Method for forming polyesters from regenerated diacids formed by depolymerization of waste materials

Abstract

A method for forming a polyester from a recycled composition comprising a regenerated diacid and a catalyst obtained from the depolymerization of polyester in waste materials is disclosed. The method includes reacting a diol with the regenerated diacid in the recycled composition to form one or more compounds that include ester bonds; optionally providing additional catalyst; and polymerizing the one or more compounds that include ester bonds to form a polyester.

Description

[Technical field]

[0001] Polyesters, such as polyethylene terephthalate, are commonly used in a variety of applications including films, textiles, and consumer products. [Background technology]

[0002] However, these materials have a limited life span and primarily end up in landfills, or waste facilities. Recently, there has been a great deal of interest in reusing and recycling these materials. In some cases, polyesters can be easily processed for reuse. However, in other cases, it may be necessary to depolymerize the polyester by breaking down the ester bonds and reducing the polymer to its monomeric components. In such depolymerization, conventional processes require steps that ultimately result in highly purified monomeric components for downstream use, potentially for use in polymerization reactions. However, this may have drawbacks, such as requiring additional capital for materials and equipment, and additional time for processing and downstream polymerization. As a result, there is a need to provide a process that utilizes components from the depolymerization of polyesters that allows for more efficient polymerization and formation of polyesters. Summary of the Invention

[0003] According to one embodiment of the present invention, a method for forming a polyester from a recycled composition comprising a regenerated diacid and a catalyst obtained from the depolymerization of polyester in waste materials is disclosed. The method includes reacting a diol with the regenerated diacid in the recycled composition to form one or more compounds containing ester bonds; optionally providing additional catalyst; and polymerizing the one or more compounds containing ester bonds to form a polyester.

[0004] Other features and aspects of the invention are described in more detail below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Those skilled in the art should appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0006] Generally speaking, the present invention relates to a method for forming a polyester. In particular, the polyester is formed from a regenerated composition comprising a regenerated diacid and a catalyst. For example, the regenerated composition is formed by depolymerizing polyester in waste materials. The inventors have discovered that this method can allow for more efficient formation / polymerization of the regenerated diacid with a diol.

[0007] The polyester formed by polymerization may include any form of polyester and is not necessarily limited by the present invention. For example, the polyester may include, but is not limited to, linear aliphatic polyester, hyperbranched polyester, heterocyclic polyester, aliphatic aromatic polyester, fully aromatic copolyester, etc. In one embodiment, the polyester may include linear aliphatic polyester. In another embodiment, the polyester may include aliphatic aromatic polyester. In a further embodiment, the polyester may be a heterocyclic polyester.

[0008] In particular, the polyester may include, but is not limited to, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, polyglycolic acid, poly-ε-caprolactone, polyhydroxybutyrate, polytrimethylene terephthalate, poly(ethylene 2,5-furandicarboxylate), poly(propylene 2,5-furandicarboxylate), poly(butylene 2,5-furandicarboxylate), poly(hexylene 2,5-furandicarboxylate), or mixtures thereof. In one embodiment, the polyester may include polybutylene terephthalate. In one particular embodiment, the polyester may include polyethylene terephthalate.

[0009] In one embodiment, the polyesters may be bio-based polyesters. In general, these polyesters may be aliphatic polyesters. These bio-based polyesters may include, but are not limited to, polylactic acid, polyglycolic acid, poly-ε-caprolactone, polyhydroxybutyrate, and the like, or mixtures thereof.

[0010] The polyester may also be a heterocyclic polyester. The heterocyclic ring may contain saturated or unsaturated bonds. In a particular embodiment, the heterocyclic ring contains at least one unsaturated carbon-carbon bond. The heterocyclic polyester may include a furan-based polyester. Generally, such polyesters can be obtained from 2,5-furandicarboxylate. For example, the furan-based polyester may include, but is not limited to, poly(ethylene 2,5-furandicarboxylate), poly(propylene 2,5-furandicarboxylate), poly(butylene 2,5-furandicarboxylate), poly(hexylene 2,5-furandicarboxylate), and copolyesters thereof.

[0011] As mentioned above, the polyester is formed from the polymerization of a regenerating composition comprising a regenerated diacid and a catalyst. In this regard, such regenerating composition is formed by depolymerizing polyester in waste materials. Thus, such polyester used in such depolymerization can be any of the aforementioned polyesters.

[0012] The polymerization to form the polymer is carried out utilizing a regenerating composition that includes a regenerating diacid (i.e., dicarboxylic acid) and a catalyst along with the diol, for example, such a polymerization may be referred to as an esterification reaction or esterification polymerization.

[0013] The diacid (or regenerating diacid) used in the polymerization may include, but is not limited to, saturated diacids, unsaturated diacids, or mixtures thereof. In one embodiment, the diacid (or regenerating diacid) includes saturated diacids. Saturated diacids include ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, or mixtures thereof.

[0014] In one embodiment, the diacid (or regenerating diacid) comprises an unsaturated diacid. For example, the unsaturated diacid comprises a linear unsaturated diacid, a branched unsaturated diacid, an aromatic diacid, or a mixture thereof. In one embodiment, the unsaturated diacid comprises a linear unsaturated diacid. In another embodiment, the unsaturated diacid comprises a branched unsaturated diacid. In a further embodiment, the unsaturated diacid comprises an aromatic diacid. The aromatic diacid may be polycyclic. For example, the polycyclic aromatic diacid may comprise a fused aromatic diacid, a bridged aromatic diacid, or a spiro aromatic diacid.

[0015] For example, the unsaturated diacid may include maleic acid, fumaric acid, glutaconic acid, or mixtures thereof. In one particular embodiment, the aromatic diacid may include terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, or mixtures thereof. In one embodiment, the aromatic diacid may include phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, or mixtures thereof. In one particular embodiment, the aromatic diacid may include terephthalic acid.

[0016] As provided herein, the regenerating composition also includes a catalyst. For the methods utilized in the depolymerization of waste materials described herein, the catalyst in the regenerating composition may maintain its catalytic activity. The catalyst may include antimony, germanium, titanium, cobalt, molybdenum, or a mixture thereof. In an embodiment, the catalyst may include germanium, titanium, cobalt, molybdenum, or a mixture thereof. In a particular embodiment, the catalyst may include antimony. For example, the antimony may include antimony trioxide, antimony acetate (e.g., antimony triacetate, also known as antimony(III) acetate), antimony glycolate, an antimony / metal complex, or a mixture thereof. For example, the antimony / metal complex may include antimony and a transition metal and / or an alkali metal. In an embodiment, the antimony / metal complex may include both a transition metal and an alkali metal. The transition metal may include, but is not limited to, cobalt, manganese, zinc, or a mixture thereof. The alkali metal may include lithium, sodium, potassium, cesium, or a mixture thereof. In one embodiment, the antimony catalyst may include antimony acetate (e.g., antimony triacetate), antimony glycolate, antimony / metal complex, or mixtures thereof. In one particular embodiment, the antimony may include antimony trioxide. In another particular embodiment, the antimony may include antimony acetate, such as antimony triacetate.

[0017] The regenerating composition may include a certain amount of catalyst. Generally, such catalyst may be present in the regenerating composition after depolymerization of polyester as shown herein. The catalyst may be present in the regenerating composition in an amount of more than 0 ppm, for example 5 ppm or more, for example 10 ppm or more, for example 15 ppm or more, for example 20 ppm or more, for example 25 ppm or more, for example 30 ppm or more, for example 40 ppm or more, for example 50 ppm or more, for example 60 ppm or more, for example 70 ppm or more, for example 75 ppm or more, for example 90 ppm or more, for example 100 ppm or more, for example 125 ppm or more, for example 150 ppm or more, for example 180 ppm or more, for example 200 ppm or more. The catalyst may be present in the regenerating composition in an amount of 350 ppm or less, such as 300 ppm or less, for example 275 ppm or less, such as 250 ppm or less, for example 225 ppm or less, such as 200 ppm or less, for example 190 ppm or less, such as 170 ppm or less, for example 150 ppm or less, such as 130 ppm or less, for example 110 ppm or less, such as 100 ppm or less, for example 90 ppm or less.

[0018] In other words, the catalyst may be present in the regenerating composition in an amount greater than 0 wt.%, such as 0.0005 wt.% or more, such as 0.001 wt.% or more, for example 0.002 wt.% or more, such as 0.003 wt.% or more, for example 0.004 wt.% or more, such as 0.005 wt.% or more, for example 0.006 wt.% or more, such as 0.007 wt.% or more, for example 0.0075 wt.% or more, such as 0.008 wt.% or more, for example 0.01 wt.% or more, such as 0.012 wt.% or more, for example 0.014 wt.% or more, such as 0.015 wt.% or more, for example 0.018 wt.% or more, such as 0.02 wt.% or more, for example 0.022 wt.% or more, such as 0.025 wt.% or more, for example 0.028 wt.% or more, such as 0.03 wt.% or more, for example 0.04 wt.% or more, based on the weight of the regenerating diacid. The catalyst may be present in an amount of 0.05 wt.% or less, such as 0.048 wt.% or less, for example 0.045 wt.% or less, such as 0.043 wt.% or less, for example 0.04 wt.% or less, such as 0.037 wt.% or less, for example 0.035 wt.% or less, such as 0.033 wt.% or less, for example 0.03 wt.% or less, such as 0.028 wt.% or less, for example 0.025 wt.% or less, such as 0.022 wt.% or less, for example 0.02 wt.% or less, such as 0.02 wt.% or less, based on the weight of the regenerated diacid. It may be present in the regenerating composition in an amount of 0.018% by weight or less, such as 0.016% by weight or less, for example 0.015% by weight or less, such as 0.013% by weight or less, for example 0.011% by weight or less, such as 0.01% by weight or less, for example 0.009% by weight or less, such as 0.008% by weight or less, for example 0.007% by weight or less, such as 0.005% by weight or less, for example 0.003% by weight or less, such as 0.002% by weight or less, for example 0.001% by weight or less.

[0019] The regenerated diacid may be present in the regenerated composition in an amount of 80% by weight or more, such as 85% by weight or more, such as 90% by weight or more, such as 95% by weight or more, such as 97% by weight or more, such as 98% by weight or more, such as 99% by weight or more, such as 99.5% by weight or more, such as 99.7% by weight or more, such as 99.8% by weight or more, such as 99.9% by weight or more, such as 99.95% by weight or more, such as 99.96% by weight or more, such as 99.97% by weight or more, such as 99.98% by weight or more, such as 99.99% by weight or more. The regenerated diacid may be present in the regenerated composition in an amount of less than 100% by weight, such as 99.99999% by weight or less, such as 99.9999% by weight or less, such as 99.9995% by weight or less, such as 99.999% by weight or less, such as 99.995% by weight or less, such as 99.9% by weight or less.

[0020] Generally, polymerization is carried out in the presence of a catalyst. However, as noted above, the composition produced may include the catalyst obtained from the depolymerization. In this regard, in one embodiment, the polymerization reaction may not require the use of any additional catalyst. In another embodiment, the polymerization reaction may require the use of an additional catalyst. However, since the regenerated composition may already include some catalyst obtained from a previous depolymerization, the amount of additional catalyst provided may be less than typically required. On the other hand, the additional catalyst may be any of the catalysts described above present in the regenerated composition. For example, in one particular embodiment, the additional catalyst may include antimony. For example, the antimony may include antimony trioxide, antimony acetate (e.g., antimony triacetate, also known as antimony(III) acetate), antimony glycolate, antimony / metal complexes, or mixtures thereof. For example, the antimony / metal complexes may include antimony and a transition metal and / or an alkali metal. In one embodiment, the antimony / metal complexes may include both a transition metal and an alkali metal. The transition metal may include, but is not limited to, cobalt, manganese, zinc, or mixtures thereof. The alkali metal may include lithium, sodium, potassium, cesium, or mixtures thereof. In one embodiment, the antimony catalyst may include antimony acetate (e.g., antimony triacetate), antimony glycolate, antimony / metal complex, or mixtures thereof. In one particular embodiment, the antimony may include antimony trioxide. In another particular embodiment, the antimony may include antimony acetate, such as antimony triacetate.

[0021] As mentioned above, a diol is also required for the polymerization. The diol may be, but is not limited to, an aliphatic diol, an aromatic diol, or a mixture thereof. In one embodiment, the diol may include an aromatic diol. The aromatic diol may be polycyclic. For example, the polycyclic aromatic diol may include a fused aromatic diol, a bridged aromatic diol, or a spiro aromatic diol. The aromatic diol may include catechol, resorcinol, hydroquinone, or a mixture thereof. In another embodiment, the regenerated diol includes an aliphatic diol. For example, the aliphatic diol may include ethylene glycol, butanediol (e.g., 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol), propanediol (e.g., 1,2-propanediol, 1,3-propanediol), pentanediol (e.g., 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol, etc.), hexanediol (e.g., 1,6-hexanediol, 2-5-hexanediol, etc.), tetraethylene glycol, or mixtures thereof. In one embodiment, the aliphatic diol includes butanediol, propanediol, or mixtures thereof. In one particular embodiment, the aliphatic diol includes ethylene glycol.

[0022] Generally, a regenerated composition including a regenerated diacid and a catalyst and a diol can be provided. In particular, they can be provided in a vessel such as a polymerization vessel. First, the regenerated diacid and diol can undergo a reaction (e.g., an esterification reaction) to form a compound including an ester bond between the diacid and the diol. In this regard, the method can include a step of reacting the regenerated diacid and the diol to form one or more compounds having an ester bond. Thereafter, to the extent necessary, a catalyst can be added as shown herein. However, it should be understood that in certain embodiments, a catalyst may not be added. For example, there may be sufficient catalyst present in the regenerated composition such that no additional catalyst is required. In any case, the one or more compounds having an ester bond can then be polymerized in a polymerization reaction to form a polyester.

[0023] The regenerated diacid, diol and catalyst may be present for the reaction in a certain amount. For example, the regenerated diacid may be present in an amount of 10% by weight or more, such as 15% by weight or more, such as 20% by weight or more, such as 25% by weight or more, such as 30% by weight or more, such as 35% by weight or more, such as 40% by weight or more, such as 45% by weight or more, such as 50% by weight or more, such as 60% by weight or more, such as 70% by weight or more, such as 75% by weight or more, based on the total weight of the monomers (i.e., regenerated diacid and diol). Also, the regenerated diacid may be present in an amount of 90% by weight or less, such as 85% by weight or less, such as 80% by weight or less, such as 75% by weight or less, such as 70% by weight or less, such as 65% by weight or less, such as 60% by weight or less, such as 50% by weight or less, such as 40% by weight or less, based on the total weight of the monomers (i.e., regenerated diacid and diol).

[0024] Similarly, the regenerated diacid may be present in an amount of 5 mol% or more, such as 10 mol% or more, such as 15 mol% or more, such as 20 mol% or more, such as 25 mol% or more, such as 30 mol% or more, such as 35 mol% or more, such as 40 mol% or more, such as 45 mol% or more, based on the total moles of monomer (i.e., regenerated diacid and diol). The regenerated diacid may be present in an amount of 60 mol% or less, such as 55 mol% or less, such as 50 mol% or less, such as 45 mol% or less, such as 40 mol% or less, such as 35 mol% or less, based on the total moles of monomer (i.e., regenerated diacid and diol).

[0025] Further, the diol may be present in an amount of 5 wt% or more, such as 10 wt% or more, such as 15 wt% or more, such as 20 wt% or more, such as 25 wt% or more, such as 30 wt% or more, such as 35 wt% or more, such as 40 wt% or more, such as 45 wt% or more, such as 50 wt% or more, based on the total weight of the monomers (i.e., regenerated diacid and diol). Also, the diol may be present in an amount of 80 wt% or less, such as 75 wt% or less, such as 70 wt% or less, such as 65 wt% or less, such as 60 wt% or less, such as 50 wt% or less, such as 40 wt% or less, such as 35 wt% or less, such as 30 wt% or less, based on the total weight of the monomers (i.e., regenerated diacid and diol).

[0026] Similarly, the diol may be present in an amount of 5 mol% or more, such as 10 mol% or more, such as 15 mol% or more, such as 20 mol% or more, such as 25 mol% or more, such as 30 mol% or more, such as 35 mol% or more, such as 40 mol% or more, such as 45 mol% or more, such as 50 mol% or more, based on the total moles of monomer (i.e., regenerated diacid and diol).The diol may be present in an amount of 80 mol% or less, such as 75 mol% or less, such as 60 mol% or less, such as 55 mol% or less, such as 50 mol% or less, such as 45 mol% or less, such as 40 mol% or less, such as 35 mol% or less, based on the total moles of monomer (i.e., regenerated diacid and diol).

[0027] The regenerated diacid and diol may be present in a specific amount relative to each other. For example, in terms of weight, in one embodiment, the diol may be present in a lesser amount than the regenerated diacid. In another embodiment, the diol may be present in a greater amount than the regenerated diacid. The weight ratio of the diol to the regenerated diacid may be 0.05 or more, such as 0.1 or more, such as 0.15 or more, such as 0.2 or more, such as 0.25 or more, such as 0.3 or more, such as 0.35 or more, such as 0.4 or more, such as 0.45 or more, such as 0.5 or more. The weight ratio may be 5 or less, such as 4 or less, such as 3 or less, such as 2.5 or less, such as 2 or less, such as 1.5 or less, such as 1 or less, such as 0.9 or less, such as 0.8 or less, such as 0.7 or less, such as 0.6 or less, such as 0.55 or less, such as 0.5 or less, such as 0.45 or less.

[0028] Also, from a molar perspective, in one embodiment, the diol may be present in a lesser amount than the regenerated diacid. In another embodiment, the diol may be present in a greater amount than the regenerated diacid. The molar ratio of diol to regenerated diacid may be 0.05 or more, such as 0.1 or more, such as 0.2 or more, such as 0.3 or more, such as 0.4 or more, such as 0.5 or more, such as 0.6 or more, such as 0.7 or more, such as 0.8 or more, such as 0.9 or more, such as 1 or more, such as 1.1 or more, such as 1.15 or more, such as 1.2 or more, such as 1.5 or more. The molar ratio may be 10 or less, such as 8 or less, such as 6 or less, such as 5 or less, such as 4 or less, such as 3 or less, such as 2.5 or less, such as 2 or less, such as 1.8 or less, such as 1.6 or less, such as 1.5 or less, such as 1.4 or less, such as 1.3 or less, such as 1.2 or less, such as 1.1 or less, such as 1 or less, such as 0.9 or less.

[0029] The total amount of catalyst required for polymerization may be 500 ppm or less, such as 450 ppm or less, for example 400 ppm or less, such as 375 ppm or less, for example 350 ppm or less, such as 325 ppm or less, for example 300 ppm or less, such as 275 ppm or less, for example 250 ppm or less, such as 225 ppm or less, for example 200 ppm or less. The total amount of catalyst required for polymerization may be more than 0 ppm, such as 10 ppm or more, for example 20 ppm or more, such as 30 ppm or more, for example 40 ppm or more, such as 50 ppm or more, for example 80 ppm or more, such as 100 ppm or more, for example 125 ppm or more, such as 150 ppm or more, for example 175 ppm or more, such as 200 ppm or more, for example 225 ppm or more, for example 250 ppm or more, such as 275 ppm or more, for example 300 ppm or more, such as 325 ppm or more, for example 350 ppm or more. The aforementioned ppm is determined based on the total amount of regenerated diacid, diol and catalyst used.

[0030] However, as shown herein, the regenerating composition may already contain a catalyst. In this regard, the catalyst provided by the regenerating composition may be 400 ppm or less, such as 375 ppm or less, such as 350 ppm or less, such as 325 ppm or less, such as 300 ppm or less, such as 275 ppm or less, such as 250 ppm or less, such as 225 ppm or less, such as 200 ppm or less. The catalyst provided by the regenerating composition may be more than 0 ppm, such as 10 ppm or more, such as 20 ppm or more, such as 30 ppm or more, such as 40 ppm or more, such as 50 ppm or more, such as 80 ppm or more, such as 100 ppm or more, such as 125 ppm or more, such as 150 ppm or more, such as 175 ppm or more, such as 200 ppm or more, such as 225 ppm or more, such as 250 ppm or more, such as 275 ppm or more, such as 300 ppm or more, such as 325 ppm or more, such as 350 ppm or more. The aforementioned ppm is determined based on the total amount of regenerated diacid, diol and catalyst used.

[0031] In this regard, in one embodiment, it may not be necessary to provide an additional catalyst for polymerization. However, in one embodiment, an additional catalyst may be provided for polymerization. Such an additional catalyst may be provided before polymerization. In another embodiment, such an additional catalyst may be provided during polymerization. In a further embodiment, such an additional catalyst may be provided before and during polymerization. In this regard, the amount of such an additional catalyst may be 400 ppm or less, such as 375 ppm or less, such as 350 ppm or less, such as 325 ppm or less, such as 300 ppm or less, such as 275 ppm or less, such as 250 ppm or less, such as 225 ppm or less, such as 200 ppm or less. The amount of additional catalyst provided can be greater than 0 ppm, such as 10 ppm or more, for example 20 ppm or more, such as 30 ppm or more, for example 40 ppm or more, such as 50 ppm or more, for example 80 ppm or more, such as 100 ppm or more, for example 125 ppm or more, such as 150 ppm or more, for example 175 ppm or more, such as 200 ppm or more, for example 225 ppm or more, such as 250 ppm or more, for example 275 ppm or more, such as 300 ppm or more. The aforementioned ppm is determined based on the total amount of regenerated diacid, diol and catalyst used.

[0032] Thus, if added, the amount of catalyst added for the polymerization reaction may be 70% or less, such as 60% or less, such as 50% or less, such as 40% or less, such as 30% or less, such as 25% or less, such as 20% or less of the amount theoretically required to effectively undergo esterification and polymerization to form a polyester. Such aforesaid amount may be a weight percentage in one embodiment. In another embodiment, such aforesaid amount may be a molar percentage.

[0033] The esterification and polymerization conditions are not necessarily limited by the present invention. For example, the esterification can be carried out at a temperature of 50°C or more, such as 70°C or more, such as 90°C or more, such as 100°C or more, such as 110°C or more, such as 130°C or more, such as 150°C or more, such as 180°C or more, such as 220°C or more, such as 240°C or more, such as 260°C or more. The temperature can be 400°C or less, such as 380°C or less, such as 350°C or less, such as 330°C or less, such as 310°C or less, such as 300°C or less, such as 280°C or less, such as 270°C or less, such as 260°C or less, such as 250°C or less, such as 220°C or less, such as 200°C or less, such as 180°C or less, such as 160°C or less, such as 150°C or less.

[0034] The polymerization may be carried out at a temperature of 50° C. or more, such as 70° C. or more, for example 90° C. or more, such as 100° C. or more, for example 110° C. or more, such as 130° C. or more, for example 150° C. or more, such as 180° C. or more, for example 220° C. or more, such as 240° C. or more, for example 260° C. or more. The temperature may be 400° C. or less, such as 380° C. or less, for example 350° C. or less, such as 330° C. or less, for example 310° C. or less, such as 300° C. or less, for example 280° C. or less, such as 270° C. or less, for example 260° C. or less, such as 250° C. or less, for example 220° C. or less, such as 200° C. or less, for example 180° C. or less, such as 160° C. or less, for example 150° C. or less.

[0035] The esterification may be carried out at a pressure of 0.01 kPa or more, such as 0.05 kPa or more, for example 0.1 kPa or more, such as 0.2 kPa or more, for example 0.3 kPa or more, such as 0.5 kPa or more, for example 1 kPa or more, such as 2 kPa or more, for example 3 kPa or more, such as 5 kPa or more, for example 10 kPa or more, such as 20 kPa or more, for example 50 kPa or more, such as 80 kPa or more, for example 100 kPa or more, such as 130 kPa or more, for example 150 kPa or more, such as 200 kPa or more, for example 250 kPa or more, such as 300 kPa or more, for example 500 kPa or more. The pressure may be 1000 kPa or less, such as 700 kPa or less, for example 500 kPa or less, such as 400 kPa or less, for example 350 kPa or less, such as 300 kPa or less, for example 280 kPa or less, such as 250 kPa or less, for example 240 kPa or less, such as 220 kPa or less, for example 200 kPa or less, such as 170 kPa or less, for example 150 kPa or less, such as 130 kPa or less, for example 100 kPa or less, such as 70 kPa or less, for example 50 kPa or less, such as 30 kPa or less, for example 20 kPa or less, such as 10 kPa or less, for example 8 kPa or less, such as 6 kPa or less, for example 3 kPa or less, such as 1 kPa or less, for example 0.5 kPa or less.

[0036] The polymerization may be carried out at a pressure of 0.01 kPa or more, such as 0.05 kPa or more, for example 0.1 kPa or more, such as 0.2 kPa or more, for example 0.3 kPa or more, such as 0.5 kPa or more, for example 1 kPa or more, such as 2 kPa or more, for example 3 kPa or more, such as 5 kPa or more, for example 10 kPa or more, such as 20 kPa or more, for example 50 kPa or more, such as 80 kPa or more, for example 100 kPa or more, such as 130 kPa or more, for example 150 kPa or more, such as 200 kPa or more, for example 250 kPa or more, such as 300 kPa or more, for example 500 kPa or more. The pressure may be 1000 kPa or less, such as 700 kPa or less, for example 500 kPa or less, such as 400 kPa or less, for example 350 kPa or less, such as 300 kPa or less, for example 280 kPa or less, such as 250 kPa or less, for example 240 kPa or less, such as 220 kPa or less, for example 200 kPa or less, such as 170 kPa or less, for example 150 kPa or less, such as 130 kPa or less, for example 100 kPa or less, such as 70 kPa or less, for example 50 kPa or less, such as 30 kPa or less, for example 20 kPa or less, such as 10 kPa or less, for example 8 kPa or less, such as 6 kPa or less, for example 3 kPa or less, such as 1 kPa or less, for example 0.5 kPa or less. In an embodiment, after completion of the esterification reaction, the pressure may be reduced such that the polymerization is carried out at a pressure lower than the pressure of the esterification reaction.

[0037] The esterification may be carried out for 0.01 hours or more, such as 0.02 hours or more, for example 0.05 hours or more, such as 0.1 hours or more, for example 0.2 hours or more, such as 0.3 hours or more, for example 0.5 hours or more, such as 1 hour or more, for example 2 hours or more, such as 3 hours or more, for example 4 hours or more, such as 5 hours or more, for example 6 hours or more, such as 8 hours or more, for example 10 hours or more, such as 12 hours or more, for example 15 hours or more. The time may be 24 hours or less, such as 20 hours or less, for example 18 hours or less, such as 15 hours or less, for example 13 hours or less, such as 11 hours or less, for example 10 hours or less, such as 8 hours or less, for example 6 hours or less, such as 5 hours or less, for example 4 hours or less, such as 3 hours or less, for example 2 hours or less, such as 1 hour or less, for example 0.8 hours or less, such as 0.6 hours or less, for example 0.5 hours or less, such as 0.4 hours or less, for example 0.3 hours or less, for example 0.2 hours or less, for example 0.1 hours or less.

[0038] The polymerization may be carried out for 0.01 hours or more, such as 0.02 hours or more, for example 0.05 hours or more, such as 0.1 hours or more, for example 0.2 hours or more, such as 0.3 hours or more, for example 0.5 hours or more, such as 1 hour or more, for example 2 hours or more, such as 3 hours or more, for example 4 hours or more, for example 5 hours or more, such as 6 hours or more, for example 8 hours or more, such as 10 hours or more, for example 12 hours or more, for example 15 hours or more. The time may be 24 hours or less, such as 20 hours or less, for example 18 hours or less, such as 15 hours or less, for example 13 hours or less, such as 11 hours or less, for example 10 hours or less, such as 8 hours or less, for example 6 hours or less, such as 5 hours or less, for example 4 hours or less, such as 3 hours or less, for example 2 hours or less, such as 1 hour or less, for example 0.8 hours or less, such as 0.6 hours or less, for example 0.5 hours or less, such as 0.4 hours or less, for example 0.3 hours or less, for example 0.2 hours or less, for example 0.1 hours or less.

[0039] The polyester may have certain properties or may be substantially similar in respect of certain properties when compared to standard polyesters. For example, when measured at 25° C., the polyester may have an intrinsic viscosity of 1.0 dL / g or less, such as 0.95 dL / g or less, such as 0.90 dL / g or less, such as 0.85 dL / g or less, such as 0.80 dL / g or less, such as 0.75 dL / g or less, such as 0.70 dL / g or less, such as 0.65 dL / g or less, such as 0.60 dL / g or less. The intrinsic viscosity may be 0.30 dL / g or more, such as 0.35 dL / g or more, such as 0.40 dL / g or more, such as 0.45 dL / g or more, such as 0.50 dL / g or more, such as 0.55 dL / g or more, such as 0.60 dL / g or more, such as 0.65 dL / g or more, such as 0.70 dL / g or more. In general, the ratio of the intrinsic viscosity of the polyester formed from the recycled composition including recycled diol to the intrinsic viscosity of a standard polyester formed according to the same conditions except utilizing virgin or unrecycled diacid may be 1.2 or less, such as 1.15 or less, such as 1.1 or less, such as 1.05 or less, such as 1 or less, such as 0.98 or less, such as 0.95 or less, such as 0.93 or less, such as 0.9 or less. This ratio may be 0.8 or more, such as 0.84 or more, such as 0.85 or more, such as 0.88 or more, such as 0.9 or more, such as 0.93 or more, such as 0.95 or more, such as 0.98 or more. Intrinsic viscosity may be determined using means known in the art, for example according to ASTM D4603-13.

[0040] The polyester may also have a particular melting temperature. For example, the melting temperature may be 200°C or more, such as 220°C or more, such as 230°C or more, such as 240°C or more, such as 245°C or more, such as 250°C or more, such as 252°C or more, such as 255°C or more, such as 258°C or more. The melting temperature may be 300°C or less, such as 290°C or less, such as 280°C or less, such as 275°C or less, such as 260°C or less, such as 258°C or less, such as 255°C or less, such as 253°C or less, such as 250°C or less. The ratio of the melting temperature of the polyester formed from the recycled composition containing recycled diol to the melting temperature of the standard polyester formed according to the same conditions except utilizing virgin or unrecycled diacid may be 1.2 or less, such as 1.15 or less, such as 1.1 or less, such as 1.05 or less, such as 1.01 or less, such as 1 or less, such as 0.98 or less, such as 0.95 or less. This ratio may be 0.8 or more, such as 0.85 or more, such as 0.88 or more, for example 0.9 or more, such as 0.93 or more, such as 0.95 or more, for example 0.96 or more, such as 0.97 or more, for example 0.98 or more, such as 0.99 or more. The melt temperature may be determined using means known in the art, for example according to ASTM D7138-16.

[0041] Further, the polyester may have a specific ash content. For example, the ash content may be 0.5% or less, such as 0.45% or less, such as 0.4% or less, such as 0.35% or less, such as 0.3% or less, such as 0.25% or less, such as 0.2% or less, such as 0.15% or less, such as 0.1% or less, such as 0.08% or less, such as 0.06% or less, such as 0.05% or less, such as 0.04% or less. The ash content may be 0% or more, such as 0.01% or more, such as 0.02% or more, such as 0.03% or more, such as 0.04% or more, such as 0.05% or more, such as 0.1% or more, such as 0.15% or more, such as 0.2% or more, such as 0.25% or more. The ratio of ash content of polyester formed from recycled composition containing recycled diol to ash content of standard polyester formed according to the same conditions except utilizing virgin or unrecycled diacid may be 1.2 or less, such as 1.1 or less, such as 1 or less, such as 0.9 or less, such as 0.8 or less, such as 0.7 or less, such as 0.6 or less, such as 0.5 or less, such as 0.45 or less, such as 0.4 or less, such as 0.3 or less, such as 0.25 or less, such as 0.2 or less, such as 0.18 or less, such as 0.15 or less, such as 0.13 or less, such as 0.1 or less. The ratio may be greater than 0, such as 0.05 or more, such as 0.1 or more, such as 0.2 or more, such as 0.3 or more, such as 0.4 or more, such as 0.5 or more, such as 0.6 or more, such as 0.7 or more, such as 0.8 or more, such as 0.9 or more. Ash content may be determined according to ASTM D5630-13.

[0042] As mentioned above, the polyester is formed by polymerization of a regenerating composition comprising a regenerated diacid and a catalyst. In this regard, such regenerating composition is formed by depolymerizing polyester in waste materials. Thus, such polyesters used in such depolymerization may be any polyester as described above. Also, without intending to be limited, the waste materials may include various materials. For example, the source of the waste materials may be post-consumer materials or recycled materials. For example, the waste materials may be pre-consumer sources such as scraps generated as a by-product or post-consumer sources such as post-consumer materials. The waste materials may be in the form of textiles, fibers, yarns, films, chips, and the like. For example, the waste materials may be textiles comprising fibers and / or yarns. In this regard, the waste materials may be waste textiles. Furthermore, the polyester may be present in various forms. For example, the polyester may be present in the form of fibers, yarns, films, chips, and the like. In one embodiment, the polyester may be present in the form of films or chips. In another embodiment, the polyester may be present in the form of fibers or yarns. For example, the polyester may be present in the form of fibers. In another embodiment, the polyester may be present in the form of yarns. Thus, the feedstock of polyester or waste material is not necessarily limited by the present invention.

[0043] When present as waste material, such as waste textiles, polyester may be present alone or in the presence of other polymers. In this regard, polyester may be part of a starting waste material, such as waste textiles, that includes polyester and at least one other polymer. In one embodiment, the at least one other polymer may be a polymer other than polyester. The at least one other polymer may include, but is not limited to, cellulose, polyamide, polyether-polyurea copolymer, polyurethane, lignocellulose, siloxane, natural polymer fibers, or combinations thereof. In one embodiment, the at least one other polymer includes polyamide. For example, the polyamide may be nylon. Also, the polyamide may specifically be a polypeptide. Furthermore, the polymer may include natural polymer fibers, such as keratin, chitin, chitosan, collagen, or mixtures thereof. In another embodiment, the at least one other polymer includes a polyether-polyurea copolymer. For example, the polyether-polyurea copolymer may be spandex (e.g., elastane). In a further embodiment, the at least one other polymer includes cellulose. The cellulose may include, but is not limited to, rayon, cotton, viscose, lyocell, cellulose acetate, etc. Also, in one embodiment, the cellulose may be regenerated cellulose.

[0044] Generally, when at least one other polymer is present with the polyester during depolymerization, the polyester is present in an amount of 0.01 wt.% or more, such as 1 wt.% or more, for example 2 wt.% or more, such as 5 wt.% or more, for example 10 wt.% or more, such as 15 wt.% or more, for example 20 wt.% or more, such as 30 wt.% or more, for example 40 wt.% or more, such as 50 wt.% or more, for example 60 wt.% or more, such as 70 wt.% or more, for example 80 wt.% or more, such as 85 wt.% or more, for example 90 wt.% or more, such as 95 wt.% or more, for example 98 wt.% or more, such as 99 wt.% or more, for example 100 wt.%, based on the total weight of the polymers (i.e., the polyester and the at least one other polymer). The polyester may be present in an amount of 100% by weight or less, such as 99.9% by weight or less, such as 99% by weight or less, for example 98% by weight or less, such as 95% by weight or less, for example 90% by weight or less, such as 80% by weight or less, for example 70% by weight or less, such as 60% by weight or less, for example 50% by weight or less, such as 40% by weight or less, for example 30% by weight or less, such as 20% by weight or less, for example 15% by weight or less, such as 10% by weight or less, for example 5% by weight or less, based on the total weight of the polymers (i.e. the polyester and the at least one other polymer).

[0045] Further, when at least one other polymer is present together with the polyester, said at least one other polymer is present in an amount of 0.01 wt% or more, such as 1 wt% or more, for example 2 wt% or more, such as 5 wt% or more, for example 10 wt% or more, such as 15 wt% or more, for example 20 wt% or more, such as 30 wt% or more, for example 40 wt% or more, such as 50 wt% or more, for example 60 wt% or more, such as 70 wt% or more, for example 80 wt% or more, such as 85 wt% or more, for example 90 wt% or more, such as 95 wt% or more, for example 98 wt% or more, such as 99 wt% or more, for example 100 wt% based on the total weight of the polymers (i.e., the polyester and the at least one other polymer). The at least one other polymer may be present in an amount of 100% by weight or less, such as 99.9% by weight or less, such as 99% by weight or less, for example 98% by weight or less, such as 95% by weight or less, such as 90% by weight or less, for example 80% by weight or less, such as 70% by weight or less, for example 60% by weight or less, such as 50% by weight or less, such as 40% by weight or less, such as 30% by weight or less, such as 20% by weight or less, for example 15% by weight or less, such as 10% by weight or less, for example 5% by weight or less, based on the total weight of the polymers (i.e. polyester and at least one other polymer). Such aforesaid weight percentages may be for a single other polymer other than the polyester or for multiple other polymers.

[0046] Generally, depolymerization of polyesters in waste materials results in a regenerated composition comprising a regenerated diacid (i.e., dicarboxylic acid) and a catalyst, as well as a regenerated diol. Additionally, the regenerated composition may include a regenerated diol. The nature of the regenerated diol and the regenerated diacid may depend on the particular polyester undergoing depolymerization. Additionally, the depolymerization method may prevent decarboxylation of the regenerated diacid, thereby allowing for the formation of the regenerated diacid, without intending to be limited by theory.

[0047] For example, the regenerative diacid may include, but is not limited to, a saturated diacid, an unsaturated diacid, or a mixture thereof. In one embodiment, the regenerative diacid includes a saturated diacid. Saturated diacids include ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, or a mixture thereof.

[0048] In one embodiment, the regenerating diacid comprises an unsaturated diacid. For example, the unsaturated diacid comprises a linear unsaturated diacid, a branched unsaturated diacid, an aromatic diacid, or a mixture thereof. In one embodiment, the unsaturated diacid comprises a linear unsaturated diacid. In another embodiment, the unsaturated diacid comprises a branched unsaturated diacid. In a further embodiment, the unsaturated diacid comprises an aromatic diacid. The aromatic diacid may be polycyclic. For example, the polycyclic aromatic diacid may comprise a fused aromatic diacid, a bridged aromatic diacid, or a spiro aromatic diacid.

[0049] For example, the unsaturated diacid may include maleic acid, fumaric acid, glutaconic acid, or mixtures thereof. In one particular embodiment, the aromatic diacid may include terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, or mixtures thereof. In one embodiment, the aromatic diacid may include phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, or mixtures thereof. In one particular embodiment, the aromatic diacid may include terephthalic acid.

[0050] As provided herein, the regenerating composition also includes a catalyst. For the purposes of the methods utilized herein, the catalyst may maintain its catalytic activity. The catalyst may include antimony, germanium, titanium, cobalt, molybdenum, or a mixture thereof. In an embodiment, the catalyst may include germanium, titanium, cobalt, molybdenum, or a mixture thereof. In a particular embodiment, the catalyst may include antimony. For example, the antimony may include antimony trioxide, antimony acetate (e.g., antimony triacetate, also known as antimony(III) acetate), antimony glycolate, an antimony / metal complex, or a mixture thereof. For example, the antimony / metal complex may include antimony and a transition metal and / or an alkali metal. In an embodiment, the antimony / metal complex may include both a transition metal and an alkali metal. The transition metal may include, but is not limited to, cobalt, manganese, zinc, or a mixture thereof. The alkali metal may include lithium, sodium, potassium, cesium, or a mixture thereof. In one embodiment, the antimony catalyst may include antimony acetate (e.g., antimony triacetate), antimony glycolate, antimony / metal complex, or mixtures thereof. In one particular embodiment, the antimony may include antimony trioxide. In another particular embodiment, the antimony may include antimony acetate, such as antimony triacetate.

[0051] The regenerating composition may contain a certain amount of catalyst. Usually, such catalyst may be present in the regenerating composition after depolymerization of polyester as described above. The catalyst may be present in the regenerating composition in an amount of more than 0 ppm, for example 5 ppm or more, for example 10 ppm or more, for example 15 ppm or more, for example 20 ppm or more, for example 25 ppm or more, for example 30 ppm or more, for example 40 ppm or more, for example 50 ppm or more, for example 60 ppm or more, for example 70 ppm or more, for example 75 ppm or more, for example 90 ppm or more, for example 100 ppm or more, for example 125 ppm or more, for example 150 ppm or more, for example 180 ppm or more, for example 200 ppm or more. The catalyst may be present in the regenerating composition in an amount of 350 ppm or less, such as 300 ppm or less, for example 275 ppm or less, such as 250 ppm or less, for example 225 ppm or less, such as 200 ppm or less, for example 190 ppm or less, such as 170 ppm or less, for example 150 ppm or less, such as 130 ppm or less, for example 110 ppm or less, such as 100 ppm or less, for example 90 ppm or less.

[0052] In other words, the catalyst may be present in an amount greater than 0 wt.%, such as 0.0005 wt.% or more, such as 0.001 wt.% or more, for example 0.002 wt.% or more, such as 0.003 wt.% or more, for example 0.004 wt.% or more, such as 0.005 wt.% or more, for example 0.006 wt.% or more, such as 0.007 wt.% or more, for example 0.0075 wt.% or more, such as 0.008 wt.% or more, for example 0.01 wt.% or more, such as 0.012 wt.% or more, for example 0.014 wt.% or more, such as 0.015 wt.% or more, for example 0.018 wt.% or more, such as 0.02 wt.% or more, for example 0.022 wt.% or more, such as 0.025 wt.% or more, for example 0.028 wt.% or more, such as 0.03 wt.% or more, for example 0.04 wt.% or more, based on the weight of the regenerated diacid. The catalyst may be present in an amount of 0.05 wt.% or less, such as 0.048 wt.% or less, for example 0.045 wt.% or less, such as 0.043 wt.% or less, for example 0.04 wt.% or less, such as 0.037 wt.% or less, for example 0.035 wt.% or less, such as 0.033 wt.% or less, for example 0.03 wt.% or less, such as 0.028 wt.% or less, for example 0.025 wt.% or less, such as 0.022 wt.% or less, for example 0.02 wt.% or less, based on the weight of the regenerated diacid. For example it may be present in an amount of 0.018% by weight or less, such as 0.016% by weight or less, for example 0.015% by weight or less, such as 0.013% by weight or less, for example 0.011% by weight or less, such as 0.01% by weight or less, for example 0.009% by weight or less, such as 0.008% by weight or less, for example 0.007% by weight or less, such as 0.005% by weight or less, for example 0.003% by weight or less, such as 0.002% by weight or less, for example 0.001% by weight or less.

[0053] The regenerated diacid may be present in an amount of 80% by weight or more, such as 85% by weight or more, such as 90% by weight or more, for example 95% by weight or more, such as 97% by weight or more, for example 98% by weight or more, such as 99% by weight or more, for example 99.5% by weight or more, such as 99.7% by weight or more, for example 99.8% by weight or more, such as 99.9% by weight or more, for example 99.95% by weight or more, such as 99.96% by weight or more, such as 99.97% by weight or more, for example 99.98% by weight or more, such as 99.99% by weight or more. The regenerated diacid may be present in an amount of less than 100% by weight, such as 99.99999% by weight or less, such as 99.9999% by weight or less, such as 99.9995% by weight or less, such as 99.999% by weight or less, for example 99.995% by weight or less, such as 99.9% by weight or less.

[0054] As mentioned above, depolymerization may also result in regenerated diol. For example, the regenerated diol may be, but is not limited to, an aliphatic diol, an aromatic diol, or a mixture thereof. In one embodiment, the regenerated diol may include an aromatic diol. The aromatic diol may be polycyclic. For example, the polycyclic aromatic diol may include a fused aromatic diol, a bridged aromatic diol, or a spiro aromatic diol. The aromatic diol may include catechol, resorcinol, hydroquinone, or a mixture thereof. In another embodiment, the regenerated diol includes an aliphatic diol. For example, the aliphatic diol may include ethylene glycol, butanediol (e.g., 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol), propanediol (e.g., 1,2-propanediol, 1,3-propanediol), pentanediol (e.g., 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol, etc.), hexanediol (e.g., 1,6-hexanediol, 2-5-hexanediol, etc.), tetraethylene glycol, or mixtures thereof. In one embodiment, the aliphatic diol includes butanediol, propanediol, or mixtures thereof. In one particular embodiment, the aliphatic diol includes ethylene glycol.

[0055] While the above provides a general description of the depolymerization process, the following provides further details. In general, the apparatus for carrying out the depolymerization is not necessarily limited. For example, the depolymerization may be carried out in a depolymerization vessel, which may be interchangeably referred to as a reactor. In particular, the vessel may be one that allows for depolymerization under hydrothermal conditions. Regardless of the apparatus, the depolymerization may be carried out in a continuous process, a batch process, or a semi-continuous process. In one embodiment, the depolymerization may be carried out in a continuous process. In another embodiment, the depolymerization may be carried out in a batch process. In a further embodiment, the depolymerization may be carried out in a semi-continuous process.

[0056] The depolymerization may be carried out using various methods that allow breaking down the ester bonds. For example, in one embodiment, the depolymerization may be carried out via alcoholysis, such as by using a monohydric or polyhydric alcohol. An example of alcoholysis may be methanolysis. In certain embodiments, the depolymerization may be carried out via hydrolysis. With regard to the latter, an alcohol such as methanol may not be provided during the depolymerization to degrade or break down the polyester.

[0057] Generally, the vessel may contain a depolymerization mixture. For example, the depolymerization mixture may include waste textiles. The depolymerization mixture may also include a liquid phase. The liquid phase may include water, a diol, or a mixture thereof. In one embodiment, the liquid phase may include water. In another embodiment, the liquid phase may include a diol, such as the example of a recycled diol mentioned above, such as ethylene glycol. When the liquid phase includes water, the water may be present in an amount of 50% by weight or more of the liquid phase, such as 60% by weight or more, such as 70% by weight or more, such as 80% by weight or more, such as 90% by weight or more, such as 95% by weight or more, such as 98% by weight or more, such as 99% by weight or more. In one embodiment, the entire liquid phase (i.e., 100% by weight) may include water.

[0058] The solids content may be 0.01 wt.% or more, such as 1 wt.% or more, for example 2 wt.% or more, such as 5 wt.% or more, for example 10 wt.% or more, such as 15 wt.% or more, for example 20 wt.% or more, such as 30 wt.% or more, for example 40 wt.% or more, such as 50 wt.% or more, for example 60 wt.% or more, such as 70 wt.% or more, for example 80 wt.% or more, such as 85 wt.% or more, for example 90 wt.% or more, such as 95 wt.% or more, for example 98 wt.% or more, such as 99 wt.% or more, based on the total weight of solids and liquids (i.e., the depolymerized mixture). The solids content may be an amount of less than 100% by weight based on the total weight of solids and liquids (i.e., the depolymerized mixture), such as 99.9% by weight or less, such as 99% by weight or less, for example 98% by weight or less, such as 95% by weight or less, for example 90% by weight or less, such as 80% by weight or less, for example 70% by weight or less, such as 60% by weight or less, for example 50% by weight or less, such as 40% by weight or less, for example 30% by weight or less, such as 20% by weight or less, for example 15% by weight or less, such as 10% by weight or less, for example 5% by weight or less.

[0059] Of the solids, waste materials such as waste textiles may be present in an amount of 0.01 wt.% or more, such as 1 wt.% or more, for example 2 wt.% or more, such as 5 wt.% or more, for example 10 wt.% or more, such as 15 wt.% or more, for example 20 wt.% or more, such as 30 wt.% or more, for example 40 wt.% or more, such as 50 wt.% or more, such as 60 wt.% or more, for example 70 wt.% or more, such as 80 wt.% or more, for example 85 wt.% or more, such as 90 wt.% or more, for example 95 wt.% or more, such as 98 wt.% or more, for example 99 wt.% or more, such as 100 wt.% based on the total weight of the solids. The waste material may be present in an amount of 100% by weight or less, such as 99.9% by weight or less, for example 99% by weight or less, such as 98% by weight or less, for example 95% by weight or less, such as 90% by weight or less, for example 80% by weight or less, such as 70% by weight or less, for example 60% by weight or less, such as 50% by weight or less, for example 40% by weight or less, such as 30% by weight or less, for example 20% by weight or less, such as 15% by weight or less, for example 10% by weight or less, such as 5% by weight or less, based on the total weight of solids.

[0060] The depolymerization may be carried out under alkaline conditions. For example, the pH may be greater than 7, for example 7.5 or more, 8 or more, for example 8.5 or more, for example 9 or more, for example 9.5 or more, for example 10 or more, for example 11 or more, for example 12 or more. The pH may be 14 or less, for example 13 or less, for example 12.5 or less, for example 12 or less, for example 11.5 or less, for example 11 or less, for example 10.5 or less, for example 10 or less, for example 9.5 or less, for example 9 or less. For example, the pH may be 12 to 13.

[0061] A base may be provided to the mixture to obtain an alkaline pH. The base may be a weak base or a strong base. In one embodiment, the base may be a weak base. For example, the base may include, but is not limited to, ammonia, methylamine, trimethylamine, hydrazine, ammonium hydroxide, and the like. In another embodiment, the base may be a strong base. For example, the base may include, but is not limited to, potassium hydroxide, sodium hydroxide, barium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, and the like. Thus, the base may be an alkali metal hydroxide, an alkaline earth metal hydroxide, ammonium hydroxide, or a mixture thereof. When utilized, the base may be present in an amount of 0.01 wt% or more, such as 0.05 wt% or more, such as 0.1 wt% or more, for example 0.2 wt% or more, such as 0.3 wt% or more, for example 0.5 wt% or more, such as 1 wt% or more, for example 2 wt% or more, such as 3 wt% or more, for example 5 wt% or more, such as 7 wt% or more, for example 10 wt% or more, such as 12 wt% or more, for example 14 wt% or more of the depolymerization mixture. The base may be present in an amount of 15 wt% or less, such as 13 wt% or less, such as 11 wt% or less, such as 10 wt% or less, for example 8 wt% or less, such as 6 wt% or less, for example 5 wt% or less, such as 4 wt% or less, for example 3 wt% or less, such as 2 wt% or less, for example 1 wt% or less, such as 0.8 wt% or less, for example 0.5 wt% or less of the depolymerization mixture.

[0062] Furthermore, the remaining depolymerization conditions are not necessarily limited. For example, the depolymerization may be carried out at a temperature of 50°C or more, such as 60°C or more, such as 70°C or more, such as 80°C or more, such as 90°C or more, such as 100°C or more, such as 110°C or more, such as 120°C or more, such as 130°C or more, such as 150°C or more, such as 180°C or more. The temperature may be 250°C or less, such as 240°C or less, such as 220°C or less, such as 200°C or less, such as 190°C or less, such as 180°C or less, such as 170°C or less, such as 160°C or less, such as 150°C or less, such as 140°C or less. In particular, the depolymerization may be carried out at a temperature between the atmospheric boiling point (100°C) and the critical temperature of water (374°C).

[0063] The depolymerisation may be carried out at a pressure of 1 kPa or more, such as 2 kPa or more, for example 3 kPa or more, such as 5 kPa or more, for example 10 kPa or more, such as 20 kPa or more, for example 50 kPa or more, such as 80 kPa or more, for example 100 kPa or more, such as 130 kPa or more, for example 150 kPa or more, such as 200 kPa or more, for example 250 kPa or more, such as 300 kPa or more, for example 500 kPa or more, such as 800 kPa or more, for example 1000 kPa or more, such as 1200 kPa or more, for example 1500 kPa or more. The pressure may be 2000 kPa or less, such as 1800 kPa or less, for example 1500 kPa or less, such as 1300 kPa or less, for example 1000 kPa or less, such as 700 kPa or less, for example 500 kPa or less, such as 400 kPa or less, for example 300 kPa or less, such as 200 kPa or less, for example 100 kPa or less, such as 70 kPa or less, for example 50 kPa or less, such as 40 kPa or less, for example 30 kPa or less, such as 25 kPa or less, for example 20 kPa or less, such as 15 kPa or less, for example 10 kPa or less. Further, the pressure may be the vapor pressure of water.

[0064] The depolymerization may be carried out for 0.01 hours or more, such as 0.02 hours or more, for example 0.05 hours or more, such as 0.1 hours or more, for example 0.2 hours or more, such as 0.3 hours or more, for example 0.5 hours or more, such as 1 hour or more, for example 2 hours or more, such as 3 hours or more, for example 4 hours or more, such as 5 hours or more, for example 6 hours or more, such as 8 hours or more, for example 10 hours or more, such as 12 hours or more, for example 15 hours or more. The time may be 24 hours or less, such as 20 hours or less, for example 18 hours or less, such as 15 hours or less, for example 13 hours or less, such as 11 hours or less, for example 10 hours or less, such as 8 hours or less, for example 6 hours or less, such as 5 hours or less, for example 4 hours or less, such as 3 hours or less, for example 2 hours or less, such as 1 hour or less, for example 0.8 hours or less, such as 0.6 hours or less, for example 0.5 hours or less, such as 0.4 hours or less, for example 0.3 hours or less, for example 0.2 hours or less, for example 0.1 hours or less.

[0065] After depolymerization, the depolymerized mixture may include regenerated diol and regenerated diacid, such as a salt of the regenerated diacid. For example, the regenerated diacid, such as a salt of the regenerated diacid, may be dissolved in a liquid medium. The salt may be an alkali metal salt or an alkaline earth metal salt. In one embodiment, the salt may be an alkali metal salt, such as a di-alkali metal salt. For example, the salt may include lithium, sodium, potassium, cesium, or a mixture thereof. In one embodiment, the salt may include di-lithium, disodium, di-potassium, di-cesium, or a mixture thereof. In another embodiment, the salt may include an alkali metal salt. For example, the salt may include beryllium, magnesium, calcium, strontium, barium, or a mixture thereof.

[0066] The depolymerized mixture may also include a catalyst as described herein. Additionally, the regenerated diacid, regenerated diol, and / or catalyst may be present as dissolved components in the depolymerized mixture. For example, in one embodiment, the regenerated diacid may be dissolved. In another embodiment, the regenerated diol may be dissolved. In a further embodiment, the catalyst may be dissolved.

[0067] As indicated herein, the waste material may include other polymers in addition to polyester. In this regard, such polymers may not be depolymerized during the depolymerization reaction. Thus, such polymers may also be present in the depolymerized mixture. As a result, after completion of the depolymerization, such polymers may be removed or separated from the depolymerized mixture. Such removal or separation may be via mechanical means, such as a filter. However, it is understood that other means commonly known in the art may be utilized to separate other polymers from the depolymerized mixture. The temperature is not necessarily limited and may be room temperature or higher. For example, the temperature may be 20° C. or higher, such as 30° C. or higher, such as 40° C. or higher, such as 50° C. or higher, such as 60° C. or higher, such as 70° C. or higher, such as 80° C. or higher, such as 90° C. or higher, such as 100° C. or higher, such as 110° C. or higher, such as 120° C. or higher, such as 130° C. or higher, such as 150° C. or higher, such as 180° C. or higher. The temperature may be 250°C or less, such as 240°C or less, for example 220°C or less, such as 200°C or less, for example 190°C or less, such as 180°C or less, for example 170°C or less, such as 160°C or less, for example 150°C or less, such as 140°C or less.

[0068] The depolymerized mixture, particularly the depolymerized and separated mixture, may be clarified. For example, the mixture may be clarified using means commonly known in the art, such as filtration (e.g., membrane filtration), centrifugation, etc. In particular, the filtration may be diatomaceous earth filtration. Such a process may allow for the reduction or removal of solids within the mixture.

[0069] Additionally or alternatively, the mixture may undergo a decolorization step using a decolorizing agent. For example, the mixture may be subjected to a decolorizing agent that includes decolorizing carbon, such as activated carbon. Other decolorizing agents that may aid in decolorization may include peroxides (e.g., hydrogen peroxide, sodium peroxide, etc.), hypochlorites (e.g., sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, etc.), carbonates (e.g., sodium carbonate), peracetic acid, sodium chloride, sodium hydrosulfite, etc.

[0070] The depolymerized mixture (e.g., with or without the aforementioned separation, clarification, and / or decolorization) may then be subjected to an isolation step, such as a precipitation step. With respect to isolation, such a process may include distillation, and the like. In a particular embodiment, the isolation may be a precipitation (or crystallization) step. For example, the precipitation step may allow for the precipitation of the regenerated diacid. Similarly, the precipitation step may also allow for the precipitation of the catalyst. To initiate the precipitation, an acid may be provided to the depolymerized mixture. The acid may be a weak acid or a strong acid. In an embodiment, the acid may be a weak acid. For example, the acid may be, but is not limited to, acetic acid, formic acid, benzoic acid, oxalic acid, hydrofluoric acid, phosphoric acid, nitrous acid, and the like. In another embodiment, the acid may be a strong acid. For example, the acid may be, but is not limited to, hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, chloric acid, perchloric acid, and the like. The concentration of the acid is not necessarily limited by the present invention. For example, the concentration may be 1% or more, such as 5% or more, for example 10% or more, such as 15% or more, for example 20% or more, such as 25% or more, for example 30% or more, such as 40% or more, for example 50% or more, such as 60% or more, for example 70% or more, such as 80% or more, for example 90% or more, such as 100%. The concentration may be 100% or less, such as 95% or less, for example 90% or less, such as 80% or less, for example 70% or less, such as 60% or less, for example 50% or less, such as 40% or less, for example 30% or less, such as 25% or less, for example 20% or less, such as 15% or less, for example 10% or less, such as 5% or less.

[0071] In this regard, the pH of the depolymerized mixture may be lowered to initiate and / or cause precipitation. For example, the pH may be 7 or less, such as 6.5 or less, such as 6 or less, such as 5.5 or less, such as 5 or less, such as 4.5 or less, such as 4 or less, such as 3.5 or less, such as 3 or less, such as 2.5 or less. The pH may be 1 or more, such as 1.5 or more, such as 2 or more, such as 2.5 or more, such as 3 or more, such as 3.5 or more, such as 4 or more, such as 4.5 or more, such as 5 or more, such as 5.5 or more. In this regard, the final pH during precipitation may be within the aforementioned pH ranges.

[0072] Also, the residence time allowing the regenerated diacid and / or catalyst to precipitate may be 0.5 minutes or more, such as 1 minute or more, for example 2 minutes or more, such as 3 minutes or more, for example 5 minutes or more, such as 10 minutes or more, for example 15 minutes or more, such as 20 minutes or more, for example 25 minutes or more, such as 30 minutes or more, for example 45 minutes or more, such as 1 hour or more. The residence time allowing the regenerated diacid and / or catalyst to precipitate may be 10 hours or less, such as 8 hours or less, for example 6 hours or less, such as 5 hours or less, for example 4 hours or less, such as 3 hours or less, for example 2 hours or less, such as 1 hour or less, for example 50 minutes or less, such as 40 minutes or less, for example 30 minutes or less, such as 25 minutes or less, for example 20 minutes or less, such as 15 minutes or less, for example 10 minutes or less, such as 8 minutes or less, for example 6 minutes or less, such as 5 minutes or less, for example 4 minutes or less, such as 3 minutes or less, for example 2 minutes or less.

[0073] In one embodiment, the decrease in pH may be gradual, allowing for more controlled precipitation. In this regard, precipitation may be carried out during at least two intervals, each at a different pH.

[0074] For example, the pH may be reduced to within the aforementioned ranges and held for a certain period of time before further reduction. For example, the initial reduction in pH may be 0.5 or more, such as 1 or more, such as 1.5 or more, such as 2 or more, such as 2.5 or more, such as 3 or more. The initial reduction in pH may be 5 or less, such as 4.5 or less, such as 4 or less, such as 3.5 or less, such as 3 or less, such as 2.5 or less. After completion of the initial reduction, the regenerated diacid may be allowed to precipitate for 0.5 minutes or more, such as 1 minute or more, such as 2 minutes or more, such as 3 minutes or more, such as 5 minutes or more, such as 10 minutes or more, such as 15 minutes or more, such as 20 minutes or more, such as 25 minutes or more, such as 30 minutes or more, such as 45 minutes or more, such as 1 hour or more. The regenerated diacid may be allowed to precipitate for 10 hours or less, such as 8 hours or less, for example 6 hours or less, such as 5 hours or less, for example 4 hours or less, such as 3 hours or less, for example 2 hours or less, such as 1 hour or less, for example 50 minutes or less, such as 40 minutes or less, for example 30 minutes or less, such as 25 minutes or less, for example 20 minutes or less, such as 15 minutes or less, for example 10 minutes or less, such as 8 minutes or less, for example 6 minutes or less, such as 5 minutes or less, for example 4 minutes or less, such as 3 minutes or less, for example 2 minutes or less.

[0075] The pH may then be further reduced in a second pH reduction step. Such a reduction in pH may be to 5 or less, such as 4.5 or less, for example 4 or less, such as 3.5 or less, for example 3 or less, such as 2.5 or less. After completion of the initial reduction, the regenerated diacid may be allowed to settle for 0.5 minutes or more, such as 1 minute or more, for example 2 minutes or more, such as 3 minutes or more, for example 5 minutes or more, such as 10 minutes or more, for example 15 minutes or more, such as 20 minutes or more, for example 25 minutes or more, such as 30 minutes or more, for example 45 minutes or more, such as 1 hour or more. The regenerated diacid may be allowed to precipitate for 10 hours or less, such as 8 hours or less, for example 6 hours or less, such as 5 hours or less, for example 4 hours or less, such as 3 hours or less, for example 2 hours or less, such as 1 hour or less, for example 50 minutes or less, such as 40 minutes or less, for example 30 minutes or less, such as 25 minutes or less, for example 20 minutes or less, such as 15 minutes or less, for example 10 minutes or less, such as 8 minutes or less, for example 6 minutes or less, such as 5 minutes or less, for example 4 minutes or less, such as 3 minutes or less, for example 2 minutes or less.

[0076] Although two pH reduction steps are mentioned above, it should be understood that the number of pH reduction steps and the extent of each pH reduction are not necessarily limited by the present invention. For example, the process may also include a third pH reduction step having the reduction and reduction time described above for the first and second reduction steps.

[0077] After precipitating the regenerated diacid and / or catalyst, the regenerated composition comprising the regenerated diacid and catalyst may be separated from the precipitated mixture, which may comprise the regenerated diol and / or liquid medium. Such separation may be performed using mechanical means. For example, separation may be performed using means commonly known in the art, such as filtration (e.g., filter press), centrifugation, decanting, etc. The regenerated composition comprising the regenerated diacid and catalyst may then be washed and dried under ambient conditions or in a heating device.

[0078] Further, the regenerated composition comprising the regenerated diacid and catalyst may be aged to obtain a desired crystal size. For example, initially, the average crystal size of the regenerated diacid may be less than 25 microns, such as 23 microns or less, such as 20 microns or less, such as 18 microns or less, such as 15 microns or less, such as 13 microns or less, such as 10 microns or less. After undergoing the aging method disclosed herein, the average crystal size may be 50 microns or more, such as 60 microns or more, such as 70 microns or more, such as 75 microns or more, such as 80 microns or more, such as 85 microns or more, such as 90 microns or more, such as 93 microns or more, such as 95 microns or more, such as 98 microns or more, such as 100 microns or more. The average crystal size can be 200 microns or less, such as 190 microns or less, such as 180 microns or less, such as 170 microns or less, such as 160 microns or less, such as 150 microns or less, such as 140 microns or less, such as 130 microns or less, such as 125 microns or less, such as 120 microns or less, such as 115 microns or less, such as 110 microns or less, such as 108 microns or less, such as 105 microns or less, such as 103 microns or less, such as 100 microns or less.Furthermore, in one embodiment, the size distribution can be a monomodal size distribution.In general, the crystal size can be determined using means known in the art, such as laser light scattering.

[0079] The purity of the regenerated diacid may be improved. In this regard, the regenerated diacid may have a purity of 80% or more, such as 85% or more, such as 90% or more, such as 93% or more, such as 95% or more, such as 97% or more, such as 98% or more, such as 99% or more. Purity may be determined using means commonly known in the art.

[0080] Once separated from the regenerated diol, the regenerated composition may be washed and / or filtered until a generally neutral pH is obtained, however, it should be understood that the regenerated diacid and catalyst may be aged to obtain the desired crystal size without washing and / or filtering.

[0081] The maturation may be carried out at a desired pH. For example, the pH may be 6 or more, such as 6.1 or more, such as 6.2 or more, such as 6.3 or more, such as 6.4 or more, such as 6.5 or more, such as 6.6 or more, such as 6.7 or more, such as 6.8 or more, such as 6.9 or more, such as 7 or more. The pH may be 8.0 or less, such as 7.9 or less, such as 7.8 or less, such as 7.7 or less, such as 7.6 or less, such as 7.5 or less, such as 7.4 or less, such as 7.3 or less, such as 7.2 or less, such as 7.1 or less, such as 7 or less.

[0082] Also, the aging is carried out in a liquid medium. For example, the liquid medium may be any of those described above with respect to the liquid medium utilized for depolymerization. The liquid medium may include water, an organic solvent, or a mixture thereof. In one particular embodiment, the liquid medium may be water. In another embodiment, the liquid medium may be an organic solvent. For example, the organic solvent may include, but is not limited to, acetic acid, dimethylformamide, and / or dimethylsulfoxide. In one particular embodiment, the solvent may include an organic solvent including acetic acid. In one embodiment, the liquid medium may include a combination of acetic acid and water.

[0083] Further, the solids content in the liquid medium may be 5 wt% or more, such as 10 wt% or more, such as 15 wt% or more, such as 20 wt% or more, such as 25 wt% or more. The solids content may be 50 wt% or less, such as 45 wt% or less, such as 35 wt% or less, such as 30 wt% or less, such as 25 wt% or less, such as 20 wt% or less, such as 15 wt% or less. The final solids content of the regenerated composition including the regenerated diacid and catalyst after aging and drying may be 90 wt% or more, such as 95 wt% or more, such as 98 wt% or more, such as 99 wt% or more. While the above generally refers to the solids content in the liquid medium, in one embodiment, the above may also refer to the solids content of the regenerated diacid in the liquid medium.

[0084] Generally, during aging, the solids may be mixed within the liquid medium using a mixing or stirring device as is commonly known in the art, however, it should be understood that in certain embodiments, a mixing or stirring device may not be utilized.

[0085] The temperature for maturation may be 120° C. or higher, such as 130° C. or higher, for example 1450° C. or higher, such as 150° C. or higher, for example 160° C. or higher, such as 170° C. or higher, for example 180° C. or higher, such as 190° C. or higher, for example 200° C. or higher, such as 210° C. or higher, for example 220° C. The temperature may be 300° C. or lower, such as 290° C. or lower, for example 280° C. or lower, such as 270° C. or lower, for example 260° C. or lower, such as 250° C. or lower, for example 240° C. or lower, such as 230° C. or lower, for example 220° C. or lower, for example 210° C. or lower.

[0086] In one embodiment, maturation may be performed by using a thermal cycle, for example a thermal cycle where the temperature oscillates between multiple temperatures. For example, the thermal cycle may span a range of within 5°C, such as within 10°C, such as within 15°C, such as within 20°C, such as within 25°C. The thermal cycle may be at least 4°C or more, such as 5°C or more, such as 7°C or more, such as 9°C or more, such as 10°C or more, such as 13°C or more, such as 15°C or more, such as 18°C ​​or more, such as 20°C or more. The thermal cycle may be 40°C or less, such as 35°C or less, such as 30°C or less, such as 25°C or less, such as 23°C or less, such as 20°C or less, such as 17°C or less, such as 15°C or less, such as 14°C or less, such as 12°C or less, such as 10°C or less, such as 9°C or less, such as 7°C or less. Such a thermal cycle may be within the temperatures mentioned above. By way of example only, the thermal cycle may be in the range of 10°C (e.g. between 210°C and 220°C). As another example, the thermal cycle may be within a temperature range of 180° C. to 250° C. within a range of 15° C. (eg, 5° C., 10° C., etc.).

[0087] The number of cycles is not necessarily limited. For example, the number of cycles may be based on the desired size. For example, the number of cycles may be 1 or more, such as 2 or more, such as 3 or more, such as 4 or more, such as 5 or more, such as 6 or more, such as 7 or more, such as 8 or more, such as 9 or more, such as 10 or more, such as 12 or more, such as 15 or more, such as 17 or more, such as 20 or more. The number of cycles may be 50 or less, such as 45 or less, such as 40 or less, such as 35 or less, such as 30 or less, such as 25 or less, such as 20 or less, such as 18 or less, such as 16 or less, such as 15 or less, such as 14 or less, such as 12 or less, such as 10 or less, such as 9 or less, such as 8 or less, such as 7 or less, such as 6 or less, such as 5 or less.

[0088] When the temperature is increased during the cycle, the temperature change may be at a rate of 0.5° C. / min or more, such as 1° C. / min or more, such as 2° C. / min or more, such as 3° C. / min or more, such as 4° C. / min or more, such as 5° C. / min or more, such as 7° C. / min or more, such as 10° C. / min or more. The temperature change may be at a rate of 20° C. / min or less, such as 18° C. / min or less, such as 15° C. / min or less, such as 13° C. / min or less, such as 11° C. / min or less, such as 10° C. / min or less, such as 8° C. / min or less, such as 6° C. / min or less, such as 5° C. / min or less, such as 4° C. / min or less, such as 3° C. / min or less, such as 2° C. / min or less.

[0089] When the temperature is decreased during the cycle, the temperature change may be at a rate of 0.5° C. / min or more, such as 1° C. / min or more, such as 2° C. / min or more, such as 3° C. / min or more, such as 4° C. / min or more, such as 5° C. / min or more, such as 7° C. / min or more, such as 10° C. / min or more. The temperature change may be at a rate of 320° C. / min or less, such as 18° C. / min or less, such as 15° C. / min or less, such as 13° C. / min or less, such as 11° C. / min or less, such as 10° C. / min or less, such as 8° C. / min or less, such as 6° C. / min or less, such as 5° C. / min or less, such as 4° C. / min or less, such as 3° C. / min or less, such as 2° C. / min or less.

[0090] Generally, the regenerating composition may undergo temperature changes and / or cycles within a single device. Alternatively, the regenerating composition may undergo temperature changes or be exposed to different temperatures using a second device. For example, the regenerating composition may be in a first device at a first temperature as described above, and then the regenerating composition may be transferred to a second device at a second temperature as described above. In this regard, the regenerating composition may be cycled between the first device and the second device, thereby undergoing temperature changes within each device.

[0091] Similarly, the regenerating composition may be in a first device at a first temperature as described above, and at least a portion of the regenerating composition may be transported through a second device at a second temperature as described above. In this regard, at least a portion of the regenerating composition may be circulated between the first and second devices, thereby undergoing a temperature change within each device.

[0092] In this regard, one of the first and second temperatures is generally higher than the other. Without intending to be limited by theory in this regard, smaller crystals of the regenerated diacid may dissolve at the higher temperature and thus grow on existing crystals when exposed to the lower or cooler temperature of the cycle. Thus, the amount of nucleation and thus the formation of new crystals leading to small size may be minimized or prevented.

[0093] As a further example, the regenerating composition may be in one device at one temperature. At least a portion of the regenerating composition may then be circulated or cycled through a second device, such as a heat exchanger, at a second and higher temperature to age the crystals. Alternatively, at least a portion of the regenerating composition may be circulated or cycled through a second device, such as a chiller or cooling device, at a second and lower temperature. Regardless of the approach, cycling through temperature changes can help control the growth of the regenerated diacid crystals.

[0094] The temperature may be increased using means known in the art. For example, the temperature may be increased by using heating devices, hot or heated air, heat exchangers, etc. Furthermore, depending on the method, the cycling and aging may be performed in a batch process. In another embodiment, the cycling and aging may be performed in a continuous or semi-continuous process.

[0095] The temperature may also be reduced using means known in the art. For example, the temperature may be reduced using chilled air, a refrigerator, or a chiller, etc. When the desired size is obtained, the regenerated composition comprising the regenerated diacid and catalyst may be separated from the liquid medium using mechanical means. For example, separation may be performed using means commonly known in the art, such as filtration (e.g., filter press), centrifugation, decanting, etc. Alternatively, the solids may simply be allowed to settle as the liquid medium is removed. The solids may then be dried using means commonly known in the art. Additionally, the aged and purified regenerated composition may also have the characteristics as described above with respect to weight percentages, etc.

[0096] As provided herein, the regenerating composition includes a regenerating diacid and a catalyst. In one embodiment, a catalyst may not be introduced during the depolymerization reaction described herein. In another embodiment, such a catalyst may not be introduced during any step of the depolymerization process described herein. For example, a catalyst may not be added to the feedstock prior to undergoing depolymerization.

[0097] Additionally, in one embodiment, catalysts typically used in the polymerization of diacids and diols to form polyesters may not be introduced during the depolymerization reactions described herein. In another embodiment, such catalysts may not be introduced during any step of the depolymerization process described herein. For example, catalysts may not be added to the feedstock prior to undergoing depolymerization.

[0098] The regenerated diacid may also have a peak temperature within a certain number of degrees of the peak temperature of a standard reference determined according to differential scanning calorimetry. For example, when the regenerated diacid is regenerated terephthalic acid, the peak temperature may be within a certain number of degrees of the peak temperature of a standard terephthalic acid reference. For example, such difference may be within 10 degrees, such as within 9 degrees, such as within 8 degrees, such as within 7 degrees, such as within 6 degrees, such as within 5 degrees, such as within 4.5 degrees, such as within 4 degrees, such as within 3.5 degrees, such as within 3 degrees, such as within 2.5 degrees, such as within 2 degrees, such as within 1.5 degrees, such as within 1 degree. For such determination, differential scanning calorimetry may be performed using a TA Instruments Discovery Model DSC utilizing a "heat-cool-heat" method to remove all thermal history based on process history. A second heating scan may be performed from (either 0°C or -90°C) to 325°C at a rate of 10°C / min.

[0099] Similarly, the regenerated diacid can have an onset temperature within a certain number of degrees of the onset temperature of a standard reference determined according to thermogravimetric analysis. For example, when the regenerated diacid is regenerated terephthalic acid, the onset temperature can be within a certain number of degrees of the onset temperature of the standard terephthalic acid reference. For example, such a difference can be within 10 degrees, such as within 9 degrees, such as within 8 degrees, such as within 7 degrees, such as within 6 degrees, such as within 5 degrees, such as within 4.5 degrees, such as within 4 degrees, such as within 3.5 degrees, such as within 3 degrees, such as within 2.5 degrees, such as within 2 degrees, such as within 1.5 degrees, such as within 1 degree, such as within 0.5 degrees. For such a determination, the thermogravimetric analysis can be performed using a TA Instruments Discovery Model TGA utilizing a temperature gradient from room temperature to 700°C at a rate of 20°C / min under a nitrogen atmosphere.

[0100] Furthermore, as mentioned above, the depolymerization may be carried out in a suitable apparatus, such as a reactor or vessel. In this regard, any subsequent steps (e.g., clarification, decolorization, separation, precipitation) may also be carried out in a suitable apparatus. In this regard, the apparatus for carrying out such steps is also not limited by the present invention. Furthermore, to the extent necessary, the apparatus may be connected together using various pipes, tubes, pumps, tanks, valves, etc.

[0101] These and other modifications and variations of the present invention may be practiced by those skilled in the art without departing from the spirit and scope of the present invention. It should also be understood that aspects of the various embodiments may be interchanged in whole or in part. Moreover, those skilled in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention as further described in such appended claims.

Claims

1. 1. A method for forming polyester from a recycled composition obtained from the depolymerization of polyester in waste materials, the recycled composition comprising a recycled diacid and a catalyst, the method comprising: reacting a diol with the regenerated diacid in the regenerated composition to form one or more compounds containing an ester bond; Optionally, providing an additional catalyst; and polymerizing said one or more compounds containing said ester linkages to form a polyester.

2. 10. The method of claim 1, wherein the catalyst in the regenerating composition comprises germanium, titanium, cobalt, molybdenum, antimony, or mixtures thereof.

3. 10. The method of claim 1, wherein the catalyst in the regenerating composition comprises antimony trioxide, antimony glycolate, antimony / metal complex, antimony acetate, or a mixture thereof.

4. 10. The method of claim 1, wherein an additional catalyst is provided, said additional catalyst comprising germanium, titanium, cobalt, molybdenum, antimony, or mixtures thereof.

5. 5. The method of claim 4, wherein the additional catalyst comprises antimony trioxide, antimony glycolate, antimony / metal complex, antimony acetate, or mixtures thereof.

6. 10. The method of claim 1, wherein the catalyst is present in the regenerating composition in an amount of from greater than 0 ppm to 300 ppm.

7. 10. The method of claim 1, wherein the catalyst is present in the regenerating composition in an amount of from greater than 0 to 0.05 wt. % based on the weight of the regenerating diacid.

8. The method of claim 1, wherein the total amount of the catalyst and the additional catalyst is greater than 0 ppm and less than or equal to 500 ppm.

9. 10. The method of claim 1, wherein the regenerated diacid comprises an aromatic diacid.

10. 10. The method of claim 9, wherein the aromatic diacid comprises terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, or a mixture thereof.

11. 10. The method of claim 1, wherein the regenerating diacid comprises a saturated diacid, an unsaturated diacid, or a mixture thereof.

12. the saturated diacid comprises ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, or mixtures thereof; and / or 12. The method of claim 11, wherein the unsaturated diacid comprises maleic acid, fumaric acid, glutaconic acid, or a mixture thereof.

13. The method of claim 1 , wherein the diol comprises an aliphatic diol, an aromatic diol, or a mixture thereof.

14. 10. The method of claim 1, wherein the diol comprises ethylene glycol, butanediol, propanediol, pentanediol, hexanediol, tetraethylene glycol, or a mixture thereof.

15. 2. The method of claim 1, wherein the molar ratio of the diol to the regenerated diacid is 1 to 5.

16. The method of claim 1 , wherein the waste material is a waste textile comprising polyester.

17. 10. The method of claim 1, wherein the depolymerization of the polyester in the waste material comprises: providing the waste material comprising the polyester to a depolymerization vessel; depolymerizing the polyester to form a depolymerized mixture comprising regenerated diol, regenerated diacid, and the catalyst; isolating the regenerated diacid and the catalyst from the regenerated diol to form the regenerated composition comprising the regenerated diacid and the catalyst; and and separating the regenerated composition from the regenerated diol.

18. 18. The method of claim 17, wherein the depolymerization is carried out at a temperature of from 100°C to 220°C.

19. 18. The method of claim 17, wherein the depolymerization is carried out in water.

20. 18. The method of claim 17, wherein the depolymerization is carried out via hydrolysis in the presence of a strong base at a pH of 10 or greater.

21. 18. The method of claim 17, wherein the isolating step comprises precipitating the regenerated diacid and the catalyst by adding a strong acid to the depolymerized mixture.

22. 17. The method of claim 16, wherein the waste material further comprises at least one other polymer comprising cellulose.

23. 17. The method of claim 16, wherein the polyester is present in an amount of 50 weight percent or greater, based on the total weight of the polymer.