding, shredding, particle formation, or a combination thereof. For example, the mechanical treatment may produce a homogeneous composition and / or particulate composition.

[0025] This method may include separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide composition having 5% by weight or less of non-polyamide components. The separation may include melting point separation, staining test separation, electrostatic separation, flotation separation, molten phase separation, hydrohydraulic technique, thermal melting technique, cold melting technique, selective melting technique, or a combination thereof. In some embodiments, the separation may include flotation separation in water. Separation of a mixed plastic stream can remove thermosetting polymers, polyesters, polyolefins, polycarbonates, or combinations thereof from the polyamide in the mixed plastic stream. For example, separation of a mixed plastic stream can remove PET, LDPE, LLDPE, PP, PVC, ABS rubber, polyacrylate, or combinations thereof from the polyamide in the mixed plastic stream.

[0026] The polyamide may be reinforced (e.g., glass fiber reinforced polyamide) or may be substantially free of reinforcement. The polyamide is a condensed polyamide. An example of a suitable condensed polyamide is the condensation product of adipic acid and hexamethylenediamine, commonly known as nylon 66 or poly-(hexamethylene adipamide). Another example of a suitable condensed polyamide is the condensation product of caprolactam, commonly known as nylon 6 or poly-(caprolactam). Yet another example of a suitable condensed polyamide is the condensation product of adipic acid and pentamethylenediamine, commonly known as nylon 56 or poly-(pentamethylene adipamide). The condensation product of sebaciic acid and hexamethylenediamine, commonly known as nylon 610 or poly-(hexamethylene sebakamid), is another example of a suitable condensed polyamide. Other condensed polyamides can be produced by changing the chain length and composition of the organic dibasic acid and diamine to create a variety of condensed polyamides with properties suited to various end applications.

[0027] The polyamide in the polyamide composition may include any preferred polyamide or nylon. For example, the polyamide in the polyamide composition may include N4, N5, N6, N7, N10, N11, N12, N46, N56, N66, N610, N612, or combinations thereof. The polyamide in the polyamide composition may include N6, N66, N56, N610, or combinations thereof. The polyamide in the polyamide composition may include N66. In various embodiments, the polyamide in the polyamide composition may include N4, N5, N6, N7, N10, N11, N12, N46, N56, N66, N610, N612, or combinations thereof, and the polyamide composition may substantially contain no other polyamides. The polyamide may be 80% to 100% by weight of the polyamide composition, or 95% to 100% by weight, or 98% to 100% by weight, or 100% or less and 80% or more by weight, and less than 82, 84, 86, 88, 90, 92, 94, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99, 99.2, 99.4, 99.6, 99.8, or less than 99.9% by weight, or the same as or greater than those amounts.

[0028] This method involves pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer composition containing a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition. The pre-treatment can depolymerize the nylon polymer into its corresponding oligomer intermediate component. The depolymerization may be partial (e.g., mild) so that mainly oligomers rather than monomers are formed. The pre-treatment can include hot water treatment, subcritical water treatment, supercritical water treatment, microwave treatment, enzymatic treatment, solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof. The pre-treatment can include solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof. The pre-treatment can include enzymatic treatment, subcritical water treatment, microwave treatment, or a combination thereof. The pre-treatment can be carried out over any suitable period of time. The pretreatment can be carried out over a period of 15 hours or less, for example, 1 minute to 15 hours, or 1 hour to 15 hours, or 5 hours to 15 hours, or 15 hours or less and 1 minute or more and less than, equal to, or exceeding 5 minutes, 10, 20, 30, 40, 50 minutes, 1 hour, 1.5, 2, 4, 6, 8, 10, 12, or 14 hours. In various embodiments, the resulting polyamide oligomer composition is d of the polyamide composition supplied for pretreatment. 50 d is at least 10 times lower 50 It may have a molecular weight. In various embodiments, the polyamide can be washed or otherwise purified to remove various impurities before pretreatment.

[0029] Pretreatment may include enzymatic treatment. In some embodiments, the enzymatic treatment may be the enzymatic treatment described by Sudhakar et al. in International Biodeterioration & Biodegradation, Vol. 60, pp. 144-151 (2007) (the whole of which is incorporated herein by reference), in which the degradation of nylon 6 and 66 was demonstrated under immersion concentration conditions in a mineral salt medium at 35°C and pH 7.5, with the polymer as the sole carbon source. Table 1 by Sudhakar et al. provides a literature summary of similar microbial degradation of nylon 66 and 6. Such process steps may be included in the pretreatment as described herein.

[0030] Enzyme treatment can be carried out at temperatures between 15°C and 45°C, or between 20°C and 30°C, or between 45°C and 15°C and below, and below, equal to, or above, 16, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 34, 36, 38, 40, 42, or 44°C. Enzyme treatment can be carried out at pressures between 0.5 atm and 2 atm, or between 1 atm and 1.5 atm, or between 2 atm and 0.5 atm and below, and below, equal to, or above, 0.6 atm, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9 atm. Enzymatic treatment can be carried out at a pH of approximately 5 to approximately 9, for example, 9 or less and 5 or more, and 5.5, 6, 6.5, 7, 7.5, 8, 8.5, or less than, equal to, or greater than 9. In one embodiment, the enzymatic treatment can be carried out in a vessel that does not require an ASTM pressure rating. The enzymatic treatment can produce a product with low concentrations of tar (e.g., a high molecular weight by-product).

[0031] The pretreatment may include subcritical water treatment. Subcritical water treatment may include treatment with water having a temperature of 200°C to less than 373.9°C, or 200°C to 300°C, or less than 373.9°C and 200°C or higher, and less than, equal to, or exceeding 210°C, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, or 370°C. Subcritical water treatment may include treatment with water having a pressure of 20 atm to 217.8 atm, or 40 atm to 100 atm, or 217.8 atm or less and 20 atm or more, and less than, equal to, or exceeding 30 atm, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, or 210 atm. In one embodiment, subcritical water conditions may include a temperature of about 250 to 300°C and a pressure range of about 65 to 75 atm, as well as treatment for 0.5 to 6 hours.

[0032] Pretreatment may include microwave treatment. Microwave treatment may include exposure to microwave energy in a solvent at a temperature of 100°C to 500°C, or 150°C to 250°C, or 500°C or less and 100°C or more, and less than, equal to, or exceeding 120°C, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 280, 300, 350, 400, or less than, equal to, or greater than 450°C. Microwave treatment can be carried out at pressures of 1 atm to 1,000 atm, or 20 atm to 80 atm, or 1,000 atm or less and 1 atm or more, and less than, equal to, or greater than 10 atm, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 250, 300, 400, 500, 600, or 800 atm. The solvent may be any suitable solvent such as an alcohol or glycol such as methanol or ethylene glycol. In one embodiment, microwave treatment may include a temperature of about 190 to 250°C and a pressure range of about 20 to 100 atm, as well as a treatment time of 0.1 to 3 hours.

[0033] In yet another embodiment, approximately 10% by weight of nylon 66 in water can be partially hydrolyzed at 270°C and 57 atm for approximately 1 hour to produce a sufficient oligomer that is 80% soluble in boiling water. Partial nylon hydrolysis can also be carried out in the presence of a heterogeneous acid catalyst, such as the strong acid Amberlyst® resin.

[0034] The polyamide oligomer composition contains a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition. The polyamide oligomer composition may contain dimers, trimers, tetramers, higher oligomers, or combinations thereof. The polyamide oligomer composition may have molecular weights of 200 g / mol to 3,000 g / mol, 200 g / mol to 3,000 g / mol, 300 g / mol to 2,800 g / mol, 400 g / mol to 2,500 g / mol, 500 g / mol to 2,000 g / mol, 500 g / mol to 1,800 g / mol, or 500 g / mol to 1,500 g / mol, or 3, The polyamide oligomer may contain a number-average molecular weight of less than or equal to 000 g / mol and greater than or equal to 500 g / mol, and less than, equal to, or greater than 600 g / mol, 700, 800, 900, 1,000, 1,100, 1,200, 1,300, 1,400, 1,500, 1,600, 1,700, 1,800, 2,000, 2,200, 2,400, 2,600, or 2,800 g / mol. The method may further include dehydrating the polyamide oligomer composition to remove water therefrom.

[0035] The method may also include exposing a polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition. Ammonialysis may include contacting the polyamide oligomer composition with a nitrogen source. The nitrogen source may be any suitable nitrogen source for ammonialysis, such as gaseous ammonia, liquid ammonia, dissolved ammonia, ammoniacal solution, and ammonia enrichment medium, or a combination thereof. The nitrogen source may include gaseous ammonia. Ammonialysis may include contacting the polyamide oligomer composition with a nitrogen source at a reaction temperature of 200°C to 350°C, or 350°C or less and 200°C or more and less than, equal to, or greater than 210°C, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, or 340°C. Ammonolisis may include contacting a polyamide oligomer composition with a nitrogen source at a reaction pressure of 500 to 2,000 Psig (34 to 136 atm), or between 140 atm and 30 atm and less than, equal to, or greater than 40 atm, 50, 60, 70, 80, 90, 100, 110, 120, or 130 atm. The method may further include recovering, purifying, and recycling the unreacted nitrogen source for reuse in ammonolisis.

[0036] Ammonolithesis of nylon 66 polymers produces a mixture of two oligomers, one containing an amide group and the other an amine group. The amide group undergoes dehydration or nitrification to nitrile under reaction conditions. The ammonolithesis reaction is chemically equilibrium-limited and facilitated by high concentrations of ammonia (nitrogen source), removal of the volatile HMD ultimately formed by stripping with excess ammonia, and conversion of the amide to nitrile. Nitrilation is also chemically equilibrium-limited and facilitated by the removal of water and ADN from the reaction mixture. Ammonolithesis of nylon 6 mainly produces caprolactam (CPLM), aminocapronitrile (ACN or N112), and 6-aminocaproamide (ACAM). However, cyclic dimers can also be formed under reaction conditions, and the nitrile group is also active in the formation of undesirable by-products.

[0037] During ammonialysis, the thermal decomposition of amide, acid, nitrile, and amine components present in the system can generate tar, CO2, and many other undesirable byproducts. The generation of tar-like decomposition materials is highly undesirable in any chemical reaction system. These materials not only reduce the desired product yield but also pose operational and processing difficulties. The method of this disclosure solves this problem of thermal decomposition product formation during nylon recycling by ammonialysis. The ammonialysis of low molecular weight oligomer / monomer intermediates obtained from partial nylon depolymerization pretreatment according to this disclosure can yield excellent ammonialysis performance in terms of monomer yield and ease of processing. The generation of high molecular weight tar-like materials can be reduced, thereby improving the overall product yield.

[0038] The polyamide precursor composition may contain polyamide monomers, polyamide oligomers, or combinations thereof. The polyamide precursor composition may contain polyamide monomers and may substantially not contain polyamide oligomers. The amount of polyamide monomers in the polyamide precursor composition may be 0% to 100% by weight or 1% to 100% by weight, or 90% to 100% by weight, or 100% or less and 80% or more by weight, and less than, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% by weight, equal to, or greater than, those amounts. The polyamide precursor composition may contain any suitable polyamide monomer corresponding to the polyamide exposed to this method, such as hexamethylene diamine (HMD), aminocapronitrile, 6-aminocaproamide, dimethyl adipate, adipic acid, methyl 6-aminocaproate, or combinations thereof.

[0039] This method may further include purifying, cleaning, or separating one or more components of a polyamide precursor composition.

[0040] This method may further include polymerizing a polyamide precursor composition or one or more components thereof to form one or more polyamides.

[0041] Various aspects of the present invention provide a method for recycling polyamide compositions that can be carried out without ammonolisis. The method involves pre-treating a polyamide composition containing polyamides to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamides in the polyamide composition, wherein the pre-treatment may include enzymatic treatment. The polyamides in the polyamide composition may include N4, N5, N6, N7, N10, N11, N12, N46, N56, N66, N610, N612, or combinations thereof. The polyamides may be 95% to 100% by weight, or 98% to 100% by weight, or 100% or less and 80% or more by weight and 82%, 84, 86, 88, 90, 92, 94, 95, 96, 97, 98, 99, or less than 99.9% by weight of the polyamide composition, equal to or greater than those amounts. Enzyme treatment can be carried out at temperatures between 15°C and 45°C, 20°C and 30°C, or below 45°C and above 15°C, and below 16, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 34, 36, 38, 40, 42, or 44°C, equal to or above these temperatures, and at pressures between 0.5 atm and 2 atm, or between 1 atm and 1.5 atm, or below 2 atm and above 0.5 atm and below 0.6 atm, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or below 1.9 atm, equal to or above these pressures. Enzymatic treatment can be carried out at a pH of approximately 5 to 9, for example, 9 or less and 5 or more, and less than, equal to, or greater than 5.5, 6, 6.5, 7, 7.5, 8, or 8.5. Enzymatic treatment can be carried out for 15 hours or less, for example, 1 minute to 15 hours, or 1 hour to 15 hours, or 5 hours to 15 hours, or 15 hours or less and 1 minute or more, and less than, equal to, or greater than 5 minutes, 10, 20, 30, 40, 50 minutes, 1 hour, 1.5, 2, 4, 6, 8, 10, 12, or 14 hours. Polyamide oligomer compositions may include dimers, trimers, tetramers, higher oligomers, or combinations thereof.The polyamide oligomer composition may contain a number average molecular weight of polyamide oligomers equal to, or greater than, 200 g / mol to 3,000 g / mol, or 500 g / mol to 1,500 g / mol, or 3,000 g / mol or less and 500 g / mol or more and less than 600 g / mol, 700, 800, 900, 1,000, 1,100, 1,200, 1,300, 1,400, 1,500, 1,600, 1,700, 1,800, 2,000, 2,200, 2,400, 2,600, or less than, equal to, or greater than, 2,800 g / mol. This method may further include dehydrating the polyamide oligomer composition. This method may further include polymerizing the polyamide oligomer composition to form one or more polyamides therefrom.

[0042] This method may further include mechanically processing a polyamide starting composition to form a polyamide composition, for example, to form a homogeneous composition and / or a particulate composition. This method may further include separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide composition having 5% by weight or less of non-polyamide components.

[0043] In various embodiments, the method for recycling a polyamide composition, including enzymatic treatment, does not need to include ammonialysis. In other embodiments, the method includes exposing a polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition. Ammonialysis may include contacting the polyamide oligomer composition with a nitrogen source. The nitrogen source may include gaseous ammonia, liquid ammonia, soluble ammonia, ammoniacal solutions, and ammonia-enriched media, or a combination thereof. The nitrogen source may be gaseous ammonia. Ammonolisis may include contacting a polyamide oligomer composition with a nitrogen source at a reaction temperature of 200°C to 350°C, or 350°C or less and 200°C or more and less than 210°C, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, or 340°C, equal to or greater than these, and a reaction pressure of 500 to 2,000 Psig (34 to 136 atm), or 140 atm or less and 30 atm or more and less than 40 atm, 50, 60, 70, 80, 90, 100, 110, 120, or 130 atm, equal to or greater than these. The method may further include recovering, purifying, and recycling the unreacted nitrogen source for reuse in ammonolisis. This method may further include polymerizing a polyamide precursor composition to form one or more polyamides.

[0044] The disclosed method proposes a practical solution for recycling nylon polymers. The disclosed method may be effective in depolymerizing various nylon components present in a mixed plastic stream into their corresponding monomer components. Further recovery and purification of these monomers yields high-purity products suitable for reuse by recycling them back to nylon production facilities. For example, nylon 66 can be treated in the disclosed method to produce purified hexamethylenediamine and adipic acid. Nylon 6 can be treated in the disclosed method to produce caprolactam. In one example, nylon 56 can be treated in the disclosed method to produce purified pentamethylenediamine and adipic acid. These monomers can be reused in the process of producing these nylons. Therefore, the disclosed method is beneficial in reducing landfill mass and, at the same time, providing the nylon industry with circularity and carbon footprint optimization. polyamide.

[0045] Various aspects of the present invention provide polyamides formed from polyamide precursor compositions or polyamide oligomer compositions formed by the method of the present disclosure for recycling polyamide compositions.

[0046] In various embodiments, polyamides can be formed from polyamide precursor compositions formed by a method that includes pre-treating a polyamide-containing polyamide composition to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamide in the polyamide composition. The method may also include exposing the polyamide oligomer composition to ammonolisis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition.

[0047] In various embodiments, the polyamide can be formed from a polyamide oligomer composition formed by pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes enzymatic treatment.

[0048] In various embodiments, the polyamide can be formed from a polyamide precursor composition, which involves pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer composition containing a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes enzymatic treatment. The method also includes exposing the polyamide oligomer composition to ammonolisis to produce a polyamide precursor composition containing a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition. [Examples]

[0049] Various aspects of the present invention can be better understood by referring to the following examples provided by illustration. The present invention is not limited to the examples described herein.

[0050] Abbreviations. Adipic acid (AA); aminocapronitrile (ACN); aminocaproamide (ACAM); adiponitrile (ADN); bis-hexamethylene triamine (BHMT); dimer of caprolactam (CLDIM); caprolactam (CPLM); cyanovaleramide (CVAM); dimer of aminocapronitrile and aminocaproamide (DNAC); hexamethylenediamine (HMD); hexamethyleneimine (HMI); polycaprolactam, polyamide 6, or nylon 6 (N6 or PA6); poly(hexamethyleneadipamide), polyamide 66, or nylon 6 (N6,6, N66, or PA66).

[0051] Materials used in the examples. The nylon 66 or "N6,6" test specimens used in the examples were obtained from the INVISTA nylon 66 production facility. The reported number-average molecular weight (Mn) of this material was determined (via NMR) to be approximately 14,000 g / mole, and the relative viscosity (RV) was approximately 36.5 (determined by an 8.4% concentration in 90% formic acid according to ASTM D789). The nylon 6,6 material used herein represents a commercially available polymer used in a variety of applications, including airbags and textile fibers. Commercial materials, namely formic acid, aqueous ammonium hydroxide solution, methanol, and ethylene glycol, were used in the examples. The nylon 6 or "N6" test specimens used in the examples were commercially available materials. The nylon 6 and nylon 66 polymer test specimens were mechanically pulverized in a blender using dry ice. The pulverized polymer test specimens could be easily filled into 25 mL test containers.

[0052] Test methods used in the examples: Analytical techniques used: GC was used for monomer components, and GC-MS was used for the specification of unknown substances. NMR was used for molecular chain end analysis and molecular weight (Mn) determination. LC-MS was used for the specification of oligomer components. FT-IR was used for oligomer identification. DSC was used for melting point characterization. TGA was used for the determination of volatile components.

[0053] For NMR analysis, the sample was prepared by dissolving approximately 0.02 g of solid in approximately 0.050 g of trifluoroacetic acid (TFA), and then deuterated methylene chloride (CD2Cl2) was added to the polymer sample dissolved in approximately 1 g of TFA.

[0054] The analytical sample for LC-MS was prepared as follows: Approximately 0.01-0.02 g of the recovered solid was dissolved in hexafluoroisopropyl alcohol (HFIP). The low molecular weight oligomer intermediate was solubilized in HFIP. The solution was filtered and analyzed by LC-MS. Example 1. Decomposition of polyamides by solvent dissolution, acid / base treatment, or enzymatic treatment.

[0055] In embodiment 100 shown in Figure 1, the mixed plastic flow 41 contains thermoplastic and thermosetting materials. The materials contain various used / end-of-life parts and articles, either in their used form or / or partially shredded form. Examples of thermoplastic components include reinforced and unreinforced nylon (polyamide), polyester (mainly PET), polyolefins (LDPE, LLDPE, polypropylene, or PP), or polycarbonate. Examples of thermosetting components include PVC, ABS rubber, and polyacrylate.

[0056] The mixed plastic stream 41 undergoes several steps of sorting / separation 102 to separate the thermoplastic material from the thermosetting material. In 102, once the thermoplastic material is separated, the stream undergoes further segregation to separate polyamides such as N6 and N66 from other non-polyamides such as PP and PET, and to separate the polyamides from each other. The separation may include melting point separation, stain test separation, electrostatic separation, flotation separation, molten phase separation, hydrohydraulic technique, thermal melting technique, cold melting technique, selective melting technique, or a combination thereof, as described below.

[0057] Melting point separation can be performed based on the melting points of PP (156°C), N6 (220°C), N66, and PET (over 256°C). N66 and PET can be further separated by staining tests, where N66 is acid-stainable, while PET is not.

[0058] Clothing and carpet fibers produced by methods such as shearing or shredding can be further classified by electrostatic separation. Nylon fibers are more susceptible to electrostatic charge than PP.

[0059] For example, in flotation separation, the material can be suspended in a liquid (e.g., water) having a density between that of PP (0.93 g / cc) and nylon 6 (1.12 g / cc) / nylon 66 (1.13 g / cc). The suspended PP portion can be scooped up / filtered from the top.

[0060] The plastic material may be melted and phase-separated. The molten PP floating at the top can be scooped up / decanted, while the molten nylon can be collected at the bottom. The molten viscosity of the nylon can be reduced by adding a small amount of adipic acid or hexamethylenediamine to seal the ends and then neutralize it.

[0061] Using hydrothermal pressure techniques (150-300 Psig; 170-200°C), non-nylon materials such as polyester, jute, and PP may be separated from the nylon component. Nylon 66 tends to melt at about 170°C in the presence of high-pressure water, while nylon 6 and PP melt at about 150°C and 175°C, respectively. Polyester and jute remain unaffected by these conditions.

[0062] In thermal fusion techniques, materials are brought into contact with a high-boiling-point solvent (having a low vapor pressure) at a high temperature (above 150°C). Under these conditions, nylon is dissolved while PP melts. PP floats to the top and can be skimmed / decanted if its solvent density is higher than that of PP. Other materials heavier than the solvent density may settle at the bottom and be filtered out. The thermally fused nylon solution may be chemically treated to depolymerize into valuable monomer precursors or oligomers. Alternatively, the polymer can be precipitated by cooling the solution and then filtered. Suitable solvents include those that boil above 100°C at atmospheric pressure, for example, those that boil above 150°C at atmospheric pressure.

[0063] In low-temperature dissolution technology, the material is brought into contact with a solvent capable of dissolving nylon at a low temperature (below 150°C, preferably ambient temperature). Once the nylon component is dissolved, the insoluble non-nylon component can be filtered out of the solution. The nylon resin can be recovered by stripping the solvent (using vapor or vacuum) or by non-solvent dilution. Suitable solvents include those that boil at ≤150°C at atmospheric pressure.

[0064] A selective dissolution technique can be used, in which the plastic material is brought into contact with a solvent selective for nylon 6 (or 66) at a controlled temperature. The nylon 6-containing solution is separated by filtration and cooled (or diluted with a non-solvent) to precipitate the nylon 6. The remaining nylon 66 material can be treated with the same (or different) solvent at a higher temperature to dissolve nylon 66 from PP and other materials. As an example, a methanol / water mixture selectively dissolves nylon 66 from nylon 66 at 120-150°C, but above 150°C it also dissolves nylon 66. In either case, the dissolved polymer precipitates as a powder when cooled to room temperature. Other solvents include benzyl alcohol, tetramethylene sulfone, and butane-1,4-diol.

[0065] Any or all of the above steps separate the nylon component from the non-nylon component.

[0066] The isolated nylon component stream 43 obtained from the collection / separation step 102 is then supplied to the chemical solution step 108. A separate mechanical pretreatment step 104 can receive the mixed nylon-containing supply stream 47 and pretreatment this stream to produce a supply stream 51 suitable for step 108. The stream 51 may contain shredded or sizing reduced carpet / clothing fibers, automotive parts, engineering polymer articles, etc.

[0067] In step 108, the long nylon chains are chemically broken down into smaller chunks using acid / base hydrolysis chemical reactions along with miscible solvent dissolution, thereby producing a nylon oligomer (or short-chain nylon component) stream 55. Any other by-product streams 63 generated during this process may be present and can be recovered for sale or used as fuel.

[0068] Alternatively, the isolated nylon component stream 53 from collection / separation 102, and the stream 51 from mechanical pretreatment 104, may undergo an enzymatic biodegradation step 110 as described by Sudhakar et al. in International Biodeterioration & Biodegradation, Vol. 60, pp. 144-151 (2007), resulting in a stream 57 of short-chain low-molecular-weight nylon monomers or oligomer components (e.g., dimers, trimers, tetramers, etc.). Although not shown, the stream 59 exiting step 108 may also be supplied to the enzymatic biodegradation step 110. These short-chain nylon oligomer materials can be readily repolymerized in either stream 57 or stream 59 in the subsequent step 112. The repolymerized material stream 61 can be recovered from the repolymerization step 112 in either a pulverized state, pellets, fibers, or other usable form. The nylon polymer stream 61 has recycled nylon contents derived from the mixed plastic stream 41 and / or the mixed nylon-containing supply stream 47. Example 2. Decomposition of polyamide via pretreatment and ammoniaxation.

[0069] This embodiment illustrates a method for recycling a nylon-containing feed 71 to obtain a purified diamine product 95 that can be used for nylon polymerization. As shown in Figure 2, in embodiment 200, a pretreatment step 206 for the nylon oligomer intermediate can be used before the ammoniaxation step 208. Depending on the quality and process economic considerations of the feed logistics 77, step 206 may be enzymatic biotreatment, subcritical water treatment, microwave decomposition treatment, or a combination thereof.

[0070] The nylon material stream 79 obtained from the collection / separation step 202 and the mechanical pretreatment step 204 (as described in Example 1) may be supplied to the ammonia monolithion step 208. However, such a mixed feed material may contain high levels of contaminants that could adversely affect the ammonia monolithion process. The pretreatment step 206 may be effective in generating a consistent low molecular weight nylon oligomer stream 81 which is favorable for the ammonia monolithion step 208. The ammonia monolithion step can be operated using an inlet stream 99 of excess ammonia. An ammonia recovery step 216 may collect the ammonia-enriched gaseous effluent 96 and purify it to form an ammonia recycling stream 97. A supplement ammonia stream 98 maintains the ammonia balance throughout the ammonia monolithion step and combines streams 97 and 98 to form a stream 99 supplied to step 208. Heavy and tarry materials are recovered from step 208 and purged as stream 121 which can be used for fuel value.

[0071] The ammonolithesis process effluent 83 may contain primary nylon monomers such as diamines and adipic acid precursors (e.g., cyanoamide or dinitrile) along with various other precursors (e.g., aminonitrile, mono- and dinitrile, lactam, etc.). The purification step 210 can process the ammonolithesis effluent 83 to recover high-purity versions of such components, e.g., lactam effluent 85 or aminonitrile effluent 87. The remaining effluent 89 can undergo one or more chemical conversions (e.g., reductive amination or hydrogenation) using a hydrogen source 91 in step 212 to generate a consistent diamine-enriched effluent 93. The diamine-enriched effluent 93 can be further purified in step 214 to obtain a purified diamine effluent 95 with a purity suitable for end-use applications. The low-diamine by-product 123 may also be useful in the nylon field. Example 3. Decomposition of polyamide via solvent dissolution and / or acid / base treatment and subsequent pretreatment.

[0072] As shown in Figure 3, the effluent 329 from the chemical solution preparation step 306 (including solvent dissolution, acid / base hydrolysis, or a combination thereof) can be supplied to a pretreatment step 308 instead of being supplied directly to the repolymerization step 310 (as indicated by the dotted line 335). The pretreatment step 308 includes enzymatic biotreatment, subcritical water treatment, microwave decomposition treatment, or a combination thereof. The pretreatment step 308 can generate a consistent flow 331 of short-chain low molecular weight nylon oligomers that may be favorable for the repolymerization step 310. The nylon polymer flow 333 obtained from step 310 has recycled nylon contents derived from the mixed nylon flow 323 and the mixed plastic flow 321, which are initially separated in the collection / separation step 302 as a mixed nylon flow 323 and a non-nylon plastic flow 325. Step 202 is a collection / separation step for generating flow 323, and step 304 represents a mechanical pretreatment step for generating a uniform mixed nylon feed material 327 from the mixed nylon flow 323, which may contain post-industrial recycled (PIR) and / or post-consumer recycled (PCR) textile / garment fibers, automotive parts, airbag fabrics, etc. Example 4. Subcritical water pretreatment for nylon oligomer intermediates.

[0073] Approximately 1.2 grams of nylon polymer, mixed with approximately 22.5 cc of deionized water, was held in a 25 mL stainless steel sealed container at a temperature of approximately 275°C and a pressure of less than 68 atm (1000 Psig) for 1 hour and 6 hours. These temperature and pressure conditions result in subcritical water test conditions. Subcritical water conditions are known as conditions below the critical point of water (i.e., 373.95°C and 217.75 atm (3200.1 Psig)).

[0074] The nylon polymer specimens tested were nylon 6 labeled "N6" and nylon 66 labeled "N6,6". The resulting product was separated into liquid and solid phases by filtration. The liquid phase was analyzed by GC-MS, NMR, and LC-MS for speciation and quantification. The recovered solid phase was dissolved in a suitable solvent, and the homogenized solution was analyzed by LC-MS and NMR. The "as-is" solid was used for FT-IR, DSC, and TGA analysis.

[0075] The test conditions included three media: i) a neutral medium (water), ii) an acidic 0.01 M formic acid medium, and iii) a basic 0.01 M ammonium hydroxide medium. For each test condition, a blank sample was tested together with the polymer sample in water. Table 1 shows the speciation measured from GC-MS and LC-MS analysis. Table 2 shows the observed measured weight yield. Table 3 shows the reduction in number-average molecular weight (Mn) from the tests performed.

[0076] [Table 1] ( a The value represents the integrated area from the GC-FID detector response. ( * Only monomers (HMD and adipic acid or AA) are considered, and oligomers are not included. All weight percentages are based on the total sample weight (1.2g polymer + 22.5cc deionized water, totaling approximately 23.7g).

[0077] [Table 2]

[0078] [Table 3]

[0079] Neutral medium tests were observed to yield good HMD yields from N6,6 depolymerization. In all tests under subcritical conditions, the formation of HMD, adipic acid, and oligomers from N6,6 depolymerization was observed. A comparison between Example 4b and Example 4g-4h showed higher monomer and oligomer product yields as the run time increased from 1 hour to 6 hours, while other factors remained the same. The 6-hour run also showed an increase in by-products, e.g., HMI and BHMT, compared to the 1-hour test results. Examples 4i and 4j of the N6 depolymerization test yielded mostly caprolactam.

[0080] Determination of molecular weight (Mn). In each case in Table 3, the solid at the end of the run (1 hour run time) was filtered from the test medium. The recovered solid was... 1 The terminal and intrachain HMD segments, as well as the terminal and intrachain adipic acid segments, were determined by analysis using 1H-NMR. From these measurements, the HMD% and adipic acid% at the chain ends were determined. The chain end value of HMD% was used to estimate the molecular weight (Mn) value.

[0081] These examples demonstrate promising results showing that nylon polymers can be effectively depolymerized into their respective monomers and oligomers under subcritical conditions. In these examples, a molecular weight reduction of more than 10 times was observed from the starting nylon polymer feed to its monomer and oligomer components.

[0082] The resulting monomers, for example, HMD and adipic acid in the case of N6,6, and caprolactam in the case of N6, can be recovered from the product and are available for recycling. Oligomers with molecular weights reduced by at least 10 times can suitably undergo further reactions for depolymerization into additional monomer products. Examples 5a-5j. Microwave pretreatment of nylon oligomer intermediates.

[0083] A laboratory-scale single-reaction chamber microwave decomposition system (Model: UltraWAVE; Manufacturer: Milestone Inc.) was used in these examples. The system included a microwave reaction monitoring panel and multiple test settings for running parallel reactions simultaneously. All nylon depolymerization tests were performed for 1 hour at a temperature of approximately 210°C and a maximum pressure of approximately 50 atmospheres.

[0084] In this example, three depolymerization test media were used: i) neutral, ii) acidic (0.01 M formic acid), and iii) basic (0.01 M ammonium hydroxide). Two solvents, methanol and ethylene glycol, were also tested. Approximately 0.1 grams of polymer were mixed with approximately 3 cc of one of the selected test media or solvents, and microwave depolymerization tests were performed. The tested polymers contained N6 and N6,6. At the end of each run, representative liquid samples of the product were analyzed using GC and GC-MS. Table 4 shows the speciation measured from GC-MS and LC-MS analysis.

[0085] [Table 4]

[0086] This example demonstrates promising results showing that nylon polymers can be rationally depolymerized into their respective monomers and oligomers by microwave technology. The monomers, e.g., HMD in the case of N6,6 and caprolactam in the case of N6, can be recovered from the product and are available for recycling. The oligomers with reduced molecular weights can suitably undergo further reactions for depolymerization into additional monomer products. Example 6. Decomposition of polyamide via pretreatment and ammoniaxation.

[0087] Figure 4 is a schematic diagram of method 400 for recycling nylon polymers. Method 400 includes step 402 of collecting mixed plastic stream 1 and separating it into non-nylon plastic stream 3 and mixed nylon stream 5. Mixed plastic stream 1 can originate from residential / community / industrial recycling facilities, consumer post-use recycling (PCR) streams, industrial post-use recycling (PIR) streams, etc. Mixed plastic stream 1 may contain polyolefin materials such as HDPE, LDPE, LLDPE, polypropylene, and polybutylene; polyester materials such as PET and PBT; polycarbonate materials; acrylic materials such as ABS and acrylate; polystyrene materials; polyamide materials such as nylon and aramid nylon; polyurethane materials, and other such thermosetting materials such as natural rubber, synthetic rubber, EPDM, VITON, and PVC.

[0088] Step 402 may include physical washing and separation techniques such as water / solvent washing, flotation separation, gravity separation, electrostatic separation, molten phase separation, separation by high / low temperature dissolution, selective solvent dissolution, and combinations thereof. Example 1 describes some of these mixed plastic separation techniques. Any or all combination of such techniques will isolate the nylon component from the non-nylon component of flow 1.

[0089] Non-nylon plastic stream 3 may contain non-nylon plastic components such as polyethylene, polypropylene, polybutylene, polycarbonate, polyurethane, and polyester. Mixed nylon stream 5 may contain components such as nylon 6, nylon 66, nylon 6X, and nylon X6. The symbol "X" used herein refers to various dicarboxylic acids or diamines used in the preparation of nylon. In one example, the X value of 10 in nylon 6X is C polymerized with hexamethylenediamine (HMD or HMDA) to produce nylon 610. 10It can represent a dicarboxylic acid. In another example, the X value of 5 in nylon X6 can represent pentamethylenediamine (PMD or PMDA), a 5-carbon diamine polymerized with adipic acid to produce nylon 56. In yet another example, the X value of 12 in nylon 6X can represent C, which is polymerized with hexamethylenediamine to produce nylon 612. 12 This can represent dicarboxylic acids. Such abbreviations and nomenclature for nylon are commonly used in the thermoplastic materials industry.

[0090] The nylon source may also include industrial post-use recycled (PIR) material, consumer post-use recycled (PCR) material, unused off-spec nylon material from production facilities, or a combination thereof. For example, the mixed nylon stream 5 may include material from end-of-life automobiles, electrical and electronic equipment, textile articles / parts, or a combination thereof. Another mixed nylon source may be engineering polymer articles / parts that may contain reinforcing materials, such as glass fibers, natural and cellulose fibers, basalt fibers, or a combination thereof.

[0091] An optional step 404 of the mechanical pretreatment may involve taking a partially mixed nylon stream 7 from step 402 to produce a nylon stream 9 containing uniformly sizing reduced nylon pieces for acceptance in the next step. Many conventional sizing techniques are known and implemented in the solids management industry. Step 404 may include such conventional methods as stripping, shredding, champing, crushing, breaking, cutting, grinding, grinding, pelletizing, or a combination thereof of the fiber / fabric. Some techniques are dry processes, while some are wet processes using water and / or other solvents.

[0092] Method 400 includes a step 406 for pre-treating a nylon material to obtain a low molecular weight oligomer intermediate. Step 406 processes the mixed nylon stream 5 (and / or stream 9) to convert the individual nylon components into their respective smaller oligomer components as an oligomer intermediate stream 11. Step 406 may include a nylon depolymerization pre-treatment step as described in Examples 4 and 5.

[0093] In one example, step 406 may include subcritical hydrodepolymerization conditions, as demonstrated in Examples 4b, 4d, 4f, and 4g-4j. The resulting product contains a mixture of several monomers from the depolymerization carried out in step 406, and dimers, trimers, tetramers, or other oligomeric components. As demonstrated in Example 4, high molecular weight nylon 66 is effectively decomposed into HMD and adipic acid monomers, along with a corresponding oligomer mixture having a number average molecular weight (Mn) at least 10 times lower than that of the supplied nylon 66. Similarly, high molecular weight nylon 6 is effectively decomposed into its caprolactam monomer, along with its corresponding oligomer mixture having a number average molecular weight (Mn) significantly lower than that of the supplied nylon 6.

[0094] In another example, step 406 may include microwave-assisted depolymerization conditions, as demonstrated in Example 5. The resulting product contains a mixture of several monomers from the depolymerization carried out in step 406, and dimers, trimers, tetramers, or other oligomeric components. As demonstrated in Example 5, high molecular weight nylon 66 is effectively decomposed into HMD and adipic acid monomers, along with the corresponding oligomer mixture having a number-average molecular weight (Mn) much lower than that of the supplied nylon 66. Similarly, high molecular weight nylon 6 is effectively decomposed into its caprolactam monomer, along with its corresponding oligomer mixture having a number-average molecular weight (Mn) significantly lower than that of the supplied nylon 6.

[0095] Step 406 pre-treats a high molecular weight nylon material to produce an oligomer intermediate stream 11 enriched with monomer components and low molecular weight oligomer components from any of the nylons supplied to step 406. In one embodiment, when nylon 56 is supplied to step 406, it yields its respective monomer components and low molecular weight oligomer components. In another embodiment, the oligomer intermediate stream 11 can be dehydrated by including a sub-step of excess water removal at the end of step 406 before being supplied to the next step.

[0096] Therefore, step 406 is useful for obtaining a low molecular weight nylon depolymerization flow in the disclosed method 400.

[0097] Method 400 includes step 408 for completely decomposing a low molecular weight oligomer intermediate stream 11 into a monomer stream 15. Step 408 uses either a catalytic or non-catalytic ammonia monolysis treatment in the presence of ammonia. Nylon ammonia monolysis is described in this disclosure and Examples 7 and 8 and will not be repeated here. Ammonia control in step 408 is via a fresh ammonia feed stream 23 to an ammonia recovery step 410. A non-condensable vapor stream 17 containing excess ammonia is collected from step 408. The ammonia recovery step 410 concentrates and purifies the excess ammonia from stream 17 and returns it to the ammonia monolysis step 408 as an ammonia recycling stream 19. A fresh replenishment ammonia stream 21 is adjusted to maintain an appropriate ammonia mass balance in Method 400.

[0098] The ammonolysis depolymerization step 408 can produce small amounts of tar-like, high-molecular-weight, and heavy components. Such heavy and high-molecular-weight by-products produced in step 408 can be concentrated via a combination of distillation separation, steam stripping, and extraction, and purged from method 400 as a heavy / high-boiling-point purge stream 13. In one example, the concentrated stream 13 may be a pyrolysis oil that can improve the quality of hydrogen and synthesis gas during high-temperature decomposition. In another example, the stream 13 may be useful as a by-product fuel due to its heat content in a boiler for steam generation.

[0099] The monomer stream 15 exiting the ammonialysis step 408 may contain a variety of nylon monomers and precursors, as described in Example 7. Some non-limiting examples of nylon monomers and precursors may include lactams (e.g., caprolactam from nylon 6 or laurolactam from nylon 12); dinitriles (e.g., butanedinitrile, pentanedinitrile, or hexanedinitrile); diamines (e.g., butanediamine, pentanediamine, hexanediamine, decanediamine, or dodecanediamine); amides (e.g., adipamide); aminonitriles (e.g., aminobutanenitrile, aminopentanenitrile, or aminohexanenitrile); cyanoamides (e.g., cyanovaleramide or cyanocaproamide); small amounts of various dimers; or combinations thereof.

[0100] Method 400 includes an initial product separation step 412 for recovering monomers and precursors that can be easily separated from the monomer stream 15 exiting step 408. Step 412 may include one or more sequential and / or parallel distillation, decantation, and extraction sub-steps to separate the monomer components based on their boiling points and extraction efficiency. For example, a semi-purified stream 29 may contain lactam, while stream 31 may contain one or more small molecule aminonitriles and diamines that are recovered as individual components or produced as a mixture. These monomers and intermediates may find use as recycled streams in the production of their respective polymers. For example, recovered caprolactam in stream 29 can be further purified and recycled to a nylon 6 production facility. In another example, recovered butanediamine in stream 31 can be further purified and recycled to a nylon 46 production facility.

[0101] The hexanedinitrile, hexanediamine, and amino-hexanenitrile components can be separated and concentrated in the hydrogenation feed stream 27 exiting the initial product separation step 412. Method 400 includes a hydrogenation step 416 for converting the hydrogenation feed stream 27 to diamine. A hydrogen source step 414 provides hydrogen via stream 33, and an ammonia feed stream 25 is supplied from a fresh replenishment ammonia stream 21. The hydrogenation step 416 may be catalytic or non-catalytic, and may be a low-pressure, medium-pressure, or high-pressure step. Some hydrogenation methods include, for example, a fixed-bed catalytic system, a slurry catalytic system, a solvent-assisted catalytic system, or a combination thereof. In one example, 1,6-hexanedinitrile can be hydrogenated in the presence of ammonia at a pressure of 4500-5000 Psig and a temperature of 100-200°C using a reduced iron-based catalytic system. In another example, amino-hexanenitrile can be hydrogenated in the presence of ammonia at a pressure of 500–1500 Psig and a temperature of 60–150°C using a Raney® nickel or Raney® cobalt catalyst system.

[0102] The hydrogenation product stream 35 from step 416 is further purified in the diamine recovery / purification step 418 of method 400. Step 418 may utilize various sub-steps based on the relative volatility of the components, such as diamine distillation, ion exchange techniques, extraction using a preferred solvent, melt crystallization, or a combination thereof. Step 418 produces a diamine product stream 37 that meets or exceeds purity requirements for downstream applications. For example, the diamine product stream 37 may be a purified HMD product with a purity of over 99.9% by weight. Such HMD products are suitable for recycling back to any nylon 6X production facility for producing nylon 66, nylon 69, nylon 610, nylon 612, or other 6X nylons.

[0103] The disclosed method 400 is effective for recycling nylon polymers by converting them into their corresponding monomer components and making them available with sufficient purity for recycling back into nylon production. The disclosed method 400 offers environmental and sustainability benefits. Example 7. Decomposition of polyamide by ammonolithesis without pretreatment.

[0104] Method 400 for recycling nylon polymers is described in Example 6 and is carried out with the exception of a pretreatment step 406 for oligomer intermediates, as schematically shown in Figure 4. The nylon-containing stream obtained from steps 402 and / or 404 is supplied directly to an ammonia-monolithesis step 408 for nylon depolymerization in the presence of excess ammonia.

[0105] Tables 5A–5G below summarize the depolymerization by ammonia lysis for the tested nylon feedstocks. Approximately 15 grams of starting nylon polymer undergoes depolymerization by ammonia lysis in excess ammonia for each test run. Approximately 1.46 g / min of gaseous ammonia is continuously supplied to the reaction for the total run time in each case. The ammonia lysis reaction temperature varies from 225°C to 350°C. The ammonia lysis reaction time is monitored to achieve a conversion rate of at least 50% of the starting material at each temperature. The ammonia lysis process is operated at a pressure of approximately 68 atm (1000 Psig). The ammonia lysis process is operated in continuous-stirred tank reactor (CSTR) mode.

[0106] The vapor and liquid products obtained from the ammonolithesis test are summarized in the tables for each nylon-containing feed, namely nylon 66 (Tables 5A-5B), nylon 6 (Tables 5C-5D), and a 50:50 (weight:weight) mixture of nylon 66:nylon 6 (Tables 5E-5G).

[0107] The following definitions are used in Tables 5A to 5G. Conversion rate (%) = (supplied mass (g) - unconverted mass (g)) / (supplied mass (g)) × 100; Monomer yield (%) for nylon 66-containing feed: Yield (%) = (moles of ADN + HMD + CVAM) / (moles of supplied polymer) × 100; Monomer yield (%) for nylon 6-containing feed: Yield (%) = (moles of CPLM + ACN + ACAM) / (moles of supplied polymer) × 100. Total monomer yield (%) for a mixed feed containing nylon 6 and nylon 66 = (monomer yield (%) from the nylon 66-containing feed) × weight % of the nylon 66 fraction in the mixed feed + (monomer yield (%) from the nylon 6-containing feed) × weight % of the nylon 6 fraction in the mixed feed. The term "tar" refers to an aggregate of high-boiling components, and in some cases high-molecular-weight components, formed for example from oligomerization of components having nitrile end groups.

[0108] [Table 5]

[0109] [Table 6] ( * )Excess NH3 can be recovered and recycled back to the ammonolysis step via step 410 (as shown in Figure 4). (^) The term "others" includes adipamide, as well as dimers of HMD with adipamide and CVAM. (&) The NH3 and CO2 values represent components that are most likely to be present in a dissolved state in the liquid phase. The liquid phase weight% values are based on the final remaining liquid mass excluding the mass of unconverted polymer.

[0110] [Table 7]

[0111] [Table 8] (^) The term "other" includes low molecular weight species. ( * Excess NH3 can be recovered and recycled back to the ammoniaxation process via process 410 (as shown in Figure 4). The (&)NH3 value represents the component that is most likely to be dissolved in the liquid phase. The liquid phase weight percentage is based on the remaining liquid mass after excluding the mass of the unconverted polymer.

[0112] [Table 9] (1) Nylon 66 monomer for HMD, ADN, and CVAM (including precursor yield). (2) Nylon 6 monomers for CPLM, ACN, and ACAM (including precursor yield).

[0113] [Table 10] (^) The term "other" includes low molecular weight species. ( * Excess NH3 can be recovered and recycled back to the ammoniaxation process via process 410 (as shown in Figure 4). The (&)NH3 value represents the component that is most likely to be dissolved in the liquid phase.

[0114] [Table 11] (^) The term "other" includes low molecular weight species. ( * Excess NH3 can be recovered and recycled back to the ammoniaxation process via process 410 (as shown in Figure 4). The (&)NH3 and CO2 values ​​represent components that are most likely to be present in a dissolved state in the liquid phase. The liquid phase weight percentage is based on the remaining liquid mass after excluding the mass of the unconverted polymer.

[0115] Nylon 66-containing feed is observed to depolymerize into its main monomer, hexamethylenediamine (HMD), and its monomer precursors, namely adiponitrile (ADN) and cyanovaleramide (CVAM). Cyanovaleramide is a precursor of adipic acid, which is formed in the ammonolithesis process. Adiponitrile is a precursor of HMD. Tar formation is thought to be due to the thermal decomposition of other nylon 66 monomers, adipic acid, and other high molecular weight species formed.

[0116] The nylon 6-containing feed is observed to depolymerize into its monomer caprolactam (CPLM) and its precursors, namely aminocapronitrile (ACN) and aminocapramid (ACAM). The two caprolactam precursors, ACN and ACAM, can be chemically converted back to caprolactam and recovered. Tar formation is thought to be due to the thermal decomposition of high molecular weight species. The liquid phase mainly contains the formed tar and dimer.

[0117] A 50:50 (weight:weight) mixed nylon 66:nylon 6-containing feed is observed to depolymerize to nylon 6 monomer caprolactam (CPLM) and its precursors, namely aminocapronitrile (ACN) and aminocapramide (ACAM), as well as nylon 66 primary monomer, hexamethylenediamine (HMD) and its monomer precursor, namely adiponitrile (ADN) and cyanovaleramide (CVAM).

[0118] In all of the above cases, significant tar formation was observed when the ammoniaxation process was carried out at high temperatures. The overall yield of nylon 6 monomer was not significantly affected by tar formation, but the monomer yield for nylon 66 decreased as tar formation increased. If the mixed nylon feed contains a nylon 66 component, adipic acid is likely to be a precursor of tar formation.

[0119] Therefore, it is desirable to have a method for nylon polymer recycling that can substantially reduce tar formation and improve the desired monomer product yield. It is also advantageous to have a method that is better in terms of processability and operating costs, such as less tar formation resulting in less frequent equipment cleaning / shutdowns. Example 8. Ammonolysis of nylon oligomer intermediates.

[0120] Method 400 for recycling nylon polymers is described in Example 6 and carried out in the presence of a pretreatment step 406 for oligomer intermediates, as schematically shown in Figure 4. The nylon-containing streams obtained from steps 402 and / or 404 are pretreated according to the steps described in Example 4. The dehydrated nylon oligomer intermediate feed is then fed to an ammonialysis step 408 for complete depolymerization in the presence of excess ammonia.

[0121] Unlike Example 7 for the nylon 66-containing feed, it was unexpectedly observed that the nylon 66 oligomer intermediate feed from pretreatment step 406 could be depolymerized in ammonia monolysis step 408 at a much lower temperature and with reduced excess ammonia.

[0122] In one example, a typical product from the subcritical water pretreatment step 406 is a nylon 66 oligomer intermediate feed having a number-average molecular weight in the range of 600 to 1500 g / mol, for example, 1100 g / mol. This low molecular weight feed is depolymerized in the ammoniaxation step 408 at a temperature 50°C lower than the temperature required for the nylon 66-containing feed shown in Example 7.

[0123] In another example, a typical product from the microwave decomposition pretreatment step 406 is a nylon 66 oligomer intermediate feed having a molecular weight lower than that of the nylon 66-containing feed. This low molecular weight feed is depolymerized in the ammoniaxation step 408 at a temperature 25°C lower than the temperature required for the nylon 66-containing feed shown in Example 7.

[0124] Similar results were observed when comparing nylon 6 and mixed nylon 66:nylon 6 oligomer intermediate products obtained from either of the two pretreatment steps, namely subcritical water pretreatment (Example 4) and microwave decomposition pretreatment (Example 5), with the nylon 6-containing feedstock.

[0125] The pretreatment step 406 allows the ammonia monolysis step 408 to be operated at a lower temperature and with a reduced ammonia content. As disclosed, tar formation is reduced when the pretreatment step is performed before the ammonia monolysis step. The yields of monomer and monomer precursor products are improved when the pretreatment step 406 is carried out. Example 9. Recovery of caprolactam from nylon 6 supply material.

[0126] A 500cc resin kettle was used for the steam stripping process. The kettle included a mechanical stirrer, N2 purge, distillation head, and condenser. During operation, the condensate was collected as it exited the condenser. Steam generated from deoxygenated distilled water was introduced into the molten packing via a stainless steel tube. The kettle was heated with an electrically heated mantle. The temperature inside the kettle was controlled by adjusting the temperature of the mantle / kettle interface via a thermocouple.

[0127] The first set of experiments was conducted to demonstrate acid-catalyzed vapor stripping of caprolactam from nylon 6 feedstock. The nylon 6 feedstock was not pretreated to obtain low molecular weight oligomer intermediates.

[0128] Approximately 500 g of nylon 6 material was packed into a kettle along with approximately 14.2 g of NaH2PO4·H2O and approximately 2.9 g of 85% phosphoric acid. Approximately 90 cc / hour (water equivalent) of steam was supplied to the kettle. At the end of each operating time up to 3 hours, an additional 25.4 g of nylon 6 feed was added to replenish the depolymerized nylon 6 in the kettle. The catalyst concentration as 85% H3PO4 ranged from 2.8 to 3.7 wt%. The temperature in the reactor ranged from 297°C to 301°C during the 4-hour operation. The caprolactam concentration in the distillate ranged from 32 to 37.3 wt%.

[0129] The second set of experiments was conducted to demonstrate base-catalyzed vapor stripping of caprolactam from nylon 6 feedstock. Approximately 100 g of nylon 6 feedstock, approximately 85.7 g of 6-aminocaproic acid, and approximately 26.1 g of NaOH (equivalent to approximately 100 g of sodium aminocaproate) were packed into a kettle. Approximately 180 cc / hour (water equivalent) of vapor was continuously supplied. At the end of each operating time up to 3 hours, an additional 100 g of nylon 6 feedstock was added to replenish the depolymerized nylon 6 in the kettle. The catalyst concentration as NaOH ranged from 7.5 to 23 wt%. The temperature in the reactor ranged from 318 to 333°C for the first 4 hours of operation and from 280 to 318°C for the next 6 hours. The caprolactam concentration in the distillate ranged from 16 to 42.5 wt% for the first 4 hours of operation and from 7 to 38 wt% for the next 6 hours.

[0130] The experiment was conducted in the same manner as the first set, except that no catalyst was used. The temperature inside the reactor ranged from 255°C to 307°C during the 5-hour operation. The caprolactam concentration in the distillate ranged from approximately 10 to 17.4% by weight.

[0131] In this example, when nylon 6 was not partially depolymerized to obtain a low molecular weight oligomeric intermediate, the overall monomer (caprolactam) recovery rate was low. Example 10. Acid catalyst experiment using mixed nylon feedstock (nylon 6 and 66).

[0132] An acid-catalyzed vapor stripping process was carried out on a mixed nylon feed containing 10:90 (weight:weight) nylon 66:nylon 6. This mixed nylon feed was not pretreated to obtain low molecular weight oligomeric intermediates. The same NaH2PO4·H2O and H3PO4 catalyst systems as in Example 9 were used, but at an initial level of 16.25% based on 85% H3PO4. Additional feed containing 25.5:2.8 (g / g) nylon 6:nylon 66 was added every hour until 1 hour before the end of the run. A high percentage of caprolactam stripping was observed. However, several nylon 66 degradation products, mainly adiponitrile, cyclopentanone, hexylamine, 6-aminocapronitrile, and nylon 66 cyclic monomers were detected. Neither HMD nor adipic acid was observed. During the first 5 hours of operation, the temperature ranged from 245 to 317°C, the catalyst composition as 85% H3PO4 ranged from 16 to 21% by weight, and the caprolactam concentration in the distillate ranged from approximately 17 to 40% by weight.

[0133] The acid-catalyzed vapor stripping process was also carried out on a mixed nylon feed containing approximately 50:50 (weight:weight) nylon 66:nylon 6. The same NaH2PO4·H2O and H3PO4 catalyst systems as in Example 9 were used, but at an initial level of 17.7% based on 85% H3PO4. An additional feed containing approximately 13:13 (g / g) nylon 6:nylon 66 was added every hour during a 5-hour run. The temperature ranged from 265 to 295°C, and the caprolactam concentration in the distillate ranged from approximately 8 to 11.5% by weight. The distillate was relatively clean, containing essentially only caprolactam, but also small amounts of nylon 66 decomposition products, mainly cyclopentanone.

[0134] In this example, when the mixed nylon feed was not partially depolymerized to obtain a low molecular weight oligomer intermediate, the overall monomer recovery rate was low. Example 11. Base catalyst experiment using mixed nylon feedstock (nylon 6 and 66).

[0135] A base-catalyzed steam stripping process was carried out on a mixed nylon feed containing approximately 50:50 (weight:weight) nylon 66:nylon 6. This mixed nylon feed was not pretreated to obtain a low molecular weight oligomeric intermediate. The starting composition contained 100 g each of nylon 6 and 66, approximately 85.7 g of 6-aminocaproic acid, and approximately 26.1 g of NaOH (equivalent to approximately 100 g of sodium aminocaproate). Approximately 90 cc / hour (water equivalent) of steam was supplied to the kettle. An additional 12.7 g of each nylon feed was added at the end of each operation time, up to a maximum of 3 hours. The catalyst concentration as NaOH ranged from 7.7 to 9.1% by weight. The temperature in the reactor ranged from 261°C to 278°C during the 4-hour operation. The caprolactam concentration in the distillate ranged from 3.5 to 3.8% by weight, while the HMD concentration ranged from 2.7 to 5.1% by weight.

[0136] In this example, when the mixed nylon feed was not partially depolymerized to obtain a low molecular weight oligomer intermediate, the overall monomer recovery rate was low. Example 12. Base catalyst experiment using nylon 66.

[0137] A base-catalyzed steam stripping process was carried out on a nylon 66 feedstock. The nylon feedstock was not pretreated to obtain a low molecular weight oligomeric intermediate. The starting composition was 200 g of nylon 66, approximately 85.7 g of 6-aminocaproic acid, and approximately 26.1 g of NaOH (equivalent to approximately 100 g of sodium aminocaproate). Approximately 90 cc / hour (water equivalent) of steam was supplied to the kettle. An additional 25.6 g of nylon 66 feedstock was added at the end of each operating time throughout a 6-hour run. The catalyst concentration as NaOH ranged from 7.8 to 10.2% by weight. The temperature in the reactor ranged from 260°C to 283°C. The HMD concentration in the distillate ranged from 3.5 to 22.1% by weight. A small amount of caprolactam (less than 5%) formed from the aminocaproic acid component was initially detected. This then decreased over time as it was consumed (to less than 1%). In this example, when the mixed nylon feed was not partially depolymerized to obtain a low molecular weight oligomer intermediate, the overall monomer recovery rate was low.

[0138] The terms and expressions used herein are not limiting but are used for illustrative purposes only, and in the use of such terms and expressions there is no intention to exclude any equivalents of the illustrated and described features or parts thereof, however it is recognized that various modifications are possible within the scope of the embodiments of the invention. Accordingly, although the invention is specifically disclosed by certain embodiments and any features, modifications and variations of the concepts disclosed herein may be reclassified by those skilled in the art, and it should be understood that such modifications and variations are considered to be within the scope of the invention as defined by the scope of the embodiments of the invention. Exemplary embodiments.

[0139] The following exemplary embodiments are provided, but the numbering should not be interpreted as indicating importance.

[0140] Embodiment 1 is a method for recycling a polyamide composition, wherein this method is Pre-treating a polyamide composition containing polyamide to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamide in the polyamide composition, The present invention provides a method comprising: exposing a polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition.

[0141] Embodiment 2 provides the method according to Embodiment 1, wherein the polyamide composition is a homogeneous composition.

[0142] Embodiment 3 provides the method according to Embodiment 2, wherein the homogeneous composition comprises a solid of uniform size, a semi-solid slurry, a slurry solution, a homogenized liquid solution of a dissolved polymer, or a combination thereof.

[0143] Embodiment 4 provides the method according to any one of Embodiments 1 to 3, wherein the polyamide composition is a particulate composition.

[0144] Embodiment 5 provides a method according to any one of Embodiments 1 to 4, further comprising mechanically treating a polyamide starting composition to form a polyamide composition.

[0145] Embodiment 6 provides the method according to Embodiment 5, wherein the mechanical processing includes size reduction, cutting, crushing, shredding, particle formation, or a combination thereof.

[0146] Embodiment 7 provides a method according to any one of Embodiments 1 to 6, further comprising separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide composition having 5% by weight or less of non-polyamide components.

[0147] Embodiment 8 provides the method according to Embodiment 7, wherein the separation includes melting point separation, stain test separation, electrostatic separation, flotation separation, molten phase separation, hydrohydraulic technique, thermal dissolution technique, cold dissolution technique, selective dissolution technique, or a combination thereof.

[0148] Embodiment 9 provides the method according to Embodiment 7 or 8, wherein the separation includes suspension separation in water.

[0149] Embodiment 10 provides a method according to any one of Embodiments 7 to 9, wherein the separation of the mixed plastic stream removes thermosetting polymers, polyesters, polyolefins, polycarbonates, or combinations thereof.

[0150] Embodiment 11 provides a method according to any one of Embodiments 7 to 10, wherein the separation of a mixed plastic stream removes PET, LDPE, LLDPE, PP, PVC, ABS rubber, polyacrylate, or a combination thereof.

[0151] Embodiment 12 provides the method according to any one of Embodiments 1 to 11, wherein the polyamide in the polyamide composition includes N4, N5, N6, N7, N10, N11, N12, N46, N56, N66, N610, N612, or a combination thereof.

[0152] Embodiment 13 provides a method according to any one of Embodiments 1 to 12, wherein the polyamide in the polyamide composition comprises N6, N66, N56, N610, or a combination thereof.

[0153] Embodiment 14 provides the method according to any one of Embodiments 1 to 13, wherein the polyamide in the polyamide composition contains N66.

[0154] Embodiment 15 provides the method according to any one of Embodiments 1 to 14, wherein the polyamide constitutes 95% to 100% by weight of the polyamide composition.

[0155] Embodiment 16 provides the method according to any one of Embodiments 1 to 15, wherein the polyamide constitutes 98% to 100% by weight of the polyamide composition.

[0156] Embodiment 17 provides a method according to any one of Embodiments 1 to 16, wherein the pretreatment includes hot water treatment, subcritical water treatment, supercritical water treatment, microwave treatment, enzymatic treatment, solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof.

[0157] Embodiment 18 provides a method according to any one of Embodiments 1 to 17, wherein the pretreatment includes solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof.

[0158] Embodiment 19 provides a method according to any one of Embodiments 1 to 18, wherein the pretreatment includes enzymatic treatment, subcritical water treatment, microwave treatment, or a combination thereof.

[0159] Embodiment 20 provides a method according to any one of Embodiments 1 to 19, wherein the pretreatment comprises an enzymatic treatment, and the enzymatic treatment is carried out at a temperature of 15°C to 45°C, a pH of 5 to 9, and a pressure of 0.5 atm to 2 atm.

[0160] Embodiment 21 provides the method according to Embodiment 20, wherein the enzymatic treatment is carried out at a temperature of 20°C to 30°C, a pH of 6 to 9, and a pressure of 1 atm to 1.5 atm.

[0161] Embodiment 22 provides a method according to any one of Embodiments 1 to 21, wherein the pretreatment includes subcritical water treatment, and the subcritical water treatment includes treatment with water having a temperature of 200°C to less than 373.9°C and a pressure of 20 atm to 217.8 atm.

[0162] Embodiment 23 provides the method according to Embodiment 22, wherein the subcritical water treatment includes treatment with water having a temperature of 200°C to 300°C and a pressure of 40 atm to 100 atm.

[0163] Embodiment 24 provides a method according to any one of Embodiments 1 to 23, wherein the pretreatment comprises microwave treatment, and the microwave treatment comprises exposing the solvent to microwave energy at a pressure of 1 atm to 1,000 atm and a temperature of 100°C to 500°C.

[0164] Embodiment 25 provides the method according to Embodiment 24, wherein the microwave treatment includes exposing the solvent to microwave energy at a pressure of 20 atm to 80 atm and a temperature of 150°C to 250°C.

[0165] Embodiment 26 provides a method according to any one of Embodiments 1 to 25, wherein the pretreatment is performed over a period of 15 hours or less.

[0166] Embodiment 27 provides the method according to any one of Embodiments 1 to 26, wherein the polyamide oligomer composition contains a polyamide oligomer having a number average molecular weight of 200 g / mol or more and 3,000 g / mol or less.

[0167] Embodiment 28 provides a method according to any one of Embodiments 1 to 27, wherein the polyamide oligomer composition contains a polyamide oligomer having a number average molecular weight of 500 g / mol or more and 1,500 g / mol or less.

[0168] Embodiment 29 provides a method according to any one of Embodiments 1 to 28, wherein the polyamide oligomer composition comprises a dimer, a trimer, a tetramer, a higher oligomer, or a combination thereof.

[0169] Embodiment 30 provides a method according to any one of Embodiments 1 to 29, further comprising dehydrating the polyamide oligomer composition.

[0170] Embodiment 31 provides a method according to any one of Embodiments 1 to 30, wherein the ammonialysis comprises contacting the polyamide oligomer composition with a nitrogen source.

[0171] Embodiment 32 provides the method according to Embodiment 31, wherein the nitrogen source comprises gaseous ammonia, liquid ammonia, dissolved ammonia, an ammoniacal solution, and an ammonia enrichment medium, or a combination thereof.

[0172] Embodiment 33 provides the method according to Embodiment 31 or 32, wherein the nitrogen source is gaseous ammonia.

[0173] Embodiment 34 provides a method according to any one of Embodiments 31 to 33, wherein the ammonialysis comprises contacting the polyamide oligomer composition with a nitrogen source at a reaction temperature of 200°C to 350°C and a reaction pressure of 30 atm to 140 atm.

[0174] Embodiment 35 provides a method according to any one of Embodiments 31 to 34, further comprising recovering, purifying, and recycling the unreacted nitrogen source for reuse in ammonialysis.

[0175] Embodiment 36 provides the method according to any one of Embodiments 1 to 35, wherein the polyamide precursor composition comprises a polyamide monomer.

[0176] Embodiment 37 provides the method according to any one of Embodiments 1 to 36, wherein the polyamide monomer is 0% to 100% by weight or 1% to 100% by weight of the total amount of polyamide monomers and polyamide oligomers in the polyamide precursor composition.

[0177] Embodiment 38 provides the method according to any one of Embodiments 1 to 37, wherein the polyamide monomer is 90% to 100% by weight of the total amount of polyamide monomers and polyamide oligomers in the polyamide precursor composition.

[0178] Embodiment 39 provides the method according to any one of Embodiments 1 to 38, wherein the polyamide precursor composition comprises hexamethylenediamine (HMD), aminocapronitrile, 6-aminocaproamide, dimethyl adipate, adipic acid, methyl 6-aminocaproate, or a combination thereof.

[0179] Embodiment 40 provides a method according to any one of Embodiments 1 to 39, further comprising purifying, cleaning, or separating one or more components of a polyamide precursor composition.

[0180] Embodiment 41 provides a method according to any one of Embodiments 1 to 40, further comprising polymerizing a polyamide precursor composition or one or more components thereof to form one or more polyamides.

[0181] Embodiment 42 is a method for recycling a polyamide composition, wherein this method is The process involves pre-treating a polyamide composition containing polyamides to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamides in the polyamide composition, wherein the pre-treatment includes enzymatic treatment, subcritical water treatment, microwave treatment, or a combination thereof. The present invention provides a method comprising: exposing a polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition.

[0182] Embodiment 43 is a method for recycling a polyamide composition, wherein this method is Separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide starting composition having 5% by weight or less of non-polyamide components, A polyamide composition is produced by mechanically treating a polyamide starting composition, wherein the polyamide composition has 5% by weight or less of non-polyamide components. The process involves pre-treating a polyamide composition containing polyamide to produce a polyamide oligomer composition containing polyamide oligomers having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes hot water treatment, subcritical water treatment, supercritical water treatment, microwave treatment, enzymatic treatment, solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof. The present invention provides a method comprising: exposing a polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition containing polyamide oligomers and / or monomers having a lower molecular weight than the polyamide oligomers in the polyamide oligomer composition.

[0183] Embodiment 44 provides a polyamide formed from the polyamide precursor composition described in any one of Embodiments 1 to 43.

[0184] Embodiment 45 is a method for recycling a polyamide composition, wherein this method is The present invention provides a method for producing a polyamide oligomer composition, which includes pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes enzymatic treatment.

[0185] Embodiment 46 provides the method according to Embodiment 45, wherein the enzymatic treatment is carried out at a temperature of 15°C to 45°C, a pH of 5 to 9, and a pressure of 0.5 atm to 2 atm.

[0186] Embodiment 47 provides the method according to Embodiment 45 or 46, wherein the enzymatic treatment is carried out at a temperature of 20°C to 30°C, a pH of 6 to 9, and a pressure of 1 atm to 1.5 atm.

[0187] Embodiment 48 provides a method according to any one of Embodiments 45 to 47, wherein the enzyme treatment is carried out over a period of time of 15 hours or less.

[0188] Embodiment 49 provides a method according to any one of embodiments 45 to 48, further comprising mechanically treating a polyamide starting composition to form a polyamide composition.

[0189] Embodiment 50 provides a method according to any one of Embodiments 45 to 49, further comprising separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide composition having 5% by weight or less of non-polyamide components.

[0190] Embodiment 51 provides the method according to any one of Embodiments 45 to 50, wherein the polyamide in the polyamide composition includes N4, N5, N6, N7, N10, N11, N12, N46, N56, N66, N610, N612, or a combination thereof.

[0191] Embodiment 52 provides a method according to any one of Embodiments 45 to 51, wherein the polyamide oligomer composition contains a polyamide oligomer having a number average molecular weight of 200 g / mol or more and 3,000 g / mol or less.

[0192] Embodiment 53 provides a method according to any one of Embodiments 45 to 52, wherein the polyamide oligomer composition contains a polyamide oligomer having a number average molecular weight of 500 g / mol or more and 1,500 g / mol or less.

[0193] Embodiment 54 provides a method according to any one of Embodiments 45 to 53, wherein the polyamide oligomer composition comprises a dimer, a trimer, a tetramer, a higher oligomer, or a combination thereof.

[0194] Embodiment 55 provides a method according to any one of Embodiments 45 to 54, further comprising exposing a polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition comprising a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition.

[0195] Embodiment 56 provides the method according to Embodiment 55, further comprising polymerizing a polyamide precursor composition to form one or more polyamides therefrom.

[0196] Embodiment 57 provides the method according to Embodiment 55 or 56, wherein the ammonialysis comprises contacting the polyamide oligomer composition with a nitrogen source.

[0197] Embodiment 58 provides the method according to Embodiment 57, wherein the nitrogen source comprises gaseous ammonia, liquid ammonia, dissolved ammonia, an ammoniacal solution, and an ammonia enrichment medium, or a combination thereof.

[0198] Embodiment 59 provides the method according to Embodiment 57 or 58, wherein the nitrogen source is gaseous ammonia.

[0199] Embodiment 60 provides a method according to any one of Embodiments 57 to 59, wherein the ammonialysis comprises contacting a polyamide oligomer composition with a nitrogen source at a reaction temperature of 200°C to 350°C and a reaction pressure of 30 atm to 140 atm.

[0200] Embodiment 61 provides a method according to any one of Embodiments 57 to 60, further comprising recovering, purifying, and recycling an unreacted nitrogen source for reuse in ammonialysis.

[0201] Embodiment 62 provides a method according to any one of Embodiments 45 to 61, further comprising dehydrating the polyamide oligomer composition.

[0202] Embodiment 63 provides a method according to any one of embodiments 45 to 62, further comprising polymerizing a polyamide oligomer composition to form one or more polyamides.

[0203] Embodiment 64 is a method for recycling a polyamide composition, wherein this method is Separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide starting composition having 5% by weight or less of non-polyamide components, A polyamide composition is produced by mechanically treating a polyamide starting composition, wherein the polyamide composition has 5% by weight or less of non-polyamide components. The present invention provides a method for producing a polyamide oligomer composition comprising a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, wherein the pretreatment includes enzymatic treatment.

[0204] Embodiment 65 provides a polyamide formed from the polyamide oligomer composition described in any one of Embodiments 45 to 64.

[0205] Embodiment 66 provides a method or polyamide in any one or any combination of Embodiments 1 to 65, wherein all enumerated elements or options are optionally configured to be available for use or selection.

Claims

1. A method for recycling a polyamide composition, wherein the method is Pre-treating the polyamide composition containing the polyamide to produce a polyamide oligomer composition containing a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, A method comprising: subjecting the polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition comprising a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition.

2. The method according to claim 1, wherein the polyamide composition comprises a particulate composition, a semi-solid slurry, a slurry solution, a homogenized liquid solution of a dissolved polymer, or a combination thereof.

3. The method according to claim 1, wherein the mechanical treatment of a polyamide starting composition is mechanically treated to form the polyamide composition, the mechanical treatment further comprising size reduction, cutting, grinding, shredding, particle formation, or a combination thereof.

4. The method according to claim 1, comprising separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide composition having 5% by weight or less of non-polyamide components, wherein the separation of the mixed plastic stream further comprises removing or forming thermosetting polymers, polyesters, polyolefins, polycarbonates, or combinations thereof.

5. The method according to claim 1, wherein the polyamide in the polyamide composition comprises N4, N5, N6, N7, N10, N11, N12, N46, N56, N66, N610, N612, or a combination thereof, and the polyamide constitutes 95% to 100% by weight of the polyamide composition.

6. The method according to claim 1, wherein the polyamide in the polyamide composition comprises N66.

7. The method according to claim 1, wherein the pretreatment includes hot water treatment, subcritical water treatment, supercritical water treatment, microwave treatment, enzymatic treatment, solvent dissolution, acid hydrolysis, base hydrolysis, or a combination thereof.

8. The method according to claim 1, wherein the polyamide oligomer composition contains a polyamide oligomer having a number average molecular weight of 200 g / mol or more and 3,000 g / mol or less.

9. The method according to claim 1, wherein the pretreatment includes an enzymatic treatment, and the enzymatic treatment is carried out at a temperature of 15°C to 45°C, a pH of 5 to 9, and a pressure of 0.5 atm to 2 atm.

10. The method according to claim 1, wherein the pretreatment includes subcritical water treatment, and the subcritical water treatment includes treatment with water having a temperature of 200°C to less than 373.9°C and a pressure of 20 atm to 217.8 atm.

11. The method according to claim 1, wherein the pretreatment includes microwave treatment, and the microwave treatment includes exposure to microwave energy at a pressure of 1 atm to 1,000 atm in a solvent at a temperature of 100°C to 500°C.

12. The method according to claim 1, wherein the ammonialysis comprises contacting the polyamide oligomer composition with a nitrogen source at a reaction temperature of 200°C to 350°C and a reaction pressure of 30 atm to 140 atm, wherein the nitrogen source includes gaseous ammonia, liquid ammonia, dissolved ammonia, ammonia-containing solutions, and ammonia-enriched media, or a combination thereof.

13. The method according to claim 1, wherein the polyamide monomer is 90% to 100% by weight of the total amount of the polyamide monomer and polyamide oligomer in the polyamide precursor composition.

14. The method according to claim 1, further comprising polymerizing the polyamide precursor composition or one or more components thereof to form one or more polyamides.

15. A method for recycling a polyamide composition, wherein the method is Separating a mixed plastic stream containing more than 5% by weight of non-polyamide components to form a polyamide starting composition having 5% by weight or less of non-polyamide components, The polyamide starting composition is mechanically treated to produce the polyamide composition, wherein the polyamide composition has 5% by weight or less of non-polyamide components. The process involves pre-treating a polyamide composition containing a polyamide to produce a polyamide oligomer composition containing a polyamide oligomer having a lower molecular weight than the polyamide in the polyamide composition, wherein the pre-treatment includes subcritical water treatment, enzymatic treatment, or a combination thereof. A method comprising: subjecting the polyamide oligomer composition to ammonialysis to produce a polyamide precursor composition comprising a polyamide oligomer and / or monomer having a lower molecular weight than the polyamide oligomer in the polyamide oligomer composition.

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