Process for preparing polyester having recycled content

Abstract

In various aspects, a method for preparing polyester with recycled content is described. The disclosed method effectively and cost-effectively introduces recycled DMT into an existing TPA-based polyester production system. Also described are recycled feed compositions for preparing polyester with recycled content and recycled content polyester.

Description

Field of the Invention

[0001] The present disclosure relates generally to the fields of polyester recycling and polyester production, and more particularly to a polyester production process including the use of methanolysis reaction products in forming polyester having recycled content. Background of the Invention

[0003] Polyester is one of the most purchased and diverse classes of polymers in the world, with the most recently reported published world production (including recycling) far exceeding 75 million tons. This level of commercial success may be attributed in part to the attractive combination of relative cost, manufacturability and competitive performance attributes of polyester. The physical, chemical and thermal properties of polyester make them useful and desirable for a wide variety of end-use applications. Polyethylene terephthalate (PET) is one of the most common types of polyesters for many end uses. With the continued commercial success of polyesters in general and PET in particular, efforts have been made to recover materials from post-consumer, post-industrial, waste and other sources, and to reuse these materials as an alternative to basic treatment methods such as landfill.

[0004] In one known recycling process, recycled PET is blended with virgin material. This process has been used, for example, to prepare blends of virgin poly(butylene terephthalate) ("PBT") with recycled PET to obtain PBT-based products with recycled content (see, for example, U.S. Patent Application Publication No. 2009 / 0275698). However, such blends can often be immiscible and produce relatively opaque materials. Therefore, blending is not a consistently satisfactory method for providing commercially valuable end products with recycled content.

[0005] In another recycling process, the polyester is depolymerized to form the monomer units originally used in its preparation. One commercially used process for polyester depolymerization is methanolysis. In methanolysis, the polyester is reacted with methanol to produce a depolymerized polyester mixture that includes polyester oligomers, dimethyl terephthalate ("DMT"), and ethylene glycol ("EG"). Depending on the composition of the polyester in the methanolysis feed stream, other monomers such as, for example, 1,4-cyclohexanedimethanol ("CHDM") and diethylene glycol may also be produced. Some representative processes for PET methanolysis are described in US Pat. Nos. 3,037,050; 3,321,510; 3,776,945; 5,051,528; 5,298,530; 5,414,022; 5,432,203; 5,576,456 and 6,262,294, the contents and disclosures of each of which are incorporated herein by reference. Representative methanol decomposition processes are also described in US Pat. No. 5,298,530, the contents and disclosure of which are incorporated herein by reference. The '530 patent describes a method for recovering ethylene glycol and dimethyl terephthalate from waste polyester. The method includes the steps of dissolving the waste polyester in oligomers of ethylene glycol (EG) and terephthalic acid (TPA) or dimethyl terephthalate (DMT), and passing superheated methanol through the mixture. The oligomers may include any low molecular weight polyester polymers having the same composition as the waste material used as the starting component, so that the waste polymers will dissolve in the low molecular weight oligomers. Dimethyl terephthalate and ethylene glycol are recovered from the methanol vapor stream emitted from the depolymerization reactor.

[0006] With the goal of producing and marketing new materials with recycled content, manufacturers are constantly investigating the use of monomer units generated via depolymerization, particularly DMT and EG. For example, the assignee of the present disclosure generally proposed in U.S. Published Patent Application No. 2013 / 0041053 that recycled monomers such as DMT can be combined with virgin monomers in polyester production. However, the proposal has its disadvantages. First, consider the operation of the esterification / ester exchange step at a temperature of typically about 150° C. to about 250° C., for about 0.5 to about 8 hours, and at a pressure of about 0.0 kPa gauge to about 414 kPa gauge (60 pounds per square inch, psig). Such conditions are inconsistent with the operating conditions suitable for current terephthalic acid-based (TPA-based) polyester production processes, in which the feed is essentially free of intentionally added esters and contains only diacids, primarily terephthalic acid, and one or more diols. Therefore, it would appear to be unfeasible to achieve recycled content by introducing recycled materials such as recycled DMT (r-DMT) and / or recycled ethylene glycol (r-EG) into current TPA-based processes without having to operate and potentially disrupt the process setup and associated product uniformity and yields. In addition, the '053 published application states that when a mixed acid / ester feed is used, a 3-stage preparation procedure as described in U.S. Pat. No. 5,290,631 should be employed. The additional process steps carry with them additional capital, preparation, and labor costs.

[0007] Therefore, there is a continuing unmet need for a process for producing polyesters with recycled content by efficiently and cost-effectively introducing recycled materials such as recycled DMT (r-DMT) and recycled ethylene glycol (r-EG) into existing TPA-based polyester production systems. Summary of the invention

[0008] In a first aspect, the present disclosure relates to a method for preparing a polyester with recycled content, wherein the method comprises the following steps: feeding a recycled feed comprising an ester recycled material to at least one reaction zone to form a reaction mixture comprising the recycled content in at least one reaction zone, wherein the ester recycled material is selected from r-DMT, transesterified r-DMT and combinations thereof; reacting the reaction mixture to form a polyester oligomer mixture with recycled content; and polycondensing the recycled content oligomer mixture to form a polyester with recycled content.

[0009] In another aspect, the present disclosure relates to a recycled feed composition for preparing a polyester having recycled content. The recycled feed composition of the present disclosure comprises an ester recycled material selected from r-DMT, transesterified r-DMT, and combinations thereof; and at least one of: dimethyl isophthalate recycled material (r-DMI) and a residual catalyst material selected from a germanium material and an antimony material, and combinations thereof.

[0010] In yet another aspect, the present disclosure relates to polyesters having recycled content.

[0011] Other aspects of the disclosure are as disclosed and claimed herein.

[0012] Detailed Description

[0013] The term "polyester" as used herein is intended to include, but is not limited to, homopolyesters as well as copolyesters, terpolyesters, and the like, and is generally prepared in a general sense by reacting a diacid, an ester thereof, or a mixture of such acids or esters, with a difunctional hydroxy compound, typically a diol or glycol, or a mixture of such diols or glycols. Alternatively, the difunctional carboxylic acid may be a hydroxycarboxylic acid, and the difunctional hydroxy compound may be an aromatic nucleus bearing 2 hydroxy substituents, such as, for example, hydroquinone. Of particular interest with respect to the present disclosure as described herein are polyesters which are produced via depolymerization by methanolysis or glycolysis with subsequent methanolysis, methanolysis, of the reaction product to produce one or both of dimethyl terephthalate and ethylene glycol.

[0014] In a first aspect, the present disclosure relates to a method for preparing a polyester having recycled content. The method of the present disclosure comprises the steps of: feeding a recycled feed comprising an ester recycled material to at least one reaction zone to form a reaction mixture comprising recycled content in at least one reaction zone, wherein the ester recycled material is selected from r-DMT, transesterified r-DMT, and combinations thereof; reacting the reaction mixture to form a polyester oligomer mixture having recycled content; and polycondensing the recycled content oligomer mixture to form a polyester having recycled content.

[0015] In one or more embodiments, the reacting step comprises reacting the reaction mixture at a temperature of at least 250°C with a total average residence time of 30 minutes to 12 hours, or 1 hour to 10 hours, or 1 hour to 8 hours. In one or more embodiments, the reacting step comprises reacting the reaction mixture at a temperature of 250°C to 350°C, or 250°C to 300°C, or 260°C to 300°C, or 250°C to 275°C.

[0016] As described above, polyesters can be prepared in a general sense by reacting a diacid, an ester thereof, or a mixture of these acids or esters with a difunctional hydroxyl compound, typically a diol or a glycol, or a mixture of these diols or glycols. Therefore, it will be understood by those of ordinary skill that in order to form the polyester with recycled components of the present disclosure, the reaction mixture in at least one reaction zone comprises components known in the art for forming polyesters, such as (i) a diacid, an ester thereof, or a mixture of such acids or esters and (ii) a difunctional hydroxyl compound, such as a diol or a glycol, or a mixture of such diols or glycols. In one or more embodiments, the reaction mixture includes recycled components. In one or more embodiments, the reaction mixture includes recycled components and virgin components. As used herein, the term "recycled" is intended to mean a source of materials such as waste, rejects, waste, post-consumer or post-industrial materials that are recycled. As used herein, the term "virgin" is intended to mean prepared from raw materials such as fossil fuel-based or bio-based raw materials, which is different from a source of materials such as waste, rejects, waste, post-consumer or post-industrial materials that are recycled.

[0017] In one or more embodiments, the feeding step of the process of the present disclosure further comprises feeding a glycol recycle material to at least one reaction zone, the glycol recycle material being selected from the group consisting of r-EG, recycled diethylene glycol (r-DEG), and combinations thereof.

[0018] In one or more embodiments, the recycle feed further includes dimethyl isophthalate recycle material (r-DMI). In one or more embodiments, r-DMI is present in the recycle feed in an amount of 2000 ppm or more, or 1500 ppm or more, or 1000 ppm or more, or 500 ppm or more. In one or more embodiments, the recycle feed may further include terephthalic acid recycle material (r-TPA), which may include r-TPA formed via hydrolysis of r-DMT. In one or more embodiments, the method may include hydrolyzing at least some of the r-DMT to form r-TPA prior to the reacting step.

[0019] In one or more embodiments, the recycle feed also includes residual catalyst material. Residual catalyst material can be one or more materials or compounds present in the recycle feed, and its source is to experience depolymerization to form the original polyester of r-DMT. In one or more embodiments, residual catalyst material can be selected from germanium material and antimony material and combination thereof. In one or more embodiments, antimony material is present in the recycle feed with an amount of 5 to 500 ppm or 10 to 500 ppm or 20 to 500 ppm or 5 or more ppm. In one or more embodiments, germanium material is present in the recycle feed with an amount of 5 to 500 ppm or 10 to 500 ppm or 20 to 500 ppm or 5 or more ppm.

[0020] In one or more embodiments, the recycle feed further comprises dimethyl isophthalate recycle material (r-DMI) and residual catalyst material selected from the group consisting of germanium material and antimony material, and combinations thereof.

[0021] In one or more embodiments, the feeding step of the method of the present disclosure also includes feeding a native feed to at least one reaction zone. In one or more embodiments, at least one diol of the native feed is a native diol. The native feed may include one or more other native materials, such as, for example, native diacids, native diesters, native branching agents such as, for example, trimellitic anhydride, etc.

[0022] In one or more embodiments, the virgin feed is substantially free of a virgin diester component. In one or more embodiments, the virgin feed is substantially free of a virgin diacid component. Therefore, in one or more embodiments, the reaction mixture may include a virgin diol component, or may be substantially free of a virgin diacid component, or may be substantially free of a virgin diester component. As used herein, the phrase "substantially free of" is generally intended to indicate that the virgin feed does not contain any intentionally added virgin acid and / or ester components. However, it will be appreciated by a person of ordinary skill that accidental diacid / diol reactions in the virgin feed may result in the formation of a small amount of virgin diester compounds. Therefore, in one or more embodiments, the phrase "substantially free of" in describing the virgin diester component of the virgin feed is intended to indicate that the virgin feed contains (based on the total moles of diacids+diesters in the virgin feed) no more than 5 mol % or no more than 4 mol % or no more than 3 mol % or no more than 2 mol % or no more than 1 mol % of virgin diester compounds. In one or more embodiments, the reaction mixture can comprise at least 95 wt %, or at least 96 wt %, or at least 97 wt %, or at least 98 wt %, or at least 99 wt %, or 100 wt % recycled feed based on the total weight of the reaction mixture.

[0023] In one or more embodiments of this aspect, the step of feeding virgin feed to the reaction zone precedes the step of feeding recycled feed. In one or more embodiments of this aspect, the method further includes the step of reacting at least some of the virgin feed in the reaction zone to form virgin polyester oligomers before or simultaneously with the step of feeding the recycled feed.

[0024] In one or more embodiments, the ester recycle material of the feed step is added in an amount sufficient to account for 1-100 mole % or 25%-100% or 90%-100% or 1%-50%, or based on the total moles of diacid in 1,4-dicarboxybenzene equivalents in the polyester with recycle content. It will be appreciated that the relative amounts of r-DMT and the diacid component (if any is present in the polyester virgin feed stream) in the reaction mixture will affect the type, structure and total recycle content of the particular polyester formed by the process of the present disclosure.

[0025] In one or more embodiments, the step of adding the virgin feed to the reaction zone begins after the step of feeding the ester recycled material to the reactor. In one or more embodiments, the step of adding the virgin feed to the reaction zone and the step of feeding the recycled feed to the reaction zone begin simultaneously or at the same physical location. Although the present disclosure is generally described above with respect to the steps of recycling the feed and in some embodiments feeding the virgin feed to the reaction zone to form a reaction mixture, it will be understood that the number and composition of the separate feed streams of the feed material are not necessarily limited. As a non-limiting example, the method may include combining the recycled feed and the virgin feed to form a combined recycled / virgin feed, and feeding the combined recycled / virgin feed to at least one reaction zone to form a reaction mixture.

[0026] In some typical TPA-based polyester preparation processes, the main acid component can be terephthalic acid, optionally with a certain amount of isophthalic acid, which is less than the amount of terephthalic acid. Therefore, in one or more embodiments, the virgin feed includes a virgin diacid component. In one or more embodiments, the virgin feed includes one or both of virgin terephthalic acid and virgin isophthalic acid. In one or more embodiments, the virgin diacid component of the virgin feed contains at least 90 mol % or at least 92 mol % or at least 94 mol % or at least 95 mol % or at least 96 mol % or at least 98 mol % of virgin terephthalic acid, based on the total moles of diacids in the virgin feed. In one or more embodiments, the virgin feed contains no more than 10 mol % or no more than 5 mol % of virgin isophthalic acid, based on the total moles of acids in the virgin feed. In one or more embodiments, the diacid component of the virgin feed contains 100 mol % terephthalic acid, based on the total moles of acids in the virgin feed.

[0027] The process for making TPA-based polyesters can be used to produce copolyesters having two or more diol residues. Thus, in one or more embodiments, the virgin feedstock comprises one or more virgin diols. Suitable diols are well known in the art, and non-limiting examples include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polytetrahydrofuran, polyoxymethylene, isosorbide, 1,3- and 1,4-cyclohexanedimethanol (CHDM), 1,4-cyclohexanedimethanol, 2,2,4,4-tetraalkylcyclobutanediols including 2,2,4,4-tetramethylcyclobutanediol (TMCD), neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylolpropane, pentaerylthritol, resorcinol, hydroquinone, and catechol, and isomers and combinations thereof. In one or more embodiments, the virgin glycol component of the virgin feed includes one or more glycols selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD), cyclohexanedimethanol (CHDM), and isomers and combinations thereof.

[0028] The ester recycling material of the feeding step is selected from recycled dimethyl terephthalate (r-DMT), transesterified r-DMT and combinations thereof. Transesterified r-DMT used herein is intended to include r-DMT that has been transesterified with one or more alcohols, such as diols, so that the methyl ester functional groups of r-DMT are replaced by ester functional groups formed by one or more alcohols. Therefore, in one or more embodiments, the method of the present disclosure includes a step of pre-reacting at least some r-DMT with one or more alcohols to form transesterified r-DMT before the feeding step. In one or more embodiments, the alcohol is a diol selected from the group consisting of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polytetrahydrofuran, polyoxymethylene, isosorbide, 1,3- and 1,4-cyclohexanedimethanol (CHDM), 1,4-cyclohexanedimethanol, 2,2,4,4-tetraalkylcyclobutanediols including 2,2,4,4-tetramethylcyclobutanediol (TMCD), neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylolpropane, pentaerythritol, resorcinol, hydroquinone, and catechol, and isomers and combinations thereof. In one or more embodiments, the alcohol is a diol selected from ethylene glycol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclohexanedimethanol, ethylene glycol, 2,2,4,4-tetramethyl-1,4-cyclobutanediol and isomers and combinations thereof. In one or more embodiments, the pre-reaction step is carried out in the presence of a metal-based catalyst. Non-limiting examples of metals of metal-based catalysts include Sb, Ti, Sn, Mo, Ge, Zn, Co, Mn, Cd, Al, Li, Pb, Mg, Ca, Ag, Na, Ce, Ba, Hg, Fe, Cu and combinations thereof. In one or more embodiments, the metal used for the metal-based catalyst is selected from titanium, manganese and zinc and combinations thereof. In one or more embodiments, the reaction conditions of the pre-reaction step will be selected to replace a majority (greater than 50 mole %) of the methyl ester functionality of the recycled material with a diol ester linkage from the diol(s) of the pre-reaction step, such as, for example, 2,2,4,4-tetramethyl-1,4-cyclobutanediol ester linkage. In one or more embodiments, the diol(s) of the pre-reaction step include 2,2,4,4-tetramethyl-1,4-cyclobutanediol, and the catalyst is a tin catalyst.

[0029] One measure of the reactants in a reaction mixture is called the "molar ratio," which is the ratio of the moles of diol in the reaction mixture to the total moles of diacid + ester in the reaction mixture:

[0030] MR = Md / (Ma + Me)

[0031] Wherein MR is the molar ratio, Md is the number of moles of diol in the reaction mixture, Ma is the number of moles of acid in the reaction mixture, and Me is the number of moles of ester in the reaction mixture. In one or more embodiments, the molar ratio of the reaction mixture is 4 or less or 3 or less or 2.5 or less or 2 or less or 1.5 or less or 1 or less or 1 to 6 or 1.5 or 6 or 2 to 6 or 2.5 to 6 or 1 to 4 or 1.5 to 4 or 2 to 4.

[0032] Applicants have unexpectedly discovered that polyesters with recycled content can be effectively and efficiently prepared by a process in which recycled monomers, particularly r-DMT, can be combined with other recycled or virgin materials and reacted to form polyesters with recycled content using process parameters, equipment, reaction conditions, etc. that are more typical for TPA-based preparation processes. Thus, in one or more embodiments, the process of the present disclosure includes reacting the reaction mixture at a temperature of at least 250°C, or at least 260°C, or at least 270°C, or at least 275°C for a total average residence time of 30 minutes to 12 hours. In one or more embodiments, the process of the present disclosure includes reacting the reaction mixture at a temperature of at least 250°C, or at least 260°C, or at least 270°C, or at least 275°C for a total average residence time of 4 hours or less, 3 hours or less, 2 hours or less, or 1 hour or less.

[0033] Although the methods described herein are about a single (at least one) reaction zone, in which the initial reaction mixture is formed, it will be understood that multiple reaction zones that can be connected in series and / or multiple reactors that can be connected in series can be used. In one or more embodiments, the reactor can define one or more reaction zones, and in one or more embodiments, the reaction zone can include one or more reactors. The number of reactors in the reaction zone can be 4 or less, or 3 or less, or 2 or less, or 1 or less. The reaction zone is defined as a container (such as a CSTR or a tubular reactor), a region or a section, in which the monomer reaction of the methyl or acid end group with the diol occurs to esterify or transesterify the methyl or acid end group. Therefore, the total average residence time of the reaction step is intended to include the sum of the average residence time in all reaction zones and all reactors. The average residence time is referred to as "average" to reflect that the average residence time based on the molecule is the average of all molecules in the reaction mixture. In one or more embodiments, the reaction step is carried out in the presence of a metal-based catalyst. The limiting examples of metals of metal-based catalysts include Sb, Ti, Sn, Mo, Ge, Zn, Co, Mn, Cd, Al, Li, Pb, Mg, Ca, Ag, Na, Ce, Ba, Hg, Fe, Cu and combinations thereof. In one or more embodiments, the metal for metal-based catalysts is selected from titanium, manganese, zinc and tin and combinations thereof. The amount of the catalyst can vary according to many factors such as reaction temperature. In one or more embodiments, the catalyst can be present in an amount of 1 to 100 ppm or 1 to 50 ppm or 1 to 40 ppm or 1 to 30 ppm or 1 to 20 ppm or 1 to 15 ppm or 1 to 10 ppm to 1 to 5 ppm or 1 to 4 ppm or 1 to 3 ppm or 1 to 2 ppm metal based on the number of reaction mixtures.

[0034] The reaction step of the method of the present disclosure includes reacting the reaction mixture to form a polyester oligomer mixture having recycled content. In one or more embodiments, the recycled content oligomer mixture has a degree of polymerization of 1-30 or 1-25 or 1-20 or 1-15, and ordinary technicians will understand that for embodiments that may include multiple reaction zones in series, the degree of polymerization can be increased in successive zones.

[0035] In one or more embodiments, the method of the present disclosure can be performed as an aspect of a waste polyester recycling process. Therefore, in one or more embodiments, the method of the present disclosure further includes, before the feeding step, a step of depolymerizing the waste polyester to form a depolymerization product comprising r-DMT. In one or more embodiments, the depolymerization step forms a depolymerization product comprising r-EG. The depolymerization step can form a depolymerization product stream, which comprises recycled dimethyl terephthalate (r-DMT) and optionally recycled ethylene glycol (r-EG). The phrase "waste polyester" as used herein is intended to include, but is not limited to, post-consumer polyester materials, post-industrial polyester materials, polyester waste, polyester selvedge, and rejects and consumer returns.

[0036] One of ordinary skill will appreciate that the depolymerization product stream may comprise a variety of materials based in part on the specific composition of the waste polyester. Thus, in one or more embodiments, the depolymerization step further comprises separating r-DMT from the depolymerization product stream to form an r-DMT-enriched stream.

[0037] Methods, techniques and systems for depolymerizing polyesters are well known in the art. A particularly suitable method is methanolysis. Methanolysis depolymerization is well known in the art and is described herein above and in at least those references incorporated herein by reference above. A polyester recycling process is generally described in U.S. Published Patent Application No. US 2013 / 0041053, assigned to the assignee of the present disclosure, the contents and disclosure of which are incorporated herein by reference. The term "methanolysis" as used herein is intended to include the so-called glycolytic process, which includes a step of forming r-DMT by a methanolysis step.

[0038] The method of the present disclosure also includes polycondensing the recycled content oligomer mixture to form a polyester with recycled content. Polycondensation is a well-known step in the preparation of polyesters, wherein esters and ester oligomers formed by direct esterification of diacids with diols and / or transesterification of esters are polymerized by polycondensation to form polyesters, typically wherein any diols that are readily volatile and removed from the system under the polycondensation conditions are eliminated. The polycondensation can be carried out under vacuum and at a temperature of typically from about 230°C to about 350°C, preferably from about 250°C to about 310°C, and most preferably from about 260°C to about 300°C, for about 0.1 to about 6 hours, or preferably from about 0.2 to about 2 hours, until a polymer having a desired degree of polymerization, as determined by intrinsic viscosity, is obtained. The polymer can undergo further polymerization in the solid state.

[0039] As described above, the recycled feed used in the feed step of the method of the present disclosure may include other components such as dimethyl isophthalate recycled material (r-DMI) and / or residual catalyst material in addition to the ester recycled material selected from r-DMT, transesterified r-DMT and combinations thereof. Therefore, on the other hand, the present disclosure relates to a recycled feed composition for preparing a polyester with recycled content. The recycled feed composition of the present disclosure comprises an ester recycled material selected from r-DMT, transesterified r-DMT and combinations thereof; and at least one selected from the following: dimethyl isophthalate recycled material (r-DMI) and residual catalyst material. In one or more embodiments, the recycled feed composition comprises dimethyl isophthalate recycled material (r-DMI). In one or more embodiments, the recycled feed composition comprises residual catalyst material. In one or more embodiments, the recycled feed composition comprises dimethyl isophthalate recycled material (r-DMI) and residual catalyst material. In one or more embodiments, the recycle feed composition includes r-TPA, such as, for example, r-TPA formed by hydrolysis of r-DMT.

[0040] In one or more embodiments, the residual catalyst material can be selected from germanium materials and antimony materials and combinations thereof. In one or more embodiments, r-DMI can be present in an amount of 3000 ppm or more, or 2000 ppm or more, or 1500 ppm or more, or 1000 ppm or more, based on the recycled feed composition. In one or more embodiments, the residual catalyst material can be present in an amount of 5 to 500 ppm based on the recycled feed composition.

[0041] Applicants have also surprisingly discovered that the process of the present disclosure produces recycled content polyesters having unique and useful properties. Thus, in another aspect, the present disclosure relates to polyesters having recycled content, or recycled content polyesters, wherein the number of carboxyl end groups present in the recycled content polyester is less than 25 meq / kg polymer, or less than 20 meq / kg polymer, or less than 15 meq / kg polymer. "Carboxyl end groups" refers to free carboxyl groups (-COOH) present at the ends of polyester macromolecules. Carboxyl end groups can be measured, for example, by acid-based titration with a dissolved polymer sample. In a suitable measurement technique, a weighed sample of the polyester polymer is dissolved in hot o-cresol (120°C). o + / - 5°C), allowed to cool, and then diluted with dichloromethane and bromocresol green indicator solution. An automatic titrator determines the endpoint optically and calculates the result.

[0042] In another aspect, the present disclosure relates to polyesters having recycled content, or recycled content polyesters, wherein the recycled content polyester has a diethylene glycol content of less than 2.0 wt % or less than 1.8 wt % or less than 1.6 wt % or less than 1.5 wt % or less than 1.4 wt % or less than 1.2 wt % or less than 1.0 wt % or less than 0.8 wt % or less than 0.6 wt %, all based on the total weight of the polymer. "Diethylene glycol content" refers to the amount of diethylene glycol [(HOCH2CH2)2O] present in the recycled content polymer. In one or more embodiments, at least some of the diethylene glycol content is an "in situ" diethylene glycol content, meaning that the diethylene glycol used to form the polymer is formed during the process of forming the polymer (as opposed to being formed separately and intentionally added during the process of forming the polymer). The diethylene glycol content can be measured, for example, by conventional GC techniques or proton NMR techniques after hydrolysis of the polymer.

[0043] The following examples further illustrate how the polyesters of the present disclosure may be prepared and evaluated, and they are intended to be exemplary only and not intended to limit the scope thereof. Unless otherwise indicated, parts are parts by weight, temperature is C (Celsius) or room temperature, and pressure is at or near atmospheric.

[0044] The present disclosure may be further illustrated by the following examples of preferred embodiments thereof, but it will be understood that these examples are included for illustrative purposes only and are not intended to limit the scope of the present disclosure unless specifically stated otherwise. Example

[0045] Example 1 - Oligomer Synthesis Section

[0046] The oligomers used to constitute the high molecular weight polymer were synthesized in a 2-gallon stainless steel autoclave with a hot oil heated partial condenser. For the series of experiments shown in Table 1, the reaction process was as follows: the raw materials were loaded into the reactor, sealed and heated to 260°C and pressurized to 30 psig, the partial condenser was heated to 130°C, and once the system was at this temperature, the reaction was carried out for 8 hours. The reactor was then heated to the target composition, the final material was PET with 5% IPA modification, and in all cases, a titanium tetraisopropoxide catalyst was added so that the content in the final polymer should be 15 ppm.

[0047] Table 1

[0048] sample TPA (g) IPA(g) DMT (g) EG(g) 1 1894 99.7 0 1340.7 2 1420.5 99.7 553.4 1340.7 3 947 99.7 1106.9 1340.7 4 473.5 99.7 1660.3 1340.7 5 0 99.7 2213.8 1340.7

[0049] Then 100g of oligomer was loaded into a 500mL single-necked round-bottom flask. The target level of antimony catalyst was added to the flask in the form of an ethylene glycol solution. A stainless steel stirring unit consisting of a 1 / 4'' diameter shaft connected to a single 2.5'' diameter stirring blade was inserted into the flask, and then the flask was equipped with a glass polymer head. A polymer head consisting of a standard tapered 24 / 40 male joint was connected to the reaction flask; the side arm was positioned at approximately 45° with the neck of the flask to allow the removal of volatile materials, and the portion of the glass tube extended above the flask neck, through which the stirring shaft passed. The portion of the tube through which the stirring shaft passed was equipped with a Teflon bushing and a rubber hose to provide a vacuum tight seal around the stirring shaft. The shaft was rotated by a 1 / 8 horsepower motor connected thereto by a flexible "universal" joint. The side arm was connected to a vacuum system consisting of a dry ice-cooled condenser and a vacuum pump. The pressure in the reaction flask was controlled by infiltrating nitrogen into the vacuum stream. The reaction flask was heated using a molten metal bath. All reaction parameters were monitored and controlled using a distributed data acquisition and control system. Table 2 shows the reaction sequence used by the automated control system, with variations of stage 8 for the production of low viscosity materials by solid stating.

[0050] Table 2

[0051] Number of reaction stages Phase duration (minutes) Temperature (° C) Pressure (mm Hg) Stirring speed (RPM axis) 1 0.1 265 Atmospheric pressure 1 2 25 265 Atmospheric pressure 125 3 5 265 130 150 4 30 265 130 150 5 10 280 4 125 6 40 280 4 125 7 5 280 1 75 8 90 (60) 280 1 75 9 2 280 Atmospheric pressure 0

[0052] After polymerization, each polymer was removed from the blades of the stirring shaft and ground in a hammer mill to a particle size small enough to pass through a screen with 6 mm holes. All tests and solidification were performed on the pellets.

[0053] Table 3 below details examples of final IVs of materials prepared with different amounts of DMT added to a TPA-based process. In Table 2, % DMT refers to the mole % in the reaction where TPA units are replaced by DMT. The intrinsic viscosity of the polyesters herein is measured in 60 / 40 (wt / wt) phenol / tetrachloroethane at 25°C at a concentration of 0.5 g / dL and reported in dL / g. The metal content of the material is measured by X-ray fluorescence in a manner similar to ASTM D6247-18 (modified for sample matrices and analytes of interest). The use and amount of DMT added to the system has no negative impact on the IV construction of the material.

[0054] Table 3

[0055] sample DMT % Ti (ppm) Sb (ppm) IV 1 0 11.6 165 0.7 2 25 14.4 203 0.82 3 50 12.4 194 0.81 4 75 13.8 202 0.76 5 100 14.3 190 0.86

[0056] A standard solid state process (24 hours at 220°C, 1 mmHg) was performed to determine the effect that DMT would have on IV enhancement. The results shown in Table 4 indicate that the addition of DMT to a PTA-based process has no negative effect as with a resin-based process. This result is unexpected given the poor reactivity of any residual methyl end groups in solid state. Without being bound by any theory, it is believed that the high temperature and long residence time in the first reactor may have reduced the methyl end group content to a point where it no longer hinders the construction of a solid IV.

[0057] Table 4

[0058] sample DMT % IV (resin) IV (Solidified) 6 0 0.629 1.605 7 50 0.66 1.482 8 100 0.742 1.961

[0059] For the avoidance of doubt, it is expressly provided that information and descriptions claimed herein regarding features or elements in relation to one aspect of the present disclosure may also be used and relied upon in support of those features and elements when described in relation to other aspects of the present disclosure.

[0060] For the purpose of illustration and description, the above description of various embodiments of the present disclosure has been presented. It is not intended to be exhaustive or to limit the present disclosure to the precise embodiments disclosed. In accordance with the above teachings, many modifications or variations are possible. The embodiments discussed are selected and described to provide the best description of the principles of the present disclosure and its practical application, so that those of ordinary skill in the art can utilize the present disclosure in various embodiments and make various modifications suitable for the specific purposes envisioned. When interpreted according to the scope of fair, legal and equitable authorization, all these modifications and variations are within the scope of the present disclosure determined by the appended claims.

Claims

1. A method for preparing polyester having recycled content, the method comprising the steps of: feeding a recycled feed comprising an ester recycled material selected from the group consisting of r-DMT, transesterified r-DMT, and combinations thereof to at least one reaction zone to form a reaction mixture comprising recycled content in the at least one reaction zone; reacting the reaction mixture to form a polyester oligomer mixture having recycled content; and polycondensing the recycled content oligomer mixture to form a polyester having recycled content, The reacting step comprises reacting the reaction mixture at a temperature of 260-300° C. for a total average residence time of 30 minutes to 12 hours.

2. The method of claim 1, wherein the feeding step further comprises feeding a glycol recycle material selected from the group consisting of r-EG, r-DEG, and combinations thereof to at least one reaction zone.

3. The process of claim 1, wherein the recycle feed further comprises dimethyl isophthalate recycle material (r-DMI).

4. The method of claim 1, wherein the recycle feed further comprises residual catalyst material selected from the group consisting of germanium materials and antimony materials, and combinations thereof.

5. The method of claim 1, wherein the feeding step further comprises feeding a native feed to at least one reaction zone, the native feed comprising at least one native glycol component.

6. The process of claim 5, wherein the virgin feedstock is substantially free of a virgin diester component; or wherein the virgin feedstock is substantially free of a virgin diacid component.

7. The method of claim 5, wherein the native feed further comprises a native diacid component.

8. The process of claim 7 wherein the native diacid component is at least 90 mole percent terephthalic acid, based on the total diacid content of the native feed.

9. The method of claim 8, wherein the native dibasic acid component comprises one or both of terephthalic acid and isophthalic acid.

10. The method of claim 1, wherein the reacting step is performed in the presence of a metal-based catalyst, wherein the metal of the metal-based catalyst is selected from the group consisting of Sb, Ti, Sn, Mo, Ge, Zn, Co, Mn, Cd, Al, Li, Pb, Mg, Ca, Ag, Na, Ce, Ba, Hg, Fe, Cu, and combinations thereof.

11. The method of claim 5, wherein the native diol component of the native feed comprises one or more of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polytetrahydrofuran, polyoxymethylene, isosorbide, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetraalkylcyclobutanediol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylolpropane, pentaerythritol, resorcinol, hydroquinone and catechol and isomers and combinations thereof.

12. The method of claim 5, wherein the glycol component of the virgin feed comprises one or more glycols selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD), cyclohexanedimethanol (CHDM), and isomers and combinations thereof.

13. The method of claim 1, further comprising, prior to the feeding step, a step of depolymerizing the waste polyester to form a depolymerization product comprising r-DMT; and wherein the depolymerization step is performed by methanolysis.

14. The process of claim 1 wherein the ester recycle material of the feeding step is fed in an amount sufficient to account for 1 to 100 mole percent of the total moles of diacid based on 1,4-dicarboxybenzene equivalents in the polyester having recycled content.

15. The method of claim 5, wherein the step of feeding the virgin feed precedes the step of feeding the recycled feed; and wherein the method further comprises the step of reacting at least some of the virgin feed in the reactor to form virgin polyester oligomers prior to or simultaneously with the step of feeding the recycled feed.

16. The process of claim 1 further comprising the step of pre-reacting at least some of the r-DMT with one or more diols selected from the group consisting of diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclohexanedimethanol, ethylene glycol, 2,2,4,4-tetramethyl-1,4-cyclobutanediol, and isomers and combinations thereof to form transesterified r-DMT prior to the feeding step.

17. The method of claim 16, wherein the pre-reaction step is carried out in the presence of a metal-based catalyst, wherein the metal of the metal-based catalyst is selected from Sb, Ti, Sn, Mo, Ge, Zn, Co, Mn, Cd, Al, Li, Pb, Mg, Ca, Ag, Na, Ce, Ba, Hg, Fe, Cu and combinations thereof.